Sewage nitrogen and phosphorus removal system and control method thereof

Abstract

The invention provides a sewage nitrogen and phosphorus removal system and a control method thereof. The sewage nitrogen and phosphorus removal system is provided with a water inlet and a water outlet, and further comprises an anaerobic tank, a front anoxic tank, an aerobic tank, a rear anoxic tank and a vibration filtering membrane tank which are communicated in sequence. The anaerobic tank is communicated with the water inlet, and the vibration filtering membrane tank is communicated with the water outlet. A first return pipeline communicated with each other is arranged between the vibration filtering membrane tank and the front anoxic tank, a second return pipeline communicated with each other is arranged between the aerobic tank and the front anoxic tank, and a third return pipeline communicated with each other is also arranged between the front anoxic tank and the anaerobic tank. The controller can control the actual reflux ratio of the first reflux pipeline to be 200%-300%, the actual reflux ratio of the second reflux pipeline to be 50%-600% and the actual reflux ratio of the third reflux pipeline to be 50%-100%. According to the application, the controller is used for automatically controlling the reflux ratio of each reflux pipeline to be within the range, so that the environmental balance of the anaerobic tank and the front anoxic tank can be maintained, and the nitrogen and phosphorus removal effect of sewage can be improved to reach the first-grade A discharge standard.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and specifically to a sewage denitrification and phosphorus removal system and a control method thereof. Background Art

[0002] At present, the denitrification and phosphorus removal system of urban sewage generally adopts the anaerobic-anoxic-aerobic process, namely the A2O process: phosphorus release reaction occurs in the anaerobic tank, denitrification reaction occurs in the anoxic tank, and nitrification reaction occurs in the aerobic tank. In the denitrification process, denitrifying bacteria use organic matter in the sewage as electron donors in the anoxic tank to denitrify the carbon source in the sewage and the nitrate and nitrite brought from the mixed liquor returned from the aerobic tank to generate nitrogen gas; in the aerobic tank, nitrifying bacteria use oxygen to gradually nitrify the ammonia nitrogen in the sewage to convert it into nitrite and nitrate, providing raw materials for the subsequent denitrification reaction in the anoxic tank to convert the nitrate nitrogen in the sewage into nitrogen gas, thereby achieving the purpose of decarbonization. During the phosphorus removal process, phosphate accumulating organisms (PAOs) convert organic matter such as volatile fatty acids (VFAs) in sewage into internal carbon sources such as polyhydroxyalkanoates (PHAs) in the anaerobic tank and release phosphate. Subsequently, excessive phosphorus absorption reactions occur in the anoxic tank and aerobic tank, thereby achieving the purpose of phosphorus removal.

[0003] However, since the water quality and quantity of urban sewage in different areas usually fluctuate greatly, the process parameters of each unit in the denitrification and phosphorus removal system will also fluctuate due to changes in the sewage influent load, causing the environment of the anaerobic tank and anoxic tank to be greatly affected by the fluctuation of the influent load, thus seriously affecting the denitrification and phosphorus removal effect of the denitrification and phosphorus removal system. Summary of the invention

[0004] The present application provides a sewage denitrification and phosphorus removal system and a control method thereof, which can maintain the environmental balance of an anaerobic tank and a pre-anoxic tank and improve the denitrification and phosphorus removal effect of sewage.

[0005] Specifically, the present application is implemented through the following technical solutions:

[0006] On one hand, the present application provides a sewage denitrification and phosphorus removal system, the sewage denitrification and phosphorus removal system having a water inlet and a water outlet, and the sewage denitrification and phosphorus removal system further comprising:

[0007] A controller and an anaerobic tank, a front anoxic tank, an aerobic tank, a rear anoxic tank and a vibration filtration membrane tank which are connected in sequence; the anaerobic tank is connected to the water inlet, and the vibration filtration membrane tank is connected to the water outlet;

[0008] A first reflux pipeline connected to each other is provided between the vibration filtration membrane pool and the front anoxic pool, and the first reflux pipeline is provided with a first reflux pump; a second reflux pipeline connected to each other is provided between the aerobic pool and the front anoxic pool, and the second reflux pipeline is provided with a second reflux pump; a third reflux pipeline connected to each other is also provided between the front anoxic pool and the anaerobic pool, and the third reflux pipeline is provided with a third reflux pump; the first reflux pump, the second reflux pump and the third reflux pump are all connected to the controller;

[0009] The controller is configured to automatically control the actual reflux ratio of the first reflux pipeline to 200% to 300% through the first reflux pump, automatically control the actual reflux ratio of the second reflux pipeline to 50% to 600% through the second reflux pump, and automatically control the actual reflux ratio of the third reflux pipeline to 50% to 100% through the third reflux pump.

[0010] Optionally, an inlet COD meter and an inlet total nitrogen meter are provided at the water inlet; an outlet total nitrogen meter and an outlet total phosphorus meter are provided at the water outlet; the anaerobic tank is provided with a VFA dosing pump; the inlet COD meter, the inlet total nitrogen meter, the outlet total nitrogen meter, the outlet total phosphorus meter and the VFA dosing pump are all connected to the controller;

[0011] The controller is also configured to automatically control the dosage of the VFA dosing pump based on the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter and the inlet chemical oxygen demand detection value of the inlet COD meter, and the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter and the outlet total phosphorus detection value of the outlet total phosphorus meter and the difference between the sum and the preset outlet total nitrogen target value.

[0012] Optionally, the front anoxic tank is provided with a front anoxic tank nitric nitrogen meter; the aerobic tank is provided with an aerobic tank nitric nitrogen meter; the front anoxic tank nitric nitrogen meter and the aerobic tank nitric nitrogen meter are both connected to the controller;

[0013] The controller is further configured to calculate the maximum denitrification denitrification amount of the front anoxic tank according to the inlet chemical oxygen demand detection value of the inlet COD meter within a first preset time period, and calculate the initial reflux ratio of the second reflux pipeline in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank;

[0014] Then, in a second time period that is shorter than the first preset time period, the reflux ratio correction amount of the second reflux pipeline is calculated according to the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank, and in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank;

[0015] Then, the initial reflux ratio of the second reflux pipeline is corrected according to the reflux ratio correction amount of the second reflux pipeline, so as to automatically control the actual reflux ratio of the second reflux pipeline.

[0016] Optionally, the controller is further configured to automatically control the actual reflux ratio of the third reflux pipeline according to the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank and the preset front anoxic tank target nitric nitrogen value;

[0017] And / or, the aerobic tank is also provided with an aerobic tank MLSS meter, and the aerobic tank MLSS meter is connected to the controller; the controller is also configured to automatically control the actual reflux ratio of the first reflux pipeline according to the sewage suspended solids concentration detection value of the aerobic tank MLSS meter.

