JP2004188332A

JP2004188332A - Water circulation type biological purification method and device for contaminated soil

Info

Publication number: JP2004188332A
Application number: JP2002360092A
Authority: JP
Inventors: Seiji Otsuka; 誠治大塚; Tatsuji Kawai; 達司河合
Original assignee: Kajima Corp
Current assignee: Kajima Corp
Priority date: 2002-12-12
Filing date: 2002-12-12
Publication date: 2004-07-08
Anticipated expiration: 2022-12-12
Also published as: JP4811979B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water circulation type biological purification method and device for purifying contaminated water and contaminated massive materials generated at a contaminated site together with contaminated soil. <P>SOLUTION: The hard massive material 7 is mounted in an air permeable layer shape on a water keeping bottom surface 3 and the contaminated soil 8 is piled up on the layer 6 of the massive material 7. Water is sprinkled to the contaminated soil 8, the massive material layer 6 is aerated and the water flowing down to the massive material layer 6 is returned to the contaminated soil 8 and circulated. The contaminated water generated at the time of excavating the contaminated soil 8 is used for water sprinkling. Also, a massive material to which contaminants are stuck is used as the massive body 7 and concrete lumps and grit in the ground, etc., for instance can be turned to the massive material 7. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は汚染土壌の水循環式生物浄化方法及び装置に関し、とくに汚染土壌を土中の微生物の活性化により浄化する生物浄化方法及び装置に関する。
【０００２】
【従来の技術】
油等の有機物その他の汚染物質で汚染された土壌を浄化する方法として、汚染土壌に微生物の生育に必要な窒素・リン等の栄養物質と適度な水分と空気（又は酸素）とを供給し、土壌中の好気性の汚染物質分解微生物を人為的に活性化させて土壌中の汚染物質を分解する生物処理法が開発されている。この生物処理法は汚染物質を直接分解する方法であり、二次廃棄物の発生がなく、処理に要するエネルギーが少なく、物理・化学的処理のみでは難しい低い濃度まで浄化できる等の効果が期待されている。
【０００３】
従来の生物処理法は、土壌に対する空気の供給方法により、掘削した汚染土壌を積み上げてパイルを作りバックホー等の重機で定期的に汚染土を切り返して新鮮な空気を供給する方法、掘削してパイル状に積み上げた汚染土壌の下部又は中間部に通気パイプを介して強制的に空気を圧入又は吸引する方法等に分類される。
【０００４】
【特許文献１】特開平１１−１７９３３６号公報
【特許文献２】特開平７−１０２２９８号公報
【非特許文献１】「MBIレポート 1996＆1997」、海洋バイオテクノロジー研究所、平成14年6月、p11-16
【０００５】
【発明が解決しようとする課題】
しかし、従来の生物処理法には以下のような問題点がある。
【０００６】
（ａ）地盤の汚染土壌を掘削する従来の生物処理法では、掘削時に汚染物質を含む水（以下、汚染水という。）が大量に発生する例が多い。また、生物浄化のため水分を供給した汚染土壌からも汚染水が浸出する。汚染土壌現場（以下、汚染サイトということがある。）で発生した汚染水は周囲に流出すると汚染の拡大を招くので、従来は回収して汚染サイト外に搬出し廃棄物として焼却処分すること多い。しかし、汚染水の焼却処分は、水の潜熱に大部分のエネルギーが浪費されるので消費エネルギーが大きくなり、処分コストが嵩むと共に環境面からも好ましくない。
【０００７】
汚染土壌サイトで発生した汚染水を利用した生物処理法として特許文献１は、図４に示すように、汚染土壌パイル31から浸出した油分及び土着微生物が含まれる汚染水を回収し、微生物用栄養組成物を加えて微生物を増殖させたのち土壌パイル31へ戻す油汚染土壌の修復方法を開示している。図４において、土壌パイル31からの浸出水は防水シート32やピット33等の回収設備により回収され、送水ポンプ35aにより第一貯水槽34に送られる。第一貯水槽34において、投入口34aから栄養組成物を添加して攪拌器34bで撹拌することにより油分解微生物を増殖させる。微生物が所定濃度（例えば10⁷個／ミリリットル）以上に増殖した段階で、第一貯水槽34の浸出水を送水ポンプ35bにより第二貯水槽36に移し、第二貯水槽36において注入口36aから水又は油分含有水を加えて攪拌器36bで撹拌することにより微生物を更に増殖させる。第二貯水槽36に加える油分含有水として、汚染土壌の掘削時に発生した汚染水や汚染土壌の洗浄に用いた洗浄水等を利用する。第二貯水槽36において微生物の油分解作用により油分濃度が所定の値以下に減少し、微生物濃度が極大（例えば10⁷〜10⁹個／ミリリットル程度）に達した時点で、第二貯水槽36内の水を送水ポンプ36c及び送水管37により土壌パイル31へ注水し、第二貯水槽36内で増殖した微生物を土壌パイル31に移植する。以上の操作を繰り返すことにより、土壌パイル31中の油分解の初動速度の向上を図り、短期間で汚染土壌の修復を図る。
【０００８】
しかし特許文献１の方法は、第一貯水槽34及び第二貯水槽36を汚染サイトに設置する必要があり、大量の汚染水を処理するためには大型の貯水槽が必要となるので、敷地が狭い汚染サイトでは設置スペース上の制約から実施が難しい。また、土壌の汚染濃度にもよるが生物浄化法では浄化完了までに数ヶ月〜１年程度を要するので、特許文献１の方法では貯水槽の攪拌・曝気に要するエネルギーが大きくなり、コストが嵩む問題点もある。消費エネルギーが少ないという汚染土壌の生物浄化法の利点を生かすためには、汚染サイトで発生する汚染水を少ないエネルギーでオンサイト処理できることが望ましい。
【０００９】
（ｂ）また、実際の汚染土壌サイトでは、土壌のみが汚染されているのではなく、周囲の構造物等も汚染されていることが多い。例えば、閉鎖したガソリンスタンドや油タンク等の敷地土壌が汚染されている場合は、敷地内のコンクリート構造物も汚染されていることが多く、汚染土壌の浄化に際しコンクリート構造物を解体すると汚染されたコンクリート塊等が発生する。従来このような汚染コンクリート塊は廃棄物として汚染サイトから搬出して焼却処分されているが、上述したように焼却処分は大量のエネルギーを消費するので経済的にも環境的にも好ましくない。汚染サイトで発生する汚染コンクリート塊等も汚染土壌や汚染水と共に少ないエネルギーでオンサイト処理できる技術の開発が望まれている。
【００１０】
そこで本発明の目的は、汚染サイトで発生する汚染水や汚染塊状体を汚染土壌と共に浄化できる水循環式生物浄化方法及び装置を提供することにある。
【００１１】
【課題を解決するための手段】
本発明者は、油等で汚染された砂、石、岩等の粒状体や塊状体（以下、両者を纏めて塊状体という。）を浄化する技術に注目した。特許文献２及び非特許文献１は、海岸の油で汚染された塊状体に界面活性物質生産能を有する微生物を散布し、微生物の生産する界面活性物質により塊状体に付着した汚染油を洗浄除去する油汚染の洗浄方法を提案している。例えば非特許文献１は、潮の干満を模擬した海浜模擬実験装置を用いて、窒素源及びリン源を添加した海水に汚染塊状体を１日に２度浸漬することにより、海水中の前記微生物の作用によって塊状体の表面に付着した重油が分解されて消失することを報告している（非特許文献１のp15)。前記油分解機能を有する微生物は、他の汚染物質の分解微生物と共に広く汚染土壌中に存在しており、汚染サイトで発生する汚染水中にも存在している。この汚染水を用いて非特許文献１の方法と同様にして汚染コンクリート塊を洗浄できれば、汚染土壌と共に汚染水や汚染塊状体を浄化することが可能となる。本発明はこの知見に基づく研究開発の結果、完成に至ったものである。
【００１２】
図１の実施例を参照するに、本発明による汚染土壌の水循環式生物浄化方法は、保水性底面３上に硬質塊状体７を通気可能な層状に載置し、塊状体７の層６上に汚染土壌８を積み上げ、汚染土壌８へ散水すると共に塊状体層６へ曝気し、塊状体層６への流下水を汚染土壌８へ戻し循環させてなるものである。
【００１３】
また、図１の実施例を参照するに、本発明による汚染土壌の水循環式生物浄化装置は、保水性底面３上に汚染土壌８が載置可能に形成された通気性硬質塊状体７の層６、保水性底面３に連通する集水槽16、集水槽16の水を塊状体層７の上方へ散水する散水装置20、及び塊状体層７に臨む曝気装置10を備えてなるものである。
【００１４】
前記散水として、汚染土壌８の掘削時に生じた汚染水を用いることができる。また、塊状体７を汚染物質付着塊状体とすることができる。汚染物質付着塊状体７の一例は、汚染土壌８の近傍でコンクリート構造物の解体等により発生したコンクリート塊である。また、汚染塊状体７を砂礫とし、地盤から掘削した汚染土壌及び砂礫を篩い分けして前記土壌８及び塊状体７とすることができる。更に好ましくは、集水槽16に汚染物質分解微生物用の栄養物質を添加する栄養添加装置25を設け、更に汚染物質分離手段17を設ける。
【００１５】
【発明の実施の形態】
図１は、油で汚染された土壌の浄化に適用した本発明の生物浄化装置の実施例を示す。但し、本発明は油汚染土壌への適用に限定されない。図示例の生物浄化装置１は、保水性底面３上に通気可能に載置された硬質塊状体７の層６を有する。保水性底面３は、例えば汚染サイトの地表に敷設したアスファルト等の遮水材４により形成する。図示例のように遮水材４の周囲に堰堤５を設けて保水可能とすることができる。保水性底面３上に砂利や小石等の塊状体７を層状に載置して汚染土壌８が上方に積み上げ可能な台（以下、汚染土壌積み上げ台ということがある。）２とする。塊状体７の層６は、後述するように汚染土壌８からの流下水が貯まる貯水ゾーンとなる。塊状体層６の深さ、すなわち図示例の堰堤５の高さは、汚染土壌８からの流下水量に応じて適当に定める。
【００１６】
塊状体層６に臨ませて曝気装置10を設ける。図示例の曝気装置10は、塊状体層６の下端に設けた複数本の細孔付き送気管12と、各送気管12に連通する送風機11とを有する。送風機11から送気管12経由で塊状体層６の流下水中に圧入された空気は、塊状体層６内で拡散されて塊状体層６の頂面全体からほぼ均一な空気流として上方に吹き出し、塊状体層６上に積み上げる汚染土壌８の全体に均一に流れる拡散空気流となる。汚染土壌８への均一な空気の供給は、汚染土壌８中での空気のショートパス等の発生を最小限に抑える効果がある。また、塊状体層６における空気の拡散は、塊状体７の表面で流下水と空気との効率的な接触を作り出し、塊状体７を微生物の付着担体として機能させる。すなわち本発明は、塊状体層６への必要最小限の曝気により、塊状体層６及びその上方の汚染土壌８の全体に汚染物質分解微生物の活性化に必要な空気を効率的に供給できる。なお、図示例の曝気装置10は、各送気管12の弁13の調節により塊状体層６及び汚染土壌８に対する送気量を適当に調整できる。
【００１７】
塊状体層６の塊状体７の一例は適当な強度を有する径２mm以上の砂利や石、岩等であるが、汚染土壌８近傍のコンクリート構造物の解体により発生したコンクリート塊や木片、金属片その他の硬質廃棄物片等を塊状体７として利用できる。また汚染土壌８中に混在する砂礫や石を汚染土壌８から篩い分けして塊状体７として利用してもよい。上述したように本発明は塊状体７を微生物担体として機能させることができるので、塊状体７の表面に付着した汚染物質の分解微生物による洗浄・分解が期待でき、汚染物質が付着したコンクリート塊や汚染土壌８中の砂礫等を積極的に塊状体７として利用することが可能である。
【００１８】
また、保水性底面３に連通させて集水槽16を設け、集水槽16の水を積み上げ台２の上方から散水する散水装置20を設ける。図示例の集水槽16は導水路18により塊状体層６の下端と連通し、塊状体層６に貯まった流下水の一部分が流入する。集水槽16は、塊状体層６から流下水の一部分を抜き出せるものであれば足り、図示例のように堰堤５と同程度の高さの比較的小さい水槽とするか又は保水性底面３に隣接して設けた側溝等とすることができ、大きな設置スペースを必要としない。図示例の散水装置20は、集水槽16から水を汲み上げるポンプ21と、汚染土壌積み上げ台２の上方に設けた散水器23と、ポンプ21から散水器23まで水を運ぶ送水路22とを有する。散水器23として従来の適当な散水器具が利用可能であるが、例えば農業分野で使用する細孔付きホース等を利用できる。図示例では散水器23として３本の細孔付きホースを利用しているが、汚染土壌８の全体に均一に散水できるように散水器23の数及び配置は適当に選択できる。
