WASTEWATER B EXAM QUESTIONS
AND ANSWERS 2026
A poly solution for a jar test needs a concentration of 10,000 mg/L. The undiluted
polymer that will be used in the process contains 40% poly by weight and has a specific
gravity of 1.04. How much undiluted poly is needed to make the poly solution? Assume
the stock solution will be made in a 1 L flask. - ANSWERS10,000 mg/L poly solution =
1% poly solution
C₁V₁ = C₂V₂
(40%)V₁ = (1%)(1L)
V₁ = 0.025L = 25 mL
Poly feed rate equation - ANSWERSPoly feed rate = Poly Dosage x Sludge Feed Rate
x 8.34
Determine the poly feed rate in lbs/d if a poly dose of 150 mg/L yields best results, the
sludge contains 4.6% solids, and the sludge flow rate is 111 gpm - ANSWERS111
gal/min * 3.785 L/gal * 1 min/s = 7 L/s
Poly feed rate = Poly dose x Sludge feed rate
Poly feed rate = 150 mg/L * 7 L/s = 1,050 mg/s
Poly feed rate = 1050 mg/s * 1 kg/10⁶ mg * 2.204 lb/kg * 60 s/min * 60 min/hr * 24 hr/d
Poly feed rate = 200 lb/d
What is the typical residential water use?
What is the typical residential BOD loading? - ANSWERSWater use: 100
gal/day/person
Loading: 0.20 lbs BOD/day/person
Describe the BOD test procedure - ANSWERS1. Collect a wastewater sample. Add a
few mL's of nutrient rich, pH buffered water to 300 mL BOD bottle. Fill rest of bottle with
wastewater.
2. Measure initial DO
3. Incubate sample for 5 days at 20⁰C
4. Measure final DO
5. BOD = (D₀-D₅)/V
D₀ - initial DO
,D₅ - DO after 5 days
V - volumetric fraction of wastewater
What is the purpose of preliminary treatment - ANSWERSremove large debris and grit
to protect downstream equipment
True/false: Fluffy white foam indicates low aerator solids concentration, while leathery
brown foam indicates high solids concentration. - ANSWERSTrue
True/false: When an anaerobic digester is becoming upset, the first sign will be
increased alkalinity and decreased volatile acid concentration - ANSWERSFalse
What is the alpha factor? - ANSWERSThe alpha factor is the mathematical value for the
reduction in oxygen transfer rate caused by impurities in the water
α = 1 means pure H₂O
α<1 means impurities in water reducing transfer efficiency
True/false: When chlorine is used before disinfection for odor control, it is not necessary
to satisfy a chlorine demand - ANSWERSFalse
True/false: Biological secondary treatment processes should remove at least 85% of the
influent BOD - ANSWERSTrue
True/false: Short detention times are normal for package plants - ANSWERSFalse
True/false: An activated sludge plant with an MCRT of over 10-days is normally
considered an extended aeration plant - ANSWERSTrue
True/false: Wasting of activated sludge on a continuous basis is the preferred method -
ANSWERSTrue
True/false: SVI is used as an indicator for clarifier stability - ANSWERSTrue
True/false: The standard BOD test measures the amount of dissolved oxygen
consumed by bacteria as they utilize waste for food during a 8 day period at 15 degrees
Celsius. - ANSWERSFalse
True/false: Any sample can be "fixed" for later testing - ANSWERSFalse
True/false: When operating an aerobic digester be sure to keep the feed sludge volatile
solid concentration high or else the percent reduction will decrease - ANSWERSFalse
True/false: Dissolved oxygen in an aeration tank should be at a minimum of 1 ppm for
biological nitrification - ANSWERSTrue
, True/false: Chlorine is lighter than air and will collect on the ceiling if a leak occurs -
ANSWERSFalse
True/false: A complete-mix activated sludge basin is normally square - ANSWERSTrue
True/false: Blanks are used in the BOD test to calculate dilution water DO uptake -
ANSWERSTrue
True/false: Flexible piping sometimes called a pigtail should connect a chlorine
container to stationary piping - ANSWERSTrue
True/false: Carbon dioxide will lower the pH of water - ANSWERSTrue
True/false: When chlorine gas combines with moisture in the air it forms hydrochloric
gas - ANSWERSTrue
True/false: A high hydrogen sulfide gas concentration is required before your sense of
smell will be dulled - ANSWERSFalse
True/false: Alkalinity is the key control for an activated sludge basin - ANSWERSFalse
True/false: 30 days is a typical detention time for anaerobic digestion - ANSWERSTrue
The first sign that an anaerobic digester is becoming sour is normally
A. a pH change.
B. a decrease in gas production.
C. a change in the volatile acid/alkalinity relationship.
D. an increase in the amount of hydrogen sulfide gas.
E. a temperature change. - ANSWERSC
Potential problems of ammonia in wastewater
A. ammonia toxicity to fish.
B. DO depletion in the receiving waters.
C. Increase algae growth.
D. Blue baby syndrome.
E. All the above - ANSWERSE
Wastewater is running full in a 6 inch gravity pipe. What is the change in velocity when
the pipe size is increased to 12 inches, if the flow remains constant?
