A system and method for enhancing efficient coupling denitrification of internal and external carbon sources

Abstract

The present invention relates to a system and method for enhancing the efficient coupling of denitrification with internal and external carbon sources, and belongs to the technical field of sewage treatment. The present invention mainly improves the existing five-stage Batum process to obtain an efficient coupling denitrification reactor with internal and external carbon sources, and specially sets up a side stream endogenous denitrification and functional bacteria acclimation and enrichment device, so that it cooperates with the efficient coupling denitrification reactor with internal and external carbon sources. It can effectively solve the problems of part of the carbon source being wasted in the aerobic tank in the AOA process, the low denitrification efficiency of pure endogenous denitrification, and the unstable effect of endogenous denitrification. It enables the efficient coupling of the two denitrification methods of traditional exogenous denitrification and endogenous denitrification, while obtaining high-quality effluent and relatively reducing the amount of commercial carbon source added, so that the denitrification efficiency and effluent stability are greatly improved compared with the pure endogenous denitrification form.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage denitrification and denitrification, and in particular to a system and method for enhancing internal-external carbon source denitrification and efficient coupled denitrification. Background Art

[0002] In the context of synergistic efficiency improvement of pollution reduction and carbon reduction, higher requirements are placed on carbon emission reduction, carbon neutrality and nitrogen pollutant control in sewage treatment plants. Traditional biological denitrification technology faces severe challenges in indirect carbon emissions and meeting emission standards. Therefore, the development of efficient deep biological denitrification technology is imminent.

[0003] In traditional AAO biological denitrification technology, achieving a higher denitrification rate often depends on a larger internal recirculation ratio and a higher carbon-nitrogen ratio. This mode of operation not only results in high recirculation power consumption and waste of commercial carbon sources, but also has a limited denitrification rate and cannot achieve the goal of deep denitrification. Endogenous denitrification is a technology that uses functional bacteria to store the carbon source in the influent as an internal carbon source within the cell under anaerobic conditions, and decomposes the intracellular carbon source under anoxic conditions to reduce nitrate / nitrite to nitrogen gas. This technology is relatively reproducible and has the advantages of significantly reducing the internal recirculation ratio, reducing the amount of commercial carbon source added, and achieving deep denitrification. It has gradually become a research hotspot in recent years. In existing research results, endogenous denitrification is mainly achieved through the AOA process, which is composed of anaerobic tanks, aerobic tanks and anoxic tanks connected in sequence. The anaerobic tank mainly completes the storage of internal carbon sources, the aerobic tank mainly completes the nitrification reaction, and the anoxic tank undergoes denitrification mainly based on internal carbon sources. Since the main denitrification method of this process is endogenous denitrification, the use of external carbon sources and reflux power consumption are greatly reduced.

[0004] However, after extensive research and analysis by the inventors, the following problems still exist in the endogenous denitrification technology in the form of the AOA process: (1) When the glycogen-accumulating bacteria store the internal carbon source, they mainly utilize the soluble and easily degradable COD in the influent, and this part of COD only accounts for 30%-40% of the total COD in the influent. The remaining COD directly enters the subsequent aerobic tank, resulting in a waste of part of the COD in the influent. (2) The rate of endogenous denitrification is lower than that of traditional exogenous denitrification. (3) Since the degree and stability of endogenous denitrification are easily affected by many factors such as influent water temperature, influent COD concentration, pH, etc., when the influent conditions are unfavorable, the endogenous denitrification effect is unstable. In order to ensure that the TN of the effluent is stable and meets the standard, a large amount of external commercial carbon source still needs to be added to the anoxic tank. However, the endogenous denitrification in the AOA process is prone to cause the effluent COD to exceed the standard because the anoxic section is the last section of the biochemical tank. (4) The aerobic tank capacity of the endogenous denitrification in this process is usually small. In order to avoid excessive ammonia nitrogen in winter, a higher proportion of fillers needs to be added to the aerobic tank, which not only increases the aeration power consumption, but also brings many risks to production. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a system and method for enhancing the efficient coupled denitrification of internal and external carbon sources. The system and method, by providing a side stream endogenous denitrification and functional bacteria acclimation and enrichment device, and redesigning the volume ratio of each tank of the existing five-stage Batum process, can effectively solve the problems of part of the carbon source being wasted in the aerobic tank in the AOA process, low denitrification efficiency of the sewage treatment system based on pure endogenous denitrification, unstable endogenous denitrification, and short aerobic nitrification time.

[0007] (2) Technical solution

[0008] In a first aspect, the present invention provides a system for enhancing the efficient coupling of denitrification by internal and external carbon sources, comprising: an inlet pool (1), an internal and external carbon source efficient coupling denitrification reactor (2), and a secondary sedimentation tank (3) connected in sequence along the flow direction of sewage;

[0009] The internal-external carbon source high-efficiency coupled denitrification reactor (2) is provided with an anaerobic zone (2-1), a first anoxic zone, a first aerobic zone (2-4), a second anoxic zone (2-5) and a second aerobic zone (2-6) in sequence along the water flow direction; the first anoxic zone is composed of anoxic zone A (2-2) and anoxic zone B (2-3); the anaerobic zone (2-1) provides a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of particulate ... The denitrification reaction zone of the carbon source is provided; the anoxic zone B (2-3) provides a reaction zone for the denitrification of the intracellular carbon source; the first aerobic zone (2-4) provides a reaction zone for the nitrification reaction; the second anoxic zone (2-5) provides a reaction zone for the denitrification of the intracellular carbon source; the second aerobic zone (2-6) provides a reaction zone for the stripping of dissolved nitrogen in the water and the nitrification reaction; the end of the first aerobic zone (2-4) returns the nitrified liquid to the front end of the anoxic zone A (2-2) through a submersible sewage pump; the concentrated sludge at the bottom of the secondary sedimentation tank (3) returns to the front end of the anaerobic zone (2-1);

[0010] Among them, the volume ratio of the anaerobic zone (2-1), the first anoxic zone, the first aerobic zone (2-4), the second anoxic zone (2-5) and the second aerobic zone (2-6) is (1±5%):2(1±5%):3(1±5%):1(1±5%):0.5(1±5%); in the first anoxic zone, the volume ratio of the anoxic zone A (2-2) and the anoxic zone B (2-3) is 0.85-1.15:0.85-1.15;

[0011] The system further comprises: a side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), which utilizes part of the sewage from the inlet pool (1) to acclimate and enrich denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria, and continuously supplies the generated muddy water mixture rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2).

