A heterotrophic autotrophic denitrification combined treatment device

Abstract

This invention provides a combined heterotrophic and autotrophic denitrification treatment device, relating to the field of water treatment technology. It includes a pretreatment unit, a heterotrophic denitrification unit, an autotrophic denitrification unit, and a deep filtration unit connected in sequence. The device employs a combined process of heterotrophic denitrification for preliminary nitrogen removal and autotrophic denitrification for deep nitrogen removal. First, heterotrophic denitrification rapidly removes most of the nitrate, reducing the influent load. Then, sulfur-based autotrophic denitrification achieves deep nitrogen removal. This method is adaptable to various wastewaters with high and low C / N ratios, resulting in more thorough nitrogen removal and stable nitrate nitrogen levels in the effluent. The heterotrophic stage requires only a small amount of organic carbon source for preliminary nitrogen removal, while the autotrophic stage uses reduced sulfur as an electron donor, eliminating the need for additional organic carbon sources and reducing carbon source addition costs. Simultaneously, the slow proliferation of autotrophic microorganisms results in sludge production far lower than that of a single heterotrophic process, reducing sludge treatment and disposal costs.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a heterotrophic-autotrophic denitrification combined treatment device. Background Technology

[0002] With increasingly stringent emission standards in industrial production, municipal wastewater treatment, and aquaculture wastewater, deep nitrate nitrogen removal has become a key technical challenge in the water treatment field. Traditional biological denitrification processes mainly rely on heterotrophic denitrification, which depends on external organic carbon sources such as methanol and sodium acetate to provide electron donors for denitrifying bacteria. While this process has advantages such as rapid start-up and high denitrification rate, it has significant shortcomings in practical applications: First, the cost of adding carbon sources is high, and the dosage is difficult to control precisely, easily leading to insufficient carbon sources resulting in incomplete denitrification, or excessive addition causing problems such as excessive COD in the effluent and secondary pollution; second, the rapid proliferation rate of heterotrophic microorganisms results in a large amount of sludge production, significantly increasing sludge treatment and disposal costs; third, when dealing with wastewater with a low carbon-to-nitrogen ratio, the denitrification efficiency drops significantly, making it difficult to meet the requirements for deep denitrification.

[0003] To compensate for the shortcomings of heterotrophic denitrification, autotrophic denitrification technology has been gradually applied. Among them, sulfur autotrophic denitrification has become the preferred solution for deep denitrification of wastewater with low C / N ratio due to its advantages such as no need for organic carbon sources, low sludge production, and low operating costs. This technology uses reduced sulfur as an electron donor and reduces nitrate to nitrogen gas through autotrophic denitrifying bacteria, which can effectively avoid the problems related to organic carbon sources. However, there are still many technical bottlenecks: First, the sulfur packing is highly hydrophobic and has low mass transfer efficiency, resulting in a slow denitrification rate and a long system start-up cycle; Second, the reaction process consumes alkalinity and produces sulfate byproducts. Excessive sulfate can disrupt the ecological balance of the water body, and the sulfur packing is a consumable that needs to be replaced regularly, making operation and maintenance cumbersome; Third, single sulfur autotrophic denitrification reactors are prone to packing caking and blockage, and backwashing can easily cause the loss of microorganisms and packing, resulting in insufficient system stability.

[0004] Currently, most existing denitrification devices utilize either a single heterotrophic or autotrophic denitrification process, making it difficult to simultaneously meet the multiple demands of efficient denitrification, low-cost operation, and stable effluent compliance. Heterotrophic denitrification cannot solve the problems of carbon source dependence and large sludge production, while autotrophic denitrification is difficult to adapt to high-load influent and is easily affected by water quality fluctuations. Furthermore, both lack comprehensive pretreatment and deep filtration units, resulting in suspended solids and biofilm fragments generated during the reaction process that can easily affect effluent quality, and the emissions of exhaust gas and sludge also pose environmental hazards. Therefore, developing a combined treatment device that integrates the advantages of rapid heterotrophic denitrification and deep autotrophic denitrification, along with supporting pretreatment and deep purification, has become an urgent need to address the pain points of wastewater nitrate denitrification technology and promote the low-carbon upgrading of water treatment processes. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by providing a heterotrophic-autotrophic denitrification combined treatment device.

