Microbial enhanced vapor extraction remediation method for contaminated soil

Abstract

The invention belongs to the technical field of soil and groundwater pollution remediation, and discloses a microbial enhanced vapor extraction remediation method for contaminated soil, which comprises the following steps: (1) injecting geobacillus stearothermophilus bacterial liquid into a soil contaminated area in situ; and (2) continuously extracting the waste gas from the soil polluted area, then purifying the extracted waste gas through catalytic combustion, and reinjecting the waste gas into the soil polluted area in situ. According to the contaminated soil remediation method, the extraction efficiency of organic pollutants can be remarkably improved and the discharge amount of waste gas can be greatly reduced by utilizing the heat and the air stripping effect of the reinjected waste gas; and the treatment efficiency is further improved by utilizing the enhanced migration effect and degradation effect of geobacillus stearothermophilus on organic pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of soil and groundwater pollution remediation, and more specifically, to a microbial enhanced gas phase extraction remediation method for contaminated soil. Background Art

[0002] Organic pollutants in the soil are mainly volatile organic pollutants and semi-volatile organic pollutants, including petroleum hydrocarbons, halogenated hydrocarbons, pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, phthalates, etc. Most of them are carcinogenic, teratogenic and mutagenic, and are easily accumulated in the environment, causing long-term impacts on the ecological environment and human health. At present, the commonly used methods for remediation of organic pollution in soil mainly include gas phase extraction, thermal desorption, chemical oxidation, microbial remediation, etc. In recent years, some patents have provided methods for treating organic pollution sites by combining gas phase extraction with microbial remediation, which has improved the removal effect of soil organic pollutants to a certain extent.

[0003] CN114956449A provides an automated intelligent device for multiphase extraction and microbial remediation of organically contaminated groundwater, including a multiphase extraction module, a remediation well module and a microbial remediation module. A gas sensor is provided at the output end of the tail gas treatment device. A monitoring sensor is provided in the remediation well. Both the multiphase extraction module and the microbial remediation module are connected to a remote time-controlled switch. The device realizes the combination of extraction and injection through the cooperation between modules, which enhances the extraction effect while improving the degree of automation and intelligence.

[0004] CN217798058U provides an in-situ remediation device for removing semi-volatile pollutants by gas phase extraction microbial degradation, including a gas phase extraction well group, an extraction unit and an aeration unit. The technical solution combines gas phase extraction technology with microbial degradation technology to strengthen the degradation effect of indigenous microorganisms, thereby significantly improving the removal rate of semi-volatile organic pollutants in the soil.

[0005] CN108273836A discloses a soil and groundwater in-situ remediation system combining microorganisms and gas phase extraction, including a nutrient storage tank, a microbial fermentation tank, a gas phase extraction system and a solar panel. The remediation system of the invention combines the advantages of microbial remediation and gas phase extraction remediation, and uses solar energy as a heat source to adjust the temperature of soil and groundwater, thereby improving the remediation efficiency. In addition, based on in-situ remediation, the diffusion of pollutants is avoided and secondary pollution is not generated.

[0006] In summary, the existing technology is basically a simple combination of gas phase extraction and microbial remediation. There are certain improvements in device intelligence and energy saving, but the remediation effect of microorganisms is relatively limited. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of low efficiency in the treatment of volatile and / or semi-volatile organic contaminated sites and insufficient microbial remediation in the prior art, and to provide a microbial enhanced gas phase extraction and remediation method for contaminated soil. The method of the present invention is used to extract volatile organic matter from soil, which can not only utilize the heat of exhaust gas combustion and the enhancement of organic pollutant migration by thermophilic microorganisms to greatly improve the extraction efficiency and degradation efficiency of organic pollutants, but also can introduce carbon dioxide-rich gas into the ground, thereby playing a role in energy saving and carbon reduction.

[0008] In order to achieve the above object, the present invention provides a microbial enhanced gas phase extraction remediation method for contaminated soil, the remediation method comprising:

[0009] (1) In situ injection of Geobacillus stearothermophilus bacterial solution into the soil contaminated area;

[0010] (2) Continuously extracting waste gas from the soil contaminated area, and then injecting the extracted waste gas back into the soil contaminated area in situ after catalytic combustion and purification.

