JP4560701B2

JP4560701B2 - Cleaning method for membrane filter module

Info

Publication number: JP4560701B2
Application number: JP2002059029A
Authority: JP
Inventors: 清士谷口; 博章中川; 慈洋吉尾
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2002-03-05
Filing date: 2002-03-05
Publication date: 2010-10-13
Anticipated expiration: 2022-03-05
Also published as: JP2003251158A

Description

【０００１】
【発明の属する技術分野】
本発明は濾過膜モジュールを設備する濾過膜を用いた濾過装置の洗浄方法に関する。特に、濾過膜モジュールの薬液洗浄を効率的に行うための洗浄方法に関する。
【０００２】
【従来の技術】
濾過膜モジュールを用いて原水から濾過水を得る膜濾過装置において、濾過膜の表面に生物分が付着したり、濾過膜の細孔に金属成分が蓄積したりして、濾過膜が詰まるため、濾過水量が低下するという問題がある。
【０００３】
このような問題に対して、濾過膜モジュールの物理洗浄や薬液洗浄が行なわれている。濾過膜モジュールの薬液洗浄方法としては、オフラインで行う方法とオンラインで行う方法がある。オフラインで循環しながら薬液洗浄を行う方法の場合は、長時間にわたり濾過膜装置を停止する必要がある。
【０００４】
一方、オンラインで薬液洗浄する場合、事前に物理的な洗浄を行わないとモジュール内に蓄積された生物分や金属分で薬液が無駄に消費され、薬液洗浄の効率を落とす問題点がある。その上、濾過膜モジュールに水が充満された状態で薬液洗浄を行うと、薬液濃度の調整が難しいという問題もある。
【０００５】
また、薬液洗浄後は、薬液によって剥離しやすくなった生物分や、膜の細孔に詰まっていて薬液中に溶け出した金属分を排出する必要がある。これらは、単に濾過膜モジュール内の水を濾過膜モジュール外に排出するだけでは完全には排出できない。
【０００６】
また、濾過膜モジュール内には、濾過膜の基材に付着した薬液成分が残留しており、このまま濾過を行うと、濾過水側に薬液成分が流出するおそれがある。
【発明が解決しようとする課題】
本発明は、濾過膜モジュールを設備する濾過膜を用いた濾過装置において、濾過膜モジュールを効率的に洗浄するためのオンライン薬液洗浄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】
本願発明者は、前記課題に対し検討を行った結果、薬液洗浄を行う前に物理的洗浄を行うこと。また、薬液洗浄を行った後にも物理的洗浄を行い、十分に濾過膜モジュール内を洗浄すること。また、薬液洗浄後に洗浄濾過を行い、膜モジュール内の薬液濃度を十分に下げること。生産水側に薬液成分が混入しない方法をとること。によって上記課題を達成することを見いだした。
【０００８】
すなわち、本発明は、以下のものである。
１）中空糸型分離膜を芯管のまわりに複数本結束し、結束端部にて熱可塑性樹脂からなるシール部材により中空糸型分離膜の生産水側と原水側を液密にシールしたエレメントを作製し、これをケースに入れ、芯管がケース外に配管にて接続できる構造を有する濾過膜モジュールの洗浄方法において、（１）濾過膜モジュールの生産水側より濾過水を流して原水側に向かって濾過を行うことにより濾過膜を洗浄し、次に前記洗浄を行いながら芯管から加圧空気を流して濾過膜を洗浄し、その後さらに芯管から加圧された濾過水を流し濾過膜を洗浄する物理的洗浄を行った後、（２）濾過膜モジュール内の水を抜き、（３）次いで原水に薬液を注入し濾過膜の原水側から生産水側に向かって濾過を行う薬液洗浄を行ない、（４）該物理的洗浄を行い、（５）濾過膜モジュール内の水を抜き、さらに（６）原水又は濾過水を濾過膜モジュールの原水側に送液する洗浄濾過を行い、（７）次いで該物理的洗浄を行い、（８）その後濾過膜モジュール内の水を抜く、（６）〜（８）の操作を繰り返し行うことで濾過膜モジュール内の残薬液濃度を洗浄薬液濃度の３／２０以上１／２以下まで低下させることを特徴とする濾過膜モジュールの洗浄方法。
【０００９】
【発明の実施の形態】
