污水处理生物膜技术(英文)

Membrane technology in water treatment
At present, there are three main kinds of processing method in wastewater treatment process which are physical method, biological method and chemical method. In the biological methods there is a process called biological membrane method. It will become the main technology of sewage treatment in the future. Bjame (2003) agreed that membrane technology is widely accepted as a means of producing various qualities of water from surface water, well water, brackish water and seawater. He also think that membrane technology is also used in industrial processes and in industrial wastewater treatment, and lately membrane technology has moved into the area of treating secondary and tertiary municipal wastewater and oil field produced water. It has been pointed out that membrane processes could be a solution for an advanced physical treatment of water for drinking purposes as well as for agroindustrial sectors (Aldo et al., 2009).
Biological membrane method is the use of microorganisms (biofilm) which attached growth in some solid surfaces for organic wastewater treatment. That is commonly used in biological activated sludge and biological membrane method. Some of the advantages of biofilm method is what other process does not have. Mark and John (1995) have pointed that membrane treatment is gaining a reputation for consistent and stable pared with the activated sludge process, biological membrane method has the following characteristics. Firstly, biofilm has strong adaptability on the change of water yield and water quality, and its operation stability is good. Secondly, it is not going to happen the sludge expansion, and more convenient operation management. Thirdly, due to the microbial fixation on solid surface, even to slow proliferation microbes can grow. Finally, it has less quantity of sludge.
Using the biofilm process to deal with the sewage can overcome every demerits of activated sludge process well.It has a good ability to inflow and it can apply to sewage disposal process in various industries. Therefore, it has a vast potential for future development. Biological membrane method belongs to the approch of aerobic biological treatment. It is an approch which purified the sewage by putting sewage through the membrane, formed by the growth and reproduction on the carrier packing of aerobic microorganisms, protozoa, and metazoan, etc., to adsorb and degrade organics. Depending on different devices, biofilm process can be devided into four kinds.
The first method is called biological contact oxidation method. Actually, biological contact oxidation process is a submerged aeration biological filter. It is a comprehensive sewage treatment process which combines biological filter with aeration tank. It also has the merits of the two processing methods at the same time—high volume load and strong resistance to the impact load. By this method, the oxygen supply is very sufficient and the update speed of membrane is very fast, greatly improved the biofilm activity and enhanced its ability to resist shock. And the use of biological membrane can attach most of the activated sludge to the carrier that reduces the sludge production and back flow, and lowers the mechanical wear and tear. However, the filter material of bio-contact oxidation process blocks up easily which increases the difficulty of management.
The second method is called Biological fluidized bed. Biological fluidized bed technology is the sewage purification technology which use of gas or liquid to fluidize the solid particle filter material which microorganisms attaching to. Biological fluidized bed method makes full use of the microbiological characteristics of different stages of life activities. According to the characteristics of its microbial growth, processing phase is divided into three stages: fixed bed, fluidized bed, and the liquid conveying stage. Biological
fluidized bed has three major advantages. Firstly, it has high volume load and strong resistance to the impact. As the carrier of biological fluidized bed uses small size of solid particles, and the carrier into the fluidization, so biological fluidized bed surface area per unit volume is much larger than that of the other biological membrane method and fighting capacity is higher than other biological treatment. Secondly, the activity of microorganisms is stronger. The biofilm thickness becomes thin and uniform due to the biological particles constantly mutual collision and friction. For the same kind of sewage, under the condition of equal treatment, biological membrane is not only fast reaction rate and respiration rate is very fast, so the activity of microorganisms is stronger. Lastly, its purification effect is good. Due to carrier particles has been in a violent motion, which leads to the interface in constantly updated. This is not only beneficial to microbial adsorption and degradation of pollutants, but also can speed up biochemical reaction rate, and then make the purification effect was improved. But the microbial particles are in the flow state in the equipment, so the equipment wears and tears seriously, and carrier particles wear themselves too. In addition, the biological fluidized bed has congestion and loss of biological particles which have not effective solution. There is no effective solution to solve the congestion and loss of biological particles of biological fluidized bed. This to a certain extent restricts the promotion of biological fluidized bed. To some extent, it’s a limitation to the promotion of biological fluidized bed.