[0018] Optionally, the aerobic pool is further provided with an aerobic pool DO meter, an air delivery pipeline and an aerator, and the air delivery pipeline is provided with an air flow regulating component; the aerobic pool DO meter, the aerator and the air flow regulating component are all connected to the controller;

[0019] The controller is further configured to calculate the initial aeration volume of the aerobic tank within a third preset time period according to the water inlet volume, the total nitrogen detection value of the inlet water, the chemical oxygen demand detection value of the inlet water, the maximum denitrification and denitrification volume of the front anoxic tank, and the oxygenation efficiency of the aerator;

[0020] Then, in a fourth time period that is shorter than the third preset time period, the aeration amount correction value of the aerobic pool is calculated according to the dissolved oxygen detection value of the aerobic pool DO meter, the preset dissolved oxygen target value of the aerobic pool, the actual reflux ratio of the second reflux pipeline, and the inlet water temperature;

[0021] Then, the initial aeration volume of the aerobic pool is corrected according to the aeration volume correction value of the aerobic pool, so as to automatically control the actual aeration volume of the aerobic pool.

[0022] Optionally, the hydraulic retention time HRT value of the anaerobic tank is 1 to 1.5 h; the sewage suspended solids concentration MLSS value of the anaerobic tank is 5 to 6 g / L; the nitrate nitrogen content of the anaerobic tank is ≤0.3 mg / L; the dissolved oxygen DO value of the anaerobic tank is ≤0.1 mg / L;

[0023] And / or, the hydraulic retention time HRT value of the front anoxic tank is 4 to 6 hours; the MLSS value of the sewage suspended solids concentration in the front anoxic tank is 10 to 12 g / L; the dissolved oxygen DO value of the front anoxic tank is ≤ 0.1 mg / L;

[0024] And / or, the hydraulic retention time HRT value of the aerobic pool is 4 to 6 hours, the MLSS value of the sewage suspended solids concentration in the aerobic pool is 10 to 12 g / L; the target value of dissolved oxygen in the aerobic pool is 0.3 to 1 mg / L;

[0025] And / or, the hydraulic retention time HRT value of the post-anoxic tank is 2 to 3 hours; the dissolved oxygen DO value of the post-anoxic tank is ≤ 0.1 mg / L;

[0026] And / or, the hydraulic retention time HRT value of the vibrating membrane pool is 1 to 1.5 h; the sewage suspended solids concentration MLSS value of the vibrating membrane pool is 15 to 18 g / L; the membrane vibration frequency of the vibrating membrane pool is 0.4 to 0.6 Hz; the amplitude is 4 to 6 cm; the membrane water production pressure difference of the vibrating membrane pool is 20 to 30 kPa;

[0027] And / or, the total phosphorus of the outlet water is ≤0.5 mg / L, and the total nitrogen of the outlet water is ≤10 mg / L;

[0028] And / or, the sludge retention time of the sewage denitrification and phosphorus removal system is 50 to 60 days.

[0029] On the other hand, the present application also provides a control method for any of the above-mentioned sewage denitrification and phosphorus removal systems, comprising:

[0030] Preliminarily introducing activated sludge into the anaerobic tank, the front anoxic tank, the aerobic tank, the rear anoxic tank and the vibrating membrane tank;

[0031] Control the sewage to flow in from the water inlet, and flow to the anaerobic tank, the front anoxic tank, the aerobic tank, the rear anoxic tank and the vibration filtration membrane tank in sequence for treatment, and discharge the clean water obtained after treatment from the water outlet;

[0032] Control a portion of the sludge in the vibration filtration membrane tank to flow back to the front anoxic tank through the first return pipeline, control a portion of the sludge in the aerobic tank to flow back to the front anoxic tank through the second return pipeline, and control a portion of the sludge in the front anoxic tank to flow back to the anaerobic tank through the third return pipeline;

[0033] Among them, the actual reflux ratio of the first reflux pipeline is 200% to 300%, the actual reflux ratio of the second reflux pipeline is 50% to 600%, and the actual reflux ratio of the third reflux pipeline is 50% to 100%.

[0034] Optionally, the sewage flows to the anaerobic tank for treatment, including:

[0035] The dosage of the VFA dosing pump is automatically controlled according to the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter and the inlet chemical oxygen demand detection value of the inlet COD meter, as well as the difference between the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter and the outlet total phosphorus detection value of the outlet total phosphorus meter and the preset outlet total nitrogen target value.

[0036] Optionally, the control process of the actual reflux ratio of the second reflux pipeline includes:

[0037] First, the maximum denitrification denitrification amount of the front anoxic tank is calculated according to the inlet chemical oxygen demand detection value of the inlet COD meter within the first preset time period, and the initial reflux ratio of the second reflux pipeline is calculated in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank;

[0038] Then, in a second time period that is shorter than the first preset time period, the reflux ratio correction amount of the second reflux pipeline is calculated according to the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank, and in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank;

[0039] Then, the initial reflux ratio of the second reflux pipeline is corrected according to the reflux ratio correction amount of the second reflux pipeline, so as to automatically control the actual reflux ratio of the second reflux pipeline;

[0040] And / or, the control process of the actual reflux ratio of the third reflux pipeline includes: automatically controlling the actual reflux ratio of the third reflux pipeline according to the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank and the preset front anoxic tank target nitric nitrogen value;

[0041] And / or, the control process of the actual reflux ratio of the first reflux pipeline includes: automatically controlling the actual reflux ratio of the first reflux pipeline according to the sewage suspended solids concentration detection value of the MLSS meter of the aerobic tank.

[0042] Optionally, the sewage flows to the aerobic tank for treatment, including:

[0043] First, within a third preset time period, the initial aeration volume of the air delivery pipeline is calculated according to the water inlet volume, the total nitrogen detection value of the inlet water, the chemical oxygen demand detection value of the inlet water, the maximum denitrification denitrification volume of the front anoxic tank, and the oxygenation efficiency of the aerator;

[0044] Then, in a fourth time period that is shorter than the third preset time period, the aeration amount correction value of the air delivery pipeline is calculated according to the dissolved oxygen detection value of the aerobic pool DO meter, the preset aerobic pool dissolved oxygen target value, the actual reflux ratio of the second reflux pipeline, and the inlet water temperature;

[0045] Then, the initial aeration volume of the air conveying pipeline is corrected according to the aeration volume correction value of the air conveying pipeline, so as to automatically control the actual aeration volume of the air conveying pipeline.

[0046] The technical solution provided by this application can achieve the following beneficial effects:

[0047] The present application provides a sewage denitrification and phosphorus removal system and a control method thereof. By utilizing a controller to automatically control the reflow ratio of each reflow pipeline within the above-mentioned range, the environmental balance of the anaerobic tank and the pre-anoxic tank can be maintained, and the denitrification and phosphorus removal effect of the sewage can be improved to meet the first-level emission standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural schematic diagram of a sewage denitrification and phosphorus removal system shown in an exemplary embodiment of the present application.

[0049] Figure numerals: 10, water inlet; 101, water inlet COD meter; 102, water inlet total nitrogen meter; 11, water outlet; 111, water outlet total nitrogen meter; 112, water outlet total phosphorus meter; 12, anaerobic tank; 121, VFA dosing pump; 122, anaerobic tank ORP meter; 13, front anoxic tank; 131, front anoxic tank nitrate meter; 14, aerobic tank; 141, aerobic tank MLSS meter; 142, aerobic tank DO meter; 143, aerobic tank nitrate meter; 15, post anoxic tank; 16, vibrating filter membrane tank; 17, first reflux pipeline; 171, first reflux pump; 18, second reflux pipeline; 181, second reflux pump; 182, air delivery pipeline; 183, air flow regulating component; 19, third reflux pipeline; 191, third reflux pump; 20, controller. DETAILED DESCRIPTION

[0050] The technical solution of the present application will be described in detail below in conjunction with the accompanying drawings.

