JP3633704B2 - Membrane separation biological treatment method of wastewater - Google Patents

Membrane separation biological treatment method of wastewater Download PDF

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JP3633704B2
JP3633704B2 JP02544796A JP2544796A JP3633704B2 JP 3633704 B2 JP3633704 B2 JP 3633704B2 JP 02544796 A JP02544796 A JP 02544796A JP 2544796 A JP2544796 A JP 2544796A JP 3633704 B2 JP3633704 B2 JP 3633704B2
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membrane
hollow fiber
biological treatment
treatment method
fiber membrane
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JPH09215980A (en
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正 松田
裕 大貫
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Mitsubishi Chemical Corp
Mitsubishi Rayon Co Ltd
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Mitsubishi Rayon Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B01D63/04—Hollow fibre modules comprising multiple hollow fibre assemblies
    • B01D63/043—Hollow fibre modules comprising multiple hollow fibre assemblies with separate tube sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • B01D63/026—Wafer type modules or flat-surface type modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/08—Flat membrane modules
    • B01D63/082—Flat membrane modules comprising a stack of flat membranes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/1236—Particular type of activated sludge installations
    • C02F3/1268—Membrane bioreactor systems
    • C02F3/1273—Submerged membrane bioreactors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2313/00—Details relating to membrane modules or apparatus
    • B01D2313/08—Flow guidance means within the module or the apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2315/00—Details relating to the membrane module operation
    • B01D2315/06—Submerged-type; Immersion type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2319/00—Membrane assemblies within one housing
    • B01D2319/02—Elements in series
    • B01D2319/022—Reject series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/18—Use of gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Microbiology (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、膜分離活性汚泥法による、有機系廃水の生物学的処理方法に関する。
