CN110280582B - Method for restoring organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms - Google Patents
Method for restoring organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms Download PDFInfo
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Abstract
The invention discloses a method for restoring organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms. The invention firstly utilizes the strong reduction action of micron zero-valent iron to remove chloro groups of organochlorine pesticides in soil, then adds biological carbon source, electron donor, nitrogen and phosphorus nutrition to promote the growth, reproduction and metabolism of indigenous microorganisms in soil to degrade organochlorine pesticides, and adds sulfate reduction inhibitor and methanogenesis inhibitor to inhibit the consumption of electrons. Using Fe0Fe produced by reduction2+And Fe3+The growth of the indigenous microorganisms is promoted by the enzymatic action of the indigenous microorganisms, and meanwhile, the organic acid secreted by the metabolic activity of the indigenous microorganisms influences the reductive dechlorination process of the organochlorine pesticide on the soil colloid interface, so that the pH value of the soil is adjusted, the etching of zero-valent iron is accelerated, and the reductive dechlorination of the zero-valent iron is promoted. Compared with the restoration method for restoring the organochlorine pesticide polluted soil by only utilizing zero-valent iron reduction or utilizing indigenous microorganisms, the method has the advantages of high restoration efficiency, short construction period, thorough restoration, no secondary pollution and the like.
Description
Technical Field
The invention belongs to the technical field of soil pollution remediation, and particularly relates to a method for remediating organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms.
Background
Organochlorine pesticides are a typical class of environmental pollutants, and they are generally characterized by high chemical stability (long half-life), lipophilic hydrophobicity, bioaccumulation, biotoxicity, and the like. The pollutants are mainly from pesticide production waste raw materials, and run, overflow, drip, leakage and the like in the production process of chemical pesticides. Among 85 pollution projects published by soil pollution risk control standards (trial) for soil environment quality construction land in China (GB36600-2018), organic chlorine accounts for 46; in other agricultural land soil pollution risk screening pollutant projects published by 'soil environment quality agricultural land soil pollution risk control standards (trial)' (GB15618-2018) in China, risk screening values of the total amount of sixty six and the total amount of dichlorodiphenyl trichloroethane are determined. Research shows that the organochlorine pesticide has strong carcinogenic, teratogenic and mutagenic effects on organisms, and most organochlorine pesticides belong to endocrine disruptors or potential endocrine disruptors. The organochlorine pesticide is difficult to naturally degrade and can stably exist in the environment for a long time, and if the organochlorine pesticide cannot be effectively repaired, the organochlorine pesticide can seriously threaten the health and even survival of human beings.
At present, the remediation methods for the soil polluted by the organochlorine pesticide mainly comprise a physical method, a thermal desorption method, advanced oxidation, chemical reduction, a biological method and the like. The physical method mainly transfers and buries the organochlorine pesticide polluted soil to the underground by means of soil dressing, landfill and the like, so that the pollutants cannot be completely eliminated, and the environmental risk still exists. The thermal desorption is a restoration method for desorbing the organochlorine pesticide in the soil and collecting the desorbed organochlorine pesticide by heating the polluted soil in situ or ex situ and raising the temperature to be higher than the boiling point of the pollutant; the method has good restoration effect and thorough restoration, but the capital investment of thermal desorption equipment is large, the operation energy consumption is high, the restoration cost is large, and the method is difficult to implement in some small-sized organochlorine pesticide polluted sites. The advanced oxidation method is a restoration method for oxidizing and degrading pollutants by adding an oxidant into soil; however, the efficiency of directly adopting an advanced oxidation method for degrading the organochlorine pesticide is not high because the chlorine-containing group on the organochlorine pesticide has strong electron-withdrawing capability. The chemical reduction method is a restoration method for removing chlorine-containing groups in organic chlorine pesticides by adding a reducing agent into soil and performing chemical reduction. The zero-valent iron is an active substance with stronger reduction property, can reduce the organochlorine pesticide, reduces the biotoxicity of the soil polluted by the organochlorine pesticide, and generates an intermediate product with higher biodegradability; and when zero-valent iron reduces pollutants, the iron oxide can be oxidized into iron oxide with larger specific surface area, the iron oxide also has certain reduction activity under anaerobic conditions, and has stronger adsorption effect on organic pollutants, and the organic chlorine pesticide and the reduction intermediate product thereof adsorbed on the surface of the iron oxide can be further decomposed. Although chemical reduction has a good reductive dechlorination effect on organochlorine pesticides, chlorine-containing groups in the organochlorine pesticides can be removed, and the biotoxicity