JP4124957B2 - Filter body washing method and apparatus - Google Patents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
【０００１】
【発明の属する技術分野】
本発明は、汚水処理に関するもので、特に活性汚泥の固液分離や余剰汚泥の濃縮等に使用する通水性ろ過体の洗浄に関するものであり、有機性工業廃水や生活排水等の処理に用いることができる通水性ろ過体を用いる有機性廃水の処理方法及び装置に関する。
【０００２】
【従来の技術】
従来、活性汚泥による水処理では、処理水を得るためには活性汚泥の固液分離を行わなければならない。通常では、活性汚泥を沈澱池に導入させ、重力沈降によって、汚泥を沈降させ、上澄液を処理水として沈澱池から流出させる方法が用いられる。この場合、活性汚泥を沈降させるため十分に広い沈降面積を有し、かつ十分な長さの滞留時間を確保できる沈澱池が必要であり、処理装置の大型化と設置容積の増大要因となっている。また、活性汚泥がバルキング等、沈降性の悪化した場合、沈澱池より汚泥が流出し、処理水の悪化を招く。
【０００３】
近年、沈澱池に代わって膜分離による活性汚泥の固液分離を行う手法も用いられている。この場合、固液分離用膜として、一般的に精密ろ過膜や限外ろ過膜が用いられる。
その際、ろ過分離手段としてポンプによる吸引や加圧が必要であり、通常数十ｋＰａ〜数百ｋＰａの圧力で行うため、ポンプによる動力が大きく、ランニングコストの増大となっている。また、膜分離でＳＳの全くない清澄な処理水が得られる一方、透過Ｆｌｕｘが低く、膜汚染を防止するため、定期的に薬洗する必要がある。
【０００４】
最近、膜分離による活性汚泥の固液分離法の一方法として、曝気槽に不織布等の通気性シートからなるろ過体を浸漬させ、低い水頭圧でろ過水を得る方法が提案されている。この方法では、ろ過体表面に汚泥のダイナミックろ過層が形成するように活性汚泥混合液の流れ設定したろ過分離手段で清澄なろ過水を得るものである。この方法では、ろ過Ｆｌｕｘ低下時にろ過体を洗浄する手段としては、ろ過体下部に設置した散気管より曝気するようにしており、それによりろ過体表面に形成された汚泥のダイナミックろ過層が容易に剥離するので、安定したろ過Ｆｌｕｘが得られるとしている。
【０００５】
【発明が解決しようとする課題】
しかし、前記ろ過体を曝気槽に浸漬しておき、ろ過Ｆｌｕｘ低下時にだけ空洗による洗浄を行う方式では、ろ過Ｆｌｕｘが徐々に低下することが認められた。すなわち、処理日数の増加にともない、空洗直後のろ過Ｆｌｕｘが初期値に比べ徐々に低下した。また、初期値に対する割合を示す回復率も同様に低下し、空洗回数の増加にともない、その低下の程度が大きくなる。ろ過体を曝気槽に浸漬した場合、ろ過体表面に形成された汚泥のダイナミックろ過層が空洗によって完全に剥離されなかった時、微細な汚泥フロックがろ過体表面に付着し、長期ろ過にともない、付着汚泥の微細化でろ過体表面の閉塞を引き起こす。また、空洗直後からダイナミックろ過層が形成されるまでの初期ろ過において、ろ過体表面を通過した汚泥が内部に堆積し、時間経過とともに徐々に濃縮されるため、ろ過抵抗が増大し、ろ過Ｆｌｕｘを著しく低下させる原因となる。
この結果、空洗では良好な洗浄効果が得られず、経過時間とともにろ過Ｆｌｕｘの低下が大きくなり、安定した処理を得ることが困難となる。
【０００６】
本発明は、このような従来の課題に鑑みてなされたものであり、通水性ろ過体の内部に対し水逆洗を行い、初期値とほぼ同様なろ過Ｆｌｕｘを、長期間にわたって安定して得られ、しかも、安定した水質も得ることができる生物処理汚水の固液分離装置のろ過体の洗浄方法及び装置を得ることを課題とする。
【０００７】
【課題を解決するための手段】
本発明者等は、前記の課題により、処理時間の経過と関係なく、常にろ過体の表面に均一なダイナミックろ過層を形成する方法について種々研究した。
そして、ろ過体の内部に対して処理水槽からのろ過水又は薬品洗浄液で逆洗すれば、通常の空洗では完全に剥離できなかったろ過体表面及び内部の微細なフロック、あるいは生物スラムも容易に洗い落とすことが可能になることが確認された。
本発明は、このような知見に基づいてなされたものであり、次の構成からなるものである。
【０００８】
（１）原水を流入させて好気的に活性汚泥による処理を行う生物反応槽からの活性汚泥混合液を、通水性ろ過体を設置したろ過分離槽に供給し、該ろ過分離槽で該通水性ろ過体表面に汚泥のダイナミックろ過層を形成させてろ過を行ってろ過水を得、ろ過後の活性汚泥混合液を生物反応槽に返送する活性汚泥混合液の固液分離法において、該ろ過分離槽内に浸漬された通水性ろ過体であって、該ろ過体の表面に該活性汚泥の付着によりダイナミックろ過を行う通水性ろ過体を具備し、前記通水性ろ過体によって汚泥のダイナミックろ過層を形成するろ過体表面とろ過水を得るろ過体内部を構成し、該通水性ろ過体には、ろ過体の内部に洗浄水を送るように逆洗水ラインと、該ろ過体内部から該内部にある汚泥をろ過体外部に排出する逆洗排水を前記生物反応槽に戻すように逆洗排水ラインとが夫々接続され、前記ろ過分離槽に、前記活性汚泥混合液を流入させ、ろ過時は該ろ過体内部からろ過水を流出させ、ろ過体洗浄時は、ろ過分離槽内の活性汚泥混合液を生物反応槽に完全に返送した後、あるいはろ過分離槽にろ過水を満たした時点で前記逆洗水ラインから洗浄水を供給して逆洗し、排出される逆洗排水を前記生物反応槽に返送することを特徴とする有機性廃水の処理方法。
（２）ろ過体内部への水逆洗は、ろ過体上部の逆洗水ラインにろ過水あるいは薬品洗浄液を流入させ、ろ過体下部の逆洗排水ラインより逆洗排水を排出することを特徴とする前記（１）記載の有機性廃水の処理方法。
