Microbial remediation method for degradation-resistant petroleum hydrocarbon pollutants in soil
By combining electrochemical treatment with microbial remediation, a suitable growth environment and control parameters are provided, which solves the problems of low degradation efficiency and long cycle of recalcitrant petroleum hydrocarbon pollutants in soil, and achieves efficient and thorough pollutant degradation and soil remediation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XI'AN PETROLEUM UNIVERSITY
- Filing Date
- 2026-04-10
- Publication Date
- 2026-05-12
AI Technical Summary
In existing technologies, the microbial remediation of recalcitrant petroleum hydrocarbon pollutants in soil suffers from problems such as low degradation efficiency, long cycle, easily inhibited microbial activity, difficulty in colonization, and potential damage to soil structure and secondary pollution.
Combining electrochemical treatment with microbial remediation, electrochemical activation is achieved by inserting cathodes and anodes into the soil, applying compound microbial agents and nutrients, and using intermittent electrochemical assistance to provide a suitable growth environment, regulate electrochemical parameters, and avoid damage to microorganisms by high-intensity electric fields.
It achieves efficient and complete degradation of recalcitrant petroleum hydrocarbon pollutants, shortens the remediation cycle by 30%-50%, ensures stable microbial activity, and avoids the generation of toxic intermediate products and secondary pollution.
Smart Images
Figure CN122007143A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of soil remediation methods, and in particular to a microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil. Background Technology
[0002] With the continuous expansion of oil extraction, transportation, processing, and application, problems such as oil spills and spilled oil pollution have become increasingly prominent, leading to a large influx of recalcitrant petroleum hydrocarbon pollutants (such as polycyclic aromatic hydrocarbons, long-chain alkanes, and aromatic hydrocarbon derivatives) into the soil environment. These pollutants are characterized by their persistence, high hydrophobicity, high biotoxicity, and difficulty in natural degradation. They easily adsorb onto the surface of soil particles and accumulate in the soil over a long period, not only damaging soil aggregate structure, reducing soil fertility, and inhibiting the activity of soil microbial communities, but also threatening plant and animal growth and human health through bioaccumulation in the food chain.
[0003] Currently, remediation technologies for recalcitrant petroleum hydrocarbon pollutants in soil mainly fall into three categories: physical remediation, chemical remediation, and microbial remediation. Among them, physical remediation (such as soil washing and thermal desorption) suffers from drawbacks such as high cost, high energy consumption, and easy damage to soil structure and secondary pollution; while chemical remediation (such as oxidant oxidation) can rapidly degrade some pollutants, the use of chemical reagents can easily disrupt the soil microecological balance, and its degradation effect on recalcitrant components such as high-ring polycyclic aromatic hydrocarbons is limited, and it is easy to generate toxic intermediate products.
[0004] Microbial remediation has become the mainstream technology for remediating petroleum hydrocarbon pollution in soil due to its advantages such as being environmentally friendly, low-cost, easy to operate, capable of in-situ remediation, and able to completely mineralize pollutants into harmless substances. However, single-microbial remediation still has significant shortcomings: the chemical structure of recalcitrant petroleum hydrocarbon pollutants is stable, resulting in low degradation efficiency and long cycles for microorganisms. Nutrient deficiency and poor aeration in the soil can inhibit the activity of degrading bacteria and hinder colonization. Furthermore, the low electrical conductivity of some contaminated soils limits the probability of contact between microorganisms and pollutants, further restricting the remediation effect. Therefore, developing a microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil has significant practical significance and application value. Summary of the Invention
[0005] The purpose of this invention is to provide a microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil. This method provides a suitable growth, metabolism, and colonization environment for compound microbial agents. At the same time, it precisely controls the electrochemical treatment parameters to avoid the damage of high-intensity electric fields to microbial activity and avoids the shortcomings of low degradation efficiency and long cycle of single microbial remediation, thereby achieving efficient and thorough degradation of recalcitrant petroleum hydrocarbon pollutants.
