JP2004202484A

JP2004202484A - System and method for treating organic waste

Info

Publication number: JP2004202484A
Application number: JP2003184434A
Authority: JP
Inventors: Reiho Kato; 玲朋加藤; Hiroshi Mizutani; 洋水谷; Kenji Nakamura; 謙治中村; Katsumi Cho; 克美長
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2002-11-07
Filing date: 2003-06-27
Publication date: 2004-07-22
Anticipated expiration: 2023-06-27
Also published as: JP3917956B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for treating an organic waste which can be operated at a low cost with good efficiency in accordance with properties of the waste to be treated and almost not requiring addition of a hydrogen donating body from the outside, and to provide a method for treating the organic waste. <P>SOLUTION: The system for treating the organic waste is provided with a methane fermentation tank 1 anaerobically fermentating the organic waste, and a water treatment plant for clarification treatment of a separated liquid of solid-liquid separation of a digested sludge in the methane fermentation tank. The water treatment plant is provided with an electrolytic cell tank 3 in which the separated liquid is electrolyzed to produce a hypochlorous acid type strong oxidative substance and nitrogen content included in the separated liquid is eliminated by oxidative action of the strong oxidative substance, and the electrolytic cell 3 is preferably made into such a constitution that BOD/nitrogen content in the separated liquid is made within approximately 1-3, and a treating tank 5 for nitrifying and denitrifying the treated liquid is provided at the back step of the electrolytic cell 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、有機性廃棄物から主として窒素分を除去する処理に関し、特に夫々の廃棄物性状に適した処理により処理効率を向上させた有機性廃棄物の処理システム及び処理方法に関する。
【０００２】
【従来の技術】
し尿、浄化槽汚泥、生ごみ、及び家畜糞尿等の有機性廃棄物には、ＳＳ（浮遊物質）、窒素分、リン分、ＢＯＤ（生物化学的酸素要求量）、ＣＯＤ（化学的酸素要求量）などの環境や人体に悪影響を及ぼす汚濁物質が含まれており、従来これらを除去する様々な方法が開発、実用化されている。
有機性廃棄物の処理は、主として固液分離によるＳＳの除去、ＢＯＤ及びＣＯＤの酸化分解、リン、窒素化合物等の無機栄養塩類の除去、汚泥固形物の処理等が単独若しくは複数組み合わせて行われる。
【０００３】
一般に、有機性廃棄物の処理は図１０に示されるようなフローにて行われる。まず、有機性廃棄物をスクリーン８に通して夾雑物を除去し、遠心分離機等の脱水機９により汚泥固形物と分離液とに分離し、分離液をさらに膜分離装置１０に通過させて浮遊物を除去した後、硝化・脱窒処理槽１４に導入して窒素分を分解除去する。一方、前記脱水機９にて分離した汚泥固形物は可溶化槽１３に導き、加温等により汚泥固形物が発酵し易いように可溶化させ、メタン発酵槽１にて嫌気性細菌の作用により汚泥固形物をメタンと二酸化炭素に転換する。そして、メタン発酵槽１の消化汚泥は脱水機２に導入し、分離液を硝化・脱窒処理槽１４にて窒素分を除去し、また汚泥固形物は堆肥化、炭化若しくは焼却処理設備に送給する。
【０００４】
従来はかかる方法により廃棄物中の汚濁物質を万遍なく除去する方法が用いられてきたが、処理対象である廃棄物により汚濁物質成分の夫々の含有量に偏りがあるため、何れかの汚濁物質成分が処理後も残留してしまうことがある。特に、富栄養化の原因となる窒素分は、廃棄物を固液分離した際にその殆どが分離液側に移行し濃縮されるため高除去率を達成することは困難である。
一般に窒素分を多く含む廃棄物の処理方法としては、硝化・脱窒処理、嫌気性処理、曝気処理等が多く用いられている。しかし、硝化・脱窒処理ではアンモニア態窒素の酸化のために膨大な曝気動力を必要とし、電力コストが向上し、嫌気性処理では消化液中に多量のアンモニア態窒素が残存して後段の生物処理での窒素負荷が高くなり処理効率が悪化し、また曝気処理の場合には硝酸態窒素が残存するため近年の水質規制に抵触する、といった問題点を有している。
【０００５】
さらに、前記硝化・脱窒処理では、脱窒の際の硝酸呼吸の為に水素供与体が必要となるため通常処理液中の易分解性有機物が利用されるが、効率良く脱窒を行うことができる易分解性有機物量、即ちＢＯＤの量が硝酸態窒素含有量の３倍に満たない場合にはメタノール、エタノール等の易分解性の有機物を添加する必要がある。
特に、近年、し尿及び浄化槽汚泥に加えて生ごみの適正処理が求められるようになり窒素分を多く含有する生ごみ主体の廃棄物処理に際して窒素分の除去率を向上させる技術が求められている。
【０００６】
そこで、特開平８−２３８４９８号公報（特許文献１）では浄化槽汚泥等の汚泥固形物をオゾン処理したのちに曝気処理し、硝化・脱窒処理を行う処理方法を提案している。これは、汚泥をオゾンと接触させることにより、脱窒菌に資化され易い成分が生成し、またＢＯＤの量が増加するため効率良く脱窒・硝化処理が行われるものである。
また、特開２００１−１１３２６５公報（特許文献２）では、有機性排水・汚泥をアンモニアストリッピングした後にメタン発酵を行う方法を開示している。かかる方法は、アンモニアストリッピングする際に、温度調整を行うとともに強アルカリ液を添加してｐＨ９〜１３に保持しており、これによりアンモニアの除去率を向上させている。
【０００７】
これらの方法によれば、アンモニアを含む窒素分を効率良く除去することができるが、窒素分のうち硝酸態窒素を除去することは困難である。そこで、硝酸態窒素を含む溶解性窒素分を効率的に除去する方法として、特開２００３−６２５７８公報（特許文献３）では、電気化学的手法により被処理水中の窒素化合物を除去する方法を提案している。
かかる方法では、カソードに導電性金属材料、アノードに不溶性材料又はカーボンを用いるとともに、塩化物イオン増量剤と凝集剤を添加した被処理水に電解処理を施すことにより、窒素化合物を除去する構成としている。これにより、生け簀や水族館、プール等において定期的な水の交換をせずに水質を保つことができる。
【０００８】
【特許文献１】
特開平８−２３８４９８号公報
【特許文献２】
特開２００１−１１３２６５公報
【特許文献３】
特開２００３−６２５７８公報
【０００９】
【発明が解決しようとする課題】
しかしながら、前記特許文献１では固液分離していない汚泥を硝化・脱窒処理しているため処理物中のＢＯＤ量が高く、これに応じた窒素分量まで低減することは容易であるが、本件発明は窒素含有量に比べＢＯＤ含有量が少ない固液分離処理液を対象としているため前記技術を適用することは難しい。さらに、かかる従来技術ではオゾンを利用しているが、オゾンは人体に有害であり装置の運転に際して注意が必要であり、また汚泥をオゾンと十分に接触させて反応させるには滞留時間を大とする必要があり装置が大型化してしまう。
【００１０】
さらに、特許文献２では、アンモニアストリッピングをする際の強アルカリ剤コストが高くつくとともに、アルカリ性の汚泥を後段で中性に戻す際にも中和剤を必要とし、薬剤コストが嵩んでしまう。また、アンモニアの揮散による大気汚染の危険性を伴っている。また、アンモニアストリッピングでは、アンモニア態窒素の除去は可能であるが、硝酸態窒素の除去は困難である。
また、特許文献３は処理対象水を水族館の水槽やプール等の固形物含有量の非常に少ない水としており、本発明のごとく固形物含有量の多いし尿や生ごみ、家畜糞尿等の処理には適用した場合、電極へのスケールの付着が著しく処理効率が非常に悪化するという問題が生じる。
そこで本発明はかかる従来技術の問題に鑑み、処理される廃棄物の性状に応じて効率良く、かつ外部からの水素供与体の添加を殆ど必要とせずに低コストで運転可能である有機性廃棄物の処理システム及び処理方法を提供することを目的とする。
【００１１】
【課題を解決するための手段】
従って、かかる課題を解決するためにかかる発明は、窒素分を含む有機性廃棄物に硝化・脱窒処理、嫌気性処理、曝気処理のうち少なくとも一の処理を施した後に固液分離した分離液から窒素分を除去する水処理設備を備えた有機性廃棄物の処理システムにおいて、
前記水処理設備が、前記分離液を電気分解することにより次亜塩素酸系の強酸化物質を生成し、該強酸化物質の酸化作用により分離液に含有される窒素分を除去する電解槽を備えたことを特徴とする。
【００１２】
かかる発明では、処理液を電気分解することにより処理液中に含有される塩素イオン、水及び硝酸イオンが下記のような反応を示す。
（陽極）２Ｃｌ⁻ →Ｃｌ_２＋２ｅ
Ｃｌ_２＋Ｈ_２Ｏ → ＨＣｌＯ＋ＨＣｌ
（陰極）ＮＯ_３ ⁻＋６Ｈ_２Ｏ＋８ｅ→ＮＨ_３＋９ＯＨ⁻
２Ｈ_２Ｏ＋２ｅ →２ＯＨ⁻＋Ｈ_２↑
陽極では、塩素が発生し、さらにその塩素が水と反応し、強力な酸化力を有する次亜塩素酸（ＨＣｌＯ）を生成する。一方、陰極では、分離液中に硝酸イオンが含まれる場合は、アンモニアへ還元される。また、硝酸イオンが含まれない場合は、水の分解により水素が発生する。
【００１３】
分離液中に含まれるアンモニア、若しくは電気分解によって生成したアンモニアは、陽極で生成した次亜塩素酸によって、下記式により反応し、分解、除去される。
２ＮＨ_３＋３ＨＣｌＯ → Ｎ_２↑＋３ＨＣｌ＋３Ｈ_２Ｏ
このように、従来用いられてきた生物学的な脱窒処理とは異なり物理化学的な処理を行うことにより、溶解性窒素分を含む窒素分を確実かつ安定して高除去率で除去可能であるとともに、脱窒のための栄養源である水素供与体を供給する必要がなくランニングコストの低廉化が可能となる。また、脱窒後の窒素分は窒素ガスの形態で排出されるため二次汚染の心配がない。
尚本発明において、窒素分とはアンモニア態窒素、亜硝酸・硝酸態窒素等をいい、前記式に表される代表的な反応と同時にこれらの酸化分解も行われるものである。
【００１４】
また、従来多用されていた窒素除去処理である生物処理に比べて、設備面積を大幅に低減できる。例えば、生物処理で窒素除去に３日程度要していたのに対し、本発明の電解処理では数時間で処理を行うことができる。また、電解処理は物理化学処理であるため、生物処理に比べて維持管理が容易である。
さらに、硝化・脱窒処理と組み合わせて電解槽を用いる場合には、電解処理の脱窒が硝酸態窒素よりもアンモニア態窒素の方が電力が小さくて済むため、硝化槽における曝気動力を削減できる。即ち、硝化槽ではＢＯＤのみを殆ど除去してアンモニア態窒素は一部のみの硝化とし、後段の電解槽でアンモニア態窒素を除去することにより、処理水中から窒素分をほぼ完全に除去することができる。
また、かかる発明は、既設のし尿処理場、下水処理場等のうち、窒素除去が不十分な施設に組み込むことも出来、コンパクトな装置で確実な窒素除去効能が得られる。
【００１５】
また、前記有機性廃棄物が生ごみ主体である有機性廃棄物の処理システムが、該有機性廃棄物を嫌気性発酵するメタン発酵槽を備え、該メタン発酵槽の消化汚泥を固液分離した分離液を浄化処理することを特徴とする。
かかる発明は、し尿、浄化槽汚泥、家畜糞尿等の有機性廃棄物に比べて窒素分比率が大きい生ごみを主体とする有機性廃棄物を処理対象としている。これは、前段でメタン発酵を行っているため高分子有機物の分解に伴い発生したアンモニア態窒素を多く含み、さらにメタン発酵後の消化汚泥を固液分離しているため分離液中には非常に高濃度の窒素分が含まれている。従って、かかる発明のように構成することで、高濃度の窒素分を高除去率で処理することができる。
【００１６】
また、前記メタン発酵槽に膜分離装置を併設し、嫌気性発酵した後の消化汚泥の一部を該膜分離装置に導き、該膜分離装置にて分離された汚泥固形物を前記メタン発酵槽に返送し、
一方、該膜分離装置を透過した透過液を前記電解槽に導入することを特徴とする。
これにより、可溶化し易く濃度を保持し難い生ごみの嫌気性発酵において、槽内を発酵に最適な濃度に維持することができ嫌気性発酵が促進される。また、膜分離した後の透過液を前記電解槽に導入しており、ＢＯＤが殆ど含まれない処理液においても窒素分を高分解率で以って除去することができる。
【００１７】
さらに、前記メタン発酵槽に膜分離装置を併設し、嫌気性発酵した後の消化汚泥の一部を該膜分離装置に導き、該膜分離装置にて分離された汚泥固形物を前記メタン発酵槽に返送し、
一方、前記膜分離装置の後段に第２の電解槽を設け、該膜分離装置を透過した透過液を第２の電解槽に導入して処理液中の窒素分を除去する構成としても良い。
前記膜分離装置は限外ろ過膜（ＵＦ）、精密ろ過膜（ＭＦ）を利用することが好適で、かかる発明のごとく膜分離装置を透過した透過液はＳＳ、ＢＯＤ、リン分、ＣＯＤ等の殆どが分離され、溶解性の窒素分のみが高濃度で含有されている。そこで、前記第２の電解槽を別系統で設けて前記透過液性状に適した運転をすることで、安定した運転ができるとともに処理後の水の性状を一定に保つことができる。
【００１８】
また、有機性廃棄物を固液分離する手段と、分離した分離液を浄化する水処理設備を備えた有機性廃棄物の処理システムにおいて、
前記水処理設備が、前記分離した分離液を電気分解することにより次亜塩素酸系の強酸化物質を生成し、該強酸化物質の酸化作用により分離液に含有される窒素分を除去する電解槽を備えたことを特徴とする。
【００１９】
前記固液分離手段には、重力沈降、浮上分離、機械的脱水、膜分離等の何れかの手段、若しくはこれらを組み合わせた手段が用いられる。好適には機械的脱水装置とその後段に設けられた膜分離装置から構成されるとよい。
かかる発明のように、固液分離した後の分離液を電解槽に導き、生成した次亜塩素酸系の強酸化物質により酸化分解することにより、水素供与体の供給が不要となりランニングコストが削減でき、また窒素を高除去率で以って処理することができる。
【００２０】
さらにまた、前記電解槽を、分離液中のＢＯＤ／窒素分が約１〜３の範囲内となるように窒素分を低減する構成とするとともに、該電解槽の後段に、窒素分を低減した前記処理液を硝化脱窒する処理槽を設けたことを特徴とする。
このように約１〜３の範囲内のＢＯＤ／窒素分比率を有する分離液を硝化・脱窒することにより効率良く窒素分を除去できるとともに、前段に電解槽を設けて脱窒を行っているために硝化・脱窒処理槽にかかる負荷が軽減される。
【００２１】
さらに、前記電解槽が、分離液を保持する反応槽と、該反応槽内に対向して配置された電極間の抵抗を測定する手段と、該反応槽内の分離液の塩素分濃度を測定する手段と、を備えるとともに、
前記抵抗測定手段により得られた電極間抵抗値及び前記塩素濃度測定手段により得られた分離液の塩素濃度値のうち少なくとも何れか一方の値に基づき、電極の劣化度を判断する手段を備えたことを特徴とする。
かかる発明では、有機性廃棄物を対象としているため、電極にスケールが付着し易い。従って、前記構成とすることにより電極の劣化を容易に判断することができ、円滑な運転を行うことができる。
【００２２】
また、前記反応槽が、該反応槽内の分離液を槽内で循環させる手段を有しており、該循環手段の循環経路上に前記塩素濃度測定手段を設けることが好ましい。これにより、槽内の濃度分布に関らず塩素濃度を適切に測定することができる。さらに、前記循環手段を設けることにより、別に撹拌手段を設けることなく槽内を撹拌することができ、電解反応効率が向上する。
【００２３】
さらにまた、前記電解槽が、前記反応槽内の泡沫量検出手段を有しており、前記電極劣化判断手段により劣化の判断がされた際に反応槽内の泡沫量を測定し、泡沫量が基準値以上である場合には消泡剤を投入することを特徴とする。
本発明のように処理対象が有機性廃棄物の場合は、泡沫が発生し易く、これにより電極間が短絡して前記抵抗値に異常が発生することがある。従って、異常が発生した場合に、かかる発明のように泡沫量を検出することにより実際に電極の劣化であるのか泡沫による短絡であるのかを判断し、泡沫である場合には消泡剤を投入して電解反応を確実に行わせるようにすると良い。
また、前記電解槽の前段に、分離液の塩素分濃度を測定する第２の塩素濃度測定手段を設けるとともに、これにより測定された塩素イオン濃度に基づき塩素イオン調整剤を投入する手段を設けたことを特徴とする。
これにより、電解槽内の塩素イオン濃度が適正に保たれ、電解反応が促進され、延いては窒素除去効率が向上する。
【００２４】
また、前記電解槽が、前記反応槽の分離液を槽内で循環させる手段を有しており、該循環手段の循環経路上若しくは電解槽内部に、塩素濃度測定手段、残留塩素測定手段、ＯＲＰ測定手段、ｐＨ測定手段、アンモニア濃度測定手段のうち少なくとも何れかを有し、この測定手段のうち単独若しくは２つ以上を組み合わせて、前記電解槽の電解処理時間を制御することも好適である。
【００２５】
また、前記した発明と略同様の効果を有する処理方法として、窒素分を含む有機性廃棄物に硝化・脱窒処理、嫌気性処理、曝気処理のうち少なくとも一の処理を施した後に固液分離した分離液から窒素分を除去する有機性廃棄物の処理方法において、
前記固液分離した分離液を電解槽で電気分解することにより次亜塩素酸系の強酸化物質を生成し、該強酸化物質の酸化作用により分離液に含有される窒素分を除去することを特徴とする。
【００２６】
また、前記有機性廃棄物が生ごみ主体である有機性廃棄物の処理方法であって、該有機性廃棄物をメタン発酵槽により嫌気性発酵し、該嫌気性発酵により生じた消化汚泥を固液分離した分離液を前記電解槽により浄化処理することを特徴とする。
また、前記嫌気性発酵した後の消化汚泥を一部抜き出し、該消化汚泥を膜分離により固液分離した後、分離した汚泥固形物をメタン発酵槽に返送し、
一方、分離した透過液を前記電気分解することを特徴とする。
【００２７】
さらにまた有機性廃棄物を固液分離した後、該分離した分離液を浄化する有機性廃棄物の処理方法において、
前記固液分離した分離液を電気分解することにより次亜塩素酸系の強酸化物質を生成し、該強酸化物質の酸化作用により分離液に含有される窒素分を除去することを特徴とする。かかる発明は、特に浄化槽汚泥主体の有機性廃棄物の処理に適している。
さらに、前記電気分解で生成した次亜塩素酸系の強酸化物質により分離液中のＢＯＤ／窒素分が約１〜３の範囲内となるように窒素分を低減した後、該処理液を硝化脱窒することが好ましい。
【００２８】
また、前記電気分解の際に、前記電解槽内に対向して配置される電極間の抵抗値及び槽内の分離液の塩素濃度値のうち少なくとも何れか一方を測定し、該測定値に基づき前記電極の劣化を判断することを特徴とする。
このとき、前記電極の劣化が判断された際に、前記槽内の泡沫量を検出し、該泡沫量が基準値以上である場合には消泡剤を投入することが好適である。
さらに、前記電気分解の前に、分離液の塩素イオン濃度を測定し、該測定された塩素イオン濃度に基づき塩素イオン調整剤を投入すると良い。
さらにまた、前記電解槽が、塩素濃度測定手段、残留塩素濃度測定手段、ＯＲＰ測定手段、ｐＨ測定手段、アンモニア濃度測定手段のうち少なくとも何れかを有し、この測定手段のうち単独若しくは２つ以上を組み合わせて、電解槽の電解処理時間を制御することが好適である。