【０００２】
【従来の技術】
従来より都市廃水や有機性廃水の処理には生物処理が用いられ、その最終的な固液分離には沈殿分離が用いられてきた。しかし、沈殿分離では負荷変動時等にＳＳの流出が生じやすかった。
【０００３】
固液分離に膜分離を用いると、沈殿槽が不要となり、ＳＳの流出が完全に阻止できるとともに、曝気槽内の活性汚泥濃度を高くすることができるので、余剰汚泥の発生も少なくなり装置のコンパクト化が図れるため、近年、膜分離活性汚泥法が注目されている。
【０００４】
生物処理による有機性廃水処理の固液分離には、主として精密濾過膜、限外濾過膜が用いられる。これらの分離膜は、平膜、管状膜あるいは中空糸膜の形で使用される。特に、最近は中空糸膜モジュールを用いて、吸引濾過により活性汚泥を固液分離する方法が多く提案されている。
【０００５】
一方、有機ゲル状物質を含む活性汚泥をこれらの分離膜で固液分離する場合、膜の目詰まりの他、膜の表面ヘの汚れの付着、膜と膜との間の汚物の保持等による性能低下が生じやすく、空気を送って膜を振動させて膜表面を洗浄したり、膜面洗浄を繰り返して行なう必要があり、更には散気管から送られた空気のエアリフト効果により被処理液は撹拌を受けてより効率的な微生物処理を受けることが提案されている（特開昭６１−１２９０９４号、特開平３−９８６９７号各公報等）。
【０００６】
しかしながら、これらの方法によっても好気性微生物濃度を高くすると酸素要求量が増し、それが律速となって処理能力が頭打ちになる傾向にある。また、汚泥濃度を高くした状態は、液の粘性も増すので溶解効率を下げる原因となっている。その対策として散気設備を大幅に増設したり、機械撹拌を併用する方法も考えられるが設備費、ランニングコストがかさむ欠点がある。
【０００７】
例えば、最近中空糸膜について膜面積を確保しながら中空糸膜間での被濾過物質の閉塞を防止することを目的にして、中空糸膜を枠部材に取り付けて、一端または両端が開口する多数の中空糸膜を一列にして両端部を上下の型枠で支持固定すると共に、多数の中空糸膜と連通する濾過液通路を備えた中空糸膜濾過部材を、所定の間隔で連設すると共に、各濾過液通路を連結した中空糸膜濾過器（実開平５−６３６３２号、特開平５−２２０３５７号各公報）が提案されている。
【０００８】
更には、中空糸膜をシート状に展開して配置し、中空糸膜の端部が、ハウジング内の固定部材で開口状態を保ちつつ固定されてなる中空糸膜モジュールであって、固定部材の中空糸膜に垂直な断面の形状が細長いほぼ矩形である中空糸膜モジュール（特開平５−２２０３５６号公報）が提案されている。
【０００９】
このような中空糸膜をシート状に並び拡げた平型の中空糸膜モジュールを用いると、多数の中空糸膜を間隔を開けて均等に配置させることが可能となり、膜面洗浄の際、中空糸膜表面を均等に洗浄することが極めて容易となるので、濾過効率の低下を抑えることができる。
【００１０】
しかし、これらの中空糸膜モジュールを用いても、高汚濁水の吸引濾過では、比較的短時間の運転で差圧が大きくなりやすいため、逆洗や休止の回数が多くなることから装置効率の良い濾過を行うことが難しかった。
【００１１】
【発明が解決しようとする課題】
本発明の目的は、膜分離活性汚泥法による廃水の処理において、酸素の溶解量を増やし、また吸引濾過の差圧上昇を抑制して装置効率を高めた膜分離生物処理方法を提供することにある。
【００１２】
【課題を解決するための手段】
すなわち、本発明は、曝気槽へ膜モジュールを配設し、膜を介して廃水を吸引濾過して膜透過水を得る工程を有する廃水の膜分離生物処理方法において、中空糸膜の繊維軸がほぼ平行になるように配してなる膜モジュールを多段に積み重ねて配設し、かつ隣接する膜モジュール内の中空糸膜の繊維軸が約９０°のねじれ角の位置関係になるように配設することを特徴とする膜分離生物処理方法である。
【００１３】
また、もう一つの本発明は、曝気槽へ膜モジュールを配設し、膜を介して廃水を吸引濾過して膜透過水を得る工程を有する廃水の膜分離生物処理方法において、複数の平膜がほぼ平行になるように配してなる膜モジュールを多段に積み重ねて配設し、かつ隣接する膜モジュール内の平膜の形成する面が水平面に対して垂直でかつ約９０°で交叉する位置関係になるように配設するとともに、下部が上部より広がった形状の外套の内部に膜モジュールを収納して配設することを特徴とする膜分離生物処理方法である。
【００１４】
【発明の実施の形態】
以下、本発明の廃水の膜分離生物処理方法を、中空糸膜モジュールを用いる場合を例にとり、図面を参照しつつより詳細に説明する。
【００１５】
本発明の方法では、曝気槽内へ中空糸膜モジュールを配設する。図１は、曝気槽に配設された複数の中空糸膜モジュール１の相互の位置関係を示す図である。この例では、７個の中空糸膜エレメントを中空糸膜２により形成されるシート状面がほぼ平行になるように配置して一つの中空糸膜モジュールを構成している。そして、このような中空糸膜モジュールを３段に積み重ねるようにして設置している。したがって、この例では合計２１個の中空糸膜エレメントが使用されている。ここで、中段の中空糸膜モジュールに含まれる中空糸膜の繊維軸は、上段および下段の各中空糸膜モジュールに含まれる中空糸膜の繊維軸とは、それぞれ約９０°のねじれ角の位置関係（約９０°回転させて上下方向に移動させた状態）になるよう配置されている。
