JP3961246B2

JP3961246B2 - Method and apparatus for treating organic wastewater

Info

Publication number: JP3961246B2
Application number: JP2001245457A
Authority: JP
Inventors: 清美荒川; 琢也小林; 俊博田中
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2001-08-13
Filing date: 2001-08-13
Publication date: 2007-08-22
Anticipated expiration: 2021-08-13
Also published as: JP2003053377A

Description

【０００１】
【発明の属する技術分野】
本発明は、汚水などの有機性廃水の処理に関するもので、詳細には有機性廃水の生物処理に伴う余剰汚泥の生成量の削減とリンの除去が達成できる有機性廃水の処理に関するものであり、特に、リン濃度の高い有機性食品廃水や生活排水等の処理に用いることができる、有機性廃水の処理方法および処理装置に関するものである。
【０００２】
【従来の技術】
有機性廃水の生物処理では、活性汚泥処理が広く行われている。従来の活性汚泥処理は、分解性の有機物の分解除去が中心であったが、近年嫌気好気法による窒素やリンの除去も行われるようになってきた。活性汚泥処理では、有機物の分解にともない汚泥量が増加するが、活性汚泥処理を維持するため、増加した汚泥を生物処理系外に排出することが必要である。ここで、汚泥を物理的、化学的手段により液化することで、汚泥の体積を減少する技術が提案されており、余剰汚泥の発生量を減少することができるが、減少した汚泥に含まれていた分のリンは処理水に流出し、このリン分に関する処理水水質が悪化する。また、汚泥減容化処理に伴って難生物分解性ＣＯＤが生成し、処理水ＣＯＤ濃度を悪化させる問題が避けられなかった。
【０００３】
リン除去に関しては、この問題を解決するために、生物脱リン装置に関する公知技術として、「嫌気好気法による生物脱リン装置において、返送汚泥の一部が導入される汚泥可溶化手段と、該汚泥可溶化手段で可溶化された汚泥を嫌気槽に返送する手段と、返送汚泥の一部が導入されるリン放出槽と、該リン放出槽の流出液が導入されるリン酸マグネシウムアンモニウム（ＭＡＰ）反応塔とを備えてなることを特徴とする生物脱リン装置」が開示されている。しかし、この技術は固液分離せずに、ＭＡＰによる脱リン反応塔に嫌気槽内液を投入しているため、使用する薬品に対するリン回収の効率を上げることが難しい。さらにこの技術では、難生物分解性ＣＯＤ生成による処理水ＣＯＤ濃度の悪化問題は、何等解決できていなかった。また、オゾン等の酸化剤にて処理した液化汚泥を直接嫌気槽に投入した場合、嫌気槽のＯＲＰの上昇、液化処理汚泥からの有機酸の生成がないということがあった。
【０００４】
【発明が解決しようとする課題】
本発明は、上記の問題を解決するために考案されたものであり、有機性廃水の生物処理においてリン回収を行い、処理水中のリンおよびＣＯＤの増加を防止することができ、かつ余剰汚泥の発生量を低減できる、有機性廃水の処理方法及び装置を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、以下の手段により上記の課題を解決することができた。
（１）嫌気槽を含む生物処理槽を用いる生物処理系で、活性汚泥により有機性廃水を処理する方法において、生物処理系活性汚泥の一部を液化処理装置に供給して液化処理を行い、前記液化処理装置から流出した液化活性汚泥を固液分離し、分離した分離汚泥を調整槽に供給し、調整槽で被処理液の全部または一部と攪拌混合して酸発酵処理し、それを生物処理槽に導入するとともに、前記固液分離で分離した分離液よりリンを回収し、リンを回収した後の液を生物処理槽に返送することを特徴とする有機性廃水の処理方法。
（２）嫌気槽を含む生物処理槽を用いる生物処理系で、活性汚泥により有機性廃水を処理する方法において、生物処理系活性汚泥の一部を液化処理装置に供給して液化処理を行い、前記液化処理装置から流出した液化活性汚泥を固液分離し、分離した分離汚泥を調整槽に供給し、攪拌混合して酸発酵処理し、その液と被処理液を生物処理槽に導入するとともに、前記固液分離で分離した分離液よりリンを回収し、リンを回収した後の液を、生物処理槽に返送することを特徴とする有機性廃水の処理方法。
【０００６】
（３）有機性廃水を嫌気好気法による生物学的脱リン脱窒素法により処理する装置において、被処理液導入管を連結された嫌気槽、脱窒槽及び好気槽からなる生物処理槽、該生物処理槽の流出液を処理水と汚泥に分離する固液分離装置Ｉ、前記固液分離装置Ｉから前記嫌気槽および汚泥液化処理装置への分離汚泥を送る返送配管、前記液化処理装置の流出液Ｉを固液分離し、上澄液をリン回収装置へ、分離汚泥を調整槽へ送出する配管を備えた固液分離装置II、前記分離汚泥と被処理液の一部もしくは全部とを攪拌混合し、その混合液中の有機物の酸発酵を行い流出液を前記嫌気槽へ供給する調整槽、前記リン回収装置からのリン回収後の流出液IIを前記嫌気槽および脱窒槽へ送る配管、および好気槽の流出液を脱窒槽へ送る返送配管を有することを特徴とする有機性廃水の処理装置。
（４）有機性廃水を嫌気好気法による生物学的脱リン脱窒素法により処理する装置において、被処理液導入管を連結された嫌気槽、脱窒槽及び好気槽からなる生物処理槽、該生物処理槽の流出液を処理水と汚泥に分離する固液分離装置Ｉ、前記固液分離装置Ｉから前記嫌気槽および汚泥液化処理装置への分離汚泥を送る返送配管、前記液化処理装置の流出液Ｉを固液分離し、上澄液をリン回収装置へ、分離汚泥を調整槽へ送出する配管を備えた固液分離装置II、前記分離汚泥を攪拌し、その液中の有機物の酸発酵を行い、流出液を前記嫌気槽へ供給する調整槽、前記リン回収装置からのリン回収後の流出液IIを前記嫌気槽および脱窒槽へ送る配管、および好気槽の流出液を脱窒槽へ送る返送配管を有することを特徴とする有機性廃水の処理装置。
【０００７】
【発明の実施の形態】
本発明の実施の形態を図面を参照して詳細に説明する。
なお、実施の形態及び実施例を説明するための全図において、同一機能を有する構成要素は同一符号を付けて説明する。
【０００８】
図１は、本発明の処理方法による一例のフローシートを示す。
本発明の処理装置の構成は、調整槽６、嫌気槽１ａを含む生物処理槽１と固液分離装置Ｉ２からなる生物処理系７、液化処理装置３、固液分離装置II４及びリン回収装置５からなる。以下、有機性廃水を原水という。
【０００９】
原水１１の全部もしくは一部が、調整槽６に供給される。その際、調整槽６には、液化処理装置３からの流出液Ｉ１４を固液分離装置II４にて固液分離した分離汚泥１６が供給されている。調整槽６は、攪拌機３３により攪拌されている。原水１１と分離汚泥１６の混合液は、調整槽６で適当な時間滞留する。この際、分離汚泥１６中のあるいは原水１１中の有機物は、１６中の微生物の働きにより酸発酵が促進され、生物分解性の高い有機酸が生成される。また、分離汚泥１６が液化処理装置３においてオゾン等の酸化剤による液化処理を行った場合のものであるときには、調整槽６にて攪拌混合することにより、調整槽流出液２０のＯＲＰが低下し、嫌気槽１ａのＯＲＰ上昇を防ぐことができる。調整槽流出液２０は、生物処理槽１に供給される。リン回収率を高めるためには、汚泥中のリンを高濃度に維持することが重要であることから、生物処理槽１は、通常の活性汚泥法より嫌気槽１ａを備える生物学的リン除去法、生物学的窒素リン除去法を用いるのが望ましい。
【００１０】
調整槽流出液２０は有機酸等の生物分解性の高い有機物が多量に含まれるものであり、このような調整槽流出液２０を原水１１とともに嫌気槽１ａに供給することにより、高リン含有率の微生物の増殖を促進し、汚泥中のリン含有率が５％以上となる。前記の液が生物処理槽１で活性汚泥処理された後、生物処理槽流出液１２は固液分離装置Ｉ２に供給されて固液分離され、上澄液は処理水１９として放流される。
【００１１】
生物処理系７の活性汚泥の一部１３ｂは、液化処理装置３に供給され液化処理される。液化処理装置３に供給される汚泥は、生物処理系７の汚泥であれば、返送汚泥１３、生物処理槽１中の活性汚泥のどちらを供給してもよい。活性汚泥は、液化処理されることにより生物分解性が高くなり、生物処理系７へ戻して処理することにより、生物処理系７から生成する余剰汚泥が減容する。とりわけ液化量と同等にすることで、生物処理系７内での余剰汚泥は生成しない状態となる。この際、液化処理装置３に供給する汚泥量は、系内全汚泥量の５〜１００％であることが望ましい。液化処理装置３は、オゾン処理、超音波処理、ミルによる細胞のすりつぶし、加熱アルカリ処理等を用いることができる。又、固液分離装置Ｉ２と固液分離装置II４としては、沈殿槽及び精密膜ろ過、ＵＦろ過、ダイナミックろ過等の膜による固液分離装置を用いることができる。
【００１２】
流出液Ｉ１４より固液分離装置II４で分離された上澄液１５は、リン回収装置５にてリンを回収した後、生物処理槽１に供給される。
上澄液１５中には、液化処理により活性汚泥が含有していたリンが多量に溶出しており、溶解性リン濃度が高くなっている。例えば、リン含有率８％（ＶＳＳ）をオゾン注入率２０ｍｇ−Ｏ₃／ｇ−ＳＳで処理した場合、ポリリン酸と菌体構成リンが溶出し、その溶出量は汚泥中のリンの２０％程度であった。この溶解性リン濃度の高い上澄液１５を用いることにより、リン回収装置５をコンパクトにでき、さらにリン回収量あたりの薬品使用量を削減することができる。上澄液１５はリン回収装置５に投入しリンを回収する。リン回収装置５は、鉄、アルミニウム、カルシウム等を用いた凝集沈殿処理、ヒドロキシアパタイト（ＨＡＰ）やＭＡＰを用いた晶析法のいずれの方法を用いてもよいが、ＣＯＤの除去効果もある凝集沈殿処理や、ヒドロキシアパタイト晶析法がなお良い。
【００１３】
また、本願発明においては、原水１１を直接生物処理槽１に導入することも可能である。この実施態様を図２に示す。この場合、調整槽６での滞留時間が極めて長くなり、酸発酵が充分行える。したがって、酸発酵の状況によっては調整槽６の容量を小さくできる。他の実施態様は、前記記載内容と同様である。
【００１４】
【実施例】
以下において、本発明を実施例によりさらに具体的に説明するが、本発明は、これらの実施例により制限されるものではない。
【００１５】
実施例１
この実施例１においては、図１に示すようなフローにより食品工場排水の処理を行った。生物処理槽１は嫌気槽１ａ；１ｍ³、脱窒槽１ｂ；１ｍ³、好気槽１ｃ；２ｍ³からなる。液化処理はオゾンにて行った。
最初に原水１１である食品工場排水の水質を第１表に示す。この実施例では、原水中には浮遊物質（ＳＳ）はほとんど含まれておらず、ＣＯＤおよびＢＯＤは主に溶解性である。
【００１６】
【表１】

