CN114289493B - System and method for repairing polluted soil - Google Patents
System and method for repairing polluted soil Download PDFInfo
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- CN114289493B CN114289493B CN202111660767.3A CN202111660767A CN114289493B CN 114289493 B CN114289493 B CN 114289493B CN 202111660767 A CN202111660767 A CN 202111660767A CN 114289493 B CN114289493 B CN 114289493B
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Abstract
The invention provides a system and a method for repairing contaminated soil, belongs to the field of soil repair, and solves the defects that in the prior art, energy is wasted due to large temperature difference of soil in the heating process, and organic contaminated soil cannot be repaired by thermal reinforcement auxiliary in-situ chemical oxidation at a part with a lower temperature, so that the pollution treatment effects of different parts of the soil are greatly different. The system for restoring the polluted soil comprises a heating unit and a pumping and injecting device for extracting groundwater in the soil and injecting restoring medicaments into the soil.
Description
Technical Field
The invention belongs to the field of soil remediation, and particularly relates to a system and a method for remediating contaminated soil.
Background
At present, the in-situ remediation technology for the organic contaminated soil mainly comprises in-situ thermal desorption, in-situ chemical oxidation and soil vapor extraction technologies. The in-situ thermal desorption technology has high restoration efficiency, wide range of pollutant treatment and thorough restoration effect, but the polluted soil needs to be heated to a high enough temperature (generally more than 100 ℃) to volatilize the pollutant, the engineering quantity is large, the energy consumption is extremely high, and the restoration cost is high. The chemical oxidation technology reduces or removes pollutants in a field through the oxidation characteristic of a chemical oxidant, the repair period is short, and the cost is low, but in the method, the chemical reaction between the repair agent and the pollutants needs proper temperature, the reaction is slow in actual use, the radius is small due to the restriction of soil heterogeneity, the pollutants in the soil cannot be effectively and comprehensively oxidized and degraded, and the pollution rebound after repair often causes a tailing effect. The soil vapor extraction technology is a technology for generating negative pressure by utilizing a vacuum pump to extract and form air flow through a soil matrix to bring volatile organic pollutants away from soil, but the technology is only suitable for volatile organic matters with high Henry coefficient, and has the problems of low treatment efficiency, high large-scale application cost, long soil restoration time and the like.
For example, chinese patent CN110014036a discloses a method for repairing organic contaminated soil by thermal strengthening assisted in-situ chemical oxidation, which achieves the purpose of repairing the soil by chemical oxidation by simply combining a high-pressure jet grouting device and a heating device. However, the invention simply and continuously operates chemical oxidation and soil heating, the heating range is not large, the soil cannot be uniformly heated, the position far away from the heating device when overheat occurs near the heating device can still be in an unheated state, on one hand, energy waste is caused, on the other hand, the temperature difference in the soil is large, the thermal strengthening auxiliary in-situ chemical oxidation can not be realized on the part with lower temperature to repair organic polluted soil, the pollutant treatment effect of different parts of the soil is larger, the treatment effect of a low-temperature area is poor, and after the treatment is stopped for a period of time, adsorbed pollutants are reversely permeated into underground water, and the phenomena of pollutant rebound, tailing and the like are caused.
Disclosure of Invention
Therefore, the invention aims to overcome the defects that in the prior art, the waste of energy is caused by large temperature difference of soil in the heating process, and the organic polluted soil cannot be repaired by the heat strengthening auxiliary in-situ chemical oxidation at the part with lower temperature, so that the pollution treatment effects of different parts of the soil are greatly different, thereby providing a system and a method for repairing the polluted soil.
For this purpose, the invention provides the following technical scheme.
In a first aspect, a system for remediating contaminated soil is provided, comprising a heating unit and a pump and injector for extracting groundwater from the soil and injecting a remediation agent into the soil.
Further, the pumping and injecting device comprises a pumping and injecting pipeline, a pumping and injecting well and a vacuum pump and a syringe pump which are respectively connected with the pumping and injecting pipeline.
Further, the pumping and injecting pipelines are provided with a plurality of rows at intervals, the pumping and injecting pipelines comprise a first group of pumping and injecting pipelines and a second group of pumping and injecting pipelines, and each row of pumping and injecting pipelines in the first group of pumping and injecting pipelines and the second group of pumping and injecting pipelines are alternately arranged.
Further, at least one of the following (1) - (2) is satisfied:
(1) The heating unit is provided with a plurality of heating units; preferably, the plurality of heating units are arranged in the soil to be remediated at intervals of a triangle method, and more preferably, the triangle method is an equilateral triangle method;
(2) Each row of pumping and injecting pipelines is provided with a plurality of pumping and injecting wells at intervals, preferably, a plurality of pumping and injecting wells are distributed according to a triangle method, and more preferably, the triangle method is an equilateral triangle method.
Further, the heating unit is an electric driving heating rod or a hot circulating water driving heating pipe; and/or the number of the groups of groups,
further, the injection pump is an injection diaphragm pump or a peristaltic pump.
