JP2004261711A

JP2004261711A - Membrane separation activated sludge treatment apparatus and membrane separation activated sludge treatment method

Info

Publication number: JP2004261711A
Application number: JP2003054573A
Authority: JP
Inventors: Yoshikimi Watanabe; 義公渡辺; Genzo Ozawa; 源三小澤; Manabu Sasagawa; 学笹川
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2004-09-24
Anticipated expiration: 2023-02-28
Also published as: JP4059790B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient membrane separation activated sludge treatment apparatus and method capable of continuously and simultaneously implementing aerobic treatment and oxygen-free treatment. <P>SOLUTION: The membrane separation activated sludge treatment apparatus has a single reaction tank for performing the aerobic treatment and oxygen-free treatment, an immersion membrane separation unit arranged in the reaction tank, and an aeration means. The reaction tank is divided at its bottom to a plurality of compartments by partition plates disposed spatially from the base surface of the reaction tank, and the immersion membrane separation unit and the aeration means are arranged in at least one of the plurality of the compartments. Also, the reaction tank is provided with a liquid level control means or a means for height control of the partition plates for changing over the inside of the remaining compartments from the aerobic state to the oxygen-free state and vice versa. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、膜分離とともに窒素除去を効率的に行うことができる膜分離活性汚泥処理装置および方法に関し、特に、窒素を含む下水等の汚水を、浸漬膜を設置した単槽式の反応槽で生物処理し、活性汚泥中の硝化細菌と脱窒細菌との作用で窒素を生物学的に連続的、かつ効率的に除去する膜分離活性汚泥処理装置および方法に関する。
【０００２】
【従来の技術】
従来、窒素やリンといった栄養塩を含む下廃水を処理するにあたっては、汚水を反応槽に導入し活性汚泥と共に曝気・攪拌して生物処理を行う活性汚泥法が用いられている。また、近年は、この活性汚泥法によって処理された処理水から清澄な処理水を得るために、膜分離活性汚泥法が多用されるようになってきた。膜分離活性汚泥法は、反応槽内に膜分離装置を浸漬させ、処理水を排出するため、沈殿池が不要で設置面積が少なく、固形物を含まない清澄な処理水が得られるという利点がある。
【０００３】
ところで、浸漬型の膜分離装置では、膜表面に汚泥が付着するのを防止するために、下部の散気管から空気を吹き込む必要があり、空気を止める時間帯は濾過処理を行えないことから、通常はほぼ連続的に散気を行っている。しかしながら、活性汚泥法では、脱窒処理のために槽内を無酸素状態にする必要がある。したがって、膜分離活性汚泥法においては、膜ろ過時の膜面洗浄のための散気の確保と、脱窒処理のための無酸素状態の確保との両立が必要であり、このための技術が種々開示されている。例えば、特許文献１には、脱窒を行う脱窒槽と膜分離装置を浸漬する硝化槽との二つを設け、汚水をそれらの槽間で移送して処理する処理装置が開示されている。また、特許文献２には、膜モジュールを設けた反応槽を間欠的に曝気して、好気工程と無酸素工程とを交互に行うことが記載されている。さらに、特許文献３には、単一の反応槽に浸漬膜を設けるとともに酸素供給用のブロワと窒素供給用のブロワを設け、活性汚泥に対しては酸素を間欠的に曝気し、浸漬膜に対しては窒素ガスを供給して膜の洗浄を行う技術が記載されている。