【００２９】
【発明の実施の形態】
以下、図面を参照して本発明の好適な実施形態を例示的に詳しく説明する。但しこの実施形態に記載されている構成部品の寸法、材質、形状、その相対的配置等は特に特定的な記載がない限りは、この発明の範囲をそれに限定する趣旨ではなく、単なる説明例に過ぎない。
図１は本発明の第１実施例に係る有機性廃棄物処理システムの概略構成図、図２は本発明の実施形態に係る処理システムに具備される電解槽の説明図、図３乃至図５は夫々図１の別の実施例である第２乃至第４実施例に係る有機性廃棄物処理システムの概略構成図である。
【００３０】
本第１実施例に係る有機性廃棄物処理システムは、生ごみを主体とした有機性廃棄物の処理に適しており、図１に示されるように、メタン発酵槽１と、該メタン発酵槽１から排出される消化汚泥を遠心分離機等で機械的脱水する脱水機２と、汚泥固形物を脱水分離した後の分離液を脱窒する電解槽３と、アルカリ剤の添加により脱窒後の処理液を中和する還元槽４と、中和された分離液に生物処理を施す硝化・脱窒処理槽５とを備えている。
【００３１】
前記メタン発酵槽１では、槽内の嫌気性菌の作用により廃棄物中の高分子有機物が二酸化炭素、メタン、アンモニア等へ分解される。ここで発生したメタンは発電装置等に送給され有効利用される。このとき、回収したメタンガスを元に発電した電力を前記電解槽３に送電して利用してもよい。
また、前記メタン発酵槽１から排出される消化汚泥は脱水機２により固液分離され、汚泥固形物は堆肥化、炭化若しくは焼却設備に送られ、一方分離液は電解槽３に送給される。
【００３２】
前記電解槽３は、メタン発酵後の固液分離した分離液を電気分解して次亜塩素酸系の強酸化物質を生成し、該強酸化性物質によりアンモニア態窒素を酸化分解する。かかる電解槽３は図２に示されるように、分離液を受け入れる反応槽３１と、該反応槽３１内に導入された分離液内に浸漬するように、対向して配された陽極３２と陰極３３からなる電極と、該電極に接続される電源装置３４とを有している。
そして、各電極での代表的な反応として、分離液中に含有される塩素イオン、水及び硝酸イオンにより下記の反応が引起される。
（陽極）２Ｃｌ⁻ →Ｃｌ_２＋２ｅ
Ｃｌ_２＋Ｈ_２Ｏ → ＨＣｌＯ＋ＨＣｌ
（陰極）ＮＯ_３ ⁻＋６Ｈ_２Ｏ＋８ｅ→ＮＨ_３＋９ＯＨ⁻
２Ｈ_２Ｏ＋２ｅ →２ＯＨ⁻＋Ｈ_２↑
陽極では、塩素が発生し、さらにその塩素が水と反応し、強力な酸化力を有する次亜塩素酸（ＨＣｌＯ）を生成する。一方、陰極では、分離液中に硝酸イオンが含まれる場合は、アンモニアへ還元される。また、硝酸イオンが含まれない場合は、水の分解により水素が発生する。
【００３３】
分離液中に含まれるアンモニア、若しくは電気分解によって生成したアンモニアは、陽極で生成した次亜塩素酸によって、下記式により反応し分解、除去される。
２ＮＨ_３＋３ＨＣｌＯ → Ｎ_２↑＋３ＨＣｌ＋３Ｈ_２Ｏ
かかる電解槽３は、電極の付着物質を除去するために一定期間毎に逆電圧をかけたり、処理を停止して洗浄したりして電解効率を維持することが好ましい。
また、本実施例のように後段に硝化・脱窒処理槽を設ける場合は、脱窒後の処理液の成分比（ＢＯＤ／窒素分）が約１〜３となるように、電解槽３での滞留時間、電解槽３の容積、若しくは電極に印加する電圧値等を制御するとよい。
【００３４】
そして、前記電解槽３にて脱窒された処理液は前記還元槽４に導入される。該処理液は前記電解槽３にて生成した強酸化物質により酸性状態であるため、還元槽４で苛性ソーダ等のアルカリ剤の添加により中和する。
中和した処理液は硝化・脱窒処理槽５に導き、槽内で硝化菌、脱窒菌等の作用によりさらに脱窒する。
このとき、前記電解槽３にて、分離液に含まれるＢＯＤ及び窒素分の成分比率をＢＯＤ／窒素分＝約１〜３となるまで窒素分を低減させた場合、処理液中の水素供与体が好適な量含まれるため高効率で以って脱窒を行うことができる。
該脱窒・硝化処理槽５で窒素分含有量が排出基準値以下に除去された処理液は、外部へ放流若しくは高度処理設備へ送られる。
【００３５】
このように、かかる実施例では、従来用いられてきた生物学的な脱窒処理とは異なり物理化学的な処理を行うことにより、確実かつ安定して窒素の高除去率が達成できるとともに、脱窒のための栄養源である水素供与体を供給する必要がなくランニングコストの低廉化が可能となる。また、脱窒後の窒素分は窒素の形態で排出されるため二次汚染の心配がない。
尚、本実施例では、前記電解槽３で排水基準値以下に窒素分を低減可能な場合には硝化・脱窒処理槽５を具備しなくても良い。
【００３６】
図３及び図４は前記第１実施例と同様に、生ごみ主体の有機性廃棄物を処理するシステムであり、図３に示される第２実施例では、メタン発酵槽１により高分子有機物を分解された後の消化汚泥を脱水機２に導入するとともに、該消化汚泥の一部を抜き出して膜分離装置６に導入する。該膜分離装置６は、限外ろ過膜（ＵＦ）、精密ろ過膜（ＭＦ）を利用することが好ましい。膜分離装置６にて消化汚泥を分離した汚泥固形物は前記メタン発酵槽１に返送される。これにより、生ごみ等の分解し易い廃棄物の処理においても、メタン発酵槽内の濃度が好適に保たれ、嫌気性発酵が効率良く行われる。一方、膜分離装置６を透過した透過液は、ＳＳ、ＢＯＤ、リン分、ＣＯＤ等が殆ど分離除去され、溶解性の窒素分が高濃度で含有された状態で電解槽３に送給される。
【００３７】
前記メタン発酵槽１から排出された消化汚泥の一部は脱水機２により汚泥固形物と分離液とに固液分離され、該汚泥固形物は堆肥化、炭化若しくは焼却設備に送られ、分離液は電解槽３に送給される。
かかる電解槽３は、前記第１実施例と同様の構成を有しており、ここで生成された次亜塩素酸系の強酸化物質により前記膜分離装置６及び脱水機２より導入された分離液中の窒素分が分解除去される。
そして、電解槽３にて脱窒された処理液は還元槽４にてアルカリ剤により中和された後に硝化・脱窒処理槽５に導かれ、窒素分濃度を排出基準値以下まで低下させた後に放流若しくは高度処理設備へ送給される。
【００３８】
図４に示される第３実施例では、前記膜分離装置６を透過した透過液に脱窒を施す第２の電解槽７を設けている。該第２の電解槽７は前記電解槽３と同様の構成を有している。該第２の電解槽７にて脱窒された処理液は前記電解槽３よりの処理液と併せて還元槽４にて中和され、硝化・脱窒処理される。
前記膜分離装置６では、溶解性の窒素分以外の殆ど全ての汚濁物質が除去されるため膜分離後の透過液は高濃度の窒素分を含むこととなる。そこで、かかる実施例のような構成とすることで、夫々の処理液の性状に適した処理を行うことができ処理システムの安定運転が容易となる。
尚、前記膜分離装置のろ過速度を保持するために、定期的に前記電解槽から処理液を抜き出して該膜分離装置に導入しても良く、これにより電解槽にて生成された次亜塩素酸系強酸化物質の洗浄効果によりろ過速度を回復できる。
【００３９】
次に、図５に示される本発明の第４実施例につき説明する。本実施例は有機性廃棄物を固液分離した後に生物学的処理、物理化学的処理により汚濁物質の除去処理を行う構成としている。
かかる処理システムは、まず有機性廃棄物をスクリーン８に通して除渣した後、脱水機９により汚泥固形物と分離液とに分離し、該汚泥固形物を可溶化槽１３に導入して加温等により汚泥中の有機物を可溶化させ、メタン発酵槽１４に導入する。該メタン発酵槽１４で高分子有機物の分解を行った後に消化汚泥は堆肥化、炭化若しくは焼却処理設備に送給する。
【００４０】
一方、前記脱水機９にて固形物を分離された分離液は、膜分離装置１０に導入されて分離液中のＢＯＤ、ＳＳ等を除去された後、電解槽１１に導かれる。このとき、前記膜分離を透過しない固形分は前記脱水機９の上流側に返送されて再度処理される。
電解槽１１は、前記第１乃至第３実施例と同様の構成を有しており、分離液中に含まれる塩類、塩素及び水等が電気分解して生成した次亜塩素酸系の強酸化物質により、分離液に含有される窒素分が分解除去される。
そして、前記電解槽１１にて排出基準値以下まで窒素分を除去された分離液は、還元槽１２にてアルカリ剤により中和された後に放流若しくは高度処理設備に送られる。
【００４１】
かかる第４実施例では、有機性廃棄物を、脱水機９及び膜分離装置１０の組み合わせにより、窒素分以外の汚濁物質を含む汚泥固形物と、アンモニア態窒素等の溶解性窒素分を含む透過液とに分離し、該透過液をさらに電解槽１１にて脱窒することにより、アンモニア態窒素等の溶解性窒素分を確実にかつ高除去率で処理することができる。尚、処理液の窒素分濃度が高い場合には、還元槽１２の後段に硝化・脱窒処理槽を設けてもよい。このとき、前記電解槽１１で透過液中のＢＯＤと窒素分の比率をＢＯＤ／窒素分＝約１〜３とすることが好ましく、これにより前記硝化・脱窒処理槽にて効率良く脱窒処理を行うことができる。
【００４２】
また、前記電解槽３の別の実施形態として、図６に各種測定手段を備えた電解槽を示す。
図６において、電解槽２３は、分離液を保持する反応槽２３ａと、該反応槽２３ａ内に対向して配置される陽極３２及び陰極３３と、これらの電極に導線を介して接続される電源装置３４と、該電源装置３４により電極間に印加される電圧を測定する電圧計３４ｂと、該電極間の抵抗値を測定する抵抗計３４ａと、前記反応槽２３ａの下部より分離液を抜き出して該反応槽上部へ導入する循環ポンプ３５と、循環経路上に設置され分離液中の塩素分濃度を測定する第１Ｃｌ濃度計３８と、同様に循環経路上に配置するバルブ３７と、前記抜き出された分離液を外部へ排出する経路上に配置するバルブ３６と、を備えた構成となっている。
【００４３】
さらに、前記電解槽２３の上流側には、前記脱水機２等の固液分離装置を経て固形分と分離された分離液を貯留する原水タンク２９が配設され、該原水タンク２９内には分離液中の塩素分濃度を検出する第２Ｃｌ濃度計３９が備えられるとともに、ＮａＣｌａｑ若しくはＮａＣｌＯ等の塩素イオン調整剤４２の添加手段が具備されている。
また、前記抵抗計３４ａ、第１Ｃｌ濃度計３８、第２Ｃｌ濃度計３９は制御回路４３に接続され、該制御回路４３に基づき前記電源装置３４の印加電圧、電圧のＯＮ／ＯＦＦ及びバルブ制御回路４４によるバルブ３６、３７の開閉が制御される。
【００４４】
かかる電解槽２３では、電解処理はバッチ式で行われ前記図２に示した化学反応式と同様の反応が各電極で行われる。通常運転においては、バルブ３６を閉、バルブ３７を開として分離液中の窒素分が基準値以下となるまで前記循環ポンプ３５により分離液が槽内を循環するようにしている。
そして、電解処理の際に前記抵抗計３４ａ及び第１Ｃｌ濃度計３８により電極間の抵抗値、反応槽２３ａ内の分離液の塩素分濃度を測定する。抵抗値及びＣｌ濃度が基準範囲内でない場合には、分離液の異常若しくは電極の劣化等の装置不良が検出され、適正な電解処理が行われない。即ち、抵抗値が高い場合にはスケールの付着、電極の消耗等、抵抗値が低い場合には泡沫量の増加による短絡等が原因として考えられる。また、Ｃｌ濃度の系時変化を追跡して電解処理状況を把握することも可能である。これは、Ｃｌ濃度が減少傾向にある場合はアンモニア態窒素の残存、即ち脱窒不備が示唆され、反応装置の停止、液全量の引き抜き等の応急処置が必要となる。
【００４５】
かかる実施形態では、対象処理水が有機性排水であるため最も頻度が高く現れる異常としては、電極へのスケールの付着による電極劣化、及び泡沫量の増加による電極間の短絡が考えられる。従って、本実施形態では前記抵抗計３４ａ、第１Ｃｌ濃度計３８のうち少なくとも何れか一方により測定された値が、前記制御回路４３により異常値と判定された場合には電極の劣化と判断し、電源装置３４及び前記バルブ駆動回路４４に信号を送信し、該電源装置３４のＯＦＦ及びバルブ駆動回路４４によりバルブ３６を開、バルブ３７を閉として分離液を引き抜くように制御する。
【００４６】
また、抵抗値若しくは塩素濃度により電極の劣化が判断された場合に、まず不図示の泡沫検出計により槽内の泡沫量を検出することが好ましい。該泡沫検出計により泡沫量が基準値以上を示した場合には消泡剤４１を投入して泡沫を消滅させる。これにより、前記抵抗値若しくは塩素濃度の異常が泡沫による短絡であった場合に、運転を停止することなく対処することができる。
尚、電解処理では塩素分濃度がＣｌ＝２０００ｍｇ／Ｌ程度での運転が適正である。これは、濃度が２０００ｍｇ／Ｌを大幅に超える値である場合には電解反応が適切に行われずに脱窒効率の低下が懸念され、１０００ｍｌ／Ｌ程度の場合には電極の消耗が著しく電極劣化が生じるためである。
従って、高塩濃度分離液の場合には希釈処理を行い、低塩濃度分離液の場合には塩素イオンを増量させる必要がある。
【００４７】
電解処理状況を把握するものとして、ＣｌＯ計４６（残留塩素計）がある。ＣｌＯ濃度が増加傾向にある場合は、脱窒が完了しているにも関わらず、電解が進行していることが示唆され、分離液へのトリハロメタン類の流出が懸念されるので、電解槽２３の停止、液全量引き抜き等の応急処置が必要である。
また、前記の測定器のほか、ｐＨ計４７、ＯＲＰ計４８、アンモニア濃度計４９等を適宜単独で若しくは併用して各種測定を行うことで、より精度の高い運転管理・制御が可能となる。
【００４８】
さらに、図７乃至図９は既設の廃棄物処理システムに前記電解槽２３を組み込んだシステムである第５乃至第７実施例である。
図７は本発明の第５実施例で、例えば固形分濃度が約２〜３％のし尿等の処理に適している。かかるシステムは、スクリーン２０で処理水中の夾雑物を除去した後に、硝化・脱窒処理槽２１にて硝化・脱窒を行い窒素分を除去した後に、固液分離装置２２で固液分離する。固液分離した汚泥の一部は適宜硝化・脱窒処理槽２１内に返送して硝化・脱窒素槽内の硝化・脱窒菌濃度を維持するようにする。該固液分離装置２２は、膜分離槽、沈殿槽、脱水装置等が好適に用いられる。
【００４９】
前記固形物を分離した分離液は前記電解槽２３に導入し、前記電解反応により残存した窒素分を除去する。そして、窒素分が規制値以下となった処理水は還元槽２４にて中和して放流若しくは高度処理して系外へ排出する。一方、前記固液分離装置２２により分離した汚泥及び電解槽２３にて引き抜かれた汚泥は適宜汚泥処理設備２５に導入して処理する。
かかる実施例によれば、硝酸態窒素及びアンモニア窒素を含む窒素分を高除去率で以って処理できるとともに、各窒素分の性質に応じた処理を行っているため効率良く処理でき、また電力コストを削減することができる。
【００５０】
図８は前記第５実施例と同様にし尿等の固形分濃度が低い有機性廃棄物の処理に適し、かかるシステムは前記第５実施例と略同様の構成をしており、前記硝化・脱窒処理槽２１の代わりに第１消化槽２６、第２消化槽２７を配設した構成となっている。前記第１消化槽２６及び第２消化槽２７では、メタン発酵等の嫌気性処理を行っており、消化処理後の固液分離装置２２の後段に電解槽２３を配設している。
これにより、消化液中に残存した多量のアンモニア態窒素を効率良く除去することができる。
【００５１】
図９は、家畜糞尿等のように窒素分を多く含有し、比較的固形物の多い有機性廃棄物に適しており、前記第５実施例と略同様の構成となっている。かかるシステムでは、まずスクリーン２０により夾雑物を除去した後に曝気槽２８にて通気撹拌下で廃棄物中の有機物を酸化し、後段の沈殿槽２２ａで固形物を沈殿分離する。分離液は原水タンク２９に一時的に貯留し、電解槽２３ａ若しくは２３ｂに導入する。該電解槽２３ａ、２３ｂは並列に接続され、夫々バルブにより分離液の導入を制御している。前記図６にて説明した各種測定器により電極劣化等の判断がなされた時に、一方の電解槽を停止して他方の電解槽に分離液を導入する。これにより、電解槽に不具合が発生した場合においても直ぐに他方の電解槽を利用して処理を行うことができ、処理効率が向上する。
尚、図７乃至図９において、前記電解槽２３として図２に用いた実施形態に係る電解槽を利用しても良いことは勿論である。
【００５２】
【発明の効果】
以上記載のごとく、従来用いられてきた生物学的な脱窒処理とは異なり本発明では物理化学的な処理を行うことにより、確実にかつ高除去率で以って脱窒を行うことができるとともに、脱窒のための栄養源である水素供与体を供給する必要がなくランニングコストの低廉化が可能となる。また、脱窒後の窒素分は窒素ガスの形態で排出されるため二次汚染の心配がない。
また、膜分離装置の後段に電解槽を設けて脱窒することにより、ＢＯＤを殆ど含まない有機性廃水であっても容易に窒素分を除去することができる。
さらにまた、電解槽にてＢＯＤ／窒素分が約１〜３となるように脱窒を行った後に硝化・脱窒処理することにより、窒素除去効率を向上させることができる。また、電解槽内の塩素分濃度、電極間の抵抗値により電極の劣化を判断することにより容易に装置の不具合を検出することができるとともに、処理物がスケールの付着し易い有機性廃棄物であっても、円滑に処理を行うことができる。
また、塩素濃度計、ＣｌＯ計、ｐＨ計、ＯＲＰ計、アンモニア濃度計により、電解状況を把握することで、精度の高い運転管理・制御を行うことができる。
【図面の簡単な説明】
【図１】本発明の第１実施例に係る有機性廃棄物処理システムの概略構成図である。
【図２】本発明の実施形態に係る処理システムに具備される電解槽の説明図である。
【図３】本発明の第２実施例に係る有機性廃棄物処理システムの概略構成図である。
【図４】本発明の第３実施例に係る有機性廃棄物処理システムの概略構成図である。
【図５】本発明の第４実施例に係る有機性廃棄物処理システムの概略構成図である。
【図６】図２の別の実施形態に係る電解槽の構成図である。
【図７】本発明の第５実施例に係る有機性廃棄物処理システムの概略構成図である。
【図８】本発明の第６実施例に係る有機性廃棄物処理システムの概略構成図である。
【図９】本発明の第７実施例に係る有機性廃棄物処理システムの概略構成図である。
【図１０】従来の有機性廃棄物処理システムの全体構成図である。
【符号の説明】
１メタン発酵槽
２脱水機
３、１１、２３電解槽
４、１２、２４還元槽
５、１４、２１硝化・脱窒処理槽
６膜分離装置
７電解槽
９脱水機
１０膜分離装置
１３可溶化槽
２２固液分離装置
３２陽極
３３陰極
３４電源装置
３４ｂ抵抗計
３８第１Ｃｌ検出計
３９第２Ｃｌ検出計
４３制御回路
４４バルブ制御回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for mainly removing nitrogen from organic waste, and more particularly, to an organic waste processing system and a processing method for improving processing efficiency by a process suitable for each waste property.
[0002]
[Prior art]
For organic waste such as human waste, septic tank sludge, garbage, and livestock manure, SS (floating matter), nitrogen, phosphorus, BOD (biochemical oxygen demand), COD (chemical oxygen demand) Contaminants that adversely affect the environment and the human body are included, and various methods for removing these have been developed and put into practical use.
The treatment of organic waste is performed mainly by removing SS by solid-liquid separation, oxidative decomposition of BOD and COD, removal of inorganic nutrients such as phosphorus and nitrogen compounds, and treatment of sludge solids alone or in combination. .
[0003]
