JP3863263B2

JP3863263B2 - Filtration method using hollow fiber membrane module

Info

Publication number: JP3863263B2
Application number: JP27143397A
Authority: JP
Inventors: 学矢能; 直也田中丸; 真澄小林; 達観下野
Original assignee: Mitsubishi Chemical Corp; Mitsubishi Rayon Co Ltd
Current assignee: Mitsubishi Chemical Corp
Priority date: 1997-10-03
Filing date: 1997-10-03
Publication date: 2006-12-27
Anticipated expiration: 2017-10-03
Also published as: JPH11104466A

Description

【０００１】
【産業上の利用分野】
本発明は、中空糸膜モジュールを用いた濾過方法に関し、特に有機物等による汚濁性の高い液体の処理に適した中空糸膜モジュールを用いた濾過方法に関する。
【０００２】
【従来の技術】
従来、中空糸膜モジュールは、無菌水、飲料水、高純度水の製造や、空気の浄化といったいわゆる精密濾過の分野において多く使用されてきたが、近年、下水処理場における二次処理、三次処理や、浄化槽における固液分離等の高汚濁性水処理用途に用いる検討が種々行われている。
【０００３】
高汚濁性水の濾過に適した中空糸膜モジュールとして、多本数の中空糸膜をシート状に並び拡げて配置し、中空糸膜の片端部または両端部が一つまたは異なる二つの構造材内において固定部材でそれぞれの開口状態を保ちつつ固定されてなる中空糸膜モジュールであって、固定部材の中空糸膜に垂直な断面の形状が細長いほぼ矩形であるような平型の中空糸膜モジュールが特開平５−２２０３５６号公報等により知られている。
【０００４】
この平型タイプの中空糸膜モジュールは、中空糸膜に気泡を当てて振動させての洗浄（スクラビング）を連続的または断続的に行いながら液体を濾過する方法により使用されているが、中空糸膜により形成されるシート状面が垂直になるように配置して用いることにより、中空糸膜の洗浄効率が向上し、高い濾過流量を長期間保てることが特開平７−２４２６４号公報により知られている。この場合、モジュールの端部に配置された構造材（導水管）が邪魔せずに気泡を中空糸膜に効率よく当てられるように、構造材を垂直に配置して中空糸膜の繊維軸が水平になるようにしていた。
【０００５】
【発明が解決しようとする課題】
しかし、本発明者等らは、スクラビングはエアーの供給量と、気泡の上昇に伴って発生する水槽内の上昇水流の速度に比例した効率で行われることを解明していたが、中空糸膜モジュールの場合には、上昇水流に対する抵抗が大きく平膜の場合ほど上昇水流の流速が上がらなかった。すなわち、エアーの供給量を増やしても比較的低い水準で洗浄効率が飽和してしまい、逆洗等の濾過を中断した大がかりな洗浄が早期に必要になり、装置効率が低下した。
【０００６】
本発明の目的は、高汚濁性水の濾過においても中空糸膜間に濁質が堆積しにくく、スクラビングがより効率的に実施でき、長期に亘って差圧の上昇及び濾過流量の低下が生じにくく、かつ中空糸膜の損傷のおそれも少い、中空糸膜モジュールを用いた濾過方法を提供することにある。
【０００７】
【課題を解決するための手段】
すなわち、本発明は、シート状に並び拡げて配設された中空糸膜と、中空糸膜の端部を開口状態を保ちつつこれを固定する固定部材と、固定部材を支持収納する構造材とを有してなる中空糸膜モジュールを用い、該モジュールの下方から気泡を連続的または断続的に供給しつつ液体を濾過する濾過方法において、該構造材の長手方向に垂直な断面形状が楕円または薬莢形である中空糸膜モジュールを用い、中空糸膜により形成されるシート状面がほぼ垂直となり、かつ中空糸膜の繊維軸方向がほぼ垂直となるように中空糸膜モジュールを配置して濾過することを特徴とする濾過方法である。
【０００８】
【発明の実施の形態】
従来、中空糸膜により形成されるシート状面が垂直になるように中空糸膜モジュールを被処理液槽中に配置して用いる濾過方法において中空糸膜を水平に配置していたのは、前述したように中空糸膜モジュールの端部に配置された導水管がスクラビングの邪魔にならないようにすることが大きな理由であった。また、通常、中空糸膜はモジュール中においてある程度緩みをもたせた状態で配設されているが、中空糸膜を垂直に配置した場合には、上昇水流が中空糸膜を引き上げるように作用し、そのため上方の固定部材による中空糸膜の固定部の近傍に中空糸膜のたるみが集中した。この際、そのたるみ部分に上昇水流により中空糸膜を折り曲げて水平方向へ引っ張る応力が発生し、固定部および折り曲げ部で中空糸膜が損傷するおそれがあることも一因であった。
【０００９】
以下、本発明の中空糸膜モジュールを用いた濾過方法につき、図面を参照しつつより詳細に説明する。
【００１０】
まず、本発明の濾過方法に用いる平型の中空糸膜モジュールにつき説明する。図１は、この中空糸膜モジュールの一例を示す平面図で、図２は、そのＡＡ線方向の断面図であり、図３は他の例を示す斜視図である。中空糸膜モジュール１は、基本的には、構造材２と、固定部材３と、中空糸膜４とを有して構成される。これらに加え、各種の付属部材が付設されてもよい。
【００１１】
構造材２は、中空糸膜モジュール全体を支持する部材として機能し、長手方向に延びる細長い開口部を有するとともに、その内部に濾液室５を有する。その材質としては機械的強度および耐久性を有するものであればよく、例えばポリカーボネート、ポリスルフォン、ポリプロピレン、アクリル樹脂、ＡＢＳ樹脂、変成ＰＰＥ樹脂、塩化ビニル樹脂等が例示される。
【００１２】
