JP4193234B2 - Pure water production method - Google Patents
Pure water production method Download PDFInfo
- Publication number
- JP4193234B2 JP4193234B2 JP23071898A JP23071898A JP4193234B2 JP 4193234 B2 JP4193234 B2 JP 4193234B2 JP 23071898 A JP23071898 A JP 23071898A JP 23071898 A JP23071898 A JP 23071898A JP 4193234 B2 JP4193234 B2 JP 4193234B2
- Authority
- JP
- Japan
- Prior art keywords
- water
- reverse osmosis
- stage
- osmosis membrane
- membrane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Landscapes
- Separation Using Semi-Permeable Membranes (AREA)
- Physical Water Treatments (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は純水の製造方法に係り、特に原水を脱気した後、３段逆浸透膜（ＲＯ膜）分離処理して高水質の純水を高回収率で製造する方法に関する。
【０００２】
【従来の技術】
半導体製造工程等で使用される純水を、主に原水のＲＯ処理を行って製造する方法として、従来、次のような方法が提案されている。
【０００３】
(1) 市水等の原水に酸を添加して炭酸イオン分解（ＣＯ２化）した水を膜脱気
装置で脱気処理した後、２段に直列配置したＲＯ膜分離装置に順次通水して
２段ＲＯ処理する方法（特公平８−２９３１５号公報）
(2) 原水を３段に直列配置したＲＯ膜分離装置に順次通水して３段ＲＯ処理す
る方法であって、１段目のＲＯ処理水にアルカリを添加して２段目のＲＯ膜
分離装置に供給する方法（特開平７−１６５６５号公報）
(3) 原水を２段に直列配置したＲＯ膜分離装置に順次通水して２段ＲＯ処理す
る方法であって、酸性条件の原水を１段目のＲＯ膜分離装置に通水し、１段
目のＲＯ処理水にアルカリを添加した後２段目のＲＯ膜分離装置に通水し、
２段目のＲＯ膜分離装置の濃縮水を１段目のＲＯ膜分離装置の給水側に返送
して水回収率を高める方法（特開昭６２−４２７８７号公報）
【０００４】
【発明が解決しようとする課題】
上記従来の純水の製造方法では、十分に純度の高い純水を得ることはできない。このため、半導体製造工程等で必要とされる比抵抗１０ＭΩ・ｃｍ以上の水質の純水を得るためには、更に後段に非再生型イオン交換装置等を設けて処理する必要があるが、この場合には、後段のイオン交換装置の負荷が過大となることから、イオン交換装置として非再生型のものを用いた場合には、数ケ月程度で交換する必要があり、メンテナンス作業が著しく手間のかかるものとなる。
【０００５】
また、特に▲３▼の方法では１段目のＲＯ処理を酸性条件で行うため、この１段目のＲＯ膜分離装置で炭酸成分を殆ど除去することができず、この炭酸成分をアルカリ条件の２段目のＲＯ膜分離装置で除去することから、１段目のＲＯ膜分離装置には炭酸成分が濃縮され、返送水として不適当な２段目ＲＯ膜分離装置の濃縮水が返送されるという欠点もある。
【０００６】
本発明は上記従来の問題点を解決し、イオン交換装置を用いることなくＲＯ処理により比抵抗１５ＭΩ・ｃｍ以上の高水質の純水を、高い水回収率で得ることができる純水の製造方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の純水の製造方法は、原水を３段に直列配置された第１段目、第２段目及び第３段目の逆浸透膜分離装置に順次通水して純水を製造する方法において、原水をｐＨ６以下に調整して脱気処理した後、第１段目の逆浸透膜分離装置に通水し、第１段目の逆浸透膜分離装置の透過水にアルカリを添加してアルカリ条件とした後、第２段目の逆浸透膜分離装置及び第３段目の逆浸透膜分離装置に順次通水し、第１段目の逆浸透膜分離装置の濃縮水を第４の逆浸透膜分離装置に通水して透過水を得、該透過水を第２段目の逆浸透膜分離装置の濃縮水及び第３段目の逆浸透膜分離装置の濃縮水と混合して脱気処理した後、第１段目の逆浸透膜分離装置に給水することを特徴とする。
【０００８】
本発明においては、活性炭処理等の前処理を行った原水をｐＨ６以下に調整して脱気処理した後第１段目の逆浸透膜分離装置（第１ＲＯ装置）に通水し、第１ＲＯ装置の透過水にアルカリを添加してアルカリ条件とした後第２段目の逆浸透膜分離装置（第２ＲＯ装置）及び第３段目の逆浸透膜分離装置（第３ＲＯ装置）に順次通水する。
【０００９】
原水をｐＨ６以下に調整した後脱気処理することにより、原水中に含まれる、ＲＯ処理では除去し難い炭酸成分をＣＯ2の形態として効率的に除去することができる。
【００１０】
