Under normal operation condition, the microbial quantity of the composite bioreactor with fixed biofilm filter bed in the lower part and mobile bed in the upper part is:
1, the SS of CBBR mixture is 1,604 mg/L, and the total amount of the microorganisms is about 2.456 g.
2, the total amount of the biofilm of the fixed filler is 12.036 g.
3, the total amount of suspended filler of the mobile bed The total amount of biofilm is 1.428 g.
4. The total amount of CBBR microorganisms is about 15.92 g.
This process plays a great role in deodorization of wastewater, and its deodorization process is simple and effective. Combined with other wastewater treatment equipment, the CBBR reduces the difficulty of wastewater treatment, thereby improving the surrounding environment and effectively curbing the spread of germs. With the continuous improvement of medical technology, the production of new agents will continue to increase the difficulty of sewage treatment, so the water treatment technology still needs to be improved to meet the needs of the times.
4 MBR research progress
Currently, MBR research is mainly focused on the following aspects: (1) reduce membrane contamination and improve membrane flux; (2) explore the appropriate working conditions and process parameters; (3) reduce the operating costs of the treatment process.
Zhang Shaohui, Zheng Ping, Hua Yumei [1] Study of an anaerobic ammonia oxidation reactor initiated with denitrifying biofilm et al. Polyethersulfone membranes (PES) with different molecular weight cut-offs (MWCOs) were selected and anaerobic MBR composed of plate-and-frame membrane modules was used to treat high concentration food wastewater, and the effects of MWCOs on membrane flux and effluent effect were investigated.
Wang Rongchang, Wen Xianghua, Qian Yi [2] analyzed the formation mechanism of aerobic granular sludge in biofilm reactor, and investigated the effect of MBR operating conditions on membrane filtration characteristics.
Yang Yu-Wang [3] studied the progress of research and application of moving bed biofilm reactor for wastewater treatment.
Xing Chuanhong et al. carried out the process design of tubular MBR (split-type) for treating municipal wastewater, and concluded that the operating cost mainly consists of three parts, such as electricity, pharmaceuticals and labor costs. Among them, the electricity cost is the most important one, and the electricity consumption is 2.3kW-h/m3.
Lu Min, Zeng Qingfu, and Zhang Yuewu [4] took a keen interest in the study of a new type of biofilm reactor for sewage treatment.
Wang Ya'e et al. analyzed the main factors affecting the ultrafiltration membrane flux and filtration resistance.
Yang Lei et al. conducted a more detailed test on membrane contamination and cleaning during MBR operation.
Li Jun, Peng Yongzhen, Yang Xiushan ,Wang Baozhen ,Yang Haiyan [5] focused on the characteristics of denitrification and phosphorus removal by sequential batch biofilm method and its mechanism.
Jiang Su et al [6] studied the integrated A/O biofilm method for domestic wastewater treatment.
Bai Yu et al [7] studied and analyzed the spatial and temporal distribution characteristics of bacteria in the biofilter layer of wastewater deep treatment.
Chen Bibo et al [8] conducted a fruitful research to demonstrate the significance of moving bed biofilm reactor and for paper wastewater treatment.
Cote P studied the power consumption of submerged membrane system, including suction pump and aeration 2 parts. Each cubic meter of produced water consumes only 0.3 to 0.6 kW-h of electricity, which is the main part of the operating cost.
Wanghong Rong et al [9] conducted a pilot study on biological phosphorus removal by sequencing batch biofilm method under laboratory conditions, and came up with promising conclusions.
Wang L-Choo Ho et al [10] compared the power consumption during the operation of submerged and split MBR process, and the result was that the former power consumption was only 0.2-0.4 kW-h /m3,while the latter power consumption was 2-10 kW-h /m3 at a flux of 18 L/(m2-h).
Bao Li-Ning et al [10] in the electrode biofilm nitrogen removal process Bao Lining et al. [10] studied the phase analysis of denitrifying bacteria in the electrode biofilm nitrogen removal process.
