JP3889254B2

JP3889254B2 - Solid-liquid separation method and apparatus for biological treatment liquid of organic wastewater

Info

Publication number: JP3889254B2
Application number: JP2001270398A
Authority: JP
Inventors: 甬生葛; 聡史小西; 克之片岡; 俊博田中
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2001-09-06
Filing date: 2001-09-06
Publication date: 2007-03-07
Anticipated expiration: 2021-09-06
Also published as: JP2003071485A

Description

【０００１】
【発明の属する技術分野】
本発明は、繊維性ＳＳやＢＯＤ含有有機性廃水（有機性汚水）処理に関するもので、特に紙パルプ工場廃水である白水の処理・回収に用いることができる有機性廃水の生物処理液の固液分離方法に関する。
【０００２】
【従来の技術】
従来、繊維性ＳＳ、ＢＯＤ等含有の有機性廃水（以下「原水」ともいう）、例えば、製紙パルプ工場の白水を処理する方法の１つとして、予め、凝集沈殿処理を行い、繊維性ＳＳや有機性ＣＯＤ等を除去した処理水に対し、砂ろ過を用いて、凝集処理で除去できなかった微細なＳＳを除去し、その処理水を再生回収する方法がある。
【０００３】
【発明が解決しようとする課題】
しかし、上記白水処理の場合、凝集沈殿処理を行っても、白水中の溶解性ＢＯＤを除去することができず、後段の砂ろ過でもＢＯＤ除去機能が無いことから、処理水のＢＯＤ残留により、良好な再生水が得られない。また、白水中繊維性ＳＳが細かい場合、凝集沈殿処理を行っても、凝集処理後の繊維性ＳＳフロックの沈降性は必ずしもよくないことから、凝集汚泥を十分沈降させ、良好な処理水を得るためには、それに見合う十分な沈降面積及び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。さらに処理水中に微細ＳＳの残留があるため、後段の砂ろ過装置が頻繁に閉塞し、逆洗頻度の上昇、水回収率の低下要因となっている。
【０００４】
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、小型の装置で、低いランニングコストで、安定した清澄なろ過水を、高速度でろ過膜の閉塞も少なく得ることのできる生物処理汚水の固液分離方法及び装置を提供することを課題とする。
【０００５】
【課題を解決するための手段】
本発明者等は、上記の課題を解決すべく鋭意調査及び研究を行い、調査結果としてろ過助剤を使用してろ過を行う場合の２方法のうちの一つのボディ・フィード法は、原液中に含まれる固形物の圧縮性が大きく、しかも、ろ過困難である場合に用いられ、原液中に少量の助剤を混入しろ過を行う方法である。例えばＭｇ（ＯＨ）₂，Ｚｎ（ＯＨ）₂，Ｆｅ（ＯＨ）₃，Ａｌ（ＯＨ）₃などの水酸化物、清酒・醤油のオリ、糖液、河川水、下水中のバクテリヤおよび有機ワニスなどの不純物はすべて圧縮性が大きく、ろ材面に堆積してろ材の目を塞ぐとともに、ろ滓自身目がつまったものになり、液の通路を塞ぎろ過量減衰を速くする原因となる。このような場合、ボディ・フィード法を行うと、ろ材面に堆積されるろ滓は不純物と多孔質のろ過助剤とが混合したものになるから、このろ滓は圧縮性が小さくなり、ろ過抵抗が低く流速の減衰が少なく、かつ長時間ろ過を行い得ることを知見した。
【０００６】
