JP3717230B2 - Method and apparatus for removing arsenic in water - Google Patents

Method and apparatus for removing arsenic in water Download PDF

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JP3717230B2
JP3717230B2 JP08891896A JP8891896A JP3717230B2 JP 3717230 B2 JP3717230 B2 JP 3717230B2 JP 08891896 A JP08891896 A JP 08891896A JP 8891896 A JP8891896 A JP 8891896A JP 3717230 B2 JP3717230 B2 JP 3717230B2
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hypochlorite
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晴輔 内藤
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株式会社マエタ
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Description

【０００１】
【発明の属する技術分野】
本発明は、水特に水道水源または井戸水等飲料水として使用される河川水、湖沼水、地下水等の自然水中に含まれる微量のヒ素またはヒ素化合物（特許請求の範囲および以下の記載においてはこれらを総称して「ヒ素」ということとする）を除去する方法および装置に関する。
【０００２】
【従来の技術】
水中には微量のヒ素が含まれていることがあるが、ヒ素は有害であるため水道法にもとずく水質基準では水道水中のヒ素の許容濃度は０．０１ｍｇ／ｌ以下と規定されている。したがって、水道原水中のヒ素の濃度がこの基準を超える場合は浄水場においてヒ素を除去してその濃度を基準値以下に下げなければならない。
【０００３】
水中のヒ素を除去する方法としては、従来工場排水中のヒ素をアルミナにより吸着除去する方法が知られている。
【０００４】
【発明が解決しようとする課題】
アルミナによりヒ素を吸着除去する従来の方法はコスト高であり、比較的小量の水を処理する場合ならば適用可能であるが大量の水道原水を処理する浄水場等で使用するには経済的に不適である。
【０００５】
本発明は、上記の事情にかんがみなされたものであって、水道水源の原水（未処理水）または井戸水等飲料水として使用される水の中のヒ素を経済的に実施可能な低コストで除去することができる方法および装置を提供しようとするものである。
【０００６】
【課題を解決するための手段】
本発明者は、上記目的を達成するため実験と研究を重ねる中、次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を被処理水に添加し混合することによって水中のヒ素と次亜塩素酸塩を反応させ、その反応生成物をＦｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤に通すと、意外なことに、この反応生成物は該吸着剤に顕著に吸着されることによって被処理水から除去されることを発見し、本発明に到達した。
【０００７】
すなわち、本発明の目的を達成する請求項１の発明にかかる水中のヒ素を除去する装置は、次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を貯蔵する貯蔵槽と、該貯蔵槽に接続され該貯蔵槽から次亜塩素酸塩が供給される次亜塩素酸塩供給部と、ヒ素を含有する被処理水の流入部と、被処理水の流出部と、次亜塩素酸塩と被処理水とを混合して被処理水中のヒ素と次亜塩素酸塩とを反応させる混合手段とを備える反応槽と、Ｆｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤が充填され該反応槽の該流出口に接続された濾過槽とを備えることを特徴とする。
【０００８】
また請求項２記載の水中のヒ素を除去する装置は、上記の構成に加え、該吸着剤はＦｅ 3 Ｏ 4 であり、該吸着剤を磁化する磁石をさらに備えることを特徴とする。
【０００９】
また請求項３記載の水中のヒ素を除去する装置は、次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を貯蔵する貯蔵槽と、該貯蔵槽に接続され該貯蔵槽から次亜塩素酸塩が供給される次亜塩素酸塩供給部と、ヒ素を含有する被処理水の流入部と、被処理水の流出部と、次亜塩素酸塩と被処理水とを混合して被処理水中のヒ素と次亜塩素酸塩とを反応させる混合手段とを備える反応槽と、Ｆｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤を該反応槽内に装入し被処理水と混合する手段とを備えることを特徴とする。
