Method and device for low-carbon ultra-deep denitrification of town sewage

Abstract

The invention provides a low-carbon ultra-deep denitrification method and device for town sewage, belongs to the field of sewage treatment, and is used for town sewage treatment. In a continuous flow anaerobic-aerobic anoxic alternating-post anoxic process, town sewage and refluxed heavy sludge enter an anaerobic zone of a biochemical pool, refluxed light sludge and added hydroxylamine enter an aerobic anoxic alternating zone of the biochemical pool, and a sludge-water mixed solution flowing out of a post anoxic zone of the biochemical pool enters a secondary sedimentation tank for sludge-water separation; and discharging the supernatant as effluent, separating the precipitated sludge into heavy sludge and light sludge in a cyclone separator, refluxing the heavy sludge and part of the light sludge into the process according to the mode, and discharging part of the light sludge as residual sludge. Microorganisms in the sludge store an internal carbon source in an anaerobic zone of the biochemical pool, short-cut nitrification-endogenous denitrification is realized in an aerobic-anoxic alternating zone of the biochemical pool, and ultra-deep endogenous denitrification nitrogen removal is realized in a rear anoxic zone of the biochemical pool. According to the invention, low-carbon ultra-deep nitrogen removal of town sewage can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and in particular, relates to a method and a device for low-carbon ultra-deep denitrification of urban sewage. Background Art

[0002] Excessive nitrogen content in sewage is one of the key factors leading to eutrophication of water bodies. In order to prevent this environmental problem, sewage must be denitrified before being discharged into natural water bodies. Especially for some sensitive water bodies, the standards for sewage discharge are more stringent. For example, the Blue Plains sewage treatment plant operated by DC Water is required to discharge no more than 3.73 mg / L of total nitrogen (TN) into the Potomac River; Florida has set an annual average TN concentration standard of no more than 3 mg / L for Class I and II sewage treatment facilities in some key river basins in the state; in the "Emission Limits of Major Water Pollutants from Urban Sewage Treatment Plants" (DB5301 / T43-2020) issued by Kunming in 2020, the Class A standard stipulates that the TN concentration of urban sewage discharge should be less than 5 mg / L. These regulations show that deep denitrification treatment of urban sewage has become an inevitable trend.

[0003] For urban sewage treatment plants that use traditional denitrification processes, a common practice to achieve deep denitrification is to add denitrification filters. For example, the Blue Plains sewage treatment plant successfully reduced the effluent TN concentration to below 4 mg / L by installing a post-denitrification filter. However, the operation of the denitrification filter not only requires additional carbon source additions, thereby increasing operating costs, but also expands the footprint of the reaction tank, which is a disadvantage for urban areas with limited land resources. In view of the necessity of deep denitrification of urban sewage, as well as the cost and technical challenges brought about by the upgrading of sewage treatment plants, it is particularly important to explore a simple, efficient and economical process upgrade solution, especially in developing countries with limited human and material resources. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for low-carbon ultra-deep denitrification of urban sewage, aiming to solve the problems of low-carbon, low-energy consumption and high-efficiency biological denitrification in existing urban sewage treatment, such as difficulty in treatment, high treatment cost and large area occupied.

[0005] To achieve the above object, the present invention is achieved through the following technical solutions: A method for low-carbon ultra-deep denitrification of urban sewage comprises the following steps: conveying sewage into a biochemical pool, the biochemical pool comprising three anaerobic zones, two aerobic-anoxic alternating zones and two post-anoxic zones; adding activated sludge from an inoculated sewage treatment plant to the anaerobic zone, the aerobic-anoxic alternating zone and the post-anoxic zone of the biochemical pool; pumping hydroxylamine in a hydroxylamine solution tank into the front end of the first compartment of the aerobic-anoxic alternating zone of the biochemical pool; the mud-water mixed liquid flowing out of the post-anoxic zone of the biochemical pool enters a secondary sedimentation tank for sedimentation, and the supernatant is discharged after the mud-water separation is achieved, and the precipitated sludge is sorted into underflow heavy sludge and overflow light sludge by a cyclone separator, and the underflow heavy sludge enters the front end of the first compartment of the anaerobic zone of the biochemical pool; a part of the overflow light sludge enters the front end of the first compartment of the aerobic-anoxic alternating zone of the biochemical pool, and the remaining overflow light sludge is discharged as residual sludge.

