In-situ microbial remediation method for organic underground polluted water and soil

Abstract

The invention relates to the technical field of soil and underground water remediation, in particular to an in-situ microbial remediation method for organic underground polluted water and soil, which comprises the following steps: S1, separating indigenous microorganisms from the soil in a polluted area; s2, adding indigenous microorganism internal and external microorganism bacterium agents into a culture medium to obtain a mixed bacterium solution; s3, soaking a carrier into the mixed bacterial liquid, and performing shaking culture to obtain a carrier loaded with microorganisms; s4, the carrier loaded with the microorganisms is sown into the soil of the contaminated area, and remediation is completed after remediation is conducted for 30-40 days; and in the remediation process, underground water in the polluted area is pumped and sprayed into the soil. In the remediation process, underground water is pumped out for spraying, the soil water content is guaranteed, meanwhile, microorganisms can infiltrate along with the underground water, the underground water is remedied at the same time, the remediation time is shortened, and the remediation effect is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of soil and groundwater remediation, and in particular to an in-situ microbial remediation method for organic underground contaminated water and soil. Background Art

[0002] Oil is one of the important energy sources of modern industry, but it is prone to leakage during the exploration and exploitation of the petroleum and petrochemical industries. Since oil contains a variety of organic matter, these organic matter will enter the soil and spread into the groundwater, changing the properties of the soil and groundwater, and enrich through the food chain, ultimately endangering human health.

[0003] At present, there are physical, chemical and biological methods for the remediation of petroleum organic contaminated soil and groundwater. Physical and chemical remediation methods are subject to many restrictions because they are prone to secondary pollution to the environment. Biological remediation technology uses microorganisms to degrade toxic and harmful organic pollutants in the soil into harmless substances such as carbon dioxide and water. It has the advantages of safety, low destructiveness, good effect, and not easy to cause secondary pollution, and is widely used. In the existing technology, soil and groundwater remediation are often carried out separately, resulting in a long remediation time. In addition, when remediating one medium, pollutants are easily diffused into another medium, resulting in the inability to fully degrade organic pollutants, affecting the remediation effect. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an in-situ microbial remediation method for organic underground contaminated water and soil.

[0005] The technical solution of the present invention is: an in-situ microbial remediation method for organic underground contaminated water and soil, comprising the following steps:

[0006] S1. Isolate indigenous microorganisms from the soil in the contaminated area;

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

[0008] S3, immersing the carrier in a mixed bacterial solution 3 to 5 times its own weight, shaking and culturing for 20 to 24 hours, then taking out the carrier, and freezing 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 carrier loaded with microorganisms into the soil of the contaminated area. The restoration is completed after 30 to 40 days. During the restoration process, extract groundwater from the contaminated area every 3 to 5 days and spray the groundwater into the soil of the contaminated area. Add microbial stimulants into the groundwater during the spraying process. The spreading amount of the carrier loaded with microorganisms is 100 to 200 g per mu. The spraying amount of groundwater is 2 to 4 L per mu.

[0010] Description: The above method improves the ability of microorganisms to degrade organic matter by combining indigenous microorganisms with exogenous microorganisms, and ensures the moisture content of the soil during the restoration process by repeatedly extracting groundwater for spraying. Microbial stimulants are used to stimulate the proliferation and metabolism of microorganisms, and some microorganisms will infiltrate into the groundwater layer with the sprayed groundwater, so that the groundwater is restored at the same time. There is no need to repair the groundwater and soil separately, which shortens the restoration time. In addition, the organic pollutants in the groundwater and soil can be fully degraded, ensuring the restoration effect.

[0011] Furthermore, the separation of the indigenous microorganisms comprises the following steps:

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

[0013] S1-2, adding the soil sample into 150-200 ml of culture medium, and then shaking and culturing the soil sample for 5-6 hours to obtain a soil mixture;

[0014] S1-3. The soil mixture is centrifuged to obtain the supernatant, which is the indigenous microorganisms.

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

[0016] Furthermore, the exogenous microbial agent is composed of Bacillus subtilis, Bacillus scaly, 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 indigenous microorganisms, they can ensure that a variety of pollutants in the soil can be effectively degraded.

[0018] Furthermore, in step S1-2 and step S3, the shaking culture temperature is 30-35°C, the amplitude is 10-20 mm, and the shaking frequency is 100-180 rpm.

