An apparatus and method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification

Abstract

The present invention discloses a device for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification, comprising: a reaction tank body, an upper partition board, a lower partition board, a photocatalyst, a first light source, an aeration disc and an external hydrogen gas cylinder; the upper partition board and the lower partition board are arranged in the reaction tank body separately along the axial direction of the reaction tank body from top to bottom, dividing the reaction tank body from top to bottom into three regions: an upper region, a middle region and a bottom region, and air-permeable micropores are opened on both the upper partition board and the lower partition board; the photocatalyst is filled in the middle region; the first light source is arranged on the side of the upper partition board facing the photocatalyst to apply light to the photocatalyst; the aeration disc is arranged at the bottom of the reaction tank body and is connected to the external hydrogen gas cylinder through a pipeline. The present invention utilizes the hydrogen generated by the photocatalyst to decompose water under light conditions to supply hydrogen autotrophic denitrifying bacteria, while improving the metabolic activity of hydrogen autotrophic bacteria, saving energy substances and avoiding the operation hazards of supplying hydrogen from the outside.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment devices, and particularly to a device and method for treating sewage by photocatalysis combined with hydrogen autotrophic denitrification. Background Art

[0002] Drinking groundwater contaminated with nitrate can seriously endanger human health, and may cause methemoglobinemia and induce cancer. Currently, nitrate-contaminated water with a low organic carbon content is widespread, which has a certain impact on the ecological environment and human health. At the same time, due to the limitation of the organic carbon content in the water body and factors such as treatment costs, the current treatment technologies for such nitrate-contaminated water bodies are still relatively limited. Compared with other current technologies for treating nitrate-contaminated groundwater, hydrogen autotrophic denitrification is a promising and more environmentally friendly technology that can provide safe drinking water. H2 neither harms the environment nor causes damage to human health, and the hydrogen autotrophic denitrification method only requires an inorganic carbon source to complete its own metabolism, which can avoid secondary pollution caused by adding external organic matter, and is very suitable for treating nitrate-contaminated groundwater with a low carbon-nitrogen ratio. Compared with heterotrophic bacteria, the amount of excess sludge produced by hydrogen autotrophic bacteria denitrification is lower, which can effectively reduce the reactor blockage and simplify the subsequent treatment process. No harmful by-products are produced due to the substrate during the denitrification process, and hydrogen as the electron donor will not persist in the treated water. However, due to the low nitrate utilization rate and the difficulties in hydrogen transportation and storage, the hydrogen autotrophic denitrification technology is limited in practical applications. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the present invention provides a device and method for treating sewage by photocatalysis combined with hydrogen autotrophic denitrification to solve the technical problems of the safety of external H2 storage and transportation required in the implementation of hydrogen autotrophic denitrification in the prior art.

[0004] The present invention provides a device for treating sewage by photocatalysis combined with hydrogen autotrophic denitrification, including: a reaction tank body, an upper partition board, a lower partition board, a photocatalyst, a first light source, an aeration disc and an external hydrogen cylinder;

[0005] The upper partition board and the lower partition board are arranged in the reaction tank body along the axial direction of the reaction tank body, dividing the reaction tank body from top to bottom into three regions: an upper region, a middle region and a bottom region. The upper partition board and the lower partition board are both provided with air-permeable micropores; the photocatalyst is filled in the middle region; the first light source is arranged on the side of the upper partition board facing the photocatalyst to apply light to the photocatalyst; the aeration disc is arranged at the bottom of the reaction tank body and is connected to the external hydrogen cylinder through a pipeline.

[0006] Further, the heights of the middle region and the bottom region account for 1 / 3 of the internal height of the reaction tank body.

[0007] Further, the height of the middle region accounts for 1 / 10 to 1 / 5 of the internal height of the reaction tank body.

[0008] Further, the upper partition plate and the lower partition plate are detachably arranged in the reaction tank body.

[0009] Further, the device for photocatalytic synergistic hydrogen autotrophic denitrification for treating sewage further includes: a second light source; the second light source is arranged on the side of the lower partition plate facing the photocatalyst to apply light to the photocatalyst.

[0010] Further, both the first light source and the second light source are waterproof lamp belts.

