JP4439149B2

JP4439149B2 - Submerged membrane separation activated sludge treatment equipment

Info

Publication number: JP4439149B2
Application number: JP2001292686A
Authority: JP
Inventors: 雅治塗師; 山田　　豊; 清司和泉; 太一上坂
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 2001-09-26
Filing date: 2001-09-26
Publication date: 2010-03-24
Anticipated expiration: 2021-09-26
Also published as: JP2003094086A

Description

【０００１】
【発明の属する技術分野】
本発明は浸漬型膜分離活性汚泥処理設備に関し、下廃水処理などで行う浸漬型膜分離活性汚泥法の技術に係るものである。
【０００２】
【従来の技術】
従来の浸漬型膜分離活性汚泥法に使用する浸漬型膜分離装置としては、例えば図９に示すものがある。図９において、浸漬型膜分離装置１は、ケーシング２の内部に複数の平板状膜カートリッジ３を膜面を鉛直方向にして、かつ膜面間に一定間隙をおいて（通常６〜１０ｍｍ）配列し、その下方に散気装置４を配設している。平板状膜カートリッジ３は樹脂などの剛性を有する濾板３Ａの表裏両面に濾過膜３Ｂを配置し、その周縁部において濾過膜３Ｂを濾板３Ａに接着あるいは溶着したものであり、透過水流路に連通する透過水取出口３Ｃをチューブ５を介して集水管６に接続している。
【０００３】
浸漬型膜分離装置１は散気装置４より散気する状態において槽内混合液を平板状膜カートリッジ３で濾過して活性汚泥と処理水とに分離し、濾過膜を透過した処理水をチューブ５、集水管６を通じて槽外へ導出する。
【０００４】
【発明が解決しようとする課題】
しかし、汚水中の汚濁物質濃度（ＢＯＤなど）が高くなると、浸漬型膜分離装置１に設けた散気装置４から供給する空気量だけでは活性汚泥が汚濁物質を分解するために必要な酸素量を供給することができず、分解に寄与する微生物量も増加させる必要がある。
【０００５】
このために、図７に示すように、汚水が流入する流量調整槽１１の後段に前曝気槽１２を配置し、前曝気槽１２の後段に配置する膜分離槽１３の内部に必要台数の浸漬型膜分離装置１を設置し、膜分離槽１３の後段に処理水槽１４を設置し、前曝気槽１２に配置した別途の散気装置１５によって不足する酸素量を補給すると共に、必要な微生物量を確保する構成がある。
【０００６】
ところで、前曝気槽１２と膜分離槽１３との２槽式にする場合に、系内の汚水の流れを一方向にすると、前曝気槽１２で増加した活性汚泥は汚水とともに膜分離槽１３へ流入して膜分離槽１３での汚泥濃度が過剰に高まるので、循環ポンプ１６によって前曝気槽１２から膜分離槽１３へ槽内混合液を供給するとともに、膜分離槽１３の槽内混合液を前曝気槽１２へ自然流下で返送して両槽間で槽内混合液を循環させるか、もしくは図８に示すように、前曝気槽１２の槽内混合液を自然流下で膜分離槽１３へ供給し、膜分離槽１３の槽内混合液を循環ポンプ１６で前曝気槽１２に返送して循環させることで、両槽における汚泥濃度をできるだけ均一にして単位水槽容積当たりの微生物量を適値に維持する必要がある。
【０００７】
この場合に、流量調整槽１１から前曝気槽１２へ流入する汚水流入量Ｑと、膜分離槽１３から前曝気槽１２へ循環する槽内混合液の循環量ＲＱとの割合である槽内混合液の循環倍率：ＲＱ／Ｑが少ないと、前曝気槽１２における汚泥濃度が低くなり、単位水槽容積当たりの微生物量が少なくなる。
【０００８】
因みに、循環倍率と前曝気槽１２における汚泥濃度の関係の一例を説明すると、膜分離槽１３における汚泥濃度が２％である場合に、循環倍率２倍で汚泥濃度１．３％、循環倍率４倍で汚泥濃度１．６％、循環倍率９倍で汚泥濃度１．８％となる。
【０００９】
したがって、前曝気槽１２と膜分離槽１３との２槽式にする場合には、活性汚泥濃度を均一にするために循環ポンプ１６に要求される定格容量が大きくなり、動力費が高くなる問題があった。
【００１０】
