JP5448285B2 - Membrane separation activated sludge treatment method - Google Patents

Membrane separation activated sludge treatment method Download PDF

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JP5448285B2
JP5448285B2 JP2005353668A JP2005353668A JP5448285B2 JP 5448285 B2 JP5448285 B2 JP 5448285B2 JP 2005353668 A JP2005353668 A JP 2005353668A JP 2005353668 A JP2005353668 A JP 2005353668A JP 5448285 B2 JP5448285 B2 JP 5448285B2
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渉 藤井
禎仁 中原
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Mitsubishi Chemical Corp
Mitsubishi Rayon Co Ltd
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    • YGENERAL 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

本発明は、工業用排水や生活用排水中に含まれる有機物やその残骸、或いは微生物や細菌類を含む排水を生物化学的に処理して分離膜を用いて固液分離を行う膜分離活性汚泥処理方法に関する。   The present invention is a membrane-separated activated sludge that performs solid-liquid separation using a separation membrane by biochemically treating organic matter and its debris contained in industrial wastewater and domestic wastewater, or wastewater containing microorganisms and bacteria. It relates to the processing method.

従来の膜分離活性汚泥処理方法によれば、微細目スクリーンにて比較的大きな固形分が除去された排水(原水)が原水調整槽に導入される。この原水調整槽では、液面を液面計により測定し、第1送液ポンプを間欠駆動して槽内の液面高さを所定の範囲内となるように調整している。第1液送ポンプによって送られる原水は嫌気槽に導入されたのち、嫌気槽から溢流する原水を隣接するばっ気槽に流入させる。このばっ気槽には膜ろ過ユニットが浸漬して配されている。この膜ろ過ユニットにて活性汚泥と処理水とに膜分して、ろ過された処理水を吸引ポンプにより処理水槽へと送液する。余剰汚泥は汚泥貯留槽に貯蔵される。また、ばっ気槽の内部の汚泥の一部は第2液送ポンプによって上記嫌気槽へと返送されて循環する。   According to the conventional membrane separation activated sludge treatment method, waste water (raw water) from which a relatively large solid content is removed by a fine screen is introduced into the raw water adjustment tank. In this raw water adjustment tank, the liquid level is measured by a liquid level gauge, and the first liquid feed pump is intermittently driven to adjust the liquid level height in the tank to be within a predetermined range. After the raw water sent by the first liquid feed pump is introduced into the anaerobic tank, the raw water overflowing from the anaerobic tank is caused to flow into the adjacent aeration tank. A membrane filtration unit is immersed in this aeration tank. This membrane filtration unit divides the membrane into activated sludge and treated water, and the filtered treated water is sent to the treated water tank by a suction pump. Excess sludge is stored in a sludge storage tank. A part of the sludge inside the aeration tank is returned to the anaerobic tank by the second liquid feed pump and circulated.

前記膜ろ過ユニットは、例えば特開2000−51672号公報(特許文献1)に開示されているように、多数の多孔性中空糸を同一平面上に平行に並べたシート状の中空糸膜エレメントを、所要の間隔をおいて複数枚並べて得られる中空糸膜モジュールと、同中空糸膜モジュールの下方に配された散気発生装置とを備えている。前記中空糸膜モジュールは、複数枚の中空糸膜エレメントからなる全体形状が略直方体をなしている。一方の散気発生装置は、例えば金属、樹脂などからなるパイプに孔やスリットを設けた複数本の散気管を平行に配設し、各散気管の一端をばっ気ブロアに接続させている。ばっ気ブロアから送られるエアを散気発生装置を介して気泡に変えて汚泥中に放出する。生活排水、工場排水などの汚水を処理する場合、好気性微生物の存在下でばっ気槽の汚泥中の有機物に、散気装置から発生した空気と接触させることにより、前記有機物を前記好気性微生物に吸着・代謝分解させて、生物学的に汚泥処理がなされる。   The membrane filtration unit includes, for example, a sheet-like hollow fiber membrane element in which a large number of porous hollow fibers are arranged in parallel on the same plane as disclosed in Japanese Patent Application Laid-Open No. 2000-51672 (Patent Document 1). And a hollow fiber membrane module obtained by arranging a plurality of sheets at a predetermined interval, and an air diffuser provided below the hollow fiber membrane module. As for the said hollow fiber membrane module, the whole shape which consists of a plurality of hollow fiber membrane element has comprised the substantially rectangular parallelepiped. On the other hand, in the air diffuser, a plurality of air diffuser tubes provided with holes and slits in a pipe made of, for example, metal or resin are arranged in parallel, and one end of each air diffuser tube is connected to an aeration blower. The air sent from the aeration blower is changed into bubbles through a diffuser and discharged into sludge. When treating sewage such as domestic wastewater and factory wastewater, the organic matter is brought into contact with the aerobic microorganisms by contacting the organic matter in the sludge of the aeration tank with the air generated from the aeration device in the presence of aerobic microorganisms. Biological sludge treatment is done by adsorption and metabolic decomposition.

前記中空糸膜モジュールと散気発生装置とは上下が開口する矩形筒状の遮閉板により囲まれている。この遮閉板は、散気発生装置から発生する気泡の上昇により気液混合流を生成し、その流れを上昇流から下降流へと導くための壁部となる。散気発生装置から放出される気泡により発生した気液混合流は、斜め方向に飛散せず、まっすぐに上昇して中空糸膜モジュールに効率よく接触する。このとき、中空糸膜モジュールの膜面に対する気液混合流の一様な分散により、中空糸膜を振動させて各中空糸膜エレメントを均一に洗浄する。また、この気液混合流の発生時にエア中の酸素が溶解して上記生物学的処理を効率的に行うとともに、中空糸膜のろ過機能により汚泥を固形分と水とに分離する。前記膜ろ過ユニットには集水配管の一端が接続され、その他端には吸引ポンプが接続されており、この集水配管を通して、膜ろ過ユニットによってろ過された処理水(ろ過水)が吸引ポンプにより吸引されて処理水槽へと送液される。   The hollow fiber membrane module and the air diffuser are surrounded by a rectangular cylindrical blocking plate that opens upward and downward. This shielding plate becomes a wall portion for generating a gas-liquid mixed flow by the rise of bubbles generated from the air diffuser and guiding the flow from the upward flow to the downward flow. The gas-liquid mixed flow generated by the bubbles released from the diffuser does not scatter in an oblique direction but rises straight and efficiently contacts the hollow fiber membrane module. At this time, the hollow fiber membrane is vibrated by the uniform dispersion of the gas-liquid mixed flow with respect to the membrane surface of the hollow fiber membrane module to uniformly wash the hollow fiber membrane elements. Further, when the gas-liquid mixed flow is generated, oxygen in the air is dissolved to efficiently perform the biological treatment, and the sludge is separated into solid and water by the filtration function of the hollow fiber membrane. One end of a water collection pipe is connected to the membrane filtration unit, and a suction pump is connected to the other end, and treated water (filtered water) filtered by the membrane filtration unit is passed through the water collection pipe by a suction pump. It is sucked and sent to the treated water tank.

膜モジュールとしては、多孔性中空糸を構成部材とするシート状の中空糸膜エレメントの他にも、複数の微細な孔を有するろ過膜を備えたものであればよく、例えば平膜タイプ、管状膜タイプ、袋状膜タイプなどの種々の公知の分離膜を適用することができる。しかして、中空糸膜エレメントを使った中空糸膜モジュールは、ろ過面積が広くなることから多用されるようになった。また、その材質としては、セルロース、ポリオレフィン、ポリスルホン、PVDF(ポリビニリデンフロライド)、PTFE(ポリ四フッ化エチレン)、セラミックスなどが挙げられる。   The membrane module may be anything provided with a filtration membrane having a plurality of fine pores in addition to a sheet-like hollow fiber membrane element having a porous hollow fiber as a constituent member. For example, a flat membrane type, tubular Various known separation membranes such as a membrane type and a bag-like membrane type can be applied. Therefore, hollow fiber membrane modules using hollow fiber membrane elements have come to be used frequently because of the wide filtration area. Examples of the material include cellulose, polyolefin, polysulfone, PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), and ceramics.

上記多孔性中空糸に形成された微細孔の平均孔径は、一般に限外ろ過膜と呼ばれる膜で平均孔径0.001〜0.1μm、一般に精密ろ過膜と呼ばれる膜では平均孔径0.1〜1μmである。例えば、活性汚泥の固液分離に用いるときは、0.5μm以下の孔径であることが好ましく、浄水のろ過のように除菌が必要な場合は0.1μm以下の孔径であることが好ましい。   The average pore diameter of the micropores formed in the porous hollow fiber is generally an average pore diameter of 0.001 to 0.1 μm for a membrane called an ultrafiltration membrane, and an average pore size of 0.1 to 1 μm for a membrane generally called a microfiltration membrane. It is. For example, when used for solid-liquid separation of activated sludge, the pore diameter is preferably 0.5 μm or less, and when sterilization is required as in the case of filtration of purified water, the pore diameter is preferably 0.1 μm or less.

膜分離活性汚泥処理装置は、原水を嫌気槽及びばっ気槽(好気槽、硝化槽)において活性汚泥を生物学的に浄化する。窒素の除去は、嫌気槽とばっ気槽との間で汚泥を循環させて、いわゆる硝化反応と脱窒反応にを繰り返すことによってなされる。BODに換算される有機物は、主としてばっ気槽4内に配置された膜ろ過ユニットの散気管から放出される空気により好気的に酸化され分解される。   The membrane separation activated sludge treatment apparatus biologically purifies activated sludge from raw water in an anaerobic tank and an aeration tank (aerobic tank, nitrification tank). Nitrogen is removed by circulating sludge between an anaerobic tank and an aeration tank and repeating so-called nitrification reaction and denitrification reaction. The organic matter converted to BOD is aerobically oxidized and decomposed mainly by the air released from the diffuser tube of the membrane filtration unit disposed in the aeration tank 4.