In general, the treatment of organic waste is performed according to a flow as shown in FIG. First, organic waste is passed through a screen 8 to remove impurities, separated into sludge solids and separated liquid by a dehydrator 9 such as a centrifugal separator, and the separated liquid is further passed through a membrane separator 10. After removing the suspended matter, it is introduced into a nitrification / denitrification treatment tank 14 to decompose and remove nitrogen. On the other hand, the sludge solids separated by the dehydrator 9 are guided to the solubilization tank 13 and solubilized so that the sludge solids are easily fermented by heating or the like, and in the methane fermentation tank 1 by the action of anaerobic bacteria. Convert sludge solids to methane and carbon dioxide. The digested sludge from the methane fermentation tank 1 is introduced into the dehydrator 2, the nitrogen content is removed from the separated liquid in the nitrification / denitrification treatment tank 14, and the sludge solids are sent to composting, carbonization or incineration treatment equipment. To pay.
[0004]
Conventionally, such a method has been used to uniformly remove pollutants in waste. However, since the content of each pollutant component is biased depending on the waste to be treated, any one of the pollutants Substance components may remain after treatment. In particular, it is difficult to achieve a high removal rate because most of the nitrogen content causing eutrophication is solidified and separated into solid-liquid separation, so that most of it moves to the separation liquid side and is concentrated.
In general, nitrification / denitrification treatment, anaerobic treatment, aeration treatment, and the like are often used as a treatment method for waste containing a large amount of nitrogen. However, nitrification / denitrification treatment requires enormous aeration power to oxidize ammonia nitrogen, which increases power costs, and anaerobic treatment leaves a large amount of ammonia nitrogen remaining in the digestive fluid, Nitrogen load in the treatment is increased, the treatment efficiency is deteriorated, and in the case of the aeration treatment, nitrate nitrogen remains and thus there is a problem that it is in conflict with the recent water quality regulation.
[0005]
Further, in the nitrification / denitrification treatment, a hydrogen donor is required for nitric acid respiration during denitrification, and thus readily decomposable organic substances in the treatment liquid are used. When the amount of easily decomposable organic substances that can be produced, that is, when the amount of BOD is less than three times the nitrate nitrogen content, it is necessary to add easily decomposable organic substances such as methanol and ethanol.
In particular, in recent years, proper treatment of garbage in addition to human waste and septic tank sludge has been demanded, and there is a need for a technique for improving the nitrogen removal rate during waste-based waste treatment containing a large amount of nitrogen. .
[0006]
In view of this, JP-A-8-238498 (Patent Document 1) proposes a treatment method in which sludge solids such as septic tank sludge are subjected to aeration treatment after being subjected to ozone treatment, and then subjected to nitrification / denitrification treatment. This is because sludge is brought into contact with ozone to generate components that are easily assimilated by denitrifying bacteria, and the amount of BOD increases, so that denitrification and nitrification are efficiently performed.
Japanese Patent Application Laid-Open No. 2001-113265 (Patent Document 2) discloses a method for performing methane fermentation after ammonia stripping of organic waste water / sludge. In this method, when ammonia stripping is performed, the temperature is adjusted and a strong alkaline solution is added to maintain the pH at 9 to 13, thereby improving the ammonia removal rate.
[0007]
According to these methods, the nitrogen content including ammonia can be efficiently removed, but it is difficult to remove nitrate nitrogen from the nitrogen content. Therefore, as a method for efficiently removing soluble nitrogen containing nitrate nitrogen, Japanese Patent Application Laid-Open No. 2003-62578 (Patent Document 3) proposes a method for removing nitrogen compounds in water to be treated by an electrochemical method. is doing.
In this method, a conductive metal material is used for the cathode, an insoluble material or carbon is used for the anode, and the nitrogen compound is removed by subjecting the water to be treated to which a chloride ion extender and a flocculant are added to the water to be treated. Yes. As a result, the water quality can be maintained without periodic exchange of water in a sacrifice, an aquarium, a pool, or the like.
[0008]
[Patent Document 1]
JP-A-8-238498
[Patent Document 2]
JP 2001-113265 A
[Patent Document 3]
JP 2003-62578 A
[0009]
[Problems to be solved by the invention]
However, in Patent Document 1, sludge that has not been solid-liquid separated is nitrified and denitrified, so the amount of BOD in the treated product is high, and it is easy to reduce the nitrogen content corresponding to this. Since the invention is directed to a solid-liquid separation treatment liquid having a BOD content smaller than the nitrogen content, it is difficult to apply the above technique. Furthermore, such conventional technology uses ozone. However, ozone is harmful to the human body, and care must be taken when operating the apparatus. In addition, the residence time is long in order to react sludge sufficiently with ozone. It is necessary to do so, and the apparatus becomes large.
[0010]
Further, in Patent Document 2, the cost of a strong alkali agent when performing ammonia stripping is high, and a neutralizing agent is required also when alkaline sludge is returned to neutral at a later stage, resulting in an increase in drug cost. In addition, there is a risk of air pollution due to volatilization of ammonia. In addition, ammonia stripping can remove ammonia nitrogen, but it is difficult to remove nitrate nitrogen.
Further, Patent Document 3 designates water to be treated as water having a very small solid content such as an aquarium tank or pool, and is used for the treatment of human waste, garbage, livestock manure, etc. having a high solid content as in the present invention. When applied, scales adhere to the electrodes, and the processing efficiency is greatly deteriorated.
Therefore, in view of the problems of the prior art, the present invention is an organic waste that can be efficiently operated according to the properties of the waste to be treated and can be operated at a low cost with little need for external hydrogen donor addition. It is an object of the present invention to provide an object processing system and method.
[0011]
[Means for Solving the Problems]
Therefore, in order to solve such a problem, the invention relates to a separated liquid that has been subjected to solid-liquid separation after performing at least one of nitrification / denitrification treatment, anaerobic treatment, and aeration treatment on organic waste containing nitrogen. In organic waste treatment system with water treatment equipment to remove nitrogen from
An electrolytic cell in which the water treatment facility generates a hypochlorous acid strong oxidizing substance by electrolyzing the separated liquid and removes nitrogen contained in the separated liquid by an oxidizing action of the strong oxidizing substance; It is characterized by having.
[0012]
In this invention, chlorine ions, water and nitrate ions contained in the treatment liquid exhibit the following reaction by electrolyzing the treatment liquid.
(Anode) 2Cl⁻ → Cl₂+ 2e
Cl₂+ H₂O → HClO + HCl
(Cathode) NO₃ ⁻+ 6H₂O + 8e → NH₃+ 9OH⁻
2H₂O + 2e → 2OH⁻+ H₂↑
At the anode, chlorine is generated, and further, the chlorine reacts with water to produce hypochlorous acid (HClO) having a strong oxidizing power. On the other hand, at the cathode, when nitrate ions are contained in the separated liquid, it is reduced to ammonia. When nitrate ions are not included, hydrogen is generated by the decomposition of water.
[0013]
Ammonia contained in the separation liquid or ammonia generated by electrolysis reacts by the following formula with hypochlorous acid generated at the anode, and is decomposed and removed.
2NH₃+ 3HClO → N₂↑ + 3HCl + 3H₂O
Thus, by performing physicochemical treatment unlike biological denitrification treatment that has been used in the past, nitrogen content including soluble nitrogen content can be reliably and stably removed at a high removal rate. In addition, it is not necessary to supply a hydrogen donor as a nutrient source for denitrification, and the running cost can be reduced. Moreover, since the nitrogen content after denitrification is discharged in the form of nitrogen gas, there is no concern about secondary contamination.
In the present invention, the nitrogen content means ammonia nitrogen, nitrous acid / nitrate nitrogen, and the like, and these oxidative decompositions are carried out simultaneously with the typical reaction represented by the above formula.
[0014]
In addition, the facility area can be greatly reduced as compared with biological treatment, which is a nitrogen removal treatment that has been widely used in the past. For example, while it takes about 3 days to remove nitrogen in biological treatment, the electrolytic treatment of the present invention can be performed in several hours. Moreover, since the electrolytic treatment is a physicochemical treatment, it is easier to maintain and manage than the biological treatment.
