JP2004160304A

JP2004160304A - Method and equipment for treating organic waste water and sludge

Info

Publication number: JP2004160304A
Application number: JP2002326967A
Authority: JP
Inventors: Takao Hagino; 隆生萩野
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2002-11-11
Filing date: 2002-11-11
Publication date: 2004-06-10
Anticipated expiration: 2022-11-11
Also published as: JP3664398B2

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably improve the removal and recovery rate of phosphorous from an organic waste water and sludge containing organic matter, phosphorous and nitrogen of a high concentration. <P>SOLUTION: The treatment method having an MAP (Magnesium Ammonium Phosphate) separation stage where MAP generated in sludge in an anaerobic digestion stage is discharged to the outside of a system, is provided with: a sludge reduction stage to MAP-free sludge after the removal of the MAP particles dispersed into the sludge in the MAP separation stage; an MAP-Mg solution contact stage where a solution containing Mg ions is mixed into the MAP concentrated suspension separated in the MAP separation stage; an MAP particle recovery stage from the liquid containing the MAP concentrated suspension after the MAP-Mg solution contact stage; and a stage where the MAP-free suspension after the removal of the recovered solid MAP particles is returned to the anaerobic digestion stage or the prestage thereto. <P>COPYRIGHT: (C)2004,JPO

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廃水及び汚泥を処理するシステムに係わり、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廃水から、リン等をリン酸マグネシウムアンモニウム（以下「ＭＡＰ」ともいう）結晶として除去するとともに、該ＭＡＰ結晶を回収する技術において、純度の高い良質のＭＡＰ結晶を効率良く回収する方法及び装置に関する。
【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等がある。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、ＭＡＰを回収する処理法等も試みられている。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という問題があった。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。
【０００３】
しかし、ＭＡＰ法の場合も、（１）ｐＨ調整剤としての水酸化ナトリウムや添加剤としての塩化マグネシウム等の薬品コストが大きい、（２）３０分程度の短時間において急速にＭＡＰを晶析させる（「急速ＭＡＰ反応」と略記する）と、微細なＭＡＰ粒子が生成され、ＭＡＰ反応槽の処理水中に微細ＭＡＰ粒子が同伴され、ＭＡＰ回収率が６０〜７０％程度に低下する場合がある、（３）急速ＭＡＰ反応は、約１０００ｍｇ／リットル以上のＳＳが液中に混在するとＳＳがＭＡＰ晶析物と絡み合い、純度の高いＭＡＰ結晶としての回収が困難である、（４）ＭＡＰ処理工程の前段に嫌気性消化工程等を採用している場合においては、嫌気性消化工程においてすでにＭＡＰ反応が行われており、生成されたＭＡＰ粒子はそのままでは有機性ＳＳとの分離が困難であるため、消化汚泥に混在した状態で、回収されないまま汚泥とともに処分されているなどの問題点が存在する。
【０００４】
