Wastewater Treatment Grade 1 - Part 1(Transcribed by Chuck)

Define sanitary sewer overflow (SSO).

A SSO is a release of wastewater from a sewage collection system or an interceptor sewer directly into a water of the state or to the land surface. All SSOs must be reported to the Department of Natural Resources within 24 hours of the occurrence

Define treatment facility overflow (TFO).

A TFO is a release of wastewater, other than through permitted outfalls, from a wastewater facility into a water of the state or the land surface. All TFOs must be reported to the Department of Natural Resources within 24 hours of the occurrence.

Define Wisconsin Pollutant Discharge Elimination System (WPDES) permit.

A WPDES permit is issued to wastewater facility owners and contains facility effluent, biosolids and sludge limitations, conditions, and reporting requirements.

Define clarifier.

A clarifier is a circular or rectangular tank used to remove floatable and settleable solids in wastewater.

composite sample

A composite sample is a sample prepared by combining a number of grab samples, typically over a 24-hour period.

Define confined space.

A confined space is a space large enough for an operator to enter and perform assigned work. It has limited or restricted means for entry or exit and is not designed for continuous occupancy.

flume

A flume is a restriction in an open channel used to measure flow.

Discuss grab and composite influent sampling.

A grab sample is a sample collected at a single instant in time. A composite sample is a collection of samples taken over a longer period of time (usually 24 hours) and mixed and stored in a larger container. A composite sample represents the average wastewater quality being received into a wastewater treatment plant. If samples collected over 24 hours are stored in a composite sampling jug or container, the jug or container must be shaken and well mixed before pouring the actual sample to be used for testing. Some samples, such as pH, dissolved oxygen (DO), and chlorine residual, must be grab samples because compositing and holding such samples would change the test results.

Define lift station.

A lift station is an underground chamber with pumps that is used to elevate (lift) wastewater to a higher grade. Lift stations are located within a collection system.

Define manhole.

A manhole is a structure that provides access to a collection system. It is typically a round opening with an iron lid.

Define microorganism.

A microorganism is a living organism too small to be seen with the naked eye, but is visible under a microscope. They include: bacteria, viruses, fungi, or protozoa.

Define sanitary sewer or collection system.

A sanitary sewer or collection system is an underground pipe system used to convey wastewater to a treatment facility.

Define selector.

A selector is part of the treatment system that selects for a specific type of microorganism by providing an environment (anaerobic, anoxic, or aerobic) that favors its growth.

grab sample

A single sample of water collected at a particular time and place that represents the composition of the water only at that time and place.

Define storm sewer.

A storm sewer is an underground pipe system that collects rainwater from streets and conveys it to a place other than the wastewater treatment plant.

Define treatment process.

A treatment process means a physical, biological, or chemical action that is applied to wastewater to remove or reduce pollutants.

Define treatment unit.

A treatment unit is an individual structure or equipment within a collection system or a wastewater treatment facility that is part of a treatment process.

Define weir.

A weir is a level control structure used to provide uniform flow.

Define wet well.

A wet well is a tank where wastewater is collected. The wastewater is then pumped from the wet well. Wet wells are commonly found in lift stations and at the headworks of the wastewater treatment plant.

Describe a wet well lift station.

A wet well lift station is a single chamber that collects wastewater. This type of lift station is commonly called a submersible lift station due to the pump and motor being completely submerged in the wet well. The submersible centrifugal pump is watertight and normally controlled by float switches. They are made to be easily removed for cleaning and maintenance using a rail system.

Describe common equipment used in suspended growth secondary (biological) treatment.

A. Aeration tanks Aeration tanks are usually square, rectangular, or circular. They contain aeration equipment for providing oxygen to the microorganisms that live and grow in the tanks. Aeration equipment also provides mixing in the tank. The mixed suspension of wastewater, solids, and microorganisms in the aeration tank is commonly referred to as activated sludge. The activated sludge is measured as MLSS in milligrams per liter (mg/L). B. Blowers Mechanical blowers provide the air to the aeration tanks. C. Diffusers Diffusers disperse the air into the aeration tank, providing oxygen and mixing in the tank. D. Final clarifiers Final clarifiers follow the aeration basins and settle the MLSS. Clear effluent is discharged over and through weirs in the clarifier. E. Sludge pumps 3.3.2 3.3.3 Discuss suspended growth systems (activated sludge). Describe common equipment used in suspended growth secondary (biological) treatment. Basic General Wastewater Study Guide - August 2015 Edition (Revised June 2016) Page 26 of 79 Printed on 01/12/17 The settled solids in the clarifier can be returned back to the aeration tank or wasted from the treatment system by the pump(s). The pump(s) are known as the return activated sludge (RAS) or waste activated sludge (WAS) pump(s).

List and discuss the process control equipment used for monitoring an activated sludge plant.

A. DO meter A DO meter is used to monitor aeration basin DO levels. Many plants have inline DO sensors to automatically control DO levels. If manual measurements are made, they should be taken in each aeration basin using a field DO probe. B. Settleometer A settleometer is used to monitor sludge settling characteristics in 30 minutes. A 1,000 mL beaker or cylinder is most commonly used. The MLSS sample for this test should be collected just before it goes to the final clarifier. C. Sludge blanket finder The sludge blanket finder is used to measure the depth of settled sludge in the bottom of a clarifier. A clear core sampler (Sludge Judge®) or an electronic device is most commonly used. Samples are usually collected before and after the scraper mechanism both near the well, midway, and near the sidewall. When and where the sludge depth is measured should be consistent each day. D. Microscope A microscope is used to observe the population and health of microorganisms living in an activated sludge system. The settled MLSS sample used for the 30-minute settling test can be used for the microscopic observation sample. E. pH and temperature meter A pH and temperature meter is used to measure pH and temperatures of wastewater entering the plant and the aeration basins. F. Flow meters Flow meters are used to measure influent, sidestream, RAS, WAS, and effluent flows.

