KR100873053B1 - Purification method of petroleum contaiminated soil using steam and microbe - Google Patents

Abstract

A method for effectively purifying contaminated soil is provided to remove volatile organic compounds, semi-volatile organic compounds, and non-volatile organic compounds using a complex process including a soil vapor extracting method, a steam injection method, and a biological treatment method. A method for purifying oil-contaminated soil comprises the steps of: digging oil-contaminated soil; injecting the contaminated soil into a reactor(1); generating steam from a steam generator(2); heating the soil within the reactor and supplying water to the soil by the generated steam; recovering and separating volatile organic compounds and semi-volatile organic compounds within the heated reactor; separating the recovered volatile organic compounds and semi-volatile organic compounds into gas and liquid; treating the separated gas in a gas treatment unit(10); storing the separated liquid and separating oil and water from the liquid; and injecting a microorganism culture into the reactor from which the volatile organic compounds and semi-volatile organic compounds have been removed to additionally purify residual contaminants.

Description

Purification method of petroleum contaiminated soil using steam and microbe}

The present invention relates to a soil purification method and apparatus, and more particularly, to purifying oil contaminated soil, and to a soil purification method through a combined process of steam extraction and microbial treatment through steam injection, and an apparatus used therefor.

With the rapid increase in oil consumption due to industrialization and the development of various kinds of organic synthetic materials, and their use continuously increasing, these materials are exposed to the natural environment due to accidents or deliberate discharge during the process of production, transportation and storage. The spill has caused serious environmental pollution. In recent years, the development of contaminated soil and groundwater restoration technology is urgently required.

In the conventional method of purifying contaminated soil, the soil vapor extraction method uses a vacuum pump on the contaminated unsaturated soil layer to create a vacuum under atmospheric pressure to induce desorption by volatilizing volatile and semi-volatile contaminants from the soil and removing desorbed organic contaminants. It is a technique to remove. Semi-volatile contaminants are difficult to desorb, lengthen the soil purification process, and have high maintenance costs.

Bioventing is a system that biodegrades and removes organic contaminants in soil by blowing air into unsaturated soil layers to increase the activity of aerobic microorganisms. Bioventing is mainly applied to large areas with low concentrations and is difficult to apply at high concentrations. Most biological treatment methods, including bioventing, can cause odors due to volatilization of contaminants when applied at high concentrations, and are difficult to degrade by microorganisms due to the toxicity of the contaminants.

Thermal treatment is economically expensive, but is known as one of the methods that can quickly remove contaminants from contaminated soil. Compared with physicochemical treatment and biological treatment, it can be seen to be very efficient in terms of efficiency and time. However, there is a problem that secondary pollutants may occur after or during the treatment.

The present invention is to overcome the limitations of the prior art in the method and apparatus for the purification of oil-contaminated soil, the soil is contaminated with high concentrations of petroleum-based organic contaminants such as gasoline, diesel, bunker C oil, engine oil, polycyclic aromatic compounds It is an object of the present invention to provide an economical and efficient polluted soil purification apparatus and a method for treating polluted soil using the same.

That is, the present invention provides a new purification method capable of removing not only volatile organic compounds but also semi-volatile organic compounds and non-volatile organic compounds by using a process of injecting steam into a soil vapor extraction method and a biological treatment method. It aims to do it.

Specifically, the present invention was created to economically and efficiently clean soil contaminated with petroleum-based organic contaminants at high concentration, and provides a steam generator to supply steam to contaminated soil and simultaneously extracts gas and liquid with an exhaust pump. The device can be configured to perform steam and steam extraction simultaneously. By supplying steam, the contaminated soil in the reactor is heated, and the supplied steam is cooled in the course of passing through the column, so that a part thereof is converted into water to increase the content of moisture in the soil. The steam supplied can lead to desorption of contaminants by increasing the solubility and vapor pressure of organic contaminants. After lowering the concentration of contaminants through steam and steam extraction, the remaining contaminants can be removed through biodegradation using microorganisms cultured in a microbial incubator. It is therefore an object of the present invention to provide a method and apparatus for effectively purifying contaminated soil.

