JP2004230225A

JP2004230225A - Method for treating ammonia-containing water

Info

Publication number: JP2004230225A
Application number: JP2003019112A
Authority: JP
Inventors: Nobuhiro Oda; 信博織田
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2003-01-28
Filing date: 2003-01-28
Publication date: 2004-08-19
Anticipated expiration: 2023-01-28
Also published as: JP4613474B2

Abstract

<P>PROBLEM TO BE SOLVED: To stably obtain high-quality treated water by nitrifying and denitrifying ammonia-containing water by making effective use of ANAMMOX bacillus while reducing the treatment cost. <P>SOLUTION: A biological membrane double structure is formed in a nitrification tank 1, by which an inclusively ANAMMOX bacillus-immobilized gel, an ANAMMOX (independently nutritive denitrification) bacillus-self-granulated material or an ANAMMOX bacillus carrying carrier having ANAMMOX bacillus on the surface is held and the outer periphery of which is covered with an ammonia oxidizing bacterium. The nitrite nitrogen produced by the ammonia oxidizing bacterium existing on the outside of the biological membrane double structure and the ammonia nitrogen remaining in the ammonia-containing water are decomposed into nitrogen by the ANAMMOX bacillus existing on the inside of the biological membrane double structure in an anaerobic atmosphere. As a result, the oxygen amount and the chemical usage equivalent to the amount of the ammonia to be decomposed by the ANAMMOX bacillus can be reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、アンモニア含有水の処理方法に係り、特に、アンモニア含有水の硝化脱窒処理に当たり、アンモニア性窒素を電子供与体とし亜硝酸性窒素を電子受容体とする独立栄養性脱窒細菌を利用することにより、処理コストの低減を図る方法に関する。
【０００２】
【従来の技術】
排液中に含まれるアンモニア性窒素は河川、湖沼及び海洋などにおける富栄養化の原因物質の一つであり、排液処理工程で効率的に除去する必要がある。一般に、排水中のアンモニア性窒素は、アンモニア性窒素をアンモニア酸化細菌により亜硝酸性窒素に酸化し、更にこの亜硝酸性窒素を亜硝酸酸化細菌により硝酸性窒素に酸化する硝化工程と、これらの亜硝酸性窒素及び硝酸性窒素を従属栄養性細菌である脱窒菌により、有機物を電子（水素）供与体として利用して窒素ガスにまで分解する脱窒工程との２段階の生物反応を経て窒素ガスにまで分解される。
【０００３】
具体的には、図１（ａ）に示す如く、原水を硝化槽１に導入して曝気下、硝化処理し、硝化処理水を脱窒槽２に導入して脱窒処理する。脱窒処理水は沈殿池３で固液分離し、分離水を処理水として取り出す。分離汚泥は必要に応じて一部を余剰汚泥として系外へ排出し、残部を硝化槽１に返送する。なお、図１（ｂ）に示す如く、脱窒槽２を硝化槽１の前段に配置し、原水を脱窒槽２、硝化槽１の順で通水し、硝化槽１の流出水の一部を脱窒槽２に循環する方法もある。
【０００４】
しかし、このような従来の硝化脱窒法では、硝化工程においてアンモニア性窒素を亜硝酸性窒素を経て硝酸性窒素に酸化するために多量の酸素を必要とし、硝化槽１への酸素供給のための曝気電力量が高い。また、アルカリ性のアンモニア性窒素を酸性の亜硝酸性窒素や硝酸性窒素に変換することから、ｐＨ条件を維持して生物活性を保つために多量のアルカリを硝化槽１に添加する必要がある。
