JP2004000861A - Method and apparatus for removing nitrate nitrogen in water - Google Patents

Method and apparatus for removing nitrate nitrogen in water Download PDF

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Publication number
JP2004000861A
JP2004000861A JP2002160953A JP2002160953A JP2004000861A JP 2004000861 A JP2004000861 A JP 2004000861A JP 2002160953 A JP2002160953 A JP 2002160953A JP 2002160953 A JP2002160953 A JP 2002160953A JP 2004000861 A JP2004000861 A JP 2004000861A
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water
sulfur
biological filtration
filtration tower
mixing
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Hajime Kono
河野　源
Yoshiaki Shibuya
渋谷　吉昭
Shinji Ichikawa
市川　真治
Miyoshi Imai
今井　三佳
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Japan Agriculture Forestry and Fisheries Ministry of
Aquas Corp
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Japan Agriculture Forestry and Fisheries Ministry of
Aquas Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

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  • Immobilizing And Processing Of Enzymes And Microorganisms (AREA)
  • Micro-Organisms Or Cultivation Processes Thereof (AREA)
  • Biological Treatment Of Waste Water (AREA)
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for continuously removing nitrate nitrogen in the water in which an organic hydrogen donor is not used, anaerobic treatment is not necessitated and nitrogen gas is not retained in the nitrogen removing system and which can be applied even to waste water containing high-concentration nitrate nitrogen. <P>SOLUTION: Nitrate nitrogen in the water is removed by using sulfur oxidizing bacteria, by mixing raw water with a circulation liquid, in a mixing/circulating tank 2, which circulates through a biological filtration column 3 packed with a sulfur carrier and formed with a biological membrane based on the sulfur oxidizing bacteria on its surface and feeding the mixture to the column 3 upward from the bottom by using a circulation pump 4 at 5-100/hourly space velocity to bring the mixture into contact with the sulfur oxidizing bacteria-based biological membrane forming the column 3 so that nitric acid is reduced to nitrogen. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、水中に含まれる硝酸性窒素を除去する方法及び装置に関する。
【０００２】
【従来の技術】
河川、海域などの水域では、これらの閉鎖性水域に流入する窒素、リンに起因する富栄養化に伴なう水質汚染が進行し、各種の植物プランクトンや藻類が増殖し、これらの生物に由来する有害物質や悪臭物質が大きな社会問題となっている。すでに、湖沼や内湾・内海に排出される産業系排水については、富栄養化防止の観点から排水基準が適用されている。
【０００３】
また、１９９９年２月に「硝酸性窒素及び亜硝酸性窒素」が人の健康の保護に関する環境基準対象項目に追加され、２０００年２月には中央環境審議会答申「第５次水質総量規制の在り方について」の中に、平成１６年度を目標年度として指定水域における窒素・リンの汚濁負荷量削減のために、総量規制を図ることが盛り込まれた。この答申を受け、平成１３年６月に水質汚濁防止法の排水基準が改正され、「一リットルにつきアンモニア性窒素に０．４を乗じたもの、亜硝酸性窒素及び硝酸性窒素の合計量百ミリグラム」と規制が強化された。なお、施行後３年間は業種毎に暫定排水基準として、これより緩やかな基準値が設けられているが、その間に削減対策を進めることが求められている。
【０００４】
このような排水中の窒素を除去する方法で最も多く利用されているのが、アンモニア態窒素を亜硝酸あるいは硝酸に酸化した後、これらの酸化態の窒素を還元し窒素ガスとして除去する生物学的硝化・脱窒素法である。脱窒素工程での亜硝酸や硝酸の還元反応には、メタノールなどの有機性水素供与体（脱窒素細菌が生育に利用可能な基質）が必要である。
【０００５】
このような脱窒素菌により脱窒するこの方法は、工場排水の三次処理として用いられることが多いが、メタノールなどの有機性水素供与体の添加が必要であり、一般には当量以上（約１．５倍程度）のメタノールを添加することになるため、メタノールの一部が残留し、放流水のＣＯＤ、ＢＯＤを上昇させてしまうおそれがある。
従って、この方法では、通常は、後段でさらに曝気槽を設置して生物処理を行う必要があり、このため設置スペースが大きくなってしまうという問題があった。
また、この方法では、上記したように、メタノールなどの有機性水素供与体の添加が必要であるため、ランニングコストが嵩み、薬液を補充するなど管理が手間となる。
さらに、メタノールは揮発性が大きく、引火しやすく、毒性も高いなど、消防設備や作業者の安全面での対策が必要となる問題があった。
【０００６】
排水中に含まれる有機物を脱窒素反応の水素供与体として使う処理方法もある（日本機械工業連合会編：閉鎖性水域の富栄養化防止技術に関する調査研究報告書「平成９年度産業排水の窒素およびリンの合理的な処理技術」、１０９〜２０１頁、１９９８年）。メタノール等の添加を必要としないが、有機物が含まれる排水にしか適用できない。
【０００７】
一方、硫黄や硫黄化合物を用いて独立栄養性の硫黄酸化細菌による有機性水素供与体を必要としない脱窒素法が提案され（橋本　奨等；第１４回下水道研究会、１９７７年）、硫黄脱窒菌による脱窒反応速度は、有機物を電子供与体とする従属栄養性の脱窒菌による脱窒反応速度に匹敵することが報告されている。さらに、嫌気条件下、硫黄馴養活性汚泥による連続脱窒試験により単体硫黄を電子供与体とした場合、１．３ｍｇＮＯ３−Ｎ／ｍｇＳＳ・日の脱窒速度を示し、メタノールを電子供与体とした場合の活性汚泥の脱窒速度（０．６ｍｇＮＯ３−Ｎ／ｍｇＳＳ・日）に比べて高い脱窒性能を有することが明らかにされた（橋本　奨；用水と廃水、３１、２８３−２９３、１９８９）。
【０００８】
この他、窒素化合物、硫黄化合物及び窒素−硫黄化合物を含有する排水処理に、硫黄脱窒菌を利用した例（特公昭６２−５６７９８号公報）、汚泥に硫黄と大理石（炭酸カルシウム）を添加し、硫黄補填好気−嫌気活性汚泥法により廃水中の窒素・リン同時除去を行った例（特公平４−９１１９号公報等）がある。
これらの方法では、コストの安い粉末あるいは粒状硫黄を電子供与体に利用することにより、極めて安価な排水の脱窒処理が期待できる。
また、前記硫黄脱窒法の特徴は、何れも酸素がない嫌気条件での硫黄酸化細菌の硫黄を電子供与体とする脱窒素反応を利用しているところにある。
【０００９】
ところで、前記硫黄脱窒速度は、メタノール添加の必要な硝酸還元菌による脱窒速度と同等ではあるが、連続的に処理する場合、硫黄を含む担体の間をゆっくりと〔例えば空間速度（以下、「ＳＶ」と称することがある。）０．２／ｈｒ程度で〕通水させて接触時間をかなり長くとらなければ充分な処理ができず、結果として、装置が大型化するため、設置スペースが大きくなってしまうという欠点を有していた。
【００１０】
また、流速を遅くせざるを得ないことから、発生する窒素ガスが床内に滞留して、被処理水と硫黄を含む担体との接触を妨げ、その結果、脱窒効率が低下し、安定した処理が行えないという問題があった。