そして、これらの知見に基づいて、パルプ工場廃水である白水の生物処理汚水のダイナミックろ過層の形成に、該処理汚水中の繊維性ＳＳが高速ろ過を行うためのボディ・フィード法のろ過助剤に相当し、安定したダイナミックろ過層の形成に大きく寄与していることを研究成果として知見した。
【０００７】
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。
（１）繊維性ＳＳ及びＢＯＤを含有する有機性廃水を曝気槽に導入して生物処理を行った後、その生物処理液を通水性ろ過体を浸漬したろ過分離槽の上部に流入させ、前記処理液に無機凝集剤を添加して凝集させ、凝集混合液を前記通水性ろ過体によりろ過して通水性ろ過体表面に凝集汚泥のダイナミックろ過層を形成させ、前記通水性ろ過体より水頭圧でろ過水を得るとともに、ろ過後の汚泥濃縮液をろ過分離槽下部より曝気槽に返送することを特徴とする有機性廃水の生物処理液の固液分離方法。
【０００８】
（２）下部に曝気用散気管が設けられ、有機性廃水が供給されて曝気により生物処理をする曝気槽と、頂部に水頭圧で処理水槽へろ過水を供給するろ過水集水管及び底部に前記曝気槽へ内部から排泥された汚泥を返送する排泥管が付設され、表面にダイナミックろ過層が形成されるろ過モジュールと前記ろ過モジュールが槽内に浸漬して配設されるろ過分離槽と、前記ろ過分離槽上部に設けられた前記曝気槽からの生物処理水の供給管と無機凝集剤の供給管と、前記ろ過分離槽下部に設けられた空洗用散気管と、前記ろ過分離槽底部に付設された前記曝気槽へ返送汚泥を返送する返送汚泥抜き取り管及び前記ろ過分離槽底部に付設された濃縮汚泥の抜き取り管及び前記ろ過水を貯留し、処理水排出管とろ過モジュールへ接続する逆洗水配管が付設されている処理水槽を有することを特徴とする有機性廃水の生物処理液の固液分離装置。
【０００９】
【発明の実施の形態】
本発明によれば、繊維性ＳＳ及びＢＯＤを含有する有機性廃水（有機性汚水）に対し、曝気槽において生物処理を行えば、排水中のＢＯＤが除去できる。ＢＯＤ残留のない処理液に対し、無機凝集剤を添加して凝集した混合液をろ過分離槽に導入すれば、ろ過分離槽内の浸漬通液性ろ過体表面に繊維性ＳＳを含む凝集汚泥のダイナミックろ過層が形成でき、このダイナミックろ過層によって、高速度で流入汚水中の繊維性ＳＳがほぼ完全にろ過分離でき、清澄なろ過水を得ることができる。
なお、ダイナミックろ過は、通常不織布、金網などの孔径が５０〜２００μｍ程度の目の粗いろ過面の表面に生物汚泥層からなる層厚の薄いろ過面（ダイナミックろ過層）を形成させ、低いろ過圧でろ過水を得るろ過方法をいう。
【００１０】
流入原水中の繊維性ＳＳが、凝集処理により凝集性の高い汚泥フロックを形成し、ろ過体表面に形成された汚泥のダイナミックろ過層が、低い水頭圧で被処理液中のＳＳをろ過分離することができる。該ダイナミックろ過層が、主として凝集した繊維性ＳＳで形成されていることから、透水性が高いうえに、除去対象である繊維性ＳＳはほぼ完全に該ダイナミックろ過層に分離除去される。本発明においては、ろ過圧として水頭圧で行うことが好ましい。
さらに曝気槽における生物処理で、流入原水中の溶解性ＢＯＤが分解除去されていることから、ろ過分離槽では、通液性ろ過体表面に生物スライムの発生がなく、安定したろ過水を得ることができる。
通水性ろ過体としては、不織布、織布、ろ布、金属網等のいずれを用いても同様な効果が得られる。また、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、複数個を束ねてろ過体モジュールとして用いることも可能である。
【００１１】
