JP4049656B2

JP4049656B2 - Hazardous substance removal method for removed seabed sludge containing organotin compounds

Info

Publication number: JP4049656B2
Application number: JP2002329252A
Authority: JP
Inventors: 健二神野; 雄治大嶋; 照憲大本
Original assignee: Kinjo Rubber Co Ltd
Current assignee: Kinjo Rubber Co Ltd
Priority date: 2002-11-13
Filing date: 2002-11-13
Publication date: 2008-02-20
Anticipated expiration: 2022-11-13
Also published as: JP2004160355A

Description

【０００１】
【発明の属する技術分野】
本発明は有機スズ化合物を含む除去海底汚泥の有害物除去処理方法に関する。詳しくは漁港、海面養殖場などの海底の土砂と混在する水生生物に極めて有害な有機スズ化合物の除去処理方法に係るものである。
【０００２】
【従来の技術】
有機スズ化合物のトリブチルスズ（ＴＢＴ）は船底塗料や魚網への付着生物の防汚塗料として使用されてきたが、このことは裏を返せば強い殺生物剤であるということで、水生生物への影響が大きいことを意味するものである。
【０００３】
この有機スズ化合物のトリブチルスズ（ＴＢＴ）が漁港、漁場区域や港湾区域での海底に海底汚泥として蓄積され、これらの海域で魚類を含む種々の海産物から高濃度のトリブチルスズ（ＴＢＴ）が検出されており、これによる魚類に与える内分泌撹乱作用による繁殖阻害やｉｍｐｏｓｅｘ（雌に雄性生殖器官が発達し遂には不妊にいたる現象）により貝類の生産量の激減など水生生物への悪影響は多大なものがある事実が証明されている。
【０００４】
このことから環境ホルモン作用が疑われる有機スズ化合物のトルブチルスズ（ＴＢＴ）の船舶や魚網への使用を禁止する環境が整ってきている。
【０００５】
しかし船舶や魚網への使用を禁止しても沈降することによる海底汚泥として長期に渡って蓄積される有機スズ化合物のトルブチルスズ（ＴＢＴ）を除去しないかぎり水生生物への悪影響は解消しないことから海底汚泥の回収およびその処理の必要性が求められているのが現状である。
【０００６】
ところでこの種の処理方法として水に含まれるダイオキシン類や環境ホルモンの除去に関する発明として図４に示すように、処理すべき水を、調整槽１０１に導入して原水供給ポンプ１０２によって触媒酸化塔１０３に送られる。そしてこの触媒酸化塔１０３において酸化触媒の存在下においてオゾン発生器１０４からのオゾンの注入散気によって酸化処理し、次いで促進酸化塔１０５において更に紫外線ランプ１０６およびオゾンによる酸化処理を行う構成とするものである（例えば、特許文献１参照）。
【０００７】
また、同様に難分解性有機物含有水の処理装置に関する発明として図５に示すように、処理すべき水は、第一混和槽１０７に導入され、凝集剤と混合されて凝集処理が行われる。更に第一混和槽１０７で得られた凝集処理水は第一沈殿槽１０８に導入されて固液分離され、その上澄水は生物処理槽１０９に導入される。
【０００８】
そして生物処理槽１０９からの生物処理水は、膜ろ過装置１１０に導入されて固液分離され、その上澄水が膜ろ過水として促進酸化処理槽１１１に導入され、オゾンと紫外線とによって促進酸化処理を行う構成とするものである（例えば、特許文献２参照）。
【０００９】
【特許文献１】
特開２００１−２０５２７７号公報（第１図）
【００１０】
【特許文献２】
特開２００１−４７０９１号公報（第１図）
【００１１】
【発明が解決しようとする課題】
しかしながらこれらの処理水は、高含水比の浚渫土砂の埋立地内投入における余水の処理のみに特定されており、有機スズ化合物含有の泥水状の土砂・懸濁物質の一連処理、特に土砂分の同時処理などはその範疇に入っていない。
【００１２】
また、海底、湖底などからの高含水比の浚渫土砂の殆どが密閉された埋立地内へ投入され、上澄水の処理のみが行われ、土砂間隙水の処理が行われないために、埋立量の増大化、および圧密対策として埋立地土中間隙水の排出などの問題がある。
【００１３】
更に土砂間隙水の処理が行われないために、埋立完了後において長期にわたり地中に有害物質が残存することとなり、雨水の地下浸透などによる有害物質の埋立地外への流出などの問題がある。
【００１４】
本発明は、以上の点に鑑みて創案されたものであって、有機スズ化合物含有の高含水比の浚渫土砂を余水と土砂とに分離してそれぞれの有機スズ化合物の除去処理を同時に行う有機スズ化合物を含む除去海底汚泥の有害物除去処理方法を提供することを目的とするものである。
【００１５】
【課題を解決するための手段】