[0051] Here, the technical solutions in the embodiments (or "implementations") of the present application will be described clearly and completely in conjunction with the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0052] If there are terms involving directional indications or positional relationships in the embodiments of the present application (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings); if the specific posture changes, the directional indication or positional relationship will also change accordingly. In addition, the terms "first", "second", etc. involved in the embodiments of the present application are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance.

[0053] The English letters mentioned in this article have the following meanings: Chemical Oxygen Demand (COD), Oxidation-Reduction Potential (ORP), Mixed Liquor Suspended Solids (MLSS), Hydraulic Retention Time (HRT), and Dissolved Oxygen (DO).

[0054] See also Figure 1 The present application provides a sewage denitrification and phosphorus removal system, which has a water inlet 10 and a water outlet 11, and also includes: a controller 20 and an anaerobic tank 12, a front anoxic tank 13, an aerobic tank 14, a rear anoxic tank 15 and a vibration filtration membrane tank 16 connected in sequence; the anaerobic tank 12 is connected to the water inlet 10, and the vibration filtration membrane tank 16 is connected to the water outlet 11.

[0055] A first return pipe 17 is provided between the vibration filtration membrane pool 16 and the front anoxic pool 13, and the first return pipe 17 is provided with a first return pump 171; a second return pipe 18 is provided between the aerobic pool 14 and the front anoxic pool 13, and the second return pipe 18 is provided with a second return pump 181; a third return pipe 19 is provided between the front anoxic pool 13 and the anaerobic pool 12, and the third return pipe 19 is provided with a third return pump 191; the first return pump 171, the second return pump 181 and the third return pump 191 are all connected to the controller 20.

[0056] The controller 20 is configured to automatically control the actual reflux ratio of the first reflux pipeline 17 to 200% to 300% through the first reflux pump 171, automatically control the actual reflux ratio of the second reflux pipeline 18 to 50% to 600% through the second reflux pump 181, and automatically control the actual reflux ratio of the third reflux pipeline 19 to 50% to 100% through the third reflux pump 191.

[0057] After the sewage enters the anaerobic tank 12 from the water inlet 10, under the anaerobic environment, the polyphosphate bacteria (PAOs) in the pre-living sludge in the anaerobic tank 12 decompose the polyphosphate compounds accumulated in the body to release a part of the energy, which is used for the polyphosphate bacteria (PAOs) to convert the volatile fatty acids (VFAs) in the sewage into internal carbon sources PHAs and store them in the body, and release phosphates into the sewage. The sewage treated by the anaerobic tank 12 enters the pre-anoxic tank 13 for denitrification reaction. Under the action of the denitrifying bacteria in the pre-living sludge in the pre-anoxic tank 13, the organic matter in the sewage and the PHAs stored in the cells are used as carbon sources to reduce the nitrate and nitrite returned from the aerobic tank 14 to nitrogen gas, so as to achieve the purpose of denitrification. Since the sludge in the pre-anoxic tank 13 contains a certain amount of polyphosphate bacteria (PAOs), by returning part of the sludge to the anaerobic tank 12 through the third return line 19, the sludge concentration in the anaerobic tank 12 can be maintained and the phosphorus release efficiency can be improved. The sewage treated by the front anoxic tank 13 enters the aerobic tank 14. The aerobic microorganisms in the pre-living sludge in the aerobic tank 14 decompose the remaining organic matter in the sewage into inorganic matter such as carbon dioxide and water. A certain type of nitrifying bacteria in the pre-living sludge in the aerobic tank 14 converts the ammonia nitrogen in the sewage into nitrite, and another type of nitrifying bacteria continues to oxidize nitrite into nitrate, and returns part of the nitrite and nitrate in the sludge to the front anoxic tank 13 through the second return line 18, and the other part of the nitrite and nitrate flows into the rear anoxic tank 15 together with the sewage to continue the denitrification reaction, which can reduce the return ratio of the second return line 18 to a certain extent and reduce the sewage treatment cost. Under the action of the denitrifying bacteria in the pre-living sludge in the rear anoxic tank 15, the organic matter in the sewage is used as a carbon source to reduce the nitrate and nitrite flowing from the aerobic tank 14 to nitrogen gas to achieve the purpose of denitrification. The sewage treated in the post-anoxic tank 15 enters the vibrating membrane tank, where the solid suspended matter and water in the sewage are separated by filtration and vibration of the membrane, and the separated clean water is discharged from the outlet 11 to achieve the purpose of purifying the water quality. Since the sludge remaining after filtration in the vibrating membrane tank contains a certain amount of organic matter, nitrate and nitrite, by returning part of the sludge in the vibrating membrane tank to the pre-anoxic tank 13 through the first loop pipeline, sufficient carbon source and nitrate can be provided for denitrifying bacteria, thereby promoting the denitrification reaction and improving the denitrification efficiency.

[0058] Affected by the impact force of sewage, the sludge concentration in the anaerobic tank 12 and the front anoxic tank 13 decreases as the sewage treatment time increases, resulting in instability of the anaerobic and anoxic environments, and the denitrifying bacteria in the front anoxic tank 13 use the sewage carbon source at a slow rate, resulting in incomplete reactions. By limiting the reflux ratio of the second reflux line 18 within the above range, the present application can allow as much sewage carbon source as possible to be used by denitrifying bacteria in the front anoxic tank to avoid oxidation and waste in the aerobic tank 14, while avoiding the reflux ratio being too large, causing the dissolved oxygen in the aerobic tank 14 to be brought into the anoxic tank, thereby affecting the rate at which denitrifying bacteria use the sewage carbon source. And by limiting the reflux ratio of the first reflux line 17 within the above range, sufficient carbon sources and nitrates can be provided for denitrifying bacteria, promoting the denitrification reaction and improving the decarbonization efficiency. By limiting the return ratio of the third return pipe 19 within the above range, the anaerobic tank 12 can be maintained at a high sludge concentration, so that the abundance of denitrification and phosphorus removal bacteria is high and the biomass is sufficient, while the nitrate and dissolved oxygen in the front anoxic tank 13 can be prevented from entering the anaerobic tank 12 as much as possible.

[0059] It should be noted that the vibrating membrane pool is an anoxic environment, and a membrane bioreactor (MBR) is usually used. A membrane vibrator connected to the biofilm is installed on the membrane bioreactor, and the vibration effect of the biofilm is controlled by adjusting the frequency and amplitude of the membrane vibrator, so as to achieve the purpose of controlling membrane fouling and increasing membrane flux. Among them, the membrane vibrator includes but is not limited to a piezoelectric vibrator or an electromagnetic membrane vibrator. In addition, the sludge concentration in the vibrating membrane pool is usually maintained at 12-18 g / L.