そこで、本発明者らは上述した従来の問題を解決すべく、特許出願「特願２０００−２３１６３３」（特開平２００２−０４５８８９−特許文献１）、「特願２００２−１８６１７９」、及び「特願２００２−１１６２５７」等において開示した、「有機性廃水の処理方法及び処理装置」により、廃水中のリンを効率良くＭＡＰとして回収する技術を提案した。すなわち、有機性廃水処理工程において発生する余剰汚泥（一般的には、最初沈殿池において沈降分離した初沈汚泥と、最終沈殿池において沈降分離した活性汚泥から返送汚泥分を除いた余剰汚泥との混合汚泥（「混合余剰汚泥」ともいえる）を意味する）に対して嫌気性消化処理を行い、かつ該工程においてマグネシウム源を供給して、反応槽内にＭＡＰを積極的に生成せしめ、生成したＭＡＰを消化汚泥から分離し回収する工程を有する有機性排液の処理方法と処理装置を提案した。該発明を実施することにより、廃水中からのリン回収効率を大幅に高めることが可能となった。そこで、本発明者らはさらに該発明を改善すべく詳細に検討した結果、ＭＡＰとしてのリン回収率のさらなる向上と安定化を可能にすることに成功した。
【０００５】
【特許文献１】
特開２００２−０４５８８９号公報
【０００６】
【発明が解決しようとする課題】
本発明は、上述した従来技術の問題点の解決及び、先の特許出願「特願２０００−２３１６３３」（特開２００２−０４５８８９）、「特願２００２−１８６１７９」、及び「特願２００２−１１６２５７」等の発明をさらに向上させることを目的とする。すなわち、本発明は、有機性廃水処理システムの中で、特に有機物、窒素、リンを含有する廃水、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廃水に対して、嫌気性処理工程を採用し、かつ、リン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処理法において、リンの除去及び回収効率を大幅に改善する技術を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
本発明は、以下に示す手段により上記課題を解決することができた。
（１）嫌気性処理工程を組み入れた有機性廃水又は汚泥処理システムであり、該嫌気性消化工程において汚泥中に発生するリン酸マグネシウムアンモニウムを系外に取り出すリン酸マグネシウムアンモニウム分離工程を有する処理方法であって、該リン酸マグネシウムアンモニウム分離工程において汚泥中に分散するリン酸マグネシウムアンモニウム粒子を除去した後のリン酸マグネシウムアンモニウム脱離汚泥に対する汚泥減量化工程、該リン酸マグネシウムアンモニウム分離工程において分離したリン酸マグネシウムアンモニウム濃縮懸濁液に対してマグネシウムイオンを含む溶液を混合又は接触させるリン酸マグネシウムアンモニウム−マグネシウム溶液接触工程、該リン酸マグネシウムアンモニウム−マグネシウム溶液接触工程後の該リン酸マグネシウムアンモニウム濃縮懸濁液を含む液体からリン酸マグネシウムアンモニウム粒子を回収する工程、及び回収された固形状のリン酸マグネシウムアンモニウム粒子を取り除いた後のリン酸マグネシウムアンモニウム脱離後懸濁液を、前記嫌気性消化工程又はその前段に戻す工程を有することを特徴とする有機性廃水及び汚泥の処理方法。
【０００８】
（２）リン酸マグネシウムアンモニウム脱離汚泥に対する汚泥減量化工程において該汚泥から分離した濃縮分離液又は脱水ろ液を、リン酸マグネシウムアンモニウム−マグネシウム溶液接触工程に導入することでリン酸マグネシウムアンモニウム粒子、マグネシウム溶液由来のマグネシウムイオン、及び濃縮分離液または脱水ろ液由来のリン酸イオンが、同時に接触することを特徴とする前記（１）に記載の有機性廃水及び汚泥の処理方法。
（３）汚泥中のリン酸マグネシウムアンモニウムを回収する手段として、液体サイクロン、ふるいやスクリーン状の分離体、沈殿分離装置、及びリン酸マグネシウムアンモニウム洗浄装置の内少なくとも１つを使用することを特徴とする前記（１）又は（２）に記載の有機性廃水及び汚泥の処理方法。
【０００９】
（４）有機性廃水又は汚泥処理システムの構成装置として、嫌気性消化反応槽を有し、該嫌気性消化反応槽には少なくとも原水供給管と消化汚泥排出管が接続し、該嫌気性消化反応槽に直接又は間接的にマグネシウム源の供給を行うことが可能なフローで構成され、該嫌気性消化反応槽から排出された汚泥又は該嫌気性消化反応槽内の汚泥から比重が大きい粒子を優先的に濃縮分離する固液分離装置を配備し、該固液分離装置により分離した粒子を多く含むスラリー状又は固形状物質に対して、マグネシウムイオン溶液又はマグネシウムイオン溶液と濃縮分離液あるいは脱水ろ液由来のリン酸イオンを接触させる装置及び、マグネシウムイオン溶液と接触後の粒子を固形物として回収する装置を含み、粒子と接触後のマグネシウムイオン溶液を直接的または間接的に前記嫌気性消化反応槽に導入することを特徴とする有機性廃水及び汚泥の処理装置。
【００１０】
【発明の実施の形態】
本発明の実施の形態を図面にしたがって説明する。図１は本発明の一実施形態であり、本発明はこの実施の形態に限定されるものではない。
図１において、有機性廃水処理システムから排出される初沈汚泥５と余剰活性汚泥６は、汚泥濃縮装置２１で濃縮分離され、濃縮汚泥７は投入汚泥混合槽２２に導かれる。投入汚泥混合槽２２には、濃縮汚泥７の他に、ＭＡＰ−Ｍｇ接触槽２５においてＭＡＰ粒子の大部分を取り除かれ、かつマグネシウムイオンが多く残留するＭＡＰ脱離汚泥１５、及び必要に応じてマグネシウム源１７、またはＭＡＰ濃縮装置２４で濃縮されたＭＡＰ濃縮汚泥１４の一部が導入される。
