JP3700932B2

JP3700932B2 - Method and apparatus for cleaning filter using ozone

Info

Publication number: JP3700932B2
Application number: JP2001226105A
Authority: JP
Inventors: 甬生葛; 聡史小西; 俊博田中
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2001-07-26
Filing date: 2001-07-26
Publication date: 2005-09-28
Anticipated expiration: 2021-07-26
Also published as: JP2003033764A

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活性汚泥の固液分離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、活性汚泥混合液を沈殿池に導入させ、重力沈降によって、汚泥を沈降させ、上澄み液を処理水として沈殿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な大きさの沈降面積及び長い滞留時間を有する沈殿池が必要であり、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、沈殿池より汚泥が流出し、処理水の悪化を招く。
【０００３】
近年、沈殿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を用いる。
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＋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、透過フラックス（透過流束）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、沈殿池に代わる活性汚泥の固液分離法として、曝気槽に不織布等の通液性シートからなるろ過体を浸漬させ、ダイナミックろ過により低い水頭圧でろ過水を得る方法が知られている。この場合、ろ過体表面に形成された汚泥のダイナミックろ過層による分離で清澄なろ過水が得られる。また、ろ過フラックス低下時のろ過体の洗浄方法としては、ろ過体下部に設置した散気管より曝気すれば、ろ過体表面に形成された汚泥のダイナミックろ過層を容易に剥離し、安定したろ過フラックスが得られるとしている。「ダイナミックろ過層」とは、ろ過の進行によりろ過体表面に形成される活性汚泥粒子の付着物槽である。ダイナミックろ過では、このダイナミックろ過層が形成され、活性汚泥粒子の通過を阻止することができる。
【０００５】
【発明が解決しようとする課題】
しかし、ろ過体を曝気槽に浸漬して活性汚泥の固液分離を行った場合、処理時間の経過とともにろ過体表面に生物スライムが徐々に付着することがある。定期的な空洗のみではダイナミックろ過層を剥離再生できても、生物スライムの剥離及び抑制が困難である。このため、処理日数の増加にともない、ろ過フラックスが徐々に低下することが認められた。さらに、空洗直後からダイナミックろ過層が形成されるまでの間に、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、ろ過抵抗の増大を招き、ろ過フラックスを著しく低下させる要因となる。
この結果、空洗のみ継続しても良好な洗浄効果が得られず、経過時間とともにろ過フラックス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、通水性ろ過体下部からオゾン含有ガスを曝気した後、内部にオゾン含有ガス及びオゾン含有ガスを注入した逆洗水を供給して洗浄を行い、初期値とほぼ同様なろ過フラックスを、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、オゾンを用いた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】
本発明者らは、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、オゾン含有ガスをろ過体下部よりろ過体表面に対して曝気すれば、通常の空洗では完全に剥離できなかったろ過体表面の微細なフロック、あるいは生物スライムさえも容易に除去することが可能になることを確認した。
また、オゾンガスやオゾン含有ガスを注入した逆洗水をろ過体内部に噴射すれば、上記と同様にろ過体内部の洗浄が可能になることも確認した。
