JP4010733B2

JP4010733B2 - Organic wastewater treatment method and apparatus

Info

Publication number: JP4010733B2
Application number: JP2000065254A
Authority: JP
Inventors: 隆生萩野; 昭渡辺; 義治入内嶋
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2000-03-09
Filing date: 2000-03-09
Publication date: 2007-11-21
Anticipated expiration: 2020-03-09
Also published as: JP2001252689A

Description

【０００１】
【発明の属する技術分野】
本発明は、下水処理場や各種廃水処理施設等において有機性排水を処理する方法及び装置に係わり、更に詳しくは、し尿や浄化槽汚泥の消化脱離液、汚泥の消化液、化学工場排水などの高濃度の有機物、リン及び窒素を含有する有機性排水から、リン等をリン酸マグネシウムアンモニウム結晶として除去する処理において、薬剤の使用量を軽減化するとともに、窒素及びリンの除去効率を大幅に改善する処理方法及び処理装置に関するものである。
【０００２】
【従来の技術】
従来の一般的な脱窒、脱リンの同時処理方法としては、嫌気無酸素好気法などの生物学的処理方法や、嫌気好気法、凝集沈殿法、アルミナ吸着法等を組み合わせた方法が多い。また、近年、し尿処理や下水処理の工程で発生する返流水や嫌気性消化脱離液等を対象として排水中のリン及び窒素をリン酸マグネシウムアンモニウム（ＭＡＰ）結晶として除去するＭＡＰ処理法等も試みられている。
【０００３】
【発明が解決しようとする課題】
しかしながら、これらの処理方法の内、嫌気無酸素好気法は、水質の変化や季節変動に伴う外部環境の変化により、処理性能が安定しない等の問題があり、嫌気好気法と凝集沈殿法等を組み合わせた方法は、処理工程が煩雑な上に薬品代をはじめとするランニングコストが大きい等の問題があった。
ＭＡＰ処理法は、先の２法に比べて運転操作の煩雑さは少なく、特にリンの回収を安定的に行える上、回収されるＭＡＰは優れた肥料としての付加価値があり、資源の有効利用の点からも優れたリン及び窒素の除去技術といえる。しかし、ＭＡＰ法の場合も、ｐＨ調整剤としての水酸化ナトリウムや添加剤として塩化マグネシウム等の薬品コストがかかる他、比較的ＳＳ濃度が小さい（３０００ｍｇ／リットル程度）場合においてのみ、正リン酸態リン濃度を約６〜７割程度除去することができる。つまり、高濃度の汚泥中に含まれる微細なＭＡＰ粒子はほとんど回収されず、汚泥とともに処分されるだけで、窒素とリンの回収技術としては問題があった。
【０００４】
本発明は、上述した従来技術の問題点を解決することを目的とする。すなわち、本発明は有機性排水処理システムの中で、特に有機物、窒素、リンを含有する有機性排水、例えばし尿や浄化槽汚泥の消化脱離液、汚泥の消化液、化学工場排水などの高濃度の有機物、リン及び窒素を含有する排水から、リン酸マグネシウムアンモニウム結晶として除去するＭＡＰ処理法において、薬剤の使用量を軽減化するとともに、窒素及びリンの除去効率を大幅に改善する処理方法及び装置を課題とするものである。
【０００５】
【課題を解決するための手段】
本発明者等は、上記課題を解決するために鋭意検討を行い、有機性排水中のリン及び窒素をリン酸マグネシウムアンモニウム結晶として除去するＭＡＰ処理工程に加えて減圧処理工程を付加することにより、薬剤の使用量の低減とともに、窒素及びリンの除去効率が大幅に向上することを知見し、本発明を完成するに至った。
【０００６】
すなわち、本発明は、下記の有機性排水の処理方法及びその装置により、上記課題を解決した。
（１）有機性排水を生物反応槽で処理し、その生物反応槽において発生した汚泥を嫌気性醗酵工程に導入し、嫌気性醗酵工程の途中または終了後生成した消化汚泥中のリン及び窒素をリン酸マグネシウムアンモニウムの形態にして系外に取り出す工程（１）を組み入れている処理方法において、前記嫌気性醗酵工程と前記工程（１）の間に、リン及び窒素を含有する該消化汚泥を減圧処理する減圧処理工程（２）を組み込むことを特徴とする有機性排水の処理方法。
（２）前記工程（１）を経た消化汚泥を前記嫌気性発酵工程に戻すことを特徴とする前記（１）記載の有機性排水の処理方法。
（３）前記嫌気性発酵工程に戻した消化汚泥を脱水装置に導入し脱水処理し、脱水処理後の脱水ろ液を減圧装置に導入して減圧処理し、減圧処理後の脱水ろ液中の正リン酸態リンとアンモニア態窒素をリン酸マグネシウムアンモニウムの形態として回収することを特徴とする前記（２）記載の有機性排水の処理方法。
【０００７】
（４）有機性排水を生物学的に処理する排水処理装置において、有機性排水を生物学的に処理する生物反応槽と、前記生物反応槽からの汚泥を嫌気性発酵させる嫌気性発酵槽と、前記嫌気性発酵槽にて生成した消化汚泥についての処理経路に、減圧処理装置を経るリン酸マグネシウムアンモニウム反応槽を設けることを特徴とする有機性排水の処理装置。
（５）有機性排水を生物学的に処理する排水処理装置において、有機性排水を流入水として供給する被処理水流入管と接続し、脱水装置への濃縮汚泥配送管を設けた最初固液分離槽と、前記最初固液分離槽の分離水排出側に設けた、前記脱水装置への濃縮汚泥配送管を有する中間分離槽、次いで生物反応槽、更に嫌気性醗酵槽への濃縮汚泥配送管を設けた最終固液分離槽と、前記脱水装置のケーキ排出側に前記嫌気性醗酵槽へのエネルギー回収手段を設置したケーキ燃焼装置と、メタンガス回収装置を設けた嫌気性醗酵槽の排出側に設けた減圧処理装置、更にリン酸マグネシウムアンモニウム反応槽を具備していることを特徴とする有機性排水の処理装置。
（６）前記リン酸マグネシウムアンモニウム反応槽を経た消化汚泥を前記嫌気性発酵槽に戻す経路を備えたことを特徴とする前記（４）又は（５）記載の有機性排水の処理装置。
