| The conventional treatment techniques for wastewater encounter many problems, such as complicated configuration, large footprint requirement, and unstable removal effectiveness for refractory organics, all of which are the reasons for the difficulties of meeting the effluent water quality standards. Membrane Bioreactor (MBR), as a new efficient and stable technology for wastewater treatment, combines activated sludge process and membrane filter. But the widespread application of the MBR is constrained by membrane fouling. Membrane fouling could lead to the rapid decline of filtration flux, which results in the increase of operation cost. Thus, settling the problem is the main aspect of research in this field.The effects of operating conditions on MBR performance and membrane fouling has been studied in this work, and the results showed that MBR in conditions that HRT for 10 h, aeration intensity for 0.6 m3/h, on/off time for 9:3 min could obtain the ideal effect. The average removal rate of COD, ammonia nitrogen, total phosphorus and turbidity reached 94.0%,96.5%, 30.0% and 96.8%, respectively; and the TMP of the system reached 45.5 kPa after running for a month. Although the pollutant removal efficiency was high, the membrane fouling was still not improved significantly. The membrane flux of contaminated membrane modules could be recovered to 95.3% of the new membrane through clean steps including tap water washing, hot water washing, sodium hypochlorite washing and soaking and ethanol backwashing. Effective washing method could extend the service life of the membrane modules.Adding carriers into submerged MBR, which existed activated sludge and bio-film in one system at the same time, and constituted the activated sludge bio-film integrated MBR system. The effect of different types of carriers (suspended carrier and granular carriers) on MBR operation was researched and analyzed in this work.Adding suspended carrier into the MBR, the surface of the carrier formed stable bio-film, which could improve the removal efficiency of pollutants. By comparing the removal efficiency of pollutants and the mitigation of membrane fouling after adding two kinds of suspended carriers into MBR, found that effect of soft carrier for MBR was more obvious, and the optimal dosage was 20% of the effective volume of the reactor. After the MBR running for a month with 20% of the soft carrier, the degree of membrane fouling was only 58.57% of the system without carrier.After adding the granular carriers into the MBR formed a kind of combined process, there was a certain degree of improvement for the sewage treatment performance. After analyzing and comparing the removal efficiency of pollutants and the control of membrane fouling of MBR with two kinds of granular carriers, the result showed that the strengthening effect of PAC on MBR was better than GAC, and the optimal dosage of PAC was 2 g/L in this study. After adding granular carrier into MBR, the TMP increasing rate was slowed down significantly than the system without adding carrier. The TMP of MBR-PAC with 2 g/L PAC was 58.71% of the MBR without carrier after running for a month, which showed that PAC could mitigate membrane fouling significantly. |
