JP2009279489A - Method of purifying contaminated soil and/or ground water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of purifying contaminated soil and/or ground water which enables improvement in purifying efficiency. <P>SOLUTION: A nutrient source feed well 10 which has an inside cylinder 12 arranged within a well casing 11 is formed. The inside cylinder 12 has a bottom surface, and its bottom or side surface has two or more holes of a maximum diameter of 1-2 mm. The inside cylinder 12 is arranged with a separation space between the bottom surface of the well 10 and the side surface of the well casing 11. A nutrient source 14 is injected into the inside cylinder 12. The nutrient source 14 contains hexitol and glycerine and has a viscosity at 10°C of ≥0.2 Pa×S. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for purifying contaminated soil and / or groundwater.

  In recent years, environmental pollution due to organic chlorine compounds such as trichlorethylene (TCE), tetrachloroethylene (PCE), and tetrachloroethane, which are included in industrial wastewater, has become a major problem. Many of these pollutants penetrate into the soil and enter groundwater, expanding the contaminated area through this groundwater. It is strongly desired to establish a technology for preventing the spread of environmental pollution and purifying and repairing contaminated soil and groundwater.

In recent years, methods (bioremediation) using biological treatment with microorganisms have been proposed as methods for purifying contaminated soil and groundwater. Bioremediation is a method of decomposing pollutants into innocuous substances by microorganisms that live in contaminated areas or introduced from outside into contaminated areas. In bioremediation, it has been proposed to supply microorganism nutrients to soil and groundwater to activate microorganisms and promote degradation of pollutants. As a nutrient source for microorganisms, for example, a composition containing an organic substance selected from sorbitol, glycerin and mannitol, an organic substance such as a fatty acid having 12 or more carbon atoms, and a calcium compound has been proposed (Patent Document 1).
Japanese Patent No. 3815464

  In bioremediation, it is required to keep the nutrient source in the soil for a long time and to continuously activate the microorganisms. However, since the liquid nutrient source mainly composed of sorbitol has excellent diffusibility, there is a problem that the injected nutrient source flows out of the contaminated area in a short time by the groundwater flow. Therefore, the present invention provides a method for purifying contaminated soil and / or groundwater using a new injection method capable of gradually injecting a nutrient source, particularly a nutrient source mainly composed of sorbitol.

  The method for purifying contaminated soil and / or groundwater of the present invention (hereinafter also referred to as “the purification method of the present invention”) includes forming a nutrient source supply well in which an inner cylinder is disposed in a well casing, and Injecting a nutrient source into the inner cylinder, the nutrient source includes hexitol and glycerin, the nutrient source has a viscosity (10 ° C.) of 0.2 Pa · S or more, and the inner cylinder has a maximum diameter. The purification method has a side surface and a bottom surface having a plurality of holes of 0.5 to 2.5 mm, and is disposed with a space apart from the bottom surface of the well and the side surface of the well casing.

  According to the purification method of the present invention, hexitol can be gradually released from the inner cylinder. For this reason, according to the purification method of this invention, for example, microorganisms can be activated continuously and the purification efficiency of contaminated soil and groundwater can be improved.

  The present invention provides a nutrient source supply well having a double structure in which an inner cylinder having a hole having a predetermined diameter is arranged, and supplying the nutrient source having a predetermined viscosity through the inner cylinder. It is based on the knowledge that it can be released slowly from the cylinder and that the released nutrient source can be diluted in the groundwater in the well to promote the diffusion of the nutrient source. In addition, if a nutrient source having a predetermined viscosity is placed in the well as it is, it can suppress the natural decomposition of hexitol and is a microorganism that uses a decomposition product of hexitol as a nutrient source, and contributes little to or contributes to the purification of pollutants. The growth and / or activation of anaerobic microorganisms (eg, Dehalococides ethenegenes) that contribute to the degradation of volatile organics (especially PCE and TCE) can be suppressed because the growth of microorganisms (especially aerobic microorganisms) that are free of odor is possible. Based on the knowledge that it can be promoted efficiently.