すなわち、従来の硫黄酸化細菌を用いる上記硝酸性窒素除去方法では、養液栽培排水や金属メッキ排水などの高濃度硝酸性窒素含有排水（窒素濃度：数百〜数千ｍｇ／Ｌ）を処理するための装置は大型化してしまい、設置スペースが大きくなり建設コストが嵩む上に、流速を遅くせざるを得ないことから、発生する窒素ガスがろ床内に滞留して、被処理水との接触を妨げ、その結果、脱窒効率が低下し、安定した処理が行えないという問題があった。また、酸素を嫌うため、高い脱窒効率を得るためには、窒素ガスを吹き込み脱酸素するなどの嫌気状態を維持する必要があり、装置設計や運転管理への対応が求められる問題があった。
【００１１】
【発明が解決しようとする課題】
本発明は、上記従来技術の問題点を悉く解消したものであって、水中の硝酸性窒素を除去するにあたり、有機性の水素供与体を使用せず、嫌気処理を行う必要がなく、また脱窒素系内に窒素ガスが滞留せず、しかも高濃度の硝酸性窒素含有排水にも適用できる連続処理方式の脱窒素方法及び装置を提供することにある。
【００１２】
すなわち、本発明の第一の課題は、メタノールのような有機性の水素供与体を使用せず、嫌気処理を行う必要がなく、また脱窒素系内に窒素ガスが滞留しない水中の硝酸性窒素の除去方法及び装置を提供することである。
【００１３】
さらに、本発明の第二の課題は、高濃度の硝酸性窒素含有排水にも適用できる連続処理方式の水中の硝酸性窒素除去の方法及び装置を提供することである。
【００１４】
【課題を解決するための手段】
上記第一の課題を解決するため、本発明者らは硫黄酸化細菌を用いる固定床生物ろ過法による脱窒素方法について鋭意検討した結果、被処理水を硫黄担体が充填された生物ろ過塔をある程度高速に上向流で循環させながら処理する方法において、一定の処理品質を得ようとすると、ＳＶ５／ｈｒ以上であれば、通水速度と循環回数が比例関係にあることを見出した。
【００１５】
図１は、原水窒素濃度が４００ｍｇ／Ｌの排水を、上記方法にて処理水窒素濃度２０ｍｇ／Ｌ或いは１００ｍｇ／Ｌまで処理する場合の必要循環回数を示したグラフである。
図１によれば、例えばＳＶ１０／ｈｒとＳＶ２０／ｈｒとで比較すると、ＳＶ１０／ｈｒの２倍の速度（ＳＶ２０／ｈｒ）で流した場合には、処理水窒素濃度２０ｍｇ／Ｌと１００ｍｇ／Ｌまで処理する場合のいずれとも、ＳＶ１０／ｈｒで流した場合の約２倍の循環回数が必要となることが明らかである。
【００１６】
すなわち、通水速度を速くした代わりに、その分だけ循環させる回数を増やして、硫黄酸化細菌が被処理液に接触する実質的な接触時間を同じ程度確保することができれば、同じレベルの処理水を得ることができることが分かった。
従って、ろ材高を１，０００ｍｍ程度までと、かなり高くすることが可能となることから、ろ材を高く充填したろ過塔内を通水することができるため、装置のコンパクト化が可能となる。
さらに、このとき、上向流で高速通水させることによって、硝酸が還元されて生成した窒素ガスをろ床上部へ追い出すことができ、その結果、窒素ガスの滞留による脱窒効率の低下を防止することができることも分かった。
また、硫黄担体上に形成された硫黄酸化細菌を主体とする生物膜は、担体に付着した領域は嫌気状態になるため、効率的に硫黄脱窒が行えると考えられる。
【００１７】
次に、上記本発明の第二の課題を解決するため、本発明者らは高濃度の硝酸性窒素含有排水を生物ろ過塔に供給する方法について鋭意検討した。その結果、高濃度の原水を直接、生物ろ過塔に供給すると、硫黄酸化細菌の脱窒性能が抑制されるため、生物ろ過塔の手前に混合循環槽を設け、この混合循環槽において、原水と生物ろ過塔からの循環液とを混合し、混合された被処理水を混合循環槽と生物ろ過塔を循環させると共に、原水を混合循環槽へ供給するにあたり、生物ろ過塔に対する容積負荷を制御して、混合循環槽における硝酸イオン濃度を脱窒性能に影響がない程度（硝酸イオン濃度０〜１００ｍｇ／Ｌ）に維持することにより、高濃度の硝酸性窒素含有排水にも適用できる連続方式の水中の硝酸性窒素除去方法を見出した。
【００１８】
図３は、後述の実施例１に示すように、図２に示す流加方式（半連続方式）の実験装置を用い、原水窒素濃度が４００ｍｇ／Ｌの排水を容積負荷を種々変化させて、混合循環槽（初期液量：２０Ｌ、窒素濃度：２ｍｇ／Ｌ、温度３０℃）に８０Ｌになるまで連続供給すると共に、硫黄担体を充填した生物ろ過塔に上向流にてＳＶ１５／ｈｒで循環させ処理したときの容積負荷と残存窒素濃度との関係を示したグラフである。
図３から、流加方式（半連続方式）の場合、容積負荷１，７００ｍｇＮ／Ｌ担体・日までは、処理水窒素濃度２０ｍｇ／Ｌ以下の安定した処理水質を得られることが明らかである。また、この場合、容積負荷が１，７００ｍｇＮ／Ｌ担体・日より増えると、残存窒素濃度が急激に増加することから、高濃度の硝酸含有排水が硫黄酸化細菌の脱窒性能を抑制することが分かる。
【００１９】
図５は、後述の実施例２に示すように、図４に示す連続方式の実験装置を用い、原水窒素濃度が４００ｍｇ／Ｌの排水を容積負荷を種々変化させて、混合循環槽（液量：４０Ｌ、窒素濃度：２ｍｇ／Ｌ、温度３５℃）に連続供給すると共に、硫黄担体を充填した生物ろ過塔に上向流にてＳＶ１５／ｈｒで循環させ処理したときの容積負荷と残存窒素濃度との関係を示したグラフである。
図５から、連続方式の場合、温度３５℃では、容積負荷約３，０００ｍｇＮ／Ｌ担体・日までは、処理水窒素濃度２０ｍｇ／Ｌ以下の安定した処理水質を得られることが明らかである。従って、容積負荷の制御の目安としては、生物ろ過塔に対する容積負荷１００〜３，５００ｍｇＮ／Ｌ担体・日で供給すると良い。
本発明は、これらの知見に基いて完成されたものである。
【００２０】
すなわち、請求項１に係る本発明は、水中の硝酸性窒素を硫黄酸化細菌により除去するにあたり、混合循環槽において、原水と、硫黄担体を充填させて前記硫黄担体上に硫黄酸化細菌を主体とする生物膜を形成させた生物ろ過塔からの循環液とを混合し、前記生物ろ過塔下部より、上向流にて空間速度５〜１００／ｈｒで循環・通水し、前記生物ろ過塔を形成する、前記硫黄酸化細菌を主体とする前記生物膜に接触させ、硝酸を窒素に還元して脱窒素処理を行うことを特徴とする、連続処理方式の水中の硝酸性窒素の除去方法を提供するものである。
【００２１】
請求項２に係る本発明は、原水を混合循環槽へ供給するにあたり、生物ろ過塔に対する容積負荷を制御して、前記混合循環槽における硝酸イオン濃度を０〜１００ｍｇ／Ｌに維持することを特徴とする、請求項１記載の水中の硝酸性窒素の除去方法を提供するものである。
【００２２】
請求項３に係る本発明は、混合循環槽における温度を２０〜４０℃に維持するように制御することを特徴とする、請求項１記載の水中の硝酸性窒素の除去方法を提供するものである。
【００２３】
請求項４に係る本発明は、水中の硝酸性窒素を硫黄酸化細菌により除去するための装置であって、硫黄担体を充填させた生物ろ過塔と、原水と前記生物ろ過塔からの循環液とを混合する混合循環槽と、前記混合循環槽の被処理水を上向流にて空間速度５〜１００／ｈｒで前記生物ろ過塔に循環させる循環ポンプと、原水を前記生物ろ過塔に対する容積負荷を制御して前記混合循環槽に供給する原水供給ポンプと、を備えたことを特徴とする、水中の硝酸性窒素の連続除去装置を提供するものである。
【００２４】
請求項５に係る本発明は、水中の硝酸性窒素を硫黄酸化細菌により除去するための装置であって、硫黄担体を充填させた生物ろ過塔と、原水と前記生物ろ過塔からの循環液とを混合する混合循環槽と、前記混合循環槽の被処理水を上向流にて空間速度５〜１００／ｈｒで前記生物ろ過塔に循環させる循環ポンプと、原水を前記生物ろ過塔に対する容積負荷を制御して前記混合循環槽に供給する原水供給ポンプと、加温器と、温度測定器と、前記温度測定器により測定された温度により前記加温器をＯＮ／ＯＦＦさせる温度制御手段と、を備えたことを特徴とする、水中の硝酸性窒素の連続除去装置を提供するものである。
【００２５】
【発明の実施の形態】
以下、本発明の実施の形態を示す。
ここで請求項１〜３に係る本発明の方法は、請求項４〜５に係る本発明の装置によって好適に実施されることから、以下、請求項１〜３に係る本発明の方法を、図６、７に示す請求項４に係る本発明の装置、及び図８に示す請求項５に係る本発明の装置を参照しつつ詳細に説明する。
図６は、請求項４に係る本発明の装置の一態様を示すフローシートである。また、図７は、請求項４に係る本発明の装置の他の態様を示すフローシートである。さらに、図８は、請求項５に係る本発明の装置の一態様を示すフローシートである。
【００２６】
図６は、請求項１に係る本発明の方法の実施に好適な装置（請求項４に係る本発明の装置）の一態様を示すフローシートであり、水中の硝酸性窒素を硫黄酸化細菌により除去するための装置であって、硫黄担体を充填させた生物ろ過塔３と、原水と前記生物ろ過塔３からの循環液とを混合する混合循環槽２と、前記混合循環槽２の被処理水を上向流にて空間速度５〜１００／ｈｒで前記生物ろ過塔３に循環させる循環ポンプ４と、原水を前記生物ろ過塔３に対する容積負荷を制御して前記混合循環槽２に供給する原水供給ポンプ１１と、を備えたことを特徴とするものである。
また、図７は、図６に示す装置において、原水を貯留する原水槽１を設置した装置（他の態様）を示すフローシートである。
【００２７】
排水のろ過処理を行う生物ろ過塔３には、硫黄担体が充填されている。該硫黄担体としては、硫黄を含むものであれば一般に使用されているものを用いればよく、例えば、硫黄を用いる場合には、市販されている硫黄粒と、中和用に固形の炭酸塩（サンゴ砂など）を組合せたものを用いればよい。また、硫黄に炭酸塩を練り混ぜた硫黄混合物（例えば、ニッチツ社製の石灰硫黄脱窒材　粒径：５〜２０ｍｍ）を用いれば、改めて中和用の炭酸塩を充填する必要はない。このような硫黄担体としては、通常、公知の硫黄酸化細菌を付着させたものが用いられる。処理すべき排水の量に応じて、ろ材量を変えることができる。なお、硫黄担体の粒径は、流出しない程度の大きさであれば特に制限はないが、好ましくは１〜２５ｍｍ、さらに好ましくは５〜２０ｍｍである。
前記生物ろ過塔３は、硫黄担体で充填層を形成した固定床式反応槽とされている。
生物ろ過塔３においては、その中に硫黄担体を充填し、この硫黄担体上に上記硫黄酸化細菌を主体とする生物膜を形成させている。