上記の目的を達成するために、本発明に係る有機スズ化合物を含む除去海底汚泥の有害物除去処理方法は、有機スズ化合物を含む高含水比の浚渫土砂を凝集沈澱地に搬送し、凝集剤を添加・撹拌させて沈澱濾過池での土砂・フロック沈降堆積物・海水の一層の分離堆積を図り、更に分離された海水および懸濁物質を砂濾過槽および活性炭吸着槽を経て浮遊フロックおよび海水に含まれる有機スズ化合物の除去処理をすると共に、前記沈澱濾過池内での土砂およびフロック沈降堆積物を取り出し、乾燥処理する有害物除去処理方法にあって、前記海水および浮遊フロックの砂濾過槽および活性炭吸着槽による濾過処理の前段階に、ポリエチレンシートにより浮遊フロックから有機スズ化合物の原土含有総量の一定率を該ポリエチレンシートに付着させる工程を備える。
【００１６】
ここで、浚渫土砂運搬船により海水と泥分とが混在した有機スズ化合物を含む高含水比の浚渫土砂を凝集沈澱池に搬送して凝集剤を添加・撹拌することによりフロックを形成させて土砂・フロック沈降堆積物・海水の一層の分離堆積化を図ることが可能となる。
【００１７】
更に海水および浮遊フロックは、同フロックがポリエチレンに付着し易い性質を利用し、凝集沈澱池内に工夫を施したポリエチレンシートを展張及び積層することにより有機スズ化合物の原土含有総量の一定率をその含有フロックからポリエチレンシートに付着させる。
【００１８】
そして前記凝集沈澱池からの濾過水は、砂濾過槽を経て有機スズ化合物の溶存で２ｎｇ/Ｌ以下まで、濾過水中に含有される有機スズ化合物を除去するために通過速度、通過距離および流量を考慮した活性炭を用いての除去が可能となる。
【００１９】
一方、海水濾過後の凝集沈澱池に残留した土砂・フロック沈降堆積物は、数日の自然乾燥後、天日乾燥場にて展開・散布されることで自然排水・天日乾燥によって脱水し、更に紫外線によって有機スズ化合物が分解され、土砂・フロック沈降堆積物に付着する有機スズ化合物の減量を可能とする。
【００２０】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参酌しながら説明し、本発明の理解に供する。
【００２１】
図１に、本発明を適用した有機スズ化合物を含む除去海底汚泥の有害物除去処理方法の一例を示すための概要説明図を示す。
【００２２】
ここで、作業船１に設けられる浚渫装置２によって汚染海域である海底の表層部分（約１０ｃｍ厚さ）を、海水と共に浚渫された高含水の浚渫海底土砂は浚渫土砂運搬船３に排送される。
【００２３】
そして浚渫土砂運搬船３は接岸された後に、浚渫海底土砂は排送管４を通じて複数の濾過槽が設置された凝集沈澱濾過池５に配送する。この浚渫土砂運搬船３から配送される土砂・海水は混合され高濃度の泥水となり、凝集沈澱濾過池５に注入されることとなる。
【００２４】
更にその過程において管注入装置６で注入された凝集沈澱促進剤によって、凝集沈澱濾過池５内で土砂、凝集増大フロックおよび上澄み水となって分離沈降堆積及び移動を行う。その過程において凝集沈澱濾過池５内に展張および被覆したポリエチレンより成る付着シート７および濾過シート８によって有機スズ化合物の相当量を包含するフロックの捕獲を行う。
【００２５】
また、凝集沈澱濾過池５内で濾過された海水は、浚渫海底土砂含有有機スズ総量の９９．９９％以下の有機スズ分が分離含有されている。この海水含有有機スズは、濾過速度、濾過距離、濾過材の効果期限などを考慮・設計された活性炭濾過装置９を通すことによって、放流可能な基準値とされる２ｎｇ/Ｌ以下に除去され、放流される。
【００２６】
一方、海水濾過後、凝集沈澱濾過池５内に沈降・堆積した浚渫土砂は数日間の放置・乾燥後、活性炭濾過による余水濾過装置の設置された天日乾燥場１０に搬出され、所定の日照時間による天日乾燥によって、更に相当量の有機スズ化合物の減量化が可能となる。
【００２７】
そして天日乾燥場１０で乾燥された土砂は、未だ有機スズ化合物を含有するが、予め仕切り堤・止水矢板・排水で水位低下・地下水の挙動を制御・区分され、自然水の非流入対策の施された埋め立て処分地１１に搬入埋め立てられる。
【００２８】
この埋め立て処分地１１内に埋め立てられる有機スズ化合物の減量された土砂は、埋め立て処分地１１内で覆土された後も通気・電極挿入などの微生物の移植・増加によっての微生物分解が促進され、有機スズ化合物は更に減量化される。又容量を残しながら機能低下した使用済みの活性炭・濾過砂は残土砂と共に埋め立て処分地１１内に密封され有害分は減量化される。
【００２９】
なお、空の状態となった使用後の付着シートおよび濾過シート、更には同付着シートおよび濾過シートに付着した有機スズ化合物は乾燥後回収され、高温焼却あるいは無酸素熱処理によって消滅させる。
【００３０】
そこで本発明の凝集沈澱濾過池における高含水の浚渫海底土砂からの有機スズ化合物の各除去過程での実験結果を以下に示す。
【００３１】
比較試験例１
有機スズ化合物含有２５００ｎｇ/ｗｅｔ−ｇの漁港底質を採取し、凝集材無添加及び高分子有機凝集材２ｍｇ/Ｌを添加の２種の試料を用意した。
【００３２】
この２種の試料に海水を１：４（実際の浚渫泥水と同様）の割合で加え、これを２時間振とうし、３時間放置後上澄み液を採取し凝集沈澱処理用試料水として調製した。
【００３３】
この凝集沈澱処理用試料水の上澄み液５００ｍｌに、凝集沈降材としてポリ塩化アルミニウム、塩化第二鉄及び無機凝集沈澱処理材を一定濃度ずつ添加し、１８０ｒｐｍで急速撹拌し、引き続き３０分間緩速撹拌し、１時間静置後の上澄み液の濁度低下率とｐＨ値を測定した結果を下記表１に示す。
【００３４】
【表１】

