KR101831387B1 - In-situ remediation method for oil-contaminated soil and device for in-situ remediation of oil-contaminated soil - Google Patents

In-situ remediation method for oil-contaminated soil and device for in-situ remediation of oil-contaminated soil Download PDF

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KR101831387B1
KR101831387B1 KR1020150172474A KR20150172474A KR101831387B1 KR 101831387 B1 KR101831387 B1 KR 101831387B1 KR 1020150172474 A KR1020150172474 A KR 1020150172474A KR 20150172474 A KR20150172474 A KR 20150172474A KR 101831387 B1 KR101831387 B1 KR 101831387B1
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groundwater
oxidant
alkali
ground
injecting
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KR20170066001A (en
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김지훈
김민균
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재단법인 포항산업과학연구원
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
    • B01D17/02—Separation of non-miscible liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
    • B09C1/002—Reclamation of contaminated soil involving in-situ ground water treatment
    • 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
    • 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
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C2101/00—In situ

Abstract

The present invention relates to a method for in-situ purification of oil-contaminated soil, and an in-situ purification apparatus for oil-contaminated soil, which is a method for in-situ purification of oil-contaminated soil using a circulation system in which groundwater circulates between the ground surface and the ground surface. An alkali injection step of injecting an alkali material; And an oxidant injecting step of injecting an oxidant into the groundwater at an upper part of the ground, wherein the alkali injecting step and the oxidant injecting step are alternately performed, and a method for purifying in- Device can be provided.

Description

TECHNICAL FIELD [0001] The present invention relates to an in-situ purification method for oil contaminated soil and an in-situ purification apparatus for oil contaminated soil. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

The present invention relates to an in-situ purification method for oil-contaminated soil and an in-situ purification apparatus for oil-contaminated soil.

At present, pollution accidents due to oil pollutants such as BTEX, diesel and gasoline are frequently occurring in the surrounding areas such as gas stations, gas stations and oil pipelines. As the large-scale soil pollution purification project to treat these oil pollutants proceeds, technology and experience are accumulating. These oil contaminated soils can be treated through various treatment methods such as biological treatment, physical treatment and chemical treatment, and appropriate treatment methods are selected according to the polluted site conditions and the characteristics of pollutants.

Among them, the biological treatment method is a treatment technique using metabolism of microorganisms, which has advantages of low cost but has a long treatment period, byproducts, and is difficult to be utilized in a high concentration contaminated area.

 Physical treatment techniques, such as thermal desorption and soil vapor extraction (SVE) techniques, remove contaminants from the soil bed, but are not fundamentally treated. In addition, only the volatile organic compound can be removed by the soil vapor extraction method. That is, the gasoline form is easy to remove, but it is difficult to remove the diesel, the high molecular weight and the less volatile form. Furthermore, since air is removed by artificially flowing it, it is difficult to apply to clay which is a soil in which air can not flow well.

These techniques are complementary to chemical oxidation methods. An oxidizing agent such as hydrogen peroxide is artificially injected into the soil to completely remove the contaminants by water and carbon dioxide. Hydrogen peroxide has been mainly used as such an oxidizing agent, and a lot of research has been conducted on the decomposition of organic compounds using hydroxyl radicals using the hydrogen peroxide. However, hydrogen peroxide has a disadvantage that the residence time in soil is very short. In order to compensate for this, peroxosulfuric acid is the oxidizing agent, sulfate radicals generated by sulfuric acid peroxide persist for a long time when injected into the soil, and hydroxyl radicals (sulfate radicals) hydroxyl radicals are also incidentally generated simultaneously.

Chemical oxidation generally has a short treatment time and high treatment efficiency. However, in the case of soils polluted by oil, the problem of the oxidation efficiency being remarkably reduced as the oil component is adsorbed on the surface and changed to hydrophobic have. In addition, when the oil is removed through the chemical reaction in the soil without desorbing the oil, the injected chemical may not react with the oil and may be consumed as it is.

As another method, there is a soil washing method in which oil components are extracted by reducing the surface energy of the soil particles by using a solvent, an acid, an alkali, a surfactant, and the like. This is a method in which a surfactant, an organic solvent, an acidic or an alkaline solution is mixed with a soil to be desorbed into a soil and brought into an aqueous solution by removing contaminants which have been adsorbed on a solid phase by a cleaning agent. However, the soil washing method has a problem that the washing efficiency is lowered at a certain concentration or less and the treatment can not be completed. In addition, since all of the input materials can not be recovered, secondary contamination due to residue of the input may be caused, or after-treatment may occur due to bubbles of groundwater caused by the surfactant.

