JP2006223956A

JP2006223956A - Polluted soil modifying method

Info

Publication number: JP2006223956A
Application number: JP2005038789A
Authority: JP
Inventors: Hitoshi Yanase; 仁志柳瀬
Original assignee: Kyowa Electric Wire Co Ltd
Current assignee: Kanzacc Co Ltd
Priority date: 2005-02-16
Filing date: 2005-02-16
Publication date: 2006-08-31

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively remove a pollutant such as heavy metals or the like, which are contained in an area set to a designated area according to the Soil Pollution Law to be blocked, in a short period using a water supply well and a water pumping-up well. <P>SOLUTION: The water supply well used for the automatic supply of water is excavated in a polluted area and a water level sensor is attached to the water supply well to always keep a predetermined water supply amount while the water pumping-up well is excavated so as to be arranged on the downstream side of the water supply well. The water pumping-up well is made deeper than the water supply well to penetrate the injected water, which is sent to the polluted area from the water supply well, in a peripheral direction and a depth direction in the ground. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、土壌汚染法によって指定区域となって封鎖された地域について、その地域に含まれる重金属類などの汚染物質を給水井と揚水井を用いて除去することにより、土壌改良を短期間に安価で行なう汚染土壌の改質方法に関する。 The present invention removes pollutants such as heavy metals contained in a designated area by the Soil Contamination Law using a water supply well and a pumping well, thereby enabling soil improvement in a short period of time. The present invention relates to a method for modifying contaminated soil at low cost.

工場排水の浸透、工場における有害物質の長期滞積、産業廃棄物の不法投棄、廃棄物の埋立て処分などによって、土壌汚染が進んで指定区域となった土地に対して、一般的に、浄化処理法や土壌の入替え法などが実施されている。この入替え法は、汚染土壌の総てを掘削撤去して良質土を埋め戻す。この入替え法は、汚染域の深度がごく浅い場合には有効な手段であっても、汚染域の深度が約５ｍ以上のように深くなると、土壌の掘削量が急増して処理費用が膨大になってしまう。 In general, purification of land that has become designated areas due to infiltration of industrial wastewater, long-term stagnation of hazardous substances in factories, illegal dumping of industrial waste, landfill disposal of waste, etc. Treatment methods and soil replacement methods are being implemented. This replacement method excavates and removes all contaminated soil and backfills it with good quality soil. This replacement method is an effective means when the depth of the contaminated area is very shallow, but if the depth of the contaminated area becomes deeper than about 5 m, the amount of excavation of the soil will increase rapidly and the processing cost will be enormous. turn into.

一方、浄化処理法として、土壌汚染対策法施行以前では、汚染土壌の周囲に複数本の井戸を穿孔し、汚染された地下水をポンプで汲み上げて浄化していた。この浄化処理法では、揚水井と同じ深さの給水井を該揚水井の上手に穿孔して地下水を処理するために、汚染区域の深度が深く且つ該汚染区域が地下水位よりも下部の帯水層にあり、該帯水層中に廃棄物または汚染土壌が含まれていても有効である。例えば、透水層の下方に存在する不透水層の高さを測定し、該不透水層の標高の高い側に給水井を穿孔して水を強制的に注入する。注入した水は標高の低い側に流れ、汚染区域を通過する際に、該汚染区域から汚染物質を溶出する。揚水井は、不透水層の標高の低い側に適宜穿孔され、汚染物質が溶出した汚染水をポンプで地上に汲み上げ、水処理プラントで汚染物質を除去し、処理済みの水を再び給水井に注入して循環させる。また、給水井および揚水井には、汚染区域の深度に対応する深さ位置においてネット状のスクリーンを設け、該スクリーンによって地下水および注水の標高差による自然な流れは期待できなくても、汚染土壌の地表面を表面遮水工で覆うことにより、雨水などが土壌中へ浸透することを防止できる。 On the other hand, prior to the enforcement of the Soil Contamination Countermeasures Law, multiple wells were drilled around the contaminated soil, and the contaminated groundwater was pumped up and purified. In this purification method, in order to treat the groundwater by drilling a water supply well having the same depth as the pumping well into the top of the pumping well, the depth of the contaminated area is deep and the contaminated area is below the groundwater level. It is effective even if the aquifer contains waste or contaminated soil. For example, the height of the impermeable layer existing below the permeable layer is measured, and a water supply well is drilled on the higher elevation side of the impermeable layer to forcibly inject water. The injected water flows to the low altitude side, and when passing through the contaminated area, pollutants are eluted from the contaminated area. The pumping well is drilled as needed on the low elevation side of the impermeable layer, pumping the contaminated water from which the pollutants have eluted, removing the pollutants at the water treatment plant, and treating the treated water again into the water supply wells. Inject and circulate. In addition, the water supply well and the pumping well are provided with a net-like screen at a depth corresponding to the depth of the contaminated area, and even if a natural flow due to the difference in elevation of groundwater and water injection cannot be expected by the screen, the contaminated soil By covering the ground surface with a surface impermeable construction, it is possible to prevent rainwater and the like from penetrating into the soil.

