The operations staff at a sewage treatment plant has decided to reduce the SRT (mean cell residence time) of their activated sludge process from 6 days to 3 days by increasing the recycle rate (Qr). The goal is to reduce the oxygen requirement. You have been called in as an expert to give a qualitative assessment of this plan. Respond to the questions below and provide your justification. No credit without explanation and or calculations. Either or are acceptable. a. Will the oxygen requirement actually be reduced? b. Will the MLVSS increase, decrease or stay about the same? c. Will the sludge settling characteristics improve, stay about the same, or worsen?
d. Will the effluent BOD concentration increase, decrease, or stay about the same?