[0006] To achieve the above objectives, the present invention provides a microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil, comprising the following steps: S1. Till the soil contaminated with recalcitrant petroleum hydrocarbon pollutants and add biochar. Bury aeration wells and extraction wells in the contaminated soil to adjust the pH of the soil to 6-8. S2. Insert cathodes and anodes in a staggered, quincunx pattern into the soil, and perform electrochemical treatment at a constant potential. The potential is controlled at 2.0-3.5V, and the electrochemical treatment time is 12-24h to perform preliminary electrochemical activation of recalcitrant petroleum hydrocarbon pollutants. S3. Apply slow-release fertilizer, growth substrate, modified straw and biosurfactant to the soil, and then apply compound microbial agent evenly. S4. Regularly spray water into the soil and regularly aerate it through aeration wells and extraction wells. During the bioremediation phase, apply a DC voltage of 1.0-2.5V intermittently for electrochemical assistance, each time for 2-6 hours. S5. Regularly sample and monitor the composition of the soil. Based on the monitoring and analysis results, supplement with slow-release fertilizers, biosurfactants, or compound microbial agents. The remediation process is completed after the remediation endpoint is reached.
[0007] Preferably, in S1, the aeration wells and the extraction wells are arranged in a staggered, quincunx pattern, with a spacing of 3-5m between them.
[0008] Preferably, in S2, the anode is an inert electrode, the cathode is a stainless steel electrode or a graphite electrode, the distance between the cathode and the anode is 2-3m, the bottom of the cathode and the anode are inserted into the soil 40-60cm, and the top of the cathode and the anode are 10-15cm above the soil surface.
[0009] Preferably, in S2, when the soil electrical conductivity is less than 1 mS / cm, a 0.1-0.5 mol / L sodium sulfate solution is sprayed into the soil.
[0010] Preferably, in S3, the slow-release fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate, and potassium chloride in a mass ratio of N:P:K of (8-12):(8-12):1.
[0011] Preferably, in S3, the growth substrate includes one or more of glucose, sucrose, sodium citrate, or straw leachate.
[0012] Preferably, in S3, the compound microbial agent includes at least two of Bacillus, Pseudomonas, Rhodococcus, Nocardia, and Microbacterium.
[0013] Preferably, in S3, the biosurfactant is one or more of rhamnolipid and sophorolipid.
[0014] Preferably, in S4, the electrochemically assisted current density is 5-10 mA / cm². 2 Intermittent treatment is administered 2-3 times per day.
[0015] Preferably, in S5, the remediation endpoint is that the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil is lower than the target risk control standard value, and the soil activity is restored to more than 80% of that of uncontaminated soil.
[0016] Therefore, the present invention employs the above-mentioned microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil, and its beneficial effects are as follows: 1. The remediation method provided by this invention combines electrochemical treatment with microbial remediation. Through preliminary electrochemical activation in stage S2, the stable carbon-hydrogen covalent bonds of recalcitrant petroleum hydrocarbons are broken, reducing their biotoxicity and improving their bioavailability, creating favorable conditions for subsequent microbial degradation. Then, through intermittent electrochemical assistance in stage S4, microbial metabolism is continuously assisted, avoiding the shortcomings of low efficiency and long cycle in single-microbial remediation. This achieves efficient and thorough degradation of recalcitrant petroleum hydrocarbon pollutants, shortening the remediation cycle by 30%-50%. 2. The repair method provided by this invention provides a suitable environment for the growth, metabolism and colonization of compound microbial agents. At the same time, it precisely controls the electrochemical treatment parameters to avoid the damage of high-intensity electric fields to microbial activity, ensuring that the degrading bacteria can colonize stably and metabolize efficiently, effectively solving the problems of easily inhibited microbial activity and difficult colonization in the prior art. 3. The repair method provided by this invention is simple to operate, cost is controllable, no toxic or harmful intermediate products are generated during the entire repair process, and waste gas and wastewater can be treated by existing mature technologies, effectively avoiding secondary pollution.
