JP3684981B2 - Contaminated soil purification method - Google Patents

Contaminated soil purification method Download PDF

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JP3684981B2
JP3684981B2 JP2000036331A JP2000036331A JP3684981B2 JP 3684981 B2 JP3684981 B2 JP 3684981B2 JP 2000036331 A JP2000036331 A JP 2000036331A JP 2000036331 A JP2000036331 A JP 2000036331A JP 3684981 B2 JP3684981 B2 JP 3684981B2
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contaminated
groundwater
water
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JP2001225054A (en
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秀憲 守武
敏郎 薦田
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鹿島建設株式会社
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【0001】
【発明の属する技術分野】
本願発明は、汚染土壌を一般環境から隔離しつつ、汚染土壌の浄化を図る地下水循環型の汚染土壌浄化方法に関するものである。
【0002】
【従来の技術】
汚染土壌浄化対策に関する出願としては、例えば特開平9−267082号公報、特開平10−258266号公報、特開平10−277531号公報記載のもの等が挙げられる。
【0003】
特開平9−267082号公報記載の発明は、揮発性有機化合物で汚染された土壌の浄化方法に関するものであり、汚染領域に対し、微生物を用いた浄化領域を形成し、汚染領域と浄化領域を循環する気体流により浄化を図るものである。特開平10−258266号公報記載の発明は、油等の有機廃棄物により汚染された土壌を原位置で浄化する方法に関するもので、汚染地区を下方の不透水層と周囲を取り囲む止水壁とで仕切り、不透水層上に洗浄水を加圧供給し、洗浄水に汚染物質を取り込ませながら、地表に流出させて回収するものである。
【0004】
また、特開平10−277531号公報記載の発明は、各種の汚染状況に幅広く対応でき、かつコスト低減が可能な地下水循環による浄化方法に関するものであり、汚染地区を囲むように注水井戸を設けるとともに、注入水が汚染域を経由するように揚水井戸を設け、揚水井戸から汲み上げた地下水を、地上の汚染処理装置で処理して、再び注水井戸から地盤中に戻すというものである。
【0005】
一方、平成11年2月に出された環境庁の指針によれば、原位置における汚染物質の封じ込め方策の基本方針は以下の通りである。
▲1▼地下に層厚5m以上、透水係数1.0×10-5cm/秒以下の不透水層がある。
【0006】
▲2▼汚染地域周囲を止水機能のある工作物で取り囲み閉塞する。具体的には、鋼矢板、SMW地中連続壁(ソイルミキシングウォール)の構築による遮水構造が考えられるが、SMW地中連続壁は幅が50cm以上で、透水係数が1.0×10-6cm/秒以下であること。また、地下の不透水層まで設置すること。
【0007】
▲3▼汚染地域内の地下水を処理する場合には、処理施設により汚染物質を環境基準値以下に除去し、外部に放出する。
▲4▼雨水などの侵入を防止するため、表面には遮水機能の高い材料を敷設する。具体的には、遮水シート材と改良混合土層の組合せの二重遮水構造となる。なお、この構造を適用する場合には、▲3▼の処理施設による処理は必ずしも必要ない。
【0008】
▲5▼汚染物質の計画地外への流出・拡散を防止するために、SMW内外の地下水位は周辺の水位以下に設定することが望ましい。
【0009】
【発明が解決しようとする課題】
上記の基本方針は、廃棄物処分場の遮水構造と同レベルの機能構築を目的としたものであり、民間開発の中において、初期投資、維持管理費の発生に対する事業計画上の調整が必要となる。
【0010】
