JP3789619B2

JP3789619B2 - Ultrapure water production equipment

Info

Publication number: JP3789619B2
Application number: JP31989897A
Authority: JP
Inventors: 真生日高; 順田中
Original assignee: Organo Corp
Current assignee: Organo Corp
Priority date: 1996-11-21
Filing date: 1997-11-20
Publication date: 2006-06-28
Anticipated expiration: 2017-11-20
Also published as: JPH10202296A

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば半導体産業におけるシリコンウエハの洗浄等に用いられる超純水の製造装置に関し、さらに詳述すると、有機物を含む被処理水中の有機物除去を行う経路（排水回収系の純水用排水回収系）における有機物除去の効率化を図った超純水製造装置に関する。なお、本明細書においては、一般には必ずしも明確に定義分けされていない純水、超純水等の語で説明される高純度な水を総称して「超純水」という。
【０００２】
【従来の技術】
シリコンウエハの洗浄等に用いられる超純水の製造装置は、一般に、図７に示すように、一次純水系２、二次純水系（サブシステム）４及び排水回収系の一部をなす純水用排水回収系６を備えている。一次純水系２は、例えば逆浸透膜装置、真空脱気装置、イオン交換装置などを備えた経路であり、市水、工業用水等の原水中に含まれる懸濁物質及び有機物の一部が前処理系（図示せず）で除去された後、その処理水８が一次純水系２に供給される。二次純水系４は、例えば紫外線酸化装置、カートリッジポリッシャ、限外濾過膜装置などを備えた経路であり、一次純水系２の処理水３（一次純水）が純水貯槽１０を経由して二次純水系４に供給される。二次純水系４で得られた超純水１２の一部は使用場所１４に送られて使用され、残部は純水貯槽１０に循環される。純水用排水回収系６は、例えば活性炭濾過装置、イオン交換装置、紫外線酸化装置などを備えた経路であり、使用場所１４で超純水を使用することにより生じた排水１６の処理を行う。純水用排水回収系６の処理水１８は、一次純水系２に戻されて再利用される。
【０００３】
なお、一般的な超純水製造装置では、使用場所１４から排出された超純水を使用することにより生じた排水１６を処理する排水回収系として、適当な処理を施してから一次純水系に戻す前記純水用排水回収系６の外に、排水の清浄度に応じて、何ら処理を施すことなく直接一次純水系に戻す経路、適当な処理を施してから雑用水として使用する経路（雑用水用排水回収系）、及び、適当な処理を施してから放流する経路（廃水処理系）を備えている。
【０００４】
【発明が解決しようとする課題】
半導体産業におけるシリコンウエハ等の洗浄工程では、イソプロピルアルコール、メタノール、アセトン等の有機系洗浄剤が使用されるため、使用場所からの超純水の排水中には微量の有機物が含まれているのが通常であるが、この使用場所からの排水は、市水、工業用水等に比べて不純物の濃度が極めて低い。したがって、超純水製造装置の純水用排水回収系で使用場所からの排水中の有機物濃度をできるだけ低くし、その処理水を一次純水系に戻せば、純度の高い超純水を得る点で非常に有利になる。そのため、純水用排水回収系では、被処理水中から有機物を可能な限り除去することが望まれている。
【０００５】
この場合、純水用排水回収系における有機物の除去方法としては、従来、被処理水（排水）に酸化剤であるオゾン又は過酸化水素を添加し、さらにオゾン又は過酸化水素を含有する被処理水に紫外線を照射して有機物を酸化分解する方法が知られている。
【０００６】
しかし、この方法においては、有機物の分解速度が遅いため処理時間が長くかかり、処理効率が悪いという欠点があった。また、高圧紫外線ランプを使用するため装置が大型化かつ複雑化する上、ランニングコストが増大し、経済的に不利であった。
【０００７】
本発明は、上記事情に鑑みてなされたもので、純水用排水回収系における有機物除去の効率化を図った超純水製造装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明者らは、有機物を含む被処理水のｐＨをアルカリ側の特定の範囲に調整するとともに、このアルカリ性の被処理水にオゾンを添加した場合、紫外線照射を行うことなく被処理水中の有機物を効率的に除去できることを知見した。この方法においては、オゾンとアルカリとの反応によって生じるヒドロキシラジカルによって有機物が酸化分解されるものである。
【０００９】
本発明者らは、上述した有機物分解方法についてさらに検討を行い、その結果、被処理水にアルカリ性条件下でオゾンを添加して有機物の酸化分解を行う場合、被処理水中にイオン性不純物、特に塩化物イオン、フッ化物イオン等の陰イオン性不純物が含まれていると有機物の酸化分解反応が阻害され、有機物の除去効率が低下すること、これに対し被処理水へのオゾン添加を行う前に被処理水を逆浸透膜装置で処理すると、被処理水中から有機物の酸化分解反応を阻害する陰イオン性不純物が除去される上、被処理水中の有機物がかなり除去されるため、オゾン添加時における有機物の除去効率が向上することを知見した。
【００１０】
本発明は、上記知見に基づいてなされたもので、原水を処理して一次純水を製造する一次純水系と、一次純水を処理して超純水を製造する二次純水系と、二次純水系で製造した超純水を使用場所で使用することによって発生した排水を処理して一次純水系に返送する排水回収系とを備えた超純水製造装置において、
逆浸透膜装置と、被処理水にアルカリ性条件下でオゾンを添加することにより被処理水中に含まれる有機物を酸化分解する有機物酸化装置とを前記排水回収系の純水用排水回収系に設置し、前記逆浸透膜装置の透過水を前記有機物酸化装置で処理して一次純水系に導入するとともに、前記逆浸透膜装置の濃縮水を前記排水回収系の雑用水用排水回収系又は廃水処理系に導入することを特徴とする超純水製造装置を提供する。
【００１１】
本発明の超純水装置は、有機物、特に微量の有機物を含む被処理水中の有機物除去を行う経路である排水回収系の純水用排水回収系に、前述した逆浸透膜装置及び有機物酸化装置を設置したものである。この場合、逆浸透膜装置の種類に制限はなく、各種の逆浸透膜装置が使用可能であり、例えばポリアミド系、アラミド系等の合成複合膜を用いた逆浸透膜装置、酢酸セルローズ膜等のセルローズ系膜を用いた逆浸透膜装置などを使用することができるが、有機物の除去性能に優れている点でポリアミド系複合膜を用いた逆浸透膜装置が特に好ましい。また、逆浸透膜装置としては、スパイラル型、中空糸型、管状型等のいかなるタイプのものでもよい。
【００１２】
また、有機物酸化装置の構成に限定はないが、下記▲１▼〜▲３▼の条件の１以上、特に全てを備えたものであることが好ましい。
▲１▼気液撹拌混合手段によって被処理水にオゾンを添加すること。
▲２▼被処理水のｐＨが９．７以上のアルカリ性条件下で被処理水にオゾンを添加すること。
▲３▼被処理水に対するオゾン添加量が３〜４０ｐｐｍとなるように被処理水にオゾンを添加すること。
【００１３】
すなわち、被処理水にオゾンを添加する場合、オゾンは水に対する溶解性が低いため、散気板を用いるバブリングでは水に十分に溶解せず、有機物の酸化分解反応が効率良く行われにくいが、気液撹拌混合手段を用いれば被処理水にオゾンを十分に溶解させることができ、有機物の酸化分解反応が効率的に行われる。したがって、有機物酸化装置としては▲１▼の条件を備えることが好ましい。
【００１４】
この場合、気液撹拌混合手段とは、気体と液体とを撹拌しながら混合して、液体中に気体を溶解させる手段をいう。このような手段を用いたオゾン溶解方法としては、例えば、回転翼を備えたポンプの吸引側に被処理水及びオゾンを導入し、回転翼の回転により被処理水とオゾンを撹拌混合し、この撹拌混合により被処理水中にオゾンを溶解せしめ、このオゾンを溶解した被処理水をポンプの吐出側に連結された配管を通して処理系に送液するという方法（オゾン溶解ポンプ）や、上記ポンプに代えてエゼクター等で加圧水流を供給し、この水流の動きで被処理水とオゾンとを撹拌混合し、被処理水中にオゾンを溶解させる方法等がある。また、配管の途中に密閉容器を形成し、この密閉容器の内部に回転翼を備えた攪拌機構を有したラインミキサー用も用いることができる。
【００１５】
また、図６は有機物を含む水（ＴＯＣ濃度２０００ｐｐｂ）を複数用意し、それぞれにアルカリを加えて種々の異なったｐＨに調整するとともに、オゾンを９．６ｐｐｍ添加して、有機物の酸化分解の程度が初期ｐＨ値によってどのように変わるかをみたものである。グラフの縦軸におけるＴＯＣはオゾン反応１０分後の残留ＴＯＣを示す。同図によれば、ｐＨ９．７以上、特にｐＨ９．７〜１１．０、中でもｐＨ１０．０〜１０．５の範囲で有機物の分解速度が大きいことがわかる。したがって、有機物酸化装置としては▲２▼の条件を備えることが好ましい。
【００１６】
さらに、被処理水に対するオゾン添加量が３ｐｐｍ未満では有機物の酸化分解が不十分となり、また４０ｐｐｍを超えて添加しても有機物の酸化分解はそれ以上促進されないばかりか反応に寄与しないオゾンが増えて処理コスト面から望ましくない。したがって、有機物酸化装置としては▲３▼の条件を備えることが好ましい。被処理水に対するオゾン添加量のより好ましい範囲は、７〜３０ｐｐｍである。
【００１７】
本発明に用いる有機物酸化装置では、被処理水のｐＨ調整を行った後に被処理水へのオゾン溶解を行ってもよく、被処理水へのオゾン溶解を行った後に被処理水のｐＨ調整を行ってもよく、被処理水のｐＨ調整と被処理水へのオゾン溶解とを同時に行ってもよい。また、被処理水のｐＨが元々適当な値であるときには、被処理水のｐＨ調整を行うことなく被処理水へのオゾン溶解を行ってもよい。被処理水にアルカリ性条件下でオゾンを添加すると、被処理水中の有機物の酸化分解反応は直ちに開始するが、被処理水を加熱することにより、有機物の酸化分解速度を速めることができる。
【００１８】
本発明の超純水製造装置においては、逆浸透膜装置の上流側又は逆浸透膜装置と有機物酸化装置との間に、ＯＨ形の陰イオン交換樹脂を用いた陰イオン交換装置を設けることができる。これにより、有機物酸化装置における有機物の酸化分解反応を阻害する陰イオン性不純物をさらに高度に除去することができ、有機物酸化装置における有機物の除去効率をさらに高めることができる。また、被処理水中にはナトリウムイオン等の陽イオンが含まれており、被処理水を陰イオン交換装置に通すと水酸化ナトリウム等が生成するため、該陰イオン交換装置では出口水がアルカリ性となる。したがって、後段の有機物酸化装置において、被処理水をアルカリ性にするためのアルカリ剤の添加を不要としたり、添加量を低減したりすることが可能となる。
