JP3862242B2

JP3862242B2 - Treatment method for waste water containing polyphosphoric acid

Info

Publication number: JP3862242B2
Application number: JP08720496A
Authority: JP
Inventors: 英之浅野; 理江矢野; 春樹明賀; ふで子角田
Original assignee: Organo Corp
Current assignee: Organo Corp
Priority date: 1995-12-14
Filing date: 1996-03-15
Publication date: 2006-12-27
Anticipated expiration: 2016-03-15
Also published as: JPH09220594A

Description

【０００１】
【発明の属する技術分野】
本発明はポリリン酸含有排水の処理方法に関し、詳しくは、排水に含まれるポリリン酸を効率良くオルトリン酸に加水分解することができるポリリン酸含有排水の処理方法に関する。
【０００２】
【従来の技術】
従来より、各種工場からの排水や下水等の排水処理は複数の処理工程を経て行なわれており、例えば、処理の前段では有機物酸化菌等の微生物の働きを利用して有機物を分解する、いわゆる生物学的処理等が行なわれ、処理の後段では、かかる生物学的処理時に混入した微生物をはじめとする懸濁物質を除去する凝集処理等が行なわれる。
【０００３】
ここで上記凝集処理は、硫酸バンドや、ポリ塩化アルミニウム（ＰＡＣ）等の凝集剤を処理水（排水）に添加して懸濁物質を凝集させることによって固液分離を行なうものであり、かかる凝集処理は、通常、処理水をｐＨ７付近の中性に保った状態で行なわれる。
【０００４】
【発明が解決しようとする課題】
ところで、凝集処理を施す際にあたり処理水にピロリン酸やトリポリリン酸等のポリリン酸が含まれている場合には、以下に述べるように凝集阻害を起こすという問題があった。尚、本発明でいうポリリン酸は「ポリリン酸又はその塩」を意味するものとする。
【０００５】
即ち、ポリリン酸には分散剤として作用する性質があるため、処理水にポリリン酸が含まれていると凝集処理時にポリリン酸の分散剤的作用に起因して、懸濁物質の凝集を阻害するという問題を生じる。
【０００６】
この場合、凝集処理時の被処理水のｐＨを酸性側に調整すれば、凝集を起こさせることができるが、その至適ｐＨ範囲が、例えば、ｐＨ４．３〜４．８の如く非常に狭いものとなる。この傾向は凝集剤として硫酸バンド、ポリ塩化アルミニウム、塩化第二鉄のいずれを用いた場合にも共通して生じる。
【０００７】
また、被処理水が上記ｐＨ範囲の如き酸性側にあると、凝集処理後の処理水を系外に排出したり、別の処理装置に送ったりするときに、金属製の配管や装置類を腐食させたり、あるいはコンクリート製の槽類を劣化させるとういう問題がある。このためアルカリ中和剤による中和処理が必要となるが、処理工程の煩雑化、処理コストの上昇を招き、経済的に得策でない。
【０００８】
更に、凝集剤として硫酸バンドやポリ塩化アルミニウムを用いた場合には、上記ｐＨ範囲にある処理水の強い酸性のためにアルミニウムイオンが凝集処理後の処理水中に比較的高濃度で残留してしまう。そして、処理水中にアルミニウムイオンが存在していると、その後の処理工程で該処理水のｐＨが上昇してその液性が中性となったときに水酸化アルミニウムが析出し、これによって処理水が白濁してしまうばかりか、例えば、必要に応じて凝集処理後の処理水に活性炭吸着処理等の各種処理を施す場合に、かかる活性炭吸着処理がなされる活性炭吸着塔内で水酸化アルミニウムの析出が起こると、活性炭のブロッキングを招き活性炭吸着塔の目詰まりによる差圧上昇を引き起こすというような問題もあった。
【０００９】
【課題を解決するための手段】
そこで、本発明者等は排水中に含まれるポリリン酸を効率良くオルトリン酸に加水分解して、排水処理の後段で行なわれる凝集処理等を支障なく行なうことができるような処理方法を確立すべく鋭意研究した結果、排水を特定のｐＨ条件下において活性汚泥等の微生物に接触させることでポリリン酸を効率良くオルトリン酸に加水分解することができるという知見を得た。更に研究を重ねた結果、ポリリン酸をオルトリン酸に加水分解するに際しては、ポリリン酸の初期濃度が高い程加水分解反応が効率良く進行すること、ポリリン酸の加水分解反応は、排水中に微生物の活性を失わせる程度の濃度の微生物阻害物質が含有されていても充分に進行するという知見も得られた。本発明はこれらの知見に基づき完成されたものである。
【００１０】
即ち、本発明は（１）ポリリン酸を含有する排水をｐＨ４．５〜６．０の条件下で微生物と接触させてポリリン酸の分解処理を行うことを特徴とするポリリン酸含有排水の処理方法、（２）ポリリン酸を含有する排水がポリリン酸以外に有機物を含有し、該排水をｐＨ４．５〜６．０の条件下で微生物と接触させてポリリン酸及び有機物の分解処理を同時に行なう上記（１）記載のポリリン酸含有排水の処理方法、（３）ポリリン酸を含有する第１の排水及びポリリン酸を含有せず有機物を含有する第２の排水を処理するにあたり、これらの排水を混合することなく、まず、第１の排水をｐＨ４．５〜６．０の条件下で微生物と接触させてポリリン酸の分解処理を行い、次いで、ポリリン酸分解処理後の処理水に第２の排水を混合してこれを微生物と接触させて生物学的処理を施し、有機物の分解処理を行なうことを特徴とするポリリン酸含有排水の処理方法、（４）ポリリン酸を含有するとともに、このポリリン酸以外に微生物の活性を失わせる程度の濃度の微生物阻害物質を含有する排水を処理するにあたり、この排水を希釈することなく、該排水をｐＨ４．５〜６．０の条件下で微生物と接触させてポリリン酸の分解処理を行なうことを特徴とするポリリン酸含有排水の処理方法、（５）ポリリン酸及び微生物阻害物質を含有する排水がこれらのポリリン酸、微生物阻害物質以外に有機物を含有し、この排水をｐＨ４．５〜６．０の条件下で微生物と接触させてポリリン酸の分解処理を行なった後、分解処理後の処理水を希釈して該処理水を微生物と接触させて生物学的処理を施し、有機物の分解処理を行なう上記（４）記載のポリリン酸含有排水の処理方法、（６）ポリリン酸の分解処理を行なうにあたり、複数の区画された反応域を有する多段式の反応槽を用いて処理を行う上記（１）、（２）、（３）、（４）、又は（５）記載のポリリン酸含有排水の処理方法、（７）ポリリン酸分解処理後、又は生物学的処理を施した後の処理水に凝集処理を施して固液分離を行なう上記（１）、（２）、（３）、（４）、（５）、又は（６）記載のポリリン酸含有排水の処理方法を要旨とする。
【００１１】
【作用】
本発明者等は、排水をいかなるｐＨ範囲において微生物と接触させれば本発明の課題を解決できるかにつき検討するため、次の如き実験を行なった。
【００１２】
ピロリン酸ナトリウムの濃度を１２．５ｍｇＰ／ｌに調整するとともに、ｐＨを変えた試験排水を数種類用意し、各試験排水に活性汚泥（微生物）を混入して試験排水を処理した。このときの処理温度は２０℃、ＭＬＳＳ濃度は２０００ｍｇＳＳ／ｌとなるように設定した。処理を始めてから１２０分経過した後の試験排水中に残存するピロリン酸ナトリウムの濃度を測定して、各ｐＨごとの加水分解率を求めた。この結果を図１にグラフで示す。
【００１３】
上記実験結果より、試験排水のｐＨが７付近の中性にあるとポリリン酸の加水分解率がきわて悪く、試験排水のｐＨが４．５〜６．０、特に４．５〜５．５の場合にポリリン酸を効率よく加水分解できることが判明した。
【００１４】
一方、試験排水に活性汚泥を混入しないで、該試験排水のｐＨを４．５〜６．０に調整して放置したところポリリン酸の濃度に変化はみられなかった。
【００１５】
このことから、単にｐＨの調整のみでポリリン酸の加水分解率を向上できる訳ではなく、あくまでもポリリン酸は特定ｐＨ範囲における微生物の働きによって効率良く加水分解されることが確認され、ｐＨが４．５未満であったり、ｐＨが６．０を超えると微生物がもっているポリリン酸分解酵素の働きが低下してしまう。
【００１６】
尚、トリポリリン酸ナトリウムを含有した試験排水について上記と同様の実験を行なったところ、ピロリン酸ナトリウムの場合と同様の結果が得られた。
【００１７】
このように、本発明においては、排水をｐＨ４．５〜６．０の条件下において微生物に接触させることによりポリリン酸が効率良く加水分解され、後段の凝集処理等が良好に行なえるという作用を生じるものである。また、ポリリン酸を完全に加水分解できなかったとしても凝集処理を阻害しない程度にまでその濃度を充分に低減することができ、いずれにしても本発明によれば、凝集処理を施すに際して凝集至適ｐＨの範囲が広くなり、該凝集処理や、必要に応じて行なわれる活性炭吸着処理等の後段における処理に支障をきたす虞がない。