【０００９】
（３）原水を流入させて好気的に活性汚泥による処理を行う生物反応槽と、該生物反応槽で得られる活性汚泥を分離してろ過水を得るろ過分離槽からなる処理装置において、該ろ過分離槽内に浸漬された通水性ろ過体であって、該ろ過体の表面に該活性汚泥の付着によりダイナミックろ過を行う通水性ろ過体を具備し、前記通水性ろ過体によって汚泥のダイナミックろ過層を形成するろ過体表面とろ過水を得るろ過体内部を構成し、該ろ過体の内部に洗浄水を送るよう接続された逆洗水ラインを具備し、該ろ過体に接続され、該ろ過体内部より、該内部にある汚泥をろ過体外部に排出する逆洗排水ラインを具備し、該逆洗排水ラインは、排出された逆洗排水を前記生物反応槽に戻すラインであることを特徴とする有機性廃水処理装置。
（４）前記通水性ろ過体の下方に空洗用の空洗散気管を具備することを特徴とした前記（３）記載の有機性廃水処理装置。
【００１０】
【発明の実施の形態】
本発明によれば、通水性ろ過体（以下単に「ろ過体」とも言う）を用い、ろ過体表面に汚泥のダイナミックろ過層を形成してろ過水を得る汚泥混合液の固液分離方法において、ろ過分離槽に浸漬する通水性ろ過体モジュールに対し、定期的にろ過分離槽内の汚泥混合液を一旦全部生物反応槽へ返送した後、あるいはろ過分離槽にろ過水を満たした時点で、処理水槽のろ過水を用い、ろ過体モジュール内部に対し水逆洗を行えば、ろ過体表面に付着した微細な汚泥粒子を容易に落とすことができ、かつろ過体内部に堆積した汚泥を逆洗によって外部に排出することができる。
この結果、ろ過体表面に汚泥微粒子閉塞による表面抵抗及び、ろ過体内部汚泥堆積による内部抵抗のいずれも低減することができ、ろ過Ｆｌｕｘがほぼ初期値に回復する。
【００１１】
なお、ここでいう「水逆洗」とは、通水性ろ過体表面からろ過体内部へ通るろ過に対し、ろ過体内部の一端へ洗浄水を供給してろ過体内部を通過させて洗浄を行い、ろ過体内部の他端から洗浄廃水を排出する操作をいう。
本発明において、ろ過体内部に対して水逆洗を行う目的は、次の２点にある。（イ）洗浄水をろ過体内部からろ過体の表面を通過させ、表面の内部に付着した微細な汚泥フロックを剥離させること。（ロ）ろ過体内部に侵入した汚泥を内部に堆積しないうちに洗浄水とともに外部に排出すること。この後者の場合、侵入汚泥を内部からろ過体表面を通過させて外部に出すことは困難であり、不合理であるため、上記した水逆洗の手段が有効と考えて、本発明方法を完成したのである。
【００１２】
本発明においては、水逆洗を行う際のろ過分離槽の状態として、次の２種の場合を設定している。
１）ろ過分離槽内の汚泥混合液を生物反応槽へ完全に返送した場合（時点）。
２）ろ過分離槽内にろ過水を満たした場合。
このケース１）の場合においては、ろ過体内部にろ過水の残留がなく、ほぼ空洞であるため、ろ過体表面にろ過分離槽内に水を満たした場合に生じる水の抵抗を受けず、内部に流れる逆洗水の流速が大きく、ろ過体内部に堆積している汚泥、及びろ過体内部表面に付着している汚泥を効率よく剥離させ、完全に外部つまり生物反応槽に排出することができる。また、この場合、逆洗水量はろ過体内部のろ過水室容積の数倍程度であれば、良好な洗浄効果が得られるので、少ない逆洗水量で対応できる。
また、ケース２）の場合においては、ろ過分離槽内に水を満たしたことで、ろ過体表面に付着した微細汚泥フロックを溶解させ、ろ過体表面への付着力を弱める効果がある。この時に逆洗水をろ過体内部に供給すれば、ろ過体表面に付着した汚泥を容易に剥離させ、逆洗排水と共に生物反応槽に排出することができる。また、ろ過体内部の堆積汚泥もろ過分離槽内のろ過水がろ過体内部への侵入により希釈され、逆洗水の供給で堆積した汚泥を逆洗排水と共に容易に生物反応槽に排出することができる。
【００１３】
水逆洗は、ろ過体上部の逆洗ラインにろ過水を注入し、下部の取水ラインより逆洗排水を排出し、生物反応槽に返送される構造により、ろ過体内部の堆積汚泥を容易に排出でき、該汚泥を再度ろ過体内部に堆積しないため、常時安定したろ過Ｆｌｕｘが得られる。
さらに水逆洗時、薬品洗浄液を逆洗水として用いれば、ろ過体表面に生物スラムが付着しても容易に洗い落とすことができる。長期ろ過にともなう生物スラム付着によるろ過Ｆｌｕｘの低下を抑制することができる。
薬品洗浄液としては、次亜塩素酸水溶液、アルカリ水溶液、酸水溶液、あるいはオゾン水溶液、過酸化水素水溶液等のいずれを用いることもできる。薬品洗浄液の選定及び洗浄頻度は処理対象汚泥、汚染状況より判断し、数日から数ヶ月に１回程度で行うのが好ましい。
【００１４】
通水性ろ過体としては、通水性で耐圧性の多孔性表面をもつシート状体であれば、不織布、織布、金属網等のいずれを用いても同様な効果が得られる。そして、ろ過体形状としては、平面型、円筒型、中空型のいずれを用いることも可能であり、複数個を束ねてモジュールろ過体として用いることが可能である。
また、ろ過体モジュール構造としては、通水性ろ過体を保持する支持板は、できるだけ中空型であることが望ましい。該ろ過体モジュール上部に逆洗水が支持板内部に注入できる逆洗水流入管を有し、ろ過水を得る取水管は、該ろ過体モジュール下部に設置されており、逆洗排水の排出ラインが取水管に接続され、逆洗時はバブルの切り替えによって、逆洗排水が生物処理槽に返送できる構造であるものが望ましい。
通水性ろ過体によるろ過分離できる対象汚泥としては、活性汚泥、凝集汚泥、初沈汚泥等の何れも可能である。また、ＳＳの高い排水、河川水等の固液分離として用いることも可能である。
【００１５】
図面により、本発明をより具体的に説明する。
図１は、団地下水に対する本発明による処理法の一例をフローシートで示すものである。
