Soil and / or groundwater purification method

Abstract

To provide a purification method for soil and / or groundwater capable of preventing excessive injection of the aqueous solution of a nutritional supplement into a well by a simple configuration.SOLUTION: An aqueous solution of a nutritional supplement is reserved in the injection tanks 61 to 6n up to the valve-closing water level WL of a ball tap 7. The top edge of each of wells (pipes) C1 to Cn is located at a higher position than the valve-closing water level WL of the ball tap. The lower parts of the injection tanks 61 to 6n are connected to the wells C1 to Cn by an injection pipeline 8 and thereby, the aqueous solution of the nutritional supplement in the injection tanks 61 to 6n is injected all the time in each of wells C1 to Cn at a prescribed injection flow by water head difference. Since the difference between the water level in the injection tank and that in the well disappears when the water level in the well rises until the valve-closing water level WL, the injection of the aqueous solution of the nutritional supplement stops and such a risk that the above aqueous solution overflows from the well does not generate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for purifying soil and / or groundwater contaminated with harmful substances.

Background Art

[0002] As a method for purifying soil contaminated with harmful substances, there is a purification technique (bioremediation) that uses microorganisms to decompose and remove harmful substances in soil and groundwater.

[0003] For example, Patent Document 1 describes a method for purifying contaminated soil and / or groundwater by injecting nutrients such as citric acid and citrate into the soil.

[0004] Patent Document 2 describes injecting nutrients from a plurality of wells.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When injecting a nutrient solution into the soil through a plurality of injection wells, the nutrient solution is simultaneously injected from one nutrient solution storage tank into each well by gravity-driven injection or injection from one pump into each well.

[0007] The control of the injection amount into each well takes into account fluctuations due to geological conditions and is addressed by the pipe diameter and injection pump specifications, but it is not sufficient, and over-injection may occur.

[0008] For example, if injection is continuously carried out, the intake volume of the well will gradually decrease, the groundwater level will rise, and there is a risk that the nutrient solution will overflow from the well.

[0009] To prevent this, if a water level sensor is provided for each well to control the injection volume, the equipment cost will increase.

[0010] An object of the present invention is to provide a method for purifying soil and / or groundwater that can prevent excessive injection of an aqueous nutrient solution into a well with a simple configuration.

Means for Solving the Problems

[0011] The method for purifying soil and / or groundwater of the present invention is a method for purifying soil and / or groundwater in which an aqueous nutrient solution is injected into a well provided in a purification target area. The well is projected above the ground, and the aqueous nutrient solution is injected into the well by a water head difference from an injection tank arranged near the well.

[0012] In one aspect of the present invention, the injection tank is provided with a ball tap, and the aqueous nutrient solution from the aqueous nutrient solution preparation tank is supplied into the injection tank through the ball tap. The upper end of the well is located above the ball tap closing valve water level in the injection tank.

[0013] In one aspect of the present invention, a plurality of wells are provided, and the injection tanks are respectively arranged for each well.

[0014] In one aspect of the present invention, the well is provided by driving a pipe into the ground.

Advantages of the Invention

[0015] According to the method of the present invention, excessive injection of the aqueous nutrient solution into the well can be prevented with a simple configuration. Also, regardless of the water level inside the well, the aqueous nutrient solution can be automatically injected from the injection tank without overflowing from the well.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0017] In the present invention, examples of the soil and / or groundwater to be treated include soil and / or groundwater contaminated with organic chlorine compounds such as chlorinated ethylene. Examples of chlorinated ethylene include tetrachloroethylene (PCE), trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), trans-1,2-dichloroethylene (trans-DCE), 1,1-dichloroethylene (1,1-DCE), chloroethylene, and their dechlorination intermediates.

[0018] Suitable nutrients include saccharides such as glucose, starch, acetic acid, citric acid or its salts, methanol, ethanol, peptone, yeast extract, biodegradable polymers such as polylactic acid, triglycerides, fatty acids, etc. Among them, acetic acid, citric acid or their salts are particularly suitable.

[0019] As the dilution water, industrial water, tap water, etc. can be used.

[0020] When injected into a well, the nutrient concentration of the nutrient solution is preferably in the range of 100 to 10000 mg / L, particularly 1000 to 3000 mg / L in terms of carbon. If the nutrient concentration is too low, the hydrogen required for the nutrient-decomposing microorganisms to decompose the nutrient is insufficient. If the nutrient concentration is too high, the activity of the nutrient-decomposing bacteria will be inhibited.

