Statistics for Texas Waste Water Treatment Ch#08 Activated Sludge Process

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General Stats

This quiz has been taken 45 times
The average score is 22 of 30

Answer Stats

Question	Answer	% Correct
The purpose of return activated sludge is to reseed the biological reactor with treatment microorganisms.	True	100%
The reason for wasting solids from an activated sludge system is to remove excess biological solids, inert solids, and old or dead microorganisms.	True	100%
The return activated sludge flow is indicated by what letter?		92%
The clarifier is indicated by what letter?		92%
Temperature has no effect on the activity of microorganisms in the activated sludge process because wastewater is always warm.	False	92%
Oxygen levels, wasting rates, sludge quality, return rates, and aerator solids levels are important control parameters for activated sludge plants.	True	92%
Dissolved Oxygen(DO) levels in activated sludge plants should be kept at the 2–4 mg/L level with 1 mg/L minimum.	True	92%
Air requirements in an activated sludge process are governed by the organic loading on the plant.	True	92%
Which of the following are the activated sludge process parameters an operator can change directly?	Aeration, waste, AND return sludge rates	83%
Dissolved Oxygen(DO) should be kept at very high levels in the aeration tank.	False	83%
Sludge bulking in an activated sludge plant can be easily corrected.	False	83%
The clarifier should concentrate the mixed liquor solids at least two times.	True	83%
An airlift sludge return pump should be turned on each morning to return activated sludge to the aeration tank.	False	75%
Good activated sludge is gray and settles rapidly, leaving a clear supernatant.	False	75%
Rising sludge and gas bubbles can be caused by denitrification in the final clarifier.	True	75%
The 30-minute settling test gives the operator a visual check on sludge quality.	True	75%
In the extended aeration process, air blowers or aerators normally run continuously to provide the oxygen needed unless the plant is small and underloaded organically.	True	75%
Testing of mixed liquor indicates the MLSS is 2,000 mg/L, and the settling test shows that a 1,000 mL sample settles to 250 mL after 30 minutes. What is the SVI and sludge quality?	125 and good	67%
Which of the following causes sludge bulking?	All of the above	67%
A conventional activated sludge process has primary clarifiers that remove about l0%–20% of the organic load.	False	67%
Complete mix plants will not handle shock loads as well as other activated sludge modifications.	False	67%
During start-up, your aeration tank produces excessive amounts of billowing white foam. This can be corrected by ________.	seeding the process with sufficient good quality sludge	67%
Which of the following happens when the return sludge rate is too low?	There will be insufficient organisms to treat the waste load entering the aeration basin AND the sludge blanket in the secondary clarifier could become too high	67%
What is the relationship between the F/M ratio and the MCRT for a particular plant when the aerator detention time is a constant value?	When one increases the other decreases	67%
F/M ratio, sludge age, and settling tests provide valuable operating information to determine proper plant oxygen levels.	False	58%
An advantage of the sequential batch reactor process is that it only requires one tank and no separate clarifier to perform its task.	True	58%
The endogenous growth phase occurs when there is more food than the microorganisms can consume.	False	50%
An old, over-oxidized sludge at an underloaded plant produces mixed liquor solids that do which of the following?	Settle rapidly leaving a turbid supernatant	50%
An advantage of the extended aeration process is that less aeration tank capacity is needed than with conventional activated sludge.	False	42%
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 ________.	increase the F/M ratio by wasting more	42%