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• 1.1: Source Water Quality A  finite amount of water on our planet (0.34%) is available to treat for human consumption. Knowing where the water comes from assists certified operators in treating raw source water to make it potable. Newer technology has been developed to treat salinized or salty water found in the ocean. These treatment methods are still extremely expensive and not widely accessible. Supplying water to the public is an extremely important function in society as water is the basic building block of life. • 1.2: Water Chemistry and Standards Water treatment is a complex process that involves parts that the human eye cannot see. In this chapter, you will learn about the basic scientific principals related to the water treatment. We will also discuss drinking water standards in the United States and different community standards. • 1.3: Microorganisms The most important job of a Water Treatment Operator is providing reliable and quality water to the public. This is accomplished through chemical deactivation or physical removal of disease-causing microorganisms in the water. Microorganisms are deactivated by the addition of a chemical such as Chlorine or Ozone while physical removal is accomplished with the use of a filtration system. • 1.4: Coagulation and Flocculation One of the most important steps in the water treatment process is the removal of suspended solids. The two-part process in water treatment involves chemical deactivation and physical removal of pathogenic organisms. The physical removal of pathogens is accomplished in several steps. The first two steps include the processes of coagulation and flocculation, where colloidal particles are destabilized to gather all the suspended material together. They can also be referred to as nonstable solids. • 1.5: Sedimentation Sedimentation is the 3rd step in a conventional treatment process. It occurs after coagulation and flocculation and before filtration. Sedimentation removes suspended solids with the use of gravity by slowing the flow of water down to allow material to settle. The settleable solids fall to the bottom of the sedimentation basin reducing the load on the filtration process. A sedimentation basin acts like a lake in the sense that it allows particles to settle naturally. • 1.6: Filtration Filtration is the final and most important removal requirement required by the Surface Water Treatment Rule (SWTR). Water passes through material such as sand, gravel, and anthracite coal to remove floc and disease-causing microorganisms from the finished water. Physical removal of colloids is also achieved during sedimentation but this filtration is the final step. This is the process where suspended colloidal particles are removed from the water. • 1.7: Disinfection The final step in the water treatment process before finished or treated water enters a clearwell for storage is the disinfection process and is the process where chemical agents are added to a water source to kill or inactivate pathogenic microorganisms. Pathogenic microorganisms are disease-causing and must be eliminated from treated water. As populations increase and freshwater sources become scarcer, the ability to remove and deactivate microorganisms becomes increasingly important. • 1.8: Chlorine Chlorine is the chemical most frequently used in the water treatment industry for disinfection purposes to meet the standards of the surface water treatment rule. Chlorine is used in several different forms and can be fed into the system in a variety of different methods. It is a very dangerous chemical, so proper safety and handling procedures must always be followed. Chlorine may also be used as a controlling agent for the removal of algae, for taste, and for odor. • 1.9: Chloramination and Nitrification The use of chlorine causes any number of disinfectant by-products with many have not been researched and are not regularly monitored. E.g., trihalomethanes are disinfectant by-products of chlorine disinfection and are classified as volatile organic chemicals and their increasing levels in raw water pushes the use of chloramine as the preferred disinfectant. In this chapter, we will discuss chloramine disinfection and the associated challenges that come with its implementation. • 1.10: Laboratory Working in a laboratory is probably something you never thought about when deciding to explore the career of water treatment. However, working in a laboratory is one of the more critical aspects of the profession. Many larger agencies have a dedicated staff of laboratory personnel that handles a lot of the day to day water quality analysis, but operators still play a key role. 01: Chapters Learning Objectives After reading this chapter you should be able to identify and explain the following: • The Earth’s Hydrologic Cycle • Sources of groundwater • Sources of Surface Water • Water math: Area and Unit Conversions A very finite amount of water on our planet (0.34%) is available to treat for human consumption. Knowing where the water comes from assists certified operators in treating raw source water to make it potable. Newer technology has been developed to treat salinized or salty water found in the ocean. These treatment methods are still extremely expensive and not widely accessible. Supplying water to the public is an extremely important function in society as water is the basic building block of life. Because water quality is of the utmost importance new regulations and water quality standards are continually changing and evolving to make sure the public has safe sources of drinking water. The first drinking water standards were written in the Safe Drinking Water Act (SDWA), which was signed into law by President Ford in 1974. Throughout the text, new concepts will be introduced and an acronym will be given and used subsequently. You are going to learn to love acronyms if you become a certified operator. We use them quite frequently! The Hydrologic Cycle The Hydrologic cycle is the continual movement of water on the surface of the planet. The water moves above, below, and across the Earth’s surface as a liquid, gas, or solid. The 12 elements of the hydrologic cycle are defined as follows: • Evaporation⁠—Water moves in the gas state from the Earth’s surface to the atmosphere • Transpiration⁠—Water moves in the gas state from plants to the atmosphere. • Advection⁠—Water in the gas state moves through air currents in the atmosphere • Condensation⁠—Water vapor converts from gas to liquid state in the form of water droplets. • Precipitation⁠—Water as a liquid and/or solid falls from the atmosphere. We commonly refer to this as rain, snow, sleet, and hail. • Interception⁠—Water in the liquid state that is captured by plants • Infiltration⁠—Water in the liquid state that soaks into the surface of the ground. This will be what is known as groundwater which will be detailed later in this chapter. • Subsurface Flow⁠—Water in the liquid state flows below the Earth’s surface. The movement is generated by gravity and obstructions below the surface of the Earth. • Runoff⁠—Water in the liquid form travels to bodies of water. This would include the ocean, lakes, rivers, and streams. This is also known as surface water which will be detailed more later in this chapter. • Channel flow⁠—Water in the liquid form that flows from small channels into rivers and streams • Storage⁠—Water is naturally stored in liquid form in lakes, ponds, wetlands, and groundwater aquifers. In solid form, water is naturally stored in ice, snow, and glaciers. This natural storage provides much of the water treated for human consumption. • Snowmelt⁠—Water in the solid form converts to water in the liquid form and is returned to the hydrologic cycle. Note: In California, snowpack is a critical water supply indicator as it is the melting snowpack that recharges rivers and the general supply of water There are other important terms to note in regard to the hydrologic cycle. The surface to atmosphere movement of water is known as evapotranspiration. This is the combination of evaporation and transpiration from plant life to the atmosphere. The most widely known movement of water is precipitation which is when water in various physical states falls from the atmosphere to the surface of the Earth. The movement of water from the surface to subsurface is known as percolation. Percolation might also be referred to as infiltration or recharge. These terms are commonly associated with underground aquifers. Finally, surface to surface flow is called runoff. Groundwater Groundwater is one of the two main sources of storage used by municipalities to produce potable water. It is formed by the percolation (infiltration and/or recharge) of water from the surface of the earth to the subsurface. Water moves through holes and cracks in the subsurface and collects in an underground aquifer. An aquifer is a geologic formation that accumulates water due to its porousness. Important characteristics of groundwater include consistent water quality and the ability to remain safe from surface contamination. With greater technology and testing methods chemicals and constituents known to be harmful to humans have been found in numerous well sites throughout the United States. Wells close to industrial areas have been contaminated with harmful chemicals and substances. New regulations are continually being updated to ensure source groundwater is safe to drink. In normal circumstances, very little treatment is required to yield groundwater. The Groundwater Treatment Rule (GWTR) was enacted in 2006 to prevent microbial contamination from underground water supplies. The purpose of the new rule was to classify water systems that were at a greater risk for fecal contamination. These systems must employ a multiple-barrier protection similar to the surface water treatment rule which will be covered in more detail in the next section. There are two kinds of aquifers, confined and unconfined. In an unconfined or water table aquifer the water table is free to rise and fall. The water table in unconfined aquifers rise and fall depending on the amount of precipitation that recharges the aquifer. Confined aquifers, also known as artesian wells, contain water that is confined due to layers of low permeability. These layers, which restrict movement, are comprised of rock or hard clay and are referred to as confining beds, aquitards, or aquicludes. Artesian wells are generally under pressure when drilled. Once drilled the water level at which the column of water will rise is known as the piezometric surface. Sometimes, the water will rise to the surface or past the surface but in the instance, the water remains below it is known as a non-flowing artesian well. Wells The construction of wells is critical in the extraction of water from underground water supplies. The placement of wells is very important because proper location will produce the greatest yield. Important terms related to underground wells: • Static Water Level⁠—The level in the well when no water is being removed from the aquifer. This level can be measured in feet or elevation. • Pumping water level⁠—The level when water is being removed from the aquifer. This level can vary depending on the rate of flow from the well. • Drawdown⁠—The difference between the pumping water level and the static water level • Cone of depression⁠—The shape or “cone” created by the movement of water in all directions during pumping. • Zone of influence⁠—The area of water affected by the drawdown of water during pumping. It is important to note that wells cannot be placed too closely together because their zones of influence may affect each other. • Well yield⁠—The amount of water drawn from an aquifer over a specific period of time • Specific capacity⁠—The amount of water produced per drawdown expressed in gpm/ft • Safe Yield/Perennial yield⁠—The amount of water that can be pulled from an aquifer per year without a drop in the water table • Overdraft⁠—Too much water removed. Greater than the safe yield of a well • Subsidence⁠—The permanent drop in the water table due to overdraft Specific Capacity Calculation $\text{Specific capacity} = \text{Flow (GPM)} ÷ \text{Drawdown (ft)} \label{Specific Capacity}$ Example $1$ A well has a yield of 600gpm and the drawdown is 50 ft. What is the specific capacity of the well? Solution This is a direct application of Equation \ref{Specific Capacity} $\text{Specific Capacity = 600\, \text{GPM} ÷ 50\, \text{ft} = 12$ Surface Water Throughout the United States, surface water is the most widely used source of water for large cities and other municipalities. Groundwater is not as widely available so is not a sufficient water supply for major cities. Surface water includes lakes, ponds, rivers, and streams. California is unique as the southern half of the state has 2/3 of the population but only 1/3 of the available water and the northern half of the state has 1/3 of the population but 2/3 of the water. Snowpack in northern California is critical to the state’s water supply. Most of Southern California is very arid and densely populated so water travels from Northern California through the State Water Project to Southern California. Surface runoff supplies water for all surface water sources. Influences of surface runoff include intensity of rainfall, duration of rainfall, composition of soil, amount of moisture in soil, slope of the ground, vegetation coverage, and human influences. One would think that a lot of rain would be ideal. However, if the rainfall density is too great, more water can be lost because the ground will no longer absorb the water. The same applies to the duration of rainfall. A prolonged rain even makes the soil too moist and unable to capture water. Vegetation coverage and the slope of the ground are very important to stopping runoff. If the slope of the ground is steep, the speed of runoff is increased. Vegetation slows the speed of runoff and allows more water to absorb or infiltrate into the ground. Human influences have a great impact on water runoff. Impervious surfaces like concrete entirely prevent infiltration. Natural Watercourses Key Terms Natural water courses include rivers, creeks, streams, washes, and arroyos. They flow in one of three ways: • Perennial streams—Watercourses which flow continuously throughout the year • EX: Colorado River • Ephemeral streams⁠—Watercourses that flow sporadically, generally after rainfall • EX: Santa Clara River which runs through Santa Clarita and Ventura County • Intermittent⁠—Watercourses which flow somewhere between ephemeral and perennial streams. Rainfall and high groundwater levels will affect how often these streams flow. Rivers and Streams are a good water supply source but are not necessarily the best source for public water supplies. Lakes Lakes are the most widely used public water supply source. However, very few “natural” lakes exist. Most lakes used for public water supply are man-made and use a dam to create the lake and contain the water. This is known as an impoundment. Water from these lakes is piped to treatment facilities. Due to variances in temperature lakes develop “layers” also known as stratification. Denser, colder water will drop to the bottom (Benthic zone) of a lake during the summer. There are three layers: • Epilimnion⁠—The strata closest to the surface • Hypolimnion⁠—The strata near the bottom • Thermocline⁠—Middle strata with the greatest variance in temperature Lake turnover will occur during seasonal temperature changes. When the temperature of a lake is uniform it is known as isothermal. Algae growth is a serious problem that causes taste and odor issues in treated water. Copper sulfate can be added to a lake to help remedy algae blooms. In severe cases, the water undergoes eutrophication which is the loss of oxygen. Complete or extreme oxygen depletion can kill all living creatures in the water including animals and fish. Introduction to Water Math Mathematics is a key component of water treatment. Operators use conversion tables and basic algebra to complete many daily tasks. Charts are available on the State Water Resources Control Board website that assist operators with most calculations you would find on the state exams or while on the job. Below is a list of basic units and their respective conversion factors: Table 1.1: Units and Conversion Factors Measurement Equivalent 1 cubic foot of water 62.3832lbs 1 gallon of water 8.34lbs 1 liter of water 1,000 grams 1 mg/L 1 part per million (ppm) 1 ug/L 1 part per billion (ppb) 1 mile 5,280 feet 1 yard 3 feet 1 yard3 27ft3 1 acre 43,560 square feet or ft2 1 cubic foot or ft3 7.48 gallons 1 gallon 3.785 Liters or L 1 L 1,000 milliliters (ml) 1 pound 454 grams Working with Fractions NumeratorDenominator 44=11 or =1 42=21 or =1 Rounding Rounding the number 324.179 3 = Hundreds The above number (324.179) rounded to the nearest tenth would be 324.2. Since the number in the hundredth place is at or above 5, the number in the tenth place is rounded up. If you were rounding this number to the nearest whole number it would be 323 since the number in the tenth place is below 5. 4 = Tens 9 = Units 1 = Tenth 7 = Hundredth 9 = Thousandth Unit Dimensional Analysis This is the most important function in most water math problems. Make sure to always place your factors in the proper place or the equation will be impossible to solve correctly. The example below will use unit measurements. Water operators will commonly convert between different units of measurement. Example 1 Convert 48 inches into feet. (There are 12 inches in a foot.) 48 inches11 foot12 inches=4 ft1 Drop the one from the denominator and the answer is 4 ft. The same process will be to convert between gallons and cubic feet. Example 2 Convert 22.44 gallons into cubic ft. or ft3 (There are 7.48 gallons in one cubic foot.) 22.44 gallons11 ft³7.48 gallons=3 ft³1 Drop the 1 from the denominator and your answer is 3 ft³ Example 3 How many gallons are there in a tank which holds 300ft³ of water? 300ft317.48 gal1ft3=2,244 gallons Area Area will be important for many applications in water math. It may be necessary to calculate the area of a tank that requires painting or an area of ground cover near equipment. Rectangles Area = L × W Circle Area = 0.785 × D2 Trapezoid Area = × H Example 1 A wall that is 10ft wide and 40ft in length needs to be painted. What is the total square feet of the wall? Area = Length x Width Area = 10ft x 40ft Area = 400ft2 Example 2 What is the area of the top of a circular storage tank that is 100 feet in diameter? (Note: Use the formula .785 x d2. In most cases in water math, we will always be dealing with the diameter and not the radius. These short cuts will help as the problems become more difficult. In this problem I will demonstrate why we will use this formula and not the standard mathematical equation for solving area problems.) Equation #1 Area= π (3.14) x r2 (100ft ÷ 2 = 50 to find radius) Area = 3.14 x 50 x 50 Area = 7,850 ft2 Equation #2 Area= .785 x d2 Area = .785 x 100 x 100 Area = 7,850 ft2 In this example, the first equation was easy to solve because we were working with a pretty friendly number. As the equations become more difficult we do not want to take the extra step to divide the diameter by two to solve for the radius. If the diameter of the tank was 357ft, this problem would have been slightly more difficult using the first equation. Example 3 The top of a circular storage tank needs to be painted. It is 100 ft. in diameter. Each gallon of paint covers approximately 200 square feet. How many gallons of paint will you need to buy? Area= .785 x d2 Area= .785 x 100ft x 100ft Area= 7,850 ft2 7850 ft²1x1 gal200 ft²=39.25 gal Chapter Review 1. What is the middle layer of a stratified lake called? 1. Thermocline 2. Benthic Zone 3. Epilimnion 4. Hypolimnion 2. What is the conversion of liquid water to gaseous water known as? 1. Advection 2. Condensation 3. Precipitation 4. Evaporation 3. Water weighs ___________. 1. 7.48 lbs/gal 2. 8.34 lbs/gal 3. 62.4 lbs/ft3 4. Both 2 and 3 4. What is the static level of an unconfined aquifer also known as? 1. Drawdown 2. Water Table 3. Pumping Water Level 4. Aquitard 5. What is the cause of taste and odor problems in raw surface water? 1. Copper sulfate 2. Blue-green algae 3. Oxygen 4. Lake turnover 6. What chemical reduces blue-green algae growth? 1. Chlorine 2. Caustic Soda 3. Copper Sulfate 4. Alum 7. A water-bearing geologic formation that accumulates water due to its porousness. 1. Aquifer 2. Lake 3. Aquiclude 4. Well 8. What kind of stream flows continuously throughout the year? 1. Ephemeral 2. Perennial 3. Intermittent 4. Stratified 9. The surface to atmosphere movement of water is known as ___________. 1. Precipitation 2. Percolation 3. Stratification 4. Evapotranspiration 10. An aquifer that is underneath a layer of low permeability is known as ___________. 1. Confined aquifer 2. Water Table aquifer 3. Unconfined aquifer 4. Unreachable groundwater 11. What is the middle layer of a stratified lake known as? 1. Hypolimnion 2. Benthic Zone 3. Thermocline 4. Epilimnion 12. The amount of water that can be pulled from an aquifer without depleting. 1. Drawdown 2. Safe yield 3. Overdraft 4. Subsidence Math Questions Please show all work. On the State exams, you will not get credit if work is not shown. 1. What is the area of the top of a storage tank that is 75 feet in diameter? 1. 4,000 ft2 2. 4416 ft2 3. 1104 ft² 4. 17,663 ft² 2. What is the area of a wall 175 ft. in length and 20 ft. wide? 1. 3,000 ft² 2. 2,500 ft² 3. 3,500 ft² 4. 4,000 ft² 3. You are tasked with filling an area with rock near some of your equipment. One (1) bag of rock covers 250 square feet. The area that needs rock cover is 400 feet in length and 30 feet wide. How many bags do you need to purchase? 1. 40 Bags 2. 42 Bags 3. 45 Bags 4. 48 Bags

textbooks/workforce/Water_Systems_Technology/Water_151/1.01%3A_Source_Water_Quality.txt

Learning Objectives After reading the chapter the student should be able to identify: • Matter, elements, and compounds • Public water systems: community and non-community • Primary and secondary standards • Water treatment violations • Volume math problems Water treatment is a complex process that involves parts that the human eye cannot see. In this chapter, you will learn about the basic scientific principals related to the water treatment. We will also discuss drinking water standards in the United States and different community standards. Matter, Elements, and Compounds Matter The smallest parts of an element are comprised of particles known as atoms. Even though they are so small, atoms still retain the characteristics of the element. Even with technological advancements, microscopes are still unable to capture atoms. The multiple arrangements of atoms make each element unique. The atom ever so small, is comprised of three particles known as the proton, neutron, and electron. Each particle is associated by different charges. • Proton-positive • Neutron-no charge • Electron- Negative charge The defining characteristic of an atom is identified by the proton. The proton, located in the nucleus, has a distinctive number. For example, carbon has six protons located in the nucleus. No other element has six protons in the nucleus. The number of protons is represented as the atomic number. The atomic weight is the number of protons and neutrons. The number of protons that exist for a given element is always the same, but the number of neutrons can vary. When there is a varying number of neutrons of a given element, it is known as an isotope. When an atom has a difference in electrons, it is called an ion. When the charges of the atom are not balanced, they become unstable. An atom that has more protons than neutrons is called a cation. An atom that has more electrons than protons is called an anion. Most common elements in the water treatment profession: • Aluminum (Al) • Antimony (Sb) • Arsenic (As) • Barium (Ba) • Beryllium (Be) • Boron (B) • Bromine (Br) • Cadmium (Cd) • Calcium (Ca) • Carbon (C) • Chlorine (Cl) • Chromium (Cr) • Copper (Cu) • Fluorine (F) • Hydrogen (H) • Iodine (I) • Iron (I) • Lead (Pb) • Magnesium (Mg) • Manganese (Mn) • Mercury (Mn) • Nickel (Ni) • Nitrogen (N) • Oxygen (O) • Phosphorus (P) • Potassium (K) • Radium (Ra) • Selenium (Se) • Silicon (Si) • Silver (Ag) • Sodium (Na) • Strontium (Sr) • Sulfur (S) • Thallium (Tl) There are elements that are pure in form, such as oxygen. Since elements are unstable, they often combine with other elements to form compounds. Water (H2O), for example, is a compound. It is a combination of two hydrogen atoms and one oxygen atom. A compound is two or more elements that are bonded together due to their attraction by reverse charges. The combining elements form a molecule. When two chemicals are mixed together without a chemical reaction it is called a mixture. The difference between a mixture and a compound is bonded together by a chemical reaction. A good example of a mixture is saltwater. The salt can be removed from the water through distillation. Water chemistry will be covered in greater detail in the Water Quality text and course. Drinking Water Standards The first drinking water standards created in the United States occurred in 1974 and were called the Safe Drinking Water Act (SDWA). The US EPA sets drinking Water Standards that all Water Municipalities must adhere to. Although States are able to come up with their own Standards, they must meet the minimum requirements set forth by the federal EPA. In California, drinking water standards are much more stringent than the federal requirements and therefore have primacy. As of 2014, the State regulatory group responsible for drinking water is the State Water Resources Control Board. Revisions to the safe drinking water act include approval techniques for treatment plants, specifying criteria for filtration of public water supplies, distinguishing different treatment techniques for surface and groundwater, and prohibiting lead products in drinking water systems. There are two sets of drinking water Standards identified as primary standards and secondary standards. Primary Standards affect human health and are mandated with Maximum Contaminant Levels (MCL). The MCL is the official safe level at which a human can consume the given contaminant without adverse health effects. Secondary Standards do not affect human health and are controlled with Maximum Contaminant Level Goals (MCLG). When a contaminant is reported, there is no such thing as zero. Levels are set to protect human health but are also set based on the best available technology. As technology improves MCL’s may be reexamined. Instrumentation to measure contaminant levels are not always capable of reading to absolute zero. Because of this, a Detection level for reporting is required. Public Water Systems There are three different categories of public water systems: • Community Public Water System: A community public water system has 15 or more service connections and serves at least 25 or more people year-round. These would include municipalities, mobile home parks, condos, and apartment buildings. • Nontransient, NonCommunity System: A nontransient, NonCommunity public water system owns its own system and serves an average of 25 people for at least six months. Schools, hospitals, and office buildings are included in this category. • Transient, NonCommunity System: A transient, NonCommunity public water system owns their own water system and serves an average of 25 people per day. In this category people consume the water for a short period of time. This category includes churches, parks, restaurants, and motels. Primary Drinking Water Standards are split into five categories. The categories include Inorganics, Organics, Turbidity, Microbiological, and Radiological. • Inorganics: Metals, Nitrate, and Fluoride • Organics: Pesticides, solvents, and Disinfectant byproducts (DBP’s)⁠—The combination of Chlorine and natural organic material. This topic will be discussed in greater detail later in the text. • Turbidity: The cloudiness of the water. Turbidity has the ability to shield microbiological material. • Microbiological: Coliform testing (This will be covered in greater detail later in the text. Water operators do not test for specific microbiological agents. We test for the indicator organism coliform. They colonize in greater numbers so if a sample comes back positive there is a greater likelihood of fecal contamination.) • Radiological: Gross alpha, beta, and radon Secondary drinking water standards are solely based on the aesthetic quality of drinking water. The main focus of secondary standards is taste, odor, and color. A glass of water that smells like fish and is orange in color may be “safe” to drink but wouldn’t be well received or readily consumed. California, as well as some other states, has endorsable secondary standards. Table 2.1: Recommended Levels for Contaminants and Characteristics Contaminant/characteristic Recommended level Aluminum 0.05 to 0.2 mg/L Chloride 250 mg/L Color 15 color units Copper 1 mg/L Corrosivity Non-corrosive Fluoride 2 mg/L Foaming agents 0.5 mg/L Iron 0.3 mg/L Manganese 0.05 mg/L Odor 3 threshold odor number pH 6.5 to 8.5 Silver 0.10 mg/L Sulfate 250 mg/L Total dissolved solids 500 mg/L Zinc 5 mg/L Source: Graph by the EPA is in the public domain Public Notification In the event that a treatment plant does not meet requirements of the SDWA, the public must be notified. There are three different tiers of notification with tier I being the worst of violations and tier III being the least. The EPA provides very specific language for public notifications in the event of a violation. Violating a SDWA compliance is bad enough, but failing to report violations brings even stiffer penalties and fines. In 2014 in Flint Michigan 15 people were criminally charged due to their negligence in the water treatment profession. It all started when the city of Flint changed their source water without properly testing. Officials knew the water was not safe to drink and numerous violations had been made. The public was not properly informed of these violations which resulted in 10 deaths and 77 others becoming severely ill. It is something that is rarely discussed because people in industrialized countries never really worry about the quality of their drinking water. The most important thing you can do as an operator is say something if there appears to be a problem with the quality of the drinking water. Otherwise, you may end up in jail. Notification options include radio or television announcements, newspapers, hand delivery, posting in public places, loudspeakers, texting, and reverse 911. The notification will vary based on the severity of the violation. Violations Tier I • Any positive fecal coliform positive test and failure to sample after an initial positive test • Nitrate or Nitrite violation • Chlorine Dioxide Maximum residual disinfection limit • Exceed treatment plants allowable turbidity level. Can be a tier II if the primacy agency does not elevate violation. • Waterborne emergency or outbreak of waterborne illness Tier II • MCL, MRDL and, Treatment Technique (TT) violations if treatment plant does not perform corrective actions to fix issues in treatment plant or fails to inform public. • Water quality monitoring violation⁠—not taking required water quality samples. Can also be a tier III violation but can be elevated for gross negligence • Noncompliance of a variance or an exemption Tier III • Water testing and monitoring violation • Any time the treatment system is running under a variance or exception. Primacy agency may give a treatment plant a variance or exemption for a short period of time. The public notification is to inform the public that a water agency is not running in accordance with an approved treatment technique. It doesn’t mean the water is unsafe to drink, but the operating manuals are very specific. Water Quality monitoring Continuous monitoring of drinking water ensures quality; reliable drinking water is being delivered to the public. The number of samples taken, frequency of sampling, sampling location, testing procedures, and requirements for record-keeping are all specified by state and federal requirements. If sampling requirements are not met, it can lead to public notification. The tier violation is based on the contaminant and whether or not the contaminant causes acute health effects. The type of monitoring is based on the source of the water, the treatment technique, and the size of the system. Reporting and record keeping is based on the primacy agency’s regulations. The state regulations must meet federal requirements at a minimum but may be more stringent as is the case in California. Record Keeping Below is a list of records that must be kept and the amount of time the records must be retained on file. • Bacteriological and Turbidity⁠—5 years • Chemical analysis⁠—10 years • Corrective actions from violations⁠—3 years • Sanitary surveys⁠—10 years • Exemptions⁠—5 years after expiration Variances and Exemptions In the event a water system is unable to meet a MCL because of the source water, a primacy agency can grant a variance or exemption. The variance is only given when the agency has incorporated the best available technology and there is zero risk to public health. In the case of Flint Michigan, the new source water was not properly tested before it was used in the system. Flint Water plant was unable to properly treat the source water which had elevated levels of lead and the City was not using the best available technology. Even if the City of Flint would have applied for a variance or exemption, it would not have been granted because the lead levels in the water create a significant risk to public health. In future chapters of the text, we will examine regulations added to the SDWA. Several changes and enhancements have been made since the exception of the original legislation. We will discuss in greater detail the Total Coliform Rule, Surface Treatment Water Rule, Long Term 2 Enhanced Surface Water Treatment Rule, Lead and Copper Rule, Ground Water Rule, and Stage 1 &2 Disinfectant Bi-Product Rule. Volume Volume calculations will become very common for water treatment operators. Operators use volume calculations to solve math questions with circles, triangles, and rectangles. If you look around a water treatment facility, it is full of geometric shapes. Tanks can be cylindrical or rectangular in nature. Settling ponds may have a triangular nature to them. The basic volume questions will become more involved later on in the text as you may have to solve a volume question first, and then solve a flow-related question. Cylinder Volume = 0.785 × D2 × H Rectangle Volume = L × W × H Trapezoid Volume = × H × L Example \(1\) What is the volume of a cubed tank that is 10 feet high? (Remember cubes have the same unit of length on all three sides. This is the easiest problem to solve.) Volume = Length × Width × Height Volume (ft3) = 10ft × 10ft × 10ft Answer is 1,000 ft3 Example \(1\) What is the volume of a rectangular tank that is 20 ft. high, 10 ft wide, and 7ft in length? Volume= Length × Width × Height Volume= 7ft × 10ft × 20ft Answer is 1,400ft3 There are two different ways to solve cylindrical math problems. The easiest formula to use is volume= .785 d2 H. This formula is easiest because in water math we are generally looking at the diameter of a cylindrical shape and not the radius. The radius of a circle is half the diameter. It is a straight line measured from the center of the circle to the edge of the circle. The diameter is a straight line that passes through the center of the circle with endpoints on the circle. Example \(2\) What is the volume of a storage tank that measures 40 ft. in diameter and is 20 ft. deep? Volume= .785 × d2 × H Volume= .785× 40ft × 40ft × 20ft Answer is 25,120ft3 Often the water math word problems will require multiple steps to solve. Typically, we want to know how many gallons a given tank will hold. Once we find the volume of the tank in cubic feet, we will then convert the cubic feet into gallons. Example \(3\) Convert the answer from Example \(3\) into gallons. 25,120 ft³ x 17.48 gal x 1 ft³ = 187,898 gal x 1 Answer: 187,898 gallons Example \(4\) A rectangular water tank is full. The dimensions are 30ft high 12ft wide and a length of 10 ft. Convert to gallons. Volume= 10ft x 12ft x 30 ft Volume= 3,600ft3 3,600 ft³ x 17.48 gal x 1 ft³ = 26,928 gal x 1 Answer: 26,928 gallons Example \(5\) A cylindrical storage tank has a diameter of 50ft and a height of 30ft. The tank is half full. How many gallons are in the tank? Volume= .785 x 50ft x 50ft x 15ft Volume= 29,437.5 rounded to 29,438ft3 29,438 ft³ x 17.48 gal x 1 ft³ = 220,196 gal x 1 Answer: 220,196 gallons Chapter Review 1. The smallest part of an element is known as ___________. 1. Proton 2. Neutron 3. Atom 4. Nucleus 2. The atomic weight is comprised of ___________. 1. Neutrons and electrons 2. Protons and neutrons 3. Nucleus and neutrons 4. Atom and nucleus 3. An atom with a negative charge is known as ___________. 1. Proton 2. Neutron 3. Nucleus 4. Electron 4. What does the symbol mg/L stand for? 1. Micrograms per liter 2. Milligrams per/L 3. parts per million 4. Both 2 and 3 5. What does the acronym MCL stand for? 1. Minimum contaminant level 2. Micron contaminant level 3. Maximum contaminant Level 4. Milligrams counted last 6. How long do sanitary surveys have to be retained for records? 1. 3 years 2. 5 years 3. 7 years 4. 10 years 7. The most severe water system violation that requires the fastest public notification is ___________. 1. Tier I 2. Tier II 3. Tier III 4. Tier IV 8. The primacy agency may grant a variance or exemption as long as ___________. 1. The agency is using the Best Available Technology 2. There is no threat to public health 3. There is never a scenario for a variance or exemption 4. Both 1 and 2 9. A public water system that serves at least 25 people six months out of the year is known as ___________. 1. Nontransient noncommunity 2. Transient noncommunity 3. Community public water system 4. None of the above 10. Regulations based on the aesthetic quality of drinking water are known as ___________. 1. Primary Standards 2. Secondary Standards 3. Microbiological Standards 4. Radiological Standards 11. The lowest reportable limit for a water sample is ___________. 1. 0.5 mg/L 2. Zero 3. Public health goal 4. Detection Level for reporting 12. Primary Standards are based on ___________ 1. Color and Taste 2. Aesthetic quality 3. Public Health 4. Odor 13. A circular clearwell is 150 feet in diameter and 40 feet tall. The Clearwell has an overflow at 35 feet. What is the maximum amount of water the clearwell can hold in Million gallons rounded to the nearest hundredth? 1. MG 2. 4.62 MG 3. 18.50 MG 4. 7.50 MG 14. A sedimentation basin is 400 feet length, 50 feet in width, and 15 feet deep. What is the volume expressed in cubic feet? 1. 100,000 ft³ 2. 200,000 ft³ 3. 300,000 ft³ 4. 400,000 ft³ 15. A clearwell holds 314,000 ft³ of water. It is 100 ft in diameter. What is the height of the clearwell? 1. 25 ft 2. 30 ft 3. 35 ft 4. 40 ft

textbooks/workforce/Water_Systems_Technology/Water_151/1.02%3A_Water_Chemistry_and_Standards.txt

