Texas Wastewater A Exam Questions
With verified Answers
A primary clarifier has a flow of 3.0 MGD and has a diameter of 100 feet. It is 12 feet
deep and has 24 inches of freeboard. What is the detention time in hours? - CORRECT
ANSWER-4.7 hrs
Anaerobic digester gas should contain? - CORRECT ANSWER-65-75% methane, 25-
35% carbon dioxide and 1-5% nitrogen.
An activated sludge plant has an average daily flow of 3.5 MG. The aeration tank
capacity is 1.2 MG with a MLSS concentration of 3200 mg/L. The clarifier has a capacity
of 400,000 gallons with a MLSS concentration of 6,000 mg/L. The wasting rate is
40,000 gallons per day with a MLSS concentration of 8, 000 mg/L. The effluent TSS is
18 mg/L. Assuming volatile concentrations of 70%, what is the MCRT and what type of
activated sludge plant should this be? - CORRECT ANSWER-16.29 Days
What are some of the causes of filaments in the aeration basin? - CORRECT
ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
When an RBC is operating correctly, how will the slime appear on the media? -
CORRECT ANSWER-Grey to brown 0.05 to 0.1 inches thick
What activated sludge process does not achieve complete nitrification? - CORRECT
ANSWER-Contact Stabilization
, In the selection of forced main wastewater piping, what is the minimum working
pressure? - CORRECT ANSWER-150 psi
The oxygen depletion of BOD dilution water should not exceed - CORRECT ANSWER-
0.2 mg/L.
What is the minimum air gap when making water and wastewater connections? -
CORRECT ANSWER-Minimum of one inch or twice the inlet pipe size whichever is
greater.
An anaerobic digester must maintain an average year round temperature of -
CORRECT ANSWER-95 degrees F.
Which of the following methods would you use to increase the degree of nitrification in
an activated sludge plant? - CORRECT ANSWER-increase dissolved oxygen levels and
increase the sludge age
Which of the following are considered normal operator controls on an activated sludge
plant? - CORRECT ANSWER-*aeration rates *return and wasting rates
Reducing the return sludge flow rate for an activated sludge system which has a good
settling sludge will ________. - CORRECT ANSWER-increase the sludge retention time
(SRT) and potentially increase the mixed liquor suspended solids (MLSS) concentration
in the aeration tank.
This can lead to a thicker sludge blanket in the clarifier, but it might also increase the
risk of sludge bulking if the solids concentration becomes too high.
An extended air activated sludge plant has a fast settling sludge and high amounts of
pin floc leaving the clarifier. One way to correct this problem is to ________. -
With verified Answers
A primary clarifier has a flow of 3.0 MGD and has a diameter of 100 feet. It is 12 feet
deep and has 24 inches of freeboard. What is the detention time in hours? - CORRECT
ANSWER-4.7 hrs
Anaerobic digester gas should contain? - CORRECT ANSWER-65-75% methane, 25-
35% carbon dioxide and 1-5% nitrogen.
An activated sludge plant has an average daily flow of 3.5 MG. The aeration tank
capacity is 1.2 MG with a MLSS concentration of 3200 mg/L. The clarifier has a capacity
of 400,000 gallons with a MLSS concentration of 6,000 mg/L. The wasting rate is
40,000 gallons per day with a MLSS concentration of 8, 000 mg/L. The effluent TSS is
18 mg/L. Assuming volatile concentrations of 70%, what is the MCRT and what type of
activated sludge plant should this be? - CORRECT ANSWER-16.29 Days
What are some of the causes of filaments in the aeration basin? - CORRECT
ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
When an RBC is operating correctly, how will the slime appear on the media? -
CORRECT ANSWER-Grey to brown 0.05 to 0.1 inches thick
What activated sludge process does not achieve complete nitrification? - CORRECT
ANSWER-Contact Stabilization
, In the selection of forced main wastewater piping, what is the minimum working
pressure? - CORRECT ANSWER-150 psi
The oxygen depletion of BOD dilution water should not exceed - CORRECT ANSWER-
0.2 mg/L.
What is the minimum air gap when making water and wastewater connections? -
CORRECT ANSWER-Minimum of one inch or twice the inlet pipe size whichever is
greater.
An anaerobic digester must maintain an average year round temperature of -
CORRECT ANSWER-95 degrees F.
Which of the following methods would you use to increase the degree of nitrification in
an activated sludge plant? - CORRECT ANSWER-increase dissolved oxygen levels and
increase the sludge age
Which of the following are considered normal operator controls on an activated sludge
plant? - CORRECT ANSWER-*aeration rates *return and wasting rates
Reducing the return sludge flow rate for an activated sludge system which has a good
settling sludge will ________. - CORRECT ANSWER-increase the sludge retention time
(SRT) and potentially increase the mixed liquor suspended solids (MLSS) concentration
in the aeration tank.
This can lead to a thicker sludge blanket in the clarifier, but it might also increase the
risk of sludge bulking if the solids concentration becomes too high.
An extended air activated sludge plant has a fast settling sludge and high amounts of
pin floc leaving the clarifier. One way to correct this problem is to ________. -
