An in-situ microbial remediation method for organically polluted groundwater and soil

Abstract

This invention relates to the field of soil and groundwater remediation technology, specifically to an in-situ microbial remediation method for organically polluted groundwater and soil, comprising the following steps: S1, isolating indigenous microorganisms from the soil of the polluted area; S2, adding the indigenous microorganisms and exogenous microbial agents to a culture medium to obtain a mixed bacterial solution; S3, immersing a carrier in the mixed bacterial solution and shaking it to obtain a carrier loaded with microorganisms; S4, spreading the carrier loaded with microorganisms into the soil of the polluted area, and completing the remediation after 30-40 days; during the remediation process, groundwater from the polluted area is extracted and sprayed into the soil. This invention ensures soil moisture content by extracting and spraying groundwater during the remediation process, while the microorganisms infiltrate with the groundwater, allowing the groundwater to be remediated simultaneously, shortening the remediation time and ensuring the remediation effect.

Description

Technical Field

[0001] This invention relates to the field of soil and groundwater remediation technology, specifically to an in-situ microbial remediation method for organically polluted groundwater and soil. Background Technology

[0002] Petroleum is one of the important energy sources for modern industry. However, leaks are prone to occur during the exploration and extraction of petroleum and petrochemical products. Since petroleum contains a variety of organic compounds, these organic compounds can enter the soil and spread into groundwater, changing the properties of the soil and groundwater. They can also accumulate through the food chain and ultimately endanger human health.

[0003] Currently, remediation methods for petroleum-contaminated soil and groundwater include physical, chemical, and biological methods. Physical and chemical remediation methods are limited due to their potential for secondary pollution. Bioremediation, on the other hand, utilizes microorganisms to degrade toxic and harmful organic pollutants in the soil into harmless substances such as carbon dioxide and water. It is widely used due to its advantages of safety, minimal damage, high effectiveness, and low likelihood of secondary pollution. However, existing technologies often separate soil and groundwater remediation, resulting in prolonged remediation times. Furthermore, when remediating one medium, pollutants can easily diffuse into the other, leading to incomplete degradation of organic pollutants and affecting the remediation outcome. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an in-situ microbial remediation method for organically polluted groundwater and soil.

[0005] The technical solution of this invention is: an in-situ microbial remediation method for organically polluted groundwater and soil, comprising the following steps:

[0006] S1. Indigenous microorganisms were isolated from the soil in the contaminated area;

[0007] S2. Add the indigenous microorganisms and exogenous microbial agents to the culture medium to obtain a mixed bacterial solution; the mass ratio of indigenous microorganisms, exogenous microbial agents and culture medium is 1:1~2:5~7;

[0008] S3. Immerse the carrier in a mixed bacterial solution with a weight of 3 to 5 times its own weight, shake and culture for 20 to 24 hours, then remove the carrier and freeze it at 5 to 10°C for 2 to 3 hours to obtain a carrier loaded with microorganisms; wherein, the carrier is a polyvinyl alcohol / activated carbon / manganese dioxide composite carrier.

[0009] S4. Spread the microbial-loaded carrier into the soil of the contaminated area. The remediation is completed after 30-40 days. During the remediation process, groundwater in the contaminated area is extracted every 3-5 days and sprayed into the soil of the contaminated area. Microbial stimulants are added to the groundwater during the spraying process. The amount of microbial-loaded carrier spread is 100-200g per acre, and the amount of groundwater sprayed is 2-4L per acre.

[0010] Explanation: The above method combines indigenous and exogenous microorganisms to enhance the microorganisms' ability to degrade organic matter. By repeatedly pumping groundwater for spraying, the soil moisture content is maintained during the remediation process. Microbial stimulants are used to stimulate the proliferation and metabolism of microorganisms, and some microorganisms infiltrate into the groundwater layer along with the sprayed groundwater, thus simultaneously remediating the groundwater. There is no need to remediate groundwater and soil separately, shortening the remediation time. Furthermore, organic pollutants in both groundwater and soil can be fully degraded, ensuring the remediation effect.

[0011] Furthermore, the isolation of the indigenous microorganisms includes the following steps:

[0012] S1-1. Take 40-60g of soil from the contaminated area, remove impurities from the soil, pulverize and sieve to obtain a soil sample;

[0013] S1-2. Add the soil sample to 150-200 ml of culture medium, then shake and incubate the soil sample for 5-6 hours to obtain a soil mixture.

