Functional design of activated sludge processes with heavy metal inhibition

Based on a laboratory study of simulated synthetic waste, a kinetic model to describe the inhibitory effects of heavy metals on growth of microorganisms during the activated sludge process was developed. The kinetic equation involves the four biokinetic constants, μm, Ks, Kd and Y, and the two metal inhibition constants, n and c, which are respectively characteristic of a specific wastewater and the metals in question. The two control variables, cell recycle ratio and cell concentration in the recycle stream, can be used to minimize the inhibitory effects without increasing either the volume of the bioreactor or the residence time.