【００３５】
また、前記凝集材無添加の上澄み液、凝集沈降材としてポリ塩化アルミニウムを添加した場合の上澄み液、高分子有機凝集材２ｍｇ/Ｌを添加した凝集沈澱処理用試料水にポリ塩化アルミニウムを添加した場合の上澄み液および凝集沈降材として無機凝集沈澱処理材を添加した場合の上澄み液に含有する有機スズ化合物の濃度測定結果を下記表２に示す。
【００３６】
【表２】

【００３７】
前記表１より静置３時間で濁度０．５にするためには、ポリ塩化アルミニウム１０ｍｇ/Ｌ、塩化第二鉄４０ｍｇ/Ｌおよび無機凝集沈澱処理材４０ｍｇ/Ｌの注入率が必要となる。
また、フロック強度では無機凝集沈澱処理材が強固であり、ｐＨ値の変化も無かった。
【００３８】
前記表２より無機凝集沈澱処理材の固液分離率が０．００３４と最も小さく、かつ有機スズ化合物の濃度が８６ｎｇ/Lと最も低い結果となった。これにより凝集沈澱処理材として無機凝集沈澱処理材が最も好ましいことが判明した。
なお無機凝集沈澱処理材としてはゼオライトなどの多孔質物質が好ましい。
【００３９】
次に図２に示すのは有機ズズ除去実験概念図であり、２１は５００ｌ容量の原水タンク、２２は撹拌装置、２３は装置外枠、２４は水位測定用としての金尺、２５は整流板、２６はポリエチレン吸着シート、２７はポリエチレンろ過シート、２８は砂フィルター、２９は活性炭フィルター、３０は採水管、３１はマノメーター、３２はバルブおよび３３はポンプを示す。
【００４０】
即ち、前記原水タンク２１内にて無機凝集沈澱処理材が添加され、撹拌装置２２によって撹拌されて固液分離された上澄み液はポンプ３３によって押す装置外枠３とポリエチレンろ過シート２７間に送水される。
【００４１】
そして、この装置外枠３とポリエチレンろ過シート２７間にポリエチレン吸着シート２６を配して、このポリエチレン吸着シート２６に有機スズ化合物を吸着させようとするものである。
【００４２】
そこで特別な材質・形状のポリエチレンシートが効率良く有機スズ化合物を付着させるかを実験すべく下記表３に示す形状に相違のある５種のシートを選定し実験に使用した。
【００４３】
【表３】

【００４４】
前記表３で示す高強力ポリエチレン繊維不織布の最厚さと同程度の厚さとなるように他に種類のシートを折り重ね境界の金具を貼付し、試験用泥水のそれぞれの水位差に差異が生じ始めるまで通水し、その後にシートの入口側と出口側を採水し、有機スズ化合物濃度を測定した結果を下記表４に示す。
【００４５】
【表４】

