JP4867097B2

JP4867097B2 - Biological denitrification method and biological denitrification apparatus

Info

Publication number: JP4867097B2
Application number: JP2001226186A
Authority: JP
Inventors: 英斉安井; 麗今城
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2001-07-26
Filing date: 2001-07-26
Publication date: 2012-02-01
Anticipated expiration: 2021-07-26
Also published as: JP2003033786A

Description

【０００１】
【発明の属する技術分野】
本発明は、アンモニア性窒素を含有する原水を、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脱窒微生物の作用で亜硝酸性窒素の存在下に生物脱窒する方法及び装置に係り、特に、この生物脱窒において、反応系内の酸素による反応阻害を防止して安定かつ効率的な生物脱窒を行うための生物脱窒方法及び生物脱窒装置に関する。
【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】
しかし、このような従来の硝化脱窒法では、脱窒工程において電子供与体としてメタノールなどの有機物を多量に必要とし、また硝化工程では多量の酸素が必要であるため、ランニングコストが高いという欠点がある。
【０００４】
これに対して、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微生物（自己栄養細菌）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。また、独立栄養性の微生物は収率が低く、汚泥の発生量が従属栄養性微生物と比較すると著しく少ないので、余剰汚泥の発生量を抑えることができる。更に、従来の硝化脱窒法で観察されるＮ_２Ｏの発生がなく、環境に対する負荷を低減できるといった特長もある。
【０００５】
この独立栄養性脱窒微生物（以下「ＡＮＡＭＭＯＸ微生物」と称す場合がある。）を利用する生物脱窒プロセスは、Strous, M et al. (1998) Appl. Microbiol. Biotechnol. Vol.50,
p.589-596に報告されており、以下の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と考えられている。
【０００６】
【化１】

