JP4647814B2

JP4647814B2 - Organic wastewater treatment equipment

Info

Publication number: JP4647814B2
Application number: JP2001090622A
Authority: JP
Inventors: 彰夫中尾; 悟手島
Original assignee: Sumitomo Heavy Industries Environment Co Ltd
Current assignee: Sumitomo Heavy Industries Environment Co Ltd
Priority date: 2001-03-27
Filing date: 2001-03-27
Publication date: 2011-03-09
Anticipated expiration: 2021-03-27
Also published as: JP2002282890A

Description

【０００１】
【発明の属する技術分野】
本発明は有機性排水の処理装置に関し、特に、活性汚泥を用いた嫌気性処理及び好気性処理によりリン成分を含有する有機性排水を処理する有機性排水の処理装置に関する。
【０００２】
【従来の技術】
産業排水、農業排水、下水、屎尿等の有機性排水は、リン酸等のリン成分やアンモニア等の窒素成分を高濃度で含む場合が多い。リン成分及び窒素成分は、富栄養化物質であり、これらの成分を含有する排水が湖沼、河川、海洋等の環境に放出されると、植物プランクトン等の生物の栄養源となり、特に、湖沼又は海洋の沿岸域においてアオコ、赤潮等が発生する原因となるおそれがある。
【０００３】
ところで、有機性排水中の有機物の処理には、活性汚泥による生物処理が極めて有効であり、代表的な方法として嫌気性処理と好気性処理を組み合わせた方法が挙げられる。このような有機物の分解処理を行いつつ富栄養化物質である窒素成分を処理するには、硝化及び脱窒処理といった生物処理を付加すると有効である。一方、有機物を生物処理で分解処理するとともにリン成分をも除去する従来の方法としては、例えば、特開平９−２６２５９９号公報及び特開平９−２６７０９９号公報、並びに、特開平８−２４８７３号公報及び特開平８−６６６８９号公報等に記載の方法がある。
【０００４】
【発明が解決しようとする課題】
しかし、上記の従来前者におけるリン成分の除去方法は、活性汚泥の一部を有機物処理系の系外へ取り出し、その活性汚泥を別の系で処理する方法であり、そのための処理系（装置）が必要であった。また、上記の従来後者における方法は、生物処理が施された処理済水又は工程処理水からリン成分を回収する方法であり、生物処理装置に別の水処理装置を連設する必要があった。このように従来の方法で有機物の処理とリン成分の回収を行う場合には、装置構成が複雑化且つ大規模化する傾向にあり、設置スペース及び処理コストの増大を招くおそれがあった。また、処理工程数も増大し、工程制御が複雑になる傾向にあった。
【０００５】
そこで、本発明はこのような事情に鑑みてなされたものであり、従来に比して簡略な装置構成及び簡素な工程により、有機系排水に含まれる有機物の分解処理とリン成分の回収を両立でき、設置スペース及び処理コストの増大を十分に抑制できる有機性排水の処理装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、本発明者らは鋭意研究を重ね、嫌気槽及び好気槽を有する従来の装置を利用し、活性汚泥を系外に取り出すことなく、リン成分を液相中に抽出できる方法を見出し、本発明を完成するに至った。
【０００７】
すなわち、本発明による有機性排水の処理装置は、本発明の有機性排水の処理方法を有効に実施するためのものであり、リン成分を含有する有機性排水が活性汚泥により嫌気性処理される嫌気槽と、嫌気性処理された前記有機性排水がその活性汚泥により好気性処理される好気槽と、好気性処理された有機性排水と活性汚泥とを固液分離する固液分離槽とを備えるものであって、固液分離された活性汚泥を嫌気槽へ返送する汚泥返送部を更に備えており、嫌気槽が、返送された活性汚泥からリン成分が液相へ放出されるリン放出部と、この液相の少なくとも一部を活性汚泥から分離して分離水を得る液相分離部とを有する前段槽、及び、該前段槽から活性汚泥が移送され、生物処理に適した汚泥濃度とＢＯＤ濃度が達成され、活性汚泥の活性が維持されて嫌気性処理を行う後段槽を備え、リン成分を含有する有機性排水は、前段槽及び後段槽に供給され、後段槽で嫌気性処理された有機性排水が好気槽に送給されるものである、ことを特徴とする。
ここで、液相分離部としては、重力沈降分離手段、膜分離手段、濾過手段等の種々の固液分離方法を用いることができる。また、嫌気槽と好気槽とを交互に複数配置してもよい。この場合には、汚泥返送部が複数の嫌気槽に活性汚泥を返送するものであっても構わない。さらに、最前段の嫌気槽を隔壁等で二槽に分割し、上流側の槽をリン放出部として、この槽内に液相分離部を設置してもよい。或いは、最前段部に嫌気槽を二槽配置し、上流側つまり最前段の嫌気槽をリン放出部として、この槽内に液相分離部を設けてもよい。このようにすれば、最前段の槽においてリン成分を放出した高濃度の活性汚泥が二段目の槽に移送され、十分な量の有機性排水の供給により、生物処理に適した活性汚泥濃度とＢＯＤ（ Biochemical Oxygen Demand ）濃度が達成され、汚泥の活性が維持されて良好な嫌気性処理が行われる。
【０００８】
このような有機性排水の処理装置では、嫌気性処理において活性汚泥中の微生物菌体からリン成分が放出され、嫌気性処理に続く好気性処理において、その微生物菌体にリン成分が過剰に摂取される。このリン成分を含む活性汚泥は、系外に取り出されることなく、固液分離槽で濃縮された状態で嫌気槽に返送される。この高濃縮の活性汚泥が嫌気性雰囲気におかれると、リン成分が活性汚泥から液相に十分に放出され、液相のリン成分濃度が顕著に高められる。そして、リン成分を高濃度で含む液相の少なくとも一部が、固形物である活性汚泥から分離され、リン成分を多量に含む分離水が得られる。
【００１０】
また、嫌気性処理で分離された液相のリン成分を吸脱着することが可能な吸着媒体を有し、且つ、液相分離部から分離水が供給されるリン吸脱着部と、脱着剤が収容され、且つ、吸脱着部にその脱着剤を供給する脱着剤供給部とを有するリン回収部を更に備えることが望ましい。ここで、従来の装置等においては、リン成分を回収するために、例えば；
（１）系外に取り出したリン成分を含む活性汚泥をそのまま回収する、
（２）リン成分を含む液相（活性汚泥からの分離水、処理済水、又は、工程処理水等）にポリ塩化アルミニウム（ＰＡＣ）、硫酸アルミニウム（硫酸バンド）、塩化第二鉄、ポリ塩化鉄等の凝集剤を添加してリン成分を凝集沈降させ、固液分離して回収する、
（３）リン成分を含む液相に特定の試薬を添加し、リン成分を特定の化学形を有する難溶又は不溶の化合物として回収する、
といった方法が採られている。
