JP3377417B2 - Purification method for underground contaminated ground - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a state in which a substance such as methylbenzene or ethylbenzene which is insoluble in water and has a specific gravity smaller than water (referred to as a sparingly soluble substance) is floating and diffused as a liquid layer above the groundwater level. The present invention relates to a method for efficiently purifying a certain underground pollution by a relatively simple operation.

[0002]

2. Description of the Related Art As a method for cleaning soil contaminated with hardly soluble substances such as methylbenzene and ethylbenzene, when hardly soluble substances exist as gas in the unsaturated layer in the ground above groundwater, As shown in FIG. 1, a method of providing a gas suction pump in the contaminated area and exhausting the hardly soluble substance in the ground from the ground in a gaseous state is effective.

However, when the pollutant concentration becomes high or when the hardly soluble substance is concentrated and descends to reach the groundwater level due to other reasons, the specific gravity of these substances is generally smaller than that of water. , As a liquid phase floating and accumulating on the water surface, as shown in Fig. 2, the hardly soluble substance stays as a liquid layer on the water surface at the natural groundwater level. This liquid layer cannot be removed by the above-mentioned gas suction method, but this concentrated hardly soluble substance migrates and diffuses with the flow of groundwater,
The processing becomes more difficult.

[0006] As a countermeasure against this, it is conceivable that the liquid near the water surface at the groundwater level is pumped up and collected in a state where the liquid is mixed with the groundwater, but the groundwater level has a spread depending on the form of the ground. Therefore, it is necessary to drill many wells with a fairly dense distribution, and after pumping, it is necessary to separate a small amount of hardly soluble substances from a large amount of pumping liquid. However, the purification efficiency cannot be expected so much even though the amount becomes large.

Therefore, it is possible to pump up only the liquid layer above the water surface at the groundwater level, but the thickness of the liquid layer is very thin, and the thickness varies depending on the location. It is practically difficult to pump well, and a large number of pumping pipes must be drilled at high density over the entire area of the contaminated area. Therefore, even in this case, great results cannot be expected despite the increased equipment and labor.

[0006]

[Problems to be Solved by the Invention]
The present invention intends to efficiently purify underground contamination in which a hardly soluble substance is floating and diffused as a liquid layer on the groundwater level by a relatively simple operation.

[0007]

[Means for Solving the Problems] According to the present invention, in an underground contaminated area where a stock solution of a hardly soluble substance exists above a natural groundwater level, a pumping well deeper than the groundwater level is drilled in the area. , The groundwater is pumped from this pumping well by a pumping pump to lower the groundwater level near the pumping well, and the concentrated liquid layer of the hardly soluble substance is collected by gravity on the surface of the lowered groundwater level . A pumping well for pumping the collected liquid
A method for purifying ground contaminated ground is provided, which comprises pumping the collected liquid of the undiluted layer to the ground with a pump for pumping .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The underground contaminated area targeted by the present invention is where a stock solution layer of a hardly soluble substance exists above the natural groundwater level. The sparingly soluble substance targeted by the present invention is
It is a substance that forms a liquid layer that is insoluble in water and has a smaller specific gravity than water, such as organic compounds such as methylbenzene, ethylbenzene, and xylene. However, if it is a liquid that floats on the water surface at the groundwater level, In principle, it can be recovered by the present invention. Also, the undiluted layer of the hardly soluble substance does not need to be completely separated from the water surface at the groundwater level, and even if the hardly soluble substance is suspended in water or mixed with other substances in a liquid state. Good.

A well for the purpose of pumping water is drilled in such an underground contaminated area. FIG. 3 schematically shows the example. FIG. 3 shows an example in which two pumping wells 1 are bored at a predetermined interval. When the pumping pump 2 of each well starts pumping, the initial natural groundwater level begins to drop, and the groundwater level near the wells 1 is lowest as shown in the figure. With the decrease in the groundwater level, the liquid layer of the hardly soluble substance that has been diffused and suspended above the natural groundwater level in this area also naturally collects in the vicinity of each well 1. However, the liquid level of the hardly soluble substance does not decrease so much even in the vicinity of each well 1, and is maintained at a level close to the liquid level before starting pumping. That is, the uppermost liquid level of both groundwater and liquid layer does not change so much even when pumping is performed. The liquid level of the hardly soluble substance shown in FIG. 3 shows the liquid level after pumping, which is almost the same as that before pumping. This means that as a result of the concentrated liquid layer of the hardly soluble substance being collected in the vicinity of each well 1, the liquid layer becomes thick.