Discuss the wastewater characteristics and problems with industrial discharges into a treatment plant.

A. Dairy operations Many different types of dairy and whey products are produced in Wisconsin. Some dairy operations have their own wastewater treatment plant, but many discharge to the treatment plant in the community in which they are located. Industrial wastes from dairy facilities consist of various dilutions of milk entering the municipal collection system. One of the largest sources of dairy wastewater come from the wash waters and rinse waters of dairy tanks, trucks, equipment, pipelines, and floors. Dairies use clean-in-place systems that alternate acidic and caustic cleaners and rinses in the cleaning of tanks, equipment, and pipes, raising or lowering pH. Milk and milk solids have a very high BOD, sometimes as high as 1,000 to 10,000 mg/L. Milk wastes also contain high amounts of nitrogen, phosphorus, and chlorides. The volume and BOD of dairy wastewater can vary greatly over a 24-hour period. Therefore the collection and equalization of dairy wastewater is very important so that the flow and BOD discharges to the collection system are more uniform. Sometimes dairy wastes have to be pretreated before discharge to a sanitary sewer. A treatment plant can be upset if it receives variable loads, high-strength wastes, high or low pH discharges, or slug loads from a dairy facility. B. Food industry Food (meats, canned foods, snacks, etc.) is processed in many different ways, and the wastes from them can vary in composition. Because food industry wastewaters can be variable and are usually high in BOD, suspended solids, nitrogen compounds, phosphorus, chlorides, and vary in pH, it is important for operators to be familiar with the wastewaters from food processors in their community. Sometimes these wastes have to be equalized or even pretreated before they can be discharged to a collection system. C. Breweries Wisconsin is known for its many breweries and microbreweries. Brewery wastewater typically has a high concentration of BOD from the carbohydrates and protein used in the brewing process and in the cleaning of brewery vessels, pipes, and equipment. Brewery wastewater can have a BOD of 1,000 to 4,000 mg/L; TSS from 200 to 1,000 mg/L; nitrogen 25 to 80 mg/L; phosphorus 1 to 50 mg/L; and a pH of 4 to 12. The volume and BOD of brewery wastewater can vary greatly over a 24-hour period. Therefore, the collection and equalization of brewery wastewater is very important so that the flow and BOD discharges to the collection system are relatively uniform. D. Metal finishing Wastewater from metal finishing has very little BOD associated with it, but has pollutants that can be toxic to fish and aquatic life and treatment plant microorganisms, even in small 2.3.2 2.3.3 Discuss the potential impacts of industrial and commercial discharges. Discuss the wastewater characteristics and problems with industrial discharges into a treatment plant. Basic General Wastewater Study Guide - August 2015 Edition (Revised June 2016) Page 12 of 79 Printed on 01/12/17 concentrations. These pollutants are not always readily removed by conventional secondary biological treatment methods. Cleaning and coating operations can result in wastewater with a pH from 1 to 12 and wastewater can contain phosphates and toxic materials such as chromate, cyanide, and metals. Many metal-finishing industries have federal or state pretreatment requirements before they can discharge their waste to a collection system. Metals can concentrate in treatment plant sludges, and, therefore, metals in sludges must be analyzed and reported to the Department of Natural Resources on sludge characteristic reports. Application of sludge with high metals concentrations is prohibited and/or restricted in rate due to potential toxicity and/or soil accumulation concerns.

Discuss control measures necessary for industrial discharges

A. Enforce sewer use ordinances B. Effective communication with industries C. Grease Control Program D. Monitoring

2.4.2 List and describe the common types of flow measurement devices.

A. Open channel flow Flow through an open channel can be measured by installing a structure in the channel. This structure is typically either a flume or weir. The most common type of flume is a Parshall Flume. The most common type of weir is either a 60° or 90° v-notch (triangular) weir. As water flows through a flume or weir, the level of water flowing through it is measured. The most common water level measurement device is an ultrasonic meter, but other devices such as pressure measurement, bubbler tubes, and staff gauges are also used. In order to get an accurate flow measurement, the weir or flume has to be sized correctly for the expected range of flows; the flow leading to it must be smooth and the water level measurement device must be properly located. The reader is referred to the 'ISCO Open Channel Handbook' for complete information about open channel flow monitoring equipment and tables. B. Pipe flow meters The most common way to measure the flow of wastewater through a pipe is a magnetic flow meter, commonly referred to as a magmeter. A magmeter operates on the principle of electromagnetic induction. Other devices, such as pressure or ultrasonic meters, are also used. As flows are metered, the flow data is recorded and stored in a computer or charted and totaled. This information is then used for operational and reporting purposes. All flow measurement devices must be calibrated annually according to the Wisconsin Administrative Code and records kept.

Explain the components of a sanitary sewer collection system.

