Activated Sludge Treatment System Quiz
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Questions and Answers

What does MCRT refer to in an activated sludge system?

  • The average number of days a cell remains in the system (correct)
  • The pH level of the activated sludge system
  • The total number of cells in the system
  • The concentration of activated sludge in the system

    • Is activated sludge an anaerobic process?

  • Only during daylight hours
  • No (correct)
  • Yes
  • It depends on the temperature

    • What is the main purpose of secondary treatment in wastewater treatment?

  • To remove heavy metals from the wastewater
  • To remove the organic content of the wastewater (correct)
  • To adjust the pH of the wastewater
  • To disinfect the wastewater

    • What does SVI measure in a wastewater treatment system?

    <p>The sludge volume that needs to be wasted</p> Signup and view all the answers

    Is it true that most bacteria in untreated wastewater are harmful to humans?

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

    What does BOD measure in wastewater?

    <p>The organic content of wastewater</p> Signup and view all the answers

    Are ppm and % considered roughly equivalent for wastewater treatment calculations?

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

    Does a one acre wastewater treatment pond, operated at a depth of 3 feet, hold approximately 1 million gallons?

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

    Are trickling filters easily upset by shock loads when compared to activated sludge?

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

    What causes ponding on the surface of trickling filters?

    <p>Plugging of underdrains immediately below the point of ponding</p> Signup and view all the answers

    What test is used to determine the organic matter found in the mixed liquor?

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

    The four (4) basic components of every activated sludge treatment system are:

    <p>Aeration, clarification, return sludge and waste sludge</p> Signup and view all the answers

    Which of the following statements is not true regarding a wastewater collection system:

    <p>A sewer is designed to allow the waste to flow at a rate of approximately 1 ft/sec.</p> Signup and view all the answers

    Velocity of flow in sewers is usually expressed in terms of

    <p>Feet per second</p> Signup and view all the answers

    One of the reasons that air should be excluded from anaerobic digesters is because:

    <p>the entrance of air mixed with the gas produced in the digester could create an explosive mixture</p> Signup and view all the answers

    The fundamental purpose of disinfection is to:

    <p>Destroy pathogenic organisms</p> Signup and view all the answers

    The difference between the amount of chlorine added and the amount of chlorine remaining after the contact period is referred to as:

    <p>the chlorine demand</p> Signup and view all the answers

    TKN is the measure of:

    <p>Ammonia/Ammonium+Organic Nitrogen</p> Signup and view all the answers

    Sludge with a specific gravity of 1.1 will weigh:

    <p>9.17lbs/gal</p> Signup and view all the answers

    What problem is associated with trickling filters?

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

    What is the primary organism responsible for treating wastewater in the trickling filter process?

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

    What does 'sloughing' refer to in the context of a trickling filter?

    <p>The periodic discharge of large quantities of slime growth with the filter effluent.</p> Signup and view all the answers

    What is the surface area of a cylindrical tank 80 feet in diameter and 25 feet in height? (Cylindrical part surface area only)

    <p>1,570 sq. ft</p> Signup and view all the answers

    Calculate the VS loading to the digester in lbs/day if 10,000 cu. ft of sludge containing 4.8% TS with an average VS content of 82%.

    <p>30,987 lbs/day</p> Signup and view all the answers

    Calculate the weir loading for a sedimentation tank with an outlet weir 480 ft long and a flow of 5 MGD.

    <p>10,420 gpd/ft</p> Signup and view all the answers

    What is the hydraulic loading on the trickling filter in gpd/ft2 if a 90 feet diameter trickling filter treats a 540,000 gpd primary effluent flow with a recirculated flow of 120,000 gpd?

    <p>104 gpd/ft2</p> Signup and view all the answers

    What is the detention time of a wastewater treatment pond that is 40 acres and receives a flow of 0.6 MGD?

    <p>87 days</p> Signup and view all the answers

    Calculate chlorine demand if chlorine is being fed at the rate of 200 pounds per day, with a plant flow of 4 MGD and a chlorine residual of 3 mg/L.

    <p>3 mg/L</p> Signup and view all the answers

    Calculate SVI for a mixed liquor sample if a sludge settleability test shows a reading of 220 ml after 30 minutes of settling in a one liter graduated cylinder, with MLSS concentration of 1850 mg/L and MLVSS concentration of 1440 mg/L.

    <p>119</p> Signup and view all the answers

    Ponding is typically caused by plugging of media by zoogleal mass and not by plugging of the underdrains. Is this statement true or false?

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

    Series operation of trickling filter is the preferred mode during very low temperature conditions during winter. Is this statement true or false?

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

    Hydrogen sulfide gas in a moist atmosphere can result in corrosion of concrete structures. Is this statement true or false?