【００１１】
これらのうち、（１）及び（２）の方法では、リン成分の純度又は濃度が必ずしも十分に高くなく、また、リン成分を再利用するために精製が必要となって手間が掛かる場合がある。一方、（３）の方法は、試薬及び回収される化合物の種類が限られてしまい、リン成分を再利用する際の汎用性が低下してしまう。このような従来の方法に対し、本発明では、リン成分を吸着媒体に吸着させるので、分離水に含まれる他の成分からリン成分を分離し得る。そして、吸着媒体に吸着されたリン成分が脱着剤に抽出されるので、リン成分を高濃度で含む溶液が得られる。また、吸着媒体としてリン成分の選択性が高いものを用いれば、回収されるリン成分の純度を高め得る。
【００１２】
具体的には、このような吸着媒体として、主としてジルコニウムフェライト系又はジルコニウムケイ酸塩系物質を含有して成る陰イオン交換体を用いると好適である。ジルコニウムフェライト系又はジルコニウムケイ酸塩系物質を主成分とする陰イオン交換体は、酸性溶液中で陰イオン交換機能を発現する。特に、リン酸イオン（ＰＯ₄ ^3-）の吸着能が、ハロゲンイオン、硫酸イオン、硝酸イオン、亜硝酸イオン、有機酸イオン等に比して高いという特性を有するものを用いることが望ましい。
【００１３】
また、有機性排水や分離水中のリン成分は、リン酸イオンの形態をとり易い。これらのことから、ジルコニウムフェライト系又はジルコニウムケイ酸塩系物質を主成分とする陰イオン交換体を吸着媒体として用いれば、リン成分の選択吸着性が格別に向上され、リン成分の回収量がより増大する。
【００１４】
さらに、嫌気槽が、返送された活性汚泥に有機性排水を供給する排水供給部を有すると好ましい。このような構成を有すると、返送された活性汚泥に、微生物菌体の栄養分である有機物が供給され、微生物菌体がその栄養分を資化することにより、活性汚泥の周囲の嫌気性が更に高められる。このように嫌気性が高められると、活性汚泥からのリン成分の放出が促進され、液相中及び分離水中のリン成分の濃度が一層高められる。
【００１８】
【発明の実施の形態】
以下、添付図を参照して本発明の実施形態について説明する。図１は、本発明による有機性排水の処理装置の好適な実施形態を示す構成図である。処理装置１００は、嫌気槽１、好気槽２、嫌気槽３及び好気槽４がこの順に設置され、好気槽４の後段に固液分離槽５が配置されたものであり、後述するように嫌気槽１で得られる濾過水（分離水）が供給される吸脱着塔１２（リン吸脱着部）を有するものである。
【００１９】
嫌気槽１は、隔壁１０によって前段槽１ａ（嫌気槽及びリン放出部）と後段槽１ｂ（嫌気槽）とに分割されている。この前段槽１ａは、攪拌機６及び浸漬式の膜濾過装置１１（液相分離部）を有している。また、前段槽１ａ及び後段槽１ｂには、移送ライン２１を通して有機性排水Ｗｓが供給されるようになっている。さらに、前段槽１ａには、汚泥返送ライン２４を通して活性汚泥が返送される。前段槽１ａに供給された有機性排水Ｗｓは、活性汚泥とともに攪拌機６で攪拌混合され、反応液Ｒとして処理の下流側へ順次移送される。
【００２０】
好気槽２，４は、ブロアＢに給気ライン２３を介して接続された散気装置７，９をそれぞれの底部に有している。ブロアＢから送気された空気等の酸素を含む気体は、給気ライン２３を通して散気装置７，９からそれぞれ好気槽２，４の内部に散気される。また、嫌気槽３には、攪拌機８が設置されている。
【００２１】
固液分離槽５の底部には、ポンプＰ２を有する汚泥返送ライン２４が接続されており、固液分離された固形分である活性汚泥が返送汚泥Ｓ２としてこの汚泥返送ライン２４を通して嫌気槽１の前段槽１ａに返送される。このように、ポンプＰ２と汚泥返送ライン２４とから汚泥返送部が構成されている。一方、固液分離された上澄み液は処理済水Ｗｐとして系外へ排出される。
【００２２】
一方、嫌気槽１の前段槽１ａ内に浸漬された膜濾過装置１１には、ポンプＰ１を有する移送ライン２５が接続されており、膜濾過装置１１で得られる濾過水がこの移送ライン２５を通して吸脱着塔１２へ移送される。また、移送ライン２５には、ポンプＰ３を有する移送ライン２６を介して酸貯留槽１３が接続されており、濾過水のｐＨを調整するための酸Ａが供給されるようになっている。
【００２３】
さらに、吸脱着塔１２は、リン成分を吸脱着することが可能な吸着剤３２（吸着媒体）を内部に収容しており、濾過水がこの吸着剤３２と接触しながら移動するようになっている。そして、吸着剤３２を通過した濾過水は、脱リン水Ｗｃとして移送ライン２８を通して排出される。また、吸脱着塔１２には、ポンプＰ４を有する移送ライン２７を介してアルカリ貯留槽１４（脱着剤供給部）が接続されており、吸着剤３２の収容部に脱着剤としてのアルカリＢが導入される。吸着剤３２と接触しながら吸脱着塔１２内を移動したアルカリＢは、リン成分含有水Ｌｐとして溶出し、移送ライン２９を通して排出される。このように、吸脱着塔１２とアルカリ貯留槽１４とからリン回収部が構成されている。
【００２４】
次に、このように構成された処理装置１００を用いた本発明による有機系排水の処理方法の好適な実施形態について説明する。まず、夾雑物等を除去した有機性排水Ｗｓを、移送ライン２１を通して嫌気槽１の前段槽１ａに供給する。有機性排水Ｗｓと活性汚泥とを攪拌機６で攪拌混合して反応液Ｒとした後、後段槽１ｂへ送給する。それから、後段槽１ｂにおいて、有機性排水Ｗｓを更に加え、嫌気性処理を実施する（嫌気性処理工程）。このとき、活性汚泥を構成する微生物菌体は、有機物をより低分子の有機酸、二酸化炭素等へ分解するとともに、体内外に保持していたリン成分を液相中へ放出する。
【００２５】
ここで、有機性排水Ｗｓとしては、下水、屎尿、農業排水、食品排水、工業排水等のリン成分を含有する有機性排水が挙げられる。また、嫌気槽１としては、空気等の酸素を含む気体と反応液Ｒとの接触をできるかぎり防止できるものが好ましく、通常の貯留槽、望ましくは密閉型の攪拌槽を用いることができる。そして、特に好ましくは、液相と接触する気相部分を窒素ガス等の不活性ガスで置換するとよい。また、前段槽１ａ及び後段槽１ｂ中の活性汚泥量は、▲１▼前段槽１ａに当初から存在する活性汚泥量と▲２▼当該処理装置１００内で増殖した活性汚泥と▲３▼返送された活性汚泥Ｓ２との合計量から、▲４▼下流側へ流出する活性汚泥量を差し引いた量となる。なお、有機系排水Ｗｓの処理に際しては、上記▲２▼＋▲３▼−▲４▼の活性汚泥量が一定となるように調整することが望ましい。
【００２６】
次に、所定時間の嫌気性処理を行った反応液Ｒを好気槽２へ送給する。そして、ブロアＢを運転し、給気ライン２３を通して空気を散気装置７へ送気し、散気装置７から反応液Ｒに空気の微細気泡を散気しながら、好気性処理を実施する（好気性処理工程）。この散気により、反応液Ｒは攪拌され、且つ、微細気泡が例えば気液混相流となって反応液Ｒ中に酸素が十分に供給される。このとき、活性汚泥中の微生物菌体は、有機物を二酸化炭素、水等へ分解するとともに、液相中のリン成分を摂取する。
【００２７】