The most important job of a Water Treatment Operator is providing reliable and quality water to the public. This is accomplished through chemical deactivation or physical removal of disease-causing microorganisms in the water. Microorganisms are deactivated by the addition of a chemical such as Chlorine or Ozone while physical removal is accomplished with the use of a filtration system. Surface Water Treatment Rule The Surface Water Treatment Rule (SWTR) was created in 1990 to further protect the public from waterborne illness. The specific diseases the SWTR seeks to prevent are those caused by viruses, legionella, and Giardia lamblia. Disease-causing microorganisms are also known as pathogens. The microbes that cause most waterborne illnesses are found in most surface water in the United States. Every public agency that uses surface water as source water must adhere to the SWTR. Surface Water is defined as any open body of water that is susceptible to surface runoff. Rainfall and snowmelt that enter open bodies of water such as lakes, rivers, and man-made reservoirs are susceptible to contamination from sewage treatment plants and animal feces. At this time there are no simple inexpensive tests for viruses, legionella, and Giardia lamblia; therefore, other protective measures are used to test the source water and treated water. Water regulations provide detailed inactivation and removal regulations for Protozoa, also known as Giardia, and viruses. Bacteria fall somewhere in the middle of both microorganisms so there is no need to “regulate” them. Bacteria will be removed and/or deactivated within the parameters or regulations that are in place. Giardia and Cryptosporidium form hard cysts that are very difficult to deactivate chemically with Chlorine. They are larger than viruses so they or more easily removed through filtration. Newer technological advances such as ozone addition are excellent ways to deactivate Giardia. Treatment plants must use a combination of disinfectant (chemical deactivation) and filtration and must achieve 99.9% removal or inactivation of Giardia cysts and 99.99% of viruses. You might also see the percentages expressed as 3 Log and 4 Log. 99.9% will be expressed as 3 Log and 99.99% will be expressed as 4 Log. Treatment plants, which use filtration, achieve their removal factor by monitoring the combined filter effluent turbidity. Turbidity is the measurement of the cloudiness in water. The reason it is important to measure turbidity is because microorganisms can hide behind the very small particles and render treatment techniques ineffective. Turbidity readings are expressed as nephelometric turbidity units (NTU). Most surface source water will not meet standards that would enable a treatment plant to refrain from using approved filtration techniques. The approved treatment techniques currently used by water operators are conventional treatment, direct filtration, slow sand, diatomaceous earth, reverse osmosis, and alternate treatment technologies approved on a case by case basis by the primacy regulating board. Newer technologies such as membrane filtration and UV treatment are being employed by some water agencies. Table 3.1: Waterborne Pathogens Bacteria Viruses Protozoa • Campylobacter • Escherichia coli (E-coli) • Salmonella • Yersinia • Vibrio • Legionella • Aermmonas • Mycobacterium • Shigella • Pseudomonas • Hepatitis A • Reovirus • Calicivirus • Enterovirus • Coxsackievirus • Adenovirus • Echovirus • Poliovirus • Giardia Lamblia • Cryptosporidium • Entameoba • Microsporidium A continuous disinfectant residual must always be in the distribution system to prevent waterborne illness. A disinfectant residual of .2 mg/L must be present at all times in the distribution system, however, most water operators will maintain somewhere between 2.5 mg/L-3.0 mg/L. The CT calculation is used to make sure proper disinfectant levels are being used during the treatment and distribution process. The effectiveness of the treatment process is calculated with the CT formula and uses data such as disinfectant used, residual of disinfectant, length of time disinfectant is in contact with water, water temperature, and pH of the water. It is important to note that during the treatment process the goal is to disinfect the water (kill all pathogens) and not to sterilize (kill all organisms). The “C” is the concentration of disinfectant while the “T” is the amount of time the disinfectant is in contact with water. On days with higher effluent plant rates, an operator may need to raise chlorine doses as the disinfectant will be in contact with the water for less time. Conversely, if plant flow rates are lower, a lower chlorine dose can be used because the disinfectant is in contact with the water for a greater time. Case Study: Milwaukee April 1993 In April of 1993, the largest outbreak of Cryptosporidium on record occurred in Milwaukee, Wisconsin. Over 400,000 people reported illness and 100 people died. All of the people who died after drinking the tainted water had the AIDS virus. It can’t be for certain that the Cryptosporidium was the cause of each of their deaths, but as will be discussed later in this chapter, people with weakened immune systems are much more susceptible to death if they drink tainted water. The Milwaukee incident was the catalyst for enhancements to the SWTR. Since Cryptosporidium creates cysts and is not killed by chlorine, the “double barrier” treatment approach was created. Treatment plants were then required to monitor turbidity effluent levels and use alternative treatment techniques, such as ozone or ultraviolet light, that would deactivate the Cryptosporidium. An effective filtration plant using coagulation, flocculation, sedimentation, and filtration, should have been able to handle the outbreak, thus turbidity levels were not within standards. The source of the Cryptosporidium was believed to be a sewage spill that was very close to the intake of the Southern Milwaukee treatment plant where the outbreak occurred. Others believe that the operators of the treatment plant were using higher quantities of waste stream water in the treatment process. Recycling washed filter water is a common practice, but after this event, it was established that only 10% of the sourced raw water can come from the wastewater. The lesson everybody learned here is water quality is ever-changing and evolving. Mother Nature throws curveballs at us that change the quality of the source water. If something is wrong, it is your duty as an operator to say something. Regulations are all well and good but if they are not being followed, people can become very ill or possibly even die. Total Coliform Rule The total coliform rule was published in 1989 and was revised in 2014. It set up minimum requirements for the frequency and amount of coliform tests that would be taken by water agencies. As discussed earlier, the coliform bacteria exist in larger quantities than other bacteria. If there is a positive coliform test, there is a greater chance the treatment process is not functioning properly and there is an increased chance of pathogens in the water. Bacterial outbreaks in water cause gastroenteritis with the associated symptoms of nausea, diarrhea, vomiting, and cramps. Very young people, elderly, and people with weakened immune systems are at an even greater danger should there be waterborne illnesses in water. Each water agency is required to have an approved sampling site map approved by the primacy agency. The Total Coliform Rule goal is zero positive coliform samples. Water systems that take less than 40 samples per month are only allowed one positive sample while systems that take greater than 40 samples must not find positive results in more than 5% of the coliform samples taken. If a positive coliform sample is found, it is not necessarily an indicator of a problem. Human sampling error could be the culprit. Once a positive is found the coliform sample is retaken within 24 hours at the positive sampling site and two additional samples are taken, one upstream and one downstream of the initial positive site. If there is a second positive coliform result, the water is then tested for E-Coli. If E-Coli is present in the sample, it is an immediate public health risk and is deemed an acute MCL violation. This would be considered a Tier I violation and public notification would have to occur within 24 hours. Long-Term 1 Enhanced Surface Water Treatment Rule The Long-Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) applies to water systems that serve less than 10,000 people. Below is a list of requirements for water agencies that fall under this category: • Must achieve 99% or 2 log removal of Cryptosporidium • Most systems are required to meet turbidity standards of 0.5 NTU from 95% of combined filter effluent turbidity readings. Smaller systems will get 2 log removal credit of Giardia with a stricter .03 NTU combined filter effluent. • Monitoring of individual filter is required. Higher turbidity reading from individual filters will require corrective action. • Some states might require a disinfectant byproduct profile • Any change in primary disinfectant must be profiled and approved • All treated water clearwells must be covered and not open to atmosphere Long-Term 2 Enhanced Surface Water Treatment Rule The Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) covers all water systems which serve more than 10,000 customers. • This rule added enhancements to the SWTR. Water providers are required to test the source raw water for Cryptosporidium and E-coli for a 2 year period. This step was put in to ensure all treatment plant equipment was capable of properly deactivating and removing pathogens from water. • After testing, systems were given a bin number which determined how susceptible the system was to contamination. • If systems were susceptible, a time frame was given to correct deficiencies • Continuous monitoring of the distribution system influent and maintaining at least .02 mg/L chlorine residual is required Filter Back Wash Recycling Rule As noted in the Milwaukee case study, water systems are able to use recycled wastewater as a raw water source. Many treatment plants utilize waste ponds, waste lagoons, and waste basins to capture recycled wash water and water from drains throughout treatment plant. In order for plants to use the recycled water, plants must put the wastewater through the same treatment process as raw untreated water. The amount of water that can be returned is based on the plants size and maximum plant flows. Lead and Copper Rule The lead and copper rule differs from most other water guidelines because these two constituents are usually found in water after it has gone through the treatment cycle. Most raw water has very low levels of lead and copper. Lead and copper are found in drinking water after a chemical reaction takes place in distribution pipes. Water that is more acidic can erode lead and copper pipes causing them to leach into water. The use of lead pipes in drinking water systems was banned in 1986 and they can no longer be used. Lead is known to cause several health problems in fetuses and young children. It can cause developmental problems. Lead can also have effects on the kidney, brain, red blood cells, and is known to cause anemia. With optimal corrosion control, the ability of water to chemically react with lead and copper pipes is lowered. Many treatment plants add chemicals such as caustic soda to raise the pH of the water. Treated water with a pH around 8 will keep a thin layer of calcium on the inside of a distribution pipe which protects the pipe from corrosion. Corrosion control is tested by monitoring the conductivity, testing pH of water, water temperature, testing for calcium, testing for alkalinity, and testing for phosphate or silica corrosion inhibiter if used to control corrosion. The Lead and Copper rule also differs from other rules because it bases its parameters on action levels. If 10 percent of the customers’ water tests in the 90th percentile of the action level for lead and copper, then further preventative actions must be met. Most customers do not have to worry about this due to advances in corrosion control in the past few decades. Stage 1 and 2 Disinfectant Bi-Product Rule When natural organic matter mixes with chemical disinfectants, it is possible for disinfectant byproduct formation (DBP). Chemical disinfectants used in water treatment that form DBP’s are chlorine, chlorine dioxide, chloramines, and ozone. The Stage 1 disinfectant byproduct rule established MCL’s for trihalomethane (TTHM), haloacitic acid (HAA5), chlorite, and bromate. Compliance is set up on a running annual average for TTHM, HAA5, and Bromate and on a monthly average for chlorite. The rule also set up maximum disinfection levels for chlorine, chloramines, and chlorine dioxide. The Stage 2 disinfectant byproduct rule applies to all community and nontransient noncommunity water systems that add a chemical disinfectant or purchase treated water that has a chemical disinfectant. The purpose of the Stage 2 rule is to monitor local sampling of individual connections. Some parts of the water system have less movement, therefore they are more susceptible to DBP formation. The Stage 2 rule covers TTHM and HAA5 and has the same MCL as the Stage 1 rule. See the chart below: Disinfectant Residual MRDL* as mg/L Compliance Based On Chlorine 4.0 mg/L Running annual average RAA Chloramines 4.0 mg/L Running annual average RAA Chlorine Dioxide 0.8 mg/L Daily samples *Maximum residual disinfectant level Disinfection Byproduct Maximum Contaminant Level Compliance Based On Trihalomethane .080 mg/L (80 ppb) Running annual average Haloacetic acid .060 mg/L (60 ppb) Running annual average bromate .010 mg/L (10 ppb) Running annual average chlorite 1.0 mg/L (1 ppm) Monthly average *ppb- parts per billion ppm- parts per million Consumer Confidence Reports The public has a right to know what is in their drinking water. As you continue to read through the text you will notice that a lot of the terminology is quite a mouthful. In 1998 consumer confidence reports were made available to the public for transparency. Eight groups of information were added to the report: • System information including contact info • Different sources of water (i.e. lakes, wells, rivers) • Definitions non-water personnel can understand including MCL’s, MCLG’s and treatment techniques • Any detected contaminants in the system along with a listing of the possible health effects if limits and goals are not met • Non-regulated contaminants found • List of violations if they occurred • Variances and exemptions • Educational tools for contaminants and affected populations The internet has made it possible for water treatment facilities to post information monthly on company websites; however, a consumer confidence report will be mailed/electronically delivered to its customers on a yearly basis. Flow Rate Calculation The flow rate calculation will be one of the most frequently used in water math. This calculation tells us a lot about what is going on in our water system. Common flow rates you will see are Gallons per Minute (GPM), Cubic Feet Per Second (CFS), Million Gallons a Day (MGD), and Acre Feet per Year (AFY). Water operators use flow rates for different purposes. If you were running a small treatment plant, you might use GPM or CFS in your day to day operations but when looking at water produced throughout the entire month or year, calculating in Acre Feet may be more appropriate. Like any algebraic formula, there will be an unknown factor you are solving for. In the case of a flow question, there will be 3 values, two known and one unknown. Flow Rate Equation Flow Rate = Volume ÷ Time The algebraic “Wheel” is a very effective way to solve many water math problems. Those students with more “mechanical” minds may find this way of solving math problems easier. Below is an example of how to solve a flow rate equation with both methods. Example 1 In 4 hours, a water tank's volume increases by 30,000 gallons. What was the flow rate of the water entering the tank? Express in gallons per minute. Flow Rate = Volume/Time Flow Rate = 30,000 gallons/4 hours 7,500 gallons/1 hour 7,500 gallons/1 hour = 1 hour/60 min = 125 gallons/minute We can also use the Flow Rate calculation to solve for volume or time. Example 2 - Solve for Time How long will it take to drain a 100,000-gallon storage tank where the water is exiting at 2,500 Gallons per minute? Time = 100,000 gal/2,500 GPM = 40 minutes Always put the unknown in the left part of the formula so your factors cancel out properly. Example 3 - Solve for Volume Your water tank pump is set to run for 90 minutes. Your pump output is 3,000 GPM. How many gallons of water will enter the tank? Volume = 3,000 GPM x 90 min Volume = 270,000 gallons Example 4 A water tank’s full capacity is 500,000 gallons. The operator will bring the tank down to half full in an 8-hour period. What is the flow rate of the water exiting the tank? (Note: The state gets very creative with their test questions. Remember to read the question multiple times before solving it. Don’t be the test taker that uses 500,000 gallons in the equation instead of 250,000 gallons!) Flow Rate = 250,000 gallons/8 hours Flow Rate = 31,250 gallons/1 hour 31,250 gal/1 hour = 1 hour/60 min = 520.83 GPM Chapter Review 1. A disease-causing microorganism: 1. Pathogen 2. Colilert 3. Pathological 4. Turbidity 2. According to the Surface Water Treatment Rule, what is the combined inactivation and removal for Giardia? 1. 1.0 Logs 2. 2.0 Logs 3. 3.0 Logs 4. 4.0 Logs 3. What is the equivalency expressed as a percentage for the SWTR inactivation and removal of viruses? 1. 99.9% 2. 99.99% 3. 99.0% 4. 99.999% 4. A water agency that takes more than 40 coliform samples must fall under what percentile? 1. 10% 2. 7% 3. 5% 4. No positive samples allowable 5. The multiple barrier treatment approach includes ___________. 1. Sterilization and filtration 2. Disinfection and filtration 3. Disinfection and sterilization 4. Infection and filtration 6. The maximum disinfectant residual allowed for chlorine in a water system is ___________. 1. .02 mg/L 2. 2.0 mg/L 3. 3.0 mg/L 4. 4.0 mg/L 7. How do water agencies monitor the effectiveness of their filtration process? 1. Alkalinity 2. Conductivity 3. Turbidity 4. pH 8. What is the disinfectant byproduct caused by ozonation? 1. Trihalomethanes 2. Bromate 3. Chlorite 4. No DBP formation 9. Haloacitic Acids are also known as ___________. 1. TTHM 2. HOCL 3. Chlorite 4. HAA5 10. What is the MCL for trihalomethanes? 1. .10 mg/L 2. .06 mg/L 3. .08 mg/L 4. .12 mg/L 11. What is the MCL for Haloacitic Acids? 1. 100 ppb 2. 60 ppb 3. 80 ppb 4. 120 ppb 12. What is the MCL for bromate? 1. .010 mg/L 2. .020 mg/L 3. .030 mg/L 4. .040 mg/L 13. A treatment plant operator must fill a clearwell with 10,000 ft3 of water in 90 minutes. What is the rate of flow expressed in GPM? 1. 111 GPM 2. 831 GPM 3. 181 GPM 4. 900 GPM 14. A water tank has a capacity of 6MG. It is currently half full. It will take 6 hours to fill. What is the flow rate of the pump? 1. 3,333 GPM 2. 6,333 GPM 3. 8,333 GPM 4. 16,666 GPM 15. A clearwell with a capacity of 2.5 MG is being filled after a maintenance period. The flow rate is 2,500 GPM. The operator begins filling at 7 AM. At what time will the clearwell be full? 1. 10:00 PM 2. 10:40 PM 3. 11:00 PM 4. 11:40 PM

textbooks/workforce/Water_Systems_Technology/Water_151/1.03%3A_Microorganisms.txt

Learning Objectives After reading this chapter you should be able to identify and explain the following: • Coagulant types • Coagulation chemistry • Mixing systems for both coagulation and flocculation • Flocculation process theory • Pounds formula One of the most important steps in the water treatment process is the removal of suspended solids. The two-part process in water treatment involves chemical deactivation and physical removal of pathogenic organisms. The physical removal of pathogens is accomplished in several steps. The first two steps include the processes of coagulation and flocculation. In this process, colloidal particles are destabilized to gather all the suspended material together. They can also be referred to as nonstable solids. This process increases particle sizes which assists in removal during the filter process. The larger floc particles will be removed during the sedimentation and filtration process. Coagulation occurs very quickly in the rapid mix or flash mix process. The flash mix process only lasts several seconds as the coagulant rapidly mixes and reacts with the raw untreated water. The floc will gain in size during the second step of flocculation. Filtration cannot occur without proper coagulation and flocculation. Coagulant Types In general, two types of coagulants are used during coagulation. A primary coagulant and a coagulant aid will be used during the rapid mix process. The colloidal surfaces are negative thus positively charged metal salts are used as primary coagulants. The coagulant dissolves in water and ionizes. To ionize is when a molecule loses or gains an electron to form an ion. The three most common coagulants used in water treatment are Aluminum Sulfate (Alum), Ferric Sulfate, and Ferric Chloride. The most commonly used primary coagulant in water treatment is Alum because of its wide availability and affordability. Synthetic polymers are often used as a coagulant and filter aid but have also been used as a primary coagulant. Operators use different charged groups of polymers known as cationic (positive), anionic (negative), and nonionic (without ionizable groups). Coagulation aids assist in the building of settable floc. Important things to consider when choosing a polymer: • Overdosing a polymer can decrease the efficiency of the coagulation process and cause filter binding and increased headloss in filters • Not all supply water is created equal. Every single water source has a different chemistry and jar tests must be performed to see what polymer works best with the specific source water. • There is no widespread standard for choosing a polymer. Different states have chemical approval standards that must be met. • The addition of chlorine can effect polymer effectiveness • As with any chemical, there is a dosage limit Chemistry Like many processes in water treatment, the theory of coagulation is very complex. As an operator, you should have a basic understanding of the chemistry involved in each process. The coagulant added to the water will react with the alkalinity in the water to form insoluble floc. Insoluble is something that will not dissolve. If the floc is not formed properly, then operators cannot effectively remove pathogens from the treated water. Alkalinity is not the same as pH. This gets very confusing as “alkaline water” has become a more widely popularized marketing term. Alkalinity is the water’s ability to neutralize an acid based on its makeup of carbonate, bicarbonate, or hydroxide. The measure of alkalinity is the amount of acid that would have to be added to water to lower the pH to 4.5 and there is where the confusion arises. Coagulation is most effective in the pH range of 5-7 because of the waters ability to react with alkalinity. In this range, the water tends to buffer or stay in the same pH range and will allow the complete mixing of coagulant chemicals. If the raw water has a low pH, agents such as soda ash can be added to increase the pH. Proper water quality tests must be performed by operators to promote the proper addition of coagulant chemicals. Underdosing coagulants will cause problems with floc formation while overdosing coagulants can cause clogging during the filter process. Clogged filters lead to head loss problems in the filters and increased filter washing. Mixing As noted earlier the coagulation process is completed within a matter of seconds. Mixing can be achieved by utilizing hydraulic mixers, mechanical mixing, diffusers, or pumped blenders. Hydraulic mixers use flow to achieve mixing. This kind of mixing requires enough flow to create a disturbance in the water to achieve proper mixing. Mechanical mixers require the greatest amount of energy because they require an electrical source to achieve mixing. Diffusers apply uniform flow during the coagulation process but may require many adjustments after flow changes. Finally, pumps can be used to push coagulant into water flow. Mixing can occur in a basin, channel, or pipeline. Flocculation Flocculation is the slow mixing process that causes smaller particles to merge into larger particles that settle more easily. The particles are then more easily removed in the sedimentation and filtration process. The process of flocculation is achieved by controlling the rate of impacts between particles as they gain size. Floc size can range between 0.1 mm-3 mm. The size of the floc produced depends on which type of treatment process is utilized at a specific plant. It is important that floc has good size but also density so the floc will not shear during the sedimentation and filtration process. This process is much longer than coagulation lasting roughly 15-45 minutes. Shown Above: The flash mix portion is also known as coagulation. The chemicals are added together and the process occurs within seconds. After flash mix, the water heads to the flocculation basins to allow floc particles to gather in size. Mechanical flocculators can be installed both horizontally and vertically. The horizontal type utilizes paddle-style mixers while the vertical style mixers can include paddle, turbine, and propeller style mixers. The shape and size of a flocculation basin is determined by the type of mixing used and the adjacent structures such as the sedimentation basins. Flocculation basins are usually split into 3 compartments. The speed of the mixing is decreased in each compartment to prevent the particles from breaking apart as they become larger. If the particles break apart during flocculation, the particles will place a heavier burden on the filters during the filtration process causing lower filter run times. This phenomenon will be discussed in further detail in Chapter 6. Monitoring and Process Control The coagulation and flocculation process requires a great amount of attention to detail along the way. An operator cannot just set a dose and “hope” everything works out. Water quality can change frequently and operators must ensure they are on top of changing conditions. One way an operator can achieve this is through jar testing. This is a laboratory procedure that finds the best coagulant dose based on water quality conditions. The efficiency of water treatment plants is determined by the combined effluent turbidity reading. Individual filter efficiency is also closely monitored. This will be discussed at length in the filtration chapter of the text, but it’s important to have a basic grasp of that concept at this point in the treatment process. Water treatment is a lengthy process. What’s occurring right now can have grave impacts down the line in the treatment process. Because of this consideration, jar testing and plant monitoring is all the more critical. Jar testing and laboratory grab sampling ensure the water which is theoretically being treated now, will be safe when entering the distribution system hours from now. During abnormal conditions, it is important for operators to take notes and inform senior operators and/or a supervisor. Record keeping is important because operators can go back to notes used from previous experiences. For example, a large rain event has changed the influent turbidity entering the treatment plant. A similar event happened three years prior and the influent turbidity is very similar to the ones operators are seeing currently. Wouldn’t it be nice to have a record of what the operators did three years ago? Hopefully, the operations staff from three years ago noted changes in coagulant dose, mixing speeds, chlorine demand, and other significant plant changes. Enhanced Coagulation The enhanced coagulation process is used to remove natural organic matter by adjusting the pH and coagulant dose to remove the greatest amount of suspended matter during the treatment process. The addition of acid is used to achieve the proper pH unlike sweep treatment were the operator overdoses the coagulant to achieve the correct pH range. Enhanced coagulation occurs at a lower pH. and accordingly will see improvements in treatment such as: • Humic and fulvic molecules separate better with lower pH. Humic and fulvic acids are organic acids commonly found in raw water sources • Less coagulant is required for treatment • Flocculation improves at a lower pH • Sulfuric Acid addition before coagulant is added preconditions organic matter The Pounds Formula (Chemical Dosage Problems) One of the most important calculations an operator will use is the “Pounds Formula.” The pounds formula can be used to solve water math problems including milligrams per liter to pounds per day, feed rate, chlorine dosage, percent strength, and dilution calculations. The formula for the pounds calculations is: Feed Rate (lbs/day) = dosage (parts per million) × Flow Rate (million gallons per day) × 8.34 lbs/gal Below is the pounds formula expressed in a mechanical wheel. The mechanical wheel can be used to solve a chemical dosage problem by plugging in the given information and then multiplying or dividing as indicated to determine the solution. For example, a treatment plant will produce 2 MG a day. The chlorine dose is 3.0 mg/L. How many pounds of chlorine will the operator use? Feed Rate = 3.0 × 2 × 8.34 Feed Rate = 50 lbs/day It is important to note that when using the pounds formula, the water production is always expressed in MGD. For example, a problem may ask what the chlorine production is for a water treatment plant that produces 1,000,000 gallons a day. This is the easiest expression because 1,000,000 ÷ 1,000,000 = 1. EX: A water treatment operator must super chlorinate a 650,000-gallon tank at 50 ppm. How much chlorine must the operator add? 50 × .65 × 8.34 = 271 pounds * You must divide 650,000 by one million to get .65 to solve the equation. Round to the nearest tenth or hundredth place to get the most accurate answer. Remember you must show all work during exams to get credit but the format is still multiple choice so be careful when rounding. Practice Pounds Formula Problems Example \(1\) The dry alum dosage rate is 15 mg/L. The daily flow rate of a treatment plant is 5 MG. How many pounds of dry alum per day is required? Solution Feed Rate= 15 mg/L × 5 MGD × 8.34 lbs/gal Feed Rate = 625.5 lbs/Day * This sample problem is pretty simple. Plug the numbers into the equation and multiply to get your answer. Example \(2\) A treatment plant uses 300 lbs of alum a day. The plant output is 2,500,000 gallons a day. What is the dose? Solution Step 1: 2,500,000 ÷ 1,000,000 = 2.5 MGD Dose = 300 lbs/day/(2.5 × 8.34) Dose = 250/20.85 Dose = 12 mg/L Example \(3\) How many pounds of 65% available chlorine must an operator add to a treatment plant with a dose of 3.0 mg/L and a plant output of 5 MGD? Solution * Start the equation as you normally would. Since you are adding a solution of chlorine that is not 100 percent an extra step is needed to solve the problem. Remember, if the chlorine solution is not 100 percent available chlorine you are going to need more to dose properly! Feed Rate = 3.0 × 5 × 8.34 = 125 lbs/day Next, you will need to make an adjustment based on chlorine strength. (.65)(x lbs/day) = 125 lbs/day x = 125.65 x = 192 lbs/Day Note: If the number is smaller than the original number, you multiplied instead of dividing. You will always need more chemical if it’s not 100% strength. Example \(4\) A water tank that is 30 ft high and 100 f in diameter must be dosed at 50 ppm for disinfection. How many pounds of 65% calcium hypochlorite must be added to dose the tank? Solution 0.785 × 100ft × 100ft × 30ft × 7.48 Gal/ft3 = 1,761,540 gallons 1,761,540 gallons/1,000,000 = 1.76MGD Feed Rate = 50 × 1.76 × 8.34 = 733.92 pounds/day (.65)(x) = 734 x = 734/.65 x = 1129 lbs Chapter Review 1. The optimal coagulant dose is determined by a ___________. 1. Chlorine test 2. Flocculation test 3. Jar test 4. Coagulation test 2. The most common primary coagulant is ___________. 1. Alum 2. Cationic polymer 3. Fluoride 4. Anionic polymer 3. Bacteria and viruses belong to a particle size known as ___________. 1. Suspended 2. Dissolved 3. Strained 4. Colloidal 4. The purpose of coagulation is to ___________. 1. Increase filter run times 2. Increase sludge 3. Increase particle size 4. Destabilize colloidal particles 5. The purpose of flocculation is to ___________. 1. Destabilize colloidal particles 2. Increase particle size 3. Decrease sludge 4. Decrease filter run times 6. Primary coagulant aids used in the treatment process are ___________. 1. Poly-aluminum chloride 2. Aluminum sulfate 3. Ferric chloride 4. All of the above 7. Flocculation is used to enhance ___________. 1. Number of particle collisions to increase floc 2. Charge neutralization 3. Dispersion of chemicals in water 4. Settling speed of floc 8. If there is a problem with floc formation, what would you consider changing? 1. Adjust coagulant dose 2. Stay the course 3. Adjust mixing intensity 4. Both 1 and 3 9. Which step in the treatment process is the shortest? 1. Filtration 2. Sedimentation 3. Flocculation 4. Coagulation 10. To lower the pH for enhanced coagulation the operator will add ___________. 1. Chlorine 2. Sulfuric acid 3. Lime 4. Caustic soda 11. The flocculation process lasts how long? 1. Seconds 2. 5-10 minutes 3. 15-45 minutes 4. Over an hour 12. The function of a flocculation basin is to ___________. 1. Settle colloidal particles 2. Destabilize colloidal particles 3. Mix chemicals 4. Allow suspended particles to grow 13. A treatment plant has a maximum output of 30 MGD and doses ferric chloride at 75 mg/L. How many pounds of Ferric Chloride does the plant use in a day? 1. 18,765 2. 17,765 3. 19,765 4. 16,765 14. A treatment plant uses 750 pounds of alum a day as it treats 15 MGD. What was the dose rate? 1. 4 mg/L 2. 5 mg/L 3. 6 mg/L 4. 7 mg/L 15. A treatment plant operates at 1,500 gallons a minute and uses 500 pounds of alum a day. What is the alum dose? 1. 18 mg/L 2. 28 mg/L 3. 8 mg/L 4. 38 mg/L

textbooks/workforce/Water_Systems_Technology/Water_151/1.04%3A_Coagulation_and_Flocculation.txt

