A biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater

Abstract

The present invention discloses a biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater, comprising an inlet pump, a carbon capture device, a carbon recovery sedimentation tank, an integrated anaerobic ammonia oxidation device, an autotrophic denitrification device and a denitrification sedimentation tank connected in sequence by pipelines, the carbon capture device comprising an anode chamber connected to the inlet pump through an inlet pipe and a cathode chamber connected to the carbon recovery sedimentation tank through a first outlet pipe, the anode chamber and the cathode chamber are separated by an ion exchange resin membrane, an anode plate electrically connected to the positive pole of a power supply is arranged in the anode chamber, a cathode plate electrically connected to the negative pole of the power supply is arranged in the cathode chamber, and an aeration head connected to the first air compressor pipeline is also arranged at the bottom of the cathode chamber; the integrated anaerobic ammonia oxidation device is a continuous flow reentry reactor, and the autotrophic denitrification device is a complete mixed flow reactor. The biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater of the present invention realizes efficient denitrification and negative carbon emission of low carbon-nitrogen ratio wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to a biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater. Background Art

[0002] With the rapid development of my country's economy and the rapid improvement of its industrial level, a large amount of nitrogen-containing industrial wastewater is discharged into water bodies, leading to serious eutrophication of rivers and lakes, ecosystem degradation and other serious problems. At present, the most widely used wastewater denitrification technology is biological denitrification technology. Traditional biological denitrification technology includes two processes: nitrification and denitrification. Nitrification requires a lot of aeration, and denitrification can only be carried out when there is sufficient carbon source. However, a large amount of high-ammonia nitrogen industrial wastewater in my country, such as wastewater from coal chemical industry, smelting, electronics and other industries, has the characteristics of high ammonia nitrogen and low carbon-nitrogen ratio. The carbon source existing in the wastewater itself is difficult to meet the needs of denitrification, so additional carbon source needs to be added, which increases the treatment cost. Therefore, it is of great significance to develop efficient and economical new biological denitrification technology for low carbon-nitrogen ratio wastewater.

[0003] Anaerobic ammonium oxidation, as a new type of efficient and low-consumption biological denitrification process, has been increasingly valued in the field of water treatment, especially in the treatment of high ammonia nitrogen and low carbon-nitrogen ratio wastewater. However, there are also many problems in practical applications. For example, the main body of the process is autotrophic bacteria, which has no removal effect on carbon source pollutants, and the COD biochemical removal process designed specifically for low-carbon source wastewater is inefficient and costly. In addition, due to its own mechanism, anaerobic ammonium oxidation will convert 10% of the total nitrogen consumed into nitric nitrogen. With the increasingly stringent environmental protection indicators, the requirements for total nitrogen emissions are gradually increasing. The nitric nitrogen left after anaerobic ammonium oxidation treatment of high ammonia nitrogen wastewater has become a major problem. Summary of the invention

[0004] The purpose of the present invention is to provide a biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater to solve the problems existing in the above-mentioned prior art and achieve efficient denitrification and negative carbon emission of low carbon-nitrogen ratio wastewater.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater, comprising an inlet pump, a carbon capture device, a carbon recovery sedimentation tank, an integrated anaerobic ammonia oxidation device, an autotrophic denitrification device and a denitrification sedimentation tank which are sequentially connected by pipelines, the carbon capture device comprising an anode chamber connected to the inlet pump through an inlet pipe and a cathode chamber connected to the carbon recovery sedimentation tank through a first outlet pipe, the anode chamber and the cathode chamber are separated by an ion exchange resin membrane, an anode plate electrically connected to the positive electrode of a power supply is arranged in the anode chamber, a cathode plate electrically connected to the negative electrode of the power supply is arranged in the cathode chamber, and an aeration head connected to a first air compressor pipeline is also arranged at the bottom of the cathode chamber; the integrated anaerobic ammonia oxidation device is a continuous flow reentry reactor, and the autotrophic denitrification device is a complete mixed flow reactor.

[0007] Preferably, the integrated anaerobic ammonium oxidation device includes a plurality of reaction compartments connected in sequence and a sedimentation compartment, the carbon recovery sedimentation tank is connected to the reaction compartment at one end through a second outlet pipe, and the top of the reaction compartment at the other end is connected to the sedimentation compartment; two adjacent reaction compartments are separated by a baffle, and an opening is provided at the top or bottom of the baffle, and the positions of the openings on the two adjacent baffles are different; each of the reaction compartments is provided with a frame, and a sponge filler for loading anaerobic ammonium oxidation sludge is fixed on the frame, and the loaded anaerobic ammonium oxidation sludge is rich in short-range nitrifying bacteria and anaerobic ammonia nitrifying bacteria; a first aeration plate is provided at the bottom of each reaction compartment, and the first aeration plate is connected to the second air compressor through a pipeline.