特開平１１−９０４１０号で開示した改質法は、地下水位より上方に位置する汚染域を浄化対象としており、給水井の透水孔および揚水井の吸引孔をともに地下水位より上方に位置させ、揚水井の吸引孔だけを地下水位の直下に配置する。給水井に注入する媒体として、熱水、加熱空気、酸性溶液、アルカリ性溶液、界面活性剤または有機溶剤を例示している。特開２００４−３１３８１５号では、汚染域および注水を加熱する媒体を該汚染域に注入することにより、粘性が高かったりまたは水への溶解度が小さい汚染物質が注入水および地下水へ溶出することを促進する。また、特開２００４−３３００８４号では、注水に弱酸性または弱アルカリ性物質を添加する。
特開平１１−９０４１０号公報特開２００４−３１３８１５号公報特開２００４−３３００８４号公報 The reforming method disclosed in Japanese Patent Application Laid-Open No. 11-90410 is intended to purify a contaminated area located above the groundwater level. Only the suction hole of the pumping well is placed directly below the groundwater level. Examples of the medium injected into the water supply well include hot water, heated air, acidic solution, alkaline solution, surfactant or organic solvent. In Japanese Patent Application Laid-Open No. 2004-313815, by introducing a medium for heating a contaminated area and water injection into the contaminated area, it is promoted that pollutants having high viscosity or low solubility in water are eluted into the injected water and groundwater. To do. In Japanese Patent Application Laid-Open No. 2004-330084, a weakly acidic or weakly alkaline substance is added to the water injection.
Japanese Patent Laid-Open No. 11-90410 JP 2004-313815 A JP 2004-330084 A

特開平１１−９０４１０号の改質法は、給水井のスクリーンが地下水位より上部に配置されているため、地下水流による汚染物質の洗浄効果が期待できず、給水井からの注水だけの洗浄効果となり、浄化期間を短縮するには大量の注水を供給する必要がある。また、汚染区域の地中において、注水の通り道にある汚染物だけを洗浄し、通り道以外の汚染物を洗浄することができない。 In the reforming method of Japanese Patent Laid-Open No. 11-90410, since the screen of the water supply well is arranged above the groundwater level, it is not possible to expect a cleaning effect of pollutants by the groundwater flow, and a cleaning effect of only water injection from the water supply well Therefore, in order to shorten the purification period, it is necessary to supply a large amount of water. Further, in the ground of the contaminated area, it is not possible to clean only the contaminants on the water injection path and not to clean the contaminants other than the path.

前記の改質法において、注入媒体として熱水、加熱空気、弱酸性または弱アルカリ性物質などを使用するため、所定の物質の製造費用分および注水に対する添加費用分がコスト高になるうえに、注入媒体による２次汚染のおそれが生じる。また、溶解度が小さい汚染物質は、土壌粒子に吸着したままで注水に溶出されにくいために、単位時間当たりの浄化効率が小さく、浄化期間が長期化する事態が発生しやすい。 In the above-described reforming method, hot water, heated air, weakly acidic or weakly alkaline substance, etc. are used as the injection medium. There is a risk of secondary contamination by the medium. In addition, since the pollutant having low solubility remains adsorbed to the soil particles and is not easily eluted into the water injection, the purification efficiency per unit time is small, and a situation in which the purification period is prolonged tends to occur.

本発明は、従来の改質法に関する前記の問題点を改善するために提案されたものであり、所定長さで所要数の給水井と揚水井ならびに水処理プラントを組み合わせることで汚染土壌の浄化を促進し、汚染域内の浄化処理を短期間に安価で行なう汚染土壌の改質方法を提供することを目的としている。本発明の他の目的は、確定した汚染域内を浄化することで土壌の入替え量を減らし且つ安価に土壌改良を行なう汚染土壌の改質方法を提供することである。 The present invention has been proposed in order to improve the above-described problems related to the conventional reforming method, and purifies contaminated soil by combining a required number of water supply wells, pumping wells and a water treatment plant with a predetermined length. The purpose is to provide a method for improving contaminated soil, in which the purification treatment in the contaminated area is performed at a low cost in a short period of time. Another object of the present invention is to provide a method for modifying contaminated soil, which reduces the amount of soil replacement by purifying the confirmed contaminated area and improves the soil at low cost.

本発明に係る汚染土壌の改質方法は、汚染域において自動給水する給水井を穿孔し、該給水井には水位センサを取り付けて常に所定の給水量を保持する。一方、揚水井を給水井より下手に配置して穿孔し、該揚水井の深さが給水井のそれよりも深いことにより、給水井から汚染域に送り込んだ注水は地中で周辺方向および深さ方向に浸透し、汚染物質を溶出させてから揚水井で地上に汲み上げる。 In the method for modifying contaminated soil according to the present invention, a water supply well for automatically supplying water in a contaminated area is drilled, and a water level sensor is attached to the water supply well to always maintain a predetermined water supply amount. On the other hand, the pumping well is located below the water supply well and drilled, and the depth of the pumping well is deeper than that of the water supply well. It penetrates in the right direction and elutes pollutants, and then pumps it up to the ground with a pumping well.

本発明の改質方法では、粘度またはシルトなどの遮水層が深さ３〜１０ｍに形成された土地において、止水壁を遮水層まで打ち込んで暫定汚染域を確定すると好ましい。この改質方法は、暫定汚染域内に設けた給水井から注水を常に地中へ送り込み、地中において暫定汚染域を経由して流通させ、汚染物質を溶出させてから注水を揚水井で取り出し、該揚水井から汲み上げた地下水を水処理プラントによって浄化すればよい。 In the reforming method of the present invention, in a land where a water-impervious layer such as viscosity or silt is formed at a depth of 3 to 10 m, it is preferable to drive a water blocking wall up to the water-impervious layer to determine a temporary contamination area. In this reforming method, water injection is always sent from the water supply well provided in the temporary contaminated area to the ground, circulated through the temporary contaminated area in the ground, the pollutant is eluted, and the injected water is taken out from the pumping well. What is necessary is just to purify the groundwater pumped up from this pumping well by a water treatment plant.

本発明の改質方法において、止水壁によって表面積５０〜２５０ｍ^２の暫定汚染域を確定し、給水井は暫定汚染域内において深さ２〜８ｍで１本または複数本であり、揚水井は深さ２．５〜９．５ｍで給水井と同数またはそれ以上の本数を有する。また、給水井への注水は、水道管から直接常圧で供給するか、または送水ポンプによって加圧しながら地中へ送り込むと好ましい。 In the reforming method of the present invention, a temporary contaminated area having a surface area of 50 to 250 m ² is determined by the water blocking wall, and the water supply well is one or more at a depth of 2 to 8 m in the temporary contaminated area. The length is 2.5 to 9.5 m, which is the same as or more than the water well. Moreover, it is preferable that the water injection to the water supply well is supplied directly from the water pipe at normal pressure or is fed into the ground while being pressurized by a water pump.

