A2o process denitrification and phosphorus removal system and sewage treatment method

Abstract

The application provides a denitrification and dephosphorization system of a strengthened A2O process and a sewage treatment method, has strong adaptability to changes of C / N of influent water, and belongs to the technical field of sewage treatment. The system provided by the application comprises an anaerobic tank, a middle sedimentation tank, a sulfur autotrophic denitrification filter tank, an aerobic tank and a final sedimentation tank which are sequentially connected, and solves the problem that the treatment system in the prior art cannot meet the requirement of treating low C / N wastewater. The system provided by the application has strong adaptability to changes of C / N of influent water, has high denitrification and dephosphorization efficiency, can effectively reduce sludge production, and has low operation energy consumption.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an enhanced A2O process for nitrogen and phosphorus removal system and wastewater treatment method. Background Technology

[0002] A2O (also known as AAO, Anaerobic-Anoxic-Oxic) is a conventional process in wastewater treatment. This process primarily relies on various functional bacteria in activated sludge to remove pollutants in different functional zones. However, in practical engineering, the treatment efficiency of the A2O process is often affected by the influent water quality. When the influent C / N ratio is low, its nitrogen and phosphorus removal efficiency is significantly limited, leading to effluent exceeding standards. Therefore, the A2O process needs to be modified to adapt to various influent water qualities. Anaerobic ammonia oxidation, under the action of autotrophic anaerobic ammonia-oxidizing bacteria, can directly remove NH4+. + -N and NO2 - -N is converted into N2, achieving autotrophic nitrogen removal. Compared with traditional denitrification processes, anaerobic ammonia oxidation (ANAO) has advantages such as no need for external carbon sources, low sludge production, and low nitrogen oxide release. Furthermore, ANAO offers good treatment efficiency, low operating costs, and a small footprint, and is widely recognized as one of the most economical biological nitrogen removal processes currently available. Sulfur autotrophic denitrification filters are also an autotrophic nitrogen removal process. This process uses elemental sulfur instead of organic carbon sources for autotrophic denitrification, offering advantages such as high nitrogen removal rate, fast start-up, and low raw material costs, making it highly suitable for improving the nitrogen removal effect of low C / N wastewater.

[0003] Chinese patent CN112850900A discloses a method for simultaneously removing nitrogen and sulfur from wastewater based on a short-cut nitrification-anaerobic ammonium oxidation-sulfur autotrophic denitrification system. The method uses a two-layer tank, with short-cut nitrification in the upper layer and anaerobic ammonium oxidation and sulfur autotrophic denitrification in the lower layer. This couples sulfur autotrophic denitrification with the PN / A process, enabling ammonia oxidizing bacteria, anaerobic ammonium oxidizing bacteria, and sulfur autotrophic denitrifying bacteria to work together to achieve deep nitrogen and sulfur removal.

[0004] Chinese patent CN111777179A discloses an A / O coupled sulfur autotrophic denitrification enhanced low C / N ratio wastewater denitrification and phosphorus removal device and method. It couples a sulfur autotrophic denitrification filter with an A / O process, using the sulfur autotrophic denitrification process to perform deep denitrification of the A / O effluent, thereby reducing the consumption of organic matter by heterotrophic denitrifying bacteria. The sulfur autotrophic denitrification process effluent is then returned to the anaerobic tank for phosphorus removal by sulfur-reducing bacteria and polyphosphate-accumulating bacteria, allowing more organic matter to be used for phosphorus removal, thus achieving efficient denitrification and phosphorus removal of low C / N wastewater.

[0005] However, in existing treatment systems, competition exists between activated sludge and sulfur-autotrophic denitrifying bacteria or anaerobic ammonia-oxidizing bacteria, hindering the enrichment of relevant functional bacteria. Furthermore, these systems often fail to meet the requirements for treating high C / N wastewater, frequently resulting in carbon source penetration into the raw water, inhibiting aerobic nitrification, and consequently leading to low carbon source utilization and reduced nitrification efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide an enhanced A2O process nitrogen and phosphorus removal system that has a strong adaptability to changes in the C / N ratio of the influent.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides an enhanced A2O process nitrogen and phosphorus removal system, which, according to the wastewater treatment sequence from upstream to downstream, includes:

[0009] Anaerobic tanks are used to synthesize PHA from organic matter in wastewater and release phosphates.