投入汚泥混合槽２２の目的は、嫌気性消化槽２３に投入すべき濃縮汚泥７を、これら種々の液体と混合し一時的に滞留させることにより、後段の嫌気性消化槽２３内での消化率の向上、ＭＡＰ生成率の向上、ＭＡＰ粒子径の拡大、消化槽内の壁面等へのＭＡＰ付着の防止等に効果を上げることである。投入汚泥混合槽２２内は撹拌機による撹拌処理、及び必要に応じて加温処理を施す場合がある。
【００１１】
投入汚泥混合槽２２において調整された消化槽投入汚泥８は、消化槽２３において嫌気的に生物分解される。同時に、嫌気的生物分解における代謝成分であるアンモニアイオン、リン酸イオン、及びマグネシウムイオンに加えて、ＭＡＰ−Ｍｇ接触槽２５や投入汚泥混合槽２２において補給されたマグネシウム源を、基質成分として消化槽２３内においてＭＡＰ粒子が晶析する。
ＭＡＰ粒子を含む消化汚泥９は、ＭＡＰ分離濃縮機２４において、粒径１００μｍ以上で比重１．５以上のＭＡＰを主体とする粒子を多く含むＭＡＰ濃縮汚泥１４とＭＡＰ脱離汚泥（１）１０に分離される。ＭＡＰ分離濃縮機としては液体サイクロン、電動式のふるいやスクリーン状の分離体、沈殿分離装置、及びＭＡＰ洗浄装置や、それらの装置原理を組み合わせた装置等を使用することができる。ＭＡＰ脱離汚泥（１）１０は一部が消化槽２３に返送され、残りが脱水装置２６により脱水され脱水ケーキ１１となる。
【００１２】
ＭＡＰ濃縮汚泥１４はＭＡＰ−Ｍｇ接触槽２５に導入される。該ＭＡＰ−Ｍｇ接触槽２５では新たなＭｇ源１７、及び必要に応じてｐＨ調整剤を供給することにより、ＭＡＰ濃縮汚泥１４中に存在するＭＡＰ粒子の表面に新たなＭＡＰが積層される。投入汚泥混合槽２２及びＭＡＰ−Ｍｇ接触槽２５に供給するＭｇ源供給量は、後段の消化槽２３内のリンをできるだけＭＡＰとして合成し、溶解性リン濃度を極小にするのに必要な量を添加することが好ましい。当然、Ｍｇ源添加剤のコストやその他のシステムのハンドリング性も考慮して、Ｍｇ源添加量を設定するべきであることは言うまでもない。また、ＭＡＰ−Ｍｇ接触槽２５の設定ｐＨを８．５以上に高くしすぎると、有機性ＳＳが絡まったＭＡＰ粒子が形成される恐れがあり好ましくない。適正設定ｐＨとしては７．５〜８．０の範囲となる場合が多い。
【００１３】
また、該ＭＡＰ−Ｍｇ接触槽２５は、ＭＡＰ粒子の洗浄用装置とすることも可能である。例えば、ＭＡＰ分離濃縮機２４として液体サイクロン単体を採用した場合は、ＭＡＰ濃縮汚泥１４はＭＡＰ粒子以外に約２％の有機性ＳＳ成分を含むので、なるべく純粋なＭＡＰ粒子として回収をしたい場合は、該ＭＡＰ濃縮汚泥１４を洗浄する必要がある。ＭＡＰ粒子の洗浄用水として上水、処理水４、または脱水ろ液１２等にＭｇ源を添加した液体を使用し、ＭＡＰ−Ｍｇ接触槽２５に供給することにより、ＭＡＰ粒子表面上に新たなＭＡＰを析出させつつ、ＳＳを多く含むＭＡＰ濃縮汚泥１４から、ＭＡＰ粒子以外の有機性ＳＳ成分を洗い流すことが可能となる。一般的にＭＡＰ−Ｍｇ接触槽２５槽内はＭＡＰ晶析反応としてはリン律速状態であるが、特に、脱水ろ液１２にＭｇ源を添加した液体をＭＡＰ洗浄水とする場合は、脱水ろ液中に残存する溶解性リン成分が供給されることになるので、ＭＡＰの析出量が増大するとともに、返流水中のリン負荷を軽減させることにつながり効率的である。
【００１４】
このような洗浄機構を含むＭＡＰ−Ｍｇ接触槽２５としては、上向流の流動層型装置を使用することにより、ＭＡＰ粒子と洗浄水希釈汚泥との分離性が良く、また、ＭＡＰ粒子の引抜き時にＭＡＰ濃縮汚泥１４の供給を一時停止し、洗浄水のみを供給することにより、有機性ＳＳ成分をほとんど含まないＭＡＰ粒子を回収することが可能となる。
【００１５】
ＭＡＰ−Ｍｇ接触槽２５から投入汚泥混合槽２２に返流されるＭＡＰ脱離汚泥（２）１５は、マグネシウムイオン濃度が大きく、溶解性リン濃度が小さく、また嫌気性消化汚泥由来であることからＭアルカリ成分を多く含む。投入汚泥混合槽２２において、該汚泥１５、ＭＡＰ種晶源としてのＭＡＰ濃縮汚泥１４、及びさらなるＭｇ源を供給し、混合及び滞留させることにより、濃縮汚泥７の酸発酵が促進されることによる消化槽２３での消化率の向上、マグネシウム濃度の高い環境下において、ＭＡＰ粒子が多く存在することによるＭＡＰ生成の促進と大粒径化、及びＭＡＰ構成成分がＭＡＰ種晶の表面に優先的に析出しやすくなるために、消化槽内の壁面、底部、配管等にこびりつくＭＡＰが減少する効果等がある。
【００１６】
以上に説明したように、嫌気性消化汚泥中に積極的にＭＡＰ粒子を発生させてそのＭＡＰ粒子を回収する技術において、システム全体を構成する各プロセスの特性を生かしたＭｇ供給ポイントと、ＭＡＰ粒子の洗浄工程の最適化を行った本発明方法を採用することにより、下水汚泥中に含有されるリン成分の大部分を、ＭＡＰとして高効率に回収することが可能であり、脱水ケーキとして系外に排出されるリンの比率を大幅に削減することが可能となる。
【００１７】
【実施例】
次に、本発明の廃水処理技術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説明する。ただし、本発明は本実施例に限定されるものではない。
【００１８】
実施例１
本実施例は、Ａ下水処理場の汚泥を使用して行ったパイロットプラント実験による実施例であり、フローは先に示した図１のフローと同じである。Ａ処理場は、嫌気好気法による活性汚泥処理を採用している。実施例のパイロットプラントでは、Ａ処理場から採取した初沈汚泥５と余剰汚泥６を約１：１で混合し、遠心濃縮機により濃縮する。濃縮汚泥７は投入汚泥混合槽２２に導入する。該投入汚泥混合槽２２には、ＭＡＰ−Ｍｇ接触槽２５からのＭＡＰ脱離汚泥（２）１５、液体サイクロンにより消化汚泥からＭＡＰ粒子を濃縮したＭＡＰ濃縮汚泥１４の一部、及び塩化マグネシウム溶液を導入する。該投入汚泥混合槽２２は滞留時間が４８時間で、水温４０度に加温し、槽内は撹拌機により混和されている。該槽にはｐＨ調整剤を添加しなかったが、ＭＡＰ濃縮汚泥１４の返送量を調整することによりｐＨはほぼ７．０に制御することが可能であった。