本発明方法を図面によって説明すると、土壌汚染法で指定区域となって封鎖された汚染土壌に本発明方法を適用するには、その土地が所定の地層で構成されていることが望ましい。この地層を図１に例示し、一般に、地下水位２６（図３）を含む第１帯水層１が重金属類などからなる汚染層であり、この汚染層は地表から地中１０ｍ程度までの深度に形成されている。地下水位２６より上方の透水層は、例えば、透水係数が１０^−２〜１０^−４ｃｍ／秒程度の地下水の流速が早い砂質土からなる層である。 The method of the present invention will be described with reference to the drawings. In order to apply the method of the present invention to contaminated soil blocked as a designated area by the soil contamination method, it is desirable that the land is composed of a predetermined stratum. This stratum is illustrated in FIG. 1. Generally, the first aquifer 1 including the groundwater level 26 (FIG. 3) is a polluted layer made of heavy metals and the like, and this polluted layer has a depth from the surface to about 10 m below the ground. Is formed. The permeable layer above the groundwater level 26 is, for example, a layer made of sandy soil having a water permeability coefficient of about 10 ⁻² to 10 ⁻⁴ cm / sec and a high groundwater flow rate.

汚染層に含まれる汚染物質は、例えば、鉛，カドミウムなどの重金属、ホウ素，フッ素，ヒ素などの化学物質、ガソリン，軽油などの油類であり、水溶性，非水溶性を問わない。本発明方法では、中性付近のｐＨ値では溶出速度が遅いとされる鉛やカドミウムの重金属類についても、注水および地下水が汚染物質または土壌粒子の隙間を常に広く且つくまなく流れることにより、浄化期間が長期化することはない。 Contaminants contained in the contaminated layer are, for example, heavy metals such as lead and cadmium, chemical substances such as boron, fluorine, and arsenic, and oils such as gasoline and light oil, which may be water-soluble or water-insoluble. In the method of the present invention, even for heavy metals such as lead and cadmium, which are said to have a slow elution rate at a pH value near neutral, water injection and groundwater always flow through the gaps between pollutants or soil particles, and thus purify them. The period will not be prolonged.

前記の地層では、粘度またはシルトなどの遮水層２は不透水層または難透水層とも称し、該遮水層の上面は深さ３〜１０ｍに形成され、その縦幅は５ｍ以上である。遮水層２は、透水係数が１０^−６〜１０^−７ｃｍ／秒程度の沖積粘土層または洪積粘土層からなることが多い。遮水層２が深さ３ｍ未満であれば、本発明方法のように給水井８および揚水井１０を穿孔して改質する必要がなく、深さ１０ｍを超えると本発明方法を適用することは困難である。 In the above-mentioned formation, the water-impervious layer 2 such as viscosity or silt is also referred to as a water-impermeable layer or a hardly water-permeable layer, and the upper surface of the water-impervious layer is formed to a depth of 3 to 10 m, and its vertical width is 5 m or more. The impermeable layer 2 is often composed of an alluvial clay layer or a diluvial clay layer having a hydraulic conductivity of about 10 ⁻⁶ to 10 ⁻⁷ cm / second. If the water shielding layer 2 is less than 3 m in depth, there is no need to drill and modify the water supply well 8 and the pumping well 10 as in the method of the present invention, and if the depth exceeds 10 m, the method of the present invention is applied. It is difficult.

本発明方法では、汚染土壌において、まず第１帯水層１の下方に位置する遮水層２の標高を測定する。この汚染土壌において、止水壁を環状平面になるように打ち込むため、例えば、多数枚の矢板５を遮水層２まで垂直に打ち込み、全周を矢板５で密に取り囲んで表面積１００〜１０００ｍ^２の暫定汚染域７を確定する。暫定汚染域７の表面積が１００ｍ^２未満であれば、本発明方法のように給水井８および揚水井１０を穿孔して改質するまでもなく、表面積が１０００ｍ^２を超えると浄化期間が長期化しやすいので、暫定汚染域７を１０００ｍ^２以下に再分割することが望ましい。例えば、汚染土壌である指定区域の全面積が３２００ｍ^２であれば、８００ｍ^２ずつ分割４回、４００ｍ^２ずつ８回などのいずれでもよいが、通常、暫定汚染域７の表面積は４００〜８００ｍ^２程度が好適である。 In the method of the present invention, in the contaminated soil, first, the altitude of the impermeable layer 2 located below the first aquifer 1 is measured. In this contaminated soil, in order to drive the water blocking wall so as to be an annular plane, for example, a large number of sheet piles 5 are driven vertically to the water shielding layer 2 and the entire circumference is closely surrounded by the sheet piles 5 to have a surface area of 100 to 1000 m ^2. Establish a temporary contamination area 7 If the surface area of the temporary contaminated area 7 is less than 100 m ^2, there is no need to drill and modify the water supply well 8 and the pump well 10 as in the method of the present invention. If the surface area exceeds 1000 m ² , the purification period will be prolonged. Since it is easy, it is desirable to subdivide the temporary contamination area 7 into 1000 m ² or less. For example, if the total area of the designated area which is contaminated soil is 3200 m ^2, it may be divided by 800 m ² by 4 times, 400 m ² by 8 times, etc. Usually, the surface area of the temporary contaminated area 7 is 400 to 800 m ^2. The degree is preferred.

