JP3848238B2

JP3848238B2 - Colored wastewater treatment method and apparatus used therefor

Info

Publication number: JP3848238B2
Application number: JP2002323427A
Authority: JP
Inventors: 大舟木
Original assignee: Seiwa Industry Co Ltd
Current assignee: Seiwa Industry Co Ltd
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2006-11-22
Anticipated expiration: 2022-11-07
Also published as: JP2004154697A

Description

【０００１】
【発明の属する技術分野】
本発明は染色廃水などの着色廃水の処理方法とそれに用いる着色廃水処理装置に関する。
【０００２】
【従来の技術】
従来、染色廃水などの着色廃水中に含まれる溶解性有機物や色素を除去する方法として、金属イオン及び高分子系凝集剤を用いて色素の除去を行う脱色工程と、活性汚泥処理法等の生物酸化法により溶解性有機物を分解する生物酸化処理工程とを組み合わせた方法が知られている。しかし、この方法では、脱色工程において多量の薬品を使用する上、脱色工程に伴う凝集沈殿処理や加圧浮上処理等で大量の残渣が発生すると共に、生物酸化処理工程において余剰汚泥が発生し、これらの残渣や余剰汚泥の処理が大きな問題となる。
【０００３】
これに対して、着色廃水をオゾンで処理して脱色する方法も知られている。しかし、着色廃水をオゾンのみで処理すると、廃水の着色度は低下するものの、ＣＯＤ値は十分に低減されず、ＢＯＤ値については増加する場合もある。そのため、オゾン処理後に微生物処理を施すことが必要であり（例えば、特許文献１及び２参照）、上記と同様、余剰汚泥の処理が問題となる。なお、難分解性廃水の処理法として、通常のオゾン処理の際に少量の過酸化水素を添加して処理を行う促進酸化法が知られているが、この方法では脱色とＣＯＤ及びＢＯＤの低減が不十分である。
【０００４】
【特許文献１】
特開昭４９−９８０５５号公報
【特許文献２】
特開平６−２５４５７５号公報
【０００５】
【発明が解決しようとする課題】
従って、本発明の目的は、着色廃水の脱色とＣＯＤ（化学的酸素要求量）及びＢＯＤ（生物化学的酸素要求量）の低減を、多量の残渣や余剰汚泥を排出させることなく効率よく行うことのできる着色廃水の処理方法とそれに用いる装置を提供することにある。
本発明の他の目的は、着色廃水に対してオゾンによる酸化処理を効率よく施すことのできる着色廃水の処理方法とそれに用いる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】
本発明者らは、前記目的を達成するため鋭意検討した結果、着色廃水に対し、まず過酸化水素処理を施してＣＯＤを９０％以下に低減した後にオゾン処理を施すと、脱色だけでなく、ＣＯＤ及びＢＯＤの低減を効率よく行うことができることを見出した。また、オゾン処理工程において、渦流ポンプ内に被処理液を送液ポンプにより圧力を加えて供給すると共にオゾン含有ガスを導入し、該渦流ポンプ内で両者を攪拌混合したり、被処理液とオゾン含有ガスとの気液混合物を、液深（高さ）と槽の内径の比及び槽内の液面と槽底間の圧力損失が特定の範囲となる気液分離反応槽に供給してオゾン酸化と共に気液分離を行うと、オゾンによる酸化処理を極めて効率よく行えることを見出した。本発明はこれらの知見に基づいて完成されたものである。
【０００７】
すなわち、本発明は、着色廃水にオゾン処理を施す着色廃水の処理方法であって、（１）渦流ポンプ内に、被処理液を送液ポンプにより圧力を加えて供給すると共にオゾン含有ガスを、オゾン含有ガスと被処理液との供給比（前者／後者；容量比）が２０／８０以上となるように導入し、該渦流ポンプ内で両者を攪拌混合する工程B1と、（２）オゾン含有ガスと被処理液との気液混合物を気液分離反応槽内で、該気液分離反応槽における液深Ｌと槽の内径Ｄとの比（Ｌ／Ｄ）が１．０〜１０であり且つ該気液分離反応槽内の液面と槽底間の圧力損失が０．０５ＭＰａ以上の条件で、オゾン酸化と共に気液分離する工程 B3 とを含むオゾン処理工程Ｂを有する着色廃水の処理方法を提供する。
【０００８】
この処理方法において、オゾン処理工程Ｂの前に、着色廃水に過酸化水素処理を施す過酸化水素処理工程Ａを設け、この工程Ａで得られた処理液を工程 B1 の被処理液として用いてもよい。
【０００９】
この処理方法において、オゾン処理工程Ｂの後、この処理液に対してさらに過酸化水素処理とオゾン処理とをこの順序で１サイクル以上施してもよい。前記過酸化水素処理は酸素曝気下で行うのが好ましい。
【００１０】
前記処理方法において、渦流ポンプ吐出側の圧力（ゲージ圧）は、０．０１〜０．１５ＭＰａであるのが好ましい。
【００１１】
前記処理方法において、オゾン処理工程Ｂは、工程 B1 において渦流ポンプ内で攪拌混合して得られた気液混合物をさらに管路内ミキサーで攪拌混合する工程 B2 を含んでいてもよい。
【００１３】
本発明は、また、着色廃水を処理するための装置であって、被処理液とオゾン含有ガスとを攪拌混合するための渦流ポンプと、前記被処理液を渦流ポンプ内に圧力を加えて供給するための送液ポンプとを備えた着色廃水処理装置を提供する。前記着色廃水処理装置は、さらに、（ｉ）着色廃水に過酸化水素処理を施す過酸化水素処理装置、（ ii ）渦流ポンプ内で攪拌混合して得られた気液混合物をさらに攪拌混合する管路内ミキサー、又は（ iii ）オゾン含有ガスと被処理液との気液混合物を供給するための供給口を有し、液深Ｌと槽の内径Ｄとの比（Ｌ／Ｄ）が１．０〜１０であり且つ槽内の液面と槽底間の圧力損失が０．０５ＭＰａ以上となる気液分離反応槽を備えていてもよい。
【００１４】
本発明は、さらにまた、着色廃水を処理するための装置であって、着色廃水に過酸化水素処理を施す過酸化水素処理装置と、過酸化水素処理を施した過酸化水素処理液とオゾン含有ガスとを攪拌混合するための渦流ポンプと、前記過酸化水素処理液を渦流ポンプ内に圧力を加えて供給するための送液ポンプと、渦流ポンプ内で攪拌混合して得られた気液混合物をさらに攪拌混合する管路内ミキサーと、管路内ミキサーで攪拌混合して得られた気液混合物をオゾン酸化と共に気液分離するための気液分離反応槽であって、液深（高さ）Ｌと槽の内径Ｄとの比（Ｌ／Ｄ）が１．０〜１０であり且つ液面と槽底間の圧力損失が０．０５ＭＰａ以上となる気液分離反応槽とを備えた着色廃水処理装置を提供する。
