Reflux control method for sewage treatment based on high total nitrogen and low flow

Abstract

The invention relates to a reflux control method for sewage treatment based on high total nitrogen and low flow, which specifically comprises the following steps: calculating the maximum nitrogen quantity # imgabs0 # which can be accepted by a sewage treatment system in each cycle in a low-temperature environment; the most conservative allowable maximum inlet water total Kjeldahl nitrogen concentration # imgabs 1 # of a sewage treatment system under actual working conditions; calculating the total nitrogen concentration # imgabs2 # of the actual effluent of the regulating reservoir; s3, setting an operation cycle, and entering the next step after the operation cycle is ended; and judging the relationship between the # imgabs3 # and the # imgabs4 #, and judging the relationship between the liquid level H of the adjusting tank and the set liquid level value # imgabs5 # of the low-water-level operation of the adjusting tank, and controlling backflow of different degrees under different conditions. The device has the advantages of stable operation, high treatment efficiency and wide application range.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a reflux control method for sewage treatment based on high total nitrogen and low flow. Background Art

[0002] Affected by low temperatures and high-concentration water inflow in winter, design units can only refer to current specifications and guidelines or rely on past experience to carry out design. However, there are often great differences between different towns; therefore, even the design scheme based on past experience is unlikely to adapt to the actual situation after the drainage facilities are built, and the effluent quality is difficult to guarantee.

[0003] As water temperatures drop in winter, the microbial activity and biological reaction rate in activated sludge will decrease significantly, with a particularly significant impact on nitrification and denitrification. At the same time, problems such as sludge bulking are prone to occur, which seriously affects the removal efficiency of pollutants and causes fluctuations in the effluent quality of sewage treatment plants or even exceeds standards. In addition, due to high-load water inflow, low temperatures have a greater impact on the treatment system, exacerbating these problems.

[0004] We urgently need to find an economically feasible and easy-to-implement solution. This is not only for environmental protection reasons, but also a necessary condition to ensure that township sewage treatment plants can operate stably and achieve sustainable development. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by this patent application is how to provide a reflux control method for sewage treatment based on high total nitrogen and low flow, which has stable operation, high treatment efficiency and wide adaptability.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A reflux control method for sewage treatment based on high total nitrogen and low flow rate, comprising an inlet end, a regulating tank, a sewage treatment system, an outlet combined tank and an outlet end arranged in sequence, wherein a reflux system for returning to the regulating tank is arranged between the sewage treatment system and the outlet combined tank, and the control method is used to regulate the reflux system, specifically comprising the following steps: S1: Calculate the maximum amount of denitrification nitrogen that the sewage treatment system can accept on average per cycle under a low temperature environment ; and combined with the actual outflow flow of the regulating pool , calculate the most conservative maximum allowable total Kjeldahl nitrogen concentration in the sewage treatment system under actual operating conditions ; S2: According to the actual water flow rate of the regulating tank , Reflux Flow And the average liquid level change height of the regulating tank per cycle , calculate the actual average water inflow per cycle , and combined with the total nitrogen concentration in the influent , reflux flow , total nitrogen concentration in effluent As well as the total nitrogen content of the existing sewage in the regulating pool, calculate the total nitrogen concentration of the actual effluent from the regulating pool ; S3: Set the operation cycle. After the operation cycle ends, enter step S4; S4: Determine the maximum allowable total Kjeldahl nitrogen concentration of the influent Compared with the actual total nitrogen concentration of the effluent from the regulating tank and the relationship between the regulating tank liquid level H and the set regulating tank low water level operation liquid level value The relationship between as well as ; S5: When the conditions in step S4 are met at the same time, no reflux is required, and after the next operation cycle ends, enter step S4; S6: When the conditions in step S4 are met ,but When the actual outflow of regulating pool is increased And keep constant, enter the next cycle, and after the end, enter step S4; S7: When there is When the water volume of the regulating pool is increased to , enter the next cycle, and after the end, enter step S4 for judgment.

