An activated sludge tank treats 1 MGD from the primary clarify and has an X of
2200 ppm SS. The water euent is 0.9 MGD. 1.0 MGD of the sludge is recycled back into the tank
and has an [SS] of 3980 ppm. The concentration of the BOD exiting the primary clarier is 200
ppm.
(a) What are Qw and Xw?
(b) What are Qc and Xc?
(c) What are Q1 and X1?
(d) What is Xe? (Answer = 24.4 ppm)
(e) Calculate the volume of the tank that will satisfy the following requirements:
(e-1) BOD loading < 35 lb BOD/1000 ft3day
(e-2) Sludge age > 5 days
(e-3) Aeration period > 4 hr