【００１５】
【発明の実施の形態】
以下、本発明を、図面を参照しつつ詳細に説明する。図１は、本発明の着色廃水の処理方法の１例を示す概略工程図である。この例では、着色廃水１は原水ピット２からポンプ３によりフィルタ４及び熱交換器５を通って曝気槽１０に導入される。フィルタ４は着色廃水１中のＳＳ（残渣）を取り除くため、また熱交換器５は着色廃水１を冷却するために設けられている。曝気槽１０の手前で、着色廃水１に放流水６（必要に応じて）とポンプ８により過酸化水素水７が添加され、それらの混合液が曝気槽１０内へ入る。曝気槽１０では、空気がブロワ９にて送られ散気板１１により曝気しており、ここで過酸化水素処理が施される。曝気槽１０は２槽に分かれており、上澄み液が２槽目に入る。なお、原水ピット２内の着色廃水を「濃厚廃水」、濃厚廃水に放流水６を加えたものを「希釈原水」と称することがある。
【００１６】
着色廃水１としては着色成分を含有する広範な廃水を使用できる。その代表的な例として、例えば、染色工場における染色工程等からの着色廃水（染色廃水）、染料工場からの着色廃水、パルプ工場におけるパルプ製造時に排出される着色廃水、化学工場や食品工場からの着色廃水、養豚場からの着色廃水、鉄鋼プラントからの着色廃水などが挙げられる。
【００１７】
過酸化水素処理により、主として着色廃水中に含まれるＣＯＤ要素が除去され、被処理液のＣＯＤが低減される。ＣＯＤはこの過酸化水素処理によって９０％以下にまで低減するのが好ましい。オゾン処理工程の前に過酸化水素処理工程を設けることにより、オゾン処理工程におけるオゾンの使用量を著しく低減できるだけでなく、着色廃水に直接オゾン処理を施す場合と比較して、オゾン処理によるＣＯＤ及びＢＯＤの低減効率が大幅に向上する。これは、過酸化水素によって、着色廃水中の有機物質がオゾンに対してより酸化されやすい物質に変換されるためであると推測される。着色廃水の種類によっては過酸化水素処理によりＢＯＤが上昇することがあるが、続いて行うオゾン処理によりこのＢＯＤは極めて低い値となる。
【００１８】
過酸化水素（Ｈ₂Ｏ₂）の使用量としては、被処理液（着色廃水）に対して、例えば１０〜１０００重量ｐｐｍ、好ましくは２０〜５００重量ｐｐｍ、さらに好ましくは４０〜３００重量ｐｐｍ程度である。処理温度は、例えば０〜３０℃程度であり、常温で好適に処理を行うことができる。処理時間は、例えば１〜８時間、好ましくは２〜４時間程度である。過酸化水素処理は酸素曝気下で行うのが好ましい。酸素曝気下で過酸化水素処理を行うことにより酸化効率が大きく向上する。酸素としては、純粋な酸素、酸素と不活性ガスとの混合ガス、空気等の何れも用いてもよい。曝気量は、酸素として、被処理液１Ｌ当たり、例えば０．００８〜１．７Ｌ／分、好ましくは０．２〜０．８Ｌ／分程度である。
【００１９】
過酸化水素処理を施された着色廃水は、曝気槽１０の２槽目からポンプ１２によりフィルタ１３を通って原水タンク１４に入り、次いで、原水タンク１４から送液ポンプ１５により圧力を加えられることで、渦流ポンプ（混合ポンプ）１７及び管路内ミキサー１８を経て気液分離反応槽１９に供給される。このとき、渦流ポンプ１７内にオゾン発生装置１６で製造されたオゾン含有ガスが導入される。渦流ポンプ１７内に導入されたオゾンは被処理液（着色廃水）と攪拌混合されて小さな気泡となり、次いで管路内ミキサー１８によりさらに細かく裁断される。
【００２０】
送液ポンプ１５としては、送液可能なポンプであれば特に限定されないが、渦流ポンプなどが好ましい。渦流ポンプ１７としては、液体と気体とを導入可能で、羽根車の回転によって液に圧力と速度の両エネルギーを与え、導入された液体と気体を混合攪拌でき、且つ得られた気液混合物を吐出可能な構造を有するポンプであれば特に限定されず、市販の渦流タービンポンプなどを使用できる。
【００２１】
オゾン発生装置１６としては、特に限定されず、公知の装置を使用できる。オゾンを発生される際に用いる原料としては、空気のほか、空気から抽出した酸素、水の電気分解により得られる酸素などの何れであってもよい。高純度の酸素（例えば、９８％酸素）を用いることもできる。管路内ミキサー１８としては、管路内に配設されたミキサーであればよく、スタティックミキサー、ラインミキサーなどを使用できる。なかでもスタティックミキサーが好ましい。管路内ミキサー１８としては、気泡径を１０００μｍ以下にすることのできるものが好ましい。
【００２２】
上記のように、渦流ポンプ１７の吸込側に送液ポンプ１５を設けて圧力を加えて送液する方法によれば、被処理液が送液ポンプ１５の圧力により渦流ポンプ１７内に強制的に供給されるので、オゾン含有ガスと被処理液との供給比（前者／後者；容量比）が高くても、被処理液とオゾン含有ガスとの気液混合物が円滑に管路内ミキサー１８にまで送られ、そこで、気液が激しく攪拌混合される。そのため、オゾンと被処理液との接触効率が大きく向上し、オゾンの溶解効率も格段に上がり、ひいては気液分離反応槽におけるオゾンによる酸化効率が大幅に改善されることになる。また、送液ポンプ１５により被処理液に圧力が加えられていることから、オゾンの溶解量も増大する。なお、渦流ポンプの前に送液ポンプを設けない場合には、オゾン含有ガスと被処理液との供給比（前者／後者；容量比）が通常１０／９０を超えると、渦流ポンプが気泡を噛み、送液が円滑に行われなくなる。
【００２３】
渦流ポンプ１７へのオゾン含有ガスと被処理液（着色廃水）との供給比（前者／後者；容量比）は、例えば２０／８０以上であり、好ましくは３０／７０以上（例えば３０／７０〜７０／３０程度）、さらに好ましくは４０／６０以上（例えば４０／６０〜７０／３０程度）である。本発明では、オゾン発生の際に用いる原料酸素濃度を選択することにより、被処理液１Ｌに対して、２００ｍｇを超える量（例えば２１０〜５００ｍｇ、好ましくは２２０〜５００ｍｇ）のオゾンを供給することが可能である。
【００２４】
送液ポンプ１５の吐出側（渦流ポンプ１７の吸込側）の圧力（ゲージ圧）は、好ましくは０．０１〜０．１５ＭＰａ、さらに好ましくは０．０５〜０．１ＭＰａ程度であり、渦流ポンプ１７の吐出側（管路内ミキサーの入口側）の圧力（ゲージ圧）は、好ましくは０．０１〜０．１５ＭＰａ、さらに好ましくは０．０５〜０．１ＭＰａ程度であり、また管路内ミキサー１８の出口側（気液分離反応槽１９，２０の入口側）の圧力（ゲージ圧）は、好ましくは０．０１〜０．１ＭＰａ、さらに好ましくは０．０１〜０．０５ＭＰａ程度である。なお、オゾンは０．３ＭＰａ以上（全圧）の圧力（絶対圧）で自己分解するので、該圧力よりも低い圧力で気液混合操作を行う必要がある。
