JP4862209B2

JP4862209B2 - Organic drainage treatment method and apparatus

Info

Publication number: JP4862209B2
Application number: JP2000045156A
Authority: JP
Inventors: ラジブゴエル; 英斉安井
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2000-02-17
Filing date: 2000-02-17
Publication date: 2012-01-25
Anticipated expiration: 2020-02-17
Also published as: JP2001225090A

Description

【０００１】
【発明の属する技術分野】
本発明は、有機性排液を活性汚泥の存在下に生物処理する方法および装置、特に活性汚泥処理系における余剰汚泥を減容化することができる有機性排液の処理方法および装置に関する。
【０００２】
【従来の技術】
活性汚泥処理法などのように、好気性微生物の作用を利用して有機性排液を好気条件で処理する好気性生物処理方法は、処理コストが安く、処理性能も優れているため、一般に広く利用されているが、難脱水性の余剰汚泥が大量に生成する。このため汚泥を減容化する処理方法が注目されている。
【０００３】
このような汚泥の減容化を行う処理方法として、曝気槽または沈殿槽から汚泥を引き抜き、この引抜汚泥をオゾン処理、加熱処理、酸またはアルカリ処理等の改質処理により易生物分解性に改質し、改質された汚泥を曝気槽に返送して生物分解させる方法が提案されている（例えば、特開平６−２０６０８８号）。
【０００４】
図４は、特開平６−２０６０８８号に記載されている有機性排液の処理方法を示すフローシートであり、４１は曝気槽、４２は汚泥分離槽、４３はオゾン処理槽である。
図４の処理方法では、曝気槽４１に有機性排液４４および返送汚泥４５を導入するとともに、オゾン処理汚泥４６を導入し、曝気槽４１内の活性汚泥と混合し、空気供給管４７から空気を送り散気装置４８から散気して好気性生物処理を行う。
【０００５】
曝気槽４１の槽内液は一部ずつ取出して汚泥分離槽４２に導入し、分離液と分離汚泥５１とに分離する。分離液は処理液５０として系外へ排出し、分離汚泥５１は一部を返送汚泥４５として曝気槽４１に返送し、他の一部を引抜汚泥５３としてオゾン処理槽４３に導入してオゾン処理し、残部を余剰汚泥５４として系外に排出する。引抜汚泥５３はオゾン処理槽４３に導入し、オゾン供給管５５からオゾンを供給してオゾンと接触させ、汚泥を酸化分解して易生物分解有機物に変換する。オゾン排ガスは排オゾン管５６から排出し、オゾン処理汚泥４６は曝気槽４１に戻して前記のように好気性生物処理を行う。
【０００６】
上記図４の従来の方法では、引抜汚泥５３を易生物分解性に改質して曝気槽４１に返送することにより、易生物分解性となった改質汚泥が曝気槽４１内の微生物に資化されるので、生成する汚泥量が減少する。この場合被処理ＢＯＤから生成する汚泥量よりも多い量の引抜汚泥５３を改質して返送すると、系外へ排出する余剰汚泥を実質的にゼロにすることができる。
【０００７】
しかし、上記従来の方法では、系外へ排出する余剰汚泥をゼロにするためには、通常、生成する汚泥量の３〜４倍程度の多量の汚泥を引抜汚泥としてオゾン処理する必要がある。これは、オゾン処理により易生物分解有機物に変換された汚泥が曝気槽に戻されて好気性生物処理される工程で、オゾン処理により生成した易生物分解有機物の３０〜４０％が再び汚泥に転換するためである。このためオゾン処理には多量のオゾン、薬品、エネルギーなどが必要となり、コスト高になる。また多量の汚泥を引き抜いてオゾン処理すると、オゾン処理により活性な微生物が失活して好気性生物処理に必要な微生物量を曝気槽内に確保できないため、ＳＲＴが短くなり、このため処理水質が悪化したり、処理効率が低下しやすいという問題点もある。
【０００８】
【発明が解決しようとする課題】
本発明の課題は、低コストで汚泥を減容化して系外へ排出する汚泥量を減少させることができ、しかも処理水質の悪化を防止し、かつ効率よく有機性排液を処理することができる有機性排液の処理方法および装置を提供することである。
【０００９】
【課題を解決するための手段】
本発明は、次の有機性排液の処理方法および装置である。
（１）有機性排液を曝気槽に導入して、活性汚泥の存在下に好気性生物処理する好気性生物処理工程、
前記曝気槽の混合液を分離汚泥と分離液とに固液分離し、分離汚泥の少なくとも一部を前記曝気槽に返送し、分離液を処理水として排出する第１の固液分離工程、
第１の固液分離工程で分離した分離汚泥または前記曝気槽の混合液から活性汚泥の少なくとも一部を引き抜き、この引抜汚泥にオゾンを０．００２〜０．０５ｇ−Ｏ₃／ｇ−ＶＳＳで添加してオゾン処理により、易生物分解性に改質する改質処理工程、
改質処理工程で改質した改質処理汚泥を膜分離装置により、改質分離汚泥と改質分離液とに固液分離する第２の固液分離工程、
第２の固液分離工程で分離した改質分離汚泥を改質処理工程に移送する改質分離汚泥移送工程、および
第２の固液分離工程で分離した改質分離液を前記好気性生物処理工程の前記曝気槽に返送する改質分離液返送工程を含み、
前記好気性生物処理工程では、前記第１の固液分離工程から返送される返送汚泥、および前記改質分離液返送工程から返送される改質分離液を混合して好気性生物処理し、
前記改質処理工程では、前記改質分離汚泥移送工程から移送される改質分離汚泥を易生物分解性に改質する
ことを特徴とする有機性排液の処理方法。
（２）有機性排液を曝気槽に導入して、活性汚泥の存在下に好気性生物処理する好気性生物処理装置、
前記曝気槽の混合液を分離汚泥と分離液とに固液分離し、分離汚泥の少なくとも一部を前記曝気槽に返送し、分離液を処理水として排出する第１の固液分離装置、
第１の固液分離装置で分離した分離汚泥または前記曝気槽の混合液から活性汚泥の少なくとも一部を引き抜き、この引抜汚泥にオゾンを０．００２〜０．０５ｇ−Ｏ₃／ｇ−ＶＳＳで添加するオゾン処理により、易生物分解性に改質する改質処理装置、
改質処理装置で改質した改質処理汚泥を膜分離装置により、改質分離汚泥と改質分離液とに固液分離する第２の固液分離装置、
第２の固液分離装置で分離した改質分離汚泥を改質処理装置に移送する改質分離汚泥移送装置、および
第２の固液分離装置で分離した改質分離液を前記好気性生物処理装置の前記曝気槽に返送する改質分離液返送装置を含み、
前記好気性生物処理装置は、前記第１の固液分離装置から返送される返送汚泥、および前記改質分離液返送装置から返送される改質分離液を混合して好気性生物処理するように構成され、
前記改質処理装置は、前記改質分離汚泥移送装置から移送される改質分離汚泥を易生物分解性に改質するように構成されている
ことを特徴とする有機性排液の処理装置。
【００１０】
本発明の課題を達成するため鋭意研究した結果、次のことがわかった。すなわち、オゾン処理などの改質処理を採用した従来の有機性排水処理方法では、改質処理した汚泥を固液分離することなく全量を曝気槽に返送しているため、有機物の好気性生物処理に寄与しない活性のなくなった汚泥（不活性汚泥）も曝気槽に返送されている。この不活性汚泥は好気性生物処理では分解されにくいため、このような不活性汚泥が曝気槽に蓄積され、次のような問題点が生じている。
【００１１】
１）曝気槽に活性な微生物からなる汚泥（活性微生物汚泥）と不活性汚泥の両方が混合しており、これらを分離することは不可能である。
２）曝気槽に不活性汚泥が蓄積するため、曝気槽の汚泥濃度が高くなり、後工程での固液分離の効率が低下する（曝気槽の汚泥濃度が高くなると沈殿しにくくなる）。