[0010] The intermediate settling tank receives the intermediate products after the anaerobic tank treatment and is used for sludge-water separation to obtain the top supernatant and bottom sludge.

[0011] The sulfur autotrophic denitrification filter receives the top supernatant after treatment in the intermediate settling tank, which is used for denitrification reaction and to consume carbonate ions in limestone particles. The calcium ions produced react with phosphate to produce calcium phosphate precipitate.

[0012] The aerobic tank receives the intermediate products from the sulfur autotrophic denitrification filter and uses them for short-cut nitrification and phosphate removal.

[0013] The final settling tank receives the intermediate products from the aerobic tank and uses them for sludge-water separation to obtain top reflux liquid, treated water, and bottom residual sludge.

[0014] Preferably, it also includes an inlet component and an outlet component, wherein the inlet component is connected to the anaerobic tank and is used to receive water to be treated;

[0015] The effluent assembly is connected to the final sedimentation tank and is used to discharge treated water.

[0016] Preferably, the intermediate settling tank and the aerobic tank are connected by a bypass pipeline for discharging bypass sludge from the bottom of the intermediate settling tank.

[0017] Preferably, it also includes a residual sludge pipeline, which is connected to the final sedimentation tank for discharging residual sludge.

[0018] Preferably, it also includes a first effluent return pipe, with a first end of the first effluent return pipe located at the top of the final sedimentation tank and a second end of the first effluent return pipe located at the bottom of the sulfur autotrophic denitrification filter, for discharging the return liquid from the top of the final sedimentation tank.

[0019] Preferably, it also includes a second effluent return pipe, with the first end of the second effluent return pipe located at the bottom of the final sedimentation tank and the second end located at the front end of the anaerobic tank, for discharging the return sludge from the bottom of the final sedimentation tank.

[0020] Preferably, a stirrer is provided at the bottom of the anaerobic tank.

[0021] Preferably, an aerator is provided at the bottom of the aerobic tank.

[0022] The present invention also provides a method for treating wastewater using the above-mentioned enhanced A2O process for nitrogen and phosphorus removal, comprising the following steps:

[0023] (1) Using the anaerobic tank, organic matter in the wastewater to be treated is synthesized into PHA and phosphate is released;

[0024] (2) Use the intermediate settling tank to separate the mud and water of the intermediate product after step (1) to obtain the top supernatant and the bottom sludge.

[0025] (3) The sulfur autotrophic denitrification filter is used to denitrify the top supernatant after step (2) and consume the carbonate in the limestone particles. The calcium ions produced react with phosphate to produce calcium phosphate precipitate.

[0026] (4) Use the aerobic tank to perform short-range nitrification and phosphate removal on the intermediate product after step (3);

[0027] (5) Use the final sedimentation tank to separate the intermediate product after step (4) into mud and water to obtain top reflux liquid, treated water and bottom residual sludge.

[0028] Preferably, the sulfur autotrophic denitrification filter contains packing material, which includes sulfur and marble. The particle size of the packing material is 2-5 mm, and the volume ratio of sulfur to marble is 1:1-3.

[0029] And / or, the biofilm of the sulfur autotrophic denitrification filter contains sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria, the concentration of the biofilm is >300 mg / L, and the anaerobic ammonia oxidizing bacteria in the sulfur autotrophic denitrification filter remove NH4 from the wastewater. + -N and NO2 in the effluent return liquid - -N, and produce NO3. --N; The heterotrophic denitrifying bacteria in the biofilm at the bottom of the sulfur autotrophic denitrification filter utilize organic matter in the wastewater for heterotrophic denitrification; The sulfur autotrophic denitrifying bacteria in the biofilm at the top of the sulfur autotrophic denitrification filter utilize sulfur particles for autotrophic denitrification; The heterotrophic denitrifying bacteria and the sulfur autotrophic denitrifying bacteria neutralize the NO3 produced by anaerobic ammonia oxidation in the effluent return liquid. - -N is reduced to N2;