また、膜分離槽１３に複数の浸漬型膜分離装置１を配置する場合には、各膜分離装置１において槽内混合液から処理水が除去される。このため、膜分離槽１３では前曝気槽１２から槽内混合液が流入する流入側と前曝気槽１２へ槽内混合液が流出する返送側とにおいて汚泥濃度に濃度差が生じ、微生物量が不均一となって効率的な生物処理が行えない。
【００１１】
ところで、汚水を曝気槽へ分散して供給する手法としては、重力沈殿法におけるステップエアレーション方式がある。しかし、ＢＯＤが高い汚水を分散して供給する場合に、供給した汚水が十分な生物処理を経ずにショートパスして浸漬型膜分離装置１に流入して膜分離される場合がある。
【００１２】
本発明は上記した課題を解決するものであり、系内に流入するＢＯＤが高い場合にあっても、一槽において生物処理に必要な十分な酸素供給と膜分離を行うことができる浸漬型膜分離活性汚泥処理設備を提供することを目的とする。
【００１３】
【課題を解決するための手段】
上記課題を解決するために、本発明の浸漬型膜分離活性汚泥処理設備は、上下が開口した膜ケースの内部に複数の平板状膜カートリッジを膜面を鉛直方向にして膜面間に一定間隙をおいて配列することで膜ケースユニットを構成し、膜分離槽内に複数の膜ケースユニットを所定間隔で配置し、各膜ケースユニットの下方に散気装置を配置し、各膜ケースユニットの側方に補助散気装置を配置し、各膜ケースユニットと補助散気装置との間に仕切壁を配置して補助散気装置の上方に仕切壁の上端側および下端側で周囲の槽内領域に連通する上向流路を形成し、被処理水の供給口を各上向流路の下部域に配置したものである。
【００１４】
上記した構成により、仕切壁を隔てた上向流路では補助散気装置から噴出する空気によって上向流が生じ、各供給口から各上向流路内に分散供給する被処理水は、上向流に伴われて仕切壁の下端側の周囲の槽内混合液とともに固気液混相流となって上向流路内を流れる。上向流路を固気液混相流で通過した被処理水は膜分離槽の上部域に流れ出た後に、仕切壁と膜ケースユニットとの間の下向流路を流れて膜分離槽の下部域に循環する。
【００１５】
一方、散気装置から噴出する空気によって上向流が生じ、上向流は周囲の槽内混合液を伴って固気液混相流となって膜ケースユニットに流入し、平板状膜カートリッジの間の流路をクロスフローで流れる間に膜分離される。各膜ケースユニットを通過した固気液混相流は膜分離槽の上部域に流れ出た後に、仕切壁と膜ケースユニットとの間に形成する下向流路を流れて膜分離槽の下部域に循環する。
【００１６】
よって、被処理水のＢＯＤが高い場合にあっても、散気装置から供給する空気量では不足する分量を補助散気装置から供給する空気で補うことで生物処理に必要な十分な酸素量が確保される。各供給口から膜分離槽へ供給する被処理水は、上向流路内で補助散気装置から噴出する空気によって十分な酸素供給を受け、しかも上向流路および下向流路を通って膜分離槽の下部域に循環することで供給口からショートパスで膜ケースユニットに流入することがなく、槽内で十分に生物処理される。膜分離槽の上部域おいて膜ケースユニットから流れ出る槽内混合液の流れが抵抗なって上向流路から流れ出る被処理水の流れを抑制することで、上向流路における被処理水の滞留時間が長くなり、補助散気装置から供給する空気と被処理水との十分な接触時間が確保され、酸素溶解率が高まる。
【００１７】
このように、膜分離槽内の膜ケースユニットを配置した各域毎に被処理水を分散供給してその生物処理と膜分離を行うことで、循環ポンプが不要な単一槽の膜分離槽内において、槽内の原水負荷（ＢＯＤ負荷）を均一となし、槽内全域を略均一な汚泥濃度に制御し、単位水槽容積当たりの微生物物量を平均化して効率の良い生物処理を行える。
【００１８】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。図１〜図２において、膜分離槽３１の内部には複数の膜ケースユニット３２を所定間隔で配置し、各膜ケースユニット３２に処理水系３２ａを接続しており、各膜ケースユニット３２の下方に散気装置３３を配置している。
【００１９】
各膜ケースユニット３２は、上下が開口した膜ケース３４の内部に複数の平板状膜カートリッジ３５を膜面を鉛直方向にして膜面間に一定間隙をおいて配列したものであり、平板状膜カートリッジ３５は先に説明したものと同様であるのでその詳細な説明を省略する。
【００２０】
