Inorganic phosphorus recovery method based on biological phosphorus removal filter tank for effluent of traditional secondary sedimentation tank

Abstract

The invention discloses an inorganic phosphorus recovery method for effluent of a traditional secondary sedimentation tank depending on a biological phosphorus removal filter tank, and belongs to the fields of pollution control, low carbon and resource regeneration. The device consists of a biological phosphorus removal treatment unit, a phosphorus enrichment and recovery treatment unit and a residual sludge phosphorus recovery unit. The biological phosphorus removal treatment unit comprises a backwashing water tank (2), a backwashing water collecting tank (3), a first biological phosphorus removal filter tank (4) and a second biological phosphorus removal filter tank (5); the phosphorus enrichment and recovery treatment unit comprises a phosphorus-rich water storage pool (6) and a chemical phosphorus recovery pool (7); and the residual sludge phosphorus recovery unit comprises an anaerobic phosphorus release tank (8), a sludge concentration tank (9) and a sludge dewatering workshop (10). Through establishment of a new phosphorus removal process method, the characteristic that phosphorus-accumulating bacteria release phosphorus in an anaerobic state and absorb phosphorus in an aerobic condition is fully utilized, ineffective circulation of phosphorus in the biological sewage treatment process is blocked, phosphorus in sewage is efficiently removed and collected to a phosphorus-rich water storage pool, and recycling of phosphorus in sewage is facilitated.

Description

Technical Field

[0001] This invention belongs to the fields of water pollution control, low carbon and resource regeneration, and specifically relates to an inorganic phosphorus recovery technology for the effluent from traditional secondary sedimentation tanks that relies on biological phosphorus removal filters. Background Technology

[0002] Phosphorus is one of the essential and irreplaceable mineral elements for life and human nutrition. In nature, phosphorus mainly exists in the form of phosphates and guano rocks. After being mined by humans or eroded by nature, it flows into the sea with surface runoff and is deposited in the sedimentary layers of the deep sea. Therefore, the biochemical cycle of phosphorus is completely different from that of other elements such as nitrogen. It is a unidirectional flow in the biosphere and is difficult to regenerate, thus it is regarded as a non-renewable and scarce resource.

[0003] Domestic sewage contains a large amount of phosphorus. Every year, my country's urban sewage discharges as much as 290,000 tons of phosphorus, equivalent to 5.5% of the country's phosphate fertilizer consumption. For a long time, the main purpose of phosphorus removal in domestic sewage treatment has been to control eutrophication of the discharged water bodies. Almost all phosphorus removal has been achieved through the discharge of excess sludge, resulting in complete mixing of the removed phosphorus with the sludge. In recent years, with a deeper understanding of the non-renewable nature of phosphorus resources, European countries have begun to focus on phosphorus recovery and utilization. Countries such as Germany, Austria, Poland, and Finland mainly use the technology of drying and incinerating phosphorus-containing excess sludge, recovering phosphorus through the treatment of inorganic ash. In my country, although phosphorus recovery has been advocated in the field of sewage treatment and related research has begun, its practical engineering application is still not widespread. Current research shows that core technologies have not yet effectively separated phosphorus from excess sludge. This may lead to the recovery of phosphorus from being contaminated by heavy metals and other harmful substances in the excess sludge during future phosphorus recovery processes, thus negatively impacting the environment and soil.

[0004] Phosphorus removal in wastewater treatment primarily relies on two techniques: biological and inorganic chemical methods. Biological phosphorus removal utilizes the characteristics of polyphosphate-accumulating bacteria (PACs). First, under anaerobic conditions, PACs decompose stored polyphosphates to produce ATP. This ATP then facilitates the active transport of volatile fatty acids from the liquid phase into the cells, synthesizing PHA, while simultaneously releasing orthophosphates. Second, under aerobic conditions, PACs decompose PHA to produce ATP, excessively absorbing orthophosphates from the liquid phase and forming even more polyphosphates within their cells. Through this difference between release and absorption, PACs effectively remove phosphorus. However, the biological phosphorus removal process is complex, requiring alternating anaerobic and aerobic reactions of sludge. In traditional wastewater treatment processes, the conflicting sludge age requirements of PACs and nitrifying bacteria mean that PACs cannot be promptly discharged from the system after phosphorus removal. With sludge recirculation, a significant amount of ineffective circulation occurs, making it difficult to maintain a low phosphorus concentration in the final treated water. Therefore, phosphorus removal in wastewater treatment plants still requires the assistance of chemical phosphorus removal. Chemical phosphorus removal technology utilizes chemical agents to react with inorganic phosphorus in water, forming insoluble phosphorus-containing inorganic compounds. These insoluble substances settle together with activated sludge in a sedimentation tank, thereby removing phosphorus from the water. Regardless of whether biological or chemical phosphorus removal is used, the phosphorus-containing sludge obtained is ultimately mixed with excess sludge and treated through a waste sludge discharge system. This treatment method results in all the removed phosphorus being mixed in with the sludge, making it difficult to recover and utilize separately. Therefore, although these methods can effectively remove phosphorus from wastewater, phosphorus recovery and utilization still face certain challenges.

[0005] In the process of biological wastewater treatment using the activated sludge process, precipitated sludge is generated in the treatment system. A portion of this sludge is concentrated, dewatered, and transported off-site as excess sludge, while the majority is recycled back to the influent of the biological treatment system. This recycling maintains the biomass within the system, ensuring the continued presence and function of various functional bacteria. The recycled sludge contains not only various functional bacteria but also those involved in biological phosphorus removal, particularly polyphosphate-accumulating bacteria (PABs). When these PPAs, containing large amounts of polyphosphate, are recycled to the anaerobic process stage, the polyphosphates they bring participate in further biological processes. Simultaneously, a large amount of phosphorus-containing sludge formed by chemical precipitation is also recycled back into the treatment system. This results in a significant ineffective cycle of phosphorus within the system.

[0006] Theoretically, there is a ratio of approximately 1:1.25 between phosphorus release by polyphosphate-accumulating bacteria (PABs) under anaerobic conditions and excessive phosphorus absorption under aerobic conditions. This means that for every unit of phosphorus that circulates from inside the cell to outside, 0.25 units of phosphorus are absorbed in excess, requiring the consumption of approximately 5 units of organic carbon source (the ratio of phosphorus removal to organic carbon consumption is 1:20). This characteristic of PPBs results in an ineffective cycle of 1 unit of phosphorus in existing biological phosphorus removal systems, thus consuming a large amount of organic carbon source. However, if, through the addition of organic carbon source and an anaerobic process, PPBs complete the release of polyphosphates within their cells, the resulting high-phosphorus water can be collected and removed from the anaerobic phosphorus release reactor. Then, the PPBs, now possessing a phosphorus uptake capacity of 1.25 units, can directly treat the effluent from the secondary sedimentation tank. This would allow the PPBs to utilize their full phosphorus uptake capacity for phosphorus removal from the secondary sedimentation tank effluent, thereby blocking the ineffective phosphorus absorption cycle and simultaneously separating phosphorus from the precipitated activated sludge. If the removed high-phosphorus water is repeatedly refluxed into the polyphosphate-accumulating bacteria (PAC) phosphorus release reactor, repeatedly receiving phosphorus released by PACs, it will form high-phosphorus water with an even higher phosphorus concentration. At this point, chemical phosphorus removal agents are used to recover the inorganic phosphorus from the high-phosphorus water. This method effectively avoids the ineffective recycling of 1 unit of phosphorus and saves the organic carbon source associated with 1 unit of phosphorus recycling, theoretically increasing the effective phosphorus uptake capacity by 4 times. Simultaneously, during the chemical precipitation of phosphorus in the high-phosphorus water, the high phosphorus concentration significantly improves the efficiency of the chemical phosphorus removal reaction, resulting in a high-purity recovered phosphorus product.

