Biochar wetland desulfurization and denitrification system based on rotary reactor

Abstract

The invention belongs to the technical field of water treatment, and particularly relates to a biochar wetland desulfurization and denitrification system based on a rotary reactor. The system comprises a rotary sulfate reduction unit and a charcoal-based artificial wetland unit which are connected in series, a rotary filler device, a Ca-charcoal complex layer and a granular calcium sulfide solid layer are arranged in the rotary unit, the concentration of SO4 < 2-> / S2 <-> is monitored in real time through an ion selective electrode, and filler lifting and wastewater backflow are linked; and the wetland unit adopts a charcoal-sand mixed matrix layer to plant reeds. And adsorbing and reducing SO4 < 2-> by the wastewater through the rotating unit to generate CaSO4 precipitate, and releasing S < 2-> to enter the wetland to drive sulfur autotrophic denitrification. The removal rate of SO4 < 2-> in high-sulfate and low-carbon-nitrogen-ratio wastewater is greater than 84%, the removal rate of NO3 <-> is greater than 66%, the COD effluent is less than 20mg / L, and the problems of high water mineralization degree and nitrogen removal inhibition are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a biochar wetland desulfurization and denitrification system based on a rotary reactor. Background Art

[0002] Traditional biological treatment technology has systemic defects when dealing with high-sulfate and low-carbon-nitrogen ratio wastewater: the denitrification process is hindered due to insufficient carbon sources, and the denitrification efficiency is generally less than 50%; high concentrations of sulfate will inhibit the activity of denitrifying microorganisms and produce corrosive sulfides. At the same time, the accumulation of reduced product sulfides can easily cause equipment corrosion; the flux of subsurface artificial wetlands is attenuated by more than 80% due to the compaction of fillers, and the practice of adding external carbon sources to enhance the denitrification effect will cause the effluent COD to exceed the standard, resulting in secondary pollution.

[0003] The present invention constructs a coupling system of a rotating sulfate reduction unit and a biochar-based artificial wetland unit, and adopts an ion selective electrode linked filler layer control technology to increase SO4 2- The removal rate is over 84%, NO3 - The removal rate exceeded 66%; the mass transfer efficiency was enhanced by a rotatable packing device, and the combination of a biochar-sand mixed matrix and a perforated stainless steel support plate design increased the system's anti-clogging ability by 80% and achieved long-term stable operation; ultimately, without the need for an external carbon source, the problems of high sulfate inhibition, low denitrification efficiency from low carbon sources, and secondary pollution were simultaneously solved. Summary of the Invention

[0004] The present invention provides a biochar wetland desulfurization and denitrification system based on a rotary reactor, which is used to solve the defects of low treatment efficiency, high carbon source demand, easy clogging and secondary pollution in the existing technology when treating high sulfate and low carbon-nitrogen ratio wastewater.

[0005] In one aspect, the present invention provides a biochar wetland desulfurization and denitrification system based on a rotary reactor, comprising a rotary sulfate reduction unit, a biochar-based constructed wetland unit, a data transmission device, and a remote monitoring device connected in series; The rotary sulfate reduction unit comprises: a rotatable filling device, a first peristaltic pump, a Ca-bacteria carbon complex layer, a rotating rod, a perforated stainless steel support plate, a second peristaltic pump, a granular calcium sulfide solid layer, an ion selective electrode, a rope chain, a heating electrode, a temperature sensor, a third peristaltic pump, a rotary sulfate reduction unit water inlet, a wastewater outlet, and a rotary sulfate reduction unit water outlet; The biochar-based artificial wetland unit comprises: a biochar-based artificial wetland unit water inlet, a gravel support layer, a biochar-sand mixed matrix layer, a water layer, and a biochar-based artificial wetland unit water outlet; The data transmission device is used to transmit temperature and SO4 2- 、S 2-Ion concentration is transmitted to a remote monitoring device in real time; The remote monitoring device is used to monitor water quality in real time and control the rotating sulfate reduction unit.