[0012] The volume ratio of the anoxic zone A (2-2) to the anoxic zone B (2-3) is preferably 0.9-1.1:0.9-1.1, more preferably 1:1. The present invention divides the first anoxic zone into two zones, the anoxic zone A located upstream of the water flow, wherein the anoxic zone A mainly focuses on denitrification of extracellular carbon sources, while the anoxic zone B mainly focuses on denitrification of intracellular carbon sources. When the extracellular carbon source in the anoxic zone A is insufficient, a commercial carbon source can be supplemented, while the anoxic zone B supplements the intracellular carbon source and endogenous denitrifying functional bacteria through the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5). If the anoxic zone B is too small, the endogenous denitrification ratio will be low due to the slow endogenous denitrification; if the anoxic zone A is too small, the ratio of external carbon source denitrification will be compressed, and residual carbon source (original sewage COD) will be easily generated in the anoxic zone A, and there will be more COD remaining in the anoxic zone B, which will affect the endogenous denitrification. Therefore, it is preferred to make the volumes of the anoxic zones A and B equivalent.

[0013] The internal-external carbon source efficient coupling denitrification reactor (2) of the present invention is obtained by redesigning the volume ratio of each zone in the original five-stage Batum process, thereby achieving the purpose of strengthening the internal-external carbon source efficient coupling denitrification. Preferably, the front end of the anaerobic zone (2-1) is provided with online instruments such as (mainly used to measure the redox potential value and temperature of the solution) and an MLSS meter (online measurement of sludge concentration). In the first anoxic zone, the anoxic zone A (2-2) mainly undergoes traditional extracellular carbon source denitrification, thereby avoiding the waste of part of the carbon source in the aerobic tank in the AOA process; and in the first anoxic zone, the anoxic zone B (2-3) mainly undergoes intracellular carbon source denitrification. Preferably, the front end of the anoxic zone A (2-2) is provided with an ORP online meter; and the end of the anoxic zone B (2-3) is provided with a nitrate nitrogen concentration sensor and an MLSS online meter. Preferably, the first aerobic zone (2-4) mainly undergoes nitrification reaction, and at least one DO (dissolved oxygen) online meter is provided at the front end, middle end, and end end of the zone to control the aeration volume at different points.

[0014] According to a preferred embodiment of the present invention, the water inlet pool (1) stores low-carbon source domestic sewage; the water inlet pool (1) is connected to the internal-external carbon source high-efficiency coupled denitrification reactor (2) through a first pipe-valve assembly (1-2), and is connected to the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) through a second pipe-valve assembly (1-3), and the sewage flow rate of the second pipe-valve assembly (1-3) is 8-12% of the total water output of the water inlet pool (1); preferably 10%. Therefore, the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) also undertakes the task of partial sewage endogenous denitrification and nitrogen removal.

[0015] According to a preferred embodiment of the present invention, the anaerobic zone (2-1), the first anoxic zone and the second anoxic zone (2-5) are all provided with a mixing and stirring device (2-7); aeration heads are distributed at the bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6); the aeration heads at the bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6) are both connected to an aeration pipe (2-9), one end of the aeration pipe (2-9) is connected to an aeration pump (2-8), and the aeration heads are immersed in the bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6).

[0016] According to a preferred embodiment of the present invention, the aeration heads in the first aerobic zone (2-4) are unevenly distributed, specifically: the aeration head arrangement density in the front 1 / 3 section and the rear 1 / 6 section of the first aerobic zone (2-4) is half the aeration head arrangement density in the middle 1 / 2 section of the first aerobic zone (2-4).

[0017] According to a preferred embodiment of the present invention, the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) includes an SBR reactor, the SBR reactor having a reactor body (5-0) and a water outlet / mud outlet (5-5); the reactor body (5-0) receives part of the sewage from the water inlet pool (1); the volume of the reactor body (5-0) is 5%-10% of the internal-external carbon source high-efficiency coupled denitrification reactor (2); the water outlet / mud outlet (5-5) is connected to the reactor body (5-10) by a condenser. The mud discharge valve (5-7) adds the mud-water mixture rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria to the front end of the anoxic zone B (2-3) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), thereby supplying endogenous carbon to the anoxic zone B; the water outlet / mud outlet (5-5) discharges the supernatant after endogenous denitrification and precipitation in the reactor body (5-0) to the front end of the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2) through the drain valve (5-6).

[0018] The reactor body (5-0) is the functional area for the production and domestication of denitrifying saccharin-accumulating bacteria and denitrifying phosphate-accumulating bacteria. The main function of the water / mud outlet (5-5) is to replenish the mud-water mixture rich in denitrifying saccharin-accumulating bacteria and denitrifying phosphate-accumulating bacteria into the internal-external carbon source efficient coupling denitrification reactor (2). The SBR reactor is a sequencing batch reactor, which includes the following six processes: water inlet → anaerobic stirring → aerobic aeration → anoxic stirring → sedimentation → drainage.

[0019] According to a preferred embodiment of the present invention, the system further comprises a carbon source supply pool (6), the carbon source supply pool (6) is provided with a first dosing line (6-1) and a second dosing line (6-2), the first dosing line (6-1) transports the carbon source to the front end of the anoxic zone A (2-2) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), and supplies commercial source carbon to the anoxic zone A to promote the denitrification process of the extracellular carbon source; the second dosing line (6-2) transports the carbon source to the bottom of the reactor body (5-0), so as to promote the rapid growth and enrichment of endogenous denitrification functional bacteria (denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria) in the reactor body (5-0).

[0020] According to a preferred embodiment of the present invention, the carbon source in the carbon source supply tank (6) is a sodium acetate solution. Preferably, the first dosing line (6-1) and the second dosing line (6-2) are powered by a metering dosing pump (6-3) and a metering dosing pump (6-4), respectively, to transport the sodium acetate solution.

[0021] According to a preferred embodiment of the present invention, the reactor body (5-0) is equipped with a stirring system (5-3), an aeration system, and an instrument assembly (5-4); the instrument assembly (5-4) includes an ORP meter, an MLSS meter (online sludge concentration measurement), and a DO (online dissolved oxygen) meter. These meters are used to guide the commissioning and operation of the reactor body (5-0) to more quickly produce a sludge-water mixture rich in endogenous denitrifying functional bacteria that meets the requirements. Preferably, the aeration system includes an aeration pump (5-1) and an aeration pipe and aeration head assembly (5-2), with the aeration head located at the bottom of the reactor body (5-0).

[0022] According to a preferred embodiment of the present invention, the water inlet side of the secondary sedimentation tank (3) is connected to the water outlet side of the second aerobic zone (2-6); the secondary sedimentation tank (3) is a functional area where mud and water separation occurs, and a mud outlet is provided at the bottom of the secondary sedimentation tank (3). A portion of the sludge discharged from the mud outlet is returned to the front end of the anaerobic zone (2-1) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), and the other portion is the remaining sludge for external discharge. An overflow weir is provided at the top of the secondary sedimentation tank (3), and the supernatant is discharged from the overflow weir into the effluent tank (4).

[0023] In a second aspect, the present invention also provides a method for enhancing the efficient coupling denitrification of internal and external carbon sources, which operates the system described in any of the above embodiments to treat low carbon-nitrogen ratio domestic sewage (C / N ratio of 4-6).