[0007] This invention, combined with existing wastewater treatment processes, establishes a new phosphorus removal process that combines biological and chemical phosphorus removal. This allows for the saving of organic carbon source additions while achieving relatively "pure" recovery of chemically precipitated phosphorus, creating better conditions for the further utilization of phosphorus recovered from wastewater treatment.

[0008] Following the above idea, instead of considering phosphorus removal in the existing activated sludge process main flow, a separate phosphorus removal stage is set up after the secondary sedimentation tank. This arrangement allows the sludge age of the main flow to fully meet the needs of ammonia nitrogen oxidizing bacteria (i.e., nitrifying bacteria). The main advantage of this adjustment is that the sludge age of the main flow can be extended, which is conducive to the growth and accumulation of nitrifying bacteria. At the same time, due to the reduction of polyphosphate-accumulating bacteria in the main flow, organic matter in the raw water can participate more fully in the denitrification process, thereby significantly reducing the total nitrogen content in the secondary sedimentation tank effluent, especially the ammonia nitrogen content. Summary of the Invention

[0009] This invention innovatively proposes a novel treatment scheme for phosphorus removal from the effluent of the secondary sedimentation tank in traditional sewage treatment plants.

[0010] The phosphorus removal device or system used consists of a biological phosphorus removal treatment unit, a phosphorus enrichment and recovery treatment unit, and a residual sludge phosphorus recovery unit. The biological phosphorus removal treatment unit includes: a backwash water tank (2), a backwash water collection tank (3), a first biological phosphorus removal filter (4), and a second biological phosphorus removal filter (5); the phosphorus enrichment and recovery treatment unit includes: a phosphorus-rich water storage tank (6) and a chemical phosphorus recovery tank (7); the residual sludge phosphorus recovery unit includes: an anaerobic phosphorus release tank (8), a sludge thickening tank (9), and a sludge dewatering workshop (10).

[0011] The outlet of the secondary sedimentation tank (1) is divided into multiple branches. One branch is connected to the backwash water tank (2) via a valve, and the others are connected in parallel to multiple biological phosphorus removal filters via valves. There are at least two biological phosphorus removal filters: the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5). The effluent from each biological phosphorus removal filter is connected to the phosphorus-rich water storage tank (6) via a valve. The phosphorus-rich water storage tank (6) is connected to the chemical phosphorus recovery tank (7). The phosphorus-rich water storage tank (6) is connected to the static mixer (61) via a pipeline through the phosphorus-rich water pump (63). The static mixer (61) Each of the following is connected to a biological phosphorus removal filter via a valve: a phosphorus-rich water storage tank (6) is used to return the phosphorus-rich water from the storage tank (6) back into the corresponding biological phosphorus removal filter; an organic carbon source dosing pipe (62) is connected to the pipeline between the phosphorus-rich water pump (63) and the static mixer (61); the blower (59) has multiple outlets, each connected to the bottom of the corresponding biological phosphorus removal filter via a valve for backwashing; the blower (59) outlets are also connected to the middle or upper part of each corresponding biological phosphorus removal filter via valves for aeration; the backwash water tank... (2) The backwash water pump (21) is then connected to each biological phosphorus removal filter via valves for backwashing each biological phosphorus removal filter; the bottom of the chemical phosphorus recovery tank (7) is conical, and the chemical phosphorus recovery tank (7) is equipped with a phosphorus removal chemical dosing pipe (71), a stirrer (72), and a screw elevator (73). The screw elevator (73) extends outward and upward from the bottom of the chemical phosphorus recovery tank (7), and the upper end of the screw elevator (73) is located outside the chemical phosphorus recovery tank (7). The upper end of the screw elevator (73) collects phosphorus recovery products through the downward extending phosphorus recovery products. Pipe (76) is connected to phosphorus recovery product tank (74); each biological phosphorus removal filter is connected to backwash water collection tank (3) via valve; the bottom of secondary sedimentation tank (1) and the bottom of backwash water collection tank (3) are connected to anaerobic phosphorus release tank (8), which is equipped with organic carbon source dosing pipe (81) and a stirrer; anaerobic phosphorus release tank (8) is connected to sludge thickening tank (9), which is connected to sludge dewatering workshop (10); sludge thickening tank (9) and sludge dewatering workshop (10) are connected to chemical phosphorus recovery tank (7).

[0012] Furthermore, as follows:

[0013] The backwash water tank (2) stores part of the effluent from the secondary sedimentation tank (1). During the backwashing of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), the backwash water is pumped into the first biological phosphorus removal filter (4) or / and the second biological phosphorus removal filter (5) by the backwash water pump (21).

[0014] Each biological phosphorus removal filter is equipped with a drain pipe, which has a drain valve.

[0015] The backwash water collection tank (3) is used to collect and treat the sludge-water mixture after backwashing of each biological phosphorus removal filter. The supernatant after sedimentation is sent to the front-end treatment system of the sewage treatment plant, while the backwash sludge after sedimentation enters the anaerobic phosphorus release tank (8).

[0016] The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) work in parallel and alternately. There are at least two biological phosphorus removal filters, or the number can be increased appropriately according to actual needs to adapt to different application scenarios. Multiple biological phosphorus removal filters are set in parallel and connected to the effluent of the secondary sedimentation tank (1). Each biological phosphorus removal filter is the same as the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), with an influent oxygenation system, a backwashing system and an organic carbon source addition system. The influent oxygenation system includes a blower (59). The backwashing system includes: a backwashing water tank (2) connected to the biological phosphorus removal filter via a backwashing water pump (21), and the backwashed water enters the backwashing water collection tank (3). The cleaning process is carried out by a blower (59). The organic carbon source addition system includes: a phosphorus-rich water storage tank (6) connected to the biological phosphorus removal filter via a static mixer (61) and a phosphorus-rich water pump (63), and an organic carbon source addition pipe (62) is provided in the connected pipeline.

[0017] The filter layer inside a biological phosphorus removal filter includes a biofilm carrier and filter media. The biofilm carrier can be selected from materials that can support polyphosphate-accumulating bacteria to form a biofilm, such as polyurethane packing, sponge packing, fiber packing, curtain packing, and elastic three-dimensional packing. The filter media can be selected from inorganic mineral materials with filtration function, or organic or macromolecular filter materials such as activated carbon. The biofilm carrier and filter media are combined to form an organic combination of biofilm reaction and filtration function. Alternatively, the biological phosphorus removal filter can directly utilize materials that can directly form biological filtration function, such as granular activated carbon, fiber balls, fiber bundle filter media, and comet-shaped fiber filter media, to establish the biological phosphorus removal filter.