【００１９】
集水槽16には窒素・リン等の汚染物質分解微生物用の栄養物質を添加する栄養添加装置25を設け、散水する水に栄養物質を適宜添加することが望ましい。栄養物質が添加された散水により、汚染土壌８及び塊状体層６での分解微生物の活性化が促進される。但し、栄養物質は集水槽16に添加する方法に限らず、汚染土壌８に直接添加してもよい。汚染土壌８に栄養物質が添加されていれば、散水時に栄養物質が水と共に塊状体層６へ流下するので、塊状体層６において分解微生物を活性化できる。
【００２０】
土壌浄化に際し、図１の生物浄化装置１の積み上げ台２上に汚染土壌８をパイル状に積み上げる。例えば積み上げ台２の平面的な大きさを８ｍ×８ｍ程度とすれば、バックホー等の重機により積み上げ台２の外側から、汚染土壌８を1.5ｍ程度の高さのパイル状に積み上げることができる。汚染土壌８上に重機を乗り上げると土壌中に圧密が生じて良好な通気が難しくなるが、８ｍ×８ｍ×1.5ｍ程度のパイルであれば重機を乗り上げずに積み上げることができ、しかも崩落するおそれも少ない。この場合パイルの容積は約80m³となり、土壌中の空隙率を30％とすると空隙の容積は約24m³（＝80×0.3）となる。
【００２１】
次いで、集水槽16に貯えた水を散水装置20によってパイル状の汚染土壌８の上方から全面に均一になるように散水すると共に、塊状体層６の曝気装置10を駆動して塊状体６及び汚染土壌８に通気する。例えば汚染土壌８の地盤からの掘削時に発生する汚染水を集水槽16に貯え、窒素・リン等の栄養物質を添加して散水に用いることができる。本発明では、後述するように汚染土壌８の上方に散水した水を塊状体層６経由で集水槽16へ戻して循環させるので、汚染土壌８及び塊状体層６の空隙中を繰り返し通過する際に汚染水の汚染物質の微生物による分解が期待できる。すなわち本発明は、汚染土壌８及び塊状体７に付着した汚染物質だけでなく散水中の汚染物質の分解も期待できる。
【００２２】
通常、土壌中には空隙の50％程度の水を保持させることが可能であり、上述した容積約80m³の汚染土壌８のパイルに保持できる水量は約12.0m³（＝24×0.5）である。例えば17.8m³の汚染水を処理する場合は、汚染土壌８に保持できない汚染水量5.8m³（＝17.8−12.0）を塊状体層６に貯える。塊状体層６の空隙率を30％とした場合、5.8m³の水を貯えるためには、上述した８ｍ×８ｍの積み上げ台２の深さを約30cm（＝5.8／（8×8×0.3））とする。積み上げ台２の深さは、水の循環を停止した場合にもオーバーフロー水が発生しないように設計することが望ましい。処理対象の汚染水量が多い場合は、塊状体層６の深さの調節により対応する。
【００２３】
塊状体層６に流下した水の一部分を集水槽16から抜き出し、散水装置20により汚染土壌８の上方に戻して循環させる。循環させる水量は、汚染土壌８及び塊状体層６内に25〜30％程度の空隙が確保できるように調節することが望ましい。また図示例では、集水槽16において水中の栄養物質濃度や酸素濃度を適当なセンサー（図示せず）で測定して制御装置27に入力し、制御装置27により栄養添加装置25の栄養物質添加量や曝気装置10の送気量を調節することにより、水中の栄養物質濃度や溶存酸素量を適宜調節する。
【００２４】
汚染土壌８の上方からの散水中には、汚染土壌８の空隙を流れ落ちる際に酸素が溶け込む。本発明において汚染土壌８は、水と酸素との接触面積を大きくする接触材としても機能する。また散水中には、汚染土壌８を流下する際及び塊状体層６に貯えられている際に、土壌８及び塊状体７の表面の微生物が産出した界面活性物質（バイオサーファクタント）が溶け込む。界面活性剤により汚染物質が水中に溶解し易くなり、微生物による水中の汚染物質の分解が促進される。また、界面活性剤が溶け込んだ水を循環させて汚染土壌８及び塊状体７の空隙に繰り返し流すことにより、汚染土壌８及び塊状体７の表面から汚染物質が剥がれ易くなり、汚染土壌８及び塊状体７の浄化を促進できる。すなわち、汚染土壌８からの流下水を塊状体層６経由で汚染土壌８へ戻して循環させることにより、汚染土壌８及び塊状体７の表面に付着した汚染物質の剥離を促進すると共に水中での汚染物質分解効率の向上が期待できる。
【００２５】
本発明によれば、汚染土壌と汚染水と汚染塊状体とをオンサイトで同時に浄化することできる。また、塊状体と汚染土壌とを同じスペース上に積み上げて汚染水を循環させ、塊状体層を貯水ゾーンとするので、従来のように貯水槽等を別途設置する必要がなく、敷地が狭い汚染サイトでも実施可能である。更に、塊状体層への必要最小限の曝気により塊状体層及び汚染土壌の全体に必要な空気を効率的に供給できるので、最小限のエネルギー消費で経済的な浄化が可能であり、環境的にも負荷が小さい理想的な汚染浄化が可能となる。
【００２６】
こうして本発明の目的である「汚染サイトで発生する汚染水や汚染塊状体を汚染土壌と共に浄化できる水循環式生物浄化方法及び装置」の提供が達成できる。
【００２７】
好ましくは、集水槽16に汚染物質分離手段17を設け、水中の分離可能な汚染物質（例えば、水面に浮いた油膜等）を除去する。上述したように、汚染水中の汚染物質は汚染土壌８及び塊状体層６を循環する間に微生物によって徐々に分解されるが、集水槽16で分離可能な汚染物質を除去することにより微生物に対する負荷を低減して短期間での汚染水の浄化が期待できる。図示例では、分離槽16に汚染物質分離手段17として油水分離ピットを設け、塊状体層６の流下水を先ず油水分離ピットに流入させて水面に浮遊する油を分離し、ピット底部の水を分離槽16に流入させて循環に供している。汚染物質分離手段17として、スポンジその他の油吸着材を利用してもよい。
【００２８】
なお、図示例では汚染土壌８をシート26で被覆し、雨が汚染土壌８中に入り込んで塊状体層６及び集水槽16からオーバーフローするのを防止している。図示例のシート26は、雨の進入は防止するが空気の通過を許す通気性のある材質製のもの、又は複数の防水シート材を空気の通過を許すように重ね合わせたものである。但し、シート28は本発明に必須のものではない。
【００２９】
【実施例】
図２は、塊状体層６から汚染土壌８に吹き出した曝気の空気流を回収して塊状体層６へ戻し、塊状体層６と汚染土壌８との間で空気を循環させる本発明の生物浄化装置の他の実施例を示す。図２の曝気装置10は、図１と同様の送風機11及び送気管12と共に送風機11の吸気口に連通した吸気管14を有し、吸気管14を汚染土壌８のパイルの中間部又は上部に挿入し、送気管12から圧入した空気を吸気管14により送風機11へ戻して循環させる。汚染土壌の生物浄化は一般的に10℃以下になると効率が極めて悪くなることが知られており、例えば外気温が10℃以下になる冬季の寒冷地等では汚染土壌の加温又は保温が必要となる。例えば曝気装置10に加熱装置を設けて加熱した空気を塊状体層６の送気管12に圧入するが、図示例のように汚染土壌８から空気流を回収して曝気装置10へ戻して循環させることにより、加熱のためのエネルギーを節約することができ、汚染土壌８及び塊状体層６内の効率的な保温が期待できる。但し、空気流の循環は本発明に必須のものではない。
【００３０】
以上、地表に設けた生物浄化装置について説明したが、本発明は地盤中で実施することも可能である。例えば、図３（Ａ）に示すように地表から地下水面に至る地盤が油で汚染されており、油が地下水面上に浮いて広がっているような汚染サイトでは、地盤掘削時に大量に発生する汚染水の処理に多大なエネルギーとコストを要する問題があった。また、汚染された砂礫等は焼却処分等により処理する必要があり、低コストでの処理技術が必要であった。本発明によれば、汚染土壌と共に汚染水や汚染塊状体も併せて浄化できるので、このような汚染サイトの効率的・経済的な浄化が可能となる。
【００３１】
図３の実施例では、先ず同図（Ｂ）に示すように地下の汚染地盤を掘削する。図示例では汚染地盤を地下水面まで掘削しているが、汚染状況によっては地下水よりも深く掘削する必要がある。なお図示例では、汚染地盤を地下水面に至る矢板28で周囲の非汚染地盤から隔離した上で掘削しているが、矢板28がなくても汚染地盤の掘削が可能であれば足りる。矢板28は汚染された地下水の拡散を防止するためにも有効であるが、地下水の拡散が問題とならない場合や揚水その他の方法で拡散が防止できる場合は矢板28を必要としない。掘削した汚染地盤は、適当な篩い分け手段30により非汚染土壌９と汚染土壌８と汚染された砂礫とに篩い分けし、篩い分けした砂礫を塊状体７として使用し、篩い分けした汚染土壌８と共に浄化対象とする。また、掘削時に発生した汚染水を集水槽16に貯え、表面に浮いた油膜を除去すると共に栄養物質を添加する。
【００３２】
地下水面まで掘削した後、同図（Ｃ）に示すように、地盤の地下水保水面を保水性底面３とし、その保水性底面３上に篩い分けした砂礫を塊状体７として埋め戻すと共に、塊状体７中に曝気装置10の送気管12を設置する。また、地下水を汲み上げるための導水路18を設置する。塊状体７を地下水の上方まで埋め戻すことにより、地下水が貯まる塊状体層６を形成する。次いで塊状体層６の上に篩い分けした汚染土壌８を埋め戻し、汚染土壌８の上方に散水装置20の散水器23を配置する。集水槽16に貯えた汚染水を散水装置20によって汚染土壌８の上方から散水すると共に送気管12へ曝気用の空気を圧入し、導水路18にポンプ19を接続して塊状体層６の地下水を集水槽16へ汲み上げ、汲み上げた地下水を散水装置20により汚染土壌８の上方から散水することにより、汚染土壌８と塊状体層６と集水槽16との間で汚染水を循環させる。
【００３３】
図３のように地盤中に塊状体層６と汚染土壌８とを積み重ねて設置し、汚染土壌８と塊状体層６とに汚染水を循環させることにより、図１を参照して説明した原理と同様に、汚染土壌８及び塊状体７の効率的な浄化と汚染水及び地下水中の汚染物質の分解が期待できる。従って、図３（Ａ）のような汚染サイトにおいても汚染土壌８と汚染塊状体７と汚染水とを同じスペースで同時に浄化できるので、効率的・経済的な汚染浄化が可能となる。また、図３のように汚染土壌８に吸気管14を設けて曝気の空気流を回収して循環させることにより、冬季における汚染土壌８及び塊状体層６内の効率的な保温が可能となる。
【００３４】
【発明の効果】
以上説明したように、本発明の汚染土の積み上げ式生物浄化方法及び装置は、保水性底面上に硬質塊状体を通気可能な層状に載置し、塊状体層上に汚染土壌を積み上げ、汚染土壌へ散水すると共に塊状体層へ曝気し、塊状体層への流下水を土壌へ戻し循環させるので、次の顕著な効果を奏する。
【００３５】
（イ）汚染土壌の汚染サイトで発生する汚染水や汚染塊状体を、汚染土壌と共に同時に浄化することができる。
（ロ）汚染土壌と塊状体層とを同じスペース上に積み上げるので、広い敷地を必要とせず浄化施設の省スペースが図れる。
（ハ）省敷地型であるため、敷地の狭い汚染土壌現場等でもオンサイト浄化施設を容易に構築できる。
（ニ）塊状体層への必要最小限の曝気により塊状体層及び汚染土壌の全体に必要な空気を効率的に供給できるので、消費エネルギーが小さく、経済的な浄化が可能である。
（ホ）エネルギー消費が少ないので、環境に対する負荷が小さい技術である。
（ヘ）塊状体層から汚染土壌に吹き出した曝気の空気流を回収して塊状体層へ戻して循環させることができ、汚染土壌及び塊状体層内の効率的な保温が可能である。
【図面の簡単な説明】
【図１】は、本発明の一実施例の説明図である。
【図２】は、本発明の他の実施例の説明図である。
【図３】は、本発明の更に他の実施例の説明図である。
【図４】は、従来の汚染土壌の生物浄化方法の一例の説明図である。
【符号の説明】
１…汚染土壌浄化装置２…汚染土壌積み上げ台
３…保水性底面４…遮水材
５…堰堤６…塊状体層
７…塊状体８…汚染土壌
９…非汚染土壌 10…曝気装置
11…送風機 12…送気管
13…弁 14…吸気管
15…弁 16…集水槽
17…汚染物質分離手段 18…導水路
19…ポンプ 20…散水装置
21…ポンプ 22…送水路
23…散水器 24…弁
25…栄養添加装置 26…シート
27…制御装置 28…矢板
30…篩い分け手段 31…汚染土壌パイル
32…防水シート 33…ピット
34…第一貯水槽 34a…投入口
34b…攪拌機 34c…センサー
35…ポンプ 36…第二貯水槽
36a…注入口 36b…散水器
36c…ポンプ 37…送水管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for purifying contaminated soil in a water cycle, and more particularly to a method and an apparatus for purifying contaminated soil by activating microorganisms in the soil.
[0002]
[Prior art]
As a method of purifying soil contaminated with organic substances such as oil and other contaminants, the contaminated soil is supplied with nutrient substances such as nitrogen and phosphorus necessary for the growth of microorganisms, and an appropriate amount of water and air (or oxygen). BACKGROUND ART Biological treatment methods for decomposing pollutants in soil by artificially activating aerobic pollutant-degrading microorganisms in soil have been developed. This biological treatment method is a method that directly decomposes pollutants, does not generate secondary waste, requires little energy for treatment, and is expected to have the effect of purifying to low concentrations that are difficult with physical / chemical treatment alone. ing.