【００４６】
表４によりシート番号２の２列配置では、シート番号１の１列配置と同程度の比率で吸着することが判明した。また、シート番号３および５は実験終了後のシートに黄土色着色があり、折り重ねのフロック捕獲効果と予想される。
【００４７】
前記表４の結果よりポリエチレンを材料とするシートを泥水通過による吸着・捕獲率は２５％程度期待できる。従って凝集沈降の進んだ有機スズ化合物含有水では、３列配置での６０％弱の濃度低下は確実であり、ろ過を経て最終活性炭処理に有効に働く。また、実際の施工では覆数列・複数千鳥列配置での工夫が可能である。
【００４８】
このようにしてポリエチレンシート、ろ過シートおよび砂フィルターを通して約６０％の有機スズ化合物が除去された有機スズ化合物含有水は、活性炭フィルターを通すことによって最終目標値まで有機スズ化合物を除去して放流されることとなる。
【００４９】
そこで活性炭による有機スズ化合物の阻止率（活性炭吸着）は、活性炭を通過する流速によって決定される。例えば図３のグラフ図で示すように、膜厚５０ｃｍの活性炭フィルターに対して通過前の有機スズ化合物含有濃度が約８６ｎｇ/Lの場合において、流速が０．１９５ｃｍ/ｓｅｃのときには破線で示すように通過後の有機スズ化合物含有濃度が約２０ｎｇ/Lとなる。
【００５０】
ここで、最終目標値である有機スズ化合物含有濃度が２ｎｇ/Lを満たすためには、理論式で計算した流速を７．７５×１０^-3ｃｍ/ｓｅｃとすることによって実線で示すように、通過後の有機スズ化合物含有濃度が約２ｎｇ/Lとなる。
【００５１】
また、流速を落とすには砂フィルターを通過した有機スズ化合物含有水を、活性炭フィルターに入れる際に、その活性炭フィルターの断面積を３０倍以上に拡大すれば、その比率に応じて流速が低下することとなる。
【００５２】
一方、海水濾過後、凝集沈澱濾過池内に沈降・堆積した有機スズ化合物を含むフロック・土砂が同時に、その含水比低下後天日乾燥場に搬出され、同天日乾燥での紫外線による有害分減量化および太陽熱による含水比の更なる低下後に最終処分される。
【００５３】
この有機スズ化合物を含むフロック・土砂が、その有害物質の２０％以上の減量化での最終処分となり、更に土砂の脱水によって最終処分場造成地の土質力学的安定が向上する。
【００５４】
そこで漁港などの海底に堆積する有機スズ化合物の含有深さはせいぜい１０ｃｍほどであり、この有機スズ化合物、有機浮泥等の有害な表層部分のみを海水と共に浚渫し、凝集沈澱濾過池における処理後の沈降した土砂およびフロック沈降堆積物を脱水処理することにより、既存のように埋立処分を主目的とする浚渫（浚渫深さ５０ｃｍ以上）に比べて大幅な減容化が可能となる。
【００５５】
ここで、搬出された有機スズ化合物を含むフロック・土砂は必ずしも天日乾燥によって有害分の減量化および脱水を行う必要性は無く、例えば屋内において人為的な紫外線照射や熱源による乾燥を行うことも考えられるものであるが、僻地における環境やコストの面から天日による乾燥が最も好ましいものである。
【００５６】
また、埋立処分地は、何らかの手段で地下水位を低下させ、その区域に天日乾燥により脱水された土砂の最終埋立処分を行う。
【００５７】
この場合には埋立区域は他区域との地下水の流入・流出が無いような措置を行う。覆土は最終埋立土砂と地上との隔離が確実な厚さとし、降雨の地下浸透がないようにする。更に埋立区域への降雨排水は周辺の排水路を設けるとともに、埋立地の蒲鉾型埋立とし、土砂の流出での窪地ができないように管理する。また次項に関連し、地中への通気孔及び電極孔・装置を設置することもある。
【００５８】
【発明の効果】
以上述べて来た如く本発明によれば、高含水の浚渫土砂の余水・土砂間隙水の無害化処理、有機スズ化合物含有懸濁物資の相当割合のシート等による吸着消滅を行うと共に、沈降・堆積した埋立処分予定土砂の脱水・有機スズ化合物減量化のプロセスを経ての埋立処分となることから処分土砂量の減容化が可能となる。
【００５９】
更に土砂間隙水が少ないことから圧密沈下も少なく、埋立完了後の用地利用を容易にする効果を奏するものである。
【図面の簡単な説明】
【図１】本発明を適用した有機スズ化合物を含む除去海底汚泥の有害物除去処理方法の一例を示すための概要説明図を示す。
【図２】本発明を適用した有機スズ化合物を含む除去海底汚泥の有害物除去処理方法の一例を示すための有機スズ除去実験概念図を示す。
【図３】本発明を適用した有機スズ化合物を含む除去海底汚泥の有害物除去処理方法による活性炭による有機スズ化合物の阻止率を示すグラフ説明図である。
【図４】特許文献１における説明図を示す。
【図５】特許文献２における説明図を示す。
【符号の説明】
１作業船
２浚渫装置
３浚渫土砂運搬船
４排送管
５凝集沈澱濾過池
６管注入装置
７付着シート
８濾過シート
９活性炭濾過装置
１０天日乾燥場
１１処分地[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing harmful substances from removed seabed sludge containing an organotin compound. Specifically, it relates to a method for removing organotin compounds that are extremely harmful to aquatic organisms mixed with sediments on the seabed such as fishing ports and sea farms.
[0002]
[Prior art]
The organotin compound tributyltin (TBT) has been used as an antifouling paint for organisms attached to ship bottom paints and fish nets, but this means that it is a strong biocide and its impact on aquatic life. Means that is large.
[0003]
This organotin compound, tributyltin (TBT), is accumulated as seabed sludge on the seabed in fishing ports, fishing grounds and harbors, and high concentrations of tributyltin (TBT) have been detected in various marine products, including fish. The fact is that there are many adverse effects on aquatic organisms, such as the reproductive inhibition caused by endocrine disrupting effects on fish and imposex (a phenomenon that eventually leads to the development of male reproductive organs in females) resulting in a sharp decline in shellfish production. Has been proven.
[0004]
For this reason, an environment for prohibiting the use of tolbutyltin (TBT), an organotin compound suspected of having an environmental hormone action, on ships and fishnets has been established.
[0005]
However, even if use on ships and fishnets is prohibited, the adverse effects on aquatic organisms will not be eliminated unless the organotin compound, tolbutyltin (TBT), accumulated over a long period of time as sedimentary seabed sludge is removed. Currently, there is a need for sludge recovery and treatment.
[0006]
By the way, as shown in FIG. 4 as an invention relating to the removal of dioxins and environmental hormones contained in water as a treatment method of this type, water to be treated is introduced into a regulating tank 101 and a catalytic oxidation tower 103 is fed by a raw water supply pump 102. Sent to. In this catalytic oxidation tower 103, an oxidation treatment is performed by injecting aeration of ozone from the ozone generator 104 in the presence of an oxidation catalyst, and then an oxidation treatment with an ultraviolet lamp 106 and ozone is further performed in the accelerated oxidation tower 105. (For example, see Patent Document 1).
[0007]
Similarly, as shown in FIG. 5 as an invention relating to a treatment apparatus for hardly decomposable organic substance-containing water, the water to be treated is introduced into the first mixing tank 107 and mixed with a flocculant to perform a coagulation treatment. Further, the agglomerated treated water obtained in the first mixing tank 107 is introduced into the first sedimentation tank 108 for solid-liquid separation, and the supernatant water is introduced into the biological treatment tank 109.
