JP2005279399A - Cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polluted soil and ground water cleaning method constituted so that anaerobic microorganism living in soil or ground water are stably propagated and activated over long period of time (always) to optimize the original position cleaning treatment or control of pollution, a DC current is applied to a well of both electrodes in order to effectively put hydrogen ions caused by electrolysis to practical use in anaerobic microorganisms and a nutrient is injected in the periphery on an anode side by using the flow of hydrogen ions generated by the electrolysis of water to the anode side to simplify each cleaning treatment equipment or facilities. <P>SOLUTION: A nutrient tank 7, which stores a nutrient based on a 6C or higher carbon straight saturated monocarboxylic acid, and a vertical injection well, which injects the nutrient salt in the soil and ground water of the polluted part 1 and the diffusion region 2 thereof by an injection machine 8 to clean the polluted part 1 and the diffusion region 2, are provided to propagate and activate anaerobic microorganisms by the injected nutrient salt using electrolysis and an organochlorine compound of the polluted part 1 and the diffusion region 2 due to the organochlorine compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for activating anaerobic microorganisms using a bioremediation method, promoting the purification of soil and groundwater contaminated with organochlorine compounds, and purifying contaminated areas in situ in a short period of time. is there.

  Conventionally, soil and groundwater contamination purification equipment and methods include vacuum extraction method, pumped water aeration method, lime method, iron powder method, soil excavation replacement method, soil moisture cleaning method, insolubilization treatment method, gas / liquid mixing Various methods are used for the well method, the air sparging method, the bioremediation method, and the purification, and the methods that can purify the soil and groundwater in a short period of time are the iron powder method and the bioremediation method.

As a method for purifying a contaminated region by electrolysis at an in-situ position, a method is known in which contaminants and the like are moved and extracted in a vacuum (see, for example, Patent Document 1).
In-situ biological treatment is possible, fatty acid having 10 or more carbon atoms, alcohol having 12 or more carbon atoms, ester of linear saturated fatty acid having 14 or more carbon atoms and monohydric alcohol, carbon number Reduces nitrate nitrogen and volatile organic compounds in soil and groundwater by embedding esters of linear saturated fatty acids and polyhydric alcohols with 14 or more, esters of fatty acids with 16 or more carbon atoms and glycerin The method of making it known is known (for example, refer to Patent Document 2).
A denitrification accelerator mainly composed of a straight-chain saturated monocarboxylic acid having 6 or more carbon atoms and formed into particles having a particle diameter of 100 mm or less, and mainly used for wastewater treatment, and water using this denitrification accelerator A processing method is known (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 5-10083 JP 2002-370085 A JP 2000-334492 A

  However, in such conventional soil and groundwater contamination purification equipment and methods, the iron powder method is a method of excavating the soil and injecting zeroized iron powder, and the soil is purified in a short time by chemical reaction. However, at present, the method of excavating the contaminated area is mainly used, and therefore, it is not possible to purify the entire contaminated area within the optimum period, and the construction cost is high.

In addition, the method for purifying the contaminated area by electrolysis requires a considerable amount of time and a large amount of electric energy, which requires a running cost of electricity usage.
Furthermore, the bioremediation method is unstable because it depends on the environment and may not be purified within the optimum period.

  In addition, as for the purification treatment agent, conventional nutrient salts have high solubility in water (for example, polylactic acid ester), and in this case, the supplied nutrient salt (consumption amount) is rapidly eluted into the ground water (many) and therefore frequently. Additional (continuous) administration of nutrients was required. Also, fatty acids with 10 or more carbon atoms are slow to elute into groundwater, the optimal amount of elution in the contaminated part cannot be controlled, and the groundwater flow rate is difficult to handle in places where the groundwater flows 8 centimeters a day, It is limited to purification in places where groundwater flows several centimeters a year. Therefore, it is optimal to over-inject nutrients in places where the flow rate of groundwater is slow. As a result, problems such as confusion and complexity of the management system may occur. Accordingly, there has been a strong demand for a purifying agent having an optimum solubility, a stable treatment, and easy maintenance.