【００１９】
この場合、陰イオン交換装置の陰イオン交換樹脂の種類に限定はなく、弱塩基性陰イオン交換樹脂でも強塩基性陰イオン交換樹脂でも使用できるが、逆浸透膜装置、有機物酸化装置及び陰イオン交換装置を排水回収系の純水用排水回収系に設置するときには、弱塩基性陰イオン交換樹脂が特に好ましい。その理由は、純水用排水回収系に送られる被処理水中には通常フッ酸等の酸が含まれているために被処理水は通常酸性であり、したがってＯＨ形の弱塩基性陰イオン交換樹脂でフッ化物イオン等の陰イオンを十分に除去することができ、しかも弱塩基性陰イオン交換樹脂はイオン交換容量が強塩基性陰イオン交換樹脂よりも大きいためである。
【００２１】
本発明の超純水製造装置では、有機物酸化装置の下流側に、少なくとも陰イオン交換樹脂を用いたイオン交換装置を設けることができる。このようにすると、有機物酸化装置で有機物が二酸化炭素まで分解されなかったときでも、有機物酸化装置で有機物がイオン性物質である有機酸にまで分解されていれば、後段のイオン交換装置に用いられている陰イオン交換樹脂で上記イオン性物質が除去されるため、全体として有機物が効率的に除去される。この場合、有機物酸化装置におけるｐＨやオゾン添加量を調整することにより、意図的に有機物を二酸化炭素まで分解せず、有機酸に分解するようにしてもよい。これにより、アルカリ剤の使用量やオゾン添加量を低減できるため、ランニングコストを低くすることができる。イオン交換装置としては、例えば、陰イオン交換樹脂のみを用いた陰イオン交換装置や、陰イオン交換樹脂と陽イオン交換樹脂とを組み合わせてなる混床式純水製造装置、複床式純水製造装置、２床３塔式純水製造装置等を用いることが可能である。
【００２２】
本発明の超純水製造装置では、有機物酸化装置の下流側に、被処理水中のオゾンを分解するオゾン分解手段を設けることができる。これにより、有機物酸化装置の処理水中に残存するオゾンが後段のイオン交換装置等に悪影響を及ぼすことを防止できる。オゾン分解手段としては、例えば、被処理水を活性炭に通水してオゾンを還元分解する手段、被処理水に還元剤を注入してオゾンを還元分解する手段等が挙げられる。なお、オゾン分解手段は、有機物酸化装置の直後に設置することが、オゾンが後段の装置に悪影響を及ぼすことを防止する点で好ましい。
【００２３】
また、本発明の超純水製造装置では、有機物酸化装置の下流側に、脱気装置を設けることができる。脱気装置は、本来被処理水中の溶存酸素を除去する装置であるが、溶存酸素が被処理水中から除去される際に被処理水中に存在する揮発性の有機物も一部除去される。したがって、有機物酸化装置の下流側に脱気装置を設けることにより、有機物濃度がさらに低減した処理水を得ることができる。脱気装置としては、例えば、真空脱気装置、膜脱気装置等を用いることができる。膜脱気装置とは、気体透過膜で仕切られた一方の室に被処理水を流すとともに、他方の室を減圧することにより、被処理水中に含まれるガスを気体透過膜を通して他方の室に移行させて除去する装置である。
【００２４】
さらに、本発明の超純水製造装置では、逆浸透膜装置の上流側に前処理用の活性炭濾過装置を設けたり、有機物酸化装置の下流側にさらに逆浸透膜装置（第２の逆浸透膜装置）を設けたりすることができる。上記第２の逆浸透膜装置を設けた場合には、処理水中の有機物濃度をより低減させることができる。
【００２５】
本発明の超純水製造装置は、逆浸透膜装置及び有機物酸化装置を排水回収系の純水用排水回収系に設置し、逆浸透膜装置の透過水を有機物酸化装置で処理して一次純水系に導入するとともに、逆浸透膜装置の濃縮水を前記排水回収系の雑用水用排水回収系又は廃水処理系に導入するものである。また、廃水処理系を設けず、使用場所からの超純水の排水を放流することなく超純水の原水又は雑用水として再利用するようにしたクローズドシステムの超純水製造装置では、上記と同様に逆浸透膜装置及び有機物酸化装置を純水用排水回収系に設置するとともに、逆浸透膜装置の濃縮水を雑用水用排水回収系に導入することができる。上記のようにすると、純水用排水回収系において被処理水中から有機物を高度に除去することができるため、その処理水を再利用することにより純度の高い超純水を得ることができるとともに、逆浸透膜装置の濃縮水の有効利用あるいは適切な処理を図ることができる。
【００２６】
【発明の実施の形態】
図１は本発明に係る超純水製造装置の一実施形態例を示す一部省略フロー図である。図１の装置において、２２は前処理系、２４は一次純水系、２６は純水用排水回収系を示す。前処理系２２には、凝集濾過装置（Ｆ）及び活性炭濾過装置（ＣＦ）が設置されている。一次純水系２４には、上流側から下流側にかけて活性炭濾過装置（ＣＦ）２８、２床３塔式純水製造装置（２Ｂ３Ｔ）３０、混床式純水製造装置（ＭＢＰ）３２、真空脱気塔（ＶＤ）３４及び逆浸透膜装置（ＲＯ）３６が順次設置されている。回収系２６には、上流側から下流側にかけて活性炭濾過装置（ＣＦ）３８、ＯＨ形の弱塩基性陰イオン交換樹脂を用いた陰イオン交換装置（ＷＡ）４０、逆浸透膜装置（ＲＯ）４２、有機物酸化装置４４が順次設置されている。
【００２７】
本装置において、前処理系２２及び純水用排水回収系２６の処理水は、タンク４６に貯留された後、一次純水系２４に導入される。一次純水系２４の処理水は二次純水系（図示せず）に送られ、二次純水系で製造された超純水は使用場所（図示せず）に供給される。使用場所で超純水を使用することにより生じた排水は、純水用排水回収系２６で処理された後、タンク４６に送られて超純水製造装置の原水の一部として再利用される。
【００２８】
なお、本例の超純水製造装置において、一次純水系２４の活性炭濾過装置２８は前述した有機物酸化装置の下流側のオゾン分解手段に該当し、２床３塔式純水製造装置３０及び混床式純水製造装置３２は前述した有機物酸化装置の下流側のイオン交換装置に該当し、真空脱気塔３４は前述した有機物酸化装置の下流側の脱気装置に該当し、逆浸透膜装置３６は前述した第２の逆浸透膜装置に該当する。ただし、これらのオゾン分解手段、イオン交換装置、脱気装置、第２の逆浸透膜装置は、純水用排水回収系２６に別途設けてもよく、これにより一次純水系２４の装置の負荷を低くすることができる。
【００２９】
本例の超純水製造装置では、使用場所からの排水は、純水用排水回収系２６及び一次純水系２４において下記のように処理される。まず活性炭濾過装置３８で前処理が行われ、逆浸透膜を劣化させる過酸化水素等が除去された後、陰イオン交換装置４０に通水され、ここでＯＨ形の弱塩基性陰イオン交換樹脂によって陰イオン性不純物が除去されるとともに、出口水がアルカリ性になる。次に、逆浸透膜装置４２で有機物の一部及び陰イオン性不純物が除去された後、有機物酸化装置４４に導入され、ここで有機物の酸化分解が行われる。
【００３０】
有機物酸化装置４４は、具体的には図２に示す構造を有している。すなわち、図２において５０は純水用排水回収系２６の被処理水が流れるラインであり、このライン５０にはアルカリ注入装置５２及びオゾン供給装置５４が連結されている。アルカリ注入装置５２の注入管５６とライン５０との連結部５８のやや後方にはｐＨ測定部（図示せず）が設置されており、このｐＨ測定部によって被処理水のｐＨを測定し、その測定結果を電気信号としてアルカリ注入装置５２に出力し、それに基づき被処理水へのアルカリ注入量を自動的に制御するようになっている。
【００３１】
オゾン供給装置５４としては、オゾン発生機構を備えたオゾン発生装置や、オゾン発生装置で製造されたオゾン含有ガスを充填したオゾンタンクが使用される。オゾン供給装置５４の供給管６０には気液撹拌混合装置６２（例えばラインミキサーやオゾン溶解ポンプ）が連結されているとともに、この気液撹拌混合装置６２はライン５０に連結されている。また、気液撹拌混合装置６２の出口側におけるライン５０の所定長さ部分が、有機物の酸化分解反応が行われる反応管部６６として構成されている。
【００３２】
本例の有機物酸化装置４４では、まず、ライン５０を流れる被処理水にアルカリ注入装置５２よりアルカリが注入されて被処理水のｐＨが９．７以上、好ましくは９．７〜１１．０に調整される。次いで、被処理水にオゾン供給装置５４よりオゾンが供給され、気液撹拌混合装置６２によってオゾンと被処理水とが撹拌混合され、オゾンの大部分が被処理水中に溶解する。ここで、被処理水中へのオゾン添加量は３〜４０ｐｐｍ、好ましくは７〜３０ｐｐｍに調整される。被処理水中では、反応管部６６において速やかに有機物の酸化分解反応が進行する。酸化分解反応の終了により得られた処理水は、タンク４６を経て前処理系２２の処理水と一緒に一次純水系２４に供給される。
【００３３】
一次純水系２４では、被処理水はまず活性炭濾過装置２８に通水され、ここで被処理水中の溶存オゾンの分解が行われた後、有機物酸化装置４４で二酸化炭素までは分解されなかったイオン性物質（有機酸）が２床３塔式純水製造装置３０及び混床式純水製造装置３２に用いられている陰イオン交換樹脂で除去される。次に、真空脱気塔３４で溶存酸素の除去及び微量の有機物の除去が行われ、さらに逆浸透膜装置３６で残存する不純物の除去が行われる。なお、有機物酸化装置４４の処理水中にアセトンが残存し、これが純水製造装置３０、３２を通過した場合でも、このアセトンは揮発性であるので真空脱気塔３４で除去することができる。
【００３４】
図３〜図５は、それぞれ本発明に係る超純水製造装置の一実施形態例を示すフロー図である。図３〜図５の装置の超純水製造系は、活性炭濾過装置（ＣＦ）、２床３塔式純水製造装置（２Ｂ３Ｔ）、混床式純水製造装置（ＭＢＰ）、真空脱気塔（ＶＤ）及び逆浸透膜装置（ＲＯ）を備えた一次純水系と、タンク（ＴＫ）、紫外線殺菌装置（ＵＶ_st）、混床式カートリッジポリッシャ（ＣＰ）及び限外濾過膜装置（ＵＦ）を備えた二次純水系とから構成されている。
【００３５】
また、図３〜図５の装置では、使用場所で超純水を使用することにより生じた排水を処理する排水回収系として、排水の清浄度に応じて、何ら処理を施すことなく直接一次純水系に戻す経路▲１▼、適当な処理を施してから一次純水系に戻す経路▲２▼（純水用排水回収系）、適当な処理を施してから雑用水としてユーティリティ設備に供給する経路▲３▼（雑用水用排水回収系）、及び、適当な処理を施してから放流する経路▲４▼（廃水処理系）を備えている。なお、使用場所から排出された超純水の排水を前記経路▲１▼〜▲４▼に分別する基準は例えば表１の通りであり、その分別は分別機構(1)〜(3)によって行われる。
【００３６】
【表１】

