JP4613474B2

JP4613474B2 - Method for treating ammonia-containing water

Info

Publication number: JP4613474B2
Application number: JP2003019112A
Authority: JP
Inventors: 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: 2011-01-19
Anticipated expiration: 2023-01-28
Also published as: JP2004230225A

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,et al.,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、メタン菌グラニュールを核として、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を自己造粒させた一次生物膜体を保持し、該硝化槽内にて、該一次生物膜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、メタン菌グラニュールを核として、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を自己造粒させた一次生物膜体を保持し、該硝化槽内にて、該一次生物膜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。
【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菌を、メタン菌グラニュールを核として自己造粒させた一次生物膜体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）］
ＮＨ₄ ⁺＋2Ｏ₂＋2ＮａＯＨ→ＮａＮＯ₃＋Ｎａ⁺＋3Ｈ₂Ｏ
［脱窒反応（脱窒槽内）］
ＮａＮＯ₃＋2.5Ｈ₂＋ＨＣｌ→0.5Ｎ₂＋ＮａＣｌ＋3Ｈ₂Ｏ
【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］
ＮＨ₄ ⁺＋1.5Ｏ₂＋2ＮａＯＨ→ＮａＮＯ₂＋Ｎａ⁺＋3Ｈ₂Ｏ
［ＡＮＡＭＭＯＸ反応］
ＮＨ₄ ⁺＋1.32ＮＯ₂ ^-＋0.066ＨＣＯ₃ ^-＋0.13Ｈ⁺
→1.02Ｎ₂＋0.26ＮＯ₃ ^-＋0.066ＣＨ₂Ｏ_0.5Ｎ_0.15（菌体）＋2.03Ｈ₂Ｏ
【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】
ＮＨ₄ ⁺＋0.853Ｏ₂＋1.14ＮａＯＨ＋0.028ＨＣＯ₃ ^-＋0.056Ｈ⁺
→0.440Ｎ₂＋0.112ＮＯ₃ ^-＋0.028ＣＨ₂Ｏ_0.5Ｎ_0.15（菌体）＋1.14Ｎａ^＋＋2.58Ｈ_２Ｏ
【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、ＡＮＡＭＭＯＸ菌の自己造粒物である。
【００２５】
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。
【００２６】
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。この場合、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の嫌気性微生物の自己造粒物を用いる。メタン菌自己造粒物は、ＵＡＳＢ（Upflow Anaerobic Sludge Blanket；上向流嫌気性汚泥床）法もしくはＥＧＳＢ（Expanded Granule Sludge Bed；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。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。
【００２７】
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。
【００２８】
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
【００２９】
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。
【００３０】
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。
【００３１】
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。
【００３２】
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。
【００３３】
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。
【００３４】
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。
【００３５】
【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。
【００３６】
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。
【００３７】
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。
【００３８】
［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
【００３９】
なお、硝化槽１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。
【００４０】
【表１】