Furthermore, when an electrolytic cell is used in combination with nitrification / denitrification treatment, the denitrification of electrolytic treatment requires less power for ammonia nitrogen than nitrate nitrogen, so the aeration power in the nitrification tank can be reduced. . That is, almost all of the BOD is removed in the nitrification tank and only a part of the ammonia nitrogen is nitrified, and the ammonia nitrogen is removed in the subsequent electrolytic tank, so that the nitrogen content can be almost completely removed from the treated water. it can.
In addition, such an invention can be incorporated in a facility where nitrogen removal is insufficient among existing human waste treatment plants, sewage treatment plants, and the like, and a reliable nitrogen removal effect can be obtained with a compact apparatus.
[0015]
In addition, the organic waste treatment system in which the organic waste is mainly garbage is provided with a methane fermentation tank for anaerobically fermenting the organic waste, and the digested sludge of the methane fermentation tank is solid-liquid separated. The separation liquid is purified.
This invention targets organic waste mainly composed of garbage having a larger nitrogen content ratio than organic waste such as human waste, septic tank sludge, and livestock manure. This is because methane fermentation is carried out in the previous stage, so it contains a lot of ammonia nitrogen generated by the decomposition of macromolecular organic matter, and the digested sludge after methane fermentation is solid-liquid separated. Contains a high concentration of nitrogen. Therefore, by configuring as in the invention, it is possible to treat a high concentration of nitrogen with a high removal rate.
[0016]
Further, a membrane separation device is provided in the methane fermentation tank, a part of the digested sludge after anaerobic fermentation is guided to the membrane separation device, and the sludge solids separated by the membrane separation device are converted into the methane fermentation tank. Returned to
On the other hand, the permeate that has permeated through the membrane separator is introduced into the electrolytic cell.
Thereby, in the anaerobic fermentation of the garbage which is easily solubilized and difficult to maintain the concentration, the inside of the tank can be maintained at an optimum concentration for fermentation, and anaerobic fermentation is promoted. Further, the permeated liquid after membrane separation is introduced into the electrolytic cell, so that the nitrogen content can be removed with a high decomposition rate even in the processing liquid containing almost no BOD.
[0017]
Further, a membrane separation device is provided in the methane fermentation tank, a part of the digested sludge after anaerobic fermentation is guided to the membrane separation device, and sludge solids separated by the membrane separation device are converted into the methane fermentation tank. Returned to
On the other hand, a second electrolytic cell may be provided after the membrane separation device, and the permeate that has permeated through the membrane separation device may be introduced into the second electrolytic cell to remove the nitrogen content in the processing solution.
The membrane separation device preferably uses an ultrafiltration membrane (UF) or a microfiltration membrane (MF), and the permeate that has permeated the membrane separation device as in the present invention is SS, BOD, phosphorus content, COD, etc. Most of them are separated and contain only a high concentration of soluble nitrogen. Therefore, by providing the second electrolytic cell in a separate system and performing an operation suitable for the properties of the permeate, a stable operation can be performed and the properties of the water after treatment can be kept constant.
[0018]
In addition, in an organic waste treatment system equipped with a means for solid-liquid separation of organic waste and a water treatment facility for purifying the separated separated liquid,
Electrolysis in which the water treatment facility generates a hypochlorous acid-based strong oxidizing substance by electrolyzing the separated separated liquid, and removes nitrogen contained in the separated liquid by the oxidizing action of the strong oxidizing substance. A tank is provided.
[0019]
As the solid-liquid separation means, any means such as gravity sedimentation, flotation separation, mechanical dehydration, membrane separation, or a combination of these is used. A mechanical dehydrator and a membrane separator provided at the subsequent stage are preferably used.
As in this invention, the separation liquid after solid-liquid separation is introduced into an electrolytic cell, and the generated hypochlorous acid-based strong oxidizing substance is oxidatively decomposed, thereby eliminating the need for supplying a hydrogen donor and reducing running costs. And can be treated with a high removal rate of nitrogen.
[0020]
Furthermore, the electrolytic cell is configured to reduce the nitrogen content so that the BOD / nitrogen content in the separation liquid is within the range of about 1 to 3, and the nitrogen content is reduced downstream of the electrolytic cell. A treatment tank for nitrifying and denitrifying the treatment liquid is provided.
Nitrogen can be efficiently removed by nitrifying and denitrifying a separation liquid having a BOD / nitrogen ratio in the range of about 1 to 3 in this way, and denitrification is performed by providing an electrolytic cell in the previous stage. This reduces the load on the nitrification / denitrification tank.
[0021]
Furthermore, the electrolytic cell measures a chlorine content concentration of the separation liquid in the reaction tank, a means for measuring the resistance between the electrodes disposed in the reaction tank facing the reaction tank, and the reaction tank. And means for
A means for judging the degree of electrode degradation based on at least one of the interelectrode resistance obtained by the resistance measuring means and the chlorine concentration value of the separated liquid obtained by the chlorine concentration measuring means; It is characterized by that.
In this invention, since organic waste is targeted, the scale easily adheres to the electrode. Therefore, with the above-described configuration, it is possible to easily determine the deterioration of the electrode, and it is possible to perform smooth operation.
[0022]
Moreover, it is preferable that the said reaction tank has a means to circulate the separated liquid in this reaction tank in a tank, and the said chlorine concentration measurement means is provided on the circulation path of this circulation means. Thereby, the chlorine concentration can be appropriately measured regardless of the concentration distribution in the tank. Furthermore, by providing the circulation means, the inside of the tank can be stirred without providing a separate stirring means, and the electrolytic reaction efficiency is improved.
[0023]
Furthermore, the electrolytic cell has foam amount detection means in the reaction tank, and when the deterioration is judged by the electrode deterioration judgment means, the foam amount in the reaction tank is measured, and the foam amount is When it is above the reference value, an antifoaming agent is added.
When the object to be treated is organic waste as in the present invention, bubbles are likely to be generated, which may cause a short circuit between the electrodes and cause an abnormality in the resistance value. Therefore, when an abnormality occurs, it is judged whether it is actually a deterioration of the electrode or a short circuit due to foam by detecting the amount of foam as in this invention. Thus, it is preferable to ensure that the electrolytic reaction takes place.
In addition, a second chlorine concentration measuring means for measuring the chlorine concentration of the separated liquid is provided in the previous stage of the electrolytic cell, and a means for introducing a chlorine ion adjusting agent based on the measured chlorine ion concentration is provided. It is characterized by that.
As a result, the chlorine ion concentration in the electrolytic cell is properly maintained, the electrolytic reaction is promoted, and the nitrogen removal efficiency is improved.
[0024]
Further, the electrolytic cell has means for circulating the separated liquid of the reaction tank in the tank, and a chlorine concentration measuring unit, a residual chlorine measuring unit, an ORP on the circulation path of the circulating unit or inside the electrolytic cell. It is also preferable to have at least one of a measurement unit, a pH measurement unit, and an ammonia concentration measurement unit, and to control the electrolytic treatment time of the electrolytic cell by combining one or more of the measurement units.
[0025]
