Basic Wastewater D Exam Questions and Complete Solutions

Basic Wastewater D Exam Questions and Complete Solutions 1. Water resources in Texas include lakes, rivers, bays, estuaries, wetlands, groundwater, and stormwater runoff. a. true b. false - Answer: b 2. Water pollutants include organic and inorganic material, heat, and radiation. a. true b. false - Answer: a 3. In Texas, clean water is needed to provide for human consumption and recreation, maintain aquatic habitats for wildlife, supply bays with fresh water, recharge groundwater, and provide for industry. a. true b. false - Answer: a 4. Two sources of water contamination are point-source discharges and pointless source discharges. a. true b. false - Answer: b 5. The fine for polluting state water is as much as $25,000 per day. a. true b. false - Answer: a 6. Examples of point-source discharges are ________. a. stormwater drainage from industry and urban areas b. seepage from septic tanks and drainfields c. municipal, industrial, and agricultural wastewater treatment facilities d. all of the above - Answer: c 7. Protecting Texas water from contamination requires ________ of wastewater. a. collection and transportation to treatment facilities b. treatment that removes contaminants c. processing and disposal of solids d. all of the above - Answer: d 8. Benefits of treating point-source and non-point-source wastes are prevention of ground and surface water pollution and ________. a. protection of human and animal health b. prevention of oxygen depletion in surface water c. prevention of landfill leakage d. a and b - Answer: d 9. The Texas Water Code establishes the following means of protecting state water: water quality standards for streams, discharge limitations for point-sources, and ________. a. monitoring air quality in urban areas b. controlling non-point sources of waste c. limiting the catch of shrimp and oysters d. requiring disinfection of drinking water - Answer: b 10. The state sets water quality standards, called ________, for rivers and lakes. a. steam standards b. extreme standards c. stream standards d. water standards - Answer: c 11. To meet stream standards, the state issues ________ for waste discharge. a. permits b. licenses c. sample containers d. certificates e. acids and alkalis - Answer: a 1. A role of supervision and management is to set job assignments and secure permits and finances to do the job. a. true b. false - Answer: a 2. Responsibilities of the licensed operator include protecting the public from waterborne disease, performing duties professionally, protecting state water from pollution, maintaining required licensing, practicing safety, and controlling inflation. a. true b. false - Answer: b 3. The Federal Water Pollution Control Act of 1972 (Clean Water Act) has a goal of eliminating pollution of the nation's water. a. true b. false - Answer: a 4. Chapter 26 of the Texas Water Code is the state law controlling water pollution. a. true b. false - Answer: a 6. To become a licensed operator it is necessary to ________. a. have work experience b. pass a test administered by the TCEQ c. hold a college degree d. be sponsored by a licensed operator - Answer: b 7. Personnel working at a domestic wastewater plant must be state licensed if they are ________. a. paid by the permit holder b. a laboratory technician c. required to take samples d. responsible for process control - Answer: d 8. Local governments have authority to inspect facilities using the collection system, enforce local pollution control laws, set discharge rules, and collect ____________. a. user charges b. state fines c. federal penalties d. all of the above - Answer: a 9. The local government may inspect and investigate water quality conditions within its jurisdiction to determine ________. a. standards are met b. dischargers have permits c. permits are followed d. all of the above - Answer: d 10. Local governments may make discharge rules to protect personnel, the wastewater system, and the ________. a. treatment facility b. wildlife sanctuary c. city parks d. public campgrounds - Answer: a 11. A local government may bring suit to enforce its ________. a. proclamations b. rules c. announcements d. edicts - Answer: b 12. Cities with more than ________ population should have a water pollution control program. a. 7,000 b. 8,000 c. 9,000 d. 10,000 - Answer: d 13. Goals of the TCEQ include maintaining water quality for public health, commercial use, and ________. a. wildlife preservation b. plumbing codes c. OSHA regulations d. private use - Answer: a 14. The TCEQ may revoke a license if the operator ________. a. violates the permit b. falsifies records c. neglects a duty d. all of the above - Answer: d 15. When an accidental discharge, bypass, or spill occurs, the discharger must notify the TCEQ within ________ hours. a. 24 b. 36 c. 48 d. 72 - Answer: a 16. An administrative penalty can be up to ________ per day. a. $5,000 b. $10,000 c. $25,000 d. $50,000 - Answer: c 17. Penalty assessment is based upon physical effect, intentions, responsibility, and ________. a. insurance b. pay scales c. economic benefit accrued d. tax rates - Answer: c 18. Penalties are levied for ________. a. failure to submit reports b. bypasses c. no discharge permit d. all of the above - Answer: d 19. In each permit, the TCEQ sets conditions including permit duration, strength of the discharge, monitoring requirements, point of discharge, and ________ of the discharge. a. odor b. taste c. quality d. color - Answer: c 20. State law requires that self-reporting forms be compiled and mailed each ________ to the TCEQ. a. day b. week c. month d. year - Answer: c 21. The authorized agent or ________ must sign the report. a. city manager b. chief operator c. city engineer d. executive officer - Answer: d 22. Required records, such as flow and effluent quality, must be kept at least ________ years. a. five b. three c. two d. seven - Answer: b 1. Because wastewater is mostly water, it weighs 8.34 lbs/gal. a. true b. false - Answer: a 2. Labs report many characteristics of wastewater as milliliters per liter (ml/L). a. true b. false - Answer: b 3. Wastewater characteristics are divided into 3 primary groups: bacteriological, physical, and chemical. a. true b. false - Answer: b 4. Bacteria are seen with a telescope and are present in soil, water, air, decaying organic matter, and the intestinal tract of humans and animals. a. true b. false - Answer: b 5. Some bacteria cause disease and are called pathogens. a. true b. false - Answer: a 6. One way to classify bacteria is by their oxygen use: aerobic, facultative, and anaerobic. a. true b. false - Answer: a 7. Aerobic bacteria require dissolved, uncombined (free) nitrogen. a. true b. false - Answer: b 8. Anaerobic bacteria cannot live when chemically combined oxygen is present. a. true b. false - Answer: b 9. Facultative bacteria live with free oxygen or chemically combined oxygen. a. true b. false - Answer: a 10. Fresh domestic wastewater contains dissolved oxygen. a. true b. false - Answer: a 11. Septic wastewater is dark, has agreeable odor, and contains dissolved oxygen. a. true b. false - Answer: b 12. Septic wastewater contains fragrant gases produced by bacteria. a. true b. false - Answer: b 13. Some chemical characteristics of wastewater include solids, grease, DO, pH, and gases. a. true b. false - Answer: a 14. Solids include total, suspended, dissolved, settleable, inorganic, organic, and soft and hard solids. a. true b. false - Answer: a Suspended solids can be filtered out, and dissolved solids pass through a filter. a. true b. false - Answer: a 16. Settleable solids are dissolved solids of sufficient weight to settle when left standing for a time. a. true b. false - Answer: b 17. Inorganic material, suspended or dissolved, is sand, grit, and minerals. a. true b. false - Answer: a 18. Two other classifications of solids are inorganic (ash) and organic (volatile). a. true b. false - Answer: a 19. Examples of organics are sugar, butter, leather, paper, and iron. a. true b. false - Answer: b Organic solids are volatile, combustible solids found by burning the residue from the total solid test or the filter from the TSS test. a. true b. false - Answer: a 21. The ash (fixed solids) left after burning consists of inorganic solids. a. true b. false - Answer: a 22. The three primary types of organics are ________, proteins, and grease. a. minerals