MBR because of its own special process also requires different from the general ultra- and microfiltration membrane materials, but the preparation of membrane materials for MBR used in the study is still very little. Obviously, choosing the right membrane material is an important way to reduce membrane contamination, which needs to be further studied.
5 MBR application examples
With the deepening of the study, there are examples of MBR applications at home and abroad. Practice shows that serious membrane contamination, low water flux, is the most important reason to limit the popularization and application of MBR.
Canada Cote P, etc. reported on the development of MBR in North America in the 1990s. Among them, ZENON environmental protection company in 1996 launched a module membrane area of 46m2, bulk density of 63m2/m3 ZW-500 type membrane bioreactor, the device has been successfully applied to municipal wastewater treatment. At present, the small-scale device is mainly used with a treatment capacity of 10-200m3/d, which is mainly promoted in office buildings, shopping centers, schools, hospitals and sanatoriums. The hydraulic retention time (HRT) of the device is 24h, and the SRT is 1~2 years. The filtrate is used as toilet flushing water after UV disinfection or activated carbon adsorption. The MBR plant built in Ontario with a daily sewage treatment of 3,800 m3 was installed with 144 ZW-500 membrane modules, with a total membrane area of 6,624 m2. The aeration tank had a volume of 440 m3, with a normal HRT of 3.8 h; the anaerobic reaction tank had a volume of 380 m3, and the HRT was 2.4 h. The concentration of MLSS during the operation period was 12,000 to 20,000 mg/L, and the concentration of MLVSS was only 1 to 2%. MLVSS concentration is only 55% to 70% of MLSS. The removal rate of BOD and organic phosphorus in the effluent is close to 100% since 9 months of operation.
Japan since 1998, focusing on promoting the development and utilization of the middle waterway system. The aim is mainly to treat the drainage water from buildings, which is mainly kitchen drainage and drainage water after washing and bathing, and then reuse it as toilet flushing water. For example, Hitachi Plant Construction uses a system combining a high-concentration activated sludge method and a rotating plate ultrafiltration membrane device as a reuse system for the building's mid-waterway. Because the membrane plate rotates, the sludge on the surface of the membrane is agitated, thus contamination of the membrane surface can be controlled.
Tianjin Tsinghua Deren Environmental Company and Tianjin University **** with the development of MBR has been some of the application examples. To deal with the sewage discharged from an office building in Tianjin, for example, the building's floor area of about 17,000m2, the use of a daily capacity of 25m3 device, the equipment body occupies an area of 3.2m2, an investment of more than 100,000 yuan, the energy consumption of 0.8kW-h/m3. The treated water can be used for flushing toilets, landscaping, and car washing, etc..
Zheng Fei et al [11] developed a new process of biofilm method - bubble-free aeration membrane bioreactor.
Lu Xiaohui et al [12] on the moving bed biofilm reactor nitrogen and phosphorus removal technology is unique, so that the nitrogen and phosphorus removal efficiency and a greater development.
6 Conclusion 1 MBR synthesizes the advantages of membrane separation technology and biological treatment technology, ultra- and microfiltration membrane components can replace the secondary sedimentation tank in CAS, more effective mud-water separation, and extend the SRT, improve the microbial treatment of organic matter in sewage. After ultra- and microfiltration membrane treatment, the effluent water quality is good enough to be used directly for non-potable water reuse. The system covers a small area, almost no discharge of residual sludge, has a high impact resistance. 2 MBR has a certain degree of practicality, but membrane pollution is still the most important factor restricting the popularization and application of MBR. Because the membrane material in MBR faces both the pollution of activated sludge, solid particles in sewage, and the erosion of microorganisms in activated sludge. Although you can control the pumping time, aeration and other process parameters as well as the use of appropriate cleaning technology to reduce the pollution of the membrane surface, but the most effective and fundamental method is to develop a new anti-pollution, anti-microbial erosion of the membrane material and membrane for appropriate modification. 3 In the application of MBR technology to treat municipal and domestic wastewater and realize water reuse, there is another key factor to consider, namely, the operating cost. Therefore, the running cost should always be taken into account in the study. As the main starting point for considering the test program and determining the test results. 7 References
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