A method of enhancing a methane-driven nitrate and perchlorate removal process

Abstract

The application discloses a method for strengthening a methane-driven nitrate and perchlorate removal process, and belongs to the technical field of environmental protection wastewater treatment. The method is coupled with a Tangnan dialysis process and a pollutant removal process of a methane substrate nitrate and perchlorate, and through concentration of the Tangnan dialysis process, microorganisms are always in a high-concentration pollutant environment, so that high activity of metabolism is maintained, and removal efficiency and stability of the perchlorate and the nitrate are enhanced. The method provided by the application is an environment-friendly technology for in-situ upgrading and efficiency enhancement of a microbial metabolism process, has strong actual operability, and can effectively enrich methane-oxidizing and pollutant-reducing bacteria in a high-pollution load and a closed internal circulation environment, and effectively strengthen methane utilization and pollutant removal efficiency. The method has important significance for responding to sustainable development of an ecological environment and realizing energy saving and emission reduction of a water treatment process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental protection wastewater treatment, and particularly relates to a method for strengthening the process of removing nitrate and perchlorate driven by methane. BACKGROUND

[0002] Nitrate and perchlorate are typical oxidized pollutants in groundwater or surface water, and have been detected all over the world. In the research of Ma Hongyu et al., the over-standard rate of perchlorate samples was 98.3% in 62 pipeline drinking water samples, and the average concentration was 233.66 μg / L, which was much higher than the national standard of 70 μg / L (GB 5749-2022). Perchlorate has a similar charge radius and ion radius to iodine ions, which can hinder the normal absorption of iodine ions by the human body, thereby affecting the metabolism of the thyroid and nervous system and normal growth and development. Nitrate pollution is mostly caused by excessive use of agricultural fertilizers. Nitrate is easily reduced to nitrite by microorganisms in the human body after entering the human body, and then reacts with hemoglobin to form methemoglobin, which poses a series of potential risks to human health.

[0003] The common removal methods of nitrate and perchlorate composite pollutants can be divided into physical and chemical methods and biological methods. Among them, biological methods can use specific functional microorganisms to convert nitrate and perchlorate into nitrogen and chloride ions, have good treatment effect, low energy consumption and operation cost, and are more promising for application. However, the current mainstream biological treatment technology (such as biological filter) has problems such as large carbon source dosage, easy secondary pollution, high cost of subsequent disinfection treatment, etc. At the same time, under the condition of coexistence of nitrate, the removal of perchlorate is significantly inhibited. The structures of the reductases of the two are similar, and they both belong to the dimethyl sulfone reductase superfamily. When nitrate coexists, the rate of microbial reduction of nitrate is faster, and the energy barrier required for the reduction process is also lower.

[0004] The reduction process of oxidized pollutants driven by methane is considered to be a pollution biological treatment technology with great low-carbon emission reduction potential. Methane-oxidizing bacteria can oxidize methane to produce small-molecule organic acids to supply the reduction of pollutants to the pollutant-reducing bacteria. This process can use cheap and readily available methane greenhouse gas as the carbon source for microbial growth and metabolism and the electron donor for pollutant reduction, greatly reducing the economic cost while promoting the reuse of greenhouse gas.

[0005] However, the currently reported methane-driven reduction process of oxidized pollutants has problems such as low efficiency and poor stability. There is also a problem that the removal of perchlorate is inhibited in the coexisting system. Therefore, in order to improve the efficiency of the process and promote the further application of the process, it is urgent to develop an effective methane oxidation process efficiency strategy through coupling, modification and other means. The Chinese invention patent with publication number CN118164616A discloses a method for simultaneous denitrification and dechlorination of perchlorate reduction by short-cut nitrification-denitrification coupling. The method sets up a sequencing batch reactor SBR, inoculates anaerobic activated sludge and aerobic nitrification sludge in turn, adopts a "three-stage" culture mode, realizes the rapid start-up of the reactor and the stable removal of perchlorate and nitrate. Under the condition of hydraulic retention time of 24 h, the total nitrogen removal rate can reach 81.92% at most, the perchlorate removal rate can reach more than 80% at most, and the effluent perchlorate concentration is as low as 1.08 mM. However, the process has a slow start-up process in the early stage, a long hydraulic retention time, and is not convenient for in-situ upgrading.

