Question

The volumetric flow to the ACME wastewater treatment plant is 25 MGD. The influent soluble BOD5 is 200 mg/L and the effluent soluble BOD5 is 8 mg/L. The plant is designed to operate with a mean cell (biomass) residence time of 10 days. The yield coefficient is 0.6 mg biomass/mg substrate, and the biomass decay rate is 0.09/day. The reactor is to operate at a biomass concentration of 2500 mg/L. The thickened underflow biomass concentration from the secondary clarifier is 9000 mg/L.

a) Draw and label a diagram from primary clarifier effluent to final plant effluent. Include RAS and WAS streams

b) Estimate the required reactor volume (m3) of the activated sludge reactor

c) What percentage of the volumetric flow to the plant is recycled to the activated sludge reactor and what percentage goes to waste sludge treatment?

Answer 1