【００４１】
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。
【００４２】
【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]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating ammonia-containing water, and in particular, in nitrifying denitrification treatment of ammonia-containing water, an autotrophic denitrifying bacterium having ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor is provided. The present invention relates to a method for reducing the processing cost by using it.
[0002]
[Prior art]
Ammonia nitrogen contained in the effluent is one of the causative substances of eutrophication in rivers, lakes and oceans, and it is necessary to remove it efficiently in the effluent treatment process. In general, ammonia nitrogen in wastewater is oxidized by ammonia oxidizing bacteria to nitrite nitrogen, and nitrifying nitrogen is oxidized to nitrate nitrogen by nitrite oxidizing bacteria. Nitrous nitrogen and nitrate nitrogen are denitrified bacteria, which are heterotrophic bacteria, and then undergo a two-stage biological reaction with a denitrification process in which organic matter is decomposed into nitrogen gas using an electron (hydrogen) donor. It is broken down into gas.
[0003]
Specifically, as shown in FIG. 1 (a), raw water is introduced into a nitrification tank 1 and subjected to nitrification under aeration, and nitrification water is introduced into a denitrification tank 2 for denitrification treatment. The denitrified water is solid-liquid separated in the sedimentation basin 3 and the separated water is taken out as treated water. A part of the separated sludge is discharged out of the system as surplus sludge as necessary, and the remainder is returned to the nitrification tank 1. As shown in FIG. 1 (b), the denitrification tank 2 is arranged in the front stage of the nitrification tank 1, raw water is passed through the denitrification tank 2 and the nitrification tank 1 in this order, and a part of the effluent from the nitrification tank 1 is passed through. There is also a method of circulating to 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 via nitrite nitrogen in the nitrification step, and for supplying oxygen to the nitrification tank 1 Aeration power is high. Moreover, since alkaline ammonia 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, in order to convert nitrate nitrogen into nitrogen, a large amount of organic matter such as methanol is required as an electron donor. Further, in the denitrification tank 2, since acidic nitrite nitrogen and nitrate nitrogen are removed as nitrogen, it is also necessary to add an acid to maintain the pH condition and maintain biological activity.
[0006]
As described above, in the conventional nitrification / denitrification method, the amount of aeration for nitrification, the amount of organic matter added for denitrification, and the amount of chemicals (alkali and acid) for maintaining biological activity are large. In addition, there is a drawback that running costs such as drug costs are high.
[0007]
In contrast to such a nitrification denitrification method, in recent years, by using an autotrophic denitrification bacterium having ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, ammonia nitrogen and nitrite nitrogen A method of denitrifying by reacting was proposed. If this method is used, it is not necessary to add an organic substance, so that the cost can be reduced as compared with a method using heterotrophic denitrifying bacteria.
[0008]
A biological denitrification process (ANAAMOX process) using this autotrophic denitrifying bacterium (hereinafter referred to as “ANAAMOX bacteria”) is Strous, M, et al., Appl. Microbiol. Biotechnol., 50, p.589. -596 (1998), ammonia nitrogen and nitrite nitrogen react and decompose into nitrogen gas in a reaction as shown in the ANAMOX reaction formula described below.
[0009]
JP 2001-293494 A proposes a method of performing nitrification and denitrification in one step using sludge in which ammonia-oxidizing bacteria and ANAMOX bacteria coexist.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-293494
[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 ammonia oxidizing bacteria cover the surface of ANAMMOX bacteria. The method of generating the body has not been studied, and in the method described in Japanese Patent Application Laid-Open No. 2001-293494, nitrification is performed in one step by the sludge that has formed such a biofilm dual structure. Therefore, it is not easy to set treatment conditions, and further improvement in the stability of treated water quality is desired. Further, as is clear from the ANAMOX reaction formula described later, nitrate nitrogen remains in the ANAMOX reaction because nitrate nitrogen is generated by the reaction of ammonia nitrogen and nitrite nitrogen.
[0012]
The present invention solves the above-described conventional problems, effectively uses ANAMMOX bacteria for nitrification denitrification treatment of ammonia-containing water, and achieves a significant reduction in treatment costs, and stably stabilizes high-quality treated water. It aims to provide a method of obtaining.
[0013]
[Means for Solving the Problems]
The method for treating ammonia-containing water according to claim 1 is a method in which ammonia-containing water is passed through a nitrification tank to decompose ammonia , and ammonia nitrogen is electron-donated into the nitrification tank using methane bacteria granules as a nucleus. A primary biofilm body that self-granulates denitrifying bacteria that performs denitrification using nitrite nitrogen as an electron acceptor is retained, and the surface of the primary biofilm body is oxidized by ammonia in the nitrification tank. It is characterized by producing a biofilm double structure covered with bacteria.
[0014]
Processing method of ammonia-containing water according to claim 2 is a method of decomposing ammonia and ammonia-containing water is passed through the nitrification tank and the denitrification tank, a the nitric reduction vessel, the methane bacteria granules as nuclei, ammonium nitrogen A primary biofilm body obtained by self-granulation of a denitrifying bacterium that performs a denitrification reaction using nitrite nitrogen as an electron acceptor and the surface of the primary biofilm body in the nitrification tank the characterized Rukoto to produce a biofilm dual structure covered with ammonium oxidizing bacteria.
[0015]
In the aerobic nitrification tank, the primary biofilm that self-granulates ANAMMOX bacteria, which denitrify using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, as a nucleus. When held, ammonia-oxidizing bacteria adhere to the outer periphery of the primary biofilm body to generate a biofilm that covers the biofilm, thereby forming a biofilm double structure. In this biofilm double structure, the NAMNOX bacteria existing in the anaerobic atmosphere inside the biofilm are formed by nitrite nitrogen generated by the nitritation reaction by the ammonia-oxidizing bacteria on the outside and the remaining ammonia nitrogen. Can be decomposed into nitrogen, and the amount of oxygen and chemical usage corresponding to the amount of decomposition by the ANAMOX bacteria can be reduced.
[0016]
Below, the reduction effect of the amount of aeration by this invention, the amount of electric power, and chemical | medical agent usage is demonstrated based on the nitrification denitrification reaction type | formula.
[0017]
In the conventional nitrification / denitrification method using ammonia-oxidizing bacteria, nitrifying bacteria, and denitrifying bacteria, the following reaction occurs.