【００１０】
また請求項４記載の発明にかかる水中のヒ素を除去する方法は、次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を自然水中に添加して自然水中のヒ素と次亜塩素酸塩とを反応させて反応生成物を生成させ、該反応生成物をＦｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤に吸着させることを特徴とする。
【００１１】
なお、本明細書において、「自然水」とは河川水、湖沼水、地下水等水道水源または井戸水源等飲料水の水源として使用される未処理または処理過程にある水を意味し、塩素処理を含むすべての浄水処理が完了し、使用可能な水として供給される水道水を含まない。
【００１２】
【作用】
次亜塩素酸ナトリウム等の次亜塩素酸塩は従来酸化剤、漂白剤等として使用されており、浄水場において塩素に代り殺菌消毒剤として添加される場合もあるが、水中のヒ素と次亜塩素酸塩の反応生成物がＦｅ 3 Ｏ 4 またはＦｅ3 Ｏ5 からなる吸着剤によって顕著に吸着されるということはこれまでまったく知られておらず、浄水場等自然水を水道水源として処理する施設においてヒ素を除去するためにこのような方法が使用された例はない。
【００１３】
本発明は、従来も水道原水の殺菌消毒用として塩素と同様に使用されていた次亜塩素酸ナトリウム等の安価な次亜塩素酸塩とＦｅ 3 Ｏ 4 等の安価な吸着剤を使用するだけで大量の水道原水または井戸水中のヒ素の濃度を水道法にもとずく基準値等所望の値に低減させることができ、浄水場等において水中のヒ素を経済的に実施可能な低コストで除去することを可能とするものであって、その社会的貢献度は極めて大きい。
【００１４】
請求項１記載の発明によれば、貯蔵槽から反応槽内に供給される次亜塩素酸塩は反応槽内に流入した被処理水と混合され、被処理水中のヒ素と次亜塩素酸塩との反応生成物が生じる。この反応生成物は濾過槽内のＦｅ 3 Ｏ 4 、Ｆｅ3 Ｏ5 からなる群から選ばれた吸着剤に吸着されることにより、被処理水中のヒ素の濃度を基準値濃度等所望の値に減少させることができる。
【００１５】
請求項２記載の発明によれば、吸着剤は磁石によって磁化されることにより、ヒ素吸着効率がいっそう向上する。
【００１６】
請求項３記載の発明によれば、貯蔵槽から反応槽内に供給される次亜塩素酸塩は反応槽内に流入した被処理水と混合され、被処理水中のヒ素と次亜塩素酸塩との反応生成物が生じる。この反応生成物は、反応槽内に装入され被処理水と混合されるＦｅ 3 Ｏ 4 、Ｆｅ3 Ｏ5 からなる群から選ばれた吸着剤に吸着される。
【００１７】
また請求項４記載の発明によれば、水道水源の原水または井戸水等飲料水として使用される自然水の中のヒ素を経済的に実施可能な低コストで除去することができる。
【００１８】
【発明の実施の形態】
以下添付図面を参照して本発明の実施の形態について説明する。図１は本発明の１実施形態を示す模式的断面図である。ヒ素除去装置１は、次亜塩素酸塩貯蔵槽２、反応槽３、濾過槽４を備えている。
【００１９】
次亜塩素酸塩貯蔵槽２には次亜塩素酸ナトリウムの水溶液が貯蔵されている。
【００２０】
反応槽３は円筒状で蓋部３ａおよび底部３ｂを有し、蓋部３ａには配管５を介して貯蔵槽２から次亜塩素酸ナトリウムが供給される供給口６と被処理水の流入口７が形成されており、底部には被処理水の流出口８が形成されている。また蓋部３ａ中央の開口３ｃを介して回転攪拌混合器９の軸９ａが挿通されており、攪拌混合器９は図示しないモータによって回転駆動される。攪拌混合器９は次亜塩素酸ナトリウムと被処理水とを混合する混合手段を形成する。
【００２１】
濾過槽４は円筒状で蓋部４ａに被処理水流入口４ｃを、底部４ｂに被処理水流出口４ｄを有している。反応槽３の流出口８は配管１０を介して濾過槽４の被処理水流入口４ｃに連通している。濾過槽４には不織布フィルター等のフィルター板１１が上部および下部に配設固定されており、これら両フィルター板１１間の空間には吸着剤として細片状の磁鉄鉱（Ｆｅ3 Ｏ4 ）が充填堆積されて吸着剤層１２を形成している。
【００２２】
またフィルター板１１、１１の上には環状マグネット１３、１４が載置されており、その磁力線により吸着剤層１２を磁化している。各環状マグネット１３、１４はそれぞれの位置が上下方向で一致するように位置決めされ、また各環状マグネット１３、１４はその磁力線の向きが互いに一致し、特に水の流れた対し逆向きとなるように一致し、かつ磁力線の方向が水の流れに沿うように配置されている。