The present invention solves such a conventional problem, and anaerobic microorganisms that inhabit soil and groundwater are stably grown and activated for a long time (always), and the in-situ purification treatment of pollution / In order to optimize the management, hydrogen ions generated by electrolysis of water flow by flowing DC current through the wells of both electrodes to effectively utilize the hydrogen ions generated by electrolysis for anaerobic microorganisms. It is an object of the present invention to provide a method for purifying contaminated soil and groundwater by injecting nutrient salts around the anode side and simplifying the facilities and facilities for each purification treatment.
In other words, focusing on bioremediation methods and electrolysis purification methods that are relatively inexpensive to construct, ionize moisture and pollutants by electrolysis using direct current, and from moisture contained in soil and groundwater. By releasing hydrogen ions, anaerobic conditions are created, and by selecting and injecting specific nutrients around the anode side, the action of anaerobic microorganisms is activated and purification of in situ soil and groundwater contamination is achieved. It is to promote.
The nutrient salt is composed of a linear saturated monocarboxylic acid having 6 or more carbon atoms as a main component (caproic acid, pentanecarboxylic acid, butylacetic acid, enanthic acid, enanthylic acid, hexanecarboxylic acid, pentylacetic acid, caprylic acid, By injecting heptane carboxylic acid, hexyl acetic acid, pelargonic acid, octane carboxylic acid, heptyl acetic acid, etc.) into the contaminated area around the anode side to be electrolyzed, the entire contaminated area can be stably purified within the optimum period. Even if the construction period is long, a purification method using a maintenance-free construction method is provided.

  In order to achieve the above object, the method for purifying contaminated soil and groundwater according to the present invention provides a vertical well outside the contaminated part diffusion area, covers the inner circumference of the pipe of the vertical well with a semipermeable membrane, Has an anode and a cathode electrode member, and electrolyzes soil and groundwater, and a nutrient injection well for injecting a nutrient salt for microbial activity is provided around the well on the anode side. Salt makes the soil and groundwater in the diffusion zone of the contaminated area anaerobic, charges and ionizes the volatile organic compounds and moisture contained therein, and attracts them to the electrode, so that the mass transfer of the volatile organic compounds and moisture Is formed, and hydrogen ions are attracted to the anode side, and anaerobic microorganisms are easily grown and activated by the substrate component of the nutrient salt eluted from the nutrient salt injection well provided around the anode side. It is intended that the volatile organic compound contaminated portion and pollution diffusion zone with a method to decompose.

  In the present invention, after grasping the situation of the contaminated area by excavation or the like, the direction of groundwater flow in the contaminated area is confirmed, and the aquifer is excavated until it reaches the hardly permeable layer. An anode-side vertical well that allows current to flow outside is installed, and the inner periphery of the anode-side vertical well pipe is covered with a semi-permeable membrane so that anion substances do not permeate and contamination of the upstream side of groundwater A vertical well on the cathode side that conducts current is installed outside the partial diffusion area, and the inner periphery of the vertical well piping on the cathode side is covered with a semi-permeable membrane so that the cation material does not penetrate. An injection well for injecting nutrients mainly composed of straight-chain saturated monocarboxylic acids with 6 or more carbon atoms is provided around the vertical well on the anode side, and an observation well is placed around the vertical well on the cathode side In a configuration that allows the injected nutrients and The generated hydrogen ions grow and activate anaerobic microorganisms that are ecological under natural conditions (anaerobic environment with extremely low dissolved oxygen concentration DO value) in the soil and aquifer, that is, by volatile organic compounds The pollutant in the contaminated area can be biodegradably decomposed (purified by reductive dechlorination reaction, detoxified), and the entire contaminated area can be purified in an optimum construction period.