【０００５】
一方、脱窒槽２では、硝酸性窒素を窒素に転換するために、電子供与体としてメタノール等の有機物が多量に必要となる。また、脱窒槽２では、酸性の亜硝酸性窒素や硝酸性窒素が窒素として除去されるために、ｐＨ条件を維持して生物活性を保つための酸の添加も必要となる。
【０００６】
このように、従来の硝化脱窒法では、硝化のための曝気量、脱窒のための有機物添加量、及び生物活性維持のための薬品（アルカリ及び酸）添加量が多く、このために電力費や薬剤費等のランニングコストが高いという欠点があった。
【０００７】
このような硝化脱窒法に対して、近年、アンモニア性窒素を電子供与体とし、亜硝酸性窒素を電子受容体とする独立栄養性脱窒細菌を利用し、アンモニア性窒素と亜硝酸性窒素とを反応させて脱窒する方法が提案された。この方法であれば、有機物の添加は不要であるため、従属栄養性の脱窒菌を利用する方法と比べて、コストを低減することができる。
【０００８】
この独立栄養性脱窒細菌（以下「ＡＮＡＭＭＯＸ菌」と称す。）を利用する生物脱窒プロセス（ＡＮＡＭＭＯＸプロセス）は、Ｓｔｒｏｕｓ，Ｍ，ｅｔａｌ．，Ａｐｐｌ．Ｍｉｃｒｏｂｉｏｌ．Ｂｉｏｔｅｃｈｎｏｌ．，５０，ｐ．５８９−５９６（１９９８）に報告されており、後述のＡＮＡＭＭＯＸ反応式に示すような反応でアンモニア性窒素と亜硝酸性窒素が反応して窒素ガスに分解される。
【０００９】
しかして、特開２００１−２９３４９４号公報には、アンモニア酸化細菌とＡＮＡＭＭＯＸ菌とが共存する汚泥を利用して一工程で硝化脱窒を行う方法が提案されている。
【００１０】
【特許文献１】
特開２００１−２９３４９４号公報
【００１１】
【発明が解決しようとする課題】
特開２００１−２９３４９４号公報には、ＡＮＡＭＭＯＸ菌の表面をアンモニア酸化細菌が覆うように生物膜二重構造体を生成させた汚泥についての記載もなされているが、このような生物膜二重構造体をどのように生成させるかについての検討はなされておらず、また、特開２００１−２９３４９４号公報記載の方法では、このような生物膜二重構造体を形成した汚泥により、一工程で硝化と脱窒を行うものであるために、処理条件の設定が容易ではなく、処理水水質の安定性において、より一層の改善が望まれる。また、後述のＡＮＡＭＭＯＸ反応式からも明らかなように、ＡＮＡＭＭＯＸ反応では、アンモニア性窒素と亜硝酸性窒素との反応で硝酸性窒素が生成するため、硝酸性窒素が残留することとなる。
【００１２】
本発明は上記従来の問題点を解決し、アンモニア含有水の硝化脱窒処理に、ＡＮＡＭＭＯＸ菌を有効に利用して処理コストの大幅な低減を図った上で、高水質な処理水を安定に得る方法を提供することを目的とする。
【００１３】
【課題を解決するための手段】
請求項１のアンモニア含有水の処理方法は、アンモニア含有水を硝化槽に通水してアンモニアを分解する方法において、該硝化槽内に、アンモニア性窒素を電子供与体とし亜硝酸性窒素を電子受容体として脱窒反応を行う脱窒細菌の包括固定ゲル、該脱窒細菌の自己造粒物、又は、該脱窒細菌を表面に担持した菌担持担体を保持し、該硝化槽内にて、該包括固定ゲル、自己造粒物、又は菌担持担体の表面をアンモニア酸化細菌で覆った生物膜二重構造体を生成させることを特徴とする。
【００１４】
請求項２のアンモニア含有水の処理方法は、アンモニア含有水を硝化槽及び脱窒槽に通水してアンモニアを分解する方法において、該硝化槽内に、アンモニア性窒素を電子供与体とし亜硝酸性窒素を電子受容体として脱窒反応を行う脱窒細菌の包括固定ゲル、該脱窒細菌の自己造粒物、又は該脱窒細菌を表面に担持した菌担持担体を保持することを特徴とする。
【００１５】
アンモニア性窒素を電子供与体とし亜硝酸性窒素を電子受容体として脱窒反応を行うＡＮＡＭＭＯＸ菌の包括固定ゲル、又は自己造粒物、或いはこのＡＮＡＭＭＯＸ菌を表面に担持した菌担持担体（以下、これらを「一次生物膜体」と称す場合がある。）を好気性の硝化槽内に保持すると、一次生物膜体の外周囲にアンモニア酸化細菌が付着してこれを覆う生物膜が生成し、生物膜二重構造体が形成される。この生物膜二重構造体では、外側のアンモニア酸化細菌による亜硝酸化反応で生じた亜硝酸性窒素と、残存するアンモニア性窒素とを、生物膜の内側の嫌気性雰囲気中に存在するＡＮＡＭＭＯＸ菌により反応させて窒素に分解することができ、このＡＮＡＭＭＯＸ菌による分解量に相当する酸素量や薬品使用量が削減される。
【００１６】
以下に、本発明による曝気量、電力量及び薬剤使用量の低減効果を、硝化脱窒反応式に基いて説明する。
【００１７】
アンモニア酸化細菌、硝酸化細菌及び脱窒菌による従来の硝化脱窒法では、次のような反応が起こる。
［硝酸化反応（硝化槽内）］
ＮＨ_４ ^＋＋２Ｏ_２＋２ＮａＯＨ→ＮａＮＯ_３＋Ｎａ^＋＋３Ｈ_２Ｏ
［脱窒反応（脱窒槽内）］
ＮａＮＯ_３＋２．５Ｈ_２＋ＨＣｌ→０．５Ｎ_２＋ＮａＣｌ＋３Ｈ_２Ｏ
【００１８】
上記の反応は各槽で個別に行われるため、ＮａＯＨ、ＨＣｌがそれぞれ必要となり、ＮＨ_４ ^＋１モルの硝化脱窒のために酸素が２モル、苛性ソーダが２モル必要となる（なお、計算を簡単にするため、脱窒での塩酸使用量は苛性ソーダと当量とする）。
