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320 Cards in this Set
- Front
- Back
Define: Influent |
Wastewater entering a treatment plant (raw sewage). |
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Define: Effluent
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Treated wastewater discharged from a treatment plant to the enviroment. |
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Define: Biochemical Oxygen Demand (BOD)
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A test that measures the organic strenght of a sample by measuring the amount of oxygen consumed.
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Define: Total suspended solids
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A test that measures the total amount of solids suspended in a sample.
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Define: pH
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A measure of the acidicty or alkalinity of a sample on a scale of 0-14. pH 7 is neutral.
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Define: Disolved Oxygen
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A measure of the amount of oxygen dissolved is water.
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Define: Gallons per Minute (GPM)
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The number of gallons flowing each minute. |
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Define: Gallons per Day (gpd)
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The number of gallons flowing each day.
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Define: Million Gallons per Day (MGD)
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The number of gallons flowing each day, expressed as millions of gallons.
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Define: Milligrams per Liter (mg/L)
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The concentration of a substance in a liquid expressed as a weight in milligrams per liter of a volume (mg/L). Milligrams per liter is the same as parts per million (ppm)
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Define: Composite Sample
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A sample prepared by combining a number of grab samples, typically over a 24 hour period.
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Define: Grab Sample
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A single sample taken at a particular time and place that is representative of the current conditions.
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Define: Weir
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A level control structure used to provide uniform flow.
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Define: Flume
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A restriction in an open channel used to measure flow.
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Define: Septage
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A high strength waste pumped out of septic tanks, sometimes disposed at WWTPs.
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Define: Hydraulic Retention Time (HRT)
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The period of time that wastewater remains in a tank. This term is also known as detention time.
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Define: Eutrophication
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The process of excessive growth of plant and algae in receiving waters due to dissolved nutrients and their decomposition.
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Define: Sludge Age
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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 mixed liquor suspended solids divided by the suspended solids, or excess cell mass, withdrawn from the system per day (lbs per day of waste activated sludge).
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Define: Food to microorganism ratio (F:M or F/M)
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The amount of food (BOD) provided to the microorganisms (MLVSS or MLSS) in the aeration basins.
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Define: Inflow/Infiltration (I/I)
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Any unwanted clearwater that leaks into a collection system. Generally it consists of groundwater, rainwater, or snowmelt.
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Define: Sanitary Sewer (Collection System)
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An underground pipe system used to convey wastewater to a treatment facility.
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Define: Storm Sewer
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An underground pipe system that collects rainwater from streets and conveys it to a place other than the wastewater treatment plant.
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Define: Combined Sewer
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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. During wet weather conditions, combined sewers used to discharge directly to a water body; now the extra wet weather volume is stored until it can be returned to the wastewater treatment plant.
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Define: Lift Station
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An underground chamber with pumps that is used to elevate (lift) wastewater to a higher grade. Lift stations are located within a collection system.
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Define: Manhole
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A manhole is a structure that provides access to a sewer system. They usually are a round opening with an iron lid.
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Define: Wet Well
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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.
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Define: Sanitary Sewer Overflow (SSO)
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The release of wastewater from a sewage collection system or an interceptor sewer directly into a water of the state or to the land surface. It is commonly referred to as a "SSO".
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Define: Microorganism
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A living organism too small to be seen with the naked eye but is visible under a microscope such as a bacteria, viruses, fungi, or protozoa.
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Define: Sidestreams
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A flow generated within the plant, usually from solids processing, that then is recycled back through the plant.
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Define: Aerobic (oxic) [O2]
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A condition in which free and dissolved oxygen is available in an aqueous environment.
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Define: Anaerobic (septic) [Ø]
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A condition in which free, dissolved, and combined oxygen is unavailable in an aqueous environment.
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Define: Anoxic
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A condition in which oxygen is only available in a combined form such as nitrate (NO3-), nitrite (NO2-), or sulfate (SO4-2) in an aqueous environment.
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Define: Treatment Process
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A physical, biological, or chemical action that is applied to wastewater to remove or reduce pollutants.
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Define: Treatment Unit
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A treatment unit is an individual structure or equipment within a sewage or wastewater treatment facility that is part of a treatment process.
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Define: Selector
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Part of the treatment system that selects for a specific type of microorganism by providing an environment (anaerobic, anoxic, aerobic) that favors its growth.
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Define: Preliminary Treatment
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A treatment process consisting of screening and grit removal before the wastewater flows on to other treatment processes.
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Define: Primary Treatment
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A treatment process that usually consists of clarification by solid-liquid separation that removes a substantial amount of suspended and floating matter.
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Define: Secondary Treatment
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A treatment process that uses biological processes utilizing bacteria to remove pollutants.
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Define: Tertiary Treatment
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A wastewater treatment process that uses physical, chemical, or biological processes to remove suspended solids and nutrients to a level that is greater than what can be achieved by secondary treatment.
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Define: Headworks
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Headworks is the beginning, or head, of a treatment plant where influent flow is measured and sampled and where preliminary treatment occurs.