of soil is effectively reduced, dechlorinated intermediates still remain in soil, and remediation is not complete. The biological method refers to a restoration method for degrading organochlorine pesticides by microorganisms; under the aerobic condition, the microorganism takes the organochlorine pesticide as an electron donor, transfers electrons to an electron acceptor such as oxygen and the like, and decomposes the organochlorine pesticide into carbon dioxide, water and chlorine; under anaerobic conditions, microorganisms start a reduction process of replacing chlorine with hydrogen by taking some food sources as electron donors and organic chlorine pesticides as electron acceptors, so that chlorine-containing groups in the organic chlorine pesticides are gradually removed, and substances which are harmless to the environment, such as olefin, alkane and the like are generated. However, the biological method for repairing the soil polluted by the organochlorine pesticide has a certain problem, and under the anaerobic condition, the reaction rate is reduced along with the replacement of the chlorine-containing groups in the organochlorine pesticide by hydrogen one by one, and the low-chlorinated intermediate product is accumulated in the environment, so that the harm to the environment is increased or decreased; under aerobic conditions, only low-chlorinated organic pollutants can be directly metabolized and decomposed into water and carbon dioxide by microorganisms as electron donors, polychlorinated organic pollutants can be gradually degraded only through microbial co-metabolism, but the microbial co-metabolism consumes a large amount of electron donors and has extremely slow metabolic rate.
Based on the method, the invention combines chemical reduction and biological repair, has high selective reduction activity and is environment-friendlyThe zero-valent iron is used for reductive dechlorination of the organochlorine pesticide, and the reductive degradation and conversion of the organochlorine pesticide in the soil are accelerated by fully utilizing the reductive characteristics of the zero-valent iron and the oxide thereof; meanwhile, zero-valent iron reduces Fe generated by oxidizing organochlorine pesticide2+And Fe3+Has enzymatic effect on the production of indigenous microorganisms, and can promote the growth of indigenous microorganisms. The method of activating indigenous microorganisms without exogenous biological addition and secondary pollution risk is selected for thoroughly degrading the dechlorinated low-chlorinated organic pollutants, and the indigenous microorganisms are utilized to decompose the organic pollutants into carbon dioxide and water; in addition, organic acid secreted by the metabolism activity of indigenous microorganisms in the soil can directly or indirectly influence the reduction dechlorination process of organochlorine pesticides on the soil colloid interface, and meanwhile, the organic acid can also effectively adjust the pH value of the soil, accelerate the etching of zero-valent iron and promote the reduction dechlorination effect of the zero-valent iron. Therefore, the method utilizes the outstanding reductive dechlorination of zero-valent iron and the oxide thereof, combines the metabolism of indigenous microorganisms and the activity of organic acid generated by metabolism, fully exerts the advantages of chemical reduction and the degradation of organochlorine pesticides by the indigenous microorganisms, combines the advantages of the chemical reduction and the organochlorine pesticides together, and establishes an economic, efficient, clean and green remediation method for soil polluted by organochlorine pesticides.
Disclosure of Invention
The invention aims to break through the technical bottleneck in the field of soil remediation, solve the problem that organochlorine pesticide-contaminated soil is difficult to be remediated to reach the standard by a chemical method, and provide a method for remediateing organochlorine-contaminated soil by zero-valent iron reduction combined with indigenous microorganisms. On the basis of removing chlorinated groups of organochlorine pesticides in soil by using the reduction action of micron zero-valent iron and reducing the biotoxicity of the soil, adding a biological carbon source, an electron donor and nitrogen and phosphorus nutrition to promote the growth, reproduction and metabolism of indigenous microorganisms in the soil to degrade the organochlorine pesticides, adding a sulfate reduction inhibitor to inhibit the consumption of sulfate in the soil to electrons, and adding a methanogenesis inhibitor to inhibit the consumption of methane in the process of metabolizing hydrocarbons to generate methane by methane bacteria. Fe generated by oxidizing zero-valent iron reduced organic chlorine pesticide2+And Fe3+Has enzymatic effect on indigenous microorganisms and can promote their productionGrowth of indigenous microorganisms. Indigenous microorganisms can completely degrade dechlorinated low-chlorinated organic pollutants into carbon dioxide and water; meanwhile, organic acid secreted by the metabolic activity of indigenous microorganisms can directly or indirectly influence the reductive dechlorination process of the organochlorine pesticide on the soil colloid interface, and the organic acid can also effectively adjust the pH value of the soil, accelerate the etching of zero-valent iron and promote the reductive dechlorination of the zero-valent iron. Compared with the restoration method for restoring the organochlorine pesticide polluted soil by only utilizing zero-valent iron reduction or utilizing indigenous microorganisms, the method has the advantages of high restoration efficiency, short construction period, less investment, thorough restoration, no secondary pollution and the like.