[0008] Preferably, the sedimentation compartment is a radial flow sedimentation tank, the bottom outlet of the sedimentation compartment is connected to the feed inlet of the integrated anaerobic ammonium oxidation device through a first sludge return pipe, and a first sludge return pump is provided on the first sludge return pipe.

[0009] Preferably, a second aeration plate is provided at the bottom of the autotrophic denitrification device, and the second aeration plate is connected to the third air compressor through a pipeline; the autotrophic denitrification device is also provided with a stirrer located above the second aeration plate.

[0010] Preferably, the integrated anaerobic ammonium oxidation device is connected to the autotrophic denitrification device through a third water outlet pipe, and the autotrophic denitrification device is connected to the denitrification sedimentation tank through a fourth water outlet pipe.

[0011] Preferably, the bottom outlet of the denitrification sedimentation tank is connected to the autotrophic denitrification device through a second sludge return pipe, and a second sludge return pump is provided on the second sludge return pipe; the top overflow port of the denitrification sedimentation tank is provided with a fifth outlet pipe; the sewage outlet at the top of the denitrification sedimentation tank is connected to the feed inlet of the integrated anaerobic ammonia oxidation device through a sewage return pipe, and a sewage return pump is provided on the sewage return pipe.

[0012] Compared with the prior art, the present invention has achieved the following technical effects:

[0013] The biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater of the present invention realizes efficient denitrification and negative carbon emission of low carbon-nitrogen ratio wastewater. The pre-mounted carbon capture device in the biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater of the present invention, namely the pre-mounted MECC process, can effectively remove COD in the wastewater. Experiments show that in the process of removing organic matter by MECC, the COD removal rate reaches 90%, which provides the precondition for the normal operation of the subsequent anaerobic ammonia oxidation process. In addition, the process is sensitive to the simulated flue gas (CO 2 The carbon capture rate of the reaction mixture (conversion efficiency of organic matter into electric current) can also reach 80-93%. The reaction coulombic efficiency (the efficiency of converting organic matter into electric current) is 80-82%, and the cathode hydrogen production efficiency (conversion of electric current into hydrogen) is 91-95%. The process as a whole is a process of energy production. The post-sulfur autotrophic denitrification in the biological denitrification and carbon emission system of the low carbon-nitrogen ratio wastewater of the present invention recovers the hydrogen sulfide produced by the anaerobic front-end treatment of high-ammonia nitrogen industrial wastewater and the sulfur produced by traditional biogas desulfurization as denitrification electron donors, thereby realizing the rapid enrichment of sulfur autotrophic denitrifying bacteria, realizing synchronous denitrification and desulfurization in the whole treatment chain, and improving the TN removal rate of the anaerobic ammonia oxidation effluent. The nitrate nitrogen removal load reaches 1.6kg / (m 3 ·d), and at the same time significantly reduced the construction and operation costs of biogas desulfurization projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a schematic structural diagram of the biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater of the present invention;

[0016] Among them: 1. water inlet pump; 2. water inlet pipe; 3. carbon capture device; 4. anode chamber; 5. cathode chamber; 6. anode plate; 7. cathode plate; 8. power supply; 9. ion exchange resin membrane; 10. aeration head; 11. first air compressor; 12. first water outlet pipe; 13. carbon recovery sedimentation tank; 14. mud outlet; 15. second water outlet pipe; 16. integrated anaerobic ammonium oxidation device; 17. reaction compartment; 18. sedimentation compartment; 19. first aeration plate; 20. Sponge filler; 21. baffle; 22. first sludge return pump; 23. first sludge return pipe; 24. third outlet pipe; 25. autotrophic denitrification device; 26. second aeration plate; 27. third air compressor; 28. agitator; 29. ​​fourth outlet pipe; 30. denitrification sedimentation tank; 31. second sludge return pump; 32. second sludge return pipe; 33. sewage return pump; 34. sewage return pipe; 35. fifth outlet pipe; 36. second air compressor. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The purpose of the present invention is to provide a biological denitrification and negative carbon emission system for low carbon-nitrogen ratio wastewater to solve the problems existing in the above-mentioned prior art and achieve efficient denitrification and negative carbon emission of low carbon-nitrogen ratio wastewater.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown: This embodiment provides a biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater, including an inlet pump 1, a carbon capture device 3, a carbon recovery sedimentation tank 13, an integrated anaerobic ammonia oxidation device 16, an autotrophic denitrification device 25 and a denitrification sedimentation tank 30 connected in sequence by pipelines.

