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JP3698093B2 - Water treatment method and water treatment apparatus - Google Patents

Water treatment method and water treatment apparatus Download PDF

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Publication number
JP3698093B2
JP3698093B2 JP2001357313A JP2001357313A JP3698093B2 JP 3698093 B2 JP3698093 B2 JP 3698093B2 JP 2001357313 A JP2001357313 A JP 2001357313A JP 2001357313 A JP2001357313 A JP 2001357313A JP 3698093 B2 JP3698093 B2 JP 3698093B2
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water
membrane
treatment
solid
activated carbon
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JP2003154362A (en
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啓一 池田
敏裕 池田
亮太 高木
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Toray Industries Inc
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Toray Industries Inc
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  • Physical Water Treatments (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Water Treatment By Sorption (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)
  • Treatment Of Water By Ion Exchange (AREA)

Description

【0001】
【発明の属する技術分野】
本発明は、河川や湖沼等の水を浄化するのに好適に用いられる水処理方法および水処理装置に関する。
【0002】
【従来の技術】
膜分離技術は、固液分離、イオンの分離、ガス分離などに用いられる技術で、近年、工業用水製造および食品、医療、浄水処理、海水淡水化など様々な分野で用いられている。中でもナノろ過膜(NF膜:Nanofiltration Membrane)や逆浸透膜(RO膜:Reverse Osmosis Membrane)は、高品質な水を生産できる膜として広く利用されている。
【0003】
RO膜、NF膜は、一般に、原水を膜面に沿って供給し、透過水を原水に対して直角方向に流すクロスフローろ過方式で使われ、膜モジュールに供給した原水の一部が循環し、膜面にせん断力を与えることで、原水中の懸濁物質やコロイド物質などのファウリング物質の膜面への付着や堆積を抑制することができる。膜を透過しなかった水は濃縮水と呼ばれ、水処理装置の回収率によって一部が排水され、残りが膜供給水側に返送される。
【0004】
回収率の設定については、水資源と水利権の観点から、また、排水量(濃縮水量)削減や前処理・排水処理工程の小規模化の観点から、高く設定することが重要である。しかしながら、回収率が高くなれば、除去対象物質の除去率に見合って各成分の濃縮倍率も上がり、膜への負荷が大きくなる。特に、微生物、中〜高分子のフミン酸等によるファウリングや、カルシウム、マグネシウム、シリカ等が炭酸カルシウム、水酸化マグネシウム、硫酸カルシウム水和物、シリカとして析出し膜表面に付着するスケールによって、透過水量の低下や差圧の上昇等が発生し、安定運転を困難にすることがあり、被処理水の水質にもよるが80%程度の回収率が限界と考えられている。
【0005】
また、RO膜やNF膜を備えた膜モジュールの濃縮水には、水質汚濁防止法の排水基準で規制されているような、農薬や微量有害有機物、塩類等の溶解性成分が濃縮されて含まれるが、回収率が高いほど水質汚濁防止法の排水基準を超えることが多くなり、濃縮水を何らかの用途に直接再利用したり河川などに直接放流することができなくなる。そのため、排水基準を超過する成分については別途処理が必要となる。低回収率では放流のための排水処理施設の規模が大きくなってしまい、例えば回収率80%の場合には造水量1万m/dに対して排水量は約1,100m/dとなり、処理コストが大きくなる。
【0006】
【発明が解決しようとする課題】
本発明の目的は、上記従来の問題点を解消し、水資源の有効利用のために、従来80%程度が限界であった回収率を大幅に引き上げるとともに、RO膜やNF膜の安定運転を可能にし、排水基準の規制強化対策に対応が可能な水処理方法および水処理装置を提供することを目的とするものである。
【0007】
【課題を解決するための手段】
上記の課題を達成するための本発明は、原水を、固液分離した後、逆浸透膜(RO膜)および/またはナノろ過膜(NF膜)を備えた膜モジュールで透過水と濃縮水とに分離する水処理方法であって、回収率が少なくとも90%になるように運転するとともに、膜モジュールの濃縮水の少なくとも一部を軟化処理法および有機物除去法で処理して原水に還流させることを特徴とする水処理方法であって、前記有機物除去法が、オゾン処理、紫外線処理、過酸化水素処理および触媒処理の群から選ばれる少なくとも2つの処理を施す促進酸化処理を含むものであることを特徴とするものである。
【0008】
このとき、軟化処理法がイオン交換を含むものであることや、有機物除去法が、さらに活性炭処理を含むものであることが好ましい。精密ろ過膜(MF膜)および/または限外ろ過膜(UF膜)を用いて固液分離を行うことや、固液分離の前段で原水に凝集剤を添加することも好ましい。
【0009】
また、本発明は、原水を固液分離する固液分離手段と、固液分離手段の処理水を透過水と濃縮水とに分離する、逆浸透膜(RO膜)および/またはナノろ過膜(NF膜)を有する膜モジュールと、膜モジュールの濃縮水の少なくとも一部を処理して原水へ還流させる、有機物除去手段および軟化処理手段を有する還流手段とを備えていることを特徴とする水処理装置であって、前記還流手段は、有機物除去手段として促進酸化処理手段を備え、促進酸化処理手段、軟化処理手段をこの順序で配置していることを特徴とするものである
【0010】
また、有機物除去手段が、さらに活性炭処理手段を備えており、前記促進酸化処理手段、該活性炭処理手段、および前記軟化処理手段をこの順序で配置していることが好ましい。
【0011】
さらに、上記いずれかの方法または装置を用いる造水方法も好ましい態様である。
【0012】
なお、本発明における回収率は下式の通り、膜モジュールへの供給水量から膜供給水側に返送される濃縮水量を差し引いた水量(a)に対する膜透過水量(b)の比であり、膜分離法における量的な処理効率を示す指標である。
【0013】
【数1】

Figure 0003698093
【0014】
【発明の実施の形態】
図1に本発明の水処理装置のフローの一例を示す。この水処理装置は、原水50を固液分離する固液分離装置3と、固液分離装置3の分離水60を透過水70と濃縮水80とに分離する、逆浸透膜(RO膜)および/またはナノろ過膜(NF膜)を有する膜モジュール6と、膜モジュール6の濃縮水80を処理して原水50へ還流させる、有機物除去手段(促進酸化処理装置7、活性炭処理装置8)および軟化処理装置9を有する還流手段10とを備えている。また、固液分離装置3よりも上流側には、原水50を一旦貯留するタンク1と、タンク1に貯留された水を加圧して固液分離装置3に送水する加圧ポンプ2を設けており、固液分離装置3と膜モジュール6の間には、固液分離装置3による分離水60を貯留するタンク4と、タンク4に貯留された分離水60を加圧して膜モジュール6に送水する加圧ポンプ5とを設けている。
【0015】
この水処理装置において、タンク1に貯留された原水50は、加圧ポンプ2によって固液分離装置3に送水され、固液分離装置3によって懸濁物質が除去される。本発明においては、原水50に含有されている濁質、微生物、有機物等の不純物がRO膜やNF膜の表面に付着してろ過差圧が急上昇するのを防ぐために、原水50を予め固液分離し、RO膜やNF膜に導かれる分離水60のFI(Fouling Index)値を調整する。FI値は、スパイラル型モジュールの場合5以下に、中空糸型モジュールの場合は4以下にすることが好ましい。FI値とはSDI(Silt Density Index)値とも称され、RO膜やNF膜への供給水(分離水60)中の不純物の管理指標であり、次式で表されるものである。
【0016】
FI=(1−T/T15)×100/15
このとき、Tは、0.45μmのメンブレンフィルターを用いて、試料水を206kPaの加圧下でろ過したときに、初めに500mlをろ過するのに要した時間であり、T15は、Tのあと同じ状態で続けて15分間ろ過した後に、試料水を再び500mlろ過するのに要した時間である。
【0017】
固液分離装置3としては、砂ろ過、保安フィルター等、原水中の懸濁物質の漏出を阻止するろ過装置が挙げられるが、微生物が膜孔内に入り込まない孔径1μm以下の精密ろ過膜(MF膜)や限外ろ過膜(UF膜)を単独あるいは組み合わせて用いることが好ましい。
【0018】
