JP2006015202A - Purification apparatus of contaminated soil and purification method for contaminated soil using the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purification apparatus of contaminated soil and a purification method for contaminated soil using the apparatus surely purifying soil, friendly to the environment, meeting the construction term and economic performance. <P>SOLUTION: The purification apparatus 1 of contaminated soil is provided with a water circulation circuit 2, a purification agent injection circuit 3, and a water sucking/injecting device 4. The water sucking/injecting device 4 is pressedly set in the contaminated soil, and the water circulation circuit 2 and purification agent injection circuit 3 are connected to the water sucking/injecting device 4. By switching a three-way selector valve 5, the water circulation circuit 2 is made to communicate with the water sucking/injecting device 4, to suck and remove contaminants in the soil. Then, by switching the three-way selector valve 5, the purification agent injection circuit 3 is made to communicate with the water sucking/injecting device 4, to inject a purification agent into the soil for purifying the contaminants. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a contaminated soil purification apparatus and a method for purifying contaminated soil using the apparatus.

Volatile organic compounds (VOC), one of the soil pollutants, are designated as Class 1 Specified Hazardous Substances by the Soil Contamination Countermeasures Law, and include trichlorethylene (TCE), various dichloroethylenes, four Ten kinds of substances such as carbon chloride are included. These compounds are generally characterized by high specific gravity, low viscosity, low adsorptivity to soil, and high volatility. Therefore, the VOC that has entered the soil not only exists as a gas in the voids of the soil particles, but also enters the groundwater through the gap as a liquid VOC having a large specific gravity, causing groundwater contamination.
In addition, VOC is easy to volatilize at normal temperature and has a higher specific gravity than water, so it penetrates deep into the ground. Furthermore, VOC is difficult to dissolve in water but dissolves to some extent, so it is most easily diffused in soil and groundwater. There is.

According to Non-Patent Document 1, the methods currently used as soil contamination countermeasure technologies can be roughly classified as follows: (1) Blocking / water shielding (isolation containment, in-situ containment), (2) Solidification / insolubilization (chemical solidification) Etc.), (3) Pyrolysis / solidification (melt solidification / glass solidification), (4) Decomposition (chemical redox / bioremediation, permeable purification wall, etc.), (5) Separation / removal (excavation removal, groundwater pumping) Soil washing, heat suction, soil gas suction, etc.).
Among these technologies, (3) thermal decomposition / solidification (for example, Patent Document 1), (4) decomposition (for example, Patent Document 2), and (5) separation / removal (for example, Patent Document 3) are performed by VOC. Used for soil contamination.

“Architecture Technology”, Architecture Technology Co., Ltd., April 1, 2003, No. 639, p. 135, Table 1 Japanese Unexamined Patent Publication No. 57-178023 JP 2003-305453 A JP 2003-94037 A

  However, among these VOC soil contamination countermeasure technologies, (3) thermal decomposition and solidification (melt solidification / glass solidification) is a technology by melting and solidifying the pollutants and solidification by melting slag. Is a technique based on molten glass solidification using electrodes in situ or in excavated soil, so it is considered that it is not the optimal technique considering that there are few examples of use at present. (4) The decomposition has a problem that although the influence on the surrounding environment is small, the period required for repair tends to be prolonged. Regarding the separation / removal of (5), since VOC easily penetrates deep into the ground, it is difficult to excavate contaminated ground by the low-temperature heating method. However, when there is a large amount of fine particles in the groundwater, there is a problem that the filter normally used for clogging of the water absorption pipe is clogged and the pumping capacity is significantly reduced. Another problem is that if the amount of pumped water is excessive, land subsidence is likely to occur.

  So far, soil pollution control technology by VOC has been described, but soil pollution is not limited to VOC, and other important pollutants include contaminated oil. Therefore, not only the VOC but also a technology for purifying the contaminated oil, or a technology for purifying the VOC and the contaminated oil by the same apparatus or the same method is required.

  The present invention has been made to solve such problems, and uses a contaminated soil purification apparatus capable of purifying soil that is friendly to the surrounding environment and satisfies the construction period and economy, and the apparatus. It aims at providing the purification method of contaminated soil.

