JPH08257570A - Purification of polluted underground water - Google Patents

Abstract

PURPOSE: To remove at least one or more kind of heavy metals and an organochlorine compd. by utilizing an iron powder by excavating the ground up to the surface of polluted underground water to form a pit and forming an iron powder bed on the bottom surface of the pit and passing polluted underground water through the iron powder bed within a specific pH range. CONSTITUTION: A pit 3 is drilled up to the surface of the underground water 2 flowing out of a contamination source 1 and an iron powder bed 4 is formed in the pit 3. By passing polluted underground water through the iron powder bed within a pH range of 2-7, at least one kind or more of heavy metal or an organochlorine compd. is removed by utilizing an iron powder. That is, by arranging the iron powder bed on the bottom surface of the pit 3 drilled up to the surface of underground water 2, the contaminants (mainly, an organochlorine compd. and inorg. heavy metal) contained in the polluted underground water 2 passing through the iron powder bed are decomposed, adsorbed and substituted within the iron powder to be detoxified. By this constitution, the heavy metal component or organochlorine compd. in the polluted underground water 2 can be collectively removed and the iron powder is replaced after the elapse of a predetermined period to permanently purify polluted underground water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying groundwater flowing in soil, and more specifically, it aims to remove heavy metals and organic chlorine compounds contained in groundwater all together by the action of iron powder.

[0002]

2. Description of the Related Art Conventionally, as a method for treating soil contaminated with heavy metals or the like, a landfill disposal method in which contaminated soil itself is solidified or insolubilized for landfilling, or a gas in which a pollutant is vaporized by heat treatment is used. A heat treatment method for making the material harmless by removing it is generally practiced.

As other special treatment methods, a cleaning and classification method of classifying contaminated soil and washing fine particles containing a large amount of heavy metals with water or the like, and an organism for treating pollutants by utilizing bacteria inhabiting the soil The processing method is also known.

As described above, each treatment method has advantages and disadvantages because the treatment method varies depending on the type of the pollutant to be treated.

The above-mentioned fixing and stabilizing method is intended for inorganic pollutants, but it is difficult to maintain it for a long period of time due to leaching due to the action of rainwater, etc. However, it is not suitable for treating contaminated soil with an alkali salt, and it can be applied only to a few kinds of inorganic heavy metals such as mercury.

Further, the cleaning and classification method can also deal with non-volatile substances, but when excavating the soil or when the pollutant extends to a deep layer, the mining cost is unsuitable and the biological treatment by bacteria is not suitable. The method also has a long reaction time and has a limit for carbohydrates having a single-chain structure, and is hardly applicable to inorganic substances.

[0007] Since the pollutants in the soil are then mixed with groundwater veins by rainwater or the like to damage water resources such as well water, a contaminated groundwater is pumped up to remove heavy metals, and a drainage treatment method or pumping There is also known an extraction method for extracting the groundwater while detonating it, but this method has a problem that it costs electricity such as electric power and extraction cost at the time of pumping.

[0008]

The method for directly treating contaminated soil as described above is a method that can be processed at a low cost if the pollution source is in a narrow range, but when it is contaminated in a wide range over a long period of time. Is not suitable for.

Therefore, an object of the present invention is to develop a novel treatment method for treating contaminated groundwater at a low cost and capable of permanently removing heavy metal components or organic chlorine compounds collectively.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve such problems, and found that iron powder which is inexpensive for removing heavy metals contained in groundwater and also for removing organic chlorine compounds. It was possible to provide the method of the present invention by discovering that

That is, according to the method of the present invention, after excavating a pit to the contaminated groundwater road surface, an iron powder layer is provided on the bottom surface of the pit, and the contaminated groundwater is allowed to pass within a pH range of 2 to 7, whereby iron powder is added to the heavy metal or A method for purifying contaminated groundwater, which comprises removing at least one kind of organic chlorine compound.

[0012]

According to the method of the present invention, by arranging iron powder in layers on the bottom surface of the pit excavated to the water table, pollutants (mainly organic chlorine compounds and inorganic compounds) contained in the contaminated ground water passing through the iron powder layer. Heavy metal) is detoxified by being decomposed or adsorbed in iron powder, and subjected to reactions such as substitution.

Of these, the mechanism of decomposition of the organic chlorine compound has not been clarified, but it is presumed that it is reduced by iron. On the other hand, in the reaction between the inorganic heavy metal and the iron powder, a reduction reaction, a substitution reaction, an adsorption reaction, a homogenization reaction, a neutralization reaction, a coprecipitation reaction, etc. occur for each heavy metal ion and are adsorbed on the iron powder.

Generally, the movement of groundwater is 1 to 1.5 m /
The contaminated groundwater to be treated in the present invention is judged to have the same speed as the daily speed, so that the contaminated groundwater in the iron powder layer is SV = 1 in the method of the present invention. Let it pass.

The present invention is described in detail below with reference to examples, but the method of the present invention is not limited to these.

[0016]

Example 1 As shown in FIG. 1, a pit was excavated up to the groundwater surface flowing out from the pollution source 1, and then an iron powder layer was formed in the pit.

When the contaminated groundwater on the upstream side before being passed through the iron powder layer was analyzed, it was found to have a pH of 4.9 and Cr ⁶⁺ 0.7.
Various heavy metals were contained in the proportions of 6 mg / l, T · Cr 1.2 mg / l and Ni 8.5 mg / l.

When the contaminated groundwater was passed through the iron powder bed at a speed of SV = 1, groundwater was collected and analyzed.
H5.5, Cr ⁶⁺ not detected, T / Cr not detected, Ni0.1
It was possible to remove mg / l and heavy metals more than enough.

[0019]

[Reference Example 1] pH 5.5, C as heavy metal-containing wastewater
Waste water containing 50 mg / l each of u ²⁺ , Cd ²⁺ and Zn ²⁺ ,
When passing through a column packed under substantially the same conditions as the iron powder layer forming conditions in Example 1, the filtrate after passing was
pH 6.6, Cd 0.01 mg / l, Cu 0.01 mg / l, Z
It was n0.01 mg / l, and it was confirmed that the method of the present invention can be applied to contaminated wastewater of this level.

[0020]

[Example 2] Iron powder was treated under substantially the same conditions as in Example 1 except that the other contaminated groundwater containing 5 mg / l each of trichlorethylene and tetrachloroethylene was targeted. The groundwater after passing contained trichlorethylene and tetrachloroethylene at 0.1 mg / l or less, respectively, and it was confirmed that the method of the present invention is also suitable for removing organic chlorine compounds.

[0021]

As described above, the method of the present invention is a treatment method capable of collectively removing heavy metal components and organic chlorine compounds of contaminated groundwater by using inexpensive iron powder as described above, and by permanently replacing iron powder after a certain period of time It can purify contaminated groundwater.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a processing system of the method of the present invention.

[Explanation of symbols]

 1 Pollution source 2 Groundwater 3 Pit 4 Iron powder layer 5 Underground

Claims (1)

[Claims] 1. After excavating a pit to the contaminated water table,
An iron powder layer is provided on the bottom of the pit, and the contaminated groundwater is adjusted to pH 2
A method for purifying contaminated groundwater, characterized in that iron powder removes at least one or more of heavy metals or organic chlorine compounds by allowing the water to pass through within the range of 7 to 7.