またリンの除去は、汚泥中の微生物(リン蓄積細菌)の作用によりポリリン酸として微生物体内に取り込まれることにより行われる。この微生物は好気状態においてリンを取り込み、嫌気状態において体内に蓄えたリンを放出する。リン蓄積細菌は、嫌気状態と好気状態に繰り返して晒されると、嫌気状態で放出したリンの量より多くのリンを好気状態で吸収する。   The removal of phosphorus is performed by being taken into the microorganism as polyphosphoric acid by the action of microorganisms (phosphorus-accumulating bacteria) in the sludge. This microorganism takes up phosphorus in an aerobic state and releases phosphorus stored in the body in an anaerobic state. When repeatedly exposed to anaerobic and aerobic conditions, phosphorus-accumulating bacteria absorb more phosphorus in the aerobic state than the amount of phosphorus released in the anaerobic state.

生物由来の排泄物や残骸などの窒素化合物の一部は、肥料として植物やバクテリアに同化される。また、こうした窒素化合物の一部は、酸素の多い好気条件下で独立栄養アンモニア酸化細菌や独立亜硝酸酸化細菌により、亜硝酸、硝酸へと酸化される。他方、酸素がない無酸素の条件下では、脱窒菌と呼ばれる微生物が酸素に代わって硝酸から亜硝酸を生成し、更には一酸化二窒素、窒素ガスへと還元する。この酸化・還元反応が上記硝化脱窒反応と称される。   Part of nitrogen compounds such as biological excrement and debris is assimilated into plants and bacteria as fertilizer. Some of these nitrogen compounds are oxidized to nitrous acid and nitric acid by autotrophic ammonia oxidizing bacteria and independent nitrite oxidizing bacteria under aerobic conditions with a lot of oxygen. On the other hand, under oxygen-free conditions without oxygen, microorganisms called denitrifying bacteria produce nitrous acid from nitric acid instead of oxygen, and further reduce to dinitrogen monoxide and nitrogen gas. This oxidation / reduction reaction is referred to as the nitrification denitrification reaction.

中空糸膜モジュールを用いてろ過を行うと、膜の微細孔により水中の懸濁物質や細菌類等が除去され、良質のろ過水が得られる。しかしながら、長時間連続してろ過運転を行うと、微細孔が懸濁物質などにより閉塞され、ろ過水量が低下してろ過圧力の上昇が起こり、中空糸膜モジュールを頻繁に交換する必要に迫られる。   When filtration is performed using a hollow fiber membrane module, suspended matter in the water, bacteria, and the like are removed by the fine pores of the membrane, and high-quality filtered water is obtained. However, if filtration operation is performed continuously for a long time, the fine pores are blocked by suspended substances, the amount of filtered water decreases, the filtration pressure rises, and it is necessary to frequently replace the hollow fiber membrane module .

この中空糸膜モジュールの早期目詰まりを防止するために、例えば上記ばっ気用の散気発生装置から放出される比較的大きな気泡により生起される気液混合流を利用して、中空糸や中空糸膜エレメントに振動を与え、膜面に付着する閉塞物質を剥離洗浄する、いわゆるエアスクラビング洗浄を行い、更には中空糸膜の中空部の内部から膜外にろ過水を逆通水する逆洗浄が行われて、ろ過膜のろ過性能の回復がなされている。   In order to prevent premature clogging of the hollow fiber membrane module, for example, by using a gas-liquid mixed flow generated by relatively large bubbles released from the aeration diffuser, the hollow fiber or hollow Performs so-called air scrubbing cleaning, which vibrates the membrane element, peels and removes clogging substances adhering to the membrane surface, and further backwashes the filtered water back from the inside of the hollow portion of the hollow fiber membrane to the outside of the membrane. The filtration performance of the filtration membrane is recovered.

近年、工業用排水処理や汚泥処理場などにおける1日の処理量は数万トンにまでおよび、従来のような1基又は2基程度の膜分離活性汚泥処理の技術だけでは到底まかないきれなくなってきたため、これを効率的に処理する技術の開発が強く望まれている。この要望に応えるべく、例えば米国特許第5,944,997号明細書(特許文献2)に記載されているように、ばっ気槽を大きくするとともに、単一のばっ気槽に多数の膜ろ過ユニットを浸漬して並置し、活性汚泥を一方向に流すようにして、同時に大量の排水処理を行おうとする技術が開発されつつある。上記中空糸膜モジュールを使った複数基の膜ろ過ユニットがばっ気槽内に所要の間隔をおいて直列的に並べて浸漬され、各膜ろ過ユニットに一本の集水管(ろ過水吸引管路)から分岐する分岐管路を介して接続させている。この複数基の中空糸膜モジュールにてろ過された処理水は集水管に集められて一括して吸引ポンプにより集水がなされる。
特開2000−51672号公報 米国特許第5,944,997号明細書
In recent years, the amount of daily treatment in industrial wastewater treatment and sludge treatment plants has reached tens of thousands of tons, and it has become impossible to complete with only one or two membrane separation activated sludge treatment techniques as in the past. Therefore, development of a technique for efficiently processing this has been strongly desired. In order to meet this demand, for example, as described in US Pat. No. 5,944,997 (Patent Document 2), the aeration tank is enlarged and a large number of membrane filtrations are performed in a single aeration tank. Techniques are being developed to immerse units and place them side by side to allow activated sludge to flow in one direction and simultaneously perform a large amount of wastewater treatment. A plurality of membrane filtration units using the hollow fiber membrane module are immersed in aeration tanks arranged in series at a required interval, and each membrane filtration unit has a single water collection pipe (filtrated water suction line). It is connected via a branch pipe that branches off from. The treated water filtered by the plurality of hollow fiber membrane modules is collected in a water collection pipe and collected by a suction pump in a lump.
JP 2000-51672 A US Pat. No. 5,944,997

因みに、20基の膜ろ過ユニットをばっ気槽に直列的に並置すると、ばっ気槽の長さは一般の競泳用プールよりも長くなる。例えば、膜ろ過ユニットの奥行き寸法を1552.5mmとして、上記特許文献2に記載されているように、前記奥行き寸法の1/2の間隔をおいてばっ気槽内に20基の膜ろ過ユニットを並設したとすると、上記吸引管の全長は46575mm以上にもおよぶことになる。   Incidentally, when 20 membrane filtration units are juxtaposed in series with the aeration tank, the length of the aeration tank becomes longer than that of a general swimming pool. For example, the depth dimension of the membrane filtration unit is set to 1552.5 mm, and as described in Patent Document 2, 20 membrane filtration units are placed in the aeration tank at intervals of 1/2 of the depth dimension. Assuming that the suction pipes are arranged side by side, the total length of the suction pipes reaches 46575 mm or more.

一方、通常の膜分離活性汚泥処理装置によれば、ばっ気槽の処理方向の一端部に隣接した嫌気槽から原水を溢流させてばっ気槽に流入させ、処理済の余剰汚泥の一部をばっ気槽から前記嫌気槽へと外部配管を通して戻し、活性汚泥を循環させている。原水流入側の汚泥は処理が進んでいないため活性汚泥濃度は低いが、ばっ気槽の汚泥回収側端部では汚泥の処理が進むため活性汚泥濃度が次第に高くなり、いわゆる濃度勾配ができる。このときの汚泥回収側端部の汚泥濃度は、膜ろ過ユニットの数が増えれば増える程大きくなる。この汚泥濃度が高い領域は汚泥処理に使われる酸素(溶存酸素)の必要量も増加する。この汚泥濃度が高い領域では好気性菌類の増殖により、通常の散気発生装置から放出されるエア量だけでは酸素量が不足しがちとなる。すなわち、上述のように多数基の膜ろ過ユニットが配された場合には、下流側の膜ろ過ユニットの周辺の汚泥中の溶存酸素量不足が際立ってくる。   On the other hand, according to the normal membrane separation activated sludge treatment apparatus, the raw water overflows from the anaerobic tank adjacent to one end of the aeration tank in the treatment direction and flows into the aeration tank. Is returned from the aeration tank to the anaerobic tank through an external pipe, and the activated sludge is circulated. Since the sludge on the raw water inflow side has not been processed, the activated sludge concentration is low. However, the sludge treatment is advanced at the sludge collection side end of the aeration tank, so that the activated sludge concentration gradually increases and a so-called concentration gradient is formed. The sludge concentration at the sludge collection side end at this time increases as the number of membrane filtration units increases. In the region where the sludge concentration is high, the required amount of oxygen (dissolved oxygen) used for sludge treatment increases. In the region where the sludge concentration is high, the amount of oxygen tends to be insufficient only by the amount of air released from a normal air diffuser due to the growth of aerobic fungi. That is, when a large number of membrane filtration units are arranged as described above, the amount of dissolved oxygen in the sludge around the downstream membrane filtration unit becomes conspicuous.

更に、上記各膜ろ過ユニットの散気発生装置から放出されるエアは、活性汚泥の生物学的処理に貢献する以上に、気液混合流を利用したエアスクラビングによる膜洗浄に貢献している。この気液混合流は、散気発生装置から放出される比較的大きな気泡の上昇流により発生し、膜モジュールに強い振動と衝撃を与えながら膜面に付着した固形物を剥離させ、ろ過能を回復させながら膜間を上昇しユニットの外に出たのち下降流となって再び散気発生装置から放出される気泡と一体化して上昇を繰り返し、ばっ気槽内の汚泥を一様に攪拌する。また、この散気発生装置から放出されるエア中の全ての酸素が汚泥中に溶解して溶存酸素を作りだすものでもない。その結果、特に汚泥濃度の高い汚泥回収側の膜ろ過ユニットの内部では溶存酸素量が不足しやすく、十分な汚泥処理がなされなくなる。   Furthermore, the air released from the air diffuser of each membrane filtration unit contributes to membrane cleaning by air scrubbing using a gas-liquid mixed flow, in addition to contributing to biological treatment of activated sludge. This gas-liquid mixed flow is generated by the upward flow of relatively large bubbles released from the air diffuser, and the solid adhering to the membrane surface is peeled off while giving strong vibration and impact to the membrane module, thereby improving the filtration performance. While recovering, it rises between the membranes, goes out of the unit, then becomes a downward flow and is integrated with the bubbles released from the air diffuser again and repeatedly rises, stirring the sludge in the aeration tank uniformly. . Further, not all oxygen in the air released from this air diffuser dissolves in the sludge and does not create dissolved oxygen. As a result, the amount of dissolved oxygen tends to be insufficient in the sludge recovery side membrane filtration unit having a particularly high sludge concentration, and sufficient sludge treatment cannot be performed.