[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0018] Figure 1 These are images showing the remediation effects of the remediation methods in Examples 1-3 and Comparative Examples 1-2 of this invention on petroleum hydrocarbon pollutants at different times. Detailed Implementation
[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.
[0020] This invention provides a microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil, comprising the following steps: S1. For soil contaminated with recalcitrant petroleum hydrocarbons, tillage is carried out and biochar is added. Aeration wells and extraction wells are buried in the contaminated soil to adjust the soil pH to 6-8. Tillage can break up soil compaction, improve soil permeability, and promote oxygen transfer. Biochar can adsorb pollutants, improve soil structure, and provide an attachment carrier for microorganisms. The layout of aeration wells and extraction wells can ensure soil aeration, provide oxygen for aerobic microbial metabolism and electrochemical oxidation, and at the same time remove volatile pollutants. Adjusting the pH to 6-8 matches the optimal growth environment for microorganisms and avoids abnormal pH that inhibits microbial activity.
[0021] S2. Insert cathodes and anodes in a staggered, quincunx pattern with the aeration wells into the soil and perform electrochemical treatment at a constant potential, with the potential controlled at 2.0-3.5V and the treatment time at 12-24h. This provides preliminary electrochemical activation of recalcitrant petroleum hydrocarbon pollutants. Through constant potential electrochemical treatment, the strong oxidizing substances such as hydroxyl radicals generated at the anode break the carbon-hydrogen covalent bonds of recalcitrant petroleum hydrocarbons, converting high-cyclic, long-chain petroleum hydrocarbons into low-cyclic, short-chain, easily degradable components, thereby achieving preliminary activation, reducing their biotoxicity, and simultaneously improving the water solubility of the pollutants, facilitating subsequent microbial contact degradation.
[0022] S3. Apply slow-release nutrient fertilizer, growth substrate, modified straw, and biosurfactant to the soil, followed by uniform application of compound microbial inoculant. The slow-release nutrient fertilizer provides microorganisms with continuous N, P, and K nutrients to meet their metabolic needs. The growth substrate provides microorganisms with additional carbon and energy, promoting their proliferation. The modified straw further improves soil permeability and adsorbs pollutants, while also serving as a carrier for microbial attachment. The biosurfactant solubilizes hydrophobic petroleum hydrocarbons on the surface of soil particles, enhancing their bioavailability. The compound microbial inoculant leverages the synergistic effects of different strains to achieve comprehensive degradation of different types of petroleum hydrocarbon components, improving the thoroughness of degradation.
[0023] S4. Regularly spray water into the soil and regularly aerate through aeration and extraction wells. During the bioremediation phase, apply a DC voltage of 1.0-2.5V intermittently for electrochemical assistance, each time for 2-6 hours. Spraying water can maintain suitable soil moisture content, ensuring the normal progress of microbial metabolism and electrochemical reactions. Regular aeration can continuously replenish oxygen and remove metabolic products and volatile pollutants. The intermittent application of 1.0-2.5V DC voltage can gently assist microbial metabolism, promote the desorption of pollutants and enhance microbial enzyme activity, while avoiding the inhibition of microbial activity by high-intensity electric fields, thus achieving continuous synergy between electrochemical and microbial remediation.
[0024] S5. Regularly sample and analyze soil components. Based on the monitoring and analysis results, supplement with slow-release nutrient fertilizers, biosurfactants, or compound microbial agents. The remediation process is complete once the remediation endpoint is reached. Regular monitoring allows for real-time tracking of the remediation progress, dynamic supplementation of slow-release nutrient fertilizers, biosurfactants, or compound microbial agents, ensuring stable microbial activity, sufficient nutrition, and continuous degradation of pollutants, thus avoiding bottlenecks in the remediation process. Clearly defining the remediation endpoint criteria ensures that the remediation effect meets the standards and avoids over-remediation or incomplete remediation.