[0021] The carbon capture device 3 includes an anode chamber 4 connected to a water inlet pump 1 through a water inlet pipe 2 and a cathode chamber 5 connected to a carbon recovery sedimentation tank 13 through a first water outlet pipe 12. The anode chamber 4 and the cathode chamber 5 are separated by an ion exchange resin membrane 9. An anode plate 6 electrically connected to the positive electrode of a power source 8 is provided in the anode chamber 4, and a cathode plate 7 electrically connected to the negative electrode of the power source 8 is provided in the cathode chamber 5. An aeration head 10 connected to a first air compressor 11 is also provided at the bottom of the cathode chamber 5. Aeration is performed through the first air compressor 11 and the aeration head 10. The wastewater first enters the anode chamber 4 of the device, and the electroactive bacteria (EAB) grown on the anode bioelectrode degrade organic matter in the wastewater to generate electrons and H + At the same time, industrial mineral waste is added to the anode chamber 4, which is rich in H + The anolyte can dissolve the released metal ions (Ca 2+ ,Mg 2+ The wastewater enters the cathode chamber 5 through the ion exchange resin membrane 9; the electrons are collected by the anode and transferred to the cathode plate 7 through the external circuit to reduce water to produce H 2 and OH - ; When metal ions migrate through the intermediate membrane to the cathode electrolyte, they react with OH - Combines to form metal hydroxides for absorbing CO in aeration 2 Convert it into stable carbonate precipitates to achieve carbon capture.

[0022] The carbon recovery sedimentation tank 13 is a radial flow sedimentation tank. The carbonate produced in the carbon recovery sedimentation tank 13 is precipitated at the bottom and collected by the mud discharge port 14. The supernatant on the top of the carbon recovery sedimentation tank 13 flows into the integrated anaerobic ammonium oxidation device 16 through the second outlet pipe 15.

[0023] The integrated anaerobic ammonium oxidation device 16 is a continuous flow return reactor. The integrated anaerobic ammonium oxidation device 16 includes 6 sequentially connected reaction compartments 17 and 1 sedimentation compartment 18. The carbon recovery sedimentation tank 13 is connected to the leftmost reaction compartment 17 through the second outlet pipe 15, and the top of the rightmost reaction compartment 17 is connected to the sedimentation compartment 18; two adjacent reaction compartments 17 are separated by a baffle 21, and an opening is provided at the top or bottom of the baffle 21, and the positions of the openings on the two adjacent baffles 21 are different to realize the up and down return flow of the water body in the reactor; each reaction compartment 17 is provided with a frame, and a sponge filler 20 for loading anaerobic ammonium oxidation sludge is fixed on the frame, and the loaded anaerobic ammonium oxidation sludge is rich in short-range nitrifying bacteria and anaerobic ammonia nitrifying bacteria, wherein the short-range nitrifying bacteria utilize the O provided by aeration 2Part of the ammonia nitrogen in the wastewater is converted into nitrite nitrogen. Anaerobic ammonia-oxidizing bacteria use ammonia nitrogen and nitrite nitrogen as reaction substrates to generate nitrogen gas which is discharged from the upper part of the reactor, thereby achieving efficient removal of nitrogen source pollutants and producing about 10% nitrate nitrogen. A first aeration plate 19 is provided at the bottom of each reaction compartment 17, and the first aeration plate 19 is connected to the second air compressor 36 through a pipeline.

[0024] The sedimentation compartment 18 is a radial flow sedimentation tank, and the bottom outlet of the sedimentation compartment 18 is connected to the feed port of the integrated anaerobic ammonium oxidation device 16 through the first sludge return pipe 23, and the first sludge return pipe 23 is provided with a first sludge return pump 22. The sludge at the bottom of the sedimentation compartment 18 is returned to the inlet of the integrated anaerobic ammonium oxidation device 16 by the sludge return pump through the sludge return pipe, and the return ratio is 100-150%, and the supernatant overflows the third outlet pipe 24 and enters the autotrophic denitrification device 25.