The invention adopts the following specific technical scheme:
a method for restoring organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms comprises the following steps:
(1) the organochlorine pesticide polluted soil to be repaired is dug to the ground surface and is transported to a closed disposal greenhouse;
(2) screening and crushing the organochlorine pesticide contaminated soil to form fine-particle soil with the particle size of less than 50 mm;
(3) stacking the screened and crushed fine particle organochlorine pesticide contaminated soil into a soil pile, adding micron zero-valent iron powder into the soil pile, and turning over the soil pile by using a turner to uniformly mix; in the turning and throwing process, a biological carbon source, an electron donor, a sulfate reduction inhibitor, a methane production inhibitor, a nitrogen fertilizer and a phosphate fertilizer are sequentially sprayed on the soil stack, so that the sprayed reagent is fully mixed with the polluted soil;
(4) covering a waterproof cloth on the surface layer of a soil stack which is uniformly mixed with micron zero-valent iron, a biological carbon source, an electron donor, a sulfate reduction inhibitor, a methanogenesis inhibitor, a nitrogen fertilizer and a phosphate fertilizer, creating an anaerobic reducing condition, standing and maintaining, keeping the water content of soil in a basically saturated state in the maintenance process, and finally realizing the complete degradation of the organochlorine pesticide by utilizing the reduction dechlorination of the micron zero-valent iron and the degradation of indigenous microorganisms.
Preferably, the closed treatment greenhouse in the step (1) is provided with an air draft device and a tail gas treatment device, and the ventilation frequency is 2-6 h/time.
Preferably, the soil pile in the step (3) is a trapezoidal long-strip pile, the width of the lower bottom is 4-8 m, the width of the upper bottom is 2-5 m, the length is 30-50 m, the height is 1-2 m, and the distance between every two adjacent piles is 1.5-2 m.
Preferably, the particle size of the micron zero-valent iron adopted in the step (3) is less than 74 microns (200 meshes), the mass proportion of the iron powder with reducibility is more than or equal to 80%, and the addition mass ratio of the micron zero-valent iron powder in the soil pile is 1.0-3.0%. The adding mass ratio of the micron zero-valent iron powder can be determined according to the content of organochlorine pesticides and other oxidizing substances in soil.
Preferably, the biological carbon source and the electron donor in the step (3) are sodium acetate solution, the sulfate reduction inhibitor is sodium molybdate solution, the methanogenesis inhibitor is BES solution, and the concentration of the sprayed sodium acetate solution, sodium molybdate solution and BES solution is 20-40 mMol/L.
Further, the concentration of the sodium acetate solution, the concentration of the sodium molybdate solution and the concentration of the BES solution sprayed in the step (3) are all 20mMol/L, and the volume ratio of the spraying to the concentration of the sodium acetate solution is as follows: sodium molybdate solution: the BES solution is 1:1:1, and the total amount of the sodium acetate solution, the sodium molybdate solution and the BES solution sprayed is 0.1-1.0 percent of the soil mass. The total amount sprayed can be determined according to the category and concentration of the organochlorine pesticide in the soil.
Preferably, the nitrogen fertilizer sprayed in the step (3) is preferably a sodium nitrate solution or a potassium nitrate solution, and the concentration of the solution is 0.25-0.5 g/L; the phosphate fertilizer is preferably a sodium phosphate solution or a potassium phosphate solution, and the concentration of the solution is 0.1g/L to 0.2 g/L; the volume ratio of the sprayed nitrogen fertilizer to the sprayed phosphorus fertilizer is 1:1, and the total amount of the sprayed nitrogen fertilizer and the sprayed phosphorus fertilizer is 0.1-1.0 percent of the soil mass. The total amount of spraying is determined according to the content of original N, P in the polluted soil, and the indigenous microorganisms in the organochlorine pesticide-polluted soil need to be ensured to stably and rapidly grow and develop to play the bioremediation effect.
