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A 1.0 � 106 gallon reactor is used in a sewage-treatment plant. The influent biochemical oxygen...

A 1.0 � 106 gallon reactor is used in a sewage-treatment plant. The influent biochemical oxygen demand (BOD) concentration is 100 mg/L, the effluent BOD concentration is 25 mg/L, and the flow rate through the reactor is 500 gal/min. (a) What is the first-order rate constant for decay of BOD in the reactor? Assume that the reactor can be modeled as a comply mixed flow reactor (CMFR). Report your answer in units of per hour. (b) Assume that the reactor should be modeled as a plug flow reactor (PFR) with first-order decay, not as a CMFR. In that case, what must the first-order decay rate constant be within the PFR reactor? (c) It has been determined the the outlet concentration is too high, so the residence time in the reactor must be doubled. Assuming all other variables remain constant, what must be the volume of the new CMFR?

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