In a second aspect, a method for restoring contaminated soil is provided, and the system for restoring contaminated soil is adopted and comprises the steps of heating the soil to be restored, extracting groundwater for treatment and injecting restoring agent for treatment.
Further, after heating for 3-5 days, the heating is carried out at least once per day for pre-extraction treatment of the groundwater; preferably, the extraction is ended after the amount of water extracted is reduced to 50-70% of the peak value of the initial extraction or 20-40 min of the extraction during each pre-extraction treatment.
Further, heating the average temperature of the soil to be repaired to 40-60 ℃, and then carrying out groundwater extraction treatment and repair agent injection treatment; preferably, the groundwater extraction treatment and the repair agent injection treatment are carried out under the heat preservation condition of 40-60 ℃.
Further, the groundwater extraction treatment and the repair agent injection treatment comprise the following steps:
step 1, starting a first group of pumping and injecting pipelines to perform groundwater extraction treatment, ending extraction, and performing injection repair medicament treatment by adopting a second group of pumping and injecting pipelines;
step 2, repeating the step 1;
step 3, starting a second group of pumping and injecting pipelines to perform groundwater extraction treatment, ending extraction, and performing injection repair medicament treatment on the first group of pumping and injecting pipelines;
step 4, repeating the step 3;
preferably, steps 1-2 and steps 3-4 are performed alternately.
Further, in the step 2, the groundwater treatment and the repair agent injection treatment are repeatedly extracted for 1 to 3 times every day, and the repeated treatment is carried out for 7 to 10 days; and/or the number of the groups of groups,
in the step 4, the groundwater treatment and the repair agent injection treatment are repeatedly extracted for 1 to 3 times every day, and the repeated treatment is carried out for 7 to 10 days;
further, at least one of the conditions a-C is satisfied:
A. the repairing agent is at least one of an oxidizing agent, a reducing agent and a biological promoting agent; preferably, the oxidizing agent is selected from at least one of hydrogen peroxide, persulfate and potassium permanganate; the reducing agent is at least one selected from sodium hydroxide solution and vegetable oil; the biological promoting agent is at least one selected from biological carbon source and urea;
preferably, the total application amount of the oxidizing agent is 0.5-2% of the mass of the soil to be repaired;
C. the injection pressure of the repairing agent is 0.1Mpa (normal pressure) to 1Mpa.
The repairing agent can be injected under normal pressure (0.1 MPa), namely, the repairing agent can be injected by self gravity under the condition of no external pressure of an injection pump.
Illustratively, the vegetable oil is canola oil; the biological carbon source is formic acid or potassium bicarbonate.
Further, after the concentration of the pollutant is reduced below the target value, the medicine is continuously injected for 5 to 30 days, and the repairing effect is consolidated.
Preferably, the method for restoring contaminated soil of the present invention is applicable to saturated aqueous soil layers having a certain permeability from silt to middlings. Hydraulic conductivity in the range of 10 -4 ～10 -6 cm/s.
When the repairing medicaments comprise a plurality of repairing medicaments, the repairing medicaments are directly injected after being mixed according to the proportion; or when the condition of underground first reduction and then oxidation is needed to be considered, the reducing agent is injected first, and then the oxidizing agent is injected.
Further, when the organic contaminant is chlorinated hydrocarbon, the repair agent includes a reducing agent and an oxidizing agent, and it is necessary to consider the case of reducing and then oxidizing. When the soil is treated, the reducing agent is injected first, and then the oxidizing agent is injected.
Specifically, (1) a first group of pumping and injecting pipelines are started to extract the underground water, and when the pumping water quantity is reduced to 50-70% of the initial pumping peak value, the first group of pumping and injecting pipelines are closed to stop the underground water extraction; injecting part of the reducing agent by adopting a second group of pumping and injecting pipelines, wherein the injection pressure of the reducing agent is 0.1-1 MPa, and the PH value is adjusted to 9-12, preferably 12;
(2) Repeating the step (1) for 1-3 times every day, stabilizing the PH value at about 12, repeating the reaction for 5-7 days, and continuously reacting for 2-5 days without extracting and injecting the medicament in the reaction process;
(3) Starting a second group of pumping and injecting pipelines to extract the underground water, and closing the second group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting part of the reducing agent by adopting a first group of pumping and injecting pipelines, wherein the injection pressure of the reducing agent is 0.1-1 MPa;
(4) Repeating the step (3) for 1-3 times every day, stabilizing the PH value at about 12, repeating the reaction for 5-7 days, and continuously reacting for 2-5 days without extracting and injecting the medicament in the reaction process;
(5) Starting a first group of pumping and injecting pipelines to extract the underground water, and closing the first group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting a part of oxidizing agent into a second group of pumping and injecting pipelines, wherein the injection pressure of the oxidizing agent is 0.1-1 MPa;
(6) Repeating the step (5) for 1-3 times every day for 7-10 days;
(7) Starting a second group of pumping and injecting pipelines to extract the underground water, and closing the second group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting a part of oxidizing agent into a first group of pumping and injecting pipelines, wherein the injection pressure of the oxidizing agent is 0.1-1 MPa;
(8) Repeating the step (7) for 1-3 times every day for 7-10 days;
(9) The steps (1) - (4) and the steps (5) - (8) are alternately carried out until the pollutants in the soil are reduced below the target value, and the soil restoration is completed; preferably, after the concentration of the pollutants in the soil is reduced below the target value, the medicaments are continuously injected for 5 to 30 days, so that the repairing effect is consolidated.