【００２５】
上記の方法によれば、被処理液とオゾン含有ガスとが効率よく攪拌混合されるため、気泡の大きさは極めて小さく、例えば平均気泡径を６００μｍ未満（一般に３００〜５００μｍ程度）とすることができる。
【００２６】
気液分離反応槽１９では、被処理液中の有機物等がオゾンにより酸化されるとともに、気液混合物が気体と液体とに分離される。このオゾン処理により、被処理液の色度が著しく低下し、且つＣＯＤ及びＢＯＤが大幅に低減する。気液分離反応槽は上記のほか、２基を並列に接続したり、３基以上を並列に接続して用いてもよい。
【００２７】
気液分離反応槽１９には、気液混合物の供給口及び分離した気体と液体を排出するための排出口が設けられている。気液分離反応槽１９としては、運転を実施しているとき、液深（高さ）Ｌと槽の内径Ｄとの比（Ｌ／Ｄ）が１．０〜１０（好ましくは１．０〜２．５、さらに好ましくは１．５〜２）であり、液面と槽底間の圧力損失が０．０５ＭＰａ以上（例えば０．０５〜０．２ＭＰａ、好ましくは０．１〜０．２ＭＰａ）となるものが好ましい。このような気液分離反応槽を用いると、反応槽の高さが低くても気液分離及び酸化反応が効率よく進行する。
【００２８】
液面と槽底間の圧力損失を０．１ＭＰａ以上にするための方法としては、例えば、反応槽内にメッシュ、多孔板、分散板などを１又は２以上（例えば２〜５枚程度）水平に配設して流路圧損を生じさせる方法などがある。メッシュや多孔板等を挿入することによりピストンフロー性が向上して、オゾン酸化効率も著しく増大する。前記圧損は、メッシュや多孔板の孔径や孔数、枚数などを適宜調整することによりコントロールできる。なお、前記気液混合物は気液分離反応槽の上部及び下部の何れより導入してもよいが、効率を高める点からは下部より導入するのが好ましい。気液分離反応槽は多段方式とすることもできる。
【００２９】
気液分離反応槽１９で分離された気体は排オゾン処理機３１で処理された後、排気される。排オゾン処理機３１としては、活性炭等の触媒や熱によるオゾン分解装置等、通常のオゾン処理装置を使用できる。
【００３０】
気液分離反応槽１９で分離された液は、渦流ポンプ（混合ポンプ）２０に導かれ、ここで再度オゾンと攪拌混合され、さらに管路内ミキサー２１で攪拌混合された後、気液分離反応槽２２に導入される。渦流ポンプ、管路内ミキサー、気液分離反応槽としては前記と同様のものを使用できる。このように、渦流ポンプでの気液の混合、管路内ミキサーによる攪拌、及び気液分離反応槽での反応と気液分離の一連の操作を２回以上繰り返すことにより、脱色及びＣＯＤとＢＯＤの低減をより確実に行うことができる。特に、オゾン処理後に再度過酸化水素処理を行うと、オゾンによって、着色廃水中の有機物質が過酸化水素に対してより分解されやすい物質に変換されるためか、次の過酸化水素処理でＢＯＤが著しく低減する。
【００３１】
気液分離反応槽２２で分離された気体は排オゾン処理機３１に送られて処理される。気液分離反応槽２２で分離された液は、途中で過酸化水素分解酵素２３がポンプ２４によって加えられ、さらに必要に応じて放流水３０が加えられ、排水ピット２７に流入する。排水ピット２７では、ｐＨ調整液２５（例えば、硫酸などの酸等）がポンプ２６により添加されてｐＨ調整がなされる。図中２８は攪拌機、２９はｐＨメーターである。排水ピット２７の内部は２つに区切られており、上澄み液が２槽目に入り、そこから河川に放流される。なお、気液分離反応槽で分離された液に過酸化水素分解酵素を加えたものを単に「処理水」と称することがある。また、この処理水に放流水を加えたものを単に「希釈処理水」と称することがある。
【００３２】
気液分離反応槽２２で分離された液に対して、再度、前記と同様の過酸化水素処理とオゾン処理とをこの順序で１回以上繰り返すと、脱色効果とＣＯＤ及びＢＯＤの低減効果は飛躍的に増大する。なお、２回目以降の過酸化水素処理においては、必ずしもＣＯＤを９０％以下に低減させなくてもよい。
【００３３】
【発明の効果】
本発明の着色廃水の処理方法によれば、多量の残渣や余剰汚泥を排出させることなく、広範な着色廃水に対して脱色とＣＯＤ及びＢＯＤの低減を行うことができる。また、着色廃水に過酸化水素処理を施してＣＯＤをある程度（例えば９０％以下にまで）低減した後にオゾン処理に付すので、オゾン処理工程におけるオゾンの使用量を減らすことができるだけでなく、脱色とＣＯＤ及びＢＯＤの低減効率も向上する。オゾン処理工程の後、この処理液に対してさらに過酸化水素処理とオゾン処理とをこの順序で１サイクル以上施す場合には、脱色とＣＯＤ及びＢＯＤの低減効率が飛躍的に向上する。過酸化水素処理を酸素曝気下で行う場合には、過酸化水素の酸化力が増大し、ＣＯＤ等の低減効率がより向上する。
【００３４】
着色廃水とオゾン含有ガスとの混合を渦流ポンプ内で行う際、着色廃水を送液ポンプを用いて圧力を加えて渦流ポンプ内に導入する場合には、渦流ポンプ内の気液混合物が強制的に押し出されるので、気泡を噛みにくくなり、気液比を大幅に増大できる。その結果、例えば、管路内ミキサーや気液分離反応槽における気液接触効率、オゾンの溶解効率が高まり、オゾンによる酸化反応効率（脱色及びＣＯＤ・ＢＯＤ低減効率）も大きく向上する。
【００３５】
着色廃水のオゾン処理を、液深（高さ）Ｌと槽の内径Ｄとの比（Ｌ／Ｄ）が１．０〜１０であり且つ槽内の液面と槽底間の圧力損失が０．０５ＭＰａ以上となるような気液分離反応槽を用いて行う場合には、該反応槽の高さが低くてもオゾン酸化効率を高くでき、しかも気液分離が効率よく進行する。
【００３６】
本発明の着色廃水処理装置は上記本発明の着色廃水の処理方法に好適に用いられる。
【００３７】
【実施例】
以下、実施例に基づいて本発明をより詳細に説明するが、本発明はこれらの実施例により何ら限定されるものではない。なお、透視度はＪＩＳＫ０１０２−９の方法、色度はＪＩＳＫ０１０１−１０．１の方法、ＳＳはＪＩＳＫ０１０２−１４．１の方法、ＣＯＤはＪＩＳＫ０１０２−１７の方法、ＢＯＤはＪＩＳＫ０１０２−２１，３２．３の方法に従って測定した。
【００３８】
実施例１
図１に示すフローに沿って染色廃水を処理した。なお、この例では過酸化水素処理工程についてのみ記す。