[0006] The Chinese invention patent with publication number CN118515366A discloses a biological co-reduction system and method for nitrate and perchlorate in fireworks wastewater. The method realizes the deep purification and discharge of wastewater by setting an anaerobic tank, a co-reduction tank, an aeration tank and a membrane separation tank in sequence. The microbial reduction of nitrate and perchlorate mainly occurs in the co-reduction tank, and a sulfur granular layer is provided in the reduction tank. S0 acts as an inorganic electron donor to reduce perchlorate and nitrate to chloride ions and nitrogen. Under the condition of hydraulic retention time of 18 h, the influent 28 mg ClO4 - / L and 12 mg NO3 - -N / L are co-reduced to 0.1 mg ClO4 - / L and 10 mg NO3 - -N / L. The effluent meets the standard. However, the process has low treatment efficiency, complex equipment, and the risk of microbial blockage of filter material is not presented in the invention description. SUMMARY

[0007] The purpose of the present application is to overcome the defects in the prior art and provide a method for strengthening the removal of nitrate and perchlorate driven by methane. The present application couples the Tangnan dialysis process without external energy consumption, so that the functional microorganisms are always in a high-pollutant-concentration environment, thereby maintaining high metabolic activity and improving the removal efficiency of perchlorate and nitrate. At the same time, by introducing an ion exchange membrane assembly, the enzyme competition between nitrate ions and perchlorate ions is solved. The problems raised in the above background art are effectively solved, and the low-carbon, efficient and simultaneous treatment of perchlorate and nitrate composite pollutants in groundwater is realized.

[0008] The specific technical scheme adopted by the present application is as follows:

[0009] The present application provides a method for strengthening the methane-driven nitrate and perchlorate removal process, which is specifically as follows:

[0010] Based on the ion exchange membrane-membrane biofilm device, the methanotrophs and the pollutant reducing bacteria are loaded on the hollow fiber membrane bundle; the pollutant reducing bacteria include denitrifying bacteria and perchlorate reducing bacteria; the biological culture medium containing chlorine ions is added into the overflow device, and the biological culture medium is used to provide chlorine ions for the ion exchange membrane biological chamber and nutrients for the growth of the microorganisms in the methane substrate membrane biofilm reactor; the polluted water body containing nitrate and perchlorate to be treated is introduced into the ion exchange membrane water chamber; the chlorine ions act as driving ions, and pass through the anion exchange membrane and exchange with the nitrate ions and the perchlorate ions in the ion exchange membrane water chamber by using the Donnan effect dominated by the concentration difference and the potential difference; at the same time, the nitrate and perchlorate in the ion exchange membrane water chamber enter the ion exchange membrane biological chamber and form the concentrated polluted water body under the driving of the potential difference by the Donnan dialysis effect of the anion exchange membrane, the water body flows out through the water outlet of the ion exchange membrane biological chamber, enters the main reaction zone of the methane substrate membrane biofilm reactor through the pipeline, and realizes the synchronous removal of the denitrifying bacteria and the perchlorate under the action of the methanotrophs and the pollutant reducing bacteria;

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

[0012] As a preferred, the ion exchange membrane-membrane biofilm device includes a methane substrate membrane biofilm reactor, an overflow device and an ion exchange device;

[0013] The methane substrate membrane biofilm reactor has a double-layer structure with an inner layer and an outer layer, the inner layer cavity serves as the main reaction zone, and the spacing area between the inner layer and the outer layer serves as a water bath interlayer; the upper part of the main reaction zone is provided with a second water outlet, the lower part is provided with a second water inlet, and the inside is provided with a hollow fiber membrane bundle in the axial direction; the top of the hollow fiber membrane bundle is connected with a methane gas cylinder through a pipeline provided with a gas pressure gauge, and is used to load the methanotrophs and the pollutant reducing bacteria; the second water outlet and the second water inlet are respectively connected with the overflow device through pipelines; the overflow device is used to add the biological culture medium containing chlorine ions, and is provided with a dissolved oxygen probe connected with a dissolved oxygen real-time detector and a rotor stirrer at the bottom;

[0014] The ion exchange device comprises an ion exchange membrane biological chamber and an ion exchange membrane water chamber separated by an anion exchange membrane, and stirring devices are arranged in the ion exchange membrane biological chamber and the ion exchange membrane water chamber respectively; a water outlet of the ion exchange membrane biological chamber is arranged on the ion exchange membrane biological chamber and is communicated with the bottom of the main reaction zone through a pipeline, and a water inlet of the ion exchange membrane biological chamber is communicated with the overflow device through a pipeline; a water outlet of the ion exchange membrane water chamber and a water inlet of the ion exchange membrane water chamber are arranged on the ion exchange membrane water chamber, and the water inlet of the ion exchange membrane water chamber is communicated with the water inlet device through a pipeline.