【００１６】
本発明の方法に用いる中空糸膜モジュールは、モジュール内に含まれる多数の中空糸膜がほぼ平行に位置するように配設して構成されたものであれば、特にその形態等については限定されずに使用できる。したがって、図１のように、一つの中空糸膜モジュールを複数の中空糸膜エレメントの集合体として構成してもよい。このような中空糸膜エレメントとしては、シート状に並び拡げられかつ繊維軸がほぼ平行になるよう配設された中空糸膜と、中空糸膜の端部を開口状態を保ちつつこれを固定する固定部材と、固定部材を支持収納する構造材とを有してなるものであって、固定部材の中空糸膜に垂直な断面の形状が細長いほぼ矩形である図２に示すタイプのものが好ましいものとして例示される。
【００１７】
図２に示した中空糸膜エレメント３は、構造材４と、固定部材５と、中空糸膜２とを有して構成されている。構造材４は、細長い矩形の開口部を有し、内部に濾液室を有する。この中空糸膜エレメントでは中空糸膜が直線状に配置され、その両端に構造材が配されているが、中空糸膜がＵ字状に折り曲げられて配され、一端にだけ構造材が配設されたタイプの中空糸膜エレメントも使用できる。
【００１８】
構造材４の開口部には、固定部材５が配設され、多数本の中空糸膜２をほぼ平行に揃えてシート状に並び拡げるとともに各端部を開口状態を保ったまま集束して固定して、中空糸膜を濾過膜として機能させている。
【００１９】
本発明の方法に用いる中空糸膜としては、種々のものが使用でき、例えばセルロース系、ポリオレフィン系、ポリビニルアルコール系、ＰＭＭＡ系、ポリスルフォン系等の各種材料からなるものが使用できるが、ポリエチレン、ポリプロピレン等の強伸度の高い材質のものが好ましい。なお、濾過膜として使用可能なものであれば、孔径、空孔率、膜厚、外径等には特に制限はないが、除去対象物や容積当たりの膜面積の確保および中空糸膜の強度等を考えると、好ましい例としては、孔径０．０１〜１μｍ、空孔率２０〜９０％、膜厚５〜３００μｍ、外径２０〜２０００μｍの範囲を挙げることができる。
【００２０】
中空糸膜の表面特性としては、表面に親水基等を持ついわゆる恒久親水化膜であることが望ましい。表面が疎水性の中空糸膜であると、被処理水中の有機物と中空糸膜表面との間に疎水性相互作用が働き膜面ヘの有機物吸着が発生し、それが膜面閉塞につながり濾過寿命が短くなる。また、吸着由来の目詰まりは膜面洗浄による濾過性能回復も一般には難しい。恒久親水化膜を用いることにより有機物と中空糸膜表面との疎水性相互作用を減少させることができ、有機物の吸着を抑えることができる。さらに疎水性膜ではスクラビングの際に気泡によって膜面が乾燥状態となることがあり、これにより疎水性が強まりフラックスの低下を招くことがあるが、恒久親水化膜では乾燥してもフラックスの低下が生じない。
【００２１】
本発明の方法に用いる中空糸膜モジュールは、上述した中空糸膜エレメントを複数個等間隔で平行に配置して、シート状に並び拡げた中空糸膜が平行に重畳されたように配されたものであることが好ましい。このような中空糸膜モジュールでは、多数の中空糸膜が間隔を開けて均等に配置されるので、膜表面を均等に洗浄できるので、濾過効率の低下を抑えることができる。また、中空糸膜が形成するシート面は、水平面に対して垂直方向とされることが好ましい。
【００２２】
本発明の膜分離生物処理方法は、このような中空糸膜モジュールを曝気槽内に多段に積み重ねて配置し、かつ隣接した段に設置された中空糸膜モジュールに含まれる中空糸膜の繊維軸が相互に約９０°のねじれ角の位置関係になるように配設する。ここで、約９０°のねじれ角とは、厳密に９０°ねじれた状態をいうのではなく、おおよそ直角状態でねじれ関係の位置にある状態をいい、より正確には、７０〜１１０°の範囲のねじれ角の状態をいう。中空糸膜モジュールをこのような位置関係に配設することにより、上昇してきた気泡が、中空糸膜の形成する面により分割されて微細化すると共に、流れ方向の変化により乱流が生ずることによって、酸素の溶解量が増加し、吸引濾過の差圧上昇が抑制されるものと推定される。中空糸膜モジュールは、２段以上であれば何段積み重ねて配設してもかまわないが、２〜５段程度が好ましい。
【００２３】
本発明の方法においては、モジュール間の中空糸膜の繊維軸が前述した位置関係を満たす複数の中空糸膜モジュールを、図３に示すように外套６内に収納するように配設することは好ましい態様である。特に、外套下部が上部より広がった逆ホッパー形状（スカート状）の集気部として形成し、下方に配設された散気装置８からの気泡を拾い集めるように構成することが好ましい。この場合には、気泡を廃水中へ酸素を溶存させる手段としてだけでなく、中空糸膜上の付着物を震い落すスクラビング手段としても利用できるとともに、気泡を推進力として外套内に上昇流を発生させて中空糸膜表面から剥離した付着物を押し流す洗浄作用も発揮させることができる。