[0024] According to a preferred embodiment of the present invention, the operation method is as follows:

[0025] S1, startup phase

[0026] The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) and the internal-external carbon source high-efficiency coupled denitrification reactor (2) are operated simultaneously, wherein 90% of the sewage volume of the inlet pool (1) enters the internal-external carbon source high-efficiency coupled denitrification reactor (2), and the remaining 10% enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5); at this time, the internal-external carbon source high-efficiency coupled denitrification reactor (2) is mainly used for the cultivation of normal activated sludge and the occurrence of traditional external carbon source denitrification, and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is used to complete the acclimation and enrichment start-up of endogenous denitrification functional bacteria, specifically including:

[0027] The internal-external carbon source efficient coupled denitrification reactor (2) is inoculated with excess sludge from the biochemical pool of a municipal sewage treatment plant. The sludge concentration in the reactor is maintained at 4000-5000 mg / L, the hydraulic retention time is 8-16 h, and the sludge retention time is 20-30 d.

[0028] The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is inoculated with excess sludge from the biochemical pool of the municipal sewage treatment plant, so that the sludge concentration in the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is maintained at 5000-7000 mg / L and the sludge retention time is maintained at 20-30 days;

[0029] S2, stable operation stage

[0030] The internal-external carbon source high-efficiency coupled denitrification reactor (2) and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) jointly treat low carbon-nitrogen ratio domestic sewage; during this stage, the sewage inlet distribution ratio is kept unchanged, and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) continuously supplies endogenous denitrification functional bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2).

[0031] According to a preferred embodiment of the present invention, in S1, the lateral flow endogenous denitrification and functional bacteria acclimation and enrichment device (5) realizes the acclimation and enrichment of endogenous denitrification functional bacteria through the following six steps:

[0032] ① 10% of the sewage volume of the inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), and the water inflow time lasts for 10-15 minutes;

[0033] ②Anaerobic stirring lasts for 1.5-2.5 hours, and the carbon source sodium acetate solution is continuously added within the first 30 minutes at a dosage of 15-25 mg / L, and the ORP is controlled below -400 mV;

[0034] ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the rest of the time.

[0035] ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV;

[0036] ⑤ Sedimentation, lasting 40-60 minutes;

[0037] ⑥ Drainage: the supernatant after precipitation is discharged into the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), with a drainage ratio of 50%;

[0038] The above six processes constitute a complete cycle. After 40-60 cycles, the nitrate nitrogen concentration in the supernatant after precipitation is stabilized within the target value, indicating that the domestication and enrichment of endogenous denitrifying functional bacteria have been completed.

[0039] According to a preferred embodiment of the present invention, in S2, the operation formula of the internal-external carbon source high-efficiency coupled denitrification reactor (2) is as follows:

[0040] 90% of the sewage volume of the inlet pool (1) enters the front end of the anaerobic zone (2-1), and the mud-water mixture flowing out from the end of the anaerobic zone (2-1) then flows through the first anoxic zone A (2-2), anoxic zone B (2-3), the first aerobic zone (2-4), the second anoxic zone (2-5), and the second aerobic zone (2-6) in sequence before entering the secondary sedimentation tank (3); the inlet water is urban domestic sewage with a C / N ratio of 4-6;

[0041] The hydraulic retention time of the anaerobic zone (2-1) is 1.5-2h, and the ORP is controlled at -200mV to -400mV;

[0042] The hydraulic retention time of the first anoxic zone is 3-4h, and the nitrification liquid at the end of the first aerobic zone (2-4) is refluxed to the front end of the anoxic zone A of the first anoxic zone. The ORP of the anoxic zone A is maintained at -100mV to -200mV, and the nitrification liquid reflux ratio is controlled at 150% to 250%. The mud-water mixture of the anoxic zone A enters the anoxic zone B, and the mud-water mixture rich in endogenous denitrification functional bacteria produced by the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is also discharged into the front end of the anoxic zone B. The discharge ratio is 3% to 5% of the effective volume of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5). The ORP of the anoxic zone B is controlled at -200mV to -300mV, and the sludge concentration is controlled at 5000-6000mg / L.

[0043] The hydraulic retention time of the first aerobic zone (2-4) is 5-6 hours, and the dissolved oxygen at the front, middle and end of the first aerobic zone (2-4) is adjusted to 0.5-1 mg / L, 1.5-2.5 mg / L and 0.8-1.5 mg / L respectively by changing the density of the aeration head distribution;

[0044] The hydraulic retention time of the second anoxic zone (2-5) is 1.5-2h, and at the same time, the supernatant of the sludge produced by the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) at the end of each cycle of reaction is discharged into the front end of the second anoxic zone (2-5);

[0045] The hydraulic retention time of the second aerobic zone (2-6) is 0.5-1h, and the dissolved oxygen concentration is controlled at 1.5-2mg / L;

[0046] The hydraulic retention time of the secondary sedimentation tank (3) is 2-4 hours, and the supernatant after sedimentation is discharged from the overflow weir; the sludge at the bottom of the secondary sedimentation tank (3) is returned to the front end of the anaerobic zone (2-1), the sludge return ratio is 60%-100%, and the return sludge concentration is controlled at 12000-15000 mg / L.

[0047] Preferably, the influent of the influent pool (1) is urban domestic sewage, and its C / N ratio is 4-6, which is low carbon-nitrogen ratio sewage.

[0048] According to a preferred embodiment of the present invention, in S2, the operation of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) and the supply of endogenous denitrification functional bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2) are as follows:

[0049] ① 10% of the sewage volume of the inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), and the water inflow time lasts for 10-15 minutes;

[0050] ② Anaerobic stirring, lasting 1.5-2.5 hours, continuously adding carbon source sodium acetate solution in the first 15 minutes, with a dosage of 5-13 mg / L, and adding sludge rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria (3-5% of the mud-water mixture of the effective volume of the side stream reactor) to the front end of the anoxic zone B (2-3) of the internal-external carbon source high-efficiency coupled denitrification reactor (2) in the last 5 minutes. The ORP of this stage is controlled below -400 mV;

[0051] ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the remaining time.

[0052] ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV;

[0053] ⑤ Sedimentation, lasting 40-60 minutes;

[0054] ⑥ Drainage: the supernatant after precipitation is discharged into the front end of the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), with a drainage ratio of 50%;

[0055] The above six processes constitute a complete cycle, and are cyclically operated on a daily basis in the S2 stage.

[0056] According to a preferred embodiment of the present invention, S2 further includes adding a commercial carbon source to the anoxic zone A of the first anoxic zone, and the commercial carbon source is added by a metering dosing pump (6-3), and its start and stop are determined according to the influent TN (total nitrogen), the nitrification liquid return ratio r, the sludge return ratio R, the effluent TN target value and the nitrate nitrogen concentration at the end of the anoxic zone B of the first anoxic zone, according to the following formula:

[0057]

[0058] When the actual NO3 at the end of the first anoxic zone - The concentration is greater than the NO3 at the end of the first anoxic zone - When the theoretical maximum concentration is reached, the metering pump (6-3) is turned on to add the commercial carbon source; when the actual NO3 - The concentration is less than the NO3 at the end of the first anoxic zone - When the theoretical maximum concentration is reached, the metering dosing pump (6-3) is turned off to stop the addition of the commercial carbon source.