ろ過分離槽への生物処理水の流入は、同槽上部とした結果、生物処理水への凝集剤添加による凝集反応で生成した凝集汚泥混合液がろ過モジュールを上から下方にゆっくりと流下することになり、その凝集汚泥混合液をろ過モジュールによりろ過してろ過水を得る際には、そのろ過により濃縮した汚泥がろ過分離槽下部に沈降する状態が形成される。このようにしてろ過分離槽下部に濃縮汚泥が溜まってくるので、ろ過分離槽下部より高濃度の濃縮汚泥を曝気槽に返送すれば、曝気槽内のＭＬＳＳ濃度を高く維持でき、安定した生物処理が得られる。また、ろ過分離槽下部より濃縮汚泥の一部を定常的に排出すれば、ろ過分離槽内部の汚泥濃度が高くなることがなく、通液性ろ過体表面に常時安定した汚泥のダイナミックろ過層を形成することができる。
【００１２】
この処理においては、通液性ろ過体表面に汚泥のダイナミックろ過層が形成されるまでに、ろ過モジュール内に汚泥の侵入が生じる。このため、モジュール内部に汚泥堆積を無くするために定期的にモジュール外部に排泥を行うことが必要となる。この排泥方法としては、ろ過モジュール下部より内部に貫通する排泥管を設け、そこから汚泥を槽外に排出するようにする。この場合、排出汚泥を曝気槽に導入するようにするのが好ましい。なお、排出動力としては水頭圧による自然流下が好ましく、水頭圧はろ過時水頭圧と同程度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、紙パルプ工場の白水再生処理に対する本発明による処理法の一例のフローシートである。
図１に示す如く、原水１を曝気槽２に流入させ、曝気ブロワ３から曝気用散気管４を通じて曝気し、生物処理によるＢＯＤ除去を行う。生物処理後の処理液をろ過分離槽５の上部から流入する。曝気槽２からの処理液に対し、無機凝集剤７である塩化第２鉄（ＦｅＣｌ₃）を添加して凝集処理を行う。凝集処理後の汚泥混合液を通水性ろ過体からなるろ過モジュール６より水頭圧差でろ過し、ろ過水１２は集水管１０、ろ過水弁１１を経て得られる。ろ過水１２は一旦処理水槽１７に流入し、その一部を逆洗水として用い、大部分は処理水１８として放流する。
【００１４】
ろ過体表面に汚泥ろ過層が過剰に成長し、ろ過水量が低下した時、ろ過モジュール６の洗浄を行う。洗浄方法としては、一旦ろ過水弁１１を閉じ、ろ過停止してから、ろ過モジュール６下部の空気用散気管９を通じて空洗ブロワ８より曝気して、ろ過体表面の汚泥ろ過層を剥離する。空洗後に、水逆洗ポンプ１５によりろ過水を逆洗水配管２０を経てろ過水集水管１０からろ過モジュール６内部に導入する水逆洗操作で、ろ過体表面付着汚泥の剥離を行った。
【００１５】
なお、付着汚泥の剥離を行ったろ過モジュール６を用いて生物処理水のろ過を再開したときには、汚泥のダイナミックろ過層が形成するまでは、ろ過モジュール６内部に汚泥の侵入が起こる。モジュール６内部侵入汚泥を外部に排出するために、水逆洗時に排泥弁１３を開放することにより、導入された逆洗排水の一部を、内部侵入汚泥とともに排出汚泥１４として排出することが可能である。水逆洗終了後もさらに排泥弁１３を数分間開放して、排出汚泥１４の排除を行う。排出汚泥１４はその大部分を返送汚泥として曝気槽２に送るようにする。
【００１６】
ろ過分離槽５のろ過モジュール６よりろ過水１２を得た後、ろ過分離槽５下部に沈降した濃縮汚泥１９の一部を返送汚泥１６として曝気槽２に返送すれば、曝気槽２内ＭＬＳＳを所定濃度に維持することができる。また、濃縮汚泥１９の一部を余剰汚泥として排出して、濃縮・脱水等の処理を行う。
【００１７】
【実施例】
以下に、本発明を実施例により詳細に説明する。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。
【００１８】
実施例１
第１図に示すフローにより紙パルプ工場の白水再生処理を行った。
第１表にこの実施例での曝気槽の処理条件を示す。第２表にろ過分離槽の処理条件を示す。
【００１９】
【表１】

【００２０】
第１表に示すように、曝気槽への原水流入量が１０ｍ³/ｄであり、ろ過分離槽からの返送汚泥量は３．０ｍ³/ｄとした。曝気槽ＭＬＳＳは約２５００ｍｇ／リットルで、ＢＯＤ負荷は０．２５ｋｇ／ｋｇ／ｄである。
