1. What is the normal detention time in the conventional activated sludge aeration tank?
a. 2 to 4 hours
b. 4 to 8 hours
c. 18 to 30 hours
2. An SVI below 75 usually indicates _.
a. young sludge
b. old sludge
c. normal conditions
3. Which of the following is not used to control the RAS rate?
a. SVI approach
b. F/M ratio
c. Settleability approach
d. Monitoring the depth of the sludge blanket
4. Denitrification in the secondary clarifier in an activated sludge system indicates _.
a. sludge withdrawal rate too fast
b. sludge withdrawal rate too slow
c. the clarifier is working properly
5. A flow proportional sample is _.
a. sampled at equal volumes
b. composited according to flow
c. a grab sample