[Nitrification reaction (in 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 carried out separately in each tank, NaOH and HCl are required, respectively, 2 mol of oxygen and 2 mol of caustic soda are required for nitrification and denitrification of NH ₄ ⁺ 1 mol (note that the calculation 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 dual structure allows ANAMMOX bacteria present in the anaerobic atmosphere inside the biofilm to be converted into the following nitrous acid by the outside ammonia oxidizing bacteria under anaerobic conditions. The nitrite nitrogen generated by the nitrification reaction and ammoniacal nitrogen in the raw water are reacted by the following ANAMOX reaction to denitrify.
[Nitrite reaction]
NH ₄ ⁺ + 1.5O ₂ + 2NaOH → NaNO ₂ + Na ⁺ + 3H ₂ O
[ANAMMOX reaction]
_{^{_{^{NH 4 + + 1.32NO 2 - +}}}} 0.066HCO 3 - + 0.13H +
_{_{^{→ 1.02N 2 + 0.26NO 3 - +}}} 0.066CH 2 O 0.5 N 0.15 ( bacteria) + 2.03H ₂ O
[0020]
Therefore, the following reaction occurs as a whole in the nitrification tank.
[0021]
NH ₄ ⁺ +0.853 O ₂ +1.14 NaOH +0.028 HCO ₃ ⁻ + 0.056H ⁺
→ 0.440N ₂ + 0.112NO ₃ ⁻ + 0.028CH ₂ O _0.5 N _0.15 (bacteria) + 1.14Na ⁺ + 2.58H ₂ O
[0022]
That is, the oxygen required for denitrification of NH ₄ ⁺ 1 mol is 0.853 mol and caustic soda is 1.14 mol, which is greatly reduced compared to the conventional method (in order to simplify the calculation). The amount of hydrochloric acid used for denitrification is equivalent to caustic soda.)
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the method for treating ammonia-containing water of the present invention will be described in detail.
[0024]
First, the primary biofilm body retained in the nitrification tank in the present invention will be described. The primary biofilm used in the present invention is a self-granulated product of ANAMOX bacteria .
[0025]
A NAMMOX self-granulated product can be formed by self-granulating ANAMMOX bacteria according to a conventional method .
[0026]
In the case of self-granulation of ANAMMOX bacteria, only ANAMMOX bacteria since it takes a period autogranulated, adding a substance serving as a nucleus, Ru to form a biofilm ANAMMOX bacteria around the nucleus. In this case, examples of the microorganisms self granulate used as a nucleus, Ru using a self-granulation of anaerobic microorganisms methane bacteria granule. The methane bacteria self-granulated product is a methane fermentation tank where methane fermentation is performed by the UASB (Upflow Anaerobic Sludge Blanket) method or the EGSB (Expanded Granule Sludge Bed) method. You can apply what is being used . Self granules of these is as it is, or can be used as the crushed material. ANAMMOX bacteria are likely to adhere to such microbial self-granulated products, and the time required for the formation of the self-granulated products is shortened. It is also more economical than using abiotic materials as the core.
[0027]
There are no particular restrictions on the shape of the primary biofilm used in the present invention, and there are a wide variety of shapes such as granular (spherical, cubic, other irregular shapes), long shapes such as strings, rods, etc., and planar shapes such as films. The shape can be adopted, and the size thereof is also arbitrary. However, from the viewpoints of handleability, the formation efficiency of the biofilm double structure, and the like, the following sizes are preferable.
[0028]
When granular: diameter or length of one side is 3-20mm
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 plane: no area limitation, thickness 0.1 to 5 mm
[0029]
In the method for treating ammonia-containing water according to the present invention, such a primary biofilm is put into a nitrification tank and is held so as not to flow out of the nitrification tank. Therefore, when there is a possibility that the primary biofilm body flows out only by introducing the primary biofilm body into the nitrification tank, it is preferable to provide a screen so that the primary biofilm body does not flow out into the nitrification tank. Alternatively, the primary biofilm body may be flowed out together with the nitrification liquid, introduced into the precipitation tank and solid-liquid separated, and the separated primary biofilm body may be returned to the nitrification tank.
[0030]
The amount of primary biofilm that is introduced into the nitrification tank is appropriately determined according to the concentration of ammonia in the raw water, the nitrification tank load such as the amount of treated water, etc., but is usually 500 to 5000 mg / L as MLSS. It is preferable to input in such a manner.
[0031]
As described above, by introducing and holding the primary biofilm in the nitrification tank, a biofilm of ammonia oxidizing bacteria is formed on the surface of the primary biofilm, and the primary biofilm of ANAMMOX is covered with the ammonia oxidizing bacteria. By the biofilm double structure, nitritation of ammonia nitrogen and the ANAMMOX reaction between the produced nitrite nitrogen and the remaining ammonia nitrogen are performed. Thus, by decomposing ammoniacal nitrogen in the nitrification tank, the amount of aeration necessary for nitrification and the amount of alkali added for pH adjustment can be greatly reduced.
[0032]
The nitrification water is then passed through a denitrification tank and denitrified as in the conventional method. In this denitrification treatment, a part of the nitrite nitrogen generated by nitrification in the nitrification tank is decomposed by ANAMMOX bacteria, so the amount of hydrogen donors such as methanol in the denitrification tank and pH adjustment in the denitrification tank The acid addition amount for is greatly reduced.
[0033]
The method for treating ammonia-containing water of the present invention may be a method of passing water sequentially through the nitrification tank 1 and the denitrification tank 2 as shown in FIG. 1 (a), and FIG. As shown, 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 from the nitrification tank 1 is circulated to the denitrification tank 2. Moreover, as shown in the below-mentioned Example, a re-aeration tank may be provided in the subsequent stage to decompose and remove the BOD component in the raw water.
[0034]
The 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. Water to be treated containing an organic nitrogen compound may be used for the present invention as it is, but may be used for the present invention after converting the organic nitrogen compound to ammonia nitrogen by anaerobic treatment or aerobic treatment. . Examples of water to be treated in the present invention include human waste, sewage, food wastewater, fertilizer factory wastewater, and the like.
[0035]
【Example】
Hereinafter, the present invention will be described more specifically with reference to comparative examples and examples.
[0036]
Comparative Example 1
As shown in FIG. 2, in a nitrification / denitrification apparatus that 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. Assuming that the amount of aeration power and the amount of caustic soda added, the amount of 35% hydrochloric acid added in the denitrification tank (capacity 240 m ³ ) 2 and the amount of methanol added are as shown in Table 1, wastewater containing 100 mg / L of ammoniacal nitrogen is 100 m ³ / Treated with h, treated water having the water quality shown in Table 1 was obtained.
[0037]
Example 1
In Comparative Example 1, as a primary biofilm body, the following was added to the nitrification tank 1 so that the MLSS was 1000 mg / L, and the aeration amount was reduced to about ½, and the same treatment was performed. As shown in Table 1, the quality of the treated water obtained was almost the same as that in Comparative Example 1, and the required amounts of caustic soda, 35% hydrochloric acid and methanol were significantly reduced as compared with Comparative Example 1 as shown in Table 1. We were able to.
[0038]
[Primary biofilm]
Self-granulated ANAMOX bacteria with anaerobic granules as the core Shape: Almost spherical (granular)
Particle size: 2-5mm
[0039]
In the nitrification tank 1 , a wedge wire screen having a mesh width of 2 mm was installed immediately before the outflow port so that the primary biofilm did not flow out of the tank.
[0040]
[Table 1]

