What Is a Biofilm Reactor?

Membrane bioreactor is a new water treatment technology combining a membrane separation unit and a biological treatment unit.

Biofilm reactor

The membrane bioreactor (MBR) and the biofilm reactor are two different types of reactors. Membrane bioreactor

The traditional activated sludge process (CAS) is widely used in various sewage treatment. Since gravity-type precipitation is used as a solid-liquid separation method, it brings many problems. For example, the solid-liquid separation efficiency is not high, the volumetric load of the treatment device is low, the floor area is large, the effluent water quality is unstable, the oxygen transfer efficiency is low, the energy consumption is high, and the remaining sludge production is large. The water treated by the traditional biological treatment technology is difficult to meet the increasingly strict sewage discharge standards. At the same time, the increasing shortage of water resources brought by economic development also urgently requires the development of suitable sewage recycling technology to ease the supply and demand of water resources. contradiction. Under the above background, a new type of water treatment technology (Membrane Biological Reactor, MBR) came into being. With the continuous development of membrane separation technology and products, (MBR) has become more practical. In recent years, many countries have invested a lot of funds to develop this high-tech.

CAS is the most widely used aerobic biological treatment technology for wastewater. The basic flow is shown in Figure 1.

MBR and its classification

MBR refers to a new sewage treatment device that combines ultrafiltration and microfiltration membrane separation technology with bioreactors in sewage treatment. This reactor combines the advantages of membrane treatment technology and biological treatment technology. The ultra- and micro-filtration membrane modules are used as mud-water separation units, which can completely replace the secondary sedimentation tank. Ultra- and micro-filtration membranes trap microbial floc and larger molecular organics in the activated sludge mixed solution, so that they stay in the reactor, so that the reactor obtains high biological concentration, and prolongs the retention time of organic solids, which greatly improves the microorganism Oxidation of organic matter. At the same time, after the ultra- and micro-filtration membrane treatment, the effluent quality is high and can be directly used for non-drinking water reuse. The system hardly discharges excess sludge and has high impact resistance. Especially in 1989, Yamamoto applied hollow fiber membranes to activated sludge treatment, which greatly reduced the process operation cost and had a broad practical application prospect. Therefore, MBR is a high-tech water treatment technology that is highly valued by experts and scholars at home and abroad.

MBR features:

1. The effluent quality is good

Due to the use of membrane separation technology, there is no need to set up, filter, and other solid-liquid separation equipment. Efficient solid-liquid separation separates suspended microorganisms, colloidal materials, and microbial flora lost in the biological unit from the purified water in the wastewater, which can be reused without third-stage treatment, and has high water quality safety.

Small footprint

The concentration of microorganisms in the biological treatment unit of the membrane bioreactor maintains a high concentration, which greatly increases the volume load. The high efficiency of the membrane separation greatly reduces the hydraulic retention time of the treatment unit and reduces the floor area. At the same time, because the membrane bioreactor uses membrane modules, it does not require a sedimentation tank and a special filtration workshop, and the system occupies only 60% of the traditional method.

Third, save operating costs

The MBR's efficient oxygen utilization efficiency and unique intermittent operation mode greatly reduce the operating time and power consumption of the aeration equipment and save power consumption. At the same time, because the membrane can filter out harmful substances such as bacteria and viruses, it can significantly save the long-term operating costs caused by drug addition and disinfection. The membrane bioreactor process does not require the addition of flocculants, reducing operating costs.

The membrane bioreactor (MBR) process is a new type of wastewater treatment technology that organically combines membrane separation technology and biotechnology. It uses membrane separation equipment to capture activated sludge and macromolecular organic matter in the biochemical reaction tank, eliminating the need for

At present, MBR research mainly focuses on the following aspects:

(1) Reduce membrane fouling and increase membrane flux;

(2) Search for suitable working conditions and process parameters;

(3) Reduce the operating cost of the treatment process.

Zhang Shaohui, Zheng Ping, Hua Yumei [1] The study of using anaerobic ammonia oxidation reactor with denitrifying biofilm to select polyethersulfone membranes (PES) with different cutoff molecular weights, and the use of plate and frame membrane modules to form anaerobic MBR pairs The treatment of high-concentration food wastewater was conducted, and the influence of molecular weight cut-off on membrane flux and effluent effect was investigated.

Wang Rongchang, Wen Xianghua, Qian Yi [2] analyzed the aerobic granular sludge formation mechanism in the biofilm reactor, and studied the effect of MBR operating conditions on membrane filtration characteristics.

Yang Yuwang [3] studied the research and application progress of moving bed biofilm reactor for wastewater treatment.

