Efficient denitrification and dephosphorization treatment method for low carbon-nitrogen ratio domestic sewage

Abstract

The application discloses a low C / N ratio domestic sewage high-efficiency denitrification and dephosphorization treatment method, which comprises the following steps: increasing the anoxic reaction time, setting two anoxic reaction zones, introducing double nitration liquid reflux, adjusting the double nitration liquid flow distribution according to the influent C / N ratio, strengthening the denitrification and dephosphorization technology, combining with a carbon source precise feeding system to ensure the deep denitrification and dephosphorization of the whole process; on the other hand, setting an MBBR nitrification treatment unit, the suspended filler can provide a good carrier for nitrifying bacteria, ensure the enrichment conditions of long sludge age of nitrifying bacteria, and the nitrification liquid is refluxed to the anoxic zone for denitrification; the method can avoid the sludge bulking problem under the long anoxic and low load operation conditions, can fully utilize the carbon source of raw water, save the aeration amount, realize the precise feeding of the carbon source, save the energy consumption and the drug consumption, and is suitable for the deep denitrification and dephosphorization standard upgrading and reconstruction of a municipal sewage treatment plant, and has a wide market application prospect.

Description

Technical Field

[0001] This invention relates to the field of urban wastewater treatment and reuse, specifically to a high-efficiency nitrogen and phosphorus removal treatment device and method for domestic wastewater with low carbon-to-nitrogen ratio. Background Technology

[0002] Under the strategic background of ecological civilization construction, my country is paying increasing attention to wastewater treatment levels. Currently, the pollutant discharge limits for urban wastewater treatment plants are implemented according to the Class A discharge standard stipulated in GB8918-2002, which requires TN to be less than 15 mg / L and TP to be less than 1 mg / L or 0.5 mg / L. As things stand, some wastewater treatment plants are still unable to consistently meet the discharge standards. At the same time, many provinces and cities have introduced new local standards, further raising the wastewater discharge limits to Class IV or even Class III surface water standards. The key and difficult point is the removal of nitrogen and phosphorus. The main difficulties encountered in practice are low carbon-to-nitrogen ratio in wastewater and insufficient carbon sources, contradictions in sludge age between nitrifying bacteria and polyphosphate-accumulating bacteria, low phosphorus release and uptake capacity, excessive external carbon source addition, and inherent deficiencies and drawbacks in the process itself. There is an urgent need for process upgrading and transformation.

[0003] Denitrification phosphorus removal technology can absorb small-molecule organic matter in water under anaerobic conditions to synthesize internal carbon source polyhydroxy fatty acid esters (PHA) and release phosphates, which are then released as NO2- and NO3- under anoxic conditions. 3－ Instead of O2 as the electron acceptor, PHA is used as the electron donor for anaerobic phosphorus uptake. By operating under alternating anaerobic / anoxic conditions, simultaneous and efficient nitrogen and phosphorus removal is achieved. Compared with traditional nitrogen and phosphorus removal processes, it can make full use of the carbon source of raw water, save aeration volume, save reaction time, and reduce the yield of residual sludge. It can remove nitrogen and phosphorus elements from wastewater in a more economical and effective manner, and is especially suitable for treating domestic sewage with low carbon-to-nitrogen ratio due to insufficient carbon source.

[0004] Moving bed biofilm reactors (MBBRs) involve adding suspended media as a microbial growth carrier within the aeration tank, thereby forming an activated sludge-biofilm composite ecosystem. The addition of suspended media effectively breaks down air bubbles in the water, increasing the gas-liquid film area and improving aeration efficiency. MBBR processes also offer advantages such as low fluidization energy consumption, large biomass, small footprint, high design flexibility, and strong resistance to shock loads. Nitrifying bacteria are typical autotrophic bacteria with long generation cycles, requiring long sludge ages, while phosphorus removal processes require short sludge ages. Balancing these conflicting sludge ages during nitrogen and phosphorus removal is difficult. Furthermore, nitrification efficiency in actual water plants typically weakens to varying degrees during winter, impacting the overall nitrogen removal efficiency. Therefore, leveraging the technological advantages of MBBR processes, setting up a single-function nitrification reactor can ensure optimal nitrification performance.

[0005] Currently A 2O, oxidation ditch modified multi-stage AO, and MBBR are all common wastewater treatment processes, but in actual operation, there are engineering problems such as "high energy consumption during process operation", "large amount of carbon source added" and "high sludge production". In addition, the carbon source in the raw water is insufficient, and a large amount of external carbon source is needed to achieve TN standard. Summary of the Invention

[0006] The purpose of this invention is to provide a high-efficiency nitrogen and phosphorus removal treatment device and method for domestic sewage with low carbon-to-nitrogen ratio, so as to solve the problems mentioned in the background art.

