KR100249273B1 - Ozone-enhanced remediation technology for soil-contaminated with organic compounds - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Apparatus and Method for Restoring Polluted Soil of Organic Compound Using Ozone

2. The technical gist of the invention

It is an object of the present invention to provide an apparatus and method for restoring soil contaminated with organic compounds using ozone which reliably removes volatile and nonvolatile contaminants in oil polluted soil using ozone and greatly reduces the extraction treatment period.

3. Summary of Solution to Invention

The present invention ozone generating means; Ozone injection means buried in contaminated soil areas; And embedding an injection well according to the contaminated site area, the apparatus comprising a means for providing ozone to the ozone injection means; Generating ozone; Providing the ozone to an ozone injection tablet; Injecting ozone discharged from the ozone injection well into unsaturated soil to form an ozone flow field; And it provides a method comprising the step of reacting volatile and non-volatile organic compounds and ozone to oxidative decomposition at the ground in situ.

4. Important uses of the invention

Ozone gas is injected directly into the contaminated soil to oxidatively decompose organic compounds in the ground.

Description

Apparatus and Method for Restoring Polluted Soil of Organic Compound Using Ozone

The present invention relates to an oil pollution soil restoration apparatus and method for decomposing volatile or nonvolatile organic compounds in soil contaminated with oil such as gasoline and diesel to restore the contaminated soil, and in particular, using an ozone gas having a strong oxidizing power. The present invention relates to an apparatus and method for restoring soil contaminated with organic compounds using ozone, which directly oxidizes and decomposes contaminants in soil medium without subsequent processes.

In general, SVE is a process that has been applied to the purification of volatile oil polluted soils since the 1980s, by injecting or simultaneously inhaling air using a pump. It is a simple physical and chemical purification technology that forms a vapor flow field and extracts and removes volatile contaminants in the soil medium. It is frequently applied in the United States and Europe, and the number of applications is increasing.

As shown in FIG. 1, the conventional SVE system includes an injection well 24 and an extraction well 25 installed by bentonite grouting 23 in an area in which oil is leaked from an oil pollution source 21 and contaminated. , Contaminant gas extraction devices and peripherals with blowers 26 or suction pump units 27, ie control valves (not shown in the drawing), pressure gauges 28, flow meters 29, Extraction contaminant gas treatment devices such as a liquid separation device 30 and primary and secondary activated carbon filters 31 and 32. Here, as the extraction pollutant gas treating apparatus, a catalyst or a thermal treating system, activated carbon adsorption, or a biological gas treating apparatus is used.

In the SVE system configured as described above, air is injected into the extraction well by an extraction or air injection pump to form a gas flow field in the ground, and contaminants contained in the ground are volatilized into the gas flow field to provide a suction pressure. It is sucked into the extraction well and extracted. When the polluted gas in the soil voids is removed, the pollutants are volatilized and removed again by the gas flow field due to the concentration difference between the phases in the soil, for example, the soil medium, the voids, the pore water, and the pollutants.

However, the SVE system requires a heat treatment device such as an activated carbon adsorption tower or an incinerator because the extraction contaminant gas has to be reprocessed, as described in the above description.

In addition, as a method of using the volatilization characteristics of soil pollutants, its application is limited only to volatile organic compounds, so there is a limit that cannot be applied to organic compounds having no volatility. In addition, even if the organic compounds adsorbed on the soil micropore or soil medium surface have a volatility and cause mass transfer to the gas flow field, once the extraction process is stopped, the soil is adsorbed on the micropore and the surface of the soil medium. There is a problem in that the complete removal of contaminants cannot be achieved because the material is diffused again into the soil voids.

In particular, since oil compounds are complex materials composed of more than 200 hydrocarbon compounds, many volatile and nonvolatile materials coexist, and the conventional SVE method is not only limited in processing but also requires a long processing time. In addition, the contaminant removal by air extraction or injection using the conventional SVE method requires at least several tens to hundreds of days, resulting in a high operation management cost.

Accordingly, the present invention has been made to solve the above problems, using the ozone organic solvent using ozone, which greatly reduces the extraction processing period of volatile and nonvolatile contaminants in oil-contaminated soil using ozone with better solubility than oxygen. It is an object of the present invention to provide an apparatus and method for recovering soil contaminated with a compound.

In addition, the present invention provides an apparatus and method for restoring contaminated soil using organic ozone to restore contaminated soil by oxidatively decomposing and removing volatile and nonvolatile organic compounds in the ground without the need for a separate post-treatment post-treatment step. Has a different purpose.