図１に示す如く、流入原水１が生物反応槽２に流入し、生物反応槽２において曝気ブロワ４より散気管３へ空気を供給することにより活性汚泥による好気処理を行う。活性汚泥混合液が、汚泥供給ポンプ５よりろ過分離槽１０に供給される。ろ過分離槽１０に流入した活性汚泥混合液は、通水性ろ過体１１より水頭圧△Ｈでろ過され、ろ過水取水弁１７を開放し、ろ過水取水管１４を通じて排出され、処理水槽１５に流入し、処理水２１として取り出される。なお、ろ過後の汚泥混合液は、汚泥循環液１９として生物反応槽２に返送される。
【００１６】
ろ過体１１の洗浄法として、ろ過体浸漬中では通常、空洗によるろ過Ｆｌｕｘの安定化を行う。この時、空洗ブロワ９から数時間毎に１回の割合でろ過体下方の空洗散気管８に送気して行われる。
ろ過水を用いた水逆洗は、数週間に１回の頻度で定期的に行う。水逆洗時は、ろ過槽１０内の混合液汚泥を、汚泥混合液供給バルブ６と汚泥混合液移送バルブ７の切り替えで、汚泥混合液ポンプ５より一旦生物反応槽２へ返送した後、逆洗ポンプ１２を起動させ、処理水槽１５の処理水（ろ過水）２１をろ過体１１上方の逆洗ライン１３を通じてろ過体１１の内部に供給される。
逆洗排水は、ろ過体１１の下部の取水管より排出し、逆洗排水返送弁１６を開き、逆洗排水返送ライン１８を通じて生物反応槽２に返送される。この場合は、ろ過水取水弁１７は閉となる。なお、この水逆洗時、ろ過体１１の内部からその表面に出てろ過分離槽１０に排出される逆洗排水は、常時汚泥混合液用ポンプ５より生物反応槽２に返送されようにする。
逆洗操作終了後は再び生物反応槽２の汚泥混合液をろ過分離槽１０に供給すれば、通水性ろ過体１１からのろ過水をろ過水取水弁１７を経て連続して得られる。
【００１７】
なお、図２において、１０はろ過分離槽、１３は逆洗水ライン、２２は逆洗排水ラインであり、円筒形のろ過体（織布）１１は、ろ過体支持部２３のスペーサ２４上にゆるやかに嵌着されている。逆洗水は逆洗水ライン１３から逆洗排水ライン２２へ流出するとともに、スペーサ２４を通してろ過体（織布）１１の内部に堆積した汚泥及び表面に付着した汚泥粒子を洗い落としながら流れ、ろ過体の内部の汚泥は洗浄排水とともに逆洗排水ライン２２から外部に出て、ろ過体１１の表面に付着した汚泥粒子でろ過体１１内部からの逆洗水で外に流れ出したものはろ過分離槽１０の底部へ流下する。
【００１８】
【実施例】
以下実施例により本発明を具体的に説明する。ただし本発明はこの実施例のみに限定されるものではない。
【００１９】
実施例１
（処理方法）
団地下水について、図１に示すフローシートで表わされる本発明による処理法により処理を行った。
この団地下水の水質は、第１表に示すとおりである。
団地下水を活性汚泥を用いて処理する生物反応槽は、活性汚泥のＭＬＳＳが約３５００ｍｇ／リットルであった。前記生物反応槽から出る活性汚泥混合液を下記に示すろ過分離槽に導き、処理水を得た。
前記ろ過分離槽で得られる処理水の水質は、第１表に示すとおりである。
【００２０】
（ろ過分離槽）
ろ過分離槽としては、有効面積０．３ｍ2 、有効容積０．６ｍ3 の固液分離槽を用いた。ろ過分離槽１０内部に有効面積１ｍ2 ／枚の平面形織布ろ過体５枚をろ過体モジュールとして浸漬設置した。織布の素材としては、ポリエステル製で、目開き２００メッシュ、厚み０．０９ｍｍのものを用いた。なお、ろ過時の平均水頭圧を約１０ｃｍとした。
このろ過分離槽の処理条件を表で示すと、第２表のとおりである。
また、第３表にろ過体の空洗及びろ過水による逆洗の条件を示す。
【００２１】
【表１】
【表２】
【表３】
（処理結果）
図３にこの実施例におけるろ過Ｆｌｕｘの経過を示す。
処理対象とする活性汚泥のＭＬＳＳが約３５００ｍｇ／リットルであり、２ヶ月の処理期間中、ろ過Ｆｌｕｘが４．２〜４．８ｍ／ｄに維持でき、２週間に１回のろ過水による逆洗を加えたことにより、安定したろ過Ｆｌｕｘが得られた。なお、ろ過水の濁度が処理期間中で平均５度前後であり、清澄であった。
【００２５】
比較例１
実施例１と同様な操作条件で、ろ過体モジュール内部に対する定期的な水逆洗を行わないで、活性汚泥混合液のろ過処理を行った。その場合の平均ろ過Ｆｌｕｘの経過を図４に示す。
平均ろ過Ｆｌｕｘは、処理開始時に実施例１とほぼ同様の約４．８ｍ／ｄであった。しかし、処理開始から約１０日後に、ろ過Ｆｌｕｘが急激に低下した。これは、ろ過体表面への汚泥微粒子付着及びろ過体内部の汚泥堆積に起因するものである。
その結果、通常の空洗を４時間に１回の頻度で実施しても、ろ過Ｆｌｕｘの回復が得られず、処理開始から２０日後に、ろ過Ｆｌｕｘが初期値の半分以下の１．８ｍ／ｄに低下した。その後も徐々に低下し、１ｍ／ｄ以下となった。なお、ろ過水濁度は常時１０度以下で実施例と大きな差異は認められなかった。
【００２６】
【発明の効果】
本発明によれば、通水性ろ過体を用い、ろ過体表面に汚泥のダイナミックろ過層を形成してろ過水を得る汚泥混合液の固液分離方法において、ろ過分離槽に浸漬するろ過体モジュールに対し、定期的にろ過分離槽内の汚泥混合液を一旦全部生物反応槽へ返送した後、処理水槽のろ過水を用い、ろ過体モジュール内部に水逆洗を行えば、ろ過体表面に付着した微細な汚泥粒子を容易に落とすことができ、かつ、ろ過体内部に堆積した汚泥を、逆洗によって外部に排出することができる。この結果、ろ過体表面の汚泥微粒子閉塞による表面抵抗及び、ろ過体内部汚泥堆積による内部抵抗のいずれも低減することができ、ろ過Ｆｌｕｘがほぼ初期値に回復する。
【００２７】
水逆洗は、ろ過体上部の逆洗ラインにろ過水を注入し、下部の取水ラインより逆洗排水を排出し、生物反応槽に返送される方式により、ろ過体内部の堆積汚泥を容易に排出でき、該汚泥を再度ろ過体内部に堆積しないため、常時安定したろ過Ｆｌｕｘが得られる。さらに水逆洗時、薬品洗浄液を逆洗水として用いれば、ろ過体表面に生物スラムが付着しても容易に洗い落とすことができる。すなわち、長期ろ過にともなう生物スラム付着による、ろ過Ｆｌｕｘの低下を抑制することができる。
