JP4743438B2 - Soil purification method - Google Patents

Description

  The present invention relates to a soil purification method for purifying contaminated soil to be purified by planting plants.

  2. Description of the Related Art Conventionally, a plant planting method has been used as a method for purifying soil contaminated with contaminants such as heavy metals, organochlorine compounds, and aromatic organic compounds. That is, when a plant is planted in soil contaminated with a pollutant, the pollutant in the soil is decomposed and removed by a group of microorganisms symbiotically present in the plant and its rhizosphere.

  In such soil purification methods, plant growth, particularly root growth, has a great influence on the purification rate. For this reason, in patent document 1, the peat which promotes the growth of a root is mixed with the purification | cleaning object area | region. According to the method described in Patent Document 1, the growth of plant roots is vigorous by the organic matter contained in the peat, and the contact area between the contaminated soil and the plant roots is increased. The processing speed can be increased.

JP 2006-102689 A

  By the way, even if the root of a plant is the effective depth which can be extended | stretched, it is hard to expand | extend below the groundwater level in which the water is saturated. Therefore, when groundwater exists in the purification target region, it is difficult to expect purification by plants for soil below the groundwater level.

  These problems related to the restriction of the purification treatment range can be solved by lowering the water level by, for example, pumping up groundwater. However, the groundwater pumped from the soil to be purified is likely to be contaminated. Therefore, when the influence on the ground environment is taken into consideration, the pumped-up groundwater must be purified, which is extremely disadvantageous in terms of purification costs, such as requiring water purification equipment.

  In view of the above circumstances, an object of the present invention is to provide a soil purification method capable of reliably purifying soil in a region to be purified without incurring a situation in which the purification processing cost is significantly increased.

  In order to achieve the above object, a soil purification method according to claim 1 of the present invention is a soil purification method for purifying contaminated soil to be purified by planting a plant. When the survey area is below the groundwater level, the groundwater is pumped up to lower the water level, and the pumped groundwater is drained to the planting part in the area to be purified. To do.

  Further, the soil purification method according to claim 2 of the present invention is characterized in that, in the above-described claim 1, when the groundwater is pumped up, the ground surface portion of the purification target region is covered with an airtight sheet. .

  The soil purification method according to claim 3 of the present invention is characterized in that in the above-described claim 1, drainage is performed in a state where plant nutrients are added to the pumped-up groundwater.

  According to the present invention, since the groundwater is pumped to lower the water level, it becomes possible to extend the roots of the plant over the entire area to be purified, and to reliably purify the soil. Become. In addition, since the pumped-up groundwater is drained to the planting part of the plant in the purification target area, there is no need for water purification equipment and there is no possibility that the purification cost will increase significantly.

  Exemplary embodiments of a soil purification method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram showing soil to which a purification method according to an embodiment of the present invention is applied. Soil area to be purified (hereinafter referred to as "Purification area A") is preliminarily surveyed in advance, so that heavy metals, organochlorine compounds, aromatic organic compounds, etc. are available at an effective depth at which plant roots can be extended. In particular, a part of the pollutant B exists further below the groundwater level C.

  In order to purify the purification target area A, a water blocking wall 10 is first constructed around the purification target area A as shown in FIG. The water blocking wall 10 is for isolating the groundwater existing in the purification target area A from the groundwater in other portions, and is provided so that the lower end thereof reaches the impermeable layer D existing below the groundwater.

  Next, a vertical hole 20 reaching the groundwater is formed in a region surrounded by the water blocking wall 10, and a pumping pump 21 is installed in the vertical hole 20. An irrigation drain pipe 23 is connected to the discharge port of the pumping pump 21 through a communication passage 22. The irrigation drain pipe 23 is a tubular member having a plurality of drain holes 23a in the peripheral wall, and as shown in FIG. 3, in the soil of the purification target area A, the irrigation drain pipe 23 is substantially horizontal to the upper part thereof. It is arranged. Further, a sensor (not shown) for measuring the concentration of the pollutant B is disposed in the communication passage 22 or the irrigation drain pipe 23.