[0021] In the present invention, in addition to the nutrient, chlorinated ethylene-decomposing bacteria may be injected to increase the decomposition efficiency of organic chlorine compounds such as chlorinated ethylene.

[0022] Examples of bacteria that decompose chlorinated ethylene include bacteria of the genus Dehalococcoides that have chlorinated ethylene decomposition activity.

[0023] Hereinafter, an example of the present invention will be described with reference to the drawings.

[0024] FIG. 1 shows an embodiment, and shows a configuration in which a nutrient agent is diluted with dilution water and injected into a plurality of wells C1 to Cn.

[0025] A plurality (n) of wells C1 to Cn (only C1 to C3 are shown in FIG. 1) for injecting a nutrient agent are provided on the ground G of the purification target area. Each well C1 to Cn is provided by driving a pipe into the ground. The upper end of each pipe protrudes upward from the ground G by a predetermined length (preferably 2 to 4 m).

[0026] A large number of holes are provided on the side peripheral surface of the tip side in the driving direction of the pipe, so that the nutrient agent aqueous solution flows out from the wells C1 to Cn into the soil. A nutrient agent aqueous solution having a specified concentration prepared in the nutrient agent aqueous solution preparation tank 1 is injected into each of the wells C1 to Cn via injection tanks 61 to 6n.

[0027] The nutrient agent aqueous solution preparation tank 1 is disposed above the injection tanks 61 to 6n and the upper ends of the respective wells (pipes) C1 to Cn by a gantry (not shown) or the like. Although not shown in the figure, a constant pressure water supply pump may be installed on the discharge side of the adjustment tank 1 without using a gantry so that a constant water pressure is always applied in the pipe 4.

[0028] A specified amount of dilution water and a nutrient agent concentrated solution are supplied to the nutrient agent aqueous solution preparation tank 1 from the dilution water supply pipe 2 and the nutrient agent concentrated solution supply pipe 3, and are stirred by a stirrer 1a to prepare a nutrient agent aqueous solution having a specified concentration.

[0029] The nutrient solution in the nutrient solution preparation tank 1 can flow out into the main pipe 4 connected to the lower part of the preparation tank 1. By installing a constant-pressure water supply pump, the main pipe 4 does not have to be arranged above the upper ends of the injection tanks 61 to 6n and each well (pipe) C1 to Cn.

[0030] n branch pipes 5 branch from the main pipe 4, and each branch pipe 5 is supplied to n injection tanks 61 to 6n (only 3 tanks 61 to 63 are shown in FIG. 1). Each of the injection tanks 61 to 6n is installed near each well C1 to Cn. For example, the injection tank 61 is installed adjacent to the well C1, the injection tank 62 is installed adjacent to the well C2, and the injection tank 63 is installed adjacent to the well C3.

[0031] Each of the injection tanks 61 to 6n is provided with a ball tap 7, and the tip of each branch pipe 5 is connected to the inlet of the ball tap 7. Therefore, the nutrient solution is stored in the injection tanks 61 to 6n up to the closed valve water level WL of the ball tap 7. The upper ends of each well (pipe) C1 to Cn are located above this ball tap closed valve water level WL.

[0032] The lower parts of the injection tanks 61 to 6n are connected to each well C1 to Cn by injection pipes 8 having flow control valves. Thereby, the nutrient solution in the injection tanks 61 to 6n is always injected into each well C1 to Cn at a predetermined injection flow rate due to the head difference. This injection flow rate can be adjusted by changing the opening degree of the flow control valve of the injection pipe 8.

[0033] When the water level in the well Ci (i is any one of 1 to n) rises to the ball tap closed valve water level WL of the injection tank 6i, the head difference between the inside of the injection tank 6i and the well Ci disappears, so the injection of the nutrient solution into the well Ci stops, and since the water level in the well Ci does not rise any further, the nutrient solution does not overflow from the well Ci.

[0034] Thus, according to this embodiment, it is possible to inject the nutrient aqueous solution at a specified flow rate into each well without providing an injection control device having a water level sensor in each well. Further, when the intake of the well deteriorates and the water level in the well rises to the ball tap closing valve water level WL, the nutrient aqueous solution is not injected any more, and the nutrient aqueous solution does not overflow from the well.