[0008]
Then, the biologically treated water from the biological treatment tank 109 is introduced into the membrane filtration device 110 and separated into solid and liquid, and the supernatant water is introduced into the accelerated oxidation treatment tank 111 as membrane filtered water, and accelerated oxidation treatment is performed by ozone and ultraviolet rays. (For example, refer to Patent Document 2).
[0009]
[Patent Document 1]
JP 2001-205277 A (FIG. 1)
[0010]
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-47091 (FIG. 1)
[0011]
[Problems to be solved by the invention]
However, these treated waters are specified only for the treatment of sewage in the landfill of dredged soil with a high water content. Simultaneous processing is not in that category.
[0012]
In addition, most of the dredged soil with high water content from the seabed, lake bottom, etc. is thrown into the closed landfill, only the supernatant water is treated, and the sediment water is not treated. There are problems such as discharge of pore water in landfills as countermeasures for increase and consolidation.
[0013]
In addition, since the interstitial water is not treated, harmful substances remain in the ground for a long time after the completion of landfill, and there is a problem such as the outflow of harmful substances outside the landfill due to underground infiltration of rainwater. .
[0014]
The present invention was devised in view of the above points, and separates dredged soil with high water content containing organotin compounds into sewage and sediment and simultaneously removes each organotin compound. An object of the present invention is to provide a method for removing harmful substances from removed seabed sludge containing an organotin compound.
[0015]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the harmful substance removal treatment method of the removed seabed sludge containing the organotin compound according to the present invention transports dredged sand having a high water content containing the organotin compound to the agglomeration sedimentation site, To separate and deposit sediment, floc sediment, and seawater in the sedimentation pond, and the separated seawater and suspended matter are passed through the sand filtration tank and activated charcoal adsorption tank to float the flock and seawater. In addition to the removal of organotin compounds contained in the sediment filtration pond, the sediment and flocced sediments in the sedimentation filtration pond are taken out and dried. Prior to the filtration process using the activated carbon adsorption tank, a certain percentage of the total amount of organic tin compound contained in the soil is added to the polyethylene sheet from the floating floc using a polyethylene sheet. Comprising the step of.
[0016]
Here, a dredged sand carrier ship transports dredged soil with a high water content containing organic tin compounds mixed with seawater and mud to a flocculating sedimentation basin, and adds and agglomerates to form flocs. It becomes possible to further separate and deposit floc sediments and seawater.
[0017]
Furthermore, seawater and floating flocs use the property that the flocs easily adhere to polyethylene, and by spreading and laminating a polyethylene sheet that has been devised in a coagulation sedimentation basin, a certain percentage of the total amount of organic tin compound contained in the soil is obtained. It is made to adhere to a polyethylene sheet from containing floc.
[0018]
And the filtered water from the said coagulation sedimentation basin is set to 2 ng / L or less by the dissolution of the organic tin compound through the sand filtration tank, and the passing speed, the passing distance and the flow rate in order to remove the organic tin compound contained in the filtered water. Removal using activated carbon in consideration is possible.
[0019]
On the other hand, the sediment and floc settled sediment remaining in the coagulation sedimentation pond after seawater filtration are dehydrated by natural drainage and sun drying by being spread and sprayed in the sun drying field after several days of natural drying. Furthermore, the organic tin compound is decomposed by ultraviolet rays, and the amount of the organic tin compound adhering to the sediment / floc sediment can be reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings to provide an understanding of the present invention.
[0021]
