Enhanced Microbial Remediation Device and Remediation Method for Organically Complex Polluted Groundwater

Abstract

The present invention belongs to the field of remediation of groundwater contaminated by organic compounds, and discloses an enhanced microbial remediation device and a remediation method for groundwater contaminated by organic compounds, which can achieve efficient and synergistic remediation of groundwater contaminated by a mixture of chlorinated hydrocarbons and benzene series compounds. The enhanced microbial remediation device includes a hollow container, a base, a first syringe, a first injection pump, a second syringe, and a second injection pump; the bottom end of the container is connected to the outlet of the first syringe through a pipeline, the first syringe is connected to the first injection pump, a medium layer, a microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation, and a microbial sphere layer of immobilized bacteria for benzene series compound degradation are provided in the container, and the microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation is located below the microbial sphere layer of immobilized bacteria for benzene series compound degradation; an injection port is provided on the side wall of the container, the injection port is connected to the outlet of the second syringe through a pipeline, and the second injection pump is connected to the second syringe.

Description

Technical Field

[0001] The invention belongs to the field of remediation of groundwater contaminated by organic compounds. Specifically, it relates to an enhanced microbial remediation device and method for groundwater contaminated by organic compounds. Background Art

[0002] In areas where pesticides are frequently used, chlorinated hydrocarbons and benzene series compounds are the most common pollutants in the site, and they mostly appear in the form of combined pollution. These organic compounds generally have carcinogenic, teratogenic, and mutagenic effects, and the risk is relatively high. Therefore, it is necessary to carry out the remediation of chlorinated hydrocarbon and benzene series compound pollution in the site contaminated by the combined pollution of chlorinated hydrocarbons and benzene series compounds.

[0003] The permeable reactive barrier (hereinafter referred to as PRB in the text, corresponding English: permeable reactive barrier) technology is a commonly used in-situ technology for groundwater pollution remediation. The commonly used filling materials include abiotic reaction materials such as zero-valent iron, iron hydroxide, activated carbon, and limestone. These materials are easily saturated by adsorption, which affects the operation time limit of PRB and needs to be replaced regularly, resulting in a high cost. In addition, since benzene series compounds are generally degraded through oxidation, and chlorinated hydrocarbons are generally degraded through reduction, and the two reaction mechanisms are opposite, adding abiotic reaction materials cannot achieve the long-term and stable reduction of the combined pollution of chlorinated hydrocarbons and benzene series compounds in PRB.

[0004] Traditional remediation technologies such as chemical oxidation-reduction and heat treatment have deficiencies such as high energy consumption and easy generation of secondary pollution. Microbial remediation is a green, low-carbon and economical remediation technology without secondary pollution and has received wide attention. At present, microbial remediation mostly focuses on the degradation of single pollutants, targeting single benzene series compounds or chlorinated hydrocarbon pollutants. Due to the competition and inhibition between the degrading functional bacteria of chlorinated hydrocarbons and benzene series compounds, between the electron donors and acceptors in the degrading matrix, and the toxic effect of intermediate products on the degrading functional bacteria, etc., the synergistic remediation of the combined pollution of chlorinated hydrocarbons and benzene series compounds is difficult, and no relevant efficient remediation method has been disclosed. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the invention provides an enhanced microbial remediation device and method for groundwater contaminated by organic compounds, which can achieve the efficient and synergistic remediation of groundwater contaminated by the combined pollution of chlorinated hydrocarbons and benzene series compounds.

[0006] To solve the above technical problems, the invention adopts the following technical solutions:

[0007] In a first aspect, the present invention employs an enhanced microbial remediation device for organically compound-polluted groundwater, where the organically compound-polluted groundwater contains chlorinated hydrocarbons and benzene series compounds. The device includes a hollow container, a base, a first syringe, a first injection pump, a second syringe, and a second injection pump. Among them, the container is located on the base, the bottom end of the container is the water inlet, the top end of the container is the outlet, the bottom end of the container is connected to the outlet of the first syringe through a pipeline, the first syringe is connected to the first injection pump, a medium layer, a microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation, and a microbial sphere layer of immobilized bacteria agent for benzene series compound degradation are provided in the container. The microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer of immobilized bacteria agent for benzene series compound degradation are embedded in the medium layer, and the microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation is located below the microbial sphere layer of immobilized bacteria agent for benzene series compound degradation. An injection port is provided on the side wall of the container, the injection port is located between the microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer of immobilized bacteria agent for benzene series compound degradation, the injection port is connected to the outlet of the second syringe through a pipeline, and the second injection pump is connected to the second syringe.

[0008] As a preferred example, the medium layer is a quartz sand layer, and the medium layer fills the container.

[0009] As a preferred example, the container is an anaerobic glass column, the pipeline is a polytetrafluoroethylene tube, and sampling ports are provided at different height positions on the side wall of the container.

[0010] As a preferred example, the thickness of the microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation is 2 - 4 cm, the thickness of the microbial sphere layer of immobilized bacteria agent for benzene series compound degradation is 2 - 4 cm, and the distance between the microbial sphere layer of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer of immobilized bacteria agent for benzene series compound degradation is 12 - 15 cm.

[0011] As a preferred example, the outlet of the container is connected to a sealed tank filled with activated carbon.

[0012] In a second aspect, the present invention employs a method for remediating organically compound-polluted groundwater, and the method includes:

[0013] Step 1: Enrich and culture the degradation bacterial liquid. Collect samples of the organically compound-polluted groundwater and soil to be remediated, and through microcosm experiments, enrich and culture to obtain an enrichment bacterial liquid for degrading chlorinated hydrocarbons and an enrichment bacterial liquid for degrading benzene series compounds.

[0014] Step 2: Based on the enrichment bacterial liquid for degrading chlorinated hydrocarbons and the enrichment bacterial liquid for degrading benzene series compounds obtained by enriching and culturing in Step 1, identify the types of degradation functional bacteria in the enrichment bacterial liquid for degrading chlorinated hydrocarbons and the types of degradation functional bacteria in the enrichment bacterial liquid for degrading benzene series compounds.

[0015] Step 3: According to the types of degrading functional bacteria in the enriched bacterial solution for degrading chlorinated hydrocarbons identified in Step 2, use an anaerobic microbial fermenter to ferment and obtain a chlorinated hydrocarbon-degrading bacterial solution; according to the types of degrading functional bacteria in the enriched bacterial solution for degrading benzene series compounds identified in Step 2, use an anaerobic microbial fermenter to ferment and obtain a benzene series compound-degrading bacterial solution.

