Method for improving anaerobic ammonia oxidation nitrogen and phosphorus removal of urban sewage plant by using suspended sludge and biological membrane mixing technology

Abstract

The invention relates to a method for improving anaerobic ammonia oxidation nitrogen and phosphorus removal of an urban sewage plant by using a suspended sludge and biological membrane mixing technology. Part of raw water, part of effluent of the sedimentation tanks and part of sludge enter the mixed reaction area together, sludge in the sedimentation tank II flows back to the front end of the reaction area through a sludge return pipeline, and effluent of the sedimentation tank I and effluent of the sedimentation tank II are combined. The first sedimentation tank guides part of sludge to the mixed reaction area, the mixing amount of suspended sludge and a biological membrane is regulated and controlled to improve the abundance of anaerobic ammonium oxidation bacteria, the sludge flows back to the front end of the reaction area through the second sedimentation tank to enhance the overall anaerobic ammonium oxidation bacteria abundance of the suspended sludge, and then the denitrification performance is improved. Meanwhile, partial carbon source saved by anaerobic ammonia oxidation strengthens biological phosphorus removal. According to the method, normal operation of the sewage treatment plant does not need to be interrupted, the nitrogen and phosphorus removal performance can be improved, and the method is suitable for upgrading and reconstruction of a built urban sewage treatment plant or deep nitrogen and phosphorus removal of a newly-built sewage treatment plant.

Description

Technical Field

[0001] The present invention relates to the technical field of urban sewage treatment, and in particular to improving the abundance of anaerobic ammonia oxidizing bacteria in the denitrification and phosphorus removal units of urban sewage treatment plants by adding a mixed reaction zone and utilizing suspended sludge and biofilm mixing technology without interrupting the original sewage treatment process of the urban sewage treatment plant, thereby improving the denitrification performance. Background Art

[0002] The compliance of urban sewage treatment plants with discharge standards is not only an important cornerstone for ensuring the health of urban water environment and achieving sustainable use of water resources, but also an indispensable part of environmental protection. With the accelerating pace of urbanization, along with the increase in population density and the expansion of industrial production, sewage discharge is growing at an unprecedented rate, which has put forward more stringent requirements on the efficiency of sewage treatment and effluent water quality standards. Among the many sewage treatment indicators that need to be improved, strengthening denitrification performance is particularly important, because it is closely related to the concentration of nitrogen compounds in the effluent, which profoundly affects the prevention and control of eutrophication of water bodies and the maintenance of the entire ecological environment. Therefore, exploring a new sewage treatment technology that can efficiently remove nitrogen, improve sewage treatment efficiency, and ensure that effluent water quality meets standards has become an important issue that needs to be solved urgently.

[0003] However, urban sewage treatment still faces many difficulties in denitrification. On the one hand, the forms of nitrogen in sewage are diverse, including ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, etc. Different forms of nitrogen have different transformation rules and removal difficulties during the treatment process. On the other hand, the water quality of urban sewage fluctuates greatly, which puts higher requirements on the stability and adaptability of sewage treatment processes. In addition, traditional sewage treatment processes have problems such as low efficiency and high energy consumption in denitrification, which makes it difficult to meet the increasingly stringent environmental protection requirements.

[0004] In order to solve these problems, anaerobic ammonium oxidation technology came into being. Anaerobic ammonium oxidation is a biological process that converts ammonia into nitrogen gas under anaerobic conditions, using ammonia as a hydrogen donor and nitrite or nitrate as the final electron acceptor through the action of anaerobic ammonium oxidizing bacteria. In the sewage treatment process, many bacteria often only convert nitric acid into nitrite, resulting in high ammonia and nitrite content in the effluent, which in turn poses a fatal threat to aquatic organisms. The introduction of anaerobic ammonium oxidizing bacteria can effectively deal with this problem. In addition, anaerobic ammonium oxidation technology has many advantages such as low energy consumption, low sludge production, and no need for external carbon source, showing great application potential in the sewage treatment industry. With the help of this technology, ammonia nitrogen and nitrite nitrogen in sewage can be effectively removed, the effluent water quality can be improved, and the treatment cost can be reduced. In recent years, anaerobic ammonium oxidation technology has received widespread attention and in-depth research from researchers due to its excellent denitrification performance and low cost. The treatment efficiency and stability of anaerobic ammonium oxidation technology are continuously improved by optimizing reaction conditions, improving microbial activity, and developing new reactors.

