Deep denitrification system and method for river and lake water body

Abstract

The invention belongs to the technical field of sewage treatment, and provides a deep denitrification system and method for a river and lake water body, and the system comprises a vacuum deaerator which is provided with a water inlet valve and a diversion valve; the upper part of the autotrophic nitrogen removal filter tank is connected with the vacuum oxygen eliminator through a water diversion pipeline, and the water diversion valve is arranged on the water diversion pipeline; the vacuumizer is respectively connected with the vacuum deaerator and the autotrophic nitrogen removal filter tank through a first vacuumizing pipeline and a second vacuumizing pipeline, and is respectively provided with a first vacuum valve and a second vacuum valve; the water outlet pump is connected with the lower part of the autotrophic nitrogen removal filter tank, and the water outlet valve and the water outlet pump are connected in series on the water outlet pipeline. The method is a deep denitrification method based on the system. According to the system and the method, the inhibition effect of high dissolved oxygen of natural water on the autotrophic denitrification nitrogen removal technology is solved, the nitrogen removal treatment of river and lake water by using the autotrophic denitrification nitrogen removal technology is realized, an organic carbon source and an oxygen scavenger do not need to be added, the operation energy consumption is low, the nitrogen removal effect is good, the operation is stable, and the risk of secondary pollution is small.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to a system and method for deep denitrification of river and lake water bodies. Background Art

[0002] Nitrogen pollutants are the main cause of eutrophication of water bodies and are important control indicators for water bodies. When the total nitrogen in the water exceeds a certain limit, there is a risk of eutrophication. Under suitable temperature and other conditions, it may lead to the rapid reproduction of algae and other plankton, causing a decrease in dissolved oxygen in the water body and deterioration of water quality. At present, the sources of nitrogen in water mainly include: non-point source pollution caused by the use of pesticides and fertilizers in agricultural activities and livestock and poultry farming, centralized discharge from municipal and industrial sewage treatment facilities, overflow sewage from the drainage system when rainwater and sewage are combined during rainfall, and the release of endogenous nitrogen and phosphorus in sediments in lakes and slow-flowing water bodies. In recent years, with the implementation of a series of policies and regulations, the treatment level and emission standards of my country's sewage treatment facilities have been significantly improved, and the total nitrogen discharged into environmental water bodies by existing sewage treatment plants is strictly controlled. However, total nitrogen pollution caused by agricultural non-point source pollution, overflow sewage and endogenous release still significantly affects the water quality of rivers and lakes, especially in some villages and towns that do not have sound sewage collection and treatment facilities. Due to unreasonable sewage discharge and agricultural non-point source pollution, the total nitrogen in some rivers can even reach 5~10 mg / L, and the water body has seriously deteriorated, greatly affecting the living environment and bringing potential health risks. Therefore, such water bodies need to be purified. With the inclusion of total nitrogen in the assessment indicators of key river basin sections and coastal river basin sections in recent years, higher requirements have been placed on the water quality of river and lake water bodies, and the total nitrogen assessment limit for some sections has reached 2 mg / L.

[0003] At present, the control methods for total nitrogen pollutants in river and lake water bodies mainly include source control, ecological restoration and water purification. Among them, the implementation cycle of ecological restoration technology is often long. In the face of rivers and lakes with prominent water pollution, water purification technology must be adopted to quickly reduce the risk of eutrophication. Water purification technology mainly includes two categories: bypass treatment and in-situ treatment. Among them, bypass treatment technology is to extract or introduce polluted water into an artificial branch, and through external treatment devices and artificial wetlands, ecological ditches, facilities and building components with filter beds or contact reaction functions set up on the branch, the pollutants are reduced and discharged back to the original water body. In-situ treatment mainly uses biological floating islands placed in the water body, suspended fillers and combined ecological restoration technologies to reduce total nitrogen.

[0004] The denitrification filter technology based on the principle of sulfur autotrophic denitrification has certain advantages in water denitrification treatment because it does not require an external organic carbon source, greatly reduces operating costs, has a high treatment depth, is simple to operate, has a wide range of adaptability, and can simultaneously remove suspended pollutants in the water body. However, when using bypass treatment technology to reduce total nitrogen in river and lake water bodies, it is often necessary to face the high dissolved oxygen situation in natural water bodies. The dissolved oxygen in the water body can reach 8~10 mg / L, which will have a significant inhibitory effect on anaerobic denitrifying microorganisms. Therefore, it seriously restricts the promotion and application of sulfur autotrophic denitrification technology in the treatment of natural river and lake water bodies. Summary of the invention

[0005] In view of the defects of the above-mentioned prior art, the present invention aims to provide a system and method for deep denitrification of river and lake water bodies, so as to solve the inhibitory effect of high dissolved oxygen in natural water bodies on autotrophic denitrification technology, and realize the denitrification treatment of river and lake water bodies using autotrophic denitrification technology, without the need to add organic carbon sources and oxygen scavengers, with low operating energy consumption, good denitrification effect, stable operation, and low risk of secondary pollution.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A deep denitrification system for river and lake water bodies, comprising: The vacuum deoxidizer has a water inlet valve at its water inlet end and a water diversion valve at its water outlet end; An autotrophic denitrification filter tank, the upper water inlet of which is connected to the water outlet of the vacuum deoxidizer via a water diversion pipeline, and the water diversion valve is arranged on the water diversion pipeline; A vacuum pump, connected to the vacuum deoxidizer and the autotrophic denitrification filter tank via a first vacuum pumping pipeline and a second vacuum pumping pipeline, respectively, a first vacuum valve is provided on the first vacuum pumping pipeline, and a second vacuum valve is provided on the second vacuum pumping pipeline; A water outlet pump is connected to the water outlet end of the lower part of the autotrophic denitrification filter tank through a water outlet pipeline. A water outlet valve is arranged on the water outlet pipeline and is connected in series with the water outlet pump.

