JP2004082107A

JP2004082107A - Equipment and method for treating waste water containing nitrogen-containing dyestuff

Info

Publication number: JP2004082107A
Application number: JP2003179530A
Authority: JP
Inventors: Tadao Shiotani; 塩谷　唯夫; Yuko Takami; 高見　優子; Seiichi Nakahara; 中原　清一
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2002-06-24
Filing date: 2003-06-24
Publication date: 2004-03-18
Anticipated expiration: 2023-06-24
Also published as: JP4663218B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste water treatment equipment in which a nitrogen-containing hardly decomposable dyestuff such as an azo compound in a waste water containing the nitrogen-containing dyestuff can easily and inexpensively be decolorized and decomposed and which is compact, has excellent durability and high throughput and can stably be operated for a long period of time. <P>SOLUTION: This waste water treatment equipment for decolorizing and denitrifying a waste water containing a nitrogen-containing dyestuff is provided with an absolute anaerobic treatment tank for bringing the waste water containing the nitrogen-containing dyestuff into contact with sulfuric acid reducing bacteria under an abslute anaerobic condition, a nitrification tank for bringing the waste water into contact with nitrifying bacteria under an aerobic condition and a denitrification tank for bringing the waste water into contact with denitrifying bacteria under an anaerobic condition. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は窒素を含有する染料を含む排水の脱色及び脱窒を生物処理にて行う排水処理装置に関する。さらに詳しくは染料を含む排水中のアゾ化合物等の窒素を含有する難分解性の窒素含有染料を、低コストで容易に脱色及び分解することができ、コンパクトで耐久性に優れる上に処理能力が高く、長期の安定運転が可能な排水処理装置に関する。
【０００２】
【従来の技術】
窒素を含有する染料、特にアゾ系染料は合成染料中最多数を占める染料であり、繊維、食品、化粧品等の各種分野で用いられている。染色工場等から排出される染料を含む排水は、環境中に放流されると周辺環境を着色してしまい環境及び美観を損ねてしまうため、上記した排水中に存在する染料を脱色し、あるいは無害化を図ろうとする要求が高まっている。従来、染料を含む排水は、主として他の排水と混合された状態で好気性条件下での活性汚泥法を用いて処理されてきた。しかし、活性汚泥法では排水中のＢＯＤ（生物化学的酸素要求量　Ｂｉｏｃｈｅｍｉｃａｌ　Ｏｘｙｇｅｎ　Ｄｅｍａｎｄ）とＳＳ（懸濁物質　Ｓｕｓｐｅｎｄｅｄ　Ｓｕｂｓｔａｎｃｅ）成分が除去されるにすぎず、しかも染料の多くがアゾ化合物等の難分解性の窒素含有化合物であり、活性汚泥法による生物処理が困難であるという理由から、染料に由来する着色や窒素成分は除去されないまま環境中に放出されていた。
【０００３】
排水中の染料を含む物質を物理的に除去する方法については、例えば、染料を含む排水を活性汚泥法により処理した後に、染料を含む物質を凝集沈殿により固形化させたり、あるいは活性炭等に吸着させることで染料を排水中から物理的に分離した後、埋め立て処理をする方法が公知である。しかしながら、この方法では、難分解性の染料が分解されない状態のままであり、このものが周辺に放出されると環境に悪影響を与えるので、このような状態が生じないようにすると、埋め立て処理する場所が限られてしまうという欠点がある。また、排水中の染料を含む物質を化学的に分解する方法については、例えば、染料をオゾンと接触させることにより分解する方法（特許文献１　参照）、湿潤下で酸素と接触させて酸化する方法（特許文献２　参照））、酵素と接触させて分解する方法（特許文献３　参照）、超臨界状態下で分解する方法（特許文献４　参照）等が提案されている。しかしながら、これらのいずれの方法も、薬剤・設備に要する費用がかかる、処理の困難な副生物が生じるといった欠点を有している。
【０００４】
【特許文献１】
特開平９−２３９３８３号公報
【特許文献２】
特開平９−２５３６６９号公報
【特許文献３】
特開２０００−２４５４６８号公報
【特許文献４】
特開２００１−１２１１３７号公報
【０００５】
【発明が解決しようとする課題】
