GATE CE 2021 Set 1 — Question 62
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Environmental Engineering → Wastewater Treatment Processes → Activated Sludge Process
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Question
A secondary clarifier handles a total flow of from the aeration tank of a conventional activated-sludge treatment system. The concentration of solids in the flow from the aeration tank is . The clarifier is required to thicken the solids to , and hence it is to be designed for a solid flux of . The surface area of the designed clarifier for thickening (in , in integer) is ________.
Correct answer
375 to 375
Solution
Step 1: Calculate the total solid load entering the clarifier.
Total flow
Concentration of solids
Total solid load per day Step 2: Convert the solid load to per hour basis.
Solid load per hour Step 3: Calculate the surface area required for thickening based on the design solid flux.
Solid flux
Surface area
Total flow
Concentration of solids
Total solid load per day Step 2: Convert the solid load to per hour basis.
Solid load per hour Step 3: Calculate the surface area required for thickening based on the design solid flux.
Solid flux
Surface area
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