Method for enhancing methane-driven nitrate and perchlorate removal process

Abstract

The invention discloses a method for strengthening a methane-driven nitrate and perchlorate removal process, and belongs to the technical field of environment-friendly wastewater treatment. According to the method, a Tangnan dialysis process is coupled with a pollutant removal process of methane matrix nitrate and perchlorate, and microorganisms are always in an environment with high-concentration pollutants through a concentration phenomenon of the Tangnan dialysis process so as to keep high activity of metabolism, so that the removal efficiency and stability of perchlorate and nitrate are enhanced. The method provided by the invention is an environment-friendly technology for carrying out in-situ quality improvement and efficiency improvement on the microbial metabolism process, the actual operability is strong, methane oxidation and pollutant reducing bacteria can be effectively enriched in a closed environment with relatively high pollution load and internal circulation, and the methane utilization and pollutant removal efficiency is effectively enhanced. The method is of great significance in responding to sustainable development of the ecological environment and realizing energy conservation and emission reduction in the water treatment process.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmentally friendly wastewater treatment, and in particular relates to a method for enhancing a methane-driven nitrate and perchlorate removal process. Background Art

[0002] Nitrates and perchlorates are typical oxidized pollutants in groundwater and surface water and have been detected worldwide. In a study by Ma Hongyu et al., 98.3% of 62 piped drinking water samples exceeded the standard for perchlorate, with an average concentration of 233.66 μg / L, far exceeding the national standard of 70 μg / L (GB 5749-2022). Perchlorates have a similar charge radius and ionic radius to iodide ions, hindering the body's normal absorption of iodide ions, thereby affecting thyroid and nervous system metabolism and normal growth and development. Nitrate pollution primarily results from excessive application of agricultural fertilizers. Once nitrate enters the human body, it is easily reduced to nitrite by microorganisms within the body, which then reacts with hemoglobin to form methemoglobin, posing a series of potential risks to human health.

[0003] Common methods for removing nitrate and perchlorate combined pollutants can be divided into physicochemical and biological methods. Biological methods, which utilize specific functional microorganisms to convert nitrate and perchlorate into nitrogen gas and chloride ions, have advantages such as good treatment effects, low energy consumption and operating costs, and have greater application prospects. However, current mainstream biological treatment technologies (such as biofilters) have problems such as large carbon source dosage, easy generation of secondary pollution, and high subsequent disinfection treatment costs. At the same time, perchlorate removal will be significantly inhibited under the coexistence of nitrate. The reductases of the two are similar in structure and belong to the dimethyl sulfone reductase superfamily. When nitrate coexists, microorganisms reduce nitrate faster and the energy barrier required for the reduction process is also lower.

[0004] Methane-driven reduction of oxidized pollutants is considered a highly promising bioremediation technology for low-carbon emissions reduction. Methane-oxidizing bacteria oxidize methane to produce small organic acids, which then feed pollutant-reducing bacteria. This process utilizes inexpensive and readily available methane as a direct carbon source for microbial growth and metabolism, as well as an electron donor for pollutant reduction. This significantly reduces economic costs while promoting the reuse of greenhouse gases.

[0005] However, most reported methane-driven reduction processes for oxidized pollutants suffer from low efficiency and poor stability. Similarly, perchlorate removal is inhibited in coexisting systems. Therefore, to improve the efficiency of this process and promote its further application, there is an urgent need to develop effective strategies for enhancing the methane oxidation process through coupling and modification. Chinese invention patent publication number CN118164616A discloses a method for simultaneous denitrification and chlorine removal by coupling nitrification and denitrification with perchlorate reduction. This method utilizes a sequencing batch reactor (SBR) with sequential inoculation of anaerobic activated sludge and aerobic nitrifying sludge, employing a three-stage culture system. This method achieves rapid reactor startup and stable perchlorate and nitrate removal. With a hydraulic retention time of 24 hours, total nitrogen removal rates reached as high as 81.92%, perchlorate removal rates exceeded 80%, and effluent perchlorate concentrations were as low as 1.08 mM. However, the initial startup process of this process is slow, the hydraulic retention time is long, and it is not convenient to carry out in-situ upgrading.

