JPH09234484A - 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 purifying and restoring polluted ground water and soil by bioremediation. SOLUTION: Plural wells 11, 12, 13 are excavated in the saturation strate 17 near the underground polluted point 1 polluted with the contaminants and >=2 electrodes 14, 15, parted from each other, are enabedded 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 wells 11 to 13 and the pumped up water is introduced into a ground bioreactor 16, where the pollutants are subjected to the decomposition treatment. The treated water is released or the saturation stratum is impregnated with the water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 (also called in-situ bioremediation) utilizing biotechnology 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 enhances and uses the purification function originally possessed by the soil ecosystem. .

FIG. 3 schematically shows an example of a purification method by a conventional bioremediation technique.
In this method, two or more wells 3 and 4 are excavated in the saturated layer 2 in the vicinity of the underground contaminated site 1 contaminated with pollutants such as organic chlorine compounds and 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 and air (oxygen), which are growth substrates for the degrading bacteria, and nutrient sources 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, organic chlorine compounds such as trichlorethylene and pollutants such as oil are easily adsorbed by clay and organic matter in soil, and Since these are gradually released into the groundwater, there is a drawback that the removal takes a relatively long time. Also, although it is possible to decompose and remove pollutants in the saturated layer where groundwater is saturated, it is difficult to decompose and remove in the unsaturated layer where groundwater is unsaturated and there are gaps where air exists. It has problems such as

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]

According to a first aspect of the present invention, a plurality of wells are excavated in a saturated layer in the vicinity of an underground contaminated site contaminated with pollutants, and at the same time, in the vicinity of the underground contaminated site. By embedding two or more electrodes apart from each other, pumping groundwater containing pollutants from the well while applying a voltage between each electrode, and guiding the pumped water to a bioreactor on the ground to decompose pollutants, A method for repairing contaminated groundwater and soil, characterized in that the treated water is discharged or injected into a saturated layer. In the invention according to claim 2, at least one of a nutrient source and a substrate for oxygen and soil microorganisms is added to at least a part of the treated water, and the injection well is located upstream of the groundwater flow at the underground pollution location. The method for remediating contaminated groundwater and soil according to claim 1, wherein the method is to inject into the saturated layer. In the invention according to claim 3, the bioreactor is
It is an anaerobic bioreactor comprised so that the said pollutant may be decomposed anaerobically, It is a contaminated groundwater of the claim 1 or 2, The restoration method of soil.

[0007]

1 shows an example of a method for repairing contaminated groundwater and soil according to the present invention. In this example, a plurality of wells 11, 12, are formed in the saturated layer 17 near the underground pollution point 1 contaminated with pollutants such as organic chlorine compounds and waste oil.
Along with excavating 13 wells, burying the electrodes 14, 15 respectively on the upstream side and the downstream side of the groundwater flow 5 in those wells 11, 12, 13 respectively.
Moreover, the groundwater pumped from each well 11, 12, 13 is introduced into the bioreactor 16 for decomposing pollutants for treatment.

[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 included. It exists in the layer 18, especially in the boundary portion of each layer, and it exists in a state where it is difficult to separate. Contaminants of organochlorine compounds such as trichlorethylene are easily adsorbed by clay and organic matter in the soil.
Then, the pollutants gradually escape into the groundwater, and the groundwater contains the pollutants.

The wells 11, 12 and 13 are excavated to a depth enough to reach the saturated layer 17 near the underground pollution site 1. Pumping pipes are inserted into these wells 11, 12 and 13 up to near the bottom, and groundwater is pumped to the ground through these pumping pipes. The number of these wells 11, 12 and 13 is appropriately set according to the contamination status of the underground contamination site 1. Further, these wells 11, 12, 13 are not only for pumping water, but are also provided with wells for water injection on the upstream side of the groundwater flow 5, from which water wells for multiplication of methane, phenol, etc. Water supplemented with nutrients (nitrogen source, inorganic salts such as phosphate, etc.) or surfactant may be supplied.

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, an electrode made of graphite or the like, which is driven to a depth sufficient to reach the saturated layer 17, can be used.
Moreover, you may use the electrode body which attached the metal wire or the metal net to the outer side of the main body which consists of non-conductive materials.

Between the electrodes 14 and 15, the electrode 14 on the upstream side of the groundwater flow 5 is the anode (+) side, and the electrode 1 on the downstream side is
A direct current is applied so that 5 is on the cathode (−) side.
The voltage applied between these electrodes 14 and 15 is
The range is such that the movement can be promoted and no loss occurs, and it may be appropriately changed within the range of several V to several hundred V depending on the conductivity of the ground. Moreover, the number and the installation positions of the electrodes 14 and 15 may be appropriately set depending on the scale of the underground pollution point 1 and the groundwater flow 5 so that a voltage can be efficiently applied around the underground pollution point 1. Alternatively, the positive and negative of the electrodes 14 and 15 may be switched at any time to perform the processing.