【図面の簡単な説明】
【図１】本発明の通水性ろ過体の洗浄装置を含む生物処理汚水の固液分離装置の説明図である。
【図２】本発明のろ過体の洗浄装置の逆洗処理状況の説明図である。
【図３】本発明の一実施例の経過日数と平均ろ過Ｆｌｕｘの関係を示すグラフである。
【図４】比較例１の経過日数と平均ろ過Ｆｌｕｘの関係を示すグラフである。
【符号の説明】
１ 流入原水
２ 生物反応槽
３ 散気管
４ 曝気ブロワ
５ 汚泥混合液用ポンプ
６ 汚泥混合液供給バルブ
７ 汚泥混合液返送バルブ
８ 空洗散気管
９ 空洗ブロワ
１０ ろ過分離槽
１１ 通水性ろ過体
１２ 逆洗ポンプ
１３ 逆洗ライン
１４ ろ過水取水管
１５ 処理水槽
１６ 逆洗排水返送弁
１７ ろ過水取水弁
１８ 逆洗排水返送ライン
１９ 汚泥循環液
２０ 排泥ライン
２１ 処理水
２２ 逆洗排水ライン
２３ ろ過体支持部
２４ スペーサ
２５ 織布[0001]
BACKGROUND OF THE INVENTION
The present invention relates to sewage treatment, and particularly relates to washing of water-permeable filter used for solid-liquid separation of activated sludge and concentration of excess sludge, and is used for treatment of organic industrial wastewater and domestic wastewater. The present invention relates to a method and an apparatus for treating organic wastewater using a water-permeable filter capable of producing water.
[0002]
[Prior art]
Conventionally, in water treatment with activated sludge, solid sludge separation of activated sludge has to be performed in order to obtain treated water. Normally, a method is used in which activated sludge is introduced into a sedimentation basin, the sludge is sedimented by gravity sedimentation, and the supernatant is discharged from the sedimentation basin as treated water. In this case, there is a need for a sedimentation basin that has a sufficiently large sedimentation area to settle the activated sludge and can secure a sufficiently long residence time, which is a factor in increasing the size of the processing apparatus and increasing the installation volume. Yes. Moreover, when activated sludge deteriorates sedimentation property, such as a bulking, sludge flows out from a sedimentation basin and causes deterioration of treated water.
[0003]
In recent years, a method of performing solid-liquid separation of activated sludge by membrane separation instead of a sedimentation basin has been used. In this case, a microfiltration membrane or an ultrafiltration membrane is generally used as the solid-liquid separation membrane.
At that time, suction or pressurization by a pump is required as a filtration separation means, and since it is usually performed at a pressure of several tens of kPa to several hundred kPa, the power of the pump is large and the running cost is increased. In addition, clear treated water having no SS is obtained by membrane separation, while permeation flux is low, and it is necessary to periodically wash the medicine in order to prevent membrane contamination.
