Method for in situ remediation of chlorinated hydrocarbon-contaminated sites and use thereof

Abstract

The application provides a method for repairing a chlorinated hydrocarbon contaminated site in situ and application thereof, the method injects polymer particles into the chlorinated hydrocarbon contaminated site for fermentation for a certain time, the polymer particles provide a carbon source and an electron donor required for in-situ microbial growth, meanwhile, the polymer particles inhibit the production of methane by methanogenic archaea in the in-situ microorganisms, help the chlorinated hydrocarbon degrading bacteria in the in-situ microorganisms to compete for the electron donor, improve the utilization of the electron donor by the chlorinated hydrocarbon degrading bacteria, and promote the degradation of the chlorinated hydrocarbon; the polymer particles are biodegradable high molecular polymer particles. By adjusting the particle size of the biodegradable high molecular polymer particles to 10 2 microns, the 10 2 micron biodegradable high molecular polymer particles can selectively inhibit the functional characteristics of the metabolism of methanogenic archaea, help the chlorinated hydrocarbon degrading bacteria to compete for the electron donor, thereby improving the utilization efficiency of the electron donor by the chlorinated hydrocarbon degrading bacteria, and improving the repair effect of the chlorinated hydrocarbon.

Description

Technical Field

[0001] The present invention belongs to the technical field of groundwater pollution remediation and treatment, and in particular relates to a method for in-situ remediation of chlorinated hydrocarbon contaminated sites and application thereof. Background Art

[0002] Trichloroethylene (TCE) is one of the most commonly detected chlorinated hydrocarbons in groundwater. As a potent carcinogen, it can persist in the natural environment. Long-term exposure to chlorinated organic pollutants such as TCE will have a great impact on people's health and safety. Therefore, there is an urgent need to develop efficient and green remediation technologies to eliminate groundwater chlorinated hydrocarbon pollution. In situ microbial remediation methods have attracted much attention due to their advantages such as environmental friendliness, economic feasibility and ease of operation. Among them, chlorinated hydrocarbon degrading bacteria use anaerobic reduction, chlorinated hydrocarbons as electron acceptors and organic matter as electron donors, and dechlorinate through hydrolysis or nucleophilic reactions, thereby repairing chlorinated hydrocarbon pollution. In view of the oligotrophic environmental characteristics of groundwater, research has been gradually carried out to release electrons and carbon sources through solid-phase electron acceptor slow-release materials to enhance the in situ microbial dechlorination and degradation of chlorinated hydrocarbons. However, when exogenous electron donors are excessively supplemented, methanogenic archaea that have a competitive advantage in electron donors will be the first to consume the added electron donors, resulting in a decrease in the efficiency of electron donor utilization by chlorohydrocarbon-degrading bacteria. Based on this, how to selectively inhibit the metabolism of methanogenic archaea has become a bottleneck problem in the current field of in situ microbial remediation of chlorohydrocarbons. Currently, there are almost no reports on promoting chlorohydrocarbon remediation by inhibiting the metabolism of methanogenic archaea. Summary of the Invention

[0003] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and provide a method for in-situ remediation of chlorinated hydrocarbon contaminated sites and its application.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The first objective of the present invention is to provide a method for in situ remediation of chlorinated hydrocarbon contaminated sites. Polymer particles are injected into the chlorinated hydrocarbon contaminated site and fermented for a certain period of time. The polymer particles provide the carbon source and electron donor required for the growth of in situ microorganisms. At the same time, the polymer particles inhibit the production of methane by methanogenic archaea in the in situ microorganisms, help the chlorinated hydrocarbon degrading bacteria in the in situ microorganisms compete for electron donors, improve the utilization of electron donors by the chlorinated hydrocarbon degrading bacteria, and promote the degradation of chlorinated hydrocarbons. The polymer particles are biodegradable high molecular polymer particles.

[0006] Furthermore, the concentration of chlorinated hydrocarbons in the chlorinated hydrocarbon contaminated site is 50-150,000 μg / L.

[0007] Furthermore, the amount of polymer particles added varies according to the pollution concentration of chlorinated hydrocarbons, and the minimum amount added is a mass ratio of the total amount of polymer particles to chlorinated hydrocarbons of 1:2.

