JP3737288B2

JP3737288B2 - Wastewater treatment system

Info

Publication number: JP3737288B2
Application number: JP26856798A
Authority: JP
Inventors: 崇伊東; 裕樹成田
Original assignee: Nishihara Environmental Technology Co Ltd
Current assignee: Nishihara Environmental Technology Co Ltd
Priority date: 1998-09-22
Filing date: 1998-09-22
Publication date: 2006-01-18
Anticipated expiration: 2018-09-22
Also published as: JP2000093992A

Description

【０００１】
【発明の属する技術分野】
本発明は、下水等の被処理水中に含まれる有機物のみならず、窒素やリンをも同時に効率よく除去するための排水処理システムに関するものである。
【０００２】
【従来の技術】
図５は従来の排水処理システムを示すフローシート図であり、同図において、１は流入する被処理水中の固形物（懸濁物質）を重力沈降させて固液分離する最初沈殿池、２は最初沈殿池１から分離液を導入し、該分離液中のＢＯＤを利用して脱窒・脱リンを同時に行うための浮遊汚泥方式の反応槽であり、この反応槽２は、嫌気槽３と無酸素槽４と好気槽５とを備えた構成となっている。かかる反応槽２において、嫌気槽３と無酸素槽４のそれぞれの槽内には攪拌手段（図示せず）が配置され、且つ、好気槽５内には曝気手段（図示せず）が配置されている。
【０００３】
６は好気槽５内の混合液を無酸素槽４に循環させるための循環手段、７は好気槽５から流出する混合液を導入して処理水と汚泥とに固液分離する最終沈殿池、８は最終沈殿池７で固液分離された汚泥の一部を嫌気槽３に返送するための返送汚泥管路であり、前記最終沈殿池７は固液分離された汚泥の一部を余剰汚泥として引き抜くための余剰汚泥引抜手段（図示せず）を有している。
【０００４】
次に動作について説明する。
まず、最初沈殿池１に被処理水が流入することにより、その最初沈殿池１では被処理水中の固形物が重力沈降して固液分離され、その分離液が嫌気槽３に導入される。この嫌気槽３には、最終沈殿池７から返送汚泥管路８を介して汚泥の一部が返送されていることにより、その返送汚泥と前記分離液が接触する。この際、前記返送汚泥に含まれるリン蓄積菌は、被処理水中の溶解性ＢＯＤ（主に揮発性有機酸）を取り込むと同時に、菌体内に蓄積していたリンを放出する。その後、嫌気槽３の流出水は無酸素槽４に導入され、ここでは、後段の好気槽５で酸化された酸化態窒素を含む混合液が循環されて無酸素状態で接触させる。この際、汚泥中に含まれる脱窒細菌が被処理水中のＢＯＤを利用して脱窒を行い、酸化態窒素は窒素ガスとして除去される。さらに、無酸素槽４の流出水は好気槽５に導入され、好気状態下で被処理水中のＢＯＤは酸化分解されると共に、汚泥中に含まれる硝化細菌によりアンモニア態窒素が硝化され、また、リンはリン蓄積菌により過剰に再摂取され液相中から除去される。
【０００５】
好気槽５から流出する混合液は、最終沈殿池７に導入されて処理水と汚泥とに固液分離され、処理水は消毒後に放流され、汚泥は返送汚泥管路８を介して嫌気槽３に一部返送される。なお、最終沈殿池７で固液分離された汚泥の一部は余剰汚泥として汚泥処理工程で処理される。この際、前記余剰汚泥を一旦最初沈殿池１に移送し、初沈汚泥と共に汚泥処理工程で処理してもよい。かかる廃水処理方法は、いわゆる嫌気・無酸素・好気法と呼ばれ、近年、国内外を問わず多く実用化されている。
【０００６】
【発明が解決しようとする課題】
従来の嫌気・無酸素・好気法を利用した排水処理システムは以上にように構成され、窒素の除去は比較的安定で且つ高効率に達成できる。しかしながら、リン除去に関しては、嫌気槽３でのリン蓄積菌のリン放出が不安定で好気槽５での十分なリン除去が得られないという課題があった。その原因としては、流入する排水の有機物（ＢＯＤ）濃度が低い、排水水質の変動が大きい、好気槽での酸化が進み返送汚泥を介して酸化態窒素が嫌気槽に持ち込まれる、雨水の流入により排水が希薄になるなどが挙げられる。さらには、嫌気・無酸素・好気法を利用した場合、反応槽２の容積が従来の標準活性汚泥法の数倍必要となり、処理施設の建設費が大きく嵩み、より広いスペースが必要になるという課題があった。また、上記従来の排水処理システムでは、まず、最初沈殿池１において、被処理水中の固形物を重力沈降により自然分離させるので、流出水質が安定せず、最初沈殿池１での被処理水の滞留時間を必要以上に長くしなければならず、このため、システム全体が大型化すると共に、処理効率が悪いという課題があった。また、嫌気槽におけるリン蓄積菌のリン放出に有効なＢＯＤ（有機炭素源）を、いかに効率よく確保して供給できるかという課題があった。
【０００７】
本発明は上記のような課題を解決するためになされたもので、とくに既存の標準活性汚泥処理施設において増設することなく、容易な改造を行うことにより、ＢＯＤのみならず窒素・リンをも合わせて効率よく同時除去が行える排水処理システムを提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明に係る排水処理システムは、濾材洗浄手段を備え、流入する被処理水中の懸濁物質を固液分離する濾過装置と、攪拌手段を備え、前記濾過装置から濾過水を導入する無酸素槽と、曝気手段を備え、前記無酸素槽から流出する混合液を導入して活性汚泥処理を行う好気槽と、この好気槽内の混合液の一部を前記無酸素槽に循環させる循環手段と、前記好気槽から流出する混合液を導入して処理水と汚泥とに固液分離する固液分離装置と、前記濾過装置から排出される汚泥を導入して調質する汚泥調質槽と、攪拌手段を備え、前記汚泥調質槽から排出される分離液および前記固液分離装置で分離された分離汚泥の一部を導入する嫌気槽と、この嫌気槽からの流出水を前記無酸素槽に導入する導入手段とからなるものである。
【０００９】
本発明に係る排水処理システムの嫌気槽は、汚泥調質槽から調質汚泥の一部を導入するようになっているものである。
【００１０】
本発明に係る排水処理システムの濾過装置は、浮遊性濾材が充填され、且つ、被処理水を上向流で濾過する高速固液分離装置から成っているものである。
【００１１】
本発明に係る排水処理システムの好気槽は、微生物を担持する担体を用いた活性汚泥処理槽から成っているものである。
【００１２】
【発明の実施の形態】
以下、本発明の実施の一形態を説明する。
実施の形態１．
図１は本発明の実施の形態１による排水処理システムを示すフローシートであり、図５と同一または相当部分には同一符号を付して重複説明を省略する。図１において、１０は被処理水を受け入れて当該被処理水中の懸濁物質を固液分離するための濾過装置、１１はその濾過装置１０から固液分離後の濾過水を無酸素槽４に導入する濾過水管路、１２は前記濾過装置１０から固液分離により生じる汚泥（汚泥混合液）を汚泥調質槽１３に導入するための汚泥管路であり、前記汚泥調質槽１３は、前記濾過装置１０から導入した汚泥を酸発酵させる汚泥酸発酵槽、もしくは前記汚泥を濃縮する汚泥濃縮槽から成るもので、要するに、濾過装置１０からの導入汚泥を酸発酵させたり濃縮したりして嫌気状態下で調質するものである。１４は汚泥調質槽１３から汚泥調質後の分離液を嫌気槽３に導入する分離液管路、１５は汚泥調質槽１３から調質汚泥を汚泥処理工程に導くための調質汚泥管路である。
