Device and method for resolving age contradiction of nitrogen and phosphorus removal sludge in municipal sewage A2 / O process

Abstract

The invention discloses a device and a method for resolving the sludge age contradiction of nitrogen and phosphorus removal in an A2 / O process of urban sewage, and belongs to the technical field of sewage treatment. The device adopts an anoxic-anaerobic-aerobic preposed anoxic process, and part of raw water is introduced into an anaerobic zone through inlet water diversion, so that a sufficient carbon source is provided for phosphorus release of phosphorus-accumulating bacteria. Part of effluent of the secondary sedimentation tank flows back to the anoxic zone to provide nitrate nitrogen, sludge flows back to the anaerobic zone and the anoxic zone respectively, and enrichment of anaerobic ammonium oxidation bacteria is enhanced by dynamically regulating and controlling the proportion of suspended sludge in the anoxic zone. According to the system, the anoxic zone and the aerobic zone are both provided with biological stuffing, anaerobic ammonium oxidation bacteria and nitrifying bacteria are enriched respectively, denitrifying bacteria and phosphorus-accumulating bacteria mainly exist in suspended sludge, and sludge age decoupling and efficient synergy of functional flora are achieved. The method effectively solves the contradiction between carbon source competition and sludge age of denitrification and dephosphorization in the traditional A2 / O process, has the advantages of high efficiency, energy conservation and stability, and is suitable for treating urban sewage with low carbon-nitrogen ratio.

Description

Technical Field

[0001] This invention relates to the field of urban wastewater treatment technology, and more particularly to a method for treating urban wastewater A 2 Devices and methods for resolving the contradiction between the nitrogen and phosphorus removal sludge age in the / O process. Background Technology

[0002] With increasingly stringent environmental protection requirements, ensuring stable and compliant discharge from urban wastewater treatment plants has become a crucial aspect of maintaining the aquatic ecological environment and promoting sustainable social development. However, existing wastewater treatment technologies, especially traditional A... 2 The / O process faces a severe challenge in consistently achieving core effluent indicators (total nitrogen and total phosphorus) when treating municipal wastewater with low C / N ratios. Furthermore, this process has inherent flaws: intense competition for carbon sources exists within the system, and the limited amount of readily degradable organic matter cannot simultaneously meet the phosphorus release needs of polyphosphate-accumulating bacteria in the anaerobic zone and the nitrogen removal needs of denitrifying bacteria in the anoxic zone, leading to a mutual constraint between phosphorus and nitrogen removal efficiency. The fundamental limitation lies in the sludge age contradiction: long-generation-cycle nitrifying bacteria require long sludge ages to maintain their population, while polyphosphate-accumulating bacteria that remove phosphorus through sludge discharge require short sludge ages. This contradiction cannot be reconciled in a single sludge system, forcing compromises in operating parameters, making it difficult to simultaneously achieve efficient nitrification and deep phosphorus removal. In addition, traditional processes rely on a high proportion of nitrification liquor recirculation to ensure nitrogen removal efficiency, which not only leads to high energy consumption, but the dissolved oxygen carried in the recirculation liquor also interferes with the stability of the anoxic environment; simultaneously, the large amount of aeration required in the aerobic zone to achieve full nitrification further increases operating costs. These limitations together constitute the technological bottlenecks that urgently need to be overcome in the current wastewater treatment field. Summary of the Invention

[0003] The purpose of this invention is to provide a method for treating urban sewage A 2 The device and method for resolving the sludge age contradiction in the / O process for nitrogen and phosphorus removal employs a pre-anoxic process of "anoxic-anaerobic-aerobic". Part of the raw water is introduced into the anaerobic zone via a branch to ensure sufficient carbon source for phosphorus release by polyphosphate-accumulating bacteria. The effluent from the secondary sedimentation tank is returned to the anoxic zone to provide nitrate nitrogen, the reaction substrate required by anaerobic ammonia oxidizing bacteria and denitrifying bacteria. A portion of the sludge from the secondary sedimentation tank is returned to the anaerobic zone through a sludge return pipeline to maintain polyphosphate-accumulating bacteria biomass, while another portion is returned to the anoxic zone through the same pipeline. The enrichment of anaerobic ammonia oxidizing bacteria in the anoxic zone is enhanced by dynamically controlling the proportion of suspended sludge. Biological packing materials are added to both the anoxic and aerobic zones. The biofilm on the packing material in the anoxic zone enriches anaerobic ammonia oxidizing bacteria, while the biofilm on the packing material in the aerobic zone enriches nitrifying bacteria. Denitrifying bacteria and polyphosphate-accumulating bacteria are mainly found in the suspended sludge, achieving decoupling of sludge age for different functional bacteria in a single system, thereby resolving the traditional A / O process contradiction. 2 The / O process presents a contradiction between denitrification and phosphorus removal.