[0008] Furthermore, the particle size of the polymer particles is 20-5000 μm.

[0009] Furthermore, the polymer particles include any one or more of polyhydroxyalkanoate particles, polycaprolactone particles, polybutylene succinate particles, polyvinyl alcohol particles and polylactic acid particles.

[0010] Furthermore, the polymer particles are polyhydroxyalkanoate particles. Polyhydroxyalkanoate refers to a class of natural biodegradable polyesters formed by microorganisms, and its components are pure substances of polyhydroxyalkanoates represented by polyhydroxybutyrate and polyhydroxyvalerate, or mixtures of different types of polyhydroxyalkanoates. The molecular weight ranges from 20 to 2×10 7 Da.

[0011] Furthermore, the particle size of the polyhydroxyalkanoate particles is 50-2000 μm.

[0012] Furthermore, the fermentation time is 5 to 40 days.

[0013] The second object of the present invention is to provide a permeable reaction wall for repairing chlorinated hydrocarbon groundwater using the above method, characterized in that the permeable reaction wall comprises polymer particles and chlorinated hydrocarbon degrading bacteria, and the polymer particles are biodegradable high molecular polymer particles.

[0014] Furthermore, the chlorinated hydrocarbon degrading bacteria include Dehalogenococcus and Dehalogenomonas.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention provides a method for in-situ remediation of chlorinated hydrocarbon contaminated sites, which comprises adjusting the particle size of biodegradable polymer particles to 10 2 Micron level, play 10 2 Micron biodegradable polymer particles can selectively inhibit the functional characteristics of methanogenic archaea metabolism, help chlorinated hydrocarbon degrading bacteria compete for electron donors, thereby improving the efficiency of chlorinated hydrocarbon degrading bacteria in utilizing electron donors and enhancing the chlorinated hydrocarbon remediation effect.

[0017] (2) The present invention provides a permeable reaction wall for repairing chlorinated hydrocarbon groundwater, comprising biodegradable polymer particles and chlorinated hydrocarbon-degrading bacteria. On the one hand, the biodegradable polymer particles have a high carbon content and are easily utilized by microorganisms, providing a carbon source and electron donor required for microbial growth; on the other hand, the micron-level biodegradable polymer particles can selectively inhibit microbial methane production, thereby reducing the conversion of organic carbon to CH4, promoting the degradation of chlorinated hydrocarbons by chlorinated hydrocarbon-degrading bacteria, and also reducing the greenhouse effect. This method can be applied not only to the remediation of chlorinated hydrocarbons, but also to the microbial ecological remediation of other halogenated organic compounds, and can effectively promote the growth rate of halogenated organic compound-reducing bacteria, thereby promoting the remediation effect.

[0018] (3) This invention will greatly promote the practice and application of in-situ chlorinated hydrocarbon remediation technology, and alleviate the contradiction between the relocation and transformation of chemical enterprises in densely populated areas and the redevelopment and utilization of contaminated sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a comparison chart of the effect of particle size on TCE degradation rate in PHA-promoted TCE degradation systems with different particle sizes;

[0020] Figure 2 This is a comparison chart of the effect of particle size on the CH4 content in the headspace in the late stage of TCE degradation reaction in the TCE degradation system promoted by PHA of different particle sizes. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention are described in further detail below in conjunction with specific examples and accompanying drawings. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0022] The polymers used in the present invention include polyhydroxyalkanoate, polycaprolactone, polybutylene succinate, polyvinyl alcohol and polylactic acid, all of which are commercially available.

[0023] The chlorinated hydrocarbon contaminated sites in the present invention refer to groundwater, sediments and soil contaminated by chlorinated hydrocarbons.

[0024] During research, the applicant discovered that biodegradable polymer particles can be any one or more of polyhydroxyalkanoate, polycaprolactone, polybutylene succinate, polyvinyl alcohol, and polylactic acid. These polymer particles, with particle sizes ranging from 20 to 5,000 μm, exhibited the ability to selectively inhibit the metabolism of methanogenic archaea when used to remediate contaminated sites containing chlorinated hydrocarbons at concentrations of 50 to 150,000 μg / L, and showed varying degrees of degradation of trichloroethylene, a representative chlorinated hydrocarbon. This description will be made using polyhydroxyalkanoate as an example.