[0030] And / or, the ammonia-oxidizing bacteria in the activated sludge of the aerobic tank will NH4+ + -N is oxidized to NO2 - -N;

[0031] And / or, the bottom sludge obtained from the intermediate settling tank enters the aerobic tank through a bypass sludge pipeline, and the bypass ratio of the bottom sludge in the intermediate settling tank is 10% to 50%.

[0032] And / or, the top reflux liquid obtained from the final settling tank is returned to the sulfur autotrophic denitrification filter, and the reflux ratio of the top reflux liquid ranges from 100% to 300%; part of the bottom residual sludge obtained from the final settling tank is returned to the anaerobic tank, and the remaining bottom residual sludge is discharged from the system, and the reflux ratio of the bottom residual sludge ranges from 50% to 100%. The sludge age of the activated sludge during the treatment process is adjusted by controlling the discharge volume of the bottom residual sludge discharge system, and the sludge age is preferably 15 to 30 days.

[0033] The beneficial effects of this invention are:

[0034] The enhanced A2O process nitrogen and phosphorus removal system provided by this invention has a strong adaptability to changes in the influent C / N ratio. When the influent C / N ratio is high, the sulfur autotrophic denitrification filter mainly performs anaerobic ammonia oxidation and heterotrophic denitrification, while when the C / N ratio is low, the sulfur autotrophic denitrification filter mainly performs anaerobic ammonia oxidation and sulfur autotrophic denitrification. This invention utilizes sulfur autotrophic denitrification and anaerobic ammonia oxidation to compensate for the problem of insufficient carbon source in the raw water and low nitrogen and phosphorus removal efficiency, using the raw water carbon source mainly for phosphorus removal. At the same time, the calcium ions generated by the sulfur autotrophic denitrification filter in this invention can perform chemical phosphorus removal, thereby achieving highly efficient nitrogen and phosphorus removal. Since both sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria are autotrophic bacteria, they utilize inorganic carbon for growth and have a slow growth rate, which can effectively reduce sludge production. The enhanced A2O process nitrogen and phosphorus removal system provided by this invention also has the advantage of low operating energy consumption. Since the aerobic tank only needs to perform short-cut nitrification and anaerobic ammonia oxidation can remove part of the ammonia nitrogen, a large amount of aeration energy is saved. Attached Figure Description

[0035] Figure 1The schematic diagram of the enhanced A2O process nitrogen and phosphorus removal system provided by the present invention includes: 1-inlet pipe; 201-anaerobic tank; 202-intermediate sedimentation tank; 203-sulfur autotrophic denitrification filter; 204-aerobic tank; 205-surplus sludge pipe; 206-effluent return pipe; 207-sludge return pipe; 208-agitator; 209-aerator; 3-final sedimentation tank; 301-effluent pipe; 302-residue sludge pipe. Detailed Implementation

[0036] In this invention, utilizing Figure 1 The enhanced A2O process for nitrogen and phosphorus removal system shown is used for wastewater treatment, preferably including the following steps:

[0037] The wastewater to be treated first enters the anaerobic tank through the inlet pipe, and part of the activated sludge from the final sedimentation tank is returned to the anaerobic tank; polyphosphate-accumulating bacteria in the activated sludge use organic matter in the water to synthesize PHA and release phosphates.

[0038] The effluent from the anaerobic tank enters the intermediate settling tank for sludge-water separation; the top supernatant enters the sulfur autotrophic denitrification filter, and the bottom sludge enters the aerobic tank through the sludge bypass pipeline; the bypass ratio of the bottom sludge in the intermediate settling tank is preferably in the range of 10% to 50%.