【００１９】
ＭＡＰ−Ｍｇ接触槽２５は、混合ゾーンとＭＡＰ堆積ゾーンに分離されており、延べ滞留時間が３時間の上向流流動層型の装置を使用した。該槽２５には液体サイクロンにより濃縮したＭＡＰ濃縮汚泥１４、及び塩化マグネシウムを脱水ろ液１２に溶解して作ったＭｇ源供給水兼ＭＡＰ洗浄水を槽底部から供給した。Ｍｇ源供給水兼ＭＡＰ洗浄水は、ＭＡＰ濃縮汚泥１４の３倍量供給した。系内に投入した全塩化マグネシウムは、濃縮汚泥７の１リットル当たりマグネシウムイオンとして３００ｍｇ添加した。槽内は５００μｍ以上に成長したＭＡＰ粒子が、ＭＡＰ堆積ゾーンのテーパーになった底部から除々に堆積し、その堆積層高さが一定レベル以内に収まるように、ＭＡＰ粒子を底部から引抜くよう制御した。ＭＡＰ粒子の引抜き時には一時的にＭＡＰ濃縮汚泥１４の供給を停止し、ＭＡＰ堆積ゾーン底部からＭｇ含有洗浄水のみを供給する操作を行った。嫌気性消化槽２３は、３５℃中温消化で、滞留時間は２５日とした。脱水機２６はスクリュープレス型脱水機を使用した。
【００２０】
また、本実施例の対照系（比較例）として、従来法の「混合濃縮＋嫌気性消化＋脱水」のプロセス（図３参照）と、「特開２００２−０４５８８９」のプロセス（図２参照）も同時に実行した。運転結果を第１表に示す。
【００２１】
【表１】

【００２２】
消化槽に投入した投入汚泥のＳＳは、従来法が４．２％、「特開２００２−０４５８８９」が４．０％、本実施例が２．９％であった。本実施例のＳＳが比較的小さいのは、投入汚泥混合槽２２において比較的濃度が低い汚泥等を混合していることによる。ＭＡＰとして回収できたリンは、消化槽投入汚泥１ｍ^３あたり、「特開２００２−０４５８８９」５．１ｋｇ／ｍ^３に対して、本発明法６．５ｋｇ／ｍ^３となり本発明法の方が１．４ｋｇ／ｍ^３大きくなった。また、回収したＭＡＰ粒子の純度は、「特開２００２−０４５８８９」と本実施例とはともに９５％以上であった。このリン回収率を下水処理場に流入するリンに対する回収率として算出すると、「特開２００２−０４５８８９」４９％に対して、本実施例６５％と１６％向上する結果となった。
【００２３】
【発明の効果】
本発明によれば、有機性廃水処理システムの中で、特に有機物、窒素、リンを含有する廃水、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廃水から、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、（１）ＭＡＰ回収率を大幅に向上することができ、（２）純度の高いＭＡＰを生成することができ、（３）処理水質の向上、及び（４）廃棄物として排出する脱水ケーキ中のリン含有率を大幅に低下することが可能になる。
【図面の簡単な説明】
【図１】本発明の一実施例のフローシートである。
【図２】比較例としての「特開２００２−０４５８８９」の方法のフローシートである。
【図３】比較例としての従来法のフローシートである。
【符号の説明】
１流入水
２最初沈殿池流出水
３生物反応装置流出水
４処理水
５初沈汚泥
６余剰汚泥
７濃縮汚泥
８消化槽投入汚泥
９消化汚泥
１０ＭＡＰ脱離汚泥（１）（消化循環汚泥）
１１脱水ケーキ
１２脱水ろ液
１３濃縮装置脱離液
１４ＭＡＰ濃縮汚泥
１５ＭＡＰ脱離汚泥（２）
１６回収ＭＡＰ
１７マグネシウム源
１８最初沈殿池
１９エアレーションタンク
２０最終沈殿池
２１汚泥濃縮装置
２２投入汚泥混合槽
２３消化槽
２４ＭＡＰ分離濃縮機（液体サイクロン）
２５ＭＡＰ−Ｍｇ接触槽
２６脱水装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a system for treating organic wastewater and sludge in a sewage treatment plant or various wastewater treatment facilities, and more particularly, to a digestion / desorption solution of human waste or septic tank sludge, a digestion solution of sludge, a wastewater of a chemical factory, and the like. In a technology for removing phosphorus and the like as magnesium ammonium phosphate (hereinafter also referred to as "MAP") crystals from wastewater containing high concentrations of organic substances, phosphorus and nitrogen, and recovering the MAP crystals, high-quality MAP with high purity is used. The present invention relates to a method and an apparatus for efficiently collecting crystals.
