KR101274588B1 - Method for selecting contaminated soil treating process - Google Patents

Abstract

The present invention relates to a method for determining the contaminated soil restoration method. The method for determining the contaminated soil restoration method according to the present invention comprises the steps of (a) taking a sample of contaminated soil, eluting contaminants in the contaminated soil using aqua regia, and (b) the amount of each contaminant eluted. Compared to 20 times of each pollutant regulation standard according to the US Environmental Protection Agency's Toxic Characteristic Leaching Procedure (TCLP) method, the first group and (C) measuring the pH of the contaminated soil classified into the first group, and classifying it into (a) group if the pH is greater than or equal to the predetermined value, and (b) if the pH is less than the predetermined group. (d) For the contaminated soil classified as Group 2, the heavy metal is eluted according to the waste process test method, and if the amount of the eluted heavy metal is less than the regulated content, the pH is measured for the contaminated soil and the pH is higher than the preset value ( All And (e) eluting heavy metals according to the Waste Process Test Method for contaminated soil classified as Group 2, and contaminating if the amount of heavy metals eluted is more than the regulated content. PH dissolution test for soil was carried out, and if the amount of heavy metals eluted was less than the standard value, it was classified into (e) group and (b) group, if it was abnormal, and (f) group A, C, E and F. It is decided to apply different restoration methods of the first treatment method to the fourth treatment method for the contaminated soil classified as.

Description

Method for selecting contaminated soil treating process

The present invention relates to a technique for reducing environmental pollution, and more particularly, to a method for determining a restoration technique suitable for the characteristics and conditions of a target soil among various techniques for restoring a contaminated soil.

The tailings refer to the mineral residues left after grinding the ore with the residues generated in the mine to select the necessary components, as shown in the photograph of Figure 1a, it is widely left in the abandoned mine area.

The neglected tailings are lost by concentrated rainfall or the tailings particles are scattered in the wind, contaminating rivers, farmland, and settlements around the mines. Soils and water systems around abandoned mines are constantly polluted and contain dozens or hundreds of times more heavy metals than ordinary soils.

In particular, the tailings and light waste-rock in metal mines contain a lot of sulfide minerals, and when reacted with dissolved oxygen in water, acidic water is generated and the heavy metals are eluted. Contaminate surface or ground water.

Therefore, it is necessary to treat tailings in an appropriate manner to prevent contamination of the abandoned mine area. Existing tailings treatment methods such as capping, retaining wall installation, and barrier type reclamation method have been proposed, but the actual mine reclamation project is carried out only by cover, a simple civil engineering method.

However, the tailings have different characteristics depending on the adult, geological and mineral species of the mine. For example, non-ferrous metal deposits and Cretaceous gold deposits have a high possibility of contamination of heavy metals, while Scarne deposits and hydrothermal shift deposits have been reported to be less likely. .

In addition, sulfide minerals differ in oxidation degree and type, transfer, and distribution characteristics of harmful heavy metals (lead, zinc, copper, cadmium, arsenic, etc.) dissolved according to mineral species. Of these, pyrite and pyrrhotite are easily oxidized in the surface environment to generate acidic drainage and promote dissolution of other sulfide minerals.

In other words, it is uneconomical to treat only the tailings of dormant and abandoned mines scattered all over the country, without any consideration of geological characteristics, physicochemical characteristics, slope stability, etc. In addition, safety is not secured and there is a limit in the follow-up management through long-term observation.

Looking at the photograph of the attained mine shown in FIG. 1B, there is a problem such that the mine drainage is leached even though the treatment is completed by covering soil.

Therefore, a protocol is required to standardize the systematic tailings evaluation method considering the characteristics of mines to derive reasonable tailings processing methods.

The present invention has been made to solve the above problems, and the structured soil treatment method that can classify the tailings according to the physical and chemical properties of the tailings and the ability to generate the contaminant, and adopt an efficient restoration method according to the characteristics of the classified tailings. The purpose is to provide a decision method.