【００１９】
これに対して、本発明では、生物膜二重構造体の形成により、生物膜の内側の嫌気性雰囲気中に存在するＡＮＡＭＭＯＸ菌が、嫌気性条件下で、外側のアンモニア酸化細菌による下記亜硝酸化反応で生じた亜硝酸性窒素と、原水中のアンモニア性窒素とを下記ＡＮＡＭＭＯＸ反応で反応させて脱窒する。
［亜硝酸化反応］
ＮＨ_４ ^＋＋１．５Ｏ_２＋２ＮａＯＨ→ＮａＮＯ_２＋Ｎａ^＋＋３Ｈ_２Ｏ
［ＡＮＡＭＭＯＸ反応］

【００２０】
従って、硝化槽では全体として、次のような反応が起こる。
【００２１】

【００２２】
即ち、ＮＨ_４ ^＋１モルの脱窒のために必要な酸素は０．８５３モル、苛性ソーダは１．１４モルであり、従来法に比べて大幅に低減される（なお、計算を簡単にするため、脱窒での塩酸使用量は苛性ソーダと当量とする。）。
【００２３】
【発明の実施の形態】
以下に本発明のアンモニア含有水の処理方法の実施の形態を詳細に説明する。
【００２４】
まず、本発明において、硝化槽内に保持する一次生物膜体について説明する。本発明で用いる一次生物膜体は、次の▲１▼〜▲３▼である。なお、本発明においては、下記▲１▼〜▲３▼の一次生物膜体のうちの１種を硝化槽内に保持しても良く、２種以上を任意の割合で硝化槽内に保持しても良い。
【００２５】
▲１▼ ＡＮＡＭＭＯＸ菌の包括固定ゲル
▲２▼ ＡＮＡＭＭＯＸ菌の自己造粒物
▲３▼ ＡＮＡＭＭＯＸ菌を担体の表面に担持した菌担持担体
【００２６】
▲１▼ＡＮＡＭＭＯＸ菌の包括固定ゲルとしては、ポリビニルアルコール（ＰＶＡ）、ポリアクリルアミド、光硬化性樹脂等の合成高分子や、カラギーナン、アルギン酸ソーダ等の天然高分子を高分子ゲル材料として用い、これにＡＮＡＭＭＯＸ菌を固定化したものを用いることができる。高分子ゲル材料へのＡＮＡＭＭＯＸ菌の固定化は、ゲル化する前の高分子材料とＡＮＡＭＭＯＸ菌とを混合した後、得られた混合物を適当な方法でゲル化することにより行うことができ、このようにして得られたゲルを適当な形状に成形して包括固定ゲルとする。
【００２７】
例えば、高分子ゲル材料としてＰＶＡを用いる場合には、ＰＶＡ溶液とＡＮＡＭＭＯＸ菌とを混合したものを適当な容器に入れ、これを冷凍してゲル化し、その後共存水等の氷体を融解し、残留するゲルを細断して包括固定ゲルを作製する方法（ＰＶＡ−冷凍法）、或いはＰＶＡ溶液とＡＮＡＭＭＯＸ菌との混合物をホウ酸溶液中に滴下することによってゲル化して作製する方法（ＰＶＡ−ホウ酸法）等が知られている。
【００２８】
高分子ゲル材料にＡＮＡＭＭＯＸ菌を固定して得られた包括固定ゲルは、円柱状、板状、繊維状、中空糸状等の任意の形状に成形することができる。
【００２９】
▲２▼ＡＮＡＭＭＯＸ菌の自己造粒物としては、常法に従って、ＡＮＡＭＭＯＸ菌を自己造粒させることによって形成することができる。また、▲３▼ＡＮＡＭＭＯＸ菌を担体の表面に担持した菌担持体についても常法に従って調製することができ、担体としては、活性炭、ゼオライト、スポンジ等の多孔質物質、三次元網状物体、ひも状物、球状物、フィルム状物等を用いることができる。
【００３０】
なお、ＡＮＡＭＭＯＸ菌の自己造粒物の場合、ＡＮＡＭＭＯＸ菌だけでは自己造粒に期間を要するので、核となる物質を添加し、その核の周りにＡＮＡＭＭＯＸ菌の生物膜を形成させることが望ましい。この場合、核として、例えば微生物自己造粒物や上述の担体等を挙げることができる。
【００３１】
核として用いられる微生物自己造粒物としては、メタン菌グラニュール等の嫌気性微生物や従属栄養性脱窒菌等の自己造粒物を挙げることができる。メタン菌自己造粒物は、ＵＡＳＢ（ＵｐｆｌｏｗＡｎａｅｒｏｂｉｃＳｌｕｄｇｅＢｌａｎｋｅｔ；上向流嫌気性汚泥床）法もしくはＥＧＳＢ（ＥｘｐａｎｄｅｄＧｒａｎｕｌｅＳｌｕｄｇｅＢｅｄ；展開粒状汚泥床）法でメタン発酵が行われているメタン発酵槽で使用されているものを適用できる。また、従属栄養性脱窒自己造粒物は、ＵＳＢ方式の通常の脱窒槽で利用されるものを適用できる。これらの自己造粒物はそのままの状態で、又はその破砕物として用いることができる。ＡＮＡＭＭＯＸ菌はこのような微生物自己造粒物に付着しやすく、自己造粒物の形成に要する時間が短縮される。また、核として非生物的な材料を用いるよりも経済的である。
【００３２】
本発明で用いる一次生物膜体の形状には特に制限はなく、粒状（球状、立方体状、その他の異形形状）、ひも状、棒状等の長尺状、フィルム状等の平面形状等の多種多様の形状を採用することができ、その大きさについても任意であるが、取り扱い性、生物膜二重構造体の形成効率等の面から、次のような大きさであることが好ましい。
【００３３】
粒状の場合：直径又は一辺の長さが３〜２０ｍｍ
長尺状の場合：長さ３〜２０００ｍｍ程度、太さ０．１〜５ｍｍφ
平面状の場合：面積制限なし、厚み０．１〜５ｍｍ
【００３４】
本発明のアンモニア含有水の処理方法は、このような一次生物膜体を硝化槽に投入し、これを硝化槽から流出しないように保持する。従って、硝化槽に一次生物膜体を投入したのみでは流出のおそれがある場合には、硝化槽に、一次生物膜体が流出しないように、スクリーンを設けることが好ましい。または、一次生物膜体を硝化液と共に流出させ、沈殿槽に導入して固液分離し、分離した一次生物膜体を硝化槽に戻してもよい。