[0002]
[Prior art]
Conventional general methods for simultaneous treatment of denitrification and dephosphorization include biological treatment methods such as anaerobic anoxic aerobic method, and methods combining anaerobic aerobic method, coagulation sedimentation method, alumina adsorption method, etc. There is. Also, in recent years, a treatment method for collecting MAP for return water, anaerobic digestion and desorbed liquid generated in the process of human waste treatment and sewage treatment, and the like have been attempted. Among these treatment methods, the anaerobic anoxic aerobic method has problems such as inconsistent treatment performance due to changes in water quality and changes in the external environment due to seasonal fluctuations. The combined method has problems that the processing steps are complicated and that the running cost including the cost of chemicals is large. In the MAP treatment method, the operation is less complicated than the above two methods, and particularly, phosphorus can be recovered stably, and the recovered MAP has an added value as an excellent fertilizer, and the effective use of resources. Therefore, it can be said that this is an excellent technology for removing phosphorus and nitrogen.
[0003]
However, also in the case of the MAP method, (1) chemical costs such as sodium hydroxide as a pH adjuster and magnesium chloride as an additive are large, and (2) MAP is rapidly crystallized in a short time of about 30 minutes. (Abbreviated as “rapid MAP reaction”), fine MAP particles are generated, and fine MAP particles are entrained in the treatment water of the MAP reaction tank, and the MAP recovery rate may be reduced to about 60 to 70%. (3) In the rapid MAP reaction, when about 1000 mg / L or more of SS is mixed in the liquid, the SS is entangled with the MAP crystallized substance, and it is difficult to recover high-purity MAP crystals. In the case where the anaerobic digestion step or the like is adopted in the first stage, the MAP reaction has already been performed in the anaerobic digestion step, and the generated MAP particles are not treated with organic S For separation of it is difficult, in a mixed state to the digested sludge, problems such as have been disposed of with the sludge without being recovered is present.
[0004]
In order to solve the conventional problems described above, the present inventors have applied for patent applications “Japanese Patent Application No. 2000-231633” (Japanese Patent Application Laid-Open No. 2002-045889-Patent Document 1), “Japanese Patent Application No. 2002-186179”, and “Japanese Patent Application No. A technique for efficiently recovering phosphorus in wastewater as MAP by "a method and apparatus for treating organic wastewater" disclosed in "2002-116257" and the like was proposed. That is, the excess sludge generated in the organic wastewater treatment process (generally, the initial sludge settled and separated in the first settling tank and the excess sludge obtained by removing the returned sludge from the activated sludge settled and separated in the final settling tank) An anaerobic digestion treatment is performed on mixed sludge (meaning "mixed excess sludge"), and a magnesium source is supplied in this step to actively generate MAP in the reaction tank and generate MAP. A method and an apparatus for treating organic effluent having a process of separating and recovering MAP from digested sludge have been proposed. By implementing the present invention, it has become possible to greatly increase the efficiency of phosphorus recovery from wastewater. Then, the present inventors have studied in detail to further improve the invention, and have succeeded in enabling further improvement and stabilization of the phosphorus recovery rate as MAP.
[0005]
[Patent Document 1]
JP-A-2002-045889
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art and discloses the above-mentioned patent applications “Japanese Patent Application No. 2000-231633” (Japanese Patent Application Laid-Open No. 2002-045889), “Japanese Patent Application No. 2002-186179”, and “Japanese Patent Application No. 2002-116257”. It is an object of the present invention to further improve such inventions. That is, the present invention, in the organic wastewater treatment system, especially organic matter, nitrogen, wastewater containing phosphorus, for example, high concentration of digestion and desorption of human waste and septic tank sludge, digestion of sludge, wastewater of chemical factories Technology that greatly improves phosphorus removal and recovery efficiency in a MAP treatment method that employs an anaerobic treatment step for wastewater containing organic matter, phosphorus, and nitrogen, and removes phosphorus as magnesium ammonium phosphate crystals. The purpose is to provide.
[0007]
[Means for Solving the Problems]
The present invention has solved the above problems by the following means.
(1) An organic wastewater or sludge treatment system incorporating an anaerobic treatment step, and a treatment method having a magnesium ammonium phosphate separation step of taking out magnesium ammonium phosphate generated in sludge in the anaerobic digestion step outside the system In the magnesium ammonium phosphate separation step, the magnesium ammonium phosphate particles dispersed in the sludge are removed, and the magnesium ammonium phosphate desorbed sludge is separated in the sludge reduction step and the magnesium ammonium phosphate separation step. A magnesium ammonium phosphate-magnesium solution contacting step of mixing or contacting a solution containing magnesium ions with the magnesium ammonium phosphate concentrated suspension, after the magnesium ammonium phosphate-magnesium solution contacting step Recovering the magnesium ammonium phosphate particles from the liquid containing the magnesium ammonium phosphate concentrated suspension, and removing the magnesium ammonium phosphate desorbed suspension after removing the collected solid magnesium ammonium phosphate particles. A method for treating organic wastewater and sludge, comprising a step of returning to the anaerobic digestion step or a step preceding the anaerobic digestion step.