次いで、所定時間の嫌気性処理を行った反応液Ｒを、嫌気槽３及び好気槽４へ順次送給し、嫌気性処理及び好気性処理の順に生物処理を繰り返す（それぞれ嫌気性処理工程及び好気性処理工程）。このようにすると、嫌気槽３では微生物菌体からリン成分が多量に放出され、好気槽４では微生物菌体にリン成分を過剰に摂取させることが可能となる。
【００２８】
好気槽４における好気性処理が完了したのち、反応液Ｒを固液分離槽５へ移送し、固液分離槽５において重力沈降分離等による固液分離を行う（固液分離工程）。このとき、固液分離槽５内の好気性を維持することが好ましい。上澄み液は、有機性排水Ｗｓに含まれていた有機物が十分に分解され、且つ、リン成分が十分に除去された処理済水Ｗｐとして系外へ排出する。一方、槽底部に沈降した固形分を濃縮された返送汚泥Ｓ２（活性汚泥）として、汚泥返送ライン２４を通して嫌気槽１の前段槽１ａへ返送する（汚泥返送工程）。嫌気性雰囲気の前段槽１ａにおいては、返送汚泥Ｓ２を構成するリン成分を過剰に摂取した微生物菌体から、そのリン成分が液相に放出される。
【００２９】
このとき、前段槽１ａに、移送ライン２１（排水供給部）を通して原水である有機性排水Ｗｓを所定量供給する。そうすると、新たに添加された有機性排水Ｗｓ中に含まれていた有機物を栄養分として微生物菌体が育生され、前段槽１ａ内が更に嫌気性となる。その結果、微生物菌体からリン成分の放出が促進され、液相中のリン成分濃度が極めて高められる。
【００３０】
ここで、返送汚泥Ｓ２への有機性排水Ｗｓの供給量を、活性汚泥１ｇ−ＭＬＳＳ（ Mixed Liquor Suspended Solids ）／Ｌ／日に対して、好ましくは０．１〜０．５ｇ−ＢＯＤ／日、より好ましくは０．２〜０．４ｇ−ＢＯＤ／日とすると好適である。
【００３１】
この供給量が上記いずれかの下限値を下回ると、嫌気性の増大効果が顕著に得られない傾向にある。一方、この供給量が上記いずれかの上限値を上回ると、有機性排水Ｗｓの液性や有機物濃度にもよるが、液相中の有機物や他の成分の濃度が増大してしまう傾向にあるので好ましくない。
【００３２】
また、嫌気槽１の前段槽１ａにおける返送汚泥Ｓ２の滞留時間としては、汚泥濃度、リン成分の摂取量、汚泥の性状等に依存するものの、好ましくは２〜１０時間、より好ましくは３〜６時間であると好適である。この滞留時間が２時間未満であると、汚泥からのリン成分の放出量（率）が十分ではない傾向にある。一方、この滞留時間が１０時間を超えると、リン成分の放出量が時間に応じて増加しなくなる、つまり飽和する傾向にある。
【００３３】
次に、返送汚泥Ｓ２からリン成分が放出された液相を膜濾過装置１１によって返送汚泥Ｓ２から濾過して分離する。一方、返送汚泥Ｓ２を、活性汚泥として後段槽１ｂへ送出する。そして、後段槽１ｂへ再び有機性排水Ｗｓを供給し、嫌気性処理を行う。これ以降の処理は上述したのと同様である。このように、活性汚泥（或いは、返送汚泥Ｓ２）を系外に取り出すことなく、有機性排水Ｗｓの連続処理を行う。
【００３４】
なお、本発明による有機性排水の処理方法及び装置は、系外に取り出した汚泥を処理してリン成分を回収する方法及び装置ではない。したがって、処理に伴い解体されて失活した汚泥を系外に取り出したり、有機性排水Ｗｓの液性等の変化により活性汚泥の不足分を補充することは、有機性排水Ｗｓの生物処理を良好に維持する観点から、好ましい処理である。
【００３５】
また、膜濾過装置１１で返送汚泥Ｓ２から分離した液相、つまり濾過水を、移送ライン２５を通して吸脱着塔１２における吸着剤３２の収容部に導入する。吸着剤３２としては、リン成分の吸脱着が可能であれば特に制限されないが、吸脱着の容易さ（吸脱着性能）、リン成分の化学形（主としてリン酸イオン：ＰＯ₄ ^3-と考えられる）を考慮すると、無機又は有機の陰イオン交換体を好ましく用いることができる。特に、リン酸イオンに対する吸着性能に優れる点で、ジルコニウムフェライト系又はジルコニウムケイ酸塩系物質を主成分とする陰イオン交換体がより好ましい。以下、吸着剤３２としてジルコニウムフェライト系又はジルコニウムケイ酸塩系物質を主成分とする陰イオン交換体を用いる場合について説明する。
【００３６】
ところで、ジルコニウムフェライト系又はジルコニウムケイ酸塩系等の陰イオン交換体は、一般に、基体表面の−ＯＨ基（酸性下で−ＯＨ₂ ⁺、アルカリ性下で−Ｏ^-）によるアニオン交換能により陰イオンの吸脱着を行う。これに対し、嫌気性処理により、有機物の分解及び／又は硝化・脱窒処理が行われると、生成されるＯＨ^-等により、液相のｐＨが、例えば７．５〜１３．５程度のアルカリ側に傾く傾向にある。そこで、濾過水を吸脱着塔１２へ導入する前及び導入時に、酸貯留槽１３から硫酸等の酸Ａを移送ライン２５に供給し、吸着剤３２の収容部を酸性状態、例えば濾過水のｐＨを約２〜４程度とする。これにより、濾過水中のリン成分を吸着剤３２へ十分に吸着せしめる。こうして濾過水を吸着剤３２と接触させながら通過させることにより、脱リン水Ｗｃが得られる。この脱リン水Ｗｃは、移送ライン２８を通して排出する。
【００３７】
そして、吸着剤３２の吸着容量が飽和に近づき、吸着効率が低下した時点で、ポンプＰ１の運転を停止し、吸脱着塔１２への濾過水の供給を中断する。このとき、ポンプＰ４を運転し、アルカリＢをアルカリ貯留槽１４から吸脱着塔１２へ供給する。アルカリＢが吸着剤３２と接触すると、吸着剤３２のアニオン交換能により、リン成分がアルカリＢへ溶離される。そして、吸脱着塔１２から溶出するアルカリＢを、リン成分含有水Ｌｐとして移送ライン２９により回収する。
【００３８】
次に、図１に示す処理装置１００を用いて有機性排水の処理試験を行ったときの物質収支の一例について説明する。有機性排水Ｗｓとしては、リン成分の濃度が３〜５ｍｇ−Ｐ／Ｌのものを用いた。ここで、「ｍｇ−Ｐ」はリンの質量であることを示す。有機性排水Ｗｓの全供給量の単位容積を１Ｑとし、嫌気槽１の前段槽１ａへ０．５Ｑ、嫌気槽３へ０．５Ｑを供給し、返送汚泥Ｓ２として１／３Ｑを嫌気槽１の前段槽１ａに返送した。すなわち、前段槽１ａで濾過を行わないときには、系内に４／３Ｑの反応液Ｒが循環している状態とした。
【００３９】
一連の工程を経て好気槽４から固液分離槽５へ送出した反応液Ｒ中の汚泥濃度は、ＭＬＳＳで約２０００ｍｇ／Ｌ（容積４／３Ｑ）であった。固液分離槽５で固液分離した上澄み液（処理済水Ｗｐ）の容積は１Ｑであり、リン成分の濃度は０．５ｍｇ−Ｐ／Ｌまで低減された。一方、固液分離槽５で沈降した容積１／３Ｑ中の汚泥濃度は、ＭＬＳＳで約８０００ｍｇ／Ｌであり、これを前段槽１ａで濾過し、容積０．２Ｑの濾過水を得た。汚泥容積は約０．１３Ｑとなり、汚泥濃度は、ＭＬＳＳで約２００００ｍｇ／Ｌまで高濃縮された。
【００４０】
このとき、濾過水のｐＨは約６〜７であり、リン成分は、約７．５〜１３．５ｍｇ−Ｐ／Ｌの濃度で含まれていた。この濾過水のｐＨを約３〜４に調整し、吸脱着塔１２へ導入して得た脱リン水Ｗｃ（容積０．２Ｑ）中のリン成分濃度は、約０．７５〜１．３５ｍｇ−Ｐ／Ｌに減少した。この例では、有機性排水Ｗｓに含まれる８０質量％強のリン成分が回収できることが確認された。