[0006] To address the aforementioned problems, this invention provides a technical solution: a heterotrophic-autotrophic denitrification combined treatment device, comprising a pretreatment unit, a heterotrophic denitrification unit, an autotrophic denitrification unit, and a deep filtration unit connected in sequence; the pretreatment unit is used to remove suspended solids, large particulate impurities, and some organic matter from the wastewater to be treated; the heterotrophic denitrification unit is used to achieve preliminary denitrification of nitrates in the wastewater and to provide suitable influent conditions for the autotrophic denitrification unit; the autotrophic denitrification unit is used to perform deep denitrification of the effluent from the heterotrophic denitrification unit; and the deep filtration unit is used to remove biofilm fragments, suspended solids, and other impurities generated during the reaction process.

[0007] Preferably, the pretreatment unit includes a pretreatment tank, a bar screen, a sedimentation tank, a baffle plate, a lift pump, a drain outlet, a ball valve, and a mounting bracket; the bar screen is located at the inlet end of the pretreatment tank; the sedimentation tank is located inside the pretreatment tank; the baffle plate is fixedly connected to the right side of the lower surface of the bar screen; a mounting bracket is fixedly connected to the right end of the pretreatment tank, and a lift pump is fixedly connected to the mounting bracket, with the input end of the lift pump communicating with the right end of the pretreatment tank; a drain outlet is provided at the bottom of the pretreatment tank, and a ball valve is provided on the drain outlet.

[0008] Preferably, the heterotrophic denitrification unit includes a heterotrophic denitrification reactor, a chemical storage tank, a metering pump, water pipes, a stirring motor, a stirring paddle, ceramsite biological packing material, a first tail gas absorption tower, a gas pipe, a first sludge discharge port, a first sludge discharge valve plate, and a first liquid pump; the top of the heterotrophic denitrification reactor is connected to the output end of the booster pump via a water pipe; the input end of the metering pump is connected to the chemical storage tank via a water pipe, and the output end of the metering pump is connected to the top of the heterotrophic denitrification reactor via a water pipe; the heterotrophic denitrification reactor chamber... The reactor is internally equipped with ceramsite biological packing material; a stirring motor is fixedly connected to the top of the heterotrophic denitrification reactor, and a stirring paddle is fixedly connected to the output end of the stirring motor, the stirring paddle being located inside the chamber of the heterotrophic denitrification reactor; a first sludge discharge port is fixedly connected to the bottom surface of the heterotrophic denitrification reactor, and a first sludge discharge valve plate is provided in the first sludge discharge port; the top of the heterotrophic denitrification reactor is connected to a first tail gas absorption tower through a gas pipe; the input end of the first liquid pump is connected to the bottom of the heterotrophic denitrification reactor through a water pipe.

[0009] Preferably, the autotrophic denitrification unit includes an autotrophic denitrification reactor, a water distributor, a water distribution plate, nozzles, a packing layer, a packing layer support frame, a Roots blower, an aeration plate, a second sludge discharge port, a second sludge discharge valve plate, a second tail gas absorption tower, and a second liquid pump. The water distributor is fixedly connected to the top of the autotrophic denitrification reactor. The input end of the water distributor is connected to the output end of the first liquid pump via a water pipe. A water distribution plate is fixedly connected to the upper part of the chamber of the autotrophic denitrification reactor, and the water distribution plate is connected to the water distributor. Several nozzles are fixedly connected to the lower end of the water distribution plate. The autotrophic denitrification reactor chamber is fixedly connected to a packing layer support frame at its middle end, and the packing layer support frame is provided with a packing layer; a second sludge discharge port is fixedly connected to the bottom surface of the autotrophic denitrification reactor, and a second sludge discharge valve plate is provided in the second sludge discharge port; an aeration disc is fixedly connected to the lower end of the autotrophic denitrification reactor chamber, and the aeration disc is connected to an external Roots blower; the top of the autotrophic denitrification reactor is connected to a second tail gas absorption tower through a gas pipe; the input end of the second liquid pump is connected to the bottom of the autotrophic denitrification reactor through a water pipe.

[0010] Preferably, the deep filtration unit includes a filter tank, a filter media support, a filter media layer, a backwash drain valve, a water outlet valve, a backwash water pump, and a backwash air pipe; the upper end of the filter tank is connected to the output end of a second liquid pump via a water pipe; a filter media support is fixedly connected to the upper and middle positions inside the filter tank chamber, and a filter media layer is provided between the filter media support; a backwash air pipe is provided on the bottom surface inside the filter tank chamber, and the backwash air pipe is connected to an external backwash water pump; a water outlet valve is fixedly connected to the middle side of the filter tank, and a backwash drain valve is fixedly connected to the bottom side of the filter tank.