[0007] In one embodiment of the present application, it also includes a water outlet tank and a backwash pipeline; the water outlet tank is connected to the water outlet pipeline; one end of the backwash pipeline is connected to the water outlet tank, and the other end is connected to the lower part of the autotrophic denitrification filter tank, and a backwash water inlet valve and a backwash flowmeter are provided on the backwash pipeline; the upper part of the autotrophic denitrification filter tank is provided with an air inlet valve and a backwash discharge valve; and / or, It also includes a lifting pump, which is connected to the vacuum deoxidizer via a water inlet pipeline, and the lifting pump is linked to the water inlet valve.

[0008] In one embodiment of the present application, it also includes an inlet flowmeter, a diversion flowmeter and an outlet flowmeter; the inlet flowmeter is arranged on the water inlet pipeline of the vacuum deoxidizer and is connected in series with the water inlet valve; the diversion flowmeter is arranged on the diversion pipeline and is connected in series with the diversion valve; the outlet flowmeter is arranged on the outlet pipeline and is connected in series with the outlet pump and the outlet valve.

[0009] In one embodiment of the present application, it also includes a first liquid level meter installed in the vacuum deoxidizer and a second liquid level meter installed in the autotrophic denitrification filter tank, wherein the first liquid level meter is used to monitor the working liquid level in the vacuum deoxidizer and is linked with the water inlet valve, the lifting pump, and the water diversion valve; the second liquid level meter is used to monitor the working liquid level in the autotrophic denitrification filter tank and is linked with the water diversion valve, the water outlet valve, and the water outlet pump; and / or, It also includes a first vacuum meter installed on the vacuum deoxidizer and a second vacuum meter installed on the autotrophic denitrification filter. The first vacuum meter is used to monitor the vacuum degree in the vacuum deoxidizer and is linked to the vacuum pump and the first vacuum valve; the second vacuum meter is used to monitor the vacuum degree in the autotrophic denitrification filter and is linked to the vacuum pump and the second vacuum valve.

[0010] In one embodiment of the present application, a first overflow valve is provided at the top of the vacuum deoxidizer, and a drain valve is provided at the bottom; a second overflow valve is provided at the top of the autotrophic denitrification filter tank, and the second overflow valve is located below the air inlet valve, and the backwash discharge valve is located below the second overflow valve and above the denitrification carrier filler layer.

[0011] A method for deep denitrification of river and lake water bodies, using any of the above-mentioned deep denitrification systems for river and lake water bodies, comprises the following steps: S1, under non-vacuum conditions, introduce water into the vacuum deoxidizer and the autotrophic denitrification filter to the overflow level; S2, evacuating the vacuum deoxidizer and the autotrophic denitrification filter tank to a first vacuum degree, and evacuating the vacuum deoxidizer to a second vacuum degree, wherein the second vacuum degree is higher than the first vacuum degree; S3, continuously introducing water into the vacuum deaerator and the autotrophic denitrification filter, and maintaining the vacuum degree in the vacuum deaerator and the autotrophic denitrification filter in dynamic balance between the first vacuum degree and the second vacuum degree, so that the water body is subjected to vacuum degassing and autotrophic denitrification treatment, and the water body after treatment in the autotrophic denitrification filter is pumped out and discharged.

[0012] In one embodiment of the present application, one or more of the following are also included: The first vacuum degree is a relative vacuum degree of -0.05 to -0.08 MPa, and the second vacuum degree is a relative vacuum degree of -0.06 to -0.09 MPa; The liquid level in the vacuum deoxidizer is higher than the liquid level in the autotrophic denitrification filter, and the liquid level difference between the vacuum deoxidizer and the autotrophic denitrification filter is ≤100 cm; The liquid level of the autotrophic denitrification filter is higher than the liquid level of the outlet tank, and the liquid level difference between the autotrophic denitrification filter and the outlet tank is ≤300 cm.

[0013] In one embodiment of the present application, in step S2, the vacuum deoxidizer and the autotrophic denitrification filter are vacuumized to a first vacuum degree, and the autotrophic denitrification filter is vacuumized to a second vacuum degree, specifically comprising: S21, close the water inlet valve, the water diversion valve, the water outlet valve, the first overflow valve of the vacuum deoxidizer, and the second overflow valve of the autotrophic denitrification filter; S22, open the first vacuum valve, the second vacuum valve and the vacuum pump, close the first vacuum valve and the water diversion valve when the first vacuum degree is reached, and close the second vacuum valve and the vacuum pump when the second vacuum degree is reached.

[0014] In one embodiment of the present application, step S3 also includes the following steps: S301, setting a working liquid level upper limit value, a working liquid level lower limit value and a working liquid level setting value for the vacuum deoxidizer and the autotrophic denitrification filter tank; When the working liquid level in the vacuum deaerator is higher than the upper limit of the working liquid level, the water inlet valve and the lifting pump are closed, and when the working liquid level reaches the working liquid level setting value, the water inlet valve and the lifting pump are reopened; when the working liquid level in the vacuum deaerator is lower than the lower limit of the working liquid level, the water diversion valve is closed, and when the working liquid level reaches the working liquid level setting value, the water diversion valve is reopened; When the working liquid level in the autotrophic denitrification filter is higher than the working liquid level upper limit, the water diversion valve is closed, and when the working liquid level reaches the working liquid level setting value, the water diversion valve is reopened; when the working liquid level in the autotrophic denitrification filter is lower than the working liquid level lower limit, the water outlet pump and the water outlet valve are closed, and when the working liquid level reaches the working liquid level setting value, the water outlet pump and the water outlet valve are reopened; S302, setting a lower limit value of working vacuum and a setting value of working vacuum for the vacuum deoxidizer and the autotrophic denitrification filter; When the vacuum degree in the vacuum deoxidizer is lower than the lower limit of the working vacuum degree, the vacuum pump is started, the first vacuum valve is opened, and after the vacuum degree reaches the set value of the working vacuum degree, the first vacuum valve is closed and the vacuum pump is closed; When the vacuum degree in the autotrophic denitrification filter is lower than the lower limit of the working vacuum degree, the vacuum pump is started, the second vacuum valve is opened, and after the vacuum degree reaches the working vacuum degree setting value, the second vacuum valve and the vacuum pump are closed.