Xing Chuanhong and others carried out the process design of the tubular MBR (separate type) treatment of urban sewage. They believed that the operating cost mainly consisted of electricity, medicine and labor. Among them, the electricity cost is the most important, and the power consumption is 2.3kW · h / m3.

Lu Min, Zeng Qingfu, and Zhang Yuewu [4] showed great interest in the research of a new type of biofilm reactor for wastewater treatment.

Wang Ya'e and others analyzed the main factors affecting the flux and filtration resistance of ultrafiltration membranes.

Yang Lei et al. Conducted a more detailed test of membrane fouling and cleaning during MBR operation.

Li Jun, Peng Yongzhen, Yang Xiushan, Wang Baozhen, Yang Haiyan [5] studied the characteristics and mechanism of denitrification and phosphorus removal in a sequential batch biofilm process.

Jiang Su et al. [6] studied the integrated A / O biofilm method for domestic sewage treatment.

Bai Yu et al. [7] studied and analyzed the spatiotemporal distribution characteristics of bacteria in the biological filter of advanced sewage treatment.

Chen Bibo et al. [8] on moving bed biofilm reactor and on papermaking

With the deepening of research, there have been examples of MBR applications at home and abroad. Practice shows that serious membrane pollution and low water flux are the main reasons for limiting the popularization and application of MBR.

Cote P of Canada reported the development of MBR in North America in the 1990s. Among them, ZENON Environmental Protection Company introduced the ZW-500 membrane bioreactor with a module membrane area of 46m2 and a bulk density of 63m2 / m3 in 1996. This equipment has been successfully applied to municipal sewage treatment. At present, it is mainly small-scale installations with a processing capacity of 10-200m3 / d. It is mainly used in office buildings, shopping centers, schools, hospitals and health resorts. The hydraulic retention time (HRT) of the device is 24 hours, and the SRT is 1 to 2 years. The filtrate is used as toilet flushing water after ultraviolet disinfection or activated carbon adsorption. The MBR unit, which has a daily sewage treatment capacity of 3,800m3, was installed in Ontario, with 144 ZW-500 membrane modules installed, with a total membrane area of 6624m2. The volume of the aeration tank is 440m3, and the normal HRT is 3.8h; the volume of the anaerobic reaction tank is 380m3, and the HRT is 2.4h. During operation, the MLSS concentration is 12 000 to 20 000 mg / L, and the MLVSS concentration is only 55% to 70% of MLSS. After 9 months of operation, the removal rate of BOD and organic phosphorus in the effluent is close to 100%.

Since 1998, Japan has promoted the development and utilization of watercourse systems. Its main purpose is to treat the drainage of the building, which is mainly composed of kitchen drainage, face washing and drainage after bathing, and then reuse it as toilet flushing water. For example, the Hitachi Plant Construction Company uses a system consisting of a high-concentration activated sludge method and a rotating flat-plate ultrafiltration membrane device as a water reuse system in the building. Because the membrane plate rotates, the sludge on the membrane surface is stirred, so that the membrane surface pollution can be controlled.

The MBR jointly developed by Tianjin Tsinghua German Environment Company and Tianjin University has some application examples. Take the treatment of sewage discharged from an office building in Tianjin as an example. The office building has a building area of about 17 000m2, and uses a device with a daily processing capacity of 25m3. The equipment itself covers an area of 3.2m2, with an investment of more than 100,000 yuan and an energy consumption of 0.8kW · h / m3. The treated water can be used for flushing, greening and car washing.

Zheng Fei et al. [11] developed a new process of biofilm method-bubble-free aerated membrane bioreactor.

Lu Xiaohui et al. [12] had a unique interest in the technology of nitrogen and phosphorus removal in moving bed biofilm reactors, which has made great progress in nitrogen and phosphorus removal efficiency.

The ge mbr membrane reactor technology uses gas and liquid two-phase countercurrent deodorization operation. The gas containing H2S enters from the bottom and is discharged from the top after passing through the biological filter bed and moving bed. At this time, the sewage can be evenly discharged from the top and then passed through. The bottom drainage pipe enters the sedimentation tank.

Effect of compound bioreactor on hospital sewage treatment

This process can carry out sewage treatment and deodorization at the same time. Its water inlet method can be divided into two types: one is to ensure continuous water inlet, and the other is intermittent water inlet. These two water inlet methods assist the bioreactor to treat sewage and deodorize at the same time, making its final treatment effect remarkable.

Under normal operating conditions, the lower part of the composite bioreactor is a fixed biofilm filter bed, and the upper part is a moving bed.

