With a neat figure, explain the four phases of baclerial population dynamics A completely mixed activated sludge process treats 700 m 3/ hr of wastewater having a BOD of 300mg/l a 90% reduction in BOD is desired in the treatment process If the maximum specific substrate utilization rate is 5d11, yield coeffioient is 0.5 and the saturation constant is 120mg/l, determine the mean cell residence time in the aeration tank. [4+6]