各膜ケースユニット３２の側方には補助散気装置３６を配置し、各膜ケースユニット３２と補助散気装置３６との間に仕切壁３７を配置しており、仕切壁３７は上端縁側に越流口３７ａを形成するとともに、下端縁側に潜流口３７ｂを形成している。この仕切壁３７によって補助散気装置３６の上方には、相互に対向する一対の仕切壁３７の間、および膜分離槽３１の槽壁と仕切壁３７の間に上向流路３８を形成しており、仕切壁３７と膜ケースユニット３２の間には下向流路３９を形成している。上向流路３８および下向流路３９は仕切壁３７の上端側および下端側で周囲の槽内領域に連通している。汚水等の被処理水を供給する被処理水供給系４０はその供給口４０ａを各上向流路３８の下部域にそれぞれ分岐配置している。
【００２１】
以下、上記した構成における作用を説明する。上向流路３８では補助散気装置３６から噴出する空気によって上向流が生じる。このため、被処理水供給系４０の各供給口４０ａから各上向流路３８の下部域に分散供給する被処理水は、仕切壁３７の潜流口３７ｂから上向流路３８に流入する周囲の槽内混合液とともに、上向流に伴われて固気液混相流となって上向流路３８を流れる。
【００２２】
上向流路３８を固気液混相流となって通過した被処理水は、膜分離槽３１の上部域に流れ出た後に、仕切壁３７と膜ケースユニット３２との間の下向流路３９を流れて膜分離槽３１の下部域に循環する。
【００２３】
一方、膜ケースユニット３２の領域では散気装置３３から噴出する空気によって上向流が生じる。上向流は周囲の槽内混合液を伴って固気液混相流となって膜ケースユニット３２に流入し、槽内混合液は平板状膜カートリッジ３５の間の流路をクロスフローで流れる間に膜分離され、処理水が処理水系３２ａを通して取出される。
【００２４】
各膜ケースユニット３２を通過した固気液混相流は膜分離槽３１の上部域に流れ出た後に、仕切壁３７と膜ケースユニット３２との間の下向流路３９を流れて膜分離槽３１の下部域に循環する。
【００２５】
したがって、被処理水のＢＯＤが高い場合にあっても、散気装置３３から供給する空気量では不足する分量を補助散気装置３６から供給する空気で補うことで十分な酸素量の下で適切に生物処理が行われる。
【００２６】
また、各供給口４０ａから膜分離槽３１へ供給する被処理水は、上向流路３８で補助散気装置３６から噴出する空気によって十分な酸素供給を受け、しかも上向流路３８および下向流路３９を通って膜分離槽３１の下部域に循環することで供給口４０ａからショートパスで膜ケースユニット３２に流入することがないので、膜分離槽３１で十分に生物処理されて膜分離される。
【００２７】
さらに、膜分離槽３１の上部域において膜ケースユニット３２から流れ出る槽内混合液の流れが抵抗なって上向流路３８から流れ出る被処理水の流れを抑制し、その流速を遅くするので、上向流路３８における被処理水の滞留時間が長くなり、補助散気装置３６から供給する空気と被処理水との十分な接触時間が確保されて酸素溶解率が高まる。
【００２８】
ところで、補助散気装置３６から供給する空気量は、設備設計時に想定する被処理水のＢＯＤに応じて異なるので、膜分離槽３１の上部域における膜ケースユニット３２から流れ出る槽内混合液の流れと、上向流路３８から流れ出る被処理水の流れとのバランスを調整するために、仕切壁３７の高さを調整する。
【００２９】
例えば、被処理水のＢＯＤが低くて補助散気装置３６から供給する空気量が少ない場合には、図３に示すように、仕切壁３７を膜ケースユニット３２より高く設定して槽内液面と仕切壁３７の上端縁との距離Ｈを短くし、仕切壁３７による越流口３７ａでの流路抵抗を大きくすることで、膜ケースユニット３２から流れ出る槽内混合液の流れが及ぼす抵抗力を低減し、上向流路３８における流速を適値に調整する。
【００３０】
逆に、被処理水のＢＯＤが高くて補助散気装置３６から供給する空気量が多い場合には、図４に示すように、仕切壁３７を膜ケースユニット３２より低く設定して仕切壁３７による越流口３７ａでの流路抵抗を小さくし、膜ケースユニット３２から流れ出る槽内混合液の流れが及ぼす抵抗力を増加させることで、上向流路３８における流速を遅くする。
【００３１】
図５〜図６に示すように、仕切壁３７は補助散気装置３６の上方に枠体状の散気ボックス４１を配置して構成することも可能である。
【００３２】
【発明の効果】
