CN111097787A - Method for restoring polluted soil and underground water - Google Patents
Method for restoring polluted soil and underground water Download PDFInfo
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- CN111097787A CN111097787A CN201811261632.8A CN201811261632A CN111097787A CN 111097787 A CN111097787 A CN 111097787A CN 201811261632 A CN201811261632 A CN 201811261632A CN 111097787 A CN111097787 A CN 111097787A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/722—Oxidation by peroxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C2101/00—In situ
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/06—Contaminated groundwater or leachate
Abstract
The invention relates to the technical field of soil remediation, in particular to a method for remediating polluted soil and underground water. The method comprises the following steps: 1) establishing an injection well upstream of the groundwater in the contaminated area and a collection trench downstream of the groundwater in the contaminated area, wherein the contaminants in the contaminated area comprise volatile and/or semi-volatile organics; 2) and (3) injecting the biosurfactant slurry into the injection well, so that the biosurfactant migrates to the polluted area under the action of underground water, and the obtained oil-water mixed solution enters a collecting ditch to obtain an upper oil phase and a lower water phase. Compared with the existing extraction method and PRB method, the method has the characteristics of high treatment efficiency and simple operation, and is particularly suitable for repairing the site above the polluted area where excavation, extraction and injection operations cannot be carried out.
Description
Technical Field
The invention relates to the technical field of soil remediation, in particular to a method for remediating polluted soil and underground water.
Background
The soil environment is one of the essential elements constituting the ecosystem, and is the basis on which humans and organisms live and develop. With the development of industrialized process in China, environmental pollution accidents and human health damage events happen occasionally. Volatile and semi-volatile organic contaminants have become the most prevalent and prominent contaminant types in industrial field soils at present. Especially, sudden environmental pollution accidents, such as oil storage tank leakage, oil pipeline breakage, gasoline and diesel oil spill accidents, can cause pollution to soil, underground water and the like in different degrees, and further bring greater harm to human health in the field.
The remediation method aiming at the volatile and semi-volatile organic pollutants in the soil mainly comprises chemical remediation, biological remediation, physical remediation and the like. The chemical remediation mainly comprises an oxidation-reduction technology and a chemical leaching technology, the biological remediation mainly utilizes microorganisms and plants to degrade pollutants, and the physical remediation comprises a soil vapor extraction technology and a thermal desorption technology.
In many engineering practices, in situ remediation of contaminated soil is required. CN103447291B discloses a method for enhanced vapor extraction and remediation of chlorobenzene-contaminated soil, which comprises a plurality of heating extractors, condensing units, gas-liquid separators, vacuum pumps, and the like arranged in regular triangles or squares, and has a significant remediation effect on chlorobenzene-contaminated soil in a short time, and a high removal rate of pollutants, but the effect is easily affected by soil characteristics (e.g., high soil viscosity and poor heat transfer effect). CN102513347A discloses a method for treating contaminated soil by an in-situ heat-strengthening combined soil vapor extraction technology, which comprises the steps of forming a heating well in a certain form in a contaminated area, deploying a heater part in the heating well, installing a casing pipe, and filling a catalyst in the casing pipe to accelerate the high-temperature decomposition of contaminants into simple small molecular substances; the method has better treatment effect on pollutants, but the extraction device has high manufacturing cost and is difficult to popularize.
Groundwater remediation technology is one of the hot issues of current environmental field research, where Permeable Reactive Barrier (PRB) and extraction treatment are the most commonly applied technical methods. PRB is a method for removing pollution components in underground water and soil in situ, and the PRB is a pollutant remediation PRB technology issued by the U.S. environmental protection agency, which indicates that PRB is a method for arranging an active material wall underground so as to intercept pollution plumes, and after the pollution plumes pass through a reaction medium, pollutants can be converted into another form which is accepted by the environment, so that the aim of enabling the concentration of the pollutants to reach the environmental standard is fulfilled. When pollutants enter the PRB treatment system along the water flow direction of underground water, precipitation reaction, adsorption reaction, catalytic reduction reaction or catalytic oxidation reaction can occur under the action of chemical active substances with lower permeability, so that the pollutants are converted into low-activity substances or degraded into nontoxic components. However, PRB has the disadvantages that the pollution source cannot be effectively treated, the construction is complex and the construction cost is high. The pumping treatment method can effectively limit the polluted area to the upstream of the pumping well, but as a long-term groundwater treatment method, the pumping treatment method has many defects, such as limitation of further diffusion of pollution, incapability of on-site remediation, high treatment cost, possibility of causing waste of groundwater resources, damage to the original local ecological environment, and incapability of fundamentally solving the pollution remediation problem of groundwater.