[0011] Preferably, the ceramsite biological packing material is a porous ceramsite packing material, with a filling rate of 50%-80% of the effective volume of the reactor.

[0012] Preferably, the packing layer is a sulfur autotrophic denitrification packing with a particle size of 3-10 mm.

[0013] Preferably, the filter media layer is a double-layer filter media of quartz sand and anthracite, with the upper layer being anthracite filter media and the lower layer being quartz sand filter media.

[0014] The beneficial effects of the present invention are: (1) The denitrification efficiency is significantly improved: The combined process of heterotrophic denitrification for preliminary denitrification and autotrophic denitrification for deep denitrification is adopted. First, most of the nitrates are quickly removed by heterotrophic denitrification to reduce the influent load. Then, deep denitrification is achieved by sulfur autotrophic denitrification. It can be adapted to various wastewaters with high and low carbon-nitrogen ratios. The denitrification is more thorough and the nitrate nitrogen in the effluent is stable and meets the standards.

[0015] (2) Operating costs are significantly reduced: The heterotrophic section only requires the addition of a small amount of organic carbon source to complete the initial denitrification. The autotrophic section uses reduced sulfur as an electron donor and does not require additional organic carbon source, thus reducing the cost of adding carbon source. At the same time, the autotrophic microorganisms proliferate slowly, and the sludge production is much lower than that of the single heterotrophic process, thus reducing the cost of sludge treatment and disposal.

[0016] (3) Strong system stability and shock resistance: The pretreatment unit at the front end effectively removes suspended solids and large particulate impurities, avoiding subsequent reactor blockage and packing caking; the heterotrophic section provides stable and suitable influent conditions for the autotrophic section, alleviating the interference of water quality fluctuations on autotrophic denitrification and ensuring long-term stable operation of the system.

[0017] (4) Optimization of mass transfer effect and reaction rate: Heterotrophic denitrification uses porous ceramic biological filler with large specific surface area and high biofilm formation efficiency, and strengthens mud-water mixing with stirring device; Autotrophic denitrification uses water distributor and nozzle to distribute water evenly, and combines aeration to improve mass transfer efficiency, solving the problems of poor mass transfer and slow start-up of single sulfur autotrophic denitrification.

[0018] (5) Cleaner effluent: The end is equipped with a deep filtration unit with a double layer of quartz sand and anthracite, which effectively removes biofilm fragments and suspended impurities generated by the reaction, further improving the clarity of the effluent and avoiding the impact of suspended matter on the effluent quality.

[0019] (6) Environmental compliance is complete: Both heterotrophic and autotrophic denitrification units are equipped with tail gas absorption towers to collect and treat the tail gas generated by denitrification and avoid waste gas pollution; each unit is equipped with an independent sludge discharge port to achieve orderly discharge of sludge and no secondary pollution risk.

[0020] (7) Wide range of applicable scenarios: It can simultaneously meet the deep denitrification needs of various scenarios such as industrial wastewater, municipal sewage, and aquaculture wastewater, breaking through the limitation that a single process can only be adapted to specific water quality, and promoting the low-carbon and high-efficiency upgrading of water treatment processes. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the preprocessing unit of the present invention.

[0023] Figure 3 This is a schematic diagram of the heterotrophic denitrification unit of the present invention.

[0024] Figure 4 This is a schematic diagram of the structure of the autotrophic denitrification unit of the present invention.

[0025] Figure 5 This is a schematic diagram of the structure of the depth filtering unit of the present invention.

[0026] Figure 6For the present invention Figure 3 A partially enlarged structural diagram.

[0027] Figure 7 For the present invention Figure 4 A partially enlarged structural diagram.