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

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

[0021] Step 1, adding activated carbon into anhydrous ethanol 5 to 7 times its own mass, and ultrasonically dispersing for 8 to 10 minutes to obtain an activated carbon dispersion;

[0022] Step 2, adding potassium permanganate into deionized water with a mass of 200 to 300 times the amount of potassium permanganate, stirring until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution;

[0023] Step 3, adding polyvinyl alcohol to a potassium permanganate solution, and heating the potassium permanganate solution to 90-100° C. under stirring, until the polyvinyl alcohol is completely dissolved and then stopping heating, then adding an activated carbon dispersion to the potassium permanganate solution, stirring for 5-10 minutes, and gradually adding a boric acid solution dropwise to the potassium permanganate solution during the stirring process, and standing for 20-30 minutes after the stirring is completed to obtain a reaction product; wherein the amount of the boric acid solution added accounts for 0.5-1% of the total mass of the potassium permanganate solution;

[0024] Step 4: Filter the reaction product to obtain a solid, and wash and dry the solid to obtain the carrier.

[0025] Description: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier has a porous structure, which can effectively fix microorganisms and avoid the large-scale loss 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 has no ecotoxicity and has little impact on the environment.

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

[0027] Description: Spherical activated carbon has uniform particle size and can be evenly distributed in the carrier. It also has higher porosity and can fix more 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 sufficient precipitation of polyvinyl alcohol.

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

[0031] Description: The above-mentioned microbial stimulants can provide trace elements such as nitrogen and phosphorus to stimulate the growth and reproduction of microorganisms. The microbial stimulants can produce oxygen under the catalytic action of the polyvinyl alcohol / activated carbon / manganese dioxide composite carrier, increase the oxygen content in the soil, carrier pores and groundwater, enable the microorganisms in the soil and groundwater to metabolize more efficiently, and improve the degradation rate of pollutants.

[0032] Furthermore, the initial addition amount of the microbial stimulant to the groundwater is 100-200 g / L, and each subsequent addition amount is increased by 5-10 g / L compared with 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 are still provided after the microorganisms proliferate.

[0034] The beneficial effects of the present invention are:

[0035] (1) During the restoration process of the present invention, groundwater is extracted multiple times for spraying to ensure soil moisture content. At the same time, microorganisms will infiltrate into the groundwater layer along with the groundwater, so that the groundwater is restored at the same time. There is no need to repair the groundwater and soil separately, which shortens the restoration time. In addition, organic pollutants in the groundwater and soil can be fully degraded, ensuring the restoration 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 avoid the large-scale loss of microorganisms in the soil. The carrier can also 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 the polyvinyl alcohol / activated carbon / manganese dioxide composite carrier, thereby increasing the oxygen content in the soil, carrier pores and groundwater, and improving the degradation rate of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the degradation rate of petroleum hydrocarbons in soil and groundwater of Experimental Example 1 of the present invention;

[0039] Figure 2 It is the degradation rate of petroleum hydrocarbons in soil and groundwater of Experimental Example 2 of the present invention;

[0040] Figure 3It is the degradation rate of petroleum hydrocarbons in soil and groundwater of Experimental Example 3 of the present invention;

[0041] Figure 4 It is the degradation rate of petroleum hydrocarbons in soil and groundwater of Experimental Example 4 of the present invention;

[0042] Figure 5 It is the degradation rate of petroleum hydrocarbons in soil and groundwater of Experimental Example 5 of the present invention. DETAILED DESCRIPTION

[0043] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0044] Example 1: An in-situ microbial remediation method for organic underground contaminated water and soil, comprising the following steps:

[0045] S1. Isolating indigenous microorganisms from the soil in the contaminated area; wherein the isolation of indigenous microorganisms comprises the following steps:

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

[0047] S1-2, adding the soil sample into 175 ml of culture medium, and then shaking and culturing the soil sample for 5.5 hours to obtain a soil mixture;

[0048] S1-3, centrifuging the soil mixture to obtain the supernatant, which is the indigenous microorganisms;

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

[0050] S3, immersing the carrier in a mixed bacterial solution 4 times its own weight, shaking and culturing for 22 hours, then taking out the carrier, and freezing 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. Spread the carrier loaded with microorganisms into the soil of the contaminated area. After 30 to 40 days of restoration, the restoration is completed. During the restoration process, extract groundwater from the contaminated area every 4 days and spray the groundwater into the soil of the contaminated area. During the spraying process, add microbial stimulants into the groundwater. The spreading amount of the carrier loaded with microorganisms is 150g per mu; the spraying amount of groundwater is 3L per mu.

