Basic Wastewater Operator Practice Exam Questions & Answers

What is the predominant organism in a healthy activated sludge treatment plant? A. Stalked ciliates B. rotifers C. nematodes D. amoebas - ANSWERSA. Stalked Ciliates AnswerA 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 - ANSWERSD. representative and sub-samples time spaced over 15 minutes apart AnswerWhat is the standard volume for a BOD sample bottle? A. 150 mL B. 200 mL C. 300 mL D. 500 mL - ANSWERSc. 300 mL AnswerIf 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 - ANSWERSA. plug valve Answer5. 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 - ANSWERSC. old sludge AnswerCalculate the BOD using the given information: Initial DO: 8.3 Final DO: 5.9 Milliliters of sample used: 2 a. 360 mg/L b. 210 mg/L c. 856 mg/L d. 36 mg/L - ANSWERSa. 360 mg/L AnswerIf 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 - ANSWERSa. settling in the clarifiers AnswerHow 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 - ANSWERSA. by measuring the pump output AnswerWhat is the chemical formula for sulfuric acid? a. HNO3 b. HCl c. NaOH d. H2SO4 - ANSWERSd. H2SO4 AnswerWhat is the most common type of activated sludge package plants? a. extended aeration b. sequential batch reactor c. oxidation ditch d. bardenpho - ANSWERSa. extended aeration AnswerWhat 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 - ANSWERSb. decrease wasting AnswerAn 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 - ANSWERSb. unequal air distribution caused by a blown diffuser AnswerWhat 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 - ANSWERSb. the pressure on the suction side of the pump AnswerThe 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 - ANSWERSd. 22.5 mg/L AnswerThe 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 - ANSWERSA. decrease the lag time for pump operation by moving the floats closer together AnswerWhat 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 - ANSWERSc. to protect chemicals that are sensitive to light AnswerCalculate SRT Given: MLSS = 2400 mg/L Aeration basin volume = 35,000 gallons = 0.0350 MG WAS concentration = 3500 mg/L WAS flow rate = 0.001 MGD A. 6 hours b. 6 days c. 24 hours d. 24 days - ANSWERSd. 24 days AnswerHow 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 - ANSWERSD. horizontal and horizontal AnswerCalculate 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. 0.01 B. 0.11 C. 0.68 D. 0.06 - ANSWERSc. 0.68 AnswerWhat 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 - ANSWERSb. clogged impeller AnswerWhich of the following are non-moving parts of a running motor? A. impeller b. shaft ngs d. stator - ANSWERSd. stator AnswerCalculate 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 - ANSWERSc. 225 AnswerWhat type of flow meters are used during normal operations of the sludge removal? a. turbine b. magnetic c. TDR d. paddle wheel - ANSWERSb. magnetic AnswerWhat 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 - ANSWERSb. waste more sludge AnswerWhy 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 - ANSWERSd. to keep valves from being submerged AnswerWhat 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 - ANSWERSa. decrease WAS AnswerCalculate 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 - ANSWERSb. 0.123 MG AnswerWhich of the following can be analyzed using composite samples? a. fecal coliform b. oil & grease c. BOD5 d. TTHM - ANSWERSc. BOD5 AnswerWhich of the following can be analyzed using composite samples? a. oil & grease b. NH3 c. fecal coliform d. HAA5 - ANSWERSb. NH3 AnswerWhat causes the pH to decrease during the anaerobic digestion process? a. production of volatile acids b. added heat c. excessive mixing d. excessive wasting - ANSWERSa. production of volatile acids AnswerWhat factors control the throat size in a chlorinator? a. chlorine pressure b. type of chlorine used c. water pressure d. distance to injection point - ANSWERSc. water pressure AnswerWhat causes a centrifugal pump discharge pressure to increase and discharge quantity to decrease? a. blockage in discharge line b. blockage in intake c. low power supply d. low flow into station - ANSWERSb. blockage in intake AnswerWhat causes reduction in pump discharge rate? c. low power supply a. blockage in discharge line b. blockage in intake d. low flow into station - ANSWERSa. blockage in discharge line