固液分離装置3に分離膜を用いる場合、膜透過流束や膜差圧の改善および処理水質の向上による処理能力と安定性の向上を目的として、原水に凝集剤を添加することもできる。凝集剤の注入率は、マイクロフロックを形成できる程度の少量として、そのまま膜分離する、あるいは凝集処理としては十分の凝集剤を添加し、凝集フロックを沈澱処理した後、その上澄み液を分離膜で処理してもよい。
【0019】
MF膜やUF膜等の分離膜は、分離水60のFI値をほぼ0に近づけることができることからもわかるように、除濁性が高まりNF膜およびRO膜をさらに長期的に安定運転できる。
【0020】
UF膜やMF膜の膜素材としては、酢酸セルロース、ポリアクリロニトリル、ポリエチレン、ポリエーテルスルホン、ポリスルホン、ポリプロピレン、ポリ弗化ビニリデン、セラミック等、いずれも適用可能である
膜形態としては、中空糸膜、管状膜、平膜など、いずれの形状のものでもよい。ここで、中空糸膜とは外径2mm未満の円管状の分離膜であり、管状膜とは外径2mm以上の円管状の分離膜である。中空糸膜は装置単位あたりの有効膜面積を大きくできる。
【0021】
そして、これらのUF膜やMF膜は、モジュール化され使用される。モジュールとしては菌体によって閉塞しがたい構造のものがよく、例えば、(1)外圧クロスフロー中空糸膜モジュール、(2)内径1mm以上の内圧クロスフロー中空糸膜モジュール等が、膜の充填率が高く、膜面積が大きくなるので好ましい。
【0022】
また、固液分離として用いる膜装置の運転方式には、定流量ろ過運転と定圧ろ過運転があるが、定流量ろ過運転は、一定の処理量を得ることができ、処理プロセスの制御が行いやすいので好ましい。
【0023】
上述の固液分離装置3で処理され懸濁物質が除去された分離水60は、タンク4に貯留された後、加圧ポンプ5によって膜モジュール6に加圧供給され、透過水70と濃縮水80とに分離される。このとき、膜モジュールにおける回収率が90%以上になるように運転する。
【0024】
膜モジュール6に使用されるナノろ過膜、逆浸透膜は以下のようなものである。
【0025】
すなわち、ナノろ過膜(NF膜:Nanofiltration Membrane)は主に分子量数百から数千程度以上の中〜高分子量の分子や二価イオン、重金属イオンなどの多価イオンの排除性能が高いもので、飲料水製造用途に用いる場合、主に、トリハロメタン前駆物質や農薬、フルボ酸等を除去することができる。除去対象物の大きさは限外ろ過膜(UF膜)と逆浸透膜(RO膜)の中間に位置するが、脱塩率が5%以上93%未満(評価条件 NaCl濃度:500〜2,000mg/l、操作圧力:0.5〜1.5MPa)とも定義されるものである。
【0026】
膜素材としては、ポリアミド系、ポリピペラジンアミド系、ポリエステルアミド系、あるいは水溶性のビニルポリマーを架橋したものなどがある。また、膜構造としては、膜の少なくとも片面に緻密層を持ち、緻密層から膜内部あるいはもう片方の面に向けて徐々に大きな孔径の微細孔を有する非対称や膜、非対称膜の緻密層の上に別の素材で形成された非常に薄い活性層を有する複合膜などがある。さらに、膜形態としては、平膜、中空糸膜等があり、たとえば膜厚を10μm〜1mmの範囲、中空糸膜の場合は外径を50μm〜4mmの範囲とする。
【0027】
また、逆浸透膜(RO膜:Reverse Osmosis Membrane)は、NF膜の除去対象物に加えて一価のイオン性物質を除去する場合(主に海水淡水化処理や鹹水脱塩、純水製造)に用いられ、脱塩率が93%以上(評価条件 NaCl濃度:500〜2,000mg/l、操作圧力:0.5〜3.0MPa)とも定義されるものである。
【0028】
膜素材としては、酢酸セルロース、セルロース系のポリマー、ポリアミド、およびビニルポリマー等の高分子材料を用いることができる。代表的な逆浸透膜としては、酢酸セルロース系またはポリアミド系の非対称膜、および、ポリアミド系の活性層を有する複合膜を挙げることができる。中でも、塩の排除性能が高い、酢酸セルロース系非対称膜、ポリアミド系活性層を有する複合膜および芳香族ポリアミド系の活性層を有する複合膜が好ましく、特に、芳香族ポリアミド複合膜は、高排除性能かつ高透水性であるので好ましい。膜構造としては、NF膜と同様、非対称膜や複合膜があり、膜形態についてもNF膜と同様、平膜、中空糸膜等があり、たとえば膜厚を10μm〜1mmの範囲、中空糸膜の場合は外径を50μm〜4mmの範囲とする。
【0029】
NF膜およびRO膜は、共に運転コストの観点から低圧で運転できるものが好ましいが、低圧運転時の造水量を考慮すると複合膜が好ましい。さらに好ましくはポリアミド系の複合膜であり、NF膜の場合は、ポリピペラジンアミド系の複合膜などが透過水量、耐薬品性等の点からより適している。
【0030】
そして、膜モジュール6は、上述のNF膜、RO膜を実際に使用するためにモジュール化されている。平膜状の場合はスパイラル型、プリーツ型、プレート・アンド・フレーム型、円盤状のディスクを積み重ねたディスクタイプに、中空糸膜の場合は、中空糸をU字状やI字状に束ねて容器に収納した中空糸膜型があるが、本発明はこれらモジュールの形態に左右されるものではない。
【0031】
また、本発明において、膜モジュール6には、RO膜、NF膜のいずれか一方を使用するのもよいし、両方を使用するのもよい。これらは、供給水(分離水60)および必要な透過水70の水質、透過水70の利用目的に応じて適宜選定すればよい。
【0032】
膜モジュール6は、多段に配置して、前段の膜モジュールの濃縮水を後段の膜モジュール6で処理するように構成してもよい。この場合には、後段のRO膜やNF膜の濃縮水中のカルシウム、マグネシウム、シリカ等の濃度が、溶解度を超えないことを注意する必要がある。
【0033】
膜モジュール6のろ過圧力は、膜供給水(分離水60)の種類、運転方法等により、0.5〜3.0MPa程度の範囲内で適宜設定することが好ましい。河川水や湖沼水等の淡水を処理する場合は浸透圧が低いため比較的低圧でろ過することができる。
【0034】
このような膜モジュール6においてRO膜やNF膜を透過した水は、透過水70として膜モジュール6から取り出される。この透過水は、トリハロメタン前駆物質や農薬、重金属イオン等が除去されているので、飲料用水や工業用水、農業用水等として利用される。
【0035】
一方、濃縮水80は、還流手段10に設けた有機物除去手段(促進酸化処理装置7、活性炭処理装置8)および軟化処理手段(軟化処理装置9)で処理し、少なくとも一部(軟化処理装置9による処理後の濃縮水100)をタンク1で原水と還流させる。原水に還流させなかった濃縮水(活性炭処理装置8による処理後の濃縮水90の一部)は、そのまま自然界に放流する有機物除去手段の除去対象は、主に臭気(カビ臭)、色度、トリハロメタン、トリハロメタン前駆物質、農薬、陰イオン界面活性剤、フェノール類、トリクロロエチレン等の低沸点有機塩素化合物となる。軟化処理手段の除去対象は、スケール成分であるカルシウム、マグネシウム等である。
【0036】
本発明は、予め固液分離で懸濁物質を除去した分離水60をRO膜やNF膜を備えた膜モジュール6で処理し、その際に得られる濃縮水80を、有機物除去手段および軟化処理手段で処理して再度固液分離や逆浸透分離、ナノろ過に導くので、水質を低下させずに回収率を高めることができ、また、膜モジュールを回収率90%以上で運転しても安定運転が可能となる。
【0037】
有機物除去手段としては、促進酸化処理装置7に加えて、活性炭処理装置8などを用いることができる。また、図1に示すように、促進酸化処理装置7単独で使うか、促進酸化処理装置7と活性炭処理装置8の両方を使うかは、濃縮水80の水質に応じて適宜決定すればよい。濃縮水における除去対象物の濃度が低い場合には、促進酸化処理装置7単独で用いればよいが、濃縮水80の各有機成分の濃度が高く、促進酸化処理単独での除去が困難な場合、両者を併用することが好ましい。また、濃縮水80中に、排水基準で規制されているようなジクロロエタン、トリクロロエチレン、テトラクロロエチレン等の有機塩素化合物やシマジン、チウラム等の農薬や内分泌撹乱物質などの生物難分解性物質が含まれている場合、もしくは含まれている可能性がある場合には、促進酸化処理を行うことが好ましい。
【0038】
促進酸化処理とはAOP(=Advanced Oxidation PROcesses)と称され、オゾン、紫外線、ガンマ線、過酸化水素、フッ素、次亜塩素酸ナトリウム、塩素、触媒(光触媒等)などの群から選ばれる少なくとも2つを併用して、酸化力の大きなヒドロキシラジカル(HOラジカル)を水中に生成し、この酸化力により有機物を分解する方法である。HOラジカルは、酸化力が非常に強力であるため、水中に存在する高い結合力を有する有機塩素化合物や内分泌かく乱物質等の難分解性有機物の分解に有効である。これらの促進酸化処理は2次廃棄物の発生がなく、効果処理が有機物の分解に加えて、脱臭、脱色、殺菌等副次的な効果も期待でき、従来にない特徴を有している。促進酸化処理の組合せとしては、環境への影響を鑑みると、オゾン処理、紫外線処理、過酸化水素処理、触媒(光触媒)処理の群から選ぶことが好ましい。また、酸化分解に寄与するHOラジカルをより多く生成するのが好ましく、過酸化水素と紫外線、オゾンと過酸化水素、オゾンと紫外線がより好ましい。また、オゾン、UV、過酸化水素の3つを組み合わせる場合には、さらに酸化分解を効率的に行うことができるので好ましい。
【0039】
一方、活性炭処理では、濃縮水中に残存している臭気(カビ臭)、色度、トリハロメタン、トリハロメタン前駆物質、農薬、陰イオン界面活性剤、フェノール類、トリクロロエチレン等の低沸点有機塩素化合物などを吸着除去する。活性炭は、木質(ヤシ殻、おが屑)、石炭等を原料として、これらの原料を炭化および賦活化処理して造られた黒色、多孔性の炭素質の物質で、その原料、炭化方法および賦活化方法により吸着特性が異なる。活性炭の特長は、水中に溶解している有機物に対する除去能力が大きく、薬品処理の場合と異なり、処理水に反応生成物を残さないことである。