[0028] 1-Pretreatment unit; 2-Heterotrophic denitrification unit; 3-Autotrophic denitrification unit; 4-Deep filtration unit; 5-Pretreatment tank; 6-Bar screen; 7-Sedimentation tank; 8-Baffle plate; 9-Lift pump; 10-Sewage outlet; 11-Ball valve; 12-Mounting bracket; 13-Heterotrophic denitrification reactor; 14-Storage tank; 15-Metering pump; 16-Water pipe; 17-Agitator motor; 18-Agitator paddle; 19-Ceramic granule biological packing; 20-First tail gas absorption tower; 21-Gas pipe; 22-First sludge discharge port; 23-First 24-Sludge discharge valve plate; 25-First liquid pump; 26-Autotrophic denitrification reactor; 27-Water distributor; 28-Water distribution tray; 29-Nozzle; 30-Packing layer; 31-Packing layer support frame; 32-Roots blower; 33-Aeration disc; 34-Second sludge discharge port; 35-Second sludge discharge valve plate; 36-Second tail gas absorption tower; 37-Second liquid pump; 38-Filter tank; 39-Filter media support frame; 40-Filter media layer; 41-Backwash drain valve; 42-Outlet valve; 43-Backwash water pump; 44-Backwash air pipe. Detailed Implementation

[0029] like Figure 1 As shown, this specific embodiment adopts the following technical solution: a heterotrophic-autotrophic denitrification combined treatment device, including a pretreatment unit 1, a heterotrophic denitrification unit 2, an autotrophic denitrification unit 3, and a deep filtration unit 4 connected in sequence; the pretreatment unit 1 is used to remove suspended solids, large particulate impurities, and some organic matter from the wastewater to be treated, reducing the subsequent treatment load and protecting the reactor and packing from clogging; the heterotrophic denitrification unit 2 is used to achieve preliminary denitrification of nitrates in the wastewater, significantly reducing the nitrate concentration, and providing suitable influent conditions for the autotrophic denitrification unit, improving the overall denitrification stability; the autotrophic denitrification unit 3 is used to perform deep denitrification of the effluent from the heterotrophic denitrification unit, ensuring that the effluent nitrate nitrogen meets the stringent discharge standards; the deep filtration unit 4 is used to remove biofilm fragments, suspended solids, and other impurities generated during the reaction process, ensuring that the final effluent is clear and meets the standards.

[0030] like Figure 2As shown, the pretreatment unit 1 includes a pretreatment tank 5, a screen 6, a sedimentation tank 7, a baffle 8, a lift pump 9, a drain outlet 10, a ball valve 11, and a mounting bracket 12. The screen 6 is located at the inlet of the pretreatment tank 5 to intercept large suspended solids and floating impurities in the wastewater, preventing pipe and equipment blockage. The sedimentation tank 7 is located inside the pretreatment tank 5 to settle fine suspended particles, achieving preliminary solid-liquid separation. The baffle 8 is fixedly connected to the right side of the lower surface of the screen 6 to guide the water flow smoothly into the sedimentation zone, improving the sedimentation effect. The mounting bracket 12 is fixedly connected to the right end of the pretreatment tank 5, and the lift pump 9 is fixedly connected to the mounting bracket 12. The input end of the lift pump 9 is connected to the right end of the pretreatment tank 5 to stably transport the pretreated wastewater to the heterotrophic denitrification unit. A drain outlet 10 is provided at the bottom of the pretreatment tank 5, and a ball valve 11 is provided on the drain outlet 10 to periodically discharge deposited sludge and impurities, keeping the inside of the pretreatment tank clean.

[0031] like Figure 3 and Figure 6 As shown, the heterotrophic denitrification unit 2 includes a heterotrophic denitrification reactor 13, a chemical storage tank 14, a metering pump 15, a water pipe 16, a stirring motor 17, a stirring paddle 18, a ceramic granule biological packing material 19, a first tail gas absorption tower 20, a gas pipe 21, a first sludge discharge port 22, a first sludge discharge valve plate 23, and a first liquid pump 24. The top of the heterotrophic denitrification reactor 13 is connected to the output end of the booster pump 9 via the water pipe 16 to receive pretreated wastewater. The input end of the metering pump 15 is connected to the chemical storage tank 14 via the water pipe 16, and the output end of the metering pump 15 is connected to the top of the heterotrophic denitrification reactor 13 via the water pipe 16, which can precisely control the amount of organic carbon source added to avoid insufficient or excessive carbon source. The chamber of the heterotrophic denitrification reactor 13 is equipped with ceramic granule biological packing material 19, which provides an attachment carrier for heterotrophic denitrifying bacteria, improving biomass and reaction efficiency. The heterotrophic denitrification reactor 13 is equipped with a stirring motor 17 fixedly connected to its top, and a stirring paddle 18 fixedly connected to the output end of the stirring motor 17. The stirring paddle 18 is located inside the chamber of the heterotrophic denitrification reactor 13 and enhances the mixing of mud, water, and reagents by stirring, thereby improving the mass transfer and reaction rate. A first sludge discharge port 22 is fixedly connected to the bottom surface of the heterotrophic denitrification reactor 13. A first sludge discharge valve plate 23 is provided in the first sludge discharge port 22 for periodically discharging aged sludge and maintaining biological activity in the reactor. The top of the heterotrophic denitrification reactor 13 is connected to the first tail gas absorption tower 20 through a gas pipe 21 to collect and purify the tail gas generated by denitrification and prevent waste gas pollution. The input end of the first liquid pump 24 is connected to the bottom of the heterotrophic denitrification reactor 13 through a water pipe 16 to transport the wastewater after preliminary denitrification to the autotrophic denitrification unit.