[0016] Step 4: Use the chlorinated hydrocarbon-degrading bacterial solution and benzene series compound-degrading bacterial solution obtained by fermentation in Step 3 to prepare chlorinated hydrocarbon-degrading immobilized bacterial agent microspheres and benzene series compound-degrading immobilized bacterial agent microspheres respectively.

[0017] Step 5: Place the chlorinated hydrocarbon-degrading immobilized bacterial agent microspheres and benzene series compound-degrading immobilized bacterial agent microspheres prepared in Step 4 into a container and assemble a strengthened microbial remediation device.

[0018] Step 6: Load the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be repaired into a first syringe. Under the action of a first injection pump, the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be repaired flow into the water inlet of the container and flow upward in the container.

[0019] Load the electron acceptor solution for degrading benzene series compounds into a second syringe. Under the action of a second injection pump, the electron acceptor solution for degrading benzene series compounds flows into the injection port of the container and flows upward in the container.

[0020] As a preferred example, Step 4 specifically includes:

[0021] Step 401: Use a centrifuge to centrifuge the chlorinated hydrocarbon-degrading bacterial solution and benzene series compound-degrading bacterial solution obtained by fermentation in Step 3, and collect the bacteria at the bottom respectively to obtain chlorinated hydrocarbon-degrading bacteria and benzene series compound-degrading bacteria.

[0022] Step 402: Prepare a bacterial suspension: Resuspend the chlorinated hydrocarbon-degrading bacteria and benzene series compound-degrading bacteria obtained in Step 401 into an embedding agent aqueous solution respectively to obtain a chlorinated hydrocarbon-degrading bacterial suspension and a benzene series compound-degrading bacterial suspension concentrated 100 times.

[0023] Step 403: Immobilization treatment: Drop the chlorinated hydrocarbon-degrading bacterial suspension prepared in Step 402 into the crosslinking agent aqueous solution drop by drop with a pipette. Under the regulation of an ice bath and magnetic stirring, after the embedding agent and the crosslinking agent react fully, form chlorinated hydrocarbon-degrading immobilized bacterial agent microspheres; drop the benzene series compound-degrading bacterial suspension prepared in Step 402 into the crosslinking agent aqueous solution drop by drop with a pipette. Under the regulation of an ice bath and magnetic stirring, after the embedding agent and the crosslinking agent react fully, form benzene series compound-degrading immobilized bacterial agent microspheres.

[0024] Step 404: Remove the remaining crosslinking agent after the reaction respectively, wash the microbial balls of the chlorohydrocarbon-degrading immobilized bacteria agent and the microbial balls of the benzene series-degrading immobilized bacteria agent with sterile and deoxygenated normal saline, and then store them in a refrigerator for standby.

[0025] As a preferred example, step 5 specifically includes:

[0026] Step 501: Sterilize and deoxygenate the container, pipeline, first syringe and second syringe, and rinse them with anaerobic medium until the rinsed anaerobic medium is colorless.

[0027] Step 502: Install the container on the base, install a filter screen at the water inlet at the bottom of the container, and conduct a sealing treatment; connect the outlet of the first syringe and the water inlet of the container with a pipeline; connect the outlet of the second syringe and the injection port of the container with a pipeline.

[0028] Step 503: Fill the container with quartz sand, microbial balls of the chlorohydrocarbon-degrading immobilized bacteria agent and microbial balls of the benzene series-degrading immobilized bacteria agent.

[0029] Step 504: Install a filter screen at the top of the container, and then conduct a sealing treatment.

[0030] As a preferred example, step 503 includes: first add anaerobic medium to the container, then add deoxygenated quartz sand, and the water level of the anaerobic medium is always higher than that of the quartz sand; then add anaerobic medium and quartz sand in sequence to the first preset position, and then add the microbial balls of the chlorohydrocarbon-degrading immobilized bacteria agent to form a layer of microbial balls of the chlorohydrocarbon-degrading immobilized bacteria agent; subsequently add anaerobic medium and quartz sand in sequence, and the water level of the anaerobic medium is always higher than that of the quartz sand. After adding to the second preset position, add the microbial balls of the benzene series-degrading immobilized bacteria agent to form a layer of microbial balls of the benzene series-degrading immobilized bacteria agent; finally add anaerobic medium and quartz sand in sequence, and the water level of the anaerobic medium is always higher than that of the quartz sand until the quartz sand is filled to the top of the container.

[0031] As a preferred example, in step 6, the volume of the solution injected into the container from the first syringe is 3 times the volume of the pore water of the quartz sand after filling.

[0032] Compared with the prior art, the enhanced microbial remediation device and remediation method for organically compound-polluted groundwater of the present invention can achieve efficient and synergistic remediation of groundwater contaminated by a mixture of chlorinated hydrocarbons and benzene series compounds. The enhanced microbial remediation device includes a hollow container, a base, a first syringe, a first injection pump, a second syringe, and a second injection pump; the container is located on the base, the bottom end of the container is the water inlet, the top end of the container is the outlet, the bottom end of the container is connected to the outlet of the first syringe through a pipeline, the first syringe is connected to the first injection pump, a medium layer, a microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation, and a microbial sphere layer of immobilized bacteria for benzene series compound degradation are provided in the container, the microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation and the microbial sphere layer of immobilized bacteria for benzene series compound degradation are embedded in the medium layer, and the microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation is located below the microbial sphere layer of immobilized bacteria for benzene series compound degradation; an injection port is provided on the side wall of the container, the injection port is located between the microbial sphere layer of immobilized bacteria for chlorinated hydrocarbon degradation and the microbial sphere layer of immobilized bacteria for benzene series compound degradation, the injection port is connected to the outlet of the second syringe through a pipeline, and the second injection pump is connected to the second syringe. The present invention is based on the organic coupling of microbial remediation, immobilized microorganism technology and PRB, which can reduce the negative impacts such as inhibition and competition, and poisoning effects existing in the synergistic remediation of organically compound-polluted microorganisms, and achieve efficient and synergistic, green and low-carbon remediation of the organic compound pollution of chlorinated hydrocarbons and benzene series compounds in the groundwater of the site. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. is a schematic structural diagram of the device according to an embodiment of the present invention, and the arrow direction in the figure indicates the liquid flow direction.

[0034] In the figure: container 1, medium layer 101, microbial sphere layer 102 of immobilized bacteria for chlorinated hydrocarbon degradation, microbial sphere layer 103 of immobilized bacteria for benzene series compound degradation, base 2, first syringe 3, first injection pump 4, second syringe 5, second injection pump 6, sealed tank 7. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] The polluted groundwater remediated by the present invention is organically compound-polluted groundwater. The organically compound-polluted groundwater contains chlorinated hydrocarbons and benzene series compounds.