脱気処理水を第１ＲＯ装置に給水する場合、この脱気処理水は酸性であるため、第１ＲＯ装置のＲＯ膜へシリカやカルシウム、アルミニウム等のスケールが析出し難く、安定運転のために有利である。また、この第１ＲＯ装置の流入水が酸性であることにより、アンモニアの除去が効率的に行われる。ただし、前段の脱気処理で残存した炭酸の除去率は酸性条件であるため低い。
【００１１】
この第１ＲＯ装置の透過水にアルカリを添加してアルカリ性とし、第２ＲＯ装置及び第３ＲＯ装置に順次通水して処理することにより、イオン交換装置を用いることなく、比抵抗１５ＭΩ・ｃｍ以上の高水質の純水を得ることができる。
【００１２】
ところで、第１ＲＯ装置の濃縮水は、イオン濃度が高いため第１ＲＯ装置の給水として返送することは不適当であるが、これを第４のＲＯ装置でＲＯ処理して得られる透過水と混合した混合水は、イオン濃度が低減されているため、第１ＲＯ装置の給水として返送することができる。このように第１ＲＯ装置の濃縮水の一部を返送することにより、水の利用効率を高め、水回収率を高めることができる。なお、第１ＲＯ装置の給水は酸性の水であるため、第１ＲＯ装置の濃縮水も酸性であり、これをＲＯ処理して得られる透過水も酸性となる。
【００１３】
一方、第２，第３ＲＯ装置の濃縮水はアルカリ性であり、このアルカリ性の第２，第３ＲＯ装置の濃縮水には、イオン形態の炭酸成分が濃縮されている。この第２，第３ＲＯ装置の濃縮水を、酸性の第４ＲＯ装置透過水と混合すると、混合水は酸性となり、炭酸成分はＣＯ2の形態となる。従って、この混合水を脱気処理することにより、該混合水中の炭酸成分を効率的に除去することができ、第１ＲＯ装置に給水する返送水として適した水質とすることができる。また、水を循環処理することによる系内の炭酸成分の蓄積が防止される。
【００１４】
本発明において、原水の脱気処理、及び、第４ＲＯ装置透過水と第２，第３ＲＯ装置の濃縮水との混合水の脱気処理は、膜脱気により行うのが好ましい。
【００１５】
なお、第３ＲＯ装置に流入する第２ＲＯ装置の透過水は、塩類濃度が十分に低減されているので、第３ＲＯ装置のＲＯ膜としては低塩類濃度域における塩類阻止率の高い正荷電膜を用いるのが好ましい。即ち、ＲＯ膜の塩類阻止率は、原水中の塩類濃度が低くなるにつれて低下する傾向があるが、第３ＲＯ装置のＲＯ膜として正荷電膜を用いることにより、第３ＲＯ装置においても著しく高いＲＯ処理効果を得ることができ、きわめて高水質の純水を製造することが可能となる。
【００１６】
【発明の実施の形態】
以下に、図面を参照して本発明の実施の形態を説明する。
【００１７】
図１は本発明の純水の製造方法の実施の形態を示す系統図である。
【００１８】
本実施の形態においては、市水、井水、工業用水等を原水として、必要に応じて凝集沈澱、膜濾過、活性炭処理等の前処理を施した後（図１では活性炭塔１に通水した後）、ＨＣｌ，Ｈ2ＳＯ4等の酸を添加して原水中のＭ−アルカリ成分の主体をなすＨＣＯ3 -，ＣＯ3 2-イオンを脱気装置で除去し易いＣＯ2の形態とする。この酸性水を膜脱気装置、真空脱気装置、窒素脱気装置、脱炭酸塔等の脱気装置２（好ましくは膜脱気装置）に通水する。なお、酸の添加量は、脱気処理される水のｐＨが６以下、好ましくは５以下、特に３〜５程度となるような量とするのが好ましい。例えば、膜脱気装置を用い、ｐＨ４．５の条件で脱気処理した場合には、炭酸除去率を９５％以上に高めることができる。
【００１９】
脱気装置２では、原水中のＣＯ2を気相に移行させて除去すると共に原水中の溶存酸素も気相に移行させて除去する。
【００２０】
脱気処理水は、第１ＲＯ装置３に導入してＲＯ処理する。この第１ＲＯ装置３では、原水に添加した酸により調整された低ｐＨ条件下において、主にＮａ+イオンやアンモニア等のカチオン成分を除去する。
【００２１】
即ち、一般にＲＯ膜処理においては、Ｎａ+イオン等のカチオン成分はｐＨ３〜５の低ｐＨ領域で高い除去率を示し、逆にＣｌ-イオン等のアニオン成分はｐＨ５．５以上で高い除去率を示すため、第１ＲＯ装置３では低ｐＨの脱気処理水について主にカチオン成分の除去を行う。
【００２２】
なお、この第１ＲＯ装置３のＲＯ処理はｐＨ３〜５の範囲で行うのが好ましい。従って、脱気処理水のｐＨがこの範囲よりも高い場合には脱気処理水に更に酸を添加してｐＨ調整を行ってから第１ＲＯ装置３に流入させるのが好ましい。
【００２３】
第１ＲＯ装置の透過水は、次いで、ＮａＯＨ等のアルカリを添加してｐＨ６．５〜８、例えばｐＨ７．５程度に調整した後、第２ＲＯ装置４に導入してＲＯ処理する。この第２ＲＯ装置４の入口側でのｐＨ調整は、得られる処理水（第３ＲＯ装置５の透過水）の比抵抗が十分に低くなるように設定すれば良く、例えば、第３ＲＯ装置５の透過水の比抵抗を測定し、この測定値に基いて最適ｐＨ設定値をフィードバック制御にて調整するようにするのが好ましい。
【００２４】
第２ＲＯ装置４の透過水の水質は比抵抗で数ＭΩ・ｃｍから最高でも６〜７ＭΩ・ｃｍ程度であるため、本発明では、更に水質を向上させるために、第２ＲＯ装置４の透過水を第３ＲＯ装置５に導入してＲＯ処理する。この第３ＲＯ装置５の透過水は処理水として系外へ取り出される。
【００２５】
本発明では、このような３段ＲＯ処理において、第１ＲＯ装置３の濃縮水を第４ＲＯ装置６でＲＯ処理し、得られた透過水を第２，第３ＲＯ装置４，５の濃縮水と共に脱気装置７で脱気処理した後、第１ＲＯ装置３の給水として再利用する。この脱気装置７としても膜脱気装置を用いるのが好ましく、膜脱気により効率的な脱気処理を行える。なお、第４ＲＯ装置の濃縮水は系外に排出される。
