Statistics for Texas Basic Waste Water Operations Ch#07 Sedimentation

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Answer Stats

Question	Answer	% Correct
Usual blanket depth in a secondary clarifier is no more than ________ of the sidewall depth.	1/4	100%
Primary clarifiers should remove 90–95% of the BOD and 35% of the settleable solids.	False	100%
Common design features of a sedimentation tank include baffles, a skimmer, a grease ring, and a sludge rake.	True	100%
The four settling zones in a sedimentation tank are the inlet zone, settling zone, sludge zone, and the outlet zone.	True	100%
Short-circuiting is the uneven flow of water through a tank.	True	100%
When sludge in an Imhoff tank is near ________ inches of the slot, withdraw sludge.	18	50%
The settling compartment provides a detention time of about ________ hour(s).	2	50%
Withdraw sludge slowly or water will break through the sludge layer, ________ the sludge.	diluting	50%
Sedimentation is the process of separating a suspended solid from water by atmospheric pressure.	False	50%
A primary clarifier settles biological sludge, and a secondary clarifier settles raw sludge.	False	50%
Floating sludge or excessive gas bubbles indicate a failure of the return sludge pump, sludge rake, or poor ________ schedule.	pumping	50%
If the skimmer fails, the sludge ________ fails.	rake	50%
Gas vents alongside the settling tank are the ________ compartment.	third	50%
Secondary sludge contains more water than primary sludge.	True	50%
The ________ compartment of an Imhoff tank is the settling tank, and the ________ compartment is the sludge digester.	upper/lower	50%
Imhoff tanks are ________ story units with ________ compartments.	2/3	0%
________ prevents septic solids from collecting and rising in the settling chamber.	Chaining	0%
Factors affecting settling include solid weight, water temperature, detention time, velocity, surface loading, wastewater condition, and short-cutting.	False	0%
Foaming can be caused by industrial waste, drawing too much sludge, low pH, and restricted ________.	gas vents	0%
A trapped slot in the bottom of the settling compartment permits ________ solids to pass into the digester, but prevents septic solids from ________ into the settling compartment.	settled/rising	0%
Control foaming by controlling industrial waste, ________, and controlling pH with lime.	wasting small amounts of sludge	0%