[0037] Such as Figure 1As shown in the figure, an enhanced microbial remediation device for organically compound - polluted groundwater according to an embodiment of the present invention includes a hollow container 1, a base 2, a first syringe 3, a first injection pump 4, a second syringe 5, and a second injection pump 6. The container 1 is located on the base 2. The bottom end of the container 1 is the water inlet, and the top end of the container 1 is the outlet. The bottom end of the container 1 and the outlet of the first syringe 3 are connected by a pipeline. The first syringe 3 is connected to the first injection pump 4. A medium layer 101, a microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation, and a microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation are provided in the container 1. The microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation are embedded in the medium layer 101, and the microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation is located below the microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation. An injection port is provided on the side wall of the container 1. The injection port is located between the microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation. The injection port and the outlet of the second syringe 5 are connected by a pipeline. The second injection pump 6 is connected to the second syringe 5.

[0038] Preferably, the medium layer 101 is a quartz sand layer, and the medium layer 101 fills the container 1. Selecting the quartz sand layer as the medium layer 101 has good permeability, which is beneficial for pollutants to migrate towards the microbial sphere layer along with the water flow.

[0039] Preferably, the container 1 is an anaerobic glass column, the pipeline is a polytetrafluoroethylene tube, and sampling ports are provided at different height positions on the side wall of the container 1. Since groundwater is generally in an anaerobic environment, in order to simulate the groundwater environment, an anaerobic glass column is used as the container 1. The adsorption amount of organic pollutants by glass can be ignored. If the pollutants are adsorbed by the device itself, then the reduction of pollutant concentration at the outlet end may not necessarily be caused by microbial degradation. Selecting a pipeline made of polytetrafluoroethylene material can avoid the adsorption of organic pollutants by the pipeline itself. Sampling ports are provided at different height positions on the side wall of the container 1. Samples are taken from the container 1 through the sampling ports and detected to obtain the remediation effect of the organically compound - polluted groundwater.

[0040] Preferably, the thickness of the microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation is 2 - 4 cm, the thickness of the microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation is 2 - 4 cm, and the distance between the microbial sphere layer 102 of immobilized bacteria agent for chlorinated hydrocarbon degradation and the microbial sphere layer 103 of immobilized bacteria agent for benzene - series compound degradation is 12 - 15 cm. Selecting these numerical ranges can ensure that a single microbial PRB system has enough time to degrade pollutants and consume the electron donor / acceptor completely, reducing the inhibitory and toxic effects on the adjacent next microbial PRB system.

[0041] Preferably, the outlet of the container 1 is connected to a sealed tank 7 filled with activated carbon. Activated carbon has a strong adsorption effect. The liquid flowing out of the outlet of the container 1 may contain volatile pollutants that have not been completely degraded. Therefore, connecting the outlet to the sealed tank 7 containing activated carbon can reduce environmental pollution caused by pollutant volatilization.

[0042] A method for repairing organically complex polluted groundwater using the enhanced microbial remediation device of the above-mentioned embodiment or preferred example includes:

[0043] Step 1: Enrich and culture the degrading bacterial liquid: Collect the organically complex polluted groundwater and soil samples to be repaired, and through microcosm experiments, enrich and culture the enriched bacterial liquid for degrading chlorinated hydrocarbons and the enriched bacterial liquid for degrading benzene series compounds.

[0044] In Step 1, collect the organically complex polluted groundwater and soil samples to be repaired. Inside an anaerobic glove box, through microcosm experiments, enrich and culture the enriched bacterial liquid for degrading chlorinated hydrocarbons and the enriched bacterial liquid for degrading benzene series compounds.

[0045] Step 2: According to the enriched bacterial liquid for degrading chlorinated hydrocarbons and the enriched bacterial liquid for degrading benzene series compounds obtained by enriching and culturing in Step 1, identify the types of degrading functional bacteria in the enriched bacterial liquid for degrading chlorinated hydrocarbons and the types of degrading functional bacteria in the enriched bacterial liquid for degrading benzene series compounds.

[0046] In Step 2, use existing methods such as 16S rRNA gene amplicon sequencing and quantitative PCR (qPCR) to identify the types of degrading functional bacteria in the enriched bacterial liquid for degrading chlorinated hydrocarbons and the types of degrading functional bacteria in the enriched bacterial liquid for degrading benzene series compounds.

[0047] Step 3: According to the types of degrading functional bacteria in the enriched bacterial liquid for degrading chlorinated hydrocarbons identified in Step 2, use an anaerobic microbial fermentation tank to ferment and obtain a chlorinated hydrocarbon degrading bacterial liquid. According to the types of degrading functional bacteria in the enriched bacterial liquid for degrading benzene series compounds identified in Step 2, use an anaerobic microbial fermentation tank to ferment and obtain a benzene series compound degrading bacterial liquid.

[0048] Step 4: Use the chlorinated hydrocarbon degrading bacterial liquid and the benzene series compound degrading bacterial liquid obtained by fermenting in Step 3 to respectively produce chlorinated hydrocarbon degrading immobilized bacterial agent microspheres and benzene series compound degrading immobilized bacterial agent microspheres.

[0049] Step 5: Load the chlorinated hydrocarbon degrading immobilized bacterial agent microspheres and the benzene series compound degrading immobilized bacterial agent microspheres produced in Step 4 into a container to assemble an enhanced microbial remediation device.

[0050] Step 6: Load the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be repaired into the first syringe 3. Under the action of the first injection pump 4, the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be repaired flow into the water inlet of the container 1 and flow upward from the bottom in the container 1. Load the electron acceptor solution for degrading benzene series into the second syringe 5. Under the action of the second injection pump 6, the electron acceptor solution for degrading benzene series flows into the injection port of the container 1 and flows upward in the container 1.

[0051] In step 6, the molar ratio of the electrons provided by the electron donor for degrading chlorinated hydrocarbons in the organic composite contaminated groundwater to be repaired to the electrons required for complete dechlorination of chlorinated hydrocarbons is greater than 10. Generally, there are other substances in the groundwater that compete with chlorinated hydrocarbons for electrons. To ensure the complete reductive dechlorination of chlorinated hydrocarbons (this process requires receiving electrons from the outside), more than 10 times the electrons are provided.

[0052] The solution flows upward from the bottom in the container 1. The solution is pushed upward by the power of the first injection pump or the second injection pump, and the flow rate is controllable, so that the overall water flow can be pushed forward. If the solution flows downward from the top in the container 1, due to the gravity and the heterogeneity of the filling medium (it is impossible to achieve absolute homogeneity of the filling medium), the water flow cannot be controlled, resulting in the actual flow rate being inconsistent with the set flow rate, and it is easy to have uneven flow rates (fast in some places and slow in some places) and form preferential channels, and the overall forward movement of the water flow cannot be controlled.

