Treatment Of Low-Temperature Municipal Wastewater By Anoxic-Oxic Moving-Bed Biofilm Reactor

In the high-latitude cold region, metabolic capability of micro-organisms of the treatment units was decreased by the low temperature, which leads to the removal efficiency reduction of the outdoor biological sewage treatment facilities. So, steady operation of the sewage treatment plant was greatly affected and the quality of the treated water can hardly reach the related standard. China is lack of maturely integrated technology with the low temperature sewage treatment in the winter. For this reason, effective strengthening technique in low temperature is seeked to make sure the quality of the treated water reaching the standard in the cold region. Therefore, the dissertation mainly studies the treatment efficiency of low temperature wastewater by A/O process MBBR(Moving Biological Bed Reactor).The lab experiment was carried out in the conditions of room temperature (T=20℃) and low temperature (T=8℃) respectively. The treatment efficiency of stimulant municipal wastewater by Oxic MBBR was studied in different conditions, and the optimal parameters of Oxic MBBR were obtained in the 8℃low temperature. The optimal parameters of Oxic MBBR were the filling radio of suspended carriers 40%. HRT 4h and DO concentration 7-8mg/L.Under the optimal conditions, when the Anoxic MBBR, whose filling radio of suspended carriers is 50%. was connected with Oxic MBBR and the internal recycle ratio was adjusted at 200%, the removal efficiencies of COD and NH4--N in the 8℃of sewage temperature can reach 90.70% and 71.65% respectively, when the influent concentration of COD and NH4+-N was about 400mg/L and 30mg/L respectively, the content of COD and NH4--N in the effluent can both reach the first level A criteria specified in the national discharge standard while the removal efficiencies of TN can reach 65.65%.To investigate the practical treatment efficiency of the domestic sewage pilot-scale models were designed and set in the east district wastewater treatment plant of Daqing city based on the lab experiment results. The Pilot-scale Research was started from summer, the experimental results showed that the starting time of this system is short in the temperature between 15℃and 20. Even in low average influent concentrations that COD, NH4(?)-N and TN was 450mg/L.45mg/L and 50mg/L. the effluent concentration of COD. NH4(?)-N and TN was below 48.1 mg/L,3.41 mg/L and 13.32mg/L respectively after treatment, which meet the first level A criteria specified in the national discharge standard.In the Pilot-scale reach, when the season went into winter from autumn to. the water temperature decreased from 20℃to 13℃suddenly, taking an obvious impact on the reactor operation. The ability of nitrification and denitrification was both decreased, the effluent concentration of COD, NH4(?)-N and TN was increased continuously. In this time, the water temperature was controlled at 13 C by building warmth retention measures, and meanwhile, the influent load was decreased to 0.4m3/h. After a period of tranquilization. with the continuous adaptation of microorganism, the removing ability of the reactors rose slowly, then the influent load was adjusted to 0.5m3/h. The results of two month operation in low temperature(8-13℃) showed that the removal efficiency of COD. NH4(?)-N and TN can reach 90%,88% and 60% respectively after the reactors was adjusted stably, and the effluent concentration of COD. NH4(?)-N and TN is below 50mg/L,5mg/L and 15mg/L, which meets the first level A criteria specified in the national discharge standard.