JPH09234487A - Restoration method for polluted ground water and soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable rapid decomposition and removal and to enable the decomposition and removal of the contaminants of unsatd. strata as well at the time of executing purification and restoration by bioremediation. SOLUTION: Plural wells 11, 12 are excavated to the saturation strata 17, in which ground water is flowed, near the underground polluted point 1 polluted with the contaminants and >=2 electrodes 14, 15 parted from each other, are embedded near the underground polluted point 1. While voltage is impressed between the respective electrodes, the ground water contg. the contaminants is pumped up from the well 11. At least one kind among the growth substrate of the pollutant decomposing microorganisms in the soil, the nutrient source for the microorganisms and oxygen are added to the pumped up water. The saturation strata 17 is impregnated with a part of the pumped up water from the impregnation well 12 existing on the upstream side of the ground water stream 5 at the underground polluted point 1. The unsatd. strata 18 which are the upper strata of the saturation strata 17 are impregnated with the other part of the water.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a technique for repairing and purifying soil and groundwater contaminated with organic chlorine compounds such as trichloroethylene and tetrachloroethylene and pollutants such as waste oil.

[0002]

2. Description of the Related Art Recently, bioremediation utilizing biotechnology (also called in-situ bioremediation) has been attracting attention as a purification method for removing pollutants from such contaminated soil and groundwater. Bioremediation is a technology that decomposes and detoxifies pollutants by utilizing the function of microorganisms that live in the soil, and artificially strengthens and uses the purification function originally possessed by the soil ecosystem. is there.

FIG. 3 schematically shows an example of a purification method by a conventional bioremediation technique. In this example, two or more wells 3 and 4 are excavated in a saturated layer 2 near an underground contamination point 1 contaminated with a contaminant such as an organic chlorine compound or oil. At least a part of the groundwater pumped from the pumping well 4 drilled on the downstream side of the groundwater flow 5 is guided to the substrate addition means 6, and methane, phenol, oxygen, nutrient sources, etc. which become growth substrates for pollutant-degrading bacteria are added. , And injects it into the injection well 3 that has been excavated upstream and circulates it. As a result, the activity of the pollutant-degrading bacteria present in the saturated layer 2 and the like can be enhanced, and the pollutant can be decomposed and removed efficiently, and the restoration method has high cost performance.

[0004]

However, in this purification method by bioremediation, pollutants of organochlorine compounds such as tetrachloroethylene are present in a liquid state or are adsorbed to clay and organic matter in soil. Since they are easy to remove, they are gradually released into the groundwater, which has the disadvantage that it takes a relatively long time to remove them. In addition, it is possible to decompose and remove pollutants in a saturated layer where groundwater in the soil is saturated, but the groundwater is unsaturated and decomposes in an unsaturated layer where there are gaps such as air, There is a problem that removal is difficult.

An object of the present invention is to provide a method capable of decomposing and removing in a short time when purifying and repairing by bioremediation and also capable of decomposing and removing contaminants in an unsaturated layer. .

[0006]

[Means for Solving the Problems] The above-mentioned problem is to excavate a plurality of wells in a saturated layer in which groundwater flows in the vicinity of an underground polluted site contaminated with pollutants, and to provide two or more wells in the vicinity of the underground polluted site. The electrodes are separated from each other and embedded, while applying a voltage between the electrodes, groundwater containing pollutants is pumped from the well on the downstream side of the groundwater flow at the underground polluted site, and the pumped water is a pollutant-degrading microorganism in soil. Of at least one of the growth substrate, the nutrient source of the microorganisms, and oxygen, and a part of the pumped water is injected into the saturated layer from the well located on the upstream side of the groundwater flow at the underground pollution point. , The other part is injected into the unsaturated layer, which is the upper layer of the saturated layer, to solve the problem. Further, in the unsaturated layer, a water pipe is embedded,
It is desirable to inject the other part of the pumped water into the unsaturated layer through the water spray pipe.