本発明に用いる中空糸膜モジュールには、図１のようにシート状に並び拡げて配設された中空糸膜が形成するシート状面の対向する二辺に構造材が配設されるタイプのものと、図３のようにシート状面の一辺にのみ構造材が配置されるタイプのものがある。通常、濾液取り出し口６が構造材２の一端もしくは両端に配設されている。濾液取り出し口６に、図４に示すようなカプラー継手２０を配設すれば、濾液吸引ポンプにつながる配管２１との接続がワンタッチで実施できるので便利である。
【００１３】
構造材は、円管状の形態のものを使用するのが一般的であるが、本発明においては、図５および図６に示すように、その長手方向に垂直な断面の形状が楕円または薬莢形の中空管のものを使用する。このような形状のものの場合には、下方から供給された気泡をモジュール内の中空糸膜に当てやすく、また気泡の上昇に伴う上昇水流の流速も上げやすく、スクラビングを効率的に実施できる。
【００１４】
固定部材３は、構造材２の開口部に充填固定され、多数の中空糸膜４の各端部を開口状態を保ったまま集束して固定するとともに、かつこれらの中空糸膜を濾過膜として機能させるために、被処理水と処理水とを液密に仕切る部材として機能する。固定部材３は、通常、エポキシ樹脂、不飽和ポリエステル樹脂、ポリウレタン等の液状樹脂、ホルムアルデヒド樹脂、フェノール樹脂、アミノ樹脂、ジアリルフタレート樹脂、シリコン樹脂等の熱硬化性樹脂、更にポリエチレン樹脂、ポリプロピレン樹脂、ポリ塩化ビニル樹脂、アクリル樹脂等の熱可塑性樹脂から形成される。
【００１５】
中空糸膜４は、多数がほぼ平行に引き揃えられて平坦なシート状に並び拡げて配設されている。このように、多数の中空糸膜をほぼ平行に揃えてシート状に並び拡げることで、中空糸膜束が一本の棒状に固着一体化するのが防止される。このようなシート状中空糸膜は、中空糸膜を緯糸とする編織物の形で準備されるのが一般的であるが、中空糸膜モジュールとして完成された際には拘束糸条としての経糸を有していてもよいし有さなくてもよい。
【００１６】
中空糸膜としては、種々のものが使用でき、例えばセルロース系、ポリオレフィン系、ポリビニルアルコール系、ＰＭＭＡ系、ポリスルフォン系等の各種材料からなるものが使用できるがポリエチレン、ポリプロピレン等の強伸度の高い材質のものが好ましい。なお、濾過膜として使用可能なものであれば、孔径、空孔率、膜厚、外径等には特に制限はないが、除去対象物や容積当たりの膜面積の確保および中空糸膜の強度等を考えると、好ましい例としては、孔径０．０１〜１μｍ、空孔率２０〜９０％、膜厚５〜３００μｍ、外径２０〜２０００μｍの範囲を挙げることができる。
【００１７】
中空糸膜の表面特性としては、表面に親水基等を持ついわゆる恒久親水化膜であることが望ましい。恒久親水化膜の製法としては、ポリビニルアルコールのような親水性高分子で中空糸膜を製造する方法、または疎水性高分子膜の表面を親水化する方法等の各種の方法が使用できる。例えば親水性高分子を膜面に付与し疎水性中空糸膜を親水化する際の親水性高分子の例としては、エチレン−酢酸ビニル系共重合体ケン化物、ポリビニルピロリドン、ポリオキシエチレン（アルキル）フェニルエーテル等の界面活性剤等を挙げることができる。別の手法による膜面親水化の例としては、親水性モノマーの膜面重合方式があり、このモノマーの例としてはジアセトンアクリルアマイド等を挙げることができる。また、他の手法としては疎水性高分子（例えばポリオレフイン）に親水性高分子をブレンドして紡糸製膜する手法を挙げることができ、使用する親水性高分子の例としては上述したものが挙げられる。表面が疎水性の中空糸膜であると、被処理水中の有機物と中空糸膜表面との間に疎水性相互作用が働き膜面ヘの有機物吸着が発生し、それが膜面閉塞につながり濾過寿命が短くなる。また、吸着由来の目詰まりは膜面洗浄による濾過性能回復も一般には難しい。恒久親水化膜を用いることにより有機物と中空糸膜表面との疎水性相互作用を減少させることができ、有機物の吸着を抑えることができる。さらに疎水性膜ではスクラビングの際に気泡によって膜面が乾燥状態となることがあり、これにより疎水性が強まりフラックスの低下を招くことがあるが、恒久親水化膜では乾燥してもフラックスの低下が生じない。
【００１８】
本発明の濾過方法は、上述した中空糸膜モジュールを用い、このモジュールの下方から気泡を連続的または断続的に供給しつつ液体を濾過する方法において、中空糸膜により形成されるシート状面がほぼ垂直となり、かつ中空糸膜の繊維軸方向がほぼ垂直となるように中空糸膜モジュールを配置して濾過する方法である。中空糸膜の繊維軸が垂直方向を向くように配置すると、水平方向を向くように配置した場合に比較して、スクラビングのエアーの供給量を増やした場合の上昇水流の流速がかなり上がり、平膜を垂直に配置した場合に近い流速が得られることが判明した。このためスクラビングによる中空糸膜の洗浄効率を向上させることが可能である。
【００１９】
本発明の濾過方法を実施するには幾つかの態様があるので、以下、これら各態様ごとに説明する。
【００２０】
第１の態様は、図７に示すように構造材がシート状面の一辺にのみ配設されてなる中空糸膜モジュールを用い、構造材がモジュールの最下方に位置し、中空糸膜のシート状面が垂直上方へ伸びるように中空糸膜モジュールを配置する方法である。構造材が配設された辺と対向する辺は、通常は、中空糸膜のＵ字状の折り曲げ部あるいは中空糸膜の封止端（以下、これらを中空糸膜の上端という）の集合からなり、移動自在の状態に構成されている。
【００２１】
中空糸膜の上端がモジュールの上方に位置するようにするには、例えば中空糸膜のＵ字部の中央に紐や針金等を通してこれを水槽内の所定位置に固定することにより行われる。但し、この中空糸膜の上端は、完全固定せずにある程度の移動が可能なようにしておくべきである。
【００２２】
このように中空糸膜の上端を固定部材によって固定しない構造にしておくと、散気管８から気泡を出してスクラビングを開始すると中空糸膜は上昇水流に沿って伸びるだけでたるむことがないので、水平方向へ引っ張る応力は発生せず、中空糸膜が損傷するおそれもない。