The present invention provides a method for in-situ purification of oil-contaminated soil and an in-situ purification apparatus for oil-contaminated soil that can effectively and economically treat soil contaminated with oil.

An embodiment of the present invention is a method for in-situ purification of oil contaminated soil using a circulation system in which groundwater circulates between a bottom of a ground and an upper surface of the ground, comprising: an alkali injection step of injecting an alkali material into groundwater; And an oxidant injecting step of injecting an oxidant into the groundwater at the upper part of the ground, wherein the alkali injecting step and the oxidant injecting step are alternately performed.

In the alkali injection step, the pH of the groundwater may be adjusted to 9 or more and 12 or less through the alkali injection step.

The step of injecting the oxidant may include the step of adding an oxidizing agent so that the concentration of the oxidizing agent in the groundwater is more than 2 g / L and less than 10 g / L.

In the in-situ purification method of the oil contaminated soil, the ratio of the alkali material injection amount in the alkali injection step to the oxidant injection amount in the oxidant injection step may be 1/10 or more and 3/1 or less.

The alkali injection step and the oxidant injection step may be alternately performed to form an alkali-oxidant superposition region in the ground.

The oxidizing agent may be activated by the alkali substance.

The oxidizing agent may be activated in the paper by the alkali substance.

The activation of the oxidizing agent by the alkaline substance may include a radical generating reaction by a reaction between a base and an oxidizing agent.

The alkali substance in the alkali injection step may be sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) 2 ), magnesium hydroxide (Mg (OH) 2 ) or a mixture thereof.

The oxidant in the oxidant injecting step may be peroxide.

The oxidizing agent in the oxidant injecting step may be selected from the group consisting of sodium persulfate (Na 2 S 2 O 8 ), hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ), ozone (O 3 ) It may be a mixture.

Another embodiment of the present invention is directed to an extraction facility for extracting groundwater from the bottom of the ground to the top of the ground; A water separation tank for separating and removing the treated free phase oil; Groundwater adjustment tank; An alkaline storage tank connected to the groundwater adjustment tank; An oxidant storage tank connected to the groundwater adjustment tank; Injection wells that inject groundwater from the top of the ground to the bottom of the ground; And a groundwater flow pipe connecting the extraction pipe, the water separation tank, the groundwater adjustment tank, and the injection pipe, wherein the groundwater flows along the groundwater flow pipe along the extraction pipe, the water separation tank, the groundwater adjustment tank, And an alkaline substance is injected into the groundwater regeneration tank from the alkali storage tank, and an oxidant is injected from the oxidizer storage tank into the groundwater regeneration tank.

The purifier may further include a water treatment tank.

The purifier may alternatively perform the steps of injecting the alkali material from the alkali storage tank into the groundwater adjustment tank and injecting the oxidant into the groundwater adjustment tank from the oxidizer storage tank so as to operate in such a manner that an alkali- .

The purifier may be operated so that the pH of the groundwater is adjusted to 9 or more and 12 or less through the process of injecting the alkali material from the alkali storage tank into the groundwater adjustment tank.

The purifier may be operated so that the concentration of the oxidizing agent in the groundwater is adjusted to be higher than 2 g / L and lower than 10 g / L through the process of injecting the oxidizer from the oxidizer reservoir to the groundwater regulator.

In the purifying apparatus, the alkali material is injected from the alkaline storage tank into the groundwater regeneration tank, and the ratio of the amount of the alkali material injected to the oxidant injection amount in the process of injecting the oxidant into the groundwater regeneration tank from the oxidant storage tank is 1/10 or more, 3/1 or less.

An embodiment of the present invention can provide an in-situ purification method for oil-contaminated soil and an in-situ purification apparatus for oil-contaminated soil that can effectively and economically treat soils contaminated with oil.

1 is an exemplary schematic diagram of an apparatus for purifying contaminated soil in accordance with an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

An embodiment of the present invention is a method for in-situ purification of oil contaminated soil using a circulation system in which groundwater circulates between a bottom of a ground and an upper surface of the ground, comprising: an alkali injection step of injecting an alkali material into groundwater; And an oxidant injecting step of injecting an oxidant into the groundwater at the upper part of the ground, wherein the alkali injecting step and the oxidant injecting step are alternately performed.