【０００４】
しかしながら、特許文献１に記載の技術では、連続的に処理をすることはできるものの、槽を複数個設ける必要があるため、設備が大きくなり浸漬膜としてのメリットを発揮することができないうえに、設備コストが高くなる。また、特許文献２に記載の技術は、単一槽であるので、設備を小さくすることは可能であるのもの、好気条件での硝化、膜分離と、無酸素条件での脱膣処理とを同時に行うことはできず、効率的でない。さらに、特許文献３に記載の技術は、空気中の窒素ガスを吸着、離脱を繰り返すことにより、高濃度の酸素ガスを生成させる酸素発生装置をが必須となり、装置が複雑、高価になる等の問題がそれぞれ存在する。
【０００５】
【特許文献１】特開平１１−２４４８９３号報公報
【特許文献２】特開２０００−５８９号公報
【特許文献３】特開２００２−１８４６８号報公報
【０００６】
【発明が解決しようとする課題】
本発明は、上記従来の問題点に鑑み、好気処理と無酸素処理とを連続的に同時に実施することが可能な、効率的な膜分離活性汚泥装置および方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本願発明者らは、鋭意研究の結果、単一の反応槽を仕切板で２つの区画に分け、一方の区画に膜分離ユニットを浸漬すると共に、液位の変化又は仕切板の位置の上下方向の変化により、仕切板よりも上の領域を介して両区画の液が流通可能な状態と、仕切板よりも上に液が存在せず、両区画の液の流通が妨げられた状態とを作り出すことにより、膜分離ユニットは空気の供給下で連続的に作動させながら、膜分離ユニットが浸漬されている区画以外の区画（以下、便宜的に「硝化／脱窒処理区画」と言うことがある）への空気の供給を行ったり停止したりすることが可能であることに想到し、これによって、硝化／脱窒処理区画を好気状態にしたり無酸素状態にしたりすることが可能であり、このため、硝化細菌による硝化処理及び脱窒細菌による脱窒処理を同一の区画内で行うことが可能であることを実験的に確認し、本発明を完成した。
【０００８】
すなわち、本発明は、好気性処理および無酸素処理を行う単一の反応槽と、その反応槽の内部に配置された浸漬膜分離ユニットと、曝気手段とを有する膜分離活性汚泥処理装置であって、反応槽は、底部が反応槽の底面から離間して設けられた仕切板によって複数個の区画に分割され、その複数個の区画内の少なくとも一つに浸漬膜分離ユニットおよび曝気手段が配置され、残りの区画内を好気状態から無酸素状態に、また、無酸素状態から好気状態に切り換えるための液位制御手段又は仕切板の高さ制御手段が設けられていることを特徴とする膜分離活性汚泥処理装置を提供する。なお、本明細書において「無酸素状態」とは、完全な無酸素状態のみを意味するものではなく、脱窒菌の作用により硝酸態窒素を窒素分子に還元できる程度に酸素濃度が低い状態をも包含する意味で用いている。
【０００９】
ここで、反応槽の中央部に浸漬膜分離ユニットが配置され、その浸漬膜分離ユニットの全周囲に仕切板が配置されている又は浸漬膜分離ユニットの全周囲が仕切板と槽壁とによって囲包されるように仕切板が配置されていることや、反応槽の一部にその反応槽の槽壁と仕切板とで仕切られた区画を有し、その区画内に浸漬膜分離ユニットおよび曝気手段が配置されていることが好ましい。
【００１０】
また、本発明は、浸漬膜分離ユニットを配置した単一の反応槽内で好気性処理および無酸素処理を行う膜分離活性汚泥方法であって、浸漬膜分離ユニットの周囲を底部が反応槽の底面から離間して設けられた仕切板で区画し、浸漬膜分離ユニットの下方から曝気を行うとともに、反応槽内の液位を調節することにより又は仕切板の位置を変化させることにより、浸漬膜分離ユニットが配置された区画内を好気状態に維持しつつ、その他の区画内を好気状態から無酸素状態に、また、無酸素状態から好気状態に切り換えることを特徴とする膜分離活性汚泥方法を提供する。
【００１１】
このとき、間欠的に無酸素状態の区画を形成し、脱窒処理を行うこと、さらには、浸漬膜分離ユニットが配置された区画内を好気状態に維持しつつ、その他の区画内を無酸素状態に切り換え、脱窒処理と膜ろ過とを同時に行うことが好ましい。
【００１２】
【発明の実施の形態】
以下、図面に基づいて、本発明に係る単槽式の膜分離活性汚泥装置および膜分離活性汚泥方法の一実施態様を説明する。
【００１３】
図１に、本発明に係る単槽式の膜分離活性汚泥装置における窒素の除去方法を示す。
【００１４】
図１の膜分離活性汚泥装置では、単槽式の反応槽１に、浸漬型の膜分離ユニット２が設けられている。この膜分離ユニット２には反応槽１の外で吸引ポンプ３が接続されるとともに、膜分離ユニット２の下方に、膜洗浄及び好気生物処理用の散気管４が設けられている。散気管４は、ブロワ５に接続され、ブロワ５からエア（空気）が供給される。
【００１５】
このような構成により、散気管４からのエアによって膜分離ユニット２の膜面に汚泥物質等が付着するのを防止しながら膜分離ユニット２によって反応槽１内の処理液をろ過し、そのろ過水を吸引ポンプ３により槽外に取り出すことができる。
【００１６】