Its microbial biomass is:

1. The CBBR mixed solution SS is 1 604 mg / L, and the total amount is about 2.456 g.

2.The total amount of fixed filler biofilm is 12.036 g

3.The total amount of suspended bed biofilm in the moving bed is 1.428 g

4.The total amount of CBBR microorganisms is about 15.92 g

This process has a great effect on sewage deodorization, and its deodorization process is simple and effective. The combined bioreactor and other sewage treatment equipment reduce the difficulty of sewage treatment, thereby improving the surrounding environment and effectively curbing the spread of germs. With the continuous improvement of medical technology, the generation of new medicaments will continue to increase the difficulty of sewage treatment, so water treatment technology still needs to be upgraded to meet the needs of the development of the times.

1. 1 MBR combines the advantages of membrane separation technology and biological treatment technology. Ultra and microfiltration membrane modules can replace the secondary sedimentation tank in CAS, more effectively carry out mud-water separation, extend SRT, and improve the ability of microorganisms to treat organic matter in sewage. After the ultrafiltration and microfiltration membrane treatment, the effluent quality is good and can be directly used for non-drinking water reuse. The system occupies a small area, hardly discharges excess sludge, and has high impact resistance.

2. 2 MBR has certain practicability, but membrane pollution is still the most important factor restricting MBR promotion and application. This is because the membrane material of MBR must not only face the pollution of activated sludge and solid particles in sewage, but also the erosion of microorganisms in activated sludge. Although it is possible to reduce the pollution of the membrane surface by controlling the process parameters such as pull-down time, aeration volume, and using appropriate cleaning techniques, the most effective and fundamental method is to develop a new membrane that is resistant to pollution and resistant to microbial attack Material and appropriate modification of the film.

3. 3 When applying MBR technology to treat municipal and domestic sewage and achieve reclaimed water reuse, another key factor must be considered, namely operating cost. Therefore, the operating cost should always be used in the research. As the main starting point for considering the test plan and determining the test results.

7 references

1 Zhang Shaohui, Zheng Ping, Hua Yumei. Study on the start of anaerobic ammonia oxidation reactor by denitrification biofilm. Journal of Environmental Sciences, 2004, 24 (2): 220 224

2 Wang Rongchang, Wen Xianghua, Qian Yi. Formation mechanism of aerobic granular sludge in biofilm reactor. China Water & Wastewater, 2004, 20 (3): 5-8.

3 Yang Yuwang. Progress in research and application of moving bed biofilm reactor for wastewater treatment. Industrial Water Treatment, 2004, 24 (2): 12-15.

4 Lu Min, Zeng Qingfu, Zhang Yuewu. Research on a new type of biofilm reactor for wastewater treatment. China Water and Wastewater, 2004, 17 (4): 5-8.

5 Li Jun, Peng Yongzhen, Yang Xiushan, Wang Baozhen, Yang Haiyan. Characteristics and mechanism of denitrification and phosphorus removal by sequential batch biofilm method. China Environmental Science 2004, 24 (2): 219 223.

6 Jiang Su, Zhou Jiwei, Guo Haiyan, Zhang Zhiyong. Integrated A / O biofilm treatment of domestic sewage. China Water and Wastewater, 2004, 20 (5): 56 58.

7 Bai Yu, Zhang Jie, Yan Lilong, Chen Shufang, Tong Yunan. Spatial and Temporal Distribution of Bacteria in Biological Filters for Advanced Wastewater Treatment. Urban Environment and Cities, 2004, 17 (4): 21-23.

8 Chen Bibo, Li Youming. Moving bed biofilm reactor and its significance for papermaking wastewater treatment. China Papermaking, 2004, 23 (8): 47 50.

9 Rong Hongwei, Lv Bingnan, Zhang Zihui. Experimental research on biological phosphorus removal by sequencing batch biofilm method. Journal of Xiangtan University of Mining and Technology, 2004, 19 (1): 88 91.

10 Bao Lining, Hong Guiyun, Huang Xianhuai. Analysis of denitrifying bacteria in the process of electrode biofilm denitrification. Journal of Anhui Institute of Architecture and Industry (Natural Science Edition), 2004, 12 (5): 1-4.

11 Zheng Fei, Zhu Wenting. New technology of biofilm methodbubble-free aerated membrane bioreactor. Industrial water and wastewater, 2004, 35 (3): 11 14.

12 Lu Xiaohui, Hu Longxing. Technology of nitrogen and phosphorus removal in moving bed biofilm reactor. Chemical Engineer, 2004, 108 (9): 20 22