A device and method for denitrification and dephosphorization based on biofilm growth cycle enhanced short-range denitrification coupled with anaerobic ammonia oxidation

Abstract

The present application relates to a device and method for short-cut denitrification coupled with anaerobic ammonia oxidation for nitrogen and phosphorus removal based on biofilm growth cycle. The device comprises two upflow anaerobic sludge beds (UASB) and a biological aerated filter (BAF). The municipal wastewater first enters UASB-I (3) for short-cut denitrification coupled with anaerobic ammonia oxidation process, and no domesticated flocculent sludge is added, but the sloughed biofilm from the backflow of UASB-II (6) is used to strengthen the formation of granular sludge, and then the granular sludge is used to improve the denitrification effect of short-cut denitrification coupled with anaerobic ammonia oxidation; the wastewater enters UASB-II, which is provided with biofilm, to further strengthen the denitrification of short-cut denitrification coupled with anaerobic ammonia oxidation; then the wastewater enters BAF (11) for aerobic nitrification process, and part of the supernatant is backflowed to the front end of the system, and part of the supernatant is effluent. The saved part of carbon source by anaerobic ammonia oxidation can strengthen biological phosphorus removal. The present application improves the denitrification and phosphorus removal effect.

Description

Technical Field

[0001] This invention relates to a device and method for nitrogen and phosphorus removal based on enhanced short-range denitrification coupled with anaerobic ammonia oxidation during the biofilm growth cycle, belonging to the field of urban wastewater treatment and biofilm-based wastewater treatment technology. Background Technology

[0002] Wastewater treatment constitutes a crucial link in the field of environmental protection, and its importance is self-evident. It is directly related to the purity of water bodies and the balance of ecosystems, playing a vital role in ensuring the health and stability of the overall ecological environment. The traditional nitrification-denitrification process involves ammonia nitrogen being converted into nitrate nitrogen by ammonia-oxidizing bacteria and nitrite-oxidizing bacteria under aerobic conditions. Under anaerobic conditions, denitrifying bacteria use organic matter as electron donors to reduce nitrate nitrogen or nitrite nitrogen back into nitrogen gas.

[0003] In contrast, short-cut denitrification (SCD) is a highly efficient biological nitrogen removal process. By controlling the denitrification process at the nitrite stage, it avoids the complete reduction of nitrate nitrogen, thereby improving nitrogen removal efficiency and reducing the demand for carbon sources and aeration. SCD, with its streamlined process, demonstrates superior nitrogen removal efficiency and significantly improves effluent quality standards. Furthermore, this technology reduces sludge production, alleviating the pressure on subsequent sludge treatment and showcasing its dual advantages in environmental friendliness and economic benefits.

[0004] Anaerobic ammonia oxidation (AAO) is a process that converts ammonia nitrogen into nitrogen gas under anaerobic conditions, using ammonia nitrogen as the electron donor and nitrate or nitrite nitrogen as the electron acceptor. This technology exhibits excellent ammonia nitrogen removal capabilities under low temperature and low dissolved oxygen conditions, typically achieving removal rates exceeding 85%, significantly improving wastewater treatment efficiency. Compared to traditional nitrification-denitrification processes, AAO requires significantly less oxygen, only about 35% of the oxygen needed, thus drastically reducing oxygen supply demands and aeration costs. Furthermore, AAO technology demonstrates high compatibility, allowing integration with other wastewater treatment methods, such as biofilm technology, to further enhance overall wastewater treatment efficiency. This flexibility and integration capability give it a unique competitive advantage in practical applications.