３）多くの汚泥を引き抜いて改質処理するため、改質処理を行わない場合に比べてＳＲＴが短くなる。例えば、余剰汚泥の発生をゼロにするために、１日に発生する生物汚泥の３〜４倍の汚泥を引き抜いて改質処理する場合、ＳＲＴは改質処理を行わない場合の１／３〜１／４程度になる。
【００１２】
本発明においては、改質処理汚泥を固液分離し、この改質分離汚泥は再び改質処理し、改質分離液のみ曝気槽に返送することにより上記問題点を解決し、本発明の課題を達成することができる。
【００１３】
本発明において処理の対象となる有機性排液は、通常の好気性生物処理法により処理される有機物を含有する排液であるが、難生物分解性の有機物または無機物が含有されていてもよく、またアンモニア性窒素等が含有されていてもよい。このような有機性排液としては、下水、し尿、食品工場排水その他の産業排液などがあげられる。
【００１４】
本発明における好気性生物処理工程は、有機性排液を曝気槽に導入して、活性汚泥の存在下に好気性生物処理を行うように構成される。また第１の固液分離工程は曝気槽から混合液（槽内液）を第１の固液分離装置に導いて分離汚泥と分離液とに固液分離し、分離汚泥の少なくとも一部を曝気槽へ返送し、分離液を処理水として排出するように構成される。このような処理系および処理装置としては、有機性排液を曝気槽で活性汚泥と混合して曝気し、混合液を固液分離装置において固液分離し、分離汚泥の一部を曝気槽に返送する標準活性汚泥処理法における好気性生物処理および処理装置が一般的であるが、これを変形した他のものでもよい。
【００１５】
改質処理工程は上記の好気性生物処理における処理系からの活性汚泥（生物汚泥）の少なくとも一部を引き抜き、この引抜汚泥を易生物分解性に改質するとともに、後工程の改質分離汚泥移送工程から移送される改質分離汚泥を易生物分解性に改質する工程である。生物汚泥を引き抜く場合、第１の固液分離工程で分離された分離汚泥の一部を引き抜くのが好ましいが、曝気槽から混合液の状態で引き抜いてもよい。分離汚泥から引き抜く場合、余剰汚泥として排出される部分の一部または全部を引抜汚泥として引き抜くことができるが、余剰汚泥に加えて、返送汚泥として曝気槽に返送される返送汚泥の一部をさらに引き抜いて改質処理することもできる。この場合系外に排出する余剰汚泥の発生量をより少なくし、場合によってはゼロにすることができる。引抜汚泥と改質分離汚泥とは同じ改質処理装置で改質処理することもできるし、別々の改質処理装置で改質処理することもできる。
【００１６】
なお、本発明では被処理液中の有機物が微生物により資化されて生成される生物汚泥を生成汚泥、第１の固液分離装置で処理液と分離されて得られる汚泥を分離汚泥、第１の固液分離装置から曝気槽に返送される分離汚泥の一部を返送汚泥、改質処理されるために曝気槽または固液分離装置から引き抜かれる汚泥を引抜汚泥、改質処理がなされた汚泥を改質処理汚泥、改質処理汚泥が第２の固液分離装置で分離されて得られる汚泥を改質分離汚泥、この時得られる分離液を改質分離液、好気性生物処理系外へ排出される汚泥を余剰汚泥、活性な微生物からなる活性汚泥を活性微生物汚泥、活性を失った微生物からなる汚泥を不活性汚泥と称する。
【００１７】
引抜汚泥を生物が分解し易い性状に改質する改質処理方法としては、オゾン処理による改質処理を採用する。この処理は公知の処理装置を改質処理装置として用いて行うことができる。オゾン処理による改質処理は、処理操作が簡単かつ処理効率が高いため好ましい。
【００１８】
改質処理としてのオゾン処理は、引抜汚泥または改質分離汚泥移送工程から移送される改質分離汚泥をオゾンと接触させればよく、オゾンの酸化作用により汚泥は易生物分解性に改質される。オゾン処理により生物汚泥は酸化分解されて、易生物分解有機物に変換される。本発明の場合、後工程に第２の固液分離工程を設けているので、汚泥を完全に易生物分解性に改質する必要はなく、不活性汚泥が残留してもかまわない。
オゾン処理はｐＨ５以下の酸性領域で行うと酸化分解効率が高くなる。このときのｐＨの調整は、硫酸、塩酸または硝酸などの無機酸をｐＨ調整剤として生物汚泥に添加する方法などを採用することができる。ｐＨ調整剤を添加する場合、ｐＨは３〜４に調整するのが好ましい。
【００１９】
オゾン処理は、引抜汚泥または改質分離汚泥をそのまま、または必要により遠心分離機などで濃縮した後、オゾンと接触させることにより行うことができる。接触方法としては、オゾン処理槽に汚泥を導入してオゾンを吹込む方法、機械撹拌による方法、充填層を利用する方法などが採用できる。オゾンとしては、オゾンガスの他、オゾン含有空気、オゾン化空気などのオゾン含有ガスが使用できる。オゾンの使用量は０．００２〜０．０５ｇ−Ｏ₃／ｇ−ＶＳＳ、好ましくは０．００５〜０．０３ｇ−Ｏ₃／ｇ−ＶＳＳとするのが望ましい。オゾン処理により難生物分解性のＣＯＤが生成する場合があるが、この場合は凝集処理、吸着等により除去することができる。
【００２４】
改質処理は１個の改質処理装置を用いて行うこともできるし、２個以上の改質処理装置を用いて行うこともできる。好ましくは２〜３個の改質処理装置を用いて行うのが望ましい。２個以上改質処理装置を用いる場合、装置は固液分離装置に対して直列に設けることもできるし、並列に設けることもできる。
【００２５】
第２の固液分離工程は改質処理工程で改質した改質処理汚泥を第２の固液分離装置に導いて改質分離汚泥と改質分離液とに固液分離する工程である。第２の固液分離工程で使用される固液分離装置は、膜分離装置を用いることができる。膜分離を利用する場合は、中空糸、チューブラー、平膜などの種々の膜形式が利用できる。また膜分離は固形物を分離することが目的であるため、ＭＦ、ＵＦなどの比較的大きなポアサイズを有する膜が好ましい。
【００２６】
改質分離汚泥移送工程は第２の固液分離工程で分離された改質分離汚泥を改質処理工程に移送する工程である。改質処理工程に２個以上の改質処理装置が設けてある場合、任意の位置の改質処理装置に移送することができ、また複数の改質処理装置に移送することもできる。本発明では、運転操作を簡便にし、また改質処理効率を向上させるため、引抜汚泥を改質処理する改質処理装置とは別の改質処理装置に移送するのが好ましい。
【００２７】
例えば、改質処理工程に２個の改質処理装置が固液分離装置に対して直列に設けてある場合は、引抜汚泥は前段の改質処理装置に導入して改質処理し、改質分離汚泥は後段の改質処理装置に移送して改質処理するのが好ましい。この場合、前段の改質処理装置で改質した汚泥はそのまま後段の改質処理装置に導入し、改質分離汚泥と混合して改質処理する。しかし、改質処理工程に２個の改質処理装置を固液分離装置に対して並列に設けて、一方の改質処理装置に引抜汚泥を導入して改質処理し、他方の改質処理装置に改質分離汚泥を移送して別々に改質処理する方が好ましい。
【００２８】
改質分離液返送工程は第２の固液分離工程で分離された改質分離液を前記好気性生物処理工程の前記曝気槽に返送する工程である。曝気槽に導入した改質分離液は、有機性排液および槽内の活性汚泥と混合されて好気性生物処理されるが、改質分離液は改質分離汚泥が分離され固形分を含んでいないので、曝気槽に不活性汚泥は導入されない。このため、曝気槽に不活性汚泥が蓄積することもない。
【００２９】
本発明の処理方法は、改質処理した汚泥の全量を曝気槽に返送している従来の方法に比べて、次の点で優れている。
１）引抜汚泥を確実に減容化することができるので、改質処理するために分離汚泥または曝気槽の混合液から引き抜く汚泥量を少なくすることができる。例えば、従来の方法では通常、生成する汚泥量の３〜４倍程度の汚泥を引抜汚泥としてオゾン処理することにより系外へ排出する余剰汚泥をゼロにすることができるが、本発明では生成汚泥量の２〜２．５倍程度の汚泥を引抜汚泥としてオゾン処理することにより、系外へ排出する余剰汚泥をゼロにすることができる。このため、多くの量の活性微生物汚泥を曝気槽内に保持することができる。これにより曝気槽のＳＲＴを長くすることができるので、処理水質の悪化を防止することができ、かつ効率よく有機性排水を好気性生物処理することができる。
