JP2021016847A - Water treatment method - Google Patents

Water treatment method Download PDF

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JP2021016847A
JP2021016847A JP2019135632A JP2019135632A JP2021016847A JP 2021016847 A JP2021016847 A JP 2021016847A JP 2019135632 A JP2019135632 A JP 2019135632A JP 2019135632 A JP2019135632 A JP 2019135632A JP 2021016847 A JP2021016847 A JP 2021016847A
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water
treated
adsorption tower
adsorption
fluorine
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吉崎 耕大
Yasuhiro Yoshizaki
耕大 吉崎
俊一 池田
Shunichi Ikeda
俊一 池田
麻未 冨田
Mami Tomita
麻未 冨田
郁 村上
Iku Murakami
郁 村上
幸男 樋口
Yukio Higuchi
幸男 樋口
張本 崇良
Suuryo Harimoto
崇良 張本
総太 岩谷
Sota IWATANI
総太 岩谷
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株式会社クボタ
Kubota Corp
クボタ化水株式会社
Kubota Kasui Corp
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Abstract

To provide a water treatment method for removing fluorine ions from water to be treated that contains fluorine ions and a high concentration of sulfate ions, which method makes it possible to treat water in a stable manner by the use of a fluorine adsorbent.SOLUTION: A water treatment method comprises: an adsorption step in which water 1 to be treated that contains fluorine ions and sulfate ions is introduced into an adsorption column 11 filled with fluorine adsorbent to obtain a first treated water 2 from which at least part of the fluorine ions contained in the water 1 to be treated has been removed; and a pretreatment step in which the first treated water 2 obtained in the adsorption step is introduced into the adsorption column 11 prior to the adsorption step, wherein the sulfate ion concentration of the water 1 to be treated introduced into the adsorption column 11 is 30,000 mg/L or more, and wherein the sulfate ion concentration of the first treated water 2 introduced into the adsorption column 11 is 30,000 mg/L or more.SELECTED DRAWING: Figure 2

Description

本発明は、フッ素イオンと硫酸イオンを含有する被処理水を処理する水処理方法に関する。 The present invention relates to a water treatment method for treating water to be treated containing fluorine ions and sulfate ions.
石炭火力発電所やコークス工場や製鉄工場等では、石炭やコークスを燃焼させることにより発生した排ガスを脱硫処理することで、硫酸イオンとともにフッ素イオンを含む排煙脱硫排水が発生する。排煙脱硫排水には、通常、硫酸イオンが数万mg/L以上含まれ、さらにフッ素イオンが数十mg/L〜数百mg/L程度含まれる。そのため、これを放流するに当たっては、当該排水中からフッ素イオンを除去することが必要となる。 In coal-fired power plants, coke factories, steel mills, etc., flue gas desulfurization wastewater containing fluorine ions as well as sulfate ions is generated by desulfurizing the exhaust gas generated by burning coal or coke. The flue gas desulfurization wastewater usually contains tens of thousands of mg / L or more of sulfate ions, and further contains tens of mg / L to several hundreds of mg / L of fluorine ions. Therefore, when releasing this, it is necessary to remove fluorine ions from the wastewater.
排煙脱硫排水からフッ素イオンを除去する方法として、従来、様々な方法が提案されている。例えば特許文献1には、フッ素イオンとマグネシウムイオンと硫酸イオンを含有する排水にカルシウムイオンを添加してpHを9.4〜9.8に調整する処理方法が開示されている。特許文献2には、水酸化マグネシウムを脱硫剤として用いた排煙脱硫排水中からフッ素イオンを除去する方法であって、排水中の懸濁物質を固液分離し、固液分離した液に水酸化ナトリウムを添加してpH9以上とし、生成した沈殿物にフッ素イオンを吸着させ、固液分離する処理方法が開示されている。特許文献3には、COD成分分解工程と第1凝集沈殿工程と第2凝集沈殿工程とフッ素吸着工程を含む排煙脱硫排水の処理方法が開示されている。 Various methods have been conventionally proposed as methods for removing fluorine ions from flue gas desulfurization wastewater. For example, Patent Document 1 discloses a treatment method for adjusting the pH to 9.4 to 9.8 by adding calcium ions to wastewater containing fluorine ions, magnesium ions and sulfate ions. Patent Document 2 describes a method of removing fluorine ions from flue gas desulfurized wastewater using magnesium hydroxide as a desulfurizing agent. Suspended substances in the wastewater are solid-liquid separated, and water is added to the solid-liquid separated liquid. A treatment method is disclosed in which sodium oxide is added to adjust the pH to 9 or higher, fluorine ions are adsorbed on the generated precipitate, and solid-liquid separation is performed. Patent Document 3 discloses a method for treating flue gas desulfurized wastewater, which includes a COD component decomposition step, a first coagulation sedimentation step, a second coagulation sedimentation step, and a fluorine adsorption step.
一方、半導体製造分野等におけるエッチング洗浄廃液やアルミニウム電解製錬工程やガラス製造工程等から排出されるフッ素含有廃液の処理方法として、フッ素吸着剤を用いたフッ素イオンの除去方法も知られている。例えば特許文献4には、フッ素含有水をカルシウム化合物と反応させてフッ化カルシウムに変換して固液分離した後、分離液をフッ素吸着剤と接触させる処理方法が開示されている。特許文献5には、フッ素含有水を低濃度フッ素含有水と高濃度フッ素含有水に分別する工程、低濃度フッ素含有水にカルシウム化合物を添加後固液分離し、分離液をフッ素吸着剤と接触させる工程、フッ素吸着剤を再生処理する工程、および、高濃度フッ素含有水にフッ素吸着剤の再生廃液を添加した後、炭酸カルシウム結晶種充填槽に通液する工程を有するフッ素含有水の処理方法が開示されている。特許文献6には、フッ素吸着剤が充填された吸着塔にフッ素含有被処理水を通水し、フッ素が低減された処理水を生じさせる水中のフッ素除去方法において、吸着塔でフッ素を吸着除去して生じるフッ素が低減された処理水を、フッ素含有被処理水と混合することにより、吸着塔入口におけるフッ素含有被処理水のフッ素濃度を15mg/L以下に調整する水中のフッ素除去方法が開示されている。 On the other hand, as a method for treating the etching cleaning waste liquid and the fluorine-containing waste liquid discharged from the aluminum electrolytic refining process, the glass manufacturing process, and the like in the field of semiconductor manufacturing, a method for removing fluorine ions using a fluorine adsorbent is also known. For example, Patent Document 4 discloses a treatment method in which fluorine-containing water is reacted with a calcium compound to convert it into calcium fluoride for solid-liquid separation, and then the separated solution is brought into contact with a fluorine adsorbent. Patent Document 5 describes a step of separating fluorine-containing water into low-concentration fluorine-containing water and high-concentration fluorine-containing water, adding a calcium compound to the low-concentration fluorine-containing water, then solid-liquid separation, and contacting the separated liquid with a fluorine adsorbent. A method for treating fluorine-containing water, which comprises a step of regenerating the fluorine adsorbent, a step of adding a recycled waste liquid of the fluorine adsorbent to high-concentration fluorine-containing water, and then passing the liquid through a calcium carbonate crystal seed filling tank. Is disclosed. In Patent Document 6, in a method for removing fluorine in water in which fluorine-containing water to be treated is passed through an adsorption tower filled with a fluorine adsorbent to generate treated water in which fluorine is reduced, fluorine is adsorbed and removed by the adsorption tower. Disclosed is a method for removing fluorine in water, which adjusts the fluorine concentration of the fluorine-containing treated water at the inlet of the adsorption tower to 15 mg / L or less by mixing the treated water with reduced fluorine generated in the process with the fluorine-containing treated water. Has been done.
特開平8−57486号公報Japanese Unexamined Patent Publication No. 8-57486 特開2000−176241号公報Japanese Unexamined Patent Publication No. 2000-176241 特開平11−137958号公報Japanese Unexamined Patent Publication No. 11-13795 特開平5−92187号公報Japanese Unexamined Patent Publication No. 5-92187 特開平5−253575号公報Japanese Unexamined Patent Publication No. 5-253575 特開2006−314957号公報Japanese Unexamined Patent Publication No. 2006-314957
従来、フッ素吸着剤を用いたフッ素除去処理は、比較的フッ素イオン濃度が低い被処理水に対して行われてきた。フッ素イオン濃度が高い被処理水を処理する場合は、通常、まず凝集沈殿や共沈等によりフッ素イオンの不溶化処理を行ってある程度フッ素イオンを除去した後、フッ素イオン濃度が低減された被処理水を吸着剤と接触させることにより、フッ素イオンの高度除去を行う。このような処理が行われる理由としては、凝集沈殿や共沈による処理と比べて吸着剤を用いればより高度にフッ素イオンを除去できることや、フッ素イオン濃度が高い被処理水を凝集沈殿や共沈等の前処理を経ずにいきなり吸着剤と接触させると、十分にフッ素濃度が低減された処理水を安定して得ることが難しいことが挙げられる。特に、フッ素イオン以外の共存イオン濃度が高い場合は、フッ素吸着処理への影響が懸念される。 Conventionally, fluorine removal treatment using a fluorine adsorbent has been performed on water to be treated having a relatively low fluorine ion concentration. When treating water to be treated with a high fluorine ion concentration, usually, first, insolubilization treatment of fluorine ions is performed by coagulation precipitation or coprecipitation to remove fluorine ions to some extent, and then the treated water having a reduced fluorine ion concentration. Is brought into contact with an adsorbent to perform advanced removal of fluorine ions. The reason why such treatment is performed is that fluorine ions can be removed to a higher degree by using an adsorbent compared to treatment by coagulation sedimentation or coprecipitation, and water to be treated having a high fluorine ion concentration is coagulation sedimentation or coprecipitation. If it is suddenly brought into contact with an adsorbent without undergoing pretreatment such as, it is difficult to stably obtain treated water having a sufficiently reduced fluorine concentration. In particular, when the concentration of coexisting ions other than fluorine ions is high, there is concern about the influence on the fluorine adsorption treatment.
本発明は前記事情に鑑みてなされたものであり、その目的は、フッ素イオンを含むとともに、硫酸イオンを高濃度に含む被処理水からフッ素イオンを除去する方法であって、フッ素吸着剤により安定して処理することができる水処理方法を提供することにある。 The present invention has been made in view of the above circumstances, and an object thereof is a method for removing fluorine ions from water to be treated containing fluorine ions and a high concentration of sulfate ions, and is stable with a fluorine adsorbent. The purpose is to provide a water treatment method that can be treated.
前記課題を解決することができた本発明の水処理方法とは、フッ素イオンと硫酸イオンを含有する被処理水をフッ素吸着剤が充填された吸着塔に導入し、被処理水中のフッ素イオンの少なくとも一部が除去された第1処理水を得る吸着工程と、吸着工程の前に、吸着工程で得られる第1処理水を吸着塔に導入する前処理工程とを有し、吸着塔に導入される被処理水の硫酸イオン濃度が30,000mg/L以上であり、吸着塔に導入される第1処理水の硫酸イオン濃度が30,000mg/L以上であるところに特徴を有する。 The water treatment method of the present invention that has been able to solve the above problems is that water to be treated containing fluorine ions and sulfate ions is introduced into an adsorption tower filled with a fluorine adsorbent, and the fluorine ions in the water to be treated are treated. It has an adsorption step of obtaining the first treated water from which at least a part has been removed, and a pretreatment step of introducing the first treated water obtained in the adsorption step into the adsorption tower before the adsorption step. It is characterized in that the sulfate ion concentration of the water to be treated is 30,000 mg / L or more, and the sulfate ion concentration of the first treated water introduced into the adsorption tower is 30,000 mg / L or more.
フッ素イオンとともに硫酸イオンを30,000mg/L以上と高濃度に含む被処理水は、これをいきなりフッ素吸着剤が充填された吸着塔に導入して処理すると、フッ素イオンが十分に吸着除去できない場合があり、特に被処理水を吸着塔に導入した初期において処理水のフッ素イオン濃度が高くなる。しかし、本発明の水処理方法は、被処理水のフッ素吸着処理に先立って、予め当該吸着処理の処理水を準備し、この処理水をフッ素吸着剤が充填された吸着塔に導入するようにしている。すなわち、吸着工程の前に、吸着工程で得られる第1処理水を吸着塔に導入する前処理工程を設けており、前処理工程で吸着塔に導入する第1処理水の硫酸イオン濃度が30,000mg/L以上となっている。このように前処理工程を設けることにより、吸着工程において被処理水を吸着塔に導入した際に、吸着工程の初期から好適にフッ素イオンが吸着除去され、十分にフッ素イオン濃度が低減された処理水を安定して得ることができる。 When the water to be treated containing fluorine ions and sulfate ions at a high concentration of 30,000 mg / L or more is suddenly introduced into an adsorption tower filled with a fluorine adsorbent and treated, the fluorine ions cannot be sufficiently adsorbed and removed. In particular, the fluorine ion concentration of the treated water becomes high at the initial stage when the water to be treated is introduced into the adsorption tower. However, in the water treatment method of the present invention, the treated water for the adsorption treatment is prepared in advance prior to the fluorine adsorption treatment of the water to be treated, and the treated water is introduced into the adsorption tower filled with the fluorine adsorbent. ing. That is, before the adsorption step, a pretreatment step of introducing the first treated water obtained in the adsorption step into the adsorption tower is provided, and the sulfate ion concentration of the first treated water introduced into the adsorption tower in the pretreatment step is 30. It is 000 mg / L or more. By providing the pretreatment step in this way, when the water to be treated is introduced into the adsorption tower in the adsorption step, fluorine ions are preferably adsorbed and removed from the initial stage of the adsorption step, and the fluorine ion concentration is sufficiently reduced. Water can be obtained stably.
前処理工程において、吸着塔に導入される第1処理水のフッ素イオン濃度は、15mg/L以下であることが好ましい。また、吸着塔に導入される第1処理水のpHは、2.0以上3.5以下であることが好ましい。前処理工程においては、第1処理水を吸着塔に循環させながら導入してもよい。 In the pretreatment step, the fluorine ion concentration of the first treated water introduced into the adsorption tower is preferably 15 mg / L or less. Further, the pH of the first treated water introduced into the adsorption tower is preferably 2.0 or more and 3.5 or less. In the pretreatment step, the first treated water may be introduced while being circulated in the adsorption tower.
前処理工程において吸着塔から排出される第2処理水のpHが4.0以下となったら、吸着工程を行うことが好ましい。 When the pH of the second treated water discharged from the adsorption tower in the pretreatment step becomes 4.0 or less, it is preferable to carry out the adsorption step.
吸着工程において、吸着塔に導入される被処理水のフッ素イオン濃度は、50mg/L以上であることが好ましい。また、吸着塔に導入される被処理水のpHは、2.0以上3.5以下であることが好ましい。フッ素吸着剤としては、セリウム系吸着剤を用いることが好ましい。 In the adsorption step, the fluorine ion concentration of the water to be treated introduced into the adsorption tower is preferably 50 mg / L or more. The pH of the water to be treated introduced into the adsorption tower is preferably 2.0 or more and 3.5 or less. As the fluorine adsorbent, it is preferable to use a cerium-based adsorbent.