Method for determining the contaminated soil treatment method according to the present invention for achieving the above object, (a) taking a sample of contaminated soil, eluting contaminants in contaminated soil using aqua regia, (b) eluted Compare the amount of each pollutant to more than 20 times that of each pollutant regulatory standard under the US Environmental Protection Agency's Toxic Characteristic Leaching Procedure (TCLP) method. Classifying the soil into the first group and the second group, respectively, (c) measuring the pH of the contaminated soil classified into the first group, and if the pH is more than a predetermined value (a), if less than ( (B) eluting the heavy metals according to the waste process test method for the contaminated soil classified into the second group, and if the amount of the eluted heavy metal is less than the regulated content, When the pH is measured and the pH is greater than or equal to a predetermined value, classifying into (C) group, and if less than (D), (E) contaminating soil classified into the second group according to the waste process test method If the amount of heavy metals eluted and the amount of eluted heavy metal is more than the regulated content, the dissolution test using pH 2-3 solution is conducted on the contaminated soil, and if the amount of heavy metals eluted is less than the standard value (e), if it is abnormal (f) (F) other restoration methods of the first to fourth treatment methods for the contaminated soil classified into the group (f), the group (c), the group (e), and the group (f), respectively. Decide to apply.

According to the present invention, the first treatment method for the (A) group contaminated soil is to install a retaining wall, and the second treatment method for the (C) group contaminated soil is to embed the contaminated soil. (E) The third treatment method for the group polluted soil is to landfill after neutralizing the contaminated soil, and the (f) the fourth treatment method for the group polluted soil is landfill after neutralizing the contaminated soil and the membrane or permeability reaction. It is to install the wall.

In addition, by measuring the pH of the contaminated soil of the group (b), if the pH is 4 or more, the same first treatment method as the (a) group is applied, and if the pH is less than 4, a separate fifth treatment method is applied. Decide to do so.

However, by evaluating acid generation capacity through the acid neutralization test on the contaminated soil of group (b), if the acid generation capacity is relatively low, it is decided to apply the same first treatment method as the group (a). If the generation capacity is relatively high, it may be decided to apply a separate fifth treatment method.

The fifth treatment method is a method of installing a retaining wall after neutralizing the contaminated soil.

In addition, the pH value preset in step (c) and the preset pH value for classifying the contaminated soil into the (C) and (D) groups in the step (d) are 5.

In addition, the acid generation capacity of the soil contaminated (D) is evaluated through acid neutralization test, and when the acid generation capacity is relatively low, it is decided to apply the same second treatment method as the above (C). If the capability is relatively high, perform the dissolution test for each pH on the contaminated soil, and if the amount of heavy metals eluted is less than the standard value, it is reclassified as (D) group, and if more than (E) group.

In the present invention, after subdividing into various groups according to the degree of contamination and characteristics through sophisticated physicochemical analysis of the contaminated soil, guide the guide to apply the most suitable restoration method for the contaminated soil, economical and efficient treatment of contaminated soil I can do it.

And all the test methods applied in the present invention has the advantage that the field applicability is also excellent because it can be simply performed.

Figure 1a is a photograph of the site of the tailings in the abandoned mine area.
1b is a photograph after restoration of the attained mine.
2 is a schematic flowchart of a method for determining a contaminated soil restoration method according to an embodiment of the present invention.
3 is a table showing the reference values of TCLP.
Figure 4 is a table showing the regulatory content of the eluted harmful substances prescribed in the Enforcement Rules of the Ministry of Environment waste management law.
5 is a table showing the pollutant discharge limit value of the Enforcement Regulations of Water Quality and Ecosystem Conservation.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail with respect to the contaminated soil restoration method determination method according to an embodiment of the present invention.

2 is a schematic flowchart of a method for determining a contaminated soil restoration method according to an embodiment of the present invention.

Referring to FIG. 2, in the method for determining a contaminated soil restoration method according to an embodiment of the present invention, first, a sample of a contaminated soil to be restored is collected and the content of contaminants, ie, heavy metals in the contaminated soil is measured.