[0005] In this context, the present invention proposes a method for improving anaerobic ammonium oxidation denitrification and phosphorus removal in urban sewage treatment plants by using suspended sludge and biofilm mixing technology. The method aims to increase the abundance of anaerobic ammonium oxidizing bacteria in the denitrification and phosphorus removal units of urban sewage treatment plants by adding a mixed reaction zone and using suspended sludge and biofilm mixing technology, thereby hoping to improve denitrification performance. The introduction of this innovative technology not only provides a new solution for urban sewage treatment, but also provides a new idea for the further development and application of anaerobic ammonium oxidation technology. Summary of the invention

[0006] A method for improving anaerobic ammonia oxidation denitrification and phosphorus removal in a municipal sewage treatment plant by using a suspended sludge and biofilm mixing technology. A portion of the effluent from a sedimentation tank (4) enters a mixed reaction zone (11) through a pipeline (9), a portion of the sludge enters the mixed reaction zone (11) through a sludge discharge pipeline (10) of the sedimentation tank (1), and a portion of the influent also enters the mixed reaction zone (11) through a pipeline (8). The sludge in the sedimentation tank (2) is returned to the denitrification and phosphorus removal unit (3) of the municipal sewage treatment plant through a sludge return pipeline (13), and the effluents from the sedimentation tank (4) and the sedimentation tank (12) are respectively combined into an effluent pipeline (15) through effluent pipelines (7) and (14) to combine the effluents. Part of the sludge from the sedimentation tank 1 (4) is led to the mixed reaction zone, and the amount of suspended sludge and biofilm mixed is regulated to increase the abundance of anaerobic ammonia oxidizing bacteria. The sludge from the sedimentation tank 2 (12) is returned to the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant to enhance the overall abundance of anaerobic ammonia oxidizing bacteria in the suspended sludge, thereby improving the denitrification performance. At the same time, part of the carbon source saved by anaerobic ammonia oxidation enhances biological phosphorus removal. Specifically, the sewage enters the system from the main water inlet pipeline (1), enters the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant from the water inlet branch line 1 (2), enters the sedimentation tank 1 (4) after treatment, and the treated sewage enters the combined water outlet pipeline (15) of the sedimentation tank 1 and 2 through the water outlet branch line (7) to be discharged; the bottom of the sedimentation tank 1 (4) is connected to the front end of the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant through the sludge return pipeline (5). The remaining sludge is subsequently treated through the discharge pipeline (6). A portion of the effluent from the sedimentation tank 1 (4) enters the mixed reaction zone (11), and a portion of the influent also enters the mixed reaction zone (11). The effluent from the sedimentation tank 2 (11) is combined with the effluent through the effluent pipeline (14) to the combined effluent pipeline (15). Part of the sludge from the sedimentation tank 1 (4) is introduced into the mixed reaction zone (11), so that the mixed reaction zone (11) is in a state of suspended sludge and biofilm mixing. When the amount of suspended sludge is small enough, the abundance of anaerobic ammonia-oxidizing bacteria can reach the highest level. The treated effluent enters the sedimentation tank 2 (12) for further treatment, and the sludge is returned to the front end of the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant through the sludge return pipeline (13).