[0011] Further, the side wall of the reaction tank body is of a double-layer structure, and there is a cavity between the inner wall and the outer wall.

[0012] Further, the photocatalyst is a photocatalyst slow-release ball, wherein the photocatalyst slow-release ball is formed by mixing sodium alginate emulsion and photocatalytic material, and the volume ratio range of the sodium alginate emulsion to the photocatalytic material is 1:10 to 1:5. The mass percentages of the components in the sodium alginate emulsion are: 8 to 15% of sodium alginate, 0.5% to 1% of kaolin, and 0.5% to 1% of Fe3O4.

[0013] Further, the cavity serves as a water bath layer or is filled with heat-insulating material.

[0014] Further, the material of the reaction tank body is: transparent acrylic material.

[0015] The present invention also provides a method for photocatalytic synergistic hydrogen autotrophic denitrification for treating sewage, using the above device for photocatalytic synergistic hydrogen autotrophic denitrification for treating sewage, including:

[0016] Step 1: Place the photocatalyst slow-release balls between the upper partition plate and the lower partition plate, add hydrogen autotrophic denitrification sludge into the reaction tank body, pour the sewage to be treated, and seal the reaction tank body;

[0017] Step 2: Introduce hydrogen into the reaction tank body to remove dissolved oxygen;

[0018] Step 3: Start entering the reaction cycle:

[0019] When the total nitrogen removal rate reaches more than 70%, add photocatalyst slow-release balls into the reaction tank body, and the addition amount is: increase by 50 - 150 mg / L based on the previous total addition amount, and reduce the external hydrogen supply amount until the total hydrogen amount in the reaction tank body reaches the minimum required amount of reaction hydrogen;

[0020] Step 4: Repeat Step 3 until the external hydrogen supply is zero, completing the coupling of the photocatalytic process and the hydrogen autotrophic denitrification biological process, and achieving hydrogen self-sufficiency in the sewage treatment process.

[0021] Further, in Step 3, during the reaction cycle, the light intensity of the light source is: 200 - 800 mW / cm 2 .

[0022] Further, the preparation method of the photocatalyst slow-release beads in Step 3 is as follows:

[0023] Dissolve sodium alginate, kaolin, and Fe3O4 in deionized water, mix and stir evenly, then heat and dissolve at 90 °C for 2 hours, and cool to room temperature to obtain a SA colloidal emulsion; dissolve the photocatalyst in deionized water, and mix and stir evenly at a volume ratio of SA colloidal emulsion:photocatalyst of 1:10 to 1:5. Slowly drip the photocatalytic material / SA mixture into a saturated boric acid solution containing 5 wt% calcium chloride using a peristaltic pump, and carry out a cross-linking reaction for 3 - 4 hours; repeatedly rinse with deionized water to remove uncrosslinked monomers to obtain the photocatalyst slow-release beads.

[0024] Advantages of the present invention:

[0025] The present invention utilizes the hydrogen generated by the photocatalyst to decompose water under light conditions to supply hydrogen autotrophic denitrifying bacteria. While enhancing the metabolic activity of hydrogen autotrophic bacteria, it saves energy substances, avoids the operation hazards of external hydrogen supply. In addition, the hydrogen production rate can be controlled by controlling the dosage of the photocatalyst and the light intensity. At the same time, the photogenerated electrons generated by the photocatalyst can be used as biologically available reducing equivalents to improve metabolism and further increase the nitrate removal rate. Description of the Drawings

[0026] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as limiting the present invention in any way. In the drawings:

[0027] Figure 1 is a schematic structural diagram of a specific embodiment of the present invention;

[0028] Figure 2 is a schematic diagram showing the change of NO3 - -N removal rate in the effluent of the reactor in Specific Embodiment 1 of the present invention;

[0029] Figure 3 is a schematic diagram showing the change of NO3 - -N removal rate in the effluent of the reactor in Specific Embodiment 2 of the present invention. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] The following further clarifies the present invention with specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Modifications to various equivalent forms of the present invention fall within the scope defined by the appended claims of this application.