Here, in order to measure the heavy metal content in the contaminated soil, it is necessary to first extract the heavy metal from the contaminated soil. There are many ways to extract heavy metals from soil. In the present invention, the total content analysis method using aqua regia is used.

The analysis of the total content of trace elements in contaminated soil is the extraction of heavy metals using aqua regia. That is, in 0.75 g of the sample, 5.4 ml of hydrochloric acid (37% HCl) and 1.8 ml of nitric acid (70% HNO ₃ ) were mixed (hydrochloric acid 3: mixed with nitric acid 1), and heated in a heating block for 1 hour while maintaining 70 ° C. After adding 22.8ml of distilled water and shaking, it is filtered through a 0.45μm filter and classified by contaminants to analyze the content.

The aqua regia is a very strong acid and all heavy metals in the contaminated soil are eluted from the aqua remnants. In Korea, the Soil Pollution Process Test was amended in 2009, and total content analysis is required to extract heavy metals from contaminated soil. Therefore, in the present invention, the heavy metal content in the contaminated soil is measured through aqua regia extraction.

The amount of heavy metals in the contaminated soil measured in this way is compared with 20 times the value of the Toxic Characteristic Leaching Procedure (TCLP) standard proposed by the US Environmental Protection Agency (EPA).

TCLP is a US EPA SW-846 (Method 1311) analysis method that assumes contaminated leachate from sanitary landfills in waste. The basis for TCLP elements and criteria can be considered whether or not a solid waste sample is hazardous based on 40 CFR 261.4. "If, after conducting a total waste content analysis, it is proven that each of the analytes is not present or is a low value that does not exceed the regulated concentration, then no TCLP is needed." In other words, if a total content analysis is performed and a metal is lower than 20 times the TCLP limit, TCLP does not need to be performed.

The reference value of the TCLP is shown in the table shown in FIG.

Referring to the table of FIG. 3, the reference values of arsenic and lead in contaminated soil are 5.0 mg / Kg, and the standard values of titanium are 7.0 mg / Kg. Multiply this threshold by 20 and compare the contents of the individual heavy metals in the contaminated soil extracted by the aqua regia. If the heavy metal content in the contaminated soil grows further, the contaminated soil is classified into the first group. If the heavy metal content in the contaminated soil is 20 times or more than the TCLP standard, the contaminated soil is classified into a second group.

For example, as the soil around the smelting plant such as Janghang is mainly contaminated by arsenic, the main contaminants are determined according to the surrounding jogging, but the above method should be applied only to the main pollutants. In order to do this, all the metals described above must be implemented.

After all the heavy metals in the contaminated soil were eluted by aqua regia extraction, they were classified into the first group and the second group based on 20 times the TCLP, and thus, the contaminated soil classified as the first group was contaminated to a low level. For example, pollution soils classified in the second group are considered to have a serious pollution level, and subsequent treatment methods vary depending on the pollution level.

PH is measured for contaminated soil classified in the first group. In Figure 2 this process is referred to as 'soil pH'. This is to avoid confusion with paste pH.

PH measurement of contaminated soil is performed by mixing 5 g of contaminated soil and 25 ml of distilled water, stirring for 1 hour, and then measuring the pH of the distilled water. If the measured soil pH is more than a predetermined value, it is subdivided into (A) group, and if it is less than a predetermined value, it is subdivided into (B) group.

Here, group (A) is a soil that has high pH and is hardly acidic and contaminated to a degree that is not particularly harmful, and thus corresponds to soil that does not require special measures. In particular, the higher the predetermined value, the greater the likelihood.

In the present invention, the pH reference value was determined as 5.

In the pH dissolution characteristics of soils, the content of heavy metals eluted from the soil was high when the pH was lower than the initial pH of 5, but the content of heavy metals eluted from the soil was low and the dissolution contents were generally constant. In addition, it was confirmed through experiments that the final pH after the reaction for each pH was lower than the initial pH when it was lower than 5 based on the initial pH 5, but when the final pH was 5 or higher. Therefore, when the soil pH is 5 or more, it was confirmed through a number of experiments that even if the samples are reacted with the solution for each pH, the final pH is almost unchanged, and the content of heavy metals eluted is also low. Therefore, it was concluded that it is reasonable to classify contaminated soils based on pH 5.