[0007] The mixed reaction zone (11) is filled with carriers, and the biofilm is filled with 50%-65%. Anaerobic ammonia oxidizing bacteria and denitrifying bacteria grow on the carriers, and are mixed with the suspended sludge drawn from the sedimentation tank (4) to form a highly efficient denitrification anaerobic ammonia oxidizing synergistic denitrification environment. The amount of suspended sludge introduced from the sedimentation tank (4) into the mixed reaction zone (11) is regulated, and the suspended sludge is returned from the sedimentation tank (4) through the pipeline (5) to the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant. This process is called sludge return, and the sludge return ratio is controlled to be 75%-100%. The influent of the mixed reaction zone accounts for 20% to 30% of the volume of the raw water, and the influent flow rate of the influent pipeline (9) of the mixed reaction zone is 1-2 times the influent flow rate of the influent pipeline (8). The hydraulic retention time of the mixed reaction zone is controlled at 4-10 hours to ensure that a mixed state of suspended sludge and biofilm is formed in the mixed reaction zone (11), thereby weakening the competition of denitrifying bacteria for nitrite nitrogen and increasing the supply of nitrite nitrogen to anaerobic ammonium oxidizing bacteria, thereby optimizing the growth environment of anaerobic ammonium oxidizing bacteria.

[0008] The amount of suspended sludge introduced from the sedimentation tank (4) into the mixed reaction zone (11) is regulated to ensure that a mixed state of suspended sludge and biofilm is formed in the mixed reaction zone (11), thereby optimizing the growth environment of anaerobic ammonia-oxidizing bacteria and increasing their abundance.

[0009] The raw water may be sewage that has passed through structures such as the water inlet well, regulating tank, coarse screen, fine screen, grit tank, and primary sedimentation tank in sequence, or it may be sewage that has passed through some of the above structures.

[0010] Technical principles and features:

[0011] 1) After passing through the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant, the sewage enters the sedimentation tank 1 (4) to achieve mud and water separation. The treated water is discharged from the effluent pipe (7) to the combined effluent pipe (15) to be combined with the effluent of the sedimentation tank 2 (12), and the sludge is returned from the sludge return pipe (5) to the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant. Part of the effluent of the sedimentation tank 1 (4) and part of the water entering the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant are introduced into the mixed reaction zone (11) to achieve the coupling of anoxic short-range denitrification and anaerobic ammonia oxidation. At the same time, part of the sludge is introduced from the sedimentation tank 1 (4) through the sludge pipe (10) to the mixed reaction zone (11), so that the mixed reaction zone (11) is in a state of suspended sludge and biofilm mixing. When the amount of suspended sludge is small enough, the abundance of anaerobic ammonia oxidizing bacteria can reach the highest level.

[0012] 2) The influent of the mixed reaction zone (11) is part of the effluent from the sedimentation tank (4) and part of the influent from the nitrogen removal and phosphorus removal unit (3) of the urban sewage treatment plant. At the same time, a certain amount of suspended sludge from the sedimentation tank (4) is also introduced, so that the mixed reaction zone (11) presents a mixed state of suspended sludge and biofilm. Short-range denitrification coupled with anaerobic ammonia oxidation is carried out in the mixed reaction zone. The raw water can provide organic matter and ammonia nitrogen, and the effluent from the sedimentation tank (4) can provide nitrate nitrogen. The carbon source in the raw water can be used by nitrate nitrogen to carry out heterotrophic denitrification process, thereby achieving denitrification. The influx of the two types of water provides a reaction matrix for short-range denitrification coupled with anaerobic ammonia oxidation.

[0013] 3) The sludge in the mixed reaction zone (11) is returned to the front end of the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant through the sludge return pipeline (13), thereby realizing the recycling of the sludge. As the biofilm grows and accumulates, part of the biofilm will naturally fall off, and these fallen biofilms are rich in anaerobic ammonium oxidizing bacteria. The fallen biofilms are then returned to the front end of the denitrification and phosphorus removal unit of the urban sewage treatment plant. This system not only does not require external biological enhancement, but also can supplement the anaerobic ammonium oxidizing bacteria of the denitrification and phosphorus removal unit of the urban sewage treatment plant by adding a mixed reaction zone, thereby further enhancing the anaerobic ammonium oxidizing biological denitrification capacity of the denitrification and phosphorus removal unit of the urban sewage treatment plant.