【００４１】
以上説明した処理装置１００及びそれを用いた有機性排水の処理方法によれば、嫌気性処理及び好気性処理により多量のリン成分を摂取した活性汚泥（返送汚泥Ｓ２）を濃縮し、その殆ど全部を最前段の嫌気槽１へ返送し、嫌気槽１の前段槽１ａで返送汚泥Ｓ２中からリン成分を液相に放出させる。このように、活性汚泥を系外に取り出すことなく、活性汚泥からリン成分を抽出できるので、従来のような活性汚泥や処理済水を系外に取り出して処理することが必要ない。よって、従来から用いられている嫌気槽及び好気槽を組み合わせた既存の装置に、必要最小限の構成部を追設した装置構成で有機系排水Ｗｓに含まれる有機物の分解処理とリン成分の回収を両立できる。したがって、従来に比して簡略な装置構成及び簡素な工程が実現され、設置スペース及び処理コストの増大を十分に抑制できる。
【００４２】
また、嫌気槽１，３及び好気槽２，４が交互に配置され、嫌気性処理及び好気性処理を複数回繰り返すので、嫌気槽１，３内での微生物菌体からのリン成分の放出が活発となり、その後の好気槽２，４におけるリン成分の摂取が円滑に且つ十分に行われる。よって、活性汚泥中の微生物菌体のリン成分摂取量が高められる。その結果、処理済水Ｗｐ中のリン成分濃度をより低減できる。
【００４３】
さらに、膜濾過装置１１で濾過したリン成分を含む液相である濾過水を、吸脱着塔１２に導入し、吸着剤３２によってリン成分を高選択的に回収するので、リン成分含有水Ｌｐ中のリン成分濃度及び純度が格別に高められる。よって、回収したリン成分を各種用途に供し易く、すなわち、汎用性を向上できる。
【００４４】
またさらに、嫌気槽１の前段槽１ａに返送された返送汚泥Ｓ２に有機性排水Ｗｓを供給するので、返送汚泥Ｓ２中の微生物菌体に栄養分である有機物が付与され、微生物菌体がその栄養分を資化することにより、前段槽１ａ内の嫌気性が一層高められる。その結果、返送汚泥Ｓ２からのリン成分の放出が促進され、液相中のリン成分の濃度が一層高められる。したがって、リン成分の回収量を増大できる利点がある。
【００４５】
さらにまた、嫌気槽１を隔壁１０により前段槽１ａと後段槽１ｂとに分割し、前段槽１ａで返送汚泥Ｓ２からリン成分を放出させ、前段槽１ａにおいてリン成分を放出した高濃度の返送汚泥Ｓ２を後段槽１ｂに移送し、これに十分な量の有機性排水Ｗｓを供給する。よって、後段槽１ｂにおいて、生物処理に適した汚泥濃度とＢＯＤ濃度が達成され、汚泥の活性が維持されて良好な嫌気性処理を行うことができる。その結果、微生物菌体による有機物の分解とリン成分の摂取を良好に維持できる。加えて、前段槽１ａは、活性汚泥が返送されるため通常よりも活性汚泥濃度が高くなる傾向にあるが、隔壁１０によって後段槽１ｂと仕切られているので、後段槽１ｂ中の活性汚泥濃度を所望の値に保持し易い利点がある。
【００４６】
なお、嫌気槽及び好気槽は一段のみでもよく、或いは三段以上設けてもよい。また、返送汚泥Ｓ２の一部を最前段の嫌気槽１以外の嫌気槽（図１では嫌気槽３）に返送しても構わない。さらに、膜濾過装置１１に代えて、他の固液分離手段、例えば、濾布、メッシュ（網）等を用いてもよい。またさらに、嫌気槽１の前段槽１ａを固液分離槽として兼用してもよく、或いは、嫌気槽１の前段に他の固液分離槽を設けてもよい。この場合、固液分離後の上澄み液を分離水として吸脱着塔１２へ導入する。
【００４７】
また、好気槽４を固液分離槽として兼用してもよく、この場合、汚泥返送ライン２４が好気槽４の底部に接続される。こうすれば、固液分離槽５を省略でき、装置構成をより簡略化できる。さらに、嫌気槽１，３及び好気槽２，４は互いに隣接していなくてもよい。加えて、前段槽１ａを隔壁１０で分割するのに代えて、最前段部に嫌気槽を二槽配置し、上流側つまり最前段の嫌気槽をリン放出部として、この槽内に膜濾過装置１１等の液相分離部を設けてもよい。
【００４８】
【発明の効果】
以上説明したように、本発明の有機性排水の処理装置によれば、活性汚泥を系外に取り出すことなく、従来から用いられている嫌気槽及び好気槽を組み合わせた既存の装置に必要最小限の構成部を追設した装置構成で有機系排水に含まれる有機物の分解処理とリン成分の回収を両立できる。よって、従来に比して簡略な装置構成及び簡素な工程が実現され、設置スペース及び処理コストの増大を十分に抑制できる。
【図面の簡単な説明】
【図１】本発明による有機性排水の処理装置の好適な実施形態を示す構成図である。
【符号の説明】
１，３…嫌気槽、１ａ…前段槽（嫌気槽、リン放出部）、１ｂ…後段槽（嫌気槽）、２，４…好気槽、５…固液分離槽、１１…膜濾過装置（液相分離部）、１２…吸脱着塔（リン吸脱着部、リン回収部）、１３…酸貯留槽、１４…アルカリ貯留槽（脱着剤供給部、リン回収部）、２１…移送ライン（排水供給部）、２４…汚泥返送ライン（汚泥返送部）、３２…吸着剤、１００…処理装置（有機系排水の処理装置）、Ｂ…アルカリ（脱着剤）、Ｌｐ…リン成分含有水、Ｐ２…ポンプ（汚泥返送部）、Ｓ２…返送汚泥（活性汚泥）、Ｗｃ…脱リン水、Ｗｐ…処理済水、Ｗｓ…有機系排水。[0001]
BACKGROUND OF THE INVENTION
  The present invention treats organic wastewater.ScienceIn particular, organic wastewater treatment that treats organic wastewater containing phosphorus components by anaerobic treatment and aerobic treatment using activated sludge.ScienceRelated to the position.
[0002]
[Prior art]
Organic wastewater such as industrial wastewater, agricultural wastewater, sewage, and manure often contains phosphorus components such as phosphoric acid and nitrogen components such as ammonia in high concentrations. Phosphorus component and nitrogen component are eutrophication substances, and when wastewater containing these components is released into the environment such as lakes, rivers, and oceans, it becomes a nutrient source for organisms such as phytoplankton. There is a risk that sea bream, red tide, etc. may occur in the coastal area of the ocean.