[0006] As one of the preferred technical solutions, in the present application, the activated sludge of the sewage treatment plant is inoculated into the anaerobic zone of the biochemical pool, the aerobic-anoxic alternating zone of the biochemical pool and the post-anoxic zone of the biochemical pool, and the double reflux technology is used to make the sludge concentration in the anaerobic zone of the biochemical pool 2200mg / L~2600mg / L, the sludge concentration in the aerobic-anoxic alternating zone of the biochemical pool and the post-anoxic zone of the biochemical pool 3600mg / L~4000mg / L, and the sludge concentration in the aerobic-anoxic alternating zone of the biochemical pool is higher than that in the anaerobic zone of the biochemical pool; the adjustment operation during operation is as follows: 1) The heavy sludge flow rate returned to the anaerobic zone of the biochemical pool is 60%~80% of the influent flow rate; 2) The flow rate of light sludge returned to the aerobic and anoxic alternating zone of the biochemical pool is 150%~170% of the influent flow rate; 3) The total hydraulic retention time of the biochemical pool 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 alternating zone of the biochemical pool is 2h~3h, and the total hydraulic retention time of the post-anoxic zone of the biochemical pool is 2h~3h; 4) The aerobic and anoxic alternating area of ​​the biochemical pool system is divided into two compartments, and the dissolved oxygen in each compartment is controlled at 1.5±0.5mg / L during aeration; 5) Add hydroxylamine to the front end of the first grid of the aerobic-anoxic alternating zone of the biochemical pool; 6) The system discharges part of the light sludge produced by the cyclone separator as residual sludge every day.

[0007] As one of the preferred technical solutions, in the present application, in step 4), the aeration / non-aeration time range of the first compartment in the aerobic-anoxic alternating zone of the biochemical pool is from 5min / 9min to 6min / 8min, and when the aeration of the first compartment stops, the second compartment starts to be aerated, 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 biochemical pool is set to 5mg / L, and it is continuously added for 4h every day; in step 6), the sludge retention time is controlled to 12 to 14 days.

[0008] A method for low-carbon ultra-deep denitrification of urban sewage is provided, which is provided with a biochemical pool, a hydroxylamine solution tank, a secondary sedimentation tank, and a cyclone separator, wherein the biochemical pool is divided into seven cells, and flow holes are arranged in an up-and-down staggered manner according to the direction of water flow to connect the cells, wherein the first cell, the second cell, and the third cell are anaerobic zones of the biochemical pool, the fourth cell and the fifth cell are aerobic and anoxic alternating zones of the biochemical pool, the sixth cell and the seventh cell are post-anoxic zones of the biochemical pool, and a stirrer is arranged in each of the seven cells of the biochemical pool; an aeration head is arranged in two cells of the aerobic and anoxic alternating zones of the biochemical pool, and the aeration head is connected to an air volume regulating valve and a blower in sequence; a dissolved oxygen probe is also arranged in two cells of the aerobic and anoxic alternating zones of the biochemical pool, and a The hydroxylamine in the hydroxylamine solution tank enters the front end of the first cell in the aerobic-anoxic alternating zone of the biochemical pool through a peristaltic pump, the urban sewage enters the biochemical pool through an inlet valve, the effluent from the biochemical pool enters the secondary sedimentation tank for sedimentation, and the final effluent is discharged through an outlet valve after the mud and water are separated; the precipitated sludge in the secondary sedimentation tank enters the cyclone separator for sorting through a pump, the heavy sludge in the bottom flow is returned to the first cell in the anaerobic zone of the biochemical pool through a heavy sludge return valve, a part of the overflow light sludge is returned to the first cell in the aerobic-anaerobic alternating zone of the biochemical pool through a sludge return valve, and the remaining light sludge is discharged through a residual sludge discharge valve; the agitator, the blower, the online sensor, the peristaltic pump and the pump are all connected to the control cabinet.

[0009] A device for low-carbon ultra-deep denitrification of urban sewage comprises a biochemical tank, a secondary sedimentation tank and a cyclone separator which are connected in sequence. The biochemical tank comprises three anaerobic zones of the biochemical tank, two aerobic-anoxic alternating zones of the biochemical tank and two post-anoxic zones of the biochemical tank. The first zone of the aerobic-anoxic alternating zones of the two biochemical tanks is connected to a hydroxylamine solution tank. The bottom of the secondary sedimentation tank is connected to an inlet of a cyclone separator. The bottom of the cyclone separator is connected to the first zone of the anaerobic zone of the biochemical tank. The top of the cyclone separator is connected to the first zone of the aerobic-anoxic alternating zone of the biochemical tank and a residual sludge discharge valve.