  A replenishment passage 24 is connected to the irrigation drain pipe 23. The supply passage 24 is for supplying nutrients and oxygen for promoting the growth of plant roots to the irrigation drain pipe 23 from the ground.

  Furthermore, the plant 30 is planted in the purification target area A, and the ground surface exposed to the outside is covered with the airtight sheet 40.

  When the pumping pump 21 is driven in the above-described state, the groundwater is pumped up sequentially, and the water level C in the region surrounded by the water blocking wall 10 is lowered as shown in FIG. It appears above the groundwater level C. As a result, the root 31 of the planted plant 30 can be extended and prospered to the entire region A to be purified, and the soil B is decomposed and absorbed together with the microorganisms in the rhizosphere to purify the soil. Will be able to.

  Although not shown in the figure, the water level C in the region surrounded by the water blocking wall 10 is targeted by detecting the water level C in the region surrounded by the water blocking wall 10 using a water level sensor. When the water level drops, the pumping pump 21 is stopped. On the other hand, when the water level C in the area surrounded by the water blocking wall 10 rises from the target water level due to rain water or the like, the pumping pump 21 is driven to pump up the groundwater. Good.

  Moreover, the groundwater pumped up by the pumping pump 21 is drained into the purification target area A via the irrigation drain pipe 23 and absorbed by the root 31 of the plant 30. For this reason, even if the groundwater pumped up is contaminated, there is no possibility of affecting the ground environment, and it is not necessary to provide water purification equipment, so the purification processing cost does not increase significantly. In this case, since the ground surface of the purification target area A is covered with the airtight sheet 40, even if the volatile pollutant B is contained in the groundwater, there is no possibility that it will vaporize and ooze out on the ground.

  Furthermore, if nutrients and oxygen are supplied to the drainage pipe 23 for irrigation, the nutrients and oxygen can be sprayed to the plant 30 together with the discharged groundwater, so that the growth of the root 31 of the plant 30 is promoted. It is possible to improve the purification processing speed.

  Furthermore, by monitoring the contamination concentration of groundwater with a concentration measurement sensor (not shown), it can be estimated that the purification is completed when the contamination concentration of the groundwater decreases and reaches the purification target value. Therefore, when the contamination concentration of the groundwater becomes equal to or less than the purification target value, the pumping pump 21 can be stopped and the pumping of the groundwater can be completed.

  Note that the method for monitoring the concentration of groundwater contamination is not necessarily limited to that described above, and monitoring may be performed periodically.

  Thus, according to the above purification method, it becomes possible to apply the pollutant B below the groundwater level C, which has been difficult to purify in the past, and solve the problem relating to the limitation of the purification treatment range. Will be able to. Moreover, since groundwater pumped up from the soil to be purified is drained into the soil, it is extremely advantageous in terms of purification treatment costs, such as eliminating the need for water purification equipment.

It is the conceptual diagram which showed the soil used as the application object of the purification method which is embodiment of this invention. It is the conceptual diagram which applied the purification method of this invention with respect to the soil shown in FIG. FIG. 3 is a plan view of FIG. 2. It is the conceptual diagram which applied the purification method of this invention with respect to the soil shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Water blocking wall 20 Vertical hole 21 Pumping pump 22 Connection passage 23 Drain pipe for irrigation 23a Drain hole 24 Supply passage 30 Plant 31 Root 40 Airtight sheet A Area to be purified B Contaminant C Groundwater level D Impervious layer

Claims (3)

In a soil purification method that purifies contaminated soil to be purified by planting a plant,
A ground survey of the area to be purified is conducted in advance, and if the area to be purified reaches below the groundwater level, the groundwater is pumped up to lower the water level, and the pumped groundwater is planted in the area to be purified. A soil purification method characterized by draining.   The soil purification method according to claim 1, wherein when the groundwater is pumped up, the surface portion of the region to be purified is covered with an airtight sheet.   The soil purification method according to claim 1, wherein drainage is performed in a state where plant nutrients are added to the pumped-up groundwater.

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