[0008]
(2) introducing the concentrated separation liquid or the dehydrated filtrate separated from the sludge in the sludge reduction step with respect to the magnesium ammonium phosphate desorbed sludge into the magnesium ammonium phosphate-magnesium solution contact step, whereby magnesium ammonium phosphate particles are obtained; The method for treating organic wastewater and sludge according to the above (1), wherein magnesium ions derived from the magnesium solution and phosphate ions derived from the concentrated separated solution or the dehydrated filtrate are simultaneously contacted.
(3) As means for recovering magnesium ammonium phosphate in sludge, at least one of a liquid cyclone, a sieve or screen-like separator, a sedimentation separation device, and a magnesium ammonium phosphate washing device is used. The method for treating organic wastewater and sludge according to the above (1) or (2).
[0009]
(4) An anaerobic digestion reaction tank is provided as a constituent device of the organic wastewater or sludge treatment system, and at least a raw water supply pipe and a digestion sludge discharge pipe are connected to the anaerobic digestion reaction tank. It is configured with a flow that can directly or indirectly supply a magnesium source to the tank, and preferentially gives particles having a large specific gravity from the sludge discharged from the anaerobic digestion reaction tank or the sludge in the anaerobic digestion reaction tank. A solid-liquid separation device for concentration and separation, and a magnesium ion solution or a magnesium ion solution and a concentrated separation solution or a dehydrated filtrate for a slurry or solid substance containing a large amount of particles separated by the solid-liquid separation device. A device for contacting phosphate ions of origin, and a device for recovering particles after contact with the magnesium ion solution as a solid, the magnesium ion solution after contact with the particles Directly or indirectly the anaerobic digestion reaction organic wastewater and sludge processing apparatus characterized by introducing the tank.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and the present invention is not limited to this embodiment.
In FIG. 1, initial sludge 5 and excess activated sludge 6 discharged from an organic wastewater treatment system are concentrated and separated by a sludge concentrator 21, and the concentrated sludge 7 is led to an input sludge mixing tank 22. In addition to the concentrated sludge 7, the input sludge mixing tank 22 removes most of the MAP particles in the MAP-Mg contact tank 25 and removes MAP desorbed sludge 15 in which a large amount of magnesium ions remain. The source 17 or a part of the MAP concentrated sludge 14 concentrated by the MAP concentration device 24 is introduced.
The purpose of the input sludge mixing tank 22 is to mix the concentrated sludge 7 to be injected into the anaerobic digestion tank 23 with these various liquids and temporarily retain the same, thereby improving the digestibility in the subsequent anaerobic digestion tank 23. To improve the MAP generation rate, increase the MAP particle diameter, and prevent MAP from adhering to the walls and the like in the digestion tank. The inside of the input sludge mixing tank 22 may be subjected to a stirring process using a stirrer and, if necessary, a heating process.
[0011]
Digestion tank input sludge 8 adjusted in input sludge mixing tank 22 is anaerobically biodegraded in digestion tank 23. At the same time, in addition to ammonia ions, phosphate ions, and magnesium ions, which are metabolic components in anaerobic biodegradation, a magnesium source supplied in the MAP-Mg contact tank 25 or the input sludge mixing tank 22 is used as a substrate component in the digestion tank. In 23, the MAP particles crystallize.
The digested sludge 9 containing MAP particles is converted into a MAP concentrated sludge 14 and a MAP desorbed sludge (1) 10 in a MAP separation / concentration machine 24, which contain a large amount of particles mainly composed of MAP having a particle diameter of 100 μm or more and a specific gravity of 1.5 or more. Separated. As the MAP separation / concentrator, a liquid cyclone, an electric sieve or screen-like separator, a sedimentation separation device, a MAP cleaning device, a device combining these device principles, or the like can be used. A part of the MAP desorbed sludge (1) 10 is returned to the digestion tank 23, and the rest is dewatered by the dewatering device 26 to become the dewatered cake 11.
[0012]
The MAP concentrated sludge 14 is introduced into a MAP-Mg contact tank 25. In the MAP-Mg contact tank 25, a new MAP is provided on the surface of the MAP particles present in the MAP concentrated sludge 14 by supplying a new Mg source 17 and, if necessary, a pH adjuster. The supply amount of the Mg source to be supplied to the input sludge mixing tank 22 and the MAP-Mg contact tank 25 is such that the phosphorus in the digestion tank 23 in the latter stage is synthesized as much as possible as MAP, and the amount necessary for minimizing the soluble phosphorus concentration. It is preferred to add. Of course, it is needless to say that the Mg source addition amount should be set in consideration of the cost of the Mg source additive and other handling characteristics of the system. On the other hand, if the set pH of the MAP-Mg contact tank 25 is set too high to 8.5 or more, MAP particles in which organic SS is entangled may be undesirably formed. The appropriate set pH is often in the range of 7.5 to 8.0.