[0005] Short-cut denitrification coupled with anaerobic ammonium oxidation (ANAO) is a novel biological nitrogen removal process that combines the advantages of both short-cut denitrification and ANAO, achieving efficient, energy-saving, and environmentally friendly wastewater treatment. Against this backdrop, this invention proposes a device and method for enhancing nitrogen and phosphorus removal through short-cut denitrification coupled with ANAO based on the biofilm growth cycle. This method aims to utilize the returned sludge to enhance the formation of granular sludge, thereby improving the nitrogen removal efficiency of short-cut denitrification coupled with ANAO through granular sludge, while avoiding the consumption of nitrite by the addition of flocculent sludge. Summary of the Invention

[0006] A device for nitrogen and phosphorus removal based on biofilm growth cycle enhanced short-cut denitrification coupled with anaerobic ammonium oxidation. The inlet pipe (1) is connected to the bottom of UASB-1 (3), through which urban sewage enters and undergoes short-cut denitrification coupled with anaerobic ammonium oxidation reaction in UASB-1 (3). UASB-1 (3) is connected to UASB-II (6) through peristaltic pump I (4), allowing sewage to enter UASB-II (6). UASB-II (6) is equipped with biological packing material (5), on which biofilm grows. UASB-II (6) is connected to UASB-1 (3) through peristaltic pump II (7), so that after the biofilm falls off, part of the detached biofilm carried by its return water is returned to UASB-1 (3). UASB-II (6) provides detached biofilm to UASB-1 (3), providing seed mud for the formation of granular sludge (2) and enhancing granulation. UASB-II (6) is connected to BAF (11) via peristaltic pump III (8), allowing the effluent from UASB-II (6) to enter BAF (11), which contains aerobic packing material (10) and aeration discs (9). The aeration discs (9) are connected to aeration pump (12). Aerobic autotrophic nitrifying bacteria grow on the packing material and nitrification occurs under aeration conditions. BAF aerated biological filter (11) is connected to UASB-I (3) via peristaltic pump IV (13), returning the supernatant to UASB-I (3) to provide it with nitrate nitrogen. BAF aerated biological filter (11) is connected to the outside via effluent pipe (14) to discharge the system effluent.

[0007] By utilizing detached biofilm instead of added acclimated flocculent sludge, the biofilm in UASB-II can be granulated for UASB-I through recirculation. Direct use of detached biofilm avoids heterotrophic denitrification that may result from the addition of pre-cultured flocculent sludge, reduces nitrite consumption, and thus optimizes the reaction effect of short-cut denitrification coupled with anaerobic ammonium oxidation. Furthermore, the reactor setup can enhance the formation of granular sludge.

[0008] Both UASB-II and BAF aerated biological filters require biological packing material. In UASB-II, the biological packing material provides an anaerobic microenvironment for denitrifying microorganisms, promoting the synergistic growth of denitrifying bacteria and anaerobic ammonia-oxidizing bacteria. In BAF, the packing material supports the growth of aerobic autotrophic nitrifying bacteria, which undergo nitrification under aeration conditions. The biological packing material filling ratio is 45%-65%, and the specific surface area is 400 m². 2 / m 3 -600m 2 / m 3 Its density is 0.96-1.00 g / cm³. 3 .

[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] Its technical principles and characteristics:

[0011] 1) The principle of this patent is based on the growth cycle of biofilm, which enhances the formation of granular sludge by detaching biofilm. It is mainly achieved through two UASB reactors: both reactors perform short-cut denitrification coupled with anaerobic ammonium oxidation. UASB-II contains biological packing material on which biofilm grows. After the biofilm detaches, it is returned to UASB-I to provide biofilm, providing seed sludge for the formation of granular sludge, thereby enhancing granulation.

[0012] 2) By utilizing detached biofilm instead of added acclimated flocculent sludge, the biofilm in UASB-II can be used for granulation of UASB-I through recirculation. Added flocculent sludge will cause heterotrophic denitrification, which will consume some of the important substrate nitrite of anaerobic ammonia oxidation, affecting the overall nitrogen removal efficiency. Utilizing detached biofilm can avoid this process and can increase the abundance of anaerobic ammonia oxidizing bacteria.

[0013] 3) The biological packing material in UASB-II is cylindrical with a specific surface area of ​​400 m². 2 / m 3 ~600m 2 / m 3 With a porosity greater than 95%, it provides an anaerobic microenvironment for denitrifying microorganisms, promoting the synergistic growth of denitrifying bacteria and anaerobic ammonia-oxidizing bacteria. Aerobic autotrophic nitrifying bacteria grow inside the BAF packing material, undergoing nitrification under aeration conditions. The biological packing material has a filling ratio of 45%-65% and a specific surface area of ​​400 m². 2 / m 3 -600m 2 / m 3 Its density is 0.96-1.00 g / cm³. 3 .