b. leather c. carbohydrates d. paper - Answer: d 23. ________ in raw wastewater comes from the water supply. a. Facultative bacteria b. Dissolved oxygen c. Organic solids d. Inorganic grease - Answer: b 24. When dissolved oxygen is present, it indicates the wastewater is ________. a. septic b. odorous c. anaerobic d. fresh - Answer: d 25. As the water temperature rises, the DO saturation level will ________. a. decrease b. increase c. not change d. none of the above - Answer: a 26. The dissolved oxygen test must be performed as soon as a sample is taken because oxygen levels can ________ change. a. quickly b. slowly c. never d. none of the above - Answer: a 27. The ________ test measures the oxygen depleting effect of the wastewater upon the receiving stream. a. COD b. BOD c. DO d. TSS - Answer: b 28. The BOD test indicates wastewater ________. a. temperature b. septicity c. strength d. pH - Answer: c 29. The BOD test measures oxygen consumed as organics are oxidized by biological and chemical action during incubation for ________ days at ________°C. a. 20/5 b. 2/20 c. 5/2 d. 5/20 - Answer: d 30. Each person contributes about ________ lbs of BOD daily. a. 0.17 b. 1.7 c. 17 d. 0.71 - Answer: a 31. The pH scale ranges from ________ to ________, with 7 being neutral. a. 1/14 b. 0/14 c. 7/14 d. 0/7 - Answer: b 32. ________ water has a pH below 7.0, while ________ water has a pH above 7.0. a. Basic/acidic b. Hot/cold c. Acidic/basic d. Cold/hot - Answer: c 33. Dangerous gases produced during the breakdown of organics in wastewater are hydrogen sulfide, carbon dioxide, and ________. a. oxygen b. chlorine c. cyanide d. methane - Answer: d 34. The ________ decomposition of organic matter produces methane which is colorless, odorless, and explosive. a. aerobic b. facultative c. anaerobic d. all of the above - Answer: c 35. Hydrogen sulfide has a ________ odor, is combustible in air, and is very toxic. a. rotten egg b. pungent c. fragrant d. sweet - Answer: a 36. ________ is odorless, colorless, heavier than air, and not combustible. a. Natural gas b. Carbon dioxide c. Hydrogen sulfide d. Gaseous chlorine - Answer: b 37. Good sampling results depend on ________. a. ensuring the sample represents the waste stream b. using proper sampling technique c. preserving the sample until analyzed d. all of the above - Answer: d 38. Select a point where ________ is thorough and the wastewater quality is uniform. a. mixing b. settling c. aeration d. disinfection - Answer: a 39. A ________ sample is collected at any point, at any time. a. composite b. grab c. timed d. none of the above - Answer: b 40. When a sample of a plant unit influent is collected at any time, and a sample of the effluent is collected corresponding to the unit's detention time, the sample is a ________. a. grab b. composite c. timed grab d. all of the above - Answer: c 41. A ________ sample consists of several portions collected at intervals, then mixed together. a. grab b. timed grab c. composite d. none of the above - Answer: c 1. Domestic waste is uniform in content. a. true b. false - Answer: b 2. Some wastes cannot be treated in a domestic wastewater treatment plant because the waste would harm the biological process or contaminate the waste sludge. a. true b. false - Answer: a 3. Sources of wastewater include domestic, I & I, food processing, agricultural operations, and industrial operations. a. true b. false - Answer: a 4. By weight, domestic wastewater is about 99.9% water and 1% solids. a. true b. false - Answer: b 5. Flows from domestic sources average about 100 gallons/day per person. a. true b. false - Answer: a 6. Inflow is stormwater that enters a collection system through openings such as house wastewater, line cleanouts, or open manholes. a. true b. false - Answer: a 7. Infiltration is stormwater that enters the collection system through broken pipe joints, manhole walls, and cracked pipe. a. true b. false - Answer: a 8. I & I floods the collection system, creating flow 5-10 times higher than the daily average. a. true b. false - Answer: a 9. I & I results in bypassing, plant washout, poor treatment, and permit violations. a. true b. false - Answer: a 10. I & I is easy and inexpensive to