In actual production and life, when volatile and semi-volatile organic compounds are polluted in underground soil of a production enterprise, operation modes such as excavation, extraction, injection and the like cannot be developed above a polluted area, such as a production device area of a chemical enterprise, a camping and gas station and the like. In addition, as volatile and semi-volatile organic compounds are often difficult to dissolve in water and slowly migrate along with underground water, the direct use of PRB or extraction treatment technology at the downstream of the polluted area is time-consuming and labor-consuming, and the pollution problem in the polluted area cannot be fundamentally solved.
Disclosure of Invention
The invention aims to provide a novel method for repairing polluted soil and underground water, which can effectively remove volatile and semi-volatile organic compounds in the polluted soil and the underground water.
In order to achieve the above objects, the present invention provides a method for remediating contaminated soil and groundwater, the method comprising:
1) establishing an injection well upstream of the groundwater in the contaminated area and a collection trench downstream of the groundwater in the contaminated area, wherein the contaminants in the contaminated area comprise volatile and/or semi-volatile organics;
2) and (3) injecting the biosurfactant slurry into the injection well, so that the biosurfactant migrates to the polluted area under the action of underground water and contacts with pollutants in the polluted area, and the obtained oil and water are mixed into the collection ditch to obtain an upper oil phase and a lower water phase.
The invention provides a feasible repairing method for a field above a polluted area where excavation, extraction and injection operations cannot be carried out. The biosurfactant can accelerate the migration speed of volatile and semi-volatile organic matters attached to the pollution source soil along with the underground water, greatly shortens the repair time of the pollution area, and simultaneously plays a role in promoting the natural degradation of the organic matters in the soil of the pollution area. In a preferred embodiment of the present invention, when the polluted groundwater flows to the collection ditch, the oil-water separator can automatically collect the organic matter (upper oil) floating on the water surface in the ditch, and the lower polluted groundwater (lower water phase) can be further repaired by adding a reaction agent into the ditch, so that the pumping treatment is not needed, and the operation cost is lower.
Drawings
Fig. 1 is a schematic view of a method for remediating soil and groundwater in accordance with an embodiment of the present invention.
Description of the reference numerals
1-an injection well; 2-a contaminated area; 3-an organic matter collecting barrel; 4-oil-water separator; 5-a water-impermeable construction; 6-a water permeable construction; 7-pollution plume.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The present invention provides a method for remediating soil and groundwater comprising:
1) establishing an injection well upstream of the groundwater in the contaminated area and a collection trench downstream of the groundwater in the contaminated area, wherein the contaminants in the contaminated area comprise volatile and/or semi-volatile organics;
2) and (3) injecting the biosurfactant slurry into the injection well, so that the biosurfactant migrates to the polluted area under the action of underground water to be contacted with pollutants in the polluted area, and the obtained oil-water mixed solution enters the collection ditch to obtain an upper oil phase and a lower water phase.
In the present invention, it should be understood by those skilled in the art that, before the injection well and the collecting groove are constructed, the present invention needs to determine the position and the pollution area of the polluted area by using the methods well known in the art, detect the content and the type of the pollutants in the polluted area, determine the position of the injection well and the collecting groove according to the investigation and laboratory experiment results, and estimate the dosage of the biosurfactant. In the invention, the content and the type of the pollutants in the polluted area can be determined according to the methods specified in HJ/T166 (soil environment monitoring technical specification) and HJ/T164 (groundwater environment monitoring technical specification).
In the present invention, the injection well is established in the groundwater upstream of the contaminated area for injecting a biosurfactant slurry into the groundwater for causing the biosurfactant to migrate with the groundwater into the contaminated area. The depth of the well should be dug below the groundwater level when the injection well is being constructed. The specific construction method and specifications of the injection well are not particularly limited in the present invention and can be selected with reference to the prior art. According to one embodiment, the diameter of said injection well is between 5 and 10 cm.
In the present invention, the contaminants in the contaminated area comprise volatile and/or semi-volatile organics. Specific examples of the contaminants include, but are not limited to, one or more of diesel oil, gasoline, benzene, toluene, di-n-octyl phthalate, and benzo (a) pyrene.