[0003]
The conventional biological treatment method uses a method of supplying air to the soil, a method of stacking excavated contaminated soil to form a pile, and periodically cutting back the contaminated soil with a heavy machine such as a backhoe to supply fresh air. It is classified into a method of forcibly injecting or sucking air into the lower or middle part of the contaminated soil piled up through a ventilation pipe.
[0004]
[Patent Document 1] JP-A-11-179336 [Patent Document 2] JP-A-7-102298 [Non-patent Document 1] "MBI Report 1996 &1997", Marine Biotechnology Institute, June 2002, p11- 16
[0005]
[Problems to be solved by the invention]
However, the conventional biological treatment method has the following problems.
[0006]
(A) In a conventional biological treatment method for excavating contaminated soil on the ground, water containing a contaminant (hereinafter referred to as “contaminated water”) is often generated in large quantities during excavation. Also, contaminated water leaches from contaminated soil that has been supplied with water for bioremediation. Contaminated water generated at the site of contaminated soil (hereinafter sometimes referred to as a contaminated site) will spread out if it leaks to the surrounding area. Therefore, conventionally, it is often collected, transported outside the contaminated site, and incinerated as waste. . However, incineration of contaminated water consumes a large amount of energy due to the latent heat of the water, so that the energy consumption is increased, the disposal cost is increased, and it is not preferable from the environmental point of view.
[0007]
Patent Document 1 discloses a biological treatment method using contaminated water generated at a contaminated soil site, as shown in FIG. 4, recovering contaminated water containing oil leached from the contaminated soil pile 31 and indigenous microorganisms, and providing microbial nutrients. Disclosed is a method for repairing oil-contaminated soil after adding the composition to grow microorganisms and then returning the soil pile 31. In FIG. 4, the leachate from the soil pile 31 is collected by a collection facility such as a waterproof sheet 32 and a pit 33 and sent to a first water storage tank 34 by a water supply pump 35a. In the first water storage tank 34, the nutrient composition is added from the input port 34a and stirred by the stirrer 34b, so that the oil-degrading microorganisms proliferate. Microorganisms at the stage of growth above a predetermined concentration (e.g., 10 ⁷ cells / ml), the water pump 35b leachate first reservoir 34 was transferred to a second reservoir 36, from the injection port 36a in the second reservoir 36 Microorganisms are further grown by adding water or oil-containing water and stirring with a stirrer 36b. As the oil-containing water to be added to the second water tank 36, contaminated water generated during excavation of contaminated soil, washing water used for cleaning contaminated soil, and the like are used. Once the oil content by the oil decomposition action of microorganism in the second reservoir 36 is reduced below a predetermined value, the microbial concentration reached a maximum (e.g., ¹⁰⁷ to about ⁹ / ml), the second reservoir 36 The water inside is poured into the soil pile 31 by the water pump 36c and the water pipe 37, and the microorganisms grown in the second water tank 36 are transplanted to the soil pile 31. By repeating the above operation, the initial speed of oil decomposition in the soil pile 31 is improved, and the contaminated soil is repaired in a short period of time.
[0008]
However, the method of Patent Document 1 requires that the first water storage tank 34 and the second water storage tank 36 be installed at the contaminated site, and a large-sized water storage tank is required to treat a large amount of contaminated water. However, it is difficult to implement at a contaminated site because of the limited installation space. Further, although depending on the soil contamination concentration, the biological purification method requires several months to about one year to complete the purification, so the method of Patent Document 1 requires a large amount of energy for stirring and aeration of the water storage tank, increasing the cost. There are also problems. In order to utilize the advantage of the bioremediation method for contaminated soil that consumes less energy, it is desirable that contaminated water generated at the contaminated site can be treated on-site with less energy.
[0009]
(B) In an actual contaminated soil site, not only the soil is contaminated, but also surrounding structures and the like are often contaminated. For example, when the soil of a site such as a closed gas station or oil tank is contaminated, the concrete structure on the site is also often contaminated, and when the concrete structure is dismantled during purification of the contaminated soil, it is contaminated. Concrete lumps are generated. Conventionally, such contaminated concrete lump is carried out from a contaminated site as waste, and is incinerated. However, as described above, incineration consumes a large amount of energy, and is not economically or environmentally preferable. There is a demand for the development of a technology that enables on-site treatment of contaminated concrete lump and the like generated at a contaminated site together with contaminated soil and contaminated water with little energy.
[0010]
Therefore, an object of the present invention is to provide a water circulation type biological purification method and apparatus capable of purifying contaminated water and contaminated lump generated at a contaminated site together with contaminated soil.
[0011]
[Means for Solving the Problems]