[0004] To achieve the above objectives, the present invention provides a method for treating urban sewage A 2 / O process denitrification and phosphorus removal sludge age contradiction device, the device includes an anoxic zone (3), an anaerobic zone (5), an aerobic zone (7) and a secondary sedimentation tank (9) connected in sequence. The anoxic zone (3) is equipped with a main inlet pipe (1), a sedimentation tank effluent return pipe (11), a sludge return pipe (14), and an anoxic zone effluent pipe (4) leading to the anaerobic zone (5). The sludge return pipeline (14) is used to connect the anoxic zone (3) and the secondary sedimentation tank (9). The anaerobic zone (5) is equipped with an inlet branch (2), an anaerobic zone outlet pipe (6), and a sludge return pipe (13). The sludge return pipeline (13) is used to connect the anaerobic zone (5) and the secondary sedimentation tank (9). The aerobic zone (7) is connected to the secondary sedimentation tank (9) through the aerobic zone outlet pipe (8); The secondary sedimentation tank (9) is equipped with a sedimentation tank outlet pipeline (10) and a sedimentation tank sludge discharge pipeline (12). The anoxic zone (3) is equipped with anoxic zone biological packing material (15); The aerobic zone (7) is equipped with aerobic zone biological packing material (16).

[0005] Optionally, the diversion ratio of the water inlet branch (2) is 20% to 50%.

[0006] Optionally, the return ratio of the sedimentation tank effluent return pipeline (11) is 50%~150%; the return ratio of the sludge return pipeline (14) is 5%~45%; and the return ratio of the sedimentation tank sludge return pipeline (13) is 50%~100%.

[0007] Optionally, the anoxic zone biological packing material (15) and the aerobic zone biological packing material (16) are both at least one of modified polyethylene suspension packing material or combined packing material; The filling ratio of the anoxic zone biological packing material (15) is 10%~40%, and the filling ratio of the aerobic zone biological packing material (16) is 20%~60%. The filling ratio is the volume ratio of the biological packing material volume in the reaction zone to the effective volume of the corresponding reaction zone. The specific surface area of ​​both the anoxic zone biological packing material (15) and the aerobic zone biological packing material (16) is 400~600 m². 2 / m 3 The densities are all 0.96~1.00 g / cm³. 3 .

[0008] Secondly, this invention provides a method for resolving urban sewage A 2The method to address the conflicting sludge ages in the / O process for nitrogen and phosphorus removal utilizes the aforementioned apparatus and includes the following steps: Wastewater enters the anoxic zone (3) through the main inlet pipe (1), while 20% to 50% of the inlet water enters the anaerobic zone (5) through the inlet branch pipe (2). Denitrification and short-cut denitrification coupled with anaerobic ammonia oxidation are carried out in the anoxic zone (3); Wastewater enters the anaerobic zone (5) for phosphorus release reaction; Wastewater enters the aerobic zone (7) for nitrification. The effluent from the aerobic zone (7) enters the secondary sedimentation tank (9) for solid-liquid separation.

[0009] Optionally, the hydraulic retention time of the anoxic zone (3) is 1.5 to 4.0 hours, the hydraulic retention time of the anaerobic zone (5) is 1.0 to 2.0 hours, and the hydraulic retention time of the aerobic zone (7) is 4.0 to 8.0 hours.

[0010] Optionally, the dissolved oxygen concentration in the aerobic zone (7) is controlled at 1.5~2.5 mg / L.

[0011] Optionally, activated sludge is inoculated when the system is started, so that the sludge concentration in the anaerobic zone (5) and aerobic zone (7) is 3000~5000mg / L, the sludge concentration in the anoxic zone (3) is controlled to be 1000~3000mg / L, and anaerobic ammonia oxidation biofilm packing is added to the anoxic zone (3). If there are no inoculation conditions, blank packing is added.