[0010] As one of the preferred technical solutions, in the present application, the biochemical pool is divided into 7 compartments, and flow holes are staggered up and down according to the water flow direction to connect the compartments, and the outlet hole of the last compartment is in the middle position; the first compartment, the second compartment, and the third compartment are the anaerobic zone of the biochemical pool, the fourth compartment and the fifth compartment are the aerobic and anoxic alternating zone of the biochemical pool, and the sixth compartment and the seventh compartment are the post-anaerobic zone of the biochemical pool.

[0011] As one of the preferred technical solutions, in the present application, the aerobic and anoxic alternating zones of the two biochemical pools are provided with dissolved oxygen probes and online sensors to display the dissolved oxygen concentration in real time, and the online sensors are connected to the control cabinet.

[0012] As one of the preferred technical solutions, in the present application, the first cell in the aerobic-anoxic alternating zone of the biochemical pool is connected to the hydroxylamine solution tank via a peristaltic pump, and the peristaltic pump is connected to the control cabinet.

[0013] As one of the preferred technical solutions, in the present application, an aeration head is provided in the aerobic-anoxic alternating zone of the biochemical pool, and the aeration head is connected to the air volume regulating valve and the blower in sequence, and the blower is connected to the control cabinet.

[0014] As one of the preferred technical solutions, in the present application, a stirrer is provided inside each of the seven cells of the biochemical pool, and the stirrer is connected to a control cabinet; the bottom of the secondary sedimentation tank is connected to the secondary sedimentation tank sludge discharge valve and a water pump in sequence, and the water pump is connected to the control cabinet.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention aims at the problem that urban sewage is difficult to achieve low-carbon, low-energy consumption, high-efficiency and ultra-deep biological denitrification. By setting a sludge cyclone separator, double sludge return is achieved. The heavy sludge is returned to the first cell of the anaerobic zone, and the light sludge is partially returned to the first cell of the aerobic-anoxic alternating zone, so that the aerobic-anoxic alternating zone has a higher sludge concentration than the anaerobic zone, providing sufficient internal carbon source for endogenous denitrification and promoting endogenous denitrification; the remaining sludge only discharges light sludge, improves the sludge sedimentation of the system, and avoids sludge swelling; hydroxylamine is added to the first cell of the aerobic-anoxic alternating zone, and the system The ability to inhibit nitrite oxidizing bacteria (NOB) is higher than that of ammonia oxidizing bacteria (AOB), and short-range nitrification can be achieved quickly. Intermittent aeration is used to form alternating aerobic and anoxic conditions. A small amount of nitrite is generated during aerobic conditions and then consumed by anoxic denitrification, reducing the possibility of NOB growth and avoiding the occurrence of high concentrations of nitrite that inhibit sludge activity. In addition, intermittent aeration can also reduce the aerobic oxidation of internal carbon sources, allowing more carbon sources to be used for post-denitrification and 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.

[0016] 2. Compared with traditional A 2 Compared with O process, this process has the following advantages: 1) By adding hydroxylamine inhibitor, the system mainly inhibits the growth of NOB, achieves short-range nitrification and reduces aeration volume.

[0017] 2) The alternation of aerobic and anoxic conditions is adopted to reduce the aerobic oxidation of internal carbon sources, strengthen the post-anaerobic endogenous denitrification, and achieve ultra-deep nitrogen removal.

[0018] 3) Use sludge cyclone separator to achieve double sludge return, increase the carbon source in the sludge in the aerobic and anoxic alternating zone, discharge light sludge as residual sludge to improve sludge settling properties and avoid system sludge expansion.

[0019] 4) In this process, more carbon sources in the sludge are used for denitrification, which reduces the sludge output of the system.

[0020] 5) This process realizes short-range nitrification, endogenous denitrification and ultra-deep nitrogen removal, with low sewage treatment costs. At the same time, there is no need to add denitrification filters, etc., and the system occupies a small area. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the device in the present invention.