FIG. 1 is a schematic explanatory diagram for illustrating an example of a harmful substance removal treatment method for removed seabed sludge containing an organotin compound to which the present invention is applied.
[0022]
Here, the high-moisture dredged seabed sediment which has been dredged with seawater from the surface layer (about 10 cm thick) of the seabed, which is a contaminated sea area, by the dredging device 2 provided on the work boat 1 is discharged to the dredged sand carrier 3. .
[0023]
Then, after dredged sand carrier 3 is berthed, dredged sea bottom sediment is delivered through a discharge pipe 4 to a coagulating sedimentation filter basin 5 in which a plurality of filtration tanks are installed. The sediment and seawater delivered from the dredged material transporter 3 are mixed to form a high-concentration mud and injected into the coagulation sedimentation filter pond 5.
[0024]
Further, in the process, the coagulation / sedimentation accelerator injected by the pipe injection device 6 forms sediment, sedimentation increased flocs and supernatant water in the coagulation / sedimentation filtration basin 5 and separates, deposits and moves. In that process, flocs containing a considerable amount of organotin compounds are captured by the adhesive sheet 7 and the filter sheet 8 made of polyethylene spread and coated in the coagulation sedimentation filter pond 5.
[0025]
Moreover, the seawater filtered in the coagulation sedimentation filter pond 5 contains an organic tin content of 99.99% or less of the total amount of the organic tin contained in the sea bottom sediment. This seawater-containing organic tin is removed to 2 ng / L or less, which is a reference value that can be released, by passing through an activated carbon filtration device 9 that is designed and designed in consideration of filtration speed, filtration distance, expiration date of filter material, and the like. It is released.
[0026]
On the other hand, after the seawater filtration, the dredged sediment settled and accumulated in the coagulation sedimentation filtration basin 5 is left to stand for several days and dried, and then transported to the sun drying place 10 where the sewage filtration device by activated carbon filtration is installed. A substantial amount of the organotin compound can be reduced by sun-drying with sunshine hours.
[0027]
And the earth and sand dried in the sun drying place 10 still contains organotin compounds, but the water level is lowered and the behavior of groundwater is controlled and divided by the partition dike, still water sheet pile and drainage in advance. It is carried in and landfilled in the landfill disposal site 11 to which is applied.
[0028]
The reduced amount of organotin compound in the landfill disposal site 11 is promoted by microbial degradation due to transplantation / increase of microorganisms such as ventilation and electrode insertion even after being covered in the landfill disposal site 11 The tin compound is further reduced. In addition, the used activated carbon / filtered sand whose function has been reduced while leaving the capacity is sealed in the landfill disposal site 11 together with the remaining sand, and the harmful amount is reduced.
[0029]
In addition, the adhesion sheet and filter sheet after use, which have become empty, and the organotin compound adhering to the adhesion sheet and filter sheet are recovered after drying and are extinguished by high-temperature incineration or oxygen-free heat treatment.
[0030]
Then, the experimental result in each removal process of the organotin compound from the high water content sea bottom sediment in the coagulation sedimentation filtration pond of this invention is shown below.
[0031]
Comparative Test Example 1
The bottom of the fishing port bottom containing 2500 ng / wet-g containing an organotin compound was collected, and two types of samples were prepared, one containing no aggregate and the other containing 2 mg / L of polymer organic aggregate.
[0032]
Seawater was added to these two samples at a ratio of 1: 4 (similar to actual dredged water), this was shaken for 2 hours, and after standing for 3 hours, the supernatant was collected and prepared as sample water for coagulation sedimentation treatment. .
[0033]
Polyaluminum chloride, ferric chloride and inorganic coagulation sedimentation material are added to 500 ml of the supernatant of the sample water for coagulation sedimentation treatment as a coagulation sedimentation material at a constant concentration, rapidly stirred at 180 rpm, and then slowly stirred for 30 minutes. Table 1 below shows the results of measuring the turbidity reduction rate and pH value of the supernatant after standing for 1 hour.
[0034]
[Table 1]