本発明の濾過膜モジュールのオンライン薬液洗浄方法は、例えば、湖沼や河川の原水から浄水を得るための膜濾過装置の洗浄方法として使用する。濾過膜モジュールとしては、例えば、限外濾過膜、精密濾過膜などの濾過膜モジュールが挙げられる。特に、図−１に示すような中空糸型分離膜を芯管のまわりに複数本結束した中空糸膜モジュールを設備した膜濾過装置は、生物分が濾過膜に付着して詰まり易いので、本発明の洗浄方法を適用することが有効である。
【００１０】
本発明の膜濾過装置は、例えば、図−２のフロー図を示したような、１０原水送液ポンプ、１１濾過膜モジュール、１２濾過水バッファータンク、１３濾過水バッファータンク加圧用加圧エアタンク、１４芯管用加圧エアタンク、１５濾過膜入口弁、１６洗浄排水弁、１７濾過水出口弁、１８濾過水バイパス弁、１９バッファータンク側から見て膜モジュールの生産水側と芯管側を切り替える切替弁、２０濾過水バッファータンク加圧用空気弁、２１芯管用空気弁、２２エアライン用空気弁、２３濾過水バッファータンク加圧用加圧エアタンク圧力設定用減圧弁、２４芯管用加圧エアタンク圧力設定用減圧弁などから構成される。
【００１１】
本発明の物理的洗浄方法としては、例えば、清澄水や空気を比較的高い流量で流す方法、清澄水や気体を流量変化を与えて流す方法、振動を与えて付着物を剥離する方法、超音波を与えて付着物を剥離する方法、熱ショックで付着物を剥離する方法などが挙げられる。特に膜の生産水側から濾過水などの清澄水を流す方法、濾過膜モジュールの生産水側から清澄水を流しながら芯管側から加圧空気を流して濾過膜モジュールを洗浄する方法、芯管側から濾過水を流し濾過膜を洗浄する方法、あるいはこれらを組み合わせる方法が好適である。
【００１２】
物理的洗浄方法としては、例えば、濾過膜の生産水側から濾過水を流して濾過膜を洗浄する方法がある。これは、バッファータンク側から見て濾過膜モジュールの生産水側と芯管側を切り替える切替弁１９を生産水側にして、その他の弁を閉にした後、濾過水バッファータンク加圧用空気弁２０を開にし、洗浄排水弁１６を開にする。この弁を開くタイミングは濾過水バッファータンク加圧用空気弁２０の開と同時か数秒後がよい。こうすることで濾過水バッファータンク１２にためられた濾過水が濾過水バッファータンク加圧用加圧エアタンク１３の空気圧で押し出されて、濾過水が濾過膜の生産水側から原水側に向かって流れ、濾過膜の外側表面に付着した濁質を剥がすことで濾過膜表面を洗浄できる。
【００１３】
別の物理洗浄方法としては、濾過膜の生産水側から濾過水を流し濾過膜を洗浄すると同時に、芯管側から加圧空気を流して濾過膜モジュールを洗浄する方法がある。この方法は、バッファータンク側から見て濾過膜モジュールの生産水側と芯管側を切り替える切替弁１９を生産水側にして、その他の弁を閉にした後、濾過水バッファータンク加圧用空気弁２０と芯管用空気弁２１を開にし、洗浄排水弁１６を開にする。この弁を開くタイミングは濾過水バッファータンク加圧用空気弁２０、芯管用空気弁２１の開と同時か数秒後がよい。こうすることで濾過水バッファータンク１２にためられた濾過水が濾過水バッファータンク加圧用加圧エアタンク１３の空気圧で押し出されて濾過水が濾過膜の生産水側から原水側に向かって流れ、濾過膜の外側表面に付着した濁質を剥がすと同時に、芯管側から中空糸束間を水が勢いよく流れ濾過膜モジュール内の濁質を効率よく排出することができる。
【００１４】
また、別の物理的洗浄方法としては、芯管側から濾過水を流し膜を洗浄する方法がある。この方法は、バッファータンク側から見て膜モジュールの生産水側と芯管側を切り替える切替弁１９を芯管側にして、その他の弁を閉にした後、濾過水バッファータンク加圧用空気弁２０を開にし、洗浄排水弁１６を開にする。この弁を開くタイミングは濾過水バッファータンク加圧用空気弁２０の開と同時か数秒後でよい。こうすることで、芯管に高速の濾過水が流れ、中空糸束間を水が勢いよく流れ膜を洗浄することができる。
【００１５】
これらの物理的洗浄を実施した後には、濾過膜モジュール内の水を排出し、剥離した生物分などの濁質を除去する。この排出方法としては、バッファータンク側から見て濾過膜モジュールの生産水側と芯管側を切り替える切替弁１９を生産水側にして、洗浄排水弁１６を開にして、その他の弁を閉にした後、芯管用空気弁２１を開にすることで、芯管からエアが供給され、濾過膜モジュール１１内の水を効率よく短時間で抜くことができる。
【００１６】
