Question

A completely mixed activated sludge plant is designed to treat 10,000 m3/d of an industrial wastewater. The wastewater has a BOD5 of 1200 mg/L. Pilot plant data indicates that a reactor volume of 6090 m3 with an MLSS concentration of 5000 mg/L should produce 83% BOD5 removal. The value for Y is determined to be 0.7 kg/kg and the value of kd is found to be 0.03 d–1. Under ow solids concentra- tion is 12,000 mg/L. The ow diagram is similar to Figure 8.6.

Determine the mean cell residence time for the reactor.

System Boundary Secondary clarifier Aeration tank Primary effluent, Effluent Q+QR X, S Q, Xo, So V,X, S Sludge oe,xs l return QR.XS Sludge l ulow Sludge wasteQue

Calculate the mass of solids wasted per day.

Calculate the volume of sludge wasted each day.

Answer 1

q= 10,000 m Ida r = 83%. meon cell Yesidence time (MCRT) 10,000 x 0, (IQ00-204) 60g0 x 500o At sad stat sRT glven by ,0500 Ongle = 6090 kg IdPg EOch dog = 60909 vs s volume solid wasted u 600/s21 ml Xu