[0015] In one embodiment of the present application, when step S3 is run for a period of time and the autotrophic denitrification filter needs to be nitrogen driven or backwashed, the following steps are also included: S4, nitrogen removal procedure: close the water inlet valve, the water diversion valve and the water outlet valve, open the backwash water inlet valve at the bottom of the autotrophic denitrification filter, and allow the water body to flow backward from bottom to top through the denitrification carrier filler layer under the action of negative pressure to remove nitrogen. After reaching the set nitrogen removal time or the set nitrogen removal liquid level, close the backwash water inlet valve, open the water outlet valve and the water outlet pump, and when the working liquid level reaches the working liquid level setting value, close the water outlet pump and the water outlet valve; if the vacuum degree is lower than the lower limit of the working vacuum degree, open the second vacuum valve and the vacuum pump, and when the vacuum degree reaches the working vacuum degree setting value, close the second vacuum valve and the vacuum pump; and repeat step S3; S5, backwash procedure: close the water inlet valve, the water diversion valve and the water outlet valve, open the backwash water inlet valve at the bottom of the autotrophic denitrification filter, and under the action of negative pressure, the water body flows backward from bottom to top through the denitrification carrier filler layer for backwashing. After reaching the set backwash time or the backwash set liquid level, close the backwash water inlet valve, open the air inlet valve on the upper part of the autotrophic denitrification filter, break the vacuum, and open the backwash discharge valve to discharge the upper backwash sewage; after the discharge is completed, close the air inlet valve and the backwash discharge valve; open the second vacuum valve and the vacuum pump, and open the backwash water inlet valve at the same time. When the working liquid level reaches the working liquid level setting value, close the backwash water inlet valve. After the vacuum reaches the working vacuum setting value, close the second vacuum valve and the vacuum pump; repeat step S3.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The system and method for deep denitrification of river and lake water bodies of the present invention are provided with a vacuum deoxidizer and an autotrophic denitrification filter tank, both of which are connected to a vacuum pump. The vacuum deoxidizer and the autotrophic denitrification filter tank can be evacuated simultaneously or separately, so that the vacuum deoxidizer and the autotrophic denitrification filter tank are both in a negative pressure state. The water body after deoxygenation treatment in the vacuum deoxidizer can be continuously sucked into the autotrophic denitrification filter tank by controlling the difference in vacuum degree (the vacuum degree of the vacuum deoxidizer is lower than the vacuum degree of the autotrophic denitrification filter tank), which can reduce the need to set a water diversion pump at the water outlet of the vacuum deoxidizer, saving equipment investment and operating costs; at the same time, the dissolved oxygen concentration of the water body in the autotrophic denitrification filter tank is extremely low under negative pressure conditions, which can avoid the occurrence of water reoxygenation, effectively promote the biological reaction of autotrophic denitrification, and improve the denitrification efficiency. The system can effectively solve the inhibitory effect of high dissolved oxygen in the water to be treated on the autotrophic denitrification denitrification technology, and realize the application of autotrophic denitrification denitrification technology in the denitrification treatment of river and lake water bodies. There is no need to add organic carbon sources and oxygen scavengers during the treatment process. It has low operating energy consumption, good denitrification effect, stable operation and low risk of secondary pollution.

[0017] 2. The deep denitrification system for river and lake water bodies of the present invention does not need to be equipped with a backwash water pump because the autotrophic denitrification filter tank is in a negative pressure state when working. Under the action of atmospheric pressure, the water from the outlet pool can flow back into the autotrophic denitrification filter tank to backwash or denitrify the denitrification carrier filler layer, saving equipment cost and operating energy consumption and simple control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a structural block diagram of the deep denitrification system for river and lake water bodies in Example 1 of the present invention.

[0020] Figure 2 This is a structural block diagram of the deep denitrification system for river and lake water bodies in Example 2 of the present invention.

[0021] Figure 3 This is a structural block diagram of the deep denitrification system for river and lake water bodies in Example 3 of the present invention.

[0022] Figure 4 This is a flow chart of the deep denitrification method for river and lake water bodies in Example 4 of the present invention.

[0023] Reference numerals: 1. Water inlet pipeline; 2. Water diversion pipeline; 3. Water outlet pipeline; 41. First vacuum pumping pipeline; 42. Second vacuum pumping pipeline; 5. Backwash pipeline. DETAILED DESCRIPTION

[0024] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0025] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0029] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Example 1

[0032] The embodiment of the present invention provides a system for deep denitrification of river and lake water bodies, which is suitable for denitrification treatment of natural river and lake water bodies, such as Figure 1 As shown, the system includes a vacuum deoxidizer, an autotrophic denitrification filter, a vacuum pump and a water outlet pump.

[0033] The vacuum deoxidizer is a closed container, with a water inlet valve at the water inlet end and a water diversion valve at the water outlet end. The water inlet valve and the water diversion valve can be adjusted to open, close and adjust the opening size to control the water flow.

[0034] The autotrophic denitrification filter is a closed container, and its interior is divided into a water inlet area, a filler area, and a water and air distribution area from top to bottom. Its water inlet end is arranged in the upper water inlet area, and the water outlet end is arranged in the bottom water and air distribution area. The filler area is filled with denitrification carriers and inoculated with autotrophic denitrifying microorganisms. The water inlet end of the upper part of the autotrophic denitrification filter is connected to the water outlet end of the vacuum deoxidizer through a water diversion pipeline 2, and a water diversion valve is installed on the water diversion pipeline 2.

[0035] The vacuum pump is connected to the vacuum deoxidizer and the autotrophic denitrification filter tank via the first vacuum pumping pipeline 41 and the second vacuum pumping pipeline 42, respectively, and the first vacuum pumping pipeline 41 is provided with a first vacuum valve, and the second vacuum pumping pipeline 42 is provided with a second vacuum valve. The vacuum pump can vacuum the vacuum deoxidizer and the autotrophic denitrification filter tank separately or simultaneously. The vacuum pump can adopt a water ring vacuum pump, a rotary vane vacuum pump or a Roots vacuum pump.

[0036] The outlet pump is connected to the outlet end of the lower part of the autotrophic denitrification filter tank through the outlet pipe 3. The outlet pipe 3 is provided with an outlet valve in parallel with the outlet pump, and the outlet valve and the outlet pump are linked. The outlet pump is a variable frequency flow pump for drawing out the water after denitrification treatment by the autotrophic denitrification filter tank.