[0015] As preferred, a first water outlet is arranged at the top of the outer layer of the methane substrate membrane biofilm reactor, a first water inlet is arranged at the bottom, and the water bath interlayer is communicated with the constant temperature water bath through the first water outlet and the first water inlet respectively through pipelines.

[0016] As preferred, a third water inlet is arranged at the top of the overflow device, a third water outlet is arranged at the middle, and a fourth water outlet is arranged at the lower part; the third water inlet is connected with the second water outlet through a pipeline, the third water outlet is connected with 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 with the second water inlet through a pipeline provided with an internal circulation pump.

[0017] As preferred, an internal circulation pump is arranged on the pipeline through which the water outlet of the ion exchange membrane biological chamber is communicated with the methane substrate membrane biofilm reactor, and an internal circulation pump is arranged on the pipeline through which the water inlet of the ion exchange membrane water chamber is communicated with the water inlet device.

[0018] As preferred, the internal circulation flow rate of the water body realized through the internal circulation pump is 72 ml / min.

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

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

[0021] As preferred, the methane with a purity higher than 99 % is introduced into the main reaction zone.

[0022] As preferred, the dissolved oxygen concentration in the ion exchange membrane biological chamber is 0.15-0.20 mg / L, and the temperature is 30℃.

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

[0024] The present application relates to coupling Tangnan dialysis process with pollutant removal process of methane matrix nitrate, perchlorate, and through concentration phenomenon of Tangnan dialysis process, microorganisms are always in high concentration pollutant environment to maintain high activity of metabolism, and then removal efficiency and stability of perchlorate and nitrate are enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the principle of the method of the present application.

[0026] Figure 2 It is a process flow diagram in the method of the present application:

[0027] 1-gauge, 2-methane matrix membrane bioreactor, 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 biological chamber, 10-ion exchange membrane biological chamber water outlet, 11-ion exchange membrane biological chamber 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 It is a long-term stable removal operation effect diagram of perchlorate and nitrate composite pollutants by using the device of the present application.

[0029] Figure 4 It is a comparison of pollutant (perchlorate and nitrate) removal flux per unit volume of the reactor before and after coupling Tangnan dialysis process.

[0030] Figure 5 It is a comparison of pollutant (perchlorate a, nitrate b) removal flux per unit membrane area of the reactor before and after coupling Tangnan dialysis process. DETAILED DESCRIPTION

[0031] The present application will be further described and explained with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment in the present application can be combined accordingly without conflict.

[0032] As Figure 1As shown, this invention provides a method for enhancing the removal of nitrates and perchlorates driven by methane. This method organically combines the Tangnan dialysis process with the microbial removal of contaminants by coupling an ion-exchange membrane unit to a methane-based biofilm reactor. Furthermore, the ion-exchange membrane-biofilm device of this invention solves the problem in existing technologies where nitrates inhibit perchlorate removal. The method and principles of this invention will be described in detail below.

[0033] The method for removing nitrates and perchlorates provided by this 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 in the diagram, the device mainly comprises a membrane biofilm reactor area and an ion exchange membrane area. The membrane biofilm reactor area mainly includes a pressure gauge 1, a methane-based membrane biofilm reactor 2, a constant temperature water bath 3, an internal circulation pump 4, a dissolved oxygen real-time detector 5, a dissolved oxygen probe 6, an overflow device 7, and a rotor agitator 8. The ion exchange membrane area mainly includes an ion exchange membrane biological chamber 9, an ion exchange membrane biological chamber outlet 10, an ion exchange membrane biological chamber 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. All components are connected by flexible hoses. This invention uses a coupled ion exchange membrane unit to achieve efficient separation of pollutants (nitrate and perchlorate) through Tangnan dialysis. Firstly, through the Tangnan dialysis process, which has relatively weak selectivity for nitrate and perchlorate ions, the simultaneous and efficient removal of both ions from the water is achieved. This process differs from enzyme-based pollutant removal processes. The former, potential difference-driven ion removal, is mainly accomplished by ion exchange membranes. These membranes have weak selectivity for different anions, enabling simultaneous and efficient removal of multiple pollutants. The latter, however, is directly catalyzed by enzyme binding sites, exhibiting strong selectivity. Furthermore, the reductase removes nitrate at a much higher rate than perchlorate, thus inhibiting the reduction of perchlorate in the presence of nitrate.