【００１３】
図２は図１中の濾過装置１０の詳細構成を示す断面図であり、同図において、２１は濾過装置１０の本体となる固液分離槽であり、この固液分離槽２１内は、被処理水の流入ゾーンを兼ねた槽内下部の沈殿ゾーン２２と、この沈殿ゾーン２２の上部に濾材支持用のグレーチング２３で仕切られた濾材充填ゾーン２４と、この濾材充填ゾーン２４の上部に濾材押え用のグレーチング２５で仕切られた槽内上部の上澄ゾーン２６とが形成されている。
【００１４】
２７は前記沈殿ゾーン２２に被処理水を供給するための原水供給手段であり、この原水供給手段２７は、原水流入管２７ａと原水ポンプ２７ｂと原水弁２７ｃとから成っている。なお、２７ｄは前記沈殿ゾーン２２における前記原水流入管２７ａの下向き開口端の下方に配置された邪魔板である。
【００１５】
２８は前記沈殿ゾーン２２の底部に沈殿した汚泥を図１中の汚泥調質槽１３に導入させるための汚泥管路１２に設けられた排泥弁、２９は前記濾材充填ゾーン２４に充填された浮遊性濾材であり、この濾材２９としては、例えばプラスチック製など比重１以下で中空状の浮遊性濾材が用いられる。また、前記濾材２９は単なる貫通円筒中空状をなしたプラスチック製の浮遊性濾材、もしくは、その浮遊性濾材の内外全面がネジ状や凹凸状に形成されて表裏面積の拡大を図ったものの何れであってもよい。
【００１６】
３０は前記浮遊性濾材２９を洗浄するための濾材洗浄手段であり、この濾材洗浄手段３０は、沈殿ゾーン２２における濾材支持用のグレーチング２３の下部近傍に配置された洗浄空気管３０ａと、この洗浄空気管３０ａに設けられた洗浄弁３０ｂと、前記洗浄空気管３０ａが接続された洗浄ブロア３０ｃとを備え、前記洗浄弁３０ｂの開弁時における前記洗浄ブロア３０ｃの稼動によって、前記洗浄空気管３０ａが濾材充填ゾーン２４に向って洗浄空気を吹き出す構成となっている。
【００１７】
３１は固液分離槽２１の槽内上部（上澄ゾーン２６）に配置されて濾過水を流入させる越流トラフであり、この越流トラフ３１内は前記濾過水管路１１によって図１中の無酸素槽２内に接続されている。
【００１８】
以上のように構成された濾過装置１０は、原水供給手段２７によって固液分離槽２１の槽内下部に被処理水が供給されることにより、その被処理水は、前記固液分離槽２１内で上向流となって濾材充填ゾーン２４を上昇通過し、該通過時に被処理水中の懸濁物質が浮遊性濾材２９で効率よく捕捉されるようになっている。従って、前記濾過装置１０は被処理水を上向流で濾過する高速固液分離装置となっている。
【００１９】
図３は図１中の反応槽２の具体構成例を示す断面図であり、同図において、３２は嫌気槽３内に配置された攪拌手段、３３は嫌気槽３から流出する混合液を無酸素槽４に導入する導入手段、４１は無酸素槽４内に配置された攪拌手段、４２は無酸素槽４から流出する混合液を好気槽５に導入するための導入手段、５１は好気槽５内に配置された曝気手段、５２は好気槽５内に充填されて微生物を担持する微生物担体である。
【００２０】
この微生物担体５２は、例えばポリビニルアルコールなどに代表されるように微生物を包括して固定化する担体材料、もしくは浮遊性を有する多孔性の素材など、微生物の担持機能を有するものを用いるが、その形状は特定されるものでなく、また、担体材質は無機性物質および有機性物質のいずれも適用可能である。かかる微生物担体５２を用いて好気槽５で活性汚泥処理を行うが、この好気槽５の混合液は循環手段６によって微生物担体５２と共に無酸素槽４に循環されるようになっている。循環手段６は主にエアリフトポンプや水中ポンプなどの移送装置と移送管路とからなるものである。
【００２１】
なお、好気槽５と無酸素槽４とでは微生物担体５２を個別的に利用するようにしてもよく、また、無酸素槽４では微生物担体５２を利用しなくてもよく、そのいずれの場合も、好気槽５の微生物担体５２が無酸素槽４に循環しないようにして、好気槽５の混合液のみを無酸素槽４に循環させるようにすればよい。
【００２２】
次に動作について説明する。
被処理水は、まず濾過装置１０に流入する。即ち、被処理水は、図２中の原水ポンプ２７ｂによって固液分離槽２１の槽内下部に供給されることにより、その固液分離槽２１内に流入した被処理水は、上向流となって濾材充填ゾーン２４を上昇通過し、その通過時に被処理水中の懸濁物質が浮遊性濾材２９で効率よく捕捉される。そして、前記濾材充填ゾーン２４を上昇通過した上澄ゾーン２６の濾過水は、越流トラフ３１から濾過水管路１１を介して無酸素槽４に流入する。この無酸素槽４には、後段の好気槽５からＮＯ_X −Ｎ（酸化態窒素）を含んだ混合液が循環手段６を介して循環していることにより、その無酸素槽４では、攪拌手段４１による無酸素攪拌状態下で、前記循環混合液中のＮＯ_X −Ｎが微生物の作用によって脱窒される。
【００２３】
ここで、無酸素槽４の運転のケースでは、当該無酸素槽４内に混合液中の酸化還元電位ＯＲＰを測定するＯＲＰセンサーを設置し、この値（ＯＲＰの範囲は概ね±０〜−３００ｍＶ）に基づいてＯＲＰ計、コンピュータによって循環水量を制御し、槽内を無酸素状態に保持させることが望ましい。循環水量は流入する廃水量の２倍量を基本としたが、ＯＲＰが高くなる（好気状態）と、循環水量を減少させ、ＯＲＰが低くなる（嫌気状態）と、循環水量を増加させる。概ね循環水量は流入する廃水量の１．５〜４．０倍が目安となる。また、循環水量ではなく好気槽５の曝気風量をコントロールして、無酸素状態を保持させてもよい。なお、嫌気槽３及び無酸素槽４に設けられた攪拌手段３２，４１は、主に攪拌羽根を備えた機械攪拌装置を用いるが、酸素供給を抑えて水流を発生させるものであればよい。
【００２４】
上述のように無酸素槽４で脱窒処理された混合液は好気槽５に導入される。ここでの移流方法もオーバーフローを基本とするが、微生物担体５２を循環させる場合には、当該微生物担体５２が移流できる方式であれば、これにとらわれるものではない。
好気槽５に導入された混合液は、無酸素槽４からの残存ＢＯＤの酸化分解、硝化細菌による窒素成分の硝化及びリン蓄積菌によるリンの過剰摂取を行わせるために、曝気手段５１で曝気されて好気性処理される。
【００２５】
この好気槽５の運転も、ここでは当該槽内にＤＯセンサー（溶存酸素濃度計）を設置し、この測定値（ＤＯ値の範囲は概ね０．５〜５ｍｇ／Ｌ）に基づいてＤＯ計、コンピュータによって曝気ブロアの回転数を自動的に制御し、送風量を調整する。つまり、ＤＯ濃度が低い場合は送風量を増加させ、高い場合は送風量を減少させる。また、この指標はＯＲＰ及びｐＨでも行うことができる。ＯＲＰの場合は概ね＋５０〜＋３００ｍＶの範囲で、ＤＯと同様に低い場合は送風量を増加させ、高い場合は送風量を減少させる。ｐＨの場合は概ね６．４〜７．２の範囲で、ＤＯ、ＯＲＰとは逆に低い場合は送風量を減少させ、高い場合は送風量を増加させることが望ましい。このような操作を行うことにより、好気槽５内で安定した効率的な残存ＢＯＤの酸化分解、窒素の硝化及びリンの過剰摂取除去が行えるわけである。なお、送風量は曝気ブロアの回転数と限らず、電動弁の操作やブロアの運転台数で調整してもよい。
【００２６】
本発明では、反応槽２の容積の縮小化を図る目的で、無酸素槽４及び好気槽５での微生物保持量を高めるため上述のように微生物担体５２を利用している。ここで、前記微生物担体５２の利用により、無酸素槽４と好気槽５の両槽における浮遊汚泥ＭＬＳＳ濃度を１５００〜２０００ｍｇ／Ｌに保持した場合、微生物担体５２に付着した汚泥（担体への汚泥付着量７０００〜１５０００ｍｇ／Ｌ）を加味した全体（実質）のＭＬＳＳ濃度は４０００〜５０００ｍｇ／Ｌに保持できる。また、前記微生物担体５２がスポンジ担体の場合における無酸素槽４及び好気槽５での全（実質）ＭＬＳＳ濃度の計算例を以下に示す。