【００３７】
図３及び図４の装置では、純水用排水回収系に、上流側から下流側にかけて活性炭濾過装置（ＣＦ）、ＯＨ形の弱塩基性陰イオン交換樹脂を用いた陰イオン交換装置（ＷＡ）、逆浸透膜装置（ＲＯ）、有機物酸化装置を順次設置してある。図３及び図４の装置の純水用排水回収系における排水の処理は図１の装置と同様であるため、説明を省略する。また、図３の装置では純水用排水回収系の逆浸透膜装置の濃縮水を廃水処理系に導入し、図４の装置では同濃縮水を雑用水用排水回収系に導入するようにしてある。逆浸透膜装置の濃縮水の清浄度が比較的高いときには該濃縮水を図４の装置のように雑用水用排水回収系に導入して再利用し、逆浸透膜装置の濃縮水の清浄度が比較的低いときには該濃縮水を図３の装置のように廃水処理系で処理してから放流すればよい。図５の装置は、図３の装置において陰イオン交換装置（ＷＡ）を省いたものである。
【００３９】
【実施例】
実施例
活性炭濾過装置（ＣＦ）、陰イオン交換装置（ＷＡ）、第１の逆浸透膜装置（ＲＯ）、有機物酸化装置、活性炭濾過装置（ＣＦ）、２床３塔式純水製造装置（２Ｂ３Ｔ）、混床式純水製造装置（ＭＢＰ）、真空脱気塔（ＶＤ）及び第２の逆浸透膜装置（ＲＯ）をこの順に接続してなる装置に超純水を使用することにより生じた排水を流して該排水の処理を行った。前記排水としては表２に示したＴＯＣ濃度のものを用いた。この場合、有機物酸化装置４４においては、アルカリ注入装置５２から被処理水に水酸化ナトリウムを添加して被処理水のｐＨを表２に示した値に調整した後、気液攪拌混合装置６２によって被処理水に対するオゾン添加量が表２に示した値となるように被処理水にオゾンを添加した。
【００４０】
なお、気液撹拌混合装置６２としてはオゾン溶解ポンプを用いた。また、陰イオン交換装置（ＷＡ）の陰イオン交換樹脂としては弱塩基性陰イオン交換樹脂であるアンバーライト（登録商標、以下同じ）ＩＲＡ−９４ＳのＯＨ形のものを用い、第１及び第２の逆浸透膜装置（ＲＯ）の逆浸透膜としては日東電工社製ポリアミド系複合膜ＥＳ−１０を用い、２床３塔式純水製造装置（２Ｂ３Ｔ）の陽イオン交換樹脂としては強酸性陽イオン交換樹脂であるアンバーライトＩＲ−１２４のＨ形、陰イオン交換樹脂としては強塩基性陰イオン交換樹脂であるアンバーライトＩＲＡ−４０２ＢＬのＯＨ形を用い、混床式純水製造装置（ＭＢＰ）のイオン交換樹脂としてはＨ形の強酸性陽イオン交換樹脂とＯＨ形の強塩基性陰イオン交換樹脂とを混合してなるアンバーライトＥＳＧ４を用いた。真空脱気装置（ＶＤ）は真空度２２Ｔｏｒｒで運転した。各装置出口水のＴＯＣ濃度の測定結果を表２に示す。
【００４２】
比較例
実施例１で用いた装置の純水用排水回収系から陰イオン交換装置及び第１の逆浸透膜装置を除いた以外は実施例１で用いたのと同じ装置を用いて、実施例１と同様にして超純水を使用することにより生じた排水の処理を行った。結果を表２に示す。
【００４３】
【表２】

