Texas Wastewater A UPDATED ACTUAL
Exam Questions and CORRECT Answers
Describe proper design of force main wastewater lines. - CORRECT ANSWER Minimum
two fps velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
Describe proper design of gravity wastewater lines. - CORRECT ANSWER Designed to
flow half full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
What is the effective chlorine disinfecting agent? - CORRECT ANSWER Hypochlorous
Acid (HOCl)
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet
inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep.
a. What is the detention time in hours? - CORRECT ANSWER 5.08. hrs
What activated process cannot nitrify in a single stage? - CORRECT ANSWER Contact
Stabilization
What is the GPM output of a piston pump with an 8-inch diameter piston with a 10-inch stroke
operating at 50 strokes per minute? - CORRECT ANSWER 108.8 gpm
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet
inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep.
What is the surface loading in gal/ft2/day?
What is the weir loading in gal linear ft/day? - CORRECT ANSWER 353.68 gallons &
5684.11
, 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.
Exam Questions and CORRECT Answers
Describe proper design of force main wastewater lines. - CORRECT ANSWER Minimum
two fps velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
Describe proper design of gravity wastewater lines. - CORRECT ANSWER Designed to
flow half full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
What is the effective chlorine disinfecting agent? - CORRECT ANSWER Hypochlorous
Acid (HOCl)
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet
inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep.
a. What is the detention time in hours? - CORRECT ANSWER 5.08. hrs
What activated process cannot nitrify in a single stage? - CORRECT ANSWER Contact
Stabilization
What is the GPM output of a piston pump with an 8-inch diameter piston with a 10-inch stroke
operating at 50 strokes per minute? - CORRECT ANSWER 108.8 gpm
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir is 2 feet
inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow channel is 3 feet deep.
What is the surface loading in gal/ft2/day?
What is the weir loading in gal linear ft/day? - CORRECT ANSWER 353.68 gallons &
5684.11
, 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.