【0040】
気体や液体中の微量有機物を吸着する性質を有している活性炭は、その形状から粉末活性炭、粒状活性炭、繊維状活性炭に分けられる。応急的あるいは短期間使用の場合は、粉末活性炭処理や繊維状活性炭処理が適し、年間連続あるいは比較的長期間使用の場合は、粒状活性炭処理のほうが有利とされていることから、本発明においては粒状活性炭のほうが好ましい。粒状活性炭のうち、木質系のヤシ殻炭は直径3nm以下の細孔が多く、30nm以上の大きな細孔は少ない。したがって、低分子量の物質が除去されやすい。一方、石炭系は3nmからかなり大きな細孔まで幅広く存在する。したがって、より大きい分子量の物質を除去しやすい。本発明においては、活性炭の原料は限定しないが、活性炭の吸着能は、共存する有機物とその量によっても変化するので、事前に濃縮水中の除去対象物質の物性、実態、処理効果等について、実験を含めた調査を十分に行い、活性炭の種類を選定することが好ましい。
【0041】
続いて、軟化処理装置9は、濃縮水80を還流して原水50とともに再度膜モジュール6に供給した場合に、膜面に、炭酸カルシウム、硫酸カルシウム、水酸化マグネシウム等のスケールが析出しないようにするもので、たとえば、(1)濃縮水80に苛性ソーダを注入してpH10程度にした水を反応槽中で炭酸カルシウムで被覆した流動媒体と接触させ、水中のカルシウムを炭酸カルシウムとして流動媒体上に晶析させる晶析軟化法や、(2)消石灰、ソーダ灰、苛性ソーダ等を添加して濃縮水80のpHを上昇させてCaCOやMg(OH)として硬度成分を除くアルカリ凝析法、(3)イオン交換樹脂等によるイオン交換法等の処理を施すものである。
【0042】
晶析軟化法は施設が比較的コンパクトで、マグネシウムは除去できないがカルシウムを除去でき、また、汚泥処理を必要としない利点がある。ただし、反応槽流出水のpH値が高くなることから、pH調整のための設備が必要となる。また、反応槽中の流動媒体は炭酸カルシウムの晶析により大きさが変化し、除去効率が低下するため、流動媒体の定期的な排出と補充が必要である。アルカリ凝析法は、硬度成分以外の濁質、重金属イオン等を同時に除去することが可能である。ただし、マグネシウムを除去するためには、pH値を11程度にまで増加させる必要があり、汚泥処理が必要になる。イオン交換法は、固体と液体間で、固体成分の主体に大きな変化を与えることなくイオンを可逆的に授受する操作で、維持管理が比較的容易である。カルシウム、マグネシウムの陽イオンが除去対象物となる水処理では、陽イオン交換樹脂を用いる。
【0043】
イオン交換樹脂の最も一般的なものは、スチレン−ジビニルベンゼン(DVB)付加共重合物を母体としたものであり、その構造体にさまざまなイオン基グループがついていて、イオン交換樹脂の化学的性質を決める。陽イオン交換樹脂には強酸性陽イオン交換樹脂と弱酸性陽イオン交換樹脂がある。強酸性陽イオン交換樹脂は、スルホン酸基のような強電解質をもつ陽イオン交換樹脂で、全pH領域で働き、中性塩を分解する能力をもつ。弱酸性陽イオン交換樹脂は、カルボキシル基をもつ陽イオン交換樹脂で、イオン交換性を示す有効pH範囲は4〜14である。本発明においてはどちらも適用可能である。
【0044】
イオン交換樹脂は有効径0.5mm程度の樹脂を数十cm程度に充填した固定床吸着装置が一般的である。イオン交換樹脂の再生には、食塩、硫酸、塩酸等の数%以上の溶液が用いられるので、装置の材質は耐食性でなければならない。
【0045】
イオン交換処理は、SV(Space Velocity,1/h)=流量(m/h)/充填樹脂量(m)が10〜30(1/h)の範囲内になる程度で運転するのが好ましい。
【0046】
なお、イオン交換法による硬度成分の除去性能が極端に高い場合は、NF膜あるいはRO膜処理後の濃縮水の一部をイオン交換処理した後、カルシウム由来のスケールが生成しない程度にイオン交換処理しなかった濃縮水と混合し、被処理水として返送すればよい。
【0047】
また、イオン交換処理する濃縮水に懸濁物質が含まれている場合、イオン交換樹脂は懸濁物質によって汚染され、硬度成分除去性能が低下する。また、イオン交換樹脂は一般的に有効径が0.5mm前後であることから、懸濁物質が樹脂層で捕捉されることになり、そのため、損失水頭が増加し、処理水量が低下する。しかしながら、本発明においては、原水50は膜モジュール6の前段で固液分離され、懸濁物質が除去されているので、この問題はない。
【0048】
本発明において、有機物除去や軟化処理の順序は特に限定されるものではないが、促進酸化処理装置7、活性炭処理装置8および軟化処理装置9を用いる場合には、促進酸化処理は水中の有機物濃度が高いほうがHOラジカルによる有機物の酸化分解効率が向上すること、また軟化処理は水中に微小有機物が存在している場合、イオン交換体の表面が速やかに汚染劣化して有効な処理を続けられないことから、図1に示すように促進酸化処理装置7、活性炭処理装置8、軟化処理装置9の順序に設けることが好ましい
【0049】
なお、本発明との比較のために示した図2は、図1の水処理装置において促進酸化処理装置7、活性炭処理装置8を設けなかった態様である。その他については図1の水処理装置と同一である。また、本発明との比較のために示した図3は、図1の水処理装置において軟化処理装置9を設けなかった態様である。その他については図1の水処理装置と同一である。
【0050】
【実施例】
<実施例1>
運転を実施した膜ろ過装置を図1に示す。原水は河川水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0051】
固液分離装置3で処理した分離水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0052】
そして、膜モジュール6によって排出される濃縮水80の全量を、オゾンと紫外線からなる促進酸化処理装置7で処理した。促進酸化処理装置7は小型の反応槽内に低圧水銀ランプ15W、3本を配置し、濃縮水に紫外線を照射するとともに、オゾンを10mg/lで発生、注入するものとした。
【0053】
促進酸化処理装置7で処理された濃縮水は活性炭処理装置8で処理された。活性炭処理装置8は固定床の粒状活性炭であり、活性炭の原料はヤシ殻とした。運転条件はLV:100m/d、ろ層厚:2.5m/dとした。活性炭処理装置8で処理された濃縮水90の20%は排水し、80%は軟化処理装置9に流入させた。
【0054】
軟化処理装置9ではイオン交換処理を行い、スルホン酸基の陽イオン交換樹脂を使用した。通水速度はSV=20(1/h)とした。軟化処理装置9で処理された濃縮水100はタンク1に返送し、原水と混合した。
【0055】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から3000時間経過後も0.42MPaで安定していた。
【0056】
また原水50((1))、固液分離装置3の分離水60((2))、膜モジュール6の透過水70((3))、膜モジュール6の濃縮水80((4))、促進酸化処理装置7および活性炭処理装置8で処理された濃縮水90((5))、軟化処理装置9で処理された濃縮水100((6))の平均水質を表1に示す。なお、平均水質とは、1日1回の頻度で1年間測定した結果の平均をとったものである。
【0057】
【表1】
Figure 0003698093
【0058】
上記の水処理の結果、膜モジュール6の透過水70((3))は水道水水質基準を満たしていた。また、促進酸化処理装置7および活性炭処理装置8で処理された濃縮水90((5))は水質汚濁防止法における排水基準を満たしていた。
【0059】
<比較例1>
運転を実施した膜ろ過装置を図4に示す。原水は実施例1と同じ河川水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0060】
固液分離装置3で処理した水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0061】
そして、膜モジュール6の濃縮水80は促進酸化処理装置7、活性炭処理装置8、軟化処理装置9で処理することなく、20%は排水し、残りの80%はそのままタンク1に返送し、原水と混合した。
【0062】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から700時間経過後には1.7MPaに達し、薬液洗浄を行わざるをえなかった。
【0063】
また原水50((1))、固液分離装置3で処理された水60((2))、膜モジュール6で処理された水70((3))、膜モジュール6の濃縮水80((4))の平均水質を表2に示す。
【0064】
【表2】
Figure 0003698093
【0065】
上記の水処理の結果、膜モジュール6で処理された水70((3))は水道水水質基準を満たしていた。しかし、膜モジュール6の濃縮水80((4))はシマジン、チウラムに関しては水質汚濁防止法における排水基準を満たしていなかった。
【0066】
比較例2>
運転を実施した膜ろ過装置を図2に示す。原水は地下水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0067】
固液分離装置3で処理した水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0068】
そして、膜モジュール6の濃縮水80は促進酸化処理装置7と活性炭処理装置8で処理することなく、濃縮水80の20%は排水し、残りの80%は軟化処理装置9に流入させた。軟化処理装置9ではイオン交換処理を行い、スルホン酸基の陽イオン交換樹脂を使用した。通水速度はSV=20(1/h)とした。軟化処理装置9で処理された濃縮水100はタンク1に返送し、原水と混合した。