[0007] As an optimization, the sewage treatment system includes an anaerobic tank, an anoxic tank, an aerobic tank, a secondary sedimentation tank, and a coagulation final sedimentation tank which are arranged in sequence, wherein a digestion liquid reflux device is arranged between the aerobic tank and the anoxic tank, and a sludge reflux device is arranged between the secondary sedimentation tank and the anaerobic tank, and the secondary sedimentation tank and the coagulation final sedimentation tank are both connected to the sludge treatment system.

[0008] As an optimization, in step S1, the maximum amount of nitrogen required for denitrification that can be accepted per cycle is The calculation formula is as follows: ; ; ; ; Where: - Calculation volume of hypoxic zone; - Actual volume of the hypoxic zone, ; - Design flow rate of the bioreactor; - Designed total Kjeldahl nitrogen concentration of the influent of the biological reactor; - Designed total nitrogen concentration of effluent from the biological reactor; - Design the maximum allowable total Kjeldahl nitrogen concentration of the influent of the bioreactor under low temperature environment conditions; - The amount of microorganisms discharged from the bioreactor system; , , - Temperature ℃, minimum temperature in winter Denitrification rate at ℃ and 20℃; - Design average concentration of suspended solids in the mixed liquor of the bioreactor; - Design temperature; - Sludge yield coefficient; - Design five-day biochemical oxygen demand concentration of the influent of the biological reactor; - Designed five-day biochemical oxygen demand concentration of the effluent from the biological reactor; The most conservative maximum allowable total Kjeldahl nitrogen concentration in the influent of the sewage treatment system under actual working conditions The calculation formula is as follows: ; Where: - The amount of microorganisms discharged from the bioreactor system, - Designed total nitrogen concentration of effluent from the biological reactor, - Actual water outflow from the regulating tank.

[0009] As an optimization, in step S2, the actual average water intake per cycle , the calculation formula is as follows: ; Where: - Actual outflow flow of regulating pool, - Final sedimentation tank effluent return flow (m3 / h), - Length of regulating pool (m), - Width of regulating pool (m), - Average liquid level change in the regulating tank per cycle; Actual total nitrogen concentration of effluent from regulating pond When calculating, dynamic data is used, that is, when calculating the nth cycle When the data collected after n-1 cycles is combined, the following formula is used ; - Average water inflow per cycle in the nth cycle, - During the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - The return flow rate of the final sedimentation tank in the nth cycle, - During the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - Length of regulating pool, - Width of regulating pool, - After the (n-1)th cycle, the regulating tank monitors the liquid level data online. - After the (n-1)th cycle, the actual total nitrogen concentration of the effluent from the regulating pond.

[0010] As an optimization, in step S7, The calculation of is obtained by the following formula ; When the liquid level drops or does not change after n cycles, ; When the liquid level rises after n cycles, ; in, .

[0011] As an optimization, in step S7, after the next cycle after adjustment, the judgment of step S4 is followed again to enter step S7. Use the maximum value.

[0012] As an optimization, the water inlet and outlet of the regulating tank are both provided with flow meters and online nitrogen concentration detectors; a liquid level detector is also provided in the regulating tank, and the water outlet of the coagulation final sedimentation tank is provided with a flow meter, an online nitrogen concentration detector and a reflux frequency conversion pump; the water outlet of the outlet combination tank is provided with a flow meter and an online nitrogen concentration detector.

[0013] As an optimization, it includes multiple partitions obliquely arranged above the sewage treatment pool, the partitions are connected by support rods arranged parallel to each other, a transparent thermal insulation film is laid above the support rods, a section of the partition located above is provided with a winding device for winding up the transparent thermal insulation film, a counterweight rod is provided at the free end of the transparent thermal insulation film, and a water temperature sensor is also provided in the sewage treatment pool.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention can improve the existing rural and urban sewage treatment equipment and optimize the reflux efficiency, especially under low temperature and reduced treatment activity, complete dynamic adjustment, start the reflux at the right time, accurately control the reflux volume, reduce manual participation, and have a high degree of automation. At the same time, it provides insulation measures to cooperate with the reflux to maximize the reduction of effluent pollutant content. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a method flow chart of a reflux control method for sewage treatment based on high total nitrogen and low flow rate described in the present invention.