【００４４】
表２より、有機物を含有する被処理水を逆浸透膜装置で処理した後、逆浸透膜装置の透過水に有機物酸化装置においてアルカリ性条件下でオゾンを添加した場合、有機物酸化装置及び後段のイオン交換装置におけるＴＯＣ除去効率が向上することが確認された。ただし、有機物酸化装置での処理時に被処理水のオゾン濃度やｐＨが低い場合（試験ＮＯ．５〜７）は、有機物酸化装置及び後段のイオン交換装置におけるＴＯＣ除去効率が低下していた。後段のイオン交換装置におけるＴＯＣ除去効率が低下したのは、有機物酸化装置での有機物の酸化が十分でなく、イオン性物質になっていないためであると考えられる。
【００４５】
【発明の効果】
請求項１の発明によれば、逆浸透膜装置において被処理水中から有機物酸化装置での有機物の酸化分解反応を阻害する陰イオン性不純物が除去される上、被処理水中の有機物がかなり除去されるため、有機物酸化装置における有機物の除去効率が向上する。また、逆浸透膜装置で被処理水中の有機物がかなり除去されるため、有機物酸化装置でのオゾン使用量の低減、オゾン発生装置の小型化を図ることができ、しかもそれほど高ｐＨでなくても有機物を酸化分解できるようになるので、被処理水に添加するアルカリ剤の消費量を減らすことができる。
【００４６】
請求項１の発明によれば、排水回収系の純水用排水回収系において被処理水中から有機物を高度に除去することができるため、その処理水を再利用することにより純度の高い超純水を得ることができるとともに、逆浸透膜装置の濃縮水の有効利用あるいは適切な処理を図ることができる。
【００４７】
請求項２の発明によれば、有機物酸化装置における有機物の酸化分解反応を阻害する陰イオン性不純物をさらに高度に除去することができ、有機物酸化装置における有機物の除去効率をさらに高めることができるとともに、陰イオン交換装置の出口水がアルカリ性となるので、被処理水をアルカリ性にするためのアルカリ剤の添加を不要としたり、添加量を低減したりすることが可能となる。
【００４９】
請求項３の発明によれば、有機物酸化装置で有機物が二酸化炭素まで分解されなかったときでも、有機物酸化装置で有機物が有機酸等のイオン性物質にまで分解されていれば、後段のイオン交換装置で上記イオン性物質が除去されるため、全体として有機物が効率的に除去される。
【００５０】
請求項４の発明によれば、有機物酸化装置の処理水中に残存する溶存オゾンが後段の装置、例えばイオン交換装置のイオン交換樹脂等に悪影響を及ぼすことを防止できる。
【００５１】
請求項５の発明によれば、脱気装置で溶存ガスが被処理水中から除去される際に被処理水中に存在する揮発性の有機物も除去されるので、有機物濃度がさらに低減した処理水を得ることができる。
【００５２】
請求項６〜８の発明によれば、有機物酸化装置における有機物の酸化分解を効率的に行うことができる。
【図面の簡単な説明】
【図１】本発明に係る超純水製造装置の一実施形態例を示す一部省略フロー図である。
【図２】図１に示した超純水製造装置の有機物酸化装置を示すフロー図である。
【図３】本発明に係る超純水製造装置の一実施形態例を示すフロー図である。
【図４】本発明に係る超純水製造装置の一実施形態例を示すフロー図である。
【図５】本発明に係る超純水製造装置の一実施形態例を示すフロー図である。
【図６】被処理水のｐＨと有機物の酸化分解速度との関係を示すグラフである。
【図７】従来の超純水製造装置の一例を示すフロー図である。
【符号の説明】
２２前処理系
２４一次純水系
２６純水用排水回収系
２８活性炭濾過装置
３０２床３塔式純水製造装置
３２混床式純水製造装置
３４真空脱気塔
３６逆浸透膜装置
３８活性炭濾過装置
４０陰イオン交換装置
４２逆浸透膜装置
４４有機物酸化装置[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an apparatus for producing ultrapure water used, for example, for cleaning silicon wafers in the semiconductor industry. More specifically, the present invention relates to a path for removing organic matter in treated water containing organic matter (Wastewater recovery system for pure water) In the ultrapure water production apparatus aiming at improving the efficiency of organic matter removal. In the present specification, high-purity water that is generally not necessarily clearly defined and described in terms of pure water, ultra-pure water, or the like is collectively referred to as “ultra-pure water”.
[0002]
[Prior art]
As shown in FIG. 7, an ultrapure water production apparatus used for cleaning silicon wafers generally has pure water that forms part of a primary pure water system 2, a secondary pure water system (subsystem) 4, and a wastewater recovery system. A waste water recovery system 6 is provided. The primary pure water system 2 is a path provided with, for example, a reverse osmosis membrane device, a vacuum deaeration device, an ion exchange device, and the like, and a part of suspended substances and organic substances contained in raw water such as city water and industrial water are used in advance. After being removed by the treatment system (not shown), the treated water 8 is supplied to the primary pure water system 2. The secondary pure water system 4 is a path provided with, for example, an ultraviolet oxidizer, a cartridge polisher, an ultrafiltration membrane device, and the like, and treated water 3 (primary pure water) of the primary pure water system 2 passes through the pure water storage tank 10. The secondary pure water system 4 is supplied. Part of the ultrapure water 12 obtained in the secondary pure water system 4 is sent to the place of use 14 for use, and the remainder is circulated to the pure water storage tank 10. The pure water wastewater collection system 6 is a path including, for example, an activated carbon filtration device, an ion exchange device, an ultraviolet oxidation device, and the like, and performs treatment of the wastewater 16 generated by using ultrapure water at the place of use 14. The treated water 18 of the pure water wastewater recovery system 6 is returned to the primary pure water system 2 and reused.
[0003]
In addition, in a general ultrapure water production apparatus, as a wastewater recovery system for treating the wastewater 16 generated by using the ultrapure water discharged from the use place 14, an appropriate treatment is performed and then the primary pure water system is used. In addition to the pure water drainage recovery system 6 to be returned, a route to return directly to the primary pure water system without any treatment depending on the cleanliness of the wastewater, a route to be used as miscellaneous water after appropriate treatment (chores) Water drainage collection system) and a route (wastewater treatment system) that discharges after appropriate treatment.
[0004]
[Problems to be solved by the invention]
In the cleaning process of silicon wafers in the semiconductor industry, organic cleaners such as isopropyl alcohol, methanol, and acetone are used, so the ultrapure water drainage from the place of use contains trace amounts of organic substances. However, the concentration of impurities in the wastewater from this place of use is extremely low compared to city water, industrial water, and the like. Therefore, if the concentration of organic substances in the wastewater from the place of use is reduced as much as possible in the ultrapure water production system of the ultrapure water production system and the treated water is returned to the primary pure water system, high purity ultrapure water can be obtained. It will be very advantageous. Therefore, in the pure water wastewater recovery system, it is desired to remove organic substances from the treated water as much as possible.
[0005]
In this case, as a method for removing organic substances in the wastewater recovery system for pure water, conventionally, ozone or hydrogen peroxide that is an oxidizing agent is added to the water to be treated (drainage), and further, ozone or hydrogen peroxide containing treatment A method for oxidatively decomposing organic substances by irradiating water with ultraviolet rays is known.
[0006]
However, this method has the disadvantage that the processing time is long because the decomposition rate of organic substances is slow, and the processing efficiency is poor. In addition, since the high-pressure ultraviolet lamp is used, the apparatus becomes large and complicated, and the running cost increases, which is economically disadvantageous.
[0007]
  The present invention has been made in view of the above circumstances,Wastewater recovery system for pure waterIt is an object of the present invention to provide an ultrapure water production apparatus that improves the efficiency of organic matter removal.
[0008]
[Means for Solving the Problems]
The present inventors adjusted the pH of water to be treated containing organic matter to a specific range on the alkali side, and when ozone was added to the alkaline water to be treated, the organic matter in the water to be treated without performing ultraviolet irradiation. It was found that can be removed efficiently. In this method, organic substances are oxidatively decomposed by hydroxy radicals generated by the reaction between ozone and alkali.
[0009]
The present inventors further examined the organic matter decomposition method described above. As a result, when oxidative decomposition of organic matter is performed by adding ozone to the water to be treated under alkaline conditions, ionic impurities, particularly in the water to be treated If anionic impurities such as chloride ion and fluoride ion are included, the oxidative decomposition reaction of the organic substance will be inhibited, and the removal efficiency of the organic substance will be reduced. On the other hand, before adding ozone to the water to be treated When the treated water is treated with a reverse osmosis membrane device, anionic impurities that inhibit the oxidative decomposition reaction of organic substances are removed from the treated water, and organic substances in the treated water are considerably removed. It has been found that the organic substance removal efficiency in the process is improved.
[0010]
  The present invention has been made based on the above findings,The primary pure water system that treats raw water to produce primary pure water, the secondary pure water system that treats primary pure water to produce ultrapure water, and the ultrapure water produced by secondary pure water system are used at the place of use. In the ultrapure water production apparatus equipped with a wastewater recovery system that treats the wastewater generated by the process and returns it to the primary pure water system,
A reverse osmosis membrane device and an organic matter oxidation device that oxidizes and decomposes organic matter contained in the treated water by adding ozone to the treated water under alkaline conditions are installed in the wastewater collection system for pure water of the wastewater collection system. In addition, the permeated water of the reverse osmosis membrane device is treated with the organic matter oxidizer and introduced into the primary pure water system, and the concentrated water of the reverse osmosis membrane device is used for the wastewater recovery system for wastewater or the wastewater treatment system of the drainage recovery system. To introduceAn ultrapure water production apparatus is provided.
[0011]