[0025] The autotrophic denitrification device 25 is a completely mixed flow reactor. The autotrophic denitrification device 25 is a completely mixed flow reactor. A second aeration plate 26 is provided at the bottom of the autotrophic denitrification device 25. The second aeration plate 26 is connected to the third air compressor 27 through a pipeline. The autotrophic denitrification device 25 is also provided with a stirrer 28 located above the second aeration plate 26. The dissolved oxygen in the autotrophic denitrification device 25 is controlled to be less than 0.5 mg / L in anoxic state through micro-aeration and stirring. The sludge in the autotrophic denitrification device 25 is mainly autotrophic denitrifying bacteria. In anoxic state, HCO 3 - ,CO 3 2- The inorganic carbon is used as the carbon source to reduce the nitric nitrogen produced by anaerobic ammonium oxidation to nitrogen gas emission, thereby achieving a higher denitrification rate. The effluent from the upper part of the autotrophic denitrification device 25 enters the denitrification sedimentation tank 30 through the fourth effluent pipe 29.

[0026] The bottom outlet of the denitrification sedimentation tank 30 is connected to the autotrophic denitrification device 25 through the second sludge return pipe 32, and the second sludge return pipe 32 is provided with a second sludge return pump 31; the top overflow port of the denitrification sedimentation tank 30 is provided with a fifth outlet pipe 35; the sewage outlet at the top of the denitrification sedimentation tank 30 is connected to the feed port of the integrated anaerobic ammonia oxidation device 16 through the sewage return pipe 34, and the sewage return pipe 34 is provided with a sewage return pump 33. The denitrification sedimentation tank 30 performs mud and water separation, and the bottom sludge is returned to the autotrophic denitrification device 25 through the second sludge return pump 31 and the second sludge return pipe 32, and the return ratio is 100-150%. A sewage return pipe 34 is provided at the top of the denitrification sedimentation tank 30, and part of the treated sewage is returned to the initial stage of the integrated anaerobic ammonium oxidation device 16 through a sewage return pump 33, and the return ratio is 300-500%, so that the water quality of the biochemical reactor is relatively balanced, and excessive ammonia nitrogen is prevented from producing free ammonia, which inhibits the activity of functional bacteria in the initial stage of the integrated anaerobic ammonium oxidation reactor. The high return ratio reduces the impact of water quality changes on the anaerobic ammonium oxidation process. The supernatant at the top of the denitrification sedimentation tank 30 overflows to the fifth outlet pipe 35 for discharge.

[0027] The pre-mounted carbon capture device 3 in the biological denitrification and carbon emission system of low carbon-nitrogen ratio wastewater in this embodiment, namely the pre-mounted MECC process, can effectively remove COD in wastewater. Experiments show that in the process of removing organic matter by MECC, the COD removal rate reaches 90%, which provides the precondition for the normal operation of the subsequent anaerobic ammonium oxidation process. In addition, the process uses the simulated flue gas (CO 2 The carbon capture rate of the reaction (conversion of organic matter into electric current) is 80-82%, and the cathode hydrogen production efficiency (conversion of electric current into hydrogen) is 91-95%. The process as a whole is a process of energy production.

[0028] In the specific experiment, the external voltage of the MECC device was 0.8V, the COD of the wastewater was 620mg / L (with sodium acetate as the main source of organic matter), the conductivity was 7.16mS / cm, and the CaSiO 3 The solution was supplemented with cations (concentration was 1g CaSiO 3 / 50ml deionized water), replenish the cationic solution every 6h, CO 2 Provided by air, it enters the reactor through the aeration device at a flow rate of 120ml / min. The pH of the reactor anode is controlled at 7.1-7.8, and the cathode is controlled at 8.2-9.4. Under this condition, the COD removal rate of the overall device is 86%, and the effluent COD is less than 100mg / L. 2 The concentration is 8.0mmol / L, the outlet concentration is 0.64mmol / L, CO 2The capture rate is 92%. Based on the hydrogen production rate of 90%, after deducting the consumed electricity, the net energy yield of MECC is 11.3 kJ / gCOD. Negative emissions of carbon source pollutants are achieved, and COD in wastewater is fully utilized for energy recovery.

[0029] In the biological denitrification and carbon emission system of low carbon-nitrogen ratio wastewater of this embodiment, the post-autotrophic denitrification of sulfur can recover the hydrogen sulfide produced by the anaerobic front-end treatment of high ammonia nitrogen industrial wastewater and the sulfur produced by traditional biogas desulfurization as denitrification electron donors, thereby realizing the rapid enrichment of sulfur autotrophic denitrifying bacteria, achieving simultaneous denitrification and desulfurization in the whole treatment chain, and improving the TN removal rate of anaerobic ammonia oxidation effluent. The nitrate nitrogen removal load reaches 1.6kg / (m 3 ·d), and at the same time significantly reduced the construction and operation costs of biogas desulfurization projects.