[0006] The Chinese invention patent with publication number CN118515366A discloses a system and method for the biological co-reduction of nitrates and perchlorates in fireworks wastewater. This method achieves deep purification and discharge of wastewater by successively setting up four units: an anaerobic tank, a co-reduction tank, an aeration tank, and a membrane separation tank. The microbial reduction of nitrates and perchlorates mainly occurs in the co-reduction tank. A sulfur granule layer is provided in the reduction tank, and SO2 acts as an inorganic electron donor to reduce perchlorates and nitrates to chloride ions and nitrogen gas. Under the condition of a hydraulic retention time of 18 h, the influent is 28 mg ClO4 - / L and 12 mg NO3 - -N / L was reduced to 0.1 mg ClO4 - / L and 10 mg NO3 - -N / L. The effluent standard was met. However, the process had low efficiency, complex equipment, and risks such as microbial clogging of the filter media were not addressed in the invention description. Summary of the Invention

[0007] The present invention aims to overcome the deficiencies of the prior art and provide a method for enhancing the methane-driven nitrate and perchlorate removal process. By coupling the Donnan dialysis process, which requires no additional energy, the present invention maintains a high metabolic activity of functional microorganisms in an environment with high pollutant concentrations, thereby improving the removal efficiency of perchlorate and nitrate. At the same time, the introduction of an ion exchange membrane assembly resolves the enzyme competition between nitrate ions and perchlorate ions. This effectively addresses the problems raised in the aforementioned background technology and achieves low-carbon, high-efficiency, and simultaneous treatment of the combined perchlorate and nitrate pollutants in groundwater.

[0008] The specific technical solutions adopted in the present invention are as follows:

[0009] The present invention provides a method for enhancing a methane-driven nitrate and perchlorate removal process, as follows:

[0010] Based on the ion exchange membrane-membrane biofilm device, methane oxidizing bacteria and pollutant reducing bacteria are loaded on the hollow fiber membrane bundle; the pollutant reducing bacteria include denitrifying bacteria and perchlorate reducing bacteria; a biological culture medium containing chloride ions is added to the overflow device, and the biological culture medium is used to provide chloride ions for the ion exchange membrane biochamber and nutrients for the growth of microorganisms in the methane-based plasma membrane biofilm reactor; contaminated water containing nitrate and perchlorate to be treated is introduced into the ion exchange membrane water chamber; chloride ions are used as driving ions, and the concentration difference and potential difference-dominated Tangential Transformation is used to reduce the concentration of the nitrate and perchlorate. The water passes through the anion exchange membrane and exchanges with the nitrate ions and perchlorate ions in the ion exchange membrane water chamber. At the same time, through the Donnan dialysis of the anion exchange membrane, the nitrate and perchlorate in the ion exchange membrane water chamber enter the ion exchange membrane biological chamber under the promotion of the potential difference and form concentrated polluted water. The water flows out through the outlet of the ion exchange membrane biological chamber and enters the main reaction area of ​​the methane-based plasma membrane biofilm reactor through the pipeline. Under the action of methane oxidizing bacteria and pollutant reducing bacteria, the water achieves the simultaneous removal of denitrifying bacteria and perchlorate.

[0011] During this process, methane is introduced into the main reaction zone; methane, as a carbon source and electron donor, can drive the pollutant removal process; the treated water overflows through the overflow device and enters the ion exchange membrane biological chamber to maintain the concentration difference on both sides of the anion exchange membrane to ensure the continuation of the Tangnan dialysis process; finally, the purified water flows out of the device from the outlet of the ion exchange membrane water chamber.

[0012] Preferably, the ion exchange membrane-membrane biofilm device comprises a methane-based plasma membrane biofilm reactor, an overflow device and an ion exchange device;

[0013] The methane-based plasma membrane biofilm reactor is a double-layer structure with an inner and outer layer, wherein the inner chamber serves as the main reaction zone, and the interval area between the inner and outer layers serves as a water bath interlayer; a second water outlet is provided at the upper portion of the main reaction zone, a second water inlet is provided at the lower portion, and a hollow fiber membrane bundle is axially arranged inside; the top of the hollow fiber membrane bundle is connected to a methane gas cylinder via a pipeline provided with a pressure gauge, and is used to load methane-oxidizing bacteria and pollutant-reducing bacteria; the second water outlet and the second water inlet are respectively connected to an overflow device via pipelines; the overflow device is used to add a biological culture medium containing chloride ions, and is provided with a dissolved oxygen probe connected to a real-time dissolved oxygen detector inside, and a rotor stirrer is provided at the bottom;

[0014] The ion exchange device includes an ion exchange membrane biological chamber and an ion exchange membrane water chamber separated by an anion exchange membrane, and a stirring device is provided in the ion exchange membrane biological chamber and the ion exchange membrane water chamber respectively; the ion exchange membrane biological chamber water outlet opened on the ion exchange membrane biological chamber is connected to the bottom of the main reaction zone through a pipeline, and the ion exchange membrane biological chamber water inlet is connected to the overflow device through a pipeline; the ion exchange membrane water chamber is provided with an ion exchange membrane water chamber water outlet and an ion exchange membrane water chamber water inlet, and the ion exchange membrane water chamber water inlet is connected to the water inlet device through a pipeline.