[0032] As Figure 1 shown, the present invention provides a device for photocatalytic synergistic hydrogen autotrophic denitrification to treat sewage, including: a reaction tank body 1, an upper partition plate 2, a lower partition plate 3, photocatalyst slow-release pellets 4, a first light source 51, a second light source 52, an aeration disc 6, and an external hydrogen cylinder 7;

[0033] The reaction tank body 1 is preferably made of transparent acrylic material, including a tank body and a sealed cover plate 12 covering the top of the tank body, and is integrally a sealed cylinder. The reaction tank body 1 can hold sewage; a gas sampling port is opened on the sealed cover plate 12 at the top of the reaction tank body 1, which can be used to sample the hydrogen condition in the reaction tank body 1; a liquid sampling port is opened on the tank wall in the upper area of the reaction tank body 1, which can be used to sample the liquid in the upper area of the reaction tank body 1; a hydrogen access hole is opened on the tank wall in the lower area of the reaction tank body 1, through which the pipeline connecting the aeration disc 6 and the external hydrogen cylinder 7 can pass; the tank wall of the reaction tank body 1 is a double-layer tank wall structure, with an inner wall and an outer wall, and there is a cavity 8 between the inner wall and the outer wall. The cavity 8 can be used as a water bath layer or filled with heat-insulating materials, etc., to adjust and maintain the temperature in the reaction tank body 1.

[0034] Both the upper partition plate 2 and the lower partition plate 3 are transparent partition plates, and air-permeable micropores are opened on the partition plates, through which hydrogen bubbles can pass. The diameter of the air-permeable micropores is smaller than that of the photocatalyst slow-release pellets 4; the upper partition plate 2 and the lower partition plate 3 are horizontally arranged in the reaction tank body 1 and are axially separated up and down along the reaction tank body 1. The upper partition plate 2 is arranged above the lower partition plate 3. The upper partition plate 2 and the lower partition plate 3 divide the reaction tank body 1 from top to bottom into three regions: an upper region, a middle region, and a bottom region; the heights of the middle region and the bottom region preferably account for 1 / 3 of the internal height of the reaction tank body 1, and the hydrogen generated by the photocatalytic reaction can escape upward and fully contact with the activated sludge; the height of the middle region accounts for 1 / 10 - 1 / 5 of the internal height of the reaction tank body 1.

[0035] The photocatalyst slow-release pellets 4 are filled in the middle region;

[0036] The first light source 51 is arranged on the bottom surface of the upper partition plate 2, that is, the side facing the photocatalyst slow-release balls 4, to apply light to the photocatalyst slow-release balls 4; the second light source 52 is arranged on the top surface of the lower partition plate 3, that is, the side facing the photocatalyst slow-release balls 4, to apply light to the photocatalyst slow-release balls 4; the first light source 51 and the second light source 52 are waterproof lamp belts, preferably visible light lamp belts or xenon lamp belts; preferably, one lamp belt is arranged in a circular or serpentine shape; it is also possible to preferably arrange multiple lamp belts at intervals; when multiple lamp belts are arranged at intervals, the lamp belts on the upper and lower partition plates 3 are arranged in a staggered manner. By setting the lamp belts, the irradiation mode of the light source can be adjusted to adapt to reaction tanks 1 of different sizes and ensure the uniformity of the light irradiation on the photocatalyst slow-release balls 4; the lamp belts are all connected to an external control circuit, and the external control circuit can control the on / off and brightness of the lamp belts;

[0037] The aeration disc 6 is arranged at the bottom of the reaction tank 1 and is connected to an external hydrogen cylinder 7 through a pipeline to provide a basic hydrogen gas volume in the reaction tank 1.