Learning Objectives After this chapter you should be able to identify and explain: • Sedimentation process • Zones of sedimentation basin • Types of sedimentation basins • Velocity math problems • Detention time Sedimentation is the 3rd step in a conventional treatment process. It occurs after coagulation and flocculation and before filtration. Sedimentation removes suspended solids with the use of gravity by slowing the flow of water down to allow material to settle. The settleable solids fall to the bottom of the sedimentation basin reducing the load on the filtration process. A sedimentation basin acts like a lake in the sense that it allows particles to settle naturally. Deeper lakes have much higher quality water entering the treatment plant because the water is able to “settle” for a longer period of time. Treatment plants that use imported water from higher turbidity water sources may be required to use conventional treatment with sedimentation for efficient treatment. Factors affecting Sedimentation Several factors can affect the sedimentation process including physical and environmental conditions. Increased pretreatment may be necessary when adverse conditions are present. Factors that affect the sedimentation process include the shape and size of particles, the density of particles, water temperature, particle charge, dissolved substances in the water, environmental effects, and characteristics of the basin. As discussed in the previous chapter, smaller particles do not settle out easily and their size must be increased with coagulation and flocculation. The larger, denser particles created are called floc. Particles greater than .01 millimeters will settle in the sedimentation process. The shape of particles is also a consideration. Smoother particles with less jagged edges settle out quicker and easier. Temperature decreases will cause the settling rate to decrease. The settling rate or velocity decreases when the water temperature is colder. Chemical dosage rates need to be adjusted during colder periods of the year or lower flows are necessary in the flocculation basins. There are three types of currents, surface, density, and eddy, found in a sedimentation basin. Surface currents are caused by wind while density currents are caused by temperature differences and the concentration of solids. Eddy currents are caused by the influent and effluent flow of water in the sedimentation basin. Currents can be beneficial as they can help to promote the building of floc, but they can also cause uneven disbursements of solids throughout a sedimentation basin reducing the efficiency. Sedimentation Zones The four zones of a Sedimentation basin include: • Inlet Zone: Where the water enters seamlessly from the flocculation basin. Water is distributed evenly throughout the sedimentation basin to prevent short-circuiting. Short-circuiting occurs when water entering a treatment process tank or basin quickly moves from influent to effluent reducing the waters detention time in a given process. • Settling Zone: Is the largest part of a sedimentation basin. The water will stay here undisturbed for three or more hours while particles settle to the bottom. • Sludge Zone: Located at the bottom of the settling zone. It is where settled particles collect in the form of sludge. Velocities at the bottom of the sludge zone should be minimized to prevent solids from re-suspending. • Outlet Zone: The location where water seamlessly enters a channel or conduit. Launders also known as effluent troughs are used to collect the clarified or settled water. Types of Sedimentation Basins There are several different types of basin designs available for engineers and planners when building a water treatment facility. Rectangular basins are typically found at large scale water facilities because of their predictable treatment and high tolerance to turbidity, color, and algae. They are cost-efficient, require lower maintenance, and have less short-circuiting issues. The figure above representing the different zones of a sedimentation basin is an example of a rectangular sedimentation basin. Circular and square basins are used in areas where space is limited. They are sometimes called clarifiers and are subject to short-circuiting in the corners. The circular variety can also include up-flow clarifiers or solids contact clarifiers. In these types of clarifiers, the coagulation, flocculation, and sedimentation process all occur in the same basin or clarifier. Detention Time Detention time is the amount of time it takes water to travel through a tank or sedimentation basin. It is also referred to as retention time. You will hear some operators use the terms CT and contact time interchangeably but it is incorrect. The term CT will be discussed in greater detail in Chapter 7. Detention time can be used to solve equations for time and flow. Formulas for both types of equations are listed below: Detention Time (Hours) = Volume gal((24Hours/day))/Flow gal/day Flow, gal/day = Volume((24Hours/day))/Detention Time, Hours Reminder: Circular volume calculation (.785)(D ft)2(Depth ft) Rectangular Volume calculation: (L ft)(W ft)(D ft) Answers will be in cubic feet so it will be multiplied by 7.48 gal/ft3 to convert to gallons. Example \(1\) A rectangular sedimentation basin is 80 ft long by 25 ft wide and is 25 ft deep. The flow per day is 2.0 MGD. What is the detention time in hours? Solution Step One: calculate the volume of the basin (80 ft)(25 ft)(25 ft)(7.48 gal/cubic ft.) = 374,000 gallons Step two: DT = (374,000 gal x 24 Hours)/2,000,000 gal day Step Three: Detention Time = 4.5 hours *Note: more complicated problems will have you solve for hours and minutes. Keep this in mind for future math equations that ask for more information. .5 hours/1 x 60 min/1 Hour = 30 min Example \(2\) A circular basin is 100 ft in diameter. The basin is 25 ft deep and has a detention time of 4 hours. What is the flow per day? Solution Step one: Calculate volume .785(100 ft)2(25 ft)(7.48 gal/cubic ft.) = 1,467,950 gal Step Two: Flow = (1,467,950 gal x 24 Hours)/4 hours Step three: Answer is 8,807,700 divide by 1,000,000 to get 8.807 or 8.8 MGD Sludge Handling and Removal Sludge that collects at the bottom of a sedimentation basin must be removed from time to time for several reasons. As discussed earlier in the chapter, sludge can become re-suspended after settling creating greater load on the downstream filter. Next, sludge buildup can cause the water source to become septic. In this scenario, microbiological growth occurs when oxygen supplies are depleted. Septic conditions can cause taste and odor problems in treated water and also require more chlorine during the disinfection process. Finally, the more sludge that builds up leads to decreased detention time because there is less area for the water to travel and for solids to settle out. Larger plants will have to remove sludge at a greater rate and with the assistance of sludge removal equipment. Smaller plants may be able to remove sludge manually with portable sanitary pumps and squeegees and hoses to complete cleanup. The amount of time between cleanups can vary with the quality of the water source and the amount of water being treated. Consequently, shutdowns for sludge clean-up will vary dramatically from treatment plant to treatment plant. Sludge removal equipment includes mechanical rakes, drag-chain and flights, and traveling bridges. The chain and flight system is used in rectangular basins. A chain with scrappers attached moves across the bottom of the basin collecting sludge and moving it to a sump. This system works well but has several moving parts. Additionally, the basin must be dewatered to perform maintenance. The traveling bridge system is also used in a rectangular basin. It travels the entire length of the basin. A pump is attached to the bottom of the system and sludge is pumped to a trough just below the top of the sedimentation basin. The bridge system is easier to perform maintenance on because the parts can be removed from the basin; therefore, dewatering the entire basin isn’t required. Finally, mechanical rakes are used in rectangular or circular basins. A rake spans the entire length of the basin while spinning around the basin. Sludge is moved into a trough that can be pumped out or moved by gravity to a sludge collection tank. Review and Daily Operations of Sedimentation Basins In review, the purpose of sedimentation is to allow suspended solids to settle through the physical process of gravity. The flow of water is slowed down to allow settling to occur. During the process, sedimentation can remove 95% or more of the total solid material operators remove during the entire water treatment process. Water treatment plants with low turbidity or fewer than 10 turbidity units may find direct filtration or clarification to be a more cost-effective process. A reoccurring theme that should be noted throughout the text is the fact that all treatment facilities are different and the factor that dictates plant processes including facility building and day to day operation is the source water. The settling characteristics of suspended material dictates how well sedimentation performs. Flow rate through the sedimentation basin drives performance as well as the control of sludge. High flow rates cause solids to carry over, and could also impact the sludge at the bottom of the sedimentation basin. Operators must perform regular jar testing and laboratory testing as well as operate sedimentation basins based on the designed capacity of the basin to ensure optimal performance. Improper operation of sedimentation basins will lead to increased load on downstream filters resulting in early filter washes, increased disinfectant use, and possibly tier violations. Velocity Math The movement of water is obviously an important thing to know if you are a water treatment operator. You will need Algebra to solve the next set of water math problems which will have two known values and one unknown value. Flow rates can be used to determine dosage rates, to identify daily averages, to dewater pipelines, to fill pipelines, and for future planning of distribution and treatment equipment. To solve a flow problem, you need the diameter of the pipe and the velocity of the water (or liquid) in the pipe. Flow rate is expressed as Volume over Time. The equation will be: \[Q(Flow) = A(area) × V(velocity).\] A velocity problem occurs when the known value is the pipe diameter and flow rate of pipe. \[V(Velocity) = Q(Flow) ÷ A(Area). \] Finally, pipe size is used when known value is pipe flow rate and velocity. \[A(Area) = Q(Flow) ÷ V(Velocity).\] Proper use of dimensional analysis is critical when attempting to solve velocity equations. These types of problems often take multiple steps because answers need to be converted to the appropriate units based on the situation. Example \(3\) A pipeline is 18” in diameter and flowing at a velocity of 125 ft per minute. What is the flow in gallons per minute? Solution Step one: Convert pipeline diameter to feet: 18 inches/(12 inches/foot) = 1.5 ft Step Two: Q(Flow) = (.785)(1.5ft.)2(125 ft./min) Step Three: 221 ft3 per minute × 7.48 gal/ft3 = 1651 gpm Example \(4\) The flow of a pipe is 2,000 gallons per minute. The diameter of pipe is 24”. What is the velocity of the pipe in ft. per minute? Solution Step one: Convert units 2,000 gpm ÷ 7.48 gal./ft3 = 267 ft3/min. 24 inches ÷ 12 inches/ft = 2 feet Step two: V(velocity) = 267 ft3/min ÷ .785(2 ft.)2 Step three: V = 85 feet per minute Example \(5\) The velocity in a pipeline is 2 ft./sec. and the flow is 3,000 gpm. What is the diameter of the pipe in inches? Solution Step One: Convert flow to match units of measurement of velocity: 3,000 gal/min x 1 min/60 sec x 1 ft³/7.48 gal = 6.68 ft³/sec Step two: Area= 6.68 ft³/sec ÷ 2 ft/sec= 3.3 feet Step three: Convert feet to inches: 3.3 ft/1 × 12 inches/1 ft = 40 inches Chapter Review 1. The treatment process that involves coagulation, flocculation, sedimentation, and filtration is known as ___________. 1. Direct filtration 2. Slow sand filtration 3. Conventional treatment 4. Pressure filtration 2. Sedimentation produces waste known as ___________. 1. Backwash water 2. Sludge 3. Wastewater 4. Mud 3. What kind of process is the sedimentation step? 1. Physical 2. Chemical 3. Biological 4. Direct 4. The weirs at the effluent of a sedimentation basin are also called ___________. 1. Effluent weirs 2. Baffling 3. Launders 4. Spokes 5. Sedimentation is used in water treatment plants to ___________. 1. Settle pathogenic material 2. Destabilize particles 3. Disinfect water 4. Reduce loading on filters 6. Scouring is a term that describes conditions in a sedimentation tank which ___________. 1. Could impact the rest of the treatment process 2. Higher flow rates in the sludge zone 3. Re-suspends settle sludge 4. All of the above 7. The four zones in a Sedimentation basin include ___________. 1. Inlet, sedimentation, sludge, outlet 2. Inlet, filter, waste, outlet 3. Inlet, top, bottom, outlet 4. Surface, sedimentation, sludge, outlet 8. Short-circuiting in a sedimentation basin could be caused by ___________. 1. Surface wind 2. Ineffective weir placement, or weirs covered in algae 3. Poor baffling in sedimentation inlet zone 4. All of the above 9. How much solids should be removed during sedimentation? 1. 95% or more 2. 80-95% 3. 70-80% 4. 60-70% 10. The type of basin that includes coagulation and flocculation is ___________. 1. Rectangular 2. Triangular 3. Up-flow 4. None of the above

textbooks/workforce/Water_Systems_Technology/Water_151/1.05%3A_Sedimentation.txt

Learning Objectives After reading this chapter you should be able to identify and explain the following: • Treatment technologies • Filter media configurations and types • Filter operation and backwashing • Filtration math Filtration is the final and most important removal requirement required by the Surface Water Treatment Rule (SWTR). Water passes through material such as sand, gravel, and anthracite coal to remove floc and disease-causing microorganisms from the finished water. Physical removal of colloids is also achieved during sedimentation but this filtration is the final step. This is the process where suspended colloidal particles are removed from the water. Along with removing possible pathogenic material in the water, removal of turbidity is also achieved which could hide pathogenic organisms and add color to the finished water. The SWTR sets forth guidelines for all public water agencies that use surface water as a source. Surface water was covered in chapter #1 and is any water open to atmosphere that is susceptible to runoff. The minimum requirements for treatment is disinfection, but most water sources do not meet these very stringent guidelines. The effectiveness of filtration is based on several important factors. Proper filtration occurs based on incoming source water quality. For example a storm event near the source water could case higher incoming turbidity than the treatment plant is used to handling. Operational changes such as washing filters may be required. The physical and chemical characteristics of suspended material also come into play during treatment. Too much or too little chemical can lead to ineffective filtration. To follow the storm event example an operator may need to make changes to coagulant and polymer doses to account for increased turbidity and particulate entering the treatment plant. Finally the type of filtration used by a treatment facility is also very important. This decision is mostly out of operators hands as engineers and water quality experts will decide what the most effective treatment process is for the source water before building a treatment facility. Pictured below is a filter in normal operation. Treatment Technologies There are four approved treatment technologies in the United States. The most widely used treatment technologies include conventional treatment, direct filtration, diatomaceous earth treatment, and slow sand filtration. Below are the descriptions: Slow sand filtration facilities are becoming less common because of the large amount of time it takes to treat water and the large amount of space the facilities require. The filtration rates for slow sand filtration are .05 to .10 GPM/sq ft. Particles are adsorbed in a chemical layer known as a schmutzdeke. After an amount of time the biological layer must be manually removed by an operator or maintenance staff. The slow time and intensive labor make this treatment method the least ideal especially in areas with larger populations. Diatomaceous Earth filtration is accomplished through pressure filtration. It can also be referred to as precoat filtration. The filter media in this case is added as slurry to the treatment vessel. Within the vessel lays a pipe known as a septum. The slurry attaches itself to the septum and water is run through the vessel where pathogenic and suspended material is captured and strained out of the finished water. This kind of treatment process is very common for swimming pool treatment and beverage companies. This type of treatment method is generally not used by larger municipalities because of the large amount of disposal of sludge and the continuous purchasing of filter media. Gravity filtration is comprised of the final two approved Water Treatment technologies. Direct Filtration and conventional treatment are the most widely used treatment technologies in the United States. It is described as gravity filtration because the head pressure of the water forces the water to travel through filtered media in order to remove impurities from the drinking water. Direct Filtration differs from conventional treatment because the sedimentation process is skipped. Areas with source water higher in quality may opt for direct filtration to reduce costs and the amount of land space for sedimentation basins can be substantial. The average filtration rate for gravity filtration beds is 3.0 GPM/Sq. ft.- 6.0 GPM/ sq. ft. Alternative treatment plant methods can be approved on a case by case basis. Newer technologies such as membrane filtration and reverse osmosis have been utilized as the technology has improved and the costs associated with running these particular operations have decreased. Santa Clarita Valley (SCV) Water utilizes an alternative technology known as Upflow Clarification. SCV Water is able to use this technology because of the very low turbidity levels in the water provided by Castaic Lake. It is a more condensed version of conventional treatment and requires much less space due to the lack of sedimentation basins. Filter Media The type of media used in gravity filters is sand, anthracite coal and garnet. Garnet is a reddish colored mineral sand comprised of silicates (calcium, iron, manganese, and magnesium) and its density is greater than sand. Gravel is also used as a filter under layer below the filter media being used. It has to be heavier than the filter media so it is able to settle back under media after a completed filter wash cycle. When choosing filter media it is important to select media that has good hydraulic characteristics, is durable, has no impurities, is insoluble in water, will not dissolve, and does not react with constituents in the water supply. Media is classified by four parameters including its effective size, uniform efficiency, specific gravity, and the hardness of the media. The effective size is the sieve opening in the media that allows water to pass through while collecting the impurities in water. 90 percent of the particles must be bigger than the opening to filter out particles. When deciding what kind of media to choose for the filer it is important to consider the amount of time it takes for filter turbidity to break through. For example, you operate a treatment plant that requires individual filters say below 0.3 NTU (or Nephelometric Turbidity Units). Once an individual filter goes above this limit it must be washed. Secondly, head loss must be a consideration. Head loss occurs after material builds up over time during the filtration process. The head loss will cause longer filtration times and cause the filter level to rise. Once a filter reaches terminal head loss it must be back washed. The media is not always the cause of head loss and turbidity breakthrough. As discussed earlier, operators must ensure they are dosing chemicals properly as improper dosage can cause the aforementioned head loss and breakthrough. The uniform coefficient is the ratio between the different sizes of media comprised in the filter bed. The lower the uniform coefficient means the media is closer to the same size than if it were higher. The lower the efficiency number adds to the cost of the media. Filter production is the amount of water that a given filter can produce in a day. This flow is usually accounted for in Million Gallons per Day (MGD). Individual filtration rates are calculated by dividing the flow rate of the filter in gallons per minute by the surface area of a filter. The filtration rate for gravity filters can be between 2gpm-10gpm/ square foot. This topic will be discussed in more detail during the math portion of this chapter. Filter Media Types Gravel Image by Martin Olsson is licensed under CC BY-SA 3.0 Sand Image by Yug is in the public domain Garnet Image by Siim is licensed under CC BY-SA 4.0 Anthracite Image is in the public domain There are several different types of media configurations. Filtration plants can utilize monomedia, duel media, and multimedia configurations. A monomedia plant has only one type of media which could be coarse sand or anthracite coal. Single media filters may have to be washed more frequently as they tend to be smaller and have more frequent head loss issues. Dual media filters consist of a lower sand level and an upper anthracite layer with larger diameter pores that allow deeper solids penetration. Finally, multimedia filters are used in pressure vessel treatment applications. Multimedia filters have sand, anthracite, and an upper garnet layer. The drawback to pressure vessels is the inability to view filter media within the pressure vessel. Filter Operation and Backwashing Filters Throughout the chapter, the subject of “washing” has come up. Filter run times are dependent on three factors but first it is important to know how filter efficiency is measured. The efficiency of a filter is measured by the filter effluent turbidity. And the overall plant efficiency measures the combined effluent turbidity of all the filters. Improper coagulation and filtration could lead to turbidity spikes and in the worst-case scenario could lead to a public health crisis. Pictured below is a photo of a typical filter deck at a water treatment plant. The first factor that an operator uses to determine whether a filter wash is necessary is the individual filter turbidity. Each treatment plant will have its own operating conditions and permits to follow. If an individual filter fails to meet the turbidity goals or limits, the filter must be put in a backwash cycle. Filters that continue to have decreased run times may need a filter profile ran to figure out why the filters are not meeting standards. High head loss is the second factor that will lead to a filter wash. After the filter is used for a certain period of time it becomes clogged with the solids the filter is removing. This condition will also lead to increased turbidity as the solids that should be getting captured “breakthrough” the effluent into the treated water supply. Finally, a filter wash will be performed after a certain period of time no matter what the operating conditions are. This is the ideal scenario for washing a filter. The backwash procedure is the reverse flow of water through the filter. This process removes solids from the filter after breakthrough or the filter run time is hit. Operators must operate the backwash rates at an optimal range because inadequate rates will not properly remove the solids from the filter and excessive rates can cause mud balls and mounds to form within the filter. Washed water is able to be recycled by sending the waste stream to collection basins. The water can then be returned to the head works of the plant and be mixed with raw water to be treated again. The filter backwash rule limits the amount of water that can be returned into the head works of the plant at a given time. Returning too much recycled water could increase the chances of allowing microorganisms such as Cryptosporidium into the treatment plant. The Filter to the left is in the process of a filter back wash. The water is moving in the opposite direction and overflowing over the weir and heads to the waste basin where it is collected and eventually returned into the head works of the plant to be treated again. Operator Actions As a Water Treatment operator, you will be expected to have knowledge of how to properly use equipment related to filtration. While running a treatment plant you will routinely: • Monitor filter performance • Check turbidity levels with online analyzers and grab samples • Adjust chemical flow rates • Backwash filters • Visually inspect filters Filters run differently under changing water conditions. The plant will not always run the same as temperature differences and storm events will make operators examine important operational considerations from time to time. It is important to look at the weather and understand how it might affect the treatment plant. A severe rainstorm near your source water could increase turbidity levels coming into the plant. Under these conditions, operators may have to wash filters more frequently and make adjustments to chemical doses. There are other abnormal conditions to consider when monitoring filter performance. Monitor filter washes to look for mud balls, excessive boiling in certain spots, and media being displaced and sent to waste basins. These conditions would indicate that the backwash flow is too high. Also identify shorter filter run times, filters that may not be coming clean, and algae growth. These factors may be due to improper chemical dosing and a backwash flow that is too low. Filtration Math Filtration Rate Calculating the filtration rate of the filters in your plant is an important function. Operating plans and permits limit the amount of water a filter can produce so it is important to have an understanding of filter rates also known as loading rates. Filtration rates will also give an operator a basic understanding of the treatment plants daily average production. The filtration rate formula is a velocity equation. These formulas are easily confused with flow problems so make sure you pay attention to the units you add into the formula and pay attention to what the problem is asking. The formula for filtration rate is: Filtration Rate = Flow Rate ÷ Area Filtration rate equations will use GPM and the area of a given filter. The area of the filter is length x width. A problem may give you the depth of a filter to confuse you. Pay very close attention to the wording in the problem. Example 1 What is the filtration rate of a treatment plant that has 3 filters that are 20 ft. wide and 20 ft. in length in a plant that produces 1 MGD? Filtration Rate = (20 ft x 20 ft x 3) ÷ 1 MGD 1,000,000 gal/1 Day x 1 Day/24 hours x 24 hours/60 min = 694 GPM1 *Note: Quick shortcut for future equations, there are 1,440 minutes in a day. Filtration Rate = 1,200 ft2 ÷ 694 GPM Filtration Rate = 1.73 gpm/ft2 Backwash Rate As discussed in the chapter, after a filter reaches its capacity due to head loss, turbidity break through, or maximum amount of hours run, the filter must be washed. The filter wash cycle water velocity will be much greater than the amount of water that flows through the filter during normal operation. Many math equations will have the operator solve for rate of rise which is expressed as in/min. The backwash is the flow of water in the opposite direction where water is moving up instead of down. Example 2 The maximum backwash rate for a filter is 5,000 GPM. The filter is 20 ft. wide and 20 ft in length. What is the rate of rise in the filter? Rise Rate = Flow Rate ÷ Area Rise Rate = 5,000 GPM ÷ 400 ft2 Rise Rate = 12.5 GPM/ sq./ft 12.5 gal/min(ft)/1 x 12 inches/1 ft x 1 ft³/7.48 gal = 20 inches rise/min Percent Back Wash Water treatment plants are very efficient at recycling waste stream water. The water sent to waste basins and lagoons is able to be recycled but only a certain amount at a time. The percent backwash math problems compare the total plant production with the amount of finished water used to backwash a filter. Example 3 A treatment plant treats 2 MGD. It has 2 filters that are washed each day and each uses 10,000 gallons during the wash. What is the percent backwash water? 2 filters x 10,000 gallons = 20,000 gallons 20,000 gal/2,000,000 gal = 0.01 100 × 0.01 = 1% 1% of the water the plant uses is for backwash water. Chapter Review 1. Solids removed from a filter are most commonly removed by what method? 1. Adsorption 2. Straining 3. Deactivation 4. Flocculation 2. What is a typical filtration rate for slow sand filters? 1. 2.0-6.0 GPM/sq. ft 2. 6.0-10.0 GPM/sq. ft 3. 1.0-2.0 GPM/sq. ft 4. 0.5-0.10 GPM/sq. ft 3. In a typical conventional treatment plant, the finished water turbidity for an individual filter should be less than ___________. 1. 1.0 NTUs 2. 0.3 NTUs 3. 5.0 NTUs 4. 3.0 NTUs 4. A filter running under normal conditions will see head loss in a filter ___________. 1. Remain constant 2. Increase slowly 3. Rapidly increase 4. Decrease slowly 5. A filter must be washed if this condition is met: 1. Head loss 2. Turbidity breakthrough 3. Maximum filter run time 4. All of the above 6. Filter performance is measured by the removal of ___________. 1. Oxygen 2. Head loss 3. Turbidity 4. Chlorine 7. What is the biologically active layer of a slow sand filter called? 1. Mixed media 2. Duel media 3. Sludge layer 4. Schmutzdecke 8. The pressure drop in a filter is called ___________. 1. Turbidity breakthrough 2. Head Loss 3. Filtration 4. Backwash 9. What is the most common reason for putting a filter into the wash cycle? 1. Head loss 2. Filter run time 3. Turbidity breakthrough 4. Water level decrease 10. Formation of mud balls and excessive boiling during a wash is an indicator of ___________. 1. Proper backwash rate 2. Too low backwash rate 3. Excessive backwash rate 4. Improper chemical dose 11. Important processes which occur during filtration are ___________. 1. Sedimentation 2. Adsorption 3. Straining 4. All of the above 12. Typical filtration rates for a conventional treatment plant are ___________. 1. 0.2-0.6 GPM/sq.ft 2. 2.0-10.0 GPM/sq.ft 3. 10.0-20.0 GPM/sq.ft 4. 200-400 GPM/sq.ft 13. There are four filters at a water treatment plant. The filters measure 20 feet wide by 30 feet in length. What is the filtration rate if the plant processes 8.0 MGD? 1. 1.51 GPM/sq.ft 2. 2.31 GPM/sq.ft 3. 2.61 GPM/sq.ft 4. 2.91 GPM/sq.ft 14. A water treatment plant treats 6.0 MGD with four filters. The filters use 60,000 gallons per wash. What is the percent backwash at the plant? 1. 10% 2. 8% 3. 6% 4. 4% 15. A treatment plant filter washes at a rate of 10,000 GPM. The filter measures 18ft. wide by 24ft. long. What is the rate of rise expressed in inches per minute? 1. 17 inch/min 2. 27 inch/min 3. 37 inch/min 4. 47 inch/min

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Learning Objectives After reading this chapter you should be able to identify and explain the following: • Disinfection terminology • Regulations • Types of disinfectants used during water treatment The final step in the water treatment process before finished or treated water enters a clearwell for storage is the disinfection process. Disinfection is the process where chemical agents are added to a water source to kill or inactivate pathogenic microorganisms. Pathogenic microorganisms are disease-causing and must be eliminated from treated water. As population sizes increase and freshwater sources become scarcer, the ability to remove and deactivate microorganisms becomes increasingly important. Another factor to consider, especially in California, is stricter regulations due to advancements in technology and water quality testing. Disinfection Basics Treatment plant operators use the two-part process of removal and deactivation of microbiological constituents in water. Most of the pathogens water treatment professionals remove and deactivate from drinking water have adapted to living in the bodies of warm-blooded animals. Pathogens thrive and survive in those environments. Outside those environments, these pathogens can stay dormant until they are consumed. Even more frightening, some of the illnesses can cause death. In the United States, our water is generally safe to drink and we often take for granted that turning on a tap will produce a flow of potable water. Because of limitations in testing, it is difficult to indicate the presence of specific waterborne illnesses caused by virus, bacteria, and Giardia. Water professionals use tests such as the total coliform test to look for the likely presence of waterborne disease. The Surface Water Treatment Rule sets specific guidelines for removal and treatment to ensure the removal and inactivation of pathogenic organisms. Strict regulations set forth by the Safe Drinking Water Act were created to ensure the public’s drinking water was safe to consume. To ensure drinking water is safe for human consumption, 3 log removal and deactivation or 99.9% of Giardia lamblia is required. For viruses, 4 log or 99.99% removal and deactivation is required. Bacteria fall in the middle of viruses and Giardia so the government determined it was not necessary to have regulations specifically regulating their inactivation and removal. Below is a list of waterborne diseases and illnesses. Table 7.1: Waterborne Diseases and Illnesses Bacteria Internal Parasite from Protozoa Virus caused • Anthrax • Dysentery • Cholera • Gastroenteritis (Stomach Flu) • Leptospirosis • Paratyphoid • Salmonella • Shigellosis (Shigella) • Typhoid fever • Dysentery • Ascariasis (round worm) • Cryptosporidiosis from Cryptosporidium • Giardiasis from Giardia • Gastroenteritis • Heart anomalies • Hepatitis A • Meningitis • Poliomyelitis Purpose of Disinfection Operators disinfect water to destroy the harmful organisms listed in the above chart. Filtration is used to remove the organisms while disinfection kills them or deactivates them. Operators do not sterilize water because sterilization would kill everything in the water. The process of disinfection relies heavily on everything that occurs downstream in the treatment process. As water enters the treatment plant in the form of raw water, the chemistry of that water affects how well the specific disinfectant will work at each stage of the treatment process. What Affects Disinfection? There are several characteristics of water that can affect treatment. Water is more easily disinfected with higher temperatures. In lower temperatures, longer contact times may be required and larger amounts of chemical must be used. Higher turbidity rates will decrease disinfection as well. The chapters before have covered how critical it is to remove suspended material early and efficiently. Excess turbidity will require greater amounts of chemical to properly disinfect the water supply. Chemicals such as chlorine can interact with organic and inorganic matter. Chlorine's ability to interact with these constituents may reduce or eliminate the effectiveness of the disinfectants. Types of Disinfectants Physical Physical disinfection is not widely used to treat potable water at this time. Ultraviolet rays are starting to be used more consistently but chemical means of disinfection must still be used as ultraviolet disinfection does not carry a disinfectant residual. The process is very expensive and thus is not used by large scale treatment operations in the United States. Other means of physical disinfection include boiling and ultrasonic wave production. Agencies will call for boil water notifications during emergencies and when there is a waterborne illness outbreak but it is not used as a primary means to disinfect drinking water. Types of Disinfectants Chemical There are several chemical disinfectants available in drinking water applications. The most commonly used in the United States is Chlorine. The topic of Chlorine will be discussed in greater detail in the following chapter. The basics will be covered below as well as a background on the other chemicals available. The chemicals will be broken down into subcategories based on their practical usage in the United States. Rare • Iodine⁠—It is commonly used for emergency treatment in the form of droplets or tablets. It is not used by the water treatment industry because of its cost and the potential health hazards to pregnant women and possible thyroid issues, which can develop with frequent use. • Bromine⁠—It is not used by water treatment facilities as it is very corrosive and can cause severe skin burns. It is used more commonly as a disinfectant in swimming pools. When it reacts with choline (a common nutrient from plants and animals) in water, it can create disinfectant byproducts. It was used by the United States Navy for a time, but most systems have been removed because of bromine’s corrosiveness. • Sodium Hydroxide and Lime⁠—More frequently used to sterilize pipes. They are not used as an everyday disinfectant because of the bitter taste that is left behind after application. Sodium hydroxide and lime are more often used to increase the ph of the water in the distribution system after treatment with gas chlorine. More Common • Chlorine Dioxide⁠—Used as a water treatment disinfectant and oxidizer. It does not react with ammonia which is an issue with chlorine. Chlorine dioxide is used as a disinfectant but is also very effective at removing iron, manganese, taste, odor, and color from treated water. Cryptosporidium is resistant to chlorine but is not resistant to chlorine dioxide. Up to 70 percent of chlorine dioxide is converted to chlorite, which is a regulated disinfectant by-product so the dosage rates when using it as a disinfectant must be lower than 1.4 mg/L. Chlorine dioxide must also be made on site which necessitates higher operational and maintenance costs. • Ozone⁠—Ozone was first used in Europe in the early 1900’s. It is a strong disinfectant that also reduces taste and odor issues. The drawback of ozone is that it is very expensive to produce, has high electrical costs, has limited solubility, and does not leave a residual in the treated water because it is so reactive. If bromide is present in the water, ozone can react with it to form bromate, an undesirable DBP (this is an issue for SCV Water). Ozone is very efficient at disinfecting Cryptosporidium so it is generally used as a secondary disinfectant along with chlorine or chloramines. Most Common • Chlorine⁠—The most widely used disinfectant in the United States is free chlorine. Chlorine can be added as a gas in the form of chlorine gas, as a solid in the form of calcium hypochlorite, or as a liquid in the form of sodium hypochlorite. Most likely, you have a bottle of sodium hypochlorite in your house. We call it bleach. The use of free available chlorine has declined over the years because of the discovery of disinfectant by-products (DBPs). This topic will be discussed in further detail in the next chapter. • Chloramines⁠—The use of chloramines has become more common in recent years in order to reduce DBPs mainly trihalomethane (THM). Chloramines are also referred to as combined chlorine as it is the combination of chlorine and ammonia. Chloramines are also effective at eliminating taste and odor problems and the residual lasts longer in the distribution system. However, chloramine disinfection is not as strong as chlorine and the improper addition of ammonia can lead to excessive amounts of ammonia in the treated water which results in nitrification. Regulations The Safe Drinking Water Act (SDWA) is the basis of all drinking water regulations in the United States. It is the umbrella in which all new regulations and rules have subsequently been created and enacted. The SDWA regulates drinking water standards in the United States along with its territories. We take for granted all of the research and technology we have available that allows us to never really be concerned about the quality of our drinking water. The SDWA was passed in 1974 and set fourth standards to regulate public water sources. It was amended in 1986 to include some basic principle definitions: • Defined regulated contaminants and approved treatment techniques • Defined criteria for filtration of drinking water • Defined criteria for disinfecting surface and groundwater • Outlawed the use of lead material in drinking water facilities After a large public health crisis in Milwaukee, Wisconsin, provisions were made to support drinking water programs through operator training and certification programs. All entities serving water to the public were required to meet program standards with regards to training and certification. In 1999, the government allowed states to hold primacy over drinking water certification programs as long as federal minimums were met. States such as California often have stricter standards than the federal standards. Surface Water Treatment Rule The Surface Water Treatment Rule (SWTR) was enacted in 1990 and sought to prevent waterborne illness from surface water sources. Water systems with supplies from surface sources which are susceptible to carrying viruses, legionella, and Giardia lamblia, have to follow new requirements with regards to filtration and disinfection known as the multiple barrier approach. The rule also required that systems that used groundwater as a source for drinking water had to adhere to SWTR standards if their water source could come into contact with surface water sources. Water treatment plants would have to achieve removal and deactivation requirements through the combined efforts of filtration and disinfection. The removal and deactivation of 99.9% of Giardia or 3 Logs and the removal and deactivation of 99.99% of viruses or 4 Logs was the new standard set forth. This requirement is measured by monitoring combined effluent turbidities in the combined filters and meeting disinfection requirements through the CT calculation. The CT calculation will be covered in greater detail in the following chapter. Groundwater Rule The Groundwater Rule (GWR) was established in 2009 in response to the frequency of groundwater contamination from surface water runoff sources. The rule requires monitoring for systems that do not disinfect to make sure microbiological contamination is not occurring. If a groundwater supplier did use disinfection, they are to meet 99.99% virus inactivation much like groundwater sources. Total Coliform Rule The final rule which indirectly relates to water disinfection is the Total Coliform Rule (TCR) which was established in 1990. As stated several times within the text, it is nearly impossible and certainly too costly to test for every type of microbiological contaminant that could lead to a public health risk. Instead, the TCR uses a risk based process which tests for the “worst case scenario”. Coliforms grow in warm blooded animals just like viruses, bacteria, and Cryptosporidium. They pose no health risk to humans and they grow more abundantly than forms of microbiological agents that will do us harm. If coliforms are present in the water supply, there is a chance for a public health concern. In the event of a positive coliform test, the downstream and upstream sampling sites as well as the site where the positive sampling occurred will be retested. System maps and sampling plans are a requirement of the TCR. The amount of samples the water supplier takes is based on the population served. Systems which collect less than 40 samples a month can only have one positive sample before notifying the public of a Maximum Contaminant Level (MCL) violation. Systems that collect more than 40 samples a month must not have positives in more than 5% of their coliform samples. If you work at a water supplier that takes 50 samples a month and had 3 positive samples are you in compliance with the TCR? \begin{align*} 47 ÷ 50 &= 0.94 \times 100 \[4pt] &= 94\% \end{align*} So 6% of the samples were positive so you would not be in compliance) or... \begin{align*} \dfrac{3}{50} &= 0.06 \times 100 \[4pt] &= 6\% \end{align*} Therefore, 3 positives are 6% of the total samples. Disinfectant By-Product Rule The disinfectant by-product rule (DBPR) was put in place to protect the public from cancer causing risks associated with disinfectants reacting with organic and inorganic matter in treated drinking water. Disinfectant by-products such as trihalomethanes are classified as volatile organic compounds. The Stage 1 DBPR established maximum contaminant levels for several DBPs including: • Trihalomethane (TTHMs) - 80 ug/L or 80 ppb • Haloacitic Acid (HAA5) - 60 ug/L or 60 ppb • Bromate - 10 ug/L or 10 ppb • Chlorite - 1.0 ppm While it is all together possible to remove DBPs from treated water with activated carbon, it is a very expensive treatment process and not cost effective for large treatment operations. Other forms of disinfection are possible but will also cause DBP formation. Chlorite formation is associated with chlorine dioxide treatment, while bromate is associated with ozone treatment. The issue of DBP formation becomes even more problematic as chlorite and bromate are often found naturally in source water. The stage II DBP Rule enhanced regulations on DBP formation by targeting water sources that are more vulnerable to DBP formation and the rule also requires monitoring for HAA5s and THMs. The number of samples taken and the number of sampling sites is based on the size of the population served by the water agency. The use of chloraminated water is being used more commonly to combat DBP formation but using chloramines instead of other disinfectants has other risks associated with its use which will be covered in greater detail in the next chapter. This is the link to the quick reference guide from the EPA with information on the Stage I and Stage II DBP rule. Chapter Review 1. What is residual chlorine? 1. Chlorine used to disinfect 2. The amount of chlorine after the demand has been satisfied 3. The amount of chlorine added before disinfection 4. Film left on DPD kit to measure residual 2. When Chlorine reacts with natural organic matter in water it can create ___________. 1. Disinfectant by-products 2. Coliform bacteria 3. Chloroform 4. Calcium 3. What are trihalomenthanes classified as? 1. Salts 2. Inorganic compounds 3. Volatile organic compounds 4. Radio 4. What disinfectant is used for emergency purposes and not utilized in the water treatment industry? 1. Chlorine 2. Iodine 3. Ozone 4. Chlorine dioxide 5. What is the disinfectant with the least killing power but that has the longest lasting residual? 1. Chlorine 2. Ozone 3. Chlorine dioxide 4. Chloramines 6. The active ingredient in household bleach is ___________. 1. Calcium hypochlorite 2. Calcium hydroxide 3. Sodium hypochlorite 4. Sodium hydroxide 7. Cryptosporidium is not resistant to this chemical: 1. Ozone 2. Chlorine dioxide 3. Chlorine 4. Both 1 and 2 8. The Removal and inactivation requirement for Giardia is? 1. 99.9% 2. 99.99% 3. 99.00% 4. 90% 9. If a coliform test is positive, how many repeat samples are required at a minimum? 1. None 2. 1 3. 3 4. Depends on the severity of the positive sample 10. Your water system takes 75 coliform tests per month. This month there were 6 positive samples. What is the percentage of samples which tested positive? Did your system violate regulations? 1. 3% Yes 2. 5 % No 3. 8 % Yes 4. 10 % No

