JP2003326244A - Method and apparatus for restoring contaminated soil by microbe on-site - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for easily decontaminating/ restoring contaminated soil at a contaminated site without moving the contaminated soil from the contaminated site and without pumping up contaminated ground water. <P>SOLUTION: A packed layer packed with a carrier carrying a microbe having the ability to decompose a soil contaminating substance is formed in a hollow tubular body arranged in the contaminated soil. Air and the ground water containing the soil contaminating substance extracted by being brought into contact with the contaminated soil are sent in the packed layer from the lower part of the packed layer and the soil contaminating substance is decomposed by bringing the sent ground water into contact with the carrier. The soil contaminating substance-decomposed/removed ground water is discharged from the upper part of the packed layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for repairing contaminated soil, and particularly to a method for repairing contaminated soil using microorganisms capable of degrading soil pollutants,
That is, it relates to bioremediation and its device.

[0002]

2. Description of the Related Art In recent years, various kinds of hardly decomposable harmful chemical substances have been detected in soil, rivers, sea, air, etc., and the progress of pollution by these substances has become a problem. In particular, soil pollution due to heavy metals and organic chlorine compounds has become a serious problem, and it is strongly desired to establish a technology to prevent the spread of pollution and to regenerate the polluted environment. For example, soil pollution has become a problem at waste treatment sites and sites such as chemical plants, gas manufacturing plants, oil refineries, oil refineries, fuel stations, and pulp plants that handle heavy metal compounds. There is a high need for improvement and development of soil remediation methods to achieve this.

In addition, soil pollution not only hinders the reuse of land, but also has a high risk of expanding the contaminated area by pollutants flowing into and diffusing into groundwater. There is a strong demand for it to be established.

Various methods have been known and tried as soil restoration methods for restoring soil to its original state by removing pollutants from polluted soil. For example,
Pumping polluted groundwater to separate volatile organic substances, aeration treatment to adsorb to activated carbon, exposing contaminated soil to the sun and heat source, heat treatment to evaporate volatile organic substances by heat, provide boring holes in contaminated soil, Vacuum extraction for sucking pollutants by vacuum, and vacuum pot processing for putting contaminated soil in a vacuum pot to heat and suck to extract are performed.

Further, in the method of pumping up and treating contaminated groundwater, a great amount of energy is required for pumping up and treating, ground facilities for purification are also required, and further ground subsidence occurs, and downstream of groundwater flow. It is also necessary to consider the problems that may occur in the use on the local side and that may occur due to changes in underground water such as impacts on downstream ecosystems. On the other hand, the method of taking out the contaminated soil itself, detoxifying it, and backfilling it requires further cost. Thus, these physicochemical methods have many problems, such as high cost, low operability, and difficulty in treating pollutants that exist at low concentrations, especially when the pollution is not at high concentrations. If that's not the practical way.

[0006] Therefore, among the soil remediation methods, expectations for remediation by soil purification using microorganisms, so-called bioremediation, are increasing. In particular, in-situ soil restoration that does not dug or move contaminated soil, that is, on-site, is considered practical from the viewpoint of cost and labor. If microorganisms, especially microorganisms that can live in soil, decompose pollutants, purification is performed by natural energy, the input energy is small, and the decomposition proceeds to water and carbon dioxide. As a soil remediation method using microorganisms, a method of enhancing the self-cleaning ability of the ecosystem by degrading pollutants and detoxifying them by enhancing the function of microorganisms that naturally exist in the target soil,
Taking this technology one step further, bacteria that have the ability to decompose pollutants (hereinafter also referred to as pollutant-decomposing bacteria or simply decomposing bacteria) are actively introduced into the contaminated soil to promote the repair of the contaminated soil. Methods are being tried.

Many microorganisms are known that decompose persistent compounds causing soil pollution, such as aromatic hydrocarbons and organic chlorine compounds. However, when these bacteria are simply sprayed directly on the actual contaminated soil,
The bacterial concentration in the soil decreases with time as compared with the initial bacterial concentration at the time of spraying, and the repair efficiency at the polluted site decreases. This is because it is difficult to match both of "distribution of pollutants" and "dispersion of microbial decomposition material" due to differences in time and physical properties. In order to overcome this difficulty, there have been used methods such as forcibly arranging the microbial decomposition material in the ground, and pumping the material with a pipe inserted into the soil layer.

For example, US Pat. No. 5,120,160 (Environ,
Reclamation Sys. Inc.), USP-5080782 (Environ. Sc
i. & Eng. Inc.), USP 5,032,042 (New Jersey Institute
of Technology) and German Patent DE-3839093 C2 (BuaerS
Each of the publications such as pezialitiefbau Gmbh) proposes a method of biologically purifying pollutants by supplying microorganisms and nutrients into the ground. However, in order to prevent a decrease in efficiency, it is necessary to repeat microbial application frequently, which is time-consuming and costly, and may cause secondary contamination due to microbial application. Moreover, spattering of microorganisms tends to cause uneven supply of contaminated soil in the depth direction, and the decontamination effect tends to remain at a low level. Therefore, it is desired to uniformly distribute the administered degrading bacteria in the contaminated soil and maintain the concentration of the bacteria high.

[0009]

As indicated by the current state of the art of remediating contaminated soil, it is common to find a simple and effective method for remediating contaminated soil that does not require pumping of contaminated groundwater or digging of contaminated soil. In response to the request, no satisfactory means have been provided yet. The present invention has been made from the background described above, and an object thereof is a method for easily purifying contaminated soil (also referred to as soil restoration) without moving the contaminated soil from the contaminated site or pumping contaminated groundwater. Is to provide. More specifically,
Soil remediation method and remediation device that can perform soil remediation (hereinafter also referred to as on-site soil remediation) in a soil contaminated area by causing a microorganism having a pollutant decomposing ability to act on the contaminated soil, and a simple remedial operation To provide.

[0010]

The above-mentioned object of the present invention can be realized by the following on-site repairing method for soil contaminated by microorganisms of the present invention and on-site repairing means to which the method is applied. .