[0034] Secondly, the pollutant concentration process significantly improves the efficiency of microbial pollutant removal. When the concentrations of nitrate and perchlorate are enriched, the removal rates of both increase accordingly. At this point, although the perchlorate reduction rate is still lower than that of nitrate, it is still able to achieve efficient pollutant removal and ensure the stable operation of the reactor as a whole.

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

[0036] Based on the above-described ion exchange membrane-membrane biomembrane device, the method of the present invention is as follows: Figure 2 As shown, methanogenic bacteria and pollutant-reducing bacteria are loaded onto hollow fiber membrane bundles. 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 culture medium is dissolved in water using a rotor agitator 8. This culture medium provides chloride ions to the ion exchange membrane biochamber 9 and nutrients for the growth of microorganisms in the methanogenic 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] Polluted water containing nitrates and perchlorates is introduced into the ion exchange membrane water chamber 15 through the inlet device 17. Chloride ions, acting as the driving ions, pass through the anion exchange membrane 12 via Donnan dialysis, driven by concentration and potential differences, and exchange with nitrate and perchlorate ions in the ion exchange membrane water chamber 15. Simultaneously, through the Donnan dialysis of the anion exchange membrane 12, nitrates and perchlorates in the ion exchange membrane water chamber 15 enter the ion exchange membrane bio-chamber 9 under the influence of potential difference, forming concentrated polluted water. This water flows out through the outlet 10 of the ion exchange membrane bio-chamber and enters the main reaction zone of the methanogenic biofilm reactor 2 via a pipeline. Under the action of methanogenic bacteria and pollutant-reducing bacteria, the water achieves simultaneous removal of denitrification bacteria and perchlorates.

[0038] In this process, methane is introduced into the main reaction zone through a methane gas cylinder. Methane acts as both a carbon source and an electron donor, driving the removal of pollutants. The treated water overflows through overflow device 7 and enters the ion exchange membrane biological chamber 9 to maintain the concentration difference across the anion exchange membrane 12, ensuring the continuous operation of the Tangnan dialysis process. Finally, the purified water flows out of the device from the ion exchange membrane water chamber outlet 14.

[0039] In other words, after polluted groundwater enters the ion exchange membrane water chamber 15, driven by the Tangnan diffusion process, nitrates and perchlorates exchange with driving ions (chlorine ions) through the anion exchange membrane 12 and enter the ion exchange membrane biological chamber 9. The effluent from the ion exchange membrane water chamber 15 thus achieves water purification. For details, see [link to detailed explanation]. Figure 1Wherein the ion exchange membrane biological chamber 9 contains high concentrations of driving ions. The nitrate and perchlorate reaching the ion exchange membrane biological chamber 9 are biologically reduced in the membrane biofilm reactor area, methane is delivered through the hollow fiber membrane lumen in a bubbleless aeration manner and serves as the electron required for the pollutant reduction process, and the methane supply amount can be read from the gas pressure gauge 1. The effluent treated by the membrane biofilm reactor area enters the ion exchange membrane biological chamber 9 of the ion exchange membrane area again, so that a non-equilibrium state is maintained on both sides of the membrane to ensure the continuous operation 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 the area in real time.

[0040] In actual use, the original polluted water body is introduced into the water inlet device 17, the perchlorate concentration is about 500 μg / L, and the nitrate (i.e. nitrate nitrogen NO3 - -N) concentration is 18~22 mg / L (i.e. 20±2 mg / L). The environmental dissolved oxygen concentration measured by the dissolved oxygen probe 6 is controlled to be 0.15~0.20 mg / L by controlling the airtightness of the device (for example, adding gaskets at each interface and the like). The methane purity in the methane gas cylinder is higher than 99%. The water body is circulated at a flow rate of 72 ml / min by the internal circulation pump 4, and the water body in the membrane biofilm area is fully mixed without disturbing the biofilm. The membrane biofilm area can be operated at room temperature, and preferably, the operating temperature of the water bath interlayer is adjusted to 30℃ by the constant temperature water bath 3.