[0053] Preferably, step 4 specifically includes:

[0054] Step 401: Use a centrifuge to centrifuge the chlorinated hydrocarbon-degrading bacterial liquid and benzene series-degrading bacterial liquid obtained by fermentation in step 3, and collect the bacterial cells at the bottom respectively to obtain chlorinated hydrocarbon-degrading bacterial cells and benzene series-degrading bacterial cells.

[0055] Step 402: Prepare a bacterial suspension: Resuspend the chlorinated hydrocarbon-degrading bacterial cells and benzene series-degrading bacterial cells obtained in step 401 in the aqueous solution of the embedding agent respectively to obtain a chlorinated hydrocarbon-degrading bacterial suspension and a benzene series-degrading bacterial suspension concentrated 100 times.

[0056] In step 402, in an anaerobic glove box, resuspend the obtained chlorinated hydrocarbon-degrading bacterial cells in 1 mL of the aqueous solution of the embedding agent to obtain a chlorinated hydrocarbon-degrading bacterial suspension concentrated 100 times. In an anaerobic glove box, resuspend the obtained benzene series-degrading bacterial cells in 1 mL of the aqueous solution of the embedding agent to obtain a benzene series-degrading bacterial suspension concentrated 100 times. The aqueous solution of the embedding agent is made of ultrapure water, 200-mesh activated carbon, sodium alginate and polyvinyl alcohol. Among them, the mass ratio of 200-mesh activated carbon, sodium alginate and polyvinyl alcohol is 1:3:6.

[0057] Step 403. Immobilization treatment: Drop the chlorohydrocarbon-degrading bacterial suspension prepared in Step 402 drop by drop (30 μL each time) into the aqueous crosslinking agent solution with a pipette. Under ice bath and magnetic stirring, after the embedding agent and the crosslinking agent react fully, chlorohydrocarbon-degrading immobilized bacterial agent microspheres are formed; Drop the benzene-series compound-degrading bacterial suspension prepared in Step 402 drop by drop (30 μL each time) into the aqueous crosslinking agent solution with a pipette. Under ice bath and magnetic stirring, after the embedding agent and the crosslinking agent react fully, benzene-series compound-degrading immobilized bacterial agent microspheres are formed.

[0058] Step 404. Remove the remaining crosslinking agent after the reaction respectively, wash the chlorohydrocarbon-degrading immobilized bacterial agent microspheres and the benzene-series compound-degrading immobilized bacterial agent microspheres with sterile and deoxygenated normal saline, and then place them in the refrigerator for storage for later use.

[0059] In Step 404, after the crosslinking reaction is completed, in an anaerobic glove box, remove the remaining crosslinking agent after the reaction, quickly wash the chlorohydrocarbon-degrading immobilized bacterial agent microspheres and the benzene-series compound-degrading immobilized bacterial agent microspheres 3 times with sterile and deoxygenated normal saline, and place them in the refrigerator for storage for later use. The aqueous crosslinking agent solution is made of ultrapure water, calcium chloride and boric acid. Among them, the mass concentrations of calcium chloride and boric acid are both 1.5%.

[0060] Preferably, Step 5 specifically includes:

[0061] Step 501. Sterilize and deoxygenate the container 1, the pipeline, the first syringe 3 and the second syringe 5, and rinse them with anaerobic culture medium until the rinsed anaerobic culture medium is colorless.

[0062] The container 1, the pipeline, the first syringe 3 and the second syringe 5 need to be sterilized and deoxygenated before use, placed in the anaerobic glove box for deoxygenation for about 2 days, and rinsed with anaerobic culture medium before use until the rinsed anaerobic culture medium is colorless.

[0063] Step 502. Install the container 1 on the base 2, install a filter screen at the water inlet at the bottom of the container 1, and perform a sealing treatment; Connect the outlet of the first syringe 3 and the water inlet of the container 1 with a pipeline; Connect the outlet of the second syringe 5 and the injection port of the container 1 with a pipeline. The base 2 can adopt a tripod. A filter screen is installed at the water inlet at the bottom of the container 1 to prevent the quartz sand from overflowing with the water flow. The filter screen is sealed with a butyl rubber stopper.

[0064] Step 503: Load quartz sand, microbial balls of immobilized bacteria for chlorinated hydrocarbon degradation, and microbial balls of immobilized bacteria for benzene series degradation into Container 1. Preferably, the quartz sand is loaded by the wet loading method. Specifically, Step 503 includes: First, add anaerobic culture medium into Container 1, and then add deoxygenated quartz sand. The water level of the anaerobic culture medium is always higher than that of the quartz sand. Then, after adding the anaerobic culture medium and quartz sand successively to the first preset position, add the microbial balls of immobilized bacteria for chlorinated hydrocarbon degradation to form the chlorinated hydrocarbon degradation immobilized bacteria microbial ball layer 102. Subsequently, add the anaerobic culture medium and quartz sand successively. The water level of the anaerobic culture medium is always higher than that of the quartz sand. After adding to the second preset position, add the microbial balls of immobilized bacteria for benzene series degradation to form the benzene series degradation immobilized bacteria microbial ball layer 103. Finally, add the anaerobic culture medium and quartz sand successively. The water level of the anaerobic culture medium is always higher than that of the quartz sand until the quartz sand is filled to the top of Container 1. During the loading process, shake and oscillate to make the quartz sand evenly filled, and finally fill Container 1. Loading the quartz sand by the wet loading method is beneficial to creating a saturated porous medium condition, avoiding the existence of air bubbles in the pores of the quartz sand, and it is difficult to discharge the enclosed air bubbles.

[0065] Step 504: Install a filter screen at the top of Container 1 and then perform a sealing treatment. Install a filter screen at the top of Container 1 and then seal it with a butyl rubber stopper. The filter screen can prevent the quartz sand from flowing out of the device along with the water flow.

[0066] In Step 503, the order of adding the immobilized bacteria microbial ball layers is such that the degradation products of the pollutants corresponding to the first-added bacteria and the required nutrients have no (or less) inhibitory effect on the subsequent microbial degradation. For the composite pollution of chlorinated hydrocarbons and benzene series, first add the immobilized bacteria microbial ball layer for chlorinated hydrocarbon degradation, and then add the immobilized bacteria microbial ball layer for benzene series degradation.

[0067] Preferably, in Step 6, the volume of the solution injected into Container 1 from the first syringe 3 is 3 times the pore water volume of the quartz sand. This solution can ensure that there is a certain volume of stable continuous water flow passing through the PRB system, proving that this system can continuously play the role of degrading pollutants instead of failing after a short period of time (or after a small amount of polluted water passes through).