以上のように本発明によれば、各供給口から膜分離槽へ供給する被処理水は、上向流路内で補助散気装置から噴出する空気によって十分な酸素供給を受け、しかも上向流路および下向流路を通って膜分離槽の下部域に循環するので、供給口からショートパスで膜ケースユニットに流入することがなく、槽内で十分に生物処理することができ、膜ケースユニットから流れ出る槽内混合液の流れが抵抗となって上向流路から流れ出る被処理水の流れを抑制することで、上向流路における被処理水の滞留時間が長くなり、補助散気装置から供給する空気と被処理水との十分な接触時間を確保して酸素溶解率を高めることができ、その結果において、膜分離槽内の膜ケースユニットを配置した各域毎に被処理水を分散供給してその生物処理と膜分離を行うことで、循環ポンプが不要な単一槽の膜分離槽内において、槽内の原水負荷（ＢＯＤ負荷）を均一となし、槽内全域を略均一な汚泥濃度に制御し、単位水槽容積当たりの微生物物量を平均化して効率の良い生物処理を行える。
【図面の簡単な説明】
【図１】本発明の実施の形態における浸漬型膜分離活性汚泥処理設備を示す断面図である。
【図２】同浸漬型膜分離活性汚泥処理設備を示す平面図である。
【図３】同浸漬型膜分離活性汚泥処理設備の要部を示す拡大図である。
【図４】同浸漬型膜分離活性汚泥処理設備の要部を示す拡大図である。
【図５】本発明の他の実施の形態における浸漬型膜分離活性汚泥処理設備を示す断面図である。
【図６】同浸漬型膜分離活性汚泥処理設備を示す平面図である。
【図７】従来の浸漬型膜分離活性汚泥処理設備を示す模式図である。
【図８】従来の他の浸漬型膜分離活性汚泥処理設備を示す模式図である。
【図９】従来の膜分離装置の斜視図である。
【符号の説明】
３１膜分離槽
３２膜ケースユニット
３２ａ処理水系
３３散気装置
３４膜ケース
３５平板状膜カートリッジ
３６補助散気装置
３７仕切壁
３７ａ越流口
３７ｂ潜流口
３８上向流路
３９下向流路
４０被処理水供給系
４０ａ供給口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a submerged membrane separation activated sludge treatment facility and relates to a technique of a submerged membrane separation activated sludge method performed in sewage wastewater treatment or the like.
[0002]
[Prior art]
An example of a submerged membrane separation apparatus used in a conventional submerged membrane separation activated sludge method is shown in FIG. In FIG. 9, the submerged membrane separation apparatus 1 has a plurality of flat membrane cartridges 3 arranged in a casing 2 with the membrane surfaces in the vertical direction and with a certain gap between the membrane surfaces (usually 6 to 10 mm). The air diffuser 4 is disposed below the air diffuser 4. The flat membrane cartridge 3 is formed by arranging filtration membranes 3B on both front and back surfaces of a filter plate 3A having rigidity such as resin, and adhering or welding the filtration membrane 3B to the filter plate 3A at the peripheral edge thereof. The permeated water outlet 3 </ b> C that communicates is connected to the water collecting pipe 6 via the tube 5.