本発明では、物理的洗浄を行った後に、薬液洗浄を行う。この薬液洗浄の方法は、濾過洗浄を行いながら原水または濾過水に薬液を注入する方法で行なう。例えば、濾過膜入口弁１５、濾過水バイパス弁１８、エアライン用空気弁２２を開の状態にして、切替弁１９を生産水側にして、その他の弁を閉にして、原水送液ポンプ１０にて原水を濾過膜モジュール１１に送液する洗浄濾過操作と同時に薬液ポンプ０９にて薬液を送液することで濾過膜モジュール１１を薬液で満たす。
原水の代わりに濾過水を用いても構わない。
【００１７】
これらの方法をとれば、濾過膜モジュール１１内の水はあらかじめ抜いてあるため、原水送液ポンプ１０の送り量と薬液ポンプ０９の薬液送り量で決まる薬液濃度で簡単に膜モジュールは所定の薬液濃度で満たされることになる。また、薬液の入った濾過水は濾過水バイパス弁１８にて排水側に排出されることで生産水タンクに薬液の入った濾過水が入ることはなく、より安全な生産水が得られることになる。
【００１８】
薬液洗浄に用いる薬液としては、例えば次亜塩素酸ソーダ、塩酸、クエン酸等が挙げられる。特に次亜塩素酸ソーダが好適である。薬液洗浄における次亜塩素酸ソーダ薬液濃度は塩素濃度として２〜５ｐｐｍが好適である。
【００１９】
本発明においては、この薬液洗浄の後に前記物理的洗浄のいずれかを再び行う。その後濾過膜モジュール１１内の水を前記方法などで完全に抜く。この後、更に原水又は濾過水を流して洗浄濾過を行う。この方法は、例えば、濾過膜入口弁１５と濾過水バイパス弁１８とエアライン用空気弁２２を開の状態にして、切替弁１９を生産水側にして、その他の弁を閉にして、原水送液ポンプ１０にて原水を濾過膜モジュール１１に送り濾過を行う。濾過膜モジュール１１には濾過膜に付着した薬液が残っているが、濾過水バイパス弁１８にて排水側に排出されることで、生産水タンクに残存した薬液が混入した濾過水が流れ込むことがなく、より安全な生産水が得られることになる。この濾過後は同様に物理洗浄を行い、その後濾過膜モジュール１１内の水を完全に抜く。この洗浄濾過、物理洗浄を数回繰り返すことで残った薬液の濃度を効率的に下げることができる。
【００２０】
【実施例】
以下、本発明を実施例により具体的に説明する。
【実施例】
本発明は図−１に示すように中空糸型分離膜を芯管のまわりに複数本結束し、当該中空膜モジュールの結束開口端部にて中空糸が他分離膜を熱可塑性樹脂素材であるシール部材を用いることにより、中空糸型分離膜の内側と外側を液密にシールしたシール部を有するエレメントを作製し、これをケースに入れ、芯管がケース外に配管にて接続できる構造を有するモジュールを作製し、膜モジュールとして使用した。
【００２１】
図−２に示すように、薬液ポンプ０９、原水送液ポンプ１０、膜モジュール１１、濾過水バッファータンク１２、濾過水バッファータンク加圧用加圧エアタンク１３、芯管用加圧エアタンク１４、膜入口弁１５、洗浄排水弁１６、濾過水出口弁１７、濾過水バイパス弁１８、バッファータンク側から見て膜モジュールの生産水側と芯管側を切り替える切替弁１９、濾過水バッファータンク加圧用空気弁２０、芯管用空気弁２１、エアライン用空気弁２２、濾過水バッファータンク加圧用加圧エアタンク圧力設定用減圧弁２３、芯管用加圧エアタンク圧力設定用減圧弁２４からなる芯管付きのモジュールを用いた膜濾過装置を作製しテストを行った。
【００２２】
原水の濾過時には、膜入口弁１５、濾過水出口弁１７、エアライン用空気弁２２を開状態、切替弁１９を生産水側、その他の弁を閉にし、原水送液ポンプ１０にて原水を膜モジュール１１に送液して濾過を行う。この時、濾過水バッファータンク加圧用加圧エアタンク１３、芯管用加圧エアタンク１４には濾過水バッファータンク加圧用加圧エアタンク圧力設定用減圧弁２３、芯管用加圧エアタンク圧力設定用減圧弁２４で設定された空気圧で圧縮空気が満たされている。
【００２３】
洗浄操作の有効性は、以下のような条件で行い、評価した。
（１）原水：琵琶湖水
（２）運転条件
濾過膜モジュール：濾過膜面積１８０ｍ²（中空糸膜外側の総面積）、
モジュール数：１本、
濾過膜素材：ＣＴＡ（セルローストリアセテート）製限外濾過（ＵＦ）膜
濾過速度及び時間：
２ｍ³／ｈｒで２４時間濾過を行なった後に洗浄操作を行った。
【００２４】
（３）洗浄操作後の流量回復率
初期流量÷洗浄後流量×１００（％）で求めた値である。
（４）洗浄操作後の残留薬液濃度
洗浄操作終了直後の生産水中の残留薬液濃度（次亜塩素酸濃度）を測定した。薬液洗浄において原水へ注入した次亜塩素酸濃度は２ｐｐｍである。濃度は比色法にて測定した。
（５）薬液洗浄方法