【００３５】
硝化槽への一次生物膜体の投入量は、原水中のアンモニア濃度や、処理水量等の硝化槽負荷等に応じて適宜決定されるが、通常の場合、ＭＬＳＳとして５００〜５０００ｍｇ／Ｌとなるように投入することが好ましい。
【００３６】
前述の如く、硝化槽に一次生物膜体を投入して保持することにより、一次生物膜体の表面にアンモニア酸化細菌の生物膜が形成され、ＡＮＡＭＭＯＸ菌の一次生物膜体をアンモニア酸化細菌で覆った生物膜二重構造体により、アンモニア性窒素の亜硝酸化と、生成した亜硝酸性窒素と残留するアンモニア性窒素とのＡＮＡＭＭＯＸ反応が行われる。このように、硝化槽内でアンモニア性窒素が分解されることにより、硝化に必要な曝気量とｐＨ調整のためのアルカリ添加量を大幅に低減することができる。
【００３７】
硝化処理水は、次いで脱窒槽に通水され、従来法と同様にして脱窒処理される。この脱窒処理に当たり、硝化槽では硝化により生成した亜硝酸性窒素の一部がＡＮＡＭＭＯＸ菌により分解されているため、従来法に比べて脱窒槽でのメタノール等の水素供与体添加量、ｐＨ調整のための酸添加量は大幅に低減される。
【００３８】
なお、本発明のアンモニア含有水の処理方法は、図１（ａ）に示す如く、硝化槽１及び脱窒槽２に順次通水して処理する方法であっても良く、図１（ｂ）に示す如く、脱窒槽２及び硝化槽１に順次通水し、硝化槽１の流出水の一部を脱窒槽２に循環する方法であっても良い。また、後述の実施例に示す如く、後段に更に再曝気槽を設けて原水中のＢＯＤ成分を分解除去するものであっても良い。
【００３９】
本発明で処理の対象となる被処理水はアンモニア性窒素を含む水であり、有機物、亜硝酸性窒素、硝酸性窒素、その他の不純物などを含んでいても良い。有機性窒素化合物を含む被処理水は、そのまま本発明に供しても良いが、嫌気性処理又は好気性処理などにより有機性窒素化合物をアンモニア性窒素に変換した後、本発明に供しても良い。本発明で処理の対象となる被処理水の例としては、し尿、下水、食品排水、肥料工場排水などが挙げられる。
【００４０】
【実施例】
以下に比較例及び実施例を挙げて、本発明をより具体的に説明する。
【００４１】
比較例１
図２に示す如く、硝化槽１、脱窒槽２、沈殿池３及び再曝気槽４で順次処理する硝化脱窒装置において、本発明を適用しない従来法では、硝化槽（容量３５０ｍ^３）１での曝気電力量及び苛性ソーダ添加量と、脱窒槽（容量２４０ｍ^３）２での３５％塩酸添加量及びメタノール添加量を表１に示す条件として、アンモニア性窒素を１００ｍｇ／Ｌ含む排水を１００ｍ^３／ｈで処理して、表１に示す水質の処理水を得ていた。
【００４２】
実施例１
比較例１において、一次生物膜体として、下記のものをＭＬＳＳとして１０００ｍｇ／Ｌとなるように硝化槽１に添加し、曝気量を約１／２に低減して同様に処理を行ったところ、得られた処理水の水質は表１に示す通り比較例１の場合とほぼ同等であり、苛性ソーダ、３５％塩酸及びメタノールの必要量も表１に示す通り、比較例１に比べて大幅に低減することができた。
【００４３】
［一次生物膜体］
嫌気性グラニュールを核としてＡＮＡＭＭＯＸ菌を自己造粒させたもの
形状：ほぼ球状（粒状）
粒径：２〜５ｍｍ
【００４４】
なお、硝化槽２は、この一次生物膜体が槽外へ流出しないように、目幅２ｍｍのウェッジワイヤスクリーンを流出口直前に設置した。
【００４５】
【表１】

【００４６】
表１より、本発明によれば、従来法に比べて曝気電力費を約半分に低減すると共に、苛性ソーダ使用量は６５％に、３５％塩酸使用量は７０％に、メタノール使用量は２５％に低減することができ、ランニングコストを大幅に低減することができることがわかる。
【００４７】
【発明の効果】
以上詳述した通り、本発明のアンモニア含有水の処理方法によれば、アンモニア含有水を低コストで処理して良好な水質の処理水を安定に得ることができる。
【図面の簡単な説明】
【図１】一般的な硝化脱窒法を示す系統図である。
【図２】実施例１及び比較例１で用いた硝化脱窒装置を示す系統図である。
【符号の説明】
１硝化槽
２脱窒槽
３沈殿池
４再曝気槽[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating ammonia-containing water, and in particular, in nitrifying and denitrifying treatment of ammonia-containing water, an autotrophic denitrifying bacterium using ammonium nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. The present invention relates to a method for reducing a processing cost by utilizing the method.