暫定汚染域７内は、給水井８および揚水井１０を除いて土地表面をコンクリート６などの舗装材で被覆する。この舗装材の厚さは、法律で１００ｍｍ以上にすることが規定されている。この舗装材は、最終的に、汚染土壌の入替を多少でも行うならば剥離されることになる。暫定汚染域７において、遮水層２に達する深さの止水壁で汚染土壌の外周を包囲し、且つ地表面を遮水性の舗装材で覆うことにより、汚染物質が周囲へ漏出することを防ぎ、雨水などが汚染土壌中へ浸透することを防止する。 In the temporary contamination area 7, the land surface is covered with a pavement material such as concrete 6 except for the water supply well 8 and the pumping well 10. The law specifies that the thickness of the paving material is 100 mm or more. This paving material will eventually be peeled off if any contamination soil is replaced. In the temporary contamination area 7, the outer periphery of the contaminated soil is surrounded by a water blocking wall having a depth reaching the water shielding layer 2, and the ground surface is covered with a water-impervious pavement so that the pollutant leaks to the surroundings. Prevent rainwater from penetrating into contaminated soil.

暫定汚染域７において、所要数の給水井８を遮水層２の標高の高い側に掘削・穿孔するし、該給水井に水を送り込む。給水井８は、直径１００〜２００ｍｍ程度であると、十分な給水量を保ちうるうえで好ましい。給水井８は、揚水井１０の上手に設置し、その深さは、深さ２〜８ｍであって、遮水層２の標高の高い側であるから揚水井１０よりも浅くなり、通常、第１帯水層１の深さの５０〜８０％の深さであると、暫定汚染域７内において注水が横方向および深さ方向に浸透しやすいので好ましい。給水井８からの注水は、送水ポンプなどの圧力装置を用いて強制的に行なうと、地中における水拡散を促進する効果が向上する反面、設備費用がアップになる。 In the provisional contaminated area 7, a required number of water wells 8 are excavated and drilled on the higher elevation side of the impermeable layer 2, and water is fed into the water wells. The water supply well 8 is preferably about 100 to 200 mm in diameter because it can maintain a sufficient amount of water supply. The water supply well 8 is installed on the upper side of the pumping well 10, and the depth is 2 to 8 m, and since it is on the higher altitude side of the impermeable layer 2, it becomes shallower than the pumping well 10, A depth of 50 to 80% of the depth of the first aquifer 1 is preferable because water injection easily permeates in the lateral direction and the depth direction in the temporary contaminated area 7. If the water injection from the water supply well 8 is forcibly performed using a pressure device such as a water pump, the effect of promoting water diffusion in the ground is improved, but the equipment cost is increased.

給水井８の本数は、該給水井の直径と深さにも依存するが、一般に暫定汚染域７の広さに応じて定め、通常は暫定汚染域７の表面積が４００ｍ^２以下であれば１本、表面積が８００ｍ^２を超えると３本程度であると、給水量が不足することが少ないので好ましい。地下水流に関して、上手側の給水井８は常に所定の給水量を保つだけでよく、水位センサを取り付けて自動給水しても、数本の給水井８であれば手動処理も可能である。 The number of the water supply wells 8 depends on the diameter and depth of the water supply wells, but is generally determined according to the size of the temporary contaminated area 7, and normally 1 if the surface area of the temporary contaminated area 7 is 400 m ² or less. When the surface area exceeds 800 m ² , it is preferable that the number is about 3 because the amount of water supply is rarely insufficient. Regarding the groundwater flow, the upper-side water supply well 8 only needs to always maintain a predetermined water supply amount, and even if the water level sensor is attached and automatic water supply is performed, if there are several water supply wells 8, manual processing is possible.

給水井８の水位センサは、例えば、給水井８内で通常２個１組に取り付けると好ましい。図示しないけれども、送水管開閉用のソレノイドバルブを水道管に介在させ、渇水用の水位センサを地表面より−３０ｃｍおよび停止用の水位センサを地表面に設置し、該バルブと両水位センサをそれぞれ接続する。給水井８の水面が地表面より−３０ｃｍ以下に下がると、渇水用の水位センサが作動し、ソレノイドバルブを開いて自動的に給水し、水面が地表面に達するとソレノイドバルブを閉じて給水を停止する。 The water level sensors of the water supply wells 8 are preferably attached to a set of usually two in the water supply well 8, for example. Although not shown, a solenoid valve for opening and closing the water pipe is interposed in the water pipe, a water level sensor for drought is -30 cm from the ground surface, and a water level sensor for stopping is installed on the ground surface. Connecting. When the water level of the water supply well 8 falls below -30 cm below the ground surface, the water level sensor for drought is activated and the solenoid valve is opened to automatically supply water. When the water surface reaches the ground surface, the solenoid valve is closed to supply water. Stop.

一方、所要数の揚水井１０を遮水層２の標高の低い側に掘削・穿孔し、汚染物質が溶出した汚染水を揚水井１０を通してポンプ１２で地上に汲み上げる。揚水井１０は、給水井８と同様に直径１００〜２００ｍｍ程度であると、十分な揚水量を確保できるので好ましい。揚水井１０は、給水井８の下手に設置し、その深さは、２．５〜９．５ｍであって、遮水層２の標高の低い側であるから給水井８の深さよりも大きく、通常、第１帯水層１の深さの７０〜９５％の深さであると、暫定汚染域７内において横方向および深さ方向に浸透した注水および地下水を汲み上げやすいので好ましい。 On the other hand, the required number of pumping wells 10 are excavated and drilled on the low elevation side of the impermeable layer 2, and the contaminated water from which the pollutants are eluted is pumped to the ground through the pumping well 10 by the pump 12. The pumping well 10 is preferably about 100 to 200 mm in diameter like the water supply well 8 because a sufficient pumping amount can be secured. The pumping well 10 is installed below the water supply well 8, and the depth thereof is 2.5 to 9.5 m, which is larger than the depth of the water supply well 8 because it is on the low elevation side of the impermeable layer 2. Usually, it is preferable that the depth is 70 to 95% of the depth of the first aquifer 1 because water injection and groundwater that have penetrated in the lateral direction and the depth direction in the temporary contaminated area 7 are easily pumped up.