[0038] When assembling the device of the present invention, first place the aeration disc 6 at the bottom of the reaction tank 1, connect it to an external hydrogen cylinder 7 through a pipeline, and the connected pipeline passes through the hydrogen access hole; then place the lower partition plate 3 equipped with a lamp belt into the reaction tank 1 and fix it at the designed height with the side with the lamp belt facing up; then pour a certain amount of photocatalyst slow-release balls 4 into the reaction tank 1, and the photocatalyst slow-release balls 4 accumulate on the lower partition plate 3; then place the upper partition plate 2 equipped with a lamp belt into the reaction tank 1 until it is above the photocatalyst slow-release balls 4 and then fix it with the side with the lamp belt facing down; the upper partition plate 2, the photocatalyst slow-release balls 4, and the lower partition plate 3 form the middle area of the reaction tank 1, and the height of the middle area can be set according to specific requirements; based on the SBR batch reaction mode, sewage and the required hydrogen autotrophic denitrifying activated sludge, etc. are added to the reaction tank 1, and then the sealing cover plate 12 is covered to seal the entire reaction tank 1 for the reaction cycle. During the process, the gas in the upper area can be sampled through the gas sampling port on the sealing cover plate 12 using the gas sampling tube 91; the liquid in the upper area can also be sampled through the liquid sampling port on the tank wall of the reaction tank 1 using the liquid sampling tube 103.

[0039] It should be noted that the fixing methods, hole-opening methods, etc. of the various components in the device all belong to conventional construction methods, which are familiar to those skilled in the art, and those skilled in the art can know how to implement them; the external control circuit is also a conventional basic control circuit for controlling the turning on and brightness adjustment of the lamp belt, which is familiar to those skilled in the art, and those skilled in the art can know how to implement it, so no specific description is made in the content of the present invention.

[0040] The following is the method process for effective simultaneous nitrogen and carbon removal from low carbon-nitrogen ratio sewage using the device of the present invention:

[0041] Step 1: Reactor acclimation stage: The anaerobic sludge from the denitrification tank of the sewage treatment plant is allowed to stand to obtain denitrifying sludge, which is placed in a Sequencing batch reactor activated sludge process (SBR) reactor and acclimated and cultured according to the operating conditions shown in Table 1 below for the SBR reactor acclimation period. Add NaHCO3, NaNO3 and trace elements, introduce H2 and exhaust the dissolved oxygen.

[0042]

[0043] Table 1

[0044] Constant temperature stirring culture. When the NO3 - removal rate reaches more than 80 - 90%, a denitrification cycle is completed. After the cycle ends, replenish NaNO3 and continue acclimation until the denitrification cycle (i.e., the hydraulic retention time, HRT) is shortened to 8 h, which is regarded as successful acclimation. Under different HRT conditions, the operating conditions within one cycle of SBR are set as shown in Table 2 Operating conditions within one cycle of SBR under different HRT conditions. During the sludge acclimation and culture period, measure the pH regularly. When the pH value exceeds 8, add NaHCO3 to adjust the pH to 6 - 7.

[0045]

[0046] Table 2

[0047] Step 2: Preparation of photocatalytic slow-release beads: Weigh a certain amount of sodium alginate (SA), kaolin and Fe3O4, dissolve them in deionized water, mix and stir evenly, and then heat and dissolve at 90 °C for 2 h to obtain an SA colloidal emulsion. Cool to room temperature. The mass percentages of each component are 8 - 15% SA, 0.5% - 1% kaolin and 0.5% - 1% Fe3O4; Take a certain amount of photocatalytic material, dissolve it in deionized water, and then mix and stir evenly with the SA emulsion in a ratio of 1:10 - 1:5; Slowly drip the photocatalytic material / SA mixture into a saturated boric acid solution containing 5 wt% calcium chloride using a peristaltic pump, and carry out a cross-linking reaction for 3 - 4 h. Use deionized water to repeatedly wash away the uncross-linked monomers to obtain photocatalyst slow-release beads;