  According to the present invention, the aquifer is drilled until it reaches the poorly permeable layer, and electrode wells, injection wells, observation wells are provided as appropriate, by flowing current to the contaminated area and injecting specific nutrients, The contaminated area can be made anaerobic, and the contaminated area is heated by the generation of heat due to the flow of electric current, causing anaerobic microorganisms to grow and activate, and the pollutants volatile organic compounds chlorine and hydrogen Can be easily substituted and decomposed into low molecules. In this case, by specifying the nutrient salt as a main component of a straight-chain saturated monocarboxylic acid having 6 or more carbon atoms, the optimal purification treatment at this location is always performed stably. Can provide a method.

  According to the present invention, a vertical well is provided outside the contaminated part diffusion area according to the local pollution situation and various surrounding situations, the inner circumference of the pipe of the vertical well is covered with a semipermeable membrane, and the vertical well is provided. The well is provided with anode and cathode electrode members, and electrolyzes the soil and groundwater, and is provided with a nutrient salt injection well for injecting a nutrient salt for microbial activity around the well on the anode side. By using a method of decomposing volatile organic compounds contained in soil and groundwater of the contaminated part diffusion area with anaerobic microorganisms using nutrient salts, direct current flows from 30 amperes to 50 amperes of soil. By permeating, moisture moves, creating an anaerobic state, hydrogen ions gather on the anode side, and specific nutrients (linear saturated monocarbohydrate having 6 or more carbon atoms) around the vertical well on the anode side By selecting and injecting acid-based nutrient salts), it is possible to promote the purification process of the contaminated area of soil and groundwater in situ, and to stably purify the entire contaminated area within the optimum period, even for long-term Even if the construction period is long, it can be a maintenance-free and inexpensive purification method.

  That is, nutrient salts mainly composed of linear saturated monocarboxylic acid having 6 or more carbon atoms (for example, caproic acid, pentanecarboxylic acid, butylacetic acid, enanthic acid, enanthylic acid, hexanecarboxylic acid, pentylacetic acid, caprylic acid , Heptanecarboxylic acid, hexylacetic acid, pelargonic acid, octanecarboxylic acid, heptylacetic acid, etc.) have a sustained release effect that dissolves gradually in groundwater (does not become eutrophic chloride) Even in such a case, the injection and supply can always be stably performed. Therefore, the degradation of the volatile organic compound due to the activation and growth of the anaerobic microorganisms can be stably and optimized over a long period of time.

  In addition, according to the present invention, since the vertical injection well and the observation well are constantly observing and monitoring the effect of the purification treatment by injecting the nutrient salt, until the pollutant purification is completed, It is possible to maintain optimum processing conditions and cope with sudden changes in the contamination status.

  Hereinafter, each Example of the purification method of the contaminated soil and groundwater of this invention is described using drawing.

FIG. 1 is a schematic cross-sectional view showing an outline of a method for purifying contaminated soil and groundwater according to the present invention.
In FIG. 1, 1 indicates a contaminated part (contamination source) contaminated with an organic chlorine compound, and the diffusion region 2 of the contaminated (contaminated part 1) is a groundwater flow (the direction of the waterflow) of the aquifer 5 with the groundwater flow → It shows a region where the contamination (contaminated part 1) is diffused by infiltration / dissolution and the like, and shows a state where it reaches the soil 4 with the aquifer 5 as the center. In the following description, the contaminated part 1 and the diffusion region 2 thereof are referred to as a contaminated region (which is tentatively defined; hereinafter the same).

  There are various substances such as trichlorethylene, tetrachloroethylene, formaldehyde, toluene, benzene, and xylene as organic chlorine compounds (or volatile organic compounds VOC) that are pollutants. These are chemically stable and difficult to decompose, and as a reaction that has become widespread for various uses in industry, it is now a cause of contamination of soil and groundwater.