[0016] Figure 2 It is a system diagram of the present invention.

[0017] Figure 3The present invention is a schematic structural diagram of a sewage treatment pool insulation device.

[0018] Figure 4 for Figure 3 sectional view of .

[0019] Figure 5 for Figure 3 Schematic diagram of the transparent thermal insulation film being opened.

[0020] Figure 6 for Figure 3 Structural schematic diagram of the transparent thermal insulation film disassembly structure.

[0021] Figure 7 for Figure 3 Schematic diagram of the structure of the middle roller.

[0022] Figure 8 for Figure 6 Side view of.

[0023] In the above drawings: 1, partition; 2, drainage trough; 11, support rod; 12, transparent thermal insulation film; 13, counterweight rod; 14, winding roller; 15, driving motor; 16, slide; 17, roller; 18, spring piece; 19, guide rod. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings. In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "upper, lower" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description. Unless otherwise stated, these directional words do not indicate or imply that the devices or components referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0025] Embodiment 1: like Figure 1-8 As shown, a reflux control method for sewage treatment based on high total nitrogen and low flow rate includes an inlet end, a regulating tank, a sewage treatment system, an outlet combined tank and an outlet end arranged in sequence, wherein a reflux system to reflux to the regulating tank is arranged between the sewage treatment system and the outlet combined tank, and the control method is used to regulate the reflux system, specifically including the following steps: S1: Calculate the maximum amount of denitrification nitrogen that the sewage treatment system can accept on average per cycle under a low temperature environment ; and combined with the actual outflow flow of the regulating pool , calculate the most conservative maximum allowable total Kjeldahl nitrogen concentration in the sewage treatment system under actual operating conditions ; S2: According to the actual water flow rate of the regulating tank , Reflux Flow And the average liquid level change height of the regulating tank per cycle , calculate the actual average water inflow per cycle , and combined with the total nitrogen concentration in the influent , reflux flow , total nitrogen concentration in effluent As well as the total nitrogen content of the existing sewage in the regulating pool, calculate the total nitrogen concentration of the actual effluent from the regulating pool ; S3: Set the operation cycle. After the operation cycle ends, enter step S4; S4: Determine the maximum allowable total Kjeldahl nitrogen concentration of the influent Compared with the actual total nitrogen concentration of the effluent from the regulating tank and the relationship between the regulating tank liquid level H and the set regulating tank low water level operation liquid level value The relationship between as well as ; S5: When the conditions in step S4 are met at the same time, no reflux is required, and after the next operation cycle ends, enter step S4; S6: When the conditions in step S4 are met ,but When the actual outflow of regulating pool is increased And keep constant, enter the next cycle, and after the end, enter step S4; S7: When there is When the water volume of the regulating pool is increased to , enter the next cycle, and after the end, enter step S4 for judgment.

[0026] In this embodiment, the sewage treatment system includes an anaerobic tank, an anoxic tank, an aerobic tank, a secondary sedimentation tank, and a coagulation final sedimentation tank which are arranged in sequence, wherein a digestion liquid reflux device is arranged between the aerobic tank and the anoxic tank, and a sludge reflux device is arranged between the secondary sedimentation tank and the anaerobic tank, and the secondary sedimentation tank and the coagulation final sedimentation tank are both connected to the sludge treatment system.

