Method and device for low-carbon ultra-deep denitrification of municipal wastewater

Abstract

This invention provides a method and apparatus for low-carbon, ultra-deep denitrification of urban wastewater, belonging to the field of wastewater treatment and applied to urban wastewater treatment. In a continuous flow anaerobic-aerobic-anoxic alternating-post-anoxic process, urban wastewater and returned heavy sludge enter the anaerobic zone of a biological treatment tank. Returned light sludge and added hydroxylamine enter the aerobic-anoxic alternating zone of the biological treatment tank. The sludge-water mixture flowing out of the post-anoxic zone of the biological treatment tank enters a secondary sedimentation tank for sludge-water separation. The supernatant is discharged as effluent, and the settled sludge enters a hydrocyclone separator to be separated into heavy sludge and light sludge. The heavy sludge and part of the light sludge are returned to the process as described above, and part of the light sludge is discharged as excess sludge. Microorganisms in the sludge store internal carbon sources in the anaerobic zone of the biological treatment tank. Short-cut nitrification and endogenous denitrification are achieved in the aerobic-anoxic alternating zone of the biological treatment tank. Ultra-deep endogenous denitrification is performed in the post-anoxic zone of the biological treatment tank. This invention can achieve low-carbon, ultra-deep denitrification of urban wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, and more specifically, relates to a method and apparatus for low-carbon ultra-deep denitrification of urban wastewater. Background Technology

[0002] Excessive nitrogen content in wastewater is a key factor contributing to eutrophication. To prevent this environmental problem, wastewater must undergo denitrification treatment before being discharged into natural water bodies. Especially for sensitive water bodies, wastewater discharge standards are more stringent, making advanced denitrification treatment of urban wastewater an inevitable trend.

[0003] For municipal wastewater treatment plants employing traditional denitrification processes, a common practice for achieving advanced denitrification is to add denitrification filters. For example, the Blue Plains wastewater treatment plant successfully reduced its effluent TN concentration to below 4 mg / L by installing a post-denitrification filter. However, operating a denitrification filter not only requires the addition of an extra carbon source, increasing operating costs, but also expands the footprint of the reaction tank, which is a disadvantage in urban areas with limited land resources. Given the necessity of advanced denitrification for municipal wastewater, and the cost and technical challenges of upgrading wastewater treatment plants, exploring a simple, efficient, and economical process upgrade solution is particularly important. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for low-carbon, ultra-deep nitrogen removal from urban wastewater, aiming to solve the problems of difficulty in low-carbon, low-energy-consumption, and high-efficiency biological nitrogen removal, high treatment costs, and large land area in existing urban wastewater treatment.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A method for low-carbon, ultra-deep denitrification of urban wastewater includes the following steps: Wastewater is transported into a biological treatment tank, which comprises a three-compartment anaerobic zone, a two-compartment aerobic-anoxic alternating zone, and a two-compartment post-anoxic zone; activated sludge from a wastewater treatment plant is added to the anaerobic zone, aerobic-anoxic alternating zone, and post-anoxic zone of the biological treatment tank; simultaneously, hydroxylamine solution from a hydroxylamine solution tank is pumped into the front end of the first compartment of the aerobic-anoxic alternating zone; the sludge-water mixture flowing out from the post-anoxic zone enters a secondary sedimentation tank for sedimentation, achieving sludge-water separation, and the supernatant is discharged; the settled sludge is separated into bottom flow heavy sludge and overflow light sludge by a hydrocyclone separator, the bottom flow heavy sludge enters the front end of the first compartment of the anaerobic zone of the biological treatment tank; a portion of the overflow light sludge enters the front end of the first compartment of the aerobic-anoxic alternating zone of the biological treatment tank, and the remaining overflow light sludge is discharged as surplus sludge.

