| Water pollution and eutrophication problem increasingly concerned puts forward urgent task for controlling nitrogen and phosphrous discharge. There are so many problems such as the worse sludge performance and treatment effect at low temperature in the north of China. Thus the study of wastewater treatment under low temperature is very important and valuable. The membrane bioreactor (MBR), the water treatment technology of 21st century, combined with the aerobic granular technology (AG), was used to treat wastewater in this study. Both advantages were taken, such as good effluent quality of MBR and simultaneous N and P removal by aerobic granules.The start-up characteristics of aerobic granular-membrane reactor (AG-MBR) at low temperature (10±1℃) were studied. The obtained granules exhibited clear and slippy surface, compact structure and better sedimentation feature after cultivated for 80 days. The results of SEM study showed that the formation of aerobic granular was finished by multi-activities. During the start-up period, achieved good effluent quality and stable performance in AG-MBR system. Furthermore, the hollow fiber membrane fouling was light and the regime membrane layer was capable of enhancing membrane filtration. When the settle time was setted at 20 min and the rigorous anaerobic condition was controlled, the sludge bulge was controlled.Based on the AG-MBR, the operating condition was optimized and the operating result affected by the DO of the bulk liquid, the C/N and high ammonia nitrogen flush of of the influent were all been investigated. The results showed that, when the DO of the bulk liquid was about 4mg/L, the C/N ratio was beyond 8.5, the settle time was 20min in SBAR, the hydraulic settle time was 12h, and the pH value was 7.0 0.2 in influent, the AG-MBR had a good effect on simultaneous removal of COD, NH4+-N and PO43--P. In addition, the system could handle high ammonia nitrogen flush in influent and showed good performance on nitrogen removal.The AG-MBR system achieved better simultaneous N and P removal effects after the parameters optimized and operated stable. The removal efficiency of COD,NH4+-N and PO43--P were 99.34±0.37%, 99.55±0.41% and 95.83±1.76%, respectively. Through the mechanism analysis, believed, the removal of COD was accomplished by microorganism and fouling layer on membrane surface; the removal of NH4+-N was accomplished by denitrification, partial nitrification and simultaneous nitrification and denitrification (SND); the removal of PO43--P was accomplished by the function of phosphorus accumulating organisms (PAOs), denitrification phosphorus accumulating organisms (DPB) in granule sludge, absorption of extracellular polymeric substances (EPS), and interception by membrane.Comparation between aerobic granular surmerged membrane bioreactor (AGsMBR) and activitied sludge surmerged bioreactor (ASsMBR) was investigated. The removal efficiencies of COD and NH4+-N in both sMBR were beyond 97% and 98%, respectively. But the removal efficiencies of PO43--P were extrusive different. One was beyond 98%, and the other was about 65%. It illustrated that the AGsMBR system operated stable had good quality of effluent. Furthermore, the trans-membrane pressure (TMP) and membrane surface SEM observation implied that the aerobic granular had a better effect on delaying membrane fouling compared with the traditional sMBR.The study of membrane fouling control by AG-MBR showed that, the AG-MBR had a better effect on membrane fouling controlling. During the continuous 120-day operation, the TMP was increasing slowly and it was low around the operation. The membrane resistance analysis displayed that the major resistance was cake layer resisitance and irreversible resistance, which was occupied 57% and 34% in total resistance. While the lower concentration of the bulk liquid in favour of the AG-MBR to be good at membrane fouling controlling. After the continuous 120-day operation, the TMP of the AG-MBR membrane didn't change sharply. Compared with the new membrane, the effluent performance also didn't have a marked change after a long-term operation. SEM analyses indicated that the excellent cleaning effectiveness was achieved.Pilot study was conducted to investigate the operational characteristics of immersed hollow-fiber membrane for micro-filtraion of wastewater. The accumulation of pollutants in the membrane tank became more serious correspondingly. Therefore, the flux exerted important influence on the membrane fouling. Aeration could remove the sludge layer on the membrane surface, thus mitigate membrane fouling to some extent. Experiments showed that 1.5m3/m2?h was the best air flow rate in this study. For the immersed membrane, backwashing could remove the surface foulants and in-pore foulants on the membrane simutaneously. Thus, higher cleaning effectiveness could be achieved by bachwashing. Therefore, combination of aeration and backwashing should be optimized in practical uses.
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