Method for optimizing the reduction efficiency of trichloroethylene by in-situ bio-sulfidized zero-valent iron

Abstract

The application provides a method for optimizing and controlling the reduction efficiency of trichloroethylene by in-situ bio-sulfidized zero-valent iron, selects zero-valent iron with particle sizes of 2 μm, 7 μm and 23 μm, and a dosage of 10 g; selects xanthan gum modified micron iron slurry with masses of 1.5 g, 3.0 g and 6.0 g; collects water medium with a buried depth of 2-3 m, enriches and domesticates trichloroethylene-tolerant and SO4 2‑ reduction function, the water medium sample is collected, and the microorganism domestication is performed within 24 hours; the xanthan gum modified zero-valent iron slurry and the domesticated bacteria liquid are injected into an in-situ groundwater remediation simulation device. ‑ Through the technical scheme of the application, the synergistic effect of multiple microorganisms is achieved, the degree of trichloroethylene dechlorination in the presence of natural electron acceptor NO3 ‑ is improved, the influence of toxic by-products is reduced, the electron selectivity is enhanced, the long-term performance of zero-valent iron is strengthened, finally the reduction path of "chemical dechlorination and biological denitrification" is realized, and the application prospect is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of groundwater in-situ remediation, in particular, and particularly relates to a method for optimizing and controlling the reduction efficiency of in-situ bio-sulfidized zero-valent iron on trichloroethylene. BACKGROUND

[0002] Trichloroethylene, a typical chlorinated hydrocarbon, is widely used in modern industry as a cleaning agent for electronic components, a solvent for other organic substances, and an important chemical raw material. Trichloroethylene is slightly soluble in water and is a heavy non-aqueous phase liquid, which has strong vertical migration ability in the aeration zone and can easily enter groundwater and accumulate in the aquiclude to form a continuously expanding pollution plume, greatly affecting the water quality of the surrounding groundwater. Trichloroethylene has low biodegradability, with a half-life of 0.5-1.5 years in soil and 1-4.5 years in groundwater, thus posing a long-term threat to human health. Currently, groundwater trichloroethylene pollution has become a key problem faced by many regions (especially industrial sites), with 48.42% of samples detecting volatile organic pollutant content exceeding the standard, and trichloroethylene being one of the main pollution components. Therefore, exploring cost-effective remediation technologies for trichloroethylene-contaminated groundwater is an inevitable demand and important prerequisite for risk control and management of contaminated sites.

[0003] Micro-scale zero-valent iron (mZVI) is a highly efficient remediation material, and the constructed injection in-situ reaction zone technology has good engineering application prospects. Sulfidation modification has been proven to effectively improve the target effectiveness of mZVI on chlorinated hydrocarbon pollutants (especially trichloroethylene). When the sulfate content in groundwater is sufficient, organic matter can stimulate the growth of sulfate-reducing bacteria (SRB), and the respiration of SRB leads to the formation of reduced iron sulfide minerals (FeS and FeS2) from naturally occurring Fe(III) oxide / hydroxide minerals in sediments, promoting the biogeochemical reductive dechlorination of chlorinated alkenes. In recent years, some studies have directly or indirectly proven that in-situ bio-sulfidized zero-valent iron can promote trichloroethylene dechlorination, improve electron transfer efficiency, and reduce hydrogen evolution rate.

[0004] However, the pH, temperature, initial concentration of trichloroethylene, dissolved oxygen, and other inorganic or organic coexisting components in the actual groundwater environment can adversely affect the removal of target pollutants. For example, the presence of natural electron acceptor NO3 - may drive nitrate-reducing-sulfur-oxidizing bacteria to re-oxidize S 2- to SO4 2- , affecting the bio-sulfidation effect of ZVI, and driving denitrifying bacteria to inhibit SRB by competing for substrates and producing toxic denitrification intermediates. At the same time, NO3 -As a highly competitive coexisting electron acceptor, it will affect the electron flow in the system, which is not conducive to the long-term dechlorination performance of the system. Moreover, the influence of different attribute parameters of zero-valent iron on the reaction activity of in-situ biological sulfidation system is not clear. Therefore, it is urgent for us to develop a method for optimizing and regulating the reduction efficiency of in-situ biological sulfidation zero-valent iron on trichloroethylene in the presence of natural electron acceptors, which is crucial for ensuring the long-term dechlorination and stability of the biological sulfidation mZVI system in actual site remediation, reducing the remediation cost and optimizing the comprehensive remediation effect. SUMMARY