そこで、従来も上記散気発生装置とは別に、溶解度の高い微細気泡を発生する補助散気発生装置を、ばっ気槽の膜ろ過ユニット間の空き領域に配置して溶存酸素量を増加させようとしている。しかしながら、前述のように膜ろ過ユニットの周辺には膜ユニットの内部を上昇したのち、その外部を下降する旋回流が発生している。この旋回流は汚泥を攪拌して槽内の汚泥分布を均一化させるのに一役かっている。一方、前記補助散気発生装置は、前述のように膜ろ過ユニットの側部の槽底部に配されることが多い。そのため、補助散気発生装置から放出される微細気泡により発生する上昇流が前記旋回流の下降する流れと干渉し、旋回流の流れを乱し、流れの生じない停滞領域が発生するおそれがあり、上記処理方向の汚泥濃度差に基づく溶存酸素量の過不足に加えて、補助散気発生装置の設置に基づく溶存酸素量にも領域により過不足が生じ、結果として均等で効率的な汚泥処理ができなくなる。   Therefore, in the past, an auxiliary aeration generating device that generates fine bubbles with high solubility will be arranged separately from the above aeration generating device in an empty area between the membrane filtration units of the aeration tank to increase the amount of dissolved oxygen. It is said. However, as described above, a swirl flow is generated around the membrane filtration unit, which rises inside the membrane unit and then descends outside the membrane unit. This swirl flow is useful for stirring the sludge and making the sludge distribution in the tank uniform. On the other hand, the auxiliary air diffuser is often arranged at the tank bottom on the side of the membrane filtration unit as described above. For this reason, the upward flow generated by the fine bubbles released from the auxiliary air diffuser may interfere with the downward flow of the swirling flow, disturb the swirling flow, and generate a stagnant region where no flow occurs. In addition to the excess and deficiency of the dissolved oxygen amount based on the sludge concentration difference in the above treatment direction, the dissolved oxygen amount based on the installation of the auxiliary aeration generator also becomes deficient depending on the region, resulting in uniform and efficient sludge treatment Can not be.

本発明は、汚泥処理量の大量化に伴う溶存酸素量不足を解消するとともに、散気発生装置から放出される気泡により生じる気液混合旋回流を維持する膜分離活性汚泥処理方法を提供することを主な目的としている。その他の目的は以下に述べる具体的な説明により明らかとされる。   The present invention provides a membrane separation activated sludge treatment method that eliminates the shortage of dissolved oxygen amount associated with an increase in the amount of sludge treatment and maintains a gas-liquid mixed swirl generated by bubbles released from the air diffuser. Is the main purpose. Other objects will become apparent from the specific description given below.

本発明の主要な構成は、無酸素槽又は嫌気槽とばっ気槽とを備え、前記ばっ気槽には膜ろ過ユニットが浸漬され、排水を嫌気槽側から生物学的に順次処理して活性汚泥を固液分
離する膜分離活性汚泥処理方法であって、前記ばっ気槽の処理方向上流側から下流側に向けて、4基以上の膜ろ過ユニットを所要の間隔をおいて浸漬配置すること、前記各膜ろ過ユニットの膜モジュールから分岐管路を介して接続されたろ過水吸引管路を通してろ過水を吸引して排出すること、前記各膜ろ過ユニットの散気発生装置からエアの気泡を発生させること、及び前記ばっ気槽における処理方向上流側の原水流入口から最も遠い位置に配された膜ろ過ユニットの下方の槽底部から上記無酸素槽又は嫌気槽の原水流入部に送液手段により処理済汚泥を返戻させて、汚泥を無酸素槽又は嫌気槽とばっ気槽との間を循環させることを含んでいる。
The main configuration of the present invention includes an anaerobic tank or an anaerobic tank and an aeration tank, and a membrane filtration unit is immersed in the aerobic tank, and the waste water is biologically processed sequentially from the anaerobic tank side and activated. A membrane separation activated sludge treatment method for separating sludge into solid and liquid, wherein four or more membrane filtration units are immersed and arranged at a predetermined interval from the upstream side to the downstream side in the treatment direction of the aeration tank. , Sucking and discharging filtered water from the membrane module of each membrane filtration unit through a filtered water suction line connected via a branch line, and removing air bubbles from the air diffuser of each membrane filtration unit And a means for feeding liquid from the bottom of the membrane filtration unit disposed farthest from the raw water inlet on the upstream side in the processing direction to the raw water inflow portion of the anaerobic tank or anaerobic tank. To return the treated sludge And circulating the sludge between an anaerobic tank or an anaerobic tank and an aeration tank .

ここで、本発明の好適な態様によれば、前述の構成に加えて更に原水を前記ばっ気槽の複数の異なる部位に流入させることを含ませることもできる Here, according to the suitable aspect of this invention, in addition to the above-mentioned structure, it can also include making raw water flow in into several different site | parts of the said aeration tank.

前記態様にあって、前記各膜モジュールにおける1以上のろ過水吸引源により吸引されるろ過水の吸引量及び/又は各散気発生装置から発生する気泡の発生量を、排水流入側から排出側の順に漸次増加させることを更に含むことができる。 In the above aspect, the suction amount of filtered water sucked by one or more filtered water suction sources in each membrane module and / or the generation amount of bubbles generated from each air diffuser is changed from the drain inflow side to the discharge side. Further increasing in order.

また、前記態様にあっても、前記ばっ気槽の原水流入口から最も遠い位置に配された膜ろ過ユニット下方の槽底部と前記無酸素槽又は嫌気槽の原水流入部とを接続する汚泥返戻管路に切替バルブを介して接続された余剰汚泥回収管路から、余剰汚泥を槽外に配された汚泥貯留槽に回収することを含ませることも可能である。 Moreover, even if it exists in the said aspect, the sludge return which connects the tank bottom part below the membrane filtration unit arranged in the position farthest from the raw | natural water inlet of the said aeration tank, and the raw | natural water inflow part of the said anoxic tank or anaerobic tank from line excess sludge recovery pipe connected via a switching exchange valve, it is also possible to include recovering the sludge storage tank arranged excess sludge out of the tank.

更に、本発明にあっては、前記ばっ気槽の汚泥排出側端部に独立して設けられた余剰汚
泥取出口から余剰汚泥を回収することを含んでいることが好ましい。
Furthermore, in this invention, it is preferable to include collect | recovering excess sludge from the excess sludge removal outlet provided independently in the sludge discharge | release side edge part of the said aeration tank.

作用効果Effect

前記ばっ気槽に4基以上の膜ろ過ユニットを所要の間隔をおいて直列状に浸漬配置する場合、各膜ろ過ユニットの膜モジュール毎に分岐管路を介して単一のろ過水吸引管路によりろ過水を吸引し、或いは各膜ろ過ユニットの散気発生装置毎に分岐管路を介して単一のエア主管によりエアが供給される。通常は各膜モジュールによりろ過されるろ過水の量は一律であり、また各散気発生装置から放出されるエアの量も一律である。本発明によれば、ばっ気槽内の処理方向の上流側から下流側に向かうにつれて膜ろ過ユニットに対するろ過水の吸引量及びエア量の放出量を順次大きくすることができる。この吸引量及び放出量の大きさは、例えば各分岐管路に流量調整バルブを配して、同バルブの開度を順次調整することにより調整でき、或いは分岐管路の内径を順次大きくすることによっても調整できる。 When four or more membrane filtration units are immersed and arranged in series in the aeration tank with a predetermined interval, a single filtrate water suction line is provided via a branch line for each membrane module of each membrane filtration unit. Then, the filtered water is sucked in, or air is supplied by a single air main pipe via a branch pipe for each of the diffuser generators of each membrane filtration unit. Usually, the amount of filtered water filtered by each membrane module is uniform, and the amount of air discharged from each air diffuser is also uniform. ADVANTAGE OF THE INVENTION According to this invention, the suction | attraction amount of filtrate water with respect to a membrane filtration unit and the discharge | release amount of air amount can be enlarged sequentially as it goes to the downstream from the upstream of the process direction in an aeration tank. The magnitude of the suction amount and the discharge amount can be adjusted by, for example, arranging a flow rate adjusting valve in each branch pipe and sequentially adjusting the opening of the valve, or increasing the inner diameter of the branch pipe sequentially. Can also be adjusted.

こうして、汚泥処理方向の上流側から下流側に向けて膜ろ過ユニットから吸引されるろ過水吸引量、或いは膜ろ過ユニットに向けて放出されるエア放出量を順次大きくすることにより、汚泥処理の少なく汚泥の固形分も少ない上流側の領域では、膜モジュールに付着する固形分の量も少ないためろ過水の吸引量を少なくするとともに、散気発生装置からのエア放出量を少なくしても十分なスクラビング洗浄が可能となる。一方、処理方向の下流側領域ではろ過水の吸引量を大きくするとともに、散気発生装置からのエア放出量も大きくすると、汚泥濃度が高く固形分も大量に発生している汚泥の攪拌が進み、更には膜面に付着する固形分をも強力な気液混合流により確実に剥離できるようになるばかりでなく、増殖したバクテリアの汚泥処理に必要な溶存酸素量も確保され、十分な汚泥処理がなされるようになる。更にはろ過水の吸引量が多く回収される汚泥濃度が高くなるため、余剰汚泥の固形分が多くなって嵩が小さくなり、取扱性も向上し、乾燥のための熱エネルギーが節約できる。   In this way, sludge treatment can be reduced by sequentially increasing the amount of filtered water sucked from the membrane filtration unit from the upstream side to the downstream side in the sludge treatment direction or the amount of air released to the membrane filtration unit. In the upstream area where the solid content of sludge is low, the amount of solid content adhering to the membrane module is also small, so it is sufficient to reduce the suction rate of filtered water and reduce the amount of air released from the air diffuser. Scrub cleaning is possible. On the other hand, in the downstream area in the processing direction, when the suction amount of filtered water is increased and the air discharge amount from the aeration generator is increased, the stirring of the sludge with a high sludge concentration and a large amount of solids proceeds. Furthermore, not only can solid solids attached to the membrane surface be reliably separated by a powerful gas-liquid mixed flow, but also the amount of dissolved oxygen necessary for sludge treatment of the grown bacteria is secured, and sufficient sludge treatment is achieved. Will be made. Furthermore, since the sludge concentration in which a large amount of filtrate is sucked is collected and the sludge concentration is increased, the solid content of the excess sludge is increased, the bulk is reduced, the handleability is improved, and the heat energy for drying can be saved.

