Steady state analysis of the coupling aerator and secondary settling tank in activated sludge process

The steady state analysis of coupling the function of aerator and secondary settling tank in activated sludge process for wastewater treatment is carried out to obtain appropriate responses of output variables and to decide optimum operating parameters. To consider the effect of the secondary settling tank, limit flux theory is applied and the aerator is assumed to be a continuous flow stirred tank reactor. By using sludge recycle ratio and sludge waste ratio as the operating parameters, the responses of the output variables—biomass concentration in aerator, dissolved pollutant and solid concentration in effluent—are represented as response surfaces and isoresponse curves. Acceptable operating zone can be obtained from the curves and optimum parameters can be determined. Coupling the function of aerator and secondary settling tank is important to consider the appropriate control of an activated sludge process.