[0018] The method for continuous recovery of inorganic phosphorus using the above-mentioned apparatus includes the following steps:

[0019] (1) Biological phosphorus removal section

[0020] The effluent from the secondary sedimentation tank (1) contains almost no activated sludge after the main process sludge-water separation is completed. The effluent from the secondary sedimentation tank (1) is effluent that has not undergone phosphorus removal treatment. In continuous flow modeAfter entering the biological phosphorus removal filter, First pass The aeration and oxygenation zone then enters the filter layer. At this time, the polyphosphate-accumulating bacteria in the filter layer have completed the phosphorus release process, and the phosphorus removal filter is in an empty state. Therefore, the effluent from the phosphorus-containing secondary sedimentation tank (1) flows into the filter layer of the first biological phosphorus removal filter (4). Under continuous aeration and oxygenation, the polyphosphate-accumulating bacteria continuously absorb the phosphorus in the water and complete the biological phosphorus removal and sewage filtration process in the filter layer. As the influent continues to flow in and filter, the polyphosphate-accumulating bacteria in the filter layer will continuously absorb phosphorus and reach a "saturated state". At this time, aeration is stopped, the influent from the secondary sedimentation tank (1) to the first biological phosphorus removal filter (4) is closed, and the influent from the secondary sedimentation tank (1) to the second biological phosphorus removal filter (5) is opened to adjust the influent from the secondary sedimentation tank (1) to the second biological phosphorus removal filter (5). At this time, the water in the first biological phosphorus removal filter (4), which has reached phosphorus saturation, is drained and then injected into the phosphorus-rich water storage tank (6). During the injection of phosphorus-rich water, an organic carbon source is added at the same time. The first biological phosphorus removal filter (4) is in an anaerobic state. In the anaerobic state, polyphosphate-accumulating bacteria in the first biological phosphorus removal filter (4) complete phosphorus release, making the phosphorus-rich water entering the first biological phosphorus removal filter (4) into phosphorus-rich water with a relatively higher phosphorus concentration. This continues until the polyphosphate-accumulating bacteria in the first biological phosphorus removal filter (4) complete the anaerobic phosphorus release and form an empty tank state again. The phosphorus-rich water with a relatively higher phosphorus concentration in the first biological phosphorus removal filter (4) is then discharged into the phosphorus-rich water storage tank (6) for storage, completing one biological phosphorus removal process. The first biological phosphorus removal filter (4) is then ready to enter the next round of biological phosphorus removal process by entering water from the secondary sedimentation tank (1). The biological phosphorus removal process begins when the water in the secondary sedimentation tank (1) is adjusted to enter the second biological phosphorus removal filter (5) by opening the secondary sedimentation tank (1). The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) undergo an alternating biological phosphorus removal process.

[0021] The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) are carried out in an alternating biological phosphorus removal process. Each time, the phosphorus-rich water from the phosphorus-rich water storage tank (6) enters the corresponding first biological phosphorus removal filter (4) or second biological phosphorus removal filter (5) and then returns to the phosphorus-rich water storage tank (6) with a relatively higher phosphorus concentration. As the biological phosphorus removal process is carried out multiple times, the phosphorus concentration of the phosphorus-rich water in the phosphorus-rich water storage tank (6) accumulates and superimposes.

[0022] During the alternating biological phosphorus removal process, as polyphosphate-accumulating bacteria continue to release phosphorus anaerobically and absorb phosphorus aerobicly, the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) work alternately. The polyphosphate-accumulating bacteria in the first biological phosphorus removal filter (4) or the second biological phosphorus removal filter (5) will continue to grow and multiply. When their number reaches a certain level, it is necessary to backwash the filter layer to remove excess polyphosphate-accumulating bacteria. The backwashing adopts the form of combined air and water backwashing. The backwash water is the effluent from the secondary sedimentation tank (1) stored in the backwash water tank (2). The air source is provided by the blower (59). The backwash mud-water mixture formed during the backwashing process is collected in the backwash water collection tank (3).

[0023] (2) Phosphorus recovery section

[0024] The phosphorus-rich water collected in the phosphorus-rich water storage tank (6) will gradually accumulate and increase in phosphorus concentration after multiple biological phosphorus removal processes. When the phosphorus concentration in the phosphorus-rich water reaches a predetermined level (e.g., 200 mg / L), it is introduced into the chemical phosphorus recovery tank (7). In the chemical phosphorus recovery tank (7), chemical phosphorus removal agent is added through the phosphorus removal chemical agent dosing pipe (71), and a stirrer (72) is used to stir it thoroughly to promote the chemical removal reaction of phosphorus. After the reaction is completed, the stirring is stopped and the precipitate is allowed to settle naturally. The precipitated chemical phosphorus precipitate is cleaned and separated by a screw conveyor (73) to obtain "pure" recovered phosphorus. These phosphorus recovery products will be stored in the phosphorus recovery product collection tank (74). At the same time, the remaining supernatant in the chemical phosphorus recovery tank (7) is returned to the secondary sedimentation tank (1) for sewage treatment.

[0025] (3) Phosphorus recovery from excess sludge

[0026] In the main process of wastewater treatment, the excess sludge generated in the secondary sedimentation tank (1) and the backwash sludge generated in the backwash water collection tank (3) are transported together to the anaerobic phosphorus release tank (8). In the anaerobic phosphorus release tank (8), organic carbon source is added to the anaerobic phosphorus release tank (8) through the organic carbon source addition pipe (81) and stirred thoroughly to fully release the phosphorus in the sludge. After the release is completed, the sludge is discharged to the excess sludge thickening tank (9) for thickening. The thickened sludge is transported to the sludge dewatering workshop (10) for dewatering. The dewatered sludge is transported off-site for treatment. The supernatant obtained from the excess sludge thickening tank (9) and the sludge dewatering liquid obtained from the sludge dewatering workshop (10) will flow together into the chemical phosphorus recovery tank (7) for further treatment of chemical phosphorus recovery.

[0027] Furthermore, regarding the phenomenon of polyphosphate-accumulating bacteria in the filter layer continuously absorbing phosphorus until reaching a "saturation state," the "saturation state" can be determined in advance through experiments by measuring the corresponding flow rate and aeration rate to pinpoint the point at which the effluent phosphorus concentration increases. During the entire system's operation, the optimal operating conditions should be determined based on seasonal variations in the phosphorus concentration of the secondary sedimentation tank effluent. The determination of the phosphorus concentration in the dephosphorized effluent should be based on the downstream discharge water conditions and the local drainage standards.

[0028] Furthermore, under anaerobic conditions, the dissolved oxygen (DO) should be controlled below 0.2 mg / L, while under aerobic conditions, the DO should be approximately 2-4 mg / L. The hydraulic retention time for both anaerobic and aerobic conditions should be no less than 40 minutes.

[0029] During backwashing of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), the water required for backwashing is supplied by the backwash water tank (2), and the backwashing intensity is <8 L / (m). 2 The air required for backwashing is provided by a fan (59), with an air supply intensity of 10~15 L / (m). 2 ·s).