[0011] The technical solution of the present invention has the following beneficial effects:

[0012] The contaminated soil remediation method of the present invention utilizes the heat and stripping effect of the reinjected waste gas to significantly improve the extraction efficiency of organic pollutants and greatly reduce the emission of waste gas; and utilizes the enhanced migration and degradation effect of thermophilic Bacillus on organic pollutants to further improve the treatment efficiency.

[0013] The contaminated soil remediation method of the present invention has the characteristics of energy saving, carbon reduction and high efficiency, and has good application prospects in contaminated soil treatment.

[0014] The contaminated soil remediation method of the present invention can be used for the remediation of soil or groundwater contaminated by volatile and / or semi-volatile organic substances, and has good application prospects in the green and sustainable remediation of related contaminated sites.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0017] Figure 1 A schematic diagram of an apparatus for a microbial enhanced gas phase extraction remediation method for contaminated soil according to an embodiment of the present invention is shown.

[0018] Description of reference numerals:

[0019] 1. Extraction well; 2. Gas-water separator; 3. Extraction fan; 4. Catalytic burner; 5. Induced draft fan; 6. Injection well; 7. Discharge pipeline DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] The present invention provides a microbial enhanced gas phase extraction remediation method for contaminated soil, the remediation method comprising:

[0022] (1) In situ injection of Geobacillus stearothermophilus bacterial solution into the soil contaminated area;

[0023] (2) Continuously extracting waste gas from the soil contaminated area, and then injecting the extracted waste gas back into the soil contaminated area in situ after catalytic combustion and purification.

[0024] According to the present invention, preferably, the bacterial solution of Geobacillus stearothermophilus comprises Geobacillus stearothermophilus, a nutrient composition and water;

[0025] Preferably, the concentration of the thermophilic Bacillus in the thermophilic Bacillus bacterial solution is 10 8 -10 10 cfu / mL; in terms of solid content, the concentration of the nutrient composition in the thermophilic Bacillus stearothermophilus bacterial liquid is 10-30 g / L.

[0026] According to the present invention, preferably, the nutritional composition comprises yeast powder and polypeptone;

[0027] The mass ratio of the yeast powder to the polypeptone is (0.4-1):1.

[0028] The Geobacillus stearothermophilus used in the present invention can be purchased from China General Microorganism Culture Collection Center with a number of CGMCC 1.16087, or China Industrial Microorganism Culture Collection Center with a number of CICC 10392; the Latin name of Geobacillus stearothermophilus is Geobacillus stearothermophilus, and its Chinese translation is Geobacillus stearothermophilus.

[0029] According to the present invention, preferably, the extracted exhaust gas is first dried before being purified by catalytic combustion;

[0030] Preferably, the drying process is performed by a gas-water separator.

[0031] According to the present invention, preferably, the stripping exhaust gas is subjected to the catalytic combustion purification by a catalytic burner.

[0032] In the present invention, the catalytic burner is a conventional device in the art, which can realize combustion treatment of the incoming gas under the action of a catalyst, and the heat generated by the combustion can preheat the incoming gas.

[0033] According to the present invention, preferably, the operation of step (2) is performed for 6-18 hours per day, and the number of operating days is at least 0.5 months.

[0034] According to the present invention, preferably, in step (2), the temperature of the soil contaminated area after in-situ reinjection is controlled to be 50-80°C.

[0035] In the present invention, the temperature of the soil contaminated area is controlled by controlling the temperature of the injected gas after catalytic combustion, so that the temperature is controlled at 50-80°C, which helps to enhance the migration of organic pollutants by thermophilic microorganisms and greatly improves the extraction efficiency and degradation efficiency of organic pollutants.

[0036] According to the present invention, preferably, the soil contaminated area is provided with extraction wells and injection wells;

[0037] Preferably, the bacterial solution of Geobacillus stearothermophilus is injected in situ into the soil contaminated area through the extraction well and the injection well;

[0038] The purified gas is preferably injected back into the soil contaminated area through the injection well.

[0039] According to the present invention, preferably, the concentration of non-methane total hydrocarbons in the extracted exhaust gas is less than 5000 mg / Nm 3 .

[0040] According to the present invention, preferably, the contaminated soil is soil contaminated by volatile organic compounds and / or semi-volatile organic compounds.