[0041] As a preferred embodiment of the present application, the ion concentration ratio of chloride ions added to the ion exchange membrane biological chamber 9 to nitrate ions and perchlorate ions is 30:1. Because, through testing and adjustment, the concentration ratio of 30:1 can achieve effective removal of the two types of pollution ions while having better economic benefits, avoiding the increase in treatment cost caused by excessive addition of chloride ions.

[0042] The bacterial flora used in the present application is a methane-oxidizing coupled nitrate and perchlorate reducing bacterial flora enriched in the membrane biofilm reactor in a laboratory environment. Such functional bacteria can oxidize methane to produce small molecular organic acid intermediates, and nitrate and perchlorate reducing bacteria can utilize the intermediates to achieve denitrification. After the functional bacterial flora is stabilized, the ion exchange membrane unit is directly coupled to realize the construction of a new reactor.

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

[0044] In the device of the present embodiment, the methane substrate membrane biofilm reactor 2 is a double-layer structure with an inner layer and an outer layer. The inner layer cavity serves as the main reaction zone, and the spacing area between the inner layer and the outer layer serves as the water bath interlayer. The upper part of the main reaction zone is provided with a second water outlet c, and the lower part is provided with a second water inlet d. A hollow fiber membrane bundle is arranged in the main reaction zone along the axial direction. The top of the hollow fiber membrane bundle is connected with a methane cylinder through a pipeline provided with a gas pressure gauge 1. The hollow fiber membrane bundle is used for supplying methane and providing a carrier for the attachment and growth of methane-oxidizing bacteria and pollutant-reducing bacteria. That is, the hollow fiber membrane bundle is used for supplying methane and providing 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 with an overflow device 7 through pipelines. The overflow device 7 is used for adding biological culture medium containing chloride ions, and is provided with a dissolved oxygen probe 6 connected with a dissolved oxygen real-time detector 5 to monitor the dissolved oxygen in the device in real time. The overflow device 7 is provided with a rotor stirrer 8 at the bottom.

[0045] In actual use, a first water outlet a can be arranged at the top of the outer layer of the methane substrate membrane biofilm reactor 2, and a first water inlet b can be arranged at the bottom. The water bath interlayer is connected with a constant-temperature water bath 3 through the first water outlet a and the first water inlet b through pipelines, so as to control the temperature of the main reaction zone. The methane supplied to the main reaction zone through the methane cylinder should have a purity higher than 99%.

[0046] In the device of the present embodiment, the ion exchange membrane biological chamber 9 and the ion exchange membrane water chamber 15 are separated by an anion exchange membrane 12 and jointly 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) and the biological system (i.e. the ion exchange membrane biological chamber 9) while removing nitrate and perchlorate. The ion exchange membrane biological chamber 9 and the ion exchange membrane water chamber 15 are respectively provided with stirring devices 13. The two stirring devices 13 can uniformly stir during the reaction to maintain the uniformity of the system. The ion exchange membrane biological chamber 9 is provided with an ion exchange membrane biological chamber water outlet 10 and an ion exchange membrane biological chamber water inlet 11. The ion exchange membrane biological chamber water outlet 10 is connected with the bottom of the main reaction zone through a pipeline, and the ion exchange membrane biological chamber water inlet 11 is connected with the overflow device 7 through a pipeline. The overflow device 7 is used to overflow water to the ion exchange membrane biological chamber 9. 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. The ion exchange membrane water chamber water inlet 16 is connected with a water inlet device 17 through a pipeline.

[0047] In actual use, a third water inlet can be opened at the top of the overflow device 7, a third water outlet can be opened in the middle, and a fourth water outlet can be opened at the lower part. The third water inlet is connected with the second water outlet c through a pipeline, the third water outlet is connected with the ion exchange membrane biological chamber water inlet 11 through a pipeline provided with an internal circulation pump 4, and the fourth water outlet is connected with the second water inlet d through a pipeline provided with an internal circulation pump 4. An internal circulation pump 4 is arranged on the pipeline through which the ion exchange membrane biological chamber water outlet 10 communicates with the methane substrate membrane biological membrane reactor 2, and an internal circulation pump 4 is arranged on the pipeline through which the ion exchange membrane water chamber water inlet 16 communicates with the water inlet device 17. The device of the present application realizes uniform mixing of the water body through the connection of the internal circulation pumps 4, the rotor stirrer 8 and the pipelines.

[0048] The device and method of the present application will be specifically described below through examples.