【００２７】
このように、硝化・脱窒にかかわる無酸素槽４及び好気槽５の全ＭＬＳＳ濃度は２倍以上保持できるため、汚泥滞留時間（ＳＲＴ）を十分に確保でき、硝化菌のような増殖速度の遅い微生物を多く保持することが可能となった。さらに、脱窒工程においても汚泥濃度が高いことから、流入水や好気槽５内の混合液が流入しても無酸素槽４では短時間で無酸素状態になり、脱窒処理の効率が図れる。
【００２８】
好気槽５から流出する混合液（処理水）は、微生物担体５２が分離された後、固液分離装置７で汚泥と上澄水に分離される。そのため、固液分離槽７に流入する好気槽５からの混合液のＭＬＳＳは１５００〜２０００ｍｇ／Ｌであり、従来の標準活性汚泥施設での沈殿池で十分に固液分離できる。そして、前記固液分離槽装置７で固液分離された上澄水は消毒槽で滅菌処理されて系外に放流される。なお、前記固液分離装置７としては、重さを利用した沈殿機構のほかに膜を利用した分離機構を採用してもよい。
【００２９】
また、前記固液分離装置７で分離した汚泥の一部は、水中ポンプやエアリフトポンプなどにより返送汚泥管路８を介して嫌気槽３に返送すると共に、余剰汚泥は引き抜かれて汚泥処理・処分される。
【００３０】
嫌気槽３へは上記返送汚泥以外に、濾過装置１０の汚泥を導入して調質する汚泥調質槽１３からの調質分離液が適宜導入される。返送汚泥と調質分離液は嫌気槽３内で攪拌手段３２により攪拌混合された後、順次導入手段３３を介して無酸素槽４に導入される。導入手段３３としては、水中ポンプやエアリフトポンプなどを用いてもよいし、嫌気槽３と無酸素槽４が隣接する場合には、オーバーフローさせたり隔壁の開口を利用して移流させてもよい。ただし、いずれの方式においても嫌気槽３を十分に嫌気状態に保つため、無酸素槽４の混合液が嫌気槽３に逆流することは避けなければならない。
【００３１】
以上のような排水処理プロセスにおいて、前記濾過装置１０の固液分離槽２１では、図２中の原水ポンプ２７ｂの運転を停止し、濾材洗浄手段３０を稼動させて洗浄空気管３０ａから吹き出す洗浄空気で濾材２９を洗浄することにより、当該濾材２９で捕捉された懸濁物質が濾材２９から分離し、排泥弁２８を開けることにより、濾過装置１０内に残存する懸濁液と共に当該懸濁物質を含む汚泥（汚泥混合液）が汚泥管路１２から汚泥調質槽１３に導入され、この汚泥調質槽１３では、導入汚泥を嫌気状態下で調質する。この調質には、処理汚泥減量化のための濃縮や汚泥成分（有機物）の低分子化を目的とした酸発酵が含まれる。その調質により、有機物を低分子化させる有機酸発酵が行われ、その結果、ＶＦＡ（主に炭素数２〜５の揮発性有機酸）が分離して水中に溶出する。そして、このＶＦＡを含む調質分離水を嫌気槽３に導入し、嫌気槽３の汚泥中に含まれるリン蓄積菌のリン放出に利用される。
【００３２】
即ち、濾過装置１０の固液分離槽２１ではＳＳ除去率が高いので、その固液分離槽２１から汚泥を導入する汚泥調質槽１３では多量の溶解性有機物及び有機酸が生成され、その溶解性有機物や有機酸を含む酸発酵液が嫌気槽３に送られることにより、嫌気槽３では、前記溶解性有機物や有機酸を利用してリン蓄積菌が多量のリンを放出する。
【００３３】
ここで、リン除去の前反応であるリン放出反応は、添加される有機酸の影響を受けるので、リン放出を十分に行わせるには如何に多量の溶解性有機物、とりわけ有機酸を添加できるかが重要なポイントである。また、本発明では、被処理水（汚水）を上述のように濾過装置１０に流入させて嫌気槽３には投入しないので、ＭＬＳＳ濃度を高く保持でき、また流入水質の変動による影響を受けないので安定した嫌気状態が保たれ、このためリン放出が容易となるのも本発明の特徴である。加えて、本発明は、被処理水を濾過装置１０で十分に固液分離するため、通常の最初沈殿池に比べＳＳ除去率が高く、その分、汚泥量が増えることになる。また、濾過装置１０の洗浄や汚泥引抜は頻繁に行われないため、濾過装置１０内の汚泥は滞留している間に嫌気状態となる。これにより、汚泥調質槽１３では多量で嫌気状態にある濾過装置１０の汚泥を導入するため、有機酸発酵が促進されやすく、ＶＦＡも十分に確保できるという特徴がある。
【００３４】
次に、被処理水を従来の最初沈殿池に流入させた場合と本発明の濾過装置１０（高速固液分離装置２１）に流入させた場合の実験結果による性能比較を以下に示す。

