JP2004057924A - Nitrogen treatment method and nitrogen treatment system - Google Patents

Nitrogen treatment method and nitrogen treatment system Download PDF

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JP2004057924A
JP2004057924A JP2002219435A JP2002219435A JP2004057924A JP 2004057924 A JP2004057924 A JP 2004057924A JP 2002219435 A JP2002219435 A JP 2002219435A JP 2002219435 A JP2002219435 A JP 2002219435A JP 2004057924 A JP2004057924 A JP 2004057924A
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water
treated
nitrogen
tank
treatment
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JP4039910B2 (en
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Motoki Kawachi
河内　基樹
Tomohito Koizumi
小泉　友人
Takeshi Rakuma
樂間　毅
Naoki Ko
広　直樹
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Sanyo Electric Co Ltd
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Sanyo Electric Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitrogen treatment method and nitrogen treatment system for efficiently treating a water to be treated which contains nitrogen compounds of contaminated ground water etc. <P>SOLUTION: The nitrogen treatment system S, to which the nitrogen treatment method is applied, treats the nitrogen compounds in the water to be treated and is provided with at least a pair of electrodes 5 which are at least partly immersed in the water to be treated and function to treat the water to be treated by an electrochemical method and a dilution vessel 11 as a dilution treatment means for lowering the concentration of the nitrogen compounds in the water to be treated by diluting the water to be treated. The system treats the water to be treated by the electrochemical method after lowering the concentration of the nitrogen compounds in the water to be treated by diluting the water to be treated. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、電気化学的手法により被処理水中の窒素化合物を処理する窒素処理方法及び窒素処理システムに関する。
【０００２】
【従来の技術】
近年、湖沼、内湾等の閉鎖性水域において、生活排水や産業排水中の窒素やリンなどの栄養塩類流入が原因と考えられる赤潮、アオコの異常発生が大きな社会問題となっている。このため、行政指導の下で大規模集中汚染源に対しては活性汚泥法などによる排水処理を行われている。閉鎖系水域への排水の水質基準は、一日当たりの排水量が５０トン以上と規模の大きな事業場に対する規制があり、この排出規制は、これまではＣＯＤ（化学的酸素要求量）のみであった。窒素については全窒素量で１２０ｍｇ／ｌの一般排出基準に留まっていたが、今後は全窒素量を現行の１／１０にすることも検討されている。
【０００３】
しかし、一般の小規模生活排水ではＢＯＤ（生物化学的酸素要求量）のみを処理するものが多く、硝酸塩などの窒素成分は処理されていないのが現状である。また、ヨーロッパ地域では、化学肥料や家畜の排泄物から、水溶性の硝酸塩が土壌中に浸透して起こる地下水の汚染が深刻な問題になっている。汚染水を人間が摂取した場合、神経障害、ガン、幼児のメトヘモグロビン血症などを引き起こすことが知られている。以上の点で、高性能な硝酸態窒素除去法の早期開発が望まれている。
【０００４】
【発明が解決しようとする課題】
硝酸態窒素の除去には、一般的には嫌気的条件下での脱窒細菌による生物的処理が用いられている。脱窒菌の殆どは従属栄養細菌であり、増殖には有機物を必要とする。それ故、無機系排水のように有機物をあまり含有しない排水を処理する場合、水素供与体としてメタノール等を添加するだけでなく、嫌気性浄化槽の設置が不可欠となる。そのため、設置場所や経費面が問題となっている。また、生物的処理では、温度や排水に含まれる有害成分の影響を受けやすいという課題もある。
【０００５】
生物的手法以外にはイオン交換法、膜分離法、触媒法等の物理化学的手法が存在するが、その経済性に問題が残されている。一方、電解法による排水処理は操作が簡単であり、装置の大きさに対して処理能力が大きく、ＢＯＤ源がない排水の処理も可能である。
【０００６】
従来の電解法による窒素除去に関する研究としては、被処理水に電流を流してアンモニア、亜硝酸態窒素、硝酸態窒素を酸化、又は、還元分解して窒素ガスにする方法がある。この場合、従来の被処理水の電気分解法では、アノードに例えば、白金、イリジウム、パラジウムなどの貴金属材料を用いていた。
【０００７】
そして、被処理水に電流を流すことにより、アノードにおいてアンモニア態窒素が活性酸素や次亜塩素酸により酸化され、窒素化合物が窒素ガスに変換されることで窒素化合物の処理が行われていた。
【０００８】
しかしながら、従来の電解による窒素化合物の処理方法では、被処理水の窒素化合物の濃度が所定の値以上、例えば１０００ｍｇ／ｌ以上では、脱窒反応の電流効率が著しく低下するため、窒素化合物の処理効率が低いという問題があった。
【０００９】
そこで、本発明は従来の技術的課題を解決するために成されたものであり、汚染地下水などの窒素化合物を含有する被処理水を効率的に処理することができる窒素処理方法及び窒素処理システム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】
請求項１の窒素処理方法は、電気化学的手法により被処理水中の窒素化合物を処理する方法であって、処理水を希釈し、当該被処理水の窒素化合物濃度を低下させた後、当該被処理水を電気化学的手法により処理することを特徴とする。
【００１１】
請求項１の発明によれば、電気化学的手法により被処理水中の窒素化合物を処理する方法において、処理水を希釈し、当該被処理水の窒素化合物濃度を低下させた後、当該被処理水を電気化学的手法により処理するので、効率的に被処理水中の窒素化合物を処理することができるようになる。
【００１２】
請求項２の発明の窒素処理方法は、上記発明において、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲に希釈することを特徴とする。
【００１３】
請求項３の発明の窒素処理方法は、請求項１の発明において、被処理水の窒素化合物濃度を、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈することを特徴とする。
【００１４】
請求項２の発明によれば、上記発明において、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲、例えば請求項３の発明の如く３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈するので、電気化学的手法による被処理水中の窒素化合物の処理に最適な窒素化合物濃度で窒素処理を行うことができるようになり、より一層窒素化合物の処理効率を向上させることができるようになる。
【００１５】
請求項４の発明の窒素処理方法は、上記各発明において、電気化学的手法により処理された後の被処理水を希釈液として用いることを特徴とする。
【００１６】
請求項４の発明によれば、上記各発明において、電気化学的手法により処理された後の被処理水を希釈液として用いるので、新たな上水等を用いることなく被処理水の希釈を行うことができるようになり、排水量の増加によるランニングコストの高騰を抑制することができると共に、環境に適した窒素処理を実現することができるようになる。
【００１７】
請求項５の発明の窒素処理方法は、上記各発明において、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度に基づいて希釈率を調整することを特徴とする。
【００１８】
請求項５の発明によれば、上記各発明において、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度に基づいて希釈率を調整するので、常に、窒素処理に最適な窒素化合物濃度に被処理水を希釈することができるようになる。
【００１９】
請求項６の発明の窒素処理システムは、被処理水中の窒素化合物を処理するものであって、被処理水に少なくとも一部が浸漬され、電気化学的手法により当該被処理水を処理するための少なくとも一対の電極と、被処理水を希釈し、当該被処理水の窒素化合物濃度を低下させる希釈処理手段を備えることを特徴とする。
【００２０】
請求項６の発明によれば、被処理水中の窒素化合物を処理する窒素処理システムにおいて、被処理水に少なくとも一部が浸漬され、電気化学的手法により当該被処理水を処理するための少なくとも一対の電極と、被処理水を希釈し、当該被処理水の窒素化合物濃度を低下させる希釈処理手段を備えるので、被処理水を希釈処理手段にて希釈処理した後、前記各電極を用いて電気化学的手法により効率的に被処理水中の窒素化合物を処理することができるようになる。
【００２１】
請求項７の発明の窒素処理システムは、上記発明に加えて、希釈処理手段は、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲に希釈することを特徴とする。
【００２２】
請求項８の発明の窒素処理システムは、請求項６の発明に加えて、希釈処理手段は、被処理水の窒素化合物濃度を、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈することを特徴とする。
【００２３】
請求項７の発明によれば、上記発明に加えて、希釈処理手段は、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲、例えば請求項８の如く３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈するので、前記各電極を用いた電気化学的手法による被処理水中の窒素化合物の処理に最適な窒素化合物濃度で窒素処理を行うことができるようになり、より一層窒素化合物の処理効率を向上させることができるようになる。
【００２４】
請求項９の発明の窒素処理システムは、請求項６、請求項７又は請求項８の発明に加えて、電気化学的手法により処理された後の被処理水を希釈液として用いることを特徴とする。
【００２５】
請求項９の発明によれば、請求項６、請求項７又は請求項８の発明に加えて、電気化学的手法により処理された後の被処理水を希釈液として用いるので、新たな上水等を用いることなく被処理水の希釈を行うことができるようになり、排水量の増加によるランニングコストの高騰を抑制することができると共に、環境に適した窒素処理を実現することができるようになる。
【００２６】
請求項１０の発明の窒素処理システムは、請求項６、請求項７又は請求項９の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯溜する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、希釈槽内には、該希釈槽内の水位を検出する水位検出手段を備え、制御手段は、当該水位検出手段の出力に基づいて供給手段及び返送手段を制御することを特徴とする。
【００２７】
請求項１０の発明によれば、請求項６、請求項７又は請求項９の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯溜する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、希釈槽内には、該希釈槽内の水位を検出する水位検出手段を備え、制御手段は、当該水位検出手段の出力に基づいて供給手段及び返送手段を制御するので、常に、窒素処理に適した窒素化合物濃度に被処理水を希釈することができるようになる。
【００２８】
請求項１１の発明の窒素処理システムは、請求項６、請求項７、請求項８又は請求項９の発明に加えて、希釈処理手段は、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段を備え、濃度検出手段の検出する濃度に基づいて当該被処理水の希釈率を調整することを特徴とする。
【００２９】
請求項１２の発明の窒素処理システムは、上記発明において、濃度検出手段は、イオンセンサであることを特徴とする。
【００３０】
請求項１１の発明によれば、請求項６、請求項７、請求項８又は請求項９の発明に加えて、希釈処理手段は、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段を備え、濃度検出手段の検出する濃度に基づいて当該被処理水の希釈率を調整するので、常に、窒素処理に最適な窒素化合物濃度に被処理水を希釈することができるようになる。
【００３１】
特に、請求項１２の発明によれば、濃度検出手段は、イオンセンサであるので、容易に硝酸態窒素としての硝酸イオン及び亜硝酸態窒素としての亜硝酸態イオンの濃度を検出することができ、容易に、且つ、低コストにて本発明を実現することができるようになる。
【００３２】
請求項１３の発明の窒素処理システムは、請求項１１又は請求項１２の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯溜する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、希釈槽内又は希釈槽の前段に設けられ、制御手段は、供給手段により被処理水を希釈槽に供給すると共に、濃度検出手段の出力に基づき、処理槽内にて電気化学的手法により処理された被処理水を返送手段により希釈槽に返送し、排出手段により処理槽内の被処理水を排出した後、希釈槽内にて希釈された被処理水を搬送手段により処理槽に搬送することを特徴とする。
【００３３】
請求項１３の発明によれば、請求項１１及び請求項１２の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯留する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、希釈槽内又は希釈槽の前段に設けられ、制御手段は、供給手段により被処理水を希釈槽に供給すると共に、濃度検出手段の出力に基づき、処理槽内にて電気化学的手法により処理された被処理水を返送手段により希釈槽に返送し、排出手段により処理槽内の被処理水を排出した後、希釈槽内にて希釈された被処理水を搬送手段により処理槽に搬送するので、希釈槽内に貯留された被処理水を濃度検出手段の出力に基づき、供給手段及び返送手段により、窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【００３４】
これにより、簡易なシステムにて、効率的に被処理水中の窒素化合物を処理することができるようになる。
【００３５】
また、希釈槽内にて窒素化合物濃度を調整された被処理水は、搬送手段により処理槽に搬送され、希釈槽とは別槽にて電解による脱窒処理を行うことができる。そのため、希釈処理及び脱窒処理を別段で行うため、処理効率の向上を図ることができる。
【００３６】
請求項１４の発明の窒素処理システムは、請求項１０又は請求項１３の発明に加えて、希釈槽内への被処理水及び希釈液の供給量の積算値を検出する供給量検出手段を備え、制御手段は、当該供給量検出手段の出力に基づいて供給手段及び返送手段を制御することを特徴とする。
【００３７】
請求項１４の発明によれば、請求項１０又は請求項１３の発明に加えて、希釈槽内への被処理水及び希釈液の供給量の積算値を検出する供給量検出手段を備え、制御手段は、当該供給量検出手段の出力に基づいて供給手段及び返送手段を制御するので、簡易なシステムにて、希釈槽内の被処理水を窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【００３８】
