A reflux control method for sewage treatment based on high total nitrogen and low flow rate

Abstract

The present invention relates to a reflux control method for sewage treatment based on high total nitrogen and low flow rate, which specifically includes the following steps: calculating the maximum denitrifying nitrogen amount that can be accepted per cycle on average by the sewage treatment system under low-temperature environment; the most conservative allowable maximum influent total Kjeldahl nitrogen concentration under actual working conditions of the sewage treatment system; calculating the total nitrogen concentration of the actual effluent from the regulating tank; S3: setting an operating cycle, and entering the next step after the end of the operating cycle; judging the relationship between and, and judging the relationship between the liquid level H of the regulating tank and the set liquid level value for low-level operation of the regulating tank, and controlling different degrees of reflux under different conditions. The present invention has the advantages of stable operation, high treatment efficiency and wide adaptability range.

Description

Technical Field

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

[0002] Affected by the dual influence of low winter temperature and high-concentration influent, design units can only carry out designs by referring to current specifications, guidelines or relying on past experience. However, there are often significant differences between different townships; therefore, even design schemes based on past experience are very likely to be unable to adapt to the actual situation after the completion of drainage facilities, and it is difficult to ensure the effluent quality.

[0003] As the water temperature in winter decreases, the microbial activity and biological reaction rate in activated sludge will both decrease significantly, especially significantly affecting nitrification and denitrification nitrogen removal; at the same time, problems such as sludge bulking are also likely to occur, thus seriously affecting the pollutant removal efficiency, resulting in fluctuations or even exceeding the standard of the effluent quality of the sewage treatment plant; coupled with the high-load influent, the impact of low temperature on the treatment system is greater, further exacerbating these problems.

[0004] We urgently need to find an economically feasible and easily implementable solution. This is not only for environmental protection considerations, but also a necessary condition to ensure the stable operation of township sewage treatment plants and achieve sustainable development. Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned 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 rate, which has stable operation, high treatment efficiency and wide adaptability.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A reflux control method for sewage treatment based on high total nitrogen and low flow rate, including an inlet end, an adjustment tank, a sewage treatment system, an effluent combination tank and an outlet end arranged in sequence, wherein a reflux system for refluxing to the adjustment tank is arranged between the sewage treatment system and the effluent combination tank, and the control method is used to adjust the reflux system, specifically including the following steps: S1: Calculate the maximum denitrification nitrogen demand that can be accepted by the sewage treatment system per cycle on average under low-temperature environment ; and combine with the actual effluent flow rate of the adjustment tank , calculate the most conservative allowable maximum influent total Kjeldahl nitrogen concentration of the sewage treatment system under actual working conditions ; S2: According to the actual effluent flow rate of the adjustment tank , reflux flow rate and the average liquid level change height of the adjustment tank per cycle , calculate the actual average water inflow per cycle , combined with the total influent nitrogen concentration , the reflux flow rate , the total effluent nitrogen concentration , and the total nitrogen content of the existing sewage in the regulating tank, calculate the total nitrogen concentration of the actual effluent from the regulating tank ; S3: Set the operation cycle. After the operation cycle ends, go to step S4; S4: Judge the allowable maximum influent total Kjeldahl nitrogen concentration and the total nitrogen concentration of the actual effluent from the regulating tank , and judge the relationship between the liquid level H of the regulating tank and the set liquid level value for the low-level operation of the regulating tank , and the judgment criteria are and ; S5: When the conditions in step S4 above are simultaneously met, no reflux is required. After the next operation cycle ends, go to step S4; S6: When is satisfied, but , increase the actual effluent flow rate of the regulating tank and keep it constant, enter the next cycle, and after the end, go to step S4; S7: When occurs, start the reflux, and at the same time increase the effluent volume of the regulating tank by on the original basis, enter the next cycle, and after the end, go to step S4 for judgment.

[0008] 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 arranged in sequence. Among them, a digestion liquid reflux device is arranged between the aerobic tank and the anoxic tank, a sludge reflux device is arranged between the secondary sedimentation tank and the anaerobic tank, and both the secondary sedimentation tank and the coagulation final sedimentation tank are connected to the sludge treatment system.