1. In a hollow tubular body installed in contaminated soil,
A land containing a soil pollutant extracted by contacting with the contaminated soil from the lower part of the packed bed, provided with a packed bed filled with a carrier carrying a microorganism capable of degrading the soil pollutant (hereinafter also referred to as a soil pollutant degrading bacterium) Sending intermediate water and air into the packed bed to bring the underground water and the carrier into contact with each other to decompose the contaminants, and decompose the underground water into which the contaminants are decomposed and removed. An on-site remediation method for contaminated soil, characterized by discharging from the upper part.

The following (a) to (j) are mentioned as particularly preferable embodiments of the on-site restoration method for contaminated soil as described above. (A) The on-site restoration method for contaminated soil according to the above 1, wherein the contaminated soil area around the tubular body is watered or poured to increase the amount of underground water reaching the suction hole. (B) An on-site remediation method for contaminated soil according to the preceding item (a), characterized in that the water to be sprinkled or poured contains nutrients of soil contaminant degrading bacteria. (C) An on-site restoration method for contaminated soil according to the above (a) or (b), wherein a reservoir for underground water taken in through a suction hole is provided at the bottom of the tubular body. (D) An underground water suction mechanism is provided above the packed bed of the tubular body so that the underground water taken into the tubular body from below the packed bed of the tubular body can be sucked up into the packed bed, and An on-site remediation method for contaminated soil, characterized in that the residence time can be adjusted.

(E) A method for on-site restoration of contaminated soil, wherein the bottom of the tubular body does not reach the groundwater vein. (F) An on-site restoration method for contaminated soil, wherein the packed layer is composed of a plurality of sub-packed layers filled with a carrier carrying different types of soil contaminant degrading bacteria. (G) The on-site restoration method for contaminated soil, wherein the packed bed is a packed bed in which carriers carrying different types of soil contaminant decomposing bacteria are mixed and packed. (H) An on-site remediation method for contaminated soil, characterized in that the carrier substance carrying soil pollutant degrading bacteria is biodegradable.

(I) An on-site remediation method for contaminated soil, wherein the soil pollutant-degrading bacterium is a microorganism having at least one of EDTA decomposing ability, phenol decomposing ability and surfactant decomposing ability. (J) On-site of contaminated soil, wherein the packed bed is a mixed packed bed filled with a carrier carrying a soil pollutant decomposing bacterium and a carrier carrying a nutrient for the decomposing bacterium so that the nutrient can be released slowly. How to repair.

2. A hollow tubular body placed in contaminated soil is provided with a packed bed filled with a carrier carrying microorganisms capable of degrading soil pollutants, and the soil extracted in contact with the contaminated soil is provided below the packed bed portion of the tubular body. A suction hole for taking underground water containing a pollutant into the tubular body and an air supply port for feeding air into the packed bed are provided, and the pollutant is passed through the packed bed above the packed bed portion of the tubular body. An on-site remediation device for contaminated soil, comprising an outlet for discharging underground water decomposed and removed and air flowing through a packed layer to the outside of the tubular body.

The following (k) to (p) modes can be mentioned as particularly preferable modes of the on-site repairing means for the contaminated soil described above. (K) An on-site remediation device for contaminated soil, which can be moved by car and can be relocated between contaminated areas. (L) An on-site remediation device for contaminated soil, wherein the packed bed portion is a detachable cassette type from a tubular body and can be exchanged as needed.

(M) An on-site remediation device for contaminated soil, characterized in that a reservoir for underground water taken in through a suction hole is provided at the bottom of the tubular body. (N) An on-site repair apparatus for contaminated soil, wherein the packed layer is composed of a plurality of sub-packed layers filled with a carrier carrying different types of soil contaminant degrading bacteria. (O) An on-site repair apparatus for contaminated soil, characterized in that a supply pipe for supplying an aqueous solution containing a nutrient for soil pollutant-decomposing bacteria is provided below the packed bed portion of the tubular body. (P) An underground water suction mechanism is provided above the packed bed of the tubular body so that the underground water taken into the tubular body from below the packed bed of the tubular body can be sucked up into the packed bed, and within the packed bed. An on-site remediation device for contaminated soil, which can be retained.

The soil remediation method and the apparatus therefor of the present invention are characterized in that groundwater containing pollutants in contact with contaminated soil is taken into the tubular body by diffusion in the soil to decompose the soil pollutants in the tubular body. The structure is simple and easy to operate, in which the carrier supporting the bacteria is filled and the packed bed activated by aeration air is passed through and discharged from the upper part of the packed bed to the outside of the tubular body. With this method and device, efficient soil purification can be achieved, secondary environmental pollution due to microorganisms can be suppressed, pumping of groundwater, excavation and movement of soil are not required, and the device and operation can be simplified. Due to its simplicity, it has the performance feature that it can be moved between contaminated areas if necessary. Hereinafter, the present invention will be described in more detail.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION First, the outline of an on-site contaminated soil restoration method and apparatus of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing an arrangement state in which an apparatus used in the on-site contaminated soil restoration method of the present invention is installed in contaminated soil.

In FIG. 1, the on-site contaminated soil remediation device is composed of a tubular body 1 and an air supply pipe 15 for supplying air A. A main part of the tubular body 1 is occupied by a packed bed 14, The layer 14 is filled with a carrier 11 carrying contaminant decomposing bacteria. A plurality of suction holes 13 for taking in the underground water W contained in the contaminated soil 4 are usually provided below the packed bed 14, and the packed bed 14 is provided above the packed bed 14.
While moving upward, the discharge port 18 that discharges underground water W that has undergone decomposition and removal of soil pollutants to the outside of the device, and the packed layer that is taken from the air supply pipe 15 into the tubular body through the air supply port. 1
There is provided an exhaust port A'for returning the air 12 that has passed through 4 to the atmosphere by an exhaust fan (not shown).

FIG. 2 is a schematic sectional view showing an apparatus of another embodiment used in the method for repairing on-site contaminated soil according to the present invention.
Similarly, it shows the arrangement state installed in the contaminated soil. Figure 1
2 and FIG. 2, common parts are given the same member numbers. FIG. 2 shows that a liquid supply pipe 16 for supplying an aqueous solution F containing a nutrient to be given to the pollutant degrading bacteria is provided, and that the aqueous solution F is taken into the tubular body 14 from the lower part of the packed bed, The apparatus is the same as that of FIG. 1 except that the packed bed is filled with water up to 17.

