JP2004305926A - Immersion membrane separation type activated sludge treatment method - Google Patents

Immersion membrane separation type activated sludge treatment method Download PDF

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JP2004305926A
JP2004305926A JP2003103512A JP2003103512A JP2004305926A JP 2004305926 A JP2004305926 A JP 2004305926A JP 2003103512 A JP2003103512 A JP 2003103512A JP 2003103512 A JP2003103512 A JP 2003103512A JP 2004305926 A JP2004305926 A JP 2004305926A
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water
treatment
membrane
sludge
separation
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Inventor
Taichi Kamisaka
太一 上坂
Kazuhisa Nishimori
一久 西森
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Kubota Corp
株式会社クボタ
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02WCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00Technologies for wastewater treatment
    • Y02W10/10Biological treatment of water, waste water, or sewage

Abstract

<P>PROBLEM TO BE SOLVED: To provide an immersion membrane separation type activated sludge treatment method capable of reducing the maintenance frequency of membrane washing by preventing a filter membrane from being clogged with a residual polymeric flocculant while keeping the predetermined permeation flux in a membrane separator. <P>SOLUTION: The sludge-separated water discharged from dehydration equipment 54 is returned to one treatment tank (e.g., 53) in such a state that the supply of water to be treated to the treatment tank 53 is stopped and the predetermined permeation flux is kept in the membrane separator 55 of other treatment tanks 51 and 52 while suppressing the predetermined permeation flux in the membrane separator 55 of the treatment tank 53. The treatment tanks 51 and 52, to which water to be treated is supplied, and the treatment tank 53, to which sludge-separated water is supplied, are altered at a predetermined time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
本発明は浸漬型膜分離活性汚泥処理方法に関し、被処理水を処理槽内に導入して活性汚泥処理し、槽内に浸漬設置した膜分離装置により活性汚泥および被処理水に含まれた汚濁物を固液分離する技術に係るものである。
【0002】
【従来の技術】
従来、産業廃水処理、生活排水処理、下水処理などにおいては、有機性汚水を活性汚泥処理することが一般的である。活性汚泥処理としては、例えば図2に示すように、処理槽1の内部に膜分離装置2を浸漬設置して固液分離を行う方法が近年普及してきた。この膜分離装置2は、上下が開口したケース3の内部に鉛直方向に配置する複数の平板状の膜カートリッジ4を平行に配列し、膜カートリッジ4の下方に散気装置5を配設したものであり、膜カートリッジ4はろ板の表裏に平膜状の有機膜を貼着したものである。
【0003】
処理槽1では散気装置5から散気する空気によって生じる固気液混相の上向流によって汚濁物を含む被処理水と活性汚泥との混合液を槽内で循環させながら混合液に酸素を溶解させ、活性汚泥の微生物により汚濁物中の有機物を生物処理して除去する。膜分離装置2には上向流によって混合液を膜カートリッジ4の間の流路に膜面に沿ったクロスフローで供給し、処理槽1の内部の水頭を駆動力(濾過水頭)として膜カートリッジ4で混合液を固液分離し、膜カートリッジ4の濾過膜を透過した膜処理水を導出系6で槽外へ導き出す。膜カートリッジ4には濾過の駆動力として吸引ポンプ等で吸引圧力を作用させることも可能である。
【0004】
処理槽1の余剰汚泥は汚泥引抜系7で攪拌槽8へ導き、凝集剤を攪拌混合してフロックを形成し、その後に脱水装置9で濃縮脱水する。脱水装置9から排出する脱水ケーキは系外へ排出して焼却処分もしくは埋立処分する。
【0005】
脱水処理工程において添加する高分子凝集剤が汚泥と完全に反応すれば未反応の高分子凝集剤(以下に残留高分子凝集剤と呼称する)が汚泥分離水中に含まれることはないが、汚泥の性状によっては高分子凝集剤との反応性が低いことがあり、汚泥分離水中に多くの残留高分子凝集剤が含まれる。
【0006】
このため、汚泥分離水は分離水系10で凝集沈殿処理槽11に導き、無害化剤を添加して凝集分離するなどの物理化学的処理によって残留高分子凝集剤を除去し、凝集沈殿処理槽11を経た脱水返流水を処理槽1に戻す。
【0007】