When the pH of the soil and the pH of the soil is 5 or more, in the present invention, the first treatment method of simply installing the retaining wall for the contaminated soil or the tailings is applied. The first treatment prevents the loss of contaminated soil and does not apply a separate physical or chemical method.

However, if the pH of soil in group (B) is less than 5, the acid generating capacity is evaluated. Acid-generating capacities include acid base accounting (ABA) and net acid generation (NAG).

Acid Base Accounting (ABA) calculates Net Acid Producing Potential (NAPP) using Acid Neutralizing Capacity (ANC) and Maximum Potential Acidity (MPA). Or by calculating the ratio of two values (ANC / MPA) (NAPP = MPA-NP).

MPA is the maximum amount of sulfuric acid produced when all the sulfide minerals in the rock are oxidized. Using the sulfur analyzer (SC-432, Leco), MPA is used to measure the total sulfur (S _t ) content in the sample. It was calculated by the following equation.

MPA (kg H ₂ SO ₄ / t) = total Sulfur (%) × 30.6

ANC used the method proposed by Sobek et al. (1978) as a test to assess the extent to which sulfide minerals can neutralize the acid derived from oxidation. ANC put 0.5g of rock powder sample into watch plate, drop 1 ~ 3 drops of 1: 3 hydrochloric acid solution, perform fizz test to determine the presence of CaCO ₃ in the sample, and then put 2.00g of sample into beaker. Put 0.1N or 0.5N HCl solution according to the result of fizz test and react to inject pH to 7.0 using 0.1N or 0.5N NaOH solution and measure the neutralization power by using HCl and NaOH injection amount.

Generally, when acid neutralizing capacity / maximum acid potential (ANC / MPA) ratio is less than 1, acid drainage is likely to occur and measures are required. If the ANC / MPA ratio is 1 or more and 2 or less, there is a possibility that acid drainage may occur to some extent, and attention is required. If it is 2 or more and 4 or less, the probability of acid drainage is rare.

In the net acid production test (NAG), 2.5 g of rock samples were placed in a 500 ml flask, and 15% H ₂ O ₂ was added little by little to 250 ml. After boiling or waiting for foaming to stop, the cover was covered with a watch glass and heated slowly until no bubble was released while maintaining a temperature of about 90 on a hot plate. After cooling to room temperature, the final volume was adjusted to 250 ml with distilled water, and then the pH was recorded and the value was set to NAG _pH .

If the acid drainage probability of soil (rock) is classified using NGA, the soil is likely to have acid drainage if the NAG _pH is 4.5 or lower and the net acid generation potential (NAPP) is 0 or higher. _{If the pH} is above 4.5 and the NAPP is below 0, it is classified as soil with low probability of acid drainage.

As described above, the first treatment method is applied to the soil which is determined to have low probability of acid drainage by testing acid generating capacity without any treatment. In other words, it is enough to treat the soil to be less harmful by installing a retaining wall to judge the soil as less harmful.

However, in the acid generation test, if the soil is classified as a high probability of acid drainage (rock), the fifth soil treatment method is to apply the retaining wall after neutralizing and mixing limestone.

You can also replace the acid production test in this way with a pH test on the soil. That is, after mixing 5g of contaminated soil and 25ml of distilled water and stirring for 1 hour, after measuring the pH of distilled water, if the value exceeds pH4, the first treatment method is applied, and if the pH is less than 4, the fifth treatment method is applied. Can be replaced with

On the other hand, for the second group, which is determined to have a heavy metal content of more than 20 times the TCLP standard due to the aqua regia extraction, the waste process test method is implemented considering the soil as a waste of various industrial activities (eg, the mining industry).