[0037] The deep denitrification system for river and lake water bodies is equipped with a vacuum deoxidizer and an autotrophic denitrification filter tank, both of which are connected to a vacuum pump. The vacuum deoxidizer and the autotrophic denitrification filter tank can be evacuated simultaneously or separately, so that both the vacuum deoxidizer and the autotrophic denitrification filter tank are in a negative pressure state. The water after deoxygenation in the vacuum deoxidizer can be continuously pumped into the autotrophic denitrification filter tank by controlling the difference in vacuum degree (the vacuum degree of the vacuum deoxidizer is lower than that of the autotrophic denitrification filter tank), which can reduce the need to set a water diversion pump at the water outlet of the vacuum deoxidizer and save equipment investment and operating costs. At the same time, the dissolved oxygen concentration in the water of the autotrophic denitrification filter tank is extremely low under negative pressure conditions, which can avoid the occurrence of water reoxygenation, effectively promote the biological reaction of autotrophic denitrification and improve the denitrification efficiency.

[0038] Example 2

[0039] like Figure 2 As described above, the deep denitrification system for river and lake water bodies provided in this embodiment further includes a water outlet pool and a backwash pipeline 5 based on Example 1.

[0040] The outlet pool is connected to the outlet pipeline 3 and is arranged at the end of the outlet pipeline 3. The water treated by the autotrophic denitrification filter is pumped into the outlet pool by the outlet pump for temporary storage, and then discharged to subsequent treatment processes or discharged back to rivers and lakes. The outlet pool is an open pool, connected to the atmosphere, and is in a normal pressure state. Its water storage is mainly used for backwashing and nitrogen removal.

[0041] One end of the backwash pipeline 5 is connected to the water outlet tank, and the other end is connected to the distributor in the lower part of the autotrophic denitrification filter tank. The backwash pipeline 5 is provided with a backwash water inlet valve and a backwash flowmeter in series.

[0042] At the same time, an air inlet valve and a backwash discharge valve are also provided on the upper part of the autotrophic denitrification filter. The air inlet valve can be opened to connect the autotrophic denitrification filter with the atmosphere, which can be used to break the vacuum in the autotrophic denitrification filter; the backwash discharge valve is used to discharge the backwash water above the denitrification carrier filler layer to ensure smooth backwashing.

[0043] The backwash pipeline 5 is used to achieve reverse flow of water in the water outlet pool into the autotrophic denitrification filter tank under atmospheric pressure without providing additional power by means of the high vacuum degree in the autotrophic denitrification filter tank, so as to wash the suspended pollutants accumulated in the denitrification carrier filler area, the detached biofilm, etc., and remove the nitrogen accumulated and attached between the filler layers, etc., to achieve backwashing and nitrogen expulsion. The backwash pipeline 5 does not need to be provided with a backwash water pump, and can be accurately controlled by the backwash water inlet valve for opening and closing control and the backwash flowmeter for flow detection.

[0044] In one embodiment, the deep denitrification system for river and lake waters further comprises a lift pump, which is arranged at the front end of the system and connected to the water inlet end of the vacuum deoxidizer via the water inlet pipeline 1. The water inlet valve is arranged on the water inlet pipeline 1, and the water inlet valve is controlled in linkage with the lift pump.

[0045] The lifting pump is used to introduce the river and lake water to be treated into the vacuum deoxidizer from the water intake point, and is coordinated and controlled with the water inlet valve. The accurate and stable regulation of the water inlet flow rate is achieved through the lifting pump frequency conversion control and the water inlet valve opening control.

[0046] Example 3

[0047] like Figure 3 As shown, the deep denitrification system for river and lake water bodies provided in this embodiment, on the basis of Example 1 or Example 2, also includes an inlet flow meter, a water diversion flow meter and an outlet flow meter, and the inlet flow meter, the water diversion flow meter and the outlet flow meter are interrelated.

[0048] The water inlet flowmeter is arranged on the water inlet pipeline 1 connected to the water inlet end of the vacuum deaerator, and is connected in series with the water inlet valve. The water inlet flowmeter is also associated with the lifting pump and the water inlet valve, and is used to detect the water flow rate introduced into the vacuum deaerator by the water inlet pipeline 1, and the lifting pump frequency and the opening of the water inlet valve can be regulated according to the detection results. The water diversion flowmeter is arranged on the water diversion pipeline 2, and the water diversion flowmeter is connected in series with the water diversion valve, and the water diversion flowmeter is also associated with the water diversion valve, and is used to detect the water flow rate introduced from the vacuum deaerator into the autotrophic denitrification filter tank, and the opening of the water diversion valve can be regulated according to the detection results. The water outlet flowmeter is installed on the water outlet pipeline 3, and is connected in series with the water outlet pump and the water outlet valve, and the water outlet flowmeter is also associated with the water outlet pump and the water outlet valve, and is used to detect the water flow rate discharged after denitrification treatment in the autotrophic denitrification filter tank, and the water outlet pump frequency and the opening of the water outlet valve can be regulated according to the detection results. During operation, the inlet flow meter, water diversion flow meter and outlet flow meter can be linked to compare their detected flow data; based on the comparison results, the corresponding lift pump, inlet valve, water diversion valve, outlet pump and outlet valve can be regulated to make the inlet flow, water diversion flow and outlet flow reach dynamic balance or equality, so that the deep denitrification system of the river and lake water body can operate stably.

[0049] In a further embodiment, the vacuum deaerator is installed and connected with a first liquid level meter, and the autotrophic denitrification filter tank is installed and connected with a second liquid level meter. The first liquid level meter is used to monitor the working liquid level in the vacuum deaerator, and is linked with the water inlet valve, the lifting pump and the water diversion valve to achieve associated control. The second liquid level meter is used to monitor the working liquid level in the autotrophic denitrification filter tank, and is linked with the water diversion valve, the water outlet valve and the water outlet pump to achieve associated control. The first liquid level meter and the second liquid level meter are set, and are linked with the corresponding pumps and valves, so as to realize the monitoring and automatic regulation of the working liquid level in the vacuum deaerator and the autotrophic denitrification filter tank, and ensure stable and reliable operation.