【００２６】
なお、本発明において、第１，第２ＲＯ装置３，４のＲＯ膜として日東電工社製「ＥＳ２０」、東レ株式会社製「ＳＵ７１０」等の負荷電膜を用いることができる。
【００２７】
また、第３ＲＯ装置５のＲＯ膜としては、前述の如く、低塩類濃度域における塩類阻止率の高い正荷電膜、例えば、塩類濃度１〜１０ｐｐｍというような低塩類濃度域における塩類阻止率が９９％以上のＲＯ膜、具体的には、日東電工社製「ＮＴＲ−７１９ＨＦ」，「ＥＳ１０Ｃ」、東レ株式会社製「ＳＵ９００」（いずれもＮａＣｌ濃度１〜１０ｐｐｍでのＮａＣｌ阻止率９９％以上）等の正荷電膜を用いるのが好ましい。
【００２８】
第４ＲＯ装置６のＲＯ膜としては、日東電工社製「Ｅ５２０」、東レ株式会社製「ＳＵ７１０」、Ｆｉｌｍｔｅｃ社製「ＢＷ３０−４４０」等の負荷電膜を用いるのが好ましい。
【００２９】
なお、正荷電膜とは、限外濾過膜の上に界面架橋のような方法で薄いスキン層を形成してなるＲＯ複合膜のうち、カチオン基、例えば第四アンモニウム基等を導入することにより、膜表面を正に帯電させたものであり、一方、負荷電膜とは、このようなＲＯ複合膜において、アニオン基、例えばカルボキシル基等を導入して膜表面を負に帯電させたものである。
【００３０】
各ＲＯ装置の採水率については特に制限はないが、給水（１００％）に対して次のような範囲とするのが好ましい。
【００３１】
【００３２】
このような本発明の方法によれば、処理水（第３ＲＯ装置の透過水）として、比抵抗１５ＭΩ・ｃｍ以上の高水質の純水を得ることができる。従って、この純水は更にイオン交換処理することなく使用することもでき、また、更にイオン交換処理する場合においては、イオン交換装置の負荷を大幅に軽減することができ、非再生型イオン交換装置の場合、その寿命を６ケ月〜１年以上に大幅に延長することができる。このため、メンテナンス作業が大幅に軽減される。
【００３３】
しかも、第１ＲＯ装置の濃縮水をＲＯ処理して得られる透過水及び第２，第３ＲＯ装置の濃縮水を返送して再利用することにより、水回収率を大幅に高めることができる。
【００３４】
【実施例】
以下に実施例を挙げて本発明をより具体的に説明する。
【００３５】
実施例１
図１に示す本発明の方法により、半導体工場の回収水と市水を混合した水を原水として純水の製造を行った。
【００３６】
まず、原水を活性炭塔１に通水後、ＨＣｌを添加してｐＨ４．５に調整して膜脱気装置（脱気膜：ポリプロピレン膜）２に通水して脱気処理した後第１ＲＯ装置３に通水した。そして、この第１ＲＯ装置３の透過水にＮａＯＨを添加してｐＨ７．５とし、第２，第３ＲＯ装置４，５に通水した。
【００３７】
第１ＲＯ装置３の濃縮水は第４ＲＯ装置６でＲＯ処理し、濃縮水は系外へ排出した。第４ＲＯ装置６の透過水と第２，第３ＲＯ装置４，５の濃縮水とを合流させて膜脱気装置（脱気膜：ポリプロピレン膜）７に通水して脱気処理し、第１ＲＯ装置３の給水とした。
【００３８】
なお、各ＲＯ装置３，４，５，６で用いたＲＯ膜及び給水、透過水及び濃縮水量は次の通りである。
【００３９】
第１ＲＯ装置３：
ＲＯ膜＝日東電工社製「ＥＳ２０」（ポリアミド製）
給水量＝１１４．８ｍ3／ｈｒ
透過水量＝９１．９ｍ3／ｈｒ
濃縮水量＝２２．９ｍ3／ｈｒ
第２ＲＯ装置４：
ＲＯ膜＝日東電工社製「ＥＳ２０」（ポリアミド製）
給水量＝９１．９ｍ3／ｈｒ
透過水量＝７３．５ｍ3／ｈｒ
濃縮水量＝１８．４ｍ3／ｈｒ
第３ＲＯ装置５：
ＲＯ膜＝日東電工社製「ＥＳ１０Ｃ」（ポリアミド製）
給水量＝７３．５ｍ3／ｈｒ
透過水量＝５８．８ｍ3／ｈｒ
濃縮水量＝１４．７ｍ3／ｈｒ
第４ＲＯ装置６：
ＲＯ膜＝日東電工社製「ＥＳ２０」（ポリアミド製）
給水量＝２２．９ｍ3／ｈｒ
透過水量＝１８．３ｍ3／ｈｒ
濃縮水量＝４．６ｍ3／ｈｒ
原水を膜脱気装置２で脱気処理して得られた脱気処理水、第１ＲＯ装置３の濃縮水のＲＯ透過水と第２，第３ＲＯ装置４，５の濃縮水とを膜脱気装置７で脱気処理して得られた返送脱気処理水及び得られた処理水（第３ＲＯ装置５の透過水）の水質を表１に示す。
【００４０】
【表１】
表１より明らかなように、返送脱気処理水は原水を脱気処理した水よりも高水質であり、各ＲＯ装置の濃縮水を再利用した上で比抵抗１５．５ＭΩ・ｃｍという極めて高水質の純水を得ることができた。
【００４２】
しかも、このように濃縮水を返送することで、水回収率を９２．７％とすることができ、濃縮水を全く返送しない場合の水回収率５１．２％に比べて、水の利用効率を大幅に高めることができた。
【００４３】
【発明の効果】
以上詳述した通り、本発明の純水の製造方法によれば、イオン交換設備を用いることなく、比抵抗１５ＭΩ・ｃｍ以上の高水質の純水を高い水回収率で得ることができる。
【図面の簡単な説明】
【図１】本発明の純水の製造方法の実施の形態を示す系統図である。
【符号の説明】
１ 活性炭塔
２ 脱気装置
３ 第１ＲＯ装置
４ 第２ＲＯ装置
５ 第３ＲＯ装置
６ 第４ＲＯ装置