In addition, as a treatment method having substantially the same effect as the above-described invention, solid-liquid separation is performed after at least one of nitrification / denitrification treatment, anaerobic treatment, and aeration treatment is performed on organic waste containing nitrogen. In the organic waste processing method for removing nitrogen from the separated liquid,
Electrolyzing the separated liquid-liquid separated liquid in an electrolytic cell to produce a hypochlorous acid-based strong oxidizing substance, and removing nitrogen contained in the separating liquid by the oxidizing action of the strong oxidizing substance. Features.
[0026]
The organic waste is a method for treating organic waste mainly composed of garbage, wherein the organic waste is subjected to anaerobic fermentation in a methane fermentation tank, and the digested sludge produced by the anaerobic fermentation is solidified. The separated liquid is purified by the electrolytic cell.
Moreover, after partially extracting the digested sludge after the anaerobic fermentation, the digested sludge is subjected to solid-liquid separation by membrane separation, and then the separated sludge solids are returned to the methane fermentation tank.
On the other hand, the separated permeate is electrolyzed.
[0027]
Furthermore, in the organic waste processing method for purifying the separated liquid after solid-liquid separation of the organic waste,
Electrolyzing the separated liquid-liquid separated liquid to produce a hypochlorous acid-based strong oxidizing substance, and removing nitrogen contained in the separating liquid by the oxidizing action of the strong oxidizing substance . This invention is particularly suitable for the treatment of organic waste mainly composed of septic tank sludge.
Further, the nitrogen content is reduced so that the BOD / nitrogen content in the separated liquid is within the range of about 1 to 3 by the hypochlorous acid strong oxidizing substance generated by the electrolysis, and then the treatment liquid is nitrified. Denitrification is preferred.
[0028]
Further, at the time of the electrolysis, at least one of a resistance value between the electrodes arranged opposite to each other in the electrolytic cell and a chlorine concentration value of the separated liquid in the cell is measured, and based on the measured value The deterioration of the electrode is judged.
At this time, when it is determined that the electrode is deteriorated, it is preferable to detect the amount of foam in the tank and to add an antifoaming agent when the amount of foam is equal to or greater than a reference value.
Furthermore, before the electrolysis, the chlorine ion concentration of the separated liquid is measured, and a chlorine ion adjusting agent is preferably added based on the measured chlorine ion concentration.
Furthermore, the electrolytic cell has at least one of chlorine concentration measuring means, residual chlorine concentration measuring means, ORP measuring means, pH measuring means, and ammonia concentration measuring means, and one or two or more of these measuring means. In combination, it is preferable to control the electrolytic treatment time of the electrolytic cell.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.
FIG. 1 is a schematic configuration diagram of an organic waste treatment system according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of an electrolytic cell provided in the treatment system according to an embodiment of the present invention, and FIGS. These are the schematic block diagrams of the organic waste disposal system which concerns on the 2nd thru | or 4th Example which is another Example of FIG. 1, respectively.
[0030]
The organic waste treatment system according to the first embodiment is suitable for the treatment of organic waste mainly composed of garbage. As shown in FIG. 1, the methane fermentation tank 1 and the methane fermentation tank After denitrification by addition of an alkali agent, a dehydrator 2 that mechanically dehydrates the digested sludge discharged from 1 with a centrifuge, an electrolytic bath 3 that denitrifies the separated liquid after dewatering and separating sludge solids, and the like. And a nitrification / denitrification treatment tank 5 for performing biological treatment on the neutralized separation liquid.
[0031]
In the methane fermentation tank 1, the macromolecular organic matter in the waste is decomposed into carbon dioxide, methane, ammonia and the like by the action of anaerobic bacteria in the tank. The methane generated here is sent to a power generator or the like for effective use. At this time, electric power generated based on the recovered methane gas may be transmitted to the electrolytic cell 3 and used.
In addition, the digested sludge discharged from the methane fermentation tank 1 is solid-liquid separated by the dehydrator 2, and the sludge solids are sent to composting, carbonization or incineration facilities, while the separated liquid is fed to the electrolytic tank 3. .
[0032]
The electrolytic cell 3 electrolyzes the separated liquid separated after methane fermentation to produce a hypochlorous acid-based strong oxidizing substance, and oxidatively decomposes ammonia nitrogen with the strong oxidizing substance. As shown in FIG. 2, the electrolytic cell 3 includes a reaction tank 31 that receives the separation liquid, and an anode 32 and a cathode that are arranged so as to be immersed in the separation liquid introduced into the reaction tank 31. And an electric power device 34 connected to the electrode.
And as a typical reaction in each electrode, the following reactions are caused by chlorine ions, water and nitrate ions contained in the separation liquid.
(Anode) 2Cl⁻ → Cl₂+ 2e
Cl₂+ H₂O → HClO + HCl
(Cathode) NO₃ ⁻+ 6H₂O + 8e → NH₃+ 9OH⁻
2H₂O + 2e → 2OH⁻+ H₂↑
At the anode, chlorine is generated, and further, the chlorine reacts with water to produce hypochlorous acid (HClO) having a strong oxidizing power. On the other hand, at the cathode, when nitrate ions are contained in the separated liquid, it is reduced to ammonia. When nitrate ions are not included, hydrogen is generated by the decomposition of water.
[0033]
Ammonia contained in the separated liquid or ammonia generated by electrolysis is decomposed and removed by hypochlorous acid generated at the anode according to the following formula.
2NH₃+ 3HClO → N₂↑ + 3HCl + 3H₂O
It is preferable to maintain the electrolytic efficiency of the electrolytic cell 3 by applying a reverse voltage every certain period in order to remove the substances adhering to the electrodes, or by stopping the treatment and washing.
Further, when a nitrification / denitrification treatment tank is provided downstream as in the present embodiment, the electrolytic cell 3 is used so that the component ratio (BOD / nitrogen content) of the treatment liquid after denitrification is about 1 to 3. The residence time, the volume of the electrolytic cell 3, or the voltage value applied to the electrodes may be controlled.
[0034]
Then, the treatment liquid denitrified in the electrolytic bath 3 is introduced into the reduction bath 4. Since the treatment liquid is in an acidic state due to the strong oxidizing substance generated in the electrolytic cell 3, it is neutralized by adding an alkaline agent such as caustic soda in the reduction tank 4.
The neutralized treatment liquid is guided to the nitrification / denitrification treatment tank 5 and further denitrified in the tank by the action of nitrifying bacteria, denitrifying bacteria and the like.
At this time, when the nitrogen content is reduced in the electrolytic cell 3 until the BOD / nitrogen content ratio in the separation liquid becomes BOD / nitrogen content = about 1 to 3, the hydrogen donor in the treatment liquid Therefore, denitrification can be performed with high efficiency.
The treatment liquid in which the nitrogen content is removed below the discharge standard value in the denitrification / nitrification treatment tank 5 is discharged to the outside or sent to an advanced treatment facility.
[0035]
As described above, in this embodiment, unlike the conventionally used biological denitrification treatment, by performing the physicochemical treatment, a high nitrogen removal rate can be achieved reliably and stably, and the denitrification treatment can be achieved. It is not necessary to supply a hydrogen donor that is a nutrient source for nitrogen, and the running cost can be reduced. Moreover, since the nitrogen content after denitrification is discharged in the form of nitrogen, there is no concern about secondary contamination.
In the present embodiment, the nitrification / denitrification treatment tank 5 does not have to be provided if the electrolytic tank 3 can reduce the nitrogen content below the drainage standard value.
[0036]