  The ultrapure water apparatus of the present invention is a path for removing organic matter in water to be treated containing organic matter, particularly trace amount of organic matter.IsWaste water recovery for waste water recovery systemSystemThe reverse osmosis membrane device and the organic matter oxidation device described above are installed. In this case, there is no limitation on the type of reverse osmosis membrane device, and various reverse osmosis membrane devices can be used. For example, reverse osmosis membrane devices using a composite composite membrane such as polyamide-based or aramid-based, cellulose acetate membrane, etc. A reverse osmosis membrane device using a cellulose-based membrane can be used, but a reverse osmosis membrane device using a polyamide-based composite membrane is particularly preferable in terms of excellent organic substance removal performance. The reverse osmosis membrane device may be of any type such as a spiral type, a hollow fiber type, and a tubular type.
[0012]
Further, the configuration of the organic matter oxidation apparatus is not limited, but it is preferable that one or more, particularly all of the following conditions (1) to (3) are provided.
(1) Add ozone to water to be treated by gas-liquid stirring and mixing means.
(2) Add ozone to the water to be treated under alkaline conditions where the pH of the water to be treated is 9.7 or higher.
(3) Add ozone to the water to be treated so that the amount of ozone added to the water to be treated is 3 to 40 ppm.
[0013]
That is, when adding ozone to the water to be treated, ozone has low solubility in water, so bubbling using a diffuser plate does not sufficiently dissolve in water, and the oxidative decomposition reaction of organic matter is difficult to be performed efficiently. If the gas-liquid stirring and mixing means is used, ozone can be sufficiently dissolved in the water to be treated, and the oxidative decomposition reaction of the organic matter is efficiently performed. Therefore, it is preferable that the organic matter oxidation apparatus has the condition (1).
[0014]
In this case, the gas-liquid stirring and mixing means means mixing while stirring gas and liquid.TogetherAnd means for dissolving the gas in the liquid. As an ozone dissolution method using such means, for example, water to be treated and ozone are introduced into the suction side of a pump having a rotor blade, and the water to be treated and ozone are stirred and mixed by rotation of the rotor blade. In place of the above-mentioned pump, the ozone is dissolved in the water to be treated by stirring and mixing, and the water to be treated in which ozone is dissolved is sent to the treatment system through a pipe connected to the discharge side of the pump. There is a method of supplying a pressurized water flow with an ejector or the like, stirring and mixing the water to be treated and ozone by the movement of this water flow, and dissolving ozone in the water to be treated. Further, it is also possible to use a line mixer having a stirring mechanism in which a sealed container is formed in the middle of a pipe and a rotating blade is provided inside the sealed container.
[0015]
In addition, FIG. 6 shows the degree of oxidative decomposition of organic matter by preparing a plurality of water containing organic matter (TOC concentration 2000 ppb), adding alkali to each to adjust to various different pH, and adding 9.6 ppm of ozone. Shows how the value changes depending on the initial pH value. The TOC on the vertical axis of the graph represents the residual TOC after 10 minutes of ozone reaction. According to the figure, it can be seen that the decomposition rate of the organic matter is large at pH 9.7 or higher, particularly at pH 9.7 to 11.0, and particularly at pH 10.0 to 10.5. Therefore, it is preferable that the organic matter oxidation apparatus has the condition (2).
[0016]
Furthermore, if the amount of ozone added to the water to be treated is less than 3 ppm, the oxidative decomposition of the organic matter becomes insufficient, and if it is added in excess of 40 ppm, the oxidative decomposition of the organic matter is not further promoted and the ozone that does not contribute to the reaction increases. It is not desirable from the viewpoint of processing cost. Therefore, it is preferable that the organic matter oxidation apparatus has the condition (3). A more preferable range of the amount of ozone added to the water to be treated is 7 to 30 ppm.
[0017]
In the organic matter oxidation apparatus used in the present invention, ozone may be dissolved in the water to be treated after adjusting the pH of the water to be treated, and pH adjustment of the water to be treated may be performed after dissolving the ozone in the water to be treated. The pH adjustment of the water to be treated and the ozone dissolution in the water to be treated may be performed simultaneously. Further, when the pH of the water to be treated is originally an appropriate value, ozone may be dissolved in the water to be treated without adjusting the pH of the water to be treated. When ozone is added to the water to be treated under alkaline conditions, the oxidative decomposition reaction of the organic matter in the water to be treated starts immediately, but the oxidative decomposition rate of the organic matter can be increased by heating the water to be treated.
[0018]
In the ultrapure water production apparatus of the present invention, an anion exchange device using an OH type anion exchange resin may be provided upstream of the reverse osmosis membrane device or between the reverse osmosis membrane device and the organic matter oxidation device. it can. Thereby, the anionic impurity which inhibits the oxidative decomposition reaction of the organic substance in the organic substance oxidizing apparatus can be further removed, and the organic substance removing efficiency in the organic substance oxidizing apparatus can be further increased. In addition, since the water to be treated contains cations such as sodium ions and sodium hydroxide is produced when the water to be treated is passed through the anion exchange device, the outlet water is alkaline in the anion exchange device. Become. Therefore, it becomes possible to eliminate the addition of an alkali agent for making the water to be treated alkaline, or to reduce the amount of addition in the latter organic matter oxidation apparatus.
[0019]
In this case, the type of anion exchange resin in the anion exchange device is not limited, and either a weakly basic anion exchange resin or a strongly basic anion exchange resin can be used, but a reverse osmosis membrane device, an organic matter oxidation device, and an anion When the exchange device is installed in the wastewater recovery system for pure water, a weakly basic anion exchange resin is particularly preferable. The reason for this is that the treated water sent to the pure water wastewater recovery system usually contains acid such as hydrofluoric acid, so the treated water is usually acidic, and therefore the OH form weakly basic anion exchange. This is because the resin can sufficiently remove anions such as fluoride ions, and the weakly basic anion exchange resin has a larger ion exchange capacity than the strongly basic anion exchange resin.
[0021]
In the ultrapure water production apparatus of the present invention, an ion exchange apparatus using at least an anion exchange resin can be provided on the downstream side of the organic matter oxidation apparatus. In this way, even when the organic matter is not decomposed to carbon dioxide by the organic matter oxidizing device, if the organic matter is decomposed to the organic acid that is an ionic substance by the organic matter oxidizing device, it is used for the ion exchange device in the subsequent stage. Since the ionic substance is removed by the anion exchange resin, the organic substances are efficiently removed as a whole. In this case, the organic substance may be intentionally decomposed into an organic acid without being decomposed to carbon dioxide by adjusting the pH and the amount of ozone added in the organic substance oxidizing apparatus. Thereby, since the usage-amount of an alkaline agent and the addition amount of ozone can be reduced, a running cost can be made low. As an ion exchange device, for example, an anion exchange device using only an anion exchange resin, a mixed bed type pure water production apparatus combining an anion exchange resin and a cation exchange resin, or a double bed type pure water production It is possible to use an apparatus, a two-bed three-column pure water production apparatus, or the like.
[0022]
In the ultrapure water production apparatus of the present invention, ozone decomposing means for decomposing ozone in the water to be treated can be provided on the downstream side of the organic matter oxidizing apparatus. Thereby, ozone remaining in the treated water of the organic matter oxidation apparatus can be prevented from adversely affecting the subsequent ion exchange apparatus and the like. Examples of the ozonolysis means include means for reducing the ozone by passing the water to be treated through activated carbon, and means for reducing and decomposing ozone by injecting a reducing agent into the water to be treated. In addition, it is preferable that the ozonolysis means is installed immediately after the organic matter oxidation apparatus in terms of preventing ozone from adversely affecting the subsequent apparatus.
[0023]
