Chapter 18, Problem 8RQE

Determine the minimum possible surface area of a secondary clarifier treating activated sludge with a design influent flow rate (Q) of 1,000 m³/d, a return activated sludge (RAS) recycling ratio of 25%, and a mixed liquor total suspended solids (MLSS) concentration of 4,000 mg/L, if the overflow rate must be less than 33 m/d and the solids loading rate must be less than 250 kg/m²/d. Express your answer in m² and round up to the next integer.

Estimate the required air flow rate for the new activated sludge plant at Pea Ridge (Problems 23-223-723-10, and 23-13). The flow rate is 8,450 m³/day, the concentration of bCOD going into the system (So) is 137 mg/L, the concentration of bCOD leaving the system (S) is 16.3 mg/L, and the mass of cells produced per day (Pxvss) is 277.4 kg/d. Use the following assumptions to estimate the required air flow rate: . Clean water correction, a = 0.50 . Salinity correction, B = 0.95 Fouling factor = 0.9 Wastewater temperature = 12°C Atmospheric pressure = 101.325 kPa .Elevation 500 m . Depth of aerator = 5.6 m Operating DO 2.0 mg/L Percent oxygen leaving aeration tank - 19% ■ Manufacturer's SOTR = 535 kg/d Manufacturer's air flow rate at standard conditions 50 m³/d - aerator Express your answer with the units of m³/d and round to the nearest integer.

Determine the required solids retention time (SRT) of a completely mixed activated sludge aeration tank for a conventional activated sludge system treating a design flow rate of 34,560 m³/d, where the effluent standards are 30.0 mg/L for BODs and 30.0 mg/L for total suspended solids (TSS). Assume that the BOD5 of the effluent TSS is 70% of the TSS concentration. Assume the BODs concentration leaving the primary clarifier is 128 mg/L that the MLVSS concentration (X₂) is 2,500 mg/L. Assume the following values for the growth constants: Ks 100 mg/L BODS ⚫ Hm - 2.5 d 1 kd = 0.050 d 1 Y = 0.50 mg VSS/mg BODs removed Express your answer in days and round to the nearest 0.1.