[0048] Step 3: Photocatalytic reaction coupling stage: Place the photocatalyst slow-release pellets prepared in Step 2 between the upper and lower partitions of the device of the present invention, install the waterproof lamp belt, and at the same time place the hydrogen autotrophic denitrifying sludge domesticated in Step 1 in the device to treat low-carbon-nitrogen ratio nitrate wastewater. Introduce H2 gas into the device to remove dissolved oxygen. The domesticated sludge, sewage, and photocatalyst slow-release pellets form a photocatalytic coupling biodegradation reactor, which is the state when the device of the present invention is in use. Under light conditions, microorganisms use the H2 generated by the photocatalyst reaction to carry out hydrogen autotrophic denitrification reaction. During the photocatalytic coupling hydrogen autotrophic denitrification reaction process, the method of gradually reducing the externally added H2 is adopted, so that the functional microorganisms in the reactor gradually use the H2 generated by water photolysis as the electron donor for denitrification. In one cycle of SBR, the water inlet is set for 15 minutes, the reaction is for 6.5 hours, the precipitation is for 1 hour, and the water outlet is for 15 minutes. As shown in Table 3, the operating conditions of the photocatalyst coupling period of the hydrogen autotrophic denitrification reactor, from the 78th to the 89th day of operation, add 50 mg / L of photocatalyst slow-release pellets to the reactor, and the externally added H2 pressure is reduced from 0.07 - 0.08 MPa to 0.05 - 0.06 MPa; from the 90th to the 105th day of operation, the dosage of photocatalyst slow-release pellets is increased to 100 mg / L, and the externally added H2 pressure is reduced from 0.05 - 0.06 MPa to 0.03 - 0.04 MPa; while from the 106th to the 126th day of operation, the dosage of photocatalyst slow-release pellets is increased to 200 mg / L, and the externally added H2 pressure is further reduced to 0.01 - 0.02 MPa; on the 127th day of operation, the dosage of photocatalyst slow-release pellets is adjusted to 300 mg / L, and at this time the externally added H2 pressure is zero. The H2 generated by the photocatalyst for water photolysis can replace part of the externally added H2, and finally realize the effective coupling of the photocatalytic reaction and the hydrogen autotrophic denitrification biological process, saving the externally added H2 energy.

[0049] During the process, the determination of the days such as the 78th to the 89th day and the 90th to the 105th day is based on whether the total nitrogen removal rate reaches more than 70%. The amount of reduced air pressure is also obtained according to actual experiments.

[0050]

[0051] Table 3

[0052] The following are two specific implementation processes of the method of the present invention:

[0053] Example 1:

[0054] Place the activated sludge in the device of the present invention for cultivation and domestication to enrich the hydrogen autotrophic denitrifying functional flora. During the domestication process, artificial water is used for water distribution, and NO3 in the influent -The concentration of -N is 30 mg / L, and the artificial influent water quality characteristics are 0.180 mg / L NaNO3, 6.50 mg / L NaHCO3, 7.3 mg / L CaCl2·2H2O, 5.0 mg / L FeSO4·7H2O, 2.5 mg / L MnCl2·4H2O, 0.5 mg / L CoCl2·6H2O, 0.5 mg / L (NH4)6Mo7O 24 ·4H2O, 0.22 mg / L ZnSO4·7H2O and 0.2 mg / L CuSO4·5H2O. The water temperature is controlled at 30 - 35 °C. Under the condition of constant temperature stirring, H2 is introduced into the reactor as an electron donor, and the inlet gas pressure is 0.07 - 0.08 MPa. The enrichment of hydrogen autotrophic denitrifying bacteria is achieved by gradually reducing the hydraulic retention time. The initial hydraulic retention time is set to 36 h. When the concentrations of NO3 - and NO2 - are reduced to 0.2 mg / L and 0.1 mg / L respectively, the hydraulic retention time is shortened to 24 h and continuous domestication is carried out until the hydraulic retention time is shortened to 8 h and the removal rate of NO3 - in the effluent is stable above 90%, which is regarded as successful domestication.

[0055] Under different HRT conditions, the operation of one cycle of SBR is set as shown in Table 2. When HRT = 36 h, the influent is for 15 min, the reaction is for 33.5 h, the sedimentation is for 2 h, and the effluent is for 15 min; when HRT = 24 h, the influent is for 15 min, the reaction is for 21.5 h, the sedimentation is for 2 h, and the effluent is for 15 min; when HRT = 12 h, the influent is for 15 min, the reaction is for 10.5 h, the sedimentation is for 1 h, and the effluent is for 15 min; when HRT = 8 h, the influent is for 15 min, the reaction is for 6.5 h, the sedimentation is for 1 h, and the effluent is for 15 min. During the domestication process of hydrogen autotrophic denitrifying sludge, the change of NO3 - -N removal rate in the effluent with time is as Figure 2 shown.