FIG. 3 is a schematic sectional view showing an apparatus of still another embodiment used in the method for repairing on-site contaminated soil according to the present invention, and shows the arrangement state installed in contaminated soil like FIG. In FIG. 3, parts common to those in FIGS. 1 and 2 are given the same member numbers. In FIG. 3, a pump P for sucking underground water is provided in the upper part (portion above the packed bed) of the tubular body, and at the same time, the air supply pipe 15, the liquid supply pipe 16 and the discharge port 18 are each provided with an opening / closing valve C1. , C2 and C3 are provided so that the air supply, the liquid supply, or the discharge can be temporarily stopped if necessary. The configuration of FIG. 3 other than the above is the same as that of FIG.

Next, the on-site repair method for contaminated soil according to the present invention will be described with reference to FIGS. 1 and 2. This remediation device is located in the soil contamination area and has an air intake A
And the air outlet A'and the supply pipe 1 for the aqueous solution F of the embodiment shown in FIG.
Other than the upper end portion of 6 is preferably buried in the ground. Further, the exhaust port 18 for returning the underground water, which has been subjected to the pollutant decomposition treatment, to the ground may be in the ground or on the surface of the ground, and the exhaust port A for returning the air penetrating the packed bed to the atmosphere. '
However, it is preferable from the viewpoint of management that the discharge port 18 is located on the ground surface.

The underground water W contained in the contaminated soil 4 contains pollutants, and is diffused and moved in the ground by the suction action of the exhaust fan (not shown) of the tubular body 1, and the suction port 1
It is taken into the upper body through 3 The underground water W taken in is moved upward in the packed bed 14 by the suction action together with the air A taken in by the air supply pipe 15, and is decomposed by the pollutant-decomposing bacteria carried on the simple substance 11 to contaminate it. Excluded. The pollutant-decomposing bacteria are usually aerobic bacteria, which are activated by the air A taken in from the air pipe, and also have an action of enhancing the effect of removing contaminants. The purified underground water is discharged from the discharge port 18.

The operation of the soil restoration device of FIG. 3 will be described. In the apparatus of FIG. 3, by operating the suction pump P, the suction action of taking the underground water into the tubular body 1 through the suction hole 13 is enhanced, and the underground water is smoothly supplied to the packed bed. Further, when the on-off valves C1, C2 and C3 are closed and the suction pump P is operated, the suction action of underground water is further enhanced. After sufficient underground water is supplied to the packed bed, the pump P can be stopped to allow the underground water to stay in the packed bed. For the retention in the packed bed, it is possible to replace the underground water in the packed bed at one time, or by moving the underground water to the upper part by a fixed amount, it is possible to slightly move the underground water in the packed bed. It can also be moved to the top one by one. By these operations, the underground water is kept in the packed bed and the microorganism carrier 11
It is possible to improve the decomposition rate of the pollutants by contacting the substrate with the target for a necessary and sufficient time, and the object of the present invention can be achieved particularly effectively by the embodiment using the apparatus of FIG.

Here, "underground water" refers to the water existing in the soil, and although it may be groundwater contained in the aquifer, the retention stored in the non-aquifer. It may be water. In the present invention, it is preferable that the suction port 13 is accumulated water that is located above the aquifer of groundwater and is stored in the non-aquifer. The reason is that the purpose of the present invention is not the purification of groundwater but the restoration of pollution of the soil itself,
If the contaminated soil is repaired, the diffusion of pollutants from the soil to the groundwater will cease, and groundwater pollution will be eliminated by itself. It is cheaper and more effective to take countermeasures in pollutant soils that are heavily contaminated but are locally limited, rather than taking measures against groundwater in which the pollution has diffused. It is preferable to perform the repairing operation with the stored water, that is, the accumulated water in the upper layer.

Further, in FIGS. 1 to 3, the air 12 sent into the tubular body from the air supply pipe is shown by bubbles.
It is a bubble as a matter of convenience, and the inside of the tubular body is not necessarily limited to the case where bubbles are generated by being filled with underground water, and the intake of underground water from the suction hole 13 to the upper zone of the tube. However, in some cases, the inside of the tubular body 1 is in the vapor phase, and thus the taken-in air is not a bubble but an air stream. In a particularly preferred embodiment of the present invention, the underground water taken into the tubular body is stored at the bottom of the tubular body and moves upward while moistening the packed bed with the airflow. There is little fluctuation in moisture in the packed bed, and the advantages of degrading bacteria are stable.

In order to stably supply the underground water W,
It is also preferable that the contaminated soil 4 around which the tubular body 1 is provided is watered or poured to recharge the underground water.
In that sense, the purified underground water discharged from the discharge port 18 is preferably returned to the contaminated soil 4 around the tubular body 1. In that case, the groundwater in contact with the contaminated soil is generally poor in nutrients.Therefore, in order to enhance the activity of the pollutant-decomposing bacteria, the water sprinkled or poured into the water should have nutrients of the pollutant-decomposing bacteria. It is also preferable to use an aqueous solution containing a substance. The concentration of nutrients should be adjusted to maximize the action of pollutant-degrading bacteria. If the concentration of nutrients is too high, the contaminant-degrading bacteria grow well, but the degrading action of the pollutants decreases, and if the concentration is too low, the degrading bacteria grow poorly and the degrading action of pollutants decreases.

As a method of supplying nutrients suitable for ensuring the activity of such pollutant-decomposing bacteria, it is also effective to include the nutrients in a packed bed in a state where they can be gradually released. The mixing ratio of the carrier carrying pollutant-degrading bacteria and the sustained-release product of nutrients in the packed bed is selected so that the feeding rate of the nutrients is the optimum rate for maintaining the activity of the pollutant-degrading bacteria. . A comprehensive method is mentioned as a suitable means for sustained-release of nutrients. The details will be described later.