[0049] Example 1

[0050] In this example, based on the configuration of the ion exchange membrane-membrane biofilm device shown in Figure 1 , the method of the present application is used to treat simulated perchlorate and nitrate compound contaminated groundwater, and the pollutant removal efficiency before and after coupling Tangnan dialysis process is compared to quantify the enhancement level. Specifically as follows:

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

[0052] Single methane substrate membrane biological membrane reactor operation (0-30 days): a single methane substrate membrane biological membrane reactor is used to remove nitrate and perchlorate compound contaminants. There is a hollow fiber membrane in the methane substrate membrane biological membrane reactor, and the total membrane area is about 210 cm 2, for providing methane, water bath control temperature was 30℃, pH was stabilized at 8.0±0.5, and dissolved oxygen was controlled at 0.15-0.20 mg / L. In the single reactor pollutant removal experiment, the perchlorate removal effect was significantly affected by the coexistence of nitrate, with an average removal rate of only 6.15%, and the effluent was extremely unstable, with little difference between the influent and effluent concentrations. The nitrate removal effect was better than that of perchlorate, with an average removal rate of 11.52%, and the average concentration of effluent nitrate was 17.39 mg / L. The results were the same as those reported in the removal of perchlorate and nitrate composite pollution by the same type of membrane biofilm reactor. That is, the coexistence of nitrate makes the reductase preferentially use nitrate, inhibiting the reduction process of perchlorate, so that only a small concentration of perchlorate is effectively reduced.

[0053] After coupling the Tangnan dialysis process (30-70 days): A methane substrate membrane biofilm reactor coupled with an ion exchange membrane module was used. After combining the Tangnan dialysis process with the biological process, perchlorate ions and nitrate nitrogen can be effectively removed at a larger treatment flux, with the effluent perchlorate ion stabilized at below 70 ppb, an average removal rate of 89.62%, and a maximum of 91.82%. The effluent nitrate nitrogen was stabilized at below 10 ppm, with an average removal rate of 56.36%, and a maximum of 62.28% ( Figure 3 ). After coupling the Tangnan dialysis process, the perchlorate pollutant removal flux per unit reactor volume was increased from 84.92 μg ClO4 - ·L -1 ·d -1 to 902.17 μg ClO4 - ·L -1 ·d -1 , with a maximum of 909.33 μg ClO4 - ·L -1 ·d -1 , an increase of 9.71 times. The nitrate pollutant removal flux per unit reactor volume was increased from 8.72 mg NO3 - ·L -1 ·d -1 to 22.74 mg NO3 - ·L -1 ·d -1 , with a maximum of 24.28 mg NO3 - ·L -1 ·d -1 , an increase of 1.78 times ( Figure 4 ).

[0054] The pollutant treatment load and removal flux per unit biofilm area were compared as Figure 5After coupling the Donnan dialysis process, the pollutant load per unit biofilm area of ​​perchlorate decreased from 33.11 mg ClO4. - ·m -2 ·d -1 Increased to 59.19 mgClO4 - ·m -2 ·d -1 This represents a 0.79-fold increase. 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 The highest concentration can reach 19.62 mg ClO4 - ·m -2 ·d -1 This represents an 11.19-fold increase. 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 increased from 0.16 g NO3. - -N·m -2 ·d -1 Increased to 0.30 g NO3 - -N·m -2 ·d -1 The maximum amount of NO3 can reach 0.34 g. - -N·m -2 ·d -1 .

[0055] Example 2

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

[0057] The results show that the average removal rate of perchlorate is increased from 89.62% to 92.32%, and the effluent perchlorate concentration is stabilized at about 40 ppb. The average removal rate of nitrate is increased from 54.93% to 75.31%, and the effluent nitrate concentration is decreased from 8.94 mgN / L to 2.74 mgN / L and remains stable. However, the removal flux of pollutants is lower than that of S2-1. The treatment flux of perchlorate is increased from 902.17 μg ClO4 - ·L -1 ·d -1 to 919.78 μg ClO4 - ·L -1 ·d -1 , increased by 1.95%. Good pollutant removal effect can be achieved for different influent pollutant concentrations. Coexisting nitrate may have a certain potential impact on perchlorate treatment in the application process.