[0004]
Recently, as a method of solid-liquid separation of activated sludge by membrane separation, a method has been proposed in which a filter body made of a breathable sheet such as a nonwoven fabric is immersed in an aeration tank to obtain filtered water with a low head pressure. In this method, clear filtered water is obtained by filtration separation means in which the flow of the activated sludge mixed liquid is set so that a sludge dynamic filtration layer is formed on the surface of the filter body. In this method, as a means for washing the filter body when the filtration flux is lowered, aeration is performed from an air diffuser installed at the lower part of the filter body, so that a sludge dynamic filtration layer formed on the surface of the filter body can be easily obtained. Since it exfoliates, it is said that a stable filtered flux is obtained.
[0005]
[Problems to be solved by the invention]
However, in the method in which the filter body is immersed in an aeration tank and washing is performed by washing with air only when the filtration flux is lowered, it is recognized that the filtration flux gradually decreases. That is, with the increase in the number of treatment days, the filtration flux immediately after the flushing gradually decreased compared to the initial value. In addition, the recovery rate indicating the ratio with respect to the initial value is similarly decreased, and the degree of the decrease is increased as the number of times of washing is increased. When the filter is immersed in an aeration tank, when the sludge dynamic filtration layer formed on the filter surface is not completely removed by air washing, fine sludge flocs adhere to the filter surface, resulting in long-term filtration. The surface of the filter body is clogged by the refinement of the attached sludge. In addition, in the initial filtration from immediately after the washing to the formation of the dynamic filtration layer, the sludge that has passed through the surface of the filter body is accumulated inside and gradually concentrated over time, so that the filtration resistance increases and the filtration flux Cause a significant decrease in
As a result, a good cleaning effect cannot be obtained by empty washing, and the drop in the filtration flux increases with the elapsed time, making it difficult to obtain a stable treatment.