[0068] For the above-mentioned remediation method, after Step 6, samples are taken at the sampling port of Container 1 every 12 h during the injection of the polluted water to analyze the pollutant degradation effect. For example, 1 mL of samples are taken respectively from the sampling port closest to the outlet and added into a headspace vial containing 5 mL of hydrochloric acid water, and the pollutant concentration is detected by headspace-gas chromatography and compared with the initial pollutant concentration injected to analyze the pollutant degradation effect.

[0069] The enhanced microbial remediation device and method of the present invention are based on the organic coupling of the immobilized microorganism technology and PRB. A single type of chlorinated hydrocarbon or benzene series compound-degrading microbial functional bacteria is made into an immobilized microbial agent, and the immobilized microbial agent is used as the filling material of PRB. By constructing a multi-stage enhanced microbial PRB system with a certain order, the enhanced microbial PRB remediation system for a single type of organic matter is separated spatially, thereby reducing the negative impacts such as inhibition and competition effects, and poisoning effects existing in the co-remediation, and realizing the efficient co-remediation of the combined pollution of chlorinated hydrocarbons and benzene series compounds in the groundwater of chemical industrial sites. Constructing a multi-stage enhanced microbial PRB system with a certain order means that the degradation products of pollutants corresponding to the first-added microbial agent and the required nutrients have no (or less) inhibitory effect on the subsequent microbial degradation.

[0070] Specifically, for the combined pollution of chlorinated hydrocarbons and benzene series compounds, if the chlorinated hydrocarbon and benzene series compound pollutants and their respective corresponding degrading bacterial solutions are mixed together for degradation, due to the competition relationship between different bacterial groups, the reduction product nitrite of the electron acceptor nitrate required for benzene series compound degradation will have a strong poisoning effect on the chlorinated hydrocarbon-degrading bacteria, the competition relationship between the electron donor required for chlorinated hydrocarbon degradation and benzene series compounds, the certain inhibitory effect of chlorinated hydrocarbons on benzene series compound degradation, the certain inhibitory effect of benzene series compounds on chlorinated hydrocarbon degradation and many other unfavorable factors, resulting in a low degradation efficiency of the combined pollution of chlorinated hydrocarbons and benzene series compounds. The remediation device of the present invention has a two-stage PRB remediation system separated spatially, which is respectively filled with a microbial sphere layer 102 of an immobilized microbial agent for chlorinated hydrocarbon degradation and a microbial sphere layer 103 of an immobilized microbial agent for benzene series compound degradation, separating the two degrading microbial agents spatially and avoiding the competition relationship between different bacterial groups. The first-stage PRB filled with the microbial sphere layer 102 of the immobilized microbial agent for chlorinated hydrocarbon degradation first degrades chlorinated hydrocarbons, and the second-stage PRB (located downstream of the first-stage PRB) filled with the microbial sphere layer 103 of the immobilized microbial agent for benzene series compound degradation then degrades benzene series compounds, avoiding the poisoning effect of the reduction product of the electron acceptor nitrate required for benzene series compound degradation on the chlorinated hydrocarbon-degrading bacteria. There is a certain distance between the two-stage PRBs to ensure that each stage of PRB has enough time for full reaction, maximizing the consumption of chlorinated hydrocarbons and their electron donors, thereby avoiding the competition relationship between the electron donor required for chlorinated hydrocarbon degradation and benzene series compounds, and the inhibitory effect of chlorinated hydrocarbons on benzene series compound degradation. Overall, the goal of maximizing the avoidance of the above unfavorable factors is achieved, and the efficient co-remediation of the combined pollution is realized. Ideally, the water flows from bottom to top, and before reaching the microbial sphere layer 103 of the immobilized microbial agent for benzene series compound degradation, the chlorinated hydrocarbons in the water have been completely degraded, and the electron donor required for chlorinated hydrocarbon degradation has been completely consumed. In this way, when the second-stage PRB degrades the benzene series compounds in the water, the adverse effects of chlorinated hydrocarbons and the electron donor required for chlorinated hydrocarbon degradation are eliminated.

[0071] A specific embodiment is provided below.

[0072] Example 1

[0073] The organic composite contaminated groundwater to be repaired contains trichloroethylene (abbreviated as TCE in the text) and toluene. The concentration of TCE is 176.5 μmol / L (23.2 mg / L), and the concentration of toluene is 145.8 μmol / L (13.4 mg / L).

[0074] The enhanced microbial remediation of the organic composite contaminated groundwater is carried out by using the remediation device of the present invention, including the following steps:

[0075] Step 1: Enrich and culture the degrading bacterial liquid. Groundwater and soil samples are collected from a trichloroethylene (TCE) and toluene contaminated site in Taixing City, Jiangsu Province. Through microcosm experiments in a laboratory anaerobic glove box (model: COY-7150220, USA), the enriched bacterial liquid for degrading TCE and the enriched bacterial liquid for degrading toluene are obtained by enrichment and culture.

[0076] Step 2: Identify the degrading functional bacteria. The types of degrading functional bacteria in the enriched bacterial liquid for degrading TCE are identified as Dehalococcoides and Dehalobacter genera by using 16S rRNA gene amplicon sequencing and quantitative PCR (qPCR) methods, and the degrading functional bacteria in the enriched bacterial liquid for degrading toluene are Aromatoleum genus.

[0077] Step 3: Ferment to obtain the degrading bacterial liquid. Using a stainless steel fully automatic sterilizing fermenter (BLBIO-20SJA, Bailun, China) for fermentation, 10 L of TCE degrading bacterial liquid and 10 L of toluene degrading bacterial liquid are obtained.

[0078] Step 4: Prepare the immobilized bacterium agent microbial balls for degrading TCE and the immobilized bacterium agent microbial balls for degrading toluene respectively. Specifically including:

[0079] Step 401: Use a centrifuge to centrifuge the TCE degrading bacterial liquid and toluene degrading bacterial liquid obtained by fermentation in Step 3, and collect the bacteria at the bottom respectively to obtain TCE degrading bacteria and toluene degrading bacteria.

[0080] Step 402: In the anaerobic glove box, the obtained TCE degrading bacteria and toluene degrading bacteria are respectively resuspended in 1 mL of embedding agent aqueous solution to obtain the TCE degrading bacterial suspension and toluene degrading bacterial suspension concentrated 100 times. The embedding agent aqueous solution is made by adding 200-mesh activated carbon, sodium alginate and polyvinyl alcohol to ultrapure water, wherein 1 g of 200-mesh activated carbon, 3 g of sodium alginate and 6 g of polyvinyl alcohol.