[0015] Preferably, a first water outlet is provided at the top of the outer layer of the methane-based plasma membrane biofilm reactor, and a first water inlet is provided at the bottom, and the water bath interlayer is connected to the constant temperature water bath via pipelines through the first water outlet and the first water inlet.

[0016] Preferably, the overflow device has a third water inlet at the top, a third water outlet in the middle, and a fourth water outlet at the bottom; the third water inlet is connected to the second water outlet through a pipeline, the third water outlet is connected to the water inlet of the ion exchange membrane biological chamber through a pipeline provided with an internal circulation pump, and the fourth water outlet is connected to the second water inlet through a pipeline provided with an internal circulation pump.

[0017] Preferably, an internal circulation pump is provided on the pipeline connecting the water outlet of the ion exchange membrane bio-chamber and the methane-based plasma membrane bio-film reactor, and an internal circulation pump is provided on the pipeline connecting the water inlet of the ion exchange membrane water chamber and the water inlet device.

[0018] Preferably, the internal circulation flow rate of the water body achieved by the internal circulation pump is 72 ml / min.

[0019] Preferably, the ion concentration ratio of chloride ions to nitrate ions and perchlorate ions added into the ion exchange membrane biochamber is 30:1.

[0020] As a preference, the nitrate in the polluted water to be treated is NO3 at a concentration of 20 mg / L. - -N, perchlorate is ClO4 at a concentration of 500 μg / L - .

[0021] Preferably, the purity of the methane introduced into the main reaction zone is higher than 99%.

[0022] Preferably, the dissolved oxygen concentration in the ion exchange membrane biochamber is 0.15-0.20 mg / L and the temperature is 30°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention relates to coupling the Donnan dialysis process with the pollutant removal process of methane-based nitrates and perchlorates. Through the concentration phenomenon of the Donnan dialysis process, the microorganisms are always in an environment with high concentrations of pollutants, thereby maintaining high metabolic activity, thereby enhancing the removal efficiency and stability of perchlorate and nitrate. The method provided by the present invention is an environmentally friendly technology for in-situ quality improvement and efficiency enhancement of microbial metabolic processes. It has strong practical operability. The higher pollution load and the closed environment of the internal circulation can effectively enrich methane oxidation and pollutant reduction bacteria, and effectively enhance methane utilization and pollutant removal efficiency. It is of great significance to achieve energy conservation and emission reduction in the water treatment process in response to the sustainable development of the ecological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the principle of the method of the present invention.

[0026] Figure 2 A process flow chart of the method of the present invention is shown below:

[0027] Wherein: 1-barometer, 2-methane alkali membrane biofilm reactor, 3-constant temperature water bath, 4-internal circulation pump, 5-dissolved oxygen real-time detector, 6-dissolved oxygen probe, 7-overflow device, 8-rotor stirrer, 9-ion exchange membrane biochamber, 10-ion exchange membrane biochamber water outlet, 11-ion exchange membrane biochamber water inlet, 12-anion exchange membrane, 13-stirring device, 14-ion exchange membrane water chamber water outlet, 15-ion exchange membrane water chamber, 16-ion exchange membrane water chamber water inlet, 17-water inlet device.

[0028] Figure 3 This is a diagram showing the effect of long-term stable removal of perchlorate and nitrate composite pollutants achieved by the device of the present invention.

[0029] Figure 4 Comparison of pollutant (perchlorate and nitrate) removal flux per unit volume of the reactor before and after coupling with the Donnan dialysis process.

[0030] Figure 5 Comparison of the pollutant (perchlorate a, nitrate b) removal flux per unit membrane area of ​​the reactor before and after coupling with the Donnan dialysis process. DETAILED DESCRIPTION

[0031] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly, provided that there is no conflict between them.

[0032] like Figure 1The present invention provides a method for enhancing methane-driven nitrate and perchlorate removal. This method couples an ion exchange membrane unit to a methane-based plasma membrane biofilm reactor, organically combining the Donnan dialysis process with microbial pollutant removal. Furthermore, the ion exchange membrane-membrane biofilm device of the present invention addresses the prior art issue of nitrate inhibiting perchlorate removal. The method and principles of the present invention are described in detail below.