揚水井１０の本数は、一般に暫定汚染域７の広さ、土質、給水井８の注水量などに依存するが、通常は暫定汚染域７の表面積が４００ｍ^２以下で２〜３本、４００〜８００ｍ^２で３〜６本、表面積が８００ｍ^２を超えると６本以上であり、暫定汚染域７内で分散配置すると、揚水量が不足することが少ないので好ましい。揚水井１０には、汚染域７の深度に対応する深さ位置に、編目状のスクリーンを設けてもよく、該スクリーンによって、汚染水を揚水井１０に吸い上げる際に土壌が揚水井１０に侵入することを防ぐ。このスクリーンが地下水および注水の標高差による自然な流れを阻害するならば、該スクリーンの取り付けを要しない。 The number of pumping wells 10 generally depends on the size of the temporary contaminated area 7, the soil quality, the amount of water injected into the water supply well 8, etc., but usually the surface area of the temporary contaminated area 7 is 400 m ² or less, 2 to 3 3-6 present in 800 m ^2, the surface area is at least six exceeds 800 m ^2, when distributed in the provisional contaminated zone 7, preferred because pumping amount that is less likely to lack. The pumping well 10 may be provided with a knitted screen at a depth corresponding to the depth of the contaminated area 7, and when the contaminated water is sucked into the pumping well 10, the soil enters the pumping well 10. To prevent. If this screen obstructs the natural flow due to the difference in elevation between groundwater and water injection, it is not necessary to install the screen.

本発明の改質方法において、給水井８は、通常、水位センサを用いて自動給水を行い、揚水井１０の上手に設置することを要する。前記の水位センサにより、給水井８への水補給は、例えば、水面が地表面より−３０ｃｍに下がると自動的に給水するように設定する。給水井８は揚水井１０よりも浅く、浅くすることで送り込まれた注水は、封鎖された暫定汚染域７内で横方向および深さ方向に浸透し、汚染土壌中の重金属の溶出して浄化を促進する。このため、給水井８を浅く穿孔する方が効果的であり、しかも水の使用量および給水井８の設置費用が安価になる。 In the reforming method of the present invention, the water supply well 8 usually requires automatic water supply using a water level sensor, and needs to be installed on the top of the pumping well 10. With the water level sensor, water supply to the water supply well 8 is set to automatically supply water when, for example, the water surface falls to −30 cm from the ground surface. The water supply well 8 is shallower than the pumping well 10, and the water injection sent by making it shallow will permeate in the lateral and depth directions within the sealed temporary contaminated area 7, and the heavy metals in the contaminated soil are eluted and purified. Promote. For this reason, it is more effective to drill the water supply well 8 shallowly, and the amount of water used and the installation cost of the water supply well 8 are reduced.

給水井８への注水について、ｐＨ値が中性であると溶出速度が遅いヒ素、カドミウムなどの重金属が多量に存在する場合、この注水に弱酸性や弱塩基性物質を少量添加して溶出を促進させることも可能である。添加剤を加えた注水および第１帯水層１を流れる地下水は、標高の低い側へ流れ、汚染区域を通過する際に、該汚染区域内の遊離または土壌粒に吸着の汚染物質を容易に注水や地下水へ溶出する。第１帯水層１中の汚染物質および土壌粒は、地下水と充分になじんでいるため、注水および地下水は汚染物質や土壌粒の隙間をくまなく流れる。したがって、注水に加えた添加剤は、汚染物質や土壌粒子および地下水と接触し、汚染物質の溶出が汚染区域の全般にわたって迅速に行われる。 For water injection into the water supply well 8, if a heavy metal such as arsenic or cadmium has a slow elution rate when the pH value is neutral, a small amount of weakly acidic or weak basic substance is added to the water injection for elution. It can also be promoted. Water injected with additives and groundwater flowing through the first aquifer 1 flows to the lower altitude side, and when passing through the contaminated area, it is easy for free contaminants in the contaminated area or adsorbed pollutants to soil grains. Elutes into injected water and groundwater. Since the pollutants and soil grains in the first aquifer 1 are sufficiently familiar with groundwater, the water injection and groundwater flow through the gaps between the pollutants and soil grains. Therefore, the additive added to the water injection comes into contact with pollutants, soil particles and groundwater, and the elution of the pollutants takes place quickly throughout the contaminated area.

所要数の揚水井１０を遮水層２の標高の低い側に位置することにより、汚染物質が溶出した汚染水を各揚水井１０を通してポンプ１２で地上に汲み上げる。汲み上げた水は、地上に設置した水処理プラント（図示しない）で順次最終処理を行い、排水の指定基準値以下になるように汚染水から汚染物質を除去した後に放流する。この浄化処理により、土壌汚染法で指定基準を超えた汚染物質を顕著に減らすかまたはほぼ完全に除去することができ、少なくとも入替えが必要な土壌の量が減少する。 By positioning the required number of pumping wells 10 on the lower side of the water shielding layer 2, the contaminated water from which the pollutants are eluted is pumped up to the ground through the pumping wells 10 by the pumps 12. The pumped water is subjected to final treatment in sequence at a water treatment plant (not shown) installed on the ground, and then discharged after removing pollutants from the contaminated water so that it falls below the specified standard value for wastewater. This purification process can significantly reduce or almost completely remove contaminants that exceed the standards specified in the Soil Contamination Law and at least reduce the amount of soil that needs to be replaced.

汚染物質が溶出した汚染水は、水処理プラントで汚染物質が除去された後に、再び給水井８に注入して循環使用することも可能である。この水の循環使用を継続すると、暫定汚染域７の浄化が次第に進行し、放流水を減らすことができる。水処理後の水を循環使用すれば、地下水も利用して汚染物質を洗い流すので浄化期間が短縮され、注水の供給量も節約できるので経済的である。 The polluted water from which the pollutants have been eluted can be reused by being injected again into the water supply well 8 after the pollutants have been removed at the water treatment plant. If the circulation of this water is continued, the purification of the temporary contaminated area 7 gradually proceeds, and the discharged water can be reduced. Recycling water after water treatment is economical because ground water is also used to wash away pollutants, shortening the purification period and saving water supply.