[0050] In one embodiment, the vacuum deoxidizer is also installed and connected with a first vacuum meter, and the autotrophic denitrification filter is installed and connected with a second vacuum meter. The first vacuum meter is used to monitor the vacuum degree in the vacuum deoxidizer, and is linked with the vacuum pump and the first vacuum valve on the first vacuum pumping pipeline 41 to achieve associated control. The second vacuum meter is used to monitor the vacuum degree in the autotrophic denitrification filter, and is linked with the vacuum pump and the second vacuum valve on the second vacuum pumping pipeline 42 to achieve associated control. The first vacuum meter and the second vacuum meter are set, and are linked with the vacuum pump and the first vacuum valve and the second vacuum valve, so as to realize the monitoring and automatic control of the vacuum degree in the vacuum deoxidizer and the autotrophic denitrification filter, ensure that the water body is effectively deoxygenated and denitrified, and the system operates stably and reliably.

[0051] Preferably, a first overflow valve is provided on the upper part of the vacuum deoxidizer, and a drain valve is provided on the bottom; a second overflow valve is provided on the upper part of the autotrophic denitrification filter, and the second overflow valve is located below the air inlet valve, and the backwash discharge valve is located below the second overflow valve and above the denitrification carrier packing layer. The first overflow valve, the drain valve and the second overflow valve are all connected back to the water intake area through pipelines.

[0052] The first overflow valve and the second overflow valve can effectively avoid the situation of liquid overload in the sealed vacuum deoxidizer and the autotrophic denitrification filter tank, and at the same time, it is convenient to provide a basic liquid level for the initial vacuum operation, and to realize the coordinated control of the liquid level and the vacuum degree. When the system is started, the coordinated control of the liquid level control and the vacuum pumping is simpler and easier, and the system safety is high.

[0053] It also includes a controller, which is connected to the lifting pump, water inlet flowmeter, water inlet valve, water diversion valve, water diversion flowmeter, water outlet pump, water outlet valve, water outlet flowmeter, backwash water inlet valve, backwash flowmeter, first vacuum valve, second vacuum valve, vacuum pump, first liquid level meter, second liquid level meter, first vacuum meter, second vacuum meter, first overflow water valve, second overflow water valve, air intake valve, backwash discharge valve, etc., to achieve the associated regulation among the components and realize the automatic control operation of the system.

[0054] Example 4

[0055] like Figure 4 As shown, based on the same invention purpose and concept, this embodiment also provides a method for deep denitrification of river and lake water bodies, which can be carried out using the deep denitrification system for river and lake water bodies of Embodiments 1 to 3. The method for deep denitrification of river and lake water bodies comprises the following steps: S1, under non-vacuum conditions, that is, without vacuuming, introduce water into the vacuum deaerator and the subsequent autotrophic denitrification filter until the vacuum deaerator and the autotrophic denitrification filter reach the overflow level. This is the water filling operation when the system is started.

[0056] Specifically, open the water inlet valve, water diversion valve, first overflow valve, second overflow valve, etc., start the lifting pump, and transport the river and lake water to be treated to the vacuum deoxidizer and the autotrophic denitrification filter tank until the liquid level in the vacuum deoxidizer and the autotrophic denitrification filter tank reaches the first overflow valve and the second overflow valve, that is, reaches the overflow liquid level, and the overflowed river and lake water flows back to the water intake area.

[0057] S2, after completing the water filling in step S1, the vacuum deoxidizer and the autotrophic denitrification filter are evacuated to a first vacuum degree, and the autotrophic denitrification filter is evacuated to a second vacuum degree, which is higher than the first vacuum degree. That is, the vacuum operation is performed when the system is started, so that the vacuum deoxidizer and the autotrophic denitrification filter meet the liquid level requirements and vacuum requirements required for operation.

[0058] Preferably, the initial vacuuming operation is performed by following steps S21 and S22: S21, close the water inlet valve, water diversion valve, water outlet valve, the first overflow valve on the vacuum deoxidizer and the second overflow valve on the autotrophic denitrification filter, and close the lifting pump.

[0059] S22, open the first vacuum valve, the second vacuum valve and the vacuum pump to remove the air on the liquid surface of the vacuum deoxidizer and the autotrophic denitrification filter. When the vacuum degree in the vacuum deoxidizer reaches the first vacuum degree, close the first vacuum valve and the water diversion valve to maintain the vacuum deoxidizer at the first vacuum degree; continue to vacuum the autotrophic denitrification filter. When the vacuum degree reaches the second vacuum degree, close the second vacuum valve and the vacuum pump to maintain the autotrophic denitrification filter at the second vacuum degree.

[0060] It is preferred to control the first vacuum degree (relative vacuum degree) within the range of -0.05~-0.08MPa, and control the second vacuum degree (relative vacuum degree) within the range of -0.06~-0.09MPa, which can well ensure that the water body is fully deoxygenated, and the dissolved oxygen concentration of the water entering the autotrophic denitrification filter tank can be reduced to below 1mg / L, so that the autotrophic denitrification treatment can be carried out efficiently.

[0061] By controlling the second vacuum degree to be higher than the first vacuum degree, the water after deoxygenation in the vacuum deoxygenator can be automatically introduced into the autotrophic denitrification filter tank for denitrification treatment under the action of pressure difference, without the need to set up a water diversion pump to lead out the water in the vacuum deoxygenator. This saves equipment investment and reduces operating energy consumption.

[0062] S3, after completing the vacuum treatment of step S2, continuously convey and introduce the water body to be treated into the vacuum deaerator and the autotrophic denitrification filter tank, maintain the vacuum degree of the vacuum deaerator within the range of the first vacuum degree, maintain dynamic balance, and maintain the vacuum degree in the autotrophic denitrification filter tank within the range of the second vacuum degree, maintain dynamic balance, so that the water body is vacuum deaerated (eliminating gases including oxygen) and autotrophic denitrification treatment in the vacuum deaerator and the autotrophic denitrification filter tank, and at the same time, the working liquid level in the vacuum deaerator and the autotrophic denitrification filter tank needs to be maintained within an appropriate range to avoid the working liquid level being too high or too low. The water body treated in the autotrophic denitrification filter tank is extracted and discharged to subsequent treatment processes or discharged back to the river and lake water body.