[0025] Example 1

[0026] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0027] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 100 μM. The PHA dosage was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and the culture was carried out at room temperature for 35 days, with the PHA being a liquid.

[0028] Example 2

[0029] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0030] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 100 μM. The PHA dosage was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and cultured at room temperature for 35 days. The PHA was in granular form with a particle size of 50 μm.

[0031] Example 3

[0032] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0033] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 100 μM. The PHA dosage was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and cultured at room temperature for 35 days. The PHA was in granular form with a particle size of 500 μm.

[0034] Example 4

[0035] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0036] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 100 μM. The PHA dosage was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and cultured at room temperature for 35 days. The PHA was in granular form with a particle size of 2000 μm.

[0037] Example 5

[0038] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0039] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 50 μM. The PHA dosage was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and cultured at room temperature for 20 days. The PHA was in granular form with a particle size of 500 μm.

[0040] Example 6

[0041] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0042] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water; the initial trichloroethylene concentration was 150 μM; the PHA dosage was 85.5 g / L; the initial pH was 7, nitrogen was aerated for 30 minutes to ensure anaerobic conditions, and the culture was carried out at room temperature for 40 days, wherein the PHA was in liquid form.

[0043] Example 7

[0044] This embodiment provides a method for remediating chlorinated hydrocarbon pollution using polyhydroxyalkanoate (PHA).

[0045] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 150 μM. The PHA dosage was 170 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and the culture was carried out at room temperature for 40 days. The PHA was in granular form with a particle size of 50 μm.

[0046] Example 8

[0047] This embodiment provides a method for repairing chlorinated hydrocarbon pollution using polycaprolactone.

[0048] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water; the initial trichloroethylene concentration was 100 μM; the polycaprolactone dosage was 17.14 g / L; the initial pH was 7, nitrogen was aerated for 30 minutes to ensure anaerobic conditions, and the culture was carried out at room temperature for 20 days. The polycaprolactone was in granular form with a particle size of 500 μm.

[0049] Example 9

[0050] This embodiment provides a method for repairing chlorinated hydrocarbon pollution using polybutylene succinate.

[0051] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water. The initial trichloroethylene concentration was 100 μM. The dosage of polybutylene succinate was 17.14 g / L. The initial pH was 7. Nitrogen was aerated for 30 minutes to ensure anaerobic conditions and cultured at room temperature for 20 days. The polybutylene succinate was in granular form with a particle size of 500 μm.

[0052] Example 10

[0053] This embodiment provides a method for repairing chlorinated hydrocarbon pollution using polyvinyl alcohol.

[0054] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water; the initial trichloroethylene concentration was 100 μM; the amount of polyvinyl alcohol added was 17.14 g / L; the initial pH was 7, nitrogen was aerated for 30 minutes to ensure anaerobic conditions, and the culture was carried out at room temperature for 20 days, wherein the polyvinyl alcohol was in granular form with a particle size of 500 μm.

[0055] Example 11

[0056] This embodiment provides a method for repairing chlorinated hydrocarbon pollution using polylactic acid.

[0057] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 mL of pure water; the initial trichloroethylene concentration was 100 μM; the amount of polyvinyl alcohol added was 17.14 g / L; the initial pH was 7, nitrogen was aerated for 30 minutes to ensure anaerobic conditions, and the culture was carried out at room temperature for 20 days, wherein the polyvinyl alcohol was in granular form with a particle size of 500 μm.

[0058] Comparative Example 1

[0059] This comparative example provides a method for repairing chlorinated hydrocarbon pollution without adding polymer.

[0060] 15 g of sediment was collected from a chlorinated hydrocarbon contaminated site and then added to 85 ml of pure water; the initial TCE concentration was 100 μM; the PHA dosage was 17.14 g / L; the initial pH was 7, nitrogen was aerated for 30 minutes to ensure anaerobic conditions, and the culture was carried out at room temperature.

[0061] Examples 1-11 all showed good degradation effects on trichloroethylene.