本発明の水処理方法は、吸着工程の後に、吸着塔にアルカリ溶液を導入し、フッ素吸着剤からフッ素イオンを脱着させる脱着工程と、脱着工程の後に、吸着塔に酸溶液を導入する酸処理工程とをさらに有し、酸処理工程の後に前処理工程を行い、その後再び吸着工程を行うものであることが好ましい。 The water treatment method of the present invention includes a desorption step of introducing an alkaline solution into the adsorption tower after the adsorption step to desorb fluorine ions from the fluorine adsorbent, and an acid treatment of introducing an acid solution into the adsorption tower after the desorption step. It is preferable that the process further comprises a step, a pretreatment step is performed after the acid treatment step, and then an adsorption step is performed again.
本発明の水処理方法は、吸着工程の後に、吸着塔にアルカリ溶液を導入し、フッ素吸着剤からフッ素イオンを脱着させる脱着工程と、脱着工程の後に、吸着塔に酸溶液を導入する酸処理工程とをさらに有し、吸着塔として第1吸着塔と第2吸着塔が設けられ、下記(1)〜(4)のステージを順に繰り返し行うことで、第1吸着塔と第2吸着塔で各工程を行うものであってもよい。
(1)第1吸着塔と第2吸着塔をこの順で直列接続し、被処理水を第1吸着塔と第2吸着塔に順次導入して、第1吸着塔で吸着工程を行い、第2吸着塔で前処理工程を行う。
(2)脱着工程と酸処理工程を第1吸着塔で行うとともに、第2吸着塔に被処理水を導入して吸着工程を行う。
(3)第2吸着塔と第1吸着塔をこの順で直列接続し、被処理水を第2吸着塔と第1吸着塔に順次導入して、第2吸着塔で吸着工程を行い、第1吸着塔で前処理工程を行う。
(4)脱着工程と酸処理工程を第2吸着塔で行うとともに、第1吸着塔に被処理水を導入して吸着工程を行う。
The water treatment method of the present invention includes a desorption step of introducing an alkaline solution into the adsorption tower after the adsorption step to desorb fluorine ions from the fluorine adsorbent, and an acid treatment of introducing an acid solution into the adsorption tower after the desorption step. The first adsorption tower and the second adsorption tower are provided as the adsorption towers, and the steps (1) to (4) below are repeated in order to form the first adsorption tower and the second adsorption tower. Each step may be performed.
(1) The first adsorption tower and the second adsorption tower are connected in series in this order, the water to be treated is sequentially introduced into the first adsorption tower and the second adsorption tower, and the adsorption step is performed in the first adsorption tower. 2 Perform the pretreatment step in the adsorption tower.
(2) The desorption step and the acid treatment step are performed in the first adsorption tower, and the water to be treated is introduced into the second adsorption tower to perform the adsorption step.
(3) The second adsorption tower and the first adsorption tower are connected in series in this order, the water to be treated is sequentially introduced into the second adsorption tower and the first adsorption tower, and the adsorption step is performed in the second adsorption tower. 1 Perform the pretreatment step in the adsorption tower.
(4) The desorption step and the acid treatment step are performed in the second adsorption tower, and the water to be treated is introduced into the first adsorption tower to perform the adsorption step.
上記のように処理する場合、(1)のステージにおいて、第1吸着塔から排出される第1処理水のフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら(2)のステージに移り、(3)のステージにおいて、第2吸着塔から排出される第1処理水のフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら(4)のステージに移ることが好ましい。あるいは、(1)のステージにおいて、第1吸着塔の吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら(2)のステージに移り、(3)のステージにおいて、第2吸着塔の吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら(4)のステージに移るようにしてもよい。 In the case of treatment as described above, in the stage (1), the fluorine ion concentration of the first treated water discharged from the first adsorption tower is measured, and when the fluorine ion concentration exceeds a predetermined value, the stage (2) It is preferable to measure the fluorine ion concentration of the first treated water discharged from the second adsorption tower in the stage (3), and move to the stage (4) when the fluorine ion concentration exceeds a predetermined value. .. Alternatively, in the stage (1), when the cumulative adsorption amount of fluorine ions adsorbed by the adsorbent in the first adsorption tower exceeds a predetermined value, the process moves to the stage (2), and in the stage (3), the second adsorption When the cumulative amount of fluorine ions adsorbed by the adsorbent in the column exceeds a predetermined value, the stage (4) may be started.
フッ素イオンとともに、硫酸イオンを比較的高濃度に含有する被処理水としては、排煙脱硫設備から排出される排煙脱硫排水を用いることが好ましい。 As the water to be treated containing sulfate ions at a relatively high concentration together with fluorine ions, it is preferable to use flue gas desulfurization wastewater discharged from the flue gas desulfurization equipment.
本発明の水処理方法によれば、硫酸イオンを高濃度に含む被処理水であっても、当該被処理水をフッ素吸着剤が充填された吸着塔に導入して処理する際に、安定してフッ素イオン濃度が低減された処理水を得ることができる。 According to the water treatment method of the present invention, even water to be treated containing a high concentration of sulfate ions is stable when the water to be treated is introduced into an adsorption tower filled with a fluorine adsorbent and treated. It is possible to obtain treated water having a reduced fluorine ion concentration.
高濃度に硫酸イオンを含む被処理水を、前処理工程を行わずに吸着工程を行った場合と、前処理工程を行った後に吸着工程を行った場合について、処理水のフッ素イオン濃度とpHの経時変化を表す。The fluorine ion concentration and pH of the treated water when the adsorption step is performed without performing the pretreatment step and when the adsorption step is performed after the pretreatment step is performed on the water to be treated containing sulfate ions at a high concentration. Represents the change over time. 本発明の水処理方法で用いられる水処理システムの構成例を表す。A configuration example of the water treatment system used in the water treatment method of the present invention is shown. 本発明の水処理方法で用いられる水処理システムの構成例を表す。A configuration example of the water treatment system used in the water treatment method of the present invention is shown. 本発明の水処理方法で用いられる水処理システムの構成例を表す。A configuration example of the water treatment system used in the water treatment method of the present invention is shown.
本発明は、フッ素イオンと硫酸イオンを含有する被処理水を処理する水処理方法に関する。詳細には、フッ素イオンとともに硫酸イオンを30,000mg/L以上の高濃度で含む被処理水を、フッ素吸着剤が充填された吸着塔に導入して、被処理水中のフッ素イオンの少なくとも一部を除去する水処理方法に関するものである。 The present invention relates to a water treatment method for treating water to be treated containing fluorine ions and sulfate ions. Specifically, water to be treated containing sulfate ions at a high concentration of 30,000 mg / L or more together with fluorine ions is introduced into an adsorption tower filled with a fluorine adsorbent to introduce at least a part of the fluorine ions in the water to be treated. It relates to a water treatment method for removing water.
石炭火力発電所やコークス工場や製鉄工場等では、石炭やコークスを燃焼させることにより硫黄分やフッ素分を含む排ガスが排出されるが、当該排ガスを排煙脱硫装置により脱硫処理を行うと、硫酸イオンとフッ素イオンを高濃度に含む排煙脱硫排水が発生する。排煙脱硫装置における脱硫方法としては、水酸化カルシウムや水酸化マグネシウムや水酸化ナトリウムを用いて湿式処理する方法が知られているが、脱硫剤として水酸化マグネシウムや水酸化ナトリウムを用いると、フッ素イオンとともに硫酸イオンが数万mg/L以上の濃度で含まれる排煙脱硫排水が発生する。 In coal-fired power plants, coke factories, steel mills, etc., exhaust gas containing sulfur and fluorine is emitted by burning coal and coke, but when the exhaust gas is desulfurized by a flue gas desulfurization device, sulfuric acid is emitted. Flue gas desulfurization wastewater containing high concentrations of ions and fluorine ions is generated. As a desulfurization method in a flue gas desulfurization apparatus, a method of wet treatment using calcium hydroxide, magnesium hydroxide or sodium hydroxide is known, but when magnesium hydroxide or sodium hydroxide is used as a desulfurization agent, fluorine is used. Flue gas desulfurization wastewater containing sulfate ions at a concentration of tens of thousands of mg / L or more is generated together with ions.
従来、このような排煙脱硫排水からフッ素イオンを除去する場合、通常、まず凝集沈殿や共沈等によりフッ素イオンの不溶化処理を行ってある程度フッ素イオンを除去し、その後必要に応じて、フッ素イオン濃度が低減された被処理水を吸着剤と接触させることにより、フッ素イオンの高度除去を行ってきた。このような処理が行われる理由としては、凝集沈殿や共沈による処理と比べて吸着剤を用いればより高度にフッ素イオンを除去できることや、フッ素イオン濃度が高い被処理水を凝集沈殿や共沈等の前処理を経ずにいきなり吸着剤と接触させると、十分にフッ素イオン濃度が低減された処理水が得られない場合があることが挙げられる。一方、排煙脱硫排水に対して凝集沈殿や共沈等の処理を行うと、フッ素イオンとともに硫酸イオンも不溶化され、多量の汚泥が発生する。そのため、汚泥処分にかかる費用が高くなり、処理コストの増大に繋がる。 Conventionally, when removing fluorine ions from such flue gas desulfurized wastewater, usually, first, insolubilization treatment of fluorine ions is performed by coagulation precipitation or coprecipitation to remove fluorine ions to some extent, and then, if necessary, fluorine ions. Fluorine ions have been highly removed by contacting the water to be treated with a reduced concentration with an adsorbent. The reason why such treatment is performed is that fluorine ions can be removed to a higher degree by using an adsorbent compared to treatment by coagulation sedimentation or coprecipitation, and water to be treated having a high fluorine ion concentration is coagulation sedimentation or coprecipitation. If it is suddenly brought into contact with an adsorbent without undergoing pretreatment such as, it may not be possible to obtain treated water having a sufficiently reduced fluorine ion concentration. On the other hand, when the flue gas desulfurized wastewater is treated by coagulation sedimentation or coprecipitation, sulfate ions are insolubilized together with fluorine ions, and a large amount of sludge is generated. Therefore, the cost of sludge disposal becomes high, which leads to an increase in treatment cost.
本発明者らは、フッ素イオンとともに硫酸イオンを高濃度に含む被処理水について、フッ素吸着剤が充填された吸着塔に導入して処理する場合に、安定してフッ素除去が行える方法を検討した。そうしたところ、フッ素イオンとともに硫酸イオンを高濃度に含む被処理水は、これをいきなりフッ素吸着剤が充填された吸着塔に導入して処理すると、フッ素イオンが十分に吸着除去できない場合があり、特に被処理水を吸着塔に導入した初期において処理水のフッ素イオン濃度が高くなる傾向を示すことが分かった。そして、この対応策として、被処理水のフッ素吸着処理に先立って、予め当該吸着処理の処理水を準備し、この処理水をフッ素吸着剤が充填された吸着塔に導入することが有効であることが明らかになった。すなわち本発明の水処理方法とは、フッ素イオンと硫酸イオンを含有する被処理水をフッ素吸着剤が充填された吸着塔に導入し、被処理水中のフッ素イオンの少なくとも一部が除去された第1処理水を得る吸着工程と、吸着工程の前に、吸着工程で得られる第1処理水を吸着塔に導入する前処理工程とを有し、吸着工程において吸着塔に導入される被処理水の硫酸イオン濃度が30,000mg/L以上であり、前処理工程において吸着塔に導入される第1処理水(吸着工程で得られた処理水)の硫酸イオン濃度が30,000mg/L以上であるものである。 The present inventors have investigated a method for stably removing fluorine when the water to be treated containing a high concentration of sulfate ions as well as fluorine ions is introduced into an adsorption tower filled with a fluorine adsorbent and treated. .. As a result, if the water to be treated, which contains a high concentration of sulfate ions together with fluorine ions, is suddenly introduced into an adsorption tower filled with a fluorine adsorbent and treated, the fluorine ions may not be sufficiently adsorbed and removed. It was found that the fluorine ion concentration of the treated water tended to increase at the initial stage when the water to be treated was introduced into the adsorption tower. Then, as a countermeasure, it is effective to prepare the treated water for the adsorption treatment in advance prior to the fluorine adsorption treatment of the water to be treated, and to introduce the treated water into the adsorption tower filled with the fluorine adsorbent. It became clear. That is, in the water treatment method of the present invention, the water to be treated containing fluorine ions and sulfate ions was introduced into an adsorption tower filled with a fluorine adsorbent, and at least a part of the fluorine ions in the water to be treated was removed. It has an adsorption step of obtaining 1 treated water and a pretreatment step of introducing the first treated water obtained in the adsorption step into the adsorption tower before the adsorption step, and the water to be treated introduced into the adsorption tower in the adsorption step. The sulfate ion concentration of is 30,000 mg / L or more, and the sulfate ion concentration of the first treated water (treated water obtained in the adsorption step) introduced into the adsorption tower in the pretreatment step is 30,000 mg / L or more. There is.
フッ素吸着剤により被処理水のフッ素吸着処理を行う場合、フッ素イオンは吸着剤が有するアニオンとイオン交換されることにより、被処理水からフッ素イオンが除去される。フッ素吸着剤が有するアニオンとしては、通常、水酸化物イオンであるため、フッ素イオンがフッ素吸着剤に吸着されると、フッ素吸着剤から水酸化物イオンが脱着し、被処理水のpHが上昇する傾向を示す。一方、フッ素吸着剤にはフッ素イオンの吸着除去に適したpH範囲が存在し、被処理水のpHが上昇すると、当該至適pH範囲から外れてフッ素イオンが十分に吸着除去されにくくなる。このようなpH上昇は、被処理水のフッ素イオン濃度が高くなるほど、水酸化物イオンとの交換量が増えるため、顕著に表れるようになる。 When the fluorine adsorbing treatment of the water to be treated is carried out with a fluorine adsorbent, the fluorine ions are removed from the water to be treated by ion exchange with the anions of the adsorbent. Since the anion contained in the fluorine adsorbent is usually a hydroxide ion, when the fluorine ion is adsorbed by the fluorine adsorbent, the hydroxide ion is desorbed from the fluorine adsorbent and the pH of the water to be treated rises. Show a tendency to do. On the other hand, the fluorine adsorbent has a pH range suitable for adsorbing and removing fluorine ions, and when the pH of the water to be treated rises, it deviates from the optimum pH range and it becomes difficult for fluorine ions to be sufficiently adsorbed and removed. Such an increase in pH becomes more pronounced as the concentration of fluorine ions in the water to be treated increases, because the amount of exchange with hydroxide ions increases.