【００１７】
原水１１は全量調整槽６に供給され、分離汚泥１６と混合された。混合液の調整槽６での滞留時間は４時間である。第２表に調整槽６の入口と出口での水質を示す。溶解性のＢＯＤ成分が増加し、酢酸などの有機酸の生成も認められ、有機物の低分子化が起きた。
【００１８】
【表２】

【００１９】
調整槽流出液２０は、生物処理槽１の嫌気槽１ａに供給し、活性汚泥による生物処理を行った。生物処理槽１の運転条件を第３表に示す。
【００２０】
【表３】

【００２１】
固液分離装置Ｉ２から処理水１９は系外に流出させ、沈殿した汚泥は返送汚泥１３ａとして、５．９ｍ³／ｄで生物処理槽の嫌気槽１ａに返送した。
返送汚泥１３ｂは液化処理装置３に供給した。オゾン発生器より発生したオゾン含有高濃度酸素ガスは、オゾン濃度が５６ｍｇ／リットルで、２リットル／ｍｉｎで液化処理装置３に供給された。返送汚泥１３ｂのＭＬＳＳは７３９０ｍｇ／リットル、液化処理装置３への供給量は１．１ｍ³／ｄであった。
【００２２】
液化処理の結果を第４表に示す。返送汚泥１３ｂと流出液Ｉ１４のＭＬＳＳ、溶解性ＢＯＤ（Ｓ−ＢＯＤ）、溶解性有機体窒素（Ｓ−Ｋｊ−Ｎ）および溶解性全リン（Ｓ−Ｔ−Ｐ）を比較すると、ＭＬＳＳが液化処理後に減少し、各溶性成分が増加しており、液化処理により汚泥の液化が進行したと考えられた。また、液化処理装置３から排出されたガスのオゾン濃度はほぼ０であり、オゾンは汚泥の液化処理にほぼ利用されたと考えられた。
【００２３】
【表４】

【００２４】
液化処理された流出液Ｉ１４は、固液分離装置II４にて上澄液１５と分離汚泥１６に分離し、分離汚泥１６は調整槽６に投入した。上澄液１５はリン回収装置５に投入した。リン回収は晶析脱リン法を用いた。リン回収装置５には粒径０．１５〜０．３ｍｍのリン鉱石を充填し、Ｃａ／Ｐの比が約５．０になるようにＣａ（ＯＨ）₂を注入し、上向流式でＬＶ２９ｍ／ｈ、反応槽内ｐＨを９．０に制御した。運転条件を第５表に示す。
【００２５】
【表５】

【００２６】
リン回収装置入口で、リン酸態リン（ＰＯ₄−Ｐ）と全リン（Ｔ−Ｐ）が、それぞれ８２ｍｇ／リットルと８６ｍｇ／リットルであったのに対し、出口でＰＯ₄−ＰとＴ−Ｐがそれぞれ３．３ｍｇ／リットルと４．８ｍｇ／リットルに低下し、リン回収量は６４．９ｇ／ｄであった。
また、溶解性ＣＯＤ（Ｓ−ＣＯＤ）についてみても、入口で１９０ｍｇ／リットルであったのに対し、出口では１５０ｍｇ／リットルとなりＣＯＤも除去されていた。
【００２７】
第６表に、処理水１９の水質を示す。処理水のＣＯＤ、ＢＯＤが２０ｍｇ／リットル以下であり、良好な処理水水質を得ることができた。また、処理水のＴ−Ｐは１．２ｍｇ／リットルとなり、原水１１に対しリン回収率は９０％となった
。
【００２８】
【表６】

【００２９】
好気槽１ｂの活性汚泥のリン含有率は８．１％（対ＶＳＳ）であり、汚泥中にリンが高濃度に蓄積されている状態であった。
約３ヶ月の連続運転中、生物処理槽１の系内汚泥量はほぼ１６ｋｇで安定しており、余剰汚泥の排出をせずに安定した運転が行えた。
【００３０】
比較例１
図３に示すような、リン回収を行わないフローを用い実験を行った。液化処理装置３および生物処理槽１の運転条件は実施例１と同様とした。
第７表に、処理水１９の水質を示す。処理水のＣＯＤ、ＢＯＤが２０ｍｇ／リットル以下であり、良好な処理水水質を得ることができたが、処理水のＴ−Ｐは１０．６ｍｇ／リットルとなり、ほとんど除去されない結果となった。
【００３１】
【表７】

【００３２】
約３ヶ月の連続運転中、生物処理槽１の系内汚泥量はほぼ１６ｋｇで安定しており、リン回収がある場合と同様に余剰汚泥の排出をせずに安定した運転が行えた。
以上の実験から、リン回収を組み込むことにより汚泥減少量が同じであるにもかかわらず、処理水のＴ−Ｐが低減されていることが判明した。
【００３３】
実施例２
この実施例２においては、図２に示すようなフローにより食品工場排水の処理を行った。原水１１は実施例１と同じものを使用し、液化処理装置３、リン回収装置５および生物処理槽１の運転条件は実施例１と同様とした。
原水１１は全量嫌気槽１ａに供給され、分離汚泥１６は全量調整槽１４に供給し攪拌混合した。調整槽６での滞留時間は６時間である。第８表に調整槽の入口と出口での水質を示す。溶解性のＢＯＤが増加し、酢酸などの有機酸の生成も認められ、有機物の低分子化が起きた。
【００３４】
【表８】

【００３５】
リン回収装置入口で、リン酸態リン（ＰＯ₄−Ｐ）と全リン（Ｔ−Ｐ）が、それぞれ６９ｍｇ／リットルと７２ｍｇ／リットルであったのに対し、出口でＰＯ₄−ＰとＴ−Ｐがそれぞれ１．９ｍｇ／リットルと２．２ｍｇ／リットルに低下し、リン回収量は５５．８ｇ／ｄであった。
また、溶解性ＣＯＤ（Ｓ−ＣＯＤ）についてみても、入口で１９０ｍｇ／リットルであったのに対し、出口では１４５ｍｇ／リットルとなりＣＯＤも除去されていた。
【００３６】
第９表に処理水１９の水質を示す。処理水のＣＯＤ、ＢＯＤが２０ｍｇ／リットル以下であり、良好な処理水水質を得ることができた。また、処理水のＴ−Ｐは３．１ｍｇ／リットルとなり、原水１１に対しリン回収率は７３％となった。
【００３７】
【表９】

