JP3679918B2 - Denitrification method for contaminated water - Google Patents
Denitrification method for contaminated water Download PDFInfo
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- JP3679918B2 JP3679918B2 JP09598598A JP9598598A JP3679918B2 JP 3679918 B2 JP3679918 B2 JP 3679918B2 JP 09598598 A JP09598598 A JP 09598598A JP 9598598 A JP9598598 A JP 9598598A JP 3679918 B2 JP3679918 B2 JP 3679918B2
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- contaminated water
- nitric acid
- potential
- nitrate
- hydrogen
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
- C02F1/4676—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electroreduction
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
- C02F2101/163—Nitrates
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/005—Combined electrochemical biological processes
Description
【0001】
【発明の属する技術分野】
本発明は、硝酸汚染水の脱窒処理方法に関し、さらに詳しくは、地下水,産業排水及び家庭排水等に含有している窒素分を除去する水処理装置に関する。
【0002】
【従来の技術】
従来、基準値を越える高濃度の硝酸態窒素汚染水に対する処理法について、イオン交換法,逆浸透法,電解還元法などの物理化学的処理法及び生物学的脱窒法が検討され、一部実用化している。しかしながら、いずれの処理法も現段階では、高塩濃度再生排水処理,運転コスト,処理能力,処理水質などに問題を有しており、有効な処理技術の開発研究が重要な課題になっている。
各種の方法の中で、生物学的脱窒法は、上述のような硝酸イオン汚染水についての適用可能な処理法の1つと考えられる。そこで、そのプロセス開発に重要な因子は、適切な水素供与体の添加,制御、及び高速処理のための脱窒菌の高濃度化,高密度化であると考えられる。
【0003】
通常の生物学的脱窒プロセスでは、有機物を水素供与体として添加しており、大きな処理速度が得られるが、十分な処理をするためには過剰量の有機物添加が必要であるため、処理水への有機物残留が問題となる。
一方、水素ガスを電子供与体としてマイクロコカスディナイトリフィカンズ(Micrococcus denitrificans) などの自栄養性細菌を用いる処理法では、残留有機物の問題は解決されるが、低溶解性の水素ガスの効率的供給,亜硝酸態窒素の残留等に問題点を有している。
このような上記問題点を解決するものとして、最近、生物学的電気化学的処理法が注目されている。
【0004】
生物学的電気化学法について、特開平8−19788号公報に開示されており、図4に基づいて該方法について説明する。
ステンレスで造られた円筒形の陰極兼反応槽9の中心に、多孔性プラスチック製円筒10で覆われた炭素から造られた陽極3を設置する。陰極兼反応槽9と多孔性プラスチック製円筒10との間で仕切られた空間に、脱窒菌を固定した炭素粒11を充填する。なお、ここで充填する炭素粒11は、陰極の役割を兼ねる粒子型電極である。
【0005】
窒素分(硝酸分)を含む処理対象排水は、陰極兼反応槽9の中に収容される。そして、陽極3と陰極兼反応槽9とをつなぐ線に直流電源8により通電した場合、陽極3では電極材質の炭素が酸化し、炭酸イオンとして液中に溶解する。陰極兼反応槽9から電流が流れてくる炭素粒11の表面上では、水が還元されて水素が発生する。
排水中の窒素分(硝酸分)は、水素を電子供与体として、炭素粒11の表面上に固定した脱窒菌を生体触媒とし、窒素まで還元される。
【0006】
しかしながら、水素(H2 )は還元剤としては非常に高エネルギー(ギブスの自由エネルギー)であるため、硝酸を還元するのに水素を使用する上記方法ではエネルギーロスが大きく、硝酸汚染水の脱窒処理方法としては運転コスト,運転効率等の面で未だ問題であった。
ここで、硝酸の還元および水素の電子供与を、それぞれエネルギーとともに反応式で示せば、以下のようになる。
(式中、zは反応に関与する電子数、Fはファラデー定数、Eは電位である。)
【0007】
【発明が解決しようとする課題】
本発明者らは、上記問題点に鑑み、水素の発生しない低電圧で生体を触媒とする電解、排水中の窒素分の還元を行うことにより、エネルギーロスの少ない硝酸汚染水の脱窒処理方法を開発すべく、鋭意検討した。
その結果、本発明者らは、硝酸汚染水の脱窒処理方法において、脱窒菌を生体触媒として用い、硝酸汚染水を水素の発生しない低電位で電解処理することによって、かかる問題点が解決されることを見い出した。
本発明は、かかる見地より完成されたものである。
【0008】
【課題を解決するための手段】
すなわち、本発明は、硝酸汚染水を還元することにより脱窒処理する硝酸汚染水の脱窒処理方法において、脱窒菌を生体触媒として用い、硝酸汚染水を水素の発生しない低電位で電解処理する硝酸汚染水の脱窒処理方法を提供するものである。
また、本発明は、硝酸汚染水を硝酸還元することにより脱窒処理する硝酸汚染水の脱窒処理方法において、陰極と陽極とを設置した反応槽内で、脱窒菌を生体触媒として用い、硝酸汚染水を水素の発生しない低電位で電解処理する硝酸汚染水の脱窒処理方法を提供するものである。
このような本発明によれば、従来の方法よりも低電位で電解が発生するので、従来法より約2〜3割程度、必要電力が低下する。これにより、硝酸汚染水の脱窒処理におけるランニングコストを低く抑えることができ、運転コスト,運転効率の面で優れた脱窒処理技術を提供できるのである。
以下、本発明について、詳細に説明する。
【0009】
【発明の実施の形態】
添付図面を参照しながら、本発明の実施の形態を説明する。
実施の形態
原理的には、硝酸(HNO3 )の還元は0.94V以下の電位であれば、反応は進行する。ところが、従来法のように水素(H2 )を介在させると0Vの電位が必要となり、差し引き0.94Vのロスになる。
そこで、本発明の硝酸汚染水の脱窒処理方法では、脱窒菌としての細菌、厳密には細菌内の電子受容体が0.94V〜0Vの間で電極から電子を受け取り、受け取った電子が硝酸の還元に寄与することにより、電位を0Vまで低下させなくても反応を進行させるようにしたものである。
【0010】
ここで、生体触媒として細菌を用いた場合の電子供与および硝酸の還元を反応式で示せば、以下のようになる。
細菌+e- (電極) → 細菌・e- (電極反応)
NO3 - +5(H+ +e- ) → 1/2 N2 +2H2 O+OH-
細菌・e- → 細菌+e-
上記電極反応では、水素発生よりも高い電位で反応が進行する。
【0011】
このようなことから、細菌等の生物の電子受け取り条件を確認するため、電流−電位曲線を測定すると図2に示すような結果になる。
ここで、試験水の組成としては、硝酸ナトリウムは窒素(N)に換算して80mg/リットルとなる量、また、リン酸1カリウムはリン(P)に換算して10mg/リットルとなる量を含有している。
図2の電流電位曲線は、生物有りと生物無しの2つのケースの硝酸溶液について測定した場合である。図2に示すように、電位を変えて電流密度を測定すると、先ず、硝酸還元と考えられる電流が現れ、次いで、生物有りの場合には生物の電子受け取り電流が現れ、最後に、水素(H2 )発生と考えられる電流が現れた。
これらの間のおおよその電位差は、硝酸還元と微生物の電子受け取りとの間で約0.4〜0.5Vであり、微生物の電子受け取りと水素発生との間で約0.5Vであった。
【0012】
したがって、硝酸汚染水を還元することにより脱窒処理する場合、脱窒菌としての微生物を生体触媒として用いることにより、微生物の電子受け取りと水素発生との間の電位差の分だけ、低電位で電解処理することができるのである。そして、この脱窒処理を、陰極と陽極とを設置した反応槽内で行うことにより、水素の発生しない硝酸汚染水の処理が可能となる。
以下、実施例により本発明をより詳細に説明するが、本発明はこれらの実施例によって何ら制限されるものではない。
【0013】
【実施例】
実施例1
図2に示した上記実験によって得られた条件にて、図1に示す装置を用いて硝酸の電解試験を実施した。
反応槽1に、陰極2,陽極3及び参照電極4を設置した。参照電極4は、陰極電位をモニターしてコントロールするためのものである。反応槽1に、硝酸および微生物の入った試験水6を満たした。そして、この反応槽1内を攪拌機7で緩やかに攪拌しながら、定電位電源5によって陰極電位を
1)微生物の電子受け取り電位(水素発生電位よりも−0.5V付近)
2)水素発生電位
の2条件に保ちながら、硝酸の還元を行った。
その結果、硝酸の還元速度は、1)微生物の電子受け取り電位の場合と、2)水素発生電位の場合とで大差はなかった。
このように硝酸の還元速度は、水素発生電位による従来法と本発明の方法とで同等であった。一方、同量の硝酸を還元するのに必要な電力は、投入した電力の比となる。したがって、図3に示したように、本発明の方法は従来法より約2〜3割程度、必要電力が低下することがわかった。
【0014】
【発明の効果】
本発明の汚染水の脱窒処理方法によれば、従来の方法よりも低電位で電解が発生するので、従来法より約2〜3割程度、必要電力が低下する。これにより、本発明は、硝酸汚染水の脱窒処理におけるランニングコストを低く抑えた効率的な運転を行うことができ、産業上の意義は極めて大きい。
【図面の簡単な説明】
【図1】図1は、実施例1において、本発明の方法を用いて硝酸の電解試験を行った装置の概略図である。
【図2】図2は、電流−電位曲線を示した図である。
【図3】図3は、本発明と従来法の必要な電力を比較した図である。
【図4】図4は、従来法による硝酸の電解試験を行う装置の概略図である。
【符号の説明】
1 反応槽
2 陰極
3 陽極
4 参照電極
5 定電位電源
6 試験水
7 攪拌機
8 直流電源
9 陰極兼反応槽
10 多孔性プラスチック製円筒
11 炭素粒[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a denitrification method for nitrate-contaminated water, and more particularly to a water treatment device that removes nitrogen contained in groundwater, industrial wastewater, household wastewater, and the like.
[0002]
[Prior art]
Conventionally, physicochemical treatment methods such as ion exchange method, reverse osmosis method, electrolytic reduction method and biological denitrification method have been studied as a treatment method for highly concentrated nitrate nitrogen contaminated water exceeding the standard value, and some practical use It has become. However, each treatment method has problems in high salt concentration reclaimed wastewater treatment, operating cost, treatment capacity, treated water quality, etc., and development of effective treatment technology is an important issue at this stage. .
Among various methods, the biological denitrification method is considered as one of applicable treatment methods for nitrate ion contaminated water as described above. Therefore, it is considered that an important factor for the process development is the addition and control of an appropriate hydrogen donor and the high concentration and high density of denitrifying bacteria for high-speed processing.
[0003]
In a normal biological denitrification process, an organic substance is added as a hydrogen donor, and a high processing speed can be obtained. However, since an excessive amount of organic substance is required for sufficient treatment, Residue of organic matter is a problem.
On the other hand, the treatment method using autotrophic bacteria such as Micrococcus denitrificans with hydrogen gas as an electron donor solves the problem of residual organic matter, but the efficient use of low-solubility hydrogen gas. There are problems with the supply and residual nitrite nitrogen.
Recently, biological electrochemical treatment methods have attracted attention as means for solving such problems.
[0004]
A biological electrochemical method is disclosed in JP-A-8-19788, and the method will be described with reference to FIG.
An
[0005]
The waste water to be treated containing nitrogen (nitric acid) is accommodated in the cathode and
The nitrogen content (nitric acid content) in the wastewater is reduced to nitrogen using hydrogen as an electron donor and denitrifying bacteria immobilized on the surface of the carbon particles 11 as a biocatalyst.
[0006]
However, since hydrogen (H 2 ) is very high energy (Gibbs free energy) as a reducing agent, the above method using hydrogen to reduce nitric acid has a large energy loss, and denitrification of nitrate contaminated water. The treatment method was still a problem in terms of operation cost, operation efficiency, and the like.
Here, if the reduction of nitric acid and the electron donation of hydrogen are shown in the reaction formula together with the energy, they are as follows.
(In the formula, z is the number of electrons involved in the reaction, F is the Faraday constant, and E is the potential.)
[0007]
[Problems to be solved by the invention]
In view of the above problems, the present inventors have carried out electrolysis using a living body as a catalyst at a low voltage at which hydrogen is not generated, and a method for denitrification of nitrate-contaminated water with little energy loss by performing reduction of nitrogen content in wastewater. In order to develop
As a result, in the method for denitrification treatment of nitrate-contaminated water, the present inventors solved this problem by electrolytically treating the nitrate-contaminated water at a low potential that does not generate hydrogen using denitrifying bacteria as a biocatalyst. I found out.
The present invention has been completed from such a viewpoint.
[0008]
[Means for Solving the Problems]
That is, the present invention relates to a method for denitrifying nitrate-contaminated water by reducing nitrate-contaminated water by using denitrifying bacteria as a biocatalyst and subjecting the nitrate-contaminated water to electrolytic treatment at a low potential without generating hydrogen. A method for denitrification treatment of nitrate-contaminated water is provided.
The present invention also relates to a method for denitrification of nitrate-contaminated water by denitrating nitrate-contaminated water by reducing the nitrate-contaminated water, using a denitrifying bacterium as a biocatalyst in a reaction vessel in which a cathode and an anode are installed. The present invention provides a method for denitrification of nitrate-contaminated water by electrolytic treatment of the contaminated water at a low potential without generating hydrogen.
According to the present invention, since electrolysis occurs at a lower potential than in the conventional method, the required power is reduced by about 20 to 30% compared to the conventional method. Thereby, the running cost in the denitrification treatment of nitric acid-contaminated water can be kept low, and a denitrification treatment technique that is excellent in terms of operation cost and operation efficiency can be provided.
Hereinafter, the present invention will be described in detail.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings.
The embodiment <br/> principle embodiment, the reduction of nitric acid (HNO 3) is as long as potential below 0.94 V, the reaction proceeds. However, when hydrogen (H 2 ) is interposed as in the conventional method, a potential of 0 V is required, and a loss of 0.94 V is subtracted.
Therefore, in the method for denitrification of nitrate-contaminated water according to the present invention, bacteria as denitrifying bacteria, strictly speaking, electron acceptors in the bacteria receive electrons from the electrode between 0.94 V and 0 V, and the received electrons are nitrates. By contributing to the reduction, the reaction is allowed to proceed without lowering the potential to 0V.
[0010]
Here, if the electron donation and the reduction of nitric acid when using bacteria as a biocatalyst are shown by the reaction formulas, the reaction is as follows.
Bacteria + e - (electrode) → bacteria · e - (electrode reaction)
NO 3 − +5 (H + + e − ) → 1/2 N 2 + 2H 2 O + OH −
Bacteria · e - → bacteria + e -
In the electrode reaction, the reaction proceeds at a higher potential than hydrogen generation.
[0011]
For this reason, when the current-potential curve is measured in order to confirm the electron receiving conditions of organisms such as bacteria, the result shown in FIG. 2 is obtained.
Here, the composition of the test water is such that sodium nitrate is 80 mg / liter converted to nitrogen (N), and 1 potassium phosphate is 10 mg / liter converted to phosphorus (P). Contains.
The current-potential curve in FIG. 2 is measured for nitric acid solutions in two cases with and without organisms. As shown in FIG. 2, when the current density is measured by changing the electric potential, first, an electric current considered to be nitrate reduction appears, then, when there is an organism, an electron receiving current of the organism appears, and finally, hydrogen (H 2 ) A current that appears to be generated appeared.
The approximate potential difference between them was about 0.4-0.5 V between nitrate reduction and microbial electron reception, and about 0.5 V between microbial electron reception and hydrogen evolution.
[0012]
Therefore, when denitrification treatment is performed by reducing nitrate-contaminated water, by using microorganisms as denitrification bacteria as biocatalysts, electrolytic treatment is performed at a low potential by the amount of potential difference between electron reception and generation of hydrogen. It can be done. And by performing this denitrification process in the reaction tank which installed the cathode and the anode, the process of nitric acid contamination water which does not generate | occur | produce hydrogen is attained.
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited at all by these Examples.
[0013]
【Example】
Example 1
Under the conditions obtained by the above-described experiment shown in FIG. 2, an electrolytic test of nitric acid was performed using the apparatus shown in FIG.
In the reaction vessel 1, a
2) Nitric acid was reduced while maintaining two conditions of hydrogen generation potential.
As a result, the reduction rate of nitric acid was not significantly different between 1) the case of microbial electron receiving potential and 2) the case of hydrogen generation potential.
Thus, the reduction rate of nitric acid was equivalent between the conventional method using the hydrogen generation potential and the method of the present invention. On the other hand, the power required to reduce the same amount of nitric acid is the ratio of the input power. Therefore, as shown in FIG. 3, it was found that the method of the present invention requires about 20 to 30% less power than the conventional method.
[0014]
【The invention's effect】
According to the method for denitrification of contaminated water of the present invention, electrolysis occurs at a lower potential than in the conventional method, so that the required power is reduced by about 20-30% compared to the conventional method. Thereby, this invention can perform the efficient driving | running which suppressed the running cost in the denitrification process of nitric acid contaminated water low, and industrial significance is very large.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus in which an electrolytic test for nitric acid was conducted using the method of the present invention in Example 1. FIG.
FIG. 2 is a diagram showing a current-potential curve.
FIG. 3 is a diagram comparing required power of the present invention and the conventional method.
FIG. 4 is a schematic view of an apparatus for performing an electrolytic test of nitric acid according to a conventional method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1
Claims (1)
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JP09598598A JP3679918B2 (en) | 1998-04-08 | 1998-04-08 | Denitrification method for contaminated water |
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JP09598598A JP3679918B2 (en) | 1998-04-08 | 1998-04-08 | Denitrification method for contaminated water |
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JP3679918B2 true JP3679918B2 (en) | 2005-08-03 |
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Cited By (1)
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CN102259978A (en) * | 2010-05-31 | 2011-11-30 | 中国地质大学(北京) | Reactor and method for removing nitrate from water |
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GB2499025A (en) * | 2012-02-03 | 2013-08-07 | Nat Nuclear Lab Ltd | Decontamination of a system and treatment of the spent decontamination fluid |
CN111675431A (en) * | 2020-06-16 | 2020-09-18 | 河海大学 | Enhanced electrochemical denitrification device for substrate sludge-based biochar electrode |
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CN102259978A (en) * | 2010-05-31 | 2011-11-30 | 中国地质大学(北京) | Reactor and method for removing nitrate from water |
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