Preferably, the biosurfactant is at least one selected from rhamnolipid, algal glycolipid, phospholipid and sophorolipid.
In the present invention, the solvent in the surfactant slurry is typically water. Wherein the biosurfactant may be present in an amount of 0.1-20 wt%.
The adding mode of the biosurfactant is not particularly limited, and it is understood that the area causing pollution is usually to be repaired, so the biosurfactant is suitable for being added intermittently and repeatedly, various indexes of pollutants in soil and underground water need to be monitored regularly, the adding amount of the biosurfactant is calculated according to actual conditions, and when the indexes of the soil and the underground water on the downstream side of the polluted area, the polluted feather and the underground water of the collecting ditch meet relevant standards, the polluted area is considered to be completely repaired. According to one embodiment, the biosurfactant is added in an amount of 0.1 to 1g relative to 100g of contaminant.
In the present invention, the length of the collecting channel is greater than the pollution plume range of the polluted region. According to a preferred embodiment, the collecting channel is of rectangular parallelepiped configuration. The width of the collecting ditch is 1-1.5m, the depth is the distance between the ground and a water-impermeable layer, one side ditch wall of the collecting ditch close to a polluted area is of a water-permeable structure, the upper part of the other opposite side ditch wall is of a water-impermeable structure, the lower part of the other opposite side ditch wall is of a water-permeable structure, and the depth of the water-impermeable structure is the distance from the ground to the position 50-100cm below an underground water level line, so that the collecting ditch is beneficial to collecting pollutants in polluted feathers and blocking floating oil on the liquid level from further migrating downstream. Generally, the collecting channel and the pre-remediated pollution plume will partially coincide.
Preferably, an oil-water separator is provided in the collecting channel for recovering the oil phase in the upper layer. It will be appreciated by those skilled in the art that within the collection gutter, under the action of the biosurfactant, the contaminant or a portion of its components (partly in the form of an emulsion) is blocked from the upper layer of the water surface within the gutter due to its poor solubility in water and low density.
In the present invention, the method further comprises: and adding a reaction agent into the collecting ditch to treat the polluted underground water at the lower layer. The reaction agent is not particularly limited in the present invention, and may be any reaction agent known in the art that can degrade or remove the organic substances.
According to one embodiment, the reactant agent comprises an oxidizing agent and optionally a catalyst to cause oxidation of the contaminants. Wherein, the oxidant can be selected from peroxide and/or persulfate, and the catalyst is ferrous salt. Non-limiting examples of the peroxide include hydrogen peroxide, calcium peroxide, and the like, the persulfate salt is, for example, sodium persulfate, potassium persulfate, and the like, and the catalyst is, for example, ferrous sulfate. In a more specific embodiment, the molar ratio of the oxidant to the iron ions in the catalyst is from 2 to 5: 1. In the present invention, the reaction agent is fed to the collecting channel in the form of an aqueous solution thereof, and the concentration of the oxidizing agent in the aqueous solution may be 5 to 35% by weight.
In the invention, the adding amount of the reaction medicament can be determined according to the content of the lower-layer water-phase pollutants in the collecting groove. Generally, the oxidizing agent is added in an amount of 20 to 200% by weight relative to the mass of the contaminants dissolved in the aqueous phase in the collection channel.
In one embodiment, the method for remediating soil and groundwater of the present invention is shown in fig. 1, and as shown in fig. 1, subsurface soil and groundwater in a plant area is contaminated to form a contaminated area 2, the method comprising:
1) an injection well 1 is built at the upstream of the groundwater in the polluted area 2, and a collecting ditch is built at the downstream; wherein the content of the first and second substances,
the bottom of the injection well 1 is positioned below the groundwater level line, the top of the injection well 1 is positioned above the ground, and the diameter of the injection well 1 is 5-10 cm; the collecting ditch is of a cuboid structure, one side ditch wall of the collecting ditch close to the pollution area 2 is a water permeable structure 6, the upper part of the other side ditch wall opposite to the collecting ditch is an impermeable structure 5, the lower part of the collecting ditch is the water permeable structure 6, the depth of the collecting ditch is formed by digging from the ground to an impermeable layer, the width of the collecting ditch (namely the distance between the ditch walls on the two sides) is 1-1.5m, the depth of the impermeable structure 5 is 50-100cm from the ground to the position below a groundwater waterline, and the length of the collecting ditch is larger than the range of pre-repairing pollution feathers 7. An oil-water separator 4 is arranged in the collecting channel and is connected with an organic matter collecting barrel 3;
2) injecting the biosurfactant slurry into a position below a groundwater level line through the injection well 1, so that the biosurfactant migrates to a pollution feather 7 comprising a pollution area 2 along with groundwater, and performing desorption treatment on pollutants in the pollution feather to obtain an oil-water mixed solution;
the oil-water mixed liquid enters the collecting channel through the water permeable structure 6, an upper oil phase and a lower water phase are obtained through gradual separation, an upper oil product is automatically collected and sent to the organic matter collecting barrel 3 through the oil-water separator 4, and a reaction agent is added into the lower water phase for treatment.