【００３８】
好気槽１ｂの活性汚泥のリン含有率は６．０％（対ＶＳＳ）であり、汚泥中にリンが高濃度に蓄積されている状態であった。
約３ヶ月の連続運転中、生物処理槽１の汚泥量はほぼ１６ｋｇで安定しており、余剰汚泥の排出をせずに安定した運転が行えた。
活性汚泥のリン含有率は、実施例１が８．１％（対ＶＳＳ）であったのに対し、実施例２は６．０％（対ＶＳＳ）に若干低下した。その結果、リン回収率も実施例１；９３％から実施例２；７９％へ若干低下した。
【００３９】
比較例２
図４に示すように、調整槽６を設置せず、分離汚泥１６および原水１１を生物処理槽１へ直接供給したフローを、比較例２として用い実験を行った。液化処理装置３、リン回収装置５および生物処理槽１の運転条件は実施例１と同様とした。
好気槽１ｃの活性汚泥のリン含有率は３．９％であり、実施例１に比べ汚泥中のリン含有率は低くなった。
【００４０】
リン回収装置入口で、リン酸態リン（ＰＯ₄−Ｐ）と全リン（Ｔ−Ｐ）が、それぞれ２４ｍｇ／リットルと２６ｍｇ／リットルであったのに対し、出口でＰＯ₄−ＰとＴ−Ｐがそれぞれ０．８ｍｇ／リットルと１．３ｍｇ／リットルに低下し、リン回収量は２０ｇ／ｄであった。また、実施例１でのリン回収装置５入口のＰＯ₄−Ｐ、Ｔ−Ｐに比べ、比較例２は約１／３の濃度であった。
また、溶解性ＣＯＤ（Ｓ−ＣＯＤ）についてみても、入口で１９０ｍｇ／リットルであったのに対し、出口では１３５ｍｇ／リットルとなり、ＣＯＤも除去されていた。
【００４１】
第１０表に、処理水の水質を示す。比較例２では、実施例１と比較して処理水ＳＳとＣＯＤが増加し、処理水水質が悪化したことが認められた。また、処理水のＴ−Ｐは８．５ｍｇ／リットルと実施例１よりも悪化し、被処理液に対しリン回収率は２８％となった。
【００４２】
【表１０】