[0059] (3) Beneficial effects

[0060] The system and method of the present invention, by providing a side stream endogenous denitrification and functional bacteria acclimation and enrichment device and redesigning the volume ratio of each tank of the existing five-stage Batum process, can effectively solve the problems of part of the carbon source being wasted in the aerobic tank in the AOA process, low denitrification efficiency based on pure endogenous denitrification, unstable endogenous denitrification, and short aerobic nitrification time. This allows the two denitrification methods of traditional exogenous denitrification and endogenous denitrification to be efficiently coupled, while obtaining high-quality effluent and relatively reducing the amount of commercial carbon source added, thereby significantly improving the denitrification efficiency and effluent stability compared to pure endogenous denitrification.

[0061] In the present invention, by increasing the effective tank capacity ratio of the first aerobic zone (2-4), the problem that the existing aerobic tank capacity of endogenous denitrification is relatively small and ammonia nitrogen exceeds the standard in the winter when the temperature is low is solved. There is no need to add a higher proportion of fillers to the aerobic tank or increase aeration power consumption, thereby saving comprehensive costs.

[0062] In view of the problem that the influent COD of the current endogenous denitrification process cannot be efficiently utilized by saccharin-accumulating bacteria and then enter the subsequent aerobic tank, resulting in the waste of part of the influent COD, the improvement measures of the present invention include: ① by appropriately extending the residence time in the anaerobic zone, the hydrolysis of part of the particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source are achieved, and the hydrolyzed COD can be further stored as an internal carbon source by saccharin-accumulating bacteria, thereby improving the utilization rate of COD in the water; ② the first anoxic zone is divided into two parts, and the anoxic zone A and the anoxic zone B of the first anoxic zone focus on traditional extracellular carbon source denitrification and intracellular carbon source denitrification, respectively. Among them, the anoxic zone A can further hydrolyze the particulate easily degradable COD adsorbed on the outside of the bacteria, and at the same time use the hydrolyzed COD and the dissolved COD partially adsorbed on the outside of the bacteria in the anaerobic zone for traditional extracellular carbon source denitrification.

[0063] In view of the current problems of low endogenous carbon denitrification rate and low system denitrification stability, the improvement measures of the present invention include: ① continuously providing rich denitrifying sugar-accumulating bacteria and denitrifying phosphate-accumulating bacteria to the front end of the anoxic zone B through the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), thereby increasing the abundance of endogenous denitrification functional bacteria and thus increasing the endogenous denitrification rate. ② setting up a flexible commercial carbon source supplementation mechanism, calculating and controlling the addition of commercial carbon sources based on the influent TN (total nitrogen), the effluent TN internal control value and the nitrate nitrogen concentration at the end of the anoxic zone B, etc., which can improve the robustness of the entire sewage treatment system and ensure the effluent denitrification effect and water quality stability.

[0064] In the present invention, the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is not only a treatment device for endogenous denitrification treatment of low carbon-nitrogen ratio urban domestic sewage, but also a functional device for continuously acclimating and producing endogenous denitrifying functional bacteria (denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria). The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is used to continuously provide denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2), thereby providing assistance to the internal-external carbon source high-efficiency coupled denitrification reactor (2), thereby solving the problem that the existing endogenous denitrification rate is lower than the traditional exogenous denitrification rate and the endogenous denitrification effect is easily affected by the environment and is relatively unstable. The reaction tank volume of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) of the present invention is only 5-10% of that of the internal-external carbon source high-efficiency coupled denitrification reactor (2), which can reduce the floor space. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of a system for enhancing the efficient coupling of denitrification with internal and external carbon sources according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0066] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0067] like Figure 1 The figure shows a schematic diagram of a system for enhancing the efficient coupling of internal and external carbon source denitrification and denitrification according to a preferred embodiment of the present invention. The system mainly consists of two parts. The first part is an internal and external carbon source efficient coupling denitrification reactor 2 that receives 90% of the sewage volume in the inlet pool 1. The second part is a side stream internal denitrification and functional bacteria acclimation and enrichment device 5 that receives 10% of the sewage volume in the inlet pool 1. Specifically, the first part is connected in sequence along the water flow direction to the inlet pool 1, the internal and external carbon source efficient coupling denitrification reactor 2, the secondary sedimentation tank 3 and the outlet tank 4. The domestic sewage (usually urban domestic sewage with a low carbon-nitrogen ratio) coming out of the inlet pool 1 flows through the internal and external carbon source efficient coupling denitrification reactor 2, the secondary sedimentation tank 3 and the outlet tank 4 in sequence.

[0068] The inlet pool 1 has two outlet pipes, connected to the anaerobic zone 2-1 of the internal-external carbon source efficient coupled denitrification reactor 2 and the sidestream endogenous denitrification and functional bacteria acclimation and enrichment device 5 through the outlet main valve 1-1, valve 1-2, and valve 1-3, respectively. The internal-external carbon source efficient coupled denitrification reactor 2 is equipped with five zones along the water flow direction: the anaerobic zone 2-1, the first anoxic zones 2-2 and 2-3 (divided into anoxic zones A and B), the first aerobic zone 2-4, the second anoxic zone 2-5, and the second aerobic zone 2-6. Each zone has a corresponding function and undergoes different main reactions. The anaerobic zone 2-1 primarily converts dissolved, easily degradable COD into an internal carbon source and hydrolyzes some particulate, easily degradable COD. Online instrumentation such as ORP and MLSS is installed at the front end of this zone. The first anoxic zone primarily utilizes denitrifying bacteria to achieve denitrification. The first anoxic zone consists of two parts: anoxic zone A2-2 and anoxic zone B2-3, with a volume ratio of 0.85-1.15:0.85-1.15, preferably 0.9-1.1:0.9-1.1, and more preferably 1:1. Anoxic zone A in the first anoxic zone is connected to the end of anaerobic zone 2-1 and primarily undergoes traditional extracellular carbon source denitrification, avoiding the waste of some carbon sources in the aerobic tank during the AOA process. An ORP online meter is installed at the front end of anoxic zone A. Anoxic zone B primarily undergoes intracellular carbon source denitrification (denitrifying sugar-accumulating bacteria and denitrifying phosphorus-accumulating bacteria, etc.), and nitrate nitrogen and MLSS online meters are installed at the end of anoxic zone B. The first aerobic zone 2-4 primarily undergoes nitrification. Three DO (dissolved oxygen) online meters are installed at the front, middle, and end of this zone to control the aeration rate at different points. Nitrification is the oxidation of ammonia nitrogen in the water into nitrate nitrogen by nitrifying bacteria. The second anoxic zone 2-5 primarily denitrifies intracellular carbon sources, utilizing endogenous functional denitrifying bacteria to achieve deep denitrification. The second aerobic zone 2-6 primarily strips nitrogen and oxidizes a very small amount of ammonia nitrogen. Aeration within the second aerobic zone 2-6 removes nitrogen dissolved in the water. From the end of the first aerobic zone 2-4, a submersible sewage pump 2-10 returns the nitrified liquid to the front end of the anoxic zone A2-2. This sludge-water mixture, containing nitrate nitrogen, is then circulated back to the anoxic zones A and B, where it undergoes denitrification of extracellular and intracellular carbon sources, respectively. The sludge separated at the bottom of the secondary clarifier 3, rich in endogenous functional denitrifying bacteria, can be returned to the anaerobic zone 2-1 to replenish these bacteria and increase the anaerobic zone 2-1's intracellular storage rate of dissolved COD. The remaining excess sludge is discharged from the sludge outlet at the bottom of the secondary clarifier 3. An overflow weir is provided at the upper portion of the secondary sedimentation tank 3 , and the supernatant is discharged from the overflow weir into the effluent tank 4 .