[0005] In order to make up for the shortcomings of the prior art, the present application provides a method for optimizing and regulating the reduction efficiency of in-situ biological sulfidation zero-valent iron on trichloroethylene. In view of the problems of poor reduction selectivity and low dechlorination efficiency of zero-valent iron caused by the presence of natural electron acceptors in actual groundwater environment, and the unclear effect of different condition parameters on the efficiency of in-situ biological sulfidation zero-valent iron in remediation of trichloroethylene contaminated groundwater, the present application provides a method for optimizing and regulating the reduction efficiency of in-situ biological sulfidation zero-valent iron on trichloroethylene. In the presence of natural electron acceptors represented by nitrate (NO3 - ), the growth of in-situ microorganisms (sulfate-reducing bacteria, nitrate-reducing bacteria, etc.) is regulated by changing the migration and particle size of zero-valent iron, the in-situ generation of pyrite minerals is promoted, the selectivity of N2 is enhanced, and the efficiency, long-term effectiveness and stability of trichloroethylene removal are strengthened, thereby providing technical and theoretical support for in-situ remediation of contaminated groundwater.

[0006] The present application is realized by the following technical scheme: a method for optimizing and regulating the reduction efficiency of in-situ biological sulfidation zero-valent iron on trichloroethylene, specifically comprising the following steps:

[0007] Step S1, selecting the particle size of zero-valent iron as 2 μm, 7 μm and 23 μm, and the dosage as 10 g;

[0008] Step S2, selecting xanthan gum modified micron iron slurry with a mass of 1.5 g, 3.0 g and 6.0 g;

[0009] Step S3, collecting water-containing medium with a burial depth of 2-3 m, and enriching in-situ microorganisms which are tolerant to trichloroethylene and have SO4 2- reduction function; after the water-containing medium sample is collected, the microorganisms are domesticated within 24 hours: 10 g of water-containing medium is added to a 500 mL serum bottle, which is filled with simulated groundwater with a dissolved oxygen concentration of less than 0.5 mg / L, and 2 mL / L of sodium lactate is added as a carbon source; the sample is cultured in a shaking bed at 25℃ and 120 rpm, and the SO4 2- concentration in the sample is determined at regular time intervals; it is observed that the solution becomes obviously black and is accompanied by a pungent odor, and the SO4 2-The concentration dropped to 28.9-86.7 mg / L, indicating that the microorganisms were successfully domesticated; in addition, the simulated groundwater was replaced once a week to maintain microbial activity;

[0010] Step S4, inject the xanthan gum modified zero-valent iron slurry and the bacteria liquid after domestication in step S3 into the simulated device for in-situ groundwater remediation, and the specific steps are as follows: the simulated device for in-situ groundwater remediation includes a seepage column, the side wall of the seepage column is opened every 5 cm for injection of the xanthan gum modified zero-valent iron slurry, and the inside of the seepage column is provided with, from bottom to top, an upper layer of silk cloth, a 3 cm thick glass bead buffer layer, quartz sand filled in 6 layers, a 3 cm thick glass bead buffer layer, and a lower layer of silk cloth; wherein, the quartz sand is filled while adding ultrapure water, after filling each layer of quartz sand, compaction is performed and air bubbles are removed, and 10 mL of the domesticated bacteria liquid is uniformly injected on the surface using a syringe to allow it to naturally penetrate into the matrix; the bottom and the top of the seepage column are closed with a three-way valve, and the top is connected with a post-treatment column; during the filling process, N2 is continuously introduced to maintain an anaerobic environment; the xanthan gum modified zero-valent iron slurry is introduced into the seepage column from the openings every 5 cm on the side wall and the bottom of the seepage column in a multi-point injection manner, and the xanthan gum modified zero-valent iron slurry is introduced at a flow rate of 50.18 µL / min for 1 h, followed by high-speed stirring for 0.5 h; then, the xanthan gum modified zero-valent iron slurry is introduced at a flow rate of 26.18 µL / min for 1 h, and stirring is performed again for 0.5 h; this process is repeated until 2 L of the slurry is completely injected;