【０００７】
この生物脱窒反応は不安定であり、極めて低濃度の酸素を含むガス（酸素分圧０．５±０．２％）の曝気で失活することがStrous, M et al. (1997) Wat.Res. Vol.31, No.8, p.1955で報告されている。この理由は、明らかにされていないが、これは極めて低濃度の分子状酸素でもＡＮＡＭＭＯＸ微生物による酵素反応を阻害するためと推定される。Strous, M et al. (1997) Wat.Res. Vol.31, No.8, p.1955で報告されている事例を考慮すると、反応液中の溶存酸素（ＤＯ）濃度が０．２ｍｇ／Ｌという極めて低濃度でも阻害が起きることが予想される。
【０００８】
従って、このような酸素による阻害を防止するためには、脱窒槽に供給する前に、予め原水中のＤＯを除去しておくことが対処の一つとして考えられる。この場合、原水中のＤＯを０．２ｍｇ／Ｌ以下まで除去する方法としては、
(1) 還元剤の添加
(2) 窒素ガスのような酸素を含まないガスによるストリッピング
などが考えられるが、(1)の方法は高価な薬品を必要とし、また(2)の方法はガスストリッピングのための動力が必要となるという欠点がある。しかも、原水のＤＯ濃度は、環境条件その他により変化する可能性があり、従って、プロセスを安定に運転させるためには、大過剰の還元剤の添加やストリッピングが必要になるという不具合もある。
【０００９】
【発明が解決しようとする課題】
本発明は上記従来の実情に鑑みてなされたものであって、ＡＮＡＭＭＯＸ微生物による生物脱窒処理において、ＤＯによる阻害を安価に、確実に防止して、安定かつ効率的な生物脱窒を行うための生物脱窒方法及び生物脱窒装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明の生物脱窒方法は、アンモニア性窒素を含有する原水を脱窒槽に供給し、該脱窒槽内の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脱窒微生物の作用により亜硝酸性窒素の存在下に生物脱窒する方法において、該原水は、当該生物脱窒において、そのままでは酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ未満となる原水であり、該脱窒槽内の前記脱窒微生物を含む混合液の酸素消費速度が０．１〜１０ｍｇ／Ｌ／ｈｒになるように、該脱窒槽にＢＯＤ源を添加する生物脱窒方法であって、該ＢＯＤ源が有機物含有水を生物処理して排出された生物処理水であることを特徴とする。
【００１１】
本発明の生物脱窒装置は、アンモニア性窒素を含有する原水の流入口と、処理液の流出口とを有し、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脱窒微生物の作用により亜硝酸性窒素の存在下に生物脱窒する脱窒槽と、該脱窒槽内の前記脱窒微生物を含む混合液の酸素消費速度を測定する酸素消費速度測定手段と、該脱窒槽へＢＯＤ源を供給するＢＯＤ源供給手段と、前記酸素消費速度測定手段の測定値に基づいて、該脱窒槽内の前記脱窒微生物を含む混合液の酸素消費速度が０．１〜１０ｍｇ／Ｌ／ｈｒになるように、前記ＢＯＤ源供給手段が供給するＢＯＤ源の供給量を制御する制御手段とを備える生物脱窒装置であって、該原水は、当該生物脱窒において、そのままでは酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ未満となる原水であり、該ＢＯＤ源が有機物含有水を生物処理して排出された生物処理水であることを特徴とする。
【００１２】
ＡＮＡＭＭＯＸ微生物による生物脱窒処理において、反応系内にＤＯを消費する微生物を共存させることにより、この微生物にＤＯを消費させてＤＯによる阻害を防止することができる。本発明では、これらの微生物によってＤＯを消費させるために、脱窒槽にＢＯＤ源を供給し、脱窒槽内のＡＮＡＭＭＯＸ微生物を含む混合液中の酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ以上となるように調整する。これにより、脱窒槽内のＤＯを低減してＤＯによる反応阻害を確実に防止することができる。
【００１３】
このＢＯＤ源としては、有機性廃棄物のような有機物含有水を生物処理して得られた生物処理水が好適である。通常の生物処理水はＢＯＤ濃度が低いため、これを更に別の生物処理プロセスに供給しても、生成する微生物はわずかで混合液の酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ以上になりにくいが、ＡＮＡＭＭＯＸ微生物による生物脱窒プロセスでは、容易に０．１ｍｇ／Ｌ／ｈｒ以上の酸素消費速度を達成できるため、安価なＢＯＤ源として有用である。
【００１４】
【発明の実施の形態】
