2. An activated sludge tank 30x30x200 ft, is designed as a plug flow reactor, with an influent BOD of 200 mg/L and a flow rate of 1mgd. a. If BOD

removal is a first order reaction, and the rate constant is 2.5 days', what is the effluent BOD concentration? b. If the same system operates as a completely mixed flow reactor, what must its volume be for the same BOD reaction? c. How much bigger is this, as a percent of the plug flow volume?