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New technology for sewage treatment - aerated biological filter. For decades, in the field of sewage treatment, the activated sludge method is undoubtedly a widely used sewage biological treatment technology with good results. However, with the continuous progress of society, the expansion of urban scale and the increasing importance of human beings to the living environment, the shortcomings of the activated sludge method have become more and more prominent in front of people's eyes. 　　Huge land area The continuous expansion of the population has made cities congested, and land in many cities is scarce. Sewage treatment plants using the activated sludge method often require several hectares or even dozens of hectares of land, which has undoubtedly become a constraint. 　　The huge sewage treatment structure with harsh environment is exposed to the atmosphere over a large area and can easily produce odor pollution, which is intolerable to the surrounding residents. Therefore, more and more residents refuse to live near sewage treatment plants. 　　Unstable performance Because it is a suspended microbial micelle, the concentration of activated sludge is usually below 6000 mg/L. The external environment (temperature, pollutant concentration, etc.) can easily affect the treatment effect, and even cause the sludge to expand, worsening the quality of the treated water. 　　In the 1980s, a new sewage treatment technology developed to address the above problems was first used in France. This is the "submerged fixed biofilm aeration filter". French OTV company has nearly 20 years of engineering design, construction and operation experience in the field of submerged fixed biofilm aeration filters, and has built more than 100 sewage treatment plants with similar processes around the world. One of the processes is BIOSTYR(r) biological filter. 　　BIOSTYR(r) is an improved new generation of upflow aerated biological filter. It can be used for secondary treatment of sewage, and can also be used for advanced treatment of sewage that requires reuse and other requirements, and can meet high discharge water quality standards. The basic structure of the BIOSTYR(r) process is a submerged upflow biological filter. The filter material is spherical particles with a specific gravity less than 1 and floating in the water. We call it BIOSTYRENETM. 　　Each biofilter unit includes: 　　 * Water inlet pipe and water distribution channel at the bottom of the filter (can also be used to drain backwash water) ； 　　 * Two air pipes (tube holes), one for process aeration and one for gas backwashing ； Two pipelines are used for nitrification/denitrification reactions, and the same pipeline is used for aeration and backwashing during single nitrification reaction. ； 　　 * 3 to 3.5 meters of filter material layer, with a large number of microorganisms attached to the surface of the filter material ； 　　 * There is a concrete filter plate on the top of the filter to prevent the loss of filter material. ； 　　 * A filter head is installed on the filter plate for water discharge from the filter tank. The process principle can control the degree of nitrification reaction and denitrification reaction according to the different settings of the aeration pipe position, and the nitrification reaction or denitrification reaction can also be carried out separately. 　　The BIOSTYR biological filter with nitrification and denitrification functions has an aeration pipe located at a calculated position in the filter bed, which separates the filter bed into a lower anaerobic zone and an upper aerobic zone. It can remove all degradable pollutants, carbonaceous pollutants (COD and BOD), suspended solids (SS), ammonia nitrogen and nitrate (i.e. total nitrogen). The backwash gas pipe is located at the bottom of the filter. 　　For the usual nitrification reaction (which requires ammonia nitrogen), a perforated pipe at the bottom of the filter is shared during aeration and gas backwashing, so that the entire filter bed is in an aerobic state. It can remove most degradable pollutants, carbon-containing pollutants (COD and BOD), suspended solids (SS) and ammonia nitrogen. 　　Water distribution and intake: The water from primary treatment or secondary treatment is evenly distributed into the water inlet channels of each filter through the water distribution weir, and then flows by gravity into the water distribution channel at the bottom of the filter. An automatic valve is installed on the water inlet pipe or channel to stop the water inflow under certain circumstances (such as during backwashing). The sewage enters the entire filter through the water distribution channel at the bottom of the filter. These designs ensure uniform water distribution across the entire section of the filter. Different from the downward flow filter (if the specific gravity of the filter material is greater than 1), the water head of this filter ensures the uniform distribution of incoming water, so there is no need for a filter head (which is easy to clog) or water distribution pipe network at the bottom of the filter, and no screen is required before treatment. 　　