以下に図面を参照して本発明の生物脱窒方法及び生物脱窒装置の実施の形態を詳細に説明する。
【００１５】
図１は、本発明の生物脱窒装置の実施の形態を示す系統図である。
【００１６】
１は、ＡＮＡＭＭＯＸ微生物を保持する脱窒槽であり、原水が導入されて脱窒処理された後、処理水が排出される。この脱窒槽１には生物処理プロセス２の生物処理水がポンプＰによりＢＯＤ源として添加される。
【００１７】
脱窒槽１には、槽内液を採取して酸素消費速度を測定した後、脱窒槽１に戻すＯＵＲ（ＯｘｙｇｅｎＵｐｔａｋｅＲａｔｅ）測定器３が設けられており、このＯＵＲ測定器３の測定結果が測定制御器４に入力され、この結果に基づいて生物処理水の供給ポンプＰの作動が制御される。
【００１８】
ＯＵＲ測定器３としては、図２に示す如く、ＤＯを与えた液を容器５内に入れて密栓し、スタラー６で攪拌しながら、ＤＯ電極７により経時的にＤＯ濃度を測定するものを用いることができ、測定結果を測定制御器４に入力し、ＤＯ濃度の減少曲線から酸素消費速度を計算することができる。このようなＯＵＲ測定器３は脱窒槽１にオンラインで設置しても良く、また、手動で混合液を採取して分析するようにすることもできる。
【００１９】
図１の装置においては、このようにして脱窒槽１の槽内液の酸素消費速度を測定し、この結果に基づいて生物処理水の添加量を制御することにより、脱窒槽１の槽内液の酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ以上となるように制御する。即ち、槽内液の酸素消費速度が制御範囲よりも低い場合には、生物処理水の添加量を増やし、ＤＯを消費する微生物を槽内液中に増殖させて、酸素消費速度を高める。逆に酸素消費速度が制御範囲よりも高い場合には生物処理水の添加量を低減する。
【００２０】
この酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ未満では、微生物によるＤＯ消費で槽内液のＤＯを十分に低下させることができず、ＤＯによる阻害で経時により脱窒効率が低下する。酸素消費速度は原水等から脱窒槽１内に持ち込まれるＤＯに対して過度に高くてもそれによる効果の向上は望めず、逆に、脱窒槽内にＡＮＡＭＭＯＸ微生物以外の微生物が増殖し、ＡＮＡＭＭＯＸ微生物の生育環境が悪化する恐れがある。従って、酸素消費速度は０．１〜１０ｍｇ／Ｌ／ｈｒ、好ましくは０．１〜２ｍｇ／Ｌ／ｈｒとなるように制御する。
【００２１】
ＢＯＤ源としては、安価簡便であることから、生物処理水を用いるのが好ましい。生物処理水としては特に制限はなく、生ゴミ等の有機性廃棄物の嫌気性消化処理液、屎尿の好気的生物処理水、下水処理水、産業排水処理水等を用いることができる。生物処理水は、脱窒槽１に直接添加しても良く、予め原水に混合して脱窒槽に導入してもよい。
【００２２】
脱窒槽１の槽内液の酸素消費速度の測定は、連続的に行っても間欠的に行っても良く、処理の安定性の程度に応じて酸素消費速度が０．１ｍｇ／Ｌ／ｈｒ以上となるように行えば良い。また、生物処理水等のＢＯＤ源の脱窒槽１への添加は連続的に行っても良く、また間欠的に行っても良い。
【００２３】
なお、脱窒槽１の型式としては特に制限はなく、ＡＮＡＭＭＯＸ微生物のグラニュール汚泥を保持するＵＳＢ（Upflow Sludge Bed；上向流汚泥床）式や、汚泥懸濁式、固定床式、流動床式、担体添加方式などのいずれの型式のものであってよい。
【００２４】
【実施例】
以下に実施例及び比較例を挙げて本発明をより具体的に説明する。
【００２５】
実施例１
窒素ガスと酸素ガスを流量計で調節して酸素分圧が０．５±０．２％となる混合ガスを作成した。酸素分圧は、コンピュータ制御付きのニードルバルブを備えた流量計で調整した。ここではコンピュータから信号を送り、バルブ開度をランダムに変化させて、酸素分圧を０．３〜０．７％の間に調整した。
【００２６】
このガスを用いて水道水を曝気し、この液に１０００ｍｇ／Ｌのアンモニアと１２００ｍｇ／Ｌの亜硝酸を加え、微量のＤＯを含む合成排水を作成した。この合成排水を使って、アンモニアを嫌気的に生物脱窒させる実験を行った。
【００２７】
脱窒槽の容積は１０Ｌであり、原水を２０Ｌ／ｄａｙ、ＢＯＤ源としての生ゴミの嫌気消化処理液を１〜１００ｍＬ／ｄａｙの速度で通液した。図２に示すＯＵＲ測定器を用いて、定期的に脱窒槽の酸素消費速度を測定した。この測定は、最初は３日ごと、１ヶ月後は２週間ごとに行い、この酸素消費速度が表１に示す値になるよう、生ゴミの嫌気消化処理液の供給速度を各測定の都度設定しなおした。
【００２８】
このときの生ゴミの嫌気消化処理液の供給速度と酸素消費速度との関係を表１に示す。また、各酸素消費速度の場合のアンモニアの除去活性の経時変化を図３に示す。なお、アンモニア除去活性は、酸素消費速度０．１ｍｇ／Ｌ／ｈｒに制御した場合の０．５ヶ月後のアンモニア除去速度を基準として相対値で示した。
【００２９】
【表１】