[0030] In the specific experiment, 5g / L Na 2 S 2 O 3 As a sulfur source, 2g / L KNO 3 The reaction conditions were controlled at 30℃, pH7.5, and dissolved oxygen was less than 0.2mg / L. Based on anaerobic sludge, after about 20 to 30 days of acclimatization, the nitrate removal load reached 1.6kg / (m 3 ·d). Based on the rapid domestication of sulfur autotrophic sludge, it is coupled with the integrated anaerobic ammonium oxidation process. The nitrate nitrogen in the effluent of the integrated anaerobic ammonium oxidation reactor is 30-40 mg / L, and after treatment by the SAD reactor, it is less than 3 mg / L, with a removal rate of 90%. The overall process ammonia nitrogen removal load can reach 0.35 kgN / (m 3 ·d), the removal rates of nitrate and nitrite were 86.1% to 100% and 96.4% to 100% respectively during the stable period, increasing the total nitrogen load of traditional anaerobic ammonium oxidation technology by 0.3-0.45kg / (m 3 ·d).

[0031] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater, characterized by: It comprises an inlet pump, a carbon capture device, a carbon recovery sedimentation tank, an integrated anaerobic ammonium oxidation device, an autotrophic denitrification device and a denitrification sedimentation tank which are sequentially connected by pipelines, the carbon capture device comprises an anode chamber connected to the inlet pump through an inlet pipe and a cathode chamber connected to the carbon recovery sedimentation tank through a first outlet pipe, the anode chamber and the cathode chamber are separated by an ion exchange resin membrane, the anode chamber is provided with an anode plate electrically connected to the positive electrode of the power supply, the cathode chamber is provided with a cathode plate electrically connected to the negative electrode of the power supply, and the bottom of the cathode chamber is also provided with an aeration head connected to the first air compressor pipeline; the integrated anaerobic ammonium oxidation device is a continuous flow reentry reactor, and the autotrophic denitrification device is a complete mixed flow reactor; Electroactive bacteria grow on the anode plate, and industrial mineral waste containing metals is arranged in the anode chamber; The bottom outlet of the denitrification sedimentation tank is connected to the autotrophic denitrification device through a second sludge return pipe, and a second sludge return pump is provided on the second sludge return pipe; The top overflow port of the denitrification sedimentation tank is provided with a fifth water outlet pipe; the sewage outlet at the top of the denitrification sedimentation tank is connected to the feed port of the integrated anaerobic ammonium oxidation device through a sewage return pipe, and a sewage return pump is provided on the sewage return pipe; The reaction type of the autotrophic denitrification in the autotrophic denitrification device is sulfur-sourced, and the hydrogen sulfide produced by the carbon capture device and the sulfur produced by the biogas desulfurization are recovered and used as denitrification electron donors in the autotrophic denitrification device.

2. The biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater according to claim 1, characterized in that: The integrated anaerobic ammonium oxidation device includes a plurality of reaction compartments connected in sequence and a sedimentation compartment, the carbon recovery sedimentation tank is connected to the reaction compartment at one end through a second outlet pipe, and the top of the reaction compartment at the other end is connected to the sedimentation compartment; two adjacent reaction compartments are separated by a baffle, and an opening is provided at the top or bottom of the baffle, and the positions of the openings on the two adjacent baffles are different; each of the reaction compartments is provided with a frame, and a sponge filler for loading anaerobic ammonium oxidation sludge is fixed on the frame, and the anaerobic ammonium oxidation sludge is rich in short-range nitrifying bacteria and anaerobic ammonium oxidizing bacteria; a first aeration plate is provided at the bottom of each reaction compartment, and the first aeration plate is connected to the second air compressor through a pipeline.

3. The biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater according to claim 2 is characterized by: The sedimentation compartment is a radial flow sedimentation tank, the bottom outlet of the sedimentation compartment is connected to the feed inlet of the integrated anaerobic ammonium oxidation device through a first sludge return pipe, and the first sludge return pipe is provided with a first sludge return pump.

4. The biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater according to claim 1, characterized in that: A second aeration plate is arranged at the bottom of the autotrophic denitrification device, and the second aeration plate is connected to the third air compressor through a pipeline; the autotrophic denitrification device is also provided with a stirrer located above the second aeration plate.

5. The biological denitrification and carbon emission system for low carbon-nitrogen ratio wastewater according to claim 1, characterized in that: The integrated anaerobic ammonium oxidation device is connected to the autotrophic denitrification device through a third water outlet pipe, and the autotrophic denitrification device is connected to the denitrification sedimentation tank through a fourth water outlet pipe.

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