請求項１５の発明の窒素処理システムは、請求項１１又は請求項１２の発明に加えて、希釈処理手段は、被処理水を貯留し、該処理水に電極が浸漬される処理槽と、該処理槽へ被処理水を供給する供給手段と、処理槽内の被処理水を排出する排出手段と、処理槽内の水位を検出する水位検出手段と、供給手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、処理槽又は処理槽の前段に設けられ、制御手段は、濃度検出手段及び水位検出手段の出力に基づき、排出手段により処理槽内にて電気化学的手法により処理された被処理水の一部を排出した後、供給手段により被処理水を処理槽に供給することを特徴とする。
【００３９】
請求項１５の発明によれば、請求項１１又は請求項１２の発明に加えて、希釈処理手段は、被処理水を貯留し、該処理水に電極が浸漬される処理槽と、該処理槽へ被処理水を供給する供給手段と、処理槽内の被処理水を排出する排出手段と、処理槽内の水位を検出する水位検出手段と、供給手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、処理槽又は処理槽の前段に設けられ、制御手段は、濃度検出手段及び水位検出手段の出力に基づき、排出手段により処理槽内にて電気化学的手法により処理された被処理水の一部を排出した後、供給手段により被処理水を処理槽に供給するので、処理槽内に貯留された被処理水を濃度検出手段及び水位検出手段の出力に基づき、供給手段及び排出手段により、窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【００４０】
これにより、簡易なシステムにて、効率的に被処理水中の窒素化合物を処理することができるようになる。
【００４１】
また、被処理水を希釈する槽と窒素処理を行う槽とを同一槽にて行うことにより、システムの簡素化を図ることができるようになる。
【００４２】
請求項１６の発明の窒素処理システムは、上記各窒素処理システムの発明に加えて、カソードを構成する電極は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものにより構成し、アノードを構成する電極は、不溶性材料又はカーボンにより構成することを特徴とする。
【００４３】
請求項１６の発明によれば、上記各窒素処理システムの発明に加えて、カソードを構成する電極は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものにより構成し、アノードを構成する電極は、不溶性材料又はカーボンにより構成するので、被処理水中の硝酸態窒素の亜硝酸態窒素及びアンモニアへの還元反応を促進することができ、還元反応に要する時間を短縮することができるようになる。また、本発明の如く被処理水中の窒素化合物濃度が低い場合であっても効率的に窒素化合物の除去を行うことができるようになる。
【００４４】
【発明の実施の形態】
以下、図面に基づいて本発明の実施形態を詳述する。図１は本発明の窒素処理方法を適用した窒素処理システムＳの概要を示す説明図である。本実施例における窒素処理システムＳによって処理される被処理水は、例えば化学肥料や家畜の排泄物により水溶性の硝酸塩、即ち、硝酸態窒素が土壌中に浸透し、当該硝酸態窒素により汚染された地下水、若しくは、工業排水又は家庭用排水であるものとする。尚、本実施例で用いられる被処理水は硝酸態窒素などを含む全窒素濃度が比較的高い、例えば１０００ｍｇ／ｌ以上の硝酸態窒素を含有する汚染地下水等であるものである。また、本実施例における被処理水は、少なくともハロゲン化物イオンとして塩化物イオンが含有されているものとする。
【００４５】
係る窒素処理システムＳは、上記被処理水を貯留するための貯留槽１０と、貯留槽１０に貯留された被処理水を希釈する希釈処理手段（詳細は後述する。）と、前記希釈処理手段にて希釈された被処理水の窒素処理を行う窒素処理手段としての窒素処理装置１とにより構成されている。
【００４６】
希釈処理手段は、希釈槽１１を備えており、この希釈槽１１内には、貯留される被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段としてのイオンセンサ２２が設けられている。また、この希釈槽１１には、供給手段としての供給電磁弁１３を介して配管１２が接続されており、これにより、貯留槽１０内の被処理水が希釈槽１１に搬送可能とされる。更に、この希釈槽１１には、搬送手段としての搬送電磁弁１５を介して配管１４が接続されており、これにより、当該希釈槽１１内の被処理水が前記窒素処理装置１（詳細は後述する処理槽２）に搬送可能とされる。
【００４７】
前記窒素処理装置１を構成する処理槽２には、返送手段としてのポンプ１７及び返送電磁弁１８を介して配管１６が接続されており、これにより、処理槽２内の被処理水を希釈液として希釈槽１１に返送可能とされている。更に、前記処理槽２には、窒素処理した後の被処理水の一部を外部に排水するための配管２３が排出手段としての排出電磁弁１９を介して接続されている。
【００４８】
尚、配管１２であって供給電磁弁１３の上流側、及び配管１４であって搬送電磁弁１５の上流側にはそれぞれポンプ２０、２１が設けられていてもよいものとする。
【００４９】
また、本実施例では、供給電磁弁１３が設けられる配管１２及び返送電磁弁１８が設けられる配管１６には、当該電磁弁１３及び１８を通過する被処理水及び希釈液の供給量の積算値を検出する供給量検出センサ（供給量検出手段）２４、２５がそれぞれ設けられているものとする。
【００５０】
尚、本実施例では、希釈槽１１への被処理水や希釈液の供給量は供給量検出センサ２４、２５のみにより検出しているが、これ以外に、希釈槽１１内の水位を検出する水位センサ（水位検出手段）を並設若しくは、該水位センサのみにより希釈槽１１内への供給量を検出してもよいものとする。
【００５１】
ここで、図２は窒素処理システムＳの制御装置としてのマイクロコンピュータ３０を示している。マイクロコンピュータ３０の入力側には、前記イオンセンサ２２及び供給量検出センサ２４、２５が接続されていると共に、マイクロコンピュータ３０の出力側には、各電磁弁１３、１５、１８、１９及び各ポンプ１７、２０、２１が接続されている。これにより、各電磁弁１３、１５、１８、１９及び各ポンプ１７、２０、２１は、各センサ２２、２４、２５の出力に基づいて制御される。
【００５２】
次に、図３を参照して窒素処理装置１について説明する。本実施例における窒素処理装置１は、電気化学的手法（電解）により被処理水の脱窒処理を行うものであり、内部に配管１４を介して希釈された被処理水を流入させる図示しない流入口と、配管２３を介して外部に被処理水を流出される流出口２９（図１のみ図示する。）及び、配管１６を介して脱窒処理された被処理水を希釈液として希釈槽１１に返送する返送口３１（図１のみ図示する。）を有する処理室４を構成する処理槽２と、該処理室４内の希釈被処理水中に少なくとも一部が浸漬するように対向して配置される一対の電極、即ち、アノード５と、カソード６と、該電極５、６に通電するための電源７とから構成されている。尚、電源７は、上記マイクロコンピュータ３０の出力側に接続されており、該マイクロコンピュータ３０により制御されている。また、図３において８は、処理槽２内を撹拌するための撹拌手段としての撹拌子である。
【００５３】
前記カソード６は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものとして、例えば、亜鉛、銅、銀、亜鉛と銅の合金である真鍮により構成されており、前記アノード５は、不溶性金属、例えば白金、イリジウム、パラジウム又はその酸化物などから構成される不溶性電極又はカーボンより構成されている。
【００５４】
また、図３に示す如くアノード５とカソード６との間に位置して、アノード５を囲繞するように、円筒状に形成された遮蔽部材９が設けられている。該遮蔽部材９は、例えばガラス繊維やプラスチックのメッシュなどの非導電性部材にて構成されており、これにより、アノード５から発生する酸素気泡が、カソード６側に通過することを阻止することができる。このとき、アノード５側に存するイオンは、該遮蔽部材９を通過してカソード６側に移動することができる。また、遮蔽部材９は、汚泥の流水により生じる撹拌又は、前記撹拌子８による撹拌によりアノードに流水の影響を与えない構成とされている。
【００５５】
以上の構成により、本実施例の窒素処理システムＳの窒素処理について説明する。まず、貯留槽１０内に予め貯留された被処理水を配管１２を介して希釈槽１１内に搬送する。初めマイクロコンピュータ３０は、搬送電磁弁１５を閉じ、供給電磁弁１３を開放する。更に、マイクロコンピュータ３０は、ポンプ２０を運転し、供給量検出センサ２４により希釈槽１１内に供給される被処理水の供給量を検出する。そして、希釈槽１１内に設けられたイオンセンサ２２により検出された被処理水中の硝酸イオン及び亜硝酸イオンの濃度及び供給量検出センサ２４によって検出された供給量に基づいて、ポンプ２０を停止し、供給電磁弁１３を閉鎖する。
【００５６】
即ち、イオンセンサ２２により検出された硝酸イオン及び亜硝酸イオンの濃度が高い場合には、供給量検出センサ２４の出力により、比較的少ない量の被処理水のみを希釈槽１１に供給し、イオンセンサ２２により検出された硝酸イオン及び亜硝酸イオンの濃度が比較的低い場合には、供給量検出センサ２４の出力により、比較的多量の被処理水を希釈槽１１に供給する。
【００５７】
その後、マイクロコンピュータ３０は、返送手段としての返送電磁弁１８を開放し、ポンプ１７を運転し、詳細は後述する窒素処理装置１によって処理された後の希釈液としての被処理水を希釈槽１１内に供給し、供給量検出センサ２５によって検出された供給量に基づいて、希釈槽１１内の被処理水中の硝酸イオン及び亜硝酸イオンの濃度が脱窒処理における電流効率が高くなる範囲、例えば、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲となるように調整する。
【００５８】
本実施例では、上述の如く検出されたイオン濃度に応じて希釈槽１１内に貯留された被処理水に希釈液を加え、希釈槽１１内に一定量の希釈被処理水を調整する。尚、特に脱窒処理における電流効率が高くなる、即ち電流効率が７０％以上となる４００ｍｇ／ｌ以上６３０ｍｇ／ｌ以下の範囲に被処理水を調整してもよい。本実施例では、上記範囲において最も電流効率の良い５００ｍｇ／ｌ程度に被処理水を調整するものとする。
【００５９】
但し、窒素処理装置１により処理された被処理水がない場合には、水道水や工業用水などを希釈槽１１に供給し、希釈槽１１内に貯留された被処理水の硝酸イオン及び亜硝酸イオンが上記濃度範囲となるように調整する。
【００６０】
上述の如く希釈槽１１において所定の濃度範囲に調整された希釈被処理水は、マイクロコンピュータ３０によりポンプ２１が運転され、搬送電磁弁１５が開放されることにより、窒素処理装置１の処理槽２に搬送される。このとき、排出電磁弁１９及び返送電磁弁１８はマイクロコンピュータ３０により閉鎖されているものとする。
【００６１】
そして、マイクロコンピュータ３０により電源７をＯＮとし、カソード６及びアノード５に通電することにより、処理槽２内に搬送された希釈被処理水は、電解処理される。カソード６側では、希釈被処理水中に含まれる硝酸イオンは、還元反応により亜硝酸イオンに変換される（反応式Ａ）。また、硝酸イオンの還元反応により生成された亜硝酸イオンは、更に、還元反応により、アンモニアに変換される（反応式Ｂ）。以下に、反応式Ａ及び反応式Ｂを示す。
反応式Ａ　ＮＯ３ −＋Ｈ２Ｏ＋２ｅ−→ＮＯ２ −＋２ＯＨ−
反応式Ｂ　ＮＯ２ −＋５Ｈ２Ｏ＋６ｅ−→ＮＨ３（ａｑ）＋７ＯＨ−
【００６２】
一方、アノード５側では、上述の如く希釈被処理水中に少なくともハロゲン化物イオンとして塩化物イオンが存在することから、アノード５の表面から次亜塩素酸やオゾン又は活性酸素が発生し、希釈被処理水中におけるアンモニアの脱窒作用を生じ、窒素ガスを生成する（反応式Ｃ）。以下に、反応Ｃを示す。
反応式Ｃ　２ＮＨ３＋３ＨＣｌＯ→Ｎ２↑＋３ＨＣｌ＋３Ｈ２Ｏ
【００６３】
尚、ここで、希釈被処理水中に含有される塩化物イオンが所定の濃度、例えば１００ｍｇ／ｌに満たない場合には、図示しない塩化物イオン調整手段により、格別に塩化物イオンとして例えば塩化カリウム又は塩化ナトリウムを濃縮被処理水中に添加する。これにより、希釈被処理水は、電解により、より一層次亜塩素酸を発生しやすい状態となり、効率的に希釈被処理水中のアンモニアの脱窒処理を行うことができるようになる。
【００６４】
これにより、５００ｍｇ／ｌ程度の硝酸イオン及び亜硝酸イオンを含有する希釈被処理水は、窒素処理装置１において、効率的に窒素化合物の除去処理を行うことができ、１０乃至３０ｍｇ／Ｌの硝酸態窒素を含有する被処理水として外部に排水処理することができるようになる。
【００６５】
また更に、本実施例では、希釈槽１１において窒素化合物としての硝酸イオンや亜硝酸イオンを５００ｍｇ／ｌ程度にまで希釈処理した後の被処理水を窒素処理装置１により電解処理するため、効率的に窒素化合物の除去処理を行うことができる。
【００６６】
ここで、図４に示される実験結果は、アノード５に白金系の電極を使用し、カソード６に真鍮の電極を使用した場合における被処理水中の硝酸態窒素濃度を示している。この実験では硝酸態窒素を含有する各溶液３００ｍｌに各電極５、６を浸漬し、該電極５、６間に２．５Ａを流し、定電流電解を行った。
【００６７】
図４は、硝酸態窒素濃度が１００ｍｇ／ｌ、３００ｍｇ／ｌ、５００ｍｇ／ｌ、８００ｍｇ／ｌ、１０００ｍｇ／ｌの各溶液を電解した場合における脱窒反応の電流効率を示している。これによると、硝酸態窒素濃度が１００ｍｇ／ｌの溶液を電解した場合の電流効率は３５．２％、３００ｍｇ／ｌの溶液を電解した場合の電流効率は６８．４％、５００ｍｇ／ｌの溶液を電解した場合の電流効率は７０．６％、８００ｍｇ／ｌの溶液を電解した場合の電流効率は６１．８％、１０００ｍｇ／ｌの溶液を電解した場合の電流効率は３０．９％であった。
【００６８】
これにより、被処理水の硝酸態窒素濃度が３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の場合において、脱窒反応の電解効率が６０％を上回っていることが分かる。特に、硝酸態窒素濃度が１００ｍｇ／ｌや１０００ｍｇ／ｌの被処理水の電解を行った場合には、電解効率が上記濃度範囲の場合と比して半分以下となっており、極端に効率が低下していることが分かる。
【００６９】
そのため、被処理水を希釈し窒素化合物濃度を低下させた後、電解することにより、効率的に被処理水中の窒素化合物の脱窒処理を行うことができるようになる。特に、被処理水を脱窒反応の電解効率が高くなる範囲、例えば３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に調整することにより、著しく脱窒反応の電解効率を向上させることができるようになり、より一層窒素化合物の処理効率を向上させることができるようになる。
【００７０】
また、本実施例では、希釈槽１１に設けられた硝酸イオン及び亜硝酸イオンの濃度を検出するイオンセンサ２２の出力に基づき貯留槽１０からの被処理水の供給量と処理槽２からの希釈液の供給量を制御し、被処理水の希釈率を調整するので、常に、窒素処理に最適な窒素化合物濃度に被処理水を希釈した後、高効率で脱窒処理を行うことができるようになる。
【００７１】
更にまた、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段は上述の如くイオンセンサ２２であるので、容易に硝酸態窒素としての硝酸イオン及び亜硝酸態窒素としての亜硝酸イオンの濃度を検出することができ、容易、且つ、低コストにて本発明を実現することができるようになる。
【００７２】
上述の如き希釈被処理水の脱窒処理が終了した後、若しくは、脱窒処理を行っている間に、マイクロコンピュータ３０は、搬送電磁弁１５を閉じ、供給電磁弁１３を開放し、再び、貯留槽１０内に貯留された被処理水を配管１２を介して希釈槽１１内に搬送する。そして、マイクロコンピュータ３０は、ポンプ２０を運転し、供給量検出センサ２４により希釈槽１１内に供給される被処理水の供給量を検出する。そして、希釈槽１１内に設けられたイオンセンサ２２により検出された被処理水中の硝酸イオン及び亜硝酸イオンの濃度及び供給量検出センサ２４によって検出された供給量に基づいて、ポンプ２０を停止し、供給電磁弁１３を閉鎖する。
【００７３】
その後、マイクロコンピュータ３０は、返送電磁弁１８を開放し、ポンプ１７を運転し、上述の如く被処理水中の脱窒処理が終了した被処理水を希釈液として希釈槽１１内に供給し、供給量検出センサ２５によって検出された供給量に基づいて、希釈槽１１内の被処理水中の硝酸イオン及び亜硝酸イオンの濃度が脱窒処理における電流効率が高くなる範囲、例えば、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲となるように調整する。
【００７４】
尚、処理槽２内の被処理水のうち、希釈液として希釈槽１１内に供給されなかった被処理水は、マイクロコンピュータ３０により排出電磁弁１９を開放することにより、外部に排水される。
【００７５】
その後、希釈槽１１内において上述の如く所定の濃度範囲に調整された希釈被処理水は、マイクロコンピュータ３０によって搬送電磁弁１５を開放することにより、窒素処理装置１の処理槽２内に搬送され、上述の如く脱窒処理される。
【００７６】
ここで、被処理水を希釈する希釈液は、上述の如く脱窒処理された後の被処理水を用いることにより、新たな上水等を用いることなく、被処理水の希釈を行うことができる。これにより、排水量の増加によるランニングコストの高騰を抑制することができると共に、環境に適した窒素処理を実現することができるようになる。
【００７７】