  That is, the purification method of the present invention includes forming a nutrient source supply well in which an inner cylinder is disposed in a well casing, and injecting the nutrient source into the inner cylinder, and the nutrient source includes hexitol and glycerin. And the viscosity of the nutrient source (10 ° C.) is 0.2 Pa · S or more, the inner cylinder has a side surface and a bottom surface including a plurality of holes having a maximum diameter of 0.5 to 2.5 mm, and It is the purification method arrange | positioned with the bottom face of a well, the side surface of a well casing, and separation space.

  According to the purification method of the present invention, the nutrient source can be gradually released from the inner cylinder, so that the microorganisms can be activated continuously. In addition, since the nutrient source can be gradually released from the inner cylinder, the nutrient source can be retained in the contaminated area for a long time, and further, the microorganism can be activated for a long time by filling the inner cylinder once with the nutrient source. can do. Therefore, according to the purification method of the present invention, the purification efficiency of contaminated soil and groundwater can be improved. Further, according to the purification method of the present invention, for example, since a liquid nutrient source can be used without diluting, the apparatus and labor for diluting can be saved and it is simple. Furthermore, according to the purification method of the present invention, the nutrient source is supplied in a state where the carbon chain is long (the number of carbon atoms is large), so that excessive growth of microorganisms in the vicinity of the pore can be suppressed, and contamination is prevented without blocking the pore. Nutrient sources can be spread throughout the area.

[Nutrition source supply well]
In the present invention, the “nutrient source supply well” refers to a well for supplying a nutrient source to contaminated soil and / or groundwater and having an inner cylinder disposed in a well casing.

[Inner cylinder]
In the present invention, the “inner cylinder” means one having a side surface and a bottom surface provided with a plurality of holes having a maximum diameter of 0.5 to 2.5 mm. Since a hole is provided in the bottom surface of the inner cylinder, for example, a nutrient source whose specific gravity is heavier than that of groundwater can be naturally diluted and / or diffused near the lower impermeable layer. The inner cylinder is preferably capable of disposing a nutrient source inside and capable of diffusing the nutrient source from the bottom and side surfaces to the outside of the inner cylinder. The maximum diameter of the hole in the inner cylinder is 0.5 to 2.5 mm, and 1.0 to 2.0 mm is preferable from the viewpoint of improving sustained release and diffusibility. In the present invention, the “maximum diameter” means the length of the longest line among lines connecting a point on the outer periphery of the hole and other points. When the hole shape is circular, the maximum diameter is the diameter of the hole, and when the hole shape is rectangular, the maximum diameter is the length of the diagonal line of the hole. The maximum diameter of the hole can be measured by a conventionally known method. Examples of the shape of the hole include a circular shape and a rectangular shape. Among them, a horizontally long ellipse and a rectangle having a long axis in a direction orthogonal to the axial direction of the inner cylinder are preferable from the viewpoint of suppressing clogging. The hole may be formed in the entire inner cylinder, or may be formed only on the bottom surface and the side surface that contacts the groundwater. The pore formation density is preferably sparser (smaller) on the bottom surface side than on the end portion (upper end portion) side opposite to the bottom surface, from the point of uniformity of nutrient source diffusion. The area of the hole is, for example, 0.2 to 4.9 mm ² , and preferably 0.7 to 3.2 mm ² . The formation density of the holes may be increased continuously from the bottom surface side or may be increased stepwise. The opening ratio of the inner cylinder is, for example, 50 to 85%, and preferably 60 to 80%. The thickness of the inner cylinder is, for example, 1 to 2 mm. The inner cylinder can be formed of, for example, a resin or a steel material having a plurality of holes.