【００２４】
本発明の膜分離生物処理方法では、曝気槽内の廃水を分離膜を介して吸引濾過を行なう。吸引濾過は、連続的に実施しても差圧の小さい濾過条件で長時間透過流束を高く保つことができるが、もちろん吸引を周期的に一時停止するいわゆる間欠吸引運転方法を採用することもできる。また、必要に応じて膜透過水を用いて中空糸膜モジュールの逆洗を行うこともできる。
【００２５】
以上においては、中空糸膜を用いた膜モジュールを使用する例について説明したが、本発明は、平膜を含む膜モジュールを下部が上部より広がった形状の外套の内部に収納して配設した場合についても同様に実施することができる。図４は、曝気槽に配設された複数の平膜モジュールの相互の位置関係を示す図１と同様な図であり、平膜以外は省略されている。
【００２６】
平膜の場合には、膜面が気泡を分割して微細化する作用は、中空糸膜を用いた膜モジュールと同等あるいはそれ以上なので、廃水に対する酸素の溶解量を大幅に増やすことが可能である。
【００２７】
【実施例】
以下、実施例により本発明を具体的に説明する。
【００２８】
実施例および比較例
本発明の方法を、食品加工工場における廃水に対して適用した例を図２のフローシートによって説明する。
【００２９】
中空糸膜モジュールとしては、図２示されるような形態の中空糸膜エレメントを２８個平行に配設して合計膜面積が１１２ｍ２ のモジュールを３段に積み重ねるようにして配設し、その下方から散気管でエアーレーションをした。なお、実施例では図１のように各段のモジュールの中空糸膜の繊維軸が交互に９０°のねじれ角の位置関係になるようにしたのに対し、比較例では、中空糸膜の繊維軸が全て同方向に向くようにして配設した。
【００３０】
処理設備は、調整槽１１が４０ｍ３ 、曝気槽１２が４０ｍ３ であり、処理水量は３０ｍ３ ／日、原水の水質はＢＯＤ３０００〜４０００ｍｇ／Ｌ、ＣＯＤｌ５００〜２０００ｍｇ／Ｌ、ＳＳ２００〜４００ｍｇ／Ｌであった。
【００３１】
運転は次の条件で実施した。ＭＬＳＳは１００００〜１５０００ｍｇ／Ｌで、汚泥濃縮貯溜槽で中空糸膜を用いて３００００ｍｇ／Ｌに濃縮した。汚泥引抜量は固形物当り１０ｋｇ／日、８０％含水ケーキ当り５０ｋｇ／日であった。また、散気管からは、２００Ｎｍ３ ／時で空気をエアレーションした。
【００３２】
その結果、曝気槽のＤＯおよび膜透過水水質のＢＯＤは、表１に示す通りであった。
【００３３】
【表１】

Figure 0003633704
比較例のように、繊維軸を同方向に揃えたものでは、殆どＤＯが検出されない状態であつたのに対し、本発明の方法のように交互に繊維軸の方向を変化させて３段に積み重ねたしたものでは、同一ブロワーによる散気でＤＯの上昇が認められ、処理水ＢＯＤも低く安定した。また、本発明の方法では、吸引濾過の差圧上昇は、比較例の場合に比べて小さかった。
【００３４】
【発明の効果】
本発明によれば、エネルギーコストを変えず、大幅に酸素の供給量を増やすことができる。また膜面の洗浄性が向上し、目詰まりの抑制効果が大きく、吸引濾過の差圧上昇が抑制され装置効率も高いという利点を有する。
【図面の簡単な説明】
【図１】本発明の方法における中空糸膜モジュールの位置関係を示す模式図である。
【図２】本発明の方法に用いる中空糸膜エレメントの一例を示す斜視図である。
【図３】本発明の方法において中空糸膜モジュールを外套内に配設した状態を示す模式図である。
【図４】本発明の方法における膜モジュールの平膜の位置関係を示す模式図である。
【図５】本発明方法を適用した一例を示すフローシートである。
【符号の説明】
１ 中空糸膜モジュール
２ 中空糸膜
３ 中空糸膜エレメント
４ 構造材
５ 固定部材
６ 外套
７ 集気部
８ 散気装置
９ 平膜
１１ 調整槽
１２ 曝気槽
１３ 汚泥濃縮貯留槽
１４ 膜モジュール
１５ 散気管
１６ 調整槽ポンプ
１７ 汚泥移送ポンプ
１８ 処理水吸引ポンプ
１９ 汚泥濃縮吸引ポンプ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biological treatment method for organic wastewater by a membrane separation activated sludge method.
[0002]
[Prior art]
Conventionally, biological treatment has been used for the treatment of municipal wastewater and organic wastewater, and precipitation separation has been used for final solid-liquid separation. However, in the precipitation separation, SS spilled out easily when the load fluctuated.