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Define: Grit
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The fine abrasive particles removed from wastewater, such as sand and eggshells.
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Define: Screenings
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The materials in wastewater that are removed on screens at the headworks of treatment plants, such as sticks, stones, plastics, and personal hygiene products.
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Define: Aeration Basin
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A tank in which wastewater is aerated to achieve biological treatment.
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Define: Clarifier
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A circular or rectangular tank used to remove floatable and settleable solids in wastewater.
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Define: Disinfection
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A process used to destroy most pathogens in the effluent to a safe level. Disinfection does not destroy all microorganisms.
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Define: Biosolids
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The nutrient-rich, organic byproduct of a wastewater treatment plant that is utilized as fertilizer.
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Define: Process Control
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The tools and methods used to optimize treatment plant operations.
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Define: Return Activated Sludge (RAS)
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The settled activated sludge (biomass) that is collected in a secondary 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.
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Define: Waste Activated Sludge (WAS)
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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 Return Activated Sludge (RAS) flow stream.
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Define: Confined Space
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A space that is 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.
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Define: Pathogens
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Infectious microorganisms in wastewater that pose health risks.
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Define: Wisconsin Pollutant Discharge Elimination System (WPDES) Permit
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This permit is issued to wastewater facility owners, and contains facility effluent and biosolids/sludge limitations, conditions, and reporting requirements.
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Where a wastewater treatment plant operator would find information on conducting
wastewater tests. |
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.
Commonly referred to simply as Standard Methods. |
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Standard Methods for the Examination of Water and Wastewater was first published in what year?
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1905
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Describe the characteristics of influent domestic wastewater.
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Sewage is >99% water. It is gray in color and has an earthy, musty odor.
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Typical influent wastewater concentrations of BOD are?
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250 mg/L
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Typical influent wastewater concentrations of TSS are?
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300 mg/L
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Typical influent wastewater concentrations of Total Nitrogen are?
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40 mg/L
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Typical influent wastewater concentrations of Ammonia are?
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25 mg/L
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Typical influent wastewater concentrations of Total Phosphorus are?
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9 mg/L
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Typical influent wastewater concentrations of Fats, Oil, and Grease (FOG) are?
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100 mg/L
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Typical influent wastewater pH is?
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6.5 - 8.0
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The most authoritative source for conducting wastewater testing can be found in
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Standard Methods for the Examination of Water and Wastewater
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A wet well lift station is a
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single chamber that collects wastewater.
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pump and motor being completely submerged in the wetwell.
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submersible lift station
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The submersible centrifugal pump is
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watertight, and normally controlled by float switches.
They are made to be easily removed for cleaning and maintenance using a rail system. |
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In wetwell/drywell lift stations
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the centrifugal pumps and other equipment are located in a separate chamber (drywell), with only the suction pipe being submersed in the wetwell.
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One of the main reasons sewers back-up and overflow is
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too much clearwater gets into the sewer pipes through
infiltration or inflow (I/I) during wet weather events |
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Sewer pipes are designed for
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only a certain flow capacity and excessive I/I can exceed that capacity
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As sewers age
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sewer defects increase, allowing for more clearwater (I/I) to get into them
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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 widescale flooding.
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Some dairy operations have their own
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wastewater treatment plant but many discharge to the wastewater treatment plant in the community they are located
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Industrial wastes from dairy facilities consist of
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various dilutions of milk that enter the municipal sewage system
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One of the largest sources of dairy wastewater come from
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washwaters and rinse waters of dairy tanks, trucks, equipment, pipelines, and floors
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Dairies use clean-in-place (CIP) systems
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that alternate acid and caustic cleaners and rinses in the cleaning of tanks, equipment, and pipes
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dairy wastewater pH
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can be high or low
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Milk and milk solids
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have a very high biochemical oxygen demand (BOD). BODs can range from 1,000-10,000 mg/L.
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Milk wastes contain
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high amounts of nitrogen, phosphorus, and chlorides.
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collection and equalization of dairy wastewater is
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very important so that the flow and BOD discharges to the sewer system are more uniform
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A wastewater treatment plant can be upset if
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it receives variable loads, high strength wastes, high or low pH discharges, or slug loads from a dairy facility.
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Food (meats, canned foods, snacks, etc) is processed in many different ways and the wastes from them
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are usually high in BOD, suspended solids, nitrogen compounds, phosphorus, chlorides, and vary in pH
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Brewery wastewater typically has a
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high concentration of biochemical oxygen demand from the carbohydrates and protein and in the cleaning of vessels, pipes, and equipment.
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Brewery wastewater can have a BOD of
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1,000-4,000 mg/L,
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Brewery wastewater can have a TSS of
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200-1,000 mg/L
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Brewery wastewater can have a Nitrogen of
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25-80 mg/L
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Brewery wastewater can have a Phosphorus of
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1-50 mg/L
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Brewery wastewater can have a pH of
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4-12.