その他の問題点としては、
▲1▼SMWの設置深度如何では、時間的、経済的な制約を及ぼす可能性が大であること。
▲2▼SMWの不透水機能が施工条件に左右され、実験室レベルの不透水機能の確保が難しいこと。
【0011】
▲3▼汚染地域内の地下水位を一律定常水位に設定することが難しく、また、周辺地盤の地下水位に連動させることも困難であること。
などが挙げられる。
また、上述した特開平9−267082号公報や特開平10−258266号公報記載の発明は、特定の汚染物質を対象としたものであり、種々の汚染物質に対応させることができない。
【0012】
特開平10−277531号公報記載の発明の場合、地上の汚染処理装置の性能に応じて種々の汚染に対応可能であるが、注水井戸と揚水井戸との配置において、地下水の循環経路の確保が難しく、汚染物質が周辺に拡散する恐れがある。また、上記各公報記載の発明は、上記の原位置における汚染物質の封じ込め方策の基本方針を満足するものではなく、代替の方法としても不十分であると考えられる。
【0013】
本願発明は、上記の基本方針で要求される汚染浄化効果と同等以上の効果が期待でき、かつコストの大幅低減が可能な実用的な汚染土壌浄化方法を提供することを目的としたものである。
【0014】
【課題を解決するための手段】
本願の請求項1に係る汚染土壌浄化方法は、汚染地区を取り囲むように、汚染地区外の地下水位以下の深さに達する地中遮水壁を設け、汚染地区内に集水施設を設け、前記集水施設を取り囲むように、前記地中遮水壁の近傍の内側に地中遮水壁から所定の距離離して、かつ地下水位以上の深さに環状に連続させて浸透施設を設置し、前記集水施設より揚水し、揚水された汚染地下水を浄化処理した後、浄化処理された地下水を前記浸透施設から再び汚染地区内に浸透させ、前記集水施設に向けて水位差による鉛直方向並びに水平方向の地下水流を発生させることを特徴とするものである。
【0015】
本発明によれば、集水施設から揚水された汚染地下水が浄化処理された後、再び汚染地区の地盤に戻され、水位の高い浸透施設位置から水位の低下した集水施設へ向けて地下水が流れることで、汚染地下水の循環経路が形成され、汚染土壌の汚染物質を取り込みながら、徐々に汚染土壌を浄化して行くことができる。
【0016】
揚水された汚染地下水の浄化処理は、例えば集水施設の近くに設けた処理プラント等により、従来から知られている種々の浄化処理を、汚染物質の種類に応じて1段階または多段階に行うことができる。また、本発明では、浸透施設を環状に連続させているので、汚染地区に設置された1または複数の集水施設に対し、偏りの少ない地下水流を形成することができ、汚染土壌を効率良く浄化しつつ、汚染地区外への汚染物質の拡散を防止することができる。
【0017】
なお、集水施設としては、従来からの集水井戸(揚水井戸)が一般的であるが、汚染地下水を揚水できるものであれば特に形態、規模等限定されない。請求項2は、請求項1に係る汚染土壌浄化方法において、前記浸透施設を汚染地区の地盤内の地下水位以上の所定深さに設置する場合である。
【0018】
集水施設位置では揚水量に応じて水位が低下するのに対し、浸透施設は、通常、地下水位以上に設置することで、浄化処理された地下水を地盤中に自然に浸透させて行くことができる。しかしながら、その場合、浸透施設位置の水位が浸透施設周辺の水位より高くなるため、設置位置や浸透量によっては浄化処理を施したものの完全には汚染物質が除去されていない地下水が汚染地区外へ拡散する恐れがある。
【0019】
これに対し、請求項2のように浸透施設を地盤内の所定深さ以下に設置すれば、集水施設の揚水量や浸透施設からの浸透量を調整することで、汚染地区外への汚染物質の拡散を抑制することができる。
【0020】
本願の請求項1、2に係る発明において、汚染地区と汚染地区外を隔離する地中遮水壁を設けたのは、汚染物質の拡散防止をより確実にするためである。
【0021】
ただし、本願発明の場合、地中遮水壁がなくてもそれなりの汚染物質の拡散防止効果が得られるため、従来のように地中遮水壁を必ずしも不透水層まで構築する必要はなく、汚染地区外の地下水位以下に達する深さとすることで、十分な拡散防止効果が期待できる。
【0022】
地中遮水壁としては、SMW地中連続壁、鋼矢板壁、その他の遮水性の期待できる任意の地中連続壁を用いることができる。請求項は、請求項1または2に係る汚染土壌浄化方法において、集水施設による汚染地下水の揚水量と、浄化処理した地下水の浸透施設からの浸透量を調整することで、前記地中遮水壁近傍において、汚染地区外の地下水位が汚染地区内の地下水位より高くなるようにする場合である。