[0014] S1-3. Centrifuge the soil mixture to obtain the supernatant, which contains indigenous microorganisms.

[0015] Note: The above method can isolate indigenous microorganisms, which are more adaptable to polluted soil. After cultivation, they can maintain good activity in polluted soil, ensuring the degradation effect of pollutants.

[0016] Furthermore, the exogenous microbial agent is composed of Bacillus subtilis, Slow-growing Marine Bacillus, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 1-2:0.5-1.5:2-3:1-3.

[0017] Note: The above-mentioned exogenous microorganisms can degrade a variety of pollutants. When combined with native microorganisms, they can ensure that a variety of pollutants in the soil can be effectively degraded.

[0018] Furthermore, in steps S1-2 and S3, the temperature of the oscillation culture is 30-35℃, the amplitude is 10-20mm, and the vibration frequency is 100-180rpm.

[0019] Note: The above shaking culture parameters can ensure the uniform distribution of nutrients in the culture medium, maintain microbial activity, and enable microorganisms to proliferate rapidly.

[0020] Furthermore, the polyvinyl alcohol / activated carbon / manganese dioxide composite carrier is prepared by polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 5-7:2-4:1-1.5, and the preparation method includes the following steps:

[0021] Step 1: Add activated carbon to anhydrous ethanol in 5 to 7 times its own weight, and ultrasonically disperse for 8 to 10 minutes to obtain activated carbon dispersion.

[0022] Step 2: Add potassium permanganate to 200-300 times its own weight of deionized water and stir until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution.

[0023] Step 3: Add polyvinyl alcohol to potassium permanganate solution and heat the potassium permanganate solution to 90-100°C while stirring until the polyvinyl alcohol is completely dissolved. Then stop heating and add activated carbon dispersion to the potassium permanganate solution. Stir for 5-10 minutes, and gradually add boric acid solution dropwise to the potassium permanganate solution during stirring. After stirring is complete, let stand for 20-30 minutes to obtain the reaction product. The amount of boric acid solution added is 0.5-1% of the total mass of potassium permanganate solution.

[0024] Step 4: After filtering the reaction product, a solid is obtained. The solid is then washed and dried to obtain the carrier.

[0025] Note: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier has a porous structure, which can effectively fix microorganisms and prevent the loss of a large number of microorganisms in the soil. The carrier can adsorb organic pollutants in the soil and be degraded by the microorganisms attached to the carrier, thereby increasing the degradation rate of organic pollutants by microorganisms. The carrier itself is non-ecotoxic and has a small impact on the environment.

[0026] Furthermore, the activated carbon is spherical activated carbon with a particle size of 1-3 mm.

[0027] Note: Spherical activated carbon has a uniform particle size, allowing it to be evenly distributed within the carrier. It also has higher porosity, enabling it to immobilize a greater number of microorganisms.

[0028] Furthermore, the mass concentration of the boric acid solution is 2-4%.

[0029] Note: The boric acid solution of the above concentration is easy to prepare and can ensure that polyvinyl alcohol is fully extracted.

[0030] Furthermore, the components of the microbial stimulant, by weight, include: 15-25 parts potassium nitrate, 3-6 parts ammonium sulfate, 15-25 parts magnesium sulfate, 10-15 parts potassium phosphate, 20-30 parts rhamnolipid, and 15-20 parts hydrogen peroxide.

[0031] Note: The above-mentioned microbial stimulants can provide trace elements such as nitrogen and phosphorus, stimulating the growth and reproduction of microorganisms. Furthermore, the microbial stimulants can generate oxygen under the catalytic action of the polyvinyl alcohol / activated carbon / manganese dioxide composite carrier, increasing the oxygen content in the soil, carrier pores, and groundwater, enabling microorganisms in the soil and groundwater to metabolize more efficiently and improving the degradation rate of pollutants.

[0032] Furthermore, the initial addition amount of the microbial stimulant in groundwater is 100-200 g / L, and the subsequent addition amount is increased by 5-10 g / L compared to the previous addition.