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）生物反応槽の活性汚泥混合液を通水性ろ過体モジュールを浸漬しているろ過分離槽に供給し、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固液分離法において、ろ過体洗浄は、ろ過分離槽内の汚泥混合液を生物反応槽に返送し、ろ過分離槽にろ過水を満たした後、ろ過体モジュール下部の散気装置よりオゾン含有ガスを曝気し、ろ過体モジュール下部から内部にオゾン含有ガスを供給し、ろ過体モジュール上部入口より内部へオゾン含有ガスの注入された逆洗水を供給し、ろ過体モジュール下部の出口より該逆洗水を排出することを同時又は交互に行うことを特徴とするオゾンを用いたろ過体の洗浄方法。
（２）前記ろ過体モジュール内部に逆洗水を供給するラインに、オゾン含有ガスを注入することを特徴とする前記（１）記載のオゾンを用いたろ過体の洗浄方法。
（３）オゾン含有ガスの注入はエジェクター方式であることを特徴とする前記（２）記載のオゾンを用いたろ過体の洗浄方法。
【０００９】
（４）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生物汚水処理の固液分離装置において、汚水が流入する生物反応槽と別個に設けたろ過分離槽内に浸漬されたダイナミックろ過層を形成した通水性ろ過体モジュールと、このろ過体モジュールの下部に配置されたオゾン含有空洗用の空洗散気管と、ろ過体モジュール上部に接続された処理水槽からのオゾン含有ガスが注入された逆洗水ラインと、ろ過体モジュール下部に接続されたオゾン含有ガス供給ラインとで構成された逆洗ユニットを有することを特徴とするろ過体の洗浄装置。
【００１０】
【発明の実施の形態】
本発明によれば、オゾン含有ガスをろ過体モジュール下部の散気装置よりろ過体表面に対し曝気すれば、ろ過体表面の汚泥ろ過層を容易に剥離することができる一方、表面に付着した生物膜や生物スライム或いは微細汚泥が、オゾンガスにより分解除去されることから、ろ過体表面に常時良好なダイナミック汚泥ろ過層が剥離再生できる。なお、本発明では、通水性ろ過体、集水部等を組み合わせて一体化したものをろ過体モジュールという。
【００１１】
オゾンガスをろ過体モジュール内部に供給すれば、ろ過体内部に侵入し、堆積した汚泥の固まりを微細化し、下部排泥管を通じて外部へ排出することが容易となる。また、ろ過体内部表面に付着した微細汚泥及び生物スライムを剥離除去することができる。オゾン含有ガスを注入した逆洗水をろ過体内部に供給すれば、ろ過体内部表面の付着生物スライムを除去することができるとともに、オゾン水がろ過体を通過し外部へ排出されることにより、生物スライムによるろ過体の目つまりを解消することができる。この結果、長期運転においても、ろ過水フラックスの低下が少なく、安定した処理水量を得ることができる。
【００１２】
通水性ろ過体は、その上にダイナミックろ過層を形成するのに適するろ過体であればどのようなものでも使用することができるが、広いろ過表面積を持ち、かつ容易に洗浄できるためにも、平面状で両面がろ過面となるようないわば板状のろ過体が適している。従来板状のろ過体として知られているものをそのまま使用することができる。
実用上、ろ過体は、ポリエステル製織布で表面を覆われた平面形ろ過体の複数枚を１組とするろ過モジュールであることが好ましい。
【００１３】
以下に本発明を実施態様の一例を示す図面を用いて詳細に説明する。
図１は、団地下水（以下「原水」という）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において活性汚泥による好気処理を行う。生物反応槽２からの活性汚泥混合液３は、汚泥供給ポンプ（Ｐ１）５よりろ過分離槽７の下部に供給される。該ろ過分離槽７に供給された活性汚泥混合液３は、ろ過体モジュール８により固液分離される。水頭圧差で得られるろ過水は、ろ過水取水管９を通じて処理水槽１１に流入し、処理水１２として放流される。ろ過後の活性汚泥混合液は、循環汚泥１８として生物反応槽２に返送される。
【００１４】
ろ過体モジュール８による活性汚泥混合液３のろ過がある時間継続されると、ろ過体モジュール８におけるろ過抵抗が増大するので、通水を停止し、ろ過体モジュール８を洗浄してそのろ過層を一旦剥離してろ過抵抗の減少を図ることが行われる。
その際、通常のろ過体表面に対する空気洗浄は、本発明によりろ過水弁１０を閉じ、ろ過を停止した後、オゾン発生器６を起動させ、空洗バルブ１５を開放して、モジュール８下部の空洗散気管１６より曝気してオゾン含有ガスによる空気洗浄として行われる。
【００１５】
ろ過体モジュール８内部へオゾン含有ガスを供給する時は、オゾン注入バブル２０を開放して行う。ろ過モジュール８への水逆洗は、モジュール８内部へオゾンガス注入直後に逆洗ポンプ（Ｐ２）１３を起動し、オゾン注入バルブ１９を開放し、オゾン含有ガスをオゾン注入口から逆洗水流入ライン２１に注入して行う。排泥は、水逆洗開始とともに排泥バルブ１７を開放して行われる。なお、排泥は水逆洗後もさらに数分継続して行う。逆洗水は逆洗水流出ラインから生物反応槽２へ入る。