第２表に示すろ過分離槽の処理条件から分かるように、本実施例では、通水性ろ過体として、有効面積０．４ｍ²の平面型織布ろ過体５枚を、ろ過体モジュール６としてろ過分離槽５に設置した。ろ過時の平均水頭圧を約１０ｃｍとした。ろ過水量が約１０ｍ³/ｄである。
【００２１】
ろ過体に対する洗浄はろ過を一旦停止し、ろ過モジュール６に対する空洗及び水逆洗を行う。空洗は風量１３５リットル／ｍｉｎで３分間行った。水逆洗は空洗後に水量５５リットル／ｍｉｎで約１分間行った。水逆洗時は排泥弁１３を開放して、内部侵入汚泥を逆洗水の一部とともに１０ｃｍの水頭圧により排出した。水逆洗終了後もさらに排泥弁１３を約１〜３分間開放して、モジュール６内部の残留汚泥混合液を排出した。
【００２２】
【表２】

【００２３】
第２表の処理条件で約２ヶ月連続処理時のろ過フラックスは、ほぼ４〜５ｍ／ｄであり、安定した処理が得られた。
第３表に約２ヶ月連続処理した時の原水及び処理水の水質の平均値を示す。
【００２４】
【表３】

【００２５】
第３表に示すように、原水のｐＨが８．２、濁度８６０度、ＳＳ５２０ｍｇ／リットルであるのに対し、ろ過後の処理水では、ｐＨ７．０、濁度５．０度以下、ＳＳ５ｍｇ／リットル以下となり、清澄なろ過水であると認められた。また、溶解性ＣＯＤ及びＢＯＤについては、原水でそれぞれ１０５ｍｇ／リットルと１００ｍｇ／リットルであるのに対し、処理水では、それぞれ１１ｍｇ／リットルと５ｍｇ／リットル以下となり、生物処理との併用により良好な水質が得られた。
【００２６】
【発明の効果】
本発明によれば、繊維性ＳＳ及びＢＯＤを含有する有機性廃水に対し、曝気槽において生物処理を行うことにより、廃水中のＢＯＤが除去できる。ＢＯＤ残留のない処理液に対し、無機凝集剤添加で凝集した混合液をろ過分離槽に導入することにより、ろ過分離槽内の浸漬ろ過体表面に、繊維性ＳＳを含む凝集汚泥のダイナミックろ過層が形成でき、ダイナミックろ過層によって流入廃水中の繊維性ＳＳがほぼ完全にろ過分離でき、清澄なろ過水を得ることができる。
【００２７】
流入原水中の繊維性ＳＳが、凝集処理により凝集性の高い汚泥フロックを形成し、ろ過体表面に形成された汚泥のダイナミックろ過層が、低い水頭圧で非処理液中のＳＳをろ過分離することができる。該ダイナミックろ過層が、主に凝集した繊維性ＳＳで形成されていることから、透水性が高いうえに、除去対象である繊維性ＳＳがほぼ完全に該ダイナミックろ過層により阻止される。
【図面の簡単な説明】
【図１】本発明の有機性廃水生物処理液の固液分離を実施する装置の概略説明図である。
【符号の説明】
１流入原水
２曝気槽
３曝気ブロワ
４曝気用散気管
５ろ過分離槽
６ろ過モジュール
７無機凝集剤
８空洗用ブロワ
９空洗用散気管
１０ろ過水集水管
１１ろ過水弁
１２ろ過水
１３排泥弁
１４排出汚泥
１５水逆洗ポンプ
１６返送汚泥
１７処理水槽
１８処理水
１９濃縮汚泥
２０逆洗水配管 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to the treatment of fibrous SS and BOD-containing organic wastewater (organic wastewater), and in particular, a solid liquid of a biological treatment liquid for organic wastewater that can be used for the treatment and recovery of white water that is paper pulp factory wastewater. It relates to a separation method.