また、本実施例によれば、上述した如く希釈槽１１と、マイクロコンピュータ３０に接続された各電磁弁１３、１５、１８、１９及びポンプ１７、２０、２１、並びにイオンセンサ２２と、供給量検出センサ２４、２５により構成された希釈処理手段を備えた簡易なシステムにて、容易に被処理水を窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【００７８】
更にまた、本実施例によれば、希釈槽１１内にて窒素処理に最適な窒素化合物濃度に調整された被処理水は、搬送電磁弁１５を介して処理槽２に搬送され、希釈槽１１とは別槽にて電解による脱窒処理を行うことができる。そのため、希釈処理及び脱窒処理を別段で行うことが可能となり、処理効率をより一層向上させることができるようになる。
【００７９】
次に、もう一つの本発明の実施例について図５を参照して説明する。図５は本発明の第２の実施例の窒素処理方法を実現するための窒素処理システムＴの概要を示す説明図である。尚、図５において図１と同一符号は同一若しくは同様の作用を奏するものとする。
【００８０】
この実施例における窒素処理システムＴも被処理水を貯留するための貯留槽１０と、貯留槽１０に貯留された被処理水を希釈する希釈処理手段と、前記希釈処理手段にて希釈された被処理水の窒素処理を行う窒素処理手段としての窒素処理装置１とにより構成されている。
【００８１】
希釈処理手段は、前記電極が少なくとも一部浸漬される処理槽２を備えている。前記貯留槽１０には、供給手段としての供給電磁弁１３を介して配管１２が接続されており、これにより、貯留槽１０内の被処理水が処理槽２に搬送可能とされる。そして、該貯留槽１０には、処理槽２への前段として該貯留槽１０に貯留される被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段としてのイオンセンサ２２が設けられている。また、処理槽２には、窒素処理した後の被処理水の一部を外部に排水するための配管２３が排出手段としての排出電磁弁１９を介して接続されている。尚、配管１２であって供給電磁弁１３の上流側にはポンプ２０が設けられていてもよいものとする。
【００８２】
また、本実施例では、処理槽２には、該処理槽２内の水位を検出する水位センサ（水位検出手段）３２が設けられているものとする。更に、この処理槽２には、電気化学的手法により、被処理水中の窒素化合物を処理する電極、即ち、アノード５と、カソード６と、該電極５、６に通電するための電源７とが設けられている。
【００８３】
尚、本実施例においても、前記カソード６は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものとして、例えば、亜鉛、銅、銀、亜鉛と銅の合金である真鍮により構成されており、前記アノード５は、不溶性金属、例えば白金、イリジウム、パラジウム又はその酸化物などから構成される不溶性電極又はカーボンより構成されている。
【００８４】
ここで、図６は窒素処理システムＴの制御装置としてのマイクロコンピュータ３３を示している。マイクロコンピュータ３３の入力側には、前記イオンセンサ２２及び水位センサ３２が接続されていると共に、マイクロコンピュータ３３の出力側には、各電磁弁１３、１９及びポンプ２０及び電源７が接続されている。これにより、各電磁弁１３、１９及びポンプ２０及び電源７は、各センサ２２、３２の出力に基づいて制御される。
【００８５】
以上の構成により、かかる実施例の窒素処理システムＴの窒素処理について説明する。尚、通常、処理槽２内には、前回の脱窒処理において脱窒処理された被処理水が貯留されているものとする。但し、処理槽２内に脱窒処理された被処理水が貯留されていない場合には、水道水や工業用水などを予め処理槽２内に貯留しておくものとする。まず、マイクロコンピュータ３３は、イオンセンサ２２により貯留槽１０内に貯留された被処理水の中の硝酸イオン及び亜硝酸イオンの濃度を検出し、この濃度に基づいて、排出弁１９を開閉制御し、処理槽２内に前記イオンセンサ２２により検出した濃度に応じた量の被処理水を残留させる。
【００８６】
次いで、マイクロコンピュータ３３は、供給電磁弁１３を開放すると共に、ポンプ２０を運転し、上記と同様にイオンセンサ２２により検出した濃度に応じた量の被処理水を供給する。
【００８７】
即ち、イオンセンサ２２により検出された硝酸イオン及び亜硝酸イオンの濃度が高い場合には、マイクロコンピュータ３３は、水位センサ３２から検出される被処理水の水位が比較的高い位置になるように排出電磁弁１９の開閉を制御し、その後、水位センサ３２が満水を検出するまで供給電磁弁１３を開き、貯留槽１０から処理槽２へ被処理水を供給する。他方、イオンセンサ２２により検出された硝酸イオン及び亜硝酸イオンの濃度が低い場合には、マイクロコンピュータ３３は、水位センサ３２から検出される被処理水の水位が低い位置になるまで排出電磁弁１９を開放し、その後、水位センサ３２が満水を検出するまで供給電磁弁１３を開き、貯留槽１０から処理槽２へ被処理水を供給する。
【００８８】
これにより、処理槽２内の被処理水は、硝酸イオン及び亜硝酸イオンの濃度が脱窒処理における電流効率が高くなる範囲、例えば、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲となるように調整される。尚、特に脱窒処理における電流効率が高くなる、即ち電流効率が７０％以上となる４００ｍｇ／ｌ以上６３０ｍｇ／ｌ以下の範囲に被処理水を調整してもよい。本実施例では、上記範囲において最も電流効率の良い５００ｍｇ／ｌ程度に被処理水を調整するものとする。
【００８９】
上述の如く処理槽２内において希釈処理された希釈被処理水は、マイクロコンピュータ３３により電源７がＯＮとされることにより、カソード６及びアノード５に通電され、処理槽２内に搬送された希釈被処理水は、電解処理される。カソード６側では、希釈被処理水中に含まれる硝酸イオンは、還元反応により亜硝酸イオンに変換される（前記反応式Ａ）。また、硝酸イオンの還元反応により生成された亜硝酸イオンは、更に、還元反応により、アンモニアに変換される（前記反応式Ｂ）。
【００９０】
一方、アノード５側では、上述の如く希釈被処理水中に少なくともハロゲン化物イオンとして塩化物イオンが存在することから、アノード５の表面から次亜塩素酸やオゾン又は活性酸素が発生し、希釈被処理水中におけるアンモニアの脱窒作用を生じ、窒素ガスを生成する（前記反応式Ｃ）。
【００９１】
これにより、かかる実施例においても、被処理水は、希釈処理手段により、脱窒処理に最適な窒素化合物濃度に希釈した後、脱窒処理されるため、効率的に被処理水中の窒素化合物を処理することができるようになる。
【００９２】
また、かかる実施例では、被処理水の窒素化合物の濃度に基づいて、処理槽２内への被処理水の供給及び排出をマイクロコンピュータ３３により制御することで、被処理水を脱窒反応に最適な窒素化合物濃度に希釈処理することができ、簡易なシステムにて本発明を実現することができるようになる。
【００９３】
更にまた、かかる実施例では、被処理水を希釈する槽と、窒素処理を行う槽とを同一の処理槽２にて行うことにより、より一層システムの簡素化を図ることができるようになる。
【００９４】
また、上記各実施例によれば、従来の如く被処理水中にメタノールなどの格別な添加剤を用いることなく、被処理水中に含有される硝酸態窒素などの窒素化合物を効率的に除去することができるため、メンテナンス作業性を向上させることができる。
【００９５】
更に、従来のように生物的処理により硝酸態窒素などの窒素化合物の処理を行わないため、細菌等の温度管理を不要とすることができると共に、窒素処理システム自体を小型化することができ、コストの削減を図ることができるようになる。
【００９６】
【発明の効果】
以上詳述した如く本発明によれば、電気化学的手法により被処理水中の窒素化合物を処理する方法において、処理水を希釈し、当該被処理水の窒素化合物濃度を低下させた後、当該被処理水を電気化学的手法により処理するので、効率的に被処理水中の窒素化合物を処理することができるようになる。
【００９７】
請求項２の発明によれば、上記発明において、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲、例えば請求項３の発明の如く３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈するので、電気化学的手法による被処理水中の窒素化合物の処理に最適な窒素化合物濃度で窒素処理を行うことができるようになり、より一層窒素化合物の処理効率を向上させることができるようになる。
【００９８】
請求項４の発明によれば、上記各発明において、電気化学的手法により処理された後の被処理水を希釈液として用いるので、新たな上水等を用いることなく被処理水の希釈を行うことができるようになり、排水量の増加によるランニングコストの高騰を抑制することができると共に、環境に適した窒素処理を実現することができるようになる。
【００９９】
請求項５の発明によれば、上記各発明において、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度に基づいて希釈率を調整するので、常に、窒素処理に最適な窒素化合物濃度に被処理水を希釈することができるようになる。
【０１００】
請求項６の発明によれば、被処理水中の窒素化合物を処理する窒素処理システムにおいて、被処理水に少なくとも一部が浸漬され、電気化学的手法により当該被処理水を処理するための少なくとも一対の電極と、被処理水を希釈し、当該被処理水の窒素化合物濃度を低下させる希釈処理手段を備えるので、被処理水を希釈処理手段にて希釈処理した後、前記各電極を用いて電気化学的手法により効率的に被処理水中の窒素化合物を処理することができるようになる。
【０１０１】
請求項７の発明によれば、上記発明に加えて、希釈処理手段は、被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲、例えば請求項８の如く３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈するので、前記各電極を用いた電気化学的手法による被処理水中の窒素化合物の処理に最適な窒素化合物濃度で窒素処理を行うことができるようになり、より一層窒素化合物の処理効率を向上させることができるようになる。
【０１０２】
請求項９の発明によれば、請求項６、請求項７又は請求項８の発明に加えて、電気化学的手法により処理された後の被処理水を希釈液として用いるので、新たな上水等を用いることなく被処理水の希釈を行うことができるようになり、排水量の増加によるランニングコストの高騰を抑制することができると共に、環境に適した窒素処理を実現することができるようになる。
【０１０３】
請求項１０の発明によれば、請求項６、請求項７又は請求項９の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯溜する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、希釈槽内には、該希釈槽内の水位を検出する水位検出手段を備え、制御手段は、当該水位検出手段の出力に基づいて供給手段及び返送手段を制御するので、常に、窒素処理に適した窒素化合物濃度に被処理水を希釈することができるようになる。
【０１０４】
請求項１１の発明によれば、請求項６、請求項７、請求項８又は請求項９の発明に加えて、希釈処理手段は、被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段を備え、濃度検出手段の検出する濃度に基づいて当該被処理水の希釈率を調整するので、常に、窒素処理に最適な窒素化合物濃度に被処理水を希釈することができるようになる。
【０１０５】
特に、請求項１２の発明によれば、濃度検出手段は、イオンセンサであるので、容易に硝酸態窒素としての硝酸イオン及び亜硝酸態窒素としての亜硝酸態イオンの濃度を検出することができ、容易に、且つ、低コストにて本発明を実現することができるようになる。
【０１０６】
請求項１３の発明によれば、請求項１１及び請求項１２の発明において、希釈処理手段は、被処理水を貯留する希釈槽と、電極が浸漬される被処理水を貯留する処理槽と、希釈槽へ被処理水を供給する供給手段と、希釈槽内の被処理水を処理槽に搬送する搬送手段と、処理槽内の被処理水を希釈液として希釈槽へ返送する返送手段と、処理槽内の被処理水を排出する排出手段と、これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、希釈槽内又は希釈槽の前段に設けられ、制御手段は、供給手段により被処理水を希釈槽に供給すると共に、濃度検出手段の出力に基づき、処理槽内にて電気化学的手法により処理された被処理水を返送手段により希釈槽に返送し、排出手段により処理槽内の被処理水を排出した後、希釈槽内にて希釈された被処理水を搬送手段により処理槽に搬送するので、希釈槽内に貯留された被処理水を濃度検出手段の出力に基づき、供給手段及び返送手段により、窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【０１０７】
これにより、簡易なシステムにて、効率的に被処理水中の窒素化合物を処理することができるようになる。
【０１０８】
また、希釈槽内にて窒素化合物濃度を調整された被処理水は、搬送手段により処理槽に搬送され、希釈槽とは別槽にて電解による脱窒処理を行うことができる。そのため、希釈処理及び脱窒処理を別段で行うため、処理効率の向上を図ることができる。
【０１０９】
請求項１４の発明によれば、請求項１０又は請求項１３の発明に加えて、希釈槽内への被処理水及び希釈液の供給量の積算値を検出する供給量検出手段を備え、制御手段は、当該供給量検出手段の出力に基づいて供給手段及び返送手段を制御するので、簡易なシステムにて、希釈槽内の被処理水を窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【０１１０】
請求項１５の発明によれば、請求項１１又は請求項１２の発明に加えて、希釈処理手段は、被処理水を貯留し、該処理水に電極が浸漬される処理槽と、該処理槽へ被処理水を供給する供給手段と、処理槽内の被処理水を排出する排出手段と、処理槽内の水位を検出する水位検出手段と、供給手段及び排出手段を制御する制御手段とを備え、濃度検出手段は、処理槽又は処理槽の前段に設けられ、制御手段は、濃度検出手段及び水位検出手段の出力に基づき、排出手段により処理槽内にて電気化学的手法により処理された被処理水の一部を排出した後、供給手段により被処理水を処理槽に供給するので、処理槽内に貯留された被処理水を濃度検出手段及び水位検出手段の出力に基づき、供給手段及び排出手段により、窒素処理に最適な窒素化合物濃度に調整することができるようになる。
【０１１１】
これにより、簡易なシステムにて、効率的に被処理水中の窒素化合物を処理することができるようになる。
【０１１２】
また、被処理水を希釈する槽と窒素処理を行う槽とを同一槽にて行うことにより、システムの簡素化を図ることができるようになる。
【０１１３】
請求項１６の発明によれば、上記各窒素処理システムの発明に加えて、カソードを構成する電極は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものにより構成し、アノードを構成する電極は、不溶性材料又はカーボンにより構成するので、被処理水中の硝酸態窒素の亜硝酸態窒素及びアンモニアへの還元反応を促進することができ、還元反応に要する時間を短縮することができるようになる。また、本発明の如く被処理水中の窒素化合物濃度が低い場合であっても効率的に窒素化合物の除去を行うことができるようになる。
【図面の簡単な説明】
【図１】本発明の窒素処理システムの概要を示す説明図である。
【図２】本発明の窒素処理システムのマイクロコンピュータのブロック図である。
【図３】窒素処理装置の概要を示す説明図である。
【図４】被処理水の硝酸態窒素濃度に対する脱窒反応の電流効率を示す図である。
【図５】他の実施例の窒素処理システムの概要を示す説明図である。
【図６】他の実施例の窒素処理システムのマイクロコンピュータのブロック図である。
【符号の説明】
Ｓ、Ｔ　窒素処理システム
１　窒素処理装置
２　処理槽
４　排水処理室
５　アノード
６　カソード
１０　貯留槽
１１　希釈槽
１２、１４、１６、２３　配管
１３、１５、１８、１９　電磁弁
１７、２０、２１　ポンプ
２２　イオンセンサ
２４、２５　供給量検出センサ
３０、３３　マイクロコンピュータ
３２　水位センサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nitrogen treatment method and a nitrogen treatment system for treating a nitrogen compound in water to be treated by an electrochemical method.
[0002]
[Prior art]
In recent years, in closed water areas such as lakes and marshes, inner bays, etc., abnormal occurrence of red tide and blue-green algae, which are considered to be caused by influx of nutrients such as nitrogen and phosphorus in domestic wastewater and industrial wastewater, has become a major social problem. For this reason, wastewater treatment by the activated sludge method is performed for large-scale intensive pollution sources under administrative guidance. Regarding the water quality standards for drainage into closed water bodies, there are regulations for large-scale business establishments with daily wastewater volumes of 50 tons or more. Until now, this emission regulation was only COD (chemical oxygen demand). . Nitrogen has remained at the general emission standard of 120 mg / l in total nitrogen content, but it is now being studied to reduce the total nitrogen content to 1/10 of the current level.