この種の先行技術文献としては特許文献1に記載するものがある。
【0008】
【特許文献1】特開平11−57799号
【0009】
【発明が解決しようとする課題】
しかし、凝集沈殿処理槽11において残留高分子凝集剤の除去はカチオン系の残留高分子凝集剤にアニオン系もしくは無機系の凝集剤を反応させて除去するので、添加する分量の調整を誤ると残留高分子凝集剤を完全に除去することは困難である。残留高分子凝集剤を含んだ脱水返流水が処理槽1に流入すると、膜分離装置2の濾過膜に高分子凝集剤のゲル層が形成され、膜の目詰まりにより透過流束が低下するなどの悪影響が生じ、膜洗浄のメンテナンスを行う頻度が多くなる。このゲル層は膜分離装置の膜カートリッジにおける透過流束が大きいほどに成長が早く、透過流束が小さいほどに成長が遅いので、透過流束を小さくした運転を行うことでゲル層の成長を抑制して膜洗浄のメンテナンス頻度を少なくできる。しかし、透過流束を小さくして膜分離装置を運転する場合に、系内に流入する被処理水によって与えられる負荷に対して膜分離装置が所定の処理能力を発揮するためには、膜カートリッジの数を増加させて膜分離装置における濾過膜の総膜面積を増加させる必要がある。
【0010】
本発明は上記した課題を解決するものであり、膜分離装置における所定の透過流束を維持しつつ、残留高分子凝集剤による濾過膜の目詰まりを抑制して膜洗浄のメンテナンス頻度を低減できる浸漬型膜分離活性汚泥処理方法を提供することを目的とする。
【0011】
【課題を解決するための手段】
上記課題を解決するために、本発明の浸漬型膜分離活性汚泥処理方法は、被処理水を複数の処理槽に導いて生物処理するとともに、各処理槽に浸漬した膜分離装置で槽内の混合液を固液分離して膜処理水を取り出し、各処理槽の余剰汚泥を脱水設備に導いて凝集剤を添加して脱水する浸漬型膜分離活性汚泥処理方法であって、
一つの処理槽に対する被処理水の供給を停止する状態で脱水設備から排出する汚泥分離水を当該処理槽へ返送し、この処理槽の膜分離装置において透過流束を抑制して運転しつつ、他の処理槽の膜分離装置において所定の透過流束で運転し、被処理水を供給する処理槽および汚泥分離水を返送する処理槽を所定時間ごとに変更するものである。
【0012】
上記した構成により、処理槽で被処理水を処理する系と処理槽で汚泥分離水を処理する系とを分けて運転することで、被処理水を処理する処理槽においては残留高分子凝集剤に由来するゲル層によって透過流束が低下するなどの悪影響が生じず、所定の透過流束で行う通常運転の継続期間、つまり逆洗が必要となる時期までの期間が長くなる。また、通常運転における所定の透過流束を大きく設定して処理能力を高めた運転も可能となり、透過流束を大きくして槽内滞留時間を短くすることで処理槽の容量を小さくし、散気装置の動力を低減できる。
【0013】
一方、汚泥分離水を処理する処理槽では汚泥分離水の性状に応じて透過流束を抑制して運転することができ、汚泥分離水の槽内滞留時間を長くして汚泥分離水に含まれた有機物および残留高分子凝集剤を生物処理することができ、発泡を抑制できるとともに、残留高分子凝集剤による濾過膜の目詰まりを抑制して逆洗が必要となる時期までの期間を長くできる。汚泥分離水は前処理を施して処理槽へ返送することも可能である。
【0014】
ところで、活性汚泥処理において槽内滞留時間の短い運転を継続すると、処理槽における活性汚泥の微生物種が少なくなって生物処理で生じる代謝物を分解することが困難となり、代謝物が膜の目詰まりの原因となることがある。
【0015】
しかし、被処理水を供給する処理槽および汚泥分離水を返送する処理槽を所定時間ごとに変更することで、各処理槽においては、所定の透過流束にて短い槽内滞留時間の下で行う高負荷運転と、抑制した透過流束にて長い槽内滞留時間の下で行う低負荷運転とを交互に行うことになり、処理槽内の環境の変化によって活性汚泥に多様な微生物群を馴養して生物処理で生じる代謝物を分解することで膜の目詰まりを防止でき、逆洗の頻度を著しく減少させることができる。また、汚泥分離水を処理していた処理槽に被処理水を供給すると槽内に残る残留高分子凝集剤によって被処理水中の汚濁物が活性汚泥に付着することを助けることができ、膜の目詰まりを防止する一助となる。
【0016】
したがって、処理槽で被処理水を処理する系と処理槽で汚泥分離水を処理する系とを分けて運転し、汚泥分離水を返送する処理槽を所定時間ごとに変更して各処理槽において高負荷運転と低負荷運転とを交互に行うことで、装置全体として被処理水に対する生物処理能力、固液分離能力を維持しつつ残留高分子凝集剤による濾過膜の目詰まりを抑制して膜洗浄のメンテナンス頻度を低減できる。
【0017】
また、処理槽で被処理水を処理する系と処理槽で汚泥分離水を処理する系とを分けて運転することで、脱水設備の濃縮脱水工程における凝集剤の節約によって汚泥分離水中に固形物が残留しても、被処理水の処理工程に影響を全く及ぼさない安全な処理系を構成できるので、高価な凝集剤の使用を極力抑制することができる。
【0018】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。図1において、被処理水50は産業廃水処理、生活排水処理、下水処理などにおける有機性汚水であり、浸漬型膜分離活性汚泥処理設備は、複数の処理槽51、52、53と脱水設備54とからなる。
【0019】
各処理槽51、52、53の内部には膜分離装置55を浸漬設置している。膜分離装置55は、上下が開口したケース56の内部に鉛直方向に配置する複数の平板状の膜カートリッジ57を平行に配列し、膜カートリッジ57の下方に散気装置58を配設したものである。膜カートリッジ57はろ板の表裏に平膜状の有機膜を貼着したものであり、膜カートリッジ57は二次側がチューブおよび集水管を介して膜処理水管59に連通し、膜処理水管59に吸引ポンプ60を設けている。
【0020】
被処理水50を供給する原水供給管61は原水分岐管62、63、64のそれぞれが原水バルブ65、66、67を介して各処理槽51、52、53に連通している。各処理槽51、52、53の余剰汚泥を排出する汚泥引抜管68、69、70は汚泥バルブ71、72、73を介して連通し、脱水設備54に連通している。脱水設備54は攪拌槽74と脱水装置75とからなり、汚泥分離水を排出する分離水管76は分離水分岐管77、78、79のそれぞれが分離水バルブ80、81、82を介して各処理槽51、52、53に連通している。
【0021】
以下、上記した構成における作用を説明する。
始めに各処理槽51、52、53および脱水設備54の基本的な作用を説明する。各処理槽51、52、53では、原水分岐管62、63、64から供給する被処理水50と槽内に滞留する活性汚泥との混合液に対して散気装置58から空気を散気し、空気のエアリフト作用によって生じる固気液混相の上向流によって混合液を処理槽51、52、53の内部で循環させながら混合液に酸素を溶解させ、活性汚泥の微生物により汚濁物中の有機物を生物処理して除去する。