  Reference numeral 7 denotes a nutrient salt tank, which is installed on the ground, for example, and stores the nutrient salt therein. As the nutrient salt, a nutrient salt mainly composed of a linear saturated monocarboxylic acid having 6 or more carbon atoms is specified, and an anaerobic microorganism group (anaerobic bacteria group in the contaminated area, An anaerobic microorganism, etc.) to grow and activate.

  Examples of the linear saturated monocarboxylic acid having 6 or more carbon atoms include caproic acid, pentanecarboxylic acid, butylacetic acid, enanthic acid, enanthic acid, hexanecarboxylic acid, pentylacetic acid, caprylic acid, heptanecarboxylic acid, hexylacetic acid, Pelargonic acid, octane carboxylic acid, heptyl acetic acid, etc. are raised

  Reference numeral 9 denotes an injection well for injecting (supplying) nutrient salts. The installation well is formed by excavating the soil 4 and the aquifer 5 vertically, and the tip thereof is a non-permeable layer (generally known impervious water). (Including layers or impervious rocks). And the arrangement | positioning (installation) is installed in the circumference | surroundings of the anode well 12 of the downstream of the groundwater flow of a contamination area | region. Preferably, by providing the injection well 9 around the anode well 12, a reducing atmosphere is obtained by attracting positive ions containing hydrogen ions to the anode plate (anode bar) 14 by the current flowing from the DC power supply 13. In an environment in which anaerobic microorganisms are liable to live, nutrient salts mainly composed of linear saturated monocarboxylic acids having 6 or more carbon atoms, which are nutrient sources for anaerobic microorganisms, are injected into the injection well 9. Thus, the anaerobic microorganism group can promote the growth and activation. Further, the current flowing from the DC power source 13 generates heat in the vicinity of the anode plate (anode rod) 14 of the anode well 12 and the cathode plate (cathode rod) 18 of the cathode well 15, and the soil 4 and the water When the layer 5 is heated, the anaerobic microorganism group is further proliferated and activated, and the organic chlorine compound as a contaminant can be reduced in molecular weight by the action of the anaerobic microorganism group.

  The anode well 12 and the cathode well 15 are covered with a semipermeable membrane 16 on the inner circumference of a pipe made of vinyl chloride chlorite, so that only positive ions are transmitted through the anode well 12 and vice versa. In addition, only negative ions permeate the cathode well 15. The anode plate (anode rod) 14 is not particularly specified, but a plate made of platinum can be used stably. Furthermore, an electrolytic solution 17 is adjusted and injected into the anode well 12 and the cathode well 15 in a regulating tank (not shown) so as to perform electrolysis efficiently.

  By installing an observation well (monitoring) 10 having a pumping pump (not shown) around the cathode well 15, the state of purification of the contaminated area can be determined.

  The nutrient salt stored in the nutrient salt tank 7 is transferred from the injection well 9 to the soil 4 and the entire aquifer 5 in the contaminated area by operation of an injector 8, an on-off valve (not shown), and the like. Injection / supply (injection well 9 and injection direction in the aquifer 5 are indicated by →, the same shall apply hereinafter), and groundwater flow (or / and solubility), infiltration / dissolution, etc. are used. And evenly spread throughout. That is, as shown in FIG. 1, the nutrient salt flows in the direction passing through the contaminated part 1 and the diffusion region 2 (the amount of groundwater is increased and the flow velocity is accelerated), and greatly surrounds the contaminated region (not shown). However, it is formed so as to be surrounded by a large plane, and the contamination is purified.

  That is, by the injected nutrient salt, anaerobic microorganisms that are ecological under natural conditions (anaerobic environment with extremely low dissolved oxygen concentration DO value) in the soil 4 and the aquifer 5 are grown and activated, In other words, this is a construction method in which the pollutants in the contaminated area due to the organic chlorine compound are stably decomposed (purification and detoxification by reductive dechlorination reaction) using electrolysis.