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

[0008] A highly efficient nitrogen and phosphorus removal method for domestic sewage with a low carbon-to-nitrogen ratio includes the following steps:

[0009] Step 1: Domestic sewage enters A from the water tank through the first inlet pump. 2 The anaerobic zone of the / O system is simultaneously filled with sludge pumped out from the bottom of the aerobic II zone via a sludge return pump. The sludge return ratio is 50% to 200%, and the concentration of the returned sludge is 4000 to 7000 mg / L. The mixture is stirred and mixed by an electric stirrer to maintain the HRT of the anaerobic zone at 2 to 3 hours. Denitrifying polyphosphate-accumulating bacteria synthesize the internal carbon source PHA in the anaerobic zone and release phosphate.

[0010] Step 2: The mixed liquor enters the anoxic zone I. At the same time, the supernatant of the mixed liquor that has completed nitrification in the MBBR reaction zone after solid-liquid separation in the secondary sedimentation tank enters the anoxic zone I through the nitrification liquor return pump. The HRT in the anoxic zone I is 5-6 hours, and the nitrification liquor return ratio is 100%-300%. The denitrifying polyphosphate-accumulating bacteria use internal carbon sources as electron donors and nitrates as electron donors to perform anoxic phosphorus uptake.

[0011] Step 3: The mixed solution enters the aerobic zone I from the anoxic zone I, with dissolved oxygen set at 1-2.5 mg / L. The main function of this aerobic zone I is to further absorb phosphorus, while enhancing the competitive advantage of denitrifying polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria and optimizing the bacterial community structure. The HRT of the aerobic zone I is 1-2 hours.

[0012] Step 4: The mixed liquor enters the anoxic zone II through the aerobic zone I, and at the same time, the supernatant from the secondary sedimentation tank enters through the nitrification liquor return pump. The nitrification liquor return ratio is 100% to 200%. The HRT in the anoxic zone II is 3-4 hours. The external carbon source storage tank is equipped with sodium acetate solution, and the dosage is added according to the mass ratio of TN removal amount / sodium acetate: 1:4 to 1:6.

[0013] Step 5: The mixed liquor enters the aerobic II zone from the anoxic II zone. The HRT in the aerobic II zone is 2-3 hours, and the dissolved oxygen is set at 1.5-2.5 mg / L. The mixed liquor achieves sludge-water separation through the MBR membrane module. The supernatant enters the intermediate water tank through a vacuum pump. The influent pump injects wastewater containing ammonia nitrogen into the MBBR reaction zone. At the bottom of the aerobic II zone, a portion of the sludge is returned to the anaerobic zone through the first sludge return pump. At the same time, the sludge age is maintained at 8-12 days by periodically discharging the mixed liquor.

[0014] Step 6: Add suspended packing material to the MBBR reaction zone, with a specific surface area of ​​600–2000 m². 2 / m 3 The filling ratio is 30%–50%, the aeration rate is 3–6 L / min, the dissolved oxygen concentration is 2–4 mg / L, the HRT is 3–4 h, the sludge concentration is 1500–3000 mg / L, the sludge age is 20–30 days, the biomass attached to the carrier particles is 1.5–2.5 mg VSS / g dry granules, and the ammonia nitrogen removal rate is 0.7–2.2 kg N / (m³). 3 ·d);

[0015] Step 7: The mixed liquor enters the secondary sedimentation tank through the MBBR reaction zone. After the sludge settles, it flows back from the bottom to the inlet of the MBBR reaction zone. Part of the supernatant is discharged and part is returned to the anoxic zone I and anoxic zone II. The distribution ratio of the two return liquids is adjusted according to the inlet C / N ratio.

[0016] Preferably, in step 1, when the influent C / P ratio is 15:1 to 40:1, the sludge return ratio in the anaerobic zone (3) is 75% to 150%, and when the C / P ratio is 40:1 to 70:1, the sludge return ratio in the anaerobic zone (3) is 50% to 100%.

[0017] Preferably, in steps 2 and 4, when the influent C / N ratio is 3:1 to 5:1, the flow rate ratio of the recirculated water to the anoxic zone I (4) and the anoxic zone II (6) is 1:1 to 1:1.5; when the influent C / N ratio is 5:1 to 8:1, the flow rate ratio of the recirculated water to the anoxic zone I (4) and the anoxic zone II (6) is 2:1 to 3:1.

[0018] Preferably, in step 4, the TN removal amount can be dynamically fed back by the water quality index of the online water quality monitoring device (31), and the TN removal amount / sodium acetate mass ratio is 1:4 to 1:6.

[0019] Preferably, in steps 1, 2, 3, 4, 5, and 6, the HRT of the anaerobic zone (3) is 2-3h, the HRT of the anoxic zone I (4) is 5-6h, the HRT of the aerobic zone I (5) is 1-2h, the HRT of the anoxic zone II (6) is 3-4h, and the HRT of the aerobic zone II (7) is 2-3h. The volume ratio of the improved A2 / O anoxic zone is 55%-62%.