[0063] Preferably, the liquid level in the vacuum deaerator is controlled to be always higher than the liquid level in the autotrophic denitrification filter, and the liquid level difference between the vacuum deaerator and the autotrophic denitrification filter is controlled to be ≤100 cm. Controlling the liquid level difference and vacuum difference between the vacuum deaerator and the autotrophic denitrification filter can better ensure that water flows into the autotrophic denitrification filter by gravity, and the flow rate is sufficient.

[0064] The liquid level of the autotrophic denitrification filter is controlled to be always higher than the liquid level of the outlet tank, and the liquid level difference between the autotrophic denitrification filter and the outlet tank is controlled to be ≤300cm; more preferably, the liquid level difference between the autotrophic denitrification filter and the outlet tank is controlled to be within the range of 100~200cm. The liquid level of the autotrophic denitrification filter is controlled to be higher than the outlet tank to ensure that the water flow in the outlet direction is discharged smoothly; but it should be noted that the outlet tank should maintain a certain liquid level and should not be too low. The difference between the liquid level of the outlet tank and the liquid level of the autotrophic denitrification filter is controlled within 300cm, which can well ensure that the water flow of the outlet tank can enter the autotrophic denitrification filter at a stable and sufficient flow rate during backwashing and nitrogen expulsion, and ensure backwashing and nitrogen expulsion without a backwashing water pump.

[0065] Preferably, step S3 further includes the following steps: S301, setting a working liquid level upper limit value, a working liquid level lower limit value and a working liquid level setting value for the vacuum deoxidizer and the autotrophic denitrification filter.

[0066] When the working liquid level in the vacuum deaerator is higher than the upper limit of the working liquid level, close the water inlet valve and the lifting pump, stop the water inlet to the vacuum deaerator, and when the working liquid level in the vacuum deaerator drops to the working liquid level setting value, reopen the water inlet valve and start the lifting pump. When the working liquid level in the vacuum deaerator is lower than the lower limit of the working liquid level, close the water diversion valve, stop the water discharge of the vacuum deaerator, and when the working liquid level in the vacuum deaerator rises to the working liquid level setting value, reopen the water diversion valve.

[0067] When the working liquid level in the autotrophic denitrification filter is higher than the upper limit of the working liquid level, close the water diversion valve, stop diverting water into the autotrophic denitrification filter, and when the working liquid level in the autotrophic denitrification filter drops to the working liquid level setting value, reopen the water diversion valve to divert water. When the working liquid level in the autotrophic denitrification filter is lower than the lower limit of the working liquid level, close the outlet pump and the outlet valve, stop discharging water from the autotrophic denitrification filter, and when the working liquid level in the autotrophic denitrification filter rises to the working liquid level setting value, reopen the outlet pump and the outlet valve to discharge water.

[0068] S302, setting a lower limit value of the working vacuum and a setting value of the working vacuum (preferably the first vacuum or the second vacuum) for the vacuum deoxidizer and the autotrophic denitrification filter.

[0069] When the vacuum degree in the vacuum deoxidizer is lower than the lower limit of the working vacuum degree, start the vacuum pump, open the first vacuum valve, and evacuate the vacuum deoxidizer. After the vacuum degree in the vacuum deoxidizer reaches the working vacuum degree set value (preferably the first vacuum degree), close the first vacuum valve and the vacuum pump, and stop evacuating.

[0070] When the vacuum degree in the autotrophic denitrification filter is lower than the lower limit of the working vacuum degree, start the vacuum pump and open the second vacuum valve to evacuate the autotrophic denitrification filter. After the vacuum degree in the autotrophic denitrification filter increases to reach the working vacuum degree set value, close the second vacuum valve and the vacuum pump to stop vacuuming.

[0071] Through steps S301 and S302, the working liquid level and vacuum degree in the vacuum deoxidizer and the autotrophic denitrification filter are automatically adjusted to ensure stable and efficient operation of the system.

[0072] Furthermore, after the system has been running for a period of time, mainly after step S3 has been running for a period of time, the denitrification carrier filler layer of the autotrophic denitrification filter accumulates a lot of nitrogen, which hinders or reduces the denitrification efficiency and needs to be treated with nitrogen expulsion; or the carrier filler layer of the autotrophic denitrification filter accumulates a lot of suspended pollutants, detached biofilm, etc., and needs to be backwashed. Therefore, the following steps are also included: S4, nitrogen expulsion procedure: close the water inlet valve, water diversion valve and water outlet valve (the valves not mentioned in this procedure are closed by default), open the backwash water inlet valve at the bottom of the autotrophic denitrification filter tank, because the autotrophic denitrification filter tank is in a negative pressure state, the water in the outlet tank flows from bottom to top through the denitrification carrier filler layer under the action of negative pressure, and the filler layer is treated with nitrogen expulsion to remove nitrogen. After reaching the set nitrogen expulsion time or the set nitrogen expulsion liquid level, close the backwash water inlet valve, stop reverse water inlet, open the outlet valve and start the outlet pump to drain water, and wait for the work in the autotrophic denitrification filter tank to stop. When the liquid level is reduced to the working liquid level setting value, the outlet pump and the outlet valve are closed to stop drainage; at this time, if the vacuum degree in the autotrophic denitrification filter is lower than the working vacuum degree lower limit, the second vacuum pump and the vacuum pump are turned on to vacuumize the autotrophic denitrification filter. After the vacuum degree in the autotrophic denitrification filter reaches the working vacuum degree setting value (the working vacuum degree setting value is preferably the second vacuum degree), the second vacuum valve and the vacuum pump are closed to stop the vacuum operation; if the vacuum degree in the autotrophic denitrification filter is greater than the working vacuum degree lower limit, there is no need to perform the vacuum operation. After completing the nitrogen expelling procedure, the liquid level in the autotrophic denitrification filter is restored to the working liquid level setting value, the vacuum degree is restored to the working vacuum degree setting value, and then the denitrification process of step S3 is restarted.