【００２８】
請求項１〜３に係る本発明の方法においては、混合循環槽２において、原水と、硫黄担体を充填させて前記硫黄担体上に硫黄酸化細菌を主体とする生物膜を形成させた生物ろ過塔３からの循環液とを混合する。
従って、混合循環槽２は、原水と生物ろ過塔３からの循環液とを混合する働きを有するものである。
混合循環槽２において、原水と生物ろ過塔３からの循環液とを混合することにより、生物ろ過塔３における脱窒性能に影響がない程度に硝酸イオン濃度を維持することができるので、請求項１〜３に係る本発明の方法は、高濃度の硝酸性窒素含有排水にも適用できる。
【００２９】
混合循環槽２への原水の供給量は、一義的には、生物ろ過塔３の処理能力によって決定され、さらに原水の窒素濃度、硫黄担体の粒径、処理温度、目標とする処理水の窒素濃度、混合循環槽２の大きさ、ＳＶ、などによっても異なるが、目安としては、生物ろ過塔３に対する容積負荷１００〜３，５００ｍｇＮ／Ｌ担体・日、好ましくは３００〜３，０００ｍｇＮ／Ｌ担体・日で供給する。
【００３０】
また、混合循環槽２の温度は、脱窒効率等を考慮して、通常１０〜４０℃、好ましくは請求項３に記載したように、２０〜４０℃、より好ましくは２５〜３７℃に維持するように制御される。
ここで混合循環槽２における温度が上記範囲を逸脱すると、硫黄酸化細菌の脱窒素処理性能が低下するので好ましくない。なお、硫黄酸化細菌の脱窒素処理性能の最適温度は、３５℃付近にある。
【００３１】
混合循環槽２の温度を上記した範囲に制御するために、請求項５に記載し、図８に示したように、加温器５と、温度測定器（温度センサ）６と、前記温度測定器６により測定された温度により前記加温器５をＯＮ／ＯＦＦさせる温度制御手段７と、を備えたものとすることが好ましい。これら加温器５、温度測定器（温度センサ）６、温度制御手段７としては、一般に使用されているものを使用することができる。
【００３２】
温度測定器（温度センサ）６により測定された温度に基づき、温度制御手段７により加温器５をＯＮ／ＯＦＦさせ、混合循環槽２の温度を上記した範囲、好ましくは請求項２に記載した範囲に制御する。
【００３３】
次に、請求項１〜３に係る本発明の方法においては、混合循環槽２において、原水と、生物ろ過塔３からの循環液とを混合する。図６〜８中において、符号８ｂとして示されている循環ライン（戻り）によって、この生物ろ過塔３からの循環液が混合循環槽２に送られている。
【００３４】
さらに、請求項１〜３に係る本発明の方法においては、上記のようにして混合循環槽２において、原水と、生物ろ過塔３からの循環液とを混合した後、この混合液（被処理水）を生物ろ過塔３下部より、上向流にてＳＶ５〜１００／ｈｒで循環・通水し、生物ろ過塔３を形成する、前記硫黄酸化細菌を主体とする前記生物膜に接触させ、硝酸を窒素に還元して脱窒素処理を行う。
【００３５】
循環ポンプ４は、前記混合循環槽２の被処理水を上向流にて、生物ろ過塔３に循環させる働きを有するものであって、しかも被処理水をＳＶ５〜１００／ｈｒという高速で循環させる能力を有するものである。
なお、硫黄酸化細菌の活動を活発にする面から、被処理水のｐＨは、６．５〜８．５の範囲に保っておくことが好ましい。
【００３６】
ここで循環ポンプ４により、混合循環槽２内の被処理水を上向流にて生物ろ過塔３に循環させることによって、窒素ガスの上昇をアシストし、窒素ガスがろ材内に滞留して脱窒効率を低下させるおそれがない。上向流でない場合には、このような目的を達成することはできない。
また、被処理水の循環は、ＳＶ５〜１００／ｈｒ、好ましくは１０〜３０／ｈｒ、より好ましくは１０〜２０／ｈｒで行う必要がある。ここで循環水のＳＶが５／ｈｒ未満であると、窒素ガスがろ材から抜けにくい為か、除去効率が劣るものとなる。一方、循環水のＳＶが１００／ｈｒを超えると、ろ材の圧力損失が増大してくるため、ポンプをかなり大きくしなければならず、無駄となる。
【００３７】
このように請求項１〜３に係る本発明の方法においては、混合液（被処理水）を生物ろ過塔３下部より、上向流にてＳＶ５〜１００／ｈｒで繰り返し循環・通水し、生物ろ過塔３を形成する、前記硫黄酸化細菌を主体とする前記生物膜に接触させる。これによって、硝酸を窒素に還元して脱窒素処理される。
【００３８】
なお、原水供給ポンプ１１としては、目安として原水を容積負荷１００〜３，５００ｍｇＮ／Ｌ担体・日で混合循環槽１に供給することができるものであれば、一般に使用されているものを用いれば良く、特に制限はない。
原水を混合循環槽２に供給するにあたり、生物ろ過塔３に対する容積負荷を制御して混合循環槽２に供給することにより、混合循環槽２における硝酸イオン濃度を低濃度に、具体的に好ましくは０〜１００ｍｇ／Ｌ、より好ましくは０．１〜５０ｍｇ／Ｌに維持することができるので、高濃度の硝酸性窒素含有排水を生物ろ過塔３に直接供給されて硫黄酸化細菌の脱窒性能が抑制される、といったおそれがない。
【００３９】
また、図６〜８中、符号８ａは循環ライン（入り）を、符号８ｂは循環ライン（戻り）を、符合９は戻りライン（撹拌）を、符号１０は処理水を、それぞれ示している。
【００４０】
図６〜８に示す請求項４、５に係る本発明の装置においては、生物ろ過塔３と混合循環槽２とは、循環ポンプ４により、上記した如き循環ライン（入り）８ａ、循環ライン（戻り）８ｂ、戻りライン（撹拌）９を形成するよう接続されており、生物ろ過塔３からの循環液が循環ライン（戻り）８ｂにより混合循環槽２に送られると共に、混合循環槽２の被処理水は、循環ライン（入り）８ａにより生物ろ過塔３に送られている。
また、請求項４、５に係る本発明の装置においては、生物ろ過塔３内に滞留する窒素ガスを抜くためのエア抜き弁（図示していない）を設けておくこともできる。さらに必要に応じて、生物ろ過塔３内のドレンを排出する手段（図示していない）を設けておくこともできる。
【００４１】
請求項１〜３に係る本発明においては、このようにして混合循環槽２において原水と硫黄担体を充填した生物ろ過塔３からの循環水とを混合し、生物ろ過塔３下部より循環・通水し生物ろ過塔３を形成する硫黄酸化細菌を主体とする生物膜に接触させ、硝酸を窒素に還元して脱窒素処理を行い、水中の硝酸性窒素を硫黄酸化細菌により除去する。
【００４２】
本発明は、以上の如き構成を有するものである。
本発明は、養液栽培の排水や金属メッキ排水をはじめとする高濃度の硝酸性窒素含有排水を含む各種排水中の硝酸性窒素の除去に適用することができる。
【００４３】
【実施例】
以下に本発明の実施例を示すが、本発明はこれによって何ら制限されるものではない。
【００４４】
実施例１〔流加方式（半連続方式）による脱窒素処理〕
原水槽１と、混合循環槽２（初期液量：２０Ｌ、窒素濃度：２ｍｇ／Ｌ）と、硫黄担体として石灰硫黄脱窒剤（ニッチツ社製、粒径：５〜２０ｍｍ）を充填した生物ろ過塔３とからなる、図２に原理を示す図８の装置（原水槽容量：２００Ｌ、混合循環槽容量：１００Ｌ、生物ろ過塔容量：φ１００×Ｈ１，１００ｍｍ）を用い、原水槽１より第１表記載のモデル排水を混合循環槽２に８０Ｌになるまで連続供給すると共に、生物ろ過塔３にＳＶ１５／ｈｒで循環した。混合循環槽２内の液量が８０Ｌになると６０Ｌを捨て、再度容積負荷を変えて検討した（混合循環槽温度：３０℃）。循環ポンプ４の後に戻りライン９を入れ、その吐出圧を利用して混合循環槽２の撹拌混合を行った。
上記した如き硝酸性窒素の除去処理の施されたモデル排水の窒素濃度の経時変化を図３に示す。
【００４５】
【表１】
第１表（モデル排水組成）

Figure 2004000861
【００４６】
＊微量金属溶液の組成（１Ｌ当たり）
Ｈ３ＢＯ４　　　　　　　　３０　ｇ
ＭｎＳＯ４・Ｈ２Ｏ　　　　２０　ｇ
ＺｎＳＯ４・７Ｈ２Ｏ　　　２．２ｇ
ＣｕＳＯ４・５Ｈ２Ｏ　　　０．５ｇ
Ｎａ２ＭｏＯ４　　　　　　０．２ｇ
Ｈ２ＳＯ４　　　　　　　　１　ｍｌ
【００４７】
図３によれば、容積負荷が１，７００ｍｇＮ／Ｌ担体・日を超えると、残存窒素濃度が急激に増加することが分かった。このことは、排水中の硝酸イオン濃度が高くなると硫黄酸化細菌の脱窒性能が抑制されることを反映していると考えられる。
【００４８】
実施例２〔連続方式による脱窒素処理〕
原水槽１と、混合循環槽２（初期液量：２０Ｌ、窒素濃度：２ｍｇ／Ｌ、温度３０℃）と、硫黄担体として石灰硫黄脱窒剤（実施例１と同じ）を充填した生物ろ過塔３とからなる、図４に原理を示す図８の装置（原水槽容量：２００Ｌ、混合循環槽液量：４０Ｌ、生物ろ過塔容量：φ１００×Ｈ１，１００ｍｍ）を用い、最初に実施例１記載の添加方式で原水槽１よりモデル排水（第１表記載）を混合循環槽２に連続的に容積負荷５００ｍｇＮ／Ｌ担体・日で供給すると共に、生物ろ過塔３にＳＶ１５／ｈｒで循環した。混合循環槽２の液量が４０Ｌになったときに連続方式に切替え、以後、ポンプで排水して混合循環槽２の液量を４０Ｌに維持すると共に、混合循環槽２の温度を加温器５により２０〜４０℃に変化させ、容積負荷を変動させたときの処理温度の影響を検討した。混合循環槽２の撹拌混合は、実施例１と同様に循環ポンプ４の戻り吐出圧を利用して行った。
【００４９】
各温度において容積負荷を変動させたときの処理水の残存硝酸濃度と生産亜硝酸濃度との関係を図９に、処理温度と処理水の窒素濃度が１０ｍｇ／Ｌ以下となる最適容積負荷との関係を図１０に示す。
【００５０】
図９のグラフから明らかな通り、残存の硝酸イオン濃度が１００ｍｇ／Ｌを超えると急激に亜硝酸イオンが蓄積していくことが認められた。
また、硝酸イオン濃度が４００ｍｇ／Ｌを超えると、亜硝酸イオン濃度の生成が横這いとなるが、これは亜硝酸イオンにより硫黄酸化細菌の生育が抑制されるためと考えられる。
一般に、硫黄酸化細菌による硝酸性窒素の還元は、亜硝酸以降の還元反応が律速することが知られているが、本発明者等が得た前記結果からも、このことが裏付けられた。
従って、硫黄脱窒法による硝酸性窒素の除去において、安定な処理水質を得るためには、亜硝酸イオンが蓄積しないように容積負荷を制御することが必要である。
【００５１】
さらに、図１０のグラフから明らかなとおり、硫黄酸化細菌の処理性能は処理温度に依存すること、また、脱窒素処理の最適温度は３５℃付近にあり、処理温度が３５℃を超えると処理性能が急激に低下すること、２０℃以下では処理性能が低下する傾向が認められた。