７ 脱気装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing pure water, and more particularly to a method for producing high-quality pure water at a high recovery rate by degassing raw water and then performing a three-stage reverse osmosis membrane (RO membrane) separation treatment.
[0002]
[Prior art]
Conventionally, the following method has been proposed as a method of manufacturing pure water used in a semiconductor manufacturing process or the like by mainly performing RO treatment of raw water.
[0003]
(1) After adding water to raw water such as city water and decomposing carbonic acid ions (CO 2 ) using a membrane deaerator, water is sequentially passed through RO membrane separators arranged in two stages. And 2-stage RO treatment (Japanese Patent Publication No. 8-29315)
(2) Raw water is passed through RO membrane separators arranged in series in three stages, and then the three-stage RO treatment is performed. Alkali is added to the first-stage RO treated water, and the second-stage RO is treated. Method of supplying to a membrane separator (Japanese Patent Laid-Open No. 7-16565)
(3) The raw water is passed through RO membrane separators arranged in series in two stages in order to perform two-stage RO treatment. The raw water under acidic conditions is passed through the first stage RO membrane separator, After adding alkali to the first-stage RO treated water, water is passed through the second-stage RO membrane separator,
How the concentrated water of the second-stage RO membrane separation device and return to the water supply side of the first-stage RO membrane separator increase the water recovery rate (Japanese Open Sho 62-4 2 787 JP)
[0004]
[Problems to be solved by the invention]
In the conventional method for producing pure water, pure water with sufficiently high purity cannot be obtained. For this reason, in order to obtain pure water having a specific resistance of 10 MΩ · cm or more required in the semiconductor manufacturing process or the like, it is necessary to further provide a non-regenerative ion exchange apparatus or the like in the subsequent stage. In this case, since the load of the ion exchange apparatus at the latter stage becomes excessive, if a non-regenerative type ion exchange apparatus is used, it needs to be replaced in several months, and maintenance work is extremely troublesome. It becomes such a thing.