The technical scheme of the invention has the following advantages:
1. the invention provides a system for repairing polluted soil, which comprises a heating unit and a pumping and injecting device; the pumping and injecting device is used for extracting groundwater in the soil and injecting a repairing agent into the soil. The pumping and injecting device accelerates the flow of groundwater by extracting the groundwater in the soil, drives heat conduction to raise the temperature and reduces the temperature difference of different areas in the soil. On one hand, the waste of energy is reduced, and compared with a traditional high-temperature in-situ thermal desorption system, the method can heat the average temperature of soil to the target temperature and enter a heat preservation state by only providing a small amount of heat, and effectively degrade pollutants, so that the energy consumption is greatly reduced, and the energy consumption of the technology is about 30% of that of the traditional in-situ heating through the development of the technology demonstration engineering, so that the restoration can reach the standard. On the other hand, the whole soil can be ensured to realize the heat strengthening auxiliary in-situ chemical oxidation restoration. The invention can prevent the pollution in the adsorption state from reverse osmosis into the groundwater after stopping the treatment for a period of time, thereby causing the phenomena of rebound and tailing of the pollution.
And the groundwater in the extracted soil can form negative pressure in the soil, so that the transmission of the repair agent in the soil is promoted, the radius of influence of the repair agent is increased, and further, the thermal strengthening auxiliary in-situ chemical oxidation repair can be realized in the soil. Meanwhile, the problems that in the prior art, in order to enlarge the propagation radius of the repairing agent in the soil, a large amount of repairing agent needs to be injected by adopting high-pressure rotary spraying injection, and the soil is possibly cracked to form cracks, the agent is preferentially distributed in the cracks, the agent cannot be uniformly distributed, the agent is insufficiently contacted with pollutants, and the real heating oxidation repairing cannot be realized are avoided.
2. The invention provides a system for repairing contaminated soil, which comprises a first group of pumping and injecting pipelines and a second group of pumping and injecting pipelines, wherein each row of pumping and injecting pipelines in the first group of pumping and injecting pipelines and the second group of pumping and injecting pipelines are alternately arranged. Through the alternative arrangement of the first group of pumping and injecting pipelines and the second group of pumping and injecting pipelines, the separation extraction can be realized, and the treatment effect is better.
3. The system for repairing the polluted soil provided by the invention is characterized in that a plurality of heating units are arranged; preferably, a plurality of heating units are arranged in the soil to be repaired at intervals according to a triangle method; multiple rows of pumping and injecting pipelines are arranged at intervals; and each row of pumping and injecting pipelines is provided with a plurality of pumping and injecting wells at intervals, and the pumping and injecting wells are distributed according to a triangle method. The heating units and the pumping and injecting pipelines are arranged, so that the uniformity of heating, groundwater extraction and drug injection distribution can be improved, the heating units and the pumping and injecting wells are distributed according to a triangle method, and the treatment effect is better.
4. The method for repairing the polluted soil provided by the invention comprises the following steps: heating the soil to be restored, extracting groundwater and injecting restoration agent. According to the invention, an in-situ heating technology is coupled with an in-situ chemical oxidation and/or an in-situ chemical reduction and/or an in-situ microorganism technology, groundwater is driven to flow through extraction, so that the soil in a field can be heated efficiently and uniformly, the defect of uneven heating caused by high temperature and low cold point temperature near a heating well in the conventional in-situ heat conduction technology is overcome, a relatively uniform soil temperature environment is provided, the desorption of adsorbed pollutants in the soil is promoted, a repairing agent is rapidly and thermally activated under a heating condition, the effective degradation of organic pollutants in the soil is realized, the improved in-situ chemical and microorganism promotion technology has high repairing efficiency, the relatively uniform repairing effect on the pollutants in different areas of the soil can be realized, and meanwhile, the time of the whole soil repairing process can be effectively shortened.
5. The method for repairing the polluted soil provided by the invention heats the polluted soil for 3-5 days, and performs pre-extraction treatment on the groundwater at least once every day. Groundwater in soil is extracted in the heating process, groundwater flow can be quickened, heat conduction is driven to rise, temperature difference of different areas in soil is reduced, overall uniform heating of soil is achieved, poor treatment effect of low-temperature areas caused by uneven heating is avoided, and the situation that adsorbed pollutants are reversely permeated into groundwater after stopping treatment for a period of time to cause phenomena of rebound, tailing and the like of the pollutants is avoided.