[0002]
[Prior art]
Conventionally, as one method for treating organic waste water containing fiber SS, BOD, etc. (hereinafter also referred to as “raw water”), for example, white water of a paper pulp mill, a coagulation sedimentation treatment is performed in advance, There is a method in which fine SS that could not be removed by agglomeration treatment is removed from the treated water from which organic COD and the like have been removed by sand filtration, and the treated water is regenerated and recovered.
[0003]
[Problems to be solved by the invention]
However, in the case of the white water treatment, the soluble BOD in the white water cannot be removed even if the coagulation sedimentation treatment is performed, and there is no BOD removal function in the subsequent sand filtration. Good reclaimed water cannot be obtained. Further, when the white SS fibrous SS is fine, even if the coagulation sedimentation treatment is performed, the sedimentation property of the fibrous SS floc after the coagulation treatment is not necessarily good, so that the coagulated sludge is sufficiently settled to obtain good treated water. For this purpose, a sedimentation basin having a sufficient sedimentation area and residence time commensurate with it is required, which is a factor in increasing the size of the processing apparatus and increasing the installation volume. Further, since fine SS remains in the treated water, the sand filtration device in the subsequent stage is frequently clogged, increasing the frequency of backwashing and decreasing the water recovery rate.
[0004]
The present invention has been made in view of such a conventional problem, and is a small-sized apparatus that can obtain a stable and clear filtrate with a low running cost and a high speed and less clogging of a filtration membrane. It is an object to provide a solid-liquid separation method and apparatus for biologically treated wastewater.
[0005]
[Means for Solving the Problems]
The present inventors have conducted extensive research and research to solve the above-mentioned problems, and one of the two body feed methods in the case of performing filtration using a filter aid as a result of the investigation This method is used when the compressibility of the solid matter contained in the material is large and filtration is difficult, and is performed by mixing a small amount of auxiliary agent in the stock solution. For example, hydroxides such as Mg (OH) ₂ , Zn (OH) ₂ , Fe (OH) ₃ , Al (OH) ₃ , refined sake / soy sauce, sugar solution, river water, sewage bacteria and organic varnish, etc. All of these impurities are highly compressible and accumulate on the filter medium surface to block the filter medium, and the filter cake itself becomes clogged, blocking the liquid passage and causing faster filtration rate attenuation. In such a case, if the body feed method is used, the filter cake deposited on the filter medium will be a mixture of impurities and a porous filter aid. It has been found that the resistance is low, the flow rate is less attenuated, and the filtration can be performed for a long time.
[0006]
And based on these knowledge, the filter aid of the body feed method for the fibrous SS in the treated sewage to perform high-speed filtration in the formation of the dynamic filtration layer of the white water biologically treated sewage that is pulp mill wastewater It was found as a research result that it contributes to the formation of a stable dynamic filtration layer.
[0007]
The present invention has been made based on such knowledge and has the following configuration.
(1) After introducing biological wastewater containing fibrous SS and BOD into an aeration tank and performing biological treatment, the biological treatment liquid is allowed to flow into the upper part of the filtration separation tank in which the aqueous filter is immersed, An inorganic flocculant is added to the treatment liquid to cause aggregation, and the aggregated liquid mixture is filtered through the water-permeable filter to form a dynamic filtration layer of coagulated sludge on the surface of the water-permeable filter. A method for solid-liquid separation of a biological treatment liquid of organic wastewater, wherein filtered water is obtained and the sludge concentrate after filtration is returned to the aeration tank from the lower part of the filtration separation tank .