【００４３】
約３ヶ月の連続運転中、生物処理槽１の系内の汚泥量はほぼ１６ｋｇで安定しており、実施例１と同様に余剰汚泥の排出をせずに安定した運転が行えた。
比較例２の実験では、実施例１にみられた調整槽６での有機酸生成がなかったため、リン含有率３．９％の低い汚泥となった。その結果、流入排水に対してのリン回収率は、実施例１では９０％であったのが、比較例１では２８％となり、リン回収効率が低下し物質収支的にみても処理水中にリンが残存した。さらに実施例１と比較例２では同じオゾン量を供給し、汚泥減少量が同じであるにもかかわらず、比較例２に比べ実施例１は処理水のＳＳおよびＣＯＤの低減が認められた。
【００４４】
【発明の効果】
本発明によれば、有機性の工場廃水や生活排水の処理において、液化処理した汚泥もしくは被処理液と液化処理した汚泥を混合し酸発酵させることにより、活性汚泥中のリン含有率が高くなることから、リン回収量が多くなり、処理水リン濃度が低減する。さらに、余剰汚泥の発生を削減できるとともに、余剰汚泥の削減に伴う処理水ＣＯＤの悪化を抑える効果もある。
【図面の簡単な説明】
【図１】本発明の有機性廃水の処理方法の一実施例のフローシートである。
【図２】本発明の有機性廃水の処理方法の別の実施例のフローシートである。
【図３】リン回収を行わない有機性廃水の処理方法の比較例の一例のフローシートである。
【図４】調整槽を設置しない有機性廃水の処理方法の比較例の別の一例のフローシートである。
【符号の説明】
１生物処理槽
１ａ嫌気槽
１ｂ脱窒槽
１ｃ好気槽
２固液分離装置Ｉ
３液化処理装置
４固液分離装置II
５リン回収装置
６調整槽
７生物処理系
１１原水
１２生物処理槽流出液
１３、１３ａ、１３ｂ返送汚泥
１４流出液Ｉ
１５上澄液
１６分離汚泥
１７流出液II
１８回収リン
１９処理水
２０調整槽流出液
２１循環液
２２散気管
２３空気
３３攪拌機[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the treatment of organic wastewater such as sewage, and particularly relates to the treatment of organic wastewater that can achieve reduction in the amount of excess sludge generated by biological treatment of organic wastewater and removal of phosphorus. In particular, the present invention relates to a method and apparatus for treating organic wastewater that can be used for treating organic food wastewater or domestic wastewater having a high phosphorus concentration.
[0002]
[Prior art]
In biological treatment of organic wastewater, activated sludge treatment is widely performed. Conventional activated sludge treatment has been centered on decomposition and removal of degradable organic substances, but in recent years, removal of nitrogen and phosphorus by an anaerobic aerobic method has also been performed. In the activated sludge treatment, the amount of sludge increases with the decomposition of organic matter, but in order to maintain the activated sludge treatment, it is necessary to discharge the increased sludge outside the biological treatment system. Here, a technology for reducing the volume of sludge by liquefying sludge by physical and chemical means has been proposed, and the amount of excess sludge generated can be reduced, but it is included in the reduced sludge. The amount of phosphorus that has flowed into the treated water deteriorates the quality of the treated water. Moreover, the problem that the biodegradable COD produced | generated with the sludge volume reduction process produced | generated and the treated water COD density | concentration was unavoidable.
[0003]
Regarding phosphorus removal, in order to solve this problem, as a known technique related to a biological dephosphorization apparatus, “a sludge solubilization means in which a part of returned sludge is introduced in a biological dephosphorization apparatus by an anaerobic aerobic method, Means for returning the sludge solubilized by the sludge solubilization means to the anaerobic tank, a phosphorus release tank into which a part of the returned sludge is introduced, and a magnesium ammonium phosphate (MAP) into which the effluent of the phosphorus release tank is introduced A biological dephosphorization device characterized by comprising a reaction tower). However, in this technique, since the liquid in the anaerobic tank is introduced into the MAP dephosphorization reaction tower without performing solid-liquid separation, it is difficult to increase the efficiency of phosphorus recovery for the chemicals used. Furthermore, with this technique, the problem of deterioration of the treated water COD concentration due to the production of hardly biodegradable COD has not been solved at all. In addition, when liquefied sludge treated with an oxidizing agent such as ozone is directly put into the anaerobic tank, there is a case where there is no increase in the ORP of the anaerobic tank and generation of organic acid from the liquefied sludge.
[0004]
[Problems to be solved by the invention]
The present invention has been devised in order to solve the above-mentioned problems, and can recover phosphorus in biological treatment of organic wastewater, can prevent an increase in phosphorus and COD in the treated water, and can eliminate excess sludge. It aims at providing the processing method and apparatus of organic wastewater which can reduce generation amount.
[0005]
[Means for Solving the Problems]
The present invention was able to solve the above problems by the following means.
(1) In a biological treatment system using a biological treatment tank including an anaerobic tank, in a method of treating organic wastewater with activated sludge, a part of the biological treatment activated sludge is supplied to a liquefaction treatment apparatus to perform liquefaction treatment, The liquefied activated sludge that has flowed out of the liquefaction treatment apparatus is subjected to solid-liquid separation, and the separated separated sludge is supplied to the adjustment tank, and is stirred and mixed with all or part of the liquid to be treated in the adjustment tank, and subjected to acid fermentation treatment. A method for treating organic wastewater, comprising introducing into a biological treatment tank, collecting phosphorus from the separated liquid separated by the solid-liquid separation, and returning the liquid after collecting the phosphorus to the biological treatment tank.
(2) In a biological treatment system using a biological treatment tank including an anaerobic tank, in a method of treating organic wastewater with activated sludge, a part of the biological treatment activated sludge is supplied to a liquefaction treatment apparatus to perform liquefaction treatment, The liquefied activated sludge that has flowed out of the liquefaction treatment device is subjected to solid-liquid separation, the separated separated sludge is supplied to the adjustment tank, stirred and mixed for acid fermentation, and the liquid and the liquid to be treated are introduced into the biological treatment tank. A method for treating organic wastewater, comprising collecting phosphorus from the separated liquid separated by the solid-liquid separation and returning the liquid after the phosphorus is collected to a biological treatment tank.
[0006]
(3) A biological treatment tank comprising an anaerobic tank, a denitrification tank and an aerobic tank connected with a liquid introduction pipe, in an apparatus for treating organic wastewater by a biological dephosphorization / denitrogenation method by an anaerobic aerobic method, A solid-liquid separator I that separates the effluent of the biological treatment tank into treated water and sludge; a return pipe that sends separated sludge from the solid-liquid separator I to the anaerobic tank and sludge liquefaction treatment apparatus; and Solid-liquid separation device II equipped with a pipe for separating the effluent I into a solid-liquid separation, sending the supernatant to the phosphorus recovery device, and sending the separated sludge to the adjustment tank, the separated sludge and a part or all of the liquid to be treated. Adjusting tank that performs stirring and mixing, acid fermentation of organic matter in the mixed liquid and supplies the effluent to the anaerobic tank, and piping for sending effluent II after phosphorus recovery from the phosphorus recovery apparatus to the anaerobic tank and denitrification tank And a return pipe that sends the aerobic tank effluent to the denitrification tank An organic wastewater treatment apparatus characterized by that.