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Learning Objectives After reading this chapter you should be able to identify and explain the following concepts related to chlorine: • Chlorine terminology • Chlorine chemistry • Chlorine safety • Advanced chlorine calculations As discussed in previous chapters, chlorine is the chemical most frequently used in the water treatment industry for disinfection purposes to meet the standards of the surface water treatment rule. Chlorine is used in several different forms and can be fed into the system in a variety of different methods. It is a very dangerous chemical, so proper safety and handling procedures must always be followed. In addition to being used as a disinfectant, Chlorine may also be used as a controlling agent for the removal of algae, for taste, and for odor. Other beneficial applications of Chlorine include disinfecting new water facility infrastructure such as pipes and tanks and the oxidation of iron, manganese, and hydrogen sulfide. Chlorine Terminology Chlorine is available in three forms: gaseous, solid, and liquid. • Gaseous(chlorine)⁠—$\ce{Cl2}$ • Solid (Calcium hypochlorite)⁠—$\ce{Ca(OCl)2}$ • Liquid (Sodium Hypochlorite)⁠—$\ce{NaOCl}$ It is not explicitly known how chlorine disinfection works. One explanation is that chlorine attacks a bacterial cell and destroys it. The other theory suggests that chlorine deactivates enzymes within the cell enabling the microorganisms to use their food supply. Adding chlorine to a water supply causes chemical reactions to take place between the water and the organic and inorganic molecules within the water. After chlorine is done combing with organic and inorganic material in the water, the demand has been satisfied. The dose of chlorine minus the demand is the residual. The reason chlorine is used in the United States over other disinfecting chemicals is Chlorine’s ability to leave a lasting residual within the framework of the water distribution system. This residual continues to fight potential disease-causing microorganisms after treatment has concluded. Assume that you are working as an operator at a water treatment plant. Your chief operator would like to maintain a residual of 2.0 mg/L of chlorine residual in the distribution system. The demand is 1.5 mg/L. What is the dose you must add to achieve a residual of 2.0 mg/L? \begin{align*} \text{Dose} &= \text{Demand} + \text{Residual} \[4pt] &= 2.0\,\text{mg/L} + 1.5 \, \text{mg/L} \[4pt] &= 3.5\,\text{mg/L}\end{align*} Therefore, you would need to maintain an average of a 3.5 mg/L dose of Chlorine to achieve the residual requested by your chief operator. Other Chlorine terminology includes Free Chlorine, Combined Chlorine, and Total Chlorine. It is important to understand these terms before taking a deeper dive into the chemistry of chloramination. The term Free or Available Chlorine refers to the amount of Chlorine that is “free” or “available” in the system to kill or deactivate pathogenic organisms. Combined Chlorine is chlorine that has combined with other molecules and Total Chlorine is the combination of Free or Available Chlorine and Combined Chlorine. Although Combined Chlorine lasts longer in the distribution system, it is a far less effective disinfectant. It is also important to note, not all Chlorine has the same strength. This will be covered more thoroughly later in the chemistry and math portion of the chapter. Chlorine Content As mentioned earlier in the chapter, Chlorine is available in different states of matter. The amount of chlorine used to dose water in a treatment plant is determined by the compound used. Below is a chart illustrating the different compounds of chlorine. The percent column indicates the percentage of Chlorine in the compound. For example, Chlorine Gas is pure Chlorine and yields the highest available percentage at 100%. Table 8.1: Chlorine Content in Different Chlorine Compounds Chlorine Compound Percent Amount needed to attain 1lb Chlorine Gas 100 1 lb Calcium Hypochlorite 65 1.54 lbs Sodium Hypochlorite 15 .8 gallons Sodium Hypochlorite 12.5 (most common) 1.0 gallons Sodium Hypochlorite 5 (household bleach) 2.4 gallons In the math section of this chapter, the impact of the Chlorine percentage will become evident. It is important to read the question and understand what concentration of chlorine is being added to the treatment plant. The third column in the table provides the lb or gallon needed of the specific compound to provide 1 lb of chlorine. For example, if your plant requires a weight or quantity of 100 lbs of chlorine and you use gas chlorine, then you will be adding 100 lbs. of Chlorine Gas. If you are using calcium hypochlorite, you will need to calculate the number of pounds required. From the table, Calcium Hypochlorite is 65% Chlorine. To determine the total number of pounds of Calcium Hypochlorite needed to provide 1 lb of Chlorine, divide the dose required by the percent chlorine. $100 ÷ 0.65 = 153.8\, lbs$ Therefore, you will need to use 153.8 lbs of Calcium Hypochlorite to obtain a 100 lbs dose of chlorine. Factors of Chlorine Success Several factors during the water treatment process will impact the effectiveness of the Chlorine. The five factors that affect chlorine treatment are: • The concentration of chlorine, more specifically the dose • The amount of time chlorine is in contact with the water • The temperature of the source water • The pH of the source water • The constituents in the source water The amount of time the chlorine is in contact with the water determines the effectiveness of the chlorine disinfection. The CT (Concentration multiplied by Contact Time) formula is used to calculate the time chlorine is in contact with the water. C is the concentration of chlorine residual, therefore CT is expressed as (mg/L-min). If water is leaving a drinking water storage tank, also referred to as a clearwell, at a rapid rate, then the chlorine concentration will have to be increased. If the concentration of chlorine is decreased, then the water will have to stay in contact with the disinfectant for a longer period of time. Combined Chlorine treatment associated with monochloramine disinfection will require longer holding periods due to its decreased effectiveness. Temperature affects chlorine treatment in a variety of ways. Chlorine is more effective at killing pathogens at higher temperatures but at lower temperatures, the chlorine residual will last longer. Practically speaking, chlorine disinfection works better in warmer temperatures as more credit is given with the CT calculation. The pH level of the water is also a significant factor when treating with chlorine. The ratio of HOCl to OCl- is affected based on the pH. HOCl will remain the dominant disinfectant in water with a lower pH while OCl- will remain in higher quantities in water with a higher pH. In the disinfection process, chlorine not only reacts with organisms that are to be killed, but it also reacts with the turbidity in the water and other substances such as ammonia. Reducing turbidity in treated water through coagulation, sedimentation, and filtration ensures disinfection will be more effective. The maximum and minimum chlorine residual in the distribution system is 4.0 mg/L and 0.2 mg/L respectively. However, corrective measures must be taken when you see the residual in the distribution system dramatically decreasing. You would never want to see the minimum chlorine residual of 0.2 in the distribution system. Chlorine Chemistry Below is the reaction that occurs between water and free available chlorine: $\ce{Cl2 \,(Chlorine) + H2O \,(Water) → HOCl \,(hypochlorous acid) + HCl\, (hydrochloric acid)}$ Hypochlorous acid is more effective of the two forms of available chlorine. First, it is important to understand how chlorine demand works. We can do this by examining the effects of adding free available chlorine to distilled water. If we were to dose distilled water with 1.0 mg/L of free available chlorine, the residual would be 1.0 mg/L chlorine because there is nothing in distilled water that will react with the chlorine other than the water itself. Distilled water lacks impurities. It is clear that the raw source water is filled with impurities. Chlorine will have many constituents to react with during the treatment process. When the Chlorine reacts with the water and the impurities, five different types of chlorine residuals result. The following chart illustrates the effectiveness of each type of residual. The most effective is hypochlorous acid (HOCl) so the effectiveness of the remaining four types of residuals are in comparison to HOCl. Table 8.2: Effectiveness of Different Residuals Residual Abbreviation Effectiveness Hypochlorous Acid HOCl 1 Hypochlorite Ion OCl- 1% Trichloramine NCl3 More info later in the chapter Dichloramine NHCl2 1.25 % Monochloramine NH2Cl .667% As the chart shows, dichloramines are a “more effective” disinfectant than monochloramines but their use may cause taste and odor problems. The effectiveness of trichloramines has not been extensively researched and as with dichloramines, a pungent taste and odor problem occurs with its use. Thus the water industry only uses monochloramines as a disinfectant. Below are the chemical formulas which illustrate when hypochlorous acid disassociates and becomes a weaker disinfectant. $\ce{HOCl \,(Hypochlorous acid) -> H^{+} (Hydrogen ion) + OCl^{-} (Hypochlorite ion)}$ $\ce{HCl\, (Hypochloric acid) -> H^{+} (Hydrogen ion) + Cl^{-} (Chlorine ion)}$ Chlorine Handling and Safety As a Treatment operator, you will come in contact with many dangerous chemicals used to treat water. One chemical that is widely used in the water treatment industry is chlorine. As discussed earlier in the chapter chlorine comes in three different states: gas, powder, and liquid. All three types of chlorine have risks associated with the handling and storage of the chemical. It is important that proper safety procedures are followed at all times. Chlorine Gas Chlorine gas is 2.5 times heavier than air. The odor is pungent and the color is greenish-yellow. Gas chlorine is only visible in very high concentrations and you don’t ever want to see it. Chlorine gas is irritating to eyes, nasal passages, and the respiratory system. It is a very dangerous substance and concentrations as low as 100 parts per million can kill a person. Chlorine gas is available in three different types of containers: 150-pound containers, 1-ton containers, and, for very large plant operations, in railroad containers. A majority of treatment operations will use chlorine tanks. The amount of chlorine used in a given day will determine which type of chlorine container your plant will use. When delivered to a treatment plant, the “150-pound” chlorine gas cylinder container weighs roughly 250-280 pounds. A chlorine cylinder consists of the cylinder body, neck ring, valve, and protective hood. Cylinders are transported around the facility with the use of a dolly or hand truck. The use of a safety chain or strap is mandatory at all times. Cylinders should never be rolled because it could lead to employee injury or the shearing off of the valve. The maximum daily withdrawal rate for a chlorine cylinder is 40 pounds. Chlorine “ton” containers hold 2000 pounds of chlorine and usually weigh around 3700 pounds when filled with chlorine. The Containers are shipped and stored horizontally. The edge of the chlorine container has a ring, which enables cranes and hoists to move them from the truck to the storage or withdrawal area. Containers are stored on trunnions that allow operators to rotate containers with the use of a special tool. Each container has two valves, one at the top and one at the bottom. The top valve allows the chlorine to be withdrawn as a gas while the bottom valve allows chlorine to be withdrawn as a liquid. When putting containers in storage, they should placed such that the liquid chlorine is allowed to settle in the bottom of the container. The maximum daily withdrawal rate for a 1-ton tank is 400 pounds. Gas chlorine cylinders and 1-ton containers use similar methods to feed chlorine into the water. Feeding systems include a scale, valves and piping, a chlorinator, and an injector or diffuser. The weighing scales are used to keep track of how much chlorine has been used or is left in the cylinder or tank. Record keeping is critical for all chemical use. Monitoring and reviewing the recorded data can help identify problems with the chlorine system and manage costs by reducing chemical waste. Pictured above is a standard chlorine scale and trunnion system. The trunnion acts as a form of storage while also keeping an accurate measure of the amount of chemical left in the tanks. In California, the tanks must also be secured with straps due to earthquakes. Valves and piping are just as important in the chlorine system as they are in the water system. Each chlorine tank or cylinder is equipped with valves which allow or prohibit the flow of the chlorine during the transfer and storage of the product. In an emergency, the valves can also be used to quickly shutoff the flow of chlorine. Large scale systems will include piping manifolds that allow for the transfer of chlorine from multiple tanks. The associated feed system will include valves and piping to provide chlorine to different feed points in the system. The chlorinator is the piece of equipment that feeds the chlorine directly into the system. Chlorine is dispersed evenly into the system based on a dosage set point using vacuum and pressure regulators. For safety, a vacuum must be maintained in the line. The vacuum ensures that the chlorine is always being pulled into the chlorine feed system. Most modern systems have emergency shutoff valves which prevent the flow of chlorine if a leak is detected. Chlorine systems will also include alarms, leak detectors, and repair kits. Other safety measures are also required when working around chlorine gas. For example, when switching tanks, the operator should be wearing a self-contained breathing apparatus (SCBA). As noted earlier, a 0.1 part per million dose of chlorine gas can be immediately fatal. Hypochlorination Gaseous chlorine is the strongest and least expensive form of chlorine even with the required use of bases such as caustic soda to increase the pH of the finished water. However, due to safety concerns associated with the use and transportation of gaseous chlorine, Hypochlorination is becoming more common in water treatment. When building or redesigning a treatment plant, an analysis of the costs and benefits of each type of chlorine will determine which type the facility will use. The two types of hypochlorite used are calcium and sodium. Calcium hypochlorite is a whiteish-yellow dry chemical. It contains 65% available chlorine. Since it is highly reactive with organic compounds, special requirements must be used when storing it. Additionally, it is flammable if enough heat and oxygen are added. Calcium hypochlorite should always be added to water and not the opposite. Generally, Calcium hypochlorite is primarily used for disinfecting new and repaired water mains and storage tanks. It is not used for the day-to-day treatment of finished water. Sodium hypochlorite is a clear to yellowish liquid available in a variety of different concentrations. Household sodium hypochlorite, known as bleach, is available in a 5% solution. Treatment plant operations will use an industrial-strength concentration of 12.5% available chlorine. Sodium hypochlorite does not have special storage requirements, but it is a strong base at 9-11 on the pH scale so it is highly corrosive. Additionally, the chemical loses its effectiveness over time in storage. Stored for a month, the chemical can lose 2% to 4% of its chlorine content. Direct exposure to sun and/or heat will further the loss of available chlorine. Therefore, it is recommended that sodium hypochlorite be stored no more than two weeks (in the event the treatment plant is offline) in a temperature-controlled room to prevent excessive strength loss. Cylinder Tank Safety and Connecting When attaching a chlorine regulator to a tank to go into service, safety precautions must be used. Any time you are dealing with gas chlorine the operator must wear a respirator, but a SCBA is recommended. The SCBA has a 30-60 minute supply of oxygen. SCBA’s operate under positive pressure, so in the event of a leak, no chlorine gas will be able to enter your mask, assuming a proper seal of the mask has been established. Along with a respirator or SCBA the operator should wear gloves and a long sleeve shirt when changing cylinders or tanks. A new lead washer should be used every time a new tank is put into service. Inspect the lead washer for any deformities, cracks, or bends. Washers must be thrown out after one use. When the chlorine tank valve is first opened, rapidly open and close the valve. Use an ammonia solution near the valve and tubing to check for leaks. The ammonia solution used is commercial Be ammonia. If chlorine is present, you will see a white cloud. In the event of a white cloud, a leak is present. The operator will have to remove the regulator from the valve and use a new lead washer. Lastly, be vigilant. Changing chlorine cylinders will become routine as it is something you will have to do often if your facility uses chlorine gas. Chlorine gas is a highly dangerous chemical that must be respected. Forgetting how dangerous it is, could lead to serious harm or death for you or your co-workers. Chapter Review 1. The form of Chlorine which is 100% available chlorine is? 1. Sodium hypochlorite 2. Calcium hypochlorite 3. Calcium hydroxide 4. Gaseous chlorine 2. What is the minimum amount of chlorine residual required in the distribution system? 1. There is no minimum 2. mg/L 3. 0.2 mg/L 4. mg/L 3. What is the approximate pH range of sodium hypochlorite? 1. 4-5 2. 6-7 3. 9-11 4. 12-14 4. What is the typical concentration of sodium hypochlorite utilized by water treatment professionals? 1. 5% 2. 65% 3. 100% 4. 12.5% 5. Chlorine demand refers to ___________. 1. Chlorine in the system for a given time 2. The difference between chlorine applied and chlorine residual—usually caused by inorganics, organics, bacteria, algae, ammonia, etc. 3. Chlorine needed to produce a higher pH 4. None of the above 6. What is the most effective chlorine disinfectant? 1. Dichloramine 2. Trichloramine 3. Hypochlorite ion 4. Hypochlorous acid 7. What can form when chlorine reacts with natural organic matter in source water? 1. Disinfectant by-products 2. Sulfur 3. Algae 4. Coliform bacteria 8. What is the maximum withdrawal rate per day for a 150-pound chlorine cylinder? 1. There is no maximum 2. 20 pounds 3. 40 pounds 4. 50 pounds 9. What kind of solution is used to check for a gas chlorine leak? 1. Sodium hydroxide 2. Ozone 3. Ammonia 4. Calcium hypochlorite 10. Chlorine is ___________. 1. Heavier than air 2. Lighter than air 3. Brown in color 4. Not harmful to your health 11. Chlorine demand may vary due to ___________. 1. Chlorine demand always stays the same 2. Temperature 3. pH 4. Both 2 and 3 12. What effect does high turbidity have on disinfection? 1. It can increase chlorine demand 2. It has no effect 3. It gives the water a milky appearance that will clear out after some time 4. You must increase the temperature of the water

textbooks/workforce/Water_Systems_Technology/Water_151/1.08%3A_Chlorine.txt

Learning Objectives After reading this chapter you should be able to explain and identify the following topics: • Why chloramine treatment has been employed, (hint) DBP formation • The use of ammonia in water treatment • Breakpoint chlorination • Nitrification The water treatment profession is constantly evolving and continuously in motion. Advancements in science and lab procedures help water professionals find constituents in drinking water that can be harmful to human beings. We take for granted the fact that clean drinking water will flow when we turn on the tap. Currently, chlorine is the best disinfectant available. However, the use of chlorine causes any number of disinfectant by-products (DBPs). Many of the DBPs have not been researched and are not regularly monitored. As screening methods improve, it is likely that more of the possible DBPs will be regulated in the future. Trihalomethanes (THMs) are a DBP of chlorine disinfection and are classified as volatile organic chemicals. Rising THM levels in raw water are increasing the use of chloramine as the preferred disinfectant. In this chapter, we will discuss chloramine disinfection and the associated challenges that come with its implementation. Nothing is easy in water treatment. Why Use Chloramines? As discussed, chlorine has been used with great effectiveness in water treatment for many years in the United States. However recently, many water agencies have been switching to Chloramine treatment. Now here is the twist; they have done it because they must, not because they necessarily want to. When natural organic matter reacts with chlorine, it can result in the formation of DBPs, specifically trihalomethanes (THM) and haloacetic acids (HAA5). It is believed that long term exposure to these DBPs should be avoided as it may lead to cancer. Because of the implementation of the Stage 2 DBP Rule in 2012, many water agencies could no longer meet the regulatory limits established, if they continued using chlorine as a primary disinfectant. To continue using chlorine alone, enhanced coagulation would have to be used but its effectiveness is limited. Carbon or GAC absorption is also a solution but it is very expensive, and thus not employed by larger water treatment facilities. The other option is to limit contact with the water and chlorine, but this is limited by the chlorine demand. The last and most effective option is to use chloramines. Chloramine treatment is also effective in limiting taste and odor problems in finished water. When free chlorine reacts with phenol it can cause taste and odor issues. Chloramine disinfection is not as strong a disinfectant as free chlorine, chlorine dioxide, or ozone, but it does leave the longest-lasting residual in finished water. Because of chloramines weaker disinfecting power, it is often added just before the treated water enters the clearwell for storage. If implementing this method, the operator must ensure the THM levels are low enough as not to violate any regulations. Determining the most effective way to treat drinking water while remaining in compliance is a complex and difficult task. Chloramine Chemistry Chlorine reacts with a number of substances in water including dissolved organic matter, particulate organic matter, iron, nitrite, sulfide, and ammonia. It reacts by taking away an electron from them. Ammonia in the water supply is undesirable as it strips away the Chlorine residual which then requires the need to use more Chlorine. What makes chloramine treatment so effective is chlorine’s quick formation with ammonia (NH3). (Ammonia is a compound of Nitrogen and Hydrogen.) \[\ce{Cl2 + NH3 → NH2Cl + HCl}\] Note that monochloramine is expressed as \(\ce{NH2Cl.}\) The unit weight of Chlorine is 70 and the unit weight of Nitrogen is 14. When chloramine treatment is employed, the ratio of chlorine to ammonia will always be 5:1 because 5 mg/L of chlorine will always combine with 1.0 mg/L of ammonia. (70 ÷ 14 = 5) You will often hear monochloramines referred to as combined chlorine due to this reaction. Below is a list of terms dealing with Chloramine disinfection: • Free Chlorine: Cl2 (Free chlorine can refer to gaseous, sodium hypochlorite, or calcium hypochlorite.) If using hypochlorite, remember you must dose the water to achieve 100 percent free chlorine. • Monochloramine: NH2Cl or combined chlorine. Chloramine with the least taste and odor problems. • Free Ammonia: NH3 Ammonia is measured as nitrogen • Chlorine: Ammonia ratio: Total chlorine to total ammonia nitrogen. You will always target a 5:1 ratio to avoid excess free chlorine or free nitrogen in the water supply. Breakpoint Chlorination The breakpoint chlorination curve is the visual representation of chlorine’s ability to react with a variety of compounds to form a combined chlorine residual or to completely react with compounds to form a free chlorine residual. When using free available chlorine as a disinfectant we want to stay out of the combined curve. Some water agencies buy imported water that has a combined residual. To treat the water more effectively or eliminate the possibility of nitrification, some of these agencies add chlorine to “break” over to a free chlorine residual. We will discuss Nitrification in greater detail later in this chapter. A common problem that operators run into when using combined chlorine is “breaking over” to free chlorine by misdiagnosing problems on the treatment plant. For example, an operator is looking at a Supervisory Control And Data Acquisition (SCADA) screen. (SCADA is the computer system that monitors and controls the plant.) For the sake of ease, we will call this operator #1. He or she notices the chlorine effluent residual is beginning to drop. Operator #1 was not aware that the previous operator (Operator #2) had raised the chlorine dose a few hours before. With the added chlorine dose, the chlorine residual was “lowering” as it got closer to breaking over. If operator #1 panics and raises the chlorine dose again the combined chlorine residual will lower even further. The important thing to remember is there are many things to look at if your chlorine dose is lowering. It may very well be an issue with your chlorine feed, but there are many other options to consider. If you check your chlorine feed system and everything is functioning normally, you may have an issue with the ammonia feed system. Many modern water treatment facilities have calculations built into the SCADA system that make chloramine dosing easier. Make sure to go to the screen with the chlorine: ammonia: ratio to make sure that it is set up correctly. Lastly, free chlorine is always the preferred disinfectant as it is 25 times stronger a disinfectant than chloramines. However, chloramines last much longer in the distribution system. There are several factors that may lead to a lowered chlorine residual. An increase in biological growth is possible, but you should see other signs such as an increase in turbidity. The most common problem in chloramine treatment with a decreasing chlorine residual is operator error or an issue with the water treatment process. Nitrification Nitrification is a process in which bacteria reduces ammonia and organic nitrogen in treated water into nitrate and then nitrite. This condition usually occurs during the summer months when water temperatures are higher. It can also occur during the improper turnover of reservoirs, when there are high levels of ammonia, and in dark environments, a typical condition for most water reservoirs. This condition is one of the drawbacks of chloramine treatment. Nitrate and Nitrite are inorganic chemicals regulated by primary drinking water standards. The MCL (Maximum Contaminate Level) for Nitrate is 10 ppm and the MCL for Nitrite is 1 ppm. High nitrate and nitrite levels in drinking water can lead to methemoglobinemia also known as “blue baby syndrome.” This condition affects infants under six months old that consume water contaminated with nitrates and nitrites. The infant's blood is not able to carry enough oxygen to blood cells and tissue within their body. The condition of Nitrification is a reoccurring cycle that can lead to the total loss of chloramine residual in the distribution system and in water storage tanks. If this was to occur, all the water in the system would have to be dumped and it would be a total loss. As an operator, this is something that you never want to happen. Not only would it be a loss of money for your company, but it could lead to an outbreak of methemoglobinemia. The cycle is below: Chloramine decay → Release of ammonia→ oxidation of ammonia to nitrite from oxidizing bacteria → Biomass increase → (back to chloramine decay until there is a possibility of total loss of residual) Some early indicators of nitrification: • Lowering chloramine residual • Increase in bacterial heterotrophic plate counts • Excess ammonia in the treated water • Total coliform positive samples In summation, nitrification can cause a variety of problems and violations within the water system. What can we as operators do to minimize any chance of nitrification from occurring? There are a few steps every operator can take to avoid nitrification. First, you want to minimize free ammonia in treated water. Sampling and equipment around the treatment plant will help operators determine if there is too much free ammonia in the treated water. Second, operators should always maintain a good chlorine residual. Isn’t that the name of the game? Sure, but it is easier said than done in some cases. Many water treatment companies will lower their target chlorine residual in the summer to save on costs because the disinfectant works more efficiently during the summer months. It is a good practice in theory, but not necessarily the best practice if you are working with chloramines and trying to combat nitrification. Reducing water age is the third step operators can use to combat nitrification. This can be done by cycling reservoirs during the summer months and taking reservoirs out of service during the winter when water demands are lower. Distribution operators are continually balancing maintaining a good amount of water for fire flow and demand, but also cycling reservoirs to fight nitrification. A good practice is to take all the reservoirs in the distribution system and divide it into thirds. At any given point during the day 1/3 of the reservoirs are full, 1/3 are in the middle range, and 1/3 are in the lower range. This allows operators to cycle water while also keeping water in the system. The last step is to keep the water system clean. This can be accomplished by flushing dead ends to prevent lower chlorine residuals at the end of the distribution system. Boosting chlorine by adding it directly to a reservoir is also an option but not always the best practice. The problem with this method is it could lead to short circuiting. Chlorine must mix adequately to be effective. Mixing can be accomplished by adding mechanical mixers in the reservoir to keep water moving and prevent short circuiting. Chlorine can also be added to the inlet of the reservoir so the water pressure acts as a mixer. Hydrant flushing is a method that can be used to get rid of stagnant water at the ends of a distribution system. Stagnant water can lead to lower chlorine residuals and possible nitrification. In summary, the use of chloramines as a disinfectant is being employed by many water agencies in the United States to prevent DBP formation. It is not the most ideal disinfectant available, but it does have some advantages. Chloramine disinfection limits DBP formation and has a longer-lasting disinfectant residual. This can be useful for larger systems where water must travel great distances to get to storage. The drawbacks include the difficulty in effectively managing the breakpoint chlorination curve and managing nitrification. Because of advancements in water quality testing and more stringent regulations with DBPs, chloramine treatment is and will continue to be a more popular option in water treatment. Chapter Review 1. What is the target chlorine to ammonia ratio? 1. 2:1 2. 3:1 3. 4:1 4. 5:1 2. What is the MCL for nitrates? 1. 1 ppm 2. 10 ppm 3. 5 ppm 4. None of the above 3. What is the atomic weight of chlorine? 1. 70 2. 14 3. 65 4. 20 4. What disinfectant has the longest-lasting residual? 1. Ozone 2. Chlorine 3. Chloramine 4. Chlorine dioxide 5. What are some of the early indicators of nitrification? 1. Lowering chlorine residual 2. Excess ammonia in treated water 3. Raise in bacterial heterotrophic plate counts 4. All of the above 6. What are THMs classified as? 1. Turbidity 2. Radiological 3. Volatile organic chemicals 4. Salts 7. What method can operators employ to combat nitrification? 1. Lower residual chlorine target 2. Keep reservoir levels static 3. Minimize free ammonia in treated water 4. Increase water age 8. How many times stronger is Chlorine compared to monochloramine? 1. 25 times 2. 20 times 3. 15 times 4. 5 times