[0033] Note: Limiting the amount of microbial stimulant added can reduce waste, and gradually increasing the amount added can ensure that sufficient nutrients and oxygen can still be provided after the microorganisms proliferate.

[0034] The beneficial effects of this invention are:

[0035] (1) In the process of this invention, groundwater is repeatedly pumped out and sprayed to ensure soil moisture content. At the same time, microorganisms will seep into the groundwater layer with the groundwater, so that the groundwater is repaired at the same time. There is no need to repair the groundwater and soil separately, which shortens the repair time. Moreover, organic pollutants in both groundwater and soil can be fully degraded, ensuring the repair effect.

[0036] (2) The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier of the present invention has a porous structure, which can effectively fix microorganisms and prevent the loss of a large number of microorganisms in the soil. The carrier can adsorb pollutants in the soil and improve the degradation effect of microorganisms on pollutants. The carrier itself has no ecotoxicity and has little impact on the environment.

[0037] (3) The present invention adds a microbial stimulant when spraying groundwater to stimulate the growth and reproduction of microorganisms. The microbial stimulant can generate oxygen under the catalytic action of polyvinyl alcohol / activated carbon / manganese dioxide composite carrier, increasing the oxygen content in soil, carrier pores and groundwater, and improving the degradation rate of pollutants. Attached Figure Description

[0038] Figure 1 This refers to the degradation rate of petroleum hydrocarbons in soil and groundwater in Experiment Example 1 of this invention.

[0039] Figure 2 This refers to the degradation rate of petroleum hydrocarbons in soil and groundwater in Experiment Example 2 of this invention.

[0040] Figure 3This refers to the degradation rate of petroleum hydrocarbons in soil and groundwater in Experiment Example 3 of this invention.

[0041] Figure 4 This refers to the degradation rate of petroleum hydrocarbons in soil and groundwater in Experiment Example 4 of this invention.

[0042] Figure 5 This is the degradation rate of petroleum hydrocarbons in soil and groundwater in Experiment Example 5 of this invention. Detailed Implementation

[0043] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0044] Example 1: An in-situ microbial remediation method for organically polluted groundwater and soil, comprising the following steps:

[0045] S1. Indigenous microorganisms are isolated from the soil of the contaminated area; wherein the isolation of indigenous microorganisms includes the following steps:

[0046] S1-1. Take 50g of soil from the contaminated area, remove impurities from the soil, pulverize and sieve to obtain a soil sample;

[0047] S1-2. Add the soil sample to 175 ml of culture medium, and then shake and incubate the soil sample for 5.5 h to obtain the soil mixture.

[0048] S1-3. Centrifuge the soil mixture and the resulting supernatant is the indigenous microorganism;

[0049] S2. Add the indigenous microorganisms and exogenous microbial agents to the culture medium to obtain a mixed bacterial solution; the mass ratio of indigenous microorganisms, exogenous microbial agents, and culture medium is 1:1.5:6; wherein, the exogenous microbial agents are composed of Bacillus subtilis, Slow-growing Marine Bacillus, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 1.5:1:2.5:2.

[0050] S3. Immerse the carrier in a mixed bacterial solution with a weight of 4 times its own weight, shake and culture for 22 hours, then remove the carrier and freeze it at 8°C for 2.5 hours to obtain a carrier loaded with microorganisms; wherein, the carrier is a polyvinyl alcohol / activated carbon / manganese dioxide composite carrier.

[0051] S4. The carrier loaded with microorganisms is spread into the soil of the contaminated area. The remediation is completed after 30-40 days. During the remediation process, groundwater in the contaminated area is extracted every 4 days and sprayed into the soil of the contaminated area. Microbial stimulants are added to the groundwater during the spraying process. The amount of carrier loaded with microorganisms is 150g per acre, and the amount of groundwater sprayed is 3L per acre.

[0052] The components of the microbial stimulant, by weight, include: 20 parts potassium nitrate, 5 parts ammonium sulfate, 20 parts magnesium sulfate, 12 parts potassium phosphate, 25 parts rhamnolipid, and 18 parts hydrogen peroxide; the initial addition amount of the microbial stimulant in groundwater is 150 g / L, and the subsequent addition amount is increased by 8 g / L compared to the previous addition.