[0003]
However, general small-scale domestic wastewater often treats only BOD (biochemical oxygen demand), and at present, nitrogen components such as nitrate are not treated. In the European region, contamination of groundwater caused by water-soluble nitrate penetrating into soil from chemical fertilizers and livestock excrement has become a serious problem. It is known that human consumption of contaminated water causes neuropathy, cancer, and methemoglobinemia in infants. In view of the above, early development of a high-performance nitrate nitrogen removal method is desired.
[0004]
[Problems to be solved by the invention]
Biological treatment with denitrifying bacteria under anaerobic conditions is generally used to remove nitrate nitrogen. Most denitrifying bacteria are heterotrophic bacteria and require organic matter for growth. Therefore, when treating wastewater that does not contain much organic matter such as inorganic wastewater, it is indispensable not only to add methanol or the like as a hydrogen donor, but also to install an anaerobic purification tank. For this reason, the installation location and cost are problematic. In addition, there is also a problem that biological treatment is easily affected by harmful components contained in temperature and wastewater.
[0005]
Other than biological methods, there are physicochemical methods such as an ion exchange method, a membrane separation method, and a catalytic method, but there remains a problem in economical efficiency. On the other hand, the wastewater treatment by the electrolytic method is simple in operation, has a large treatment capacity with respect to the size of the apparatus, and can treat wastewater without a BOD source.
[0006]
As a study on nitrogen removal by a conventional electrolytic method, there is a method in which an electric current is applied to water to be treated to oxidize or reductively decompose ammonia, nitrite nitrogen, and nitrate nitrogen to nitrogen gas. In this case, in the conventional electrolysis method of the water to be treated, a noble metal material such as platinum, iridium, or palladium is used for the anode.
[0007]
Then, when an electric current is passed through the water to be treated, ammonia nitrogen is oxidized at the anode by active oxygen or hypochlorous acid, and the nitrogen compound is converted into nitrogen gas, thereby treating the nitrogen compound.
[0008]
However, in the conventional method of treating a nitrogen compound by electrolysis, when the concentration of the nitrogen compound in the water to be treated is equal to or higher than a predetermined value, for example, 1000 mg / l or more, the current efficiency of the denitrification reaction is significantly reduced. There was a problem that efficiency was low.
[0009]
Therefore, the present invention has been made to solve the conventional technical problem, and a nitrogen treatment method and a nitrogen treatment system capable of efficiently treating water to be treated containing nitrogen compounds such as contaminated groundwater. The purpose is to provide.
[0010]
[Means for Solving the Problems]
The nitrogen treatment method according to claim 1 is a method for treating a nitrogen compound in the water to be treated by an electrochemical method. The method comprises diluting the treated water to lower the concentration of the nitrogen compound in the water to be treated, and then reducing the concentration of the nitrogen compound. It is characterized in that the treated water is treated by an electrochemical method.
[0011]
According to the invention of claim 1, in the method for treating a nitrogen compound in the water to be treated by an electrochemical method, the water to be treated is diluted after diluting the treated water to lower the concentration of the nitrogen compound in the water to be treated. Is treated by an electrochemical method, so that nitrogen compounds in the water to be treated can be efficiently treated.
[0012]
A nitrogen treatment method according to a second aspect of the present invention is characterized in that, in the above invention, the concentration of the nitrogen compound in the water to be treated is diluted to a range where the current efficiency of the denitrification reaction is increased.
[0013]
According to a third aspect of the present invention, there is provided the nitrogen treatment method according to the first aspect, wherein the nitrogen compound concentration of the water to be treated is diluted to a range of 300 mg / l to 800 mg / l.
[0014]
According to the second aspect of the present invention, in the above invention, the concentration of the nitrogen compound in the water to be treated is adjusted to a range where the current efficiency of the denitrification reaction is high, for example, 300 mg / l to 800 mg / l as in the third aspect of the invention. Since the dilution is performed within the range, the nitrogen treatment can be performed at an optimal nitrogen compound concentration for the treatment of the nitrogen compound in the water to be treated by the electrochemical method, and the treatment efficiency of the nitrogen compound can be further improved. Become like
[0015]
A nitrogen treatment method according to a fourth aspect of the present invention is characterized in that, in each of the above inventions, the water to be treated after being treated by an electrochemical method is used as a diluent.
[0016]
According to the invention of claim 4, in each of the above-mentioned inventions, the water to be treated after being treated by the electrochemical method is used as the diluent, so that the water to be treated is diluted without using fresh water or the like. As a result, it is possible to suppress a rise in running cost due to an increase in the amount of drainage, and to realize nitrogen treatment suitable for the environment.
[0017]
A nitrogen treatment method according to a fifth aspect of the present invention is characterized in that, in each of the above inventions, the dilution ratio is adjusted based on the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated.
[0018]
According to the invention of claim 5, in each of the above inventions, the dilution rate is adjusted based on the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated, so that the concentration of the nitrogen compound is always adjusted to the optimum concentration for nitrogen treatment. The treated water can be diluted.
[0019]
The nitrogen treatment system according to the invention of claim 6 is for treating a nitrogen compound in the water to be treated, wherein at least a part of the nitrogen treatment system is immersed in the water to be treated and is used for treating the water to be treated by an electrochemical method. At least one pair of electrodes and a diluting means for diluting the water to be treated and reducing the nitrogen compound concentration of the water to be treated are provided.
[0020]
According to the invention of claim 6, in a nitrogen treatment system for treating a nitrogen compound in the water to be treated, at least a part is immersed in the water to be treated, and at least one pair for treating the water to be treated by an electrochemical method. And the diluting means for diluting the water to be treated and reducing the nitrogen compound concentration of the water to be treated. The nitrogen compound in the water to be treated can be efficiently treated by the chemical method.