【００２３】
第２の態様は、図８に示すように構造材がシート状面の一辺にのみ配設されなる中空糸膜モジュールを用い、構造材がモジュールの最上方に位置するように配置するとともに、シート状面の構造材の配設辺と対向する辺に、中空糸膜の浮き上がりを防止する重りを取り付けて濾過する方法である。
【００２４】
重り１０は、全ての中空糸膜に均等に荷重が加わり張力が働くような構成にすることが適当なので、一個の球状の重りを取り付けるよりは、長く延びた棒状の重りの方が好ましく、また、鎖のような形態の重りであって、全体としては一つにまとまっているが、それぞれが独立して中空糸膜に荷重を加えられるようなものが好ましい。
【００２５】
この態様の場合には、重りにより中空糸膜には絶えず下方へ引っ張る力が働いているので、荷重を適切に選べば中空糸膜がたるむことはないので中空糸膜が損傷するおそれもない。また、モジュールの下方には構造材はなく、中空糸膜を除けば重りだけが存在するので、重りの形状を適切に選べば、スクラビング用の気泡を効率よく中空糸膜に当てることができ、それにともなう上昇水流の流速も上げることができる。
【００２６】
第３の態様は、図９に示すように構造材の少なくとも一部が液面より上方に位置するように配置して濾過する方法である。
【００２７】
中空糸膜が垂直となるように中空糸膜モジュールを配置した場合、特に多くの中空糸膜モジュールをそのように配置して濾過する場合には、上方に位置する構造材が密に近接して配設されることになる。このため、スクラビング用の気泡が水面上へ抜けるのを構造材が邪魔をする。したがって、モジュールの上方部では気泡は構造材を回避してモジュールの横方向から抜けようとするので、上昇水流の流速が落ち、洗浄効率が低下する。しかし、上部に位置する構造材が液面より上方に位置していると、水面下にある中空糸膜の膜面積は低下するが、スクラビング用の気泡はまっすぐ水面上へ抜けることができ、上昇水流の流速が落ちないので、中空糸膜の洗浄効率を高く保つことができる。
【００２８】
この態様に用いる中空糸膜モジュールは、シート状面の対向する二辺に構造材が配設されたものでも一辺にのみ構造材が配設されたものでもよい。また、上記の説明からも明らかなように、多数の中空糸膜モジュールを配設する場合に上方に位置する構造材の全てを液面上に位置させる必要はない。構造材の配設密度を低くしてスクラビング用の気泡がまっすぐ液面上へ抜けることができれば目的が達成されるからである。
【００２９】
更に、この態様で使用する場合、水面上に出た中空糸膜部は空気が吸い込まれないようにすることが好ましい。例えば、水面上に出る部分の中空糸膜外周面を樹脂でコーティングする方法等が挙げられる。また、使用形態によっては、そのまま空気が吸い込まれてもよい。
【００３０】
第４の態様は、図１０に示すように中空糸膜モジュールのシート状面を少なくとも一ヶ所で折り返して配置して濾過する方法である。
【００３１】
シート状面の折り返しは、例えば折り返し部１１に丸棒等を配して、この丸棒に沿ってシート状面を１８０°反転させて行う。折り返しの箇所は、一ケ所以上であれば何ケ所でもよい。シート状面を折り返すことによって、水槽内の中空糸膜の垂直方向に伸びる距離が短くなり（例えば一ケ所で半分に折り返せば垂直方向に伸びる距離は半分になる）、そのため中空糸膜にたるみがあってもそのたるみ部分は小さくなるため、水平方向の応力が発生したとしても小さいものとなり、中空糸膜の損傷の可能性は殆どなくなる。
【００３２】
また、折り返し部を上方に位置する非固定端とすると、各中空糸膜については第１の態様の場合と同様に考えることができ、中空糸膜を水平方向に引っ張る応力が発生しないので中空糸膜が損傷するおそれはない。更に、折り返し部を下方に位置する非固定端として、その部分に中空糸膜の浮き上がりを防止する重りを取り付けると、今度は第２の態様の場合と同様に考えることができ、中空糸膜にたるみが発生しないので中空糸膜が損傷するおそれもない。
【００３３】
第５の態様は、図１１に示すように水槽内の液深方向に中空糸膜モジュールを少なくとも２段以上に連ねて配置して濾過する方法である。
【００３４】
すなわち、多数のモジュールを連ねて使用することにより、自然に１モジュール当りの中空糸膜の水槽内での垂直方向に伸びる距離が短くなり、上述した第４の態様の場合と同様に、中空糸膜に発生するたるみ部分が小さくなるため、中空糸膜の損傷の可能性が低減する。したがって、液深方向に中空糸膜モジュールを連ねて配置する段数は、多いほど中空糸膜の損傷を防止する観点からは好ましいが、段数が増加するにつれて水槽内に設置される中空糸膜の膜面積は低減するので、１モジュール当りの中空糸膜の垂直方向に伸びる距離が１０〜２００ｃｍとなるように設置して濾過することが好ましく、１０〜１００ｃｍとなるように設置することが特に好ましい。
【００３５】
以上説明した本発明の濾過方法は、密閉容器内に中空糸膜を配設して被処理水を加圧して中空糸膜を透過させるいわゆる加圧濾過法にも使用できるが、その場合にはスクラビングが容易には実施しにくいため、開放水槽中に中空糸膜モジュールを配設し、中空糸膜を透過した処理水を回収するサイドを吸引する吸引濾過法で使用することが好ましい。また、周期的に一時吸引を停止する、いわゆる間欠吸引運転方法を採用することもできる。
【００３６】
本発明の濾過方法は、特に高汚濁性水の濾過に適しており、具体的な利用分野としては、河川水の濾過、工業用水濾過、下水の固液分離、排水処理（例えば合併浄化槽での処理）等が挙げられる。
【００３７】
【発明の効果】
本発明の濾過方法では、スクラビングの際の気泡の上昇に伴う上昇水流の流速を平膜を用いて濾過する場合と同程度まで上げられるので、中空糸膜の膜面洗浄が効率よく実施でき、特に高汚濁性水の濾過において長期に亙って差圧の上昇及び流量低下が防止できる。また、濾過中に中空糸膜にたるみが発生しにくいので、中空糸膜が損傷するおそれも殆どなく安定した濾過が可能である。
