Wastewater Treatment Flashcards
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Questions and Answers

What is the equivalent in total percent solids of a sludge sample that has a concentration of 15,000 mg/l?

1.57%

Which aeration foam may indicate an old sludge condition?

  • Green
  • Yellow
  • White
  • Black (correct)

    • Which is a common type of level control system?

  • Bubbler (correct)
  • Ultrasonic
  • Hydrostatic
  • Float

    • Which type of sewer system contains both sanitary wastewater and storm water?

    <p>Combined sewer system</p> Signup and view all the answers

    What is the formula that defines chlorine residual?

    <p>Supply-demand=residual</p> Signup and view all the answers

    What happens to the trickling filter effluent D.O. when the recirculation rate increases?

    <p>It increases the D.O.</p> Signup and view all the answers

    Why should air be prevented from entering an anaerobic digester tank?

    <p>It can react with the digester gas and create a potential for an explosion.</p> Signup and view all the answers

    Which component in the chlorination process is responsible for creating a vacuum condition?

    <p>Gas injector</p> Signup and view all the answers

    Where does the D.O. come from in an unrated lagoon?

    <p>Algae growth</p> Signup and view all the answers

    What does H2S smell like at high concentrations?

    <p>No smell</p> Signup and view all the answers

    Which chemical is typically used for conditioning the sludge feed applied to a gravity thickener process?

    <p>Polymer</p> Signup and view all the answers

    What is the relationship of gas chlorine to air?

    <p>Gas chlorine is 2 1/2 times heavier than air</p> Signup and view all the answers

    What should be done if a neighbor complains about the plant odor?

    <p>Evaluate the odor source and use the best management practice to minimize the odor.</p> Signup and view all the answers

    Where does denitrification primarily occur?

    <p>Anoxic zone</p> Signup and view all the answers

    Where does nitrification primarily occur?

    <p>Aerobic</p> Signup and view all the answers

    What should a supervisor do if he or she finds an employee sleeping on the job?

    <p>Find out why the employee was sleeping and then follow the prescribed policy for sleeping on the job.</p> Signup and view all the answers

    Which is the physical process that follows an aeration tank?

    <p>Secondary clarification</p> Signup and view all the answers

    What is a typical RAS to Q ratio for an extended aeration activated sludge process?

    <p>75% to 100%</p> Signup and view all the answers

    What does it mean if gas and rising sludge is occurring in a gravity thickener?

    <p>Not enough sludge is being withdrawn from the thickener</p> Signup and view all the answers

    What is generally required when the sludge blanket is too high on the floor of a gravity thickener?

    <p>Increase the withdrawal rate of sludge from the gravity thickener</p> Signup and view all the answers

    Associated with primary clarifier scum, what does FOG mean?

    <p>Fat Oil Grease</p> Signup and view all the answers

    What is it called when all of the demand for chlorine has been satisfied?

    <p>Breakpoint</p> Signup and view all the answers

    What is a typical percent solids in the thickener sludge product of a gravity belt thickener?

    <p>4% to 8%</p> Signup and view all the answers

    What may be the recommended action to perform if the top belt of a belt filter press was flooded?

    <p>Decrease the sludge feed rate or increase the belt speed and adjust the polymer dose rate</p> Signup and view all the answers

    Which term is most related to vector attraction reduction in an aerobic digester?

    <p>SOUR (specific oxygen utilization rate)</p> Signup and view all the answers

    Which test is better to use for process control of an anaerobic digestion process?

    <p>Acid/alkalinity</p> Signup and view all the answers

    What does it mean when there is a lack of any odor coming from a lift station manhole?

    <p>Dangerous gases may be present because some gases do not emit an odor.</p> Signup and view all the answers

    Which gases may be found in a sewer collection system?

    <p>All of the above</p> Signup and view all the answers

    What is a typically accepted D.O. in an aerobic digester?

    <p>0.5 to 1.5 mg/l</p> Signup and view all the answers

    What should management do if they see a large increase in the facility's monthly power bill?

    <p>Evaluate the practice of starting high horsepower equipment and meet with the power company to discuss alternate billing methods.</p> Signup and view all the answers

    What two laboratory analyses are necessary to calculate the F/M ratio?

    <p>Aeration MLVSS and influent CBOD5</p> Signup and view all the answers

    What is the term when ammonia-N and organic-N are added together?