【0022】
膜分離装置55には上向流によって混合液を膜カートリッジ57の間の流路に膜面に沿ったクロスフローで供給する。膜分離装置55は吸引ポンプ60で与える吸引圧力によって膜カートリッジ57の一次側と二次側の間に生じる膜間差圧を駆動力として運転し、膜カートリッジ57の濾過膜で濾過して混合液を固液分離し、濾過膜を透過した膜処理水を膜処理水管59を通して系外へ排出する。
【0023】
膜分離装置55の各膜カートリッジ57における透過流束は膜間差圧が増加するほどに大きくなり、濾過膜の膜面に付着するケーキ層に由来する濾過抵抗が経時的に増加するほどに小さくなる。このため、膜分離装置55の通常運転時には吸引ポンプ60で与える吸引圧力を調整して膜間差圧を制御し、流量計83で計測する膜処理水の流量を一定に維持することで透過流束を所定値に制御する。
【0024】
本実施の形態では、膜分離装置55の運転は吸引ポンプ60で与える吸引圧力により強制吸引濾過して行っている。他の方法としては、吸引ポンプ60で与える吸引圧力で生じる膜間差圧を各処理槽51、52、53における水面から膜分離装置55までの水頭の範囲内で制御し、膜カートリッジ57の二次側を正圧(大気圧以上の圧力)とすることで重力濾過を行うことも可能である。
【0025】
処理槽51、52、53の余剰汚泥は汚泥引抜68、69、70を通して脱水設備54の攪拌槽74へ導き、凝集剤を攪拌混合してフロックを形成し、その後に脱水装置75で濃縮脱水する。脱水装置75から排出する脱水ケーキは系外へ排出して焼却処分もしくは埋立処分する。
【0026】
残留高分子凝集剤を含む汚泥分離水は脱水返流水として分離水管76を通して処理槽51、52、53の何れかに戻す。汚泥分離水の量は被処理水50の性状によっても変わるが、例えばBOD100−500mg/L程度の下水である場合には被処理水50の2〜10%程度である。
【0027】
以下に、浸漬型膜分離活性汚泥処理設備の運転時について説明する。原水バルブ65、66を開栓して原水バルブ67を閉栓し、分離水バルブ82を開栓して分離水バルブ80、81を閉栓することで、第1および第2の処理槽51、52へ被処理水50を供給し、第3の処理槽53に対する被処理水50の供給を停止し、脱水設備54から排出する汚泥分離水を第3の処理槽53へ返送し、第1および第2の処理槽51、52に対する汚泥分離水の供給を停止する。
【0028】
この状態で、被処理水50を供給する第1および第2の処理槽51、52の膜分離装置55を通常運転における所定の透過流束である上位設定値で運転しつつ、汚泥分離水を供給する第3の処理槽53の膜分離装置55を所定の透過流束以下の下位設定値に抑制して運転する。
【0029】
そして、所定時間経過するごとに被処理水50を供給する処理槽51、52および汚泥分離水を返送する処理槽53を変更する。処理槽51、52、53を変更する所定時間は被処理水50を生物処理する槽内の生物増殖速度、もしくは汚泥分離水を生物処理する槽内の生物増殖速度に依存し、増殖速度が速い場合は所定時間の設定値を短くし、増殖速度が遅い場合は所定時間の設定値を長くする。
【0030】
処理槽51、52、53の変更は原水バルブ65、66、67および分離水バルブ80、81、82を開閉操作して行い、上述した状態から被処理水50を第2、第3の処理槽52、53へ供給し、汚泥分離水を第1の処理槽51へ供給する状態へ変更し、あるいは被処理水50を第1、第3の処理槽51、53へ供給し、汚泥分離水を第2の処理槽52へ供給する状態へ変更し、所定時間毎に順次に状態を変更する。
【0031】
汚泥引抜68、69、70を通して余剰汚泥を引抜くタイミングは分離水管76を通して戻す脱水返流水の水質による。例えば、脱水返流水の汚濁物質量が比較的多ければ、脱水返流水の処理時に余剰汚泥が多く発生するので被処理水の受入時に余剰汚泥を引抜き、逆に比較的少なければ被処理水を処理した後の脱水返流水の受入時に余剰汚泥を引抜く。
【0032】
なお、処理槽51、52、53の変更はバルブ操作によらず、ポンプを個別に設けてその運転制御によって行うことも当然可能である。
膜分離装置55の透過流束は処理槽51、52、53における被処理水50の槽内滞留時間に影響し、透過流束が大きいほどに槽内滞留時間が短くなり、透過流束が小さいほどに槽内滞留時間が長くなる。このため、透過流束の上位設定値は被処理水50の性状に応じて経験則で設定し、被処理水50を十分に生物処理するのに必要な槽内滞留時間を実現する透過流束をとする。また、透過流束の下位設定値は汚泥分離水の性状に応じて経験則で設定し、残留高分子凝集剤を含む汚泥分離水を生物処理するのに必要な槽内滞留時間を実現し、かつ残留高分子凝集剤に由来するゲル層の成長を抑制できる透過流束をとする。
【0033】
上述したように、処理槽51、52で被処理水50を処理する系と処理槽53で汚泥分離水を処理する系とを分けて運転することで、被処理水50を処理する処理槽51、52においては残留高分子凝集剤に由来するゲル層によって透過流束が低下するなどの悪影響が生じずに被処理水50を生物処理でき、所定の透過流束で行う通常運転の継続期間、つまり逆洗が必要となる時期までの期間が長くなる。また、通常運転における所定の透過流束を大きく設定して処理能力を高めた運転も可能となり、透過流束を大きくして槽内滞留時間を短くすることで処理槽51、52、53の容量を小さくし、散気装置58の動力を低減できる。
【0034】
一方、汚泥分離水を処理する処理槽53では透過流束を抑制して運転することで、残留高分子凝集剤による濾過膜の目詰まりを抑制して逆洗が必要となる時期までの期間を長くでき、汚泥分離水の槽内滞留時間を長くして汚泥分離水に含まれた有機物および残留高分子凝集剤を生物処理することができる。
【0035】
ところで、活性汚泥処理において槽内滞留時間の短い運転を継続すると、処理槽51、52、53における活性汚泥の微生物種が少なくなって生物処理で生じる代謝物を分解することが困難となり、代謝物が膜の目詰まりの原因となることがある。
【0036】
しかし、被処理水50を供給する処理槽51、52、53および汚泥分離水を返送する処理槽51、52、53を所定時間ごとに変更することで、各処理槽51、52、53においては、所定の透過流束にて短い槽内滞留時間の下で行う高負荷運転と、抑制した透過流束にて長い槽内滞留時間の下で行う低負荷運転とを交互に行うことになり、各処理槽51、52、53の内部環境の変化によって活性汚泥に多様な微生物群を馴養して生物処理で生じる代謝物を分解することで膜の目詰まりを防止でき、逆洗の頻度を著しく減少させることができる。
【0037】
【発明の効果】
