Wastewater Treatment Plant Operations, Exams of Water and Wastewater Engineering

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Basic Wastewater Operator Practice Exam

1. What is the predominant organism in a healthy activated sludge treatment plant? A. Stalked ciliates B. rotifers C. nematodes D. amoebas: A. Stalked Ciliates 2. A composite sample must be? A. sporadically collected in the treatment plant B. taken at one time C. analyzed immediately D. representative and sub-samples time spaced over 15 minutes apart: D. representative and sub-samples time spaced over 15 minutes apart 3. What is the standard volume for a BOD sample bottle? A. 150 mL B. 200 mL C. 300 mL D. 500 mL: c. 300 mL 4. If you have a lime slurry feed line, what is the best valve to use? A. plug valve B. butterfly valve C. RPZ dual check valve D. gate valve: A. plug valve 5. 5. If you notice a predominance of rotifers in your activated sludge sample while looking at it under a microscope, what does this indicate? A. healthy sludge B. young sludge C. old sludge D. middle age sludge: C. old sludge 6. Calculate the BOD using the given information: Initial DO: 8. Final DO: 5. Milliliters of sample used: 2

a. 360 mg/L b. 210 mg/L c. 856 mg/L d. 36 mg/L: a. 360 mg/L

7. If your activated sludge plant begins to nitrify, what conditions would you expect to decrease? A. settling in clarifiers B. chlorine demand C. BOD effluent D. TSS in effluent: a. settling in the clarifiers 8. How do you calibrate a chemical feed pump? A. by measuring the pump output B. using the SWAG method C. jar test D. with a microscope: A. by measuring the pump output 9. What is the chemical formula for sulfuric acid? a. HNO b. HCl c. NaOH d. H2SO4: d. H2SO 10. What is the most common type of activated sludge package plants? a. extended aeration b. sequential batch reactor c. oxidation ditch d. bardenpho: a. extended aeration 11. What is the most appropriate method of reducing the F:M ratio? A. increase wasting b. decrease wasting c. reduce BOD from influent flow D. add polymer to RAS to increase settling: b. decrease wasting 12. An operator notices a portion of the aeration tank with large bubbles rising up. What is the most likely problem? a. equal air distribution

b. unequal air distribution caused by a blown/clogged diffuser

c. normal operation d. reason to believe the air filter in the blower is clogged: b. unequal air distrib- ution caused by a blown diffuser

13. What is suction lift? a. a team approach to lifting heavy objects b. the pressure on the suction side of the pump c. the measurement of liquid pressure at the pump d. the measure of how bad your workers lift heavy objects: b. the pressure on the suction side of the pump 14. The primary effluent to a RBC system is 350 mg/L BOD. The primary unit removes 83% the secondary unit removes 50% and the final unit removes 25%. What is the BOD leaving the final unit of the RBC train? A. 290 mg/L b. 60 mg/L c. 30 mg/L d. 22.5 mg/L: d. 22.5 mg/L 15. The influent to the treatment plant is septic. it is determined that it is coming from a lift station upstream from the plant. What should the operator do? A. decrease the lag time for pump operation by moving the floats closer together b. add pH adjuster to the influent flow c. install larger capacity pumps in the lift stations d. the her nothing you can do to correct this problem: A. decrease the lag time for pump operation by moving the floats closer together 16. What is the purpose of amber storage bottles? A. the color is pretty b. they are cheaper c. to protect chemicals that are sensitive to light d. so you can not see what is inside the container: c. to protect chemicals that are sensitive to light 17. Calculate SRT Given: MLSS = 2400 mg/L Aeration basin volume = 35,000 gallons = 0. MG WAS concentration = 3500 mg/L

WAS flow rate = 0.001 MGD A. 6 hours b. 6 days c. 24 hours d. 24 days: d. 24 days

