In-situ anaerobic microorganism remediation method for deep petroleum hydrocarbon contaminated soil

Abstract

The invention discloses an in-situ anaerobic microorganism remediation method for deep petroleum hydrocarbon contaminated soil. The method comprises the following steps: 1, investigating petroleum hydrocarbon pollution in deep soil on site; step 2, preparing an anaerobic biological stimulant; step 3, preparing a microbial nutrient; step 4, preparing a biosurfactant; and step 5, activating indigenous microorganism degrading flora: adding the anaerobic biological stimulant in the step 2 into the polluted soil according to 1-3% of the total weight of the soil, and then adjusting the water content of the soil to 15%. After the anaerobic biological stimulant is uniformly mixed with the soil through full turning and stirring, the soil is not turned and stirred in the whole treatment process, and standing is performed for one week in the natural environment to activate indigenous microorganisms for anaerobically degrading petroleum hydrocarbon in the soil; 6, anaerobic microorganism in-situ remediation; and 7, soil property evaluation after remediation. The method has the characteristics of low economic cost, short remediation period, small secondary pollution, no need of plowing a large amount of soil, and good microbial remediation effect.

Description

Technical Field

[0001] The invention relates to the technical field of in-situ anaerobic microbial restoration of soil, and in particular to an in-situ anaerobic microbial restoration method for deep petroleum hydrocarbon-contaminated soil. Background Art

[0002] Soil is an important natural resource on which human beings depend for survival. However, with the continuous deepening of the development of my country's petroleum industry, soil pollution caused by petroleum hydrocarbon leakage during oil extraction, well repair, fracturing and other operations has become increasingly serious. Its toxicity and harmfulness have seriously threatened environmental safety and directly affected human health and economic and social development.

[0003] Currently, various methods such as physical, chemical and biological methods have been used to repair soil contaminated by petroleum hydrocarbons. However, physical and chemical repairs have high economic costs and are prone to secondary pollution, resulting in damage to soil properties. The duration of plant repair in biological repair is usually measured in years, which is a long cycle and cannot meet the actual needs of rapid repair of soil contaminated by petroleum hydrocarbons.

[0004] Aerobic microbial remediation in bioremediation has the advantages of low economic cost, high efficiency, and low secondary pollution. However, petroleum hydrocarbons have low density, strong adhesion, and low emulsification ability. They are easy to adhere to soil particles and block soil pores. Aerobic microbial remediation requires frequent soil turning to obtain sufficient air, especially when facing deep petroleum hydrocarbon contaminated soil. The workload is large and the remediation effect will be significantly affected. Summary of the invention

[0005] In order to overcome the above technical problems, the purpose of the present invention is to provide an in situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil, which has the characteristics of low economic cost, short remediation cycle, small secondary pollution, no need for large-scale soil tillage operations and good microbial remediation effect.

[0006] The technical solution adopted by the present invention is:

[0007] An in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil comprises the following steps;

[0008] Step 1: Conduct on-site investigation of petroleum hydrocarbon contamination in deep soil. Soil samples for on-site investigation should be taken from soil layers 1m or deeper from the surface.

[0009] Step 2: Preparation of anaerobic biostimulants: Determine the type and method of use of anaerobic biostimulants based on the investigation results of step 1;

[0010] Step 3: Preparation of microbial nutrients: According to the investigation results of step 1, determine the proportion of microbial nutrients, which include constant inorganic salt solution, trace element solution and vitamin mixture;

[0011] Step 4: Preparation of biosurfactant: According to the investigation in step 1, determine the ratio of biosurfactant;

[0012] Step 5: Activation of indigenous microbial degradation flora: Add the anaerobic biostimulant in step 2 to the contaminated soil at 1-3% of the total weight of the soil, adjust the soil moisture content to 15%, stir the soil thoroughly to make the anaerobic biostimulant and the soil evenly mixed, and then stir the soil again during the entire treatment process. Let it stand in a natural environment for one week to activate the indigenous microorganisms in the soil that anaerobically degrade petroleum hydrocarbons;