【0069】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から3000時間経過後も0.63MPaで安定しており、まだ薬液洗浄を行う時期ではなかった。
【0070】
また原水50((1))、固液分離装置3で処理された水60((2))、膜モジュール6で処理された水70((3))、膜モジュール6の濃縮水80((4))、軟化処理装置9で処理された濃縮水100((6))の平均水質を表3に示す。
【0071】
【表3】
Figure 0003698093
【0072】
上記の水処理の結果、膜モジュール6の透過水70((3))は水道水水質基準を満たしていた。また、膜モジュール6の濃縮水80((4))は水質汚濁防止法における排水基準を満たしていた。
【0073】
<比較例
運転を実施した膜ろ過装置を図4に示す。原水は比較例2と同じ地下水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0074】
固液分離装置3で処理した水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0075】
そして、膜モジュール6の濃縮水80は促進酸化処理装置7、活性炭処理装置8、軟化処理装置9で処理することなく、20%は排水し、残りの80%はそのままタンク1に返送し、原水と混合した。
【0076】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から700時間経過後には1.6MPaに達し、薬液洗浄を行わざるをえなかった。
【0077】
また原水50((1))、固液分離装置3で処理された水60((2))、膜モジュール6で処理された水70((3))、膜モジュール6の濃縮水80((4))の平均水質を表4に示す。
【0078】
【表4】
Figure 0003698093
【0079】
上記の水処理の結果、膜モジュール6で処理された水70((3))は水道水水質基準を満たしていた。また、膜モジュール6の濃縮水80((4))は水質汚濁防止法における排水基準を満たしていた。
【0080】
比較例4
運転を実施した膜ろ過装置を図3に示す。原水は湖沼水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0081】
固液分離装置3で処理した水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0082】
そして、膜モジュール6によって排出される濃縮水全量80を、オゾンとUVからなる促進酸化処理装置7で処理した。促進酸化処理装置7は小型の反応槽内に低圧水銀ランプ15W、3本を配置し、濃縮水にUVを照射するとともに、オゾンを10mg/lで発生、注入するものとした。
【0083】
促進酸化処理装置7で処理された濃縮水は活性炭処理装置8で処理された。活性炭処理装置8は固定床の粒状活性炭であり、活性炭の原料はヤシ殻とした。運転条件はLV:100m/d、ろ層厚:2.5m/dとした。活性炭処理装置8で処理された濃縮水90の20%は排水し、80%は軟化処理装置9で処理することなく、タンク1にそのまま返送し、原水と混合した。
【0084】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から3000時間経過後も0.83MPaで安定しており、まだ薬液洗浄を行う時期ではなかった。
【0085】
また原水50((1))、固液分離装置3で処理された水60((2))、膜モジュール6で処理された水70((3))、膜モジュール6の濃縮水80((4))、促進酸化処理装置7および活性炭処理装置8で処理された濃縮水90((5))の平均水質を表5に示す。
【0086】
【表5】
Figure 0003698093
【0087】
上記の水処理の結果、膜モジュール6で処理された水70((3))は水道水水質基準を満たしていた。また、促進酸化処理装置7および活性炭処理装置8で処理された濃縮水90((5))は水質汚濁防止法における排水基準を満たしていた。
【0088】
<比較例
運転を実施した膜ろ過装置を図4に示す。原水は比較例4と同じ湖沼水とした。まず、原水50は加圧ポンプ2を通して固液分離装置3で処理された。固液分離装置3には外圧式中空糸膜UF膜モジュール(膜材質:ポリアクリロニトリル、公称孔径:0.01μm)を使用した。運転方式は定流量運転とし、膜透過流束を0.8m/dとした。
【0089】
固液分離装置3で処理した水60はタンク4に貯水した後、加圧ポンプ5を通してナノろ過膜モジュール(モジュール形状:スパイラル型、膜素材:ポリアミド製、脱塩率:55%)を具備した膜モジュール6で処理した。運転方式は、定流量運転(膜透過流束:0.5m/d)とし、回収率を95%に設定した。
【0090】
そして、膜モジュール6の濃縮水80は促進酸化処理装置7、活性炭処理装置8、軟化処理装置9で処理することなく、20%は排水し、残りの80%はそのままタンク1に返送し、原水と混合した。
【0091】
その結果、運転開始直後のNF膜の運転圧力は0.35MPaであったが、運転開始から700時間経過後には1.8MPaに達し、薬液洗浄を行わざるをえなかった。
【0092】
また原水50((1))、固液分離装置3で処理された水60((2))、膜モジュール6で処理された水70((3))、膜モジュール6の濃縮水80((4))の平均水質を表6に示す。
【0093】
【表6】
Figure 0003698093
【0094】
上記の水処理の結果、膜モジュール6で処理された水70((3))は水道水水質基準を満たしていた。しかし、膜モジュール6の濃縮水80((4))はシマジン、チウラムに関しては水質汚濁防止法における排水基準を満たしていなかった。
【0095】
【発明の効果】
本発明においては、予め固液分離した逆浸透ろ過(RO)膜および/またはナノろ過膜(NF膜)の濃縮水を軟化処理法および、オゾン処理、紫外線処理、過酸化水素処理および触媒処理の群から選ばれる少なくとも2つの処理を施す促進酸化処理を含む有機物除去法で処理することによって、高回収率運転でもファウリングやスケールを抑制でき、さらに濃縮水を排水基準値以下に低減できることから、そのまま放流することが可能となる。
【図面の簡単な説明】
【図1】本発明の水処理装置の一実施態様を示すフロー図である。
【図2】比較例2の水処理装置の実施態様を示すフロー図である。
【図3】比較例4の水処理装置の実施態様を示すフロー図である。
【図4】比較例1、3、5の水処理装置の態様を示すフロー図である。
【符号の説明】
1、4:タンク
2、5:加圧ポンプ
3:固液分離装置
6:膜モジュール
7:促進酸化処理装置
8:活性炭処理装置
9:軟化処理装置
10:還流手段
50:原水
60:固液分離装置3の分離水
70:膜モジュール6の透過水
80:膜モジュール6の濃縮水
90:促進酸化処理装置7および活性炭処理装置8で処理された濃縮水
100:軟化処理装置9で処理された濃縮水[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a water treatment method and a water treatment apparatus suitably used for purifying water such as rivers and lakes.
[0002]
[Prior art]
  Membrane separation technology is a technology used for solid-liquid separation, ion separation, gas separation, and the like, and has recently been used in various fields such as industrial water production and food, medicine, water purification, seawater desalination. Among them, nanofiltration membranes (NF membranes) and reverse osmosis membranes (RO membranes) are widely used as membranes that can produce high-quality water.
[0003]
  RO membranes and NF membranes are generally used in a cross-flow filtration system in which raw water is supplied along the membrane surface and permeate is passed in a direction perpendicular to the raw water, and a portion of the raw water supplied to the membrane module circulates. By applying a shearing force to the film surface, it is possible to suppress adhesion and deposition of fouling substances such as suspended substances and colloidal substances in the raw water. The water that has not permeated the membrane is called concentrated water, part of which is drained depending on the recovery rate of the water treatment device, and the rest is returned to the membrane supply water side.