染色廃水１（濃厚廃水）に放流水６を加えて得られた希釈原水（透視度１ｃｍ、色度７５０、ｐＨ１０．２、ＳＳ９ｍｇ／Ｌ、ＣＯＤ３８０ｍｇ／Ｌ、ＢＯＤ２４０ｍｇ／Ｌ）５８Ｌと、３５重量％過酸化水素水６０ｍｌを曝気槽１０に入れ、空気を２０ｌ／分の流量で供給し、３．５時間曝気した。その結果、透視度１ｃｍ、色度８３０、ｐＨ９．７、ＳＳ１６ｍｇ／Ｌ、ＣＯＤ３０４ｍｇ／Ｌ、ＢＯＤ３３８ｍｇ／Ｌの液が得られた。ＣＯＤは８０％に低減された。
【００３９】
実施例２
希釈原水として、透視度１ｃｍ、色度８７０、ｐＨ１０．２、ＳＳ２０ｍｇ／Ｌ、ＣＯＤ３８０ｍｇ／Ｌ、ＢＯＤ２２０ｍｇ／Ｌのものを用いた点、３５重量％過酸化水素水を３０ｍｌ用いた点以外は実施例１と同様の操作を行った。その結果、透視度１ｃｍ、色度９３０、ｐＨ９．８、ＳＳ２９ｍｇ／Ｌ、ＣＯＤ３３４ｍｇ／Ｌ、ＢＯＤ４２８ｍｇ／Ｌの液が得られた。ＣＯＤは８７．９％に低減された。
【００４０】
実施例３
図１に示すフローに沿って染色廃水を処理した。なお、過酸化水素処理液を原水タンク１４に移すまではバッチ式で、それ以後は連続式で運転した。
染色廃水１（濃厚廃水）（透視度１ｃｍ、色度３３０、ｐＨ１０．１、ＳＳ１１ｍｇ／Ｌ、ＣＯＤ３０１ｍｇ／Ｌ、ＢＯＤ３０９ｍｇ／Ｌ）１．３ｔに放流水６（透視度１５ｃｍ、色度５０、ｐＨ６．６、ＳＳ３０ｍｇ／Ｌ、ＣＯＤ４５ｍｇ／Ｌ、ＢＯＤ３０ｍｇ／Ｌ）０．７ｔを加えて得られた希釈原水（透視度２ｃｍ、色度１７０、ｐＨ９．８、ＳＳ２４ｍｇ／Ｌ、ＣＯＤ１８７ｍｇ／Ｌ、ＢＯＤ２２０ｍｇ／Ｌ）２ｔと、３５重量％過酸化水素水［該希釈原水に対して８０重量ｐｐｍ（Ｈ₂Ｏ₂として）］とを曝気槽１０に入れ、空気を供給し、１６時間曝気した。この過酸化水素処理により、液のＣＯＤは９０％以下にまで低減した。
得られた過酸化水素処理液を原水タンク１４に移した後、送液ポンプ１５［（株）荏原製作所製、商品名「Ｐ１２１−６１．５」］により渦流ポンプ１７［（株）ニクニ製、商品名「２５ＵＰＤ」］内に１．０ｍ³／時の流量で送液すると共に、オゾン発生装置１６［（株）ササクラ製、商品名「ＯＭ−２６０」］で製造したオゾン含有ガスを、１１２３Ｌ／時の流量で渦流ポンプ１７に導入し、気液混合させた［オゾン含有ガス／過酸化水素処理液（容量比）＝１１２／１００；オゾン／過酸化水素処理液（重量比）＝０．２３／１００］。気液混合物をスタティックミキサー１８［日本エンジニアリングプロダクツ（株）製、商品名「Statioflo Static Mixer」］を経由して気液分離反応槽１９に底部より導入した。気液分離反応槽１９の液深（高さ）は１６００ｍｍ、内径は１３００ｍｍであり、槽の内部には孔径２ｍｍの孔を有する多孔板３枚が水平に略等間隔で配設されている。気液分離反応槽１９における液面と槽底間の圧力損失は０．１ＭＰａであった。なお、送液ポンプ１５の吐出側（渦流ポンプ１７の吸込側）の圧力（ゲージ圧）は、０．３５ＭＰａ、渦流ポンプ１７の吐出側（スタティックミキサーの入口側）の圧力（ゲージ圧）は０．２５ＭＰａ、スタティックミキサー１８の出口側（気液分離反応槽１９の入口側）の圧力（ゲージ圧）は、０．２２ＭＰａであった。
気液分離反応槽１９で分離された気体は、排オゾン処理機３１に導いて活性炭で処理した後、大気中に排出した。一方、気液分離反応槽１９で分離された液は、渦流ポンプ２０に導き、ここで再度オゾンと攪拌混合し、さらにスタティックミキサー２１で攪拌混合し、気液分離反応槽２２に導入した。渦流ポンプ、スタティックミキサー、気液分離反応槽としては前記と同様のものを使用した。気液分離反応槽２２で分離された気体は、排オゾン処理機３１に導いて処理した。気液分離反応槽２２で分離された液は、過酸化水素分解酵素２３を加えて処理水とし、さらにこれに放流水３０（透視度１６ｃｍ、色度３０、ｐＨ６．８、ＳＳ２２ｍｇ／Ｌ、ＣＯＤ４８ｍｇ／Ｌ、ＢＯＤ３８ｍｇ／Ｌ）を、前記処理水１００容量部に対して３００容量部加え、排水ピット２７に入れた。排水ピット２７内の液は、ｐＨ調整を行った後、河川に放流した。処理水の透視度は１６ｃｍ、色度は６０、ｐＨは９．２、ＳＳは１４ｍｇ／Ｌ、ＣＯＤは１２７ｍｇ／Ｌ、ＢＯＤは１１０ｍｇ／Ｌであり、希釈処理水の透視度は１３ｃｍ、色度は４０、ｐＨは８．０、ＳＳは２７ｍｇ／Ｌ、ＣＯＤは７２ｍｇ／Ｌ、ＢＯＤは８３ｍｇ／Ｌであった。
【００４１】
実施例４
図１に示すフローに沿って染色廃水を処理した。なお、実施例３と同様、過酸化水素処理液を原水タンク１４に移すまではバッチ式で、それ以後は連続式で運転した。
染色廃水（濃厚廃水）（透視度１ｃｍ、色度１７０、ｐＨ１０．１、ＳＳ７ｍｇ／Ｌ、ＣＯＤ３０６ｍｇ／Ｌ、ＢＯＤ３９６ｍｇ／Ｌ）１．３ｔに放流水６（透視度１４ｃｍ、色度３０、ｐＨ６．６、ＳＳ２０ｍｇ／Ｌ、ＣＯＤ４０ｍｇ／Ｌ、ＢＯＤ２９ｍｇ／Ｌ）０．７ｔを加えて得られた希釈原水（透視度２ｃｍ、色度１８０、ｐＨ９．８、ＳＳ２８ｍｇ／Ｌ、ＣＯＤ２１５ｍｇ／Ｌ、ＢＯＤ２１２ｍｇ／Ｌ）２ｔと、３５重量％過酸化水素水［該希釈原水に対して８０重量ｐｐｍ（Ｈ₂Ｏ₂として）］とを曝気槽１０に入れ、空気を供給し、４時間曝気した。この過酸化水素処理により、液のＣＯＤは９０％以下にまで低減した。
得られた過酸化水素処理液を、実施例３と同様にしてオゾン処理し、処理水を得た。この処理水の透視度は１９ｃｍ、色度は７０、ｐＨは９．０、ＳＳは１８ｍｇ／Ｌ、ＣＯＤは１４０ｍｇ／Ｌ、ＢＯＤは１２９ｍｇ／Ｌであった。
次いで、得られた処理水に対して、再度、上記と同様にして、過酸化水素処理及びオゾン処理を施し、処理水を得た。この２回目の処理水の透視度は３０ｃｍ以上、色度は３０、ｐＨは７．５、ＳＳは７ｍｇ／Ｌ、ＣＯＤは１１１ｍｇ／Ｌ、ＢＯＤは１２２ｍｇ／Ｌであった。
【図面の簡単な説明】
【図１】本発明の着色廃水の処理方法の１例を示す概略工程図である。
【符号の説明】
１着色廃水（染色廃水等）
２原水ピット
６放流水
７過酸化水素水
９ブロワ
10 曝気槽
11 散気板
14 原水タンク
15 送液ポンプ
16 オゾン発生装置
17，20 渦流ポンプ
18，21 管路内ミキサー
19，22 気液分離反応槽
23 過酸化水素分解酵素
25 ｐＨ調整液
27 排水ピット
30 放流水
31 排オゾン処理機[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating colored wastewater such as dyeing wastewater and a colored wastewater treatment apparatus used therefor.