[0027] In this embodiment, in step S1, the maximum amount of nitrogen required for denitrification that can be accepted per cycle is The calculation formula is as follows: ; ; ; ; Where: - Calculation volume of hypoxic zone; - Actual volume of the hypoxic zone, ; - Design flow rate of the bioreactor; - Designed total Kjeldahl nitrogen concentration of the influent of the biological reactor; - Designed total nitrogen concentration of effluent from the biological reactor; - Design the maximum allowable total Kjeldahl nitrogen concentration of the influent of the bioreactor under low temperature environment conditions; - The amount of microorganisms discharged from the bioreactor system; , , - Temperature ℃, minimum temperature in winter Denitrification rate at ℃ and 20℃; - Design average concentration of suspended solids in the mixed liquor of the bioreactor; - Design temperature; - Sludge yield coefficient; - Design five-day biochemical oxygen demand concentration of the influent of the biological reactor; - Designed five-day biochemical oxygen demand concentration of the effluent from the biological reactor; The most conservative maximum allowable total Kjeldahl nitrogen concentration in the influent of the sewage treatment system under actual working conditions The calculation formula is as follows: ; Where: - The amount of microorganisms discharged from the bioreactor system, - Designed total nitrogen concentration of effluent from the biological reactor, - Actual water outflow from the regulating tank.

[0028] In this embodiment, in step S2, the actual average water intake per cycle is , the calculation formula is as follows: ; Where: - Actual outflow flow of regulating pool, - Final sedimentation tank effluent return flow (m3 / h), - Length of regulating pool (m), - Width of regulating pool (m), - Average liquid level change in the regulating tank per cycle; Actual total nitrogen concentration of effluent from regulating pond When calculating, dynamic data is used, that is, when calculating the nth cycle When the data collected after n-1 cycles is combined, the following formula is used ; - Average water inflow per cycle in the nth cycle, - During the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - The return flow rate of the final sedimentation tank in the nth cycle, - During the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - Length of regulating pool, - Width of regulating pool, - After the (n-1)th cycle, the regulating tank monitors the liquid level data online. - After the (n-1)th cycle, the actual total nitrogen concentration of the effluent from the regulating pond.

[0029] In this embodiment, in step S7, The calculation of is obtained by the following formula ; (When the liquid level drops or does not change after n cycles) (When the liquid level rises after n cycles) .

[0030] In this embodiment, in step S7, after the next cycle after adjustment, the process goes to step S7 again after the judgment in step S4. Use the maximum value.

[0031] In this embodiment, the water inlet and outlet of the regulating tank are both provided with flow meters and online nitrogen concentration detectors; a liquid level detector is also provided in the regulating tank, and the water outlet of the coagulation final settling tank is provided with a flow meter, an online nitrogen concentration detector and a reflux frequency conversion pump; the water outlet of the outlet combination tank is provided with a flow meter and an online nitrogen concentration detector.

[0032] In this embodiment, the sewage treatment system is also provided with an insulation device, including a plurality of partitions 1 obliquely arranged above the sewage treatment pool, the partitions 1 are connected by support rods 11 arranged parallel to each other, a transparent insulation film 12 is laid above the support rods 11, a section of the partition 1 located above is provided with a winding device for winding the transparent insulation film, a counterweight rod 13 is provided at the free end of the transparent insulation film, and a water temperature sensor is also provided in the sewage treatment pool.

[0033] When in use, the sewage treatment pool has a suitable operating temperature. When the water temperature entering the water is lower than the suitable temperature, the winding device is started and reversed to release the rolled transparent thermal insulation film. Under the action of the counterweight rod, the transparent thermal insulation film is unfolded and covers the sewage treatment pool. When the water temperature reaches the suitable temperature, the winding device is started again to roll up the transparent thermal insulation film and open the sewage treatment pool. The device has a simple structure and can be installed on the basis of an existing open sewage treatment pool. It has low cost, high economic benefits, and is easy to use. It can realize the opening and rolling of the transparent thermal insulation film according to the water temperature.

[0034] In this embodiment, on the basis of the above embodiment, the partition 1 is provided with a perforation, in which a winding roller 14 is rotatably installed through a bearing, the winding roller is wound with the transparent heat-insulating film, the winding roller is in transmission connection with a driving motor 15, and a protective cover is provided above the winding roller and the driving motor. In this way, the driving motor rotates to drive the winding roller to rotate forward and reverse, so as to realize the winding and unwinding of the winding roller, and the transparent heat-insulating film can be automatically rolled up and unfolded, reducing the labor intensity of manual winding and unwinding, and the protective cover can play a protective role, reducing the influence of rain and snow on the winding device.