２）分解を受けにくい改質処理汚泥中の固形分（改質分離汚泥）を繰り返し改質処理することで改質分離汚泥が分解されやすくなり、例えばオゾン使用量を少なくすることができる。
３）曝気槽内の不活性汚泥の量が少なくなるので、曝気槽内の汚泥濃度（活性微生物汚泥と不活性汚泥との合計濃度）が低くなり、このため第１の固液分離工程での固液分離が容易になる。
４）活性微生物汚泥と不活性汚泥とを分離した状態で好気性生物処理および改質処理を行うことができる。
【００３０】
【発明の効果】
本発明の有機性排液の処理方法は、好気性生物処理工程の曝気槽に有機性排液を導入し、返送汚泥および改質分離液と混合して好気性生物処理を行い、第１の固液分離工程で分離した分離汚泥または前記曝気槽の混合液から活性汚泥の少なくとも一部を引き抜き、改質処理工程でオゾンを０．００２〜０．０５ｇ−Ｏ₃／ｇ−ＶＳＳで添加するオゾン処理により改質した改質処理汚泥を第２の固液分離工程で膜分離装置により、改質分離汚泥と改質分離液とに固液分離し、この改質分離汚泥を改質処理工程に移送して改質処理し、改質分離液を前記好気性生物処理工程の前記曝気槽に返送して好気性生物処理するので、低コストで汚泥を減容化して系外へ排出する汚泥量を減少させ、しかも処理水質の悪化を防止し、かつ効率よく有機性排水を処理することができる。
【００３１】
本発明の有機性排液の処理装置は、改質処理装置、第２の固液分離装置、改質分離汚泥移送装置および改質分離液返送装置を備え、改質処理装置で改質した改質処理汚泥を第２の固液分離装置で改質分離汚泥と改質分離液とに固液分離し、この改質分離汚泥を改質処理工程に移送して改質処理し、改質分離液を好気性生物処理工程の曝気槽に返送し、有機性排液および返送汚泥と混合して好気性生物処理するように構成されているので、有機性排液を処理するに際し、低コストで汚泥を減容化して系外へ排出する汚泥量を減少させ、しかも処理水質の悪化を防止し、かつ効率よく有機性排水を処理することができる。
【００３２】
【発明の実施の形態】
次に本発明の実施例を図面により説明する。
図１は本発明の実施形態の有機性排液の生物処理装置を示す系統図であり、改質処理としてオゾン処理する場合の例、図２は改質処理としてオゾン処理槽を固液分離装置に対して２個直列に設けた場合の例、図３は改質処理としてオゾン処理槽を固液分離装置に対して２個並列に設けた場合の例を示している。図１において、１は曝気槽、２は固液分離槽、３ａはオゾン処理槽、４は膜分離装置である。
【００３３】
曝気槽１には原水路１１、透過液返送路１２および返送汚泥路１３が連絡し、また底部には散気装置１５が設けられて、空気供給路１４が連絡している。曝気槽１から固液分離槽２に連絡路１６が連絡している。固液分離槽２の上部には処理水路１７が連絡し、下部には汚泥排出路１８が連絡し、返送汚泥路１３に連絡している。固液分離槽２が第１の固液分離装置を構成している。１９は余剰汚泥排出路である。
【００３４】
オゾン処理槽３ａには汚泥排出路１８から分岐する引抜汚泥路２１、濃縮液移送路２２ａおよび排オゾン路２３ａが上部に連絡している。またオゾン発生機２５ａから連絡するオゾン供給路２６ａおよびオゾン処理汚泥路２７ａが下部に連絡している。濃縮液移送路２２ａには固形物排出路２８ａが連絡し、オゾン処理汚泥路２７ａにはポンプ３０ａが設けられている。
【００３５】
膜分離装置４には濃縮液移送路２２ａ、オゾン処理汚泥路２７ａおよび透過液返送路１２が連絡し、内部には分離膜３１が設けられている。膜分離装置４が第２の固液分離装置を構成し、濃縮液移送路２２ａが改質分離汚泥移送装置を構成し、透過液返送路１２が改質分離液移送装置を構成している。
【００３６】
図１の処理装置により有機性排液（原水）を処理するには、原水路１１から原水を曝気槽１に導入し、透過液返送路１２から返送される透過液３２、返送汚泥路１３から返送される返送汚泥および曝気槽１内の活性汚泥と混合し、空気供給路１４から供給される空気を散気装置１５から散気して好気性生物処理する。
【００３７】
曝気槽１内の混合液は連絡路１６から一部ずつ取り出して固液分離槽２に導入し、分離液と分離汚泥とに固液分離する。分離液は処理水として処理水路１７から系外へ排出し、分離汚泥は汚泥排出路１８から取り出し、その一部を返送汚泥として返送汚泥路１３から曝気槽１に返送し、残部を引抜汚泥としてオゾン処理する。なお、系外へ排出する汚泥が生じる場合は余剰汚泥排出路１９から系外へ排出する。
【００３８】
オゾン処理槽３ａでは、引抜汚泥を引抜汚泥路２１から導入するとともに、濃縮液移送路２２ａから移送される濃縮液３３を導入し、オゾン発生機２５ａで発生させたオゾンをオゾン供給路２６ａから供給し、引抜汚泥および濃縮液３３と接触させてオゾン処理（改質処理）を行う。これにより引抜汚泥中の汚泥が易生物分解有機物化するとともに、濃縮液３３中の不活性汚泥も酸化されて易生物分解有機物に変換する。この場合、分解されにくい濃縮液３３が繰り返しオゾン処理されることにより分解され易くなり、効率よくオゾン処理を行うことができ、このためオゾンの使用量を少なくして、汚泥を確実に減容化することができる。オゾン処理汚泥は膜分離装置４に導入する。オゾン排ガスは排オゾン路２３ａから排出する。オゾン処理汚泥中に無機ＳＳ成分が含まれる場合には、連続的または間欠的に固形物排出路２８ａから排出する。
【００３９】
オゾン処理汚泥はオゾン処理汚泥路２７ａから取り出し、ポンプ３０ａで加圧して膜分離装置４に導き、分離膜３１により膜分離する。この膜分離により透過液３２と濃縮液３３とに分離される。
濃縮液３３は濃縮液移送路２２ａから一部ずつ取り出してオゾン処理槽３ａに戻し、前記のようにオゾン処理する。
【００４０】
透過液３２は透過液返送路１２から一部ずつ取り出して曝気槽１へ返送し、前記のように好気性生物処理する。この場合、透過液３２には不活性汚泥が含まれていないので、曝気槽１内の不活性汚泥の量が増加することはなく、曝気槽１内の汚泥濃度（活性微生物汚泥と不活性汚泥との合計濃度）の増加は抑制される。このため固液分離槽２での固液分離は容易になる。またオゾン処理するための引抜汚泥の量を少なくすることができるので、曝気槽１のＳＲＴを長くすることができる。これにより、処理水質の悪化を防止することができ、かつ効率よく有機性排水を好気性生物処理することができる。
【００４１】
図１の装置では固液分離槽２の分離汚泥を引抜汚泥として引き抜いてオゾン処理しているが、曝気槽１から混合液（槽内液）を引抜汚泥として引き抜いてオゾン処理することもできる。
【００４２】
図２の装置は、オゾン処理槽３ａ、３ｂが膜分離装置４に対して直列に２個設けられ、改質分離液３３が後段のオゾン処理槽３ｂに戻されるように濃縮液移送路２２ｂが設けられている以外は図１と同様に構成されている。
図２の装置による処理方法は、オゾン処理槽３ａでオゾン処理したオゾン処理汚泥を後段のオゾン処理槽３ｂに導入してさらにオゾン処理するとともに、濃縮液移送路２２ｂから濃縮液３３をオゾン処理槽３ｂに導入してオゾン処理する以外は図１と同様に処理する。図２の場合、図１と比べて、汚泥のオゾン処理効率を向上させることが可能である。オゾン処理槽は３個以上設けることもできる。
【００４３】
図３の装置は、オゾン処理槽３ａ、３ｃが膜分離装置４に対して並列に２個設けられ、改質分離液３３が引抜汚泥をオゾン処理するオゾン処理槽３ａとは別のオゾン処理槽３ｃに戻されるように濃縮液移送路２２ｃが設けられている以外は図１と同様に構成されている。