[0021]
The nitrogen treatment system according to a seventh aspect of the present invention is characterized in that, in addition to the above invention, the dilution treatment means dilutes the concentration of the nitrogen compound in the water to be treated to a range where the current efficiency of the denitrification reaction is high.
[0022]
The nitrogen treatment system according to an eighth aspect of the present invention, in addition to the sixth aspect, is characterized in that the dilution means dilutes the nitrogen compound concentration of the water to be treated to a range of 300 mg / l to 800 mg / l. And
[0023]
According to the invention of claim 7, in addition to the above-mentioned invention, the diluting means sets the concentration of the nitrogen compound in the water to be treated in a range in which the current efficiency of the denitrification reaction is high, for example, 300 mg / l or more as in claim 8. Since the dilution is performed to a range of 800 mg / l or less, the nitrogen treatment can be performed at an optimal nitrogen compound concentration for the treatment of the nitrogen compound in the water to be treated by the electrochemical method using the respective electrodes. The processing efficiency of the nitrogen compound can be improved.
[0024]
A nitrogen treatment system according to a ninth aspect of the present invention is the nitrogen treatment system according to the sixth, seventh or eighth aspect, wherein the water to be treated after being treated by an electrochemical method is used as a diluent. I do.
[0025]
According to the ninth aspect of the present invention, in addition to the sixth, seventh or eighth aspect of the present invention, the water to be treated after being treated by the electrochemical method is used as a diluent, so that a new water supply is provided. It becomes possible to dilute the water to be treated without using any other means, thereby suppressing a rise in running costs due to an increase in the amount of drainage and realizing a nitrogen treatment suitable for the environment. .
[0026]
In a nitrogen treatment system according to a tenth aspect of the present invention, in the invention of the sixth, seventh or ninth aspect, the diluting means includes a diluting tank for storing the water to be treated and a water to be treated in which the electrode is immersed. A treatment tank for storing, a supply means for supplying the water to be treated to the dilution tank, a conveying means for conveying the water to be treated in the dilution tank to the treatment tank, and A return means for returning, a discharge means for discharging the water to be treated in the treatment tank, and a control means for controlling these supply means, transport means, return means and discharge means; A water level detecting means for detecting a water level in the inside, wherein the control means controls the supply means and the return means based on the output of the water level detecting means.
[0027]
According to a tenth aspect of the present invention, in the sixth, seventh or ninth aspect of the invention, the dilution processing means stores the dilution tank for storing the water to be treated and the water to be treated in which the electrode is immersed. A treatment tank, a supply means for supplying the water to be treated to the dilution tank, a transport means for carrying the water to be treated in the dilution tank to the treatment tank, and a return of the water to be treated in the treatment tank to the dilution tank as a diluent. Return means, discharge means for discharging the water to be treated in the treatment tank, and control means for controlling these supply means, transport means, return means and discharge means, and in the dilution tank, A water level detecting means for detecting a water level, wherein the control means controls the supply means and the return means based on the output of the water level detecting means, so that the water to be treated is always diluted to a nitrogen compound concentration suitable for nitrogen treatment. Will be able to do it.
[0028]
In the nitrogen treatment system according to the eleventh aspect of the present invention, in addition to the invention according to the sixth, seventh, eighth or ninth aspect, the diluting treatment means may further comprise a nitrate nitrogen and a nitrite nitrogen in the water to be treated. A concentration detecting means for detecting the concentration is provided, and the dilution ratio of the water to be treated is adjusted based on the concentration detected by the concentration detecting means.
[0029]
According to a twelfth aspect of the present invention, in the above-described invention, the concentration detecting means is an ion sensor.
[0030]
According to the eleventh aspect of the present invention, in addition to the sixth, seventh, eighth or ninth aspect of the present invention, the dilution processing means may further include controlling the concentrations of the nitrate nitrogen and the nitrite nitrogen in the water to be treated. Since the dilution rate of the water to be treated is adjusted based on the concentration detected by the concentration detection means, the water to be treated can always be diluted to the nitrogen compound concentration optimal for the nitrogen treatment. Become like
[0031]
In particular, according to the invention of claim 12, since the concentration detecting means is an ion sensor, it is possible to easily detect the concentrations of nitrate ions as nitrate nitrogen and nitrite ions as nitrite nitrogen. The present invention can be realized easily and at low cost.
[0032]
In the nitrogen treatment system according to a thirteenth aspect of the present invention, in the eleventh or twelfth aspect of the invention, the diluting means includes a diluting tank for storing the water to be treated and a processing tank for storing the water to be treated in which the electrodes are immersed. Supply means for supplying the water to be treated to the dilution tank, transport means for transporting the water to be treated in the dilution tank to the treatment tank, and return means for returning the water to be treated in the treatment tank to the dilution tank as a diluent And a discharge means for discharging the water to be treated in the treatment tank, and a control means for controlling these supply means, transport means, return means and discharge means, and the concentration detection means is provided in the dilution tank or in the upstream of the dilution tank. The control means supplies the water to be treated to the dilution tank by the supply means, and, based on the output of the concentration detection means, returns the water to be treated which has been treated by the electrochemical method in the treatment tank by the return means. Return to dilution tank and process by discharge means After draining water to be treated inside, characterized in that it transported to the processing tank by the conveying means water to be treated is diluted with the dilution tank.
[0033]
According to a thirteenth aspect of the present invention, in the eleventh and twelfth aspects of the present invention, the diluting means includes a diluting tank for storing the water to be treated, a processing tank for storing the water to be treated in which the electrodes are immersed, Supply means for supplying the water to be treated to the dilution tank, conveying means for conveying the water to be treated in the dilution tank to the treatment tank, and return means for returning the water to be treated in the treatment tank to the dilution tank as a diluent, A discharge unit for discharging the water to be treated in the treatment tank, and a control unit for controlling the supply unit, the conveyance unit, the return unit, and the discharge unit are provided, and the concentration detection unit is provided in the dilution tank or at a stage preceding the dilution tank. The control means supplies the water to be treated to the dilution tank by the supply means, and, based on the output of the concentration detecting means, returns the water to be treated in the treatment tank by an electrochemical method in the dilution tank. To the processing tank in the processing tank After the water is discharged, the water to be treated diluted in the dilution tank is transported to the processing tank by the transport means, so that the water to be treated stored in the dilution tank is supplied to the supply means and returned based on the output of the concentration detection means. By this means, it becomes possible to adjust the nitrogen compound concentration to be optimal for the nitrogen treatment.
[0034]
This makes it possible to efficiently treat nitrogen compounds in the water to be treated with a simple system.
[0035]
Further, the water to be treated, whose nitrogen compound concentration has been adjusted in the dilution tank, is transported to the treatment tank by a transport means, and can be subjected to electrolytic denitrification in a separate tank from the dilution tank. Therefore, since the dilution treatment and the denitrification treatment are performed separately, the treatment efficiency can be improved.
[0036]
A nitrogen treatment system according to a fourteenth aspect of the present invention further includes, in addition to the tenth or thirteenth aspect, a supply amount detection unit that detects an integrated value of supply amounts of the water to be treated and the diluent into the dilution tank. The control means controls the supply means and the return means based on the output of the supply amount detection means.
[0037]
According to the fourteenth aspect, in addition to the tenth aspect or the thirteenth aspect, there is provided a supply amount detecting means for detecting an integrated value of supply amounts of the water to be treated and the diluent into the dilution tank, Since the means controls the supply means and the return means based on the output of the supply amount detection means, the water to be treated in the dilution tank can be adjusted to a nitrogen compound concentration optimal for nitrogen treatment by a simple system. become able to.
[0038]
The nitrogen treatment system according to a fifteenth aspect of the present invention is the nitrogen treatment system according to the eleventh or twelfth aspect, wherein the dilution treatment means stores a water to be treated, and a treatment tank in which an electrode is immersed in the treatment water. Supply means for supplying the water to be treated to the treatment tank, discharge means for discharging the water to be treated in the treatment tank, water level detection means for detecting the water level in the treatment tank, and control means for controlling the supply means and the discharge means Wherein the concentration detecting means is provided in the processing tank or in the preceding stage of the processing tank, and the control means performs processing by an electrochemical method in the processing tank by the discharging means based on the outputs of the concentration detecting means and the water level detecting means. After discharging a part of the water to be treated, the water to be treated is supplied to the treatment tank by the supply means.
[0039]
According to a fifteenth aspect of the present invention, in addition to the eleventh or twelfth aspect, the dilution processing means stores the water to be treated, and the treatment tank in which the electrode is immersed in the treatment water; Supply means for supplying the water to be treated to water, discharge means for discharging the water to be treated in the treatment tank, water level detection means for detecting the water level in the treatment tank, and control means for controlling the supply means and the discharge means. The concentration detection means is provided in the processing tank or in the preceding stage of the processing tank, and the control means is processed by the discharge means in the processing tank by an electrochemical method based on the outputs of the concentration detection means and the water level detection means. After a part of the water to be treated is discharged, the water to be treated is supplied to the treatment tank by the supply means, so that the water to be treated stored in the treatment tank is supplied to the supply means based on the outputs of the concentration detection means and the water level detection means. The best nitrogen compound for nitrogen treatment It is possible to adjust the density.
[0040]
This makes it possible to efficiently treat nitrogen compounds in the water to be treated with a simple system.
[0041]
Further, by performing the tank for diluting the water to be treated and the tank for performing the nitrogen treatment in the same tank, the system can be simplified.
[0042]
In the nitrogen treatment system according to the present invention, the electrode constituting the cathode may be a conductor containing Group Ib or Group IIb of the periodic table or a conductor containing the same. And the electrode constituting the anode is made of an insoluble material or carbon.
[0043]
According to the sixteenth aspect of the present invention, in addition to the above-described respective nitrogen treatment systems, the electrode constituting the cathode is a conductor containing Group Ib or Group IIb of the periodic table, or a conductor coated with the same group. Since the electrode constituting the anode is composed of an insoluble material or carbon, the reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia can be promoted, and The required time can be shortened. Further, even when the concentration of the nitrogen compound in the water to be treated is low as in the present invention, the nitrogen compound can be efficiently removed.
[0044]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a nitrogen treatment system S to which the nitrogen treatment method of the present invention is applied. The water to be treated which is treated by the nitrogen treatment system S in the present embodiment is, for example, water-soluble nitrate, that is, nitrate nitrogen penetrates into the soil by chemical fertilizer or animal excrement, and is contaminated by the nitrate nitrogen. Wastewater or industrial wastewater or domestic wastewater. The water to be treated used in this embodiment is contaminated groundwater having a relatively high total nitrogen concentration including nitrate nitrogen and the like, for example, containing 1000 mg / l or more of nitrate nitrogen. It is assumed that the water to be treated in this embodiment contains at least chloride ions as halide ions.
[0045]
The nitrogen treatment system S includes a storage tank 10 for storing the water to be treated, dilution processing means for diluting the water to be treated stored in the storage tank 10 (details will be described later), and the dilution processing means. And a nitrogen treatment device 1 as a nitrogen treatment means for performing a nitrogen treatment of the water to be treated diluted in.
[0046]
The dilution processing means includes a dilution tank 11, in which an ion sensor 22 as a concentration detection means for detecting the concentrations of nitrate nitrogen and nitrite nitrogen in the stored water to be treated is provided. Is provided. Further, a pipe 12 is connected to the dilution tank 11 via a supply electromagnetic valve 13 as a supply means, whereby the water to be treated in the storage tank 10 can be transported to the dilution tank 11. Further, a pipe 14 is connected to the dilution tank 11 via a transfer electromagnetic valve 15 as transfer means, whereby the water to be treated in the dilution tank 11 is supplied to the nitrogen treatment apparatus 1 (details will be described later). To a processing tank 2).
[0047]
A pipe 16 is connected to the processing tank 2 constituting the nitrogen processing apparatus 1 via a pump 17 as a return means and a return electromagnetic valve 18, whereby the water to be treated in the processing tank 2 is diluted with a diluent. And can be returned to the dilution tank 11. Further, a pipe 23 for draining part of the water to be treated after the nitrogen treatment to the outside is connected to the treatment tank 2 via a discharge solenoid valve 19 as discharge means.
[0048]
Note that pumps 20 and 21 may be provided on the pipe 12 upstream of the supply solenoid valve 13 and on the pipe 14 upstream of the transfer solenoid valve 15, respectively.
[0049]
In the present embodiment, the integrated value of the supply amounts of the water to be treated and the diluent passing through the electromagnetic valves 13 and 18 is provided in the pipe 12 provided with the supply electromagnetic valve 13 and the pipe 16 provided with the return electromagnetic valve 18. It is assumed that supply amount detection sensors (supply amount detection means) 24 and 25 are provided, respectively.
[0050]
In the present embodiment, the supply amounts of the water to be treated and the diluting liquid to the dilution tank 11 are detected only by the supply amount detection sensors 24 and 25. In addition, the water level in the dilution tank 11 is detected. A water level sensor (water level detection means) may be provided in parallel, or the supply amount into the dilution tank 11 may be detected only by the water level sensor.