A. Private building lateral sewer A private building lateral sewer is a 6-inch pipe that conveys sewage from the building to the 2.1.6 2.2.1 2.2.2 Discuss the effect of I/I on a collection system. Trace the sequence of events from the time one flushes a toilet until treated wastewater reaches a receiving stream. Explain the components of a sanitary sewer collection system. Basic General Wastewater Study Guide - August 2015 Edition (Revised June 2016) Page 9 of 79 Printed on 01/12/17 public sewer main, usually under the street. B. Mainline sewer Mainline sewers are pipes that collect sewage from buildings and flow by gravity to the treatment plant. C. Force mains Force main sewer pipes are where wastewater is pumped (forced) under pressure to a specific location. Force mains are used when sewage cannot flow by gravity. D. Lift (pump) stations A lift station is a location in the collection system where wastewater is collected (wet well) and then pumped to another location. The purpose of a lift station is to lift (pump) wastewater to a higher elevation where it can flow by gravity. E. Inverted siphon An inverted siphon is a pipe that must dip below an obstruction and will normally form a Ushaped flow path. The liquid flowing in one end simply forces liquid up and out the other end. Inverted siphons are commonly used when a sewer pipe must be routed under a river or other deep obstructions. F. Manholes A manhole is a structure, usually circular, at the surface that allows access to the sewer pipes buried below.

Discuss suspended growth systems (activated sludge).

Activated sludge is a suspension of wastewater and microorganisms in an aeration basin. The mixture of wastewater and microorganisms is referred to as mixed liquor suspended solids (MLSS). Aeration equipment provides dissolved oxygen (DO) to promote the growth of microorganisms that substantially remove organic material. Some common types of suspended growth processes are conventional and extended aeration activated sludge plants, oxidation ditches, and sequencing batch reactors (SBR). The reader is referred to the 'Biological Treatment - Suspended Growth Process Study Guide' for more detailed information about suspended growth processes.

Define aerobic (oxic) [O2].

Aerobic is a condition under which free and dissolved oxygen (DO) is available in an aqueous environment.

Explain why some treatment plants have to meet ammonia nitrogen limits.

Ammonia is toxic to fish and aquatic life, and its toxicity is dependent on temperature and pH. The actual limits for ammonia nitrogen are calculated based on stream flow, stream temperature, stream pH, and the type of fishery classification.

Define aeration basin.

An aeration basin is a tank where wastewater is aerated to achieve biological treatment.

Discuss attached growth systems (rotating biological contactor (RBC), trickling filter, and biotower).

An attached growth system (some times referred to as a fixed-film process) utilizes microorganisms that are fixed in place on a solid surface (attached). As wastewater passes through and around the solid surface, the microorganisms remove the food (organic content) from the wastewater. This attached growth type aerobic biological treatment process creates an environment that supports the growth of microorganisms. Some common types of fixed-film processes are trickling filters, biotowers, and RBCs. The reader is referred to the 'Biological Treatment - Attached Growth Study Guide' for more detailed information about attached growth processes.

Define anaerobic (septic) [Ø].

Anaerobic is a condition under which free, dissolved, and combined oxygen is unavailable in an aqueous environment.

Define anoxic.

Anoxic is a condition under which oxygen is only available in a combined form such as nitrate (NO3-), nitrite (NO2-), or sulfate (SO4-2) in an aqueous environment.

Describe common equipment used in attached growth secondary (biological) treatment.

Attached growth systems make use of microorganisms that attach themselves to a medium or substrate of some type. Common equipment used in attached growth systems such as trickling filters and biotowers are different types of media, pumps, distribution arm and piping, and underdrains. Common equipment used in attached growth systems such as RBCs are basins, shafts, circular plastic disks, motors, and drives and sometimes blowers and diffusers (for air driven shafts). A. Pumps and distribution piping After wastewater receives primary treatment, primary effluent is collected and pumps are used to convey the wastewater to a trickling filter or biotower distribution arm or to RBC basins for secondary biological treatment. B. Media The media is where biological organisms and bacteria attach themselves for treatment of the incoming wastewater. Trickling filter and biotower media most commonly consists of rock beds, gravel, or plastic (providing surface area for bacteria to grow) through which the wastewater flows. RBCs consist of closely spaced, circular plastic disks (providing surface area for bacteria to grow) that rotate on a shaft through the wastewater. C. Underdrain system After wastewater flows down through a trickling filter or biotower, it is collected in a drain where some of it is recirculated back through the media by pumps for further treatment. Because of temperature difference between outside air temperature and the temperature inside the filter, natural air drafts upward through the filter media providing oxygen. D. RBC motors, drives, and shafts The circular plastic disks of RBCs are on a shaft that is turned by a motor and drive system.

Discuss the information that must be recorded for influent wastewater samples.

Automatic composite samplers must be refrigerated and maintained at a temperature not to exceed 6°C (Celsius) and must never be frozen. A thermometer immersed in a small capped bottle of liquid is usually kept in the sampler to check and record temperatures on a daily basis. A 24-hour composite sample is the common requirement. For Discharge Monitoring Reporting (DMR), the date on which the majority of the composite sample was taken is the date of the sample. A sampling log must be maintained at the automatic composite sampler and the following information recorded: A. Sample identification B. Date started C. Time started D. Date collected E. Time collected F. Sampler temperature G. Operator initials H. Comments

Biochemical Oxygen Demand (BOD)

BOD, expressed in mg/L, is a measurement of the organic strength of a sample by measuring the amount of oxygen consumed over a given period of time.

Define biosolids.

Biosolids are the nutrient-rich, organic byproduct of a municipal wastewater treatment plant that is utilized as fertilizer.