[0081] Step 403: Dropwise add (30 μL each drop) the TCE-degrading bacterial suspension prepared in Step 402 into the aqueous crosslinker solution. Under ice bath and magnetic stirring, after the embedding agent and the crosslinker react fully, TCE-degrading immobilized bacteria agent microspheres are formed; Dropwise add (30 μL each drop) the toluene-degrading bacterial suspension prepared in Step 402 into the aqueous crosslinker solution. Under ice bath and magnetic stirring, after the embedding agent and the crosslinker react fully, toluene-degrading immobilized bacteria agent microspheres are formed.

[0082] Step 404: Remove the remaining crosslinker after the reaction respectively, wash the TCE-degrading immobilized bacteria agent microspheres and the toluene-degrading immobilized bacteria agent microspheres 3 times with sterile and deoxygenated normal saline, and then store them in the refrigerator for standby. The aqueous crosslinker solution is made of ultrapure water, calcium chloride and boric acid. Among them, the mass concentrations of calcium chloride and boric acid are both 1.5%.

[0083] Step 5: Load the TCE-degrading immobilized bacteria agent microspheres and the toluene-degrading immobilized bacteria agent microspheres prepared in Step 4 into a container and assemble an enhanced microbial remediation device.

[0084] Container 1 uses an anaerobic glass column with an inner diameter of 6 cm and a height of 40 cm; the injection port is located at a height of 20 cm on the side of the anaerobic glass column. A sampling port is set every 5 cm on the side of the column. To simulate the anaerobic microbial PRB remediation of organic compound pollution in the groundwater environment, quartz sand is filled in the anaerobic glass column to simulate the underground aquifer medium; the microbial liquid is added into the quartz sand in layers in the form of immobilized bacteria agent microspheres to simulate a multi-stage microbial PRB system, and the specific number of layers is determined according to the types of pollutants. The TCE and toluene composite polluted water solution and the electron donors / acceptors required for microbial degradation are injected into the anaerobic glass column filled with quartz sand through an injection pump connected to a syringe to simulate the polluted groundwater flow and pollutant migration. The syringe can use a 100 mL airtight syringe, and the connecting pipe is a polytetrafluoroethylene pipe.

[0085] Step 5 specifically includes:

[0086] Step 501: Sterilize and deoxygenate Container 1, the pipeline, the first syringe 3 and the second syringe 5 before use, place them in an anaerobic glove box for 2 days for deoxygenation, and rinse them with anaerobic culture medium before use until the rinsed anaerobic culture medium is colorless. This ensures that the device is in an anaerobic state.

[0087] Step 502: Fix the anaerobic glass column with a tripod. After installing a filter screen at the lower end of the anaerobic glass column, seal it with a rubber stopper. Use the wet packing method to fill the anaerobic glass column with quartz sand, which specifically includes: first add 10 mL of anaerobic culture medium, then add the deoxygenated quartz sand, and then sequentially add the anaerobic culture medium and quartz sand to a height of about 5 cm, and add the first layer of TCE-degrading immobilized bacteria microbial balls to form a 3-cm-thick layer of TCE-degrading immobilized bacteria microbial balls; continue to add the anaerobic culture medium and quartz sand to a height of about 28 cm, and add the second layer of toluene-degrading immobilized bacteria microbial balls to form a 3-cm-thick layer of toluene-degrading immobilized bacteria microbial balls; continue to add the anaerobic culture medium and quartz sand until the anaerobic glass column is filled. During the filling process, shake and oscillate to make the quartz sand evenly filled. Install a filter screen at the upper end of the anaerobic glass column, and then seal it with a butyl rubber stopper. Connect the syringe and the anaerobic glass column in sequence through a polytetrafluoroethylene tube. Place the syringe on the injection pump and control the injection flow rate through the injection pump.

[0088] Step 6: Inject the contaminated water body to be repaired and the electron donor / acceptor solution. Prepare a composite contaminated water body solution with a concentration of 176.5 μmol / L (23.2 mg / L) of TCE and a concentration of 145.8 μmol / L (13.4 mg / L) of toluene, prepare a mixed electron donor solution with a concentration of 1 mmol / L required for degrading TCE, and an aqueous solution of sodium nitrate as the electron acceptor with a concentration of 1 mmol / L required for degrading toluene. The mixed electron donor solution required for degrading TCE is a mixture of methanol, ethanol, sodium formate, sodium acetate, and sodium lactate, where the molar ratio of methanol, ethanol, sodium formate, sodium acetate, and sodium lactate is 4:2:12:3:2. Use the first injection pump of model ISPLab01 produced by Deke Industrial Technology (Shanghai) Co., Ltd. to continuously inject the TCE and toluene composite contaminated water body solution and the mixed electron donor solution required for degrading TCE from the lower end of the anaerobic glass column at a flow rate of 0.1 mL / min. The total volume of the injected composite contaminated water body solution and the mixed electron donor solution required for degrading TCE is 3 times the pore water volume of the quartz sand, about 540 mL. Use the second injection pump of model ISPLab01 produced by Deke Industrial Technology (Shanghai) Co., Ltd. to inject the aqueous solution of sodium nitrate as the electron acceptor required for degrading toluene from the injection port on the side of the anaerobic glass column at an injection speed of 0.1 mL / min, and the injection volume is 1.5 times the pore water volume of the quartz sand, about 270 mL.

[0089] The composite contaminated water body and the mixed electron donor solution required for degrading TCE flow upward and enter the first layer of TCE-degrading immobilized bacteria microbial balls. The TCE-degrading immobilized bacteria microbial balls use the electron donor in the contaminated water body to reduce the chlorinated hydrocarbon, and the chlorinated hydrocarbon reduction dechlorination reaction occurs to achieve the degradation and detoxification of the chlorinated hydrocarbon.

[0090] When the composite contaminated water body and the mixed electron donor solution required for degrading TCE flow upward and enter the area between the first layer of microbial spheres of immobilized bacteria for TCE degradation and the second layer of microbial spheres of immobilized bacteria for toluene degradation, and are located upstream of the injection port, free microorganisms in the upstream microbial spheres of immobilized bacteria for TCE degradation may exist in the water body of this area. If TCE in the water body of this area has not been completely degraded, the reductive dechlorination reaction of TCE continues. At this time, the mixed electron donor is basically consumed.

[0091] When the composite contaminated water body solution flows upward and enters the area between the first layer of microbial spheres of immobilized bacteria for TCE degradation and the second layer of microbial spheres of immobilized bacteria for toluene degradation, and is located downstream of the injection port, and an aqueous solution of sodium nitrate, the electron acceptor required for degrading toluene, is injected into the injection port, there are fewer free microorganisms in this area and the intensity of the microbial reaction is very small.