[0035] An example of a system for supplying a nutrient concentrated solution and dilution water to the nutrient aqueous solution preparation tank 1 is shown in FIG. 2.

[0036] The dilution water is introduced into the dilution water tank 10 and stored. The dilution water in the dilution water tank 10 can be introduced into the nutrient dissolution tank 14 via the pump 11 and the pipe 12. Water level sensors LS are provided in the dilution water storage tank 10 and the nutrient dissolution tank 14, respectively.

[0037] The nutrient dissolution tank 14 is capable of being supplied with nutrients by the nutrient supply means 13.

[0038] By introducing a specified amount of nutrient and dilution water into the nutrient dissolution tank 14 and stirring with the stirrer 14a, a concentrated solution of the nutrient is prepared. This concentrated nutrient solution is transferred to the nutrient concentrated solution storage tank 17 via the pump 15 and the pipe 16 and stored. A water level sensor LS is provided in the nutrient concentrated solution storage tank 17. When the liquid level reaches the lower limit value, a nutrient concentrated solution replenishment request signal is transmitted, and the nutrient concentrated solution is prepared by the nutrient dissolution tank 14 and replenished to the nutrient concentrated solution storage tank 17.

[0039] The nutrient concentrated solution in the nutrient concentrated solution storage tank 17 can be supplied to a plurality of (k) nutrient aqueous solution preparation tanks 1 via the pipe (main pipe) 18 having the pump 19 and k branch pipes 21 to 2k (only 21, 22, 23 are shown in FIG. 2) branched from the pipe 18.

[0040] Valves V1 are provided in each of the branch pipes 21 to 2k. By opening the valve V1, a specified amount of the nutrient concentrated solution is introduced into the nutrient aqueous solution preparation tank 1.

[0041] In addition, the dilution water in the dilution water tank 10 can be supplied to each nutrient aqueous solution preparation tank 1 via a pipe (main pipe) 31 having a pump 32 and branch pipes 41 to 4k (only 41, 42, and 43 are shown in FIG. 2). By opening the valves V2 provided in the branch pipes 41 to 4k, a specified amount of dilution water is introduced into the nutrient aqueous solution preparation tank 1.

[0042] In order to supply a specified amount of nutrient solution and dilution water to the nutrient aqueous solution preparation tank 1, it is preferable to provide a water level sensor in the nutrient aqueous solution preparation tank 1 or flow meters in each of the pipes 21 to 2k and 41 to 4k.

[0043] As described above, the nutrient aqueous solution is sent from each nutrient aqueous solution preparation tank 1 to each injection tank 61 to 6n via the main pipe 4, the branch pipes 5, and the ball tap 7.

[0044] The above embodiment is an example of the present invention, and the present invention may be in a form other than that shown. In the above embodiment, the nutrient aqueous solution is injected from one injection tank into one well, but the nutrient aqueous solution may be injected from one injection tank into a plurality of wells. Further, in the present invention, a constant water level liquid supply mechanism other than the ball tap may be used.

Explanation of Reference Numerals

[0045] 1 Nutrient aqueous solution preparation tank 7 Ball tap 10 Dilution water storage tank 14 Nutrient dissolution tank 17 Nutrient concentrated solution storage tank 61 to 63 Injection tanks C1 to C3 Wells

Claims

1. In a method for purifying soil and / or groundwater by injecting an aqueous nutrient solution into a well provided in an area to be purified, a method for purifying soil and / or groundwater, wherein the well protrudes above the ground and the aqueous nutrient solution is injected into the well by a head difference from an injection tank arranged in the vicinity of the well, the injection tank is provided with a ball tap, and the aqueous nutrient solution from the aqueous nutrient solution preparation tank is supplied into the injection tank through the ball tap, a method for purifying soil and / or groundwater, characterized in that the upper end of the well is located above the ball tap closing valve water level in the injection tank.

2. A method for purifying soil and / or groundwater according to Claim 1, characterized in that a plurality of wells are provided, and the injection tanks are respectively arranged in each well.

3. A method for purifying soil and / or groundwater according to Claim 1 or 2, characterized in that the well is provided by driving a pipe into the ground.

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