[0053] The culture medium consists of the following components by weight: 10 parts peptone, 3 parts beef extract, 5 parts sodium chloride, 15 parts lactose, 5 parts disodium hydrogen phosphate, 20 parts agar, and 1000 parts distilled water.

[0054] In steps S1-2 and S3, the temperature of the oscillation culture is 33℃, the amplitude is 15mm, and the vibration frequency is 140rpm.

[0055] The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier is prepared by mixing polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 6:3:1.25, and the preparation method includes the following steps:

[0056] Step 1: Add activated carbon to anhydrous ethanol at 6 times its own weight and ultrasonically disperse for 9 minutes to obtain activated carbon dispersion; wherein the activated carbon is spherical activated carbon with a particle size of 1-3 mm.

[0057] Step 2: Add potassium permanganate to 250 times its own weight of deionized water and stir until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution.

[0058] Step 3: Add polyvinyl alcohol to potassium permanganate solution and heat the potassium permanganate solution to 95°C while stirring until the polyvinyl alcohol is completely dissolved. Then stop heating and add activated carbon dispersion to the potassium permanganate solution. Stir for 8 minutes, and gradually add 3% boric acid solution dropwise to the potassium permanganate solution during stirring. After stirring is complete, let stand for 25 minutes to obtain the reaction product. The amount of boric acid solution added accounts for 0.75% of the total mass of potassium permanganate solution.

[0059] Step 4: After filtering the reaction product, a solid is obtained. The solid is then washed and dried to obtain the carrier.

[0060] Example 2: This example is basically the same as Example 1, except that the mass ratio of indigenous microorganisms, exogenous microbial agents, and culture medium is 1:1:5.

[0061] Example 3: This example is basically the same as Example 1, except that the mass ratio of indigenous microorganisms, exogenous microbial agents, and culture medium is 1:2:7.

[0062] Example 4: The exogenous microbial agent is composed of Bacillus subtilis, Slow-growing Marine Bacillus, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 1:0.5:2:1.

[0063] Example 5: The exogenous microbial agent is composed of Bacillus subtilis, Slow-growing Marine Bacillus, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 2:1.5:3:3.

[0064] Example 6: The carrier was immersed in a mixed bacterial solution with a mass three times its own weight.

[0065] Example 7: The carrier was immersed in a mixed bacterial solution with a weight of 5 times its own weight.

[0066] Example 8: The shaking culture time of the mixed bacterial solution was 20 hours.

[0067] Example 9: The shaking culture time of the mixed bacterial solution was 24 hours.

[0068] Example 10: Groundwater in the contaminated area was extracted every 3 days during the remediation process.

[0069] Example 11: Groundwater in the contaminated area was extracted every 5 days during the remediation process.

[0070] Example 12: The amount of groundwater sprayed was 2L per acre.

[0071] Example 13: The amount of groundwater sprayed was 4L per acre.

[0072] Example 14: The amount of microbial-loaded carriers spread was 100g per acre.

[0073] Example 15: The amount of microbial-loaded carriers spread was 200g per acre.

[0074] Example 16: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier was made from polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 5:2:1.

[0075] Example 17: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier was made from polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 7:4:1.5.

[0076] Example 18: Add activated carbon to anhydrous ethanol at a volume of 5 times its own weight.

[0077] Example 19: Activated carbon was added to anhydrous ethanol at a volume of 7 times its own weight.

[0078] Example 20: Add potassium permanganate to deionized water at a volume of 200 times its own weight.

[0079] Example 21: Add potassium permanganate to deionized water at a volume of 300 times its own weight.

[0080] Example 22: The components of the microbial stimulant, by weight, include: 15 parts potassium nitrate, 3 parts ammonium sulfate, 15 parts magnesium sulfate, 10 parts potassium phosphate, 20 parts rhamnolipid, and 15 parts hydrogen peroxide.

[0081] Example 23: The components of the microbial stimulant, by weight, include: 25 parts potassium nitrate, 6 parts ammonium sulfate, 25 parts magnesium sulfate, 15 parts potassium phosphate, 30 parts rhamnolipid, and 20 parts hydrogen peroxide.

[0082] Example 24: The initial addition amount of the microbial stimulant in groundwater was 100 g / L, and the subsequent addition amount was increased by 5 g / L compared to the previous addition.