反応槽１には、原水ポンプ８が接続されるとともに、レベルセンサ６および仕切板７が設けられている。レベルセンサ６は、液位、すなわち、液表面の位置を調べるセンサであり、それ自体は周知である。また、仕切板７は、図示のように底部が反応槽の底面から離間して設けられている。図示の例では、仕切板７は、膜分離ユニット２の全周囲を囲包しており（「全周囲」は横方向における全周囲であり、図示のように上下は開放）、この場合には仕切板７は、図３に示すように、槽壁と共働して矩形の領域を規定する、２枚の平板状のものが好ましい。あるいは、図４に示すように、仕切板７が膜分離ユニット２の全周囲を囲包するものでもよい。原水ポンプ８は、原水槽９に接続されており、原水槽９中の原水が原水ポンプ８により反応槽１に導入される。
【００１７】
以上の構成で、反応槽１へ原液を供給するとともに、レベルセンサ６によって原水ポンプ８をＯＮ−ＯＦＦ制御して、その供給量を制御し、槽内の液位が一定の範囲内に保たれるようにする。原水ポンプ８は、ＬＷＬ（ＬｏｗＷａｔｅｒＬｅｖｅｌ）でポンプＯＮ、ＨＷＬ（ＨｉｇｈＷａｔｅｒＬｅｖｅｌ）でＯＦＦとなるように設定されている。
【００１８】
反応槽１には、微生物を含有する汚泥が収容されており、この微生物が、有機物の分解菌、さらにはそれら微生物の分解菌として作用し、生物処理を行う。従って、反応槽１は、汚泥が部分的に偏在することがないように、また、酸素が均一に供給されるように、内表面に角がないものや凹凸がないものが好ましい。この結果、反応槽１内では処理液の温度やｐＨが均一になり、安定に分解処理を進めることができる。また、汚泥に含有される微生物は、細菌類、酵母およびカビを含む真菌類など、溶解性有機物などの分解に寄与するもので、土壌、堆肥、汚泥など、自然界から集積培養及び馴養によって取得される。またこの馴養液から分解に関与する主要な微生物群を単離して用いることも可能である。なお、これらの微生物を含有する汚泥自体はこの分野において周知である。
【００１９】
さらに、この反応槽１に浸漬させる膜分離ユニットは、膜そのものとして汚れにくい素材を用いたものや、膜表面に汚れがつきにくくなるように、膜間に適当な隙間を有するものを用いることが好ましい。膜分離ユニット２には、精密ろ過膜、限外ろ過膜、ナノろ過膜、逆浸透膜などを用いて形成されたモジュールを用いることができる。経済性の観点からは、ろ過速度が高くコンパクト化が可能で、メンテナンスが容易である精密ろ過膜、限外ろ過膜を用いたモジュールが好ましい。膜の形状は平膜、中空糸膜等のものが用いられる。浸漬型の膜分離ユニットによれば、省スペース化を図ることができる。なお、ここで用いられる浸漬型膜分離ユニット自体はこの分野において広く用いられており、市販もされている。
【００２０】
次に、この設備の作用について説明する。下水処理場等の汚水処理施設に流入した汚水は、前処理設備において砂やごみ等の分離・除去を行った後、原水槽９から原水ポンプ８により反応槽１へと導入される。一方、反応槽１内で生物学的に処理された汚水は、吸引ポンプ３により吸引され、処理水として、消毒等の最終処理の後、場外に排出される。
【００２１】
反応槽１の液位がＨＷＬにある状態から具体的に説明すると、液位は仕切板７より高いため仕切板７の影響はなく、散気管４からのエアで槽全体に及ぶ循環流（膜ユニット収容区画から、仕切板７の上を越えて硝化／脱窒処理区画に入り、該区画内を下降し、仕切板７よりも下の領域を介して膜ユニット収容区画に戻る循環流）が形成され、槽内の流入水のアンモニア成分が、硝化細菌の作用により、硝酸態に酸化される。このとき原水ポンプ８は液位がＨＷＬでＯＦＦの動作であり、ろ過により徐々に液位が下がることになる。
【００２２】
ついで、液位が仕切板７よりも低くなると、散気管４からのエアは仕切板７で囲まれた空間内でとどまることになる。仕切板７の外側の領域にはエアが循環しないため無酸素状態にすることができ、脱窒菌が流入水中の有機物をエネルギー源として利用しながら、硝酸態の窒素を窒素分子に還元する反応が起こる。なお、このとき、膜ユニット２の洗浄エアは変わらないため、ろ過を停止する必要はない。
【００２３】
ついで、液位がＬＷＬになると原水ポンプ８がＯＮとなり、液位がＨＷＬとなったところで停止する。
【００２４】
このように、液位レベルにより単一槽にて好気運転と無酸素・好気混在運転をろ過連続で実施でき、流入水中の窒素成分の効率的な除去が可能となる。
【００２５】
なお、上記操作方法において、本発明は、液又は仕切板の位置を制御することにより、仕切板７よりも上の領域を介する反応液の流通を可能にしたり不可能にしたりすることにより、単一の硝化／脱窒処理区画内に好気状態と無酸素状態とを交互に作り出す点に特徴があり、これ以外の処理条件及び原水の前処理は、従来より周知の方法と同様の条件で行うことができる。
【００２６】
なお、図１の具体例では、仕切板７が膜ユニット２の横方向の全周囲を囲包している（上下は開放）が、仕切板７は、膜分離ユニット２の周囲を実質的に取り囲むものであれば良く、たとえば図２及び図５に示すように、槽壁と組合せて膜分離ユニット２の周囲を取り囲むもの（すなわち、上から見た場合、膜分離ユニット２の周囲４面のうち、一面を仕切板７が、他の３面を槽壁で囲包）でも良い。
【００２７】
また、図１の具体例では、膜ユニット収容区画が１つだけであるが、大型の下水処理等の場合には、単位時間当たりの処理量を大きくするために、所望により、膜ユニットを収容する区画を複数設け、これらの各区画にそれぞれ膜ユニットを浸漬してもよい。この場合、硝化／脱窒処理区画を複数設けることも可能であるが、硝化／脱窒処理区画は１つの方が構造が単純で反応液の均一性も確保しやすいので好ましい。