[0033] The method for removing nitrate and perchlorate provided by the present invention is based on an ion exchange membrane-membrane biofilm device. The ion exchange membrane-membrane biofilm device of this embodiment is as follows: Figure 2 As shown, the device primarily comprises a membrane biofilm reactor (MBR) area and an ion exchange membrane area. The MBR area primarily includes a barometer 1, a methane-based MBR reactor 2, a constant-temperature water bath 3, an internal circulation pump 4, a real-time dissolved oxygen detector 5, a dissolved oxygen probe 6, an overflow device 7, and a rotor stirrer 8. The ion exchange membrane area primarily comprises an ion exchange membrane biochamber 9, an ion exchange membrane biochamber outlet 10, an ion exchange membrane biochamber inlet 11, an anion exchange membrane 12, a stirring device 13, an ion exchange membrane water chamber outlet 14, an ion exchange membrane water chamber 15, an ion exchange membrane water chamber inlet 16, and a water inlet device 17. These components are connected by flexible hoses. The coupled ion exchange membrane unit of the present invention achieves efficient separation of pollutants (nitrate and perchlorate) through Donnan dialysis. First, through the Donnan dialysis process, which has low selectivity for nitrate and perchlorate ions, both ions are simultaneously and efficiently removed from the water. This process differs from enzyme-based pollutant removal processes. The former involves potential-difference-driven ion removal, primarily accomplished by ion exchange membranes. These membranes have weak selectivity for different anions, enabling efficient and simultaneous removal of multiple pollutants. The latter, however, is achieved directly through catalysis at enzyme binding sites, exhibiting strong selectivity. Furthermore, the reductase removes nitrate at a much higher rate than perchlorate, thereby inhibiting the perchlorate reduction process in the presence of nitrate.

[0034] Secondly, the pollutant concentration process significantly improved the efficiency of microbial pollutant removal. When the concentrations of nitrate and perchlorate were enriched, the removal rates of both increased accordingly. Although the perchlorate reduction rate was still lower than that of nitrate, it was able to achieve efficient pollutant removal and ensure the overall stable operation of the reactor.

[0035] Finally, methane is used as a carbon source and electron donor to drive the degradation of pollutants, offering the advantages of being green, low-carbon, and inexpensive. By combining the advantages of each process, a highly efficient and green denitrification process for polluted water is achieved. The device operates in continuous flow, maintaining consistently high effluent quality.

[0036] Based on the above-mentioned ion exchange membrane-membrane biofilm device, the method of the present invention is as follows Figure 2 As shown, methane-oxidizing bacteria and pollutant-reducing bacteria are loaded onto the hollow fiber membrane bundle. Pollutant-reducing bacteria include denitrifying bacteria and perchlorate-reducing bacteria. A biological culture medium containing chloride ions is added to the overflow device 7 and dissolved in water using a rotor agitator 8. The biological culture medium provides chloride ions to the ion exchange membrane biochamber 9 and nutrients for the growth of microorganisms in the methane-based plasma membrane biofilm reactor 2. A dissolved oxygen probe 6 installed in the overflow device 7 is connected to a real-time dissolved oxygen detector 5 to monitor the dissolved oxygen level within the device in real time.

[0037] Contaminated water containing nitrate and perchlorate to be treated is introduced into the ion exchange membrane water chamber 15 through the water inlet device 17. Chloride ions, acting as driving ions, utilize the Donnan effect, driven by concentration and potential differences, to penetrate the anion exchange membrane 12 and exchange with nitrate ions and perchlorate ions in the ion exchange membrane water chamber 15. Simultaneously, through the Donnan dialysis effect of the anion exchange membrane 12, the nitrate and perchlorate in the ion exchange membrane water chamber 15, driven by the potential difference, enter the ion exchange membrane bioreactor 9, forming concentrated contaminated water. This water then flows out through the ion exchange membrane bioreactor outlet 10 and enters the main reaction zone of the methane-based plasma membrane biofilm reactor 2 through a pipeline. Under the action of methane-oxidizing bacteria and pollutant-reducing bacteria, the water achieves the simultaneous removal of denitrifying bacteria and perchlorate.

[0038] During this process, methane is introduced into the main reaction zone via a methane gas cylinder. Methane, acting as a carbon source and electron donor, drives the pollutant removal process. The treated water flows through overflow device 7 and into ion exchange membrane biochamber 9, maintaining the concentration difference across anion exchange membrane 12 and ensuring the continuation of the Donnan dialysis process. Finally, the purified water exits the device through ion exchange membrane water chamber outlet 14.