[0013]
In addition, the MAP-Mg contact tank 25 can be used as a device for cleaning MAP particles. For example, when a liquid cyclone alone is adopted as the MAP separation / concentrator 24, the MAP concentrated sludge 14 contains about 2% of an organic SS component in addition to the MAP particles. It is necessary to wash the MAP concentrated sludge 14. By using a tap water, treated water 4, or a liquid obtained by adding a Mg source to the dewatered filtrate 12 or the like as washing water for MAP particles and supplying the MAP particles to the MAP-Mg contact tank 25, a new MAP is formed on the MAP particle surface. It is possible to wash out the organic SS components other than the MAP particles from the MAP concentrated sludge 14 containing a large amount of SS while precipitating out. Generally, the inside of the MAP-Mg contact tank 25 is in a phosphorus-controlled state as the MAP crystallization reaction. In particular, when the liquid obtained by adding the Mg source to the dehydrated filtrate 12 is used as the MAP washing water, the dehydrated filtrate is used. Since the soluble phosphorus component remaining inside is supplied, the precipitation amount of MAP increases, and the phosphorus load in the return water is reduced, which is efficient.
[0014]
As the MAP-Mg contact tank 25 including such a washing mechanism, by using an upward flow fluidized bed type device, the separation property between the MAP particles and the washing water diluted sludge is good, and the MAP particles are drawn out. At times, the supply of the MAP concentrated sludge 14 is temporarily stopped, and only the washing water is supplied, so that the MAP particles containing almost no organic SS component can be collected.
[0015]
The MAP desorbed sludge (2) 15 returned from the MAP-Mg contact tank 25 to the input sludge mixing tank 22 has a high magnesium ion concentration, a low soluble phosphorus concentration, and is derived from anaerobic digested sludge. Contains a large amount of M alkaline components. In the input sludge mixing tank 22, the sludge 15, the MAP concentrated sludge 14 as a MAP seed crystal source, and a further Mg source are supplied, mixed and retained, thereby promoting the acid fermentation of the concentrated sludge 7 by digestion. Improvement of digestibility in the tank 23, promotion of MAP generation and large particle size due to the presence of many MAP particles in an environment with high magnesium concentration, and preferential precipitation of MAP components on the surface of MAP seed crystals This facilitates MAP, which has the effect of reducing MAP sticking to walls, bottoms, pipes and the like in the digestion tank.
[0016]
As described above, in a technology for actively generating MAP particles in anaerobic digested sludge and recovering the MAP particles, a Mg supply point utilizing characteristics of each process constituting the entire system, and a MAP particle By adopting the method of the present invention in which the washing step of the present invention has been optimized, most of the phosphorus component contained in the sewage sludge can be recovered with high efficiency as MAP. It is possible to greatly reduce the ratio of phosphorus discharged into the furnace.
[0017]
【Example】
Next, an example of an operation result of an experimental plant that actually incorporates the wastewater treatment technology of the present invention will be described. However, the present invention is not limited to this embodiment.
[0018]
Example 1
This embodiment is an embodiment based on a pilot plant experiment performed using sludge from the A sewage treatment plant, and the flow is the same as the flow of FIG. 1 described above. Treatment plant A adopts activated sludge treatment by the anaerobic aerobic method. In the pilot plant of the embodiment, the initial sludge 5 and the excess sludge 6 collected from the A treatment plant are mixed at about 1: 1 and concentrated by a centrifugal concentrator. The concentrated sludge 7 is introduced into the input sludge mixing tank 22. In the input sludge mixing tank 22, MAP desorbed sludge (2) 15 from the MAP-Mg contact tank 25, a part of MAP concentrated sludge 14 in which MAP particles are concentrated from digested sludge by a liquid cyclone, and a magnesium chloride solution Introduce. The sludge mixing tank 22 has a residence time of 48 hours and is heated to a water temperature of 40 ° C., and the inside of the tank is mixed by a stirrer. No pH adjuster was added to the tank, but the pH could be controlled to approximately 7.0 by adjusting the amount of MAP concentrated sludge 14 returned.
[0019]
The MAP-Mg contact tank 25 was separated into a mixing zone and a MAP deposition zone, and used an upward flow fluidized bed type apparatus having a total residence time of 3 hours. The tank 25 was supplied with MAP concentrated sludge 14 concentrated by a liquid cyclone and Mg source supply water and MAP washing water produced by dissolving magnesium chloride in the dehydrated filtrate 12, from the bottom of the tank. Mg source supply water and MAP cleaning water were supplied in an amount three times the amount of the MAP concentrated sludge 14. The total magnesium chloride charged in the system was added as 300 mg of magnesium ion per liter of the concentrated sludge 7. In the tank, MAP particles grown to 500 μm or more are gradually deposited from the tapered bottom of the MAP deposition zone, and the MAP particles are pulled out from the bottom so that the height of the deposited layer falls within a certain level. did. At the time of drawing out the MAP particles, the supply of the MAP concentrated sludge 14 was temporarily stopped, and only the Mg-containing cleaning water was supplied from the bottom of the MAP deposition zone. The anaerobic digestion tank 23 was digested at a medium temperature of 35 ° C., and the residence time was 25 days. As the dehydrator 26, a screw press type dehydrator was used.
[0020]
Further, as a control system (comparative example) of the present example, a process of “mixed concentration + anaerobic digestion + dehydration” (see FIG. 3) and a process of “JP-A-2002-045889” (see FIG. 2) of the conventional method were used. Was also run at the same time. Table 1 shows the operation results.
