| Anoxic/aerobic membrane bioreactor contained AO-PMBR and AO-SMBR process for treatment the prophylactic wastewater was adopted in this study. The wastewater was characterized with high-strength ammonium, high pH, refractory and toxicity. The parameters of AO-PMBR and AO-SMBR process, the efficiency of contamination removal, stability of system and the characteristic of membrane pollution were studied in the experiment.The results of AO-PMBR process showed that the prophylactic wastewater treated by the AO-PMBR was feasible.The process could obtain better removal effect of organics, ammonia and total nitrogen. The optimal conditions were HRT 10 h, DO 4 mg·L-1 in the aerobic phase and return mixed fluid ratio(R) 300%. Under the condition of 30℃and pH﹥8.0, the accumulation rate of NO2--N could reach 85% by short-cut nitrification and denitrification and in turn to improve the removal rate of total nitrigen.The stability experiment of AO-PMBR process showed that the removal rate of COD changed within the range of 83%～90% when the COD of influent was from 600 mg·L-1 to 1700 mg·L-1. In the case of 0.20～0.46 kg NH3-H /(m3·d), the ammonium rate was over 64% while the rate could not be enhanced when the loading was over 0.46 kg/(m3·d). It was found that the rate of total nitrogen was controlled by the effect of nitrification. The process showed relatively stable in case of shock load.During the operation of AO-PMBR process, the actived sludge was always bulked. In the process, the indicative microorganism was rotifer,Vorticella campanula etc which were dominant population. In this process, the refractory substances were accumulated, which showed that MBR had some advantages to treat refractory wastewater. The process could domesticate superiority bacteria, strengthen the biodegradation and improve the removal effect of pollutants.The results of AO-SMBR process showed that the removal rate of the organic pollutants only could increase 1～2% by prolonging HRT within the range of 10 h～20 h. However,the removal rate of NH3-N and TN increased 30% and 25%, respectively.The increase in DO in the aerobic phase could obtain better organic removal. The relation between the removal rate of NH3-N and DO was positively correlated. Under the three operation conditions, it was found that the control of DO and the prolonging of the anoxic time would facilitate denitrification, but went against organics degradation. In this process, the refractory and toxicity steroid would possibly inhibite simultaneous nitrification and denitrification.The experiment of membrane fouling revealed that dissolved organic matter was the main fouling substarnces. The membrane flux reduced with the increases in MLSS and viscosity. The membrane flux fitted for the equation of Jv=-5.80681nMLSS+14.086. Backwashing and chemical cleaning were used to clean the membrane fouled, which proveded to be an effective method. The membrane flux was recovered to 76% of initial flux value after cleaning.It was noted from the experiments that AO-MBR process could potentially be used to treat the prophylactic wastewater. The studies of AO-PMBR and AO-SMBR process in this paper could provide further contributions to the late study and industrial applications. |