図３の装置による処理方法は、濃縮液移送路２２ｃから濃縮液３３をオゾン処理槽３ｃに導入してオゾン処理する以外は図１と同様に処理する。図３の場合、図１および図２に比べて、さらに不活性汚泥の易生物分解有機物化を促進することができる。なお、オゾン処理装置３ｃでオゾン処理されたオゾン処理汚泥の移送路２７ｃはオゾン処理装置３ａに接続するオゾン処理汚泥路２７ａのポンプ３０ａの前段と連絡するようにしてポンプ３０ｃを省略することもできる。オゾン処理槽は３個以上設けることもできる。
【００４４】
【実施例】
次に本発明の試験例について説明する。
試験として、図１（実施例）および図４（比較例）の装置により原水の処理を行った。曝気槽容量は１０Ｌとした。ただし、いずれの装置においても、引抜汚泥は固液分離槽の分離汚泥の代わりに曝気槽内の混合液を引き抜いた。原水としては、炭素源として酵母エキス、肉エキスおよび果糖と含むＢＯＤ濃度５００ｐｐｍの合成排水を使用した。
【００４５】
試験開始前にどちらの系もＳＲＴを２０日として２か月間、オゾン処理することなく通常の活性汚泥処理を行った。この処理の期間中、どちらの系の曝気槽もＭＬＶＳＳ濃度は４〜４．５ｇＭＬＶＳＳ／Ｌ前後であり、安定していた。また固液分離槽から流出する処理水ＢＯＤは５ｐｐｍ前後であった。
【００４６】
比較例１
上記のような装置において、１日あたり１．５Ｌの混合液を曝気槽から引き抜き、これを引抜汚泥として回分式でオゾン処理し、その後過負荷とならないように一定の時間で曝気槽に返送した。
この処理では曝気槽のＭＬＶＳＳは４〜４．５ｇＭＬＶＳＳ／Ｌ前後で安定した。
オゾン処理を行った引抜汚泥の固形物は１日あたり６．７５ｇで、１日あたりの生成汚泥量の３〜３．３倍、オゾン処理に要したオゾン量は固形物量の１．５重量％で、１日あたり１００ｍｇであった。なお、固液分離槽から流出する処理水のＢＯＤは１０〜１５ｐｐｍで、余剰汚泥の発生量はゼロであった。
【００４７】
実施例１
上記のような装置において、１日あたり１．０Ｌの混合液を曝気槽から引き抜き、これを引抜汚泥として回分式でオゾン処理したあと、オゾン処理汚泥は遠心分離により固液分離し、オゾン処理分離液（上澄液）は曝気槽に戻した。オゾン処理分離汚泥は４℃で保存し、翌日にオゾン処理槽３ａに戻して引抜汚泥と混合し、オゾン処理を行った。
【００４８】
この処理では曝気槽のＭＬＶＳＳは３〜３．５ｇＭＬＶＳＳ／Ｌ前後で安定した。またオゾン処理槽３ａの固形分濃度は２０ｇ／Ｌ程度まで増加して一定となった。このとき、固液分離槽から流出する処理水ＢＯＤは５〜６ｐｐｍで余剰汚泥の発生はなかった。
【図面の簡単な説明】
【図１】本発明の実施形態の有機性排液の処理装置を示す系統図である。
【図２】本発明の他の実施形態の有機性排液の処理装置を示す系統図である。
【図３】本発明の他の実施形態の有機性排液の処理装置を示す系統図である。
【図４】従来の有機性排液の処理方法を示すフローシートである。
【符号の説明】
１、４１曝気槽
２固液分離槽
３ａ、３ｂ、３ｃ、４３オゾン処理槽
４膜分離装置
１１原水路
１２透過液移送路
１３返送汚泥路
１４空気供給路
１５、４８散気装置
１６連絡路
１７処理水路
１８汚泥排出路
１９余剰汚泥排出路
２１引抜汚泥路
２２ａ、２２ｂ、２２ｃ濃縮液移送路
２３ａ、２３ｂ、２３ｃ排オゾン路
２５ａ、２５ｂ、２５ｃオゾン発生機
２６ａ、２６ｂ、２６ｃオゾン供給路
２７ａ、２７ｂ、２７ｃオゾン処理汚泥路
２８ａ、２８ｂ、２８ｃ固形物排出路
３０ａ、３０ｂ、３０ｃポンプ
３１分離膜
３２透過液
３３濃縮液
４２汚泥分離槽
４４有機性排液
４５返送汚泥
４６オゾン処理汚泥
４７空気供給管
５１分離汚泥
５０処理液
５３引抜汚泥
５４余剰汚泥
５５オゾン供給管
５６排オゾン管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for biologically treating organic wastewater in the presence of activated sludge, and more particularly to a method and apparatus for treating organic wastewater that can reduce the volume of excess sludge in an activated sludge treatment system.
[0002]
[Prior art]
The aerobic biological treatment method that treats organic wastewater under aerobic conditions using the action of aerobic microorganisms, such as the activated sludge treatment method, is generally low in processing cost and excellent in processing performance. Although it is widely used, it generates a large amount of non-dewatering excess sludge. For this reason, a treatment method for reducing the volume of sludge has attracted attention.
[0003]
As a treatment method for reducing the volume of such sludge, the sludge is extracted from an aeration tank or a sedimentation tank, and the extracted sludge is modified to be easily biodegradable by modification treatment such as ozone treatment, heat treatment, acid or alkali treatment. A method has been proposed in which the refined and modified sludge is returned to the aeration tank for biodegradation (for example, JP-A-6-206088).
[0004]
FIG. 4 is a flow sheet showing the organic drainage treatment method described in JP-A-6-206088, wherein 41 is an aeration tank, 42 is a sludge separation tank, and 43 is an ozone treatment tank.
In the treatment method of FIG. 4, the organic waste liquid 44 and the return sludge 45 are introduced into the aeration tank 41, the ozone treatment sludge 46 is introduced, mixed with the activated sludge in the aeration tank 41, and air is supplied from the air supply pipe 47. Is aerated from the aeration device 48 to perform aerobic biological treatment.