In addition, the present invention provides a simple configuration that does not require a separate extraction contaminant post-treatment device to install the injection well according to the contaminated site area and to inject ozone while circulating with one ozone generator to induce oxidation and decomposition of organic compounds during a sufficient injection period. Another object of the present invention is to provide an apparatus for restoring soil contaminated with organic compounds using ozone that can be extracted.

Another object of the present invention is to provide an apparatus and method for restoring soil contamination of organic compounds using ozone, which reduces power consumption due to ozone generation by injecting ozone into the ground by intermittent injection.

1 is a schematic configuration diagram for performing a polluted gas extraction process in the organic compound contaminated soil restoration apparatus according to the prior art.

Figure 2 is a schematic diagram showing an embodiment of an organic compound contaminated soil restoration apparatus using ozone according to the present invention.

* Explanation of symbols for main parts of the drawings

1: ozone generator 2: first pipe

3: pump 4: ozone injection tablet

5: unsaturated soil layer 6: ozone flow field

7: pressure gauge 8: extraction well

9: recirculation pump 10: 2nd pipeline

11: groundwater layer 12: oil pollution source

In order to achieve the above object, the present invention is installed on the ground movably, means for generating ozone; An ozone injection means buried in an unsaturated soil layer in a contaminated soil area and having a plurality of through holes formed in a predetermined portion to form an ozone flow field; And means for providing ozone to the ozone injection means mounted on the ozone generating means.

In addition, the present invention comprises the first step of embedding the injection well in unsaturated soil according to the contaminated site area; A second step of generating ozone from an ozone generator installed on the ground; A third step of forcibly sucking the ozone generated from the ozone generator through a pump and providing the ozone to a plurality of ozone injection wells; A fourth step of injecting ozone discharged from the ozone injection well into each phase of unsaturated soil to form an ozone flow field; And a fifth step of reacting the volatile and nonvolatile organic compounds with ozone to oxidatively decompose at the ground-in-situ location.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

In the ozone-based organic compound contaminated soil restoring apparatus and method, ozone gas, a powerful oxidant, is injected into the contaminated soil instead of air injection in the conventional SVE method, thereby completely oxidizing and decomposing volatile or nonvolatile organic compounds in the soil. In this embodiment, as shown in Figure 1, the ozone generator (1) and the ozone generator (1), which is installed on the ground to generate ozone, and the first pipe (2) as a medium, 1) and a pump 3 for forcibly suctioning ozone generated therefrom, and having a shape in which a plurality of through holes 4a are formed at predetermined lower portions, and are buried in the unsaturated soil layer 5 of the contaminated soil area. An ozone injection well (4) and an injection well (4) connected to the pump (3) via a conduit (2) to inject ozone provided therein into the ground to form an ozone flow field (6). ) Is provided with a pressure gauge (7) for measuring the ozone supply pressure to adjust the amount of ozone supplied on the first pipe (2).

Here, the ozone injection well 4 in this embodiment is formed of a vertically buried round, oval or polygonal tube to inject ozone into the unsaturated soil layer 5 in all directions. Alternatively, the ozone injection well 4 may be formed as a channel formed in a horizontal channel so that ozone can be injected in both directions of the unsaturated soil layer 5.

In addition, in the present embodiment, in order to facilitate the formation of the ozone flow field 6 in the contaminated area, a hole is provided at a lower predetermined position to suck and extract the ozone gas at a position opposite to the ozone injection well 4 by a predetermined distance. 8a) is provided with an extraction well (8) is formed, the extraction well (8) is provided with a suction force so that the ozone flow rate in the ozone flow field (6) to be extracted, and the extracted ozone gas to the ozone generator ( Recirculation pump 9 for recycling with air or oxygen generator (not shown) provided in 1) has a structure connected via a second conduit 10.

At this time, the extraction well 8 is formed in the shape of a circle, a polygon or a water channel in the same manner as the ozone injection well.

Reference numeral 11 denotes the groundwater layer and 12 denotes an oil pollution source.

In the present invention configured as described above, the gas ozone produced by the ozone generator 1 is injected into the ground through the through hole 4a of the injection well 4 instead of the air extraction, and the ozone flow field 6 is formed in the soil. It induces a reaction between absorbed volatile and nonvolatile organic compounds and ozone, and oxidizes and decomposes in-situ to be completely purified.