[0025] In some embodiments of the present invention, in step S1, the aeration wells and extraction wells are arranged in a staggered, quincunx pattern, with a spacing of 3-5 m between them. This ensures uniform aeration of the contaminated soil area, guarantees even oxygen distribution in the soil, and prevents localized oxygen deficiency that could inhibit aerobic microbial activity and reduce electrochemical oxidation efficiency.
[0026] In some embodiments of the present invention, in step S2, the anode is an inert electrode, such as a titanium-based IrO2 electrode or a graphite electrode. This avoids the dissolution of metal ions during electrochemical treatment, preventing secondary soil pollution, while ensuring the anode can stably generate strong oxidizing substances, achieving efficient activation of pollutants. The cathode is a stainless steel electrode or a graphite electrode, which has the advantages of good conductivity, low cost, and strong stability, ensuring the normal progress of the cathode reaction. The distance between the cathode and anode is 2-3m, ensuring uniform electric field coverage of the polluted area and avoiding differences in activation effect caused by uneven electric field strength. The bottoms of the cathode and anode are inserted into the soil 40-60cm, matching the depth of the polluted soil layer and ensuring effective activation of pollutants in deep soil layers. The tops of the cathode and anode are 10-15cm above the soil surface, facilitating electrode fixation and insulation, avoiding the risk of electric shock, and also facilitating subsequent electrode maintenance and replacement.
[0027] In some embodiments of the present invention, in step S2, when the soil electrical conductivity is below 1 mS / cm, a 0.1-0.5 mol / L sodium sulfate solution is sprayed into the soil. Sodium sulfate is an inert electrolyte; spraying it can significantly increase the soil electrical conductivity without producing toxic or harmful products, and it does not affect subsequent microbial metabolism, ensuring that the electrochemical treatment can proceed stably and efficiently.
[0028] In some embodiments of the present invention, in step S3, the slow-release fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate, and potassium chloride in a mass ratio of N:P:K of (8-12):(8-12):1. The coated urea and slow-release potassium dihydrogen phosphate have slow-release properties, enabling continuous release of nutrients and avoiding nutrient loss, soil eutrophication, or insufficient nutrient supply caused by single application.
[0029] In some embodiments of the present invention, in step S3, the growth substrate includes one or more of glucose, sucrose, sodium citrate, or straw leachate. Glucose, sucrose, and sodium citrate are all small-molecule carbon sources and energy substances that are easily utilized by microorganisms. Straw leachate contains abundant organic matter and small-molecule nutrients, which can be rapidly absorbed and utilized by microorganisms, promoting rapid proliferation and enhanced activity of microorganisms. It does not inhibit the soil microenvironment and microbial metabolism, and can also help increase the soil organic matter content.
[0030] In some embodiments of the present invention, in step S3, the compound microbial agent includes at least two of Bacillus, Pseudomonas, Rhodococcus, Nocardia, and Microbe. Pseudomonas and Rhodococcus have strong degradation capabilities for long-chain alkanes and aromatic hydrocarbons; Bacillus is highly tolerant and adaptable to complex soil environments; and Nocardia and Microbe have good degradation effects on polycyclic aromatic hydrocarbons. The combined use of strains can leverage the synergistic effect between strains, achieving comprehensive degradation of different types of recalcitrant petroleum hydrocarbon components, avoiding the shortcomings of single strains having a narrow degradation range and low degradation efficiency.
[0031] In some embodiments of the present invention, in S3, the biosurfactant is one or more of rhamnolipid and sophorolipid. It possesses excellent solubilizing and emulsifying properties, and can dissolve hydrophobic, recalcitrant petroleum hydrocarbons on the surface of soil particles into aqueous micelles, significantly improving the bioavailability of pollutants and facilitating microbial contact degradation.
[0032] In some embodiments of the present invention, in S4, the electrochemically assisted current density is 5-10 mA / cm². 2 Intermittent treatment is performed 2-3 times daily. During the main stage of bioremediation, the microorganisms are in a highly efficient metabolic state. At this time, the core purpose of electrochemical assistance is to gently enhance the microbial degradation efficiency, rather than forcefully oxidize pollutants. This avoids damaging microbial activity with high-intensity electric fields, while simultaneously promoting pollutant desorption and enhancing microbial enzyme activity through gentle electrochemical action.