  A contaminated soil purification apparatus according to the present invention includes a high-pressure pump that boosts and circulates water stored in a water tank, a water circulation circuit that includes a purification means that purifies the circulated water, a storage tank that stores a purification agent, and A water-absorbing / injecting device comprising a purifying agent injection circuit having an infusion pump for injecting a purifying agent, a circulating water pipe having a nozzle, and an outer pipe attached to the nozzle so as to include the nozzle and having a slit at a position above the nozzle The water circulation circuit and the purifier injection circuit can be switched, and either one communicates with the water absorption / injection device, and the water absorption / injection device is contaminated from the slit when the water circulation circuit is selected. When the substance can be sucked and the cleaning agent injection circuit is selected, the cleaning agent can be injected from the slit.

The method for purifying contaminated soil according to the present invention uses the contaminated soil purifying device according to the present invention, the step of penetrating the water absorption / injection device to the depth where the pollutant exists, and the water stored in the water tank The pollutant is sucked from the slit by the negative pressure generated when the circulating water is circulated and the flow velocity is increased by the nozzle, and the pollutant carried to the ground together with the circulated water is purified by the purification means. And a step of injecting the purification agent from the water absorption / injection device into the ground after the contaminant is sucked.
When the pollutant is contaminated water containing a volatile organic compound, it is preferable to use a reducing agent that reduces the volatile organic compound as a purification agent.
When the pollutant is contaminated water containing contaminated oil, it is preferable to use a decomposing agent that decomposes the contaminated oil as the purifier.

  According to the present invention, by switching and connecting the water circulation circuit and the purification agent injection circuit to the water absorption / injection device, the contaminants in the soil are sucked and removed, and then the purification agent is injected into the soil to cause residual contamination. Since the substance is expected to have a long-term purification effect, it is possible to purify soil that is friendly to the surrounding environment and that satisfies the construction period and economy.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, a contaminated soil purification device 1 according to this embodiment includes a water circulation circuit 2, a purification agent injection circuit 3, and a water absorption / injection device 4.
The water circulation circuit 2 includes a water tank 11 in which water circulating in the water circulation circuit 2 (hereinafter referred to as circulation water) is stored, a high-pressure pump 12 that boosts the circulating water stored in the water tank 11 and circulates in the water circulation circuit 2, and circulation A sand screen 13 for removing sand and the like mixed in water, a purification tank 14 for removing contaminants from the circulating water, and a storage tank 15 for storing the contaminants separated in the purification tank 14 are provided. Here, the sand screen 13 and the septic tank 14 are devices for purifying the circulating water, and constitute a purification means.
The purification agent injection circuit 3 includes a storage tank 16 that stores the purification agent, and an injection pump 17 that injects the purification agent stored in the storage tank 16 into the soil.

  As shown in FIG. 2, the water absorption / injection device 4 includes a circulating water pipe 22 and an outer pipe 23 along the flange 21 a of the H-shaped steel 21. The circulating water pipe 22 is bent in a U shape near the lower end portion 21b of the H-shaped steel 21 to change its direction by 180 °, and a nozzle 24 for injecting the circulating water as a jet water stream is provided at the tip thereof. The outer tube 23 is attached to the tip of the circulating water tube 22 so as to include the nozzle 24 therein, and a slit 25 is formed at a position above the nozzle 24.

  As shown in FIG. 1, the water circulation circuit 2 and the purification agent injection circuit 3 are connected by a three-way valve 5 and further connected to a water absorption / injection device 4. By switching the three-way valve 5, one of the water circulation circuit 2 and the purifier injection circuit 3 communicates with the water absorption / injection device 4.

Next, operation | movement of the contaminated soil purification apparatus 1 which concerns on this embodiment is demonstrated.
As a result of the preliminary survey, as shown in Fig. 3 (a), it was found that soil and groundwater contaminated by VOCs were deep in the ground and contaminated oil was present in shallow ground. Assuming that
A crane 6 is installed on the ground, and the water absorption / injection device 4 is press-fitted vertically into the ground. At this time, the water absorption / injection device 4 was pressed into a deep part of the ground in order to purify soil and groundwater contaminated by VOC, and pressed into a shallow part of the ground to purify contaminated oil. There are two types of thing 4b. The two types of water absorption / injection devices 4a and 4b are press-fitted so as to alternate on the ground at an equal pitch, for example, as shown in FIG. 3B when the ground is viewed from above.