The third method is called Moving bed biofilm reactor (MBBR). Moving bed biofilm is a new kind of biofilm wastewater treatment process which between biological contact oxidation and biological fluidized bed method. It is very good solving the filter material jam problem in biological contact oxidation method, but also overcomes the drawback of three-phase separation difficulties in biological fluidized bed. So it has good processing effect. Moving bed biofilm reactor use density close to water of granular material as biofilm carrier,
access to the reactor in the continuous sewage aeration at the same time, creates a good mix of contact conditions, using the biological activity of microorganisms for the purpose of sewage treatment. Moving bed biofilm reactor characteristics with high microorganism concentration, food chain length, flow and the concentration change of water has a strong ability to adapt. At the same time, as a result of chosen biofilm carrier density and close to the water, reducing the fluidization process of energy consumption, increase the mass transfer rate, and not easy to happen jams, significantly less than the quantity of sludge activated sludge process. In addition, because this method structure tightly, so has the characteristics of less land, low energy consumption, significantly lower the cost of investment and operation maintenance. The moving bed biofilm reactor has been widely used in the process of sewage treatment because of above advantages.
The last method called bio-filter process. The basic flow of Bio-filter process consists of primary settling tank, biofilter and secondary sedimentation tank. Biofilter itself is mainly devided into two kinds. One is biological filter of high load. It’s advantage is good treatment effect. Its removal rate can reach more than 90%. Its water can fall below 25 mg/L and the effluent water quality is very stable. However, its disadvantage is occupying too large area, easier to jam, and has a bad impact on environment. The other is tower biological filter. Compared with traditional biofilter, it has the merits of high load, layering obviously, small possibility of blocking, and occupying less area.
The above four processes each have each advantages, they will be widely used in the sewage wastewater. Chen (2010) claimed that the prospect of biofilm process’application in urban sewage treatment is very broad. It will become a main technology of urban sewage treatment as well as activated sludge process. For instance, there are only 160 seats urban sewage treatment plants in China now, and the sewage treatment rate is only 10%. So,
it needs to build a large number of urban sewage treatment plants, however, the urban construction funds are so far to satisfy the demand. There are two ways to raise money: one is broaden the sources of funding, the other one is to adopt new technology to reduce the project cost to save money. The two biological membrane technologies are obviously can sharply reduce the engineering cost of new technology, and so is the technology urban sewage treatment required for. This shows that the membrane technology has great market value。

Also this biofilm processes have some technical problems needs to research and improve. Biofilm process has less than 20 years of research so far, and the project constructed is rare. Thus, it must be lots of places in need of improvement. There are four main problems need to solve. First of all, no matter TF/SC technology or BAF technology, the study of the theory is not enough. If there is some development on the theoretical research, it is bound to push biofilm process to a great development. Secondly, there is some need to study the optimization of process design, such as each unit’s processing degree of optimization of TF/SC technology, the optimization of relationship between batching load and backwash of BAF technology, etc. Thirdly, need to study TF/SC and BAF applicable of lightweight, high strength, low price and long service life of filter material. It is the key to the two kinds of process problems. Lastly, BAF has a large filter cloth water gas uniformity problem; it is the relationship between the project cost, and also the technology of the suitable size.
So the sewage treatment which use of biological membrane method, can very good to overcome the activated sludge process in all kinds of faults. And it to into water has good ability to adapt, can be applied to a variety of industry wastewater treatment process. So it has wide development prospects. Membrane bioreactor technology is a promising method which is used for
wastewater treatment, and the reason is that it can produce high quality of discharge water which can satisfy the quality requirements (Aileen, 2007).
References:
Bjame, N. (2003) ‘Developments in membrane techno logy for water treatment’. Journal of Desalination [0011-9164] 153(1), 355 -360
Mark, D and John, E. (1995) ‘Membrane treatment is versatile - A single treatment facility producing boiler feed, food processing water, and drinking water ’. Journal of Desalination, 313-319
Aldo, B et al. (2009) ‘Membrane technologies for water treatment and agroindustrial sectors’. Journal of Comptes rendus Chimie 12(8), 882-888 Gao. (2011) ‘Membrane fouling control in ultrafiltration technology for drinking water producti on: A review’. Journal of Desalination 272(1), 1-8
Zhang. (2012) ‘Membrane biofouling and scaling in forward osmosis membrane bioreactor’. Journal of Membrane Science 403-404, 8-14
Chen, L., Tong, J., and Jia, Y. (2010) Science&Engineering. Fuzhou: Fujian Agric & Forestry University.
Thomas, W. (2010) ‘MBR design and operation using MPE-technology (Membrane Performance Enhancer)’. Journal of Desalination 250(2), 723-728 Liu, Q et al. (2010) ‘Performance of a hybrid membrane bioreactor in municipal wastewater treatment’. Journal of Desalination 258(1), 143-147。