（７）前記嫌気性発酵槽に戻した消化汚泥を導入して脱水処理する脱水装置、前記脱水装置からの脱水処理後の脱水ろ液を導入して減圧処理する減圧装置、前記減圧装置からの減圧処理後の脱水ろ液を導入して脱水ろ液中の正リン酸態リンとアンモニア態窒素をリン酸マグネシウムアンモニウムの形態として回収する第２のリン酸マグネシウムアンモニウム反応槽を有することを特徴とする前記（６）記載の有機性排水の処理装置。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態を作用とあわせて説明する。
上記課題を解決する方法として、本発明では以下に図１及び図２に示す基本処理フローからなる有機性排水の処理方法を提案する。
すなわち、有機性排水を処理する方法であって、該排水中のリン及び窒素をリン酸マグネシウムアンモニウムの形態にして系外に取り出す工程（１）（「ＭＡＰ処理工程」という）を組み入れている方法において、リン及び窒素を含有する排水を減圧処理する工程（２）を組み込むことで、対象液中に溶存する炭酸や硫化水素等の成分を気相に排出することにより、対象液中のｐＨを高めることになる。その結果、従来対象液にｐＨ調整剤として比較的多量に添加する必要のあった水酸化ナトリウムなどの薬剤の添加量を軽減することができる。
【０００９】
図１において、有機性排水を流入ＳＳ固液分離槽１に導入して固形分を沈殿させ、その上澄み水を膜分離手段を備えた中間分離槽６（これは場合によっては設けなくてもよい）へ送り、沈殿した汚泥又はその濃縮汚泥は脱水装置１０へ送る。中間分離槽６で分離した分離水は、生物反応槽３へ送り、そこで例えば活性汚泥法で好気性生物反応を行わせて処理し、微生物固液分離槽５で汚泥を沈殿分離して清浄化された処理水として流出する。
この処理方法において、微生物固液分離槽５で沈殿分離された汚泥は濃縮汚泥３１として系外に出されるが、この濃縮汚泥３１はリン及び窒素をより高度に濃縮されたものとなっているので、これからリン及び窒素をリン酸マグネシウムアンモニウムの形態にして得ることができれば有価物の回収ができる。
【００１０】
そこで、この濃縮汚泥３１を嫌気性発酵槽４に入れて嫌気性発酵工程を行わせると、有機物が分解してメタンガスが発生し、有機物の量が減少した消化汚泥４１が得られる。そこでは、数百〜数千のアンモニア態窒素及び正リン酸態リンを含有し、Ｍアルカリ成分や硫化水素の高い含有率を持つ消化汚泥を生成される。その消化汚泥４１または消化工程途中の汚泥４２の全部または一部を減圧装置２に送り、減圧処理を行う。消化汚泥４１、消化途中汚泥４２は、減圧下の条件下にすると液から炭酸ガスや硫化水素、及び遊離アンモニアが放出され、それに伴って水酸イオン分が増加する。この液をＭＡＰ第１槽２１に送り、Ｍｇ源としてのＭｇＣｌ₂等を添加すると、水酸化ナトリウム等のｐＨ調整剤を添加しない、または少量添加するだけでＭＡＰ生成反応が進行する。ＭＡＰ第１槽２１は、ＭＡＰ粒子を形成する機能とＭＡＰ粒子を系外に分離する機能を兼ね備えている。ＭＡＰ第１槽２１を経た消化汚泥４３は、嫌気性発酵槽４に戻されて、再び嫌気性発酵工程を経る。消化汚泥４３は、減圧装置２とＭＡＰ槽２１を経る間に、液中の炭酸ガス、硫化水素、遊離アンモニア、正リン酸態リン、水酸イオン、アンモニウムイオン等の嫌気性発酵の活性を低下させる物質が減少している上、汚泥中の微生物の一部が減圧処理によるダメージを受けて分解されやすい形態となっていることから、他の微生物の分解対象となり消化汚泥４３は、汚泥４１、４２と比較して嫌気性発酵工程が進行し易く、嫌気性発酵槽４の有機物の分解率を向上させる。
【００１１】
このように、汚泥は嫌気性発酵槽４、減圧装置２、ＭＡＰ第１槽を循環することにより、発酵による分解率を高くすることができ、分解された炭素分はメタンガスに、窒素分、リン分はＭＡＰに、それぞれ有用な形態で回収される。さらにＭＡＰ第１槽から嫌気性発酵槽４に戻して循環させてもよい。
この場合の嫌気性発酵槽４、減圧装置２、ＭＡＰ第１槽はこの順序に限定されなくてもよく、汚泥の性状によっては例えば嫌気性発酵槽４、ＭＡＰ第１槽、減圧装置２の順に循環する場合も有効である。さらに減圧装置２から嫌気性発酵槽４に戻して循環させてもよい。また、この一連の工程において汚泥中に析出したＭＡＰ粒子の多くはＭＡＰ第１槽において回収されるが、嫌気発酵槽の有機物分解レベルによっては、汚泥中に正リン酸態リンやアンモニア態窒素が依然高濃度で存在する場合がある。そのため、ＭＡＰ粒子を取り除かれた後の消化汚泥４１は、高分子凝集剤等で凝集した後に脱水処理し、その脱水ろ液をＭＡＰ第２槽、Ｍｇ源としてのＭｇＣｌ₂等と、水酸化ナトリウム等のｐＨ調整剤を添加することにより脱水ろ液中の正リン酸態リンとアンモニア態窒素をＭＡＰ粒子として回収することができる。
【００１２】
減圧装置２に於ける減圧の条件としては、減圧の程度が大きい程、炭酸ガスや硫化水素の放出量が多くなり、効果的ではあるが、減圧のための動力が大きくなる。適切な減圧の程度としては８０〜３６０ｈｐａｓが好ましい。
一方、脱水装置１０に入った濃縮汚泥１１及び濃縮汚泥６１は脱水され、脱水汚泥はケーキ燃焼装置７に送られ、そこで燃焼し、エネルギー回収手段８により嫌気性醗酵槽４を加温して嫌気性醗酵が助長するようにすると効果的である。さらに、嫌気性醗酵槽４で発生するメタンガスはメタンガス回収手段９により回収して、それを別に燃焼させ、その燃焼熱で嫌気性醗酵槽４を加温するようにすることができる。
【００１３】
このように、生物反応槽３において発生した汚泥の一部を嫌気性醗酵工程４に導入し、嫌気性醗酵工程の途中または終了後の消化汚泥４１に対して減圧処理を行う工程（２）と、ＭＡＰ処理工程（１）を組み入れることにより、数百〜数千のアンモニア態窒素及び正リン酸態リンを含有し、炭酸や硫化水素の高い含有率を持つ消化汚泥を生成させつつ、脱炭酸や脱硫化水素による水酸化イオンの増加に伴い、ＭＡＰ生成の進行が促進され易くなるとともに、ＭＡＰ粒子回収後の汚泥を嫌気性発酵槽に戻すことで、嫌気性発酵反応が促進される。
【００１４】