The present inventor has paid attention to a technique for purifying granular materials and aggregates such as sand, stones and rocks contaminated with oil and the like (hereinafter, both are collectively referred to as aggregates). Patent Literature 2 and Non-Patent Literature 1 disperse microorganisms having a surfactant-producing ability on a lump contaminated with shore oil, and wash and remove contaminated oil attached to the lump by the surfactant produced by the microorganism. It proposes a method for cleaning oil contamination. For example, Non-Patent Document 1 discloses that the microorganisms in seawater are immersed twice a day in seawater to which a nitrogen source and a phosphorus source have been added, using a beach simulation test device simulating the ebb and flow of the tide. Reported that heavy oil adhering to the surface of a lump was decomposed and disappeared by the action of lump (p15 in Non-Patent Document 1). The microorganisms having an oil-decomposing function are present widely in contaminated soil together with microorganisms that decompose other pollutants, and are also present in contaminated water generated at a contaminated site. If the contaminated concrete lump can be washed using the contaminated water in the same manner as in the method of Non-Patent Document 1, it becomes possible to purify the contaminated water and the contaminated lump together with the contaminated soil. The present invention has been completed as a result of research and development based on this finding.
[0012]
Referring to the embodiment of FIG. 1, the method for purifying contaminated soil by water circulation according to the present invention comprises placing a hard lump 7 on a water-retentive bottom surface 3 in a gas-permeable layer and placing the lump 7 on a layer 6 of the lump 7. The contaminated soil 8 is piled up, water is sprinkled on the contaminated soil 8 and the agglomerate layer 6 is aerated, and the water flowing down to the lump body layer 6 is returned to the contaminated soil 8 and circulated.
[0013]
Referring to the embodiment of FIG. 1, the water circulation type biological purification apparatus for contaminated soil according to the present invention includes a layer of a gas-permeable hard lump 7 on which a contaminated soil 8 can be placed on a water retention bottom surface 3. 6, a water collecting tank 16 communicating with the water retention bottom surface 3, a water spraying device 20 for spraying water in the water collecting tank 16 above the massive layer 7, and an aeration device 10 facing the massive layer 7.
[0014]
As the water spray, contaminated water generated during excavation of the contaminated soil 8 can be used. In addition, the block 7 can be a pollutant-attached block. An example of the contaminant-attached lump 7 is a concrete lump generated by dismantling a concrete structure in the vicinity of the contaminated soil 8. Further, the contaminated lump 7 can be made into gravel, and the contaminated soil and the gravel excavated from the ground can be sieved to form the soil 8 and the lump 7. More preferably, a nutrient addition device 25 for adding a nutrient for pollutant-decomposing microorganisms to the water collecting tank 16 is provided, and a contaminant separating means 17 is further provided.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an embodiment of the biological purification apparatus of the present invention applied to purification of soil contaminated with oil. However, the invention is not limited to application to oil contaminated soil. The biological purification device 1 in the illustrated example has a layer 6 of a hard lump 7 that is placed on the water retention bottom surface 3 so as to be able to ventilate. The water-retentive bottom surface 3 is formed by a water-blocking material 4 such as asphalt laid on the surface of a contaminated site, for example. As shown in the illustrated example, a dam 5 can be provided around the water-blocking material 4 so as to be able to retain water. Blocks 7 such as gravel and pebbles are placed in layers on the water retention bottom surface 3 so that contaminated soil 8 can be piled up (hereinafter referred to as a contaminated soil stacking table) 2. The layer 6 of the lump 7 serves as a water storage zone for storing the water flowing down from the contaminated soil 8 as described later. The depth of the massive layer 6, that is, the height of the embankment 5 in the illustrated example is appropriately determined according to the amount of water flowing down from the contaminated soil 8.
[0016]
An aeration device 10 is provided so as to face the mass layer 6. The illustrated aeration apparatus 10 includes a plurality of air supply pipes 12 with pores provided at the lower end of the massive layer 6 and a blower 11 communicating with each air supply pipe 12. The air pressed into the flowing water of the massive layer 6 from the blower 11 via the air pipe 12 is diffused in the massive layer 6 and blows upward from the entire top surface of the massive layer 6 as a substantially uniform air flow, The diffused air flow uniformly flows throughout the contaminated soil 8 piled up on the massive layer 6. The uniform supply of air to the contaminated soil 8 has the effect of minimizing the occurrence of short paths of air in the contaminated soil 8. In addition, the diffusion of air in the mass layer 6 creates an efficient contact between the flowing water and the air on the surface of the mass 7 and makes the mass 7 function as an attachment carrier for microorganisms. That is, according to the present invention, the air required for activating the pollutant-degrading microorganisms can be efficiently supplied to the bulk layer 6 and the entire contaminated soil 8 thereabove by the minimum necessary aeration of the bulk layer 6. The aeration apparatus 10 in the illustrated example can appropriately adjust the amount of air supplied to the bulk layer 6 and the contaminated soil 8 by adjusting the valves 13 of the air supply pipes 12.
[0017]