【００２８】
また、原水流入の制御も、タイマー設定やｐＨ制御、ＯＲＰ計制御等種々の方法が有り、本実施例に限定されるものではない。さらに、図１の具体例においては、吸引ポンプ３でろ過圧を得ているが、反応槽内の水位と濾過水取り出し口との水位との差、すなわち自然水頭のみによって濾過圧を得てもよく、さらに原液側から加圧することによって濾過圧を得てもよい。
【００２９】
【実施例】
以下、本発明を実施例に基づきより詳細に説明する。
【００３０】
実施例１、比較例１
図１に示す処理装置で、下水処理場の最初沈殿池流出水を凝集沈殿処理した原水を処理した。なお、仕切板７は運転を開始して１５０日を経過した時点で設置した。
【００３１】
凝集沈殿処理は、多孔板と傾斜管によってフロック形成と沈殿を同時に行う噴流撹拌型固液分離装置にて、凝集剤にはポリシリカト鉄を１０ｍｇ−Ｆｅ／Ｌとなるように添加し、滞留時間は１．５時間の条件で実施した。
【００３２】
この凝集沈殿処理後の処理水を反応槽１に供給した。反応槽１は運転時容量５００Ｌで、仕切板７で区分される容量が、仕切板７の内（膜分離ユニット２を配置した区画）：外（その他の部分）＝３：１の比率になるように仕切板を設置した。膜分離ユニット２の分離膜には、公称孔径０．１μｍのＰＶＤＦ製ＭＦ膜（有効面積０．６ｍ^２の平膜１０枚を膜間距離が７．５ｍｍに保たれるようにケースに装填）を用いた。
【００３３】
曝気エア量１００Ｌ／分、ろ過水量２．５ｍ^３／日にてろ過を実施した。ＭＳＬＬ（ＭｉｘｅｄＬｉｑｕｏｒＳｕｓｐｅｎｄｅｄＳｏｌｉｄ）濃度は１２０００〜１５０００ｍｇ／Ｌとし、ＨＲＴ（水理学的滞留時間）４．８時間の生物処理条件のもと、初めの１５０日間は仕切板のない運転で（比較例１）、続く１５０日間は、仕切板を設置し、仕切板７より液位が上になる好気運転を３０分間した後、液位が仕切板７の頂部よりも下になるように切換え、部分好気・無酸素混合運転を３０分間行う運転を繰り返し（実施例１）、計３００日間実施した。この結果を下記表１に示す。
【００３４】
【表１】
表１

ＴＯＣ：全有機性炭素濃度、Ｔ−Ｎ：総窒素濃度、ＮＨ_４−Ｎ：アンモニア態窒素濃度、ＮＯｘ−Ｎ：硝酸態・亜硝酸態窒素濃度、Ｔ−Ｐ：総リン濃度
【００３５】
この結果、本発明によれば、仕切板の設置と原水供給制御のみで、充分な脱窒効果が見られ、全窒素濃度１０ｍｇ／Ｌ程度の処理水を得ることができた。
【００３６】
【発明の効果】
本発明の単槽式膜分離活性汚泥法における汚水処理装置によれば、従来、単一槽での脱窒反応は、無酸素状態とするために膜洗浄用空気及びろ過の停止が必要であったが、仕切板の設置と反応槽液位制御を行うことにより、単一槽で無酸素状態の空間を得ることができ、硝化・脱窒を連続ろ過運転で効率的にすることができるものとなる。また、原水は無酸素部分に供給されるため、流入水中の有機炭素源を優先的に脱窒反応に利用できる。更には、膜による固液分離のため、微生物を高濃度に保持することで、短時間でのＤＯ消費と高い内生脱窒効果が期待できる。
【図面の簡単な説明】
【図１】本発明の単槽式膜分離活性汚泥法における汚水処理装置の一実施例を模式的に示す図である。
【図２】本発明の単槽式膜分離活性汚泥法における汚水処理装置の他の一実施例を模式的に示す図である。
【図３】膜分離ユニットを反応槽の中央部に配置した、本発明の汚水処理装置の一実施例における仕切板の配置を模式的に示す上面図及び側面図である。
【図４】膜分離ユニットを反応槽の中央部に配置した、本発明の汚水処理装置の他の一実施例における仕切板の配置を模式的に示す上面図及び側面図である。
【図５】膜分離ユニットを反応槽の片側に寄せて配置した、本発明の汚水処理装置の一実施例における仕切板の配置を模式的に示す上面図及び側面図である。
【符号の説明】
１反応槽
２膜分離ユニット
３吸引ポンプ
４散気管
５ブロワ
６レベルセンサ
７仕切板
８原水ポンプ
９原水槽[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a membrane separation activated sludge treatment apparatus and method capable of efficiently performing nitrogen removal together with membrane separation, and in particular, sewage such as sewage containing nitrogen in a single tank type reaction tank provided with an immersion membrane. The present invention relates to a membrane-separated activated sludge treatment apparatus and method for biologically treating and removing nitrogen continuously and efficiently biologically by the action of nitrifying bacteria and denitrifying bacteria in activated sludge.