3 and 4 show a system for treating organic waste mainly composed of garbage, as in the first embodiment. In the second embodiment shown in FIG. The digested sludge after decomposition is introduced into the dehydrator 2, and a part of the digested sludge is extracted and introduced into the membrane separation device 6. The membrane separator 6 preferably uses an ultrafiltration membrane (UF) or a microfiltration membrane (MF). Sludge solids separated from the digested sludge by the membrane separator 6 are returned to the methane fermentation tank 1. Thereby, also in the process of the waste which is easy to decompose | disassemble, such as garbage, the density | concentration in a methane fermentation tank is maintained suitably, and anaerobic fermentation is performed efficiently. On the other hand, the permeate that has permeated through the membrane separation device 6 is separated and removed from SS, BOD, phosphorus, COD, etc., and is fed to the electrolytic cell 3 in a state of containing a high concentration of soluble nitrogen. .
[0037]
Part of the digested sludge discharged from the methane fermentation tank 1 is solid-liquid separated into sludge solids and a separated liquid by a dehydrator 2, and the sludge solids are sent to a composting, carbonization or incineration facility, and the separated liquid Is fed to the electrolytic cell 3.
The electrolytic cell 3 has the same configuration as that of the first embodiment, and the separation introduced from the membrane separation device 6 and the dehydrator 2 by the hypochlorous acid-based strong oxidant generated here. Nitrogen in the liquid is decomposed and removed.
The treatment liquid denitrified in the electrolytic tank 3 is neutralized with an alkaline agent in the reduction tank 4 and then introduced into the nitrification / denitrification treatment tank 5 to reduce the nitrogen concentration to below the discharge standard value. Later it is discharged or sent to advanced processing equipment.
[0038]
In the third embodiment shown in FIG. 4, a second electrolytic cell 7 is provided for denitrifying the permeate that has permeated through the membrane separation device 6. The second electrolytic cell 7 has the same configuration as the electrolytic cell 3. The treatment liquid denitrified in the second electrolytic tank 7 is neutralized in the reduction tank 4 together with the treatment liquid from the electrolytic tank 3, and is subjected to nitrification / denitrification treatment.
In the membrane separation device 6, almost all of the pollutant other than the soluble nitrogen content is removed, so that the permeate after membrane separation contains a high concentration of nitrogen content. Therefore, by adopting such a configuration as in this embodiment, processing suitable for the properties of each processing liquid can be performed, and stable operation of the processing system is facilitated.
In order to maintain the filtration rate of the membrane separator, the treatment liquid may be periodically extracted from the electrolytic cell and introduced into the membrane separator, thereby generating hypochlorous acid in the electrolytic cell. The filtration rate can be recovered by the cleaning effect of the acid strong oxidizing substance.
[0039]
Next, a fourth embodiment of the present invention shown in FIG. 5 will be described. In this embodiment, the organic waste is separated into solid and liquid, and then the contaminants are removed by biological treatment and physicochemical treatment.
In such a treatment system, organic waste is first removed through a screen 8 and then separated into sludge solids and a separation liquid by a dehydrator 9, and the sludge solids are introduced into a solubilization tank 13 and added. The organic matter in the sludge is solubilized by temperature or the like and introduced into the methane fermentation tank 14. The digested sludge is fed to composting, carbonization or incineration facilities after the decomposition of the polymer organic matter in the methane fermentation tank 14.
[0040]
On the other hand, the separation liquid from which the solid matter has been separated by the dehydrator 9 is introduced into the membrane separation apparatus 10 to remove BOD, SS and the like in the separation liquid, and then guided to the electrolytic cell 11. At this time, the solid content that does not pass through the membrane separation is returned to the upstream side of the dehydrator 9 and processed again.
The electrolytic cell 11 has the same configuration as the first to third embodiments, and is a strong hypochlorous acid-based oxidation produced by electrolysis of salts, chlorine, water, etc. contained in the separated liquid. Nitrogen contained in the separation liquid is decomposed and removed by the substance.
And the separated liquid from which the nitrogen content was removed to below the discharge standard value in the electrolytic bath 11 is neutralized with an alkaline agent in the reducing bath 12 and then sent to the discharge or advanced treatment equipment.
[0041]
In the fourth embodiment, the organic waste is permeated containing sludge solids containing pollutants other than nitrogen and soluble nitrogen such as ammonia nitrogen by combining the dehydrator 9 and the membrane separator 10. By separating into permeate and further denitrifying the permeate in the electrolytic cell 11, soluble nitrogen components such as ammonia nitrogen can be reliably treated with a high removal rate. When the nitrogen concentration of the treatment liquid is high, a nitrification / denitrification treatment tank may be provided downstream of the reduction tank 12. At this time, it is preferable that the ratio of BOD and nitrogen content in the permeate in the electrolytic cell 11 is BOD / nitrogen content = about 1 to 3, so that the denitrification treatment can be efficiently performed in the nitrification / denitrification treatment tank. It can be performed.
[0042]
Further, as another embodiment of the electrolytic cell 3, FIG. 6 shows an electrolytic cell equipped with various measuring means.
In FIG. 6, an electrolytic cell 23 includes a reaction vessel 23a for holding a separation liquid, an anode 32 and a cathode 33 arranged opposite to each other in the reaction vessel 23a, and a power source connected to these electrodes via conductive wires. A separation liquid is extracted from a device 34, a voltmeter 34b for measuring a voltage applied between the electrodes by the power supply device 34, a resistance meter 34a for measuring a resistance value between the electrodes, and a lower portion of the reaction tank 23a. A circulation pump 35 to be introduced into the upper part of the reaction tank, a first Cl concentration meter 38 installed on the circulation path for measuring the chlorine concentration in the separated liquid, a valve 37 similarly disposed on the circulation path, and the extraction And a valve 36 disposed on a path for discharging the separated liquid to the outside.
[0043]
Further, on the upstream side of the electrolytic cell 23, a raw water tank 29 for storing a separated liquid separated from a solid content through a solid-liquid separation device such as the dehydrator 2 is disposed. A second Cl concentration meter 39 for detecting the chlorine concentration in the separated liquid is provided, and means for adding a chlorine ion adjusting agent 42 such as NaClaq or NaClO is provided.
The resistance meter 34 a, the first Cl concentration meter 38, and the second Cl concentration meter 39 are connected to a control circuit 43. Based on the control circuit 43, the applied voltage of the power supply device 34, the voltage ON / OFF, and the valve control circuit 44. The opening and closing of the valves 36 and 37 is controlled.
[0044]
In the electrolytic bath 23, the electrolytic treatment is performed in a batch manner, and the same reaction as the chemical reaction formula shown in FIG. In normal operation, the valve 36 is closed and the valve 37 is opened, so that the separation liquid is circulated in the tank by the circulation pump 35 until the nitrogen content in the separation liquid becomes a reference value or less.
Then, during the electrolytic treatment, the resistance value between the electrodes and the chlorine content concentration of the separation liquid in the reaction tank 23a are measured by the resistance meter 34a and the first Cl concentration meter 38. When the resistance value and the Cl concentration are not within the reference range, an apparatus failure such as an abnormality in the separation liquid or electrode deterioration is detected, and proper electrolytic treatment is not performed. That is, when the resistance value is high, it may be caused by scale adhesion, electrode wear, or the like, when the resistance value is low, short circuit due to an increase in the amount of foam. It is also possible to grasp the electrolytic treatment status by tracking changes in the Cl concentration over time. This suggests that when the Cl concentration tends to decrease, ammonia nitrogen remains, that is, lack of denitrification, and emergency measures such as shutting down the reactor and drawing out the total amount of liquid are required.
[0045]
In such an embodiment, since the target treated water is organic wastewater, abnormalities that appear most frequently include electrode deterioration due to adhesion of scale to the electrodes and short-circuiting between electrodes due to an increase in the amount of foam. Therefore, in this embodiment, when the value measured by at least one of the resistance meter 34a and the first Cl concentration meter 38 is determined to be an abnormal value by the control circuit 43, it is determined that the electrode is deteriorated, Signals are transmitted to the power supply device 34 and the valve drive circuit 44, and the valve 36 is opened and the valve 37 is closed by the OFF of the power supply device 34 and the valve drive circuit 44, and the separation liquid is drawn out.