【００１８】
また、本発明者等は、ポリリン酸の加水分解速度に及ぼすポリリン酸の初期濃度の影響をみるため、次の如き実験を行なった。
【００１９】
ピロリン酸ナトリウムを、３０ｍｇＰ／ｌの濃度で含有させた試験排水ａと、１０ｍｇＰ／ｌの濃度で含有させた試験排水ｂを、それぞれｐＨ５．５に調整するとともにこれに活性汚泥（微生物）を混入した。ピロリン酸ナトリウムの初期濃度以外は全て同一の条件下で両試験排水を処理し、時間経過に伴うピロリン酸ナトリウムの濃度を測定した。この結果を図２にグラフで示す。
【００２０】
上記グラフからピロリン酸ナトリウムの加水分解速度はその初期濃度が高いほど速くなっていることが判る。
【００２１】
即ち、生物学的処理を開始してから最初の３０分で比較すると試験排水ａでは約１５ｍｇＰ／ｌのピロリン酸ナトリウムが加水分解されているのに対して、これよりも濃度の低い試験排水ｂでは約７ｍｇＰ／ｌのピロリン酸ナトリウムしか加水分解されておらず、また、試験排水ｂでは１０ｍｇＰ／ｌのピロリン酸ナトリウムを加水分解するのに９０分もの時間を要するのに対して、試験排水ａにあっては約２０分で１０ｍｇＰ／ｌのピロリン酸ナトリウムが加水分解されており、同じ分量のピロリン酸ナトリウムを加水分解するのに要する時間はその初期濃度が高いほど短くなる。
【００２２】
尚、トリポリリン酸ナトリウムについてもその濃度を変えて加水分解速度を調べてみたところ、ピロリン酸ナトリウムの場合と同様の結果が得られることが確認された。
【００２３】
このように、ポリリン酸をオルトリン酸に加水分解するに際しては、ポリリン酸の初期濃度が高い程加水分解反応が効率良く進行する。この原理に基づき本発明は複数の排水系統から生じる排水を処理する必要がある場合、各排水系統から生じる排水を混合せずに、まずポリリン酸を含む排水を処理し、次いでこの処理水に他の排水を混合して処理を行なうものである。このようにすることにより、排水中のポリリン酸が希釈されず、ポリリン酸の初期濃度を高く維持することができ、その結果、ポリリン酸をより効率良く加水分解することができる。
【００２４】
更に、本発明者等は、処理の対象となる排水に含まれているポリリン酸以外の成分の存在、特に、微生物の活性を失わせる程度の濃度の微生物阻害物質、例えば重金属や高濃度の塩類が処理排水に含まれている場合があることに着目し、微生物の活性がポリリン酸の加水分解反応に如何なる影響を及ぼすかについて調べるため、次の如き実験を行なった。
【００２５】
水道水にピロリン酸ナトリウム２００ｍｇＰ／ｌと塩化ナトリウム２％を溶解した試験排水ｃを三角フラスコＡにとり、ピロリン酸ナトリウム２００ｍｇＰ／ｌと塩化ナトリウム２０％を溶解した試験排水ｄを三角フラスコＢにとり、それぞれにＭＬＳＳ濃度約２０００ｍｇＳＳ／ｌとなるように活性汚泥を添加してｐＨ５に調整した後、マグネチックスターラーで攪拌し、ピロリン酸ナトリウムの加水分解により生じたオルトリン酸ナトリウムの濃度を測定し、時間経過に伴うオルトリン酸ナトリウムの濃度変化を求めた。結果を図３（α）にグラフで示す。実験開始後３時間までのピロリン酸ナトリウムの平均分解速度（オルトリン酸ナトリウムの生成速度をピロリン酸ナトリウムの加水分解速度とみなす、以下同じ）は、試験排水ｃについては０．５０ｇＰ／ｇＳＳ／日であり、試験排水ｄについては０．３５ｇＰ／ｇＳＳ／日であった。
【００２６】
３日後、活性汚泥を残して三角フラスコＡ、Ｂの上澄み液を棄て、それぞれに新たに試験排水ｃ、ｄを入れ、上記と同様にオルトリン酸ナトリウムの濃度変化を求めた。結果を図３（β）にグラフで示す。実験開始後３時間までのピロリン酸ナトリウムの平均分解速度は、試験排水ｃについては０．５３ｇＰ／ｇＳＳ／日であり、試験排水ｄについては０．２６ｇＰ／ｇＳＳ／日であった。
【００２７】
続いて８日後に活性汚泥を残して三角フラスコＡ、Ｂの上澄み液を棄て、それぞれに再度試験排水ｃ、ｄを入れ、同様にオルトリン酸ナトリウムの濃度変化を求めた。結果を図３（γ）にグラフで示す。実験開始後３時間までのピロリン酸ナトリウムの平均分解速度は、試験排水ｃについては０．４５ｇＰ／ｇＳＳ／日であり、試験排水ｄについては０．０８ｇＰ／ｇＳＳ／日であった。
【００２８】
活性汚泥の増殖・生育のための有機物の供給を全く行なっていないにもかかわらず、試験排水ｃでは８日間にわたりピロリン酸ナトリウムの加水分解速度は略一定の高い値に保たれた（０．４５〜０．５３ｇＰ／ｇＳＳ／日）。また、試験排水ｄでは、塩化ナトリウム濃度２０％という活性汚泥の活性が全く保てない高塩濃度条件下であっても、実験１日目のピロリン酸ナトリウムの加水分解速度は０．３５ｇＰ／ｇＳＳ／日と非常に高く、実験８日目でも０．０８ｇＰ／ｇＳＳ／日と実用的な加水分解速度を保っていることが判った。
【００２９】
尚、トリポリリン酸ナトリウムについても同様の結果が得られることが確認された。
【００３０】
以上のことからポリリン酸の加水分解は微生物の増殖・生育に必要な有機物の有無に関わらずなされ、長期にわたって高い加水分解速度が保たれること、また、微生物の増殖・生育に不適な高塩濃度条件下において、微生物の活性が失われてもポリリン酸の加水分解反応は充分に進行することが見出された。
【００３１】
尚、上記結果から本発明者らは、微生物によるポリリン酸の加水分解は、従来から行われているいわゆる生物学的処理による有機物等の分解の如く微生物の生命活動に係わる増殖、代謝作用によりなされるのではなく、微生物にはポリリン酸加水分解酵素が含まれ、この酵素の働きによりポリリン酸が加水分解され、このため微生物の活性が失われてもポリリン酸の加水分解反応が充分に進行するものと考える。
【００３２】
本発明は、ポリリン酸以外に、微生物の活性を失わせる程度の濃度の微生物阻害物質を含有する排水を処理するにあたり、上記知見に基づき排水を希釈することなく排水をそのまま処理するものである。このような方法により、排水中のポリリン酸濃度を高い濃度に維持し、ポリリン酸の加水分解を効率良く行なうことができる。
【発明の実施の形態】
次に、本発明の実施の形態を図面に基づき詳細に説明する。尚、図４は本発明処理方法を実施する装置の一例を示す略図である。
【００３３】
図中、１はポリリン酸の加水分解反応を行なわせる反応槽であり、処理すべき排水が流入配管２から該槽１に導かれ、また、加水分解に必要な微生物は微生物供給ライン３を経て該槽１に導かれる。４は攪拌装置で該攪拌装置４により反応槽１内を攪拌して排水が槽１内の微生物と充分に接触するよう構成されている。
【００３４】
本発明において利用可能な微生物としては下水処理、し尿処理、産業排水処理等で生じる活性汚泥や生物膜汚泥、嫌気性生物処理で生じる汚泥、或いは土壌等から分離した細菌等が例示できる。
【００３５】
反応槽１内に微生物を存在させる手段としては、微生物を微生物付着担体に着生させたものを槽内に固定させる固定床式のもの、又はこれを槽内で流動させる流動床式のもの、或いは微生物付着担体に微生物を着生させないで槽内に浮遊状態にしておく浮遊式のもの等が例示できるが、本発明では浮遊式を採用した場合に特に実益が大きい。尚、上記微生物付着担体としては、砂、砂利、砕石、各種プラスチック成形体、繊維状活性炭、粒状活性炭、球状活性炭等が挙げられる。
【００３６】
また、反応槽１内を攪拌する具体的な手段としては、回転翼等による機械攪拌、空気、酸素富化空気、窒素等のガスを槽１内に吹き込むガス攪拌、槽１の下方から排水を流入させ槽１の上方から排水を流出させるか、或いはその逆を行なう向流攪拌等が例示される。
【００３７】
本発明において、排水はｐＨ４．５〜６．０の条件下で微生物と接触することによりそのなかに含まれるポリリン酸がオルトリン酸に加水分解される。
【００３８】
本発明方法では、上記ポリリン酸分解処理をバッチ式で行なっても、連続的に行なっても良い。反応時のｐＨを調整するには、例えば、反応槽１の前段にｐＨ調整槽（図示せず）を設けておき、かかるｐＨ調整槽で排水のｐＨを調整した後に反応槽１に排水を流入させるのが好ましいが、ラインミキサー等を用いることによりｐＨ調整槽を省略することもできる。尚、反応槽１内の水のｐＨを上記範囲に維持するために、必要に応じて直接反応槽１内でｐＨ調整を行っても良い。
【００３９】
本発明においてポリリン酸加水分解処理を行なうにあたり、ポリリン酸−ＳＳ負荷は０．０４〜０．６ｇＰ／ｇＳＳ／日であるのが好ましく、より好ましくは０．１〜０．４ｇＰ／ｇＳＳ／日である。また、ポリリン酸容積負荷は０．０６〜１０ｋｇＰ／ｍ³／日であるのが好ましく、より好ましくは０．２〜４ｋｇＰ／ｍ³／日である。
【００４０】
尚、反応槽１への排水の流量をＱ、排水中のポリリン酸濃度をＣ、反応槽の容積をＶ、ＭＬＳＳ濃度をＸとしたときに、ポリリン酸−ＳＳ負荷は下記（１）式で与えられるものであり、ポリリン酸容積負荷は下記（２）式で与えられるものである。
【数１】