[0073] S5 backwash procedure: close the water inlet valve, water diversion valve and water outlet valve (valves not mentioned in this procedure are closed by default), open the backwash water inlet valve at the bottom of the autotrophic denitrification filter, because the autotrophic denitrification filter is in a negative pressure state, the water in the outlet tank flows from bottom to top through the denitrification carrier packing layer under the action of negative pressure, and the packing layer is backwashed to remove suspended pollutants and detached biofilms in the denitrification carrier packing layer. When the set backwash time is reached or the backwash set liquid level is reached, close the backwash water inlet valve and stop backwashing; then open the air inlet valve set on the upper part of the autotrophic denitrification filter to break the air in the autotrophic denitrification filter. Vacuum, then open the backwash discharge valve set on the top of the autotrophic denitrification filter tank to discharge the backwash sewage above the denitrification carrier filler layer; after the backwash sewage is discharged, close the air inlet valve and the backwash discharge valve; open the second vacuum valve and the vacuum pump, and at the same time open the backwash water inlet valve, re-vacuum the autotrophic denitrification filter tank, and make the water in the outlet pool flow into the autotrophic denitrification filter tank under the action of atmospheric pressure, when the working liquid level in the autotrophic denitrification filter tank rises to the working liquid level setting value, close the backwash water inlet valve, and when the vacuum degree reaches the working vacuum degree setting value (preferably the second vacuum degree), close the second vacuum valve and the vacuum pump. After completing the backwash procedure, the liquid level in the autotrophic denitrification filter tank is restored to the working liquid level setting value, and the vacuum degree is restored to the working vacuum degree setting value, and then the denitrification treatment of step S3 is restarted.

[0074] In summary, the deep denitrification system and method for river and lake water bodies of the present invention avoids the inhibitory effect of saturated natural water bodies on anaerobic denitrification microorganisms in the autotrophic denitrification filter after the water enters the autotrophic denitrification filter, and effectively reduces the influence of oxygen enrichment of natural water bodies on denitrification efficiency. Stable control of the flow rate is achieved through the frequency conversion of valves and water pumps, as well as the control of the vacuum degree and working liquid level in the vacuum deoxidizer and the autotrophic denitrification filter. The design of the water diversion pump after the vacuum deoxidizer is omitted, which greatly reduces the operating energy consumption. At the same time, the autotrophic denitrification filter can use vacuum negative pressure for backwashing and nitrogen expulsion, eliminating the design of the backwash water pump and saving investment costs. In addition, since the water outlet of the vacuum deoxidizer directly enters the autotrophic denitrification filter, and the autotrophic denitrification filter also maintains a high vacuum degree, it is beneficial to maintain low dissolved oxygen in the denitrification process and improve the denitrification efficiency.

Claims

1. A deep denitrification system for river and lake water bodies, characterized in that: include: The vacuum deoxidizer has a water inlet valve at its water inlet end and a water diversion valve at its water outlet end; An autotrophic denitrification filter tank, the upper water inlet of which is connected to the water outlet of the vacuum deoxidizer via a water diversion pipeline, and the water diversion valve is arranged on the water diversion pipeline; A vacuum pump, connected to the vacuum deoxidizer and the autotrophic denitrification filter tank via a first vacuum pumping pipeline and a second vacuum pumping pipeline, respectively, a first vacuum valve is provided on the first vacuum pumping pipeline, and a second vacuum valve is provided on the second vacuum pumping pipeline; A water outlet pump is connected to the water outlet end of the lower part of the autotrophic denitrification filter tank through a water outlet pipeline. A water outlet valve is arranged on the water outlet pipeline and is connected in series with the water outlet pump.

2. The deep denitrification system for river and lake water bodies according to claim 1 is characterized in that: It also includes a water outlet tank and a backwash pipeline; the water outlet tank is connected to the water outlet pipeline; one end of the backwash pipeline is connected to the water outlet tank, and the other end is connected to the lower part of the autotrophic denitrification filter tank, and a backwash water inlet valve and a backwash flowmeter are arranged on the backwash pipeline; the upper part of the autotrophic denitrification filter tank is provided with an air inlet valve and a backwash discharge valve; and / or, It also includes a lifting pump, which is connected to the vacuum deoxidizer via a water inlet pipeline, and the lifting pump is linked to the water inlet valve.

3. The deep denitrification system for river and lake water according to claim 1 or 2, characterized in that: It also includes an inlet flowmeter, a diversion flowmeter and an outlet flowmeter; the inlet flowmeter is arranged on the water inlet pipeline of the vacuum deoxidizer and is connected in series with the water inlet valve; the diversion flowmeter is arranged on the diversion pipeline and is connected in series with the diversion valve; the outlet flowmeter is arranged on the outlet pipeline and is connected in series with the outlet pump and the outlet valve.

4. The deep denitrification system for river and lake water bodies according to claim 2 is characterized in that: It also includes a first liquid level meter installed on the vacuum deoxidizer and a second liquid level meter installed on the autotrophic denitrification filter tank, wherein the first liquid level meter is used to monitor the working liquid level in the vacuum deoxidizer and is linked with the water inlet valve, the lifting pump and the water diversion valve; the second liquid level meter is used to monitor the working liquid level in the autotrophic denitrification filter tank and is linked with the water diversion valve, the water outlet valve and the water outlet pump; and / or, It also includes a first vacuum meter installed on the vacuum deoxidizer and a second vacuum meter installed on the autotrophic denitrification filter. The first vacuum meter is used to monitor the vacuum degree in the vacuum deoxidizer and is linked to the vacuum pump and the first vacuum valve; the second vacuum meter is used to monitor the vacuum degree in the autotrophic denitrification filter and is linked to the vacuum pump and the second vacuum valve.

5. The deep denitrification system for river and lake water bodies according to claim 2 is characterized in that: The vacuum deoxidizer is provided with a first overflow valve at the top and an emptying valve at the bottom; the autotrophic denitrification filter is provided with a second overflow valve at the top, the second overflow valve is located below the air inlet valve, and the backwash discharge valve is located below the second overflow valve and above the denitrification carrier filler layer.