薬液洗浄は、原水に薬液を注入し濾過膜の原水側から生産水側に向かって濾過を行いながら、３分間行った。
（６）物理的洗浄方法
物理的洗浄は発明の実施形態に記載の物理的洗浄方法を組み合わせて行った。即ち、濾過膜の生産水側から濾過水を流して濾過膜を洗浄する方法を７秒間行い、次に濾過膜の生産水側から濾過水を流し濾過膜を洗浄すると同時に、芯管側から加圧空気を流して濾過膜モジュールを洗浄する方法を１０秒間、次に芯管側から加圧された濾過水を流し膜を洗浄する方法を１０秒間実施し、その後モジュール内の水を抜いた。
＜比較例１＞薬液洗浄のみを実施した。
＜比較例２＞物理的洗浄後に濾過膜モジュール内を排水せずに、引続き薬液洗浄を実施し、その後、再び物理的洗浄を実施した。
＜実施例１＞物理的洗浄後に濾過膜モジュール内を排水し、次いで薬液洗浄を実施した後、再び物理的洗浄を実施した後、濾過膜モジュール内を排水した。
＜実施例２＞物理洗浄＋排水＋薬液洗浄＋物理洗浄＋排水＋洗浄濾過＋物理洗浄＋排水（最後の洗浄濾過＋物理洗浄＋排水は各々３回繰り返した）
【００２５】
洗浄操作テスト結果は次ぎのとおりであった。
それぞれの洗浄方法を実施した後の濾過水の流量回復率は、
比較例１(90%)＜比較例２(95%)＜＜実施例１(100%)＝実施例２(100%)であった。
また、テスト開始後１ヶ月後の濾過水の流量回復率は、
比較例１(70%)＜比較例２(85%)＜＜実施例１(95%)＝実施例２(96%)であり、実施例１と実施例２はほとんど濾過水量の変動は見られなかったが、比較例１は初期水量に対し約３０％の水量低下、比較例２は初期水量に対し約１５％の水量低下が見られた。
洗浄終了後の残留薬液濃度に関して比較した。原水へ注入した次亜塩素酸濃度は２ｐｐｍに対して、
比較例１：１．８ｐｐｍ
比較例２：１．４ｐｐｍ
実施例１：１．０ｐｐｍ
実施例２：０．３ｐｐｍ
であった。
【００２６】
【発明の効果】
上記のとおり、本発明の薬液洗浄方法によれば、オンラインで効率的に濾過膜モジュールの洗浄ができ、かつ濾過モジュールの濾過流量の回復性が高い。また、効率的に残留薬液濃度を低下させるこのとできる。
【図面の簡単な説明】
【図１】本発明で使用した濾過膜モジュールの一例である。
【図２】本発明による膜濾過装置のフロー図の一例である。
【符号の説明】
０１原水入口
０２濾過水入口
０３中空糸型分離膜束
０４シール材
０５ケース
０６芯管
０７芯管継ぎ手
０８Ｏリング
０９薬液ポンプ
１０原水送液ポンプ
１１濾過膜モジュール
１２濾過水バッファータンク
１３濾過水バッファータンク加圧用加圧エアタンク
１４芯管用加圧エアタンク
１５濾過膜入口弁
１６洗浄排水弁
１７濾過水出口弁
１８濾過水バイパス弁
１９バッファータンク側から見て膜モジュールの生産水側と芯管側を切り替える切替弁
２０濾過水バッファータンク加圧用空気弁
２１芯管用空気弁
２２エアライン用空気弁
２３濾過水バッファータンク加圧用加圧エアタンク圧力設定用減圧弁
２４芯管用加圧エアタンク圧力設定用減圧弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cleaning a filtration apparatus using a filtration membrane equipped with a filtration membrane module. In particular, the present invention relates to a cleaning method for efficiently performing chemical cleaning of a filtration membrane module.
[0002]
[Prior art]
In a membrane filtration device that obtains filtered water from raw water using a filtration membrane module, biological matter adheres to the surface of the filtration membrane or metal components accumulate in the pores of the filtration membrane, causing the filtration membrane to clog. There is a problem that the amount of filtered water decreases.