【数２】

【００４１】
図４に示す装置にあっては、反応槽１の後段にライン５を介して沈殿槽６が連結されており、反応槽１から流出した微生物は該沈殿槽８で沈殿する。微生物は一度の処理でポリリン酸分解性能が失われるわけではなく、ポリリン酸分解性能が失われるまで繰り返し利用が可能であり、沈殿槽６で沈殿させた微生物の一部はライン７を経て反応槽１に返送され、残りはライン８を経て廃棄される。
【００４２】
また、図中、９は沈殿槽６から処理水を系外に導く流出配管であり、ポリリン酸加水分解処理が施された後の処理水は、必要に応じて凝集槽１６に導かれる。尚、１７は凝集処理後の処理水を凝集槽１６外に導くラインである。
【００４３】
凝集槽１６に導かれた排水は、これに硫酸バンド等の凝集剤を添加して排水中の懸濁物質を凝集させた後、凝集物を沈殿せしめこれを分離除去する凝集沈殿方式、或いは凝集物の周囲に多数の気泡を付着せしめて該凝集物を浮上させこれを分離除去する加圧浮上方式により固液分離される。この際、排水に含まれていたポリリン酸は既にオルトリン酸に加水分解されているので、ポリリン酸による凝集阻害の問題は生じない。
【００４４】
尚、排水にポリリン酸以外の除去すべき成分が含まれていない場合等において、特に問題がなければポリリン酸加水分解処理後の排水はそのまま放流しても良い。
【００４５】
本発明処理方法は、ポリリン酸以外に有機物を含む有機系排水、有機物を含まない無機系排水のいずれについても適用することができる。
【００４６】
無機系排水を処理する場合、反応槽１から流出した微生物を沈殿槽６で沈殿させて反応槽１に返送すると良い。更に、これだけでは反応槽１内での微生物の増殖・生育が期待できないのでポリリン酸分解性能を持つ微生物の数が次第に減少してしまうため、微生物供給ライン３を経て外部から微生物を供給する必要がある。
【００４７】
このときの微生物の供給は連続的であっても、間欠的であっても良い。また、その供給元は特に限定されず、例えば、後述するようにポリリン酸の加水分解処理を行なった後にいわゆる生物学的処理を行なう態様で本発明方法を実施する場合には、生物学的処理において増殖した微生物を供給しても良く（図５、６参照）、或いは本発明方法が実施される装置設備以外（例えば、生物学的処理が行なわれている他の設備における生物学的処理反応槽等）から運んで供給しても良い。
【００４８】
有機系排水を処理する場合には、反応槽１において、ポリリン酸の分解反応のみを行わせるようにしても良く、また微生物による有機物の酸化分解反応とポリリン酸の加水分解反応とを同時に進行させるようにしても良い。このとき、反応槽１内の水のｐＨが４．５〜６．０の範囲にあっても有機物の分解にはほとんど影響がない。
【００４９】
有機系排水について本発明方法を適用する場合は、有機物の酸化分解反応により微生物が反応槽１で増殖するため、ポリリン酸の加水分解、及び有機物の酸化分解に必要なだけの微生物が反応槽１内に存在するならば、微生物の外部からの供給は特に必要ない。尚、有機系排水の処理にあたり、反応槽１内においてポリリン酸の分解と同時に有機物の分解を行う場合は、酸化分解に必要な酸素を供給して反応槽１内を曝気する必要がある。
【００５０】
本発明方法は、複数の排水系統から生じる排水を処理する場合にも有効に適用することができる。
【００５１】
本発明処理方法により排水に含まれるポリリン酸を加水分解するにあたっては、前述したようにポリリン酸の初期濃度が高い程効率良く加水分解反応が進行する。このため、複数の排水系統から生じる排水を処理する必要がある場合には、各排水系統から生じる排水を混合することなく、まずポリリン酸を含有する排水を処理し、次いでこの処理水に他の排水を混合して処理を行なうのが好ましい。
【００５２】
尚、この場合にも、処理の対象となるポリリン酸含有排水が有機系排水、無機系排水のいづれであっても本発明の適用が可能である。
【００５３】
上記の場合にポリリン酸を含む排水が二系統以上あるときは、それらのポリリン酸濃度が等しいか、或いは濃度差が小さければポリリン酸含有排水どうしを混合してもかまわない。
【００５４】
但し、本発明方法によりポリリン酸含有排水を処理するにあたっては、排水中のポリリン酸濃度は１０ｍｇＰ／ｌ以上であるのが好ましく、より好ましくは５０ｍｇＰ／ｌ以上であり、かかる濃度のときにポリリン酸の加水分解反応がより効率的となる。また、ポリリン酸濃度が高い程その加水分解反応はより効率良く進行するが、１００ｍｇＰ／ｌ以上ではポリリン酸の加水分解速度は略一定となる。このことを考慮に入れて、ポリリン酸含有排水どうしを混合するか否かは、高濃度ポリリン酸含有排水が低濃度のもので希釈されることによる加水分解効率の低下と、混合による処理の簡略化（混合しない場合は当然各ポリリン酸含有排水を別々に処理しなければならない）とを比較考慮して決定する。
【００５５】
このようにして複数の排水系統から生じる排水を処理する場合、本発明では、ポリリン酸を含有する第１の排水にポリリン酸加水分解処理を施した後、これにポリリン酸を含有しない第２の排水を混合して所定の処理を施すこともでき、例えば、ポリリン酸加水分解処理した後の処理水、及び／又はこれに混合する排水に有機物が含まれている場合には有機物を分解するための生物学的処理が施される。
【００５６】
ポリリン酸加水分解処理後の処理水に他の排水を混合する時期はポリリン酸含有排水にポリリン酸加水分解処理を施した直後であっても、ポリリン酸加水分解処理を施した後これに他の一以上の後処理を施してからであっても良い。
【００５７】
ポリリン酸を含有する第１の排水にポリリン酸分解処理を施した後の処理水に、ポリリン酸を含有せず有機物を含有する第２の排水を混合して生物学的処理を行なう場合の具体的な処理操作を図５に基づき以下に説明する。
【００５８】
第１の排水は流入管２から反応槽１に導かれ、該槽１内でｐＨ４．５〜６．０の条件下において微生物と接触することによりポリリン酸分解処理が施され、ポリリン酸がオルトリン酸に加水分解される。このとき反応槽１に導かれた排水は微生物と充分に接触するよう攪拌装置４により攪拌される。
【００５９】
次いで、ポリリン酸分解処理が施された処理水は、ライン９を経て反応槽１から生物学的処理反応槽１１へと導かれる。このとき第２の排水がライン９に接続された流入ライン１０から流入し、ポリリン酸分解処理後の処理水と混合される。
【００６０】
生物学的処理反応槽１１に導かれた処理水には微生物の存在下で生物学的処理が施され有機物が分解される。生物学的処理反応槽１１には所定濃度の微生物が維持されている。該生物学的処理反応槽１１における生物学的処理においては、反応槽１の如く槽内の水のｐＨを４．５〜６．０の範囲に維持する必要はなく、生物学的処理に最適なｐＨ条件（ｐＨ６〜８）で行うことができるという利点がある。尚、図中、１２は生物学的処理に必要な酸素を供給するための空気導入管、１３は散気管である。
【００６１】
生物学的処理が施された処理水はライン１４を経て沈殿槽６′に導かれ、生物学的処理反応槽１１から流出した微生物が該沈殿槽６′に沈殿する。沈殿槽６′で沈殿した微生物の一部はライン７′を経て反応槽１と生物学的処理反応槽１１とに分配返送され、残りはライン８′を経て廃棄される。尚、沈殿槽６′からの微生物の返送を反応槽１のみに行い、生物学的処理反応槽１１には反応槽１を介して微生物が導入されるようにしても良く、この場合は該反応槽１１への微生物の返送は特に必要ない。
【００６２】
これらの処理が施された排水は、流出配管１５を経て放流されるか、或いは更に凝集処理等の他の後処理が施される他の処理槽に導かれ、その後放流される。尚、本発明では、ポリリン酸含有排水と分別された他の排水を該ポリリン酸含有排水とは混合せずに別系統で処理し、ポリリン酸含有排水についてはこれにポリリン酸分解処理を施した後に放流、又は単独で所定の後処理を施すことも可能である。
【００６３】
また、本発明方法は、処理の対象となるポリリン酸含有排水に、ポリリン酸以外にも、微生物の活性が失われる程度の濃度の微生物阻害物質が含まれている場合、例えば３％以上の濃度で塩化ナトリウム等の塩類が含まれている場合にも有効に適用することができる。
【００６４】
従って、微生物の活性が失われない、例えば２％以下の濃度にまで塩濃度を下げる必要がなく、上記排水を希釈せずにそのまま処理の対象とすることで、ポリリン酸濃度を高い濃度に維持してポリリン酸加水分解処理を効率良く行なうことができる。
【００６５】
但し、微生物は死滅してその生物的な活性が失われていても、ポリリン酸分解性能は一度の処理で失われず、死滅後も繰り返し利用が可能であるが、永久にポリリン酸分解性能を示すわけではないので、適当な時期に微生物を反応槽１に新たに供給する必要がある。
【００６６】
ポリリン酸を含有するとともに、このポリリン酸以外に微生物の活性を失わせる程度の濃度の微生物阻害物質、例えば高濃度の塩類と、有機物を含有するポリリン酸含有排水（処理排水）を、本発明方法で処理する場合の具体的な処理操作を図６に基づき以下に説明する。
【００６７】
処理排水は流入管２から反応槽１に導かれ、該槽１内でｐＨ４．５〜６．０の条件下において微生物と接触することによりポリリン酸加水分解処理が施される。このとき反応槽１内の排水を攪拌装置４により攪拌するのは図４、５に示す場合と同様である。
【００６８】
次いで、ポリリン酸加水分解処理が施された処理水は、ライン５を経て沈殿槽６に導かれ、処理水とともに反応槽１から流出した微生物は沈殿槽６で沈殿し、その一部はライン７を経て反応槽１に返送され、残りはライン８を経て廃棄される。
【００６９】
ここまでは図４に基いて説明した態様で本発明方法を実施する場合と略同様であるが、本具体例では、沈殿槽６は特に設けなくても良い。また、処理排水には高濃度の塩類が含まれているので反応槽１内の微生物は活性を失い、処理排水は有機物を含んでいるがその酸化分解はなされず、微生物の増殖・生育も期待できない。このため、後述するように反応槽１には生物学的処理で増殖した微生物を供給し、ポリリン酸分解処理に必要なだけの微生物が確保されるようにする。
【００７０】
次に、処理水はライン９を経て沈殿槽６から生物学的処理反応槽１１へと導かれるが、このときライン９に接続された流入ライン１０から水道水、又はポリリン酸を含有しない且つ塩類濃度の低い他の排水等を流入させて、ポリリン酸分解処理後の処理水を希釈する。該処理水には未だ高濃度の塩類が含まれており、そのまま生物学的処理反応槽１１に導いたのでは、該反応槽１１内の微生物が死滅してしまうので、処理水を希釈しその塩濃度を低くして微生物の活性が失われないようにするためである。
【００７１】
生物学的処理反応槽１１に導かれた処理水には生物学的処理が施される。生物学的処理反応槽１１には前述の場合と同様に所定濃度の微生物が維持されている。図中、１２、１３は図５に示す場合と同様に、それぞれ生物学的処理に必要な酸素を供給するための空気導入管、散気管である。尚、この場合も生物学的処理反応槽１１における生物学的処理を、反応槽１のｐＨ条件とは無関係に生物学的処理に最適なｐＨ条件で行うことができる。
【００７２】
生物学的処理が施された処理水はライン１４を経て沈殿槽６′に導かれ、生物学的処理反応槽１１から流出した微生物が該沈殿槽６′に沈殿する。沈殿槽６′で沈殿した微生物の一部はライン７′を経て反応槽１と生物学的処理反応槽１１とに分配返送され、残りはライン８′を経て廃棄される。
【００７３】
これらの処理が施された排水は流出配管１５を経て放流されるか、或いは更に凝集処理等の他の後処理が施される他の処理槽に導かれ、その後放流される。
【００７４】
以上の如くして実施される本発明では、図６に示すように複数の区画された反応域１ａ、１ｂ、１ｃ、１ｄを有する多段式の反応槽１を用いてポリリン酸加水分解処理を行なうのが好ましい。該反応槽１に複数の区画された反応域１ａ、１ｂ、１ｃ、１ｄを形成するため、槽内に複数の区画板１８が設けられている。
【００７５】
このように構成される反応槽１を用いてポリリン酸加水分解処理を行なうと、区画板１８を設けない通常の反応槽を用いる場合に比べてポリリン酸の加水分解をより効率良く行なうことができる。
【００７６】
即ち、前述したように、ポリリン酸の加水分解速度はポリリン酸の初期濃度が高い程大きいから、図６に示す反応槽１において、１番目の反応域１ａにおけるポリリン酸の加水分解速度は他の反応域に比べて最もその速度が大きいことになる。つまり、区画板１８があることによって、流入配管２より槽内に流入したポリリン酸含有排水は、槽全体への拡散が直ちには行なわれず全体としてはほぼプラグフローとなり、そのため排水中のポリリン酸濃度に関しても、槽全体への均一希釈化が行なわれないため反応域１ａにおいて最もポリリン酸濃度が高くなる。従って、反応域１ａにおけるポリリン酸の加水分解速度は他の反応域に比べて最も大きい。
【００７７】
各反応域は相互に連通しているので、１番目の反応域１ａにて或る程度加水分解が行なわれた被処理水は、反応域１ｂ、１ｃ、１ｄへと順次に流れていくが、後段の反応域になる程、被処理水中のポリリン酸濃度が希薄となるので、それに伴ってポリリン酸の加水分解速度も順次小さくなる。しかし、例えば、２番目の反応域１ｂにおいては、区画板１８のない反応槽における場合と比べてポリリン酸濃度が高く、ポリリン酸の加水分解速度が大きい。反応槽に区画板１８を設けない場合には、槽内に流入した排水はほぼ均一に拡散されるため、ポリリン酸濃度も希釈され、ポリリン酸の加水分解速度も全体的に小さくなる。
【００７８】
反応槽に区画板１８を設けると、各反応域間で加水分解の速度勾配が生じるが、前半の反応域において高い加水分解速度が得られるため、全体的には区画板１８を設けない場合よりもポリリン酸の加水分解速度が大きくなる。
【００７９】
本発明において好ましく用いられる多段式の反応槽１の具体的な構成は図示するものには限られず、流入した排水が反応槽全体に直ちには拡散しないようにしてポリリン酸分解処理を段階的に行うことが可能なものであれば良い。また、反応槽１は少なくとも２つの反応域に区画されていれば良いが、ポリリン酸の加水分解効率の向上を図るには３つ以上の反応域に区画されているのが好ましい。尚、ポリリン酸の分解処理と有機物の分解とを同時に行う場合は、生物学的処理反応槽を複数に区画すれば良い。
【００８０】
【実施例】
次に、具体的実施例を挙げて本発明を更に詳細に説明する。
【００８１】
実施例１
ピロリン酸ナトリウムを濃度１２．５ｍｇＰ／ｌで含有させた試験排水を、処理温度を２０℃に、ＭＬＳＳを２０００ｍｇＳＳ／ｌに設定した浮遊式の生物学的処理反応槽において槽内水のｐＨを５．５に調整して生物学的処理を１２０分間施し、得られた処理水を凝集処理槽に導き、ここでｐＨを種々変えて凝集処理を行なった。尚、凝集処理を行なうにあたり硫酸バンドと高分子凝集助剤は、それぞれ２００ｍｇ／ｌ、１ｍｇ／ｌの濃度で添加した。凝集処理後、処理水である上澄水の濁度を測定した。凝集処理時のｐＨに対する凝集処理後の処理水（凝集処理水）の濁度を図７にグラフで示す。
【００８２】
比較例１
槽内水のｐＨを６．５に調整した以外は実施例１と同様にして凝集処理を施した。凝集処理時のｐＨに対する凝集処理後の処理水の濁度を図８にグラフで示す。
【００８３】
上記比較例１では、凝集処理時のｐＨが５以下のときには濁度１以下（尚、凝集処理前の生物処理水の濁度は約２０度であった）となり凝集処理を良好に行なうことができたが、凝集処理時のｐＨが５以上では濁度が２０程度となり良好な凝集処理がなされなかった。これに対して、上記実施例１にあっては、凝集処理時のｐＨが５以上であっても濁度は１以下であり、良好な凝集処理を行なうことができた。
【００８４】
尚、実施例１、及び比較例１の凝集処理水に残存するピロリン酸ナトリウムの濃度を測定したところ、実施例１の凝集処理水ではピロリン酸ナトリウムはほとんど検出されなかったが、比較例１の凝集処理水にはピロリン酸ナトリウムは３ｍｇＰ／ｌの濃度で残存していた。
【００８５】
【発明の効果】
以上説明したように、本発明によればポリリン酸を含有する排水をｐＨ４．５〜６．０の条件下で微生物に接触させることによりポリリン酸が効率良く加水分解され、排水が比較的高濃度のポリリン酸を含有する場合にも凝集処理を何ら支障なく行なうことができる。また、本発明によれば処理後の処理水に凝集処理を施すに際して凝集至適ｐＨ範囲が広いという利点があり、処理が容易となると共に、必要に応じて行なわれる活性炭吸着処理等の後段における処理に支障をきたす虞がない。更に本発明では処理の対象となる排水中に微生物の増殖・育成に必要な有機物が含まれていなくても良いので、幅広い対応が可能となる。
【００８６】