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Metal finishing wastewater
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has very little BOD associated with it, but has pollutants that can be toxic to fish and aquatic life, even in small concentrations, as well as wastewater treatment plant microorganisms.
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Metal finishing wastewater
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can contain phosphates and toxic materials such as
chromate, cyanide and metals. |
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Many metal finishing industries have federal or state pretreatment requirements before
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they can discharge their waste to a sanitary sewer
system |
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Metals can concentrate in treatment plant sludges and therefore metals in sludges must be analyzed and reported to
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the DNR on sludge characteristic reports
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Sludge with high metals concentrations are prohibited
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or restricted in the rate of application due to potential toxicity and/or soil accumulation concerns.
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Cleaning products
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They are important in ensuring public health
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used frequently and in large quantities at
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industries, businesses, schools, nursing homes, medical facilities, or restaurants
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Many effective cleaners contain
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phosphates and thus can contribute a lot of phosphorus to wastewater.
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quaternary ammonium compounds (commonly known as "quats")
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can have toxic effects at a treatment plant.
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Ammonia-based cleaning products
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contribute ammonia to the wastestream, which will need to be removed since ammonia can be toxic to fish and aquatic life.
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Surfactants can interfere and
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keep solids from settling in clarifiers as well as create foam in aeration basins
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Fats, oils, and grease are
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found in meats, dairy products, cooking oils, shortenings, food scraps, and sauces.
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The most common cause of sewage overflows from sewer
pipes are |
blockages caused by grease
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If grease makes its way to the treatment plant, it can
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plug valves, meters and pipes at the plant.
It floats to tank surfaces and can create settling problems. |
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Grease can favor growth
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of filamentous organisms that create surface foam and scum
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The best practice for controlling grease
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is keeping it out of the sewer system in the first place by having a Grease Control Program in a community
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A Grease Control Program usually involves
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regular inspections of restaurant and institutional (nursing home, hospital, and school kitchens) grease traps or interceptors and an ongoing information & education program with residents and businesses.
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Volatile organics
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such as gasoline or solvents that can cause an explosive atmosphere in the sewer system or at the treatment plant.
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Heavy metals
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such as 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.
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Acidic and alkaline wastes can
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damage the sewer system or upset the treatment plant. Generally, pH's lower than 5.0 or greater than 10.0 should be neutralized prior to discharge to the sewer system.
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Fats, Oils, and Grease (FOG)
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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.
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High strength loadings of BOD or suspended soils
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could organically overload the treatment plant. This would especially be a problem with "batch" dumping that would cause large slug loads. Any "batch" type operation should be handled by flow equalization to prevent plant upsets.
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High temperature wastewaters
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could affect biological activity
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solid or viscous materials
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could cause sewer blockages
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debris such as rags or other materials
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could cause sewer blockages or pump clogging.
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While flow monitoring is required in WPDES permits for measuring
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influent and effluent flows
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In an activated sludge plant, measuring
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return and waste activated sludge is extremely important as they are the key to successful operations
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In-plant flow meters are used for measuring
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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 |
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Flow proportional sampling is
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the most representative method of collecting wastewater samples for wastewater coming into and being discharged from a treatment plant on a continuous basis.
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For most treatment plants in Wisconsin, flow proportional sampling is
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a permit requirement
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The sampler is programmed to collect a certain sample volume per
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unit volume of flow (flow pulse interval)
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It is better to take a small sample
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more often than it is to take a large sample less often
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As a starting point in programming the sampler correctly,
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make sure a sample is collected at least every 10-15 minutes (4-6 samples every hour) during the peak flow period of the day
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if a peak hourly flow of 60,000 gallons flows into the plant between 8 am - 9 am, the sampler should be programmed
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take a sample every 10,000-15,000 gallons of flow (60,000 gallons per hour/6 samples per hour = 10,000 gallons/sample).
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The volume of sample collected each flow pulse interval should be
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to fill at least 1/4 to 1/2 of the compositing container in 24 hours during average flows.
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A flow proportional sample
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MUST sample during a full 24 hour period, even during wet weather peak flows.
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The purpose of preliminary treatment is
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to remove larger materials (rags, sticks, stones, plastics, personal hygiene products, etc.) and grit from the wastestream before it flows to downstream treatment units.
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Preliminary treatment equipment primarily consists
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of screening and grit removal systems. Septage handling, grinders, odor control, and flow equalization are also considered preliminary treatment.
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Common screening systems are
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manually cleaned bar screens, mechanically cleaned bar screens, and rotary fine screens. These processes simply remove debris which is then land filled.
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Common grit removal systems are
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aerated grit chambers and vortex-type (Pista®). An aerated grit chamber uses air that separates light from heavier solids (grit). A vortex-type (Pista®) unit consists of cylindrical tank creating a vortex flow in which the heavier grit settles to the bottom.
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how an aerated grit chamber works
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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.
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how a vortex-type (Pista®) grit chamber works
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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.