【００１６】
ろ過体の洗浄作業を行うに当たっては、先にろ過分離槽７の汚泥混合液を生物反応槽２に返送し、空にしたろ過分離槽７にろ過水を満たした後にろ過体洗浄を行う手段を取ると、さらに高い洗浄効果が得られる。ろ過水を槽内に満たした時、ろ過モジュール８表面に対し、オゾン含有ガスで曝気すれば、ろ過分離槽７内に活性汚泥混合液が無いため、散気装置１６より供給されたオゾンガスが、活性汚泥で消費されないため高い効率でろ過体表面に接触反応することができる。この場合槽７内ろ過水の溶存オゾン濃度が高く維持でき、ろ過体表面生物スライム等との酸化反応により、それらの付着物を分解除去することができる。
【００１７】
ろ過体内部にオゾン含有ガスを供給して洗浄を行う場合、ろ過水を槽内に満たしておくようにする時には、ろ過体内部に汚泥混合液の侵入がなく、注入オゾンガスがろ過体表面付着の微細汚泥及び生物スライムを直接処理することができる。オゾン処理を受けた付着物質が汚泥混合液存在時より容易に剥離し、ろ過水に溶出することが可能である。オゾン含有の逆洗水をろ過体内部に導入した場合も同様に、オゾン処理を受けたろ過体表面生物スライムがろ過水に溶出することができる一方、活性汚泥混合液がオゾンから直接処理を受けることなく、オゾン処理による活性汚泥性状の変化を懸念する必要が全く無い。
【００１８】
なお、ろ過分離槽７の濃縮汚泥混合液４を生物反応槽２へ返送する場合は、汚泥供給ポンプ５を用い、汚泥返送バルブＶ３、Ｖ４と汚泥供給バルブＶ１、Ｖ２を切り替えることにより行われる。
【００１９】
【実施例】
以下に本発明を実施態様の一例を示す図面を用いて詳細に説明する。ただし、本発明は下記の実施例のみに限定されるものではない。
【００２０】
実施例１
団地下水（以下「原水」という）を図１のフローシートで示す処理法によって処理した。
本実施例では、有効床面積０．１ｍ²、有効容積０．４ｍ³のろ過分離槽を用いた。ろ過体モジュールとして有効表面積０．４ｍ²の平面形ろ過体５枚をろ過分離槽に設置した。ろ過体表面は織布により覆われており、織布の素材としてはポリエステル製のものであり、厚み０．１ｍｍ、２００ｍｅｓｈで孔径約７２μｍのものを用いた。
生物反応槽２はＭＬＳＳ２５００〜３０００ｍｇ／リットル、ＢＯＤ負荷０．２５ｋｇ／ｋｇ／ｄの条件とされ、そこからの活性汚泥混合液がろ過分離槽７に導入された。
この処理法におけるろ過分離槽の処理条件を第１表に示す。
【００２１】
【表１】

【００２２】
ろ過時の平均水頭圧をほぼ１０ｃｍとした。生物反応槽の汚泥混合液をろ過分離槽の下部に供給し、ろ過体表面通過時の平均流速は、０．０２５ｍ／ｓとなるように汚泥供給量を設定した。
ろ過体に対する洗浄は、所定ろ過時間毎にろ過を停止して行う。洗浄方法としては、ろ過体表面に対し、オゾン含有ガスによる曝気、ろ過体内部へのオゾン含有ガスの注入、そして、ろ過体内部へのオゾン含有ガスを注入した逆洗水供給と、ろ過体内部からの排泥の順で行う。
【００２３】
ろ過体表面への曝気は、ろ過体分離槽７下部の空洗散気管１６より約３分間曝気を行った。ろ過体内部へのオゾンガス注入は約５秒行った。ろ過体内部への水逆洗は約５分行った。水逆洗開始と同時にろ過体内部からの排泥を行い、逆洗終了後さらに１分間継続した。排泥は重力流下方式で行い、水頭圧差としてはろ過時と同様の１０ｃｍとした。上記の洗浄は基本的にろ過２時間毎に実施する。汚泥性状や流入原水の性状、ＢＯＤ負荷等を考慮して、洗浄までのろ過時間を１−５時間とすることが好ましい。
【００２４】
第１表に示すように、ろ過体表面に対する曝気風量は９０リットル／ｍｉｎ、内部へのオゾンガス注入量は２０リットル／ｍｉｎ、水逆洗量は１４リットル／ｍｉｎ、逆洗時のオゾンガス注入量は３リットル／ｍｉｎとした。なお、オゾンガス濃度は１０ｍｇ／リットルとした。
オゾンガス注入時間は洗浄、ろ過を含めた１サイクル中で数分程度であり、オゾン発生器６の利用効率が低い。このため、オゾン発生器６の代わりにオゾンガス貯蔵タンクを用いることも可能である。また、複数ろ過分離槽７、７…に対し、オゾン発生器６を交互に使用することも可能である。
【００２５】
上記のような処理条件で、ＭＬＳＳ２５００〜３０００ｍｇ／リットル、ＢＯＤ負荷約０．２５ｋｇ／ｋｇ／ｄの曝気槽活性汚泥混合液を用いた連続実験を行った。図２にろ過フラックスの経過を示す。
実験当初では、通常の空洗及びろ過水逆洗を用いた洗浄を行ったところ、ろ過フラックスが経過日数とともに低下し、１０日後に約２ｍ／ｄに低下した。その後にオゾンガス注入を用いた洗浄を実施した結果、実験期間中の約４０日間において、ろ過フラックスが３．４〜４ｍ／ｄとなり、安定した処理が得られた。なお、実験期間中のろ過水濁度は約５度以下であり、処理水質としても安定していた。
【００２６】
【発明の効果】
本発明によれば、オゾン含有ガスをろ過体下部の散気装置よりろ過体表面に対し曝気すれば、ろ過体表面の汚泥ろ過層を容易に剥離することができる一方、表面に付着した生物膜や生物スライム或いは微細汚泥がオゾンガスにより分解除去されることから、ろ過体表面に常時良好なダイナミック汚泥ろ過層が剥離再生できる。