[0022] In the figure: 1. Biochemical tank; 2. Secondary sedimentation tank; 3. Cyclone separator; 4. Hydroxylamine solution tank; 5. Control cabinet; 6. Anaerobic zone of biochemical tank; 7. Aerobic-anoxic alternating zone of biochemical tank; 8. Post-anoxic zone of biochemical tank; 9. Suction 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. Secondary sedimentation tank sludge discharge valve; 20. Light sludge return valve; 21. Heavy sludge return valve; 22. Residual sludge discharge valve. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] According to the method of the present invention, low-carbon urban sewage and heavy sludge at the lower end of the return cyclone separator 3 enter the front end of the first compartment of the anaerobic zone 6 of the biochemical pool, and the microorganisms in the sludge first decompose the protein into amino acids and polypeptides, and then convert them into internal carbon sources for storage. The mud-water mixture flowing out of the anaerobic zone 6 of the biochemical pool and a part of the light sludge at the upper end of the return cyclone separator enter the front end of the first compartment of the aerobic-anoxic alternating zone 7 of the biochemical pool, and short-range nitrification-endogenous denitrification is achieved by adding hydroxylamine and intermittent aeration. The mud-water mixture then enters the post-anoxic zone 8 of the biochemical pool for ultra-deep denitrification. The muddy and water mixture flowing out of the post-anoxic zone 8 of the biochemical tank enters the secondary sedimentation tank 2 for sedimentation, and the supernatant is discharged after the mud and water are separated. The precipitated sludge enters the cyclone separator 3 for sorting, and the heavy bottom flow sludge enters the first grid of the anaerobic zone 6 of the biochemical tank to supplement the activated sludge in the anaerobic zone 6 of the biochemical tank; a part of the light overflow sludge enters the first grid of the aerobic and anoxic alternating zone 7 of the biochemical tank to increase the sludge concentration in the aerobic and anoxic alternating zone 7 of the biochemical tank and provide more protein and other activated sludge extracellular polymers as available carbon sources, which promotes endogenous denitrification, and the remaining light sludge is discharged as residual sludge. The present invention can realize low-carbon ultra-deep denitrification of urban sewage.

[0025] Example 1

[0026] like Figure 1 As shown, a device for low-carbon ultra-deep denitrification of urban sewage comprises a biochemical tank 1, a secondary sedimentation tank 2, a cyclone separator 3, a hydroxylamine solution tank 4, and a control cabinet 5. The biochemical tank 1, the secondary sedimentation tank 2, and the cyclone separator 3 are connected in sequence; the biochemical tank 1 is connected to a water inlet valve 17; the biochemical tank 1 is divided into three areas and provided with seven cells, the first cell, the second cell and the third cell are the anaerobic zone 6 of the biochemical tank, the fourth cell and the fifth cell are the aerobic and anoxic alternating zone 7 of the biochemical tank, and the sixth cell and the seventh cell are the post-anoxic zone 8 of the biochemical tank; flow holes are arranged in an up-and-down staggered manner according to the direction of water flow to connect the seven cells; the seven cells are all provided with a stirrer 11; each cell in the aerobic and anoxic alternating zone 7 of the biochemical tank is provided with an aeration head 14, and the aeration head 14 is connected to an air volume regulating valve 15 and a blower 10 in sequence, and the aerobic and anoxic alternating zone 7 of the biochemical tank is connected to the aerobic and anoxic alternating zone 7 of the biochemical tank. The alternating zone 7 is also provided with a dissolved oxygen probe 16 and an online sensor 12; the hydroxylamine solution tank 4 is connected to the first cell of the aerobic-anoxic alternating zone 7 of the biochemical tank through a peristaltic pump 13; the biochemical tank 1 is connected to the secondary sedimentation tank 2, and the secondary sedimentation tank 2 is connected to the outlet valve 18 for discharging the final effluent; the cyclone separator 3 is connected to the secondary sedimentation tank 2 through a pumping pump 9 and a sludge discharge valve 19 of the secondary sedimentation tank, the cyclone separator 3 is connected to the first cell of the anaerobic zone 6 of the biochemical tank through a heavy sludge return valve 21, and the cyclone separator 3 is connected to the first cell of the aerobic-anoxic alternating zone 7 of the biochemical tank through a light sludge return valve 20; the cyclone separator 3 is also connected to a residual sludge discharge valve 22 for discharging residual sludge; the agitator 11, the blower 10, the online sensor 12, the peristaltic pump 13 and the pumping pump 9 are all automatically controlled by the control cabinet 5.