[0069] The anaerobic zone 2-1, the first anoxic zone, and the second anoxic zone 2-5 are each equipped with a mixing device 2-7. Aeration heads are distributed at the bottom of the first aerobic zone 2-4 and the second aerobic zone 2-6. These aeration heads are connected to an aeration pipe 2-9, one end of which is connected to an aeration pump 2-8. The aeration heads are submerged in the bottoms of the first aerobic zone 2-4 and the second aerobic zone 2-6. In a preferred embodiment of the present invention, the aeration heads in the aerobic zone are not evenly distributed. Specifically, the aeration head density in the front 1 / 3 and rear 1 / 6 of the first aerobic zone 2-4 is half the density of the aeration heads in the middle 1 / 2 of the first aerobic zone 2-4. This allows the detection points in the front, middle, and rear sections of the aerobic zone to have different dissolved oxygen values under the same aeration pressure.

[0070] In order to improve the denitrification effect and effluent stability in different seasons and avoid excessive ammonia nitrogen in winter, the present invention redesigns the volume ratio of each zone of the internal-external carbon source high-efficiency coupled denitrification reactor 2, so that the volume ratio of the anaerobic zone 2-1, the first anoxic zone, the first aerobic zone 2-4, the second anoxic zone 2-5 and the second aerobic zone 2-6 is (1±5%):2(1±5%):3(1±5%):1(1±5%):0.5(1±5%). In a preferred embodiment of the present invention, the volume ratio is preferably 1:2:3:1:0.5.

[0071] The sidestream endogenous denitrification and functional bacteria acclimation and enrichment unit 5 utilizes approximately 10% of the water from the inlet pool 1 (the inlet water volume can be adjusted via the second pipe and valve assemblies 1-3) to perform denitrification and nitrogen removal, acclimate and cultivate endogenous denitrifying functional bacteria, and continuously feed the resulting muddy-water mixture rich in endogenous denitrifying functional bacteria to the internal-external carbon source efficient coupled denitrification reactor 2. The sidestream endogenous denitrification and functional bacteria acclimation and enrichment unit 5 is both an internal carbon source denitrification wastewater treatment device and a device for continuously cultivating and enriching endogenous denitrifying functional bacteria. In the present invention, the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 includes an SBR (sequencing batch reactor) reactor, which has a compact structure, simple principle and operation process, and small footprint. The tank volume of its reaction body is only about 5-10% of the internal-external carbon source high-efficiency coupled denitrification reactor 2, but the SBR reactor can efficiently acclimate endogenous denitrification functional bacteria with strong adaptability and high activity to domestic sewage, and can ensure the abundance of endogenous denitrifying bacteria in the anoxic zone of the internal-external carbon source high-efficiency coupled denitrification reactor 2, so as to improve the endogenous denitrification rate and ensure the stability of the effluent.

[0072] The SBR reactor has a water inlet 5-8, a reactor body 5-0 and a water / mud outlet 5-5; the reactor body 5-0 is a tank body (preferably open and closed), which is provided with a stirring device inside and an aeration device at the bottom. The effective tank capacity of the reactor body 5-0 is only 5-10% of the internal-external carbon source high-efficiency coupled denitrification reactor 2. Specifically, the reactor body 5-0 is provided with a stirring device 5-3, an aeration device and an instrument combination 5-4; the instrument combination 5-4 includes an ORP meter, an MLSS meter (online measurement of sludge concentration) and a DO (online dissolved oxygen) meter. These instruments are used to guide the debugging operation of the reactor body 5-0 to produce a mud-water mixture rich in endogenous denitrification functional bacteria that meets the needs more quickly. Preferably, the aeration equipment includes an aeration pump 5-1 and an aeration pipe and aeration head assembly 5-2, and the aeration head is located at the bottom of the reactor body 5-0. By periodically controlling the stirring 5-3 and the start and stop of the aeration equipment, the processes of anaerobic stirring → aerobic aeration → anoxic stirring can be realized in sequence in the reactor body 5-0.

[0073] Among them, the water inlet 5-8 is connected to the water inlet pool 1, and is used to receive domestic sewage from the water inlet pool 1. The water outlet / mud outlet 5-5 replenishes the sludge produced in the reactor body 5-0 to the front end of the anoxic zone B of the internal-external carbon source high-efficiency coupled denitrification reactor 2 through the mud discharge valve 5-7, so as to continuously supply endogenous denitrification functional bacteria to the anoxic zone B. The water outlet / mud outlet 5-5 transports the supernatant produced after the sludge is precipitated in the reactor body 5-0 to the front end of the second anoxic tank 2-5 through the drain valve 5-6. After the intracellular carbon source denitrification occurs in the second anoxic zone 2-5, it enters the second aerobic zone 2-6 for nitrogen stripping and ammonia nitrogen nitrification. The nitrified liquid in the aerobic zone then flows back to the front end of the anoxic zone A, so that the extracellular-internal carbon source denitrification enhancement reaction can be realized in a cycle.

[0074] The reactor body 5-0 is the functional area primarily responsible for producing and cultivating denitrifying sugar-accumulating bacteria and denitrifying phosphate-accumulating bacteria. It also diverts domestic sewage from the inlet pool 1, reducing the operational burden of the highly efficient internal-external carbon source coupled denitrification reactor 2. The SBR reactor is a sequencing batch reactor, consisting of the following six processes: water inlet → anaerobic agitation → aerobic aeration → anoxic agitation → sedimentation → drainage.