[0035] In this embodiment, on the basis of the above embodiment, a slide groove 16 is provided on the partition, and rollers 17 are provided at both ends of the counterweight rod, and the rollers are slidably arranged in the slide groove. In this way, when unwinding and rewinding, the rollers can reduce the friction of the transparent thermal insulation film and ensure the smoothness of unwinding and unfolding.

[0036] In this embodiment, on the basis of any of the above embodiments, a transparent heat-insulating film disassembly structure is provided on the winding roller, and the transparent heat-insulating film disassembly structure includes spring pieces 18 uniformly provided on the winding roller, and a guide rod 19 is clamped in the spring piece, and the guide rod is fixedly connected to the transparent heat-insulating film. In this way, when the transparent heat-insulating film is damaged or needs to be replaced regularly, the transparent heat-insulating film is unfolded, and the guide rod is removed from the spring piece, and the entire transparent heat-insulating film can be pulled out and replaced. This method can ensure that the film can be replaced separately under the same power, and the replacement is convenient and efficient.

[0037] In this embodiment, a drainage ditch 2 is provided on the side of the sewage treatment pool. In this way, when the thermal insulation film is in an unfolded state in rainy and snowy days, the accumulated water and snow above can slide along the thermal insulation film into the drainage ditch, which can avoid damage to the film caused by accumulation and will not dirty the surrounding environment.

[0038] In summary, this solution can improve the existing rural and urban sewage treatment equipment and optimize the reflux efficiency, especially under low temperature and reduced treatment activity. It can complete dynamic adjustment, start the reflux at the right time, accurately control the reflux volume, reduce manual participation, and have a high degree of automation. At the same time, it can provide insulation measures and cooperate with the reflux to maximize the reduction of effluent pollutant content.

[0039] Embodiment 2: The precise control of the return flow from the final settling tank outlet tank, the specific process steps from the beginning of the implementation example are as follows: The cycle is 1 hour. (1) “0” - Initial state: the system is not running; the liquid level in the regulating tank is controlled at a low water level The total nitrogen concentration of sewage stored in the pool is .

[0040] (2) “1” - Normal operation: In order to improve the sewage treatment plant’s ability to resist shock loads in winter, the liquid level in the regulating tank should be kept as low as possible; the liquid level should be determined based on the low water level control situation of the regulating tank. The initial value of the system; in the first hour of system operation, the effluent return of the final sedimentation tank is not turned on; the inlet flow rate is The total nitrogen concentration in the inlet water is , regulating pool outflow Determined by the initial value, the liquid level in the regulating tank is .

[0041] First, the most conservative maximum allowable total nitrogen concentration in the sewage treatment system in the first hour is obtained as ; Then calculate the average water inflow Then calculate the total nitrogen concentration of the actual effluent after mixing in the regulating tank at the end of the first hour of system operation. ; Final comparison and ; Use the following formula: ; ; ; ; Judgment logic: Condition ①: ;②: Regulating tank liquid level ;in, It is the artificially set liquid level value for the low water level operation of the regulating tank. Design the maximum water level for the regulating pond.

[0042] When conditions ① and ② are met at the same time, there is no need to open the final sedimentation tank effluent return, the operation remains the same, and the effluent can meet the standard; if conditions ① and ② cannot be met at the same time, control is carried out according to the following steps: (3) “2” - Abnormal situation 1: At the end of the (m-1)th hour, if condition ① is met , but does not meet condition ② , indicating that the outflow of the regulating pool is too small, the liquid level of the regulating pool is on the rise, and there is an overflow risk; then at the mth hour, according to the rising trend of the liquid level, the outflow of the regulating pool is increased to ; The system program will refer to step (2) to re-judge: ; ; ; ; Judgment logic: When , and adjust the pool level There is no need to open the final sedimentation tank effluent return, the operation remains the same, and the effluent can meet the standard; if ,but , repeat step (3).

