Process and technology for treating domestic and industrial composite wastewater in small town for meeting the discharging standard

With the development of township enterprise and rural urbanization, water pollution of small town is getting more and more serious. In the investigation, the dynamic simulation test was employed to study the process and method of treating the composite wastewater containing domestic sewage and chemical industry discharge of small town. The results showed that the combined process including anoxic/oxic cell and flocculation sedimentation cell was suitable for the wastewater. The suitable hydraulic retention time(HRT) for anoxic reactor and aerobic reactor was 3 hours and 10 hours, respectively. The next flocculation sedimentation (HRT, 2 h) was necessary guarantee for each item in wastewater satisfying the national discharging standards. The operational parameters of 3 hours anoxic and 10 hours aerobic and 2 hours flocculation sedimentation in combined process could make pollutants including Chemistry Oxygen Demand(COD), Ammonia Nitrogen(NH₃-N), Suspended Solid(SS) and Chroma, etc. in effluent steadily reach the No.1 rank discharging standard of the comprehensive sewage discharge standard(GB8978-1996) in the composite wastewater containing pharmacy industrial discharging, dyeing and printing discharging and domestic sewage. And in effluent, COD was about 35.8～50.5 mg/L and the removal rate was up to 89.6%～92.5% and the mean value was 90.4%. NH₃-N in effluent was about 1.13～10.8 mg/L and the mean removal rate was 77.4%, even if the removal rate was up to 90% in the steady running. The SS in effluent was 10.1～15.6 mg/L and the removal rate was between 92.0% and 97.0%. And the dilution rate of chroma in effluent was only 0～5 and the removal rate was up to 95.0%～100%.