[0027] Working method: Sewage is input into the biochemical pool 1, and the activated sludge of the inoculated sewage treatment plant is added to the biochemical pool anaerobic zone 6, the biochemical pool aerobic anoxic alternating zone 7 and the biochemical pool post-anoxic zone 8 of the biochemical pool 1; the hydroxylamine in the hydroxylamine solution tank 4 is input into the first grid of the biochemical pool aerobic anoxic alternating zone 7 through the peristaltic pump 13; the mud and water mixed liquid flowing out of the biochemical pool post-anoxic zone 8 of the biochemical pool 1 enters the secondary sedimentation tank 2 for sedimentation, and the supernatant after the mud and water separation is realized passes through the outlet valve 18 Discharge: The precipitated sludge in the secondary sedimentation tank 2 enters the cyclone separator 3 through the secondary sedimentation tank sludge discharge valve 19 and the water pump 9. The cyclone separator 3 separates the sludge into underflow heavy sludge and overflow light sludge. The underflow heavy sludge is returned to the anaerobic zone 6 of the biochemical tank 1 through the heavy sludge return valve 21; part of the overflow light sludge is returned to the aerobic and anoxic alternating zone 7 of the biochemical tank 1 through the light sludge return valve 20; the remaining overflow light sludge is discharged through the residual sludge discharge valve 22.

[0028] Example 2

[0029] A method for low-carbon ultra-deep denitrification of urban sewage, comprising a biochemical pool 1, a secondary sedimentation tank 2, a cyclone separator 3, a hydroxylamine solution tank 4, and a control cabinet 5 in the device for low-carbon ultra-denitrification of urban sewage described in Example 1, wherein the biochemical pool 1, the secondary sedimentation tank 2, and the cyclone separator 3 are connected in sequence; the biochemical pool 1 is connected to a water inlet valve 17; the biochemical pool 1 is divided into three areas and provided with seven cells, wherein the first cell, the second cell, and the third cell are an anaerobic zone 6 of the biochemical pool, the fourth cell and the fifth cell are an aerobic-anoxic alternating zone 7 of the biochemical pool, and the sixth cell and the seventh cell are a post-anoxic zone 8 of the biochemical pool; flow holes are arranged in an up-and-down staggered manner according to the direction of water flow to connect the seven cells; all seven cells are provided with a stirrer 11; each cell of the aerobic-anoxic alternating zone 7 of the biochemical pool is provided with an aeration head 14, and the aeration head 14 is connected to an air volume regulating valve 15 and a blower 10 in sequence, and the aerobic-anoxic alternating zone 7 A dissolved oxygen probe 16 and an online sensor 12 are also provided; the hydroxylamine solution tank 4 is connected to the first cell of the aerobic-anoxic alternating zone 7 through a peristaltic pump 13; the biochemical tank 1 is connected to the secondary sedimentation tank 2, and the secondary sedimentation tank 2 is connected to a drain valve 18 for discharging final effluent; the precipitated sludge in the secondary sedimentation tank 2 enters the cyclone separator 3 through the secondary sedimentation tank sludge discharge valve 19 and the water pump 9, and the cyclone separator 3 sorts the sludge into underflow heavy sludge and overflow light sludge, and the underflow heavy sludge is returned to the first cell of the biochemical tank anaerobic zone 6 of the biochemical tank 1 through the heavy sludge return valve 21; part of the overflow light sludge is returned to the first cell of the biochemical tank aerobic-anoxic alternating zone 7 of the biochemical 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, the blower 10, the online sensor 12, the peristaltic pump 13 and the water pump 9 are all automatically controlled by the control cabinet 5.

[0030] The test uses the effluent from the grit chamber of Changliu Sewage Treatment Plant as the influent. The specific water quality is as follows: the influent ammonia nitrogen is 13.62mg / L~26.93mg / L, the influent TN is 13.96mg / L~27.27mg / L, the influent COD is 52.65mg / L~130.84mg / L, and the average C / N is 3.12. The test system is as follows: Figure 1 As shown, the total reaction volume of the reactor is 22.4m 3 , divided into 7 compartments, of which the total volume of the anaerobic zone of the biochemical pool is 9.9m 3 The total volume of the aerobic and anoxic alternating zones in the biochemical pool is 6.4m 3 The total volume of the post-anoxia zone is 6.1m 3 , the volume of the secondary sedimentation tank is 4m 3 .