[0002]
[Prior art]
Conventionally, as a method for removing soluble organic substances and pigments contained in colored wastewater such as dyeing wastewater, a decolorization step in which pigments are removed using metal ions and a polymer flocculant, and biological treatment such as activated sludge treatment A method is known which is combined with a biological oxidation treatment step for decomposing soluble organic substances by an oxidation method. However, in this method, in addition to using a large amount of chemicals in the decolorization process, a large amount of residue is generated in the coagulation sedimentation process or the pressure flotation process associated with the decolorization process, and surplus sludge is generated in the biooxidation process. The treatment of these residues and excess sludge becomes a big problem.
[0003]
On the other hand, a method is also known in which colored wastewater is treated with ozone and decolorized. However, when the colored wastewater is treated only with ozone, the coloration degree of the wastewater is lowered, but the COD value is not sufficiently reduced, and the BOD value may be increased. Therefore, it is necessary to perform microbial treatment after ozone treatment (see, for example, Patent Documents 1 and 2), and the treatment of excess sludge becomes a problem as described above. In addition, as a method for treating hardly decomposable wastewater, there is known an accelerated oxidation method in which a small amount of hydrogen peroxide is added during normal ozone treatment. In this method, decolorization and reduction of COD and BOD are known. Is insufficient.
[0004]
[Patent Document 1]
JP 49-98055 A
[Patent Document 2]
JP-A-6-254575
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to efficiently perform decolorization of colored wastewater and reduction of COD (chemical oxygen demand) and BOD (biochemical oxygen demand) without discharging a large amount of residue and excess sludge. It is an object of the present invention to provide a colored wastewater treatment method and an apparatus used therefor.
Another object of the present invention is to provide a colored wastewater treatment method and an apparatus used therefor, which can efficiently perform oxidation treatment with ozone on the colored wastewater.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned object, the present inventors have first performed a hydrogen peroxide treatment on the colored wastewater to reduce the COD to 90% or less and then an ozone treatment. It has been found that COD and BOD can be efficiently reduced. Further, in the ozone treatment process, the liquid to be treated is supplied into the vortex pump by applying pressure by the liquid feed pump, and the ozone-containing gas is introduced, and both are stirred and mixed in the vortex pump, or the liquid to be treated and ozone are mixed. The gas-liquid mixture with the contained gas is supplied to a gas-liquid separation reaction tank in which the ratio of the liquid depth (height) to the inner diameter of the tank and the pressure loss between the liquid level in the tank and the tank bottom are within a specific range. It has been found that when gas-liquid separation is performed together with oxidation, oxidation treatment with ozone can be performed very efficiently. The present invention has been completed based on these findings.
[0007]
That is, the present invention is a colored wastewater treatment method for applying ozone treatment to colored wastewater,(1)Into the vortex pump, the liquid to be treated is supplied with pressure applied by the liquid feed pump and the ozone-containing gas is supplied.The supply ratio of the ozone-containing gas and the liquid to be treated (the former / the latter; the volume ratio) is 20/80 or more.Step B1 for introducing and stirring and mixing both in the vortex pumpAnd (2) the ratio of the liquid depth L in the gas-liquid separation reaction tank to the inner diameter D of the gas-liquid mixture of the ozone-containing gas and the liquid to be treated (L / D). Step of gas-liquid separation with ozone oxidation under the condition that the pressure loss between the liquid level in the gas-liquid separation reaction tank and the tank bottom is 0.05 MPa or more, 1.0 to 10 B3 WhenThe processing method of the colored wastewater which has the ozone treatment process B containing this is provided.
[0008]
In this processing method,Before the ozone treatment step B, a hydrogen peroxide treatment step A for subjecting the colored wastewater to a hydrogen peroxide treatment is provided, and the treatment liquid obtained in this step A is a step. B1 You may use as a to-be-processed liquid.
[0009]
In this treatment method, after the ozone treatment step B, the treatment liquid may be further subjected to hydrogen peroxide treatment and ozone treatment in this order for one cycle or more. The hydrogen peroxide treatment is preferably performed under oxygen aeration.
[0010]
In the processing methodVortexThe pressure (gauge pressure) on the discharge side of the flow pump is preferably 0.01 to 0.15 MPa.
[0011]
In the treatment method, the ozone treatment process B is a process. B1 A step of stirring and mixing the gas-liquid mixture obtained by stirring and mixing in a vortex pump in a pipe mixer B2 May be included.
[0013]
The present invention is also an apparatus for treating colored wastewater,Colored wastewater treatment apparatus comprising: a vortex pump for stirring and mixing a liquid to be treated and an ozone-containing gas; and a liquid feed pump for supplying the liquid to be treated by applying pressure to the vortex pump.I will provide a.The colored wastewater treatment apparatus further comprises (i) a hydrogen peroxide treatment apparatus that performs a hydrogen peroxide treatment on the colored wastewater, ii ) In-pipe mixer for further stirring and mixing the gas-liquid mixture obtained by stirring and mixing in the vortex pump, or ( iii ) It has a supply port for supplying a gas-liquid mixture of the ozone-containing gas and the liquid to be treated, the ratio (L / D) of the liquid depth L to the inner diameter D of the tank is 1.0 to 10, and the tank There may be provided a gas-liquid separation reaction tank in which the pressure loss between the inner liquid level and the tank bottom is 0.05 MPa or more.
[0014]
Furthermore, the present invention is an apparatus for treating colored wastewater, which includes a hydrogen peroxide treatment apparatus that performs a hydrogen peroxide treatment on the colored wastewater, a hydrogen peroxide treatment liquid that has undergone a hydrogen peroxide treatment, and an ozone-containing solution. A vortex pump for stirring and mixing gas, a liquid feed pump for supplying the hydrogen peroxide treatment liquid under pressure into the vortex pump, and a gas-liquid mixture obtained by stirring and mixing in the vortex pump And a gas-liquid separation reaction tank for gas-liquid separation of the gas-liquid mixture obtained by stirring and mixing in the pipe mixer with ozone oxidation together with ozone oxidation. ) Coloring provided with a gas-liquid separation reaction tank in which the ratio (L / D) of L to the inner diameter D of the tank is 1.0 to 10 and the pressure loss between the liquid surface and the tank bottom is 0.05 MPa or more. Provide wastewater treatment equipment.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic process diagram showing an example of a method for treating colored wastewater according to the present invention. In this example, the colored waste water 1 is introduced into the aeration tank 10 from the raw water pit 2 through the filter 4 and the heat exchanger 5 by the pump 3. The filter 4 is provided for removing SS (residue) in the colored wastewater 1, and the heat exchanger 5 is provided for cooling the colored wastewater 1. Before the aeration tank 10, the waste water 6 (if necessary) and the hydrogen peroxide solution 7 are added to the colored waste water 1 by the pump 8, and the mixed solution thereof enters the aeration tank 10. In the aeration tank 10, air is sent by the blower 9 and aerated by the diffuser plate 11, where hydrogen peroxide treatment is performed. The aeration tank 10 is divided into two tanks, and the supernatant liquid enters the second tank. The colored waste water in the raw water pit 2 may be referred to as “concentrated waste water”, and the waste water 6 added to the concentrated waste water may be referred to as “diluted raw water”.