[0005]
Particularly, in the method (3), since the first-stage RO treatment is carried out under acidic conditions, the first-stage RO membrane separation apparatus can hardly remove the carbonic acid components. Since it is removed by the second-stage RO membrane separator, the carbonate component is concentrated in the first-stage RO membrane separator, and the concentrated water of the second-stage RO membrane separator that is inappropriate as the return water is returned. There is also a drawback.
[0006]
The present invention solves the above-mentioned conventional problems, and a method for producing pure water capable of obtaining high-quality pure water having a specific resistance of 15 MΩ · cm or more by a RO treatment without using an ion exchange device at a high water recovery rate. The purpose is to provide.
[0007]
[Means for Solving the Problems]
The pure water production method of the present invention produces pure water by sequentially passing raw water through the first, second, and third-stage reverse osmosis membrane separators arranged in series in three stages. In the method, after the raw water is adjusted to pH 6 or less and deaerated, water is passed through the first-stage reverse osmosis membrane separator, and alkali is added to the permeated water of the first-stage reverse osmosis membrane separator. Then, the water is passed through the second-stage reverse osmosis membrane separator and the third-stage reverse osmosis membrane separator sequentially, and the concentrated water from the first-stage reverse osmosis membrane separator is passed through the fourth condition. Water is passed through the reverse osmosis membrane separator to obtain permeate, and the permeate is mixed with the concentrated water of the second-stage reverse osmosis membrane separator and the concentrated water of the third-stage reverse osmosis membrane separator. After the deaeration treatment, water is supplied to the first-stage reverse osmosis membrane separation device.
[0008]
In the present invention, the raw water subjected to preprocessing such as activated carbon treatment was passed through the adjustment to the reverse osmosis membrane separation apparatus of the first stage was deaerated (first 1RO device) to pH6 below, the After adding alkali to the permeated water of the 1 RO apparatus to obtain an alkaline condition, sequentially pass through the second-stage reverse osmosis membrane separation apparatus (second RO apparatus) and the third-stage reverse osmosis membrane separation apparatus (third RO apparatus). Water.
[0009]
By adjusting the raw water to pH 6 or lower and then performing a degassing treatment, the carbonic acid component contained in the raw water, which is difficult to remove by the RO treatment, can be efficiently removed in the form of CO 2 .
[0010]
When supplying degassed treated water to the first RO device, since this degassed treated water is acidic, scales such as silica, calcium, and aluminum hardly deposit on the RO membrane of the first RO device, which is advantageous for stable operation. It is. Further, ammonia is efficiently removed because the inflow water of the first RO device is acidic. However, the removal rate of carbonic acid remaining in the preceding degassing treatment is low because of the acidic conditions.
[0011]
Alkali is added to the permeated water of the first RO device to make it alkaline, and water is sequentially passed through the second RO device and the third RO device for treatment, so that a specific resistance of 15 MΩ · cm or higher is achieved without using an ion exchange device. Water quality pure water can be obtained.
[0012]
By the way, the concentrated water of the first RO device is unsuitable to be returned as the feed water of the first RO device due to its high ion concentration, but this was mixed with the permeated water obtained by RO treatment with the fourth RO device . mixing water, the ion concentration is reduced, Ru can be returned as feed water of the 1RO device. By returning a part of the concentrated water of the first RO device in this way, it is possible to increase the water use efficiency and the water recovery rate. In addition, since the water supply of a 1st RO apparatus is acidic water, the concentrated water of a 1st RO apparatus is also acidic, and the permeated water obtained by carrying out RO process also becomes acidic.
[0013]
On the other hand, the concentrated water of the second and third RO devices is alkaline, and the ionic carbonic acid component is concentrated in the concentrated water of the alkaline second and third RO devices. When the concentrated water of the second and third RO devices is mixed with the acidic fourth RO device permeated water, the mixed water becomes acidic and the carbonic acid component is in the form of CO 2 . Therefore, by degassing the mixed water, the carbonic acid component in the mixed water can be efficiently removed, and the water quality suitable for the return water supplied to the first RO device can be obtained. In addition, accumulation of carbonic acid components in the system by circulating water is prevented.
[0014]
In this invention, it is preferable to perform the deaeration process of raw | natural water and the deaeration process of the mixed water of a 4th RO apparatus permeated water and the concentrated water of a 2nd, 3rd RO apparatus by membrane deaeration.
[0015]
Since the permeated water of the second RO device flowing into the third RO device has a sufficiently low salt concentration, a positively charged membrane having a high salt rejection in the low salt concentration region is used as the RO membrane of the third RO device. Is preferred. That is, the salt rejection rate of the RO membrane tends to decrease as the salt concentration in the raw water decreases, but by using a positively charged membrane as the RO membrane of the third RO device, the RO treatment is also extremely high in the third RO device. An effect can be acquired and it becomes possible to manufacture pure water of very high quality.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
FIG. 1 is a system diagram showing an embodiment of a method for producing pure water according to the present invention.