Perform the pretreatment method according to the Korean Waste Process Test Method, and measure the heavy metal content eluted from the contaminated soil and compare it with the regulations prescribed in the Enforcement Rules of the Waste Process Test Method. In the analysis according to the domestic waste process test method, only heavy metal elements such as arsenic (As), cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) are considered.

In order to measure the elution content of trace elements as prescribed in the pretreatment regulations of the waste process test method, samples with a particle diameter of 5 mm or less are ground as they are. The test method was to put 30 g of the sample into a 1000 ml Teflon container, put 300 ml of a solution having a pH of 5.8 to 6.3 using hydrochloric acid, and then use a constant temperature shaker (200 times / min, amplitude of 4 to 5 cm) at room temperature and atmospheric pressure. After shaking for 6 hours, filtered with glass fiber filter paper (1.0) and analyzed. If filtration is difficult, centrifuge at 3,000 rpm for 20 minutes using a centrifuge and then take an appropriate amount for analysis.

  The analyzed results are compared with the regulated content of the eluted harmful substances defined in the Enforcement Rules of the Ministry of Environment's Waste Management Act as shown in the table of FIG.

As described above, after the heavy metals are eluted from the sample according to the waste process test method, compared with the regulated contents shown in the table of FIG. Classify it as low and measure the pH of this contaminated soil.

The method of measuring pH is the same as the method of measuring pH for the contaminated soil classified in the first group. After measuring the pH of the contaminated soil in this way, the contaminated soil when the value is more than the predetermined value is divided into (C) group, and the contaminated soil when the value is less than the predetermined value is divided into the (D) group. Here, the preset value was selected to pH 5 for the same reason as above.

The contaminated soil classified in Group (C) applies the second treatment method, which is a method of landfilling without neutralization treatment, since the heavy metal content is above a certain level but the acid generation capacity is low. And for soil contaminated in (D), perform acid test again. The acid generation test is the same as that performed for the first group, so detailed description thereof will be omitted. If it is determined that the neutralization treatment is not necessary due to the acid generation ability test result, the second treatment method which is simply landfill without neutralization treatment is applied as in (C).

However, if it is deemed necessary for treatment due to the high acid generation capacity in the contaminated soil of group (D), the dissolution test using a solution of pH 2-3 is carried out. Reclassify into (F). The dissolution test will be described later.

You can also replace the acid production test in this way with a pH test on the soil. That is, after mixing 5 g of contaminated soil and 25 ml of distilled water and stirring for 1 hour, the pH of the distilled water is measured, and when the value exceeds pH 4, the second treatment method is applied as in (C). Apply a dissolution test of ~ 3.

On the other hand, the dissolution test using a solution of pH 2-3 is also performed for the contaminated soil containing heavy metal content above the standard.

In the dissolution test, 20 g of a sample was mixed with 200 ml of a reaction solution adjusted to pH 2 (sample: reaction solution = 1: 10), stirred at room temperature, filtered through a 0.45 μm membrane, and analyzed. At this time, the pH of the reaction solution used in the dissolution test is adjusted by adding nitric acid and sulfuric acid in a ratio of 4 to 6 by weight ratio in deionized water (deionized water).

In the dissolution test results, contaminants were eluted from the sample through the solutions of pH 2 and 3, and their contents were compared with the limit values for the emission of pollutants, where the reference values are shown in the table of FIG. It refers to the clean area standard of the pollutant emission allowance value in the Enforcement Regulations of the Act, which assumes the worst case conditions including the effects of acidic drainage.

The pH2 ~ 3 dissolution test was used to determine the possibility of heavy metals being discharged and moved from the contaminated soil according to the surrounding environment (pH, Eh). If the content is low, the mobility of heavy metals is determined to be low, and in many cases, the mobility of heavy metals is determined to be high.

Therefore, if the content of contaminants in the contaminated soil is higher than the reference value, it is classified as (B) group which is the most heavily polluted soil, and if it is lower than the standard value, it is classified as (E) group.

Contaminated soil classified as group (e) is neutralized by mixing limestone, etc., and then reclaimed, and the soil is classified as group (ne) neutralized with limestone, and then reclaimed. Permeate reaction walls are installed together to thoroughly prevent the discharge of pollutants to the outside.