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Learning Objectives • After reading this chapter you should be able to identify and explain the following topics related to treatment plant laboratories: • Equipment in the laboratory • Laboratory safety • Water quality testing • Contaminants tested in the laboratory and throughout the treatment plant Working in a laboratory is probably something you never thought about when deciding to explore the career of water treatment. However, working in a laboratory is one of the more critical aspects of the profession. Many larger agencies have a dedicated staff of laboratory personnel that handles a lot of the day to day water quality analysis, but operators still play a key role. After all, the operator is the person in charge of running the plant, monitoring chemical feeds, and performing routine plant checks to ensure the system is running smoothly. A laboratory scientist can run all the tests in the world, but since they are not the ones running the plant, a lower chlorine residual may not stand out to them. The responsibility falls squarely on the shoulders of the operator. State regulations require operators to take grab samples throughout the day to ensure monitoring equipment throughout the plant is running correctly. This topic is discussed at length in the water quality course. This is meant to be a brief overview if you have not taken that course yet. Laboratory Instruments and Equipment Throughout the lab, you will find a variety of beakers, flasks, dilution bottles, and graduated cylinders. A lot of these instruments look the same or similar but they all have a unique job and purpose. Beakers range in size from 25 to 4000 mL. They are used to mix samples during chemical analysis. A burette is a long skinny tube-like glass receptacle used to measure and disperse liquid. Flasks have a narrow neck and are round at the bottom. Each kind of flask serves a different purpose, but they all look very similar. Graduated cylinders are tall and cylindrical and range in size from 10 mL-4000 mL. They are used to measure liquid, but not with accuracy. For example, they can be used during a chlorine test to gather a general volume of water. If you need an exact amount, it should be measured with a pipette or other similar and accurate liquid measuring device. The pipette measures a liquid with 100 percent accuracy. You will find sample bottles in any laboratory. The bottles can be made of plastic or glass. They are used to store water for future lab tests and not used for measuring liquid. Sample bottles are used to collect bacteriological samples and for organic chemical analysis. The bacteriological bottle is one of the most important sample bottles you find in a lab. They are made of plastic and are 100 mL. Water treatment operators must take bacteriological samples per the Total Coliform Rule. These tests will be performed daily in the lab and throughout the distribution system based on your coliform sampling plan. Other Items Found In the Laboratory Incubators will be found in every lab at a water treatment plant. They are used to hold a temperature for bacteriological cultures. There are two types of incubators used, dry heat and water baths. Common uses for incubators include coliform testing, multiple tube testing, and heterotrophic plate counts. Ovens are other pieces of equipment found in the lab. Autoclaves, for example, are used to sterilize glassware items but can also be used to sterilize material that has been contaminated from perhaps a positive coliform test. Refrigerators are used to store samples for future testing and to store chemicals used for water quality testing. These refrigerators are for work use only and should not be used to store food and beverages. Laboratory Safety Operators should always be aware of safety regardless of where they are at the treatment plant. The laboratory should be treated no differently than if an operator was changing chlorine cylinders. There are chemicals that are combustible and others that can cause severe burns if they are exposed to skin. Some common safety equipment found in water treatment plant laboratories: • Eye protection⁠—Eye protection should include safety goggles, safety glasses, or face shields. It is not recommended to wear contact lenses if working with dangerous chemicals. Prescription safety eyewear is available. You only have one set of eyes, so it is important to protect them. Water laboratories have liquids and solids that can easily penetrate your eyes if you are not wearing the proper PPE (personal protective equipment). • Safety Showers/Eyewash Bottles⁠—In the event that something gets in your eyes, every lab is equipped with a safety shower. The shower should have a pull lever and an eyewash sink. • Fire Extinguisher⁠—Fire extinguishers are located throughout any building in the United States. Most water treatment companies will provide formal training on proper use of a fire extinguisher. In the event that you cannot put a lab fire out with the use of an extinguisher, exit the room right away and call the fire department. Fire extinguishers are meant to put out very small fires very quickly. Meters Laboratories use a variety of meters for water quality testing. Although meters are located throughout the treatment plant, the meters in the lab are used to verify that equipment throughout the treatment plant is functioning correctly. The most common meters used by water treatment operators are pocket colorimeters for chlorine testing in the field, turbidity meters, and pH meters. Pocket colorimeters are great to be used in the field, but the results are not reportable. For compliance purposes, you must use an electric colorimeter or photometer. pH meters and turbidimeters are used to verify equipment is working throughout the plant. At a minimum, an operator will run labs on turbidity, chlorine residual, water temperature, and pH. All of these parameters are required for CT compliance and verification. These measurements are important in ensuring the treatment plant is operating in compliance with the surface water treatment rule. Microbiological Testing Microbiological testing is probably the most important testing done by water treatment professionals. As discussed at length in this text, treatment water operators aim to remove and deactivate pathogenic organisms from drinking water through filtration and disinfection. Water regulations require 3Log removal and deactivation of Giardia and 4 log removal and deactivation of viruses. Bacteria fall in the middle of Giardia and viruses. Therefore, it is safely assumed bacteria will be removed and deactivated along the same process. Water professionals test for microbiological agents by testing for the indicator organism coliform. Coliform bacteria cause no harm to humans but are generally present when pathogens are present in the water. The reason coliforms have been used to identify contaminated water for over 100 years is because they are always present in contaminated water. Even if there is no fecal contamination, they are still present. They survive longer in water than pathogens and they are easy to identify with proper testing. When a positive sample is identified, we assume the water is contaminated until it can be proven otherwise. Water treatment facilities use four different tests for coliform monitoring. The easiest, least expensive, and the most common method for coliform testing is the presence absence test (P-A). Both the P-A and multiple tube fermentation (MTF) tests work based on the fact that coliform produces gas from the fermentation of lactose within 24-48 hours. The MTF method uses three steps for the test. It includes the presumptive, confirmed, and completed test cycle. The presumptive test is accomplished in 24 hours. Samples are incubated at 35 degrees Celsius for 24 hours and then checked to see if a gas bubble has formed or if the sample is cloudy. You want to see no bubble or gas. The samples are then incubated for another 24 hours. If gas does not form, the test is over and the sample is absent. If there is a gas bubble, you move on to the confirmed test. The confirmed test verifies the sample is positive from coliform and not another type of bacteria. Brilliant Green Lactose Vile is added to the sample and then incubated for another 48 hours. The same method is used. The lab technician or operator checks to see if gas is produced during the incubation period. The minimum requirement for water treatment operations is the presumptive and confirmed test. The completed tests are rarely used except for quality control by laboratory personnel. In the event of a positive confirmed test, coliform bacteria violation protocol will go into effect. The P-A method is the most common method for treatment operators and field sampling staff. The bottles are easily transferred in an ice chest and the set-up is very simple. This method is commonly referred to as the Colilert method. The test uses a 100 mL plastic sample bottle. A nutrient is added to the sample, which is then incubated for a period of 24 hours at 35 degrees Celsius. The nutrient will cause the water to turn yellow if coliforms are present. In the event of a positive test, the bottle can be placed behind a fluorescent light that will turn a blue color which indicates fecal E. coli contamination. The other two bacteriological tests include MMO-MUG and the membrane filter method. The MMO-MUG tests come with the testing agent already in the vials. A 10 mL sample is simply added to the vial. As with the P-A test, samples positive for coliform will turn yellow and for fecal contamination will turn blue. The membrane process begins with filtering 100 mL of water through a membrane filter. Then the sample is added to a petri dish and incubated for a 24-hour period. Coliform positive samples turn a red-pink color. Confirmative tests require incubation of a broth for another 24 hours. Physical Water Quality Operators test the water for both physical properties and contaminants that will cause harm to humans. There are secondary standards related to many of the physical tests operators perform. Acidity is the ability to neutralize a base. Alkalinity is the ability of water to neutralize acid. The reason operators are concerned with the acidity and alkalinity of drinking water is different pH scales have different effects on water treatment. When acids are added to water, they lower the pH of the water. A strong base may need to be added to boost the pH. Operators want a small amount of calcium carbonate present in the water to deposit around the pipes of the distribution system. This helps combat corrosion. When we think of water drinkability, we might think of color, taste, odor, and temperature. The physical aesthetic of the water matters and impacts our desire to drink the water. The color of the drinking water may indicate water with higher levels of organic compounds and water with THMs. Taste and odor issues in treated drinking water are hard to test. Many customers complain of a strong chlorine smell in their drinking water. Taste and odor problems can come from organic matter, chlorine, dissolved gases, and even industrial wastes. The threshold odor test is measured on the TON scale. (Water sample of 100 mL + dilution divided by 100 = TON.) Water registering as a 3 will most likely draw complaints from customers. Water temperature plays a key role in water treatment because disinfectants work better at higher temperatures. However, nitrification occurs during the warmer months of the year so the water temperature has to be carefully managed. Water agencies in colder regions of the country must deal with freezing conditions within their treatment and distribution system. During the winter even in warmer regions, lake turnover can cause vast changes in water quality. Turbidity is the suspension of particles in water. High levels of turbidity can signify major issues within the treatment plant. Therefore, turbidity is used to verify how efficiently the treatment plant is operating. High turbidity values may indicate higher levels of organic and inorganic matter. Pathogenic organisms can hide behind turbidity and render disinfection ineffective. Turbidity is measured in the lab with a nephelometric counter. A light source is added and, in the presence of turbidity, the light scatters, producing higher numbers with greater amounts of turbidity. The final two water quality testing procedures most commonly performed by water treatment operators are chlorine and pH. The chlorine or chloramine feed system is one of the most critical components of a water treatment plant that operators monitor through online testing and grab samples. The measurement of the hydrogen ion concentration in water is pH. The pH scale ranges from 1- 14 with 1 being the most acidic and 14 the most basic. The higher ends of both ranges produce the most corrosiveness. 7 is considered neutral. Do not confuse pH with acidity or alkalinity. It is important to monitor pH because the pH is used to control many chemical reactions in the treatment plant including coagulation, disinfection, corrosion control, and the removal of ammonia. pH also plays a key role in the CT calculation. Chapter Review 1. An organism used to indicate the possible presence of E. coli contamination is ___________. 1. Cryptosporidium 2. Giardia 3. Coliform 4. Brilliant green vile 2. The presence-absence (P-A) test used for microbiological testing is also commonly referred to as ___________. 1. Multiple tube fermentation 2. Membrane filtration 3. Confirmed test 4. Colilert 3. When testing for coliform bacteria with the multiple tube fermentation (MFT) method what is the best indicator for a positive test? 1. Color change 2. Gas bubble formation 3. Formation of a cyst 4. Formation of turbidity 4. Coliform bacteria share many characteristics with pathogenic organisms. Which of the following is not true? 1. They survive longer in water 2. They grow in the intestines 3. There are less coliform than pathogenic organisms 4. They are still present in water without fecal contamination 5. What is the second step in the multiple tube fermentation test? 1. Presumptive test 2. Negative test 3. Completed 4. Confirmed 6. What is the removal and deactivation requirement for Giardia? 1. 2 Log 2. 3 Log 3. 4 Log 4. There is no requirement 7. The multiple barrier approach to water treatment includes removal through which method? 1. Filtration 2. Coagulation 3. Disinfection 4. Both 1 and 3 8. A pH reading of 7 is considered ___________. 1. Slightly acidic 2. Acidic 3. Basic 4. Neutral 9. A higher than normal turbidity reading could signify ___________. 1. A change in water quality 2. Nothing. Keep operating as normal 3. Microbiological contamination 4. Both 1 and 3 10. What is the ingredient used during the second multiple tube fermentation test? 1. Colilert 2. MMO/MUG 3. Brilliant green vile 4. Chlorine

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Learning Outcomes • Understand the importance of proper wastewater treatment • Describe and construct the urban water cycle • Analyze wastewater origins and how it is conveyed • Differentiate between residential and industrial/commercial wastewater • Evaluate the typical job function of a wastewater treatment operator • Explain the certified wastewater treatment operator licensing requirements Introduction Proper wastewater treatment and disposal is essential for the vitality of a functioning society. Without it, a community’s environment can be severely polluted and the health of the public is at great risk. To better understand the relationship between wastewater treatment and water treatment and distribution, examine the urban water cycle. Like the typical hydrologic cycle, which shows the natural movement of water in the environment, the urban water cycle shows how water is moved in an urban environment. In some cases, wastewater that has been treated by a wastewater treatment plant will be discharged back into a natural water body. Water from that water body will then be used by downstream communities as source water for their water treatment plants. If either of these two treatment facilities are not operating to current regulations and standards, public health is at risk. In addition, if the wastewater treatment facility is not operating properly there can also be additional environmental damage to the water body. Currently, there is a paradigm shift in water treatment and the line between water, wastewater, and stormwater is becoming thinner and thinner. For example, the use of reclaimed water from wastewater treatment plants can be used for various beneficial uses instead of being discharged into a water body. The term “One Water” is being used more frequently to encompass the idea that all of these water sources are beneficial and more innovation is needed to use these sources more efficiently. However, the focus of this textbook will be on the inner workings of a conventional wastewater treatment plant. The goal is to give you the vocabulary and knowledge needed to understand how wastewater treatment operators can take a contaminated water source and treat it to a level of quality that will not endanger the environment or public health. The term wastewater has become the common term to describe sewage. In fact, when we talk about conventional wastewater treatment plants we are talking about facilities that take the used water from residences and businesses of a community and clean it up. Wastewater is anything and everything that goes down the drains of these households and businesses. All the water from sinks, garbage disposals, toilets, dishwashers, bathroom drains, and washing machines are considered residential wastewater. There is also commercial or industrial wastewater. Many manufacturing processes that use water, typically for washing or cooling purposes, need to properly dispose of this water. In some cases, this wastewater may be treated onsite before it is discharged into the wastewater collection system. Some municipalities will require the manufacturer to obtain an industrial waste permit that regulates what they are allowed to discharge. Wastewater Treatment Plant Operators A wastewater treatment plant operator’s main responsibility is to ensure the wastewater treatment facility is being operated and maintained so the wastewater leaving the facility meets the limits of their National Pollutant Discharge Elimination System (NPDES) permit. We will learn the specifics of exactly what an NPDES is in later chapters. Throughout the rest of this book, we will look at the main roles and functions that wastewater treatment plant operators do every day. Licensing Requirements The State Water Resources Control Board (SWRCB) is the regulatory authority in California for many aspects of water laws and regulations. They are also responsible for overseeing the Operator Certification Program. In California, it is mandatory to be certified by the SWRCB if you are employed in the operation of a water distribution system, water treatment facility, or wastewater treatment plant. To become certified there are three things that must be accomplished by the individual seeking certification. First, is to obtain the required amount of education for the level of certification. Each vocation has five levels of certification, with grade five being the highest. As the level of certification increases, more education is needed. The second requirement is experience. Just like education, higher certifications require more experience. However, these two requirements work together. The more education one has, the less amount of experience needed. Likewise, if one doesn’t have a significant amount of education, they can still obtain higher certifications by gaining more work experience. The education and experience requirements for the Wastewater Treatment Operator certifications can be found here. The final thing is to pass the certification exams which are offered twice a year, in the spring and fall. Becoming certified as a Wastewater Treatment Operator Grade 1 requires that the applicant has gained one year of work experience. This one year of work experience is one of the hardest hurdles for many people to overcome. Many employers want to hire people that already have certifications, but you can’t get certified if you don’t have experience. Many wastewater treatment facilities understand this predicament and offer what is called an Operator-In-Training (OIT) position. To obtain a Grade 1 OIT certificate you must have a high school diploma or GED, have six educational points by taking a college-level math or science course, and be employed by a wastewater treatment facility. These positions are becoming more competitive and often employers require additional related work experience or additional education. Successfully passing the certification examination can help set you apart from other applicants. Type of Work The type of work a wastewater treatment operator is involved in will be varied and depends on a lot of different factors. A common job description will include something along the lines of “to ensure the operation of the treatment facility and ancillary equipment in order to meet effluent requirements”. The effluent of a wastewater treatment plant is the water that leaves the facility once it has been treated. To ensure the effluent requirements are met, an operator's typical job will include monitoring and logging critical information such as pump pressures and flow rates, tank levels, and water quality parameters such as turbidity and chlorine residual. There is also preventative maintenance that is required. Some tasks could include taking portions of the treatment system offline for cleaning and/or repairs. Throughout the treatment system water samples will need to be taken and tested for various constituents, either for regulatory compliance or process control. Depending on the facility, the sampling may be done by operators or by laboratory technicians. However, it will almost always be the certified operators that will review the laboratory results and determine if any adjustments to the treatment process are needed. It’s important to note that wastewater treatment plants are industrial facilities and some of the work can be very dangerous. Operators can be working with heavy machinery such as forklifts, large pumps, and cranes. There is also high voltage electrical equipment that the operator will interact with on a daily basis. There can be situations where there are high-pressure lines and even the possibility to be exposed to harmful chemicals. This book will have a whole section dedicated to covering these safety topics and more. Jobs There are many different types of work available in the wastewater treatment industry as a whole. While this textbook will focus on the specifics of the job duties of a wastewater treatment operator (WTO), there are many other supporting jobs in both the public and private sectors. Most of the WTO positions are available through the public sector. For example, a city will be the owner and operator of a municipal wastewater treatment facility. That city will then employ as many WTOs as necessary to operate the plant. However, there will be many other jobs required to keep the facility running aside from the operators. Depending on the size of the plant, there can also be workers skilled in the maintenance of pumps and machinery, electricians, and instrumentation technicians. These jobs can also have their own trade certifications that may be required by the employer. In addition, there may be laboratory staff, administration personnel, engineers, managers, and financial experts. All of these positions will work together to keep the plant running. But it’s important to remember that at the end of the day, it’s the certified Wastewater Treatment Operators that can be legally responsible for the quality of water leaving the facility and compliance with the NPDES permit. There are also many job opportunities in the private sector. There are many “package plants” that smaller private industries will operate to treat residual waste from a large scale manufacturing process. A brewery, for example, may need to treat their brewing process wastewater before the water can be disposed of in the municipal sewer system. As of 2013, these privately run wastewater treatment plants require workers that are involved in the operation of the plant to meet the same licensing requirements as publicly operated wastewater treatment plants.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.01%3A_Basic_Overview_Introduction_To_Wastewater_Treatment.txt

Learning Outcomes • Understand the purpose of NPDES permits • Explain how TMDLs are obtained and how they improve water quality • Assess the difference between chemical and physical water quality contaminants • Describe how different contaminants can affect water bodies National Pollutant Discharge Elimination System (NPDES) Permits Wastewater treatment plants typically discharge their treated water into a water body that is nearby. Since 1972, with the passage of the Clean Water Act, it is illegal to discharge water from a point source into waters of the United States unless an NPDES permit is obtained. Since wastewater treatment facilities have all of their discharge leaving the plant from a single discharge pipe, it is considered a point source. This differs from nonpoint sources that have large areas of discharge like runoff from agricultural fields. An NPDES permit allows discharging the treated wastewater into a water body as long as it meets the requirements of the permit. These requirements can include limits on what can be discharged, how frequently samples must be taken, and other reporting requirements. There may also be other requirements specific to the discharger to assure that the water being discharged does not harm public health or the environment. Total Maximum Daily Loads (TMDL) The total maximum daily load (TMDL) is a calculated value of the maximum amount of a specific pollutant that a waterbody can receive without negatively impacting that water body. For example, 10,000lbs of pollutant X naturally occurs within a stream that has a TMDL of 50,000lbs for pollutant X and contains three point source discharges. Therefore, an additional 40,000lbs of pollutant X may be discharged into the stream without exceeding the TMDL. It’s the job of permit writers to use the TMDLs of a water body and the total number of point source discharges to determine the waste load allocation (WLA) for each discharge and incorporate that into the NPDES permit as a limit. To continue with the example, a permit writer could determine that with three point source discharges each one would be allowed to discharge 10,000lbs of pollutant X. This would leave a margin of safety of 10,000lbs. So in theory, the discharge of pollutant X would not negatively impact the water body because the sum of all the discharges and naturally occurring contamination is below the TMDL of the water body. Wastewater Solids The solids found in wastewater are comprised of many different constituents including organic and inorganic material. A variety of laboratory tests can be performed to determine the total amount of solids. The total suspended solids (TSS) test will determine the total amount of solids that are suspended and that are easily settleable. This test is done by filtering a specific volume of the wastewater through a filter pad. The water and dissolved solids will pass through the filter; and the settleable solids and suspended solids will remain on top of the filter. The difference in weight of the filter before and after filtration is used to calculate the amount of TSS. While all the solids remaining on the filter after the TSS test are suspended, not all of the solids are settleable. Settleable solids can be determined by using an Imhoff cone. Again, a specific volume, typically 1,000 mL, is poured into the Imhoff cone and allowed to settle. The settleable solids will collect on the bottom of the Imhoff cone. After an hour, the amount of solids that settled can be determined by the graduations on the Imhoff cone as seen in the figure below. The water that filtered through the filter pad during the TSS test still contains solids of contaminants that are dissolved into the water. Collectively this can be determined by completing a Total Dissolved Solids (TDS) test. This test takes the water left over from the TSS test and pours it into a pre-weighed dish. The water is then evaporated from the dish and weighed again. The difference in weight is then used to calculate the TDS. Whether the solids are settleable, suspended, or dissolved, wastewater is generally made up of less than 1% solids. The other 99% is just water. The focus of the remainder of this text will be on treating the 1% of solids in wastewater. The difference in the type of solids will determine what type of treatment process is used. Settleable solids will easily settle during the primary sedimentation process. Suspended solids will require a secondary treatment process. TDS can only be removed by advanced treatment methods like membrane filtration or reverse osmosis. TDS will not be removed by conventional wastewater treatment methods. Biochemical Oxygen Demand Biochemical oxygen demand (BOD) is a measure of how much organic material is in the wastewater. When wastewater with high amounts of BOD is released to a water body, the organic material will consume the dissolved oxygen in the water body. If the BOD exceeds the TMDL of the water body, then the oxygen levels can be completely depleted. Without the dissolved oxygen, fish and other aquatic life will not be able to survive. The BOD5 test is completed in a laboratory by taking a sample of wastewater and measuring the dissolved oxygen concentration. The sample is kept in an airtight container in a refrigerator set to a temperature of 25C. After 5 days, yes, that’s why there is a subscript 5 in BOD5, the dissolved oxygen concentration is measured again. The difference in oxygen concentrations is how much oxygen was consumed by the organic material in the wastewater. The more organic material there is, the higher the BOD5 will be. The BOD5 test is the standard test that is used to measure the organic contamination in wastewater. It is one of the main regulatory components in an NPDES. However, it has one big drawback which is that it takes five days to get results. Another test that gives similar results is the chemical oxygen demand (COD). COD will measure the amount of oxygen needed to decompose organic material as well as inorganic chemicals. The difference between COD and BOD5 is that COD will also measure other chemicals that can be oxidized besides ones that are biological. COD laboratory results can be determined in approximately 6 hours. If a wastewater treatment facility is only treating wastes from a community that is mainly residential and does not have many industrial discharges, then the COD and BOD5 can be correlated after a significant number of samples are analyzed side by side. BOD5 is routinely done to meet regulatory requirements while COD results are used for process control to make sure the treatment plant is operating efficiently. Microbiological Contaminants and Pathogens There are many different types of microorganisms that can be found in wastewater. Some of these microbes are pathogenic. A pathogen is a microorganism that is capable of causing disease. Some common pathogens that can be found in untreated wastewater are Cholera, Giardia, Streptococcus, E. Coli, Cryptosporidium, and Salmonella. However, not all microorganisms are pathogenic and some non-pathogenic bacteria will actually be utilized as a treatment aide to reduce the amount of BOD5 in the wastewater. One classification of microorganisms is a protozoa. A protozoa is a single-celled organism and is essential to the biological treatment processes. Amoebae, flagellates, and ciliates are some examples of protozoa commonly found in wastewater samples. Metazoa are multi-celled organisms that can also be found in wastewater treatment facilities. Some examples of metazoa are rotifers, nematodes, tardigrade (water bears). When we discuss the various biological treatment methods later in this textbook, we will learn that a microscopic examination of wastewater samples can show the health of the treatment system by comparing the quantities of protozoa and metazoa organisms. Viruses can also be detected in wastewater samples. Viruses must have a host organism in order to live and reproduce. Unfortunately, they can remain dormant in water until they find such a host. Hepatitis A and polio are examples of viruses that can be found in wastewater samples. Viruses can be difficult to identify in the laboratory and are not routinely tested for in wastewater samples. Coliform bacteria is the most common laboratory test done to determine the potential of the presence of pathogenic organisms. Coliform bacteria are abundant in the natural environment and can be found in water and soils. Coliform bacteria are not pathogenic but their presence can determine if pathogenic organisms may also be present. For example, if a tested wastewater sample has large amounts of coliform bacteria, then we can say that there is a high chance that pathogenic organisms are also in that sample. If we find that there are very low amounts of coliform bacteria, then we can say that there is a very small chance that pathogenic bacteria are also present. Because of this, coliform bacteria are often called an indicator organism. The laboratory test results can be used to indicate whether the sample has the potential for containing pathogens. Since there are so many pathogenic organisms, it would be extremely cumbersome to test for each one individually. It is much more economical to complete the coliform test instead. Now if the coliform test does indicate that there are coliforms present, further testing can be done to determine if pathogenic bacteria are also there. Typically, the test to determine if E. coli is present. Eutrophication Effects of Nitrogen and Phosphorus Algae typically is not present in wastewater but wastewater can contain nutrients such as nitrogen and phosphorus which will promote algae growth in waterbodies. In pond treatment systems, algae will actually be used to aide the treatment process by supplying oxygen to beneficial bacteria that will reduce BOD5. When treated wastewater is discharged into a waterway, the amount of nitrogen and phosphorus must be closely examined. If there is too much nitrogen and phosphorus in the waterbody, it can lead to an overabundance of algae. When there is too much algae growth, the algae will consume more oxygen from the waterbody. With large amounts of algae consuming the oxygen, there is not enough oxygen for other aquatic organisms to sustain life. This excess growth of algae resulting from the increased nutrient loading on a waterbody is called eutrophication. Other Chemical Contaminants In addition to nitrogen and phosphorus, there are other chemical contaminants that can be found in wastewater. Almost every element that can be found on the periodic table will molecularly combine with water under the right conditions. Collectively these will be determined when completing the TDS analysis. There are some elements that we are particularly concerned about and these concentrations are measured independently. Chlorides can be introduced into wastewater from road salts, food waste, water softeners, and naturally occurring surface water contamination. Chlorides can be found in water as sodium chloride, potassium chloride, calcium chloride, and magnesium chloride. When there are excess levels of chlorides in a waterbody, it can have adverse effects on aquatic organisms. Excessive chlorides can interfere with the biological processes going on inside the bodies of freshwater aquatic organisms. Heavy metals found in wastewater typically come from industrial discharges. Metal finishing, electroplating processing, mineral extraction operations, and textile industries can contribute to heavy metals in wastewater. Lead, copper, zinc, mercury, arsenic, nickel, and silver are some common heavy metals that can be found in wastewater samples. Although, any metal on the periodic table can find their way into the sewer system. Heavy metals are a concern due to their toxicity in aquatic systems and adverse effects on plants and animals. The pH of wastewater is very important and can influence the treatability of wastewater. If the pH is not between 6.5 and 8.5, chemicals may need to be added to bring the pH into that range. Alkalinity is another important characteristic of wastewater. Alkalinity is the ability of the wastewater to buffer against changes in pH. Alkalinity is measured by determining the amount of acid-neutralizing basics. It is commonly measured in mg of CaCO3 equivalents per liter. Alkalinity is critical to the physical, chemical, and biological treatment processes we will discuss throughout this book. These processes do not operate well under acidic conditions. Sufficient alkalinity is needed to ensure the pH stays within the 6.5 to 8.5 range. Other Physical Contaminants Odor, color, turbidity, and temperature are all physical characteristics of wastewater. Unlike the biological and chemical characteristics discussed previously, physical contaminants can be observed by the human senses. We can see what the color is, we can smell if the odor is foul, and we can feel if the sample is warm or cold. Although laboratory equipment can be used to obtain more quantitative data. As you can imagine, untreated wastewater can give off a foul odor. However, odor can give an operator great insight. If the wastewater smells like rotten eggs, this is a sign that there can be high amounts of hydrogen sulfide in the wastewater. In densely populated areas where the wastewater treatment plant is in close proximity to residents, odors may be captured and sent to an air treatment unit to reduce the objectionable odors from the facility. Color can also provide insight into what’s happening in the wastewater or where it’s coming from. An unusual color in the wastewater can indicate an industrial discharge such as dye from a manufacturing process. If the wastewater is dark or black, then it has most likely undergone septic or anaerobic conditions. Fresh wastewater typically has a murky yellowish/brown color. Turbidity can be physically seen in wastewater samples and is often described as the cloudiness in the water. In the laboratory, a nephelometer is used to obtain a quantitative result measured in Nephelometric Turbidity Units (NTU). A nephelometer works by shining a light through the sample of wastewater. If the water has high amounts of turbidity the light will scatter and not make it to the detector on the other side of the sample. High amounts of turbidity can impact the effectiveness of disinfection. The small particles that cause turbidity can shield microorganisms from coming in contact with the disinfectant.

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Learning Outcomes • Examine how wastewater is conveyed from the source to a wastewater treatment facility • Assess the impacts and causes of odor in a collection system and explain how to mitigate the negative impacts for a community • Analyze how gravity sewer design is used to maintain sufficient velocity • Evaluate system conditions to determine when a sewer pump station is needed • Differentiate between the various methods to maintain and clean sewer systems Gravity Sewers The main purpose of a wastewater collection system is to convey the wastewater from the source to a treatment facility. Recall from Chapter 1 that the source of wastewater contains anything and everything that goes down the drain. There are residential sources such as homes, apartments, and office buildings. And, there are industrial sources like restaurants and manufacturing processes. These sources will have laterals that are connected to a main sewer line. Laterals are usually privately owned and the maintenance on them is the responsibility of the property owner. The lateral is a direct connection from the source to the main sewer line. The main sewer line is typically owned, operated, and maintained by a public utility. The main line is several sizes larger than the laterals as it will be required to have enough capacity to accommodate all of the laterals that are being discharged into it. In larger cities, there may also be interceptors or trunk lines. These larger trunk lines collect all of the main lines through the city and send the wastewater to the wastewater treatment facility. Whenever possible the collection system will utilize gravity to send the wastewater from a higher point to a lower point. To achieve gravity flow, the main sewer lines are designed and constructed on a slope. The amount the line is sloped is dependent on the size of the pipe and the expected quantity of wastewater. The collection system must have a minimum wastewater flow velocity of 2 ft/second (fps). At this velocity, solids will be kept in suspension. Slower velocities will allow settling in the piping collection system. If solids settle in the collection system, these depositions will accumulate over time and can cause a blockage. If the blockage becomes too severe, then wastewater will not be able to flow freely. If the blockage is large enough, it can cause the wastewater to back up and overflow onto the streets. Pressure or Force Mains Gravity sewer lines cannot be used in every situation. Areas that are very flat or communities that are located in a valley will require a lift or pump station. A lift station uses pumps to lift the wastewater from a lower elevation to a higher elevation. The section of pipe from the discharge to the gravity sewer connection is known as a force main. Unlike a gravity sewer, a force main is completely full and under pressure. The pressure comes from the energy of the pump which is needed to lift the wastewater to a higher elevation. Different Types of Sewers There are three different types of sewer systems; sanitary, stormwater, and combined. Sanitary sewer systems only convey wastewater that was derived from sanitary sources. As discussed in Chapter 1, this is wastewater from household toilets, showers, and dishwashers, as well as industrial sources of wastewater from manufacturing processes. Sanitary sewers differ from stormwater sewers in that they contain fecal matter from human waste. It’s paramount that these wastes are conveyed to a wastewater treatment facility so they can be removed and stabilized to protect public health and the environment. Stormwater sewers are a network of pipes that collect only stormwater runoff and directs the flow to a nearby waterbody or the ocean. While stormwater does have a direct connection to human or animal waste, it is considered less harmful and can be discharged without treatment. However, it’s important to understand that stormwater is by no means “fresh water”. Stormwater can have large amounts of trash, plant material, silt gravel, oil & grease. There are even fairly high amounts of harmful bacteria from animal wastes. The theory is that during storm events there is a significant amount of water flowing through these systems that these contaminants become diluted and are not as concentrated. This theory is constantly being challenged and stormwater is now being seen as another water source that can be treated and even beneficially reused. A combined sewer is a network of pipes that conveys both sanitary wastes as well as stormwater. This can be beneficial during dry weather flows where there is minimal stormwater. The stormwater that does exist is sent to a wastewater treatment facility where harmful contaminants are removed prior to discharge to a waterbody. However, combined sewer systems can be overwhelmed during storm events. Systems that have older infrastructure which has not been upgraded to deal with larger populations and storm events are especially vulnerable. When this happens, instead of only diluted stormwater being sent to a waterbody, sewage containing high amounts of fecal matter from the sanitary sewer is also discharged. This can cause increased pollution to the waterbody. Infiltration and Inflow Collectively referred to as I & I, infiltration and inflow is wastewater that has entered into the collection system unregulated. An inflow is when water other than sanitary wastewater enters the collection system through an illicit connection such as rain gutters, basement drains, or foundation drains. Infiltration is water such as groundwater and stormwater that finds its way into the sewer piping from manhole covers and cracks in the piping. Odor Control Sewage can have an extremely foul odor. As the organic material starts to break down in the sewer system, it will generate foul odors. Often, this breakdown of organic material and the biological reduction of sulfates in the wastewater will create hydrogen sulfide (H2S). H2S has a very distinctive rotten egg smell and can cause several problems in a wastewater collection system. H2S is extremely toxic and workers working near or inside a wastewater collection system must continuously monitor the atmospheric conditions and properly ventilate the workspace to ensure that the environment is free of H2S and other hazardous atmospheric conditions. H2S will also breakdown in the collection system forming sulfuric acid which can corrode pipes, manholes, and other parts of the system. Although H2S is heavier than air, it is still able to escape the collection system and cause nuisance odor conditions to the surrounding community. These sewer gases can be mitigated in several different ways. One way is to add chemicals to the collection system that will prohibit the formation of H2S. For example, iron salts such as ferric chloride will react with the sulfides in the wastewater and do not allow the molecules to form H2S. Another way to remove H2S is to let it form in the sewer system and then have a fan that will pull the foul sewer gases from the sewer and convey the odors to a treatment site. Typically, the air treatment is achieved by carbon adsorption or bio-filtration. Carbon in this filter form is extremely porous when examined under a microscope. When the foul sewer gases are forced through a media of carbon particles, the gasses will adhere to these microscopic pores and be removed from the airflow. In a bio-filtration setup, the sewer gases are conveyed to a large tank where bacteria will metabolize the H2S and thus remove it from the airflow. Collection System Maintenance Collection systems, while underground and out of sight from the general public, still require a significant amount of maintenance to ensure that the wastewater flowing through the system stays underground. If the wastewater cannot flow through the network of pipes, it will begin to back up and overflow out of the manhole covers in the streets. When this happens, it is called either a Sanitary Sewer Overflow (SSO) or a Combined Sewer Overflow (CSO) depending on which type of wastewater collection system is used within the community. To prevent this from happening, wastewater professionals have several tools available to them. Bucketing, rodding, flushing, jetting, and closed-circuit television are the primary means used to maintain a wastewater collection system. Flushing is a hydraulic process that is great for light cleaning of wastewater lines. Flushing moves a high volume of water with low pressure through the wastewater line that needs to be cleaned. Adding this extra water increases the velocity in the line. At high velocities, the flushing water scours the sediments and debris in the line and pushes everything downstream. Rodding and bucketing are both mechanical mechanisms that use machinery to physically remove any obstructions and debris from the wastewater pipeline. This is typically used when flushing is insufficient to remove the debris. Rodding occurs when a cable with a special attachment at the end of it is sent down the wastewater pipe that needs to be cleaned. The rod is then rotated and the tool can break through the obstruction in the line. Jetting combines both hydraulic and mechanical tools. Jetting is similar to rodding except a heavy-duty hose that can handle high pressures is used instead of a rod. At the end of the hose, there is a nozzle specifically designed to send concentrated streams of water at high pressures against the interior wall of the pipe to remove any debris or obstructions.

