Modeling a biological wastewater treatment system

Abstract

Abstract The treatment of domestic wastewater of housing and communal services and the subsequent use of separation products are one of the important environmental problems of our time, its solution contributes to resource conservation and the development of non-waste (green) technologies. The article described the design of the local treatment station, for which centralized sewage systems are not provided, including an aeration tank and a secondary sump with an aeration system for regulating biological processes. For regeneration of the biocenosis in the aeration tank, there is a recirculation system for activated sludge accumulated in the secondary sump. The rational composition and organization of the biological wastewater treatment process ensure deep destruction of biogenic elements and efficient deposition of the dispersed phase. A mathematical model of the probability of particle deposition in a secondary sump during a free flow with a free surface is proposed, which allows predicting the composition of the settled and not trapped dispersed phase and determining the degree of purification of the liquid phase, considering the productivity and deposition surface of the apparatus and technological parameters of the effluents. By the method of simulation modeling, the local degrees of particle deposition in the secondary sump, calculated for an average nominal diameter d0 of 25 and 20 μm, were estimated. Established that a decrease in d0 from 25 μm to 20 μm makes it possible to increase the integral degree of wastewater treatment from the dispersed phase from 87% to 94%, but the surface of the secondary settler increases by more than 1.5 times.