[0003]
By the way, biological treatment with activated sludge is extremely effective for treatment of organic matter in organic wastewater, and a representative method includes a method combining anaerobic treatment and aerobic treatment. In order to treat the nitrogen component, which is a eutrophication substance, while performing such organic substance decomposition treatment, it is effective to add biological treatment such as nitrification and denitrification treatment. On the other hand, as conventional methods for decomposing organic substances by biological treatment and removing phosphorus components, for example, JP-A-9-262599, JP-A-9-267099, and JP-A-8-24873. And a method described in JP-A-8-66689.
[0004]
[Problems to be solved by the invention]
However, the phosphorus component removal method in the former former is a method in which part of the activated sludge is taken out of the organic matter treatment system and the activated sludge is treated in another system, and the treatment system (apparatus) therefor Was necessary. Further, the above-described conventional method in the latter is a method of recovering a phosphorus component from treated water or process-treated water subjected to biological treatment, and it is necessary to connect another biological treatment device to the biological treatment device. . As described above, when organic substances are processed and phosphorus components are recovered by a conventional method, the configuration of the apparatus tends to be complicated and large-scale, which may increase the installation space and the processing cost. In addition, the number of processing steps has increased and the process control tends to be complicated.
[0005]
  Therefore, the present invention has been made in view of such circumstances, and has achieved both the decomposition of organic matter contained in organic wastewater and the recovery of phosphorus components with a simpler apparatus configuration and simpler process than conventional ones. Organic wastewater treatment that can sufficiently suppress the increase in installation space and treatment costsScienceThe purpose is to provide a device.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have conducted intensive research and utilized a conventional apparatus having an anaerobic tank and an aerobic tank, and without removing activated sludge out of the system, the phosphorus component was put into the liquid phase. A method that can be extracted has been found and the present invention has been completed.
[0007]
  That is, the organic wastewater treatment apparatus according to the present invention is for effectively carrying out the organic wastewater treatment method of the present invention, and the organic wastewater containing phosphorus components is anaerobically treated with activated sludge. An anaerobic tank, an aerobic tank in which the organic wastewater subjected to anaerobic treatment is aerobically treated by the activated sludge, and a solid-liquid separation tank for solid-liquid separation of the aerobically treated organic wastewater and the activated sludge. Further comprising a sludge return section for returning the solid-liquid separated activated sludge to the anaerobic tank, wherein the anaerobic tank releases phosphorus from the returned activated sludge to the liquid phase. And a liquid phase separation part that separates at least a part of the liquid phase from the activated sludge to obtain separated water, and the sludge concentration suitable for biological treatment by transferring the activated sludge from the preceding tank. And BOD concentration achieved, activated sludge activity It is maintained with a subsequent vessel to perform the anaerobic treatmentOrganic wastewater containing phosphorus components is supplied to the front and rear tanks, and organic wastewater that has been anaerobically treated in the rear tank is fed to the aerobic tank.It is characterized by being.
  Here, as the liquid phase separation unit, various solid-liquid separation methods such as gravity sedimentation separation means, membrane separation means, and filtration means can be used. A plurality of anaerobic tanks and aerobic tanks may be alternately arranged. In this case, the sludge return unit may return activated sludge to a plurality of anaerobic tanks. Further, the anaerobic tank in the foremost stage may be divided into two tanks by a partition wall or the like, and the liquid phase separation part may be installed in this tank with the upstream tank as a phosphorus discharge part. Alternatively, two anaerobic tanks may be arranged in the foremost stage, and the upstream side, that is, the anaerobic tank in the foremost stage may be used as a phosphorus discharge part, and a liquid phase separation part may be provided in this tank. In this way, the activated sludge having a high concentration released from the phosphorus component in the first tank is transferred to the second tank, and the activated sludge concentration suitable for biological treatment is provided by supplying a sufficient amount of organic waste water. And BOD (Biochemical Oxygen Demand) concentrations are achieved, the sludge activity is maintained, and good anaerobic treatment is performed.
[0008]
  Treatment of such organic wastewaterapparatusThen, the phosphorus component is released from the microbial cells in the activated sludge in the anaerobic treatment, and the microbial cells are excessively ingested in the aerobic treatment following the anaerobic treatment. The activated sludge containing this phosphorus component is not taken out of the system and separated into solid and liquid.TankAnaerobically concentrated inTankWill be returned. When this highly concentrated activated sludge is placed in an anaerobic atmosphere, the phosphorus component is sufficiently released from the activated sludge into the liquid phase, and the concentration of the phosphorus component in the liquid phase is significantly increased. Then, at least a part of the liquid phase containing the phosphorus component at a high concentration is separated from the activated sludge, which is a solid, and separated water containing a large amount of the phosphorus component is obtained.
[0010]
  Also anaerobic placeIn reasonIsolated liquid phaseA phosphorus adsorbing / desorbing part that has an adsorbing medium capable of adsorbing and desorbing the phosphorous component, and supplied with separated water from the liquid phase separating part, and a desorbing agent is housed in the adsorbing / desorbing part. It is desirable to further include a phosphorus recovery unit having a desorbent supply unit for supplying the agent.Where conventionalapparatusIn order to recover the phosphorus component, for example;
(1) Collecting activated sludge containing phosphorus components taken out of the system as it is,
(2) Polyaluminum chloride (PAC), aluminum sulfate (sulfuric acid band), ferric chloride, polychlorinated liquid phase containing phosphorus component (separated water from activated sludge, treated water, process treated water, etc.) Add a flocculant such as iron to agglomerate and settle the phosphorus component, and separate and collect it by solid-liquid separation.
(3) A specific reagent is added to the liquid phase containing the phosphorus component, and the phosphorus component is recovered as a hardly soluble or insoluble compound having a specific chemical form.
The method is taken.
[0011]
Among these, in the methods (1) and (2), the purity or concentration of the phosphorus component is not necessarily high enough, and purification may be required in order to reuse the phosphorus component. . On the other hand, in the method (3), the types of reagents and recovered compounds are limited, and versatility when reusing the phosphorus component is reduced. In contrast to such a conventional method, in the present invention, since the phosphorus component is adsorbed on the adsorption medium, the phosphorus component can be separated from other components contained in the separated water. And since the phosphorus component adsorbed by the adsorption medium is extracted to the desorbent, a solution containing the phosphorus component at a high concentration is obtained. In addition, if an adsorption medium having a high selectivity for the phosphorus component is used, the purity of the recovered phosphorus component can be increased.
[0012]
Specifically, it is preferable to use an anion exchanger mainly containing a zirconium ferrite-based or zirconium silicate-based material as such an adsorption medium. An anion exchanger mainly composed of a zirconium ferrite-based or zirconium silicate-based substance exhibits an anion exchange function in an acidic solution. In particular, phosphate ions (PO_Four ^3-It is desirable to use a material having a property that the adsorbing ability is high as compared with halogen ions, sulfate ions, nitrate ions, nitrite ions, organic acid ions, and the like.
[0013]
Moreover, the phosphorus component in organic waste water or separated water tends to take the form of phosphate ions. From these facts, if an anion exchanger mainly composed of zirconium ferrite or zirconium silicate is used as the adsorption medium, the selective adsorption of the phosphorus component is significantly improved, and the recovery amount of the phosphorus component is further increased. Increase.