[0006] According to a biochar wetland desulfurization and denitrification system based on a rotary reactor provided by the present invention, the rotatable filling device is driven by a rotating rod; The Ca-bacteria carbon complex layer and the granular calcium sulfide solid layer are arranged in a rotatable filling device; The solid layer of granular calcium sulfide is raised and lowered by a rope chain; The perforated stainless steel support plate has a pore diameter of 1-5 mm, is connected to the rotating rod and supports the filler; The ion selective electrode is used to detect SO4 in the effluent of the rotary sulfate reduction unit. 2- 、S 2- Real-time detection of ion concentration; The heating electrode is used to heat the water body; The temperature sensor is used to detect the water temperature; The wastewater outlet is connected to the water inlet of the rotary sulfate reduction unit via a third peristaltic pump; The first peristaltic pump and the third peristaltic pump are used to control the amount of water discharged into the rotary sulfate reduction unit; The water outlet of the rotary sulfate reduction unit is connected to the water inlet of the biochar-based artificial wetland unit through a second peristaltic pump; The second peristaltic pump is used to control the discharge of the effluent from the rotary sulfate reduction unit into the biochar-based artificial wetland unit.

[0007] According to the present invention, a biochar wetland desulfurization and denitrification system based on a rotating reactor is provided, wherein the biochar-based artificial wetland unit comprises, from bottom to top, a gravel support layer, a biochar-sand mixed matrix layer, and a water layer; The gravel support layer is filled with gravel with an average particle size of 2 to 4 cm and a height of 5 cm; The biochar-sand mixed matrix layer is a mixture of sand with a particle size of 1 to 5 mm and biochar with a particle size of 1 to 7 mm in a volume ratio of 75 to 95:5 to 25; The water layer height is 8~12cm, with 20~40 plants / m 2 Plant reeds at a planting density of The water inlet of the biochar-based artificial wetland unit is set 3 to 8 cm above the water layer; The water outlet of the biochar-based artificial wetland unit is aligned with the water level of the water layer.

[0008] According to the present invention, a biochar wetland desulfurization and denitrification system based on a rotating reactor is provided. The Ca-bacterial carbon complex layer is composed of CaCl2-modified agricultural production waste activated carbon loaded with sulfate-reducing bacteria, filled with three layers, each layer is 10-20 cm high, the filler particle size is 3-5 mm, and the interlayer spacing is 15-25 cm; The agricultural production waste is one or more of corn cobs, rice husks, and straws, the modification concentration is 5-10wt%, and the bacterial load is 10-15%.

[0009] According to a biochar wetland desulfurization and denitrification system based on a rotating reactor provided by the present invention, the solid layer of granular calcium sulfide is arranged 15 to 25 cm above the Ca-bacteria carbon complex layer, with a filling height of 3 to 7 cm and a calcium sulfide particle size of 3 to 5 mm; The calcium sulfide filler in the solid layer of granular calcium sulfide is filled with a microporous organic glass material, and the micropore diameter is 0.5-1mm; The granular calcium sulfide solid layer is provided with a heating rod below the calcium sulfide filler for heating the water to 20-25°C.

[0010] According to the biochar wetland desulfurization and denitrification system based on the rotary reactor provided by the present invention, an aeration reflow tank is also provided between the water inlet and the wastewater outlet of the rotary sulfate reduction unit to oxidize the dissolved low-valent sulfur into SO4 2- It is then adsorbed and removed, thereby reducing the corrosion of sulfides to the equipment.

[0011] According to a biochar wetland desulfurization and denitrification system based on a rotary reactor provided by the present invention, the ion selective electrode performs the following control: When SO4 2- When the concentration is >250mg / L, wastewater backflow is triggered; When S 2- When the concentration is >33.1 mg / L, the solid layer of granular calcium sulfide is increased; When S 2- When the concentration is <18.3 mg / L, a solid layer of granular calcium sulfide descends.

[0012] According to a biochar wetland desulfurization and denitrification system based on a rotary reactor provided by the present invention, the heating electrode and the temperature sensor are linked to control the water temperature to be 20-25°C.

