JP2006006996A - Purification method of pollution vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method for enhancing pollution cleaning efficiency of polluted medium like polluted ground 1. <P>SOLUTION: A water injection well 4 generating underground water flow GWF passing through a polluted region 2, and a pumping well 3 are formed in the ground 1. An additive 8 like oxygenated water forming substances not violating environmental standards by reacting with pollutant like trichloroethylene in the polluted region 2 is injected to the injection well 4, is made to penetrate into the polluted region 2 by the underground water flow GWF, voltage is applied from an AC power source 9 to electrodes installed in the injection well 4 and pumping well 3, and the ground of the polluted region 2 is heated to accelerate the reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for purifying contaminated media such as ground contaminated with contaminants such as organochlorine compounds.

In recent years, contamination of the ground due to trichlorethylene or the like used as a solvent has become a problem. Conventionally, as a method for purifying the ground contaminated with such substances, there are methods disclosed in Patent Document 1 or Patent Document 2 below.
JP-A-6-322796 JP-A-10-309562

  FIG. 3 is an explanatory view showing a conventional pollution purification method by pumping up groundwater corresponding to the above-mentioned Patent Document 1. In FIG. 3, reference numeral 100 is the ground, 101 is the contaminated area in the ground 100, and 102 is the contaminated area 101. A plurality of pumping wells drilled in the ground 100 so as to surround the periphery, 103 is a submersible pump installed in the pumping well 102, and GWL is a groundwater level. That is, in this purification method, the groundwater GW is pumped from the pumping well 102 by the submersible pump 103, and the pumped water GW is treated so that there is no problem in a water treatment plant (not shown), and then discharged or drilled as necessary. It is injected from the injection well into the ground.

  When such a pollution purification method by pumping up groundwater is adopted, purification efficiency is high at the initial stage of construction in which the contaminated area 101 is contaminated with a high concentration, and the effect is quite effective even considering the construction cost. it is conceivable that. However, as the concentration of the pollutant in the contaminated area 101 decreases as the construction progresses, the purification efficiency also decreases. I can't say that.

  Moreover, the electroosmosis method like patent document 2 makes a groundwater flow compulsorily generate | occur | produce by an electroosmosis phenomenon by sending a direct current through the ground, and discharges underground pollutants with a groundwater to a pumping well. Therefore, it is considered effective for repairing contamination on the ground with low water permeability. However, even with this method, it has been difficult to dramatically improve water permeability and increase purification efficiency.

  The present invention has been made in view of the above-described problems, and a technical problem thereof is to provide a purification method capable of increasing the pollution purification efficiency for contaminated media such as contaminated ground. .

  In order to effectively solve the above-described conventional technical problem, a method for purifying a contaminated medium according to the invention of claim 1 includes forming, on the medium, a water injection section and a pumping section that generate an osmotic water flow passing through the contaminated area, An additive that generates a substance that does not violate environmental standards by reacting with contaminants in the contaminated area is injected into the water injection section to infiltrate the contaminated area with the osmotic water flow. The reaction is promoted by heating.

  In the above method, the purpose of applying a voltage to the medium (for example, the ground) is to cause a phenomenon that the temperature of the medium rises due to the generation of Joule heat when a current flows through the medium, thereby causing a problem in the contaminated area of the medium. It is to promote chemical reaction between pollutants and additives. In other words, this is different from the conventional voltage application method in which a water flow is forcibly generated in the medium by the electroosmosis phenomenon and the pollutant is discharged together with water.

  According to a second aspect of the present invention, there is provided a method for purifying a contaminated medium, wherein the contaminant is an organic chlorine compound such as trichlorethylene and the additive is an oxidizing agent such as hydrogen peroxide. It is a feature.

When hydrogen peroxide is added to trichlorethylene, the following chemical reaction occurs. The substance after the reaction will eventually be decomposed into carbon dioxide and chlorine. Similarly, other organic chlorine compounds can be oxidatively decomposed by adding an oxidizing agent.

  According to a third aspect of the present invention, there is provided a method for purifying a contaminated medium, wherein the voltage applied to the medium is an alternating voltage in the configuration of the first or second aspect.

  The voltage is applied to the medium because Joule heat is generated by the current and the temperature of the medium is raised. Therefore, the medium may be basically direct current or alternating current. When energized, the electrolysis of water is activated too much near the electrode, and gas such as oxygen, hydrogen, or chlorine is excessively generated at the electrode and the bubbles adhere to it, so that the current efficiency is lowered, so AC is desirable. .

  According to the method for purifying a contaminated medium according to the invention of claim 1, the pollutant in the medium such as the ground generates a substance that does not violate environmental standards by reacting with the additive that penetrates into the medium. Since this reaction is promoted by an increase in the temperature of the medium due to energization, the purification efficiency can be improved. Therefore, the purification can be efficiently performed by applying to the stage where the purification is advanced in the medium with high water permeability or the purification of the medium with low water permeability.