The packed bed is composed of two or more sub-packed layers of the carrier carrying contaminant-degrading bacteria, for reasons such as easy replacement and the need to repair two or more soil contaminations. May be. The former is for ensuring portability, and the latter is for repairing soil contaminated with both a surfactant and an aminopolycarboxylic acid type chelating agent. Further, in some cases, the packed bed may be a packed bed in which two or more kinds of contaminant-degrading bacteria-supporting carriers are mixed and packed, instead of the above-described multi-composite structure. The carrier carrying pollutants degrading bacteria constituting the packed bed is more preferable from the viewpoint of environmental improvement, which is the basic object of the present invention, as long as it is a biodegradable carrier, it does not add a new environmental load due to disposal. .

[Microorganism capable of degrading soil pollutants] In the present invention, as the microorganism capable of degrading soil pollutants to be held on the carrier, a microorganism corresponding to the type of soil contamination can be used, and biodegradability against pollutants can be increased. As long as you have
Although not particularly limited, in addition to bacteria belonging to the genus Pseudomonas that decompose aromatic hydrocarbon compounds (eg, phenols) organic solvents (eg, toluene, trichlorethylene, etc.), organic chlorine compounds (eg, dioxins, PCBs, etc.) , Methylosinus, Methylomonas, which are known to have the ability to decompose various harmful substances including the above,
Methylobacterium, Hethylocystis, Alcaligenes, Myco
bacterium, Nitrosomonas, Xanthomonas, Spirillum, V
ibrio, Bacterium, Achromobacter, Acinetobacter, Fl
avobacterium, Chromobacterium, Desulfovibrio, Desu
lfotomaculum, Micrococcus, Sarcina, Bacillus, Stre
ptomyces, Nocardia, Corynebacterium, Pseudobacteri
um, Arthrobacter, Brevibacterium, Saccharomyces, L
A microorganism belonging to each genus of actobacillus can be used.

Further, metal chelating agents such as EDTA and heavy metal chelates in which they are complex-bonded with heavy metals are also soil pollutants for heavy metals, but microorganisms capable of degrading these are bacteria belonging to the genus Bacillus. As Bacillus editabidus
, Bacillus subtilis, Bacillus megaterium, Bacillus sphaericus, and the like. These are, for example, Bacillus edtabidus-1 (Microbiology Research Institute No. 13449), Bacillus subtilis NRIC 0068.
, B. megaterium NRIC 1009, B. sphaericus NRIC 101
It can be easily obtained as 3.

Other microorganisms having the ability to decompose EDTA include Pseudomonas spp., Alcaligenes spp., Applid and Environmental Mic described in JP-A-58-43782.
Applid and Environmental Microb, a species of the genus Agrobacterium described in robiology vol.56, p.3346-3353 (1990).
Gram- described in Biology Vol.58, No.2, Feb.1992, p.671-676
An example is negative isolate. Of these, for example, Pseudomonas ed
itabidus) is available as Pseudomonas editabidus-1 (Microtechnological Research Institute, No. 13634).

Further microorganisms having the ability to decompose EDTA include Bacillus editabidus and Mesophilobacter editabidus, which are marine fungi. This organic aminocarboxylic acid degrading bacterium Bacillus
Editor Vidas (Bacilluseditabidus) is Bacilled
itabidus-M1 (Microtechnology Research Institute, No. 14868) and Bac
illus editabidus-M2
No.) belongs to. In addition, organic aminocarboxylic acid degrading bacteria Mesophyllobacter editor Vidas (Mesophilob
acter editabidus) is Mesophilobacter editabidus
-M3 (Ministry of Industrial Science, Microbiology No. 14870) belongs to.

Examples of microorganisms that decompose phenols and cresol compounds include Pseudomonas putida cb-173 (atcc described in US Pat. Nos. 4,352,886 and 4,556,638).
31800). The contaminated soils to which these microorganisms are applied include, for example, phenol resin factory wastewater, cresol resin factory wastewater, factory wastewater of polyphenols obtained from bisphenol A, plate-making processes and photoresist formation for handling those phenolic resins. It is soil contaminated with wastewater containing phenols discharged from the process. Examples of the surfactant-degrading bacteria include USP4
Pseudomonas fluorescens 3p (atcc31483) described in No. 274954 can be mentioned. Contaminated soils to which these microorganisms are applied are, for example, anionic,
Wastewater containing nonionic or cationic surfactant,
Particularly, it is soil contaminated with a so-called hard surfactant-containing wastewater containing a surfactant having a poor biodegradability, especially a wastewater containing a sulfonic acid group-containing surfactant.

As the microorganisms to be administered, in addition to those already isolated, those newly screened from soil or the like according to the purpose can be used, and a mixed system of a plurality of strains may be used. In the case of those separated by screening, they may be unidentified.

[Contaminant-degrading bacterium-supporting carrier] A carrier and a supporting method for supporting a microorganism to be packed in the packed bed will be described. As a carrier for supporting microorganisms, any known material can be used as long as it can support microorganisms and can be administered to contaminated soil, but from the viewpoint of effectively supporting useful microorganisms, microorganisms are strongly adsorbed on the surface of the carrier. It is preferable that the microparticles are porous, the retention can be enhanced by invading the micropores, and the microparticles are aggregated to substantially increase the adsorption or occlusion surface. Specifically, polysaccharides such as cellulose, dextran and agarose; inactivated proteins such as collagen, gelatin and albumin; synthetic polymer compounds such as ion exchange resins and polyvinyl chloride; inorganic substances such as ceramics and porous glass; Examples include natural carbohydrates such as agar, alginic acid, and carrageenan; and polymer compounds used as comprehensive carriers such as cellulose acetate, polyacrylamide, polyvinyl alcohol, epoxy resin, photocurable resin, polyester, polystyrene, and polyurethane.