[0008]
(2) An aeration pipe for aeration is provided at the bottom, an aeration tank that is supplied with organic wastewater and performs biological treatment by aeration, a filtered water collection pipe that supplies filtered water to the treated water tank with head pressure at the top, and a bottom A filtration module in which a sludge pipe for returning sludge discharged from the inside to the aeration tank is attached, a dynamic filtration layer is formed on the surface, and a filtration separation tank in which the filtration module is immersed in the tank. When the supply pipe biologically treated water from the aeration tank provided in the filtration separation tank top and the inorganic flocculant supply tube, and sparge tube for air washing provided in the filtration separation tank bottom, the filtration separation A return sludge removal pipe for returning the returned sludge to the aeration tank attached to the bottom of the tank, a concentrated sludge extraction pipe attached to the bottom of the filtration separation tank, and the filtered water are stored, to a treated water discharge pipe and a filtration module . backwash water pipe to be connected Solid-liquid separator of the biological treatment liquid organic waste water characterized by having a process water tank that has been set.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, if biological treatment is performed in an aeration tank on organic wastewater (organic wastewater) containing fibrous SS and BOD, BOD in the wastewater can be removed. If a mixed liquid obtained by adding an inorganic flocculant to the treatment liquid without BOD residue is introduced into the filtration separation tank, the surface of the flocculated sludge containing fibrous SS on the surface of the immersion liquid-permeable filter in the filtration separation tank A dynamic filtration layer can be formed, and by this dynamic filtration layer, the fibrous SS in the inflowing sewage can be almost completely separated by filtration at high speed, and clear filtered water can be obtained.
In addition, dynamic filtration usually forms a thin filtration surface (dynamic filtration layer) composed of a biological sludge layer on the surface of a coarse filtration surface having a pore diameter of about 50 to 200 μm, such as a nonwoven fabric or a wire mesh, and has a low filtration pressure. Refers to a filtration method for obtaining filtered water.
[0010]
The fibrous SS in the inflowing raw water forms a highly cohesive sludge floc by the coagulation treatment, and the sludge dynamic filtration layer formed on the filter body filters and separates the SS in the liquid to be treated with a low head pressure. be able to. Since the dynamic filtration layer is mainly formed of aggregated fibrous SS, the water permeability is high, and the fibrous SS to be removed is almost completely separated and removed by the dynamic filtration layer. In this invention, it is preferable to carry out by the water head pressure as a filtration pressure.
Furthermore, since the soluble BOD in the inflowing raw water is decomposed and removed by biological treatment in the aeration tank, in the filtration separation tank, there is no generation of biological slime on the surface of the liquid-permeable filter body, and stable filtered water is obtained. Can do.
The same effect can be obtained by using any of nonwoven fabric, woven fabric, filter fabric, metal net, etc. as the water-permeable filter. Moreover, as a filter body shape, any of a plane type, a cylindrical type, and a hollow type can be used, and it is also possible to bundle a plurality and use it as a filter body module.
[0011]
As a result of inflow of biologically treated water into the filtration / separation tank, the flocculated sludge mixture produced by the flocculation reaction by adding the flocculant to the biologically treated water slowly flows down from the top to the bottom of the filtration module. When the flocculated sludge mixed liquid is filtered through a filtration module to obtain filtered water, a state is formed in which sludge concentrated by the filtration settles in the lower part of the filtration separation tank. Since concentrated sludge accumulates in the lower part of the filtration separation tank in this way, if the concentrated sludge having a high concentration is returned to the aeration tank from the lower part of the filtration separation tank, the MLSS concentration in the aeration tank can be maintained high, and stable biological treatment Is obtained. Moreover, if a part of the concentrated sludge is discharged from the lower part of the filtration separation tank constantly, the sludge concentration inside the filtration separation tank will not increase, and a stable sludge dynamic filtration layer will be provided on the surface of the liquid-permeable filter at all times. Can be formed.
[0012]
In this process, sludge enters the filtration module before the sludge dynamic filtration layer is formed on the surface of the liquid-permeable filter body. For this reason, in order to eliminate sludge accumulation inside the module, it is necessary to periodically discharge the mud outside the module. As this drainage method, a drainage pipe that penetrates from the lower part of the filtration module is provided, and the sludge is discharged out of the tank from there. In this case, it is preferable to introduce the discharged sludge into the aeration tank. The discharge power is preferably natural flow due to water head pressure, and the water head pressure is preferably about the same as the head pressure during filtration.
