A primary wastewater treatment uses centrifugation for dewatering of primary sedimentation sludge. The raw wastewater contains 300 mg/L TSS and 250 mg/L BOD5. The average daily flow to the treatment plant is 5000 m3/d. In primary sedimentation basin, TSS removal is 55%, and BOD5 removal is 30% of the incoming flow.  The primary sludge contains 3.5 % solids. The TSS and BOD5 capture efficiency of centrifugation is 90 % each, and the moisture (water) content of the sludge cake is 70 %.  Assume the specific gravities of the primary and sludge cake are 1.01 and 1.06 g/cm3. 1. Calculate the primary sludge flowrate (underflow rate) (m3/d). 2. Calculate sludge cake flowrate (m3/d).

The characteristics of the synthetic textile wastewater are 1500 mg/L BOD, 2000 mg/L SS, 30 mg/L nitrogen, and no phosphorus. The characteristics of the domestic wastewater are 200 mg/L BOD, 240 mg/L SS, 35 mg/L nitrogen, and 7 mg/L phosphorus. Find the nitrogen concentrations in the mixture. The ratio of flow rate is domestic/textile = 4/1

The 750-bed Associated Center of Medical Excellence (ACME) Hospital has a small activated sludge plant to treat its wastewater. The average daily Medical Center discharge is 1,250 L per day per bed, and the average soluble BOD5 after primary settling is 450 mg/L. The aeration tank has effective liquid dimensions of 10.0 m wide by 25.0 m long by 3.5 m deep. The plant operating parameters are as follows: MLVSS = 2,750 mg/L MLSS = 1.25 (MLVSS) Settled sludge volume after 30 min = 250 mL/LDetermine the following: aeration period, F/M ratio, SVI, solids concentration in return sludge.

A complete-mixed activated sludge process (CMAS) is to be designed to treat 6.0 MGD of primary effluent having a BOD5 of 190 mg/L. The requirement is that the effluent BOD5 and TSS concentrations be 20 mg/L or less on an annual average basis. The following biokinetic coefficient obtained at 15°C: Y = 0.6 mg VSS/mg BOD5, k = 2.85 d-1, Ks = 70 mg/L BOD5, and kd = 0.041 d-1. Assume that the MLVSS concentration in the aeration basin is maintained at 2,500 mg/L. Determine: a. The minimum MCRT (d) b. The MCRT necessary to meet the requirement (d) c. The volume of the aeration basin (ft3)