【００２７】
オゾン含有ガスをろ過体モジュール内部に供給すれば、ろ過体内部に侵入し、堆積した汚泥の固まりを微細化し、下部排泥管を通じて外部へ排出することが容易となる。また、ろ過体内部表面に付着した微細汚泥及び生物スライムを剥離除去することができる。オゾン含有ガスを注入した逆洗水をろ過体内部に供給すれば、ろ過体内部表面の付着生物スライムを除去することができるとともに、オゾン水がろ過体を通過し外部へ排出されることにより、生物スライムによるろ過体の目つまりを解消することができる。この結果、長期運転においても、ろ過水フラックスの低下が少なく、安定した処理水量を得ることができる。
【図面の簡単な説明】
【図１】本発明のオゾンを用いたろ過体の洗浄装置を備えた生物処理汚水の固液分離装置の説明図である。
【図２】本発明の実施例１における時間によるフラックスの変化の経過を表すグラフを示す。
【符号の説明】
１流入原水
２生物反応槽
３活性汚泥混合液
４濃縮汚泥混合液
５汚泥供給ポンプ
６オゾン発生器
７ろ過分離槽
８ろ過体モジュール
９ろ過水取水管
１０ろ過水弁
１１処理水槽
１２処理水
１３水逆洗ポンプ
１４オゾン注入口
１５空洗用バルブ
１６空洗散気管
１７排泥バルブ
１８循環汚泥
１９オゾン注入バルブ
２０オゾン注入バルブ
２１逆洗水流入ライン
２２逆洗水流出ライン
２３ガス出口
Ｖ１汚泥供給バルブ１
Ｖ２汚泥供給バルブ２
Ｖ３汚泥返送バルブ１
Ｖ４汚泥返送バルブ２[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to sewage treatment, and more particularly to solid-liquid separation of activated sludge, concentration of surplus sludge, etc., and a solid-liquid separation method of activated sludge that can be used for treatment of organic industrial wastewater, domestic wastewater, etc. And an apparatus.
[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. Usually, a method is used in which an activated sludge mixed liquid is introduced into a sedimentation basin, the sludge is sedimented by gravity sedimentation, and the supernatant liquid is discharged from the sedimentation basin as treated water. In this case, a sedimentation basin having a sufficiently large sedimentation area and a long residence time is required to settle the activated sludge, which is a factor for increasing the size of the processing apparatus and increasing the installation volume. Moreover, when activated sludge deteriorates sedimentation property, such as 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 necessary as a filtration separation means, and since it is normally performed at a pressure of several + kPa to several hundred kPa, the power by the pump is large and the running cost is increased. In addition, clear treated water having no SS can be obtained by membrane separation, while permeation flux (permeation flux) is low, and it is necessary to regularly wash the medicine in order to prevent membrane contamination.