[0039] That is, after the groundwater containing pollutants enters the ion exchange membrane water chamber 15, under the promotion of Donnan diffusion, nitrates and perchlorates are exchanged with the driving ion chloride ions through the anion exchange membrane 12 and enter the ion exchange membrane biological chamber 9, thus achieving water purification in the ion exchange membrane water chamber 15. Figure 1, wherein the ion exchange membrane bio-chamber 9 contains a high concentration of driving ions. The nitrate and perchlorate that reach the ion exchange membrane bio-chamber 9 enter the membrane biofilm reactor area and are biologically reduced. Methane is transferred through the hollow fiber membrane lumen in a bubble-free aeration manner and serves as the electrons required for the pollutant reduction process. The methane supply can be read by the barometer 1. The effluent treated in the membrane biofilm reactor area enters the ion exchange membrane bio-chamber 9 in the ion exchange membrane area again, so that both sides of the membrane maintain a non-equilibrium state to ensure the continuous progress of the Donnan dialysis process. Among them, the membrane biofilm reactor area is provided with a dissolved oxygen probe 6, which can monitor the biological environment of this area in real time.

[0040] In actual use, the original contaminated water entering the water inlet device 17 has a perchlorate concentration of ~500 μg / L and a nitrate concentration of ~500 μg / L. - -N) concentration is 18-22 mg / L (i.e., 20±2 mg / L). By controlling the tightness of the device (e.g., by adding gaskets at each interface), the dissolved oxygen concentration measured by the dissolved oxygen probe 6 is maintained at 0.15-0.20 mg / L. The methane purity in the methane cylinder is greater than 99%. The internal circulation pump 4 is used to maintain a water circulation rate of 72 ml / min, achieving complete mixing of the water in the biofilm area without disturbing the biofilm. The biofilm area can operate at room temperature. Preferably, the operating temperature of the water bath interlayer is adjusted to 30°C using a constant temperature water bath 3.

[0041] In a preferred embodiment of the present invention, the ion concentration ratio of chloride ions to nitrate ions and perchlorate ions added to the ion exchange membrane bio-chamber 9 is 30:1. This is because, after testing and adjustment, a concentration ratio of 30:1 has been found to effectively remove both contaminant ions while providing better economic benefits, thereby avoiding the increased treatment costs associated with excessive chloride ion addition.

[0042] The bacterial community employed in this study is a methane-oxidizing, nitrate- and perchlorate-reducing bacterial community, enriched in a membrane biofilm reactor under laboratory conditions. These functional bacteria oxidize methane to produce small organic acid intermediates, which the nitrate- and perchlorate-reducing bacteria utilize to achieve denitrification. Once the functional bacterial community stabilizes, it is directly coupled to an ion exchange membrane unit to complete the construction of the new reactor.

[0043] As a preferred embodiment of the present invention, the ion exchange membrane-membrane biofilm device is as follows Figure 1 As shown, the structure and connection method of each component are as follows:

[0044] In the device of this embodiment, the methane-based plasma membrane biofilm reactor 2 is a double-layer structure with an inner and outer shell. The inner chamber serves as the main reaction zone, and the interval area between the inner and outer layers serves as a water bath interlayer. A second water outlet c is provided at the upper part of the main reaction zone, a second water inlet d is provided at the lower part, and a hollow fiber membrane bundle is provided axially inside. The top of the hollow fiber membrane bundle is connected to the methane gas cylinder via a pipeline provided with a barometer 1, which is used to load methane oxidizing bacteria and pollutant reducing bacteria. In other words, the hollow fiber membrane bundle is used to supply methane and provide a carrier for the attachment and growth of methane oxidizing bacteria and pollutant reducing bacteria. The second water outlet c and the second water inlet d are respectively connected to the overflow device 7 through pipelines. The overflow device 7 is used to add a biological culture medium containing chloride ions, and a dissolved oxygen probe 6 connected to a dissolved oxygen real-time detector 5 is provided inside to monitor the dissolved oxygen situation in the device in real time. A rotor stirrer 8 is provided at the bottom of the overflow device 7.

[0045] In actual use, a first water outlet a can be provided at the top of the outer layer of the methane-based plasma membrane biofilm reactor 2, and a first water inlet b can be provided at the bottom. The water bath interlayer is connected to the constant temperature water bath 3 through the first water outlet a and the first water inlet b via pipes, thereby regulating the temperature of the main reaction zone. The purity of the methane introduced into the main reaction zone via the methane gas cylinder should be higher than 99%.