従って、硫黄脱窒法による硝酸性窒素の除去において、安定な処理水質を得るためには、処理温度を２０〜４０℃に維持することが好ましいことが分かる。硫黄脱窒法は発熱を伴わないので、混合循環槽の冷却は特に考慮する必要はないが、２０℃以下とならないように加温することが望ましいことが分かる。
【００５２】
実施例３〔ホウレンソウ養液栽培施設でのフィールド試験〕
図８に示す如き装置をホウレンソウ養液栽培施設に設置し、養液栽培廃水の実排水を使用して約５０日間、下記の条件下で硫黄酸化細菌による硝酸性窒素の除去処理を実施した。脱窒素された処理水は混合循環槽２からオーバーフローで放流した。混合循環槽２の温度は制御せず、成り行きとした。
【００５３】
〔処理条件〕
（１）原水：窒素濃度　１７２ｍｇ／Ｌ、ｐＨ６．３
（２）混合循環槽２：２２〜３０℃、液量：２８０Ｌ
（３）生物ろ過塔３：石灰硫黄脱窒材（実施例１に同じ）４０Ｌ充填
（４）原水供給：２００Ｌ／日
【００５４】
上記の処理条件の下、約５０日間運転を行った結果、処理水の残存窒素濃度は２〜１３ｍｇ／Ｌ、ｐＨ６．３〜６．８と良好であった。
混合循環槽２の温度制御は行わなかったが、装置を施設内に設置したため、実施時期が１〜３月の冬季にもかかわらず、２０〜３０℃以上に維持された。
【００５５】
【発明の効果】
請求項１に係る本発明によれば、水中の硝酸性窒素を硫黄酸化細菌により除去するにあたり、有機性の水素供与体を使用せず、嫌気処理を行う必要がなく、また脱窒素系内に窒素ガスを滞留させることなく、しかも高濃度の硝酸性窒素含有排水を処理することができる。
【００５６】
請求項２に係る本発明によれば、原水を混合循環槽に供給するにあたり、生物ろ過塔に対する容積負荷を制御して前記混合循環槽に供給することにより、前記混合循環槽における硝酸イオン濃度を０〜１００ｍｇ／Ｌに維持することができ、高濃度の硝酸性窒素含有排水が生物ろ過塔に直接供給されて硫黄酸化細菌の脱窒性能が抑制されることがないので、より高濃度の硝酸性窒素含有排水の処理を行うことができる。
【００５７】
請求項３に係る本発明によれば、混合循環槽における温度を２０〜４０℃に維持するように制御することにより、硫黄酸化細菌の脱窒素処理性能の低下が防止されるので、より高濃度の硝酸性窒素含有排水の処理を行うことができる。
【００５８】
また、請求項４に係る本発明によれば、水中の硝酸性窒素を硫黄酸化細菌により除去するにあたり、有機性の水素供与体を使用せず、嫌気処理を行う必要がなく、また脱窒素系内に窒素ガスを滞留させることなく、しかも高濃度の硝酸性窒素含有排水を処理することのできる装置が提供される。
【００５９】
さらに、請求項５に係る本発明によれば、加温器と、温度測定器と、前記温度測定器により測定された温度により前記加温器をＯＮ／ＯＦＦさせる制御手段とを備えることにより、混合循環槽における温度を１０〜４０℃に維持するように制御することが可能となり、硫黄酸化細菌の脱窒素処理性能の低下が防止されるので、より高濃度の硝酸性窒素含有排水の処理を行うことができる装置を提供できる。
【図面の簡単な説明】
【図１】原水窒素濃度が４００ｍｇ／Ｌの排水を処理水窒素濃度２０ｍｇ／Ｌ或いは１００ｍｇ／Ｌまで処理する場合の必要循環回数を示したグラフである。
【図２】実施例１で用いた流加方式（半連続方式）の実験装置を示す説明図である。
【図３】実施例１に示す流加方式（半連続方式）の実験装置で処理したときの容積負荷と処理水の残存窒素濃度との関係を示したグラフである。
【図４】実施例２で用いた連続方式の実験装置を示す説明図である。
【図５】図４に示す連続方式の実験装置で処理したときの３５℃における容積負荷と処理水の残存窒素濃度との関係を示したグラフである。
【図６】請求項４に係る本発明の装置の一態様を示すフローシートである。
【図７】請求項４に係る本発明の装置の他の態様を示すフローシートである。
【図８】請求項５に係る本発明の装置の一態様を示すフローシートである。
【図９】実施例２（図４）に示す連続方式の実験装置で処理したときの処理水の残存硝酸濃度と生産亜硝酸濃度との関係を示すグラフである。
【図１０】実施例２（図４）に示す連続方式の実験装置で処理したときの処理温度と処理水の窒素濃度が１０ｍｇ／Ｌ以下となる最適容積負荷との関係を示すグラフである。
【符号の説明】
１　原水槽
２　混合循環槽
３　生物ろ過塔
４　循環ポンプ
５　加温器
６　温度測定器（温度センサ）
７　制御手段
８ａ　循環ライン（入り）
８ｂ　循環ライン（戻り）
９　戻りライン（撹拌）
１０　処理水
１１　原水供給ポンプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for removing nitrate nitrogen contained in water.
[0002]
[Prior art]
In water bodies such as rivers and seas, water pollution due to eutrophication caused by nitrogen and phosphorus flowing into these closed water bodies progresses, and various phytoplankton and algae proliferate and originate from these organisms. Toxic substances and odorous substances have become a major social problem. For industrial wastewater discharged into lakes and marshes, inner bays and inland seas, drainage standards have already been applied from the viewpoint of preventing eutrophication.
[0003]
In February 1999, "Nitrate nitrogen and nitrite nitrogen" were added to the items subject to environmental standards related to the protection of human health. In February 2000, the report of the Central Environment Council, "Fifth Water Quality Control In the "How should be?", It is included that the total amount should be regulated in order to reduce the pollutant load of nitrogen and phosphorus in designated water areas with the target year being 2004. In response to this report, the drainage standard of the Water Pollution Control Law was amended in June 2001, stating that "a liter of ammonia nitrogen multiplied by 0.4, a total amount of nitrite nitrogen and nitrate nitrogen of 100 Milligrams "and regulations have been tightened. In addition, for three years after the enforcement, provisional effluent standards have been set as tentative standard values for each type of industry, but it is required to implement reduction measures in the meantime.
[0004]
The most widely used method for removing nitrogen in wastewater is to oxidize ammonia nitrogen to nitrous acid or nitric acid, and then reduce these oxidized nitrogen to remove it as nitrogen gas. Nitrification and denitrification. The reduction reaction of nitrous acid or nitric acid in the denitrification step requires an organic hydrogen donor such as methanol (a substrate that can be used by denitrifying bacteria for growth).
[0005]
This method of denitrification with such a denitrifying bacterium is often used as a tertiary treatment of industrial wastewater, but requires the addition of an organic hydrogen donor such as methanol, and is generally equivalent or more (about 1. (Approximately 5 times) methanol is added, so that part of the methanol remains, which may increase the COD and BOD of the discharge water.