[0002]
[Prior art]
Conventionally, when treating sewage wastewater containing nutrient salts such as nitrogen and phosphorus, an activated sludge method is used in which sewage is introduced into a reaction tank and aerated and agitated together with activated sludge for biological treatment. In recent years, the membrane separation activated sludge method has come to be used frequently in order to obtain clear treated water from the treated water treated by this activated sludge method. The membrane-separated activated sludge method has the advantage that a clarified treated water that does not require a sedimentation basin, has a small installation area, and does not contain solids can be obtained because the membrane separation device is immersed in the reaction tank and the treated water is discharged. is there.
[0003]
By the way, in the submerged membrane separation apparatus, in order to prevent sludge from adhering to the membrane surface, it is necessary to blow air from the lower air diffuser, and since the time zone during which the air is stopped cannot be filtered, Usually, the air is diffused almost continuously. However, in the activated sludge method, it is necessary to make the inside of the tank oxygen-free for the denitrification treatment. Therefore, in the membrane separation activated sludge method, it is necessary to ensure both aeration for cleaning the membrane surface during membrane filtration and an oxygen-free state for denitrification treatment. Various disclosures have been made. For example, Patent Document 1 discloses a processing apparatus in which two denitrification tanks for denitrification and a nitrification tank in which a membrane separation apparatus is immersed are provided, and wastewater is transferred between the tanks for processing. Patent Document 2 describes that a reaction tank provided with a membrane module is intermittently aerated to alternately perform an aerobic process and an oxygen-free process. Furthermore, in Patent Document 3, an immersion film is provided in a single reaction tank, and a blower for supplying oxygen and a blower for supplying nitrogen are provided. Oxygen is intermittently aerated from the activated sludge, and the immersion film is formed. On the other hand, a technique for supplying a nitrogen gas to clean a film is described.
[0004]
However, in the technique described in Patent Document 1, although it is possible to continuously process, it is necessary to provide a plurality of tanks, the equipment becomes large, and the merit as an immersion film cannot be exhibited. Equipment costs increase. In addition, since the technique described in Patent Document 2 is a single tank, it is possible to reduce the equipment, nitrification under aerobic conditions, membrane separation, and devagination treatment under anoxic conditions. Cannot be performed simultaneously and is not efficient. Furthermore, the technique described in Patent Document 3 requires an oxygen generation device that generates high-concentration oxygen gas by repeatedly adsorbing and releasing nitrogen gas in the air, making the device complicated and expensive. Each problem exists.
[0005]
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-244893 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-589 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-18468
[Problems to be solved by the invention]
In view of the above-described conventional problems, an object of the present invention is to provide an efficient membrane separation activated sludge apparatus and method capable of continuously performing an aerobic treatment and an oxygen-free treatment simultaneously. .
[0007]
[Means for Solving the Problems]
As a result of earnest research, the inventors of the present application divided a single reaction tank into two compartments with a partition plate, immersed the membrane separation unit in one compartment, and changed the liquid level or the vertical direction of the partition plate position. The state in which the liquid in both compartments can flow through the region above the partition plate and the state in which the liquid does not exist above the partition plate and the flow of liquid in both compartments is hindered due to the change in By creating the membrane separation unit continuously operating under the supply of air, the compartment other than the compartment where the membrane separation unit is immersed (hereinafter referred to as “nitrification / denitrification treatment compartment” for convenience). It is possible to supply or stop the air supply to the nitrification / denitrification section, thereby making it possible to make the nitrification / denitrification section aerobic or oxygen-free. Therefore, nitrification treatment and denitrification bacteria with nitrifying bacteria That denitrification processes can be performed in the same compartment confirmed experimentally by, the present invention has been completed.
[0008]
That is, the present invention is a membrane separation activated sludge treatment apparatus having a single reaction tank for performing an aerobic treatment and an oxygen-free treatment, a submerged membrane separation unit disposed in the reaction tank, and an aeration means. The reaction tank is divided into a plurality of compartments by a partition plate having a bottom portion spaced apart from the bottom surface of the reaction tank, and an immersion membrane separation unit and an aeration means are disposed in at least one of the plurality of compartments. Characterized in that liquid level control means or partition plate height control means for switching the remaining compartment from an aerobic state to an anaerobic state and from an anaerobic state to an aerobic state is provided. A membrane separation activated sludge treatment apparatus is provided. In the present specification, the “anoxic state” does not mean only a complete anoxic state but also a state where the oxygen concentration is low enough to reduce nitrate nitrogen to nitrogen molecules by the action of denitrifying bacteria. It is used in the meaning of inclusion.