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Common primary treatment units are
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rectangular clarifiers, circular clarifiers, and dissolved
air flotation. |
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The purpose of primary treatment is to
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settle wastewater solids and capture floatable substances (such as oil & grease).
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Well designed and operated primary facilities
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can expect removal efficiencies of 60-75% for suspended solids and 20-35% for BOD.
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The purpose of secondary biological treatment
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is to remove dissolved and suspended organic material from wastewater to produce an environmentally-safe treated effluent and biosolids/sludge.
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A secondary treatment system can
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achieve overall BOD and suspended solids removal in the 85-95% range.
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Common equipment used in suspended growth secondary biological treatment are
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aeration tanks, blowers, diffusers, final clarifiers, and sludge pumps.
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Aeration tanks are usually
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square, rectangular, or circular
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Aeration tanks contain
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aeration equipment for providing oxygen to the microorganisms that live and grow in the tanks
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Aeration equipment
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provides mixing in the tank
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The mixed suspension of sewage, solids, and microorganisms in the aeration tank is commonly referred to as
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activated sludge
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activated sludge is measured as mixed liquor suspended solids in
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milligrams per liter (mg/L)
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Diffusers disperse the air into the aeration tank
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providing oxygen and mixing in the tank.
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Final clarifiers follow the aeration basins and
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settle the mixed liquor suspended solids.
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Clear effluent is discharged over and through weirs in
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final clarifiers
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The settled solids in the clarifier can be returned back to the aeration tank or wasted from the treatment system by a pump(s). The pump(s) are known as
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return activated sludge (RAS) or waste activated sludge (WAS) pump(s)
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Common equipment used in attached growth systems such as trickling filters and biotowers are
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different types of media, pumps, distribution arm and
piping, and underdrains |
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Common equipment used in attached growth systems such as rotating biological contactors are
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basins, shafts, circular plastic disks, motors, and drives and sometimes blowers/diffusers (for air driven shafts).
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After wastewater receives primary treatment, primary effluent is collected and pumps are used to convey the wastewater to
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a trickling filter, a biotower distribution arm, or to RBC
basins for secondary biological treatment. |
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The media is the place where biological organisms and bacteria
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attach themselves for treatment of the incoming wastewater
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Trickling filter media most commonly consists of
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bed of rocks, gravel, or plastic through which the wastewater flows
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Rotating biological contactors (RBC) consist of
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closely spaced, circular plastic disks that rotate on a shaft
through the wastewater. |
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After wastewater flows down through a trickling filter or biotower, it is
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collected through a drain where some of it is recirculated back through the media by pumps for further treatment
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temperature difference between outside air temperature and the temperature inside the filter
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natural air drafts upward through the filter media, providing oxygen.
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The circular plastic disks of RBCs
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are on a shaft that is turned by a motor/drive system.
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Used to monitor aeration basin dissolved oxygen levels
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Dissolved Oxygen Meter
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Many plants have in-line dissolved oxygen sensors to
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automatically control DO levels
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Used to monitor sludge settling characteristics in 30 minutes
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Settleometer
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Settleometer, A ______ mL beaker or cylinder is most commonly used.
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1000
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The mixed liquor suspended solids sample for a Settleometer test should be collected
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just before it goes to the final clarifier.
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Used to measure the depth of settled sludge in the bottom of a clarifier
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Sludge Blanket Finder
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Used to observe the population and health of microorgansims living in an activated sludge
system |
Microscope
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Used to measure pHs and temperatures of wastewater entering the plant and the aeration
basins. |
pH/Temperature Meter
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Used to measure influent, sidestream, RAS, WAS, and effluent flows.
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Flow Meters
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Nitrification
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is a biological process where nitrifying bacteria convert nitrogen in the form of ammonia (NH3) into nitrite (NO2-) and nitrate (NO3-) under aerobic conditions
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Treatment plants that have ammonia limits will use
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nitrification to remove ammonia
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Many plants that discharge to surface waters have ammonia limits
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to protect fish and aquatic life from ammonia toxicity.
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Denitrification
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is a biological process where bacteria convert nitrate (NO3-) and nitrite (NO2-) to nitrogen gas (N2) under anoxic conditions
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Treatment plants that have total nitrogen limits will use
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denitrification to remove nitrogen
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Plants that discharge to groundwater have total nitrogen limits
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to protect groundwater from nitrates
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Plants that remove phosphorus biologically will also employ denitrification
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to remove nitrates that interfere with biological phosphorus removal
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Ammonia is toxic to fish and aquatic life and its toxicity is temperature
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and pH dependent
|
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limits for ammonia nitrogen are calculated based on
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stream flow, stream temperature, stream pH, and the type of fishery classification
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Phosphorus is one of the key nutrients that contribute to
|
eutrophication and excess algae/plant growth in rivers and lakes.