[0007] As one of the preferred technical solutions, in this application, activated sludge from a wastewater treatment plant is inoculated into the anaerobic zone, aerobic-anoxic alternating zone, and post-anoxic zone of the biological treatment tank, and a double reflux technology is used to achieve a sludge concentration of 2200 mg / L~2600 mg / L in the anaerobic zone, and 3600 mg / L~4000 mg / L in the aerobic-anoxic alternating zone and post-anoxic zone. The sludge concentration in the aerobic-anoxic alternating zone is higher than that in the anaerobic zone. The adjustment operation during operation is as follows:

[0008] 1) The flow rate of heavy sludge returned to the anaerobic zone of the biological treatment tank is 60%~80% of the influent flow rate;

[0009] 2) The flow rate of light sludge returned to the aerobic-anoxic alternation zone of the biological treatment tank is 150%~170% of the influent flow rate;

[0010] 3) The total hydraulic retention time of the biological treatment tank system is 7h~10h, of which the total hydraulic retention time of the anaerobic zone is 3h~4h, the total hydraulic retention time of the aerobic-anoxic alternation zone of the biological treatment tank is 2h~3h, and the total hydraulic retention time of the post-anoxic zone of the biological treatment tank is 2h~3h.

[0011] 4) The biological treatment tank of the biological treatment tank system is divided into two compartments for alternating aerobic and anoxic zones. The dissolved oxygen in each compartment is controlled at 1.5±0.5mg / L during aeration.

[0012] 5) Add hydroxylamine to the front end of the first compartment of the aerobic-anoxic alternation zone in the biological treatment tank;

[0013] 6) The system discharges a portion of the light sludge produced by the cyclone separator daily as excess sludge.

[0014] As one of the preferred technical solutions, in this application, in step 4), the aeration / non-aeration time range of the first compartment in the aerobic-anoxic alternating zone of the biological treatment tank is from 5min / 9min to 6min / 8min. When the aeration in the first compartment stops, the second compartment starts aeration, and the aeration / non-aeration time range is from 2min / 12min to 4min / 10min. In step 5), the theoretical concentration of hydroxylamine in the aerobic-anoxic alternating zone of the biological treatment tank is set to 5mg / L, and it is added continuously for 4 hours every day. In step 6), the sludge retention time is controlled to be 12 to 14 days.

[0015] A method for low-carbon, ultra-deep nitrogen removal from urban wastewater includes a biological treatment tank, a hydroxylamine solution tank, a secondary sedimentation tank, and a hydrocyclone separator. The biological treatment tank is divided into seven compartments, each connected by flow holes arranged vertically according to the water flow direction. The first, second, and third compartments are the anaerobic zone; the fourth and fifth compartments are the aerobic-anoxic alternating zone; and the sixth and seventh compartments are the post-anoxic zone. Each of the seven compartments is equipped with a stirrer. Aeration heads are installed in two compartments of the aerobic-anoxic alternating zone, connected sequentially to an air volume regulating valve and a blower. Dissolved oxygen probes are also installed in the two compartments of the aerobic-anoxic alternating zone. The system includes an online sensor, where hydroxylamine in the hydroxylamine solution tank is pumped into the first compartment of the aerobic-anaerobic alternating zone of the biological treatment tank via a peristaltic pump. Urban sewage enters the biological treatment tank through an inlet valve, and the effluent from the biological treatment tank enters a secondary sedimentation tank for sedimentation, achieving sludge-water separation. The final effluent is discharged through an outlet valve. The settled sludge in the secondary sedimentation tank is pumped into a hydrocyclone separator for separation. The heavy sludge from the underflow is returned to the first compartment of the anaerobic zone of the biological treatment tank via a heavy sludge return valve, and a portion of the overflowing light sludge is returned to the first compartment of the aerobic-anaerobic alternating zone of the biological treatment tank via a sludge return valve. The remaining light sludge is discharged through a residual sludge discharge valve. The agitator, blower, online sensor, peristaltic pump, and water pump are all connected to the control cabinet.

[0016] A device for low-carbon ultra-deep denitrification of urban sewage includes a biological treatment tank, a secondary sedimentation tank, and a hydrocyclone separator connected in sequence. The biological treatment tank consists of a three-compartment anaerobic zone, a two-compartment aerobic-anoxic alternating zone, and a two-compartment post-anoxic zone. The first compartment of the two-compartment aerobic-anoxic alternating zone is connected to a hydroxylamine solution tank. The bottom of the secondary sedimentation tank is connected to the inlet of the hydrocyclone separator. The bottom of the hydrocyclone separator is connected to the first compartment of the anaerobic zone of the biological treatment tank. The top of the hydrocyclone separator is connected to the first compartment of the aerobic-anoxic alternating zone of the biological treatment tank and a residual sludge discharge valve.