また、減圧処理工程（２）としては特開平７−１３６４０６号公報に開示されているような脱気装置（以後、薄膜真空脱気装置と称する）を使用することが望ましい。すなわち、真空容器内で回転する有底のふるい体の遠心力により対象液体を加速して対象液体を該真空容器内の壁面に衝突させ、対象液体中の気体を除去する方式の連続脱気装置を採用する方法を採用することにより、減圧処理による脱炭酸や脱硫化水素の効果を大幅に増すことが可能となる。
また、減圧処理工程はＭＡＰ処理工程の前後いずれであってもよい。更に、図１に示すように嫌気性醗酵工程とＭＡＰ処理工程と減圧処理工程を繰り返し行ってもよい。すなわち、嫌気性発酵工程、ＭＡＰ処理工程、減圧処理工程間の循環はそれぞれ往復させることもできる。
図２は、図１の汚泥処理系のものを排水処理系に応用したもので汚泥系のものと同様の作用効果が得られた。図２では、排水又は生物処理水１２を減圧処理槽２で処理後、ＭＡＰ反応槽２３でＭＡＰ処理する。この際、ＭＡＰ反応槽２３より減圧処理槽２に対し循環させてもよい。ＭＡＰ反応槽２３で処理した水はＭＡＰ処理水１４として、生成物はＭＡＰ生成物１５として排水される。
【００１５】
【実施例】
次に、本発明を実際に組み込んだ実験プラントの運転結果の一例について詳細に説明する。図１に実験プラントのフローを示す。
実施例１
すなわち、本発明では、流入ＳＳ固液分離槽１、活性汚泥が浮遊する生物反応槽３、微生物固液分離槽５を含む有機性排水処理システムにおいて、流入ＳＳ固液分離槽１において分離した初沈汚泥の濃縮汚泥１１、すなわち脱水性が比較的良く、高カロリーで、窒素とリンの含有率が低いＳＳ成分を、脱水装置１０により脱水処理することにより、排水処理系から多量の有機成分を取り除き、脱水ケーキをケーキ燃焼装置７において燃焼する。
また、微生物固液分離槽５において分離した余剰汚泥またはその濃縮汚泥３１、すなわち脱水性が比較的悪く、低カロリーで、窒素とリンの含有率が高い成分を、嫌気性醗酵槽４において消化し、嫌気性醗酵工程で生成する消化汚泥４１、すなわち高濃度の窒素、リン及びアルカリ成分を含有する成分からリン酸マグネシウムアンモニウムの形態でリンと窒素を回収する。
【００１６】
その際、有機性排水が活性汚泥が浮遊する生物反応槽３に流入する工程の前に、流入ＳＳ固液分離槽１の分離水中に残存する懸濁成分を分離する中間固液分離槽６を設け、かつ、中間固液分離槽６において分離した中間汚泥またはその濃縮汚泥６１を、脱水装置１０により脱水する工程を含むことにより、カロリーが高く、脱水性の良いＳＳ性有機物を脱水し、脱水ケーキとして排出することで水処理系外に分離する。
【００１７】
更に、脱水装置１０により脱水処理した初沈汚泥またはその濃縮汚泥１１、または中間汚泥またはその濃縮汚泥６１の脱水ケーキを燃焼させるケーキ燃焼装置７、ケーキ燃焼装置７において発生するエネルギーを回収する燃焼エネルギー回収手段８、嫌気性醗酵槽４で生成するメタンガス等を回収するメタンガス回収手段９などの手段を利用することにより、プラントのエネルギー消費量の軽減化を効率的に行う。
【００１８】
その上に、ＭＡＰ第１槽２１の後に、生物反応槽３において発生した汚泥の一部を嫌気性醗酵槽４に導入し、嫌気性醗酵工程の途中または終了後の消化汚泥４１に薄膜真空脱気装置を減圧装置２として使用することにより、脱炭酸や脱硫化水素による水酸化イオンの増加を行い、ＭＡＰ生成の進行を促進する。ＭＡＰ粒子回収後の汚泥は嫌気性発酵槽に戻した。
ＭＡＰ第１槽では、０．５ｍｍ以上に成長したＭＡＰ粒子を、比重比を利用して系外に取出す機構を組み込んだ。また嫌気性発酵槽４から排出される消化汚泥は脱水装置１０により脱水し、脱水ケーキは、ケーキ燃焼装置７により燃焼し、脱水ろ液はＭＡＰ第２槽により再び窒素とリンを回収した。対象水は、下水処理場に流入する汚水を利用した。
【００１９】
図１に示す実施例では、水質がＢＯＤ２００ｍｇ／リットル、ＳＳ１８０ｍｇ／リットル、流量が９００ｍ³／日の流入水に対し、処理水の水質がＢＯＤ２０ｍｇ／リットル、ＳＳ１０ｍｇ／リットルであった。また、流入ＳＳ固液分離槽１からの濃縮汚泥１１と中間分離槽６からの濃縮汚泥６１を混合したものは、ＳＳ３０ｇ／リットル、流量が３．５ｍ³／日であった。これを脱水装置１０で脱水した汚泥ケーキは含水率６８％、２４０ｋｇ／日であった。また、この時ＭＡＰ反応槽２１で得られたＭＡＰは１４ｋｇ／日（ＭｇＮＨ₄ＰＯ₄・６Ｈ₂Ｏとして）であった。ＭＡＰ第１槽２１に添加するｐＨ調整剤であるＮａＯＨの量は０．２ｋｇ／日であり、減圧がないＭＡＰ処理のみの場合の３．０ｋｇ／日に対して約９３％以上削減できた。ＭＡＰ第２槽に添加するｐＨ調整剤であるＮａＯＨの量は１．１ｋｇ／日であった。また、嫌気性発酵槽の有機物の消化率は、ＭＡＰ処理のみの場合が４５％に対して本発明では８５％であり、消化汚泥中の窒素、リンからのＭＡＰとしての回収率は、ＭＡＰ処理のみの場合がそれぞれ４％、３２％に対して本発明ではそれぞれ１２％、８４％であり、本発明の回収率が高かった。
【００２０】
実施例２
また、図２に示すように、ＭＡＰ処理を組み込んだ有機性排水の処理システムの中のＭＡＰ反応槽に対するプロセス水に対して、減圧処理槽において減圧処理を行うことにより、ＭＡＰ生成効率は高まる。
第１表にＡ工場排水の排水処理システムにおけるＭＡＰ反応槽に流入する流入水に対してＭＡＰ処理を施した場合と施さない場合の処理水質とＭＡＰ生成量の比率を示す。表に示すように、既存のＭＡＰ処理施設では、Ｍｇ添加剤、及びアルカリ剤を十分添加しているにもかかわらず、処理対象のリン、及び窒素をそれぞれ９．８ｍｇ／リットル、４１０ｍｇ／リットルまでしか処理することができなかったのに対し、本発明のフローの減圧処理工程をＭＡＰ処理工程の前段に行うことにより、Ｍｇ添加剤、及びアルカリ剤を既存設備より少なくしているにもかかわらず、処理水中のリン、及び窒素はそれぞれ２．１ｍｇ／リットル、３３０ｍｇ／リットルまで低下しており、省薬品量、高効率除去を可能にした。
ＮＨ₃−Ｎの濃度が化学量論的なマスバランスと食い違う点に関しては、減圧処理とアルカリ処理の併用によるアンモニアストリッピングによる減少が生じている可能性があるが、現時点においては明確にわかっていない。
【００２１】
【表１】