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decomposition of excess plant matter may
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reduce the level of dissolved oxygen in the receiving water which affects aquatic life
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The principle role microorganisms have in the activated sludge process is
|
to convert dissolved and particulate organic matter, measured as biochemical oxygen demand (BOD), into cell mass
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In a conventional activated sludge process
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microorganisms use oxygen to break down organic matter (food) for their growth and survival
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In a conventional activated sludge process, over time and as wastewater moves through the aeration basin
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food (BOD) decreases with a resultant increase in cell mass (MLSS concentration).
|
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The activated sludge wastewater treatment process must operate under proper environmental conditions
|
to support a healthy, growing population of microorganisms.
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The operator must monitor the activated sludge process to
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ensure the right environmental conditions are being provided for the microorganisms.
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Incoming wastewater to a treatment plant provides the food that microorganisms
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need for their growth and reproduction
|
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The more soluble the organic material is
|
the more easily microorganisms can use it
|
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Since the amount and type 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
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Incoming wastewater must flow through a treatment plant at a rate that allows
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microorganisms sufficient time to consume the incoming food and to settle properly
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High flows can shorten
|
the time necessary for the full treatment of wastewater
|
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Extremely high flows can wash
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microorganisms out of the plant through the final clarifier
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Conventional activated sludge is an
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aerobic process
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Many bacteria in the activated sludge process need
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free oxygen (O2) to convert food into energy for their growth
|
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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 1.0-3.0 mg/L)
|
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Aeration basin dissolved oxygen concentrations (milligrams per liter)
|
typically 1.0-3.0 mg/L
|
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Aeration basin dissolved oxygen concentrations
|
are measured continuously in many plants to ensure adequate oxygen is available.
|
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All biological and chemical reactions are affected by
|
temperature
|
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Microorganisms' growth and reaction rates are slow
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at cold temperatures
|
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Microorganisms' growth and reaction rates are much faster
|
at warmer temperatures
|
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Most microorganisms do best under moderate temperatures
|
(10-25 ºC)
|
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Most microorganisms do well in a pH environment between
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6.0-9.0
|
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Acidic (low pH) or alkaline (high pH) conditions can adversely affect
|
microorganism growth and survival
|
|
Operators measure both influent pH and aeration
basin pH |
to ensure proper plant pH conditions
|
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Microorganisms need trace nutrients such as
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nitrogen, phosphorus, and some metals for their metabolism
|
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The ratio of BOD5 to nitrogen (N) to phosphorus (P)
|
should be at least 100:5:1
|
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Depending on the concentration of toxic material
|
microorganisms could be destroyed or their metabolic rates affected, thus impairing the
wastewater treatment plant efficiency |
|
The secondary clarifier is a large basin or tank designed to
|
allow organic solids to settle from effluents discharged from trickling filters, rotating biological contactors (RBC’s), and/or the activated sludge process
|
|
Hydraulic overloads or operational problems in the secondary system can cause
|
major problems in the efficiency of the secondary clarifier,
because the biologic solids to be removed have a density very close to that of water |
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The purpose of final clarification is to
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settle secondary biological treatment solids and discharge clear effluent.
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Motor and Drive System
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The device used to turn the surface skimmer and sludge collector.
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Center Stilling Well
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The suspended column in the center of a clarifier which provides an area for mixed liquor flow to slow down and spread out.
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Scum Skimmer
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C. Scum Skimmer The flat device at the surface of the clarifier which is moved by the drive system, to remove
floating scum. |
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Scum Beach/Trough
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The equipment used to receive the collected scum.
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Scum Baffles
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The ring or plate at the clarifiers surface that prevents scum from entering the effluent trough
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Effluent Weirs
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Weirs that rest just below the clarifier surface which allows effluent to flow over and through
into the trough |
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Effluent Trough
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The open channel on which the effluent weir is mounted and conveys the effluent
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Sludge Collection and Removal Mechanism
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The assembly and piping arrangement at the bottom of the clarifier which is moved by the drive system and used to gather and remove settled sludge.
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RAS/WAS Pump
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A pump that returns or wastes the settled solids from the final clarifier
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The purpose of tertiary treatment is to
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provide advanced wastewater treatment beyond secondary biological treatment when the need to meet stringent effluent limits is required
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the most common method of tertiary treatment is
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filtration
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The overall efficiency in removing pollutants by filtration
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could exceed 95% removal of suspended solids and phosphorus
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less used methods of tertiary treatment are
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carbon adsorption and physical-chemical methods.
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The filtering of very fine suspended particles in the effluent is accomplished using
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sand or mixed media, cloth or membranes, depending on the level of tertiary treatment needed
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As fine particles are filtered from the wastewater, eventually the particles start to plug the filter media and
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cleaning becomes necessary
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Backwashing sand filters or cloth disks is done to
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re-open the filtering pore space to restore the performance of the filter
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Membranes are subject to fouling and
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are cleaned in using one or a combination of a variety of these methods; backwashing, air sparging, relaxation and chemical clean-in-place
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The purpose of disinfection of treated wastewater is to
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kill and thus reduce the discharge of waterborne pathogenic organisms that cause illness, as the final step of the treatment processes
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Prior to disinfection, wastewater must be treated through
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the headworks, aeration basins, and final clarifiers.