An example of the lumps 7 of the lumps layer 6 is a gravel, a stone, a rock, or the like having a suitable strength and a diameter of 2 mm or more, but concrete lumps, wood chips, and metal fragments generated by dismantling a concrete structure near the contaminated soil 8. Other hard waste pieces can be used as the lump 7. Gravel or stones mixed in the contaminated soil 8 may be sieved from the contaminated soil 8 and used as the block 7. As described above, since the present invention can make the block 7 function as a microorganism carrier, it can be expected to clean and decompose the pollutant adhered to the surface of the block 7 by the decomposing microorganisms. Gravel and the like in the contaminated soil 8 can be actively used as the lumps 7.
[0018]
Further, a water collecting tank 16 is provided so as to communicate with the water retention bottom surface 3, and a water spray device 20 for spraying water from the water collecting tank 16 from above the stacking table 2 is provided. The water collecting tank 16 in the illustrated example communicates with the lower end of the massive layer 6 through the water conduit 18, and a part of the flowing water stored in the massive layer 6 flows in. It is sufficient that the water collecting tank 16 is capable of extracting a part of the flowing water from the massive layer 6. The collecting tank 16 may be a relatively small water tank having the same height as the dam 5 as shown in the illustrated example, or the water retaining bottom 3 may be used. A side groove or the like provided adjacently can be used, and a large installation space is not required. The illustrated water sprinkling device 20 includes a pump 21 for pumping water from the water collecting tank 16, a water sprinkler 23 provided above the contaminated soil stacking platform 2, and a water passage 22 that carries water from the pump 21 to the water sprinkler 23. . Although a conventional appropriate watering device can be used as the watering device 23, for example, a hose with a fine hole used in the agricultural field can be used. In the illustrated example, three hoses with fine holes are used as the water sprinklers 23. However, the number and arrangement of the water sprinklers 23 can be appropriately selected so that water can be uniformly sprayed over the entire contaminated soil 8.
[0019]
The water collecting tank 16 is provided with a nutrient addition device 25 for adding a nutrient for pollutant-decomposing microorganisms such as nitrogen and phosphorus, and it is desirable to appropriately add the nutrient to water sprinkled. The watering to which the nutrient substance has been added promotes the activation of the degrading microorganisms in the contaminated soil 8 and the clump layer 6. However, the nutrient substance is not limited to the method of being added to the water collecting tank 16, but may be directly added to the contaminated soil 8. If a nutrient substance is added to the contaminated soil 8, the nutrient substance flows down to the mass layer 6 together with water at the time of watering, so that the degrading microorganisms can be activated in the mass layer 6.
[0020]
At the time of soil purification, the contaminated soil 8 is piled up on the stacking stand 2 of the biological purification device 1 of FIG. For example, if the planar size of the stacking stand 2 is about 8 m × 8 m, the contaminated soil 8 can be piled up from the outside of the stacking stand 2 in a pile shape of about 1.5 m by a heavy machine such as a backhoe. When heavy equipment is run on the contaminated soil 8, consolidation occurs in the soil and good ventilation becomes difficult, but piles of about 8m x 8m x 1.5m can be piled up without riding heavy equipment and may collapse. Also less. In this case, the pile volume is about 80 m ³ , and if the porosity in the soil is 30%, the void volume is about 24 m ³ (= 80 × 0.3).
[0021]
Next, the water stored in the water collecting tank 16 is sprayed uniformly from above the piled contaminated soil 8 by the water spraying device 20 and the aerator 10 for the massive layer 6 is driven to drive the massive 6 Vent the contaminated soil 8. For example, contaminated water generated during excavation of the contaminated soil 8 from the ground can be stored in the water collecting tank 16 and used for watering by adding nutrients such as nitrogen and phosphorus. In the present invention, since water sprinkled above the contaminated soil 8 is returned to the water collecting tank 16 via the massive layer 6 and circulated as described later, the water is repeatedly passed through the gaps between the contaminated soil 8 and the massive layer 6. Microbial decomposition of pollutants in contaminated water can be expected. That is, the present invention can be expected to decompose not only the contaminants attached to the contaminated soil 8 and the lump 7 but also the contaminants in sprinkling water.
[0022]
Usually, the soil is capable of holding 50% of water voids, water that can be held in a pile of contaminated soil 8 of volume of about 80 m ³ described above is about 12.0m ³ (= 24 × 0.5) is there. For example, when treating 17.8 m ³ of contaminated water, 5.8 m ³ (= 17.8-12.0) of contaminated water that cannot be retained in the contaminated soil 8 is stored in the massive layer 6. Assuming that the porosity of the block layer 6 is 30%, in order to store 5.8 m ³ of water, the depth of the above-mentioned 8 m × 8 m stacking platform 2 is set to about 30 cm (= 5.8 / (8 × 8 × 0.3 )). It is desirable that the depth of the stacking stand 2 is designed so that overflow water does not occur even when the circulation of water is stopped. If the amount of contaminated water to be treated is large, it is dealt with by adjusting the depth of the massive layer 6.
[0023]
A part of the water that has flowed down to the mass layer 6 is extracted from the water collecting tank 16 and returned to and circulated above the contaminated soil 8 by the sprinkler 20. The amount of water to be circulated is desirably adjusted so that a void of about 25 to 30% can be secured in the contaminated soil 8 and the lump layer 6. Further, in the illustrated example, the nutrient substance concentration and oxygen concentration in the water in the water collecting tank 16 are measured by a suitable sensor (not shown) and input to the control device 27. By adjusting the air supply amount of the aeration device 10, the concentration of the nutrient substance in water and the dissolved oxygen amount are appropriately adjusted.