[0018]
In this embodiment, city water, well water, industrial water, etc. are used as raw water, and after pre-treatment such as coagulation precipitation, membrane filtration, activated carbon treatment, etc. as necessary (in FIG. 1, water is passed through activated carbon tower 1). after), HCl, HCO 3 forming a main body of the acid addition to M- alkaline component in the raw water and the like H 2 SO 4 -, and the form of easily CO 2 to remove CO 3 2- ions in the degasser To do. This acidic water is passed through a degassing device 2 (preferably a membrane degassing device) such as a membrane degassing device, a vacuum degassing device, a nitrogen degassing device, or a decarbonation tower. The amount of acid added is preferably such that the pH of the water to be degassed is 6 or less, preferably 5 or less, particularly about 3 to 5. For example, when a membrane deaerator is used and a deaeration process is performed under the condition of pH 4.5, the carbonation removal rate can be increased to 95% or more.
[0019]
In the deaeration device 2, CO 2 in the raw water is transferred to the gas phase and removed, and dissolved oxygen in the raw water is also transferred to the gas phase and removed.
[0020]
The degassed water is introduced into the first RO device 3 for RO treatment. The first RO device 3 mainly removes cation components such as Na + ions and ammonia under the low pH condition adjusted by the acid added to the raw water.
[0021]
That is, in general, in RO membrane treatment, cation components such as Na + ions show a high removal rate at a low pH range of pH 3 to 5, and conversely, anion components such as Cl − ions show a high removal rate at pH 5.5 or more. For the sake of illustration, the first RO device 3 mainly removes the cation component from the low pH degassed water.
[0022]
In addition, it is preferable to perform RO processing of this 1st RO apparatus 3 in the range of pH 3-5. Therefore, when the pH of the degassed treated water is higher than this range, it is preferable to add an acid to the degassed treated water to adjust the pH before flowing into the first RO device 3.
[0023]
Next, the permeated water of the first RO device is adjusted to pH 6.5-8, for example, about pH 7.5 by adding an alkali such as NaOH, and then introduced into the second RO device 4 for RO treatment. The pH adjustment on the inlet side of the second RO device 4 may be set so that the specific resistance of the treated water (permeated water of the third RO device 5) obtained is sufficiently low. For example, the permeation of the third RO device 5 It is preferable to measure the specific resistance of water and adjust the optimum pH set value by feedback control based on the measured value.
[0024]
Since the water quality of the permeated water of the second RO device 4 is several MΩ · cm in specific resistance to 6-7 MΩ · cm at the maximum, in the present invention, the permeated water of the second RO device 4 is used to further improve the water quality. It introduces into the 3rd RO device 5, and performs RO processing. The permeated water of the third RO device 5 is taken out of the system as treated water.
[0025]
In the present invention, in such a three-stage RO treatment, the concentrated water of the first RO device 3 is RO-treated by the fourth RO device 6, and the obtained permeate is removed together with the concentrated water of the second and third RO devices 4 and 5. After deaeration processing in the air device 7, the air is reused as water supply for the first RO device 3. It is preferable to use a membrane deaerator as the deaerator 7 and an efficient deaeration process can be performed by the membrane deaeration. The concentrated water of the fourth RO device is discharged out of the system.
[0026]
In the present invention, a negative electrode membrane such as “ES20” manufactured by Nitto Denko Corporation or “SU710” manufactured by Toray Industries, Inc. can be used as the RO membrane of the first and second RO devices 3 and 4.
[0027]
Further, as described above, the RO membrane of the third RO device 5 is a positively charged membrane having a high salt rejection rate in a low salt concentration range, for example, a salt rejection rate in a low salt concentration range such as a salt concentration of 1 to 10 ppm is 99. % RO membrane, specifically, “NTR-719HF”, “ES10C” manufactured by Nitto Denko Corporation, “SU900” manufactured by Toray Industries, Inc. (all with a NaCl rejection of 99% or higher at a NaCl concentration of 1-10 ppm), etc. It is preferable to use a positively charged film.
[0028]
As the RO membrane of the fourth RO device 6, it is preferable to use a load membrane such as “E520” manufactured by Nitto Denko Corporation, “SU710” manufactured by Toray Industries, Inc., “BW30-440” manufactured by Filmtec.
[0029]
The positively charged membrane is a RO composite membrane formed by forming a thin skin layer on the ultrafiltration membrane by a method such as interfacial crosslinking, by introducing a cation group such as a quaternary ammonium group. On the other hand, the negatively charged membrane is a negatively charged membrane surface by introducing an anion group such as a carboxyl group in such an RO composite membrane. is there.
[0030]
Although there is no restriction | limiting in particular about the water collection rate of each RO apparatus, It is preferable to set it as the following ranges with respect to water supply (100%).