Further, lignin, starch, chitin, chitosan, filter paper, wood chips and the like can also be used. Carriers made of these materials have a relatively gentle retention of microorganisms, are easy to remove proliferated microorganisms, are inexpensive, and in some cases, serve as nutrients of the administered microorganisms themselves, particularly, nutrients in sustained release form. It is preferable because it can

In the present invention, the packed bed is constituted by supporting, that is, immobilizing a microorganism having a soil pollutant decomposing ability on a carrier. As a method for immobilizing microorganisms, any type and format can be used as long as it is a method in which biodegradable bacteria are immobilized so as not to flow out from the carrier. Specific immobilization methods include, for example, an adherent biofilm method using a carrier to which a microorganism adheres to form a biofilm, a supported culture method in which a carrier and a medium are mixed to culture a microorganism, and a pore space under reduced pressure. A method of encapsulating microorganisms inside, a method of entrapping entrapment of microorganisms in a gel, and the like can be used. Among them, the adherent biofilm method and the entrapping immobilization method are preferable, and the entrapping immobilization method is particularly excellent.

The feature of the adherent microbial membrane method is that the concentration of microorganisms can be increased and the treatment efficiency can be improved. In addition, bacteria with a slow growth rate that would normally be washed out of the system can be retained in the system. Another feature is that microorganisms can be kept in a stable habitat.

The feature of the entrapping immobilization method is that the bacterial cells can be maintained at a high concentration, so that the treatment efficiency can be improved and the bacteria that grow slowly can be immobilized. Further, it has a wide resistance to changes in conditions such as pH and temperature, and can withstand a high load condition. As the entrapping immobilization method, acrylamide method, agar-acrylamide method, PVA-boric acid method, PVA-freezing method, photocurable resin method, acrylic synthetic polymer resin method, sodium polyacrylate method, sodium alginate method, K-
The carrageenan method or the like can be used as long as the microorganisms can be confined, the activity of the microorganisms can be maintained in the soil, and the physical strength is large and the material can be used for a long time.

As a typical example of the entrapping immobilization method, a method for preparing a microorganism-immobilized gel in the case of the acrylamide method will be described. The immobilized gel suspends an acrylamide monomer solution containing a cross-linking agent (for example, N, N′-methylenebisacrylamide) and bacteria (concentrated bacterial cells of MLSS of about 20,000 ppm), and a polymerization accelerator (for example, N, N,
N ′, N′-tetramethylethylenediamine), a polymerization initiator (for example, potassium persulfate) are added, and the mixture is put into a molded form such as a vinyl chloride tube having a diameter of 3 mm and polymerized at 20 ° C.,
After completion of the polymerization, it is obtained by extruding from a molded form and cutting it into a certain length. Since the pores on the surface of the immobilized gel are smaller than bacteria, the entrapped and immobilized bacteria are unlikely to leak, and they grow inside and self-decompose. Only the contaminants in the soil enter the gel through the pores and are treated by the bacteria inside.

For more specific methods of these immobilization methods, “Wastewater Treatment by Microbial Immobilization Method” edited by Ryuichi Sudo (Industrial Water Research Committee), Yuhei Inamori, “Higher and more efficient wastewater treatment by biofilm method” Trend ”, Water Pollution Research, vol.13, N
o.9,1990, p.563-574, Yuhei Inamori's "Trends, Challenges and Prospects of Advanced Water Treatment Technology Development", Water and Wastewater, vol.34, No.10,1
992, P.829-835 etc.

Further, it is preferable to form the carrier itself from a biodegradable material, since there is no problem in terms of environmental protection regarding disposal of the carrier when it is no longer needed when renewing the carrier. If such a biodegradable carrier is used, the administered microorganisms released into the soil due to the disappearance of the carrier even if they are discarded in the contaminated soil region, for example, compete with the dominant indigenous microorganisms in the soil and prey on the protozoa. Or, it is exterminated by being placed in a harsh environment for growth and the number gradually decreases,
It will eventually disappear, and as a result the ecosystem in the soil can be restored.

Preferred biodegradable carriers include cellulosic carriers such as Viscopearl (manufactured by Rengo Co.) and chitin chito acid, microbial polyester, polylactic acid, polylactone, polyglyoxylic acid, polymalic acid, starch-added plastic, polycaprolactone. , A (hydroxybutyric acid)-(hydroxyvaleric acid) copolymer, a polymeric carrier composed of alginic acid / polyethylene glycol, for example, KP Pearl (manufactured by Kansai Paint Co., Ltd.), a polyamino acid, a biodegradable polysaccharide polymer, etc. A carrier using a polymer material is preferable, and among them, a cellulose-based carrier, for example, Viscopearl (manufactured by Rengo Co., Ltd.) and chitin chito acid are more preferable, and examples thereof include Chitopearl (manufactured by Fuji Spinning Co., Ltd.).

The preferred carrier shape is substantially spherical,
It is preferably a substantially cubic shape, a substantially rectangular parallelepiped shape, a cylindrical shape or a tube shape, and among them, a substantially spherical shape that is easy to manufacture or a substantially rectangular parallelepiped shape that can increase the specific area is preferable.
As a method for producing the carrier, any known method can be used. For example, microorganisms and carrier substances (or their precursors)
A method of making a dispersion of microorganism-supporting carrier particles by dropping and suspending the mixed solution of the above in an insoluble liquid and solidifying the droplets in the liquid, a mixed solution of the microorganism and the carrier substance (or its precursor) at low temperature. After solidifying by adding a gelling agent or a solidifying agent, the solidified body is cut into an appropriate size and pulverized to obtain particles carrying microorganisms, microorganisms and carrier substances (or precursors thereof). A method for producing a filamentous solidified substance of a microorganism-supporting carrier by injecting the mixed solution of 1. into an insoluble liquid through an extrusion nozzle and solidifying in the liquid, and appropriately cutting this to form cylindrical particles, and at this time The method of obtaining an annular (tube-shaped) microorganism-supporting carrier particle by using the extrusion molding die as an annular shape can be mentioned.

The size of the carrier particles may be any size as long as the filling degree that allows underground water to move at an appropriate speed is secured,
Outer diameter 0.1-70 mm, preferably 0.5-40 mm
It is more preferably 1 to 10 mm, and the uniform passability of the packed bed is restricted. Therefore, a preferred size is selected according to the application target.

The water content of the carrier is 1 to 99% by mass, preferably 5 to 90% by mass, more preferably 10 to 85% by mass.
Is. If the water content is too low, the survival of microorganisms will be hindered, and if it is too high, the physical strength of the carrier will be reduced, and this will hinder handling.