Therefore, in this method, usually, it is necessary to further install an aeration tank at a later stage to perform biological treatment, and thus there is a problem that an installation space is increased.
Further, in this method, as described above, since an organic hydrogen donor such as methanol is required to be added, the running cost is increased, and management such as replenishment of a chemical solution is troublesome.
In addition, methanol has high volatility, is easily flammable, and has high toxicity. For this reason, there is a problem that fire safety equipment and safety measures for workers are required.
[0006]
There is also a treatment method that uses organic matter contained in wastewater as a hydrogen donor for the denitrification reaction (edited by the Japan Federation of Machinery Industries: Research and research report on technology to prevent eutrophication in closed water areas, "Nitrogen in 1997 And rational processing techniques for phosphorus ", 109-201, 1998). It does not require the addition of methanol or the like, but can only be applied to wastewater containing organic matter.
[0007]
On the other hand, a denitrification method that does not require an organic hydrogen donor by an autotrophic sulfur-oxidizing bacterium using sulfur or a sulfur compound has been proposed (Hashimoto, S. et al .; 14th Sewerage Study Group, 1977) It has been reported that the rate of denitrification by nitrifying bacteria is comparable to that of heterotrophic denitrifying bacteria using organic substances as electron donors. Further, when a simple sulfur was used as an electron donor in a continuous denitrification test using sulfur acclimated activated sludge under anaerobic conditions, 1.3 mg NO 3 -N / mg SS · day, denitrification rate of activated sludge (0.6 mg NO 3 -N / mg SS · day) (Hashimoto's recommendation; water and wastewater, 31, 283-293, 1989).
[0008]
In addition, an example in which sulfur denitrifying bacteria are used for wastewater treatment containing nitrogen compounds, sulfur compounds and nitrogen-sulfur compounds (Japanese Patent Publication No. 62-56798), sulfur and marble (calcium carbonate) are added to sludge, There is an example of simultaneous removal of nitrogen and phosphorus in wastewater by a sulfur supplemented aerobic-anaerobic activated sludge method (Japanese Patent Publication No. 4-11919).
In these methods, an extremely inexpensive wastewater denitrification treatment can be expected by using inexpensive powder or granular sulfur for the electron donor.
Further, a feature of the sulfur denitrification method is that any of the methods utilizes a denitrification reaction using sulfur of a sulfur-oxidizing bacterium as an electron donor under anaerobic conditions without oxygen.
[0009]
By the way, the sulfur denitrification rate is equivalent to the denitrification rate by nitrate-reducing bacteria requiring addition of methanol. It may be referred to as “SV”.) At about 0.2 / hr], sufficient treatment cannot be performed unless water is passed and the contact time is considerably long, and as a result, the apparatus becomes large, and the installation space is large. There was a drawback that it became large.
[0010]
In addition, since the flow velocity must be reduced, the generated nitrogen gas stays in the bed and hinders the contact between the water to be treated and the carrier containing sulfur, and as a result, the denitrification efficiency decreases and the stability is reduced. However, there is a problem that such processing cannot be performed.
That is, in the above-mentioned conventional nitrate nitrogen removal method using sulfur oxidizing bacteria, wastewater containing high concentration of nitrate nitrogen (nitrogen concentration: several hundred to several thousand mg / L) such as nutrient solution cultivation wastewater or metal plating wastewater is treated. The size of the equipment is large, the installation space is large, the construction cost is high, and the flow velocity has to be slowed down.The generated nitrogen gas stays in the filter bed, and There was a problem that the contact was hindered, and as a result, the denitrification efficiency was reduced and stable treatment could not be performed. In addition, since oxygen is disliked, in order to obtain high denitrification efficiency, it is necessary to maintain an anaerobic state such as blowing in nitrogen gas for deoxygenation, and there is a problem that it is necessary to respond to equipment design and operation management. .
[0011]
[Problems to be solved by the invention]
The present invention has solved all of the problems of the above-mentioned prior art, and does not require the use of an organic hydrogen donor, does not require anaerobic treatment, and eliminates nitrate nitrogen in water. It is an object of the present invention to provide a continuous treatment type denitrification method and apparatus in which nitrogen gas does not stay in a nitrogen system and can be applied to wastewater containing high-concentration nitrate nitrogen.
[0012]
That is, the first object of the present invention is to use an organic hydrogen donor such as methanol, do not need to perform anaerobic treatment, and use nitrate nitrogen in water in which nitrogen gas does not stay in the denitrification system. The present invention provides a method and apparatus for removing carbon.
[0013]
Further, a second object of the present invention is to provide a method and an apparatus for removing nitrate nitrogen in water by a continuous treatment method applicable to wastewater containing high concentration of nitrate nitrogen.
[0014]
[Means for Solving the Problems]
In order to solve the first problem, the present inventors have conducted intensive studies on a denitrification method using a fixed-bed biofiltration method using sulfur-oxidizing bacteria. In the method of processing while circulating in an upward flow at high speed, in order to obtain a constant processing quality, it has been found that the water flow rate and the number of circulations are proportional to SV5 / hr or more.
[0015]
FIG. 1 is a graph showing the required number of circulations when treating wastewater with a raw water nitrogen concentration of 400 mg / L to a treated water nitrogen concentration of 20 mg / L or 100 mg / L by the above method.
According to FIG. 1, for example, when SV10 / hr and SV20 / hr are compared, when flowing at twice the speed (SV20 / hr) of SV10 / hr, the nitrogen concentration of treated water is 20 mg / L and 100 mg / L. It is evident that in each of the cases where the processing is performed up to the maximum, the number of circulation times is about twice that in the case where the flow is performed at SV10 / hr.
[0016]
In other words, instead of increasing the water flow rate, if the number of circulations is increased by that amount, and if the same contact time for the sulfur oxidizing bacteria to come into contact with the liquid to be treated can be assured, the same level of treated water Was found to be able to be obtained.
Therefore, since the height of the filter medium can be considerably increased to about 1,000 mm, water can be passed through a filtration tower filled with a high filter medium, so that the apparatus can be made compact.
In addition, at this time, the nitrogen gas generated by the reduction of nitric acid can be expelled to the upper part of the filter bed by flowing water at high speed in the upward flow, thereby preventing the denitrification efficiency from decreasing due to the retention of nitrogen gas. I knew that I could do that.
Further, in a biofilm mainly composed of sulfur oxidizing bacteria formed on a sulfur carrier, the region attached to the carrier becomes anaerobic, and thus it is considered that sulfur denitrification can be performed efficiently.
[0017]
Next, in order to solve the second problem of the present invention, the present inventors diligently studied a method of supplying a high-concentration nitrate-nitrogen-containing wastewater to a biological filtration tower. As a result, when high-concentration raw water is directly supplied to the biological filtration tower, the denitrification performance of sulfur-oxidizing bacteria is suppressed.Therefore, a mixing circulation tank is provided before the biological filtration tower. Mix the circulating liquid from the biological filtration tower, circulate the mixed water to be processed through the mixing circulation tank and the biological filtration tower, and control the volume load on the biological filtration tower when supplying raw water to the mixing circulation tank. By maintaining the nitrate ion concentration in the mixing and circulating tank to a level that does not affect the denitrification performance (nitrate ion concentration 0 to 100 mg / L), the continuous type of water that can be used for wastewater containing high concentration nitrate nitrogen A method for removing nitrate nitrogen was found.
[0018]
FIG. 3 shows, as shown in Example 1 to be described later, using the experimental apparatus of the fed-batch system (semi-continuous system) shown in FIG. 2 and changing the volume load of wastewater with a raw water nitrogen concentration of 400 mg / L, It is continuously supplied to a mixing and circulating tank (initial liquid volume: 20 L, nitrogen concentration: 2 mg / L, temperature: 30 ° C.) until the volume reaches 80 L, and is circulated in a biological filtration tower filled with a sulfur carrier at an upward flow of SV15 / hr. 5 is a graph showing the relationship between the volume load and the residual nitrogen concentration when the treatment is performed.
From FIG. 3, it is clear that in the case of the fed-batch system (semi-continuous system), a stable treated water quality with a treated water nitrogen concentration of 20 mg / L or less can be obtained up to a volume load of 1,700 mg N / L carrier / day. Also, in this case, when the volume load increases more than 1,700 mg N / L carrier / day, the residual nitrogen concentration sharply increases, so that the wastewater containing high concentration of nitric acid can suppress the denitrification performance of sulfur oxidizing bacteria. I understand.
[0019]
FIG. 5 shows a mixing and circulation tank (liquid volume) using the continuous type experimental apparatus shown in FIG. 4 and varying the volume load of wastewater having a raw water nitrogen concentration of 400 mg / L, as shown in Example 2 described later. : 40 L, nitrogen concentration: 2 mg / L, temperature 35 ° C.), and the volume load and residual nitrogen concentration when circulating at a flow rate of 15 / hr in a biological filtration tower filled with a sulfur carrier at an SV of 15 / hr for treatment. 6 is a graph showing a relationship with the graph.
It is clear from FIG. 5 that in the case of the continuous system, at a temperature of 35 ° C., a stable treated water quality of a treated water nitrogen concentration of 20 mg / L or less can be obtained up to a volume load of about 3,000 mg N / L carrier / day. Therefore, as a standard for controlling the volume load, it is preferable to supply the biofiltration tower with a volume load of 100 to 3,500 mg N / L carrier / day.
The present invention has been completed based on these findings.
