JP3708160B2 - Purification method of contaminated groundwater - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for purifying groundwater flowing in soil, and more specifically, an object is to collectively remove heavy metals and organic chlorine compounds contained in groundwater by the action of iron powder.
[0002]
[Prior art]
Conventionally, soil contaminated with heavy metals, etc. is treated as a landfill disposal method in which the contaminated soil itself is solidified or insolubilized and landfilled, or by heat treatment to remove the gas vaporized by the pollutant and harmless. In general, a heat treatment method is employed.
[0003]
As other special treatment methods, there are washing classification methods that classify contaminated soil and wash fine particles containing a lot of heavy metals with water, and biological treatment methods that treat bacteria using bacteria that live in the soil. Are known.
[0004]
As described above, each of these methods has advantages and disadvantages so that the treatment method varies depending on the type of pollutant to be processed.
[0005]
The above-mentioned fixation stabilization method is intended for inorganic pollutants, but its maintenance is difficult due to leaching due to the action of rainwater etc. over a long period of time, while the heat treatment method is applicable to organic pollutants. Although it is suitable, it is particularly unsuitable for the treatment of soil contaminated with alkali salts, and can be applied only to a few types of inorganic heavy metals such as mercury.
[0006]
Furthermore, the cleaning classification method can also deal with non-volatile substances, etc., but when soil excavation and pollutants are deep, it is unsuitable for mining costs, and the biological treatment method by bacteria is also The reaction time is long, and there is a limit to carbohydrates having a single chain structure, and it is hardly applicable to inorganic substances.
[0007]
Contaminants in the soil are then mixed into the groundwater veins by rainwater, etc., and the water resources such as well water are harmed. Therefore, wastewater treatment methods for removing contaminated groundwater and removing heavy metals, An extraction method for extracting while explosive gas is also known, but this method has a problem that costs such as power costs and extraction costs at the time of pumping are required.
[0008]
[Problems to be solved by the invention]
The method for directly treating contaminated soil as described above is a method that can treat the cost at a low cost if the pollution source is in a narrow range, but is not suitable for a case where it is contaminated in a wide range over a long period of time.
[0009]
Accordingly, an object of the present invention is to develop a novel treatment method capable of removing heavy metals or organochlorine compounds all at once at a low cost and using contaminated groundwater as a treatment target.
[0010]
[Means for Solving the Problems]
As a result of intensive research to solve such problems, the present inventors have found that inexpensive iron powder can be used for heavy metal contained in groundwater and for removal of organic chlorine compounds. Could be provided.
[0011]
That is, in the method of the present invention, an pit having an opening is excavated to the groundwater surface that flows in the soil and is contaminated with heavy metals and organochlorine compounds, and then an iron powder layer is formed in contact with the air atmosphere on the bottom surface of the pit in an atmosphere communicating with the air. The contaminated groundwater flow is allowed to pass through the iron powder layer within a pH range of 2 to 7, so that the adsorption and removal of the heavy metal and the decomposition and removal of the organochlorine compound are collectively performed with the iron powder for a predetermined period of time. It is a purification method of contaminated groundwater, wherein the water flow is permanently purified by replacing the iron powder layer after the passage.
[0012]
[Action]
According to the method of the present invention, pollutants (mainly organochlorine compounds and inorganic heavy metals) contained in contaminated groundwater that passes through the iron powder layer by arranging iron powder in layers on the bottom of the pit excavated to the groundwater surface Is detoxified by the reaction of decomposition, adsorption or substitution in the iron powder.
[0013]
Of these, the mechanism of decomposition of organochlorine compounds has not been elucidated, but is presumed to be reduced by iron. On the other hand, the reaction between the inorganic heavy metal and the iron powder is adsorbed to the iron powder by a reduction reaction, a substitution reaction, an adsorption reaction, a homogenization reaction, a neutralization reaction, a coprecipitation reaction, etc. for each heavy metal ion.
[0014]
In general, the movement of groundwater is assumed to be 1 to 1.5 m / day, and the contaminated groundwater to be treated in the present invention is also judged to have the same speed. Contaminated groundwater was passed through the bed so that SV = 1.
[0015]
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention method is not limited to these.
[0016]
[Example 1]
As shown in FIG. 1, after excavating a pit to the groundwater surface that flowed out from the pollution source 1, an iron powder layer was formed in the pit.
[0017]
As a result of analysis of upstream contaminated groundwater before passing through the iron powder layer, the pH was 4.9, and various kinds of Cr ⁶⁺ 0.76 mg / l, T · Cr 1.2 mg / l, Ni 8.5 mg / l were used. Contains heavy metals.
[0018]
When the contaminated groundwater was collected and analyzed after passing through the iron powder layer at a rate of SV = 1, pH 5.5, Cr ⁶⁺ not detected, T / Cr not detected, Ni 0.1 mg / l And heavy metals could be removed.
[0019]
[Reference Example 1]
As a heavy metal-containing wastewater, a wastewater containing 50 mg / l each of pH 5.5, Cu ²⁺ , Cd ²⁺ , and Zn ²⁺ was packed in a column packed under substantially the same conditions as the iron powder layer forming conditions in Example 1. After passing, the filtrate after passing was pH 6.6, Cd 0.01 mg / l, Cu 0.01 mg / l, Zn 0.01 mg / l, and it was confirmed that the method of the present invention can be applied to this level of contaminated waste water. did.
[0020]
[Example 2]
Except for other contaminated groundwater containing 5 mg / l each of trichlorethylene and tetrachlorethylene, the iron powder was treated under almost the same conditions as shown in Example 1, and the groundwater after passing through the iron powder layer was , Trichlorethylene and tetrachlorethylene were each 0.1 mg / l or less, and it was confirmed that the method of the present invention was suitable for removing organic chlorine compounds.
[0021]
【The invention's effect】
As described above, the method of the present invention is a treatment method that can remove heavy metals and organochlorine compounds from contaminated groundwater at once by using inexpensive iron powder, and permanently purifies contaminated groundwater by replacing the iron powder after a certain period of time. It can be done.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a processing system according to the present invention.
[Explanation of symbols]
1 Pollution source 2 Groundwater 3 Pit 4 Iron powder layer 5 In the soil

Claims (1)

After excavating a pit with an opening through the soil to the groundwater surface contaminated with heavy metals and organochlorine compounds, an iron powder layer is provided in contact with the air atmosphere at the bottom of the pit in an atmosphere communicating with the atmosphere , and the contaminated groundwater flow Is allowed to pass through the iron powder layer within a pH range of 2 to 7, and the iron powder is used to collectively remove the heavy metal and decompose and remove the organochlorine compound, and after a predetermined period of time, the iron powder layer. A method for purifying contaminated groundwater, wherein the water flow is permanently purified by replacing the water.

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