[0014]
  Furthermore, anaerobicTankSupplies organic wastewater to the returned activated sludgeWastewater supply sectionPreferably it has. like thisHave a different configurationThen, the returned activated sludge is supplied with organic substances that are nutrients of microbial cells, and the microbial cells assimilate the nutrients to further enhance the anaerobic environment around the activated sludge. When the anaerobic property is increased in this way, the release of the phosphorus component from the activated sludge is promoted, and the concentration of the phosphorus component in the liquid phase and the separated water is further increased.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a preferred embodiment of an organic wastewater treatment apparatus according to the present invention. In the processing apparatus 100, an anaerobic tank 1, an aerobic tank 2, an anaerobic tank 3, and an aerobic tank 4 are installed in this order, and a solid-liquid separation tank 5 is disposed at a subsequent stage of the aerobic tank 4, which will be described later. Thus, it has the adsorption / desorption tower 12 (phosphorus adsorption / desorption part) to which the filtered water (separated water) obtained in the anaerobic tank 1 is supplied.
[0019]
The anaerobic tank 1 is divided into a front tank 1 a (anaerobic tank and phosphorus release part) and a rear tank 1 b (anaerobic tank) by a partition wall 10. The pre-stage tank 1a includes a stirrer 6 and an immersion type membrane filtration device 11 (liquid phase separation unit). Moreover, the organic waste water Ws is supplied to the front tank 1a and the rear tank 1b through the transfer line 21. Furthermore, the activated sludge is returned to the front tank 1a through the sludge return line 24. The organic waste water Ws supplied to the front tank 1a is stirred and mixed by the stirrer 6 together with the activated sludge, and sequentially transferred to the downstream side of the process as the reaction liquid R.
[0020]
The aerobic tanks 2 and 4 have air diffusers 7 and 9 connected to the blower B through an air supply line 23 at their bottoms. A gas containing oxygen such as air sent from the blower B is diffused into the aerobic tanks 2 and 4 from the air diffusers 7 and 9 through the air supply line 23, respectively. The anaerobic tank 3 is provided with a stirrer 8.
[0021]
A sludge return line 24 having a pump P2 is connected to the bottom of the solid-liquid separation tank 5, and activated sludge, which is a solid content separated by solid-liquid separation, is returned to the sludge return line 24 through the sludge return line 24. Returned to the previous tank 1a. Thus, the sludge return part is comprised from the pump P2 and the sludge return line 24. FIG. On the other hand, the supernatant liquid separated into solid and liquid is discharged out of the system as treated water Wp.
[0022]
On the other hand, a transfer line 25 having a pump P1 is connected to the membrane filtration device 11 immersed in the preceding tank 1a of the anaerobic tank 1, and filtered water obtained by the membrane filtration device 11 is sucked through the transfer line 25. It is transferred to the desorption tower 12. Moreover, the acid storage tank 13 is connected to the transfer line 25 via the transfer line 26 which has the pump P3, and the acid A for adjusting pH of filtrate water is supplied.
[0023]
Further, the adsorption / desorption tower 12 contains an adsorbent 32 (adsorption medium) capable of adsorbing and desorbing phosphorus components inside, and the filtered water moves while in contact with the adsorbent 32. Yes. The filtered water that has passed through the adsorbent 32 is discharged through the transfer line 28 as dephosphorized water Wc. The adsorption / desorption tower 12 is connected to an alkali storage tank 14 (desorption agent supply unit) via a transfer line 27 having a pump P4, and alkali B as a desorption agent is introduced into the storage unit of the adsorbent 32. Is done. The alkali B that has moved through the adsorption / desorption tower 12 while being in contact with the adsorbent 32 is eluted as the phosphorus component-containing water Lp and discharged through the transfer line 29. As described above, the adsorption / desorption tower 12 and the alkali storage tank 14 constitute a phosphorus recovery unit.
[0024]
Next, a preferred embodiment of the organic wastewater treatment method according to the present invention using the treatment apparatus 100 configured as described above will be described. First, the organic waste water Ws from which impurities and the like are removed is supplied to the upstream tank 1 a of the anaerobic tank 1 through the transfer line 21. The organic waste water Ws and the activated sludge are stirred and mixed with the stirrer 6 to obtain the reaction solution R, and then fed to the rear tank 1b. Then, in the rear tank 1b, the organic waste water Ws is further added to perform anaerobic treatment (anaerobic treatment step). At this time, the microbial cells constituting the activated sludge decompose organic substances into lower molecular organic acids, carbon dioxide and the like, and release the phosphorus component held inside and outside the body into the liquid phase.
[0025]
Here, as the organic waste water Ws, organic waste water containing phosphorus components such as sewage, human waste, agricultural waste water, food waste water, and industrial waste water can be cited. The anaerobic tank 1 is preferably one that can prevent contact between a gas containing oxygen such as air and the reaction liquid R as much as possible, and an ordinary storage tank, desirably a sealed stirring tank, can be used. Particularly preferably, the gas phase portion in contact with the liquid phase is replaced with an inert gas such as nitrogen gas. The amount of activated sludge in the first-stage tank 1a and the second-stage tank 1b is returned to (1) the amount of activated sludge existing in the first-stage tank 1a from the beginning, and (2) the activated sludge grown in the processing apparatus 100 and (3). The total amount with the activated sludge S2 is the amount obtained by subtracting the amount of activated sludge flowing out to (4) downstream side. In the treatment of the organic waste water Ws, it is desirable to adjust the activated sludge amount of the above (2) + (3)-(4) so as to be constant.
[0026]
Next, the reaction solution R that has been subjected to the anaerobic treatment for a predetermined time is fed to the aerobic tank 2. Then, the blower B is operated, air is supplied to the diffuser 7 through the air supply line 23, and aerobic treatment is performed while the fine bubbles of air are diffused from the diffuser 7 to the reaction solution R ( Aerobic treatment process). Due to this aeration, the reaction solution R is agitated, and fine bubbles become, for example, a gas-liquid mixed phase flow, and oxygen is sufficiently supplied into the reaction solution R. At this time, the microbial cells in the activated sludge decompose organic substances into carbon dioxide, water and the like, and ingest the phosphorus component in the liquid phase.
[0027]
Subsequently, the reaction solution R that has been subjected to the anaerobic treatment for a predetermined time is sequentially fed to the anaerobic tank 3 and the aerobic tank 4, and the biological treatment is repeated in the order of anaerobic treatment and aerobic treatment (respectively anaerobic treatment step and Aerobic treatment process). In this way, a large amount of phosphorus component is released from the microbial cells in the anaerobic tank 3, and it becomes possible for the aerobic tank 4 to allow the microbial cells to take in an excessive amount of phosphorus component.
[0028]
After the aerobic treatment in the aerobic tank 4 is completed, the reaction liquid R is transferred to the solid-liquid separation tank 5 and solid-liquid separation is performed in the solid-liquid separation tank 5 by gravity sedimentation separation (solid-liquid separation step). At this time, it is preferable to maintain aerobicity in the solid-liquid separation tank 5. The supernatant liquid is discharged out of the system as treated water Wp in which the organic matter contained in the organic waste water Ws is sufficiently decomposed and the phosphorus component is sufficiently removed. On the other hand, the solid content settled at the bottom of the tank is returned to the upstream tank 1a of the anaerobic tank 1 through the sludge return line 24 as the concentrated return sludge S2 (activated sludge) (sludge return process). In the pre-stage tank 1a in an anaerobic atmosphere, the phosphorus component is released into the liquid phase from the microbial cells that have ingested the phosphorus component constituting the return sludge S2.
[0029]
At this time, a predetermined amount of organic waste water Ws, which is raw water, is supplied to the upstream tank 1a through the transfer line 21 (drainage supply unit). Then, the microbial cells are grown using the organic matter contained in the newly added organic waste water Ws as nutrients, and the inside of the front tank 1a becomes more anaerobic. As a result, release of the phosphorus component from the microbial cells is promoted, and the concentration of the phosphorus component in the liquid phase is extremely increased.