また、ポリリン酸を加水分解するに際しては、ポリリン酸の初期濃度が高い程加水分解反応が効率良く進行し、従って、複数の排水系統から生じる排水を処理する必要がある場合、本発明における如く、各排水系統から生じる排水を混合せずに、まずポリリン酸を含む排水を処理し、次いでこの処理水に他の排水を混合して処理を行なうという方法を採用することにより、排水中のポリリン酸が希釈されず、これによってポリリン酸の初期濃度を高く維持することができ、ポリリン酸をより効率良く加水分解することができる。
【００８７】
また、本発明は、ポリリン酸以外に微生物の活性を失わせる程度の濃度の微生物阻害物質を含有する排水、例えば高濃度の塩類を含有する排水を処理するにあたって、該排水を希釈することなく、そのまま処理するものであるから、ポリリン酸濃度を高い濃度に維持し、処理効率の低下を招かず、ポリリン酸加水分解処理を効率良く行なうことができる。
【００８８】
更に、本発明を実施するにあたり複数の区画された反応域を有する多段式の反応槽でポリリン酸分解処理を行なうことによって、より効率の高いポリリン酸の加水分解が可能となる。
【図面の簡単な説明】
【図１】排水のｐＨとポリリン酸の加水分解率との関係を示すグラフである。
【図２】ピロリン酸ナトリウムの濃度と加水分解速度との関係を示すグラフである。
【図３】ピロリン酸ナトリウムの加水分解速度と処理排水中に含まれる塩類の濃度との関係を示すグラフである。
【図４】本発明処理方法を実施する装置の一例を示す略図である。
【図５】本発明処理方法を実施する装置の他の一例を示す略図である。
【図６】本発明処理方法を実施する装置の他の一例を示す略図である。
【図７】本発明で用いる反応槽の好ましい態様を示す略図である。
【図８】実施例１、比較例１のそれぞれの結果を示すグラフである。
【符号の説明】
１反応槽
１ａ、１ｂ、１ｃ、１ｄ反応域
１１生物学的処理反応槽
１６凝集槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating polyphosphoric acid-containing wastewater, and more particularly, to a method for treating polyphosphoric acid-containing wastewater that can efficiently hydrolyze polyphosphoric acid contained in wastewater into orthophosphoric acid.
[0002]
[Prior art]
Conventionally, wastewater treatment such as wastewater and sewage from various factories has been performed through a plurality of treatment steps. For example, in the preceding stage of treatment, so-called organic matter is decomposed using the action of microorganisms such as organic matter oxidizing bacteria, so-called Biological treatment or the like is performed, and in the subsequent stage of the treatment, agglomeration treatment or the like is performed to remove suspended substances including microorganisms mixed during the biological treatment.
[0003]
Here, the agglomeration treatment is performed by solid-liquid separation by adding a flocculant such as a sulfate band or polyaluminum chloride (PAC) to the treated water (drainage) to agglomerate suspended solids. The treatment is usually performed in a state where the treated water is kept neutral at around pH 7.
[0004]
[Problems to be solved by the invention]
By the way, there is a problem of causing aggregation inhibition as described below when the treatment water contains polyphosphoric acid such as pyrophosphoric acid or tripolyphosphoric acid when the aggregation treatment is performed. In addition, polyphosphoric acid as used in the field of this invention shall mean "polyphosphoric acid or its salt."
[0005]
That is, since polyphosphoric acid has the property of acting as a dispersant, if the treated water contains polyphosphoric acid, aggregation of suspended substances is inhibited due to the dispersing agent action of polyphosphoric acid during the coagulation treatment. This causes a problem.
[0006]
In this case, if the pH of the water to be treated at the time of flocculation treatment is adjusted to the acidic side, flocculation can be caused, but the optimum pH range is very narrow, for example, pH 4.3 to 4.8. It will be a thing. This tendency is commonly caused when any of a sulfate band, polyaluminum chloride, and ferric chloride is used as a flocculant.
[0007]
In addition, when the water to be treated is on the acidic side as in the above pH range, when the treated water after the coagulation treatment is discharged out of the system or sent to another treatment device, metal pipes and devices are connected. There is a problem of corroding or deteriorating concrete tanks. For this reason, neutralization with an alkali neutralizing agent is required, but this complicates the processing steps and increases the processing cost, which is not economically advantageous.
[0008]
Furthermore, when sulfuric acid band or polyaluminum chloride is used as the flocculant, aluminum ions remain in the treated water after the coagulation treatment at a relatively high concentration due to the strong acidity of the treated water in the above pH range. . When aluminum ions are present in the treated water, aluminum hydroxide is precipitated when the pH of the treated water is increased and the liquidity becomes neutral in the subsequent treatment step. For example, when various treatments such as activated carbon adsorption treatment are performed on the treated water after the coagulation treatment as necessary, precipitation of aluminum hydroxide in the activated carbon adsorption tower where the activated carbon adsorption treatment is performed is performed. When this occurs, there is a problem in that activated carbon is blocked, and the differential pressure is increased due to clogging of the activated carbon adsorption tower.
[0009]
[Means for Solving the Problems]
Therefore, the inventors of the present invention should establish a treatment method that can efficiently hydrolyze polyphosphoric acid contained in wastewater into orthophosphoric acid and perform a coagulation treatment or the like performed at a later stage of the wastewater treatment without any trouble. As a result of earnest research, we have obtained the knowledge that polyphosphoric acid can be efficiently hydrolyzed to orthophosphoric acid by bringing wastewater into contact with microorganisms such as activated sludge under specific pH conditions. As a result of further research, when polyphosphoric acid is hydrolyzed to orthophosphoric acid, the higher the initial concentration of polyphosphoric acid, the more efficiently the hydrolysis reaction proceeds. It was also found that even if a microbial inhibitor was present at a concentration that would cause the activity to be lost, it would proceed sufficiently. The present invention has been completed based on these findings.
[0010]
That is, the present invention provides (1) a method for treating polyphosphoric acid-containing wastewater, wherein the wastewater containing polyphosphoric acid is brought into contact with microorganisms under the conditions of pH 4.5 to 6.0 to decompose polyphosphoric acid. (2) The above-mentioned wastewater containing polyphosphoric acid contains organic matter in addition to polyphosphoric acid, and the wastewater is brought into contact with microorganisms under the condition of pH 4.5 to 6.0 to simultaneously decompose polyphosphoric acid and organic matter. (1) The treatment method of the wastewater containing polyphosphoric acid according to (1), (3) the first wastewater containing polyphosphoric acid and the second wastewater containing no organic material but containing organic matter are mixed. First, the first waste water is brought into contact with microorganisms under the condition of pH 4.5 to 6.0 to perform polyphosphoric acid decomposition treatment, and then the second waste water is added to the treated water after polyphosphoric acid decomposition treatment. Mix this A method for treating wastewater containing polyphosphoric acid, characterized by performing biological treatment in contact with living organisms and decomposing organic matter, and (4) containing polyphosphoric acid, and having the activity of microorganisms in addition to polyphosphoric acid In treating wastewater containing a concentration of microorganism-inhibiting substances that can be lost, the wastewater is brought into contact with microorganisms under the conditions of pH 4.5 to 6.0 without diluting the wastewater to decompose polyphosphoric acid. (5) wastewater containing polyphosphoric acid and microbial inhibitor contains organic matter in addition to these polyphosphoric acid and microbial inhibitor, and the wastewater is treated with pH 4.5. After the polyphosphoric acid is decomposed by contacting with microorganisms under the conditions of ˜6.0, the treated water after the decomposition treatment is diluted and the treated water is brought into contact with the microorganisms for biological treatment. (6) The polyphosphoric acid-containing wastewater treatment method described in (4) above, wherein the organic matter is decomposed, and (6) a multistage reaction tank having a plurality of partitioned reaction zones is used for the polyphosphoric acid decomposition treatment. (1), (2), (3), (4), or (5) the method for treating polyphosphoric acid-containing waste water according to the above, (7) after polyphosphoric acid decomposition treatment, or biological treatment The treatment of polyphosphoric acid-containing wastewater according to (1), (2), (3), (4), (5), or (6), wherein the treated water is subjected to agglomeration treatment and subjected to solid-liquid separation. The method is summarized.