[0004]
  It is important to set a high recovery rate from the viewpoint of water resources and water rights, and from the viewpoint of reducing the amount of wastewater (concentrated water) and downsizing the pretreatment and wastewater treatment processes. However, if the recovery rate is increased, the concentration ratio of each component is increased in accordance with the removal rate of the substance to be removed, and the load on the membrane is increased. In particular, fouling due to microorganisms, medium to high molecular humic acid, etc., and scales where calcium, magnesium, silica, etc. are deposited as calcium carbonate, magnesium hydroxide, calcium sulfate hydrate, silica and adhere to the membrane surface, are transmitted. A decrease in the amount of water, an increase in differential pressure, etc. may occur, making stable operation difficult. Depending on the quality of the water to be treated, a recovery rate of about 80% is considered the limit.
[0005]
  Concentrated water of membrane modules equipped with RO membranes and NF membranes contains a concentration of soluble components such as agricultural chemicals, trace amounts of harmful organic substances, and salts as regulated by the wastewater standards of the Water Pollution Control Law. However, the higher the recovery rate, the more often the wastewater standards of the Water Pollution Control Law are exceeded, and the concentrated water cannot be directly reused for some purpose or discharged directly into rivers. Therefore, a separate treatment is required for components that exceed wastewater standards. If the recovery rate is low, the scale of the wastewater treatment facility for discharge becomes large. For example, if the recovery rate is 80%, the amount of water produced is 10,000 m.3/ D is approximately 1,100m3/ D, which increases the processing cost.
[0006]
[Problems to be solved by the invention]
  The object of the present invention is to solve the above-mentioned conventional problems, and to increase the recovery rate, which has been limited to about 80%, in order to effectively use water resources, and to stably operate RO membranes and NF membranes. It is an object of the present invention to provide a water treatment method and a water treatment apparatus that can be used and can cope with measures for strengthening regulations on wastewater standards.
[0007]
[Means for Solving the Problems]
  In the present invention for achieving the above-mentioned object, the raw water is subjected to solid-liquid separation, and then the permeated water, concentrated water and the membrane module having a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane). The water treatment method for separating the water into the membrane module is operated so that the recovery rate is at least 90%, and at least a part of the concentrated water of the membrane module is softened.Law and existenceA water treatment method characterized in that it is treated with the machine removal method and refluxed to the raw water.The organic matter removal method includes an accelerated oxidation treatment for performing at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment.It is a feature.
[0008]
  At this time, that the softening treatment method includes ion exchange, the organic matter removal method,furtherIt is preferable to include activated carbon treatment.. SpiritIt is also preferable to perform solid-liquid separation using a tight filtration membrane (MF membrane) and / or an ultrafiltration membrane (UF membrane), or to add a flocculant to raw water before solid-liquid separation.
[0009]
  The present invention also provides a solid-liquid separation means for solid-liquid separation of raw water and a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (separated into permeated water and concentrated water). A water treatment comprising: a membrane module having an NF membrane; and a reflux means having an organic matter removing means and a softening treatment means for treating at least a part of the concentrated water of the membrane module and returning it to raw water apparatusThe reflux means includes an accelerated oxidation treatment means as an organic substance removal means, and the accelerated oxidation treatment means and the softening treatment means are arranged in this order.It is a characteristic.
[0010]
  Moreover, it is preferable that the organic substance removing means further includes an activated carbon treatment means, and the accelerated oxidation treatment means, the activated carbon treatment means, and the softening treatment means are arranged in this order.
[0011]
  Furthermore, a fresh water generation method using any one of the above methods or apparatuses is also a preferred embodiment.
[0012]
  The recovery rate in the present invention is the ratio of the membrane permeated water amount (b) to the water amount (a) obtained by subtracting the amount of concentrated water returned to the membrane feed water side from the amount of water supplied to the membrane module, as shown in the following formula, It is an index showing the quantitative processing efficiency in the separation method.
[0013]
[Expression 1]
Figure 0003698093
[0014]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 shows an example of the flow of the water treatment apparatus of the present invention. This water treatment device includes a solid-liquid separation device 3 that separates the raw water 50 into a solid and a liquid, a reverse osmosis membrane (RO membrane) that separates the separated water 60 of the solid-liquid separation device 3 into permeated water 70 and concentrated water 80, and Organic membrane removing means (promoted oxidation treatment device 7, activated carbon treatment device 8) and softening that treat membrane module 6 having a nanofiltration membrane (NF membrane) and concentrated water 80 of membrane module 6 to return to raw water 50 And a reflux means 10 having a processing device 9. Further, on the upstream side of the solid-liquid separator 3, a tank 1 that temporarily stores the raw water 50 and a pressure pump 2 that pressurizes the water stored in the tank 1 and feeds the water to the solid-liquid separator 3 are provided. In addition, between the solid-liquid separation device 3 and the membrane module 6, the tank 4 storing the separation water 60 from the solid-liquid separation device 3 and the separation water 60 stored in the tank 4 are pressurized and supplied to the membrane module 6. And a pressurizing pump 5 is provided.
[0015]
  In this water treatment device, the raw water 50 stored in the tank 1 is sent to the solid-liquid separation device 3 by the pressurizing pump 2, and suspended solids are removed by the solid-liquid separation device 3. In the present invention, in order to prevent impurities such as turbidity, microorganisms, and organic matter contained in the raw water 50 from adhering to the surface of the RO membrane or NF membrane, the filtration differential pressure is rapidly increased. Separating and adjusting the FI (Fouling Index) value of the separated water 60 led to the RO membrane or NF membrane. The FI value is preferably 5 or less for spiral type modules and 4 or less for hollow fiber type modules. The FI value is also referred to as an SDI (Silt Density Index) value, which is a management index of impurities in the supply water (separated water 60) to the RO membrane or NF membrane, and is represented by the following equation.
[0016]
    FI = (1-T0/ T15) × 100/15
At this time, T0Is the time required to initially filter 500 ml when the sample water is filtered under a pressure of 206 kPa using a 0.45 μm membrane filter.15T0Then, after filtering for 15 minutes in the same state, the time required to filter 500 ml of sample water again.
[0017]
  Examples of the solid-liquid separation device 3 include a filtration device that prevents leakage of suspended substances in raw water, such as sand filtration and a safety filter, but a microfiltration membrane (MF) having a pore diameter of 1 μm or less that prevents microorganisms from entering the membrane pores. Membrane) and ultrafiltration membrane (UF membrane) are preferably used alone or in combination.
[0018]
  When a separation membrane is used in the solid-liquid separation device 3, a flocculant can be added to the raw water for the purpose of improving the membrane permeation flux and the membrane differential pressure and improving the treatment capacity and stability by improving the quality of the treated water. The flocculant injection rate is such that the micro floc can be formed in a small amount so that the membrane can be separated as it is, or a sufficient flocculant is added for the agglomeration treatment and the floc floc is precipitated, and then the supernatant liquid is separated with a separation membrane. It may be processed.
[0019]
  Separation membranes such as MF membranes and UF membranes can improve the turbidity and can stably operate the NF membrane and the RO membrane for a longer period, as can be seen from the fact that the FI value of the separation water 60 can be brought close to 0.
[0020]
  As membrane materials for UF membranes and MF membranes, cellulose acetate, polyacrylonitrile, polyethylene, polyethersulfone, polysulfone, polypropylene, polyvinylidene fluoride, ceramic, etc. can be applied.
  The membrane may have any shape such as a hollow fiber membrane, a tubular membrane, or a flat membrane. Here, the hollow fiber membrane is a tubular separation membrane having an outer diameter of less than 2 mm, and the tubular membrane is a tubular separation membrane having an outer diameter of 2 mm or more. The hollow fiber membrane can increase the effective membrane area per unit.
[0021]
  These UF membranes and MF membranes are modularized and used. The module should have a structure that is difficult to block by cells, such as (1) external pressure crossflow hollow fiber membrane module, (2) internal pressure crossflow hollow fiber membrane module with an inner diameter of 1 mm or more, etc. Is preferable because the film area is large.
[0022]
  In addition, there are a constant flow filtration operation and a constant pressure filtration operation as the operation method of the membrane device used for solid-liquid separation, but the constant flow filtration operation can obtain a constant processing amount and is easy to control the treatment process. Therefore, it is preferable.
[0023]
  The separated water 60 that has been treated by the solid-liquid separation device 3 and from which suspended substances have been removed is stored in the tank 4 and then pressurized and supplied to the membrane module 6 by the pressure pump 5, and the permeated water 70 and concentrated water. 80. At this time, the membrane module is operated so that the recovery rate is 90% or more.
[0024]
  The nanofiltration membrane and reverse osmosis membrane used in the membrane module 6 are as follows.
[0025]
  That is, the nanofiltration membrane (NF membrane: Nanofiltration Membrane) is mainly high in the removal performance of polyvalent ions such as medium to high molecular weight molecules, divalent ions, heavy metal ions of several hundred to several thousand or more, When used for drinking water production applications, trihalomethane precursors, agricultural chemicals, fulvic acid and the like can be mainly removed. Although the size of the removal target is located between the ultrafiltration membrane (UF membrane) and the reverse osmosis membrane (RO membrane), the desalination rate is 5% or more and less than 93% (evaluation condition NaCl concentration: 500-2, 000 mg / l, operating pressure: 0.5 to 1.5 MPa).