[0075] The system is further provided with a commercial carbon source supply pool 6, which works in conjunction with the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 and the internal-external carbon source efficient coupling denitrification reactor 2. The carbon source supply pool 6 is provided with a first dosing line 6-1 and a second dosing line 6-2. The first dosing line 6-1 transports the carbon source (sodium acetate solution) to the front end of the anoxic zone A of the internal-external carbon source efficient coupling denitrification reactor 2, and supplies commercial source carbon to the anoxic zone A to compensate for the problem of too low COD content in the sewage and promote the denitrification intensity of the extracellular carbon source in the anoxic zone A. The second dosing line 6-2 transports the carbon source to the bottom of the reactor body 5-0 to compensate for the problem of too low COD content in the water source (or low temperature), so that the endogenous denitrification functional bacteria can grow rapidly and stably in the reactor body 5-0. The first dosing pipeline 6 - 1 and the second dosing pipeline 6 - 2 are provided with power for quantitatively conveying the sodium acetate solution through a metering dosing pump 6 - 3 and a metering dosing pump 6 - 4 respectively.

[0076] The present invention Figure 1 The system shown in the figure can be operated as follows:

[0077] Step 1: System startup

[0078] The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) and the internal-external carbon source high-efficiency coupled denitrification reactor (2) are operated simultaneously, wherein 90% of the water volume of the inlet pool (1) enters the internal-external carbon source high-efficiency coupled denitrification reactor (2), and the remaining 10% enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5); at this time, the internal-external carbon source high-efficiency coupled denitrification reactor (2) is mainly used for the cultivation of normal activated sludge and the occurrence of traditional external carbon source denitrification, and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is used to complete the acclimation and enrichment preparation of endogenous denitrification functional bacteria, specifically including:

[0079] The inoculation of the internal-external carbon source efficient coupled denitrification reactor 2 is from the residual sludge of the municipal domestic sewage treatment plant. The sludge concentration in the reactor is maintained at 4000-5000 mg / L, the hydraulic retention time is 8-16 hours, and the sludge retention time is 20-30 days.

[0080] The side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 is operated to complete the acclimation and enrichment start-up of the endogenous denitrification functional bacteria, specifically including: inoculating the reactor body 5-0 of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device with residual sludge from the biochemical pool of the urban domestic sewage treatment plant, so that the sludge concentration is maintained at 5000-7000 mg / L and the sludge retention time is maintained at 20-30 days.

[0081] The endogenous denitrifying functional bacteria acclimation and enrichment device achieves the acclimation and enrichment of endogenous denitrifying functional bacteria through the following six steps: water inlet → anaerobic stirring → aerobic aeration → anoxic stirring → sedimentation → sludge discharge / supernatant discharge. The steps are described as follows:

[0082] ① 10% of the sewage volume of the inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), and the water inflow time lasts for 10-15 minutes;

[0083] ②Anaerobic stirring lasts for 1.5-2.5 hours, and the carbon source sodium acetate solution is continuously added within the first 30 minutes at a dosage of 15-25 mg / L, and the ORP is controlled below -400 mV;

[0084] ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the remaining time.

[0085] ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV;

[0086] ⑤ Sedimentation, lasting 40-60 minutes;

[0087] ⑥ Drainage: the supernatant after precipitation is discharged into the second anoxic zone 2-5 of the internal-external carbon source high-efficiency coupled denitrification reactor 2, with a drainage ratio of 50%;

[0088] The above six processes constitute a complete cycle. After 40-60 cycles, the nitrate nitrogen concentration in the supernatant after precipitation is stable within the target value, indicating that the domestication of endogenous denitrifying functional bacteria has been completed.

[0089] Step 2: Stable operation stage

[0090] After the domestication and enrichment of the endogenous denitrifying functional bacteria are completed, the daily operation mode of the sidestream endogenous denitrification and functional bacteria domestication and enrichment device 5 is maintained, and the endogenous denitrifying functional bacteria community is supplemented to the internal-external carbon source efficient coupled denitrification reactor 2 to jointly achieve internal-external carbon source coupled synergistic denitrification of low carbon-nitrogen ratio domestic sewage. During this process, 90% of the influent water enters the internal-external carbon source efficient coupled denitrification reactor 2, and the remaining 10% enters the sidestream endogenous denitrification and functional bacteria domestication and enrichment device 5. This part of the water source is mainly used to continuously domesticate and produce high-activity endogenous denitrifying functional bacteria adapted to the sewage environment. The daily operation of the sidestream endogenous denitrification and functional bacteria domestication and enrichment device 5 can continuously assist the endogenous denitrification process of the internal-external carbon source efficient coupled denitrification reactor 2.

[0091] During the operation of the internal-external carbon source high-efficiency coupled denitrification reactor 2, the parameters such as sludge concentration, hydraulic retention time, and sludge retention time are the same as those in the first step. At the same time, the control conditions of its five functional zones are as follows:

[0092] The hydraulic retention time of sewage entering the anaerobic zone 2-1 is 1.5-2h, and the ORP is controlled at -200mV~-400mV;

[0093] The residence time of the first anoxic zone (2-2, 2-3) is 3-4h. The nitrified liquid at the end of the first aerobic zone 2-4 is refluxed to the front end of the anoxic zone A. The ORP of the anoxic zone A is maintained at -100mV to -200mV, and the nitrified liquid reflux ratio is controlled at 150% to 250%. The muddy water mixture rich in endogenous denitrifying functional bacteria produced by the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 is also discharged into the front end of the anoxic zone B. The discharge ratio is 3% to 5% of the effective volume of the reaction zone body 5-0. The ORP of the anoxic zone B is controlled at -200mV to -300mV, and the sludge concentration is controlled at 5000-6000mg / L.

[0094] The hydraulic retention time of the first aerobic zone 2-4 is 5-6 hours, and the dissolved oxygen at the front, middle and end of the first aerobic zone 2-4 is adjusted to 0.5-1 mg / L, 1.5-2.5 mg / L and 0.8-1.5 mg / L respectively by changing the distribution density of the aeration heads.

[0095] The hydraulic retention time of the second anoxic zone 2-5 is 1.5-2h, and at the same time, the supernatant after the sludge precipitation produced at the end of each cycle reaction of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 is discharged into the second anoxic zone 2-5;

[0096] The hydraulic retention time of the second aerobic zone 2-6 is 0.5-1h, and the dissolved oxygen concentration is controlled at 1.5-2mg / L;

[0097] The hydraulic retention time of the secondary sedimentation tank 3 is 2-4 hours, and the supernatant after sedimentation is discharged from the overflow weir; the sludge at the bottom of the secondary sedimentation tank 3 is returned to the front end of the anaerobic zone 2-1, the sludge return ratio is 60%-100%, and the return sludge concentration is controlled at 12000-15000 mg / L.

[0098] The daily operation mode of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5 is as follows:

[0099] ① 10% of the water in the water inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device 5. The water inlet time lasts for 10-15 minutes;

[0100] ② Anaerobic stirring, continued for 1.5-2.5h, the carbon source sodium acetate solution was continuously added in the first 15min, the dosage was 5-13mg / L, and in the last 5min, the sludge rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria (mud-water mixture of 3-5% of the volume of the SBR reactor body) was added to the front end of the anoxic zone B of the internal-external carbon source efficient coupled denitrification reactor 2 to supply endogenous denitrifying functional bacteria to the anoxic zone B. The ORP of this stage was controlled below -400mV;

[0101] ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the remaining time.