[0060] In one embodiment, the water inlet 10 is provided with an inlet COD meter 101 and an inlet total nitrogen meter 102; the water outlet 11 is provided with an outlet total nitrogen meter 111 and an outlet total phosphorus meter 112; the anaerobic tank 12 is provided with a VFA dosing pump 121; the inlet COD meter 101, the inlet total nitrogen meter 102, the outlet total nitrogen meter 111, the outlet total phosphorus meter 112 and the VFA dosing pump 121 are all connected to the controller 20.

[0061] The controller 20 is also configured to automatically control the dosage of the VFA dosing pump 121 based on the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter 102 and the inlet chemical oxygen demand detection value of the inlet COD meter 101, and the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter 111 and the outlet total phosphorus detection value of the outlet total phosphorus meter 112 and the difference between the sum and the preset outlet total nitrogen target value.

[0062] For urban sewage with a low carbon element C / nitrogen element N ratio, insufficient organic matter content will lead to low phosphorus release, which in turn causes low subsequent phosphorus absorption, and the biological phosphorus removal effect is difficult to guarantee. Therefore, chemical agents need to be added for chemical phosphorus removal to meet the effluent phosphorus standard. In order to achieve the effluent total phosphorus standard, most of the existing actual water plants excessively add iron and aluminum chemical phosphorus removal agents to the system to assist in phosphorus removal. The high content of iron and aluminum salts in the sludge seriously inhibits the activity of denitrification and phosphorus removal microorganisms, resulting in the weakening or even disappearance of the biological phosphorus removal effect. In addition, chemical phosphorus removal produces a large amount of chemical sludge, which increases the cost of sludge disposal.

[0063] The above scheme can promote the synthesis of internal carbon source by polyphosphate bacteria in the anaerobic section by automatically and accurately controlling the dosage of VFA dosing pump 121, and can also avoid excessive dosage of the dosing to react with phosphate ions in the activated sludge to form precipitation, thereby avoiding the inhibition of microbial surface activity and affecting the effect of anaerobic phosphorus release of microorganisms, and achieving stable effluent total phosphorus reaching Class A standard (TP≤0.5mg / L) by strengthening biological phosphorus removal. In addition, it also avoids the adverse effects of reduced biological activity, increased sludge disposal costs, and accelerated membrane pollution caused by the large-scale addition of iron, aluminum and other dephosphorization drugs.

[0064] It should be noted that the drugs added by the VFA dosing pump 121 include but are not limited to sludge fermentation liquid such as sodium acetate or acetic acid.

[0065] For example, the dosage of the VFA dosing pump 121 can be calculated according to the following formula (1):

[0066] C t =α(βTN i -COD i )+β(TN e +γTP e -TN t ) (1)

[0067] Among them, C t is the dosage of VFA dosing pump 121 (mg / L); TN i is the total nitrogen detection value of the influent (mg / L); COD i TN is the COD value of the influent chemical oxygen demand; e is the total nitrogen detection value of the effluent (mg / L); TP e TN is the total phosphorus test value of effluent; t It is the preset effluent total nitrogen target value (mg / L).

[0068] In one embodiment, TN tThe value can be 15, of course, you can also select any value that meets the first-level emission standards, and it is not limited to this; α, β, γ are proportional coefficients. For example, based on actual process debugging experience, it can be determined that the value range of α is 1.05-1.45, the value range of β is 4.1-8.5, and the value range of γ is 5.5-10.5.

[0069] In one embodiment, the front anoxic tank 13 is provided with a front anoxic tank nitric nitrogen meter 131; the aerobic tank 14 is provided with an aerobic tank nitric nitrogen meter 143; the front anoxic tank nitric nitrogen meter 131 and the aerobic tank nitric nitrogen meter 143 are both connected to the controller 20.

[0070] The controller 20 is also configured to calculate the maximum denitrification denitrification amount of the front anoxic tank 13 according to the inlet chemical oxygen demand detection value of the inlet COD meter 101 within a first preset time period, and calculate the initial reflux ratio of the second reflux pipeline 18 in combination with the terminal nitric nitrogen detection value of the aerobic tank nitric nitrogen meter 143.

[0071] Then, within a second time period that is smaller than the first preset time period, the reflux ratio correction amount of the second reflux pipeline 18 is calculated based on the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the front anoxic tank nitric nitrogen meter 131, and combined with the terminal nitric nitrogen detection value of the aerobic tank nitric nitrogen meter 143.

[0072] Then, the initial reflux ratio of the second reflux pipeline 18 is corrected according to the reflux ratio correction amount of the second reflux pipeline 18 to automatically control the actual reflux ratio of the second reflux pipeline 18 .

[0073] Therefore, the actual reflux ratio of the second reflux pipeline 18 can be accurately controlled through the correction process to achieve the purpose of accurately controlling the nitrate-nitrogen value of the front anoxic tank 13, and the environmental stability of the anoxic tank and the aerobic tank 14 can be maintained in the case of water inlet load fluctuations.

[0074] Exemplarily, first, the controller 20 calculates the initial reflux ratio of the second reflux pipeline 18 according to the following formula (2) within a first preset time period, for example, every 2 hours based on the influent water quality and the nitrate nitrogen concentration in the aerobic tank:

[0075]

[0076] Wherein, R2 is the initial reflux ratio of the second reflux pipeline 18; DN p is the maximum denitrification capacity of the front anoxic pool 13 (mg / L); N o It is the terminal nitrate nitrogen detection value (mg / L) of the aerobic tank nitrate nitrogen meter 143.

[0077] Then, the controller 20 adjusts the initial reflux ratio of the second reflux pipeline 18 once in a second preset time period that is less than the first preset time period, for example, every 0.5 h, according to the nitric nitrogen concentration in the front anoxic tank according to the reflux ratio correction amount of the second reflux pipeline 18 calculated according to the following formula (3) to obtain the actual reflux ratio of the second reflux pipeline 18:

[0078]

[0079] Wherein, ΔR2 is the reflux ratio correction amount of the second reflux pipeline 18; N t The target nitrate value for the former anoxic pool 13; N a is the nitrate detection value at the end of the anoxic pool 13 (mg / L); N o It is the terminal nitrate nitrogen detection value (mg / L) of the aerobic tank nitrate nitrogen meter 143.

[0080] It should be noted that the anaerobic tank 12 is also provided with an anaerobic tank ORP meter 122, and the target nitrate nitrogen value of the front anoxic tank 13 is set to be within the range of -200 to -250 according to the ORP detection value of the anaerobic tank ORP meter 122. The maximum denitrification denitrification amount of the front anoxic tank 13 can be estimated according to the influent COD concentration and the denitrification COD / N ratio. Among them, the denitrification COD / N ratio refers to the mass of organic matter required for the unit mass of nitrogen consumed in the denitrification process, and the value range is generally 2.86 to 5.0.

[0081] In one embodiment, the controller 20 is further configured to automatically control the actual return ratio of the third return pipe 19 according to the terminal nitrate nitrogen detection value of the front anoxic tank nitrate nitrogen meter 131 and the preset target nitrate nitrogen value of the front anoxic tank 13. Thus, the actual return ratio of the third return pipe 19 can be accurately controlled to maintain the environmental stability of the anaerobic tank 12 and the front anoxic tank 13 in the case of water inlet load fluctuations.