After the water absorption / injection device 4 is pressed into the contaminated soil in this way, the water circulation circuit 2 and the purifier injection circuit 3 are connected to the water absorption / injection device 4a for purifying the soil and groundwater contaminated by the VOC. By switching the three-way valve 5, the water circulation circuit 2 is communicated with the water absorption / injection device 4a.
As shown in FIG. 1, the high-pressure pump 12 is activated to feed the circulating water in the water tank 11 to the water absorption / injection device 4a. The circulating water sent to the water absorption / injection device 4a is jetted from the nozzle 24 (see FIG. 2) into the outer tube 23 (see FIG. 2). At this time, the circulating water jetted from the nozzle 24 becomes a jet jet, and creates a negative pressure around it. Under this negative pressure, groundwater contaminated by VOC in the soil is sucked from the slit 25 (see FIG. 2) formed in the outer tube 23. The sucked VOC ascends in the outer pipe 23, and after the earth and sand content is filtered by the sand screen 13, it is sent to the septic tank 14. In the septic tank 14, the volatile VOC and water are separated by aeration processing or the like. The volatilized VOC is sent to the storage tank 15 where it is adsorbed with activated carbon and appropriately transported. On the other hand, the circulating water separated from the VOC is returned to the water tank 11.
By repeating this operation in the other water absorption / injection device 4a, the groundwater contaminated by the VOC is removed.

Thereafter, the switching operation of the three-way valve 5 is performed, and the purifier injection circuit 3 is communicated with the water absorption / injection device 4a.
As shown in FIG. 1, by starting the infusion pump 17, a reducing agent such as an iron powder suspension as a purifying agent in the storage tank 16 passes through both the circulating water pipe 22 and the outer pipe 23. It is sent to the water absorption / injection device 4a. The iron powder suspension sent to the water absorption / injection device 4b is injected from the slit 25 into the soil into which the groundwater contaminated with VOC has been sucked.
The iron powder suspension injected into the soil reacts with VOC contained in the residual groundwater and VOC present as gas in the voids of the soil particles, and is reduced to hydrocarbons. For example, VOCs such as trichlorethylene, dichloroethylene, and carbon tetrachloride are reduced to hydrocarbons such as ethylene and ethane.

In this way, after purifying the deep depth in the ground, the shallow depth in the ground contaminated by the contaminated oil is washed.
The water circulation circuit 2 and the purification agent injection circuit 3 are connected to a water absorption / injection device 4b for purifying contaminated oil. Then, after removing the contaminated oil by suction in the same manner as the method of purifying deep underground, the purifier is injected into the soil. Here, even if a reducing agent similar to that in the case of VOC is injected as the purifying agent, the contaminated oil cannot be decomposed. Here, as the cleaning agent used, a nutrient solution for growing microorganisms in the soil that decomposes contaminated oil is optimal. By injecting such nutrients into the soil, microorganisms in the soil that decompose the contaminated oil are propagated and activated, and the contaminated oil is decomposed into hydrocarbons having a small number of carbon atoms. Examples of nutrient salts include inorganic nutrient salts containing nitrogen and phosphorus as nutrient sources, and certain hydrogen donors.

In this way, by switching the water circulation circuit 2 and the purification agent injection circuit 3 to communicate with the water absorption / injection device 4, after removing the contaminants in the soil by suction, the purification agent is injected into the soil, Since a long-term purification effect can be expected for residual pollutants, it is possible to purify soil that is friendly to the surrounding environment and that satisfies the construction period and economy. Further, it is possible to reliably remove the contaminants and inject the cleaning agent without clogging at the depth of presence of the contaminants.
Further, the water absorption / injection device 4 due to the negative pressure generated when the flow rate of the high-pressure water circulating in the water circulation circuit is increased by the nozzle has a much higher pumping capacity than a vacuum pump, and from a deep layer of 10 m or more. Can be easily pumped to the ground. Furthermore, simultaneously with water absorption, soil particles such as gravel (particle size within about 10 mm) less than the size of the slit 25 are sent to the ground together with circulating water circulating at high speed. For this reason, since clogging does not occur in the slit 25, the contaminants can be reliably removed by suction, and a filter can be omitted.

