A CMAS treatment system is to be designed to treat 22,700 m3/d of municipal wastewater having a soluble BOD5 (SBOD5) of 250 mg/L leaving the primary clarifier. To meet the NPDES permit, the effluent SBOD5 leaving the secondary clarifier must be 5.0 mg/L or less. The following biokinetic coefficients will be used to design the system: μm = 2.64 d-1; Ks = 60 mg-SBOD5/L; kd = 0.06 d-1; and Y = 0.6 mg-VSS/mg-SBOD5 Assume that the MLVSS concentration in the aeration basin is maintained at 3,000 mg/L and the VSS : TSS ratio is 0.80. Determine the following: (a) The required SRT of the CMAS system (in d). (b) The volume of the aeration basin (in m3) and the HRT of the CMAS system (in h). (c) The daily production of total sludge (in kg-TSS/d). (d) The minimum daily mass of oxygen required (in kg/d). Assume BOD5/ BODL = 0.68. (e) Assume that there are negligible suspended solids in the effluent from the secondary clarifier and that the secondary clarifier can thicken the sludge to SVI = 120 mL/g. Determine the design values for QE, QR and QW (in m3/d and as a percentage of Q).