    <p>TKN (Total Kjeldahl Nitrogen)</p> Signup and view all the answers

    Which group of bacteria are strictly aerobic and responsible for nitrification in the activated sludge process?

    <p>Autotrophic</p> Signup and view all the answers

    Which time of day will generally produce the highest D.O. in an unaerated stabilization pond?

    <p>3 pm</p> Signup and view all the answers

    Which test is not used to indicate the performance of an anaerobic digester?

    <p>Chlorine residual</p> Signup and view all the answers

    What percentage of settleable solids are typically removed in a primary clarifier?

    <p>100%</p> Signup and view all the answers

    What is the top blanket of sludge called in the DAF process?

    <p>Float</p> Signup and view all the answers

    How many lbs/day of WAS are removed each day from a plant with a volume of 14,000 gpd and a concentration of 1% Total Solids?

    <p>1,168 lbs/day</p> Signup and view all the answers

    Which bar screen will capture more debris on its screen?

    <p>Bar screen that runs on either timer control or level control</p> Signup and view all the answers

    What does this formula represent associated with primary clarifier performance? IN - OUT ÷ IN x 100 = ?

    <p>Removal Efficiency, %</p> Signup and view all the answers

    What is the term for water seeping into a sanitary sewer line?

    <p>Infiltration</p> Signup and view all the answers

    What is it called when sludge and polymer plug the belts of a belt filter press?

    <p>Blinding</p> Signup and view all the answers

    Which chemical is used to identify a chlorine leak?

    <p>Ammonia</p> Signup and view all the answers

    What does the '5' mean in the BOD5 test?

    <p>That the sample is incubated for 5 days</p> Signup and view all the answers

    What happens to the activity rate of activated sludge microorganisms when the temperature increases?

    <p>It increases</p> Signup and view all the answers

    What is the makeup of typical screenings debris?

    <p>Organic material</p> Signup and view all the answers

    What form of chlorine comes in one-ton containers?

    <p>Gas from the top valve and liquid from the bottom valve</p> Signup and view all the answers

    What is the organism growth on the media of a trickling filter called?

    <p>Zoogleal</p> Signup and view all the answers

    Which of the following materials is not commonly used in the construction of a collection system?

    <p>Aluminum</p> Signup and view all the answers

    What does the production of foam indicate in an anaerobic digester?

    <p>That the acid production is too high</p> Signup and view all the answers

    What is a common volume make-up of gases in a properly operated anaerobic digester?

    <p>70% CH4 and 30% CO2</p> Signup and view all the answers

    Which type of bacteria is responsible for stabilization of organic material (CBOD5) in wastewater?

    <p>Heterotrophic</p> Signup and view all the answers

    Which best describes the nitrification cycle?

    <p>Ammonia is converted to nitrites and then to nitrates</p> Signup and view all the answers

    What is a common method of determining the quantity of chlorine used each day?

    <p>Read the chlorine scale weight</p> Signup and view all the answers

    What is the weir overflow rate for the secondary clarifier?

    <p>3,662 gpd per foot of weir</p> Signup and view all the answers

    What does this formula represent? π r2 x depth, ft x 7.48

    <p>It calculates volume in gallons</p> Signup and view all the answers

    What happens to the pH and alkalinity of the sludge after lime is added to it?

    <p>The pH goes up and the alkalinity goes up</p> Signup and view all the answers

    What is the surface area of the secondary clarifier?

    <p>1,963 ft2</p> Signup and view all the answers

    What adjustment may be the best to make if the secondary clarifier, and the settleometer test, show an abundance of small pin floc in the effluent?

    <p>Decrease the SRT</p> Signup and view all the answers

    What does the unit parts per million (ppm) mean?

    <p>8.34 pounds per million gallons</p> Signup and view all the answers

    What are the two major zones of a belt filter press called?

    <p>Gravity drainage and pressure filtration</p> Signup and view all the answers

    Which lab test requires the use of an analytical balance, a drying oven, filter papers, and a desiccator?

    <p>TSS</p> Signup and view all the answers

    What is the makeup of typical grit debris?

    <p>Inorganic material</p> Signup and view all the answers

    Which factors affect the operation of an aerobic digester?

    <p>All of the above</p> Signup and view all the answers

    What color should digested sludge be in a properly operated anaerobic digestion process?

    <p>Black</p> Signup and view all the answers

    What happens to the alkalinity in wastewater during the denitrification process?