[0031] (1) Start the system: inoculate the activated sludge of the sewage treatment plant into the anaerobic zone, aerobic-anoxic alternating zone and post-anoxic zone of the biochemical tank and use double recirculation technology to make the sludge concentration in the anaerobic zone of the biochemical tank 2500 mg / L, and the sludge concentration in the aerobic-anoxic alternating zone and post-anoxic zone of the biochemical tank 4000 mg / L; (2) The adjustment operations during operation are as follows: 1) The heavy sludge flow rate returned to the anaerobic zone 6 of the biochemical pool is 70% of the influent flow rate; 2) The flow rate of light sludge returned to the aerobic-anoxic alternating zone 7 of the biochemical pool is 160% of the influent flow rate; 3) The total HRT (total hydraulic retention time) of the biochemical pool system is 8.91h, of which the HRT of the anaerobic zone 6 of the biochemical pool is 3.81h, the HRT of the aerobic-anoxic alternating zone 7 of the biochemical pool is 2.55h, and the HRT of the post-anoxic zone 8 of the biochemical pool is 2.55h; 4) The aerobic and anoxic alternating zone 7 of the biochemical pool 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 of the first compartment stops, the second compartment starts aeration. The aeration / non-aeration time ranges from 2min / 12min to 4min / 10min. The total aeration time is 0.64h, and the non-aeration time is 1.91h. When the aeration of the aerobic and anoxic alternating zone is controlled, DO (dissolved oxygen) is controlled at 1.5±0.5mg / L; 5) Add hydroxylamine to the front end of the first cell in the aerobic-anoxic alternating zone 7 of the biochemical pool, set the theoretical concentration of hydroxylamine in the aerobic-anoxic alternating zone 7 of the biochemical pool to 5 mg / L, and add it continuously for 4 hours every day; 6) The system discharges part of the light sludge produced by cyclone separator 3 as residual sludge every day, and controls the SRT (sludge retention time) to 12 days.

[0032] The test results show that after stable operation, the average effluent ammonia nitrogen of the system is 0.02 mg / L, the average effluent TN is 0.59 mg / L, and the average effluent COD is 16.53 mg / L.

[0033] In addition, the activated sludge of the sewage treatment plant is inoculated into the anaerobic zone 6 of the biochemical tank, the aerobic-anoxic alternating zone 7 of the biochemical tank and the post-anoxic zone 8 of the biochemical tank, and the double reflux technology is used, so that the sludge concentration of the anaerobic zone 6 of the biochemical tank is 2200mg / L~2600mg / L, the sludge concentration of the aerobic-anoxic alternating zone 7 of the biochemical tank and the post-anoxic zone 8 of the biochemical tank is 3600mg / L~4000mg / L, and the sludge concentration of the aerobic-anoxic alternating zone 7 of the biochemical tank is higher than that of the anaerobic zone 6 of the biochemical tank; 1) The heavy sludge flow rate returned to the anaerobic zone 6 of the biochemical pool is 60%~80% of the influent flow rate; 2) The flow rate of light sludge returned to the aerobic-anoxic alternating zone 7 of the biochemical pool is 150%~170% of the influent flow rate; 3) The total HRT of the biochemical pool system is 7h~10h, of which the HRT of the anaerobic zone of the biochemical pool is 3h~4h, the HRT of the aerobic-anoxic alternating zone 7 of the biochemical pool is 2h~3h, and the HRT of the post-anoxic zone 8 of the biochemical pool is 2h~3h; 4) The aerobic-anoxic alternating zone 7 of the biochemical pool 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 of the first compartment stops, the second compartment starts to be aerated. The aeration / non-aeration time range is from 2min / 12min to 4min / 10min. The DO of the aerobic-anoxic alternating zone 7 of the biochemical pool is controlled at 1.5±0.5mg / L during aeration. 5) Add hydroxylamine to the front end of the first grid of the aerobic-anoxic alternating zone 7 of the biochemical pool, set the theoretical concentration of hydroxylamine in the aerobic-anoxic alternating zone 7 of the biochemical pool to 5 mg / L, and add it continuously for 4 hours every day; 6) The system discharges part of the light sludge produced by the cyclone separator 3 as residual sludge every day, and controls the SRT to 12 to 14 days.

[0034] By adjusting the process within the above range, the purpose of the present invention can be achieved.

[0035] Comparative study example In the wastewater treated in the embodiment, without cyclone separator 3, double sludge return, hydroxylamine addition, intermittent aeration, long anaerobic time and post-anoxic to promote intracellular carbon source storage and strengthen endogenous denitrification, ammonia nitrogen, TN and COD in the treated water will increase significantly. 2 For process O, under the same influent and environmental conditions, the average TN concentration of the effluent is 5.91 mg / L, which is much higher than the TN concentration of the effluent of this process (0.59 mg / L).