[0004]
Recently, as a solid-liquid separation method for activated sludge that replaces a sedimentation basin, a method is known in which a filtration body made of a liquid-permeable sheet such as a nonwoven fabric is immersed in an aeration tank and filtrate is obtained at a low head pressure by dynamic filtration. . In this case, clear filtered water can be obtained by separating the sludge formed on the surface of the filter body by the dynamic filtration layer. In addition, as a method of washing the filter body when the filtration flux is reduced, if the aeration pipe installed at the bottom of the filter body is aerated, the sludge dynamic filtration layer formed on the surface of the filter body can be easily peeled off to stabilize the filtration flux. Is supposed to be obtained. The “dynamic filtration layer” is a deposit tank of activated sludge particles formed on the surface of the filter body by the progress of filtration. In dynamic filtration, this dynamic filtration layer is formed, and the passage of activated sludge particles can be prevented.
[0005]
[Problems to be solved by the invention]
However, when the filter is immersed in an aeration tank and solid-liquid separation of activated sludge is performed, biological slime may gradually adhere to the surface of the filter as the treatment time elapses. Even if the dynamic filtration layer can be peeled and regenerated only by regular air washing, it is difficult to peel and suppress the biological slime. For this reason, it was recognized that the filtration flux gradually decreased as the number of treatment days increased. Furthermore, sludge that has passed through the surface of the filter body accumulates in the interior from the time immediately after washing to the formation of the dynamic filtration layer, and is gradually concentrated over time. Is a factor that significantly lowers.
As a result, a good cleaning effect cannot be obtained even if only the rinsing is continued, and the decrease in the filtration flux increases with the passage of time, making it difficult to obtain a stable treatment.
[0006]
The present invention has been made in view of such conventional problems, and after supplying ozone-containing gas from the lower part of the water-permeable filter body, backwash water into which ozone-containing gas and ozone-containing gas are injected is supplied. Filtration using ozone of the solid-liquid separator for biologically treated sewage that can be stably obtained over a long period of time with a filtration flux that is almost the same as the initial value. It is an object to obtain a body cleaning method and apparatus.
[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 a filter body regardless of the lapse of processing time due to the above-mentioned problems. If the ozone-containing gas is aerated from the lower part of the filter body to the filter surface, fine flocs or even biological slime on the filter surface that could not be completely removed by normal air washing can be easily removed. Confirmed that it would be possible.
It was also confirmed that if the backwash water into which ozone gas or ozone-containing gas was injected was sprayed into the filter body, the inside of the filter body could be cleaned in the same manner as described above.
The present invention has been made based on such knowledge and has the following configuration.
[0008]
(1) The activated sludge mixed liquid in the biological reaction tank is supplied to the filtration separation tank in which the aqueous filter module is immersed, and a sludge dynamic filtration layer is formed on the filter surface to perform filtration. In the solid-liquid separation method in which the activated sludge mixed solution after filtration is returned to the biological reaction tank, the filter washing is performed by returning the sludge mixed liquid in the filtration separation tank to the biological reaction tank and supplying filtered water to the filtration separation tank. After filling, the ozone-containing gas is aerated from the diffuser at the bottom of the filter module, the ozone-containing gas is supplied from the bottom of the filter module to the inside, and the ozone-containing gas is injected into the inside through the filter module upper inlet. the wash water is supplied, the method of cleaning a filtration material using ozone, which comprises carrying out simultaneously or alternately to discharge the backwash water from an outlet of the filtration body module lower.
(2) The method for cleaning a filter body using ozone according to (1), wherein ozone-containing gas is injected into a line for supplying backwash water into the filter module module .
(3) The method for cleaning a filter body using ozone according to the above (2), wherein the ozone-containing gas is injected by an ejector method.