In order to achieve the above object, the present invention injects the steam generated by using a steam generator into the reactor to increase the soil temperature inside the reactor, while supplying water and steam in the reactor using a steam discharge pump connected to the reactor Removes water and volatile gases generated by At this time, a large amount of volatile organic compounds and quasi-volatile organic compounds are removed from the soil by volatilization and removal, and the semi-volatile organic compounds and non-volatile organic compounds remaining in the soil are removed by the decomposition by microorganisms using microbial culture medium. . By this method, the present invention was able to remove more than 70% of non-volatile organic compounds in the oil-contaminated soil, more than 85% of semi-volatile organic compounds, 95% or more of volatile organic compounds.

Therefore, the purification method and apparatus according to the present invention are suitable for oil contaminated soil in which not only volatile but also non-volatile organic compounds are mixed, and after the steam supply through the steam generator, a complex process for contacting the microbial culture medium supplied from the microorganism incubator. The present invention provides a new purification method that can remove not only volatile organic compounds but also quasi-volatile and nonvolatile organic compounds.

First, the purification method of the present invention is as follows.

a) digging soil contaminated with oil;

b) introducing contaminated soil into the reactor;

c) generating steam in a steam generator;

d) heating the soil inside the reactor by the generated steam and supplying water to the soil;

e) recovering and separating the volatile organic compounds and the quasi-volatile organic compounds in the heated reactor;

f) separating the recovered compound into a gas and a liquid;

g) treating the separated gas in a gas treatment device;

h) storing the separated liquid and separating oil and water;

i) adding a microbial culture medium into the reactor from which the volatile organic compounds and the quasi-volatile organic compounds have been removed to further purify the remaining contaminants;

It is a method for purifying contaminated soil, characterized in that it comprises a.

In addition, the present invention may repeat the steps c) to i) one or more times as necessary.

When the excavated soil is put into the reactor, steam injected from the top of the reactor is moved from the top to the bottom of the column through the porous gas distributor in the steam generator. At this time, while the supplied steam moves through the pores of the contaminated soil in the reactor, it is desorbed by increasing the vapor pressure and solubility of the contaminants in the soil. By supplying steam, the temperature of the contaminated soil is increased to increase the vapor pressure of adsorbed organic pollutants, thereby increasing volatility, and the desorption increases the solubility of water in the soil. In addition, since the moisture content of the soil increases due to the supply of steam to the soil, the desorption of the pollutants is accelerated due to the increase in the concentration gradient between the liquid phase and the solid phase. In this way, the steam supply increases the soil temperature and the water supply at the same time to accelerate the desorption and volatilization of the adsorbed organic pollutants. At the same time as the steam supply, the discharge pump is operated to discharge organic pollutants and water desorbed from the soil through the pipe connected to the reactor. The supply of steam accelerates the desorption of the quasi-volatile organic compounds, and the extraction of the volatile and quasi-volatile organic compounds at the same time by simultaneously extracting the steam using the discharge pump has the advantage.

After supplying steam and extracting steam, microorganisms are introduced using a microbial incubator connected to the reactor to allow biodegradation of contaminants in the soil. Soil whose temperature is elevated by steam injection in the first process reduces the concentration of pollutants by removing volatile and semi-volatile substances by performing steam extraction process, and decomposes the remaining pollutants by injecting microorganisms in the second process. When the liquid microorganisms are injected, some of the residual contaminants adsorbed in the soil are desorbed into the liquid phase, and the contaminants dissolved in the liquid are decomposed by the microorganisms. Since the microbial fluid contains organic substances (biosurfactants, microbial metabolites, enzymes, etc.) secreted by the microorganisms, solubility of the adsorbable and non-desorbable organic contaminants increases, so that the desorption of these contaminants increases when the microbial fluid is injected. Contaminants that are not dissolved and adsorbed on the soil organic matter or surface are contaminated by the microbial membrane when the microorganisms are attached to the soil contaminant, and then degraded due to contaminant transfer into the microorganism. Wild microorganisms such as Pseudomonas sp., Agrobacterium sp., Crostridium sp., Sphingomonas sp., Ralstonia sp. Microorganisms belonging to are chemical and mobile to organic contaminants Because of their chemotaxis and mobility, these microorganisms do not dissolve but migrate toward the adsorbed contaminants and degrade the contaminants through close contact or direct contact.

In the first process, the concentration of contaminants decreases, so the purification time by microorganisms in the second process can be shortened.In the case of high concentrations of soil contaminants, the purification efficiency is low due to the microbial activity due to the toxicity of the contaminants. When the concentration of contaminants is lowered and microorganisms are introduced in the process, the activity of microorganisms can be effectively used, thereby reducing the input amount (or concentration) of the microbial culture solution and increasing the purification efficiency.