【００３５】
以上説明した実施の形態１によれば、被処理水を先ず濾過装置（高速固液分離装置）１０に流入させ、流入した被処理水を上向流で濾過するので、被処理水の固液分離を高速で効率よく行うことができ、排水処理システム全体のコンパクト化が実現できるという効果がある。
また、前記濾過装置１０ではＳＳ除去率が高くなるので、その濾過装置１０から汚泥を導入する汚泥調質槽１３では多量の有機酸などの溶解性有機物を生成させることができるという効果がある。
さらには、前記汚泥調質槽１３から嫌気槽３に多量の有機酸などの溶解性有機物を流入させ、且つ、前記嫌気槽３には被処理水（汚水）を流入させないので、嫌気槽３を高ＭＬＳＳ濃度に保持でき、また流入水質の変動による影響を受けないので安定して嫌気状態が保たれ、このため、嫌気槽３でのリン放出が安定して行われ、リン除去効率が大幅に向上するという効果がある。
【００３６】
実施の形態２．
図４は本発明の実施の形態２による排水処理システムを示すフローシートであり、図１および図３と同一または相当部分については同一符号を付して重複説明を省略する。図４において、１５ａは調質汚泥管路１５から分岐して汚泥調質槽１３からの調質汚泥の一部を嫌気槽３に導入する調質汚泥導入管路である。即ち、上述した実施の形態１では、汚泥調質槽１３の調質分離液のみを嫌気槽３に導入するようにしたが、この実施の形態２では、前記調質分離液と共に調質汚泥の一部をも嫌気槽３に導入するようにしたものである。
【００３７】
この実施の形態２によれば、嫌気槽３に汚泥調質槽１３から調質汚泥を導入することによって、その調質汚泥は低分子化した有機物質を豊富に含有しているため、嫌気槽３でのリン蓄積菌のリン放出を安定して効率よく行わせることができるという効果がある。
【００３８】
【発明の効果】
以上のように、本発明によれば、嫌気槽・無酸素槽・好気槽を備えた排水処理システムにおいて、被処理水を嫌気槽には流入させずに濾過装置に流入させるので、その濾過装置では被処理水の滞留時間を従来の最初沈殿池の場合に比して大幅に短縮でき、このため、システム全体のコンパクト化が実現できるという効果がある。また、前記濾過装置ではＳＳ除去率が高くなり、その汚泥を汚泥調質槽に導入するので、汚泥調質槽では多量の溶解性有機物や有機酸が生成されるという効果がある。さらには、前記汚泥調質槽から前記多量の溶解性有機物や有機酸を嫌気槽に流入させ、当該嫌気槽には上述のように被処理水を流入させないので、嫌気槽を高ＭＬＳＳ濃度に保持でき、また流入水質の変動による影響を受けないので安定して嫌気状態が保たれ、このため、リン放出を安定して行わせることができ、その結果、リン除去効率を大幅に向上させることができるという効果がある。
【００３９】
本発明によれば、嫌気槽に汚泥調質槽から調質汚泥の一部を導入することによって、その調質汚泥は低分子化した有機物質を豊富に含有しているため、嫌気槽でのリン蓄積菌のリン放出を一層効率的に行わせることができるという効果がある。
【００４０】
本発明によれば、浮遊性濾材が充填され、且つ、被処理水を上向流で濾過する高速固液分離装置から成る濾過装置としたことにより、被処理水中に含まれる懸濁物質を前記濾材で効率よく捕捉除去することができ、高速固液分離機能を一層高めることができるという効果がある。また、前記濾材は洗浄時において自由に流動するので、大きな濾材洗浄効果を得ることができる。
【００４１】
本発明によれば、微生物を担持する微生物担体を用いた活性汚泥処理槽によって好気槽が構成されていることにより、混合液（ＭＬＳＳ）濃度を通常より低くしても十分に好気性生物学的水処理を行うことができ、後段の固液分離装置への負荷を軽減でき、また好気槽の混合液を無酸素槽へ循環させることにより、効率よく窒素除去することができるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施の形態１による排水処理システムを示すフローシートである。
【図２】図１中の濾過装置の詳細構成を示す断面図である。
【図３】図１中の反応槽の具体構成例を示す断面図である。
【図４】本発明の実施の形態２による排水処理システムを示すフローシートである。
【図５】従来の排水処理システムを示すフローシートである。
【符号の説明】
３嫌気槽
４無酸素槽
５好気槽
６循環手段
７固液分離装置（沈殿池）
１０濾過装置（高速固液分離装置）
１３汚泥調質槽
２９浮遊性濾材
３０濾材洗浄手段
３２，４１攪拌手段
３３，４２導入手段
５１曝気手段
５２微生物担体（担体）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment system for efficiently removing not only organic substances contained in treated water such as sewage but also nitrogen and phosphorus simultaneously.
[0002]
[Prior art]
FIG. 5 is a flow sheet diagram showing a conventional wastewater treatment system, in which 1 is a first sedimentation basin in which solids (suspended substances) in the treated water flowing in are gravity settled and separated into solid and liquid. This is a floating sludge type reaction tank for introducing a separation liquid from the first sedimentation basin 1 and simultaneously performing denitrification and dephosphorization using BOD in the separation liquid. An anaerobic tank 4 and an aerobic tank 5 are provided. In the reaction tank 2, agitation means (not shown) is arranged in each of the anaerobic tank 3 and the anoxic tank 4, and an aeration means (not shown) is arranged in the aerobic tank 5. Has been.
[0003]
6 is a circulating means for circulating the mixed solution in the aerobic tank 5 to the anaerobic tank 4, and 7 is a final precipitation in which the mixed liquid flowing out from the aerobic tank 5 is introduced and solid-liquid separated into treated water and sludge. A pond 8 is a return sludge conduit for returning a part of the sludge separated from the solid and liquid in the final sedimentation basin 7 to the anaerobic tank 3, and the final sedimentation basin 7 contains a part of the sludge separated from the solid and liquid. Excess sludge extraction means (not shown) for extracting as excess sludge is provided.
[0004]
Next, the operation will be described.
First, when the water to be treated flows into the first sedimentation basin 1, the solids in the water to be treated are gravity settled and separated into solid and liquid in the first sedimentation basin 1, and the separated liquid is introduced into the anaerobic tank 3. A part of the sludge is returned to the anaerobic tank 3 through the return sludge pipe line 8 from the final sedimentation basin 7 so that the return sludge and the separated liquid come into contact with each other. At this time, the phosphorus accumulating bacteria contained in the return sludge take in soluble BOD (mainly volatile organic acid) in the water to be treated and simultaneously release the phosphorus accumulated in the cells. Thereafter, the effluent water from the anaerobic tank 3 is introduced into the anaerobic tank 4, where a mixed liquid containing oxidized nitrogen oxidized in the aerobic tank 5 at the subsequent stage is circulated and brought into contact in an oxygen-free state. At this time, denitrifying bacteria contained in the sludge perform denitrification using BOD in the water to be treated, and oxidized nitrogen is removed as nitrogen gas. Furthermore, the effluent from the anaerobic tank 4 is introduced into the aerobic tank 5, and the BOD in the water to be treated is oxidatively decomposed under aerobic conditions, and ammonia nitrogen is nitrified by nitrifying bacteria contained in the sludge, Phosphorus is excessively retaken by the phosphorus accumulating bacteria and removed from the liquid phase.
[0005]
The mixed liquid flowing out from the aerobic tank 5 is introduced into the final sedimentation basin 7 and separated into solid and liquid into treated water and sludge, the treated water is discharged after disinfection, and the sludge is returned to the anaerobic tank via the return sludge pipe line 8. Part 3 is returned. A part of the sludge separated into solid and liquid in the final sedimentation basin 7 is treated as surplus sludge in the sludge treatment process. At this time, the excess sludge may be first transferred to the settling basin 1 and processed in the sludge treatment step together with the initial settling sludge. Such a wastewater treatment method is called a so-called anaerobic / anoxic / aerobic method and has been put into practical use in recent years regardless of whether it is in Japan or abroad.