上記の通り、染料を含む排水の処理において、アゾ化合物等の難分解性の窒素含有染料を、低コストで環境に影響を与えない程度にまで脱色及び分解する処理装置はいまだ知られていない。しかして本発明の目的は、窒素を含有する染料を含む排水中のアゾ化合物等の難分解性の窒素含有染料を、低コストで容易に脱色及び分解することができ、コンパクトで耐久性に優れる上に処理能力が高く、長期の安定運転が可能な排水処理装置を提供することにある。
【０００６】
【課題を解決するための手段】
本発明によれば、上記課題は、窒素を含有する染料を含む排水を絶対嫌気条件下で硫酸還元細菌と接触させる絶対嫌気槽、排水を好気条件下で硝化菌と接触させる硝化槽及び排水を嫌気条件下で脱窒菌と接触させる脱窒槽を備え、窒素を含有する染料を含む排水の脱色及び脱窒が行われるようにした排水処理装置により達成される。より詳細には、絶対嫌気工程にて脱色を行った後に、復色を防ぐために、硝化／脱窒工程あるいは脱窒／硝化工程にて脱窒が行われるようにした排水処理装置である。
【０００７】
上記した本発明の排水処理装置としては、例えば、絶対嫌気槽、脱窒槽及び硝化槽をこの順に設置し、硝化槽から流出する硝化処理水の一部を脱窒槽へ返送・循環するようにした構成としても良い。好適な実施態様では、絶対嫌気槽、硝化槽及び脱窒槽から選ばれる少なくとも１槽において、菌体が微生物固定化担体により固定化されている。また、絶対嫌気槽、硝化槽、脱窒槽をこの順に設置し、脱窒槽の後にＢＯＤ分解菌を好気条件下で排水と接触させる再曝気槽を設けるようにした構成としても良い。好適な実施態様では、絶対嫌気槽、硝化槽、脱窒槽及び再曝気槽から選ばれる少なくとも１槽において、菌体が微生物固定化担体により固定化されている。
【０００８】
更に好適な実施態様では、微生物固定化担体が、ゲル状担体、プラスチック担体及び繊維状担体から選ばれる１種以上の担体であり、より好適には、微生物固定化担体がポリビニルアルコール系含水ゲルである。
【０００９】
【発明の実施の形態】
本発明において窒素を含有する染料とは、酸性染料、酸性媒染染料、金属錯塩染料、塩基性染料、直接アゾ染料、アゾイック染料及び反応染料等の内、その化学構造式に窒素を含む水溶性染料、特にアゾ結合を含有する染料である。窒素を含有する染料としては、Ａｃｉｄ　Ｏｒａｎｇｅ１０といったアニリン系アゾ染料、Ａｃｉｄ　Ｏｒａｎｇｅ１やＡｃｉｄ　Ｏｒａｎｇｅ２４といったスルファニル酸系アゾ染料、Ａｃｉｄ　Ｏｒａｎｇｅ７やＡｃｉｄ　Ｏｒａｎｇｅ８といったナフトール系アゾ染料、Ａｃｉｄ　Ｂｌｕｅ９２やＡｃｉｄ　Ｂｌｕｅ１２０といったナフチルアミン系アゾ染料、Ａｃｉｄ　Ｂｌｕｅ８２やＡｃｉｄ　Ｂｌｕｅ１２６といったアントラキノン系染料、Ａｃｉｄ　Ｙｅｌｌｏｗ１１やＡｃｉｄ　Ｙｅｌｌｏｗ１７といったピラゾロン系アゾ染料、Ａｚｏｉｃ　Ｄｉａｚｏ　Ｃｏｍｐｏｎｅｎｔ１やＡｚｏｉｃ　Ｄｉａｚｏ　Ｃｏｍｐｏｎｅｎｔ２７といったアゾイック染料等が挙げられる。
【００１０】
本発明において用いられる硫酸還元細菌とはＤｅｓｕｌｆｏｖｉｂｒｉｏ　ｄｅｓｕｌｆｕｒｉｃａｎ等の絶対嫌気性細菌であり、硫酸塩を硫酸呼吸によって硫化水素に還元する公知の細菌である。絶対嫌気槽においては、上記した硫酸還元細菌により絶対嫌気条件下で窒素を含有する染料が分解される。
【００１１】
絶対嫌気条件とは、液中の酸化還元電位で表すと、液中のｐＨが７の時に、一般には−２００ｍＶ以下の状態をいう。
【００１２】
本発明において、絶対嫌気槽には、硫酸還元細菌の呼吸基質又は細胞を合成するときや窒素を含有する染料を分解するには一定量の有機物が存在することが必要であり、有機物の含まれる量が少ない排水を処理する場合には、絶対嫌気槽に外部から必要量の有機物を添加するのがよい。添加する有機物としては、一般にアルコール類が挙げられ、特にメタノール及びエタノールが用いられる。
【００１３】
本発明において、上記した絶対嫌気槽、硝化槽、脱窒槽及び再曝気槽から選ばれる少なくとも１槽において、菌体が微生物固定化担体により固定化されていることが好ましい。微生物固定化担体を用いる方法（以下担体法と略記する。）が活性汚泥法と比較して優れている点としては、汚泥を返送する必要が無いために、各槽の維持管理が容易である点、特に絶対嫌気槽においては、担体表面から担体の中央部まで細孔が全通しており担体内部に嫌気性微生物を棲息させ易いアセタール化ポリビニルアルコール系ゲル（ａｃｅｔａｌｉｚｅｄ　ｐｏｌｙｖｉｎｙｌａｌｃｏｈｏｌ　ｇｅｌ）を用いることにより、硫酸還元細菌の棲息性が向上する点、絶対嫌気条件下の活性汚泥法のように完全密閉をする必要が無い点、及び反応槽の容量をコンパクトにできる点が挙げられる。
【００１４】
本発明において好適に用いられる微生物固定化担体とは、微生物の住処となる細孔を有する固体である。その素材としては、ポリビニルアルコールといったビニルアルコール系樹脂、ポリエチレングリコールといったエーテル系樹脂、ポリメタクリル酸といったアクリル系樹脂、ポリアクリルアミドといったアクリルアミド系樹脂、ポリエチレン、ポリプロピレンといったオレフィン系樹脂、ポリスチレンといったスチレン系樹脂、ポリエチレンテレフタレートやポリブチレンテレフタレートといったエステル系樹脂、ポリアクリロニトリルといったアクリロニトリル系樹脂、ポリウレタンスポンジといったウレタン系樹脂、アルギン酸カルシウム、κ（カッパ）カラギーナン、寒天、セルロース誘導体といった多糖類、ポリエステルエアクリレート、エポキシアクリレート、ウレタンアクリレートといった光硬化性樹脂、活性炭といった多孔質無機化合物などを例示することができる。より好適には、内部に至るまで多孔質で網目状となった構造を有する点、及びゲル内に多量の水を取り込むことができる点で、ポリビニルアルコール系含水ゲル、より好ましくは、ホルマール化ポリビニルアルコール系含水ゲルやアセタール化ポリビニルアルコール系含水ゲルを挙げることができる。微生物固定化担体は、１種類でも、組み合わせても使用することができる。その充填率としては、排水処理効率と担体流動性の観点から、槽容積の１％以上５０％以下であることが好ましく、３％以上３０％以下であることがより好ましい。