[0009]
Here, an immersion membrane separation unit is arranged at the center of the reaction vessel, and a partition plate is arranged around the entire immersion membrane separation unit, or the entire circumference of the immersion membrane separation unit is surrounded by the partition plate and the vessel wall. A partition plate is arranged so as to be wrapped, or a part of the reaction tank has a partition partitioned by a tank wall and a partition plate of the reaction tank, and the submerged membrane separation unit and the aeration in the partition Preferably means are arranged.
[0010]
Further, the present invention is a membrane separation activated sludge method for performing an aerobic treatment and an oxygen-free treatment in a single reaction tank in which an immersion membrane separation unit is disposed, and the bottom of the reaction vessel is around the immersion membrane separation unit. Partitioned by a partition plate provided apart from the bottom surface, aerated from the bottom of the immersion membrane separation unit, and adjusted by the liquid level in the reaction tank or by changing the position of the partition plate, Membrane separation activity characterized by maintaining the aerobic state in the compartment where the separation unit is placed, and switching the other compartments from an aerobic state to an anaerobic state and from an anaerobic state to an aerobic state Provide sludge method.
[0011]
At this time, anaerobic compartments are intermittently formed and denitrification is performed, and the compartments where the submerged membrane separation units are placed are kept in an aerobic state while the other compartments are kept empty. It is preferable to switch to the oxygen state and simultaneously perform the denitrification treatment and membrane filtration.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a single tank membrane separation activated sludge apparatus and a membrane separation activated sludge method according to the present invention will be described based on the drawings.
[0013]
FIG. 1 shows a method for removing nitrogen in a single tank membrane separation activated sludge apparatus according to the present invention.
[0014]
In the membrane separation activated sludge apparatus of FIG. 1, an immersion type membrane separation unit 2 is provided in a single tank type reaction tank 1. A suction pump 3 is connected to the membrane separation unit 2 outside the reaction tank 1, and an aeration tube 4 for membrane cleaning and aerobic biological treatment is provided below the membrane separation unit 2. The air diffuser 4 is connected to a blower 5, and air (air) is supplied from the blower 5.
[0015]
With such a configuration, the treatment liquid in the reaction tank 1 is filtered by the membrane separation unit 2 while preventing the sludge substance and the like from adhering to the membrane surface of the membrane separation unit 2 by the air from the diffuser tube 4, and the filtration Water can be taken out of the tank by the suction pump 3.
[0016]
A raw water pump 8 is connected to the reaction tank 1, and a level sensor 6 and a partition plate 7 are provided. The level sensor 6 is a sensor that checks the liquid level, that is, the position of the liquid surface, and is well known per se. Further, as shown in the figure, the partition plate 7 is provided with a bottom portion separated from the bottom surface of the reaction tank. In the illustrated example, the partition plate 7 surrounds the entire periphery of the membrane separation unit 2 (“the entire periphery” is the entire periphery in the horizontal direction, and the upper and lower sides are open as shown). As shown in FIG. 3, the partition plate 7 is preferably two flat plates that cooperate with the tank wall to define a rectangular region. Alternatively, as shown in FIG. 4, the partition plate 7 may surround the entire periphery of the membrane separation unit 2. The raw water pump 8 is connected to the raw water tank 9, and the raw water in the raw water tank 9 is introduced into the reaction tank 1 by the raw water pump 8.
[0017]
With the above configuration, the raw solution is supplied to the reaction tank 1 and the raw water pump 8 is ON / OFF controlled by the level sensor 6 to control the supply amount, so that the liquid level in the tank is kept within a certain range. To be. The raw water pump 8 is set so that the pump is turned on by LWL (Low Water Level) and turned off by HWL (High Water Level).
[0018]
The reaction tank 1 contains sludge containing microorganisms, and these microorganisms act as organic matter-degrading bacteria and further as microorganisms-degrading bacteria for biological treatment. Therefore, it is preferable that the reaction tank 1 has no corners or irregularities on the inner surface so that sludge is not partially unevenly distributed and oxygen is supplied uniformly. As a result, the temperature and pH of the treatment liquid become uniform in the reaction tank 1, and the decomposition treatment can proceed stably. Microorganisms contained in sludge contribute to the degradation of soluble organic matter such as bacteria, yeasts and fungi including fungi, and are obtained from nature, such as soil, compost, and sludge, by accumulating culture and acclimatization. The It is also possible to isolate and use the main microbial group involved in the degradation from this conditioned solution. In addition, the sludge itself containing these microorganisms is well known in this field.
[0019]
Further, the membrane separation unit immersed in the reaction tank 1 may be one that uses a material that is not easily contaminated as the membrane itself, or one that has an appropriate gap between the membranes so that the surface of the membrane is not easily contaminated. preferable. The membrane separation unit 2 may be a module formed using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, or the like. From the economical point of view, a module using a microfiltration membrane or an ultrafiltration membrane that has a high filtration rate and can be made compact and is easy to maintain is preferable. The membrane may be a flat membrane, a hollow fiber membrane or the like. According to the submerged membrane separation unit, space can be saved. The submerged membrane separation unit itself used here is widely used in this field and is also commercially available.