[0051]
Here, FIG. 2 shows a microcomputer 30 as a control device of the nitrogen treatment system S. The input side of the microcomputer 30 is connected to the ion sensor 22 and the supply amount detection sensors 24 and 25, and the output side of the microcomputer 30 is connected to the solenoid valves 13, 15, 18, 19 and the pumps. 17, 20, and 21 are connected. Thus, the solenoid valves 13, 15, 18, 19 and the pumps 17, 20, 21 are controlled based on the outputs of the sensors 22, 24, 25.
[0052]
Next, the nitrogen processing apparatus 1 will be described with reference to FIG. The nitrogen treatment apparatus 1 according to the present embodiment performs denitrification treatment of the water to be treated by an electrochemical method (electrolysis). An inlet 29, an outlet 29 through which the water to be treated is discharged to the outside via the pipe 23 (only FIG. 1 is shown), and the treatment tank denitrified through the pipe 16 as a diluting liquid. A processing tank 2 constituting a processing chamber 4 having a return port 31 (only FIG. 1 is shown) for returning to the processing chamber 4 is disposed so as to face at least partially soaked in the water to be diluted in the processing chamber 4. A pair of electrodes, that is, an anode 5, a cathode 6, and a power supply 7 for supplying electricity to the electrodes 5, 6 are provided. The power supply 7 is connected to the output side of the microcomputer 30 and is controlled by the microcomputer 30. In FIG. 3, reference numeral 8 denotes a stirrer as stirring means for stirring the inside of the processing tank 2.
[0053]
The cathode 6 is made of a conductor containing Group Ib or Group IIb of the periodic table, or a conductor coated with the same group, and is made of, for example, zinc, copper, silver, or brass, which is an alloy of zinc and copper. The anode 5 is made of an insoluble electrode made of an insoluble metal such as platinum, iridium, palladium or an oxide thereof, or carbon.
[0054]
As shown in FIG. 3, a cylindrical shielding member 9 is provided between the anode 5 and the cathode 6 so as to surround the anode 5. The shielding member 9 is formed of a non-conductive member such as a glass fiber or a plastic mesh, for example, thereby preventing oxygen bubbles generated from the anode 5 from passing through to the cathode 6 side. it can. At this time, ions existing on the anode 5 side can pass through the shielding member 9 and move to the cathode 6 side. Further, the shielding member 9 is configured so as not to affect the anode flowing water by the stirring generated by the flowing water of the sludge or the stirring by the stirring bar 8.
[0055]
With the above configuration, the nitrogen processing of the nitrogen processing system S of the present embodiment will be described. First, the water to be treated previously stored in the storage tank 10 is transported into the dilution tank 11 via the pipe 12. First, the microcomputer 30 closes the transfer solenoid valve 15 and opens the supply solenoid valve 13. Further, the microcomputer 30 operates the pump 20 and detects the supply amount of the water to be treated supplied into the dilution tank 11 by the supply amount detection sensor 24. Then, the pump 20 is stopped based on the concentrations of nitrate ions and nitrite ions in the water to be treated detected by the ion sensor 22 provided in the dilution tank 11 and the supply amount detected by the supply amount detection sensor 24. Then, the supply solenoid valve 13 is closed.
[0056]
That is, when the concentrations of the nitrate ion and the nitrite ion detected by the ion sensor 22 are high, only a relatively small amount of the water to be treated is supplied to the dilution tank 11 by the output of the supply amount detection sensor 24. When the concentrations of nitrate ions and nitrite ions detected by the sensor 22 are relatively low, a relatively large amount of water to be treated is supplied to the dilution tank 11 by the output of the supply amount detection sensor 24.
[0057]
Thereafter, the microcomputer 30 opens the return electromagnetic valve 18 as the return means, operates the pump 17, and stores the water to be treated as the diluent after being processed by the nitrogen treatment apparatus 1 described later in detail in the dilution tank 11. And the concentration of nitrate ions and nitrite ions in the water to be treated in the dilution tank 11 is based on the supply amount detected by the supply amount detection sensor 25. And 300 mg / l or more and 800 mg / l or less.
[0058]
In the present embodiment, a diluent is added to the water to be treated stored in the dilution tank 11 in accordance with the ion concentration detected as described above, and a certain amount of the water to be diluted is adjusted in the dilution tank 11. In addition, the water to be treated may be adjusted to a range of 400 mg / l or more and 630 mg / l or less at which the current efficiency in the denitrification treatment becomes high, that is, the current efficiency becomes 70% or more. In the present embodiment, the water to be treated is adjusted to have a current efficiency of about 500 mg / l in the above range.
[0059]
However, when there is no water to be treated which has been treated by the nitrogen treatment apparatus 1, tap water or industrial water is supplied to the dilution tank 11, and nitrate ions and nitrite of the water to be treated stored in the dilution tank 11 are supplied. The concentration is adjusted so that the ions are in the above concentration range.
[0060]
The water to be treated, which has been adjusted to a predetermined concentration range in the dilution tank 11 as described above, is supplied to the treatment tank 2 of the nitrogen treatment apparatus 1 by operating the pump 21 by the microcomputer 30 and opening the transfer electromagnetic valve 15. Transported to At this time, it is assumed that the discharge solenoid valve 19 and the return solenoid valve 18 are closed by the microcomputer 30.
[0061]
Then, when the power source 7 is turned on by the microcomputer 30 and the cathode 6 and the anode 5 are energized, the diluted water to be treated transported into the treatment tank 2 is subjected to electrolytic treatment. On the cathode 6 side, nitrate ions contained in the diluted water to be treated are converted into nitrite ions by a reduction reaction (reaction formula A). Further, nitrite ions generated by the reduction reaction of nitrate ions are further converted to ammonia by a reduction reaction (reaction formula B). The reaction formulas A and B are shown below.
Reaction formula A NO3 −+ H2O + 2e−→ NO2 −+ 2OH−
Reaction formula B NO2 −+ 5H2O + 6e−→ NH3(Aq) + 7OH−
[0062]
On the other hand, on the anode 5 side, since at least chloride ions exist as halide ions in the diluted water to be treated as described above, hypochlorous acid, ozone or active oxygen is generated from the surface of the anode 5, and It produces a denitrification effect of ammonia in water and generates nitrogen gas (reaction formula C). The reaction C is shown below.
Reaction formula C 2NH3+ 3HClO → N2↑ + 3HCl + 3H2O
[0063]
Here, when the chloride ions contained in the diluted water to be treated are less than a predetermined concentration, for example, 100 mg / l, potassium chloride is specifically converted into chloride ions by chloride ion adjusting means (not shown). Alternatively, sodium chloride is added to the concentrated water to be treated. Thereby, the diluted water to be treated is in a state where hypochlorous acid is more easily generated by electrolysis, and the denitrification treatment of ammonia in the diluted water to be treated can be efficiently performed.
[0064]
As a result, the water to be diluted containing about 500 mg / l of nitrate ions and nitrite ions can be efficiently subjected to the removal treatment of nitrogen compounds in the nitrogen treatment apparatus 1, and 10 to 30 mg / L of nitrate ions can be removed. The wastewater can be discharged to the outside as treated water containing nitrogen.
[0065]
Furthermore, in the present embodiment, the water to be treated after diluting nitrate ions or nitrite ions as nitrogen compounds to about 500 mg / l in the diluting tank 11 is subjected to electrolytic treatment by the nitrogen treatment device 1, so that it is efficient. Can be subjected to a nitrogen compound removal treatment.
[0066]
Here, the experimental results shown in FIG. 4 show the concentration of nitrate nitrogen in the water to be treated when a platinum-based electrode is used for the anode 5 and a brass electrode is used for the cathode 6. In this experiment, each of the electrodes 5 and 6 was immersed in 300 ml of each solution containing nitrate nitrogen, and 2.5 A was flowed between the electrodes 5 and 6 to perform constant current electrolysis.
[0067]
FIG. 4 shows the current efficiency of the denitrification reaction when each solution having a nitrate nitrogen concentration of 100 mg / l, 300 mg / l, 500 mg / l, 800 mg / l, and 1000 mg / l was electrolyzed. According to this, the current efficiency when electrolyzing a solution having a nitrate nitrogen concentration of 100 mg / l is 35.2%, and the current efficiency when electrolyzing a 300 mg / l solution is 68.4%, and a current efficiency of 500 mg / l is obtained. Was 70.6%, the current efficiency was 61.8% when the 800 mg / l solution was electrolyzed, and the current efficiency was 30.9% when the 1000 mg / l solution was electrolyzed. Was.
[0068]
This indicates that the electrolytic efficiency of the denitrification reaction exceeds 60% when the concentration of the nitrate nitrogen in the water to be treated is 300 mg / l or more and 800 mg / l or less. In particular, in the case of electrolyzing the water to be treated with a nitrate nitrogen concentration of 100 mg / l or 1000 mg / l, the electrolysis efficiency is less than half that in the case of the above concentration range, and the efficiency is extremely low. It can be seen that it has decreased.
[0069]
Therefore, after the water to be treated is diluted to lower the nitrogen compound concentration and then electrolyzed, the nitrogen compound in the water to be treated can be efficiently denitrified. In particular, by adjusting the water to be treated to a range where the electrolytic efficiency of the denitrification reaction is high, for example, a range of 300 mg / l or more and 800 mg / l or less, the electrolytic efficiency of the denitrification reaction can be significantly improved. Thus, the processing efficiency of the nitrogen compound can be further improved.
[0070]
In this embodiment, the supply amount of the water to be treated from the storage tank 10 and the dilution from the treatment tank 2 are based on the output of the ion sensor 22 that detects the concentration of nitrate ions and nitrite ions provided in the dilution tank 11. Since the supply rate of the liquid is controlled and the dilution ratio of the water to be treated is adjusted, the denitrification treatment can be performed with high efficiency after always diluting the water to be treated to the optimum nitrogen compound concentration for the nitrogen treatment. become.
[0071]
Furthermore, since the concentration detecting means for detecting the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated is the ion sensor 22 as described above, it is easy to use nitrate ions as nitrate nitrogen and nitrite nitrogen as nitrite nitrogen. The concentration of nitrite ions can be detected, and the present invention can be realized easily and at low cost.
[0072]
After completion of the denitrification treatment of the diluted water to be treated as described above, or during the denitrification treatment, the microcomputer 30 closes the transfer electromagnetic valve 15 and opens the supply electromagnetic valve 13, and again, The water to be treated stored in the storage tank 10 is transported into the dilution tank 11 via the pipe 12. Then, the microcomputer 30 operates the pump 20 and detects the supply amount of the water to be treated supplied into the dilution tank 11 by the supply amount detection sensor 24. Then, the pump 20 is stopped based on the concentrations of nitrate ions and nitrite ions in the water to be treated detected by the ion sensor 22 provided in the dilution tank 11 and the supply amount detected by the supply amount detection sensor 24. Then, the supply solenoid valve 13 is closed.
[0073]
Thereafter, the microcomputer 30 opens the return electromagnetic valve 18, operates the pump 17, supplies the treated water, which has been subjected to the denitrification treatment in the treated water as described above, to the dilution tank 11 as a diluent, Based on the supply amount detected by the amount detection sensor 25, the concentration of nitrate ions and nitrite ions in the water to be treated in the dilution tank 11 is in a range where the current efficiency in the denitrification treatment is high, for example, 300 mg / l or more and 800 mg. It is adjusted so as to fall within the range of / l or less.
[0074]
Of the water to be treated in the treatment tank 2, the water to be treated that has not been supplied to the dilution tank 11 as a diluting liquid is drained to the outside by opening the discharge electromagnetic valve 19 by the microcomputer 30.
[0075]
Thereafter, the diluted water to be treated, which has been adjusted to the predetermined concentration range in the dilution tank 11 as described above, is transferred into the processing tank 2 of the nitrogen treatment apparatus 1 by opening the transfer electromagnetic valve 15 by the microcomputer 30. The denitrification treatment is performed as described above.
[0076]
Here, as the diluting liquid for diluting the water to be treated, by using the water to be treated after the denitrification treatment as described above, the water to be treated can be diluted without using fresh water or the like. it can. As a result, it is possible to suppress a rise in running cost due to an increase in the amount of drainage, and to realize an environment-friendly nitrogen treatment.
[0077]
Further, according to the present embodiment, as described above, the dilution tank 11, the solenoid valves 13, 15, 18, 19 and the pumps 17, 20, 21 connected to the microcomputer 30, the ion sensor 22, and the supply amount With a simple system including the dilution processing means constituted by the detection sensors 24 and 25, the water to be treated can be easily adjusted to the optimum nitrogen compound concentration for the nitrogen treatment.
[0078]
Furthermore, according to the present embodiment, the water to be treated, which has been adjusted to the optimum nitrogen compound concentration for the nitrogen treatment in the dilution tank 11, is transferred to the treatment tank 2 via the transfer electromagnetic valve 15, A denitrification treatment by electrolysis can be performed in a separate tank. Therefore, the dilution process and the denitrification process can be performed separately, and the processing efficiency can be further improved.