【0023】
上述のように集水施設近傍では揚水により水位が低下し、それによって浸透施設位置と集水施設位置、さらに浸透施設位置と地中遮水壁位置とで地下水について水位差が生じる。
従って、これらを調整することで、地中遮水壁近傍における汚染地区側の地下水位を汚染地区外の地下水位より低くすることができ、前述した環境庁指針における基本方針の▲5▼を満たすことができる。
【0026】
浸透施設を暗渠の形で地盤内の所定深さ以下に設置すれば、浸透施設位置での水位を必要以上に高くすることなく、集水施設の揚水量や浸透施設からの浸透量を調整することで、汚染地区外への汚染物質の拡散を抑制することができる。
このような暗渠型の浸透施設の具体的な形態としては、例えば硬質塩化ビニル管等の樹脂パイプあるいは金属パイプに浸透用の多数の小孔を設けた有孔パイプの外側に砕石等を設置し、さらに土粒子等の吸い込みを防止するための不織布等を巻いたもの、砕石の代わりに人工的な透水材料を用いたもの、あるいは有孔パイプを用いずに砕石あるいは人工的な透水材料の周囲に吸込み防止材を巻いたものなどが考えられる。また、この浸透施設は、内側から外へ向けて処理水を注水するものであるため、周辺の土砂等による目詰まりの恐れがない場合には、吸込み防止材や砕石、透水材料等を省いたより簡単な構造のものでもよい。
【0027】
なお、以上は単なる具体例を挙げたに過ぎず、地盤中の所定深さに設置でき、浄化処理した汚染地下水を地盤中に浸透させることができるものであれば、寸法、形態等特に限定されない。
【0028】
【発明の実施の形態】
図1は、本願発明の一実施形態を概略的に示したものであり、汚染地区Iに集水施設として集水井戸1を設け、汚染物質を含む汚染地下水を揚水する。図では、単一の集水井戸1を示しているが、勿論、集水井戸を複数箇所に設けてもよい。なお、集水井戸1は水質のモニタリングにも利用される。
【0029】
揚水された汚染地下水は処理プラント2で処理された後、汚染地区Iの地盤内所定深さに敷設された暗渠型浸透施設3から地盤内に浸透させる。
また、この例では汚染地区Iを取り囲むように地中遮水壁4を構築している。この地中遮水壁4は不透水層Uに達しておらず、汚染地区外Oの地下水位以下のレベルの構築深さとしている。
【0030】
地下水位についてみると、揚水が行われる集水井戸1部分の水位が低く、処理水を再び地盤に戻す暗渠型浸透施設3部分で水位が高くなっている。本実施形態において、この暗渠型浸透施設3は汚染地区Iを取り囲む地中遮水壁4の内側に地中遮水壁4から所定の距離離して環状に配置されており、暗渠型浸透施設3から集水井戸1に向けて、また暗渠型浸透施設3から地中遮水壁4に向けて水位差による地下水流が発生する構造となっている。
【0031】
従って、集水井戸1からの揚水量や暗渠型浸透施設3の深さ、処理水の浸透量等を調整することにより、地中遮水壁4近傍において汚染地区I内の地下水位を汚染地区外Oの地下水位以下とすることができ、それにより汚染の拡散を防止することができる。
【0032】
一方、集水井戸1と処理プラント2、暗渠型浸透施設3との間では汚染地下水の循環経路が形成され、この循環を繰り返すことで、土壌中の汚染物質を徐々に除去し、汚染地下水を浄化して行くことができる。また、処理プラント2で処理されて出てくる汚染レベルの低い余剰処理水や除去された汚染物質は、条件によっては域外に搬出して処分することができる。
【0033】
また、この汚染地区Iの地表面には、必要に応じて雨水等の地盤への浸透を阻止するための表面遮水工5を設置するものとする。この表面遮水工については、指針等によって示されているものを利用することができる。
図2(a) 〜(d) は、暗渠型浸透施設3の具体例を示したものである。図2(a) の浸透施設3は、透水孔を形成した硬質塩化ビニル管等の有孔パイプ11を芯材として、その回りに透水域を確保するための単粒度砕石12を敷設し、さらにその周囲に不織布等からなる吸込み防止材13を巻いて、土粒子の侵入による目詰まり等を防止するようにしたものである。この形式は処理水を地盤に戻す際の透水性が良好である反面、敷設費用が大きくなる傾向がある。
【0034】
図2(b) の浸透施設3は、図2(a) の砕石12の代わりに、繊維製排水材14を有孔パイプ11の周囲に巻き、その回りに吸込み防止材13を巻いた構造となっている。透水性は図2(a) のものに劣るが、コスト低減が可能である。市販の繊維製排水材14としては、例えば繊條の相互節点を溶着成形して一体化したポーラス材(商品名:ヘチマロン)などがある。