The effective time of the repairing agent is limited, usually 1 day to 1 month, the soil heating rate is low, if the agent is injected first and then heated, the repairing agent may be invalid when a thermal field arrives, and the agent is injected under the condition of heat preservation after the soil temperature rises to a target temperature, so that the combination effect of the thermal field and the repairing agent can be ensured.
6. The method for restoring the polluted soil provided by the invention comprises the following steps of: step 1, starting a first group of pumping and injecting pipelines to perform groundwater extraction treatment, ending extraction, and performing injection repair medicament treatment by adopting a second group of pumping and injecting pipelines; step 2, repeating the step 1; step 3, starting a second group of pumping and injecting pipelines to perform groundwater extraction treatment, ending extraction, and performing injection repair medicament treatment on the first group of pumping and injecting pipelines; step 4, repeating the step 3; preferably, steps 1-2 and steps 3-4 are performed alternately.
By adopting the mode of separate extraction and intermittent extraction and injection, the water head difference and negative pressure brought can lead the injected medicament to be better diffused, and the uniformity of radius and distribution is improved, thereby ensuring the removal effect of pollutants in different areas of the soil.
Compared with the traditional in-situ chemical oxidation repair technology, the method has the advantages that the applicable pollutant concentration range is wider, and the defect that the traditional in-situ chemical oxidation repair technology cannot achieve the repair of a standard concentration interval is overcome. Through development of the technical demonstration project, the consumption of chemical agents is only about 50% of the target addition amount of the traditional in-situ chemical oxidation technology, and the problems of rebound and tailing which occur in the conventional chemical oxidation are avoided.
7. The injection pressure of the repairing agent is 0.1-1 MPa. The injection pressure of the repairing agent is lower, the soil cracks are not caused during injection, and the repairing agent can be matched with proper negative pressure caused by groundwater extraction, so that larger influence radius and better distribution uniformity can be obtained in the soil.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a system for restoring contaminated soil according to example 1 of the present invention;
FIG. 2 is a schematic view showing a partial distribution of a heating unit and a pumping well according to embodiment 1 of the present invention;
FIG. 3 shows temperature monitoring points T5 (1.5 m), T6 (1.73 m), T7 (0.5 m) and T8 (1 m) at different distances from the heating well H6 in example 2 of the present invention;
FIG. 4 is a temperature monitoring graph of temperature monitoring points in example 2;
(a) a T5 temperature monitoring map, (b) a T6 temperature monitoring map, (c) a T7 temperature monitoring map, and (d) a T8 temperature monitoring map;
FIG. 5 is a plot of the concentration of four contaminants in groundwater for example 2;
(a) a chloroform concentration profile, (b) a trichloroethylene concentration profile, (c) a tetrachloroethane concentration profile, and (d) a tetrachloroethylene concentration profile;
FIG. 6 is a graph of temperature monitoring at different distances from the same heating well in comparative example 1;
(a) a T9 (1.5 m) temperature monitor map, (b) a T10 (1 m) temperature monitor map, and (c) a T11 (0.5 m) temperature monitor map;
FIG. 7 is a graph showing the concentration of four contaminants in groundwater in comparative example 1;
(a) a chloroform concentration profile, (b) a trichloroethylene concentration profile, (c) a tetrachloroethane concentration profile, and (d) a tetrachloroethylene concentration profile;
reference numerals:
1-pumping and injecting well; 2-pumping and injecting pipelines; 201-a first set of pump lines; 202 a second set of pump lines; 3-a syringe pump; 4-a vacuum pump; 5-heating unit.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
Example 1
The embodiment provides a system for restoring polluted soil, which is shown in fig. 1 and 2 and comprises a heating unit 5 and a pumping and injecting device; the pumping and injecting device is used for extracting groundwater in the soil and injecting a repairing agent into the soil. The heating unit 5 is, for example, an electrically driven heating rod or a hot water driven heating tube.
The heating unit 5 is used for heating the polluted soil, the pumping and injecting device accelerates the flow of the underground water by extracting the underground water in the soil, promotes the high-temperature underground water nearby the heating unit 5 to migrate to a low-temperature area and drives heat conduction to raise the temperature, and reduces the temperature difference of different areas in the soil.
Specifically, the pumping and injecting device comprises a pumping and injecting pipeline 2, and a vacuum pump 4 and a syringe pump 3 which are respectively connected with the pumping and injecting pipeline 2. Illustratively, the vacuum pump 4 is a water ring vacuum pump 4 and the syringe pump 3 is an infusion diaphragm pump or peristaltic pump. When the underground water is required to be extracted from the soil, starting the vacuum pump 4; when the soil needs to be injected with the repairing agent, the injection pump 3 is turned on.