[0046]
Moreover, when deterioration of an electrode is judged by resistance value or chlorine concentration, it is preferable to detect the foam amount in a tank first by a foam detector not shown. When the amount of foam indicates a reference value or more by the foam detector, the antifoaming agent 41 is added to eliminate the foam. Thereby, when the abnormality in the resistance value or the chlorine concentration is a short circuit due to foam, it can be dealt with without stopping the operation.
In the electrolytic treatment, operation with a chlorine concentration of Cl = 2000 mg / L is appropriate. This is because when the concentration is a value that greatly exceeds 2000 mg / L, the electrolytic reaction is not performed properly, and there is a concern about a decrease in denitrification efficiency. When the concentration is about 1000 ml / L, electrode consumption is remarkably deteriorated. This is because.
Therefore, it is necessary to dilute in the case of a high salt concentration separation liquid and increase the amount of chloride ions in the case of a low salt concentration separation liquid.
[0047]
There is a ClO meter 46 (residual chlorine meter) for grasping the state of electrolytic treatment. When the ClO concentration tends to increase, it is suggested that electrolysis is proceeding despite the completion of denitrification, and there is a concern about the outflow of trihalomethanes to the separation liquid. It is necessary to take emergency measures such as stopping the operation and drawing out the entire liquid.
In addition to the above-described measuring instrument, a pH meter 47, an ORP meter 48, an ammonia concentration meter 49, etc. can be appropriately used alone or in combination to perform various measurements, thereby enabling more accurate operation management and control.
[0048]
Further, FIGS. 7 to 9 show fifth to seventh embodiments which are systems in which the electrolytic cell 23 is incorporated in an existing waste treatment system.
FIG. 7 shows a fifth embodiment of the present invention, which is suitable for the treatment of, for example, human waste having a solid content concentration of about 2-3%. In this system, after removing impurities in the treated water with the screen 20, nitrification / denitrification is performed in the nitrification / denitrification treatment tank 21 to remove nitrogen, and then the solid-liquid separation device 22 performs solid-liquid separation. A part of the solid-liquid separated sludge is appropriately returned to the nitrification / denitrification treatment tank 21 to maintain the nitrification / denitrification bacteria concentration in the nitrification / denitrification tank. As the solid-liquid separation device 22, a membrane separation tank, a precipitation tank, a dehydration apparatus, or the like is preferably used.
[0049]
The separated liquid from which the solid has been separated is introduced into the electrolytic bath 23 to remove the nitrogen remaining by the electrolytic reaction. The treated water whose nitrogen content is below the regulation value is neutralized in the reduction tank 24 and discharged or advanced, and discharged out of the system. On the other hand, the sludge separated by the solid-liquid separator 22 and the sludge extracted by the electrolytic cell 23 are appropriately introduced into the sludge treatment facility 25 for treatment.
According to such an embodiment, the nitrogen content including nitrate nitrogen and ammonia nitrogen can be treated with a high removal rate, and the treatment according to the properties of each nitrogen content can be performed efficiently, and the power Cost can be reduced.
[0050]
FIG. 8 is suitable for the treatment of organic waste having a low solid content, such as urine, as in the fifth embodiment, and this system has substantially the same configuration as in the fifth embodiment, and the nitrification / desorption is performed. Instead of the nitrogen treatment tank 21, a first digestion tank 26 and a second digestion tank 27 are provided. In the first digestion tank 26 and the second digestion tank 27, an anaerobic process such as methane fermentation is performed, and an electrolytic cell 23 is disposed at the subsequent stage of the solid-liquid separation device 22 after the digestion process.
Thereby, a large amount of ammonia nitrogen remaining in the digestive juice can be efficiently removed.
[0051]
FIG. 9 is suitable for organic waste containing a large amount of nitrogen, such as livestock manure, and having a relatively large amount of solids, and has substantially the same configuration as that of the fifth embodiment. In such a system, first, impurities are removed by the screen 20, and then organic substances in the waste are oxidized in the aeration tank 28 with aeration and stirring, and solid substances are precipitated and separated in the subsequent precipitation tank 22 a. The separation liquid is temporarily stored in the raw water tank 29 and introduced into the electrolytic cell 23a or 23b. The electrolytic cells 23a and 23b are connected in parallel, and the introduction of the separation liquid is controlled by valves. When the determination of electrode deterioration or the like is made by the various measuring devices described with reference to FIG. 6, one electrolytic cell is stopped and the separation liquid is introduced into the other electrolytic cell. As a result, even when a failure occurs in the electrolytic cell, the other electrolytic cell can be immediately used to perform the treatment, and the processing efficiency is improved.
7 to 9, the electrolytic cell according to the embodiment used in FIG. 2 may be used as the electrolytic cell 23.
[0052]
【The invention's effect】
As described above, unlike the conventional biological denitrification treatment, the present invention can perform denitrification reliably and with a high removal rate by performing a physicochemical treatment. At the same time, it is not necessary to supply a hydrogen donor as a nutrient source for denitrification, and the running cost can be reduced. Moreover, since the nitrogen content after denitrification is discharged in the form of nitrogen gas, there is no concern about secondary contamination.
In addition, by providing an electrolytic cell at the subsequent stage of the membrane separator and performing denitrification, even organic wastewater containing almost no BOD can easily remove nitrogen.
Furthermore, nitrogen removal efficiency can be improved by performing nitrification / denitrification treatment after performing denitrification in an electrolytic cell so that the BOD / nitrogen content is about 1 to 3. In addition, it is possible to easily detect the malfunction of the device by judging the deterioration of the electrode based on the chlorine content concentration in the electrolytic cell and the resistance value between the electrodes, and the treated product is an organic waste that easily adheres to the scale. Even if it exists, a process can be performed smoothly.
In addition, highly accurate operation management and control can be performed by grasping the electrolysis state with a chlorine concentration meter, a ClO meter, a pH meter, an ORP meter, and an ammonia concentration meter.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an organic waste treatment system according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram of an electrolytic cell provided in the processing system according to the embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of an organic waste treatment system according to a second embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of an organic waste treatment system according to a third embodiment of the present invention.
FIG. 5 is a schematic configuration diagram of an organic waste treatment system according to a fourth embodiment of the present invention.
6 is a configuration diagram of an electrolytic cell according to another embodiment of FIG. 2. FIG.
FIG. 7 is a schematic configuration diagram of an organic waste treatment system according to a fifth embodiment of the present invention.
FIG. 8 is a schematic configuration diagram of an organic waste treatment system according to a sixth embodiment of the present invention.
FIG. 9 is a schematic configuration diagram of an organic waste treatment system according to a seventh embodiment of the present invention.
FIG. 10 is an overall configuration diagram of a conventional organic waste treatment system.
[Explanation of symbols]
1 Methane fermentation tank
2 Dehydrator
3, 11, 23 Electrolyzer
4, 12, 24 Reduction tank
5, 14, 21 Nitrification / denitrification tank
6 Membrane separator
7 Electrolysis tank
9 Dehydrator
10 Membrane separator
13 Solubilization tank
22 Solid-liquid separator
32 Anode
33 Cathode
34 Power supply
34b Resistance meter
38 1st Cl detector
39 Second Cl detector
43 Control circuit
44 Valve control circuit

