TEXAS WASTEWATER CLASS C EXAM
2025 LATEST ACTUAL EXAM AND
PRACTICE EXAM QUESTIONS AND
DETAILED CORRECT ANSWERS| A+
GRADE STUDYGUIDE
When operating an activated sludge plant, Which TSS
concentration is most important for process control?
A. Primary effluent
B. Aeration tank mixed liquor.
C. Return Sludge
D. Digester.
E. Plant influent Correct Answer B. Aeration tank mixed
liquor.
How many aeration tanks does a contact stabilization
plant have?
A. one, like all the others
B. Four: contact, mix, reaeration and stabilization
C. Two if you count the digester as an aeration tank
D. a contact tank and a reaeration tank
E. none of this makes any sense to me. Correct Answer D.
a contact tank and a reaeration tank
Reducing the return sludge flow rate for an activated
sludge system which has a good settling sludge will.
,A. Decrease the hydraulic detention time in the aeration
basin
B. Increase the solids concentration in the aeration basin
C. cause the return sludge concentration to decrease
D. have no effect on process performance.
E. increase the RAS concentration ad the clarifier blanket
thickness. Correct Answer E. increase the RAS
concentration ad the clarifier blanket thickness.
What items would you check if an activated sludge plant
becomes upset?
A. Influent temperature.
B. Monthly average flow rates
C. BOD loadings MLSS sludge settle-ability D.O. and
oxygen uptake rate
D. digester operation. E. Chlorinator settings. Correct
Answer C. BOD loadings MLSS sludge settle-ability D.O.
and oxygen uptake rate
Causes of sludge bulking include:
A. Low DO and presence of sulfides
B. Air supply too low
C. organic loading rate too high
D. nutrient imbalance.
E. All the above can cause bulking. Correct Answer E. All
the above can cause bulking.
,Industrial waste materials which are usually not
compatible with municipal treatment plants include:
A. chemical oxygen demand
B. Heavy metals.
C. petroleum fats , oils and greases
D. nitrogen and phosphorus compounds.
E. B and C Correct Answer B. Heavy metals.
Sludge is observed to accumulate in the final clarifier. This
may be caused by :
A. plugged sludge collectors return pumps or waste
pumps
B. too high a return rate.
C. excessive solids wasting.
D. hydraulically overloaded clarifier
E. All of the above. Correct Answer A. plugged sludge
collectors return pumps or waste pumps
What is the relationship between the F/M ratio and the
MCRT sludge age for a particular plant when the aerator
detention time is a constant value.
A. these to control parameters are unrelated.
B. When one increases the other increases.
C. When one increases the other decreases.
D. it is a direct relationship
E. The F/M ratio is one tenth of the MCRT (Sludge Age)
Correct Answer C. When one increases the other
decreases.
, Using results only from the settle-ability test and MLSS
test of activated sludge solids the operator will be able to
A. calculate the F/M ratio
B. Set the doge for chlorinating the return activated sludge
C. Calculate the MCRT
D. Calculate the SVI
E. A and C Correct Answer D. Calculate the SVI
Which of the following F/M ratios would be in the proper
rage for a contact stabilization activated sludge plant?
A. 0.08
B. 0.12
C. 0.30
D. 0.75
E. 1.25 Correct Answer C. 0.30
Short circuiting in a final sedimentation process:
A. is probably caused by mechanical failures.
B. usually represents a hydraulic deficiency of design or
operation
C. Increases efficiency by facilitating rapid movement of
treatment plant effluent
D. has no effect on plant performance.
E. All of the above. Correct Answer B. usually represents
a hydraulic deficiency of design or operation
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