[0003]
When membrane separation is used for solid-liquid separation, a sedimentation tank is not required, SS can be completely prevented from flowing out, and the activated sludge concentration in the aeration tank can be increased, resulting in less generation of excess sludge. In recent years, the membrane separation activated sludge method has attracted attention because it can be made compact.
[0004]
A microfiltration membrane and an ultrafiltration membrane are mainly used for solid-liquid separation in organic wastewater treatment by biological treatment. These separation membranes are used in the form of flat membranes, tubular membranes or hollow fiber membranes. In particular, recently, many methods for solid-liquid separation of activated sludge by suction filtration using a hollow fiber membrane module have been proposed.
[0005]
On the other hand, when activated sludge containing organic gel-like substances is solid-liquid separated with these separation membranes, it is due to clogging of the membrane, adhesion of dirt on the surface of the membrane, retention of dirt between the membranes, etc. Performance degradation is likely to occur, and it is necessary to wash the membrane surface by sending air to vibrate the membrane, and to repeat the membrane surface cleaning.Furthermore, the liquid to be treated is due to the air lift effect of the air sent from the air diffuser It has been proposed to receive more efficient microbial treatment by receiving agitation (JP-A-61-129094, JP-A-3-98697, etc.).
[0006]
However, even with these methods, when the aerobic microorganism concentration is increased, the oxygen demand increases, which tends to be rate-limiting and the processing capacity tends to reach its peak. Moreover, when the sludge concentration is increased, the viscosity of the liquid increases, which causes a decrease in dissolution efficiency. As countermeasures, it is possible to increase the number of diffusers or to use mechanical agitation in combination, but there is a drawback that the equipment and running costs are increased.
[0007]
For example, recently, a hollow fiber membrane is attached to a frame member for the purpose of preventing obstruction of a substance to be filtered between the hollow fiber membranes while securing a membrane area of the hollow fiber membrane. The hollow fiber membranes are arranged in a row, and both ends are supported and fixed by upper and lower molds, and a hollow fiber membrane filtration member having a filtrate passage communicating with a large number of hollow fiber membranes is continuously provided at a predetermined interval. A hollow fiber membrane filter (Japanese Utility Model Laid-Open No. 5-63632 and Japanese Patent Laid-Open No. 5-220357) in which the filtrate passages are connected has been proposed.
[0008]
Furthermore, the hollow fiber membrane is a hollow fiber membrane module in which a hollow fiber membrane is developed and arranged in a sheet shape, and an end of the hollow fiber membrane is fixed while being kept open by a fixing member in the housing, There has been proposed a hollow fiber membrane module (Japanese Patent Laid-Open No. 5-220356) having a substantially rectangular shape with a cross section perpendicular to the hollow fiber membrane.
[0009]
When a flat hollow fiber membrane module in which such hollow fiber membranes are arranged and expanded in a sheet shape is used, a large number of hollow fiber membranes can be evenly arranged at intervals. Since it becomes extremely easy to evenly clean the surface of the thread membrane, it is possible to suppress a decrease in filtration efficiency.
[0010]
However, even with these hollow fiber membrane modules, the suction filtration of highly polluted water tends to increase the differential pressure in a relatively short period of time, so the number of backwashes and pauses increases, so the efficiency of the device is high. It was difficult to perform good filtration.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a membrane separation biological treatment method that increases the amount of dissolved oxygen and suppresses the increase in the differential pressure of suction filtration to increase the efficiency of the apparatus in the treatment of wastewater by the membrane separation activated sludge method. is there.
[0012]
[Means for Solving the Problems]
That is, the present invention relates to a wastewater membrane separation biological treatment method comprising a step of disposing a membrane module in an aeration tank and suction-filtering wastewater through the membrane to obtain membrane permeated water. Membrane modules arranged so as to be approximately parallel are stacked and arranged in multiple stages, and the fiber axes of the hollow fiber membranes in adjacent membrane modules are arranged in a positional relationship of about 90 ° twist angle. And a membrane separation biological treatment method.
[0013]
Another aspect of the present invention relates to a wastewater membrane separation biological treatment method comprising a step of disposing a membrane module in an aeration tank and suction-filtering wastewater through the membrane to obtain membrane permeate. The membrane modules arranged so as to be substantially parallel to each other are stacked in multiple stages, and the plane of the flat membrane in the adjacent membrane modules is perpendicular to the horizontal plane and intersects at about 90 ° The membrane separation biological treatment method is characterized in that the membrane module is housed and arranged inside a mantle having a lower portion that is wider than the upper portion .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the membrane separation biological treatment method of wastewater of the present invention will be described in more detail with reference to the drawings, taking the case of using a hollow fiber membrane module as an example.