The observation well 10 is installed vertically upstream of the contaminated area (excavated in the same manner as the injection well 9 described above), and the effect of purifying the contamination by injecting (supplying / injecting) nutrients is set and the processing conditions are set. Detect changes in the state of pollutants. The arrangement will be set as appropriate according to the contamination status at the site (original position). Needless to say, the observation well 10 performs various measurements by collecting or pumping groundwater from the aquifer 5 (pumping direction is indicated by →, the same shall apply hereinafter).
For example,
1) The oxidation / reduction potential is measured using an ORP meter (oxidation-reduction potentiometer), and the suitability (purification effect) of the injection amount of nutrient salt is measured and judged.

2) In addition, over time, organochlorine compounds (contaminants) of tetrachlorethylene (PCE), trichlorethylene (TCE), dichloroethylene (cis-1,2-DCE), dichloroethylene (1,1-DCE), vinyl chloride ( VC) etc. are selected according to each site, and the daily change (decrease state) of each concentration (mg / l) is observed (measured or monitored).
In addition, although detailed explanation is omitted, a separate control device is provided, and the optimum type (or blending) of nutrient salts is determined by the above-described data detection / measurement (input) unit, calculation / analysis / judgment (output) unit, etc. It is obvious that it is possible to control the supply / injection amount (or flow rate), injection time, pumping amount (flow rate) described later, groundwater return amount, construction period estimation, maintenance time, etc. Naturally, this makes it easy to expand and expand to unmanned remote control and management.

  In addition, although arrangement | positioning of the said injection well 9 and the observation well 10 with respect to the said contaminated area is based on the said observation well 10 provided with the said injection well 9 in the downstream of a groundwater flow direction and the pumping pump upstream, as mentioned above. However, the present invention is not limited to this (detailed description is not given), and it is obvious that it can be made freely according to the state of contamination on the site (not necessarily an arbitrary arrangement based on upstream to downstream). For example, depending on the extent of the contaminated area and the state of contamination, they are placed side by side surrounded by a plurality of wells. In this case, it is obvious that the purification treatment can be further optimized by setting and controlling the amount and timing of injection and pumping of each well for each well.

  As the carboxylic acid of the nutrient salt of the present application, it is essential that the number of carbon atoms is 6 or more, and a stable nutrient salt can be provided over a long period of time. In other words, when the number of carbon atoms is less than 6 (for example, formic acid, butyric acid), the solubility in water is too high, which leads to a short-term supply and consumption, and this temporary excessive dissolution results in a short period of excess nutrients. This will give an adverse effect on the anaerobic environment and anaerobic bacteria as described above (described in the section of the problem).

  In addition, although it is not necessary to set the upper limit of the carbon number, it is considered that the carbon number is about 18 as industrially available in large quantities (but not necessarily limited to those having 18 or less carbon atoms). Needless to say that there is nothing.) If the carbon number is too large, water solubility is further deteriorated (it takes time to dissolve), and the effect (effectiveness) as a nutrient salt is lowered.

  In addition, the carboxylic acid of the present application has a linear structure, and is preferably a saturated monocarboxylic acid (the basic contents thereof are described in JP 2000-334492 A). )

The nutrient salt of the present application is mainly composed of linear saturated monocarboxylic acid having 6 or more carbon atoms, and is based on a solid (molded solid product) such as granular to pellet.
Since the groundwater in the aquifer 5 is rich in nitrate nitrogen, it becomes a nutrient salt for anaerobic microorganisms, but it cannot be activated only by the nitrogen component, and is a linear saturated monocarboxylic acid having 6 or more carbon atoms as the C component. , The activation of anaerobic microorganisms (degrading bacteria) is promoted, the exchange of hydrogen and chlorine by the microorganisms becomes active, and the contaminated area can be stably purified (detoxification treatment). (Judgment is based on measurement of ORP meter).