【0035】
図2(c) の浸透施設3は、有孔パイプを用いずに、単粒度砕石12の周囲に吸込み防止材13を巻いて、連続する暗渠を形成したものである。コストは最も低いが透水性の面では、図2(a) 、(b) のものに比べて劣る。
図2(d) の浸透施設3は、図2(c) の砕石12の代わりに、繊維製排水材14を用い、その回りに吸込み防止材13を巻いたものである。
【0036】
【発明の効果】
(1) 本発明によれば、集水施設から揚水された汚染地下水が浄化された後、再び汚染地区の地盤に戻され、地下水の循環経路が形成されることで、徐々に汚染土壌を浄化して行くことができる。
【0037】
(2) 揚水された汚染地下水の浄化処理は、例えば集水施設の近くに設けた処理プラント等により処理することで、汚染物質の種類に応じた処理が可能である。
(3) 浸透施設を環状に連続させれば、集水施設に向けて偏りの少ない地下水流を形成することができ、汚染土壌を効率良く浄化しつつ、汚染地区外への汚染物質の拡散を防止することができる。
【0038】
(4) 浄化した水を再び地中に浸透させることで、地下水位低下に伴う地盤沈下等の影響を予防することが可能となる。
【図面の簡単な説明】
【図1】 本願発明の一実施形態を概略的に示す断面図である。
【図2】 (a) 〜(d) はそれぞれ請求項2に用いる浸透施設の形態例を示す断面図である。
【符号の説明】
I…汚染地区、O…汚染地区外、U…不透水層、W…地下水位、
1…集水井戸、2…処理プラント、3…暗渠型浸透施設、4…地中遮水壁、5…表面遮水工、
11…有孔パイプ、12…砕石、13…吸込み防止材、14…繊維製排水材
[0001]
BACKGROUND OF THE INVENTION
The present invention, while isolating the contaminated soil from the general environment, it relates to the contaminated soil remediation how the groundwater recycling to achieve remediation of contaminated soils.
[0002]
[Prior art]
Examples of applications relating to measures against contaminated soil purification include those described in JP-A-9-267082, JP-A-10-258266, and JP-A-10-277531.
[0003]
The invention described in Japanese Patent Application Laid-Open No. 9-267082 relates to a method for purifying soil contaminated with volatile organic compounds, and forms a purification region using microorganisms against the contaminated region, and the contaminated region and the purified region are separated from each other. Purification is achieved by a circulating gas flow. The invention described in Japanese Patent Application Laid-Open No. 10-258266 relates to a method for purifying soil contaminated with organic waste such as oil in its original position. In this case, the washing water is pressurized and supplied onto the water-impermeable layer, and the washing water is allowed to flow out to the ground while collecting the contaminants.