一方、本発明者らが様々な被処理水についてフッ素吸着処理を行ったところ、硫酸イオン濃度が30,000mg/L以上と高濃度に硫酸イオンを含む被処理水をフッ素吸着剤で処理する場合は、被処理水のフッ素イオン濃度が低い場合でも処理水のpH上昇が見られ、フッ素イオンの吸着性能が低下することが分かった。この原因について検討したところ、フッ素吸着剤はフッ素イオンを優先的に吸着するものの、被処理水中の硫酸イオン濃度が過度に高い場合は、硫酸イオンのフッ素吸着剤への吸着が無視できない程度となり、その結果、吸着剤から多量の水酸化物イオンが脱離して、処理水のpHが上昇することが考えられた。なお、この場合にフッ素吸着剤に吸着される硫酸イオンの量は、被処理水に含まれる硫酸イオンのごく一部に過ぎない。そして、その対応策として、吸着工程において被処理水のフッ素吸着処理を行うのに先立って、前処理工程を設け、フッ素吸着剤が有する水酸化物イオンを強制的に硫酸イオンに置換することが有効であることが明らかになった。これによりフッ素吸着剤がアニオンとして硫酸イオンを有するものとなり、その後、被処理水をフッ素吸着剤と接触させると、吸着剤の有する硫酸イオンがフッ素イオンとイオン交換され、処理水のpH上昇を抑えることができる。そして、フッ素吸着剤が有する水酸化物イオンを硫酸イオンに置き換えるためには、高濃度に硫酸イオンを含有する被処理水をフッ素吸着剤と接触させることにより得られた処理水を用いることが効率的であることが明らかになった。 On the other hand, when the present inventors have performed fluorine adsorption treatment on various waters to be treated, the case where the water to be treated containing sulfate ions at a high concentration of 30,000 mg / L or more is treated with a fluorine adsorbent. It was found that the pH of the treated water increased even when the fluorine ion concentration of the treated water was low, and the adsorption performance of the fluorine ions decreased. As a result of investigating the cause of this, although the fluorine adsorbent preferentially adsorbs fluorine ions, if the sulfate ion concentration in the water to be treated is excessively high, the adsorption of sulfate ions to the fluorine adsorbent cannot be ignored. As a result, it was considered that a large amount of hydroxide ions were desorbed from the adsorbent and the pH of the treated water increased. In this case, the amount of sulfate ion adsorbed on the fluorine adsorbent is only a small part of the sulfate ion contained in the water to be treated. Then, as a countermeasure, a pretreatment step is provided prior to performing the fluorine adsorption treatment of the water to be treated in the adsorption step, and the hydroxide ion of the fluorine adsorbent is forcibly replaced with the sulfate ion. It turned out to be effective. As a result, the fluorine adsorbent has sulfate ions as anions, and when the water to be treated is subsequently brought into contact with the fluorine adsorbent, the sulfate ions of the adsorbent are ion-exchanged with the fluorine ions to suppress the pH rise of the treated water. be able to. Then, in order to replace the hydroxide ion contained in the fluorine adsorbent with sulfate ion, it is efficient to use the treated water obtained by contacting the treated water containing sulfate ion at a high concentration with the fluorine adsorbent. It became clear that it was a target.
図1には、硫酸イオン濃度が30,000mg/L以上の被処理水を、前処理工程を行わずに吸着工程を行った場合と、前処理工程を行った後に吸着工程を行った場合について、得られた処理水のフッ素イオン濃度とpHの測定結果を示した。被処理水のフッ素イオン濃度は100mg/Lであり、被処理水を空間速度(SV)20hr-1で吸着塔に導入した。図1に示した結果からも分かるように、前処理工程を設けることにより、吸着工程において特に初期の処理水のpH上昇が抑えられ、高度にフッ素イオンが除去された処理水を容易に得ることができる。また、吸着工程で得られた処理水を、前処理工程でフッ素吸着剤の改質のために用いることにより、簡便にフッ素吸着剤の改質を行うことができる。以下、本発明の水処理方法について詳しく説明する。 FIG. 1 shows a case where the water to be treated having a sulfate ion concentration of 30,000 mg / L or more is adsorbed without performing the pretreatment step, and a case where the adsorption step is performed after performing the pretreatment step. , The measurement results of the fluorine ion concentration and pH of the obtained treated water are shown. The fluorine ion concentration of the water to be treated was 100 mg / L, and the water to be treated was introduced into the adsorption tower at a space velocity (SV) of 20 hr -1 . As can be seen from the results shown in FIG. 1, by providing the pretreatment step, the pH increase of the treated water at the initial stage is suppressed particularly in the adsorption step, and the treated water from which fluorine ions are highly removed can be easily obtained. Can be done. Further, by using the treated water obtained in the adsorption step for modifying the fluorine adsorbent in the pretreatment step, the fluorine adsorbent can be easily modified. Hereinafter, the water treatment method of the present invention will be described in detail.
吸着工程では、フッ素イオンと硫酸イオンを含有する被処理水をフッ素吸着剤が充填された吸着塔に導入し、被処理水中のフッ素イオンの少なくとも一部が除去された第1処理水を得る。なお、吸着工程で吸着塔から排出される処理水を「第1処理水」と称する。被処理水は、少なくともフッ素イオンと硫酸イオンを含有するものであれば特に限定されないが、本発明では、そのようなイオンを比較的高濃度に含む被処理水として、石炭火力発電所やコークス工場や製鉄工場等の排煙脱硫排水を用いることが好ましい。 In the adsorption step, water to be treated containing fluorine ions and sulfate ions is introduced into an adsorption tower filled with a fluorine adsorbent to obtain first treated water from which at least a part of fluorine ions in the water to be treated has been removed. The treated water discharged from the adsorption tower in the adsorption step is referred to as "first treated water". The water to be treated is not particularly limited as long as it contains at least fluorine ions and sulfate ions, but in the present invention, the water to be treated is a coal-fired power plant or a coke factory as water to be treated containing such ions at a relatively high concentration. It is preferable to use flue gas desulfurization wastewater from coal and steel factories.
吸着工程において吸着塔に導入される被処理水の硫酸イオン濃度は30,000mg/L以上であるが、硫酸イオン濃度はこれより高くてもよく、例えば35,000mg/L以上であってもよく、40,000mg/L以上、または50,000mg/L以上であってもよい。被処理水の硫酸イオン濃度の上限は特に限定されないが、例えば150,000mg/L以下であってもよく、100,000mg/L以下、または80,000mg/L以下であってもよい。本発明において、硫酸イオン濃度は、遊離イオンの形態のみならず塩形成している形態も含む濃度を意味し、硫酸イオン濃度はイオンクロマトグラフィー等により求めることができる。 The sulfate ion concentration of the water to be treated introduced into the adsorption tower in the adsorption step is 30,000 mg / L or more, but the sulfate ion concentration may be higher than this, for example, 35,000 mg / L or more. It may be 40,000 mg / L or more, or 50,000 mg / L or more. The upper limit of the sulfate ion concentration of the water to be treated is not particularly limited, but may be, for example, 150,000 mg / L or less, 100,000 mg / L or less, or 80,000 mg / L or less. In the present invention, the sulfate ion concentration means a concentration including not only a free ion form but also a salt-forming form, and the sulfate ion concentration can be determined by ion chromatography or the like.
吸着工程において吸着塔に導入される被処理水のフッ素イオン濃度は特に限定されず、例えば10mg/L以上であってもよく、15mg/L以上、20mg/L以上、または25mg/L以上であってもよい。なお、本発明の効果、すなわち、前処理工程を組み合わせることにより吸着工程で得られる第1処理水のフッ素イオン濃度を十分に低減できるという効果がより奏効されるから、被処理水のフッ素イオン濃度は50mg/L以上が好ましく、60mg/L以上がより好ましく、70mg/L以上がさらに好ましい。本発明によれば、このような高いフッ素イオン濃度の被処理水であっても、高度にフッ素イオンを吸着除去することができる。一方、被処理水のフッ素イオン濃度の上限は、安定してフッ素濃度の低い第1処理水を得る点から、200mg/L以下が好ましく、150mg/L以下がより好ましく、120mg/L以下がさらに好ましく、100mg/L以下がさらにより好ましい。フッ素イオン濃度は、イオンクロマトグラフィー等により求めることができる。 The fluorine ion concentration of the water to be treated introduced into the adsorption tower in the adsorption step is not particularly limited, and may be, for example, 10 mg / L or more, 15 mg / L or more, 20 mg / L or more, or 25 mg / L or more. You may. Since the effect of the present invention, that is, the effect that the fluorine ion concentration of the first treated water obtained in the adsorption step can be sufficiently reduced by combining the pretreatment steps, is more effective, the fluorine ion concentration of the water to be treated is more effective. Is preferably 50 mg / L or more, more preferably 60 mg / L or more, and even more preferably 70 mg / L or more. According to the present invention, even in water to be treated having such a high fluorine ion concentration, fluorine ions can be highly adsorbed and removed. On the other hand, the upper limit of the fluorine ion concentration of the water to be treated is preferably 200 mg / L or less, more preferably 150 mg / L or less, and further preferably 120 mg / L or less from the viewpoint of stably obtaining the first treated water having a low fluorine concentration. Preferably, 100 mg / L or less is even more preferable. The fluorine ion concentration can be determined by ion chromatography or the like.
被処理水は、マグネシウムイオンやナトリウムイオン等を含有していてもよい。被処理水が石炭火力発電所やコークス工場や製鉄工場等の排煙脱硫排水を含む場合は、硫酸イオンとともにマグネシウムイオンやナトリウムイオンも被処理水中に含まれうる。排煙脱硫排水が脱硫剤として水酸化マグネシウムを用いたものである場合は、被処理水中のマグネシウムイオンと硫酸イオンの含有比は、例えばマグネシウムイオン/硫酸イオンのモル比で2/8〜8/2の範囲が好ましく、3/7〜7/3の範囲がより好ましく、4/6〜6/4の範囲がさらに好ましい。排煙脱硫排水が脱硫剤として水酸化ナトリウムを用いたものである場合は、被処理水中のナトリウムイオンと硫酸イオンの含有比は、例えばナトリウムイオン/硫酸イオンのモル比で3/7〜9/1の範囲が好ましく、4/6〜8/2の範囲がより好ましく、5/5〜7/3の範囲がさらに好ましい。なお、被処理水は、脱硫剤として水酸化マグネシウムを用いた排煙脱硫排水を含むことが好ましく、これにより吸着剤の長寿命化を図ることができ、例えば、吸着剤からフッ素の吸着に寄与する有効成分(金属成分)の流出を抑えやすくなる。 The water to be treated may contain magnesium ions, sodium ions and the like. When the water to be treated contains flue gas desulfurization wastewater from coal-fired power plants, coke factories, steel mills, etc., magnesium ions and sodium ions may be contained in the water to be treated as well as sulfate ions. When the flue gas desulfurization wastewater uses magnesium hydroxide as a desulfurization agent, the content ratio of magnesium ions to sulfate ions in the water to be treated is, for example, 2/8 to 8/8 / molar ratio of magnesium ions / sulfate ions. The range of 2 is preferable, the range of 3/7 to 7/3 is more preferable, and the range of 4/6 to 6/4 is further preferable. When the flue gas desulfurization wastewater uses sodium hydroxide as the desulfurization agent, the content ratio of sodium ion and sulfate ion in the water to be treated is, for example, 3/7 to 9 / in the molar ratio of sodium ion / sulfate ion. The range of 1 is preferable, the range of 4/6 to 8/2 is more preferable, and the range of 5/5 to 7/3 is further preferable. The water to be treated preferably contains flue gas desulfurized wastewater using magnesium hydroxide as a desulfurizing agent, whereby the life of the adsorbent can be extended, and for example, it contributes to the adsorption of fluorine from the adsorbent. It becomes easier to suppress the outflow of the active ingredient (metal component).
フッ素吸着剤としては、フッ素イオンを吸着することができる公知の吸着剤を用いればよく、例えば、アルミナ系吸着剤、フェライト鉄系吸着剤、ジルコニウム系吸着剤、セリウム系吸着剤等を用いることができる。なかでも、高度にフッ素イオンを吸着除去できる吸着剤として、セリウム系吸着剤を用いることが好ましい。セリウム系吸着剤としては、酸化セリウム(CeO2)、特に含水酸化セリウム(CeO2・nH2O)を含む吸着剤が挙げられる。当該吸着剤は樹脂を含有し、酸化セリウムまたは含水酸化セリウムが樹脂によって固定化あるいは補強されていてもよい。 As the fluorine adsorbent, a known adsorbent capable of adsorbing fluorine ions may be used. For example, an alumina-based adsorbent, a ferrite iron-based adsorbent, a zirconium-based adsorbent, a cerium-based adsorbent, or the like may be used. it can. Among them, it is preferable to use a cerium-based adsorbent as an adsorbent capable of adsorbing and removing fluorine ions to a high degree. Examples of the cerium-based adsorbent include an adsorbent containing cerium oxide (CeO 2 ), particularly cerium-containing hydroxide (CeO 2 · nH 2 O). The adsorbent may contain a resin, and cerium oxide or cerium hydroxide may be immobilized or reinforced by the resin.
被処理水のpHは、吸着剤によるフッ素イオンの吸着除去が好適に行われるようにする点から、2.0以上が好ましく、2.1以上がより好ましく、2.2以上がさらに好ましく、また3.5以下が好ましく、3.3以下がより好ましく、3.1以下がさらに好ましい。被処理水のpHが高い場合は、酸を添加することにより被処理水のpHを調整すればよく、当該酸としては塩酸や硫酸を用いることが好ましい。逆に被処理水のpHが低い場合は、アルカリを添加することにより被処理水のpHを調整すればよく、当該アルカリとしてはアルカリ金属水酸化物を用いることが好ましく、水酸化ナトリウムを用いることがより好ましい。なお、被処理水として排煙脱硫排水を用いる場合は、排煙脱硫排水のpHが常時このような範囲となるとは限らないため、吸着塔に導入される被処理水は、酸またはアルカリを添加することによって所定のpH範囲に調整することが好ましい。 The pH of the water to be treated is preferably 2.0 or more, more preferably 2.1 or more, still more preferably 2.2 or more, from the viewpoint of allowing the adsorption and removal of fluorine ions to be preferably performed by the adsorbent. It is preferably 3.5 or less, more preferably 3.3 or less, and even more preferably 3.1 or less. When the pH of the water to be treated is high, the pH of the water to be treated may be adjusted by adding an acid, and hydrochloric acid or sulfuric acid is preferably used as the acid. On the contrary, when the pH of the water to be treated is low, the pH of the water to be treated may be adjusted by adding an alkali, and it is preferable to use an alkali metal hydroxide as the alkali, and sodium hydroxide should be used. Is more preferable. When flue gas desulfurized wastewater is used as the water to be treated, the pH of the flue gas desulfurized wastewater is not always in such a range. Therefore, acid or alkali is added to the water to be treated introduced into the adsorption tower. It is preferable to adjust the pH to a predetermined pH range.
被処理水のpHの調整は、吸着塔の前にpH調整手段を設けることにより行えばよい。pH調整手段は、吸着塔の前に酸またはアルカリ添加手段を備えたpH調整槽を設けたり、被処理水を吸着塔に供給する流路に酸またはアルカリ添加手段を設ければよい。酸またはアルカリ添加手段としては、薬注ポンプ等が挙げられる。またpH調整手段として、酸またはアルカリ添加手段とともにpH測定手段を設けてもよい。pH測定手段は、pH調整槽に設置したり、被処理水を吸着塔に供給する流路の酸またはアルカリ添加手段と吸着塔の間に設置することが好ましい。 The pH of the water to be treated may be adjusted by providing a pH adjusting means in front of the adsorption tower. As the pH adjusting means, a pH adjusting tank provided with an acid or alkali adding means may be provided in front of the adsorption tower, or an acid or alkali adding means may be provided in the flow path for supplying the water to be treated to the adsorption tower. Examples of the acid or alkali addition means include a chemical injection pump and the like. Further, as the pH adjusting means, a pH measuring means may be provided together with the acid or alkali adding means. The pH measuring means is preferably installed in a pH adjusting tank or between the acid or alkali adding means and the adsorption tower in the flow path for supplying the water to be treated to the adsorption tower.