本発明に係る汚染土壌の改質方法では、地下水位よりも下方の汚染域に水を常に供給することにより、所定の汚染域内において汚染物質が地下水へ溶出することを促進し、これを揚水井で汲み出すことだけで汚染土壌の浄化期間を短縮できる。本発明方法において、上手の給水井は常に所定の給水量を保つだけでよく、水位センサを取り付けても手動処理することも可能であり、一方、下手の揚水井から汲み上げた水は水処理プラントに送った後に、該水処理プラントで最終処理を行ってから下水へ排水すればよい。 In the method for reforming contaminated soil according to the present invention, by always supplying water to the contaminated area below the groundwater level, it is promoted that the pollutant elutes into the groundwater within the predetermined contaminated area, It is possible to shorten the purification period of the contaminated soil simply by pumping it out. In the method of the present invention, the upper water supply well only needs to always maintain a predetermined water supply amount, and can be manually processed even if a water level sensor is attached. On the other hand, the water pumped from the lower water well is treated as a water treatment plant. After being sent to the wastewater, the final treatment is performed at the water treatment plant and then drained into sewage.

本発明方法により、指定基準を超えた汚染物質を土壌から排出し、入替えが必要な土壌の量を顕著に減少させることができ、場合によっては汚染物質がほぼ完全に除去されて入れ替え土壌が不要になる。例えば、地下約５ｍまで汚染されていた土壌は、約半年で地下約１ｍまで浄化でき、本発明方法を適用すると、約半年という短期間で汚染土壌の入替量が約１/５となる。したがって、１立方メートル当たりで非常に高価格な土壌入替え費用を節減でき、本発明方法によって汚染土壌の改質処理を安価に実施可能になる。 With the method of the present invention, pollutants exceeding specified standards can be discharged from the soil, and the amount of soil that needs to be replaced can be significantly reduced. In some cases, contaminants are almost completely removed and no replacement soil is required. become. For example, soil contaminated to about 5 m underground can be purified to about 1 m underground in about half a year. When the method of the present invention is applied, the replacement amount of contaminated soil becomes about 1/5 in a short period of about half a year. Therefore, it is possible to save a very expensive soil replacement cost per cubic meter, and the method of the present invention makes it possible to implement a modification treatment of contaminated soil at a low cost.

次に、本発明を実施例に基づいて説明するが、本発明は実施例に限定されるものではない。土壌汚染法によって指定区域となった汚染土壌は、図１に示すような地層を有し、汚染土壌の第１帯水層１の下方において、深さ５．０ｍ以下に不透水層である遮水層２が存在し、さらに深さ１０．０〜１０．５ｍ以下に第２帯水層３が存在する。 Next, the present invention will be described based on examples, but the present invention is not limited to the examples. The contaminated soil that has become a designated area by the Soil Contamination Law has a stratum as shown in FIG. 1 and is an impervious layer having a depth of 5.0 m or less below the first aquifer 1 of the contaminated soil. The water layer 2 exists, and the second aquifer 3 exists at a depth of 10.0 to 10.5 m or less.

ホウ素、フッ素、鉛の重金属に関して指定区域となった汚染土壌について、多数枚の矢板５を遮水層２まで垂直に打ち込み、表面積４００ｍ^２の土地の周囲を矢板５で密に取り囲んだうえに、土地表面をコンクリート６で被覆する。コンクリート６の厚さは、駐車場所となるので２００ｍｍである。図２に例示するように、矩形平面に囲い込んだ暫定汚染域７において、直径１５０ｍｍで深さ３ｍの給水井８を１本穿孔し、該給水井の位置は暫定汚染域７の隅部近傍である。給水井８には、水位センサ（図示しない）を取り付け、該給水井の水面が地表面より−３０ｃｍ以下に下がると、水位センサが作動することによって自動的に給水し、給水井８には常に一定の給水量を保持する。 For contaminated soil that has become a designated area for heavy metals such as boron, fluorine, and lead, a number of sheet piles 5 are driven vertically to the water shielding layer 2 and the area around the surface area of 400 m ² is closely surrounded by the sheet piles 5, Cover the land surface with concrete 6. Since the thickness of the concrete 6 becomes a parking place, it is 200 mm. As illustrated in FIG. 2, in the temporary contamination area 7 surrounded by a rectangular plane, one water supply well 8 having a diameter of 150 mm and a depth of 3 m is drilled, and the position of the water supply well is near the corner of the temporary contamination area 7. It is. A water level sensor (not shown) is attached to the water supply well 8, and when the water level of the water supply well drops below -30 cm below the ground surface, the water level sensor is activated automatically to supply water. Maintain a constant water supply.

一方、給水井８よりも深い揚水井１０を該給水井の下手に穿孔し、揚水井１０の位置は暫定汚染域７において該給水井から離している。揚水井１０の制御システムを図３に例示し、該揚水井に設置するポンプ１２は、例えば、給水量９リットル／分、全揚定７ｍの給水ポンプ（商品名：エバラフレッシャー・ミニ２０ＨＰＮ５、荏原製作所製）である。ポンプ１２の揚水管路１４は、揚水井１０の下端部近傍から揚水井内を上方へ垂直に延設され、地表において水平に屈曲してポンプ１２に至る。一方、ポンプ１２の排水管路１６は、流量計１８を取り付けて水平に延設し、水処理システム（図示しない）へ排水を送る。 On the other hand, a pumping well 10 deeper than the water supply well 8 is drilled below the water supply well, and the position of the pumping well 10 is separated from the water supply well in the temporary contamination area 7. The control system of the pumping well 10 is illustrated in FIG. 3, and the pump 12 installed in the pumping well is, for example, a water supply pump having a feed rate of 9 liters / minute and a total lift of 7 m (trade name: Ebara Fresher Mini 20HPN5, Manufactured by Ebara Corporation. The pumping pipe line 14 of the pump 12 extends vertically upward from the vicinity of the lower end of the pumping well 10 and bends horizontally on the ground surface to reach the pump 12. On the other hand, the drainage pipe line 16 of the pump 12 is attached with a flow meter 18 and extends horizontally to send wastewater to a water treatment system (not shown).