[0003]
The submerged membrane separation apparatus 1 filters the mixed liquid in the tank through the flat membrane cartridge 3 in a state of being diffused from the air diffuser 4 to separate into activated sludge and treated water, and the treated water that has permeated the filtration membrane is tubed 5. Lead out of the tank through the water collecting pipe 6.
[0004]
[Problems to be solved by the invention]
However, when the pollutant concentration (such as BOD) in the sewage becomes high, the amount of oxygen necessary for the activated sludge to decompose the pollutants only with the amount of air supplied from the air diffuser 4 provided in the submerged membrane separator 1. Therefore, it is necessary to increase the amount of microorganisms that contribute to degradation.
[0005]
For this purpose, as shown in FIG. 7, a pre-aeration tank 12 is disposed downstream of the flow rate adjustment tank 11 into which sewage flows, and a necessary number of pieces are immersed in the membrane separation tank 13 disposed downstream of the pre-aeration tank 12. The mold membrane separation apparatus 1 is installed, the treated water tank 14 is installed in the subsequent stage of the membrane separation tank 13, and the deficient oxygen amount is replenished by a separate air diffuser 15 arranged in the preaeration tank 12, and the necessary amount of microorganisms There is a configuration to ensure.
[0006]
By the way, in the case of a two-tank system including the pre-aeration tank 12 and the membrane separation tank 13, if the flow of sewage in the system is unidirectional, the activated sludge increased in the pre-aeration tank 12 is transferred to the membrane separation tank 13 together with the sewage. Since the sludge concentration in the membrane separation tank 13 increases excessively, the mixed liquid in the tank is supplied from the pre-aeration tank 12 to the membrane separation tank 13 by the circulation pump 16, and the mixed liquid in the membrane separation tank 13 is supplied. Either return to the pre-aeration tank 12 under natural flow and circulate the mixed liquid in the tank between the two tanks, or, as shown in FIG. 8, the internal mixed liquid in the pre-aeration tank 12 flows to the membrane separation tank 13 under natural flow. By supplying and circulating the liquid mixture in the membrane separation tank 13 back to the pre-aeration tank 12 with the circulation pump 16, the sludge concentration in both tanks is made as uniform as possible, and the amount of microorganisms per unit water tank volume is appropriate. Need to be maintained.
[0007]
In this case, in-tank mixing, which is a ratio of the sewage inflow amount Q flowing from the flow rate adjusting tank 11 into the pre-aeration tank 12 and the circulation amount RQ of the mixed liquid in the tank circulating from the membrane separation tank 13 to the pre-aeration tank 12. When the liquid circulation ratio: RQ / Q is small, the sludge concentration in the pre-aeration tank 12 is low, and the amount of microorganisms per unit water tank volume is small.
[0008]
Incidentally, an example of the relationship between the circulation rate and the sludge concentration in the pre-aeration tank 12 will be described. When the sludge concentration in the membrane separation tank 13 is 2%, the sludge concentration is 1.3% at a circulation rate of 2 and the circulation rate is 4 Double the sludge concentration is 1.6%, and if the circulation magnification is 9 times, the sludge concentration is 1.8%.
[0009]
Therefore, in the case of using a two-tank system with the pre-aeration tank 12 and the membrane separation tank 13, the rated capacity required for the circulation pump 16 in order to make the activated sludge concentration uniform, and the power cost increases. was there.
[0010]
Further, when a plurality of submerged membrane separation devices 1 are arranged in the membrane separation tank 13, the treated water is removed from the mixed liquid in the tank in each membrane separation apparatus 1. For this reason, in the membrane separation tank 13, a difference in the concentration of sludge occurs between the inflow side where the mixed liquid in the tank flows from the preaeration tank 12 and the return side where the mixed liquid in the tank flows out to the preaeration tank 12, and the amount of microorganisms is reduced. It becomes uneven and efficient biological treatment cannot be performed.