correct. a. true b. false - Answer: b 11. Food processing discharges large amounts of ________ material into the wastewater system. a. liquid b. inorganic c. organic d. solid - Answer: c 12. Pesticides and herbicides used by the agricultural industry can be ________ to the treatment plant biological system. a. helpful b. toxic c. healthy d. useful - Answer: b 13. Some industries that may contribute a shock load to the treatment plant are refineries, paper mills, and ________. a. public restrooms b. swimming pools c. garbage disposals d. metal platers - Answer: d 14. EPA requires some industries to pretreat waste before discharge to a ________. a. POWT b. PTOW c. POTW d. PWTO - Answer: c 15. The most important problem prevented by monitoring or restricting industrial waste is ________. a. sludge contamination b. worker exposure c. effluent pollutants d. wastewater fires - Answer: b 16. Federal regulations require cities to have an industrial waste control program when ________. a. flow exceeds 5 MGD and industrial waste is regulated by federal standards b. flow exceeds 0.5 MGD and any industry discharges waste c. flow exceeds 50 MGD and industrial waste is regulated by federal standards d. none of the above - Answer: a 17. ________ results in the rapid die-off of treatment organisms. a. Acute toxicity b. Chronic toxicity c. Acquired toxicity d. Chronicle toxicity - Answer: a 18. While the TCEQ does not have specific pretreatment standards, ________ provides specific pretreatment standards. a. OSHA b. EPA c. USDA d. DOT - Answer: b 19. Restricted discharges include those that ________. a. create a fire or explosion hazard b. create toxic conditions c. cause shock loads d. all of the above - Answer: d 20. Some pretreatment processes include ________. a. spill control b. metal removal c. pH control d. all of the above - Answer: d 1. The purpose of the collection system is to collect and transport waste to the point of treatment. a. true b. false - Answer: a 2. The most important benefit of a collection system is comfort and convenience. a. true b. false - Answer: b 3. Parts of a collection system include wastewater lines, wastewater crossings, inverted siphons, cleanouts, manholes, and lift stations. a. true b. false - Answer: a 4. If gasoline or solvent odors are detected in a manhole, bolt and gasket the coverthe operator should . a. true b. false - Answer: b 5. Safety rules for manholes include checking for gases and sufficient oxygen, wearing a lifeline, and having two workers assisting at the surface. a. true b. false - Answer: a 6. Clay and PVC are the most common pipe material. a. true b. false - Answer: a 7. Pipe materials used in collection system construction include polyvinyl chloride, clay, concrete, and iron. a. true b. false - Answer: b 8. Grade (or slope) and flow velocity are important to wastewater pipe installation. a. true b. false - Answer: a 9. For any gravity wastewater, the minimum velocity required to keep solids in suspension is 1ft/sec. a. true b. false - Answer: b 10. Pipe should be laid down so that the bell end is facing downstream or downhill. a. true b. false - Answer: b 11. Wastewater flowing into a collection system should come from ________. a. storm drainage b. homes and businesses c. industry d. b and c - Answer: d 12. Install wastewater lines no closer to a water line than ________ feet. a. 7 b. 8 c. 9 d. 10 - Answer: c 13. OSHA sets standards for shoring, sloping, or trench boxes for trenches ________ feet or deeper. a. 6 b. 5 c. 4 d. 3 - Answer: b 14. If the trench is ________ feet or deeper, a means of exit is required. a. 7 b. 6 c. 5 d. 4 - Answer: d 15. If a ladder is used, it must be portable and extend ________ feet above the trench, in addition to being secured. a. 2 b. 3 c. 4 d. 5 - Answer: b 16. A ladder must be within ________ feet of anyone in the trench. a. 25 b. 24 c. 23 d. 22 - Answer: a 17. Excavation spoil must be at least ________ feet from the edge of the trench. a. 5 b. 4 c. 3 d. 2 - Answer: d 18. The primary cause of stoppages is roots or ________. a. gases b. sand c. grease d. rain - Answer: c 19. Wastewater cleaning can increase pipe capacity, prevent septic conditions, maintain flow velocity, and ________. a. increase BOD b. reduce stoppages c. kill pathogens d. reduce flow - Answer: b 20. Hydraulic cleaners (jetting units) use ________ under pressure, which is forced through nozzles. a. air b. water c. gas d. oil - Answer: b 21. Maps should be as built, showing corrections made in the field during ________. a. planning b. construction c. bidding d. designing - Answer: b 22. When chemicals are used in the system, consider worker and public ________. a. safety b. relations c. complaints d. approval - Answer: a 23. When wastewater cannot flow to treatment by ________, a lift station is used. a. pressure b. gravity c. force d. vacuum - Answer: b 24. Lift station designs include ________. a. dry well b. wet well c. pneumatic ejector d. all of the above - Answer: d 25. Dry well stations have the ________ and pumps in a dry well separated from the adjacent wet well. a. wastewater b. floats c. motors d. vents - Answer: c 26. The ________ pump is most commonly used in a lift station. a. displacement b. ejector c. diaphragm d. centrifugal - Answer: d 27. Foreign matter in the ________ can cause noisy operation and should be investigated. a. impeller b. discharge c. controls d. all of the above - Answer: a 28. The centrifugal pump must be ________ or it will not pump. a. leaking b. primed c. vented d. flushed - Answer: b 29. Discharge valves on a positive displacement pump must be ________. a. packed b. leaking c. closed d. open - Answer: d 30. The ________ valve, usually a swing type, prevents water on the discharge side of the pump from flowing backwards through the pump when it is off. a. gate b. check c. swing d. discharge - Answer: b 31. The best design of isolation valve is the ________ valve because it leaves an unrestricted path when fully open. a. gate b. discharge c. swing d. check - Answer: a 32. The ________ valve is the most commonly used valve in the collection system. a. swing b. check c. discharge d. gate - Answer: d 33. Motors used in wastewater are typically three-phase ________ motors. a. deduction b. reduction c. induction d. subjection - Answer: c 34. The speed of an electric motor is measured in ________. a. rbi b. rpm c. ppm d. rmp - Answer: b 35. To reduce gases, the TCEQ requires lift stations to have a ________ system. a. safety b. detection c. ventilation d. buddy - Answer: c 36. Hydrogen sulfide is very toxic and deadens the sense of ________. a. sight b. smell c. taste d. touch - Answer: b 37. If a pump loses prime, it will heat up and damage the ________. a. seal b. valves c. impeller d. volute - Answer: a 38. Common methods to detect liquid depths and control pumps are ________, pneumatic bubblers, electric probes, and ultrasonic sensors. a. weirs b. floats c. meters d. flumes - Answer: b 39. ________ pumps in dry wells collect packing seal leakage as well as cleanup water. a. Slump b. Dump c. Bump d. Sump - Answer: d 40. A ________ maintenance program keeps emergency repairs to a minimum. a. predetermined b. premeditated c. preventive d. prefabricated - Answer: c 41. ________ are important to lift station operation and maintenance. a. Bypasses b. Records c. Siphons d. Bacteria - Answer: b 42. Records include a ________ checklist. a. yearly b. monthly c. weekly d. daily - Answer: d 1. Preliminary treatment is usually the first step in the treatment process. a. true b. false - Answer: a 2. Types of screens include bar screens and rotating barrel screens. a. true b. false - Answer: b 3. Before making screen repairs, the power should be turned off and the controls locked. a. true b. false - Answer: a 4. Types of grinding units include comminutor and barminutor. a. true b. false - Answer: a 5. Grinding units return the debris to the wastewater stream for removal later. a. true b. false - Answer: a 6. Grit removal takes place in a grit chamber after primary treatment. a. true b. false - Answer: b 7. Grit removal prevents buildup of settleable organic solids. a. true b. false - Answer: b 8. Common designs of grit removal units are hand-cleaned chambers, mechanically cleaned chambers, aerated chambers, cyclone separators, and screw washers. a. true b. false - Answer: a 9. Water velocity in a grit chamber is about 2 ft/sec. a. true b. false - Answer: b 10. A cyclone separator spins the wastewater in a spiral flow and throws the grit, by centrifugal force, to the wall of the unit, where it falls to the bottom. a. true b. false - Answer: a 11. The purpose of a grit washer is to remove ________ material from the grit. a. inorganic b. greasy c. organic d. all of the above - Answer: c 12. ________ interferes with the biological treatment process. a. BOD b. Grease c. Grit d. Water - Answer: b 13. Diffused ________ causes lightweight grease particles to rise to the surface. a. air b. gas c. oxygen d. nitrogen - Answer: a 14. Chlorine helps ________ grease, making it easy to skim. a. melt b. oxidize c. float d. congeal - Answer: d 15. Final disposal of grit, screenings, and grease is by burial in a ________. a. landfill b. compost c. park d. garden - Answer: a 16. Pre-aeration is used to remove grit, reduce ________, add oxygen, and promote grease flotation. a. chlorine b. pH c. gases d. temperature - Answer: c 17. Use flow equalization to control variations in flow patterns or ________ loads. a. shake b. slow c. slam d. shock - Answer: d 18. It is important to monitor the flow in order to calculate plant load, as well as to determine ________. a. inflow/infiltration b. treatment cost c. flow trends d. all of the above - Answer: d 19. Flow is the water volume passing a given point, in a specified interval, in gallons per minute or cubic feet per ________. a. day b. hour c. minute d. second - Answer: d 20. A weir is an obstruction placed in a channel, causing the water to ________. a. back up b. pressurize c. evaporate d. run off - Answer: a 21. The ________ of the water flowing over the weir determines the flow rate. a. weight b. depth c. velocity d. volume - Answer: b 22. Common weir designs are rectangular, Cipolletti, and ________. a. A-notch b. Z-notch c. B-notch d. V-notch - Answer: d 23. An ultrasonic flow monitoring device works on the principle of ________. a. radar b. solar c. radio d. sonar - Answer: d 24. The magnetic meter works by the law of ________. a. conductance b. reduction c. induction d. production - Answer: c 25. ________ calibrate flow measuring devices. a. Hourly b. Daily c. Monthly d. Annually - Answer: d 26. Flow measuring devices must be ± ________% accurate. a. 1 b. 5 c. 10 d. 15 - Answer: c 1. Sedimentation is the process of separating a suspended solid from water by atmospheric pressure. a. true b. false - Answer: b 2. Common design features of a sedimentation tank include baffles, a skimmer, a grease ring, and a sludge rake. a. true b. false - Answer: a 3. A primary clarifier settles biological sludge, and a secondary clarifier settles raw sludge. a. true b. false - Answer: b 4. Factors affecting settling include solid weight, water temperature, detention time, velocity, surface loading, wastewater condition, and short-cutting. a. true b. false - Answer: b 5. The four settling zones in a sedimentation tank are the inlet zone, settling zone, sludge zone, and the outlet zone. a. true b. false - Answer: a 6. Short-circuiting is the uneven flow of water through a tank. a. true b. false - Answer: a 7. Primary clarifiers should remove 90-95% of the BOD and 30-40% of the settleable solids. a. true b. false - Answer: b 8. Secondary sludge contains more water than primary sludge. a. true b. false - Answer: a 9. Maintenance of a clarifier includes ________ inspection of the skimmer. a. yearly b. monthly c. weekly d. daily - Answer: d 10. If the skimmer fails, the sludge ________ fails. a. pump b. sump c. rake d. baffle - Answer: c 11. Floating sludge or excessive gas bubbles indicate a failure of the return sludge pump, sludge rake, or poor ________ schedule. a. skimming b. pumping c. settling d. digesting - Answer: b 12. Withdraw sludge slowly or water will break through the sludge layer, ________ the sludge. a. diluting b. thickening c. wetting d. stirring - Answer: a 13. Usual blanket depth in a secondary clarifier is no more than ________ of the sidewall depth. a. 3/4 b. 1/2 c. 1/3 d. 1/4 - Answer: d 14. Imhoff tanks are ________ story units with ________ compartments. a. 3/2 b. 3/3 c. 2/3 d. 2/2 - Answer: c 15. The ________ compartment of an Imhoff tank is the settling