[0015]
In the method of the present invention, the hollow fiber membrane module is disposed in the aeration tank. FIG. 1 is a diagram showing a mutual positional relationship between a plurality of hollow fiber membrane modules 1 arranged in an aeration tank. In this example, one hollow fiber membrane module is configured by arranging seven hollow fiber membrane elements such that the sheet-like surfaces formed by the hollow fiber membranes 2 are substantially parallel. And such hollow fiber membrane modules are installed so as to be stacked in three stages. Therefore, a total of 21 hollow fiber membrane elements are used in this example. Here, the fiber axis of the hollow fiber membrane included in the middle hollow fiber membrane module is the position of the twist angle of about 90 ° from the fiber axis of the hollow fiber membrane included in each of the upper and lower hollow fiber membrane modules. They are arranged so as to be in a relationship (a state in which they are rotated about 90 ° and moved up and down).
[0016]
The hollow fiber membrane module used in the method of the present invention is not particularly limited in terms of its form as long as a large number of hollow fiber membranes included in the module are arranged and arranged substantially in parallel. Can be used without Therefore, as shown in FIG. 1, one hollow fiber membrane module may be configured as an assembly of a plurality of hollow fiber membrane elements. As such a hollow fiber membrane element, a hollow fiber membrane that is arranged in a sheet shape and disposed so that the fiber axes are substantially parallel to each other, and an end portion of the hollow fiber membrane is fixed in an open state. A fixing member and a structural member that supports and stores the fixing member, and is preferably of the type shown in FIG. 2, in which the shape of the cross-section perpendicular to the hollow fiber membrane of the fixing member is a substantially rectangular shape. It is illustrated as a thing.
[0017]
The hollow fiber membrane element 3 shown in FIG. 2 includes a structural material 4, a fixing member 5, and a hollow fiber membrane 2. The structural member 4 has an elongated rectangular opening and has a filtrate chamber therein. In this hollow fiber membrane element, the hollow fiber membranes are arranged in a straight line, and structural materials are arranged at both ends thereof, but the hollow fiber membranes are arranged in a U-shape and the structural materials are arranged only at one end. The types of hollow fiber membrane elements that are made can also be used.
[0018]
A fixing member 5 is disposed at the opening of the structural material 4 and a large number of hollow fiber membranes 2 are arranged almost in parallel and spread in a sheet shape, and each end is converged and fixed while maintaining the open state. Thus, the hollow fiber membrane functions as a filtration membrane.
[0019]
Various hollow fiber membranes used in the method of the present invention can be used. For example, those made of various materials such as cellulose, polyolefin, polyvinyl alcohol, PMMA, and polysulfone can be used. A material having high strength such as polypropylene is preferred. In addition, as long as it can be used as a filtration membrane, there is no particular limitation on the pore diameter, porosity, film thickness, outer diameter, etc., but the membrane area per removal object and volume and the strength of the hollow fiber membrane In view of the above, preferable examples include a pore diameter of 0.01 to 1 μm, a porosity of 20 to 90%, a film thickness of 5 to 300 μm, and an outer diameter of 20 to 2000 μm.
[0020]
As a surface characteristic of the hollow fiber membrane, a so-called permanent hydrophilic membrane having a hydrophilic group on the surface is desirable. If the surface is a hydrophobic hollow fiber membrane, hydrophobic interaction occurs between the organic matter in the water to be treated and the surface of the hollow fiber membrane, causing organic matter adsorption to the membrane surface, which results in blockage of the membrane surface and filtration. Life is shortened. Moreover, it is generally difficult to recover the filtration performance by cleaning the membrane surface due to clogging due to adsorption. By using a permanent hydrophilized membrane, the hydrophobic interaction between the organic matter and the hollow fiber membrane surface can be reduced, and adsorption of the organic matter can be suppressed. Furthermore, in the hydrophobic membrane, the membrane surface may become dry due to bubbles during scrubbing, which may increase the hydrophobicity and reduce the flux. Does not occur.