[0009] As an optimization, in step S1, the maximum denitrification nitrogen amount that can be accepted per cycle on average is calculated as follows:

[0010] ;

[0011] ;

[0012] ;

[0013] ;

[0014] In the formula: - Calculated volume of the anoxic zone; - Actual volume of the anoxic zone, ; - Design flow rate of the biological reaction tank; -Total Kjeldahl nitrogen concentration of the influent water designed for the biological reaction tank; -Total nitrogen concentration of the effluent water designed for the biological reaction tank; -Maximum allowable total Kjeldahl nitrogen concentration of the influent water for the biological reaction tank under the designed low-temperature environmental conditions; -Microbial mass discharged from the biological reaction tank system; 、 、 -Denitrification rates at temperatures of ℃, the lowest temperature in winter ℃, and 20℃ respectively; -Designed average concentration of mixed liquor suspended solids in the biological reaction tank; -Designed temperature; -Sludge yield coefficient; -Five-day biochemical oxygen demand concentration of the influent water designed for the biological reaction tank; -Five-day biochemical oxygen demand concentration of the effluent water designed for the biological reaction tank;

[0015] The most conservative maximum allowable total Kjeldahl nitrogen concentration of the influent water for the sewage treatment system under actual working conditions The calculation formula is as follows:

[0016] ;

[0017] In the formula: -Microbial mass discharged from the biological reaction tank system, -Total nitrogen concentration of the effluent water designed for the biological reaction tank, -Actual effluent flow rate of the regulating tank.

[0018] As an optimization, in step S2, the actual average water inflow per cycle The calculation formula is as follows:

[0019] ;

[0020] In the formula: -Actual effluent flow rate of the regulating tank, -Return flow rate of the effluent from the secondary sedimentation tank (m3 / h), -Length of the regulating tank (m), -Width of the regulating tank (m), -Average height change of the liquid level in the regulating tank per cycle;

[0021] Total nitrogen concentration of the actual effluent from the regulating tank During the calculation, dynamic data is used, that is, when calculating the in the nth cycle, the data collected after n - 1 cycles is combined, and the following formula is used

[0022] ;

[0023] - The average water inflow per cycle in the nth cycle, - The total nitrogen data detected by the automatic sampling of the on-line monitoring equipment during the nth cycle, - The return flow rate of the effluent from the final sedimentation tank in the nth cycle, - The total nitrogen data detected by the automatic sampling of the on-line monitoring equipment during the nth cycle, - The length of the regulating tank, - The width of the regulating tank, - The on-line monitoring liquid level data of the regulating tank after the (n - 1)th cycle, - The actual total nitrogen concentration of the effluent from the regulating tank after the (n - 1)th cycle.

[0024] As an optimization, in step S7, is calculated by the following formula

[0025] ;

[0026] When the liquid level drops or remains unchanged after n cycles, ;

[0027] When the liquid level rises after n cycles, ;

[0028] Among them, .

[0029] As an optimization, in step S7, in the next cycle after adjustment, after passing through step S4, it enters step S7 again, The maximum value is adopted.

[0030] As an optimization, flow meters and on-line nitrogen concentration detectors are provided at both the inlet end and the outlet of the regulating tank; a liquid level detector is also provided in the regulating tank, and a flow meter, an on-line nitrogen concentration detector and a reflux variable frequency pump are provided at the outlet end of the coagulation final sedimentation tank; a flow meter and an on-line nitrogen concentration detector are provided at the outlet end of the effluent combination tank.

[0031] As an optimization, it includes a plurality of partitions obliquely arranged above the sewage treatment tank, the partitions are connected by support rods arranged in parallel with each other, a transparent heat preservation film is laid above the support rods, a winding device for winding the transparent heat preservation film is provided at a section of the partition located above, a counterweight rod is provided at the free end of the transparent heat preservation film, and a water temperature sensor is also provided in the sewage treatment tank.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention can be improved on the basis of existing rural and urban sewage treatment equipment to optimize the reflux efficiency. Especially in the case of low temperature and reduced treatment activity, it can complete dynamic adjustment, timely start the reflux, accurately control the reflux volume, reduce manual participation, and has a high degree of automation. At the same time, it provides heat preservation measures to cooperate with the reflux to maximize the reduction of the pollutant content in the effluent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flowchart of a reflux control method for sewage treatment based on high total nitrogen and low flow rate according to the present invention.