[0020]
That is, in the present invention according to claim 1, in removing nitrate nitrogen in water by sulfur oxidizing bacteria, in a mixing circulation tank, raw water and a sulfur carrier are filled and sulfur oxidizing bacteria are mainly contained on the sulfur carrier. The circulating liquid from the biological filtration tower on which a biofilm is formed is mixed and circulated and passed from the lower part of the biological filtration tower at a space velocity of 5 to 100 / hr in an upward flow. A method for removing nitrate nitrogen from water in a continuous treatment method, wherein the method comprises contacting the biofilm mainly composed of the sulfur oxidizing bacteria to be formed, reducing nitric acid to nitrogen, and performing a denitrification treatment. Is what you do.
[0021]
The present invention according to claim 2 is characterized in that when supplying raw water to the mixing and circulating tank, the volume load on the biological filtration tower is controlled to maintain the nitrate ion concentration in the mixing and circulating tank at 0 to 100 mg / L. It is intended to provide a method for removing nitrate nitrogen in water according to claim 1.
[0022]
The present invention according to claim 3 provides a method for removing nitrate nitrogen in water according to claim 1, characterized in that the temperature in the mixing and circulating tank is controlled to be maintained at 20 to 40 ° C. is there.
[0023]
The present invention according to claim 4 is an apparatus for removing nitrate nitrogen in water by sulfur oxidizing bacteria, comprising a biological filtration tower filled with a sulfur carrier, raw water and a circulating liquid from the biological filtration tower. And a circulating pump for circulating the water to be treated in the mixing and circulating tank in an upward flow at a space velocity of 5 to 100 / hr through the biological filtration tower, and loading the raw water on the biological filtration tower And a raw water supply pump for supplying the raw water to the mixing and circulating tank while controlling the water supply to the mixing and circulation tank.
[0024]
The present invention according to claim 5 is an apparatus for removing nitrate nitrogen in water by sulfur oxidizing bacteria, a biological filtration tower filled with a sulfur carrier, raw water and circulating liquid from the biological filtration tower. And a circulating pump for circulating the water to be treated in the mixing and circulating tank in an upward flow at a space velocity of 5 to 100 / hr through the biological filtration tower, and loading the raw water on the biological filtration tower A raw water supply pump for controlling the mixing and circulation tank to supply the raw water to the mixing and circulation tank, a heating device, a temperature measurement device, and a temperature control unit for turning on / off the heating device based on the temperature measured by the temperature measurement device; And a device for continuously removing nitrate nitrogen in water.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
Here, since the method of the present invention according to claims 1 to 3 is suitably implemented by the apparatus of the present invention according to claims 4 to 5, the method of the present invention according to claims 1 to 3 will be described below. This will be described in detail with reference to the apparatus of the present invention according to claim 4 shown in FIGS. 6 and 7, and the apparatus of the present invention according to claim 5 shown in FIG.
FIG. 6 is a flow sheet showing one embodiment of the apparatus of the present invention according to claim 4. FIG. 7 is a flow sheet showing another embodiment of the apparatus according to the fourth aspect of the present invention. FIG. 8 is a flow sheet showing one embodiment of the apparatus according to the present invention.
[0026]
FIG. 6 is a flow sheet showing one embodiment of an apparatus suitable for carrying out the method of the present invention according to claim 1 (the apparatus of the present invention according to claim 4), wherein nitrate nitrogen in water is removed by sulfur-oxidizing bacteria. A biological filtration tower 3 filled with a sulfur carrier, a mixing circulation tank 2 for mixing raw water and a circulating liquid from the biological filtration tower 3, and a treatment target of the mixing circulation tank 2. A circulating pump 4 for circulating water in the upward direction at a space velocity of 5 to 100 / hr through the biological filtration tower 3, and supplying raw water to the mixing and circulating tank 2 by controlling a volume load on the biological filtration tower 3; And a raw water supply pump 11.
FIG. 7 is a flow sheet showing an apparatus (another embodiment) in which the raw water tank 1 for storing raw water is installed in the apparatus shown in FIG.
[0027]
The biological filtration tower 3 that performs the filtration treatment of the wastewater is filled with a sulfur carrier. As the sulfur carrier, those generally used may be used as long as they contain sulfur. For example, in the case of using sulfur, commercially available sulfur particles and solid carbonate for neutralization ( A combination of coral sand and the like may be used. If a sulfur mixture obtained by mixing carbonate with sulfur (for example, a lime sulfur denitrifying material manufactured by Nichetsu Co., Ltd., particle size: 5 to 20 mm), there is no need to refill the neutralizing carbonate. As such a sulfur carrier, a carrier to which a known sulfur-oxidizing bacterium is adhered is usually used. The amount of filter media can be varied according to the amount of wastewater to be treated. The particle size of the sulfur carrier is not particularly limited as long as it does not flow out, but is preferably 1 to 25 mm, more preferably 5 to 20 mm.
The biological filtration tower 3 is a fixed bed type reaction tank in which a packed bed is formed with a sulfur carrier.
In the biological filtration tower 3, a sulfur carrier is filled therein, and a biofilm mainly composed of the sulfur-oxidizing bacteria is formed on the sulfur carrier.
[0028]
In the method of the present invention according to any one of claims 1 to 3, in the mixing circulation tank 2, a biological filtration tower is formed by filling raw water and a sulfur carrier to form a biofilm mainly composed of sulfur-oxidizing bacteria on the sulfur carrier. 3. Mix with the circulating fluid from 3.
Therefore, the mixing and circulating tank 2 has a function of mixing the raw water and the circulating liquid from the biological filtration tower 3.
By mixing the raw water and the circulating liquid from the biological filtration tower 3 in the mixing circulation tank 2, the nitrate ion concentration can be maintained to the extent that the denitrification performance in the biological filtration tower 3 is not affected. The method of the present invention according to 1 to 3 can also be applied to wastewater containing high concentration of nitrate nitrogen.
[0029]
The amount of raw water supplied to the mixing and circulating tank 2 is primarily determined by the processing capacity of the biological filtration tower 3, and further includes the raw water nitrogen concentration, the particle size of the sulfur carrier, the processing temperature, and the target nitrogen of the treated water. Although it varies depending on the concentration, the size of the mixing circulation tank 2, the SV, etc., as a guide, the volume load on the biological filtration tower 3 is 100 to 3,500 mg N / L carrier / day, preferably 300 to 3,000 mg N / L carrier.・ Supply on a daily basis.
[0030]
In addition, the temperature of the mixing and circulating tank 2 is generally maintained at 10 to 40 ° C., preferably 20 to 40 ° C., more preferably 25 to 37 ° C., as described in claim 3, in consideration of the denitrification efficiency and the like. Is controlled to
Here, if the temperature in the mixing and circulating tank 2 deviates from the above range, the denitrification performance of the sulfur-oxidizing bacteria is undesirably reduced. The optimum temperature for the denitrification performance of the sulfur-oxidizing bacteria is around 35 ° C.
[0031]
In order to control the temperature of the mixing and circulating tank 2 within the above-described range, as described in claim 5, as shown in FIG. 8, a heater 5, a temperature measuring device (temperature sensor) 6, and the temperature measurement And a temperature control means 7 for turning on / off the heater 5 based on the temperature measured by the heater 6. As the heating device 5, the temperature measuring device (temperature sensor) 6, and the temperature control means 7, those generally used can be used.
[0032]
On the basis of the temperature measured by the temperature measuring device (temperature sensor) 6, the heater 5 is turned on / off by the temperature control means 7, and the temperature of the mixing and circulating tank 2 is set in the above-mentioned range, preferably in claim 2. Control over the range.
[0033]
Next, in the method of the present invention according to claims 1 to 3, raw water and the circulating liquid from the biological filtration tower 3 are mixed in the mixing circulation tank 2. In FIGS. 6 to 8, the circulating liquid from the biological filtration tower 3 is sent to the mixing and circulating tank 2 by a circulating line (return) indicated by reference numeral 8 b.
[0034]
Further, in the method of the present invention according to claims 1 to 3, after mixing the raw water and the circulating liquid from the biological filtration tower 3 in the mixing and circulating tank 2 as described above, the mixed liquid (to be treated) Water) is circulated and passed from the lower part of the biological filtration tower 3 in an upward flow at an SV of 5 to 100 / hr, and is brought into contact with the biofilm mainly composed of the sulfur-oxidizing bacteria forming the biological filtration tower 3, The nitric acid is reduced to nitrogen for denitrification.
[0035]
The circulation pump 4 has a function of circulating the water to be treated in the mixing and circulating tank 2 in an upward flow to the biological filtration tower 3, and circulates the water to be treated at a high speed of SV5 to 100 / hr. Have the ability to
In addition, it is preferable to keep the pH of the water to be treated in the range of 6.5 to 8.5 from the viewpoint of increasing the activity of the sulfur-oxidizing bacteria.
[0036]
Here, the circulation pump 4 circulates the water to be treated in the mixing and circulating tank 2 in an upward flow to the biological filtration tower 3, thereby assisting in the rise of the nitrogen gas, and the nitrogen gas stays in the filter medium to be removed. There is no risk of lowering the nitrogen efficiency. If it is not upward flow, such an objective cannot be achieved.
It is necessary to circulate the water to be treated at a SV of 5 to 100 / hr, preferably 10 to 30 / hr, more preferably 10 to 20 / hr. If the SV of the circulating water is less than 5 / hr, the removal efficiency is inferior, probably because the nitrogen gas is difficult to escape from the filter medium. On the other hand, when the SV of the circulating water exceeds 100 / hr, the pressure loss of the filter medium increases, so that the pump must be considerably increased, which is wasteful.