[0033] In some embodiments of the present invention, in step S5, the remediation endpoint is defined as the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil falling below the target risk control standard value, and the soil activity recovering to more than 80% of that of uncontaminated soil. A total concentration of recalcitrant petroleum hydrocarbons in the soil falling below the target risk control standard value ensures effective control of soil pollution and avoids subsequent environmental risks. A soil activity recovery to more than 80% of that of uncontaminated soil ensures the basic restoration of soil microecological functions, facilitating subsequent soil reuse and further restoration of ecological functions.
[0034] Example 1 S1. Till the soil contaminated with recalcitrant petroleum hydrocarbons and add biochar. Bury aeration wells and extraction wells in the contaminated soil. The aeration wells and extraction wells are arranged in a staggered quincunx pattern with a spacing of 3m between them. Adjust the pH of the soil to 6-8.
[0035] S2. Insert cathodes and anodes in a staggered, quincunx pattern into the soil, interspersed with the aeration wells. The anodes are inert electrodes, and the cathodes are stainless steel or graphite electrodes. The distance between the cathodes and anodes is 2 m. The bottoms of the cathodes and anodes are inserted 40 cm into the soil, and the tops are 10 cm above the soil surface. Electrochemical treatment is performed at a constant potential, controlled at 2.0 V, for 24 h, to preliminarily electrochemically activate recalcitrant petroleum hydrocarbon pollutants. When the soil conductivity is below 1 mS / cm, spray a 0.1 mol / L sodium sulfate solution into the soil.
[0036] S3. Apply slow-release nutrient fertilizer to the soil. The slow-release nutrient fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate, and potassium chloride in a mass ratio of N:P:K of 10:10:1. Add the growth substrate (a mixture of glucose, sodium citrate, and straw leachate in a mass ratio of 1:1:1), modified straw, and biosurfactants (rhamnolipids and sophorolipids). Then, evenly apply a compound microbial inoculant, a mixture of Pseudomonas aeruginosa, Microbacterium oxysporum, and Bacillus in a mass ratio of 1:1:2.
[0037] S4. Regularly spray water into the soil and periodically aerate the soil through aeration and extraction wells. During the bioremediation phase, apply a 1.0V DC voltage intermittently for electrochemical assistance, each time for 5 hours. The current density for electrochemical assistance is 8mA / cm². 2 Intermittent treatment was performed 4 days a week, and electrochemical assistance was performed twice a day.
[0038] S5. Regularly sample and monitor the composition of the soil. Based on the monitoring and analysis results, supplement with slow-release nutrient fertilizers, biosurfactants, or compound microbial agents. The remediation process is completed after the remediation endpoint is reached. The remediation endpoint is defined as the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil being lower than the target risk control standard value, and the soil activity being restored to more than 80% of that of uncontaminated soil.
[0039] Example 2 S1. Till the soil contaminated with recalcitrant petroleum hydrocarbons and add biochar. Bury aeration wells and extraction wells in the contaminated soil. The aeration wells and extraction wells are arranged in a staggered quincunx pattern with a spacing of 5m between them. Adjust the pH of the soil to 6-8.
[0040] S2. Insert cathodes and anodes in a staggered, quincunx pattern into the soil, interspersed with the aeration wells. The anodes are inert electrodes, and the cathodes are stainless steel or graphite electrodes. The distance between the cathodes and anodes is 3m, with the bottoms of the cathodes and anodes inserted 60cm into the soil and the tops of the cathodes and anodes 15cm above the soil surface. Perform electrochemical treatment at a constant potential, controlling the potential at 3.5V, for 12 hours to preliminarily electrochemically activate recalcitrant petroleum hydrocarbon pollutants. When the soil conductivity is below 1mS / cm, spray the soil with a 0.1mol / L sodium sulfate solution.