[0056] Example 2:

[0057] A photocatalyst slow-release sphere is prepared by using the photocatalytic material graphite-phase carbon nitride (g-C3N4) and sodium alginate, and the photocatalyst released by the sphere is used to photocatalytically decompose water to produce hydrogen, providing an electron donor for the hydrogen autotrophic denitrification process.

[0058] Among them, the preparation steps of g-C3N4 are as follows: Weigh a certain mass of melamine and put it into a crucible with a lid. Place the crucible in a muffle furnace and heat it in an air atmosphere. The initial temperature is 20 °C, and it is heated to 500 °C at a heating rate of 5 °C / min and kept for 300 min. After the calcined product is naturally cooled, it is ground, dried and stored to prepare g-C3N4.

[0059] The domesticated hydrogen autotrophic denitrifying activated sludge was placed in the device of the present invention to treat nitrate wastewater with a low carbon-nitrogen ratio. The artificial simulated wastewater had a NO3 - concentration of 30 mg / L, a COD concentration of 60 mg / L, a C / N of 2, a sludge concentration set at 2000 mg / L, and a hydraulic retention time set at 8 h.

[0060] In one cycle of SBR, the water inlet was set for 15 min, the reaction was for 6.5 h, the sedimentation was for 1 h, and the water outlet was for 15 min. At the initial stage of the reactor operation, 50 mg / L of g-C3N4 / SA slow-release pellets were added. Under the illumination condition, the functional bacteria used the H2 generated by the photocatalytic water splitting reaction of g-C3N4 for hydrogen autotrophic denitrification reaction. The illumination intensity was 500 mW / cm 2 2. Aeration was carried out with H2 through a needle for 5 - 10 minutes to create an anoxic / anaerobic environment. At this time, the external H2 pressure was 0.05 - 0.06 MPa; as the reactor continued to operate, the microorganisms in the activated sludge gradually adapted to the photocatalytic reaction and coupled with it, increasing the dosage of g-C3N4 / SA slow-release pellets to 100 mg / L. At this time, the external H2 pressure decreased to 0.03 - 0.04 MPa; when the dosage of g-C3N4 / SA slow-release pellets reached 200 mg / L, the external H2 pressure was 0.01 - 0.02 MPa; when the dosage of g-C3N4 / SA slow-release pellets reached 300 mg / L, the photocatalytic reaction was successfully coupled with hydrogen autotrophic denitrification. At this time, the external H2 pressure was 0 MPa. To ensure sufficient reaction, the reaction temperature was controlled at 30 °C.

[0061] During the operation of the photocatalyst slow-release pellet coupled hydrogen autotrophic denitrification reactor, the change of the NO3 - -N removal rate in the effluent with time was as shown in Figure 3 . From the NO3 - -N removal performance, it can be seen that by using the method provided by the present invention to treat NO3 - -N in groundwater with a low C / N ratio, when the reactor ran to the 148th - 158th day, the NO3 - -N concentration in the effluent was 2.43 - 2.94 mg / L, and the removal rate of NO3 - -N in water reached 90.2 - 91.9%.

[0062] It can be seen from this that adding a photocatalyst can effectively improve the degradation efficiency of hydrogen autotrophic denitrifying bacteria on NO3 - -N in groundwater with a low carbon-nitrogen ratio, reduce the total nitrogen content in the effluent, and at the same time improve the metabolic activity of hydrogen autotrophic denitrifying bacteria. In addition, the photogenerated electrons produced by the photocatalytic reaction can also improve the denitrification efficiency of hydrogen autotrophic denitrifying bacteria through the electron transfer chain.