In the present invention, the soil contaminated with petroleum-based organic pollutants (volatile, semi-volatile and non-volatile) at high concentrations can be quickly removed from the steam heating and steam extraction, and can be easily removed from heating and steam extraction using steam. Uncontaminated contaminants can additionally decompose and remove contaminants adsorbed on the soil through microbial injection.

Hereinafter, the soil purification method and apparatus of the present invention will be described in detail with reference to the accompanying drawings.

  1 is a simplified view of the soil purification apparatus according to an embodiment of the present invention. As shown in Figure 1, the contaminated soil purification system of the present invention

A reactor 1 for excavating contaminated soil;

Steam generator (2) for soil heating and water supply of the reactor (1);

Discharge pump 30 for discharging the aqueous solution and steam generated in the reactor (1);

A water-cooled gas-liquid separator 40 for cooling the steam discharged from the reactor 1 to separate the liquid and the gas;

A gas treatment device 10 for treating the gas separated by the gas-liquid separator 40;

An oil / water separation tank 20 for storing the liquid separated from the gas-liquid separator 40 and separating oil and water; And

A microbial incubator 4 for introducing a microbial culture liquid into the reactor 1;

Disclosed is a contaminated soil purification apparatus provided with.

It is preferable that the porous distributor 5 is installed at the top of the reactor 1 so that it can be evenly sprayed when steam or microbial culture fluid is injected. In addition, the lower end of the reactor (1) is preferably equipped with a porous filter (6) to facilitate the discharge of volatile, semi-volatile vapor or microbial culture liquid generated during heating.

The contaminated soil purifying apparatus of the present invention includes the reactor (1) in which the contaminated soil is placed and a steam generator (2) for generating steam supplied to the reactor.

It is provided with a heater (3) for supplying heat inside the steam generator (2) to heat the water in the steam generator (2) to generate steam. When the high temperature heat is supplied using the heater 3, the steam generator 2 is heated to generate steam. When the steam generated by heating once is continuously supplied through the heater (3) to provide a constant amount of steam continuously.

It is preferable to have a porous gas distributor 5 on the top of the reactor 1 containing the contaminated soil so that the steam provided from the steam generator 2 can be evenly distributed in the soil inside the reactor.

Simultaneously with the injection of steam, the discharge pump 30 is operated to provide volatile or semi-volatile pollutants discharged to the outside of the soil due to the temperature rise of the water or the contaminated soil generated by the change of steam while the steam is provided in the reactor 1. Remove it.

After operating the steam generator 2 and the discharge pump 30 at the same time to remove the volatile, semi-volatile substances, the remaining contaminants and non-volatile contaminants to use the microbial incubator (4). The microorganisms cultured in the microorganism incubator 4 are injected into the reactor 1 to remove contaminants by the microorganisms.

The discharge pump 30 is preferably provided with a water-cooled gas-liquid separation device 40 to separate the vapor discharged from the reactor 1 into a liquid and a gas.

The gas treatment apparatus 10 for processing the gas separated by the gas-liquid separator 40 and the oil-water separation tank 20 for storing the liquid separated from the gas-liquid separator 40 and separating the oil and water. .

As described above, the soil purification method and apparatus of the present invention can simultaneously perform extraction of contaminants and injection of steam, and can remove volatile, semi-volatile and non-volatile contaminants by injecting microorganisms sequentially. have. In addition, steam generation is possible with a simple device, and it is economical method because it does not require a complicated device even if it is large in field application. By supplying steam, the temperature of the contaminated soil increases, increasing the vapor pressure of organic contaminants, increasing the volatility, and increasing the solubility of water in the soil. In addition, since the moisture content in the soil increases due to the supply of steam to the soil, the desorption of the pollutants is accelerated due to an increase in the concentration gradient between the liquid phase and the solid phase. In this way, the steam supply increases the soil temperature and the water supply at the same time to accelerate the desorption and volatilization of the adsorbed organic pollutants.

The present invention is to purify the contaminated soil by mixing volatile, semi-volatile and non-volatile contaminants, by heating the soil through the steam supply, increasing the moisture content, so as to increase the organic pollutant solubility and vapor pressure, desorption Induces steam extraction to remove volatile and semivolatile organic contaminants in the soil. Semi-volatile and non-volatile organic contaminants remaining after removal are further characterized by the decomposition and removal by injecting microorganisms.