[0020]
Next, the operation of this facility will be described. The sewage flowing into the sewage treatment facility such as a sewage treatment plant is introduced into the reaction tank 1 from the raw water tank 9 by the raw water pump 8 after separating and removing sand, garbage and the like in the pretreatment equipment. On the other hand, the sewage biologically treated in the reaction tank 1 is sucked by the suction pump 3 and discharged as treated water after final treatment such as disinfection.
[0021]
Specifically, from the state where the liquid level of the reaction tank 1 is in the HWL, the liquid level is higher than that of the partition plate 7, so there is no influence of the partition plate 7. From the unit accommodation section, it enters the nitrification / denitrification treatment section over the partition plate 7, descends in the section, and returns to the membrane unit accommodation section through the region below the partition plate 7). The ammonia component of the inflow water formed in the tank is oxidized to nitrate by the action of nitrifying bacteria. At this time, the raw water pump 8 is turned off when the liquid level is HWL, and the liquid level is gradually lowered by filtration.
[0022]
Next, when the liquid level becomes lower than that of the partition plate 7, the air from the air diffuser 4 stays in the space surrounded by the partition plate 7. Since air does not circulate in the region outside the partition plate 7, it can be made oxygen-free, and the denitrifying bacteria can reduce nitrate nitrogen to nitrogen molecules while using the organic matter in the inflowing water as an energy source. Occur. At this time, since the cleaning air of the membrane unit 2 does not change, it is not necessary to stop the filtration.
[0023]
Next, when the liquid level becomes LWL, the raw water pump 8 is turned on and stops when the liquid level becomes HWL.
[0024]
Thus, the aerobic operation and the oxygen-free / aerobic mixed operation can be continuously performed in a single tank depending on the liquid level, and the nitrogen component in the inflowing water can be efficiently removed.
[0025]
Note that in the above operation method, the present invention enables the flow of the reaction liquid through the region above the partition plate 7 by controlling the position of the liquid or the partition plate, thereby making it simple. It is characterized in that an aerobic state and an oxygen-free state are alternately produced in one nitrification / denitrification treatment section, and other treatment conditions and raw water pretreatment are performed under the same conditions as conventionally known methods. It can be carried out.
[0026]
In the specific example of FIG. 1, the partition plate 7 surrounds the entire periphery of the membrane unit 2 in the horizontal direction (the top and bottom are open), but the partition plate 7 substantially surrounds the periphery of the membrane separation unit 2. As long as it surrounds the membrane separation unit 2 in combination with a tank wall, for example, as shown in FIGS. Of these, one side may be a partition plate 7 and the other three sides may be enclosed by a tank wall).
[0027]
Further, in the specific example of FIG. 1, there is only one membrane unit accommodating section. However, in the case of large sewage treatment, etc., in order to increase the processing amount per unit time, the membrane unit is accommodated as desired. A plurality of compartments may be provided, and the membrane unit may be immersed in each of these compartments. In this case, it is possible to provide a plurality of nitrification / denitrification treatment sections. However, one nitrification / denitrification treatment section is preferable because the structure is simple and the uniformity of the reaction solution is easily secured.
[0028]
In addition, control of raw water inflow has various methods such as timer setting, pH control, ORP meter control, and is not limited to the present embodiment. Furthermore, in the specific example of FIG. 1, the filtration pressure is obtained by the suction pump 3, but even if the filtration pressure is obtained only by the difference between the water level in the reaction tank and the water level at the filtrate water outlet, that is, by the natural head. In addition, the filtration pressure may be obtained by further applying pressure from the stock solution side.
[0029]
【Example】
Hereinafter, the present invention will be described in more detail based on examples.
[0030]
Example 1 and Comparative Example 1
In the treatment apparatus shown in FIG. 1, raw water obtained by coagulating and precipitating the first settling basin effluent of the sewage treatment plant was treated. In addition, the partition plate 7 was installed when 150 days passed since the operation was started.
[0031]
In the coagulation-precipitation process, polysilicate iron is added to the coagulant to a concentration of 10 mg-Fe / L in a jet-stirring type solid-liquid separator that simultaneously performs floc formation and precipitation using a perforated plate and an inclined tube. Was carried out under conditions of 1.5 hours.
[0032]
The treated water after the coagulation sedimentation treatment was supplied to the reaction tank 1. The reaction tank 1 has an operating capacity of 500 L, and the capacity divided by the partition plate 7 is a ratio of the inside of the partition plate 7 (section in which the membrane separation unit 2 is arranged): outside (other portions) = 3: 1. A partition plate was installed. The separation membrane of the membrane separation unit 2 includes a PVDF MF membrane with a nominal pore diameter of 0.1 μm (10 flat membranes with an effective area of 0.6 m ² in a case so that the distance between the membranes is maintained at 7.5 mm). Loading) was used.
