Wastewater Exam Class C Comprehensive Questions & Verified
Detailed Answers (MULTIPLE CHOICES)
1. Which of the following flow rates should be measured if the operator is to control plant
properly?
A. Aeration rate or resulting dissolved oxygen level.
B. Influent or effluent.
C. return sludge
D. waste sludge
E. all the above - ANS ✔ - E. all the above
2. During start up your aeration tank produces excessive amounts of billowing white foam. This can
be corrected by:
A. Doing nothing, it will go away in a few hours
B. Increasing the sludge wasting rate
C. Seeding the process with sufficient good quality sludge
D. Spraying water on the foam until it is gone
E. Taking a weeks vacation - ANS ✔ - C. Seeding the process with sufficient good quality
sludge
3. In solving an operational problem at a treatment plant:
A. there is almost always a good technical solution. It may require considerable experience
and time to learn what it is.
B. Human errors have to be corrected since the operator is at fault.
C. don't let the laboratory personnel influence you're judgement as to what the best
solution is.
D. standard textbooks in sanitary engineering are the best source of information.
E. It is best to do nothing until the TNRCCC sends a violation notice. - ANS ✔ - A. there is
almost always a good technical solution. It may require considerable experience and
time to learn whaat it is.
4. When the return sludge rate is too low, what happens?
A. the aeration tank will not fill
B. There will be insufficient organisms to treat the wast load entering the aeration basin
C. the activated sludge in the aerator will starve.
D. the sludge blanket in the secondary clarifier could become too high.
E. B and D - ANS ✔ - E. B and D
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, 5. The Activated Sludge Process:
A. requires pre-aeration
B. requires Activated Carbon
C. is an aerobic biological process.
D. Usually precedes primary sedimentation.
E. Requires 50% by volume old sludge to work effectively. - ANS ✔ - C. Is an Aerobic
biological process
6. A complete mix 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 :
A. Increase the RAS Flow
B. Reduce Wasting Rates
C. Increase dissolved oxygen levels.
D. Increase the F/M ratio by wasting more
E. Increase the sludge age by wasting less. - ANS ✔ - D. Increase the F/M Ratio by Wasting
More
7. What factors affect how well the mixed liquor suspended solids settle in the final clarifier?
A. flow velocity and or turbulence
B. temperature
C. quality of the mixed liquor solids
D. Short circuiting
E. All of the above - ANS ✔ - E. All of the above
8. The Active sludge process parameters which n operator can change directly are:
A. aeration rates.
B. waste rates.
C. the ratio of free swimming to stalked ciliates.
D. Return sludge rates.
E. All the above except C. - ANS ✔ - E. All the above except C.
9. Which of the following would you use to increase the degree of nitrification in an activated
sludge plant?
A. increase the waste rates
B. increase dissolved oxygen levels and increase the sludge age
C. Remove excess alkalinity from the wastewater
D. Maintain a thicker sludge blanket n the clarifier
E. Inhibit the growth of the nitrifying bacteria with chemicals. - ANS ✔ - B. increase
dissolved oxygen levels and increase the sludge age
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Detailed Answers (MULTIPLE CHOICES)
1. Which of the following flow rates should be measured if the operator is to control plant
properly?
A. Aeration rate or resulting dissolved oxygen level.
B. Influent or effluent.
C. return sludge
D. waste sludge
E. all the above - ANS ✔ - E. all the above
2. During start up your aeration tank produces excessive amounts of billowing white foam. This can
be corrected by:
A. Doing nothing, it will go away in a few hours
B. Increasing the sludge wasting rate
C. Seeding the process with sufficient good quality sludge
D. Spraying water on the foam until it is gone
E. Taking a weeks vacation - ANS ✔ - C. Seeding the process with sufficient good quality
sludge
3. In solving an operational problem at a treatment plant:
A. there is almost always a good technical solution. It may require considerable experience
and time to learn what it is.
B. Human errors have to be corrected since the operator is at fault.
C. don't let the laboratory personnel influence you're judgement as to what the best
solution is.
D. standard textbooks in sanitary engineering are the best source of information.
E. It is best to do nothing until the TNRCCC sends a violation notice. - ANS ✔ - A. there is
almost always a good technical solution. It may require considerable experience and
time to learn whaat it is.
4. When the return sludge rate is too low, what happens?
A. the aeration tank will not fill
B. There will be insufficient organisms to treat the wast load entering the aeration basin
C. the activated sludge in the aerator will starve.
D. the sludge blanket in the secondary clarifier could become too high.
E. B and D - ANS ✔ - E. B and D
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, 5. The Activated Sludge Process:
A. requires pre-aeration
B. requires Activated Carbon
C. is an aerobic biological process.
D. Usually precedes primary sedimentation.
E. Requires 50% by volume old sludge to work effectively. - ANS ✔ - C. Is an Aerobic
biological process
6. A complete mix 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 :
A. Increase the RAS Flow
B. Reduce Wasting Rates
C. Increase dissolved oxygen levels.
D. Increase the F/M ratio by wasting more
E. Increase the sludge age by wasting less. - ANS ✔ - D. Increase the F/M Ratio by Wasting
More
7. What factors affect how well the mixed liquor suspended solids settle in the final clarifier?
A. flow velocity and or turbulence
B. temperature
C. quality of the mixed liquor solids
D. Short circuiting
E. All of the above - ANS ✔ - E. All of the above
8. The Active sludge process parameters which n operator can change directly are:
A. aeration rates.
B. waste rates.
C. the ratio of free swimming to stalked ciliates.
D. Return sludge rates.
E. All the above except C. - ANS ✔ - E. All the above except C.
9. Which of the following would you use to increase the degree of nitrification in an activated
sludge plant?
A. increase the waste rates
B. increase dissolved oxygen levels and increase the sludge age
C. Remove excess alkalinity from the wastewater
D. Maintain a thicker sludge blanket n the clarifier
E. Inhibit the growth of the nitrifying bacteria with chemicals. - ANS ✔ - B. increase
dissolved oxygen levels and increase the sludge age
2|Page