[0035] Figure 2 It is a system diagram of the present invention.

[0036] Figure 3 It is a schematic structural diagram of a heat preservation device for a sewage treatment tank according to the present invention.

[0037] Figure 4 It is Figure 3 a cross-sectional view of.

[0038] Figure 5 It is Figure 3 a schematic diagram of the state where the transparent heat preservation film in is opened.

[0039] Figure 6 It is Figure 3 a schematic structural diagram of the disassembly structure of the transparent heat preservation film in.

[0040] Figure 7 It is Figure 3 a schematic structural diagram of the roller in.

[0041] Figure 8 It is Figure 6 a side view of.

[0042] In the above-mentioned drawings: 1, partition board; 2, drainage trough; 11, support rod; 12, transparent heat preservation film; 13, counterweight rod; 14, winding roller; 15, driving motor; 16, chute; 17, roller; 18, elastic sheet; 19, guide rod. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The present invention will be further described in detail below with reference to the drawings. In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the orientation words such as "upper, lower" and "top, bottom" is usually based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description. Without contrary explanation, these orientation words do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the protection scope of the present invention; the orientation words "inner, outer" refer to the inside and outside relative to the contour of each component itself.

[0044] Example 1:

[0045] As Figures 1-8 shown, a reflux control method for sewage treatment based on high total nitrogen and low flow rate includes an inlet end, an adjustment tank, a sewage treatment system, an effluent combination tank, and an outlet end arranged in sequence. A reflux system for refluxing to the adjustment tank is arranged between the sewage treatment system and the effluent combination tank. The control method is used to adjust the reflux system, and specifically includes the following steps: S1: Calculate the maximum denitrifying nitrogen amount that can be accepted by the sewage treatment system per cycle on average under low-temperature environment ; and combine with the actual effluent flow rate of the adjustment tank to calculate the most conservative allowable maximum influent total Kjeldahl nitrogen concentration of the sewage treatment system under actual working conditions ; S2: According to the actual effluent flow rate of the adjustment tank , reflux flow rate , and the average height change of the liquid level in the adjustment tank per cycle , calculate the actual average water inflow per cycle , and combine with the influent total nitrogen concentration , reflux flow rate , effluent total nitrogen concentration , and the existing total nitrogen content of the sewage in the adjustment tank to calculate the total nitrogen concentration of the actual effluent from the adjustment tank ; S3: Set the operation cycle, and after the operation cycle ends, enter step S4; S4: Judge the relationship between the allowable maximum influent total Kjeldahl nitrogen concentration and the total nitrogen concentration of the actual effluent from the adjustment tank , and judge the relationship between the liquid level H of the adjustment tank and the set liquid level value for low-level operation of the adjustment tank . The judgment criteria are and ; S5: When the conditions in step S4 above are simultaneously met, no reflux is required. After the next operation cycle ends, enter step S4; S6: When is satisfied, but , increase the actual effluent flow rate of the adjustment tank and keep it constant, enter the next cycle, and after the end, enter step S4; S7: When occurs, start reflux, and at the same time increase the effluent volume of the adjustment tank by on the original basis, enter the next cycle, and after the end, enter step S4 for judgment.

[0046] 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 arranged in sequence. Among them, a digestion liquid reflux device is arranged between the aerobic tank and the anoxic tank, a sludge reflux device is arranged between the secondary sedimentation tank and the anaerobic tank, and both the secondary sedimentation tank and the coagulation final sedimentation tank are connected to the sludge treatment system.