【００２３】
この環状マグネット１３、１４の配置により、環状マグネット１３、１４のそれぞれの磁力線は互いに結合して増強し合い、特に上向き、すなわち水の流れに沿いかつそれとは逆向きの均一で強力な磁場を形成し、磁鉄鉱からなる吸着剤層１２を強力に磁化している。
【００２４】
次にこの装置の動作について説明する。反応槽３の流入口７からは被処理水が流入する一方供給口６からは貯蔵槽２からの次亜塩素酸ナトリウムが流入する。次亜塩素酸ナトリウムは攪拌混合器９により被処理水と混合され、被処理水中のヒ素は次亜塩素酸ナトリウムと反応して反応生成物が生成される。
【００２５】
次いで被処理水は反応槽３の流出口８から配管１０を介して濾過槽４の流入口４ａに流入し、フィルター１１を介して磁化されたＦｅ3 Ｏ4 からなる吸着剤層１２を通過し流出口４ｄから装置外に流出する。この間にヒ素と次亜塩素酸ナトリウムの反応生成物の大部分は吸着剤層１２の吸着剤に吸着される結果、濾過槽４の流出口４ｄから流出する被処理水中のヒ素の濃度は所望の値（たとえば０．０１ｍｇ／ｌ）に低減している。
【００２６】
図２は本発明の他の実施形態を示す模式的断面図である。この実施形態において、装置２１は次亜塩素酸塩貯蔵槽２２、反応槽２３、吸着剤貯蔵槽２４を備えている。
【００２７】
次亜塩素酸塩貯蔵槽２には次亜塩素酸ナトリウム水溶液が貯蔵されている。また吸着剤貯蔵槽２４には粉状のＦｅ2 Ｏ3 が貯蔵されている。
【００２８】
反応槽２３は四角筒状で蓋部２３ａおよび底部２３ｂを有し、蓋部２３ａには配管２５を介して貯蔵槽２２から次亜塩素酸ナトリウムが供給される供給口２６と、被処理水の流入口２７と、吸着剤貯蔵槽２４から配管２８を介して吸着剤が供給される供給口２９が形成されている。また底部２３ｂには被処理水の流出口３０が形成されている。また蓋部２３ａ中央の開口２３ｃを介して回転攪拌混合器３１の軸３１ａが挿通されており、攪拌混合器３１は図示しないモータによって回転駆動される。攪拌混合器３１は次亜塩素酸塩と被処理水とを混合する混合手段を形成するとともに吸着剤を被処理水と混合する手段を兼用している。
【００２９】
３２は不織布フィルター等からなる四角形のフィルター板であり、その下側にはキャスター３３が取付けられている。フィルター板３２のフィルターの目は粉状吸着剤を通さないような値に設定されている。また反応槽２３の一側の下部はヒンジ３４により反応槽２３の壁部２３ｄに開閉可能にヒンジ結合された開閉窓部３５として形成されており、把手３５ａにより開閉ができるようになっている。したがって開閉窓部３５を開いてフィルター板３２を外部に取出すことが可能である。
【００３０】
次にこの装置２１の動作について説明する。反応槽２３の流入口２７からは被処理水が流入する一方供給口２６からは貯蔵槽２２からの次亜塩素酸ナトリウムが流入する。また供給口２９からは貯蔵槽２４からのＦｅ2 Ｏ3 粉末が吸着剤として連続的または間欠的に装入される。次亜塩素酸ナトリウムは攪拌混合器３１により被処理水と混合され、被処理水中のヒ素は次亜塩素酸ナトリウムと反応して反応生成物が生成される。
【００３１】
ヒ素と次亜塩素酸ナトリウムの反応生成物の大部分を吸着する。その結果反応槽の流出口３０から流出する被処理水中のヒ素の濃度は所望の値に低減している。
【００３２】
吸着剤による反応生成物の吸着が飽和状態に達した場合等吸着能力が低下した場合は装置の運転を中止し、反応槽２３内の被処理水を流出口３０からすべて排出すると、吸着剤はフィルター板３２上に堆積する。次いで開閉窓部３５を開いてフィルター板３２を外部に取出し吸着剤を取除いた後フィルター板３２を反応槽２３内に戻し開閉窓部３５を閉じ、装置の運転を再開する。
【００３３】
上記各装置においては、混合手段として攪拌混合器９、３１を用いたが、混合手段としてはこれに限らず、たとえば反応槽を回転駆動する等他の方法を使用してもよい。
【００３４】
図１の装置において、濾過槽４内の吸着剤は環状マグネット１３、１４により磁化しているが、磁石としては他の磁石を使用してもよい。また磁石を用いず、磁化されない吸着剤により反応生成物を磁化するようにしてもよい。ただし実験の結果磁化された吸着剤は磁化されない同一の吸着剤に比べて反応生成物の吸着効果が良く、したがってヒ素の除去を迅速に行うことができ、同じ時間内により大量の被処理水を処理することができる。
【００３５】
次に本発明の１実験例について説明する。反応容器内に１００ｐｐｂのＡｓ(III) を添加した井戸水１ｌを入れ、これに０．１ｍＭ次亜塩素酸ナトリウムを添加し、次いで吸着剤として所定量のＦｅ2Ｏ3 粉末を添加し、１５分間振とうした後ろ紙（Ｎｏ．２）で濾過した。また比較のため次亜塩素酸ナトリウムを加えずＦｅ2 Ｏ3 粉末のみを添加し上記と同様の処理を行った。濾水のヒ素濃度を水素化物発生ＩＣＰ発光分析法により測定した。この測定法による定量限界は１ｐｐｂであった。ヒ素濃度測定の結果を表１に示す。