(4) A biological treatment tank comprising an anaerobic tank, a denitrification tank, and an aerobic tank connected with a liquid introduction pipe in an apparatus for treating organic wastewater by a biological dephosphorization / denitrogenation method by an anaerobic aerobic method, A solid-liquid separator I that separates the effluent of the biological treatment tank into treated water and sludge; a return pipe that sends separated sludge from the solid-liquid separator I to the anaerobic tank and sludge liquefaction treatment apparatus; and Solid-liquid separator II equipped with a pipe for separating the effluent I into a solid-liquid separator, sending the supernatant liquid to the phosphorus recovery device, and sending the separated sludge to the adjustment tank, stirring the separated sludge, and the organic acid in the liquid An adjustment tank that performs fermentation and supplies the effluent to the anaerobic tank, a pipe that sends the effluent II after phosphorus recovery from the phosphorus recovery device to the anaerobic tank and the denitrification tank, and a nitrous acid effluent from the aerobic tank Organic wastewater treatment apparatus characterized by having a return pipe to be sent to .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments and examples.
[0008]
FIG. 1 shows an example flow sheet according to the processing method of the present invention.
The configuration of the treatment apparatus of the present invention is that a biological treatment system 7 comprising a biological treatment tank 1 including an adjustment tank 6 and an anaerobic tank 1a and a solid-liquid separation device I2, a liquefaction treatment device 3, a solid-liquid separation device II4, and a phosphorus recovery device 5 Consists of. Hereinafter, organic wastewater is referred to as raw water.
[0009]
All or a part of the raw water 11 is supplied to the adjustment tank 6. At that time, separation sludge 16 obtained by solid-liquid separation of the effluent I14 from the liquefaction processing device 3 by the solid-liquid separation device II4 is supplied to the adjustment tank 6. The adjustment tank 6 is agitated by the agitator 33. The mixed solution of the raw water 11 and the separated sludge 16 stays in the adjustment tank 6 for an appropriate time. At this time, the organic matter in the separated sludge 16 or in the raw water 11 is accelerated by acid fermentation by the action of the microorganisms in 16 and an organic acid having high biodegradability is generated. Further, when the separated sludge 16 is obtained when liquefaction treatment with an oxidizing agent such as ozone is performed in the liquefaction treatment apparatus 3, the ORP of the adjustment tank effluent 20 is reduced by stirring and mixing in the adjustment tank 6. The ORP rise of the anaerobic tank 1a can be prevented. The adjustment tank effluent 20 is supplied to the biological treatment tank 1. In order to increase the phosphorus recovery rate, it is important to maintain the phosphorus in the sludge at a high concentration. Therefore, the biological treatment tank 1 is equipped with an anaerobic tank 1a than a normal activated sludge method. It is desirable to use a biological nitrogen phosphorus removal method.
[0010]
The adjustment tank effluent 20 contains a large amount of highly biodegradable organic substances such as organic acids. By supplying such an adjustment tank effluent 20 together with the raw water 11 to the anaerobic tank 1a, a high phosphorus content is obtained. The growth of microorganisms is promoted, and the phosphorus content in the sludge becomes 5% or more. After the liquid is subjected to activated sludge treatment in the biological treatment tank 1, the biological treatment tank effluent 12 is supplied to the solid-liquid separator I 2 for solid-liquid separation, and the supernatant is discharged as treated water 19.
[0011]
A part 13b of the activated sludge of the biological treatment system 7 is supplied to the liquefaction treatment apparatus 3 and liquefied. If the sludge supplied to the liquefaction processing apparatus 3 is sludge of the biological treatment system 7, either the return sludge 13 or the activated sludge in the biological treatment tank 1 may be supplied. The activated sludge becomes highly biodegradable by being liquefied, and the excess sludge generated from the biological treatment system 7 is reduced by returning to the biological treatment system 7 for treatment. In particular, by making it equal to the amount of liquefaction, excess sludge in the biological treatment system 7 is not generated. At this time, the amount of sludge supplied to the liquefaction treatment apparatus 3 is desirably 5 to 100% of the total amount of sludge in the system. The liquefaction treatment apparatus 3 can use ozone treatment, ultrasonic treatment, cell grinding with a mill, heated alkali treatment, or the like. Moreover, as the solid-liquid separator I2 and the solid-liquid separator II4, a solid-liquid separator using a precipitation tank and a membrane such as precision membrane filtration, UF filtration, and dynamic filtration can be used.
[0012]
The supernatant 15 separated from the effluent I14 by the solid-liquid separator II4 is supplied to the biological treatment tank 1 after phosphorus is recovered by the phosphorus recovery device 5.
In the supernatant 15, a large amount of phosphorus contained in the activated sludge is eluted by liquefaction treatment, and the soluble phosphorus concentration is high. For example, when a phosphorus content of 8% (VSS) is treated with an ozone injection rate of 20 mg-O ₃ / g-SS, polyphosphoric acid and fungal constituent phosphorus are eluted, and the elution amount is about 20% of phosphorus in sludge. Met. By using the supernatant 15 having a high soluble phosphorus concentration, the phosphorus recovery device 5 can be made compact and the amount of chemical used per amount of phosphorus recovered can be reduced. The supernatant 15 is put into the phosphorus recovery device 5 to recover phosphorus. The phosphorus recovery device 5 may use any of a coagulation precipitation process using iron, aluminum, calcium, or the like, or a crystallization method using hydroxyapatite (HAP) or MAP, but also has an effect of removing COD. Precipitation and hydroxyapatite crystallization are still better.
[0013]
In the present invention, the raw water 11 can be directly introduced into the biological treatment tank 1. This embodiment is shown in FIG. In this case, the residence time in the adjustment tank 6 becomes extremely long, and acid fermentation can be sufficiently performed. Therefore, the capacity | capacitance of the adjustment tank 6 can be made small depending on the condition of acid fermentation. Other embodiments are the same as described above.
[0014]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
[0015]
Example 1
In Example 1, the food factory waste water was treated according to the flow shown in FIG. Biological treatment tank 1 is anaerobic tank 1a; 1 m ^3, a denitrification tank 1b; 1 m ^3, the aerobic tank 1c; consisting 2m ^3. The liquefaction treatment was performed with ozone.
Table 1 shows the water quality of the food factory effluent which is the raw water 11 first. In this embodiment, the raw water contains almost no suspended solids (SS), and COD and BOD are mainly soluble.
[0016]
[Table 1]