[0005]
The liquid in the tank of the aeration tank 41 is taken out part by part and introduced into the sludge separation tank 42 and separated into the separated liquid and the separated sludge 51. The separation liquid is discharged out of the system as a treatment liquid 50, a part of the separation sludge 51 is returned to the aeration tank 41 as a return sludge 45, and the other part is introduced into the ozone treatment tank 43 as a drawn sludge 53 for ozone treatment. The remaining portion is discharged out of the system as excess sludge 54. The drawn sludge 53 is introduced into the ozone treatment tank 43, supplied with ozone from an ozone supply pipe 55 and brought into contact with ozone, and the sludge is oxidatively decomposed to be easily biodegradable organic matter. The ozone exhaust gas is discharged from the exhaust ozone pipe 56, and the ozone treatment sludge 46 is returned to the aeration tank 41 to perform the aerobic biological treatment as described above.
[0006]
In the conventional method of FIG. 4 described above, the extracted sludge 53 is modified to be readily biodegradable and returned to the aeration tank 41, so that the modified sludge that has become readily biodegradable contributes to microorganisms in the aeration tank 41. As a result, the amount of sludge produced is reduced. In this case, if the amount of the extracted sludge 53 larger than the amount of sludge generated from the treated BOD is reformed and returned, the excess sludge discharged outside the system can be made substantially zero.
[0007]
However, in the above conventional method, in order to make the excess sludge discharged outside the system zero, it is usually necessary to perform ozone treatment as a drawn sludge with a large amount of sludge that is about 3 to 4 times the amount of sludge to be generated. This is a process in which sludge that has been converted to easily biodegradable organic matter by ozone treatment is returned to the aeration tank and aerobic biological treatment is performed. 30-40% of the easily biodegradable organic matter produced by ozone treatment is converted back to sludge. It is to do. For this reason, a large amount of ozone, chemicals, energy, and the like are required for the ozone treatment, which increases the cost. Also, if a large amount of sludge is extracted and treated with ozone, active microorganisms are deactivated by the ozone treatment, and the amount of microorganisms required for aerobic biological treatment cannot be secured in the aeration tank. There is also a problem that the processing efficiency is deteriorated and the processing efficiency is likely to be lowered.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to reduce sludge volume at low cost and reduce the amount of sludge discharged out of the system, while preventing deterioration of treated water quality and efficiently treating organic drainage. It is an object of the present invention to provide an organic drainage treatment method and apparatus that can be used.
[0009]
[Means for Solving the Problems]
The present invention provides the following organic drainage treatment method and apparatus.
(1) organic draining is introduced into the aeration tank, the aerobic biological treatment step of aerobic biological treatment in the presence of the active sludge,
A first solid-liquid separation step of separating the liquid mixture of the aeration tank into a separated sludge and a separated liquid, returning at least a part of the separated sludge to the aeration tank, and discharging the separated liquid as treated water;
At least a part of the activated sludge is extracted from the separated sludge separated in the first solid-liquid separation step or the mixed solution of the aeration tank, and ozone is added to the extracted sludge at 0.002 to 0.05 g-O ₃ / g-VSS. the addition to ozone treatment, modification treatment step that inquire break the easily biodegradable,
A second solid-liquid separation step in which the reformed sludge reformed in the reforming step is solid-liquid separated into a reformed separation sludge and a reformed separation liquid by a membrane separator;
A reformed separation sludge transfer step for transferring the reformed separation sludge separated in the second solid-liquid separation step to the reforming treatment step; and the aerobic biological treatment for the reformed separation liquid separated in the second solid-liquid separation step Including a reformed separation liquid returning step of returning to the aeration tank of the process ,
In the aerobic biological treatment step, an aerobic biological treatment is performed by mixing the return sludge returned from the first solid-liquid separation step and the reformed separation liquid returned from the reformed separation liquid return step,
In the reforming treatment step, the reformed separated sludge transferred from the reformed separated sludge transfer step is modified to be easily biodegradable.
An organic drainage treatment method characterized by the above .
(2) organic draining is introduced into the aeration tank, aerobic organisms in the presence of the active sludge process for the aerobic biological treatment apparatus,
A first solid-liquid separator that separates the mixed liquid in the aeration tank into a separated sludge and a separated liquid, returns at least a part of the separated sludge to the aerated tank, and discharges the separated liquid as treated water;
At least a part of the activated sludge is extracted from the separated sludge separated by the first solid-liquid separator or the mixed solution in the aeration tank, and ozone is added to the extracted sludge at 0.002 to 0.05 g-O ₃ / g-VSS. the ozone treatment for adding, modification apparatus that inquire break the easily biodegradable,
A second solid-liquid separator that separates the reformed sludge reformed by the reformer into a reformed separation sludge and a reformed separation liquid using a membrane separator;
A reformed separation sludge transfer device for transferring the reformed separated sludge separated by the second solid-liquid separation device to the reforming treatment device, and the aerobic biological treatment of the reformed separation liquid separated by the second solid-liquid separation device Including a reformed liquid return device for returning to the aeration tank of the device ,
The aerobic biological treatment apparatus mixes the return sludge returned from the first solid-liquid separation apparatus and the reformed separation liquid returned from the reformed separation liquid return apparatus so as to perform an aerobic biological treatment. Configured,
The reforming treatment apparatus is configured to reform the reformed separated sludge transferred from the reformed separated sludge transfer apparatus to easily biodegradable.
An organic drainage treatment apparatus.
[0010]
As a result of intensive studies to achieve the objects of the present invention, the following has been found. In other words, the conventional organic wastewater treatment method that employs reforming treatment such as ozone treatment returns the entire amount to the aeration tank without solid-liquid separation of the reformed sludge. Inactive sludge (inactive sludge) that does not contribute to the waste is also returned to the aeration tank. Since this inert sludge is difficult to be decomposed by the aerobic biological treatment, such inert sludge is accumulated in the aeration tank, causing the following problems.
[0011]
1) In the aeration tank, both sludge composed of active microorganisms (active microorganism sludge) and inert sludge are mixed, and it is impossible to separate them.
2) Since inert sludge accumulates in the aeration tank, the sludge concentration in the aeration tank increases and the efficiency of solid-liquid separation in the subsequent process decreases (if the sludge concentration in the aeration tank increases, precipitation becomes difficult).
3) Since a large amount of sludge is extracted and reformed, the SRT becomes shorter than when no reforming is performed. For example, in order to the occurrence of excess sludge to zero, when the reforming process pulled can pull 3-4 times the sludge biological sludge generated in the day, when SRT does not perform modification treatment 1 / It becomes about 3 to 1/4.
[0012]
In the present invention, the reformed sludge is subjected to solid-liquid separation, the reformed separated sludge is reformed again, and only the reformed separation liquid is returned to the aeration tank to solve the above-mentioned problems. Can be achieved.
[0013]
The organic effluent to be treated in the present invention is an effluent containing an organic substance treated by a normal aerobic biological treatment method, but may contain a hardly biodegradable organic substance or an inorganic substance. In addition, ammonia nitrogen may be contained. Such organic effluents include sewage, human waste, food factory effluents and other industrial effluents.
[0014]
The aerobic biological treatment process in the present invention is configured to introduce an organic waste liquid into an aeration tank and perform an aerobic biological treatment in the presence of activated sludge. In the first solid-liquid separation step, the mixed liquid (liquid in the tank) is guided from the aeration tank to the first solid-liquid separation apparatus to separate the liquid into separated sludge and the separated liquid, and at least a part of the separated sludge is aerated. It is configured to return to the tank and discharge the separated liquid as treated water. As such a treatment system and treatment apparatus, organic waste liquid is mixed with activated sludge in an aeration tank and aerated, and the mixed liquid is solid-liquid separated in a solid-liquid separation apparatus, and a part of the separated sludge is put in an aeration tank. The aerobic biological treatment and treatment apparatus in the standard activated sludge treatment method to be returned is common, but other modified versions may be used.