  The inner cylinder is arranged with a space apart from the bottom surface of the nutrient source supply well and the side surface of the well casing in the well. In the present invention, “arranged with a separation space” means that they are arranged in a state of being separated at a certain distance. Accordingly, spaces are formed between the bottom surface of the inner cylinder and the bottom surface of the well, and between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the well casing. By forming a space between the bottom surface of the inner cylinder and the bottom surface of the well, for example, a nutrient source whose specific gravity is heavier than groundwater can be naturally diluted and / or diffused in the vicinity of the lower impermeable layer. The distance between the bottom surface of the inner cylinder and the bottom surface of the well is preferably 30 to 50 mm. Moreover, although the distance of the side surface (outer peripheral side) of an inner cylinder and the side surface (inner peripheral side) of a well casing is suitably determined by the injection amount of a nutrient source, it should be about 1/6 of the diameter of a well casing. preferable. It is preferable that the inner cylinder is arranged substantially concentrically with the well casing from the viewpoint of uniformly diffusing nutrient sources.

  As the well casing, known well casings used for ordinary pumping wells, nutrient source supply wells, and the like can be used. The well casing is only required to be able to flow into and out of the groundwater, and includes, for example, a screen formed of a water-permeable material, a resin having a plurality of holes, a steel material, or the like. From the viewpoint of suppressing the inflow of soil into the well, a well casing in which a screen is formed at least in a portion disposed in the permeable layer is preferable.

[Nutrition source]
In the present invention, the “nutrient source” is a substance for activating microorganisms, and includes hexitol and glycerin. The viscosity (10 ° C.) of the nutrient source is 0.2 Pa · S (× 1000 cp) or more, preferably 0.3 to 0.95 Pa · S, more preferably about from the point that the nutrient source is gradually released from the inner cylinder. 0.9 Pa · S. The viscosity can be measured using, for example, a B-type viscometer.

  Examples of hexitol include sorbitol, mannitol and the like. Among them, sorbitol is preferable from the viewpoint of affinity with glycerin. The main component of the nutrient source is preferably hexitol, more preferably sorbitol. The content of hexitol in the nutrient source is, for example, preferably 40 to 70% by weight, more preferably 50 to 65% by weight from the viewpoint of activating microorganisms and improving sustained release. The content of glycerin in the nutrient source is preferably 5 to 20% by weight, more preferably 7 to 15% by weight from the viewpoint of improving sustained release. As a nutrient source, a nutrient source containing approximately 60% by weight hexitol and 10% by weight glycitol is preferable.

  The nutrient source may further include water. The content of water in the nutrient source is, for example, 35% by weight or less, and preferably 20-30% by weight from the viewpoint of sustained release. As other components, for example, polyoxyethylene sorbitan fatty acid ester may be further included from the viewpoint of improving the permeability to a silty soil layer or a reservoir of contaminants, and in particular, polyoxyethylene glycol (20) -sorbitan -Monooleate (polysorbate 20) is preferred. The content of the polyoxyethylene sorbitan fatty acid ester in the nutrient source is, for example, 0 to 10% by weight, and preferably 1 to 5% by weight. The nutrient source may further contain, for example, citric acid from the viewpoint of clogging of the holes of the inner cylinder and the screen of the well casing and suppressing the rise of the groundwater surface.

  A commercially available product may be used as the nutrient source. Examples of commercially available products include Amteclean P SL6-90SRW (trade name, manufactured by Matsushita Electric Industrial Co., Ltd., components: about 60% sorbitol, about 10% glycerin, about 2% polyoxyethylene (20) sorbitan monooleate, about about water. 28%, viscosity (10 ° C.): about 0.90 Pa · S, viscosity (20 ° C.): about 0.34 Pa · S).