本発明にあって、ばっ気槽の回収側端部の槽底部から嫌気槽の原水導入側端部の槽底部へと余剰汚泥の一部を返送して循環させる場合には、溶存酸素量の極めて少ない汚泥を嫌気槽へと戻すため、脱窒菌による脱窒反応が効率的に進ませることができる。このとき、嫌気槽に戻される余剰汚泥以外の余剰汚泥は、上記構成により返送と同時に又は選択的に汚泥貯蔵槽へと送液される。このとき汚泥貯蔵槽に送られる余剰汚泥は、その活性汚泥濃度が上述のごとく極めて高く且つ水分が少ないため扱いやすくなり、その後の処理も効率的な処理が可能となる。   In the present invention, when a part of excess sludge is returned and circulated from the tank bottom at the collection end of the aeration tank to the tank bottom at the raw water introduction end of the anaerobic tank, Since very little sludge is returned to the anaerobic tank, the denitrification reaction by the denitrifying bacteria can proceed efficiently. At this time, surplus sludge other than the excess sludge returned to the anaerobic tank is sent to the sludge storage tank simultaneously or selectively with the above configuration. At this time, the surplus sludge sent to the sludge storage tank becomes easy to handle because the activated sludge concentration is extremely high as described above and the water content is low, and the subsequent processing can be performed efficiently.

更に本発明にあって、嫌気槽からの原水をばっ気槽の異なる複数の部位に流入させるようにすると、上述のごとき汚泥濃度差の大きな上流部と中流部との間の濃度勾配を小さくすることができ、上記構成と相まって生物的汚泥処理とエアスクラビングによる洗浄がより効果的になされるようになる。   Furthermore, in the present invention, when the raw water from the anaerobic tank is allowed to flow into a plurality of different parts of the aeration tank, the concentration gradient between the upstream portion and the midstream portion where the sludge concentration difference is large as described above is reduced. In combination with the above configuration, the biological sludge treatment and the cleaning by air scrubbing can be performed more effectively.

以下、本発明の好適な実施形態を図面に基づいて具体的に説明する。
図1は、本発明の膜分離活性汚泥処理方法を実施するための代表的な処理装置の概略構造を示している。
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a schematic structure of a typical treatment apparatus for carrying out the membrane separation activated sludge treatment method of the present invention.

この膜分離活性汚泥処理装置によれば、微細目スクリーン1にて比較的大きな固形分が除去された排水(原水)は、原水調整槽2に導入される。ここでは、液面を図示せぬ液面計測器により測定し、第1送液ポンプP1を間欠作動して槽内の液面高さを所定の範囲内で調整している。第1液送ポンプP1によって送られる原水は無酸素槽3に導入されたのち、無酸素槽3から溢流する原水を使って隣接するばっ気槽4に流入させる。このばっ気槽4には多数基の膜ろ過ユニット5を浸漬して配している。この膜ろ過ユニット5にて活性汚泥と処理水とに膜分離された処理水は吸引ポンプPvにより処理水槽8に送液される。一方、ばっ気槽4にてばっ気処理されて増殖した微生物などからなる汚泥の固形分(懸濁物質)は、自重で槽底部へと沈殿し、その余剰汚泥は汚泥貯留槽7に貯蔵される。また、ばっ気槽4の内部の汚泥の一部は第2液送ポンプP2によって上記無酸素槽3へと返送されて循環する。   According to this membrane separation activated sludge treatment apparatus, waste water (raw water) from which a relatively large solid content has been removed by the fine screen 1 is introduced into the raw water adjustment tank 2. Here, the liquid level is measured by a liquid level measuring instrument (not shown), and the first liquid feed pump P1 is intermittently operated to adjust the liquid level in the tank within a predetermined range. The raw water sent by the first liquid feed pump P1 is introduced into the anoxic tank 3, and then flows into the adjacent aeration tank 4 using the raw water overflowing from the anoxic tank 3. A large number of membrane filtration units 5 are immersed in the aeration tank 4. The treated water separated into activated sludge and treated water by the membrane filtration unit 5 is sent to the treated water tank 8 by the suction pump Pv. On the other hand, the sludge solid matter (suspension material) consisting of microorganisms and the like that have been aerated in the aeration tank 4 is settled to the bottom of the tank by its own weight, and the excess sludge is stored in the sludge storage tank 7. The A part of the sludge inside the aeration tank 4 is returned to the anoxic tank 3 by the second liquid feed pump P2 and circulated.

この膜分離活性汚泥処理装置によれば、原水は無酸素槽3及びばっ気槽(好気槽)4において、活性汚泥により生物学的に浄化される。窒素の除去は、無酸素槽3とばっ気槽4との間で汚泥を循環させて、いわゆる硝化脱窒反応によってなされる。BOD(生物化学的酸素要求量)に換算される有機物は、主としてばっ気槽4内に配置されたばっ気装置である膜ろ過ユニット5の散気発生装置15から放出されるエアにより好気的に酸化され分解される。またリンの除去は、汚泥中の微生物(リン蓄積細菌)の作用によりポリリン酸として微生物の体内に取り込まれることにより行われる。   According to this membrane separation activated sludge treatment apparatus, raw water is biologically purified by activated sludge in the anoxic tank 3 and the aeration tank (aerobic tank) 4. Nitrogen is removed by a so-called nitrification denitrification reaction by circulating sludge between the anoxic tank 3 and the aeration tank 4. The organic matter converted to BOD (biochemical oxygen demand) is aerobic by the air released from the diffuser generator 15 of the membrane filtration unit 5 which is mainly an aeration apparatus disposed in the aeration tank 4. It is oxidized and decomposed. The removal of phosphorus is performed by being taken into the body of the microorganism as polyphosphoric acid by the action of microorganisms (phosphorus-accumulating bacteria) in the sludge.

この微生物は好気状態においてリンを取り込み、嫌気状態において体内に蓄えたリンを放出する。リン蓄積細菌は、嫌気状態、好気状態に繰り返して晒されると、嫌気状態で放出したリンの量より多くのリンを好気状態で吸収する。生物由来の排泄物や残骸などの窒素化合物の一部は、肥料として植物やバクテリアに同化される。また、こうした窒素化合物の一部は、酸素の多い好気条件下で独立栄養アンモニア酸化細菌や独立亜硝酸酸化細菌により、亜硝酸、硝酸へと酸化される。他方、酸素がない嫌気条件下では、脱窒菌と呼ばれる微生物が酸素に代わって硝酸から亜硝酸を生成し、更には一酸化二窒素、窒素ガスへと還元する。   This microorganism takes up phosphorus in an aerobic state and releases phosphorus stored in the body in an anaerobic state. When repeatedly exposed to anaerobic and aerobic conditions, phosphorus-accumulating bacteria absorb more phosphorus in an aerobic state than the amount of phosphorus released in the anaerobic state. Part of nitrogen compounds such as biological excrement and debris is assimilated into plants and bacteria as fertilizer. Some of these nitrogen compounds are oxidized to nitrous acid and nitric acid by autotrophic ammonia oxidizing bacteria and independent nitrite oxidizing bacteria under aerobic conditions with a lot of oxygen. On the other hand, under anaerobic conditions without oxygen, microorganisms called denitrifying bacteria produce nitrous acid from nitric acid instead of oxygen, and further reduce to dinitrogen monoxide and nitrogen gas.

無酸素槽3及びばっ気槽4の間での汚泥の循環は、どちらの槽からポンプを用いて送液するかは必ずしも限定されないが、通常は第2液送ポンプP2を用いてばっ気槽から無酸素槽3へと送液し、無酸素槽3から溢流によってばっ気槽4に流入させる。このときのばっ気槽4からの汚泥の取出口は、ばっ気槽4の汚泥回収側端部の槽底部とし、無酸素槽3の汚泥導入口は無酸素槽3の上流側の原水調整槽2からの原水導入端部の槽底部としている。このように設定することにより、ばっ気槽4からの循環液が無酸素槽3に導入口付近のDO(溶存酸素濃度)を0.2mg/L以下とすることができ、ばっ気槽4より循環液を取出口付近のDOを0.5mg/L以下とすることにより、無酸素槽3への溶存酸素の流入を抑制し、無酸素槽3内の嫌気度を十分維持し、これによりリンの放出を促進させる。   The circulation of the sludge between the anaerobic tank 3 and the aeration tank 4 is not necessarily limited from which tank the liquid is fed using the pump, but normally the aeration tank using the second liquid feeding pump P2. From the oxygen-free tank 3 to the aeration tank 4 by overflow. At this time, the sludge outlet from the aeration tank 4 is the bottom of the sludge collection side end of the aeration tank 4, and the sludge inlet of the anaerobic tank 3 is the raw water adjustment tank upstream of the anoxic tank 3. 2 is the tank bottom of the raw water introduction end. By setting in this way, the circulating fluid from the aeration tank 4 can make DO (dissolved oxygen concentration) in the vicinity of the inlet to the anoxic tank 3 0.2 mg / L or less. By setting the DO in the vicinity of the outlet of the circulating fluid to 0.5 mg / L or less, the inflow of dissolved oxygen into the anoxic tank 3 is suppressed, and the anaerobic degree in the anoxic tank 3 is sufficiently maintained. Promote the release of.