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Common disinfection processes used are
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chlorination and ultraviolet (UV) radiation.
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The process of chlorination uses
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chlorine as a gas, solid, or as a liquid
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Chlorine contact tanks gives
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time for the chlorine to react with the wastewater killing the pathogenic organisms
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is added to remove the excess chlorine
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sodium bisulfite or sulfur dioxide)
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Chemical feed pumps that are flow proportional are
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commonly used in feeding liquid chlorine
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When feeding chlorine as a gas
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special equipment is used that creates a vacuum which draws the gas into the treated wastewater
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The process of UV radiation use
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ultraviolet light to destroy the pathogenic organism’s
ability to reproduce |
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The purpose of pond and lagoon systems are to
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accomplish secondary biological treatment in an economical way.
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Ponds are lined with
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a clay or synthetic liner to prevent leakage to groundwater
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Wastewater is pumped into one end of the pond. On the other end the flow exits through a
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control manhole, which may consist of stop logs or a telescopic valve, allowing the operator to control the pond depth
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Most stabilization pond systems have a detention time
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150 days or greater and use more than one pond to effectively treat the wastewater
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Aerated lagoons can use surface aerators or
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subsurface diffusers to provide aeration and mix the wastewater
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Aerated lagoons are usually deeper and
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have shorter detention times(60 days) to effectively treat the wastewater
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Photosynthesis is a chemical process in nature in which
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green plants (algae in ponds) that contain chlorophyll use carbon dioxide in the presence of sunlight to produce carbohydrates to grow
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In wastewater treatment ponds, photosynthesis releases
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oxygen as a byproduct, providing oxygen to the bacteria that stabilize the suspended organic material in wastewater
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Photosynthesis can be summarized by the equation:
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Carbon dioxide + Water => Carbohydrate + Water + Oxygen
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Photosynthesis can be summarized by the equation:
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CO2 + 2H2O => CH2O + H2O + O2
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List the basic components of an activated sludge system.
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A. Aeration tanks
B. Blowers and diffusers or mechanical aerators C. Clarifiers D. RAS/WAS pumps |
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The aeration system in the activated sludge provides
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oxygen to the microorganisms and mixes the contents of the aeration basins
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Centrifugal:
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A blower consisting of an impeller fixed on a rotating shaft and enclosed in a casing having an inlet and a discharge connection
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Positive Displacement:
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A positive displacement (PD) blower forces air to move by
trapping a fixed amount, then displacing that trapped volume into the discharge pipe. |
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Fine Bubble Diffusers
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A device through which air is pumped and divided into very small bubbles that are used to introduce and dissolve oxygen into the liquid. Fine bubble diffusers are normally disks or tubes that use membranes or ceramic materials to create the bubbles and gentle mixing action.
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Coarse Bubble Diffusers
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A device through which air is pumped and divided into large bubbles that are transferred and dissolved into the liquid.
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Fine bubble diffusers are normally
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disks or tubes that use membranes or ceramic materials to create the bubbles and gentle mixing action.
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Coarse bubble diffusers normally
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discharge air at a high rate and are installed to induce a spiral or cross roll mixing pattern
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The most common types of mechanical aerators utilize
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paddles or discs and spray or turbine mechanisms
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Cavitation occurs in wastewater systems when
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the vacuum pressure at any point in the system is lowered to the vapor pressure of the liquid.
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Cavitation usually occurs
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in pumps, on impellers, or at restrictions in a flowing liquid
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Cavitation can make a pump very noisy. This noise has been described as
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popping sound, clattering, or like marbles rattling around in the pump
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Calibrating pumps is a way to check on wear. Regular calibration also helps determine actual flow rates and
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whether any plugging or infiltration is occurring.
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To calibrate pumps you first must find the
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drawn down distance, draw down time, refill
distance and refill time for each pump. |
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In the operation and management of a wastewater system there are four major separate budgetary items needed:
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Operation and Maintenance Budget,
Capital Improvement Budget, Replacement Fund, Debt Retirement |
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Operation and Maintenance Budget
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Sufficient funds must be available to cover the daily operational and maintenance expenses for the wastewater treatment plant and collection system, including salaries, electric bills for running all the equipment, lubricating pumps and drives, and cleaning sewer pipes
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Capital Improvements Budget or Loan
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Significant upgrading or improvement projects often require large expenditures of money. Utilities should establish a capital improvements budget to plan for future treatment plant needs. Sometimes it is not possible to save enough money for a project and in those cases there are a variety of funding methods available including grants, loans, and municipal bonds.
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Replacement Fund
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Treatment plant equipment, such as pumps, motors, or aeration equipment have projected lifespans and need to be replaced when reaching the end of their design life. A replacement fund, with readily available funds, allows an operator to replace old or worn out equipment during the useful life of the treatment works to maintain the capacity and performance for which the treatment works were designed and constructed.