[0011]
By the way, there is a step aeration method in the gravity precipitation method as a method of supplying the sewage in a distributed manner to the aeration tank. However, when the sewage having a high BOD is distributed and supplied, the supplied sewage may be short-passed without sufficient biological treatment and flow into the submerged membrane separation apparatus 1 for membrane separation.
[0012]
The present invention solves the above-mentioned problems, and even when the BOD flowing into the system is high, a submerged membrane that can perform sufficient oxygen supply and membrane separation necessary for biological treatment in one tank It aims at providing the separation activated sludge processing equipment.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the submerged membrane separation activated sludge treatment facility of the present invention has a plurality of flat membrane cartridges in a membrane case opened at the top and bottom, and a fixed gap between the membrane surfaces with the membrane surface in the vertical direction. A plurality of membrane case units are arranged at predetermined intervals in the membrane separation tank, and an air diffuser is arranged below each membrane case unit. An auxiliary air diffuser is arranged on the side, a partition wall is arranged between each membrane case unit and the auxiliary air diffuser, and inside the surrounding tank on the upper end side and the lower end side of the partition wall above the auxiliary air diffuser. An upward flow path communicating with the region is formed, and a supply port of water to be treated is disposed in a lower area of each upward flow path.
[0014]
With the above-described configuration, the upward flow generated by the auxiliary air diffuser is generated in the upward flow path separating the partition walls, and the water to be treated distributedly supplied from the supply ports into the upward flow paths is Along with the countercurrent flow, it flows in the upward flow path as a solid-gas / liquid mixed phase flow together with the mixed liquid in the tank around the lower end side of the partition wall. The water to be treated that has passed through the upward flow path as a solid-gas mixed phase flow flows out to the upper area of the membrane separation tank, and then flows through the downward flow path between the partition wall and the membrane case unit to the lower part of the membrane separation tank. Cycle to the area.
[0015]
On the other hand, an upward flow is generated by the air ejected from the air diffuser, and the upward flow flows into the membrane case unit as a mixed gas-liquid mixed flow with the surrounding liquid mixture in the tank, and between the flat membrane cartridges. The membrane is separated while flowing in the cross-flow path. After the solid-gas-liquid mixed phase flow that has passed through each membrane case unit flows out to the upper area of the membrane separation tank, it flows through the downward flow path formed between the partition wall and the membrane case unit to the lower area of the membrane separation tank. Circulate.
[0016]
Therefore, even when the BOD of the water to be treated is high, a sufficient amount of oxygen necessary for biological treatment can be obtained by supplementing the amount of air supplied from the air diffuser with the air supplied from the auxiliary air diffuser. Secured. The treated water supplied from each supply port to the membrane separation tank is supplied with sufficient oxygen by the air ejected from the auxiliary air diffuser in the upward flow path, and passes through the upward flow path and the downward flow path. By circulating to the lower region of the membrane separation tank, the biological treatment is sufficiently performed in the tank without flowing into the membrane case unit from the supply port through a short path. In the upper area of the membrane separation tank, the flow of the mixed liquid in the tank flowing out from the membrane case unit is resisted and the flow of the treated water flowing out from the upper flow path is suppressed, so that the treated water stays in the upper flow path. Time is increased, sufficient contact time between the air supplied from the auxiliary air diffuser and the water to be treated is secured, and the oxygen dissolution rate is increased.
[0017]
In this way, a single tank membrane separation tank that does not require a circulation pump by dispersing and supplying the water to be treated to each region where the membrane case unit in the membrane separation tank is arranged to perform biological treatment and membrane separation. In the inside, the raw water load (BOD load) in the tank is made uniform, the entire area in the tank is controlled to a substantially uniform sludge concentration, and the amount of microorganisms per unit water tank volume is averaged to perform efficient biological treatment.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 2, a plurality of membrane case units 32 are arranged at predetermined intervals in the membrane separation tank 31, and a treated water system 32 a is connected to each membrane case unit 32, below each membrane case unit 32. An air diffuser 33 is disposed in the front.
[0019]
Each membrane case unit 32 is configured by arranging a plurality of flat membrane cartridges 35 inside a membrane case 34 that is open at the top and bottom, with the membrane surface in the vertical direction, with a certain gap between the membrane surfaces. Since the cartridge 35 is the same as that described above, its detailed description is omitted.