[0015]
In the reforming treatment step, at least a part of the activated sludge (biological sludge) from the treatment system in the aerobic biological treatment described above is drawn, and this drawn sludge is modified to be easily biodegradable, and the modified separated sludge in the subsequent step This is a process for reforming the reformed separated sludge transferred from the transfer process to be easily biodegradable. When extracting biological sludge, it is preferable to extract a part of the separated sludge separated in the first solid-liquid separation step, but it may be extracted from the aeration tank in a mixed liquid state. When extracting from the separated sludge, part or all of the portion discharged as excess sludge can be extracted as extraction sludge, but in addition to the excess sludge, a part of the return sludge returned to the aeration tank as return sludge is further added. It can also be pulled out and reformed. In this case, the amount of excess sludge generated outside the system can be reduced, and in some cases, it can be reduced to zero. The drawn sludge and the reformed separated sludge can be reformed by the same reforming apparatus, or can be reformed by separate reforming apparatuses.
[0016]
In the present invention, the biological sludge produced by the organic matter in the liquid to be treated is assimilated by microorganisms is produced, the sludge obtained by being separated from the treatment liquid by the first solid-liquid separator is separated sludge, the first Part of the separated sludge that is returned from the solid-liquid separator to the aeration tank is returned to the aeration tank, and the sludge that has been extracted from the aeration tank or the solid-liquid separator to be subjected to the modification process is sludge that has been subjected to the sludge and modification treatment. Reformed sludge, sludge obtained by separation of the reformed sludge by the second solid-liquid separation device is reformed separated sludge, and the separated liquid obtained at this time is removed from the reformed separated liquid and the aerobic biological treatment system. The discharged sludge is referred to as excess sludge, the activated sludge composed of active microorganisms is referred to as activated microbial sludge, and the sludge composed of microorganisms that have lost activity is referred to as inactive sludge.
[0017]
The modification treatment method of the extracted sludge organisms to modify the decomposition and easy nature, we adopt a modified treatment by ozone treatment. Process This can be done using a known processing device as the modifying processor. O modification treatment by Zon process is preferable because processing operations is high simple and processing efficiency.
[0018]
In the ozone treatment as the reforming treatment, it is only necessary to contact the extracted sludge or the reformed separated sludge transferred from the reformed separated sludge transfer process with ozone, and the sludge is easily biodegradable by the oxidation of ozone. The Biological sludge is oxidatively decomposed by ozone treatment and converted into readily biodegradable organic matter. In the case of the present invention, since the second solid-liquid separation step is provided in the post-process, it is not necessary to completely modify the sludge to be readily biodegradable, and inert sludge may remain.
When the ozone treatment is performed in an acidic region having a pH of 5 or less, the oxidative decomposition efficiency is increased. Adjustment of pH at this time can employ | adopt the method of adding inorganic acids, such as a sulfuric acid, hydrochloric acid, or nitric acid, to biological sludge as a pH adjuster. When adding a pH adjuster, it is preferable to adjust pH to 3-4.
[0019]
The ozone treatment can be performed by bringing the extracted sludge or the reformed separated sludge as it is or after concentrating it with a centrifuge if necessary, and then bringing it into contact with ozone. As a contact method, a method of introducing sludge into an ozone treatment tank and blowing ozone, a method of mechanical stirring, a method of using a packed bed, or the like can be employed. As ozone, ozone-containing gas such as ozone-containing air and ozonized air can be used in addition to ozone gas. The amount of ozone used is 0.002 to 0.05 g-O ₃ / g-VSS, preferably 0.005 to 0.03 g-O ₃ / g-VSS. In some cases, the biodegradable COD may be generated by ozone treatment. In this case, it can be removed by coagulation treatment, adsorption, or the like.
[0024]
The reforming process can be performed using one reforming apparatus, or can be performed using two or more reforming apparatuses. It is preferable to use 2 to 3 reforming treatment apparatuses. When using two or more modification apparatus, the apparatus may be provided in the series to solid-liquid separator, Ru can also be provided in parallel.
[0025]
The second solid-liquid separation step is a step in which the reformed sludge reformed in the reforming step is guided to the second solid-liquid separation device and separated into the reformed separation sludge and the reformed separation liquid. Solid-liquid separation apparatus used in the second solid-liquid separation step may be carried out using a membrane separation equipment. When membrane separation is used, various membrane types such as hollow fiber, tubular, and flat membrane can be used. Moreover, since the purpose of membrane separation is to separate solids, membranes having a relatively large pore size such as MF and UF are preferred.
[0026]
The reformed separation sludge transfer step is a step of transferring the reformed separation sludge separated in the second solid-liquid separation step to the reforming treatment step. When two or more reforming processing apparatuses are provided in the reforming process, the reforming process can be transferred to a reforming apparatus at an arbitrary position, or can be transferred to a plurality of reforming apparatuses. In the present invention, in order to simplify the operation and improve the reforming treatment efficiency, it is preferable to transfer the extracted sludge to a reforming treatment device different from the reforming treatment device that performs the reforming treatment.
[0027]
For example, when two reforming treatment devices are provided in series with the solid-liquid separation device in the reforming treatment step, the extracted sludge is introduced into the reforming device in the previous stage and reformed. It is preferable that the separated sludge is transferred to a subsequent reforming apparatus and reformed. In this case, the sludge reformed by the reformer at the former stage is directly introduced into the reformer at the latter stage and mixed with the reformed and separated sludge to be reformed. However, two reforming treatment devices are provided in parallel with the solid-liquid separation device in the reforming treatment process, the sludge is introduced into one reforming treatment device, the reforming treatment is performed, and the other reforming treatment is performed. It is preferable to transfer the reformed separated sludge to the apparatus and perform the reforming treatment separately.
[0028]
Reforming separated liquid return feed step is a step to return your reforming separated liquid separated by the second solid-liquid separation step to the aeration tank of the aerobic biological treatment process. The reformed separation liquid introduced into the aeration tank is mixed with the organic waste liquid and the activated sludge in the tank to be subjected to aerobic biological treatment, but the reformed separation liquid contains the solid content after separation of the reformed separation sludge. Inactive sludge is not introduced into the aeration tank. For this reason, inert sludge does not accumulate in the aeration tank.
[0029]
The treatment method of the present invention is superior to the conventional method in which the total amount of the modified sludge is returned to the aeration tank in the following points.
1) Since the volume of the extracted sludge can be reliably reduced, the amount of sludge extracted from the separated sludge or the mixed solution in the aeration tank for the reforming treatment can be reduced. For example, in the conventional method, the excess sludge discharged outside the system can be made zero by treating the sludge of about 3 to 4 times the amount of sludge to be generated with ozone treatment as the extracted sludge. Excess sludge discharged to the outside of the system can be made zero by performing ozone treatment as about 2 to 2.5 times the amount of sludge as drawn sludge. Therefore, a large amount of activated microbial sludge can be held in the aeration tank. Thereby, since SRT of an aeration tank can be lengthened, deterioration of the quality of treated water can be prevented, and organic waste water can be efficiently aerobic biologically treated.
2) Nari solid (reforming separated sludge by treating reforming separated sludge) repeating modification of susceptible modification treatment sludge degradation is rather easy is decomposed, it can be reduced, for example, ozone usage.
3) Since the amount of inert sludge in the aeration tank is reduced, the concentration of sludge in the aeration tank (the total concentration of activated microbial sludge and inert sludge) is lowered, and therefore in the first solid-liquid separation step. Solid-liquid separation becomes easy.
4) The aerobic biological treatment and the reforming treatment can be performed in a state where the activated microbial sludge and the inert sludge are separated.