【００２２】
【発明の効果】
本発明によれば、有機性排水処理システムの中で、特に有機物、窒素、リンを含有する排水、例えばし尿や浄化槽汚泥の消化脱離液、汚泥の消化液、化学工場排水などの高濃度の有機物、リン及び窒素を含有する排水から、リン酸マグネシウムアンモニウム結晶として除去するＭＡＰ処理法において、薬剤の使用量を低減化するとともに、窒素、及びリンの除去効率を大幅に改善することができた。
【図面の簡単な説明】
【図１】本発明の有機性排水の処理方法を示すブロック図である。
【図２】本発明における、ＭＡＰ反応槽に対するプロセス水に対して、減圧処理槽において減圧処理を行う処理方法のブロック図を示す。
【符号の説明】
１流入ＳＳ固液分離槽
２減圧装置
３生物反応槽
４嫌気性醗酵槽
５微生物固液分離槽
６中間分離槽
７ケーキ燃焼装置
８エネルギー回収手段
９メタンガス回収手段
１０脱水装置
１１濃縮汚泥
１２排水
１３減圧処理水
１４ＭＡＰ処理水
１５ＭＡＰ生成物
２１ＭＡＰ第１槽
２２ＭＡＰ第２槽
２３ＭＡＰ反応槽
３１濃縮汚泥
４１、４２、４３消化汚泥
６１濃縮汚泥[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for treating organic wastewater at a sewage treatment plant or various wastewater treatment facilities, and more specifically, such as digestion and desorption liquid of human waste and septic tank sludge, sludge digestion liquid, and chemical factory wastewater. In the treatment to remove phosphorus, etc. as magnesium ammonium phosphate crystals from organic wastewater containing high concentrations of organic matter, phosphorus and nitrogen, the amount of chemicals used is reduced and nitrogen and phosphorus removal efficiency is greatly improved. The present invention relates to a processing method and a processing apparatus.
[0002]
[Prior art]
Conventional simultaneous denitrification and dephosphorization simultaneous treatment methods include biological treatment methods such as anaerobic anaerobic anaerobic method, anaerobic aerobic method, coagulation precipitation method, alumina adsorption method and the like. Many. In addition, in recent years, there is also a MAP treatment method for removing phosphorus and nitrogen in wastewater as magnesium ammonium phosphate (MAP) crystals for return water and anaerobic digestion and detachment liquid generated in the process of human waste treatment and sewage treatment. Has been tried.
[0003]
[Problems to be solved by the invention]
However, among these treatment methods, the anaerobic anaerobic aerobic method has problems such as unstable treatment performance due to changes in the water environment and changes in the external environment due to seasonal fluctuations. The method combining these methods has problems such as complicated processing steps and high running costs including chemical costs.
The MAP treatment method is less complicated to operate than the previous two methods, and in particular, it can stably recover phosphorus, and the recovered MAP has an added value as an excellent fertilizer, making effective use of resources. From this point of view, it can be said to be an excellent removal technique of phosphorus and nitrogen. However, in the case of the MAP method, chemical phosphate such as sodium hydroxide as a pH adjusting agent and magnesium chloride as an additive is required, and only when the SS concentration is relatively small (about 3000 mg / liter), the normal phosphate state About 60 to 70% of the phosphorus concentration can be removed. In other words, the fine MAP particles contained in the high-concentration sludge are hardly recovered, and are disposed of together with the sludge. Thus, there is a problem as a technique for recovering nitrogen and phosphorus.
[0004]
The object of the present invention is to solve the above-mentioned problems of the prior art. That is, the present invention is an organic wastewater treatment system, particularly organic wastewater containing organic matter, nitrogen and phosphorus, such as digestion and desorption liquid of human waste and septic tank sludge, sludge digestion liquid, chemical factory wastewater, etc. Method and apparatus for reducing the amount of chemicals used and drastically improving nitrogen and phosphorus removal efficiency in a MAP treatment method for removing magnesium ammonium phosphate crystals from wastewater containing organic substances, phosphorus and nitrogen Is an issue.
[0005]
[Means for Solving the Problems]
The present inventors have intensively studied to solve the above problems, and by adding a reduced pressure treatment step in addition to the MAP treatment step of removing phosphorus and nitrogen in organic wastewater as magnesium ammonium phosphate crystals, The inventors have found that the removal efficiency of nitrogen and phosphorus is greatly improved along with the reduction of the amount of the drug used, and the present invention has been completed.
[0006]
That is, this invention solved the said subject with the following processing method and apparatus of organic waste_water | drain.
(1) Treat organic wastewater in a biological reaction tank, introduce sludge generated in the biological reaction tank into the anaerobic fermentation process, and remove phosphorus and nitrogen in the digested sludge generated during or after the anaerobic fermentation process. In the treatment method incorporating the step (1) of taking out in the form of magnesium ammonium phosphate, the digested sludge containing phosphorus and nitrogen is reduced in pressure between the anaerobic fermentation step and the step (1). A method for treating organic wastewater, characterized by incorporating a reduced pressure treatment step (2) to be treated.
(2) The method for treating organic waste water according to the above (1), wherein the digested sludge having undergone the step (1) is returned to the anaerobic fermentation step.
(3) the digested sludge was returned to the anaerobic fermentation process is introduced dehydrated in a dehydrator, dehydrated filtrate was dehydrated under reduced pressure treatment is introduced into a vacuum apparatus, dehydration filtrate liquid after vacuum treatment The method for treating organic waste water according to (2), wherein the normal phosphate phosphorus and ammonia nitrogen are recovered in the form of magnesium ammonium phosphate.
[0007]
(4) In a wastewater treatment apparatus for biologically treating organic wastewater, a biological reaction tank for biologically treating organic wastewater, an anaerobic fermentation tank for anaerobically fermenting sludge from the biological reaction tank, the processing pathways for digested sludge generated by the anaerobic fermentation tank, vacuum processing apparatus processing device for organic waste water, characterized in providing a magnesium ammonium phosphate reaction vessel undergoing.
(5) In a wastewater treatment device that biologically treats organic wastewater, it is connected to a treated water inflow pipe that supplies the organic wastewater as inflow water, and the first solid-liquid separation is provided with a concentrated sludge delivery pipe to the dewatering device. An intermediate separation tank having a concentrated sludge delivery pipe to the dehydrator, a biological reaction tank, and a concentrated sludge delivery pipe to an anaerobic fermentation tank provided on the separation water discharge side of the first solid-liquid separation tank; the final solid-liquid separation tank provided, and cake combustion apparatus installed energy recovery unit to the anaerobic fermentation tank to cake discharge side of the dewatering device, the discharge side of the anaerobic fermentation tank provided with a methane gas recovery system An organic wastewater treatment apparatus comprising a reduced pressure treatment apparatus and a magnesium ammonium phosphate reaction tank.
(6) The organic wastewater treatment apparatus according to (4) or (5), further comprising a path for returning the digested sludge that has passed through the magnesium ammonium phosphate reaction tank to the anaerobic fermentation tank.
(7) A dehydrator that introduces the digested sludge that has been returned to the anaerobic fermenter to perform dehydration, a depressurizer that introduces dehydrated filtrate after dehydration from the dehydrator and depressurizes, and a depressurizer from the depressurizer It is characterized by having a second magnesium ammonium phosphate reaction tank that introduces the dehydrated filtrate after the reduced pressure treatment and recovers normal phosphate phosphorus and ammonia nitrogen in the dehydrated filtrate in the form of magnesium ammonium phosphate. The organic wastewater treatment apparatus as described in (6) above.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described together with actions.