18. How should a 1-ton chlorine cylinder be moved and stored? A. Horizontal and vertical B. vertical and horizontal C. vertical and vertical D. horizontal and horizontal: D. horizontal and horizontal 19. Calculate F:M ratio Given: Influent BOD5 = 290 mg/L Influent flow = 5.0 MGD Aeration basin MLSS = 2650 mg/L Aeration basin volume = 0.8 MG A. 0. B. 0. C. 0. D. 0.06: c. 0. 20. What would most likely cause a submersible pump to an AMP reading that is above the optimum level? A. nothing, pumps normally run highs AMPs b. clogged impeller c. low voltage at power supply d. low flow to pump station: b. clogged impeller 21. Which of the following are non-moving parts of a running motor? A. impeller b. shaft c.windings d. stator: d. stator 22. Calculate SVI Given: 30 minute settling test = 1800 mL in a 2000 mL container MLSS = 4000 mg/L

A. 200

b. 450 c. 225 d. 115: c. 225

23. What type of flow meters are used during normal operations of the sludge removal? a. turbine b. magnetic c. TDR d. paddle wheel: b. magnetic 24. What should be done when the bioreactor in an SBR plant is organically overloaded? a. nothing - it is normal for bioreactors to be organically overloaded b. waste more sludge c. add more fresh water d. increase effluent flow: b. waste more sludge 25. Why are approved black flow devices installed above ground level? a. ease of access b. because the plummers union requires it c. cost of vault d. to keep valves from being submerged: d. to keep valves from being submerged 26. What is the most appropriate method to decrease F:M ratio? a. decrease WAS b. Decrease influent flow c. add lime to the return sludge d. add NaOH to influent flow: a. decrease WAS 27. Calculate the total volume in million gallons. of both tanks. Given: Tank A. = 20 ft diameter, 35 ft tall Tank B = 45 ft long, 20 ft wide, 6 ft deep a. 0.0123 MG b. 0.123 MG c. 0.0445 MG d. 0.445 MG: b. 0.123 MG

28. Which of the following can be analyzed using composite samples? a. fecal coliform b. oil & grease c. BOD d. TTHM: c. BOD 29. Which of the following can be analyzed using composite samples? a. oil & grease b. NH c. fecal coliform d. HAA5: b. NH 30. What causes the pH to decrease during the anaerobic digestion process? a. production of volatile acids b. added heat c. excessive mixing d. excessive wasting: a. production of volatile acids 31. What factors control the throat size in a chlorinator? a. chlorine pressure b. type of chlorine used c. water pressure d. distance to injection point: c. water pressure 32. What causes a centrifugal pump discharge pressure to increase and dis- charge quantity to decrease? a. blockage in discharge line b. blockage in intake c. low power supply d. low flow into station: b. blockage in intake 33. What causes reduction in pump discharge rate? a. blockage in discharge line b. blockage in intake c. low power supply d. low flow into station: a. blockage in discharge line 34. What should an operator expect to occur when flow increases to

the secondary clarifiers?

a. increased settling rate b. decreased settling rate c. nitrification d. increase in filamentous bacteria: b. decreased settling rate (blankets rise)

35. What is Total Kjeldahl Nitrogen (TKN) comprised of? a. phosphorous and nitrogen b. nitrogen, oxygen, and magnesium c. nitrogen, potassium, and ammonia d. organic nitrogen and ammonia: d. organic nitrogen and ammonia 36. What is the term used when the nitrifiers convert the ammonia to nitrites and nitrates under aerobic conditions? A. nitrification B. denitrification C. assimilation D. neutering: a. nitrification 37. What is the term used when bacteria convert nitrates and nitrites to nitro- gen gas under anoxic conditions? a. nitrification b. denitrification c. assimilation d. neutering: b. denitrification 38. What is the chemical symbol for hydrogen sulfide? a. HFS b. H2SO c. H2S d. HNO3: c. H2S 39. How should lime slurry lines be cleaned? a. replace feed line after each shift b. flush with water c. clean feed line with a stiff bristle brush d. flush with muriatic acid: b. flush with water 40. The ammonia loading on a plant is increasing. What should the

operator expect regarding the amount of alkalinity in the system?

a. the alkalinity will decrease b. the alkalinity will remain the same c. the alkalinity will not change d. ammonia has nothing to do with alkalinity: a. the alkalinity will decrease