[0011] The simulated groundwater is placed in a sterile sampling bag, and is continuously injected into the seepage column from bottom to top at a flow rate of 96.00 µL / min; when the simulated groundwater is configured, N2 is filled to ensure that the dissolved oxygen content is less than 0.5 mg / L.

[0012] As a preferred solution, the preparation steps of the xanthan gum modified micron-sized iron slurry, i.e., mZVI slurry, are as follows: 1 L of ultrapure water is added to a conical flask, and N2 is introduced to ensure that the dissolved oxygen concentration in the water is less than 0.5 mg / L; xanthan gum XG is added to the conical flask, and high-speed stirring is performed using a mechanical stirrer for 1 h while keeping the bottle mouth sealed, until the xanthan gum is completely dissolved; then, 10 g of ZVI is added, and the sealed stirring is continued for 1 h to obtain a uniformly dispersed mZVI slurry.

[0013] As a preferred solution, the bottom surface of the seepage column has a diameter of 4 cm and a height of 36 cm.

[0014] As a preferred solution, the quartz sand filled in the seepage column in 6 layers is 5 cm per layer.

[0015] Compared with the prior art, the present application has the following beneficial effects: (1) The present application improves the dechlorination degree of trichloroethylene, reduces the influence of toxic by-products, enhances the electronic selectivity, and strengthens the long-term performance of zero-valent iron, so that the reduction path of "chemical dechlorination and biological denitrification" is realized, and the present application has good application prospect.

[0016] (2) The optimization and control method of the migration and particle size of zero-valent iron used in the present application realizes the rapid and complete dechlorination of trichloroethylene, and the trichloroethylene removal rate can still be maintained after running for 4 months, so that the long-term performance and stability of the efficient removal of trichloroethylene in groundwater are strengthened.

[0017] (3) The method for repairing trichloroethylene contaminated groundwater by optimizing and controlling in-situ biological sulfidation of zero-valent iron used in the present application has simple preparation process and low cost, and will not affect the soil and groundwater environment.

[0018] (4) The method for repairing trichloroethylene contaminated groundwater by optimizing and controlling in-situ biological sulfidation of zero-valent iron used in the present application can be applied to actual groundwater, and since there are rich sulfate and activated sulfate-reducing bacteria in the actual groundwater layer, the application of the present application will provide a good application background. The additional aspects and advantages of the present application will become apparent in the description part below or through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments combined with the following drawings, in which:

[0020] Figure 1 It is an in-situ groundwater remediation indoor experimental simulation device;

[0021] Figure 2 It is a settling curve of different mZVI slurries in application example 1;

[0022] Figure 3 It is a rheological curve of different mZVI slurries in application example 1;

[0023] Figure 4 It is the trichloroethylene content in the effluent of different systems in application example 2 changes with time and the cumulative removal amount;

[0024] Figure 5 It is the dechlorination product distribution diagram after reaction of different systems in application example 2;

[0025] Figure 6 It is the cumulative diagram of denitrogenation products of different systems in application example 2;

[0026] Figure 7For the application example 2, the community abundance of each layer of microbial sample after the reaction of different systems is completed at the genus level. DETAILED DESCRIPTION

[0027] In order to enable the above-mentioned objects, features and advantages of the present application to be more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0028] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be practiced without the specific details, which are different from those described herein. Therefore, the scope of protection of the present application is not limited by the specific embodiments disclosed below.

[0029] The following will be described in conjunction with Figures 1 to 7 The method for optimizing and regulating the in-situ biological sulfuration of zero-valent iron to repair the efficiency of trichloroethylene is specifically described.