[0020] Preferably, in step 5, the dissolved oxygen is set to 1.5–2.5 mg / L, and the sludge age is 8–12 days.

[0021] Preferably, in step 6, the dissolved oxygen concentration in the MBBR reaction zone (13) is 2-4 mg / L, the HRT is 3-4 h, and the sludge age is 20-30 d.

[0022] A further preferred embodiment of the method for efficient nitrogen and phosphorus removal from low carbon-to-nitrogen ratio domestic sewage includes the following steps:

[0023] Step 8: The water tank and anoxic zone I 4 are equipped with online water quality monitoring equipment, which can feed back COD, ammonia nitrogen, total nitrogen, and total phosphorus indicators to the computer in real time. The computer can adjust the nitrification liquor return ratio according to the influent C / N ratio. When the influent C / N ratio is 3:1 to 5:1, the nitrification liquor flow rate ratio returned to anoxic zone I 4 and anoxic zone II 6 is 1:1 to 1:1.5; when the influent C / N ratio is 5:1 to 8:1, the nitrification liquor flow rate ratio returned to anoxic zone I 4 and anoxic zone II 6 is 2:1 to 3:1. The sludge return ratio in the anaerobic zone can be adjusted according to the influent C / P ratio. When the C / P ratio is 15:1 to 40:1, the sludge return ratio in the anaerobic zone is 75% to 150%; when the C / P ratio is 40:1 to 70:1, the sludge return ratio in the anaerobic zone is 50% to 100%.

[0024] Preferably, the method for efficient nitrogen and phosphorus removal treatment of low carbon-to-nitrogen ratio domestic sewage uses the following apparatus:

[0025] This high-efficiency nitrogen and phosphorus removal treatment device for low carbon-to-nitrogen ratio domestic sewage includes a water tank, a first influent pump, anaerobic zone, anoxic zone I, aerobic zone I, anoxic zone II, aerobic zone II, MBR membrane modules, pressure gauges, a vacuum pump, an intermediate water tank, a second influent pump, an MBBR reaction zone, a secondary sedimentation tank, a first nitrification liquor return pump, a second nitrification liquor return pump, a first sludge return pump, a second sludge return pump, a blower, a gas flow meter, aeration pipes, aeration heads, an external carbon source storage tank, a carbon source dosing pump, an online DO monitoring probe, a handheld dissolved oxygen meter, a computer, and a PLC. The controller, electric stirrer, suspended packing material, and online water quality monitoring equipment are characterized in that: the water tank is connected to the anaerobic zone via a first inlet pump; the anaerobic zone, anoxic zone I, aerobic zone I, anoxic zone II, and aerobic zone II are sequentially connected; the aerobic zone II is connected to the anaerobic zone via a first sludge return pump; an MBR membrane module is placed in the aerobic zone II; the MBR membrane module is connected to an intermediate water tank via a pressure gauge and a vacuum pump; the intermediate water tank is connected to the MBBR reaction zone via a second inlet pump; and suspended packing material is placed in the MBBR reaction zone. The material is fed into the MBBR reaction zone, which is connected to the secondary sedimentation tank. The upper end of the secondary sedimentation tank is connected to the anoxic zone I and anoxic zone II via a first nitrification liquid return pump and a second nitrification liquid return pump, respectively. The lower end of the secondary sedimentation tank is connected to the MBBR reaction zone via a second sludge return pump. One end of the blower is connected to the aeration pipe via a gas flow meter, and the aeration pipe is located at the bottom of the MBBR reaction zone. The other end of the blower is connected to the aeration head. The external carbon source storage tank is connected to the anoxic zone II via a carbon source addition pump. The aerobic zone I, aerobic zone II, and MBBR reaction zone are connected to the secondary sedimentation tank. Online DO monitoring probes are installed in all BR reaction zones, and these probes are connected to handheld dissolved oxygen meters, providing real-time signal feedback to a computer. Two online water quality monitoring devices are connected to the water tank and the anoxic zone II, respectively, providing real-time signal feedback to the computer. The computer is connected to a PLC controller, which can adjust the flow rates of the first nitrification liquor return pump, the second nitrification liquor return pump, the first sludge return pump, the carbon source addition pump, and the blower. Electric stirrers are installed in the anaerobic zone, the anoxic zone I, and the anoxic zone II.

[0026] The outstanding advantages of this invention compared to the prior art are:

[0027] 1. By improving A 2 The / O system increases the volume of the anoxic zone and HRT, enhancing the efficiency of denitrification and phosphorus removal, saving carbon sources and aeration energy consumption. After anoxic phosphorus absorption, a low-oxygen aeration reaction zone is set up, which can further improve phosphorus removal efficiency while reducing the competitive advantage of polysaccharide bacteria in the system, ensuring the stable operation of the system.