[0013] Step 6: Anaerobic microbial in-situ remediation: After the indigenous microbial degradation flora is activated, the microbial nutrient agent in step 3 and the biological surfactant in step 4 are mixed in a ratio of 1-2:1 to form a composite nutrient solution, and a portion is evenly sprayed on the surface of the contaminated soil. The concentration of the composite nutrient solution is monitored and appropriately supplemented every 15 days thereafter; when the content of petroleum hydrocarbons in the contaminated soil is reduced to less than 1% of the total weight of the soil, the monitoring and supplementation of the composite nutrient solution concentration is changed to once every 30 days, and the supplementation method is still uniformly spraying on the surface of the contaminated soil. The contaminated soil samples used for monitoring should be taken from the remediation area, with a depth of 1m or more from the surface soil;

[0014] Step 7: Evaluation of soil properties after restoration.

[0015] In step 1, the petroleum hydrocarbon pollution conditions include the total petroleum hydrocarbon content, total organic carbon content, major ion content, soil pH value, pollution depth, and pollution range in the soil.

[0016] In step 2, the preparation method of the anaerobic biostimulant is as follows:

[0017] Strengthening the electron acceptor of the anaerobic oxidation process of microorganisms: preparing an electron acceptor solution with a concentration of 1 mol / L, which can continuously provide the necessary electron acceptors for the anaerobic oxidation process of microorganisms;

[0018] Preferably, the electron acceptor is NaNO 3 、Na 2 SO 4 At least one of .

[0019] In step 3, the preparation method of different nutrients in the microbial nutrient is as follows:

[0020] The composition and concentration of each component of the constant inorganic salt solution: 10g / L NaCl, 5g / LMgCl 2 6H 2 O, 20g / LKH 2 PO 4 、40g / L NH 4Cl, 30g / L KCl, 0.5g / L CaCl 2 ·2H 2 O; This solution provides conventional nutrients and inorganic salts for indigenous microorganisms, ensuring their normal growth and reproduction;

[0021] The composition and concentration of trace element solution: 10mL / L 25% HCl, 1.5g / L FeCl 2 ·4H 2 O, 0.19 g / L CoCl 2 6H 2 O, 0.1g / LMnCl 2 ·4H 2 O, 70mg / LZnCl 2 , 6mg / LH 3 BO 3 、36mg / L Na 2 MoO 4 ·2H 2 O, 24mg / LNiCl 2 6H 2 O, 2mg / LCuCl 2 ·2H 2 O, 6mg / L Na 2 SeO 3 ·5H 2 O, 8mg / L Na 2 WO 4 ·2H 2 O, 0.5 g / L NaOH;

[0022] The solution can enhance the reproduction capacity of microorganisms and increase the activity of cells and enzymes in biological processes related to petroleum hydrocarbon metabolism;

[0023] Composition and concentration of vitamin mixture: 2mg / L folic acid, 10mg\L pyridoxine hydrochloride, 5mg / L vitamin B 2 , 2mg / L vitamin H, 5mg / L niacin, 5mg / L vitamin B 1 , 5mg / L calcium pantothenate, 0.1mg / L vitamin B 12 , 5mg / L p-aminobenzoic acid, 5mg / L lipoic acid, 900mg / L K 2 HPO 4 Vitamins participate in different biochemical reactions in indigenous microorganisms, regulate microbial metabolic functions, and enhance microbial activity.

[0024] Mix the constant inorganic salt solution, trace element solution and vitamin mixture in a ratio of 5-10:1:1 to prepare a microbial nutrient for use.

[0025] In step 4, the biosurfactant preparation method is as follows:

[0026] The composition of the biosurfactant is 5-10g / L rhamnolipid (obtained by microbial fermentation and extraction), which is used to increase the contact area between petroleum hydrocarbons and microorganisms and enhance the ability of microorganisms to chemotaxis and absorb petroleum hydrocarbons.