Discuss the impact cleaning agents and products can have on a treatment plant.

Cleaning products and sanitizers are used widely in communities and are important in ensuring public health. When used frequently and in large quantities at industries, businesses, schools, nursing homes, medical facilities, or restaurants, they have the potential to affect treatment. Many effective cleaners contain phosphates and thus can contribute a significant amount of phosphorus to wastewater. Wastewater treatment plants with phosphorus limits, especially those with stringent limits, will have to remove nearly all this phosphorus. While ammonia is a very effective cleaning agent, quaternary ammonium compounds (commonly known as quats) can have toxic effects on treatment. Ammoniabased cleaning products also contribute ammonia to the waste stream, which must in turn be removed since ammonia can be toxic to fish and aquatic life. Surfactants can interfere and keep solids from settling in clarifiers as well as create foam in aeration basins.

Define combined sewer.

Combined sewers are pipe conveyances that carry both wastewater and storm water in a single pipe. During dry weather conditions, combined sewers discharge to a wastewater treatment plant. In the past, combined sewers discharged directly to a water body during wet weather conditions. Today, the extra wet weather volume is stored until it can be returned to the wastewater treatment plant.

dissolved oxygen (DO)

DO is the measure of the amount of oxygen dissolved in water and is expressed in mg/L.

Define disinfection.

Disinfection is a process used to destroy most pathogens to a safe level in the effluent. Disinfection does not destroy all microorganisms.

Discuss the early historical methods of dealing with wastewater.

Early on, human waste and wastewater was basically disposed of directly on the land surface. In urban communities, it was common to discharge human waste in gutters and ditches. This situation created sanitary problems (illnesses and diseases), nuisance odors, and unsightliness. Rains were counted on to flush the waste away. Later development of the pit toilet or outhouse facility continued until underground collection systems were developed. The development of water supply systems increased the volume of wastewater generated. Early health concerns led to the building of pipe collection systems to convey this material away from human habitation, usually to a river, stream, or other body of water. Early systems received both wastewater and storm water. This improved public health concerns, but transferred the problem to receiving water streams.

effluent

Effluent is the treated wastewater discharged from a treatment plant to the environment.

eutrophication

Eutrophication is the excessive growth of plant and algae in receiving waters due to dissolved nutrients and their decomposition.

food to microorganism ratio (F:M or F/M)

F/M is the amount of food (BOD) provided to the microorganisms [mixed liquor volatile suspended solids (MLVSS) or mixed liquor suspended solids (MLSS)].

Discuss the impact FOG can have on a collection system and a treatment facility.

FOGs are waste byproducts of cooking. They are found in meats, dairy products, cooking oils, shortenings, food scraps, and sauces. FOG collects and can form grease plugs in sewer pipes if washed down the drain or through unmaintained grease traps at restaurants or institutions. The most common cause of sanitary sewer overflows (SSO) from sewer pipes are blockages caused by grease. If grease makes its way to the treatment plant, it can plug valves, meters, and pipes. It floats to tank surfaces and can create settling problems. Grease can also favor the growth of filamentous organisms that create surface foam and scum. Grease can involve costly and unpleasant clean-ups. The best practice for controlling grease is to keep it out of the collection system in the first place by having a Grease Control Program in a community. A Grease Control Program usually involves regular inspections of restaurant and institutional (nursing home, hospital, and school kitchens) grease traps or interceptors and an ongoing information and education program with residents and businesses.

2.5.2 Describe how flow-proportional sampling works.

Flow-proportional sampling is the most representative method of collecting wastewater samples for wastewater coming into and being discharged from a wastewater treatment plant on a continuous basis. For most treatment plants in Wisconsin, flow-proportional sampling is a permit requirement. The volume of each sample collected is based on the flow, and this is accomplished by having a flow meter send a signal to an automatic composite sampler. The sampler is programmed to collect a certain sample volume per unit volume of flow (flow pulse interval). For instance, the sampler may take a 50 mL sample every 10,000 gals of flow. It is more representative to take a small sample more often than it is to take a large sample less often. A sample should be collected at least every 10 to 15 mins (4 to 6 samples every hour) during the peak flow period of the day, such as in the morning of a normal work day. For instance, if a peak hourly flow of 60,000 gals flows into the plant between 8 am and 9 am, the sampler should be programmed to take a sample every 10,000 to 15,000 gals of flow (60,000 gals/hr and 6 samples per hour = 10,000 gals/sample). Conversely, in the middle of the night when flows may drop to only 10,000 to 20,000 gals/hr, the flowproportional sampler will only collect 1 to 2 samples in an hour. The volume of sample 2.5.2 Describe how flow-proportional sampling works. Basic General Wastewater Study Guide - August 2015 Edition (Revised June 2016) Page 17 of 79 Printed on 01/12/17 Chapter 3 - Wastewater Treatment collected each flow pulse interval should be adjusted, as a general rule, to fill at least 1/4 to 1/2 of the compositing container in 24 hours during average flows. This will allow the container to fill, without overfilling, during wet weather periods when daily flows increase 2 to 4 times the average flow. If peak flows are higher than this, then the sample volume will have to be reduced during wet weather so as to not overfill the container and cause the sampler to shut off, thereby not collecting a true 24-hour composite sample. A flowproportional sample MUST sample during a full 24-hour period, even during wet weather peak flows.

Define grit.

Grit is the fine, abrasive particles removed from wastewater, such as sand and eggshells.