以上のように、本発明によれば、処理槽で被処理水を処理する系と処理槽で汚泥分離水を処理する系とを分けて運転し、汚泥分離水を返送する処理槽を所定時間ごとに変更して各処理槽において高負荷運転と低負荷運転とを交互に行うことで、被処理水を処理する処理槽では残留高分子凝集剤の悪影響を受けずに所定の透過流束で通常運転を長く継続して行って逆洗頻度を低減でき、汚泥分離水を処理する処理槽では汚泥分離水の性状に応じて透過流束を抑制した運転により槽内滞留時間を長くして汚泥分離水に含まれた有機物および残留高分子凝集剤を生物処理し、残留高分子凝集剤による濾過膜の目詰まりを抑制して逆洗頻度を低減できる。また、各処理槽において高負荷運転と低負荷運転とを交互に行うことで活性汚泥に多様な微生物群を馴養して生物処理で生じる代謝物を分解することで膜の目詰まりを防止でき、逆洗の頻度を著しく減少させることができる。よって、装置全体として被処理水に対する生物処理能力、固液分離能力を維持しつつ残留高分子凝集剤による濾過膜の目詰まりを抑制して膜洗浄のメンテナンス頻度を低減できる。
【図面の簡単な説明】
【図1】本発明の実施の形態における浸漬型膜分離活性汚泥処理設備を示すフローシート図である。
【図2】従来の浸漬型膜分離活性汚泥処理設備を示すフローシート図である。
【符号の説明】
50 被処理水
51、52、53 処理槽
54 脱水設備
55 膜分離装置
56 ケース
57 膜カートリッジ
58 散気装置
59 膜処理水管
60 吸引ポンプ
61 原水供給管
62、63、64 原水分岐管
65、66、67 原水バルブ
68、69、70 汚泥引抜管
71、72、73 汚泥バルブ
74 攪拌槽
75 脱水装置
76 分離水管
77、78、79 分離水分岐管
80、81、82 分離水バルブ
[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a submerged membrane separation activated sludge treatment method, in which water to be treated is introduced into a treatment tank to be subjected to activated sludge treatment, and the contamination contained in the activated sludge and the treated water is carried out by a membrane separation apparatus immersed and installed in the tank. The present invention relates to a technique for solid-liquid separation of an object.
[0002]
[Prior art]
BACKGROUND ART Conventionally, in industrial wastewater treatment, domestic wastewater treatment, sewage treatment, and the like, it is general to treat organic wastewater with activated sludge. As the activated sludge treatment, for example, as shown in FIG. 2, a method of immersing and installing a membrane separation device 2 in a treatment tank 1 to perform solid-liquid separation has recently become widespread. This membrane separation device 2 has a plurality of flat plate-shaped membrane cartridges 4 arranged vertically in a case 3 having an open top and bottom, and an air diffuser 5 disposed below the membrane cartridge 4. The membrane cartridge 4 has a flat membrane-like organic membrane adhered to the front and back of a filter plate.
[0003]
In the treatment tank 1, oxygen is added to the mixed liquid while circulating the mixed liquid of the water to be treated and the activated sludge containing the pollutants in the tank by the upward flow of the solid-gas-liquid mixed phase generated by the air diffused from the diffuser 5. It is dissolved and the organic matter in the polluted matter is biologically removed by the microorganism of the activated sludge. The mixed solution is supplied to the flow path between the membrane cartridges 4 by a cross-flow along the membrane surface by the upward flow to the membrane separation device 2, and the water head inside the treatment tank 1 is used as a driving force (filtration water head). In 4, the mixed solution is separated into solid and liquid, and the membrane-treated water that has passed through the filtration membrane of the membrane cartridge 4 is led out of the tank by the outlet system 6. A suction pressure can be applied to the membrane cartridge 4 by a suction pump or the like as a driving force for filtration.