41. What is a check valve? a. a valve that is closed by the pressure of a fluid so that the fluid does not flow back in the direction it came from b. a valve to check the flow volume of a pump c. a valve that allows for flow of water to go in multiple directions d. a valve that creates a check point for sampling: a. a valve that is closed by the pressure of a fluid so that the fluid does not flow back in the direction it came from 42. What should an operator do when excess solids enter a media filter? a. improve the performance of secondary treatment units b. increase the backwash frequency c. employ air-scour and/or surface jetting d. put additional filters on line: b. increase the backwash frequency 43. Suction lift pressure is measured from the center line of the pump to ? a. center of discharge line at ground level b. center of the power line c. top of the highest manhole lid d. bottom of the lowest manhole lid: A. center of discharge line at ground level 44. What type of supply pipe is recommended for gaseous chlorine & water? a. galvanized steel b. polyvinyl chloride c. rubber d. stainless steel: b. polyvinyl chlorine (PVC) 45. Which activated sludge processes handles shock loads of high organic waste most effectively? a. bardenpho b. conventional

c. SBR d. complete mix: b. conventional

46. What occurs to hydrogen sulfide when it reacts with chlorine? a. sulfur and hydrochloric acid are formed b. an explosion c. a pleasant odor d. nitrification: a. sulfur and hydrochloric acid are formed 47. What chemical is used for dechlorination? a. sodium sulfate b. sodium hydroxide c. sulfur dioxide d. UV light: c. sulfur dioxide 48. What is a vector? a. the third point of a tripod b. an organism that transfers disease or parasite from one to another c. the total of three points of measurement d. the intersection of two dissecting lines: b. an organism that transfers disease 49. To prevent wear pattern on a piston pump shaft what kind of strokes should be made? a. long, fast strokes b. short, slow strokes c. long, slow strokes d. short, fast strokes: c. long, slow strokes 50. What is the purpose for adding copper sulfamic acid to a D.O. sample? a. to increase the pH b. as an inhibitor solution for the DO analysis using the APHA method c. to kill bacteria d. to increase biological activity: b. as an inhibitor solution for the DO analysis using the APHA method 51. what is the best valve for throttling flow? a. plug valve b. butterfly vavle c. check valve d. gate valve: b. butterfly valve

52. What information does a mixed liquor test provide? a. flow into the clarifiers b. F:M ratio c. amount of solids in the sample d. return flow volume: c. amount of solids in the sample 53. When organic wastes are discharged to receiving waters, what depletes oxygen? a. excessive flow b. bacteria c. color d. high pH: b. bacteria 54. Hydrogen sulfide gives off an odor similar to what? a. peanut butter b. rotten eggs c. rotten apples d. dirt: b. rotten eggs 55. What is first aid for someone getting chlorine gas in their eyes? a. bandage tightly with gause b. slather with vaseline c. flush with cold water for 15 minutes d. flush with sodium dioxide solution to neutralized the chlorine: c. flush with cold water for 15 minutes 56. Diseases potentially carried by wastewater include? a. typhoid fever b. dysentery c. cholera d. all of the above: d. all of the above 57. What immediate first aid should be given for burns? a. hot compress b. clean with an antiseptic c. flush with cold water d. cover tightly with bandage: c. flush with cold water

58. What is one of the most likely causes of electric motor failure? a. running too long b. short run times c. excessive moisture d. dry conditions: c. excessive moisture 59. What is a valve called that allows water to flow in one direction only? a. plug valve b. butterfly valve c. check valve d. gate valve: c. check valve 60. What is one component of a centrifugal pump? a. impeller b. primer c. hose bib d. piston: a. impeller 61. Chlorine gas is what? a. lighter than air b. same weight as air c. heavier than air d. purple in color: c. heavier than air 62. The highest concentration of algae growth in a facultative lagoon is usually observed where? a. near the top b. near the middle c. at the bottom d. at the effluent: a. near the top 63. Common hydraulic detention times for primary clarifiers range from? a. 1-2 hours b. 5-10 hours c. 18-24 hours d. 2-3 hours: d. 2-3 hours 64. Which gas is produced in an anaerobic digester?