[0016]
As the colored wastewater 1, a wide range of wastewater containing colored components can be used. Representative examples include, for example, colored wastewater from dyeing processes in dyeing plants (dyed wastewater), colored wastewater from dye factories, colored wastewater discharged during pulp production in pulp factories, chemical factories and food factories. Colored wastewater, colored wastewater from pig farms, colored wastewater from steel plants and the like.
[0017]
By the hydrogen peroxide treatment, COD elements mainly contained in the colored wastewater are removed, and the COD of the liquid to be treated is reduced. COD is preferably reduced to 90% or less by this hydrogen peroxide treatment. By providing a hydrogen peroxide treatment step before the ozone treatment step, not only can the amount of ozone used in the ozone treatment step be significantly reduced, but also compared with the case where ozone treatment is performed directly on colored wastewater, BOD reduction efficiency is greatly improved. This is presumably because hydrogen peroxide converts the organic substance in the colored wastewater into a substance that is more easily oxidized by ozone. Depending on the type of the colored wastewater, the BOD may be increased by the hydrogen peroxide treatment, but this BOD becomes a very low value by the subsequent ozone treatment.
[0018]
Hydrogen peroxide (H₂O₂) Is, for example, about 10 to 1000 ppm by weight, preferably 20 to 500 ppm by weight, and more preferably about 40 to 300 ppm by weight with respect to the liquid to be treated (colored wastewater). Processing temperature is about 0-30 degreeC, for example, and it can process it suitably at normal temperature. The treatment time is, for example, about 1 to 8 hours, preferably about 2 to 4 hours. The hydrogen peroxide treatment is preferably performed under oxygen aeration. Oxidation efficiency is greatly improved by performing hydrogen peroxide treatment under oxygen aeration. As oxygen, any of pure oxygen, a mixed gas of oxygen and an inert gas, air, or the like may be used. The amount of aeration is, for example, 0.008 to 1.7 L / min, preferably about 0.2 to 0.8 L / min per 1 L of the liquid to be processed as oxygen.
[0019]
The colored wastewater that has been subjected to hydrogen peroxide treatment enters the raw water tank 14 through the filter 13 by the pump 12 from the second tank of the aeration tank 10, and then is pressurized by the liquid feed pump 15 from the raw water tank 14. Then, the gas is supplied to the gas-liquid separation reaction tank 19 through the vortex pump (mixing pump) 17 and the in-pipe mixer 18. At this time, the ozone-containing gas produced by the ozone generator 16 is introduced into the vortex pump 17. The ozone introduced into the vortex pump 17 is agitated and mixed with the liquid to be treated (colored wastewater) to form small bubbles, and then further finely cut by the in-pipe mixer 18.
[0020]
The liquid feed pump 15 is not particularly limited as long as it is a pump capable of liquid feed, but a vortex pump or the like is preferable. As the vortex pump 17, liquid and gas can be introduced, both energy of pressure and speed can be given to the liquid by rotation of the impeller, the introduced liquid and gas can be mixed and stirred, and the obtained gas-liquid mixture can be The pump is not particularly limited as long as it has a dischargeable structure, and a commercially available vortex turbine pump or the like can be used.
[0021]
It does not specifically limit as the ozone generator 16, A well-known apparatus can be used. The raw material used when ozone is generated may be any of oxygen extracted from air, oxygen obtained by electrolysis of water, etc. in addition to air. High purity oxygen (eg, 98% oxygen) can also be used. The in-pipe mixer 18 may be a mixer provided in the pipe line, and a static mixer, a line mixer, or the like can be used. Of these, a static mixer is preferable. As the in-pipe mixer 18, a mixer capable of setting the bubble diameter to 1000 μm or less is preferable.
[0022]
As described above, according to the method in which the liquid feed pump 15 is provided on the suction side of the vortex pump 17 and the liquid is fed by applying pressure, the liquid to be processed is forced into the vortex pump 17 by the pressure of the liquid feed pump 15. Since the gas is supplied, even if the supply ratio of the ozone-containing gas to the liquid to be processed (the former / the latter; volume ratio) is high, the gas-liquid mixture of the liquid to be processed and the ozone-containing gas smoothly flows into the in-pipe mixer 18. Where the gas and liquid are vigorously stirred and mixed. Therefore, the contact efficiency between ozone and the liquid to be treated is greatly improved, the ozone dissolution efficiency is significantly increased, and the oxidation efficiency by ozone in the gas-liquid separation reaction tank is greatly improved. Further, since pressure is applied to the liquid to be treated by the liquid feed pump 15, the amount of ozone dissolved also increases. In the case where a liquid feed pump is not provided before the vortex pump, when the supply ratio (the former / the latter; volume ratio) between the ozone-containing gas and the liquid to be treated normally exceeds 10/90, Biting and liquid feeding are not performed smoothly.
[0023]
The supply ratio (the former / the latter; volume ratio) of the ozone-containing gas and the liquid to be treated (colored wastewater) to the vortex pump 17 is, for example, 20/80 or more, preferably 30/70 or more (for example, 30/70 to About 70/30), more preferably 40/60 or more (for example, about 40/60 to 70/30). In the present invention, by selecting the raw material oxygen concentration used for generating ozone, an amount of ozone exceeding 200 mg (for example, 210 to 500 mg, preferably 220 to 500 mg) is supplied to 1 L of the liquid to be treated. Is possible.
[0024]
The pressure (gauge pressure) on the discharge side of the liquid feed pump 15 (the suction side of the vortex pump 17) is preferably about 0.01 to 0.15 MPa, more preferably about 0.05 to 0.1 MPa. The pressure (gauge pressure) on the discharge side (the inlet side of the in-pipe mixer) is preferably about 0.01 to 0.15 MPa, more preferably about 0.05 to 0.1 MPa, and the in-pipe mixer 18 The pressure (gauge pressure) on the outlet side (the inlet side of the gas-liquid separation reaction tanks 19 and 20) is preferably about 0.01 to 0.1 MPa, more preferably about 0.01 to 0.05 MPa. Since ozone self-decomposes at a pressure (absolute pressure) of 0.3 MPa or more (total pressure), it is necessary to perform a gas-liquid mixing operation at a pressure lower than the pressure.
[0025]
According to the above method, since the liquid to be treated and the ozone-containing gas are efficiently stirred and mixed, the size of the bubbles is extremely small. For example, the average bubble diameter is less than 600 μm (generally about 300 to 500 μm). it can.
[0026]
In the gas-liquid separation reaction tank 19, organic substances in the liquid to be treated are oxidized by ozone, and the gas-liquid mixture is separated into gas and liquid. By this ozone treatment, the chromaticity of the liquid to be treated is remarkably lowered, and COD and BOD are greatly reduced. In addition to the above, two gas-liquid separation reaction tanks may be connected in parallel, or three or more may be connected in parallel.
[0027]
The gas-liquid separation reaction tank 19 is provided with a gas-liquid mixture supply port and a discharge port for discharging the separated gas and liquid. As the gas-liquid separation reaction tank 19, the ratio (L / D) between the liquid depth (height) L and the inner diameter D of the tank is 1.0 to 10 (preferably 1.0 to 10). 2.5, more preferably 1.5-2), and the pressure loss between the liquid level and the tank bottom is 0.05 MPa or more (for example, 0.05-0.2 MPa, preferably 0.1-0.2 MPa). Is preferred. When such a gas-liquid separation reaction tank is used, gas-liquid separation and oxidation reaction proceed efficiently even if the height of the reaction tank is low.