[0041] The present invention is further described below by examples:

[0042] The Bacillus stearothermophilus bacterial solution used in the following examples includes: Bacillus stearothermophilus, a nutrient composition and water. The nutrient composition used includes yeast powder and polypeptone.

[0043] The Geobacillus stearothermophilus used were from China General Microbiological Culture Collection Center (with the collection number of CGMCC 1.16087) and China Industrial Microbiological Culture Collection Center (with the collection number of CICC10392).

[0044] Yeast powder was purchased from Beijing Inokai Technology Co., Ltd.

[0045] Polypeptone was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0046] In the following embodiments, the method for detecting the concentration of total non-methane hydrocarbons in the gas is based on the "Gas Chromatography Method for Determination of Total Hydrocarbons, Methane and Non-methane Hydrocarbons in Waste Gas from Stationary Sources" (HJ 38-2017).

[0047] The detection method of petroleum hydrocarbon content in contaminated soil is based on the Petroleum Hydrocarbons in Soil and Sediment (C 10 -C 40 )Determination of 2-Hydrogen-2-nitrogen by Gas Chromatography (HJ 1021-2019).

[0048] The detection method for the volatile organic compound content in contaminated soil refers to the "Determination of Volatile Organic Compounds in Soil and Sediment by Purge and Trap / Gas Chromatography-Mass Spectrometry" (HJ 605-2011).

[0049] Example 1

[0050] The microbial enhanced gas phase extraction remediation method for contaminated soil of the present invention was used to remediate the underground 1-3 m soil seriously contaminated by isoprene, n-pentane, benzene, etc. at a chemical site in Tianjin.

[0051] like Figure 1 As shown, (1) a bacterial solution of Geobacillus stearothermophilus and a nutrient solution containing Geobacillus stearothermophilus and a nutrient solution is injected into the soil through an extraction well 1 and an injection well 6 (wherein the Geobacillus stearothermophilus is deposited with a number of CGMCC 1.16087 and a bacterial concentration of 1.3×10 8 cfu / mL, yeast powder concentration (in terms of solid content) is 3g / L, polypeptone concentration (in terms of solid content) is 7.5g / L); (2) turn on the catalytic burner 4 to preheat the system to 260°C; start the extraction fan 3 to extract volatile and / or semi-volatile organic matter in the soil, and the exhaust gas is extracted from the extraction well 1. The concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 1500mg / Nm 3 ; The trace amount of water in the extracted waste gas is removed by the gas-water separator 2; the waste gas then enters the catalytic burner 4, where the organic matter in the waste gas is burned to generate carbon dioxide, wherein the catalyst bed is heated to 380°C; the concentration of non-methane total hydrocarbons in the gas at the outlet of the catalytic burner 4 is reduced to 50mg / Nm 3 The temperature is about 180°C; the high-temperature gas discharged from the catalytic burner 4 is directly introduced into the underground soil contaminated area through the induced draft fan 5 and the injection well 6, and the concentration of non-methane total hydrocarbons in the extracted waste gas rises to about 3200 mg / Nm 3The contaminated soil temperature rises to 60-80℃; the extraction fan 3, catalytic burner 4 and induced draft fan 5 are operated for 6 hours, and the concentration of non-methane total hydrocarbons at the outlet of catalytic burner 4 is always maintained at 50mg / Nm 3 the following.

[0052] The above step (2) was performed once a day for 20 days, during which the isoprene, n-pentane and benzene contents in the soil dropped from approximately 580 mg / kg, 730 mg / kg and 200 mg / kg to below 0.9 mg / kg, respectively.

[0053] During the same period, a control test was conducted. The difference between this control test method and the above-mentioned repair method is only that the above-mentioned thermophilic Bacillus stearothermophilus bacterial solution is not injected and the combustion purification exhaust gas is not reinjected (that is, the high-temperature gas discharged from the above-mentioned catalytic burner 4 is not reinjected), and the rest is the same as the above-mentioned repair method; that is, only the above-mentioned gas phase extraction, gas-water separation and combustion purification process steps are performed (in this control test method, the combustion purified exhaust gas is passed through Figure 1 After 20 days of repair, the contents of isoprene, n-pentane and benzene in the soil decreased from about 580 mg / kg, 730 mg / kg and 200 mg / kg to 15 mg / kg, 17 mg / kg and 5 mg / kg, respectively.