[0030] On the basis of the device shown in Figure 1 The present application proposes a method for optimizing and regulating the in-situ biological sulfuration of zero-valent iron to reduce the efficiency of trichloroethylene, which specifically comprises the following steps:

[0031] Step S1, selecting the particle size of zero-valent iron as 2 μm, 7 μm and 23 μm, and the dosage as 10 g;

[0032] Step S2, selecting xanthan gum modified micron iron slurry with a mass of 1.5 g, 3.0 g and 6.0 g; the preparation steps of the xanthan gum modified micron iron slurry, i.e., mZVI slurry, are as follows: 1 L of ultrapure water is added to a conical flask, and N2 is introduced to ensure that the dissolved oxygen concentration in the water is lower than 0.5 mg / L; xanthan gum XG is added to the conical flask, and a mechanical stirrer is used for high-speed stirring for 1 h under the condition that the bottle opening is sealed, until the xanthan gum is completely dissolved; then, 10 g of mZVI is added, and the sealed stirring is continued for 1 h to ensure that the mZVI is uniformly dispersed and modified, so that the uniformly dispersed mZVI slurry is obtained.

[0033] Step S3, collecting the aqueous medium with a buried depth of 2~3 m, and the sampling point is located in a high SO4 2- concentration area of groundwater (coordinates: 36°20′33″N, 120°8′18″E) in Jiaozhou City, Shandong Province. The collected water is rich in SO4 2-The in-situ microorganisms with reduction function were collected within 24 hours after the sample collection of the aqueous medium and were sent to the laboratory for microbial domestication: 10 g of the aqueous medium was added to a 500 mL serum bottle, which was filled with simulated groundwater with a dissolved oxygen concentration of less than 0.5 mg / L (Table 1), and 2 mL / L of sodium lactate was added as a carbon source; the sample was cultured in a 25℃, 120 rpm shaker, and the SO4 2- concentration in the sample was determined at regular time intervals, and it was observed that the solution became obviously black and was accompanied by a pungent odor, while the SO4 2- concentration dropped to 28.9~86.7 mg / L, indicating that the microbial domestication was successful; in addition, the simulated groundwater was replaced once a week to maintain microbial activity and ensure that it could be used for subsequent experiments;

[0034] Step S4, the xanthan gum modified zero-valent iron slurry and the bacteria liquid after domestication in step S3 are injected into the groundwater in-situ remediation simulation device, and the specific steps are as follows: the groundwater in-situ remediation simulation device includes a seepage column, the side wall of the seepage column is opened every 5 cm for injection of the xanthan gum modified zero-valent iron slurry, and the inside of the seepage column is provided with, from bottom to top, an upper layer of silk cloth, a 3 cm thick glass bead buffer layer, quartz sand filled in 6 layers (5 cm per layer), a 3 cm thick glass bead buffer layer, and a lower layer of silk cloth; wherein, the quartz sand is filled while adding ultrapure water, after filling each layer of quartz sand, the quartz sand is compacted and bubbles are removed, and 10 mL of the domesticated bacteria liquid is uniformly injected on the surface using a syringe to allow it to naturally penetrate into the substrate; the bottom and the top of the seepage column are closed with a three-way valve, and the top is connected to a post-treatment column to reduce the pollution of experimental wastewater to the environment; during the filling process, N2 is continuously introduced to maintain an anaerobic environment; the xanthan gum modified zero-valent iron slurry is introduced into the seepage column through the openings every 5 cm on the side wall and the bottom of the seepage column in a multi-point injection manner, and the xanthan gum modified zero-valent iron slurry is introduced at a flow rate of 50.18 µL / min for 1 h, followed by high-speed stirring for 0.5 h; then, the xanthan gum modified zero-valent iron slurry is introduced at a flow rate of 26.18 µL / min for 1 h, and stirred again for 0.5 h; this process is repeated until 2 L of the slurry is completely injected;