[0026]
  Examples of the film material include polyamide-based, polypiperazine amide-based, polyester amide-based, and water-soluble vinyl polymer crosslinked. In addition, the membrane structure has a dense layer on at least one side of the membrane, and has a fine pore with a gradually increasing pore size from the dense layer to the inside of the membrane or the other side. And a composite film having a very thin active layer formed of another material. Further, there are flat membranes, hollow fiber membranes, etc. as membrane forms, for example, the film thickness is in the range of 10 μm to 1 mm, and in the case of hollow fiber membranes, the outer diameter is in the range of 50 μm to 4 mm.
[0027]
  In addition, reverse osmosis membrane (RO membrane: Reverse Osmosis Membrane) removes monovalent ionic substances in addition to the removal target of NF membrane (mainly seawater desalination treatment, brine desalination, pure water production) And a desalting rate of 93% or more (evaluation conditions NaCl concentration: 500 to 2,000 mg / l, operating pressure: 0.5 to 3.0 MPa).
[0028]
  As the film material, polymer materials such as cellulose acetate, cellulose polymer, polyamide, and vinyl polymer can be used. Typical reverse osmosis membranes include cellulose acetate or polyamide asymmetric membranes and composite membranes having polyamide active layers. Among them, a cellulose acetate asymmetric membrane, a composite membrane having a polyamide-based active layer, and a composite membrane having an aromatic polyamide-based active layer, which have a high salt rejection performance, are preferred. In particular, an aromatic polyamide composite membrane has a high exclusion performance. And it is preferable because of its high water permeability. As the membrane structure, there are asymmetric membranes and composite membranes as with NF membranes, and there are flat membranes, hollow fiber membranes, etc., as with NF membranes. For example, film thickness ranges from 10 μm to 1 mm, hollow fiber membranes In this case, the outer diameter is in the range of 50 μm to 4 mm.
[0029]
  Both the NF membrane and the RO membrane can be operated at a low pressure from the viewpoint of operation cost, but a composite membrane is preferable in consideration of the amount of water produced during low pressure operation. More preferably, it is a polyamide-based composite membrane. In the case of an NF membrane, a polypiperazine amide-based composite membrane is more suitable from the viewpoint of the amount of permeated water and chemical resistance.
[0030]
  And the membrane module 6 is modularized in order to actually use the above-mentioned NF membrane and RO membrane. In the case of flat membrane, spiral type, pleated type, plate-and-frame type, disk type disc type is stacked, and in the case of hollow fiber membrane, hollow fiber is bundled in U shape or I shape. Although there is a hollow fiber membrane type housed in a container, the present invention is not affected by the form of these modules.
[0031]
  In the present invention, either one of the RO membrane or the NF membrane may be used for the membrane module 6, or both may be used. These may be appropriately selected according to the supply water (separated water 60), the required water quality of the permeated water 70, and the purpose of use of the permeated water 70.
[0032]
  The membrane module 6 may be arranged in multiple stages so that the concentrated water from the preceding membrane module is processed by the subsequent membrane module 6. In this case, it should be noted that the concentration of calcium, magnesium, silica, etc. in the concentrated water of the subsequent RO membrane or NF membrane does not exceed the solubility.
[0033]
  The filtration pressure of the membrane module 6 is preferably set as appropriate within a range of about 0.5 to 3.0 MPa depending on the type of membrane supply water (separated water 60), the operation method, and the like. When treating fresh water such as river water and lake water, it can be filtered at a relatively low pressure because the osmotic pressure is low.
[0034]
  The water that has passed through the RO membrane and the NF membrane in such a membrane module 6 is taken out from the membrane module 6 as the permeated water 70. Since this permeated water is free of trihalomethane precursors, agricultural chemicals, heavy metal ions, etc., it is used as drinking water, industrial water, agricultural water or the like.
[0035]
  On the other hand, the concentrated water 80 is obtained by removing the organic matter provided in the reflux means 10 (accelerated oxidation treatment device 7, activated carbon treatment device 8) And softTreatment is performed by the softening treatment means (softening treatment device 9), and at least a part (the concentrated water 100 after the treatment by the softening treatment device 9) is returned to the raw water in the tank 1. Concentrated water that has not been refluxed to the raw water (a part of the concentrated water 90 that has been treated by the activated carbon treatment device 8) is discharged into nature as it is..The removal target of the organic substance removing means is mainly low-boiling organic chlorine compounds such as odor (mold odor), chromaticity, trihalomethane, trihalomethane precursor, agricultural chemical, anionic surfactant, phenols, and trichloroethylene. The removal target of the softening treatment means is calcium, magnesium, etc., which are scale components.
[0036]
  The present invention treats separated water 60 from which suspended substances have been removed by solid-liquid separation in advance with a membrane module 6 equipped with an RO membrane or NF membrane, and the concentrated water 80 obtained at that time is treated with an organic matter removing hand.Stepped and softSince it is processed by the chemical treatment means and again leads to solid-liquid separation, reverse osmosis separation, and nanofiltration, the recovery rate can be increased without reducing the water quality, and the membrane module is operated at a recovery rate of 90% or more. Can be operated stably.
[0037]
  As an organic substance removal means, accelerated oxidation treatment equipmentIn addition to 7,An activated carbon treatment apparatus 8 or the like can be used. In addition, as shown in FIG.7 can be used alone or activated with the accelerated oxidation treatment device 7Use both of the charcoal treatment equipment 8KakahaWhat is necessary is just to determine suitably according to the water quality of the concentrated water 80. FIG. When the concentration of the removal target in concentrated water is low, Accelerated oxidation treatment unit 7 singleIt can be used alone, but the concentration of each organic component in the concentrated water 80 is high.UrgeWhen it is difficult to remove the oxidative treatment alone, it is preferable to use both in combination. Concentrated water 80 contains organic chlorinated compounds such as dichloroethane, trichloroethylene, and tetrachloroethylene that are regulated by the drainage standards, pesticides such as simazine and thiuram, and biodegradable substances such as endocrine disrupting substances. In such a case, or when there is a possibility that it is contained, it is preferable to perform accelerated oxidation treatment.
[0038]
  The accelerated oxidation treatment is called AOP (= Advanced Oxidation Processes) and is at least two selected from the group of ozone, ultraviolet rays, gamma rays, hydrogen peroxide, fluorine, sodium hypochlorite, chlorine, catalyst (photocatalyst, etc.), etc. Is used to generate hydroxy radicals (HO radicals) with high oxidizing power in water, and decompose organic substances by this oxidizing power. Since the HO radical has a very strong oxidizing power, it is effective in decomposing refractory organic substances such as organochlorine compounds and endocrine disrupting substances having a high binding force existing in water. These accelerated oxidation treatments do not generate secondary waste, and the effect treatment can be expected to have secondary effects such as deodorization, decolorization, and sterilization in addition to the decomposition of organic matter, and has an unprecedented feature. The combination of the accelerated oxidation treatment is preferably selected from the group of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment, and catalyst (photocatalyst) treatment in view of the influence on the environment. Further, it is preferable to generate more HO radicals that contribute to oxidative decomposition, and hydrogen peroxide and ultraviolet light, ozone and hydrogen peroxide, and ozone and ultraviolet light are more preferable. In addition, a combination of ozone, UV, and hydrogen peroxide is preferable because oxidative decomposition can be performed more efficiently.
[0039]
  On the other hand, activated carbon treatment adsorbs odor (mold odor), chromaticity, trihalomethane, trihalomethane precursors, agricultural chemicals, anionic surfactants, phenols, low-boiling organic chlorine compounds such as trichloroethylene, etc. remaining in the concentrated water. Remove. Activated carbon is a black, porous carbonaceous material made from wood (coconut shells, sawdust), coal, etc. as raw materials, and carbonized and activated. These raw materials, carbonization method and activation The adsorption characteristics differ depending on the method. The feature of activated carbon is that it has a large ability to remove organic substances dissolved in water, and unlike the case of chemical treatment, it does not leave a reaction product in the treated water.
[0040]
  Activated carbon having the property of adsorbing trace organic substances in gas and liquid is classified into powdered activated carbon, granular activated carbon, and fibrous activated carbon according to its shape. In the case of emergency or short-term use, powdered activated carbon treatment or fibrous activated carbon treatment is suitable, and for continuous or relatively long-term use, granular activated carbon treatment is more advantageous. Granular activated carbon is preferred. Of the granular activated carbon, woody coconut shell charcoal has many pores with a diameter of 3 nm or less and few large pores with a diameter of 30 nm or more. Therefore, low molecular weight substances are easily removed. On the other hand, coal systems exist widely from 3 nm to considerably large pores. Therefore, it is easy to remove a substance having a higher molecular weight. In the present invention, the activated carbon raw material is not limited, but the adsorptive capacity of the activated carbon varies depending on the coexisting organic matter and the amount thereof, so the physical properties, actual conditions, treatment effects, etc. of the substance to be removed in the concentrated water are tested in advance. It is preferable to conduct a thorough investigation including, and select the type of activated carbon.