[0020]
An auxiliary air diffuser 36 is disposed on the side of each membrane case unit 32, and a partition wall 37 is disposed between each membrane case unit 32 and the auxiliary air diffuser 36. The partition wall 37 is located on the upper edge side. The overflow port 37a is formed, and the latent flow port 37b is formed on the lower edge side. An upper flow path 38 is formed above the auxiliary air diffuser 36 by the partition wall 37 between the pair of partition walls 37 facing each other and between the tank wall of the membrane separation tank 31 and the partition wall 37. A downward flow path 39 is formed between the partition wall 37 and the membrane case unit 32. The upward flow path 38 and the downward flow path 39 communicate with the surrounding tank area on the upper end side and the lower end side of the partition wall 37. In the treated water supply system 40 for supplying treated water such as sewage, the supply port 40 a is branched and arranged in the lower area of each upward flow path 38.
[0021]
Hereinafter, the operation of the above-described configuration will be described. In the upward flow path 38, an upward flow is generated by the air ejected from the auxiliary air diffuser 36. For this reason, the water to be treated distributedly supplied from the supply ports 40 a of the treated water supply system 40 to the lower regions of the upward flow paths 38 flows into the upward flow path 38 from the latent flow ports 37 b of the partition wall 37. Together with the liquid mixture in the tank, the gas flows in the upward flow path 38 as a solid-gas / liquid mixed phase flow accompanying the upward flow.
[0022]
The water to be treated that has passed through the upward flow path 38 as a solid-gas-liquid mixed phase flow flows out to the upper region of the membrane separation tank 31 and then flows downward in the downward flow path 39 between the partition wall 37 and the membrane case unit 32. And circulates in the lower region of the membrane separation tank 31.
[0023]
On the other hand, in the region of the membrane case unit 32, an upward flow is generated by the air ejected from the air diffuser 33. The upward flow flows into the membrane case unit 32 together with the surrounding mixed liquid in the tank and flows into the membrane case unit 32, and the mixed liquid in the tank flows through the flow path between the flat membrane cartridges 35 in a cross flow. The treated water is taken out through the treated water system 32a.
[0024]
After the solid-gas / liquid mixed phase flow that has passed through each membrane case unit 32 flows out to the upper region of the membrane separation tank 31, it flows through the downward flow path 39 between the partition wall 37 and the membrane case unit 32 and flows into the membrane separation tank 31. It circulates in the lower area.
[0025]
Therefore, even when the BOD of the water to be treated is high, the amount of air supplied from the air diffuser 33 is adequately compensated for by the air supplied from the auxiliary air diffuser 36 under a sufficient amount of oxygen. Biological treatment is performed.
[0026]
In addition, the water to be treated supplied from each supply port 40a to the membrane separation tank 31 is supplied with sufficient oxygen by the air ejected from the auxiliary air diffuser 36 in the upward flow path 38, and the upward flow path 38 and the lower flow path By circulating to the lower region of the membrane separation tank 31 through the counter flow path 39, the membrane does not flow into the membrane case unit 32 from the supply port 40a through a short path. To be separated.
[0027]
Furthermore, in the upper region of the membrane separation tank 31, the flow of the mixed liquid in the tank flowing out from the membrane case unit 32 is resisted to suppress the flow of water to be treated flowing out from the upward flow path 38, and the flow velocity is reduced. The residence time of the water to be treated in the counter flow path 38 becomes longer, a sufficient contact time between the air supplied from the auxiliary air diffuser 36 and the water to be treated is secured, and the oxygen dissolution rate is increased.
[0028]
By the way, the amount of air supplied from the auxiliary air diffuser 36 differs depending on the BOD of the water to be treated which is assumed at the time of facility design, so the flow of the mixed liquid in the tank flowing out from the membrane case unit 32 in the upper area of the membrane separation tank 31. And the height of the partition wall 37 is adjusted in order to adjust the balance with the flow of the to-be-processed water which flows out from the upward flow path 38. FIG.