[0030]
【Effect of the invention】
The organic drainage treatment method according to the present invention introduces organic drainage into the aeration tank of the aerobic biological treatment step, mixes with the returned sludge and the reformed separation liquid, performs the aerobic biological treatment, At least a part of the activated sludge is extracted from the separated sludge separated in the solid-liquid separation step or the mixed solution in the aeration tank, and ozone is added at 0.002 to 0.05 g-O ₃ / g-VSS in the reforming treatment step. The reformed sludge reformed by ozone treatment is solid-liquid separated into the reformed separated sludge and the reformed separation liquid by the membrane separation device in the second solid-liquid separation step, and this reformed separated sludge is reformed. and transferring processes modification, since the reforming separated liquid to the in-feed returned to the aeration tank the aerobic biological treatment of the aerobic biological treatment step is discharged by volume reduction of the sludge at a low cost out of the system to Reduce the amount of sludge, prevent deterioration of treated water quality, and efficiently drain organic wastewater It can be processed.
[0031]
Processor of organic waste liquid of the present invention, modification apparatus, the second solid-liquid separation apparatus, comprising a feed return reforming separation sludge transfer device and reforming the separated liquid system, modified with modification apparatus The reformed sludge is solid-liquid separated into the reformed separated sludge and the reformed separated liquid by the second solid-liquid separator, and this reformed separated sludge is transferred to the reforming process for reforming and reforming. the separated liquid to feed return to the aeration tank of the aerobic biological treatment step, since mixed with organic drainage and return sludge is configured to process aerobic organisms, upon processing the organic drainage, low The volume of sludge can be reduced at a cost to reduce the amount of sludge discharged out of the system, and the quality of treated water can be prevented from deteriorating, and organic wastewater can be treated efficiently.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system diagram showing a biological treatment apparatus for organic drainage according to an embodiment of the present invention, in which an ozone treatment is performed as a reforming process, and FIG. FIG. 3 shows an example in which two ozone treatment tanks are provided in parallel to the solid-liquid separator as a reforming process. In FIG. 1, 1 is an aeration tank, 2 is a solid-liquid separation tank, 3a is an ozone treatment tank, and 4 is a membrane separation apparatus.
[0033]
Aeration tank Hara waterway 11 to 1, to contact the permeate return sending passage 12 and the return sludge line 13, also in the bottom provided with an air diffuser 15, the air supply passage 14 is in communication. A communication path 16 communicates from the aeration tank 1 to the solid-liquid separation tank 2. A treatment water channel 17 communicates with the upper part of the solid-liquid separation tank 2, a sludge discharge channel 18 communicates with the lower part, and communicates with the return sludge channel 13. The solid-liquid separation tank 2 constitutes a first solid-liquid separation device. 19 is a surplus sludge discharge channel.
[0034]
The ozone treatment tank 3a is connected to an upper portion of a drawn sludge passage 21, a concentrated liquid transfer passage 22a, and a waste ozone passage 23a branched from the sludge discharge passage 18. An ozone supply path 26a and an ozone treatment sludge path 27a communicated from the ozone generator 25a communicate with the lower part. A solid material discharge passage 28a communicates with the concentrate transfer passage 22a, and a pump 30a is provided in the ozone treatment sludge passage 27a.
[0035]
The membrane separation unit 4 contact concentrate flow path 22a, ozonation sludge passage 27a and permeate return sending passage 12, the separation film 31 is provided inside. Membrane separation unit 4 constitute a second solid-liquid separator, concentrated liquid flow path 22a constitutes a reforming separator sludge transfer device, permeate return sending passage 12 constitutes a reformed separated liquid transfer device .
[0036]
Organic drainage by the processor of FIG. 1 to process (raw water) is the raw water from the raw water passage 11 is introduced into the aeration tank 1, the permeate 32, return sludge passage is sent returned from the permeate return sending passage 12 13 is mixed with the return sludge returned from the aeration tank 13 and the activated sludge in the aeration tank 1, and the air supplied from the air supply path 14 is diffused from the aeration device 15 for aerobic biological treatment.
[0037]
The mixed liquid in the aeration tank 1 is partially removed from the communication path 16 and introduced into the solid-liquid separation tank 2 for solid-liquid separation into separated liquid and separated sludge. The separation liquid is discharged out of the system from the treatment water channel 17 as treated water, the separated sludge is taken out from the sludge discharge channel 18, a part thereof is returned to the aeration tank 1 from the return sludge channel 13 as return sludge, and the remainder is drawn as sludge. Treat with ozone. In addition, when the sludge discharged | emitted out of the system arises, it discharges out of the system from the excess sludge discharge channel 19.
[0038]
In the ozone treatment tank 3a, the drawn sludge is introduced from the drawn sludge passage 21, the concentrated liquid 33 transferred from the concentrated liquid transfer passage 22a is introduced, and the ozone generated by the ozone generator 25a is supplied from the ozone supply passage 26a. Then, the ozone treatment (reforming treatment) is performed in contact with the extracted sludge and the concentrated liquid 33. As a result, the sludge in the extracted sludge is converted into an easily biodegradable organic material, and the inert sludge in the concentrated liquid 33 is also oxidized and converted into an easily biodegradable organic material. In this case, the concentrated liquid 33 that is difficult to be decomposed is easily decomposed by repeated ozone treatment, so that the ozone treatment can be efficiently performed. For this reason, the amount of ozone used is reduced and the sludge is reliably reduced in volume. can do. The ozone-treated sludge is introduced into the membrane separator 4. The ozone exhaust gas is discharged from the exhaust ozone passage 23a. When the ozone treatment sludge contains an inorganic SS component, it is discharged from the solid matter discharge passage 28a continuously or intermittently.
[0039]
The ozone-treated sludge is taken out from the ozone-treated sludge passage 27a, pressurized by the pump 30a, guided to the membrane separation device 4, and subjected to membrane separation by the separation membrane 31. By this membrane separation, the permeate 32 and the concentrate 33 are separated.
The concentrated liquid 33 is taken out part by part from the concentrated liquid transfer path 22a, returned to the ozone treatment tank 3a, and subjected to ozone treatment as described above.
[0040]
The permeate 32 then transfers return removed in portions from the return permeate sending passage 12 to the aeration tank 1, to aerobic biological treatment as described above. In this case, since the permeate 32 does not contain inert sludge, the amount of inert sludge in the aeration tank 1 does not increase, and the sludge concentration in the aeration tank 1 (activated microbial sludge and inert sludge). The increase in the total concentration) is suppressed. For this reason, the solid-liquid separation in the solid-liquid separation tank 2 becomes easy. Moreover, since the amount of the extracted sludge for the ozone treatment can be reduced, the SRT of the aeration tank 1 can be lengthened. Thereby, deterioration of the quality of treated water can be prevented, and organic waste water can be efficiently aerobic biologically treated.
[0041]
In the apparatus of FIG. 1, the separated sludge in the solid-liquid separation tank 2 is extracted as the extracted sludge and subjected to the ozone treatment. However, the mixed liquid (liquid in the tank) can be extracted from the aeration tank 1 as the extracted sludge and subjected to the ozone treatment.
[0042]
In the apparatus shown in FIG. 2, two ozone treatment tanks 3a and 3b are provided in series with respect to the membrane separation apparatus 4, and a concentrated liquid transfer path 22b is provided so that the reformed separation liquid 33 is returned to the subsequent ozone treatment tank 3b. Except for being provided, the configuration is the same as in FIG.
The treatment method using the apparatus shown in FIG. 2 introduces ozone-treated sludge that has been subjected to ozone treatment in the ozone treatment tank 3a into the ozone treatment tank 3b in the subsequent stage and further performs ozone treatment, and the concentrate 33 is removed from the concentrate transfer path 22b. The treatment is the same as in FIG. 1 except that it is introduced into 3b and treated with ozone. In the case of FIG. 2, compared with FIG. 1, it is possible to improve the ozone treatment efficiency of sludge. Three or more ozone treatment tanks can be provided.