[0002]
[Prior art]
Ammoniacal nitrogen contained in the effluent is one of the causative substances of eutrophication in rivers, lakes and oceans, and needs to be efficiently removed in the effluent treatment process. In general, ammonia nitrogen in wastewater is a nitrification step in which ammonia nitrogen is oxidized to nitrite nitrogen by ammonia oxidizing bacteria, and this nitrite nitrogen is oxidized to nitrate nitrogen by nitrite oxidizing bacteria. Nitrogen is passed through a two-stage biological reaction with a denitrification step in which nitrite and nitrate nitrogen are decomposed into nitrogen gas by using a heterotrophic bacterium, a denitrifying bacterium, by utilizing organic substances as electron (hydrogen) donors. Decomposes to gas.
[0003]
Specifically, as shown in FIG. 1 (a), raw water is introduced into a nitrification tank 1, subjected to nitrification under aeration, and nitrification-treated water is introduced into a denitrification tank 2 for denitrification. The denitrification treatment water is solid-liquid separated in the sedimentation basin 3 and the separated water is taken out as treatment water. A part of the separated sludge is discharged out of the system as surplus sludge as necessary, and the rest is returned to the nitrification tank 1. As shown in FIG. 1 (b), the denitrification tank 2 is disposed in front of the nitrification tank 1, raw water flows through the denitrification tank 2 and the nitrification tank 1 in this order, and a part of the effluent of the nitrification tank 1 is discharged. There is also a method of circulating in the denitrification tank 2.
[0004]
However, in such a conventional nitrification denitrification method, a large amount of oxygen is required to oxidize ammonia nitrogen to nitrate nitrogen through nitrite nitrogen in the nitrification step, so that oxygen supply to the nitrification tank 1 is required. Aeration power is high. Further, since alkaline ammonium nitrogen is converted into acidic nitrite nitrogen or nitrate nitrogen, it is necessary to add a large amount of alkali to the nitrification tank 1 in order to maintain pH conditions and maintain biological activity.
[0005]
On the other hand, in the denitrification tank 2, a large amount of an organic substance such as methanol is required as an electron donor in order to convert nitrate nitrogen into nitrogen. Further, in the denitrification tank 2, since acidic nitrite nitrogen and nitrate nitrogen are removed as nitrogen, it is necessary to add an acid for maintaining pH conditions and maintaining biological activity.
[0006]
As described above, in the conventional nitrification and denitrification method, the amount of aeration for nitrification, the amount of addition of organic substances for denitrification, and the amount of addition of chemicals (alkali and acid) for maintaining biological activity are large. There is a drawback that running costs such as drug costs and drug costs are high.
[0007]
In recent years, in response to such nitrification and denitrification methods, autotrophic denitrifying bacteria using ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor have been used. And a method of denitrification by reacting the same was proposed. This method does not require the addition of an organic substance, so that the cost can be reduced as compared with the method using heterotrophic denitrifying bacteria.
[0008]
The biological denitrification process (ANAMMOX process) using this autotrophic denitrifying bacterium (hereinafter referred to as “ANAMMOX bacteria”) is described in Straus, M, et al. , Appl. Microbiol. Biotechnol. , 50, p. 589-596 (1998), and ammonia nitrogen and nitrite nitrogen are reacted and decomposed into nitrogen gas by a reaction as shown in the following ANAMMOX reaction formula.
[0009]
Japanese Patent Application Laid-Open No. 2001-293494 proposes a method of performing nitrification and denitrification in one step by using sludge in which ammonia-oxidizing bacteria and ANAMMOX bacteria coexist.