被処理水を吸着塔に導入するのに先立って、被処理水の酸化還元電位の調整を行ってもよい。例えば被処理水中に還元物質が多く含まれていると、フッ素吸着剤を構成するセリウム等の金属が溶出しやすくなるため、被処理水の酸化還元電位を所定値以上に調整することで、フッ素吸着剤からの金属の溶出を抑えることができる。そのような観点から、被処理水の酸化還元電位は600mV以上とすることが好ましく、700mV以上がより好ましい。一方、フッ素吸着樹脂の劣化(例えば、フッ素吸着剤を構成する樹脂の劣化)を抑制する観点から、被処理水の酸化還元電位は1000mV以下とすることが好ましく、950mV以下がより好ましい。被処理水は、pHとともに酸化還元電位を調整するようにしてもよい。 The redox potential of the water to be treated may be adjusted prior to introducing the water to be treated into the adsorption tower. For example, if the water to be treated contains a large amount of reducing substances, metals such as cerium constituting the fluorine adsorbent are likely to elute. Therefore, by adjusting the redox potential of the water to be treated to a predetermined value or more, fluorine Elution of metal from the adsorbent can be suppressed. From such a viewpoint, the redox potential of the water to be treated is preferably 600 mV or more, more preferably 700 mV or more. On the other hand, from the viewpoint of suppressing deterioration of the fluorine-adsorbing resin (for example, deterioration of the resin constituting the fluorine adsorbent), the redox potential of the water to be treated is preferably 1000 mV or less, more preferably 950 mV or less. The water to be treated may adjust the redox potential together with the pH.
被処理水の酸化還元電位を調整するための薬剤としては、次亜塩素酸ナトリウム等の塩素系酸化剤を用いることが簡便である。当該薬剤は、被処理水が吸着塔に導入される前段で、被処理水に供給されることが好ましい。被処理水の酸化還元電位の調整は、吸着塔の入側に連通した被処理水流路に酸化還元電位計を設置し、被処理水の酸化還元電位を測定することにより行うことができる。また、被処理水の酸化還元電位を測定する代わりに、あるいは酸化還元電位を測定するとともに、被処理水の残留塩素濃度を調整することも好ましい。この場合、吸着塔に導入する被処理水の残留塩素濃度は0.5mg/L以上が好ましく、1.0mg/L以上がより好ましく、また18mg/L以下が好ましく、15mg/L以下がより好ましい。 As a chemical for adjusting the redox potential of the water to be treated, it is convenient to use a chlorine-based oxidizing agent such as sodium hypochlorite. The chemical is preferably supplied to the water to be treated before the water to be treated is introduced into the adsorption tower. The redox potential of the water to be treated can be adjusted by installing an oxidation-reduction potential meter in the water flow path to be treated which is connected to the entrance side of the adsorption tower and measuring the redox potential of the water to be treated. Further, instead of measuring the redox potential of the water to be treated, or while measuring the redox potential, it is also preferable to adjust the residual chlorine concentration of the water to be treated. In this case, the residual chlorine concentration of the water to be treated introduced into the adsorption tower is preferably 0.5 mg / L or more, more preferably 1.0 mg / L or more, preferably 18 mg / L or less, and more preferably 15 mg / L or less. ..
被処理水とフッ素吸着剤との接触は、フッ素吸着剤が充填された吸着塔に被処理水を導入することにより行う。被処理水は、吸着塔を上向流式で通液させてもよく、下向流式で通液させてもよい。このときの通液速度は、被処理水の性状やフッ素吸着剤の充填量などに応じて適宜設定すればよく、例えば空間速度(SV)として1hr-1〜50hr-1の範囲で適宜調整すればよい。なお、吸着塔設備が過大にならないようにする観点から、空間速度(SV)は3hr-1以上が好ましく、5hr-1以上がより好ましく、8hr-1以上がさらに好ましく、12hr-1以上がさらにより好ましい。また、安定してフッ素イオン濃度が低減された第1処理水が得やすくなる観点から、空間速度(SV)は40hr-1以下が好ましく、30hr-1以下がより好ましく、25hr-1以下がさらに好ましい。 The contact between the water to be treated and the fluorine adsorbent is performed by introducing the water to be treated into an adsorption tower filled with the fluorine adsorbent. The water to be treated may be passed through the adsorption tower by an upward flow type or by a downward flow type. The liquid passing rate at this time may be appropriately set according to the properties of the water to be treated, the filling amount of the fluorine adsorbent, etc. For example, the space velocity (SV) should be appropriately adjusted in the range of 1 hr -1 to 50 hr -1. Just do it. From the viewpoint of the avoid excessive adsorption column system, the space velocity (SV) is preferably at least 3 hr -1, more preferably 5 hr -1 or more, more preferably -8 hr -1 or more, 12hr -1 or more More preferred. Also, from a stable fluoride ion concentration is easy to obtain a first treated water which is reduced in view, the space velocity (SV) is preferably 40 hr -1 or less, more preferably 30 hr -1 or less, 25Hr -1 or less is more preferable.
被処理水を吸着塔に導入しフッ素吸着剤と接触させることにより、フッ素イオン濃度が低減された第1処理水が得られる。吸着塔によるフッ素吸着処理は1段で行ってもよく、多段(2段以上)で行ってもよい。特に、被処理水のフッ素イオン濃度が高い場合は、多段接続した吸着塔により被処理水を処理したり、吸着塔1段による処理と多段接続した吸着塔による処理を組み合わせて被処理水を処理することが好ましい。これにより第1処理水のフッ素イオン濃度を安定して低減させることが可能となる。多段接続する吸着塔の数は2以上であればよいが、直列接続する吸着塔の数(すなわち被処理水が通過する吸着塔の数)が多すぎても吸着塔の管理が煩雑になることから、5以下が好ましく、4以下がより好ましく、3以下がさらに好ましい。 By introducing the water to be treated into the adsorption tower and bringing it into contact with the fluorine adsorbent, the first treated water having a reduced fluorine ion concentration can be obtained. The fluorine adsorption treatment by the adsorption tower may be performed in one stage or in multiple stages (two or more stages). In particular, when the fluorine ion concentration of the water to be treated is high, the water to be treated is treated by a multi-stage connected adsorption tower, or the water to be treated is treated by combining the treatment by one stage of the adsorption tower and the treatment by the adsorption tower connected in multiple stages. It is preferable to do so. This makes it possible to stably reduce the fluorine ion concentration of the first treated water. The number of adsorption towers connected in multiple stages may be two or more, but if the number of adsorption towers connected in series (that is, the number of adsorption towers through which the water to be treated passes) is too large, the management of the adsorption towers becomes complicated. Therefore, 5 or less is preferable, 4 or less is more preferable, and 3 or less is further preferable.
吸着塔を多段に直列接続する場合、被処理水は、多段に直列接続された各吸着塔に導入する前にそれぞれpHを調整してもよい。このときの各pHは、上記に説明したように、2.0以上が好ましく、2.1以上がより好ましく、2.2以上がさらに好ましく、また3.5以下が好ましく、3.3以下がより好ましく、3.1以下がさらに好ましい。なお本発明の水処理方法では、吸着工程において被処理水を吸着塔に通液した際のpH変化は小さく、通常は、被処理水を最初の吸着塔に導入する際にpH調整を行うだけで十分である。 When the adsorption towers are connected in series in multiple stages, the pH of the water to be treated may be adjusted before being introduced into each of the adsorption towers connected in series in multiple stages. As described above, each pH at this time is preferably 2.0 or more, more preferably 2.1 or more, further preferably 2.2 or more, and preferably 3.5 or less, and 3.3 or less. More preferably, 3.1 or less is further preferable. In the water treatment method of the present invention, the pH change when the water to be treated is passed through the adsorption tower in the adsorption step is small, and usually, the pH is only adjusted when the water to be treated is introduced into the first adsorption tower. Is enough.
吸着工程で得られる第1処理水のフッ素イオン濃度は、吸着塔に導入する被処理水のフッ素イオン濃度よりも基本的に低いものとなる。吸着工程により得られる第1処理水は、環境中に放流するのに適した程度までのフッ素イオン濃度が低減されていることが好ましい。例えば環境省の定めた一律排水基準によれば、フッ素およびその化合物の許容限度は、海域に排出されるもので15mgF/Lと定められ、海域以外の公共用水域に排出されるもので8mgF/Lと定められている。従って、第1処理水のフッ素イオン濃度は15mg/L以下であることが好ましく、8mg/L以下がより好ましい。第1処理水のフッ素イオン濃度はそれよりも低くてもよく、例えば5mg/L以下、3mg/L以下、あるいは1mg/L以下であってもよい。吸着塔を多段に直列接続して吸着処理を行う場合は、最も後段の吸着塔から得られる第1処理水のフッ素イオン濃度がこのような範囲となればよい。なお、吸着工程で得られる第1処理水の硫酸イオン濃度は、通常、被処理水の硫酸イオン濃度と大きく変わらない。 The fluorine ion concentration of the first treated water obtained in the adsorption step is basically lower than the fluorine ion concentration of the water to be treated introduced into the adsorption tower. It is preferable that the first treated water obtained by the adsorption step has a fluorine ion concentration reduced to a level suitable for being discharged into the environment. For example, according to the uniform effluent standard set by the Ministry of the Environment, the permissible limit of fluorine and its compounds is set at 15 mgF / L for those discharged into the sea area, and 8 mgF / L for those discharged into public water areas other than the sea area. It is defined as L. Therefore, the fluorine ion concentration of the first treated water is preferably 15 mg / L or less, more preferably 8 mg / L or less. The fluorine ion concentration of the first treated water may be lower than that, for example, 5 mg / L or less, 3 mg / L or less, or 1 mg / L or less. When the adsorption towers are connected in series in multiple stages to perform the adsorption treatment, the fluorine ion concentration of the first treated water obtained from the adsorption tower in the latter stage may be in such a range. The sulfate ion concentration of the first treated water obtained in the adsorption step is usually not significantly different from the sulfate ion concentration of the water to be treated.
吸着工程に先立って前処理工程を行う。前処理工程では、吸着工程で得られる第1処理水を吸着塔に導入する。なお、前処理工程で吸着塔から排出される処理水を「第2処理水」と称する。前処理工程において第1処理水を吸着塔に導入することにより、吸着塔に充填されたフッ素吸着剤の有する水酸化物イオンを硫酸イオンに置換することができる。これにより、前処理工程に続いて行う吸着工程においてフッ素吸着剤がフッ素イオンを吸着した際に、得られる第1処理水のpH上昇が抑えられ、被処理水中のフッ素イオンを高度に吸着除去することが可能となる。前処理工程で吸着塔から排出された第2処理水は、フッ素イオンが除去された処理水として、系外に排出することができる。 A pretreatment step is performed prior to the adsorption step. In the pretreatment step, the first treated water obtained in the adsorption step is introduced into the adsorption tower. The treated water discharged from the adsorption tower in the pretreatment step is referred to as "second treated water". By introducing the first treated water into the adsorption tower in the pretreatment step, the hydroxide ion contained in the fluorine adsorbent filled in the adsorption tower can be replaced with sulfate ion. As a result, when the fluorine adsorbent adsorbs fluorine ions in the adsorption step performed following the pretreatment step, the pH increase of the first treated water obtained is suppressed, and the fluorine ions in the water to be treated are highly adsorbed and removed. It becomes possible. The second treated water discharged from the adsorption tower in the pretreatment step can be discharged to the outside of the system as treated water from which fluorine ions have been removed.
前処理工程で吸着塔に導入する第1処理水は、同じ吸着塔で吸着工程を行うことにより得られた第1処理水であってもよく、別の吸着塔で吸着工程を行うことにより得られた第1処理水であってもよい。後者の場合、別の吸着塔に吸着工程で導入される被処理水は、第1処理水が導入される吸着塔で吸着工程を行う場合に当該吸着塔に導入される被処理水と同じ由来であることが好ましい。 The first treated water introduced into the adsorption tower in the pretreatment step may be the first treated water obtained by performing the adsorption step in the same adsorption tower, or may be obtained by performing the adsorption step in another adsorption tower. It may be the first treated water obtained. In the latter case, the water to be treated introduced into another adsorption tower in the adsorption step has the same origin as the water to be treated introduced into the adsorption tower when the adsorption step is performed in the adsorption tower into which the first treated water is introduced. Is preferable.
前処理工程において吸着塔に導入される第1処理水の硫酸イオン濃度は30,000mg/L以上であるが、硫酸イオン濃度はこれより高くてもよく、例えば35,000mg/L以上であってもよく、40,000mg/L以上、または50,000mg/L以上であってもよい。被処理水の硫酸イオン濃度の上限は特に限定されないが、例えば150,000mg/L以下であってもよく、100,000mg/L以下、または80,000mg/L以下であってもよい。 The sulfate ion concentration of the first treated water introduced into the adsorption tower in the pretreatment step is 30,000 mg / L or more, but the sulfate ion concentration may be higher than this, for example, 35,000 mg / L or more. It may be 40,000 mg / L or more, or 50,000 mg / L or more. The upper limit of the sulfate ion concentration of the water to be treated is not particularly limited, but may be, for example, 150,000 mg / L or less, 100,000 mg / L or less, or 80,000 mg / L or less.
前処理工程において吸着塔に導入される第1処理水のフッ素イオン濃度は、上記に説明したように、15mg/L以下であることが好ましく、8mg/L以下がより好ましい。第1処理水のフッ素イオン濃度はそれよりも低くてもよく、例えば5mg/L以下、3mg/L以下、あるいは1mg/L以下であってもよい。このようにフッ素イオン濃度の低い第1処理水を前処理工程において吸着塔に導入することにより、前処理工程で第1処理水中のフッ素イオンが吸着除去されなくても、吸着塔から排出される第2処理水のフッ素イオン濃度が十分に低いものとなる。 As described above, the fluorine ion concentration of the first treated water introduced into the adsorption tower in the pretreatment step is preferably 15 mg / L or less, more preferably 8 mg / L or less. The fluorine ion concentration of the first treated water may be lower than that, for example, 5 mg / L or less, 3 mg / L or less, or 1 mg / L or less. By introducing the first treated water having a low fluorine ion concentration into the adsorption tower in the pretreatment step, even if the fluorine ions in the first treated water are not adsorbed and removed in the pretreatment step, they are discharged from the adsorption tower. The fluorine ion concentration of the second treated water becomes sufficiently low.
前処理工程において吸着塔に導入される第1処理水のpHは、2.0以上が好ましく、2.1以上がより好ましく、2.2以上がさらに好ましく、また3.5以下が好ましく、3.3以下がより好ましく、3.1以下がさらに好ましい。第1処理水のpHが高い場合は、酸を添加することにより第1処理水のpHを調整すればよく、当該酸としては塩酸や硫酸を用いることが好ましい。逆に第1処理水のpHが低い場合は、アルカリを添加することにより第1処理水のpHを調整すればよく、当該アルカリとしてはアルカリ金属水酸化物を用いることが好ましく、水酸化ナトリウムを用いることがより好ましい。このように吸着塔に導入する第1処理水のpHを調整することにより、前処理工程においてフッ素吸着剤の有する水酸化物イオンを効率的に硫酸イオンに置換することができる。 The pH of the first treated water introduced into the adsorption tower in the pretreatment step is preferably 2.0 or more, more preferably 2.1 or more, further preferably 2.2 or more, and preferably 3.5 or less. It is more preferably 0.3 or less, and further preferably 3.1 or less. When the pH of the first treated water is high, the pH of the first treated water may be adjusted by adding an acid, and hydrochloric acid or sulfuric acid is preferably used as the acid. On the contrary, when the pH of the first treated water is low, the pH of the first treated water may be adjusted by adding an alkali, and it is preferable to use an alkali metal hydroxide as the alkali, and sodium hydroxide is used. It is more preferable to use it. By adjusting the pH of the first treated water introduced into the adsorption tower in this way, the hydroxide ion contained in the fluorine adsorbent can be efficiently replaced with sulfate ion in the pretreatment step.