[0047] In this embodiment, in step S1, the maximum denitrifying nitrogen amount that can be received per cycle on average is calculated as follows:

[0048] ;

[0049] ;

[0050] ;

[0051] ;

[0052] In the formula: -Calculated volume of the anoxic zone; -Actual volume of the anoxic zone, ; -Design flow of the biological reaction tank; -Total Kjeldahl nitrogen concentration of the design influent of the biological reaction tank; -Total nitrogen concentration of the design effluent of the biological reaction tank; -Allowable maximum total Kjeldahl nitrogen concentration of the design influent of the biological reaction tank under the design low-temperature environment condition; -Microbial mass discharged from the biological reaction tank system; , , -Are the denitrification rates at temperatures ℃, the lowest winter temperature ℃ and 20℃ respectively; -Design average concentration of mixed liquid suspended solids in the biological reaction tank; -Design temperature; -Sludge yield coefficient; -Concentration of five-day biochemical oxygen demand of the design influent of the biological reaction tank; -Concentration of five-day biochemical oxygen demand of the design effluent of the biological reaction tank;

[0053] The most conservative allowable maximum total Kjeldahl nitrogen concentration of the sewage treatment system under actual working conditions is calculated as follows:

[0054] ;

[0055] In the formula: -Microbial mass discharged from the biological reaction tank system, -Total nitrogen concentration of the designed effluent from the biological reaction tank -Actual effluent flow rate of the regulating tank

[0056] In this embodiment, in step S2, the actual average water inflow per cycle , and the calculation formula is as follows:

[0057] ;

[0058] In the formula: -Actual effluent flow rate of the regulating tank -Return flow rate of the effluent from the final sedimentation tank (m3 / h) -Length of the regulating tank (m) -Width of the regulating tank (m) -Average height change of the liquid level in the regulating tank per cycle

[0059] Total nitrogen concentration of the actual effluent from the regulating tank When calculating, dynamic data is used, that is, when calculating the in the nth cycle, the data collected after n - 1 cycles is combined, and the following formula is used

[0060] ;

[0061] -Average water inflow per cycle in the nth cycle -Total nitrogen data automatically sampled and detected by the on-line monitoring equipment within the nth cycle -Return flow rate of the effluent from the final sedimentation tank in the nth cycle -Total nitrogen data automatically sampled and detected by the on-line monitoring equipment within the nth cycle -Length of the regulating tank -Width of the regulating tank -On-line monitoring liquid level data of the regulating tank after the (n - 1)th cycle -Total nitrogen concentration of the actual effluent from the regulating tank after the (n - 1)th cycle

[0062] In this embodiment, in step S7, is calculated by the following formula

[0063] ;

[0064] (when the liquid level drops or remains unchanged after n cycles)

[0065] (when the liquid level rises after n cycles)

[0066] .

[0067] In this embodiment, in step S7, in the next cycle after adjustment, after passing through step S4, it enters step S7 again. The maximum value is adopted.

[0068] In this embodiment, flow meters and on-line nitrogen concentration detectors are provided at both the water inlet end and the water outlet of the regulating tank; a liquid level detector is also provided in the regulating tank, and a flow meter, an on-line nitrogen concentration detector and a reflux variable-frequency pump are provided at the water outlet end of the coagulation final sedimentation tank; flow meters and on-line nitrogen concentration detectors are provided at the water outlet end of the effluent combination tank.

[0069] In this embodiment, a heat preservation device is further provided on the sewage treatment system, including a plurality of partition plates 1 inclined above the sewage treatment tank. The partition plates 1 are connected by support rods 11 arranged in parallel with each other. A transparent heat preservation film 12 is laid above the support rods 11. A winding device for winding the transparent heat preservation film is provided at a section of the partition plate 1 located above. A counterweight rod 13 is provided at the free end of the transparent heat preservation film. A water temperature sensor is also provided in the sewage treatment tank.

[0070] During use, when the sewage treatment tank has a suitable operating temperature and the water temperature of the incoming water is lower than the suitable temperature, the winding device is started and runs in the reverse direction to release the wound transparent heat preservation film. Under the action of the counterweight rod, the transparent heat preservation film unfolds and covers the sewage treatment tank. When the water temperature reaches the suitable temperature, the winding device is started again to wind the transparent heat preservation film and open the sewage treatment tank. The structure of this device is simple, it can be installed on the basis of the existing open sewage treatment tank, with low cost, high economic benefits, convenient use, and can realize the opening and winding of the transparent heat preservation film according to the water temperature.