[0017] As one of the preferred technical solutions, in this application, the biological treatment tank is divided into 7 compartments, with flow holes arranged vertically and vertically to connect each compartment according to the water flow direction, and the outlet of the last compartment is in the middle position; the first, second, and third compartments are the anaerobic zone of the biological treatment tank, the fourth and fifth compartments are the aerobic-anoxic alternation zone of the biological treatment tank, and the sixth and seventh compartments are the post-anoxic zone of the biological treatment tank.

[0018] As one of the preferred technical solutions, in this application, the aerobic and hypoxic alternation zone of the two-compartment biological treatment tank is equipped with a dissolved oxygen probe and an online sensor to display the dissolved oxygen concentration in real time. The online sensor is connected to the control cabinet.

[0019] As one of the preferred technical solutions, in this application, the first compartment in the aerobic-anoxic alternating zone of the biochemical tank is connected to the hydroxylamine solution tank via a peristaltic pump, and the peristaltic pump is connected to the control cabinet.

[0020] As one of the preferred technical solutions, in this application, the aerobic-anoxic alternation zone of the biological treatment tank is equipped with an aeration head, which is connected in sequence to an air volume regulating valve and a blower, and the blower is connected to a control cabinet.

[0021] As one of the preferred technical solutions, in this application, each of the seven compartments of the biochemical tank is equipped with a stirrer, which is connected to the control cabinet; the bottom of the secondary sedimentation tank is connected in sequence to the secondary sedimentation tank sludge discharge valve and the water pump, which is connected to the control cabinet.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention addresses the challenge of low-carbon, low-energy, and highly efficient ultra-deep biological nitrogen removal from urban wastewater. It achieves dual sludge recirculation by incorporating a sludge hydrocyclone separator. Heavy sludge is recirculated to the first compartment of the anaerobic zone, while a portion of the light sludge is recirculated to the first compartment of the aerobic-anoxic alternating zone. This results in a higher sludge concentration in the aerobic-anoxic alternating zone compared to the anaerobic zone, providing a sufficient internal carbon source for endogenous denitrification and promoting its development. Only light sludge is discharged as excess sludge, improving the system's sludge settling properties and preventing sludge bulking. Hydroxylamine is added to the first compartment of the aerobic-anoxic alternating zone, further enhancing the system's performance. It has a higher inhibitory capacity against nitrite-oxidizing bacteria (NOB) than ammonia-oxidizing bacteria (AOB), and can rapidly achieve short-cut nitrification. Intermittent aeration creates an alternation between aerobic and anoxic conditions. During aerobic aeration, a small amount of nitrite is generated and then consumed by anoxic denitrification, reducing the possibility of NOB growth and avoiding high concentrations of nitrite that inhibit sludge activity. In addition, intermittent aeration can reduce the aerobic oxidation of internal carbon sources, allowing more carbon sources to be used for post-denitrification. On the other hand, by extending the anaerobic and anoxic stages, the internal carbon source storage and endogenous denitrification of denitrifying bacteria can also be enhanced.

[0024] 2. Compared with traditional A 2 Compared with the O process, this invention has the following advantages:

[0025] 1) By adding hydroxylamine inhibitors, the system mainly inhibits the growth of NOB, achieving short-cut nitrification and reducing aeration volume.

[0026] 2) By adopting alternating aerobic and anoxic methods, the oxidation of internal carbon sources by aerobic processes is reduced, and post-anoxic internal denitrification is enhanced to achieve ultra-deep denitrification.

[0027] 3) Using a sludge hydrocyclone separator to achieve dual sludge recirculation increases the carbon source in the sludge in the aerobic-anoxic alternation zone. Discharging light sludge as excess sludge improves sludge settling properties and avoids sludge bulking in the system.

[0028] 4) This process utilizes more carbon sources within the sludge for denitrification, resulting in lower sludge production in the system.