【００１５】
図１は、本発明の第一の実施態様である、絶対嫌気槽、脱窒槽及び硝化槽をこの順に設置し、硝化槽から流出する硝化処理水の一部を脱窒槽へ返送・循環するようにした排水処理装置のフローチャートである。図１において、絶対嫌気槽１、脱窒槽２及び硝化槽３内の菌体はそれぞれ微生物固定化担体１１、１４及び１８により固定化されている。窒素を含有する染料を含んだ排水４を絶対嫌気槽１に供給し、絶対嫌気条件下で硫酸還元細菌と接触させることにより窒素を含有する染料は分解される。
【００１６】
絶対嫌気槽１には、底部に微生物固定化担体の摩擦を生じさせないように攪拌を行う攪拌装置９が設置される。絶対嫌気槽１内の硫酸還元細菌等の微生物を含む混合液１０中に微生物固定化担体１１が投入されている。攪拌装置９を作動させると、絶対嫌気槽１内に混合液１０の循環流が生じ、この循環流により微生物固定化担体１１が絶対嫌気槽１内を流動し、その間に混合液１０中に存在する硫酸還元細菌を主体とする微生物が微生物固定化担体１１に付着・結合固定化される。
【００１７】
被処理水５は脱窒槽２において嫌気条件下で槽内の脱窒菌により脱窒処理される。脱窒槽２内には、底部に微生物固定化担体の摩擦を生じさせないように攪拌を行う攪拌装置１２が設置され、脱窒槽２内の脱窒菌等の微生物を含む混合液１３中に微生物固定化担体１４が投入されている。攪拌装置１２を作動させると、脱窒槽２内に混合液１３の循環流が生じ、この循環流により微生物固定化担体１４が脱窒槽２内を流動し、その間に混合液１３中に存在する脱窒菌を主体とする微生物が微生物固定化担体１４に付着・結合固定化される。混合液１３中の有機物は、脱窒菌の呼吸基質又は細胞合成の源として利用されるが、必要に応じて、絶対嫌気槽で添加したものと同様に、アルコール類（メタノールやエタノール等）を系外から添加すればよい。
【００１８】
脱窒処理水６を硝化槽３に供給し、好気条件下で硝化槽３内の硝化菌と接触させることにより脱窒処理水６は硝化処理される。硝化槽３内における底部には、酸素を含有する空気などの気体を供給する散気装置１５がブロアー１６に接続して設置されており、硝化槽３内の硝化菌等の微生物を含む混合液１７に微生物固定化担体１８が投入されている。散気装置１５より空気を吹き出すと、硝化槽３内の混合液１７に酸素が供給されるとともに、このときの上昇気泡流によって混合液１７の循環流が生じる。この循環流により微生物固定化担体１８が硝化槽３内を流動する間に、混合液１７中に存在する硝化菌を主体とする微生物が微生物固定化担体１８に付着・結合し固定化される。この固定化された硝化菌と浮遊硝化菌とにより、硝化槽３内の混合液１７は生物的に処理される。
【００１９】
硝化処理水７の一部は、返送・循環水８として硝化槽３の前段である脱窒槽２に導入され、嫌気条件下において脱窒処理される。硝化処理水７の残りは、硝化処理水７に含まれている固形分を凝集沈殿処理又は膜処理等の一般的な方法により除去した後、放流又は再利用される。なお、脱窒処理及び／又はＢＯＤ成分の分解処理をより完全に行うために、硝化処理水７の残りを硝化槽３に続けて脱窒槽２′、ＢＯＤ分解菌により好気性条件下で処理する再曝気槽１９の順に処理した後に、処理水７′に含まれている固形分を凝集沈殿処理あるいは膜処理等の一般的な方法により除去した後、放流又は再利用してもよい。
【００２０】
また、図１で示した絶対嫌気槽と脱窒槽を一つにして脱窒槽とし、絶対嫌気条件下で硫酸還元細菌及び脱窒菌と接触させて脱色及び脱窒処理した後に、処理水を好気条件下で硝化菌と接触させてもよい。このとき、硝化槽から排出される処理水の一部を脱窒槽へ返送・循環することが好ましい。
【００２１】
次に、図２には、本発明の第二の実施態様である、絶対嫌気槽、硝化槽、脱窒槽をこの順に設置し、脱窒槽の後にＢＯＤ分解菌を好気条件下で排水と接触させる再曝気槽を設けた排水処理装置のフローチャートを示す。図２において、絶対嫌気槽１、硝化槽３、脱窒槽２及び再曝気槽１９内の菌体はそれぞれ微生物固定化担体により固定化されている。
【００２２】
窒素を含有する染料を含んだ排水２０を絶対嫌気槽１に供給し、絶対嫌気条件下で硫酸還元細菌と接触させることにより、窒素を含有する染料は分解される。
【００２３】
被処理水２１を硝化槽３に供給し、好気条件下で硝化菌と接触させることにより、被処理水２１は硝化処理され、硝化処理水２２として脱窒槽２に供給される。脱窒槽２では、硝化処理水２２を嫌気条件下で脱窒菌と接触させることにより、硝化処理水２２は脱窒処理される。このとき、脱窒槽２には有機物が脱窒菌の呼吸基質又は細胞の合成の源として利用されるが、必要に応じて系外から添加すればよい。
【００２４】
脱窒槽２の後に再曝気槽１９を設け、脱窒槽２から流出する処理水２３に含まれる脱窒反応で消費されなかった有機物を処理する。曝気処理水２４に含まれている固形分は、凝集沈殿処理あるいは膜処理等、一般的な方法により除去されて、放流又は再利用される
【００２５】
図１及び２において、窒素を含有する染料、特にアゾ染料は、絶対嫌気槽１で硫酸還元細菌と接触させることによりアゾ染料中のアゾ結合が還元的に開裂分解され、無色の芳香族アミンに分解される。更に、アゾ染料から分解された芳香族アミンを、硝化槽３で硝化菌と接触させることにより芳香族環及びヘテロ環等の構造が分解される。
【００２６】
絶対嫌気槽１で発生する硫化水素ガスは一般的な方法により処理することができるが、図１においては、絶対嫌気槽の後ろの脱窒槽２に導入することにより嫌気状態を促すことができ、また、図２においては、絶対嫌気槽の後ろの硝化槽３に導入することにより酸化反応にて除去することができる。
【００２７】
図１における絶対嫌気槽１、脱窒槽２及び硝化槽３の各槽の出口、並びに図２における絶対嫌気槽１、硝化槽３、脱窒槽２及び再曝気槽１９の各槽出口には、微生物固定化担体の流出を防止するために、スクリーン２５を取り付けることが望ましい。
【００２８】