[0011]
[Action]
The present inventors conducted the following experiment in order to examine whether the problem of the present invention can be solved by contacting the wastewater with microorganisms in any pH range.
[0012]
While adjusting the concentration of sodium pyrophosphate to 12.5 mg P / l, several types of test effluents with different pH were prepared, and the test effluent was treated by mixing activated sludge (microorganisms) into each test effluent. The treatment temperature at this time was set to 20 ° C., and the MLSS concentration was set to 2000 mgSS / l. The concentration of sodium pyrophosphate remaining in the test waste water after 120 minutes from the start of the treatment was measured to determine the hydrolysis rate for each pH. The results are shown graphically in FIG.
[0013]
From the above experimental results, when the pH of the test wastewater is neutral at around 7, the hydrolysis rate of polyphosphoric acid is extremely bad, and the pH of the test wastewater is 4.5 to 6.0, particularly 4.5 to 5.5. In this case, it was found that polyphosphoric acid can be efficiently hydrolyzed.
[0014]
On the other hand, when the activated sewage was not mixed in the test effluent and the pH of the test effluent was adjusted to 4.5 to 6.0 and left to stand, no change was observed in the concentration of polyphosphoric acid.
[0015]
From this, it is not possible to improve the hydrolysis rate of polyphosphoric acid simply by adjusting the pH, but it is confirmed that polyphosphoric acid is efficiently hydrolyzed by the action of microorganisms in a specific pH range. When it is less than 5 or when the pH exceeds 6.0, the function of the polyphosphate degrading enzyme possessed by the microorganism is lowered.
[0016]
In addition, when the experiment similar to the above was performed about the test waste_water | drain containing sodium tripolyphosphate, the result similar to the case of sodium pyrophosphate was obtained.
[0017]
As described above, in the present invention, polyphosphoric acid is efficiently hydrolyzed by bringing wastewater into contact with microorganisms under the condition of pH 4.5 to 6.0, and the subsequent aggregation treatment and the like can be performed satisfactorily. It will occur. Even if the polyphosphoric acid cannot be completely hydrolyzed, the concentration can be sufficiently reduced to such an extent that the aggregation treatment is not hindered. The range of the appropriate pH is widened, and there is no risk of hindering the subsequent treatment such as the aggregation treatment or the activated carbon adsorption treatment performed as necessary.
[0018]
In addition, the present inventors conducted the following experiment in order to examine the influence of the initial concentration of polyphosphoric acid on the hydrolysis rate of polyphosphoric acid.
[0019]
Test wastewater a containing sodium pyrophosphate at a concentration of 30 mgP / l and test wastewater b containing 10 mgP / l are adjusted to pH 5.5 and mixed with activated sludge (microorganisms). did. Both test effluents were treated under the same conditions except for the initial concentration of sodium pyrophosphate, and the concentration of sodium pyrophosphate with time was measured. The results are shown graphically in FIG.
[0020]
From the graph, it can be seen that the hydrolysis rate of sodium pyrophosphate increases as the initial concentration increases.
[0021]
That is, in comparison with the first 30 minutes after the start of the biological treatment, about 15 mg P / l sodium pyrophosphate is hydrolyzed in the test waste water a, whereas the test waste water b having a lower concentration than this has been hydrolyzed. Only about 7 mg P / l sodium pyrophosphate is hydrolyzed, and in test waste water b, it takes 90 minutes to hydrolyze 10 mg P / l sodium pyrophosphate, whereas test waste water a In that case, 10 mg P / l sodium pyrophosphate is hydrolyzed in about 20 minutes, and the time required to hydrolyze the same amount of sodium pyrophosphate is shorter as the initial concentration is higher.
[0022]
In addition, when the hydrolysis rate was examined by changing the concentration of sodium tripolyphosphate, it was confirmed that the same result as in the case of sodium pyrophosphate was obtained.
[0023]
Thus, when polyphosphoric acid is hydrolyzed to orthophosphoric acid, the hydrolysis reaction proceeds more efficiently as the initial concentration of polyphosphoric acid is higher. Based on this principle, when it is necessary to treat wastewater from a plurality of drainage systems, the present invention first treats wastewater containing polyphosphoric acid without mixing wastewater from each drainage system, and then treats this treated water with other wastewater. The waste water is mixed and processed. By doing in this way, the polyphosphoric acid in waste_water | drain is not diluted, but the initial concentration of polyphosphoric acid can be maintained high, As a result, polyphosphoric acid can be hydrolyzed more efficiently.
[0024]
Furthermore, the present inventors have determined that the presence of components other than polyphosphoric acid contained in the wastewater to be treated, particularly microbial inhibitory substances such as heavy metals and high-concentration salts, at such a level that the activity of the microorganisms is lost. In order to investigate how the activity of microorganisms affects the hydrolysis reaction of polyphosphoric acid, the following experiment was conducted.
[0025]
Test drainage c in which 200 mgP / l sodium pyrophosphate and 2% sodium chloride are dissolved in tap water is placed in an Erlenmeyer flask A, and test wastewater d in which 200 mgP / l sodium pyrophosphate and 20% sodium chloride is dissolved is taken in an Erlenmeyer flask B. After adding activated sludge to an MLSS concentration of about 2000 mgSS / l and adjusting the pH to 5, the mixture was stirred with a magnetic stirrer and the concentration of sodium orthophosphate generated by hydrolysis of sodium pyrophosphate was measured. The change in the concentration of sodium orthophosphate accompanying the test was determined. The results are shown graphically in FIG. The average decomposition rate of sodium pyrophosphate up to 3 hours after the start of the experiment (the formation rate of sodium orthophosphate is regarded as the hydrolysis rate of sodium pyrophosphate, the same applies hereinafter) is 0.50 gP / gSS / day for the test wastewater c. Yes, the test wastewater d was 0.35 gP / gSS / day.