【００３６】
【表１】

Figure 0003717230
【００３７】
以上の結果から、次亜塩素酸ナトリウムを添加しない場合ヒ素を完全に除去することはできないが、次亜塩素酸ナトリウムで反応させた場合ヒ素をほぼ完全に除去することができることが判る。
【００３８】
また吸着剤としてＦｅ2 Ｏ3 のかわりに粉末状Ｆｅ3 Ｏ4 を用いた以外は上記と同一条件でヒ素除去実験を行った。その結果を表２に示す。
【００３９】
【表２】
Figure 0003717230
【００４０】
吸着剤としてＦｅ3 Ｏ4 を使用した実験では、Ｆｅ3 Ｏ4 はＦｅ2 Ｏ3 よりも粒径が大きいため合計吸着表面積が小さく、またＦｅ3 Ｏ4 はＦｅ2 Ｏ3 よりも重く容器の底に沈む割合が大きいため吸着効率がＦｅ2 Ｏ3 よりも劣り、ヒ素の除去率がそれだけ劣っていた。しかしＦｅ3 Ｏ4 を吸着剤として用いた場合でも、次亜塩素酸ナトリウムを添加した場合の方が添加しない場合に比べてヒ素除去率が優れていることは明らかである。また図１に示す実施形態においてＦｅ3 Ｏ4 を使用し、特に磁石によりＦｅ3 Ｏ4 を磁化した場合はヒ素除去率はＦｅ2 Ｏ3 に比べて特に劣るものではなく、むしろ優れている場合もある。
【００４１】
【発明の効果】
以上述べたように、請求項１記載の発明によれば、貯蔵槽から反応槽内に供給される次亜塩素酸塩は反応槽内に流入した被処理水と混合され、被処理水中にヒ素と次亜塩素酸塩との反応生成物が生じる。この反応生成物は濾過槽内のＦｅ 3 Ｏ 4 、Ｆｅ3 Ｏ5 からなる群から選ばれた吸着剤に吸着されることにより、被処理水中のヒ素の濃度を基準値濃度等所望の値に減少させることができる。
【００４２】
請求項２記載の発明によれば、吸着剤は磁石によって磁化されることにより、ヒ素吸着効率がいっそう向上する。
【００４３】
請求項３記載の発明によれば、貯蔵槽から反応槽内に供給される次亜塩素酸塩は反応槽内に流入した被処理水と混合され、被処理水中のヒ素と次亜塩素酸塩との反応生成物が生じる。この反応生成物は、反応槽内に装入され被処理水と混合されるＦｅ 3 Ｏ 4 、Ｆｅ3 Ｏ5 からなる群から選ばれた吸着剤に吸着される。
【００４４】
また請求項４記載の発明によれば、水道水源の原水または井戸水等飲料水として使用される自然水の中のヒ素を経済的に実施可能な低コストで除去することができる。
【図面の簡単な説明】
【図１】本発明の１実施形態を模式的に示す断面図である。
【図２】本発明の他の実施例を模式的に示す断面図である。
【符号の説明】
２、２２ 次亜塩素酸塩貯蔵槽
３、２３ 反応槽
４ 濾過槽
１２ 吸着剤層
１３，１４ 磁石
２４ 吸着剤貯蔵槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to trace amounts of arsenic or arsenic compounds contained in natural water such as river water, lake water, and groundwater used as drinking water such as tap water source or well water (in the claims and the following description, these are referred to as The present invention relates to a method and an apparatus for removing (arsenic).
[0002]
[Prior art]
Trace amounts of arsenic may be contained in water, but since arsenic is harmful, water quality standards based on the Water Supply Law specify that the allowable concentration of arsenic in tap water is 0.01 mg / l or less . Therefore, if the concentration of arsenic in the raw tap water exceeds this standard, arsenic must be removed at the water purification plant and the concentration must be reduced below the standard value.