[0014] 4) The filling ratio of biological packing material in UASB-II is controlled between 25-45%, and the filling ratio of aerobic packing material in BAF aerated biological filter is controlled between 45-65% to ensure the growth conditions of microorganisms.

[0015] 5) This method not only improves the denitrification effect, but also enhances biological phosphorus removal by saving some carbon source due to anaerobic ammonia oxidation, thus achieving multiple wastewater treatment goals.

[0016] 6) By using a short-cut denitrification coupled with anaerobic ammonia oxidation process, efficient, energy-saving, and environmentally friendly wastewater treatment has been achieved, reducing operating costs and environmental burden.

[0017] This invention has the following advantages:

[0018] 1) High abundance of anaerobic ammonia oxidizing bacteria: Utilizing detached biofilm instead of added acclimated flocculent sludge, the biofilm in UASB-II can be granulated for UASB-I through recirculation. Added flocculent sludge will cause heterotrophic denitrification, which consumes some of the important substrate nitrite in the anaerobic ammonia oxidation reaction, affecting the overall nitrogen removal efficiency. Utilizing flocculent sludge from the detached biofilm can avoid this process and can increase the abundance of anaerobic ammonia oxidizing bacteria, thereby optimizing the reaction effect of short-cut denitrification coupled with anaerobic ammonia oxidation. Furthermore, the reactor setup can enhance the formation of granular sludge.

[0019] 2) Carbon source saving: 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.

[0020] 3) 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.

[0021] 4) 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, which helps to reduce sludge disposal costs and also reduces operating costs.

[0022] 5) Compact layout and small footprint: It not only improves denitrification efficiency but also improves effluent quality, meeting stricter environmental protection requirements. At the same time, the high load of UASB saves space and enhances market competitiveness. Attached Figure Description

[0023] Figure 1 This is a device for nitrogen and phosphorus removal based on short-range denitrification coupled with anaerobic ammonia oxidation, enhanced by the biofilm growth cycle.

[0024] Specifically: 1-Inlet pipe; 2-UASB-I granular sludge; 3-UASB-I; 4-Peristaltic pump I; 5-UASB-II biological packing material; 6-UASB-II; 7-Peristaltic pump II; 8-Peristaltic pump III; 9-Aeration disc; 10-Aerobic packing material; 11-BAF aerated biological filter; 12-Aeration pump; 13-Peristaltic pump IV; 14-Outlet pipe. Detailed Implementation

[0025] Combination Figure 1 The following describes the implementation scheme of the present invention in detail:

[0026] 1) System Startup: Wastewater first enters UASB-I for short-cut denitrification coupled with anaerobic ammonium oxidation, then enters UASB-II, where the same short-cut denitrification coupled with anaerobic ammonium oxidation process occurs. A peristaltic pump returns a portion of the effluent to UASB-I to enhance granular sludge formation, while the remaining effluent enters the BAF (Bathed Aerated Filter) for aerobic nitrification. The supernatant is returned to UASB-I. The biological packing ratio in UASB-II is controlled between 25-45%, and in the BAF, it is controlled between 45-65%. The biological packing material is cylindrical with a specific surface area of ​​400-600 m². 2 / m 3 The porosity is greater than 95%.

[0027] 2) Main operating parameters:

[0028] ① Hydraulic residence time (HRT):

[0029] UASB-I: The hydraulic retention time is designed to be 4 hours to ensure sufficient time for short-cut denitrification coupled with anaerobic ammonium oxidation.

[0030] UASB-II: The hydraulic retention time is designed to be 6 hours to further enhance the denitrification effect.

[0031] BAF aerated biological filter: The hydraulic retention time is designed to be 2 hours to complete aerobic nitrification.

[0032] ② Dissolved oxygen (DO) control:

[0033] UASB-I and UASB-II: Dissolved oxygen is controlled below 0.5 mg / L to promote anaerobic ammonia oxidation.

[0034] BAF aerated biological filter: Dissolved oxygen is controlled at 2.5-3.5 mg / L to ensure the aerobic nitrification process.