[0014] This method of mixing suspended sludge and biofilm to improve anaerobic ammonia oxidation denitrification and phosphorus removal in urban sewage plants has the following advantages:

[0015] 1) Mixing suspended sludge with biofilm increases the abundance of anaerobic ammonium oxidizing bacteria. The present invention applies the technology of mixing suspended sludge with biofilm to the anaerobic ammonium oxidation denitrification and phosphorus removal process of urban sewage treatment plants. By controlling the amount of introduced suspended sludge to optimize the state of the mixed reaction zone, the abundance and activity of anaerobic ammonium oxidizing bacteria are increased, thereby significantly enhancing the denitrification performance. The integrated application of this technology provides a new solution for urban sewage treatment and promotes the progress of sewage treatment technology.

[0016] 2) Improve the stability of the system. The coexistence of suspended sludge and biofilm provides a stable growth environment for anaerobic ammonia-oxidizing bacteria, improves the complex metabolic potential of the microbial system, and helps to form a more stable microbial ecosystem. This stability enables the system to maintain a good treatment effect when facing external interference such as water quality fluctuations and load changes, and reduces operational risks.

[0017] 3) Optimize the sludge treatment process. The present invention realizes the recycling of sludge through the sludge return mechanism. The system reaction process is partial autotrophic denitrification. The removal of 1 mol of ammonia nitrogen only generates 3g of organisms, and the sludge production is effectively reduced. At the same time, the detached biofilm is rich in anaerobic ammonia-oxidizing bacteria, which can further supplement and strengthen the denitrification capacity of the system. This is conducive to reducing the cost of sludge disposal and also reduces the operating cost.

[0018] 4) Improve the treatment capacity of the sewage treatment plant. Under the premise of keeping the original treatment process unchanged, the anaerobic ammonia oxidation treatment capacity is further improved by adding a mixed reaction zone and combining biofilm and suspended sludge mixing technology, optimizing the sludge state and increasing the activity of microorganisms to achieve improved effluent water quality and improved treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a system based on suspended sludge and biofilm mixing technology to enhance the anaerobic ammonia oxidation denitrification and phosphorus removal performance of urban sewage treatment plants. Specifically: 1-total water inlet pipeline; 2-water inlet branch 1; 3-denitrification and phosphorus removal unit of urban sewage treatment plant; 4-sedimentation tank 1; 5-sludge return pipeline 1; 6-residual sludge discharge pipeline; 7-sedimentation tank 1 effluent discharge pipeline; 8-water inlet branch 2; 9-sedimentation tank 1 effluent branch; 10-sedimentation tank 1 sludge discharge pipeline; 11-mixed reaction zone; 12-sedimentation tank 2; 13-sludge return pipeline 2; 14-sedimentation tank 2 effluent discharge pipeline; 15-sedimentation tank 1 and 2 effluent combined pipeline. DETAILED DESCRIPTION

[0020] Combination Figure 1 , describe the embodiments of the present invention in detail:

[0021] 1) Control of the water inlet ratio of the denitrification and phosphorus removal unit and the mixed reaction zone of the urban sewage treatment plant: The present invention needs to reasonably distribute the water inlet flow rate to achieve the control of the mixed water quality, so as to ensure that the denitrification and phosphorus removal unit and the mixed reaction zone of the urban sewage treatment plant can operate efficiently. The water inlet of the mixed reaction zone is designed to account for less than 30% of the raw water, and the water inlet flow rate of the mixed reaction zone inlet pipeline (9) is 1-2 times the water inlet flow rate of the mixed reaction zone inlet pipeline (8). Specifically, the water inlet flow rate of the mixed reaction zone inlet branch (8) is set to 10% of the raw water, and the water inlet flow rate of the mixed reaction zone inlet branch (9) is set to 20% of the raw water, to control COD / NO 3 - -N is between 2.0 and 5.0, NO 3 - -N / NH 4 +-N is between 1.0-3.0. This distribution method can not only meet the water inlet demand of the mixed reaction zone, but also the denitrification and phosphorus removal units and the mixed reaction zone of the urban sewage treatment plant can achieve efficient operation under this distribution rate. In actual operation, the water inflow of each pipeline can be controlled by adjusting the flow of the water inlet valve or pump station. At the same time, the flow of each pipeline needs to be monitored regularly to ensure that it meets the design requirements.