[0033]
Filtration was performed with an aeration air amount of 100 L / min and a filtered water amount of 2.5 m ³ / day. MSLL (Mixed Liquid Suspended Solid) concentration is 12000-15000 mg / L, under the biological treatment conditions of HRT (hydraulic residence time) 4.8 hours, operation without partition for the first 150 days (comparison) Example 1) For the next 150 days, after installing a partition plate and performing an aerobic operation in which the liquid level rises above the partition plate 7 for 30 minutes, the liquid level is switched below the top of the partition plate 7. The operation in which the partial aerobic / anoxic mixing operation was performed for 30 minutes was repeated (Example 1), and the operation was performed for 300 days in total. The results are shown in Table 1 below.
[0034]
[Table 1]
Table 1

TOC: total organic carbon concentration, TN: total nitrogen concentration, NH ₄ -N: ammonia nitrogen concentration, NOx-N: nitrate / nitrite nitrogen concentration, TP: total phosphorus concentration
As a result, according to the present invention, a sufficient denitrification effect was observed only by installing the partition plate and controlling the raw water supply, and treated water having a total nitrogen concentration of about 10 mg / L could be obtained.
[0036]
【The invention's effect】
According to the sewage treatment apparatus in the single tank membrane separation activated sludge method of the present invention, conventionally, the denitrification reaction in a single tank has been required to stop the membrane cleaning air and filtration in order to make it oxygen-free. However, by installing the partition plate and controlling the reaction tank liquid level, an oxygen-free space can be obtained in a single tank, and nitrification and denitrification can be efficiently performed by continuous filtration operation. It becomes. Moreover, since raw | natural water is supplied to an anoxic part, the organic carbon source in inflow water can be utilized preferentially for denitrification reaction. Furthermore, because of the solid-liquid separation by the membrane, it is possible to expect DO consumption and a high endogenous denitrification effect in a short time by keeping the microorganisms at a high concentration.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an embodiment of a sewage treatment apparatus in the single tank membrane separation activated sludge method of the present invention.
FIG. 2 is a diagram schematically showing another embodiment of the sewage treatment apparatus in the single tank membrane separation activated sludge method of the present invention.
FIGS. 3A and 3B are a top view and a side view schematically showing the arrangement of partition plates in one embodiment of the sewage treatment apparatus of the present invention in which a membrane separation unit is arranged at the center of a reaction tank.
FIGS. 4A and 4B are a top view and a side view schematically showing the arrangement of partition plates in another embodiment of the sewage treatment apparatus of the present invention in which a membrane separation unit is arranged at the center of a reaction tank. FIGS.
FIGS. 5A and 5B are a top view and a side view schematically showing the arrangement of partition plates in an embodiment of the sewage treatment apparatus of the present invention in which a membrane separation unit is arranged close to one side of a reaction tank.
[Explanation of symbols]
1 Reaction tank 2 Membrane separation unit 3 Suction pump 4 Aeration pipe 5 Blower 6 Level sensor 7 Partition plate 8 Raw water pump 9 Raw water tank

Claims

A membrane separation activated sludge treatment apparatus having a single reaction tank for performing an aerobic treatment and an anaerobic treatment, an immersion membrane separation unit disposed inside the reaction tank, and an aeration means, The bottom part is divided into a plurality of compartments by a partition plate provided apart from the bottom surface of the reaction tank, and the submerged membrane separation unit and the aeration means are arranged in at least one of the compartments, and the remaining compartments Is provided with liquid level control means or partition plate height control means for switching the aerobic state to the anaerobic state and from the anaerobic state to the aerobic state. apparatus.

The apparatus according to claim 1, wherein an immersion membrane separation unit is disposed at a central portion of the reaction tank, and the entire periphery of the immersion membrane separation unit is surrounded by a partition plate or the partition plate and the tank wall.

The apparatus according to claim 1 or 2, wherein there is one section for switching from an aerobic state to an anoxic state and from an anaerobic state to an aerobic state.

The apparatus according to claim 1, wherein a part of the reaction tank has a section partitioned by a tank wall of the reaction tank and a partition plate, and the submerged membrane separation unit and the aeration means are disposed in the section.

A membrane separation activated sludge method that performs aerobic treatment and oxygen-free treatment in a single reaction tank in which a submerged membrane separation unit is disposed, and the bottom of the submerged membrane separation unit is provided with the bottom part separated from the bottom surface of the reaction tank. The submerged membrane separation unit was placed by aerating from below the submerged membrane separation unit and by adjusting the liquid level in the reaction vessel or changing the position of the partition plate. A membrane-separated activated sludge treatment method characterized by switching the other compartments from an aerobic state to an anoxic state and from an anaerobic state to an aerobic state while maintaining the inside of the compartment in an aerobic state.

The method according to claim 5, wherein anaerobic compartments are intermittently formed and denitrification treatment is performed.

6. The filtration by the submerged membrane separation unit is continued even after the inside of the compartment in which the submerged membrane separation unit is disposed is maintained in an aerobic state and the other compartment is switched to the oxygen-free state. Or the method of 6.

The method according to any one of claims 5 to 7, wherein the number of sections for switching from an aerobic state to an anaerobic state and from an anaerobic state to an aerobic state is one.