On the other hand, the organic compound contaminated soil purification method of the present invention configured and acting as described in detail as follows.

First, the injection well (3) is embedded in unsaturated soil (2) according to the contaminated site area contaminated by organic compounds from the underground oil storage tank. ) As many times as necessary. Then, the ozone generator 1 is driven to generate ozone, forcibly sucked through the pump 3, and provided to the plurality of ozone injection wells 4.

Here, the ozone amount injected into the ozone injection well (4) is ozone injection and extraction process after injecting ozone corresponding to 2-3 times the total pore volume (typically the entire contaminated site volume x 0.3 times) of the entire contaminated site. Stop it.

In addition, ozone injected through the through hole 4a of the ozone injection well 4 is injected into each phase of unsaturated soil, for example, a phase divided into soil medium, voids, pore water, and the like. Will form. In the ozone flow field 6, the volatile and nonvolatile organic compounds are induced to react with ozone to be oxidized and decomposed at the in situ. In addition, ozone generated in the ozone generator 6 is 13 times higher in solubility than oxygen, so that it can be decomposed by reacting in water with volatile or nonvolatile organic compounds dissolved in pore water.

In the process of injecting ozone discharged from the injection well (4) into the unsaturated soil layer (5), the recirculation pump (9) is driven to provide a suction force to the extraction well (8) to form the ozone flow field (6) At the same time, the ozone gas having passed through the ozone flow field 6 is introduced into the oxygen generator of the ozone generator 1 to enable reuse.

When restoring contaminated soil through a series of processes as described above, the rate of autolysis is significantly slower than in water due to the long half-life, which is the time it takes for gaseous ozone to decrease from concentration 1 to concentration 0.5. Therefore, in the present embodiment, it is intermittently injected rather than continuous injection of ozone, and the contact period is 3 to 4 days, thereby sufficiently reacting with volatile organic compounds present in the pore space of the soil medium to reliably remove it. To be able.

Therefore, the ozone injected into the contaminated soil site starts to react with organic compounds in the soil during the contact period of 3 to 4 days, and the organic compounds present in the gas and liquid phases are oxidized and decomposed and purified. After a given contact time, ozone is injected again in the same manner as described above to continuously induce oxidation and decomposition of contaminants.

At this time, when the decomposition of the volatiles is completely purified and the non-volatiles remain, in order to shorten the treatment time, the frequency of ozone injection is increased by about once every 1 to 3 hours, or the minimum allowable injection speed is 0.1 to Ozone is continuously injected at 0.3m 3 / m 2 · h to accelerate the decomposition reaction.

On the other hand, the present invention to remove the organic compound through a series of processes as described above was able to know the ozone treatment efficiency through the following experiment.

In this experiment, the ozone treatment efficiencies for the contaminated soils are compared.

Here, the ozone recovery method (OERT) for diesel consisting of volatile organic compounds (VOCs) gasoline and quasi-volatile (SVOCs) and nonvolatile (NVOCs) organic compounds was operated.

After 3.6 days of the first ozone injection, the gasoline concentration in the extract gas was 2750ppmv, about 89% lower than the initial 25,000ppmv, and when intermittent ozone was injected once every 3 ~ 4 days, 12 days after the first ozone contact. It can be seen that the gasoline concentration in the extract gas is within the detection limit within the time limit.

On the other hand, diesel polluted soils showed 51% removal for about 6 days after ozone treatment, and after that, the total amount was more than 92% by 24 days.

As shown in this experiment, it can be seen that the ground treatment of volatile and non-volatile organic compound contaminated soil by ozone is very effective. As described above, in the case of volatile organic compounds, the present method does not require any extraction gas treatment device, and in the case of non-volatile materials, it is excavated like other methods, and does not require a separate reaction device for physical, chemical or biological treatment. It can be clearly seen that it can be localized and decomposed.

Treatment Effect of Gasoline and Diesel Polluted Soil by the Invention Method

Table 2 compares the results of diesel contaminated soil treatment according to the present invention method and the conventional SVE method. As described above, the diesel polluted soil by the invention method showed a recovery effect of up to 90% or more, but the existing SVE method was not removed any more after the initial removal of about 23%. This means that some initial volatiles have been extracted and the remaining non-volatile organics are no longer removed. Moreover, the extracted volatile organic compounds require further treatment by activated carbon filter or heat treatment device on the ground, and thus, the inventive method is more effective and superior to the conventional restoration method.