[0037]
As described above, in the method of the present invention according to claims 1 to 3, the mixed solution (water to be treated) is repeatedly circulated and passed from the lower portion of the biological filtration tower 3 in an upward flow at SV 5 to 100 / hr, The biological filtration tower 3 is brought into contact with the biofilm mainly composed of the sulfur-oxidizing bacteria. Thereby, nitric acid is reduced to nitrogen and denitrification treatment is performed.
[0038]
As the raw water supply pump 11, a generally used pump can be used as long as it can supply raw water to the mixing and circulating tank 1 with a volume load of 100 to 3,500 mg N / L carrier / day. Good, no restrictions.
In supplying the raw water to the mixing and circulating tank 2, the nitrate ion concentration in the mixing and circulating tank 2 is reduced to a low concentration by controlling the volume load on the biological filtration tower 3 and supplying the raw water to the mixing and circulating tank 2. Since the concentration can be maintained at 0 to 100 mg / L, more preferably 0.1 to 50 mg / L, the wastewater containing high concentration of nitrate nitrogen is directly supplied to the biological filtration tower 3 to improve the denitrification performance of the sulfur-oxidizing bacteria. There is no danger of being suppressed.
[0039]
6 to 8, reference numeral 8a denotes a circulation line (enter), reference numeral 8b denotes a circulation line (return), reference numeral 9 denotes a return line (stirring), and reference numeral 10 denotes treated water.
[0040]
In the apparatus of the present invention according to claims 4 and 5 shown in FIGS. 6 to 8, the biological filtration tower 3 and the mixing and circulating tank 2 are circulated by the circulating pump 4 into the circulating line (entering) 8 a and the circulating line ( (Return) 8b and a return line (stirring) 9 so that the circulating liquid from the biological filtration tower 3 is sent to the mixing and circulating tank 2 by the circulating line (return) 8b. The treated water is sent to the biological filtration tower 3 through the circulation line (entering) 8a.
In the apparatus of the present invention according to claims 4 and 5, an air release valve (not shown) for releasing nitrogen gas staying in the biological filtration tower 3 may be provided. Further, if necessary, a means (not shown) for discharging the drain from the biological filtration tower 3 may be provided.
[0041]
In the present invention according to claims 1 to 3, raw water and circulating water from the biological filtration tower 3 filled with a sulfur carrier are mixed in the mixing and circulating tank 2 in this way, and circulated and passed through the lower part of the biological filtration tower 3. The water is brought into contact with a biofilm mainly composed of sulfur oxidizing bacteria forming the biological filtration tower 3, and nitric acid is reduced to nitrogen to perform a denitrification treatment, and nitrate nitrogen in the water is removed by the sulfur oxidizing bacteria.
[0042]
The present invention has the above configuration.
INDUSTRIAL APPLICABILITY The present invention can be applied to the removal of nitrate nitrogen in various wastewaters including high-concentration nitrate nitrogen-containing wastewater such as hydroponic wastewater and metal plating wastewater.
[0043]
【Example】
Examples of the present invention will be described below, but the present invention is not limited thereto.
[0044]
Example 1 [Denitrification treatment by fed-batch method (semi-continuous method)]
Biological filtration filled with a raw water tank 1, a mixing circulation tank 2 (initial liquid volume: 20 L, nitrogen concentration: 2 mg / L), and a lime sulfur denitrifying agent (Nichetz, particle size: 5 to 20 mm) as a sulfur carrier The apparatus shown in FIG. 8 comprising the tower 3 and having the principle shown in FIG. 2 (raw water tank capacity: 200 L, mixing and circulating tank capacity: 100 L, biological filtration tower capacity: φ100 × H1, 100 mm) is used. The model wastewater described in the table was continuously supplied to the mixing and circulating tank 2 until it reached 80 L, and was circulated to the biological filtration tower 3 at an SV of 15 / hr. When the liquid volume in the mixing and circulating tank 2 reached 80 L, 60 L was discarded, and the volume load was changed again and examined (mixing and circulating tank temperature: 30 ° C.). A return line 9 was inserted after the circulation pump 4, and the mixing and circulation tank 2 was stirred and mixed using the discharge pressure.
FIG. 3 shows the time-dependent changes in the nitrogen concentration of the model wastewater subjected to the nitrate nitrogen removal treatment as described above.
[0045]
[Table 1]
Table 1 (model wastewater composition)
Figure 2004000861
[0046]
* Trace metal solution composition (per liter)
H 3 BO 4 30 g
MnSO 4 ・ H 2 O 20 g
ZnSO 4 ・ 7H 2 2.2 g of O
CuSO 4 ・ 5H 2 O 0.5g
Na 2 MoO 4 0.2g
H 2 SO 4 1 ml
[0047]
According to FIG. 3, it was found that when the volume load exceeded 1,700 mg N / L carrier / day, the residual nitrogen concentration sharply increased. This is considered to reflect that when the concentration of nitrate ions in the wastewater increases, the denitrification performance of sulfur-oxidizing bacteria is suppressed.
[0048]
Example 2 [Denitrification treatment by continuous method]
Biological filtration tower filled with raw water tank 1, mixing circulation tank 2 (initial liquid volume: 20 L, nitrogen concentration: 2 mg / L, temperature 30 ° C.), and lime sulfur denitrifying agent (same as in Example 1) as a sulfur carrier The apparatus shown in FIG. 8 consisting of 3 units and having the principle shown in FIG. 4 (raw water tank capacity: 200 L, mixed circulation tank liquid volume: 40 L, biological filtration tower capacity: φ100 × H1, 100 mm) was first described in Example 1. The model wastewater (described in Table 1) was continuously supplied from the raw water tank 1 to the mixing circulation tank 2 at a volume load of 500 mgN / L carrier / day from the raw water tank 1 and circulated to the biological filtration tower 3 at an SV of 15 / hr. When the liquid amount in the mixing and circulating tank 2 reaches 40 L, the system is switched to the continuous method. Thereafter, the liquid is drained by a pump to maintain the liquid amount in the mixing and circulating tank 2 at 40 L, and the temperature of the mixing and circulating tank 2 is increased by a heater. 5, the temperature was changed to 20 to 40 ° C., and the effect of the processing temperature when the volume load was changed was examined. The stirring and mixing of the mixing and circulating tank 2 was performed by using the return discharge pressure of the circulating pump 4 as in Example 1.
[0049]
FIG. 9 shows the relationship between the concentration of residual nitric acid and the concentration of produced nitrite when the volume load was varied at each temperature. The relationship between the treatment temperature and the optimal volume load at which the nitrogen concentration of the treated water was 10 mg / L or less was shown. FIG. 10 shows the relationship.
[0050]
As is clear from the graph of FIG. 9, it was recognized that nitrite ions rapidly accumulated when the concentration of the remaining nitrate ions exceeded 100 mg / L.
Further, when the nitrate ion concentration exceeds 400 mg / L, the generation of the nitrite ion concentration becomes flat, which is considered to be because the growth of the sulfur-oxidizing bacteria is suppressed by the nitrite ion.
In general, it is known that reduction of nitrate nitrogen by sulfur-oxidizing bacteria is limited by the reduction reaction after nitrous acid. The above results obtained by the present inventors have supported this.
Therefore, in removing nitrate nitrogen by the sulfur denitrification method, in order to obtain stable treated water quality, it is necessary to control the volume load so that nitrite ions do not accumulate.
[0051]
Furthermore, as is clear from the graph of FIG. 10, the treatment performance of the sulfur-oxidizing bacteria depends on the treatment temperature, and the optimum temperature of the denitrification treatment is around 35 ° C. Rapidly decreased, and at 20 ° C. or lower, the processing performance tended to decrease.
Therefore, it can be seen that in the removal of nitrate nitrogen by the sulfur denitrification method, it is preferable to maintain the treatment temperature at 20 to 40 ° C. in order to obtain stable treated water quality. Since the sulfur denitrification method does not generate heat, it is not necessary to particularly consider cooling of the mixing and circulating tank, but it is understood that it is desirable to heat the mixture so as not to be 20 ° C. or lower.
[0052]
Example 3 [Field test in spinach hydroponics facility]
The apparatus as shown in FIG. 8 was installed in a spinach nutrient solution cultivation facility, and the nitrate nitrogen removal treatment by sulfur oxidizing bacteria was carried out under the following conditions for about 50 days using actual drainage of the nutrient solution cultivation wastewater. The denitrified treated water was discharged from the mixing circulation tank 2 by overflow. The temperature of the mixing and circulating tank 2 was not controlled and was determined.
[0053]
[Processing conditions]
(1) Raw water: nitrogen concentration 172 mg / L, pH 6.3
(2) Mixing circulation tank 2: 22-30 ° C, liquid volume: 280 L
(3) Biological filtration tower 3: Lime sulfur denitrification material (same as in Example 1) 40L filling
(4) Raw water supply: 200 L / day
[0054]
As a result of operating for about 50 days under the above treatment conditions, the residual nitrogen concentration of the treated water was as good as 2 to 13 mg / L and pH 6.3 to 6.8.
Although the temperature of the mixing and circulating tank 2 was not controlled, the temperature was maintained at 20 to 30 ° C. or higher despite the winter season of January to March because the apparatus was installed in the facility.
[0055]
【The invention's effect】
According to the present invention according to claim 1, in removing nitrate nitrogen in water with sulfur oxidizing bacteria, it is not necessary to perform anaerobic treatment without using an organic hydrogen donor, and in the denitrification system. It is possible to treat wastewater containing high-concentration nitrate nitrogen without retaining nitrogen gas.
