Method for improving anaerobic ammonia oxidation denitrification and phosphorus removal of urban sewage plant by mixing suspended sludge and biofilm

Abstract

The present application relates to a method for improving anaerobic ammonia oxidation denitrification and phosphorus removal in urban sewage treatment plant by mixing suspended sludge and biofilm. Part of raw water, part of effluent from the first sedimentation tank and part of sludge are jointly introduced into the mixing reaction zone, and the sludge in the second sedimentation tank is backflowed to the front end of the reaction zone through a sludge backflow pipeline. The effluent from the first sedimentation tank and the second sedimentation tank is combined. The first sedimentation tank introduces part of the sludge into the mixing reaction zone to control the mixing amount of suspended sludge and biofilm, so as to improve the abundance of anaerobic ammonia oxidation bacteria. The sludge in the second sedimentation tank is backflowed to the front end of the reaction zone to strengthen the overall abundance of anaerobic ammonia oxidation bacteria of suspended sludge, thereby improving the denitrification performance. At the same time, part of the carbon source is saved due to anaerobic ammonia oxidation, thereby strengthening biological phosphorus removal. The method does not need to interrupt the normal operation of the sewage treatment plant and can improve the denitrification and phosphorus removal performance. It is suitable for upgrading and reconstruction of the existing urban sewage treatment plant or deep denitrification and phosphorus removal of the newly built sewage treatment plant.

Description

Technical Field

[0001] This invention relates to the field of urban wastewater treatment technology, and in particular, to improve denitrification performance by adding a mixing reaction zone and using suspended sludge and biofilm mixing technology to increase the abundance of anaerobic ammonia-oxidizing bacteria in the denitrification and phosphorus removal unit of an urban wastewater treatment plant without interrupting the original wastewater treatment process. Background Technology

[0002] The compliant discharge of wastewater from urban wastewater treatment plants is not only a crucial foundation for ensuring the health of urban water environments and achieving sustainable water resource utilization, but also an indispensable part of environmental protection. With the rapid pace of urbanization, coupled with increasing population density and expanding industrial production, wastewater discharge is growing at an unprecedented rate, placing increasingly stringent demands on wastewater treatment efficiency and effluent quality standards. Among the many wastewater treatment indicators that urgently need improvement, enhancing denitrification performance is particularly important, as it is closely related to the concentration of nitrogen oxides in the effluent, thus profoundly impacting the prevention and control of eutrophication and the maintenance of the entire ecological environment. Therefore, exploring a new wastewater treatment technology capable of efficient denitrification to improve wastewater treatment efficiency and ensure effluent quality meets standards has become a critical issue that urgently needs to be addressed.

[0003] However, urban wastewater treatment still faces many challenges in nitrogen removal. On the one hand, nitrogen in wastewater exists in various forms, including ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen, and these different forms exhibit different transformation patterns and removal difficulties during treatment. On the other hand, urban wastewater quality fluctuates significantly, placing higher demands on the stability and adaptability of wastewater treatment processes. Furthermore, traditional wastewater treatment processes suffer from low efficiency and high energy consumption in nitrogen removal, making it difficult to meet increasingly stringent environmental protection requirements.

[0004] To address these issues, anaerobic ammonia oxidation (ANA) technology has emerged. ANA 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 ammonia-oxidizing bacteria. In wastewater treatment processes, many bacteria often only convert nitrate to nitrite, resulting in high ammonia and nitrite levels in the effluent, posing a fatal threat to aquatic organisms. Introducing ANA can effectively address this problem. Furthermore, ANA has many advantages, including low energy consumption, low sludge production, and no need for external carbon sources, showing great application potential in the wastewater treatment industry. This technology can effectively remove ammonia nitrogen and nitrite nitrogen from wastewater, improving effluent quality while reducing treatment costs. In recent years, ANA has received widespread attention and in-depth research from researchers due to its excellent nitrogen removal performance and low cost. By optimizing reaction conditions, improving microbial activity, and developing new reactors, the treatment efficiency and stability of ANA are continuously being improved.