tank, and the ________ compartment is the sludge digester. a. upper/lower b. lower/upper c. digester/settling d. second/first - Answer: a 16. Gas vents alongside the settling tank are the ________ compartment. a. first b. second c. third d. fourth - Answer: c 17. The settling compartment provides a detention time of about ________ hour(s). a. 4 b. 3 c. 2 d. 1 - Answer: c 18. A trapped slot in the bottom of the settling compartment permits ________ solids to pass into the digester, but prevents septic solids from ________ into the settling compartment. a. rising/settling b. septic/settling c. digested/rising d. settled/rising - Answer: d 19. The sloping bottom of the settling compartment ________ gas bubbles and grease, causing them to ________ into the gas vents. a. deflects/rise b. produces/settle c. collects/rise d. deflects/settle - Answer: a 20. ________ prevents septic solids from collecting and rising in the settling chamber. a. Pumping b. Chaining c. Rodding d. Skimming - Answer: b 21. When sludge in an Imhoff tank is near ________ inches of the slot, withdraw sludge. a. 14 b. 16 c. 18 d. 20 - Answer: c 22. Foaming can be caused by industrial waste, drawing too much sludge, low pH, and restricted ________. a. weirs b. settling chamber c. digester d. gas vents - Answer: d 23. Control foaming by controlling industrial waste, ________, and controlling pH with lime. a. wasting small amounts of sludge b. wasting large amounts of sludge c. cleaning the bar screen daily d. skimming the settling tank often - Answer: a 1. The five components of the activated sludge process are the oxygen supply system, aeration tank, clarifier, return sludge system, and waste sludge system. a. true b. false - Answer: a 2. Mixed liquor is the mixture of raw wastewater and microorganisms. a. true b. false - Answer: a 3. In the clarifier, the biological solids separate by gravity settling. a. true b. false - Answer: a 4. The settled biological solids accumulate in the clarifier, then are always wasted from the process. a. true b. false - Answer: b 5. Wasting removes excess solids, inert solids, and old or dead solids from the system. a. true b. false - Answer: a 6. The aeration tank should be observed weekly for a uniform aeration pattern, low amount of light colored foam, mild, earthy odor, and medium brown color. a. true b. false - Answer: b 7. The clarifier should have very little scum, a sludge blanket in the bottom ¼ of the clarifier, uniform weir flow, rising solids, and turbid supernatant. a. true b. false - Answer: b 8. Process control parameters include dissolved oxygen, quantity and quality of solids, return rate, and wasting rate. a. true b. false - Answer: a 9. Normally, DO should be kept between 20 and 40 mg/L. a. true b. false - Answer: b 10. At least 1 mg/L DO should be kept in the aeration basin to maintain the health of the anaerobic microorganisms. a. true b. false - Answer: b 11. The primary purpose of returning sludge is to have enough ________ in the aerator to match the food supply. a. water b. microorganisms c. BOD d. air - Answer: b 12. If the ________ loading on the plant is high, DO levels should be increased. a. organic b. inorganic c. hydraulic d. all of the above - Answer: a 13. A simple method indicating when to waste is the ________. a. sludge volume index b. mixed liquor suspended solids c. 30-minute settling test d. F/M ratio - Answer: a 14. ________ are the smallest, most numerous, and most important of the activated sludge microorganisms. a. Protozoa b. Fungi c. Rotifers d. bacteria - Answer: d 15. ________ settles gently and uniformly, compacts slowly, and has sharp edges like a sponge. a. quality sludge b. Old sludge c. Young sludge d. Bulky sludge - Answer: a 16. The ________ modification of the activated sludge process has no primary clarifier, no digester, 24-hour aeration time, a low F/M ratio, and complete nitrification. a. conventional process b. extended aeration c. contact stabilization d. none of the above - Answer: b 17. The ________ modification has no return sludge and the aeration tank is used as the clarifier. a. centennial batch reactor b. sequential box reactor c. sequential batch reactor d. sequential batch retractor - Answer: c