[0041]
  Subsequently, the softening treatment device 9 prevents the scales of calcium carbonate, calcium sulfate, magnesium hydroxide, etc. from depositing on the membrane surface when the concentrated water 80 is refluxed and supplied to the membrane module 6 together with the raw water 50 again. For example, (1) injecting caustic soda into concentrated water 80 to bring the pH to about 10 is brought into contact with a fluid medium coated with calcium carbonate in a reaction tank, and calcium in the water is converted into calcium carbonate onto the fluid medium. A crystallization softening method for crystallization, (2) adding slaked lime, soda ash, caustic soda, etc. to increase the pH of the concentrated water 80 to increase the CaCO3And Mg (OH)2As described above, an alkali coagulation method excluding hardness components and (3) an ion exchange method using an ion exchange resin or the like are applied.
[0042]
  The crystallization softening method has the advantage that the facility is relatively compact, magnesium cannot be removed but calcium can be removed, and sludge treatment is not required. However, since the pH value of the reaction tank effluent becomes high, equipment for pH adjustment is required. Moreover, since the size of the fluid medium in the reaction tank changes due to crystallization of calcium carbonate and the removal efficiency is lowered, the fluid medium must be periodically discharged and replenished. The alkali coagulation method can simultaneously remove turbidity, heavy metal ions and the like other than the hardness component. However, in order to remove magnesium, it is necessary to increase the pH value to about 11, and sludge treatment is required. The ion exchange method is an operation in which ions are reversibly exchanged between a solid and a liquid without causing a major change in the main component of the solid component, and is relatively easy to maintain. In water treatment in which calcium and magnesium cations are to be removed, a cation exchange resin is used.
[0043]
  The most common ion exchange resin is based on styrene-divinylbenzene (DVB) addition copolymer, and the structure has various ionic group groups. Decide. Cation exchange resins include strong acid cation exchange resins and weak acid cation exchange resins. The strong acid cation exchange resin is a cation exchange resin having a strong electrolyte such as a sulfonic acid group, and works in the entire pH range and has an ability to decompose a neutral salt. The weakly acidic cation exchange resin is a cation exchange resin having a carboxyl group, and the effective pH range showing ion exchange is 4 to 14. Both are applicable in the present invention.
[0044]
  As the ion exchange resin, a fixed bed adsorbing apparatus in which a resin having an effective diameter of about 0.5 mm is filled to about several tens of cm is common. Since a solution of several percent or more of salt, sulfuric acid, hydrochloric acid or the like is used for regeneration of the ion exchange resin, the material of the apparatus must be corrosion resistant.
[0045]
  The ion exchange process is performed using SV (Space Velocity, 1 / h) = flow rate (m3/ H) / filled resin amount (m3) Is preferably within a range of 10 to 30 (1 / h).
[0046]
  In addition, when the removal performance of the hardness component by the ion exchange method is extremely high, the ion exchange treatment is performed to such an extent that calcium-derived scale is not generated after ion exchange treatment of a part of the concentrated water after the NF membrane or RO membrane treatment. What is necessary is just to mix with the concentrated water which was not done and to return as treated water.
[0047]
  Moreover, when the suspended water is contained in the concentrated water subjected to the ion exchange treatment, the ion exchange resin is contaminated by the suspended material, and the hardness component removal performance is lowered. In addition, since the effective diameter of an ion exchange resin is generally around 0.5 mm, suspended substances are trapped in the resin layer, so that the loss head is increased and the amount of treated water is reduced. However, in the present invention, the raw water 50 is solid-liquid separated at the front stage of the membrane module 6 and the suspended substances are removed, so this problem does not occur.
[0048]
  In the present invention, the order of organic substance removal and softening treatment is not particularly limited. However, when the accelerated oxidation treatment device 7, activated carbon treatment device 8 and softening treatment device 9 are used, the accelerated oxidation treatment is performed with the concentration of organic matter in water. The higher the value, the higher the oxidative decomposition efficiency of organic substances by HO radicals, and the softening treatment cannot continue effective treatment because the surface of the ion exchanger is quickly contaminated and deteriorated when minute organic substances are present in the water. Therefore, as shown in FIG. 1, it is preferable to provide in the order of the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9..
[0049]
  It is shown for comparison with the present invention.FIG. 2 is a mode in which the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 are not provided in the water treatment device of FIG. About others, it is the same as the water treatment apparatus of FIG.Also shown for comparison with the present invention.FIG. 3 is a mode in which the softening device 9 is not provided in the water treatment device of FIG. About others, it is the same as the water treatment apparatus of FIG.
[0050]
【Example】
  <Example 1>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was river water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0051]
  The separated water 60 treated by the solid-liquid separation device 3 is stored in the tank 4 and then passed through the pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). The membrane module 6 was processed. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0052]
  And the whole quantity of the concentrated water 80 discharged | emitted by the membrane module 6 was processed with the accelerated oxidation processing apparatus 7 which consists of ozone and an ultraviolet-ray. The accelerated oxidation treatment apparatus 7 has three low-pressure mercury lamps 15W arranged in a small reaction tank, irradiates the concentrated water with ultraviolet rays, and generates and injects ozone at 10 mg / l.
[0053]
  The concentrated water treated with the accelerated oxidation treatment device 7 was treated with the activated carbon treatment device 8. The activated carbon treatment device 8 was fixed bed granular activated carbon, and the raw material of the activated carbon was coconut shell. The operating conditions were LV: 100 m / d and filter layer thickness: 2.5 m / d. 20% of the concentrated water 90 treated with the activated carbon treatment device 8 was drained, and 80% was allowed to flow into the softening treatment device 9.
[0054]
  The softening treatment apparatus 9 performed ion exchange treatment and used a cation exchange resin having a sulfonic acid group. The water flow rate was SV = 20 (1 / h). The concentrated water 100 treated by the softening device 9 was returned to the tank 1 and mixed with raw water.
[0055]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but was stable at 0.42 MPa even after 3000 hours had elapsed since the start of operation.
[0056]
  Also, raw water 50 ((1)), separated water 60 ((2)) of the solid-liquid separator 3, permeated water 70 ((3)) of the membrane module 6, concentrated water 80 ((4)) of the membrane module 6, Table 1 shows the average water quality of the concentrated water 90 ((5)) treated with the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 and the concentrated water 100 ((6)) treated with the softening treatment device 9. The average water quality is the average of the results measured for one year at a frequency of once a day.
[0057]
[Table 1]
Figure 0003698093
[0058]
  As a result of the above water treatment, the permeated water 70 ((3)) of the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 satisfied the drainage standard in the Water Pollution Control Law.
[0059]
  <Comparative Example 1>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was the same river water as in Example 1. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0060]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0061]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0062]
  As a result, the operating pressure of the NF film immediately after the start of operation was 0.35 MPa, but after 700 hours had elapsed from the start of operation, it reached 1.7 MPa, and chemical cleaning had to be performed.
[0063]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 2 shows the average water quality of 4)).
[0064]
[Table 2]
Figure 0003698093
[0065]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. However, the concentrated water 80 ((4)) of the membrane module 6 did not satisfy the drainage standards in the Water Pollution Control Law for simazine and thiuram.
[0066]
  <Comparative example2>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was groundwater. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0067]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0068]
  The concentrated water 80 of the membrane module 6 was not treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8, but 20% of the concentrated water 80 was drained and the remaining 80% was allowed to flow into the softening treatment device 9. The softening treatment apparatus 9 performed ion exchange treatment and used a cation exchange resin having a sulfonic acid group. The water flow rate was SV = 20 (1 / h). The concentrated water 100 treated by the softening device 9 was returned to the tank 1 and mixed with raw water.
[0069]
  As a result, although the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, it was stable at 0.63 MPa even after 3000 hours had elapsed from the start of operation, and it was not yet time for chemical cleaning.
[0070]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 3 shows the average water quality of the concentrated water 100 ((6)) treated by the softening device 9).
[0071]
[Table 3]
Figure 0003698093
[0072]
  As a result of the above water treatment, the permeated water 70 ((3)) of the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 80 ((4)) of the membrane module 6 satisfied the drainage standard in the Water Pollution Control Law.
[0073]
  <Comparative example3>
  The membrane filtration apparatus which carried out the operation is shown in FIG. Raw waterComparative exampleThe same groundwater as 2. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0074]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0075]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0076]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but reached 700 MPa after 700 hours from the start of operation, and chemical cleaning had to be performed.