[0041] S3. Apply slow-release nutrient fertilizer to the soil. The slow-release nutrient fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate, and potassium chloride in a mass ratio of N:P:K of 10:12:1. Add the growth substrate (sodium citrate and straw leachate mixed in a 1:1 mass ratio), modified straw, and biosurfactants (rhamnolipid and sophorolipid). Then, evenly apply a compound microbial inoculant, a mixture of Pseudomonas aeruginosa, Microbacterium oxysporum, and Bacillus in a mass ratio of 1:1:2.
[0042] S4. Regularly spray water into the soil and periodically aerate the soil through aeration and extraction wells. During the bioremediation phase, apply a 2.5V DC voltage intermittently for electrochemical assistance, each time for 4 hours. The current density for electrochemical assistance is 6mA / cm². 2 Intermittent treatment was performed 3 days a week, and electrochemical assistance was performed 3 times a day.
[0043] S5. Regularly sample and monitor the composition of the soil. Based on the monitoring and analysis results, supplement with slow-release nutrient fertilizers, biosurfactants, or compound microbial agents. The remediation process is completed after the remediation endpoint is reached. The remediation endpoint is defined as the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil being lower than the target risk control standard value, and the soil activity being restored to more than 80% of that of uncontaminated soil.
[0044] Example 3 S1. Till the soil contaminated with recalcitrant petroleum hydrocarbon pollutants and add biochar. Bury aeration wells and extraction wells in the contaminated soil. The aeration wells and extraction wells are arranged in a staggered quincunx pattern with a spacing of 4m between them. Adjust the pH of the soil to 6-8.
[0045] S2. Insert cathodes and anodes in a staggered, quincunx pattern into the soil, interspersed with the aeration wells. The anodes are inert electrodes, and the cathodes are stainless steel or graphite electrodes. The distance between the cathodes and anodes is 2.5 m. The bottoms of the cathodes and anodes are inserted 50 cm into the soil, and the tops are 12 cm above the soil surface. Electrochemical treatment is performed at a constant potential, controlled at 2.5 V, for 18 hours to preliminarily electrochemically activate recalcitrant petroleum hydrocarbon pollutants. When the soil conductivity is below 1 mS / cm, spray a 0.1 mol / L sodium sulfate solution into the soil.
[0046] S3. Apply slow-release nutrient fertilizer to the soil. The slow-release nutrient fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate, and potassium chloride in a mass ratio of N:P:K of 11:10:1. Add the growth substrate (a mixture of glucose and straw leachate in a 1:1 mass ratio), modified straw, and biosurfactants (rhamnolipids and sophorolipids). Then, evenly apply a compound microbial inoculant, a mixture of Pseudomonas aeruginosa, Microbacterium oxysporum, and Bacillus in a mass ratio of 1:1:2.
[0047] S4. Regularly spray water into the soil and periodically aerate the soil through aeration and extraction wells. During the bioremediation phase, apply a 2.0V DC voltage intermittently for electrochemical assistance, each time for 6 hours. The current density for electrochemical assistance is 6mA / cm². 2 Intermittent treatment was performed 3 days a week, and electrochemical assistance was performed 3 times a day.
[0048] S5. Regularly sample and monitor the composition of the soil. Based on the monitoring and analysis results, supplement with slow-release nutrient fertilizers, biosurfactants, or compound microbial agents. The remediation process is completed after the remediation endpoint is reached. The remediation endpoint is defined as the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil being lower than the target risk control standard value, and the soil activity being restored to more than 80% of that of uncontaminated soil.
[0049] Comparative Example 1 The difference between this comparative example and Example 2 is that step S3 was not performed; all other steps are the same as in Example 2, for treating recalcitrant petroleum hydrocarbon pollutants in the soil.
[0050] Comparative Example 2 The difference between this comparative example and Example 2 is that the electrochemical assistance in steps S2 and S4 was not performed, while the rest of the steps were the same as in Example 2, for treating recalcitrant petroleum hydrocarbon pollutants in the soil.