As a method for solving the above-mentioned problems, the present invention proposes a method for treating organic waste water comprising the basic treatment flow shown in FIGS. 1 and 2 below.
That is, a method for treating organic wastewater, which incorporates a step (1) (referred to as “MAP treatment step”) in which phosphorus and nitrogen in the wastewater are taken out of the system in the form of magnesium ammonium phosphate. In the above, by incorporating a step (2) of depressurizing waste water containing phosphorus and nitrogen, components such as carbonic acid and hydrogen sulfide dissolved in the target liquid are discharged into the gas phase, thereby adjusting the pH in the target liquid. Will increase. As a result, it is possible to reduce the amount of chemicals such as sodium hydroxide that have been conventionally required to be added in a relatively large amount as a pH adjuster to the target liquid.
[0009]
In FIG. 1, the organic waste water is introduced into the inflow SS solid-liquid separation tank 1 to precipitate solids, and the supernatant water is provided with an intermediate separation tank 6 equipped with membrane separation means (this may not be provided in some cases). ) And the precipitated sludge or its concentrated sludge is sent to the dehydrator 10. The separated water separated in the intermediate separation tank 6 is sent to the biological reaction tank 3, where it is treated by, for example, an aerobic biological reaction by the activated sludge method, and sludge is separated and purified in the microbial solid-liquid separation tank 5. Discharged as treated water.
In this treatment method, the sludge precipitated and separated in the microbial solid-liquid separation tank 5 is discharged out of the system as the concentrated sludge 31, but this concentrated sludge 31 is more highly concentrated in phosphorus and nitrogen. If phosphorus and nitrogen can be obtained in the form of magnesium ammonium phosphate, valuable materials can be recovered.
[0010]
Therefore, when the concentrated sludge 31 is put into the anaerobic fermentation tank 4 and an anaerobic fermentation process is performed, the organic matter is decomposed to generate methane gas, and the digested sludge 41 in which the amount of the organic matter is reduced is obtained. There, hundreds to thousands of ammonia nitrogen and orthophosphoric phosphorus are contained, and digested sludge having a high content of M alkali components and hydrogen sulfide is generated. All or part of the digested sludge 41 or sludge 42 in the middle of the digestion process is sent to the decompression device 2 to perform decompression processing. When the digested sludge 41 and the digested sludge 42 are subjected to conditions under reduced pressure, carbon dioxide, hydrogen sulfide, and free ammonia are released from the liquid, and the amount of hydroxide ions increases accordingly. When this liquid is sent to the MAP first tank 21 and MgCl ₂ or the like as an Mg source is added, the MAP generation reaction proceeds by adding no pH adjusting agent such as sodium hydroxide or adding a small amount. The MAP first tank 21 has a function of forming MAP particles and a function of separating the MAP particles out of the system. The digested sludge 43 that has passed through the MAP first tank 21 is returned to the anaerobic fermentation tank 4 and undergoes the anaerobic fermentation process again. Digested sludge 43 reduces the activity of anaerobic fermentation of carbon dioxide, hydrogen sulfide, free ammonia, normal phosphate phosphorus, hydroxide ions, ammonium ions, etc. in the liquid while passing through the decompression device 2 and the MAP tank 21. Since the amount of substances to be reduced is reduced and a part of the microorganisms in the sludge is easily decomposed due to damage caused by the decompression process, the digested sludge 43 becomes a target for decomposition of other microorganisms. Compared with 42, the anaerobic fermentation process is easy to proceed, and the decomposition rate of the organic matter in the anaerobic fermentation tank 4 is improved.
[0011]
Thus, the sludge can increase the decomposition rate by fermentation by circulating through the anaerobic fermentation tank 4, the decompression device 2, and the MAP first tank, and the decomposed carbon content is converted into methane gas, nitrogen content, phosphorus content. Minutes are recovered in MAP, each in useful form. Further, the MAP first tank may be returned to the anaerobic fermentation tank 4 and circulated.
In this case, the anaerobic fermentation tank 4, the decompression device 2, and the MAP first tank may not be limited to this order. For example, the anaerobic fermentation tank 4, the MAP first tank, and the decompression device 2 may be used in this order depending on the properties of the sludge. It is also effective when circulating. Furthermore, you may return and circulate from the decompression device 2 to the anaerobic fermenter 4. In addition, most of the MAP particles precipitated in the sludge in this series of steps are collected in the MAP first tank, but depending on the organic matter decomposition level in the anaerobic fermenter, normal phosphate phosphorus and ammonia nitrogen may be present in the sludge. May still be present at high concentrations. Therefore, the digested sludge 41 from which the MAP particles have been removed is dehydrated after being agglomerated with a polymer flocculant or the like, and the dehydrated filtrate is treated with MAP second tank, MgCl ₂ as an Mg source, and sodium hydroxide. By adding a pH adjuster such as, it is possible to recover normal phosphate phosphorus and ammonia nitrogen in the dehydrated filtrate as MAP particles.
[0012]
As conditions for decompression in the decompression device 2, the greater the degree of decompression, the greater the amount of carbon dioxide gas and hydrogen sulfide released, which is effective, but the power for decompression increases. An appropriate degree of pressure reduction is preferably 80 to 360 hpas.
On the other hand, the concentrated sludge 11 and the concentrated sludge 61 that have entered the dehydrator 10 are dehydrated, and the dehydrated sludge is sent to the cake combustor 7 where it is burned, and the anaerobic fermentation tank 4 is heated by the energy recovery means 8 and anaerobic. It is effective to promote sexual fermentation. Furthermore, the methane gas generated in the anaerobic fermentation tank 4 can be recovered by the methane gas recovery means 9 and burned separately, and the anaerobic fermentation tank 4 can be heated by the combustion heat.
[0013]
Thus, the process (2) which introduce | transduces some sludge which generate | occur | produced in the biological reaction tank 3 into the anaerobic fermentation process 4, and performs the pressure reduction process with respect to the digested sludge 41 in the middle of anaerobic fermentation process or after completion | finish By incorporating the MAP treatment step (1), decarboxylation while producing digested sludge containing hundreds to thousands of ammonia nitrogen and normal phosphate phosphorus and having a high content of carbonic acid and hydrogen sulfide. As the hydroxide ions increase due to hydride and desulfurized hydrogen, the progress of MAP generation is facilitated, and the sludge after MAP particle recovery is returned to the anaerobic fermentation tank, thereby promoting the anaerobic fermentation reaction.
[0014]