[0058] The present application relates to coupling the Tangnan dialysis process with the pollutant removal process of the methane substrate nitrate and perchlorate, and through the concentration phenomenon of the Tangnan dialysis process, the microorganisms are always in a high-concentration pollutant environment to maintain high metabolic activity, thereby enhancing the removal efficiency and stability of perchlorate and nitrate. The method provided by the present application is an environment-friendly technology for in-situ upgrading and efficiency enhancement of microbial metabolic process, which has strong actual operability, and the high pollutant load and closed internal circulation environment can effectively enrich methane-oxidizing and pollutant-reducing bacteria, and effectively enhance methane utilization and pollutant removal efficiency. It has important significance for responding to sustainable development of ecological environment and realizing energy saving and emission reduction of water treatment process.

[0059] The above-described embodiments are only a preferred scheme of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical scheme obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A method of enhancing a methane-driven nitrate and perchlorate removal process, characterized in that, The specific process is as follows: Based on the ion exchange membrane-membrane biofilm device, the methane-oxidizing bacteria and the pollutant-reducing bacteria are loaded on the hollow fiber membrane bundle; the pollutant-reducing bacteria include denitrifying bacteria and perchlorate-reducing bacteria; The biological medium containing chlorine ions is added into the overflow device (7), and the biological medium is used to provide chlorine ions for the ion exchange membrane biological chamber (9) and provide nutrients for the growth of microorganisms in the methane substrate membrane biofilm reactor (2); the polluted water containing nitrate and perchlorate to be treated is introduced into the ion exchange membrane water chamber (15); the chlorine ions act as driving ions, and the Donnan effect dominated by the concentration difference and the potential difference is used to pass through the anion exchange membrane (12) and exchange with the nitrate ions and the perchlorate ions in the ion exchange membrane water chamber (15); at the same time, the nitrate and perchlorate in the ion exchange membrane water chamber (15) enter the ion exchange membrane biological chamber (9) under the driving of the potential difference through the Donnan dialysis of the anion exchange membrane (12) and form a concentrated polluted water, which flows out through the ion exchange membrane biological chamber outlet (10) and enters the main reaction zone of the methane substrate membrane biofilm reactor (2) through a pipeline; under the action of the methane-oxidizing bacteria and the pollutant-reducing bacteria, the nitrate and the perchlorate are simultaneously removed; In the process, methane is introduced into the main reaction zone; The methane acts as a carbon source and an electron donor to drive the pollutant removal process; the treated water overflows through the overflow device (7) and then enters the ion exchange membrane biological chamber (9) to maintain the concentration difference on both sides of the anion exchange membrane (12) and ensure the continuous Donnan dialysis process; finally, the purified water flows out of the device through the ion exchange membrane water chamber outlet (14).

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

3. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 2, characterized in that, The outer top of the methane matrix 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 communicated with the constant temperature water bath kettle (3) through the first water outlet (a) and the first water inlet (b) through pipelines.

4. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 2, characterized in that, The top of the overflow device (7) is provided with a third water inlet, the middle is provided with a third water outlet, and the lower part is provided with a fourth water outlet; the third water inlet is connected with the second water outlet (c) through a pipeline, the third water outlet is connected with the ion exchange membrane biological chamber water inlet (11) through a pipeline provided with an internal circulating pump (4), and the fourth water outlet is connected with the second water inlet (d) through a pipeline provided with an internal circulating pump (4).

5. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 4, characterized in that, An internal circulating pump (4) is arranged on the pipeline through which the ion exchange membrane biological chamber water outlet (10) is communicated with the methane matrix membrane biofilm reactor (2), and an internal circulating pump (4) is arranged on the pipeline through which the ion exchange membrane water chamber water inlet (16) is communicated with the water inlet device (17).

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

7. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 1, characterized in that, The ion concentration ratio of chloride ions to nitrate ions and perchlorate ions added into the ion exchange membrane biological chamber (9) is 30:

1.

8. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 1, characterized in that, The concentration of nitrate in the polluted water body to be treated is 20 mg / L of NO3 - The concentration of perchlorate is 500 μg / L of CIO4 - .

9. A method of enhancing a nitrate and perchlorate removal process driven by methane according to claim 1, characterized in that, The purity of methane introduced into the main reaction zone is higher than 99%.

10. A method of enhancing a process for the removal of nitrates and perchlorates driven by methane according to claim 1, characterized in that, The dissolved oxygen concentration in the ion exchange membrane biological chamber (9) is 0.15-0.20 mg / L, and the temperature is 30℃.

Images