Basic Wastewater Operator Practice
Exam Questions and answers | Updated
2024/25 RATED A+
What is the predominant organism in a healthy activated sludge treatment plant?
II II II II II II II II II II II
A. Stalked ciliates
II II
B. rotifers II
C. nematodes II
D. amoebas - A. Stalked Ciliates
II II II II II II II
II A composite sample must be?
II II II II
A. sporadically collected in the treatment plant
II II II II II II
B. taken at one time
II II II II
C. analyzed immediately
II II
D. representative and sub-samples time spaced over 15 minutes apart - D.
II II II II II II II II II II II II II
representative and sub-samples time spaced over 15 minutes apart
II II II II II II II II II
II What is the standard volume for a BOD sample bottle?
II II II II II II II II II
A. 150 mL II II
B. 200 mL II II
C. 300 mL II II
D. 500 mL - c. 300 mL
II II II II II II II II
II If you have a lime slurry feed line, what is the best valve to use?
II II II II II II II II II II II II II II
A. plug valve II II
B. butterfly valve
II II
C. RPZ dual check valve
II II II II
D. gate valve - A. plug valve
II II II II II II II II
5. If you notice a predominance of rotifers in your activated sludge sample while looking at
II II II II II II II II II II II II II II II II
it under a microscope, what does this indicate?
II II II II II II II II
A. healthy sludge
II II
B. young sludge II II
C. old sludge II II
D. middle age sludge - C. old sludge
II II II II II II II II II
Calculate the BOD using the given information:
II II II II II II II
Initial DO: 8.3 II II
,Final DO: 5.9 II II
Milliliters of sample used: 2 II II II II
a. 360 mg/L
II II
b. 210 mg/L
II II
c. 856 mg/L
II II
d. 36 mg/L - a. 360 mg/L
II II II II II II II II
If your activated sludge plant begins to nitrify, what conditions would you expect to
II II II II II II II II II II II II II II
decrease?
II
A. settling in clarifiers
II II II
B. chlorine demand
II II
C. BOD effluent
II II
D. TSS in effluent - a. settling in the clarifiers
II II II II II II II II II II II
II How do you calibrate a chemical feed pump?
II II II II II II II
A. by measuring the pump output
II II II II II
B. using the SWAG method
II II II II
C. jar testII II
D. with a microscope - A. by measuring the pump output
II II II II II II II II II II II II
II What is the chemical formula for sulfuric acid?
II II II II II II II
a. HNO3
II
b. HClII
c. NaOH
II
d. H2SO4 - d. H2SO4
II II II II II II
II What is the most common type of activated sludge package plants?
II II II II II II II II II II
a. extended aeration
II II
b. sequential batch reactor
II II II
c. oxidation ditch
II II
d. bardenpho - a. extended aeration
II II II II II II II
II What is the most appropriate method of reducing the F:M ratio?
II II II II II II II II II II
A. increase wasting
II II
b. decrease wasting
II II
c. reduce BOD from influent flow
II II II II II
D. add polymer to RAS to increase settling - b. decrease wasting
II II II II II II II II II II II II II
An operator notices a portion of the aeration tank with large bubbles rising up. What is the
II II II II II II II II II II II II II II II II II
most likely problem?
II II II
, a. equal air distribution
II II II
b. unequal air distribution caused by a blown/clogged diffuser
II II II II II II II II
c. normal operation
II II
d. reason to believe the air filter in the blower is clogged - b. unequal air distribution
II II II II II II II II II II II II II II II II II II
caused by a blown diffuser
II II II II II
II What is suction lift? II II II
a. a team approach to lifting heavy objects
II II II II II II II
b. the pressure on the suction side of the pump
II II II II II II II II II
c. the measurement of liquid pressure at the pump
II II II II II II II II
d. the measure of how bad your workers lift heavy objects - b. the pressure on the suction
II II II II II II II II II II II II II II II II II II II
side of the pump
II II II II
The primary effluent to a RBC system is 350 mg/L BOD. The primary unit removes 83%
II II II II II II II II II II II II II II II II
the secondary unit removes 50% and the final unit removes 25%. What is the BOD
II II II II II II II II II II II II II II II
leaving the final unit of the RBC train?
II II II II II II II II
A. 290 mg/LII II
b. 60 mg/L
II II
c. 30 mg/L
II II
d. 22.5 mg/L - d. 22.5 mg/L
II II II II II II II II
The influent to the treatment plant is septic. it is determined that it is coming from a lift
II II II II II II II II II II II II II II II II II II
station upstream from the plant. What should the operator do?
II II II II II II II II II II
A. decrease the lag time for pump operation by moving the floats closer together
II II II II II II II II II II II II II
b. add pH adjuster to the influent flow
II II II II II II II
c. install larger capacity pumps in the lift stations
II II II II II II II II
d. the her nothing you can do to correct this problem - A. decrease the lag time for pump
II II II II II II II II II II II II II II II II II II II II
operation by moving the floats closer together
II II II II II II II
II What is the purpose of amber storage bottles?
II II II II II II II
A. the color is pretty
II II II II
b. they are cheaper
II II II
c. to protect chemicals that are sensitive to light
II II II II II II II II
d. so you can not see what is inside the container - c. to protect chemicals that are
II II II II II II II II II II II II II II II II II II II
sensitive to light
II II II
Calculate SRT
II II
Given: MLSS = 2400 mg/L II II II II
Aeration basin volume = 35,000 gallons = 0.0350 MG II II II II II II II II
WAS concentration = 3500 mg/L II II II II
WAS flow rate = 0.001 MGD II II II II II
Exam Questions and answers | Updated
2024/25 RATED A+
What is the predominant organism in a healthy activated sludge treatment plant?