[0032] like Figures 4 to 7As shown, the autotrophic denitrification unit 3 includes an autotrophic denitrification reactor 25, a water distributor 26, a water distribution plate 27, nozzles 28, a packing layer 29, a packing layer support frame 30, a Roots blower 31, an aeration plate 32, a second sludge discharge port 33, a second sludge discharge valve plate 34, a second tail gas absorption tower 35, and a second liquid pump 36. The water distributor 26 is fixedly connected to the top of the autotrophic denitrification reactor 25 for uniformly collecting the influent. The input end of the water distributor 26 is connected to the output end of the first liquid pump 24 through a water pipe 16 to receive the effluent from the heterotrophic denitrification unit. The upper part of the chamber of the autotrophic denitrification reactor 25 is fixedly connected to the water distribution plate 27, which is connected to the water distributor 26. Several nozzles 28 are fixedly connected to the lower end of the water distribution plate 27 to ensure that the wastewater is in full contact with the packing through multi-point uniform water distribution. The middle part of the chamber of the autotrophic denitrification reactor 25 is also connected to the water distributor 26. A packing layer support frame 30 is fixedly connected to the autotrophic denitrification reactor 25, on which a packing layer 29 is provided to provide an attachment and reaction carrier for sulfur autotrophic denitrifying bacteria. A second sludge discharge port 33 is fixedly connected to the bottom surface of the autotrophic denitrification reactor 25, and a second sludge discharge valve plate 34 is provided in the second sludge discharge port 33 to discharge the sludge deposited in the reactor and prevent blockage. An aeration disc 32 is fixedly connected to the lower end of the chamber of the autotrophic denitrification reactor 25. The aeration disc 32 is connected to an external Roots blower 31 to improve the mass transfer environment through micro-aeration and alleviate the problem of packing caking. The top of the autotrophic denitrification reactor 25 is connected to a second tail gas absorption tower 35 through a gas pipe 21 to purify the tail gas generated in the deep denitrification process. The input end of the second liquid pump 36 is connected to the bottom end of the autotrophic denitrification reactor 25 through a water pipe 16 to transport the wastewater after deep denitrification to the deep filtration unit.

[0033] like Figure 5 As shown, the deep filtration unit 4 includes a filter tank 37, a filter media support 38, a filter media layer 39, a backwash drain valve 40, a water outlet valve 41, a backwash water pump 42, and a backwash air pipe 43. The upper end of the filter tank 37 is connected to the output end of the second liquid pump 36 via a water pipe 16 to receive wastewater after deep denitrification. Filter media support 38 is fixedly connected to the upper and middle positions inside the chamber of the filter tank 37, and a filter media layer 39 is provided between the filter media support 38, achieving high efficiency through the double-layer filter media. The filter tank 37 traps biofilm fragments and fine suspended solids. A backwashing air pipe 43 is installed on the bottom surface of the chamber, connected to an external backwashing water pump 42. This combined air-water backwashing restores the filter media's filtration performance and extends its service life. A water outlet valve 41 is fixedly connected to the middle side of the filter tank 37 for discharging compliant clean water. A backwash drain valve 40 is fixedly connected to the bottom side of the filter tank 37 for discharging wastewater generated during backwashing, ensuring stable operation of the filtration unit.