[0004]
Excess sludge in the treatment tank 1 is guided to a stirring tank 8 by a sludge extraction system 7, and a flocculant is formed by stirring and mixing a flocculant. The dewatered cake discharged from the dewatering device 9 is discharged out of the system and incinerated or landfilled.
[0005]
If the polymer flocculant added in the dehydration process completely reacts with the sludge, unreacted polymer flocculant (hereinafter referred to as residual polymer flocculant) is not contained in the sludge separation water. Depending on the properties of the polymer, the reactivity with the polymer flocculant may be low, and the sludge separation water contains a large amount of the residual polymer flocculant.
[0006]
For this reason, the sludge separation water is guided to the coagulation and sedimentation treatment tank 11 in the separation water system 10, and the residual polymer coagulant is removed by a physicochemical treatment such as adding a detoxifying agent to coagulate and separate the sludge. Is returned to the treatment tank 1.
[0007]
As a prior art document of this kind, there is one described in Patent Document 1.
[0008]
[Patent Document 1] JP-A-11-57799
[Problems to be solved by the invention]
However, since the residual polymer flocculant is removed by reacting the cationic residual polymer flocculant with the anionic or inorganic flocculant in the flocculation / sedimentation treatment tank 11, the residual polymer flocculant is removed if the added amount is incorrectly adjusted. It is difficult to completely remove the polymer flocculant. When the dewatered return water containing the residual polymer flocculant flows into the treatment tank 1, a gel layer of the polymer flocculant is formed on the filtration membrane of the membrane separation device 2, and the permeation flux decreases due to clogging of the membrane. Adversely affects the maintenance of the membrane cleaning. Since the gel layer grows faster as the permeation flux in the membrane cartridge of the membrane separation device is larger, and grows slower as the permeation flux is smaller, the gel layer is grown by performing the operation with a smaller permeation flux. The frequency of maintenance of membrane cleaning can be reduced by suppressing the frequency. However, when the membrane separation device is operated with a small permeation flux, in order for the membrane separation device to exhibit a predetermined processing capacity with respect to the load given by the water to be treated flowing into the system, the membrane cartridge is required. It is necessary to increase the total membrane area of the filtration membrane in the membrane separation device by increasing the number of membranes.
[0010]
The present invention solves the above-described problems, and can reduce the maintenance frequency of membrane cleaning by suppressing clogging of a filtration membrane due to a residual polymer flocculant while maintaining a predetermined permeation flux in a membrane separation device. An object of the present invention is to provide a submerged membrane separation activated sludge treatment method.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the immersion type membrane separation activated sludge treatment method of the present invention conducts biological treatment by guiding the water to be treated to a plurality of treatment tanks, and the inside of the tank is separated by a membrane separation device immersed in each treatment tank. A immersion type membrane separation activated sludge treatment method in which the mixed liquid is subjected to solid-liquid separation to take out the membrane treatment water, and the excess sludge in each treatment tank is guided to a dehydration facility, and a coagulant is added and dewatered.
The sludge separation water discharged from the dehydration equipment is returned to the processing tank in a state in which the supply of the water to be processed to one processing tank is stopped, and the operation is performed while suppressing the permeation flux in the membrane separation device of the processing tank. In a membrane separation device of another treatment tank, the treatment tank is operated at a predetermined flux and the treatment tank for supplying the water to be treated and the treatment tank for returning the sludge separation water are changed every predetermined time.
[0012]
By the above-described configuration, the system for treating the water to be treated in the treatment tank and the system for treating the sludge separation water in the treatment tank are operated separately, so that the residual polymer flocculant is treated in the treatment tank for treating the water to be treated. There is no adverse effect such as a decrease in the permeation flux due to the gel layer derived from the above, and the duration of the normal operation performed at a predetermined permeation flux, that is, the period up to the time when backwashing is required, is lengthened. In addition, it is also possible to increase the processing capacity by setting a predetermined permeation flux in the normal operation to be large, and to reduce the capacity of the treatment tank by increasing the permeation flux and shortening the residence time in the tank. The power of the pneumatic device can be reduced.
[0013]
On the other hand, in a treatment tank for treating sludge separated water, it is possible to operate the sludge separated water in accordance with the properties of the sludge separated water while suppressing the permeation flux. Biological treatment of waste organic matter and residual polymer flocculant, foaming can be suppressed, and clogging of the filter membrane due to the residual polymer flocculant can be suppressed, and the period until backwashing becomes necessary can be extended. . The sludge separation water can be pretreated and returned to the treatment tank.
[0014]
By the way, if the operation with a short residence time in the tank is continued in the activated sludge treatment, the number of microorganisms in the activated sludge in the treatment tank decreases, and it becomes difficult to decompose metabolites generated in the biological treatment. May cause
[0015]
However, by changing the treatment tank for supplying the water to be treated and the treatment tank for returning the sludge separation water at predetermined time intervals, in each treatment tank, a predetermined permeation flux and a short residence time in the tank are used. The high load operation to be performed and the low load operation to be performed under a long residence time in the tank with suppressed permeation flux are performed alternately. By accumulating and decomposing metabolites generated in biological treatment, membrane clogging can be prevented and the frequency of backwashing can be significantly reduced. In addition, when the water to be treated is supplied to the treatment tank that has treated the sludge separation water, the residual polymer flocculant remaining in the tank can help the pollutants in the water to be treated to adhere to the activated sludge. It helps to prevent clogging.
