Engineering, 11.12.2019 22:31 graceaowen

Aheated low-rate digester is to be designed for an activated sludge plant treating the wastewater from 20,000 persons. (the flow diagram is shown below.) the waste activated sludge flow, qw, is returned ahead of the primary clarifier, and the secondary sludge solids settle along with the influent solids that are removed. both primary and secondary sludge solids are removed by the primary sludge pipe from the bottom of the unit — that is, the underflow from the unit.

the primary sludge flow amounts to 1586 ft3/day, and the digested sludge flow amounts to 564 ft3/day. the digestion time at 98°f is 23 days and the storage time provided is 45 days. when the contents are stratified, digested sludge occupies the bottom half of the side water depth. (this is 19.1 in the text book)

determine:

(a) the average volume of the digesting sludge? (cubic feet/day)
(b) the volume of the digesting sludge? (cubic feet)
(c) the volume of the stored digested sludge? (cubic feet)
(d) the volume of the digester? (cubic feet)

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