[0056]
According to the present invention according to claim 2, when supplying raw water to the mixing and circulating tank, by controlling the volume load on the biological filtration tower and supplying the raw water to the mixing and circulating tank, the nitrate ion concentration in the mixing and circulating tank is reduced. 0 to 100 mg / L, and high concentration nitrate nitrogen-containing wastewater is not supplied directly to the biological filtration tower, and the denitrification performance of sulfur oxidizing bacteria is not suppressed. The treatment of the wastewater containing nitrogen can be performed.
[0057]
According to the third aspect of the present invention, since the temperature in the mixing and circulating tank is controlled to be maintained at 20 to 40 ° C., a decrease in the denitrification treatment performance of the sulfur-oxidizing bacteria is prevented, so that a higher concentration can be achieved. Of wastewater containing nitrate nitrogen can be treated.
[0058]
According to the present invention, in removing nitrate nitrogen in water by sulfur oxidizing bacteria, an organic hydrogen donor is not used, anaerobic treatment is not required, and denitrification system is not required. There is provided an apparatus capable of treating high-concentration nitrate-nitrogen-containing wastewater without retaining nitrogen gas therein.
[0059]
Furthermore, according to the present invention according to claim 5, by including a heating device, a temperature measurement device, and a control unit that turns on / off the heating device based on the temperature measured by the temperature measurement device, It is possible to control the temperature in the mixing and circulating tank to be maintained at 10 to 40 ° C., and it is possible to prevent a decrease in the denitrification treatment performance of the sulfur oxidizing bacteria. An apparatus capable of performing the above can be provided.
[Brief description of the drawings]
FIG. 1 is a graph showing the required number of circulations when treating wastewater having a raw water nitrogen concentration of 400 mg / L to a treated water nitrogen concentration of 20 mg / L or 100 mg / L.
FIG. 2 is an explanatory view showing an experimental apparatus of a fed-batch system (semi-continuous system) used in Example 1.
FIG. 3 is a graph showing the relationship between the volume load and the residual nitrogen concentration of treated water when treated by the experimental apparatus of the fed-batch method (semi-continuous method) shown in Example 1.
FIG. 4 is an explanatory view showing a continuous-type experimental apparatus used in Example 2.
FIG. 5 is a graph showing the relationship between the volume load at 35 ° C. and the residual nitrogen concentration of treated water when treated with the continuous experimental apparatus shown in FIG. 4;
FIG. 6 is a flow sheet showing one embodiment of the apparatus of the present invention according to claim 4;
FIG. 7 is a flow sheet showing another embodiment of the apparatus of the present invention according to claim 4.
FIG. 8 is a flow sheet showing one embodiment of the apparatus of the present invention according to claim 5;
FIG. 9 is a graph showing the relationship between the concentration of residual nitric acid and the concentration of produced nitrite when treated with the continuous experimental apparatus shown in Example 2 (FIG. 4).
FIG. 10 is a graph showing the relationship between the processing temperature and the optimal volume load at which the nitrogen concentration of the processing water is 10 mg / L or less when the processing is performed by the continuous experimental apparatus shown in Example 2 (FIG. 4).
[Explanation of symbols]
1 Raw water tank
2 Mixing circulation tank
3 Biological filtration tower
4 Circulation pump
5 heater
6. Temperature measuring device (temperature sensor)
7 control means
8a Circulation line (entering)
8b Circulation line (return)
9 Return line (stirring)
10 treated water
11 Raw water supply pump

Claims (5)

水中の硝酸性窒素を硫黄酸化細菌により除去するにあたり、混合循環槽において、原水と、硫黄担体を充填させて前記硫黄担体上に硫黄酸化細菌を主体とする生物膜を形成させた生物ろ過塔からの循環液とを混合し、前記生物ろ過塔下部より、上向流にて空間速度５〜１００／ｈｒで循環・通水し、前記生物ろ過塔を形成する、前記硫黄酸化細菌を主体とする前記生物膜に接触させ、硝酸を窒素に還元して脱窒素処理を行うことを特徴とする、連続処理方式の水中の硝酸性窒素の除去方法。In removing nitrate nitrogen in water by sulfur oxidizing bacteria, in a mixing circulation tank, from a biological filtration tower in which raw water and a sulfur carrier are filled to form a biofilm mainly composed of sulfur oxidizing bacteria on the sulfur carrier. Circulating fluid from the lower part of the biological filtration tower, and circulating and passing water at a space velocity of 5 to 100 / hr from the lower part of the biological filtration tower to form the biological filtration tower. A method for removing nitrate nitrogen from water in a continuous treatment method, comprising contacting the biofilm with nitric acid, reducing nitric acid to nitrogen, and performing a denitrification treatment. 原水を混合循環槽へ供給するにあたり、生物ろ過塔に対する容積負荷を制御して、前記混合循環槽における硝酸イオン濃度を０〜１００ｍｇ／Ｌに維持することを特徴とする、請求項１記載の水中の硝酸性窒素の除去方法。2. The water according to claim 1, wherein when supplying the raw water to the mixing circulation tank, the volume load on the biological filtration tower is controlled to maintain the nitrate ion concentration in the mixing circulation tank at 0 to 100 mg / L. 3. Method of removing nitrate nitrogen. 混合循環槽における温度を２０〜４０℃に維持するように制御することを特徴とする、請求項１記載の水中の硝酸性窒素の除去方法。The method for removing nitrate nitrogen in water according to claim 1, wherein the temperature in the mixing and circulating tank is controlled to be maintained at 20 to 40C. 水中の硝酸性窒素を硫黄酸化細菌により除去するための装置であって、硫黄担体を充填させた生物ろ過塔と、原水と前記生物ろ過塔からの循環液とを混合する混合循環槽と、前記混合循環槽の被処理水を上向流にて空間速度５〜１００／ｈｒで前記生物ろ過塔に循環させる循環ポンプと、原水を前記生物ろ過塔に対する容積負荷を制御して前記混合循環槽に供給する原水供給ポンプと、を備えたことを特徴とする、水中の硝酸性窒素の連続除去装置。An apparatus for removing nitrate nitrogen in water by sulfur-oxidizing bacteria, a biological filtration tower filled with a sulfur carrier, a mixing circulation tank for mixing raw water and a circulating fluid from the biological filtration tower, A circulating pump that circulates the water to be treated in the mixing circulation tank in an upward flow at a space velocity of 5 to 100 / hr to the biological filtration tower, and controls a volume load of the raw water to the biological filtration tower to the mixing circulation tank. An apparatus for continuously removing nitrate nitrogen in water, comprising: a raw water supply pump for supplying water. 水中の硝酸性窒素を硫黄酸化細菌により除去するための装置であって、硫黄担体を充填させた生物ろ過塔と、原水と前記生物ろ過塔からの循環液とを混合する混合循環槽と、前記混合循環槽の被処理水を上向流にて空間速度５〜１００／ｈｒで前記生物ろ過塔に循環させる循環ポンプと、原水を前記生物ろ過塔に対する容積負荷を制御して前記混合循環槽に供給する原水供給ポンプと、加温器と、温度測定器と、前記温度測定器により測定された温度により前記加温器をＯＮ／ＯＦＦさせる温度制御手段と、を備えたことを特徴とする、水中の硝酸性窒素の連続除去装置。An apparatus for removing nitrate nitrogen in water by sulfur-oxidizing bacteria, a biological filtration tower filled with a sulfur carrier, a mixing circulation tank for mixing raw water and a circulating fluid from the biological filtration tower, A circulating pump that circulates the water to be treated in the mixing circulation tank in an upward flow at a space velocity of 5 to 100 / hr to the biological filtration tower, and controls a volume load of the raw water to the biological filtration tower to the mixing circulation tank. A raw water supply pump for supplying, a warmer, a temperature measuring device, and a temperature control unit for turning on / off the warming device based on a temperature measured by the temperature measuring device, Continuous removal device for nitrate nitrogen in water.
JP2002160953A 2002-06-03 2002-06-03 Method and apparatus for removing nitrate nitrogen in water Pending JP2004000861A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006272161A (en) * 2005-03-29 2006-10-12 Nippon Steel Chem Co Ltd Method and apparatus for treating nitrate nitrogen-containing waste water
JP2015512771A (en) * 2012-07-10 2015-04-30 ソリュックス ライティング フィクスチャＳｏｌｕｘ Ｌｉｇｈｔｉｎｇ Ｆｉｘｔｕｒｅ Method for removing nitrates from solutions containing salt components
CN109368785A (en) * 2018-11-05 2019-02-22 宁波水思清环境科技有限公司 A kind of denitrification denitrogenation microbiologic population and its application
CN111778235A (en) * 2020-07-20 2020-10-16 东华理工大学 Solidifying and continuous culture method of microorganism

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006272161A (en) * 2005-03-29 2006-10-12 Nippon Steel Chem Co Ltd Method and apparatus for treating nitrate nitrogen-containing waste water
JP2015512771A (en) * 2012-07-10 2015-04-30 ソリュックス ライティング フィクスチャＳｏｌｕｘ Ｌｉｇｈｔｉｎｇ Ｆｉｘｔｕｒｅ Method for removing nitrates from solutions containing salt components
CN109368785A (en) * 2018-11-05 2019-02-22 宁波水思清环境科技有限公司 A kind of denitrification denitrogenation microbiologic population and its application
CN111778235A (en) * 2020-07-20 2020-10-16 东华理工大学 Solidifying and continuous culture method of microorganism

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