【００３０】
図３より、次のことが明らかである。即ち、酸素消費速度を０．０５ｍｇ／Ｌ／ｈｒ以下としたＮｏ．１の系では、約２ヶ月後と４ヶ月後に除去活性が不安定になり、５ヵ月後に失活した。これに対して、酸素消費速度を０．１ｍｇ／Ｌ／ｈｒ又は１．０ｍｇ／Ｌ／ｈｒとしたＮｏ．２，３では、アンモニアの除去活性は６ヶ月以上に亘って安定であった。
【００３１】
実施例２
実施例１において、ＢＯＤ源として生ゴミの嫌気消化処理液の代りに屎尿の好気的生物処理水を用いたこと以外は同様にして実験を行った。
【００３２】
このときの屎尿の好気的生物処理水の供給速度と酸素消費速度との関係は表２に示す通りであり、同じ酸素消費速度を維持するためには、屎尿の好気的生物処理水は生ゴミの嫌気消化処理液よりも多く供給する必要があった。
【００３３】
【表２】

【００３４】
また、各酸素消費速度の場合のアンモニアの除去活性は図４に示す通りであり、生ゴミの嫌気消化処理液の場合と同様、酸素消費速度が０．０５ｍｇ／Ｌ／ｈｒ以下のＮｏ．４では、途中で除去活性が不安定になり、その後に失活したが、酸素消費速度を０．１ｍｇ／Ｌ／ｈｒ又は１．０ｍｇ／Ｌ／ｈｒとしたＮｏ．５，６では、６ヶ月以上に亘って、アンモニアの除去活性は安定していた。
【００３５】
【発明の効果】
以上詳述した通り、本発明の生物脱窒方法及び生物脱窒装置によれば、ＡＮＡＭＭＯＸ微生物による生物脱窒処理において、ＤＯによる反応阻害を安価に、確実に防止して、安定かつ効率的な生物脱窒処理を行うことができる。
【図面の簡単な説明】
【図１】本発明の生物脱窒装置の実施の形態を示す系統図である。
【図２】酸素消費速度の測定器の一例を示す模式図である。
【図３】実施例１における、各酸素消費速度でのアンモニア除去活性の経時変化を示すグラフである。
【図４】実施例２における、各酸素消費速度でのアンモニア除去活性の経時変化を示すグラフである。
【符号の説明】
１脱窒槽
２生物処理プロセス
３ＯＵＲ測定器
４測定制御器[0001]
BACKGROUND OF THE INVENTION
The present invention biologically denitrifies raw water containing ammonia nitrogen in the presence of nitrite nitrogen by the action of a denitrification microorganism using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. In particular, the present invention relates to a biological denitrification method and a biological denitrification apparatus for performing stable and efficient biological denitrification by preventing reaction inhibition by oxygen in the reaction system in this biological denitrification.
[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. Nitrite nitrogen and nitrate nitrogen are denitrified bacteria, which are heterotrophic bacteria, and are converted into nitrogen gas through a two-stage biological reaction with a denitrification process that decomposes organic matter into nitrogen gas using an electron donor. Disassembled.
[0003]
However, such a conventional nitrification denitrification method requires a large amount of organic matter such as methanol as an electron donor in the denitrification step, and also requires a large amount of oxygen in the nitrification step, so that the running cost is high. is there.
[0004]
In contrast, in recent years, ammonia nitrogen and nitrite nitrogen are reacted using autotrophic microorganisms (autotrophic bacteria) using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. A method of denitrifying by letting go 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. Moreover, since the yield of autotrophic microorganisms is low and the amount of sludge generated is significantly less than that of heterotrophic microorganisms, the amount of surplus sludge generated can be suppressed. Furthermore, there is also a feature that there is no generation of N ₂ O observed by the conventional nitrification denitrification method, and the burden on the environment can be reduced.
[0005]
A biodenitrification process using this autotrophic denitrifying microorganism (hereinafter sometimes referred to as “ANAMMOX microorganism”) is described in Strous, M et al. (1998) Appl. Microbiol. Biotechnol. Vol.50,
p.589-596, and it is considered that ammonia nitrogen and nitrite nitrogen react and decompose into nitrogen gas in the following reaction.
[0006]
[Chemical 1]