[0029] 5) This process achieves ultra-deep nitrogen removal through short-cut nitrification and endogenous denitrification, resulting in low wastewater treatment costs. It also eliminates the need for additional denitrification filters, thus requiring a small system footprint. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the device in this invention.

[0031] In the diagram: 1. Biological treatment tank; 2. Secondary sedimentation tank; 3. Cyclone separator; 4. Hydroxylamine solution tank; 5. Control cabinet; 6. Anaerobic zone of biological treatment tank; 7. Alternating aerobic and anoxic zone of biological treatment tank; 8. Post-anoxic zone of biological treatment tank; 9. Water pump; 10. Blower; 11. Agitator; 12. Online sensor; 13. Peristaltic pump; 14. Aeration head; 15. Air volume regulating valve; 16. Dissolved oxygen probe; 17. Inlet valve; 18. Outlet valve; 19. Sludge discharge valve of secondary sedimentation tank; 20. Light sludge return valve; 21. Heavy sludge return valve; 22. Excess sludge discharge valve. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Using the method of this invention, low-carbon municipal sewage and heavy sludge from the lower end of the return swirl separator 3 enter the front end of the first compartment of the anaerobic zone 6 of the biological treatment tank. Microorganisms in the sludge first decompose proteins into amino acids and peptides, and then convert them into internal carbon sources for storage. The sludge-water mixture flowing out of the anaerobic zone 6 of the biological treatment tank and a portion of the light sludge from the upper end of the return swirl separator enter the front end of the first compartment of the aerobic-anoxic alternating zone 7 of the biological treatment tank. By adding hydroxylamine and intermittent aeration, short-cut nitrification-endogenous denitrification is achieved. The sludge-water mixture then enters the post-anoxic zone 8 of the biological treatment tank for ultra-deep denitrification. The sludge-water mixture flowing out of the anoxic zone 8 of the biological treatment tank enters the secondary sedimentation tank 2 for sedimentation, achieving sludge-water separation. The supernatant is discharged, and the settled sludge enters the hydrocyclone separator 3 for sorting. The heavier bottom sludge enters the first compartment of the anaerobic zone 6 of the biological treatment tank to replenish the activated sludge in the anaerobic zone 6. A portion of the lighter overflow sludge enters the first compartment of the aerobic-anoxic alternating zone 7 of the biological treatment tank, increasing the sludge concentration in the aerobic-anoxic alternating zone 7 and providing more proteins and other extracellular polymers of activated sludge as usable carbon sources, promoting endogenous denitrification. The remaining light sludge is discharged as excess sludge. This invention can achieve low-carbon, ultra-deep denitrification of urban wastewater.

[0034] Example 1

[0035] like Figure 1As shown, a device for low-carbon ultra-deep denitrification of urban sewage includes a biological treatment tank 1, a secondary sedimentation tank 2, a hydrocyclone separator 3, a hydroxylamine solution tank 4, and a control cabinet 5. The biological treatment tank 1, secondary sedimentation tank 2, and hydrocyclone separator 3 are connected in sequence. The biological treatment tank 1 is connected to an inlet valve 17. The biological treatment tank 1 is divided into three areas with seven compartments. The first, second, and third compartments are the anaerobic zone 6, the fourth and fifth compartments are the aerobic-anoxic alternating zone 7, and the sixth and seventh compartments are the post-anoxic zone 8. Flow holes are staggered according to the water flow direction to connect the seven compartments. Each of the seven compartments is equipped with a stirrer 11. Each compartment in the aerobic-anoxic alternating zone 7 is equipped with an aeration head 14, which is connected in sequence to an air volume regulating valve 15 and a blower 10. The alternating zone 7 is also equipped with a dissolved oxygen probe 16 and an online sensor 12; the hydroxylamine solution tank 4 is connected to the first compartment of the aerobic-anoxic alternating zone 7 of the biological treatment tank via a peristaltic pump 13; the biological treatment tank 1 is connected to the secondary sedimentation tank 2, and the secondary sedimentation tank 2 is connected to the effluent valve 18 for discharging the final effluent; the hydrocyclone separator 3 is connected to the secondary sedimentation tank 2 via a water pump 9 and a sludge discharge valve 19 of the secondary sedimentation tank, the hydrocyclone separator 3 is connected to the first compartment of the anaerobic zone 6 of the biological treatment tank via a heavy sludge return valve 21, and the hydrocyclone separator 3 is connected to the first compartment of the aerobic-anoxic alternating zone 7 of the biological treatment tank via a light sludge return valve 20; the hydrocyclone separator 3 is also connected to a residual sludge discharge valve 22 for discharging residual sludge; the agitator 11, blower 10, online sensor 12, peristaltic pump 13 and water pump 9 are all automatically controlled by the control cabinet 5.