[0024]
Oxygen dissolves in water sprinkling from above the contaminated soil 8 when flowing down the voids of the contaminated soil 8. In the present invention, the contaminated soil 8 also functions as a contact material for increasing the contact area between water and oxygen. In addition, a surfactant (biosurfactant) produced by microorganisms on the surface of the soil 8 and the mass 7 dissolves in the sprinkling water when flowing down the contaminated soil 8 and when the contaminated soil 8 is stored in the mass layer 6. The surfactant facilitates dissolution of the contaminants in the water, and promotes the decomposition of the contaminants in the water by microorganisms. Further, by circulating the water in which the surfactant is dissolved and repeatedly flowing the water into the gaps between the contaminated soil 8 and the block 7, the contaminants are easily peeled off from the surfaces of the contaminated soil 8 and the block 7, and the contaminated soil 8 and the block Purification of the body 7 can be promoted. That is, by circulating the water flowing down from the contaminated soil 8 back to the contaminated soil 8 via the lump layer 6, the separation of the contaminants adhering to the surfaces of the contaminated soil 8 and the lump 7 is promoted, and the water in the water is removed. Improvement of pollutant decomposition efficiency can be expected.
[0025]
ADVANTAGE OF THE INVENTION According to this invention, contaminated soil, contaminated water, and a contaminated lump can be simultaneously purified on site. In addition, since the lump and contaminated soil are piled up on the same space to circulate contaminated water and the lump layer is used as a storage zone, there is no need to separately install a water tank, etc. It can also be implemented on the site. Furthermore, since the required air can be efficiently supplied to the mass layer and the entire contaminated soil by the minimum necessary aeration of the mass layer, economical purification can be performed with minimum energy consumption and environmentally friendly. Therefore, ideal pollution purification with a small load can be achieved.
[0026]
Thus, the object of the present invention is to provide "a water-circulating biological purification method and apparatus capable of purifying contaminated water and contaminated lump generated at a contaminated site together with contaminated soil".
[0027]
Preferably, the water collecting tank 16 is provided with a contaminant separating means 17 to remove separable contaminants in the water (for example, an oil film floating on the water surface). As described above, the contaminants in the contaminated water are gradually decomposed by the microorganisms while circulating through the contaminated soil 8 and the clump layer 6. Therefore, purification of contaminated water in a short period of time can be expected. In the illustrated example, an oil / water separation pit is provided as a pollutant separation means 17 in the separation tank 16, and the water flowing down from the massive layer 6 flows into the oil / water separation pit first to separate the oil floating on the water surface, and the water at the bottom of the pit is removed. It flows into the separation tank 16 for circulation. A sponge or other oil adsorbent may be used as the pollutant separating means 17.
[0028]
In the illustrated example, the contaminated soil 8 is covered with a sheet 26 to prevent rain from entering the contaminated soil 8 and overflowing from the massive layer 6 and the water collecting tank 16. The sheet 26 in the illustrated example is made of a breathable material that prevents the entry of rain but allows the passage of air, or a plurality of waterproof sheet materials that are overlapped to allow the passage of air. However, the sheet 28 is not essential to the present invention.
[0029]
【Example】
FIG. 2 shows an organism according to the present invention in which the aerated airflow blown out from the lump layer 6 to the contaminated soil 8 is collected and returned to the lump layer 6, and air is circulated between the lump layer 6 and the contaminated soil 8. 5 shows another embodiment of the purifying device. The aeration apparatus 10 in FIG. 2 has an air intake pipe 14 communicating with the air intake of the air blower 11 together with the air blower 11 and the air air pipe 12 as in FIG. After being inserted, the air press-fitted from the air supply pipe 12 is returned to the blower 11 by the intake pipe 14 and circulated. It is known that the efficiency of bioremediation of contaminated soil is generally extremely poor when the temperature is below 10 ° C. For example, it is necessary to heat or keep the contaminated soil warm in cold regions where the outside air temperature is below 10 ° C. It becomes. For example, a heating device is provided in the aeration device 10 and heated air is pressed into the air supply pipe 12 of the massive layer 6. As shown in the illustrated example, an air flow is collected from the contaminated soil 8 and returned to the aeration device 10 for circulation. As a result, energy for heating can be saved, and efficient heat retention in the contaminated soil 8 and the bulk layer 6 can be expected. However, circulation of the air flow is not essential to the present invention.
[0030]
As described above, the biological purification device provided on the surface of the ground has been described, but the present invention can also be implemented on the ground. For example, as shown in FIG. 3 (A), the ground from the ground surface to the groundwater surface is contaminated with oil, and a large amount of oil is generated during ground excavation at a contaminated site where the oil is floating on the groundwater surface and spreading. There is a problem that a large amount of energy and cost are required for treating contaminated water. In addition, contaminated sand and gravel had to be disposed of by incineration, etc., and low-cost processing technology was required. According to the present invention, since contaminated water and contaminated lump can be purified together with contaminated soil, such a contaminated site can be efficiently and economically purified.