[0028] 2. For operating conditions where the raw water carbon source is insufficient and the C / N ratio is low, and the emission limit requirements are high, a double reflux of nitrification liquid is set up. While making full use of the raw water carbon source, external carbon source denitrification is coupled, which can achieve deep nitrogen and phosphorus removal in the main process.

[0029] 3. This process combines the characteristics of MBR technology, avoiding the problem of sludge bulking under long-term anoxic and low-load operation conditions.

[0030] 4. It solves the contradiction between the sludge age of denitrification and phosphorus removal. The MBBR reactor has a separate sludge return system, and the parameters can be adjusted to enhance the nitrification effect. At the same time, it can also realize partial short-cut nitrification, simultaneous nitrification and denitrification, further saving energy consumption and carbon source addition.

[0031] 5. Through online water quality monitoring and real-time signal feedback, process operating parameters can be flexibly adjusted, carbon source can be accurately added, energy and chemical consumption can be saved, and a reference can be provided for the efficient operation and management of actual projects.

[0032] 6. This invention is applicable to the upgrading and renovation of urban sewage treatment plants for deep nitrogen and phosphorus removal, and has broad market application prospects. Attached Figure Description

[0033] Figure 1 : A schematic diagram of a high-efficiency nitrogen and phosphorus removal treatment device for domestic sewage with a low carbon-to-nitrogen ratio.

[0034] In the diagram: 1. Water tank; 2. First inlet pump; 3. Anaerobic zone; 4. Anoxic zone I; 5. Aerobic zone I; 6. Anoxic zone II; 7. Aerobic zone II; 8. MBR membrane module; 9. Pressure gauge; 10. Vacuum pump; 11. Intermediate water tank; 12. Second inlet pump; 13. MBBR reaction zone; 14. Secondary sedimentation tank; 15. First nitrification liquor return pump; 16. Second nitrification liquor return pump; 17. First sludge return pump; 18. Second sludge return pump; 19. Blower; 20. Gas flow meter; 21. Aeration pipe; 22. Aeration head; 23. External carbon source storage tank; 24. Carbon source dosing pump; 25. Online DO monitoring probe; 26. Handheld dissolved oxygen meter; 27. Computer; 28. PLC controller; 29. ​​Electric stirrer; 30. Suspended packing; 31. Online water quality monitoring equipment. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0036] Please see Figure 1 .

[0037] The present invention provides a method for efficient nitrogen and phosphorus removal treatment of domestic wastewater with a low carbon-to-nitrogen ratio, using the following apparatus:

[0038] A high-efficiency nitrogen and phosphorus removal treatment device for low carbon-to-nitrogen ratio domestic sewage includes: 1. Water tank; 2. First influent pump; 3. Anaerobic zone; 4. Anoxic zone I; 5. Aerobic zone I; 6. Anoxic zone II; 7. Aerobic zone II; 8. MBR membrane module; 9. Pressure gauge; 10. Vacuum pump; 11. Intermediate water tank; 12. Second influent pump; 13. MBBR reaction zone; 14. Secondary sedimentation tank; 15. First nitrification liquor return pump; 16. Second nitrification liquor return pump; 17. First sludge return pump; 18. Second sludge return pump; 19. Blower; 20. Gas flow meter; 21. Aeration pipe; 22. Aeration head; 23. External carbon source storage tank; 24. Carbon source dosing pump; 25. Online DO monitoring probe; 26. Handheld solvent generator. The system comprises an oxygen deaerator 26, a computer 27, a PLC controller 28, an electric stirrer 29, suspended packing material 30, and an online water quality monitoring device 31. Its features include: a water tank 1 connected to an anaerobic zone 3 via a first inlet pump 2; the anaerobic zone 3, anoxic zone I 4, aerobic zone I 5, anoxic zone II 6, and aerobic zone II 7 connected sequentially; aerobic zone II 7 connected to an anaerobic zone 3 via a first sludge return pump 17; an MBR membrane module 8 placed within aerobic zone II 7; the MBR membrane module 8 connected to an intermediate water tank 11 via a pressure gauge 9 and a vacuum pump 10; and the intermediate water tank 11 connected to an MBBR reaction zone 13 via a second inlet pump 12. Suspended packing material 30 is placed inside the MBBR reaction zone 13, which is connected to the secondary sedimentation tank 14. The upper end of the secondary sedimentation tank 14 is connected to the anoxic zone I 4 and anoxic zone II 6 via the first nitrification liquid return pump 15 and the second nitrification liquid return pump 16, respectively. The lower end of the secondary sedimentation tank 14 is connected to the MBBR reaction zone 13 via the second sludge return pump 18. One end of the blower 19 is connected to the aeration pipe 21 via the gas flow meter 20, and the aeration pipe 21 is located at the bottom of the MBBR reaction zone 13. The other end of the blower 19 is connected to the aeration head 22. The external carbon source storage tank 23 is connected to the anoxic zone II 6 via the carbon source addition pump 24. Aerobic zone I 5 and aerobic zone II 7 are also connected to the secondary sedimentation tank 14. Online DO monitoring probes 25 are installed in both the anaerobic zone 13 and the MBBR reaction zone 13. The online DO monitoring probes 25 are connected to handheld dissolved oxygen meters 26, and the real-time signals are fed back to the computer 27. Two online water quality monitoring devices 31 are connected to the water tank 1 and the anoxic zone II 6, respectively, and the real-time signals are fed back to the computer 27. The computer 27 is connected to the PLC controller 28, which can adjust the flow rate of the first nitrification liquid return pump 15, the second nitrification liquid return pump 16, the first sludge return pump 17, the carbon source addition pump 24, and the air volume of the blower 19. Electric stirrers 29 are installed in the anaerobic zone 3, the anoxic zone I 4, and the anoxic zone II 6.