[0013]
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an embodiment.
FIG. 1 is a flow sheet of an example of a treatment method according to the present invention for white water regeneration treatment in a paper pulp factory.
As shown in FIG. 1, raw water 1 is introduced into an aeration tank 2 and aerated from an aeration blower 3 through an aeration diffuser 4 to remove BOD by biological treatment. The treatment liquid after the biological treatment flows from the upper part of the filtration separation tank 5. Agglomeration treatment is performed on the treatment liquid from the aeration tank 2 by adding ferric chloride (FeCl ₃ ) as the inorganic flocculant 7. The sludge mixed solution after the coagulation treatment is filtered with a water head pressure difference from a filtration module 6 made of an aqueous filter, and filtered water 12 is obtained through a water collection pipe 10 and a filtered water valve 11. The filtered water 12 once flows into the treated water tank 17, a part of which is used as backwash water, and most is discharged as treated water 18.
[0014]
When the sludge filtration layer grows excessively on the surface of the filter body and the amount of filtered water decreases, the filtration module 6 is washed. As a washing method, the filtration water valve 11 is once closed and the filtration is stopped, and then aeration is performed from the air washing blower 8 through the air diffusing tube 9 below the filtration module 6 to peel off the sludge filtration layer on the surface of the filter body. After air washing, the filter surface adhering sludge was peeled off by a water backwashing operation in which filtered water was introduced from the filtered water collecting pipe 10 into the filtration module 6 through the backwash water pipe 20 by the water backwash pump 15.
[0015]
In addition, when filtration of biologically treated water is resumed using the filtration module 6 from which the attached sludge has been removed, sludge enters the filtration module 6 until a sludge dynamic filtration layer is formed. In order to discharge the invading sludge inside the module 6 to the outside, it is possible to discharge a part of the introduced backwash drainage as the discharged sludge 14 together with the intruding sludge by opening the drainage valve 13 during backwashing with water. Is possible. Even after the end of the water backwash, the sludge valve 13 is further opened for several minutes to remove the discharged sludge 14. Most of the discharged sludge 14 is sent to the aeration tank 2 as return sludge.
[0016]
After obtaining filtered water 12 from the filtration module 6 of the filtration / separation tank 5, if a part of the concentrated sludge 19 settled in the lower part of the filtration / separation tank 5 is returned to the aeration tank 2 as the return sludge 16, the MLSS in the aeration tank 2 is A predetermined concentration can be maintained. Further, a part of the concentrated sludge 19 is discharged as excess sludge, and processing such as concentration and dehydration is performed.
[0017]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to this example.
[0018]
Example 1
The white water regeneration treatment of the paper pulp factory was performed according to the flow shown in FIG.
Table 1 shows the processing conditions of the aeration tank in this example. Table 2 shows the processing conditions of the filtration separation tank.
[0019]
[Table 1]

[0020]
As shown in Table 1, the amount of raw water flowing into the aeration tank was 10 m ³ / d, and the amount of sludge returned from the filtration separation tank was 3.0 m ³ / d. The aeration tank MLSS is about 2500 mg / liter, and the BOD load is 0.25 kg / kg / d.
As can be seen from the processing conditions of the filtration separation tank shown in Table 2, in this example, as a water-permeable filter, five flat woven filter bodies having an effective area of 0.4 m ² are filtered as a filter module 6. It was installed in the separation tank 5. The average head pressure during filtration was about 10 cm. The amount of filtered water is about 10 m ³ / d.
[0021]
In the washing of the filter body, the filtration is temporarily stopped, and the filtration module 6 is washed with water and backwashed with water. The air washing was performed for 3 minutes at an air volume of 135 l / min. Water backwashing was performed for about 1 minute at a water volume of 55 liters / min after air washing. At the time of water backwashing, the mud valve 13 was opened, and the internally penetrating sludge was discharged with a head pressure of 10 cm together with a part of the backwash water. The drainage valve 13 was further opened for about 1 to 3 minutes after the end of the water backwashing, and the residual sludge mixed liquid inside the module 6 was discharged.