In the case of soil contaminated by oil in the lower part of the ground and an underground water flows, an extraction well for extracting ground water from the lower part of the ground and an injection well for re-injecting ground water from the upper part of the ground to the lower part of the ground are installed, Can be configured. At this time, it is possible to inject the alkaline substance or the oxidizing agent into the ground water at the upper part of the ground, and to re-inject the ground water to the lower part of the ground through the injection pipe. When the groundwater is re - injected into the ground by injecting alkali material into the groundwater at the upper part of the ground, an alkaline saturated area is formed at the lower part of the ground, and the oil can be eluted from the soil. Thereafter, when the oxidant is injected into the extracted groundwater by circulating the upper part of the ground again, the oxidant saturated area may be formed in the lower part of the ground by re-injecting into the ground bottom part. As a result, a region where an alkali substance and an oxidizer overlap each other can be formed at the bottom of the ground, an oxidizing agent is activated by an alkali substance to generate radicals, and the oil eluted into the groundwater due to the oxidation reaction by radicals forms carbon dioxide (CO 2 ) , Water (H 2 O), or harmless to the human body.

The alkali substance in the alkali injection step may be sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) 2 ), magnesium hydroxide (Mg (OH) 2 ) or a mixture thereof.

The oxidizing agent in the oxidant injecting step may be peroxide. More specifically, sodium persulfate (Na 2 S 2 O 8 ) hydrogen peroxide (H 2 O 2 ), potassium permanganate , KMnO 4), ozone (O 3) or may be a mixture thereof.

The pH of the groundwater can be adjusted to 9 or more and 12 or less through the alkali injection step. More specifically 10 or more, and 12 or less. From this range, elution of the oil component into the groundwater can be facilitated.

The step of injecting the oxidant may include the step of adding an oxidizing agent so that the concentration of the oxidizing agent in the groundwater is more than 2 g / L and less than 10 g / L. More concretely, 3 g / L or more and 10 g / L or less; 3 g / L or more, and 7 g / L or less; Or 3 g / L or more, and 5 g / L or less; When too much oxidant is added, the pH of the groundwater may be lowered, and the elution of the oil component into the groundwater may be insignificant. When the oxidizing agent is added too little, the decomposition effect of the oil component may be insignificant.

The ratio of the alkali material injection amount in the alkali injection step to the oxidant injection amount in the oxidant injection step may be 1/10 or more and 3/1 or less. For the amount of oxidizing agent injected, if the amount of injected alkaline substance is too large, the occlusion phenomenon may occur in the injection well due to the increase of the suspended matter. When the injection amount of the alkaline substance is too small with respect to the amount of the oxidizing agent injected, the pH of the groundwater is lowered and the elution of the oil component into the groundwater may be insignificant.

Hereinafter, the role of the oxidizing agent and the alkaline substance injected into the groundwater will be described.

When an alkaline substance is injected into the soil, the charge of the soil particles is changed and the oil is eluted into the groundwater. In addition, saponification reaction occurs between a part of the oil and the alkaline substance, and the surfactant is generated, so that the elution of the oil is facilitated and the oil eluted into the groundwater is prevented from re-adsorption to the soil.

However, when only the dissolution of contaminants by alkaline substances is carried out, salts (Ca (OH) 2 , Mg (OH) 2 ) are precipitated due to the increase of pH and the total concentration of suspended solids (TSS) Clumping phenomenon may occur, and the pH of the soil after the completion of the extraction may be increased, so that a neutralization operation may be further required.

The oil eluted into the groundwater by the alkaline substance can be oxidized by a peroxide, for example persulfuric acid. Persulfate oxidation technique is a technique to treat various organic and inorganic materials by generating persulfate anion (2S 2 O 8 2 - ). The persulfate anion has a high solubility in water and can be applied to a wide pH range. And the value of the sulfate anion half-cell redox potential (half-cell oxidation reduction potential, E 0) of the to 2.01 V, the ozone (E 0 = 2.07 V) and hydrogen peroxide (E 0 = 1.78 V), and permanganate (E 0 = 1.70 V), and it produces sulfate radicals (SO 4 - , E 0 ~2.6 V) which are stronger oxidants through the activation process. Generally, the following methods can be used to generate sulfate radicals by activating persulfate anions.