[0035] The xanthan gum modified zero-valent iron slurry is injected into the seepage column in a multi-point injection manner to ensure uniform distribution of the slurry in the seepage column. Specifically, a three-way valve is connected to the openings on the side and bottom of the seepage column, and the slurry is injected through a pump pipe; the slurry is introduced at a flow rate of 50.18 µL / min for 1 h, followed by high-speed stirring for 0.5 h to prevent the zero-valent iron from sinking; then, the slurry is introduced at a flow rate of 26.18 µL / min for 1 h, and stirred again for 0.5 h; this process is repeated until 2 L of the slurry is completely injected. To improve the injection efficiency, two bottles of the slurry can be prepared and injected alternately.

[0036] The simulated groundwater was placed in a sterile sampling bag and continuously injected from bottom to top at a flow rate of 96.00 µL / min (equivalent to a groundwater flow rate of 11.01 cm / d); in order to prevent O2 from entering, when the simulated groundwater was configured, sufficient N2 was filled to ensure that the dissolved oxygen content was less than 0.5 mg / L. In addition, the simulated groundwater should be replaced regularly.

[0037] Table 1 Composition of simulated groundwater

[0038]

[0039] Example 1

[0040] The influence of the above different mass xanthan gum on the migration of different particle size zero-valent iron was studied, 1.5 g, 3.0 g and 6.0 g xanthan gum (XG) were respectively used to modify mZVI with particle sizes of 2 μm, 7 μm and 23 μm, and the slurry of different formulations was respectively named as XG1.5+ZVI2, XG3.0+ZVI2, XG1.5+ZVI7, XG3.0+ZVI7, XG1.5+ZVI23, XG3.0+ZVI23 and XG6.0+ZVI23, and the remaining experimental operation steps were consistent.

[0041] The settling curves of different mZVI slurries obtained by the present application are shown in Figure 2 When the xanthan gum concentration was 1.5 g / L, the relative absorbance value of the group with mZVI particle size of 23 μm decreased to 0.193 at 10 min, when the xanthan gum concentration increased to 3 g / L, the relative absorbance value gradually decreased to 0.3497 at 240 min, which indicated that xanthan gum could effectively alleviate the settlement of ZVI, and when the xanthan gum concentration continued to increase to 6 g / L, there was almost no settlement within 4 h. This indicates that when the mZVI particle size is the same, the greater the xanthan gum concentration, the better the stability and the worse the settlement performance.

[0042] The rheological curves of different mZVI slurries obtained by the present application are shown in Figure 3The viscosity of the slurry with different particle sizes of mZVI is similar under the condition of the same xanthan gum concentration, indicating that the viscosity of the slurry has no obvious correlation with the particle size of mZVI. Under the same particle size and the same shear rate, when the xanthan gum concentration is 1.5 g / L, the corresponding viscosity range is 0-111 mPa·s; when the xanthan gum concentration is increased to 3 g / L, the corresponding viscosity range is 76-396 mPa·s; and when the xanthan gum concentration is increased to 6 g / L, the corresponding viscosity range reaches 100-999 mPa·s, indicating that the viscosity of the slurry increases significantly with the increase of the xanthan gum concentration. The higher the viscosity of the slurry, the greater the flow resistance and the greater the energy consumption of the slurry injection. Therefore, the concentration is not the higher the better. In combination with the settling performance and viscosity of the xanthan gum modified mZVI slurry, 3 g / L of xanthan gum is finally selected to modify the mZVI.

[0043] Example 2

[0044] The influence of the optimal mass of the xanthan gum obtained in Research Example 1 on the dechlorination performance of in-situ biological sulfidation zero-valent iron was studied. The biological sulfidation system of 2 μm mZVI without xanthan gum modification was set as a control group, named BS2, which was injected into the seepage column from the side opening by using a manual syringe; the biological sulfidation systems of 3.0 g xanthan gum (XG) modified mZVI with particle sizes of 2 μm, 7 μm and 23 μm were experimental groups, respectively named XG-BS2, XG-BS7 and XG-BS23, and the remaining experimental operation steps were kept consistent.