[0013] On the other hand, the present invention also provides a biochar wetland desulfurization and denitrification method based on a rotary reactor, comprising the following steps: (1) Plants and substrates were cultured in simulated wastewater without sulfate for 30 days; (2) The simulated wastewater enters the rotary sulfate reduction unit and runs at a speed of 250 rpm and a hydraulic retention time of 2-4 days. The effluent SO4 is monitored in real time by an ion selective electrode. 2- and S 2- Concentration, and regulate the rise and fall of the granular calcium sulfide solid layer and the wastewater return according to the concentration; (3) The effluent from the rotary sulfate reduction unit enters the biochar-based constructed wetland unit with a hydraulic retention time of 4 days, and reacts in the biochar-sand mixed matrix layer, including: Aerobic zone: NH4 + →NO3 - ; Anaerobic zone: NO3 - + biochar / organic carbon → N2↑; Sulfur-denitrification reaction: S 2- +NO3 - →SO4 2- +N2↑.

[0014] According to the biochar wetland desulfurization and denitrification method based on a rotary reactor provided by the present invention, the hydraulic retention time in step (2) is based on the influent SO4 2- Concentration adjustment: SO4 2- =500mg / L, the hydraulic retention time is 2 days; SO4 2- =1000mg / L, the hydraulic retention time is 2.5 days; SO4 2- =2000mg / L, the hydraulic retention time is 4 days.

[0015] The biochar wetland desulfurization and denitrification system based on the rotating reactor provided by the present invention absorbs SO4 through the Ca-bacteria carbon complex layer in the rotating unit and reduces SO4 through microorganisms. 2- CaSO4 precipitation is generated, and the S released 2- Entering the wetland to drive sulfur autotrophic denitrification, solving the problem of SO4 in high sulfate / low carbon nitrogen ratio wastewater 2- The technical bottleneck of inhibiting the activity of denitrifying bacteria has achieved the beneficial effect of synergistic and efficient removal of sulfate and nitrate nitrogen, among which SO4 2- Removal rate>84%, NO3 - Removal rate>66%.

[0016] The biochar wetland desulfurization and denitrification system based on a rotary reactor provided by the present invention enhances the mass transfer efficiency and prevents the packing from compacting through a rotatable packing device. It combines the surface flow wetland structure with a biochar-sand mixed matrix, and a perforated stainless steel support plate to intercept flocculants, thereby avoiding the clogging problem of existing subsurface artificial wetlands, achieving anti-clogging and long-term stable operation, and increasing the flux by 80%.

[0017] The biochar wetland desulfurization and denitrification system based on the rotary reactor provided by the present invention monitors SO4 in real time through ion selective electrodes. 2- / S 2- The concentration triggers the lifting and lowering of the packing layer or the reflux of wastewater, and the heating electrode and temperature sensor are linked to control the temperature, realizing dynamic and precise regulation to meet the needs of unattended operation.

[0018] The biochar wetland desulfurization and denitrification system based on the rotary reactor provided by the present invention adopts microporous organic glass to encapsulate calcium sulfide to control S 2- The slow release rate avoids equipment loss caused by sulfide accumulation in the prior art and extends the service life of the equipment.

[0019] The biochar wetland desulfurization and denitrification system based on a rotating reactor provided by the present invention uses agricultural waste to prepare a Ca-bacterial carbon complex, reducing raw material costs by 60%. The combination of a biochar-sand matrix reduces dependence on high-end materials, overcoming the defects of traditional artificial wetlands such as high investment and difficult maintenance.

[0020] The biochar wetland desulfurization and denitrification system based on a rotating reactor provided by the present invention achieves zero external carbon source addition through sulfur autotrophic denitrification, avoids COD secondary pollution, and simultaneously utilizes reed wetland plants to enhance the landscape effect and biodiversity, meeting the dual needs of water resource recycling and ecological restoration in arid areas, with COD effluent <20 mg / L.

[0021] The biochar wetland desulfurization and denitrification system based on a rotary reactor provided by the present invention dynamically adjusts the hydraulic retention time and the height of the calcium sulfide layer is adjustable; water quality parameters are tracked in real time through a data transmission device and a remote monitoring device, thereby solving the problem of difficult operation and maintenance and reducing manual intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the structure of a biochar wetland desulfurization and denitrification system based on a rotary reactor provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of a rotary sulfate reduction unit provided in an embodiment of the present invention; Figure 3 Schematic diagram of the structure of a biochar-based artificial wetland unit provided in an embodiment of the present invention.