[0039] Example 1

[0040] 1) Sludge from a sludge thickening tank at a wastewater treatment plant was inoculated. After washing and settling, the sludge concentration was MLSS: 8400 mg / L, SV: 37%. Modified A was added. 2 In the / O, MBBR reactor, the improved A 2MLSS in reaction zone 13: 5000 mg / L; MLSS in reaction zone 13 of MBBR: 4000 mg / L; 30 PPC suspension packing material with a specific surface area of ​​2000 m² is added to reaction zone 13 of MBBR. 2 / m 3 The filling ratio is 40%. The quality of domestic sewage is shown in Table 1.

[0041] Table 1 Summary of Influent Water Quality

[0042]

[0043] 2) Domestic sewage enters A from water tank 1 through the first inlet pump 2. 2 The anaerobic zone 3 of the / O system simultaneously receives sludge from the bottom of the aerobic zone II 7 via the first sludge return pump 17. The average C / P ratio of the influent is 35.9:1, the sludge return ratio is set to 100%, and the HRT of the anaerobic zone 3 is 2 hours for anaerobic phosphorus release.

[0044] 3) The mixed liquor enters the anoxic zone I 4. At the same time, the supernatant of the mixed liquor that has completed nitrification in the MBBR reaction zone 13 after solid-liquid separation in the secondary sedimentation tank 14 enters the anoxic zone I 4 through the first nitrification liquor return pump 15. The anoxic zone I 4 has a 4-hour response time of 5 hours, the average C / N ratio of the influent is about 4.6:1, the nitrification liquor return ratio is 150%, and phosphorus uptake is carried out in anoxic conditions. At the same time, based on the feedback of ammonia nitrogen, TN, and COD values ​​measured by the online water quality monitoring equipment 31 in the water tank 1, the nitrification liquor return ratio fluctuates by 25% above or below the 150% base.

[0045] 4) The mixed liquor enters the aerobic I zone 5 through the anoxic zone I 4, with dissolved oxygen set at 1.5 mg / L. The HRT of aerobic I zone 5 is 1.5 h. Based on the average C / N ratio of the influent, which is approximately 4.6:1, the nitrification liquor reflux ratio of anoxic II zone 6 is 150%, and the HRT of anoxic II zone 6 is 3 h. Based on the feedback of ammonia nitrogen, TN, and COD signals from the online water quality monitoring equipment 31, the flow rate of the carbon source dosing pump 24 is precisely controlled. During stable operation, the TN removal rate of anoxic II zone 6 is 5-10 mg / L, and it is dynamically and precisely added according to the TN / sodium acetate mass ratio of 1:4.

[0046] 5) The mixed liquor enters the aerobic II zone 7 through the anoxic II zone 6. The aerobic II zone 7 has an HRT of 2h and the dissolved oxygen is set to 1.5mg / L. The mixed liquor achieves sludge-water separation through the MBR membrane module 8. The supernatant enters the intermediate water tank 11 through the vacuum pump 10. The second inlet pump 12 injects the wastewater containing ammonia nitrogen into the MBBR reaction zone 13.

[0047] 6) MBBR reaction zone 13: aeration rate 5 L / min, dissolved oxygen concentration 3 mg / L, HRT 3 h, sludge concentration 1700 mg / L, biomass attached to carrier particles: 1.723 mg VSS / g dry particles, ammonia nitrogen removal rate: 0.85 kg N / (m³) 3 ·d).

[0048] 7) The mixed liquor enters the secondary sedimentation tank 14 through the MBBR reaction zone 13. After the sludge settles, it flows back from the bottom to the inlet of the MBBR reaction zone 13. Part of the supernatant is discharged and part is returned to the anoxic zone I 4 and anoxic zone II 6. The distribution ratio of the two return liquids is set at 1:1 (determined based on the inlet C / N ratio of 4.6:1).