Define hydraulic retention time (HRT).

HRT is a period of time that wastewater remains in a tank. This term is also known as detention time

Define headworks.

Headworks is the beginning, or head, of a treatment plant where influent flow is measured and sampled and where preliminary treatment occurs.

Define inflow and infiltration (I/I)

I/I is any unwanted clearwater that leaks into a collection system. Generally, it consists of groundwater, rainwater, or snowmelt.

List and define common sources of I/I.

I/I is unwanted clearwater that gets into the collection system. Clearwater is classified by how fast it gets into the collection system and is determined by weather and groundwater conditions. If the flow increases as soon as there is significant rainfall and subsides soon after the rain stops, it is called inflow. If the flow goes up gradually after a rainfall and stays up as long as the groundwater remains high, it is called infiltration. Common sources of clearwater (I/I) are: A. Roof leaders connected to the sanitary sewer B. Storm and sanitary crossovers C. Low lying manholes in roads or ditches subject to flooding D. Uncapped lateral connections E. Sump pumps and foundation drains F. Cracks and offset joints in the sanitary sewer G. Manhole cracks and defects H. Buried manholes I. Cracks and leaks in building sewers

Explain how a wet well and dry well pumping station works.

In wet well and dry well lift stations, the centrifugal pumps and other equipment are located in a separate chamber (dry well), with only the suction pipe being submersed in the wet well. The pump is turned on when the wastewater reaches a certain depth. If the wastewater continues to rise, more pumps will be turned on. The pumps are turned off when the wet well is empty or reach the minimal set point. It is important that the dry well be well ventilated and dehumidified to protect the equipment and ensure the safety of the operator.

Discuss the potential impacts of industrial and commercial discharges.

Industrial discharges may vary in strength and volume. Slug loads are of special concern and can upset or pass through the treatment plant and out with the final effluent. High levels of BOD, TSS, phosphorus, ammonia, and FOG can effect treatment. High or low pH can also be a problem.

Define influent.

Influent is the raw (or untreated) wastewater entering a treatment process.

Describe a good sampling location and procedure for collecting representative influent wastewater samples.

It is important that raw influent wastewater be sampled in a location where it is well mixed and represents the actual wastewater coming into the treatment plant. It is best to collect the sample after the headworks (after screenings and grit removal), as this is most representative of the BOD and TSS going into downstream treatment units.

Discuss the importance of wastewater flow measurement.

It is very important to know how much influent is flowing and being treated in the plant. Treatment efficiency is dependent on loadings and detention time. It is also required to report how much final effluent flows into a receiving water body. To measure the influent entering a treatment plant from the community, flow measurements should be taken before sidestreams. To know the actual flow and loading to the treatment units, sidestreams need to be included in the flow measurements.

Define million gallons per day (MGD).

MGD is a common wastewater flow measurement in a treatment plant, expressed as millions of gallons (MG) of wastewater flowing each day.

3.3.7 Describe the differences between nitrification and denitrification in wastewater treatment.

Nitrification is a biological process where nitrifying bacteria (nitrifiers) convert nitrogen in the form of ammonia (NH3) into nitrite (NO2-) and nitrate (NO3-) under aerobic conditions. Treatment plants that have ammonia limits on their permit will use nitrification to remove ammonia. Many plants that discharge to surface waters have ammonia limits to protect fish and aquatic life from ammonia toxicity. Denitrification is a biological process where bacteria convert nitrate (NO3-) and nitrite (NO2-) to nitrogen gas (N2) under anoxic conditions. Treatment plants that have total nitrogen limits will use denitrification to remove nitrogen. Plants that discharge to groundwater have total nitrogen limits to protect groundwater from nitrates. Plants that remove phosphorus biologically will also employ denitrification to remove nitrates that interfere with enhanced biological phosphorus removal (EBPR).

Define pathogens.

Pathogens are infectious microorganisms in wastewater that pose health risks.

Explain why some treatment plants have total phosphorus limits.

Phosphorus is one of the key nutrients that contribute to eutrophication and excess algae and plant growth in rivers and lakes. The decomposition of excess plant matter reduces the level of DO in the receiving water which affects aquatic life.

Trace the sequence of events from the time one flushes a toilet until treated wastewater reaches a receiving stream.

Potable water is provided by the water supply system into a building and is used to flush or drain wastes into the building's sanitary sewer pipes and into the wastewater collection system. Wastewater is conveyed through gravity sewers, lift stations, and force mains until it makes its way into the headworks of a wastewater treatment plant. The wastewater is then treated by both physical and biological unit operations and processes and then clean water is discharged into a receiving water body.

Define primary treatment.

Primary treatment is a treatment process usually consisting of clarification by solid and liquid separation removing a substantial amount of suspended and floating matter.

Define process control.

Process control is the tools and methods used to optimize treatment plant operations.

Define return activated sludge (RAS).

RAS is the settled activated sludge (biomass) collected in a final clarifier and returned to the secondary treatment process to mix with incoming wastewater. This returns a concentrated population of microorganisms back into the aeration basin.

Describe the characteristics of influent domestic wastewater.

Raw influent is less than 99% water and is gray in color with an earthy, musty odor. Typical influent wastewater concentrations are: BOD - 250 Total Suspended Solids - 300 Total Nitrogen - 40 Ammonia - 25 Total Phosphorous - 9 Fats, Oils, and Grease (FOG) - 100 pH - 6.5 to 8.0

Discuss how a vortex-type (Pista®) grit chamber works.

Raw wastewater is introduced along the side of a cylindrical tank designed for vortex flow. The water and grit combination rotates slowly around the vertical access of the tank. The flow spirals gradually down the tank perimeter, allowing the heavier solids to settle to the tank bottom where they are then removed.

Discuss how an aerated grit chamber works.

Raw wastewater is introduced into the end of an aerated grit chamber, which is typically rectangular in shape. Injected air creates a spiral flow of wastewater as it moves through the chamber. As the flow velocity diminishes along the tank, heavier grit particles gradually settle from the water. The settled solids are typically gathered at the tank bottom by a rake mechanism and removed by pumping.

Describe sanitary sewer overflows (SSO) and their causes.

SSOs occur for many different reasons. One of the main reasons sewers back-up and overflow is too much clearwater gets into the sewer pipes through infiltration or inflow (I/I) during wet weather events. Sewer pipes are designed for only a certain flow capacity and excessive I/I can exceed that capacity. As sewers age, sewer defects increase, allowing for more clearwater (I/I) to get into them. Other circumstances that can cause an overflow are power outages, plugged sewers due to grease or large objects, broken or collapsed pipes, equipment failure such as a lift station pump, or wide-scale flooding

Define screenings.

Screenings are the materials in wastewater removed with screens at the headworks of treatment plants. They include: sticks, stones, plastics, and personal hygiene products.

Define secondary treatment.

Secondary treatment is a treatment process using biological processes that utilize bacteria to remove pollutants.

Define septage.

Septage is the high strength waste pumped out of septic tanks, sometimes disposed at wastewater treatment plants.

Define sidestreams.

Sidestreams are flows generated within the plant, usually from solids processing that has been recycled back through the plant.

Discuss the possible impacts of sidestreams or recycle flows back to the secondary process.

Sidestreams or recycle flows usually come from solids handling treatment or dewatering processes, such as decanting digesters or sludge storage tanks. Sidestreams may be high in BOD, suspended solids, ammonia, phosphorus, and sulfides or very low in temperature. It is best to return sidestreams slowly and regularly so microorganisms adjust and acclimate to this loading. If the permit limits phosphorus or ammonia, it is critical to know the loading from sidestreams. Sidestreams can upset a treatment plant or result in a pass-through of pollutants to the effluent, resulting in permit violations. If the permit limits phosphorus or ammonia, sometimes it is necessary to separately treat the sidestream.

Define sludge age.

Sludge age is the theoretical length of time a particle of activated sludge stays in the treatment plant, measured in days. In an activated sludge plant, sludge age is the amount (lbs) of MLSS divided by the suspended solids or excess cell mass withdrawn from the system per day [lbs per day of waste activated sludge (WAS)].

Define total suspended solids (TSS).

TSS is the measure of the total amount of solids suspended in a sample and is expressed in mg/L.

Define tertiary treatment.

Tertiary treatment is a treatment process using physical, chemical, or biological processes to remove suspended solids and nutrients in wastewater to accomplish a level of treatment greater than what can be achieved by secondary treatment.

Discuss the Clean Water Act

The Clean Water Act is a federal law created in 1972 with the main objective of chemically, physically, and biologically restoring and maintaining the nation's waters. It was created to stop the continuous dumping of pollutants, both point source and non-point source, into surface waters and wetlands.

Describe the environmental factors that influence the health and growth of microorganisms.

The activated sludge wastewater treatment process must operate under proper environmental conditions to support a healthy, growing population of microorganisms. The operator must monitor the activated sludge process to ensure the right environmental conditions are being provided for the microorganisms. Efficient wastewater treatment plant performance will then be achieved. A. Food Incoming wastewater to a treatment plant provides the food that microorganisms need for their growth and reproduction. This food is mostly organic material. The more soluble the organic material is, the more easily microorganisms can use it. Since the amount and type 3.3.8 3.3.9 3.3.10 3.3.11 Explain why some treatment plants have to meet ammonia nitrogen limits. Explain why some treatment plants have total phosphorus limits. Describe the role microorganisms have in the activated sludge process. Describe the environmental factors that influence the health and growth of microorganisms. Basic General Wastewater Study Guide - August 2015 Edition (Revised June 2016) Page 29 of 79 Printed on 01/12/17 of organic loading in the treatment plant affects the growth of the microorganisms, influent total BOD and soluble BOD are measurements an operator can make to determine the amount and type of incoming food for the microorganisms. B. Flow Incoming wastewater must flow through a treatment plant at a rate that allows the microorganisms sufficient time to consume the incoming food and to settle properly. High flows can shorten the time necessary for the full treatment of wastewater. Extremely high flows can wash microorganisms out of the plant through the final clarifier. C. Oxygen Conventional activated sludge is an aerobic process. Many bacteria in the activated sludge process need free oxygen (O2) to convert food into energy for their growth. For optimal performance, it is very important for an operator to be sure enough oxygen is being provided in the aeration tanks for the microorganisms (typically 1.0 to 3.0 mg/L). Aeration basin DO concentrations (mg/L) are measured continuously in many plants to ensure adequate oxygen is available. D. Temperature All biological and chemical reactions are affected by temperature. Microorganisms' growth and reaction rates are slow at cold temperatures and much faster at warmer temperatures. Most microorganisms do best under moderate temperatures (10 to 25°C). Aeration basin temperatures should be routinely measured and recorded. E. pH Biological and chemical reactions are affected by pH. Most microorganisms do well in a pH environment between 6.0 and 9.0. Acidic (low pH) or alkaline (high pH) conditions can adversely affect microorganisms' growth and survival. Operators measure both influent pH and aeration basin pH to ensure proper plant pH conditions. F. Nutrients Microorganisms need trace nutrients such as nitrogen, phosphorus, and some metals for their metabolism. Most incoming wastewater to a treatment plant, especially domestic sewage, contains an abundance of these trace nutrients. The ratio of BOD to nitrogen to phosphorus should be 100:5:1. Influent wastewater is measured to determine this nutrient ratio. G. Toxicity Incoming wastewater to a treatment plant may, at times, contain materials or compounds that are toxic to microorganisms. Depending on the concentration of toxic material, microorganisms could be destroyed or their metabolic rates affected, thus impairing the wastewater treatment plant efficiency.