[0003]
In order to solve such problems, physical cleaning and chemical cleaning of the filtration membrane module are performed. There are two methods for cleaning a membrane membrane chemical solution: an offline method and an online method. In the case of the method of performing chemical cleaning while circulating off-line, it is necessary to stop the filtration membrane device for a long time.
[0004]
On the other hand, when chemical cleaning is performed online, there is a problem in that the chemical solution is wasted due to the biological and metal components accumulated in the module unless physical cleaning is performed in advance, and the efficiency of the chemical cleaning is reduced. In addition, there is a problem that it is difficult to adjust the chemical concentration when the chemical cleaning is performed in a state where the filtration membrane module is filled with water.
[0005]
In addition, after the chemical cleaning, it is necessary to discharge the biological component that has been easily peeled off by the chemical solution or the metal component that is clogged in the pores of the membrane and dissolved in the chemical solution. These cannot be completely discharged simply by discharging the water in the filtration membrane module out of the filtration membrane module.
[0006]
Further, the chemical liquid component adhering to the base material of the filtration membrane remains in the filtration membrane module. If filtration is performed as it is, the chemical liquid component may flow out to the filtered water side.
[Problems to be solved by the invention]
An object of this invention is to provide the online chemical | medical solution washing | cleaning method for wash | cleaning a filtration membrane module efficiently in the filtration apparatus using the filtration membrane which equips a filtration membrane module.
[0007]
[Means for Solving the Problems]
As a result of studying the above problems, the inventor of the present application performs physical cleaning before performing chemical cleaning. In addition, after the chemical cleaning, perform physical cleaning and thoroughly clean the inside of the membrane filter module. In addition, wash and filter after cleaning the chemical solution to sufficiently reduce the chemical concentration in the membrane module. Take measures to prevent chemical components from entering the production water. Has found that the above-mentioned problems can be achieved.
[0008]
That is, the present invention is as follows.
1) An element in which a plurality of hollow fiber type separation membranes are bundled around a core tube, and the production water side and the raw water side of the hollow fiber type separation membrane are liquid-tightly sealed by a sealing member made of a thermoplastic resin at the binding end. In a method for cleaning a filtration membrane module having a structure in which the core tube can be connected to the outside of the case by piping , (1) the filtered water is flowed from the production water side of the filtration membrane module to the raw water side The filtration membrane is washed by performing filtration, and then the filtration membrane is washed by flowing pressurized air from the core tube while performing the washing, and then the filtered water is further fed from the core tube and filtered. After performing physical washing to wash the membrane, (2) drain the water in the filtration membrane module, and (3) then inject the chemical into the raw water and perform the filtration from the raw water side of the filtration membrane to the production water side It performs washing, row (4) the physical cleaning , (5) disconnect the water in the filtration membrane module, and (6) was washed filtering the raw water or the filtered water is pumped to the raw water side of the filtration membrane module, and then perform the physical cleaning (7), ( 8) Thereafter, the water in the filtration membrane module is drained, and the concentration of the remaining chemical solution in the filtration membrane module is reduced to 3/20 or more and 1/2 or less of the cleaning chemical solution concentration by repeating the operations (6) to (8). A method for cleaning a filtration membrane module.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The on-line chemical cleaning method for a filtration membrane module according to the present invention is used, for example, as a method for cleaning a membrane filtration device for obtaining purified water from raw water of a lake or a river. Examples of the filtration membrane module include filtration membrane modules such as an ultrafiltration membrane and a microfiltration membrane. In particular, a membrane filtration device equipped with a hollow fiber membrane module in which a plurality of hollow fiber type separation membranes as shown in Fig. 1 are bundled around a core tube is easy to clog because the biological matter adheres to the filtration membrane. It is effective to apply the cleaning method of the invention.
[0010]
The membrane filtration apparatus of the present invention includes, for example, a 10 raw water feed pump, an 11 filtration membrane module, a 12 filtrate buffer tank, a pressurized air tank for pressurizing a 13 filtrate buffer tank, as shown in the flowchart of FIG. 14 core pipe pressurized air tank, 15 filtration membrane inlet valve, 16 washing drain valve, 17 filtrate outlet valve, 18 filtrate bypass valve, 19 switching to switch the production water side and core pipe side of the membrane module as seen from the buffer tank side Valve, 20 filtrate water tank pressurization air valve, 21 core pipe air valve, 22 air line air valve, 23 filtrate water buffer tank pressurization air tank pressure setting pressure reducing valve, 24 core pipe pressurization air tank pressure setting It consists of a pressure reducing valve.