In addition, it is desirable to use a deaerator (hereinafter referred to as a thin film vacuum deaerator) as disclosed in JP-A-7-136406 as the decompression process step (2). That is, a continuous deaeration apparatus of a type in which a target liquid is accelerated by a centrifugal force of a bottomed sieve rotating in a vacuum container, and the target liquid collides with a wall surface in the vacuum container to remove a gas in the target liquid. By adopting the method, it becomes possible to greatly increase the effects of decarboxylation and desulfurization by depressurization.
Further, the decompression process may be performed before or after the MAP process. Furthermore, as shown in FIG. 1, you may repeat an anaerobic fermentation process, a MAP processing process, and a pressure reduction processing process. That is, the circulation between the anaerobic fermentation process, the MAP treatment process, and the decompression treatment process can be reciprocated.
FIG. 2 is an application of the sludge treatment system of FIG. 1 to the waste water treatment system, and the same effects as the sludge system were obtained. In FIG. 2, waste water or biologically treated water 12 is treated in the reduced pressure treatment tank 2 and then MAP treated in the MAP reaction tank 23. At this time, the MAP reaction tank 23 may be circulated to the vacuum treatment tank 2. The water treated in the MAP reaction tank 23 is drained as MAP treated water 14 and the product is drained as MAP product 15.
[0015]
【Example】
Next, an example of the operation result of the experimental plant that actually incorporates the present invention will be described in detail. Fig. 1 shows the flow of the experimental plant.
Example 1
That is, in the present invention, in the organic wastewater treatment system including the inflow SS solid-liquid separation tank 1, the biological reaction tank 3 in which activated sludge floats, and the microbial solid-liquid separation tank 5, the first separation in the inflow SS solid-liquid separation tank 1 is performed. Concentrated sludge 11 of settled sludge, that is, SS component with relatively good dewaterability, high calorie content and low nitrogen and phosphorus content, is dehydrated by the dehydrator 10 to remove a large amount of organic components from the wastewater treatment system. The dehydrated cake is removed and burned in the cake combustion device 7.
In addition, the excess sludge separated in the microbial solid-liquid separation tank 5 or its concentrated sludge 31, that is, a component with relatively low dehydration, low calories, and high nitrogen and phosphorus content is digested in the anaerobic fermentation tank 4. The phosphorus and nitrogen are recovered in the form of magnesium ammonium phosphate from the digested sludge 41 produced in the anaerobic fermentation process, that is, the component containing high concentration of nitrogen, phosphorus and alkali components.
[0016]
At that time, an intermediate solid-liquid separation tank 6 that separates suspended components remaining in the separated water of the inflow SS solid-liquid separation tank 1 before the step of flowing the organic wastewater into the biological reaction tank 3 in which activated sludge floats is provided. By providing the step of dehydrating the intermediate sludge or the concentrated sludge 61 separated in the intermediate solid-liquid separation tank 6 with the dehydrator 10, the SS organic material having a high calorie and good dehydrating properties can be dehydrated and dehydrated. Separated from the water treatment system by discharging as a cake.
[0017]
Furthermore, the initial combustion sludge dehydrated by the dewatering device 10 or its concentrated sludge 11, or the cake combustion device 7 for burning the dewatered cake of the intermediate sludge or its concentrated sludge 61, and the combustion energy for recovering the energy generated in the cake combustion device 7 By using means such as the recovery means 8 and the methane gas recovery means 9 for recovering the methane gas generated in the anaerobic fermentation tank 4, the energy consumption of the plant is efficiently reduced.
[0018]
In addition, after the MAP first tank 21, a part of the sludge generated in the biological reaction tank 3 is introduced into the anaerobic fermentation tank 4, and the digested sludge 41 is removed from the digested sludge 41 during or after the anaerobic fermentation process. By using the gas device as the pressure reducing device 2, the hydroxide ions are increased by decarboxylation or desulfurization, and the progress of MAP generation is promoted. The sludge after MAP particle recovery was returned to the anaerobic fermenter.
In the MAP first tank, a mechanism for taking out MAP particles grown to 0.5 mm or more out of the system using a specific gravity ratio was incorporated. The digested sludge discharged from the anaerobic fermenter 4 was dehydrated by the dehydrator 10, the dehydrated cake was burned by the cake combustor 7, and the dehydrated filtrate recovered nitrogen and phosphorus again by the MAP second tank. The target water used was sewage flowing into the sewage treatment plant.
[0019]
In the example shown in FIG. 1, the water quality was BOD 200 mg / liter, SS 180 mg / liter, the flow rate was 900 m ³ / day, and the quality of treated water was BOD 20 mg / liter and SS 10 mg / liter. In addition, the mixture of the concentrated sludge 11 from the inflow SS solid-liquid separation tank 1 and the concentrated sludge 61 from the intermediate separation tank 6 had an SS of 30 g / liter and a flow rate of 3.5 m ³ / day. The sludge cake dehydrated by the dehydrator 10 had a water content of 68% and 240 kg / day. At this time, the MAP obtained in the MAP reaction vessel 21 was 14 kg / day (as MgNH ₄ PO ₄ .6H ₂ O). The amount of NaOH as a pH adjusting agent added to the MAP first tank 21 was 0.2 kg / day, which was reduced by about 93% or more compared to 3.0 kg / day in the case of only MAP treatment without decompression. The amount of NaOH, which is a pH adjuster, added to the MAP second tank was 1.1 kg / day. In addition, the digestibility of organic matter in the anaerobic fermenter is 85% in the present invention compared to 45% in the case of MAP treatment alone, and the recovery rate as MAP from nitrogen and phosphorus in the digested sludge is MAP treatment. In the present invention, the recovery rates were 4% and 32%, respectively, and 12% and 84% in the present invention, respectively.
[0020]
Example 2
Moreover, as shown in FIG. 2, the MAP generation efficiency is increased by performing the decompression process in the decompression process tank on the process water for the MAP reaction tank in the organic wastewater treatment system incorporating the MAP process.
Table 1 shows the ratio between the treated water quality and the amount of MAP produced when the MAP treatment is applied to the inflow water flowing into the MAP reaction tank in the wastewater treatment system for factory A wastewater. As shown in the table, in the existing MAP treatment facilities, the phosphorus and nitrogen to be treated are up to 9.8 mg / liter and 410 mg / liter respectively, even though Mg additive and alkali agent are sufficiently added. However, it was possible to treat only the reduced pressure treatment step of the flow of the present invention before the MAP treatment step, thereby reducing the amount of Mg additive and alkaline agent compared to the existing equipment. In addition, phosphorus and nitrogen in the treated water were reduced to 2.1 mg / liter and 330 mg / liter, respectively, which enabled chemical saving and high-efficiency removal.
Regarding the point where the concentration of NH ₃ -N is inconsistent with the stoichiometric mass balance, there may be a decrease due to ammonia stripping due to the combined use of vacuum treatment and alkali treatment, but at this time it is clearly known. Absent.
[0021]
[Table 1]