[0045] The content of trichloroethylene in the effluent of different systems obtained by the application changes with time, as shown in Figure 4 At the initial stage of the experiment, the particle size has a greater influence on the removal rate of trichloroethylene, and the reaction rate of mZVI with a smaller particle size is faster; at the middle stage, the xanthan gum has an influence on the persistence of trichloroethylene removal, and the groups containing xanthan gum can prolong the reaction time by 12 d, indicating that the addition of xanthan gum effectively slows down the passivation process of mZVI. Finally, the cumulative trichloroethylene removal amount of the XG-BS7 group is the highest (64.58 mgC), followed by the XG-BS23 group (62.86 mgC), the XG-BS2 group (29.99 mgC) and the BS2 group (28.84 mgC), which indicates that the biological sulfidation mZVI system with a larger particle size exhibits a higher dechlorination degree in the trichloroethylene dechlorination process.

[0046] The distribution diagram of dechlorination products after the reaction of different systems obtained by the application is as shown in Figure 5As shown in the figure, the proportions of products after the reaction were similar in the BS2 and XG-BS2 groups, indicating that the addition of xanthan gum did not significantly affect the reductive dechlorination pathway of trichloroethylene. Compared with the 2μm group, the content of chlorinated byproducts in the XG-BS7 and XG-BS23 groups was lower, especially in the XG-BS7 group, where the proportion of DCE was 14.48%, and in the XG-BS23 group, it was 12.18%. In both groups, the amount of ethylene generated increased linearly, and the final proportions of ethylene were 59.48% (XG-BS7) and 51.37% (XG-BS23), respectively. These results indicate that the larger particle size bio-sulfurized mZVI system exhibits a higher degree of dechlorination during the dechlorination of trichloroethylene.

[0047] Cumulative chromatograms of denitrification products in different systems obtained by this invention are shown below. Figure 6 As shown. Smaller particle sizes (mZVI, such as 2 μm) have a greater impact on NO3 in the initial stage. - The removal rate was relatively fast, but the long-term effect was poor; however, the xanthan gum-modified 2μm mZVI (XG-BS2 group) showed improved removal persistence, indicating that xanthan gum modification alleviated the rapid consumption of iron particles to some extent and improved its stability. The cumulative NO3 in the XG-BS23 group... - The highest removal amount was observed in the XG-BS7 group (272.4 mgN), followed by the XG-BS2 group (245.7 mgN), while the BS2 group had the lowest removal amount (238.4 mgN). Furthermore, the introduction of large-particle-size mZVI not only promoted the stability of the denitrification process but also improved N2 generation efficiency, demonstrating the unique advantage of large-particle-size zero-valent iron in promoting the activity of denitrifying bacteria.

[0048] The community abundance at the genus level of microbial samples at each layer after the reaction of different systems obtained in this invention, such as... Figure 7 As shown. In groups XG-BS7 and XG-BS23, the genus SRB is as follows: Desulfobulbus , Desulfomicrobium The relative abundance of [unspecified compounds] was relatively high (29.07%–39.74%), and the relative abundance of the dsrA gene in the DSR process was also relatively high (1.31%). This result indicates that the larger particle size xanthan gum-modified bio-sulfurized mZVI system provides a more suitable environment for SRB growth, promoting SO42- [unspecified process]. 2- The biological reduction process. Azospira , Pseudomonas , Thauera , Stutzerimonas and Azoarcus The relative abundance of denitrifying bacteria was relatively high (13.13%~26.78%), effectively reducing NO3 in the system. - The content of.

[0049] The results of the above application examples show that under the regulation of an appropriate amount (3 g) of xanthan gum and large particle size (23 μm) of zero-valent iron, the abundance of sulfate-reducing bacteria and denitrifying bacteria is improved, the reaction activity of sulfate-reducing bacteria in reducing sulfate is promoted, the influence of natural electron acceptors is reduced, and the remediation efficiency of zero-valent iron for trichloroethylene-contaminated groundwater is significantly improved.