The pumping and injecting pipelines 2 are arranged in a plurality of rows at intervals, the plurality of rows of pumping and injecting pipelines 2 comprise a first group of pumping and injecting pipelines 201 and a second group of pumping and injecting pipelines 202, and the first group of pumping and injecting pipelines 201 and the second group of pumping and injecting pipelines 202 are arranged at intervals. Groundwater is extracted using either the first set of extraction lines 201 or the second set of extraction lines 202, and then a repair agent is injected using the other set of extraction lines. The head difference and the negative pressure caused by the separation extraction can lead the injected medicament to be better diffused, and improve the uniformity of influencing radius and distribution, thereby promoting the repair efficiency of chemical oxidation.
The heating units 5 are provided in plurality and uniformly spread over the contaminated soil area; the pumping and injecting pipelines 2 are provided with a plurality of rows which are uniformly distributed over the polluted soil area, and a plurality of pumping and injecting wells 1 are arranged at intervals in each row of pumping and injecting pipelines 2. Preferably, the heating units 5 are uniformly distributed in a triangular method, and more preferably, the heating units 5 are uniformly distributed in an equilateral triangle method in this embodiment. The plurality of pumping wells 1 are distributed according to a triangle method, more preferably, in the embodiment, the plurality of pumping wells 1 are distributed according to a regular triangle, the distance between the two heating units 5 is 2.5-5 m, and the distance between the two pumping wells 1 is 4-8 m. As shown in fig. 2, the distance between the two heating units 5 in this embodiment is 3m, and the distance between the two pumping wells 1 is 4m.
The system for remediating contaminated soil further includes a temperature monitoring unit, which may be, for example, a conventional temperature sensor, preferably provided with a plurality of temperature monitoring units uniformly distributed throughout the contaminated soil area for detecting the temperature throughout the contaminated soil area.
Example 2
The embodiment provides a method for repairing polluted soil, wherein the soil to be repaired is a silt saturated water-containing soil layer, and the hydraulic conductivity is 10 -5 ～10 -6 cm/s. The organic pollutants comprise chloroform, trichloroethylene, tetrachloroethylene and tetrachloroethane (specifically 1,2 tetrachloroethane), and the repairing agent is as follows: 10% sodium persulfate solution and 32% sodium hydroxide solution by mass fraction, 2800m of soil formula to be repaired 3 (about 5000 tons), the total application amount of the finished repair sodium persulfate is 25 tons, the sodium hydroxide solution is 9 cubic meters, and the total application amount of the sodium persulfate is 0.5 percent of the mass fraction of the soil to be repaired.
The embodiment provides a method for restoring polluted soil, specifically adopting the system for restoring polluted soil of embodiment 1, comprising the following steps:
s1, heating soil to be restored by adopting a heating unit;
s2, starting a vacuum pump and all pumping and injecting pipelines after heating is started for 5 days, pre-extracting groundwater in soil, ending extraction after the pumping water quantity is reduced to 70% of a peak value of the initial extraction, and repeating the pre-extraction of the groundwater for 2 times every day; and preserving heat when the average temperature of the soil to be repaired reaches 55 ℃.
S3, (1) opening a first group of pumping and injecting pipelines to extract the groundwater, and closing the first group of pumping and injecting pipelines to stop groundwater extraction after the pumping water quantity is reduced to 70% of the initial pumping peak value; the sodium hydroxide solution was injected by using a second set of suction and injection lines, 167L of sodium hydroxide solution was injected each time, and the injection pressure of the sodium hydroxide solution was 0.1MPa.
(2) Repeating the step (1) for 2 times every day for 7 days, and then carrying out heat preservation reaction for 3 days to enable the sodium hydroxide solution to react with pollutants;
(3) Starting a second group of pumping and injecting pipelines to extract the groundwater, and closing the second group of pumping and injecting pipelines to stop groundwater extraction after the pumping water quantity is reduced to 70% of the initial pumping peak value; the sodium hydroxide solution was injected by using a first set of suction and injection lines, 167L of sodium hydroxide solution was injected each time, and the injection pressure of the sodium hydroxide solution was 0.1MPa.
(4) Repeating the step (3) for 2 times every day for 7 days, and then carrying out heat preservation reaction for 3 days to enable the sodium hydroxide solution to react with pollutants;
(5) Starting a first group of pumping and injecting pipelines to extract the underground water, and closing the first group of pumping and injecting pipelines to stop the extraction of the underground water after the pumping water quantity is reduced to 70% of the initial extraction peak value; injecting sodium persulfate solution into a second group of pumping and injecting pipelines, wherein the application amount of sodium persulfate is 625kg each time, and the injection pressure of the sodium persulfate solution is 0.1MPa;
(6) Repeating the step (5) for 2 times every day for 10 days;
(7) Starting a second group of pumping and injecting pipelines to extract the groundwater, and closing the second group of pumping and injecting pipelines to stop groundwater extraction after the pumping water quantity is reduced to 70% of the initial pumping peak value; injecting sodium persulfate solution into a first group of pumping and injecting pipelines, wherein the application amount of sodium persulfate is 625kg each time, and the injection pressure of the sodium persulfate solution is 0.1MPa;
(8) Repeating the step (7) for 2 times every day for 10 days;
(9) Steps (1) to (4) and steps (5) to (8) are alternately performed.