[0035]
In addition, the polyaluminum chloride was added to the supernatant liquid without addition of the aggregating material, the supernatant when polyaluminum chloride was added as the aggregating sedimentation material, and the sample water for the agglomeration sedimentation treatment to which 2 mg / L of the polymer organic aggregating material was added. Table 2 below shows the measurement results of the concentration of the organotin compound contained in the supernatant when the inorganic coagulation / sedimentation treatment material was added as the supernatant and coagulation / sedimentation material.
[0036]
[Table 2]

[0037]
From Table 1 above, in order to obtain a turbidity of 0.5 after standing for 3 hours, injection rates of 10 mg / L of polyaluminum chloride, 40 mg / L of ferric chloride and 40 mg / L of the inorganic coagulation-precipitated material are required. .
Moreover, in the floc strength, the inorganic coagulation precipitation treatment material was strong, and there was no change in pH value.
[0038]
From Table 2, the solid-liquid separation rate of the inorganic agglomerated sedimentation treatment material was the smallest as 0.0034, and the concentration of the organotin compound was the lowest as 86 ng / L. As a result, it was found that the inorganic coagulation precipitation treatment material is most preferable as the coagulation precipitation treatment material.
The inorganic coagulation / precipitation treatment material is preferably a porous material such as zeolite.
[0039]
Next, FIG. 2 is a conceptual diagram of an organic dust removal experiment, in which 21 is a 500-liter raw water tank, 22 is a stirring device, 23 is an outer frame of the device, 24 is a metal scale for measuring the water level, and 25 is a current plate. , 26 is a polyethylene adsorption sheet, 27 is a polyethylene filter sheet, 28 is a sand filter, 29 is an activated carbon filter, 30 is a water collection pipe, 31 is a manometer, 32 is a valve, and 33 is a pump.
[0040]
That is, the inorganic coagulating sediment treatment material is added in the raw water tank 21, and the supernatant liquid stirred and solid-liquid separated by the stirring device 22 is sent between the device outer frame 3 pushed by the pump 33 and the polyethylene filter sheet 27. The
[0041]
Then, a polyethylene adsorbing sheet 26 is disposed between the apparatus outer frame 3 and the polyethylene filter sheet 27 so that the organotin compound is adsorbed on the polyethylene adsorbing sheet 26.
[0042]
Therefore, five types of sheets having different shapes shown in Table 3 below were selected and used in the experiment in order to test whether a polyethylene sheet of a special material and shape efficiently attaches the organotin compound.
[0043]
[Table 3]