The bioreactor 16 brings microorganisms capable of decomposing substances to be treated, such as tetrachloroethylene, into contact with the groundwater pumped from the wells 11, 12, and 13,
It is for biologically decomposing pollutants contained in the groundwater by microorganisms. This bioreactor 1
As for the apparatus configuration of 6 and the bacteria to be used, an appropriate type can be selected and used according to the type of contaminant. For example, as a bioreactor using anaerobic bacteria, a treatment device of an anaerobic digestion method (methane fermentation method) or the like which is usually carried out in sewage treatment or industrial wastewater treatment may be applied. In addition, a closed bioreactor using aerobic bacteria is used, and in addition, a reactor equipped with buoyant particles or a porous support for retaining bacteria having the ability of degrading pollutants can be anaerobic or aerobic. A bioreactor of the type that contacts groundwater under conditions may be used.

The bioreactor 16 may be equipped with either an anaerobic bioreactor or an aerobic bioreactor, depending on the type of pollutant to be treated, or may be an anaerobic bioreactor or an aerobic bioreactor. Both bioreactors may be arranged in series. When the pollutant is an organic chlorine compound such as tetrachloroethylene, anaerobic bacteria isolated in soil or from anaerobic sludge, for example, Fathepure et al. (Fathepure, BZ, Nengu, J.
P. and Boyd, SA: Appl. Environ. Microbiol., 53,267
1-2674 (1987); Fathepure, BZ and Boyd, SA: Appl.
Environ. Microbiol., 54, 2976-2980 (1988)), an anaerobic bacterium (Methanosarucina sp., Methanosaruc).
ina metai, Methanosarucina acetivorans, Methanothr
ix sp., Dechlorinating bacterium DCB-1, Methanosar
ucina sp.DCM), Belay et al. (Belay, N. and Daniels, L.:A
Microbiol., 53,1604-1609 (1987)), a reported methanogenic bacterium (Methanococcus thermoli).
thotrophics, M. thermodeltae, Methanobacterium the
rmoautotrophicum), Egli et al. (Egli, CE, Tschan, T.,
Scholtz, RS, Cook, AM and Leisinger, T .: Appl. En
viron. Microbiol., 54, 2819-2824 (1988)) and other sulfate-reducing bacteria (Desulfobacterium autotrophic
um, Acetobacterium woodii, Clostridium thermoaceti
cum), Galli et al. (Galli, R. and McCaryt, PL: Appl. En
Microbiol., 55,837-844 (1989)), an anaerobic bacterium (Clostridium sp.TCA2B strain), Yaguchi et al. (Kumiko Yaguchi, Manabu Watanabe, Ichiro Hirata, Takeshi Ito, Akira Hamada: Water Pollution Research, 14,479). -486 (1991)), such as Gram-negative tetrachloroethylene-degrading bacterium T strain, can be used.

In the case of aerobically decomposing organic chlorine compounds such as trichlorethylene, aerobic bacteria separated from soil or aerobic sludge, such as Fox et al.
x, BG et al .: Biochemistry, 26, 6419-6427 (1990))
Microorganisms reported by Pseudomonas mendocin
a, P. putida F1, Nitrosomonas europaea, Mycobacter
ium sp., etc.) can be used.

In order to repair the underground pollution point 1 by bioremediation, that is, to decompose and remove the pollutants, by constructing such an equipment structure around the underground pollution point 1, the ground water is connected between the electrodes 14 and 15. A voltage is applied so that the electrode 14 on the upstream side of the stream 5 becomes the anode (+) side and the electrode 15 on the downstream side becomes the cathode (−), and groundwater is pumped from the plurality of wells 11, 12, 13.

As a result, desorption and migration of pollutants in the saturated layer 17 are significantly promoted, the amount of pollutants in the groundwater pumped from the wells 11, 12, 13 can be increased, and the desorption of pollutants can be achieved. The pollutants contained in the boundary between the unsaturated layer 18 and the impermeable layer 19 which were difficult to remove are also released from the respective layers into the groundwater flow 5, and the pollutants are pumped from the wells 11, 12, 13 by the pumping. Will be able to be collected.

The groundwater pumped from each well 11, 12, 13 is guided to the bioreactor 16 to biologically decompose pollutants such as contained organic chlorine compounds.
In the bioreactor 16, the nutrient source necessary for the growth of the pollutant degrading bacteria is added, the temperature in the bioreactor,
The oxygen concentration is maintained under conditions suitable for the growth of the degrading bacterium to grow the bacterium.

The water in which the pollutant is decomposed and removed in the bioreactor 16 and the pollutant disappears or has an extremely low concentration is discharged after performing treatment such as activated carbon adsorption as necessary.

By continuing this treatment, the pollutants existing in the underground pollution site 1 and the like can be efficiently released into the groundwater and safely decomposed by the degrading bacteria, and the underground pollution can be achieved within a short period of time. It is possible to remove the contaminants at the point 1 and repair the point. The treated water may be used to increase the groundwater flow 5 by injecting it into the saturated layer 17 from a well drilled on the upstream side of the groundwater flow 5 at the underground pollution location 1.