ポンプ１２は、ポンプ制御盤２０と電気的に接続する。制御盤２０には、揚水井１０の下方部に渇水電極２２を、および揚水井上方部に再起動電極２４を設置する。暫定汚染域７において、地下水位２６が渇水電極２２の位置まで下降すると、該電極がオンになって稼働中のポンプ１２を停止する。地下水位２６が再起動電極２４の位置まで上昇すると、該電極がオンになって停止中のポンプ１２が稼動する。ポンプ制御盤２０は揚水制御装置２８と接続し、該装置は流量計１８とも電気的に接続する。 The pump 12 is electrically connected to the pump control panel 20. The control panel 20 is provided with a drought electrode 22 in the lower part of the pumping well 10 and a restart electrode 24 in the upper part of the pumping well. When the groundwater level 26 descends to the position of the drought electrode 22 in the temporary contamination zone 7, the electrode is turned on and the pump 12 in operation is stopped. When the groundwater level 26 rises to the position of the restart electrode 24, the electrode is turned on and the stopped pump 12 is operated. The pump control panel 20 is connected to a pumping control device 28, which is also electrically connected to the flow meter 18.

揚水制御装置２８は、揚水井１０内で該揚水井の下方部に取り付けた水位センサ３０と電気的に接続し、さらに２孔まで測定可能な観測井３２内において、その下方に取り付けた水位センサ３４と接続する。観測井３２は、暫定汚染域７を確定する矢板５の外側に配置し、暫定汚染域７と汚染域外の地下水位２６の差を測定するために用いる。 The pumping control device 28 is electrically connected to the water level sensor 30 attached to the lower part of the pumping well in the pumping well 10, and further attached to the lower part of the observation well 32 that can measure up to two holes. 34 is connected. The observation well 32 is disposed outside the sheet pile 5 that defines the temporary contaminated area 7, and is used to measure the difference between the temporary contaminated area 7 and the groundwater level 26 outside the contaminated area.

図２に示す暫定汚染域７では、３本の揚水井１０を給水井８より下手に配置する。深さ４ｍの揚水井１０ａは、暫定汚染域７のほぼ中央に穿孔する。深さ５ｍの揚水井１０ｂは、暫定汚染域７において給水井８と反対側の側壁中間付近に穿孔する。また、深さ５ｍの揚水井１０ｃは、暫定汚染域７において給水井８と反対側の前後壁中間付近に穿孔する。 In the temporary contaminated area 7 shown in FIG. 2, the three pumping wells 10 are arranged below the water supply well 8. The pumping well 10 a having a depth of 4 m is drilled in the approximate center of the temporary contaminated area 7. The pumping well 10b having a depth of 5 m is drilled near the middle of the side wall on the opposite side to the water supply well 8 in the temporary contamination area 7. Further, the pumping well 10c having a depth of 5 m is drilled near the middle of the front and rear walls on the side opposite to the water supply well 8 in the temporary contamination area 7.

この実施例では、給水井８を揚水井１０の上手に設置し、水位センサを用いて自動給水を行う。給水井８の深さは、各揚水井１０の深さと同等以下に浅くしており、浅くすることで給水された水は、封鎖された暫定汚染域７の範囲内で横方向および深さ方向に浸透し、土壌中の重金属を溶出して浄化を促進する。浄化された水は、最深度の深さまで掘られた揚水井１０によって汲み上げ、ついで水処理プラントに送る。この揚水は、水処理プラント中で順次最終処理を行い、排水の指定基準値以下にした後に放流する。 In this embodiment, the water supply well 8 is installed at the top of the pumping well 10, and automatic water supply is performed using a water level sensor. The depth of the water supply well 8 is shallower than or equal to the depth of each pumping well 10, and the water supplied by making the water well shallower is in the lateral direction and depth direction within the range of the provisional contaminated area 7 that is blocked. Infiltrate the soil and elute heavy metals in the soil to promote purification. The purified water is pumped by the pumping well 10 dug to the deepest depth and then sent to the water treatment plant. This pumped water is finally treated in a water treatment plant, and discharged after it falls below the specified standard value for drainage.

この実施例によって、表面積４００ｍ^２の暫定汚染域７の浄化処理を行なった。暫定汚染域７では、浄化処理を実施する前の深度方向について各重金属の溶出量を表１の左側に示す。比較のために、図４に示す同面積の別の汚染域について、各重金属の溶出量を表１の右側に示す。比較例では、３本の揚水井を１０ａ、１０ｂ、１０ｃと同じ深さと位置に穿孔し、給水井だけを設置せずに浄化処理を行なった。下記の各表は、図２または図４に示す位置において、各日数処理後にそれぞれ深さ５ｍまでのコアサンプルを採取し、土壌溶出の分析を行なった結果である。この採集位置はＡ（図２）である。 According to this example, purification treatment of the temporary contamination area 7 having a surface area of 400 m ² was performed. In the temporary contamination area 7, the elution amount of each heavy metal is shown on the left side of Table 1 in the depth direction before the purification treatment is performed. For comparison, the elution amount of each heavy metal is shown on the right side of Table 1 for another contaminated area of the same area shown in FIG. In the comparative example, three pumping wells were drilled at the same depth and position as 10a, 10b, and 10c, and purification treatment was performed without installing only the water supply well. The following tables show the results of analyzing the soil elution by collecting core samples up to a depth of 5 m after each day treatment at the positions shown in FIG. 2 or FIG. 4. This collection position is A (FIG. 2).