a. ethanol b. alcohol c. methane d. hydrogen sulfide: c. methane

65. The rock in a trickling filter is usually placed where? a. around the outer edge of the filter b. in the center of the filter c. on the tile underdrain system d. at the discharge of the filter: c. on the tile underdrain system 66. Chlorine is primarily used to what? a. increase pH b. increase dissolved oxygen c. disinfection d. decrease solids: c. disinfection 67. What is the purpose of heating and mixing a primary anaerobic digester? a. to slow down the digestion rate b. to increase the digestion rate c. to allow for more room in the digester d. to increase effluent quality: b. to increase the digestion rate 68. Name a device which is used to measure the flow of wastewater? a. rotometer b. ruler c. parshall flume d. sight glass: c. parshall flume 69. Where in a parshall flume does an operator take a manual flow reading? a. 4x the throat width back b. at the beginning of the throat c. at the end of the throat d. 2/3 the length of the converging wall measured back from the throat: d. 2/3 the length of the converging wall measured back from the throat 70. Where should the exhaust from a chlorinator room be taken from? a. at the door b. at the ceiling

c. at floor level d. in the window: c. at floor level

71. What is the main concern when a chemical spill occurs? a. written report to state officials b. containment and clean up c. replacement of the chemical in stock d. keeping the supervisor from finding out: b. containment and clean up 72. What is the correct valve position when starting a reciprocating pump? a. in valve open; out valve open b. in valve closed; out valve closed c. in valve closed; out valve open d. in valve open; out valve closed: a. in valve open; out valve open 73. What is normal daily maintenance for an automatic bar screen? a. watch full cycle b. grease sprocket c. grease drive chain d. replace teeth: a. watch full cycle 74. What is the force that can send current down the line when the breaker is off? a. voltage b. amps c. frequency d. resistance: a. voltage 75. How does an operator improve the filter cake exiting a belt press? a. slow wash water b. speed up the belt c. slow down the belt d. tighten the belt: c. slow down the belt 76. What causes a white slimy coating on an RBC filter? a. oil and grease b. high BOD c. sulfides d. high pH: c. sulfides

77. What reagent is used to determine chlorine residual? a. diethyl-p-phenylene diamine or DPD b. sulfur dioxide (SO2) c. sodium metabisulfite (Na2S2O2) d. sodium bisulfate: a. diethyl-p-phenylene diamine or DPD 78. What test is typically never performed on wastewater influent? a. BOD b. TSS c. Fecal coliform d. Oil & grease: d. O&G 79. A local college has an outbreak of giardia in the water system. A hose that was connected to a spigot found in a grease trape was determined to be where the bacteria entered the system. What is this an example of? a. cross-connection by back siphonage b. cross-connection by back pressure c. cross-connection from an unapproved treatment system d. normal system operation: a. cross-connection by back siphonage 80. Considering the layout and flow diagram for the complete treatment plant, oxidation ditch plants would be most similar to which of the following? a. SBR b. plug flow c. Extended aeration d. contact stabilization: c. extended aeration 81. A WWTP flow is 5.0 MGD. How many gallons per minute is this? a. 3472 gpm b. 0.24 gpm c. 57.8 gpm d. 7200 gpm: a. 3472 gpm 82. A trickling filter arm is moving slow. How do you speed it up? a. add more orfices on the distribution arms b. close orifices on the distribution arms c. decrease recirculation

d. increase recirculation: d. increase recirculation

83. What is the best way to clean up a polymer spill? a. with bleach b. with phosphate detergent c. with paint thinner d. with a chemical absorbent: d. with a chemical absorbent 84. How do you mix acid and water? a. add acid to water slowly while stirring to dissipate heat b. water to acid c. do not mix d. pour both into a beaker at the same time: a. add acid to water slowly while stirring to dissipate heat 85. In an RBC plant, the microscopic investigation revealed some amoebas and flagellates in the first set of discs, the second set showed free- swimming ciliates and some rotifers, the third set had blood worms and nematodes. What is this an indication of? a. normal operation b. toxic waste entering the plant c. flow running too slow through discs d. flow running too fast: c. flow running too slow through discs 86. Your system serves 2740 people and an industry contributes 300 lbs/day of BOD. How many pounds of BOD are received at your plant? a. can not calculate, not enough information b. 766 lbs/day c. 466 lbs/day d. 383 lbs/day: b. 766 lbs/day 87. When you install a new packing gland, you notice that there is a slow, steady stream of water flow coming out of the packing area. What is this an indication of? a. you need more packing b. you need to tighten the bolts until no water is leaking out c. normal operation d. you need to loosen the bolts until a fast, heavy stream of water is spraying out of the packing: c. normal operation