[0036] Working method: Wastewater is fed into biological treatment tank 1. Activated sludge from the wastewater treatment plant is added to the anaerobic zone 6, the aerobic-anoxic alternating zone 7, and the post-anoxic zone 8 of biological treatment tank 1. Hydroxylamine from hydroxylamine solution tank 4 is fed into the first compartment of the aerobic-anoxic alternating zone 7 of biological treatment tank 1 via peristaltic pump 13. The sludge-water mixture flowing out of the post-anoxic zone 8 of biological treatment tank 1 enters the secondary sedimentation tank 2 for sedimentation. After sludge-water separation, the supernatant is discharged through effluent valve 18. Discharge; The settled sludge in the secondary sedimentation tank 2 enters the hydrocyclone separator 3 through the secondary sedimentation tank sludge discharge valve 19 and the water pump 9. The hydrocyclone separator 3 separates the sludge into bottom flow heavy sludge and overflow light sludge. The bottom flow heavy sludge is returned to the anaerobic zone 6 of the biological treatment tank 1 through the heavy sludge return valve 21; part of the overflow light sludge is returned to the aerobic-anoxic alternating zone 7 of the biological treatment tank 1 through the light sludge return valve 20; the remaining overflow light sludge is discharged through the excess sludge discharge valve 22.

[0037] Example 2

[0038] A method for low-carbon ultra-deep denitrification of urban sewage includes a biological treatment tank 1, a secondary sedimentation tank 2, a hydrocyclone separator 3, a hydroxylamine solution tank 4, and a control cabinet 5, as described in Example 1. The biological treatment tank 1, secondary sedimentation tank 2, and hydrocyclone separator 3 are connected sequentially. The biological treatment tank 1 is connected to an inlet valve 17. The biological treatment tank 1 is divided into three areas with seven compartments: the first, second, and third compartments are the anaerobic zone 6; the fourth and fifth compartments are the aerobic-anoxic alternating zone 7; and the sixth and seventh compartments are the post-anoxic zone 8. Flow holes are staggered according to the water flow direction to connect the seven compartments. Each of the seven compartments is equipped with a stirrer 11. Each compartment in the aerobic-anoxic alternating zone 7 is equipped with an aeration head 14, which is connected sequentially to an air volume regulating valve 15 and a blower 10. It is also equipped with a dissolved oxygen probe 16 and an online sensor 12; the hydroxylamine solution tank 4 is connected to the first compartment of the aerobic-anoxic alternating zone 7 via a peristaltic pump 13; the biological treatment tank 1 is connected to the secondary sedimentation tank 2, and the secondary sedimentation tank 2 is connected to the drain valve 18 for discharging the final effluent; the settled sludge in the secondary sedimentation tank 2 enters the hydrocyclone separator 3 through the secondary sedimentation tank sludge discharge valve 19 and the water pump 9, and the hydrocyclone separator 3 separates the sludge into bottom flow heavy sludge and overflow light sludge. The bottom flow heavy sludge is returned to the first compartment of the anaerobic zone 6 of the biological treatment tank 1 through the heavy sludge return valve 21; some of the overflow light sludge is returned to the first compartment of the aerobic-anoxic alternating zone 7 of the biological treatment tank 1 through the light sludge return valve 20; the remaining overflow light sludge is discharged through the remaining sludge discharge valve 22; the agitator 11, blower 10, online sensor 12, peristaltic pump 13 and water pump 9 are all automatically controlled by the control cabinet 5.