第1処理水は、吸着塔を上向流式で通液させてもよく、下向流式で通液させてもよい。このときの通液速度は、例えば空間速度(SV)として1hr-1〜100hr-1の範囲で適宜調整すればよい。当該空間速度(SV)は、前処理工程に要する時間の短縮化や吸着塔から排出される第2処理水のpHの過度な上昇を抑える観点から、3hr-1以上が好ましく、5hr-1以上がより好ましく、8hr-1以上がさらに好ましく、12hr-1以上がさらにより好ましい。また、吸着剤の有する水酸化物イオンの硫酸イオンへの置換効率を高める観点から、空間速度(SV)は70hr-1以下が好ましく、50hr-1以下がより好ましく、30hr-1以下がさらに好ましい。 The first treated water may be passed through the adsorption tower by an upward flow type or by a downward flow type. The liquid passing speed at this time may be appropriately adjusted in the range of 1 hr -1 to 100 hr -1 as the space velocity (SV), for example. The space velocity (SV) is preferably 3 hr -1 or higher, preferably 5 hr -1 or higher, from the viewpoint of shortening the time required for the pretreatment step and suppressing an excessive increase in the pH of the second treated water discharged from the adsorption tower. still more preferably, -8 hr -1 or more, and even more preferably 12hr -1 or more. Further, in view of enhancing the replacement efficiency of the sulfate ion of the hydroxide ions with the adsorbent, the space velocity (SV) is preferably 70Hr -1 or less, more preferably 50 hr -1 or less, more preferably 30 hr -1 or less ..
前処理工程では、第1処理水を吸着塔に循環させながら導入してもよい。例えば、第1処理水の保持タンクを準備し、当該保持タンクと吸着塔との間を第1処理水を循環させることができる。この場合、吸着塔から排出された第2処理水が、前処理工程において吸着塔に導入される第1処理水として再び使用されることとなる。もちろん、第1処理水を吸着塔に循環供給せずに、吸着塔から排出された第2処理水を、フッ素イオンが除去された処理水として、そのまま系外に排出してもよい。 In the pretreatment step, the first treated water may be introduced while being circulated in the adsorption tower. For example, a holding tank for the first treated water can be prepared, and the first treated water can be circulated between the holding tank and the adsorption tower. In this case, the second treated water discharged from the adsorption tower will be used again as the first treated water introduced into the adsorption tower in the pretreatment step. Of course, instead of circulating and supplying the first treated water to the adsorption tower, the second treated water discharged from the adsorption tower may be discharged as it is to the outside of the system as treated water from which fluorine ions have been removed.
前処理工程では、吸着工程で得られた第1処理水の全部を吸着塔に導入してもよく、一部のみを吸着塔に導入してもよい。前処理工程においてフッ素吸着剤の有する水酸化物イオンが十分に硫酸イオンに置換されれば、第1処理水の吸着塔への供給を止め、前処理工程を終了してもよい。 In the pretreatment step, all of the first treated water obtained in the adsorption step may be introduced into the adsorption tower, or only a part thereof may be introduced into the adsorption tower. If the hydroxide ion contained in the fluorine adsorbent is sufficiently replaced with the sulfate ion in the pretreatment step, the supply of the first treated water to the adsorption tower may be stopped and the pretreatment step may be terminated.
前処理工程の終了のタイミングは、第2処理水のpHを測定することにより判断することができる。第2処理水は、前処理工程の初期はpHが高く、あるいはpHが上昇し、例えばpHが6〜9程度となる。一方、前処理工程を継続していくと、フッ素吸着剤の有する水酸化物イオンの硫酸イオンとの交換量が減り、第2処理水のpHは徐々に低下する。従って、前処理工程において第2処理水のpHが所定値以下となったら、前処理工程を終了して、吸着工程に移行することができる。目安となる第2処理水のpHは、4.0以下が好ましく、3.8以下がより好ましく、3.5以下がさらに好ましい。 The timing of the end of the pretreatment step can be determined by measuring the pH of the second treated water. The pH of the second treated water is high or the pH rises at the initial stage of the pretreatment step, and the pH is, for example, about 6 to 9. On the other hand, when the pretreatment step is continued, the amount of hydroxide ion exchanged with the sulfate ion of the fluorine adsorbent decreases, and the pH of the second treated water gradually decreases. Therefore, when the pH of the second treated water becomes equal to or less than a predetermined value in the pretreatment step, the pretreatment step can be terminated and the process can proceed to the adsorption step. The pH of the second treated water as a guide is preferably 4.0 or less, more preferably 3.8 or less, and even more preferably 3.5 or less.
前処理工程の終了のタイミングは、第1処理水の吸着塔への供給量に基づき決定してもよい。例えば、前処理工程における第1処理水の吸着塔への供給量(体積)は、吸着塔に充填されたフッ素吸着剤の見かけ体積の20倍以上とすることが好ましく、30倍以上がより好ましく、40倍以上がさらに好ましい。第1処理水の吸着塔への供給量の上限は特に限定されないが、過剰に供給しても第1処理水を導入することの効果がそれほど向上しないことから、第1処理水の吸着塔への供給量は、吸着塔に充填されたフッ素吸着剤の見かけ体積の200倍以下が好ましく、150倍以下がより好ましく、100倍以下がさらに好ましい。なお、ここで説明した第1処理水の吸着塔への供給量は、第1処理水を吸着塔に循環供給する場合は、吸着塔に導入する第1処理水の延べ量を意味する。 The timing of the end of the pretreatment step may be determined based on the amount of the first treated water supplied to the adsorption tower. For example, the amount (volume) of the first treated water supplied to the adsorption tower in the pretreatment step is preferably 20 times or more, more preferably 30 times or more the apparent volume of the fluorine adsorbent filled in the adsorption tower. , 40 times or more is more preferable. The upper limit of the amount of the first treated water supplied to the adsorption tower is not particularly limited, but since the effect of introducing the first treated water is not so improved even if it is excessively supplied, the first treated water is supplied to the adsorption tower. The supply amount of the fluorine adsorbent is preferably 200 times or less, more preferably 150 times or less, still more preferably 100 times or less, the apparent volume of the fluorine adsorbent filled in the adsorption tower. The amount of the first treated water supplied to the adsorption tower described here means the total amount of the first treated water to be introduced into the adsorption tower when the first treated water is circulated and supplied to the adsorption tower.
上記のように前処理工程を行うことにより、フッ素吸着剤がアニオンとして硫酸イオンを有するものとなる。そして、その後、吸着工程において被処理水をフッ素吸着剤と接触させると、吸着剤の有する硫酸イオンがフッ素イオンとイオン交換され、第1処理水のpH上昇を抑えることができる。そのため、第1処理水のpHをフッ素吸着除去に適したpH範囲に維持することが容易になり、被処理水からのフッ素吸着除去を安定して行えるようになる。 By performing the pretreatment step as described above, the fluorine adsorbent has a sulfate ion as an anion. After that, when the water to be treated is brought into contact with the fluorine adsorbent in the adsorption step, the sulfate ion of the adsorbent is ion-exchanged with the fluorine ion, and the pH increase of the first treated water can be suppressed. Therefore, it becomes easy to maintain the pH of the first treated water in a pH range suitable for removing fluorine by adsorption, and it becomes possible to stably remove fluorine by adsorption from the water to be treated.
前処理工程は、吸着工程の後、フッ素吸着剤を脱着・再生処理して、次の吸着工程でフッ素吸着処理を行う前に行うものであってもよい。この場合の本発明の水処理方法は、吸着工程の後に、吸着塔にアルカリ溶液を導入し、フッ素吸着剤からフッ素イオンを脱着させる脱着工程と、脱着工程の後に、吸着塔に酸溶液を導入する酸処理工程とをさらに有し、酸処理工程の後に前処理工程を行い、その後再び吸着工程を行うものとなる。このように吸着工程の後に脱着工程と酸処理工程を設けることにより、フッ素吸着剤を繰り返し使用できるようになる。 The pretreatment step may be performed after the adsorption step, before the fluorine adsorbent is desorbed and regenerated, and before the fluorine adsorption treatment is performed in the next adsorption step. In this case, the water treatment method of the present invention introduces an alkaline solution into the adsorption tower after the adsorption step to desorb fluorine ions from the fluorine adsorbent, and introduces an acid solution into the adsorption tower after the desorption step. The acid treatment step is further provided, and the pretreatment step is performed after the acid treatment step, and then the adsorption step is performed again. By providing the desorption step and the acid treatment step after the adsorption step in this way, the fluorine adsorbent can be used repeatedly.
脱着工程では、吸着工程でフッ素イオンを吸着した吸着剤をアルカリ溶液と接触させる。これにより、フッ素イオンが吸着剤から脱着して、フッ素イオンを含有する脱離液が得られる。このようにして得られた脱離液は、被処理水よりもフッ素イオンを濃縮することができ、しかも高純度のフッ素イオン含有液となるため、フッ素の効率的な回収が可能となる。 In the desorption step, the adsorbent that has adsorbed fluorine ions in the adsorption step is brought into contact with the alkaline solution. As a result, fluorine ions are desorbed from the adsorbent to obtain a desorbed liquid containing fluorine ions. The desorbed liquid thus obtained can concentrate fluorine ions more than the water to be treated, and is a high-purity fluorine ion-containing liquid, so that fluorine can be efficiently recovered.
アルカリ溶液としては、アルカリ金属水酸化物の溶液を用いることが好ましい。アルカリ金属水酸化物としては、水酸化リチウム、水酸化カリウム、水酸化ナトリウム、水酸化ルビジウム、水酸化セシウム等を用いることができ、これらは1種のみを用いてもよく、2種以上を併用してもよい。なお、アルカリ金属水酸化物としては、コスト面から水酸化ナトリウムを用いることが好ましい。 As the alkaline solution, it is preferable to use a solution of alkali metal hydroxide. As the alkali metal hydroxide, lithium hydroxide, potassium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide and the like can be used, and only one of these may be used, or two or more thereof may be used in combination. You may. As the alkali metal hydroxide, it is preferable to use sodium hydroxide from the viewpoint of cost.
脱着工程で用いるアルカリ溶液は、水酸化物イオン濃度が高いほどフッ素イオンを高濃度に含む脱離液が得られることから、ある程度高い水酸化物イオン濃度を有するアルカリ溶液を使用することが好ましい。アルカリ溶液の水酸化物イオン濃度は、例えば0.05mol/L以上が好ましく、0.1mol/L以上がより好ましく、0.2mol/L以上がさらに好ましい。一方、アルカリ溶液の取り扱い性や設備仕様への影響を考慮すると、アルカリ溶液の水酸化物イオン濃度は3mol/L以下が好ましく、1mol/L以下がより好ましい。 As the alkaline solution used in the desorption step, it is preferable to use an alkaline solution having a somewhat high hydroxide ion concentration because a desorbed solution containing a higher concentration of fluorine ions can be obtained as the hydroxide ion concentration increases. The hydroxide ion concentration of the alkaline solution is, for example, preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more, still more preferably 0.2 mol / L or more. On the other hand, in consideration of the handleability of the alkaline solution and the influence on the equipment specifications, the hydroxide ion concentration of the alkaline solution is preferably 3 mol / L or less, more preferably 1 mol / L or less.
脱着工程でフッ素イオンを脱着させた吸着剤は、次に酸処理工程で酸溶液と接触させることにより、再びフッ素吸着剤として使用することができる。このときの酸としては、塩酸や硫酸を用いることが好ましい。酸溶液の水素イオン濃度は、例えば0.01mol/Lより高いことが好ましく、0.03mol/L以上がより好ましく、また2.0mol/L以下が好ましく、1.0mol/L以下がより好ましい。なお、酸処理工程の前に、脱着工程でフッ素イオンを脱着させた吸着剤を水洗してもよい。また、酸処理工程の後に、吸着剤を水洗してもよい。 The adsorbent from which the fluorine ions have been desorbed in the desorption step can be used again as the fluorine adsorbent by contacting it with the acid solution in the acid treatment step. As the acid at this time, it is preferable to use hydrochloric acid or sulfuric acid. The hydrogen ion concentration of the acid solution is, for example, preferably higher than 0.01 mol / L, more preferably 0.03 mol / L or more, preferably 2.0 mol / L or less, and more preferably 1.0 mol / L or less. Before the acid treatment step, the adsorbent to which the fluorine ions have been desorbed in the desorption step may be washed with water. Further, the adsorbent may be washed with water after the acid treatment step.
酸処理工程の後に上記に説明した前処理工程を行う。酸処理工程で酸溶液と接触させた後に水洗した場合は、この水洗の後で前処理工程を行う。このようにフッ素吸着剤を再生処理した後に前処理工程を行い、その後再び吸着工程を行うことで、再び行う吸着工程において、初期段階からフッ素イオン濃度が十分に低減された第1処理水が得られるようになる。 After the acid treatment step, the pretreatment step described above is performed. When washing with water after contacting with an acid solution in the acid treatment step, a pretreatment step is performed after this washing with water. By performing the pretreatment step after the fluorine adsorbent is regenerated in this way and then performing the adsorption step again, the first treated water in which the fluorine ion concentration is sufficiently reduced from the initial stage can be obtained in the adsorption step to be performed again. Will be able to.
なお、酸処理工程で硫酸を用いた場合に、酸処理工程が上記に説明した前処理工程を兼ねることが可能か検討したが、酸処理工程で硫酸を用いても前処理工程を行った場合と同等の効果を得ることはできなかった。すなわち、酸処理工程を行った後、前処理工程を行わずに吸着工程を行った場合は、吸着工程において第1処理水のpH上昇が見られ、特に吸着工程の初期において第1処理水のフッ素イオン濃度が高くなる傾向を示した。 In addition, when sulfuric acid was used in the acid treatment step, it was examined whether the acid treatment step could also serve as the pretreatment step described above, but when the pretreatment step was performed even if sulfuric acid was used in the acid treatment step. It was not possible to obtain the same effect as. That is, when the adsorption step is performed without performing the pretreatment step after the acid treatment step, the pH of the first treated water is increased in the adsorption step, and the pH of the first treated water is particularly increased at the initial stage of the adsorption step. It showed a tendency for the fluorine ion concentration to increase.
上記に説明した前処理工程は、フッ素吸着剤により最初に吸着工程を行う前や、フッ素吸着剤を再生処理後、最初に吸着工程を行う前に行うことが有効である。従って、吸着工程を一旦中断して、その後吸着工程を再開するような場合には、再開した吸着工程の前に前処理工程を行わなくてもよい。 It is effective that the pretreatment step described above is performed before the first adsorption step is performed by the fluorine adsorbent, or after the fluorine adsorbent is regenerated and before the first adsorption step is performed. Therefore, when the adsorption step is interrupted once and then the adsorption step is restarted, the pretreatment step may not be performed before the restarted adsorption step.
次に、本発明の水処理方法で用いるシステム構成例について、図面を参照して説明する。なお、本発明は、図面に示した実施態様に限定されるものではない。 Next, a system configuration example used in the water treatment method of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown in the drawings.