[0009]
(4) In a solid-liquid separator for biological sewage treatment that uses a water-permeable filter and forms a sludge dynamic filtration layer on the surface of the filter to obtain filtered water, filtration provided separately from the biological reaction tank into which sewage flows A water-permeable filter module formed with a dynamic filtration layer immersed in the separation tank, an ozone-containing air-washing air diffuser disposed at the lower part of the filter module, and an upper part of the filter module. A filter cleaning apparatus comprising a backwash unit comprising a backwash water line into which ozone-containing gas from a treated water tank is injected and an ozone-containing gas supply line connected to the lower part of the filter module. .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, if the ozone-containing gas is aerated from the air diffuser at the lower part of the filter module to the filter body surface, the sludge filtration layer on the filter body surface can be easily peeled off, while the organism attached to the surface Since a membrane, biological slime, or fine sludge is decomposed and removed by ozone gas, a good dynamic sludge filtration layer can always be peeled and regenerated on the filter body surface. In addition, in this invention, what combined and integrated the water-permeable filter body, the water collection part, etc. is called a filter body module.
[0011]
If ozone gas is supplied to the inside of the filter module, it becomes easy to enter the filter body, refine the accumulated sludge, and discharge it to the outside through the lower sludge pipe. Moreover, the fine sludge and biological slime adhering to the filter body internal surface can be peeled and removed. If the backwash water into which the ozone-containing gas has been injected is supplied to the inside of the filter body, the attached biological slime on the inner surface of the filter body can be removed, and the ozone water passes through the filter body and is discharged to the outside. The filter clogging caused by biological slime can be eliminated. As a result, even during long-term operation, the filtrate water flux is hardly reduced and a stable amount of treated water can be obtained.
[0012]
As the water-permeable filter, any filter can be used as long as it is suitable for forming a dynamic filtration layer thereon, but also because it has a large filtration surface area and can be easily washed, A plate-like filter body that is flat and does not become a filtration surface on both sides is suitable. What is conventionally known as a plate-shaped filter body can be used as it is.
Practically, the filter body is preferably a filtration module including a set of a plurality of flat filter bodies whose surfaces are covered with a polyester woven fabric.
[0013]
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment.
FIG. 1 is a flow sheet showing an example of a treatment method according to the present invention for collective groundwater (hereinafter referred to as “raw water”).
As shown in FIG. 1, inflow raw water 1 flows into a biological reaction tank 2, and an aerobic treatment with activated sludge is performed in the biological reaction tank 2. The activated sludge mixed liquid 3 from the biological reaction tank 2 is supplied to the lower part of the filtration separation tank 7 from a sludge supply pump (P1) 5. The activated sludge mixed solution 3 supplied to the filtration separation tank 7 is solid-liquid separated by the filter module 8. The filtered water obtained by the water head pressure difference flows into the treated water tank 11 through the filtered water intake pipe 9 and is discharged as treated water 12. The filtered activated sludge mixed liquid is returned to the biological reaction tank 2 as the circulating sludge 18.
[0014]
If the filtration of the activated sludge mixed liquid 3 by the filter module 8 is continued for a certain period of time, the filtration resistance in the filter module 8 increases, so the water flow is stopped, the filter module 8 is washed, and the filter layer is removed. It is peeled once to reduce the filtration resistance.
At that time, the normal air cleaning of the filter surface is performed by closing the filtered water valve 10 and stopping the filtration according to the present invention, starting the ozone generator 6, opening the air washing valve 15, Aeration is performed from the air washing air diffuser 16 and air cleaning with an ozone-containing gas is performed.
[0015]
When supplying the ozone-containing gas into the filter module 8, the ozone injection bubble 20 is opened. In the backwashing of water into the filtration module 8, the backwash pump (P2) 13 is started immediately after the ozone gas is injected into the module 8, the ozone injection valve 19 is opened, and the ozone-containing gas is supplied from the ozone inlet to the backwash water inflow line. 21. The mud is discharged by opening the mud valve 17 at the same time when the water backwashing is started. In addition, drainage continues for several minutes after backwashing with water. The backwash water enters the biological reaction tank 2 from the backwash water outflow line.