[0041]
From Table 1, according to the present invention, the aeration power cost is reduced by about half compared with the conventional method, the caustic soda usage is 65%, the 35% hydrochloric acid usage is 70%, and the methanol usage is 25%. It can be seen that the running cost can be significantly reduced.
[0042]
【The invention's effect】
As described in detail above, according to the method for treating ammonia-containing water of the present invention, it is possible to treat the ammonia-containing water at low cost and stably obtain treated water with good water quality.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a general nitrification denitrification method.
2 is a system diagram showing a nitrification denitrification apparatus used in Example 1 and Comparative Example 1. FIG.
[Explanation of symbols]
1 Nitrification tank 2 Denitrification tank 3 Sedimentation tank 4 Re-aeration tank

Claims

In a method for decomposing ammonia by passing ammonia-containing water through a nitrification tank,
In the nitrification tank, a primary biofilm body is formed by self-granulating denitrifying bacteria that perform denitrifying reaction using methane bacteria granules as a nucleus, ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. Hold and
A method for treating ammonia-containing water, comprising producing a biofilm dual structure in which the surface of the primary biofilm is covered with ammonia-oxidizing bacteria in the nitrification tank.

In a method for decomposing ammonia by passing ammonia-containing water through a nitrification tank and a denitrification tank,
In the nitrification tank, a primary biofilm body is formed by self-granulating denitrifying bacteria that perform denitrifying reaction using methane bacteria granules as a nucleus, ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. Hold and
At the nitric of vessel, the processing method of the ammonia-containing water, wherein Rukoto to produce a biofilm double structure of the surface of the primary biofilm bodies covered with ammonia-oxidizing bacteria.