[0030] The chemical phosphorus recovery tank (7) is equipped with a chemical reagent dosing pipe (71), a stirrer (72), a screw conveyor (73), and a phosphorus recovery product collection tank (74). The chemical reagents added through the chemical reagent dosing pipe (71) can be calcium salts, iron salts, magnesium salts, aluminum salts, etc., with calcium salts being preferred. During the phosphorus recovery reaction in the chemical phosphorus recovery tank (7), the pH should be controlled within the range of 8 to 11, the reaction time should be no less than 10 minutes, and the sedimentation time should be no less than 30 minutes.

[0031] The sludge thickening tank (9) should have a sludge moisture content of no more than 97% after thickening, and the sludge should be introduced into the sludge dewatering workshop (10). The dewatered water should be introduced into the chemical phosphorus recovery tank (7) for phosphorus recovery. The hydraulic retention time in the sludge thickening tank (9) is 10~16h, and the effective water depth is generally 4m.

[0032] The sludge dewatering workshop (10) dewaters the concentrated sludge. The water content of the dewatered sludge is generally 60%~80%, which facilitates the next step of sludge transportation and disposal. The dewatered sludge liquid is fed into the chemical phosphorus recovery tank (7) for phosphorus recovery.

[0033] The specific advantages of this invention are reflected in the following aspects:

[0034] 1. This system makes full use of the characteristics of polyphosphate-accumulating bacteria to release phosphorus under anaerobic conditions and absorb phosphorus under aerobic conditions, reducing the ineffective circulation of phosphorus in the sewage treatment process, efficiently removing phosphorus from sewage, and collecting it into a phosphorus-rich water storage tank for easy recovery and utilization of phosphorus in sewage.

[0035] 2. During the phosphorus recovery process, no heavy metals or other harmful substances are released. The high-phosphorus water contains only "pure" inorganic phosphorus, and the high purity of the phosphorus recovery product is beneficial for further utilization.

[0036] 3. By using high-concentration phosphorus-containing water for chemical treatment, the dosage of chemical phosphorus removal agents can be significantly reduced, by 46% to 65%. Simultaneously, more than 70% of the organic carbon source required for phosphorus removal can be saved, thereby substantially reducing the cost of agents and external carbon sources in the operating process.

[0037] 4. Since the sludge age of the main process does not need to consider the timely sludge discharge required for phosphorus removal (short sludge age), the sludge age of part of the main process can be increased, thereby improving the ammonia nitrogen oxidation performance of the main process, while also increasing the supply and utilization of raw water organic matter for denitrification and nitrogen removal.

[0038] 5. The recovered inorganic phosphorus has a relatively high purity.

[0039] In summary, this system not only optimizes biological treatment technically, but also brings significant energy-saving, emission-reduction, and cost-reduction benefits economically. Attached Figure Description

[0040] Figure 1This is a schematic diagram of the process for inorganic phosphorus recovery technology based on biological phosphorus removal filters in the effluent of traditional secondary sedimentation tanks, according to the present invention. In the diagram, 1-secondary sedimentation tank, 2-backwash water tank, 3-backwash water collection tank, 4-biological phosphorus removal filter, 5-biological phosphorus removal filter, 6-phosphorus-rich water storage tank, 7-chemical phosphorus recovery tank, 8-anaerobic phosphorus release tank, 9-sludge thickening tank, 10-sludge dewatering workshop, 11-secondary sedimentation tank inlet pipe, 12-secondary sedimentation tank sludge return pipe, 13-secondary sedimentation tank excess sludge discharge pipe, 14-secondary sedimentation tank effluent pipe, 21-backwash water pump, 22-backwash water 23 - Backwash water tank inlet pipe; 31 - Backwash water collection tank inlet pipe; 32 - Backwash water collection tank supernatant outlet pipe; 33 - Backwash water collection tank sludge discharge pipe; 41 - Biological phosphorus removal filter inlet pipe; 42 - Biological phosphorus removal filter backwash water outlet pipe; 43 - Biological phosphorus removal filter backwash inlet pipe; 44 - Biological phosphorus removal filter backwash air supply pipe; 45 - Biological phosphorus removal filter phosphorus-rich water outlet pipe; 46 - Biological phosphorus removal filter outlet pipe; 47 - Biological phosphorus removal filter phosphorus-rich water inlet pipe; 48 - Biological phosphorus removal filter supernatant oxygenation pipe; 5 1-Inlet pipe of biological phosphorus removal filter; 52-Outlet pipe of biological phosphorus removal filter backwash water; 53-Inlet pipe of biological phosphorus removal filter backwash water; 54-Aeration pipe of biological phosphorus removal filter backwash water; 55-Outlet pipe of phosphorus-rich water of biological phosphorus removal filter; 56-Outlet pipe of biological phosphorus removal filter; 57-Inlet pipe of phosphorus-rich water of biological phosphorus removal filter; 58-Aeration pipe for filtered water of biological phosphorus removal filter; 59-Blower; 61-Static mixer; 62-Organic carbon source addition pipe; 63-Phosphorus-rich water pump; 64-Phosphorus-rich water storage tank, supply pipe from phosphorus-rich water to biological phosphorus removal filter; 65-Phosphorus-rich water storage tank. 66-Phosphorus-rich water storage tank outlet pipe; 71-Phosphorus removal chemical agent dosing pipe; 72-Agitator; 73-Screw elevator; 74-Phosphorus recovery product tank; 75-Chemical phosphorus recovery tank supernatant return pipe; 76-Phosphorus recovery product collection pipe; 81-Organic carbon source dosing pipe; 82-Agitator; 83-Anaerobic phosphorus release tank inlet pipe; 84-Anaerobic phosphorus release tank sludge discharge pipe; 91-Sludge thickening tank sludge discharge pipe; 92-Sludge thickening tank supernatant conveying pipe; 101-Dewatered sludge external delivery pipe; 102-Sludge dewatering workshop supernatant conveying pipe. Detailed Implementation

[0041] The phosphorus removal device or system used consists of a biological phosphorus removal treatment unit, a phosphorus enrichment and recovery treatment unit, and a residual sludge phosphorus recovery unit. The biological phosphorus removal treatment unit includes: a backwash water tank (2), a backwash water collection tank (3), a first biological phosphorus removal filter (4), and a second biological phosphorus removal filter (5); the phosphorus enrichment and recovery treatment unit includes: a phosphorus-rich water storage tank (6) and a chemical phosphorus recovery tank (7); the residual sludge phosphorus recovery unit includes: an anaerobic phosphorus release tank (8), a sludge thickening tank (9), and a sludge dewatering workshop (10).

[0042] The backwash water tank (2) stores part of the effluent from the secondary sedimentation tank (1). During the backwashing of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), the effluent is pumped into the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) by the pump (21).

[0043] The backwash water collection tank (3) is used to collect and treat the sludge-water mixture after backwashing of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), and send its supernatant into the front-end treatment system of the sewage treatment plant, while the settled backwash sludge enters the anaerobic phosphorus release tank (8).

[0044] The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) operate alternately in parallel. The system has at least two biological phosphorus removal filters, and the number can be increased appropriately according to actual needs to adapt to different application scenarios. Multiple biological phosphorus removal filters should be set up in parallel and connected to the effluent of the secondary sedimentation tank (1) respectively. The biological phosphorus removal filter should have an influent oxygenation system, a backwashing system and an organic carbon source addition system. The influent oxygenation system includes a blower (59); the backwashing system includes a backwash water tank (2), a backwash water pump (21), a backwash water collection tank (3) and a blower (59); the organic carbon source addition system includes a static mixer (61), an organic carbon source addition pipe (62) and a phosphorus-rich water pump (63).