The temperature of the packed bed needs to be a temperature suitable for the activity of microorganisms, and is 3 to 50 ° C., preferably 10 to 10.
It is 45 ° C, more preferably 18-40 ° C.

When the biodegradable carrier is used, the rate of decomposition of the carrier itself can be controlled by selecting the material and properties thereof. For example, in consideration of the material, the pore diameter of the pores, the morphology of the pores, The shape and size of the carrier are appropriately selected. In the present invention, since the nutrients need to be supplied in a sustained-release manner, the biodegradable carrier needs to be decomposed at a slow rate within the range where sustained-release conditions are maintained. When selecting these requirements, the factors that affect the decomposition rate should be taken into consideration: the type, amount and decomposition activity of the microorganisms that decompose the carrier (indigenous microorganisms or administered microorganisms in the soil), or the treated soil. The volume can be mentioned, and it is advisable to confirm in advance by field experiments how long the pollutant decomposes and how long the carrier decomposes, and then design the carrier.

[Supply of Microbial Nutrients] In many cases, the contaminated soil is oligotrophic, and the groundwater is sufficient for the microorganisms contained in the packed bed to survive in the carrier and sufficiently maintain the pollutant decomposing ability. It does not contain enough nutrients. In such a case, it is necessary to supply nutrients to the microorganisms in the packed bed, and the water to be sprayed or injected into the contaminated soil around the tubular body may contain nutrients, and as shown in FIG. As in the embodiment, the nutrient-containing water may be supplied to the lower part of the upper body of the pipe by piping. It is necessary to carefully control the supply amount of nutrients. When nutrients are excessive, the ability of microorganisms to decompose pollutants deteriorates and the intended function is not exerted. When the nutrients are too small, the function of microorganisms declines. Therefore,
It is preferable to adjust the supply of nutrients so that the activity of the soil-remediating microorganisms can be maintained and the efficiency of degrading pollutants can be suppressed at a low level and low fluctuation.

As the nutrients, those containing carbon, nitrogen and phosphorus are preferable, and examples thereof include a culture solution suitable for the growth of microorganisms. As the culture solution, for example, a mixture of broth, yeast extract, malt extract, bactopeptone, glucose, inorganic salts, minerals and the like at an appropriate ratio is often used, but a suitable mixture depending on the type of microorganism. You can choose a ratio. As the nutrient used in the present invention, any nutrient can be used as long as it appropriately contains organic and inorganic nutrients in addition to the above culture solution.
For example, any microorganism collected from the natural world or added with culture may be dried and ground, and the ground fine powder may be used as a nutrient. Furthermore, a coexisting microorganism that activates a degrading bacterium can also be used. The coexisting microorganisms themselves serve as nutrients for the degrading bacteria, and substances secreted by the microorganisms include components that activate the degrading bacteria. Preferred microorganisms include a mixture of microorganisms commercially available as so-called EM bacteria.

As a special embodiment of the present invention, the nutrients can be contained in the packed bed in a sustained release state. When adopting the method of incorporating sustained-release nutrients into the packed bed, the concentration of nutrients released from the carrier is sufficient for survival and activity maintenance of the microorganism, but low concentration that does not deteriorate the pollutant decomposition function. Any method may be used as long as it is a method of maintaining the administration level at which the concentration fluctuation is small. As a specific sustained release form, for example, a method of adsorbing a nutrient on the surface of a carrier material in which particles are dispersed so as to satisfy the sustained release condition, or more effectively, a surface of the carrier material so that the nutrient is satisfied Chemisorption, nutrients mixed and granulated with a support material under conditions that satisfy sustained release, nutrients stored in a support material under conditions that satisfy sustained release, and nutrients sustained release Depending on the conditions, a supporting substance, for example, a trapping method in which the substance is confined inside the gel can be used. Among these, the comprehensive method is particularly excellent. The “comprehensive method” in this specification is
It is used in accordance with the definition of "Comprehensive Law" described in "Scientific Term Dictionary" edited by the Ministry of Education, Culture, Sports, Science and Technology and "Chemical Dictionary of Standard Chemistry" edited by the Chemical Society of Japan. "Comprehensive method" is a bioimmobilization method in which a biocatalyst such as cells is incorporated into a polymer gel or encapsulated in a membrane or the like by microencapsulation. For details, see an appropriate textbook, for example, The Chemical Society of Japan. Chapter, Chemistry Handbook, Applied Chemistry II,
It is described on page 1197.

The inclusion method is characterized in that the nutrient-supporting substance can encapsulate the nutrient in a high concentration and the release concentration thereof can be controlled to a sufficiently low concentration. Living conditions are secured and the release can be stably maintained over a long period of time, which means that biological management is easy. The entrapping method is the same as the entrapping immobilization method for microorganisms, which is effective for immobilizing the microorganisms in the reaction system, in principle, and the embodiment substantially complies with the method. As the supporting material for the entrapping method for encapsulating nutrients, an acrylamide method, an agar-acrylamide method, PV
A-boric acid method, PVA-freezing method, photocurable resin method, acrylic synthetic polymer resin method, sodium polyacrylate method, sodium alginate method, K-carrageenan method, etc. can be included in nutrition, There is no limitation on the kind as long as it releases the nutrients to the extent that the activity of the microorganism can be maintained in the treatment tank (reactor) and effectively and stably releases the nutrients for a long time.

As a typical example of the comprehensive method, a method for preparing a nutrient gel in the case of the acrylamide method will be described. The nutrient-encapsulated gel suspends a acrylamide monomer solution containing a cross-linking agent (for example, N, N′-methylenebisacrylamide) and a nutrient (for example, about 20,000 ppm), and a polymerization accelerator (for example, N, N). , N ', N'-tetramethylethylenediamine) and a polymerization initiator (for example, potassium persulfate) are added, and the mixture is put into a molded form such as a tube made of vinyl chloride having a diameter of 1 to 3 mm and polymerized at 20 ° C to complete the polymerization. After that, it is obtained by extruding from a molded form, cutting it to a certain length, or crushing. The release of nutrients is controlled by adjusting the particle size of the gelled product and the concentration of inclusion in the gel.