[0071] In this embodiment, on the basis of the above embodiment, through holes are provided on the partition plate 1, and a winding roller 14 is rotatably installed in the through holes through bearings. The transparent heat preservation film is wound around the winding roller. The winding roller is in transmission connection with a driving motor 15. Protective covers are provided above both the winding roller and the driving motor. In this way, the driving motor rotates to drive the winding roller to rotate forward and backward, realizing the winding and unwinding of the winding roller, and can automatically wind up and unfold the transparent heat preservation film, reducing the labor intensity of manual winding and unwinding. The protective cover can play a protective role and reduce the influence of rain, snow and the winding device.

[0072] In this embodiment, on the basis of the above embodiment, a sliding groove 16 is provided on the partition plate, and rollers 17 are provided at both ends of the counterweight rod. The rollers are slidably arranged in the sliding groove. In this way, when unwinding and winding, the rollers can reduce the friction force of the transparent heat preservation film and ensure the smoothness of unwinding and unfolding.

[0073] In this embodiment, based on any of the above embodiments, a disassembly structure for the transparent heat-insulating film is provided on the winding roller. The disassembly structure for the transparent heat-insulating film includes elastic pieces 18 uniformly arranged on the winding roller. A guide rod 19 is clamped inside the elastic 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, the guide rod is removed from the elastic piece, and the entire transparent heat-insulating film can be pulled out and replaced. This method can ensure single replacement under the same power, with convenient replacement and high efficiency.

[0074] In this embodiment, a drainage groove 2 is provided on the side of the sewage treatment tank. In this way, when the heat-insulating film is in the unfolded state during rainy or snowy days, the accumulated water and snow above can slide along the heat-insulating film into the drainage groove, which can not only prevent damage to the film caused by accumulation but also not dirty the surrounding environment.

[0075] To sum up, this solution can be improved on the basis of existing rural and urban sewage treatment equipment, optimize the reflux efficiency, especially in the case of low temperature and reduced treatment activity, complete dynamic adjustment, start reflux in a timely manner, accurately control the reflux volume, reduce manual participation, and have a high degree of automation. At the same time, heat-insulating measures are provided to cooperate with the reflux to maximize the reduction of the content of effluent pollutants.

[0076] Embodiment 2:

[0077] Precise control of the return flow of the final sedimentation tank effluent pool. The specific process steps from the start of use are as follows:

[0078] The cycle is 1 hour for 1 cycle;

[0079] (1) "0" - Initial state: The system is not running; the liquid level of the regulating tank is controlled at a low level , and the total nitrogen concentration of the sewage stored in the tank is .

[0080] (2) "1" - Normal operation: To improve the winter shock load resistance ability of the sewage treatment plant, the liquid level of the regulating tank needs to be kept at a low level as much as possible; determine the initial value of according to the control situation of the low liquid level of the regulating tank; in the first hour of system operation, the return flow of the final sedimentation tank effluent is not started; the influent flow rate is , the total nitrogen concentration of the influent is , the effluent flow rate of the regulating tank is determined according to the initial value, and the liquid level of the regulating tank at the end of 1 hour of system operation is .

[0081] First, obtain the most conservative allowable maximum total nitrogen concentration of the influent of the sewage treatment system in the first hour as ; then calculate the average influent flow rate , 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. ; Finally, compare and ; Use the following formula:

[0082] ;

[0083] ;

[0084] ;

[0085] ;

[0086] Judgment logic: Condition ①: ; ②: The liquid level of the regulating tank ; Among them, is the liquid level value set artificially for the low water level operation of the regulating tank, is the designed maximum water level of the regulating tank.

[0087] When both Condition ① and Condition ② are satisfied, there is no need to start the return of the effluent from the final sedimentation tank, and the operation maintains the current situation, and the effluent can meet the standards; if both Condition ① and Condition ② cannot be satisfied at the same time, then control is carried out according to the following steps:

[0088] (3) "2" - Abnormal situation 1: At the end of the (m - 1)th hour, if Condition ① is satisfied, but Condition ② is not satisfied, it means that the effluent flow rate of the regulating tank is small, the liquid level of the regulating tank shows an upward trend, and there is a risk of overflow; then in the mth hour, increase the effluent flow rate of the regulating tank to according to the upward trend of the liquid level; The system program will re-judge with reference to the steps in the (2)nd step:

[0089] ;

[0090] ;

[0091] ;

[0092] ;

[0093] Judgment logic: When , and the liquid level of the regulating tank , there is no need to start the return of the effluent from the final sedimentation tank, and the operation maintains the current situation, and the effluent can meet the standards; if , but , repeat step (3).