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

    It is common for primary clarifiers to remove 80-85% of the BOD and 90-95% of the TSS. Is this statement true or false?

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

    Detention time is the time required to fill a tank at a given flow. Is this statement true or false?

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

    Fresh wastewater is characterized by a blackish color, foul and unpleasant odors with floating materials and suspended solids. Is this statement true or false?

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

    Algae is primarily responsible for the effective working of an anaerobic pond. Is this statement true or false?

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

    Study Notes

    Activated Sludge System

    • MCRT (Mean Cell Residence Time) refers to the average time that microbial cells or biomass remain in the activated sludge system before being removed.
    • Activated sludge processes are primarily aerobic, relying on the presence of oxygen for microbial activity, not anaerobic.

    Secondary Treatment in Wastewater

    • The main purpose of secondary treatment is to further reduce BOD (Biochemical Oxygen Demand) and TSS (Total Suspended Solids) after primary treatment.

    Wastewater Treatment Measurements

    • SVI (Sludge Volume Index) measures the settleability of sludge in a wastewater treatment system, reflecting the amount of space the sludge occupies during settling.
    • BOD measures the amount of oxygen required by aerobic microorganisms to decompose organic matter in wastewater.

    Bacteria in Wastewater

    • Most bacteria present in untreated wastewater are indeed harmful to humans, posing health risks.

    Wastewater Treatment Units

    • PPM (parts per million) and % (percentage) are considered roughly equivalent in calculations for wastewater treatment, as both express concentration.
    • A one-acre wastewater treatment pond with a depth of 3 feet can hold approximately 1 million gallons of water.

    Trickling Filters and Challenges

    • Trickling filters are more easily upset by shock loads compared to activated sludge systems.
    • Ponding on the surface of trickling filters occurs mainly due to the plugging of media by zoogleal mass.

    Organic Matter and Sludge

    • An organic matter test for mixed liquor is commonly performed to assess overall microbial function.
    • Fundamental components of every activated sludge system include aeration tank, clarifier, return activated sludge (RAS), and waste activated sludge (WAS).

    Wastewater Collection System

    • Not all statements regarding wastewater collection systems are true; verification is needed for specific cases.
    • Velocity of flow in sewers is usually expressed in terms of feet per second (fps).

    Anaerobic Digesters

    • Excluding air from anaerobic digesters is crucial to prevent the introduction of oxygen, which would disrupt the anaerobic processes.
    • Disinfection's fundamental purpose is to eliminate pathogens from treated effluent.

    Chlorine and TKN

    • The difference between added chlorine and remaining chlorine is referred to as chlorine demand.
    • TKN (Total Kjeldahl Nitrogen) measures the total concentration of organic and ammonia nitrogen in wastewater.

    Sludge Weight and Problems

    • Sludge with a specific gravity of 1.1 is heavier than water, significantly affecting its management.
    • Trickling filters may experience issues like flooding due to improper media loading.

    Treatment Processes

    • Primary organisms in trickling filter processes mainly include heterotrophic bacteria, assisting in organic matter degradation.
    • ‘Sloughing’ in trickling filters describes the shedding of biofilm from the media, impacting treatment efficiency.

    Calculations and Measurements

    • The surface area of a cylindrical tank can be calculated using its diameter (80 feet) and height (25 feet).
    • VS loading to a digester in lbs/day can be calculated by considering the volume of sludge, total solids, and volatile solids ratio.

    Flow and Detention Time

    • Weir loading for a sedimentation tank can be calculated based on flow rate and weir length.
    • Hydraulic loading on a trickling filter is derived from the total wastewater flow and surface area.
    • Detention time in a wastewater treatment pond calculates how long wastewater stays in the system before treatment.

    Key True/False Statements

    • Statements regarding ponding caused by zoogleal mass and plugging of underdrains should be evaluated for accuracy.
    • Series operation of trickling filters is preferred in low temperatures, verifying the flexibility of this setup.
    • Hydrogen sulfide gas can indeed corrode concrete structures in moist conditions.
    • Primary clarifiers commonly remove 80-85% of BOD and 90-95% of TSS, aligning with operational standards.
    • Detention time is accurately defined as the time a tank takes to fill at a given flow rate.
    • Fresh wastewater is characterized by blackish color, foul odors, and suspended solids; this is a standard identifier.
    • The role of algae in anaerobic ponds is overstated; primary treatment relies on bacteria rather than algae for efficiency.

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    Module 4 - Practice Exam 2 Solutions PDF

    Description

    Test your knowledge about activated sludge treatment systems with this quiz. Explore topics such as outlet weirs, density of sludge, flow distribution, and testing for organic matter in mixed liquor.

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