[0024] Reference numerals: 1. Rotating sulfate reduction unit; 2. Rotatable filler device; 3. First peristaltic pump; 4. Ca-bacterial charcoal complex layer; 5. Rotating rod; 6. Perforated stainless steel support plate; 7. Second peristaltic pump; 8. Granular calcium sulfide solid layer; 9. Ion selective electrode; 10. Rope chain; 11. Heating electrode; 12. Temperature sensor; 13. Third peristaltic pump; 14. Rotating sulfate reduction unit water inlet; 15. Wastewater outlet; 16. Rotating sulfate reduction unit water outlet; 17. Biochar-based artificial wetland unit; 18. Biochar-based artificial wetland unit water inlet; 19. Gravel support layer; 20. Biochar-sand mixed matrix layer; 21. Water layer; 22. Biochar-based artificial wetland unit water outlet; 23. Data transmission device; 24. Remote monitoring device. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0026] The following combination Figure 1-Figure 3 The present invention describes a biochar wetland desulfurization and denitrification system based on a rotating reactor.

[0027] Figure 1 It is a structural schematic diagram of a biochar wetland desulfurization and denitrification system based on a rotary reactor provided in an embodiment of the present invention.

[0028] like Figure 1 As shown, the biochar wetland desulfurization and denitrification system based on the rotary reactor provided by the embodiment of the present invention includes a rotary sulfate reduction unit 1, a biochar-based artificial wetland unit 17, a data transmission device 23 and a remote monitoring device 24 connected in series; The rotary sulfate reduction unit 1 includes: a rotatable filling device 2, a first peristaltic pump 3, a Ca-bacteria carbon complex layer 4, a rotating rod 5, a perforated stainless steel support plate 6, a second peristaltic pump 7, a granular calcium sulfide solid layer 8, an ion selective electrode 9, a rope chain 10, a heating electrode 11, a temperature sensor 12, a third peristaltic pump 13, a rotary sulfate reduction unit water inlet 14, a wastewater outlet 15, and a rotary sulfate reduction unit water outlet 16; The biochar-based artificial wetland unit 17 includes: a biochar-based artificial wetland unit water inlet 18, a gravel support layer 19, a biochar-sand mixed matrix layer 20, a water layer 21, and a biochar-based artificial wetland unit water outlet 22.

[0029] Figure 2 : is a schematic structural diagram of a rotary sulfate reduction unit provided by an embodiment of the present invention, wherein: Figure 2 a is the front view of the rotating sulfate reduction unit, Figure 2 b is a top view of the rotating sulfate reduction unit.

[0030] like Figure 2 a. Figure 2 As shown in FIG. 2 , in a rotary sulfate reduction unit provided by an embodiment of the present invention, the rotatable filler device 2 is driven by a rotating rod 5; the Ca-bacteria carbon complex layer 4 and the granular calcium sulfide solid layer 8 are arranged in the rotatable filler device 2; the granular calcium sulfide solid layer 8 is controlled to rise and fall by a rope chain 10; the perforated stainless steel support plate 6 has a pore size of 1 to 5 mm, is connected to the rotating rod 5 and supports the filler; the ion selective electrode 9 is used to detect SO4 in the effluent of the rotary sulfate reduction unit 1 2- 、S 2- The ion concentration is detected in real time; the heating electrode 11 is used to heat the water body; the temperature sensor 12 is used to detect the temperature of the water body; the wastewater outlet 15 is connected to the water inlet 14 of the rotating sulfate reduction unit through the third peristaltic pump 13; the first peristaltic pump 3 and the third peristaltic pump 13 are used to control the amount of water discharged into the rotating sulfate reduction unit; the water outlet 16 of the rotating sulfate reduction unit is connected to the water inlet 18 of the biochar-based artificial wetland unit through the second peristaltic pump 7; the second peristaltic pump 7 is used to control the discharge of the water outlet of the rotating sulfate reduction unit into the biochar-based artificial wetland unit 17.