[0016]
Therefore, the system for treating the water to be treated in the treatment tank and the system for treating the sludge separated water in the treatment tank are operated separately, and the treatment tank for returning the sludge separated water is changed at predetermined time intervals. By alternately performing high-load operation and low-load operation, membrane clogging of the filtration membrane due to residual polymer flocculant is suppressed while maintaining biological treatment capacity and solid-liquid separation capacity for the water to be treated as a whole. Cleaning maintenance frequency can be reduced.
[0017]
In addition, by separately operating the system for treating the water to be treated in the treatment tank and the system for treating the sludge separated water in the treatment tank, the solid matter is contained in the sludge separated water by saving the flocculant in the concentration and dewatering process of the dewatering equipment. Even if the residue remains, a safe treatment system that does not affect the treatment process of the water to be treated can be configured at all, so that the use of an expensive flocculant can be suppressed as much as possible.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, treated water 50 is organic sewage in industrial wastewater treatment, domestic wastewater treatment, sewage treatment, etc., and the immersion type membrane separation activated sludge treatment equipment includes a plurality of treatment tanks 51, 52, 53 and a dewatering equipment 54. Consists of
[0019]
A membrane separation device 55 is immersed in each of the processing tanks 51, 52, 53. The membrane separation device 55 has a plurality of flat plate-shaped membrane cartridges 57 arranged vertically in a case 56 having an open top and bottom, and an air diffuser 58 disposed below the membrane cartridge 57. is there. The membrane cartridge 57 has a flat membrane-like organic membrane adhered to the front and back of the filter plate. The membrane cartridge 57 has a secondary side connected to the membrane water pipe 59 through a tube and a water collection pipe, and is sucked into the membrane water pipe 59. A pump 60 is provided.
[0020]
In a raw water supply pipe 61 for supplying the water 50 to be treated, raw water branch pipes 62, 63, and 64 communicate with the processing tanks 51, 52, and 53 via raw water valves 65, 66, and 67, respectively. Sludge extraction pipes 68, 69, and 70 for discharging excess sludge from the processing tanks 51, 52, and 53 communicate with each other through sludge valves 71, 72, and 73, and communicate with the dewatering facility 54. The dewatering equipment 54 is composed of a stirring tank 74 and a dewatering device 75. Separated water pipes 76 for discharging sludge separated water are connected to respective separated water branch pipes 77, 78, 79 through separated water valves 80, 81, 82, respectively. It communicates with tanks 51, 52, and 53.
[0021]
Hereinafter, the operation of the above configuration will be described.
First, the basic operation of each of the processing tanks 51, 52, 53 and the dewatering equipment 54 will be described. In each of the treatment tanks 51, 52, and 53, air is diffused from a diffuser 58 to a mixed solution of the water 50 to be treated supplied from the raw water branch pipes 62, 63, and 64 and the activated sludge retained in the tanks. By dissolving oxygen in the mixed solution while circulating the mixed solution inside the processing tanks 51, 52 and 53 by the upward flow of the solid-gas-liquid mixed phase generated by the air lift action of air, the organic matter in the polluted matter by the microorganisms of the activated sludge Is removed by biological treatment.
[0022]
The mixed solution is supplied to the membrane separation device 55 to the flow path between the membrane cartridges 57 by an upward flow in a cross flow along the membrane surface. The membrane separation device 55 operates by using a transmembrane pressure generated between the primary side and the secondary side of the membrane cartridge 57 as a driving force by the suction pressure given by the suction pump 60, and filters the mixed solution by filtering through the filtration membrane of the membrane cartridge 57. Is separated into solid and liquid, and the membrane-treated water that has passed through the filtration membrane is discharged out of the system through the membrane-treated water pipe 59.
[0023]
The permeation flux in each membrane cartridge 57 of the membrane separation device 55 increases as the transmembrane pressure increases, and decreases as the filtration resistance due to the cake layer attached to the membrane surface of the filtration membrane increases with time. Become. For this reason, during normal operation of the membrane separation device 55, the suction pressure given by the suction pump 60 is adjusted to control the transmembrane pressure difference, and the flow rate of the membrane treatment water measured by the flow meter 83 is kept constant, so that the permeate flow is maintained. The bundle is controlled to a predetermined value.
[0024]
In the present embodiment, the operation of the membrane separation device 55 is performed by forcible suction filtration using suction pressure given by the suction pump 60. As another method, the transmembrane pressure generated by the suction pressure given by the suction pump 60 is controlled within the range of the head from the water surface in each of the processing tanks 51, 52, 53 to the membrane separation device 55, and the two Gravity filtration can be performed by setting the next side to a positive pressure (a pressure higher than the atmospheric pressure).
[0025]
Excess sludge in the treatment tanks 51, 52, and 53 is led to the stirring tank 74 of the dewatering facility 54 through the sludge withdrawals 68, 69, and 70, and the flocculant is formed by stirring and mixing the flocculant. . The dewatered cake discharged from the dehydrator 75 is discharged out of the system and incinerated or landfilled.
[0026]
The sludge separation water containing the residual polymer flocculant is returned to any of the treatment tanks 51, 52, 53 through the separation water pipe 76 as dewatered return water. The amount of the sludge separation water varies depending on the properties of the water to be treated 50, but is about 2 to 10% of the water to be treated 50, for example, when the sewage is about 100 to 500 mg / L BOD.