[0092] When the composite contaminated water body and the aqueous solution of sodium nitrate, the electron acceptor required for degrading toluene, flow upward and enter the second layer of microbial spheres of immobilized bacteria for toluene degradation, the microbial spheres of immobilized bacteria for toluene degradation use nitrate as the electron acceptor to carry out the toluene oxidation degradation reaction to degrade toluene.

[0093] When the composite contaminated water body and the aqueous solution of sodium nitrate, the electron acceptor required for degrading toluene, flow upward and enter the downstream of the second layer of microbial spheres of immobilized bacteria for toluene degradation, the free toluene-degrading bacteria continue to degrade the residual toluene in the water body.

[0094] To detect the remediation effect of the above remediation method on the organic composite contaminated water body of TCE and toluene, after all the volume of the organic composite contaminated water body is injected into the container, at the sampling port closest to the outlet on the side of the anaerobic glass column, 1 mL of samples are taken separately with a syringe and added to a headspace vial containing 5 mL of hydrochloric acid water. The headspace-gas chromatography method is used to detect the change in pollutant concentration to evaluate the ability of the constructed secondary enhanced microbial PRB system to reductively dechlorinate TCE and oxidatively degrade toluene. A headspace sampler of model HS-10 of Shimadzu brand of Japan and a gas chromatograph of model GC2010plus of Shimadzu brand of Japan are used for the above detection.

[0095] The pollutant concentrations monitored at the above sampling port are as follows: when continuously injecting the composite contaminated water body with a TCE concentration of 176.5 μmol / L and a toluene concentration of 145.8 μmol / L, after the action of the secondary enhanced microbial PRB system, the TCE concentration in the water body drops to 5.6 μmol / L, and the removal rate of the 95.3 μmol of TCE injected cumulatively is 96.8%; the toluene concentration in the water body drops to 4.2 μmol / L, and the removal rate of the 78.7 μmol of toluene injected cumulatively is 97.1%. This realizes the efficient synergistic remediation of the composite contamination of TCE and toluene in groundwater.

[0096] A comparative example is provided below, in which two types of pollutants and two kinds of immobilized bacterium agent microspheres are mixed together for degradation.

[0097] In an anaerobic serum bottle, add 12 TCE-degrading immobilized bacterium agent microspheres and 12 toluene-degrading immobilized bacterium agent microspheres, add a composite polluted water body with TCE at a concentration of 176.5 μmol / L and toluene at a concentration of 145.8 μmol / L, add a mixed electron donor solution required for degrading TCE at a concentration of 1 mmol / L, and add an aqueous solution of sodium nitrate as the electron acceptor required for degrading toluene at a concentration of 1 mmol / L, with a total of 60 mL. Among them, the molar ratio of methanol, ethanol, sodium formate, sodium acetate, and sodium lactate in the mixed electron donor required for degrading TCE is 4:2:12:3:2. A total of 10.6 μmol of TCE is added, and 8.7 μmol of toluene is added. The TCE-degrading immobilized bacterium agent microspheres and the toluene-degrading immobilized bacterium agent microspheres are prepared by steps 1 to 4 of the above-mentioned Example 1. On the 16th day after the solution is mixed, the headspace-gas chromatography method is used to detect the change in pollutant concentration to evaluate the ability to reductively dechlorinate TCE and oxidatively degrade toluene. A headspace sampler of model HS-10 of Shimadzu brand in Japan and a gas chromatograph of model GC2010plus of Shimadzu brand in Japan are used for the above detection. The detection results are as follows: the concentration of TCE in the water body is 155.3 μmol / L, and the degradation rate is only 12%, and the concentration of toluene is 134.1 μmol / L, and the degradation rate is only 8%. The degradation rate of pollutants in this comparative example is relatively low.

[0098] The above has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above specific embodiments, and the above specific embodiments and the descriptions in the specification are only for further explaining the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. An enhanced microbial remediation device for organic composite contaminated groundwater, wherein the organic composite contaminated groundwater contains chlorinated hydrocarbons and benzene series, characterized in that: The device comprises a hollow container (1), a base (2), a first syringe (3), a first injection pump (4), a second syringe (5), and a second injection pump (6); wherein: The container (1) is located on the base (2); the bottom end of the container (1) is a water inlet; the top end of the container (1) is an outlet; the bottom end of the container (1) is connected to the outlet of the first syringe (3) via a pipeline; the first syringe (3) is connected to the first injection pump (4); a medium layer (101), a chlorinated hydrocarbon degrading immobilized bacteria microbial sphere layer (102) and a benzene series degrading immobilized bacteria microbial sphere layer (103) are provided in the container (1); the chlorinated hydrocarbon degrading immobilized bacteria microbial sphere layer (102) and the benzene series degrading immobilized bacteria microbial sphere layer (103) are provided in the container (1); The microbial sphere layer (103) is embedded in the medium layer (101), and the microbial sphere layer (102) of the immobilized bacteria agent for degrading chlorinated hydrocarbons is located below the microbial sphere layer (103) of the immobilized bacteria agent for degrading benzene series substances; the thickness of the microbial sphere layer (102) of the immobilized bacteria agent for degrading chlorinated hydrocarbons is 2 to 4 cm, the thickness of the microbial sphere layer (103) of the immobilized bacteria agent for degrading benzene series substances is 2 to 4 cm, and the distance between the microbial sphere layer (102) of the immobilized bacteria agent for degrading chlorinated hydrocarbons and the microbial sphere layer (103) of the immobilized bacteria agent for degrading benzene series substances is 12 to 15 cm; The container (1) has an injection port on its side wall, the injection port being located between the chlorinated hydrocarbon-degrading immobilized bacterial agent microbial sphere layer (102) and the benzene-related substance-degrading immobilized bacterial agent microbial sphere layer (103), the injection port being connected to the outlet of the second syringe (5) via a pipeline, and the second syringe pump (6) being connected to the second syringe (5); Under the action of the first injection pump (4), the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be remediated flow into the water inlet of the container (1); under the action of the second injection pump (6), the electron acceptor solution for degrading benzene series flows into the injection port of the container (1); the water flows from bottom to top, and before it flows to the benzene series degrading immobilized bacterial agent microbial sphere layer (103), the chlorinated hydrocarbons in the water flow have been completely degraded, and the electron donors required for degrading the chlorinated hydrocarbons have been completely consumed; when the second-stage PRB filled with the benzene series degrading immobilized bacterial agent microbial sphere layer (103) degrades the benzene series in the water flow, the adverse effects of the chlorinated hydrocarbons and the electron donors required for degrading the chlorinated hydrocarbons are eliminated.