[0021]
The hollow fiber membrane module used in the method of the present invention is arranged in such a manner that a plurality of the above-described hollow fiber membrane elements are arranged in parallel at equal intervals, and the hollow fiber membranes arranged in a sheet form are superposed in parallel. It is preferable. In such a hollow fiber membrane module, since many hollow fiber membranes are arrange | positioned equally spaced apart, since the membrane surface can be wash | cleaned equally, the fall of filtration efficiency can be suppressed. Moreover, it is preferable that the sheet | seat surface which a hollow fiber membrane forms is a perpendicular | vertical direction with respect to a horizontal surface.
[0022]
In the membrane separation biological treatment method of the present invention, such hollow fiber membrane modules are stacked and arranged in multiple stages in an aeration tank, and the fiber axes of the hollow fiber membranes included in the hollow fiber membrane modules installed in adjacent stages Are arranged so as to have a positional relationship of about 90 ° with respect to each other. Here, the twist angle of about 90 ° does not mean a state where the twist is strictly 90 °, but a state where the twist angle is in a substantially right angle state, and more precisely, a range of 70 to 110 °. The state of the twist angle. By arranging the hollow fiber membrane module in such a positional relationship, the rising air bubbles are divided and refined by the surface formed by the hollow fiber membrane, and a turbulent flow is generated by a change in the flow direction. It is presumed that the amount of dissolved oxygen increases and the increase in the differential pressure of suction filtration is suppressed. As long as the hollow fiber membrane module has two or more stages, the hollow fiber membrane module may be stacked and arranged, but about 2 to 5 stages are preferable.
[0023]
In the method of the present invention, a plurality of hollow fiber membrane modules in which the fiber axes of the hollow fiber membranes between the modules satisfy the positional relationship described above are disposed so as to be housed in the outer sheath 6 as shown in FIG. This is a preferred embodiment. In particular, it is preferable that the outer lower portion is formed as an inverted hopper-shaped (skirt-shaped) air collecting portion that spreads from the upper portion, and is configured to collect air bubbles from the air diffuser 8 disposed below. In this case, it can be used not only as a means for dissolving bubbles in wastewater but also as a scrubbing means for shaking the deposits on the hollow fiber membrane, and ascending flow in the mantle with the bubbles as a driving force. It is also possible to exert a cleaning action that sweeps away deposits that are generated and peeled off the surface of the hollow fiber membrane.
[0024]
In the membrane separation biological treatment method of the present invention, the wastewater in the aeration tank is subjected to suction filtration through the separation membrane. Suction filtration can keep the permeation flux high for a long time under filtration conditions with a small differential pressure even if it is continuously performed, but of course it is also possible to adopt a so-called intermittent suction operation method in which suction is temporarily stopped it can. Moreover, the hollow fiber membrane module can be back-washed using membrane permeated water as required.
[0025]
In the above, an example of using a membrane module using a hollow fiber membrane has been described. However, in the present invention, a membrane module including a flat membrane is accommodated and disposed inside a mantle having a shape in which the lower part is wider than the upper part. The case can be similarly implemented. FIG. 4 is a view similar to FIG. 1 showing the mutual positional relationship of a plurality of flat membrane modules arranged in the aeration tank, except for the flat membrane.
[0026]
In the case of flat membranes, the action of the membrane surface to divide and refine bubbles is equal to or greater than that of membrane modules using hollow fiber membranes, so it is possible to greatly increase the amount of dissolved oxygen in wastewater. is there.
[0027]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
[0028]
Examples and Comparative Examples An example in which the method of the present invention is applied to wastewater in a food processing factory will be described with reference to the flow sheet of FIG.
[0029]
As the hollow fiber membrane module, 28 hollow fiber membrane elements of the form as shown in FIG. 2 are arranged in parallel, and modules having a total membrane area of 112 m 2 are stacked in three stages, and below that Aerated with a diffuser. In the examples, the fiber axes of the hollow fiber membranes of the modules in the respective stages are alternately positioned at a twist angle of 90 ° as shown in FIG. 1, whereas in the comparative example, the fibers of the hollow fiber membranes All the shafts were arranged in the same direction.
[0030]
Treatment facility, adjusting tank 11 is 40 m 3, the aeration tank 12 is 40 m 3, the process water is 30 m 3 / day, the water quality of raw water BOD3000~4000mg / L, CODl500~2000mg / L, at SS200~400mg / L there were.
[0031]
The operation was performed under the following conditions. MLSS was 10,000-15000 mg / L, and it concentrated to 30000 mg / L using the hollow fiber membrane in the sludge concentration storage tank. Sludge withdrawal was 10 kg / day per solid and 50 kg / day per 80% wet cake. In addition, air was aerated from the air diffuser at 200 Nm 3 / hour.