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Learning Outcomes • Understand why preliminary treatment is necessary • Compare and contrast the different types of preliminary treatment methods • Evaluate the benefits of different treatment methods Nuisance Substances Preliminary treatment is the first step in treating raw wastewater. When the wastewater first enters the wastewater treatment facility there are a lot of nuisance materials that have found their way into the collection system. Items such as large rags, bottles, tree branches, and numerous other nuisance items can be found in the influent to the treatment facility. These large items can cause damage to downstream pumps, take up valuable space in settling tanks, and can be hazardous to other mechanical equipment needed in the treatment process. So the first, or preliminary step is to remove these large items. Screening One method to remove large debris items is by using a bar screen. Bar screens are capable of removing items that are larger than the spacing between the bars. For example, a ¾” bar screen will hold back any debris that is larger than ¾” and anything smaller will pass through it. Common items that are removed in this preliminary treatment step are rags, roots, large rocks and aggregate, bottles, cans, and numerous other large objects that can make their way into the wastewater collection system. Over time, the debris collected behind the bar screen will need to be removed. This is done either manually or automatically. Manual bar screens typically have large spacing, 2” to 4” is common, between the bars. To manually clean a bar screen an operator will use a rake and pull out all of the debris stuck behind the bar screen. This can be extremely laborious and dangerous as the operator is lifting heavy objects over an open trench. Ideally, a wastewater treatment plant will have two or more channels with bar screens. This way one channel can be isolated and the debris can be removed without having wastewater flowing through it. Although this is safer, it is still laborious. Newer bar screens are raked automatically. On more sophisticated systems, the channel where the bar screen is installed will have an upstream and downstream level sensor. When the debris is blocked by the bar screen it will also inhibit the flow of wastewater through the screen. This will cause the upstream water level to rise. When the difference between the upstream and downstream levels reaches a predetermined setpoint, the motorized rake will swing down and automatically pull the debris out of the channel and into a hopper. Other systems will automatically initiate the raking sequence based on a timer or will just run continuously. Most automatic bar screens will have a washer/compactor that receives the removed debris. The washer/compactor will wash the debris removing any of the organic matter and then compact it. Washing is important because in this preliminary step we are only trying to remove the large inorganic items. We want to keep the organic material in the wastewater stream as it will be utilized in subsequent treatment processes. Compacting the debris is critical as it removes most of the water and makes it easier to transport for disposal. Since automatic bar screens can run autonomously, the bar spacing can be smaller. Most models are around ⅝” to ¾” but newer models can be ½” or less. While automatic bar screens are capable of removing more debris with less manual labor, there is still a skill set required to properly operate this machinery. Operators will check the equipment multiple times during a day. Checks can include monitoring the rake arm and motor for proper function, removing compacted debris to a larger disposal truck, checking motor amps are within range, and calibrating level sensors. Comminution and Barminution An alternative to screen these large debris items is to shred or grind them. A comminutor is a device that sits inside the channel where wastewater is flowing into the treatment facility. The comminutor will grind the large debris items, turning them into smaller items. Communitors are designed to produce a solid size of a certain diameter. By breaking up the debris into smaller diameters, the downstream pumps and equipment will not be as impacted. It’s important to note that comminutors do not remove the debris from the flow of wastewater. The debris is just broken down into more manageable sizes. The debris will still need to be removed in the subsequent treatment process. Barminutors combine a bar screen with a comminutor. There is a bar screen set inside of a channel where the wastewater flows. The debris is trapped behind the bars and then a device travels up and down the bars which breaks up the large solids into smaller pieces. The ground-up solids stay within the flow of wastewater and move onto the treatment process. Grit Removal Once the large items are managed, the next step in the treatment process is to remove the smaller inorganic solids, such as coffee grounds, eggshells, sand, silt, and gravel. These small diameter solids are collectively called grit. Grit must be removed because it will cause excessive wear on plant equipment such as the impeller of a pump. Also, this inorganic material can settle in the subsequent treatment process and take up valuable space in tanks which decreases plant efficiency and can inhibit further treatment. While most gritty materials are inorganic, large organic solids such as corn kernels and other food waste may also be removed. There are several methods that can be used to remove grit but all of the methods rely on the fact the gritty material is relatively heavy. Compared to the organic solids, grit is much heavier and will settle faster. Grit can be removed by controlling the velocity of wastewater through a tank, adding air to the tank to aide in settling, or by using centrifugal force. The basic concept of removing grit is to reduce the velocity of the wastewater flowing through a tank to less than 2 fps. Recall that in the collection system we want to achieve a velocity of 2 fps. The higher velocity in the collection system will keep all of the solids in suspension so they make their way to the treatment plant. But now that we are trying to remove these solids, we want to get the velocity between 0.7 and 1.4 fps. At this lower velocity, the heavy inorganic solids will settle to the bottom of the tank. Detention time is a critical factor in designing the tank dimension for grit removal. The detention time needs to be long enough to allow the gritty material to settle to the bottom. The typical detention time of grit chambers is around 2 to 5 minutes. However, if the detention time is too great, then smaller organic solids will also settle out. These items are better dealt with in the next step of primary treatment. Aerated grit chambers are set up in a similar manner except there will be air piped to diffusers at the bottom of the tank. The addition of air in the tank creates a rolling action of solids which helps keep the lighter organic solids in suspension while the heavier grit material is directed to the bottom of the tank. In aerated grit chambers, the amount of air sent to the chamber is a critical operating parameter. If too much air is supplied, then the grit material will stay in suspension and not be removed. If not enough air is supplied, then the lighter organic material can settle out. Cyclone separators are another method of removing grit. These separators use centrifugal force to push the gritty solids to the edge of a circular chamber where they are then directed to the bottom of the tank. To create the centrifugal force, cyclone separators will require a higher velocity of wastewater moving through the unit. Typically a velocity of 2 fps to 3 fps will be sufficient. Any of the grit removal methods described will result in an accumulation of material at the bottom of the unit. If these solids are not removed periodically, they will accumulate to the point where the unit will be ineffective. The tanks are designed to direct the gritty material toward the bottom of the tank which is sloped towards one end. This allows the settled grit to be removed from the tank for further treatment. The mixture of grit and wastewater is pumped and sent to a grit washer. Grit washers will wash out the organic material and send it back into the flow of wastewater as it moves onto the next treatment process. This allows only the inorganic abrasive solids to be collected for ultimate disposal. Once the gritty material is washed and collected it is sent to a landfill.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.04%3A_Preliminary_Treatment.txt

Learning Outcomes • Describe different methods to measure wastewater flow • Examine the purpose of primary treatment • Compare and contrast conventional primary treatment with chemically enhanced primary treatment • Assess how specific gravity and density relates to the removal of solids able to settle Flow measurement After preliminary treatment, and all of the large debris and inorganic solids are removed, it’s vital to measure the amount of wastewater flowing into the treatment facility. This flow rate will be an important number for process control. Many wastewater treatment plants have a typical diurnal flow pattern as flow into the wastewater treatment plant is not constant. Over a 24 hour period, the flow can fluctuate significantly. There are usually two peaks during the day, typically in the late morning and evening. In the morning, the population that the treatment facility serves is waking up, taking showers, making coffee, cooking breakfast, and using the restroom. The flow tends to lessen in the late afternoon and then increases again in the evening. In the evening, a majority of the population is cooking dinner, washing dishes, doing laundry, and taking showers. In the middle of the night, most people are sleeping and not sending water down the drain. There are several ways that flow can be measured. A simple way to measure flow is by using a weir. Weirs can either be square or V-notched, but the principle behind them is the same. As the flow of wastewater travels through a channel, the weir is placed in its path. The wastewater is then forced to move over the crest of the weir. Based on the dimension of the square or v-notched section in the weir, the flow can be determined by the height of the wastewater over the weir crest. If there is a significant amount of flow, then the height of wastewater will also be large. When the flow decreases, the height of wastewater over the weir will be lessened. A Parshall Flume is another way to determine the flow rate entering or leaving the treatment facility. It works similarly to a weir in that the water is forced through a restriction in the channel and the height of water before and after the restriction is used to calculate a flow rate. All Parshall Flumes have a similar shape. There is a converging section, a throat section, and a diverging section. The converging section is where the flow is channeled and forced through a narrow section. The throat section is where the wastewater flow is restricted by traveling through a slimmer channel. This restriction will increase the velocity of the wastewater as it passes through the throat section and cause the level to rise in the converging section. Just like in a weir, higher flow rates will cause the wastewater level to increase and lower flow rates will show a decrease in the wastewater level. Many treatment plants have markings in the converging section to indicate the wastewater level. Modern treatment plants will have ultrasonic level transmitters that will record the level precisely. This data can be automatically transferred to a computer system where the flow rate is instantly calculated and recorded. A benefit of using the Parshall Flume instead of a weir is that the restriction in the channel will not cause any solids to settle out. In a weir, as water builds up behind it, the velocity is reduced and solids can settle out. Those solids will have to be removed periodically or odors can become problematic. The most modern method of monitoring flow throughout a treatment facility is a magnetic flow meter, or “mag meter” for short. Mag meters work by having the wastewater flow through a pipe. The mag meter is connected to the pipe either by strapping the device to the outside of the pipe or more permanently, by bolting it between two sections of pipe. The device creates a magnetic field inside the pipe and as the water moves through, it creates a disturbance that is measured by the meter. Higher flow rates cause more of a disturbance. The meter can very accurately measure the flow of wastewater moving through the pipe. The benefit to mag meters is that there are no moving parts inside the pipe. So influent wastewater with lots of solids and organics will not interfere with the flow measurement. Mag meters are also very reliable and require little maintenance. Some treatment facilities may have flow equalization. Recall that the incoming wastewater has an inconsistent flow rate that fluctuates drastically throughout a 24-hour period. This change in flow will also result in changing detention times which many of the treatment processes are dependent on. A treatment plant that utilizes flow equalization will attempt to even out the flow so it is consistent throughout the treatment plant all the time. By looking at historical data the plant operators will have a good idea of what the average flow rate for the plant is. This average flow rate is the target of the flow equalization. When the incoming wastewater is greater than the average flow, the excess amount will be directed towards a holding basin. When the flow is less than the average, typically in the middle of the night, the wastewater is pumped from the holding tank into the treatment facility. This can also reduce energy cost as day time pumping will be reduced. Energy costs are usually higher during peak periods. Some treatment facilities have flow equalization at the end of the treatment process. They may have restrictions in their discharge permit which may limit the flow rate leaving the facility. Other treatment plants don't have any flow equalization. Sedimentation After the incoming flow rate is measured the next step in the treatment process is primary sedimentation. The primary goal of sedimentation is to remove the settleable solids. A well-operated primary sedimentation tank can remove around 90% - 95% of settleable solids. There will also be a reduction in total suspended solids and a slight reduction in BOD5. Recall that settleable solids are the large solids in the wastewater and are measured by an Imhoff cone in the laboratory. The sedimentation process works because these solids are heavier, relative to the wastewater, and will, therefore, settle to the bottom of the tank. These tanks are referred to as Primary Clarifiers or Primary Sedimentation Basins. A clarifier is a tank or basin where the sedimentation process will occur. The rate at which the solids will settle is determined by Stokes Law, which takes into account the size of the solid particle, the specific gravity of the particle, and the specific gravity of the liquid. Specific gravity is a unitless number and is a measure of density relative to a reference liquid. For this book when talking about specific gravity, we will assume water is the reference liquid and it has a specific gravity of 1. When determining how quickly solids will settle in the sedimentation tank, the specific gravity of the solids will be a significant factor. If the solids have a specific gravity less than 1, they will not settle at all, in fact, they will float on the water. If the specific gravity is only slightly greater than one, the solids will settle but at a much slower rate than another particle with a larger specific gravity. This is fairly intuitive. Clearly the heavier the solids the quicker they will settle. Another phenomenon that occurs in the sedimentation process is that as the solids collect at the bottom of the tank, the weight of the solids begin to compact and compress. This causes the solids to be thickened and have slightly less water content. Detention time, or how long the wastewater takes to travel through the tank, is a critical design parameter of primary sedimentation tanks. There needs to be enough time to allow the solids to settle but not so much time that the solids start to decompose. Decomposition will cause gas bubbles to form which can hinder solids settling and create foul odors. Primary sedimentation tanks can either be circular or rectangular. Regardless of the configuration, the tanks will have similar components. At the inlet structure where the wastewater enters the tank, the velocity is typically high in order to prevent solids settling in the piping network as the wastewater comes from the preliminary unit process to the primary tank. Once in the primary tank, the velocity must be slowed. To accomplish this there will be some type of diffuser at the inlet end that will redirect flow and prevent short-circuiting. The dimensions of the primary sedimentation tank must be able to accommodate the flow of wastewater but must also reduce the velocity. Flotation As discussed earlier, the specific gravity of the material in the wastewater will determine how it interacts with the wastewater in the sedimentation tank. In addition to settling solids, primary tanks will also remove floatables. Typically, these floatables are classified as fats, oils, and grease (FOG). The specific gravity of these materials is less than 1 so they will rise to the top of the sedimentation tank and be removed. A rectangular primary tank will have flights that span the width of the tank. They are connected by a chain that is motor driven to slowly move with the flow of wastewater. The flights provide several functions. They prevent short-circuiting of material on the surface, they convey the FOG on the surface to a collection trough at the end of the tank, and they convey the settled solids to a hopper at the beginning of the tank. Circular tanks have a similar mechanism called a swing arm that provides the same functions. Sludge Removal Once the solids have settled to the bottom of the tank, they are conveyed to a hopper in the tank. Circular tanks are typically coned at the bottom so the solids build up in the center. Rectangular tanks have a hopper at the front of the tank and the flights convey the solids there. The solids must be removed from the tank periodically so they do not cause adverse conditions. There is organic matter in the solids and if it starts to decompose, it will create foul odors and gas bubbles that will hinder other solids from settling. Typically incoming wastewater is around 1% solids. Due to the sedimentation process, the percent solids concentration increases to around 4% to 8%. Due to the high amounts of solids, a standard pump cannot be used. Instead, special pumps including a progressive cavity type pump or a stator/rotor pump are commonly used. The stator/rotor pump has a stationary part, the stator, and a rotating element, the rotor. Both have a corkscrew type shape and the rotor moves within the stator. As it rotates, it is passing the mixture of solids and water progressively through the pump. These pumps are designed to be able to handle the abrasive nature of the solids and not clog up. The solids are sent to an anaerobic digester where they are further treated and stabilized. Eventually, they will be dewatered and sent to a landfill for disposal. Chemical Addition To further enhance the sedimentation process, chemicals can be added. These chemicals will adhere to the solids and increase their specific gravity. With a higher specific gravity, the solids will settle more quickly. This can either be done to increase the amounts of solids and BOD5 or can be used to achieve average results in a smaller footprint. This process is referred to as chemically enhanced primary treatment (CEPT). Typically, ferrous or ferric chloride is used as the chemical aide. Other chemicals such as polymers may also be used. Polymers make the solids clump together which subsequently results in quicker settling in the sedimentation tank. This process is not used as often anymore due to increasing regulatory requirements. Early in the wastewater industry, a treatment plant could have removed enough solids and BOD5 using the CEPT process. But as regulations became more stringent, many utilities upgraded to secondary treatment systems. This secondary biological treatment process is dependent on the BOD5. If too much is removed in the primary process, it will adversely affect treatment.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.05%3A_Primary_Treatment.txt

Learning Outcomes • Describe different methods to biologically treat wastewater • Examine what target contaminants are being removed by the different biological processes • Compare and contrast different biological processes and the type of bacteria and environmental conditions needed Aerobic, Anaerobic, and Facultative Organisms Aerobic bacteria require an environment that has free dissolved oxygen. The bacteria use that oxygen for respiration to live. They feed on the organic matter and other nutrients in the wastewater. As the bacteria consume these materials, they are removed from the wastewater, making it less contaminated. The byproduct of the aerobic decomposition of organic matter is carbon dioxide (\(\ce{CO2}\)). Anaerobic bacteria require an environment that has no free or combined oxygen. Free oxygen is when there is excess oxygen dissolved in the water and is available as O2. Combined oxygen is when the oxygen molecule is bound to another element. Common examples of combined oxygen in wastewater is nitrate (NO3). In anaerobic conditions, there is absolutely no oxygen available to the bacteria for respiration. Anaerobic bacteria have more sophisticated means of respiration by using other chemical reactions instead of using oxygen directly. However, similar to aerobic bacteria, when anaerobic bacteria breakdown the chemicals in wastewater for respiration and feed off other organics, they subsequently remove the contaminants from the wastewater. The byproduct of anaerobic decomposition is methane gas. Facultative bacteria have the ability to thrive in either aerobic or anaerobic conditions. While they prefer aerobic conditions, they have the ability to adapt when no oxygen is available and survive in anaerobic conditions. Stabilization Ponds Stabilization ponds are a simple way to reduce the amount of organic material in wastewater and require low maintenance. However, they require a lot of land and are mainly used for smaller rural communities. The concept of ponds is pretty simple. You have a large pond filled with wastewater. The size of the pond allows for a very long detention time. The pond creates an ecosystem for bacteria to thrive and those bacteria breakdown the organic matter. Since the detention time is very long, typically 45 days or longer, solids will also settle to the bottom and be removed from the effluent. Eventually, the solids will have to be removed but a well-operated pond can go a few decades before that is needed to be done. As discussed earlier there are several different types of ponds depending on what type of bacteria are expected to be prevalent. Aerobic ponds utilize aerobic bacteria and require oxygen. These ponds are typically more shallow, around 2ft to 5ft, since the oxygen is provided by the atmosphere and algae that is produced on the surface of the pond. Ponds have a complex relationship between how much dissolved oxygen is available to the bacteria. This is driven by sunlight over a 24-hour period and photosynthesis. Photosynthesis is where plants such as algae use sunlight and carbon dioxide (CO2) to thrive. During the day when there is plenty of sunlight, the algae will utilize the CO2 in the water and produce oxygen. This will cause the pH in the pond to decrease and the dissolved oxygen concentration to increase. This is a good thing because, in an aerobic pond, the bacteria need oxygen to live and breakdown the organic waste. During the night when the sun goes down, the reverse happens. Without sunlight, photosynthesis is reduced and the algae will utilize the oxygen and produce CO2. This causes the pH to increase and the dissolved oxygen will decrease. Because sunlight is an important factor in pond performance, there will also be seasonal variations in addition to daily fluctuations. During the winter when the sun isn’t as prevalent, the amount of oxygen produced via algae and photosynthesis will be reduced. If more oxygen is required than what can be produced naturally, it can be provided by mechanical means. Surface aerators and a mixing system can be installed. However, the mechanical systems in these aerated ponds will require more maintenance. They will also require more electricity to run the aeration equipment. Anaerobic ponds utilize anaerobic bacteria which require no oxygen. To create this environment in a pond system, the depth is increased. Typically depths can range from 6 ft to 16 ft. At these increased depths, oxygen from the atmosphere is unable to penetrate the water, and a no oxygen environment, ideal for the anaerobic bacteria to thrive, is created. In these types of ponds, the bacteria are breaking down the more complex solids and organics that are found in the wastewater. It can provide sufficient removal of nitrogen, phosphorus, and BOD5. The solids are further stabilized, broken down, and collected as sludge at the bottom of the pond. Like the aerobic ponds, these solids will eventually need to be removed. Facultative ponds are a mix of aerobic and anaerobic ponds. Their depth is on the order of 3ft to 8ft. Recall, that facultative bacteria can switch from living in anaerobic conditions to aerobic conditions. This can be useful during seasonal variations where little oxygen is available. The facultative bacteria can then focus on breaking down organics by anaerobic decomposition. When sufficient oxygen is available they will switch mechanisms and break down the organic matter by aerobic decomposition. Pond Performance To improve pond performance, it is very common to have multiple types of ponds in series. Anaerobic ponds can handle higher influent BOD5 loading, so they would be the first pond. Then a facultative pond would follow, where further BOD5 reduction is achieved. Lastly would be an aerobic pond that would reduce organic wastes and remove pathogenic organisms. Pond performance is going to be dependent on the loading of organic wastes and detention time. Typically a max of 30lbs of BOD5/day/acre is the desired loading rate. However, ponds are able to handle fluctuations if loading rates are exceeded for short periods of time. The wastewater must remain in the pond long enough so the bacteria can come in contact with the organic matter and consume it. Anaerobic ponds will maintain a detention time of 1 to 7 days. Facultative ponds have a detention time of 5 to 30 days and aerobic ponds are usually 30 days or greater.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.06%3A_Biological_Treatment_Overview.txt

Learning Outcomes • Describe different methods to biologically treat wastewater • Compare and contrast fixed film treatment methods with other biological treatment methods • Understand the operation of a trickling filter and how to control it Fixed Film Processes A fixed film treatment process is still a biological treatment method and utilizes the same type of bacteria as discussed in Chapter 6. The difference is that instead of the bacteria floating near the bottom of a pond, they are fixed to some type of medium. The media can either be natural stone, synthetic plastics, or large rotating disks. Rotating Biological Contactors Rotating biological contactors (RBCs) utilize aerobic bacteria to decompose the incoming BOD5. They are composed of a series of closely spaced circular disks. The disks are connected to a shaft that is coupled to a motor. The set of disks lay horizontally in a tank and rotate at a slow speed. The incoming wastewater enters the tank and submerges approximately 40% of the disks. The water moves through the tank and comes in contact with the aerobic bacteria that are growing on the disks. When the disks are submerged in the wastewater, the bacteria have access to the BOD5 and will consume it. As the disks rotate out of the liquid in the tank, they are exposed to the atmosphere where the bacteria can utilize oxygen for the aerobic decomposition of the BOD5. The disks are typically 12 feet in diameter and multiple disks are combined together to make a long cylinder. Common lengths are 25 feet. The motor spins the disks at approximately 1.5 rpm. It’s not uncommon to see multiple RBCs being used in both parallel and series configurations. As the bacteria thrive in this environment, eventually they will build up on the disks and start to slough off. The effluent of the RBC is sent to a finishing pond or clarifier to further treat these solids. Each of the RBCs is covered for several reasons. Disks are commonly made out of plastic so covers will protect the disks from becoming brittle due to sun damage. Foul odors from the wastewater and H2S gasses will be present in the RBCs. Covering them will reduce these odors and prevent nuisance complaints from the community. Lastly, covers will protect the bacteria from being washed off the disks during rain events. Fiberglass covers are commonly used and are more cost-effective than building the RBCs in a building. The humidity and wastewater gases can be corrosive to cement, metals, and other building materials. Trickling Filters Trickling filters are another form of fixed film biological treatment. They are comprised of circular tanks filled with stone, lava rock, ceramic, or synthetic material all of which are referred to as media. Standard media is approximately 1 inch to 4 inches in diameter. The bacteria will become fixed to this media and aerobic decomposition will occur as the incoming wastewater comes in contact with the bacteria. While trickling filters can be relatively deep, around 3 to 8 feet, there is ample airflow in the voids of the media to allow for aerobic bacteria to thrive. Trickling filters often have ventilation ports near the bottom to ensure there is sufficient airflow to the bacteria. The wastewater enters the trickling filter at the top of the filter. Then gravity takes over and the wastewater trickles down through the media to the bottom of the tank where it is captured in an underdrain system. The wastewater is conveyed from the primary sedimentation tanks to the trickling filters. This is either done by gravity or by using a pump. Either way, a trickling filter uses this pressure in the water to evenly distribute the wastewater to the trickling filter. There is a distributor arm that expands the diameter of the circular tank. The wastewater is forced out through small outlets on the distributor arm that will cause the arm to rotate. The wastewater trickles through the media and comes in contact with the bacteria fixed to media. The bacteria are now in a sufficient environment where aerobic decomposition will occur and reduce the BOD5 of the wastewater. Over time the bacteria will build up on the media and eventually will fall or slough off. These solids will be captured in the underdrain system and sent to the secondary clarifier. In the clarifier, sedimentation will occur and the solids will settle to the bottom of the clarifier and be removed. Recirculation Recirculation of the clarified effluent is a key operational component of a trickling filter. Water from the secondary clarifiers has already gone through the biological treatment process of the trickling filter and has a lower amount of BOD5. By recirculating this treated water with the incoming wastewater, it will dilute the incoming BOD5. Recirculation will also be able to control the dissolved oxygen level in the trickling filters. Increasing the recirculation rate will cause the dissolved oxygen to increase and lowering the recirculation rate will cause it to decrease. An optimal concentration of dissolved oxygen in the trickling filter is 1.5 mg/L to 2.0 mg/L. Organic Loading Trickling filters can be further classified by how much BOD5 is being sent to the treatment unit. Low rate trickling filters receive up to 25 lbs of BOD5/1000 cubic feet/day. At this lower organic load, an operator can expect to achieve 80% - 90% BOD5 removal. Intermediate filters can handle up to 40 lbs of BOD5/1000 cubic feet/day but will see lower removal efficiencies of BOD5. High rate and roughing filters will have BOD5 loading in excess of 50 lbs of BOD5/1000 cubic feet/day. At these higher loadings, BOD5 removal significantly drops and will not meet current regulatory requirements. High rate and roughing filters are often used as a preliminary step and are combined with other forms of treatment to ensure regulatory compliance is achieved.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.07%3A_Biological_Treatment_Methods.txt

Learning Outcomes • Compare and contrast the difference between fixed film and suspended growth biological treatment systems • Describe how the activated sludge process can more efficiently reduce organic wastes • Understand how different process control strategies work in an activated sludge system • Examine how a secondary clarifier is utilized in an activated sludge system Suspended Growth Processes Unlike the fixed film biological systems discussed in Chapter 7, activated sludge uses a suspended growth process. This means that there is no media for the bacteria to become fixed to. The microorganisms are suspended in the tanks either by a mixer or air diffusers and are then mixed in with the incoming wastewater. This mixture of wastewater and microorganisms is referred to as the Mixed Liquor Suspended Solids (MLSS). A sample can be taken from the activated sludge system and analyzed in a laboratory to determine how many mg/L there are of MLSS in the system. This laboratory result will be a critical design and operational parameter that will need to be continually monitored to ensure effective treatment. Activated Sludge Treatment The activated sludge process was developed by two scientists, Edward Arden and William Lockett, in England in 1914. Their experiments showed that by taking the microorganisms that were already established from aerobic decomposition and introducing them to fresh wastewater, it would speed up the decomposition of the new organic wastes. Instead of relying on the 30 to 45 days that it would normally take to breakdown these organic wastes, the activated sludge process can achieve the same level of treatment in less than one day. This means that an activated sludge wastewater treatment system will be able to handle higher flow rates and higher organic loading than pond treatment or fixed film systems. To achieve this on a large scale, conventional activated sludge systems are comprised of an aeration tank followed by a secondary clarifier. In the secondary clarifier, the microorganisms will separate from the now treated wastewater. A majority of those microorganisms will be returned back to the reactor and are now activated to treat more of the incoming wastewater. In the aeration tanks, the bacteria are in an environment with dissolved oxygen readily available and organic matter to consume. Like the other biological processes, this is how the reduction of BOD5 occurs, through aerobic decomposition. What makes activated sludge unique is that in the secondary clarifier, the bacteria become stressed because their food source has been drastically decreased and there is no more dissolved oxygen. They begin to go through endogenous respiration. The bacteria basically become so starved that they begin to breakdown their own cellular structure. Before the bacteria completely cannibalize themselves, they are sent back to the aeration tank where they are re-introduced to readily available dissolved oxygen and organic matter. The starved bacteria are then able to rapidly re-start aerobic decomposition and quickly reduce the BOD5 in the wastewater. Food to Microorganism Ratio A key parameter to determine the effectiveness of activated sludge systems is the food to microorganism ratio, or F/M. The food is determined by the amount of BOD5 in the incoming wastewater and the amount of microorganisms available to consume that food is determined by the amount of MLSS in the aeration tanks. Since it’s a ratio, the units of these two laboratory results must be the same. The mg/L concentration of the laboratory results is converted into a mass with the units of lbs. While each treatment plant will determine which level of F/M has historically given effective treatment, a common range is around 0.2 to 0.5. Return Activated Sludge The return activated sludge, or RAS, are the bacteria that have settled in the secondary clarifier and are being sent back to the aeration tank. The rate of speed at which the microorganisms are returned is something that the operator can control. Waste Activated Sludge (WAS) Like the other biological process discussed, the bacteria, overtime will grow and their population will increase. To control the amount of bacteria in the system, a portion of the RAS will not be returned to the aeration tank but instead is directed to a separate solids handling treatment unit. Typically, these solids are combined with the settled solids from the primary sedimentation tanks and sent to an anaerobic digester. After anaerobic digestions, the solids will be dewatered and ultimately sent to a landfill for disposal. How much bacteria remains in the system and how much is wasted can be determined by the mean cell residence time or MCRT. The MCRT is a theoretical calculation of the average time a single bacteria will stay within the activated sludge system before being wasted. To calculate the MCRT an operator would determine how many pounds of MLSS there is in the system and divide that by how many pounds were removed from the system. Process Control The F/M ratio, MCRT, RAS, WAS, and dissolved oxygen concentrations can all be manipulated by the operators of a wastewater treatment facility to optimize the effectiveness of treatment. In fact, those parameters are the only things that can be easily controlled. The amount of incoming wastewater is going to be what it is and it will fluctuate throughout a 24 hour period as well as vary by season. The incoming BOD5 loading is what it’s going to be and the operators can’t control it. If the F/M is too low, it means that there are more bacteria than what is needed to consume the available food. This is inefficient because supplying oxygen to the bacteria requires a significant amount of energy. If there is too much bacteria in the system and not enough food, the bacteria will still be consuming oxygen but the BOD5 won’t be further reduced. To increase the F/M ratio operators can only control the “M” portion of the equation. By increasing the wasting rate, the MLSS will be reduced causing the F/M ratio to increase. If the F/M ratio is high, then there is not enough bacteria to consume the large amounts of incoming BOD5. This will lead to poor treatment and the effluent will have a high BOD5 concentration. Operators cannot decrease the amount of BOD5 coming into the plant so they will have to increase the amount of MLSS in the system. They can do this by decreasing or stopping the wasting rate. Decreasing the wasting rate will cause the MLSS to increase and the F/M ratio will be reduced. The MCRT is another process control tool that is used to determine the wasting rate by manipulating the equation to calculate the MCRT. Often the desired MCRT rate is determined by the design of the treatment facility or from historical data. By taking the pounds of MLSS in the system and dividing it by the desired MCRT, you will determine what the wasting rate needs to be to achieve that MCRT. However, the MCRT and F/M methods for determining the wasting rate can often conflict with each other. Operators need to look at the changes in MCRT and F/M over time and make minor adjustments to the process so the bacteria aren’t “shocked”. Alternative Process Configurations There are many different types of process configurations of activated sludge systems that differ by how the wastewater enters the aeration tanks. A plug flow reactor has all of the wastewater and RAS entering at the beginning of the tank. This will have a large organic loading at the beginning of the tank and as the wastewater moves through the tank, the load will lessen. Often, tapered aeration will be used in plug flow reactors. Tapered aeration will have lots of air diffusers at the beginning of the tank so more oxygen is available to the bacteria to handle the increased organic loading. As the wastewater flows through and the BOD5 is reduced, the air diffusers are also reduced. An alternative is a step feed reactor where the incoming wastewater is split and sent to different portions of the tank. For example, 25% of the flow is sent to the first ¼ of the tank, another 25% to the second ¼ of the tank, and so on. This allows for a more even distribution of the organic loading as well as a more uniform demand for the air diffusers. Typically, a steep feed system will use less air overall than a plug flow reactor. Secondary Clarification A secondary clarifier is a key component of the activated sludge system. Not only does it separate out the microorganisms from the now treated wastewater, but it will also concentrate them through the sedimentation process. A secondary clarifier works exactly as discussed previously in primary sedimentation. The only difference is that in a primary sedimentation tank the main goal is to remove unwanted solids. In a secondary sedimentation (or clarifier) tank, the goal is to concentrate the MLSS so it can be returned to the aeration tanks. How the biomass is settling in the clarifier can be difficult to see in real-time as the tanks are typically below-grade and made of concrete. A “sludge judge” is used to determine how many feet of MLSS are settled on the bottom and how much clear water there is on top. The tool is simply a clear PVC pipe with a ball check valve at the bottom. As the pipe is inserted into the water, the ball check valve opens, letting liquid in. When the stick hits the bottom, the operator will pull the PVC pipe out of the water forcing the ball check to close producing a cross-sectional sample of MLSS on the bottom and clear water on top. There are markings on the PVC pipe for every foot. So as the operator pulls it out of the clarifier, they can see where the clear water stops and where the MLSS is settling. Typically a sludge blanket of 1 to 3 feet on the bottom of the clarifier is optimal. The settleability of the MLSS can also be seen in the laboratory by taking a sample of the MLSS and putting it into a 1000 mL beaker. After 30-minutes have gone by, the graduations of where the MLSS has settled will be recorded. Dividing the settled sludge volume in mLl/L, dividing by the MLSS in mg/L, and multiplying by 1,000 mg/g will yield the Sludge Volume Index (SVI) in mL/g. The SVI is utilized to gauge how well the MLSS will settle in the clarifier and will also shed light on how the activated sludge plant is operating. Typical SVI is around 100 to 200 mL/g. Less than 100 mL/g will often show rapid settling of the sludge in the clarifier. When the MLSS settles too quickly, smaller “pin floc” particles will remain suspended in the middle of the clarifier. This will also be seen in the sludge judge test where there is clear water on top of the sludge judge, murky water in the middle, and darker solids on the bottom. This is usually caused by having a higher MCRT. An SVI greater than 200 mL/g will have sludge settling very slowly in the clarifier. This can be caused by having a low MCRT. The water leaving the secondary clarifier has now gone through all of the previous treatment steps from preliminary screening, to primary sedimentation, and activated sludge treatment. In some areas with less stringent regulations, this water is clean enough to be discharged to the ocean or a nearby waterbody. However, some additional treatment like filtration and disinfection may be needed to meet regulatory compliance. Also, the solids that were removed from the primary and secondary process will still need to be treated and disposed of.

textbooks/workforce/Water_Systems_Technology/Water_160%3A_Wastewater_Treatment_and_Disposal_I_(Steffen)/1.08%3A_Activated_Sludge.txt