[0006]
[Problems to be solved by the invention]
A conventional wastewater treatment system using an anaerobic / anoxic / aerobic method is configured as described above, and nitrogen removal can be achieved relatively stably and with high efficiency. However, with regard to phosphorus removal, there has been a problem that the phosphorus release of the phosphorus accumulating bacteria in the anaerobic tank 3 is unstable and sufficient phosphorus removal in the aerobic tank 5 cannot be obtained. The cause of this is the inflow of rainwater that has low organic matter (BOD) concentration in the influent wastewater, large fluctuations in the wastewater quality, oxidation in the aerobic tank proceeds, and oxidized nitrogen is brought into the anaerobic tank through the returned sludge. As a result, the waste water becomes diluted. Furthermore, when the anaerobic / anoxic / aerobic method is used, the volume of the reaction tank 2 is several times that of the conventional standard activated sludge method, and the construction cost of the treatment facility is increased and a larger space is required. There was a problem of becoming. In the conventional waste water treatment system, first, solids in the treated water are naturally separated by gravity sedimentation in the first sedimentation basin 1, so that the quality of the outflow water is not stable and the treated water in the first sedimentation basin 1 is not stable. The residence time has to be made longer than necessary, which causes a problem that the entire system is enlarged and the processing efficiency is poor. In addition, there has been a problem of how efficiently BOD (organic carbon source) effective for phosphorus release of phosphorus accumulating bacteria in an anaerobic tank can be secured and supplied.
[0007]
The present invention has been made to solve the above-described problems. In particular, the present invention can be easily modified without increasing the number of existing standard activated sludge treatment facilities, so that not only BOD but also nitrogen and phosphorus can be combined. The purpose is to provide a wastewater treatment system that can be removed simultaneously and efficiently.
[0008]
[Means for Solving the Problems]
The wastewater treatment system according to the present invention comprises a filter medium cleaning means, a filtration device for solid-liquid separation of suspended substances in the inflowing water, and an agitation means, and an oxygen-free tank for introducing filtrate water from the filtration device And an aerobic tank having aeration means for introducing the mixed liquid flowing out from the anaerobic tank to perform activated sludge treatment, and a circulation for circulating a part of the mixed liquid in the aerobic tank to the anoxic tank Means, a solid-liquid separation device that introduces the mixed liquid flowing out from the aerobic tank and separates it into treated water and sludge, and sludge tempering that introduces and refines the sludge discharged from the filtration device An anaerobic tank comprising a tank and an agitation means, and introducing a part of the separated liquid discharged from the sludge tempering tank and the separated sludge separated by the solid-liquid separator, and the effluent from the anaerobic tank And introducing means for introducing the oxygen-free tank.
[0009]
The anaerobic tank of the waste water treatment system according to the present invention is configured to introduce a part of the conditioned sludge from the sludge conditioned tank.
[0010]
The filtration device of the wastewater treatment system according to the present invention is composed of a high-speed solid-liquid separation device that is filled with a floating filter medium and that filters the water to be treated in an upward flow.
[0011]
The aerobic tank of the wastewater treatment system according to the present invention comprises an activated sludge treatment tank using a carrier supporting microorganisms.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a flow sheet showing a wastewater treatment system according to Embodiment 1 of the present invention. The same or corresponding parts as those in FIG. In FIG. 1, reference numeral 10 denotes a filtration device for receiving water to be treated and solid-liquid separation of suspended substances in the water to be treated, and 11 denotes filtered water after solid-liquid separation from the filtration device 10 to the anoxic tank 4. A filtration water pipe to be introduced, 12 is a sludge pipe for introducing sludge (sludge mixed liquid) generated by solid-liquid separation from the filtration device 10 into the sludge tempering tank 13, and the sludge tempering tank 13 is It consists of a sludge acid fermentation tank for acid fermentation of sludge introduced from the filtration device 10 or a sludge concentration tank for concentrating the sludge. In short, the sludge introduced from the filtration device 10 is anaerobically fermented or concentrated. It is tempered under conditions. 14 is a separation liquid pipe for introducing the separated liquid after sludge conditioning from the sludge refining tank 13 to the