[0062] refer to Figure 1The applicant investigated the effect of polyhydroxyalkanoate particles of different particle sizes on the degradation of trichloroethylene and found that the methane production rate in the experimental group with the addition of 500 μm PHA was significantly reduced while the removal rate of chlorinated hydrocarbons was significantly increased. The trichloroethylene degradation effect was significantly better than that of the 50 μm and 2000 μm groups.

[0063] refer to Figure 2 Compared to other particle sizes, 500μm PHA produced more reactive oxygen species, with its reactive oxygen production increasing by 9.89 and 5.95 times compared to the 50μm and 2000μm groups, respectively. This selectively inhibited the abundance of methanogens and methanogenic functional genes, while promoting the increase in the abundance of dechlorinating bacteria and functional genes.

[0064] In order to better illustrate the application effect of the method for in-situ remediation of chlorinated hydrocarbon contaminated sites provided by this application, a detailed description is given below for an actual project.

[0065] The actual engineering application of using PHA particles to promote the in-situ remediation of chlorinated hydrocarbons can be achieved through injection into contaminated wells or in-situ permeable reaction walls. PHA particles are injected into the chlorinated hydrocarbon contaminated plume. Since the hydraulic conductivity coefficient of the chlorinated hydrocarbon contaminated plume in groundwater is slow, PHA particles can simultaneously play the role of slowly releasing electron donors and selectively inhibiting methanogenic archaea in the in-situ microbial remediation method. In some embodiments, the manufacturing process of the permeable reaction wall can be prepared using the manufacturing process commonly used in the art. The permeable reaction wall can be filled with polymer particles and chlorinated hydrocarbon degrading bacteria, and the chlorinated hydrocarbon degrading bacteria can be Dehalogenococcus Dehalococcoides mccartyi and Dehalogenomonas Dehalogenimonas of mixed bacteria.

[0066] An in-situ chlorinated hydrocarbon degradation experiment was conducted in sediments at a relocated chemical plant site in Wuhan. A permeable reaction wall (1m high, 1m wide, 50cm thick) consisting of a mixture of quartz sand, PHA, and chlorinated hydrocarbon-degrading bacteria was buried 2m below the sediment groundwater. After 28 days of incubation, the trichloroethylene content in the chlorinated hydrocarbon-contaminated groundwater after passing through the permeable reaction wall was reduced by 99.93%.

[0067] Any matters not mentioned above shall be subject to the existing technology.

[0068] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for in-situ remediation of a chlorinated hydrocarbon contaminated site, characterized in that: Polyhydroxyalkanoate particles are injected into a chlorinated hydrocarbon contaminated site and fermented for a certain period of time. The polyhydroxyalkanoate particles provide the carbon source and electron donor required for the growth of in-situ microorganisms. At the same time, the polyhydroxyalkanoate particles inhibit the production of methane by methanogenic archaea in the in-situ microorganisms, help the chlorinated hydrocarbon degrading bacteria in the in-situ microorganisms compete for electron donors, improve the utilization of electron donors by the chlorinated hydrocarbon degrading bacteria, and promote the degradation of chlorinated hydrocarbons. The particle size of the polyhydroxyalkanoate particles is 500 μm, and active oxygen is generated. The amount of polyhydroxyalkanoate particles added varies according to the concentration of chlorinated hydrocarbon pollution, and the minimum addition amount is a mass ratio of the total mass of the polyhydroxyalkanoate particles to the chlorinated hydrocarbons of 1:

2.

2. The method according to claim 1, wherein The concentration of chlorinated hydrocarbons in the chlorinated hydrocarbon contaminated site is 50-150000 μg / L.

3. The method according to claim 1, wherein The fermentation time is 5 to 40 days.

4. A method for repairing a permeable reactive wall of chlorinated hydrocarbon groundwater using the method according to any one of claims 1 to 3, characterized in that: The permeable reactive wall includes polyhydroxyalkanoate particles and chlorinated hydrocarbon degrading bacteria.

5. The permeable reactive wall according to claim 4, characterized in that: The chlorinated hydrocarbon degrading bacteria include Dehalogenococcus and Dehalogenomonas.

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