[0007]
This biological denitrification reaction is unstable and can be deactivated by aeration with a gas containing very low concentration of oxygen (oxygen partial pressure 0.5 ± 0.2%). Strous, M et al. (1997) Wat Vol.31, No.8, p.1955. The reason for this is not clarified, but this is presumed to be because the enzyme reaction by the ANAMOX microorganism is inhibited even at a very low concentration of molecular oxygen. Considering the case reported in Strous, M et al. (1997) Wat. Res. Vol.31, No.8, p.1955, the dissolved oxygen (DO) concentration in the reaction solution is 0.2 mg / L. Inhibition is expected to occur even at extremely low concentrations.
[0008]
Therefore, in order to prevent such inhibition by oxygen, it can be considered as one countermeasure to remove DO in the raw water in advance before supplying it to the denitrification tank. In this case, as a method of removing DO in raw water to 0.2 mg / L or less,
(1) Addition of reducing agent
(2) Stripping with a gas that does not contain oxygen, such as nitrogen gas, can be considered, but the method (1) requires expensive chemicals, and the method (2) requires power for gas stripping. There is a disadvantage that it is necessary. Moreover, the DO concentration of the raw water may change depending on environmental conditions and the like, and therefore there is a problem that a large excess of reducing agent needs to be added or stripped in order to operate the process stably.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described conventional situation, and in order to perform stable and efficient biological denitrification by inexpensively and reliably preventing inhibition by DO in the biological denitrification treatment by the ANAMOX microorganism. An object of the present invention is to provide a biological denitrification method and biological denitrification apparatus.
[0010]
[Means for Solving the Problems]
The biological denitrification method of the present invention supplies raw water containing ammonia nitrogen to a denitrification tank, the ammonia nitrogen in the denitrification tank is used as an electron donor, and a denitrification microorganism using nitrite nitrogen as an electron acceptor. In the method of biological denitrification in the presence of nitrite nitrogen by the action of the above , the raw water is raw water having an oxygen consumption rate of less than 0.1 mg / L / hr as it is in the biological denitrification. wherein in denitrification tank so that the oxygen consumption rate of the mixed solution containing the denitrifying organisms is 0.1 ~10 mg / L / h r , a biological denitrification method of adding BOD source denitrification tank, the The BOD source is biologically treated water discharged by biologically treating organic substance-containing water .
[0011]
The biological denitrification apparatus of the present invention has an inlet for raw water containing ammonia nitrogen and an outlet for treatment liquid, and uses ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. A denitrification tank that biologically denitrifies in the presence of nitrite nitrogen by the action of a denitrifying microorganism, an oxygen consumption rate measuring means that measures an oxygen consumption rate of a mixed solution containing the denitrifying microorganism in the denitrification tank, Based on the measurement value of the BOD source supply means for supplying the BOD source to the denitrification tank and the oxygen consumption rate measurement means, the oxygen consumption rate of the mixed liquid containing the denitrifying microorganisms in the denitrification tank is 0.1 to 10 mg. / L / hr, a biological denitrification apparatus comprising a control means for controlling the supply amount of the BOD source supplied by the BOD source supply means , the raw water being left as it is in the biological denitrification Oxygen consumption rate is 0.1 mg / L / hr Be a raw water becomes full, the BOD source is characterized in that the organic substance-containing water is biologically treated water discharged by the biological treatment.
[0012]
In the biological denitrification treatment by the ANAMOX microorganism, the microorganism that consumes DO coexists in the reaction system, so that the microorganism can consume DO and prevent inhibition by DO. In the present invention, in order to consume DO by these microorganisms, a BOD source is supplied to the denitrification tank, and the oxygen consumption rate in the mixed solution containing the ANAMOX microorganisms in the denitrification tank becomes 0.1 mg / L / hr or more. Adjust as follows. Thereby, DO in a denitrification tank can be reduced and reaction inhibition by DO can be prevented reliably.
[0013]
As this BOD source, biologically treated water obtained by biologically treating organic substance-containing water such as organic waste is suitable. Since normal biologically treated water has a low BOD concentration, even if it is supplied to another biological treatment process, the amount of microorganisms produced is small, and the oxygen consumption rate of the mixed solution does not easily exceed 0.1 mg / L / hr. However, the biological denitrification process by the ANAMOX microorganism can easily achieve an oxygen consumption rate of 0.1 mg / L / hr or more, and thus is useful as an inexpensive BOD source.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a biological denitrification method and a biological denitrification apparatus according to the present invention will be described below in detail with reference to the drawings.
[0015]
FIG. 1 is a system diagram showing an embodiment of the biological denitrification apparatus of the present invention.
[0016]