【図面の簡単な説明】
【図１】本発明に用いる中空糸膜モジュールの一例を示す平面図である。
【図２】図１のＡＡ線方向の断面図である。
【図３】本発明に用いる中空糸膜モジュールの他の例を示す斜視図である。
【図４】本発明に用いる中空糸膜モジュールの濾液取り出し口近傍の拡大図である。
【図５】本発明に用いる中空糸膜モジュールの一例の断面図である。
【図６】本発明に用いる中空糸膜モジュールの一例の断面図である。
【図７】本発明の濾過方法の第１の態様を示す模式図である。
【図８】本発明の濾過方法の第２の態様を示す模式図である。
【図９】本発明の濾過方法の第３の態様を示す模式図である。
【図１０】本発明の濾過方法の第４の態様を示す模式図である。
【図１１】本発明の濾過方法の第５の態様を示す模式図である。
【符号の説明】
１中空糸膜モジュール
２構造材
３固定部材
４中空糸膜
５濾液室
６濾液取り出し口
７カプラー継手
８散気管
９水槽
１０重り
１１折り返し部[0001]
[Industrial application fields]
The present invention relates to a filtration method using a hollow fiber membrane module, and more particularly to a filtration method using a hollow fiber membrane module suitable for processing a highly pollutant liquid with an organic substance or the like.
[0002]
[Prior art]
Conventionally, hollow fiber membrane modules have been widely used in the field of so-called microfiltration such as the production of aseptic water, drinking water and high-purity water, and purification of air. Recently, secondary treatment and tertiary treatment in sewage treatment plants Various studies have been conducted for use in highly polluting water treatment applications such as solid-liquid separation in septic tanks.
[0003]
As a hollow fiber membrane module suitable for the filtration of highly polluted water, a large number of hollow fiber membranes are arranged side by side in a sheet, and one end or both ends of the hollow fiber membrane are in one or two different structural materials. The hollow fiber membrane module is a hollow fiber membrane module that is fixed while maintaining the respective open states with a fixing member, and is a flat hollow fiber membrane module whose cross-sectional shape perpendicular to the hollow fiber membrane of the fixing member is a substantially rectangular shape Is known from JP-A-5-220356.
[0004]
This flat type hollow fiber membrane module is used by a method of filtering liquid while continuously or intermittently cleaning (scrubbing) by applying bubbles to the hollow fiber membrane and vibrating it. It is known from Japanese Patent Laid-Open No. 7-24264 that the cleaning efficiency of the hollow fiber membrane is improved and the high filtration flow rate can be maintained for a long time by using the sheet-like surface formed by the membrane so as to be vertical. ing. In this case, the structural material is vertically arranged so that the fiber shaft of the hollow fiber membrane is arranged so that air bubbles can be efficiently applied to the hollow fiber membrane without disturbing the structural material (water guide tube) arranged at the end of the module. It was to be horizontal.
