1. Basic Process Design Parameters Food to mass ratio (F/M) = Q x BOD MLSS x V Where Q = average daily sewage flow to aeration (Ml/d) BOD = Average settled sewage BOD (mg/l) MLSS = mixed liquor suspended solids concentration (mg/l) V = volume of aeration tank (Ml)

2. Exercises Using the information on the ASP diagram calculate the following; 1.RT in hours at average and max flow? 2.The F:M ratio of the plant at average flow? 3.What would the plant MLSS be to ensure an F:M ratio of 0.08 Kg BOD/Kg MLSS/ Day 4.The sludge age of the plant at average flow? 5.What would the sludge age be if the MLSS increased to 3500mg/l.

3. Factor (SLF) or F/M ratio Example Calculation Average Daily Flow (Q)=19.2 Ml / day Average BOD (settled sewage)=125 mg / l Mixed Liquor Solids (MLSS)=2500 mg / l Aeration Basin Volume=8000 m3 (8Ml) F/M= Q (Ml/d) x BOD (mg/l)Kg BOD /MLSS / day MLSS (mg/l) x V (ml) =19.2 x 125 2500 x 8 =0.12 Kg BOD / Kg MLSS / day