Preferably, during the standing maintenance in the step (4), tap water or a sodium acetate solution, a sodium molybdate solution and a BES solution are sprayed to keep the water content of the soil in a basically saturated state.
Further, the saturated water content of the soil is different according to different soil properties, and is generally 30-60%.
Preferably, the standing and curing period in the step (4) is 14 to 28 days.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method is environment-friendly: the invention utilizes the high reducibility, environment friendliness and enzymatic action of zero-valent iron and oxides thereof and the metabolism action of indigenous microorganisms with superiority in soil on the pollution of organochlorine pesticides, utilizes the high reducibility of micron zero-valent iron to remove chloro groups of the organochlorine pesticides in soil, greatly reduces the biotoxicity of soil, adds nutrients such as biological carbon sources, electron donors, nitrogen and phosphorus and the like to promote the growth, reproduction and metabolic degradation of the indigenous microorganisms with superiority in soil and chlorine-containing intermediate products generated by metabolism thereof, and finally realizes the complete degradation of the organochlorine pesticides by using carbon dioxide and water as final products. The introduction of exogenous pollutants and microorganisms is avoided in the repairing process, and the whole repairing process is clean, safe, environment-friendly and free of secondary pollution.
(2) The cost is low: the micron zero-valent iron adopted by the invention can be prepared by ball milling industrial waste materials such as cheap scrap iron, iron wires, iron powder, iron sheets and the like as raw materials, and has wide sources; sodium acetate and nitrogen and phosphorus nutrient substances for promoting the production of indigenous microorganisms are common chemical raw materials and agricultural fertilizers and are also common repairing materials in the field of soil repair. The restoration investment for restoring the organochlorine contaminated soil in an ectopic mode through zero-valent iron reduction and indigenous microorganisms can be controlled within 1000 yuan/ton of soil, and compared with the restoration investment cost of 2000 yuan/ton of soil of the existing common thermal desorption restoration technology, the investment cost is reduced by at least 50%.
(3) The repair objects are wide: most of the organochlorine pesticides in the soil can be effectively degraded.
Drawings
FIG. 1 is a schematic flow chart of the operation of the method for restoring organochlorine contaminated soil by zero-valent iron reduction combined with indigenous microorganisms.
FIG. 2 is a diagram showing the content and degradation rate of hexachloro cyclohexane in soil.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description.
The soil polluted by the organochlorine pesticide to be repaired contains the dominant indigenous anaerobic microorganisms capable of degrading the organochlorine pesticide of a proper type; the dominant indigenous microorganisms in the invention are usually bacteria, fungi, actinomycetes and partial protozoa, and can directly degrade partial organochlorine pesticides and some dechlorinated intermediate products, namely carbon dioxide and water, in an anaerobic environment after the zero-valent iron dechlorination is carried out to reduce the biotoxicity of the soil, thereby realizing the purpose of completely degrading the organochlorine pesticides in the soil. The flow of the repairing method of the invention is shown in figure 1.
The method utilizes the characteristics of strong vitality, adaptability and degradation capability of indigenous microorganisms in the environment polluted by the organochlorine pesticide for a long time, fully utilizes anaerobic indigenous microorganisms in the organochlorine pesticide-polluted soil to create a proper anaerobic environment, adds a biological carbon source, an electron donor and nitrogen and phosphorus nutrition to stimulate the growth and the reproduction of the indigenous microorganisms after reducing and dechlorinating by utilizing zero-valent iron and reduce the biological toxicity of the soil, and degrades the organochlorine pesticide at the same time, thereby greatly shortening the repair time of the organochlorine pesticide-polluted soil, ensuring that the removal rate of the repaired organochlorine pesticide is close to 80 percent, and greatly weakening the harm brought by the organochlorine pesticide-polluted soil.
Example 1
In the embodiment, a site to be repaired polluted by organochlorine pesticide is selected, and site investigation results show that the total concentration of pollutants mainly including hexachloro cyclohexane, α -hexachloro cyclohexane, β -hexachloro cyclohexane and gamma-hexachloro cyclohexane is 500-10000 mg/kg, and the pollution depth is 1m underground to 6m underground.