[0016]
In performing the washing operation of the filter body, means for returning the sludge mixed liquid in the filtration separation tank 7 to the biological reaction tank 2 and filling the filtered filtration tank 7 with the filtered water before washing the filter body is provided. If taken, a higher cleaning effect can be obtained. When filtered water is aerated with the ozone-containing gas when the filtered water is filled in the tank, there is no activated sludge mixed liquid in the filtration separation tank 7, so the ozone gas supplied from the air diffuser 16 is Since it is not consumed by activated sludge, it can contact and react with the filter surface with high efficiency. In this case, the dissolved ozone concentration of the filtered water in the tank 7 can be maintained high, and these deposits can be decomposed and removed by an oxidation reaction with the biological surface slime of the filter body.
[0017]
When cleaning with ozone-containing gas supplied to the inside of the filter body, when the filtered water is filled in the tank, there is no intrusion of sludge mixed liquid inside the filter body, and the injected ozone gas adheres to the surface of the filter body. Fine sludge and biological slime can be treated directly. Adhering substances that have been subjected to ozone treatment can be easily separated from the sludge mixture and eluted into filtered water. Similarly, when ozone-containing backwash water is introduced into the filter body, the biological surface slime that has been subjected to ozone treatment can be eluted into the filtrate, while the activated sludge mixture is directly treated from ozone. And there is absolutely no need to worry about changes in activated sludge properties due to ozone treatment.
[0018]
In addition, when returning the concentrated sludge mixed liquid 4 of the filtration separation tank 7 to the biological reaction tank 2, the sludge supply pump 5 is used to switch the sludge return valves V3 and V4 and the sludge supply valves V1 and V2.
[0019]
【Example】
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment. However, the present invention is not limited only to the following examples.
[0020]
Example 1
Group groundwater (hereinafter referred to as “raw water”) was treated by the treatment method shown in the flow sheet of FIG.
In this example, a filtration separation tank having an effective floor area of 0.1 m ² and an effective volume of 0.4 m ³ was used. As a filter module, five flat filter bodies having an effective surface area of 0.4 m ² were installed in a filtration separation tank. The surface of the filter body was covered with a woven fabric, and the material of the woven fabric was made of polyester, and the one having a thickness of 0.1 mm, 200 mesh and a pore diameter of about 72 μm was used.
The biological reaction tank 2 was subjected to MLSS 2500 to 3000 mg / liter and a BOD load of 0.25 kg / kg / d, and the activated sludge mixed liquid was introduced into the filtration separation tank 7.
The processing conditions of the filtration separation tank in this processing method are shown in Table 1.
[0021]
[Table 1]

[0022]
The average water head pressure during filtration was approximately 10 cm. The sludge mixed liquid of the biological reaction tank was supplied to the lower part of the filtration separation tank, and the sludge supply amount was set so that the average flow velocity when passing through the filter surface was 0.025 m / s.
Washing of the filter body is performed by stopping filtration every predetermined filtration time. The cleaning method includes aeration of ozone-containing gas on the surface of the filter body, injection of ozone-containing gas into the filter body, supply of backwash water into which the ozone-containing gas is injected into the filter body, and inside of the filter body It is done in the order of the mud from.
[0023]
The aeration to the surface of the filter body was aerated for about 3 minutes from the empty washing air diffuser 16 at the lower part of the filter body separation tank 7. The ozone gas was injected into the filter body for about 5 seconds. Water backwashing into the filter was performed for about 5 minutes. Simultaneously with the start of water backwashing, mud was drained from the inside of the filter, and continued for another 1 minute after the backwashing. The mud was drained by a gravity flow method, and the water head pressure difference was 10 cm, the same as during filtration. The above washing is basically carried out every 2 hours of filtration. In consideration of sludge properties, inflow raw water properties, BOD load, etc., it is preferable to set the filtration time until washing to 1-5 hours.
[0024]
As shown in Table 1, the amount of aeration air to the filter surface is 90 liters / min, the amount of ozone gas injected into the interior is 20 liters / min, the amount of water backwash is 14 liters / min, and the amount of ozone gas injected during backwashing is It was 3 liters / min. The ozone gas concentration was 10 mg / liter.
The ozone gas injection time is about several minutes in one cycle including cleaning and filtration, and the utilization efficiency of the ozone generator 6 is low. For this reason, an ozone gas storage tank can be used instead of the ozone generator 6. Moreover, it is also possible to use the ozone generator 6 alternately with respect to the multiple filtration separation tanks 7, 7,.
