TEXAS WASTEWATER A QUESTIONS
AND ANSWERS (GRADED A+)
What is TCEQ doing to control "point source" pollution of the Texas waterways? -
ANSWER-*Permitting of domestic wastewater plants
*Permitting of industrial wastewater plants
Describe proper design of force main wastewater lines. - ANSWER-Minimum two fps
velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
What is Standard Dimension Ratio? - ANSWER-Ratio of outside pipe diameter (OD) to
wall thickness (PVC)
Describe proper design of gravity wastewater lines. - ANSWER-Designed to flow half
full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
Manholes should have a minimum opening of? - ANSWER-24 inches and be at least 4
feet wide.
pH meters should be calibrated how often? What standards should be used for
calibration purposes? - ANSWER-Daily with at least two buffers.
What is the standard chlorine residual and minimum contact time on Texas wastewater
permits? - ANSWER-a. 1.0 mg/L for a minimum 20 minutes detention time at peak flow
b. No chlorine residual needed if detention time is greater than 21 days
As the complexity of an organization increases, what management function becomes
most important? - ANSWER-Planning
What is the effective chlorine disinfecting agent? - ANSWER-Hypochlorous Acid (HOCl)
Does pH affect the chlorination process? Explain your answer. - ANSWER-When using
free chlorine the disinfectant is HOCl acid. As such it is much more effective at pH's
below 7.0. Above 7.0 pH the acid begins to be neutralized.
What is the effluent chlorine residual in Texas that is standard on permits and the
minimum detention time? What is the maximum residual allowed? - ANSWER-Texas
standard is 1.0 mg/L for a minimum 20 minutes detention time at peak flow. Maximum
residual allowed is 4.0 mg/L.
, 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? - ANSWER-Formula
What activated process cannot nitrify in a single stage? - 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? - ANSWER-Formula
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?
b. What is the surface loading in gal/ft2/day?
c. What is the weir loading in gal/linear ft/day? - ANSWER-Formulas
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? - ANSWER-
Formulas
Anaerobic digester gas should contain? - 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? - ANSWER-Formulas MCRT
What are some of the causes of filaments in the aeration basin? - ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
Good sludge quality will have a predominance of what organisms in the MLSS? -
ANSWER-Ciliated protozoa
When an RBC is operating correctly, how will the slime appear on the media? -
ANSWER-Grey to brown 0.05 to 0.1 inches thick
According to design criteria, what are the minimum allowable diameters for a manhole?
- ANSWER-24 inch opening and 48 inch inside diameter
AND ANSWERS (GRADED A+)
What is TCEQ doing to control "point source" pollution of the Texas waterways? -
ANSWER-*Permitting of domestic wastewater plants
*Permitting of industrial wastewater plants
Describe proper design of force main wastewater lines. - ANSWER-Minimum two fps
velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
What is Standard Dimension Ratio? - ANSWER-Ratio of outside pipe diameter (OD) to
wall thickness (PVC)
Describe proper design of gravity wastewater lines. - ANSWER-Designed to flow half
full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
Manholes should have a minimum opening of? - ANSWER-24 inches and be at least 4
feet wide.
pH meters should be calibrated how often? What standards should be used for
calibration purposes? - ANSWER-Daily with at least two buffers.
What is the standard chlorine residual and minimum contact time on Texas wastewater
permits? - ANSWER-a. 1.0 mg/L for a minimum 20 minutes detention time at peak flow
b. No chlorine residual needed if detention time is greater than 21 days
As the complexity of an organization increases, what management function becomes
most important? - ANSWER-Planning
What is the effective chlorine disinfecting agent? - ANSWER-Hypochlorous Acid (HOCl)
Does pH affect the chlorination process? Explain your answer. - ANSWER-When using
free chlorine the disinfectant is HOCl acid. As such it is much more effective at pH's
below 7.0. Above 7.0 pH the acid begins to be neutralized.
What is the effluent chlorine residual in Texas that is standard on permits and the
minimum detention time? What is the maximum residual allowed? - ANSWER-Texas
standard is 1.0 mg/L for a minimum 20 minutes detention time at peak flow. Maximum
residual allowed is 4.0 mg/L.
, 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? - ANSWER-Formula
What activated process cannot nitrify in a single stage? - 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? - ANSWER-Formula
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?
b. What is the surface loading in gal/ft2/day?
c. What is the weir loading in gal/linear ft/day? - ANSWER-Formulas
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? - ANSWER-
Formulas
Anaerobic digester gas should contain? - 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? - ANSWER-Formulas MCRT
What are some of the causes of filaments in the aeration basin? - ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
Good sludge quality will have a predominance of what organisms in the MLSS? -
ANSWER-Ciliated protozoa
When an RBC is operating correctly, how will the slime appear on the media? -
ANSWER-Grey to brown 0.05 to 0.1 inches thick
According to design criteria, what are the minimum allowable diameters for a manhole?
- ANSWER-24 inch opening and 48 inch inside diameter