[0004]
The invention described in Japanese Patent Application Laid-Open No. 10-277531 relates to a purification method by groundwater circulation that can cope with a wide variety of pollution situations and can reduce costs, and has a water injection well surrounding a contaminated area. A pumping well is provided so that the injected water passes through the contaminated area, and the groundwater pumped up from the pumping well is treated with the above-mentioned pollution treatment equipment and returned from the water injection well to the ground again.
[0005]
On the other hand, according to the guidelines of the Environment Agency issued in February 1999, the basic policy for in-situ containment of pollutants is as follows.
(1) There is an impermeable layer in the basement with a layer thickness of 5m or more and a permeability coefficient of 1.0 × 10 -5 cm / sec or less.
[0006]
(2) Enclose the area around the contaminated area with a work with water stop function and close it. Specifically, a water shielding structure by constructing steel sheet piles and SMW underground continuous walls (soil mixing walls) can be considered, but the SMW underground continuous walls have a width of 50 cm or more and a water permeability of 1.0 × 10 −. 6 cm / sec or less. Install underground impermeable layers.
[0007]
(3) When treating the groundwater in the contaminated area, remove the pollutant below the environmental standard value by the treatment facility and release it to the outside.
(4) In order to prevent the intrusion of rainwater, etc., a material with a high water shielding function is laid on the surface. Specifically, it becomes a double water-impervious structure of a combination of a water-impervious sheet material and an improved mixed soil layer. When this structure is applied, the processing by the processing facility (3) is not necessarily required.
[0008]
(5) It is desirable to set the groundwater level inside and outside the SMW below the surrounding water level in order to prevent the outflow and diffusion of contaminants outside the planned area.
[0009]
[Problems to be solved by the invention]
The above basic policy is aimed at building the same level of function as the water-impervious structure of the waste disposal site, and it is necessary to make adjustments in the business plan for the initial investment and the occurrence of maintenance costs during private development. It becomes.
[0010]
Other issues are:
(1) Depending on the installation depth of the SMW, there is a great potential for time and economic constraints.
(2) The impervious function of SMW depends on the construction conditions, and it is difficult to secure the impervious function at the laboratory level.
[0011]
(3) It is difficult to set the groundwater level in the contaminated area to a uniform steady water level, and it is difficult to link it to the groundwater level of the surrounding ground.
Etc.
The inventions described in Japanese Patent Laid-Open Nos. 9-267082 and 10-258266 are directed to specific pollutants and cannot be applied to various pollutants.
[0012]
In the case of the invention described in Japanese Patent Application Laid-Open No. 10-277531, it is possible to cope with various types of pollution according to the performance of the ground pollution treatment apparatus. However, in the arrangement of the water injection well and the pumping well, it is possible to secure a circulation route of groundwater. Difficult, there is a risk of contaminants spreading around. Further, the inventions described in the above-mentioned publications do not satisfy the basic policy of the above-mentioned contamination containment policy, and are considered to be insufficient as an alternative method.
[0013]
The present invention has an object to provide a practical polluted soil remediation how capable contaminated cleaning effect equal to or higher than the effect can be expected by, and significant cost reduction in the request by the basic policy is there.
[0014]
[Means for Solving the Problems]
Contaminated soil remediation method according to claim 1 of the present application, so as to surround the contaminated areas, underground impervious wall to reach the groundwater level below the depth of the outer contaminated areas provided, set the water collecting facility contamination in the district A permeation facility is installed inside the vicinity of the underground impermeable wall so as to surround the water collecting facility, at a predetermined distance from the underground impermeable wall, and continuously in a ring shape at a depth equal to or higher than the groundwater level. Then, after pumping up the contaminated groundwater pumped from the water collection facility, the purified groundwater is again infiltrated into the contaminated area from the infiltration facility, and the water is directed vertically to the water collection facility due to the difference in water level. It is characterized by generating horizontal and horizontal groundwater flows .
