In: Civil Engineering
Design a set of activated sludge aeration tanks. The flow rate to treat is 5.6 MGD and the BOD concentration is 150 mg/L. The design solids concentration (X) at steady-state is 2,000 mg/l. The design MCRT is 7 days. The kinetic coefficients are as follows: K = 2 g BODg cells⋅d, Ks = 25 BOD/L, Kd = 0.06 day-1, Y = 0.5 g BODg cells⋅d. The influent ammonia concentration is 40 mg/l and nitrification is needed. It takes 1400 ft3of air per pound of BOD. Use rectangular tanks with a depth of 12 ft, a length to width ratio of 6 to 1, and a maximum length of 110 ft. Determine the following:
a) The hydraulic retention time (hr)
b) The steady-state effluent BOD concentration (mg/L)
c) The number of tanks and their lengths (ft) and widths (ft)
d) The air requirement (ft3/min)