[0054] Example 2

[0055] The microbial enhanced gas phase extraction remediation method of contaminated soil of the present invention was used to treat a chemical site in Beijing that was contaminated by benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) and other severely contaminated underground soil 2-5m to be repaired.

[0056] like Figure 1 As shown, (1) a bacterial solution of Geobacillus stearothermophilus and a nutrient solution containing Geobacillus stearothermophilus and a nutrient solution is injected into the soil through an extraction well 1 and an injection well 6 (wherein the Geobacillus stearothermophilus is deposited with a number of CGMCC 1.16087 and a bacterial concentration of 2.6×10 9 cfu / mL, yeast powder concentration (in terms of solid content) is 8 g / L, and polypeptone concentration (in terms of solid content) is 12 g / L); (2) the catalytic burner 4 is turned on to preheat the system to 300°C; the extraction fan 3 is turned on to extract volatile and / or semi-volatile organic matter in the soil, and the exhaust gas is extracted from the extraction well 1. The total non-methane hydrocarbon concentration of the extracted exhaust gas is about 800 mg / Nm 3 ; The trace amount of water in the extracted waste gas is removed by the gas-water separator 2; the waste gas then enters the catalytic burner 4, where the organic matter in the waste gas is burned to generate carbon dioxide, wherein the catalyst bed is heated to 420°C; the concentration of non-methane total hydrocarbons in the gas at the outlet of the catalytic burner 4 is reduced to 50mg / Nm 3The temperature is about 180°C; the high-temperature gas discharged from the catalytic burner 4 is directly introduced into the underground soil contaminated area through the induced draft fan 5 and the injection well 6, and the concentration of non-methane total hydrocarbons in the extracted waste gas rises to about 2500 mg / Nm 3 The contaminated soil temperature rises to 55-70°C; the extraction fan 3, catalytic burner 4 and induced draft fan 5 are operated for 8 hours, and the concentration of non-methane total hydrocarbons at the outlet of catalytic burner 4 is always maintained at 50mg / Nm 3 the following.

[0057] The above step (2) was repeated once a day for 30 days. The soil benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) content decreased from about 1280mg / kg, 3360mg / kg, 1530mg / kg and 4300mg / kg to 3mg / kg, 30mg / kg, 20mg / kg and 420mg / kg respectively.

[0058] During the same period, a control test was conducted. The difference between this control test method and the above-mentioned repair method is only that the above-mentioned thermophilic Bacillus stearothermophilus bacterial solution is not injected and the combustion purification exhaust gas is not reinjected (that is, the high-temperature gas discharged from the above-mentioned catalytic burner 4 is not reinjected), and the rest is the same as the above-mentioned repair method; that is, only the above-mentioned gas phase extraction, gas-water separation and combustion purification process steps are performed (in this control test method, the combustion purified exhaust gas is passed through Figure 1 7 discharge pipe in the middle), 30 days after repair, soil benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) content decreased from about 1280mg / kg, 3360mg / kg, 1530mg / kg and 4300mg / kg to about 50mg / kg, 1320mg / kg, 350mg / kg and 2540mg / kg respectively.

[0059] Example 3

[0060] The microbial enhanced gas phase extraction remediation method of contaminated soil of the present invention was used to treat a chemical site in Beijing that was contaminated by benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) and other severely contaminated underground soil 2-5m to be repaired.

[0061] like Figure 1 As shown, (1) a bacterial solution of Geobacillus stearothermophilus and a nutrient solution containing Geobacillus stearothermophilus and a nutrient solution is injected into the soil through an extraction well 1 and an injection well 6 (wherein the Geobacillus stearothermophilus is deposited with a number of CICC 10392 and a bacterial concentration of 9.2×10 9cfu / mL, yeast powder concentration (in terms of solid content) is 15 g / L, polypeptone concentration (in terms of solid content) is 15 g / L); (2) turn on the catalytic burner 4 to preheat the system to 300°C; start the extraction fan 3 to extract volatile and / or semi-volatile organic matter in the soil, and the exhaust gas is extracted from the extraction well 1. The concentration of non-methane total hydrocarbons in the extracted exhaust gas is about 800 mg / Nm 3 ; The trace amount of water in the extracted waste gas is removed by the gas-water separator 2; the waste gas then enters the catalytic burner 4, where the organic matter in the waste gas is burned to generate carbon dioxide, wherein the catalyst bed is heated to 420°C; the concentration of non-methane total hydrocarbons in the gas at the outlet of the catalytic burner 4 is reduced to 50mg / Nm 3 The temperature is about 180°C; the high-temperature gas discharged from the catalytic burner 4 is directly introduced into the underground soil contaminated area through the induced draft fan 5 and the injection well 6, and the concentration of non-methane total hydrocarbons in the extracted waste gas rises to about 2500 mg / Nm 3 The contaminated soil temperature rises to 55-70°C; the extraction fan 3, catalytic burner 4 and induced draft fan 5 are operated for 8 hours, and the concentration of non-methane total hydrocarbons at the outlet of catalytic burner 4 is always maintained at 50mg / Nm 3 the following.