[0044]
Another kind of sheet is folded and a metal fitting at the boundary is pasted so that the thickness is the same as the maximum thickness of the high-strength polyethylene fiber nonwoven fabric shown in Table 3 above, and a difference in the water level difference between the test muds begins to occur. Table 4 below shows the results of measuring the organotin compound concentration by sampling the inlet side and outlet side of the sheet.
[0045]
[Table 4]

[0046]
From Table 4, it was found that the two-row arrangement with sheet number 2 adsorbs at the same ratio as the one-row arrangement with sheet number 1. Sheets Nos. 3 and 5 have an ocher color on the sheet after the end of the experiment, and are expected to have a folding floc capturing effect.
[0047]
From the results shown in Table 4, the adsorption / capture rate of the sheet made of polyethylene by passing the muddy water can be expected to be about 25%. Therefore, in the organic tin compound-containing water in which the coagulation and sedimentation has progressed, a concentration drop of slightly less than 60% in the three-row arrangement is sure and works effectively for the final activated carbon treatment through filtration. Also, in actual construction, it is possible to devise arrangements with several rows and multiple staggered rows.
[0048]
The organotin compound-containing water from which about 60% of the organotin compound has been removed through the polyethylene sheet, the filter sheet and the sand filter in this way is discharged after removing the organotin compound to the final target value by passing through the activated carbon filter. The Rukoto.
[0049]
Therefore, the rejection rate (activated carbon adsorption) of the organotin compound by activated carbon is determined by the flow rate passing through the activated carbon. For example, as shown in the graph of FIG. 3, when the concentration of the organotin compound before passing through an activated carbon filter having a film thickness of 50 cm is about 86 ng / L, the broken line is shown when the flow rate is 0.195 cm / sec. The concentration of the organotin compound after passing through is about 20 ng / L.
[0050]
Here, in order for the organotin compound-containing concentration, which is the final target value, to satisfy 2 ng / L, the flow rate calculated by the theoretical formula is 7.75 × 10 ⁻³ cm / sec, as indicated by a solid line, The concentration of the organotin compound after passing is about 2 ng / L.
[0051]
In order to reduce the flow rate, when the organic tin compound-containing water that has passed through the sand filter is put into the activated carbon filter, the flow rate decreases according to the ratio if the cross-sectional area of the activated carbon filter is increased by 30 times or more. It will be.
[0052]
On the other hand, floc and earth and sand containing organotin compounds settled and accumulated in the coagulation sedimentation filtration basin after seawater filtration are simultaneously transported to the sun drying field after the water content ratio is reduced, and the harmful content is reduced by ultraviolet rays in the sun drying. And finally disposed after further reduction of water content by solar heat.
[0053]
The floc and earth and sand containing this organotin compound will be final disposed of by reducing the harmful substances by 20% or more, and the soil and soil will be dehydrated to improve the soil mechanical stability of the landfill site.
[0054]
Therefore, the content depth of the organic tin compound deposited on the seabed such as fishing ports is at most about 10 cm. After the treatment in the coagulation sedimentation filtration pond, only the harmful surface layer such as this organic tin compound and organic floating mud is dredged with seawater. By dehydrating the settled sediment and floc sediment, it is possible to reduce the volume significantly compared to existing dredging (the depth of dredging is 50 cm or more) for the purpose of landfill disposal.
[0055]
Here, flocs and earth and sand containing organotin compounds that have been transported do not necessarily need to be dehydrated and dehydrated by sun drying. For example, indoors may be artificially irradiated with ultraviolet rays or dried by a heat source. Although it can be considered, drying by the sun is the most preferable from the viewpoint of environment and cost in remote areas.
[0056]
In addition, the landfill site lowers the groundwater level by some means, and performs final landfill disposal of the soil dehydrated by sun drying in that area.
[0057]
In this case, the landfill area will take measures to prevent inflow and outflow of groundwater from other areas. Cover the soil so that the final landfill is separated from the ground so that there is no underground penetration of rainfall. In addition, rainfall drainage to the landfill area will be provided with surrounding drainage channels, and dredged landfill in the landfill will be managed so that no depression will be created due to sediment runoff. In addition, in connection with the next item, there are cases where ventilation holes, electrode holes and devices are installed.
[0058]
【The invention's effect】
As described above, according to the present invention, the dewatering treatment of the sewage / sediment interstitial water of the high-moisture dredged sand, the adsorption and extinction by the sheet of the organic tin compound-containing suspension material, and the like are settled.・ Since the accumulated sediments to be landfilled are landfilled through the process of dehydration and organic tin compound reduction, it is possible to reduce the volume of the sediment.
[0059]
Furthermore, since there is little sediment water between the sand and sand, there is little consolidation settlement, and it has the effect of facilitating the use of the land after completion of landfill.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram for illustrating an example of a harmful substance removal treatment method for removed seabed sludge containing an organotin compound to which the present invention is applied.
FIG. 2 shows a conceptual diagram of an organic tin removal experiment for illustrating an example of a harmful substance removal treatment method for removed seabed sludge containing an organic tin compound to which the present invention is applied.
FIG. 3 is an explanatory graph showing the rejection rate of organotin compounds by activated carbon by the method for removing harmful substances from removed seabed sludge containing organotin compounds to which the present invention is applied.
FIG. 4 is an explanatory diagram in Patent Document 1. FIG.
FIG. 5 shows an explanatory diagram in Patent Document 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Work ship 2 Dredging apparatus 3 Dredged sand carrier 4 Discharge pipe 5 Coagulation sedimentation filtration pond 6 Pipe injection apparatus 7 Adhesion sheet 8 Filtration sheet 9 Activated carbon filtration apparatus 10 Sun drying place 11 Disposal site

Claims

The high-moisture ratio dredged soil containing organotin compound was transported to the coagulation sedimentation site, and the flocculant was added and stirred to separate the sediment, floc sediment and seawater in the sedimentation pond, and further separated. Seawater and floating floc are removed from the suspended solids and organic tin compounds contained in seawater through a sand filtration tank and activated carbon adsorption tank, and the sediment and floc sediment in the sedimentation filtration pond are taken out and dried. In the hazardous material removal processing method,
A step of adhering a certain percentage of the total amount of the organic tin compound contained in the soil from the floating flock to the polyethylene sheet by a polyethylene sheet is provided before the filtration process of the seawater and the floating floc by the sand filtration tank and the activated carbon adsorption tank. A method for removing harmful substances from removed seabed sludge containing compounds.

The method for removing harmful substances from removed seabed sludge containing organotin compounds according to claim 1, further comprising the step of decomposing and reducing the amount of organotin compounds from the sediment and floc sediments extracted from the sedimentation filter basin by ultraviolet rays.

The method for removing harmful substances from removed seabed sludge containing an organotin compound according to claim 1 or 2, wherein an inorganic coagulated sediment is used as the coagulant in consideration of an increase in physical strength of floc sediment.