[0031]
[0032]
According to such a method of the present invention, high-quality pure water having a specific resistance of 15 MΩ · cm or more can be obtained as treated water (permeated water of the third RO device). Therefore, this pure water can be used without further ion exchange treatment, and in the case of further ion exchange treatment, the load of the ion exchange device can be greatly reduced. In this case, the lifetime can be extended significantly from 6 months to 1 year or more. For this reason, the maintenance work is greatly reduced.
[0033]
Moreover, the water recovery rate can be greatly increased by returning and reusing the permeated water obtained by RO treatment of the concentrated water of the first RO device and the concentrated water of the second and third RO devices.
[0034]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0035]
Example 1
By the method of the present invention shown in FIG. 1, pure water was produced using raw water obtained by mixing water collected from a semiconductor factory and city water.
[0036]
First, after passing raw water through the activated carbon tower 1, HCl is added to adjust the pH to 4.5, and water is passed through the membrane deaerator (deaerator membrane: polypropylene membrane) 2 for deaeration treatment, followed by the first RO device. 3 was passed through. Then, NaOH was added to the permeated water of the first RO device 3 to adjust the pH to 7.5, and the water was passed through the second and third RO devices 4 and 5.
[0037]
The concentrated water of the first RO device 3 was subjected to RO treatment by the fourth RO device 6, and the concentrated water was discharged out of the system. The permeated water of the fourth RO device 6 and the concentrated water of the second and third RO devices 4 and 5 are merged and passed through a membrane deaerator (deaeration membrane: polypropylene membrane) 7 for deaeration treatment. The water supply for the device 3 was used.
[0038]
The RO membrane, water supply, permeated water, and concentrated water used in each RO device 3, 4, 5, 6 are as follows.
[0039]
First RO device 3:
RO membrane = Nitto Denko "ES20" (polyamide)
Water supply amount = 114.8 m 3 / hr
Permeated water amount = 91.9 m 3 / hr
Concentrated water amount = 22.9 m 3 / hr
Second RO device 4:
RO membrane = Nitto Denko "ES20" (polyamide)
Water supply amount = 91.9 m 3 / hr
Permeated water amount = 73.5m 3 / hr
Concentrated water amount = 18.4 m 3 / hr
Third RO device 5:
RO membrane = Nitto Denko “ES10C” (polyamide)
Water supply amount = 73.5m 3 / hr
Permeated water volume = 58.8m 3 / hr
Concentrated water volume = 14.7 m 3 / hr
Fourth RO device 6:
RO membrane = Nitto Denko "ES20" (polyamide)
Water supply amount = 22.9m 3 / hr
Permeated water volume = 18.3m 3 / hr
Concentrated water amount = 4.6 m 3 / hr
Membrane deaeration of degassed treated water obtained by degassing raw water with the membrane deaerator 2, RO permeated water of the first RO device 3, and concentrated water of the second and third RO devices 4, 5 Table 1 shows the water quality of the returned degassed treated water obtained by the degassing treatment with the device 7 and the obtained treated water (permeated water of the third RO device 5).
[0040]
[Table 1]
As is clear from Table 1, the return degassed water is higher in quality than the water degassed from the raw water, and the specific resistance of 15.5 MΩ · cm is extremely high after reusing the concentrated water of each RO device. Pure water with high quality could be obtained.
[0042]
Moreover, by returning the concentrated water in this way, the water recovery rate can be 92.7%, compared with the water recovery rate of 51.2% when the concentrated water is not returned at all, and the water utilization efficiency. We were able to raise significantly.