[0027]
Hereinafter, the operation of the immersion type membrane separation activated sludge treatment facility will be described. By opening the raw water valves 65 and 66 and closing the raw water valve 67 and opening the separation water valve 82 and closing the separation water valves 80 and 81, the first and second treatment tanks 51 and 52 can be opened. The water to be treated 50 is supplied, the supply of the water to be treated 50 to the third treatment tank 53 is stopped, and the sludge separation water discharged from the dehydration equipment 54 is returned to the third treatment tank 53, and the first and second waters are returned. The supply of the sludge separation water to the processing tanks 51 and 52 is stopped.
[0028]
In this state, while operating the membrane separation device 55 of the first and second treatment tanks 51 and 52 for supplying the water to be treated 50 at a higher set value which is a predetermined permeation flux in normal operation, sludge separation water is removed. The membrane separation device 55 of the third processing tank 53 to be supplied is operated while being suppressed to a lower set value equal to or lower than a predetermined permeation flux.
[0029]
Then, the processing tanks 51 and 52 for supplying the water to be treated 50 and the processing tank 53 for returning the sludge separation water are changed every time a predetermined time elapses. The predetermined time during which the treatment tanks 51, 52, 53 are changed depends on the biological growth rate in the biological treatment tank for treating the water to be treated 50 or the biological growth rate in the biological treatment tank for sludge separation water, and the growth rate is high. In this case, the set value of the predetermined time is shortened, and when the growth rate is low, the set value of the predetermined time is increased.
[0030]
The treatment tanks 51, 52 and 53 are changed by opening and closing the raw water valves 65, 66 and 67 and the separation water valves 80, 81 and 82, and the water to be treated 50 is changed from the above-described state to the second and third treatment tanks. 52, 53, and change to a state in which the sludge separated water is supplied to the first treatment tank 51, or the water to be treated 50 is supplied to the first and third treatment tanks 51, 53, and the sludge separated water is supplied. The state is changed to the state of supplying to the second processing tank 52, and the state is sequentially changed every predetermined time.
[0031]
The timing of extracting the excess sludge through the sludge extraction 68, 69, 70 depends on the quality of the dewatered return water returned through the separation water pipe 76. For example, if the amount of pollutants in the dewatered return water is relatively large, excess sludge will be generated during the treatment of the dewatered return water. After receiving the dewatered return water, the excess sludge is extracted.
[0032]
It should be noted that the processing tanks 51, 52, and 53 can be changed by operating pumps individually instead of operating valves.
The permeation flux of the membrane separation device 55 affects the residence time of the water 50 to be treated in the treatment tanks 51, 52, and 53. The larger the permeation flux, the shorter the residence time in the tank, and the smaller the permeation flux. The residence time in the tank becomes longer. For this reason, the upper set value of the permeation flux is set by an empirical rule according to the properties of the water 50 to be treated, and the permeation flux that realizes the residence time in the tank necessary for sufficiently biologically treating the water 50 to be treated. And In addition, the lower set value of the permeate flux is set by an empirical rule according to the properties of the sludge separation water, and the residence time in the tank necessary for biologically treating the sludge separation water containing the residual polymer flocculant is realized. In addition, a permeation flux that can suppress the growth of the gel layer derived from the residual polymer flocculant is used.
[0033]
As described above, by separately operating the system for treating the water 50 to be treated in the treatment tanks 51 and 52 and the system for treating the sludge separated water in the treatment tank 53, the treatment tank 51 for treating the water 50 to be treated is separated. , 52, the water to be treated 50 can be biologically treated without adverse effects such as a decrease in the permeation flux due to the gel layer derived from the residual polymer flocculant, In other words, the period until the time when backwashing is required becomes longer. In addition, it is also possible to increase the processing capacity by setting a predetermined permeation flux in the normal operation to be large, and to shorten the residence time in the tank by increasing the permeation flux to reduce the capacity of the processing tanks 51, 52, and 53. And the power of the air diffuser 58 can be reduced.
[0034]
On the other hand, in the treatment tank 53 for treating the sludge separation water, the operation is performed while suppressing the permeation flux, thereby suppressing the clogging of the filtration membrane due to the residual polymer flocculant to reduce the period up to the time when back washing is required. The sludge separation water can be made longer, and the residence time in the tank of the sludge separation water can be lengthened to biologically treat the organic matter and the residual polymer flocculant contained in the sludge separation water.
[0035]
By the way, when the operation in which the residence time in the tank is short is continued in the activated sludge treatment, the number of microorganisms in the activated sludge in the treatment tanks 51, 52, and 53 decreases, and it becomes difficult to decompose metabolites generated in biological treatment. May cause clogging of the membrane.
[0036]
However, by changing the processing tanks 51, 52, 53 for supplying the water to be treated 50 and the processing tanks 51, 52, 53 for returning the sludge separation water at predetermined time intervals, the processing tanks 51, 52, 53 have A high-load operation performed under a short tank residence time at a predetermined permeation flux and a low-load operation performed under a long tank residence time at a suppressed permeation flux are alternately performed, Changes in the internal environment of each of the processing tanks 51, 52, 53 acclimate various microorganisms to activated sludge and decompose metabolites generated in biological treatment, thereby preventing clogging of the membrane and significantly increasing the frequency of backwashing. Can be reduced.