[0026]
Three days later, the supernatants of the Erlenmeyer flasks A and B were discarded while leaving the activated sludge, and the test effluents c and d were newly added to each, and the change in the concentration of sodium orthophosphate was determined in the same manner as described above. The results are shown graphically in FIG. The average decomposition rate of sodium pyrophosphate for 3 hours after the start of the experiment was 0.53 gP / gSS / day for the test wastewater c and 0.26 gP / gSS / day for the test wastewater d.
[0027]
Subsequently, 8 days later, the activated sludge was left, the supernatants of the Erlenmeyer flasks A and B were discarded, and the test effluents c and d were again added to each, and the change in the concentration of sodium orthophosphate was similarly determined. The results are shown graphically in FIG. 3 (γ). The average decomposition rate of sodium pyrophosphate for 3 hours after the start of the experiment was 0.45 gP / gSS / day for the test wastewater c and 0.08 gP / gSS / day for the test wastewater d.
[0028]
In spite of no supply of organic matter for the growth and growth of activated sludge, the hydrolysis rate of sodium pyrophosphate was maintained at a substantially constant high value for 8 days in the test wastewater c (0.45). ˜0.53 gP / gSS / day). In addition, in the test wastewater d, the hydrolysis rate of sodium pyrophosphate on the first day of the experiment was 0.35 gP / gSS even under the high salt concentration condition where the activated sludge activity of 20% sodium chloride concentration cannot be maintained. It was found that the practical hydrolysis rate was maintained at 0.08 gP / gSS / day even on the 8th day of the experiment.
[0029]
It was confirmed that similar results were obtained with sodium tripolyphosphate.
[0030]
From the above, polyphosphoric acid is hydrolyzed regardless of the presence or absence of organic substances necessary for the growth and growth of microorganisms, a high hydrolysis rate can be maintained over a long period of time, and a high salt unsuitable for the growth and growth of microorganisms. Under the concentration conditions, it was found that the hydrolysis reaction of polyphosphoric acid proceeds sufficiently even if the activity of the microorganism is lost.
[0031]
From the above results, the present inventors show that the hydrolysis of polyphosphoric acid by microorganisms is carried out by the proliferation and metabolic action related to the biological activities of microorganisms, such as the decomposition of organic substances and the like by so-called biological treatment. Rather, the microorganism contains polyphosphate hydrolase, which is hydrolyzed by the action of this enzyme, so that the hydrolysis reaction of polyphosphate proceeds sufficiently even if the activity of the microorganism is lost. Think of things.
[0032]
The present invention treats wastewater as it is without diluting the wastewater based on the above knowledge when treating wastewater containing a microorganism-inhibiting substance at such a concentration that the activity of microorganisms is lost in addition to polyphosphoric acid. By such a method, the polyphosphoric acid density | concentration in waste_water | drain can be maintained at a high density | concentration, and a polyphosphoric acid can be hydrolyzed efficiently.
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 4 is a schematic diagram showing an example of an apparatus for carrying out the processing method of the present invention.
[0033]
In the figure, reference numeral 1 denotes a reaction tank for conducting a hydrolysis reaction of polyphosphoric acid, and wastewater to be treated is led from the inflow pipe 2 to the tank 1, and microorganisms necessary for hydrolysis pass through a microorganism supply line 3. Guided to the tank 1. Reference numeral 4 denotes a stirring device, which is configured so that the inside of the reaction tank 1 is stirred by the stirring device 4 so that the waste water sufficiently comes into contact with microorganisms in the tank 1.
[0034]
Examples of microorganisms that can be used in the present invention include activated sludge and biofilm sludge produced by sewage treatment, human waste treatment, industrial wastewater treatment, etc., sludge produced by anaerobic biological treatment, bacteria isolated from soil, and the like.
[0035]
As a means for causing microorganisms to be present in the reaction tank 1, a fixed bed type for fixing the microorganisms deposited on the microorganism-adhering carrier in the tank, or a fluidized bed type for allowing the microorganisms to flow in the tank, Or the floating type etc. which are made to float in a tank without making microorganisms settle on a microorganism adhesion carrier can be illustrated, but especially in the case of adopting a floating type in the present invention, a profit is large. In addition, as said microorganisms adhesion | attachment carrier, sand, gravel, crushed stone, various plastic moldings, fibrous activated carbon, granular activated carbon, spherical activated carbon, etc. are mentioned.
[0036]
Specific means for agitating the inside of the reaction tank 1 include mechanical agitation using a rotor blade, gas agitation in which a gas such as air, oxygen-enriched air, and nitrogen is blown into the tank 1, and drainage from the bottom of the tank 1 For example, countercurrent agitation or the like in which drainage is allowed to flow out from above the tank 1 or vice versa is exemplified.
[0037]
In the present invention, when the waste water comes into contact with microorganisms under the condition of pH 4.5 to 6.0, polyphosphoric acid contained therein is hydrolyzed to orthophosphoric acid.
[0038]
In the method of the present invention, the polyphosphoric acid decomposition treatment may be performed batchwise or continuously. In order to adjust the pH during the reaction, for example, a pH adjustment tank (not shown) is provided in the front stage of the reaction tank 1, and after adjusting the pH of the wastewater in the pH adjustment tank, the wastewater flows into the reaction tank 1. However, the pH adjusting tank can be omitted by using a line mixer or the like. In addition, in order to maintain the pH of the water in the reaction tank 1 within the above range, the pH may be directly adjusted in the reaction tank 1 as necessary.
[0039]
In carrying out the polyphosphate hydrolysis treatment in the present invention, the polyphosphate-SS load is preferably 0.04 to 0.6 gP / gSS / day, more preferably 0.1 to 0.4 gP / gSS / day. is there. Moreover, polyphosphoric acid volume load is 0.06-10 kgP / m. ^Three / Day, more preferably 0.2 to 4 kg P / m ^Three / Day.
[0040]
In addition, when the flow rate of the waste water to the reaction tank 1 is Q, the polyphosphoric acid concentration in the waste water is C, the reaction tank volume is V, and the MLSS concentration is X, the polyphosphoric acid-SS load is expressed by the following equation (1). The polyphosphoric acid volume load is given by the following equation (2).
[Expression 1]

