Answer Happy

Question 24 (10 points) A complete mixed activated sludge system with recycle is used to treat flow from a roughing filter (4.2 MGD). The influent BOD, into the activated sludge system is 92 mg/L and the required effluent is 10 mg/L. The MLSS concentration is 2800 mg/L and is 80% volatile. The HRT of the system is 1.2 hours and a recycle ratio of 0.5 is used. The temperature in the winter of the activated sludge system is 13 C and controls the design. The kinetic constants are given as follows: Ks = 55 mg/L at 20C Hmax = 3.7/day at 20 C ke = 0.05/day at 13 C Y = 0.6 lb MLVSS/ID BOD5 What is the MCRT in days required for this tank to achieve the desired effluent concentration (answer to the nearest tenth of a day)? Your Answer: Answer