[0003]
As a method for removing arsenic in water, a method of adsorbing and removing arsenic in factory wastewater with alumina is conventionally known.
[0004]
[Problems to be solved by the invention]
The conventional method of adsorbing and removing arsenic with alumina is costly and can be applied if a relatively small amount of water is treated, but it is economical to use in a water purification plant that treats a large amount of raw water. Not suitable for.
[0005]
The present invention has been considered in view of the above circumstances, and removes arsenic in water used as drinking water such as raw water (untreated water) for tap water sources or well water at an economically feasible cost. It is intended to provide a method and apparatus that can be used.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventor treated hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite during repeated experiments and research. By adding to water and mixing, arsenic and hypochlorite in water are reacted, and the reaction product is adsorbed in the form of flakes or powders selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 Surprisingly, the reaction product was found to be removed from the water to be treated by being significantly adsorbed by the adsorbent when passed through the agent, and the present invention was reached.
[0007]
That is, the apparatus for removing arsenic in water according to the invention of claim 1 that achieves the object of the present invention is the following selected from the group consisting of sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite. A storage tank for storing chlorite, a hypochlorite supply section connected to the storage tank and supplied with hypochlorite from the storage tank, and an inflow section of treated water containing arsenic A reaction vessel comprising an outflow part of the water to be treated, and a mixing means for mixing hypochlorite and water to be treated to react arsenic and hypochlorite in the water to be treated; and Fe 3 O And a filtration tank filled with a strip-like or powdery adsorbent selected from the group consisting of 4 and Fe 3 O 5 and connected to the outlet of the reaction tank.
[0008]
The device for removing arsenic in water according to claim 2, in addition to the above configuration, the adsorbent is Fe 3 O 4, and further comprising a magnet magnetizing the adsorbent.
[0009]
The apparatus for removing arsenic in water according to claim 3 comprises a storage tank for storing hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite; A hypochlorite supply section connected to the storage tank to which hypochlorite is supplied from the storage tank, an inflow section of treated water containing arsenic, an outflow section of treated water, A reaction vessel comprising a mixing means for mixing chlorite and water to be treated and reacting arsenic and hypochlorite in the water to be treated; and from the group consisting of Fe 3 O 4 and Fe 3 O 5 And a means for charging the selected strip-like or powdery adsorbent into the reaction vessel and mixing it with the water to be treated.
[0010]
The method for removing arsenic from water according to the invention of claim 4 is characterized in that a hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite is added to natural water. To form a reaction product by reacting arsenic and hypochlorite in natural water, and the reaction product is in the form of a strip selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 Or it is made to adsorb | suck to a powdery adsorbent.
[0011]
In this specification, “natural water” means untreated or in-process water that is used as a source of drinking water such as river water, lake water, groundwater, or tap water or well water, and is treated with chlorination. All water purification treatments are completed and do not include tap water supplied as usable water.
[0012]
[Action]
Hypochlorites such as sodium hypochlorite are conventionally used as oxidizing agents, bleaching agents, etc., and may be added as disinfectants instead of chlorine in water purification plants. It has not been known so far that the reaction product of chlorate is significantly adsorbed by an adsorbent composed of Fe 3 O 4 or Fe 3 O 5, and natural water such as a water purification plant is treated as a tap water source. There is no example where such a method has been used to remove arsenic in a facility.
[0013]
In the present invention, an inexpensive hypochlorite salt such as sodium hypochlorite and Fe 3 O 4 that have been used in the same manner as chlorine for sterilization and disinfection of raw water for water supply. It is possible to reduce the concentration of arsenic in a large amount of raw water or well water to a desired value such as a standard value based on the Waterworks Law simply by using an inexpensive adsorbent, etc. It can be removed at a low cost that is economically feasible, and its social contribution is extremely large.
[0014]
According to the first aspect of the present invention, the hypochlorite supplied from the storage tank into the reaction tank is mixed with the treated water flowing into the reaction tank, and arsenic and hypochlorite in the treated water are mixed. To form a reaction product. This reaction product is adsorbed by an adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 in the filtration tank, so that the concentration of arsenic in the water to be treated is set to a desired value such as a reference value concentration. Can be reduced.
[0015]
According to the invention described in claim 2, the adsorbent is magnetized by the magnet, so that the arsenic adsorption efficiency is further improved.
[0016]
According to the invention described in claim 3, hypochlorite supplied from the storage tank into the reaction tank is mixed with the water to be treated which has flowed into the reaction tank, and arsenic and hypochlorite in the water to be treated. To form a reaction product. The reaction product, Fe 3 O 4 which is charged to the reaction vessel and mixed with the water to be treated And adsorbent selected from the group consisting of Fe 3 O 5 .