  According to the method for purifying a contaminated medium according to the invention of claim 2, the ground contaminated with an organic chlorine compound such as trichlorethylene which is chemically stable and hardly decomposed by microorganisms can be efficiently purified.

  According to the method for purifying a contaminated medium according to the invention of claim 3, by applying an AC voltage to the medium, the temperature of the medium is increased by generating Joule heat without causing an inhibition of current due to polarization, It is possible to promote the purification of the medium by the reaction between the pollutants therein and the additives.

  FIG. 1 is an explanatory diagram showing a preferred first embodiment of a method for purifying a contaminated medium according to the present invention. In the method for purifying a contaminated medium according to this embodiment, the present invention is applied to a method for purifying contaminated ground by pumping up groundwater.

  That is, in FIG. 1, reference numeral 1 is the ground, 2 is a contaminated area due to an organic chlorine compound such as trichlorethylene in the ground 1, 3 is a plurality of pumping wells drilled in the ground 1 so as to surround the contaminated area 2, 4 Is a water injection well drilled in the ground 1 toward the contaminated area 2, and GWL is the groundwater level. The ground 1 corresponds to the medium described in claim 1, the pumping well 3 corresponds to the pumping unit described in claim 1, and the water pouring well 4 corresponds to the water pouring unit described in claim 1. To do.

  The pumping well 3 and the water injection well 4 are excavated to a position deeper than the groundwater level GWL, and porous cylindrical casings 3a and 4a are inserted therein. Moreover, the water stop wall 5 by a sheet pile etc. is inserted so that the outer side of the pumping well 3 may be enclosed, and the submersible pump 6 is installed in the pumping well 3 in the position deeper than the groundwater level GWL, The discharge port Is connected to a pumping pipe 7 extending to the ground.

  In the purification process, while injecting water into the water injection well 4, the submersible pump 6 of each pumping well 3 is driven to pump up the groundwater GW. The water injected into the water injection well 4 penetrates into the ground through a number of small holes established in the casing 4a, while in the pumping well 3, the water level drops due to pumping by the submersible pump 6, so that the water is established in the casing 3a. In addition, groundwater GW flows from a large number of small holes.

  Here, between each pumping well 3 and the pumping well 4, since the gradient which becomes low in the pumping well 3 arises in the groundwater level GWL, it goes to the pumping well 3 from the pumping well 4 via the inside of the contaminated area 2 A groundwater flow GWF is generated. The groundwater flow GWF corresponds to the seepage water flow described in claim 1.

  For this reason, contaminants such as trichlorethylene in the contaminated area 2 are also attracted to the groundwater flow GWF, gradually move to the pumping well 3, and are pumped up and collected together with the groundwater GW. The groundwater GW containing the contaminated pumped water is treated so that there is no problem in a water treatment plant (not shown) and then discharged or condensed from the water injection well 4 as in situ groundwater.

  Since the outside of the pumping well 3 is restrained from flowing in groundwater from the outside by the water blocking wall 5 such as a sheet pile, the groundwater flow GWF from the water injection well 4 to the pumping well 3 through the contaminated area 2 is efficiently generated. Can be generated.

  As described above, in such a purification method by pumping up groundwater, the purification efficiency decreases as the contamination concentration in the contaminated area 2 decreases as the purification proceeds. Moreover, in the ground with low water permeability, the efficiency for recovery is considerably low only by the method of pumping up the groundwater GW. This is because the groundwater flow is extremely slow on the ground with low water permeability, and most of the groundwater that is pumped is from the ground such as sandy soil with high water permeability. .

Therefore, in this embodiment, the additive 8 is introduced into the ground 1 from the water injection well 4 together with water for condensate. The additive 8 is desirably a substance that does not violate environmental standards by reaction with trichlorethylene or the like, and the additive 8 itself is desirably a substance that does not violate environmental standards. Hydrogen water H ₂ O ₂ is used. That is, an aqueous hydrogen peroxide solution is injected into the water injection well 4.

When the pollutant is trichlorethylene, the following chemical reaction is caused by the addition of hydrogen peroxide. The product resulting from this reaction will eventually be decomposed into carbon dioxide and chlorine.

  The above reaction can be facilitated by the supply of energy. In the embodiment shown in FIG. 1, the casings 3a and 4a of the pumping wells 3 and the water injection wells 4 are made of metal conductors, which are connected via an AC power source 9 as electrodes, and the casings 3a and 4a. By applying an AC voltage between them, an AC current is generated in the contaminated area 2 in the ground 1 and the reaction by the additive 8 is promoted by Joule heat at this time.

