Optimal policies for activated sludge treatment systems with multi effluent stream generation

Most industrial processes generate liquid waste, which requires treatment p rior to disposal. These processes are divided into sectors that generate ef fluents with time dependent characteristics. Each sector sends the effluent to wastewater treatment plants through pumping-stations. In general, activ ated sludge is the most suitable treatment and consists of equalization, ae ration and settling tanks. During the treatment, there is an increase in th e mass of microorganisms, which needs to be removed. Sludge removal represe nts the major operating costs for wastewater treatment plants. The objectiv e of this work is to propose an optimization model to minimize sludge gener ation using a superstructure in which the streams from pumping-stations can be sent to the equalization tank. In addition, the aeration tank is divide d into cells that can be fed in series and parallel. The model relies on ma ss balances, kinetic equations, and the resulting Nonlinear Programming pro blem generates the best operational strategy for the system feed streams wi th a high substrate removal. Reductions of up to 30 % can be achieved with the proposed strategy maintened BOD efficiency removal upper than 98 %.