Describe the types of materials prohibited from discharge into collection systems and the reasons they should not be discharged.

The materials with the characteristics listed below are generally prohibited from discharge to the sewer system. These prohibitions are included in local sewer use ordinances. Generally, materials that can interfere with wastewater treatment, pass through the treatment system and cause a water quality violation, or accumulate in sludges, making the sludges toxic or hazardous are prohibited. Many of the industrial materials can be handled with proper pretreatment or segregation of waste streams that cannot be pretreated. A. Volatile organics, including gasoline or solvents, can cause an explosive atmosphere in the collection system or at the treatment plant. B. Heavy metals, including chromium, zinc, copper, nickel, and cadmium, are very toxic and can cause a treatment plant upset, pass through the plant, or accumulate in the sludge. C. Acidic and alkaline wastes can damage the collection system or upset the treatment plant. Generally, a pH lower than 5.0 or greater than 10.0 should be neutralized prior to discharge to the collection system. D. FOG must be controlled at industrial and commercial sources with oil separators and grease traps to prevent maintenance problems in wet wells and at the treatment plant. E. High-strength loadings of BOD or suspended solids can organically overload the treatment plant. This can especially be a problem with batch dumping that causes large slug loads. Any batch type operation should be handled by flow equalization to prevent plant upsets. F. High temperature wastewaters can affect biological activity. G. Solid or viscous materials can cause sewer blockages. H. Any debris including rags or other materials can cause sewer blockages or pump clogging. I. Other toxic materials can impair or interfere with the treatment process.

Define milligrams per liter (mg/L).

The measurement mg/L is a concentration of a substance in a liquid expressed as a weight in milligrams per liter of volume (mg/L). Milligrams per liter is the same as parts per million (ppm). 1 mg/L = 1 ppm (One liter of water weighs 1,000,000 mg)

Discuss where a wastewater treatment plant operator would find information on conducting wastewater tests.

The most authoritative source for conducting wastewater testing can be found in 'Standard Methods for the Examination of Water and Wastewater', prepared and published jointly by the American Public Health Association, American Water Works Association, and Water Environment Federation. It is commonly referred to simply as 'Standard Methods'. The first edition was published in 1905 and many editions have since been published as information is updated and instrumentation and methodologies change.

List common sidestreams within a treatment plant

The most common recycle streams are from: A. Thickening and dewatering process 1. Gravity belt thickening filtrate 2. Centrifuge centrate 3. Gravity thickening supernatant 4. Dissolved air flotation (DAF) subnatant 5. Rotary drum thickening filtrate 6. Belt filter press filtrate 7. Sludge drying bed underdrain 8. Plate and frame filtrate 9. Reed bed filtrate B. Stabilization and storage 1. Aerobic digester decant 2. Anaerobic digestion supernatant 3. Biosolids storage decant 4. Granular filter backwash

Discuss the operation and maintenance (O&M) of a collection system.

The primary activities of operating and maintaining a sanitary sewer collection system are: A. Cleaning B. Root removal C. Televising D. Flow monitoring E. Smoke testing F. Manhole inspections G. Lift station maintenance H. Manhole rehabilitation I. Mainline rehabilitation J. Private sewer inspections K. Private sewer I/I removal L. Fat, oil and grease (FOG) control program Operating and maintaining a sewer system will ensure the wastewater flows to the treatment plant, without any overflows or basement back-ups anywhere in the sewer system. Regularly televising a certain percentage of the sewer system each year to assess pipe conditions is the most important inspection tool available to operators, as it is the only way to see the pipe.

Describe the role microorganisms have in the activated sludge process.

The principle role microorganisms have in the activated sludge process is to convert dissolved and particulate organic matter, measured as BOD, into cell mass. In a conventional activated sludge process, microorganisms use oxygen to break down organic matter (food) for their growth and survival. Over time, and as wastewater moves through the aeration basin, food (BOD) decreases with a resultant increase in cell mass (MLSS concentration)

Discuss the preliminary treatment process.

The purpose of preliminary treatment is to remove larger materials (rags, sticks, stones, plastics, personal hygiene products, etc.) and grit from the waste stream before it flows to downstream treatment units. This is done to significantly reduce the plugging and clogging of pumps and pipes, the abrasive action of grit on equipment, and the settling of these materials in down streams tanks and basins. Preliminary treatment usually consists of screening and grit-removal equipment. Sewage grinders and comminutors that shred larger materials into smaller pieces are not commonly used anymore. Newer preliminary treatment units now automatically clean, dewater, and bag or containerize these materials thus greatly reducing exposure to operators.

Describe common equipment used in preliminary treatment.