[0030]
Here, the supply amount of the organic waste water Ws to the return sludge S2 is preferably 0.1 to 0.5 g-BOD / day, with respect to the activated sludge 1 g-MLSS (Mixed Liquor Suspended Solids) / L / day, More preferably 0.2 to 0.4 g-BOD / day is suitable.
[0031]
When this supply amount is less than any one of the above lower limit values, the anaerobic increase effect tends not to be remarkably obtained. On the other hand, when this supply amount exceeds any one of the above upper limit values, the concentration of organic substances and other components in the liquid phase tends to increase, depending on the liquidity and organic substance concentration of the organic waste water Ws. Therefore, it is not preferable.
[0032]
The residence time of the return sludge S2 in the preceding tank 1a of the anaerobic tank 1 is preferably 2 to 10 hours, more preferably 3 to 6 hours, although it depends on the sludge concentration, the amount of phosphorus component intake, the sludge properties, and the like. Time is preferred. If the residence time is less than 2 hours, the amount (rate) of phosphorus component released from the sludge tends to be insufficient. On the other hand, when the residence time exceeds 10 hours, the release amount of the phosphorus component does not increase with time, that is, tends to be saturated.
[0033]
Next, the liquid phase from which the phosphorus component is released from the return sludge S2 is filtered and separated from the return sludge S2 by the membrane filtration device 11. On the other hand, the return sludge S2 is sent to the rear tank 1b as activated sludge. And the organic waste_water | drain Ws is again supplied to the back | latter stage tank 1b, and an anaerobic process is performed. The subsequent processing is the same as described above. Thus, the continuous treatment of the organic waste water Ws is performed without taking out the activated sludge (or the return sludge S2) from the system.
[0034]
The organic wastewater treatment method and apparatus according to the present invention is not a method and apparatus for treating sludge taken out of the system and recovering phosphorus components. Therefore, taking out sludge that has been dismantled and deactivated during processing out of the system, or supplementing the deficiency of activated sludge due to changes in the liquidity of organic wastewater Ws, makes biological treatment of organic wastewater Ws good. From the viewpoint of maintaining the above, this is a preferable treatment.
[0035]
Further, the liquid phase separated from the returned sludge S 2 by the membrane filtration device 11, that is, filtered water, is introduced through the transfer line 25 into the adsorbent 32 accommodating portion in the adsorption / desorption tower 12. The adsorbent 32 is not particularly limited as long as the adsorption and desorption of the phosphorus component is possible, but the ease of adsorption and desorption (adsorption and desorption performance), the chemical form of the phosphorus component (mainly phosphate ion: PO_Four ^3-In this case, an inorganic or organic anion exchanger can be preferably used. In particular, an anion exchanger mainly composed of a zirconium ferrite-based or zirconium silicate-based material is more preferable because of its excellent adsorption performance for phosphate ions. Hereinafter, the case where an anion exchanger mainly composed of a zirconium ferrite-based or zirconium silicate-based material is used as the adsorbent 32 will be described.
[0036]
By the way, an anion exchanger such as a zirconium ferrite type or a zirconium silicate type generally has a -OH group (-OH under acidic conditions) on the substrate surface.₂ ⁺-O under alkaline^-Adsorption / desorption of anions is performed by the anion exchange capacity of In contrast, when an organic substance is decomposed and / or nitrified and denitrified by anaerobic treatment, OH is produced.^-For example, the pH of the liquid phase tends to be inclined toward the alkali side of about 7.5 to 13.5. Therefore, before and at the time of introducing the filtrate into the adsorption / desorption tower 12, the acid A such as sulfuric acid is supplied from the acid storage tank 13 to the transfer line 25, and the accommodating portion of the adsorbent 32 is in an acidic state, for example, the pH of the filtrate. TheAbout 2-4To the extent. Thereby, the phosphorus component in filtered water is fully adsorbed to the adsorbent 32. In this way, the dephosphorized water Wc is obtained by passing the filtered water while making contact with the adsorbent 32. The dephosphorized water Wc is discharged through the transfer line 28.
[0037]
When the adsorption capacity of the adsorbent 32 approaches saturation and the adsorption efficiency decreases, the operation of the pump P1 is stopped and the supply of filtered water to the adsorption / desorption tower 12 is interrupted. At this time, the pump P4 is operated to supply the alkali B from the alkali storage tank 14 to the adsorption / desorption tower 12. When the alkali B comes into contact with the adsorbent 32, the phosphorus component is eluted into the alkali B by the anion exchange ability of the adsorbent 32. Then, the alkali B eluted from the adsorption / desorption tower 12 is recovered by the transfer line 29 as phosphorus component-containing water Lp.
[0038]
Next, an example of a material balance when an organic wastewater treatment test is performed using the treatment apparatus 100 shown in FIG. 1 will be described. As the organic waste water Ws, one having a phosphorus component concentration of 3 to 5 mg-P / L was used. Here, “mg-P” indicates the mass of phosphorus. The unit volume of the total supply amount of the organic waste water Ws is 1Q, 0.5Q is supplied to the anterior tank 1a of the anaerobic tank 1, 0.5Q is supplied to the anaerobic tank 3, and 1 / 3Q is returned to the anaerobic tank 1 as the return sludge S2. It returned to the front tank 1a. That is, when filtration was not performed in the pre-stage tank 1a, the 4 / 3Q reaction liquid R was circulated in the system.
[0039]
The sludge concentration in the reaction liquid R sent from the aerobic tank 4 to the solid-liquid separation tank 5 through a series of steps was about 2000 mg / L (volume 4 / 3Q) in MLSS. The volume of the supernatant liquid (processed water Wp) separated in the solid-liquid separation tank 5 was 1Q, and the concentration of the phosphorus component was reduced to 0.5 mg-P / L. On the other hand, the sludge concentration in the volume 1 / 3Q settled in the solid-liquid separation tank 5 was about 8000 mg / L in MLSS, and this was filtered in the preceding tank 1a to obtain 0.2Q of filtered water. The sludge volume was about 0.13Q, and the sludge concentration was highly concentrated to about 20000 mg / L with MLSS.
[0040]
At this time, the pH of filtered water was about 6-7, and the phosphorus component was contained at a concentration of about 7.5-13.5 mg-P / L. The pH of this filtered water is adjusted to about 3 to 4, and the phosphorus component concentration in the dephosphorized water Wc (volume 0.2Q) obtained by introducing it into the adsorption / desorption tower 12 is about 0.75 to 1.35 mg- Reduced to P / L. In this example, it was confirmed that 80% by mass or more of the phosphorus component contained in the organic waste water Ws can be recovered.
[0041]
According to the treatment apparatus 100 and the organic wastewater treatment method using the treatment apparatus 100 described above, the activated sludge (returned sludge S2) that has ingested a large amount of phosphorus components by anaerobic treatment and aerobic treatment is concentrated, almost all of them. Is returned to the anaerobic tank 1 in the foremost stage, and the phosphorus component is released into the liquid phase from the returned sludge S2 in the front tank 1a of the anaerobic tank 1. As described above, since the phosphorus component can be extracted from the activated sludge without taking the activated sludge out of the system, it is not necessary to take out the activated sludge and the treated water from the outside and treat them. Therefore, the decomposition of organic matter contained in the organic wastewater Ws and the phosphorous component of the existing apparatus combining the anaerobic tank and the aerobic tank used in the past with the apparatus configuration additionally provided with the minimum necessary components. Both recovery can be achieved. Therefore, a simple apparatus configuration and a simple process can be realized as compared with the conventional case, and an increase in installation space and processing cost can be sufficiently suppressed.