More specifically, these comprehensive methods are described in “High-efficiency / efficiency of wastewater treatment by biofilm method” by Ryuichi Sudo (Industrial Water Research Committee), “Wastewater treatment by microorganism immobilization method” described above, by Yuhei Inamori. Trend ”, Water Pollution Research, vol.13, N
o.9,1990, p.563-574, Yuhei Inamori's "Trends, Challenges and Prospects of Advanced Water Treatment Technology Development", Water and Wastewater, vol.34, No.10,1
992, P.829-835, etc. can be carried out in accordance with the comprehensive immobilization method for microorganisms.

As a method of supporting a nutrient in a sustained release form different from the entrapping method, it is also possible to incorporate the nutrient into a gel entrapping carrier such as carrageenan or alginic acid to exert a sustained release effect. As the method, a method including a step of 1) mixing a solution containing a nutrient with a solution containing a gelling material (carrageenan, alginic acid, etc.), and 2) controlling the shape of the carrier with gelation to obtain a carrier is used. You can also

As another method for supporting a nutrient in a sustained-release form, a natural polymer having a slow biodegradation rate can be used as a supporting substance as a nutrient. For example, a lignocellulosic or chitin-based natural polymer may be pulverized to about 10 μm to 3 mm so as to obtain an appropriate sustained release rate and then administered.

[0059]

The present invention will be described in more detail below with reference to examples, but these examples do not limit the scope of the present invention. In addition, the "bacteria" in the examples are "bacteria" classified into the "microorganisms" described in the present specification, and may be substantially synonymous.

Example 1 [Preparation of carrier for supporting contaminant-decomposing bacteria] EDTA-degrading bacterium Bacillus editorvidus (Bacill) described in JP-A-6-261771
Useditabidus-1, 1 Platinum loop of Micro Incorporated Research Institute No. 13449), 0.5% polypeptone (Far East Pharmaceutical Industry), 0.1% yeast extract (manufactured by Wako Pure Chemical Industries, Ltd.) and NH4Fe (III) ) EDTA
(Manufactured by Wako Pure Chemical Industries, Ltd.) 1/30 M phosphate buffer (pH 5.8) containing 0.01% (both by mass) was cultivated for 1 day at 37 ° C. in 200 ml of a basic medium, A culture containing this cell at a high concentration was obtained. The culture was separated into wet bacterial cells of this strain and the culture supernatant by centrifugation. Washing with purified water whose purity was regulated by the Japanese Pharmacopoeia and collection of wet cells by centrifugation were repeated 3 times to obtain washed wet cells from which the culture supernatant was sufficiently removed. This was redispersed in 80 ml of purified water, and 10 g of modified Viscopearl AZ4200-cc (manufactured by Rengo Co., Ltd.) was added to the redispersion liquid as a microorganism retention carrier.
After stirring and shaking for a period of time, unsupported cells were removed by filtration and washing. The cell-supported body obtained here is designated as A.

On the other hand, a microbial cell carrier prepared by the same procedure as above except that the above medium was used in place of the purified water in the above procedure was obtained. The obtained microbial cell carrier is designated as microbial cell carrier B. This bacterial cell support B contains a nutrient medium component.

[Preparation of Nutrient Sustained Release Carrier] Agar was added to 150 ml of the above basic medium to a concentration of 3%, and the mixture was heated and dissolved, and the cooled agar gel was freeze-dried, and then the mass average particle diameter was adjusted to 10 μm with a ball mill. Crushed and nutrient sustained-release carrier
Got D.

[Preparation of Model Contaminated Soil] Soil collected from the green zone in Fuji Photo Film Co., Ltd. Ashigara Factory was left to dry at room temperature for 1 week, then 1000 kg was added to a rectangular parallelepiped storage tank and spread evenly at 30 cm. After spraying 750 liters of a 1% solution of NH4Fe (III) / EDTA (manufactured by Wako Pure Chemical Industries, Ltd.), they were mixed well. This prepared contaminated soil was left to dry at room temperature for 1 week. This is called EDTA contaminated soil. Inner method bottom is 70c
It is a rectangular parallelepiped with a size of mx 50 cm and a height of 40 cm, and a drain hole on the bottom surface and an overflow discharge hole for maintaining the liquid level at a height of 5 cm from the bottom surface.
The above-mentioned EDTA-contaminated soil was filled so as to be 5 cm, and water was sprayed so that 1 cm of water was accumulated on the bottom surface to obtain wet soil contaminated with EDTA.

[Model Test Device for Repairing Contaminated Soil] A model test device for repairing contaminated soil of the type shown in FIG. 1 was used.
A rigid PVC tube having an inner diameter of about 40 mm and a length of 30 cm was used as a model body of the tubular body described above in this specification. One end of the PVC pipe was sealed, and a hole with a diameter of 3 mm was pierced as a suction hole over the length of 5 cm from the end on the sealed side at a rate of 1 per 5 mm square, and one of the suction holes was connected to the air supply pipe. As an air supply port for sending air, a solenoid valve was installed at the tip of the air supply port to shut off the air supply when pumping underground water.
20c from 5cm to 25cm from the closed end of the PVC pipe
m was used as a packed bed for packing the carrier carrying contaminant-degrading bacteria and the like. Furthermore, a suction device and a separation / exhaust device for the sucked water / air mixture are installed at the upper end of the PVC pipe, and the water and air that have been sucked up from the lower part of the PVC pipe and passed through the packed bed are separated, and the water returns to the contaminated soil, Air was allowed to vent into the laboratory environment. The suction rate of underground water, which was intermittently performed every 5 minutes for 1 minute, was 10 ml / min, and air was fed at 20 ml / sec. Air supply was stopped during suction. A PVC pipe was inserted into the model-contaminated soil so that the upper end portion of 3 cm appeared on the soil surface almost vertically, to obtain a model test device.