[0082] For example, the actual reflux ratio R3 of the third reflux pipeline 19 can be determined in real time according to the nitrate nitrogen detection amount N of the front anoxic tank 13 at every time period. a ≤ 13 target nitrate value N in the front anoxic pool t , determine the reflow ratio R3 is 100%, the current nitric nitrogen detection amount N in the anoxic pool 13 a > Target nitrate value N in front anoxic pool 13 t , determine the reflux ratio R3 to be 50%.

[0083] In one embodiment, the aerobic tank 14 is further provided with an aerobic tank MLSS meter 141, and the aerobic tank MLSS meter 141 is connected to the controller 20; the controller 20 is also configured to automatically control the actual return ratio of the first return pipe 17 according to the sewage suspended solids concentration detection value of the aerobic tank MLSS meter 141. Thus, the actual return ratio of the first return pipe 17 can be accurately controlled to maintain the environmental stability of the pre-anaerobic anoxic tank 13 in the case of water inlet load fluctuations.

[0084] Exemplarily, the actual reflux ratio R1 of the first reflux pipeline 17 can be determined in real time according to the MLSS detection value of the aerobic tank at intervals. For example, when the MLSS detection value of the aerobic tank is ≤ the MLSS preset threshold value, such as 10 g / L, the reflux ratio R1 is determined to be 300%, and when the MLSS detection value of the aerobic tank is > the MLSS preset threshold value, such as 10 g / L, the reflux ratio R1 is determined to be 200%.

[0085] In one embodiment, the aerobic tank 14 is further provided with an aerobic tank DO meter 142 , an air delivery pipeline 182 and an aerator, and the air delivery pipeline 182 is provided with an air flow regulating component 183 ; the aerobic tank DO meter 142 , the aerator and the air flow regulating component 183 are all connected to the controller 20 .

[0086] The controller 20 is also configured to calculate the initial aeration volume of the aerobic tank 14 within a third preset time period based on the water inlet volume of the water inlet 10, the inlet total nitrogen detection value, the inlet chemical oxygen demand detection value, the maximum denitrification and denitrification volume of the front anoxic tank 13, and the oxygenation efficiency of the aerator.

[0087] Then, within a fourth time period that is less than the third preset time period, the aeration amount correction value of the aerobic tank 14 is calculated based on the dissolved oxygen detection value of the aerobic tank DO meter 142, the preset aerobic tank dissolved oxygen target value, the actual return ratio of the second return pipe 18, and the inlet water temperature.

[0088] Then, the initial aeration volume of the aerobic pool 14 is corrected according to the aeration volume correction value of the aerobic pool 14 , so as to automatically control the actual aeration volume of the aerobic pool 14 .

[0089] Therefore, the controller 20 can accurately control the actual aeration volume of the aerobic pool 14 in real time through the aerator and the air flow regulating component 183, and provide sufficient dissolved oxygen to the aerobic pool 14 by aeration, so that the DO concentration of the aerobic pool 14 reaches the target range of 0.3 to 1 mg / L.

[0090] It should be noted that the air flow regulating component may be a fan or a valve, but is not limited thereto.

[0091] Exemplarily, first, the controller 20 calculates the aeration rate of the aerobic pool 14 once every 2 hours within the third preset time period according to the following formula (4):

[0092]

[0093] Among them, Q t is the initial aeration volume of the aerobic pool 14; Q is the influent volume (m 3 / h); COD i The COD value of the influent chemical oxygen demand; DN p is the maximum denitrification capacity of the front anoxic pool 13 (mg / L); TN i is the total nitrogen detection value of the influent (mg / L); E a is the aerator oxygenation efficiency (%).

[0094] Then, the controller 20 adjusts the initial aeration volume of the aerobic pool 14 once in a fourth preset time period that is less than the third preset time period, for example, every 15 minutes, according to the aeration volume correction amount of the aerobic pool 14 calculated by the following formula (5), to obtain the actual aeration volume of the aerobic pool 14:

[0095]

[0096] Among them, ΔQ t is the aeration correction value of the aerobic tank 14 (m 3 / h); DO t is the DO target value of the aerobic pool; DO o is the DO test value of the aerobic pool (mg / L); θ do is the temperature coefficient of dissolved oxygen, which is 1.15; t is the water temperature of sewage (℃).

[0097] In one embodiment, the hydraulic retention time HRT value of the anaerobic tank 12 is 1-1.5h; the sewage suspended solids concentration MLSS value of the anaerobic tank 12 is 5-6g / L; the nitrate nitrogen content of the anaerobic tank 12 is ≤0.3mg / L; the dissolved oxygen DO value of the anaerobic tank 12 is ≤0.1mg / L.

[0098] In one embodiment, the hydraulic retention time HRT value of the front anoxic tank 13 is 4 to 6 hours; the sewage suspended solids concentration MLSS value of the front anoxic tank 13 is 10 to 12 g / L; the dissolved oxygen DO value of the front anoxic tank 13 is ≤0.1 mg / L.

[0099] In one embodiment, the hydraulic retention time HRT value of the aerobic tank 14 is 4-6 hours, the sewage suspended solids concentration MLSS value of the aerobic tank 14 is 10-12 g / L; the dissolved oxygen target value of the aerobic tank 14 is 0.3-1 mg / L.

[0100] In one embodiment, the hydraulic retention time HRT value of the post-anoxic tank 15 is 2 to 3 hours; the dissolved oxygen DO value of the post-anoxic tank 15 is ≤0.1 mg / L.

[0101] In one embodiment, the hydraulic retention time HRT value of the vibrating membrane pool is 1 to 1.5h; the MLSS value of the sewage suspended solids concentration of the vibrating membrane pool is 15 to 18g / L; the membrane vibration frequency of the vibrating membrane pool is 0.4 to 0.6Hz; the amplitude is 4 to 6cm; the membrane water production pressure difference of the vibrating membrane pool is 20 to 30kPa. In one embodiment, the membrane vibration frequency and the membrane water production pressure difference are linearly related, that is, the membrane vibration frequency = f*membrane water production pressure difference, f is a constant set according to experience, and illustratively, the value range of f is 0.015 to 0.03. In this way, the sewage filtration effect of the vibrating membrane pool can be guaranteed as much as possible.

[0102] In one embodiment, the total phosphorus in the outlet water of the water outlet 11 is ≤0.5 mg / L, and the total nitrogen in the outlet water of the water outlet 11 is ≤10 mg / L.

[0103] In one embodiment, the sludge retention time (SRT) of the sewage denitrification and phosphorus removal system is 50 to 60 days.

[0104] On the other hand, the present application also provides a control method for a sewage denitrification and dephosphorization system as described above, comprising:

[0105] S1. Preliminarily introduce activated sludge into the anaerobic tank, the front anoxic tank, the aerobic tank, the post anoxic tank and the vibrating membrane tank.

[0106] S2. Control the sewage to flow in from the water inlet and flow to the anaerobic tank, the front anoxic tank, the aerobic tank, the rear anoxic tank and the vibration filtration membrane tank in sequence for treatment, and discharge the clean water obtained after treatment from the water outlet.