As shown in fig. 5, the time immediately after the start of the injection of the restoration agent is set to be 0 th day, and after 39 days of the injection of the agent, the contamination in the soil is reduced to be less than the target value, and the injection of the agent is continued for 56 days, thereby completing the restoration of the soil.
Example 3
This example provides a method for remediation of contaminated soil, which is a high permeability field with a hydraulic conductivity of 10 -4 ～10 -5 cm/s. The organic pollutant is benzene petroleum hydrocarbon, including benzene, toluene, xylene and ethylbenzene, and the repairing agent is: sodium persulfate solution with mass fraction of 10% and soil formula quantity to be repaired of 5500m 3 (about 10000 tons), the total application amount of the remediation agent is 100 tons, which is 1% of the mass of the contaminated soil to be remediated.
This example employs the system for restoring contaminated soil of example 1, and the method for restoring contaminated soil comprises the steps of:
s1, heating soil to be restored at a low temperature by adopting a heating unit;
s2, starting a vacuum pump and all pumping and injecting pipelines after heating for 5 days, pre-extracting groundwater in the soil, finishing extraction after 20min of each extraction, repeating the pre-extraction of the groundwater for 3 times every day, and preserving heat when the average temperature of the soil to be repaired reaches 60 ℃.
S3, (1) opening a first group of pumping and injecting pipelines to extract the groundwater, and closing the first group of pumping and injecting pipelines after 20 minutes of extraction, and stopping groundwater extraction; injecting sodium persulfate solution into the second group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.5Mpa;
(2) Repeating the step (1) for 1 time every day for 7 days;
(3) Starting a second group of pumping and injecting pipelines to extract the underground water, and closing the second group of pumping and injecting pipelines after 20 minutes of extraction, and stopping the extraction of the underground water; injecting sodium persulfate solution into the first group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.5Mpa;
(4) Repeating the step (3) 1 time every day for 7 days;
(5) And (3) alternately performing the steps (1) and (2) and the steps (3) and (4), and reducing the concentration of the pollutants below a target value to finish the restoration of the soil to be restored.
Example 4
This example provides a method for remediation of contaminated soil with a hydraulic conductivity of 10 -5 ～10 -6 cm/s. The organic pollutant is polycyclic aromatic hydrocarbon including naphthalene, anthracene, phenanthrene and benzo [ a ]]Pyrene. The repairing agent comprises the following components: sodium persulfate solution with mass fraction of 10% and soil formula to be repaired of 2800m 3 (about 5000 tons), the total application amount of the remediation agent is 80 tons, which is 1.6% of the mass of the contaminated soil to be remediated.
This example employs the system for restoring contaminated soil of example 1, and the method for restoring contaminated soil comprises the steps of:
s1, heating soil to be restored at a low temperature by adopting a heating unit;
s2, starting a vacuum pump and all pumping and injecting pipelines after heating for 4 days, pre-extracting groundwater in the soil, ending the extraction after the pumping water quantity is reduced to 60% of the initial extraction peak value, repeating the pre-extraction of the groundwater for 3 times every day, and preserving heat after the average temperature of the soil to be repaired reaches 50 ℃.
S3, (1) opening a first group of pumping and injecting pipelines to extract the groundwater, and closing the first group of pumping and injecting pipelines to stop groundwater extraction after the pumping water quantity is reduced to 60% of the initial pumping peak value; injecting sodium persulfate solution into the second group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.3Mpa;
(2) Repeating the step (1) 3 times each day for 8 days;
(3) Starting a second group of pumping and injecting pipelines to extract the groundwater, and closing the second group of pumping and injecting pipelines to stop groundwater extraction after the pumping water quantity is reduced to 60% of the initial pumping peak value; injecting sodium persulfate solution into the first group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.3Mpa;
(4) Repeating the step (3) for 3 times every day for 8 days;
(5) And (3) alternately performing the steps (1) and (2) and the steps (3) and (4), and reducing the concentration of the pollutants below a target value to finish the restoration of the soil to be restored.
Comparative example 1
The present comparative example provides a method of restoring contaminated soil, in which contaminated sites, kinds and amounts of restoration drugs, and injection methods of restoration drugs are the same as those of example 2, except that groundwater extraction was not performed during the temperature raising process and the subsequent drug injection process.
The method comprises the following steps:
s1, heating soil to be restored by adopting a heating unit;
s2, heating time is the same as that adopted in the heating process of S2 in the embodiment 2;
s3. (1) sodium hydroxide solution was injected using a second set of pump injection lines, the injection pressure of the sodium hydroxide solution being 0.1MPa.
(2) Repeating the step (1) for 2 times every day for 7 days, and then carrying out heat preservation reaction for 3 days to enable the sodium hydroxide solution to react with pollutants;
(3) Sodium hydroxide solution was injected using a first set of pump lines at a pressure of 0.1MPa.