[0027] Beneficial effects of the present invention:

[0028] (1) This remediation method applies NO to the indigenous microorganisms in the contaminated soil. 3 - or SO 4 2- As a biological stimulus, it can enhance the denitrification or sulfate reduction in the metabolic process of indigenous microorganisms, thereby enhancing the ability of indigenous microorganisms to anaerobicly oxidize and degrade petroleum hydrocarbons, thereby increasing the degradation rate of petroleum hydrocarbons in deep contaminated soils and shortening the remediation cycle.

[0029] (2) This remediation method maintains the growth and metabolic activity of indigenous microorganisms at a high level by applying constant inorganic salt solutions, trace element solutions, vitamin mixtures, etc. to the contaminated soil, ensuring that this method can be directly applied to the remediation of soil contaminated with high concentrations of petroleum hydrocarbons. At the same time, this method has a high degree of automation and can ensure the efficient remediation of deep petroleum hydrocarbon contaminated soil without the need for large-scale tillage operations. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for in-situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil, comprising the following steps:

[0033] Step 1. Conduct on-site investigation of petroleum hydrocarbon pollution in deep soil, where the total petroleum hydrocarbon content is about 50,000 mg / kg soil, the total organic carbon content is about 70,000 mg / kg soil, the total nitrogen content of major soil ions is about 1,100 mg / kg soil, the total phosphorus content is about 500 mg / kg soil, the total salt content is about 2,600 mg / kg soil, the soil pH is 7.8, the pollution depth exceeds 1m, and the soil in all remediation areas is contaminated by petroleum hydrocarbons to the same extent.

[0034] Step 2. Preparation of anaerobic biostimulants: Determine the type and method of use of anaerobic biostimulants based on the investigation results of step 1. The preparation method of anaerobic biostimulants is as follows:

[0035] Electron acceptor for enhancing microbial anaerobic oxidation: Prepare NaNO at a concentration of 1 mol / L 3 Solution.

[0036] Step 3. Preparation of microbial nutrients: prepare constant inorganic salt solution, trace element solution, and vitamin mixture solution respectively according to the method. According to the investigation results of step 1, the proportion of microbial nutrients is determined as follows:

[0037] Mix the constant inorganic salt solution, trace element solution and vitamin mixture in a ratio of 10:1:1 to prepare a microbial nutrient for use.

[0038] Step 4. Preparation of biosurfactant: Based on the investigation in step 1, prepare 10 g / L rhamnolipid as a biosurfactant.

[0039] Step 5. Activation of indigenous microbial degradation flora: Add the anaerobic biostimulant in step 2 to the contaminated soil at 3% of the total weight of the soil, adjust the soil moisture content to 15%, stir the soil thoroughly to make the anaerobic biostimulant and the soil evenly mixed, and do not stir the soil during the entire treatment process. Leave it in a natural environment for one week to activate the indigenous microorganisms in the soil that anaerobically degrade petroleum hydrocarbons.

[0040] Step 6. Anaerobic microbial in-situ remediation: After the activation of the indigenous microbial degradation flora, the microbial nutrient agent in step 3 and the biological surfactant in step 4 are mixed in a ratio of 2:1 to form a composite nutrient solution, which is evenly sprayed on the surface of the contaminated soil, and the concentration of the composite nutrient solution is monitored and appropriately supplemented every 15 days thereafter; when the content of petroleum hydrocarbons in the contaminated soil is reduced to less than 1% of the total weight of the soil, the monitoring and supplementation of the composite nutrient solution concentration is changed to once every 30 days, and the supplementation method is still to spray evenly on the surface of the contaminated soil. The contaminated soil samples used for monitoring should be taken from the remediation area, with a depth of 1m or more from the surface soil.

[0041] Step 7. Evaluation of soil properties after remediation.

[0042] Example 2

[0043] A method for in situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil is basically the same as Example 1 except for the following steps: The situation of petroleum hydrocarbon contamination in the deep soil is basically the same as Example 1.

[0044] Preparation method of anaerobic biostimulant: prepare Na 2 SO4 Solution.