[0046] In the device of this embodiment, the ion exchange membrane bio-chamber 9 and the ion exchange membrane water chamber 15 are separated by an anion exchange membrane 12 and together constitute an ion exchange device. The anion exchange membrane 12 is used to isolate the treated water (i.e., the ion exchange membrane water chamber 15) from the biological system (i.e., the ion exchange membrane bio-chamber 9), while simultaneously removing nitrate and perchlorate. A stirring device 13 is provided in each of the ion exchange membrane bio-chamber 9 and the ion exchange membrane water chamber 15. Both stirring devices 13 provide uniform stirring during the reaction to maintain system homogeneity. The ion exchange membrane bio-chamber 9 is provided with an ion exchange membrane bio-chamber outlet 10 and an ion exchange membrane bio-chamber inlet 11. The ion exchange membrane bio-chamber outlet 10 is connected to the bottom of the main reaction zone via a pipeline, while the ion exchange membrane bio-chamber inlet 11 is connected to an overflow device 7 via a pipeline. The overflow device 7 is used to discharge the overflow water into the ion exchange membrane bio-chamber 9. The ion exchange membrane water chamber 15 is provided with an ion exchange membrane water chamber outlet 14 and an ion exchange membrane water chamber inlet 16 , and the ion exchange membrane water chamber inlet 16 is connected to the water inlet device 17 through a pipeline.

[0047] In actual use, a third water inlet can be provided at the top of the overflow device 7, a third water outlet can be provided in the middle, and a fourth water outlet can be provided at the bottom. The third water inlet is connected to the second water outlet c via a pipeline, the third water outlet is connected to the ion exchange membrane bioreactor water inlet 11 via a pipeline provided with an internal circulation pump 4, and the fourth water outlet is connected to the second water inlet d via a pipeline provided with an internal circulation pump 4. The pipeline connecting the ion exchange membrane bioreactor water outlet 10 and the methane-based plasma membrane biofilm reactor 2 is provided with an internal circulation pump 4, and the pipeline connecting the ion exchange membrane water chamber water inlet 16 and the water inlet device 17 is provided with an internal circulation pump 4. The device of the present invention achieves uniform mixing of the water body through the connection of each internal circulation pump 4, the rotor agitator 8, and the pipeline.

[0048] The device and method of the present invention will be described in detail below through examples.

[0049] Example 1

[0050] In this embodiment, based on Figure 1 The method of the present invention was used to treat groundwater contaminated with simulated perchlorate and nitrate based on an ion exchange membrane-membrane biofilm device configuration. The pollutant removal efficiency before and after coupling with the Donnan dialysis process was compared to quantify the enhancement level. The details are as follows:

[0051] Prepare simulated wastewater containing perchlorate and nitrate. The water quality is: pH 7.0±0.5, perchlorate ion (ClO4 - ) concentration was set to 500 μg / L, and nitrate ion (NO3 - -N) concentration was set to 20 mg N / L, and the concentrations of perchlorate ions and nitrate ions were determined by ion chromatography. The results are shown in Figure 3 shown.

[0052] Single methane-based plasma membrane biofilm reactor operation (0-30 days): A single methane-based plasma membrane biofilm reactor was used to remove nitrate and perchlorate combined pollutants. The methane-based plasma membrane biofilm reactor was equipped with a hollow fiber membrane with a total membrane area of ​​approximately 210 cm 2, used to provide methane, the water bath temperature was controlled at 30°C, the pH was stabilized at 8.0±0.5, and the dissolved oxygen was controlled at 0.15-0.20 mg / L. In the pollutant removal experiments using a single reactor, the removal of perchlorate was significantly affected by the coexistence of nitrate, with an average removal rate of only 6.15%. The effluent was also extremely unstable, with minimal difference in inlet and outlet concentrations. Nitrate removal was more effective than perchlorate, with an average removal rate of 11.52% and an average effluent nitrate concentration of 17.39 mg / L. This result is consistent with previously reported removal of combined perchlorate and nitrate pollution by similar membrane biofilm reactors. Specifically, the coexistence of nitrate causes the reductase to preferentially utilize nitrate, inhibiting the reduction process of perchlorate, resulting in only a very small concentration of perchlorate being effectively reduced.

[0053] After coupling with the Donnan dialysis process (30-70 days): A methane-based membrane biofilm reactor coupled with an ion exchange membrane assembly was used. The organic combination of the Donnan dialysis process and the biological process enabled the effective removal of perchlorate ions and nitrate nitrogen at a higher treatment flux. The perchlorate ion effluent was stabilized below 70 ppb, with an average removal rate of 89.62% and a maximum of 91.82%. The nitrate nitrogen effluent was stabilized below 10 ppm, with an average removal rate of 56.36% and a maximum of 62.28%. Figure 3 After coupling with the Donnan dialysis process, the pollutant removal flux per unit reactor volume of perchlorate increased from 84.92 μg ClO4 - ·L -1 ·d -1 Increased to 902.17 μg ClO4 - ·L -1 ·d -1 , up to 909.33 μgClO4 - ·L -1 ·d -1 , which increased by 9.71 times. The nitrate pollutant removal flux per unit reactor volume increased from 8.72 mgNO3 - ·L -1 ·d -1 Increased to 22.74 mg NO3 - ·L -1 ·d -1 , up to 24.28 mg NO3 - ·L -1 ·d -1 , increased by 1.78 times ( Figure 4 ).