[0010]
[Patent Document 1]
JP 2001-293494 A
[Problems to be solved by the invention]
Japanese Patent Application Laid-Open No. 2001-293494 also describes a sludge in which a biofilm double structure is formed so that the surface of an ANAMMOX bacterium is covered with ammonia-oxidizing bacteria. No study has been made on how to produce the body, and in the method described in Japanese Patent Application Laid-Open No. 2001-293494, nitrification is performed in one step by using sludge having such a biofilm double structure. Therefore, setting of treatment conditions is not easy, and further improvement in stability of treated water quality is desired. Further, as is apparent from the below-described ANAMMOX reaction formula, in the ANAMMOX reaction, nitrate nitrogen is generated by the reaction between ammonia nitrogen and nitrite nitrogen, so that nitrate nitrogen remains.
[0012]
The present invention solves the above-mentioned conventional problems and effectively uses ANAMMOX bacteria for nitrification and denitrification treatment of ammonia-containing water, thereby significantly reducing the treatment cost and stably treating high-quality treated water. The purpose is to provide a way to obtain.
[0013]
[Means for Solving the Problems]
The method for treating ammonia-containing water according to claim 1 is a method for decomposing ammonia by passing ammonia-containing water through a nitrification tank. In the nitrification tank, ammonia nitrogen is used as an electron donor and nitrite nitrogen is used as an electron. An entrapping fixed gel of a denitrifying bacterium that performs a denitrification reaction as a receptor, a self-granulated product of the denitrifying bacterium, or a bacteria-carrying carrier that has the denitrifying bacterium on its surface is held in the nitrification tank. And forming a biofilm double structure in which the surface of the entrapping fixed gel, the self-granulated substance, or the bacteria-carrying carrier is covered with ammonia-oxidizing bacteria.
[0014]
The method for treating ammonia-containing water according to claim 2 is a method for decomposing ammonia by passing ammonia-containing water through a nitrification tank and a denitrification tank. In the nitrification tank, ammonia nitrate is used as an electron donor and nitrite is added. An entrapping fixed gel of a denitrifying bacterium that performs a denitrification reaction using nitrogen as an electron acceptor, a self-granulated product of the denitrifying bacterium, or a bacteria-carrying carrier having the denitrifying bacterium on its surface is held. .
[0015]
An entrapping gel or self-granulated material of ANAMMOX bacteria that performs a denitrification reaction using ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, or a bacteria-carrying carrier that carries the ANAMMOX bacteria on its surface (hereinafter, referred to as When these are referred to as “primary biofilm bodies” in an aerobic nitrification tank, ammonia-oxidizing bacteria adhere to the outer periphery of the primary biofilm bodies and form a biofilm covering the bacteria. A biofilm duplex is formed. In this biofilm double structure, the nitrite nitrogen generated by the nitrite reaction by the outer ammonia-oxidizing bacteria and the remaining ammonia nitrogen are combined with the ANAMMOX bacteria present in the anaerobic atmosphere inside the biofilm. To reduce the amount of oxygen and the amount of chemicals used corresponding to the amount of decomposition by the ANAMMOX bacteria.
[0016]
Hereinafter, the effects of the present invention for reducing the amount of aeration, the amount of electric power, and the amount of drug used will be described based on a nitrification denitrification reaction formula.
[0017]
In the conventional nitrification and denitrification method using ammonia-oxidizing bacteria, nitrifying bacteria, and denitrifying bacteria, the following reactions occur.
[Nitration reaction (in a nitrification tank)]
NH ₄ ⁺ + 2O ₂ + 2NaOH → NaNO ₃ + Na ⁺ + 3H ₂ O
[Denitrification reaction (in the denitrification tank)]
NaNO ₃ + 2.5H ₂ + HCl → 0.5N ₂ + NaCl + 3H ₂ O
[0018]
Since the above reaction is performed individually in each tank, NaOH and HCl are required, and 2 mol of oxygen and 2 mol of caustic soda are required for nitrification and denitrification of 1 mol of NH ₄ ⁺¹ For simplicity, the amount of hydrochloric acid used in denitrification is equivalent to caustic soda).
[0019]
On the other hand, in the present invention, the formation of the biofilm double structure causes the ANAMMOX bacteria present in the anaerobic atmosphere inside the biofilm to undergo the following nitrite by the ammonia-oxidizing bacteria under the anaerobic condition. The nitrite nitrogen generated in the chemical reaction and the ammonia nitrogen in the raw water are reacted by the following ANAMOX reaction to denitrify.
[Nitrite reaction]
NH ₄ ⁺ +1.5 O ₂ + 2NaOH → NaNO ₂ + Na ⁺ + 3H ₂ O
[ANAMMOX reaction]

[0020]
Therefore, the following reaction occurs in the nitrification tank as a whole.
[0021]

[0022]
That is, oxygen required for denitrification of NH ₄ ⁺¹ mol is 0.853 mol and caustic soda is 1.14 mol, which are greatly reduced as compared with the conventional method. The amount of hydrochloric acid used for denitrification is equivalent to caustic soda.)
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the method for treating ammonia-containing water of the present invention will be described in detail.