[0039] The experiment used effluent from the grit chamber of the long-flow wastewater treatment plant as the influent. Specific water quality parameters were as follows: influent ammonia nitrogen 13.62 mg / L~26.93 mg / L, influent total nitrogen (TN) 13.96 mg / L~27.27 mg / L, influent COD 52.65 mg / L~130.84 mg / L, and an average C / N ratio of 3.12. The experimental system was as follows: Figure 1 As shown, the total reaction volume of the reactor is 22.4 m³. 3 It is divided into 7 compartments, with the total volume of the anaerobic zone in the biological treatment tank being 9.9 m³. 3 The total volume of the aerobic and anoxic alternation zone in the biological treatment tank is 6.4 m³. 3 The total volume of the post-anoxic zone is 6.1 m³. 3 Secondary sedimentation tank volume 4m³ 3 .

[0040] (1) Start-up system: Inoculate the activated sludge from the sewage treatment plant into the anaerobic zone, aerobic-anoxic alternating zone and post-anoxic zone of the biological treatment tank and use double reflux technology to make the sludge concentration in the anaerobic zone of the biological treatment tank 2500mg / L, and the sludge concentration in the aerobic-anoxic alternating zone and post-anoxic zone of the biological treatment tank 4000mg / L;

[0041] (2) The adjustment operation during operation is as follows:

[0042] 1) The flow rate of heavy sludge returned to the anaerobic zone 6 of the biological treatment tank is 70% of the influent flow rate;

[0043] 2) The flow rate of light sludge returned to the aerobic-anoxic alternation zone 7 of the biological treatment tank is 160% of the influent flow rate;

[0044] 3) The total HRT (hydraulic retention time) of the biological treatment system is 8.91h, of which the HRT of anaerobic zone 6 is 3.81h, the HRT of aerobic-anoxic alternation zone 7 is 2.55h, and the HRT of post-anoxic zone 8 is 2.55h.

[0045] 4) The aerobic / anoxic alternating zone of the biological treatment tank system is divided into two compartments. The aeration / non-aeration time range in the first compartment is from 5 min / 9 min to 6 min / 8 min. When aeration in the first compartment stops, aeration in the second compartment begins, with the aeration / non-aeration time range from 2 min / 12 min to 4 min / 10 min. The total aeration time is 0.64 h, and the non-aeration time is 1.91 h. During aeration in the aerobic / anoxic alternating zone, the dissolved oxygen (DO) is controlled at 1.5 ± 0.5 mg / L.

[0046] 5) Add hydroxylamine to the front end of the first cell in the aerobic-anoxic alternation zone 7 of the biological treatment tank. Set the theoretical concentration of hydroxylamine in the aerobic-anoxic alternation zone 7 of the biological treatment tank to 5 mg / L and add it continuously for 4 hours every day.

[0047] 6) The system discharges a portion of the light sludge generated by the cyclone separator 3 as residual sludge every day, and controls the SRT (sludge retention time) to be 12 days.

[0048] The test results show that after the system is in stable operation, the average effluent ammonia nitrogen is 0.02 mg / L, the average effluent TN is 0.59 mg / L, and the average effluent COD is 16.53 mg / L.

[0049] In addition, activated sludge from the wastewater treatment plant was inoculated into the anaerobic zone 6, the aerobic-anoxic alternating zone 7, and the post-anoxic zone 8 of the biological treatment tank, and a double reflux technology was used to make the sludge concentration in the anaerobic zone 6 of the biological treatment tank 2200mg / L~2600mg / L, and the sludge concentration in the aerobic-anoxic alternating zone 7 and the post-anoxic zone 8 of the biological treatment tank 3600mg / L~4000mg / L. The sludge concentration in the aerobic-anoxic alternating zone 7 of the biological treatment tank was higher than that in the anaerobic zone 6 of the biological treatment tank.

[0050] 1) The flow rate of heavy sludge returned to the anaerobic zone 6 of the biological treatment tank is 60%~80% of the influent flow rate;

[0051] 2) The flow rate of light sludge returned to the aerobic-anoxic alternation zone 7 of the biological treatment tank is 150%~170% of the influent flow rate;

[0052] 3) The total HRT of the biological treatment tank system is 7h~10h, of which the HRT of the anaerobic zone of the biological treatment tank is 3h~4h, the HRT of the aerobic-anoxic alternation zone 7 of the biological treatment tank is 2h~3h, and the HRT of the post-anoxic zone 8 of the biological treatment tank is 2h~3h.

