Q. 4: with a neat figure, esplaim the four phares of bacterial population dynamics. A completely mired activabed sludge process theats 700m3/hr of wastecuter having a BoD of 300mggL. a 90% reduction in BOD is desired in the trearm treatement process. If the mariinum specific substrate utitization rate is 5d1, yicld coefficient is 0.5 and the saturation constant is 120mg/L, determine the mean cell residence time in the aeration tank