[0045] Example 3

[0046] A method for in situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil is basically the same as Example 1 except for the following steps: The situation of petroleum hydrocarbon contamination in the deep soil is basically the same as Example 1.

[0047] Preparation method of anaerobic biostimulant: prepare NaNO with a concentration of 1 mol / L 3 Solution as anaerobic biostimulant 1 and 1 mol / L Na 2 SO 4 The solution is used as an anaerobic biostimulant2.

[0048] Activation of indigenous microbial degradation flora: Anaerobic biostimulant 1 and anaerobic biostimulant 2 were added to the contaminated soil at 1.5% of the total weight of the soil, respectively. The other treatment steps were basically the same as in Example 1.

[0049] Comparative Example 1

[0050] A method for in situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil is basically the same as Example 1 except for the following steps: The situation of petroleum hydrocarbon contamination in the deep soil is basically the same as Example 1.

[0051] Anaerobic biostimulant preparation: No anaerobic biostimulant preparation was performed.

[0052] Activation of indigenous microbial degradation flora: No activation of indigenous microbial degradation flora was performed.

[0053] Comparative Example 2

[0054] A method for in situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil is basically the same as Example 1 except for the following steps: The situation of petroleum hydrocarbon contamination in the deep soil is basically the same as Example 1.

[0055] Preparation of microbial nutrients: No preparation of microbial nutrients is carried out.

[0056] Anaerobic microbial in situ remediation: No microbial nutrients are added during the remediation process.

[0057] From May 2023 to May 2024, five pieces of petroleum hydrocarbon contaminated soil of the same area in Yanchang Oilfield were repaired, and Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 were respectively processed, and the content of petroleum hydrocarbons in the deep soil was continuously monitored. The results are shown in the following table:

[0058]

[0059] As can be seen from the table above, applying NO 3 - or SO 4 2- Biostimulation of indigenous flora can greatly improve the removal rate of petroleum hydrocarbons in deep contaminated soil. At the same time, the addition of microbial nutrients such as constant inorganic salt solution, trace element solution, vitamin mixture, etc. can also improve the degradation rate of petroleum hydrocarbons in deep contaminated soil.

[0060] The present invention applies NO to the petroleum hydrocarbon contaminated soil. 3 - or SO 4 2- As an anaerobic biostimulant, it can promote the denitrification or sulfate reduction of indigenous microorganisms in contaminated soil, thereby improving the removal rate of petroleum hydrocarbons in deep contaminated soil and shortening the remediation cycle; the process of removing petroleum hydrocarbons in soil by in-situ anaerobic biodegradation is highly automated, which can greatly reduce the number of land tillage operations while still ensuring the efficient degradation of petroleum hydrocarbons in contaminated soil, especially for the degradation of petroleum hydrocarbons in deep contaminated soil. Constant inorganic salt solution can provide conventional nutrients and inorganic salts for indigenous microorganisms to ensure that microorganisms grow and reproduce in the most suitable soil environment; microorganisms need the participation of trace elements when carrying out life activities, and the addition of trace element solution will enhance the activity of microbial cells and enzymes; vitamins will participate in different biochemical reactions in microorganisms, and the addition of vitamin solution can regulate the metabolic function of microorganisms and enhance the metabolic activity of microorganisms; biosurfactants can reduce the surface tension of the soil, making petroleum hydrocarbons in the soil easier to be taken up by indigenous microorganisms. At the same time, biosurfactants can interact with the hydrophilic and lipophilic groups on the cell membrane of indigenous microorganisms, change the structure and permeability of the cell membrane, and promote the utilization of petroleum hydrocarbons by indigenous microorganisms.