In the treatment process, various indexes of pollutants in soil and underground water are regularly monitored, and the adding amount of the surfactant and the reaction agent is calculated according to actual conditions.
The invention provides a feasible repairing method for a field above a polluted area where excavation, extraction and injection operations cannot be carried out. Compared with the existing extraction method and PRB method, the construction cost of the collecting ditch is low, when polluted underground water flows into the collecting ditch, the upper-layer organic matters floating on the water surface in the ditch can be automatically collected through the oil-water interface separator, and the lower-layer polluted underground water can be treated by adding a small amount of redox reagent without pumping treatment, so that the operation cost is lower.
The present invention will be described in detail below by way of examples.
In the following examples, the soil and underground water samples in the polluted area, at the collection ditch, and downstream of the underground water in the collection ditch are detected and analyzed by the methods specified in HJ/T166 (soil environment monitoring technical specification) and HJ/T164 (underground water environment monitoring technical specification). The repairing effect of the embodiment method is judged by relevant regulations of GB36600-2018 (soil pollution risk control standard of soil environment quality construction land) and GB/T14848-2017 (underground water quality standard).
The following examples are all provided in conjunction with fig. 1 to illustrate the method for remediating soil and groundwater according to the present invention. The description of fig. 1 is as introduced above unless otherwise described.
Example 1
Before the method is implemented, the total petroleum hydrocarbon (C10-C40) content of soil in a polluted area is 17439mg/kg, exceeds the screening value of class II land use in GB36600-2018 by 4500mg/kg, the benzene content of underground water is 402 mu g/L, and exceeds the conventional index limit value of class IV water in GB/T14848-2017 by 120 mu g/L. The total petroleum hydrocarbon (C10-C40) content of the soil at the collecting ditch is 5591mg/kg, and the benzene content of the underground water is 57.1 mu g/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 5cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, the wall of one side of the ditch is of a permeable structure, the upper part of the wall of the other side of the ditch is of a watertight structure, the depth of the wall of the other side of the ditch is from the ground; an oil-water separator is arranged in the collecting channel.
Sending rhamnolipid slurry with the concentration of 0.1 weight percent into an injection well, injecting the rhamnolipid slurry into underground water below the water surface of the underground water, automatically collecting the diesel oil floating on the upper layer of the water surface in a ditch when the polluted underground water flows to a collection ditch, adding a reaction agent solution (the reaction agents are hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 5 weight percent, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 2.5:1) into the collection ditch to treat a lower water phase, periodically monitoring various indexes of pollutants in soil and underground water in the treatment process, and calculating the adding amount of a biological surfactant and a chemical agent according to actual conditions, wherein the adding amount of the biological surfactant is 0.1g and the adding amount of an oxidant is 200g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the total content of petroleum hydrocarbon (C10-C40) in the soil of the polluted area is 243mg/kg, and the benzene content of the underground water is 7 mug/L; the total petroleum hydrocarbon (C10-C40) content of the soil on the downstream side of the underground water of the collection ditch is 163mg/kg, and the benzene content of the underground water is 1 mu g/L. The indexes of soil and underground water meet the screening values and limits specified in GB36600-2018 and GB/T14848-2017.
Example 2
The method is characterized in that a ground pipeline buried in a sewage pond leaks to cause sewage containing di-n-octyl phthalate to permeate underground, before the method is implemented, the content of the di-n-octyl phthalate in soil is 5617mg/kg in a polluted area, exceeds the screening value 2812mg/kg of the second type land used in GB36600-2018, the content of the di-n-octyl phthalate in underground water is 554 mu g/L, and exceeds the unconventional index limit value of IV type water in GB/T14848-2017 by 300 mu g/L. The content of di-n-octyl phthalate in the soil at the collecting ditch is 4124mg/kg, and the content of di-n-octyl phthalate in the underground water is 472 mu g/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 10cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1.2m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, one side ditch wall is of a water permeable structure, the upper part of the other side ditch wall is of a watertight structure, the depth of the other side ditch wall is from the ground to 50cm below the groundwater waterline, and the; an oil-water separator is arranged in the collecting channel.