[0022]
【The invention's effect】
According to the present invention, in an organic wastewater treatment system, wastewater containing organic matter, nitrogen, phosphorus in particular, such as digestion and desorption liquid of human waste and septic tank sludge, sludge digestion liquid, chemical factory wastewater, etc. In the MAP treatment method for removing magnesium and ammonium phosphate from wastewater containing organic matter, phosphorus, and nitrogen, the amount of chemicals used was reduced, and the removal efficiency of nitrogen and phosphorus could be greatly improved. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing an organic wastewater treatment method of the present invention.
FIG. 2 is a block diagram of a processing method for performing a decompression process in a decompression treatment tank on process water for the MAP reaction tank in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inflow SS solid-liquid separation tank 2 Depressurization apparatus 3 Biological reaction tank 4 Anaerobic fermentation tank 5 Microbial solid-liquid separation tank 6 Intermediate separation tank 7 Cake combustion apparatus 8 Energy recovery means 9 Methane gas recovery means 10 Dehydration apparatus 11 Concentrated sludge 12 Drainage 13 Reduced pressure treated water 14 MAP treated water 15 MAP product 21 MAP first tank 22 MAP second tank 23 MAP reaction tank 31 Concentrated sludge 41, 42, 43 Digested sludge 61 Concentrated sludge