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Debt Retirement
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The large investment a community has to make in constructing and upgrading a wastewater treatment system often requires loans or bonds from a funding agency and/or financial institutions to be obtained and paid back over the terms of the loan.
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Aeration basins and clarifiers should be emptied on a regular basis to:
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A. Perform a detailed inspection of the structure, valves, and control gates
B. Clean out grit and settled solids C. Maintain equipment and piping. |
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List the items to include in a maintenance schedule for final clarifiers
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Daily observations should be performed such as checking for oil leaks, unusual vibrations or noises, scum collection, weirs, and floating solids. All maintenance and repairs should be documented
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Measurements needed to calculate the volume of a retangular well are
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Length, Width, and Depth
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Primary sludges are
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the solids that settle out of the raw wastewater in the primary clarifiers
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The primary sludges are usually
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fairly coarse with a specific gravity (density) significantly
greater than water, allowing for rapid settling |
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Primary sludges are typicaly
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60-80% volatile solids (organic) varying depending on the raw wastewater characteristics.
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Primary sludge is
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odorous and requires additional treatment prior to ultimate disposal.
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Secondary sludges are
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those solids generated as a part of the secondary treatment process and settle out in the secondary clarifiers
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Secondary sludges are
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mainly composed of the microorganisms generated in the secondary process (activated sludge or fixed film systems).
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Excess Secondary sludge amounts
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must be removed to keep the secondary system in balance.
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Secondary sludges are
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more flocculent, with a specific gravity (density) very close to that of water making them more difficult to settle than primary sludges.
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Secondary sludges are typicaly
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75 to 80 percent volatile solids (organic) and contain bound water in the cells of the microorganism, making them difficult to dewater or thicken.
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Secondary sludges with higher the volatile solids (organics) content
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the more difficult the sludge is to dewater.
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Both primary and secondary sludges should be
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as concentrated as possible by proper operation of clarifiers.
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The purpose of sludge thickening is to
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further concentrate and thicken solids settled and wasted from treatment plant processes.
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Sludge is thickened prior to
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being pumped to the digester or sludge storage.
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Common sludge thickening unit processes are
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Gravity Settling Thickener
Dissolved Air Flotation |
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Gravity thickening consists of
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a circular tank (usually with a conical bottom) that is fitted with collectors or scrapers at the bottom.
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With a Gravity Settling Thickener
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The solids settle to the bottom of the tank by gravity, and the scrapers slowly move the settled, thickened solids to a discharge pipe at the bottom of the tank.
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Dissolved air flotation thickens sludge by
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adding dissolved air under pressure and then
releasing the air at atmospheric pressure in a flotation tank or basin |
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With a Cissolved Air Flotation
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The released air forms tiny bubbles which adhere to the suspended matter causing the suspended matter to float to the surface where it is removed by a skimming device.
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The purpose of sludge treatment, sometimes also referred to as sludge stabilization, is to
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reduce the pathogens in the sludge and the attraction of vectors (flies, mosquitos, vermin, birds, etc.)
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Define: Vectors
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(flies, mosquitos, vermin, birds, etc.)
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Class B sludges are
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sludges that can be applied to agricultural lands
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Adequate pathogen control for a Class B sludge is
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< 2,000,000 CFU/g or mpn fecal coliforms or by Anerobic Digestion, Air Drying, Composting, Alkaline Stabilization, & Process to Significantly Reduce Pathogens (PSRP)
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Anaerobic Digestion is
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treated in the absence of air for a certain amount of time at a specific temperature. The time and temperature shall be between 15 days at 35 °C to 55 °C and 60 days at 20 °C.
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Air Drying is
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dried on sand beds or on paved or unpaved basins for a minimum of 3 months. During 2 of the 3 months, the average daily temperature has to be above 0 °C.
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Composting is
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using either a within-vessel, static aerated pile, or windrow composting method and the temperature of the sludge raised to 40 °C or higher for 5 days. For 4 hours during the 5 days, the temperature in the compost pile has to exceed 55 °C.
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Alkaline Stabilization is when
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Lime is added to sludge to raise the pH to 12 for 2 hours of contact.
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Process to Significantly Reduce Pathogens (PSRP) Equivalent is
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treated in a process that is equivalent to a process to significantly reduce pathogens, as approved by the department. Many such processes are proprietary.
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The purpose of dewatering sludge is to
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significantly concentrate the solids and reduce the liquid content of the sludge.
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EPA defines biosolids as a
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“primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled” as soil amendments (fertilizer and conditioners).
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Recycling biosolids through land application is a
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sustainable management method to reuse nutrients and soil conditioners in place of commercial fertilizers, and avoid disposal in landfills.
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In activated sludge aeration basins
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mixed liquor suspended solids is expressed in milligrams per liter (mg/L)
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As solids are thickened and the concentration gets to 10,000 mg/L or above
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the solids are then often expressed as a percent. Every 10,000 mg/L is 1%
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A treatment plant operator has to maintain a daily application log for
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biosolids land applied each day when land application occurs.