[0031]
In the embodiment shown in FIG. 3, an underground contaminated ground is first excavated as shown in FIG. In the illustrated example, the contaminated ground is excavated to the groundwater surface, but depending on the state of contamination, it may be necessary to excavate deeper than the groundwater. In the illustrated example, the contaminated ground is excavated after being separated from the surrounding non-contaminated ground by a sheet pile 28 reaching the groundwater surface, but it is sufficient if the contaminated ground can be excavated without the sheet pile 28. The sheet pile 28 is also effective in preventing the diffusion of contaminated groundwater, but the sheet pile 28 is not required when the diffusion of the groundwater is not a problem or when the diffusion can be prevented by pumping or other methods. The excavated contaminated ground is sieved into non-contaminated soil 9, contaminated soil 8 and contaminated gravel by a suitable sieving means 30. And the object of purification. In addition, the contaminated water generated during excavation is stored in the water collecting tank 16, the oil film floating on the surface is removed, and nutrients are added.
[0032]
After excavation to the groundwater surface, as shown in FIG. 3 (C), the groundwater retaining surface of the ground is used as the water-retaining bottom surface 3, and the gravels sieved on the water-retaining bottom surface 3 are buried back as a lump 7, The air supply pipe 12 of the aerator 10 is installed in the body 7. In addition, a headrace 18 for pumping groundwater will be installed. By backfilling the block 7 above the groundwater, the block layer 6 in which the groundwater is stored is formed. Next, the sieved contaminated soil 8 is back-filled on the mass layer 6, and the sprinkler 23 of the sprinkler 20 is arranged above the contaminated soil 8. The contaminated water stored in the water collecting tank 16 is sprinkled from above the contaminated soil 8 by the water sprinkling device 20, and air for aeration is injected into the air supply pipe 12, and the pump 19 is connected to the water conduit 18 to connect the groundwater of the massive layer 6. The contaminated water is circulated between the contaminated soil 8, the clump layer 6 and the water collection tank 16 by pumping the groundwater into the water collecting tank 16 and spraying the pumped ground water from above the contaminated soil 8 with the watering device 20.
[0033]
As shown in FIG. 3, the massive layer 6 and the contaminated soil 8 are stacked and installed in the ground, and the contaminated water is circulated through the contaminated soil 8 and the massive layer 6, thereby the principle described with reference to FIG. Similarly to the above, efficient purification of the contaminated soil 8 and the block 7 and decomposition of the contaminated water and contaminants in the groundwater can be expected. Therefore, even in the contaminated site as shown in FIG. 3A, the contaminated soil 8, the contaminated lump 7, and the contaminated water can be simultaneously purified in the same space, so that efficient and economical purification can be achieved. Further, as shown in FIG. 3, by providing an intake pipe 14 in the contaminated soil 8 to collect and circulate the air flow of aeration, it is possible to efficiently maintain the heat in the contaminated soil 8 and the bulk layer 6 in winter. .
[0034]
【The invention's effect】
As described above, the piled-up biocontamination method and apparatus for contaminated soil according to the present invention, the hard lump is placed on the water-retaining bottom surface in a permeable layer, the contaminated soil is piled up on the lump layer, and the contaminated soil is piled up. Since water is sprinkled on the soil and aerated in the lump layer, and the water flowing down to the lump layer is returned to the soil and circulated, the following remarkable effects are obtained.
[0035]
(B) Contaminated water and contaminated lump generated at the contaminated site of the contaminated soil can be purified together with the contaminated soil.
(B) Since the contaminated soil and the lump layer are stacked in the same space, a large site is not required, and the space for the purification facility can be saved.
(C) Since it is a site-saving type, an on-site purification facility can be easily constructed even at contaminated soil sites where the site is narrow.
(D) Since the required air can be efficiently supplied to the bulk layer and the entire contaminated soil by the minimum necessary aeration of the bulk layer, energy consumption is small and economical purification is possible.
(E) The technology consumes less energy and therefore has less impact on the environment.
(F) The air flow of the aerated air blown out from the lump layer to the contaminated soil can be collected and returned to the lump layer to be circulated, thereby enabling efficient heat retention in the contaminated soil and the lump layer.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of one embodiment of the present invention.
FIG. 2 is an explanatory diagram of another embodiment of the present invention.
FIG. 3 is an explanatory view of still another embodiment of the present invention.
FIG. 4 is an explanatory diagram of an example of a conventional method for purifying contaminated soil.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Contaminated soil purification apparatus 2 ... Contaminated soil stacking stand 3 ... Water retention bottom surface 4 ... Water barrier 5 ... Dam 6 ... Lump layer 7 ... Lump 8 ... Contaminated soil 9 ... Non-polluted soil 10 ... Aeration device
11… Blower 12… Air pipe
13… Valve 14… Intake pipe
15… Valve 16… Water collecting tank
17: Means for separating contaminants 18 ... Headrace
19 ... pump 20 ... sprinkler
21 ... pump 22 ... water channel
23 ... Sprinkler 24 ... Valve
25 ... nutrition adding device 26 ... sheet
27 ... Control device 28 ... Pile
30 ... means of sieving 31 ... contaminated soil pile
32 ... tarpaulin 33 ... pit
34… First water tank 34a… Inlet
34b… Agitator 34c… Sensor
35… pump 36… second water tank
36a… Inlet 36b… Sprinkler
36c… pump 37… water pipe