[0007]

1 shows an example of a method for repairing contaminated groundwater and soil according to the present invention. In this example, in the saturated layer 17 near the underground pollution point 1 contaminated with pollutants such as organic chlorine compounds and waste oil, the underground pollution point 1
While excavating two or more wells 11 and 12 on the upstream side and the downstream side of the groundwater flow 5 across the well,
Electrodes 14 on the upstream side and the downstream side of the groundwater flow 5 of
15 is buried, and further, the water sprinkler pipe 16 is horizontally buried near the ground surface in the soil near the ground surface between the wells 11 and 12,
Part of the groundwater pumped from the downstream pumping well 11 is injected into the saturated layer through the groundwater flow 5 upstream injection well 12, and the other part is injected through the sprinkler pipe 16 into the saturated layer 1
7 is configured to be injected into the unsaturated layer 18 which is the upper layer.

[0008] The stratum at this underground pollution point 1 is composed of a groundwater flow 5
As shown in Fig. 2, the saturated layer 17 in which groundwater flows, the unsaturated layer 18 above it, and the impermeable layer 19 below the saturated layer 17 are provided. It is abundant in the layer 17, and is particularly accumulated in the boundary portion between the unsaturated layer 18 and the saturated layer 17 and the boundary portion between the unsaturated layer 18 and the impermeable layer 19. Contaminants of organochlorine compounds such as trichlorethylene are adsorbed and present in clay and organic matter in the soil. Therefore, in the saturated layer 17, the contaminants are gradually released into the groundwater, and in the groundwater. Contains pollutants.

The wells 11 and 12 are deep enough to reach the saturated layer 17 in the vicinity of the underground pollution point 1 and the underground pollution point 1
It is excavated on the upstream side and the downstream side of the groundwater flow 5. A pumping pipe is inserted into the pumping well 11 on the downstream side up to near the bottom, and groundwater is pumped to the ground through these pumping pipes. The upstream injection well 12 is for returning pumped water to the saturated layer 17 again.

The electrodes 14 and 15 may be conductors inserted to a depth enough to reach the saturated layer 17, and the material and shape are not limited. For example, it is possible to use an electrode plate formed of graphite or the like that is driven to a depth that reaches the saturation layer 17 sufficiently.

A direct current can be applied between the electrodes 14 and 15 by using the electrode 14 on the upstream side of the groundwater flow 5 as an anode (+) and the electrode 15 on the downstream side as a cathode (-). As a result, contaminants in the soil can be separated from clay and organic matter, and can be electrophoresed to promote the movement in the downstream direction of the groundwater flow 5. The voltage applied to these electrodes 14 and 15 is in a range that can promote the detachment and movement of pollutants and does not cause loss, and is appropriately in the range of several V to several hundred V depending on the conductivity of the ground. You can set it. In addition, the electrodes 14 and 15
The number and the installation position of the above may be appropriately set according to the scale of the underground pollution point 1 and the groundwater flow 5 so that a voltage can be efficiently applied to the surroundings of the underground pollution point 1.

Further, a substrate adding means 6 is provided on the ground so that methane, phenol, a nutrient source, or oxygen, which is a growth substrate for pollutant-degrading bacteria in soil, can be added to the pumped water as needed. You can do it. As the nutrient source, inorganic salts such as ammonia salt and phosphate are used, and contaminant decomposing bacteria are added as necessary. As a method of adding oxygen, a method of bubbling pumped water with air or pure oxygen to increase the dissolved oxygen concentration, a method of injecting hydrogen peroxide, and the like are applied.