[0051] Performance testing Soil was treated using the methods described in Examples 1-3 and Comparative Examples 1-2, respectively, and the total petroleum hydrocarbon content in the soil was measured at 2 weeks, 6 months, and 9 months after remediation. Figure 1 As shown, after 6 months and 9 months of remediation, the degradation rate of petroleum hydrocarbon pollutants by the remediation methods in Examples 1-3 is significantly better than that of the remediation methods in Comparative Examples 1-2. This demonstrates that the remediation method provided by this invention combines electrochemical treatment with microbial remediation, avoiding the shortcomings of low degradation efficiency and long cycle associated with single microbial remediation, achieving efficient and thorough degradation of recalcitrant petroleum hydrocarbon pollutants, and significantly shortening the remediation cycle.
[0052] Therefore, the present invention employs the above-mentioned microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil, providing a suitable growth, metabolism, and colonization environment for compound microbial agents. At the same time, it precisely controls the electrochemical treatment parameters to avoid the damage of high-intensity electric fields to microbial activity, and avoids the shortcomings of low degradation efficiency and long cycle of single microbial remediation, thereby achieving efficient and thorough degradation of recalcitrant petroleum hydrocarbon pollutants.
[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil, characterized in that: Includes the following steps: S1. Till the soil contaminated with recalcitrant petroleum hydrocarbon pollutants and add biochar. Bury aeration wells and extraction wells in the contaminated soil to adjust the pH of the soil to 6-8. S2. Insert cathodes and anodes in a staggered, quincunx pattern into the soil, and perform electrochemical treatment at a constant potential. The potential is controlled at 2.0-3.5V, and the electrochemical treatment time is 12-24h to perform preliminary electrochemical activation of recalcitrant petroleum hydrocarbon pollutants. S3. Apply slow-release fertilizer, growth substrate, modified straw and biosurfactant to the soil, and then apply compound microbial agent evenly. S4. Regularly spray water into the soil and regularly aerate it through aeration wells and extraction wells. During the bioremediation phase, apply a DC voltage of 1.0-2.5V intermittently for electrochemical assistance, each time for 2-6 hours. S5. Regularly sample and monitor the composition of the soil. Based on the monitoring and analysis results, supplement with slow-release fertilizers, biosurfactants, or compound microbial agents. The remediation process is completed after the remediation endpoint is reached.
2. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S1, aeration wells and extraction wells are arranged in a staggered, quincunx pattern, with a spacing of 3-5m between them.
3. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S2, the anode is an inert electrode, and the cathode is a stainless steel electrode or a graphite electrode. The distance between the cathode and the anode is 2-3m. The bottom of the cathode and the anode are inserted into the soil 40-60cm, and the top of the cathode and the anode are 10-15cm above the soil surface.
4. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S2, when the soil electrical conductivity is below 1 mS / cm, spray the soil with a 0.1-0.5 mol / L sodium sulfate solution.
5. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S3, the slow-release fertilizer is a mixture of coated urea, slow-release potassium dihydrogen phosphate and potassium chloride in a mass ratio of N:P:K of (8-12):(8-12):
1.
6. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S3, the growth substrate includes one or more of glucose, sucrose, sodium citrate, or straw leachate.
7. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S3, the compound microbial agent includes at least two of Bacillus, Pseudomonas, Rhodococcus, Nocardia, and Microbacterium.
8. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S3, the biosurfactant is one or more of rhamnolipin and sophorolipid.
9. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S4, the electrochemically assisted current density is 5-10 mA / cm². 2 Intermittent treatment is administered 2-3 times per day.
10. The microbial remediation method for recalcitrant petroleum hydrocarbon pollutants in soil according to claim 1, characterized in that: In S5, the remediation endpoint is that the total concentration of recalcitrant petroleum hydrocarbon pollutants in the soil is lower than the target risk control standard value, and the soil activity is restored to more than 80% of that of uncontaminated soil.