図１の絶対嫌気槽１、脱窒槽２及び硝化槽３の各槽内、並びに図２の絶対嫌気槽１、硝化槽３、脱窒槽２及び再曝気槽１９の各槽内には、硫酸還元細菌、脱窒菌、硝化菌及びＢＯＤ分解菌を固定化した担体がそれぞれ充填される。担体の種類は所望に応じて適宜決定すればよい。硫酸還元細菌、脱窒菌、硝化菌及びＢＯＤ分解菌は予め微生物固定化担体に包括固定化して使用してもよいが、微生物固定化担体を各槽に投入し、菌が自然に付着するのを利用してもよい。
【００２９】
【実施例】
以下、実施例により本発明を詳細に説明するが、本発明は実施例によって何ら制限されるものでない。なお、実排水及び処理水の色度、ＢＯＤ濃度及びＴ−Ｎ（総窒素：Ｔｏｔａｌ−Ｎｉｔｒｏｇｅｎ）濃度は工業用水試験方法（ＪＩＳ　Ｋ　０１０１−１９９１）により測定した。
【００３０】
実施例１
絶対嫌気槽、脱窒槽及び硝化槽をこの順に設置し、硝化槽から流出する硝化処理水の７５％を脱窒槽へ返送・循環するようにした排水処理装置を製作した。各反応槽の槽容量は１５０Ｌであった。微生物固定化担体として硫酸還元細菌を固定化したアセタール化ポリビニルアルコール系含水ゲル（以下ＰＶＡゲルと略記する。）を絶対嫌気槽内に１０％（体積比率、以下同様。）充填し、攪拌機を用いてＰＶＡゲルを流動させた。脱窒槽は、脱窒菌を固定化したＰＶＡゲルを１０％充填し、攪拌機を用いて同様にＰＶＡゲルを流動させた。硝化槽は硝化菌を固定化したＰＶＡゲルを１０％充填し、散気管により曝気を行った。排水にはＡｃｉｄ　Ｏｒａｎｇｅ７及びＡｃｉｄ　Ｂｌｕｅ１２６を含む実排水を用いた。実排水の色度は３６０、ＢＯＤ濃度は１５４５ｍｇ／Ｌ、Ｔ−Ｎ量は４０８ｍｇ／Ｌであった。硝化槽出口での処理水の色度は１８であり、脱色されたことが明瞭に判別できた。処理水のＢＯＤ濃度及びＴ−Ｎ濃度は、それぞれ１８ｍｇ／Ｌ及び２０ｍｇ／Ｌであった。
【００３１】
比較例
絶対嫌気槽を使用しないこと以外は実施例１と同様に排水処理を実施した。硝化槽出口での処理水のＢＯＤ濃度は、それぞれ１９ｍｇ／Ｌと実施例と変わらなかったが、Ｔ−Ｎ濃度は６８ｍｇ／Ｌ、色度は２０３であり、処理水には明らかな着色が見られた。
【００３２】
実施例２
絶対嫌気槽、硝化槽、脱窒槽および再曝気槽をこの順に設置した排水処理装置を製作した。各反応槽の槽容量は１５０Ｌであった。微生物固定化担体として硫酸還元細菌を固定化したＰＶＡゲルを絶対嫌気槽内に１０％充填し、攪拌機を用いて流動させた。硝化槽は硝化菌を固定化したＰＶＡゲルを１０％充填し、散気管により曝気を行った。脱窒槽は脱窒菌を固定化したＰＶＡゲルを１０％充填し、攪拌機を用いて絶対嫌気槽と同様にＰＶＡゲルを流動させた。このとき、脱窒反応に必要なメタノールを添加した。再曝気槽は、ＢＯＤ分解菌を固定化したＰＶＡゲルを１０％充填し、散気管により曝気を行いながら、脱窒反応で消費されなかったＢＯＤ成分を処理した。排水は、Ａｃｉｄ　Ｏｒａｎｇｅ２０およびＡｃｉｄ　Ｂｌｕｅ９２以外に、尿素を主成分とするＴ−Ｎ濃度の高い実排水を用いた。実排水の色度は４２０、ＢＯＤ濃度は４６０ｍｇ／Ｌ、Ｔ−Ｎ濃度は５９０ｍｇ／Ｌであった。再曝気槽出口での処理水の色度は１９であり、脱色されたことが明瞭に判別できた。処理水のＢＯＤ濃度及びＴ−Ｎ濃度は、それぞれ１７ｍｇ／Ｌ及び１８ｍｇ／Ｌであった。
【００３３】
実施例３
脱窒槽および硝化槽をこの順に設置し、硝化槽から流出する処理水の７５％を脱窒槽へ返送・循環するようにした排水処理装置を製作した。各反応槽の槽容量はそれぞれ３００Ｌと１５０Ｌであった。脱窒槽は、硫酸還元細菌および脱窒細菌を固定化したＰＶＡゲルを１０％充填し、攪拌機を用いてＰＶＡゲルを流動させた。硝化槽は、硝化菌を固定化したＰＶＡゲルを１０％充填し、散気管により曝気を行った。排水には、Ａｃｉｄ　Ｏｒａｎｇｅ７及びＡｃｉｄ　Ｂｌｕｅ９２を含む実排水を用いた。実排水の色度は３１０、ＢＯＤ濃度は１２３０ｍｇ／Ｌ、Ｔ−Ｎ濃度は３７５ｍｇ／Ｌであった。硝化槽出口での処理水の色度は２１であり、脱色されたことが判明できた。処理水のＢＯＤ濃度及びＴ−Ｎ濃度は、それぞれ１９ｍｇ／Ｌ及び２４ｍｇ／Ｌであった。
【００３４】
【発明の効果】
本発明の廃水処理装置は、窒素を含有する染料を含む排水中の難分解性の窒素化合物を、容易に低コストで脱色及び分解し、コンパクトで耐久性に優れ、しかも処理能力が高く、長期に安定運転可能である。
【図面の簡単な説明】
【図１】本発明の排水処理装置の第一の実施態様を示すフローチャートである。
【図２】本発明の排水処理装置の第二の実施態様を示すフローチャートである。
【符号の説明】
１　　絶対嫌気槽
２　　脱窒槽
３　　硝化槽
４　　排水
５　　被処理水
６　　脱窒処理水
７　　硝化処理水
８　　返送・循環水
９　　攪拌装置
１０　脱窒槽内混合液
１１　微生物固定化担体
１２　攪拌装置
１３　脱窒槽内混合液
１４　微生物固定化担体
１５　散気装置
１６　ブロワー
１７　硝化槽内混合液
１８　微生物固定化担体
１９　再曝気槽
２０　排水
２１　被処理水
２２　硝化処理水
２３　脱窒処理水
２４　曝気処理水
２５　微担体流出防止スクリーン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment apparatus for performing decolorization and denitrification of wastewater containing a dye containing nitrogen by biological treatment. More specifically, it is possible to easily decolorize and decompose nitrogen-containing dyes that contain nitrogen such as azo compounds in wastewater containing dyes at low cost, and it is compact and has excellent durability and processing capability. The present invention relates to a wastewater treatment apparatus that is high and capable of long-term stable operation.