[0039] The effluent from the intermediate sedimentation tank and the return effluent from the final sedimentation tank are jointly fed into a sulfur autotrophic denitrification filter for nitrogen removal. The anaerobic ammonia-oxidizing bacteria on the biofilm of the sulfur autotrophic denitrification filter can remove NH4 from the wastewater. + -N and NO2 in the effluent return liquid - -N, and produces a small amount of NO3. - -N; Simultaneously, heterotrophic denitrifying bacteria on the biofilm at the bottom of the sulfur autotrophic denitrification filter utilize organic matter in the wastewater for heterotrophic denitrification, while sulfur autotrophic denitrifying bacteria on the top biofilm utilize sulfur particles for autotrophic denitrification. The denitrifying bacteria and sulfur autotrophic denitrifying bacteria neutralize the NO3 produced by anaerobic ammonia oxidation in the effluent return liquid. --N is reduced to N2; in addition, sulfur autotrophic denitrification consumes carbonate ions in limestone, and the resulting calcium ions react with phosphate to produce calcium phosphate precipitate; the packing material in the sulfur autotrophic denitrification filter is a mixture of granular sulfur and marble, with the volume ratio of sulfur to limestone preferably being 1:1 to 3, and the particle size preferably being 2 to 5 mm; the biofilm of the sulfur autotrophic denitrification filter contains sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria, wherein the anaerobic ammonia oxidizing bacteria are obtained from sludge inoculated with anaerobic ammonia oxidizing bacteria, and the sulfur autotrophic denitrifying bacteria grow through in-situ enrichment, with the biofilm concentration preferably >300 mg / L; wherein the culture source of the anaerobic ammonia oxidizing bacteria is concentrated sludge from a municipal wastewater treatment plant, with the sludge concentration diluted to 3000 to 6000 mg / L, and the culture medium is prepared using tap water or well water, wherein the concentrations of ammonia nitrogen and nitrite are both 50 to 100 mg / L. The culture method uses continuous water intake, with a hydraulic retention time of 8–16 hours and a culture temperature of 30–35℃. The culture is considered successful when the total nitrogen removal rate is above 80% for 5 consecutive days.

[0040] The effluent from the sulfur autotrophic denitrification filter enters the aerobic tank; the ammonia-oxidizing bacteria in the activated sludge of the aerobic tank carry out a short-cut nitrification reaction, converting NH4+ into nitrogen. + -N is oxidized to NO2 - -N, NH4 in the effluent from the aerobic tank + -N is preferably <1.0 mg / L, and NO2 - -N accumulation rate is preferably >60%; at the same time, polyphosphate-accumulating bacteria in activated sludge perform excessive phosphorus uptake to complete phosphate removal; the DO in the aerobic tank is preferably controlled at 0.5-2 mg / L;

[0041] The activated sludge in the system described in this invention is taken from the concentrated sludge of a municipal wastewater treatment plant, and the sludge concentration is preferably 3000-6000 mg / L;

[0042] The effluent from the aerobic tank enters the final sedimentation tank for sludge-water separation; the top portion of the effluent from the final sedimentation tank is returned to the sulfur autotrophic denitrification filter, and the remaining effluent is discharged from the system; the bottom portion of the activated sludge is returned to the anaerobic tank, and the remaining sludge is discharged from the system through the remaining activated sludge pipeline; the return ratio of the effluent from the final sedimentation tank is preferably in the range of 100% to 300%, and the return ratio of the returned sludge is preferably in the range of 50% to 100%. The amount of remaining sludge discharged from the final sedimentation tank is adjusted to preferably control the activated sludge SRT at 15 to 30 days;

[0043] In the above steps, the HRT of the anaerobic tank is preferably 1-2 hours, the HRT of the intermediate sedimentation tank is preferably 2-4 hours, the HRT of the sulfur autotrophic denitrification filter is preferably 1-3 hours, the HRT of the aerobic tank is preferably 2-4 hours, and the HRT of the final sedimentation tank is preferably 1-3 hours.