[0015]
According to the present invention, after the contaminated groundwater pumped from the water collection facility is purified, the groundwater is returned to the ground of the contaminated area again, and the groundwater flows from the high penetration level to the water collection facility where the water level is lowered. By flowing, a contaminated groundwater circulation path is formed, and the contaminated soil can be gradually purified while taking in contaminants in the contaminated soil.
[0016]
For the purification treatment of the pumped contaminated groundwater, various conventionally known purification treatments are performed in one or more stages depending on the type of the pollutant, for example, by a treatment plant provided near the water collection facility. be able to. Further, in the present invention, since is sequencing infiltration facilities in the ring shape, for one or more water collection facilities installed in the contaminated areas, it can form a low groundwater flow biased, contaminated soil efficiency While purifying well, it is possible to prevent the diffusion of pollutants outside the contaminated area.
[0017]
In addition, as a water collection facility, a conventional water collection well (pumping well) is generally used, but the form and scale are not particularly limited as long as it can pump contaminated groundwater. A second aspect of the present invention is the contaminated soil purification method according to the first aspect, wherein the infiltration facility is installed at a predetermined depth equal to or higher than the groundwater level in the ground of the contaminated area.
[0018]
Whereas the water level is lowered according to the amount of pumped water at the water collection facility, the infiltration facility is usually installed above the groundwater level so that the purified groundwater can naturally penetrate into the ground. it can. However, in this case, the water level at the infiltration facility is higher than the water level around the infiltration facility, so depending on the installation location and the amount of infiltration, groundwater that has been subjected to purification treatment but has not been completely removed of pollutants will be discharged outside the contaminated area. There is a risk of spreading.
[0019]
On the other hand, if the infiltration facility is installed at a predetermined depth or less in the ground as described in claim 2, the contamination outside the contaminated area can be controlled by adjusting the pumping amount of the water collection facility and the infiltration amount from the infiltration facility. Ru can be suppressed diffusion of the substance.
[0020]
In the invention according to claim 1, 2 of the present application, it was provided underground barrier water wall to isolate the contaminated areas outside fouling Somechi Zone is order to secure a diffusion preventing pollutant.
[0021]
However, in the case of the present invention, it is not necessary to construct the underground impermeable wall up to the impermeable layer, as in the conventional case, since there is an effect of preventing diffusion of the contaminants without the underground impermeable wall, Sufficient anti-diffusion effect can be expected by setting the depth below groundwater level outside the contaminated area.
[0022]
As the underground water-impervious wall, an SMW underground continuous wall, a steel sheet pile wall, or any other underground continuous wall that can be expected to be water-impervious can be used. According to claim 3 , in the contaminated soil purification method according to claim 1 or 2 , by adjusting the amount of contaminated groundwater pumped by the water collection facility and the amount of seepage from the infiltration facility of the purified groundwater, This is a case where the groundwater level outside the contaminated area is higher than the groundwater level inside the contaminated area near the water wall.
[0023]
As described above, in the vicinity of the water collection facility, the water level is lowered by pumping, thereby causing a difference in the groundwater level between the infiltration facility position and the water collection facility position, and further between the infiltration facility position and the underground impermeable wall position.
Therefore, by adjusting them, the groundwater level on the contaminated area near the underground impermeable wall can be made lower than the groundwater level outside the contaminated area, and satisfies the basic policy (5) in the aforementioned Environmental Agency Guidelines. be able to.
[0026]
If the infiltration facility is installed in the form of a culvert below the specified depth in the ground, the amount of pumped water in the water collection facility and the amount of infiltration from the infiltration facility can be adjusted without making the water level at the infiltration facility higher than necessary. Thus, the diffusion of pollutants outside the contaminated area can be suppressed.