The method for restoring organochlorine contaminated soil by zero-valent iron reduction and indigenous microorganisms provided by the embodiment is implemented by the following steps:
(1) and (3) excavating the hexasix polluted soil from the underground to the ground surface by using an excavator, and sampling and inspecting the detection result of a third-party detection laboratory to show that the total concentration of the hexasix polluted soil is 1296.495 mg/kg. The sixty-six polluted soil is transferred to a closed greenhouse for temporary storage by a loader, the greenhouse is a steel-structure closed greenhouse, the greenhouse is provided with an air draft device and a tail gas treatment device, and air exchange frequency is 1 time of air exchange every 4 hours.
(2) Sieving out stones in the soil polluted by the organic chlorine pesticide by using a sieving and crushing device, and after crushing large consolidated organic chlorine pesticide polluted soil into fine particle soil with the particle size of less than 50mm, piling the soil into a pile, wherein the pile is a trapezoidal strip pile, the bottom of the pile is 4m wide, the top of the pile is 2m wide, the length of the pile is 30m, the height of the pile is 1m, and the distance between every two piles is 1.5 m.
(3) Micron zero-valent iron is added according to the mass ratio of 1.64 percent (namely 1.64 percent of the mass of the soil in the soil pile), the particle size of the micron zero-valent iron is 325 meshes, and the effective content is more than or equal to 90 percent. Turning and throwing for 3-5 times by using a turning and throwing machine to uniformly mix the polluted soil and the micron zero-valent iron, and spraying 20mMol/L of sodium acetate solution, 20mMol/L of sodium molybdate solution, 20mMol/L of BES solution, 0.25g/L of sodium nitrate solution and 0.1g/L of sodium phosphate solution in turn in the turning and throwing process, wherein the volume ratio V of the sprayed sodium acetate solution, the sprayed sodium molybdate solution and the sprayed BES solutionSodium acetate solution:VSodium molybdate solution:VBESThe total amount of the sodium acetate solution, the sodium molybdate solution and the BES solution sprayed is 0.1 percent of the mass of the soil; volume ratio V of sprayed sodium nitrate solution to sprayed sodium phosphate solutionSodium nitrate solution:VSodium phosphate solution1:1, and the total amount of the sodium nitrate solution and the sodium phosphate solution sprayed was 0.1% of the soil mass.
In the step, sodium acetate is used as a biological carbon source and an electron donor, sodium molybdate is used as a sulfate reduction inhibitor, BES solution is a methane production inhibitor, sodium nitrate solution is used as a nitrogen fertilizer (N nutrient solution), and sodium phosphate is used as a phosphate fertilizer (P nutrient solution).
(4) And (4) spraying tap water on the surface layer of the soil pile and continuously turning and throwing to ensure that the water content of the polluted soil is close to saturation. And (3) after the repairing agent, the nutrient and the polluted soil are uniformly mixed by turning and throwing, covering a waterproof cloth on the surface layer of the soil pile, compacting and sealing, creating an anaerobic reduction environment, standing and maintaining, and sampling and detecting the content of the sixteen-six in the soil after 8 days and 16 days of maintenance. The results of the detection are shown in FIG. 2.
The detection result shows that in the sample cured for 16 days, the total amount of the sixteenmo is reduced from 1296.495mg/kg to 278.1424mg/kg, the degradation efficiency reaches 78.547%, and the biological toxicity of the soil is greatly reduced.
In the repairing process, the zero-valent iron and the indigenous microorganisms play a coupling effect, the chlorinated groups of the organochlorine pesticide in the soil are removed by the micron zero-valent iron through reduction, the organochlorine pesticide is degraded by the growth, reproduction and metabolism of the indigenous microorganisms in the soil through the addition of a biological carbon source, an electron donor and nitrogen and phosphorus nutrition on the basis of reducing the biological toxicity of the soil, a sulfate reduction inhibitor is added to inhibit the consumption of sulfate to electrons in the soil, and a methanogenesis inhibitor is added to inhibit the consumption of methane in the process of metabolizing a hydrocarbon compound by methane bacteria to generate methane. Fe generated by oxidizing zero-valent iron reduced organic chlorine pesticide2+And Fe3+Has enzymatic effect on the production of indigenous microorganisms, and can promote the growth of indigenous microorganisms. Indigenous microorganisms can completely degrade dechlorinated low-chlorinated organic pollutants into carbon dioxide and water; meanwhile, organic acid secreted by the metabolic activity of indigenous microorganisms can directly or indirectly influence the reductive dechlorination process of the organochlorine pesticide on the soil colloid interface, and the organic acid can also effectively adjust the pH value of the soil, accelerate the etching of zero-valent iron and promote the reductive dechlorination of the zero-valent iron. Compared with the restoration method for restoring the organochlorine pesticide polluted soil by only utilizing zero-valent iron reduction or utilizing indigenous microorganisms, the combined method of the method has the advantage that the restoration efficiency is obviously improved.