[Expression 2]

[0041]
In the apparatus shown in FIG. 4, a precipitation tank 6 is connected to the subsequent stage of the reaction tank 1 via a line 5, and microorganisms flowing out from the reaction tank 1 are precipitated in the precipitation tank 8. Microorganisms do not lose their polyphosphate degradation performance in a single treatment, but can be used repeatedly until the polyphosphate degradation performance is lost. Some of the microorganisms precipitated in the sedimentation tank 6 pass through the line 7 to the reaction tank. 1 and the rest is discarded via line 8.
[0042]
In the figure, 9 is an outflow pipe for guiding the treated water from the precipitation tank 6 to the outside of the system, and the treated water after the polyphosphoric acid hydrolysis treatment is guided to the coagulating tank 16 as necessary. Reference numeral 17 denotes a line for guiding the treated water after the coagulation treatment to the outside of the coagulation tank 16.
[0043]
The wastewater led to the agglomeration tank 16 is agglomeration-precipitation system in which a flocculant such as a sulfuric acid band is added to agglomerate suspended matter in the wastewater, and then agglomerates are precipitated and separated and removed. Solid-liquid separation is performed by a pressurized flotation method in which a large number of bubbles are attached to the periphery of the object to float the aggregate and separate and remove the aggregate. At this time, since the polyphosphoric acid contained in the waste water has already been hydrolyzed to orthophosphoric acid, there is no problem of aggregation inhibition by polyphosphoric acid.
[0044]
In addition, in the case where the drainage does not contain any components to be removed other than polyphosphoric acid, the drainage after the polyphosphoric acid hydrolysis treatment may be discharged as it is unless there is a particular problem.
[0045]
The treatment method of the present invention can be applied to both organic wastewater containing organic substances in addition to polyphosphoric acid and inorganic wastewater not containing organic substances.
[0046]
In the case of treating inorganic wastewater, the microorganisms flowing out from the reaction tank 1 are preferably precipitated in the precipitation tank 6 and returned to the reaction tank 1. Furthermore, since the number of microorganisms having the ability to decompose polyphosphate gradually decreases because the microorganisms cannot be expected to grow and grow in the reaction tank 1 alone, it is necessary to supply microorganisms from the outside through the microorganism supply line 3. is there.
[0047]
The supply of microorganisms at this time may be continuous or intermittent. In addition, the supply source is not particularly limited. For example, when the method of the present invention is performed in a mode in which so-called biological treatment is performed after hydrolysis of polyphosphoric acid as described later, biological treatment is performed. May be supplied (see FIGS. 5 and 6), or other than equipment in which the method of the present invention is carried out (for example, biological treatment reaction in other equipment where biological treatment is performed). You may carry and supply from a tank etc.).
[0048]
In the case of treating organic wastewater, the reaction vessel 1 may be allowed to perform only the decomposition reaction of polyphosphoric acid, and the oxidative decomposition reaction of organic matter and the hydrolysis reaction of polyphosphoric acid are simultaneously performed by microorganisms. You may do it. At this time, even when the pH of the water in the reaction tank 1 is in the range of 4.5 to 6.0, there is almost no influence on the decomposition of organic matter.
[0049]
When the method of the present invention is applied to organic wastewater, since microorganisms grow in the reaction tank 1 due to the oxidative decomposition reaction of organic matter, only the microorganisms necessary for hydrolysis of polyphosphoric acid and oxidative decomposition of organic matter are present in the reaction tank 1 If present within, no external supply of microorganisms is required. In the treatment of organic waste water, when the organic matter is decomposed simultaneously with the decomposition of polyphosphoric acid in the reaction tank 1, it is necessary to supply oxygen necessary for oxidative decomposition to aerate the inside of the reaction tank 1.
[0050]
The method of the present invention can also be applied effectively when treating wastewater generated from a plurality of drainage systems.
[0051]
In hydrolyzing polyphosphoric acid contained in waste water by the treatment method of the present invention, as described above, the higher the initial concentration of polyphosphoric acid, the more efficiently the hydrolysis reaction proceeds. For this reason, when it is necessary to treat the wastewater generated from a plurality of drainage systems, first, the wastewater containing each of the drainage systems is treated, and the wastewater containing polyphosphoric acid is treated first, and then the treated water is treated with other treated water. It is preferable to perform treatment by mixing waste water.
[0052]
In this case as well, the present invention can be applied even if the polyphosphoric acid-containing wastewater to be treated is either organic wastewater or inorganic wastewater.
[0053]
In the above case, when there are two or more wastewaters containing polyphosphoric acid, the polyphosphoric acid-containing wastewaters may be mixed if the polyphosphoric acid concentrations are equal or the concentration difference is small.
[0054]
However, in the treatment of wastewater containing polyphosphoric acid by the method of the present invention, the concentration of polyphosphoric acid in the wastewater is preferably 10 mgP / l or more, more preferably 50 mgP / l or more. The hydrolysis reaction becomes more efficient. Further, the higher the concentration of polyphosphoric acid, the more efficiently the hydrolysis reaction proceeds, but the hydrolysis rate of polyphosphoric acid becomes substantially constant at 100 mg P / l or more. Taking this into consideration, whether or not to mix wastewater containing polyphosphoric acid depends on the decrease in hydrolysis efficiency due to dilution of wastewater containing high-concentration polyphosphoric acid with low concentration, and simplification of treatment by mixing (When not mixed, naturally, each polyphosphoric acid-containing wastewater must be treated separately).
[0055]
Thus, when processing the waste_water | drain produced from a some drainage system, in this invention, after giving a polyphosphoric acid hydrolysis process to the 1st waste_water | drain containing polyphosphoric acid, it does not contain the polyphosphoric acid to this. The waste water can be mixed and subjected to a predetermined treatment, for example, to decompose the organic matter when the treated water after the polyphosphoric acid hydrolysis treatment and / or the waste water mixed therewith contains organic matter. Biological treatment is applied.
[0056]
Even when other wastewater is mixed into the treated water after polyphosphoric acid hydrolysis treatment, immediately after the polyphosphoric acid hydrolysis treatment is performed on the polyphosphoric acid-containing wastewater, after the polyphosphoric acid hydrolysis treatment, It may be after performing one or more post-treatments.
[0057]
Specific example in which biological treatment is performed by mixing the first waste water containing polyphosphoric acid with the treated waste water after the polyphosphoric acid decomposition treatment and the second waste water containing no organic material but containing polyphosphoric acid A typical processing operation will be described below with reference to FIG.
[0058]
The first waste water is led from the inflow pipe 2 to the reaction tank 1 and is subjected to polyphosphoric acid decomposition treatment by contacting with microorganisms in the tank 1 under the condition of pH 4.5 to 6.0. Hydrolyzed to acid. At this time, the waste water led to the reaction tank 1 is stirred by the stirring device 4 so as to be in sufficient contact with the microorganisms.
[0059]
Subsequently, the treated water subjected to the polyphosphoric acid decomposition treatment is led from the reaction tank 1 to the biological treatment reaction tank 11 via the line 9. At this time, the second waste water flows from the inflow line 10 connected to the line 9 and is mixed with the treated water after the polyphosphoric acid decomposition treatment.
[0060]
The treated water introduced into the biological treatment reaction tank 11 is subjected to biological treatment in the presence of microorganisms to decompose organic matter. A predetermined concentration of microorganisms is maintained in the biological treatment reaction tank 11. In the biological treatment in the biological treatment reaction tank 11, it is not necessary to maintain the pH of the water in the tank in the range of 4.5 to 6.0 unlike the reaction tank 1, and it is optimal for biological treatment. There is an advantage that it can be carried out under various pH conditions (pH 6 to 8). In the figure, 12 is an air introduction tube for supplying oxygen necessary for biological treatment, and 13 is an air diffuser.
[0061]
The treated water subjected to the biological treatment is led to the sedimentation tank 6 'via the line 14, and the microorganisms flowing out from the biological treatment reaction tank 11 are precipitated in the sedimentation tank 6'. A part of the microorganisms precipitated in the settling tank 6 'is distributed and returned to the reaction tank 1 and the biological treatment reaction tank 11 via the line 7', and the rest is discarded via the line 8 '. The microorganisms from the sedimentation tank 6 ′ may be returned only to the reaction tank 1, and the microorganisms may be introduced into the biological treatment reaction tank 11 via the reaction tank 1, in which case the reaction is performed. It is not particularly necessary to return the microorganisms to the tank 11.
[0062]
The wastewater that has been subjected to these treatments is discharged through the outflow pipe 15, or is further guided to another treatment tank to which other post-treatment such as agglomeration treatment is performed, and then discharged. In the present invention, the other wastewater separated from the polyphosphoric acid-containing wastewater is treated separately from the polyphosphoric acid-containing wastewater, and the polyphosphoric acid-containing wastewater is subjected to polyphosphoric acid decomposition treatment. It is also possible to discharge later or to carry out predetermined post-treatment alone.
[0063]
In addition, the method of the present invention can be used when the polyphosphoric acid-containing wastewater to be treated contains, in addition to polyphosphoric acid, a microbial inhibitory substance at such a concentration that the activity of the microorganism is lost. It can also be applied effectively when salts such as sodium chloride are contained.
[0064]
Therefore, it is not necessary to reduce the salt concentration to a concentration of 2% or less, for example, so that the activity of microorganisms is not lost. Thus, the polyphosphoric acid hydrolysis treatment can be performed efficiently.
[0065]
However, even if the microorganisms are killed and their biological activity is lost, the polyphosphate degradation performance is not lost by a single treatment and can be used repeatedly after death, but it exhibits polyphosphate degradation performance permanently. However, it is necessary to newly supply the microorganism to the reaction tank 1 at an appropriate time.
[0066]
In addition to polyphosphoric acid, in addition to this polyphosphoric acid, a microbial inhibitory substance at a concentration that can lose the activity of microorganisms, for example, high-concentration salts and polyphosphoric acid-containing wastewater (treated wastewater) containing organic matter, A specific processing operation in the case of processing in will be described below with reference to FIG.
[0067]
The treated waste water is led from the inflow pipe 2 to the reaction tank 1 and is subjected to polyphosphoric acid hydrolysis treatment by contacting with microorganisms in the tank 1 under the condition of pH 4.5 to 6.0. At this time, the waste water in the reaction tank 1 is stirred by the stirring device 4 in the same manner as shown in FIGS.
[0068]
Next, the treated water subjected to the polyphosphoric acid hydrolysis treatment is guided to the sedimentation tank 6 through the line 5, and the microorganisms flowing out of the reaction tank 1 together with the treated water are precipitated in the sedimentation tank 6, and a part thereof is the line 7. Is returned to the reaction tank 1 and the rest is discarded via the line 8.
[0069]
The steps so far are substantially the same as the case of carrying out the method of the present invention in the embodiment described with reference to FIG. 4, but in this specific example, the precipitation tank 6 may not be provided. In addition, since the treated wastewater contains high-concentration salts, the microorganisms in the reaction tank 1 lose their activity, and the treated wastewater contains organic matter, but its oxidative decomposition does not occur, and the growth and growth of microorganisms are also expected. Can not. For this reason, as will be described later, the microorganisms grown by biological treatment are supplied to the reaction tank 1 so as to secure enough microorganisms for the polyphosphate decomposition treatment.
[0070]
Next, the treated water is led from the sedimentation tank 6 to the biological treatment reaction tank 11 via the line 9. At this time, the tap water or polyphosphoric acid-free salt from the inflow line 10 connected to the line 9 is contained. Dilute the treated water after polyphosphoric acid decomposition treatment by injecting other waste water with low concentration. The treated water still contains high-concentration salts. If the treated water is introduced into the biological treatment reaction tank 11 as it is, the microorganisms in the reaction tank 11 will be killed. This is because the salt concentration is lowered so that the activity of the microorganism is not lost.
[0071]
The treated water led to the biological treatment reaction tank 11 is subjected to biological treatment. In the biological treatment reaction tank 11, a predetermined concentration of microorganisms is maintained as in the case described above. In the figure, 12 and 13 are an air introduction tube and an air diffusion tube for supplying oxygen necessary for biological treatment, respectively, similarly to the case shown in FIG. In this case as well, the biological treatment in the biological treatment reaction tank 11 can be performed under optimum pH conditions for biological treatment regardless of the pH conditions of the reaction tank 1.
[0072]
The treated water subjected to the biological treatment is led to the sedimentation tank 6 'via the line 14, and the microorganisms flowing out from the biological treatment reaction tank 11 are precipitated in the sedimentation tank 6'. A part of the microorganisms precipitated in the settling tank 6 'is distributed and returned to the reaction tank 1 and the biological treatment reaction tank 11 via the line 7', and the rest is discarded via the line 8 '.
[0073]
The wastewater that has been subjected to these treatments is discharged through the outflow pipe 15, or is further guided to another treatment tank to which other post-treatment such as agglomeration treatment is performed, and then discharged.
[0074]
In the present invention carried out as described above, polyphosphoric acid hydrolysis treatment is performed using a multistage reaction tank 1 having a plurality of partitioned