FIG. 2 shows another example of the method for repairing contaminated groundwater and soil according to the present invention. In this example, the treated water treated in the bioreactor 16 is actively injected underground, and substrates such as methane and phenol that promote the growth of pollutant degrading bacteria existing in the ground, nutrient sources and air ( This is a method for increasing the activity of pollutant degrading bacteria existing in the ground by adding and injecting (oxygen) to perform more aggressive decomposition and removal of pollutants.

In this example, as shown in FIG. 2, at least one injection well 21 and an electrode 1 are provided upstream of the underground contamination site 1.
4 is provided, and at least 1 is provided on the downstream side of the underground contamination point 1.
A pumping well 22 of a book and an electrode 14 are provided. Pumping well 22
A pumping pipe reaching the saturated layer 17 is inserted in the pump, groundwater is pumped through the pumping pipe by a pump, and this water (groundwater containing pollutants) is guided to the bioreactor 16 placed on the ground to remove pollutants. Biodegrades. The water treated in the bioreactor 16 is a nutrient source,
The injection well 2 is introduced to the substrate adding means 23 for adding an appropriate amount of air or a surfactant and the like, after adding growth substrates such as methane of decomposing bacteria and phenol, air (oxygen), nutrient sources, etc.
Inject from 1 to the upstream side of underground pollution point 1.

In the treatment according to this example, groundwater pumped from the pumping well 22 on the downstream side of the underground polluted site 1 is guided to the bioreactor 16 and efficiently decomposed by the degrading bacteria having high decomposing ability of pollutants in the bioreactor 16. Then, since the treated water is injected into the saturated layer 17 from the injection well 21 on the upstream side of the underground pollution place 1 through the injection well 21,
Water can be forcibly circulated in the vicinity of the underground pollution point 1, the amount of the groundwater flow 5 flowing from the upstream side to the downstream side of the underground pollution point 1 is increased, and the pollution caused by the voltage application between the electrodes 14 and 15 In addition to the effect of releasing the substance, the release of the pollutant from the ground can be further promoted. Moreover, the treatment of pollutants can be executed even in a place where the groundwater flow 5 is not sufficient.

Further, in this example, when the treated water (which may be water from another water source) is injected into the saturated layer 17 from the injection well 21 on the upstream side of the underground pollution point 1, contaminants existing in the ground Substrates such as methane and phenol that promote the growth of degrading bacteria, nutrient sources, and air (oxygen) are added and injected to enhance the activity of pollutant degrading bacteria existing in the ground, and pollutants even in the ground. The decomposition of the pollutants can promote the decomposition of the pollutants. Furthermore, by adding a small amount of a surfactant to the treated water to be injected as necessary, the pollutants strongly adsorbed on the clay in the ground can be very effectively released into the groundwater.

[0024]

As described above, the method for remediating contaminated groundwater and soil according to the present invention excavates a plurality of wells in a saturated layer in the vicinity of a contaminated underground contaminated site, Two or more electrodes are buried in the vicinity of the space apart from each other, groundwater containing pollutants is pumped from the well while applying a voltage between each electrode, and the pumped water is guided to a bioreactor on the ground to decompose pollutants. By treating and then discharging or injecting the treated water into the saturated layer, it is possible to remarkably accelerate the desorption and migration of pollutants in the saturated layer,
It is possible to accelerate the removal of pollutants contained in formations other than the saturated layer, which was difficult to remove by conventional methods, and to decompose and remove the pollutants in a short period of time. Further, at least one of a nutrient source and a substrate for oxygen of soil microorganisms is added to at least a part of the treated water, and the saturated layer is injected from an injection well located upstream of the groundwater flow at the underground pollution location. As a result, the pollutant-degrading bacteria existing in the vicinity of the underground pollutant can be grown and the decomposition of the pollutant underground can be promoted. Furthermore, since the bioreactor is an anaerobic bioreactor configured to anaerobically decompose the pollutants, it is possible to decompose tetrachloroethylene, which cannot be decomposed under aerobic conditions.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing an example of a method for repairing contaminated groundwater and soil according to the present invention.

FIG. 3 is a cross-sectional view showing a conventional bioremediation method.

[Explanation of symbols]

 1 ... Underground contamination 17 ... Saturated layer 11, 12, 13 ... Well 14, 15 ... Electrode 16 ... Bioreactor 21 ... Injection well 22 ... Pumping well

Claims (3)

[Claims] 1. A plurality of wells are excavated in a saturated layer in the vicinity of an underground polluted site contaminated with pollutants, and two or more electrodes are buried in the vicinity of the underground polluted site with a space between the electrodes. The groundwater containing pollutants is pumped from the well while applying a voltage to the well, the pollutants are decomposed by introducing the pumped water to an on-ground bioreactor, and the treated water is discharged or injected into a saturated layer. How to remediate contaminated groundwater and soil. 2. At least one of a nutrient source and a substrate for soil microorganisms is added to at least a part of the treated water, and a saturated layer is formed from an injection well located upstream of the groundwater flow at the underground pollution location. Injecting into
Remediation method for contaminated groundwater and soil described. 3. The method for remediating contaminated groundwater and soil according to claim 1 or 2, wherein the bioreactor is an anaerobic bioreactor configured to anaerobically decompose the pollutants.