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

[0053] The components of the culture medium include, by mass, 10 parts of peptone, 3 parts of beef extract, 5 parts of sodium chloride, 15 parts of lactose, 5 parts of disodium hydrogen phosphate, 20 parts of agar, and 1000 parts of distilled water;

[0054] In step S1-2 and step S3, the shaking culture temperature is 33°C, the amplitude is 15 mm, and the shaking frequency is 140 rpm;

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

[0056] Step 1, adding activated carbon into anhydrous ethanol 6 times its own mass, and ultrasonically dispersing for 9 minutes to obtain an activated carbon dispersion; wherein the activated carbon is spherical activated carbon with a particle size of 1 to 3 mm;

[0057] Step 2, adding potassium permanganate into deionized water with a volume of 250 times its own mass, stirring until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution;

[0058] Step 3, adding polyvinyl alcohol to a potassium permanganate solution, and heating the potassium permanganate solution to 95° C. while stirring, and stopping heating until the polyvinyl alcohol is completely dissolved, then adding an activated carbon dispersion to the potassium permanganate solution, stirring for 8 minutes, and gradually dropping a boric acid solution with a mass concentration of 3% into the potassium permanganate solution during the stirring process, and standing for 25 minutes after the stirring is completed to obtain a reaction product; wherein the amount of the boric acid solution added accounts for 0.75% of the total mass of the potassium permanganate solution;

[0059] Step 4: Filter the reaction product to obtain a solid, and wash and dry the solid 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, Marinobacterium lentivirides, 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, Marinobacterium lentivirides, Pseudomonas putida, and Rhodopseudomonas palustris in a mass ratio of 2:1.5:3:3.

[0064] Example 6: Soak the carrier in a mixed bacterial solution that is 3 times its own weight.

[0065] Example 7: Soak the carrier in a mixed bacterial solution that is 5 times its own weight.

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

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

[0068] Example 10: During the remediation process, groundwater from the contaminated area is extracted every 3 days.

[0069] Example 11: During the remediation process, groundwater from the contaminated area is extracted every 5 days.

[0070] Embodiment 12: The spraying amount of groundwater is 2L per mu.

[0071] Embodiment 13: The spraying amount of groundwater is 4L per mu.

[0072] Example 14: The spreading amount of the carrier loaded with microorganisms is 100g per mu.

[0073] Example 15: The spreading amount of the carrier loaded with microorganisms is 200g per mu.

[0074] Example 16: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier is made of 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 is made of polyvinyl alcohol, activated carbon and potassium permanganate in a mass ratio of 7:4:1.5.

[0076] Example 18: Add activated carbon into anhydrous ethanol that is 5 times its own mass.

[0077] Example 19: Add activated carbon into anhydrous ethanol that is 7 times its own mass.

[0078] Example 20: Add potassium permanganate into deionized water with a volume 200 times its own mass.

[0079] Example 21: Add potassium permanganate into deionized water with a volume 300 times its own mass.

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

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

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

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

[0084] Comparative Example 1: Using Example 1 as a reference, only indigenous microorganisms were used in the mixed bacterial solution.

[0085] Comparative Example 2: Using Example 1 as a reference, only exogenous microbial agents were used in the mixed bacterial solution.

[0086] Comparative Example 3: Using Example 1 as a reference, the carrier was immersed in a mixed bacterial solution twice its own mass.

[0087] Comparative Example 4: Taking Example 1 as a reference, the shaking culture time of the mixed bacterial solution was 18 hours.

[0088] Comparative Example 5: Taking Example 1 as a reference, an external non-polluted water source is used to replace the extracted groundwater.

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

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

[0091] Comparative Example 8: Taking Example 1 as a reference, the hydrogen peroxide in the microbial stimulant was removed, and the oxygen content was increased by directly aerating the groundwater.

[0092] Comparative Example 9: Using Example 1 as a reference, no microbial stimulant was added.

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

[0094] Experimental example: In order to explore the influence of the parameters of each embodiment on the repair effect, and to avoid mutual interference between groundwater layers when repairing at the same location, oil-contaminated areas at different locations were selected as test areas for each embodiment and comparative example, and the petroleum hydrocarbon content in the soil and groundwater of each test area before and after repair was measured to obtain the petroleum hydrocarbon degradation rate before and after repair. The specific exploration is as follows:

[0095] 1. Explore the effects of mixed bacterial solution ratio and exogenous microbial agent ratio on the repair effect

[0096] like Figure 1 As shown, by comparing Examples 1 to 5, it can be seen that the degradation rate of petroleum hydrocarbons in soil and groundwater of Example 1 is the highest, indicating that the remediation effect of Example 1 is the best. This may be because the mixed bacterial solution and the exogenous microbial agent of Example 1 have a reasonable ratio, and the internal microorganisms can proliferate rapidly. Therefore, the mixed bacterial solution and the exogenous microbial agent ratio selected in Example 1 are optimal;

[0097] From the comparison between Example 1 and Comparative Examples 1 to 2, it can be seen that the use of a single indigenous microorganism or exogenous microbial agent will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the use of only indigenous microorganisms or exogenous microbial agents will result in the inability to effectively degrade some petroleum hydrocarbon pollutants. Therefore, the mixed bacterial solution selected in Example 1 is optimal.