[0034] The ceramsite biological packing material 19 is a porous ceramsite packing material with a filling rate of 50%-80% of the effective volume of the reactor. It has a large specific surface area, fast biofilm formation speed, and large amount of biological attachment. The packing layer 29 is a sulfur autotrophic denitrification packing material with a particle size of 3-10mm. It has a moderate particle size, low mass transfer resistance, and stable nitrogen removal efficiency. The filter media layer 39 is a double-layer filter media of quartz sand and anthracite. The upper layer is anthracite filter media, and the lower layer is quartz sand filter media. It has good layered filtration effect, strong interception capacity, and low effluent turbidity.

[0035] The usage state of this invention is as follows: the wastewater to be treated first enters the pretreatment unit 1, where large particulate impurities are intercepted by the screen 6 and suspended solids are settled in the sedimentation tank 7. Then, it is sent to the heterotrophic denitrification unit 2 by the lift pump 9. In the heterotrophic denitrification reactor 13, under the action of the ceramsite biological packing 19 and the stirring device, an appropriate amount of carbon source is added to complete the initial denitrification of nitrates. The tail gas is purified by the first tail gas absorption tower 20, and the sludge is discharged from the first sludge discharge port 22. The initially denitrified wastewater is sent to the autotrophic denitrification unit 3 by the first liquid pump 24, where water is evenly distributed through the water distributor 26 and nozzles 28. Sulfur-self-growth packing achieves deep denitrification through full contact. Roots blower 31 aerates the packing to prevent caking. The exhaust gas is purified by the second exhaust gas absorption tower 35, and the sludge is discharged from the second sludge discharge port 33. The deep denitrification wastewater is sent to the deep filtration unit 4 by the second liquid pump 36. After the suspended impurities are removed by the double-layer filter media, the qualified clean water is discharged through the outlet valve 41. The filtration unit is periodically backwashed by the backwash water pump 42 and the backwash air pipe 43. The backwash wastewater is discharged through the backwash drain valve 40. The whole set of equipment operates continuously and stably, achieving efficient and deep denitrification of nitrates in the wastewater.

[0036] In the description of this invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "other end," "upper," "side," "top," "inner," "front," "center," "both ends," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

[0039] The control method of this invention is to control the device by manually starting and stopping the switch. The wiring diagram of the power element and the supply of power are common knowledge in the field. Since this invention is mainly used to protect mechanical devices, the control method and wiring layout will not be explained in detail.

Claims

1. A heterotrophic autotrophic denitrification combined treatment device, characterized in that: It includes a pretreatment unit (1), a heterotrophic denitrification unit (2), an autotrophic denitrification unit (3), and a deep filtration unit (4) connected in sequence. The pretreatment unit (1) is used to remove suspended solids, large particulate impurities and some organic matter from the wastewater to be treated; The heterotrophic denitrification unit (2) is used to achieve preliminary denitrification of nitrates in wastewater and to provide suitable influent conditions for the autotrophic denitrification unit; The autotrophic denitrification unit (3) is used for deep denitrification of the effluent from the heterotrophic denitrification unit; The deep filtration unit (4) is used to remove impurities such as biofilm fragments and suspended matter generated during the reaction process.

2. A heterotrophic autotrophic denitrification combined treatment apparatus according to claim 1, characterized by: The pretreatment unit (1) includes a pretreatment tank (5), a bar screen (6), a sedimentation tank (7), a baffle plate (8), a booster pump (9), a drain outlet (10), a ball valve (11), and a mounting bracket (12). The bar screen (6) is installed at the inlet end of the pretreatment tank (5); The sedimentation tank (7) is located inside the pretreatment tank (5); The partition (8) is fixedly connected to the right side of the lower surface of the grille (6); The right end of the pretreatment tank (5) is fixedly connected to an installation bracket (12), and a lift pump (9) is fixedly connected to the installation bracket (12). The input end of the lift pump (9) is connected to the right end of the pretreatment tank (5). The pretreatment tank (5) is provided with a drain outlet (10) at the bottom, and a ball valve (11) is provided on the drain outlet (10).