[0083] Example 25: The initial addition amount of the microbial stimulant in groundwater was 200 g / L, and the subsequent addition amount was increased by 10 g / L compared to the previous addition.

[0084] Comparative Example 1: Referring to Example 1, only indigenous microorganisms were used in the mixed bacterial solution.

[0085] Comparative Example 2: Referring to Example 1, only exogenous microbial agents were used in the mixed bacterial solution.

[0086] Comparative Example 3: Referring to Example 1, the carrier was immersed in a mixed bacterial solution with a mass twice its own weight.

[0087] Comparative Example 4: With reference to Example 1, the shaking culture time of the mixed bacterial solution was 18h.

[0088] Comparative Example 5: Referring to Example 1, an external, unpolluted water source was used to replace the extracted groundwater.

[0089] Comparative Example 6: Referring to Example 1, polyvinyl alcohol, spherical activated carbon particles and manganese dioxide powder were directly mixed as a carrier.

[0090] Comparative Example 7: Referring to Example 1, the mixed bacterial solution was applied directly to the soil without using a carrier.

[0091] Comparative Example 8: Referring to Example 1, hydrogen peroxide was removed from the microbial stimulant, and the oxygen content was increased by directly aerating the groundwater.

[0092] Comparative Example 9: With reference to Example 1, no microbial stimulants were added.

[0093] Comparative Example 10: Referring to Example 1, the amount of microbial stimulant added to the groundwater was kept constant at 150 g / L.

[0094] Experimental Example: To investigate the influence of parameters in each embodiment on the remediation effect, and to avoid interference between groundwater layers during remediation at the same location, petroleum-contaminated areas at different locations were selected as test areas for each embodiment and comparative example. The petroleum hydrocarbon content in the soil and groundwater of each test area before and after remediation was measured to obtain the petroleum hydrocarbon degradation rate before and after remediation. The specific investigation is as follows:

[0095] 1. To investigate the effects of the ratio of mixed bacterial solution and exogenous microbial agent on the remediation effect.

[0096] like Figure 1 As shown, a comparison of Examples 1 to 5 reveals that Example 1 exhibits the highest degradation rate of petroleum hydrocarbons in soil and groundwater, indicating that Example 1 has the best remediation effect. This may be because the ratio of mixed bacterial solution and exogenous microbial agent in Example 1 is reasonable, allowing internal microorganisms to proliferate rapidly. Therefore, the ratio of mixed bacterial solution and exogenous microbial agent selected in Example 1 is optimal.

[0097] As can be seen from the comparison of Example 1 and Comparative Examples 1-2, the use of either indigenous microorganisms or exogenous microbial agents will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the use of either indigenous microorganisms or exogenous microbial agents will result in some petroleum hydrocarbon pollutants not being effectively degraded. Therefore, the mixed bacterial solution selected in Example 1 is the optimal solution.

[0098] 2. Investigate the effects of the proportion of mixed bacterial solution and shaking culture time on the remediation effect.

[0099] like Figure 2 As shown, a comparison of Examples 1, 6-9, and Comparative Examples 3-4 reveals that increasing the proportion of mixed bacterial solution and extending the shaking culture time both increase the petroleum hydrocarbon degradation rate, until the petroleum hydrocarbon degradation rate in Example 1 reaches its maximum. As the proportion of mixed bacterial solution continues to increase and the shaking culture time continues to extend, the petroleum hydrocarbon degradation rate begins to show no significant change. This may be because the number of microorganisms that the carrier can support has reached its maximum value. Therefore, from a cost perspective, the proportion of mixed bacterial solution and the shaking culture time selected in Example 1 are optimal.

[0100] 3. Investigate the effects of groundwater extraction frequency, groundwater spraying volume, and microbial carrier application volume on remediation efficacy.

[0101] like Figure 3 As shown, a comparison between Examples 1 and Examples 10-13 reveals that excessively high or low groundwater extraction frequency and excessively high or low groundwater spraying volume both lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the groundwater extraction frequency and groundwater spraying volume selected in Example 1 can ensure suitable soil moisture content and guarantee the growth environment for microorganisms. Therefore, the groundwater extraction frequency and groundwater spraying volume selected in Example 1 are optimal.