[0042]
Moreover, since the anaerobic tanks 1 and 3 and the aerobic tanks 2 and 4 are alternately arranged and the anaerobic treatment and the aerobic treatment are repeated a plurality of times, the release of phosphorus components from the microbial cells in the anaerobic tanks 1 and 3 Becomes active, and the subsequent intake of the phosphorus component in the aerobic tanks 2 and 4 is performed smoothly and sufficiently. Therefore, the phosphorus component intake of the microbial cell in the activated sludge is increased. As a result, the phosphorus component concentration in the treated water Wp can be further reduced.
[0043]
Furthermore, since the filtered water which is a liquid phase containing the phosphorus component filtered by the membrane filtration device 11 is introduced into the adsorption / desorption tower 12, and the phosphorus component is highly selectively recovered by the adsorbent 32, the phosphorus component-containing water Lp The concentration and purity of the phosphorus component are significantly increased. Therefore, the recovered phosphorus component can be easily used for various purposes, that is, versatility can be improved.
[0044]
Furthermore, since the organic waste water Ws is supplied to the returned sludge S2 returned to the preceding tank 1a of the anaerobic tank 1, organic matter that is a nutrient is added to the microbial cells in the returned sludge S2, and the microbial cells are the nutrients. By assimilating the anaerobic property, the anaerobic property in the front tank 1a is further enhanced. As a result, release of the phosphorus component from the return sludge S2 is promoted, and the concentration of the phosphorus component in the liquid phase is further increased. Therefore, there is an advantage that the recovery amount of the phosphorus component can be increased.
[0045]
Furthermore, the anaerobic tank 1 is divided into a front tank 1a and a rear tank 1b by a partition 10, and a phosphorus component is released from the returned sludge S2 in the front tank 1a, and a high-concentration return sludge that has released the phosphorus component in the front tank 1a. S2 is transferred to the rear tank 1b, and a sufficient amount of organic waste water Ws is supplied thereto. Therefore, in the latter tank 1b, the sludge concentration and the BOD concentration suitable for the biological treatment are achieved, and the sludge activity is maintained and a favorable anaerobic treatment can be performed. As a result, it is possible to satisfactorily maintain the decomposition of organic substances and the intake of phosphorus components by microbial cells. In addition, the activated sludge tends to have a higher activated sludge concentration than usual because the activated sludge is returned to the front tank 1a, but the activated sludge concentration in the rear tank 1b is separated from the rear tank 1b by the partition wall 10. Is easily maintained at a desired value.
[0046]
In addition, an anaerobic tank and an aerobic tank may be only one step | paragraph, or you may provide three or more steps | paragraphs. Moreover, you may return a part of return sludge S2 to anaerobic tanks (anaerobic tank 3 in FIG. 1) other than the anaerobic tank 1 of the foremost stage. Further, instead of the membrane filtration device 11, other solid-liquid separation means, for example, a filter cloth, a mesh (net) or the like may be used. Furthermore, the front tank 1a of the anaerobic tank 1 may be used as a solid-liquid separation tank, or another solid-liquid separation tank may be provided in the front stage of the anaerobic tank 1. In this case, the supernatant liquid after solid-liquid separation is introduced into the adsorption / desorption tower 12 as separated water.
[0047]
Further, the aerobic tank 4 may also be used as a solid-liquid separation tank. In this case, the sludge return line 24 is connected to the bottom of the aerobic tank 4. By doing so, the solid-liquid separation tank 5 can be omitted, and the apparatus configuration can be further simplified. Furthermore, the anaerobic tanks 1 and 3 and the aerobic tanks 2 and 4 may not be adjacent to each other. In addition, instead of dividing the front tank 1a by the partition wall 10, two anaerobic tanks are arranged in the foremost stage, and the upstream side, that is, the foremost anaerobic tank is used as a phosphorus discharge part, and a membrane filtration device is provided in this tank. A liquid phase separation unit such as 11 may be provided.
[0048]
【The invention's effect】
  As described above, the treatment of the organic waste water of the present invention.ScienceAccording to the installation, the organic wastewater with the equipment configuration that additionally installed the minimum necessary components to the existing equipment combining the anaerobic tank and aerobic tank conventionally used without taking activated sludge out of the system It is possible to achieve both the decomposition treatment of the organic matter contained in and the recovery of the phosphorus component. Therefore, a simple apparatus configuration and a simple process are realized as compared with the conventional case, and an increase in installation space and processing cost can be sufficiently suppressed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a preferred embodiment of an organic wastewater treatment apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,3 ... Anaerobic tank, 1a ... Pre-stage tank (anaerobic tank, phosphorus discharge | release part), 1b ... Later stage tank (anaerobic tank), 2,4 ... Aerobic tank, 5 ... Solid-liquid separation tank, 11 ... Membrane filtration apparatus ( Liquid phase separation unit), 12 ... adsorption / desorption tower (phosphorus adsorption / desorption unit, phosphorus recovery unit), 13 ... acid storage tank, 14 ... alkali storage tank (desorbent supply unit, phosphorus recovery unit), 21 ... transfer line (drainage) Supply part), 24 ... sludge return line (sludge return part), 32 ... adsorbent, 100 ... treatment device (treatment device for organic wastewater), B ... alkali (desorbent), Lp ... phosphorus component-containing water, P2 ... Pump (sludge return part), S2 ... Return sludge (activated sludge), Wc ... Dephosphorized water, Wp ... Treated water, Ws ... Organic waste water.

Claims

Anaerobic tank in which organic wastewater containing phosphorus component is anaerobically treated, aerobic tank in which the organic wastewater subjected to anaerobic treatment is aerobically treated, and the organic wastewater and activated sludge subjected to aerobic treatment A solid-liquid separation tank for solid-liquid separation, and an organic wastewater treatment device comprising:
It further comprises a sludge return section that returns the activated sludge separated into solid and liquid to the anaerobic tank,
The anaerobic tank is a phosphorus release part for releasing the phosphorus component from the returned activated sludge to the liquid phase, and a liquid phase separation part for separating at least part of the liquid phase from the activated sludge to obtain separated water. And a post-stage tank in which the activated sludge is transferred from the pre-stage tank, the sludge concentration and the BOD concentration suitable for biological treatment are achieved, and the activity of the activated sludge is maintained and an anaerobic treatment is performed. Prepared,
The organic wastewater containing the phosphorus component is supplied to the front tank and the rear tank,
The organic wastewater that has been anaerobically treated in the rear tank is fed to the aerobic tank,
Organic wastewater treatment equipment characterized by that.

A phosphorus adsorption / desorption part having an adsorption medium capable of adsorbing and desorbing a phosphorus component, and being supplied with the separated water from the liquid phase separation part;
A desorption agent supply unit that contains a desorption agent and supplies the desorption agent to the adsorption / desorption unit;
The organic wastewater treatment apparatus according to claim 1, further comprising: a phosphorus recovery unit having

The said anaerobic tank has the waste_water | drain supply part which supplies the said organic waste_water | drain to the said activated sludge returned, The processing apparatus of the organic waste_water | drain of Claim 1 or 2 characterized by the above-mentioned.

3. The organic waste water treatment apparatus according to claim 2, wherein the adsorption medium is mainly an anion exchanger of zirconium ferrite type or zirconium silicate type.