[0012] Optionally, it also includes a post-treatment step: part of the effluent from the secondary sedimentation tank (9) is returned to the anoxic zone (3) via the sedimentation tank effluent return pipeline (11), part of the sludge is returned to the anaerobic zone (5) via the sludge return pipeline (13), and another part of the sludge is returned to the anoxic zone (3) via the sludge return pipeline (14).

[0013] Compared with the prior art, the beneficial effects of the present invention include: 1. Principle of Pre-Anoxic Process Restructuring and Targeted Carbon Source Allocation: The system of this invention adopts a "anoxic-anaerobic-aerobic" process flow. Influent and returned sludge first enter the pre-anoxic zone, utilizing the high-quality carbon source in the influent to complete pre-denitrification of nitrates, completely eliminating the interference of nitrates on the subsequent anaerobic environment. This creates pure conditions for polyphosphate-accumulating bacteria to exclusively occupy the carbon source and fully release phosphorus in the anaerobic zone, fundamentally solving the carbon source competition contradiction in traditional processes.

[0014] 2. Dual-Recirculation Path Optimization and Anaerobic Ammonium Oxidation Driving Principle: The system adopts a unique dual-recirculation design. The sludge from the secondary sedimentation tank is returned to the anaerobic zone to circulate and enrich functional polyphosphate-accumulating bacteria; while the effluent from the secondary sedimentation tank is returned to the anoxic zone. Its main function is to supply the necessary reaction substrates for short-cut denitrification coupled with anaerobic ammonium oxidation in the anoxic zone, thereby activating and maintaining this highly efficient and energy-saving denitrification main path that does not require organic carbon sources or large amounts of aeration.

[0015] 3. Principle of Sludge Age Decoupling and System Stability Enhanced by Dual-Zone Packing: Biological packing is added to both the anoxic and aerobic zones, constructing a composite biological system where suspended and attached growth coexist. This design allows slow-growing nitrifying bacteria and anaerobic ammonia-oxidizing bacteria to remain within the biofilm, enjoying an extremely long sludge age; while suspended sludge can operate with a shorter sludge age, facilitating efficient phosphorus removal through sludge discharge. This achieves the ideal state of "one system, two sludge ages," perfectly resolving the sludge age conflict between functional microbial communities and significantly improving the system's biomass and resistance to shock loads.

[0016] 4. Save carbon source: The anaerobic ammonia oxidation process saves some carbon source, which is then used to enhance biological phosphorus removal, thereby improving resource utilization efficiency and reducing operating costs.

[0017] 5. Improved Nitrogen Removal Efficiency: Short-cut denitrification technology controls conditions to reduce nitrate nitrogen only to nitrite nitrogen, rather than completely reducing it to nitrogen gas, thus accumulating nitrite. This intermediate product, nitrite, then acts as an electron acceptor in the anaerobic ammonia oxidation process, being converted into nitrogen gas along with ammonia nitrogen, achieving highly efficient nitrogen removal. This process not only saves carbon sources and aeration energy consumption but also reduces greenhouse gas emissions and improves total nitrogen removal rate.

[0018] 6. Low residual sludge production: The system reaction process is a partial autotrophic denitrification process. The removal of 1 mol of ammonia nitrogen only generates 3g of biological matter, which effectively reduces sludge production, helps to reduce sludge disposal costs, and also reduces operating costs. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This invention addresses the treatment of urban sewage A 2 A schematic diagram of the device for the / O process denitrification and phosphorus removal sludge age contradiction.

[0020] In the diagram: 1 represents the main inlet pipe; 2 represents the inlet branch pipe; 3 represents the anoxic zone; 4 represents the anoxic zone effluent pipe; 5 represents the anaerobic zone; 6 represents the anaerobic zone effluent pipe; 7 represents the aerobic zone; 8 represents the aerobic zone effluent pipe; 9 represents the secondary sedimentation tank; 10 represents the sedimentation tank effluent pipe; 11 represents the sedimentation tank effluent return pipe; 12 represents the sedimentation tank sludge discharge pipe; 13 represents the sludge return pipe leading to the anaerobic zone; 14 represents the sludge return pipe leading to the anoxic zone; 15 represents the biological packing material in the anoxic zone; 16 represents the biological packing material in the aerobic zone. Detailed Implementation

[0021] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0022] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0023] In this invention, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between the associated objects, indicating that three relationships can exist.