[0043] (4) “3” - Abnormal situation 2: As the water volume increases , total nitrogen concentration in influent And the water flow rate of the regulating pool The change of total nitrogen concentration in the effluent of the regulating pond will inevitably affect and the maximum allowable total nitrogen concentration in the sewage treatment system ; If at the end of the (n-1)th hour, the first occurrence of not meeting condition ① , it is very likely that the effluent will exceed the standard due to exceeding the treatment capacity of the sewage treatment system. The effluent return pump of the final sedimentation tank needs to be turned on immediately. The return flow rate is At the same time, the outflow rate of the regulating pool needs to be increased ,Right now: ; When the system enters the nth hour of operation, the most conservative maximum allowable total nitrogen concentration in the sewage treatment system at the nth hour can be obtained as , and then calculate the average water inflow Then calculate the total nitrogen concentration of the actual effluent after mixing in the regulating tank at the end of the nth hour of system operation. : ; ; ; ; Judgment logic: Condition ①: After the nth hour, ,Right now: ; In the above formula, If all other data are confirmed, we can find The critical value of Condition ②: After the nth hour, 1) If the liquid level in the regulating tank does not change, ,but ; 2) If the liquid level in the regulating tank drops, ,by Make a judgment, that is: ,but ; 3) If the liquid level in the regulating tank rises, ,by Make a judgment, that is: ,but

[0044] in, .

[0045] <1> If the final sedimentation tank effluent return flow The above two conditions can be met at the same time, namely: According to conditions ① and ②, after the end of the nth hour, there is no risk of the outlet water exceeding the standard; the system operation returns to step (2) and enters the (n+1)th hour.

[0046] <2> If the final sedimentation tank effluent return flow If the above two conditions cannot be met at the same time, Take the maximum value in condition ②; it may not be possible to ensure that the standard is met at the first time, but it can greatly alleviate the water inlet load pressure of the sewage treatment plant, and the effluent water quality will gradually improve until it meets the standard; after meeting the standard, the system operation will return to step (2).

[0047] (5) Similarly, the sewage treatment plant can complete a calculation and determination every hour, and control the return flow rate of the final sedimentation tank through frequency conversion, thereby minimizing the risk of exceeding the standard in the plant and ensuring that the effluent meets the standard.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A reflux control method for sewage treatment based on high total nitrogen and low flow, characterized in that: The invention comprises a water inlet, a regulating tank, a sewage treatment system, a water outlet combination tank and a water outlet, wherein a reflux system for returning water to the regulating tank is arranged between the sewage treatment system and the water outlet combination tank, and the control method is used to regulate the reflux system, and specifically comprises the following steps: S1: Calculate the maximum amount of denitrification nitrogen that the sewage treatment system can accept per cycle under low temperature conditions ; and combined with the actual outflow of the regulating pool , calculate the most conservative maximum allowable total Kjeldahl nitrogen concentration in the sewage treatment system under actual operating conditions ; S2: According to the actual water flow rate of the regulating tank , Reflux Flow And the average liquid level change height of the regulating tank per cycle , calculate the actual average water inflow per cycle , and combined with the total nitrogen concentration in the influent , reflux flow , total nitrogen concentration in effluent As well as the total nitrogen content of the existing sewage in the regulating pool, calculate the total nitrogen concentration of the actual effluent from the regulating pool ; S3: Setting the operation cycle, after the operation cycle ends, proceeding to step S4; S4: Determine the maximum allowable total Kjeldahl nitrogen concentration in the inlet water Compared with the actual total nitrogen concentration of the effluent from the regulating tank and the relationship between the regulating tank liquid level H and the set regulating tank low water level operation liquid level value The relationship between as well as ; S5: When the conditions in the above step S4 are met at the same time, no reflux is required, and after the next operation cycle ends, the process proceeds to step S4; S6: When satisfied ,but When the actual outflow of regulating pool is increased And keep it constant, enter the next cycle, and after the end, enter step S4; S7: When it appears When the water volume of the regulating pool is increased to , enter the next cycle, and after the end, enter step S4 for judgment.

2. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 1, characterized in that: The sewage treatment system comprises an anaerobic tank, an anoxic tank, an aerobic tank, a secondary sedimentation tank, and a coagulation final sedimentation tank which are arranged in sequence, wherein a digestion liquid reflux device is arranged between the aerobic tank and the anoxic tank, and a sludge reflux device is arranged between the secondary sedimentation tank and the anaerobic tank, and the secondary sedimentation tank and the coagulation final sedimentation tank are both connected to the sludge treatment system.

3. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 2, characterized in that: In step S1, the maximum amount of nitrogen required for denitrification that can be accepted per cycle is The calculation formula is as follows: ； ； ； ； Where: - Calculation volume of hypoxic zone; - Actual volume of the hypoxic zone, ; - Design flow rate of the biological reactor; - Designed total Kjeldahl nitrogen concentration of the influent of the biological reactor; - Designed total nitrogen concentration of effluent from the biological reactor; - Design the maximum allowable total Kjeldahl nitrogen concentration of the influent of the bioreactor under low temperature environment conditions; - The amount of microorganisms discharged from the bioreactor system; , , - Temperature ℃, minimum temperature in winter Denitrification rate at ℃ and 20℃; - Design average concentration of suspended solids in the mixed liquor of the bioreactor; - Design temperature; - Sludge yield coefficient; - Design five-day biochemical oxygen demand concentration of the influent of the biological reactor; - Designed five-day biochemical oxygen demand concentration of the effluent from the biological reactor; The most conservative maximum allowable total Kjeldahl nitrogen concentration in the influent of the sewage treatment system under actual working conditions The calculation formula is as follows: ； Where: - The amount of microorganisms discharged from the bioreactor system, - Designed total nitrogen concentration of effluent from the biological reactor, - Actual water outflow from the regulating tank.

4. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 3, characterized in that: In step S2, the actual average water intake per cycle , the calculation formula is as follows: ； Where: - Actual outflow flow of regulating pool, - Final sedimentation tank effluent return flow (m3 / h), - Length of regulating pool (m), - Width of regulating pool (m), - Average liquid level change in the regulating tank per cycle; Actual total nitrogen concentration of effluent from regulating pool When calculating, dynamic data is used, that is, when calculating the nth cycle When the data collected after n-1 cycles is combined, the following formula is used ； - Average water inflow per cycle in the nth cycle, - In the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - The return flow rate of the final sedimentation tank in the nth cycle, - In the nth cycle, the online monitoring equipment automatically samples and detects the total nitrogen data. - Length of regulating pool, - Width of regulating pool, - After the (n-1)th cycle, the regulating tank monitors the liquid level data online. - After the (n-1)th cycle, the actual total nitrogen concentration of the effluent from the equalization tank.

5. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 4, characterized in that: In step S7, The calculation of is obtained by the following formula: ； When the liquid level drops or does not change after n cycles, ; When the liquid level rises after n cycles, ; in, .

6. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 5, characterized in that: In step S7, after the next cycle after adjustment, the process goes to step S7 again after the judgment in step S4. Use the maximum value.

7. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 6, characterized in that: The water inlet and outlet of the regulating tank are both provided with flow meters and nitrogen concentration online detectors; a liquid level detector is also provided in the regulating tank, and the water outlet of the coagulation final sedimentation tank is provided with a flow meter, a nitrogen concentration online detector and a reflux frequency conversion pump; the water outlet of the outlet combined tank is provided with a flow meter and a nitrogen concentration online detector.

8. A reflux control method for sewage treatment based on high total nitrogen and low flow according to claim 7, characterized in that: It includes a plurality of partitions obliquely arranged above the sewage treatment pool, the partitions are connected by support rods arranged parallel to each other, a transparent thermal insulation film is laid above the support rods, a section of the partition located above is provided with a winding device for winding up the transparent thermal insulation film, a counterweight rod is provided at the free end of the transparent thermal insulation film, and a water temperature sensor is also provided in the sewage treatment pool.

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