[0094] (4) "3" - Abnormal situation 2: As the influent water volume , Total influent nitrogen concentration and the effluent flow rate of the regulating tank change, which will inevitably affect the total nitrogen concentration of the effluent from the regulating tank and the maximum allowable total nitrogen concentration of the influent to the sewage treatment system ; If at the end of the (n - 1)th hour, condition ① is not satisfied for the first time, it is very likely that the effluent exceeds the standard due to exceeding the treatment capacity of the sewage treatment system. It is necessary to immediately start the effluent reflux pump of the final sedimentation tank, and the reflux flow rate is ; At the same time, the effluent flow rate of the regulating tank needs to be increased by , that is:

[0095] ;

[0096] When the system runs into the nth hour, similarly, the most conservative allowable maximum total nitrogen concentration of the influent to the sewage treatment system in the nth hour can be obtained as , and then the average influent volume is obtained, and then the total nitrogen concentration of the actual effluent after mixing in the regulating tank at the end of the nth hour of the system operation is calculated as :

[0097] ;

[0098] ;

[0099] ;

[0100] ;

[0101] Judgment logic:

[0102] Condition ①: After the end of the nth hour, , that is:

[0103] ;

[0104] In the above formula, except , the others have definite data, then the critical value of can be found;

[0105] Condition ②: After the end of the nth hour,

[0106] 1) If the liquid level of the regulating tank does not change, , then ;

[0107] 2) If the liquid level of the regulating tank drops, , judged by , that is: , then ;

[0108] 3) If the liquid level of the regulating tank rises, , to make a judgment, that is: , then

[0109]

[0110] Among them, .

[0111] <1> If the return flow rate of the effluent from the final sedimentation tank can meet the above two conditions simultaneously, that is: Obtained according to Condition ① and Condition ②. Then after the nth hour ends, there is no risk of exceeding the standard for the effluent; the system operation returns to step (2) again and enters the (n + 1)th hour.

[0112] <2> If the return flow rate of the effluent from the final sedimentation tank cannot meet the above two conditions simultaneously, then take the maximum value in Condition ②; it may not be possible to ensure compliance immediately, but it can greatly relieve the influent load pressure of the sewage treatment plant, and the effluent quality will gradually improve until it meets the standard; after meeting the standard, the system operation will also return to step (2) again.