[0049] 8) Improved A 2 The sludge age in the / O zone is 12 days, and the sludge age in the MBBR reaction zone 13 is 30 days.

[0050] 9) Implementation effect: The treated effluent can meet the Class III standard of the Surface Water Environmental Quality Standard (GB3838-2002). Specific water quality parameters are shown in Table 2.

[0051] Table 2. Overview of Effluent Water Quality

[0052]

[0053] Example 2

[0054] 1) Sludge from a sludge thickening tank at a wastewater treatment plant was inoculated. After washing and settling, the sludge concentration was MLSS: 9000 mg / L, SV: 40%. Modified A was added. 2 In the / O, MBBR reactor, the improved A 2 MLSS in reaction zone 13: 4000 mg / L; MLSS in reaction zone 13 of MBBR: 3000 mg / L; HDPE suspension filler 30 with a specific surface area of ​​1200 m² is added to reaction zone 13 of MBBR. 2 / m 3 The filling ratio is 50%. The influent is artificially distributed, and the water quality parameters are shown in Table 3.

[0055] Table 3 Summary of Influent Water Quality

[0056]

[0057] 2) Wastewater enters A from water tank 1 through the first inlet pump 2. 2 The anaerobic zone 3 of the / O system simultaneously receives sludge from the bottom of the aerobic zone II 7 via the first sludge return pump 17. The average C / P ratio of the influent is 30:1, the sludge return ratio is set at 120%, and the anaerobic zone 3 has a 3-hour anaerobic phosphorus release time.

[0058] 3) The mixed liquor enters the anoxic zone I 4. At the same time, the supernatant of the mixed liquor that has completed nitrification in the MBBR reaction zone 13 after solid-liquid separation in the secondary sedimentation tank 14 enters the anoxic zone I 4 through the first nitrification liquor return pump 15. The anoxic zone I 4 has a 4-hour response time of 6 hours, the average influent C / N ratio is about 7.5:1, the nitrification liquor return ratio is 300%, and phosphorus uptake is carried out in anoxic conditions.

[0059] 4) The mixed liquor enters the aerobic I zone 5 from the anoxic zone I 4, with dissolved oxygen set at 1.5 mg / L. The HRT of aerobic I zone 5 is 1.5 h. Based on the average C / N ratio of the influent, which is approximately 4.6:1, the nitrification liquor reflux ratio in anoxic II zone 6 is 100%, and the HRT of anoxic II zone 6 is 4 h. Based on the feedback signals of ammonia nitrogen, TN, and COD values ​​measured by the online water quality monitoring equipment 31, the flow rate of the carbon source addition pump 24 is precisely controlled. The TN removal in anoxic II zone 6 is 2-5 mg / L, and it is dynamically and precisely added according to the TN / sodium acetate mass ratio of 1:4.

[0060] 5) The mixed liquor enters the aerobic II zone 7 through the anoxic II zone 6. The aerobic II zone 7 has an HRT of 2h and the dissolved oxygen is set to 2mg / L. The mixed liquor achieves sludge-water separation through the MBR membrane module 8. The supernatant enters the intermediate water tank 11 through the vacuum pump 10. The second inlet pump 12 injects the wastewater containing ammonia nitrogen into the MBBR reaction zone 13.

[0061] 6) MBBR reaction zone 13: aeration rate 3 L / min, dissolved oxygen concentration 2 mg / L, HRT 4 h, sludge concentration 1900 mg / L, biomass attached to carrier particles: 2.047 mg VSS / g dry particles, ammonia nitrogen removal rate: 2.17 kg N / (m³) 3 ·d).

[0062] 7) The mixed liquor enters the secondary sedimentation tank 14 through the MBBR reaction zone 13. After the sludge settles, it flows back from the bottom to the inlet of the MBBR reaction zone 13. Part of the supernatant is discharged and part is returned to the anoxic zone I 4 and anoxic zone II 6. The distribution ratio of the two return liquids is set to 3:1 according to the influent C / N ratio.

[0063] 8) Improved A 2 The sludge age in the / O zone is 10 days, and the sludge age in the MBBR reaction zone 13 is 20 days.

[0064] 9) Implementation Results: After the system is running stably, the specific water quality parameters after treatment are shown in Table 4. Denitrification phosphorus removal accounts for 91.38% of the total phosphorus removal. The remaining phosphorus is removed by subsequent aerobic phosphorus adsorption. The entire process can achieve phosphorus discharge compliance (<0.1mg / L) without adding a chemical phosphorus removal unit. The total nitrogen in the effluent can be less than 10mg / L without adding an external carbon source. Combined with the online water quality monitoring equipment 31, the TN value changes are dynamically monitored. Precise addition of carbon source can ensure that the total nitrogen in the effluent is less than 5mg / L. Moreover, the amount of carbon source added is not increased compared with the traditional A2 / O, while reducing energy consumption and residual sludge.