Learning Outcomes • Describe the difference between wastewater, stormwater, and combined collection systems • Understand the general treatment process of wastewater • Compare and contrast the different stages of wastewater treatment Wastewater Collection The wastewater collection system is the network of pipes that convey the wastewater from households and business to a wastewater treatment facility. Each customer will have a lateral connected to the main sewer lines. In order to keep sediment from settling out in the collection system and causing a blockage, the pipe is sloped to ensure a velocity of 2 ft/sec. A majority of the system will utilize the slope of the pipe and gravity so the water travels downhill. However, that is not always feasible and when needed a lift station will be installed. The lift station is comprised of a wet well where the wastewater is collected and pumps the water to a higher elevation where it can then resume to flow by gravity. The portion of the pressure pipe that is connected to the lift station is called a force main. The force main is always under pressure and the wastewater completely fills the pipe. Where a gravity sewer has minimal pressure and under normal conditions only about ⅓ of the pipe is filled with wastewater. There are three different types of sewer systems; sanitary, stormwater, and combined. Sanitary sewer systems only convey wastewater that was derived from sanitary sources. This includes wastewater from household toilets, showers, and dishwashers, as well as industrial sources of wastewater from manufacturing processes. Sanitary sewers differ from stormwater sewers in that they contain fecal matter from human waste. It’s paramount that these wastes are conveyed to a wastewater treatment facility so they can be removed and stabilized to protect public health and the environment. Stormwater sewers are a network of pipes that collect only stormwater runoff and direct the flow to a nearby waterbody or the ocean. While stormwater does have a direct connection to human or animal waste, it is considered less harmful and can be discharged without treatment. However, it’s important to understand that stormwater is by no means “fresh water”. Stormwater can have large amounts of trash, plant material, silt gravel, oil & grease. There are even fairly high amounts of harmful bacteria from animal wastes. The theory is that during storm events there is a significant amount of water flowing through these systems that these contaminants become diluted and are not as concentrated. This theory is constantly being challenged and stormwater is now being seen as another water source that can be treated and even beneficially reused. A combined sewer is a network of pipes that conveys both sanitary wastes as well as stormwater. This can be beneficial during dry weather flows where there is minimal stormwater. The stormwater that does exist is sent to a wastewater treatment facility where harmful contaminants are removed prior to discharge to a waterbody. However, combined sewer systems can be overwhelmed during storm events. Systems that have older infrastructure which has not been upgraded to deal with larger populations and storm events are especially vulnerable. When this happens, instead of only diluted stormwater being sent to a waterbody, sewage containing high amounts of fecal matter from the sanitary sewer is also discharged. This can cause increased pollution to the waterbody. Preliminary Treatment Preliminary treatment is the first step in treating raw wastewater. When the wastewater first enters the wastewater treatment facility there are a lot of nuisance materials that have found their way into the collection system. Items such as large rags, bottles, tree branches, and numerous other nuisance items can be found in the influent to the treatment facility. These large items can cause damage to downstream pumps, take up valuable space in settling tanks, and can be hazardous to other mechanical equipment needed in the treatment process. So the first, or preliminary step is to remove these large items. Methods used in preliminary treatment include screening, communition, and grit removal. A wastewater treatment facility may use one or all of these methods to handle the large items that may enter the treatment facility. Bar screens are capable of removing items that are larger than the spacing between the bars. For example, a ¾” bar screen will hold back any debris that is larger than ¾” and anything smaller will pass through it. Common items that are removed in this preliminary treatment step are rags, roots, large rocks and aggregate, bottles, cans, and numerous other large objects that can make their way into the wastewater collection system. An alternative to screen these large debris items is to shred or grind them. A comminutor is a device that sits inside the channel where wastewater is flowing into the treatment facility. The comminutor will grind the large debris items, turning them into smaller items. Communitors are designed to produce a solid size of a certain diameter. By breaking up the debris into smaller diameters, the downstream pumps and equipment will not be as impacted. Smaller inorganic solids, such as coffee grounds, eggshells, sand, silt, and gravel are collectively called grit. Grit must be removed because it will cause excessive wear on plant equipment such as the impeller of a pump. Also, this inorganic material can settle in the subsequent treatment process and take up valuable space in tanks which decreases plant efficiency and can inhibit further treatment. While most gritty materials are inorganic, large organic solids such as corn kernels and other food waste may also be removed. There are several methods in removing grit. One common method is an aerated grit chamber. Aerated grit chambers will have air piped to diffusers at the bottom of the tank. The addition of air in the tank creates a rolling action of solids which helps keep the lighter organic solids in suspension while the heavier grit material is directed to the bottom of the tank. In aerated grit chambers, the amount of air sent to the chamber is a critical operating parameter. If too much air is supplied, then the grit material will stay in suspension and not be removed. If not enough air is supplied, then the lighter organic material can settle out. Primary Treatment The primary goal of sedimentation is to remove the settleable solids. A well-operated primary sedimentation tank can remove around 90% - 95% of settleable solids. There will also be a reduction in total suspended solids and a slight reduction in BOD5. The sedimentation process works because these solids are heavier, relative to the wastewater, and will, therefore, settle to the bottom of the tank. Another phenomenon that occurs in the sedimentation process is that as the solids collect at the bottom of the tank, the weight of the solids begin to compact and compress. This causes the solids to be thickened and have slightly less water content. Detention time, or how long the wastewater takes to travel through the tank, is a critical design parameter of primary sedimentation tanks. There needs to be enough time to allow the solids to settle but not so much time that the solids start to decompose. Decomposition will cause gas bubbles to form which can hinder solids settling and create foul odors. Primary sedimentation tanks can either be circular or rectangular. Regardless of the configuration, the tanks will have similar components. At the inlet structure where the wastewater enters the tank, the velocity is typically high in order to prevent solids settling in the piping network as the wastewater comes from the preliminary unit process to the primary tank. Once in the primary tank, the velocity must be slowed. To accomplish this there will be some type of diffuser at the inlet end that will redirect flow and prevent short-circuiting. The dimensions of the primary sedimentation tank must be able to accommodate the flow of wastewater but must also reduce the velocity. In addition to settling solids, primary tanks will also remove floatables. Typically, these floatables are classified as fats, oils, and grease (FOG). A rectangular primary tank will have flights that span the width of the tank. They are connected by a chain that is motor driven to slowly move with the flow of wastewater. The flights provide several functions. They prevent short-circuiting of material on the surface, they convey the FOG on the surface to a collection trough at the end of the tank, and they convey the settled solids to a hopper at the beginning of the tank. Circular tanks have a similar mechanism called a swing arm that provides the same functions. Once the solids have settled to the bottom of the tank, they are conveyed to a hopper in the tank. Circular tanks are typically coned at the bottom so the solids build up in the center. Rectangular tanks have a hopper at the front of the tank and the flights convey the solids there. The solids must be removed from the tank periodically so they do not cause adverse conditions. There is organic matter in the solids and if it starts to decompose, it will create foul odors and gas bubbles that will hinder other solids from settling. Typically incoming wastewater is around 1% solids. Due to the sedimentation process, the percent solids concentration in the sedimentation tanks increases to around 4% to 8%. Due to the high amounts of solids, a standard pump cannot be used. Instead, special pumps including a progressive cavity type pump or a stator/rotor pump are commonly used. Secondary Treatment Secondary treatment methods typically involved some form of biological treatment to further reduce the amount of BOD5. Trickling filters and activated sludge treatment plants will utilize a secondary clarifier to separate the treated wastewater from the microorganisms of the biological treatment step. A key component of a trickling filter is the recirculation of the clarified effluent back to the trickling filter. Water from the secondary clarifiers has already gone through the biological treatment process of the trickling filter and has a lower amount of BOD5. By recirculating this treated water with the incoming wastewater, it will dilute the incoming BOD5. Recirculation will also be able to control the dissolved oxygen level in the trickling filters. A secondary clarifier is also a key component of the activated sludge system. Not only does it separate out the microorganisms from the now treated wastewater, but it will also concentrate them through the sedimentation process. A secondary clarifier works exactly as discussed previously in primary sedimentation. The only difference is that in a primary sedimentation tank the main goal is to remove unwanted solids. In a secondary sedimentation tank, the goal is to concentrate the Mixed Liquor Suspended Solids(MLSS) so it can be returned to the aeration tanks.

textbooks/workforce/Water_Systems_Technology/Water_161%3A_Wastewater_Treatment_and_Disposal_II_(Steffen)/1.01%3A_Conventional_Treatment_Review.txt

Learning Outcomes • Understand which environments the different types of bacteria thrive • Explain how activated sludge treatment process is more efficient than other methods • Describe the nitrogen cycle and how it’s used to remove nitrogen from wastewater Aerobic, Facultative, and Anaerobic Organisms Aerobic bacteria require an environment that has free dissolved oxygen. The bacteria use that oxygen for respiration to live. They feed on the organic matter and other nutrients in the wastewater. As the bacteria consume these materials, they are removed from the wastewater, making it less contaminated. The byproduct of the aerobic decomposition of organic matter is carbon dioxide (CO2). Anaerobic bacteria require an environment that has no free or combined oxygen. Free oxygen is when there is excess oxygen dissolved in the water and is available as O2. Combined oxygen is when the oxygen molecule is bound to another element. A common example of combined oxygen in wastewater is nitrate (NO3). In anaerobic conditions, there is absolutely no oxygen available to the bacteria for respiration. The byproduct of anaerobic decomposition is methane gas. Facultative bacteria have the ability to thrive in either aerobic or anaerobic conditions. While they prefer aerobic conditions, they have the ability to adapt when no oxygen is available and survive in anaerobic conditions. Activated Sludge Treatment The activated sludge process was developed by two scientists, Edward Arden and William Lockett, in England in 1914. Their experiments showed that by taking the microorganisms that were already established from aerobic decomposition and introducing them to fresh wastewater, it would speed up the decomposition of the new organic wastes. Instead of relying on the 30 to 45 days it would normally take to breakdown these organic wastes, the activated sludge process can achieve the same level of treatment in less than one day. This means that an activated sludge wastewater treatment system will be able to handle higher flow rates and higher organic loading than pond treatment or fixed film systems. Activated sludge treatment systems consist of an aeration tank followed by a secondary clarifier. These two tanks each provide a unique function but also work together to reduce the BOD5 in the wastewater. In the aeration tanks, oxygen is diffused into the water so the bacteria can survive in aerobic conditions. The air diffusers also keep the bacteria in suspension so it can continually be in contact with the incoming wastewater. In the secondary clarifiers, the bacteria will be separated from the treated wastewater. The treated wastewater will continue on to the tertiary treatment step. A majority of the settled bacteria will be sent back to the beginning of the aeration tanks. In the clarifier, the bacteria were stressed due to a lack of food and oxygen. They begin to undergo endogenous respiration and are so starved they begin to breakdown their own cells to survive. When the stressed bacteria are reintroduced into the aeration tanks they are now in an environment with plenty of oxygen and food. These bacteria will now quickly begin to breakdown the organic wastes in the wastewater much faster than before. Return Activated Sludge The return activated sludge, or RAS, are the bacteria that have settled in the secondary clarifier and are being sent back to the aeration tank. The rate of speed at which the microorganisms are returned is something that the operator can control. Waste Activated Sludge Like the other biological process discussed, the bacteria, overtime will grow and their population will increase. To control the amount of bacteria in the system, a portion of the RAS will not be returned to the aeration tank but instead is directed to a separate solids handling treatment unit. Typically, these solids are combined with the settled solids from the primary sedimentation tanks and sent to an anaerobic digester. Food to Microorganism Ratio A key parameter to determine the effectiveness of activated sludge systems is the food to microorganism ratio, or F/M. The food is determined by the amount of BOD5 in the incoming wastewater and the amount of microorganisms available to consume that food is determined by the amount of MLSS in the aeration tanks. Since it’s a ratio, the units of these two laboratory results must be the same. The mg/L concentration of the laboratory results is converted into a mass with the units of lbs. While each treatment plant will determine which level of F/M has historically given effective treatment, a common range is around 0.2 to 0.5. Mean Cell Residence Time How much bacteria remains in the system and how much is wasted can be determined by the mean cell residence time or MCRT. The MCRT is a theoretical calculation of the average time a single bacteria will stay within the activated sludge system before being wasted. To calculate the MCRT an operator would determine how many pounds of MLSS there is in the system and divide that by how many pounds were removed from the system; typically over a 24 hour period. Review of Basic Principles of Operation The F/M ratio, MCRT, RAS, WAS, and dissolved oxygen concentrations can all be manipulated by the operators of a wastewater treatment facility to optimize the effectiveness of treatment. In fact, those parameters are the only things that can be easily controlled. The amount of incoming wastewater is going to be what it is and it will fluctuate throughout a 24 hour period as well as vary by season. The incoming BOD5 loading is what it’s going to be and the operators can’t control it. If the F/M is too low, it means that there are more bacteria than what is needed to consume the available food. This is inefficient because supplying oxygen to the bacteria requires a significant amount of energy. If there is too much bacteria in the system and not enough food, the bacteria will still be consuming oxygen but the BOD5 won’t be further reduced. To increase the F/M ratio operators can only control the “M” portion of the equation. By increasing the wasting rate, the MLSS will be reduced causing the F/M ratio to increase. If the F/M ratio is high, then there is not enough bacteria to consume the large amounts of incoming BOD5. This will lead to poor treatment and the effluent will have a high BOD5 concentration. Operators cannot decrease the amount of BOD5 coming into the plant so they will have to increase the amount of MLSS in the system. They can do this by decreasing or stopping the wasting rate. Decreasing the wasting rate will cause the MLSS to increase and the F/M ratio will be reduced. The MCRT is another process control tool that is used to determine the wasting rate by manipulating the equation to calculate the MCRT. Often the desired MCRT rate is determined by the design of the treatment facility or from historical data. By taking the pounds of MLSS in the system and dividing it by the desired MCRT, you will determine what the wasting rate needs to be to achieve that MCRT. However, the MCRT and F/M methods for determining the wasting rate can often conflict with each other. Operators need to look at the changes in MCRT and F/M over time and make minor adjustments to the process so the bacteria aren’t “shocked”. Toxic Substances Toxic substances can be detrimental to the efficacy of activated sludge systems. Activated sludge treatment relies on living bacteria to feed off the organic wastes, thus removing it from the wastewater. If toxic substances are introduced to the activated sludge system, the bacteria can die off. Without a significant population of bacteria, the organic wastes will not be consumed and the effluent of the treatment plant will have high amounts of BOD5. Toxic substances can include heavy metals, pesticides, high concentrations of salts, cyanide, PCBs, and other chemicals. These toxic substances, if introduced in the wastewater collection system, will be sent to the wastewater treatment facility and can destroy the population of bacteria that treats organic wastes. To prevent toxic substances from entering the collection system, municipalities will have pre-treatment programs. These programs will have a public outreach component to inform the community of its wastewater infrastructure and the harm it can cause if chemicals and other toxic materials are dumped down the drain. In addition to household waste, pre-treatment programs will also work closely with manufacturing and processing facilities to ensure they are not discharging toxic materials into the wastewater collection system. Pure Oxygen Treatment Many treatment plants utilize air blowers or surface aerators to provide oxygen to the bacteria in the aeration tanks. These systems provide oxygen that’s in the atmosphere and diffuses it into the wastewater in the tank. One drawback of these methods is that our atmosphere is only around 21% oxygen. A majority of the atmosphere is nitrogen. Having a pure oxygen system is more efficient because the oxygen concentrations can be as high as 99% pure oxygen. However, there are many drawbacks to pure oxygen plants. First off, extra equipment will be needed to create pure oxygen. This equipment will have electrical, maintenance, and operational costs associated with it. Secondly, pure oxygen can be extremely hazardous to deal with. At higher purities oxygen can be explosive. Extra caution must be taken to ensure no sparks, oil, or other contaminants are near the pure oxygen generators. Enhanced Biological Treatment If the treated wastewater leaving a treatment facility is being discharged into an impaired waterbody, the NPDES permit will most likely have limits on ammonia, nitrogen, and phosphorus. These nutrients at high concentrations can cause eutrophication in a waterbody. Eutrophication occurs when there is an excess of nutrients in a waterbody that spurs algae growth. The algae population will become out of control and consume dissolved oxygen in the waterbody to the point where fish and other aquatic life can not survive. Nitrogen and phosphorus can be removed from the treatment plant by utilizing biological nutrient removal (BNR) processes. Nitrogen Removal Nitrogen can be removed from the wastewater by making slight modifications to the activated sludge treatment process. Nitrogen enters the treatment plant as ammonia (NH3). In the aeration tank, aerobic bacteria will nitrify this ammonia to create nitrite (NO2) and nitrate (NO3). In a well-operated plant, a majority of the nitrogen formed is nitrate. The wastewater is then conveyed to an anoxic tank. Anoxic means that the environment where the bacteria are living contains no free dissolved oxygen but there is combined oxygen. The combined oxygen is due to the NO3 sent to the tank from the aeration tanks. In this anoxic condition facultative bacteria break apart the NO3 bond and use the oxygen for respiration. The nitrogen molecules combine to form nitrogen gas (N2) which is vented back to the atmosphere. Recall that 78% of the Earth’s atmosphere is N2 gas. The anoxic tanks in a BNR system can be placed in a number of different configurations. Since the nitrification process is required first to create the NO3 one would expect to have the anoxic tanks following the aeration tanks. While there are treatment plants that operate in this manner, it may require additional chemicals as the denitrification process requires a certain amount of carbon for the bacteria to feed off of. The amount of carbon available in the wastewater can be measured by the CBOD5 or carbonaceous biochemical oxygen demand. At the end of the aeration tank, the aerobic bacteria have significantly reduced the amount of CBOD5 in the wastewater. A process alternative is having the anoxic tank prior to the aeration tank. The wastewater at the end of the aeration tank that has been nitrified is then recycled back to the anoxic tank. Here, fresh wastewater with high amounts of CBOD5 is mixed with the NO3 and the conditions will be just right for denitrification to occur. This will also lessen the aeration demands since some of the CBOD5 will be reduced in the anoxic tanks before it enters the aeration tank. One drawback is that not all of the nitrate will be captured and sent back to the anoxic tank. Therefore, another process set up is to have alternating zones of anoxic, aerobic, anoxic, aerobic. Phosphorus Phosphorus can also be reduced in a well-operated wastewater treatment facility. The amount of phosphorus coming into the facility will determine the level of treatment required. Much of the phosphorus can be removed during the primary and secondary sedimentation processes. If more phosphorus removal is required then treatment plants can utilize enhanced biological phosphorus removal (EBPR). EBPR uses polyphosphate accumulating bacteria (PAO) that, under anaerobic conditions, will accumulate phosphorus in their cells and remove it from the wastewater. A typical configuration of an EBPR process is the RAS and influent wastewater will be mixed in an anaerobic tank where phosphorus reduction occurs. Then the wastewater enters the anoxic tank where the RAS, influent wastewater, and nitrified effluent from the aeration tanks create the ideal environment for denitrification. Then everything is conveyed to the aeration tanks where free dissolved air is added. The incoming ammonia is nitrified to NO3 and the remaining BOD5 is reduced.

textbooks/workforce/Water_Systems_Technology/Water_161%3A_Wastewater_Treatment_and_Disposal_II_(Steffen)/1.02%3A_Biological_Treatment_Overview.txt

Learning Outcomes • Explain which water quality characteristics tertiary treatment is targeted to remove • Describe the breakpoint chlorination curve • Understand how the mixture of ammonia and chlorine creates chloramines • Compare different methods of wastewater disinfection Filtration After the wastewater leaves the secondary clarifiers, filtration is commonly used to remove fine particles that were carried over in the clarifier. Conventional filtration methods use sand and anthracite coal to filter the treated wastewater. The sand and anthracite coal are referred to as media. The filtration process works by gravity. If needed, the water will be pumped to a higher elevation, then the gravity will force the water through the media. The media creates small voids between the grains of sand and coal. These voids are small enough that water molecules will pass through but the solids will be trapped. Underneath the media, there is an underdrain system that will collect the treated water and convey it to the next treatment process. Eventually, the media will be clogged with solids and needed to be backwashed. During a backwash cycle, the filter is isolated so water is entering the filter. Air is then piped into the filter that agitates the media and separates the solids from the media. The air is then turned off and water is pumped from the bottom of the tank and is directed towards a backwash drain. The media is typically heavier than the solids being removed so the media will settle back to the bottom of the filter while the solids are carried with the water into the backwash drain. When the backwash cycle is complete the filter is put back online. More advanced filtration methods include membrane filtration such as microfiltration and reverse osmosis. These filtration methods work in a similar manner as sand filters but are able to filter smaller sizes. The membranes are manufactured and can have very small pores. Membrane filtration is able to remove contaminants such as arsenic, asbestos, atrazine, fluoride, lead, mercury, nitrate, radium, benzene, and other unwanted chemicals. With the very small micro-holes in the membrane, gravity does not provide enough pressure to force the water through the membrane. Therefore, the water is pumped through the membrane filtration system which increases the pressure. Disinfection Disinfection is a critical treatment step to ensure that the wastewater treatment facility is protecting public health and the environment. Pathogenic organisms, such as E. coli, Vibrio cholerae, and Salmonella, can spread disease to aquatic life and humans. There are other bacteria, microorganisms, and viruses that can be present in wastewater. The disinfection process will limit the presence of pathogens. It’s important to note that the disinfection process is not the same as sterilization. Sterilization will remove all of the bacteria but comes at an extremely high cost that is uneconomical considering the volume of wastewater that must be treated. However, disinfection is still highly effective at limiting pathogens to a level that is acceptable to protect public health and the environment. Chlorination and Chloramination Chlorine is the most common form of disinfectant in the United States and has been in use for over one hundred years in the water and wastewater industry. Chlorine is commercially available as gaseous chlorine or in the liquid form as sodium hypochlorite. Gaseous chlorine is purer, so less gas is needed for disinfection. However, because of the high purity, gaseous chlorine can be very dangerous to work around. Treatment facilities that use gaseous chlorine have to comply with rigorous safety training and purchasing regulations. Sodium hypochlorite is commonly sold with a chlorine concentration of 12.5%. Safety precautions must still be used when handling sodium hypochlorite but is a lot safer and easier to work with than gaseous chlorine. Chlorination works due to the fact that chlorine is highly reactive. When chlorine is added to the wastewater it begins to react with all of the chemicals and organic matter in the wastewater. This is known as demand. Once the chlorine demand is met the extra chlorine added will begin to react with the water creating hypochlorous and hydrochloric acid. Both of these chemicals will be created and the amount of each will depend on the pH of the water. Hypochlorous acid is more efficient at disinfection and is more prominent at lower pH values. Typical wastewater has a pH of around 6.5 - 7.5 and hypochlorous is the predominant acid. If the pH is above 7.5, treatment facilities may look into adding chemicals to reduce the pH to increase the efficacy of disinfection. When operating chlorination in this manner it’s called free chlorine. Enough chlorine has been added to satisfy the demand and the residual is measured as free chlorine. Free chlorine is highly reactive and is a strong disinfectant. Because it’s highly reactive, the residual does not persist for a long time. An alternative to chlorination is chloramination. Chloramination is a combined chlorine compound and is created by mixing chlorine and ammonia. Depending on the ratio of chlorine to ammonia, the chloramines created are monochloramine, dichloramine, and trichloramine. Monochloramine is the desired form as it provides a better disinfectant. A ratio of five parts chlorine to one part ammonia will typically yield monochloramine. Chloramination provides some benefits to chlorination. Less chlorine is used since all of the demand doesn’t have to be met. Free chlorine has the potential of creating disinfection-by-products. Since chloramination is not as reactive, there is less chance of creating disinfection-by-products. One disadvantage of chloramination is that, since it’s not as reactive as free chlorine, it takes a longer time to achieve the same level of disinfection as free chlorine. The relationship between the different chloramines and free chlorine is best understood by examining the breakpoint chlorination curve. In the first part of the breakpoint curve, chlorine is applied but no residual is seen. This is because there is an excess demand for organic matter and other chemicals. Once that initial demand has been met, more chlorine is applied and a combined residual is formed. In this second zone, ammonia begins to react with the chlorine to create chloramines. In this early stage, monochloramine is the predominant form. If the treatment plant is utilizing chloramination, then ammonia will be added to purposefully stay in this zone. As more chlorine is applied, the ratio of chlorine to ammonia increases. In the third zone, the chlorine residual will decrease as the extra chlorine further reacts with the ammonia creating dichloramine and trichloramine. Once the chlorine has reacted with all of the ammonia, it reaches a breakpoint. After the breakpoint, only free chlorine is available. Dechlorination Once the wastewater has been properly disinfected the chlorine residual must be neutralized. Chlorine can be harmful to aquatic life and the environment. Since most wastewater is discharged into a waterbody it must be dechlorinated. There are two common chemicals used for dechlorination, sulfur dioxide, and sodium bisulfite. Sulfur dioxide is available in its gaseous form and has a lot of the same equipment and safety regulations requirements as gaseous chlorine. Therefore, if a treatment plant uses gaseous chlorine for disinfection, it will most likely be using sulfur dioxide for dechlorination. Sodium bisulfite is available in its liquid form is commonly used at treatment facilities that use sodium hypochlorite for disinfection. UV disinfection Chlorine is not the only method that can be used for disinfecting pathogens in wastewater. Ultraviolet (UV) light is becoming a popular alternative. UV disinfection is a physical process rather than a chemical process, like chlorination and chloramination. Because no chemicals are used, there is no residual effect that could be harmful to public health and the environment. UV disinfection works by the intensity of the UV light that disrupts the cell walls of the pathogens. Because the light needs to come in contact with the bacteria, it is critical that the turbidity of the water being disinfected is low. If there is too much turbidity in the wastewater, the pathogens will be shielded by the material causing the high turbidity. Ozonation Ozonation is more widely used in Europe and Asia. Ozone is three oxygen molecules bonded together, O3. Ozone is highly reactive and must be generated onsite and directly mixed in with the wastewater being disinfected. Ozone is made by taking atmospheric oxygen, O2, and using electricity to break apart the bond between the two oxygen molecules. The individual oxygen molecules then combine with existing O2 molecules to create O3. When the O3 reacts with the wastewater it will create hydrogen peroxide (H2O2) and hydroxyl (OH). These compounds are highly reactive and will disinfect the pathogenic organisms in the wastewater.

textbooks/workforce/Water_Systems_Technology/Water_161%3A_Wastewater_Treatment_and_Disposal_II_(Steffen)/1.03%3A_Tertiary_Treatment.txt

Learning Outcomes • Understand the requirements of Title 22 for recycled water • Know what level of treatment is needed for different recycled water uses Discharge By now the wastewater has been completely treated. By undergoing preliminary, primary, biological, secondary, tertiary, and disinfection treatment the water should now meet the rigorous requirements of a National Pollutant Discharge Elimination System (NPDES) permit and be able to discharge in a nearby waterbody. Often, the addition of this treated water provides a riparian habitat to many aquatic species. However, a lot of time, money, and energy were put into treating this water. If advanced treatment methods like BNR and membrane filtration were utilized, then the water can be used for other beneficial reuses. Non-Potable Reuse & Reclamation To reuse treated wastewater for non-potable reuse, meaning it cannot be consumed, it must comply with Title 22 of the California Code of Regulations. Title 22 outlines what level of treatment is required for different types of reuse applications. There are four different types of classifications of water under Title 22, undisinfected secondary recycled water, disinfected secondary-23 recycled water, disinfected secondary-2.2 recycled water, and disinfected tertiary recycled water. Undisinfected secondary recycled water is the lowest level of treatment and therefore has limited application uses. It can be used for orchards or vineyards where the recycled water does not come into contact with the edible portion of the crop. It can also be used for ornamental nursery stock and non-food-bearing trees as longs as no water is applied to the plants for 14 days prior to harvesting, retail sale, or allowing access by the general public. Disinfected secondary 23 and 2.2 differ in the level of disinfection. The 23 and 2.2 are referring to results from the Most Probable Number (MPN) test used to determine the effectiveness of the disinfectant. An MPN of 2.2 is the lowest level of detection for the test and therefore a lower chance of pathogenic organisms existing in the sample. As the wastewater goes through higher levels of treatment it can be used for more non-restrictive uses. Disinfected secondary-23 recycled water can be used for irrigation purposes but only in areas where there is a limited chance of the water coming in contact with the general public. For example, it can be used to water freeway landscaping, cemeteries, and golf courses with restricted access. Disinfected secondary 2.2 recycled water can be used for irrigation of food crops where the edible portion is produced above ground and not contacted by the recycled water. Disinfected tertiary recycled water is the highest level of treatment defined by Title 22 and can be used for pretty much any type of irrigation. It can be used on food crops where the recycled water does come into contact with the edible portion of the crop. It can be used to irrigate parks, playgrounds, schoolyards, and residential landscaping. Disinfected tertiary recycled water can also be used for other purposes such as flushing toilets, industrial processes, fire fighting, decorative fountains, and car washes. Indirect Potable Reuse Title 22 also regulates using recycled water for indirect potable reuse. It outlines two ways to do this, either by surface application or subsurface application of groundwater replenishment. Surface application is when the recycled water is sent to a percolation basin. The water is forced by gravity through the voids in the soil which adds an extra layer of filtration as the water enters a groundwater aquifer. The water is then pumped out of the aquifer and sent to a water treatment facility where it is further treated and ultimately is used for potable water. Subsurface application is when the water is pumped directly from the treatment plant discharge to the groundwater aquifer. Since this method does have the added treatment benefit of the water percolating through the soil, additional advanced treatment methods are needed at the wastewater treatment facility. The tertiary treated wastewater will typically go through reverse osmosis membrane filtration prior to being injected into the groundwater aquifer.

textbooks/workforce/Water_Systems_Technology/Water_161%3A_Wastewater_Treatment_and_Disposal_II_(Steffen)/1.04%3A_Water_Recycling.txt

Learning Outcomes • Understand where solids from the wastewater treatment are generated • Compare the different ways to thicken wastewater solids Biosolids For many years the solids leaving the wastewater treatment plant were referred to as sludge. The term sludge is still used but typically refers to the untreated raw sludge leaving the primary clarifiers or the waste activated sludge (WAS) leaving the secondary clarifiers. However, once the sludge has been treated, it can be converted to biosolids. Biosolids can be used for many beneficial purposes such as compost, fertilizer, and landfill cover. In the liquid portion of wastewater treatment, the goal was reduction of organic matter. Much of that organic matter ends up in the sludge. In biosolids, it’s that organic matter that can be used for composting. There is also an ample amount of nitrogen and phosphorus which are key components in fertilizer. That organic matter has a lot of potential energy. During the digestion treatment stages, this energy can be captured and used to power other portions of the treatment process. Primary Treatment Sludge Thickening Gravity thickening is commonly used to thicken primary solids. The purpose of thickening is to reduce the water content. This makes a more concentrated sludge that will require smaller digesters in the next treatment stage. Gravity thickening works very similarly to primary sedimentation. However, instead of starting with raw wastewater we are starting with concentrated sludge. In the primary sedimentation tank, the raw wastewater will increase from around 1% solids to up to between 4% and 6% solids. Starting with the higher percent solids concentration and putting it through a similar treatment process can further increase the solids concentration to 10% or greater. By increasing the percent solids the sludge becomes thicker. It’s getting thicker because the water is being removed. Similar to the sedimentation process gravity thickeners rely on the heavy solids in the sludge to settle by gravity to the bottom of the thickener. As the solids settle the water will be separated out. The tank will become stratified with larger amounts of solids on the bottom of the tank and layer of water with less solids on top. The top layer is referred to as the supernatant and the bottom layer is called subnatant. To optimize the performance of a gravity thickener it’s critical to have “fresh” primary sludge. Sludge that is becoming or has already gone septic will not settle as easily as newer sludge. Therefore, controlling the rate of pumping from the primary sedimentation tank to the gravity thickener must be closely watched. If the sludge is going septic in the primary tanks then the pumping rate will need to be increased. This will lower the detention time and keep the sludge from going septic. However, if it’s pumped too quickly then the percent solids might be decreased which is also not optimal. Another way to deal with septic sludge is to add chlorine to reduce biological activity. Secondary Treatment Sludge Thickening When thickening secondary sludge or a mixture of secondary and primary sludge, a dissolved air flotation thickener (DAFT) is commonly used. A DAFT works by taking a portion of the clear subnatant leaving the DAFT and pressurizes the water with an air compressor. The water is then conveyed back into the DAFT where it is exposed to atmospheric pressure. The difference in pressure causes lots of tiny air bubbles to be released, just like opening a soda bottle. The tiny air bubbles will float to the top of the DAFT. The incoming sludge will not be able to settle to the bottom because of the rising air bubbles. Therefore, the solids remain on the top layer and the bottom layer is clearer water. The solids will be skimmed off and sent to a hopper where it will be pumped to the next stabilization treatment stage. The clearer water on the bottom will be sent back to the headworks to be further treated in the liquid portion of the treatment process. A DAFT can typically create a solids concentration between 4% and 8%. The return water is pressurized between 40 and 70 psi. A key parameter to a well operated DAFT is the air to solids ratio. A common air to solids ratio is around 0.02 to 0.04. If not enough air is supplied to the tank, the solids will settle to the bottom. Other operational parameters are the speed of the skim arm. Operators should set the speed to slowly skim the thickened sludge into a hopper. If the skim arm speed is set too high it will thin out the solids and reduce the percent solids concentration. There should be about a 1 to 3 foot blanket of thickened sludge on the DAFT. Polymer is often added to aid the coagulation of solids. This also causes the solids to bind together and make larger particles that will more easily float to the top of the unit.

textbooks/workforce/Water_Systems_Technology/Water_161%3A_Wastewater_Treatment_and_Disposal_II_(Steffen)/1.05%3A_Solids_Handling_Processes.txt

Learning Outcomes • Compare and contrast the various sludge stabilization methods • Understand the different biological processes to stabilize wastewater solids • Describe the different types of bacteria used during anaerobic digestion at different temperatures Sludge Stabilization Once the solids have been thickened they are ready to be stabilized. At this point, the solids have only been thickened and they are the waste products of the liquid portion of the treatment process. There is a large amount of volatile organic material that needs to be stabilized. Stabilization will also help reduce odors and destroy pathogens. There are several different methods to achieve this. Digestion is the most common but stabilization can also be achieved by adding chemical or thermal stabilization by heating the sludge. Aerobic Digestion Aerobic decomposition is very similar to the aeration tanks discussed earlier in the activated sludge systems. The primary and/or secondary sludge is digested aerobically, meaning that aerobic bacteria will break down the organic matter. The digesters can either be rectangular or round. The bacteria are aerobic so air must be applied to the digester. One major difference between the aeration tank in the activated sludge tanks and the aerobic digester is that there is not a continual supply of fresh BOD5. In the digester, there is no fresh wastewater coming in only the settled solids. In the digester, the aerobic bacteria will be able to breathe but with no food source, they will undergo endogenous respiration. In this state, the bacteria begin to breakdown their own cell mass and thus reduce the amount of volatile suspended solids. Aerobic digesters will have a longer detention time, typically on the order of 30 days or more. Common volatile solids reduction can be around 45% to 70%. Anaerobic Digestion Recall that anaerobic means the environment has no free or combined sources of oxygen. Bacteria must find a different source of respiration. Anaerobic digestion is a two-step biological treatment process. The first step is done by a group of bacteria that breakdown solids to form volatile acids. The second step is another group of bacteria breaking down those volatile acids to form methane, carbon dioxide, and water. When checking the operation of a digester, pH is a critical parameter. The first step of the digestion process is to create volatile acids. Excessive acids will cause a drop in pH. A pH between 6.6 and 7.6 is considered an acceptable range. If the pH drops below this, that is a sign that there are not enough methane forming bacteria to breakdown the volatile acids. Another way to examine this is by looking at the volatile acid to alkalinity ratio. Large amounts of alkalinity in the sludge will be able to buffer drastic changes in pH. If there isn’t enough alkalinity the pH could drop significantly and adversely affect the bacteria in the digester. Mixing is also an important design and operation requirement. Good mixing will distribute the sludge evenly throughout the tank. This allows the bacteria to come in contact with the raw sludge and aid the digestion process. Proper mixing will also prevent the separation of grit and other inert solids. It will also prevent the development of a scum layer at the top of the digester. There are three different types of anaerobic digestion based on what the operating temperature of the digester is. They are classified by the type of bacteria that is most abundant at the specified temperature ranges. The most common type is mesophilic, which operates between 85℉ and 100℉. This is the same type of anaerobic digestion that occurs in the human stomach. Psychrophilic digesters will operate between 50℉ and 68℉. The advantage of this type of digester is external heating systems are not needed to raise the temperature. However, at these colder temperatures, the bacteria are not as active. Therefore, psychrophilic digesters will require a longer detention time to achieve stabilization of the solids. Going hotter than mesophilic is thermophilic. These digesters operate between 120℉ and 135℉. At these higher temperatures, a detention time of 5 to 12 days can sufficiently stabilize the solids. However, there is an added cost to heat the sludge to these higher temperatures. Chemical Stabilization Chemical stabilization is achieved by adding calcium hydroxide, \(\ce{Ca(OH)2}\). It is also commonly known as slaked lime. Adding the lime will raise the pH of sludge to the point where biological activity is drastically reduced. This is much different from digestion because the organic matter is not reduced. The lime temporarily halts the biological activity and thus stabilizes the sludge. The sludge is then disposed of to a landfill. Chemical stabilization is not as common due to the high costs, regulations, and environmental impacts of handling chemicals.