The seaweed glycolipid slurry with the concentration of 8 weight percent is delivered into an injection well, the seaweed glycolipid slurry is injected below the water surface of underground water, when the polluted underground water flows to a collection ditch, di-n-octyl phthalate is blocked at the upper layer of the water surface in the ditch, the di-n-octyl phthalate floating at the upper layer of the water surface in the ditch is automatically collected through an oil-water separator, and a reaction agent solution (the reaction agents are hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 30 mass percent, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 2.8:1) is added into the collection ditch to treat the lower-layer water phase. In the treatment process, each index of pollutants in soil and underground water is regularly monitored, and the adding amount of the biosurfactant and the chemical agent is calculated according to actual conditions, wherein the adding amount of the biosurfactant is 0.5g and the adding amount of the oxidant is 20g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the content of di-n-octyl phthalate in the soil of the polluted area is 255mg/kg, and the content of di-n-octyl phthalate in the underground water is 0.7 mug/L; the content of di-n-octyl phthalate in the soil on the downstream side of the underground water of the collection ditch is 32mg/kg, and the content of di-n-octyl phthalate in the underground water is 0.1 mug/L. The indexes of soil and underground water both meet the screening values and the limit values specified in GB36600-2018 and GB/T14848-2017.
Example 3
Before the method is implemented, the total petroleum hydrocarbon (C10-C40) content of soil in a polluted area is 9532mg/kg, exceeds the screening value of two types of land used in GB36600-2018 by 4500mg/kg, the toluene content of underground water is 2487 mu g/L, and exceeds the conventional index limit value of IV type water in GB/T14848-2017 by 1400 mu g/L. The total petroleum hydrocarbon (C10-C40) content of the soil at the collecting ditch is 6588mg/kg, and the toluene content of the underground water is 1832 mug/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 5cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1.3m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, one side ditch wall is of a water permeable structure, the upper part of the other side ditch wall is of a watertight structure, the depth of the other side ditch wall is from the ground to 50cm below the groundwater waterline, and the; an oil-water separator is arranged in the collecting channel.
The phospholipid slurry with the concentration of 12 weight percent is delivered into an injection well and injected below the water surface of underground water, when the polluted underground water flows to a collection ditch, gasoline is blocked at the upper layer of the water surface in the ditch, the gasoline floating at the upper layer of the water surface in the ditch is automatically collected through an oil-water separator, and reaction agents (the reaction agents are hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 10 mass percent, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 3:1) are added into the collection ditch to treat the lower-layer aqueous phase. In the treatment process, each index of pollutants in soil and underground water is regularly monitored, and the adding amount of the biosurfactant and the chemical agent is calculated according to actual conditions, wherein the adding amount of the biosurfactant is 1g and the adding amount of the oxidant is 100g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the content of total petroleum hydrocarbons (C10-C40) in the soil of the polluted area is 143mg/kg, and the content of methylbenzene in underground water is 79 mug/L; the total petroleum hydrocarbon (C10-C40) content of the soil on the downstream side of the underground water of the collection ditch is 57mg/kg, and the toluene content of the underground water is 43 mu g/L. The indexes of soil and underground water both meet the screening values and the limit values specified in GB36600-2018 and GB/T14848-2017.
Example 4
A buried pipeline in a certain tank area leaks to cause a small amount of benzo (a) pyrene to permeate underground, before the method is implemented, the content of the benzo (a) pyrene in a polluted area is 76.1mg/kg and exceeds the screening value of the two types of places in GB36600-2018 by 1.5mg/kg, the content of the benzo (a) pyrene in underground water is 4.9 mu g/L and exceeds the conventional index limit value of IV type water in GB/T14848-2017 by 0.5 mu g/L. The content of benzo (a) pyrene in the soil at the collecting ditch is 29.7mg/kg, and the content of benzo (a) pyrene in the groundwater is 3.1 mu g/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 10cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1.5m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, one side ditch wall is of a water permeable structure, the upper part of the other side ditch wall is of a watertight structure, the depth of the other side ditch wall is from the ground to 50cm below the groundwater waterline, and the; an oil-water separator is arranged in the collecting channel.