[0002]
[Prior art]
Nitrogen-containing dyes, particularly azo dyes, occupy the largest number of synthetic dyes, and are used in various fields such as fibers, foods, and cosmetics. Wastewater containing dyes discharged from dyeing factories, etc., when discharged into the environment, discolors the surrounding environment and damages the environment and aesthetics. There is an increasing demand to make it easier. Conventionally, wastewater containing dyes has been treated using an activated sludge process under aerobic conditions, mainly in a state mixed with other wastewater. However, the activated sludge method only removes BOD (Biochemical Oxygen Demand) and SS (Suspended Substance Suspension Substance) components in wastewater, and most of the dyes are difficult to decompose such as azo compounds. Because it is a natural nitrogen-containing compound and biological treatment by the activated sludge method is difficult, coloring and nitrogen components derived from dyes have been released into the environment without being removed.
[0003]
Regarding the method of physically removing the dye-containing substance in the wastewater, for example, after treating the wastewater containing the dye by the activated sludge method, the substance containing the dye is solidified by coagulation precipitation or adsorbed on activated carbon or the like. A method of performing landfill treatment after physically separating the dye from the wastewater by making it known is known. However, in this method, the hard-to-decompose dye remains in an undegraded state, and if it is released to the surrounding area, it has an adverse effect on the environment. There is a disadvantage that the place is limited. Moreover, about the method of chemically decomposing | disassembling the substance containing the dye in waste_water | drain, for example, the method of decomposing | disassembling a dye by making it contact with ozone (refer patent document 1), The method of oxidizing by making it contact with oxygen under humidity (See Patent Document 2)), a method of decomposing by contacting with an enzyme (see Patent Document 3), a method of decomposing in a supercritical state (see Patent Document 4), and the like. However, any of these methods has drawbacks such as high costs for chemicals / equipment and generation of by-products that are difficult to process.
[0004]
[Patent Document 1]
JP-A-9-239383 [Patent Document 2]
JP-A-9-253669 [Patent Document 3]
JP 2000-245468 A [Patent Document 4]
Japanese Patent Laid-Open No. 2001-121137
[Problems to be solved by the invention]
As described above, a treatment apparatus for decolorizing and decomposing a hardly decomposable nitrogen-containing dye such as an azo compound to an extent that does not affect the environment at low cost has not yet been known. Therefore, the object of the present invention is to be able to easily decolorize and decompose difficult-to-decompose nitrogen-containing dyes such as azo compounds in wastewater containing nitrogen-containing dyes at low cost, and is compact and excellent in durability. Another object of the present invention is to provide a wastewater treatment apparatus having a high treatment capacity and capable of long-term stable operation.
[0006]
[Means for Solving the Problems]
According to the present invention, the above-mentioned problems are an absolute anaerobic tank in which wastewater containing a nitrogen-containing dye is brought into contact with sulfate-reducing bacteria under absolute anaerobic conditions, a nitrification tank in which wastewater is brought into contact with nitrifying bacteria under aerobic conditions, and wastewater. It is achieved by a wastewater treatment apparatus that includes a denitrification tank that is brought into contact with denitrifying bacteria under anaerobic conditions, and is configured to decolorize and denitrify wastewater containing a dye containing nitrogen. More specifically, it is a wastewater treatment apparatus in which denitrification is performed in the nitrification / denitrification process or the denitrification / nitrification process in order to prevent recoloring after decolorization in the absolute anaerobic process.
[0007]
As the above-described wastewater treatment apparatus of the present invention, for example, an absolute anaerobic tank, a denitrification tank and a nitrification tank are installed in this order, and a part of the nitrification water flowing out from the nitrification tank is returned and circulated to the denitrification tank. It is good also as a structure. In a preferred embodiment, the bacterial cells are immobilized by a microorganism-immobilized carrier in at least one tank selected from an absolute anaerobic tank, a nitrification tank, and a denitrification tank. Further, an absolute anaerobic tank, a nitrification tank, and a denitrification tank may be installed in this order, and a re-aeration tank may be provided after the denitrification tank to bring the BOD-degrading bacteria into contact with the wastewater under aerobic conditions. In a preferred embodiment, the bacterial cells are immobilized by a microorganism-immobilized carrier in at least one tank selected from an absolute anaerobic tank, a nitrification tank, a denitrification tank, and a re-aeration tank.
[0008]
In a further preferred embodiment, the microorganism-immobilized carrier is at least one carrier selected from a gel-like carrier, a plastic carrier, and a fibrous carrier, and more preferably, the microorganism-immobilized carrier is a polyvinyl alcohol-based hydrogel. is there.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the dye containing nitrogen is an acid dye, an acid mordant dye, a metal complex dye, a basic dye, a direct azo dye, an azoic dye, a reactive dye, etc., and a water-soluble dye containing nitrogen in its chemical structural formula In particular, it is a dye containing an azo bond. Nitrogen-containing dyes include aniline azo dyes such as Acid Orange 10; sulfanilic acid azo dyes such as Acid Orange 1 and Acid Orange 24; naphthol azo dyes such as Acid Orange 7 and Acid Orange 8; and azo dyes such as Acid Blue 92 and Acid Blue 120 dyes. Anthraquinone dyes such as Acid Blue 82 and Acid Blue 126, pyrazolone azo dyes such as Acid Yellow 11 and Acid Yellow 17, and azoic dyes such as Azoic Diazo Component 1 and Azoic Diazo Component 27, and the like.
[0010]
The sulfate-reducing bacteria used in the present invention are absolute anaerobic bacteria such as Desulfovibrio desulfurican, and are known bacteria that reduce sulfates to hydrogen sulfide by sulfate respiration. In the absolute anaerobic tank, the dye containing nitrogen is decomposed under the absolute anaerobic condition by the sulfate-reducing bacteria described above.
[0011]
The absolute anaerobic condition generally means a state of −200 mV or less when the pH in the liquid is 7 in terms of the oxidation-reduction potential in the liquid.