(1) Photochemical activation: S 2 O 8 2- + e - → SO 4 - + SO 4 2-

(2) Thermally activation: S 2 O 8 2- + heat → 2SO 4 -

(3) Metal ion activation: S 2 O 8 2- + Fe 2+ ? SO 4 - + Fe 3+ + SO 4 2-

(4) Alkali activation: 2S 2 O 8 2- + 2H 2 O + Alkali 3SO 4 2- + SO 4 - + O 2 - + 4H +

The sulfuric acid can be activated by an already introduced alkali substance as shown in the formula (4) to generate a radical to cause an oxidation reaction. Finally, the oil can be decomposed into carbon dioxide, water, or a harmless substance to the human body.

However, when only persulfate is injected into the groundwater and re-injected into the bottom of the ground, the contaminated soil surface becomes hydrophobic due to the oil, which lowers the oxidation reaction efficiency. When the surrounding structure is lowered, Lt; / RTI >

In order to solve the problems that may occur when only the alkali substance is injected or only the oxidizing agent is injected as described above, a method of simultaneously injecting the alkali substance and the oxidizing agent may be considered.

However, when an alkaline substance and an oxidizing agent such as persulfuric acid are injected at the same time, persulfuric acid radicals are generated rapidly in a high pH condition, and persulfuric acid is consumed before being put into the ground, , It may be difficult to induce oxidation reaction to a desired region because the radius at which the oxidation reaction occurs is shortened.

However, as in an embodiment of the present invention, the process of re-injecting groundwater circulating in the lower part of the ground and the upper part of the ground to the lower part of the ground is repeated by alternately injecting the alkali material and the oxidant at the upper part of the ground, When the oxidizing agent superposition region is formed, the pH raised by the alkali substance is lowered to the neutral condition again by the oxidizing agent such as persulfuric acid, so that the damage of the surrounding environment can be minimized.

In addition, when alkali is injected into the ground, clogging of the sludge may occur due to accumulation of sludge in the injection well, but it is possible to maintain the pH at a certain level by repeating alkali and persulfuric acid, .

In addition, when the alkali material and persulfate are alternately injected, it is possible to generate persulfate radicals in the ground, minimize persulfuric acid consumption, extract residual oil pollution, and then utilize the residual alkali material in the production of persulfate radicals do. Further, since the alkali substance is neutralized by persulfuric acid, no additional neutralization work is required, and the occlusion phenomenon of the injection port can be prevented.

Another embodiment of the present invention is an apparatus for treating groundwater, comprising: an extraction conduit (4) for extracting groundwater from the bottom of the ground to the top of the ground; A water separation tank (5) for separating and removing the treated free phase oil; Groundwater conditioning tank 7; An alkaline storage tank (8) connected to the groundwater adjustment tank; An oxidant storage tank (9) connected to the groundwater adjustment tank; An injection well 10 for injecting groundwater from the top of the ground to the bottom of the ground; And a groundwater flow pipe (3) connecting the extraction pipe, the water separation tank, the groundwater adjustment tank, and the injection pipe, wherein the ground water includes the extraction pipe, the water separation tank, the groundwater adjustment tank, And then an alkaline substance is injected into the groundwater regeneration tank from the alkali storage tank and the oxidant is injected from the oxidizer storage tank into the groundwater regeneration tank.

The purifier may further comprise a water treatment tank 6 for further purifying the purified water, if necessary. The water treatment tank may be located, for example, next to the water separation tank 5, with reference to the groundwater flow direction above the ground surface.

The soil 2 contaminated by the oil 2 may be present in the lower part of the ground 1 and the extraction conduit 4 and the injection conduit 10 may be installed when the ground water flows therein, . ≪ / RTI > At this time, the alkaline substance (8) is introduced into the groundwater from the alkali storage tank (8) to the groundwater adjustment tank (7), and the groundwater can be re-injected into the groundwater. As a result, the alkali saturation region 11 is formed in the lower part of the ground, and the oil in the groundwater can be eluted. Thereafter, the oxidant 9 is injected into the groundwater regeneration tank 7 from the oxidant storage tank 7 to the groundwater circulated upward to the upper surface of the ground, and the groundwater is re-injected to the ground bottom, . As a result, an area 13 where an alkali substance and an oxidizing agent are overlapped can be formed in the lower part of the ground according to the flow of the groundwater under the ground. At this time, the oxidizing agent is activated by the alkali substance to generate radicals, and the oil eluted into the groundwater by the oxidation reaction by the radical can be converted into carbon dioxide (CO 2 ), water (H 2 O) have. Free-phase oil extracted without reacting with alkaline or oxidizing agent can be separated and removed from the water separator 5 installed on the upper surface of the ground.