Conveying the sophorolipid slurry with the concentration of 20 wt% into an injection well, injecting the sophorolipid slurry into underground water below the water surface, automatically collecting benzo (a) pyrene floating on the upper layer of the water surface in a ditch through an oil-water separator when polluted underground water flows to a collection ditch, and then adding a reaction medicament solution (the reaction medicaments comprise hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 10 wt%, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 3.4:1) into the collection ditch to treat the lower-layer water phase. In the treatment process, each index of pollutants in soil and underground water is regularly monitored, and the adding amount of the biosurfactant and the chemical agent is calculated according to actual conditions, wherein the adding amount of the biosurfactant is 0.5g and the adding amount of the oxidant is 150g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the content of benzo (a) pyrene in the soil of the polluted area is 0.3mg/kg, and the content of benzo (a) pyrene in the groundwater is 0.2 mug/L; the content of benzo (a) pyrene in soil on the downstream side of underground water of the collecting ditch is 0.4mg/kg, and the content of benzo (a) pyrene in the underground water is 0.1 mu g/L. The indexes of soil and underground water both meet the screening values and the limit values specified in GB36600-2018 and GB/T14848-2017.
Example 5
Before the method is implemented, the total petroleum hydrocarbon (C10-C40) content of soil in a polluted area is 16232mg/kg, exceeds the screening value of two types of land used in GB36600-2018 by 4500mg/kg, the toluene content of underground water is 4145 mu g/L, exceeds the conventional index limit value 1400 mu g/L of IV-type water in GB/T14848-2017 by 659 mu g/L and exceeds the conventional index limit value of IV-type water in GB/T14848-2017 by 120 mu g/L. The total petroleum hydrocarbon (C10-C40) content of the soil at the collecting ditch is 5748mg/kg, the toluene content of the underground water is 1773 mug/L, and the benzene content is 163 mug/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 5cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, one side ditch wall is of a water permeable structure, the upper part of the other side ditch wall is of a watertight structure, the depth of the other side ditch wall is from the ground to 50cm below the groundwater waterline, and the lower; an oil-water separator is arranged in the collecting channel.
The mixed slurry containing 5 wt% of algal glycolipid and 5 wt% of phospholipid is sent to an injection well and injected below the surface of underground water, when the polluted underground water flows to a collection ditch, oil is blocked at the upper layer of the water surface in the ditch, the oil floating at the upper layer of the water surface in the ditch is automatically collected through an oil-water separator, and reaction agent solution (the reaction agents are hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 20 wt%, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 3.8:1) is added into the collection ditch to treat the lower-layer water phase. In the treatment process, each index of pollutants in soil and underground water is regularly monitored, and the addition amount of a surfactant and a chemical agent is calculated according to actual conditions, wherein the addition amount of the biosurfactant is 0.7g and the addition amount of the oxidant is 40g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the total petroleum hydrocarbon (C10-C40) content of the soil in the polluted area is 217mg/kg, the toluene content of the underground water is 157 mug/L, and the benzene content is 72 mug/L; the total petroleum hydrocarbon (C10-C40) content of the soil on the downstream side of the underground water of the collection ditch is 188mg/kg, the toluene content of the underground water is 58 mu g/L, and the benzene content is 29 mu g/L. The indexes of soil and underground water both meet the screening values and the limit values specified in GB36600-2018 and GB/T14848-2017.
Example 6
Before the method is implemented, the content of soil total petroleum hydrocarbons (C10-C40) in a polluted area is 6638mg/kg, exceeds the screening value of two types of land used in GB36600-2018 by 4500mg/kg, the content of methylbenzene in underground water is 1659 mu g/L, exceeds the conventional index limit value of IV type water in GB/T14848-2017 by 1400 mu g/L, the content of benzene is 284 mu g/L, and exceeds the conventional index limit value of IV type water in GB/T14848-2017 by 120 mu g/L. The total petroleum hydrocarbon (C10-C40) content of the soil at the collecting ditch is 2804mg/kg, the toluene content of the underground water is 921 mu g/L, and the benzene content is 173 mu g/L.