[0029]
For example, when the BOD of the water to be treated is low and the amount of air supplied from the auxiliary air diffuser 36 is small, the partition wall 37 is set higher than the membrane case unit 32 as shown in FIG. The resistance force exerted by the flow of the liquid mixture in the tank flowing out from the membrane case unit 32 is shortened by increasing the distance H between the upper end edge of the partition wall 37 and the flow path resistance at the overflow port 37a by the partition wall 37. And the flow velocity in the upward flow path 38 is adjusted to an appropriate value.
[0030]
On the contrary, when the BOD to be treated is high and the amount of air supplied from the auxiliary air diffuser 36 is large, the partition wall 37 is set lower than the membrane case unit 32 as shown in FIG. By reducing the flow resistance at the overflow port 37a due to the flow and increasing the resistance force exerted by the flow of the mixed liquid in the tank flowing out from the membrane case unit 32, the flow velocity in the upward flow path 38 is slowed down.
[0031]
As shown in FIGS. 5 to 6, the partition wall 37 can be configured by disposing a frame-like air diffusion box 41 above the auxiliary air diffusion device 36.
[0032]
【The invention's effect】
As described above, according to the present invention, the water to be treated supplied from each supply port to the membrane separation tank is supplied with sufficient oxygen by the air ejected from the auxiliary air diffuser in the upward flow path, and is Since it circulates in the lower region of the membrane separation tank through the flow path and the downward flow path, it does not flow into the membrane case unit through a short path from the supply port, and can be sufficiently biologically treated in the tank. The flow of the mixed liquid in the tank flowing out from the case unit becomes a resistance and suppresses the flow of the treated water flowing out from the upward flow path, thereby increasing the residence time of the treated water in the upward flow path, and the auxiliary air diffusion A sufficient contact time between the air supplied from the apparatus and the water to be treated can be secured and the oxygen dissolution rate can be increased. As a result, the water to be treated is provided for each region where the membrane case unit in the membrane separation tank is arranged. For the biological treatment and membrane separation Thus, in a single tank membrane separation tank that does not require a circulation pump, the raw water load (BOD load) in the tank is made uniform, and the entire tank interior is controlled to a substantially uniform sludge concentration, per unit tank volume. Efficient biological treatment can be performed by averaging the amount of microbial matter.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a submerged membrane separation activated sludge treatment facility in an embodiment of the present invention.
FIG. 2 is a plan view showing the same submerged membrane separation activated sludge treatment facility.
FIG. 3 is an enlarged view showing a main part of the submerged membrane separation activated sludge treatment facility.
FIG. 4 is an enlarged view showing a main part of the submerged membrane separation activated sludge treatment facility.
FIG. 5 is a sectional view showing a submerged membrane separation activated sludge treatment facility according to another embodiment of the present invention.
FIG. 6 is a plan view showing the submerged membrane separation activated sludge treatment facility.
FIG. 7 is a schematic view showing a conventional submerged membrane separation activated sludge treatment facility.
FIG. 8 is a schematic view showing another conventional submerged membrane separation activated sludge treatment facility.
FIG. 9 is a perspective view of a conventional membrane separation apparatus.
[Explanation of symbols]
31 Membrane separation tank 32 Membrane case unit 32a Treated water system 33 Air diffuser 34 Membrane case 35 Flat membrane cartridge 36 Auxiliary air diffuser 37 Partition wall 37a Overflow port 37b Underflow port 38 Upstream channel 39 Downstream channel 40 Covered Treated water supply system 40a supply port

Claims

A membrane case unit is configured by arranging a plurality of flat membrane cartridges inside a membrane case opened at the top and bottom with a fixed gap between the membrane surfaces with the membrane surface in the vertical direction, and a plurality of membrane cartridge units are provided in the membrane separation tank. Membrane case units are arranged at predetermined intervals, an air diffuser is disposed below each membrane case unit, an auxiliary air diffuser is disposed on the side of each membrane case unit, and each membrane case unit and auxiliary air diffuser are A partition wall is disposed between the upper and lower auxiliary air diffusers to form an upward flow path communicating with the surrounding tank area on the upper end side and the lower end side of the partition wall. A submerged membrane separation activated sludge treatment facility characterized by being arranged in the lower area of the counter flow channel.