[0012]
In the present invention, the absolute anaerobic tank must contain a certain amount of organic matter when synthesizing the respiratory substrate or cells of sulfate-reducing bacteria or decompose nitrogen-containing dyes. When treating a small amount of wastewater, it is preferable to add a necessary amount of organic matter from the outside to the absolute anaerobic tank. Examples of the organic substance to be added generally include alcohols, and methanol and ethanol are particularly used.
[0013]
In the present invention, it is preferable that at least one tank selected from the absolute anaerobic tank, the nitrification tank, the denitrification tank, and the re-aeration tank described above is immobilized with a microorganism-immobilized carrier. The method using a microorganism-immobilized carrier (hereinafter abbreviated as the carrier method) is superior to the activated sludge method in that it is not necessary to return the sludge, so that each tank can be easily maintained and managed. In particular, in an absolute anaerobic tank, by using an acetalized polyvinyl alcohol gel that allows all the pores to pass from the surface of the carrier to the center of the carrier and allows the anaerobic microorganisms to inhale inside the carrier, The point which improves the habitability of a sulfate reduction bacterium, the point which does not need complete sealing like the activated sludge method of absolute anaerobic conditions, and the point which can make the capacity | capacitance of a reaction tank compact are mentioned.
[0014]
The microorganism-immobilized carrier preferably used in the present invention is a solid having pores serving as microorganisms. The materials include vinyl alcohol resins such as polyvinyl alcohol, ether resins such as polyethylene glycol, acrylic resins such as polymethacrylic acid, acrylamide resins such as polyacrylamide, olefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene, polyethylene Ester resins such as terephthalate and polybutylene terephthalate, acrylonitrile resins such as polyacrylonitrile, urethane resins such as polyurethane sponge, calcium alginate, kappa carrageenan, agar, cellulose derivatives, polyester acrylate, epoxy acrylate, urethane acrylate Porous such as photo-curable resin, activated carbon Machine compounds and the like may be exemplified. More preferably, it is a polyvinyl alcohol-based water-containing gel, more preferably formalized polyvinyl, in that it has a porous and network-like structure up to the inside and a large amount of water can be taken into the gel. Examples thereof include alcohol-based hydrogels and acetalized polyvinyl alcohol-based hydrogels. The microorganism immobilization carriers can be used alone or in combination. The filling rate is preferably 1% or more and 50% or less of the tank volume, more preferably 3% or more and 30% or less, from the viewpoint of wastewater treatment efficiency and carrier fluidity.
[0015]
FIG. 1 shows a first embodiment of the present invention, in which an absolute anaerobic tank, a denitrification tank, and a nitrification tank are installed in this order, and a part of the nitrification water flowing out from the nitrification tank is returned and circulated to the denitrification tank. It is a flowchart of the wastewater treatment apparatus made. In FIG. 1, the cells in the absolute anaerobic tank 1, the denitrification tank 2 and the nitrification tank 3 are immobilized by the microorganism immobilization carriers 11, 14 and 18, respectively. The wastewater 4 containing the nitrogen-containing dye is supplied to the absolute anaerobic tank 1 and brought into contact with sulfate-reducing bacteria under the absolute anaerobic condition, whereby the nitrogen-containing dye is decomposed.
[0016]
The absolute anaerobic tank 1 is provided with a stirring device 9 for stirring so as not to cause friction of the microorganism-immobilized carrier at the bottom. A microorganism-immobilized carrier 11 is placed in a mixed solution 10 containing microorganisms such as sulfate-reducing bacteria in the absolute anaerobic tank 1. When the stirring device 9 is operated, a circulating flow of the mixed solution 10 is generated in the absolute anaerobic tank 1, and the microorganism immobilization support 11 flows in the absolute anaerobic tank 1 by this circulating flow, and exists in the mixed solution 10 during that time. Microorganisms mainly composed of sulfate-reducing bacteria that adhere to and adhere to the microorganism-immobilized carrier 11.
[0017]
The treated water 5 is denitrified in the denitrification tank 2 by denitrifying bacteria in the tank under anaerobic conditions. In the denitrification tank 2, a stirrer 12 that stirs so as not to cause friction of the microorganism-immobilized carrier at the bottom is installed, and the microorganism is immobilized in the mixed solution 13 containing microorganisms such as denitrifying bacteria in the denitrification tank 2. A carrier 14 is loaded. When the agitator 12 is operated, a circulating flow of the mixed solution 13 is generated in the denitrification tank 2, and the microorganism-immobilized carrier 14 flows in the denitrifying tank 2 by this circulating flow, and the dehydration existing in the mixed solution 13 in the meantime. Microorganisms mainly composed of nitrogen bacteria are attached and bound and immobilized on the microorganism immobilization carrier 14. The organic matter in the mixed solution 13 is used as a respiration substrate for denitrifying bacteria or a source of cell synthesis. If necessary, alcohols (methanol, ethanol, etc.) are used in the same manner as those added in an absolute anaerobic tank. What is necessary is just to add from the outside.
[0018]
The denitrification water 6 is supplied to the nitrification tank 3 and brought into contact with the nitrifying bacteria in the nitrification tank 3 under aerobic conditions, whereby the denitrification water 6 is nitrified. A diffuser 15 for supplying a gas such as oxygen-containing air is connected to the blower 16 at the bottom of the nitrification tank 3 and is a mixed liquid containing microorganisms such as nitrifying bacteria in the nitrification tank 3. Reference numeral 17 denotes a microorganism-immobilized carrier 18. When air is blown out from the air diffuser 15, oxygen is supplied to the mixed liquid 17 in the nitrification tank 3, and a circulating flow of the mixed liquid 17 is generated by the rising bubble flow at this time. While the microorganism-immobilized carrier 18 flows in the nitrification tank 3 by this circulation flow, microorganisms mainly composed of nitrifying bacteria present in the mixed solution 17 adhere to and bind to the microorganism-immobilized carrier 18 and are immobilized. The mixed solution 17 in the nitrification tank 3 is biologically treated by the immobilized nitrifying bacteria and floating nitrifying bacteria.