[0005]
[Problems to be solved by the invention]
However, the present inventors have clarified that scrubbing is performed with an efficiency proportional to the amount of air supplied and the speed of the rising water flow in the water tank generated as the bubbles rise. In the case of the module, the resistance to the rising water flow was large, and the flow velocity of the rising water flow did not increase as in the case of the flat membrane. That is, even if the supply amount of air is increased, the cleaning efficiency is saturated at a relatively low level, and large-scale cleaning in which filtration such as backwashing is interrupted is required at an early stage, resulting in a reduction in apparatus efficiency.
[0006]
The object of the present invention is to prevent turbidity from being deposited between the hollow fiber membranes even in the filtration of highly polluted water, and to perform scrubbing more efficiently, resulting in an increase in differential pressure and a decrease in filtration flow rate over a long period of time. It is an object of the present invention to provide a filtration method using a hollow fiber membrane module which is difficult and less likely to damage the hollow fiber membrane.
[0007]
[Means for Solving the Problems]
That is, the present invention includes a hollow fiber membrane arranged in a sheet shape, a fixing member for fixing the hollow fiber membrane while maintaining an end of the hollow fiber membrane, and a structural material for supporting and storing the fixing member. A filtration method for filtering liquid while continuously or intermittently supplying air bubbles from below the module, wherein the cross-sectional shape perpendicular to the longitudinal direction of the structural material is elliptical or Using a hollow fiber membrane module that is in the form of a cartridge , the hollow fiber membrane module is arranged and filtered so that the sheet-like surface formed by the hollow fiber membrane is almost vertical and the fiber axis direction of the hollow fiber membrane is almost vertical. It is the filtration method characterized by doing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Conventionally, the hollow fiber membrane was horizontally arranged in the filtration method used by arranging the hollow fiber membrane module in the liquid tank to be treated so that the sheet-like surface formed by the hollow fiber membrane is vertical. As described above, the main reason is to prevent the water conduit arranged at the end of the hollow fiber membrane module from interfering with the scrubbing. In addition, the hollow fiber membrane is usually arranged in a state with some looseness in the module, but when the hollow fiber membrane is arranged vertically, the rising water flow acts to pull up the hollow fiber membrane, Therefore, the slack of the hollow fiber membrane is concentrated in the vicinity of the fixing portion of the hollow fiber membrane by the upper fixing member. At this time, a stress that bends the hollow fiber membrane by the rising water flow and pulls it in the horizontal direction at the slack portion is generated, which may cause damage to the hollow fiber membrane at the fixed portion and the bent portion.
[0009]
Hereinafter, the filtration method using the hollow fiber membrane module of the present invention will be described in more detail with reference to the drawings.
[0010]
First, a flat hollow fiber membrane module used in the filtration method of the present invention will be described. FIG. 1 is a plan view showing an example of the hollow fiber membrane module, FIG. 2 is a cross-sectional view in the AA line direction, and FIG. 3 is a perspective view showing another example. The hollow fiber membrane module 1 basically includes a structural material 2, a fixing member 3, and a hollow fiber membrane 4. In addition to these, various attachment members may be attached.
[0011]
The structural member 2 functions as a member that supports the entire hollow fiber membrane module, has a long and narrow opening extending in the longitudinal direction, and has a filtrate chamber 5 therein. Any material may be used as long as it has mechanical strength and durability. Examples thereof include polycarbonate, polysulfone, polypropylene, acrylic resin, ABS resin, modified PPE resin, and vinyl chloride resin.
[0012]
The hollow fiber membrane module used in the present invention is a type in which structural materials are disposed on two opposite sides of a sheet-like surface formed by hollow fiber membranes arranged in a sheet-like manner as shown in FIG. There is a type in which a structural material is arranged only on one side of a sheet-like surface as shown in FIG. Usually, the filtrate outlet 6 is disposed at one or both ends of the structural material 2. If the coupler joint 20 as shown in FIG. 4 is provided at the filtrate outlet 6, it is convenient because the connection with the pipe 21 connected to the filtrate suction pump can be performed with one touch.
[0013]
In general, the structural material is in the shape of a circular tube. In the present invention, as shown in FIGS. 5 and 6, the shape of the cross section perpendicular to the longitudinal direction is an ellipse or a cartridge case. Use a hollow tube . In the case of such a shape, it is easy to apply the bubbles supplied from below to the hollow fiber membrane in the module, and it is easy to increase the flow rate of the rising water flow accompanying the rising of the bubbles, so that scrubbing can be performed efficiently.
[0014]
The fixing member 3 is filled and fixed in the opening of the structural material 2, and fixes and fixes each end of a large number of hollow fiber membranes 4 while maintaining the open state, and these hollow fiber membranes are used as filtration membranes. In order to make it function, it functions as a member which partitions treated water and treated water liquid-tightly. The fixing member 3 is usually a liquid resin such as epoxy resin, unsaturated polyester resin, polyurethane, formaldehyde resin, phenol resin, amino resin, diallyl phthalate resin, thermosetting resin such as silicone resin, polyethylene resin, polypropylene resin, It is formed from a thermoplastic resin such as polyvinyl chloride resin or acrylic resin.