Comparative Example 2

When the present invention method and the existing SVE method were applied, the effect of removing volatile organic compounds in soil was compared. In the case of the present invention method and the existing SVE method, the extraction gas concentration after the treatment of both volatile organic compounds under the similar contamination conditions appeared below the detection limit, but the present invention method was treated within a much shorter period than the existing SVE method, As in the case of SVE, it is an economical restoration method that does not require an extraction gas treatment device.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those who have knowledge.

As described above, according to the present invention, unlike the passive mechanism by physical air extraction, the basic principle of removing organic compounds in soil is an active mechanism of direct oxidation treatment of pollutants and ozone to be removed. As a result, the treatment speed is significantly faster than before, and it can reliably perform oxidative decomposition of volatile, semi-volatile and non-volatile oils, which are pollutants, and has no effect on commercial activities when the treatment area is a commercial site. Have

In addition, since the ozone injection method injected into the unsaturated soil layer through the injection well can be intermittent rather than continuous, power consumption for ozone generation is reduced, and operation management cost is reduced. In addition, the injection well can be installed according to the area of the contaminated site, and the ozone is injected into one ozone generator to induce oxidation and decomposition of the organic compound for a sufficient contact period. There is no need for various control devices such as pressure and flow rate control device required for the extraction, and there is no need for an extraction harmful gas treatment device, i.e., an activated carbon adsorption tower or a heat treatment device, so that the installation cost can be significantly reduced.

Claims (14)

A means for generating ozone, the device being movable on the ground; An ozone injection means buried in an unsaturated soil layer in a contaminated soil area and having a plurality of through holes formed in a predetermined portion to form an ozone flow field; And And a means for providing ozone to the ozone injecting means mounted on the ozone generating means. The method of claim 1, The ozone injection means is a contaminated soil restoration apparatus consisting of a vertical well. The method of claim 1, The ozone injection means is a contaminated soil restoration device consisting of a horizontal wells. The method according to any one of claims 1 to 3, The ozone providing means Organic compound contamination including an ozone supply pipe mounted between the ozone generating means and an ozone injection means to provide a transport path of ozone, and a pump mounted at a predetermined position of the ozone supply pipe to forcibly suck ozone generated from the ozone generating means; Soil Restoration System. The method of claim 4, wherein And a pressure gauge mounted on the ozone supply pipe between the ozone injection means and the pump to measure the ozone supply pressure. The method according to any one of claims 1 to 3, The organic compound contaminated soil restoring apparatus, further comprising an extraction tube mounted at a position opposite to the ozone injecting means and sucking and extracting gas through the ozone flow field. The method of claim 6, And a circulation pump connected to the extraction well and recycling the extracted gas discharged therefrom to the ozone generating means. A first step of embedding the injection well in unsaturated soil according to the contaminated site area; A second step of generating ozone from an ozone generator installed on the ground; A third step of forcibly sucking the ozone generated from the ozone generator through a pump and providing the ozone to a plurality of ozone injection wells; A fourth step of injecting ozone discharged from the ozone injection well into each phase of unsaturated soil to form an ozone flow field; And A fifth step of oxidizing and decomposing the volatile and nonvolatile organic compounds with ozone at the ground-in situ Soil restoration method of an organic compound comprising a. The method of claim 8, The third step is to restore the contaminated soil soil organic compound comprising the step of injecting ozone during the intermittent period. The method of claim 9, The method of restoring the contaminated soil of the organic compound is the process of injecting the ozone during the intermittent period every 3 to 4 days. The method according to any one of claims 8 to 10, The method of restoring contaminated soil for valuable compounds includes the second step of continuously injecting ozone and recycling the ozone gas to an ozone generator through an extraction well installed on the opposite side of the ozone injection pipe after performing the process. . The method according to any one of claims 8 to 10, And terminating the ozone injection and extraction process after injecting ozone corresponding to 2-3 times the total pore volume of the entire contaminated site. The method according to any one of claims 8 to 10, And the fifth step includes increasing the ozone injection frequency once every 1 to 3 hours in order to shorten the treatment time when only the nonvolatile material remains after the decomposition of the volatile material. The method according to any one of claims 8 to 10, Organic compound comprising a step of accelerating the decomposition reaction by continuously injecting ozone at 0.1 ~ 0.3 ㎥ / ㎡ · h to reduce the processing time when only the non-volatile material remains after the decomposition of the volatile material is completed in the fifth step How to restore polluted soil.