Example 2
In this example, the site to be remediated contaminated with an organochlorine pesticide was selected as in example 1.
The method for restoring organochlorine contaminated soil by zero-valent iron reduction and indigenous microorganisms provided by the embodiment is implemented by the following steps:
(1) the method comprises the following steps of cleaning and digging the sextant soil from underground to the ground surface by using an excavator, transferring the sextant soil into a closed greenhouse for temporary storage by using a loader, wherein the greenhouse is a steel-structure closed greenhouse, the greenhouse is provided with an air draft device and a tail gas treatment device, and the air exchange frequency is 1 time of air exchange every 6 hours.
(2) Sieving out stones in the organochlorine pesticide-polluted soil by using a sieving and crushing device, and after crushing large consolidated organochlorine pesticide-polluted soil into fine particle soil with the particle size of less than 50mm, piling the soil into a pile, wherein the soil pile is a trapezoidal strip pile, the bottom of the pile is 8m wide, the top of the pile is 5m wide, the length of the pile is 50m, the height of the pile is 2m, and the distance between every two piles is 2 m.
(3) According to the mass ratio of 3 percent (namely 3 percent of the mass of the soil in the soil pile), micron zero-valent iron is added, the particle size of the micron zero-valent iron is 325 meshes, and the effective content is more than or equal to 80 percent. Turning and throwing for 3-5 times by using a turning and throwing machine to uniformly mix the polluted soil and the micron zero-valent iron, and spraying 40mMol/L of sodium acetate solution, 40mMol/L of sodium molybdate solution, 40mMol/L of BES solution, 0.5g/L of potassium nitrate solution and 0.2g/L of potassium phosphate solution in turn in the turning and throwing process, wherein the volume ratio V of the sprayed sodium acetate solution, sodium molybdate solution and BES solutionSodium acetate solution:VSodium molybdate solution:VBESThe total amount of the sodium acetate solution, the sodium molybdate solution and the BES solution sprayed is 1 percent of the mass of the soil; volume ratio V of potassium nitrate solution and potassium phosphate solution sprayedPotassium nitrate solution:VPotassium phosphate solution1:1, and the total amount of the potassium nitrate solution and the potassium phosphate solution sprayed is 1 percent of the soil mass.
In the step, sodium acetate is used as a biological carbon source and an electron donor, sodium molybdate is used as a sulfate reduction inhibitor, a BES solution is a methane production inhibitor, a potassium nitrate solution is used as a nitrogen fertilizer (N nutrient solution), and potassium phosphate is used as a phosphate fertilizer (P nutrient solution).