The pH of the groundwater may be controlled to be 9 or more and 12 or less through the process of injecting the alkali material from the alkali storage tank into the groundwater adjustment tank. More specifically 10 or more, and 12 or less. From this range, elution of the oil component into the groundwater can be facilitated.

The concentration of the oxidizing agent in the groundwater may be controlled to be controlled to be higher than 2 g / L and lower than 10 g / L by injecting the oxidizing agent from the oxidizing agent reservoir into the groundwater regulator. More concretely, 3 g / L or more and 10 g / L or less; 3 g / L or more, and 7 g / L or less; Or 3 g / L or more, and 5 g / L or less. When too much oxidant is added, the pH of the groundwater may be lowered, and the elution of the oil component into the groundwater may be insignificant. When the oxidizing agent is added too little, the decomposition effect of the oil component may be insignificant.

The ratio of the amount of the alkali substance injected to the amount of the oxidizing agent injected in the process of injecting the alkali substance into the groundwater regeneration tank from the alkaline storage tank and injecting the oxidizing agent into the groundwater regeneration tank from the oxidizing agent storage tank is 1/10 or more and 3/1 or less . For the amount of oxidizing agent injected, if the amount of injected alkaline substance is too large, the occlusion phenomenon may occur in the injection well due to the increase of the suspended matter. When the injection amount of the alkaline substance is too small with respect to the amount of the oxidizing agent injected, the pH of the groundwater is lowered and the elution of the oil component into the groundwater may be insignificant.

Hereinafter, the role of the oxidizing agent and the alkaline substance injected into the groundwater will be described.

When an alkaline substance is injected into the soil, the charge of the soil particles is changed and the oil is eluted into the groundwater. In addition, saponification reaction occurs between a part of the oil and the alkaline substance, and the surfactant is generated, so that the elution of the oil is facilitated and the oil eluted into the groundwater is prevented from re-adsorption to the soil.

However, when only the dissolution of contaminants by alkaline substances is carried out, salts (Ca (OH) 2 , Mg (OH) 2 ) are precipitated due to the increase of pH and the total concentration of suspended solids (TSS) Clumping phenomenon may occur, and the pH of the soil after the completion of the extraction may be increased, so that a neutralization operation may be further required.

The oil eluted into the groundwater by the alkaline substance can be oxidized by a peroxide, for example persulfuric acid. Persulfate oxidation technique is a technique to treat various organic and inorganic materials by generating persulfate anion (2S 2 O 8 2 - ). The persulfate anion has a high solubility in water and can be applied to a wide pH range. And the value of the sulfate anion half-cell redox potential (half-cell oxidation reduction potential, E 0) of the to 2.01 V, the ozone (E 0 = 2.07 V) and hydrogen peroxide (E 0 = 1.78 V), and permanganate (E 0 = 1.70 V), and it produces sulfate radicals (SO 4 - , E 0 ~2.6 V) which are stronger oxidants through the activation process. Generally, the following methods can be used to generate sulfate radicals by activating persulfate anions.

(1) Photochemical activation: S 2 O 8 2- + e - → SO 4 - + SO 4 2-

(2) Thermally activation: S 2 O 8 2- + heat → 2SO 4 -

(3) Metal ion activation: S 2 O 8 2- + Fe 2+ ? SO 4 - + Fe 3+ + SO 4 2-

(4) Alkali activation: 2S 2 O 8 2- + 2H 2 O + Alkali 3SO 4 2- + SO 4 - + O 2 - + 4H +

The sulfuric acid can be activated by an already introduced alkali substance as shown in the formula (4) to generate a radical to cause an oxidation reaction. Finally, the oil can be decomposed into carbon dioxide, water, or a harmless substance to the human body.

However, when only persulfate is injected into the groundwater and re-injected into the bottom of the ground, the contaminated soil surface becomes hydrophobic due to the oil, which lowers the oxidation reaction efficiency. When the surrounding structure is lowered, Lt; / RTI >

In order to solve the problems that may occur when only the alkali substance is injected or only the oxidizing agent is injected as described above, a method of simultaneously injecting the alkali substance and the oxidizing agent may be considered.