[0021]
[Table 1]

[0022]
The SS of the sludge charged into the digestion tank was 4.2% in the conventional method, 4.0% in "JP-A-2002-045889", and 2.9% in the present example. The reason why the SS of this embodiment is relatively small is that sludge having a relatively low concentration is mixed in the input sludge mixing tank 22. Phosphorus could be recovered as MAP, the digester charged sludge 1 m ³ per for "JP 2002-045889" 5.1 kg / ^{m 3,} towards the present invention method 6.5 kg / ^{m 3} next invention method 1 0.4 kg / m ³ increased. In addition, the purity of the collected MAP particles was 95% or more in both "JP-A-2002-045889" and this example. When this phosphorus recovery rate was calculated as a recovery rate for phosphorus flowing into the sewage treatment plant, the result was 65% in this example, which is 16% higher than 49% in “JP-A-2002-045889”.
[0023]
【The invention's effect】
According to the present invention, in the organic wastewater treatment system, in particular, organic matter, nitrogen, wastewater containing phosphorus, for example, high concentration of digestion and desorption of human waste and septic tank sludge, digestion of sludge, wastewater of chemical plants, etc. In the MAP treatment method for removing magnesium ammonium phosphate crystals from waste water containing organic substances, phosphorus and nitrogen, (1) the MAP recovery rate can be greatly improved, and (2) MAP with high purity is produced. This makes it possible to (3) improve the quality of treated water and (4) significantly reduce the phosphorus content in the dewatered cake discharged as waste.
[Brief description of the drawings]
FIG. 1 is a flow sheet of one embodiment of the present invention.
FIG. 2 is a flow sheet of the method of “JP-A-2002-045889” as a comparative example.
FIG. 3 is a flow sheet of a conventional method as a comparative example.
[Explanation of symbols]
Reference Signs List 1 Inflow water 2 First settling tank effluent 3 Bioreactor effluent 4 Treated water 5 First settled sludge 6 Excess sludge 7 Condensed sludge 8 Digestion tank input sludge 9 Digested sludge 10 MAP desorbed sludge (1) (digestion circulation sludge)
11 Dewatered cake 12 Dewatered filtrate 13 Concentrator desorbed liquid 14 MAP concentrated sludge 15 MAP desorbed sludge (2)
16 Collection MAP
17 Magnesium source 18 First sedimentation basin 19 Aeration tank 20 Final sedimentation basin 21 Sludge concentrator 22 Input sludge mixing tank 23 Digestion tank 24 MAP separation concentrator (liquid cyclone)
25 MAP-Mg contact tank 26 Dehydrator

Claims

An organic wastewater or sludge treatment system incorporating an anaerobic treatment step, comprising a magnesium ammonium phosphate separation step of taking out magnesium ammonium phosphate generated in sludge in the anaerobic digestion step. A step of reducing the amount of sludge separated from the magnesium ammonium phosphate desorbed sludge after removing the magnesium ammonium phosphate particles dispersed in the sludge in the step of separating magnesium ammonium phosphate, and the step of separating the magnesium phosphate separated in the step of separating magnesium ammonium phosphate A magnesium ammonium phosphate-magnesium solution contacting step of mixing or contacting a solution containing magnesium ions with the ammonium-concentrated suspension; and the phosphorus after the magnesium ammonium phosphate-magnesium solution contacting step. Recovering magnesium ammonium phosphate particles from the liquid containing the magnesium ammonium concentrated suspension, and removing the magnesium ammonium phosphate desorbed suspension after removing the collected solid magnesium ammonium phosphate particles, A method for treating organic wastewater and sludge, comprising an anaerobic digestion step or a step of returning to an earlier stage thereof.

The magnesium ammonium phosphate particles and magnesium solution-derived particles are introduced by introducing the concentrated separated solution or the dehydrated filtrate separated from the sludge in the sludge reduction step for the magnesium ammonium phosphate desorbed sludge to the magnesium ammonium phosphate-magnesium solution contacting step. 2. The method for treating organic wastewater and sludge according to claim 1, wherein the magnesium ion and the phosphate ion derived from the concentrated separated solution or the dehydrated filtrate come into contact simultaneously. 3.

The means for recovering magnesium ammonium phosphate in sludge uses at least one of a hydrocyclone, a sieve or screen-like separator, a sedimentation separation device, and a magnesium ammonium phosphate washing device. The method for treating organic wastewater and sludge according to claim 1 or 2.

As a constituent device of the organic wastewater or sludge treatment system, it has an anaerobic digestion reaction tank, and at least a raw water supply pipe and a digestion sludge discharge pipe are connected to the anaerobic digestion reaction tank, and directly connected to the anaerobic digestion reaction tank. Or, it is constituted by a flow capable of indirectly supplying a magnesium source, and preferentially concentrates particles having a large specific gravity from sludge discharged from the anaerobic digestion reaction tank or sludge in the anaerobic digestion reaction tank. A solid-liquid separation device for separation is provided, and a slurry or solid substance containing a large amount of particles separated by the solid-liquid separation device is treated with a magnesium ion solution or a magnesium ion solution and phosphorus derived from a concentrated separated solution or a dehydrated filtrate. Includes a device for contacting acid ions and a device for recovering particles after contact with the magnesium ion solution as a solid, and directly transferring the magnesium ion solution after contact with the particles. Or organic wastewater and sludge processing apparatus characterized by indirectly introduced into the anaerobic digestion reactor.