[0017]
Further, according to the invention described in claim 4, arsenic in natural water used as drinking water such as raw water or well water for a tap water source can be removed at a low cost that is economically feasible.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an embodiment of the present invention. The arsenic removing apparatus 1 includes a hypochlorite storage tank 2, a reaction tank 3, and a filtration tank 4.
[0019]
An aqueous solution of sodium hypochlorite is stored in the hypochlorite storage tank 2.
[0020]
The reaction tank 3 is cylindrical and has a lid portion 3a and a bottom portion 3b. The lid portion 3a has a supply port 6 to which sodium hypochlorite is supplied from the storage tank 2 through a pipe 5 and an inlet port for water to be treated. 7 is formed, and an outlet 8 of the water to be treated is formed at the bottom. The shaft 9a of the rotary stirring mixer 9 is inserted through the opening 3c in the center of the lid 3a, and the stirring mixer 9 is driven to rotate by a motor (not shown). The stirring mixer 9 forms mixing means for mixing sodium hypochlorite and water to be treated.
[0021]
The filtration tank 4 has a cylindrical shape, and has a treated water inlet 4c in the lid 4a and a treated water outlet 4d in the bottom 4b. The outlet 8 of the reaction tank 3 communicates with the to-be-treated water inlet 4 c of the filtration tank 4 through the pipe 10. A filter plate 11 such as a nonwoven fabric filter is disposed and fixed in the upper and lower portions of the filtration tank 4, and a space between the two filter plates 11 is filled with strip-shaped magnetite (Fe 3 O 4 ) as an adsorbent. It is deposited to form the adsorbent layer 12.
[0022]
Further, annular magnets 13 and 14 are placed on the filter plates 11 and 11, and the adsorbent layer 12 is magnetized by the magnetic lines of force. The annular magnets 13 and 14 are positioned so that their positions coincide with each other in the vertical direction, and the annular magnets 13 and 14 have their magnetic lines of force coincide with each other, particularly in the opposite direction to the flow of water. They are arranged so that they coincide and the direction of the lines of magnetic force follows the flow of water.
[0023]
Due to the arrangement of the annular magnets 13, 14, the magnetic lines of force of the annular magnets 13, 14 are combined and strengthened to form a uniform and strong magnetic field especially upward, that is, along the flow of water and in the opposite direction. The adsorbent layer 12 made of magnetite is strongly magnetized.
[0024]
Next, the operation of this apparatus will be described. Water to be treated flows from the inlet 7 of the reaction tank 3, while sodium hypochlorite from the storage tank 2 flows from the supply port 6. Sodium hypochlorite is mixed with the water to be treated by the stirring mixer 9, and arsenic in the water to be treated reacts with sodium hypochlorite to produce a reaction product.
[0025]
Next, the water to be treated flows from the outlet 8 of the reaction tank 3 into the inlet 4 a of the filtration tank 4 through the pipe 10 and passes through the adsorbent layer 12 made of magnetized Fe 3 O 4 through the filter 11. It flows out of the apparatus from the outlet 4d. During this time, most of the reaction product of arsenic and sodium hypochlorite is adsorbed by the adsorbent of the adsorbent layer 12, so that the concentration of arsenic in the treated water flowing out from the outlet 4d of the filtration tank 4 is as desired. The value is reduced to a value (for example, 0.01 mg / l).
[0026]
FIG. 2 is a schematic cross-sectional view showing another embodiment of the present invention. In this embodiment, the apparatus 21 includes a hypochlorite storage tank 22, a reaction tank 23, and an adsorbent storage tank 24.
[0027]
The hypochlorite storage tank 2 stores an aqueous sodium hypochlorite solution. The adsorbent storage tank 24 stores powdered Fe 2 O 3 .
[0028]
The reaction tank 23 has a rectangular tube shape and has a lid portion 23a and a bottom portion 23b. The lid portion 23a has a supply port 26 to which sodium hypochlorite is supplied from the storage tank 22 through a pipe 25, and water to be treated. An inlet 27 and a supply port 29 through which the adsorbent is supplied from the adsorbent storage tank 24 through the pipe 28 are formed. An outlet 30 for water to be treated is formed at the bottom 23b. The shaft 31a of the rotary stirring mixer 31 is inserted through the opening 23c in the center of the lid 23a, and the stirring mixer 31 is driven to rotate by a motor (not shown). The stirring mixer 31 forms a mixing means for mixing the hypochlorite and the water to be treated and also serves as a means for mixing the adsorbent with the water to be treated.