anaerobic tank

3, and 15 is a reconditioned sludge pipe for guiding the reconditioned sludge from the sludge refining tank 13 to the sludge treatment process. Road.
[0013]
2 is a cross-sectional view showing a detailed configuration of the filtration device 10 in FIG. 1. In FIG. 2, reference numeral 21 denotes a solid-liquid separation tank serving as a main body of the filtration device 10, and the inside of the solid-liquid separation tank 21 is covered. A sedimentation zone 22 in the lower part of the tank that also serves as an inflow zone for the treated water, a filter medium filling zone 24 partitioned by a grating 23 for supporting the filter medium at the top of the precipitation zone 22, and a filter medium presser at the top of the filter medium charge zone 24 A supernatant zone 26 in the upper part of the tank partitioned by the grating 25 for use is formed.
[0014]
Reference numeral 27 denotes raw water supply means for supplying water to be treated to the sedimentation zone 22, and this raw water supply means 27 comprises a raw water inflow pipe 27a, a raw water pump 27b, and a raw water valve 27c. In addition, 27d is a baffle plate arranged below the downward opening end of the raw water inflow pipe 27a in the sedimentation zone 22.
[0015]
28 is a sludge valve provided in the sludge conduit 12 for introducing the sludge precipitated at the bottom of the sedimentation zone 22 into the sludge refining tank 13 in FIG. 1, and 29 is filled in the filter medium filling zone 24. The filter medium 29 is a floatable filter medium having a specific gravity of 1 or less, such as plastic. Further, the filter medium 29 is either a plastic floating filter medium having a simple through-cylindrical hollow shape, or one in which the entire inner and outer surfaces of the floating filter medium are formed in a screw shape or an uneven shape to increase the front and back area. There may be.
[0016]
Reference numeral 30 denotes a filter medium cleaning means for cleaning the floating filter medium 29. The filter medium cleaning means 30 includes a cleaning air pipe 30a disposed in the vicinity of the lower part of the grating 23 for supporting the filter medium in the precipitation zone 22, and this cleaning medium. A cleaning valve 30b provided in the air pipe 30a and a cleaning blower 30c connected to the cleaning air pipe 30a are provided, and the cleaning air pipe 30a is operated by the operation of the cleaning blower 30c when the cleaning valve 30b is opened. However, the cleaning air is blown out toward the filter medium filling zone 24.
[0017]
Reference numeral 31 denotes an overflow trough which is arranged in the upper part (supernatant zone 26) of the solid-liquid separation tank 21 and allows filtrate to flow in. The overflow trough 31 is not shown in FIG. The oxygen tank 2 is connected.
[0018]
In the filtration device 10 configured as described above, the water to be treated is supplied to the lower part of the solid-liquid separation tank 21 by the raw water supply means 27, so that the water to be treated is contained in the solid-liquid separation tank 21. As a result, the flow passes upward through the filter medium filling zone 24, and suspended substances in the water to be treated are efficiently captured by the floating filter medium 29 during the passage. Therefore, the filtration device 10 is a high-speed solid-liquid separation device that filters the water to be treated in an upward flow.
[0019]
FIG. 3 is a cross-sectional view showing a specific configuration example of the reaction tank 2 in FIG. 1. In FIG. 3, 32 is a stirring means arranged in the

anaerobic tank

3, and 33 is a mixture liquid flowing out of the anaerobic tank 3. Introducing means for introducing into the oxygen tank 4, 41 is an agitating means arranged in the anaerobic tank 4, 42 is introducing means for introducing the mixed solution flowing out of the anaerobic tank 4 into the

aerobic tank

5, and 51 is a favorable one. Aeration means 52 and 52 arranged in the air tank 5 are microbial carriers that are filled in the aerobic tank 5 and carry microorganisms.
[0020]
As this microbial carrier 52, for example, a carrier material that comprehensively immobilizes microorganisms, such as polyvinyl alcohol, or a porous material having a floating property such as a porous material is used. The shape is not specified, and the carrier material can be either an inorganic substance or an organic substance. The activated sludge treatment is performed in the aerobic tank 5 using the microbial carrier 52, and the mixed solution of the aerobic tank 5 is circulated to the anoxic tank 4 together with the microbial carrier 52 by the circulation means 6. The circulation means 6 mainly comprises a transfer device such as an air lift pump or a submersible pump and a transfer pipe line.
[0021]
The aerobic tank 5 and the anaerobic tank 4 may use the microbial carrier 52 individually, and the anaerobic tank 4 may not use the microbial carrier 52. However, the microbial carrier 52 in the aerobic tank 5 may not be circulated to the anaerobic tank 4, and only the mixed solution in the aerobic tank 5 may be circulated to the anaerobic tank 4.
[0022]
Next, the operation will be described.
The treated water first flows into the filtration device 10. That is, the water to be treated is supplied to the lower part of the solid-liquid separation tank 21 by the raw water pump 27b in FIG. Then, it passes through the filter medium filling zone 24, and suspended substances in the water to be treated are efficiently trapped by the floating filter medium 29 during the passage. The filtered water in the supernatant zone 26 that has passed through the filter medium filling zone 24 flows from the overflow trough 31 into the anoxic tank 4 through the filtered water pipe 11. In the anaerobic tank 4, the mixed liquid containing NO _x -N (oxidized nitrogen) is circulated through the circulation means 6 from the aerobic tank 5 at the subsequent stage. under oxygen-free stirring condition by the stirring means 41, NO _X -N of the circulating mixed liquid is denitrification by the action of microorganisms.
[0023]
Here, in the case of the operation of the oxygen-free tank 4, an ORP sensor for measuring the oxidation-reduction potential ORP in the mixed solution is installed in the oxygen-free tank 4, and this value (the range of the ORP is approximately ± 0 to −300 mV). ) Based on the ORP meter and computer, it is desirable to keep the inside of the tank in an oxygen-free state. The amount of circulating water is basically twice the amount of wastewater that flows in, but when the ORP becomes high (aerobic state), the amount of circulating water decreases, and when the ORP becomes low (anaerobic state), the amount of circulating water increases. In general, the amount of circulating water is 1.5 to 4.0 times the amount of inflowing wastewater. Further, not the circulating water amount but the aeration air amount in the aerobic tank 5 may be controlled to maintain the oxygen-free state. The agitating means 32 and 41 provided in the anaerobic tank 3 and the anaerobic tank 4 mainly use a mechanical stirring device provided with stirring blades. However, any means may be used as long as the oxygen supply is suppressed and a water flow is generated.
[0024]
As described above, the mixed liquid denitrified in the oxygen-free tank 4 is introduced into the aerobic tank 5. The advection method here is also based on overflow, but when the microbial carrier 52 is circulated, the method is not limited to this as long as the microbial carrier 52 can be circulated.
The mixed solution introduced into the aerobic tank 5 is aerated by the aeration means 51 in order to cause oxidative decomposition of residual BOD from the anaerobic tank 4, nitrification of nitrogen components by nitrifying bacteria, and excessive intake of phosphorus by phosphorus accumulating bacteria. Aerated and aerobic processed.
[0025]
In the operation of the aerobic tank 5, a DO sensor (dissolved oxygen concentration meter) is installed in the tank here, and the DO meter is based on the measured value (the range of the DO value is approximately 0.5 to 5 mg / L). Then, the rotational speed of the aeration blower is automatically controlled by a computer to adjust the air flow rate. That is, when the DO concentration is low, the blowing amount is increased, and when the DO concentration is high, the blowing amount is decreased. This index can also be performed with ORP and pH. In the case of ORP, in the range of approximately +50 to +300 mV, the air flow rate is increased when it is low, and the air flow rate is decreased when it is high, similarly to DO. In the case of pH, it is generally in the range of 6.4 to 7.2, and it is desirable to decrease the blowing rate when it is low, as opposed to DO and ORP, and increase the blowing rate when it is high. By performing such an operation, stable and efficient oxidative decomposition of residual BOD, nitrification of nitrogen, and excessive intake removal of phosphorus can be performed in the aerobic tank 5. Note that the air flow rate is not limited to the number of rotations of the aeration blower, but may be adjusted by operating the motorized valve or the number of operating blowers.
[0026]
In the present invention, in order to reduce the volume of the reaction tank 2, the microbial carrier 52 is used as described above in order to increase the amount of microorganisms retained in the oxygen-free tank 4 and the aerobic tank 5. Here, when the suspended sludge MLSS concentration in both the anaerobic tank 4 and the aerobic tank 5 is maintained at 1500 to 2000 mg / L by using the microbial carrier 52, the sludge adhering to the microbial carrier 52 (to the carrier) The total (substantial) MLSS concentration taking into account the sludge adhesion amount of 7000 to 15000 mg / L can be maintained at 4000 to 5000 mg / L. An example of calculating the total (substantially) MLSS concentration in the anaerobic tank 4 and the aerobic tank 5 when the microbial carrier 52 is a sponge carrier is shown below.