2. The enhanced microbial remediation device according to claim 1, characterized in that: The medium layer (101) is a quartz sand layer, and the medium layer (101) fills the container (1).

3. The enhanced microbial remediation device according to claim 1, characterized in that: The container (1) is an anaerobic glass column, the pipeline is a polytetrafluoroethylene tube, and the side wall of the container (1) is provided with sampling ports at different heights.

4. The enhanced microbial remediation device according to claim 1, characterized in that: The outlet of the container (1) is connected to a sealed tank (7) containing activated carbon.

5. A method for remediating organic compound contaminated groundwater using the enhanced microbial remediation device according to claim 1, characterized in that: The method comprises: Step 1, enriching and culturing the degradation bacterial solution: Collecting the organic compound contaminated groundwater and soil samples to be remediated, and enriching and culturing them to obtain the enriched bacterial solution for degrading chlorinated hydrocarbons and the enriched bacterial solution for degrading benzene series through microcosm experiments; Step 2: According to the enriched bacterial solution for degrading chlorinated hydrocarbons and the enriched bacterial solution for degrading benzene series obtained by enrichment culture in step 1, the types of functional bacteria for degrading chlorinated hydrocarbons and the types of functional bacteria for degrading benzene series in the enriched bacterial solution for degrading chlorinated hydrocarbons are identified; Step 3, according to the types of degrading functional bacteria in the enriched bacterial solution for degrading chlorinated hydrocarbons identified in step 2, using an anaerobic microbial fermentation tank to ferment and obtain a chlorinated hydrocarbon degrading bacterial solution; According to the degrading functional bacteria species in the enriched bacterial solution for degrading BTEX identified in step 2, using an anaerobic microbial fermentation tank to ferment to obtain a BTEX-degrading bacterial solution; Step 4, using the chlorinated hydrocarbon-degrading bacterial solution and the benzene-related substance-degrading bacterial solution obtained by fermentation in step 3 to prepare chlorinated hydrocarbon-degrading immobilized bacterial agent microbial pellets and benzene-related substance-degrading immobilized bacterial agent microbial pellets, respectively; Step 5, placing the chlorinated hydrocarbon degradation immobilized bacteria agent microbial pellets and the benzene series degradation immobilized bacteria agent microbial pellets prepared in step 4 into a container to assemble an enhanced microbial remediation device; Step 6: The electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be remediated are loaded into the first syringe (3); under the action of the first injection pump (4), the electron donor solution for degrading chlorinated hydrocarbons and the organic composite contaminated groundwater to be remediated flow into the water inlet of the container (1) and flow from bottom to top in the container (1); The electron acceptor solution for degrading benzene series is loaded into the second syringe (5), and under the action of the second injection pump (6), the electron acceptor solution for degrading benzene series flows into the injection port of the container (1) and flows upward in the container (1).

6. The repair method according to claim 5, characterized in that: The step 4 specifically includes: Step 401, centrifuging the chlorinated hydrocarbon-degrading bacterial solution and the benzene-degrading bacterial solution obtained by fermentation in step 3 using a centrifuge, collecting the bacterial cells at the bottom respectively, to obtain chlorinated hydrocarbon-degrading bacterial cells and benzene-degrading bacterial cells; Step 402, preparing a bacterial suspension: resuspending the chlorinated hydrocarbon-degrading bacterial cells and the benzene-degrading bacterial cells obtained in step 401 in an embedding agent aqueous solution to obtain a chlorinated hydrocarbon-degrading bacterial suspension and a benzene-degrading bacterial suspension that are concentrated 100 times, respectively; Step 403, immobilization treatment: dripping the chlorinated hydrocarbon degrading bacteria suspension prepared in step 402 into the cross-linking agent aqueous solution drop by drop with a pipette, and allowing the embedding agent and the cross-linking agent to fully react under the regulation of ice bath and magnetic stirring to form chlorinated hydrocarbon degrading immobilized bacteria agent microbial balls; dripping the benzene series degrading bacteria suspension prepared in step 402 into the cross-linking agent aqueous solution drop by drop with a pipette, and allowing the embedding agent and the cross-linking agent to fully react under the regulation of ice bath and magnetic stirring to form benzene series degrading immobilized bacteria agent microbial balls; Step 404, respectively remove the cross-linking agent remaining after the reaction, wash the chlorinated hydrocarbon-degrading immobilized bacteria agent microbial pellets and the benzene-degrading immobilized bacteria agent microbial pellets with sterilized and deoxygenated physiological saline, and then store them in a refrigerator for later use.

7. The repair method according to claim 5, characterized in that: The step 5 specifically includes: Step 501, sterilizing and deoxygenating the container (1), the pipeline, the first syringe (3) and the second syringe (5), and rinsing them with anaerobic culture medium until the anaerobic culture medium after rinsing is colorless; Step 502: Mount the container (1) on the base (2), install a filter screen at the water inlet at the bottom of the container (1), and perform sealing treatment; connect the outlet of the first syringe (3) and the water inlet of the container (1) with a pipe; and connect the outlet of the second syringe (5) and the injection port of the container (1) with a pipe; Step 503, filling the container (1) with quartz sand, microbial pellets of immobilized bacteria agent for degradation of chlorinated hydrocarbons, and microbial pellets of immobilized bacteria agent for degradation of benzene series; Step 504: Install a filter screen on the top of the container (1), and then seal it.

8. The repair method according to claim 7, characterized in that: The step 503 comprises: firstly adding an anaerobic culture medium to the container (1), and then adding deoxygenated quartz sand, wherein the water level of the anaerobic culture medium is always higher than that of the quartz sand; then, after adding the anaerobic culture medium and quartz sand in sequence to a first preset position, adding microbial balls of immobilized bacteria for chlorinated hydrocarbon degradation to form a microbial ball layer (102) of immobilized bacteria for chlorinated hydrocarbon degradation; then, adding the anaerobic culture medium and quartz sand in sequence, wherein the water level of the anaerobic culture medium is always higher than that of the quartz sand, and after adding the anaerobic culture medium to a second preset position, adding microbial balls of immobilized bacteria for BTEX degradation to form a microbial ball layer (103) of immobilized bacteria for BTEX degradation; and finally, adding the anaerobic culture medium and quartz sand in sequence, wherein the water level of the anaerobic culture medium is always higher than that of the quartz sand, until the quartz sand is filled to the top of the container (1).

9. The repair method according to claim 5, characterized in that: In step 6, the volume of the solution injected into the container (1) from the first syringe (3) is 3 times the volume of the pore water of the quartz sand after filling.

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