[0043]
The apparatus of FIG. 3 is provided with two ozone treatment tanks 3a and 3c in parallel to the membrane separation apparatus 4, and an ozone treatment tank different from the ozone treatment tank 3a in which the reformed separation liquid 33 ozone-treats the extracted sludge. The configuration is the same as that in FIG. 1 except that a concentrated liquid transfer path 22c is provided so as to be returned to 3c.
The processing method using the apparatus of FIG. 3 is the same as that of FIG. 1 except that the concentrated liquid 33 is introduced from the concentrated liquid transfer path 22c into the ozone processing tank 3c and subjected to ozone treatment. In the case of FIG. 3, as compared with FIGS. 1 and 2, it is possible to further promote the easy biodegradation of the inert sludge into an organic material. In addition, the transfer path 27c of the ozone treatment sludge ozone-treated by the ozone treatment apparatus 3c can be omitted from the pump 30a so as to communicate with the upstream stage of the pump 30a of the ozone treatment sludge path 27a connected to the ozone treatment apparatus 3a. . Three or more ozone treatment tanks can be provided.
[0044]
【Example】
Next, test examples of the present invention will be described.
As a test, the raw water was treated by the apparatus shown in FIG. 1 (Example) and FIG. 4 (Comparative Example). The aeration tank capacity was 10 L. However, in any of the apparatuses, the extracted sludge extracted the mixed liquid in the aeration tank instead of the separated sludge in the solid-liquid separation tank. As raw water, synthetic wastewater having a BOD concentration of 500 ppm containing yeast extract, meat extract and fructose as carbon sources was used.
[0045]
Before the start of the test, both systems were subjected to normal activated sludge treatment without ozone treatment for 2 months with SRT of 20 days. During this treatment, the MLVSS concentration in both aeration tanks was around 4 to 4.5 g MLVSS / L and was stable. The treated water BOD flowing out from the solid-liquid separation tank was around 5 ppm.
[0046]
Comparative Example 1
In the apparatus as described above, 1.5 L of the mixed liquid per day was drawn out from the aeration tank, and this was treated with ozone as a drawn sludge, and then returned to the aeration tank in a certain time so as not to be overloaded. .
In this treatment, the MLVSS of the aeration tank was stabilized at around 4 to 4.5 g MLVSS / L.
The solid matter of the extracted sludge treated with ozone was 6.75 g per day, 3 to 3.3 times the amount of sludge produced per day, and the amount of ozone required for the ozone treatment was 1.5% by weight of the solid matter amount. And 100 mg per day. In addition, the BOD of the treated water flowing out from the solid-liquid separation tank was 10 to 15 ppm, and the amount of surplus sludge generated was zero.
[0047]
Example 1
In the above equipment, 1.0L of liquid mixture per day is drawn out from the aeration tank, and after this is treated with ozone as a drawn sludge, the ozone-treated sludge is separated into solid and liquid by centrifugal separation. The liquid (supernatant liquid) was returned to the aeration tank. The ozone-treated separated sludge was stored at 4 ° C., returned to the ozone treatment tank 3a the next day, mixed with the drawn sludge, and subjected to ozone treatment.
[0048]
In this treatment, the MLVSS of the aeration tank was stabilized at around 3 to 3.5 g MLVSS / L. Moreover, the solid content concentration of the ozone treatment tank 3a increased to about 20 g / L and became constant. At this time, the treated water BOD flowing out from the solid-liquid separation tank was 5 to 6 ppm, and no excess sludge was generated.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an organic drainage treatment apparatus according to an embodiment of the present invention.
FIG. 2 is a system diagram showing an organic drainage treatment apparatus according to another embodiment of the present invention.
FIG. 3 is a system diagram showing an organic drainage treatment apparatus according to another embodiment of the present invention.
FIG. 4 is a flow sheet showing a conventional organic drainage treatment method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,41 Aeration tank 2 Solid-liquid separation tank 3a, 3b, 3c, 43 Ozone treatment tank 4 Membrane separation device 11 Raw water channel 12 Permeate transfer channel 13 Return sludge channel 14 Air supply channel 15, 48 Air diffuser 16 Communication channel 17 Treated water channel 18 Sludge discharge channel 19 Excess sludge discharge channel 21 Extracted sludge channels 22a, 22b, 22c Concentrated liquid transfer channels 23a, 23b, 23c Exhaust ozone channels 25a, 25b, 25c Ozone generators 26a, 26b, 26c Ozone supply channels 27a, 27b, 27c Ozone treatment sludge passages 28a, 28b, 28c Solid matter discharge passages 30a, 30b, 30c Pump 31 Separation membrane 32 Permeate 33 Concentrate 42 Sludge separation tank 44 Organic waste liquid 45 Return sludge 46 Ozone treatment sludge 47 Air supply Pipe 51 Separation sludge 50 Treatment liquid 53 Extracted sludge 54 Excess sludge 55 Ozone supply pipe 56 Waste ozone pipe

Claims

The organic drainage is introduced into the aeration tank, the aerobic biological treatment step of aerobic biological treatment in the presence of the active sludge,
A first solid-liquid separation step of separating the liquid mixture of the aeration tank into a separated sludge and a separated liquid, returning at least a part of the separated sludge to the aeration tank, and discharging the separated liquid as treated water;
At least a part of the activated sludge is extracted from the separated sludge separated in the first solid-liquid separation step or the mixed solution in the aeration tank, and ozone is added to the extracted sludge at 0.002 to 0.05 g-O ₃ / g-VSS. the addition to ozone treatment, modification treatment step that inquire break the easily biodegradable,
A second solid-liquid separation step in which the reformed sludge reformed in the reforming step is solid-liquid separated into a reformed separation sludge and a reformed separation liquid by a membrane separator;
A reformed separation sludge transfer step for transferring the reformed separation sludge separated in the second solid-liquid separation step to the reforming treatment step; and the aerobic biological treatment for the reformed separation liquid separated in the second solid-liquid separation step Including a reformed separation liquid returning step of returning to the aeration tank of the process ,
In the aerobic biological treatment step, an aerobic biological treatment is performed by mixing the return sludge returned from the first solid-liquid separation step and the reformed separation liquid returned from the reformed separation liquid return step,
In the reforming treatment step, the reformed separated sludge transferred from the reformed separated sludge transfer step is modified to be easily biodegradable.
An organic drainage treatment method characterized by the above .

The organic drainage is introduced into the aeration tank, the aerobic biological treatment apparatus for aerobic biological treatment in the presence of the active sludge,
A first solid-liquid separator that separates the mixed liquid in the aeration tank into a separated sludge and a separated liquid, returns at least a part of the separated sludge to the aerated tank, and discharges the separated liquid as treated water;
At least a part of the activated sludge is extracted from the separated sludge separated by the first solid-liquid separator or the mixed solution in the aeration tank, and ozone is added to the extracted sludge at 0.002 to 0.05 g-O ₃ / g-VSS. the ozone treatment for adding, modification apparatus that inquire break the easily biodegradable,
A second solid-liquid separator that separates the reformed sludge reformed by the reformer into a reformed separation sludge and a reformed separation liquid using a membrane separator;
A reformed separation sludge transfer device for transferring the reformed separated sludge separated by the second solid-liquid separation device to the reforming treatment device, and the aerobic biological treatment of the reformed separation liquid separated by the second solid-liquid separation device Including a reformed liquid return device for returning to the aeration tank of the device ,
The aerobic biological treatment apparatus mixes the return sludge returned from the first solid-liquid separation apparatus and the reformed separation liquid returned from the reformed separation liquid return apparatus so as to perform an aerobic biological treatment. Configured,
The reforming treatment apparatus is configured to reform the reformed separated sludge transferred from the reformed separated sludge transfer apparatus to easily biodegradable.
An organic drainage treatment apparatus.