The concentration of bod u in a river entering the first of two
lakes connected in series is equal to 20 g/m 3 . if the first-order
bod rate coefficient k is 0.35 d -1 and each lake behaves as a
complete-mix reactor, determine the bod u concentration in the
outlet of each lake. the steady-state river flow rate is 4,000 m 3
/d, and the lake volumes are 20,000 and 12,000 m 3 ,
respectively.