[0098] 2. Explore the effects of mixed bacterial solution ratio and oscillation culture time on the repair effect

[0099] like Figure 2 As shown, by comparing Example 1, Examples 6 to 9 and Comparative Examples 3 to 4, it can be seen that the increase in the proportion of mixed bacterial liquid and the extension of the oscillation culture time will increase the degradation rate of petroleum hydrocarbons, until the degradation rate of petroleum hydrocarbons in Example 1 reaches the highest. As the proportion of mixed bacterial liquid continues to increase and the oscillation culture time continues to extend, the degradation rate of petroleum hydrocarbons begins to have no obvious change. This may be because the number of microorganisms that the carrier can carry has reached the maximum value. Therefore, from a cost perspective, the proportion of mixed bacterial liquid and the oscillation culture time selected in Example 1 are both optimal.

[0100] 3. Explore the effects of groundwater extraction frequency, groundwater spraying volume, and microbial carrier spreading volume on the restoration effect

[0101] like Figure 3 As shown, by comparing Example 1 and Examples 10 to 13, it can be seen that: too high or too low groundwater extraction frequency, too high or too low groundwater spraying amount will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the groundwater extraction frequency and groundwater spraying amount selected in Example 1 can ensure that the soil moisture content is appropriate and ensure the growth environment of microorganisms. Therefore, the groundwater extraction frequency and groundwater spraying amount selected in Example 1 are both optimal;

[0102] Compared with Example 5, the degradation rate of petroleum hydrocarbons in groundwater decreased after the extracted groundwater was replaced by an external water source in Example 1. This may be because after the groundwater is extracted and sprayed, the microorganisms in the groundwater can exchange with the microorganisms in the soil, changing the microbial flora and improving the adaptability of the microorganisms to the environment. Therefore, the repair method of Example 1 is the best.

[0103] By comparing Example 1 and Examples 14 to 15, it can be seen that increasing the amount of microorganism-loaded carrier sowing will increase the degradation rate of petroleum hydrocarbons, until the petroleum hydrocarbon degradation rate of Example 1 reaches the highest. As the amount of microorganism-loaded carrier sowing continues to increase, the petroleum hydrocarbon degradation rate begins to have no obvious change. This may be because the soil has limited carrying capacity for microorganisms. Therefore, the amount of microorganism-loaded carrier sowing selected in Example 1 is optimal.

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

[0105] like Figure 4 As shown, by comparing Example 1 and Examples 16 to 17, it can be seen that the degradation rate of petroleum hydrocarbons in soil and groundwater in Example 1 is the highest. This may be because the raw material ratio of 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] By comparing Example 1 and Examples 18 to 21, it can be seen that: too high or too low anhydrous ethanol content in the activated carbon dispersion, and too high or too low deionized water content 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] From the comparison between Example 1 and Comparative Example 6, it can be seen that after 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 the activated carbon and manganese dioxide cannot be evenly distributed in polyvinyl alcohol by direct mixing, resulting in fewer carrier pores, poor fixation effect for microorganisms, and insufficient oxygen can be generated in the pores after contact with the microbial stimulant. Therefore, the carrier selected in Example 1 is the best;

[0108] From the comparison between Example 1 and Comparative Example 7, it can be seen that after not using a carrier, the degradation rate of petroleum hydrocarbons in the soil and groundwater is significantly reduced. This may be because without carrier fixation, the loss of microorganisms is more serious, resulting in the inability to degrade organic pollutants. Therefore, the repair method selected in Example 1 is the best.

[0109] 5. Explore the effects of microbial stimulant composition and amount on the repair effect

[0110] like Figure 5 As shown, by comparing Example 1 and Examples 22 to 23, it can be seen that the degradation rate of petroleum hydrocarbons in the soil and groundwater of Example 1 is the highest. This may be because the microbial stimulant of 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 optimal;

[0111] From the comparison between Example 1 and Comparative Example 8, it can be seen that 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 amount of oxygen dissolved in water is limited, and the oxygen increased by direct aeration cannot be transported to the soil and the carrier. Therefore, the microbial stimulant selected in Example 1 is the best.