[0079]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 5 is an explanatory diagram showing an outline of a nitrogen treatment system T for realizing the nitrogen treatment method according to the second embodiment of the present invention. In FIG. 5, the same reference numerals as those in FIG. 1 have the same or similar functions.
[0080]
The nitrogen treatment system T in this embodiment also has a storage tank 10 for storing the water to be treated, dilution processing means for diluting the water to be treated stored in the storage tank 10, and a treatment tank diluted by the dilution processing means. And a nitrogen treatment device 1 as a nitrogen treatment means for performing nitrogen treatment of the treated water.
[0081]
The dilution means includes a treatment tank 2 in which the electrode is at least partially immersed. A pipe 12 is connected to the storage tank 10 via a supply electromagnetic valve 13 as a supply means, whereby water to be treated in the storage tank 10 can be transported to the processing tank 2. The storage tank 10 is provided with an ion sensor 22 as a concentration detection means for detecting the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated stored in the storage tank 10 as a preceding stage to the treatment tank 2. Is provided. Further, a pipe 23 for draining a part of the water to be treated after the nitrogen treatment to the outside is connected to the treatment tank 2 via a discharge solenoid valve 19 as discharge means. Note that a pump 20 may be provided in the pipe 12 and on the upstream side of the supply solenoid valve 13.
[0082]
In the present embodiment, it is assumed that the processing tank 2 is provided with a water level sensor (water level detecting means) 32 for detecting a water level in the processing tank 2. Further, the processing tank 2 is provided with electrodes for processing nitrogen compounds in the water to be treated, that is, an anode 5, a cathode 6, and a power source 7 for supplying electricity to the electrodes 5, 6 by an electrochemical method. Is provided.
[0083]
In the present embodiment, the cathode 6 is formed of a conductor containing Group Ib or Group IIb of the periodic table, or a conductor coated with the same group, such as zinc, copper, silver, and zinc. The anode 5 is made of an insoluble electrode made of an insoluble metal, for example, platinum, iridium, palladium or an oxide thereof, or carbon.
[0084]
Here, FIG. 6 shows a microcomputer 33 as a control device of the nitrogen treatment system T. The input side of the microcomputer 33 is connected to the ion sensor 22 and the water level sensor 32, and the output side of the microcomputer 33 is connected to the solenoid valves 13, 19, the pump 20, and the power supply 7. . Thus, the solenoid valves 13 and 19, the pump 20 and the power supply 7 are controlled based on the outputs of the sensors 22 and 32.
[0085]
With the above configuration, the nitrogen processing of the nitrogen processing system T of this embodiment will be described. Normally, it is assumed that the water to be treated which has been denitrified in the previous denitrification treatment is stored in the treatment tank 2. However, when the denitrified water to be treated is not stored in the treatment tank 2, tap water, industrial water, and the like are stored in the treatment tank 2 in advance. First, the microcomputer 33 detects the concentrations of nitrate ions and nitrite ions in the water to be treated stored in the storage tank 10 by the ion sensor 22, and controls the opening and closing of the discharge valve 19 based on these concentrations. The amount of water to be treated is left in the treatment tank 2 in accordance with the concentration detected by the ion sensor 22.
[0086]
Next, the microcomputer 33 opens the supply electromagnetic valve 13 and operates the pump 20 to supply the water to be treated in an amount corresponding to the concentration detected by the ion sensor 22 as described above.
[0087]
That is, when the concentrations of nitrate ions and nitrite ions detected by the ion sensor 22 are high, the microcomputer 33 discharges the water to be treated, which is detected by the water level sensor 32, to a relatively high position. The opening and closing of the solenoid valve 19 is controlled. Thereafter, the supply solenoid valve 13 is opened until the water level sensor 32 detects that the water is full, and the water to be treated is supplied from the storage tank 10 to the treatment tank 2. On the other hand, when the concentrations of the nitrate ion and the nitrite ion detected by the ion sensor 22 are low, the microcomputer 33 sets the discharge electromagnetic valve 19 until the water level of the water to be treated detected by the water level sensor 32 becomes a low position. Then, the supply solenoid valve 13 is opened until the water level sensor 32 detects that the water is full, and the water to be treated is supplied from the storage tank 10 to the treatment tank 2.
[0088]
Thereby, the water to be treated in the treatment tank 2 is adjusted so that the concentrations of nitrate ions and nitrite ions are in a range where the current efficiency in the denitrification treatment is high, for example, in a range of 300 mg / l to 800 mg / l. Is done. In addition, the water to be treated may be adjusted to a range of 400 mg / l or more and 630 mg / l or less at which the current efficiency in the denitrification treatment becomes high, that is, the current efficiency becomes 70% or more. In the present embodiment, the water to be treated is adjusted to have a current efficiency of about 500 mg / l in the above range.
[0089]
The diluted water to be diluted, which has been diluted in the processing tank 2 as described above, is supplied with electricity to the cathode 6 and the anode 5 by turning on the power supply 7 by the microcomputer 33, and is conveyed into the processing tank 2. The water to be treated is subjected to electrolytic treatment. On the cathode 6 side, nitrate ions contained in the diluted water to be treated are converted into nitrite ions by a reduction reaction (the above-mentioned reaction formula A). Further, nitrite ions generated by the reduction reaction of nitrate ions are further converted to ammonia by the reduction reaction (the above-mentioned reaction formula B).
[0090]
On the other hand, on the anode 5 side, since at least chloride ions are present as halide ions in the water to be diluted as described above, hypochlorous acid, ozone or active oxygen is generated from the surface of the anode 5, and The denitrification of ammonia in water is caused to generate nitrogen gas (the above-mentioned reaction formula C).
[0091]
Thereby, also in this embodiment, since the water to be treated is diluted by the diluting means to a nitrogen compound concentration optimal for the denitrification treatment and then denitrified, the nitrogen compounds in the water to be treated are efficiently removed. Can be processed.
[0092]
In this embodiment, the supply and discharge of the water to be treated into and from the treatment tank 2 are controlled by the microcomputer 33 based on the concentration of the nitrogen compound in the water to be treated, whereby the water to be treated is subjected to the denitrification reaction. Dilution treatment can be performed to an optimum nitrogen compound concentration, and the present invention can be realized with a simple system.
[0093]
Furthermore, in this embodiment, by performing the tank for diluting the water to be treated and the tank for performing the nitrogen treatment in the same treatment tank 2, the system can be further simplified.
[0094]
Further, according to each of the above-described embodiments, it is possible to efficiently remove nitrogen compounds such as nitrate nitrogen contained in the water to be treated without using a special additive such as methanol in the water to be treated as in the related art. Therefore, maintenance workability can be improved.
[0095]
Furthermore, since treatment of nitrogen compounds such as nitrate nitrogen is not performed by biological treatment as in the related art, temperature control of bacteria and the like can be unnecessary, and the nitrogen treatment system itself can be downsized. Costs can be reduced.
[0096]
【The invention's effect】
As described above in detail, according to the present invention, in a method for treating a nitrogen compound in water to be treated by an electrochemical method, the treated water is diluted, the nitrogen compound concentration of the water to be treated is reduced, and then the concentration of the nitrogen compound is reduced. Since the treated water is treated by the electrochemical method, the nitrogen compounds in the treated water can be treated efficiently.
[0097]
According to the second aspect of the present invention, in the above invention, the concentration of the nitrogen compound in the water to be treated is adjusted to a range where the current efficiency of the denitrification reaction is high, for example, 300 mg / l to 800 mg / l as in the third aspect of the invention. Since the dilution is performed within the range, the nitrogen treatment can be performed at an optimal nitrogen compound concentration for the treatment of the nitrogen compound in the water to be treated by the electrochemical method, and the treatment efficiency of the nitrogen compound can be further improved. Become like
[0098]
According to the invention of claim 4, in each of the above-mentioned inventions, the water to be treated after being treated by the electrochemical method is used as the diluent, so that the water to be treated is diluted without using fresh water or the like. As a result, it is possible to suppress a rise in running cost due to an increase in the amount of drainage, and to realize nitrogen treatment suitable for the environment.
[0099]
According to the invention of claim 5, in each of the above inventions, the dilution rate is adjusted based on the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated, so that the concentration of the nitrogen compound is always adjusted to the optimum concentration for nitrogen treatment. The treated water can be diluted.
[0100]
According to the invention of claim 6, in a nitrogen treatment system for treating a nitrogen compound in the water to be treated, at least a part is immersed in the water to be treated, and at least one pair for treating the water to be treated by an electrochemical method. And the diluting means for diluting the water to be treated and reducing the nitrogen compound concentration of the water to be treated. The nitrogen compound in the water to be treated can be efficiently treated by the chemical method.
[0101]
According to the invention of claim 7, in addition to the above-mentioned invention, the diluting means sets the concentration of the nitrogen compound in the water to be treated in a range in which the current efficiency of the denitrification reaction is high, for example, 300 mg / l or more as in claim 8. Since the dilution is performed to a range of 800 mg / l or less, the nitrogen treatment can be performed at an optimal nitrogen compound concentration for the treatment of the nitrogen compound in the water to be treated by the electrochemical method using the respective electrodes. The processing efficiency of the nitrogen compound can be improved.
[0102]
According to the ninth aspect of the present invention, in addition to the sixth, seventh or eighth aspect of the present invention, the water to be treated after being treated by the electrochemical method is used as a diluent, so that a new water supply is provided. It becomes possible to dilute the water to be treated without using any other means, thereby suppressing a rise in running costs due to an increase in the amount of drainage and realizing a nitrogen treatment suitable for the environment. .
[0103]
According to a tenth aspect of the present invention, in the sixth, seventh or ninth aspect of the invention, the dilution processing means stores the dilution tank for storing the water to be treated and the water to be treated in which the electrode is immersed. A treatment tank, a supply means for supplying the water to be treated to the dilution tank, a transport means for carrying the water to be treated in the dilution tank to the treatment tank, and a return of the water to be treated in the treatment tank to the dilution tank as a diluent. Return means, discharge means for discharging the water to be treated in the treatment tank, and control means for controlling these supply means, transport means, return means and discharge means, and in the dilution tank, A water level detecting means for detecting a water level, wherein the control means controls the supply means and the return means based on the output of the water level detecting means, so that the water to be treated is always diluted to a nitrogen compound concentration suitable for nitrogen treatment. Will be able to do it.
[0104]
According to the eleventh aspect of the present invention, in addition to the sixth, seventh, eighth or ninth aspect of the present invention, the dilution processing means may further include controlling the concentrations of the nitrate nitrogen and the nitrite nitrogen in the water to be treated. Since the dilution rate of the water to be treated is adjusted based on the concentration detected by the concentration detection means, the water to be treated can always be diluted to the nitrogen compound concentration optimal for the nitrogen treatment. Become like
[0105]
In particular, according to the invention of claim 12, since the concentration detecting means is an ion sensor, it is possible to easily detect the concentrations of nitrate ions as nitrate nitrogen and nitrite ions as nitrite nitrogen. The present invention can be realized easily and at low cost.
[0106]
According to a thirteenth aspect of the present invention, in the eleventh and twelfth aspects of the present invention, the diluting means includes a diluting tank for storing the water to be treated, a processing tank for storing the water to be treated in which the electrodes are immersed, Supply means for supplying the water to be treated to the dilution tank, conveying means for conveying the water to be treated in the dilution tank to the treatment tank, and return means for returning the water to be treated in the treatment tank to the dilution tank as a diluent, A discharge unit for discharging the water to be treated in the treatment tank, and a control unit for controlling the supply unit, the conveyance unit, the return unit, and the discharge unit are provided, and the concentration detection unit is provided in the dilution tank or at a stage preceding the dilution tank. The control means supplies the water to be treated to the dilution tank by the supply means, and, based on the output of the concentration detecting means, returns the water to be treated in the treatment tank by an electrochemical method in the dilution tank. To the processing tank in the processing tank After the water is discharged, the water to be treated diluted in the dilution tank is transported to the processing tank by the transport means, so that the water to be treated stored in the dilution tank is supplied to the supply means and returned based on the output of the concentration detection means. By this means, it becomes possible to adjust the nitrogen compound concentration to be optimal for the nitrogen treatment.
[0107]
This makes it possible to efficiently treat nitrogen compounds in the water to be treated with a simple system.
[0108]
Further, the water to be treated, whose nitrogen compound concentration has been adjusted in the dilution tank, is transported to the treatment tank by a transport means, and can be subjected to electrolytic denitrification in a separate tank from the dilution tank. Therefore, since the dilution treatment and the denitrification treatment are performed separately, the treatment efficiency can be improved.
[0109]
According to the fourteenth aspect, in addition to the tenth aspect or the thirteenth aspect, there is provided a supply amount detecting means for detecting an integrated value of supply amounts of the water to be treated and the diluent into the dilution tank, Since the means controls the supply means and the return means based on the output of the supply amount detection means, the water to be treated in the dilution tank can be adjusted to a nitrogen compound concentration optimal for nitrogen treatment by a simple system. become able to.