reaction zones

1a, 1b, 1c and 1d as shown in FIG. Is preferred. In order to form a plurality of partitioned

reaction zones

1a, 1b, 1c, and 1d in the reaction tank 1, a plurality of partition plates 18 are provided in the tank.
[0075]
When the polyphosphoric acid hydrolysis treatment is performed using the reaction tank 1 configured as described above, the polyphosphoric acid can be hydrolyzed more efficiently than in the case of using a normal reaction tank in which the partition plate 18 is not provided. .
[0076]
That is, as described above, since the hydrolysis rate of polyphosphoric acid is higher as the initial concentration of polyphosphoric acid is higher, the hydrolysis rate of polyphosphoric acid in the first reaction zone 1a in the reaction tank 1 shown in FIG. The speed is the highest compared to the reaction zone. That is, the presence of the partition plate 18 causes the polyphosphoric acid-containing wastewater that has flowed into the tank from the inflow pipe 2 not to be immediately diffused into the tank, but as a whole becomes almost plug flow, so that the concentration of polyphosphoric acid in the wastewater is reduced. Also, since the uniform dilution of the entire tank is not performed, the polyphosphoric acid concentration is highest in the reaction zone 1a. Therefore, the hydrolysis rate of polyphosphoric acid in the reaction zone 1a is the highest as compared with other reaction zones.
[0077]
Since the reaction zones communicate with each other, the water to be treated that has been hydrolyzed to some extent in the first reaction zone 1a sequentially flows to the

reaction zones

1b, 1c, and 1d. Since the polyphosphoric acid concentration in the water to be treated becomes thinner as the reaction zone is in the latter stage, the hydrolysis rate of polyphosphoric acid is also gradually reduced accordingly. However, for example, in the second reaction zone 1b, the concentration of polyphosphoric acid is higher and the rate of hydrolysis of polyphosphoric acid is higher than in the case of the reaction tank without the partition plate 18. When the partition plate 18 is not provided in the reaction tank, the wastewater that has flowed into the tank is almost uniformly diffused, so that the polyphosphoric acid concentration is diluted and the hydrolysis rate of the polyphosphoric acid is also reduced as a whole.
[0078]
When the partition plate 18 is provided in the reaction tank, a hydrolysis speed gradient is generated between the reaction zones. However, since a high hydrolysis rate is obtained in the first reaction zone, as compared with the case where the partition plate 18 is not provided as a whole. Also, the hydrolysis rate of polyphosphoric acid increases.
[0079]
The specific configuration of the multistage reaction vessel 1 preferably used in the present invention is not limited to that shown in the figure, and the polyphosphoric acid decomposition treatment is performed stepwise so that the influent wastewater does not immediately diffuse throughout the reaction vessel. Anything is possible. The reaction tank 1 may be partitioned into at least two reaction zones, but is preferably partitioned into three or more reaction zones in order to improve the hydrolysis efficiency of polyphosphoric acid. In addition, what is necessary is just to partition a biological treatment reaction tank into two or more, when performing the decomposition process of polyphosphoric acid, and decomposition | disassembly of organic substance simultaneously.
[0080]
【Example】
Next, the present invention will be described in more detail with specific examples.
[0081]
Example 1
The test wastewater containing sodium pyrophosphate at a concentration of 12.5 mg P / l was adjusted to a pH of 5 in a floating biological treatment reaction tank in which the treatment temperature was set to 20 ° C. and MLSS was set to 2000 mg SS / l. And the biological treatment was conducted for 120 minutes, and the obtained treated water was led to a flocculation treatment tank, where the flocculation treatment was carried out with various pH changes. In the aggregation treatment, the sulfuric acid band and the polymer aggregation assistant were added at concentrations of 200 mg / l and 1 mg / l, respectively. After the flocculation treatment, the turbidity of the supernatant water as the treated water was measured. FIG. 7 is a graph showing the turbidity of the treated water (flocculated water) after the flocculation treatment relative to the pH during the flocculation treatment.
[0082]
Comparative Example 1
Aggregation treatment was performed in the same manner as in Example 1 except that the pH of the water in the tank was adjusted to 6.5. FIG. 8 is a graph showing the turbidity of the treated water after the coagulation treatment relative to the pH during the coagulation treatment.
[0083]
In Comparative Example 1 described above, when the pH during the flocculation treatment is 5 or less, the turbidity is 1 or less (the turbidity of the biologically treated water before the flocculation treatment was about 20 degrees), and the flocculation treatment can be performed satisfactorily. However, when the pH during the agglomeration treatment was 5 or more, the turbidity was about 20 and a good agglomeration treatment was not performed. On the other hand, in Example 1, the turbidity was 1 or less even when the pH during the agglomeration treatment was 5 or more, and a good agglomeration treatment could be performed.
[0084]
In addition, when the density | concentration of the sodium pyrophosphate which remains in the aggregation processing water of Example 1 and Comparative Example 1 was measured, although sodium pyrophosphate was hardly detected in the aggregation processing water of Example 1, In the agglomerated water, sodium pyrophosphate remained at a concentration of 3 mg P / l.
[0085]
【The invention's effect】
As described above, according to the present invention, polyphosphoric acid is efficiently hydrolyzed by bringing wastewater containing polyphosphoric acid into contact with microorganisms under conditions of pH 4.5 to 6.0, and the wastewater has a relatively high concentration. Even when the polyphosphoric acid is contained, the aggregating treatment can be performed without any trouble. In addition, according to the present invention, there is an advantage that the optimum pH range for aggregation is wide when the treated water after the treatment is subjected to agglomeration treatment, the treatment becomes easy, and in the subsequent stage such as activated carbon adsorption treatment performed as necessary. There is no risk of disturbing the processing. Furthermore, in the present invention, the wastewater to be treated does not need to contain organic substances necessary for the growth and growth of microorganisms, so that a wide range of correspondence is possible.
[0086]
Further, when polyphosphoric acid is hydrolyzed, the hydrolysis reaction proceeds more efficiently as the initial concentration of polyphosphoric acid is higher. Therefore, when it is necessary to treat wastewater generated from a plurality of drainage systems, as in the present invention, By mixing the wastewater generated from each drainage system, the wastewater containing polyphosphoric acid is first treated, and then the other wastewater is mixed with this treated water for treatment. Is not diluted, whereby the initial concentration of polyphosphoric acid can be kept high, and polyphosphoric acid can be hydrolyzed more efficiently.
[0087]
Further, the present invention, in treating wastewater containing a concentration of microbial inhibitors other than polyphosphoric acid to a degree that causes loss of microorganisms, for example, wastewater containing high concentrations of salts, without diluting the wastewater, Since the treatment is performed as it is, the polyphosphoric acid concentration can be maintained at a high concentration and the polyphosphoric acid hydrolysis treatment can be efficiently performed without causing a decrease in the treatment efficiency.
[0088]
Furthermore, when the present invention is carried out, polyphosphoric acid decomposition treatment is performed in a multistage reaction tank having a plurality of partitioned reaction zones, thereby enabling more efficient hydrolysis of polyphosphoric acid.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the pH of waste water and the hydrolysis rate of polyphosphoric acid.
FIG. 2 is a graph showing the relationship between sodium pyrophosphate concentration and hydrolysis rate.
FIG. 3 is a graph showing the relationship between the hydrolysis rate of sodium pyrophosphate and the concentration of salts contained in the treated waste water.
FIG. 4 is a schematic diagram showing an example of an apparatus for carrying out the processing method of the present invention.
FIG. 5 is a schematic view showing another example of an apparatus for carrying out the processing method of the present invention.
FIG. 6 is a schematic diagram showing another example of an apparatus for carrying out the processing method of the present invention.
FIG. 7 is a schematic diagram showing a preferred embodiment of a reaction vessel used in the present invention.
8 is a graph showing the results of Example 1 and Comparative Example 1. FIG.
[Explanation of symbols]
1 reaction tank
1a, 1b, 1c, 1d reaction zone
11 Biological treatment reactor
16 Coagulation tank

Claims

A method for treating polyphosphoric acid-containing wastewater, wherein the wastewater containing polyphosphoric acid is brought into contact with microorganisms under conditions of pH 4.5 to 6.0 to decompose polyphosphoric acid.

The wastewater containing polyphosphoric acid contains organic matter in addition to polyphosphoric acid, and the wastewater is brought into contact with microorganisms under the condition of pH 4.5 to 6.0 to simultaneously decompose polyphosphoric acid and organic matter. Treatment method for waste water containing polyphosphoric acid.

In the treatment of the first wastewater containing polyphosphoric acid and the second wastewater containing no polyphosphoric acid and containing organic matter, the first wastewater is first adjusted to pH 4.5 to 6 without mixing these wastewaters. The polyphosphoric acid is decomposed by contacting with microorganisms under the condition of 0.0, and then the second waste water is mixed with the treated water after the polyphosphoric acid decomposing treatment and brought into contact with the microorganisms for biological treatment A method for treating drainage containing polyphosphoric acid, characterized in that the organic matter is decomposed.

When treating wastewater containing polyphosphoric acid and containing a microbial inhibitor in a concentration other than the polyphosphoric acid, the pH of the wastewater is adjusted to 4.5 to 6 without diluting the wastewater. A method for treating polyphosphoric acid-containing wastewater, comprising decomposing polyphosphoric acid by contacting with microorganisms under the conditions of 0.0.

The wastewater containing polyphosphoric acid and microbial inhibitor contains organic substances in addition to these polyphosphoric acid and microbial inhibitor, and the wastewater is brought into contact with microorganisms under the condition of pH 4.5 to 6.0 to decompose polyphosphoric acid. 5. The method for treating polyphosphoric acid-containing wastewater according to claim 4, wherein the treated water after the decomposition treatment is diluted, the treated water is brought into contact with microorganisms to perform biological treatment, and the organic matter is decomposed.

The method for treating polyphosphoric acid-containing wastewater according to claim 1, wherein the polyphosphoric acid is decomposed using a multistage reaction tank having a plurality of partitioned reaction zones. .

The polyphosphoric acid-containing wastewater according to claim 1, 2, 3, 4, 5, or 6, wherein the treated water after the polyphosphoric acid decomposition treatment or the biological treatment is subjected to a flocculation treatment for solid-liquid separation. Processing method.