Statistics for Texas Waste Water Treatment Ch#15.2 Primary Clarifier

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Question	Answer	% Correct
The flow into a primary clarifier averages 2.6 MGD. A settleable solids test is performed using an Imhoff cone on the clarifier inlet and outlet. The inlet test shows15 mL/L settleable solids and the outlet shows 3 mL/L. How many gallons of sludge should be pumped from the bottom of the clarifier each day?	31,200 gpd	100%
A primary clarifier is 50 ft. in diameter and 10 ft. deep. What is the capacity of the tank in gallons?	146,795 GAL	75%
What is the detention time in hours of a tank 50 ft. long, 25 ft. wide and 10 ft. deep, with a flow of 1,500,000 gallons per day?	1.5 HOURS	75%
A sedimentation tank is 10 ft. deep, and 60 ft. in diameter. The flow is 1 MGD. Under these conditions, what is the detention time in hours?	5 HRS	50%
How many pounds of BOD5 are removed from the primary clarifier per day? \| Raw BOD entering primary clarifier: 280 mg/L BOD \| leaving primary clarifier: 180 mg/L \| Flow: 170,000 gpd \| In - Out = Removed => 280 - 180 = 100 mg/L Removed	142 lbs/day	25%
Each clarifier in problem 5 has a circular weir 1 ft. from the side wall. Find the weir loading at a peak flow of 4.0 MGD in gallons per day per linear foot of weir length.	18,692 gal/linear ft/day	0%
A treatment plant has two primary clarifiers. Each has a diameter of 36 ft. and a depth of 10 ft. If the design flow is 1.0 MGD, find the surface loading on each clarifier in gal./ft.2 /day. Assume the flow is equally split between the two clarifiers.	492 gal/ft^2/day	0%