[0065] Table 4. Overview of Effluent Water Quality

[0066]

[0067] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for efficient nitrogen and phosphorus removal treatment of domestic sewage with low carbon-to-nitrogen ratio, characterized in that, Includes the following steps: Step 1: Domestic sewage enters A from the water tank (1) through the first inlet pump (2). 2 The anaerobic zone (3) of the / O system is simultaneously fed with sludge pumped out by the first sludge return pump (17) at the bottom of the aerobic zone (7). The sludge return ratio is 50% to 200%, and the concentration of the returned sludge is 4000 to 7000 mg / L. The anaerobic zone (3) is kept at an HRT of 2 to 3 hours by stirring and mixing with an electric stirrer (29). Step 2: The mixed liquor enters the anoxic zone I (4), and at the same time, the supernatant of the mixed liquor that has completed nitrification in the MBBR reaction zone (13) after solid-liquid separation in the secondary sedimentation tank (14) enters the anoxic zone I (4) through the first nitrification liquor return pump (15). The HRT of the anoxic zone I (4) is 5-6 hours, and the nitrification liquor return ratio is 100%-300%. Step 3: The mixture enters the aerobic zone I (5) through the anoxic zone I (4), with dissolved oxygen set at 1-2.5 mg / L and HRT in the aerobic zone I (5) set at 1-2 h; Step 4: The mixed liquor enters the anoxic zone II (6) through the aerobic zone I (5), and at the same time, the supernatant flowing out of the secondary sedimentation tank (14) enters through the second nitrification liquor return pump (16). The nitrification liquor return ratio is 100% to 200%. The HRT of the anoxic zone II (6) is 3 to 4 hours. The external carbon source storage tank (23) is equipped with sodium acetate solution, and the dosage is added according to the mass ratio of TN removal amount / sodium acetate: 1:4 to 1:

6. The external carbon source storage tank (23) is connected to the anoxic zone II (6) through the carbon source addition pump (24). Step 5: The mixed liquor enters the aerobic II zone (7) through the anoxic II zone (6). The HRT of the aerobic II zone (7) is 2-3 hours, and the dissolved oxygen is set to 1.5-2.5 mg / L. The mixed liquor achieves sludge-water separation through the MBR membrane module (8). The supernatant enters the intermediate water tank (11) through the vacuum pump (10). The second influent pump (12) injects the wastewater containing ammonia nitrogen into the MBBR reaction zone (13). The sludge age is 8-12 days. Step 6: Add suspended packing material (30) with a specific surface area of ​​600-2000 m² to the MBBR reaction zone (13). 2 / m 3 The filling ratio is 30%–50%, the aeration rate is 3–6 L / min, the dissolved oxygen concentration is 2–4 mg / L, the HRT is 3–4 h, the sludge concentration is 1500–3000 mg / L, the sludge age is 20–30 days, the biomass attached to the carrier particles is 1.5–2.5 mg VSS / g dry particles, and the ammonia nitrogen removal rate is 0.7–2.2 kg N / (m³). 3 ·d); Step 7: The mixed liquor enters the secondary sedimentation tank (14) through the MBBR reaction zone (13). After the sludge settles, it flows back from the bottom to the inlet of the MBBR reaction zone (13). Part of the supernatant is discharged and part of it flows back to the anoxic zone I (4) and anoxic zone II (6). In step 1, when the influent C / P ratio is 15:1 to 40:1, the sludge return ratio in the anaerobic zone (3) is 75% to 150%, and when the C / P ratio is 40:1 to 70:1, the sludge return ratio in the anaerobic zone (3) is 50% to 100%. In steps 2 and 4, when the influent C / N ratio is 3:1 to 5:1, the flow rate ratio of the recirculated water to anoxic zone I (4) and anoxic zone II (6) is 1:1 to 1:1.5; when the influent C / N ratio is 5:1 to 8:1, the flow rate ratio of the recirculated water to anoxic zone I (4) and anoxic zone II (6) is 2:1 to 3:

1. In step 4, the TN removal amount can be dynamically fed back by the water quality indicators of the online water quality monitoring equipment (31), and the TN removal amount / sodium acetate mass ratio is 1:4 to 1:

6. In steps 1, 2, 3, 4, 5, and 6, the HRT in the anaerobic zone (3) is 2–3 h, the HRT in the anoxic zone I (4) is 5–6 h, the HRT in the aerobic zone I (5) is 1–2 h, the HRT in the anoxic zone II (6) is 3–4 h, and the HRT in the aerobic zone II (7) is 2–3 h. Improved A 2 / O hypoxic zone volume percentage: 55%–62%.

2. The method for efficient nitrogen and phosphorus removal from low carbon-to-nitrogen ratio domestic sewage according to claim 1, characterized in that: In step 5, the dissolved oxygen is set to 1.5–2.5 mg / L, and the sludge age is 8–12 days.