II II II II II II II II II II II
A. Stalked ciliates
II II
B. rotifers II
C. nematodes II
D. amoebas - A. Stalked Ciliates
II II II II II II II
II A composite sample must be?
II II II II
A. sporadically collected in the treatment plant
II II II II II II
B. taken at one time
II II II II
C. analyzed immediately
II II
D. representative and sub-samples time spaced over 15 minutes apart - D.
II II II II II II II II II II II II II
representative and sub-samples time spaced over 15 minutes apart
II II II II II II II II II
II What is the standard volume for a BOD sample bottle?
II II II II II II II II II
A. 150 mL II II
B. 200 mL II II
C. 300 mL II II
D. 500 mL - c. 300 mL
II II II II II II II II
II If you have a lime slurry feed line, what is the best valve to use?
II II II II II II II II II II II II II II
A. plug valve II II
B. butterfly valve
II II
C. RPZ dual check valve
II II II II
D. gate valve - A. plug valve
II II II II II II II II
5. If you notice a predominance of rotifers in your activated sludge sample while looking at
II II II II II II II II II II II II II II II II
it under a microscope, what does this indicate?
II II II II II II II II
A. healthy sludge
II II
B. young sludge II II
C. old sludge II II
D. middle age sludge - C. old sludge
II II II II II II II II II
Calculate the BOD using the given information:
II II II II II II II
Initial DO: 8.3 II II
,Final DO: 5.9 II II
Milliliters of sample used: 2 II II II II
a. 360 mg/L
II II
b. 210 mg/L
II II
c. 856 mg/L
II II
d. 36 mg/L - a. 360 mg/L
II II II II II II II II
If your activated sludge plant begins to nitrify, what conditions would you expect to
II II II II II II II II II II II II II II
decrease?
II
A. settling in clarifiers
II II II
B. chlorine demand
II II
C. BOD effluent
II II
D. TSS in effluent - a. settling in the clarifiers
II II II II II II II II II II II
II How do you calibrate a chemical feed pump?
II II II II II II II
A. by measuring the pump output
II II II II II
B. using the SWAG method
II II II II
C. jar testII II
D. with a microscope - A. by measuring the pump output
II II II II II II II II II II II II
II What is the chemical formula for sulfuric acid?
II II II II II II II
a. HNO3
II
b. HClII
c. NaOH
II
d. H2SO4 - d. H2SO4
II II II II II II
II What is the most common type of activated sludge package plants?
II II II II II II II II II II
a. extended aeration
II II
b. sequential batch reactor
II II II
c. oxidation ditch
II II
d. bardenpho - a. extended aeration
II II II II II II II
II What is the most appropriate method of reducing the F:M ratio?
II II II II II II II II II II
A. increase wasting
II II
b. decrease wasting
II II
c. reduce BOD from influent flow
II II II II II
D. add polymer to RAS to increase settling - b. decrease wasting
II II II II II II II II II II II II II
An operator notices a portion of the aeration tank with large bubbles rising up. What is the
II II II II II II II II II II II II II II II II II
most likely problem?
II II II
, a. equal air distribution
II II II
b. unequal air distribution caused by a blown/clogged diffuser
II II II II II II II II
c. normal operation
II II
d. reason to believe the air filter in the blower is clogged - b. unequal air distribution
II II II II II II II II II II II II II II II II II II
caused by a blown diffuser
II II II II II
II What is suction lift? II II II
a. a team approach to lifting heavy objects
II II II II II II II
b. the pressure on the suction side of the pump
II II II II II II II II II
c. the measurement of liquid pressure at the pump
II II II II II II II II
d. the measure of how bad your workers lift heavy objects - b. the pressure on the suction
II II II II II II II II II II II II II II II II II II II
side of the pump
II II II II
The primary effluent to a RBC system is 350 mg/L BOD. The primary unit removes 83%
II II II II II II II II II II II II II II II II
the secondary unit removes 50% and the final unit removes 25%. What is the BOD
II II II II II II II II II II II II II II II
leaving the final unit of the RBC train?
II II II II II II II II
A. 290 mg/LII II
b. 60 mg/L
II II
c. 30 mg/L
II II
d. 22.5 mg/L - d. 22.5 mg/L
II II II II II II II II
The influent to the treatment plant is septic. it is determined that it is coming from a lift
II II II II II II II II II II II II II II II II II II
station upstream from the plant. What should the operator do?
II II II II II II II II II II
A. decrease the lag time for pump operation by moving the floats closer together
II II II II II II II II II II II II II
b. add pH adjuster to the influent flow
II II II II II II II
c. install larger capacity pumps in the lift stations
II II II II II II II II
d. the her nothing you can do to correct this problem - A. decrease the lag time for pump
II II II II II II II II II II II II II II II II II II II II
operation by moving the floats closer together
II II II II II II II
II What is the purpose of amber storage bottles?
II II II II II II II
A. the color is pretty
II II II II
b. they are cheaper
II II II
c. to protect chemicals that are sensitive to light
II II II II II II II II
d. so you can not see what is inside the container - c. to protect chemicals that are
II II II II II II II II II II II II II II II II II II II
sensitive to light
II II II
Calculate SRT
II II
Given: MLSS = 2400 mg/L II II II II
Aeration basin volume = 35,000 gallons = 0.0350 MG II II II II II II II II
WAS concentration = 3500 mg/L II II II II
WAS flow rate = 0.001 MGD II II II II II