[0045] The biofilm carriers for the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) can be polyurethane packing, sponge packing, fiber packing, curtain packing, elastic three-dimensional packing, or other materials that can support polyphosphate-accumulating bacteria to form a biofilm. The filter media can be inorganic mineral materials with filtration functions, or organic or macromolecular filter materials such as activated carbon. These materials are combined to form an organic combination of biofilm reaction and filtration functions. Alternatively, granular activated carbon, fiber balls, fiber bundle filter media, comet-shaped fiber filter media, etc., which can directly form biological filtration functions, can be used to establish biological phosphorus removal filters.

[0046] In terms of operation, the DO should be controlled below 0.2 mg / L under anaerobic conditions and about 2-4 mg / L under aerobic conditions. The hydraulic retention time should be greater than 40 minutes.

[0047] During backwashing of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), the water required for backwashing is supplied by the backwash water tank (2), and the backwashing intensity is <8 L / (m). 2 The air required for backwashing is supplied by a blower (59), with an air supply intensity of 10~15 L / (m). 2 ·s).

[0048] The phosphorus-rich water storage tank (6) is used to store the phosphorus-rich water after anaerobic phosphorus release from the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5).

[0049] The chemical phosphorus recovery tank (7) is equipped with a chemical reagent dosing pipe (71), a stirrer (72), a screw conveyor (73), and a phosphorus recovery product collection tank (74). Calcium salts, iron salts, magnesium salts, aluminum salts, etc., can be used for chemical reagent dosing, with calcium salts being preferred. During the phosphorus recovery reaction, the pH should be controlled within the range of 8-11, the reaction time should be no less than 10 minutes, and the precipitation time should be no less than 30 minutes.

[0050] The anaerobic phosphorus release tank (8) is equipped with an organic carbon dosing pipe (81) and a stirrer (82).

[0051] The sludge thickening tank (9) should have a sludge moisture content of no more than 97% after thickening, and the sludge should be introduced into the sludge dewatering workshop (10). The dewatered water should be introduced into the chemical phosphorus recovery tank (7) for phosphorus recovery. The hydraulic retention time in the sludge thickening tank (9) is 10~16h, and the effective water depth is generally 4m.

[0052] The sludge dewatering workshop (10) dewaters the concentrated sludge and separates the water. The water content of the dewatered sludge is generally 60%~80%, which facilitates the next step of sludge transportation and disposal. The dewatered wastewater is fed into the chemical phosphorus recovery tank (7) for phosphorus recovery.

[0053] Features of phosphorus removal and recovery systems:

[0054] Biological phosphorus removal section

[0055] The effluent from the secondary sedimentation tank (1) contains almost no activated sludge after the main process sludge-water separation is completed. This invention relates to the secondary sedimentation tank (1). The effluent is untreated effluent that enters the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) before being aerated. After oxygenation, the material enters the filter bed. At this time, in the biological filter bed of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5), polyphosphate... The bacteria are in an empty tank state after completing the phosphorus release process. The effluent from the phosphorus-containing secondary sedimentation tank (1) flows into the first biological phosphorus removal filter. (4) or one of the filter layers of the second biological phosphorus removal filter (5), the biological phosphorus removal and wastewater filtration process is completed in the filter layer. As the influent continues to flow in and out of the filter, the polyphosphate-accumulating bacteria in the filter layer will continuously absorb phosphorus and reach a "saturated state". At this time, the influent will be adjusted to the second biological phosphorus removal filter (5) or the first biological phosphorus removal filter (4), and the biological phosphorus removal filter that has reached phosphorus saturation will be emptied and injected with phosphorus-rich water stored in the phosphorus-rich water storage tank (6). During the water injection process, an organic carbon source is added at the same time, so that the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) in the anaerobic state can complete the phosphorus release and form phosphorus-rich water with a higher phosphorus concentration. After the biological phosphorus removal filter completes the anaerobic phosphorus release, it is emptied again and the phosphorus-rich water is discharged into the phosphorus-rich water storage tank (6) for storage. The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) are then ready to enter the next round of phosphorus absorption process.

[0056] During the above process, as polyphosphate-accumulating bacteria continue to release phosphorus anaerobically and absorb phosphorus aerobicly, polyphosphate-accumulating bacteria in the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) will continuously grow and multiply. When their number reaches a certain level, the filter layer needs to be backwashed to remove excess polyphosphate-accumulating bacteria. The backwashing adopts the form of air-water combined backwashing. The backwash water is the effluent from the secondary sedimentation tank (1) stored in the backwash water tank (2). The air source is provided by the air supply system, which includes a blower (59) and an air supply pipe (44 or 54). The backwash mud-water mixture formed during the backwashing process is collected in the backwash water collection tank (3).

[0057] Phosphorus recovery section

[0058] The phosphorus-rich water collected in the phosphorus-rich water storage tank (6) will gradually increase in phosphorus concentration after multiple phosphorus release cycles. When the phosphorus concentration in the phosphorus-rich water reaches a predetermined level (e.g., 200 mg / L), it is introduced into the chemical phosphorus recovery tank (7). In the chemical phosphorus recovery tank (7), a chemical phosphorus removal agent is added through the phosphorus removal chemical agent dosing pipe (71), and a stirrer (72) is used to fully stir the mixture to promote the chemical removal reaction of phosphorus. After the reaction is completed, the stirring is stopped, and the precipitate is allowed to settle naturally. The precipitated chemical phosphorus precipitate will be cleaned and separated by a screw conveyor (73) to obtain "pure" recovered phosphorus. These phosphorus recovery products will be stored in the phosphorus recovery product collection tank (74). At the same time, the remaining supernatant is returned to the influent section of the main wastewater treatment process.

[0059] Phosphorus recovery section of residual sludge

[0060] In the main process of wastewater treatment, the excess sludge generated in the secondary sedimentation tank (1) and the backwash sludge generated in the backwash water collection tank (3) are transported together to the anaerobic phosphorus release tank (8). In the anaerobic phosphorus release tank (8), organic carbon source is added to the tank through the organic carbon source addition pipe (81), and the tank is thoroughly stirred by a mixer (82) to fully release the phosphorus in the sludge. The sludge after release is discharged to the excess sludge thickening tank (9) for thickening. The thickened sludge is transported to the sludge dewatering workshop (10) for dewatering, and the dewatered sludge is transported off-site for treatment. The concentrated supernatant and the sludge dewatering liquid will flow together into the chemical phosphorus recovery tank (7) for further treatment of chemical phosphorus recovery.

