Method for enhancing anaerobic ammonia oxidation nitrogen and phosphorus removal of urban sewage treatment plant by using exfoliated biological membrane

Abstract

The invention discloses a method for reinforcing anaerobic ammonia oxidation denitrification and dephosphorization of an urban sewage treatment plant by using a falling biological membrane. The method is realized based on a system consisting of two main units, namely a functional area I and a functional area II. Inlet water of the first functional area and part of outlet water of the settling pond enter a second functional area anoxic zone (8), and sludge of the second functional area flows back to a first functional area nitrogen and phosphorus removal unit (1) of the urban sewage treatment plant from a second functional area settling pond (9) through a sludge backflow pipeline (10). Therefore, the overall anaerobic ammonium oxidation bacteria abundance of the suspended sludge in the system of the functional area I is enhanced, and the denitrification performance is further improved. The anoxic zone reduces the nitrogen load of the whole system, and meanwhile, part of carbon sources saved in the anaerobic ammonia oxidation process are beneficial to biological phosphorus removal. According to the method, the nitrogen and phosphorus removal performance can be effectively improved without interrupting operation of the sewage treatment plant, 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 particularly to enhancing the overall anaerobic ammonia-oxidizing bacteria abundance of suspended sludge in functional zone one by adding a second functional zone and utilizing anaerobic ammonia-oxidizing bacteria contained in detached biofilms without interrupting the original sewage treatment process of an urban sewage treatment plant, thereby expecting to improve denitrification performance. Background Art

[0002] The compliance of urban sewage treatment plants with discharge standards is an important part of environmental protection, and the improvement of nitrogen removal performance is the key. 2 Although the / O process can achieve nitrogen and phosphorus removal to a certain extent, its nitrogen removal efficiency is often limited when treating low carbon-nitrogen ratio sewage, and the large amount of aeration and external carbon source required for aerobic nitrification greatly increase the cost of sewage treatment. In addition, in order to meet increasingly stringent emission standards, many sewage treatment plants have to be upgraded, and traditional upgrading methods often require shutdown construction, which brings inconvenience to urban drainage. Therefore, seeking low-cost and high-efficiency sewage denitrification technology to upgrade and transform urban sewage treatment plants without stopping water is a difficult problem in the current environmental field.

[0003] Anaerobic ammonium oxidation (Anammox) is a new type of autotrophic biological denitrification process. After its discovery and confirmation, it has made autotrophic denitrification of sewage possible. In the field of environment, especially in wastewater treatment, anaerobic ammonium oxidation technology has shown significant advantages and development potential. In the anaerobic ammonium oxidation autotrophic denitrification process, part of the ammonia nitrogen needs to be oxidized into nitrite nitrogen, and then this nitrite nitrogen will oxidize the remaining part of the ammonia nitrogen to finally achieve the purpose of denitrification. Only 0.8 mol of oxygen is consumed in this process; organic matter is not required as a carbon source, but carbon dioxide is used as a carbon source; because it is a full autotrophic denitrification, the amount of sludge produced is low, and the removal of 1 mol of ammonia nitrogen only generates 3g of organisms. However, there are still some difficulties in applying anaerobic ammonium oxidation technology to functional area-urban sewage. For example, the ammonia nitrogen content in urban sewage is particularly low, which cannot provide sufficient substrate for anaerobic ammonium oxidation and is difficult to complete; the water temperature of urban sewage is relatively low, and the optimal temperature for anaerobic ammonium oxidation is 28-37°C, and the reaction activity doubles with every 10 degrees Celsius increase. The temperature of urban sewage is difficult to stably reach the optimal temperature, and the system is unstable; the amount of urban sewage is large, and the types and numbers of microorganisms in the system may be more complex, making it more difficult to directional control of competitive microorganisms (such as NOB); when introducing anaerobic ammonium oxidation technology into the municipal sewage functional area-process application, it is necessary to solve the technical bottlenecks caused by the differences in water quality, water temperature, water volume, etc. between domestic sewage and high-nitrogen wastewater.