However, when an alkaline substance and an oxidizing agent such as persulfuric acid are injected at the same time, persulfuric acid radicals are generated rapidly in a high pH condition, and persulfuric acid is consumed before being put into the ground, , It may be difficult to induce oxidation reaction to a desired region because the radius at which the oxidation reaction occurs is shortened.

However, as in an embodiment of the present invention, the process of re-injecting groundwater circulating in the lower part of the ground and the upper part of the ground to the lower part of the ground is repeated by alternately injecting the alkali material and the oxidant at the upper part of the ground, When the oxidizing agent superposition region is formed, the pH raised by the alkali substance is lowered to the neutral condition again by the oxidizing agent such as persulfuric acid, so that the damage of the surrounding environment can be minimized.

In addition, when alkali is injected into the ground, clogging of the sludge may occur due to accumulation of sludge in the injection well, but it is possible to maintain the pH at a certain level by repeating alkali and persulfuric acid, .

In addition, when the alkali material and persulfate are alternately injected, it is possible to generate persulfate radicals in the ground, minimize persulfuric acid consumption, extract residual oil pollution, and then utilize the residual alkali material in the production of persulfate radicals do. Further, since the alkali substance is neutralized by persulfuric acid, no additional neutralization work is required, and the occlusion phenomenon of the injection port can be prevented.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example

Example 1: Analysis of TPH elution amount according to pH

The contaminated soil and groundwater used in this example were collected at a contaminated soil purification site in Gangneung. The soil was subjected to TPH analysis by soil pollution process test method and found to be about 19,800 mg / kg. The pollutants were mainly alkyl compounds and aromatic compounds.

Table 1 below shows the results of TPH elution from contaminated soil to groundwater according to pH. TPH analysis was carried out by soil pollution process test method. The pH was changed as shown in Table 1 by changing the concentration of the alkaline substance (NaOH, manufactured by Sigma Aldirch, hereinafter the same) to the ground water. The weight ratio of the contaminated soil and the groundwater was 1: 2 and the mixture was stirred for 2 hours. The concentration of TPH dissolved in groundwater was measured. As a result, it was confirmed that the amount of TPH eluted from soil to groundwater rapidly increased from pH 10 or higher. (Examples 1 and 2). However, at pH lower than 10, TPH eluted into groundwater was limited. (Comparative Examples 1 to 3)

pH TPH in groundwater (ppm) Example 1 10.42 813.1 Example 2 11.53 1930.7 Comparative Example 1 5.43 320.1 Comparative Example 2 7.69 330.4 Comparative Example 3 9.61 600.5

Example 2: Analysis of TPH degradation efficiency according to the concentration of oxidizing agent in ground water and pH

Table 2 shows the TPH degradation test results in the groundwater according to the concentration and pH of persulfate in the groundwater. TPH analysis was carried out by soil pollution process test method. Groundwater was prepared by varying the concentration of alkaline substance and persulfuric acid (manufacturer: Sigma Aldirch, hereinafter the same) in the groundwater, and the soil and groundwater were mixed at a weight ratio of 1: 2 for 2 hours. The supernatant was collected, . It was confirmed that the amount of TPH eluted into the groundwater increases as the pH of the groundwater increases (Comparative Examples 4 to 6), but it is confirmed that the eluted TPH is sufficiently removed when persulfuric acid is added in an amount of 3 g / L or more (Examples 3 and 4 ) When the pH was low, the decomposition effect of TPH due to the addition of sulfuric acid was not significant. (Comparative Example 7)

pH Sulfuric acid (g / L) TPH in groundwater (ppm) Example 3 10.42 3 145.2 Example 4 11.53 5 115.1 Comparative Example 4 11.53 0 1930.7 Comparative Example 5 11.53 One 1815.2 Comparative Example 6 11.53 2 1545.2 Comparative Example 7 7.69 5.0 281.0

Example  3: Groundwater Alkaline  Analysis of change of pH and suspended matter according to concentration of substance and oxidizer

Table 3 shows experimental results of changes in pH and total suspended solids of groundwater according to concentrations of alkaline and persulfate in groundwater. The concentration of suspended solids in the groundwater was calculated by measuring the difference in weight before and after drying the suspended solids and filter by filtering groundwater using 0.45 μm pore size filter. (Comparative Example 10 and Comparative Example 11) However, when a certain concentration of persulfuric acid was added together (Example 5), the concentration of the total suspended solids did not add the alkali (Comparative Example 8 and Comparative Example 9) That is, when the pH is maintained at a constant level by adding persulfuric acid and an alkali substance together, it is possible to prevent obstruction Can be confirmed.