[0006]
The present invention has been made in view of the above-described conventional problems, and the inside of a water-permeable filter body is back-washed with water to obtain a filtration flux almost the same as the initial value stably over a long period of time. Furthermore, it is an object of the present invention to obtain a method and an apparatus for cleaning a filter body of a solid-liquid separator for biologically treated sewage that can obtain stable water quality.
[0007]
[Means for Solving the Problems]
The present inventors have made various studies on methods for always forming a uniform dynamic filtration layer on the surface of the filter body regardless of the lapse of processing time due to the above-mentioned problems.
And if the inside of the filter body is back-washed with filtered water from the treatment water tank or chemical cleaning liquid, the surface of the filter body and fine flocs inside the body that could not be completely removed by normal air washing, or biological slums are easy. It was confirmed that it was possible to wash it off.
The present invention has been made based on such knowledge and has the following configuration.
[0008]
(1) Supply the activated sludge mixed liquid from the biological reaction tank in which raw water is introduced and aerobically treat with activated sludge to the filtration separation tank in which the water-permeable filter is installed. In the solid-liquid separation method of the activated sludge mixed liquid, a sludge dynamic filtration layer is formed on the surface of the aqueous filter body to obtain filtered water by filtration, and the filtered activated sludge mixed liquid is returned to the biological reaction tank. A water-permeable filter immersed in a separation tank, comprising a water-permeable filter that performs dynamic filtration by adhering the activated sludge to the surface of the filter, and the sludge dynamic filtration layer by the water-permeable filter The filter body surface and the inside of the filter body for obtaining filtrate water are formed, and the water-permeable filter body includes a backwash water line so as to send wash water to the inside of the filter body, and the inside of the filter body from the inside of the filter body. Backwash drainage to discharge sludge in the filter A backwash drainage line is connected so as to return to the biological reaction tank, the activated sludge mixed solution is allowed to flow into the filtration separation tank, and filtered water is allowed to flow out from the inside of the filter body during filtration. When the activated sludge mixture in the filtration / separation tank is completely returned to the biological reaction tank, or when the filtration / separation tank is filled with filtered water, the washing water is supplied from the backwash water line and backwashed. A method for treating organic wastewater, wherein the discharged backwash wastewater is returned to the biological reaction tank.
(2) Water backwashing into the filter body is characterized in that filtered water or chemical cleaning liquid is allowed to flow into the backwash water line at the top of the filter body and backwash drainage is discharged from the backwash drainage line at the bottom of the filter body. The method for treating organic wastewater according to (1) above.
[0009]
(3) In a treatment apparatus comprising a bioreactor tank in which raw water is introduced and aerobically treated with activated sludge and a filtration separation tank for separating activated sludge obtained in the bioreactor tank to obtain filtered water, A water-permeable filter immersed in a filtration separation tank, comprising a water-permeable filter that performs dynamic filtration by adhering the activated sludge to the surface of the filter, and sludge dynamic filtration by the water-permeable filter The surface of the filter body forming a layer and the inside of the filter body for obtaining filtered water are constituted, and the backwash water line connected to send the wash water to the inside of the filter body is provided, connected to the filter body, and the filtration It comprises a backwash drainage line that discharges sludge inside the filter body from the inside of the body, and the backwash drainage line is a line that returns the drained backwash drainage to the biological reaction tank. Organic wastewater treatment equipment.
(4) The organic wastewater treatment apparatus as described in (3) above, further comprising an air washing air diffuser for air washing below the water-permeable filter.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, in a solid-liquid separation method of a sludge mixed liquid that uses a water-permeable filter body (hereinafter also simply referred to as “filter body”) and forms a sludge dynamic filtration layer on the surface of the filter body to obtain filtered water, For the water-permeable filter module immersed in the filtration / separation tank, once the sludge mixture in the filtration / separation tank is periodically returned to the biological reaction tank or when the filtration / separation tank is filled with filtered water, By using the filtered water in the aquarium and backwashing the inside of the filter body module, fine sludge particles adhering to the surface of the filter body can be easily removed, and sludge accumulated inside the filter body can be removed by backwashing. It can be discharged to the outside.
As a result, both the surface resistance due to sludge fine particle blockage on the filter body surface and the internal resistance due to accumulation of sludge inside the filter body can be reduced, and the filtration flux is almost restored to the initial value.