[Contaminated soil and / or groundwater]
In the present invention, “contaminated soil and / or groundwater” refers to soil and groundwater containing pollutants. Examples of pollutants include volatile organic compounds (VOC), heavy metals, oils, nitrate nitrogen, nitrite nitrogen, and the like. Examples of volatile organic compounds include organic chlorine compounds, benzene, formaldehyde, toluene, xylene, and the like. Among these, the purification method of the present invention is suitable for the purification of contaminated soil and / or groundwater containing a volatile organic compound, more preferably an organic chlorine compound. Examples of the organic chlorine compound include carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,3-dichloropropene, dichloromethane, tetrachloroethylene (PCE), 1,1, Examples thereof include 1-trichloroethane, 1,1,2-trichloroethane, trichlorethylene (TCE) and the like. Among these, the purification method of the present invention is particularly suitable for purification of soil and / or groundwater contaminated with tetrachloroethylene, trichloroethylene, cis-1,2-dichloroethylene, 1,1-dichloroethylene, vinyl chloride, and the like.

[Purification method]
In the purification method of the present invention, first, a nutrient source supply well is formed. The nutrient source supply well can be formed, for example, by forming a well casing on the wall surface of a hole mined by boring or the like, and disposing an inner cylinder therein. It is preferable that the nutrient source supply well reaches at least the lower part of the permeable layer from the viewpoint of improving the diffusion of the nutrient source and efficiently activating the microorganisms, and reaches the impermeable layer located below the permeable layer. More preferably. In the present invention, the “permeable layer” refers to a layer in which groundwater exists, and includes an aquifer layer, a saturated layer, and an aquifer layer.

  The diameter of the nutrient source supply well can be appropriately determined depending on the size of the contaminated area, the concentration and type of the contaminant, and is preferably 100 to 150 mm, for example. The diameter of the inner cylinder can be appropriately determined depending on the diameter of the nutrient source supply well, the size of the contaminated area, the concentration and type of the contaminant, and is preferably 65 to 100 mm, for example, 2/3 of the diameter of the nutrient source supply well. More preferably. When the diameter of the well is 100 to 150 mm, the diameter of the inner cylinder is 65 to 100 mm, the distance between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the well casing is 17 to 50 mm, the bottom of the inner cylinder and the bottom of the well The distance is preferably 50 to 80 mm.

  Nutrient source supply wells are preferably formed in and / or around the contaminated area, and more preferably formed so as to surround the contaminated area from the viewpoint of suppressing the diffusion of contaminants. From the viewpoint of effectively functioning the nutrient source supply well as a purification wall, the interval between the nutrient source supply wells on the downstream side of the groundwater flow is preferably narrower than that on the upstream side of the groundwater flow. In this case, for example, the interval between nutrient source supply wells located on the downstream side of the groundwater flow is preferably 0 to 50 mm, and the interval between nutrient source supply wells located on the upstream side of the groundwater flow is preferably set to 50 to 100 mm. In the present invention, the “polluted area” refers to an area including at least soil and / or groundwater having a pollutant concentration equal to or higher than a predetermined concentration. In the present invention, the “interval of nutrient source supply wells” is a line connecting a point on the outer periphery of the nutrient source supply well and a point on the outer periphery of the adjacent well and is the shortest one.

  Next, a nutrient source is injected into the inner cylinder. When multiple nutrient source supply wells are formed, the order of injecting the nutrient sources is not particularly limited, but the diffusion of nutrient sources in the nutrient source supply well located upstream can be suppressed, so the downstream side of the groundwater flow from the upstream side It is preferable to inject a nutrient source toward. The nutrient source may be injected while being pressurized using a pump or the like, or may be performed without being pressurized.

  As another aspect, the present invention is a nutrient source supply well used in the purification method of the present invention, having a well casing inserted into at least a hole reaching the bottom of the permeable layer, a bottom surface, and a maximum diameter of 1 to 2 mm. A nutrient source supply well, wherein the inner cylinder is disposed in the well casing with a space apart from the bottom surface of the well and the side surface of the well casing. Including.

  Moreover, this invention is a pipe | tube used for the purification method of this invention, and the nutrient source supply well of this invention as another aspect, Comprising: A well casing and the inner cylinder which has a bottom face, The said inner cylinder Has a bottom surface and a side surface having a plurality of holes having a maximum diameter of 1 to 2 mm, and the inner cylinder can be arranged in the well casing with a side surface and a separation space of the well casing. Including tubes.