[0036] Finally, although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of 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 implementation methods that can be understood by those skilled in the art.

Claims

1. A method for low-carbon ultra-deep denitrification of urban sewage, characterized in that: The following steps are involved: The sewage is transported into a biochemical pool (1), wherein the biochemical pool (1) comprises three biochemical pool anaerobic zones (6), two biochemical pool aerobic anoxic alternating zones (7) and two biochemical pool post-anoxic zones (8); activated sludge from a sewage treatment plant is added to the biochemical pool anaerobic zone (6), the biochemical pool aerobic anoxic alternating zone (7) and the biochemical pool post-anoxic zone (8); and at the same time, hydroxylamine in a hydroxylamine solution tank (4) is pumped into the front end of the first cell of the biochemical pool aerobic anoxic alternating zone (7); The sludge-water mixture flowing out from the post-anoxic zone (8) of the biochemical tank enters the secondary sedimentation tank (2) for sedimentation, and the supernatant is discharged after the sludge-water separation is achieved. The precipitated sludge is sorted into underflow heavy sludge and overflow light sludge by the cyclone separator (3). The underflow heavy sludge enters the front end of the first compartment of the anaerobic zone (6) of the biochemical tank; a part of the overflow light sludge enters the front end of the first compartment of the aerobic-anoxic alternating zone (7) of the biochemical tank, and the remaining overflow light sludge is discharged as residual sludge.

2. A method for low-carbon ultra-deep denitrification of urban sewage according to claim 1, characterized in that: The activated sludge of the sewage treatment plant is inoculated into the anaerobic zone (6), the aerobic-anoxic alternating zone (7) and the post-anoxic zone (8) of the biochemical pool (1) and the double recirculation technology is used to make the sludge concentration in the anaerobic zone (6) of the biochemical pool 2200mg / L~2600mg / L, the sludge concentration in the aerobic-anoxic alternating zone (7) of the biochemical pool and the post-anoxic zone (8) of the biochemical pool 3600mg / L~4000mg / L, and the sludge concentration in the aerobic-anoxic alternating zone (7) of the biochemical pool higher than that in the anaerobic zone (6) of the biochemical pool. The adjustment operation during operation is as follows: 1) The heavy sludge flow rate returned to the anaerobic zone (6) of the biochemical pool is 60% to 80% of the influent flow rate; 2) The flow rate of light sludge returned to the aerobic-anoxic alternating zone (7) of the biochemical pool is 150%~170% of the influent flow rate; 3) The total hydraulic retention time of the biochemical pool 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 alternating zone (7) of the biochemical pool is 2h~3h, and the total hydraulic retention time of the post-anoxic zone of the biochemical pool is 2h~3h; 4) The aerobic and anoxic alternating zone (7) of the biochemical pool system is divided into two compartments, and the dissolved oxygen in each compartment is controlled at 1.5±0.5mg / L during aeration; 5) Add hydroxylamine to the front end of the first compartment of the aerobic-anoxic alternating zone (7) of the biochemical pool; 6) The system discharges part of the light sludge produced by the cyclone separator (3) as residual sludge every day.

3. A method for low-carbon ultra-deep denitrification of urban sewage according to claim 2, characterized in that: In step 4), the aeration / non-aeration time range of the first compartment of the aerobic-anoxic alternating zone (7) of the biochemical pool is from 5min / 9min to 6min / 8min. When the aeration of the first compartment stops, the second compartment starts to be aerated, 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 (7) of the biochemical pool is set to 5mg / L, and it is continuously added for 4h every day. In step 6), the sludge retention time is controlled to be 12 to 14 days.

4. A method for low-carbon ultra-deep denitrification of urban sewage, characterized in that: A biochemical pool (1), a hydroxylamine solution tank (4), a secondary sedimentation tank (2), and a cyclone separator (3) are provided, wherein the biochemical pool (1) is divided into seven cells, and flow holes are arranged in an up-and-down staggered manner according to the direction of water flow to connect the cells, wherein the first cell, the second cell, and the third cell are the anaerobic zone (6) of the biochemical pool, the fourth cell and the fifth cell are the aerobic-anoxic alternating zone (7) of the biochemical pool, and the sixth cell and the seventh cell are the post-anoxic zone (8) of the biochemical pool. A stirrer (11) is provided in each of the seven cells of the biochemical pool (1); an aeration head (14) is provided in two cells of the aerobic-anoxic alternating zone (7) of the biochemical pool, and the aeration head (14) is connected to an air volume regulating valve (15) and a blower in sequence; a dissolved oxygen probe (16) and an online sensor (12) are also provided in the two cells of the aerobic-anoxic alternating zone (7) of the biochemical pool, and the hydroxylamine solution tank (4) is provided with a hydroxylamine solution. Amine enters the front end of the first compartment in the aerobic-anoxic alternating zone (7) of the biochemical pool through a peristaltic pump (13), and urban sewage enters the biochemical pool (1) through an inlet valve (17). The effluent of the biochemical pool (1) enters the secondary sedimentation tank (2) for sedimentation. After the mud and water are separated, the final effluent is discharged through an outlet valve (18); the precipitated sludge in the secondary sedimentation tank (2) enters the cyclone separator (3) for sorting through a pumping pump (9), the heavy sludge in the bottom flow is returned to the first compartment in the anaerobic zone (6) of the biochemical pool through a heavy sludge return valve (21), a part of the overflow light sludge is returned to the first compartment of the aerobic-anaerobic alternating zone (7) of the biochemical pool through a sludge return valve (20), and the remaining light sludge is discharged through a remaining sludge discharge valve (22); the agitator (11), the blower (10), the online sensor (12), the peristaltic pump (13) and the pumping pump (9) are all connected to the control cabinet (5).

5. A device for low-carbon ultra-deep denitrification of urban sewage, characterized in that: The invention comprises a biochemical pool (1), a secondary sedimentation tank (2) and a cyclone separator (3) which are connected in sequence. The biochemical pool (1) comprises three anaerobic zones (6) of the biochemical pool, two aerobic and anoxic alternating zones (7) of the biochemical pool and two post-anoxic zones (8) of the biochemical pool. The first zone of the two aerobic and anoxic alternating zones (7) of the biochemical pool is connected to a hydroxylamine solution tank (4). The bottom of the secondary sedimentation tank (2) is connected to an inlet of the cyclone separator (3). The bottom of the cyclone separator (3) is connected to the first zone of the anaerobic zone (6) of the biochemical pool. The top of the cyclone separator (3) is connected to the first zone of the aerobic and anoxic alternating zones (7) of the biochemical pool and a residual sludge discharge valve (22).

6. A device for low-carbon ultra-deep denitrification of urban sewage according to claim 5, characterized in that: The biochemical pool (1) is divided into 7 cells, and flow holes are arranged in an up-and-down staggered manner according to the direction of water flow to connect the cells, and the water outlet hole of the last cell is in the middle position; the first cell, the second cell, and the third cell are the anaerobic zone (6) of the biochemical pool, the fourth cell and the fifth cell are the aerobic-anoxic alternating zone (7) of the biochemical pool, and the sixth cell and the seventh cell are the post-anoxic zone (8) of the biochemical pool.

7. The device for low-carbon ultra-deep denitrification of urban sewage according to claim 5, characterized in that: The aerobic and anoxic alternating zones (7) of the two biochemical pools are provided with a dissolved oxygen probe (16) and an online sensor (12) for real-time display of dissolved oxygen concentration, and the online sensor (12) is connected to the control cabinet (5).

8. The device for low-carbon ultra-deep denitrification of urban sewage according to claim 5, characterized in that: The first cell in the aerobic-anoxic alternating zone (7) of the biochemical pool is connected to the hydroxylamine solution tank (4) via a peristaltic pump (13), and the peristaltic pump (13) is connected to the control cabinet (5).

9. The device for low-carbon ultra-deep denitrification of urban sewage according to claim 5, characterized in that: The aerobic-anoxic alternating zone (7) of the biochemical pool is provided with an aeration head (14), the aeration head (14) is connected to the air volume regulating valve (15) and the blower (10) in sequence, and the blower (10) is connected to the control cabinet (5).

10. The device for low-carbon ultra-deep denitrification of urban sewage according to claim 5, characterized in that: Each of the seven cells of the biochemical pool (1) is provided with an agitator (11), which is connected to a control cabinet (5); the bottom of the secondary sedimentation tank (2) is connected to a secondary sedimentation tank sludge discharge valve (19) and a water pump (9) in sequence, and the water pump (9) is connected to the control cabinet (5).

Images