(4) Repeating the step (3) for 2 times every day for 7 days, and then carrying out heat preservation reaction for 3 days to enable the sodium hydroxide solution to react with pollutants;
(5) Injecting sodium persulfate solution by adopting a second group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.1MPa;
(6) Repeating the step (5) for 2 times every day for 10 days;
(7) Injecting sodium persulfate solution by adopting a first group of pumping and injecting pipelines, wherein the injection pressure of the sodium persulfate solution is 0.1MPa;
(8) Repeating the step (7) for 2 times every day for 10 days;
(9) Steps (1) to (4) and steps (5) to (8) are alternately performed, and the time from the start of the injection of the chemical to the end of the treatment is the same as in example 2.
Experimental example 1
The groundwater contamination levels before and after soil remediation of example 2 and comparative example 1 were tested according to HJ 605-2011- -determination of soil and sediment volatile organics purge trap- -gas chromatograph-Mass Spectrometry. Organic contaminants include vinyl chloride, cis-1, 2-dichloroethylene, chloroform, 1, 2-dichloroethane, trichloroethylene, 1, 2-trichloroethane, tetrachloroethane, tetrachloroethylene, and hexachloroprene. Various pollutants at random monitoring points (respectively marked as M1-M5) in the soil are detected at different times, the time when the repair agent starts to be injected is marked as day 0, the heating process without the agent is carried out before 0, and the time is marked as negative. The detection results are shown in tables 1 and 2, and ND is undetected.
Table 1 example 2 contaminant remediation targets and contaminant content
Table 2 comparative example 1 groundwater contaminant content
As can be seen from fig. 5 and table 1, the concentrations of chloroform, trichloroethylene, tetrachloroethane and tetrachloroethylene, which are organic pollutants at four monitoring points, were all reduced below the target value after 39 days of injection of the reagent in the pollutant of example 2, and the reagent was continuously injected for 56 days, and the concentration of the pollutant was still below the target value without rebound. And after the treatment is finished, the organic pollutants are detected again every 3 months, so that the rebound phenomenon is avoided.
As can be seen from fig. 7 and table 2, the pollutant concentration of comparative example 1 did not decrease below the target value after 39 days of injection of the chemical, and the chemical was continuously injected, and the pollutant concentration was rebound after 56 days, so that the soil restoration effect was poor and incomplete. And (3) detecting the organic pollutants again every 3 months after the treatment is finished, wherein rebound occurs.
FIG. 4 is a graph of temperature monitoring at the temperature monitoring points in example 2, and each of the graphs (a) - (d) in FIG. 4 further comprises temperature monitoring curves of the same temperature monitoring points at different distances (1 m, 4.5m, 8m, 11.5m, 15 m) from the ground.
FIG. 6 is a graph of temperature monitoring at different distances from the same heating well in comparative example 1, T9 distance of 1.5m, T10 distance of 1m, and T11 distance of 0.5m. The graphs (a) - (d) of fig. 6 further contain temperature monitoring curves of the same temperature monitoring point at different distances (1 m, 4.5m, 8m, 11.5m, 15 m) from the ground.
As can be seen from fig. 3 and fig. 4, the temperature monitoring points at different distances from the same heating well have more consistent heating rates in the heating stage, the heating effect achieved by heating is consistent, and the temperature ranges of the different temperature monitoring points after heating for 45 days are also more consistent, so that the heating uniformity of the invention is reflected. As can be seen from fig. 6, in comparative example 1 in which groundwater extraction was not performed, the temperature rising rates of the different temperature monitoring points were different, the heating effects achieved by the rising were different, the temperature ranges where the different temperature monitoring points were located were different greatly after 45 days of heating, the temperatures near the heating well reached 50 ° to 70 °, and the temperatures in the areas farther from the heating well were still only 20 ° to 30 °, and the soil temperatures were greatly different.
FIG. 5 is a graph of the concentration of four contaminants in groundwater for example 2, each of (a) - (d) further comprising four different locations M1, M2, M3, M4; fig. 7 is a graph showing concentration changes of four contaminants in groundwater in comparative example 1. The soil restoration effect of the invention is obviously higher than that of the soil restoration effect of which the groundwater extraction is not performed and only the heating and restoration agent is combined.