[0015]
A large number of hollow fiber membranes 4 are arranged substantially in parallel and arranged in a flat sheet shape. In this way, by aligning a large number of hollow fiber membranes substantially in parallel with each other and expanding them in a sheet shape, it is possible to prevent the hollow fiber membrane bundles from being fixed and integrated into a single rod shape. Such a sheet-like hollow fiber membrane is generally prepared in the form of a knitted fabric having a hollow fiber membrane as a weft, but when it is completed as a hollow fiber membrane module, it is a warp yarn as a constraining yarn. May or may not be included.
[0016]
Various hollow fiber membranes can be used, for example, those made of various materials such as cellulose, polyolefin, polyvinyl alcohol, PMMA, and polysulfone can be used. High material is preferable. In addition, as long as it can be used as a filtration membrane, there is no particular limitation on the pore diameter, porosity, film thickness, outer diameter, etc., but the membrane area per removal object and volume and the strength of the hollow fiber membrane In view of the above, preferable examples include a pore diameter of 0.01 to 1 μm, a porosity of 20 to 90%, a film thickness of 5 to 300 μm, and an outer diameter of 20 to 2000 μm.
[0017]
As a surface characteristic of the hollow fiber membrane, a so-called permanent hydrophilic membrane having a hydrophilic group on the surface is desirable. Various methods such as a method for producing a hollow fiber membrane with a hydrophilic polymer such as polyvinyl alcohol or a method for hydrophilizing the surface of a hydrophobic polymer membrane can be used as a method for producing a permanent hydrophilic membrane. For example, examples of the hydrophilic polymer used to impart hydrophilic polymer to the membrane surface to hydrophilize the hydrophobic hollow fiber membrane include saponified ethylene-vinyl acetate copolymer, polyvinylpyrrolidone, polyoxyethylene (alkyl ) Surfactant such as phenyl ether. An example of hydrophilizing the membrane surface by another method is a membrane surface polymerization method of a hydrophilic monomer, and examples of this monomer include diacetone acrylate. Further, as another technique, a technique of blending a hydrophilic polymer with a hydrophobic polymer (for example, polyolefin) to form a film by spinning may be mentioned, and examples of the hydrophilic polymer to be used include those mentioned above. It is done. If the surface is a hydrophobic hollow fiber membrane, hydrophobic interaction occurs between the organic matter in the water to be treated and the surface of the hollow fiber membrane, causing organic matter adsorption to the membrane surface, which results in blockage of the membrane surface and filtration. Life is shortened. Moreover, it is generally difficult to recover the filtration performance by cleaning the membrane surface due to clogging due to adsorption. By using a permanent hydrophilized membrane, the hydrophobic interaction between the organic matter and the hollow fiber membrane surface can be reduced, and adsorption of the organic matter can be suppressed. Furthermore, in the hydrophobic membrane, the membrane surface may become dry due to bubbles during scrubbing, which may increase the hydrophobicity and reduce the flux. Does not occur.
[0018]
The filtration method of the present invention uses the above-described hollow fiber membrane module, and in the method of filtering liquid while continuously or intermittently supplying bubbles from below the module, the sheet-like surface formed by the hollow fiber membrane is In this method, the hollow fiber membrane module is arranged and filtered so that the fiber axis direction of the hollow fiber membrane is substantially vertical. If the fiber axis of the hollow fiber membrane is oriented in the vertical direction, the flow rate of the ascending water flow increases considerably when the amount of scrubbing air supplied is increased, compared with the case where the fiber axis is oriented in the horizontal direction. It was found that a flow rate close to that obtained when the membrane was arranged vertically was obtained. For this reason, it is possible to improve the cleaning efficiency of the hollow fiber membrane by scrubbing.
[0019]
Since there are several modes for carrying out the filtering method of the present invention, each mode will be described below.
[0020]
The first embodiment uses a hollow fiber membrane module in which the structural material is disposed only on one side of the sheet-like surface as shown in FIG. 7, and the structural material is located at the lowermost part of the module, and the hollow fiber membrane sheet This is a method of arranging the hollow fiber membrane module so that the shape surface extends vertically upward. The side opposite to the side where the structural material is disposed is usually from a set of U-shaped bent portions of the hollow fiber membrane or a sealed end of the hollow fiber membrane (hereinafter referred to as the upper end of the hollow fiber membrane). It is configured to be movable.
[0021]
The upper end of the hollow fiber membrane is positioned above the module, for example, by fixing the hollow fiber membrane at a predetermined position in the water tank through a string or wire in the center of the U-shaped portion. However, the upper end of the hollow fiber membrane should be able to move to some extent without being completely fixed.
[0022]
If the structure is such that the upper end of the hollow fiber membrane is not fixed by the fixing member in this way, the hollow fiber membrane only stretches along the rising water flow and does not sag when the bubbles are released from the air diffuser tube 8 and scrubbing is started. No stress is pulled in the horizontal direction, and the hollow fiber membrane is not damaged.
[0023]
The second aspect uses a hollow fiber membrane module in which the structural material is disposed only on one side of the sheet-like surface as shown in FIG. 8 and is arranged so that the structural material is positioned at the top of the module. This is a method in which a weight that prevents the hollow fiber membrane from being lifted is attached to a side opposite to the side where the structural material on the surface is disposed and filtered.
[0024]
Since it is appropriate that the weight 10 has a structure in which a load is applied evenly to all the hollow fiber membranes and the tension works, a long rod-like weight is preferable to a single spherical weight, and The weights are in the form of chains, and are combined into one as a whole, but are preferably such that each can independently apply a load to the hollow fiber membrane.