Claims

Organic equipped with a water treatment facility that removes nitrogen from the separated liquid after it has been subjected to at least one of nitrification / denitrification, anaerobic treatment, and aeration treatment to organic waste containing nitrogen In the treatment system of radioactive waste,
An electrolytic cell in which the water treatment facility generates a hypochlorous acid strong oxidizing substance by electrolyzing the separated liquid and removes nitrogen contained in the separated liquid by an oxidizing action of the strong oxidizing substance; An organic waste treatment system comprising:

The organic waste treatment system according to claim 1, wherein the organic waste is mainly garbage, and includes a methane fermentation tank for anaerobically fermenting the organic waste, and the digested sludge of the methane fermentation tank is solidified. An organic waste treatment system characterized by purifying the separated liquid.

A membrane separator is provided in the methane fermentation tank, a part of the digested sludge after anaerobic fermentation is guided to the membrane separator, and sludge solids separated by the membrane separator are returned to the methane fermentation tank. And
On the other hand, the organic waste treatment system according to claim 2, wherein the permeate permeated through the membrane separator is introduced into the electrolytic cell.

A membrane separator is provided in the methane fermentation tank, a part of the digested sludge after anaerobic fermentation is guided to the membrane separator, and sludge solids separated by the membrane separator are returned to the methane fermentation tank. And
On the other hand, a second electrolytic cell is provided after the membrane separator, and the permeate that has permeated through the membrane separator is introduced into the second electrolytic cell to remove the nitrogen content in the permeate. The organic waste processing system according to claim 2.

In an organic waste treatment system equipped with a means for solid-liquid separation of organic waste and a water treatment facility for purifying the separated liquid,
An electrolytic cell in which the water treatment facility generates a hypochlorous acid strong oxidizing substance by electrolyzing the separated liquid and removes nitrogen contained in the separated liquid by an oxidizing action of the strong oxidizing substance; An organic waste treatment system comprising:

6. The organic waste treatment system according to claim 5, wherein the solid-liquid separation means includes a mechanical dehydration device and a membrane separation device provided in a subsequent stage.

The electrolytic cell is configured to reduce the nitrogen content so that the BOD / nitrogen content during processing is within the range of about 1 to 3, and the treatment liquid with reduced nitrogen content is nitrified at the subsequent stage of the electrolytic cell. 6. The organic waste treatment system according to claim 1, further comprising a treatment tank for denitrification.

A means for measuring a resistance of a separation liquid in the reaction tank; a means for measuring a resistance between electrodes disposed opposite to the reaction tank; And comprising
A means for judging the degree of electrode degradation based on at least one of the interelectrode resistance obtained by the resistance measuring means and the chlorine concentration value of the separated liquid obtained by the chlorine concentration measuring means; The organic waste treatment system according to claim 1, 2, or 5.

9. The reaction tank has means for circulating the separation liquid in the reaction tank in the tank, and the chlorine concentration measuring means is provided on a circulation path of the circulation means. Organic waste treatment system.

The electrolytic cell according to claim 8 has a foam amount detection means in the reaction tank, and measures the foam amount in the reaction tank when the electrode deterioration determination means determines the deterioration. An organic waste treatment system is characterized in that an antifoaming agent is added when the value is equal to or greater than a reference value.

A second chlorine concentration measuring means for measuring the chlorine content concentration of the separation liquid is provided in the previous stage of the electrolytic cell, and a means for supplying a chlorine ion adjusting agent based on the chlorine ion concentration measured thereby is provided. 9. The organic waste processing system according to claim 1, 2, 5, or 8.

The electrolytic cell has a means for circulating the separation liquid of the reaction tank in the tank, and a chlorine concentration measuring unit, a residual chlorine measuring unit, an ORP measuring unit on the circulation path of the circulating unit or inside the electrolytic cell. 9. The method according to claim 8, further comprising at least one of pH measurement means and ammonia concentration measurement means, wherein the electrolytic treatment time of the electrolytic cell is controlled by combining one or more of the measurement means. The organic waste treatment system described.

A method for treating organic waste that removes nitrogen from the separated liquid after applying at least one of nitrification / denitrification treatment, anaerobic treatment, and aeration treatment to organic waste containing nitrogen In
Electrolyzing the separated liquid-liquid separated liquid in an electrolytic cell to produce a hypochlorous acid-based strong oxidizing substance, and removing nitrogen contained in the separating liquid by the oxidizing action of the strong oxidizing substance. A characteristic method for treating organic waste.

The organic waste treatment method according to claim 13, wherein the organic waste is mainly garbage, and the digestion caused by the anaerobic fermentation is performed by anaerobic fermentation of the organic waste in a methane fermentation tank. A method for treating organic waste, comprising purifying a separated liquid obtained by solid-liquid separation of sludge using the electrolytic cell.

A part of the digested sludge after the anaerobic fermentation is extracted, and the digested sludge is solid-liquid separated by membrane separation, and then the separated sludge solids are returned to the methane fermentation tank.
15. The method for treating organic waste according to claim 14, wherein the separated permeate is electrolyzed.

In the organic waste processing method for purifying the separated liquid after solid-liquid separation of the organic waste,
Electrolyzing the separated liquid-liquid separated liquid to produce a hypochlorous acid-based strong oxidizing substance, and removing nitrogen contained in the separating liquid by the oxidizing action of the strong oxidizing substance Organic waste disposal methods.

The nitrogen content is reduced so that the BOD / nitrogen content in the treatment liquid is within the range of about 1 to 3 by the hypochlorous acid strong oxidizing substance generated by the electrolysis, and then the treatment liquid is nitrified and denitrified. The organic waste processing method according to any one of claims 13 to 16, wherein the organic waste is processed.

At the time of the electrolysis, at least one of a resistance value between electrodes arranged opposite to each other in the electrolytic cell and a chlorine concentration value of a separation liquid in the cell is measured, and the electrode is based on the measured value. The method for treating organic waste according to claim 13, 14 or 16, wherein deterioration of the organic waste is judged.

The organic solvent according to claim 18, wherein when the deterioration of the electrode is determined, the amount of foam in the tank is detected, and if the amount of foam is equal to or greater than a reference value, an antifoaming agent is added. Waste disposal method.

17. The organic waste according to claim 13, 14 or 16, wherein a chlorine ion concentration of the separated liquid is measured before the electrolysis, and a chlorine ion adjusting agent is introduced based on the measured chlorine ion concentration. How to handle things.

The electrolytic cell has at least one of chlorine concentration measurement means, residual chlorine concentration measurement means, ORP measurement means, pH measurement means, and ammonia concentration measurement means, and one or a combination of two or more of these measurement means. The method for treating organic waste according to claim 13, 14 or 16, wherein the electrolytic treatment time of the electrolytic cell is controlled.