[0044] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] Example 1

[0048] Figure 1 This is a schematic diagram of the enhanced A2O process nitrogen and phosphorus removal system provided by the present invention, as shown below. Figure 1 As shown, the enhanced A2O process nitrogen and phosphorus removal system provided by the present invention includes: 1-inlet pipeline; 201-anaerobic tank; 202-intermediate sedimentation tank; 203-sulfur autotrophic denitrification filter; 204-aerobic tank; 205-surplus sludge pipeline; 206-effluent return pipeline; 207-sludge return pipeline; 208-agitator; 209-aerator; 3-final sedimentation tank; 301-effluent pipeline; 302-residue sludge pipeline.

[0049] The enhanced A2O process nitrogen and phosphorus removal system provided by the present invention includes a reaction tank, an inlet pipe (1), and an outlet pipe (301) in sequence. The reaction tank includes an anaerobic tank (201), a secondary sedimentation tank (202), a sulfur autotrophic denitrification filter (203), an aerobic tank (204), and a final sedimentation tank (3). The inlet pipe is connected to the anaerobic tank, and the outlet pipe is connected to the final sedimentation tank. The water to be treated enters from the inlet pipe, passes through the anaerobic tank, the secondary sedimentation tank, the sulfur autotrophic denitrification filter, the aerobic tank, and the final sedimentation tank in sequence, and is discharged through the outlet pipe. The residual sludge in the final sedimentation tank is discharged through the residual sludge pipe (302).

[0050] A bypass pipeline (205) is provided between the intermediate settling tank and the aerobic tank, through which bypass sludge flows from the bottom of the intermediate settling tank to the front end of the aerobic tank; an effluent return pipeline (206) is provided between the final settling tank and the sulfur autotrophic denitrification filter, through which return liquid flows from the top of the final settling tank to the bottom of the sulfur autotrophic denitrification filter; a sludge return pipeline (207) is provided between the final settling tank and the anaerobic tank, through which return sludge flows from the bottom of the final settling tank to the front end of the anaerobic tank; a stirrer (208) is provided at the bottom of the anaerobic tank; and an aerator (209) is provided at the bottom of the aerobic tank.

[0051] In this invention, polyphosphate-accumulating bacteria in the anaerobic tank first utilize the carbon source in the influent to release phosphorus into the wastewater. Then, the effluent from the anaerobic tank undergoes sludge-water separation in the intermediate settling tank. The water then enters a sulfur autotrophic denitrification filter for autotrophic denitrification, where calcium ions dissolved from the sediment also contribute to phosphorus removal. Additionally, the sludge from the intermediate settling tank enters the aerobic tank. Subsequently, the water from the sulfur autotrophic denitrification filter and the sludge from the intermediate settling tank enter the aerobic tank together for short-cut nitrification and excessive phosphorus uptake by polyphosphate-accumulating bacteria. Finally, the effluent enters the final settling tank for sludge-water separation. In this invention, the sulfur autotrophic denitrification filter is connected to both the aerobic and anaerobic tanks. The connection to the aerobic tank is achieved through the recirculation of the effluent from the secondary settling tank, utilizing the NO2-N generated in the aerobic tank for anaerobic ammonia oxidation and sulfur autotrophic denitrification, thus achieving autotrophic denitrification. Next is the connection with the anaerobic tank. The effluent ammonia nitrogen from the anaerobic tank can be used for anaerobic ammonia oxidation, and the released phosphate can be used for chemical phosphorus removal, reducing the phosphorus removal pressure on the aerobic tank. However, because the sulfur autotrophic denitrification filter is easily clogged by activated sludge, a sedimentation tank needs to be added between the anaerobic tank and the sulfur autotrophic denitrification filter. The intermediate sedimentation tank separates the sludge and water; the effluent enters the sulfur autotrophic denitrification filter, and the concentrated bottom sludge enters the aerobic tank. The main purposes of this setup are twofold: first, to reduce the suspended solids (SS) in the sulfur autotrophic denitrification filter influent; and second, to minimize the influent flow to the aerobic tank while maintaining the sludge concentration in the aerobic tank, thus avoiding excessive influent ammonia nitrogen and resulting in excessive total nitrogen in the effluent.