As a concrete form of such a culvert type infiltration facility, for example, a crushed stone or the like is installed outside a perforated pipe provided with a large number of small holes for infiltration in a resin pipe such as a hard vinyl chloride pipe or a metal pipe. In addition, those wound with non-woven fabric to prevent inhalation of soil particles, etc., those using artificial water-permeable materials instead of crushed stones, or around crushed stones or artificial water-permeable materials without using perforated pipes It is conceivable that the material is wound with a suction prevention material. In addition, this infiltration facility is for injecting treated water from the inside to the outside, so if there is no risk of clogging due to surrounding earth and sand, etc., we removed suction prevention materials, crushed stones, and water-permeable materials. A simpler structure may be used.
[0027]
Note that the above is merely a specific example, and there is no particular limitation on the size, form, etc., as long as it can be installed at a predetermined depth in the ground and can infiltrate the contaminated groundwater after purification treatment. .
[0028]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows an embodiment of the present invention. A water collecting well 1 is provided as a water collecting facility in a contaminated area I to pump up contaminated groundwater containing pollutants. In the figure, a single water collecting well 1 is shown, but of course, water collecting wells may be provided at a plurality of locations. The water collection well 1 is also used for water quality monitoring.
[0029]
The pumped contaminated groundwater is treated at the treatment plant 2 and then infiltrated into the ground from a culvert type infiltration facility 3 laid at a predetermined depth in the ground of the contaminated area I.
In this example, the underground impermeable wall 4 is constructed so as to surround the contaminated area I. This underground impermeable wall 4 does not reach the impermeable layer U and has a construction depth of a level below the groundwater level outside the contaminated area O.
[0030]
Looking at the groundwater level, the water level in the drainage well 1 where pumping is performed is low, and the water level is high in the culvert type infiltration facility 3 where the treated water is returned to the ground again. In the present embodiment, the culvert type infiltration facility 3 is arranged in an annular shape inside the underground impermeable wall 4 surrounding the contaminated area I and spaced apart from the underground impermeable wall 4 by a predetermined distance. It is structured to generate a groundwater flow due to the difference in water level from the basin to the water collecting well 1 and from the culvert type infiltration facility 3 to the underground impermeable wall 4.
[0031]
Therefore, the groundwater level in the contaminated area I in the vicinity of the underground impermeable wall 4 is adjusted by adjusting the amount of pumped water from the drainage well 1, the depth of the culvert type infiltration facility 3, the amount of treated water infiltrated, etc. It can be below the groundwater level of the outer O, thereby preventing the diffusion of contamination.
[0032]
On the other hand, a polluted groundwater circulation path is formed between the catchment well 1, the treatment plant 2, and the underdrainage infiltration facility 3. By repeating this circulation, pollutants in the soil are gradually removed, You can go clean. In addition, surplus treated water with a low contamination level that is processed and processed by the treatment plant 2 and removed contaminants can be carried out of the area and disposed of depending on conditions.
[0033]
Further, on the ground surface of the contaminated area I, a surface water-impervious work 5 for preventing permeation of rainwater or the like into the ground is installed as necessary. About this surface impermeable work, what is shown by the guideline etc. can be utilized.
2A to 2D show specific examples of the culvert type infiltration facility 3. FIG. 2 (a) has a perforated pipe 11 such as a hard vinyl chloride pipe having a water permeable hole as a core material, and a single-grain crushed stone 12 for securing a water permeable area is laid around it. A suction preventive material 13 made of a nonwoven fabric or the like is wound around the periphery to prevent clogging or the like due to intrusion of soil particles. This form has good water permeability when returning treated water to the ground, but tends to increase laying costs.
[0034]
The infiltration facility 3 in FIG. 2 (b) has a structure in which a fiber drainage material 14 is wound around a perforated pipe 11 in place of the crushed stone 12 in FIG. It has become. The water permeability is inferior to that of FIG. 2 (a), but the cost can be reduced. Examples of the commercially available fiber drainage material 14 include a porous material (trade name: Hetimaron) in which mutual nodes of fibers are welded and integrated.
[0035]
The infiltration facility 3 in FIG. 2 (c) is formed by winding a suction prevention material 13 around a single-grain crushed stone 12 without using a perforated pipe to form a continuous underdrain. Although the cost is the lowest, the water permeability is inferior to that of FIGS. 2 (a) and 2 (b).