An injection well is built at the upper stream of the groundwater in the polluted area, the diameter of the injection well is 5cm, a collection ditch is built at the lower stream of the groundwater in the polluted area, the width of the formed collection ditch is 1.5m, the length of the formed collection ditch is larger than the range of the pre-repair pollution plume, the collection ditch is dug to a watertight layer in depth, one side ditch wall is of a water permeable structure, the upper part of the other side ditch wall is of a watertight structure, the depth of the other side ditch wall is from the ground to 50cm below the groundwater waterline, and the; an oil-water separator is arranged in the collecting channel.
The mixed slurry containing 10 wt% of rhamnolipid and 10 wt% of sophorolipid is sent to an injection well and injected below the water surface of underground water, when polluted underground water flows to a collection ditch, oil is separated from the upper layer of the water surface in the ditch, the oil floating on the upper layer of the water surface in the ditch is automatically collected through an oil-water separator, and reaction agent solution (the reaction agents are hydrogen peroxide and ferrous sulfate, the concentration of the hydrogen peroxide is 25 wt%, and the molar ratio of the hydrogen peroxide to the ferrous sulfate is 3.8:1) is added into the collection ditch to treat the lower water phase. In the treatment process, each index of pollutants in soil and underground water is regularly monitored, and the addition amount of the biosurfactant and the chemical agent is calculated according to actual conditions, wherein the addition amount of the biosurfactant is 0.8g and the addition amount of the oxidant is 120g relative to 100g of pollutants. And when the indexes of the soil and the underground water at the downstream side of the polluted area and the underground water of the collecting ditch meet the relevant standards, completing the restoration.
After the treatment of the embodiment, the content of total petroleum hydrocarbons (C10-C40) in the soil of the polluted area is 102mg/kg, the content of methylbenzene in underground water is 104 mu g/L, and the content of benzene is 43 mu g/L; the total petroleum hydrocarbon (C10-C40) content of the soil on the downstream side of the underground water of the collection ditch is 171mg/kg, the toluene content of the underground water is 79 mug/L, and the benzene content is 45 mug/L. The indexes of soil and underground water both meet the screening values and the limit values specified in GB36600-2018 and GB/T14848-2017.
The results of the above examples show that the method of the invention can effectively repair the soil and the groundwater in the polluted area, and the repaired soil and groundwater both meet the regulations of the national relevant standards.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (10)
1. A method for remediating contaminated soil and groundwater, the method comprising:
1) establishing an injection well upstream of the groundwater in the contaminated area and a collection trench downstream of the groundwater in the contaminated area, wherein the contaminants in the contaminated area comprise volatile and/or semi-volatile organics;
2) and (3) injecting the biosurfactant slurry into the injection well, so that the biosurfactant migrates to the polluted area under the action of underground water and contacts with pollutants in the polluted area, and the obtained oil-water mixed solution enters the collection ditch to obtain an upper oil phase and a lower water phase.
2. The method of claim 1, wherein the contaminant is one or more of diesel, gasoline, benzene, toluene, di-n-octyl phthalate, and benzo (a) pyrene.
3. The method according to claim 1 or 2, wherein the biosurfactant is selected from at least one of rhamnolipids, algal glycolipids, phospholipids and sophorolipids.
4. The method according to claim 1, wherein the biosurfactant slurry has a biosurfactant content of 0.1-20 wt%.
5. The method of claim 1, wherein the biosurfactant is added in an amount of 0.1-1g relative to 100g of contaminant.
6. The method of claim 1 wherein the diameter of the injection well is between 5 and 10 cm.
7. The method of claim 1, wherein the collection trench is of rectangular parallelepiped configuration having a width of 1-1.5m and a depth of a distance from the ground to the impermeable layer, one side wall of the collection trench adjacent to the contaminated area being of permeable construction, an upper portion of the opposite side wall being of impermeable construction and a lower portion being of permeable construction, the impermeable construction having a depth of 50-100cm from the ground to below the groundwater level.
8. The method according to any one of claims 1 and 6 to 7, wherein an oil-water separator is provided in the collecting gutter for recovering the oil phase of the upper layer.
9. The method of claim 1 or 8, wherein the method further comprises: adding a reaction reagent into the collection groove;
preferably, the reaction agent comprises an oxidizing agent selected from peroxides and/or persulfates and optionally a catalyst which is a ferrous salt;
more preferably, the molar ratio of the oxidant to the iron ions in the catalyst is 2-5: 1.
10. The method of claim 9, wherein the oxidant is added in an amount of 20-200 wt% relative to the mass of contaminants dissolved in the aqueous phase in the collection trench.
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