[0102] ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV;

[0103] ⑤ Sedimentation, lasting 40-60 minutes;

[0104] ⑥ Drainage: the supernatant after precipitation is discharged into the front end of the second anoxic zone 2-5 of the internal-external carbon source high-efficiency coupled denitrification reactor 2, with a drainage ratio of 50%;

[0105] The above six processes constitute a complete cycle, and are cyclically operated on a daily basis in the S2 stage.

[0106] Whether to start the dosing pump of the carbon source supply tank 6 to add the commercial carbon source to the anoxic zone A can be determined according to the following formula:

[0107] Based on the influent TN (total nitrogen), nitrification solution return ratio r, sludge return ratio R, effluent TN target value and the nitrate nitrogen concentration at the end of the anoxic zone B in the first anoxic zone, it is calculated and determined according to the following formula:

[0108]

[0109] When the actual NO3 at the end of the first anoxic zone - The concentration is greater than the NO3 at the end of the first anoxic zone - When the theoretical maximum concentration is reached, the metering pump 6-3 is turned on to add the commercial carbon source; when the actual NO3 at the end of the first anoxic zone is - The concentration is less than the NO3 at the end of the first anoxic zone - When the theoretical maximum concentration is reached, the metering dosing pump 6-3 is turned off to stop the addition of the commercial carbon source.

[0110] Controlling the addition of an external commercial carbon source based on this formula can significantly reduce the amount of external carbon source added, thus saving on commercial carbon source costs. The carbon source supply pool 6 and commercial carbon source supply model can improve the environmental stability and operational robustness of the entire sewage treatment system, ensuring effluent denitrification effectiveness and stable water quality.

[0111] Application Examples

[0112] A certain town domestic sewage treatment plant, whose influent C / N ratio is 3-6, is treated by the method of strengthening internal-external carbon source denitrification high-efficiency coupled denitrification of the present invention. The total hydraulic retention time of the biochemical pool of the internal-external carbon source high-efficiency coupled denitrification reactor (2) is 12-15 hours, and the hydraulic retention time of the secondary sedimentation tank (3) is 3-4 hours. The treatment results are: the internal denitrification ratio is stable at more than 30%, the denitrification rate of the entire system is more than 78%, the effluent TN is stable ≤10 mg / L, the nitrification liquid reflux ratio in the main reactor (2) is actually 140%-200%, and the sludge reflux ratio is actually 40%-80%, saving more than 40% of reflux power consumption; through the system and method, the carbon source dosage is reduced by more than 30% compared with the same effluent standard.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for enhancing the efficient coupling of denitrification by internal and external carbon sources, characterized in that: include: An inlet pool (1), an internal-external carbon source high-efficiency coupled denitrification reactor (2), and a secondary sedimentation tank (3) are sequentially connected along the sewage flow direction; The internal-external carbon source high-efficiency coupled denitrification reactor (2) is provided with an anaerobic zone (2-1), a first anoxic zone, a first aerobic zone (2-4), a second anoxic zone (2-5) and a second aerobic zone (2-6) in sequence along the water flow direction; the first anoxic zone is composed of anoxic zone A (2-2) and anoxic zone B (2-3); the anaerobic zone (2-1) provides a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of dissolved easily degradable COD into an internal carbon source; the anoxic zone A (2-2) of the first anoxic zone is a reaction zone for the hydrolysis of particulate easily degradable COD and the conversion of particulate ... The reaction zone is provided for denitrification of external carbon sources; the anoxic zone B (2-3) provides a reaction zone for denitrification of intracellular carbon sources; the first aerobic zone (2-4) provides a reaction zone for nitrification; the second anoxic zone (2-5) provides a reaction zone for denitrification of intracellular carbon sources; the second aerobic zone (2-6) provides a reaction zone for stripping of dissolved nitrogen in water and nitrification; the end of the first aerobic zone (2-4) returns the nitrified liquid to the front end of the anoxic zone A (2-2) through a submersible sewage pump; the concentrated sludge at the bottom of the secondary sedimentation tank (3) returns to the front end of the anaerobic zone (2-1); Among them, the volume ratios of the anaerobic zone (2-1), the first anoxic zone, the first aerobic zone (2-4), the second anoxic zone (2-5) and the second aerobic zone (2-6) are (1±5%):2(1±5%):3(1±5%):1(1±5%):0.5(1±5%); in the first anoxic zone, the volume ratios of the anoxic zone A (2-2) and the anoxic zone B (2-3) are 0.85-1.15:0.85-1.15; The system further comprises: a side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), which utilizes part of the sewage from the inlet pool (1) to acclimate and enrich denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria, and continuously supplies the generated muddy water mixture rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2).

2. The system according to claim 1, wherein: The inlet pool (1) stores low-carbon source domestic sewage; the inlet pool (1) is connected to an internal-external carbon source high-efficiency coupled denitrification reactor (2) via a first pipe-valve assembly (1-2), and is connected to a side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) via a second pipe-valve assembly (1-3), and the sewage flow rate of the second pipe-valve assembly (1-3) is 8-12% of the total water output of the inlet pool (1).

3. The system according to claim 1, wherein: The anaerobic zone (2-1), the first anoxic zone, and the second anoxic zone (2-5) are all provided with mixing and stirring equipment (2-7); aeration heads are distributed at the bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6); the aeration heads at the bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6) are both connected to an aeration pipe (2-9), one end of the aeration pipe (2-9) is connected to an aeration pump (2-8), and the aeration heads are immersed in the water bottom of the first aerobic zone (2-4) and the second aerobic zone (2-6).

4. The system according to claim 3, characterized in that The aeration heads in the first aerobic zone (2-4) are unevenly distributed. Specifically, the aeration head arrangement density in the front 1 / 3 section and the rear 1 / 6 section of the first aerobic zone (2-4) is half of the aeration head arrangement density in the middle 1 / 2 section of the first aerobic zone (2-4).

5. The system according to claim 1, wherein: The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) comprises an SBR reactor, which comprises a reactor body (5-0) and a water outlet / mud outlet (5-5); the reactor body (5-0) receives part of the influent from the water inlet pool (1); the volume of the reactor body (5-0) is 5%-10% of the internal-external carbon source high-efficiency coupled denitrification reactor (2); the water outlet / mud outlet (5-5) replenishes the mud-water mixture rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria to the front end of the anoxic zone B (2-3) of the internal-external carbon source high-efficiency coupled denitrification reactor (2) through a mud discharge valve (5-7), thereby supplying endogenous denitrifying functional bacteria to the anoxic zone B; the water outlet / mud outlet (5-5) discharges the supernatant after endogenous denitrification and precipitation in the reactor body (5-0) to the front end of the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2) through a drain valve (5-6).