In the present invention, various pollutant-degrading bacteria existing in soil can be used for promoting the growth of the pollutant to decompose the pollutant, and bacteria that decompose the pollutant to be treated. It can be actively sent underground to grow and be used for decomposition of pollutants. Microorganisms used in this manner differ depending on the type of pollutant to be treated, but when the pollutant is an organochlorine compound such as tetrachloroethylene, anaerobic bacteria isolated in soil or from anaerobic sludge, for example, Fathepure et al. (Fathepure, B.
Z., Nengu, JP and Boyd, SA: Appl. Environ. Micro
biol., 53,2671-2674 (1987); Fathepure, BZ, and Boy
d, SA: Appl. Environ. Microbiol., 54,2976-2980 (198
8)) reported anaerobes (Methanosarcina sp., Me
thanosarcina metai, Methanosarcina acetivorans, Me
thanothrix sp., Dechlorinating bacterium DCB-1, Me
thanosarcina sp.DCM), Belay et al. (Belay, N. and Daniel
s, L.: Appl.Environ. Microbiol., 53, 1604-1609 (198
7)) reported a methanogenic bacterium (Methanococcus th
ermolithotrophicus, M. thermodeltae, Methanobacter
ium thermoautrophicum), Egli et al. (Egli, CE, Tschan,
T., Scholtz, RS, Cook, AMand Leisinger, T.: Appl.
Environ. Microbiol., 54, 2819-2824 (1988)).
hicum, Acetobcteriumwoodii, Clostridium thermoacet
icum), Galli et al. (Galli, R. and McCaryt, PL: Appl. Env
Iron. Microbiol., 55, 837-844 (1989)), an anaerobic bacterium (Clostridium sp.TCA2B strain), Yaguchi et al. (Kumiko Yaguchi, Manabu Watanabe, Ichiro Hirata, Itobu, Akira Hamada: Water Pollution Research. , 14, 479-486 (1991)), such as Gram-negative tetrachloroethylene-degrading bacterium T strain can be used.

The microorganisms that aerobically decompose the pollutants include aerobic bacteria isolated from soil or aerobic sludge, such as Fox et al. (Fox, BG et al .: Biochemist).
ry, 26, 6419-6427 (1990)) and various microorganisms (Pseudomonas mendocina, P. putida F1, Nitrosomona
s europaea, Mycobacterium sp., etc.) can be used.

The water sprinkling pipe 16 is for injecting a part or all of the pumped ground water into the unsaturated layer 18, and is a tubular material or the like having a plurality of water sprinkling holes formed along its length. As the material, plastic or metal is used. This sprinkler pipe 16 is used for the well 1 of the unsaturated layer 18.
It is provided horizontally between 1 and the well 12, preferably in or near the surface of the earth. Further, the number of sprinkler tubes 16 and the installation positions thereof may be appropriately set according to the concentration of pollutants in the unsaturated layer 18, the contamination range, and the like. A part of the pumped water can be discharged through the discharge water channel 21.

A method for repairing contaminated groundwater and soil using the wells 11, 12, the electrodes 14, 15 and the sprinkler pipe 16,
The procedure will be described below. Under the condition that a voltage of several V to several hundred V is applied between the electrodes 14 and 15, groundwater containing pollutants is pumped from the pumping well 11 by a pump (not shown). By applying the voltage as described above, the pollutants adsorbed to the clay and organic matter in the saturated layer 17 and the unsaturated layer 18 are released into the groundwater, and the groundwater containing the pollutants is pumped from the pumping well 11. .

Next, to the pumped water, methane, phenol, a nutrient source, oxygen, etc., which are growth substrates for soil microorganisms, are supplied by the substrate addition means 6. Here, when utilizing anaerobic bacteria in the soil depending on the type of pollutants to be treated and environmental conditions in the soil, oxygen is not supplied, and only the above nutrient sources are supplied. It is desirable to selectively set conditions such that oxygen is also supplied when using aerobic bacteria.