[0050] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "a specific embodiment", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0051] The above only is the preferred embodiment of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for optimizing and regulating the reduction efficiency of in-situ bio-sulfurized zero-valent iron on trichloroethylene, characterized in that, Specifically, the following steps are included: Step S1: Select zero-valent iron with particle sizes of 2 μm, 7 μm, and 23 μm, and add 10 g. Step S2: Select xanthan gum-modified micronized iron slurry with masses of 1.5 g, 3.0 g, and 6.0 g respectively. The preparation steps of xanthan gum-modified micronized iron slurry, i.e., mZVI slurry, are as follows: Add 1 L of ultrapure water to an Erlenmeyer flask and introduce N2 to ensure that the dissolved oxygen concentration in the water is below 0.5 mg / L; add xanthan gum XG to the Erlenmeyer flask, and stir at high speed with a mechanical stirrer for 1 h while keeping the flask mouth sealed until the xanthan gum is completely dissolved; then add 10 g of mZVI, and continue to stir in a sealed manner for 1 h to obtain a uniformly dispersed mZVI slurry. Step S3: Collect water-bearing media at a burial depth of 2-3 m, enrich and acclimate them to trichloroethylene and contain SO42-. 2- In situ microorganisms with reducing function were used for microbial acclimatization within 24 hours after the collection of aqueous media samples: 10 g of aqueous media was added to a 500 mL serum bottle, and the bottle was filled with simulated groundwater with dissolved oxygen concentration below 0.5 mg / L. 2 mL / L sodium lactate was added as a carbon source. The samples were then cultured in a shaker at 25℃ and 120 rpm, and the SO4 content in the samples was measured periodically. 2- The concentration was high, and the solution was observed to turn noticeably darker and have an irritating odor, while SO4... 2- The concentration decreased to 28.9~86.7 mg / L, indicating successful microbial acclimatization; in addition, the simulated groundwater was replaced weekly to maintain microbial activity. Step S4: Inject xanthan gum-modified zero-valent iron slurry and the bacterial solution acclimated in step S3 into the groundwater in-situ remediation simulation device. Specifically, the groundwater in-situ remediation simulation device includes a seepage column, with the sidewalls of the seepage column spaced 5... The 5cm opening is used for injecting xanthan gum-modified zero-valent iron slurry. The interior of the percolation column, from bottom to top, consists of an upper layer of silk cloth, a 3cm thick glass bead buffer layer, six layers of quartz sand, another 3cm thick glass bead buffer layer, and a lower layer of silk cloth. Ultrapure water is added simultaneously during quartz sand filling. After each layer of quartz sand is filled, it is compacted and air bubbles are removed. Then, 10mL of acclimated bacterial solution is evenly injected onto the surface using a syringe, allowing it to naturally permeate into the matrix. The bottom and top of the percolation column are sealed with three-way valves, and the top is connected to a post-treatment column. During filling, N2 is continuously introduced to maintain an anaerobic environment. The xanthan gum-modified zero-valent iron slurry is injected through multiple points, from openings every 5cm on the sidewall and from the bottom of the percolation column, at a flow rate of 50.18µL / min for 1 hour, followed by high-speed stirring for 0.5 hours. h; then, pass through at a flow rate of 26.18µL / min for 1h, and stir again for 0.5h; repeat this process until 2 L of slurry is completely injected; Simulated groundwater was placed in a sterile sampling bag and continuously injected into the seepage column from bottom to top at a flow rate of 96.00 µL / min; when preparing the simulated groundwater, N2 was added to ensure that the dissolved oxygen content was below 0.5 mg / L.

2. The method for optimizing and regulating the reduction efficiency of in-situ bio-sulfurized zero-valent iron to trichloroethylene according to claim 1, characterized in that, The seepage column has a bottom diameter of 4 cm and a height of 36 cm.

3. The method for optimizing and regulating the reduction efficiency of in-situ bio-sulfurized zero-valent iron to trichloroethylene according to claim 1, characterized in that, The seepage column is filled with 6 layers of quartz sand, each layer being 5cm thick.

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