[0029]
Reference numeral 32 denotes a rectangular filter plate made of a nonwoven fabric filter or the like, and a caster 33 is attached to the lower side thereof. The filter eyes of the filter plate 32 are set to a value that does not allow the powdery adsorbent to pass through. A lower portion on one side of the reaction tank 23 is formed as an opening / closing window 35 that is hingedly connected to a wall 23d of the reaction tank 23 by a hinge 34, and can be opened and closed by a handle 35a. Therefore, it is possible to open the opening / closing window 35 and take out the filter plate 32 to the outside.
[0030]
Next, the operation of the device 21 will be described. Water to be treated flows from the inlet 27 of the reaction tank 23, while sodium hypochlorite from the storage tank 22 flows from the supply port 26. Further, Fe 2 O 3 powder from the storage tank 24 is continuously or intermittently charged from the supply port 29 as an adsorbent. Sodium hypochlorite is mixed with the water to be treated by the stirring mixer 31, and arsenic in the water to be treated reacts with sodium hypochlorite to produce a reaction product.
[0031]
Adsorbs most of the reaction products of arsenic and sodium hypochlorite. As a result, the concentration of arsenic in the water to be treated flowing out from the outlet 30 of the reaction tank is reduced to a desired value.
[0032]
If the adsorption capacity is reduced, such as when the adsorption of the reaction product by the adsorbent reaches a saturated state, the operation of the apparatus is stopped, and when all the water to be treated in the reaction tank 23 is discharged from the outlet 30, the adsorbent is Deposit on the filter plate 32. Next, the open / close window 35 is opened, the filter plate 32 is taken out, the adsorbent is removed, the filter plate 32 is returned into the reaction tank 23, the open / close window 35 is closed, and the operation of the apparatus is resumed.
[0033]
In each of the above apparatuses, the stirring mixers 9 and 31 are used as the mixing means. However, the mixing means is not limited to this, and other methods such as, for example, rotationally driving the reaction vessel may be used.
[0034]
In the apparatus of FIG. 1, the adsorbent in the filtration tank 4 is magnetized by the annular magnets 13 and 14, but other magnets may be used as the magnet. Moreover, you may make it magnetize a reaction product by the adsorbent which is not magnetized without using a magnet. However, as a result of experiments, the magnetized adsorbent has a better adsorption effect on the reaction product than the same adsorbent that is not magnetized, so that arsenic can be removed quickly, and a larger amount of water to be treated can be obtained within the same time. Can be processed.
[0035]
Next, one experimental example of the present invention will be described. Into the reaction vessel, 1 liter of well water added with 100 ppb As (III) was added, 0.1 mM sodium hypochlorite was added thereto, and then a predetermined amount of Fe 2 O 3 powder was added as an adsorbent, and 15 minutes It filtered with the back paper (No. 2) which was shaken. For comparison, only Fe 2 O 3 powder was added without adding sodium hypochlorite and the same treatment as above was performed. The arsenic concentration of the filtrate was measured by hydride generation ICP emission spectrometry. The limit of quantification by this measuring method was 1 ppb. The results of arsenic concentration measurement are shown in Table 1.
[0036]
[Table 1]
Figure 0003717230
[0037]
From the above results, it can be seen that arsenic cannot be completely removed when sodium hypochlorite is not added, but arsenic can be almost completely removed when reacted with sodium hypochlorite.
[0038]
An arsenic removal experiment was performed under the same conditions as described above except that powdered Fe 3 O 4 was used instead of Fe 2 O 3 as the adsorbent. The results are shown in Table 2.
[0039]
[Table 2]
Figure 0003717230
[0040]
In an experiment using Fe 3 O 4 as the adsorbent, Fe 3 O 4 has a larger particle size than Fe 2 O 3 , so the total adsorption surface area is small, and Fe 3 O 4 is heavier than Fe 2 O 3. Since the ratio of sinking to the bottom is large, the adsorption efficiency is inferior to Fe 2 O 3 and the arsenic removal rate is inferior. However, even when Fe 3 O 4 is used as the adsorbent, it is clear that the arsenic removal rate is superior when sodium hypochlorite is added compared to when it is not added. Further, when Fe 3 O 4 is used in the embodiment shown in FIG. 1, and especially when Fe 3 O 4 is magnetized by a magnet, the arsenic removal rate is not particularly inferior to Fe 2 O 3 , but rather excellent. There is also.