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A treatment plant operator has to maintain a daily application log for biosolids land applied each day when land application occurs. The following minimum records must be kept |
A. Approved site used |
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When sending samples to a certified lab one must make sure that
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A. The lab is certified in the test you are submitting your sample. |
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An automatic sampler takes a series of
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small samples throughout the day and stores it in a large container.
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automatic sampler takes a series of small samples throughout the day and
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At the end of 24 hours, you have a 24 hour composite sample |
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“flow proportional” composite samples are
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the automatic sampler receives a signal from a flow meter, and takes a sample every so many gallons of flow. |
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The operator wants to take 100 samples per day and wind up with 10 liters of sample. |
10 liters = 10,000 mL, |
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what is in a Wisconsin Pollutant Discharge Elimination System (WPDES) permit. |
A. Influent Requirements |
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(WPDES) permit. Influent Requirements
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This section of the permit lists the specific influent sampling points and associated monitoring requirements at each point. This provides how much flow and pollutants are coming into the plant. |
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(WPDES) permit. Surface Water or Land Disposal Requirements
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This section of the permit lists the specific effluent sampling points with associated monitoring requirements and effluent limitations at each point. This provides information on treatment efficiency and the amount and quality of the treated wastewater being discharged from the plant. |
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(WPDES) permit. Land Application Requirements
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This section of the permit lists the specific sampling points and associated monitoring requirements and limitations at each point. This provides information on the biosolids/sludge that is hauled from the plant and landspread.
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(WPDES) permit. Schedules of Compliance
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This section of the permit establishes a time schedule for any reports, upgrading construction requirements or other actions to be met by the permittee.
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(WPDES) permit. Standard Requirements
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This section of the permit contains the more general requirements regarding wastewater reporting and monitoring, system operations, surface water discharge, and land application.
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(WPDES) permit. Summary of Reports Due
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The end of the permit contains a table that lists and summarizes all the reports that must be submitted and when they are due. Many operators copy this page and post it for ready reference.
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Discharge Monitoring Report (DMR) is
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an electronic submittal required by DNR, which includes routine monitoring data from a wastewater facility primarily to determine compliance with permit limits.
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Discharge Monitoring Report (DMR) reports are submitted electronically
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to WDNR on a monthly basis, but some facilities submit them quarterly.
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Monthly Discharge Monitoring Report (DMR).
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are due on the 15th of the following month.
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Sanitary Sewer Overflow (SSO)
Whenever there is an overflow occurrence at the treatment works or from the collection system |
the permittee must notify the Department within 24 hours of initiation of the overflow occurrence by telephoning the wastewater staff in the regional office as soon as reasonably possible (FAX, email or voice mail, if staff are unavailable). |
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Chemical Storage tanks must
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have secondary containment that equals the volume of the storage tank.
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Given the average daily plant flow, calculate the programming of a flow proportional sampler to collect the correct number and volume of samples. |
Flow interval (gals/sample) = 850,000 gpd ÷ 100 samples/day = 8500 gal/sample |
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Given data, determine if an unused circular tank at a treatment plant can be used for 180 day sludge storage. The volume of sludge generated each day is 2500 gallons and the tank is 20 feet deep with a diameter of 50 feet. |
Sludge Volume Needed = 2500 gallons/day × 180 days |
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Given data, during wet weather, determine if a chlorine contact tank is of sufficient volume to meet a 30 minute detention time at peak hourly flow. |
Tank volume (gallons) = [20 ft × 15 ft × 15 ft] × 7.48 gal/cu.ft. |
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Given data, calculate the pounds of BOD5 entering the treatment plant each day. |
= (0.845 MGD) × (320 mg/L) × 8.34 lbs/gal |
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Given data, determine the food to microorganism ratio (F/M) in the aeration basin of an activated sludge treatment plant. |
= [(0.125 MGD) × (280 mg/L) × 8.34 lbs/gal] ÷ [(0.2 MG) × (2100 mg/L) × 8.34 lbs/gal] |
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Given data, calculate the size of an emergency (trash) pump that will be needed to pump to a downstream manhole during a power outage at a lift station wet well to avoid a sewage overflow or basement backup. |
Wetwell volume (gal) = [10 ft × 10 ft × 15 ft] × 7.48 gal/cu.ft |
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Given data, calculate the pump rate in gallons per minute of this lift station pump. |
Pump rate (gpm) = [(3.14 × (3.5 ft × 3.5 ft) × 1.33 ft × 7.48 gal/cu.ft) ÷ (250 sec ÷ 60 |
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Given data, calculate detention time for multiple clarifiers operating in parallel. |
Volume (gal) = 2 clarifiers × (3.14 × [40 ft × 40 ft] × 12 ft) × 7.48 gal/cu.ft |
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Given data, calculate the percent of BOD5 being treated and removed. |
BOD5 removed (lbs) = [(1.2 MGD) × (240 mg/L) × 8.34 lbs/gal] - [(1.2 MGD) × (10 mg/L) × |