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Learning Outcomes • Compare and contrast the different methods of biosolids dewatering • Understand the limits of different biosolids dewatering methods • Compare the energy and labor requirements of different biosolids dewatering methods Sludge Dewatering Sludge dewatering is exactly what it sounds like. At this point, the sludge has been stabilized by reducing the amount of volatile organic material. It’s almost ready for disposal which usually means it will need to be transported somewhere. This can be very expensive because the sludge is still mostly water. Dewatering removes a lot of the water and increases the percent of solids. This will make transporting the dewatered biosolids much more cost-effective. Drying Beds The simplest and cheapest way to dewater sludge is by drying beds. The sludge is sent to the drying beds where the sun heats it up and evaporates the water. This process can take several weeks or even months to achieve the desired percent solids. Also, the process is dependent on the weather. In colder months it can take even longer. There are some adaptations to increase the process. Some drying beds will be slightly sloped with sand in the middle. There is an underdrain system beneath the sand. With sand beds, the water is being evaporated by the sun but is also being directed towards the sand and filtered through to the underdrain system where it is then sent back to the headworks of the treatment plant. There are also vacuum assisted drying beds. Similar to sand drying beds but instead of relying on gravity for the water to drain a vacuum is created to force the water out. Drying beds are efficient and cost-effective for smaller systems and where land is available. Belt Presses A belt filter press consists of two long filters. The sludge will be conveyed in between these two filters and then sent through progressively higher areas of pressure where water is squeezed through the filter and the solids are left behind. The first part of the belt filter press is the gravity zone. Here the digested sludge is mixed with polymer and begins to coagulate the solids. The solids are then conveyed and sandwiched between the other filter. There is then a low-pressure section where water is forced between the filters and removed. The pressure then gradually increases as the filters are rolled through the belt press. This gradual increase allows more and more water to be removed. At the end of the belt press, the two filters separate and the biosolids are scraped off and sent to a conveyor belt. Belt presses can achieve around 13% to 18% solids. Oftentimes belt presses are combined with drying beds to further increase the percent solids. Filter Presses There are a couple of different types of filter presses. The most common is the plate and frame filter press. The unit consists of a series of filter plates. The plates are forced together with a hydraulic press and sludge is conveyed in between each of the plates. As the sludge is pumped into the filters the solids are trapped by the filter and the water passes through and is collected in a drain system. As more and more sludge is pumped into the filters the pressure will begin to increase. This extra pressure will cause even more water to be forced through the filters and out of the sludge. When the pressure reaches its maximum the operator will stop feeding sludge to the filters. The plates are then released from the hydraulic press and separated. As the plates separate, the dried biosolids will fall off the filter plates and drop below to either a conveyor belt or oftentimes to the bed of a dump truck. The biosolids will then be sent off for ultimate disposal. A well-operated plate and frame press can achieve a solids concentration of 40% to 50%. Another type of filter press is vacuum filtration. This consists of a circular drum with a filter material on the outside. The drum is submerged into a trough filled with the digested sludge. The drum slowly rotates while a vacuum is being created inside the drum. The vacuum pulls the water out of the trough. The solids are stuck on the outside of the filter while water is able to filter through and be sent to the drain system. By the time the drum does a full circle, the percent solids has increased significantly and the biosolids are scraped off to a conveyor system where they are sent to a dump truck. Waste Stream Recycling The water being removed from the dewatering process needs to be sent back to the liquid portion of the treatment plant to be further treated. However, this water is often very high in ammonia and can overwhelm the bacteria in the activated sludge process. Some treatment plants will slowly pump this water back to the treatment plant so there isn’t a large slug of ammonia going through the system. Others will only pump the water back during the night time hours when ammonia coming into the treatment plant is often lower. Some newer technologies will actually treat the water prior to being sent back to the headworks. Sludge Disposal Now that the sludge from the primary sedimentation and secondary clarifiers have been stabilized and dewatered we can call it biosolids. The biosolids need to either be disposed of or reused. Biosolids are classified into two separate types by the EPA. Class B biosolids have been treated by the processes discussed in this chapter but can contain high levels of pathogenic organisms. Therefore, Class B biosolids have greater restrictions on land application and crop harvesting. Class A biosolids typically undergo a combination of the treatment processes discussed in this chapter to achieve lower levels of pathogens. Class A biosolids that meet EPA regulations can legally be resold as fertilizers.

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Introduction No matter what your job is, you will need to communicate with other people. Your communication skills determine how successfully you receive and transmit information. Communication is arguably the most important of all life skills and plays a significant role in all aspects of work and home life. Communication is verbal, written, and non-verbal, and every gesture, voice inflection, or facial movement speaks volumes and conveys information to others. An effective communicator is also an active listener. Employers actively seek out Individuals who are good communicators. Objectives When you have completed the Learning Tasks in this Competency, you will be able to: • describe the principles of communication • describe effective listening techniques • describe the procedures for giving and receiving feedback • describe assertive communication • describe conflict resolution techniques • describe effective problem solving and decision making Resources You will be required to reference publications and videos available online. 2.01: Verbal Communication Communication is the act of transferring information from one person or place to another. It can be verbal, non-verbal, written, or visual (e.g., photographs, diagrams, symbols). The purpose of communication is to understand and to be understood, and it involves expressing thoughts, ideas, and feelings. Interpersonal communication is a process by which we exchange information, feelings, and meaning with others through verbal and non-verbal messages. It is face-to-face communication. It is impossible for humans not to communicate. Even when we are not speaking, we are still communicating through our body language. We spend about 75% of our days communicating in some way: about 9% is spent writing, 16% reading, 30% talking, and 45% listening. Effective communication is one of the most important skills that people need in their personal lives and in their work lives. Figure 1: All aspects of communication are integral to building good working relationships. 02: Learning Task 1- Describe the Principles of Communication Verbal communication is how we express ourselves in words, both spoken and written. Spoken language includes enunciation, pauses, stutters, emphasis, and word choice. Spoken language can occur in face-to-face encounters, by telephone, by voice mail, on television, by Web conferencing, or on radio. 2.02: Written Communication Written communication can be in the form of letters, handwritten notes, emails, text or instant messages, faxes, books, newspapers, magazines, and signs. Increasingly, daily written communication takes the form of emails and text messages. While these messages may be brief, the potential for miscommunication is significant. In general, people are better at communicating and interpreting tone in vocal messages than in text-based messages. In emails and text messages, where there is a tendency to reduce the number of words in a message and use abbreviations or slang, the recipient may miss the full meaning or tone intended. To reduce miscommunication: • Determine how the information should best be communicated. • If the subject of your communication is sensitive, consider talking by phone or meeting in person to convey your message rather than sending an email or text message. • Take your time to compose your message. • Think about the words you’re writing from the recipient’s perspective. • Use the KISS principle and “keep it super simple.” The more simply something is stated, the less opportunity there is for confusion or misunderstanding. In the absence of body language and voice tone, the receiver can only rely on the written word. • Never use email or social networking tools when you are angry or upset. Always wait until you are calm and composed before addressing an issue.

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In 1967, a University of California, Los Angeles (UCLA) study found that more than 90% of face-to-face communication between people is non-verbal (Mehrabian and Ferris, 1967). Non-verbal communication is communication without words. That’s why it’s often referred to as “body language.” It includes facial expressions, gestures, body movements, posture, and eye contact. Often a person’s body language reveals his or her thoughts and feelings more directly than spoken words. Generally, when people are feeling confident, their stance is strong and they easily make contact with others. When people are flirting, they can be seen playing with their hair, arching their bodies, and standing close to another person. How you use body language can attract or detract from the message that you want to communicate. Some elements of body language are discussed below. Facial expressions The most obvious indicator of emotions is facial expressions. By observing a smile, laughter, tears, a frown, or even the level of eye contact, you can tell much about how a person is feeling. Figure 2: Your facial expressions can often convey more than your words. Appearance Your personal appearance also communicates an impression. The clothes and accessories you wear, the colours and styles you choose, as well as the piercings and/or tattoos you have all communicate a message about who you are and what you value. Personal space The distance you maintain between yourself and others will vary with the nature of the activity and the emotion involved. For example, people tend to communicate in close proximity if they are affectionate or angry, but at a distance if they are afraid or have a dislike. Culture also plays a role in determining personal space. In North America, people tend to keep each other at arm’s length. In some other cultures, individuals stand very close to one another; in others they put significantly more distance between them. Misinterpreting body language Body language, like verbal communication, can be misinterpreted. You might see a woman stomping her foot and think she must be angry. But maybe she’s just trying to get mud off her shoe! Or perhaps you think a co-worker you are talking to is upset with you because his arms are crossed, but maybe he’s just cold. You shouldn’t focus on just one non-verbal signal and think you’re interpreting effectively. You need to look at the whole package of both verbal and non-verbal cues to better understand what’s being communicated. Cultural differences Body language also varies from culture to culture and even from region to region in some countries. The smile may be the one and only gesture that can be understood worldwide. On large job sites or in other countries, you may be working with individuals from several different cultures, and body language displayed by your supervisors and co-workers may differ from your own. As already noted, North Americans usually converse about an arm’s length apart, but people from other cultures may keep more or less space between them. As well, while maintaining direct eye contact is considered positive for most North Americans, people from other cultures may view it as being confrontational or a sign of disrespect, and therefore they avoid eye contact, particularly with persons of authority. An understanding of body language is something you will need to acquire when working with others. If your work or travels take you to other countries, understanding the differences between cultures can greatly improve your working relationships and reduce conflict on the job site. 2.04: Effective Listening To ensure that you are an effective listener, make sure you provide signals that indicate you’re engaged. Make eye contact and use verbal cues or nodding to show that you’re following the conversation. To indicate that you understand what’s been communicated, ask questions or paraphrase what you’ve heard. Try to use “open” body language; that is, don’t cross your arms or slouch. Good posture is a way of conveying alertness, and it indicates that you’re paying attention.

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Working in the trades usually includes working with others. Whether you are communicating with only one other person or you are in a group setting, effective communication skills are equally important. As you have learned, effective communication spans a variety of different forms, including spoken, written, and non-verbal communication. When working in groups, respecting the principles of effective communication is especially important, as the possibility of interrupting, misinterpreting, or being interrupted or misinterpreted is even greater when more people are involved. Effective communication is the cornerstone of strong relationships and is one of the factors that helps people work well in groups, whether at home, in school, or in the workplace. Figure 3 lists some of the factors that constitute both effective and ineffective communication when working with others. Figure 3: Examples of effective and ineffective communication At times we all communicate effectively, and at other times we fall short of perfection. As with any skill, some people are innately better at communicating than others. As you learn to develop or hone your communication skills, think about those people who have the strongest impact on your ability to express your thoughts, feelings, and attitudes. These people are generally parents, siblings, teachers, coaches, team members, co-workers, and other role models in your life. When working in groups it is also important to use formal or information communication appropriately, depending on the individuals involved. Formal communication has conventions that govern spoken and written words and body language. Informal communication is much more relaxed, with fewer rules and conventions. Figure 4 illustrates some of the differences between formal and informal communication. Figure 4: Informal and formal communication You may use more than one type of communication with the same individual. For example, you may use formal communication with a family member or friend in a working context when you are both part of a team. Informal communication may be limited to when you are alone with the individual or strictly outside of the office or work site. Misunderstandings can have a negative impact on the work environment if they are not corrected quickly and constructively. A negative group environment can affect individuals’ motivation, which in turn can affect productivity. When people are not feeling good about what they’re doing, their ability to remain on task and do good work is often compromised. Having discussions in a quiet setting without distractions can go a long way toward communicating effectively. While word choice determines factual information, voice quality or tone of voice expresses how a person truly feels. Just by listening to the way words are spoken, you can distinguish between boredom, sarcasm, annoyance, humour, fear, and excitement. Voice quality includes the rate of speech (how quickly or slowly you speak), pitch (how high or low your voice sounds), and volume (how loud we speak). When you are listening to someone speak, make sure you are paying careful attention to what is being said. Hearing is just as important as being heard! Here are some basic guidelines that may prove useful to you when working in groups: • Avoid interrupting while someone else is talking. • Before either accepting or rejecting the ideas of others, take some time to reflect on them. Always try to put yourself into others’ shoes and understand their point of view. • If you must disagree with the ideas of others, do so without being condescending or rude. • When working in a group setting, try to withhold your personal values, opinions, or prejudices if they are not relevant to your work. • Try to build on the ideas of others during meetings. This creates a constructive, collaborative atmosphere. Staying positive is also an important feature of effective communication. Complaining and talking behind people’s backs at work (or even when you’re not at work) is disrespectful and can lead to a negative working atmosphere. Now complete the Learning Task Self-Test. 2.06: Self-Test 1 1. Communication is the act of transferring information from one person to another. 1. True 2. False 2. Which of the following are forms of communication? 1. Visual and written 2. Verbal and non-verbal 3. All of the above 4. None of the above 3. Interpersonal communication is the exchange of information, feelings, and meanings through verbal and non-verbal messages. 1. True 2. False 4. If you are a good talker, you are a good communicator. 1. True 2. False 5. Approximately what percentage of our day is spent communicating? 1. 25% 2. 50% 3. 75% 4. 90% 6. What is the most widely used form of communication? 1. Talking 2. Writing 3. Reading 4. Listening 7. Verbal communication is how we express ourselves in words and includes enunciation, pauses, and stutters. 1. True 2. False 8. The potential for miscommunication through short communication by email or text is insignificant. 1. True 2. False 9. In what format do people best communicate and interpret tone? 1. Texts 2. Letters 3. Emails 4. Vocal messages 10. Why is the KISS principle used? 1. People are simple. 2. Not everyone is able to understand complex communications. 3. The more simply something is stated, the less opportunity there is for confusion. 4. The more complexly something is stated, the less opportunity there is for confusion. 11. Which of the following is considered non-verbal communication? 1. Facial expressions and body language 2. Personal space and personal appearance. 3. All of the above 4. None of the above 12. Body language is the same regardless of where you come from or what your culture is. 1. True 2. False 13. There are cultural differences in how people communicate and what is considered acceptable. 1. True 2. False 14. Which of the following is not an example of open body language? 1. Staying alert 2. Sitting and facing the speaker 3. Closing your eyes while an individual is speaking 4. Nodding to acknowledge you’ve heard what was said 15. A negative group environment can harmfully impact the motivation of co-workers and reduce productivity. 1. True 2. False 16. Which of the following does not constitute effective communication? 1. Being an active listener 2. Accepting people’s differences 3. Treating all people with respect 4. Providing conditional acceptance 17. Effective communication promotes understanding. 1. True 2. False 18. In general, with whom is a more formal communication style used? 1. Suppliers 2. Friends and colleagues 3. Employers, supervisors, and clients 4. Colleagues, friends, suppliers, and clients 19. An informal communication style is used more with employers than with friends. 1. True 2. False

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Listening is critical to learning and an important part of the communication process. In a training institution some of the course material may be delivered through lectures, through audio, and through verbal instructions. Even with practical demonstrations and instructional videos, much of the content is delivered through the spoken word. If you are not fully involved in listening, you will miss some important information and can easily be distracted. On a job site, effective listening can be critical in ensuring the safety of you and your co-workers, and ensuring that a job is completed accurately and on time. 03: Learning Task 2- Describe Effective Listening Techniques Active listening is a way of listening and responding to another person so that the message is fully understood. The following are several techniques that you can use to demonstrate active listening. The techniques you use will vary depending on the situation. For example, active listening during a lecture will require different techniques than active listening about a personnel matter at the job. Concentrate Eliminate distractions. Shut off shop equipment, radios, or other competing sounds. Try to put personal problems aside. Limit engagement in other activities such as texting or working on other assignments. If you are having difficulty concentrating, use techniques to keep your mind from wandering. This may include taking very brief notes or jotting down questions you might want to ask at the appropriate time. Empathize Put yourself inside the speaker’s thoughts and feelings to better understand what he or she is saying to you. Suspend your own judgment and position until you clearly understand the other person’s perspective. Listen for feelings Try to “listen between the lines” to understand the attitudes, needs, and motives behind the words. Changes in volume and tone, as well as non-verbal clues such as facial expressions and gestures, can help you determine how the speaker is feeling. Connect Use “listener-friendly” body language: make eye contact with the speaker or focus on the audio or visual presentation at hand. Try to connect the information you are hearing with what you may have previously learned or already know. Pay attention to any visuals that may accompany the audio, such as, an instructor writing on a board or asking you to look at a visual in your textbook or online while they continue speaking. Validate Even if you don’t agree with what the speaker is saying, it is important that the person knows you are listening and that you understand what they have said. Use nods and “uh-huhs” and respectful comments that show you have heard what was said. Paraphrase When the speaker has finished talking, repeat in your own words what the speaker said so they know they have been understood. Clarify Ask questions to get more information, especially if you’re not clear on what was said. It is important to take your cues from the presenter on when to ask questions. While some instructors may ask you to interrupt and ask questions at any time, others may ask you to hold questions until the appropriate time. Participate Participate in discussions and respond to questions. Now complete the Learning Task Self-Test. 3.02: Self-Test 2 1. Listening is not part of the communication process. 1. True 2. False 2. Active listening is a way of listening and responding to another person so that the message is fully understood. 1. True 2. False 3. You are in a meeting with your colleagues. What is required in order to send effective messages? 1. Listening and non-verbal communication 2. Both verbal and non-verbal communication 3. Verbal communication and facial expressions 4. Listening, non-verbal, and verbal communication

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The ability to give and receive feedback is integral to a healthy working relationship. Feedback is intended to provide information and observations about an individual’s work behaviour or performance and can be positive and/or negative. All too often feedback is perceived as negative and associated with criticism. However, if given in the right way and at the right time, feedback can be highly beneficial for both the giver and the receiver. 04: Learning Task 3- Describe the Procedures for Giving and Receiving Feedback If half of communication is listening, the other half is speaking and expressing thoughts and feelings in a clear way. Sending effective messages includes both verbal communication (the words you use) and non-verbal communication (body language). Figure 1: Giving and receiving feedback includes being aware of body language and facial expressions Effective feedback should let the receiver know which behaviour or performance is desired and which is not. It should allow both the giver and the receiver the opportunity to ask questions and get further clarification, and it can result in discussions that can benefit both parties. Effective feedback can also lead to advice or recommendations on how to handle an issue or situation better in the future. As an apprentice, you should receive a lot of feedback from your employer, supervisor, coworkers, and even clients. You’ll get feedback on the job site, and if you work for a larger company you may also have a performance review that will provide you with feedback. Should you not be receiving any feedback, take the initiative to ask your employer or co-workers to comment on your performance. 4.02: Constructive Criticism Constructive criticism is feedback aimed at collaboratively improving the overall performance of an individual or quality of a service. It often includes suggestions for positive change or improvement. Guidelines for giving and taking feedback The following are general guidelines on how to give feedback: • Relax and take a few deep breaths if you are anxious. • Remain respectful and calm at all times. If you are angry or unable to control your emotions, wait until you have calmed down. • Remember that feedback is both positive and negative. Make sure the information you convey does not focus only on only one or the other. • Provide the feedback in an appropriate location. Negative feedback should be given in private space without interruption. • Put your feedback into context, particularly if it is negative. This will help the receiver understand the points you are making. • If you notice that the receiver is distressed, slow down, take a short break, or reschedule the discussion if necessary. • Allow the receiver the opportunity to answer or ask questions and provide their own input. This will require active listening on the part of the giver. • Focus on the issues and not the person. • Provide feedback at the appropriate time so that an employee or co-worker can address the issues. Don’t stockpile the feedback or criticism and unload it void of context. • Make sure that it is within your purview to provide the feedback. The following are general guidelines on how to receive feedback: • Relax and take a few deep breaths if you are anxious. • Actively listen to what is being said. Ask questions or for clarification if required at the appropriate time. • Remain respectful at all times. If you are angry or unable to control your emotions, wait until you are calm to respond or ask questions. • Remember that feedback is both positive and negative. Acknowledge the feedback by paraphrasing it and asking for clarification on any points if necessary. • Take responsibility for your role. Acknowledge any errors you have made or situations that could have been handled better. Ask for advice on how to handle these situations better in the future. • If you disagree with the assessment, be assertive, not aggressive. Clearly address the issues. Now complete the Learning Task Self-Test. 4.03: Self-Test 3 1. Which of the following is essential for giving and receiving feedback? 1. Effective listening 2. Healthy working and personal relationships 3. All of the above d. None of the above 2. What does effective feedback help the receiver of the information do? 1. Know what behaviour or performance is acceptable or not acceptable. 2. Know about their work performance and have the ability to ask questions for further clarification 3. All of the above 4. None of the above 3. As an apprentice, from whom will you receive feedback? 1. Your direct supervisor only 2. Your employer, supervisor, and co-workers 3. Your employer, supervisor, co-workers, and clients 4. Your direct supervisor and his or her superior or human resources 4. What is the purpose of constructive criticism? 1. To let you down easily when you make a mistake 2. To improve your performance or the quality of service 3. To keep track of what you have done well and advise your supervisor 4. To keep track of the problems you’ve had and go through them with you at a meeting 5. Most people find it easy to give and receive effective feedback or constructive criticism. 1. True 2. False 6. Which of the following is not a step used in giving effective feedback? 1. Remain calm at all times. 2. Put the feedback into context. 3. Focus on the person and not the issue. 4. Remember to give both positive and negative feedback. 7. Which of the following is not a step used for receiving feedback or constructive criticism? 1. Listen to what is being said. 2. Keep your emotions in check and remain respectful at all times. 3. Ask questions or for advice on how the issue can be handled better in the future. 4. Be prepared and challenge the speaker on everything that you do not believe is correct.

textbooks/workforce/Workforce_Fundamentals/04%3A_Learning_Task_3-_Describe_the_Procedures_for_Giving_and_Receiving_Feedback/4.01%3A_Sending_Messages.txt

Communication can be assertive, non-assertive, or aggressive. Assertive communication is asking what you want and expressing yourself clearly, firmly, and honestly. When you communicate assertively, you take responsibility for your thoughts and feelings and state your position with confidence. Assertive communication is respectful–even when you are expressing negative emotions, you don’t hurt others. When you communicate assertively, you express your needs, wants, thoughts, and feelings without guilt. Figure 1: Being assertive does not mean being aggressive Non-assertive communication is failing to stand up for yourself and express personal feelings, needs, ideas, or opinions in the workplace. Individuals who use this form of communication can easily be ignored or have their rights violated. Non-assertive communication is viewed as emotionally dishonest, indirect, and inhibiting. It can lead to hurt and anger on the part of the individual, and pity and irritation by others. Aggressive communication is rude, hostile, and destructive. An individual who is acting aggressively has little respect for the rights and needs of others and achieves a goal at the expense of others. Aggressive communication may include shouting, threatening behaviour, and humiliating others. It is inappropriate for the workplace and can lead to negative consequences with both supervisors and colleagues. One of the best tools for ensuring that you use assertive communication is to use “I” statements. “You” statements in general create defensiveness and emotional resistance and shut down communication. They can promote conflict. “I” statements, on the other hand, avoid destructive blaming, criticizing, ridiculing, and name-calling. The speaker just makes a statement expressing his or her feelings. “I” statements can help prevent conflict. Figure 2 shows examples of assertive behaviour and aggressive or passive behaviour. Figure 2: Examples of assertive and aggressive or passive behaviours Remember that you can only accurately speak about your own intentions. In addition to offering accurate information, the use of “I” statements allows the other person to be receptive rather than defensive. Effective communication needs a sender of accurate information and a willing, open receiver. Remember, too, that you communicate in ways other than words. For example, assertive communication includes the following non-verbal behaviours: • making eye contact and looking directly at a person when you are speaking. This shows that you are sincere, interested in the conversation, and confident about what you are saying. • standing or sitting in an erect posture and maintaining an appropriate personal distance • leaving your hands by your sides and making appropriate non-threatening gestures • keeping your voice pleasant, steady, and strong and accompanied by appropriate facial expressions Now complete the Learning Task Self-Test. 5.02: Self-Test 4 1. Which of the following are considered three ways of communicating? 1. Passive, aggressive, and normal 2. Passive, effective, and ineffective 3. Assertive, aggressive, and passive 4. Assertive, non-assertive, and aggressive 2. Which of the following is an example of assertive communication? 1. Expressing yourself clearly and firmly 2. Conveying your feelings and ideas honestly 3. All of the above d. None of the above 3. Which of the following is an example of non-assertive communication? 1. Standing up for yourself 2. Failing to stand up for yourself 3. Speaking through body language 4. Being easygoing and not taking offence 4. Which of the following applies to people who don’t speak up in the workplace? 1. They aren’t good employees. 2. They aren’t good team members. 3. They deserve what happens to them. 4. They are easily ignored and can have their rights violated. 5. Which of the following most applies to aggressive behaviour? 1. It shows a lack of respect for supervisors and co-workers. 2. It should not be tolerated in the workplace and is considered rude, hostile, and/or destructive. 3. All of the above d. None of the above 6. Using “you” at the beginning of each sentence is key to assertive communication. 1. True 2. False 7. Only you can speak accurately about your own intentions. 1. True 2. False 8. Ninety percent of all communication is non-verbal. 1. True 2. False

textbooks/workforce/Workforce_Fundamentals/05%3A_Learning_Task_4-_Describe_Assertive_Communication/5.01%3A_Assertive_Communication.txt

Conflict can be defined as disagreement between two or more individuals or groups arising from differences of opinions, beliefs, or actions. It is a normal part of everyday life, given that individuals have different experiences, values, and beliefs that shape their perception of the world. Conflict in the workplace can usually be associated with resource allocation, perceptions, and/ or values. In general, conflicts over resource allocation are the easiest to solve, since they can be looked at objectively and separated from personal opinions. Both parties may decide on an equitable solution or agree to let a superior make a decision and live with the consequences. Conflicts that involve perceptions and values are often personal, and if left to fester it can take significant time and effort to determine the actual source of the problem and come to a decision that is satisfactory to both parties. They can also spread and create a toxic work environment for individuals on all sides of the conflict. The following are some easy steps you can take to reduce conflict in the workplace: • Remember that conflict is inevitable and does not reflect badly on you and that there are no winners and losers. The goal of conflict resolution is to come to an agreement that is of mutual benefit to both parties. • Be proactive. If you feel that you have annoyed or made someone angry, ask to discuss it with them at the onset. Likewise, if you feel that you have been unfairly treated, use an assertive communication style and discuss it with your colleagues to resolve the issue. In this way, simple misunderstandings can be cleared up. • The sooner you handle the conflict, the better. The longer a conflict goes unresolved, the larger it becomes and the more difficult it is to find the root of the problem. • Take responsibility for your part in the conflict. If you’ve intentionally or unintentionally offended someone through your actions, acknowledge your part and move on. • Once the conflict has been resolved, agree to move forward with a positive working relationship. Ineffective ways to reduce conflict at work include being passive and thinking that a problem will go away if it is left unchecked. This only leads to resentment and further issues. Now complete the Learning Task Self-Test. 6.02: Self-Test 5 1. Conflict is a disagreement between two or more people based on differences concerning which of the following? 1. Beliefs 2. Actions 3. Opinions 4. All of the above 2. What do the most common workplace conflicts result from? 1. Personal problems between staff members 2. Jealousy and mistrust of other staff members 3. Problems between employers and employees 4. Resource allocations (e.g., differences in department budgets), perceptions, and values 3. What is the best way for two individuals to settle a resource allocation-related conflict? 1. Limit interactions with the other individual. 2. Complain formally in writing to his or her superior. 3. Agree to disagree and let someone else come up with the solution. 4. Remove personal opinions, be objective, look at the issue, and try and find a solution that works. 4. Conflict is inevitable and does not reflect badly on you. 1. True 2. False 5. There is always a winner and a loser in a workplace conflict. 1. True 2. False 6. It is always best to wait until you are calm before discussing a workplace conflict. 1. True 2. False 7. The longer a conflict goes unresolved, the more difficult it becomes to find the source of the problem. 1. True 2. False 8. Being passive or non-assertive is a good strategy when dealing with a conflict. 1. True 2. False 7.01: Effective Problem Solving and Dec Key to communicating effectively is the development of skills related to problem solving and decision making. These skills are highly regarded by employers and required if you aspire to move into a position of management or intend on starting your own business. The following are steps to take into account when solving problems related to communication: • Approach the issue from a neutral or objective position. • Treat all individuals involved with respect. • Let the individuals involved provide their information without interruption. • Make sure that you understand the problem. If you need more information or clarification, ask questions in a non-threatening manner. Now complete the Learning Task Self-Test. 7.02: Self-Test 6 1. The key to effective communication is the development of problem-solving and decisionmaking skills. 1. True 2. False 8.01: Summary and References Summary Success in finding and maintaining a job is primarily about communication, since work involves being in relationships with other people. The principles of effective communication apply equally to all relationships throughout a person’s life. You and the people around you all stand to benefit from practising attentive and engaged listening, providing constructive feedback, communicating assertively as required, applying effective communication skills to conflict management, and using strong problem-solving and decision-making skills in your interactions with others. 8.02: Essential Skills Resources Essential skills videos Oral communication http://hebergement-hosting.ca/hostin...rview_full.mp4 Oral communication – conflict http://hebergement-hosting.ca/hostin...flict_full.mp4 8.03: Answer Key Self-Test 1 1. a. True 2. c. All of the above 3. a. True 4. b. False 5. c. 75% 6. d. Listening 7. a. True 8. b. False 9. d. Vocal messages 10. c. The more simply something is stated, the less opportunity there is for confusion. 11. c. All of the above 12. b. False 13. a. True 14. c. Closing your eyes while an individual is speaking 15. a. True 16. d. Providing conditional acceptance 17. a. True 18. c. Employers, supervisors, and clients 19. b. False Self-Test 2 1. b. False 2. a. True 3. d. Listening, non-verbal, and verbal communication Self-Test 3 1. c. All of the above 2. c. All of the above 3. c. Your employer, supervisor, co-workers, and clients 4. b. To improve your performance or the quality of service 5. b. False 6. c. Focus on the person and not the issue. 7. d. Be prepared and challenge the speaker on everything that you do not believe is correct. Self-Test 4 1. d. Assertive, non-assertive, and aggressive 2. c. All of the above 3. b. Failing to stand up for yourself 4. d. They are easily ignored and can have their rights violated. 5. c. All of the above 6. b. False 7. a. True 8. a. True Self-Test 5 1. d. All of the above 2. d. Resource allocations (e.g., differences in department budgets), perceptions, and values 3. d. Remove personal opinions, be objective, look at the issue, and try and find a solution that works. 4. a. True 5. b. False 6. a. True 7. a. True 8. b. False Self-Test 6 1. a. True

textbooks/workforce/Workforce_Fundamentals/06%3A_Learning_Task_5-_Describe_Conflict_Resolution_Techniques/6.01%3A_Conflict_Resolution_Techniques.txt