[0102] Compared with Comparative Example 5, in Example 1, the degradation rate of petroleum hydrocarbons in the groundwater decreased after the external water source was used to replace the extracted groundwater. This may be because after the groundwater is extracted and sprayed, the microorganisms in the groundwater can exchange with the microorganisms in the soil, change the microbial community, and improve the microorganisms' adaptability to the environment. Therefore, the remediation method in Example 1 is optimal.

[0103] A comparison of Examples 1 and 14-15 shows that increasing the amount of microbial carriers applied increases the degradation rate of petroleum hydrocarbons, until the petroleum hydrocarbon degradation rate in Example 1 reaches its maximum. As the amount of microbial carriers applied continues to increase, the petroleum hydrocarbon degradation rate begins to show no significant change. This may be because the soil has limited carrying capacity for microorganisms. Therefore, the amount of microbial carriers applied in Example 1 is optimal.

[0104] 4. Investigate the effects of preparation parameters of polyvinyl alcohol / activated carbon / manganese dioxide composite carrier on the remediation effect.

[0105] like Figure 4 As shown, a comparison between Examples 1 and Examples 16-17 shows that Example 1 has the highest petroleum hydrocarbon degradation rate in soil and groundwater. This may be because the raw material ratio in Example 1 is reasonable, the prepared carrier has more pores, and the ability to load microorganisms is stronger. Therefore, the raw material ratio selected in Example 1 is optimal.

[0106] A comparison of Examples 1 and 18-21 shows that an excessively high or low proportion of anhydrous ethanol in the activated carbon dispersion and an excessively high or low proportion of deionized water in the potassium permanganate solution will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the activated carbon dispersion ratio and potassium permanganate solution concentration selected in Example 1 can prepare a polyvinyl alcohol / activated carbon / manganese dioxide composite carrier with uniform composition and high conversion rate.

[0107] As can be seen from the comparison between Example 1 and Comparative Example 6, when polyvinyl alcohol, spherical activated carbon particles and manganese dioxide powder are directly mixed as a carrier, the degradation rate of petroleum hydrocarbons in soil and groundwater is significantly reduced. This may be because when the carrier is directly mixed, the activated carbon and manganese dioxide cannot be evenly distributed in the polyvinyl alcohol, resulting in fewer carrier pores, poor fixation effect on microorganisms, and insufficient oxygen generation in the pores after contact with microbial stimulants. Therefore, the carrier selected in Example 1 is the best.

[0108] As can be seen from the comparison between Example 1 and Comparative Example 7, the degradation rate of petroleum hydrocarbons in soil and groundwater decreased significantly after the carrier was not used. This may be because without the carrier to fix them, the loss of microorganisms was more serious, resulting in the inability to degrade organic pollutants. Therefore, the remediation method selected in Example 1 is the best.

[0109] 5. Investigate the effects of microbial stimulant composition and dosage on the repair effect.

[0110] like Figure 5 As shown, a comparison between Examples 1 and Examples 22-23 shows that the degradation rate of petroleum hydrocarbons in soil and groundwater in Example 1 is the highest. This may be because the microbial stimulant in Example 1 has the strongest stimulating effect on microorganisms and can effectively promote the growth and metabolism of microorganisms. Therefore, the microbial stimulant component selected in Example 1 is the best.

[0111] As can be seen from the comparison between Example 1 and Comparative Example 8, after removing hydrogen peroxide from the microbial stimulant and increasing the oxygen content by aeration, the degradation rate of petroleum hydrocarbons decreased. This may be because the oxygen dissolved in water is limited, and the oxygen increased by direct aeration cannot be transported to the soil and carrier. Therefore, the microbial stimulant selected in Example 1 is the best.

[0112] As can be seen from the comparison between Example 1 and Comparative Example 9, the degradation rate of petroleum hydrocarbons decreased after the removal of the microbial stimulant. This may be because there is insufficient oxygen in the soil and groundwater, and the microorganisms cannot carry out effective aerobic respiration. Therefore, the remediation method selected in Example 1 is the best.

[0113] A comparison of Examples 1 and 24-25 shows that both excessively high and excessively low amounts of microbial stimulant can lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the amount of microbial stimulant added in Example 1 can provide sufficient influence to the microorganisms and avoid excessive nutrition leading to the proliferation of a single microorganism. Therefore, the amount of microbial stimulant added in Example 1 is optimal.