[0062] The above step (2) was repeated once a day for 15 days. The soil benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) content decreased from about 1280 mg / kg, 3360 mg / kg, 1530 mg / kg and 4300 mg / kg to 0.5 mg / kg, 12 mg / kg, 8 mg / kg and 180 mg / kg respectively.

[0063] During the same period, a control test was conducted. The difference between this control test method and the above-mentioned repair method is only that the above-mentioned thermophilic Bacillus stearothermophilus bacterial solution is not injected and the combustion purification exhaust gas is not reinjected (that is, the high-temperature gas discharged from the above-mentioned catalytic burner 4 is not reinjected), and the rest is the same as the above-mentioned repair method; that is, only the above-mentioned gas phase extraction, gas-water separation and combustion purification process steps are performed (in this control test method, the combustion purified exhaust gas is passed through Figure 1 Discharge pipe 7 in the middle), 15 days after repair, soil benzene, toluene, ethylbenzene, petroleum hydrocarbons (C 10 -C 40 ) content decreased from about 1280 mg / kg, 3360 mg / kg, 1530 mg / kg and 4300 mg / kg to 120 mg / kg, 1980 mg / kg, 830 mg / kg and 3850 mg / kg respectively.

[0064] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for remediation of contaminated soil by microbial enhanced gas phase extraction, characterized in that: The fix includes: (1) In situ injection of Geobacillus stearothermophilus bacterial solution into the soil contaminated area; (2) Continuously extracting waste gas from the soil contaminated area, and then injecting the extracted waste gas back into the soil contaminated area in situ after catalytic combustion and purification.

2. The repair method according to claim 1, wherein: The Geobacillus stearothermophilus bacterial liquid comprises Geobacillus stearothermophilus, a nutrient composition and water; Preferably, the concentration of the thermophilic Bacillus in the thermophilic Bacillus bacterial solution is 10 8 -10 10 cfu / mL; in terms of solid content, the concentration of the nutrient composition in the thermophilic Bacillus stearothermophilus bacterial liquid is 10-30 g / L.

3. The repair method according to claim 2, wherein: The nutritional composition comprises yeast powder and polypeptone; The mass ratio of the yeast powder to the polypeptone is (0.4-1):

1.

4. The repair method according to claim 1, wherein: The extracted waste gas is first dried before being purified by catalytic combustion; Preferably, the drying process is performed by a gas-water separator.

5. The repair method according to claim 1, wherein: The catalytic combustion purification is performed on the extracted exhaust gas through a catalytic burner.

6. The repair method according to claim 1, wherein: The operation of step (2) is performed for 6-18 hours per day, and the number of operating days is at least 0.5 months.

7. The repair method according to claim 1, wherein: In step (2), the temperature of the soil contaminated area after in-situ reinjection is controlled to be 50-80°C.

8. The repair method according to claim 1, wherein: The soil contaminated area is provided with extraction wells and injection wells; Preferably, the bacterial solution of Geobacillus stearothermophilus is injected in situ into the soil contaminated area through the extraction well and the injection well; The purified gas is preferably injected back into the soil contaminated area through the injection well.

9. The repair method according to claim 1, wherein: The concentration of non-methane total hydrocarbons in the extracted exhaust gas is less than 5000 mg / Nm 3 .

10. The repair method according to claim 1, wherein: The contaminated soil is soil contaminated by volatile organic matter and / or semi-volatile organic matter.

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