[0025]
Under the above processing conditions, a continuous experiment was performed using an aeration tank activated sludge mixed solution having MLSS 2500 to 3000 mg / liter and a BOD load of about 0.25 kg / kg / d. FIG. 2 shows the course of filtration flux.
At the beginning of the experiment, when normal washing with air and backwashing with filtered water was performed, the filtration flux decreased with the elapsed days and decreased to about 2 m / d after 10 days. As a result of subsequent cleaning using ozone gas injection, the filtration flux was 3.4 to 4 m / d in about 40 days during the experiment period, and a stable treatment was obtained. In addition, the turbidity of the filtered water during the experiment period was about 5 degrees or less, and the treated water quality was stable.
[0026]
【The invention's effect】
According to the present invention, if the ozone-containing gas is aerated from the air diffuser at the lower part of the filter body to the surface of the filter body, the sludge filtration layer on the surface of the filter body can be easily peeled, while the biofilm attached to the surface Since biological slime or fine sludge is decomposed and removed by ozone gas, a good dynamic sludge filtration layer can always be peeled and regenerated on the filter surface.
[0027]
If the ozone-containing gas is supplied to the inside of the filter module, it becomes easy to enter the filter body, refine the lump of the accumulated sludge, and discharge it to the outside through the lower sludge pipe. Moreover, the fine sludge and biological slime adhering to the filter body internal surface can be peeled and removed. If the backwash water into which the ozone-containing gas has been injected is supplied to the inside of the filter body, the attached biological slime on the inner surface of the filter body can be removed, and the ozone water passes through the filter body and is discharged to the outside. The filter clogging caused by biological slime can be eliminated. As a result, even during long-term operation, the filtrate water flux is hardly reduced and a stable amount of treated water can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a solid-liquid separator for biologically treated wastewater provided with a filter cleaning device using ozone of the present invention.
FIG. 2 is a graph showing the change of flux with time in Example 1 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inflow raw water 2 Biological reaction tank 3 Activated sludge mixed liquid 4 Concentrated sludge mixed liquid 5 Sludge supply pump 6 Ozone generator 7 Filtration separation tank 8 Filter body module 9 Filtration water intake pipe 10 Filtration water valve 11 Treatment water tank 12 Treatment water 13 Water Backwash pump 14 Ozone inlet 15 Air washing valve 16 Air washing air pipe 17 Drainage valve 18 Circulating sludge 19 Ozone injection valve 20 Ozone injection valve 21 Backwash water inflow line 22 Backwash water outflow line 23 Gas outlet V1 Sludge supply Valve 1
V2 Sludge supply valve 2
V3 Sludge return valve 1
V4 Sludge return valve 2

Claims

The activated sludge mixed solution in the biological reaction tank is supplied to the filtration separation tank in which the aqueous filter module is immersed, and a sludge dynamic filtration layer is formed on the filter surface to perform filtration to obtain filtered water. In the solid-liquid separation method in which the activated sludge mixed liquid afterwards is returned to the biological reaction tank, the filter washing is performed after the sludge mixed liquid in the filtration separation tank is returned to the biological reaction tank and the filtered separation tank is filled with filtered water. The ozone-containing gas is aerated from the air diffuser at the lower part of the filter module, the ozone-containing gas is supplied from the lower part of the filter module to the inside, and the backwash water into which the ozone-containing gas is injected from the upper inlet of the filter module is supplied. Supplying and discharging the backwash water from the outlet at the lower part of the filter module is performed simultaneously or alternately, and the filter is cleaned using ozone.

The method for cleaning a filter using ozone according to claim 1, wherein ozone-containing gas is injected into a line for supplying backwash water into the filter module .

The method for cleaning a filter body using ozone according to claim 2, wherein the injection of the ozone-containing gas is an ejector method.

In a solid-liquid separator for biological sewage treatment that uses a water-permeable filter and forms a sludge dynamic filtration layer on the surface of the filter to obtain filtered water, in a filtration and separation tank provided separately from the biological reaction tank into which sewage flows A water-permeable filter module formed with a dynamic filter layer immersed in the filter module, an ozone-containing air-washing air diffuser disposed at the lower part of the filter module, and a treated water tank connected to the upper part of the filter module. A filter washing device comprising a backwash unit comprising a backwash water line into which the ozone-containing gas is injected and an ozone-containing gas supply line connected to the lower part of the filter module.