[0004] With the continuous deepening of research on anaerobic ammonium oxidation technology and the continuous expansion of engineering applications, this technology is expected to be applied in more fields, such as urban sewage treatment, industrial wastewater treatment, etc. The combination of anaerobic ammonium oxidation technology with membrane technology, bio-augmentation technology, etc. will also become an important direction for future development to improve treatment efficiency and reduce costs. Summary of the invention

[0005] A method for strengthening anaerobic ammonium oxidation denitrification and phosphorus removal in a municipal sewage treatment plant by shedding biofilm, the method is implemented based on a system consisting of two main units: functional zone one and functional zone two. Functional zone one includes a denitrification and phosphorus removal unit (1) in functional zone one of a municipal sewage treatment plant; a sedimentation tank (2) in functional zone one; a sludge return pipeline (3); a residual sludge discharge pipeline (4); and a effluent discharge pipeline (5) in the sedimentation tank in functional zone one. Functional zone two includes an anoxic zone inlet pipeline (6) in functional zone two; an effluent branch of the sedimentation tank in functional zone one (7); an anoxic zone in functional zone two (8); a sedimentation tank in functional zone two (9); a sludge return pipeline (10) in functional zone two; an effluent discharge pipeline (11) in the sedimentation tank in functional zone two; and a combined effluent pipeline (12) for sedimentation tanks in functional zone one and functional zone two. A portion of the effluent from the functional zone 1 sedimentation tank (2) enters the functional zone 2 anoxic zone (8) through a pipeline (7), and a portion of the influent also enters the functional zone 2 anoxic zone (8) through a pipeline. Only the sludge is returned to the functional zone 1 through a sludge return pipeline (10). The anaerobic ammonia-oxidizing bacteria contained in the detached biofilm are utilized to enhance the overall anaerobic ammonia-oxidizing bacteria abundance of the suspended sludge in the functional zone 1 system, thereby improving the denitrification performance. Specifically, in the functional zone 1, the sewage enters the denitrification and phosphorus removal unit (1) of the functional zone 1 of the urban sewage treatment plant, and after treatment, enters the sedimentation tank (2) of the functional zone 1, and the treated sewage is directly discharged; the bottom of the sedimentation tank (2) of the functional zone 1 is connected to the front end of the denitrification and phosphorus removal unit (1) of the functional zone 1 of the urban sewage treatment plant through a sludge return pipeline (3). The remaining sludge is subsequently treated through a discharge pipeline (4). A portion of the effluent from the functional zone 1 sedimentation tank (2) enters the functional zone 2 anoxic zone (8), and a portion of the influent also enters the functional zone 2 anoxic zone (8). The treated effluent enters the functional zone 2 sedimentation tank (9), and the sludge is returned to the front end of the functional zone 1 denitrification and phosphorus removal unit (1) of the urban sewage treatment plant through the sludge return pipeline (10). The effluents from the functional zone 1 sedimentation tank (2) and the functional zone 2 sedimentation tank (9) are respectively combined into the effluent of the pipeline (12) through the pipeline (5) and the pipeline (11). The functional zone 2 anoxic zone (8) is composed of a carrier that is easy to form a biofilm, and the biofilm is arranged in a manner that is easy to fluidize. Then, the effluent from the functional zone 2 anoxic zone is returned to the front end of the functional zone 1 through the functional zone 2 sedimentation tank (9), so that the anaerobic ammonia oxidizing bacteria in the detached biofilm can be supplemented to the functional zone 1 process, thereby strengthening the autotrophic biological denitrification capacity of the functional zone 1.

[0006] The process of functional area 1 can be plug flow A2 / O process, or its improved plug flow process, such as A / O, multi-stage A / O, AOA, UCT process, etc. The sludge return ratio is generally controlled at 50% to 100%.

[0007] 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.

[0008] Its technical principles and characteristics:

[0009] 1) After passing through the denitrification and phosphorus removal unit (1) of the functional area of ​​the urban sewage treatment plant, the sewage enters the sedimentation tank (2) of the functional area to achieve mud and water separation. The treated water is discharged from the effluent pipe (5) into the combined effluent pipe (12) to be combined with the effluent of the sedimentation tank (9) of the functional area, and the sludge is discharged from the residual sludge discharge pipe (4). Part of the effluent of the sedimentation tank and part of the water entering the denitrification and phosphorus removal unit (1) of the functional area of ​​the urban sewage treatment plant are introduced into the anoxic area (8) of the functional area to achieve the coupling of anoxic short-range denitrification and anaerobic ammonia oxidation.

[0010] 2) The influent of the anoxic zone (8) of the functional zone II is part of the effluent of the sedimentation tank (2) of the functional zone I and part of the influent of the nitrogen removal and phosphorus removal unit (1) of the functional zone I of the urban sewage treatment plant. The nitrate nitrogen uses the carbon source in the raw water to undergo heterotrophic denitrification, i.e., the process of reducing the nitrate nitrogen to nitrogen gas. At the same time, short-range denitrification occurs in a low C / N ratio environment to produce nitrite nitrogen. Nitrite nitrogen and ammonia nitrogen are important substrates for anaerobic ammonium oxidation. The combination of the two can also produce nitrogen gas by anaerobic ammonium oxidation.