図2に示した水処理システムは、フッ素吸着剤が充填された吸着塔11と、吸着塔11の入側に連通し、被処理水1が供給される被処理水流路21を有している。吸着塔11に導入される被処理水1は、少なくともフッ素イオンと硫酸イオンを含有し、硫酸イオン濃度が30,000mg/L以上となっている。被処理水1を吸着塔11に導入してフッ素吸着剤と接触させることにより、フッ素イオン濃度が低減された第1処理水2が得られる(吸着工程)。第1処理水2は、環境中に放流できる程度までフッ素イオン濃度が低減されたものとなる。第1処理水2は、吸着塔11の出側に連通して設けられた処理水流路22を通して得られ、その少なくとも一部が処理水タンク23に一時的に貯留される。 The water treatment system shown in FIG. 2 has an adsorption tower 11 filled with a fluorine adsorbent and a water flow path 21 to be treated, which communicates with the inlet side of the adsorption tower 11 and supplies water 1 to be treated. .. The water to be treated 1 introduced into the adsorption tower 11 contains at least fluorine ions and sulfate ions, and has a sulfate ion concentration of 30,000 mg / L or more. By introducing the water to be treated 1 into the adsorption tower 11 and bringing it into contact with the fluorine adsorbent, the first treated water 2 having a reduced fluorine ion concentration can be obtained (adsorption step). The first treated water 2 has a fluorine ion concentration reduced to such an extent that it can be discharged into the environment. The first treated water 2 is obtained through a treated water flow path 22 provided in communication with the outlet side of the adsorption tower 11, and at least a part thereof is temporarily stored in the treated water tank 23.
吸着塔11の入側には、被処理水1のpHを調整するためのpH調整手段12が設けられることが好ましい。pH調整手段12としては、酸やアルカリを添加する薬注ポンプ等が挙げられる。酸やアルカリは被処理水流路21の配管内に供給してもよく、被処理水流路21にpH調整槽を設けて、pH調整槽で酸やアルカリを供給してもよい。この際、被処理水1のpHを測定しながら酸やアルカリを供給することが好ましい。従って、吸着塔11の入側にはpH計が設けられることが好ましい。被処理水1のpHを吸着に好適な範囲に調整することにより、被処理水1を吸着塔11に導入した際にフッ素イオンを効率的に吸着除去できるようになる。 It is preferable that the pH adjusting means 12 for adjusting the pH of the water to be treated 1 is provided on the entrance side of the adsorption tower 11. Examples of the pH adjusting means 12 include a chemical injection pump that adds an acid or an alkali. The acid or alkali may be supplied into the pipe of the water flow path 21 to be treated, or a pH adjustment tank may be provided in the water flow path 21 to be treated and the acid or alkali may be supplied in the pH adjustment tank. At this time, it is preferable to supply the acid or alkali while measuring the pH of the water to be treated 1. Therefore, it is preferable to provide a pH meter on the entrance side of the adsorption tower 11. By adjusting the pH of the water to be treated 1 to a range suitable for adsorption, fluorine ions can be efficiently adsorbed and removed when the water to be treated 1 is introduced into the adsorption tower 11.
吸着塔11の出側には、フッ素イオン濃度計が設けられることが好ましい。フッ素イオン濃度計によって第1処理水2のフッ素イオン濃度を測定することにより、吸着工程を終了するタイミングを判断することができる。例えば、第1処理水2のフッ素イオン濃度の基準値を予め定めておき、当該基準値を超えたら吸着工程を終了することができる。なお、吸着塔11の入側にもフッ素イオン濃度計を設けてもよく、被処理水1のフッ素イオン濃度と第1処理水2のフッ素イオン濃度の差分および被処理水1の供給量(または第1処理水2の排出量)から吸着塔11に充填された吸着剤へのフッ素イオンの累積吸着量を計算し、当該累積吸着量が所定値を超えたら、吸着工程を終了するようにしてもよい。 It is preferable that a fluorine ion densitometer is provided on the outlet side of the adsorption tower 11. By measuring the fluorine ion concentration of the first treated water 2 with a fluorine ion concentration meter, it is possible to determine the timing at which the adsorption step is completed. For example, a reference value for the fluorine ion concentration of the first treated water 2 can be set in advance, and the adsorption step can be terminated when the reference value is exceeded. A fluorine ion concentration meter may also be provided on the entrance side of the adsorption tower 11, and the difference between the fluorine ion concentration of the water to be treated 1 and the fluorine ion concentration of the first treated water 2 and the supply amount of the water to be treated 1 (or The cumulative adsorption amount of fluorine ions to the adsorbent filled in the adsorption tower 11 is calculated from the discharge amount of the first treated water 2), and when the cumulative adsorption amount exceeds a predetermined value, the adsorption step is terminated. May be good.
フッ素イオンを吸着した吸着剤は、アルカリ溶液と接触させることにより、吸着剤からフッ素イオンを脱着させることができる(脱着工程)。従って、吸着塔11の入側には薬液流路25が連通して設けられることが好ましい。吸着塔11の出側には、吸着剤と接触したアルカリ溶液すなわち脱離液3を排出する廃液流路26が連通して設けられることが好ましい。なお、図2では、薬液流路25が吸着塔11の入側に直接接続しているが、被処理水流路21に接続するものであってもよい。薬液流路25からアルカリ溶液を供給する際には、吸着塔11への被処理水1の供給を止め、吸着塔11から廃液流路26を通って排出された脱離液3を回収する。 The adsorbent that has adsorbed fluorine ions can desorb fluorine ions from the adsorbent by contacting it with an alkaline solution (desorption step). Therefore, it is preferable that the chemical liquid flow path 25 is provided in communication with the entrance side of the adsorption tower 11. It is preferable that a waste liquid flow path 26 for discharging the alkaline solution in contact with the adsorbent, that is, the desorbed liquid 3, is provided in communication with the outlet side of the adsorption tower 11. Although the chemical flow path 25 is directly connected to the inlet side of the adsorption tower 11 in FIG. 2, it may be connected to the water flow path 21 to be treated. When the alkaline solution is supplied from the chemical liquid flow path 25, the supply of the water to be treated 1 to the adsorption tower 11 is stopped, and the desorbed liquid 3 discharged from the adsorption tower 11 through the waste liquid flow path 26 is collected.
フッ素イオンを脱着した吸着剤は、酸溶液と接触させることにより再生され、再びフッ素吸着能が付与される(酸処理工程)。図2では、薬液流路25から酸溶液を供給することができ、吸着剤と接触した酸溶液すなわち酸洗浄廃液4が廃液流路26を通して排出される。なお、酸溶液はアルカリ溶液とは異なる流路を通して吸着塔11に供給されてもよく、酸洗浄廃液4は脱離液3とは異なる流路を通して吸着塔11から排出されてもよい。また、吸着塔11への酸溶液の供給に先立って、吸着塔11に水を供給して、吸着塔11内のアルカリ溶液を洗い流してもよい。酸溶液と接触させた吸着剤は、フッ素イオンの吸着サイトに水酸化物イオンを有するものとなる。 The adsorbent desorbed from fluorine ions is regenerated by contacting it with an acid solution, and the fluorine adsorbing ability is imparted again (acid treatment step). In FIG. 2, the acid solution can be supplied from the chemical flow path 25, and the acid solution in contact with the adsorbent, that is, the acid cleaning waste liquid 4, is discharged through the waste liquid flow path 26. The acid solution may be supplied to the adsorption tower 11 through a flow path different from that of the alkaline solution, and the acid cleaning waste liquid 4 may be discharged from the adsorption tower 11 through a flow path different from that of the desorption liquid 3. Further, prior to the supply of the acid solution to the adsorption tower 11, water may be supplied to the adsorption tower 11 to wash away the alkaline solution in the adsorption tower 11. The adsorbent brought into contact with the acid solution has hydroxide ions at the adsorption sites of fluorine ions.
酸溶液との接触により再生した吸着剤は、再び被処理水1のフッ素イオンの吸着除去に使用することができるが、被処理水1の吸着塔11への導入に先立って、処理水タンク23に貯留された第1処理水2を返送流路24を通して吸着塔11に導入する(前処理工程)。吸着塔11からは第2処理水5が得られる。第1処理水2の硫酸イオン濃度は30,000mg/L以上となっており、このように高濃度に硫酸イオンを含む第1処理水2を吸着塔11に導入することにより、吸着塔11に充填された吸着剤の有する水酸化物イオンが硫酸イオンに置換される。これにより、その後、被処理水1を吸着塔11に導入した際に、吸着塔11から排出される第1処理水2のpHの上昇が抑えられ、被処理水1からフッ素イオンを安定して吸着除去できるようになる。なお、酸溶液との接触後、第1処理水2の導入前に、吸着塔11に水を供給して、吸着塔11内の酸溶液を洗い流すことも好ましい。 The adsorbent regenerated by contact with the acid solution can be used again for adsorbing and removing fluorine ions in the water to be treated 1, but prior to introducing the water to be treated 1 into the adsorption tower 11, the treated water tank 23 The first treated water 2 stored in the water is introduced into the adsorption tower 11 through the return flow path 24 (pretreatment step). The second treated water 5 is obtained from the adsorption tower 11. The sulfate ion concentration of the first treated water 2 is 30,000 mg / L or more, and by introducing the first treated water 2 containing sulfate ions at a high concentration into the adsorption tower 11, the adsorption tower 11 can be reached. The hydroxide ion contained in the packed adsorbent is replaced with sulfate ion. As a result, when the water to be treated 1 is subsequently introduced into the adsorption tower 11, the increase in the pH of the first treated water 2 discharged from the adsorption tower 11 is suppressed, and the fluorine ions from the water to be treated 1 are stabilized. It becomes possible to remove by adsorption. It is also preferable to supply water to the adsorption tower 11 to wash away the acid solution in the adsorption tower 11 after the contact with the acid solution and before the introduction of the first treated water 2.
前処理工程の終了のタイミングは、吸着塔11の出側にpH計を設け、第2処理水5のpHを測定することにより判断することができる。具体的には、第2処理水5のpHが所定値以下(例えば、pHが4.0以下)となったら、前処理工程を終了して、吸着工程に移行することができる。なお、前処理工程における第1処理水2の吸着塔11への供給量は、吸着塔11に充填された吸着剤の見かけ体積の20倍以上とすることが好ましい。 The timing of the end of the pretreatment step can be determined by providing a pH meter on the outlet side of the adsorption tower 11 and measuring the pH of the second treated water 5. Specifically, when the pH of the second treated water 5 becomes a predetermined value or less (for example, the pH is 4.0 or less), the pretreatment step can be terminated and the process can be started to the adsorption step. The amount of the first treated water 2 supplied to the adsorption tower 11 in the pretreatment step is preferably 20 times or more the apparent volume of the adsorbent filled in the adsorption tower 11.
本発明の水処理システムの他の例について、図3および図4を参照して説明する。なお下記の説明において、図2と重複する部分の説明は省く。 Other examples of the water treatment system of the present invention will be described with reference to FIGS. 3 and 4. In the following description, the description of the part overlapping with FIG. 2 will be omitted.
図3に示した構成例では、吸着塔として第1吸着塔11Aと第2吸着塔11Bが並列して設けられ、第1吸着塔11Aと第2吸着塔11Bのそれぞれに被処理水流路21と処理水流路22と処理水タンク23と返送流路24と薬液流路25と廃液流路26が設けられている。図3に示した構成例によれば、第1吸着塔11Aと第2吸着塔11Bのそれぞれで吸着工程と脱着・酸洗浄・前処理工程を行うことができる。そのため、第1吸着塔11Aで吸着処理を行うのと同時に第2吸着塔11Bで脱着・再生処理および吸着剤の前処理を行うことができ、またその逆も可能となるため、被処理水の連続的な吸着処理が可能となる。 In the configuration example shown in FIG. 3, the first adsorption tower 11A and the second adsorption tower 11B are provided in parallel as the adsorption tower, and the water flow path 21 to be treated is provided in each of the first adsorption tower 11A and the second adsorption tower 11B. A treated water flow path 22, a treated water tank 23, a return flow path 24, a chemical liquid flow path 25, and a waste liquid flow path 26 are provided. According to the configuration example shown in FIG. 3, the adsorption step and the desorption / acid cleaning / pretreatment step can be performed in each of the first adsorption tower 11A and the second adsorption tower 11B, respectively. Therefore, at the same time as the adsorption treatment is performed in the first adsorption tower 11A, the desorption / regeneration treatment and the pretreatment of the adsorbent can be performed in the second adsorption tower 11B, and vice versa. Continuous adsorption processing becomes possible.
図3に示した構成例では、第1吸着塔11Aと第2吸着塔11Bの2つの吸着塔を交互に吸着工程と脱着・酸洗浄・前処理工程に供することで、被処理水の連続的な吸着処理を可能としたが、3つ以上の吸着塔を用いて被処理水の連続的な吸着処理を行うこともできる。例えば、第1吸着塔と第2吸着塔と第3吸着塔の3つの吸着塔を用いる場合は、第1吸着塔と第2吸着塔をこの順で直列接続して吸着工程を行い、第3吸着塔で脱着・酸洗浄・前処理工程を行い、次に第2吸着塔と第3吸着塔をこの順で直列接続して吸着工程を行い、第1吸着塔で脱着・酸洗浄・前処理工程を行い、さらにその次に第3吸着塔と第1吸着塔をこの順で直列接続して吸着工程を行い、第2吸着塔で脱着・酸洗浄・前処理工程を行うことを繰り返すことで、3つの吸着塔を用いて被処理水の連続的な吸着処理を行うことができる。4つ以上の吸着塔を用いる場合は、3つ以上の吸着塔を多段に直列接続して吸着処理を行ってもよく、2つ以上の吸着塔で脱着・酸洗浄・前処理工程を行ってもよい。 In the configuration example shown in FIG. 3, the two adsorption towers of the first adsorption tower 11A and the second adsorption tower 11B are alternately subjected to the adsorption step and the desorption / acid cleaning / pretreatment step to continuously perform the water to be treated. It is possible to carry out a continuous adsorption treatment of the water to be treated by using three or more adsorption towers. For example, when three adsorption towers of the first adsorption tower, the second adsorption tower, and the third adsorption tower are used, the first adsorption tower and the second adsorption tower are connected in series in this order to perform the adsorption step, and the third adsorption step is performed. The adsorption tower performs desorption, acid cleaning, and pretreatment, then the second adsorption tower and the third adsorption tower are connected in series in this order to perform the adsorption process, and the first adsorption tower desorbs, acid cleans, and pretreats. By performing the step, then the third adsorption tower and the first adsorption tower are connected in series in this order to perform the adsorption step, and then the desorption, acid cleaning, and pretreatment steps are repeated in the second adsorption tower. The water to be treated can be continuously adsorbed using the three adsorption towers. When four or more adsorption towers are used, three or more adsorption towers may be connected in series in multiple stages to perform adsorption treatment, and two or more adsorption towers are subjected to desorption, acid cleaning, and pretreatment steps. May be good.
図4には、吸着塔が多段に直列接続された構成例を示した。図4では、吸着塔として第1吸着塔11Aと第2吸着塔11Bを設け、第1吸着塔11Aの出側と第2吸着塔11Bの入側に連通して直列接続流路27が設けられ、これにより第1吸着塔11Aと第2吸着塔11Bをこの順で直列接続することができる。このように吸着塔を直列接続した場合、被処理水1を第1吸着塔11Aに導入して第1吸着塔11Aで吸着工程を行って第1処理水2Aを得た後、得られた第1処理水2Aを直列接続流路27を通して第2吸着塔11Bに導入し、第2吸着塔11Bで前処理工程を行うことができる。従って、前処理工程を行うための第1処理水2Aの処理水タンクの設置が不要となる。第2吸着塔11Bから排出された第2処理水5Bは、環境中に放流することができる。なお、第2吸着塔11Bに第1処理水2Aを導入するのに先立って、第2吸着塔11Bにおいて、脱着工程と酸処理工程を行うことが好ましい。従って、第2吸着塔11Bにおいて脱着工程と酸処理工程を行っている間は、第1吸着塔11Aから排出された第1処理水2Aは、第2吸着塔11Bを介さずにそのまま系外に排出することが好ましい。 FIG. 4 shows a configuration example in which the adsorption towers are connected in series in multiple stages. In FIG. 4, a first suction tower 11A and a second suction tower 11B are provided as suction towers, and a series connection flow path 27 is provided so as to communicate with the outlet side of the first suction tower 11A and the entrance side of the second suction tower 11B. As a result, the first suction tower 11A and the second suction tower 11B can be connected in series in this order. When the adsorption towers are connected in series in this way, the water to be treated 1 is introduced into the first adsorption tower 11A and the adsorption step is performed in the first adsorption tower 11A to obtain the first treated water 2A, and then the obtained first. 1 The treated water 2A can be introduced into the second adsorption tower 11B through the series connection flow path 27, and the pretreatment step can be performed in the second adsorption tower 11B. Therefore, it is not necessary to install a treated water tank for the first treated water 2A for performing the pretreatment step. The second treated water 5B discharged from the second adsorption tower 11B can be discharged into the environment. Prior to introducing the first treated water 2A into the second adsorption tower 11B, it is preferable to perform the desorption step and the acid treatment step in the second adsorption tower 11B. Therefore, during the desorption step and the acid treatment step in the second adsorption tower 11B, the first treated water 2A discharged from the first adsorption tower 11A goes out of the system as it is without going through the second adsorption tower 11B. It is preferable to discharge.