[0035] ③ Reflux ratio:

[0036] The reflux ratio from UASB-II to UASB-I is 100% to enhance the formation of granular sludge.

[0037] The reflux ratio of BAF to supernatant to UASB-I is 200% to provide sufficient nitrate nitrogen.

[0038] ④ Parameters of biological packing material:

[0039] UASB-II: The biological packing material is cylindrical with a specific surface area of ​​400 m². 2 / m 3 ~600m 2 / m 3With a porosity greater than 95%, it provides an anaerobic microenvironment for denitrifying microorganisms, which is conducive to the synergistic growth of denitrifying bacteria and anaerobic ammonia oxidizing bacteria. The filling ratio is controlled between 25% and 45%.

[0040] BAF (Biofilter Aerated Filter): The BAF packing material harbors aerobic, autotrophic nitrifying bacteria that undergo nitrification under aeration. The biological packing material fills 45%-65% of the surface area, with a specific surface area of ​​400 m². 2 / m 3 -600m 2 / m 3 Its density is 0.96-1.00 g / cm³. 3 .

Claims

1. A device for nitrogen and phosphorus removal based on short-range denitrification coupled with anaerobic ammonium oxidation enhanced by biofilm growth cycle, characterized in that: The inlet pipe (1) is connected to the bottom of UASB-1 (3). UASB-1 (3) is connected to UASB-II (6) through peristaltic pump I (4), allowing sewage to enter UASB-II (6). UASB-II (6) is equipped with biological packing material (5). UASB-II (6) is connected to UASB-1 (3) through peristaltic pump II (7). UASB-II (6) provides detached biofilm to UASB-1 (3). UASB-II (6) is connected to BAF aerated biological filter (11) via peristaltic pump III (8), so that the effluent from UASB-II (6) enters BAF aerated biological filter (11), which is equipped with aerobic packing material (10) and aeration disc (9). The aeration disc (9) is connected to aeration pump (12). BAF aerated biological filter (11) is connected to UASB-I (3) via peristaltic pump IV (13), so that the supernatant is returned to UASB-I (3). BAF aerated biological filter (11) is connected to the outside via effluent pipe (14). Wastewater first enters UASB-I for short-cut denitrification coupled with anaerobic ammonia oxidation process, and then enters UASB-II for short-cut denitrification coupled with anaerobic ammonia oxidation process. Part of the effluent is returned to UASB-I via peristaltic pump II, and the detached biofilm is used to enhance the formation of granular sludge.

2. The method of using the apparatus as described in claim 1, characterized in that, System startup: Wastewater first enters UASB-I for short-cut denitrification coupled with anaerobic ammonium oxidation, and then enters UASB-II for short-cut denitrification coupled with anaerobic ammonium oxidation. Peristaltic pump II returns part of the effluent to UASB-I to enhance the formation of granular sludge by utilizing the detached biofilm. Part of the effluent enters the BAF aerated biological filter for aerobic nitrification, and the supernatant is returned to UASB-I. Operating parameters: Hydraulic Retention Time (HRT): UASB-I: Design hydraulic residence time is 4 hours; UASB-II: Design hydraulic residence time is 6 hours; BAF aerated biological filter: designed hydraulic retention time is 2 hours; Dissolved oxygen (DO) control: UASB-I and UASB-II: Dissolved oxygen should be controlled below 0.5 mg / L; BAF aerated biological filter: dissolved oxygen controlled at 2.5-3.5 mg / L; Reflux ratio: Reflux ratio from UASB-II to UASB-I: 100%; The supernatant recirculation ratio from the BAF aerated biological filter to the UASB-I is 200%. Biological packing parameters: UASB-II: The specific surface area of ​​the biological packing material is 400 m². 2 / m 3 ~600m 2 / m 3 The porosity is greater than 95%, and the filling ratio is controlled between 25-45%. BAF Aerated Biological Filter: The biological packing material inside the BAF is filled with 45%-65% biological material, and the specific surface area is 400 m². 2 / m 3 -600m 2 / m 3 Its density is 0.96-1.00 g / cm³. 3 .

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