[0019]
A part of the nitrification water 7 is introduced as return / circulation water 8 into the denitrification tank 2 which is the preceding stage of the nitrification tank 3 and denitrified under anaerobic conditions. The remainder of the nitrification water 7 is discharged or reused after the solid content contained in the nitrification water 7 is removed by a general method such as coagulation precipitation or membrane treatment. In order to perform the denitrification process and / or the decomposition process of the BOD component more completely, the remaining nitrification water 7 is treated under the aerobic condition by the denitrification tank 2 ′ and the BOD-decomposing bacteria after the nitrification tank 3. After processing in the order of the re-aeration tank 19, the solid content contained in the treated water 7 ′ may be removed by a general method such as coagulation sedimentation treatment or membrane treatment, and then discharged or reused.
[0020]
In addition, the absolute anaerobic tank and denitrification tank shown in FIG. 1 are combined into a denitrification tank, and after decolorization and denitrification treatment by contacting with sulfate-reducing bacteria and denitrification bacteria under absolute anaerobic conditions, the treated water is aerobic. It may be contacted with nitrifying bacteria under conditions. At this time, it is preferable to return and circulate a part of the treated water discharged from the nitrification tank to the denitrification tank.
[0021]
Next, in FIG. 2, an absolute anaerobic tank, a nitrification tank, and a denitrification tank, which are the second embodiment of the present invention, are installed in this order. The flowchart of the waste water treatment equipment which provided the re-aeration tank to be made is shown. In FIG. 2, the cells in the absolute anaerobic tank 1, the nitrification tank 3, the denitrification tank 2, and the re-aeration tank 19 are each immobilized by a microorganism immobilization carrier.
[0022]
The wastewater 20 containing the nitrogen-containing dye is supplied to the absolute anaerobic tank 1 and brought into contact with sulfate-reducing bacteria under the absolute anaerobic condition, whereby the nitrogen-containing dye is decomposed.
[0023]
The treated water 21 is supplied to the nitrification tank 3 and brought into contact with the nitrifying bacteria under aerobic conditions, whereby the treated water 21 is nitrified and supplied as the nitrified water 22 to the denitrification tank 2. In the denitrification tank 2, the nitrification water 22 is denitrified by contacting the nitrification water 22 with denitrification bacteria under anaerobic conditions. At this time, the organic matter is used in the denitrification tank 2 as a respiration substrate of denitrifying bacteria or a source of cell synthesis, but may be added from outside the system as necessary.
[0024]
A re-aeration tank 19 is provided after the denitrification tank 2 to treat organic matter that has not been consumed in the denitrification reaction contained in the treated water 23 flowing out from the denitrification tank 2. The solid content contained in the aerated treated water 24 is removed by a general method such as coagulation sedimentation treatment or membrane treatment, and discharged or reused.
1 and 2, a nitrogen-containing dye, particularly an azo dye, is brought into contact with a sulfate-reducing bacterium in an absolute anaerobic tank 1, whereby the azo bond in the azo dye is reductively cleaved and decomposed into a colorless aromatic amine. Disassembled. Furthermore, the aromatic amine decomposed from the azo dye is brought into contact with the nitrifying bacteria in the nitrification tank 3 to decompose the structures such as aromatic rings and heterocycles.
[0026]
Although the hydrogen sulfide gas generated in the absolute anaerobic tank 1 can be treated by a general method, in FIG. 1, an anaerobic state can be promoted by introducing it into the denitrification tank 2 behind the absolute anaerobic tank. Moreover, in FIG. 2, it can remove by an oxidation reaction by introduce | transducing into the nitrification tank 3 behind an absolute anaerobic tank.
[0027]
At the outlets of the absolute anaerobic tank 1, denitrification tank 2 and nitrification tank 3 in FIG. 1 and at the outlets of the absolute anaerobic tank 1, nitrification tank 3, denitrification tank 2 and re-aeration tank 19 in FIG. In order to prevent the immobilization carrier from flowing out, it is desirable to attach a screen 25.
[0028]
In each of the absolute anaerobic tank 1, the denitrification tank 2 and the nitrification tank 3 of FIG. 1 and in each of the absolute anaerobic tank 1, the nitrification tank 3, the denitrification tank 2 and the re-aeration tank 19 of FIG. Carriers on which bacteria, denitrifying bacteria, nitrifying bacteria and BOD-degrading bacteria are immobilized are filled, respectively. What is necessary is just to determine the kind of support | carrier suitably as desired. Sulfate-reducing bacteria, denitrifying bacteria, nitrifying bacteria, and BOD-degrading bacteria may be pre-immobilized and immobilized on a microorganism-immobilized carrier, but the microorganism-immobilized carrier is put into each tank and the bacteria are naturally attached. May be used.
[0029]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited at all by an Example. The chromaticity, BOD concentration, and TN (Total Nitrogen) concentration of actual wastewater and treated water were measured by an industrial water test method (JIS K 0101-1991).
[0030]
Example 1
An absolute anaerobic tank, a denitrification tank, and a nitrification tank were installed in this order, and a wastewater treatment device was constructed to return and circulate 75% of the nitrification water flowing out of the nitrification tank to the denitrification tank. The tank capacity of each reaction tank was 150L. An acetalized polyvinyl alcohol-based hydrogel (hereinafter abbreviated as PVA gel) in which sulfate-reducing bacteria are immobilized as a microorganism-immobilizing carrier is filled in an absolute anaerobic tank by 10% (volume ratio, the same applies hereinafter), and a stirrer is used. The PVA gel was allowed to flow. The denitrification tank was filled with 10% of PVA gel in which denitrifying bacteria were immobilized, and the PVA gel was flowed in the same manner using a stirrer. The nitrification tank was filled with 10% PVA gel in which nitrifying bacteria were immobilized, and aerated with an air diffuser. The actual wastewater containing Acid Orange7 and Acid Blue126 was used for the wastewater. The actual wastewater had a chromaticity of 360, a BOD concentration of 1545 mg / L, and a TN amount of 408 mg / L. The chromaticity of the treated water at the exit of the nitrification tank was 18, and it was possible to clearly discern that it was decolorized. The BOD concentration and TN concentration of treated water were 18 mg / L and 20 mg / L, respectively.
[0031]
Comparative Example Waste water treatment was carried out in the same manner as in Example 1 except that an absolute anaerobic tank was not used. The BOD concentration of the treated water at the exit of the nitrification tank was 19 mg / L, which was the same as the example, but the TN concentration was 68 mg / L and the chromaticity was 203. It was.