[0037]
【The invention's effect】
As described above, according to the present invention, the system for treating the water to be treated in the treatment tank and the system for treating the sludge separated water in the treatment tank are operated separately, and the treatment tank for returning the sludge separated water is operated for a predetermined time. By alternately performing high-load operation and low-load operation in each treatment tank in each treatment tank, the treatment tank that treats the water to be treated has a predetermined permeation flux without being affected by the residual polymer flocculant. Normal operation can be continued for a long time to reduce the frequency of backwashing.In the treatment tank that treats sludge separation water, the sludge retention time in the tank is lengthened by reducing the permeation flux according to the properties of the sludge separation water to increase the sludge retention time. The organic matter and the residual polymer flocculant contained in the separated water are subjected to biological treatment, whereby clogging of the filtration membrane by the residual polymer flocculant can be suppressed, and the frequency of backwashing can be reduced. In addition, by alternately performing high-load operation and low-load operation in each treatment tank, it is possible to accumulate various microorganisms in activated sludge and decompose metabolites generated in biological treatment, thereby preventing membrane clogging, The frequency of backwashing can be significantly reduced. Therefore, clogging of the filtration membrane due to the residual polymer flocculant can be suppressed while maintaining the biological treatment ability and solid-liquid separation ability for the water to be treated as the entire apparatus, and the maintenance frequency of membrane cleaning can be reduced.
[Brief description of the drawings]
FIG. 1 is a flow sheet diagram showing a submerged membrane separation activated sludge treatment facility according to an embodiment of the present invention.
FIG. 2 is a flow sheet diagram showing a conventional immersion type membrane separation activated sludge treatment facility.
[Explanation of symbols]
50 treated water 51, 52, 53 treatment tank 54 dehydration equipment 55 membrane separation device 56 case 57 membrane cartridge 58 air diffuser 59 membrane treatment water pipe 60 suction pump 61 raw water supply pipes 62, 63, 64 raw water branch pipes 65, 66, 67 Raw water valves 68, 69, 70 Sludge extraction pipes 71, 72, 73 Sludge valve 74 Stirrer tank 75 Dehydrator 76 Separated water pipes 77, 78, 79 Separated water branch pipes 80, 81, 82 Separated water valves

Claims (1)

  1. 被処理水を複数の処理槽に導いて生物処理するとともに、各処理槽に浸漬した膜分離装置で槽内の混合液を固液分離して膜処理水を取り出し、各処理槽の余剰汚泥を脱水設備に導いて凝集剤を添加して脱水する浸漬型膜分離活性汚泥処理方法であって、
    一つの処理槽に対する被処理水の供給を停止する状態で脱水設備から排出する汚泥分離水を当該処理槽へ返送し、この処理槽の膜分離装置において透過流束を抑制して運転しつつ、他の処理槽の膜分離装置において所定の透過流束で運転し、被処理水を供給する処理槽および汚泥分離水を返送する処理槽を所定時間ごとに変更することを特徴とする浸漬型膜分離活性汚泥処理方法。
    The water to be treated is guided to a plurality of treatment tanks for biological treatment, and the mixed liquid in the tanks is separated into solid and liquid by a membrane separator immersed in each treatment tank to take out the membrane treatment water, and excess sludge in each treatment tank is removed. A immersion type membrane separation activated sludge treatment method in which a coagulant is added and dewatered by leading to a dehydration facility,
    The sludge separation water discharged from the dehydration equipment is returned to the processing tank in a state in which the supply of the water to be processed to one processing tank is stopped, and the operation is performed while suppressing the permeation flux in the membrane separation device of the processing tank. An immersion type membrane operated by a predetermined permeation flux in a membrane separation device of another processing tank, and a processing tank for supplying water to be treated and a processing tank for returning sludge separation water are changed every predetermined time. Separation activated sludge treatment method.
JP2003103512A 2003-04-08 2003-04-08 Immersion membrane separation type activated sludge treatment method Pending JP2004305926A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007108175A1 (en) * 2006-03-23 2007-09-27 Matsushita Electric Industrial Co., Ltd. Waste liquid treating apparatus
KR20110079253A (en) * 2009-12-31 2011-07-07 코오롱건설주식회사 Apparatus for purifying water comprising equalization tank
JP2011140017A (en) * 2009-12-07 2011-07-21 Sekisui Chem Co Ltd Sewage cleaning apparatus and sewage cleaning method
JP2012101154A (en) * 2010-11-08 2012-05-31 Sekisui Chem Co Ltd Sewage cleaning apparatus and sewage cleaning method
CN104860503A (en) * 2015-05-20 2015-08-26 饶宾期 Secondary deep dewatering device for sewage sludge

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007108175A1 (en) * 2006-03-23 2007-09-27 Matsushita Electric Industrial Co., Ltd. Waste liquid treating apparatus
JP2011140017A (en) * 2009-12-07 2011-07-21 Sekisui Chem Co Ltd Sewage cleaning apparatus and sewage cleaning method
KR20110079253A (en) * 2009-12-31 2011-07-07 코오롱건설주식회사 Apparatus for purifying water comprising equalization tank
KR101601878B1 (en) * 2009-12-31 2016-03-09 코오롱글로벌 주식회사 Apparatus for Purifying Water Comprising Equalization Tank
JP2012101154A (en) * 2010-11-08 2012-05-31 Sekisui Chem Co Ltd Sewage cleaning apparatus and sewage cleaning method
CN104860503A (en) * 2015-05-20 2015-08-26 饶宾期 Secondary deep dewatering device for sewage sludge

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