06-20 (mz 4.14, modified) you are designing a reactor that uses chlorine in a pfr or cmfr to destroy pathogens in water. a minimum contact time of 30 min is required to reduce the pathogen concentration from 100 pathogens/l to below 1 pathogen/l through a first-order decay process. you plan on treating water at a rate of 1,000 gal/min. (a) what is the first-order decay rate constant? (b) what is the minimum size (in gallons) of the reactor required for a plug flow reactor? (c) what size (in gallons) of cmfr would be required to reach the same outlet concentration? (hint: k will be the same but not h.) (no part d) (e) if the desired chlorine residual in the treated water after it leaves the reactor is 0.20 mg/l and the chlorine demand used during treatment is 0.15 mg/l, what must be the daily mass of chlorine added to the reactor (in kg/d)? (hint: chlorine demand is the chlorine that reacts with various constituents in the water. it is the difference between the concentration added and the concentration that is measured in the solution, i. e. the residual.) 0.154/min, 30,000 gal, 643,000 gal, 0.35 mg/l added or 1.91 kg/d