[0025]
In the case of this aspect, since the weight constantly pulls downward on the hollow fiber membrane due to the weight, the hollow fiber membrane does not sag if the load is appropriately selected, so that the hollow fiber membrane is not damaged. In addition, there is no structural material under the module, and there is only a weight except for the hollow fiber membrane, so if the shape of the weight is selected appropriately, scrubbing bubbles can be efficiently applied to the hollow fiber membrane, Along with this, the flow velocity of the rising water flow can be increased.
[0026]
A third aspect is a method of filtering by arranging the filter so that at least a part of the structural material is located above the liquid level as shown in FIG.
[0027]
When the hollow fiber membrane modules are arranged so that the hollow fiber membranes are vertical, especially when many hollow fiber membrane modules are so arranged and filtered, the structural material located above is in close proximity. Will be disposed. For this reason, the structural material prevents the scrubbing bubbles from falling onto the water surface. Therefore, since air bubbles try to escape from the lateral direction of the module avoiding the structural material in the upper part of the module, the flow rate of the rising water flow is lowered and the cleaning efficiency is lowered. However, if the upper structural material is positioned above the liquid level, the membrane area of the hollow fiber membrane below the water surface decreases, but the scrubbing bubbles can escape straight above the water surface and rise. Since the flow rate of the water flow does not drop, the cleaning efficiency of the hollow fiber membrane can be kept high.
[0028]
The hollow fiber membrane module used in this aspect may be one in which a structural material is disposed on two opposite sides of the sheet-like surface or one in which a structural material is disposed on only one side. Further, as is clear from the above description, when a large number of hollow fiber membrane modules are provided, it is not necessary to place all of the structural material located above on the liquid level. This is because the object can be achieved if the arrangement density of the structural material is lowered and the bubbles for scrubbing can escape straight onto the liquid surface.
[0029]
Furthermore, when used in this mode, it is preferable that air is not sucked into the hollow fiber membrane portion that has come out on the water surface. For example, a method of coating the outer peripheral surface of the hollow fiber membrane at the part that comes out on the water surface with a resin, and the like can be mentioned. Further, depending on the usage, air may be sucked as it is.
[0030]
The fourth aspect is a method of filtering by placing folded at least one position of the sheet-like surface of the hollow fiber membrane module shown in FIG. 10.
[0031]
The sheet-shaped surface is folded, for example, by placing a round bar or the like in the folded portion 11 and inverting the sheet-shaped surface by 180 ° along the round bar. There may be any number of the folded portions as long as the number is one or more. By folding the sheet-like surface, the distance extending in the vertical direction of the hollow fiber membrane in the water tank is shortened (for example, if it is folded in half at one place, the distance extending in the vertical direction is halved), so there is a slack in the hollow fiber membrane. Even if it exists, since the slack part becomes small, even if the stress of a horizontal direction generate | occur | produces, it will become small, and the possibility of damage to a hollow fiber membrane will be almost eliminated.
[0032]
Further, if the folded portion is an unfixed end positioned above, each hollow fiber membrane can be considered in the same manner as in the first embodiment, and no stress is generated to pull the hollow fiber membrane in the horizontal direction. There is no risk of damage to the membrane. Furthermore, if the folded portion is positioned as a non-fixed end located below and a weight is attached to that portion to prevent the hollow fiber membrane from being lifted up, it can be considered in the same manner as in the second embodiment. Since sagging does not occur, there is no possibility of damaging the hollow fiber membrane.
[0033]
Fifth aspect is a method of filtering by arranging the liquid depth direction of the water tank lined hollow fiber membrane module with at least two or more stages as shown in FIG. 11.
[0034]
That is, by using a large number of modules in a row, the distance of the hollow fiber membrane per module that extends in the vertical direction in the water tank is naturally shortened, and as in the case of the fourth aspect described above, the hollow fiber membrane Since the slack portion generated in the membrane is reduced, the possibility of damage to the hollow fiber membrane is reduced. Therefore, the higher the number of stages in which the hollow fiber membrane modules are arranged in the liquid depth direction, the better from the viewpoint of preventing damage to the hollow fiber membrane, but the hollow fiber membrane membrane installed in the water tank as the number of stages increases. Since the area is reduced, it is preferable to install and filter so that the distance extending in the vertical direction of the hollow fiber membrane per module is 10 to 200 cm, and particularly preferably 10 to 100 cm.
[0035]
The filtration method of the present invention described above can also be used in a so-called pressure filtration method in which a hollow fiber membrane is disposed in a sealed container, pressurizes water to be treated, and permeates the hollow fiber membrane. Since scrubbing is difficult to carry out, it is preferable to use a suction filtration method in which a hollow fiber membrane module is disposed in an open water tank and the side for collecting treated water that has permeated through the hollow fiber membrane is sucked. Also, a so-called intermittent suction operation method in which temporary suction is periodically stopped can be employed.
[0036]
The filtration method of the present invention is particularly suitable for the filtration of highly polluted water. Specific application fields include river water filtration, industrial water filtration, sewage solid-liquid separation, wastewater treatment (for example, in a combined septic tank). Treatment) and the like.