Claims

1. A method for in-situ anaerobic microbial remediation of deep petroleum hydrocarbon contaminated soil, characterized in that: The steps include: Step 1: Conduct on-site investigation of petroleum hydrocarbon contamination in deep soil. Soil samples for on-site investigation should be taken from soil layers 1m or deeper from the surface. Step 2: Preparation of anaerobic biostimulants: Determine the type and method of use of anaerobic biostimulants based on the investigation results of step 1; Step 3: Preparation of microbial nutrients: According to the investigation results of step 1, determine the proportion of microbial nutrients, which include constant inorganic salt solution, trace element solution and vitamin mixture; Step 4: Preparation of biosurfactant: According to the investigation in step 1, determine the ratio of biosurfactant; Step 5: Activation of indigenous microbial degradation flora: Add the anaerobic biostimulant in step 2 to the contaminated soil at 1-3% of the total weight of the soil, adjust the soil moisture content to 15%, stir the soil thoroughly to make the anaerobic biostimulant and the soil evenly mixed, and then stir the soil again during the entire treatment process. Let it stand in a natural environment for one week to activate the indigenous microorganisms in the soil that anaerobically degrade petroleum hydrocarbons; Step 6: Anaerobic microbial in-situ remediation: After the indigenous microbial degradation flora is activated, the microbial nutrient agent in step 3 and the biological surfactant in step 4 are mixed in a ratio of 1-2:1 to form a composite nutrient solution, and a portion is evenly sprayed on the surface of the contaminated soil. The concentration of the composite nutrient solution is monitored and appropriately supplemented every 15 days thereafter; when the content of petroleum hydrocarbons in the contaminated soil is reduced to less than 1% of the total weight of the soil, the monitoring and supplementation of the composite nutrient solution concentration is changed to once every 30 days, and the supplementation method is still uniformly spraying on the surface of the contaminated soil. The contaminated soil samples used for monitoring should be taken from the remediation area, with a depth of 1m or more from the surface soil; Step 7: Evaluation of soil properties after restoration.

2. The in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil according to claim 1, characterized in that: In step 1, the petroleum hydrocarbon pollution conditions include the total petroleum hydrocarbon content, total organic carbon content, major ion content, soil pH value, pollution depth, and pollution range in the soil.

3. The in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil according to claim 1, characterized in that: In step 2, the preparation method of the anaerobic biostimulant is as follows: Strengthening the electron acceptor of the anaerobic oxidation process of microorganisms: preparing an electron acceptor solution with a concentration of 1 mol / L, which can continuously provide the necessary electron acceptors for the anaerobic oxidation process of microorganisms; The electron acceptor is at least one of NaNO3 and Na2SO4.

4. The in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil according to claim 1, characterized in that: In step 3, the preparation method of different nutrients in the microbial nutrient is as follows: The composition and concentration of each component of the constant inorganic salt solution: 10g / L NaCl, 5g / LMgCl2·6H2O, 20g / L KH2PO4, 40g / L NH4Cl, 30g / L KCl, 0.5g / L CaCl2·2H2O; The composition and concentration of each component of the trace element solution: 10mL / L 25% HCl, 1.5g / LFeCl2·4H2O, 0.19g / LCoCl2·6H2O, 0.1g / LMnCl2·4H2O, 70mg / LZnCl2, 6mg / L H3BO3, 36mg / L Na2MoO4·2H2O, 24mg / LNiCl2·6H2O, 2mg / LCuCl2·2H2O, 6mg / L Na2SeO3·5H2O, 8mg / L Na2WO4·2H2O, 0.5g / LNaOH; The ingredients and concentration of each ingredient in the vitamin mixture are: 2mg / L folic acid, 10mg\L pyridoxine hydrochloride, 5mg / L vitamin B2, 2mg / L vitamin H, 5mg / L niacin, 5mg / L vitamin B1, 5mg / L calcium pantothenate, 0.1mg / L vitamin B 12 , 5mg / L p-aminobenzoic acid, 5mg / L lipoic acid, 900mg / LK2HPO4.

5. The in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil according to claim 4, characterized in that: The constant inorganic salt solution, trace element solution and vitamin mixture are mixed in a ratio of 5-10:1:1 to form a microbial nutrient.

6. The in-situ anaerobic microbial remediation method for deep petroleum hydrocarbon contaminated soil according to claim 1, characterized in that: In step 4, the biosurfactant preparation method is as follows: The composition of the biosurfactant is 5-10 g / L rhamnolipid.

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