[0061] The method for continuous phosphorus recovery using the above-mentioned apparatus includes the following steps:

[0062] After the main biological treatment process, the wastewater first enters the secondary sedimentation tank (1) through the inlet pipe (11) for sludge-water separation. The supernatant enters the first biological phosphorus removal filter (4) through the outlet pipe (14) of the secondary sedimentation tank (1) and the inlet pipe (41) of the first biological phosphorus removal filter (4), where biological phosphorus removal and filtration are completed. During the water intake process, the filtered water is oxygenated through the air supply pipe (48) and the blower (59) of the first biological phosphorus removal filter (4). The water after aerobic phosphorus absorption is discharged through the outlet pipe (46) of the biological phosphorus removal filter (4). When the phosphorus removal capacity of the first biological phosphorus removal filter (4) reaches saturation, the effluent from the secondary sedimentation tank (1) enters the second biological phosphorus removal filter (5) through the effluent pipe (14) of the secondary sedimentation tank (1) and the influent pipe (51) of the second biological phosphorus removal filter (5). After completing the same biological phosphorus removal and filtration process as the first biological phosphorus removal filter (4), the effluent is finally discharged through the effluent pipe (56) of the second biological phosphorus removal filter (5). When the phosphorus removal capacity of the second biological phosphorus removal filter (5) reaches saturation, the effluent from the secondary sedimentation tank (1) enters the first biological phosphorus removal filter (4) again through the effluent pipe (14) of the secondary sedimentation tank (1) and the influent pipe (41) of the first biological phosphorus removal filter (4) for the next phosphorus removal cycle. When the second biological phosphorus removal filter (5) is filled with water, the first biological phosphorus removal filter (4) will stop filling with water but continue to drain water until it is empty. Subsequently, phosphorus-rich water from the phosphorus-rich water storage tank (6) is injected into the first biological phosphorus removal filter (4) through the phosphorus-rich water inlet pipe (47), while organic carbon source is added through the organic carbon source addition pipe (62). The organic carbon source and high-phosphorus water are mixed in a static mixer (61) installed on the phosphorus-rich water supply pipe (64) of the phosphorus-rich water storage tank (6). After the phosphorus-rich water fills the first biological phosphorus removal filter (4), the water intake is stopped, and the anaerobic state is maintained for phosphorus release. After the first biological phosphorus removal filter (4) completes phosphorus release, the phosphorus-rich water is discharged into the phosphorus-rich water storage tank (6) through the phosphorus-rich water outlet pipe (45) of the first biological phosphorus removal filter (4) and the inlet pipe (65) of the phosphorus-rich water storage tank (6). At this time, the first biological phosphorus removal filter (4) returns to a state with biological phosphorus removal capacity and is ready for the next cycle. The process described above also applies to the second biological phosphorus removal filter (5). After its phosphorus removal capacity reaches saturation, the process of draining the water in the tank, injecting phosphorus-rich water, releasing phosphorus, and then draining the phosphorus-rich water again is repeated. The above process is continuously cyclical to achieve continuous phosphorus removal from the effluent of the secondary sedimentation tank (1). After completing multiple phosphorus absorption cycles, the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) will respectively need to undergo backwashing of the filter layers.

[0063] The backwashing system of the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) includes a backwash water tank (2), a backwash water collection tank (3), and an air source from a blower (59). The system operates using a combined air-water backwashing method. The backwashing process generally takes place after phosphorus release is completed in the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) and the phosphorus-rich water is drained. The specific backwashing procedure is as follows: After the phosphorus-rich water is drained from the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) (when backwashing is required), the system starts the combined air-water backwashing. Backwash water is transported to the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) through the inlet pipes (23) and (43 or 53) of the backwash water tank (2), while backwash air is provided by a blower (59) and transported to the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) through the backwash air supply pipes (44 or 54). The backwash process lasts for 5 minutes, and the backwash effluent flows into the backwash water collection tank (3) through the backwash effluent pipe (42) or (52). Backwash cement water separation is completed in the backwash water collection tank (3). The resulting supernatant is discharged to the inlet of the sewage treatment system through the supernatant outlet pipe (32) of the backwash water collection tank (3). The settled backwash sludge enters the anaerobic phosphorus release tank (8) through the sludge discharge pipe (33) of the backwash water collection tank (3) and the inlet pipe (83) of the anaerobic phosphorus release tank (8).

[0064] During the above continuous cycle, the water in the phosphorus-rich water storage tank (6) is recycled until the phosphorus concentration reaches a predetermined level (e.g., 200 mg / L). At this time, the phosphorus-rich water is discharged to the chemical phosphorus recovery tank (7) through the phosphorus-rich water outlet pipe (66) of the phosphorus-rich water storage tank (6). When the chemical phosphorus recovery tank (7) is full, the phosphorus removal chemical agent is added to the tank through the chemical phosphorus removal agent dosing pipe (71), and the agitator (72) is started to fully agitate the tank water. After the agent reacts fully with the phosphorus-rich water, the agitation is stopped and the sedimentation process begins. The inorganic phosphorus precipitate will gradually settle to the bottom during the sedimentation process. Then, the inorganic phosphorus precipitate is cleaned and separated by the screw conveyor (73) and transported to the phosphorus recovery product collection tank (74) through the phosphorus recovery product collection pipe (76) to complete the phosphorus recovery. The supernatant in the chemical phosphorus recovery tank (7) is returned to the influent part of the main sewage treatment process through the supernatant return pipe (75).

[0065] Phosphorus recovery section of residual sludge

[0066] In the main wastewater treatment process, the excess sludge formed in the secondary sedimentation tank (1) enters the anaerobic phosphorus release tank (8) through the excess sludge discharge pipe (13) and the inlet pipe (83) of the anaerobic phosphorus release tank (8). After entering the anaerobic phosphorus release tank (8), organic carbon is added to the tank through the organic carbon source addition pipe (81), and the agitator (82) of the anaerobic phosphorus release tank (8) is started to fully stir and release phosphorus from the sludge. After phosphorus release, the sludge is discharged into the excess sludge thickening tank (9) through the sludge discharge pipe (84) of the anaerobic phosphorus release tank (8) for thickening treatment. The thickened sludge is transported to the sludge dewatering workshop (10) through the sludge discharge pipe (91) of the sludge thickening tank (9) for dewatering treatment. The treated dewatered sludge is then transported to external treatment facilities through the dewatered sludge delivery pipe (101). Meanwhile, the concentrated supernatant and the sludge dewatering liquid flow into the chemical phosphorus recovery tank (7) through the supernatant conveying pipe (92) of the sludge thickening tank (9) and the supernatant conveying pipe (102) of the sludge dewatering workshop, respectively, for further chemical phosphorus recovery.

[0067] Example 1

[0068] Wastewater influent flow rate Q: 12 m 3 / d, 500 L / h, influent phosphorus concentration is 3 mg / L.

[0069] After being treated by the main process, the wastewater enters the secondary sedimentation tank (1) for sludge-water separation.

[0070] 1. Biological phosphorus removal filter (4): hydraulic retention time is 40 min, effective volume is about 335 L;

[0071] 2. Biological phosphorus removal filter (5): hydraulic retention time is 40 min, effective volume is about 335 L;

[0072] 3. Phosphorus-rich water storage tank (6): effective volume approximately 335L;

[0073] 4. Chemical phosphorus recovery tank (7): The hydraulic retention time is 40 min and the effective volume is about 335 L; calcium salt is added to form hydroxyapatite precipitate, and the hydroxyapatite precipitate is cleaned and separated by a spiral elevator (73) and sent to the phosphorus recovery product collection tank (74).