[0022] 2) Regulate the amount of suspended sludge introduced: By adjusting the amount of suspended sludge introduced into the mixed reaction zone of sedimentation tank 1, the ratio of suspended sludge to biofilm in sedimentation tank 2 is controlled, so that the amount of suspended sludge is small enough but can form a good mixing state with the biofilm, so that the abundance of anaerobic ammonia oxidizing bacteria can reach the highest. The concentration of suspended sludge in the mixed reaction zone was regulated to decrease from 4067±382mg VSS / L to 2046±261mg VSS / L. During this process, the denitrification performance gradually improved, and the anaerobic ammonia oxidizing bacteria were significantly enriched to (6.12±0.22)×10 9 Copy / g VSS.

[0023] 3) The main operating parameters are set as follows: the sludge return ratio is controlled at 75% to 100%. The hydraulic retention time of the mixing reaction zone (11) is controlled at 4 to 10 hours. After the entire system is running stably, the influent NH 4 + When the -N concentration is 40mg / L and the inlet COD / TN is 4, the outlet COD concentration is 20-50mg / L, and the NH 4 + -N concentration is 0~1mg / L, NO 3 - -N concentration is 4~8mg / L, and TN concentration is 3~10mg / L.

Claims

1. A method for improving anaerobic ammonia oxidation denitrification and phosphorus removal in urban sewage treatment plants by using suspended sludge and biofilm mixing technology, characterized in that: Sewage enters from an inlet pipe (1), a part of it enters a denitrification and phosphorus removal unit (3) of a municipal sewage treatment plant from a pipe (2), and a part of it enters a mixed reaction zone from a pipe (8); after being treated by the denitrification and phosphorus removal unit (3) of the municipal sewage treatment plant, the sewage enters a sedimentation tank (4), a part of the effluent from the sedimentation tank (4) enters a mixed reaction zone (11) through a pipe (9), a part of the sludge enters the mixed reaction zone (11) through a sludge discharge pipe (10) of the sedimentation tank, and another part of the sludge flows back to the denitrification unit of the municipal sewage treatment plant through a sludge return pipe (5). The phosphorus removal unit (3) is discharged through the pipeline (6); a portion of the raw water enters the mixed reaction zone from the pipeline (8) and then enters the sedimentation tank 2 (12) after reaction; the sludge in the sedimentation tank 2 is returned to the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant through the sludge return pipeline (13); the effluents of the sedimentation tank 1 (4) and the sedimentation tank 2 (12) are respectively combined into the effluent pipeline (15) through the effluent pipelines (7) and (14); part of the sludge in the sedimentation tank 1 (4) is led to the mixed reaction zone (11) so that it is in a state of mixed suspended sludge and biofilm; The mixed reaction zone (11) is filled with a carrier, and the biofilm filling ratio is 50% to 65%. The amount of suspended sludge introduced from the sedimentation tank (4) into the mixed reaction zone (11) is regulated, and the sludge is returned from the sedimentation tank (4) through the pipeline (5) to the denitrification and phosphorus removal unit (3) of the urban sewage treatment plant. This process is called sludge return, and the sludge return ratio is controlled to be 75%-100%; the water inlet to the mixed reaction zone accounts for 20% to 30% of the volume of the original water, and the water inlet flow rate of the mixed reaction zone water inlet pipeline (9) is 1-2 times the water inlet flow rate of the water inlet pipeline (8); the hydraulic retention time of the mixed reaction zone is controlled to be 4-10h.

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