filter material: BIOSTYRENETM filter material is a spherical filter material with small particle size and consistent shape. Its specific gravity is less than 1 and has a large specific surface area, which gives it the following characteristics: 　　 * The filter material has a large specific surface area, high purification capacity, and high processing load. ； 　　 * Good mechanical and physical and chemical properties, not easy to wear ； 　　 * The raw materials of the filter material come from domestic industrial raw materials, which can be produced and processed on-site at low cost. ； 　　 * The loss of filter material is very small and almost does not need to be replaced. 　　The filter material is used as a carrier of microorganisms, and a large number of microorganisms are attached to its huge surface area. Under the action of oxygen provided by the bottom aeration pipe, the carbon-containing pollutants (COD and BOD) in the sewage are degraded, and ammonia nitrogen is oxidized into nitro nitrogen. 　　In the case of nitrification/denitrification, the treated effluent needs to be refluxed. The reflux water and the raw water are mixed in the inlet channel and then enter the filter. The sewage first enters the anaerobic zone at the bottom of the filter bed, where the denitrification reaction takes place and the nitro-nitrogen in the reflux water is removed. ； It then enters the upper aerobic zone, where carbonaceous pollutants are decomposed and ammonia nitrogen is converted into nitro nitrogen. 　　Since the reaction mechanisms of nitrification and denitrification are greatly affected by the inlet water temperature, low inlet water temperature will significantly affect the pool capacity of the biochemical reaction. However, the BIOSTYR(r) filter has sufficient residence time (1 to 2 hours) and continuous influx of process air at 80 to 100°C, so the biochemical reaction is minimally affected by external climate conditions. ； At the same time, because the microorganisms in the filter are fixed on the carrier, unlike the activated sludge method, which is suspended in the water, the biomass per unit volume is extremely large, which improves the treatment efficiency. Due to the above two reasons, lower inlet water temperature has less impact on its biochemical reaction, and the BIOSTYR(r) filter can operate normally in the range of 8 to 30°C. 　　Finally, the direction of sewage flow through the filter bed is the direction of compressing the filter material, rather than the direction of expanding the filter material, which also strengthens the interception of suspended substances, eliminating the need for a sedimentation tank. 　　Filter treatment effluent: The floating filter material is blocked in the filter tank by the concrete cover plate. Many filter heads are installed on the cover plate to allow the treated effluent to flow out. Since these filter heads only contact the treated water, blockage is avoided. ； At the same time, since there is no filter material on these filter heads, they are easy to maintain. 　　Filter backwash: With the interception of suspended matter and the continuous growth of biofilm, the filter bed needs to be backwashed regularly, that is, gravity backwash and air backwash. The water after backwash is collected by the water collection ditch at the bottom of the filter (i.e., the inlet culvert) and discharged into a collection tank. Backwash water is a clear water layer of a certain height stored above the filter plate at the top of the filter. This clear water layer is connected in a group of filters. The height of the clear water layer is calculated so that the amount of stored water is sufficient for the backwash of the filter. Since backflushing is by gravity and in the opposite direction of normal filtration, a backflush pump is no longer required. 　　Periodic countercurrent backwashing removes excess biofilm and trapped suspended matter without passing it through the entire filter bed. The downward water flushing can flush the retained material out of the filter bed in the shortest route, and is the direction in which the retained material falls due to gravity, saving energy and being highly efficient. 　　The backwash process is as follows: 　　 * Close the water inlet valve of the filter and open the backwash drain valve at the bottom of the filter. ； 　　 * The clean water from the top of the filter flows down by gravity for pre-rinsing ； 　　 * Then it is supplemented by air backwash to carry out combined air and water backwash ； 　　 * Alternate flushing with air only and flushing with water only ； 　　 * Finally rinse with water only. 　　There are two types of backwash control procedures:: That is, time control (normally backwashing once every 24 hours) and pressure difference control (that is, automatic starting operation through the pressure difference between the upper and lower filter material layers). 　　Aeration of the filter: The process air and backwash air of each filter are supplied by the same blower, and the blower does not stop working. However, in nitrification/denitrification type filters, their gas distribution pipe networks are separated and switched by valves. ； In a single nitrification filter, process air and backwash air are distributed through the same air distribution pipe network, and the air supply in both modes is regulated by the regulating valve at the filter inlet. 　　Filter process performance: According to the different pollutants removed, BIOSTYR(r) filters can be divided into carbon removal type, nitrification type, nitrification/denitrification type and post-denitrification type. 　　