Study On The Modified Composite A~2/O Process Treatment Of Low Carbon Resource Municipal Wastewater

In the paper, the performance and variation of the modified A2/O process whentreating municipal wastewater with low carbon sources are studied. By changing theratio of reactor volume, influent flow distribution, mixed liquid reflux, sludge return andC/N ratio and so on. To investigate the characteristics of pollutants removal in differentoperation parameters by analyzing the test results.The best operating parameters of the process were identified. When reactor volumeratio was1:1:3, influent flow distribution ratio was3:2, mixed liquid reflux ratio was200%, sludge return ratio50%, the system can achieve the optimal performance ofpollutant removal. The average concentrations of COD, TN, NH4+-N and TP in theinfluent respectively were239.57mg/L,37.44mg/L,43.25mg/L and4.90mg/L, theaverage effluent concentration were31.86mg/L,1.39mg/L,11.29mg/L and0.23mg/L,respectively, average removal efficiency of COD, TN, NH4+-N and TP were85.70%,96.18%,73.49%and95.93%. The effluent could meet to Grade A discharging standardof pollutants for municipal wastewater treatment plant (WWTP)(GB18918-2002).Through the analysis of the test results, the volume of nitrate nitrogen removal inthe anoxic tank and anaerobic tank can be calculated accounted for only about63%ofTN removal when the system operated by the optimal operating conditions, to be sure,microbial assimilation and other factors played an important role in TN removal. At thesame time, the volume of phosphorus uptake in the anoxic tank accounted for TPremoval of about25%. Denitrifying phosphorus removal bacterium presented in thesystem, this was good for improving the treatment effect of nitrogen and phosphorusremoval the system treating municipal wastewater with low carbon sources.The performance of pollutant removal of system were have been investigated by thetest at low water temperature. When the water temperature in the range of12℃~18℃and the system the system with the optimal operating conditions, average concentrationsof COD, TN, NH4+-N and TP in the influent respectively were276.29mg/L,39.10mg/L,49.50mg/L and6.28mg/L, the average effluent concentration were42.43mg/L,2.91mg/L,13.85mg/L,0.34mg/L, respectively, average removal efficiency of COD, TN,NH4+-N and TP were84.42%,92.62%,71.84%and94.50%. The effluent could meet toGrade A discharging standard of pollutants for municipal wastewater treatment plant(WWTP)(GB18918-2002). When the water temperature in the range of9℃~12℃, the efficiency of denitrification in the system decreased rapidly, denitrification effectbecame the main factor limiting the nitrogen removal system. When the watertemperature in the range of7~9℃, The nitrification effect became the main factorlimiting the nitrogen removal system. The removal rate of TP increased slightly.Using methanol as supplementary carbon source, the influent C/N ratio isimproved about of5.5by adding methanol to the raw water， the process could achievethe optimal performance of nitrogen and phosphorus removal.By monitoring the reaction system for pH, we found that in each reactor ofmodified A2/O system，the effect of pH on the mixture ratio of the sludge return lineand by the other operating parameters. The system could keep pH stabal without addingpH adjustment at runtime optimal.