[0024]
First, in the present invention, a primary biofilm body held in a nitrification tank will be described. The primary biofilms used in the present invention are the following (1) to (3). In the present invention, one of the following primary biofilms (1) to (3) may be held in the nitrification tank, and two or more kinds may be held in the nitrification tank at an arbitrary ratio. May be.
[0025]
(1) An inclusive fixed gel of ANAMMOX bacteria (2) A self-granulated product of ANAMMOX bacteria (3) A bacteria-supported carrier in which ANAMMOX bacteria are supported on the surface of a carrier
{Circle around (1)} A synthetic gel such as polyvinyl alcohol (PVA), polyacrylamide, or a photo-curable resin, or a natural polymer such as carrageenan or sodium alginate is used as a polymer gel material for the inclusive fixation gel of the ANAMMOX bacteria. Can be used. The immobilization of the ANAMMOX bacteria on the polymer gel material can be performed by mixing the polymer material before gelation with the ANAMMOX bacteria and then gelling the resulting mixture by an appropriate method. The gel thus obtained is formed into an appropriate shape to obtain a comprehensive fixed gel.
[0027]
For example, when using PVA as a polymer gel material, a mixture of a PVA solution and an ANAMMOX bacterium is placed in an appropriate container, which is frozen and gelled, and then ice bodies such as coexisting water are melted. A method in which the remaining gel is shredded to prepare a comprehensive fixed gel (PVA-freezing method), or a method in which a mixture of a PVA solution and an ANAMMOX bacterium is dropped into a boric acid solution to form a gel (PVA- Boric acid method) and the like are known.
[0028]
The inclusive immobilized gel obtained by immobilizing the ANAMMOX bacteria on the polymer gel material can be formed into an arbitrary shape such as a columnar shape, a plate shape, a fiber shape, a hollow fiber shape, and the like.
[0029]
{Circle over (2)} The self-granulated material of the ANAMMOX bacteria can be formed by self-granulating the ANAMMOX bacteria according to a conventional method. In addition, (3) a bacterial carrier in which ANAMMOX bacteria are carried on the surface of a carrier can also be prepared according to a conventional method. Examples of the carrier include activated carbon, zeolites, sponges, and other porous materials, three-dimensional meshes, and strings. Objects, spheres, films and the like can be used.
[0030]
In the case of the self-granulated material of the ANAMMOX bacterium, the ANAMMOX bacterium alone requires a period of time for self-granulation, so it is preferable to add a substance serving as a nucleus and form a biofilm of the ANAMMOX bacterium around the nucleus. In this case, as the nucleus, for example, a microorganism self-granulated substance, the above-mentioned carrier, and the like can be given.
[0031]
Examples of the microorganism self-granulated material used as a core include anaerobic microorganisms such as methanogen granules and self-granulated materials such as heterotrophic denitrifying bacteria. The methane fermentation is carried out by methane fermentation in a UASB (Upflow Anaerobic Sludge Blanket) method or an EGSB (Expanded Granule Sludge Bed) method. The ones used can be applied. Further, as the heterotrophic denitrification self-granulating substance, a substance used in an ordinary USB type denitrification tank can be applied. These self-granulated products can be used as they are or as crushed products thereof. The ANAMMOX bacterium easily adheres to such a microorganism self-granulated substance, and the time required for forming the self-granulated substance is reduced. It is more economical than using non-living material as the core.
[0032]
There is no particular limitation on the shape of the primary biofilm used in the present invention, and a wide variety of shapes such as a granular shape (spherical shape, cubic shape, and other irregular shapes), a long shape such as a string shape, a rod shape, and a planar shape such as a film shape are provided. The shape can be adopted, and the size is also arbitrary. However, from the viewpoints of handleability, formation efficiency of the biofilm double structure, and the like, the following size is preferable.
[0033]
In the case of granular: 3 to 20 mm in diameter or length of one side
In the case of a long shape: about 3 to 2000 mm in length, 0.1 to 5 mm in thickness
In the case of a planar shape: no area limitation, thickness 0.1 to 5 mm
[0034]
According to the method for treating ammonia-containing water of the present invention, such a primary biofilm is charged into a nitrification tank and is held so as not to flow out of the nitrification tank. Therefore, when there is a risk of outflow simply by putting the primary biofilm into the nitrification tank, it is preferable to provide a screen in the nitrification tank so that the primary biofilm does not flow out. Alternatively, the primary biofilm may be discharged together with the nitrification solution, introduced into a precipitation tank, subjected to solid-liquid separation, and the separated primary biofilm may be returned to the nitrification tank.
[0035]
The amount of the primary biofilm added to the nitrification tank is appropriately determined according to the ammonia concentration in the raw water, the nitrification tank load such as the amount of treated water, and the like. In a normal case, the MLSS is 500 to 5000 mg / L. It is preferable to put in such a manner.
[0036]
As described above, by putting the primary biofilm into the nitrification tank and holding it, a biofilm of the ammonia-oxidizing bacteria is formed on the surface of the primary biofilm, and the primary biofilm of the ANAMMOX bacteria is covered with the ammonia-oxidizing bacteria. The nitrification of ammonia nitrogen and the ANAMMOX reaction between the generated nitrite nitrogen and the remaining ammonia nitrogen are performed by the biofilm double structure. As described above, by decomposing the ammoniacal nitrogen in the nitrification tank, the amount of aeration required for nitrification and the amount of alkali added for pH adjustment can be significantly reduced.