図4ではまた、第2吸着塔11Bの出側と第1吸着塔11Aの入側に連通してさらに直列接続流路28が設けられており、これにより第2吸着塔11Bと第1吸着塔11Aをこの順で直列接続することができる。このように吸着塔を直列接続した場合、被処理水1を第2吸着塔11Bに導入して第2吸着塔11Bで吸着工程を行って第1処理水2Bを得た後、得られた第1処理水2Bを直列接続流路28を通して第1吸着塔11Aに導入し、第1吸着塔11Aで前処理工程を行うことができる。従って、前処理工程を行うための第1処理水2Bの処理水タンクの設置が不要となる。第1吸着塔11Aから排出された第2処理水5Aは、環境中に放流することができる。なお、第1吸着塔11Aに第1処理水2Bを導入するのに先立って、第1吸着塔11Aにおいて、脱着工程と酸処理工程を行うことが好ましい。従って、第1吸着塔11Aにおいて脱着工程と酸処理工程を行っている間は、第2吸着塔11Bから排出された第1処理水2Bは、第1吸着塔11Aを介さずにそのまま系外に排出することが好ましい。 In FIG. 4, a series connection flow path 28 is further provided so as to communicate with the outlet side of the second suction tower 11B and the entrance side of the first suction tower 11A, whereby the second suction tower 11B and the first suction tower 11B and the first suction tower are provided. 11A can be connected in series in this order. When the adsorption towers are connected in series in this way, the water to be treated 1 is introduced into the second adsorption tower 11B and the adsorption step is performed in the second adsorption tower 11B to obtain the first treated water 2B, and then the obtained first. 1 The treated water 2B can be introduced into the first adsorption tower 11A through the series connection flow path 28, and the pretreatment step can be performed in the first adsorption tower 11A. Therefore, it is not necessary to install a treated water tank for the first treated water 2B for performing the pretreatment step. The second treated water 5A discharged from the first adsorption tower 11A can be discharged into the environment. It is preferable that the desorption step and the acid treatment step are performed in the first adsorption tower 11A prior to introducing the first treated water 2B into the first adsorption tower 11A. Therefore, during the desorption step and the acid treatment step in the first adsorption tower 11A, the first treated water 2B discharged from the second adsorption tower 11B goes out of the system as it is without going through the first adsorption tower 11A. It is preferable to discharge.
図4に示した構成例では、具体的には次のように各吸着塔で吸着工程と脱着工程と酸処理工程と前処理工程を行うことが好ましい。すなわち、次の(1)〜(4)のステージを順に行うことで、第1吸着塔11Aと第2吸着塔11Bで吸着工程と脱着工程と酸処理工程と前処理工程の各工程を行うことが好ましい。(1)第1吸着塔11Aと第2吸着塔11Bをこの順で直列接続し、被処理水1を第1吸着塔11Aと第2吸着塔11Bに順次導入して、第1吸着塔11Aで吸着工程を行い、第2吸着塔11Bで前処理工程を行う。(2)脱着工程と酸処理工程を第1吸着塔11Aで行うとともに、第2吸着塔11Bに被処理水1を導入して吸着工程を行う。(3)第2吸着塔11Bと第1吸着塔11Aをこの順で直列接続し、被処理水1を第2吸着塔11Bと第1吸着塔11Aに順次導入して、第2吸着塔11Bで吸着工程を行い、第1吸着塔11Aで前処理工程を行う。(4)脱着工程と酸処理工程を第2吸着塔11Bで行うとともに、第1吸着塔11Aに被処理水1を導入して吸着工程を行う。これらの(1)〜(4)のステージは繰り返し行うことができ、すなわち(4)のステージが終わったら次に(1)のステージに戻ることができる。これにより、吸着塔の脱着・再生処理頻度を減らして、被処理水からの効率的なフッ素イオン除去が可能となる。 In the configuration example shown in FIG. 4, specifically, it is preferable to perform the adsorption step, the desorption step, the acid treatment step, and the pretreatment step in each adsorption tower as follows. That is, by sequentially performing the following stages (1) to (4), each step of the adsorption step, the desorption step, the acid treatment step, and the pretreatment step is performed in the first adsorption tower 11A and the second adsorption tower 11B. Is preferable. (1) The first adsorption tower 11A and the second adsorption tower 11B are connected in series in this order, the water to be treated 1 is sequentially introduced into the first adsorption tower 11A and the second adsorption tower 11B, and the first adsorption tower 11A The adsorption step is performed, and the pretreatment step is performed in the second adsorption tower 11B. (2) The desorption step and the acid treatment step are performed in the first adsorption tower 11A, and the water to be treated 1 is introduced into the second adsorption tower 11B to perform the adsorption step. (3) The second adsorption tower 11B and the first adsorption tower 11A are connected in series in this order, the water to be treated 1 is sequentially introduced into the second adsorption tower 11B and the first adsorption tower 11A, and the second adsorption tower 11B The adsorption step is performed, and the pretreatment step is performed in the first adsorption tower 11A. (4) The desorption step and the acid treatment step are performed in the second adsorption tower 11B, and the water to be treated 1 is introduced into the first adsorption tower 11A to perform the adsorption step. These stages (1) to (4) can be repeated, that is, when the stage (4) is completed, the stage (1) can be returned to the next stage. As a result, the frequency of desorption / regeneration treatment of the adsorption tower can be reduced, and efficient fluorine ion removal from the water to be treated becomes possible.
(1)のステージでは、第1吸着塔11Aと第2吸着塔11Bをこの順で直列接続し、被処理水1を第1吸着塔11Aと第2吸着塔11Bに順次導入する。(1)のステージではまず、硫酸イオン濃度が30,000mg/L以上の被処理水1を第1吸着塔11Aに導入し、被処理水1からフッ素イオンの少なくとも一部が除去された第1処理水2Aが得られる。第1処理水2Aのフッ素イオン濃度は、環境中に放流できる程度までフッ素イオンが除去され、硫酸イオン濃度は30,000mg/L以上に維持される。第1吸着塔11Aで得られた第1処理水2Aは第2吸着塔11Bに導入され、第2吸着塔11Bから第2処理水5Bが得られる。第2処理水5Bは、処理水流路22を通って系外に排出される。第2吸着塔11Bでは、次の(2)のステージで吸着工程が行われるのに先立って前処理工程が行われ、第2吸着塔11Bに充填された吸着剤が有する水酸化物イオンが硫酸イオンに置換される。 In the stage (1), the first adsorption tower 11A and the second adsorption tower 11B are connected in series in this order, and the water to be treated 1 is sequentially introduced into the first adsorption tower 11A and the second adsorption tower 11B. In the stage (1), first, water 1 to be treated having a sulfate ion concentration of 30,000 mg / L or more was introduced into the first adsorption tower 11A, and at least a part of fluorine ions was removed from the water 1 to be treated. Treated water 2A is obtained. The fluorine ion concentration of the first treated water 2A is such that fluorine ions are removed to the extent that it can be discharged into the environment, and the sulfate ion concentration is maintained at 30,000 mg / L or more. The first treated water 2A obtained in the first adsorption tower 11A is introduced into the second adsorption tower 11B, and the second treated water 5B is obtained from the second adsorption tower 11B. The second treated water 5B is discharged to the outside of the system through the treated water flow path 22. In the second adsorption tower 11B, a pretreatment step is performed prior to the adsorption step being performed in the next stage (2), and the hydroxide ion contained in the adsorbent filled in the second adsorption tower 11B is sulfate. It is replaced by an ion.
(1)のステージでは、第2吸着塔11Bから排出される第2処理水5BのpHを測定することにより、第2吸着塔11Bに充填された吸着剤の有する水酸化物イオンの硫酸イオンへの置換がどの程度進行したのか把握することができる。第2処理水5BのpHは、通常は、一旦pHが6〜9程度まで上昇した後、処理の継続に従いpHが低下する。(1)のステージは、第2処理水5BのpHが所定値以下(例えば、pHが4.0以下)となるまで行うことが好ましい。なお、(1)のステージにおいて、第2処理水5BのpHが所定値以下となっても、第2吸着塔11Bへの第1処理水2Aの導入を継続してもよい。これにより、仮に第1吸着塔11Aから排出された第1処理水2Aのフッ素イオン濃度が基準値を超えた場合に、第1処理水2Aが第2吸着塔11Bに導入されることで、第1処理水2Aに含まれるフッ素イオンを第2吸着塔11Bによって吸着除去することができる。 In the stage (1), by measuring the pH of the second treated water 5B discharged from the second adsorption tower 11B, the hydroxide ion contained in the adsorbent filled in the second adsorption tower 11B becomes sulfate ion. It is possible to grasp how much the replacement of is progressed. The pH of the second treated water 5B usually rises to about 6 to 9 once, and then decreases as the treatment is continued. The stage (1) is preferably performed until the pH of the second treated water 5B becomes a predetermined value or less (for example, the pH is 4.0 or less). In the stage (1), even if the pH of the second treated water 5B becomes equal to or lower than a predetermined value, the introduction of the first treated water 2A into the second adsorption tower 11B may be continued. As a result, if the fluorine ion concentration of the first treated water 2A discharged from the first adsorption tower 11A exceeds the reference value, the first treated water 2A is introduced into the second adsorption tower 11B. Fluorine ions contained in 1 treated water 2A can be adsorbed and removed by the second adsorption tower 11B.
(1)のステージにおいて、第1吸着塔11Aのフッ素イオンの吸着除去性能が低下した段階で、あるいは低下する前段階で、(2)のステージに移る。例えば、(1)のステージにおいて、第1吸着塔11Aから排出される第1処理水2Aのフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら(2)のステージに移るようにすればよい。あるいは、(1)のステージにおいて、第1吸着塔11Aの吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら(2)のステージに移るようにしてもよい。第1吸着塔11Aの吸着剤によって吸着されたフッ素イオンの累積吸着量は、被処理水1のフッ素イオン濃度と第1処理水2Aのフッ素イオン濃度の差分および被処理水1の第1吸着塔11Aへの供給量(または第1処理水2Aの排出量)から求めることができる。 In the stage (1), the stage moves to the stage (2) at the stage where the adsorption / removal performance of fluorine ions of the first adsorption tower 11A is lowered or before the deterioration. For example, in the stage (1), the fluorine ion concentration of the first treated water 2A discharged from the first adsorption tower 11A is measured, and when the fluorine ion concentration exceeds a predetermined value, the process moves to the stage (2). do it. Alternatively, in the stage (1), when the cumulative adsorption amount of the fluorine ions adsorbed by the adsorbent of the first adsorption tower 11A exceeds a predetermined value, the stage may be moved to the stage (2). The cumulative amount of fluorine ions adsorbed by the adsorbent of the first adsorption tower 11A is the difference between the fluorine ion concentration of the water to be treated 1 and the fluorine ion concentration of the first treated water 2A and the first adsorption tower of the water to be treated 1. It can be obtained from the supply amount to 11A (or the discharge amount of the first treated water 2A).
(2)のステージでは、第1吸着塔11Aの吸着剤の脱着・再生処理が行われ、第2吸着塔11Bでは、被処理水1のフッ素イオンの吸着処理が行われる。第2吸着塔11Bは、(1)のステージで前処理工程が行われたことにより、硫酸イオン濃度が30,000mg/L以上と高濃度に硫酸イオンを含む被処理水1が導入されても、得られる第1処理水2BのpHの上昇が抑えられ、環境中に放流できる程度までフッ素イオンが除去された第1処理水2Bが得られる。 In the stage (2), the adsorbent of the first adsorption tower 11A is desorbed and regenerated, and in the second adsorption tower 11B, the fluorine ion of the water to be treated 1 is adsorbed. In the second adsorption tower 11B, even if the water to be treated 1 containing sulfate ions is introduced at a high concentration of 30,000 mg / L or more due to the pretreatment step performed in the stage (1). The increase in pH of the obtained first treated water 2B is suppressed, and the first treated water 2B from which fluorine ions have been removed to the extent that it can be discharged into the environment can be obtained.
(2)のステージで第1吸着塔11Aの吸着剤の脱着・再生処理が終わったら、次に(3)のステージに移行する。(3)のステージでは、第2吸着塔11Bと第1吸着塔11Aをこの順で直列接続し、被処理水1を第2吸着塔11Bと第1吸着塔11Aに順次導入する。(3)のステージではまず、硫酸イオン濃度が30,000mg/L以上の被処理水1を第2吸着塔11Bに導入し、被処理水1からフッ素イオンの少なくとも一部が除去された第1処理水2Bが得られる。第1処理水2Bのフッ素イオン濃度は、環境中に放流できる程度までフッ素イオンが除去され、硫酸イオン濃度は30,000mg/L以上に維持される。第1吸着塔11Bで得られた第1処理水2Bは第1吸着塔11Aに導入され、第1吸着塔11Aから第2処理水5Aが得られる。第1吸着塔11Aでは、(2)のステージで行われた脱着工程と酸処理工程に引き続いて前処理工程が行われ、第1吸着塔11Aに充填された吸着剤が有する水酸化物イオンが硫酸イオンに置換される。 After the desorption / regeneration treatment of the adsorbent of the first adsorption tower 11A is completed in the stage (2), the process proceeds to the stage (3). In the stage (3), the second adsorption tower 11B and the first adsorption tower 11A are connected in series in this order, and the water to be treated 1 is sequentially introduced into the second adsorption tower 11B and the first adsorption tower 11A. In the stage (3), first, water 1 to be treated having a sulfate ion concentration of 30,000 mg / L or more was introduced into the second adsorption tower 11B, and at least a part of fluorine ions was removed from the water 1 to be treated. Treated water 2B is obtained. The fluorine ion concentration of the first treated water 2B is such that fluorine ions are removed to the extent that it can be discharged into the environment, and the sulfate ion concentration is maintained at 30,000 mg / L or more. The first treated water 2B obtained in the first adsorption tower 11B is introduced into the first adsorption tower 11A, and the second treated water 5A is obtained from the first adsorption tower 11A. In the first adsorption tower 11A, a pretreatment step is performed following the desorption step and the acid treatment step performed in the stage (2), and the hydroxide ion contained in the adsorbent filled in the first adsorption tower 11A is generated. It is replaced with sulfate ion.