無酸素槽3内に溶存酸素、硝酸イオン、亜硝酸イオンが実質的に存在しないと有機物が嫌気的に分解され、このとき菌に蓄積されたポリリン酸がリン酸として菌体外に放出される。本実施形態において循環汚泥がばっ気槽4から無酸素槽3に返送される部位のDOは0.2mg/L以下とすることが好ましく、0.1mg/L以下であるとリンの除去性がより安定し、さらに0.05mg/L以下とするとより安定化するため好ましい。なお、DOの測定は、隔膜電極法による通常のDO計を用いて測定することができる。   If dissolved oxygen, nitrate ions, and nitrite ions are not substantially present in the anoxic tank 3, the organic matter is decomposed anaerobically, and at this time, the polyphosphate accumulated in the bacteria is released out of the cells as phosphoric acid. . In this embodiment, the DO at the site where the circulating sludge is returned from the aeration tank 4 to the anaerobic tank 3 is preferably 0.2 mg / L or less, and if it is 0.1 mg / L or less, phosphorus removability is obtained. It is more stable, and 0.05 mg / L or less is preferable because it is more stable. In addition, the measurement of DO can be measured using the normal DO meter by the diaphragm electrode method.

ばっ気槽4から循環液(汚泥)を取り出す部位のDOを0.5mg/L以下とするためには、ばっ気槽4から無酸素槽3へ汚泥を取り出す部位を汚泥の滞留部とすることが好ましい。汚泥の滞留部とは、ばっ気による汚泥の流動の影響を受けにくい部位を意味する。例えば、膜ろ過ユニット5とばっ気槽4の底部との間に空間を設けてやると、膜ろ過ユニット5の下の部分に存在する汚泥は良く撹拌されないため、滞留部となる。   In order to set the DO of the part where the circulating fluid (sludge) is taken out from the aeration tank 4 to 0.5 mg / L or less, the part where the sludge is taken out from the aeration tank 4 to the anoxic tank 3 is made a sludge retention part. Is preferred. The sludge retention part means a part that is not easily affected by sludge flow caused by aeration. For example, if a space is provided between the membrane filtration unit 5 and the bottom of the aeration tank 4, the sludge present in the lower part of the membrane filtration unit 5 is not well agitated, and thus becomes a retention part.

したがって図1に示すように膜ろ過ユニット5の位置よりも下から汚泥を取り出すことにより、ばっ気槽4より循環液(汚泥)を取り出す部位6のDOを0.5mg/L以下とすることができる。なお、ばっ気槽4内に複数基の膜ろ過ユニット5が並列されて配される場合は、循環液(汚泥)を取り出す部位をばっ気装置の下方とする。また、膜ろ過ユニット5から汚泥を取り出す部位までの距離は20cm以上下方に離すことが好ましく、30cm以上離すことがさらに好ましい。   Therefore, as shown in FIG. 1, the DO of the site 6 where the circulating fluid (sludge) is taken out from the aeration tank 4 can be made 0.5 mg / L or less by taking out the sludge from below the position of the membrane filtration unit 5. it can. In addition, when a plurality of membrane filtration units 5 are arranged in parallel in the aeration tank 4, the part from which the circulating fluid (sludge) is taken out is below the aeration apparatus. Further, the distance from the membrane filtration unit 5 to the site where the sludge is taken out is preferably 20 cm or more downward, more preferably 30 cm or more.

ばっ気槽4内における汚泥の流動は、主として膜ろ過ユニット5による領域において散気発生装置の気体放出孔からの気泡の上昇に伴って汚泥も上昇し、ばっ気されていない部分において汚泥が下降し、これにより全体が撹拌される。この際、ばっ気槽4内の汚泥の酸素利用速度(rr )を高く維持すると、ばっ気されていない部分で酸素が急速に消費されることから、ばっ気槽4中で溶存酸素が低くなる部位を形成しやすくなる。ここで、ばっ気槽4内の汚泥の酸素利用速度(rr )とは、ばっ気槽4のばっ気されている部分から取った汚泥の酸素利用速度をいい、測定方法は下水道試験方法(1997年、社団法人日本下水道協会)に従って求めることができる。 The flow of sludge in the aeration tank 4 mainly increases in the region by the membrane filtration unit 5 as the bubbles rise from the gas discharge holes of the air diffuser, and the sludge falls in the non-aerated portion. Thus, the whole is stirred. At this time, if the oxygen utilization rate (r r ) of the sludge in the aeration tank 4 is kept high, oxygen is rapidly consumed in the non-aerated area, so that the dissolved oxygen is low in the aeration tank 4. It becomes easy to form the part which becomes. Here, the oxygen utilization rate (r r ) of the sludge in the aeration tank 4 refers to the oxygen utilization rate of the sludge taken from the aerated portion of the aeration tank 4, and the measuring method is the sewer test method ( 1997, according to the Japan Sewerage Association.

図2は、通常の膜ろ過ユニット5の代表的な例を示している。同図に示すように膜ろ過ユニット5は、糸長さ方向を垂直に配した複数枚の中空糸膜エレメント10を並列させて支持固定された中空糸膜モジュール9と、同中空糸膜モジュール9の下方に所要の間隔をおいて配される散気発生装置15とを含んでいる。前記中空糸膜エレメント10は、多数本の多孔性中空糸10aを平行に並列させた膜シート11の上端開口端部をポッティング材11aを介してろ過水取出管12に連通支持させるとともに、下端を閉塞して同じくポッティング材11aを介して下枠13により固定支持させ、前記ろ過水取出管12及び下枠13の各両端を一対の縦杆14により支持して構成される。多数枚の膜エレメント10が、シート面を鉛直にして上下端面が開口した矩形筒状の上部壁材20のほぼ全容積内に収容されて並列支持される。ここで、上記中空糸膜エレメント10は、一般には図3に示すように多数本の多孔性中空糸10aが同じ間隙をもたせて同一平面上を並列して配されている。   FIG. 2 shows a typical example of a normal membrane filtration unit 5. As shown in the figure, the membrane filtration unit 5 includes a hollow fiber membrane module 9 in which a plurality of hollow fiber membrane elements 10 arranged in a direction perpendicular to the yarn length are supported and fixed in parallel, and the hollow fiber membrane module 9 And a diffuser generating device 15 arranged at a predetermined interval below. The hollow fiber membrane element 10 communicates and supports the upper end opening end of a membrane sheet 11 in which a large number of porous hollow fibers 10a are arranged in parallel to the filtered water discharge pipe 12 through a potting material 11a, and the lower end thereof. It is closed and fixed and supported by the lower frame 13 via the potting material 11a, and both ends of the filtered water outlet pipe 12 and the lower frame 13 are supported by a pair of vertical rods 14. A large number of membrane elements 10 are accommodated and supported in parallel in substantially the entire volume of a rectangular cylindrical upper wall member 20 whose upper and lower end surfaces are open with the sheet surface vertical. Here, in the hollow fiber membrane element 10, generally, as shown in FIG. 3, a large number of porous hollow fibers 10a are arranged in parallel on the same plane with the same gap.

本実施形態にあって、前記中空糸10aは中心部に沿って長さ方向に中空とされたPVDF(ポリフッ化ビニデン)の多孔質中空糸が使われており、そのろ過孔の孔径は0.4μmである。また、1枚あたりの有効膜面積は25m2 である。上記シート状の膜エレメント10は1膜ろ過ユニット5あたり20枚が使われ、その大きさは奥行きが30mm、幅が1250mm、ろ過水取出管12の上面から下枠13の下面までの長さが2000mmである。散気発生装置15をも含めた1膜ろ過ユニット5の大きさは、奥行きが1552.5mm、幅が1447mm、高さが3043.5mmである。上記ろ過水取出管12の長さが1280mm、その材質はABS樹脂であり、縦杆14の材質はSUS304が使われている。 In this embodiment, the hollow fiber 10a is made of PVDF (polyvinylidene fluoride) porous hollow fiber that is hollow in the longitudinal direction along the center, and the pore diameter of the filtration hole is 0. 0. 4 μm. The effective membrane area per sheet is 25 m 2 . The sheet-like membrane element 10 is used in 20 pieces per membrane filtration unit 5 and has a depth of 30 mm, a width of 1250 mm, and a length from the upper surface of the filtrate extraction pipe 12 to the lower surface of the lower frame 13. 2000 mm. The size of the single membrane filtration unit 5 including the air diffuser 15 is 1552.5 mm in depth, 1447 mm in width, and 3043.5 mm in height. The filtered water extraction pipe 12 has a length of 1280 mm, its material is ABS resin, and the vertical rod 14 is made of SUS304.

ただし、多孔性中空糸10a、ろ過水取出管12及び縦杆14などの材質、膜エレメント10の大きさ、1膜ろ過ユニット5の大きさやユニット1基あたりの膜エレメント10の枚数などは、用途に応じて多様に変更が可能である。例えば、膜エレメント10の枚数で言えば処理量に合わせて20枚、40枚、60枚、…と任意に設定でき、或いは多孔中空糸10aの材質には、セルロース系、ポリオレフィン系、ポリスルホン系、ポリビニルアルコール系、ポリメチルメタクリレート、ポリフッ化エチレンなど、従来公知のものを適用することができる。   However, the materials such as the porous hollow fiber 10a, the filtrate take-out pipe 12 and the vertical rod 14, the size of the membrane element 10, the size of the membrane filtration unit 5, the number of the membrane elements 10 per unit, etc. Various changes can be made depending on the situation. For example, the number of membrane elements 10 can be arbitrarily set to 20, 40, 60,... According to the processing amount, or the material of the porous hollow fiber 10a can be cellulose, polyolefin, polysulfone, Conventionally known materials such as polyvinyl alcohol, polymethyl methacrylate, and polyfluorinated ethylene can be applied.