    <p>It increases</p> Signup and view all the answers

    What is an acceptable surface loading rate for a primary clarifier?

    <p>800 to 1,200 gpd/ft2</p> Signup and view all the answers

    What process test can be performed in about 10 minutes and identifies the amount of oxygen being consumed by the microorganisms?

    <p>OUR, mg/l/hr (Oxygen Uptake Rate)</p> Signup and view all the answers

    What component is used to convert liquid chlorine into chlorine gas?

    <p>Evaporator</p> Signup and view all the answers

    What is the system called that requires proper documentation associated with sampling?

    <p>Chain of custody</p> Signup and view all the answers

    What is the volume of 1 cubic foot of water?

    <p>7.48 gals</p> Signup and view all the answers

    What is the best adjustment to make if the RAS in a secondary clarifier is black and the sludge blanket depth is high?

    <p>Increase the RAS rate</p> Signup and view all the answers

    What term is most related to free chlorine residual?

    <p>Breakpoint</p> Signup and view all the answers

    What adjustment should be made if solids are rising in the secondary clarifier accompanied by large, smelly gas bubbles?

    <p>Increase aeration D.O.</p> Signup and view all the answers

    What does an open circuit mean in electrical terms?

    <p>That power is disengaged...dead</p> Signup and view all the answers

    What percentage of total suspended solids (TSS) is typically removed in a primary clarifier?

    <p>50%</p> Signup and view all the answers

    What is another term for inorganic solids?

    <p>Non-volatile</p> Signup and view all the answers

    What is the term for the collection of one (1) sample in which an analysis is performed?

    <p>Grab</p> Signup and view all the answers

    What component of a pump keeps the material in the discharge pipe from emptying out through the pump suction when the pump is off?

    <p>Check valve</p> Signup and view all the answers

    What percentage of CBOD5 is typically removed in a primary clarifier?

    <p>25%</p> Signup and view all the answers

    Why is flooding of trickling filter media sometimes recommended?

    <p>To control filter flies</p> Signup and view all the answers

    What are the two major gases produced in a properly operated anaerobic digestion process?

    <p>Methane and carbon dioxide</p> Signup and view all the answers

    What is the solids loading rate on the secondary clarifier?

    <p>13.2 lbs/day/ft2</p> Signup and view all the answers

    What is a common spacing between the bars for a fine bar screen?

    <p>¼ inch</p> Signup and view all the answers

    What is the purpose of an Imhoff cone test?

    <p>To identify settleable solids</p> Signup and view all the answers

    Which problem is the more likely cause of pumps and pipes clogging and requiring cleaning to restore normal flow rates?

    <p>Poor screenings removal</p> Signup and view all the answers

    Given the provided data, what is the SRT of this activated sludge plant? - Plant flow = 0.575 mgd - MLSS = 3,500 ppm - Aeration tank dimensions = 100 ft long, 25 ft wide, and 14 ft deep - WAS volume = 14,000 gpd - WAS concentration = 1% total solids - Effluent TSS = 2.5 ppm

    <p>6.5 days SRT</p> Signup and view all the answers

    What does the term aliquot mean?

    <p>A portion of a sample</p> Signup and view all the answers

    What is the main purpose of a trickling filter?

    <p>To oxidize organic material</p> Signup and view all the answers

    What is the main purpose for a comprehensive maintenance program?

    <p>To allow the plant to operate at its peak performance</p> Signup and view all the answers

    What is a common problem associated with trickling filters?

    <p>Ponding</p> Signup and view all the answers

    What type of maintenance is performed on a piece of equipment before it breaks?

    <p>Preventive</p> Signup and view all the answers

    What item is important in the development of a maintenance program?

    <p>Equipment data, maintenance frequencies, repair procedures, list of emergency phone numbers</p> Signup and view all the answers

    Which dangerous gas will be more likely to rise near the surface of a manhole?

    <p>Methane</p> Signup and view all the answers

    What is the amount of oxygen required to convert 1 ppm of ammonia-nitrogen?

    <p>4.6 pounds</p> Signup and view all the answers

    What does a recirculation rate of 1:1 mean in a trickling filter process?

    <p>The total flow applied to the trickling filter is twice the volume of the raw wastewater flow</p> Signup and view all the answers

    What type of maintenance is performed on a piece of equipment after it breaks?

    <p>Corrective</p> Signup and view all the answers

    What piece of equipment is used in the volatile solids test?