[0107] S3. Control a portion of the sludge in the vibration filtration membrane tank to flow back to the front anoxic tank through the first return pipe, control a portion of the sludge in the aerobic tank to flow back to the front anoxic tank through the second return pipe, and control a portion of the sludge in the front anoxic tank to flow back to the anaerobic tank through the third return pipe.

[0108] Among them, the actual reflux ratio of the first reflux pipeline is 200% to 300%, the actual reflux ratio of the second reflux pipeline is 50% to 600%, and the actual reflux ratio of the third reflux pipeline is 50% to 100%.

[0109] It should be noted that activated sludge refers to a mixture of various microorganisms, organic matter and inorganic matter, usually taken from the activated sludge produced by urban sewage treatment plants.

[0110] In one embodiment, in step S2, the sewage flows to the anaerobic tank for treatment, including:

[0111] The dosage of the VFA dosing pump is automatically controlled according to the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter and the inlet chemical oxygen demand detection value of the inlet COD meter, as well as the difference between the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter and the outlet total phosphorus detection value of the outlet total phosphorus meter and the preset outlet total nitrogen target value.

[0112] In one embodiment, in step S3, the control process of the actual reflux ratio of the second reflux pipeline includes:

[0113] First, the maximum denitrification denitrification amount of the front anoxic tank is calculated according to the inlet chemical oxygen demand detection value of the inlet COD meter within the first preset time period, and the initial reflux ratio of the second reflux pipeline is calculated in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter in the aerobic tank.

[0114] Then, within a second time period that is smaller than the first preset time period, the reflux ratio correction amount of the second reflux pipeline is calculated based on the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the front anoxic tank nitric nitrogen meter, and combined with the terminal nitric nitrogen detection value of the aerobic tank nitric nitrogen meter.

[0115] Then, the initial reflux ratio of the second reflux pipeline is corrected according to the reflux ratio correction amount of the second reflux pipeline, so as to automatically control the actual reflux ratio of the second reflux pipeline.

[0116] In one embodiment, the control process of the actual reflux ratio of the third reflux pipeline includes: automatically controlling the actual reflux ratio of the third reflux pipeline according to the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank and the preset front anoxic tank target nitric nitrogen value.

[0117] In one embodiment, the control process of the actual reflux ratio of the first reflux pipeline includes: automatically controlling the actual reflux ratio of the first reflux pipeline according to the sewage suspended solids concentration detection value of the MLSS meter of the aerobic tank.

[0118] In one embodiment, in step S2, the sewage flows to the aerobic tank for treatment, including:

[0119] First, within a third preset time period, the initial aeration volume of the air delivery pipeline is calculated based on the water inlet volume, the inlet total nitrogen detection value, the inlet chemical oxygen demand detection value, the maximum denitrification denitrification volume of the front anoxic tank, and the oxygenation efficiency of the aerator.

[0120] Then, within a fourth time period that is less than the third preset time period, the aeration amount correction value of the air delivery pipeline is calculated based on the dissolved oxygen detection value of the aerobic tank DO meter, the preset aerobic tank dissolved oxygen target value, the actual reflux ratio of the second reflux pipeline, and the inlet water temperature.

[0121] Then, the initial aeration volume of the air conveying pipeline is corrected according to the aeration volume correction value of the air conveying pipeline, so as to automatically control the actual aeration volume of the air conveying pipeline.

[0122] For the specific process of the control method in each of the above embodiments, please refer to the content description of the above sewage denitrification and phosphorus removal system, and no further details will be given here.

[0123] The following will take the actual pilot plant as an example. The effective volume of the anaerobic tank is 1.5m 3 The effective volume of the front anoxic pool is 6m 3 The effective volume of the aerobic pool is 6m 3 The effective volume of the anoxic pool is 3m 3 The effective volume of the vibrating membrane pool is 1.4m 3 Each pool is pre-filled with activated sludge from the sewage treatment plant, and the amount of sewage treated is 24m 3 / d. The inlet water quality is shown in Table 1, and the inlet water temperature is 12-28°C (Note: the inlet water quality will fluctuate greatly due to seasonality, which may easily cause fluctuations in the biochemical unit parameters of anaerobic, anoxic and aerobic tanks).

[0124] Table 1 Actual influent water concentration range for pilot test

[0125] index Influent COD Influent ammonia nitrogen Total nitrogen in influent Total phosphorus in influent Range (mg / L) 100.5～445.5 15.1～45.3 20.6～55 1.5～6.5

[0126] Example 1

[0127] (1) When the instrument detects that the inlet COD value of the sewage is 200 mg / L, the inlet total nitrogen value is 32 mg / L, the effluent total nitrogen value is 7 mg / L, and the effluent total phosphorus value is 0.3 mg / L, and the effluent total nitrogen target value is set to 12 mg / L, α is 1.2, β is 5.5, and γ is 6. The signal is transmitted to the controller for calculation, and the inlet COD / total nitrogen is calculated to be about 6.3. The maximum denitrification denitrification capacity DN of the front anoxic tank is estimated based on the inlet COD value and the denitrification COD / N ratio. p It is 20mg / L.

[0128] The dosage of VFAs is calculated according to the following formula:

[0129] C t =α(βTN i -COD i )+β(TN e +γTP e -TN t )

[0130] The calculated VFAs dosage is -46.4. Since the calculated VFA dosage is lower than 0, the controller program takes the value of 0, that is, the initial VFA dosage = 0.

[0131] At certain intervals, such as 30 minutes, the controller can re-acquire the various detection values ​​of the above instruments and re-calculate the real-time dosage according to the above process for accurate monitoring.

[0132] (2) The initial reflux ratio of the second reflux pipeline is calculated according to the following formula:

[0133]

[0134] The reflux ratio correction of the second reflux pipeline is calculated according to the following formula:

[0135]

[0136] Assume that the MLSS value of the aerobic pool is detected at the beginning of the cycle 2h = 9.5g / L, and the nitrate detection value N at the end of the aerobic pool is o =5mg / L, the nitrate nitrogen detection value at the end of the front anoxic pool N a =2mg / L, target nitrate value N in the anoxic pool t =2.5mg / L, then the initial reflux ratio of the second reflux pipeline is calculated to be R2=400%, and the reflux ratio correction amount of the second reflux pipeline is ΔR2=0.5, that is, the actual reflux ratio of the second reflux pipeline is controlled to be R2=450% according to the reflux ratio correction amount of the second reflux pipeline. a =2mg / L<2.5mg / L, the return ratio from the front anoxic tank to the anaerobic tank R3=100%, the MLSS of the aerobic tank is<10g / L, and the return ratio from the membrane tank to the anoxic tank R1=300%.

[0137] After another 0.5h interval, the MLSS value of the aerobic pool was detected to be 9.8g / L, and the nitrate nitrogen detection value at the end of the aerobic pool was N o =5mg / L, the nitrate nitrogen detection value at the end of the front anoxic pool N a =2.3mg / L, target nitrate value N in the anoxic pool t=2.5mg / L. After receiving the corresponding detection value signal, the controller recalculates the reflux ratio correction amount ΔR2=0.2 of the second reflux pipeline according to the above formula, that is, adjusts the actual reflux ratio of the second reflux pipeline to R2=470%, and R1 and R3 remain unchanged.