[0017]
Raw water 11 was supplied to the total adjustment tank 6 and mixed with the separated sludge 16. The residence time of the mixed liquid in the adjustment tank 6 is 4 hours. Table 2 shows the water quality at the inlet and outlet of the adjustment tank 6. The soluble BOD component increased, the production of organic acids such as acetic acid was also observed, and the molecular weight of organic substances was reduced.
[0018]
[Table 2]

[0019]
The adjustment tank effluent 20 was supplied to the anaerobic tank 1a of the biological treatment tank 1 and subjected to biological treatment with activated sludge. Table 3 shows operating conditions of the biological treatment tank 1.
[0020]
[Table 3]

[0021]
The treated water 19 was discharged out of the system from the solid-liquid separator I2, and the precipitated sludge was returned to the anaerobic tank 1a of the biological treatment tank at 5.9 m ³ / d as a return sludge 13a.
The returned sludge 13b was supplied to the liquefaction processing apparatus 3. The ozone-containing high-concentration oxygen gas generated from the ozone generator was supplied to the liquefaction processing apparatus 3 at an ozone concentration of 56 mg / liter and 2 liter / min. The MLSS of the returned sludge 13b was 7390 mg / liter, and the supply amount to the liquefaction processing apparatus 3 was 1.1 m ³ / d.
[0022]
The results of the liquefaction treatment are shown in Table 4. MLSS of return sludge 13b and effluent I14, soluble BOD (S-BOD), soluble organic nitrogen (S-Kj-N) and soluble total phosphorus (S-TP) are compared, and MLSS is liquefied It decreased after treatment, and each soluble component increased, and it was thought that liquefaction of sludge progressed by liquefaction treatment. Further, the ozone concentration of the gas discharged from the liquefaction treatment apparatus 3 was almost 0, and it was considered that the ozone was almost used for the sludge liquefaction treatment.
[0023]
[Table 4]