Due to the huge and abundant biofilm attached to the filter material, the processing capacity of the BIOSTYR(r) filter * * Higher than activated sludge method. Main advantages 　　 * Since the BIOSTYR(r) process combines a filter and a bioreactor, a settling tank is no longer needed ； 　　 * It occupies a small area and is 1/4 to 1/5 of the conventional process, saving a lot of land acquisition and foundation treatment costs. ； 　　 * The pool capacity is small, and the amount of civil engineering work is 20% to 40% less than other processes. ； 　　 * All modular structure, easy to modify and expand, short construction period ； 　　 * The water coming out of the upper part is clean water, the filter head is not easy to be blocked, and it is easy to repair and replace. No need to drain the filter media in the filter tank ； 　　 * The factory area can be fully enclosed, no odor pollution, and good visual and landscape effects ； 　　 * There is no need for separate backwash water and backwash pumps, which reduces equipment investment and operating costs. ； 　　 * Perforated tube aeration saves equipment investment and maintenance costs and is highly efficient. Membrane aeration heads usually begin to lose their efficiency after two years of operation. ； 　　 * High degree of automation and few operators ； * Stable operation at low temperatures, little affected by temperature ； 　　 * Due to its continuous physical filtration ability, once a problem occurs in the biological reaction, the filter can still remove most of the suspended solids ； And it only takes a few days to restore biological treatment capacity, while the activated sludge method takes several weeks to restore ； 　　 * The process operation is flexible, and the functions of nitrification and denitrification can be completed simultaneously in the same filter tank.

Generally speaking, aerated biological filters have the following characteristics: 　　(1) Use granular fillers as biological carriers, such as ceramsite, coke, quartz sand, activated carbon, etc. 　　(2) Different from general biological filters and biological filter towers, aeration is required when removing BOD and ammonia nitrogen. 　　(3) High hydraulic load, high volume load and high biofilm activity. 　　(4) It has the dual functions of biological oxidative degradation and interception of SS. There is no need to set up a secondary sedimentation tank after the biological treatment unit. 　　(5) Regular backwashing is required to clean the SS trapped in the filter and renew the biofilm. Let me show you a picture and think about it yourself. This post was finally edited by libj520 on 2009-3-18 12:51 ]

Biological Aerated Filter (BAF) is one of the most advanced sewage treatment processes in the world today, and is called the Third-Generation Biofilter. So far, there are thousands of them around the world * * The small BAF sewage treatment plant. In addition to utilizing the oxidative degradation characteristics of biofilms, this process also takes advantage of the bioflocculation adsorption and biohydrolysis effects of active bioflocs, making it a reactor that truly combines the advantages of both the activated sludge method and the biofilm method. Compared with traditional processes, aerated biological filters are a qualitative leap forward in terms of effluent quality, floor space, and processing capacity. Core filter technology: The core of the aerated biological filter is the filter material. The filter material developed by our company was identified by the expert group as "reaching the international advanced level and is an ideal filter material for aerated biological filters. It solves the core problem for the application of aerated biological filters in sewage treatment in my country." On this basis, our company has completely localized, engineered and equipped the aerated biological filter process, which has greatly reduced infrastructure investment and operating costs, making it the most suitable sewage treatment process for my country's national conditions and a new milestone in the history of my country's sewage treatment. Water and gas distribution system: The water and gas distribution system includes water and gas distribution during normal operation (filtration) and water and gas distribution during backwashing (generally considered as a unified system during design). Its main function is to evenly distribute the water (including water to be treated and backwash water) and air (including normal aeration and backwash air) entering the filter on the entire cross-section of the filter. The technical key to the water and air distribution system is to ensure uniform water and air distribution, and to absolutely avoid clogging. Based on many years of BAF experience, our company has fully absorbed domestic and foreign experience in water and gas distribution and developed a water and gas distribution system with independent intellectual property rights. It mainly has the following 2 innovation points: Solved the problem of uniform air distribution with small air volume ； Solved the clogging problem. Automatic control system: The automatic control system is also a key factor that BAF needs to consider. Backwashing is a necessary step to maintain normal operation of BAF. Through backwashing, the biofilm is renewed, the head loss is reduced, and the BAF returns to its original state. The automatic control system determines the time of backwashing, and determines the method and intensity of backwashing based on the condition of the filter. Poor backwash control will not only cause a lot of inconvenience to the operation of the BAF, but also affect the normal operation of the BAF.