[0052] The above system is used for the treatment of wastewater with high influent C / N ratios:

[0053] The wastewater used in this embodiment is the influent from a wastewater treatment plant in Beijing, with average influent COD and NH4 content. + -N, TN, and TP were 284.33, 43.81, 45.16, and 8.12 mg / L, respectively, with an influent C / N ratio of 6.3. The influent flow rate was 200 m³ / L. 3The hydraulic retention times (H / d) of the anaerobic tank, intermediate settling tank, sulfur autotrophic denitrification filter, aerobic tank, and final settling tank were 2, 2.5, 2, 3.5, and 1.5 h, respectively, totaling 11.5 h. The excess ratio in the intermediate settling tank was 15%, the effluent recirculation ratio in the final settling tank was 200%, and the sludge recirculation ratio was 70%. Dissolved oxygen in the aerobic tank was controlled at 1.0–1.5 mg / L, and the sludge retention time in the A / O process was controlled at 20 days. In the sulfur autotrophic denitrification filter, the volume ratio of sulfur to limestone was 1:1.5, and the particle size of both sulfur and limestone was 2–5 mm. After stable operation, the system achieved stable nitrogen and phosphorus removal, with effluent TN and TP reduced to approximately 9.29 mg / L and 0.17 mg / L, respectively. The influent and effluent water quality are shown in Table 1.

[0054] Table 1. Influent and Effluent Water Quality (High Influent C / N Ratio)

[0055] CODcr <![CDATA[NH4 + -N]]> TN TP Water ingress 284.33±13.37 43.81±2.28 45.16±2.22 8.12±0.27 Out of water 29.40±0.54 0.22±0.14 9.29±0.40 0.17±0.05

[0056] Example 2

[0057] The system is the same as in Example 1, performing conventional influent C / N wastewater treatment:

[0058] The wastewater used in this embodiment is the influent from a wastewater treatment plant in Beijing, with average influent COD and NH4 content. + -N, TN, and TP were 206.57, 48.48, 49.68, and 7.82 mg / L, respectively, with an influent C / N ratio of approximately 4.16. The influent flow rate was 500 m³ / L. 3 The hydraulic retention times (H / d) of the anaerobic tank, intermediate settling tank, sulfur autotrophic denitrification filter, aerobic tank, and final settling tank are 1.5, 2, 1.5, 4, and 1.5 hours, respectively, totaling 10.5 hours. The overrun ratio in the intermediate settling tank is 25%, the effluent recirculation ratio in the final settling tank is 250%, and the sludge recirculation ratio is 50%. Dissolved oxygen in the aerobic tank is controlled at 1.0–1.5 mg / L, and the sludge retention time in the A / O process is controlled at 20 days. In the sulfur autotrophic denitrification filter, the volume ratio of sulfur to limestone is 1:2, and the particle size of both sulfur and limestone is 2–5 mm. After stable operation, the nitrous oxide accumulation rate in the aerobic tank reaches 80%, and the effluent TN and TP can be reduced to below 10 and 0.5 mg / L, respectively, with removal rates of over 80% and 90%, achieving highly efficient nitrogen and phosphorus removal. Meanwhile, the sulfur autotrophic denitrification filter contributed 68.92% to nitrogen removal, of which anaerobic ammonia oxidation accounted for 29.32%. The influent and effluent water quality are shown in Table 2.

[0059] Table 2. Influent and Effluent Water Quality (Conventional Influent C / N)

[0060] CODcr <![CDATA[NH4 + -N]]> TN TP Water ingress 206.57±5.77 48.48±0.90 49.68±1.01 7.82±0.31 Out of water 28.32±1.02 0.15±0.14 9.43±0.23 0.18±0.08

[0061] Example 3

[0062] The system is the same as in Example 1, performing low influent C / N wastewater treatment:

[0063] The wastewater used in this embodiment is the influent from a wastewater treatment plant in Beijing, with average influent COD and NH4 content. + -N, TN, and TP were 114.58, 41.00, 42.16, and 7.29 mg / L, respectively, with an influent C / N ratio of approximately 2.72. The influent flow rate was 300 m³ / L. 3 The hydraulic retention times (H / d) of the anaerobic tank, intermediate settling tank, sulfur autotrophic denitrification filter, aerobic tank, and final settling tank were 1.5, 2.5, 2, 3, and 2 hours, respectively, totaling 11 hours. The overrun ratio in the intermediate settling tank was 30%, the effluent recirculation ratio in the final settling tank was 300%, and the sludge recirculation ratio was 50%. Dissolved oxygen in the aerobic tank was controlled at 0.5–1.0 mg / L, and the sludge retention time in the A / O process was controlled at 25 days. In the sulfur autotrophic denitrification filter, the volume ratio of sulfur to limestone was 1:2.5, and the particle size of both sulfur and limestone was 2–5 mm. After stable operation, the nitrite accumulation rate in the aerobic tank reached over 80%, and the effluent TN and TP stabilized at around 6.71 and 0.22 mg / L, respectively. Simultaneously, the nitrogen removal contribution rate of the sulfur autotrophic denitrification filter reached 74.01%, with anaerobic ammonia oxidation accounting for 41.08%, achieving highly efficient autotrophic nitrogen removal. The influent and effluent water quality are shown in Table 3.

[0064] Table 3. Influent and Effluent Water Quality (Lower Influent C / N Ratio)

[0065] CODcr <![CDATA[NH4 + -N]]> TN TP Water ingress 114.58±10.00 41.00±2.22 42.16±2.04 7.29±0.35 Out of water 27.30±1.53 0.16±0.14 6.71±0.51 0.22±0.07

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nitrogen and phosphorus removal system for enhanced A2O process, characterized in that, According to the wastewater treatment sequence, from upstream to downstream, it includes: Anaerobic tanks are used to synthesize PHA from organic matter in wastewater and release phosphates. The intermediate settling tank receives the intermediate products after the anaerobic tank treatment and is used for sludge-water separation to obtain the top supernatant and bottom sludge. The sulfur autotrophic denitrification filter receives the top supernatant after treatment in the intermediate settling tank, which is used for denitrification reaction and to consume carbonate ions in limestone particles. The calcium ions produced react with phosphate to produce calcium phosphate precipitate. The aerobic tank receives the intermediate products from the sulfur autotrophic denitrification filter and uses them for short-cut nitrification and phosphate removal. The final settling tank receives the intermediate product after treatment in the aerobic tank and is used for sludge-water separation to obtain top reflux liquid, treated water and bottom residual sludge. The biofilm in the sulfur autotrophic denitrification filter contains sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria, with a concentration >300 mg / L. The anaerobic ammonia oxidizing bacteria in the sulfur autotrophic denitrification filter remove NH4 from the wastewater. + -N and NO2 in the effluent return liquid - -N, and produce NO3. - -N; The heterotrophic denitrifying bacteria in the biofilm at the bottom of the sulfur autotrophic denitrification filter utilize organic matter in the wastewater for heterotrophic denitrification; the sulfur autotrophic denitrifying bacteria in the biofilm at the top of the sulfur autotrophic denitrification filter utilize sulfur particles for autotrophic denitrification. The heterotrophic and sulfur autotrophic denitrifying bacteria oxidize anaerobic ammonia to produce NO3. - -N is reduced to N2; The ammonia-oxidizing bacteria in the activated sludge of the aerobic tank will NH4+. + -N is oxidized to NO2 - -N; The bottom sludge obtained from the intermediate settling tank enters the aerobic tank through a bypass sludge pipeline, and the bypass ratio of the bottom sludge in the intermediate settling tank is 10%~50%. The top reflux liquid obtained from the final settling tank is returned to the sulfur autotrophic denitrification filter, and the reflux ratio of the top reflux liquid is in the range of 100%~300%; part of the bottom residual sludge obtained from the final settling tank is returned to the anaerobic tank, and the rest of the bottom residual sludge is discharged from the system.

2. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, It also includes an inlet component and an outlet component, wherein the inlet component is connected to the anaerobic tank and is used to receive water to be treated; The effluent assembly is connected to the final sedimentation tank and is used to discharge treated water.

3. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, The intermediate settling tank and the aerobic tank are connected by an bypass pipeline for discharging bypass sludge from the bottom of the intermediate settling tank.

4. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, It also includes a residual sludge pipeline, which is connected to the final sedimentation tank for discharging residual sludge.

5. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, It also includes a first effluent return pipeline, with the first end of the first effluent return pipeline located at the top of the final sedimentation tank and the second end of the first effluent return pipeline located at the bottom of the sulfur autotrophic denitrification filter, for discharging the return liquid from the top of the final sedimentation tank.

6. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, It also includes a second effluent return pipeline, with the first end of the second effluent return pipeline located at the bottom of the final sedimentation tank and the second end located at the front end of the anaerobic tank, for discharging the return sludge from the bottom of the final sedimentation tank.

7. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, A stirrer is installed at the bottom of the anaerobic tank.

8. The enhanced A2O process nitrogen and phosphorus removal system according to claim 1, characterized in that, An aerator is installed at the bottom of the aerobic tank.

9. A method for treating wastewater using the enhanced A2O process for nitrogen and phosphorus removal as described in claim 1, characterized in that, Includes the following steps: (1) The anaerobic tank is used to synthesize PHA from the organic matter in the wastewater to be treated and release phosphates; (2) Use the intermediate settling tank to separate the intermediate product after step (1) into mud and water to obtain the top supernatant and the bottom sludge; (3) The sulfur autotrophic denitrification filter is used to denitrify the top supernatant after step (2) and consume the carbonate in the limestone particles. The calcium ions produced react with phosphate to produce calcium phosphate precipitate. (4) Use the aerobic tank to perform short-range nitrification and phosphate removal on the intermediate product after treatment in step (3); (5) Use the final settling tank to separate the intermediate product after step (4) into mud and water to obtain top reflux liquid, treated water and bottom residual sludge; The sulfur autotrophic denitrification filter contains packing material, which includes sulfur and marble. The particle size of the packing material is 2-5 mm, and the volume ratio of sulfur to marble is 1:1-3. And / or, the biofilm of the sulfur autotrophic denitrification filter contains sulfur autotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria, the concentration of the biofilm is >300 mg / L, and the anaerobic ammonia oxidizing bacteria in the sulfur autotrophic denitrification filter remove NH4 from the wastewater. + -N and NO2 in the effluent return liquid - -N, and produce NO3. - -N; The heterotrophic denitrifying bacteria in the biofilm at the bottom of the sulfur autotrophic denitrification filter utilize organic matter in the wastewater for heterotrophic denitrification; The sulfur autotrophic denitrifying bacteria in the biofilm at the top of the sulfur autotrophic denitrification filter utilize sulfur particles for autotrophic denitrification; The heterotrophic denitrifying bacteria and the sulfur autotrophic denitrifying bacteria oxidize anaerobic ammonia to produce NO3. - -N is reduced to N2; And / or, the ammonia-oxidizing bacteria in the activated sludge of the aerobic tank will NH4+ + -N is oxidized to NO2 - -N; And / or, the bottom sludge obtained from the intermediate settling tank enters the aerobic tank through a bypass sludge pipeline, and the bypass ratio of the bottom sludge in the intermediate settling tank is 10%~50%; And / or, the top reflux liquid obtained from the final settling tank is returned to the sulfur autotrophic denitrification filter, and the reflux ratio of the top reflux liquid ranges from 100% to 300%; part of the bottom residual sludge obtained from the final settling tank is returned to the anaerobic tank, and the remaining bottom residual sludge is discharged from the system, and the reflux ratio of the bottom residual sludge ranges from 50% to 100%. The sludge age of the activated sludge during the treatment process is adjusted by controlling the discharge volume of the bottom residual sludge discharge system, and the sludge age is 15 to 30 days.

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