[0054] The pollutant treatment load and removal flux per unit biofilm area were compared. Figure 5After coupling the Donnan dialysis process, the perchlorate pollutant load per unit biofilm area was 33.11 mg ClO4 - ·m -2 ·d -1 Increased to 59.19 mgClO4 - ·m -2 ·d -1 , which increased by 0.79 times. The corresponding pollutant removal flux per unit membrane area increased from 1.61 mg ClO4 - ·m -2 ·d -1 Increased to 18.10 mg ClO4 - ·m -2 ·d -1 , up to 19.62 mg ClO4 - ·m -2 ·d -1 , increased by 11.19 times. The nitrate pollutant load per unit biofilm area increased from 1.29 g NO3 - -N·m -2 ·d -1 Increased to 3.88 gNO3 - -N·m -2 ·d -1 ， The corresponding pollutant removal flux per unit membrane area is 0.16 g NO3 - -N·m -2 ·d -1 Increased to 0.30 g NO3 - -N·m -2 ·d -1 , up to 0.34 g NO3 - -N·m -2 ·d -1 .

[0055] Example 2

[0056] The treatment process and operating conditions of this embodiment are basically the same as those of Example 1. The difference is that the pollutant concentration ratio of the influent water of the reactor is adjusted to the concentration of perchlorate ions (ClO4 - ) concentration was set to 500 μg / L, and nitrate ion (NO3 - -N) concentration was set to 11 mg N / L.

[0057] The results showed that the average removal rate of perchlorate increased from 89.62% to 92.32%, and the effluent perchlorate concentration was stable at around 40 ppb. The average removal rate of nitrate increased from 54.93% to 75.31%, and the effluent nitrate concentration decreased from 8.94 mgN / L to 2.74 mgN / L and remained stable. However, the removal flux of pollutants decreased compared with S2-1. The treatment flux of perchlorate increased from 902.17 μg ClO4 - ·L -1 ·d -1 Increased to 919.78 μg ClO4 - ·L -1 ·d -1 , an increase of 1.95%. Good pollutant removal effects can be achieved for different pollutant influent concentrations. During the application process, the coexistence of nitrates will have a certain potential impact on the treatment of perchlorate.

[0058] The present invention relates to coupling the Donnan dialysis process with the pollutant removal process of methane-based nitrates and perchlorates. Through the concentration phenomenon of the Donnan dialysis process, the microorganisms are always in an environment with high concentrations of pollutants, thereby maintaining high metabolic activity, thereby enhancing the removal efficiency and stability of perchlorate and nitrate. The method provided by the present invention is an environmentally friendly technology for in-situ quality improvement and efficiency enhancement of microbial metabolic processes. It has strong practical operability. The higher pollution load and the closed environment of the internal circulation can effectively enrich methane oxidation and pollutant reduction bacteria, and effectively enhance methane utilization and pollutant removal efficiency. It is of great significance to achieve energy conservation and emission reduction in the water treatment process in response to the sustainable development of the ecological environment.

[0059] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for enhancing a methane-driven nitrate and perchlorate removal process, characterized in that: The details are as follows: Based on the ion exchange membrane-membrane biofilm device, methane oxidizing bacteria and pollutant reducing bacteria are loaded on the hollow fiber membrane bundle; the pollutant reducing bacteria include denitrifying bacteria and perchlorate reducing bacteria; A biological culture medium containing chloride ions is added to the overflow device (7), and the biological culture medium is used to provide chloride ions to the ion exchange membrane biological chamber (9) and provide nutrients for the growth of microorganisms in the methane-based plasma membrane biofilm reactor (2); the contaminated water containing nitrate and perchlorate to be treated is introduced into the ion exchange membrane water chamber (15); the chloride ions act as driving ions, and use the Donnan effect dominated by concentration difference and potential difference to pass through the anion exchange membrane (12) and react with nitrate ions in the ion exchange membrane water chamber (15) to form a nitrate-containing water body. and perchlorate ions are exchanged. At the same time, through the Donnan dialysis of the anion exchange membrane (12), the nitrate and perchlorate in the ion exchange membrane water chamber (15) enter the ion exchange membrane biological chamber (9) under the promotion of the potential difference and form a concentrated polluted water body. The water body flows out through the outlet (10) of the ion exchange membrane biological chamber and enters the main reaction zone of the methane-based plasma membrane biofilm reactor (2) through the pipeline. Under the action of methane oxidizing bacteria and pollutant reducing bacteria, the water body realizes the simultaneous removal of denitrifying bacteria and perchlorate. In this process, methane is introduced into the main reaction zone; Methane, as a carbon source and electron donor, can drive the pollutant removal process; the treated water overflows through the overflow device (7) and enters the ion exchange membrane biological chamber (9) to maintain the concentration difference on both sides of the anion exchange membrane (12) to ensure the continuation of the Tangnan dialysis process; finally, the purified water flows out of the device from the ion exchange membrane water chamber outlet (14).

2. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 1, characterized in that: The ion exchange membrane-membrane biofilm device comprises a methane-based plasma membrane biofilm reactor (2), an overflow device (7) and an ion exchange device; The methane-based plasma membrane biofilm reactor (2) is a double-layer structure with an inner and outer chamber, the inner chamber serves as the main reaction zone, and the interval area between the inner and outer layers serves as a water bath interlayer; a second water outlet (c) is provided at the upper portion of the main reaction zone, a second water inlet (d) is provided at the lower portion, and a hollow fiber membrane bundle is provided axially inside; the top of the hollow fiber membrane bundle is connected to a methane gas cylinder via a pipeline provided with a pressure gauge (1), and is used to load methane oxidizing bacteria and pollutant reducing bacteria; the second water outlet (c) and the second water inlet (d) are respectively connected to an overflow device (7) via pipelines; the overflow device (7) is used to add a biological culture medium containing chloride ions, a dissolved oxygen probe (6) connected to a dissolved oxygen real-time detector (5) is provided inside, and a rotor stirrer (8) is provided at the bottom; The ion exchange device comprises an ion exchange membrane biological chamber (9) and an ion exchange membrane water chamber (15) separated by an anion exchange membrane (12), and a stirring device (13) is provided in the ion exchange membrane biological chamber (9) and the ion exchange membrane water chamber (15). The ion exchange membrane biological chamber water outlet (10) provided on the ion exchange membrane biological chamber (9) is connected to the bottom of the main reaction zone through a pipeline, and the ion exchange membrane biological chamber water inlet (11) is connected to the overflow device (7) through a pipeline. The ion exchange membrane water chamber (15) is provided with an ion exchange membrane water chamber water outlet (14) and an ion exchange membrane water chamber water inlet (16), and the ion exchange membrane water chamber water inlet (16) is connected to the water inlet device (17) through a pipeline.

3. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 2, characterized in that: The outer top of the methane-based plasma membrane biofilm reactor (2) is provided with a first water outlet (a), and the bottom is provided with a first water inlet (b); the water bath interlayer is connected to the constant temperature water bath (3) through pipelines via the first water outlet (a) and the first water inlet (b).

4. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 2, characterized in that: The overflow device (7) has a third water inlet at the top, a third water outlet in the middle, and a fourth water outlet at the bottom; the third water inlet is connected to the second water outlet (c) via a pipeline, the third water outlet is connected to the ion exchange membrane bio-chamber water inlet (11) via a pipeline provided with an internal circulation pump (4), and the fourth water outlet is connected to the second water inlet (d) via a pipeline provided with an internal circulation pump (4).

5. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 4, characterized in that: An internal circulation pump (4) is provided on a pipeline connecting the water outlet (10) of the ion exchange membrane bio-chamber to the methane-based plasma membrane bio-film reactor (2), and an internal circulation pump (4) is provided on a pipeline connecting the water inlet (16) of the ion exchange membrane water chamber to the water inlet device (17).

6. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 5, characterized in that: The internal circulation flow rate of the water body achieved by the internal circulation pump (4) is 72 ml / min.

7. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 1, wherein: The ion concentration ratio of chloride ions to nitrate ions and perchlorate ions added to the ion exchange membrane biological chamber (9) is 30:

1.

8. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 1, wherein: In the polluted water to be treated, the nitrate concentration is 20 mg / L NO3 - -N, perchlorate is ClO4 at a concentration of 500 μg / L - .

9. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 1, wherein: The purity of the methane introduced into the main reaction zone is higher than 99%.

10. The method of enhancing methane-driven nitrate and perchlorate removal process according to claim 1, wherein: The dissolved oxygen concentration in the ion exchange membrane biological chamber (9) is 0.15-0.20 mg / L, and the temperature is 30°C.

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