[0114] As can be seen from the comparison between Example 1 and Comparative Example 10, keeping the microbial stimulant constant will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because as the number of microorganisms in the soil increases, increasing the amount of microbial stimulant added can ensure nutrient supply. Therefore, the method of adding microbial stimulant selected in Example 1 is optimal.

Claims

1. An in-situ microbial remediation method for organically polluted groundwater and soil, characterized in that, Includes the following steps: S1. Indigenous microorganisms were isolated from the soil in the contaminated area; S2. Add indigenous microorganisms and exogenous microbial agents to the culture medium to obtain a mixed bacterial solution; the mass ratio of indigenous microorganisms, exogenous microbial agents and culture medium is 1:1~2:5~7; S3. Immerse the carrier in a mixed bacterial solution with a weight of 3 to 5 times its own weight, shake and culture for 20 to 24 hours, then remove the carrier and freeze it at 5 to 10°C for 2 to 3 hours to obtain a carrier loaded with microorganisms; wherein, the carrier is a polyvinyl alcohol / activated carbon / manganese dioxide composite carrier. S4. The carrier loaded with microorganisms is spread into the soil of the contaminated area. The remediation is completed after 30-40 days. During the remediation process, groundwater in the contaminated area is extracted every 3-5 days and sprayed into the soil of the contaminated area. Microbial stimulants are added to the groundwater during the spraying process. The amount of carrier loaded with microorganisms is 100-200g per acre. The amount of groundwater sprayed is 2-4L per acre. The composition of the microbial stimulant by weight includes: 15-25 parts potassium nitrate, 3-6 parts ammonium sulfate, 15-25 parts magnesium sulfate, 10-15 parts potassium phosphate, 20-30 parts rhamnolipid, and 15-20 parts hydrogen peroxide. The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier is prepared by polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 5~7:2~4:1~1.5, and the preparation method includes the following steps: Step 1: Add activated carbon to anhydrous ethanol in 5 to 7 times its own weight, and ultrasonically disperse for 8 to 10 minutes to obtain activated carbon dispersion. Step 2: Add potassium permanganate to 200-300 times its own weight of deionized water and stir until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution. Step 3: Add polyvinyl alcohol to potassium permanganate solution and heat the potassium permanganate solution to 90-100℃ while stirring until the polyvinyl alcohol is completely dissolved. Then stop heating, add activated carbon dispersion to the potassium permanganate solution, stir for 5-10 minutes, and gradually add boric acid solution dropwise to the potassium permanganate solution during stirring. After stirring is complete, let stand for 20-30 minutes to obtain the reaction product; wherein the amount of boric acid solution added accounts for 0.5-1% of the total mass of potassium permanganate solution. Step 4: After filtering the reaction product, a solid is obtained. The solid is then washed and dried to obtain the carrier.

2. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 1, characterized in that, The isolation of the indigenous microorganisms includes the following steps: S1-1. Take 40-60g of soil from the contaminated area, remove impurities from the soil, pulverize and sieve to obtain a soil sample; S1-2. Add the soil sample to 150-200 ml of culture medium, then shake and incubate the soil sample for 5-6 hours to obtain the soil mixture. S1-3. Centrifuge the soil mixture to obtain the supernatant, which contains indigenous microorganisms.

3. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 1, characterized in that, The exogenous microbial agent is composed of Bacillus subtilis, Slow-growing Marine Bacillus, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 1~2:0.5~1.5:2~3:1~3.

4. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 2, characterized in that, In steps S1-2 and S3, the temperature of the oscillation culture is 30~35℃, the amplitude is 10~20mm, and the vibration frequency is 100~180rpm.

5. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 1, characterized in that, The activated carbon is spherical activated carbon with a particle size of 1~3mm.

6. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 1, characterized in that, The boric acid solution has a mass concentration of 2-4%.

7. The in-situ microbial remediation method for organically polluted groundwater and soil according to claim 1, characterized in that, The initial addition amount of the microbial stimulant in groundwater is 100~200g / L, and the subsequent addition amount is increased by 5~10g / L compared to the previous addition.

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