[0074] 5. Anaerobic phosphorus release tank (8): hydraulic retention time is 40 min, effective volume is 20 L;

[0075] 6. Sludge thickening tank (9): The hydraulic retention time is 10h, the effective volume is 50L, and the sludge moisture content after thickening is about 97%;

[0076] 7. Sludge dewatering workshop (10): After sludge dewatering, the sludge moisture content is about 80%.

[0077] Operational results show that the system maintains stable phosphorus removal and recovery efficiency, with effluent phosphorus concentration below 0.1 mg / L and 98% of phosphorus in the influent being removed and recovered. During the recovery process, compared to the traditional activated sludge method, it can save 71% of the dosage of chemical phosphorus removal agents. Because the system avoids the ineffective phosphorus recycling found in traditional biological phosphorus removal systems, it saves nearly 71% of the organic carbon source required for phosphorus removal, thus significantly reducing the cost of chemical inputs in operating costs.

Claims

1. A device for recovering inorganic phosphorus from the effluent of a conventional two-sludge tank, relying on a biological phosphorus removal filter, characterized in that, The device is composed of a biological phosphorus removal treatment unit, a phosphorus enrichment recovery treatment unit and a residual sludge phosphorus recovery unit; the biological phosphorus removal treatment unit comprises a backwashing pool (2), a backwashing water collecting pool (3), a first biological phosphorus removal filter (4) and a second biological phosphorus removal filter (5); the phosphorus enrichment recovery treatment unit comprises a phosphorus-rich water storage pool (6) and a chemical phosphorus recovery pool (7); and the residual sludge phosphorus recovery unit comprises an anaerobic phosphorus release pool (8), a sludge concentration pool (9) and a sludge dewatering workshop (10); The outlet of the secondary sedimentation tank (1) is divided into multiple branches, one of which is connected with the backwashing pool (2) through a valve, and the others are respectively connected with multiple biological phosphorus removal filters in parallel through valves, and at least two biological phosphorus removal filters are the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5); the outlet of each biological phosphorus removal filter is connected with the phosphorus-rich water storage pool (6) through a valve, the phosphorus-rich water storage pool (6) is connected with the chemical phosphorus recovery pool (7), the phosphorus-rich water storage pool (6) is connected with the static mixer (61) through a pipeline by a phosphorus-rich water pump (63), the static mixer (61) is respectively connected with each biological phosphorus removal filter through a valve, which is used for returning the phosphorus-rich water in the phosphorus-rich water storage pool (6) to the corresponding biological phosphorus removal filter, and an organic carbon source adding pipe (62) is connected on the pipeline between the phosphorus-rich water pump (63) and the static mixer (61); the outlet of the fan (59) is divided into multiple branches, which are respectively connected with the bottom of each corresponding biological phosphorus removal filter through valves to blow air for backwashing; meanwhile, the outlet of the fan (59) is also respectively connected with the middle or upper part of each corresponding biological phosphorus removal filter through valves to blow air for oxygenation; the backwashing pool (2) is respectively connected with each biological phosphorus removal filter through a backwashing pump (21) and a valve, which is used for washing each biological phosphorus removal filter; the bottom of the chemical phosphorus recovery pool (7) is in a conical structure, the chemical phosphorus recovery pool (7) is provided with a phosphorus removal chemical agent adding pipe (71), a stirrer (72) and a screw elevator (73), the screw elevator (73) extends outward and upward from the bottom of the chemical phosphorus recovery pool (7), the upper end of the screw elevator (73) is located outside the chemical phosphorus recovery pool (7), and the upper end of the screw elevator (73) is connected with a phosphorus recovery product pool (74) through a downward extending phosphorus recovery product collecting pipe (76); each biological phosphorus removal filter is connected with the backwashing water collecting pool (3) through a valve; the bottom of the secondary sedimentation tank (1) and the bottom of the backwashing water collecting pool (3) are respectively connected with the anaerobic phosphorus release pool (8), the anaerobic phosphorus release pool (8) is provided with an organic carbon source adding pipe (81) and a stirrer; the anaerobic phosphorus release pool (8) is connected with the sludge concentration pool (9), the sludge concentration pool (9) is connected with the sludge dewatering workshop (10); the sludge concentration pool (9) and the sludge dewatering workshop (10) are respectively connected with the chemical phosphorus recovery pool (7); each biological phosphorus removal filter is provided with a drain pipe, and the drain pipe is provided with a drain valve.

2. The apparatus of claim 1, wherein The backwash water pool (2) stores part of the effluent of the secondary sedimentation tank (1), and when the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) are backwashed, the backwash water pump (21) is used to pump the effluent into the first biological phosphorus removal filter (4) and / or the second biological phosphorus removal filter (5).

3. The apparatus of claim 1, wherein The backwash water collection tank (3) is used to collect and treat the sludge-water mixture after backwashing of each biological phosphorus removal filter, and the supernatant of the sludge-water mixture after sedimentation is sent to the front-end treatment system of the sewage treatment plant, and the backwash sludge after sedimentation is sent to the anaerobic phosphorus release tank (8).

4. The apparatus of claim 1, wherein The first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) are connected in parallel and work alternately, and there are at least two biological phosphorus removal filters, or the number thereof can be appropriately increased according to actual needs to adapt to different application scenarios; a plurality of biological phosphorus removal filters are connected in parallel and connected to the effluent of the secondary sedimentation tank (1); each biological phosphorus removal filter is the same as the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) and has a water inlet oxygenation system, a backwashing system and an organic carbon source adding system, the water inlet oxygenation system includes a fan (59); the backwashing system includes: the backwash water pool (2) is connected to the biological phosphorus removal filter through the backwash water pump (21), and the backwashed water enters the backwash water collection tank (3); the cleaning process uses the fan (59) to blow air; the organic carbon source adding system includes: the phosphorus-rich water storage tank (6) is connected to the biological phosphorus removal filter through the static mixer (61) and the phosphorus-rich water pump (63), and an organic carbon source adding pipe (62) is arranged in the connecting pipeline.

5. The apparatus of claim 1, wherein The filter layer in the biological phosphorus removal filter includes a biological membrane carrier and a filter material, the biological membrane carrier can be selected from polyurethane filler, sponge filler, fiber filler, curtain filler, elastic three-dimensional filler and other materials that can support polyphosphorus bacteria film formation; the filter material can be selected from inorganic mineral materials with filtering function, or organic or macromolecular filter materials such as activated carbon; the biological membrane carrier and the filter material are combined to form an organic combination of biological membrane reaction and filtering function; or the biological phosphorus removal filter directly uses granular activated carbon, fiber ball, fiber bundle filter material, comet-shaped fiber filter material and other materials that can form biological filtration function to establish the biological phosphorus removal filter.