  The voltage value applied by the AC power supply 9 between the casings 3a and 4a serving as electrodes is generally different because the electric resistance differs depending on the type of soil in the contaminated area 2 even if the ground 1 is saturated with groundwater. However, according to the experiments by the inventors, when the distance between the electrodes is on the order of several meters, by applying a voltage of 1 V per 1 cm, movement of soil water (electron migration) by electroosmosis or electrophoresis It is confirmed that the temperature of the soil skeleton and moisture in the casings 3a and 4a and its surroundings reaches 100 ° C within a few hours due to the generation of Joule heat at this time. Yes.

  Moreover, since soil has a strong adiabatic property, it is considered that the contaminated area 2 surrounded by the pumping wells 3, 3,... Almost reaches this temperature and becomes steady. The time required for this steady state varies depending on the specific heat of the soil. Although 100 ° C. corresponds to the boiling point of water, the boiling point of the organic chlorine compound is lower than this, and thus a volatilization phenomenon occurs, but it is sufficient as a temperature for promoting the chemical reaction.

  In the embodiment shown in FIG. 1, the AC voltage is applied because the movement of water in the soil (electron flow) by electroosmosis or electrophoresis is a phenomenon caused by electrolysis of water. This is because, when the DC voltage is applied, polarization occurs when applied for a long period of time, and bubbles such as oxygen, hydrogen, and chlorine in some cases adhere to the casings 3a and 4a as the electrodes, and current efficiency decreases. Therefore, when the polarization does not occur or the degree thereof is small, the electrodes (casings 3a and 4a) may be connected via a DC power source to apply a DC voltage.

  In addition, in the case where harmful substances are contained in the product resulting from the chemical reaction between the contaminants such as trichlorethylene and the additive 8, a different additive may be added, or the reaction route may be changed with a catalyst or the like. It is also possible to change.

  Moreover, when the reaction in the casings 3a and 4a (in the pumping well 3 and the water injection well 4) is superior, the addition of the additive 8 and the application of the alternating voltage between the casings 3a and 4a are not performed simultaneously. Add the additive 8 to the water injection well 4, pump up the groundwater GW from the pumping well 3, infiltrate the additive 8 into the contaminated area 2 by the groundwater flow GWF, and then temporarily stop the addition of the additive 8. The timing of the addition of the additive 8 and the voltage application may be appropriately changed such that the AC power source 9 is driven.

  Next, FIG. 2 is explanatory drawing which shows the preferable 2nd form of the purification method of the contaminated ground which concerns on this invention. This form is also basically the same as the first form shown in FIG. 1, but the casings 3 a and 4 a are not connected via the AC power supply 9, but instead of each pumping well 3 and water injection well 4. 1 is different from FIG. 1 in that electrodes 10 and 11 made of metal flat bars are inserted therein and connected to each other via an AC power source 9. That is, according to the form of FIG. 1, the casings 3 a and 4 a to which an alternating voltage is applied corrode over time due to an electrochemical action, but such a casing 3 a, The corrosion of 4a can be prevented.

  In each of the above-described embodiments, the method for purifying a contaminated medium according to the present invention is applied to a method for purifying contaminated ground by pumping up groundwater, but soil contaminated with an organic chlorine compound such as trichlorethylene, etc. The present invention can also be applied to other medium purification methods, treatment plants that purify excavated contaminated media, and intermediate treatment facilities.

It is explanatory drawing which shows the preferable 1st form of the purification method of the contaminated medium which concerns on this invention. It is explanatory drawing which shows the preferable 2nd form of the purification method of the contaminated medium which concerns on this invention. It is explanatory drawing which shows the purification method of the contaminated ground by the conventional pumping of groundwater.

Explanation of symbols

1 Ground (medium)
2 Contaminated area 3 Pumping well (pumping section)
3a, 4a Casing (electrode)
4. Water injection well (water injection part)
5 Water stop wall 6 Submersible pump 7 Water pump 8 Additive 9 AC power supply 10, 11 Electrode

Claims (3)

  An additive that forms a water injection part and a pumping part for generating an osmotic water flow passing through the contaminated area in the medium, and generates a substance that does not conflict with environmental standards by reacting with the pollutant in the contaminated area in the water injection part. A method for purifying a contaminated medium, wherein the contaminated area is permeated into the contaminated area by the permeated water flow, and the contaminated area is heated by applying a voltage to promote the reaction.   The method for purifying a contaminated medium according to claim 1, wherein the pollutant is an organic chlorine compound such as trichlorethylene and the additive is an oxide such as hydrogen peroxide. The method for purifying a contaminated medium according to claim 1, wherein the voltage applied to the medium is an AC voltage.

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