Moreover, in the ultrapure water manufacturing apparatus of this invention, a deaeration apparatus can be provided in the downstream of an organic matter oxidation apparatus. The deaeration device is a device that originally removes dissolved oxygen in the water to be treated, but when the dissolved oxygen is removed from the water to be treated, some volatile organic substances present in the water to be treated are also removed. Therefore, by providing a deaeration device on the downstream side of the organic matter oxidation device, treated water with a further reduced organic matter concentration can be obtained. As the degassing device, for example, a vacuum degassing device, a membrane degassing device, or the like can be used. A membrane deaerator is a flow of water to be treated into one chamber partitioned by a gas permeable membrane, and the pressure in the other chamber is reduced to allow gas contained in the water to be treated to pass through the gas permeable membrane to the other chamber. It is a device that moves and removes.
[0024]
Furthermore, in the ultrapure water production apparatus of the present invention, an activated carbon filtration device for pretreatment is provided upstream of the reverse osmosis membrane device, or a reverse osmosis membrane device (second reverse osmosis membrane) is further provided downstream of the organic matter oxidation device. Apparatus). When the second reverse osmosis membrane device is provided, the organic matter concentration in the treated water can be further reduced.
[0025]
  In the ultrapure water production apparatus of the present invention, a reverse osmosis membrane device and an organic matter oxidation device are installed in a wastewater collection system for pure water of a wastewater collection system, and the permeated water of the reverse osmosis membrane device is treated with an organic matter oxidation device to produce a primary pure water. In addition to introducing into the water system, the concentrated water from the reverse osmosis membrane device is introduced into the wastewater recovery system for wastewater or the wastewater treatment system of the wastewater recovery system.Is a thing. In addition, in a closed system ultrapure water production apparatus that does not have a wastewater treatment system and is reused as raw or miscellaneous water for ultrapure water without discharging ultrapure water drainage from the place of use, Similarly, the reverse osmosis membrane device and the organic matter oxidation device can be installed in the pure water wastewater recovery system, and the concentrated water of the reverse osmosis membrane device can be introduced into the miscellaneous water wastewater recovery system. As described above, since it is possible to highly remove organic matter from the water to be treated in the wastewater recovery system for pure water, it is possible to obtain ultrapure water with high purity by reusing the treated water, Effective use of the concentrated water of the reverse osmosis membrane device or appropriate treatment can be achieved.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partially omitted flow diagram showing an embodiment of an ultrapure water production apparatus according to the present invention. In the apparatus of FIG. 1, 22 is a pretreatment system, 24 is a primary pure water system, and 26 is a pure water wastewater recovery system. The pretreatment system 22 is provided with a coagulation filtration device (F) and an activated carbon filtration device (CF). The primary pure water system 24 includes an activated carbon filtration device (CF) 28, a two-bed three-column pure water production device (2B3T) 30, a mixed-bed pure water production device (MBP) 32, vacuum degassing from the upstream side to the downstream side. A tower (VD) 34 and a reverse osmosis membrane device (RO) 36 are sequentially installed. The recovery system 26 includes an activated carbon filtration device (CF) 38, an anion exchange device (WA) 40 using an OH type weakly basic anion exchange resin, and a reverse osmosis membrane device (RO) 42 from the upstream side to the downstream side. The organic matter oxidation device 44 is sequentially installed.
[0027]
In this apparatus, the treated water of the pretreatment system 22 and the pure water wastewater collection system 26 is stored in a tank 46 and then introduced into the primary pure water system 24. The treated water of the primary pure water system 24 is sent to a secondary pure water system (not shown), and ultrapure water produced in the secondary pure water system is supplied to a place of use (not shown). Wastewater generated by using ultrapure water at the place of use is processed by a pure water drainage recovery system 26 and then sent to a tank 46 to be reused as part of the raw water of the ultrapure water production apparatus. .
[0028]
In the ultrapure water production apparatus of this example, the activated carbon filtration device 28 of the primary pure water system 24 corresponds to the ozonolysis means on the downstream side of the organic matter oxidation device described above, and the two-bed / three-column pure water production device 30 and the mixing device. The floor-type pure water production apparatus 32 corresponds to the ion exchange apparatus on the downstream side of the organic substance oxidizing apparatus described above, and the vacuum degassing tower 34 corresponds to the degassing apparatus on the downstream side of the organic substance oxidizing apparatus described above, and the reverse osmosis membrane apparatus. 36 corresponds to the second reverse osmosis membrane device described above. However, these ozonolysis means, ion exchange device, deaeration device, and second reverse osmosis membrane device may be provided separately in the pure water wastewater recovery system 26, thereby loading the primary pure water system 24. Can be lowered.
[0029]
In the ultrapure water production apparatus of this example, the wastewater from the place of use is treated in the pure water drainage recovery system 26 and the primary pure water system 24 as follows. First, pretreatment is performed by the activated carbon filtration device 38, hydrogen peroxide and the like that deteriorate the reverse osmosis membrane are removed, and then water is passed through the anion exchange device 40, where an OH-type weakly basic anion exchange resin is used. Removes anionic impurities and makes the outlet water alkaline. Next, after a part of the organic matter and anionic impurities are removed by the reverse osmosis membrane device 42, the organic matter is introduced into the organic matter oxidizing device 44, where the organic matter is oxidatively decomposed.
[0030]
Specifically, the organic matter oxidation apparatus 44 has a structure shown in FIG. That is, in FIG. 2, 50 is a line through which water to be treated of the pure water wastewater recovery system 26 flows, and an alkali injection device 52 and an ozone supply device 54 are connected to the line 50. A pH measuring part (not shown) is installed slightly behind the connecting part 58 between the injection pipe 56 and the line 50 of the alkali injecting device 52. The pH measuring part measures the pH of the water to be treated. The measurement result is output as an electric signal to the alkali injection device 52, and the amount of alkali injection into the water to be treated is automatically controlled based on the measurement result.
[0031]
As the ozone supply device 54, an ozone generation device provided with an ozone generation mechanism or an ozone tank filled with an ozone-containing gas manufactured by the ozone generation device is used. A gas-liquid stirring and mixing device 62 (for example, a line mixer or an ozone dissolution pump) is connected to the supply pipe 60 of the ozone supply device 54, and the gas-liquid stirring and mixing device 62 is connected to the line 50. Moreover, the predetermined length part of the line 50 in the exit side of the gas-liquid stirring mixing apparatus 62 is comprised as the reaction tube part 66 in which the oxidative decomposition reaction of organic substance is performed.
[0032]
In the organic matter oxidizer 44 of this example, first, alkali is injected into the water to be treated flowing through the line 50 from the alkali injector 52 so that the pH of the water to be treated is 9.7 or more, preferably 9.7 to 11.0. Adjusted. Next, ozone is supplied to the water to be treated from the ozone supply device 54, and ozone and the water to be treated are stirred and mixed by the gas-liquid stirring and mixing device 62, and most of the ozone is dissolved in the water to be treated. Here, the amount of ozone added to the water to be treated is adjusted to 3 to 40 ppm, preferably 7 to 30 ppm. In the water to be treated, the oxidative decomposition reaction of the organic matter proceeds rapidly in the reaction tube portion 66. The treated water obtained by the end of the oxidative decomposition reaction is supplied to the primary pure water system 24 together with the treated water of the pretreatment system 22 through the tank 46.
[0033]
In the primary pure water system 24, the water to be treated is first passed through the activated carbon filter 28, where dissolved ozone in the water to be treated is decomposed, and then the ions that have not been decomposed to carbon dioxide by the organic matter oxidizer 44. The active substance (organic acid) is removed by an anion exchange resin used in the two-bed / three-column pure water production apparatus 30 and the mixed bed pure water production apparatus 32. Next, the dissolved oxygen and trace amounts of organic substances are removed in the vacuum deaeration tower 34, and the remaining impurities are removed in the reverse osmosis membrane device 36. Even when acetone remains in the treated water of the organic matter oxidation apparatus 44 and passes through the pure