[0043]
【The invention's effect】
As described above in detail, according to the method for producing pure water of the present invention, high-quality pure water having a specific resistance of 15 MΩ · cm or more can be obtained at a high water recovery rate without using an ion exchange facility.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a method for producing pure water according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Activated carbon tower 2 Deaeration apparatus 3 1st RO apparatus 4 2nd RO apparatus 5 3rd RO apparatus 6 4th RO apparatus 7 Deaeration apparatus
Claims (3)
原水をｐＨ６以下に調整して脱気処理した後、第１段目の逆浸透膜分離装置に通水し、
第１段目の逆浸透膜分離装置の透過水にアルカリを添加してアルカリ条件とした後、第２段目の逆浸透膜分離装置及び第３段目の逆浸透膜分離装置に順次通水し、
第１段目の逆浸透膜分離装置の濃縮水を第４の逆浸透膜分離装置に通水して透過水を得、該透過水を第２段目の逆浸透膜分離装置の濃縮水及び第３段目の逆浸透膜分離装置の濃縮水と混合して脱気処理した後、第１段目の逆浸透膜分離装置に給水することを特徴とする純水の製造方法。In a method for producing pure water by sequentially passing raw water through the reverse osmosis membrane separation devices of the first stage, the second stage, and the third stage arranged in series in three stages,
After the raw water is adjusted to pH 6 or less and degassed, it is passed through the first-stage reverse osmosis membrane separator,
After adding alkali to the permeated water of the first-stage reverse osmosis membrane separation apparatus to make the alkaline condition, water is sequentially passed through the second-stage reverse osmosis membrane separation apparatus and the third-stage reverse osmosis membrane separation apparatus. And
The concentrated water of the first-stage reverse osmosis membrane separation device is passed through the fourth reverse osmosis membrane separation device to obtain permeated water, and the permeated water is used as the concentrated water of the second-stage reverse osmosis membrane separation device and A method for producing pure water, comprising: mixing with concentrated water of a third-stage reverse osmosis membrane separator and deaeration treatment, and then supplying water to the first-stage reverse osmosis membrane separator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23071898A JP4193234B2 (en) | 1998-08-17 | 1998-08-17 | Pure water production method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23071898A JP4193234B2 (en) | 1998-08-17 | 1998-08-17 | Pure water production method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000061464A JP2000061464A (en) | 2000-02-29 |
| JP4193234B2 true JP4193234B2 (en) | 2008-12-10 |
Family
ID=16912232
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23071898A Expired - Fee Related JP4193234B2 (en) | 1998-08-17 | 1998-08-17 | Pure water production method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4193234B2 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004167423A (en) * | 2002-11-21 | 2004-06-17 | Kurita Water Ind Ltd | Apparatus and method for pure water production |
| JP5910675B2 (en) * | 2014-07-03 | 2016-04-27 | 栗田工業株式会社 | Pure water production apparatus and pure water production method |
| CN108495822A (en) * | 2016-02-18 | 2018-09-04 | 奥加诺株式会社 | Using there is the anti-water treatment system and method for treating water for being impregnated with film |
| KR102291224B1 (en) * | 2016-10-25 | 2021-08-19 | 오르가노 코포레이션 | Water treatment method and water treatment device using reverse osmosis membrane |
| JP6532494B2 (en) * | 2017-03-16 | 2019-06-19 | 栗田工業株式会社 | Reverse osmosis processing method and apparatus |
| JP2018153799A (en) * | 2018-01-10 | 2018-10-04 | 栗田工業株式会社 | Reverse osmosis treatment method and device |
| JP2019205966A (en) * | 2018-05-29 | 2019-12-05 | イーセップ株式会社 | Method for separation of carbon dioxide (co2) membrane |
| JP7074169B2 (en) * | 2020-09-16 | 2022-05-24 | 栗田工業株式会社 | Membrane filtration system and its control method |
| JP7460729B1 (en) | 2022-10-26 | 2024-04-02 | 野村マイクロ・サイエンス株式会社 | Pure water production method, pure water production equipment, and ultrapure water production system |
-
1998
- 1998-08-17 JP JP23071898A patent/JP4193234B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000061464A (en) | 2000-02-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3187629B2 (en) | Reverse osmosis membrane treatment method | |
| US8491795B2 (en) | Conversion of seawater to drinking water at room temperature | |
| CN108249646A (en) | Can resource recycling power plant desulfurization wastewater Zero-discharge treating process and device | |
| JP3575271B2 (en) | Pure water production method | |
| JP5135749B2 (en) | Method and apparatus for recovering phosphoric acid from phosphoric acid-containing water | |
| CN105692989B (en) | The comprehensive utilization process of viscose fiber acid waste water | |
| CN209602165U (en) | A kind of ferric phosphate wastewater zero discharge processing unit | |
| JP4193234B2 (en) | Pure water production method | |
| US20240116002A1 (en) | Systems and methods for direct lithium hydroxide production | |
| KR20150070895A (en) | A Draw Solution for forward osmosis using salt of organic acid and use thereof | |
| JPH11502460A (en) | Method and apparatus for purifying mixed acid | |
| CN103663774A (en) | Method for treating low-concentration ammonia-containing wastewater by use of membrane separation technology | |
| JP2004167423A (en) | Apparatus and method for pure water production | |
| JPH10314735A (en) | Pure water preparation process | |
| JPH05269463A (en) | Membrane separation apparatus | |
| JP3690032B2 (en) | Pure water production method | |
| CN106587450A (en) | Treatment system and treatment method for calcium ammonium nitrate production wastewater | |
| JPH09141260A (en) | Method for desalination of seawater | |
| JP4403622B2 (en) | Electrodemineralization treatment method and electrodesalination treatment apparatus | |
| JP3534155B2 (en) | Pure water production equipment | |
| JPH06296966A (en) | Decarbonating device and pure water producer assembled with the device | |
| KR19980042307A (en) | How to remove sulfate from magnesium chloride brine | |
| JP3115750B2 (en) | Pure water production method | |
| JPH09234349A (en) | Membrane separation apparatus | |
| JP2000061465A (en) | Production of demineralized water |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20050726 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20070413 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20070424 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20070621 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20080902 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20080915 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20111003 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20121003 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20131003 Year of fee payment: 5 |
|
| LAPS | Cancellation because of no payment of annual fees |