Claims

The hard lump is placed on the water-retentive bottom surface in a permeable layer, the contaminated soil is piled up on the lump layer, water is sprayed on the soil and the agglomerate is aerated to the lump layer, and the downflow to the lump layer is performed. A water circulation type biological purification method for contaminated soil, wherein water is returned to the soil and circulated.

2. The method according to claim 1, wherein the effluent is separated from residual contaminants and returned to the soil.

The method according to claim 1 or 2, wherein contaminated water generated during excavation of the contaminated soil is used for watering, and the method for purifying contaminated soil in a water-circulating manner.

The method according to any one of claims 1 to 3, wherein the sprinkling water is supplemented with a nutrient for pollutant-decomposing microorganisms.

The method according to any one of claims 1 to 4, wherein the lumps are contaminated substance-adhered lumps.

The method according to any one of claims 1 to 5, wherein the block is a concrete block, and the contaminated soil is subjected to water circulation.

The method according to any one of claims 1 to 5, wherein the lumps are formed as gravel, and the contaminated soil and the gravels excavated from the ground are sieved to form the soil and the contaminated soil as the lumps.

The method according to any one of claims 1 to 7, wherein the water-retentive bottom surface is made of a water-blocking material.

The method according to any one of claims 1 to 7, wherein the water-retentive bottom surface serves as a groundwater-retaining surface for the ground.

A water-permeable hard massive layer formed so that contaminated soil can be placed on the water-retentive bottom surface, a water collecting tank communicating with the water-retentive bottom surface, a watering device for watering the water in the water-collecting tank above the massive layer, And a water circulation type biological purification apparatus for contaminated soil, comprising: an aeration apparatus facing the mass layer.

The apparatus according to claim 10, wherein the water collecting tank is provided with a contaminant separating means.

The apparatus according to claim 10 or 11, wherein the water collecting tank is provided with a nutrient addition device for adding a nutrient for pollutant-decomposing microorganisms.

The apparatus according to any one of claims 10 to 12, wherein the block is a concrete block, and the contaminated soil is subjected to water circulation.

The apparatus according to any one of claims 10 to 12, wherein the mass is converted into sand and gravel.

The apparatus according to any one of claims 10 to 14, wherein the water-retentive bottom surface is made of a water-blocking material.