6. A method for deep denitrification of river and lake water bodies, characterized in that: The method is carried out using the deep denitrification system for river and lake water bodies as described in any one of claims 1 to 5, comprising the following steps: S1, under non-vacuum conditions, introduce water into the vacuum deoxidizer and the autotrophic denitrification filter to the overflow level; S2, evacuating the vacuum deoxidizer and the autotrophic denitrification filter tank to a first vacuum degree, and evacuating the vacuum deoxidizer to a second vacuum degree, wherein the second vacuum degree is higher than the first vacuum degree; S3, continuously introducing water into the vacuum deaerator and the autotrophic denitrification filter, and maintaining the vacuum degree in the vacuum deaerator and the autotrophic denitrification filter in dynamic balance between the first vacuum degree and the second vacuum degree, so that the water body is subjected to vacuum degassing and autotrophic denitrification treatment, and the water body after treatment in the autotrophic denitrification filter is pumped out and discharged.

7. The method for deep denitrification of river and lake water bodies according to claim 6, characterized in that: Also include one or more of the following: The first vacuum degree is a relative vacuum degree of -0.05 to -0.08 MPa, and the second vacuum degree is a relative vacuum degree of -0.06 to -0.09 MPa; The liquid level in the vacuum deoxidizer is higher than the liquid level in the autotrophic denitrification filter, and the liquid level difference between the vacuum deoxidizer and the autotrophic denitrification filter is ≤100 cm; The liquid level of the autotrophic denitrification filter is higher than the liquid level of the outlet tank, and the liquid level difference between the autotrophic denitrification filter and the outlet tank is ≤300 cm.

8. The method for deep denitrification of river and lake water bodies according to claim 6, characterized in that: In step S2, the vacuum deoxidizer and the autotrophic denitrification filter are subjected to vacuum treatment, the vacuum deoxidizer is vacuumed to a first vacuum degree, and the autotrophic denitrification filter is vacuumed to a second vacuum degree, specifically comprising: S21, close the water inlet valve, the water diversion valve, the water outlet valve, the first overflow valve of the vacuum deoxidizer, and the second overflow valve of the autotrophic denitrification filter; S22, open the first vacuum valve, the second vacuum valve and the vacuum pump, close the first vacuum valve and the water diversion valve when the first vacuum degree is reached, and close the second vacuum valve and the vacuum pump when the second vacuum degree is reached.

9. The method for deep denitrification of river and lake water according to claim 6 or 8, characterized in that: Step S3 also includes the following steps: S301, setting a working liquid level upper limit value, a working liquid level lower limit value and a working liquid level setting value for the vacuum deoxidizer and the autotrophic denitrification filter tank; When the working liquid level in the vacuum deaerator is higher than the upper limit of the working liquid level, the water inlet valve and the lifting pump are closed, and when the working liquid level reaches the working liquid level setting value, the water inlet valve and the lifting pump are reopened; when the working liquid level in the vacuum deaerator is lower than the lower limit of the working liquid level, the water diversion valve is closed, and when the working liquid level reaches the working liquid level setting value, the water diversion valve is reopened; When the working liquid level in the autotrophic denitrification filter is higher than the working liquid level upper limit, the water diversion valve is closed, and when the working liquid level reaches the working liquid level setting value, the water diversion valve is reopened; when the working liquid level in the autotrophic denitrification filter is lower than the working liquid level lower limit, the water outlet pump and the water outlet valve are closed, and when the working liquid level reaches the working liquid level setting value, the water outlet pump and the water outlet valve are reopened; S302, setting a lower limit value of working vacuum and a setting value of working vacuum for the vacuum deoxidizer and the autotrophic denitrification filter; When the vacuum degree in the vacuum deoxidizer is lower than the lower limit of the working vacuum degree, the vacuum pump is started, the first vacuum valve is opened, and after the vacuum degree reaches the set value of the working vacuum degree, the first vacuum valve is closed and the vacuum pump is closed; When the vacuum degree in the autotrophic denitrification filter is lower than the lower limit of the working vacuum degree, the vacuum pump is started, the second vacuum valve is opened, and after the vacuum degree reaches the working vacuum degree setting value, the second vacuum valve and the vacuum pump are closed.

10. The method for deep denitrification of river and lake water bodies according to claim 9, characterized in that: When step S3 is run for a period of time and the autotrophic denitrification filter needs to be nitrogen driven or backwashed, the following steps are also included: S4, nitrogen removal procedure: close the water inlet valve, the water diversion valve and the water outlet valve, open the backwash water inlet valve at the bottom of the autotrophic denitrification filter, and allow the water body to flow backward from bottom to top through the denitrification carrier filler layer under the action of negative pressure to remove nitrogen. After reaching the set nitrogen removal time or the set nitrogen removal liquid level, close the backwash water inlet valve, open the water outlet valve and the water outlet pump, and when the working liquid level reaches the working liquid level setting value, close the water outlet pump and the water outlet valve; if the vacuum degree is lower than the lower limit of the working vacuum degree, open the second vacuum valve and the vacuum pump, and when the vacuum degree reaches the working vacuum degree setting value, close the second vacuum valve and the vacuum pump; and repeat step S3; S5, backwash procedure: close the water inlet valve, the water diversion valve and the water outlet valve, open the backwash water inlet valve at the bottom of the autotrophic denitrification filter, and under the action of negative pressure, the water body flows backward from bottom to top through the denitrification carrier filler layer for backwashing. After reaching the set backwash time or the backwash set liquid level, close the backwash water inlet valve, open the air inlet valve on the upper part of the autotrophic denitrification filter, break the vacuum, and open the backwash discharge valve to discharge the upper backwash sewage; after the discharge is completed, close the air inlet valve and the backwash discharge valve; open the second vacuum valve and the vacuum pump, and open the backwash water inlet valve at the same time. When the working liquid level reaches the working liquid level setting value, close the backwash water inlet valve. After the vacuum reaches the working vacuum setting value, close the second vacuum valve and the vacuum pump; repeat step S3.

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