[0053] 4) The aerobic-anoxic alternation zone 7 of the biological treatment tank system is divided into two compartments. The aeration / non-aeration time range of the first compartment is from 5min / 9min to 6min / 8min. When the aeration in the first compartment stops, the aeration in the second compartment starts. The aeration / non-aeration time range is from 2min / 12min to 4min / 10min. When the aerobic-anoxic alternation zone 7 of the biological treatment tank is aerated, the DO is controlled at 1.5±0.5mg / L.

[0054] 5) Add hydroxylamine to the front end of the first compartment of the aerobic-anoxic alternation zone 7 in the biological treatment tank. Set the theoretical concentration of hydroxylamine in the aerobic-anoxic alternation zone 7 of the biological treatment tank to 5 mg / L and add it continuously for 4 hours every day.

[0055] 6) The system discharges a portion of the light sludge produced by the cyclone separator 3 as residual sludge every day, controlling the SRT to be 12-14 days.

[0056] Adjusting the process within the above-mentioned range can achieve the objective of this invention.

[0057] Comparative study examples

[0058] In the wastewater treated in the example, without hydrocyclone separator 3, without dual sludge recirculation, without hydroxylamine addition, without intermittent aeration, without long anaerobic time and post-anoxic conditions to promote intracellular carbon source storage and enhance endogenous denitrification, the ammonia nitrogen, TN, and COD in the treated effluent will increase significantly. For example, a wastewater treatment plant in Haikou uses traditional A... 2 The average TN of the effluent from the O process, under the same influent and environmental conditions, is 5.91 mg / L, which is much higher than the TN concentration of the effluent from this process (0.59 mg / L).

[0059] Finally, although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for low-carbon, ultra-deep nitrogen removal from urban wastewater, characterized in that, Includes the following steps: Wastewater is transported into a biological treatment tank (1), which consists of a three-compartment anaerobic zone (6), a two-compartment aerobic-anoxic alternating zone (7), and a two-compartment post-anoxic zone (8). Activated sludge from a wastewater treatment plant is added to the anaerobic zone (6), the aerobic-anoxic alternating zone (7), and the post-anoxic zone (8) of the biological treatment tank. At the same time, hydroxylamine in the hydroxylamine solution tank (4) is pumped into the front end of the first compartment of the aerobic-anoxic alternating zone (7) of the biological treatment tank. The sludge-water mixture flowing out from the post-anoxic zone (8) of the biological treatment tank enters the secondary sedimentation tank (2) for sedimentation. After sludge-water separation, the supernatant is discharged. The settled sludge is separated into bottom flow heavy sludge and overflow light sludge by a hydrocyclone separator (3). The bottom flow heavy sludge enters the front end of the first compartment of the anaerobic zone (6) of the biological treatment tank; part of the overflow light sludge enters the front end of the first compartment of the aerobic-anoxic alternation zone (7) of the biological treatment tank, and the remaining overflow light sludge is discharged as surplus sludge. Activated sludge from the sewage treatment plant is inoculated into the biological treatment tank (1). The biological treatment tank consists of an anaerobic zone (6), an aerobic-anoxic alternating zone (7), and a post-anoxic zone (8). A double reflux technique is used to ensure that the sludge concentration in the anaerobic zone (6) is 2200 mg / L to 2600 mg / L, and the sludge concentration in the aerobic-anoxic alternating zone (7) and the post-anoxic zone (8) is 3600 mg / L to 4000 mg / L. The sludge concentration in the aerobic-anoxic alternating zone (7) is higher than that in the anaerobic zone (6). The adjustment procedures during operation are as follows: 1) The flow rate of heavy sludge returned to the anaerobic zone (6) of the biological treatment tank is 60%~80% of the influent flow rate; 2) The flow rate of light sludge returned to the aerobic-anoxic alternation zone (7) of the biological treatment tank is 150%~170% of the influent flow rate; 3) The total hydraulic retention time of the biological treatment system is 7h~10h, of which the total hydraulic retention time of the anaerobic zone is 3h~4h, the total hydraulic retention time of the aerobic-anoxic alternation zone (7) of the biological treatment system is 2h~3h, and the total hydraulic retention time of the post-anoxic zone of the biological treatment system is 2h~3h. 4) The aerobic-anoxic alternation zone (7) of the biological tank system is divided into two compartments. The dissolved oxygen in each compartment is controlled at 1.5±0.5mg / L during aeration. The aeration / non-aeration time range of the first compartment of the aerobic-anoxic alternation zone (7) is from 5min / 9min to 6min / 8min. When the aeration in the first compartment stops, the second compartment starts aeration. The aeration / non-aeration time range is from 2min / 12min to 4min / 10min. 5) Add hydroxylamine to the front end of the first compartment of the aerobic-anoxic alternation zone (7) in the biological treatment tank; The theoretical concentration of hydroxylamine in the aerobic-anoxic alternating zone (7) of the biological treatment tank is set at 5 mg / L, and it is added continuously for 4 hours every day. 6) The system discharges part of the light sludge generated by the cyclone separator (3) as residual sludge every day; the sludge retention time is controlled to be 12 to 14 days.