[0027]
As described above, since the total MLSS concentration in the anaerobic tank 4 and the aerobic tank 5 involved in nitrification / denitrification can be maintained more than twice, the sludge retention time (SRT) can be sufficiently secured, and the growth rate like nitrifying bacteria. It was possible to retain a large number of slow microorganisms. Furthermore, since the sludge concentration is high also in the denitrification process, even if the influent water or the mixed liquid in the aerobic tank 5 flows in, the anaerobic tank 4 becomes anoxic in a short time, and the efficiency of the denitrification process is improved. I can plan.
[0028]
The mixed liquid (treated water) flowing out from the aerobic tank 5 is separated into sludge and supernatant water by the solid-liquid separator 7 after the microorganism carrier 52 is separated. Therefore, MLSS of the liquid mixture from the aerobic tank 5 which flows into the solid-liquid separation tank 7 is 1500-2000 mg / L, and it can fully solid-liquid separate in the sedimentation basin in the conventional standard activated sludge facility. The supernatant water separated from the solid-liquid separation tank 7 is sterilized in the disinfection tank and discharged outside the system. The solid-liquid separation device 7 may employ a separation mechanism using a membrane in addition to a precipitation mechanism using weight.
[0029]
A part of the sludge separated by the solid-liquid separator 7 is returned to the anaerobic tank 3 via a return sludge pipe line 8 by an underwater pump, an air lift pump, etc., and surplus sludge is pulled out to treat and dispose of sludge. Is done.
[0030]
In addition to the returning sludge, the anaerobic tank 3 is appropriately introduced with a tempered separation liquid from the sludge tempering tank 13 that is tempered by introducing the sludge of the filtration device 10. The return sludge and the tempered separation liquid are stirred and mixed in the anaerobic tank 3 by the stirring means 32 and then sequentially introduced into the anoxic tank 4 through the introducing means 33. As the introducing means 33, a submersible pump, an air lift pump, or the like may be used. When the anaerobic tank 3 and the oxygen-free tank 4 are adjacent to each other, overflow may be performed or advection may be performed using an opening of the partition wall. However, in any system, in order to keep the anaerobic tank 3 sufficiently in an anaerobic state, it is necessary to avoid the mixed liquid in the anaerobic tank 4 from flowing back into the anaerobic tank 3.
[0031]
In the wastewater treatment process as described above, in the solid-liquid separation tank 21 of the filtration device 10, the operation of the raw water pump 27b in FIG. 2 is stopped, the filter medium cleaning means 30 is operated, and the cleaning air blown out from the cleaning air pipe 30a By washing the filter medium 29, the suspended substance trapped by the filter medium 29 is separated from the filter medium 29, and by opening the mud valve 28, the suspended substance together with the suspension remaining in the filter device 10 is collected. Sludge (sludge mixture) is introduced into the sludge tempering tank 13 from the sludge conduit 12, and in this sludge tempering tank 13, the introduced sludge is conditioned under anaerobic conditions. This tempering includes acid fermentation for the purpose of reducing the sludge components (organic matter) and concentrating to reduce the treated sludge. Due to the tempering, organic acid fermentation is performed to lower the molecular weight of the organic substance. As a result, VFA (mainly volatile organic acid having 2 to 5 carbon atoms) is separated and eluted into water. And the tempered separation water containing this VFA is introduce | transduced into the anaerobic tank 3, and is utilized for the phosphorus discharge | release of the phosphorus accumulating bacteria contained in the sludge of the anaerobic tank 3.
[0032]
That is, since the SS removal rate is high in the solid-liquid separation tank 21 of the filtration device 10, a large amount of soluble organic substances and organic acids are generated and dissolved in the sludge refining tank 13 for introducing sludge from the solid-liquid separation tank 21. By sending an acid fermentation broth containing an oxidative organic substance and an organic acid to the anaerobic tank 3, in the anaerobic tank 3, the phosphorus accumulating bacteria release a large amount of phosphorus using the soluble organic substance and the organic acid.
[0033]
Here, since the phosphorus release reaction, which is a reaction prior to phosphorus removal, is affected by the added organic acid, how much a soluble organic substance, particularly an organic acid, can be added to sufficiently release phosphorus. Is an important point. In the present invention, since the treated water (sewage) flows into the filtration device 10 as described above and does not enter the anaerobic tank 3, the MLSS concentration can be kept high and is not affected by fluctuations in the quality of the influent water. Therefore, it is a feature of the present invention that a stable anaerobic state is maintained, and phosphorous release is thus facilitated. In addition, according to the present invention, since the water to be treated is sufficiently solid-liquid separated by the filtration device 10, the SS removal rate is higher than that of a normal first settling basin, and the amount of sludge increases accordingly. In addition, since the filtration device 10 is not frequently cleaned and the sludge is drawn, the sludge in the filtration device 10 is in an anaerobic state while it remains. Thereby, in the sludge refining tank 13, since the sludge of the filtration apparatus 10 in a large amount of anaerobic state is introduced, organic acid fermentation is easily promoted, and VFA can be sufficiently secured.
[0034]
Next, the performance comparison by the experimental result when the treated water is made to flow into the conventional first sedimentation basin and when it is made to flow into the filtration device 10 (high-speed solid-liquid separation device 21) of the present invention is shown below.