water production apparatuses

30 and 32, the acetone is volatile and can be removed by the vacuum deaeration tower 34.
[0034]
3-5 is a flowchart which shows one Embodiment of the ultrapure water manufacturing apparatus based on this invention, respectively. The ultrapure water production system of the apparatus shown in FIGS. 3 to 5 includes an activated carbon filtration device (CF), a two-bed three-column pure water production device (2B3T), a mixed-bed pure water production device (MBP), and a vacuum deaeration tower. (VD) and primary pure water system with reverse osmosis membrane device (RO), tank (TK), UV sterilizer (UV)_st), And a secondary pure water system equipped with a mixed bed type cartridge polisher (CP) and an ultrafiltration membrane device (UF).
[0035]
Moreover, in the apparatus of FIGS. 3-5, as a waste_water | drain collection | recovery system which processes the waste_water | drain produced by using ultrapure water at a use place, according to the cleanliness of waste_water | drain, it does not process directly but primary pure water directly. Route to return to water system (1), Route to return to primary pure water system after appropriate treatment (2) (pure water drainage recovery system), Route to supply utility facilities as miscellaneous water after appropriate treatment (▲) 3) (drainage collection system for miscellaneous water) and a path (4) (waste water treatment system) for discharging after appropriate treatment. The standard for separating the ultrapure water discharged from the place of use into the routes (1) to (4) is as shown in Table 1, for example, and the separation is performed by the separation mechanisms (1) to (3). Is called.
[0036]
[Table 1]

[0037]
3 and 4, an activated carbon filter (CF) and an anion exchanger (WA) using an OH-type weakly basic anion exchange resin from the upstream side to the downstream side in the pure water wastewater recovery system. A reverse osmosis membrane device (RO) and an organic oxidizer are installed sequentially. The treatment of waste water in the pure water waste water recovery system of the apparatus of FIGS. 3 and 4 is the same as that of the apparatus of FIG. In addition, in the apparatus of FIG. 3, the concentrated water of the reverse osmosis membrane device of the drainage recovery system for pure waterWastewater treatment systemIn the device shown in FIG.Wastewater recovery system for miscellaneous waterIntroduced to. When the cleanliness of the concentrated water in the reverse osmosis membrane device is relatively high,4When the reverse osmosis membrane device has a relatively low cleanliness level, it can be reused by introducing it into the wastewater recovery system for miscellaneous water as in the previous device.3It is only necessary to treat the wastewater treatment system and then discharge it. The apparatus of FIG. 5 is obtained by omitting the anion exchange apparatus (WA) from the apparatus of FIG.
[0039]
【Example】
Example
Activated carbon filtration device (CF), anion exchange device (WA), first reverse osmosis membrane device (RO), organic matter oxidation device, activated carbon filtration device (CF), two-bed three-column pure water production device (2B3T), Wastewater generated by using ultrapure water in an apparatus that connects a mixed bed type pure water production apparatus (MBP), a vacuum degassing tower (VD), and a second reverse osmosis membrane apparatus (RO) in this order. The waste water was treated by flowing. As the waste water, one having a TOC concentration shown in Table 2 was used. In this case, in the organic matter oxidizer 44, the pH of the water to be treated is adjusted to the value shown in Table 2 by adding sodium hydroxide from the alkali injection device 52 to the water to be treated. Ozone was added to the water to be treated so that the amount of ozone added to the water to be treated had the value shown in Table 2.
[0040]
Note that an ozone dissolution pump was used as the gas-liquid stirring and mixing device 62. In addition, as the anion exchange resin of the anion exchange apparatus (WA), an OH type of Amberlite (registered trademark, hereinafter the same) IRA-94S, which is a weakly basic anion exchange resin, is used. As the reverse osmosis membrane of the reverse osmosis membrane device (RO), polyamide composite membrane ES-10 manufactured by Nitto Denko is used, and as the cation exchange resin of the two-bed / three-column pure water production device (2B3T), a strongly acidic cation Amberlite IR-124, which is an ion exchange resin, is in the H form, and an OH form of Amberlite IRA-402BL, which is a strongly basic anion exchange resin, is used as an anion exchange resin. As the ion exchange resin, Amberlite ESG4 obtained by mixing H-type strongly acidic cation exchange resin and OH-type strongly basic anion exchange resin was used. The vacuum deaerator (VD) was operated at a degree of vacuum of 22 Torr. Table 2 shows the measurement results of the TOC concentration of each device outlet water.
[0042]
Comparative example
Using the same apparatus as used in Example 1 except that the anion exchange apparatus and the first reverse osmosis membrane apparatus were excluded from the pure water wastewater recovery system of the apparatus used in Example 1, Example 1 and Similarly, wastewater generated by using ultrapure water was treated. The results are shown in Table 2.
[0043]
[Table 2]