[0028]
As a method for setting the pressure loss between the liquid surface and the tank bottom to 0.1 MPa or more, for example, one or more meshes, perforated plates, dispersion plates, etc. (for example, about 2 to 5 sheets) are horizontally placed in the reaction tank. For example, there is a method of causing flow path pressure loss by disposing them. By inserting a mesh, a perforated plate or the like, the piston flow property is improved and the ozone oxidation efficiency is remarkably increased. The pressure loss can be controlled by appropriately adjusting the hole diameter, the number of holes, the number of holes, etc. of the mesh or perforated plate. The gas-liquid mixture may be introduced from either the upper part or the lower part of the gas-liquid separation reaction tank, but is preferably introduced from the lower part from the viewpoint of increasing efficiency. The gas-liquid separation reaction tank may be a multistage system.
[0029]
The gas separated in the gas-liquid separation reaction tank 19 is processed by the exhaust ozone processor 31 and then exhausted. As the exhaust ozone treatment device 31, a normal ozone treatment device such as a catalyst such as activated carbon or a heat ozone decomposition device can be used.
[0030]
The liquid separated in the gas-liquid separation reaction tank 19 is guided to a vortex pump (mixing pump) 20, where it is again stirred and mixed with ozone, and further stirred and mixed in the in-pipe mixer 21, and then the gas-liquid separation reaction. It is introduced into the tank 22. As the vortex pump, the in-pipe mixer, and the gas-liquid separation reaction tank, the same ones as described above can be used. In this way, decolorization and COD and BOD are repeated by repeating a series of operations of gas-liquid mixing with a vortex pump, stirring with a mixer in a pipe, and reaction and gas-liquid separation in a gas-liquid separation reaction tank twice or more. Can be more reliably reduced. In particular, if the hydrogen peroxide treatment is performed again after the ozone treatment, the organic substance in the colored wastewater is converted into a substance that is more easily decomposed by hydrogen peroxide due to ozone. Is significantly reduced.
[0031]
The gas separated in the gas-liquid separation reaction tank 22 is sent to the exhaust ozone processor 31 for processing. The liquid separated in the gas-liquid separation reaction tank 22 is added with a hydrogen peroxide-degrading enzyme 23 by a pump 24 along the way, and further discharged water 30 is added as necessary, and flows into the drain pit 27. In the drainage pit 27, the pH adjustment liquid 25 (for example, an acid such as sulfuric acid) is added by the pump 26 to adjust the pH. In the figure, 28 is a stirrer and 29 is a pH meter. The inside of the drainage pit 27 is divided into two, and the supernatant liquid enters the second tank and is discharged into the river from there. In addition, what added the hydrogen peroxide decomposing enzyme to the liquid isolate | separated in the gas-liquid separation reaction tank may only be called "treated water." Further, this treated water added with effluent water may be simply referred to as “diluted treated water”.
[0032]
If the hydrogen peroxide treatment and the ozone treatment similar to the above are repeated once or more in this order for the liquid separated in the gas-liquid separation reaction tank 22, the decolorization effect and the COD and BOD reduction effect will jump dramatically. Increase. In the second and subsequent hydrogen peroxide treatments, the COD need not necessarily be reduced to 90% or less.
[0033]
【The invention's effect】
According to the method for treating colored wastewater of the present invention, decolorization and reduction of COD and BOD can be performed on a wide range of colored wastewater without discharging a large amount of residue and excess sludge. In addition, since the colored wastewater is treated with hydrogen peroxide to reduce COD to some extent (for example, to 90% or less) and then subjected to ozone treatment, not only can the amount of ozone used in the ozone treatment process be reduced, Reduction efficiency of COD and BOD is also improved. After the ozone treatment step, when the hydrogen peroxide treatment and the ozone treatment are further performed in this order for one cycle or more, the decolorization and the COD and BOD reduction efficiency are dramatically improved. When the hydrogen peroxide treatment is performed under oxygen aeration, the oxidizing power of hydrogen peroxide increases and the COD reduction efficiency is further improved.
[0034]
When mixing colored wastewater and ozone-containing gas in a vortex pump, if the colored wastewater is introduced into the vortex pump by applying pressure using a liquid pump, the gas-liquid mixture in the vortex pump is forced. As a result, it is difficult to bite the bubbles, and the gas-liquid ratio can be greatly increased. As a result, for example, the gas-liquid contact efficiency and ozone dissolution efficiency in the in-pipe mixer and gas-liquid separation reaction tank are increased, and the oxidation reaction efficiency (decolorization and COD / BOD reduction efficiency) by ozone is greatly improved.
[0035]
In the ozone treatment of colored wastewater, the ratio (L / D) of the liquid depth (height) L to the inner diameter D of the tank is 1.0 to 10, and the pressure loss between the liquid level in the tank and the tank bottom is 0. In the case of using a gas-liquid separation reaction tank of 0.05 MPa or higher, the ozone oxidation efficiency can be increased even if the height of the reaction tank is low, and the gas-liquid separation proceeds efficiently.
[0036]
The colored wastewater treatment apparatus of the present invention is suitably used for the colored wastewater treatment method of the present invention.
[0037]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by these Examples. The transparency is the method of JIS K 0102-9, the chromaticity is the method of JIS K 0101-10.1, the SS is the method of JIS K 0102-14.1, the COD is the method of JIS K 0102-17, and the BOD is JIS JIS. Measurement was carried out according to the method of K 0102-21, 32.3.
[0038]
Example 1
Dyeing wastewater was treated along the flow shown in FIG. In this example, only the hydrogen peroxide treatment step will be described.
Diluted raw water 1 (concentrated waste water) and diluted raw water obtained by adding effluent 6 (transparency 1 cm, chromaticity 750, pH 10.2, SS 9 mg / L, COD 380 mg / L, BOD 240 mg / L) 58 L, 35% by weight Hydrogen peroxide water (60 ml) was placed in the aeration tank 10, air was supplied at a flow rate of 20 l / min, and aeration was performed for 3.5 hours. As a result, liquids having a transparency of 1 cm, chromaticity of 830, pH of 9.7, SS of 16 mg / L, COD of 304 mg / L, and BOD of 338 mg / L were obtained. COD was reduced to 80%.
[0039]
Example 2
Examples other than the point of using raw water for dilution of 1 cm, chromaticity 870, pH 10.2, SS 20 mg / L, COD 380 mg / L, BOD 220 mg / L, and 30 wt% of hydrogen peroxide water The same operation as 1 was performed. As a result, liquids having a transparency of 1 cm, chromaticity of 930, pH of 9.8, SS of 29 mg / L, COD of 334 mg / L, and BOD of 428 mg / L were obtained. The COD was reduced to 87.9%.
[0040]
Example 3
Dyeing wastewater was treated along the flow shown in FIG. The batch operation was performed until the hydrogen peroxide treatment solution was transferred to the raw water tank 14, and the continuous operation was performed thereafter.
Dyeing wastewater 1 (concentrated wastewater) (permeability 1 cm, chromaticity 330, pH 10.1, SS 11 mg / L, COD 301 mg / L, BOD 309 mg / L) 1.3 t discharged water 6 (permeability 15 cm, chromaticity 50, pH 6. 6, SS 30 mg / L, COD 45 mg / L, BOD 30 mg / L) Diluted raw water obtained by adding 0.7 t (transparency 2 cm, chromaticity 170, pH 9.8, SS 24 mg / L, COD 187 mg / L, BOD 220 mg / L) 2t, 35 wt% hydrogen peroxide water [80 wt ppm (H₂O₂As)) was placed in the aeration tank 10, supplied with air, and aerated for 16 hours. By this hydrogen peroxide treatment, the COD of the liquid was reduced to 90% or less.