(3)のステージでは、第1吸着塔11Aから排出される第2処理水5AのpHを測定することにより、第1吸着塔11Aに充填された吸着剤の有する水酸化物イオンの硫酸イオンへの置換がどの程度進行したのか把握することができる。第2処理水5AのpHは、通常は、一旦pHが6〜9程度まで上昇した後、処理の継続に従いpHが低下する。(3)のステージは、第2処理水5AのpHが所定値以下(例えば、pHが4.0以下)となるまで行うことが好ましい。なお、(3)のステージにおいて、第2処理水5AのpHが所定値以下となっても、第1吸着塔11Aへの第1処理水2Bの導入を継続してもよい。これにより、仮に第2吸着塔11Bから排出された第1処理水2Bのフッ素イオン濃度が基準値を超えた場合に、第1処理水2Bが第1吸着塔11Aに導入されることで、第1処理水2Bに含まれるフッ素イオンを第1吸着塔11Aによって吸着除去することができる。 In the stage (3), by measuring the pH of the second treated water 5A discharged from the first adsorption tower 11A, the hydroxide ion contained in the adsorbent filled in the first adsorption tower 11A becomes sulfate ion. It is possible to grasp how much the replacement of is progressed. The pH of the second treated water 5A usually rises to about 6 to 9 once, and then decreases as the treatment is continued. The stage (3) is preferably performed until the pH of the second treated water 5A becomes a predetermined value or less (for example, the pH is 4.0 or less). In the stage (3), even if the pH of the second treated water 5A falls below a predetermined value, the introduction of the first treated water 2B into the first adsorption tower 11A may be continued. As a result, if the fluorine ion concentration of the first treated water 2B discharged from the second adsorption tower 11B exceeds the reference value, the first treated water 2B is introduced into the first adsorption tower 11A. Fluorine ions contained in 1 treated water 2B can be adsorbed and removed by the first adsorption tower 11A.
(3)のステージにおいて、第2吸着塔11Bのフッ素イオンの吸着除去性能が低下した段階で、あるいは低下する前段階で、(4)のステージに移る。例えば、(3)のステージにおいて、第2吸着塔11Bから排出される第1処理水2Bのフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら(4)のステージに移るようにすればよい。あるいは、(3)のステージにおいて、第2吸着塔11Bの吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら(4)のステージに移るようにしてもよい。第2吸着塔11Bの吸着剤によって吸着されたフッ素イオンの累積吸着量は、被処理水1のフッ素イオン濃度と第1処理水2Bのフッ素イオン濃度の差分および被処理水1の第2吸着塔11Bへの供給量(または第1処理水2Bの排出量)から求めることができる。 In the stage (3), the stage moves to the stage (4) at the stage where the adsorption / removal performance of fluorine ions of the second adsorption tower 11B is lowered or before the deterioration. For example, in the stage (3), the fluorine ion concentration of the first treated water 2B discharged from the second adsorption tower 11B is measured, and when the fluorine ion concentration exceeds a predetermined value, the process moves to the stage (4). do it. Alternatively, in the stage (3), when the cumulative adsorption amount of the fluorine ions adsorbed by the adsorbent in the second adsorption tower 11B exceeds a predetermined value, the stage may be moved to the stage (4). The cumulative amount of fluorine ions adsorbed by the adsorbent of the second adsorption tower 11B is the difference between the fluorine ion concentration of the water to be treated 1 and the fluorine ion concentration of the first treated water 2B and the second adsorption tower of the water 1 to be treated. It can be obtained from the supply amount to 11B (or the discharge amount of the first treated water 2B).
(4)のステージでは、第2吸着塔11Bの吸着剤の脱着・再生処理が行われ、第1吸着塔11Aでは、被処理水1のフッ素イオンの吸着処理が行われる。第1吸着塔11Aは、(3)のステージで前処理工程が行われたことにより、硫酸イオン濃度が30,000mg/L以上と高濃度に硫酸イオンを含む被処理水1が導入されても、得られる第1処理水2AのpHの上昇が抑えられ、環境中に放流できる程度までフッ素イオンが除去された第1処理水2Aが得られる。 In the stage (4), the adsorbent of the second adsorption tower 11B is desorbed and regenerated, and in the first adsorption tower 11A, the fluorine ion of the water to be treated 1 is adsorbed. In the first adsorption tower 11A, even if the water to be treated 1 containing sulfate ions is introduced at a high concentration of 30,000 mg / L or more due to the pretreatment step performed in the stage (3). The first treated water 2A obtained is obtained in which the increase in pH of the obtained first treated water 2A is suppressed and the fluorine ions are removed to the extent that it can be discharged into the environment.
(4)のステージで第2吸着塔11Bの吸着剤の脱着・再生処理が終わったら、次に再び(1)のステージに移行する。このように(1)〜(4)のステージからなるサイクルを繰り返し行うことで、吸着塔に充填された吸着剤の脱着・再生処理頻度を減らして、被処理水からの効率的なフッ素イオン除去が可能となる。吸着剤の脱着・再生処理頻度の減少は、吸着剤の長寿命化にも繋がり、これにより処理コストの低減を図ることができる。 After the desorption / regeneration treatment of the adsorbent of the second adsorption tower 11B is completed in the stage (4), the process proceeds to the stage (1) again. By repeating the cycle consisting of the stages (1) to (4) in this way, the frequency of desorption / regeneration treatment of the adsorbent filled in the adsorption tower is reduced, and efficient fluorine ion removal from the water to be treated. Is possible. The reduction in the frequency of desorption / regeneration treatment of the adsorbent also leads to a longer life of the adsorbent, which can reduce the treatment cost.
図4に示した構成例では、吸着塔が2段に直列接続されていたが、吸着塔は3段以上直列接続されていてもよい。この場合、上記の(1)のステージと(3)のステージに相当するステージにおいて、最後段の吸着塔で前処理工程を行い、最前段の吸着塔は次のステージにおいて脱着工程と酸処理工程を行うようにすればよい。 In the configuration example shown in FIG. 4, the suction towers are connected in series in two stages, but the suction towers may be connected in series in three or more stages. In this case, in the stages corresponding to the above-mentioned stages (1) and (3), the pretreatment step is performed in the adsorption tower at the last stage, and the adsorption tower at the front stage is the desorption step and the acid treatment step in the next stage. You just have to do.
本発明は、石炭火力発電所、コークス工場、製鉄工場等の排煙脱硫排水の処理に用いることができる。 The present invention can be used for treating flue gas desulfurization wastewater from coal-fired power plants, coke factories, steel mills, and the like.
1:被処理水
2,2A,2B:第1処理水
3:脱離液
4:酸洗浄廃液
5,5A,5B:第2処理水
11:吸着塔、11A:第1吸着塔、11B:第2吸着塔
12:pH調整手段
21:被処理水流路
22:処理水流路
23:処理水タンク
24:返送流路
25:薬液流路
26:廃液流路
27,28:直列接続流路
1: Water to be treated 2, 2A, 2B: First treated water 3: Desorbed liquid 4: Acid cleaning waste liquid 5, 5A, 5B: Second treated water 11: Adsorption tower, 11A: First adsorption tower, 11B: No. 2 Adsorption tower 12: pH adjusting means 21: Water flow path to be treated 22: Treated water flow path 23: Treated water tank 24: Return flow path 25: Chemical solution flow path 26: Waste liquid flow path 27, 28: Series connection flow path

Claims (13)

  1. フッ素イオンと硫酸イオンを含有する被処理水をフッ素吸着剤が充填された吸着塔に導入し、被処理水中のフッ素イオンの少なくとも一部が除去された第1処理水を得る吸着工程と、
    前記吸着工程の前に、前記吸着工程で得られる第1処理水を前記吸着塔に導入する前処理工程とを有し、
    前記吸着塔に導入される被処理水の硫酸イオン濃度が30,000mg/L以上であり、
    前記吸着塔に導入される第1処理水の硫酸イオン濃度が30,000mg/L以上であることを特徴とする水処理方法。
    An adsorption step of introducing water to be treated containing fluorine ions and sulfate ions into an adsorption tower filled with a fluorine adsorbent to obtain a first treated water from which at least a part of fluorine ions in the water to be treated has been removed.
    Prior to the adsorption step, there is a pretreatment step of introducing the first treated water obtained in the adsorption step into the adsorption tower.
    The sulfate ion concentration of the water to be treated introduced into the adsorption tower is 30,000 mg / L or more.
    A water treatment method characterized in that the sulfate ion concentration of the first treated water introduced into the adsorption tower is 30,000 mg / L or more.
  2. 前記前処理工程において、前記吸着塔に導入される第1処理水のフッ素イオン濃度が15mg/L以下である請求項1に記載の水処理方法。 The water treatment method according to claim 1, wherein in the pretreatment step, the fluorine ion concentration of the first treated water introduced into the adsorption tower is 15 mg / L or less.
  3. 前記前処理工程において、前記吸着塔に導入される第1処理水のpHが2.0以上3.5以下である請求項1または2に記載の水処理方法。 The water treatment method according to claim 1 or 2, wherein in the pretreatment step, the pH of the first treated water introduced into the adsorption tower is 2.0 or more and 3.5 or less.
  4. 前記前処理工程において前記吸着塔から排出される第2処理水のpHが4.0以下となったら前記吸着工程を行う請求項3に記載の水処理方法。 The water treatment method according to claim 3, wherein when the pH of the second treated water discharged from the adsorption tower in the pretreatment step becomes 4.0 or less, the adsorption step is performed.
  5. 前記前処理工程において、前記第1処理水を前記吸着塔に循環させながら導入する請求項1〜4のいずれか一項に記載の水処理方法。 The water treatment method according to any one of claims 1 to 4, wherein in the pretreatment step, the first treated water is introduced while being circulated in the adsorption tower.
  6. 前記吸着工程の後に、前記吸着塔にアルカリ溶液を導入し、前記フッ素吸着剤からフッ素イオンを脱着させる脱着工程と、
    前記脱着工程の後に、前記吸着塔に酸溶液を導入する酸処理工程とをさらに有し、
    前記酸処理工程の後に前記前処理工程を行い、その後再び前記吸着工程を行う請求項1〜5のいずれか一項に記載の水処理方法。
    After the adsorption step, an alkaline solution is introduced into the adsorption tower to desorb fluorine ions from the fluorine adsorbent, and a desorption step.
    After the desorption step, an acid treatment step of introducing an acid solution into the adsorption tower is further provided.
    The water treatment method according to any one of claims 1 to 5, wherein the pretreatment step is performed after the acid treatment step, and then the adsorption step is performed again.
  7. 前記吸着工程において、前記吸着塔に導入される被処理水のフッ素イオン濃度が50mg/L以上である請求項1〜6のいずれか一項に記載の水処理方法。 The water treatment method according to any one of claims 1 to 6, wherein in the adsorption step, the fluorine ion concentration of the water to be treated introduced into the adsorption tower is 50 mg / L or more.
  8. 前記吸着工程において、前記吸着塔に導入される被処理水のpHが2.0以上3.5以下である請求項1〜7のいずれか一項に記載の水処理方法。 The water treatment method according to any one of claims 1 to 7, wherein in the adsorption step, the pH of the water to be treated introduced into the adsorption tower is 2.0 or more and 3.5 or less.
  9. 前記フッ素吸着剤がセリウム系吸着剤である請求項1〜8のいずれか一項に記載の水処理方法。 The water treatment method according to any one of claims 1 to 8, wherein the fluorine adsorbent is a cerium-based adsorbent.
  10. 前記吸着工程の後に、前記吸着塔にアルカリ溶液を導入し、前記フッ素吸着剤からフッ素イオンを脱着させる脱着工程と、
    前記脱着工程の後に、前記吸着塔に酸溶液を導入する酸処理工程とをさらに有し、
    前記吸着塔として第1吸着塔と第2吸着塔が設けられ、下記(1)〜(4)のステージを順に繰り返し行うことで、第1吸着塔と第2吸着塔で各工程を行う請求項1〜9のいずれか一項に記載の水処理方法。
    (1)第1吸着塔と第2吸着塔をこの順で直列接続し、被処理水を第1吸着塔と第2吸着塔に順次導入して、第1吸着塔で吸着工程を行い、第2吸着塔で前処理工程を行う。
    (2)脱着工程と酸処理工程を第1吸着塔で行うとともに、第2吸着塔に被処理水を導入して吸着工程を行う。
    (3)第2吸着塔と第1吸着塔をこの順で直列接続し、被処理水を第2吸着塔と第1吸着塔に順次導入して、第2吸着塔で吸着工程を行い、第1吸着塔で前処理工程を行う。
    (4)脱着工程と酸処理工程を第2吸着塔で行うとともに、第1吸着塔に被処理水を導入して吸着工程を行う。
    After the adsorption step, an alkaline solution is introduced into the adsorption tower to desorb fluorine ions from the fluorine adsorbent, and a desorption step.
    After the desorption step, an acid treatment step of introducing an acid solution into the adsorption tower is further provided.
    A first suction tower and a second suction tower are provided as the suction tower, and each step is performed by the first suction tower and the second suction tower by repeating the following stages (1) to (4) in order. The water treatment method according to any one of 1 to 9.
    (1) The first adsorption tower and the second adsorption tower are connected in series in this order, the water to be treated is sequentially introduced into the first adsorption tower and the second adsorption tower, and the adsorption step is performed in the first adsorption tower. 2 Perform the pretreatment step in the adsorption tower.
    (2) The desorption step and the acid treatment step are performed in the first adsorption tower, and the water to be treated is introduced into the second adsorption tower to perform the adsorption step.
    (3) The second adsorption tower and the first adsorption tower are connected in series in this order, the water to be treated is sequentially introduced into the second adsorption tower and the first adsorption tower, and the adsorption step is performed in the second adsorption tower. 1 Perform the pretreatment step in the adsorption tower.
    (4) The desorption step and the acid treatment step are performed in the second adsorption tower, and the water to be treated is introduced into the first adsorption tower to perform the adsorption step.
  11. 前記(1)のステージにおいて、第1吸着塔から排出される第1処理水のフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら前記(2)のステージに移り、
    前記(3)のステージにおいて、第2吸着塔から排出される第1処理水のフッ素イオン濃度を測定し、当該フッ素イオン濃度が所定値を超えたら前記(4)のステージに移る請求項10に記載の水処理方法。
    In the stage (1), the fluorine ion concentration of the first treated water discharged from the first adsorption tower is measured, and when the fluorine ion concentration exceeds a predetermined value, the process proceeds to the stage (2).
    In the step (3), the fluorine ion concentration of the first treated water discharged from the second adsorption tower is measured, and when the fluorine ion concentration exceeds a predetermined value, the process proceeds to the stage (4). The water treatment method described.
  12. 前記(1)のステージにおいて、第1吸着塔の吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら前記(2)のステージに移り、
    前記(3)のステージにおいて、第2吸着塔の吸着剤によって吸着されたフッ素イオンの累積吸着量が所定値を超えたら前記(4)のステージに移る請求項10または11に記載の水処理方法。
    In the stage (1), when the cumulative adsorption amount of fluorine ions adsorbed by the adsorbent in the first adsorption tower exceeds a predetermined value, the process proceeds to the stage (2).
    The water treatment method according to claim 10 or 11, wherein when the cumulative adsorption amount of fluorine ions adsorbed by the adsorbent of the second adsorption tower in the stage (3) exceeds a predetermined value, the stage moves to the stage (4). ..
  13. 前記被処理水が、排煙脱硫設備から排出される排煙脱硫排水である請求項1〜12のいずれか一項に記載の水処理方法。 The water treatment method according to any one of claims 1 to 12, wherein the water to be treated is flue gas desulfurization wastewater discharged from a flue gas desulfurization facility.
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