When the layer thickness becomes thick, the pumping well 3 is pierced and the pumping pump 4 discharges the liquid of the hardly soluble substance to the ground. Since the liquid layer is thick, the proportion of water in the lower layer entrained when pumping up is low, and a large amount of highly concentrated hardly soluble substance liquid can be efficiently pumped to the ground.

In this way, when the pumping from the pumping well 1 and the pumping from the pumping well 3 are repeatedly continued, the hardly soluble substance liquid in the area where the pumping well 1 performs the collecting action is Since it will be depleted soon, only water will be pumped from the pumping well 3 as well, and with this, the discharge of the hardly soluble substance in the area at that point is completed.

FIG. 3 shows an example in which one pumping well 3 is pierced at an intermediate position between two pumping wells 1. This example shows a contaminated area as shown on the left side of FIG. Can be applied when is relatively narrow. When the contaminated area is wide, as shown on the right side of Fig. 4, a larger number of pumping wells 1 are provided, and one or several pumping wells 3 are surrounded by these wells. You can do well.

[0013]

As described above, according to the present invention,
It is possible to efficiently discharge the liquid of the hardly soluble substance from the ground with a small number of the wells. In other words, the number of pumping wells is increased as compared to the case where the pumping wells are not drained and only the pumping wells are used to discharge the liquid, but in the former case, pumping is performed. Since a large number of wells for use are used and the liquid is pumped little by little from these many wells, the total number of the wells is much larger than that of the latter, and the pumping efficiency is poor. , The concentration of hardly soluble substances in the pumped liquid will also be low.

On the other hand, according to the method of the present invention, since the pumping water from the pumping well exerts the effect of collecting the hardly soluble substance, it is possible to discharge the solution intensively with a small number of pumping wells. You can Further, according to the present invention, in the pumping well, since the liquid of the hardly soluble substance can be pumped up from the liquid layer having a large thickness, it is possible to obtain the drainage having a high concentration of the hardly soluble substance. For this reason, the efficiency of the secondary treatment of the waste liquid is improved as compared with the case of pumping up a liquid having a large water content. On the other hand, since only water that does not contain hardly soluble substances is pumped from the pumping well, this can be directly treated as waste water. Therefore, the effect of facilitating the drainage treatment is achieved, and the liquid can be discharged to the ground very efficiently in terms of equipment and labor as a whole.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a conventional example in which an insoluble pollutant layer in which a hardly soluble substance is present in a gas state in the ground is removed by a gas suction pump.

FIG. 2 is a schematic cross-sectional view schematically showing a state in which a hardly soluble substance exists in a liquid layer on the surface of water at the natural groundwater level in the ground.

FIG. 3 is a diagram for explaining the method of the present invention, showing a state in which a liquid of a hardly soluble substance is collected on the surface of the groundwater level lowered by pumping from a pumping well, and a pumping well for pumping this liquid. It is a schematic sectional drawing which shows the state in which it was well.

FIG. 4 is an arrangement plan view of wells showing an example in which a pumping well and a pumping well are crossed according to the present invention when the contaminated area is narrow and wide.

[Explanation of symbols]

1 pumping well 2 Pumping pump 3 pumping well 4 Lifting pump

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-284753 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 17/00-17/12 B09C 1 / 04

Claims (2)

(57) [Claims] 1. A ground contaminated areas there is a stock layer hardly soluble substance on the natural water table, drilled deeper pumping wells than the groundwater level in the area, pumping Pont from this pumping wells
Flop in lowering the water table pumping wells near pumped the groundwater, the stock layer hardly soluble substance on the water surface of the reduced water table is condensed liquid by gravity, to the liquid being pumped the liquid collection of the stock solution layer
For the pumping well to collect the liquid in the undiluted layer
A method for purifying ground that is contaminated underground. 2. A pumping wells is a plurality of drilled purification method of underground pollution ground according to claim 1, well drilling the liquid being pumped well within the ranges or surrounded sandwiched these pumping wells.