The infiltration facility 3 in FIG. 2 (d) uses a fiber drainage material 14 instead of the crushed stone 12 in FIG. 2 (c), and a suction prevention material 13 is wound around it.
[0036]
【The invention's effect】
(1) According to the present invention, after the contaminated groundwater pumped from the water collection facility is purified, it is returned to the ground of the contaminated area again, and the groundwater circulation path is formed, thereby gradually purifying the contaminated soil. Can go.
[0037]
(2) Pumped contaminated groundwater can be purified by, for example, a treatment plant installed near the water collection facility, according to the type of pollutant.
(3) penetration if ask facility is continuous ring shape, toward the water collecting facility can form a low groundwater flow biased, while the contaminated soil was purified efficiently, the diffusion of pollutants into the contaminated areas outside Can be prevented.
[0038]
(4) By infiltrating the purified water into the ground again, it is possible to prevent the effects of land subsidence due to the groundwater level drop.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an embodiment of the present invention.
2 (a) to (d) are cross-sectional views each showing an example of an infiltration facility used in claim 2. FIG.
[Explanation of symbols]
I ... Contaminated area, O ... Outside contaminated area, U ... Impermeable layer, W ... Groundwater level,
DESCRIPTION OF SYMBOLS 1 ... Water collection well, 2 ... Treatment plant, 3 ... Underdrain type penetration facility, 4 ... Underground impermeable wall, 5 ... Surface impermeable construction,
DESCRIPTION OF SYMBOLS 11 ... Perforated pipe, 12 ... Crushed stone, 13 ... Suction prevention material, 14 ... Textile drainage material

Claims (3)

  1. 汚染地区を取り囲むように、汚染地区外の地下水位以下の深さに達する地中遮水壁を設け、汚染地区内に集水施設を設け、前記集水施設を取り囲むように、前記地中遮水壁の近傍の内側に地中遮水壁から所定の距離離して、かつ地下水位以上の深さに環状に連続させて浸透施設を設置し、前記集水施設より揚水し、揚水された汚染地下水を浄化処理した後、浄化処理された地下水を前記浸透施設から再び汚染地区内に浸透させ、前記集水施設に向けて水位差による鉛直方向並びに水平方向の地下水流を発生させることを特徴とする汚染土壌浄化方法。So as to surround the contaminated areas, underground impervious wall to reach the groundwater level below the depth of the outer contaminated areas provided only set the catchment facility contamination area, so as to surround the water collecting facilities, the underground An infiltration facility was installed inside the vicinity of the impermeable wall at a predetermined distance from the underground impermeable wall and continuously in a ring shape at a depth equal to or higher than the groundwater level . After purifying the contaminated groundwater, the purified groundwater is again permeated into the contaminated area from the infiltration facility, and a vertical and horizontal groundwater flow due to a water level difference is generated toward the water collection facility. Contaminated soil purification method.
  2. 前記浸透施設を汚染地区の地盤内の地下水位以上の所定深さに設置する請求項1記載の汚染土壌浄化方法。 The contaminated soil purification method according to claim 1, wherein the infiltration facility is installed at a predetermined depth equal to or higher than a groundwater level in the ground of a contaminated area.
  3. 集水施設による汚染地下水の揚水量と、浄化処理した地下水の浸透施設からの浸透量を調整することで、前記地中遮水壁近傍において、汚染地区外の地下水位が汚染地区内の地下水位より高くなるようにする請求項1または2記載の汚染土壌浄化方法。 By adjusting the amount of contaminated groundwater pumped by the water collection facility and the amount of infiltrated from the infiltration facility for purified groundwater, the groundwater level outside the contaminated area near the underground impermeable wall The method for purifying contaminated soil according to claim 1 or 2, wherein the method is made higher.
JP2000036331A 2000-02-15 2000-02-15 Contaminated soil purification method Expired - Lifetime JP3684981B2 (en)

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