[0041]
【The invention's effect】
As described above, according to the first aspect of the present invention, the hypochlorite supplied from the storage tank into the reaction tank is mixed with the treated water flowing into the reaction tank, and the arsenic is contained in the treated water. And a reaction product of hypochlorite is formed. This reaction product is adsorbed by an adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 in the filtration tank, so that the concentration of arsenic in the water to be treated is set to a desired value such as a reference value concentration. Can be reduced.
[0042]
According to the invention described in claim 2, the adsorbent is magnetized by the magnet, so that the arsenic adsorption efficiency is further improved.
[0043]
According to the invention described in claim 3, hypochlorite supplied from the storage tank into the reaction tank is mixed with the water to be treated which has flowed into the reaction tank, and arsenic and hypochlorite in the water to be treated are mixed. To form a reaction product. This reaction product is adsorbed by an adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 charged in the reaction vessel and mixed with the water to be treated.
[0044]
Further, according to the invention described in claim 4, arsenic in natural water used as drinking water such as raw water for tap water or well water can be removed at a low cost that can be economically implemented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing one embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing another embodiment of the present invention.
[Explanation of symbols]
2,22 Hypochlorite storage tank 3,23 Reaction tank 4 Filtration tank 12 Adsorbent layer 13,14 Magnet 24 Adsorbent storage tank

Claims (4)

次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を貯蔵する貯蔵槽と、
該貯蔵槽に接続され該貯蔵槽から次亜塩素酸塩が供給される次亜塩素酸塩供給部と、ヒ素を含有する被処理水の流入部と、被処理水の流出部と、次亜塩素酸塩と被処理水とを混合して被処理水中のヒ素と次亜塩素酸塩とを反応させる混合手段とを備える反応槽と、
Ｆｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤が充填され該反応槽の該流出口に接続された濾過槽とを備えることを特徴とする水中のヒ素を除去する装置。A storage tank for storing hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite;
A hypochlorite supply unit connected to the storage tank to which hypochlorite is supplied from the storage tank, an inflow portion of treated water containing arsenic, an outflow portion of treated water, A reaction vessel comprising mixing means for mixing chlorate and water to be treated to react arsenic and hypochlorite in the water to be treated;
A filtration tank filled with a strip-like or powdery adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 and connected to the outlet of the reaction tank. For removing arsenic in water. 該吸着剤はＦｅ 3 Ｏ 4 であり、該吸着剤を磁化する磁石をさらに備えることを特徴とする請求項１記載の装置。The apparatus of claim 1 , wherein the adsorbent is Fe 3 O 4 , further comprising a magnet that magnetizes the adsorbent. 次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を貯蔵する貯蔵槽と、
該貯蔵槽に接続され該貯蔵槽から次亜塩素酸塩が供給される次亜塩素酸塩供給部と、ヒ素を含有する被処理水の流入部と、被処理水の流出部と、次亜塩素酸塩と被処理水とを混合して被処理水中のヒ素と次亜塩素酸塩とを反応させる混合手段とを備える反応槽と、
Ｆｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤を該反応槽内に装入し被処理水と混合する手段とを備えることを特徴とする水中のヒ素を除去する装置。A storage tank for storing hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite;
A hypochlorite supply unit connected to the storage tank to which hypochlorite is supplied from the storage tank, an inflow portion of treated water containing arsenic, an outflow portion of treated water, A reaction vessel comprising mixing means for mixing chlorate and water to be treated to react arsenic and hypochlorite in the water to be treated;
And a means for charging a strip-like or powdery adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5 into the reaction vessel and mixing it with the water to be treated. For removing arsenic in water. 次亜塩素酸ナトリウム、次亜塩素酸カリウムおよび次亜塩素酸カルシウムからなる群から選ばれた次亜塩素酸塩を自然水中に添加して自然水中のヒ素と次亜塩素酸塩とを反応させて反応生成物を生成させ、該反応生成物をＦｅ 3 Ｏ 4 およびＦｅ3 Ｏ5 からなる群から選ばれた細片状または粉状の吸着剤に吸着させることを特徴とする水中のヒ素を除去する方法。Hypochlorite selected from the group consisting of sodium hypochlorite, potassium hypochlorite and calcium hypochlorite is added to natural water to react arsenic with hypochlorite in natural water. A reaction product is produced, and the reaction product is adsorbed on a strip-like or powdery adsorbent selected from the group consisting of Fe 3 O 4 and Fe 3 O 5. How to remove.
JP08891896A 1996-03-18 1996-03-18 Method and apparatus for removing arsenic in water Expired - Fee Related JP3717230B2 (en)

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