[0077]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 4 shows the average water quality of 4)).
[0078]
[Table 4]
Figure 0003698093
[0079]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 80 ((4)) of the membrane module 6 satisfied the drainage standard in the Water Pollution Control Law.
[0080]
  <Comparative Example 4>
  The membrane filtration apparatus which carried out the operation is shown in FIG. The raw water was lake water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0081]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0082]
  And the concentrated water whole quantity 80 discharged | emitted by the membrane module 6 was processed with the accelerated oxidation processing apparatus 7 which consists of ozone and UV. The accelerated oxidation treatment apparatus 7 has three low-pressure mercury lamps 15W arranged in a small reaction tank, irradiates the concentrated water with UV, and generates and injects ozone at 10 mg / l.
[0083]
  The concentrated water treated with the accelerated oxidation treatment device 7 was treated with the activated carbon treatment device 8. The activated carbon treatment device 8 was fixed bed granular activated carbon, and the raw material of the activated carbon was coconut shell. The operating conditions were LV: 100 m / d and filter layer thickness: 2.5 m / d. 20% of the concentrated water 90 treated with the activated carbon treatment device 8 was drained, and 80% was returned to the tank 1 without being treated with the softening treatment device 9 and mixed with raw water.
[0084]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa, but it remained stable at 0.83 MPa even after 3000 hours had elapsed from the start of operation, and it was not yet time for chemical cleaning.
[0085]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 5 shows the average water quality of the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8).
[0086]
[Table 5]
Figure 0003698093
[0087]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. Further, the concentrated water 90 ((5)) treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8 satisfied the drainage standard in the Water Pollution Control Law.
[0088]
  <Comparative example5>
  The membrane filtration apparatus which carried out the operation is shown in FIG. Raw waterComparative Example 4The same lake water. First, the raw water 50 was processed by the solid-liquid separator 3 through the pressure pump 2. An external pressure type hollow fiber membrane UF membrane module (membrane material: polyacrylonitrile, nominal pore diameter: 0.01 μm) was used for the solid-liquid separator 3. The operation method was constant flow operation, and the membrane permeation flux was 0.8 m / d.
[0089]
  The water 60 treated by the solid-liquid separator 3 was stored in the tank 4 and then passed through a pressure pump 5 to be equipped with a nanofiltration membrane module (module shape: spiral type, membrane material: polyamide, desalination rate: 55%). Treated with membrane module 6. The operation method was constant flow operation (membrane permeation flux: 0.5 m / d), and the recovery rate was set to 95%.
[0090]
  The concentrated water 80 of the membrane module 6 is not treated by the accelerated oxidation treatment device 7, the activated carbon treatment device 8, and the softening treatment device 9, 20% is drained, and the remaining 80% is returned to the tank 1 as it is. Mixed with.
[0091]
  As a result, the operating pressure of the NF membrane immediately after the start of operation was 0.35 MPa. However, after 700 hours had elapsed from the start of operation, it reached 1.8 MPa, and chemical cleaning had to be performed.
[0092]
  The raw water 50 ((1)), the water 60 ((2)) treated by the solid-liquid separator 3, the water 70 ((3)) treated by the membrane module 6, and the concentrated water 80 ((( Table 6 shows the average water quality of 4)).
[0093]
[Table 6]
Figure 0003698093
[0094]
  As a result of the above water treatment, the water 70 ((3)) treated with the membrane module 6 satisfied the tap water quality standard. However, the concentrated water 80 ((4)) of the membrane module 6 did not satisfy the drainage standards in the Water Pollution Control Law for simazine and thiuram.
[0095]
【The invention's effect】
  In the present invention, the concentrated water of a reverse osmosis filtration (RO) membrane and / or a nanofiltration membrane (NF membrane) that has been solid-liquid separated in advance is subjected to a softening treatment method andAnd an accelerated oxidation treatment that includes at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment.By treating with the machine removal method, fouling and scale can be suppressed even in high recovery rate operation, and the concentrated water can be reduced below the drainage standard value, so that it can be discharged as it is.
[Brief description of the drawings]
FIG. 1 is a flowchart showing one embodiment of a water treatment apparatus of the present invention.
[Figure 2]Of the water treatment apparatus of Comparative Example 2It is a flowchart which shows an embodiment.
[Fig. 3]Comparative Example 4Water treatment equipmentThe fruitIt is a flowchart which shows an embodiment.
[Fig. 4]Comparative Examples 1, 3, 5It is a flowchart which shows the aspect of this water treatment apparatus.
[Explanation of symbols]
1, 4: Tank
2, 5: Pressurizing pump
    3: Solid-liquid separator
    6: Membrane module
    7: Accelerated oxidation treatment equipment
    8: Activated carbon treatment equipment
    9: Softening device
  10: Recirculation means
  50: Raw water
  60: Separation water of the solid-liquid separator 3
  70: Permeated water of membrane module 6
  80: Concentrated water of the membrane module 6
  90: Concentrated water treated by the accelerated oxidation treatment device 7 and the activated carbon treatment device 8
100: Concentrated water treated by the softening treatment device 9

Claims (8)

原水を、固液分離した後、逆浸透膜(RO膜)および/またはナノろ過膜(NF膜)を備えた膜モジュールで透過水と濃縮水とに分離する水処理方法であって、回収率が少なくとも90%になるように運転するとともに、膜モジュールの濃縮水の少なくとも一部を軟化処理法および有機物除去法で処理して原水に還流させることを特徴とする水処理方法であって、前記有機物除去法が、オゾン処理、紫外線処理、過酸化水素処理および触媒処理の群から選ばれる少なくとも2つの処理を施す促進酸化処理を含むものであることを特徴とする水処理方法A water treatment method in which raw water is separated into solid and liquid and then separated into permeate and concentrated water by a membrane module equipped with a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane), and the recovery rate there as well as operation to be at least 90%, a water treatment method characterized by processing the at least part of the concentrated water of the membrane module in the softening treatment and organic matter removal method is refluxed in raw water The water treatment method is characterized in that the organic substance removal method includes an accelerated oxidation treatment in which at least two treatments selected from the group consisting of ozone treatment, ultraviolet treatment, hydrogen peroxide treatment and catalyst treatment are performed . 軟化処理法がイオン交換を含むものである、請求項1に記載の水処理方法。The water treatment method according to claim 1, wherein the softening treatment method includes ion exchange. 有機物除去法が、さらに活性炭処理を含むものである、請求項1または2に記載の水処理方法。The water treatment method according to claim 1 or 2, wherein the organic substance removal method further includes activated carbon treatment. 精密ろ過膜(MF膜)および/または限外ろ過膜(UF膜)を用いて固液分離を行う、請求項1〜3のいずれかに記載の水処理方法。The water treatment method according to any one of claims 1 to 3 , wherein solid-liquid separation is performed using a microfiltration membrane (MF membrane) and / or an ultrafiltration membrane (UF membrane). 固液分離の前段で原水に凝集剤を添加する、請求項1〜5のいずれかに記載の水処理方法。Adding a coagulant to the raw water in front of the solid-liquid separation, water treatment method according to any one of claims 1-5. 原水を固液分離する固液分離手段と、固液分離手段の処理水を透過水と濃縮水とに分離する、逆浸透膜(RO膜)および/またはナノろ過膜(NF膜)を有する膜モジュールと、膜モジュールの濃縮水の少なくとも一部を処理して原水へ還流させる、有機物除去手段および軟化処理手段を有する還流手段とを備えていることを特徴とする水処理装置であって、前記還流手段は、有機物除去手段として促進酸化処理手段を備え、促進酸化処理手段、軟化処理手段をこの順序で配置していることを特徴とする水処理装置A membrane having a reverse osmosis membrane (RO membrane) and / or a nanofiltration membrane (NF membrane) that separates the raw water into solid-liquid separation means and the treated water of the solid-liquid separation means into permeated water and concentrated water. A water treatment apparatus comprising: a module; and a reflux means having an organic substance removing means and a softening treatment means for treating at least a part of the concentrated water of the membrane module and returning it to raw water , The reflux means comprises an accelerated oxidation treatment means as the organic substance removal means, and the accelerated oxidation treatment means and the softening treatment means are arranged in this order . 有機物除去手段が、さらに活性炭処理手段を備えており、前記促進酸化処理手段、該活性炭処理手段、および前記軟化処理手段をこの順序で配置していることを特徴とする請求項6に記載の水処理方法。7. The water according to claim 6, wherein the organic matter removing means further comprises an activated carbon treatment means, and the accelerated oxidation treatment means, the activated carbon treatment means, and the softening treatment means are arranged in this order. Processing method. 請求項1〜5のいずれかの方法、または、請求項6または7に記載の装置を用いることを特徴とする造水方法。A fresh water generation method using the method according to any one of claims 1 to 5 , or the device according to claim 6 or 7 .
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