Therefore, the present invention can remove the volatile organic compounds, quasi-volatile organic compounds and non-volatile organic compounds at a lower concentration than the conventional soil vapor extraction method, so that the petroleum-based organic compounds are applied to the purification of complex contaminated soil. It is possible.

Hereinafter, the present invention will be described with reference to Examples for specific description of the present invention, but the present invention is not limited to the following Examples.

[Preparation for experiment]

Uncontaminated soil was collected and the toluene (volatile), naphthalene (semi-volatile) and phenanthrene (non-volatile) were artificially contaminated with 292.7ppm, 97.6ppm and 54.0ppm, respectively. The organic carbon content (TOC) of the experimental soil was 0.386%. In this case, when steam extraction was carried out by using this (Comparative Example 1) and steam injection and steam extraction were performed in parallel (Comparative Example 2), the steam injection and steam extraction were performed in parallel and then treated with microorganisms (Example). I saw the result.

[Measurement method for pollutants]

After the soil was treated by each treatment method, 10g of soil sample was transferred to a 20ml glass vial, 10ml of methanol was injected, and the mixture was extracted with methanol by rotation mixing 9 times per minute for 2 days. The extracted samples were analyzed by using high performance liquid chromatography (HPLC). HPLC used Supelcosil LC-PAH 15 cm × 4.6 mm (5 μm) and UV / VIS 254 nm as the detector.

Comparative Example 1

Put 12g of the contaminated soil into the reactor and steam extraction for 10 minutes using the discharge pump, take 10g of soil as a sample, extract the remaining pollutants and measure the concentration according to the above measurement method. The results of calculating the concentration of the substance are shown in Table 1 below.

Comparative Example 2

12 g of the contaminated soil is placed in a reactor and steam is injected into the soil purifier using a steam generator. While steam is injected, steam is extracted for 10 minutes using a discharge pump. After the treatment, 10g of the soil was collected, the concentration of the remaining pollutants was extracted and the concentration was measured according to the measurement method of the above pollutants, and the results of calculating the concentration of the pollutants remaining in the soil are shown in Table 1 below.

EXAMPLE

12 g of the contaminated soil was put in a reactor and steam was extracted from boiled water at 100 ° C. while steaming for 10 minutes, and then microbial culture liquid (Pseudomonas sp. In Pseudomonas sp.) Was injected into the reactor at the same weight as the soil. After leaving for a period of time, the microbial culture was removed to collect 10 g of soil as a sample, and the concentration of the contaminants remaining in the soil was measured according to the measurement method of the above contaminants. The results of calculating the concentration of contaminants remaining in the soil are shown in Table 1 below.

TABLE 1

As can be seen in the attached Table 1, in Comparative Example 2 in which steam was injected, volatile toluene was removed by 98% or more, and naphthalene was removed by about 70% and phenanthrene by about 60%. Compared with Comparative Example 1, it was effective in removing volatile, semivolatile, and nonvolatile materials. However, the removal effect of quasi-volatile and non-volatile materials was insignificant. However, in the embodiment in which the microbial culture solution was added after steam injection, more than 90% of the semi-volatile material was removed and more than 70% of the non-volatile material was removed to clean the contaminated soil by mixing volatile, semi-volatile and non-volatile contaminants. Was found to be very effective.

Figure 1 schematically shows a device used in the soil purification method according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: reactor 2: steam generator

3: heater 4: microbial incubator

5: porous dispenser 6: porous filter

10: gas treatment device 20: oil and water separation tank

30: discharge pump 40: gas-liquid separator

Claims (2)

a) digging soil contaminated with oil; b) introducing contaminated soil into the reactor; c) generating steam in a steam generator; d) heating the soil inside the reactor by the generated steam and supplying water to the soil; e) recovering and separating the volatile organic compounds and the quasi-volatile organic compounds in the heated reactor; f) separating the recovered volatile organic compounds and quasi-volatile organic compounds into a gas and a liquid; g) treating the separated gas in a gas treatment device; h) storing the separated liquid and separating oil and water; i) adding a microbial culture medium into the reactor from which the volatile organic compounds and the quasi-volatile organic compounds have been removed to further purify the remaining contaminants; Oil pollution soil purification method characterized by having a. The method of claim 1, The method of purifying the oil-contaminated soil, characterized in that to repeat the step c) ~ i) connected to the whole at least once.

Images