[0011]
Examples of the physical cleaning method of the present invention include, for example, a method of flowing clear water and air at a relatively high flow rate, a method of flowing clear water and gas by changing the flow rate, a method of peeling off deposits by applying vibration, Examples thereof include a method of peeling off the adhered matter by applying a sound wave, and a method of removing the adhered matter by heat shock. In particular methods of producing water side of the membrane flow clarification of water, such as filtered water, a method of cleaning a filtration membrane module by flowing pressurized air from the core tube side while passing clarified water from the production water side of the filter membrane modules, core tube A method of washing filtered membrane by flowing filtered water from the side, or a method of combining them is suitable.
[0012]
As a physical cleaning method, for example, there is a method of cleaning the filtration membrane by flowing filtered water from the production water side of the filtration membrane. This is because the switching valve 19 for switching between the production water side and the core tube side of the filtration membrane module as viewed from the buffer tank side is set to the production water side, the other valves are closed, and then the air valve 20 for pressurizing the filtrate water buffer tank. And the cleaning drain valve 16 is opened. The timing for opening this valve may be the same as the opening of the filtered water buffer tank pressurizing air valve 20 or several seconds later. By doing so, the filtrate stored in the filtrate buffer tank 12 is pushed out by the air pressure of the pressurized air tank 13 for pressurizing the filtrate buffer tank, and the filtrate flows from the production water side of the filtration membrane toward the raw water side , The surface of the filtration membrane can be cleaned by removing the turbidity adhering to the outer surface of the filtration membrane.
[0013]
Another physical cleaning methods, there is a method of cleaning a filtration membrane module at the same time, flow of pressurized air from the core pipe side when cleaning a filtration membrane flowing filtered water from the production water side of the filter membrane. In this method, the switching valve 19 for switching between the production water side and the core pipe side of the filtration membrane module as viewed from the buffer tank side is set to the production water side, the other valves are closed, and then the filtered water buffer tank pressurizing air valve 20 and the core tube air valve 21 are opened, and the cleaning drain valve 16 is opened. The timing for opening the valve may be the same as the opening of the filtered water buffer tank pressurizing air valve 20 and the core tube air valve 21 or several seconds later. In this way, the filtrate stored in the filtrate buffer tank 12 is pushed out by the air pressure of the pressurized air tank 13 for pressurizing the filtrate buffer tank, and the filtrate flows from the production water side to the raw water side of the filtration membrane. At the same time as the turbidity adhering to the outer surface of the membrane is peeled off, water vigorously flows between the hollow fiber bundles from the core tube side, and the turbidity in the filtration membrane module can be efficiently discharged.
[0014]
Further, as another physical cleaning method, there is a method of cleaning the membrane by flowing filtered water from the core tube side. In this method, the switching valve 19 for switching between the production water side and the core pipe side of the membrane module as viewed from the buffer tank side is set to the core pipe side, the other valves are closed, and then the filtered water buffer tank pressurizing air valve 20 And the cleaning drain valve 16 is opened. The timing for opening the valve may be the same as the opening of the filtered water buffer tank pressurizing air valve 20 or a few seconds later. By doing so, high-speed filtered water flows through the core tube, and the water can vigorously flow between the hollow fiber bundles to wash the membrane.
[0015]
After performing these physical washings, the water in the filtration membrane module is drained to remove turbidity such as exfoliated organisms. As a discharge method, the switching valve 19 for switching between the production water side and the core pipe side of the filtration membrane module as viewed from the buffer tank side is set to the production water side, the washing drain valve 16 is opened, and the other valves are closed. After that, by opening the air valve 21 for the core tube, air is supplied from the core tube, and the water in the filtration membrane module 11 can be drained efficiently and in a short time.
[0016]
In the present invention, chemical cleaning is performed after physical cleaning. This chemical cleaning method is performed by injecting chemical into raw water or filtered water while performing filtration cleaning. For example, the filtration membrane inlet valve 15, the filtrate water bypass valve 18, and the air line air valve 22 are opened, the switching valve 19 is set to the production water side, the other valves are closed, and the raw water feed pump 10 The filtration membrane module 11 is filled with the chemical solution by feeding the chemical solution with the chemical pump 09 simultaneously with the washing and filtration operation for sending the raw water to the filtration membrane module 11.
Filtered water may be used instead of raw water.
[0017]
If these methods are taken, the water in the filtration membrane module 11 is drained in advance, so that the membrane module can be easily set to a predetermined chemical solution at a chemical concentration determined by the feed amount of the raw water feed pump 10 and the chemical solution feed amount of the chemical solution pump 09. It will be filled with concentration. Further, the filtered water containing the chemical solution is discharged to the drain side by the filtered water bypass valve 18 so that the filtered water containing the chemical solution does not enter the production water tank, and safer production water can be obtained. Become.