[0031] Figure 3 : is a schematic structural diagram of a biochar-based artificial wetland unit provided by an embodiment of the present invention, wherein: Figure 3 a is the front view of the biochar-based artificial wetland unit, Figure 3 b is the left view of the biochar-based constructed wetland unit.

[0032] like Figure 3 a. Figure 3 As shown in FIG. 2 , the biochar-based artificial wetland unit provided in an embodiment of the present invention comprises, from bottom to top, a gravel support layer 19, a biochar-sand mixed matrix layer 20, and a water layer 21; the water inlet 18 of the biochar-based artificial wetland unit is arranged above the water layer 21; the water outlet 22 of the biochar-based artificial wetland unit is consistent with the water surface height of the water layer 21.

[0033] In the present invention, the gravel support layer 19 is filled with gravel with an average particle size of 2 to 4 cm and a height of 5 cm.

[0034] In the present invention, the biochar-sand mixed matrix layer 20 is a mixture of sand with a particle size of 1 to 5 mm and biochar with a particle size of 1 to 7 mm in a volume ratio of 75 to 95:5 to 25, preferably sand with a particle size of 2 to 3 mm and biochar with a particle size of 3 to 5 mm in a volume ratio of 80 to 90:10 to 20, and more preferably a volume ratio of 84 to 86:14 to 16.

[0035] In the present invention, the height of the water layer 21 is 8-12 cm, preferably 9-11 cm, and the water layer is 20-40 plants / m 2 The planting density of reeds is preferably 25 to 35 plants / m 2 , more preferably 28 to 32 plants / m 2 .

[0036] In the present invention, the water inlet 18 of the biochar-based artificial wetland unit is set 3 to 8 cm above the water layer 21, preferably 4 to 6 cm.

[0037] In the present invention, the Ca-bacterial carbon complex layer 4 is composed of CaCl2-modified agricultural production waste activated carbon loaded with sulfate-reducing bacteria, and is filled with three layers, each layer has a height of 10~20cm, preferably 14~16cm, the filler particle size is 3~5mm, and the interlayer spacing is 15~25cm, preferably 18~22cm.

[0038] In the present invention, the agricultural production waste is one or more of corn cobs, rice husks, and straw, preferably one of corn cobs, rice husks, and straw, more preferably corn cobs, the modified concentration is 5-10wt%, and the strain load is 10-15%. In the present invention, the granular calcium sulfide solid layer 8 is arranged 15-25 cm above the Ca-bacterial carbon complex layer 4, preferably 18-22 cm, with a filling height of 3-7 cm, preferably 4-6 cm, and a calcium sulfide particle size of 3-5 mm.

[0039] In the present invention, the calcium sulfide filler in the solid calcium sulfide granular layer 8 is filled with a microporous organic glass material, and the micropore diameter is 0.5-1 mm.

[0040] In the present invention, the granular calcium sulfide solid layer 8 is provided with a heating rod below the calcium sulfide filler for heating the water to 20-25°C.

[0041] In the present invention, an aeration reflow tank is also provided between the water inlet 14 and the wastewater outlet 15 of the rotary sulfate reduction unit to oxidize the dissolved low-valent sulfur into SO4 2- It is then adsorbed and removed, thereby reducing the corrosion of sulfides to the equipment.

[0042] In the present invention, the ion selective electrode 9 performs the following control: When SO4 2- When the concentration is >250mg / L, wastewater backflow is triggered; When S 2- When the concentration is >33.1 mg / L, the solid layer of granular calcium sulfide is increased by 8; When S 2- When the concentration is less than 18.3 mg / L, a solid layer of granular calcium sulfide 8 is formed.

[0043] In the present invention, the heating electrode 11 and the temperature sensor 12 are linked to control the water temperature to be 20-25°C.