[0110]
According to a fifteenth aspect of the present invention, in addition to the eleventh or twelfth aspect, the dilution processing means stores the water to be treated, and the treatment tank in which the electrode is immersed in the treatment water; Supply means for supplying the water to be treated to water, discharge means for discharging the water to be treated in the treatment tank, water level detection means for detecting the water level in the treatment tank, and control means for controlling the supply means and the discharge means. The concentration detection means is provided in the processing tank or in the preceding stage of the processing tank, and the control means is processed by the discharge means in the processing tank by an electrochemical method based on the outputs of the concentration detection means and the water level detection means. After a part of the water to be treated is discharged, the water to be treated is supplied to the treatment tank by the supply means, so that the water to be treated stored in the treatment tank is supplied to the supply means based on the outputs of the concentration detection means and the water level detection means. The best nitrogen compound for nitrogen treatment It is possible to adjust the density.
[0111]
This makes it possible to efficiently treat nitrogen compounds in the water to be treated with a simple system.
[0112]
Further, by performing the tank for diluting the water to be treated and the tank for performing the nitrogen treatment in the same tank, the system can be simplified.
[0113]
According to the sixteenth aspect of the present invention, in addition to the above-described respective nitrogen treatment systems, the electrode constituting the cathode is a conductor containing Group Ib or Group IIb of the periodic table, or a conductor coated with the same group. Since the electrode constituting the anode is composed of an insoluble material or carbon, the reduction reaction of nitrate nitrogen in the water to be treated to nitrite nitrogen and ammonia can be promoted, and The required time can be shortened. Further, even when the concentration of the nitrogen compound in the water to be treated is low as in the present invention, the nitrogen compound can be efficiently removed.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of a nitrogen treatment system of the present invention.
FIG. 2 is a block diagram of a microcomputer of the nitrogen treatment system of the present invention.
FIG. 3 is an explanatory diagram showing an outline of a nitrogen treatment apparatus.
FIG. 4 is a diagram showing the current efficiency of the denitrification reaction with respect to the concentration of nitrate nitrogen in the water to be treated.
FIG. 5 is an explanatory diagram showing an outline of a nitrogen treatment system of another embodiment.
FIG. 6 is a block diagram of a microcomputer of a nitrogen treatment system according to another embodiment.
[Explanation of symbols]
S, T nitrogen treatment system
1 Nitrogen treatment equipment
2 Processing tank
4 Wastewater treatment room
5 anode
6 cathode
10 storage tank
11 dilution tank
12, 14, 16, 23 ° piping
13, 15, 18, 19 Solenoid valve
17, 20, 21mm pump
22 ion sensor
24, 25 ° supply amount detection sensor
30, 33 microcomputer
32 water level sensor

Claims (16)

電気化学的手法により被処理水中の窒素化合物を処理する方法であって、
前記被処理水を希釈し、当該被処理水の窒素化合物濃度を低下させた後、当該被処理水を電気化学的手法により処理することを特徴とする窒素処理方法。A method for treating a nitrogen compound in water to be treated by an electrochemical method,
A nitrogen treatment method comprising: diluting the water to be treated, reducing the concentration of nitrogen compounds in the water to be treated, and treating the water to be treated by an electrochemical method. 前記被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲に希釈することを特徴とする請求項１の窒素処理方法。The nitrogen treatment method according to claim 1, wherein the nitrogen compound concentration of the water to be treated is diluted to a range where the current efficiency of the denitrification reaction is increased. 前記被処理水の窒素化合物濃度を、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈することを特徴とする請求項１の窒素処理方法。The nitrogen treatment method according to claim 1, wherein the nitrogen compound concentration of the water to be treated is diluted to a range of 300 mg / l to 800 mg / l. 前記電気化学的手法により処理された後の前記被処理水を希釈液として用いることを特徴とする請求項１、請求項２又は請求項３の窒素処理方法。4. The nitrogen treatment method according to claim 1, wherein the water to be treated after being treated by the electrochemical method is used as a diluent. 前記被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度に基づいて希釈率を調整することを特徴とする請求項１、請求項２、請求項３又は請求項４の窒素処理方法。5. The nitrogen treatment method according to claim 1, wherein the dilution ratio is adjusted based on the concentrations of nitrate nitrogen and nitrite nitrogen in the water to be treated. 被処理水中の窒素化合物を処理する窒素処理システムであって、
前記被処理水に少なくとも一部が浸漬され、電気化学的手法により当該被処理水を処理するための少なくとも一対の電極と、
前記被処理水を希釈し、当該被処理水の窒素化合物濃度を低下させる希釈処理手段を備えることを特徴とする窒素処理システム。A nitrogen treatment system for treating a nitrogen compound in water to be treated,
At least a part is immersed in the water to be treated, and at least one pair of electrodes for treating the water to be treated by an electrochemical method,
A nitrogen treatment system, comprising: dilution treatment means for diluting the treatment water and lowering the concentration of nitrogen compounds in the treatment water. 前記希釈処理手段は、前記被処理水の窒素化合物濃度を、脱窒反応の電流効率が高くなる範囲に希釈することを特徴とする請求項６の窒素処理システム。7. The nitrogen treatment system according to claim 6, wherein the dilution treatment means dilutes the concentration of the nitrogen compound in the water to be treated so as to increase the current efficiency of the denitrification reaction. 前記希釈処理手段は、前記被処理水の窒素化合物濃度を、３００ｍｇ／ｌ以上８００ｍｇ／ｌ以下の範囲に希釈することを特徴とする請求項６の窒素処理システム。7. The nitrogen treatment system according to claim 6, wherein said dilution means dilutes the nitrogen compound concentration of the water to be treated to a range of 300 mg / l or more and 800 mg / l or less. 前記電気化学的手法により処理された後の前記被処理水を希釈液として用いることを特徴とする請求項６、請求項７又は請求項８の窒素処理システム。9. The nitrogen treatment system according to claim 6, wherein the water to be treated after being treated by the electrochemical method is used as a diluent. 前記希釈処理手段は、
前記被処理水を貯留する希釈槽と、
前記電極が浸漬される被処理水を貯溜する処理槽と、
前記希釈槽へ前記被処理水を供給する供給手段と、
前記希釈槽内の被処理水を前記処理槽に搬送する搬送手段と、
前記処理槽内の被処理水を希釈液として前記希釈槽へ返送する返送手段と、
前記処理槽内の前記被処理水を排出する排出手段と、
これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、
前記希釈槽内には、該希釈槽内の水位を検出する水位検出手段を備え、
前記制御手段は、当該水位検出手段の出力に基づいて前記供給手段及び前記返送手段を制御することを特徴とする請求項６、請求項７又は請求項９の窒素処理システム。The dilution processing means,
A dilution tank for storing the water to be treated,
A treatment tank that stores the water to be treated in which the electrode is immersed,
Supply means for supplying the water to be treated to the dilution tank,
Transport means for transporting the water to be treated in the dilution tank to the treatment tank,
Return means for returning the water to be treated in the treatment tank to the dilution tank as a diluent,
Discharging means for discharging the water to be treated in the treatment tank,
Control means for controlling these supply means, transport means, return means and discharge means,
In the dilution tank, a water level detection unit for detecting a water level in the dilution tank,
10. The nitrogen treatment system according to claim 6, wherein the control unit controls the supply unit and the return unit based on an output of the water level detection unit. 前記希釈処理手段は、前記被処理水中の硝酸態窒素及び亜硝酸態窒素の濃度を検出する濃度検出手段を備え、
前記濃度検出手段の検出する濃度に基づいて当該被処理水の希釈率を調整することを特徴とする請求項６、請求項７、請求項８又は請求項９の窒素処理システム。The dilution treatment means includes a concentration detection means for detecting the concentration of nitrate nitrogen and nitrite nitrogen in the water to be treated,
10. The nitrogen treatment system according to claim 6, wherein the dilution rate of the water to be treated is adjusted based on the concentration detected by the concentration detection means. 前記濃度検出手段は、イオンセンサであることを特徴とする請求項１１の窒素処理システム。The nitrogen treatment system according to claim 11, wherein the concentration detecting means is an ion sensor. 前記希釈処理手段は、
前記被処理水を貯留する希釈槽と、
前記電極が浸漬される被処理水を貯溜する処理槽と、
前記希釈槽へ前記被処理水を供給する供給手段と、
前記希釈槽内の被処理水を前記処理槽に搬送する搬送手段と、
前記処理槽内の被処理水を希釈液として前記希釈槽へ返送する返送手段と、
前記処理槽内の前記被処理水を排出する排出手段と、
これら供給手段、搬送手段、返送手段及び排出手段を制御する制御手段とを備え、
前記濃度検出手段は、前記希釈槽内又は前記希釈槽の前段に設けられ、
前記制御手段は、前記供給手段により前記被処理水を前記希釈槽に供給すると共に、前記濃度検出手段の出力に基づき、前記処理槽内にて電気化学的手法により処理された前記被処理水を前記返送手段により前記希釈槽に返送し、前記排出手段により前記処理槽内の前記被処理水を排出した後、前記希釈槽内にて希釈された前記被処理水を前記搬送手段により前記処理槽に搬送することを特徴とする請求項１１又は請求項１２の窒素処理システム。The dilution processing means,
A dilution tank for storing the water to be treated,
A treatment tank that stores the water to be treated in which the electrode is immersed,
Supply means for supplying the water to be treated to the dilution tank,
Transport means for transporting the water to be treated in the dilution tank to the treatment tank,
Return means for returning the water to be treated in the treatment tank to the dilution tank as a diluent,
Discharging means for discharging the water to be treated in the treatment tank,
Control means for controlling these supply means, transport means, return means and discharge means,
The concentration detection means is provided in the dilution tank or at a stage prior to the dilution tank,
The control means supplies the water to be treated to the dilution tank by the supply means and, based on an output of the concentration detecting means, controls the water to be treated which has been treated by an electrochemical method in the treatment tank. After returning the water to be treated in the treatment tank by the return means and returning the water to be treated in the treatment tank by the return means, the treatment water diluted in the dilution tank is transported by the transfer means to the treatment tank. 13. The nitrogen treatment system according to claim 11, wherein the nitrogen treatment system is transported. 前記希釈槽内への前記被処理水及び前記希釈液の供給量の積算値を検出する供給量検出手段を備え、
前記制御手段は、当該供給量検出手段の出力に基づいて前記供給手段及び前記返送手段を制御することを特徴とする請求項１０及び請求項１３の窒素処理システム。A supply amount detection unit that detects an integrated value of supply amounts of the water to be treated and the diluent into the dilution tank,
14. The nitrogen treatment system according to claim 10, wherein the control unit controls the supply unit and the return unit based on an output of the supply amount detection unit. 前記希釈処理手段は、
前記被処理水を貯留し、該処理水に前記電極が浸漬される処理槽と、
該処理槽へ前記被処理水を供給する供給手段と、
前記処理槽内の前記被処理水を排出する排出手段と、
前記処理槽内の水位を検出する水位検出手段と、
前記供給手段及び排出手段を制御する制御手段とを備え、
前記濃度検出手段は、前記処理槽又は前記処理槽の前段に設けられ、
前記制御手段は、前記濃度検出手段及び水位検出手段の出力に基づき、前記排出手段により前記処理槽内にて電気化学的手法により処理された前記被処理水の一部を排出した後、前記供給手段により前記被処理水を前記処理槽に供給することを特徴とする請求項１１又は請求項１２の窒素処理システム。The dilution processing means,
A treatment tank that stores the water to be treated, and in which the electrode is immersed in the treated water,
Supply means for supplying the water to be treated to the treatment tank,
Discharging means for discharging the water to be treated in the treatment tank,
Water level detection means for detecting a water level in the treatment tank,
Control means for controlling the supply means and the discharge means,
The concentration detection means is provided in the processing tank or in a preceding stage of the processing tank,
The control means discharges a part of the water to be treated, which has been treated by the electrochemical method in the treatment tank by the discharge means, based on outputs of the concentration detection means and the water level detection means, and then supplies the water. 13. The nitrogen treatment system according to claim 11, wherein the water to be treated is supplied to the treatment tank by means. カソードを構成する前記電極は、周期表の第Ｉｂ族又は第ＩＩｂ族を含む導電体、若しくは、同族を導電体に被覆したものにより構成し、アノードを構成する前記電極は、不溶性材料又はカーボンにより構成することを特徴とする請求項６、請求項７、請求項８、請求項９、請求項１０、請求項１１、請求項１２、請求項１３、請求項１４又は請求項１５の窒素処理システム。The electrode constituting the cathode is formed of a conductor containing Group Ib or Group IIb of the periodic table, or a conductor coated with the same group, and the electrode constituting the anode is formed of an insoluble material or carbon. The nitrogen treatment system according to claim 6, claim 7, claim 8, claim 9, claim 10, claim 11, claim 12, claim 13, claim 14, or claim 15, wherein .
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JP2010175185A (en) * 2009-01-30 2010-08-12 Noritz Corp Latent heat recovery type water heating system

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