    <p>Muffle furnace, desiccator, analytical balance</p> Signup and view all the answers

    What is the equivalent in gpm of a pipe that has 1 mgd flowing through it?

    <p>694 gals per min</p> Signup and view all the answers

    Which activated sludge growth phase is considered to have the lowest F/M ratio?

    <p>Extended aeration</p> Signup and view all the answers

    Study Notes

    Sludge and Wastewater Treatment

    • Total percent solids of sludge with a concentration of 15,000 mg/l is 1.57%.
    • Black-colored aeration foam indicates old sludge conditions.
    • Level control systems commonly use bubblers.

    Sewer Systems and Waste Treatment Processes

    • Combined sewer systems carry both sanitary wastewater and stormwater.
    • The formula for chlorine residual is Supply - Demand = Residual.
    • Increasing the recirculation rate of a trickling filter effluent results in higher dissolved oxygen (D.O.).

    Anaerobic Digestion

    • Air should be prevented from entering anaerobic digesters to avoid explosion risks.
    • Gas injectors create vacuum conditions for mixing chlorine gas with solution.
    • Algae growth generates D.O. in unrated lagoons.

    Chemical and Physical Properties

    • Hydrogen sulfide (H2S) has no smell at high concentrations.
    • Polymer is commonly used for conditioning sludge feed in gravity thickening.
    • Gas chlorine is 2.5 times heavier than air.

    Odor Management and Biological Processes

    • Neighbor complaints about plant odor should prompt an evaluation of the odor source and use of management practices.
    • Denitrification primarily occurs in anoxic zones; nitrification occurs in aerobic zones.
    • The presence of pin floc in secondary clarifier effluent indicates a need to decrease the solid retention time (SRT).

    Clarifiers and Solids Management

    • RAS to influent flow ratio for extended aeration activated sludge processes typically ranges from 75% to 100%.
    • Rising sludge in gravity thickeners suggests insufficient sludge withdrawal.
    • Increasing sludge withdrawal rate is required when sludge blankets are too high in gravity thickeners.

    Chlorination and Chemical Measurements

    • Breakpoint occurs when all chlorine demand is satisfied.
    • Typical percent solids in gravity belt thickener sludge product ranges from 4% to 8%.
    • Algae contribute to the D.O. levels in water bodies, enhancing water treatment processes.

    Solids Management and Microbial Activity

    • SOUR (Specific Oxygen Utilization Rate) is related to vector attraction reduction in aerobic digesters.
    • Analysis of acid/alkalinity is critical for anaerobic digestion process control.
    • The pH and alkalinity of sludge increase when lime is added.

    Measurement and Testing

    • Total suspended solids (TSS) analysis requires analytical balances, drying ovens, and desiccators.
    • Settling tests like the Imhoff cone tests identify settleable solids.
    • The SRT can be calculated using volumes of aeration and waste activated sludge.

    Equipment and Process Adjustments

    • Flooded belt filter press belts indicate the need to adjust sludge feed rate or belt speed.
    • Bar screens with timer or level control capture more debris.
    • Proper documentation in operations is ensured through chain of custody procedures.

    Gas and Safety Considerations

    • Methane and carbon dioxide are the primary gases produced in well-operated anaerobic digesters.
    • Dangerous gases, such as methane, tend to rise near the surface of manholes.

    Maintenance Practices

    • Preventive maintenance is executed before equipment failure; corrective maintenance follows failures.
    • A comprehensive maintenance program includes tracking equipment data, frequencies, and emergency contacts.

    Operational Parameters and Ratios

    • Secondary clarifiers' surface loading rates are acceptable between 800 to 1,200 gpd/ft².
    • The oxygen required to convert 1 ppm of ammonia-nitrogen is typically 4.6 pounds.
    • The extended aeration phase in activated sludge processes features the lowest food-to-microorganism (F/M) ratio and highest SRT.

    Environmental and Treatment Outcomes

    • The production of foam in anaerobic digesters signals high acid production levels.
    • Screening debris typically comprises organic materials, while grit debris is mainly inorganic.

    Conclusion

    • Continuous monitoring and maintenance of operational parameters in wastewater treatment processes are essential for effective management and compliance with environmental standards.

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    Description

    Test your knowledge on wastewater treatment concepts and terms with these flashcards. From sludge concentration to level control systems, this quiz covers essential topics crucial for understanding wastewater management.

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