The purpose of preliminary treatment is to remove larger, inorganic materials (rags, sticks, stones, plastics, personal hygiene products, etc.) and grit from the waste stream before it flows to downstream treatment units. Preliminary treatment equipment primarily consists of screening and grit removal systems. Septage handling, grinders, odor control, and flow equalization are also considered preliminary treatment. A. Screening Common screening systems are manually cleaned bar screens, mechanically cleaned bar screens, and rotary fine screens. These processes simply remove debris which is then land filled. B. Grit removal Common grit removal systems are aerated grit chambers and vortex-type (Pista®) unit. An aerated grit chamber uses air that separates light from heavier solids (grit). A vortex-type (Pista®) unit consists of a cylindrical tank creating a vortex flow in which the heavier grit settles to the bottom.

Describe common equipment used in primary treatment.

The purpose of primary treatment is to settle wastewater solids and capture floatable substances (such as FOG). Well-designed and operated primary facilities can expect removal efficiencies of 40% to 60% for suspended solids and 20% to 35% for BOD. Common primary treatment units are rectangular clarifiers, circular clarifiers, and DAF.

3.2.1 Discuss the primary treatment process.

The purpose of primary treatment is to settle wastewater solids and capture floatable substances [such as fats, oil, and grease (FOG)]. Some biochemical oxygen demand (BOD) is also removed in the settling of these solids. The solids that settle in primary clarifiers and the FOG skimmed off the surface are directly removed from the process. Primary treatment commonly consists of circular or rectangular clarifiers. Sometimes dissolved air flotation (DAF) thickeners or other processes are used for primary treatment. Primary effluent containing soluble BOD and some suspended solids flows to a secondary biological treatment process for further treatment.

Discuss the secondary biological treatment process.

The purpose of secondary biological treatment is to remove dissolved and suspended organic material from wastewater to produce an environmentally safe treated effluent and biosolids or sludge. A secondary treatment system can achieve overall biochemical oxygen demand (BOD) and suspended solids removal in the 85% to 95% range. Secondary biological treatment consists of microorganisms (bacteria), either in mixed suspension in a basin or attached to a media of some type where the organic material is broken down and consumed by the microorganisms. Most secondary treatment processes require oxygen for the bacteria.

gallons per day (gpd)

The term gpd is a common wastewater flow measurement expressed as the number of gallons flowing each day.

gallons per hour (gph).

The term gph is a common wastewater flow measurement expressed as the number of gallons flowing each hour.

gallons per minute (gpm).

The term gpm is a common wastewater flow measurement expressed as the number of gallons flowing each minute.

Discuss the difference between a time-proportional and flow-proportional composite sample

Time-proportional composite samples are a collection of samples over time, usually after so many minutes. Flow-proportional composite samples are samples collected per unit of flow, after so many gallons. The frequency at which flow-proportional samples are collected is directly proportional to the flow, with more samples taken when flows are higher and less samples when flows are lower. Automatic flow-proportional composite samplers are required for almost all wastewater treatment plants, as they are the most representative means of collecting samples from continuous flowing treatment systems, especially for biochemical oxygen demand (BOD) and total suspended solids (TSS).

Define waste activated sludge (WAS).

WAS is the activated sludge (excess biomass or cell mass) removed from the secondary treatment process. For most treatment plants, this will be a portion of the RAS flow stream.

Discuss the importance of treating wastewater.

Wastewater is treated for two main reasons: A. Protect public health by destroying pathogens B. Protect the environment by removing pollutants Pathogenic organisms are disease-causing microorganisms. They include various bacteria, viruses, and parasites. The discharge of waterborne human wastes will contain these organisms from ailing individuals and would be expected to be present in wastewater entering a wastewater treatment plant. Although wastewater treatment is taken for granted in the United States, rivers and lakes are more polluted and waterborne diseases are more prevalent in countries that do not properly treat wastewater.

Describe the sources of wastewater in a community.

Wastewater is used water that goes down the drain and flows to the wastewater treatment plant. Flows originate from domestic (household), industrial, and commercial sources. Some wastewater is trucked to the wastewater treatment plant as septage, holding tank waste, leachate, and some high strength industrial wastewater. In addition, clearwater (rain, snow, and groundwater) from inflow and infiltration (I/I) can get into the collection system.

Discuss the effect of I/I on a collection system.

When I/I enters collection system pipes, it can exceed the flow capacity of the pipes and result in surcharging, basement backups, and sanitary sewer overflows (SSO). I/I in the collection system can also lead to very high flows entering the treatment facility and can lead to wastewater pumping and treatment problems. Too much flow going through aeration basins and clarifiers can wash out solids, creating a loss of treatment efficiency and resulting in permit violations.

List flow measuring applications in a wastewater treatment plant.

While flow monitoring is required in Wisconsin Pollution Discharge Elimination System (WPDES) permits for measuring influent and effluent flows, flow measurements are needed in many other places within the plant for proper process control. In an activated sludge plant, measuring return and waste activated sludge is extremely important as they are the key to successful operations. In-plant flow meters are used for measuring: A. Return activated sludge (RAS) B. Waste activated sludge (WAS) C. Recycle or recirculation flows D. Sidestream flows E. Sludge flows to digesters F. Sludge feed rates to sludge dewatering equipment G. Sludge withdrawal volumes from storage tanks

Define pH.

pH is a measure of the acidity or alkalinity of a sample on a scale of 0 to 14 (acidic to alkaline). A pH of 7 is neutral.