[0024] like Figure 1 As shown, this invention addresses the treatment of urban sewage A. 2 A schematic diagram of the device for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal. In the diagram: 1 represents the main inlet pipe; 2 represents the inlet branch pipe; 3 represents the anoxic zone; 4 represents the anoxic zone effluent pipe; 5 represents the anaerobic zone; 6 represents the anaerobic zone effluent pipe; 7 represents the aerobic zone; 8 represents the aerobic zone effluent pipe; 9 represents the secondary sedimentation tank; 10 represents the sedimentation tank effluent pipe; 11 represents the sedimentation tank effluent return pipe; 12 represents the sedimentation tank sludge discharge pipe; 13 represents the sludge return pipe to the anaerobic zone; 14 represents the sludge return pipe to the anoxic zone; 15 represents the biological packing material in the anoxic zone; 16 represents the biological packing material in the aerobic zone.

[0025] A method for resolving urban sewage A 2 The method to address the conflicting sludge age issue in the / O process for nitrogen and phosphorus removal is carried out using the aforementioned device, with the following steps: (1) System startup and inoculation Activated sludge was retrieved from the secondary sedimentation tank of a traditional urban wastewater treatment plant and inoculated into the main biological reaction zone of this system, so that the sludge concentration in the anaerobic zone (5) and aerobic zone (7) was 4000 mg / L, and the sludge concentration in the anoxic zone (3) was controlled at 2000 mg / L, thus providing a growth basis for microorganisms such as denitrifying bacteria, polyphosphate-accumulating bacteria, and nitrifying bacteria. At the same time, modified polyethylene suspended packing was added to the anoxic zone and aerobic zone. All packing materials were purchased from environmentally friendly packing material manufacturers; the filling ratio of biological packing material (15) in the anoxic zone was 25%, and the filling ratio of biological packing material (16) in the aerobic zone was 40%. Anaerobic ammonia oxidation biofilm packing was added to the anoxic zone (3). Blank packing material could be added if there were no inoculation conditions.

[0026] (2) Main operating parameters and control The main operating parameters of the system are set as follows: A portion of the sludge from the secondary sedimentation tank is returned to the anaerobic zone via a sludge return pipeline, with the sludge return ratio controlled at 80%. A portion of the effluent from the secondary sedimentation tank is returned to the anoxic zone via a nitrification liquor return pipeline, with the nitrification liquor return ratio controlled at 150%. The dissolved oxygen concentration in the aerobic zone is precisely controlled at 2.0 mg / L through the aeration system to ensure complete nitrification while also saving energy. The hydraulic retention time (HRT) in the anoxic zone is controlled at 2.0 hours, in the anaerobic zone at 1.5 hours, and in the aerobic zone at 6.0 hours. To ensure effective phosphorus release in the anaerobic zone, 30% of the raw water is directly introduced into the anaerobic zone through a diversion pipeline to provide a sufficient carbon source.

[0027] (3) Treatment effect Once the entire system is running stably, with an influent COD concentration of 250-400 mg / L and NH4+ concentration of... + Under typical urban wastewater conditions with -N concentration of 40~50 mg / L and TP concentration of 5~7 mg / L, the effluent COD concentration of the system can be reduced to <30 mg / L, and NH4+ concentration can be reduced to <30 mg / L. + -N concentration can be reduced to <1.0 mg / L, TN concentration can be reduced to <10 mg / L, and TP concentration can be reduced to <0.5 mg / L. All major indicators can meet the Class A standard in the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002).