  In this embodiment, the water circulation circuit 2 and the purification agent injection circuit 3 are connected by the three-way valve 5 and further connected to the water absorption / injection device 4, and the water circulation circuit 2 and the purification agent injection are switched by the switching operation of the three-way valve 5. Although either one of the circuits 3 is communicated with the water absorption / injection device 4, it is not limited to such a form. The water circulation circuit 2 and the purifier injection circuit 3 may be provided separately, and each may be connected to the water absorption / injection device 4 separately. By connecting each to the water absorption / injection device 4 separately, either the water circulation circuit 2 or the purifier injection circuit 3 can be communicated with the water absorption / injection device 4.

  In this embodiment, the iron powder suspension is used as the reducing agent, but the present invention is not limited to this. Other known reducing agents can be appropriately selected, and two kinds of reducing agents can be mixed and used as necessary. When mixing and injecting two types of reducing agents, two series of storage tanks 16 and injection pumps 17 are provided, and the two types of reducing agents are supplied to the water absorption / injection device 4 via the circulating water pipe 22 and the outer pipe 23, respectively. It can also be made to mix immediately before injecting from the slit 25.

  In this embodiment, the case where both the VOC and the contaminated oil are present has been described. However, the present invention can be applied even when either the VOC or the contaminated oil is present alone. A conceptual diagram of the embodiment in the case where either VOC or contaminated oil is present alone is shown in FIGS. 4 and 5, respectively.

It is a block diagram of the contaminated soil purification apparatus which concerns on embodiment of this invention. It is a general view of the suction / injection device of the contaminated soil purification device according to this embodiment. It is a figure for demonstrating the method to press-fit the suction / injection apparatus of the contaminated soil purification apparatus which concerns on this embodiment to the ground. It is a figure for demonstrating the method to press-fit the suction / injection apparatus of the contaminated soil purification apparatus which concerns on this embodiment in order to purify VOC in soil. It is a figure for demonstrating the method to press-fit the suction / injection apparatus of the contaminated soil purification apparatus which concerns on this embodiment in order to purify the contaminated oil in soil.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Contaminated soil purification apparatus, 2 Water circulation circuit, 3 Purification agent injection circuit, 4, 4a, 4b Water absorption / injection apparatus, 11 Water tank, 12 High pressure pump, 13 Sand screen, 14 Septic tank, 15 Reservoir tank, 21 H type steel, 22 Circulation Water pipe, 23 outer pipe, 24 nozzle, 25 slit, 31 storage tank, 32 infusion pump.

Claims (4)

A water circulation circuit comprising a water tank, a high-pressure pump for boosting and circulating the water stored in the water tank, and a purification means for purifying the circulated water;
A purifying agent injection circuit comprising a storage tank for storing the purifying agent and an infusion pump for injecting the purifying agent;
A circulating water pipe having a nozzle, and a water absorption / injection device provided with an outer pipe having a slit at a position above the nozzle attached so as to include the nozzle inside.
The water circulation circuit and the purifier injection circuit can be switched, and either one communicates with the water absorption / injection device,
The water absorption / injection device can suck contaminants from the slit when the water circulation circuit is selected, and can inject purification agent from the slit when the purification agent injection circuit is selected. The contaminated soil purification apparatus characterized by being. A method for purifying contaminated soil containing contaminants using the contaminated soil purification apparatus according to claim 1,
Penetrating the water absorption / injection device to a depth at which the contaminants are present;
The water stored in the water tank circulates in the water circulation circuit, and the pollutant is sucked from the slit by the negative pressure generated when the circulated water is increased in flow rate by the nozzle, and the circulation A step of purifying the pollutant carried on the ground together with the purified water by the purification means;
A method for purifying contaminated soil, comprising the step of injecting the purification agent from the water absorption / injection device into the ground after the contaminant is sucked. The pollutant is contaminated water containing volatile organic compounds,
The method for purifying contaminated soil according to claim 2, wherein the purification agent is a reducing agent that reduces the volatile organic compound. The pollutant is contaminated water containing contaminated oil,
The method for purifying contaminated soil according to claim 2, wherein the purification agent is a decomposition agent that decomposes the contaminated oil.

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