6. Process for the continuous recovery of inorganic phosphorus using the apparatus according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) Biological phosphorus removal part The effluent of the secondary sedimentation tank (1) contains almost no activated sludge after the main process of sludge-water separation, and the effluent of the secondary sedimentation tank (1) is the effluent without phosphorus removal treatment. After entering the filter layer, the polyphosphorus bacteria are in the empty pool state of phosphorus release. Therefore, the effluent of the secondary sedimentation tank (1) containing phosphorus flows into the first biological phosphorus removal filter tank (4) filter layer, and the polyphosphorus bacteria continuously absorb phosphorus in the water under the condition of continuous aeration and oxygenation to complete the process of biological phosphorus removal and sewage filtration in the filter layer. With the continuous inflow and filtration of the influent, the polyphosphorus bacteria in the filter layer will continuously absorb phosphorus to reach the "saturation state". At this time, the aeration is stopped, the secondary sedimentation tank (1) into the first biological phosphorus removal filter tank (4) is closed, the secondary sedimentation tank (1) into the second biological phosphorus removal filter tank (5) is opened, and the secondary sedimentation tank (1) influent is adjusted into the second biological phosphorus removal filter tank (5). The water in the first biological phosphorus removal filter tank (4) whose polyphosphorus bacteria have reached the phosphorus saturation state is emptied, and then the phosphorus-rich water in the phosphorus-rich water storage tank (6) is injected. In the process of injecting the phosphorus-rich water, organic carbon sources are also added. During this process, the first biological phosphorus removal filter tank (4) is in an anaerobic state. In the first biological phosphorus removal filter tank (4) in the anaerobic state, the polyphosphorus bacteria complete phosphorus release again, so that the phosphorus-rich water entering the first biological phosphorus removal filter tank (4) forms phosphorus-rich water with relatively higher phosphorus concentration. After the polyphosphorus bacteria in the first biological phosphorus removal filter tank (4) complete anaerobic phosphorus release, the first biological phosphorus removal filter tank (4) again forms an empty pool state. The phosphorus-rich water with relatively higher phosphorus concentration in the first biological phosphorus removal filter tank (4) is discharged into the phosphorus-rich water storage tank (6) again to reserve, and the biological phosphorus removal process is completed. The first biological phosphorus removal filter tank (4) is ready for the next round of influent from the secondary sedimentation tank (1) and biological phosphorus removal process. The process of opening the secondary sedimentation tank (1) into the second biological phosphorus removal filter tank (5) to adjust the secondary sedimentation tank (1) influent into the second biological phosphorus removal filter tank (5) starts the biological phosphorus removal process. The above-mentioned first biological phosphorus removal filter tank (4) and second biological phosphorus removal filter tank (5) perform an alternating biological phosphorus removal process. The above-mentioned first biological phosphorus removal filter tank (4) and second biological phosphorus removal filter tank (5) perform an alternating biological phosphorus removal process. Each time the phosphorus-rich water in the phosphorus-rich water storage tank (6) enters the corresponding first biological phosphorus removal filter tank (4) or second biological phosphorus removal filter tank (5), and then returns to the phosphorus-rich water storage tank (6) as phosphorus-rich water with relatively higher phosphorus concentration. With the multiple biological phosphorus removal processes, the phosphorus concentration of the phosphorus-rich water in the phosphorus-rich water storage tank (6) accumulates and superimposes. In the above-mentioned alternating biological phosphorus removal process, with the continuous anaerobic phosphorus release and aerobic phosphorus absorption of the polyphosphorus bacteria, the first biological phosphorus removal filter tank (4) and the second biological phosphorus removal filter tank (5) work alternately. When the number of polyphosphorus bacteria in the first biological phosphorus removal filter tank (4) or the second biological phosphorus removal filter tank (5) reaches a certain degree, backwashing of the filter layer is needed to remove excess polyphosphorus bacteria. The backwashing adopts the form of air-water combined backwashing, and the backwashing water uses the effluent of the secondary sedimentation tank (1) reserved in the backwashing water tank (2), and the air source fan (59) provides the air source. The backwashing sludge-water mixture formed in the backwashing process is collected into the backwashing water collection tank (3). (2) Phosphorus recovery section The phosphorus-rich water collected in the phosphorus-rich water storage tank (6) is subjected to multiple biological phosphorus removal processes, and the phosphorus concentration gradually increases. When the phosphorus concentration in the phosphorus-rich water reaches a predetermined level (e.g., 200 mg / L), it is introduced into the chemical phosphorus recovery tank (7). In the chemical phosphorus recovery tank (7), a chemical phosphorus removal agent is added through the chemical agent dosing pipe (71), and a stirrer (72) is used for thorough stirring to promote the chemical removal reaction of phosphorus. After the reaction is complete, stirring is stopped, and the precipitate is allowed to settle naturally. The precipitated chemical phosphorus sludge is removed and separated by a screw elevator (73) to obtain "pure" recovered phosphorus. These phosphorus recovery products are stored in the phosphorus recovery product collection tank (74). At the same time, the supernatant remaining in the chemical phosphorus recovery tank (7) is returned to the secondary sedimentation tank (1) for wastewater treatment. (3) Residual sludge phosphorus recovery section In the main process of wastewater treatment, the residual sludge produced in the secondary sedimentation tank (1) and the backwash sludge produced in the backwash sludge collection tank (3) are transported together to the anaerobic phosphorus release tank (8). In the anaerobic phosphorus release tank (8), an organic carbon source is added through the organic carbon source dosing pipe (81), and the sludge is thoroughly stirred to release the phosphorus. The released sludge is discharged to the residual sludge concentration tank (9) for concentration. The concentrated sludge is transported to the sludge dewatering workshop (10) for dewatering, and the dewatered sludge is transported for disposal. The concentrated supernatant from the residual sludge concentration tank (9) and the sludge dewatering liquid from the sludge dewatering workshop (10) are jointly discharged into the chemical phosphorus recovery tank (7) for further chemical phosphorus recovery treatment.

7. The method of claim 6, wherein, The DO under anaerobic conditions should be controlled below 0.2 mg / L, and the DO under aerobic conditions is about 2-4 mg / L. The hydraulic retention time under both anaerobic and aerobic conditions is greater than 40 minutes.

8. The method of claim 6, wherein, When the first biological phosphorus removal filter (4) and the second biological phosphorus removal filter (5) are backwashed, the water required for backwashing is provided by the backwashing tank (2), the backwashing intensity is <8 L / (m 2 ·s); the air required for backwashing is provided by the fan (59), the air supply intensity is 10~15 L / (m 2 ·s).

9. The method of claim 6, wherein, The chemical phosphorus recovery tank (7) is equipped with a chemical agent dosing pipe (71), a stirrer (72), a screw elevator (73), and a phosphorus recovery product collection tank (74). The chemical agent dosing pipe (71) can add calcium salt, iron salt, magnesium salt, aluminum salt, etc., preferably calcium salt. The pH during the phosphorus recovery reaction in the chemical phosphorus recovery tank (7) should be controlled within the range of 8-11, the reaction time should be not less than 10 minutes, and the sedimentation time should be not less than 30 minutes.

10. The method of claim 6, wherein, The sludge concentration tank (9) should have a water content of not more than 97% after concentration, and be connected to the sludge dewatering workshop (10). The dewatering water is introduced into the chemical phosphorus recovery tank (7) for phosphorus recovery. The hydraulic retention time in the sludge concentration tank (9) is 10-16 h, and the effective water depth is generally 4 m. The sludge dewatering workshop (10) dewatered the concentrated sludge to separate the water, and the dewatered sludge generally has a water content of 60%-80%, which is convenient for the next step of sludge transportation and disposal. The dewatering water is introduced into the chemical phosphorus recovery tank (7) for phosphorus recovery.

Images