Reference numeral 1 denotes a denitrification tank that holds the ANAMOX microorganisms. After the raw water is introduced and denitrified, the treated water is discharged. Biologically treated water of the biological treatment process 2 is added to the denitrification tank 1 as a BOD source by a pump P.
[0017]
The denitrification tank 1 is provided with an OUR (Oxygen Uptake Rate) measuring instrument 3 that collects the liquid in the tank and measures the oxygen consumption rate and then returns it to the denitrification tank 1. The measurement result of the OUR measuring instrument 3 is Input to the measurement controller 4 and the operation of the biological treatment water supply pump P is controlled based on the result.
[0018]
As the OUR measuring device 3, as shown in FIG. 2, a device in which DO is put in a container 5 and tightly sealed and stirred with a stirrer 6 and the DO concentration is measured over time by a DO electrode 7 is used. The measurement result can be input to the measurement controller 4 and the oxygen consumption rate can be calculated from the decrease curve of the DO concentration. Such an OUR measuring device 3 may be installed in the denitrification tank 1 online, or the mixed solution can be manually collected and analyzed.
[0019]
In the apparatus of FIG. 1, the oxygen consumption rate of the liquid in the denitrification tank 1 is measured in this way, and the amount of biological treatment water added is controlled based on this result, so that the liquid in the tank of the denitrification tank 1 is controlled. The oxygen consumption rate is controlled to be 0.1 mg / L / hr or more. That is, when the oxygen consumption rate of the liquid in the tank is lower than the control range, the amount of biological treatment water added is increased, and microorganisms that consume DO are grown in the liquid in the tank to increase the oxygen consumption rate. Conversely, when the oxygen consumption rate is higher than the control range, the amount of biologically treated water added is reduced.
[0020]
When the oxygen consumption rate is less than 0.1 mg / L / hr, the DO in the tank cannot be sufficiently reduced due to the consumption of DO by microorganisms, and the denitrification efficiency decreases with time due to inhibition by DO. Even if the oxygen consumption rate is excessively high for DO brought into the denitrification tank 1 from raw water or the like, the improvement of the effect cannot be expected. On the contrary, microorganisms other than the ANAMOX microorganisms grow in the denitrification tank, and the ANAMOX microorganisms There is a risk that the growth environment will deteriorate. Therefore, the oxygen consumption rate is 0.1 to 10 mg / L / hr, preferably that controls so that 0.1~2mg / L / hr.
[0021]
The B OD source, because it is cheaper simple, it is preferable to use a biologically treated water. The biologically treated water is not particularly limited, and anaerobic digestion treatment liquid of organic waste such as garbage, aerobic biologically treated water of urine, sewage treated water, industrial wastewater treated water and the like can be used. The biologically treated water may be added directly to the denitrification tank 1 or may be mixed with raw water in advance and introduced into the denitrification tank.
[0022]
The measurement of the oxygen consumption rate of the liquid in the denitrification tank 1 may be performed continuously or intermittently, and the oxygen consumption rate is 0.1 mg / L / hr or less depending on the degree of stability of the treatment. Just go to the top . Further, the addition of a BOD source such as biologically treated water to the denitrification tank 1 may be performed continuously or intermittently.
[0023]
In addition, there is no restriction | limiting in particular as a model of the denitrification tank 1, USB (Upflow Sludge Bed: Upflow sludge bed) type | mold which hold | maintains the granular sludge of ANAMOX microorganisms, sludge suspension type, a fixed bed type, a fluid bed type Any type of carrier addition method may be used.
[0024]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0025]
Example 1
Nitrogen gas and oxygen gas were adjusted with a flow meter to create a mixed gas with an oxygen partial pressure of 0.5 ± 0.2%. The oxygen partial pressure was adjusted with a flow meter equipped with a needle valve with computer control. Here, a signal was sent from the computer, the valve opening was randomly changed, and the oxygen partial pressure was adjusted between 0.3 and 0.7%.
[0026]
Using this gas, tap water was aerated, 1000 mg / L of ammonia and 1200 mg / L of nitrous acid were added to this liquid, and a synthetic waste water containing a small amount of DO was created. Using this synthetic wastewater, an experiment was conducted to anaerobically biodenitrify ammonia.
[0027]
The volume of the denitrification tank was 10 L, the raw water was fed at 20 L / day, and the anaerobic digestion treatment solution for raw garbage as a BOD source was passed at a rate of 1 to 100 mL / day. The oxygen consumption rate of the denitrification tank was measured periodically using the OUR measuring device shown in FIG. This measurement is performed every three days at the beginning, every two weeks after one month, and the supply rate of the anaerobic digestion treatment solution for garbage is set for each measurement so that the oxygen consumption rate becomes the value shown in Table 1. I did it again.
[0028]
Table 1 shows the relationship between the supply rate of the anaerobic digestion treatment solution for raw garbage and the oxygen consumption rate. Further, FIG. 3 shows changes with time in the ammonia removal activity at each oxygen consumption rate. The ammonia removal activity was expressed as a relative value based on the ammonia removal rate after 0.5 months when the oxygen consumption rate was controlled to 0.1 mg / L / hr.
[0029]
[Table 1]