As described above, in the present invention, first, the contaminated soil is classified on the basis of the heavy metal content, and the soil and pH are tested to classify the contaminated soil. If the heavy metal content is high, it is regarded as industrial waste and analyzed for the possibility of contamination through waste process test method and pH 2 ~ 3 dissolution test.

Conventionally, the soil was treated by applying the method of covering soil without any physical and chemical analysis as described above, but in the present invention, the soil is economically and efficiently managed through physicochemical analysis and detailed differentiation of the soil. I can handle it.

And all the test methods applied in the present invention has the advantage that the field applicability is also excellent because it can be simply performed.

Claims (8)

(a) taking a sample of contaminated soil, and then eluting contaminants in the contaminated soil using aqua regia;
(b) Contamination of less than 20 times the amount of pollutants by comparing the amount of each of the pollutants leached above 20 times of each pollutant regulatory standard according to the US Environmental Protection Agency's Toxic Characteristic Leaching Procedure (TCLP) method Classifying soil and contaminated soil 20 times or more into a first group and a second group, respectively;
(c) measuring the pH of the contaminated soil classified into the first group, and classifying it into (a) group when the pH is greater than or equal to a preset value, and (b) when it is less than;
(d) eluting the heavy metals according to the waste process test method for the contaminated soil classified into the second group, and when the amount of the eluted heavy metal is less than the regulated content, the pH is measured for the contaminated soil and the pH is equal to or greater than the preset value. If classified into (c) group, and less than (d) group;
(e) Elution of heavy metals according to the waste process test method for the contaminated soil classified into the second group, and if the amount of the eluted heavy metal is more than the regulated content, dissolution test using a solution of pH 2-3 for the contaminated soil If the amount of heavy metals that have been carried out and eluted is less than the reference level, and classified into group (e), and if more than (bar) group: and
(f) determining to apply different reconstruction methods of the first to fourth treatment methods to the contaminated soil classified into (A), (C), (E), and (F), respectively. Method for determining the contaminated soil restoration method characterized in that. The method of claim 1,
The first treatment method for the (A) group contaminated soil is to install a retaining wall,
The second treatment method for the (c) group contaminated soil is to embed the contaminated soil,
The third treatment method for the (e) group contaminated soil is to neutralize the contaminated soil and then reclaim it.
The fourth treatment method for the contaminated soil in the (F) group is to neutralize the contaminated soil and to bury it therein, and to install a water repellent membrane or a permeable reactive wall. The method of claim 1,
By measuring the pH of the contaminated soil of the group (B), if the pH is 4 or more, the same first treatment method as the (A) group is applied, and if the pH is less than 4, it is decided to apply a separate fifth treatment method. Method for determining the contaminated soil restoration method, characterized in that. The method of claim 1,
Evaluate the acid generation capacity of the contaminated soil of group (b), and if the acid generation capacity is lower than a predetermined value, determine to apply the same first treatment method as the group (a), and the acid generation capacity is set in advance. If it is higher than the value, the soil pollution recovery method determination method, characterized in that to determine to apply a separate fifth treatment method. The method according to claim 3 or 4,
The fifth treatment method is a method of restoring a contaminated soil recovery method comprising neutralizing the contaminated soil and installing a retaining wall. The method of claim 1,
The method of claim 1, wherein the predetermined value in step (c) is pH 5. The method of claim 1,
In step (d), the predetermined value for classifying the contaminated soil into (C) and (D) groups is pH 5. The method of claim 1,
Evaluating acid generation capacity for the contaminated soil in group (D), if the acid generation capacity is lower than a predetermined value, it is determined to apply the same second treatment method as the group (C), and the acid generation capacity is set in advance. If higher, the dissolution test using a solution of pH 2 ~ 3 for the contaminated soil, and if the amount of the eluted heavy metal is less than the reference value (D) group, if more than (E) group further comprises the step of reclassification Method for determining the contaminated soil restoration method, characterized in that.

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