[0037]
The nitrified water is then passed through a denitrification tank and denitrified in the same manner as in the conventional method. During this denitrification treatment, part of the nitrite nitrogen generated by nitrification in the nitrification tank was decomposed by the ANAMMOX bacteria, so that the amount of added hydrogen donor such as methanol in the denitrification tank and the pH were adjusted as compared with the conventional method. The amount of acid added for is significantly reduced.
[0038]
As shown in FIG. 1 (a), the method for treating ammonia-containing water of the present invention may be a method in which water is passed through a nitrification tank 1 and a denitrification tank 2 sequentially. As shown in the figure, a method may be used in which water is sequentially passed through the denitrification tank 2 and the nitrification tank 1 and a part of the effluent of the nitrification tank 1 is circulated to the denitrification tank 2. Further, as shown in an example described later, a re-aeration tank may be further provided at a subsequent stage to decompose and remove BOD components in raw water.
[0039]
The target water to be treated in the present invention is water containing ammonia nitrogen, and may contain organic matter, nitrite nitrogen, nitrate nitrogen, other impurities, and the like. The water to be treated containing the organic nitrogen compound may be subjected to the present invention as it is, or may be subjected to the present invention after converting the organic nitrogen compound into ammonia nitrogen by anaerobic treatment or aerobic treatment or the like. . Examples of the water to be treated in the present invention include human waste, sewage, food wastewater, and fertilizer factory wastewater.
[0040]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Comparative Examples and Examples.
[0041]
Comparative Example 1
As shown in FIG. 2, in a nitrification denitrification apparatus which sequentially processes in a nitrification tank 1, a denitrification tank 2, a sedimentation tank 3, and a re-aeration tank 4, in a conventional method to which the present invention is not applied, a nitrification tank (capacity: 350 m ³ ) 1 is used. and aeration amount of power and sodium hydroxide addition amount of the denitrification tank (capacity 240 m ³⁾ 35% hydrochloric acid amount and methanol added amount of 2 as the conditions shown in Table 1, the waste water containing ammoniacal nitrogen 100mg / L 100m ³ / h to obtain treated water having the quality shown in Table 1.
[0042]
Example 1
In Comparative Example 1, as a primary biofilm, the following were added to the nitrification tank 1 so that the MLSS became 1000 mg / L, and the aeration amount was reduced to about 量, and the same treatment was performed. The quality of the obtained treated water is almost the same as that of Comparative Example 1 as shown in Table 1, and the required amounts of caustic soda, 35% hydrochloric acid and methanol are also greatly reduced as compared with Comparative Example 1 as shown in Table 1. We were able to.
[0043]
[Primary biofilm]
Self-granulated ANAMMOX bacteria with anaerobic granules as the core Shape: almost spherical (granular)
Particle size: 2-5mm
[0044]
The nitrification tank 2 was provided with a wedge wire screen having a mesh width of 2 mm immediately before the outlet so as to prevent the primary biofilm from flowing out of the tank.
[0045]
[Table 1]

[0046]
From Table 1, according to the present invention, the aeration power cost is reduced to about half compared with the conventional method, the amount of caustic soda used is reduced to 65%, the amount of 35% hydrochloric acid is reduced to 70%, and the amount of methanol is reduced to 25%. It can be seen that the running cost can be greatly reduced.
[0047]
【The invention's effect】
As described above in detail, according to the method for treating ammonia-containing water of the present invention, it is possible to treat ammonia-containing water at low cost and to obtain treated water of good quality in a stable manner.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a general nitrification and denitrification method.
FIG. 2 is a system diagram showing a nitrification denitrification apparatus used in Example 1 and Comparative Example 1.
[Explanation of symbols]
1 Nitrification tank 2 Denitrification tank 3 Sedimentation tank 4 Re-aeration tank

Claims

In a method of decomposing ammonia by passing ammonia-containing water through a nitrification tank,
In the nitrification tank, an entrapping fixed gel of a denitrifying bacterium that performs a denitrification reaction using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, a self-granulated product of the denitrification bacterium, or the denitrification bacterium Holding a bacteria-carrying carrier carrying the nitrifying bacteria on its surface,
A method for treating ammonia-containing water, comprising forming a biofilm double structure in which the surface of the entrapping fixed gel, self-granulated material, or bacteria-carrying carrier is covered with ammonia-oxidizing bacteria in the nitrification tank. .

In a method of decomposing ammonia by passing ammonia-containing water through a nitrification tank and a denitrification tank,
In the nitrification tank, an entrapping fixed gel of a denitrifying bacterium performing a denitrification reaction using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, a self-granulated product of the denitrification bacterium, or the denitrification A method for treating ammonia-containing water, comprising holding a bacteria-carrying carrier having bacteria on the surface.