[0024]
The liquefied effluent I14 was separated into the supernatant 15 and the separated sludge 16 by the solid-liquid separator II4, and the separated sludge 16 was put into the adjustment tank 6. The supernatant 15 was put into the phosphorus recovery device 5. For the phosphorus recovery, a crystallization dephosphorization method was used. The phosphorus recovery device 5 is filled with phosphorus ore having a particle size of 0.15 to 0.3 mm, and Ca (OH) ₂ is injected so that the Ca / P ratio is about 5.0. The LV was 29 m / h, and the pH in the reaction vessel was controlled to 9.0. Table 5 shows the operating conditions.
[0025]
[Table 5]

[0026]
Phosphorus phosphorus (PO ₄ -P) and total phosphorus (TP) were 82 mg / liter and 86 mg / liter respectively at the inlet of the phosphorus recovery apparatus, whereas PO ₄ -P and T- P decreased to 3.3 mg / liter and 4.8 mg / liter, respectively, and the phosphorus recovery amount was 64.9 g / d.
Also, regarding soluble COD (S-COD), it was 190 mg / liter at the inlet, whereas it was 150 mg / liter at the outlet, and COD was also removed.
[0027]
Table 6 shows the quality of the treated water 19. The COD and BOD of the treated water were 20 mg / liter or less, and good treated water quality could be obtained. Further, the TP of the treated water was 1.2 mg / liter, and the phosphorus recovery rate relative to the raw water 11 was 90%.
[0028]
[Table 6]

[0029]
The phosphorus content of the activated sludge in the aerobic tank 1b was 8.1% (vs. VSS), and phosphorus was accumulated at a high concentration in the sludge.
During continuous operation for about three months, the amount of sludge in the system of the biological treatment tank 1 was stable at approximately 16 kg, and stable operation could be performed without discharging excess sludge.
[0030]
Comparative Example 1
Experiments were performed using a flow that does not perform phosphorus recovery as shown in FIG. The operating conditions of the liquefaction processing apparatus 3 and the biological treatment tank 1 were the same as in Example 1.
Table 7 shows the water quality of the treated water 19. The COD and BOD of the treated water were 20 mg / liter or less and good treated water quality could be obtained, but the TP of the treated water was 10.6 mg / liter, resulting in almost no removal.
[0031]
[Table 7]

[0032]
During the continuous operation for about three months, the amount of sludge in the system of the biological treatment tank 1 was stable at about 16 kg, and the stable operation could be performed without discharging excess sludge as in the case of phosphorus recovery.
From the above experiments, it was found that the TP of the treated water was reduced by incorporating phosphorus recovery even though the sludge reduction amount was the same.
[0033]
Example 2
In Example 2, the wastewater from the food factory was treated according to the flow shown in FIG. The raw water 11 was the same as that in Example 1, and the operating conditions of the liquefaction treatment device 3, the phosphorus recovery device 5 and the biological treatment tank 1 were the same as in Example 1.
The raw water 11 was supplied to the whole amount of the anaerobic tank 1a, and the separated sludge 16 was supplied to the whole amount adjustment tank 14 and mixed with stirring. The residence time in the adjustment tank 6 is 6 hours. Table 8 shows the water quality at the inlet and outlet of the adjustment tank. The solubility BOD increased, the production of organic acids such as acetic acid was also observed, and the molecular weight of organic substances was reduced.
[0034]
[Table 8]

[0035]
Phosphorous phosphorus (PO ₄ -P) and total phosphorus (TP) were 69 mg / liter and 72 mg / liter at the inlet of the phosphorus recovery device, whereas PO ₄ -P and T- P decreased to 1.9 mg / liter and 2.2 mg / liter respectively, and the phosphorus recovery amount was 55.8 g / d.
Also, regarding soluble COD (S-COD), it was 190 mg / liter at the inlet, whereas it was 145 mg / liter at the outlet, and COD was also removed.
[0036]
Table 9 shows the quality of the treated water 19. The COD and BOD of the treated water were 20 mg / liter or less, and good treated water quality could be obtained. Further, the TP of the treated water was 3.1 mg / liter, and the phosphorus recovery rate relative to the raw water 11 was 73%.
[0037]
[Table 9]

[0038]
The phosphorus content of the activated sludge in the aerobic tank 1b was 6.0% (vs. VSS), and phosphorus was accumulated at a high concentration in the sludge.
During continuous operation for about 3 months, the amount of sludge in the biological treatment tank 1 was stable at approximately 16 kg, and stable operation could be performed without discharging excess sludge.
The phosphorus content of the activated sludge was 8.1% (vs. VSS) in Example 1, whereas Example 2 slightly decreased to 6.0% (vs. VSS). As a result, the phosphorus recovery rate slightly decreased from 93% in Example 1 to 79% in Example 2;
[0039]
Comparative Example 2
As shown in FIG. 4, the experiment was performed using the flow in which the separation sludge 16 and the raw water 11 were directly supplied to the biological treatment tank 1 without using the adjustment tank 6 as Comparative Example 2. The operating conditions of the liquefaction treatment device 3, the phosphorus recovery device 5 and the biological treatment tank 1 were the same as in Example 1.
The phosphorus content of the activated sludge in the aerobic tank 1c was 3.9%, and the phosphorus content in the sludge was lower than that in Example 1.
[0040]
Phosphorous phosphorus (PO ₄ -P) and total phosphorus (TP) were 24 mg / liter and 26 mg / liter at the inlet of the phosphorus recovery apparatus, whereas PO ₄ -P and T- P decreased to 0.8 mg / liter and 1.3 mg / liter, respectively, and the phosphorus recovery amount was 20 g / d. Further, compared with PO ₄ -P and TP at the inlet of the phosphorus recovery apparatus 5 in Example 1, the concentration in Comparative Example 2 was about 1/3.
Also, regarding soluble COD (S-COD), it was 190 mg / liter at the inlet, whereas it was 135 mg / liter at the outlet, and COD was also removed.
[0041]
Table 10 shows the quality of the treated water. In Comparative Example 2, it was recognized that the treated water SS and COD increased as compared with Example 1, and the treated water quality deteriorated. Further, the TP of treated water was 8.5 mg / liter, which was worse than that of Example 1, and the phosphorus recovery rate was 28% with respect to the liquid to be treated.
[0042]
[Table 10]