[0113] (5) And so on, the sewage treatment plant can complete a calculation and determination every hour, and adjust the return flow rate of the effluent from the final sedimentation tank through frequency conversion to minimize the risk of exceeding the standard of the plant and ensure the compliance of the effluent.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by 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 rate, characterized in that, It includes an inlet end, an adjustment tank, a sewage treatment system, an effluent combination tank and an outlet end arranged in sequence. A reflux system for refluxing to the adjustment tank is arranged between the sewage treatment system and the effluent combination tank. The control method is used to adjust the reflux system, and specifically includes the following steps: S1: Calculate the maximum amount of denitrifying nitrogen that can be accepted per cycle on average by the sewage treatment system in a low-temperature environment ; and combine with the actual effluent flow rate of the regulating tank , calculate the most conservative allowable maximum influent total Kjeldahl nitrogen concentration of the sewage treatment system under actual working conditions ; S2: According to the actual effluent flow rate of the equalization tank , the reflux flow rate , and the height change of the average liquid level per cycle in the equalization tank , calculate the actual average water inflow per cycle , and combine it with the total nitrogen concentration of the influent , the reflux flow rate , the total nitrogen concentration of the effluent , and the total nitrogen content of the existing sewage in the equalization tank to calculate the total nitrogen concentration of the actual effluent from the equalization tank ; S3: Set the operation cycle, and after the operation cycle ends, go to step S4; S4: Determine the allowable maximum influent total Kjeldahl nitrogen concentration and the total nitrogen concentration of the actual effluent from the regulating tank and determine the relationship between the liquid level H of the regulating tank and the set liquid level value for the low water level operation of the regulating tank The judgment criteria are and ; S5: When the conditions in step S4 above are satisfied simultaneously, there is no need for reflux. After the next operation cycle ends, go to step S4; S6: When is satisfied, but , increase the actual effluent flow rate of the regulating pond and keep it constant, enter the next cycle, and after the end, enter step S4; S7: When occurs, start the reflux, and at the same time increase the water output of the regulating pond by on the original basis, enter the next cycle, and after the end, enter step S4 for judgment; In step S1, the maximum amount of nitrate nitrogen to be denitrified that can be accepted per cycle on average is calculated as follows: ； ； ； ； In the formula: - Calculated volume of the anoxic zone; - Actual volume of the anoxic zone, ; - Design flow rate of the biological reaction tank; - Total Kjeldahl nitrogen concentration of the influent water designed for the biological reaction tank; - Total nitrogen concentration of the effluent water designed for the biological reaction tank; - Allowable maximum total Kjeldahl nitrogen concentration of the influent water for the biological reaction tank under the designed low-temperature environment condition; - Microbial mass discharged from the biological reaction tank system; 、 、 - Are respectively the denitrification rates at temperatures °C, the lowest temperature in winter °C and 20°C; - Designed average concentration of mixed liquor suspended solids in the biological reaction tank; - Designed temperature; - Sludge yield coefficient; - Five-day biochemical oxygen demand concentration of the influent water designed for the biological reaction tank; - Five-day biochemical oxygen demand concentration of the effluent water designed for the biological reaction tank; The most conservative allowable maximum influent total Kjeldahl nitrogen concentration of the sewage treatment system under actual working conditions The calculation formula is as follows: ； In the formula: - The microbial mass discharged from the biological reaction tank system - The total nitrogen concentration of the designed effluent from the biological reaction tank - The actual effluent flow rate of the regulating tank In step S2, the actual average water inflow per cycle , and the calculation formula is as follows: ； In the formula: - The actual effluent flow rate of the equalization tank - The return flow rate of the effluent from the final sedimentation tank (m3 / h) - The length of the equalization tank (m) - The width of the equalization tank (m) - The average height change of the liquid level in the equalization tank per cycle Total nitrogen concentration of the actual effluent from the regulating tank During the calculation, dynamic data is used, that is, when calculating the of the nth cycle, the data collected after n - 1 cycles is combined, and the following formula is used ； - Average water inflow per cycle in the nth cycle, - Total nitrogen data detected by automatic sampling of the on-line monitoring equipment during the nth cycle, - Return flow rate of the effluent from the final sedimentation tank in the nth cycle, - Total nitrogen data detected by automatic sampling of the on-line monitoring equipment during the nth cycle, - Length of the regulating tank, - Width of the regulating tank, - On-line monitoring liquid level data of the regulating tank after the (n - 1)th cycle, - Actual total nitrogen concentration of the effluent from the regulating tank after the (n - 1)th cycle.

2. The reflux control method for sewage treatment based on high total nitrogen and low flow rate according to claim 1, wherein The sewage treatment system includes an anaerobic tank, an anoxic tank, an aerobic tank, a secondary sedimentation tank, and a coagulation final sedimentation tank arranged in sequence. Among them, a nitrification 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. Both the secondary sedimentation tank and the coagulation final sedimentation tank are connected to the sludge treatment system.

3. A reflux control method for sewage treatment based on high total nitrogen and low flow rate according to claim 1, characterized in that, In step S7, is calculated by the following formula: ； When the liquid level drops or remains unchanged after n cycles, ; When the liquid level rises after n cycles, ; Among them, 。 4. A reflux control method for sewage treatment based on high total nitrogen and low flow rate according to claim 3, characterized in that, In step S7, in the next cycle after adjustment, after passing step S4, it enters step S7 again. The maximum value is selected.

5. A reflux control method for sewage treatment based on high total nitrogen and low flow rate according to claim 4, characterized in that, Flow meters and online nitrogen concentration detectors are arranged at both the inlet end and the outlet of the adjustment tank; a liquid level detector is also arranged in the adjustment tank. A flow meter, an online nitrogen concentration detector and a reflux frequency conversion pump are arranged at the outlet end of the coagulation final sedimentation tank; a flow meter and an online nitrogen concentration detector are arranged at the outlet end of the effluent combination tank.

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