[0005] Against this backdrop, this invention proposes a method for improving anaerobic ammonia oxidation (ANAO) nitrogen and phosphorus removal in urban wastewater treatment plants using a suspended sludge-biofilm hybridization technology. This method aims to enhance nitrogen removal performance by adding a mixing reaction zone and utilizing the ANAO-biofilm hybridization technology to increase the abundance of anaerobic ammonia-oxidizing bacteria in the nitrogen and phosphorus removal units of urban wastewater treatment plants. This innovative technology not only provides a new solution for urban wastewater treatment but also offers new insights for the further development and application of anaerobic ammonia oxidation technology. Summary of the Invention

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

[0007] The mixed reaction zone (11) is filled with a carrier, with 50%-65% biofilm filling. Anaerobic ammonia oxidizing bacteria and denitrifying bacteria grow on the carrier, and at the same time, they mix with the suspended sludge drawn from sedimentation tank one (4) to form a highly efficient denitrification and anaerobic ammonia oxidation synergistic denitrification environment. The amount of suspended sludge introduced into the mixed reaction zone (11) from sedimentation tank one (4) is controlled, and the sludge is returned from sedimentation tank one (4) to the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant through pipeline (5). This process is called sludge return, and the sludge return ratio is controlled at 75%-100%. The influent of the mixed reaction zone accounts for 20%-30% of the raw water volume, and the influent flow rate of the mixed reaction zone influent pipeline (9) is 1-2 times that of the influent flow rate of the influent pipeline (8). The hydraulic retention time in the mixed reaction zone is controlled at 4-10h to ensure that the mixed state of suspended sludge and biofilm is formed in the mixed reaction zone (11), which weakens the competition of denitrifying bacteria for nitrite nitrogen, increases the supply of nitrite nitrogen to anaerobic ammonia oxidizing bacteria, and thus optimizes the growth environment of anaerobic ammonia oxidizing bacteria.

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

[0009] Raw water can be sewage that has passed through a series of structures, such as an inlet well, equalization tank, coarse screen, fine screen, grit chamber, and primary sedimentation tank, or sewage that has passed through some of the aforementioned structures.

[0010] Technical principles and characteristics:

[0011] 1) After passing through the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant, the wastewater enters the sedimentation tank (4) to achieve sludge-water separation. The treated water is discharged from the effluent pipe (7) to the combined effluent pipe (15) and combined with the effluent from the sedimentation tank (2) (12). The sludge is returned to the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant from the sludge return pipe (5). Part of the effluent from the sedimentation tank (4) and part of the water entering the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant are introduced into the mixing reaction zone (11) to achieve the coupling of anoxic short-cut denitrification and anaerobic ammonia oxidation. At the same time, part of the sludge is drawn from the sedimentation tank (4) through the sludge pipe (10) to the mixing reaction zone (11), so that the mixed reaction zone (11) is in a mixed state of suspended sludge and biofilm. 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 to the mixed reaction zone (11) is part of the effluent from sedimentation tank 1 (4) and part of the influent from the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant. At the same time, a certain amount of suspended sludge from sedimentation tank 1 (4) is also introduced, so that the mixed reaction zone (11) is in a mixed state of suspended sludge and biofilm. Short-cut denitrification coupled with anaerobic ammonia oxidation is carried out in the mixed reaction zone. The raw water can provide organic matter and ammonia nitrogen, while the effluent from sedimentation tank 1 (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 substrate for short-cut denitrification coupled with anaerobic ammonia oxidation.

[0013] 3) The sludge from the mixed reaction zone (11) is returned to the front end of the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant through the sludge return pipeline (13), realizing the recycling of sludge. As the biofilm grows and accumulates, some of the biofilm will naturally detach. These detached biofilms are rich in anaerobic ammonia oxidizing bacteria. The detached biofilm is then returned to the front end of the denitrification and phosphorus removal unit of the municipal wastewater treatment plant. This system not only does not require external bio-enhancing, but also supplements the anaerobic ammonia oxidizing bacteria in the denitrification and phosphorus removal unit of the municipal wastewater treatment plant by increasing the mixed reaction zone, further enhancing the anaerobic ammonia oxidation biological denitrification capacity of the denitrification and phosphorus removal unit of the municipal wastewater treatment plant.