[0044]
  From Table 2, reverse osmosis membrane treatment is applied to water to be treated containing organic substances.In placePermeation of reverse osmosis membrane device after processingin waterWhen ozone was added under alkaline conditions in the organic matter oxidation apparatus, it was confirmed that the TOC removal efficiency in the organic matter oxidation apparatus and the subsequent ion exchange apparatus was improved. However, when the ozone concentration and pH of the water to be treated were low at the time of treatment with the organic matter oxidation apparatus (test Nos. 5 to 7), the TOC removal efficiency in the organic matter oxidation apparatus and the subsequent ion exchange apparatus was lowered. The reason why the TOC removal efficiency in the ion exchange apparatus at the latter stage is lowered is considered to be that the organic substance is not sufficiently oxidized in the organic substance oxidizing apparatus and is not an ionic substance.
[0045]
【The invention's effect】
According to the first aspect of the present invention, in the reverse osmosis membrane apparatus, anionic impurities that inhibit the oxidative decomposition reaction of the organic substance in the organic substance oxidizing apparatus are removed from the treated water, and organic substances in the treated water are considerably removed. Therefore, the organic substance removal efficiency in the organic substance oxidation apparatus is improved. In addition, since the organic matter in the water to be treated is considerably removed by the reverse osmosis membrane device, the amount of ozone used in the organic matter oxidation device can be reduced, the size of the ozone generator can be reduced, and even if the pH is not so high Since organic matter can be oxidatively decomposed, consumption of the alkaline agent added to the water to be treated can be reduced.
[0046]
  Claim1According to the invention, since the organic matter can be highly removed from the treated water in the wastewater recovery system for the pure water of the wastewater recovery system, ultrapure water with high purity can be obtained by reusing the treated water. In addition, effective use of the concentrated water of the reverse osmosis membrane device or appropriate treatment can be achieved.
[0047]
  Claim2According to the invention, it is possible to further remove anionic impurities that inhibit the oxidative decomposition reaction of the organic matter in the organic matter oxidizing apparatus, and further improve the organic substance removing efficiency in the organic matter oxidizing apparatus, and an anion. Since the outlet water of the exchange device becomes alkaline, it becomes possible to eliminate the addition of an alkali agent for making the water to be treated alkaline, or to reduce the amount of addition.
[0049]
  Claim3According to the invention, even when the organic matter is not decomposed to carbon dioxide in the organic matter oxidizing device, if the organic matter is decomposed to an ionic substance such as an organic acid in the organic matter oxidizing device, the ion exchange device in the latter stage may Since the ionic substance is removed, the organic matter is efficiently removed as a whole.
[0050]
  Claim4According to the invention, it is possible to prevent the dissolved ozone remaining in the treated water of the organic matter oxidation apparatus from adversely affecting the subsequent apparatus, for example, the ion exchange resin of the ion exchange apparatus.
[0051]
  Claim5According to the invention, when the dissolved gas is removed from the water to be treated by the degassing device, volatile organic substances present in the water to be treated are also removed, so that treated water with a further reduced organic matter concentration can be obtained. it can.
[0052]
  Claim6~8According to the invention, it is possible to efficiently perform the oxidative decomposition of the organic matter in the organic matter oxidizing apparatus.
[Brief description of the drawings]
FIG. 1 is a partially omitted flow diagram illustrating an embodiment of an ultrapure water production apparatus according to the present invention.
FIG. 2 is a flowchart showing an organic matter oxidation apparatus of the ultrapure water production apparatus shown in FIG.
FIG. 3 is a flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention.
FIG. 4 is a flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention.
FIG. 5 is a flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention.
FIG. 6 is a graph showing the relationship between the pH of water to be treated and the rate of oxidative decomposition of organic substances.
FIG. 7 is a flowchart showing an example of a conventional ultrapure water production apparatus.
[Explanation of symbols]
22 Pretreatment system
24 Primary pure water system
26 Wastewater recovery system for pure water
28 Activated carbon filter
30 2-bed 3-tower pure water production system
32 Mixed floor type pure water production equipment
34 Vacuum deaeration tower
36 Reverse osmosis membrane device
38 Activated carbon filter
40 Anion exchanger
42 Reverse osmosis membrane device
44 Organic matter oxidation equipment

Claims

The primary pure water system that processes raw water to produce primary pure water, the secondary pure water system that processes primary pure water to produce ultrapure water, and the ultrapure water produced by secondary pure water system are used at the place of use. In the ultrapure water production apparatus equipped with a wastewater recovery system that treats the wastewater generated by the process and returns it to the primary pure water system,
A reverse osmosis membrane device and an organic matter oxidation device that oxidizes and decomposes organic matter contained in the treated water by adding ozone to the treated water under alkaline conditions are installed in the wastewater recovery system for pure water. In addition, the permeated water of the reverse osmosis membrane device is treated with the organic matter oxidizer and introduced into the primary pure water system, and the concentrated water of the reverse osmosis membrane device is used for the wastewater recovery system for wastewater or the wastewater treatment system of the drainage recovery system. An ultrapure water production apparatus characterized by being introduced into

The ultrapure water production apparatus according to claim 1 , wherein an anion exchange device using an OH-type anion exchange resin is provided upstream of the reverse osmosis membrane device or between the reverse osmosis membrane device and the organic matter oxidation device.

The ultrapure water production apparatus according to claim 1 or 2 , wherein an ion exchange apparatus using at least an anion exchange resin is provided on the downstream side of the organic matter oxidation apparatus.

The ultrapure water production apparatus according to any one of claims 1 to 3 , wherein an ozone decomposition means for decomposing ozone in the water to be treated is provided on the downstream side of the organic matter oxidation apparatus.

The ultrapure water production apparatus according to any one of claims 1 to 4 , wherein a deaeration device is provided downstream of the organic matter oxidation device.

The ultrapure water production apparatus according to any one of claims 1 to 5 , wherein the organic matter oxidation apparatus adds ozone to the water to be treated by a gas-liquid stirring and mixing means.

The apparatus for producing ultrapure water according to any one of claims 1 to 6 , wherein the organic matter oxidizing device adds ozone to the water to be treated under an alkaline condition where the pH of the water to be treated is 9.7 or more.

The ultrapure water production apparatus according to any one of claims 1 to 7 , wherein the organic matter oxidation apparatus adds ozone to the water to be treated so that the amount of ozone added to the water to be treated is 3 to 40 ppm.