[0037]
【The invention's effect】
In the filtration method of the present invention, the flow rate of the ascending water flow accompanying the rise of bubbles during scrubbing can be increased to the same level as when filtering using a flat membrane, so the membrane surface cleaning of the hollow fiber membrane can be carried out efficiently, In particular, in the filtration of highly polluted water, an increase in differential pressure and a decrease in flow rate can be prevented over a long period of time. In addition, since it is difficult for sagging to occur in the hollow fiber membrane during filtration, stable filtration is possible with little risk of damage to the hollow fiber membrane.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of a hollow fiber membrane module used in the present invention.
2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is a perspective view showing another example of a hollow fiber membrane module used in the present invention.
FIG. 4 is an enlarged view of the vicinity of the filtrate outlet of the hollow fiber membrane module used in the present invention.
FIG. 5 is a cross-sectional view of an example of a hollow fiber membrane module used in the present invention.
FIG. 6 is a cross-sectional view of an example of a hollow fiber membrane module used in the present invention.
FIG. 7 is a schematic view showing a first embodiment of the filtration method of the present invention.
FIG. 8 is a schematic view showing a second embodiment of the filtration method of the present invention.
FIG. 9 is a schematic view showing a third aspect of the filtration method of the present invention.
FIG. 10 is a schematic view showing a fourth embodiment of the filtration method of the present invention.
FIG. 11 is a schematic view showing a fifth embodiment of the filtration method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module 2 Structural material 3 Fixing member 4 Hollow fiber membrane 5 Filtrate chamber 6 Filtrate outlet 7 Coupler joint 8 Aeration pipe 9 Water tank 10 Weight 11 Folding part

Claims

A hollow having a hollow fiber membrane arranged in a sheet shape, a fixing member that fixes an end of the hollow fiber membrane while maintaining an open state, and a structural material that supports and stores the fixing member In a filtration method in which a liquid is filtered while bubbles are continuously or intermittently supplied from below the module using a yarn membrane module, the sheet-like surface formed by the hollow fiber membrane is substantially vertical, and the hollow fiber membrane The hollow fiber membrane module is arranged so that the fiber axis direction is substantially perpendicular, the structural material is disposed only on one side of the sheet-like surface , and the cross-sectional shape perpendicular to the longitudinal direction of the structural material is elliptical or A filtration method comprising: using a hollow fiber membrane module having a shell shape, and arranging and filtering so that the structural material is positioned at the lowermost part of the module.

A hollow having a hollow fiber membrane arranged in a sheet shape, a fixing member that fixes an end of the hollow fiber membrane while maintaining an open state, and a structural material that supports and stores the fixing member In a filtration method in which a liquid is filtered while bubbles are continuously or intermittently supplied from below the module using a yarn membrane module, the sheet-like surface formed by the hollow fiber membrane is substantially vertical, and the hollow fiber membrane The hollow fiber membrane module is arranged so that the fiber axis direction is substantially perpendicular, the structural material is disposed only on one side of the sheet-like surface , and the cross-sectional shape perpendicular to the longitudinal direction of the structural material is elliptical or Using a hollow fiber membrane module in the form of a shell , the structural material is placed so as to be positioned at the top of the module, and the hollow fiber membrane is prevented from being lifted on the side opposite to the side where the structural material is disposed on the sheet-like surface. Install weight Filtration method characterized by filtering.

A hollow having a hollow fiber membrane arranged in a sheet shape, a fixing member that fixes an end of the hollow fiber membrane while maintaining an open state, and a structural material that supports and stores the fixing member A hollow fiber in which a cross-sectional shape perpendicular to the longitudinal direction of the structural material is an ellipse or a medicine cup shape in a filtration method using a yarn membrane module and filtering a liquid while continuously or intermittently supplying bubbles from below the module Using the membrane module , the hollow fiber membrane module is arranged so that the sheet-like surface formed by the hollow fiber membrane is substantially vertical and the fiber axis direction of the hollow fiber membrane is substantially vertical, and at least a part of the structural material A filtration method, wherein the filter is disposed so as to be positioned above the liquid level and filtered.

A hollow having a hollow fiber membrane arranged in a sheet shape, a fixing member that fixes an end of the hollow fiber membrane while maintaining an open state, and a structural material that supports and stores the fixing member A hollow fiber in which a cross-sectional shape perpendicular to the longitudinal direction of the structural material is an ellipse or a medicine cup shape in a filtration method using a yarn membrane module and filtering a liquid while continuously or intermittently supplying bubbles from below the module Using the membrane module , the hollow fiber membrane module is arranged so that the sheet-like surface formed by the hollow fiber membrane is substantially vertical, and the fiber axis direction of the hollow fiber membrane is substantially perpendicular, and at least the sheet-like surface is A filtration method characterized by being folded and arranged at one place.

A hollow having a hollow fiber membrane arranged in a sheet shape, a fixing member that fixes an end of the hollow fiber membrane while maintaining an open state, and a structural material that supports and stores the fixing member A hollow fiber in which a cross-sectional shape perpendicular to the longitudinal direction of the structural material is an ellipse or a medicine cup shape in a filtration method using a yarn membrane module and filtering a liquid while continuously or intermittently supplying bubbles from below the module Using the membrane module , the hollow fiber membrane module is disposed so that the sheet-like surface formed by the hollow fiber membrane is substantially vertical and the fiber axis direction of the hollow fiber membrane is substantially vertical. A filtration method characterized by arranging and filtering at least two or more stages in the liquid depth direction.