[Soil Restoration Test] Test 1: The microbial cell carrier A was filled in the packed bed. During the test, water was sprinkled on the contaminated soil around the tubular body of the PVC pipe at a rate of 100 ml / h. On the other hand, the suction device was operated to infiltrate the contaminated soil, and the diffused water (model underground water) was introduced from the suction hole into the PVC pipe. The taken-in water was sucked up into the packed bed together with air, the water was returned to the contaminated soil at the upper part of the packed bed (included in the amount of water sprayed on the soil), and the air was discharged into the environment. The operation of sucking underground water from the lower part, moving the packed bed, discharging from the upper part, and reflux was continuously performed for 20 days.

Test 2: In Test 1, the same apparatus and operation as in Test 1 were used except that the packed bed was filled with the same amount of the bacterial cell carrier B instead of being packed with the bacterial cell carrier A. Was done. Test 3: In Test 1, instead of packing only the bacterial cell carrier A in the packed bed, the same amount of the bacterial cell carrier A and the nutrient sustained-release carrier D were mixed at a mass ratio of 9: 1. Test 3 was conducted using the same equipment and operation as in Test 1 except that the filling was performed by filling. Test 4: In Test 1, instead of sprinkling water on the contaminated soil, a culture solution having the same composition as the basal medium used for preparing the pollutant-degrading bacteria was diluted 10 times to obtain a nutrient solution in the same amount. Sprayed. Test 4 was performed using the same apparatus and operation as in Test 1 except for this change. Test 5: In Test 2, the same apparatus and operation as Test 2 were used except that the depth of water on the bottom of the model contaminated soil was changed from 10 cm to 10 cm so that the bottom of the PVC pipe was immersed in the stored water.
Was done. Test 0: In Test 1, the packed bed before loading the degrading bacteria of modified Viscopearl AZ4200-cc (manufactured by Rengo Co., Ltd.), which was used as a carrier for loading instead of loading the bacterial cell carrier A A comparative test was conducted using the same apparatus and operation as in Test 1, except that the same amount was used. This is designated as test 0.

On the 5th, 10th and 20th days after the start of the test, 1 g of model underground water flowing in from the lower part of each PVC pipe and 1 g of discharge water from the upper part were collected, and the amount of dissolved EDTA was determined by ion chromatography. went. The test results are shown in Table 1.

[0068]

[Table 1]

In the contaminated soil restoration test according to the method of the present invention shown in Table 1, decomposition and reduction of EDTA in the soil were observed even in Test 1 in which nutrients were not supplied, but in Test 2, nutrients were also included. By using the cell support B,
The decomposition reduction effect of EDTA is increasing. However, the effect diminishes over time, likely due to the consumption of nutrients, approaching that of Test 1. In addition, test 3
Show that the degradation and reduction rate of EDTA can be further increased by controlling the release rate of nutrients by mixing a nutrient-free carrier supporting degrading bacteria and a nutrient sustained-release agent D. Has been done. In Test 4, a carrier containing a degrading bacterium containing no nutrient was used, but the effect similar to that in Test 3 was obtained by including a low concentration of nutrient in ground water. In Test 5 using model groundwater, although the effect is lower than the case of using groundwater which is not groundwater, it is understood that the decomposition of pollutants is still progressing. In any case, it was shown that the methods of the present invention shown in Tests 1 to 5 can effectively remediate contaminated soil.

Example 2 In Example test 1, at the end of the one-day test, a culture solution having the same composition as the basal medium was introduced from a pipe 16 for supplying the nutrient-containing water F of the apparatus shown in FIG. Supplied to. The other operations were the same as those in Test 1.
The results show a degradation rate equal to the pollutant degradation rate that Test 1 showed 5 days after the start of the test, and
It was shown to be maintained in tests up to the day.

[0071]

The present invention is characterized in that the ground water contaminated by contacting the contaminated soil from the lower part of the packed bed containing soil pollutant decomposing bacteria is taken in, treated in the packed bed, and then discharged from the upper part. The on-site remediation method and means for remediating contaminated soil can easily purify and repair contaminated soil at the contaminated site without moving the contaminated soil from the contaminated site or pumping contaminated groundwater. In addition, support of bacterial cells,
Soil remediation ability can be maintained continuously for a long time by supplying nutrients directly or with sustained release, and the effect of the invention can be enhanced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a contaminated soil restoration device showing a typical embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a contaminated soil restoration device showing another embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of an example of a contaminated soil repairing apparatus showing still another embodiment of the present invention.

[Explanation of symbols]

1. Hollow tubular body 11. Carrier 12. Air taken into the tubular body 13. Suction hole 14. Packed bed 15. Air pipe 16 Liquid supply pipe 17. Liquid surface 18. Vent 4. Contaminated surface 41. Contaminated soil surface A Supply air into the tubular body Air discharged from A'tubular body C1, C2, C3 open / close valve F Nutrition supply pipe P suction pump W underground water

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4B029 AA02 AA21 BB01 CC05 CC10                       DA06 DG06                 4B065 AA99X AC20 CA56                 4D003 AA06 AB02 DA18 EA01 EA30                       FA04 FA06                 4D004 AA41 AB05 AB06 AC07 CA13                       CC03

Claims (2)

[Claims] 1. A soil extracted from a hollow tubular body placed in a contaminated soil with a packed bed filled with a carrier carrying microorganisms capable of degrading soil pollutants, and in contact with the contaminated soil from the lower part of the packed bed. Underground where pollutants are decomposed and removed by sending underground water containing pollutants and air into the packed bed to bring the underground water and the carrier into contact with each other to decompose the pollutants. A method for on-site restoration of contaminated soil, comprising discharging water from the upper part of the packed bed. 2. A hollow tubular body installed in contaminated soil,
A packed bed filled with a carrier carrying microorganisms capable of degrading soil pollutants is provided, and underground water containing soil pollutants extracted in contact with contaminated soil is provided under the packed bed portion of the tubular body. A suction hole for taking in the air and an air supply port for feeding air into the packed bed are provided, and the upper part of the packed bed portion of the tubular body is filled with underground water in which pollutants are decomposed and removed while flowing through the packed bed. An on-site repairing device for contaminated soil, comprising an outlet for discharging air flowing through a layer to the outside of the tubular body.