[0035]
According to the first embodiment described above, the water to be treated is first flowed into the filtration device (high-speed solid-liquid separation device) 10, and the inflowing water to be treated is filtered in an upward flow. Separation can be performed efficiently at high speed, and the entire waste water treatment system can be made compact.
Further, since the SS removal rate is high in the filtration device 10, the sludge refining tank 13 into which sludge is introduced from the filtration device 10 has an effect that a large amount of soluble organic matter such as organic acid can be generated.
Furthermore, since a large amount of soluble organic matter such as organic acid is caused to flow from the sludge refining tank 13 to the anaerobic tank 3 and water to be treated (sewage) does not flow into the anaerobic tank 3, the anaerobic tank 3 is provided. Since it can be maintained at a high MLSS concentration and is not affected by fluctuations in the influent water quality, the anaerobic state is stably maintained. For this reason, the phosphorus release in the anaerobic tank 3 is stably performed, and the phosphorus removal efficiency is greatly increased. There is an effect of improving.
[0036]
Embodiment 2. FIG.
FIG. 4 is a flow sheet showing a waste water treatment system according to Embodiment 2 of the present invention. The same or corresponding parts as those in FIGS. In FIG. 4, reference numeral 15 a denotes a tempered sludge introduction pipe that branches from the tempered sludge pipe 15 and introduces part of the tempered sludge from the sludge tempered tank 13 into the anaerobic tank 3. That is, in the first embodiment described above, only the tempered separation liquid of the sludge tempering tank 13 is introduced into the anaerobic tank 3, but in this second embodiment, the tempered sludge is mixed with the tempered separation liquid. A part is also introduced into the anaerobic tank 3.
[0037]
According to the second embodiment, by introducing the conditioned sludge into the anaerobic tank 3 from the sludge conditioned tank 13, the conditioned sludge contains abundant low molecular weight organic substances. 3 has an effect that the phosphorus release of the phosphorus accumulating bacteria can be stably and efficiently performed.
[0038]
【The invention's effect】
As described above, according to the present invention, in the wastewater treatment system provided with the anaerobic tank, the anaerobic tank, and the aerobic tank, the water to be treated flows into the filtration device without flowing into the anaerobic tank. In the apparatus, the residence time of the water to be treated can be greatly shortened as compared with the case of the conventional first settling basin, and therefore, there is an effect that the entire system can be made compact. Moreover, since the SS removal rate is increased in the filtration device and the sludge is introduced into the sludge refining tank, there is an effect that a large amount of soluble organic substances and organic acids are generated in the sludge refining tank. Furthermore, since the large amount of soluble organic substances and organic acids are allowed to flow into the anaerobic tank from the sludge refining tank, and the water to be treated does not flow into the anaerobic tank as described above, the anaerobic tank is maintained at a high MLSS concentration. In addition, because it is not affected by fluctuations in the quality of the influent water, the anaerobic state can be stably maintained. As a result, phosphorus release can be stably performed, and as a result, the phosphorus removal efficiency can be greatly improved. There is an effect that can be done.
[0039]
According to the present invention, by introducing a part of the conditioned sludge from the sludge tempering tank into the anaerobic tank, the tempered sludge contains abundant low molecular weight organic substances. There is an effect that phosphorus can be released more efficiently by the phosphorus accumulating bacteria.
[0040]
According to the present invention, the suspended substance contained in the water to be treated is obtained by the filtration device comprising the high-speed solid-liquid separator that is filled with the floating filter medium and filters the water to be treated in an upward flow. The filter medium can be efficiently captured and removed, and the high-speed solid-liquid separation function can be further enhanced. Moreover, since the said filter medium flows freely at the time of washing | cleaning, the big filter medium washing | cleaning effect can be acquired.
[0041]
According to the present invention, since the aerobic tank is constituted by the activated sludge treatment tank using the microorganism carrier carrying microorganisms, the aerobic biology can be sufficiently achieved even when the concentration of the mixed solution (MLSS) is lower than usual. Water treatment can be performed, the load on the subsequent solid-liquid separation device can be reduced, and the mixed liquid in the aerobic tank can be circulated to the anoxic tank to effectively remove nitrogen. is there.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a wastewater treatment system according to Embodiment 1 of the present invention.
FIG. 2 is a cross-sectional view showing a detailed configuration of the filtration device in FIG.
FIG. 3 is a cross-sectional view showing a specific configuration example of the reaction tank in FIG.
FIG. 4 is a flow sheet showing a wastewater treatment system according to Embodiment 2 of the present invention.
FIG. 5 is a flow sheet showing a conventional wastewater treatment system.
[Explanation of symbols]
3 Anaerobic tank 4 Anoxic tank 5 Aerobic tank 6 Circulating means 7 Solid-liquid separation device (sedimentation basin)
10 Filtration device (High-speed solid-liquid separator)
13 Sludge refining tank 29 Floating filter medium 30 Filter medium cleaning means 32, 41 Stirring means 33, 42 Introduction means 51 Aeration means 52 Microorganism carrier (carrier)

Claims

A filtering device that includes a filtering medium cleaning means, and a solid-liquid separator for separating suspended solids in the water to be treated; a stirring means; an oxygen-free tank that introduces filtered water from the filtering device; an aeration means; An aerobic tank for introducing activated liquid sludge by introducing a mixed liquid flowing out from the oxygen tank, a circulation means for circulating a part of the mixed liquid in the aerobic tank to the anaerobic tank, and an outflow from the aerobic tank A solid-liquid separation device that introduces a mixed liquid and separates it into treated water and sludge, a sludge tempering tank that introduces and refines sludge discharged from the filtration device, and a stirring means, An anaerobic tank for introducing a part of the separated liquid discharged from the sludge refining tank and the separated sludge separated by the solid-liquid separator, and an introducing means for introducing the effluent water from the anaerobic tank to the anoxic tank; A wastewater treatment system comprising:

The wastewater treatment system according to claim 1, wherein the anaerobic tank is configured to introduce a part of the conditioned sludge from the sludge tempered tank.

The wastewater treatment system according to claim 1, wherein the filtration device is composed of a high-speed solid-liquid separation device that is filled with a floating filter medium and filters the water to be treated in an upward flow.

The waste water treatment system according to claim 1, wherein the aerobic tank is composed of an activated sludge treatment tank using a carrier supporting microorganisms.