Studies On Sewage Treatment And Reuse In Scattered Neighborhoods Based On Anoxic/Aerobic Membrane Bioreactor

The dissertation project was from the foundation item on state key lab of western architecture and technology (cultivating base)-studies on sewage treatment and recycling technology in scattered neighborhoods. Anoxic/aerobic membrane bioreactor (A/O-MBR) was choosed to treat the sewage from scattered neighborhoods, according to whose characteristics. The operating conditions, membrane fouling, denitrification performance and application development of A/O-MBR were studied in the dissertation.Anoxic/aerobic activated sludge process is combined with membrane separation technology to produce a new process namely A/O-MBR system. The key operating conditions on A/O-MBR and their primary and secondary relation should be found, in order to keep the system running well. In this dissertation,4 parallel bench scale equipments were established to make orthogonal tests. Through observing membrane fouling and denitrification performance under different conditions, the primary and secondary relation of them is:sludge retention time (SRT)>Internal reflux ratio (IR)> aeration intensity (Qair)>the volume ratio of anoxic and aerobic zone (VA/VO).The relationship between SRT and MBR was studied by 4 bench scale equipments above. The essential reason on membrane fouling was revealed. The SRT of 4 parallel test was 5d,30d,90d and 180d respectively from low to high level. By contrast the fouling degree was least under middle level SRT (30d) for the parallel tests of A/O-MBR. The mixed liquor characteristics, contribution rate of each mixed liquor component (suspended solid, colloid and solute) to fouling and critical flux were detemined under different level SRT. Finally, it was known that soluble microbial products (SMP) was the most critical factor to impact on membrane fouling. The entire fouling process was divided into three stages namely initial, slow and rapid. Numerical fitting was done to initial and slow fouling stage by filter mechanism models. According the fitting results, medium clogging and cake blockage played a major role in initial and slow fouling separately.Meanwhile, using 4 bench scale equipments, it was studied that the denitrification performance of A/O-MBR was affaced by SRT and the ratio of carbon and nitrogen source in influent (C/N). Kinetic equations of nitrification and denitrification were constructed. Colony structures were analyzed in the bioreactor by PCR-DGGE technology. From the experimental results, When the nitrification bacteria reach the minimum generation time, the effect of SRT and influent C/N on denitrification are more significant. The kinetic equation was qN= (32.0+5.60θC)/θC between nitrification rate and SRT, while it was qD= (54.4+3.54θC)/θC between denitrification rate and SRT. The colony structure in the bioreactor was different with other under each SRT.To investigate the applicability and the condition of dispersed wastewater treatment by A/O-MBR, multi-process integrated wastewater treatment equipment in key laboratory of environmental engineering in shandong province was used. A pilot study on A/O-MBR process as a wastewater treatment and reuse technology in the scattered residential districts is conducted. Long-term operating conditions of A/O-MBR is studied, whose effluent quality met the standards of GB/T18920-2002. Meanwhile, in order to investigate the membrane fouling, four-time washing of membrane was gone, and the condition of membrane fouling was analyzed by SEM. Through this research, the periodic cleaning of the membrane is drawed preliminary. PAC is dosed in membrane bioreactor in the third phase of the pilot, and the operation effect was discussed. The results showed that:fouling in membrane surface is mainly biological pollution; After rapid decline of 10 days, flux entered gently downward phase, and average daily drop rate is 0.211 L/m2·h·d; PAC dosage can extend cleaning cycles. The project of sewage treatment in Qingdao Liuting International Airport is studied and researched. The results show that, A/O-MBR process is fitted for a wastewater treatment and reuse in the scattered residential districts.To facilitate practical application and popularization, the spatial arrangement of anoxic zone and aerobic zone was redesigned. And the operational effect of this system was investigated. The results showe that the reactor have many characteristics, such as good treatment effect, small occupation of land, the volume of anoxic zone and aerobic zone can be easily adjusted, and the pumping time can be controlled automatically. The equipment has been applied for patent. The preliminary technical and economic analysis of MBR system was studied in order to discuss the economic feasibility of this system. Meanwhile, the treatment cost and the major factors affecting the cost of this system were conducted. At last, the technical and economic comparison of this system for other wastewater reuse technology was maked.