[0011] 3) The sludge from the sedimentation tank (9) of functional area 2 is returned to the front end of the denitrification and phosphorus removal unit (1) of functional area 1 of the urban sewage treatment plant through the sludge return pipeline (10) of functional area 2. As the biofilm grows and accumulates, part of the biofilm will fall off naturally. These fallen biofilms are rich in anaerobic ammonium oxidizing bacteria, which can use ammonia nitrogen and nitrite nitrogen for anaerobic ammonium oxidation denitrification, thereby significantly enhancing the denitrification capacity of the system. The fallen biofilm is then returned to the front end of functional area 1, replenishing the anaerobic ammonium oxidizing bacteria in functional area 1, further strengthening the anaerobic ammonium oxidation denitrification capacity of functional area 1.

[0012] This method has the following advantages:

[0013] 1) Improve the efficiency of autotrophic nitrogen removal and reduce energy consumption. The detached biofilm is rich in anaerobic ammonia-oxidizing bacteria. In the anaerobic ammonia-oxidizing autotrophic nitrogen removal process, part of the ammonia nitrogen in the nitrite nitrogen oxidation can be oxidized, and finally the purpose of nitrogen removal is achieved. In this process, only 0.8 mol of oxygen is consumed; no organic matter is required as a carbon source, but carbon dioxide is used as a carbon source; compared with the traditional nitrification / denitrification process, anaerobic ammonia oxidation can reduce aeration and carbon source requirements, and convert ammonia nitrogen and nitrite nitrogen into nitrogen. Through the reflux of the functional area two system, the anaerobic ammonia-oxidizing bacteria in the detached biofilm can be supplemented to the functional area one process, effectively improving the autotrophic nitrogen removal efficiency of the entire system. Therefore, the present invention significantly reduces the dependence on aeration volume and organic carbon sources, thereby reducing operating energy consumption and operating costs.

[0014] 2) Low residual sludge production. The system reaction process is partial autotrophic denitrification. The removal of 1 mol of ammonia nitrogen only generates 3g of organisms. The sludge production is effectively reduced, which is conducive to reducing the cost of sludge disposal and also reduces the operating cost.

[0015] 3) Improve the robustness and stability of the system. The introduction of anaerobic ammonium oxidizing bacteria enhances the system's ability to treat low C / N ratio sewage. Even when the influent carbon-nitrogen ratio is insufficient, the system can still maintain a high denitrification efficiency. In addition, the presence of biofilm provides a stable growth environment for anaerobic ammonium oxidizing bacteria, improves the complex metabolic potential of the microbial system, enhances the system's shock resistance and stability, and makes the effluent water quality more stable and reliable.

[0016] 4) Upgrading and transformation measures are simple. The process of the present invention is simple and flexible, and it is easy to upgrade and transform existing urban sewage treatment plants without stopping water supply. By adding functional area 2, the denitrification performance can be significantly improved. This transformation method does not require large-scale changes to the existing process or water supply shutdown transformation, which reduces the difficulty and construction period of the transformation, will not have a serious impact on urban drainage, and is conducive to rapid promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a system for strengthening the anaerobic ammonium oxidation denitrification and phosphorus removal of urban sewage treatment plants by using detached biofilm. It mainly includes: functional area one and functional area two. Specifically: 1-denitrification and phosphorus removal unit of functional area one of urban sewage treatment plant; 2-sedimentation tank of functional area one; 3-sludge return pipeline; 4-residual sludge discharge pipeline; 5-effluent discharge pipeline of sedimentation tank of functional area one; 6-inlet pipeline of anoxic zone of functional area two; 7-effluent branch of sedimentation tank of functional area one; 8-anoxic zone of functional area two; 9-sedimentation tank of functional area two; 10-sludge return pipeline of functional area two; 11-effluent discharge pipeline of sedimentation tank of functional area two; 12-merged effluent pipeline of sedimentation tanks of functional area one and functional area two. DETAILED DESCRIPTION

[0018] Combination Figure 1 , describe the embodiments of the present invention in detail:

[0019] 1) Construction of functional area II anoxic zone: In the urban sewage treatment plant, the anoxic zone is constructed with reinforced concrete structure to ensure smooth connection with the entire treatment system and not affect the original sewage treatment facilities. After calculation, it was determined that the volume of the anoxic zone is 5,000 cubic meters to meet the water treatment and denitrification needs.