A. 1/4 as much
B. Twice as much
C. four times as much
D. half as much
AND ANSWERS 2026
A poly solution for a jar test needs a concentration of 10,000 mg/L. The undiluted
polymer that will be used in the process contains 40% poly by weight and has a specific
gravity of 1.04. How much undiluted poly is needed to make the poly solution? Assume
the stock solution will be made in a 1 L flask. - ANSWERS10,000 mg/L poly solution =
1% poly solution
C₁V₁ = C₂V₂
(40%)V₁ = (1%)(1L)
V₁ = 0.025L = 25 mL
Poly feed rate equation - ANSWERSPoly feed rate = Poly Dosage x Sludge Feed Rate
x 8.34
Determine the poly feed rate in lbs/d if a poly dose of 150 mg/L yields best results, the
sludge contains 4.6% solids, and the sludge flow rate is 111 gpm - ANSWERS111
gal/min * 3.785 L/gal * 1 min/s = 7 L/s
Poly feed rate = Poly dose x Sludge feed rate
Poly feed rate = 150 mg/L * 7 L/s = 1,050 mg/s
Poly feed rate = 1050 mg/s * 1 kg/10⁶ mg * 2.204 lb/kg * 60 s/min * 60 min/hr * 24 hr/d
Poly feed rate = 200 lb/d
What is the typical residential water use?
What is the typical residential BOD loading? - ANSWERSWater use: 100
gal/day/person
Loading: 0.20 lbs BOD/day/person
Describe the BOD test procedure - ANSWERS1. Collect a wastewater sample. Add a
few mL's of nutrient rich, pH buffered water to 300 mL BOD bottle. Fill rest of bottle with
wastewater.
2. Measure initial DO
3. Incubate sample for 5 days at 20⁰C
4. Measure final DO
5. BOD = (D₀-D₅)/V
D₀ - initial DO
,D₅ - DO after 5 days
V - volumetric fraction of wastewater
What is the purpose of preliminary treatment - ANSWERSremove large debris and grit
to protect downstream equipment
True/false: Fluffy white foam indicates low aerator solids concentration, while leathery
brown foam indicates high solids concentration. - ANSWERSTrue
True/false: When an anaerobic digester is becoming upset, the first sign will be
increased alkalinity and decreased volatile acid concentration - ANSWERSFalse
What is the alpha factor? - ANSWERSThe alpha factor is the mathematical value for the
reduction in oxygen transfer rate caused by impurities in the water
α = 1 means pure H₂O
α<1 means impurities in water reducing transfer efficiency
True/false: When chlorine is used before disinfection for odor control, it is not necessary
to satisfy a chlorine demand - ANSWERSFalse
True/false: Biological secondary treatment processes should remove at least 85% of the
influent BOD - ANSWERSTrue
True/false: Short detention times are normal for package plants - ANSWERSFalse
True/false: An activated sludge plant with an MCRT of over 10-days is normally
considered an extended aeration plant - ANSWERSTrue
True/false: Wasting of activated sludge on a continuous basis is the preferred method -
ANSWERSTrue
True/false: SVI is used as an indicator for clarifier stability - ANSWERSTrue
True/false: The standard BOD test measures the amount of dissolved oxygen
consumed by bacteria as they utilize waste for food during a 8 day period at 15 degrees
Celsius. - ANSWERSFalse
True/false: Any sample can be "fixed" for later testing - ANSWERSFalse
True/false: When operating an aerobic digester be sure to keep the feed sludge volatile
solid concentration high or else the percent reduction will decrease - ANSWERSFalse
True/false: Dissolved oxygen in an aeration tank should be at a minimum of 1 ppm for
biological nitrification - ANSWERSTrue
, True/false: Chlorine is lighter than air and will collect on the ceiling if a leak occurs -
ANSWERSFalse
True/false: A complete-mix activated sludge basin is normally square - ANSWERSTrue
True/false: Blanks are used in the BOD test to calculate dilution water DO uptake -
ANSWERSTrue
True/false: Flexible piping sometimes called a pigtail should connect a chlorine
container to stationary piping - ANSWERSTrue
True/false: Carbon dioxide will lower the pH of water - ANSWERSTrue
True/false: When chlorine gas combines with moisture in the air it forms hydrochloric
gas - ANSWERSTrue
True/false: A high hydrogen sulfide gas concentration is required before your sense of
smell will be dulled - ANSWERSFalse
True/false: Alkalinity is the key control for an activated sludge basin - ANSWERSFalse
True/false: 30 days is a typical detention time for anaerobic digestion - ANSWERSTrue
The first sign that an anaerobic digester is becoming sour is normally
A. a pH change.
B. a decrease in gas production.
C. a change in the volatile acid/alkalinity relationship.
D. an increase in the amount of hydrogen sulfide gas.
E. a temperature change. - ANSWERSC
Potential problems of ammonia in wastewater
A. ammonia toxicity to fish.
B. DO depletion in the receiving waters.
C. Increase algae growth.
D. Blue baby syndrome.
E. All the above - ANSWERSE
Wastewater is running full in a 6 inch gravity pipe. What is the change in velocity when
the pipe size is increased to 12 inches, if the flow remains constant?
A. 1/4 as much
B. Twice as much
C. four times as much
D. half as much
