JP3794838B2 - Minamata creature breeding equipment and breeding water purification method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は水棲生物飼育装置及び飼育水浄化法に関し、例えば水棲生物の畜養・輸送設備、水族館水槽及びこのような閉鎖系循環水の浄化に適用して有利である。
【０００２】
【従来の技術】
従来、水棲生物飼育水の浄化対象は、飼育生物に対し毒性を持つアンモニア態窒素および亜硝酸態窒素であり、特に亜硝酸態窒素は低濃度でも非常に毒性があった。従来このような水中のアンモニア態窒素及び亜硝酸態窒素については、硝化菌のような微生物を利用して硝酸態窒素にまで酸化し、処理済水としていた。ここで、硝化菌とは好気的条件でアンモニアを酸化して亜硝酸を生成する亜硝酸菌、及び同様に好気的条件で亜硝酸を硝酸に酸化する反応を行なう硝酸菌の総称である。硝化菌は上述の反応から得られるエネルギーを利用して、炭酸固定を行い増殖する独立栄養細菌であり、一般的には増殖に有機物を必要としない。
【０００３】
硝化菌のような微生物を利用した浄化法では、アンモニア態窒素は硝酸態窒素に酸化されるのみであり、いぜん循環水には硝酸態窒素が含まれており、これが飼育水のｐＨ低下を招いている。しかし、硝酸態窒素はある程度高濃度（例えば１００〜２００ｐｐｍ程度、ただし飼育生物種により異なる）まで、飼育生物に悪影響を与えないため、これまで特に処理はなされていなかった。しかし、この硝酸態窒素も蓄積されるとｐＨ等への影響は無視できないものとなるため、より広範な生物の長期間飼育を可能にするためには、この硝酸態窒素も除去する必要がある。
水中の硝酸態窒素の処理方法としては、脱窒菌を利用して硝酸を窒素にまで還元する方法が、産業排水処理のような一般排水処理分野において知られている。脱窒菌とは、多くは嫌気条件で、硝酸もしくは亜硝酸を還元する反応を有する多種多様な種類の微生物の総称であり、この脱窒菌は増殖に有機物を必要とする従属栄養微生物及び独立栄養微生物である。
【０００４】
【発明が解決しようとする課題】
閉鎖循環系で長期間にわたり水棲生物を飼育しようとすると、上記の理由から飼育水中のアンモニア態窒素とともに硝酸態窒素も処理することが要求される。飼育水は飼育生物の生命維持のため、高い溶存酸素濃度を必要としており、高流速で循環させているのが現状である。
しかし、従来の脱窒菌を利用した硝酸態窒素処理においては処理槽（脱窒槽）内を還元雰囲気にせねばならず、そのためシステム的にアンモニア態窒素及び亜硝酸態窒素を処理する硝化槽と脱窒槽を直列に配置すると、リアクターとして大容量を要求される。
【０００５】
これに対し、硝化槽と脱窒槽を並列に配置して処理する方法も試みられた。従来排水処理で脱窒工程における水素供与体として用いられているメタノールは可燃物であり、また飼育生物に対し毒性を持つものであるため、代替としてグルコース等を用いて処理を行ったが、硝酸態窒素処理はできるものの飼育水の汚濁を招いてしまい、好ましくない。
本発明の課題は、閉鎖循環系で広範な種類の水棲生物を長期間にわたり飼育できる水棲生物飼育水の浄化法であって、生物への毒性や水の汚濁の問題がなく、装置構成がコンパクトであり、しかも浄化処理能力が高く循環水の健全性の向上する方法及びこれを実現した水棲生物飼育装置を提供することにある。
【０００６】
【課題を解決するための手段】
上記課題を解決する本発明は、
(1) 閉鎖循環系において水棲生物を飼育した飼育水を硝化工程と脱窒工程に付すことにより該飼育水中のアンモニア態窒素、亜硝酸態窒素及び硝酸態窒素を除去する方法であって、前記硝化工程及び脱窒工程を並列に配置し、硝化工程には循環飼育水を常時通水しながら硝化菌により硝化反応を行わせ、且つ脱窒工程には弁の切替えにより循環飼育水を間歇通水することにより嫌気性雰囲気とするとともに、電極から電解水素を発生させて脱窒菌に取り込ませながら、もしくは電極からの電子を直接脱窒菌に供与しながら脱窒反応を行わせることを特徴とする水棲生物飼育水浄化法、
(2) 閉鎖循環系で水棲生物を飼育するために飼育水槽、硝化槽及び脱窒槽が飼育水循環ラインで連通されてなる水棲生物飼育装置であって、前記硝化槽及び前記脱窒槽は並列に配置されており、該硝化槽には循環飼育水を常時通水しながら硝化菌によりアンモニア態窒素及び亜硝酸態窒素の硝化反応を行わせ、且つ該脱窒素槽は入口又は出口に設けた弁の切替えにより循環飼育水を間歇通水することにより嫌気性雰囲気とし、電極から電解水素を発生させて脱窒菌に取り込ませながらもしくは電極からの電子を直接脱窒菌に供与しながら硝酸態窒素の脱窒反応を行わせるように構成されたことを特徴とする水棲生物飼育装置、及び
(3)閉鎖循環系において水棲生物を飼育した飼育水を硝化工程と脱窒工程に付すことにより、好気性雰囲気下において循環飼育水中のアンモニア態窒素、亜硝酸態窒素及び硝酸態窒素を除去する方法であって、前記硝化工程の後流に前記脱窒工程を設け、硝化工程は硝化菌により硝化反応を行わせ、且つ該脱窒工程においては光照射下で水草又は植物プランクトンにより脱窒反応させることを特徴とする水棲生物飼育水浄化法、である。
【０００７】
【発明の実施の形態】
本発明は、閉鎖循環系におけるアンモニア態窒素、亜硝酸態窒素及び硝酸態窒素を含有する飼育水を硝化工程及び脱窒工程に付して浄化し再度飼育水として循環させることを特徴とする方法であって、特に硝酸態窒素処理工程（脱窒工程）を工夫して、生物学的処理法による硝化工程と組み合わせることにより高い浄化性能を得て、飼育水の健全性を向上し、長期間の水質維持を可能としたものである。
【０００８】
本発明の第一の発明は、好気性条件で行なう硝化工程は循環水（飼育水）を常時通水しながら硝化菌でアンモニア態窒素及び亜硝酸態窒素をそれぞれ亜硝酸及び硝酸に酸化する生物学的処理法で行い、硝化工程と並列に設けた脱窒工程では、飼育循環水を間歇通水することにより嫌気性雰囲気とするとともに生物学的処理法と電気化学的手法の組み合わせで処理することに特徴がある。
すなわち、硝酸態窒素処理槽（脱窒槽）の出口側あるいは入口側に電磁弁等の弁を設置することによって間歇通水し、脱窒槽内に一定時間保持することにより槽内を嫌気性雰囲気とする。該脱窒槽内に電極を設置し、例えば電極表面に脱窒菌を付着させるなどして、槽内に脱窒菌を充填し、この電極に電流を流すことにより電解水素を発生させ、脱窒菌に取り込ませるか、あるいは電子を直接脱窒菌に供与することにより脱窒素処理を行わせる。このように従来の生物学的脱窒素処理に水素供与体として用いられたメタノール或いはグルコース等の有機物は必要としないので、毒性や水の汚濁の問題はない。
本発明の生物学的硝化工程に用いる硝化菌としてはこの種の硝化菌として公知のもの、例えばニトロソモナス属 Nitrosomonas sp. 、ニトロバクター属 Nitrobacter sp.等を用いることができる。
また、電気化学的手法に組み合わせる生物学的脱窒工程に用いる脱窒菌としては、この種の脱窒菌として公知のもの例えば下水処理場由来活性汚泥等が挙げられる。
硝化菌や脱窒菌の固定，担持に用いる担体も、この種技術分野で公知のものを用いることができる。
【０００９】
図１は第一発明の一実施態様を示すものであり、装置は飼育水槽（ａ）、センサホルダ（ｂ）、循環ポンプ（ｃ）、硝化槽（ｄ）、脱窒槽（ｅ）、人工肺（ｆ）、流量計（ｇ）、電磁弁（ｏ）及び飼育水循環ラインから構成される。センサホルダ（ｂ）には、ｐＨセンサ，溶存酸素計を設置できる。硝化槽（ｄ）には、例えばガラスビーズなどの担体（ｈ）を用いて硝化菌を固定する。脱窒槽（ｅ）には、例えば陰極（ｉ）には炭素（カーボン）製の電極を、陽極（ｊ）には炭素電極あるは白金電極を設置し、かつ、導電性の良い担体（ｋ）を充填し脱窒菌を固定する。電磁弁（ｆ）はタイマーにより一定時間毎に開閉を制御する。
このようにアンモニア態窒素及び亜硝酸態窒素処理槽〔硝化槽（ｄ）〕と硝酸態窒素処理槽〔脱窒槽（ｅ）〕は並列に設置し、かつ脱窒槽（ｅ）の出口ラインには電磁弁（ｏ）を設けて、硝化槽（ｄ）へのラインは常時通水状態であるのに対し、脱窒槽（ｅ）へは間歇通水とする。脱窒槽（ｅ）への循環水の供給を間歇とし、一定時間保持することで、脱窒槽（ｅ）内を嫌気状態にでき、硝酸態窒素を処理することができるようになる。図１では電磁弁（ｏ）の例を示したが、弁は手動のものであってもかまわない。また、弁は脱窒槽（ｅ）の出口ライン及び／又は入口ラインに設けることができる。
なお、人工肺（ｆ）とは外部から酸素を取り込み、循環水中の二酸化炭素と交換する機能をもつ装置であり、これを設置することにより、循環水中の溶存酸素濃度を高く維持することができる。
【００１０】
本発明装置における脱窒槽（ｅ）は、機械的撹拌等によって槽内の被処理水を均一化できる槽（完全混合槽）ではない。したがって陽極反応によって酸素が発生するとしても陽極（ｊ）に面した部分のみが好気的雰囲気になるだけであって、脱窒槽（ｅ）全体に影響を及ぼすものではない。従って、陽極で発生する酸素に対する特別な対策は必要としない。また、酸素発生電位より炭素の酸化電位のほうが低いため、炭酸ガスのほうがより生じ易い可能性がある。さらに、本発明者らが試験したところでは、電流値が低いため電極反応は脱窒槽（ｅ）全体に悪影響を及ぼす程活発ではないと考えられる。本発明を実施した結果が良好であったことからも、この推察が正しいと思われる。
【００１１】
本発明の第二の発明は、生物学的にアンモニア態窒素，亜硝酸態窒素を酸化して亜硝酸態窒素、硝酸態窒素とする硝化工程は第一発明と同様であり、この硝化工程に直列に配置する硝酸態窒素処理工程（脱窒工程）として、植物又は植物プランクトンの窒素化合物吸収能を利用するものである。硝酸態窒素処理槽（脱窒槽）内に、水質にあった水草あるいは微細藻等の植物プランクトンを固定，担持しておき、循環水中の硝酸態窒素を吸収させ、処理する。植物又は植物プランクトンは窒素化合物を窒素源として細胞中に取り込み、体合成成分として処理するので、脱窒素のために嫌気性雰囲気とする必要はなく好気性で行えること、そのために両工程は直列に配置できること、さらに淡水だけでなく、海水のような塩濃度の高い水に対しても適用可能であるため、飼育できる生物種が広くなること等の利点がある。
植物又は植物プランクトンを利用する場合、光合成のために脱窒槽を光照射する必要がある。また、植物又は植物プランクトンを例えばネット、ガラスビーズやハニカム形状の担持体、などに固定して用いることが好ましい。固定に用いる材料は上記に限定されるところはなく、この種技術分野で公知のものを用いることができる。
利用できる植物としては、例えばキンギョソウ、アヌビアスナナ、アマゾンソード等の水草が挙げられる。また植物プランクトンとしては例えば微細藻等が挙げられる。
硝化工程において利用できる硝化菌は第一の発明の場合と同様である。
【００１２】
図２は本発明の第二発明の一実施態様を示すものであり、飼育水槽（ａ）、センサホルダ（ｂ）、循環ポンプ（ｃ）、硝化槽（ｄ）、脱窒槽（ｅ）、人工肺（ｆ）、流量計（ｇ）、照明（ｌ）及び飼育水循環ラインから構成される。センサホルダ（ｂ）には、ｐＨセンサ、溶存酸素計を設置できる。硝化槽（ｄ）には、例えばガラスビーズなどの担体（ｈ）を用いて、硝化菌を固定し、アンモニア態窒素、亜硝酸態窒素を処理できる。脱窒槽（ｅ）には、脱窒槽（ｅ）の底にネット（ｍ）を張り、これに例えばキンギョソウなどの水草を固定し、脱窒槽（ｅ）内に保持することにより、循環水内の硝酸態窒素化合物を除去処理することができる。
【００１３】
本発明の第二発明の他の実施態様においては、アンモニア態窒素及び亜硝酸態窒素処理槽（硝化槽）は上記と同様であり、アンモニア態窒素及び亜硝酸態窒素をそれぞれ亜硝酸態窒素、硝酸態窒素に酸化する。硝酸態窒素処理槽（脱窒槽）内には、水質にあった植物プランクトンを固定しておき、植物プランクトンの窒素化合物吸収能を利用して循環水中の硝酸態窒素を吸収させ、処理する。処理装置は図３に示すように飼育水槽（ａ）、センサホルダ（ｂ）、循環ポンプ（ｃ）、硝化槽（ｄ）、脱窒槽（ｅ）、人工肺（ｆ）、流量計（ｇ）、照明（ｌ）および飼育水循環ラインから構成されており、センサホルダ（ｂ）には、ｐＨセンサ、溶存酸素計を設置できる。硝化槽（ｄ）には、例えばガラスビーズなどの担体（ｈ）を用いて、硝化菌を固定する。脱窒槽（ｅ）には、例えばハニカムろ材などの担持体（ｎ）を充填し、これに例えば微細藻類など植物プランクトンを固定させ、脱窒槽（ｅ）内に保持することにより、循環水内の硝酸態窒素化合物を除去処理することができる。脱窒槽（ｅ）としては、照射光を有効に利用するために平べったい偏平な形状が好ましい。十分量の植物プランクトンを利用することで、水草よりも速い処理速度を得ることができる。この理由は、植物プランクトンも水草と同様に窒素化合物を窒素源として細胞中に取り込み体合成成分として処理するが、植物プランクトンの方がその合成速度が速いためである。
【００１４】
【実施例】
以下、本発明を実施例により具体的に説明するがこれに限定されるところはない。
〔実施例１〕
図１の装置を用いて、硝化菌としてニトロソモナス属 Nitrosomonas sp. およびニトロバクター属 Nitrobacter sp.を３０００ｐｐｍ、ガラスビーズを担体として固定して用いた。また脱窒菌としては下水処理場由来活性汚泥を粒状炭素を担体として固定したものを用いた。電極は炭素電極を用い通電条件は５ｍＡの定電流で行った。弁としては電磁弁を用い、開閉間隔は６時間とし、飼育水は１リットル／ｍｉｎの流速で循環使用して浄化を行った。日々、３．４ｐｐｍのアンモニア態窒素を飼育水槽（ａ）内に添加し、循環水中のアンモニア態窒素、亜硝酸態窒素及び硝酸態窒素の濃度を測定、その処理性能を検討した。その結果、本装置によりアンモニア態窒素を０．１ｐｐｍ以下、亜硝酸態窒素を０．１ｐｐｍ以下、硝酸態窒素は１５ｐｐｍ以下、ｐＨ８前後、循環水中ＴＯＣ（全有機炭素）濃度を１０ｍｇ／リットル程度の水質を９０日以上維持することができた。この結果を図４に示す。
【００１５】
図４は実施例１における循環水質の変移を示すグラフであって、横軸は経過日数、縦軸は循環水中ＴＯＣ濃度（ｍｇ／リットル）、ｐＨ値及び循環水中の窒素量（ｍｇ／リットル）であり、■はアンモニア態窒素（ＮＨ4 −Ｎ）、▲は亜硝酸態窒素（ＮＯ2 −Ｎ）、●は硝酸態窒素（ＮＯ3 −Ｎ）を示すが、アンモニア態窒素■と亜硝酸態窒素▲は０．１ｐｐｍ以下であるため、Ｘ軸に重なって表示されている。
【００１６】
〔実施例２〕
まず実験として、硝酸態窒素処理のみを対象にビーカースケールで行った。１０ｍｇ／リットルの硝酸態窒素を含む被処理水中に水草としてキンギョソウを入れ、被処理水中の残存硝酸態窒素濃度を測定することにより、その処理性能を評価した。その結果、今回の実験では１．０ｍｇ−Ｎ／リットル・ｄａｙの処理速度を得ることができた。すなわち、一日あたり脱窒槽１リットル当たり１ｍｇの硝酸態窒素を処理できることがわかった。
そこで、図２の構成において、硝化槽には硝化菌を固定したガラスビーズ３００ｍｌ（硝化菌ニトロソモナス属 Nitrosomonas sp. およびニトロバクター属 Nitrobacter sp.３０００ｐｐｍに相当する量を担持）を入れ、脱窒槽にはキンギョソウをネットで固定し、光照射６０００ルクスの条件で、アンモニア態窒素を飼育槽に３．４ｐｐｍ／ｄａｙの割合で添加した。飼育水を１リットル／ｍｉｎの流速で循環使用したが、残存アンモニア濃度０．１ｐｐｍ以下、亜硝酸態窒素０．１ｐｐｍ以下、硝酸態窒素５０ｐｐｍ以下、ｐＨ７．５の水質に９０日間維持できた。
【００１７】
〔実施例３〕
まず実験として、硝酸態窒素処理のみを対象にビーカースケールで行った。１０ｍｇ／リットルの硝酸態窒素を含む被処理水中に植物プランクトン（微細藻）を入れ、被処理水中の残存硝酸態窒素濃度を測定することにより、その処理性を評価した。その結果、今回の実験系では、植物プランクトン乾燥重量として３０ｍｇ／リットルで１．０ｍｇ・Ｎ／リットル・ｄａｙの処理速度を得ることができた。すなわち、３０ｐｐｍの植物プランクトンが固定されている槽１リットルあたり１ｍｇの窒素を１日で処理できる。
そこで、図３の装置において、硝化槽には硝化菌を固定したガラスビーズ３００ｍｌ（硝化菌ニトロソモナス属 Nitrosomonas sp. およびニトロバクター属 Nitrobacter sp.３０００ｐｐｍに相当する量を担持）を入れ、脱窒槽には微細藻をハニカムろ材に固定して入れ、光照射６０００ルクスの条件で、アンモニア態窒素を飼育槽に３．４ｐｐｍ／ｄａｙの割合で添加した。飼育水を１リットル／ｍｉｎの流速で循環使用したが、残存アンモニア濃度０．１ｐｐｍ以下、亜硝酸態窒素０．１ｐｐｍ以下、硝酸態窒素５０ｐｐｍ以下、ｐＨ７．５の水質に９０日間維持できた。
【００１８】
【発明の効果】
以上説明のように本発明の第一又は第二の発明によれば、脱窒槽ではメタノールやグルコース等を用いることなく脱窒反応を行なうので、毒性や汚濁の問題なく循環水中の硝酸態窒素を低減できる。特に本発明の第一の発明によれば、硝化槽と脱窒槽を並列に配置したコンパクトな装置構成によりアンモニア態窒素及び硝酸態窒素の両者の高速処理が可能となり、閉鎖循環系の飼育水質を非常に良好な状態に保持することができる。
また、本発明の第二の発明では脱窒工程として好気条件で脱窒反応を行なう植物、植物プランクトンを用いるので、硝化工程後の循環水をそのまま脱窒工程に流入させることができる。また淡水のみならず海水での飼育にも適用でき、閉鎖循環系の飼育水質を非常に良好な状態に保持することができる。
【図面の簡単な説明】
【図１】 本発明の一実施態様を説明する概略図である。
【図２】 本発明の他の実施態様を説明する概略図である。
【図３】 本発明のさらに他の実施態様を説明する概略図である。
【図４】 本発明の実施例１における循環水質の変移を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aquatic organism breeding apparatus and a breeding water purification method, and is advantageous when applied to, for example, aquatic organism breeding / transportation equipment, an aquarium tank, and purification of such closed circulating water.
[0002]
[Prior art]
Conventionally, the aquatic organism breeding water purification targets are ammonia nitrogen and nitrite nitrogen which are toxic to the breeding organisms, and nitrite nitrogen was particularly toxic even at low concentrations. Conventionally, such ammonia nitrogen and nitrite nitrogen in water have been oxidized to nitrate nitrogen using microorganisms such as nitrifying bacteria to obtain treated water. Here, nitrifying bacteria is a general term for nitrite bacteria that oxidize ammonia under aerobic conditions to produce nitrite, and nitrite bacteria that similarly react to oxidize nitrous acid to nitric acid under aerobic conditions. . Nitrifying bacteria are autotrophic bacteria that grow by performing carbon fixation using the energy obtained from the above reaction, and generally do not require organic substances for growth.
[0003]
In the purification method using microorganisms such as nitrifying bacteria, ammonia nitrogen is only oxidized to nitrate nitrogen, and the circulating water always contains nitrate nitrogen, which causes a drop in the pH of the breeding water. It is. However, nitrate nitrogen has not been particularly treated so far because it does not adversely affect the reared organisms to a certain high concentration (for example, about 100 to 200 ppm, but varies depending on the species reared). However, if this nitrate nitrogen is also accumulated, the effect on pH and the like cannot be ignored. Therefore, it is necessary to remove this nitrate nitrogen in order to allow long-term breeding of a wider range of organisms. .
As a method for treating nitrate nitrogen in water, a method of reducing nitric acid to nitrogen using denitrifying bacteria is known in the general wastewater treatment field such as industrial wastewater treatment. Denitrifying bacteria are a general term for a wide variety of microorganisms that have a reaction to reduce nitric acid or nitrous acid, mostly under anaerobic conditions. These denitrifying bacteria are heterotrophic microorganisms and autotrophic microorganisms that require organic substances to grow. It is.
[0004]
[Problems to be solved by the invention]
If an aquatic organism is bred for a long time in a closed circulatory system, it is required to treat nitrate nitrogen as well as ammonia nitrogen in the breeding water for the above reasons. The breeding water requires a high dissolved oxygen concentration to maintain the life of the breeding organisms, and is currently circulated at a high flow rate.
However, in conventional nitrate nitrogen treatment using denitrifying bacteria, the inside of the treatment tank (denitrification tank) must be in a reducing atmosphere. Therefore, a nitrification tank and a denitrification tank that treat ammonia nitrogen and nitrite nitrogen systematically. If these are arranged in series, a large capacity is required as a reactor.
[0005]
On the other hand, a method in which a nitrification tank and a denitrification tank are arranged in parallel has also been tried. Methanol, which is conventionally used as a hydrogen donor in the denitrification process in wastewater treatment, is a flammable substance and is toxic to domesticated organisms. Although it can be treated with nitrogen, it causes contamination of breeding water, which is not preferable.
An object of the present invention is a purification method of aquatic organism breeding water that can breed a wide variety of aquatic organisms in a closed circulatory system for a long period of time, and there is no problem of toxicity to water or water pollution, and the device configuration is compact. In addition, it is an object of the present invention to provide a method for improving the soundness of circulating water with high purification capacity and aquatic organism breeding apparatus that realizes the method.
[0006]
[Means for Solving the Problems]
The present invention for solving the above problems
(1) A method for removing ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the breeding water by subjecting the breeding water in which the aquatic organisms are bred in a closed circulation system to a nitrification step and a denitrification step, Nitrification process and denitrification process are arranged in parallel, nitrification process is performed by nitrifying bacteria while constantly circulating circulating breeding water in nitrification process, and circulating breeding water is intermittently passed through denitrification process by switching valves An anaerobic atmosphere is created by watering, and a denitrification reaction is performed while generating electrolytic hydrogen from the electrode and taking it into the denitrifying bacteria, or by donating electrons from the electrode directly to the denitrifying bacteria. Minamata Breeding Water Purification Law,
(2) An aquatic organism breeding device in which a breeding aquarium, a nitrification tank, and a denitrification tank are connected by a breeding water circulation line to breed aquatic organisms in a closed circulation system, and the nitrification tank and the denitrification tank are arranged in parallel. The nitrification tank is allowed to conduct nitrification of ammonia nitrogen and nitrite nitrogen by nitrifying bacteria while constantly circulating circulating breeding water, and the denitrification tank is a valve provided at the inlet or outlet. Nitrogen nitrogen denitrification while intermittently passing circulating breeding water by switching to an anaerobic atmosphere, generating electrolytic hydrogen from the electrode and taking it into the denitrifying bacteria, or donating electrons from the electrode directly to the denitrifying bacteria An aquatic organism rearing device configured to cause a reaction; and
(3) Ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the circulating water are removed in an aerobic atmosphere by subjecting the breeding water that has been bred with aquatic organisms in a closed circulation system to a nitrification process and a denitrification process. A denitrification step is provided downstream of the nitrification step, wherein the nitrification step is performed by nitrifying bacteria, and in the denitrification step, denitrification reaction is performed by aquatic plants or phytoplankton under light irradiation. A method for purifying water from aquatic organisms, characterized in that
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a method characterized in that the breeding water containing ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in a closed circulation system is purified by subjecting it to a nitrification step and a denitrification step and circulated as breeding water again. In particular, the nitrate nitrogen treatment process (denitrification process) is devised, combined with the nitrification process by biological treatment method to obtain high purification performance, improve the soundness of breeding water, and Water quality can be maintained.
[0008]
According to the first aspect of the present invention, the nitrification step performed under aerobic conditions is a organism that oxidizes ammonia nitrogen and nitrite nitrogen to nitrite and nitric acid, respectively, by nitrifying bacteria while constantly circulating circulating water (bred water). In the denitrification process, which is performed in parallel with the nitrification process, an anaerobic atmosphere is created by intermittently passing the breeding circulation water, and the treatment is performed by a combination of biological treatment method and electrochemical method. There is a special feature.
That is, water is intermittently passed by installing a valve such as a solenoid valve on the outlet side or the inlet side of the nitrate nitrogen treatment tank (denitrification tank), and the tank is maintained in the denitrification tank for a certain period of time to create an anaerobic atmosphere. To do. An electrode is installed in the denitrification tank, and denitrifying bacteria are attached to the surface of the electrode, for example, the denitrifying bacteria are filled in the tank, and by passing an electric current through the electrode, electrolytic hydrogen is generated and taken into the denitrifying bacteria. Or by directly donating electrons to denitrifying bacteria. Thus, since organic substances such as methanol or glucose used as a hydrogen donor in the conventional biological denitrification treatment are not required, there is no problem of toxicity or water pollution.
As nitrifying bacteria used in the biological nitrification process of the present invention, those known as this type of nitrifying bacteria, such as Nitrosomonas sp., Nitrobacter sp.
Moreover, as a denitrifying bacterium used in the biological denitrifying step combined with the electrochemical method, a known one such as this type of denitrifying bacterium, such as activated sludge derived from a sewage treatment plant, can be mentioned.
As the carrier used for fixing and supporting nitrifying bacteria and denitrifying bacteria, those known in this technical field can be used.
[0009]
FIG. 1 shows an embodiment of the first invention. The apparatus is a breeding aquarium (a), a sensor holder (b), a circulation pump (c), a nitrification tank (d), a denitrification tank (e), an artificial lung. (F) It consists of a flow meter (g), a solenoid valve (o), and a breeding water circulation line. A pH sensor and a dissolved oxygen meter can be installed in the sensor holder (b). In the nitrification tank (d), nitrifying bacteria are fixed using a carrier (h) such as glass beads. In the denitrification tank (e), for example, a carbon (carbon) electrode is installed in the cathode (i), a carbon electrode or a platinum electrode is installed in the anode (j), and a carrier (k) having good conductivity. To fix the denitrifying bacteria. The solenoid valve (f) controls opening and closing at regular intervals by a timer.
In this way, the ammonia nitrogen and nitrite nitrogen treatment tank [nitrification tank (d)] and the nitrate nitrogen treatment tank [denitrification tank (e)] are installed in parallel, and the denitrification tank (e) has an outlet line. An electromagnetic valve (o) is provided, and the line to the nitrification tank (d) is always in a water-flowing state, while intermittent water is passed to the denitrification tank (e). By supplying the circulating water to the denitrification tank (e) intermittently and holding it for a certain period of time, the inside of the denitrification tank (e) can be made anaerobic and nitrate nitrogen can be treated. Although FIG. 1 shows an example of the electromagnetic valve (o), the valve may be a manual one. Moreover, a valve can be provided in the exit line and / or inlet line of a denitrification tank (e).
The artificial lung (f) is a device having a function of taking in oxygen from the outside and exchanging it with carbon dioxide in the circulating water. By installing this, the dissolved oxygen concentration in the circulating water can be kept high. .
[0010]
The denitrification tank (e) in the apparatus of the present invention is not a tank (complete mixing tank) that can make the water to be treated in the tank uniform by mechanical stirring or the like. Therefore, even if oxygen is generated by the anodic reaction, only the portion facing the anode (j) becomes an aerobic atmosphere and does not affect the entire denitrification tank (e). Therefore, no special measures against oxygen generated at the anode are required. Further, since the oxidation potential of carbon is lower than the oxygen generation potential, carbon dioxide gas may be more likely to be generated. Furthermore, when the present inventors have tested, since the current value is low, it is considered that the electrode reaction is not active so as to adversely affect the entire denitrification tank (e). This inference seems to be correct because the results of practicing the present invention were good.
[0011]
According to the second aspect of the present invention, the nitrification step that biologically oxidizes ammonia nitrogen and nitrite nitrogen to nitrite nitrogen and nitrate nitrogen is the same as that of the first invention. As the nitrate nitrogen treatment step (denitrification step) arranged in series, the nitrogen compound absorbing ability of a plant or phytoplankton is used. In a nitrate nitrogen treatment tank (denitrification tank), phytoplankton such as aquatic plants or microalgae that are in water quality are fixed and supported, and nitrate nitrogen in the circulating water is absorbed and treated. Plants or phytoplankton take nitrogen compounds into cells as a nitrogen source and treat them as body synthesis components, so it is not necessary to use an anaerobic atmosphere for denitrification, and both processes can be performed in series. Since it can be applied to not only fresh water but also water having a high salt concentration such as seawater, there are advantages such as widening of species that can be reared.
When using a plant or phytoplankton, it is necessary to light-irradiate a denitrification tank for photosynthesis. Moreover, it is preferable to fix and use a plant or a phytoplankton, for example to a net | network, a glass bead, a honeycomb-shaped support body, etc. The material used for fixing is not limited to the above, and materials known in this technical field can be used.
Examples of plants that can be used include water plants such as Snapdragon, Anubius nana, Amazon sword and the like. Examples of phytoplankton include microalgae.
The nitrifying bacteria that can be used in the nitrification step are the same as in the first invention.
[0012]
FIG. 2 shows one embodiment of the second invention of the present invention, which is a breeding aquarium (a), sensor holder (b), circulation pump (c), nitrification tank (d), denitrification tank (e), artificial It consists of lung (f), flow meter (g), illumination (l) and breeding water circulation line. A pH sensor and a dissolved oxygen meter can be installed in the sensor holder (b). In the nitrification tank (d), for example, a carrier (h) such as glass beads can be used to fix nitrifying bacteria and treat ammonia nitrogen and nitrite nitrogen. In the denitrification tank (e), a net (m) is attached to the bottom of the denitrification tank (e), and aquatic plants such as snapdragons are fixed to the net, and are retained in the denitrification tank (e), so that A nitrate nitrogen compound can be removed.
[0013]
In another embodiment of the second invention of the present invention, the ammonia nitrogen and nitrite nitrogen treatment tank (nitrification tank) is the same as described above, and the ammonia nitrogen and nitrite nitrogen are respectively nitrite nitrogen, Oxidizes to nitrate nitrogen. In the nitrate nitrogen treatment tank (denitrification tank), phytoplankton suitable for water quality is fixed, and nitrate nitrogen in the circulating water is absorbed and treated using the nitrogen compound absorption capacity of phytoplankton. As shown in FIG. 3, the treatment apparatus includes a breeding water tank (a), a sensor holder (b), a circulation pump (c), a nitrification tank (d), a denitrification tank (e), an artificial lung (f), and a flow meter (g). The sensor holder (b) can be equipped with a pH sensor and a dissolved oxygen meter. In the nitrification tank (d), nitrifying bacteria are fixed using a carrier (h) such as glass beads. The denitrification tank (e) is filled with a carrier (n) such as a honeycomb filter medium, and phytoplankton such as microalgae is fixed to the denitrification tank (e) and held in the denitrification tank (e). A nitrate nitrogen compound can be removed. As the denitrification tank (e), a flat shape that is flat to effectively use the irradiation light is preferable. By using a sufficient amount of phytoplankton, it is possible to obtain a treatment speed faster than that of aquatic plants. The reason for this is that phytoplankton is also incorporated into cells using nitrogen compounds as a nitrogen source and processed as a synthesis component, as is the case with aquatic plants, but phytoplankton has a faster synthesis rate.
[0014]
【Example】
Hereinafter, the present invention will be specifically described by way of examples, but is not limited thereto.
[Example 1]
Using the apparatus of FIG. 1, 3000 ppm of Nitrosomonas sp. And Nitrobacter sp. Were used as nitrifying bacteria, and glass beads were used as a carrier. As denitrifying bacteria, activated sludge derived from a sewage treatment plant was used with granular carbon as a carrier. The electrode was a carbon electrode, and the energization condition was a constant current of 5 mA. A solenoid valve was used as the valve, the opening / closing interval was 6 hours, and the breeding water was circulated and purified at a flow rate of 1 liter / min. Every day, 3.4 ppm of ammonia nitrogen was added to the breeding water tank (a), and the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the circulating water were measured, and the treatment performance was examined. As a result, with this apparatus, ammonia nitrogen is 0.1 ppm or less, nitrite nitrogen is 0.1 ppm or less, nitrate nitrogen is 15 ppm or less, pH is around 8, and TOC (total organic carbon) concentration in circulating water is about 10 mg / liter. The water quality could be maintained for over 90 days. The result is shown in FIG.
[0015]
FIG. 4 is a graph showing changes in circulating water quality in Example 1, where the horizontal axis represents the number of days elapsed, the vertical axis represents the TOC concentration in circulating water (mg / liter), the pH value, and the amount of nitrogen in circulating water (mg / liter). □ indicates ammonia nitrogen (NH 4 -N), ▲ indicates nitrite nitrogen (NO 2 -N), and ● indicates nitrate nitrogen (NO 3 -N). Ammonia nitrogen ■ and nitrous acid Since the state nitrogen ▲ is 0.1 ppm or less, it is displayed overlapping the X axis.
[0016]
[Example 2]
First, as an experiment, a beaker scale was performed only for nitrate nitrogen treatment. The treatment performance was evaluated by placing snapdragon as aquatic plants in treated water containing 10 mg / liter of nitrate nitrogen and measuring the concentration of residual nitrate nitrogen in the treated water. As a result, a treatment rate of 1.0 mg-N / liter · day could be obtained in this experiment. That is, it was found that 1 mg of nitrate nitrogen could be treated per liter of denitrification tank per day.
Therefore, in the configuration of FIG. 2, 300 ml of glass beads (with an amount corresponding to nitrifying bacteria Nitrosomonas sp. And Nitrobacter sp. 3000 ppm) are placed in the nitrification tank, and the denitrification tank is loaded. Snapdragon was fixed with a net, and ammonia nitrogen was added to the breeding tank at a rate of 3.4 ppm / day under the condition of light irradiation of 6000 lux. Although breeding water was circulated and used at a flow rate of 1 liter / min, it was maintained for 90 days at a residual ammonia concentration of 0.1 ppm or less, nitrite nitrogen of 0.1 ppm or less, nitrate nitrogen of 50 ppm or less, and pH 7.5.
[0017]
Example 3
First, as an experiment, a beaker scale was performed only for nitrate nitrogen treatment. The phytoplankton (microalgae) was placed in the water to be treated containing 10 mg / liter of nitrate nitrogen, and the treatability was evaluated by measuring the residual nitrate nitrogen concentration in the water to be treated. As a result, in this experimental system, a treatment rate of 1.0 mg · N / liter · day was obtained at a dry weight of phytoplankton of 30 mg / liter. That is, 1 mg of nitrogen per liter of tank in which 30 ppm of phytoplankton is fixed can be treated in one day.
Therefore, in the apparatus shown in FIG. 3, 300 ml of glass beads fixed with nitrifying bacteria (containing an amount corresponding to nitrifying bacteria Nitrosomonas sp. And Nitrobacter sp. 3000 ppm) are placed in the nitrification tank, and the denitrification tank is placed. Put a microalgae fixed on a honeycomb filter medium, and added ammonia nitrogen to the breeding tank at a rate of 3.4 ppm / day under conditions of light irradiation of 6000 lux. The breeding water was circulated and used at a flow rate of 1 liter / min, but could be maintained for 90 days at a residual ammonia concentration of 0.1 ppm or less, nitrite nitrogen of 0.1 ppm or less, nitrate nitrogen of 50 ppm or less, and pH 7.5.
[0018]
【The invention's effect】
As described above, according to the first or second invention of the present invention, the denitrification tank performs the denitrification reaction without using methanol, glucose, etc., so that nitrate nitrogen in the circulating water can be removed without any problem of toxicity or pollution. Can be reduced. In particular, according to the first invention of the present invention, the compact apparatus configuration in which the nitrification tank and the denitrification tank are arranged in parallel enables high-speed treatment of both ammonia nitrogen and nitrate nitrogen, and the breeding water quality of the closed circulation system is improved. It can be kept in a very good state.
In the second invention of the present invention, since the plant and phytoplankton that perform the denitrification reaction under aerobic conditions are used as the denitrification step, the circulating water after the nitrification step can be directly introduced into the denitrification step. Moreover, it can be applied to breeding not only in fresh water but also in sea water, and the breeding water quality of the closed circulation system can be maintained in a very good state.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating one embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating another embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating still another embodiment of the present invention.
FIG. 4 is a graph showing changes in circulating water quality in Example 1 of the present invention.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30689398A JP3794838B2 (en) | 1998-10-28 | 1998-10-28 | Minamata creature breeding equipment and breeding water purification method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30689398A JP3794838B2 (en) | 1998-10-28 | 1998-10-28 | Minamata creature breeding equipment and breeding water purification method |
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| Publication Number | Publication Date |
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| JP2000126794A JP2000126794A (en) | 2000-05-09 |
| JP3794838B2 true JP3794838B2 (en) | 2006-07-12 |
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| JP30689398A Expired - Fee Related JP3794838B2 (en) | 1998-10-28 | 1998-10-28 | Minamata creature breeding equipment and breeding water purification method |
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| CN110143674A (en) * | 2019-06-18 | 2019-08-20 | 昆山绿晶林环保科技有限公司 | A kind of aquaculture water quality regulating system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4620761B2 (en) * | 2007-06-18 | 2011-01-26 | 宏樹 八馬 | Marine aquaculture system |
| EP3284829A1 (en) * | 2009-06-16 | 2018-02-21 | Cambrian Innovation, Inc. | Systems and devices for treating and monitoring water, wastewater and other biodegradable matter |
| AU2010328173B9 (en) | 2009-12-08 | 2015-07-23 | Cambrian Innovation, Inc. | Microbially-based sensors for environmental monitoring |
| US10851003B2 (en) | 2010-07-21 | 2020-12-01 | Matthew Silver | Denitrification and pH control using bio-electrochemical systems |
| EP2721677B1 (en) | 2011-06-14 | 2017-11-22 | Cambrian Innovation, Inc. | Biological oxygen demand sensors |
| JP5935076B2 (en) * | 2012-03-15 | 2016-06-15 | 大成建設株式会社 | Water treatment equipment |
| WO2014184948A1 (en) * | 2013-05-17 | 2014-11-20 | Takada Shunsuke | Apparatus and method for purifying water |
| CN107279031B (en) * | 2017-07-04 | 2023-10-27 | 浙江工商大学 | Device and method for purifying water in fish tank |
| CN113754047B (en) * | 2021-09-29 | 2022-12-30 | 浙江大学 | Nitration and denitrification integrated water treatment system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110143674A (en) * | 2019-06-18 | 2019-08-20 | 昆山绿晶林环保科技有限公司 | A kind of aquaculture water quality regulating system |
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