[0112] From the comparison between Example 1 and Comparative Example 9, it can be seen that after removing the microbial stimulant, the degradation rate of petroleum hydrocarbons decreased. This may be because there is insufficient oxygen in the soil and groundwater, and the microorganisms cannot undergo effective aerobic respiration. Therefore, the repair method selected in Example 1 is the best.

[0113] From the comparison between Example 1 and Examples 24-25, it can be seen that: too high or too low an addition amount of the microbial stimulant will lead to a decrease in the degradation rate of petroleum hydrocarbons. This may be because the addition amount of the microbial stimulant selected in Example 1 can provide sufficient influence on the microorganisms and avoid the large-scale proliferation of a single microorganism caused by excessive nutrition. Therefore, the addition amount of the microbial stimulant selected in Example 1 is optimal;

[0114] By comparing Example 1 with Comparative Example 10, it can be seen that 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 microbial stimulant addition method selected in Example 1 is optimal.

Claims

1. An in-situ microbial remediation method for organic underground contaminated water and soil, characterized in that: The following steps are involved: S1. Isolate indigenous microorganisms from the soil in the contaminated area; S2, adding indigenous microorganisms and exogenous microbial agents into 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, immersing the carrier in a mixed bacterial solution 3 to 5 times its own weight, shaking and culturing for 20 to 24 hours, then taking out the carrier, and freezing 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. Spread the carrier loaded with microorganisms into the soil of the contaminated area. The restoration is completed after 30 to 40 days. During the restoration process, extract groundwater from the contaminated area every 3 to 5 days and spray the groundwater into the soil of the contaminated area. Add microbial stimulants into the groundwater during the spraying process. The spreading amount of the carrier loaded with microorganisms is 100 to 200 g per mu. The spraying amount of groundwater is 2 to 4 L per mu.

2. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 1, characterized in that: The separation of the indigenous microorganisms comprises the following steps: S1-1. Take 40-60 g of soil from the polluted area, remove impurities from the soil, crush it, and sieve it to obtain a soil sample; S1-2, adding the soil sample into 150-200 ml of culture medium, and then shaking and culturing the soil sample for 5-6 hours to obtain a soil mixture; S1-3. The soil mixture is centrifuged to obtain the supernatant, which is the indigenous microorganisms.

3. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 1, characterized in that: The exogenous microbial agent is composed of Bacillus subtilis, Marinobacterium lentifolium, 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 organic underground contaminated water and soil according to claim 2, characterized in that: In step S1-2 and step S3, the shaking culture temperature is 30-35°C, the amplitude is 10-20 mm, and the shaking frequency is 100-180 rpm.

5. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 1, characterized in that: The polyvinyl alcohol / activated carbon / manganese dioxide composite carrier is prepared from polyvinyl alcohol, activated carbon, and potassium permanganate in a mass ratio of 5-7:2-4:1-1.5, and the preparation method comprises the following steps: Step 1, adding activated carbon into anhydrous ethanol 5 to 7 times its own mass, and ultrasonically dispersing for 8 to 10 minutes to obtain an activated carbon dispersion; Step 2, adding potassium permanganate into deionized water with a mass of 200 to 300 times the amount of potassium permanganate, stirring until the potassium permanganate is completely dissolved to obtain a potassium permanganate solution; Step 3, adding polyvinyl alcohol to a potassium permanganate solution, and heating the potassium permanganate solution to 90-100° C. under stirring, until the polyvinyl alcohol is completely dissolved and then stopping heating, then adding an activated carbon dispersion to the potassium permanganate solution, stirring for 5-10 minutes, and gradually adding a boric acid solution dropwise to the potassium permanganate solution during the stirring process, and standing for 20-30 minutes after the stirring is completed to obtain a reaction product; wherein the amount of the boric acid solution added accounts for 0.5-1% of the total mass of the potassium permanganate solution; Step 4: Filter the reaction product to obtain a solid, and wash and dry the solid to obtain the carrier.

6. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 5, characterized in that: The activated carbon is spherical activated carbon with a particle size of 1 to 3 mm.

7. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 5, characterized in that: The mass concentration of the boric acid solution is 2-4%.

8. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 1, characterized in that: The components of the microbial stimulant include, by weight: 15-25 parts of potassium nitrate, 3-6 parts of ammonium sulfate, 15-25 parts of magnesium sulfate, 10-15 parts of potassium phosphate, 20-30 parts of rhamnolipid, and 15-20 parts of hydrogen peroxide.

9. The in-situ microbial remediation method for organic underground contaminated water and soil according to claim 8, characterized in that: The initial addition amount of the microbial stimulant in the groundwater is 100-200 g / L, and the subsequent addition amount is increased by 5-10 g / L each time compared with the previous addition.

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