Subsequently, a part of the pumped water added with this substrate is introduced into the injection well 12. The introduced pumping water moves from the injection well 12 into the soil, and again moves in the downstream direction of the groundwater flow 5. The other part is introduced into the water sprinkling pipe 16, and is supplied to the unsaturated layer 18 through the opening of the water sprinkling pipe 16.
The pumped water supplied to the unsaturated layer 18 flows downward in the unsaturated layer 18 while supplying substrates such as methane and phenol, oxygen, and nutrient sources to this layer, and eventually the saturated layer 17
And reaches the downstream side by the groundwater flow 5. As described above, a part of the groundwater flowing downstream of the groundwater flow 5 is
The water is pumped again in the injection well 12. This process is repeated to circulate groundwater. During this circulation process, pollutants are decomposed and rendered harmless by the action of microorganisms in the soil.

In the above example, the electrodes 14 and 15 are used to pass a current through the underground contamination site 1, and the wells 11 and 12
Since groundwater is circulated by adding substrates, oxygen, nutrient sources, etc., contaminants such as organochlorine compounds and oil adsorbed to clay and organic matter in the soil are released into the groundwater and pollution in the soil It can activate substance-degrading microorganisms and accelerate the decomposition of pollutants. In addition, pumping well 1
Part of the pumped water from No. 1 is passed through the sprinkler pipe 16 to the unsaturated layer
Since it is supplied to 8, the water flow is also generated in the unsaturated layer 18, and substrates, oxygen, nutrient sources, etc. are supplied. As a result, the contaminant-decomposing bacteria can be activated and the decomposition of the contaminants in the unsaturated layer 18 can be promoted. Further, since the tubular sprinkler pipe 16 is used, it can be installed by a simple construction, and the pumped water can be supplied to a wide range of the target soil.

In the above example, the tubular water sprinkling pipe 16 is used as a means for supplying the pumped water to the unsaturated layer 18, but the present invention is not limited to this, and as shown in FIG. A part or all of the pumped water may be supplied to the unsaturated layer 18 through one or a plurality of sprinklers 20.

[0021]

In the method for repairing contaminated groundwater and soil according to the present invention, an electric current is passed through the electrode to the underground contaminated site, and the groundwater is circulated through the well by adding the substrate, oxygen, nutrients, etc. It releases pollutants such as organochlorine compounds and oils adsorbed on clay and organic matter into groundwater, activates pollutant-degrading microorganisms in soil, and promotes the decomposition of pollutants by these microorganisms. Therefore, it is possible to quickly treat the pollutants. Further, by supplying a part of the pumped water from the pumping well to the unsaturated layer through the sprinkler pipe, it is possible to accelerate the decomposition of pollutants in the unsaturated layer without the groundwater flow, which has been difficult in the past.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an example of a method for repairing contaminated groundwater and soil according to the present invention.

FIG. 2 is a cross-sectional view of essential parts for explaining another example of the method for repairing contaminated groundwater and soil according to the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a conventional method for repairing contaminated groundwater and soil.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Underground pollution place, 11 ... Pumping well, 12 ... Injection well, 14 ... Anode, 15 ... Cathode, 16 ... Sprinkler pipe, 17 ...
..Saturated layer, 18 ... Unsaturated layer,

Claims (2)

[Claims] 1. A plurality of wells are excavated in a saturated layer in which groundwater flows near a polluted underground polluted site, and two or more electrodes are buried in the vicinity of the underground polluted site in a spaced manner. While applying a voltage between the electrodes, groundwater containing pollutants is pumped from the well on the groundwater flow downstream side of the underground polluted site, and to the pumping, a growth substrate for pollutant-degrading microorganisms in soil, and of the microorganisms. A nutrient source and at least one of oxygen are added, and a part of the pumped water is injected into the saturated layer from the well located on the upstream side of the groundwater flow of the underground pollution point, and the other part is added to the saturated layer. A method for repairing contaminated groundwater and soil, characterized by injecting into the unsaturated layer, which is the upper layer. 2. The contaminated groundwater and soil restoration according to claim 1, wherein a sprinkler pipe is buried in the unsaturated layer, and the other part of the pumping water is injected into the unsaturated layer through the sprinkler pipe. Method.