各膜エレメント10の上記ろ過水取出管12の一端には各多孔性中空糸10aによってろ過された高水質のろ過水(処理水)の取出口12aが形成されている。本実施例にあって、各取出口12aには、図2に示す膜ろ過ユニット5と同様に、それぞれL型継手12bがシール材を介して液密に取り付けられる。また、図3に示すように、上記上部壁材20の上端の前記取出口12aが形成されている側の端縁に沿って集水ヘッダー管21が横設されている。この集水ヘッダー管21は複数の前記取出口12aに対応する位置にはそれぞれに集水口21aが形成されており、各集水口21aに上記取出口12aと同様のL型継手21bがシール材を介して液密に取り付けられている。前記ろ過水取出管12の処理水取出口12aと前記集水ヘッダー管21の集水口21aとが、それぞれに取り付けられたL型継手12b,21b同士を接続することにより通水可能に連結される。集水ヘッダー管21の一端部には吸引ポンプPvとろ過水吸引管路22を介して接続される吸水口21cが形成されている。各集水ヘッダー管21ごとに形成された吸水口21cと前記ろ過水吸引管路22とは、図1に示すように、同ろ過水吸引管路22からそれぞれ分岐した分岐管路22a内に介装された流量調整バルブ23を介して連結されている。   An outlet 12a for high-quality filtered water (treated water) filtered by each porous hollow fiber 10a is formed at one end of the filtrate extraction pipe 12 of each membrane element 10. In this embodiment, L-shaped joints 12b are attached to the respective outlets 12a in a liquid-tight manner through a sealing material, similarly to the membrane filtration unit 5 shown in FIG. Moreover, as shown in FIG. 3, the water collection header pipe | tube 21 is installed horizontally along the edge by the side in which the said outlet 12a is formed in the upper end of the said upper wall material 20. As shown in FIG. The water collecting header pipe 21 is formed with water collecting ports 21a at positions corresponding to the plurality of outlets 12a, and an L-shaped joint 21b similar to the outlet 12a serves as a sealing material in each water collecting port 21a. It is liquid-tightly attached. The treated water outlet 12a of the filtered water outlet 12 and the water outlet 21a of the water header 21 are connected to each other by connecting the L-shaped joints 12b and 21b attached to each other. . At one end of the water collection header pipe 21, a water suction port 21 c connected to the suction pump Pv via the filtered water suction pipe line 22 is formed. As shown in FIG. 1, the water inlet 21 c formed for each water collection header pipe 21 and the filtered water suction pipe 22 are inserted into branch pipes 22 a branched from the filtered water suction pipe 22. It is connected via a mounted flow rate adjusting valve 23.

一方、前記散気発生装置15は、図4に示すように、前記上部壁材20の下端に結合された同じく上下が開口する矩形筒体からなり、その4隅の下端から下方に延びる4本の支柱24aを備えた下部壁材24の底部に収容固設されている。前記散気発生装置15は、前記下部壁材24の正面側内壁面に沿って幅方向に水平に延設され、図1に示すように外部に配されたばっ気ブロアBとエア主管18を介して接続される分岐管路であるエア導入管16と、同エア導入管16の長さ方向に所定の間隔をおいて配され、一端が固設されるとともに、他端が背面側の内壁面に沿って水平に固設された複数本の散気管17とを有している。散気管17の前記エア導入管16との接続側端部は同エア導入管16の内部と連通しており、散気管17の他端は閉塞されている。   On the other hand, as shown in FIG. 4, the air diffuser 15 is composed of a rectangular cylindrical body that is coupled to the lower end of the upper wall member 20 and that is open at the top and bottom, and extends downward from the lower ends of the four corners. It is accommodated and fixed at the bottom of the lower wall member 24 provided with the column 24a. The air diffuser 15 extends horizontally in the width direction along the front-side inner wall surface of the lower wall member 24, and includes an aeration blower B and an air main pipe 18 arranged outside as shown in FIG. The air introduction pipe 16 which is a branch pipe connected via the air introduction pipe 16 is arranged at a predetermined interval in the length direction of the air introduction pipe 16, one end is fixed, and the other end is an inner side of the rear side. And a plurality of air diffusers 17 fixed horizontally along the wall surface. The end of the diffuser pipe 17 connected to the air inlet pipe 16 communicates with the inside of the air inlet pipe 16, and the other end of the diffuser pipe 17 is closed.

図示例によれば、この散気管17の本体はスリット付きゴム管から構成されており、水平に配された下面には、長さ方向に沿って内外に連通する図示せぬスリットが形成されている。前記散気発生装置15は上記中空膜エレメント10の下端から下方に45cmの間隔をおいて配されることが好ましく、前記支柱24aを下部壁材24から下方に突出させて、外部に露呈させることは汚泥の流動を円滑にするため望ましい。このとき、ばっ気槽4から循環液(汚泥)を取り出す部位のDOを0.5mg/L以下とするため、膜ろ過ユニット5から汚泥を取り出す部位までの距離を、既述したとおり20cm以上下方に離すことが好ましく、30cm以上離すことがさらに好ましい。また、本実施例による散気発生装置15は複数基の膜ろ過ユニット5ごとに対応して配され、同じばっ気ブロアBから送られるエアを、それぞれの散気発生装置15に分流させるため、前記ばっ気ブロアBに直接接続されたエア主管18を有し、同エア主管18から分岐管路であるエア導入管16を介して各散気発生装置15に接続される。   According to the illustrated example, the main body of the air diffuser 17 is composed of a rubber tube with a slit, and a slit (not shown) that communicates inward and outward along the length direction is formed on the horizontally disposed lower surface. Yes. The air diffuser 15 is preferably disposed at a distance of 45 cm downward from the lower end of the hollow membrane element 10, and the column 24 a protrudes downward from the lower wall member 24 to be exposed to the outside. Is desirable to facilitate the flow of sludge. At this time, in order to set the DO of the part where the circulating fluid (sludge) is taken out from the aeration tank 4 to 0.5 mg / L or less, the distance from the membrane filtration unit 5 to the part where the sludge is taken out is 20 cm or more downward as described above. It is preferable that the distance is 30 cm or more. In addition, the air diffuser 15 according to the present embodiment is arranged corresponding to each of the plurality of membrane filtration units 5, and in order to divert the air sent from the same aeration blower B to each air diffuser 15, The main air pipe 18 directly connected to the aeration blower B is connected to each air diffuser 15 from the main air pipe 18 through an air introduction pipe 16 which is a branch pipe.

本発明は、例示した上述のような構成を備えた4基以上の膜ろ過ユニット5を同一ばっ気槽4に浸漬して並置し、無酸素槽3とばっ気槽4との間で汚泥を循環させながら、上述のような生物学的な活性汚泥処理を大量に行うことを前提としている。そのため、上述のように膜ろ過ユニット5の間をそれぞれ流量調整バルブ23を介して同一のろ過水吸引管路22に接続している。しかし、この汚泥処理を長期間にわたって継続して行うと、膜ろ過ユニット5のろ過膜の表面に目詰まりが進行するため、ろ過流量の低下、或いは膜間差圧の上昇が生じる。   In the present invention, four or more membrane filtration units 5 having the above-described configuration illustrated are immersed in the same aeration tank 4 and juxtaposed, and sludge is removed between the anaerobic tank 3 and the aeration tank 4. It is assumed that a large amount of biological activated sludge treatment as described above is performed while circulating. Therefore, as described above, the membrane filtration units 5 are connected to the same filtrate suction line 22 via the flow rate adjusting valve 23. However, if this sludge treatment is continuously performed over a long period of time, clogging progresses on the surface of the membrane of the membrane filtration unit 5, so that the filtration flow rate decreases or the transmembrane pressure difference increases.

このような膜間差圧の上昇を抑えるため、中空糸膜エレメント10の下方に配された上記散気発生装置15から噴出するエアと汚泥液との混合流体を利用して、生物学的処理を行うとともに、いわゆるエアスクラビングを行い、各中空糸10aを振動させて表面に付着した懸濁物質を剥がして離脱させ、物理的な洗浄を行う。ところが、このエアスクラビングは、エアスクラビングと同時に中空糸10aの中空部を通してろ過水を積極的に外部の吸引ポンプPvから吸引して汚泥とろ過水とに分離させているため、処理が長期にわたると相変わらず懸濁物質が膜表面に吸引されて、目詰まりが生じろ過流量が著しく低下する。その結果、汚泥処理を一旦停止して、定期的に大がかりな洗浄をする必要があった。   In order to suppress such an increase in the transmembrane pressure difference, a biological treatment is performed using a mixed fluid of air and sludge discharged from the air diffuser 15 disposed below the hollow fiber membrane element 10. At the same time, so-called air scrubbing is performed, and each hollow fiber 10a is vibrated to peel off and remove the suspended substances adhering to the surface, thereby performing physical cleaning. However, in this air scrubbing, the filtered water is actively sucked from the external suction pump Pv through the hollow portion of the hollow fiber 10a simultaneously with the air scrubbing to separate the sludge and the filtered water. As usual, suspended substances are sucked onto the membrane surface, resulting in clogging and a marked reduction in filtration flow rate. As a result, it was necessary to temporarily stop the sludge treatment and periodically perform extensive washing.

ところで、上述のように膜ろ過ユニットの奥行きの寸法を1552.5mmとして、前記奥行き寸法の1/2の間隔をおいてばっ気槽内に25基の膜ろ過ユニットを並設したとすると、上記ろ過水吸引管路22やエア主管18の全長は58219mm以上にもおよぶ。   By the way, if the depth dimension of the membrane filtration unit is 1552.5 mm as described above, and 25 membrane filtration units are arranged in parallel in the aeration tank with an interval of 1/2 of the depth dimension, The total length of the filtered water suction pipe 22 and the air main pipe 18 reaches 58219 mm or more.