Claims

Organic wastewater is treated in a biological reaction tank, sludge generated in the biological reaction tank is introduced into the anaerobic fermentation process, and phosphorus and nitrogen in the digested sludge generated during or after the anaerobic fermentation process are converted to magnesium phosphate. In the treatment method incorporating the step (1) to be taken out of the system in the form of ammonium, a reduced pressure for treating the digested sludge containing phosphorus and nitrogen under reduced pressure between the anaerobic fermentation step and the step (1). A method for treating organic wastewater, characterized by incorporating a treatment step (2) .

The method for treating organic waste water according to claim 1, wherein the digested sludge having undergone the step (1) is returned to the anaerobic fermentation step.

The anaerobic digested sludge was returned to the fermentation step is introduced into a dehydrator and dehydrated, the dehydrating filtrate was dehydrated under reduced pressure treatment is introduced into a vacuum apparatus, orthophosphoric the dehydration filtrate liquid after vacuum treatment The method for treating organic waste water according to claim 2, wherein acid phosphorus and ammonia nitrogen are recovered in the form of magnesium ammonium phosphate.

In a wastewater treatment apparatus for biologically treating organic wastewater, a biological reaction tank for biologically treating organic wastewater, an anaerobic fermentation tank for anaerobically fermenting sludge from the biological reaction tank, and the anaerobic An organic wastewater treatment apparatus, characterized in that a magnesium ammonium phosphate reaction tank that passes through a reduced pressure treatment apparatus is provided in a treatment path for digested sludge produced in a fermentative fermentation tank.

In a wastewater treatment device for biologically treating organic wastewater, an initial solid-liquid separation tank connected to a treated water inflow pipe that supplies organic wastewater as inflow water, and provided with a concentrated sludge delivery pipe to the dehydrator, An intermediate separation tank having a concentrated sludge delivery pipe to the dehydrator, provided on the separated water discharge side of the first solid-liquid separation tank, then a biological reaction tank, and further a concentrated sludge delivery pipe to an anaerobic fermentation tank A solid-liquid separation tank, a cake combustion apparatus provided with energy recovery means for the anaerobic fermentation tank on the cake discharge side of the dehydrator, and a decompression process provided on the discharge side of the anaerobic fermentation tank provided with a methane gas recovery apparatus An organic wastewater treatment apparatus comprising an apparatus and a magnesium ammonium phosphate reaction tank.

The organic wastewater treatment apparatus according to claim 4 or 5, further comprising a path for returning the digested sludge that has passed through the magnesium ammonium phosphate reaction tank to the anaerobic fermentation tank.

Dehydration device that introduces the digested sludge that has been returned to the anaerobic fermenter and dehydrates it, decompression device that introduces dehydrated filtrate after the dehydration treatment from the dehydrator and decompresses, and after decompression treatment from the decompressor And a second magnesium ammonium phosphate reaction vessel for recovering normal phosphate phosphorus and ammonia nitrogen in the dehydrated filtrate in the form of magnesium ammonium phosphate. 6. The organic wastewater treatment apparatus according to 6.