6. The system according to claim 5, characterized in that The system further comprises a carbon source supply pool (6), which is provided with a first dosing line (6-1) and a second dosing line (6-2). The first dosing line (6-1) transports the carbon source to the front end of the anoxic zone A (2-2) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), thereby supplying the anoxic zone A with a commercial carbon source to promote the denitrification process of the extracellular carbon source; the second dosing line (6-2) transports the carbon source to the bottom of the reactor body (5-0), thereby promoting the rapid growth and enrichment of endogenous denitrification functional bacteria in the reactor body (5-0).

7. A method for enhancing the efficient coupled denitrification of internal and external carbon sources, comprising operating the system of any one of claims 1 to 6 to treat low carbon-nitrogen ratio domestic sewage; the method comprising the following steps: S1, startup phase The side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) and the internal-external carbon source high-efficiency coupled denitrification reactor (2) are operated simultaneously, wherein 90% of the water volume of the inlet pool (1) enters the internal-external carbon source high-efficiency coupled denitrification reactor (2), and the remaining 10% enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5); at this time, the internal-external carbon source high-efficiency coupled denitrification reactor (2) is mainly used for the cultivation of normal activated sludge and the occurrence of traditional external carbon source denitrification, and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is used to complete the acclimation and enrichment start-up of endogenous denitrification functional bacteria, specifically including: The internal-external carbon source highly efficient coupled denitrification reactor (2) is inoculated with excess sludge from a municipal sewage treatment plant. The sludge concentration in the reactor is maintained at 4000-5000 mg / L, the hydraulic retention time is 8-16 h, and the sludge retention time is 20-30 d. The lateral endogenous denitrification and functional bacteria acclimation and enrichment device (5) is inoculated with excess sludge from the biochemical pool of the municipal sewage treatment plant, so that the sludge concentration in the lateral endogenous denitrification and functional bacteria acclimation and enrichment device (5) is maintained at 5000-7000 mg / L and the sludge retention time is maintained at 20-30 days; S2, stable operation stage The internal-external carbon source high-efficiency coupled denitrification reactor (2) and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) jointly treat low carbon-nitrogen ratio domestic sewage; during this stage, the sewage inlet distribution ratio is kept unchanged, and the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) continuously supplies endogenous denitrification functional bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2).

8. The method according to claim 7, characterized in that In S1, the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) realizes the acclimation and enrichment of endogenous denitrification functional bacteria through the following six steps: ① 10% of the sewage volume in the inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), and the water inflow time lasts for 10-15 minutes; ②Anaerobic stirring lasts for 1.5-2.5 hours, and the carbon source sodium acetate solution is continuously added within the first 30 minutes at a dosage of 15-25 mg / L, and the ORP is controlled below -400 mV; ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the rest of the time. ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV; ⑤ Sedimentation, lasting 40-60 minutes; ⑥ Drainage: the supernatant after precipitation is discharged into the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), with a drainage ratio of 50%; The above six processes constitute a complete cycle. After 40-60 cycles, the nitrate nitrogen concentration in the supernatant after precipitation is stabilized within the target value, indicating that the domestication of endogenous denitrifying functional bacteria has been completed.

9. The method according to claim 7, characterized in that In S2, the operation formula of the internal-external carbon source high-efficiency coupled denitrification reactor (2) is as follows: 90% of the sewage volume of the inlet pool (1) enters the front end of the anaerobic zone (2-1), and the mud-water mixture flowing out of the end of the anaerobic zone (2-1) then flows through the first anoxic zone A (2-2), anoxic zone B (2-3), the first aerobic zone (2-4), the second anoxic zone (2-5), the second aerobic zone (2-6) and then enters the secondary sedimentation tank (3); the inlet water is urban domestic sewage with a C / N ratio of 4-6; The hydraulic retention time of the anaerobic zone (2-1) is 1.5-2h, and the ORP is controlled at -200mV~-400mV; The hydraulic retention time of the first anoxic zone is 3-4h. The nitrification liquid at the end of the first aerobic zone (2-4) is refluxed to the front end of the anoxic zone A of the first anoxic zone. The ORP of the anoxic zone A is maintained at -100mV~-200mV, and the nitrification liquid reflux ratio is controlled at 150%-250%. The mud-water mixture of the anoxic zone A enters the anoxic zone B, and the mud-water mixture rich in endogenous denitrification functional bacteria produced by the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) is also discharged into the front end of the anoxic zone B. The discharge ratio is 3%-5% of the effective volume of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5). The ORP of the anoxic zone B is controlled at -200mV~-300mV, and the sludge concentration is controlled at 5000-6000 mg / L. The hydraulic retention time of the first aerobic zone (2-4) is 5-6 hours. The density of the aeration head distribution is changed to make the dissolved oxygen at the front, middle and end of the first aerobic zone (2-4) 0.5-1 mg / L, 1.5-2.5 mg / L and 0.8-1.5 mg / L respectively. The hydraulic retention time of the second anoxic zone (2-5) is 1.5-2h. At the same time, the supernatant of the sludge produced by the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) at the end of each cycle of reaction is discharged into the second anoxic zone (2-5); The hydraulic retention time of the second aerobic zone (2-6) is 0.5-1h, and the dissolved oxygen concentration is controlled at 1.5-2mg / L; The hydraulic retention time of the secondary sedimentation tank (3) is 2-4 hours, and the supernatant after sedimentation is discharged from the overflow weir; The sludge at the bottom of the secondary sedimentation tank (3) is returned to the front end of the anaerobic zone (2-1), with a sludge return ratio of 60%-100%, and the return sludge concentration is controlled at 12000-15000 mg / L.

10. The method according to claim 7, characterized in that In S2, the operation of the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5) and the supply of endogenous denitrification functional bacteria to the internal-external carbon source high-efficiency coupled denitrification reactor (2) are as follows: ① 10% of the sewage volume in the inlet pool enters the side stream endogenous denitrification and functional bacteria acclimation and enrichment device (5), and the water inflow time lasts for 10-15 minutes; ② Anaerobic stirring, lasting 1.5-2.5 hours, with carbon source sodium acetate solution continuously added in the first 15 minutes at a dosage of 5-13 mg / L, and within the last 5 minutes, the muddy water mixture rich in denitrifying polysaccharide bacteria and denitrifying polyphosphate bacteria is added to the front end of the anoxic zone B (2-3) of the internal-external carbon source high-efficiency coupled denitrification reactor (2). The ORP at this stage is controlled below -400 mV; ③ Aerobic aeration, lasting 3-4 hours. Maintain dissolved oxygen at 0.5-1 mg / L for 30-60 minutes before aerobic aeration. Increase aeration intensity to keep dissolved oxygen at 1.5-2.5 mg / L during the remaining time. ④Anoxic stirring, continue for 3-4 hours, control ORP at -100mV~-200mV; ⑤ Sedimentation, lasting 40-60 minutes; ⑥ Drainage: the supernatant after precipitation is discharged into the front end of the second anoxic zone (2-5) of the internal-external carbon source high-efficiency coupled denitrification reactor (2), with a drainage ratio of 50%; The above six processes constitute a complete cycle, and are cyclically operated on a daily basis in the S2 stage.

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