BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
What is the predominant organism in a healthy activated sludge treatment
plant?
A. Stalked ciliates
B. Rotifers
C. Nematodes
D. Amoebas - (ANSWERS)A. Stalked Ciliates
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 -
(ANSWERS)D. Representative and sub-samples time spaced over 15
minutes apart
What is the standard volume for a BOD sample bottle?
A. 150 ml
B. 200 ml
C. 300 ml
D. 500 ml - (ANSWERS)c. 300 ml
,BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
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 - (ANSWERS)A. Plug valve
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 - (ANSWERS)C. Old sludge
Calculate 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
,BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
D. 36 mg/L - (ANSWERS)a. 360 mg/L
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 - (ANSWERS)a. Settling in the clarifiers
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 - (ANSWERS)A. By measuring the pump output
What is the chemical formula for sulfuric acid?
A. HNO3
B. Hcl
C. Naoh
D. H2SO4 - (ANSWERS)d. H2SO4
, BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
What is the most common type of activated sludge package plants?
A. Extended aeration
B. Sequential batch reactor
C. Oxidation ditch
D. Bardenpho - (ANSWERS)a. Extended aeration
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 - (ANSWERS)b. Decrease
wasting
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 - (ANSWERS)b.
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
What is the predominant organism in a healthy activated sludge treatment
plant?
A. Stalked ciliates
B. Rotifers
C. Nematodes
D. Amoebas - (ANSWERS)A. Stalked Ciliates
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 -
(ANSWERS)D. Representative and sub-samples time spaced over 15
minutes apart
What is the standard volume for a BOD sample bottle?
A. 150 ml
B. 200 ml
C. 300 ml
D. 500 ml - (ANSWERS)c. 300 ml
,BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
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 - (ANSWERS)A. Plug valve
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 - (ANSWERS)C. Old sludge
Calculate 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
,BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
D. 36 mg/L - (ANSWERS)a. 360 mg/L
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 - (ANSWERS)a. Settling in the clarifiers
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 - (ANSWERS)A. By measuring the pump output
What is the chemical formula for sulfuric acid?
A. HNO3
B. Hcl
C. Naoh
D. H2SO4 - (ANSWERS)d. H2SO4
, BASIC WASTEWATER OPERATOR PRACTICE EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) (LATEST UPDATE 2026)
UPDATE!!
What is the most common type of activated sludge package plants?
A. Extended aeration
B. Sequential batch reactor
C. Oxidation ditch
D. Bardenpho - (ANSWERS)a. Extended aeration
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 - (ANSWERS)b. Decrease
wasting
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 - (ANSWERS)b.