[0032]
Example 2
A wastewater treatment apparatus was manufactured in which an absolute anaerobic tank, nitrification tank, denitrification tank, and re-aeration tank were installed in this order. The tank capacity of each reaction tank was 150L. A 10% PVA gel in which sulfate-reducing bacteria were immobilized as a microorganism-immobilized carrier was filled in an absolute anaerobic tank and fluidized using a stirrer. The nitrification tank was filled with 10% PVA gel in which nitrifying bacteria were immobilized, and aerated with an air diffuser. The denitrification tank was filled with 10% of PVA gel in which denitrifying bacteria were immobilized, and the PVA gel was flowed in the same manner as the absolute anaerobic tank using a stirrer. At this time, methanol required for the denitrification reaction was added. The re-aeration tank was filled with 10% of PVA gel in which BOD-degrading bacteria were immobilized, and the BOD component that was not consumed in the denitrification reaction was treated while aeration was performed using an air diffuser. In addition to Acid Orange 20 and Acid Blue 92, actual waste water having a high TN concentration mainly composed of urea was used as the waste water. The actual wastewater had a chromaticity of 420, a BOD concentration of 460 mg / L, and a TN concentration of 590 mg / L. The chromaticity of the treated water at the outlet of the re-aeration tank was 19, and it was possible to clearly discern that it was decolored. The BOD concentration and TN concentration of treated water were 17 mg / L and 18 mg / L, respectively.
[0033]
Example 3
A denitrification tank and a nitrification tank were installed in this order, and a wastewater treatment device was constructed in which 75% of the treated water flowing out of the nitrification tank was returned and circulated to the denitrification tank. The tank capacity of each reaction tank was 300 L and 150 L, respectively. The denitrification tank was filled with 10% of PVA gel in which sulfate-reducing bacteria and denitrifying bacteria were immobilized, and the PVA gel was fluidized using a stirrer. The nitrification tank was filled with 10% of PVA gel in which nitrifying bacteria were immobilized, and aerated with an air diffuser. The actual wastewater containing Acid Orange7 and Acid Blue92 was used for the wastewater. The actual wastewater had a chromaticity of 310, a BOD concentration of 1230 mg / L, and a TN concentration of 375 mg / L. The chromaticity of the treated water at the exit of the nitrification tank was 21, and it was found that the color was decolored. The BOD concentration and TN concentration of treated water were 19 mg / L and 24 mg / L, respectively.
[0034]
【The invention's effect】
The wastewater treatment apparatus of the present invention easily and inexpensively decolorizes and decomposes nitrogen compounds in wastewater containing nitrogen-containing dyes, is compact and excellent in durability, and has a high treatment capacity for a long time. Stable operation.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a first embodiment of a wastewater treatment apparatus of the present invention.
FIG. 2 is a flowchart showing a second embodiment of the waste water treatment apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Absolute anaerobic tank 2 Denitrification tank 3 Nitrification tank 4 Drainage 5 To-be-treated water 6 Denitrification treatment water 7 Nitrification treatment water 8 Return / circulation water 9 Stirring device 10 Liquid mixture in denitrification tank 11 Microorganism immobilization support 12 Stirring device 13 Denitrification tank Inner liquid mixture 14 Microorganism immobilization carrier 15 Aeration device 16 Blower 17 Nitrification tank inner liquid mixture 18 Microorganism immobilization carrier 19 Re-aeration tank 20 Drain 21 Water to be treated 22 Nitrification water 23 Denitrification water 24 Aeration water 25 Fine Carrier outflow prevention screen

Claims

Contacting wastewater containing nitrogen-containing dyes with sulfate-reducing bacteria under absolute anaerobic conditions, contacting wastewater with nitrifying bacteria under aerobic conditions, and contacting wastewater with denitrifying bacteria under anaerobic conditions Wastewater treatment equipment equipped with a denitrification tank.

The waste water treatment apparatus according to claim 1, wherein an absolute anaerobic tank, a denitrification tank, and a nitrification tank are installed in this order, and a part of the treated water discharged from the nitrification tank is returned and circulated to the denitrification tank.

The waste water treatment apparatus according to claim 1, wherein an absolute anaerobic tank, a nitrification tank, and a denitrification tank are installed in this order, and a re-aeration tank is provided after the denitrification tank to bring the BOD-degrading bacteria into contact with the waste water under aerobic conditions.

A denitrification tank that contacts wastewater containing dye containing nitrogen with sulfate-reducing bacteria and denitrifying bacteria under absolute anaerobic conditions and a nitrification tank that contacts wastewater with nitrifying bacteria under aerobic conditions are installed in this order and discharged from the nitrification tank. Waste water treatment equipment that returns and circulates part of the treated water to the denitrification tank.

The wastewater treatment apparatus according to claim 1 or 2, wherein the cells are immobilized by a microorganism-immobilized carrier in at least one tank selected from an absolute anaerobic tank, a nitrification tank, and a denitrification tank.

The waste water treatment apparatus according to claim 3, wherein the cells are immobilized by a microorganism-immobilized carrier in at least one tank selected from an absolute anaerobic tank, a nitrification tank, a denitrification tank, and a re-aeration tank.

The waste water treatment apparatus according to claim 4, wherein the cells are immobilized by a microorganism-immobilized carrier in at least one tank selected from a nitrification tank and a denitrification tank.

The wastewater treatment apparatus according to any one of claims 5 to 7, wherein the microorganism-immobilized carrier is at least one carrier selected from a gel carrier, a plastic carrier, and a fibrous carrier.

The wastewater treatment apparatus according to claim 8, wherein the gel carrier is a polyvinyl alcohol-based hydrogel.

A method for treating wastewater containing a dye containing nitrogen, comprising the following steps (1) to (3).
(1) An absolute anaerobic process in which wastewater containing a nitrogen-containing dye is brought into contact with sulfate-reducing bacteria under absolute anaerobic conditions.
(2) A nitrification process in which wastewater is contacted with nitrifying bacteria under aerobic conditions.
(3) A denitrification step in which wastewater is brought into contact with denitrifying bacteria under anaerobic conditions.