[0018]
Examples of the chemical solution used for the chemical cleaning include sodium hypochlorite, hydrochloric acid, citric acid and the like. Sodium hypochlorite is particularly preferred. The concentration of sodium hypochlorite chemical in chemical cleaning is preferably 2 to 5 ppm as the chlorine concentration.
[0019]
In the present invention, after the chemical cleaning, any of the physical cleaning is performed again. Thereafter, the water in the filtration membrane module 11 is completely drained by the method described above. Thereafter, the raw water or filtered water is further poured to perform washing filtration. In this method, for example, the filtration membrane inlet valve 15, the filtrate water bypass valve 18, and the air line air valve 22 are opened, the switching valve 19 is set to the production water side, the other valves are closed, and the raw water The raw water is sent to the filtration membrane module 11 by the liquid feed pump 10 and filtered. Although the chemical solution adhering to the filtration membrane remains in the filtration membrane module 11, the filtered water mixed with the chemical solution remaining in the production water tank may flow in by being discharged to the drain side by the filtered water bypass valve 18. Therefore, safer production water can be obtained. After this filtration, physical washing is performed in the same manner, and then the water in the filtration membrane module 11 is completely drained. By repeating this washing filtration and physical washing several times, the concentration of the remaining chemical solution can be lowered efficiently.
[0020]
【Example】
Hereinafter, the present invention will be specifically described by way of examples.
【Example】
In the present invention, as shown in FIG. 1, a plurality of hollow fiber type separation membranes are bundled around a core tube, and the hollow fibers are made of a thermoplastic resin material at the binding opening end of the hollow membrane module. By using a seal member, an element having a seal part in which the inner side and the outer side of the hollow fiber type separation membrane are sealed in a liquid-tight manner is manufactured, and this is put in a case, and a structure in which the core tube can be connected to the outside of the case by piping A module having the same was produced and used as a membrane module.
[0021]
As shown in FIG. 2, the chemical liquid pump 09, the raw water feed pump 10, the membrane module 11, the filtrate water buffer tank 12, the pressurized water tank 13 for pressurizing the filtrate water buffer tank, the pressurized air tank 14 for the core tube, and the membrane inlet valve 15. , A washing drain valve 16, a filtrate outlet valve 17, a filtrate bypass valve 18, a switching valve 19 for switching the production water side and the core pipe side of the membrane module as viewed from the buffer tank side, an air valve 20 for pressurizing the filtrate buffer tank, A module with a core pipe comprising a core pipe air valve 21, an air line air valve 22, a pressurized air tank pressure setting pressure reducing valve 23 for pressurizing a filtrate buffer tank, and a core pipe pressing air tank pressure setting pressure reducing valve 24 was used. A membrane filtration device was fabricated and tested.
[0022]
During raw water filtration, the membrane inlet valve 15, the filtrate water outlet valve 17, and the air line air valve 22 are opened, the switching valve 19 is closed on the production water side, the other valves are closed, and the raw water feed pump 10 supplies the raw water. The solution is sent to the membrane module 11 and filtered. At this time, the pressurized air tank 13 for pressurizing the filtrate water buffer tank and the pressurized air tank 14 for the core tube are provided with a pressure reducing valve 23 for setting the pressurized air tank pressure for the filtered water buffer tank and a pressure reducing valve 24 for setting the pressure air tank pressure for the core tube. Compressed air is filled with the set air pressure.
[0023]
The effectiveness of the washing operation was evaluated under the following conditions.
(1) Raw water: Lake Biwa water (2) Operating conditions Filtration membrane module: Filtration membrane area 180 m ² (total area outside the hollow fiber membrane),
Number of modules: 1
Filtration membrane material: CTA (cellulose triacetate) ultrafiltration (UF) membrane filtration rate and time:
After 24 hours of filtration at 2 m ³ / hr, a washing operation was performed.
[0024]
(3) Flow rate recovery rate after cleaning operation Initial flow rate / flow rate after cleaning × 100 (%).
(4) Residual chemical concentration after the cleaning operation The residual chemical concentration (hypochlorous acid concentration) in the production water immediately after the completion of the cleaning operation was measured. The concentration of hypochlorous acid injected into the raw water during chemical cleaning is 2 ppm. The density was measured by a colorimetric method.
(5) Chemical liquid cleaning method The chemical liquid cleaning was performed for 3 minutes while injecting the chemical liquid into the raw water and filtering from the raw water side of the filtration membrane toward the production water side .