[0028] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0029] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A method for treating urban sewage A 2 The device for resolving the conflict between the nitrogen and phosphorus removal sludge age in the / O process is characterized by... The device includes an anoxic zone (3), an anaerobic zone (5), an aerobic zone (7), and a secondary sedimentation tank (9) connected in sequence. The anoxic zone (3) is equipped with a main inlet pipe (1), a sedimentation tank effluent return pipe (11), a sludge return pipe (14), and an anoxic zone effluent pipe (4) leading to the anaerobic zone (5). The sludge return pipeline (14) is used to connect the anoxic zone (3) and the secondary sedimentation tank (9). The anaerobic zone (5) is equipped with an inlet branch (2), an anaerobic zone outlet pipe (6), and a sludge return pipe (13). The sludge return pipeline (13) is used to connect the anaerobic zone (5) and the secondary sedimentation tank (9). The aerobic zone (7) is connected to the secondary sedimentation tank (9) through the aerobic zone outlet pipe (8); The secondary sedimentation tank (9) is equipped with a sedimentation tank outlet pipeline (10) and a sedimentation tank sludge discharge pipeline (12). The anoxic zone (3) is equipped with anoxic zone biological packing material (15); The aerobic zone (7) is equipped with aerobic zone biological packing material (16).

2. A method for treating urban sewage A according to claim 1 2 The device for resolving the conflict between the nitrogen and phosphorus removal sludge age in the / O process is characterized by... The diversion ratio of the inlet branch (2) is 20%~50%.

3. A method for treating urban sewage A according to claim 1 2 The device for resolving the conflict between the nitrogen and phosphorus removal sludge age in the / O process is characterized by... The return ratio of the sedimentation tank effluent return pipeline (11) is 50%~150%; the return ratio of the sludge return pipeline (14) is 5%~45%; and the return ratio of the sludge return pipeline (13) is 50%~100%.

4. A method for treating urban sewage A according to claim 1 2 The device for resolving the conflict between the nitrogen and phosphorus removal sludge age in the / O process is characterized by... The anoxic zone biological packing material (15) and the aerobic zone biological packing material (16) are both at least one of modified polyethylene suspension packing material or combined packing material; The filling ratio of the anoxic zone biological packing material (15) is 10%~40%, and the filling ratio of the aerobic zone biological packing material (16) is 20%~60%. The filling ratio is the volume ratio of the biological packing material volume in the reaction zone to the effective volume of the corresponding reaction zone. The specific surface area of ​​both the anoxic zone biological packing material (15) and the aerobic zone biological packing material (16) is 400~600 m². 2 / m 3 The densities are all 0.96~1.00 g / cm³. 3 .

5. A method for treating urban sewage A 2 The method for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal is characterized by... Using the apparatus according to any one of claims 1 to 4, the process includes the following steps: Wastewater enters the anoxic zone (3) through the main inlet pipe (1), while 20% to 50% of the inlet water enters the anaerobic zone (5) through the inlet branch pipe (2). Denitrification and short-cut denitrification coupled with anaerobic ammonia oxidation are carried out in the anoxic zone (3); Wastewater enters the anaerobic zone (5) for phosphorus release reaction; Wastewater enters the aerobic zone (7) for nitrification. The effluent from the aerobic zone (7) enters the secondary sedimentation tank (9) for solid-liquid separation.

6. A method for treating urban sewage A according to claim 5 2 The method for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal is characterized by... The hydraulic retention time in the anoxic zone (3) is 1.5 to 4.0 hours, the hydraulic retention time in the anaerobic zone (5) is 1.0 to 2.0 hours, and the hydraulic retention time in the aerobic zone (7) is 4.0 to 8.0 hours.

7. A method for treating urban sewage A according to claim 5 2 The method for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal is characterized by... The dissolved oxygen concentration in the aerobic zone (7) is controlled at 1.5~2.5 mg / L.

8. A method for treating urban sewage A according to claim 5 2 The method for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal is characterized by... When the system is started, activated sludge is inoculated to make the sludge concentration in the anaerobic zone (5) and aerobic zone (7) 3000~5000mg / L, and the sludge concentration in the anoxic zone (3) is controlled to be 1000~3000mg / L. Anaerobic ammonia oxidation biofilm packing is added to the anoxic zone (3). If there is no inoculation condition, blank packing is added.

9. A method for treating urban sewage A according to claim 5 2 The method for resolving the sludge age conflict in the / O process for nitrogen and phosphorus removal is characterized by... It also includes post-treatment steps: part of the effluent from the secondary sedimentation tank (9) is returned to the anoxic zone (3) via the sedimentation tank effluent return pipeline (11), part of the sludge is returned to the anaerobic zone (5) via the sludge return pipeline (13), and another part of the sludge is returned to the anoxic zone (3) via the sludge return pipeline (14).

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