88. When collecting a sludge sample, where is the most representative sample location? a. at the beginning of the aeration basin b. at the end of the aeration basin c. in the middle, after all return flows have been well mixed d. right before the RAS and WAS return flows: c. in the middle, after all the return flows have been well mixed 89. Your system has two clarifiers with equal flow going to both. One of the clarifiers is operating fine with good clarity. The other is having pop-ups. What is the most likely cause? a. filamentous bacteria b. old sludge c. young sludge d. broken clarifier drive: d. broke clarifier drive 90. What is the term used to refer to the action taken to prepare for an emergency? a. response b. reaction c. mitigation d. recovery: c. mitigation 91. An equipment failure warning light did not turn on, but a failure was reported and repaired. What is the first thing the operator needs to do? a. inspect the system for damages b. check the unit with a volt meter c. check/replace the bulb in the indicator light d. call an electrician: c. check/replace the bulb in the indicator light 92. Calculate the pounds per day of chemical dosage with a flow of 5 MGD doing at a rate of 218 ppm. a. 1090 lbs/day b. 9090 lbs/day c. 8153.2 lbs/day d. 1818 lbs/day: b. 9090 lbs.day 93. If you are collecting a manual flow proportional composite sample with

the following flows, and you want to collect a total of 1000 mL, how much sample

would be needed for sample #4? Flow #1: 12367 Flow #2: 12452 Flow #3: 12511 Flow #4: 12612 Flow #5: 12710 a. 246 mL b. 171 mL c. 293 mL d. 284 mL: d. 284 mL

94. The pressure against which a pump must operate is measured in terms of what? a. PSI b. SBR c. LLL d. OM: a. PSI 95. How is an air-gap used? a. it takes the gap of air and creates space for more bugs b. to prevent contamination of potable water systems c. to allow for less air to enter the system d. to discharge excess air in the pressure line: b. to prevent contamination of potable water systems 96. A horizontal centrifugal pump has "rope" packing. When the pump is operation water slowly drips from the packing glad. What does this indicate? a. the packing bolts or nuts on the packing gland are properly adjusted b. the packing bolts or nuts on the packing gland are not properly adjusted c. the pump needs more coolant d. the pump is not operating efficiently: a. the packing bolts or nuts on the packing gland are properly adjusted 97. Why are check valves used in conjunction with centrifugal pumps? a. to increase head pressure b. to cause more work for the installers

c. to prevent wastewater in the discharge line from flowing back through the

pump d. to allow for less water to leave the pump: c. to prevent wastewater in the discharge line from flowing back through the pump

98. What should an operator do if a fuse continues to blow? a. inspect the affected equipment to determine the cause b. replace it with a larger capacity fuse c. nothing. fuses blow from time to time d. keep it a secret. it may cause you more work: a. inspect the affected equipment to determine the cause 99. Valves should be closed slowly to avoid what? a. water sledge b. water saw c. water blasting d. water hammer: d. water hammer 100. Assuming a constant suction head, the discharge of a centrifugal pump a. will increase with a decreased in discharge head b. will decrease with a decrease in discharge head c. will decrease with an increase in discharge head d. will increase with an increase in discharge head: c. will decrease with an increase in discharge head 101. A positive displacement sludge pump should never be placed into oper- ation a. true b. false c. with the discharge valve closed d. with the discharge open: c. with the discharge valved closed 102. How does the addition of chlorine, acid, carbon dioxide, or sulfuric acid effect the pH of wastewater? a. increase the pH b. decrease the pH c. pH remains the same d. normalize the pH: b. decrease the pH 103. controlling the sludge wasting rate by constant mixed liquor