The energy consumption of the method is about 34% of that of the traditional in-situ heating repair of the same site (the traditional in-situ heating is simply to 100 ℃, and the volatilized pollutant steam is always extracted and removed in the process), and the repair agent injection amount of the method can be only 30% (mass ratio) of the repair agent amount of the in-situ chemical oxidation repair of the same site, so that the repair of the polluted soil can be completed, and acceptance inspection can be realized. The invention breaks through the limit that the standard can not be achieved by pure chemical injection in the same place. The traditional in-situ chemical injection is suitable for repairing chlorinated hydrocarbon with medium concentration or lower, for example, in groundwater with a few PPM levels, the concentration is high again, a tailing effect can be formed, and the pollution concentration rebounds again after the chemical injection reaction. The invention can be developed in the range of hundreds to 1000PPM of chlorinated hydrocarbon concentration, as shown in figure 5, the sum of the highest concentration of the four pollutants in the embodiment 2 is up to more than 600 PPM.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (6)
1. The method for repairing the polluted soil is characterized in that the adopted system for repairing the polluted soil comprises a heating unit and a pumping and injecting device for extracting groundwater in the soil and injecting a repairing agent into the soil, and the pumping and injecting device comprises a pumping and injecting pipeline, a pumping and injecting well, and a vacuum pump and an injection pump which are respectively connected with the pumping and injecting pipeline; the pumping and injecting pipelines are arranged at intervals, the pumping and injecting pipelines comprise a first group of pumping and injecting pipelines and a second group of pumping and injecting pipelines, and each row of pumping and injecting pipelines in the first group of pumping and injecting pipelines and the second group of pumping and injecting pipelines are alternately arranged;
the method for repairing the polluted soil comprises the steps of heating the soil to be repaired, extracting groundwater for treatment and injecting a repairing agent for treatment;
heating for 3-5 days, and pre-extracting groundwater at least once every day; heating the average temperature of the soil to be repaired to 40-60 ℃, and then carrying out groundwater extraction treatment and repair agent injection treatment; carrying out groundwater extraction treatment and repair agent injection treatment under the heat preservation condition of 40-60 ℃;
the organic pollutant is chlorinated hydrocarbon, the repairing agent comprises a reducing agent and an oxidizing agent, and the reducing agent is injected first and then the oxidizing agent is injected;
the steps of extracting groundwater treatment and injecting repairing agent treatment comprise:
(1) Starting a first group of pumping and injecting pipelines to extract the underground water, and closing the first group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting part of the reducing agent by adopting a second group of pumping and injecting pipelines, wherein the injection pressure of the reducing agent is 0.1MPa, and the PH value is adjusted to 12;
(2) Repeating the step (1) for 1-3 times every day, stabilizing the PH value at 12, repeating the reaction for 5-7 days, and continuously reacting for 2-5 days, wherein extraction and injection of medicament are not performed in the reaction process;
(3) Starting a second group of pumping and injecting pipelines to extract the underground water, and closing the second group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting part of the reducing agent by adopting a first group of pumping and injecting pipelines, wherein the injection pressure of the reducing agent is 0.1MPa;
(4) Repeating the step (3) for 1-3 times every day, stabilizing the PH value at 12, repeating the reaction for 5-7 days, and continuously reacting for 2-5 days, wherein extraction and injection of medicament are not performed in the reaction process;
(5) Starting a first group of pumping and injecting pipelines to extract the underground water, and closing the first group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting a part of oxidizing agent by adopting a second group of pumping and injecting pipelines, wherein the injection pressure of the oxidizing agent is 0.1MPa;
(6) Repeating the step (5) for 1-3 times every day for 7-10 days;
(7) Starting a second group of pumping and injecting pipelines to extract the underground water, and closing the second group of pumping and injecting pipelines to stop the extraction of the underground water after the extraction water quantity is reduced to 50-70% of the extraction peak value; injecting a part of oxidizing agent by adopting a first group of pumping and injecting pipelines, wherein the injection pressure of the oxidizing agent is 0.1MPa;
(8) Repeating the step (7) for 1-3 times every day for 7-10 days;
(9) The steps (1) - (4) and the steps (5) - (8) are alternately carried out until the pollutants in the soil are reduced below the target value, and the soil restoration is completed;
after the concentration of the pollutants in the soil is reduced below a target value, continuously injecting the medicament for 5-30 days;
the total application amount of the oxidizing agent is 0.5-2% of the mass of the soil to be repaired.
2. The method of remediating contaminated soil according to claim 1, wherein at least one of the following (1) - (2) is satisfied:
(1) The heating unit is provided with a plurality of heating units;
(2) And a plurality of pumping and injecting wells are arranged at intervals on each row of pumping and injecting pipelines.
3. A method of remediating contaminated soil according to claim 2, wherein a plurality of said heating units are positioned in the soil to be remediated at triangular intervals.
4. A method of remediating contaminated soil according to claim 2, wherein a plurality of said extraction and injection wells are triangularly distributed.
5. The method for remediating contaminated soil according to any of claims 1-4, wherein said reducing agent is selected from at least one of sodium hydroxide solution, vegetable oil.
6. The method for remediating contaminated soil according to any of claims 1-4, wherein said oxidizing agent is selected from at least one of hydrogen peroxide, persulfate, potassium permanganate.
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| CN115780493A (en) * | 2022-10-24 | 2023-03-14 | 武汉轻工大学 | Soil normal position thermal activation repair system |
| CN116037639B (en) * | 2023-01-31 | 2023-10-03 | 江苏省环境科学研究院 | Drip irrigation type automatic injection process and device for in-situ restoration agent of soil and underground water |
| CN116393501B (en) * | 2023-06-08 | 2023-08-29 | 北京建工环境修复股份有限公司 | Repairing system and method for trichloromethane polluted site |
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