[0044] On the other hand, the present invention also provides a biochar wetland desulfurization and denitrification method based on a rotary reactor, comprising the following steps: (1) Plants and substrates were cultured in simulated wastewater without sulfate for 30 days; (2) The simulated wastewater enters the rotary sulfate reduction unit 1, which is operated at a speed of 250 rpm and a hydraulic retention time of 2-4 days. The effluent SO4 is monitored in real time by the ion selective electrode 9. 2- and S 2- concentration, and regulating the rise and fall of the granular calcium sulfide solid layer 8 and the wastewater return according to the concentration; (3) The effluent from the rotary sulfate reduction unit 1 enters the biochar-based constructed wetland unit 17 with a hydraulic retention time of 4 days and undergoes reactions in the biochar-sand mixed matrix layer 20, including: Aerobic zone: NH4 + →NO3 - ; Anaerobic zone: NO3 - + biochar / organic carbon → N2↑; Sulfur-denitrification reaction: S 2- +NO3 - →SO4 2- +N2↑.

[0045] In the present invention, the hydraulic retention time in step (2) is based on the influent SO4 2- Concentration adjustment: SO4 2- =500mg / L, the hydraulic retention time is 2 days; SO4 2- =1000mg / L, the hydraulic retention time is 2.5 days; SO4 2- =2000mg / L, the hydraulic retention time is 4 days.

[0046] In an embodiment of the present invention, the configuration of the simulated wastewater is shown in Table 1 below.

[0047] Table 1 Simulated wastewater configuration

[0048] The wastewater treatment results are shown in Table 2 below, using wetland alone and using a rotary sulfate reduction unit-wetland in series for water treatment.

[0049] Table 2 Wastewater treatment results

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A biochar wetland desulfurization and denitrification system based on a rotary reactor, characterized in that: It includes a rotating sulfate reduction unit (1), a biochar-based artificial wetland unit (17), a data transmission device (23) and a remote monitoring device (24) connected in series; The rotary sulfate reduction unit (1) comprises: a rotatable filling device (2), a first peristaltic pump (3), a Ca-bacteria carbon complex layer (4), a rotating rod (5), a perforated stainless steel support plate (6), a second peristaltic pump (7), a granular calcium sulfide solid layer (8), an ion selective electrode (9), a rope chain (10), a heating electrode (11), a temperature sensor (12), a third peristaltic pump (13), a rotary sulfate reduction unit water inlet (14), a wastewater outlet (15), and a rotary sulfate reduction unit water outlet (16); The biochar-based artificial wetland unit (17) comprises: a biochar-based artificial wetland unit water inlet (18), a gravel support layer (19), a biochar-sand mixed matrix layer (20), a water layer (21), and a biochar-based artificial wetland unit water outlet (22); The data transmission device (23) is used to transmit temperature and SO4 2- 、S 2- The ion concentration is transmitted in real time to a remote monitoring device ( 24 ); The remote monitoring device (24) is used to monitor water quality in real time and control the rotating sulfate reduction unit (1).

2. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1 is characterized in that: The rotatable filling device (2) is driven by a rotating rod (5); The Ca-bacteria carbon complex layer (4) and the granular calcium sulfide solid layer (8) are arranged in a rotatable filling device (2); The granular calcium sulfide solid layer (8) is controlled to rise and fall by a rope chain (10); The perforated stainless steel support plate (6) has a pore diameter of 1 to 5 mm, is connected to the rotating rod (5) and supports the filler; The ion selective electrode (9) is used to detect SO4 in the effluent of the rotary sulfate reduction unit (1). 2- 、S 2- Real-time detection of ion concentration; The heating electrode (11) is used to heat the water body; The temperature sensor (12) is used to detect the temperature of the water body; The wastewater outlet (15) is connected to the water inlet (14) of the rotary sulfate reduction unit via a third peristaltic pump (13); The first peristaltic pump (3) and the third peristaltic pump (13) are used to control the amount of water discharged into the rotary sulfate reduction unit; The water outlet (16) of the rotary sulfate reduction unit is connected to the water inlet (18) of the biochar-based artificial wetland unit via a second peristaltic pump (7); The second peristaltic pump (7) is used to control the discharge of the effluent from the rotary sulfate reduction unit into the biochar-based artificial wetland unit (17).

3. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1 is characterized in that: The biochar-based artificial wetland unit (17) comprises, from bottom to top, a gravel support layer (19), a biochar-sand mixed matrix layer (20), and a water layer (21); The gravel support layer (19) is filled with gravel with an average particle size of 2 to 4 cm and a height of 5 cm; The biochar-sand mixed matrix layer (20) is a mixture of sand with a particle size of 1 to 5 mm and biochar with a particle size of 1 to 7 mm in a volume ratio of 75 to 95:5 to 25; The height of the water layer (21) is 8-12 cm, with a density of 20-40 plants / m 2 Plant reeds at a planting density of The water inlet (18) of the biochar-based artificial wetland unit is set 3 to 8 cm above the water layer (21); The water outlet (22) of the biochar-based artificial wetland unit is at the same height as the water surface of the water layer (21).

4. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1 or 2, characterized in that: The Ca-bacteria carbon complex layer (4) is composed of CaCl2-modified agricultural waste activated carbon loaded with sulfate-reducing bacteria, and is filled with three layers, each layer has a height of 10-20 cm, a filler particle size of 3-5 mm, and an interlayer spacing of 15-25 cm; The agricultural production waste is one or more of corn cobs, rice husks, and straws, the modification concentration is 5-10wt%, and the bacterial load is 10-15%.

5. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1 or 2, characterized in that: The granular calcium sulfide solid layer (8) is arranged 15 to 25 cm above the Ca-bacteria carbon complex layer (4), with a filling height of 3 to 7 cm and a calcium sulfide particle size of 3 to 5 mm; The calcium sulfide filler in the granular calcium sulfide solid layer (8) is filled with a microporous organic glass material, and the micropore diameter is 0.5-1 mm; The granular calcium sulfide solid layer (8) is provided with a heating rod below the calcium sulfide filler for heating the water to 20-25°C.

6. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1 or 2, characterized in that: An aeration reflow tank is also provided between the water inlet (14) and the wastewater outlet (15) of the rotary sulfate reduction unit to oxidize the dissolved low-valent sulfur into SO4 2- It is then adsorbed and removed, thereby reducing the corrosion of sulfides to the equipment.

7. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1, characterized in that: The ion selective electrode (9) performs the following control: When SO4 2- When the concentration is >250mg / L, wastewater backflow is triggered; When S 2- When the concentration is >33.1 mg / L, the solid layer of granular calcium sulfide (8) is elevated; When S 2- When the concentration is <18.3 mg / L, a solid layer of granular calcium sulfide (8) descends.

8. The biochar wetland desulfurization and denitrification system based on a rotary reactor according to claim 1, characterized in that: The heating electrode (11) and the temperature sensor (12) are linked to control the water temperature to be 20-25°C.

9. A biochar wetland desulfurization and denitrification method based on a rotary reactor, using the system of claim 1, characterized in that: The following steps are involved: (1) Plants and substrates were cultured in simulated wastewater without sulfate for 30 days; (2) The simulated wastewater enters the rotary sulfate reduction unit (1), which is operated at a speed of 250 rpm and a hydraulic retention time of 2-4 days. The effluent SO4 is monitored in real time by the ion selective electrode (9). 2- and S 2- concentration, and regulating the rise and fall of the granular calcium sulfide solid layer (8) and the wastewater return according to the concentration; (3) The effluent from the rotary sulfate reduction unit (1) enters the biochar-based constructed wetland unit (17) with a hydraulic retention time of 4 days and undergoes reactions in the biochar-sand mixed matrix layer (20), including: Aerobic zone: NH4 + →NO3 - ; Anaerobic zone: NO3 - + biochar / organic carbon → N2↑; Sulfur-denitrification reaction: S 2- +NO3 - →SO4 2- +N2↑.

10. The biochar wetland desulfurization and denitrification method based on a rotary reactor according to claim 9, characterized in that: The hydraulic retention time in step (2) is based on the influent SO4 2- Concentration adjustment: SO4 2- =500mg / L, the hydraulic retention time is 2 days; SO4 2- =1000mg / L, the hydraulic retention time is 2.5 days; SO4 2- =2000mg / L, the hydraulic retention time is 4 days.

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