このような長い管路を通過する間に吸引源やブロア源に近い、ろ過水吸引管路22と各膜ろ過ユニット5の中空糸膜モジュール9とを接続する分岐管路22aや、ばっ気ブロアBからエアがエア主管18を通して送られる各導入管路(分岐管路)16と、処理方向の上流側端部に配された分岐管路22a,16とでは管路抵抗の影響により、ろ過水の吸引量やエアの放出量にさが生じる。一方、処理方向の上流側端部と下流側端部とでは活性汚泥処理が進むことから、25基もの膜ろ過ユニット5が並設されていると、ばっ気槽4の活性汚泥濃度にも上流側端部と下流側端部とでは特に大きな差が生じる。この活性汚泥濃度が大きくなればなるほど溶存酸素の必要量が増加する。   While passing through such a long pipe line, a branch pipe line 22a that connects the filtered water suction pipe line 22 and the hollow fiber membrane module 9 of each membrane filtration unit 5 close to the suction source or blower source, or an aeration blower In each of the introduction pipes (branch pipes) 16 through which air is sent from B through the air main pipe 18 and the branch pipes 22a and 16 arranged at the upstream end in the processing direction, filtered water is affected by the influence of the pipe resistance. The amount of suction and the amount of air released are reduced. On the other hand, since the activated sludge treatment proceeds at the upstream end and the downstream end in the treatment direction, when as many as 25 membrane filtration units 5 are arranged in parallel, the activated sludge concentration in the aeration tank 4 is also upstream. There is a particularly large difference between the side end and the downstream end. The required amount of dissolved oxygen increases as the activated sludge concentration increases.

しかるに、配管抵抗に基づくろ過水の吸引量やエア放出量の上記低下量と溶存酸素の必要量とは直接関係はなく、配管抵抗が低い分、ばっ気ブロアBに最も近い膜ろ過ユニット5に向けて散気発生装置15から放出されるエア量は他の散気発生装置15から放出されるエア量よりも多いものの、汚泥濃度が高いため膜面に付着する固形分の量も多くなり、早期に目が詰まるばかりでなく、そこに存在する汚泥濃度に見合った溶存酸素量をまかないきれない。一方、配管抵抗の関係で吸引源に最も近い膜ろ過ユニット5から吸引されるろ過水の吸引量も他の膜ろ過ユニット5から吸引されるろ過水の吸引量よりも多くはなるが、余剰汚泥の処理の点から見ると、汚泥貯留槽7に集められる余剰汚泥の濃度は可能な限り高い方が好ましい。この汚泥貯留槽7の汚泥は、乾燥させたのち焼却処分に付される。そのためには汚泥中に含まれる水分が少なければ、嵩が小さくなって取扱性が容易となるばかりでなく、乾燥時間の短縮にもつながり、省エネルギーに貢献する。しかるに、通常のろ過水の吸引量では前述のような好適な汚泥濃度までには至らない。   However, there is no direct relationship between the above-mentioned reduction amount of filtered water suction amount or air discharge amount based on the pipe resistance and the required amount of dissolved oxygen, and the membrane filtration unit 5 closest to the aeration blower B has a lower pipe resistance. Although the amount of air released from the diffuser generator 15 is larger than the amount of air released from the other diffuser generators 15, the amount of solids adhering to the membrane surface increases because the sludge concentration is high, Not only does it get clogged early, but it can't cover the amount of dissolved oxygen that matches the concentration of sludge. On the other hand, the amount of filtered water sucked from the membrane filtration unit 5 closest to the suction source is larger than the amount of filtered water sucked from other membrane filtration units 5 due to the piping resistance, but excess sludge From the viewpoint of the treatment, the concentration of excess sludge collected in the sludge storage tank 7 is preferably as high as possible. The sludge in the sludge storage tank 7 is dried and then subjected to incineration. For that purpose, if the moisture contained in the sludge is small, not only the bulk becomes small and the handling becomes easy, but also the drying time is shortened, which contributes to energy saving. However, the normal amount of suction of filtered water does not reach a suitable sludge concentration as described above.

そこで本発明では、図5に矢印で示すように、ばっ気槽4内の汚泥濃度を上流側端部から下流側端部にかけて順次汚泥濃度を積極的に高めていき、最終的な廃棄処理をするに好適な濃度をもつ汚泥とすべく、膜ろ過ユニット5から吸引するろ過水の吸引量を処理方向の上流側から下流側に順に順次増加させている。具体的には、上流側から下流側の順にろ過水吸引管路22に接続された各分岐管路22aに流量調整バルブ23を配して、上流側から下流側の順にその開度を大きくしている。このとき同時に、ばっ気ブロアBのエア主管18に接続された各エア導入管路16に配された流量調整バルブ19の開度を、ばっ気ブロアBから遠い順に調整して、ばっ気ブロアBに最も近い散気発生装置15から放出するエア放出量を最も多くなるようにしている。   Therefore, in the present invention, as shown by an arrow in FIG. 5, the sludge concentration in the aeration tank 4 is gradually increased from the upstream end to the downstream end in order to increase the final disposal process. In order to obtain a sludge having a suitable concentration, the suction amount of the filtered water sucked from the membrane filtration unit 5 is sequentially increased from the upstream side to the downstream side in the processing direction. Specifically, a flow rate adjusting valve 23 is arranged in each branch line 22a connected to the filtrate water suction line 22 in order from the upstream side to the downstream side, and the opening degree is increased in order from the upstream side to the downstream side. ing. At the same time, the opening degree of the flow rate adjusting valve 19 arranged in each air introduction pipe line 16 connected to the air main pipe 18 of the aeration blower B is adjusted in order of increasing distance from the aeration blower B. The amount of air discharged from the air diffuser 15 closest to the maximum is set to be the largest.

かかる構成により、汚泥が最も少なく、その膜面への固形物の付着が最も少ない原水流入側端部の膜ろ過ユニット5へのエア供給量を生物学的汚泥処理に必要で且つエアスクラビング洗浄が効率的に行える必要量に抑えるとともに、汚泥濃度が最も高く、固形物の付着量が最も多い余剰汚泥回収側端部の膜ろ過ユニット5へのエア供給量を最も多くして、その領域における気液混合旋回流の勢いを強くしてスクラビング洗浄を強力に行うとともに、汚泥の攪拌機能を増加させて、生物学的汚泥処理に十分な溶存酸素量を確保する。また、汚泥貯留槽7に貯蔵される余剰汚泥の濃度が増すため、その嵩が小さくなり取扱いがしやすくなるばかりか、乾燥時に使われる熱エネルギーの量が減少し省エネルギーにもつながる。   With this configuration, the amount of air supplied to the membrane filtration unit 5 at the raw water inflow side end portion with the least amount of sludge and the least amount of solid matter adhering to the membrane surface is required for biological sludge treatment and air scrubbing cleaning is performed. The amount of air supplied to the membrane filtration unit 5 at the end of the excess sludge recovery side where the sludge concentration is the highest and the amount of solids attached is the largest is maximized to reduce the amount of air in that region. In addition to strengthening the scrubbing cleaning by increasing the momentum of the liquid mixing swirl flow, the agitation function of the sludge is increased to ensure a sufficient amount of dissolved oxygen for biological sludge treatment. Moreover, since the density | concentration of the excess sludge stored in the sludge storage tank 7 increases, not only the volume becomes small and it becomes easy to handle, but also the amount of heat energy used at the time of drying decreases, leading to energy saving.

図6は本発明の第2の実施形態を示している。この実施形態によれば、ばっ気槽4に4基を一組として3組、計12基の膜ろ過ユニット5が並設されている。この各膜ろ過ユニット5の構成は、図2に示した構成と実質的に変わるところがない。ただし、膜ろ過ユニット5の各組ごとに第1〜第3のろ過水吸引ポンプPv1 〜Pv3 が接続され、各ろ過水吸引ポンプPv1 〜Pv3 の吐出側配管路22' は合流して図示せぬ処理水槽へと延びている。そして、原水流入側の第1ろ過水吸引ポンプPv1 から第3ろ過水吸引ポンプPv3 へと、そのろ過水の吸引量を順次増加させている。また、各膜ろ過ユニット5の図示せぬ中空糸膜モジュールの下方には同じく図示せぬ散気発生装置が配されており、原水流入側の第1組目の散気発生装置、第2組目の散気発生装置、第3組目の散気発生装置から放出されるエア量もまた、第1の上記実施形態吸引量と同様に順次多くしている。この実施形態では、1組4基の膜ろ過ユニット5ごとに原水流入側から汚泥回収側へとろ過水の吸引量とエア放出量を増加させている。その作用効果は、上記第1実施形態と同様である。 FIG. 6 shows a second embodiment of the present invention. According to this embodiment, a total of 12 membrane filtration units 5 are arranged in parallel in the aeration tank 4, with 4 groups as 3 groups. The configuration of each membrane filtration unit 5 is not substantially different from the configuration shown in FIG. However, the first to third filtered water suction pumps Pv 1 to Pv 3 are connected to each set of the membrane filtration unit 5, and the discharge side piping paths 22 ′ of the filtered water suction pumps Pv 1 to Pv 3 are joined. It extends to a treated water tank (not shown). The suction amount of the filtrate is sequentially increased from the first filtrate suction pump Pv 1 on the raw water inflow side to the third filtrate suction pump Pv 3 . Also, an unshown air diffuser is disposed below the hollow fiber membrane module (not shown) of each membrane filtration unit 5, and the first air diffuser on the raw water inflow side, the second set The amount of air released from the air diffuser of the eye and the third set of air diffuser is also sequentially increased in the same manner as the suction amount of the first embodiment. In this embodiment, the suction amount and the air discharge amount of filtered water are increased from the raw water inflow side to the sludge recovery side for each set of four membrane filtration units 5. The effect is the same as that of the first embodiment.

図7は、前記第2実施形態の変形例を示している。この変形例にあっても、ばっ気槽4には4基1組の膜ろ過ユニットが3組並設されており、ただ無酸素槽3とばっ気槽4との間を循環する汚泥の送液方向が第2実施形態とは逆になっている。しかも、槽内をばっ気槽4から無酸素槽3へと流入する部位に原水を流入させている点が上記第2実施形態と異なっているが、この実施形態にあってもばっ気槽4の汚泥濃度の高い領域の槽底部から無酸素槽3の原水流入部位の槽底部へと汚泥が送られる点では上記第1実施形態と同じである。   FIG. 7 shows a modification of the second embodiment. Even in this modified example, the aeration tank 4 has three sets of four membrane filtration units arranged in parallel, and only sends sludge circulating between the anoxic tank 3 and the aeration tank 4. The liquid direction is opposite to that of the second embodiment. Moreover, although the point in which the raw water is allowed to flow into the portion of the tank that flows from the aeration tank 4 to the anaerobic tank 3 is different from the second embodiment, even in this embodiment, the aeration tank 4. This is the same as the first embodiment in that the sludge is sent from the tank bottom in the region where the sludge concentration is high to the tank bottom of the raw water inflow portion of the anoxic tank 3.