As described above, when the number of carbon atoms is large, it takes time to dissolve in groundwater (poor water solubility and permeability), and the effect as a nutrient salt is low (slow effect). For example, the carboxylic acid (higher fatty acid) of the present application Alcohol (glycerin) may be added to form an ester (oil or fat). That is, the carboxylic acid is converted to an ester bond with glycerin, so that the water solubility of the carboxylic acid is increased, and an auxiliary contribution to the purification by the carboxylic acid can be expected (for these contents and the like, see JP-A-2002-370085). Is described in the publication number).
Therefore, the injector 8 selects and supplies the nutrient salt as described above from the nutrient tank 7 through the injection well 9.

  Temporarily, from the viewpoint of the pollution purification treatment period, there are short-term to medium-term to long-term, etc. For example, if it is short-term, a carboxylic acid having a small carbon number and a carboxylic acid esterified with glycerin It can be considered. On the contrary, if it is long-term, it can be considered to use a carboxylic acid having a large number of carbons (eg, stearic acid) or a nutrient salt that does not use glycerin. In other words, if the carbon number of carboxylic acid and the amount of glycerin added can be freely selected and determined by involving the amount and timing of injection, the optimum purification treatment conditions and treatment period can be determined and controlled, and the response at the current position can be achieved. It can be done freely.

  From the above explanation, it is not a purification treatment method using a vertical well that is simply a combination of electrolysis and biotechnologies, but the feature of the present application is that groundwater can be obtained by reversing the injection well 9 and the observation well equipped with a pump to the groundwater flow. The anode well 12 is placed downstream of the flow of groundwater using electrolysis, and attracts hydrogen ions by electrolyzing the soil and groundwater, and at the same time the anode By injecting specific nutrients around the well 12, the action of anaerobic microorganisms and the replacement of hydrogen and chlorine by electrolysis are stably maintained, and the organic chlorine compounds that are pollutants are reduced in molecular weight in a short period of time. By detoxifying (decomposing into water and carbon dioxide), a specific effect is newly produced by selecting a specific nutrient salt.

  In the above, one embodiment in the action and electrolysis of anaerobic microorganisms has been described. However, it is obvious that each embodiment can be appropriately combined and expanded in accordance with the pollution situation in the field. That is.

The present invention can be applied to an apparatus that activates anaerobic microorganisms using a bioremediation method, promotes purification of soil and groundwater contaminated with organochlorine compounds, and purifies a contaminated area in situ in a short period of time. .

Simulated sectional view showing the outline of the purification method of contaminated soil and groundwater of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polluted part 2 Diffusion zone 4 Soil 5 Aquifer 6 Difficult-permeable layer 7 Nutrient tank 8 Injection machine 9 Injection well 10 Observation (monitoring) well 12 Anode well 13 DC power supply 14 Anode plate (anode rod)
15 Cathode well 16 Semi-permeable membrane 17 Electrolyte 18 Cathode plate (cathode bar)

Claims (3)

A vertical well is provided outside the diffusion zone of the contaminated part, the inner periphery of the vertical well pipe is covered with a semi-permeable membrane, and the vertical well is provided with anode and cathode electrode members to electrolyze soil and groundwater. In addition, a nutrient salt injection well for injecting a nutrient salt for microbial activity is provided around the well on the anode side, and the volatile organic contained in the soil and groundwater of the contaminated part diffusion area by the electrolysis and the nutrient salt A method for purifying contaminated soil and groundwater using a method of decomposing compounds with anaerobic microorganisms. The method for purifying contaminated soil and groundwater according to claim 1, wherein the nutrient salt is a nutrient salt mainly composed of a linear saturated monocarboxylic acid having 6 or more carbon atoms. 2. The contamination according to claim 1, wherein a vertical observation well for monitoring a purification state of the soil and the groundwater by injecting the nutrient salt is installed around the vertical well having the cathode electrode member. Soil and groundwater purification methods.

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