2. The method for low-carbon ultra-deep nitrogen removal from urban wastewater according to claim 1, characterized in that, The apparatus used in this method includes a biological tank (1), a hydroxylamine solution tank (4), a secondary sedimentation tank (2), and a hydrocyclone separator (3). The biological tank (1) is divided into seven compartments, with flow holes staggered vertically according to the water flow direction to connect each compartment. The first, second, and third compartments are the anaerobic zone (6) of the biological tank, the fourth and fifth compartments are the aerobic-anoxic alternating zone (7) of the biological tank, and the sixth and seventh compartments are the post-anoxic zone (8) of the biological tank. Agitators (11) are installed in each of the seven compartments of the biological tank (1). Aeration heads (14) are installed in two compartments of the aerobic-anoxic alternating zone (7) of the biological tank. The aeration heads (14) are connected in sequence to an air volume regulating valve (15) and a blower (10). Dissolved oxygen probes (16) and online sensors (12) are also installed in two compartments of the aerobic-anoxic alternating zone (7) of the biological tank. The hydroxylamine solution tank... (4) Hydroxylamine enters the first compartment of the aerobic-anoxic alternating zone (7) of the biochemical tank through the peristaltic pump (13). Urban sewage enters the biochemical tank (1) through the inlet valve (17). The effluent from the biochemical tank (1) enters the secondary sedimentation tank (2) for sedimentation. After the sludge and water are separated, the effluent is discharged through the outlet valve (18). The sedimented sludge in the secondary sedimentation tank (2) enters the cyclone separator (3) through the pump (9) for sorting. The heavy sludge in the bottom flow is returned to the first compartment of the anaerobic zone (6) of the biochemical tank through the heavy sludge return valve (21). A portion of the overflow light sludge is returned to the first compartment of the aerobic-anaerobic alternating zone (7) of the biochemical tank through the sludge return valve (20). The remaining light sludge is discharged through the remaining sludge discharge valve (22). The agitator (11), blower (10), online sensor (12), peristaltic pump (13) and pump (9) are all connected to the control cabinet (5).

3. The method for low-carbon ultra-deep nitrogen removal from urban wastewater according to claim 2, characterized in that, The bottom of the secondary sedimentation tank (2) is connected to the inlet of the cyclone separator (3), the bottom of the cyclone separator (3) is connected to the first compartment of the anaerobic zone (6) of the biological treatment tank, and the top of the cyclone separator (3) is connected to the first compartment of the aerobic-anoxic alternating zone (7) of the biological treatment tank and the residual sludge discharge valve (22).

4. The method for low-carbon ultra-deep nitrogen removal from urban wastewater according to claim 2, characterized in that: The bottom of the secondary sedimentation tank (2) is connected in sequence to the secondary sedimentation tank sludge discharge valve (19) and the water pump (9).

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