処理開始１ヶ月後における各重金属の溶出量を表２に示す。この採集位置はＢ（図２）である。 Table 2 shows the elution amount of each heavy metal one month after the start of the treatment. This collection position is B (FIG. 2).

処理開始３ヶ月後における各重金属の溶出量を表３に示す。この採集位置はＣ（図２）である。 Table 3 shows the elution amount of each heavy metal 3 months after the start of the treatment. This collection position is C (FIG. 2).

処理開始６ヶ月後における各重金属の溶出量を表４に示す。この採集位置はＤ（図２）である。 Table 4 shows the elution amount of each heavy metal 6 months after the start of the treatment. This collection position is D (FIG. 2).

下手の各揚水井から汲み上げられた揚水は、水処理プラントまで管路を通して送った後に、該水処理プラントにおいて順次最終処理を行い、排水基準値以下としたから下水へ排水した。比較例の揚水についても、同様の処理を行なった。 The pumped water from each lower pumping well was sent to the water treatment plant through a pipe line, and finally subjected to final treatment in the water treatment plant, and was discharged to the sewage because it was below the drainage standard value. The same treatment was performed for the pumped water of the comparative example.

前記の各表から明らかなように、この実施例によると、深さ５ｍまで汚染されていた土壌も、６カ月間の浄化処理によって、各汚染物質の溶出量が深さ約１ｍまで１．０ｍｇ／ｌ以下になり、本発明方法で汚染土壌が速やかに浄化されることが判る。一方、比較例では、６ケ月後もほとんど浄化が進んでいない。この結果、本発明方法を用いることにより、約半年という短期間で土壌の入替量を約１/５に減らすことができ、安価な改質処理が可能になる。 As is clear from the above tables, according to this example, even if the soil was contaminated to a depth of 5 m, the elution amount of each pollutant was 1.0 mg to a depth of about 1 m by the purification treatment for 6 months. / L or less, indicating that the contaminated soil is quickly purified by the method of the present invention. On the other hand, in the comparative example, purification has hardly progressed even after 6 months. As a result, by using the method of the present invention, the amount of replacement of soil can be reduced to about 1/5 in a short period of about half a year, and an inexpensive reforming treatment can be performed.

本発明方法を実施した汚染土壌を含む地層の一例を示す概略縦断面図である。It is a schematic longitudinal cross-sectional view which shows an example of the stratum containing the contaminated soil which implemented the method of this invention. 実施例における給水井および揚水井の配置状態の一例を示す汚染域の概略平面図である。It is a schematic plan view of the contaminated area which shows an example of the arrangement state of the water supply well and the pumping well in an Example. 揚水井における揚水制御システムを示す説明図である。It is explanatory drawing which shows the pumping control system in a pumping well. 比較例における揚水井の配置状態を示す図２と同様の概略平面図である。It is the same schematic plan view as FIG. 2 which shows the arrangement | positioning state of the pumping well in a comparative example.

符号の説明Explanation of symbols

１第１帯水層
２遮水層
５矢板
７暫定汚染域
８給水井
１０揚水井
１２ポンプ
DESCRIPTION OF SYMBOLS 1 1st aquifer 2 impermeable layer 5 sheet pile 7 provisional pollution area 8 water supply well 10 pumping well 12 pump

Claims

汚染域において自動給水する給水井を穿孔し、該給水井には水位センサを取り付けて常に所定の給水量を保ち、一方、揚水井を給水井より下手に配置して穿孔し、該揚水井の深さが給水井のそれよりも深いことにより、給水井から汚染域に送り込んだ注水は地中で周辺方向および深さ方向に浸透し、汚染物質を溶出させてから揚水井で地上へ汲み上げる汚染土壌の改質方法。 A water supply well that automatically feeds water in a contaminated area is drilled, and a water level sensor is attached to the water supply well to always maintain a predetermined amount of water supply. Due to the depth being deeper than that of the water supply well, the water injected from the water supply well into the contaminated area penetrates in the surrounding direction and depth direction in the ground, elutes the pollutant, and then pumps it up to the ground with the pumping well. Soil modification method.

粘度またはシルトなどの遮水層の上面が深さ３〜１０ｍに形成された土地において、止水壁を遮水層まで打ち込んで暫定汚染域を確定し、暫定汚染域内に穿孔した給水井から注水を常に地中へ送り込み、地中において暫定汚染域を経由して流通させ、汚染物質を溶出させてから注水を揚水井で取り出し、該揚水井から汲み上げた地下水を水処理プラントによって浄化する汚染土壌の改質方法。 In the land where the upper surface of the impermeable layer such as viscosity or silt is formed to a depth of 3 to 10 m, water is injected from the water supply well that has been pierced in the temporary contaminated area by driving the water blocking wall to the impermeable layer Contaminated soil in which groundwater is always sent to the ground, distributed via a temporary polluted area in the ground, the pollutant is eluted, the injected water is taken out from the pumping well, and the groundwater pumped from the pumping well is purified by the water treatment plant Reforming method.

止水壁によって暫定汚染域を確定し、給水井は暫定汚染域内において深さ２〜８ｍで１本または複数本を有し、且つ揚水井は深さ２．５〜９．５ｍで給水井と同数またはそれ以上の本数を有する請求項１または２記載の改質方法。 The temporary contamination area is determined by the water barrier, the water supply well has one or more at a depth of 2 to 8 m in the temporary contamination area, and the pumping well is at a depth of 2.5 to 9.5 m. The reforming method according to claim 1 or 2, which has the same number or more.

給水井への注水は、水道管から直接常圧で供給するか、または送水ポンプによって加圧しながら地中へ強制的に送り込む請求項１または２記載の方法。
The method according to claim 1 or 2, wherein the water injection to the water supply well is supplied directly from the water pipe at normal pressure or forcedly fed into the ground while being pressurized by a water pump.