NaOH (g / L) Sulfuric acid (g / L) pH Suspended substance (mg / L) Example 5 0.3 3 7.67 15.5 Comparative Example 8 0 3 6.7 11.2 Comparative Example 9 0 0 7.5 12 Comparative Example 10 0.3 0 10.55 257 Comparative Example 11 0.6 0 11.27 483.5

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1. Ground 2. Oil polluted area 3. Groundwater flow pipe
4. Extraction well 5. Oil separation tank 6. Water treatment tank
7. Groundwater adjustment tank 8. Alkaline storage tank 9. Oxidant storage tank
10. Injection well 11. Alkali saturated area
12. Oxidizer saturated area 13. Alkali-oxidizer overlap area
14. Groundwater flow direction

Claims (17)

This is a method for in-situ purification of oil-contaminated soil using a circulation system in which groundwater circulates through the bottom of the ground and above the ground,
An alkali injection step of injecting an alkaline substance into the groundwater at the upper part of the ground; And
And an oxidant injecting step of injecting an oxidant into the groundwater at the top of the ground,
The alkali injection step, and the oxidant injection step are alternately performed,
The pH of the groundwater is adjusted to 10.42 to 11.53 through the alkali injection step,
Wherein the oxidant is injected such that the concentration of the oxidant in the groundwater is 3 to 5 g / L. delete delete The method of claim 1,
Wherein the mass ratio of the alkali material injection amount in the alkali injection step to the oxidizing agent injection amount in the oxidizing agent injection step is 1/10 or more and 3/1 or less. 5. The method of claim 4,
Wherein the alkali injection step and the oxidant injection step are alternately performed to form an alkaline-oxidant superposition region in the ground. The method of claim 5,
Wherein the oxidizing agent is activated by the alkaline substance. The method of claim 6,
Wherein the oxidizing agent is activated in the ground by the alkaline substance. 8. The method of claim 7,
Wherein the step of activating the oxidizing agent with the alkaline substance comprises a radical generating reaction by a reaction between a base and an oxidizing agent. 9. The method of claim 8,
Wherein the alkaline material in the alkali injection step is selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca (OH) 2 ), magnesium hydroxide (Mg (OH) 2 ) . The method of claim 9,
Wherein the oxidant in the oxidant injecting step is peroxide. 11. The method of claim 10,
The oxidizing agent in the oxidant injecting step may be selected from the group consisting of sodium persulfate (Na 2 S 2 O 8 ), hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ), ozone (O 3 ) In-situ purification of oil contaminated soil. An extraction well for extracting groundwater from the bottom of the ground to the top of the ground;
A water separation tank for separating and removing the treated free phase oil;
Groundwater adjustment tank;
An alkaline storage tank connected to the groundwater adjustment tank;
An oxidant storage tank connected to the groundwater adjustment tank;
Injection wells that inject groundwater from the top of the ground to the bottom of the ground; And
And a groundwater flow pipe connecting the extraction well, the water separation tank, the groundwater adjustment tank, and the injection well,
The groundwater circulates through the lower part of the ground and the upper part of the ground along the extraction gutters, the water seepage trough, the ground water regulating trough, the injection gutters,
An alkaline substance is injected from the alkali storage tank into a groundwater regulating tank,
An oxidant is injected into the groundwater regeneration tank from the oxidant storage tank,
Wherein the pH of the groundwater is adjusted to 10.42 to 11.53 through the process of injecting the alkali material from the alkali storage tank into the groundwater adjustment tank,
Wherein the concentration of the oxidizing agent in the groundwater is adjusted to 3 to 5 g / L by injecting the oxidizing agent from the oxidizing agent reservoir into the groundwater regulator.
In situ purification of oil contaminated soil. The method of claim 12,
Wherein the purifying apparatus further comprises a water treatment tank. The method of claim 12,
The process of injecting the alkaline substance from the alkali storage tank into the groundwater regeneration tank and the process of injecting the oxidant into the groundwater regeneration tank from the oxidizer storage tank are alternately performed to operate to form an alkaline- In situ purification device. delete delete The method of claim 12,
In the course of injecting the alkali material from the alkali storage tank into the groundwater adjustment tank and injecting the oxidant from the oxidizer storage tank into the groundwater adjustment tank,
Wherein the mass ratio of the alkali material injection amount to the oxidant injection amount is 1/10 or more and 3/1 or less.
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