3. The method for efficient nitrogen and phosphorus removal from low carbon-to-nitrogen ratio domestic sewage according to claim 1, characterized in that: In step 6, the dissolved oxygen concentration in the MBBR reaction zone (13) is 2-4 mg / L, the HRT is 3-4 h, and the sludge age is 20-30 d.

4. The method for efficient nitrogen and phosphorus removal from low carbon-to-nitrogen ratio domestic sewage according to claim 1, characterized in that, It also includes the following steps: Step 8: Water tank (1) and anoxic zone I (4) are equipped with online water quality monitoring equipment (31), which can feed back COD, ammonia nitrogen, total nitrogen, and total phosphorus indicators to the computer (27) in real time. The nitrification liquid recirculation ratio can be adjusted according to the influent C / N ratio. When the influent C / N ratio is 3:1 to 5:1, the nitrification liquid flow rate ratio recirculated to anoxic zone I (4) and anoxic zone II (6) is 1:1 to 1:1.

5. When the water C / N ratio is 5:1 to 8:1, the nitrification liquid flow rate ratio returned to the anoxic zone I (4) and the anoxic zone II (6) is 2:1 to 3:

1. The sludge return ratio in the anaerobic zone can be adjusted according to the value of the influent C / P ratio. When the C / P ratio is 15:1 to 40:1, the sludge return ratio in the anaerobic zone is 75% to 150%. When the C / P ratio is 40:1 to 70:1, the sludge return ratio in the anaerobic zone is 50% to 100%.

5. The method for efficient nitrogen and phosphorus removal from low carbon-to-nitrogen ratio domestic sewage according to claim 1, characterized in that, The method for efficient nitrogen and phosphorus removal treatment of low carbon-to-nitrogen ratio domestic sewage uses the following equipment: A high-efficiency nitrogen and phosphorus removal treatment device for domestic sewage with low carbon-to-nitrogen ratio includes a water tank (1), a first influent pump (2), an anaerobic zone (3), anoxic zone I (4), aerobic zone I (5), anoxic zone II (6), aerobic zone II (7), an MBR membrane module (8), a pressure gauge (9), a vacuum pump (10), an intermediate water tank (11), a second influent pump (12), an MBBR reaction zone (13), a secondary sedimentation tank (14), a first nitrification liquid return pump (15), a second nitrification liquid return pump (16), a first sludge return pump (17), a second sludge return pump (18), a blower (19), a gas flow meter (20), an aeration pipe (21), an aeration head (22), an external carbon source storage tank (23), a carbon source dosing pump (24), and an online DO converter. The system includes a monitoring probe (25), a handheld dissolved oxygen meter (26), a computer (27), a PLC controller (28), an electric stirrer (29), a suspended packing material (30), and an online water quality monitoring device (31). The water tank (1) is connected to the anaerobic zone (3) via a first inlet pump (2). The anaerobic zone (3), anoxic zone I (4), aerobic zone I (5), anoxic zone II (6), and aerobic zone II (7) are connected sequentially. The aerobic zone II (7) is connected to the anaerobic zone (3) via a first sludge return pump (17). An MBR membrane module (8) is placed in the aerobic zone II (7). The MBR membrane module (8) is connected to an intermediate water tank (11) via a pressure gauge (9) and a vacuum pump (10). The intermediate water tank (11)... The second inlet pump (12) is connected to the MBBR reaction zone (13), which contains suspended packing material (30) and is connected to the secondary sedimentation tank (14). The upper end of the secondary sedimentation tank (14) is connected to the anoxic zone I (4) and the anoxic zone II (6) via the first nitrification liquid return pump (15) and the second nitrification liquid return pump (16), respectively. The lower end of the secondary sedimentation tank (14) is connected to the MBBR reaction zone (13) via the second sludge return pump (18). One end of the blower (19) is connected to the aeration pipe (21) via the gas flow meter (20), and the aeration pipe (21) is located at the bottom of the MBBR reaction zone (13). The other end of the blower (19) is connected to the aeration pipe (21). The aeration head (22) is connected to the aeration head (22); online DO monitoring probes (25) are installed in the aerobic I zone (5), aerobic II zone (7) and MBBR reaction zone (13), and the online DO monitoring probes (25) are connected to the handheld dissolved oxygen meter (26), and the real-time signal is fed back to the computer (27). The two online water quality monitoring devices (31) are connected to the water tank (1) and the anoxic II zone (6) respectively, and the real-time signal is fed back to the computer (27); the computer (27) is connected to the PLC controller (28) and can adjust the flow rate of the first nitrification liquid return pump (15), the flow rate of the second nitrification liquid return pump (16), the flow rate of the first sludge return pump (17), the flow rate of the carbon source addition pump (24) and the air volume of the blower (19);Electric stirrers (29) are installed in the anaerobic zone (3), the anoxic zone I (4), and the anoxic zone II (6).

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