[0138] At intervals of 2 hours, the sewage inlet data at the water inlet and the instrument detection data of each tank are transmitted to the controller, and the actual return ratio of each return pipeline is recalculated according to the above process.

[0139] (3) The controller periodically calculates the aeration volume and controls the fan adjustment. The calculation method is as follows:

[0140] The controller calculates the initial aeration volume of the aerobic pool every 2 hours according to the following formula:

[0141]

[0142] The controller calculates the aeration correction value of the aerobic pool every 15 minutes according to the following formula:

[0143]

[0144] Assume that the influent COD value is 200 mg / L, the influent total nitrogen is 32 mg / L, and the aerobic pool DO is t =0.8mg / L, DO o =0.5mg / L, R2=450%, water temperature t=18℃. Controller calculates DN p The maximum denitrification capacity of the anoxic tank is 20 mg / L. 3 / h, oxygenation efficiency E a =10%, calculate the aeration volume Q t =5.9m3 / h, aeration correction ΔQ t =1.9m 3 / h, that is, the fan air volume is controlled to 7.8m 3 / h.

[0145] When the interval is 15min, the DO of the aerobic pool is detected o =0.7mg / L, R2=400%. After receiving the corresponding detection value signal, the controller starts to calculate the aeration volume correction value ΔQ t =0.5m 3 / h, that is, the fan air volume is controlled to 8.3m 3 / h.

[0146] At intervals of 2 hours, the sewage inlet data and the instrument detection data of each pool are transmitted to the controller, and the aeration volume is recalculated.

[0147] Example 2

[0148] When the meter detects that the inlet COD of the sewage is 180mg / L, the inlet total nitrogen is 35mg / L, the inlet total phosphorus is 4mg / L, the effluent total nitrogen is 8.8mg / L, the effluent total phosphorus is 0.382mg / L, and the effluent total nitrogen target value is set to 12, α is 1.2, β is 5.5, and γ is 6, the dosage is calculated to be 10 according to the above dosage formula. And the inlet COD / total nitrogen is calculated to be 5.1.

[0149] Therefore, VFAs = 10 mgCOD / L is first added to the anaerobic tank through the dosing pump. Denitrifying polyphosphate bacteria (DPAOs) and denitrifying polysaccharide bacteria (DGAOs) use VFAs in the system to synthesize internal carbon sources. Denitrifying polyphosphate bacteria (DPAOs) and other phosphorus release about 16 mg / L (set according to experience) in the anaerobic tank, and the total phosphorus concentration in the anaerobic tank increases. Then, the nitrate nitrogen returned from the front anoxic tank is removed by denitrification, and the total nitrogen concentration decreases. Denitrifying polyphosphate bacteria (DPAOs) remove nitrogen and phosphorus simultaneously in the front anoxic tank by denitrification and phosphorus removal, and the denitrification phosphorus removal is about 8 mg / L. Denitrifying bacteria use sewage carbon sources to remove total nitrogen, and the total nitrogen and total phosphorus concentrations in the front anoxic tank both decrease. The polyphosphate bacteria in the aerobic pool absorb phosphorus to remove about 11.5 mg / L of total phosphorus, and the total nitrogen remains unchanged. Endogenous denitrification mainly occurred in the post-anoxic tank and the vibrating membrane tank, and the total nitrogen was further reduced. The removal of nitrogen and phosphorus in each reaction tank along the process is shown in Table 2.

[0150] Table 2 Total nitrogen and phosphorus removal in each reaction tank along the process

[0151]

[0152] After being processed by Example 1 and Example 2, the total nitrogen in the effluent was finally detected to be 9 mg / L, and the total phosphorus in the effluent was 0.4 mg / L, reaching the Class A emission standard.

[0153] It should be noted that the technical solutions or technical features described in the above embodiments can be combined or supplemented with each other without causing conflicts. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the drawings; all modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A sewage denitrification and phosphorus removal system, the sewage denitrification and phosphorus removal system having a water inlet and a water outlet, characterized in that: The sewage denitrification and phosphorus removal system also includes: A controller and an anaerobic tank, a front anoxic tank, an aerobic tank, a rear anoxic tank and a vibration filtration membrane tank which are connected in sequence; the anaerobic tank is connected to the water inlet, and the vibration filtration membrane tank is connected to the water outlet; A first reflux pipeline connected to each other is provided between the vibration filtration membrane pool and the front anoxic pool, and the first reflux pipeline is provided with a first reflux pump; a second reflux pipeline connected to each other is provided between the aerobic pool and the front anoxic pool, and the second reflux pipeline is provided with a second reflux pump; a third reflux pipeline connected to each other is also provided between the front anoxic pool and the anaerobic pool, and the third reflux pipeline is provided with a third reflux pump; the first reflux pump, the second reflux pump and the third reflux pump are all connected to the controller; The controller is configured to automatically control the actual reflux ratio of the first reflux pipeline to 200% to 300% through the first reflux pump, automatically control the actual reflux ratio of the second reflux pipeline to 50% to 600% through the second reflux pump, and automatically control the actual reflux ratio of the third reflux pipeline to 50% to 100% through the third reflux pump.

2. The sewage denitrification and phosphorus removal system according to claim 1, characterized in that: The water inlet is provided with an inlet COD meter and an inlet total nitrogen meter; the water outlet is provided with an outlet total nitrogen meter and an outlet total phosphorus meter; the anaerobic tank is provided with a VFA dosing pump; the inlet COD meter, the inlet total nitrogen meter, the outlet total nitrogen meter, the outlet total phosphorus meter and the VFA dosing pump are all connected to the controller; The controller is also configured to automatically control the dosage of the VFA dosing pump based on the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter and the inlet chemical oxygen demand detection value of the inlet COD meter, and the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter and the outlet total phosphorus detection value of the outlet total phosphorus meter and the difference between the sum and the preset outlet total nitrogen target value.

3. The sewage denitrification and phosphorus removal system according to claim 2, characterized in that: The front anoxic tank is provided with a front anoxic tank nitric nitrogen meter; the aerobic tank is provided with an aerobic tank nitric nitrogen meter; the front anoxic tank nitric nitrogen meter and the aerobic tank nitric nitrogen meter are both connected to the controller; The controller is further configured to calculate the maximum denitrification denitrification amount of the front anoxic tank according to the inlet chemical oxygen demand detection value of the inlet COD meter within a first preset time period, and calculate the initial reflux ratio of the second reflux pipeline in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank; Then, in a second time period that is shorter than the first preset time period, the reflux ratio correction amount of the second reflux pipeline is calculated according to the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank, and in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank; Then, the initial reflux ratio of the second reflux pipeline is corrected according to the reflux ratio correction amount of the second reflux pipeline, so as to automatically control the actual reflux ratio of the second reflux pipeline.