After the obtained hydrogen peroxide treatment liquid was transferred to the raw water tank 14, the vortex pump 17 [manufactured by Nikuni Co., Ltd.] with a liquid feed pump 15 [manufactured by Ebara Corporation, product name “P121-61.5”] Product name "25UPD"] 1.0m^ThreeThe ozone-containing gas produced by the ozone generator 16 [trade name “OM-260”, manufactured by Sasakura Co., Ltd.] is introduced into the vortex pump 17 at a flow rate of 1123 L / hour. Gas-liquid mixing was performed [ozone-containing gas / hydrogen peroxide treatment liquid (volume ratio) = 112/100; ozone / hydrogen peroxide treatment liquid (weight ratio) = 0.23 / 100]. The gas-liquid mixture was introduced into the gas-liquid separation reaction tank 19 from the bottom via a static mixer 18 [manufactured by Nippon Engineering Products Co., Ltd., trade name “Statioflo Static Mixer”]. The gas-liquid separation reaction tank 19 has a liquid depth (height) of 1600 mm and an inner diameter of 1300 mm. Inside the tank, three perforated plates having holes with a diameter of 2 mm are horizontally arranged at substantially equal intervals. The pressure loss between the liquid surface and the bottom of the gas-liquid separation reaction tank 19 was 0.1 MPa. The pressure (gauge pressure) on the discharge side of the liquid feed pump 15 (suction side of the vortex pump 17) is 0.35 MPa, and the pressure (gauge pressure) on the discharge side (static mixer inlet side) of the vortex pump 17 is 0. The pressure (gauge pressure) on the outlet side of the static mixer 18 (inlet side of the gas-liquid separation reaction tank 19) was 0.22 MPa.
The gas separated in the gas-liquid separation reaction tank 19 was guided to the exhaust ozone processor 31 and treated with activated carbon, and then discharged into the atmosphere. On the other hand, the liquid separated in the gas-liquid separation reaction tank 19 was guided to the vortex pump 20, where it was again stirred and mixed with ozone, further stirred and mixed with the static mixer 21, and introduced into the gas-liquid separation reaction tank 22. The same vortex pump, static mixer, and gas-liquid separation reactor as those described above were used. The gas separated in the gas-liquid separation reaction tank 22 was guided to the exhaust ozone processor 31 for processing. The liquid separated in the gas-liquid separation reaction tank 22 is treated with hydrogen peroxide-degrading enzyme 23 and further treated with effluent 30 (transparency 16 cm, chromaticity 30, pH 6.8, SS 22 mg / L, COD 48 mg). / L, BOD 38 mg / L) was added to the drainage pit 27 by adding 300 parts by volume to 100 parts by volume of the treated water. The liquid in the drainage pit 27 was discharged into the river after pH adjustment. The transparency of treated water is 16 cm, chromaticity is 60, pH is 9.2, SS is 14 mg / L, COD is 127 mg / L, BOD is 110 mg / L, and the transparency of diluted treated water is 13 cm, chromaticity Was 40, pH was 8.0, SS was 27 mg / L, COD was 72 mg / L, and BOD was 83 mg / L.
[0041]
Example 4
Dyeing wastewater was treated along the flow shown in FIG. Note that, as in Example 3, the batch type operation was performed until the hydrogen peroxide treatment liquid was transferred to the raw water tank 14, and the continuous operation was performed thereafter.
Dyeing wastewater (concentrated wastewater) (permeability 1 cm, chromaticity 170, pH 10.1, SS 7 mg / L, COD 306 mg / L, BOD 396 mg / L) 1.3t and effluent 6 (permeability 14 cm, chromaticity 30, pH 6.6) , SS20 mg / L, COD 40 mg / L, BOD 29 mg / L) Diluted raw water (transparency 2 cm, chromaticity 180, pH 9.8, SS28 mg / L, COD 215 mg / L, BOD 212 mg / L) 2 t And 35 wt% hydrogen peroxide water [80 wt ppm (H₂O₂As)) was placed in the aeration tank 10, supplied with air, and aerated for 4 hours. By this hydrogen peroxide treatment, the COD of the liquid was reduced to 90% or less.
The obtained hydrogen peroxide treatment liquid was subjected to ozone treatment in the same manner as in Example 3 to obtain treated water. The treated water had a transparency of 19 cm, a chromaticity of 70, a pH of 9.0, an SS of 18 mg / L, a COD of 140 mg / L, and a BOD of 129 mg / L.
Next, the obtained treated water was again subjected to hydrogen peroxide treatment and ozone treatment in the same manner as described above to obtain treated water. The transparency of this second treated water was 30 cm or more, the chromaticity was 30, the pH was 7.5, the SS was 7 mg / L, the COD was 111 mg / L, and the BOD was 122 mg / L.
[Brief description of the drawings]
FIG. 1 is a schematic process diagram showing an example of a method for treating colored wastewater according to the present invention.
[Explanation of symbols]
1 Colored wastewater (dyeing wastewater, etc.)
2 Raw water pit
6 Discharged water
7 Hydrogen peroxide solution
9 Blower
10 Aeration tank
11 Diffuser
14 Raw water tank
15 Liquid feed pump
16 Ozone generator
17, 20 Vortex pump
18, 21 Pipeline mixer
19, 22 Gas-liquid separation reactor
23 Hydrogen peroxide-degrading enzyme
25 pH adjuster
27 Drainage pit
30 Effluent water
31 Waste ozone treatment machine

Claims

A method for treating colored wastewater by subjecting the colored wastewater to ozone treatment, comprising: (1) supplying a liquid to be treated into a vortex pump by applying pressure by a liquid feed pump, and supplying an ozone-containing gas to an ozone-containing gas. Step B1 in which the supply ratio to the liquid (the former / the latter; volume ratio) is 20/80 or more, and both are stirred and mixed in the vortex pump ; (2) the ozone-containing gas and the liquid to be treated; In the gas-liquid separation reaction tank, the ratio (L / D) of the liquid depth L in the gas-liquid separation reaction tank to the inner diameter D of the tank is 1.0 to 10, and the gas-liquid separation reaction under the conditions the pressure loss is more than 0.05MPa between the liquid surface and the bottom of the tank in the tank, the processing method of the colored wastewater with ozone treatment step B and a step B3 of gas-liquid separation with ozone oxidation.

The coloring according to claim 1, wherein a hydrogen peroxide treatment step A for subjecting the colored wastewater to a hydrogen peroxide treatment is provided before the ozone treatment step B, and the treatment liquid obtained in this step A is used as the liquid to be treated in step B1. Wastewater treatment method.

The method for treating colored wastewater according to claim 2, wherein after the ozone treatment step B, the treatment solution is further subjected to hydrogen peroxide treatment and ozone treatment in this order for one cycle or more.

The method for treating colored wastewater according to claim 2 or 3, wherein the hydrogen peroxide treatment is performed under oxygen aeration.

The method for treating colored wastewater according to claim 1, wherein the pressure (gauge pressure) on the vortex pump discharge side is 0.01 to 0.15 MPa.

The method for treating colored wastewater according to claim 1, wherein the ozone treatment step B includes a step B2 in which the gas-liquid mixture obtained by stirring and mixing in the vortex pump in step B1 is further stirred and mixed by an in-pipe mixer.