(4) And (4) spraying tap water on the surface layer of the soil pile and continuously turning and throwing to ensure that the water content of the polluted soil is close to saturation. And (3) after the repairing agent, the nutrient and the polluted soil are uniformly mixed by turning and throwing, covering a waterproof cloth on the surface layer of the soil pile, compacting and sealing to create an anaerobic reduction environment, standing and maintaining, and continuously spraying tap water or a sodium acetate solution, a sodium molybdate solution and a BES solution to keep the water content of the soil in a saturated state in the standing and maintaining process. After the soil is maintained for 14 days, the content of the hexachloro cyclohexane in the soil is sampled and detected, the degradation efficiency of the hexachloro cyclohexane reaches 71.235 percent, and the biological toxicity of the soil is greatly reduced.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. For example, the shape and size of the soil pile can be adjusted according to the site. Various process parameters of the soil in the treatment process can be adjusted according to the degradation condition of pollutants in the soil. In addition, it is anticipated that based on this remediation mechanism, although the contaminant targeted in the examples is sixty-six, this method is effective for most chlorinated organic contaminants in the soil. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (10)
1. A method for restoring organochlorine contaminated soil by zero-valent iron reduction and indigenous microorganisms is characterized by comprising the following steps:
(1) the organochlorine pesticide polluted soil to be repaired is dug to the ground surface and is transported to a closed disposal greenhouse;
(2) screening and crushing the organochlorine pesticide contaminated soil to form fine-particle soil with the particle size of less than 50 mm;
(3) stacking the screened and crushed fine particle organochlorine pesticide contaminated soil into a soil pile, adding micron zero-valent iron powder into the soil pile, and turning over the soil pile by using a turner to uniformly mix; in the turning and throwing process, a biological carbon source, an electron donor, a sulfate reduction inhibitor, a methane production inhibitor, a nitrogen fertilizer and a phosphate fertilizer are sequentially sprayed on the soil stack, so that the sprayed reagent is fully mixed with the polluted soil;
(4) covering a waterproof cloth on the surface layer of a soil stack which is uniformly mixed with micron zero-valent iron powder, a biological carbon source, an electron donor, a sulfate reduction inhibitor, a methane production inhibitor, a nitrogen fertilizer and a phosphate fertilizer, creating an anaerobic reducing condition, standing and maintaining, keeping the water content of soil in a basically saturated state in the maintenance process, and finally realizing the complete degradation of the organochlorine pesticide by utilizing the reduction dechlorination and the degradation of indigenous microorganisms by the micron zero-valent iron powder.
2. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: and (2) the airtight treatment greenhouse in the step (1) is provided with an air draft device and a tail gas treatment device, and the air exchange frequency is that air exchange is carried out for 1 time every 2-6 hours.
3. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: in the step (3), the soil pile is in a trapezoidal strip pile, the width of the lower bottom is 4-8 m, the width of the upper bottom is 2-5 m, the length is 30-50 m, the height is 1-2 m, and the distance between every two adjacent piles is 1.5-2 m.
4. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: the particle size of the micron zero-valent iron powder adopted in the step (3) is less than 74 microns, the mass proportion of the iron powder with reducibility is more than or equal to 80%, and the addition mass ratio of the micron zero-valent iron powder in the soil pile is 1.0-3.0%.
5. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: the biological carbon source and the electron donor in the step (3) are sodium acetate solution, the sulfate reduction inhibitor is sodium molybdate solution, the methane production inhibitor is BES solution, and the concentration of the sprayed sodium acetate solution, sodium molybdate solution and BES solution is 20-40 mMol/L.
6. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 5, wherein: the concentrations of the sodium acetate solution, the sodium molybdate solution and the BES solution sprayed in the step (3) are all 20mMol/L, and the volume ratio of spraying is that of the sodium acetate solution: sodium molybdate solution: BES solution =1:1:1, and the total amount of the sodium acetate solution, the sodium molybdate solution and the BES solution sprayed is 0.1-1.0% of the soil mass.
7. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: the nitrogen fertilizer sprayed in the step (3) is a sodium nitrate solution or a potassium nitrate solution, and the concentration of the solution is 0.25-0.5 g/L; the phosphate fertilizer is a sodium phosphate solution or a potassium phosphate solution, and the concentration of the solution is 0.1-0.2 g/L; the volume ratio of the sprayed nitrogen fertilizer to the sprayed phosphorus fertilizer is 1:1, and the total amount of the sprayed nitrogen fertilizer and the sprayed phosphorus fertilizer is 0.1-1.0% of the soil mass.
8. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: in the standing and maintaining process in the step (4), tap water is sprayed, or sodium acetate solution is adopted according to the volume ratio: sodium molybdate solution: BES solution =1:1:1 sodium acetate solution, sodium molybdate solution and BES solution are sprayed to keep the water content of the soil in a saturated state.
9. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 8, wherein: the saturated water content of the soil is 30% -60%.
10. The method for remediating organochlorine contaminated soil by zero-valent iron reduction in combination with indigenous microorganisms according to claim 1, wherein: and (4) standing and maintaining for 14-28 days.
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| CN115124384A (en) * | 2022-06-28 | 2022-09-30 | 张珈毓 | Pesticide-contaminated soil remediation agent, preparation method and application thereof, and method for remediating pesticide-contaminated soil |
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