[0011]
In addition, “water backwashing” as used herein refers to the filtration that passes from the surface of the water-permeable filter body to the inside of the filter body, and supplies the wash water to one end inside the filter body to allow the inside of the filter body to be washed. An operation for discharging washing wastewater from the other end inside the filter body.
In the present invention, there are the following two points for the purpose of backwashing the inside of the filter body. (B) The cleaning water is allowed to pass from the inside of the filter body through the surface of the filter body, and the fine sludge floc adhering to the inside of the surface is peeled off. (B) Discharge sludge that has entered the filter body to the outside together with cleaning water before it accumulates inside. In this latter case, it is difficult and unreasonable to pass the invading sludge from the inside through the surface of the filter body, and it is unreasonable. It was.
[0012]
In the present invention, the following two cases are set as the state of the filtration separation tank when performing water backwashing.
1) When the sludge mixture in the filtration separation tank is completely returned to the biological reaction tank (time point).
2) When the filtration separation tank is filled with filtered water.
In the case of this case 1), there is no residue of filtered water inside the filter body, and it is almost hollow, so it is not subject to the resistance of water that occurs when the filter separation tank is filled with water. The flow rate of backwash water flowing through the filter is large, and the sludge accumulated inside the filter body and the sludge adhering to the inner surface of the filter body can be efficiently separated and completely discharged to the outside, that is, the biological reaction tank. . In this case, if the amount of backwash water is about several times the volume of the filtrate water chamber inside the filter body, a good cleaning effect can be obtained, so that it can be handled with a small amount of backwash water.
In case 2), the filtration separation tank is filled with water, so that the fine sludge flocs adhering to the surface of the filter body are dissolved, and the adhesive force on the surface of the filter body is weakened. At this time, if backwash water is supplied to the inside of the filter body, sludge adhering to the surface of the filter body can be easily peeled off and discharged into the biological reaction tank together with the backwash waste water. The sludge accumulated in the filter body is also diluted by the penetration of the filtered water in the filtration separation tank into the filter body, and the sludge accumulated by the supply of backwash water is easily discharged into the biological reaction tank along with the backwash drainage. Can do.
[0013]
Water backwashing injects filtered water into the backwash line at the top of the filter body, discharges backwash wastewater from the bottom water intake line, and returns it to the biological reaction tank, making it easy to remove accumulated sludge inside the filter body. Since the sludge can be discharged and the sludge is not deposited again in the filter body, a stable filtration flux can be obtained at all times.
Further, when the chemical cleaning liquid is used as the backwash water during the water backwashing, even if the biological slam adheres to the surface of the filter body, it can be easily washed off. The fall of the filtration flux by the biological slam adhesion accompanying long-term filtration can be suppressed.
As the chemical cleaning solution, any of hypochlorous acid aqueous solution, alkaline aqueous solution, acid aqueous solution, ozone aqueous solution, hydrogen peroxide aqueous solution and the like can be used. The selection of chemical cleaning liquid and the frequency of cleaning are determined from the sludge to be treated and the state of contamination, and it is preferable to carry out the cleaning once every few days to several months.
[0014]
If the water-permeable filter is a sheet-like body having a water-permeable and pressure-resistant porous surface, the same effect can be obtained by using any of nonwoven fabric, woven fabric, metal net, and the like. And as a filter body shape, any of a plane type, a cylindrical type, and a hollow type can be used, and a plurality can be bundled and used as a module filter body.
Moreover, as a filter body module structure, it is desirable for the support plate holding a water-permeable filter body to be as hollow as possible. There is a backwash water inflow pipe through which the backwash water can be injected into the support plate at the top of the filter module, and the intake pipe for obtaining filtered water is installed at the bottom of the filter module, and the discharge line for backwash drainage is It is desirable to have a structure that is connected to a water intake pipe and can return backwash wastewater to the biological treatment tank by switching bubbles during backwashing.
As the target sludge that can be filtered and separated by the water-permeable filter body, any of activated sludge, agglomerated sludge, initial settling sludge, and the like are possible. It can also be used for solid-liquid separation of drainage with high SS and river water.
[0015]
The present invention will be described more specifically with reference to the drawings.
FIG. 1 is a flow sheet showing an example of a treatment method according to the present invention for a group groundwater.
As shown in FIG. 1, inflow raw water 1 flows into a
[0016]
As a washing method for the
Water backwashing using filtered water is performed periodically at a frequency of once every several weeks. At the time of water backwashing, the mixed liquid sludge in the
The backwash drainage is discharged from the intake pipe below the
If the sludge mixed liquid of the
[0017]
In FIG. 2, 10 is a filtration separation tank, 13 is a backwash water line, 22 is a backwash drainage line, and the cylindrical filter body (woven fabric) 11 is placed on the
[0018]
【Example】
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to this example.
[0019]
Example 1
(Processing method)
About the collective groundwater, it processed by the processing method by this invention represented with the flow sheet shown in FIG.
The quality of the groundwater is as shown in Table 1.