[0022]
[Table 2]

[0023]
The filtration flux during the continuous treatment for about 2 months under the treatment conditions in Table 2 was about 4 to 5 m / d, and a stable treatment was obtained.
Table 3 shows the average values of the quality of raw water and treated water when treated continuously for about 2 months.
[0024]
[Table 3]

[0025]
As shown in Table 3, the pH of raw water is 8.2, turbidity is 860 degrees, and SS520 mg / liter, whereas in treated water after filtration, pH is 7.0, turbidity is 5.0 degrees or less, and SS5 mg / Liter or less, and it was recognized as clear filtered water. In addition, soluble COD and BOD are 105 mg / liter and 100 mg / liter respectively for raw water, whereas treated water is 11 mg / liter and 5 mg / liter or less, respectively. was gotten.
[0026]
【The invention's effect】
According to the present invention, BOD in wastewater can be removed by performing biological treatment on an organic wastewater containing fibrous SS and BOD in an aeration tank. Dynamic filtration layer of coagulated sludge containing fibrous SS on the surface of the immersed filter body in the filtration separation tank by introducing the mixed liquid aggregated by adding the inorganic flocculant to the treatment liquid having no BOD residue into the filtration separation tank The fibrous SS in the inflow wastewater can be almost completely filtered and separated by the dynamic filtration layer, and clear filtered water can be obtained.
[0027]
The fibrous SS in the inflow raw water forms a highly cohesive sludge floc by the coagulation treatment, and the sludge dynamic filtration layer formed on the filter surface filters and separates the SS in the untreated liquid at a low head pressure. be able to. Since the dynamic filtration layer is mainly formed of aggregated fibrous SS, the water permeability is high, and the fibrous SS to be removed is almost completely blocked by the dynamic filtration layer.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of an apparatus for performing solid-liquid separation of an organic wastewater biological treatment liquid of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inflow raw water 2 Aeration tank 3 Aeration blower 4 Aeration pipe 5 Filtration separation tank 6 Filtration module 7 Inorganic flocculant 8 Air washing blower 9 Air washing aeration pipe 10 Filtration water collection pipe 11 Filtration water valve 12 Filtration water 13 Drainage Mud valve 14 Discharged sludge 15 Water backwash pump 16 Return sludge 17 Treated water tank 18 Treated water 19 Concentrated sludge
20 Backwash water piping

Claims

After introducing organic wastewater containing fibrous SS and BOD into the aeration tank and performing biological treatment, the biological treatment liquid is allowed to flow into the upper part of the filtration separation tank in which the aqueous filter is immersed, and then into the treatment liquid. An inorganic flocculant is added and agglomerated, and the agglomerated mixed solution is filtered through the water-permeable filter to form a dynamic filtration layer of agglomerated sludge on the surface of the water-permeable filter. The solid-liquid separation method of the biological treatment liquid of organic wastewater is characterized in that the sludge concentrate after filtration is returned to the aeration tank from the lower part of the filtration separation tank .

An aeration tank is provided at the bottom, organic waste water is supplied to perform biological treatment by aeration, a filtered water collecting pipe for supplying filtered water to the treated water tank at the top with head pressure, and the aeration tank at the bottom hydro pipe to return the waste sludge sludge from the inside is attached to the filtration separation tank in which the filtration module with a filtration module dynamic filtering layer is formed is disposed is immersed in the bath on the surface, the and filtration separation tank feed pipe biologically treated water from the aeration tank provided above the supply tube of the inorganic coagulant, a sparge tube for air washing provided in the filtration separation tank bottom, the filtration separation tank bottom The return sludge removal pipe for returning the return sludge to the attached aeration tank, the concentrated sludge extraction pipe attached to the bottom of the filtration separation tank, and the filtered water are stored and connected to the treated water discharge pipe and the filtration module . A flush pipe is attached. Solid-liquid separation equipment of the biological treatment liquid organic waste water characterized by having a process water tank are.