3. The heterotrophic autotrophic denitrification combined treatment device according to claim 1, characterized in that: The heterotrophic denitrification unit (2) includes a heterotrophic denitrification reactor (13), a chemical storage tank (14), a metering pump (15), a water pipe (16), a stirring motor (17), a stirring paddle (18), a ceramic biofiller (19), a first tail gas absorption tower (20), a gas pipe (21), a first sludge discharge port (22), a first sludge discharge valve plate (23), and a first liquid pump (24). The top of the heterotrophic denitrification reactor (13) is connected to the output end of the booster pump (9) via a water pipe (16); The input end of the metering pump (15) is connected to the storage tank (14) via a water pipe (16), and the output end of the metering pump (15) is connected to the top of the heterotrophic denitrification reactor (13) via a water pipe (16). The chamber of the heterotrophic denitrification reactor (13) is equipped with ceramic granule biological packing material (19). A stirring motor (17) is fixedly connected to the top of the heterotrophic denitrification reactor (13), and a stirring paddle (18) is fixedly connected to the output end of the stirring motor (17). The stirring paddle (18) is located inside the chamber of the heterotrophic denitrification reactor (13). The bottom surface of the heterotrophic denitrification reactor (13) is fixedly connected to a first sludge discharge port (22), and a first sludge discharge valve plate (23) is provided in the first sludge discharge port (22). The top of the heterotrophic denitrification reactor (13) is connected to the first tail gas absorption tower (20) via a gas pipe (21); The input end of the first pump (24) is connected to the bottom end of the heterotrophic denitrification reactor (13) through a water pipe (16).

4. The heterotrophic autotrophic denitrification combined treatment device according to claim 1, characterized in that: The autotrophic denitrification unit (3) includes an autotrophic denitrification reactor (25), a water distributor (26), a water distribution plate (27), a nozzle (28), a packing layer (29), a packing layer support frame (30), a Roots blower (31), an aeration plate (32), a second sludge discharge port (33), a second sludge discharge valve plate (34), a second tail gas absorption tower (35), and a second liquid pump (36). The water distributor (26) is fixedly connected to the top of the autotrophic denitrification reactor (25); The input end of the water distributor (26) is connected to the output end of the first liquid pump (24) through a water pipe (16); The upper part of the chamber of the autotrophic denitrification reactor (25) is fixedly connected to a water distribution plate (27), which is connected to a water distributor (26). Several nozzles (28) are fixedly connected to the lower part of the water distribution plate (27). The autotrophic denitrification reactor (25) has a packing layer support frame (30) fixedly connected to the middle of the chamber, and a packing layer (29) is provided on the packing layer support frame (30). The bottom surface of the autotrophic denitrification reactor (25) is fixedly connected to a second sludge discharge port (33), and a second sludge discharge valve plate (34) is provided in the second sludge discharge port (33). The lower end of the chamber of the autotrophic denitrification reactor (25) is fixedly connected to an aeration disc (32), which is connected to an external Roots blower (31). The top of the autotrophic denitrification reactor (25) is connected to the second tail gas absorption tower (35) via a gas pipe (21); The input end of the second pump (36) is connected to the bottom end of the autotrophic denitrification reactor (25) through a water pipe (16).

5. The heterotrophic autotrophic denitrification combined treatment device according to claim 1, characterized in that: The deep filtration unit (4) includes a filter tank (37), a filter media support (38), a filter media layer (39), a backwash drain valve (40), a water outlet valve (41), a backwash water pump (42), and a backwash air pipe (43). The upper end of the filter tank (37) is connected to the output end of the second liquid pump (36) through a water pipe (16); The filter tank (37) has filter media layer brackets (38) fixedly connected at the upper and middle positions inside the chamber, and filter media layers (39) are provided between the filter media layer brackets (38). The filter tank (37) has a backwashing air pipe (43) on the bottom surface inside the chamber, and the backwashing air pipe (43) is connected to the external backwashing water pump (42). The filter tank (37) is fixedly connected to the middle side with a water outlet valve (41), and the filter tank (37) is fixedly connected to the bottom side with a backwash drain valve (40).

6. The heterotrophic autotrophic denitrification combined treatment device according to claim 3, characterized in that: The ceramsite biological packing material (19) is a porous ceramsite packing material with a filling rate of 50%-80% of the effective volume of the reactor.

7. The heterotrophic autotrophic denitrification combined treatment device according to claim 4, characterized in that: The packing layer (29) is a sulfur autotrophic denitrification packing with a particle size of 3-10 mm.

8. The heterotrophic autotrophic denitrification combined treatment device according to claim 5, characterized in that: The filter media layer (39) is a double-layer filter media of quartz sand and anthracite, with the upper layer being anthracite filter media and the lower layer being quartz sand filter media.

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