In the biological reaction tank that treats the groundwater with activated sludge, the MLSS of activated sludge was about 3500 mg / liter. The activated sludge mixed solution exiting from the biological reaction tank was guided to the filtration / separation tank shown below to obtain treated water.
The quality of the treated water obtained in the filtration separation tank is as shown in Table 1.
[0020]
(Filtration separation tank)
As the filtration separation tank, a solid-liquid separation tank having an effective area of 0.3 m 2 and an effective volume of 0.6 m 3 was used. Five flat woven fabric filter bodies having an effective area of 1 m 2 / sheet were immersed in the
Table 2 shows the processing conditions of the filtration / separation tank.
Table 3 shows the conditions for washing the filter body with air and backwashing with filtered water.
[0021]
[Table 1]
[Table 2]
[Table 3]
(Processing result)
FIG. 3 shows the course of the filtration flux in this example.
The MLSS of the activated sludge to be treated is about 3500 mg / liter, and the filtration flux can be maintained at 4.2 to 4.8 m / d during the treatment period of 2 months, and backwashing with filtered water once every 2 weeks. Was added to obtain a stable filtered flux. In addition, the turbidity of filtered water was around 5 degrees on average during the treatment period, and it was clear.
[0025]
Comparative Example 1
Under the same operating conditions as in Example 1, the filtration treatment of the activated sludge mixture was performed without performing regular water backwashing on the inside of the filter module. The course of the average filtration flux in that case is shown in FIG.
The average filtration flux was about 4.8 m / d, which was almost the same as in Example 1 at the start of the treatment. However, after about 10 days from the start of the treatment, the filtration flux dropped rapidly. This is due to sludge fine particles adhering to the surface of the filter body and sludge accumulation inside the filter body.
As a result, even if normal empty washing was carried out once every 4 hours, recovery of the filtration flux was not obtained, and after 20 days from the start of the treatment, the filtration flux was 1.8 m / m or less of half of the initial value. d. After that, it gradually decreased to 1 m / d or less. In addition, filtration water turbidity was always 10 degrees or less, and the big difference with an Example was not recognized.
[0026]
【The invention's effect】
According to the present invention, in a solid-liquid separation method of a sludge mixed liquid that uses a water-permeable filter and forms a sludge dynamic filtration layer on the surface of the filter to obtain filtrate, a filter module that is immersed in a filtration separation tank. On the other hand, after all the sludge mixed liquid in the filtration separation tank has been returned to the biological reaction tank on a regular basis, using the filtered water of the treated water tank, if the water is back-washed inside the filter module, it adheres to the filter surface. Fine sludge particles can be easily dropped, and sludge accumulated inside the filter can be discharged to the outside by backwashing. As a result, both the surface resistance due to the sludge fine particle blockage on the surface of the filter body and the internal resistance due to the accumulation of sludge inside the filter body can be reduced, and the filtration flux recovers to almost the initial value.
[0027]
In water backwashing, filtered water is injected into the backwash line at the top of the filter body, drained backwash water is discharged from the intake line at the bottom, and returned to the biological reaction tank to facilitate sedimentation of the sludge inside the filter body. Since the sludge can be discharged and the sludge is not deposited again in the filter body, a stable filtration flux can be obtained at all times. Further, when the chemical cleaning liquid is used as the backwash water during the water backwashing, even if the biological slam adheres to the surface of the filter body, it can be easily washed off. That is, it is possible to suppress the decrease in the filtration flux due to the biological slam adhesion accompanying long-term filtration.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a solid-liquid separation device for biologically treated wastewater including a water-permeable filter cleaning device of the present invention.
FIG. 2 is an explanatory view of a backwashing status of the filter cleaning device of the present invention.
FIG. 3 is a graph showing the relationship between the number of days elapsed and the average filtration flux in one example of the present invention.
4 is a graph showing the relationship between the number of days elapsed and the average filtration flux in Comparative Example 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inflow
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP2000378981A JP4124957B2 (en) | 2000-12-13 | 2000-12-13 | Filter body washing method and apparatus |
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| JP2000378981A JP4124957B2 (en) | 2000-12-13 | 2000-12-13 | Filter body washing method and apparatus |
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| JP2005285179A Division JP4335193B2 (en) | 2005-09-29 | 2005-09-29 | Method and apparatus for treating organic wastewater |
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| JP4124957B2 true JP4124957B2 (en) | 2008-07-23 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1054354A (en) * | 1996-08-01 | 1998-02-24 | Ritsuan Ro | Cover device of vacuum container |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002205087A (en) * | 2001-01-09 | 2002-07-23 | Kubota Corp | Air diffuser |
| CN114699932B (en) * | 2022-03-23 | 2023-05-16 | 深圳市东方祺胜实业有限公司 | Dynamic membrane filter and method for treating sewage using the same |
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2000
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1054354A (en) * | 1996-08-01 | 1998-02-24 | Ritsuan Ro | Cover device of vacuum container |
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