[0020] 2) Start the system: The sewage first enters the functional area 1 and is treated by the existing process treatment equipment of the urban sewage treatment plant. Subsequently, part of the influent and part of the effluent of the functional area enter the anoxic area of ​​the functional area 2 through the pipeline. The influent of the functional area 2 accounts for 20% to 30% of the volume of the original water. The influent flow rate of the influent pipeline (7) of the functional area 2 is twice the influent flow rate of the influent pipeline (6) of the functional area 2. In order to ensure that the biofilm in the anoxic area can be successfully formed and function, polyethylene fillers (diameter 25mm) with anaerobic ammonium oxidation biofilms already formed are inoculated, and the total amount of fillers is 1000 cubic meters.

[0021] 3) The process of functional area 1 can be plug flow A 2 A / O process, or its improved push flow process, such as A / O, multi-stage A / O, AOA, UCT process, etc. 2 / O as an example to explain the operating parameters in detail.

[0022] When the functional zone 1 is A / O process, the sludge return ratio of the functional zone 1 is controlled at 50% to 100%, the hydraulic retention time of the anoxic zone is controlled at 2 to 4 hours, and the hydraulic retention time of the aerobic zone is controlled at 4 to 6 hours. 4 + Under the conditions of -N concentration of 50mg / L and influent COD / TN of 5, after system treatment, the effluent NH 4 + -N concentration dropped to 0-0.5 mg / L, TN concentration dropped to 0-10 mg / L, and the denitrification efficiency was significantly improved.

[0023] When the function area is A 2 When the / O process is used, the sludge return ratio is controlled at 50% to 100%, the hydraulic retention time of the anaerobic tank is controlled at 12 hours, the hydraulic retention time of the anoxic tank is controlled at 24 hours, and the hydraulic retention time of the aerobic tank is controlled at 46 hours. The sludge return ratio is controlled at 50% to 125%. A portion of the effluent from the sedimentation tank (2) of functional area 1 enters the anoxic area (8) of functional area 2 through the pipeline (7), and at the same time, a portion of the influent from the functional area also enters the anoxic area (8) of functional area 2 through the pipeline (6), so as to control COD / NO 3 - -N is between 2.0-5.0, NO 3- -N / NH 4 + -N is between 1.0 and 3.0. The hydraulic retention time of the second functional zone, the anoxic zone (8), is controlled at 10 to 15 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 strengthening anaerobic ammonium oxidation denitrification and phosphorus removal in a municipal sewage treatment plant by shedding biofilm, characterized in that: The method is implemented based on a system consisting of two main units, functional zone one and functional zone two; the functional zone one comprises a denitrification and phosphorus removal unit (1) of the functional zone one of the urban sewage treatment plant, a sedimentation tank (2) of the functional zone one, a sludge return pipeline (3), a residual sludge discharge pipeline (4) and a effluent discharge pipeline (5) of the sedimentation tank of the functional zone one; the functional zone two comprises an anoxic zone inlet pipeline (6) of the functional zone two, an effluent branch (7) of the sedimentation tank of the functional zone one, an anoxic zone (8) of the functional zone two, a sedimentation tank of the functional zone two (9), a sludge return pipeline (10) of the functional zone two, an effluent discharge pipeline (11) of the sedimentation tank of the functional zone two and a combined effluent pipeline (12) of the sedimentation tanks of the functional zone one and the functional zone two; a portion of the effluent of the sedimentation tank of the functional zone one enters the anoxic zone (8) of the functional zone two through a pipeline (7), while a portion of the inlet The sludge from the second functional area also enters the anoxic zone (8) of the second functional area through the pipeline. The sludge from the second functional area flows back from the second functional area sedimentation tank (9) through the sludge return pipeline (10) to the first denitrification and phosphorus removal unit (1) of the first functional area urban sewage treatment plant. The effluents from the first functional area and the second functional area are combined into the combined pipeline (12) of the effluents from the first functional area and the second functional area sedimentation tanks. The second functional area anoxic zone (8) is filled with carriers. The second functional area anoxic zone (8) is not provided with suspended sludge. The effluent from the second functional area anoxic zone flows back to the front end of the first functional area through the second functional area sedimentation tank (9), so that the anaerobic ammonia oxidizing bacteria in the detached biofilm can be replenished to the first functional area. The influent from the second functional area accounts for 20% to 30% of the volume of the raw water. The influent flow rate of the influent pipeline (7) of the second functional area is 1 to 2 times the influent flow rate of the influent pipeline (6) of the second functional area.

2. The method of claim 1, characterized in that The process of functional area 1 is plug flow A 2 / O process, A / O, multi-level A / O, AOA or UCT process.

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