(6) Physical cleaning method Physical cleaning was performed in combination with the physical cleaning method described in the embodiment of the invention. That is, the filtration membrane is washed by flowing filtered water from the production water side of the filtration membrane for 7 seconds, then the filtration water is washed from the production water side of the filtration membrane to wash the filtration membrane, and at the same time, added from the core tube side. A method of washing the filtration membrane module by flowing pressurized air was carried out for 10 seconds, and then a method of washing the membrane by flowing pressurized filtered water from the core tube side was carried out for 10 seconds, and then the water in the module was drained.
<Comparative Example 1> Only chemical cleaning was performed.
<Comparative Example 2> After the physical cleaning, the inside of the filtration membrane module was not drained, followed by chemical cleaning, and then physical cleaning again.
<Example 1> The inside of the filtration membrane module was drained after the physical cleaning, and then the chemical cleaning was performed, and then the physical cleaning was performed again, and then the filtration membrane module was drained.
<Example 2> Physical washing + drainage + chemical washing + physical washing + drainage + washing filtration + physical washing + drainage (last washing filtration + physical washing + drainage was repeated three times each)
[0025]
The cleaning operation test results were as follows.
The flow rate recovery rate of filtered water after each cleaning method is
Comparative Example 1 (90%) <Comparative Example 2 (95%) << Example 1 (100%) = Example 2 (100%).
The flow rate recovery rate of filtered water one month after the start of the test is
Comparative Example 1 (70%) <Comparative Example 2 (85%) << Example 1 (95%) = Example 2 (96%). In Examples 1 and 2, almost no change in the amount of filtered water was observed. However, Comparative Example 1 showed about a 30% decrease in water amount relative to the initial water amount, and Comparative Example 2 showed a decrease in water amount of about 15% relative to the initial water amount.
A comparison was made with respect to the concentration of the remaining chemical solution after completion of washing. The hypochlorous acid concentration injected into the raw water is 2 ppm,
Comparative Example 1: 1.8 ppm
Comparative Example 2: 1.4 ppm
Example 1: 1.0 ppm
Example 2: 0.3 ppm
Met.
[0026]
【The invention's effect】
As described above, according to the chemical solution cleaning method of the present invention, the filtration membrane module can be efficiently cleaned online, and the filtration flow rate of the filtration module is highly recoverable. In addition, this can effectively reduce the concentration of the residual chemical solution.
[Brief description of the drawings]
FIG. 1 is an example of a filtration membrane module used in the present invention.
FIG. 2 is an example of a flow diagram of a membrane filtration device according to the present invention.
[Explanation of symbols]
01 Raw water inlet 02 Filtration water inlet 03 Hollow fiber type separation membrane bundle 04 Seal material 05 Case 06 Core pipe 07 Core pipe joint 08 O-ring 09 Chemical liquid pump 10 Raw water feed pump 11 Filtration membrane module 12 Filtration water buffer tank 13 Filtration water buffer tank 13 Pressurized air tank for tank pressurization 14 Pressurized air tank for core pipe 15 Filtration membrane inlet valve 16 Washing drain valve 17 Filtration water outlet valve 18 Filtration water bypass valve 19 Switching between the production water side and core pipe side of the membrane module as seen from the buffer tank side Switch valve 20 Filtration water buffer tank pressurization air valve 21 Core pipe air valve 22 Air line air valve 23 Filtration water buffer tank pressurization air tank pressure setting pressure reducing valve 24 Core pipe pressure air tank pressure setting pressure reducing valve

Claims

A plurality of hollow fiber type separation membranes are bundled around the core tube, and an element is produced in which the production water side and the raw water side of the hollow fiber type separation membrane are liquid-tightly sealed with a sealing member made of thermoplastic resin at the binding end. In the method for cleaning a filtration membrane module having a structure in which the core tube can be connected to the outside of the case by piping , (1) the filtrate is flowed from the production water side of the filtration membrane module toward the raw water side. The filtration membrane is washed by performing filtration, and then the filtration membrane is washed by flowing pressurized air from the core tube while performing the washing, and then the filtered water is further poured from the core tube to remove the filtration membrane. After performing physical washing to wash, (2) drain the water in the filtration membrane module, (3) then inject chemical into the raw water and perform chemical washing to perform filtration from the raw water side of the membrane to the production water side deeds, performs (4) the physical cleaning, 5) disconnect the water in the filtration membrane module, and (6) was washed filtration to feed the raw water side of the filtration membrane module raw or filtered water, subjected to (7) followed by the physical cleaning, (8) Thereafter, the water in the filtration membrane module is drained, and the residual chemical solution concentration in the filtration membrane module is reduced to 3/20 or more and 1/2 or less of the cleaning chemical solution concentration by repeating the operations (6) to (8). A method for cleaning a filtration membrane module.