[0032]
As a result, DO of the aeration tank and BOD of the membrane permeated water quality were as shown in Table 1.
[0033]
[Table 1]
Figure 0003633704
As in the comparative example, when the fiber axes were aligned in the same direction, almost no DO was detected. On the other hand, the direction of the fiber axes was changed alternately in three steps as in the method of the present invention. In the stacked ones, an increase in DO was observed due to aeration by the same blower, and the treated water BOD was also low and stable. Moreover, in the method of the present invention, the increase in the differential pressure of suction filtration was smaller than that in the comparative example.
[0034]
【The invention's effect】
According to the present invention, the supply amount of oxygen can be significantly increased without changing the energy cost. In addition, the membrane surface has improved cleaning properties, has a great effect of suppressing clogging, has an advantage that the differential pressure increase in suction filtration is suppressed, and the apparatus efficiency is high.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the positional relationship of hollow fiber membrane modules in the method of the present invention.
FIG. 2 is a perspective view showing an example of a hollow fiber membrane element used in the method of the present invention.
FIG. 3 is a schematic view showing a state in which the hollow fiber membrane module is disposed in the mantle in the method of the present invention.
FIG. 4 is a schematic diagram showing a positional relationship of flat membranes of a membrane module in the method of the present invention.
FIG. 5 is a flow sheet showing an example to which the method of the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module 2 Hollow fiber membrane 3 Hollow fiber membrane element 4 Structural material 5 Fixing member 6 Outer jacket 7 Air collecting part 8 Air diffuser 9 Flat membrane 11 Adjustment tank 12 Aeration tank 13 Sludge concentration storage tank 14 Membrane module 15 Aeration pipe 16 Adjustment tank pump 17 Sludge transfer pump 18 Treated water suction pump 19 Sludge concentration suction pump

Claims (4)

曝気槽へ膜モジュールを配設し、膜を介して廃水を吸引濾過して膜透過水を得る工程を有する廃水の膜分離生物処理方法において、中空糸膜の繊維軸がほぼ平行になるように配してなる膜モジュールを多段に積み重ねて配設し、かつ隣接する膜モジュール内の中空糸膜の繊維軸が約９０°のねじれ角の位置関係になるように配設することを特徴とする膜分離生物処理方法。In a membrane separation biological treatment method having a step of arranging a membrane module in an aeration tank and sucking and filtering wastewater through the membrane to obtain membrane permeate, so that the fiber axes of the hollow fiber membranes are substantially parallel to each other The arranged membrane modules are stacked in multiple stages, and the fiber axes of the hollow fiber membranes in the adjacent membrane modules are arranged so as to have a twist angle of about 90 °. Membrane separation biological treatment method. 膜モジュールの下方に散気装置を配設する請求項１記載の膜分離生物処理方法。The membrane separation biological treatment method according to claim 1, wherein an aeration device is disposed below the membrane module. 下部が上部より広がった形状の外套の内部に膜モジュールを収納して配設する請求項１または２記載の膜分離生物処理方法。The membrane separation biological treatment method according to claim 1 or 2, wherein the membrane module is housed and disposed in a mantle having a shape in which the lower part extends from the upper part. 曝気槽へ膜モジュールを配設し、膜を介して廃水を吸引濾過して膜透過水を得る工程を有する廃水の膜分離生物処理方法において、複数の平膜をほぼ平行になるように配してなる膜モジュールを多段に積み重ねて配設し、かつ隣接する膜モジュール内の平膜の形成する面が水平面に対して垂直でかつ約９０°で交叉する位置関係になるように配設するとともに、下部が上部より広がった形状の外套の内部に膜モジュールを収納して配設することを特徴とする膜分離生物処理方法。In a membrane separation biological treatment method for wastewater having a process of arranging a membrane module in an aeration tank and obtaining a membrane permeated water by suction filtration of the wastewater through the membrane, a plurality of flat membranes are arranged substantially in parallel. The membrane modules are stacked and arranged in multiple stages, and the flat membranes in the adjacent membrane modules are arranged so that the planes of the membranes are perpendicular to the horizontal plane and intersect at about 90 °. A membrane-separated biological treatment method, wherein a membrane module is housed and disposed in a mantle having a shape in which the lower part is wider than the upper part.
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