[0063] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification, characterized in that, Sewage treatment is carried out using a device for treating sewage by photocatalysis combined with hydrogen autotrophic denitrification. The device includes: a reaction tank body, an upper partition board, a lower partition board, a first light source, an aeration disc and an external hydrogen cylinder; The upper partition board and the lower partition board are arranged in the reaction tank body separately along the axial direction of the reaction tank body, dividing the reaction tank body from top to bottom into three regions: an upper region, a middle region and a bottom region. The upper partition board and the lower partition board are both provided with breathable micropores; photocatalytic slow-release balls are filled in the middle region; the first light source is arranged on the side of the upper partition board facing the photocatalyst to apply light to the photocatalytic slow-release balls; the aeration disc is arranged at the bottom of the reaction tank body and is connected to the external hydrogen cylinder through a pipeline; The method includes the following steps: Step 1: Add NaHCO3, NaNO3 and trace elements to the sewage, and introduce hydrogen to domesticate the activated sludge; Step 2: Prepare photocatalytic slow-release balls, specifically: Dissolve sodium alginate, kaolin and Fe3O4 in deionized water, with mass percentages of: sodium alginate 8-15%, kaolin 0.5%-1% and Fe3O4 0.5%-1%. After mixing and stirring evenly, heat and dissolve at 90°C for 2 hours, and cool to room temperature to obtain an SA colloidal emulsion; dissolve the photocatalyst in deionized water, and mix and stir evenly at a volume ratio of SA colloidal emulsion:photocatalyst of 1:10-1:

5. Slowly drip the photocatalytic material / SA mixture into a saturated boric acid solution containing 5wt% calcium chloride using a peristaltic pump, and carry out a cross-linking reaction for 3-4 hours; repeatedly rinse with deionized water to remove uncross-linked monomers to obtain photocatalyst slow-release balls; Step 3: Place the photocatalytic slow-release balls between the upper partition board and the lower partition board, add hydrogen autotrophic denitrification sludge to the reaction tank body, pour the sewage to be treated, and seal the reaction tank body; Step 4: Introduce hydrogen into the reaction tank body to remove dissolved oxygen; Step 5: Start the reaction cycle: When the total nitrogen removal rate reaches more than 70%, add photocatalytic slow-release balls to the reaction tank body, and the addition amount is: increase by 50-150 mg / L on the basis of the previous total addition amount, and reduce the external hydrogen supply until the total amount of hydrogen in the reaction tank body reaches the minimum required amount of reaction hydrogen; Step 6: Repeat Step 5 until the external hydrogen supply is zero, complete the coupling of the photocatalytic process and the hydrogen autotrophic denitrification biological process, and achieve hydrogen self-sufficiency in the sewage treatment process.

2. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 1, characterized in that, In Step 1, the specific domestication process is: Set the pressure of introducing hydrogen to be 0.07-0.08 MPa, and the total domestication time is 77 days. Among them, from 1 to 10 days, the HRT is 36 hours, the water inlet is for 15 minutes, the reaction is for 33.5 hours, the precipitation is for 2 hours, and the water outlet is for 15 minutes; from 11 to 25 days, the HRT is 24 hours, the water inlet is for 15 minutes, the reaction is for 21.5 hours, the precipitation is for 2 hours, and the water outlet is for 15 minutes; from 26 to 46 days, the HRT is 12 hours, the water inlet is for 15 minutes, the reaction is for 10.5 hours, the precipitation is for 1 hour, and the water outlet is for 15 minutes; from 47 to 77 days, the HRT is 8 hours, the water inlet is for 15 minutes, the reaction is for 6.5 hours, the precipitation is for 1 hour, and the water outlet is for 15 minutes.

3. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 1, characterized in that, The height of the middle area and the bottom area accounts for 1 / 3 of the internal height of the reaction tank body, and / or the height of the middle area accounts for 1 / 10 to 1 / 5 of the internal height of the reaction tank body.

4. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification as described in claim 3, characterized in that, The upper partition plate and the lower partition plate are detachably arranged in the reaction tank body.

5. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 1, wherein, The device for photocatalytic synergistic hydrogen autotrophic denitrification to treat sewage further includes: a second light source; the second light source is arranged on the side of the lower partition plate facing the photocatalyst to apply light to the photocatalyst.

6. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 1, wherein, The side wall of the reaction tank body is of a double-layer structure, and there is a cavity between the inner wall and the outer wall.

7. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 6, characterized in that, The cavity serves as a water bath layer or is filled with heat-insulating materials.

8. The method for treating sewage by photocatalytic synergistic hydrogen autotrophic denitrification according to claim 1, characterized in that In step 3, during the reaction cycle, the light intensity of the light source is: 200 - 800 mW / cm 2 .

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