[0030]
From FIG. 3, the following is clear. That is, the oxygen consumption rate was set to 0.05 mg / L / hr or less. In the system 1, the removal activity became unstable after about 2 months and 4 months, and was deactivated after 5 months. On the other hand, the oxygen consumption rate was 0.1 mg / L / hr or 1.0 mg / L / hr. In Nos. 2 and 3, the ammonia removal activity was stable over 6 months.
[0031]
Example 2
In Example 1, an experiment was conducted in the same manner except that an aerobic biologically treated water of manure was used as the BOD source instead of the anaerobic digestion treatment liquid of garbage.
[0032]
The relationship between the supply rate of the aerobic biologically treated water of urine and the oxygen consumption rate at this time is as shown in Table 2, and in order to maintain the same oxygen consumption rate, the aerobic biologically treated water of urine is It was necessary to supply more than the anaerobic digestion treatment solution of raw garbage.
[0033]
[Table 2]

[0034]
In addition, the ammonia removal activity at each oxygen consumption rate is as shown in FIG. 4, and as in the case of the anaerobic digestion treatment solution of raw garbage, the oxygen consumption rate is 0.05 mg / L / hr or less. In No. 4, the removal activity became unstable in the middle and then deactivated, but the oxygen consumption rate was 0.1 mg / L / hr or 1.0 mg / L / hr. In Nos. 5 and 6, the ammonia removal activity was stable over 6 months.
[0035]
【Effect of the invention】
As described above in detail, according to the biological denitrification method and the biological denitrification apparatus of the present invention, in the biological denitrification treatment by the ANAMOX microorganisms, reaction inhibition by DO is reliably prevented at low cost, and is stable and efficient. Biological denitrification treatment can be performed.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a biological denitrification apparatus of the present invention.
FIG. 2 is a schematic diagram showing an example of an oxygen consumption rate measuring device.
3 is a graph showing changes with time in ammonia removal activity at various oxygen consumption rates in Example 1. FIG.
4 is a graph showing changes with time in ammonia removal activity at various oxygen consumption rates in Example 2. FIG.
[Explanation of symbols]
1 Denitrification tank 2 Biological treatment process 3 OUR measuring instrument 4 Measurement controller

Claims

Supply of raw water containing ammonia nitrogen to the denitrification tank, and the presence of nitrite nitrogen by the action of denitrification microorganisms using ammonia nitrogen in the denitrification tank as an electron donor and nitrite nitrogen as an electron acceptor In the method of biological denitrification below,
In the biological denitrification, the raw water is raw water having an oxygen consumption rate of less than 0.1 mg / L / hr as it is,
As oxygen consumption rate of the mixed solution containing the denitrifying organisms in denitrification tank is 0.1 ~10 mg / L / h r , a biological denitrification method of adding BOD source denitrification tank ,
A biological denitrification method, wherein the BOD source is biologically treated water discharged by biologically treating organic substance-containing water .

It has an inlet for raw water containing ammonia nitrogen and an outlet for the treatment liquid. It is nitrite-based by the action of a denitrifying microorganism using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. A denitrification tank for biological denitrification in the presence of nitrogen;
Oxygen consumption rate measuring means for measuring the oxygen consumption rate of the mixed solution containing the denitrifying microorganisms in the denitrification tank;
BOD source supply means for supplying a BOD source to the denitrification tank;
Based on the measurement value of the oxygen consumption rate measuring means , the BOD source supply means so that the oxygen consumption rate of the mixed liquid containing the denitrifying microorganisms in the denitrification tank is 0.1 to 10 mg / L / hr. A biological denitrification device comprising control means for controlling the supply amount of the BOD source supplied by
In the biological denitrification, the raw water is raw water having an oxygen consumption rate of less than 0.1 mg / L / hr as it is,
A biological denitrification apparatus, wherein the BOD source is biologically treated water discharged by biologically treating organic substance-containing water .