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(civl242)[2008](f)midterm~wmma^_10063.pdf
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Preparation for the mid-term
exam
16 October 2008

Mock Questions


MC Problem

1.Sludge age is defined as ( ).


a) amount of biomass in a secondary clarifier divided by the sludge wasting rate
b) amount of biomass in aeration tank divided by the sludge escaping rate through effluent;
c) amount of biomass in aeration tank divided by the sludge wasting rate
d) hydraulic retention time in the aeration tank.
e) none of the above.
Answer: C


2. Determination of oxygen requirement for a specific aeration tank of activated sludge (AS) process is based on ( ):
a) BOD loading rate
b) Required DO level in the aeration tank
c) Oxidation rate of organic matter
d) Oxidation rate of organic matter and endogenous respiration rate of sludge
e) None of the above.
Answer: d


3. Which statement is true?
a) A well-mixing aeration tank is in favor of both BOD and ammonia oxidation.
b) A mechanical aerator generally provides less mixing in aeration tank than a bubble diffusion aerator does.
c) A conventional plug-flow AS has higher oxygen utilization efficiency as compared to a step-aeration AS.
d) An AS system has a lower sludge wastage than a submerged bio-filter.
e) None of the above.
Answer: E


4. In addition to SS, COD, BOD, there are other two typical parameters used to characterize municipal sewage quality. They are ( ):
a) DO and pH
b) TOC and S-COD
c) VSS and nitrate
d) TKN and TOP
e) TKN and Ammonia
Answer: E


5.A wastewater treatment process is a system combining the following relevant treatment unit:
1) Liquid/particle separation
2) Biological conversion
3) Soil treatment
4) Bacteria removing processes
a) (1)+(2)+(3);
b) (2)+(3)+(4);
c) (1)+(2)+(4);
d) (1)+(3)+(4);
e) None of the above
Answer: C


6. F/M ratio can be estimated from ( ):
a) Excess sludge withdrawal
b) Sewage retention time in aeration tank
c) Sludge BOD loading rate
d) Reactor volume and MLSS
Answer: C


7. Zero-order substrate removal rate indicates that ( ):
a) Substrate utilization rate is dependent on substrate concentration
b) Substrate utilization rate is zero
c) Substrate is not a limiting factor for the biomass growth.
d) Microbes are not growing
e) None of the above.
Answer: C


8. Pick up the true description from below ( ):
a) A stationary phase of bacterial growth is caused by dead bacteria.
b) A stationary phase of bacterial growth is caused by biomass growth rate close to sludge decay rate
c) A stationary phase of bacterial growth is caused by too much substrates.
d) A stationary phase of bacterial growth is caused by large substrate removal rate.
Answer: B


9. A yield coefficient of biomass is defined as ( ):
a) Biomass growth per substrate oxidized
b) Biomass growth per substrate utilized
e) Biomass growth per oxygen consumed
d) Biomass growth per substrate converted
e) None of the above.
Answer: B


10. A high SVI is mainly attributable to:
a) low te