[0014] This method of using a mixture of suspended sludge and biofilm to improve anaerobic ammonia oxidation for nitrogen and phosphorus removal in urban wastewater treatment plants has the following advantages:

[0015] 1) Mixing suspended sludge with biofilm increases the abundance of anaerobic ammonia oxidizing bacteria. This invention applies the technology of mixing suspended sludge with biofilm to the anaerobic ammonia oxidation process for nitrogen and phosphorus removal in urban wastewater treatment plants. By controlling the amount of suspended sludge introduced, the state of the mixing reaction zone is optimized, increasing the abundance and activity of anaerobic ammonia oxidizing bacteria, thereby significantly enhancing nitrogen removal performance. This integrated application of technology provides a new solution for urban wastewater treatment and promotes the advancement of wastewater treatment technology.

[0016] 2) Enhanced system stability. The coexistence of suspended sludge and biofilm provides a stable growth environment for anaerobic ammonia-oxidizing bacteria, enhancing the complex metabolic potential of the microbial system and contributing to the formation of a more stable microbial ecosystem. This stability enables the system to maintain good treatment performance when faced with external disturbances such as water quality fluctuations and load changes, reducing operational risks.

[0017] 3) Optimized sludge treatment process. This invention achieves sludge recycling through a sludge return mechanism. The system reaction process is a partially autotrophic denitrification process; the removal of 1 mol of ammonia nitrogen generates only 3g of biomass, effectively reducing sludge production. Simultaneously, the detached biofilm is rich in anaerobic ammonia-oxidizing bacteria, which can further supplement and enhance the system's denitrification capacity. This helps reduce sludge disposal costs and also lowers operating costs.

[0018] 4) Enhance the treatment capacity of wastewater treatment plants. While maintaining the original treatment process, the anaerobic ammonia oxidation treatment capacity is further enhanced by adding a mixing reaction zone and combining biofilm and suspended sludge mixing technology. This optimizes the sludge state and improves microbial activity, thereby improving effluent quality and treatment efficiency. Attached Figure Description

[0019] Figure 1 This system enhances the nitrogen and phosphorus removal performance of anaerobic ammonia oxidation in urban wastewater treatment plants based on a suspended sludge and biofilm hybridization technology. Specifically, it comprises: 1-Main influent pipeline; 2-Influent branch pipeline one; 3-Urban wastewater treatment plant nitrogen and phosphorus removal unit; 4-Sedimentation tank one; 5-Sludge return pipeline one; 6-Excess sludge discharge pipeline; 7-Sedimentation tank one effluent discharge pipeline; 8-Influent branch pipeline two; 9-Sedimentation tank one effluent branch pipeline; 10-Sedimentation tank one sludge discharge pipeline; 11-Mixed reaction zone; 12-Sedimentation tank two; 13-Sludge return pipeline two; 14-Sedimentation tank two effluent discharge pipeline; 15-Combined effluent pipeline of sedimentation tanks one and two. Detailed Implementation

[0020] Combination Figure 1 The following describes the implementation scheme of the present invention in detail:

[0021] 1) Control of the influent ratio between the denitrification and phosphorus removal unit and the mixing reaction zone in urban wastewater treatment plants: This invention requires reasonable allocation of influent flow rate to control the mixed water quality, ensuring efficient operation of both the denitrification and phosphorus removal unit and the mixing reaction zone in urban wastewater treatment plants. The influent to the mixing reaction zone is designed to account for less than 30% of the raw water, and the influent flow rate of the mixing reaction zone influent pipe (9) is 1-2 times that of the mixing reaction zone influent pipe (8). Specifically, the influent flow rate of the mixing reaction zone influent branch (8) is set to 10% of the raw water, and the influent flow rate of the mixing reaction zone influent branch (9) is set to 20% of the raw water, controlling the COD / NO3 ratio. - -N is between 2.0 and 5.0, NO3 - -N / NH4 +-N is between 1.0 and 3.0. This allocation method not only meets the influent requirements of the mixing reaction zone, but also ensures efficient operation of both the nitrogen and phosphorus removal units and the mixing reaction zone in the municipal wastewater treatment plant. In practice, the influent flow rate of each pipeline can be controlled by adjusting the flow rate of the influent valves or pump stations. Simultaneously, the flow rate of each pipeline needs to be monitored regularly to ensure it meets design requirements.

[0022] 2) Controlling the amount of suspended sludge introduced: By adjusting the amount of suspended sludge introduced into the mixing reaction zone from sedimentation tank one, the ratio of suspended sludge to biofilm in sedimentation tank two is controlled. This ensures that the amount of suspended sludge is sufficiently small yet forms a good mixture with the biofilm, thereby maximizing the abundance of anaerobic ammonia-oxidizing bacteria. The concentration of suspended sludge in the mixing reaction zone was reduced from 4067±382 mg VSS / L to 2046±261 mg VSS / L. During this process, the denitrification performance gradually improved, and anaerobic ammonia-oxidizing bacteria significantly enriched to (6.12±0.22)×10⁻⁶. 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 in the mixing reaction zone (11) is controlled at 4 to 10 hours. After the entire system is running stably, the influent NH4 + When the -N concentration is 40 mg / L and the influent COD / TN ratio is 4, the effluent COD concentration is 20–50 mg / L, and NH4+ concentration is... + -N concentration is 0-1 mg / L, NO3 - -N concentration is 4–8 mg / L, and TN concentration is 3–10 mg / L.

Claims

1. A method for improving anaerobic ammonia oxidation denitrification and phosphorus removal in urban wastewater treatment plants using a suspended sludge and biofilm mixing technology, characterized in that: Wastewater enters through the inlet pipe (1), part of which enters the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant through pipe one (2), and part of which enters the mixing reaction zone through pipe two (8). After being treated by the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant, the wastewater enters the sedimentation tank one (4). Part of the effluent from the sedimentation tank one (4) enters the mixing reaction zone (11) through pipe three (9), part of the sludge enters the mixing reaction zone (11) through the sludge discharge pipe (10) of the sedimentation tank one, and a portion of the sludge is returned to the municipal wastewater treatment plant for denitrification and phosphorus removal through the sludge return pipe one (5). Unit (3), the remaining sludge is discharged through pipe (6); a portion of the raw water enters the mixing reaction zone through pipe two (8) and then enters sedimentation tank two (12). The sludge in sedimentation tank two is returned to the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant through sludge return pipe two (13). The effluent from sedimentation tank one (4) and sedimentation tank two (12) are combined through effluent pipe one (7) and effluent pipe two (14) to effluent pipe three (15) for combined effluent discharge. A portion of the sludge from sedimentation tank one (4) is introduced to the mixing reaction zone (11) to make it a mixed state of suspended sludge and biofilm. The mixed reaction zone (11) is filled with biofilm, with a biofilm filling ratio of 50% to 65%. The amount of suspended sludge introduced into the mixed reaction zone (11) from the sedimentation tank (4) is controlled. The sludge is returned from the sedimentation tank (4) to the denitrification and phosphorus removal unit (3) of the municipal wastewater treatment plant through the sludge return pipeline (5). This process is called sludge return. The sludge return ratio is controlled at 75%-100%. The influent of the mixed reaction zone accounts for 20% to 30% of the original water volume. The influent flow rate of the mixed reaction zone pipeline (9) is 1 to 2 times that of the influent flow rate of the pipeline (8). The hydraulic retention time of the mixed reaction zone is controlled at 4-10 hours.

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