[0043]
During the continuous operation for about 3 months, the amount of sludge in the system of the biological treatment tank 1 was stable at about 16 kg, and the stable operation could be performed without discharging excess sludge as in Example 1.
In the experiment of the comparative example 2, since there was no organic acid production | generation in the adjustment tank 6 seen in Example 1, it became a low sludge with a phosphorus content rate of 3.9%. As a result, the phosphorus recovery rate with respect to the influent wastewater was 90% in Example 1, but 28% in Comparative Example 1. Phosphorus recovery efficiency was reduced, and even in terms of material balance, phosphorus recovery in the treated water Remained. Furthermore, although Example 1 and Comparative Example 2 supplied the same amount of ozone and the amount of sludge reduction was the same, Example 1 showed a reduction in SS and COD of treated water compared to Comparative Example 2.
[0044]
【The invention's effect】
According to the present invention, in the treatment of organic factory wastewater and domestic wastewater, the liquefied sludge or the liquid to be treated and the liquefied sludge are mixed and subjected to acid fermentation, whereby the phosphorus content in the activated sludge increases. Therefore, the amount of phosphorus recovered increases and the concentration of treated water phosphorus decreases. Furthermore, generation | occurrence | production of excess sludge can be reduced and there exists an effect which suppresses the deterioration of the treated water COD accompanying reduction of excess sludge.
[Brief description of the drawings]
FIG. 1 is a flow sheet of one embodiment of a method for treating organic wastewater according to the present invention.
FIG. 2 is a flow sheet of another embodiment of the method for treating organic wastewater of the present invention.
FIG. 3 is a flow sheet as an example of a comparative example of a method for treating organic wastewater without phosphorus recovery.
FIG. 4 is a flow sheet of another example of a comparative example of a method for treating organic wastewater without installing a regulating tank.
[Explanation of symbols]
1 biological treatment tank 1a anaerobic tank 1b denitrification tank 1c aerobic tank 2 solid-liquid separator I
3 Liquidizer 4 Solid-liquid separator II
5 Phosphorus recovery device 6 Adjustment tank 7 Biological treatment system 11 Raw water 12 Biological

treatment tank effluent

13, 13a, 13b Return sludge 14 Effluent I
15 Supernatant 16 Separation Sludge 17 Effluent II
18 Recovery phosphorus 19 Treated water 20 Regulating tank effluent 21 Circulating liquid 22 Aeration pipe 23 Air 33 Stirrer

Claims

In a method for treating organic wastewater with activated sludge in a biological treatment system using a biological treatment tank including an anaerobic tank, a part of the biological treatment activated sludge is supplied to a liquefaction treatment apparatus to perform liquefaction treatment, and the liquefaction treatment The liquefied activated sludge flowing out from the device is solid-liquid separated, the separated separated sludge is supplied to the adjustment tank, mixed with all or part of the liquid to be treated in the adjustment tank, and subjected to acid fermentation treatment, which is the biological treatment tank The organic wastewater treatment method is characterized in that phosphorus is collected from the separated liquid separated by the solid-liquid separation and the liquid after the phosphorus is collected is returned to the biological treatment tank.

In a method for treating organic wastewater with activated sludge in a biological treatment system using a biological treatment tank including an anaerobic tank, a part of the biological treatment activated sludge is supplied to a liquefaction treatment apparatus to perform liquefaction treatment, and the liquefaction treatment The liquefied activated sludge flowing out from the apparatus is subjected to solid-liquid separation, and the separated separated sludge is supplied to the adjustment tank, stirred and mixed for acid fermentation treatment, the liquid and the liquid to be treated are introduced into the biological treatment tank, A method for treating organic wastewater, wherein phosphorus is collected from a separated liquid separated by liquid separation, and the liquid after the phosphorus is collected is returned to a biological treatment tank.

A biological treatment tank comprising an anaerobic tank, a denitrification tank and an aerobic tank connected with a liquid introduction pipe in an apparatus for treating organic wastewater by a biological dephosphorization / denitrogenation method using an anaerobic aerobic method, and the biological treatment Solid-liquid separator I for separating the effluent from the tank into treated water and sludge, return piping for sending the separated sludge from the solid-liquid separator I to the anaerobic tank and sludge liquefaction processor, and the effluent I of the liquefaction processor The solid-liquid separator II equipped with a pipe that feeds the supernatant liquid to the phosphorus recovery device and the separated sludge to the adjustment tank. An adjustment tank that performs acid fermentation of organic matter in the mixed liquid and supplies the effluent to the anaerobic tank, a pipe that sends the effluent II after phosphorus recovery from the phosphorus recovery apparatus to the anaerobic tank and a denitrification tank, and Have a return pipe to send the effluent of the air tank to the denitrification tank. An organic wastewater treatment device.

A biological treatment tank comprising an anaerobic tank, a denitrification tank and an aerobic tank connected with a liquid introduction pipe in an apparatus for treating organic wastewater by a biological dephosphorization / denitrogenation method using an anaerobic aerobic method, and the biological treatment Solid-liquid separator I for separating the effluent from the tank into treated water and sludge, return piping for sending the separated sludge from the solid-liquid separator I to the anaerobic tank and sludge liquefaction processor, and the effluent I of the liquefaction processor The solid-liquid separator II equipped with a pipe that feeds the supernatant liquid to the phosphorus recovery device and the separated sludge to the adjustment tank, stirs the separated sludge and performs acid fermentation of the organic matter in the liquid Adjustment tank for supplying effluent to the anaerobic tank, piping for sending effluent II after phosphorus recovery from the phosphorus recovery device to the anaerobic tank and denitrification tank, and return piping for sending effluent from the aerobic tank to the denitrification tank An organic wastewater treatment apparatus characterized by comprising: