JP2004337808A - Selenium treatment agent, and method and apparatus for treating selenium-containing water - Google Patents
Selenium treatment agent, and method and apparatus for treating selenium-containing water Download PDFInfo
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- JP2004337808A JP2004337808A JP2003140523A JP2003140523A JP2004337808A JP 2004337808 A JP2004337808 A JP 2004337808A JP 2003140523 A JP2003140523 A JP 2003140523A JP 2003140523 A JP2003140523 A JP 2003140523A JP 2004337808 A JP2004337808 A JP 2004337808A
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- 239000011669 selenium Substances 0.000 title claims abstract description 93
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 title claims abstract description 88
- 229910052711 selenium Inorganic materials 0.000 title claims abstract description 87
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
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- 229910001385 heavy metal Inorganic materials 0.000 description 4
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 3
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、セレン含有水よりセレンを除去するためのセレン処理剤、該セレン含有水の処理方法及び処理装置に関するものである。
【０００２】
【従来の技術】
水処理において、上水用原水や工場廃水などのその被処理水中にセレンが含有されている場合がある。被処理水中に含有されているセレンは生体必須元素であるが、毒性が強いという特殊な元素である。現在、環境保全のためのセレンに対する規制で、水質汚濁防止法に基づくセレンの排水基準は０．１ｍｇ／リットル、公共用水域におけるセレンの環境基準は０．０１ｍｇ／リットル、水道法の水質基準は０．０１ｍｇ／リットルと規定されている。セレンを含有する水を無害化する処理方法として、水酸化第一鉄による還元法、水酸化鉄（ＩＩＩ）による共沈処理、イオン交換樹脂による吸着法などが提案されている。
【０００３】
水酸化第一鉄による還元法では除去率を高めるために、１）排水のｐＨを９以上、温度を７０℃以上に加温することで反応速度の向上を図る方法、２）反応液中で溶存酸素による鉄の酸化を促進してしまうＣｕ２＋を事前に中和剤を添加することで共沈除去する方法、３）セレン含有重金属排水にアルカリを添加し除去可能な重金属を水酸化物として沈殿させる方法がとられている。
【０００４】
そして具体的には、１）その１次処理水に不活性ガスを吹き込み溶存酸素を除去した後、第１鉄塩を添加して該処理水中の溶存セレンを元素状セレン沈殿物に還元する。２）その処理液に空気を吹き込み液中に残留する重金属をフェライト法で除去する方法（例えば、特許文献１参照）、３）セレン含有排水に水素化ホウ素化合物、ヒドラジン及びその化合物、亜硫酸塩、第１鉄塩などの還元剤を添加した後、活性炭を充填した活性炭塔に通水する方法（例えば、特許文献２参照）などが提案されている。いずれの処理方法も除去効率を上げるための複数の工程、操作を要する。
【０００５】
共沈法はｐＨの影響が大きく、中性から弱酸性では処理可能であるが、アルカリ性では処理できなく、また多量の薬剤を必要とする。イオン交換樹脂による吸着法は吸着量が少なく、再生廃液の処理が必要になるなどの問題点がある。
【０００６】
その他、生物反応を利用した処理方法としては、（亜）セレン酸還元菌によりラクトースの存在下、Ｓｅ６＋およびＳｅ４＋が還元されることが報告されている。しかし、この方法ではセレン化合物に汚染された場所から、（亜）セレン還元菌を分離して培養する必要があるという問題がある。また硫酸塩還元菌によるセレンの還元も知られており、有機物及び硫酸イオンの存在下にセレン含有水を生物汚泥と嫌気状態で接触させると、セレン化合物は還元され、セレンが沈殿除去される。しかし、この場合も硫化水素が発生するなどの問題がある。
【０００７】
【特許文献１】
特開２００２−３２６０９０号公報
【特許文献２】
特開平１１−２０７３６５号公報
【０００８】
【発明が解決しようとする課題】
本発明は、このような従来の課題に鑑みてなされたものであり、従来重金属排水処理法として公知のフェライト法及び生物反応利用処理法の上述のような問題点を解決する、セレン含有水からセレンを容易に除去する処理剤、処理方法及び装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
本発明者等は、セレン含有水からのセレンの除去について、従来の技術とは全く異なる新規の技術を開発すべく鋭意研究を行ない、更に、上記の問題点を解消するための手段を鋭意検討をした結果、水中に含有されるセレンをヒドロキシアパタイトに吸着し、除去できるという知見を得た。
【００１０】
すなわち、本発明は、下記の手段により上記の課題を解決した。
（１）ヒドロキシアパタイトを含有することを特徴とするセレン処理剤。
（２）セレン含有水をヒドロキシアパタイトを含有するセレン処理剤と接触させた後、固液分離して該セレン含有水よりセレンを除去することを特徴とするセレン含有水の処理方法。
（３）ヒドロキシアパタイトを含有する粒状のセレン処理剤が充填された充填塔に、セレン含有水を通水して、該セレン含有水よりセレンを除去することを特徴とするセレン含有水の処理方法。
（４）セレン含有水の導入管、ヒドロキシアパタイトを含有するセレン処理剤の供給管、撹拌機、上澄み液流出管及び沈殿物排出管を具備した反応槽を備えたことを特徴とするセレン含有水の処理装置。
【００１１】
【発明の実施の形態】
本発明において処理の対象となるセレン含有水は、Ｓｅ６＋またはＳｅ４＋のセレン化合物を含む排水などの有害な水である。具体的なセレン含有水としては、金属精錬工場排水、及び石油、石炭又は燃焼排ガス処理プロセスの排水などが挙げられる。本発明で用いるヒドロキシアパタイトは合成品でもよく、排水のリン除去に際して生成するリン酸カルシウム化合物でもよく、ボイラー水、冷却水の水処理薬剤としてリン酸塩が使用されている場合に、水中のカルシウム成分と反応し形成されるスケールや浮遊状固形物などを利用してもよく、特に限定されるものではない。
【００１２】
また、本処理剤に含有させるヒドロキシアパタイトは結晶形でも無定形でもよい。使用形態は粉末状や粒状、顆粒、ペレット、円柱状などの成形物などでもよく、特に限定されない。ただ、ヒドロキシアパタイトが充填された充填塔にセレン含有水を通水する場合には、ヒドロキシアパタイトの粒径が小さいと通水抵抗が大きく、かつすぐに目詰まりがしやすくなるので、その粒径はある程度大きいものの方がこのましい。また、本処理剤は含有されるヒドロキシアパタイトが１００％のものでなくてもよく、ある程度他の物質が混入していても差し支えない。ヒドロキシアパタイトとセレンを接触させる方法としては、特に限定されないが、次のような方法で容易に処理できる。
【００１３】
ａ）セレン含有水にヒドロキシアパタイトを添加し撹拌する方法、ｂ）ヒドロキシアパタイトが充填された充填塔にセレン含有水を通水する方法、ｃ）ヒドロキシアパタイトを紙に抄き込み、これをセレン含有水と接触させる方法、ｄ）ヒドロキシアパタイトを繊維に担持させ、これをセレン含有水と接触させる方法などがある。ｃ）の場合、ヒドロキシアパタイトを抄き込んだ紙、ｄ）の場合、ヒドロキシアパタイト担持させた繊維をろ過膜として用い、セレン含有水をろ過する工程で、セレンをヒドロキシアパタイトに吸着させ除去することもできる。さらに、ヒドロキシアパタイトによる処理と従来の還元処理、共沈処理、イオン交換樹脂による吸着処理、生物反応を利用した処理などを組み合わせて処理してもよい。なお、前記ヒドロキシアパタイトとしては、純粋なヒドロキシアパタイトに限られず、不純物を含有するものや、何かの反応における副生物などでもよい。
【００１４】
使用形態が粒状、顆粒、ペレットのヒドロキシアパタイトは、充填塔に充填し、ヒドロキシアパタイトの充填層に被処理水を通水することにより、被処理水の溶解性のセレンを吸着除去することができる。ヒドロキシアパタイトの粒径に特に制限はない。細かい方が反応性がよいが、ろ過抵抗が大きくなって通水性が悪くなるので、反応性が良くかつ通水が容易な範囲であることが好ましい。通水方法は、上向流でも下向流でも良い。また、高分子凝集剤や無機凝集剤を用いた凝集沈殿処理、活性炭などの吸着剤を用いた吸着処理などを組み合わせてもよい。
【００１５】
複数の処理方法を組み合わせて処理する方法の一例として、被処理水にヒドロキシアパタイトとヒドラジンを添加し撹拌した後、硫酸第１鉄や塩化第２鉄などの無機凝集剤、有機高分子凝集剤を加えて凝集沈殿処理し、固液分離する方法が挙げられる。
被処理水に対するセレン処理剤の添加量としては、被処理水におけるセレン含有量、処理目標値によっても変わるが、被処理水に対するヒドロキシアパタイトの添加量として表して、０．１ｇ／リットル以上、好ましくは１．０ｇ／リットル以上を添加するとよいが、いずれにしても、処理後のセレン濃度がセレンの排水基準を満たすに十分な量を使用することが必要である。
【００１６】
【実施例】
以下に実施例により本発明をさらに詳しく説明するが、本発明の範囲は、これらによって限定されるものではない。
【００１７】
（実施例１）
被処理水として、下水汚泥の燃焼排ガス処理プロセスのスクラバー排水を用いた。この被処理水は、ｐＨ：１２．７、ＳＳ：５．８ｍｇ／リットル、Ｓｅ６＋：０．４６ｍｇ／リットル、Ｓｅ４＋：０．９３ｍｇ／リットル、ＴＤＳ（全溶解物）：０．９３ｍｇ／リットルであった。この排水１リットルに対して所定量のヒドロキシアパタイト（富山化学社製、ＨＡ−３００ＢＰ）（平均粒径：２．９μｍ）を添加量を変えて添加し、室温で３時間撹拌した。室温で２４時間静置し固液分離した後、上澄み液中のセレン濃度を、水素化物発生ＩＣＰ発光分光分析法により測定した（ＪＩＳ Ｋ０１０２に準拠）。（図１参照）。
ヒドロキシアパタイト添加率と上澄み液中の総セレン濃度を第１表に示す。
【００１８】
【表１】
無添加のとき１．３９ｍｇ／リットルであった総セレン濃度は、ヒドロキシアパタイト添加率が１ｇ／リットルのとき０．０８０ｍｇ／リットル、５ｇ／リットルのとき０．０２６ｍｇ／リットルまで低下し、水質汚濁防止法に基づくセレンの排水基準である０．１ｍｇ／リットル以下となった。
【００２０】
（実施例２）
実施例１の被処理水１リットルに、ヒドロキシアパタイト（富山化学製、ＨＡ−３００ＢＰ）５ｇ／リットル、ヒドラジン５００ｍｇ／リットル（Ｎ２Ｈ４として）を添加し、硫酸でｐＨ１０に調整した後、室温で３時間撹拌した。次に、これに硫酸第１鉄（無機凝集剤）２００ｍｇ／リットルを添加し、次いで、水酸化ナトリウムでｐＨ１０とし、有機高分子凝集剤（荏原製作所製、エバグロースＡ−１５１）１ｍｇ／リットルを添加して凝集沈殿処理した。この凝集沈殿処理水は、ＳＳが３．５ｍｇ／リットル、総セレン濃度が０．００２ｍｇ／リットル以下であった。（図２参照）。
【００２１】
（実施例３）
被処理水として、実施例１で用いた排水を用いた。粒径０．３ｍｍ、有効径１．５ｍｍ、均等係数１．３の粒状ヒドロキシアパタイト１００ｋｇを内径３５０ｍｍのアクリル樹脂製カラムに充填し、ヒドロキシアパタイト充填塔とした。そして、排水を上向流方式でカラムにＳＶ２／ｈの条件で連続的に通水した。また、１時間に１回処理水をカラム下部からカラム内に導入し、ヒドロキシアパタイトを３０秒間流動させ、ヒドロキシアパタイトに付着した排水中のＳＳ（浮遊物質）分を洗浄、除去した。被処理水の総セレン濃度０．３９ｍｇ／リットルに対して、処理水の総セレン濃度は０．０２９ｍｇ／リットルになった。（図３参照）。
【００２２】
（比較例１）
被処理水として、実施例１で用いた排水を用いた。被処理水１リットルにヒドラジン５００ｍｇ／リットル（Ｎ２Ｈ４として）を添加し、水酸化ナトリウムでｐＨ１０に調整した後、室温で３時間撹拌した。次に、これに硫酸第１鉄（無機凝集剤）２００ｍｇ／リットルを添加して、再度水酸化ナトリウムでｐＨ１０とし、有機高分子凝集剤（荏原製作所製、エバグロースＡ−１５１）１ｍｇ／リットルを添加して凝集沈殿処理した。この凝集沈殿処理水は、ＳＳ：３．４ｍｇ／リットル、総セレン濃度が０．０９ｍｇ／リットルであった。
【００２３】
実施例１では、ヒドロキシアパタイトの添加による凝集沈殿処理により、処理水のセレン濃度が低下した。実施例３では、ヒドロキシアパタイトを充填した充填塔に排水を通水させることによる吸着処理により、処理水のセレン濃度が低下し、連続的に処理することができた。また、ヒドラジン、無機凝集剤、有機高分子凝集剤を組み合わせて処理した比較例１に比べ、ヒドラジン、無機凝集剤、有機高分子凝集剤に加え、ヒドロキシアパタイトを組み合わせて処理した実施例２の総セレン濃度はより低下させることができた。以上のように、本発明によるヒドロキシアパタイトによるセレン除去効果は明らかである。
【００２４】
【発明の効果】
本発明によれば、ヒドロキシアパタイトをセレン含有水と接触させることにより、セレン除去を容易かつ安全に実施することができる。
【図面の簡単な説明】
【図１】本発明に係るセレン含有水の処理装置の概略を示す説明図である。
【図２】従来技術を組み合わせた方法による、セレン含有水の処理装置の概略を示す説明図である。
【図３】ヒドロキシアパタイト充填塔を利用する、本発明に係るセレン含有水の処理装置の概略を示す説明図である。
【符号の説明】
１ 反応槽
２ セレン含有水
３ ヒドロキシアパタイト
４ 撹拌機
５ 上澄み液流出管
６ 沈殿物排出管
７ ヒドラジン
８ ｐＨ計
９ 硫酸
１０ 硫酸第１鉄
１１ 水酸化ナトリウム（ＮａＯＨ）
１２ 有機高分子凝集剤
１３ アクリル樹脂製カラム
１４ ヒドロキシアパタイト充填塔
１５ 処理水[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a selenium-treating agent for removing selenium from selenium-containing water, a method of treating the selenium-containing water, and a treatment apparatus.
[0002]
[Prior art]
In water treatment, selenium may be contained in the water to be treated such as raw water for domestic use or factory wastewater. Selenium contained in the water to be treated is an essential element for living organisms, but is a special element that is highly toxic. At present, there is a regulation on selenium for environmental protection. The selenium drainage standard based on the Water Pollution Control Law is 0.1 mg / liter, the environmental standard for selenium in public water bodies is 0.01 mg / liter, and the water quality standard under the Water Supply Law is It is specified as 0.01 mg / liter. As a treatment method for detoxifying water containing selenium, a reduction method using ferrous hydroxide, a coprecipitation treatment using iron (III) hydroxide, an adsorption method using an ion exchange resin, and the like have been proposed.
[0003]
In the reduction method using ferrous hydroxide, in order to increase the removal rate, 1) a method of improving the reaction rate by heating the pH of the waste water to 9 or more and the temperature to 70 ° C. or more, 2) In the reaction solution Coprecipitation removal of Cu 2+ that promotes iron oxidation by dissolved oxygen by adding a neutralizing agent in advance, 3) Addition of alkali to selenium-containing heavy metal wastewater and removal of heavy metal as hydroxide A method of precipitation is employed.
[0004]
Then, specifically, 1) an inert gas is blown into the primary treatment water to remove dissolved oxygen, and then ferrous salt is added to reduce dissolved selenium in the treatment water to elemental selenium precipitate. 2) A method in which air is blown into the treatment solution to remove heavy metals remaining in the solution by a ferrite method (for example, see Patent Document 1). 3) Boron hydride compound, hydrazine and its compound, sulfite, A method has been proposed in which a reducing agent such as a ferrous salt is added, and then water is passed through an activated carbon tower filled with activated carbon (for example, see Patent Document 2). Each treatment method requires a plurality of steps and operations to increase the removal efficiency.
[0005]
The coprecipitation method is greatly affected by pH, and can be processed under neutral to weakly acidic conditions, but cannot be processed under alkaline conditions, and requires a large amount of chemicals. The adsorption method using an ion-exchange resin has problems such as a small amount of adsorption and the necessity of treating a regenerated waste liquid.
[0006]
In addition, as a treatment method utilizing a biological reaction, it is reported that Se 6+ and Se 4+ are reduced by selenite-reducing bacteria in the presence of lactose. However, this method has a problem that it is necessary to separate and culture (sub) selenium-reducing bacteria from a place contaminated with a selenium compound. It is also known to reduce selenium by sulfate-reducing bacteria. When selenium-containing water is brought into contact with biological sludge in an anaerobic state in the presence of organic substances and sulfate ions, the selenium compound is reduced and selenium is precipitated and removed. However, also in this case, there is a problem that hydrogen sulfide is generated.
[0007]
[Patent Document 1]
JP 2002-326090 A [Patent Document 2]
JP-A-11-207365
[Problems to be solved by the invention]
The present invention has been made in view of such a conventional problem, and solves the above-described problems of the ferrite method and the biological reaction utilizing treatment method conventionally known as heavy metal wastewater treatment methods. An object of the present invention is to provide a processing agent, a processing method, and an apparatus for easily removing selenium.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive research on the removal of selenium from selenium-containing water in order to develop a new technology completely different from the conventional technology, and further intensively studied means for solving the above problems. As a result, it was found that selenium contained in water can be adsorbed to hydroxyapatite and removed.
[0010]
That is, the present invention has solved the above problems by the following means.
(1) A selenium-treating agent containing hydroxyapatite.
(2) A method for treating selenium-containing water, comprising contacting the selenium-containing water with a selenium-treating agent containing hydroxyapatite, followed by solid-liquid separation to remove selenium from the selenium-containing water.
(3) A method for treating selenium-containing water, comprising passing selenium-containing water through a packed tower filled with a granular selenium-treating agent containing hydroxyapatite to remove selenium from the selenium-containing water. .
(4) A selenium-containing water comprising a selenium-containing water inlet pipe, a supply pipe for a hydroxyapatite-containing selenium treating agent, a stirrer, a supernatant liquid outlet pipe, and a sediment discharge pipe. Processing equipment.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The selenium-containing water to be treated in the present invention is harmful water such as wastewater containing a Se 6+ or Se 4+ selenium compound. Specific selenium-containing waters include metal smelting plant effluent, and oil, coal or flue gas treatment process effluent. Hydroxyapatite used in the present invention may be a synthetic product, may be a calcium phosphate compound generated when removing phosphorus from wastewater, boiler water, when a phosphate is used as a water treatment agent for cooling water, the calcium component in the water and A scale or a suspended solid formed by the reaction may be used, and is not particularly limited.
[0012]
The hydroxyapatite contained in the present treatment agent may be in a crystalline form or an amorphous form. The form of use may be a molded product such as powder, granule, granule, pellet, and columnar shape, and is not particularly limited. However, when passing selenium-containing water through a packed column filled with hydroxyapatite, the smaller the particle size of hydroxyapatite, the greater the water flow resistance, and the easier the clogging becomes. Is better to some extent. The treating agent does not need to contain 100% of hydroxyapatite, and may contain other substances to some extent. The method of bringing hydroxyapatite into contact with selenium is not particularly limited, but can be easily treated by the following method.
[0013]
a) a method of adding hydroxyapatite to selenium-containing water and stirring the mixture; b) a method of passing selenium-containing water through a packed tower filled with hydroxyapatite; c) papering hydroxyapatite into selenium-containing paper; There are a method of contacting with water, d) a method of supporting hydroxyapatite on fibers, and contacting the fibers with water containing selenium. In the case of c), paper containing hydroxyapatite, and in the case of d), a fiber loaded with hydroxyapatite is used as a filtration membrane, and in the step of filtering selenium-containing water, selenium is adsorbed to and removed from hydroxyapatite. You can also. Further, the treatment with hydroxyapatite may be combined with a conventional reduction treatment, coprecipitation treatment, adsorption treatment with an ion exchange resin, treatment using a biological reaction, or the like. The hydroxyapatite is not limited to pure hydroxyapatite, but may be a substance containing impurities or a by-product of any reaction.
[0014]
Hydroxyapatite in the form of granules, granules and pellets is packed in a packed tower, and by passing water to be treated through a packed layer of hydroxyapatite, it is possible to adsorb and remove soluble selenium in the water to be treated. . There is no particular limitation on the particle size of hydroxyapatite. The finer the particle, the better the reactivity. However, since the filtration resistance becomes large and the water permeability deteriorates, it is preferable that the fineness is within a range where the reactivity is good and the water permeability is easy. The water flow method may be an upward flow or a downward flow. Further, a coagulation-precipitation treatment using a polymer coagulant or an inorganic coagulant, an adsorption treatment using an adsorbent such as activated carbon, or the like may be combined.
[0015]
As an example of a method of treating by combining a plurality of treatment methods, after adding hydroxyapatite and hydrazine to the water to be treated and stirring, an inorganic flocculant such as ferrous sulfate and ferric chloride, and an organic polymer flocculant are added. In addition, a method of performing coagulation and sedimentation and performing solid-liquid separation can be used.
The amount of the selenium-treating agent added to the water to be treated depends on the content of selenium in the water to be treated and the target value of the treatment, but is preferably 0.1 g / L or more, expressed as the amount of hydroxyapatite added to the water to be treated. It is advisable to add 1.0 g / liter or more, but in any case, it is necessary to use an amount sufficient for the selenium concentration after treatment to satisfy the selenium drainage standard.
[0016]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the scope of the present invention is not limited thereto.
[0017]
(Example 1)
As the water to be treated, scrubber wastewater from a sewage sludge combustion exhaust gas treatment process was used. The water to be treated was pH: 12.7, SS: 5.8 mg / liter, Se 6+ : 0.46 mg / liter, Se 4+ : 0.93 mg / liter, TDS (total dissolved): 0.93 mg / liter. Met. A predetermined amount of hydroxyapatite (HA-300BP, manufactured by Toyama Chemical Co., Ltd.) (average particle size: 2.9 μm) was added to 1 liter of the drainage in a different amount, and the mixture was stirred at room temperature for 3 hours. After standing at room temperature for 24 hours for solid-liquid separation, the selenium concentration in the supernatant was measured by hydride generation ICP emission spectroscopy (based on JIS K0102). (See FIG. 1).
Table 1 shows the hydroxyapatite addition rate and the total selenium concentration in the supernatant.
[0018]
[Table 1]
The total selenium concentration, which was 1.39 mg / l when no hydroxyapatite was added, was reduced to 0.080 mg / l when the hydroxyapatite addition rate was 1 g / l, and decreased to 0.026 mg / l when the hydroxyapatite addition rate was 5 g / l, thus preventing water pollution. It was 0.1 mg / liter or less, which is the selenium drainage standard based on the law.
[0020]
(Example 2)
5 g / l of hydroxyapatite (HA-300BP, manufactured by Toyama Chemical Co., Ltd.) and 500 mg / l of hydrazine (as N 2 H 4 ) were added to 1 liter of the water to be treated in Example 1, and the pH was adjusted to 10 with sulfuric acid. For 3 hours. Next, 200 mg / liter of ferrous sulfate (inorganic flocculant) was added thereto, and then adjusted to pH 10 with sodium hydroxide, and 1 mg / liter of an organic polymer flocculant (Ebagrose A-151 manufactured by Ebara Corporation) was added. And subjected to coagulation sedimentation treatment. This coagulated sedimentation-treated water had an SS of 3.5 mg / l and a total selenium concentration of 0.002 mg / l or less. (See FIG. 2).
[0021]
(Example 3)
The wastewater used in Example 1 was used as the water to be treated. 100 kg of granular hydroxyapatite having a particle diameter of 0.3 mm, an effective diameter of 1.5 mm, and a uniformity coefficient of 1.3 was packed in an acrylic resin column having an inner diameter of 350 mm to prepare a hydroxyapatite packed tower. Then, the waste water was continuously passed through the column in an upward flow manner under the condition of SV2 / h. Also, treated water was introduced into the column from the bottom of the column once an hour, and hydroxyapatite was allowed to flow for 30 seconds to wash and remove the SS (floating substance) component in the wastewater attached to the hydroxyapatite. The total selenium concentration of the treated water was 0.029 mg / liter against the total selenium concentration of the treated water of 0.39 mg / liter. (See FIG. 3).
[0022]
(Comparative Example 1)
The wastewater used in Example 1 was used as the water to be treated. Hydrazine 500 mg / liter (as N 2 H 4 ) was added to 1 liter of the water to be treated, adjusted to pH 10 with sodium hydroxide, and then stirred at room temperature for 3 hours. Next, 200 mg / liter of ferrous sulfate (inorganic flocculant) was added thereto, and the pH was adjusted to 10 again with sodium hydroxide, and 1 mg / liter of an organic polymer flocculant (Ebagrose A-151, manufactured by Ebara Corporation) was added. And subjected to coagulation sedimentation treatment. This coagulated sedimentation treated water had an SS of 3.4 mg / liter and a total selenium concentration of 0.09 mg / liter.
[0023]
In Example 1, the selenium concentration of the treated water was reduced by the aggregation and precipitation treatment by adding hydroxyapatite. In Example 3, the selenium concentration of the treated water was reduced by the adsorption treatment by passing the wastewater through the packed tower filled with hydroxyapatite, and the treatment could be continuously performed. Further, compared to Comparative Example 1 in which hydrazine, an inorganic flocculant and an organic polymer flocculant were combined, the total of Example 2 in which hydroxyapatite was combined and treated in addition to hydrazine, an inorganic flocculant and an organic polymer flocculant, was used. The selenium concentration could be reduced further. As described above, the effect of removing selenium by hydroxyapatite according to the present invention is apparent.
[0024]
【The invention's effect】
According to the present invention, selenium can be easily and safely removed by bringing hydroxyapatite into contact with selenium-containing water.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing an apparatus for treating selenium-containing water according to the present invention.
FIG. 2 is an explanatory view schematically showing an apparatus for treating selenium-containing water by a method combining conventional techniques.
FIG. 3 is an explanatory view schematically showing an apparatus for treating selenium-containing water according to the present invention using a hydroxyapatite packed tower.
[Explanation of symbols]
Reference Signs List 1
12 Organic polymer flocculant 13 Acrylic resin column 14 Hydroxyapatite packed tower 15 Treated water
Claims (4)
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