  Next, an example of the purification method of the present invention will be described with reference to FIGS. However, the present invention is not limited to the following examples.

  FIG. 1 is a schematic configuration diagram showing an embodiment of the purification method of the present invention. In FIG. 1, the nutrient source supply well 10 is formed in the contaminated area 14. The holes of the nutrient supply well 10 are mined in a substantially vertical direction from the ground surface to a depth reaching the inside of the impermeable layer 4 beyond the surface layer 1, the impermeable layer 2, and the lower part of the permeable layer 3. A well casing 11 is provided on the wall surface of the nutrient source supply well 10, and an inner cylinder 12 is disposed therein. The well casing 11 includes a screen (strainer) 11a through which groundwater can pass. The screen 11 a is formed from the bottom surface of the water permeable layer 3 nutrient source supply well 10 to the vicinity of the upper part of the water permeable layer 3. The inner cylinder 12 is arranged in the well 10 while maintaining a space apart from the bottom of the well and the well casing 11. The inner cylinder 12 has a nutrient source 13 disposed therein. Since the inner cylinder 12 has a plurality of holes on the side surface and the bottom surface, the nutrient source 13 can be released to the outside of the inner cylinder as indicated by arrows in the figure. Thereby, anaerobic microorganisms (for example, Dehalococides genus) can be activated, and decomposition | disassembly and purification | cleaning of the contaminant by anaerobic microorganisms can be accelerated | stimulated.

  FIG. 2 is a schematic configuration diagram showing an example in which a plurality of nutrient source supply wells 10 are formed in one contaminated area 14. The arrows in FIG. 2 indicate the direction of groundwater flow. In FIG. 2, 14 nutrient source supply wells 10 are formed so as to surround the contaminated region 14, and one nutrient source supply well 10 is formed in a contaminated region 24 having a particularly high contamination concentration in the contaminated region 14. . Further, the five nutrient source supply wells 10 located on the downstream side (right side in the figure) of the groundwater flow are formed at a narrower interval than the nutrient source supply wells 10 located on the upstream side. Thus, by narrowing the interval between the nutrient source supply wells 10 on the downstream side, these wells can function as purification walls, and the diffusion of contaminants to the outside of the contaminated region 14 due to the flow of groundwater can be suppressed. .

  The present invention is useful for the purification of contaminated soil and groundwater.

FIG. 1 is a schematic configuration diagram showing an example of the purification method of the present invention. FIG. 2 is a schematic configuration diagram showing another example of the purification method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface layer 2 ... Impervious layer 3 ... Impervious layer 4 ... Impervious layer 10 ... Nutrient source supply well 11 ... Well casing 11a ... Screen 12 ...・ Inner cylinder 13 ... Nutrient sources 14, 24 ... Contaminated area

Claims (4)

Forming a nutrient supply well in which an inner cylinder is arranged in a well casing; and
Injecting a nutrient source into the inner cylinder,
The nutrient source includes hexitol and glycerin, and the viscosity (10 ° C.) of the nutrient source is 0.2 Pa · S or more,
The inner cylinder has a side surface and a bottom surface including a plurality of holes having a maximum diameter of 0.5 to 2.5 mm, and is disposed with a space apart from the bottom surface of the well and the side surface of the well casing. A method for purifying soil and / or groundwater. The purification method according to claim 1, wherein the hexitol is sorbitol. A plurality of the nutrient source supply wells are formed so as to surround the contaminated area,
The purification method according to claim 1 or 2, wherein an interval between the nutrient source supply wells on the downstream side of the groundwater flow is narrower than an interval between the nutrient source supply wells on the upstream side of the groundwater flow. The purification method according to any one of claims 1 to 3, wherein the nutrient source supply well reaches at least the bottom of the permeable layer.

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