Treatment of Domestic Sewage by Chemical and Biological Flocculation Process

Chemical and biological flocculation process(CBFP) was adopted to pretreat the domestic sewage. The effects of flocculant dosage, DO, sludge return ratio, hydraulic retention time(HRT), low temperature on the treatment of pollutants were investigated and the role of biological flocculation in CBFP was analysed in this study. The results showed that Fe3+ dosage had great influence on COD, SCOD, SS and PO43--P removal efficiency. But it had almost no effect on NH3-N removal. Tapered aeration process could be used in the control of DO in three channels of the reaction tank. The optimum sludge return ratio was 70% for the removal of COD, NH3-N and SS, 100% for PO43--P removal. HRT could affect pollutant removal, the optimum HRT was 30min. In low temperature, the removal rate of pollutants didn't decrease obviously. Pollutant removal of CBFP was comprehensive effect of chemical flocculation and biological flocculation.