4. The sewage denitrification and phosphorus removal system according to claim 3, characterized in that: The controller is also configured to automatically control the actual reflux ratio of the third reflux pipeline according to the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank and the preset front anoxic tank target nitric nitrogen value; And / or, the aerobic tank is also provided with an aerobic tank MLSS meter, and the aerobic tank MLSS meter is connected to the controller; the controller is also configured to automatically control the actual reflux ratio of the first reflux pipeline according to the sewage suspended solids concentration detection value of the aerobic tank MLSS meter.

5. The sewage denitrification and phosphorus removal system according to claim 3, characterized in that: The aerobic pool is also provided with an aerobic pool DO meter, an air delivery pipeline and an aerator, and the air delivery pipeline is provided with an air flow regulating component; the aerobic pool DO meter, the aerator and the air flow regulating component are all connected to the controller; The controller is further configured to calculate the initial aeration volume of the aerobic tank within a third preset time period according to the water inlet volume, the total nitrogen detection value of the inlet water, the chemical oxygen demand detection value of the inlet water, the maximum denitrification and denitrification volume of the front anoxic tank, and the oxygenation efficiency of the aerator; Then, in a fourth time period that is shorter than the third preset time period, the aeration amount correction value of the aerobic pool is calculated according to the dissolved oxygen detection value of the aerobic pool DO meter, the preset aerobic pool dissolved oxygen target value, the actual reflux ratio of the second reflux pipeline, and the inlet water temperature; Then, the initial aeration volume of the aerobic pool is corrected according to the aeration volume correction value of the aerobic pool, so as to automatically control the actual aeration volume of the aerobic pool.

6. The sewage denitrification and phosphorus removal system according to claim 5, characterized in that: The hydraulic retention time HRT value of the anaerobic tank is 1 to 1.5 hours; the MLSS value of the sewage suspended solids concentration in the anaerobic tank is 5 to 6 g / L; the nitrate nitrogen content in the anaerobic tank is ≤0.3 mg / L; the dissolved oxygen DO value in the anaerobic tank is ≤0.1 mg / L; And / or, the hydraulic retention time HRT value of the front anoxic tank is 4 to 6 hours; the MLSS value of the sewage suspended solids concentration in the front anoxic tank is 10 to 12 g / L; the dissolved oxygen DO value of the front anoxic tank is ≤0.1 mg / L; And / or, the hydraulic retention time HRT value of the aerobic pool is 4 to 6 hours, the MLSS value of the sewage suspended solids concentration in the aerobic pool is 10 to 12 g / L; the target value of dissolved oxygen in the aerobic pool is 0.3 to 1 mg / L; And / or, the hydraulic retention time HRT value of the post-anoxic tank is 2 to 3 hours; the dissolved oxygen DO value of the post-anoxic tank is ≤ 0.1 mg / L; And / or, the hydraulic retention time HRT value of the vibrating membrane pool is 1 to 1.5 h; the sewage suspended solids concentration MLSS value of the vibrating membrane pool is 15 to 18 g / L; the membrane vibration frequency of the vibrating membrane pool is 0.4 to 0.6 Hz; the amplitude is 4 to 6 cm; the membrane water production pressure difference of the vibrating membrane pool is 20 to 30 kPa; And / or, the total phosphorus of the outlet water is ≤0.5 mg / L, and the total nitrogen of the outlet water is ≤10 mg / L; And / or, the sludge retention time of the sewage denitrification and phosphorus removal system is 50 to 60 days.

7. A control method for a sewage denitrification and dephosphorization system according to any one of claims 1 to 6, characterized in that: include: Preliminarily introducing activated sludge into the anaerobic tank, the front anoxic tank, the aerobic tank, the rear anoxic tank and the vibrating membrane tank; Control the sewage to flow in from the water inlet, and flow to the anaerobic tank, the front anoxic tank, the aerobic tank, the rear anoxic tank and the vibration filtration membrane tank in sequence for treatment, and discharge the clean water obtained after treatment from the water outlet; Control a portion of the sludge in the vibration filtration membrane tank to flow back to the front anoxic tank through the first return pipeline, control a portion of the sludge in the aerobic tank to flow back to the front anoxic tank through the second return pipeline, and control a portion of the sludge in the front anoxic tank to flow back to the anaerobic tank through the third return pipeline; Among them, the actual reflux ratio of the first reflux pipeline is 200% to 300%, the actual reflux ratio of the second reflux pipeline is 50% to 600%, and the actual reflux ratio of the third reflux pipeline is 50% to 100%.

8. The control method according to claim 7, characterized in that: The sewage flows to the anaerobic tank for treatment, which includes: The dosage of the VFA dosing pump is automatically controlled according to the difference between the inlet total nitrogen detection value of the inlet total nitrogen meter and the inlet chemical oxygen demand detection value of the inlet COD meter, as well as the difference between the sum of the outlet total nitrogen detection value of the outlet total nitrogen meter and the outlet total phosphorus detection value of the outlet total phosphorus meter and the preset outlet total nitrogen target value.

9. The control method according to claim 8, characterized in that: The control process of the actual reflux ratio of the second reflux pipeline includes: First, the maximum denitrification denitrification amount of the front anoxic tank is calculated according to the inlet chemical oxygen demand detection value of the inlet COD meter within the first preset time period, and the initial reflux ratio of the second reflux pipeline is calculated in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank; Then, in a second time period that is shorter than the first preset time period, the reflux ratio correction amount of the second reflux pipeline is calculated according to the difference between the preset front anoxic tank target nitric nitrogen value and the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank, and in combination with the terminal nitric nitrogen detection value of the nitric nitrogen meter of the aerobic tank; Then, the initial reflux ratio of the second reflux pipeline is corrected according to the reflux ratio correction amount of the second reflux pipeline, so as to automatically control the actual reflux ratio of the second reflux pipeline; And / or, the control process of the actual reflux ratio of the third reflux pipeline includes: automatically controlling the actual reflux ratio of the third reflux pipeline according to the terminal nitric nitrogen detection value of the nitric nitrogen meter of the front anoxic tank and the preset front anoxic tank target nitric nitrogen value; And / or, the control process of the actual reflux ratio of the first reflux pipeline includes: automatically controlling the actual reflux ratio of the first reflux pipeline according to the sewage suspended solids concentration detection value of the MLSS meter of the aerobic tank.

10. The control method according to claim 8, characterized in that: The sewage flows to the aerobic pool for treatment, which includes: First, within a third preset time period, the initial aeration volume of the air delivery pipeline is calculated according to the water inlet volume, the total nitrogen detection value of the inlet water, the chemical oxygen demand detection value of the inlet water, the maximum denitrification denitrification volume of the front anoxic tank, and the oxygenation efficiency of the aerator; Then, in a fourth time period that is shorter than the third preset time period, the aeration amount correction value of the air delivery pipeline is calculated according to the dissolved oxygen detection value of the aerobic pool DO meter, the preset aerobic pool dissolved oxygen target value, the actual reflux ratio of the second reflux pipeline, and the inlet water temperature; Then, the initial aeration volume of the air conveying pipeline is corrected according to the aeration volume correction value of the air conveying pipeline, so as to automatically control the actual aeration volume of the air conveying pipeline.

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