図8は、本発明の第3実施形態を示している。この第3実施形態は余剰汚泥の循環管路の途中に3ポート2方向切換バルブ25を介して余剰汚泥の回収管路26を汚泥貯留槽7に臨ませている。汚泥循環路の汚泥取出口は上述の汚泥循環管路の汚泥取出口と同様に第3組目の膜ろ過ユニット5の下方槽底部に設けられる。余剰汚泥の取出口から取り出された余剰汚泥は3ポート2方向切換バルブ25を切り換えることにより、共通の液槽ポンプ28により無酸素槽3に返送するか、或いは汚泥貯蔵槽に送液する。このときも、膜ろ過ユニット5から吸引されるろ過水の吸引量及び散気発生装置15から放出されるエア量は、第1組目から第3組目へと順次増加させている。図9に示す前記第3実施形態の変形例では、汚泥循環管路と汚泥回収管路26とを切り離して、それぞれに循環用ポンプPrと汚泥回収用ポンプPcとを設け、循環用汚泥と回収用汚泥とを任意の時期に独立して送液出来るようにしている。   FIG. 8 shows a third embodiment of the present invention. In the third embodiment, the surplus sludge recovery pipe 26 faces the sludge storage tank 7 via a three-port two-way switching valve 25 in the middle of the surplus sludge circulation pipe. The sludge outlet of the sludge circulation path is provided at the bottom of the lower tank of the third set of membrane filtration units 5 in the same manner as the sludge outlet of the sludge circulation pipe described above. The excess sludge taken out from the excess sludge outlet is returned to the anoxic tank 3 by a common liquid tank pump 28 by switching the three-port two-way switching valve 25 or is sent to the sludge storage tank. Also at this time, the suction amount of the filtered water sucked from the membrane filtration unit 5 and the air amount discharged from the air diffuser 15 are sequentially increased from the first set to the third set. In the modification of the third embodiment shown in FIG. 9, the sludge circulation line and the sludge recovery line 26 are separated from each other, and a circulation pump Pr and a sludge recovery pump Pc are provided respectively, and the circulation sludge and the recovery are provided. The sludge can be sent independently at any time.

図10は、本発明の更なる第4実施形態を示している。この実施形態では、無酸素槽3からばっ気槽4に流入させる流入路を、第1組目〜第3組目の各4基の膜ろ過ユニット5の処理方向上流側に分散して配するとともに、ばっ気槽4から無酸素槽3へと汚泥を返送する汚泥取出口を第1組目〜第3組目の各4基の膜ろ過ユニット5の下方槽底部にそれぞれ設けている。更に、各汚泥取出口に接続された各汚泥送液管路の途中に第1〜第3の循環用ポンプPr1 〜Pr3 を配して、これを合流させて無酸素槽3の原水流入側端部の槽底部へと送液するようにしている。この実施形態にあっても、上記実施形態と同様に1組4基の膜ろ過ユニット5ごとに原水流入側から汚泥回収側へとろ過水の吸引量とエア放出量を増加させている。 FIG. 10 shows a further fourth embodiment of the present invention. In this embodiment, the inflow path for flowing into the aeration tank 4 from the oxygen-free tank 3 is distributed and arranged on the upstream side in the processing direction of each of the four membrane filtration units 5 of the first group to the third group. At the same time, sludge outlets for returning sludge from the aeration tank 4 to the anoxic tank 3 are provided at the bottom of the bottom tank of each of the four membrane filtration units 5 of the first to third groups. Further, the first to third circulating pump Pr 1 to PR 3 of arranged in the middle of each sludge feeding conduit connected to the sludge outlet, water inlet of the anoxic tank 3 by merging it The liquid is fed to the tank bottom at the side end. Even in this embodiment, the suction amount and the air discharge amount of the filtrate are increased from the raw water inflow side to the sludge recovery side for each set of four membrane filtration units 5 as in the above embodiment.

このように、ばっ気槽4の膜ろ過ユニット5の組ごとに原水を流入させるとともに、循環用汚泥の取り出し口も各組ごとに設けることにより、処理方向の上流側から下流側にかけて増加する濃度勾配を小さくし、可能な限り濃度分布を均等にすることにより、原水流入側から汚泥回収側へとろ過水の吸引量とエア放出量を増加させることに基づく各膜ろ過ユニット5の負担を軽減させて、長期の使用に耐えられるようにしている。   In this way, the concentration that increases from the upstream side to the downstream side in the treatment direction by allowing the raw water to flow into each group of the membrane filtration unit 5 of the aeration tank 4 and also providing a circulation sludge outlet for each group. By reducing the gradient and making the concentration distribution as uniform as possible, the burden on each membrane filtration unit 5 based on increasing the amount of filtrate suction and air release from the raw water inflow side to the sludge recovery side is reduced. Let it withstand long-term use.

本発明の実施形態に係る処理方法を実施するために好適な膜分離汚泥処理装置の一例を示す概略図である。It is the schematic which shows an example of the membrane separation sludge processing apparatus suitable in order to implement the processing method which concerns on embodiment of this invention. 通常の膜ろ過ユニットの全体構成を一部破断して示す立体図である。FIG. 3 is a three-dimensional view showing the entire configuration of a normal membrane filtration unit with a part broken away. 糸膜モジュールの構成部材である膜エレメントの構成例を模式的に示す斜視図である。It is a perspective view which shows typically the structural example of the membrane element which is a structural member of a thread membrane module. 膜ろ過ユニットの構成部材の一つである散気発生装置の立体図である。It is a three-dimensional view of an air diffuser that is one of the constituent members of the membrane filtration unit. 本発明の第1実施形態に係るばっ気処理の一例を示す工程説明図である。It is process explanatory drawing which shows an example of the aeration process which concerns on 1st Embodiment of this invention. 本発明の第2実施形態に係る膜分離活性汚泥処理方法の一例を示す工程説明図である。It is process explanatory drawing which shows an example of the membrane separation activated sludge processing method which concerns on 2nd Embodiment of this invention. 第2実施形態の変形例を示す工程説明図である。It is process explanatory drawing which shows the modification of 2nd Embodiment. 本発明の第3実施形態に係る膜分離活性汚泥処理方法の一例を示す工程説明図である。It is process explanatory drawing which shows an example of the membrane separation activated sludge processing method which concerns on 3rd Embodiment of this invention. 第3実施形態の変形例を示す工程説明図である。It is process explanatory drawing which shows the modification of 3rd Embodiment. 本発明の第4実施形態に係る膜分離活性汚泥処理方法の一例を示す工程説明図である。It is process explanatory drawing which shows an example of the membrane separation activated sludge processing method which concerns on 4th Embodiment of this invention.

符号の説明Explanation of symbols

1 微細目スクリーン
2 原水調整槽
3 無酸素槽
4 ばっ気槽
5 膜ろ過ユニット
6 循環液の取出し部位
7 汚泥貯留槽
8 処理水槽
9 糸膜モジュール
10 膜エレメント
10a 中空糸
11 膜シート
11a ポッティング材
12 ろ過水取出管
12a ろ過水取出口
12b L型継手
13 下枠
14 縦杆
15 散気発生装置
16 エア導入管(分岐管路)
17 散気管
18 エア主管
19 流量調整バルブ
20 上部壁材
21 集水ヘッダー管
21a 集水口
21b L型継手
21c 吸水口
22 吸引管路
22' 吐出側配管路
22a 分岐管路
23 流量調整バルブ
24 下部壁材
24a 支柱
25 3ポート2方向切換バルブ
26 回収管路
P1 第1送液ポンプ
P2 第2送液ポンプ
Pv 吸引ポンプ
Pv1 〜Pv3 第1〜第3吸引ポンプ
Pr 循環用ポンプ
Pc 汚泥回収用ポンプ
B ばっ気ブロア
DESCRIPTION OF SYMBOLS 1 Fine screen 2 Raw water adjustment tank 3 Anoxic tank 4 Aeration tank 5 Membrane filtration unit 6 Circulating fluid extraction part 7 Sludge storage tank 8 Treated water tank 9 Yarn membrane module 10 Membrane element 10a Hollow fiber 11 Membrane sheet 11a Potting material 12 Filtrated water extraction pipe 12a Filtration water outlet 12b L-shaped joint 13 Lower frame 14 Vertical gutter 15 Air diffuser 16 Air introduction pipe (branch pipe)
17 Aeration pipe 18 Air main pipe 19 Flow rate adjustment valve 20 Upper wall material 21 Water collection header pipe 21a Water collection port 21b L-type joint 21c Water intake port 22 Suction pipe line 22 'Discharge side pipe line 22a Branch pipe line 23 Flow rate adjustment valve 24 Lower wall Material 24a strut 25 3 port 2-way switching valve 26 the recovery pipe P1 first liquid feeding pump P2 second liquid supply pump Pv suction pump Pv 1 ~Pv 3 first to third suction pump Pr circulation pump Pc sludge withdrawal pump B aeration blower

Claims (3)

無酸素槽又は嫌気槽とばっ気槽とを備え、前記ばっ気槽には膜ろ過ユニットが浸漬され、排水を嫌気槽側から生物学的に順次処理して活性汚泥を固液分離する膜分離活性汚泥処理方法であって、
前記ばっ気槽の処理方向上流側から下流側に向けて、4基以上の膜ろ過ユニットを所要の間隔をおいて浸漬配置すること、
前記各膜ろ過ユニットの膜モジュールから分岐管路を介して接続されたろ過水吸引管路を通してろ過水を吸引して排出すること、
前記各膜ろ過ユニットの散気発生装置からエアの気泡を発生させること、及び
前記ばっ気槽における処理方向上流側原水流入口から最も遠い位置に配された膜ろ過ユニット下方の槽底部から上記無酸素槽又は嫌気槽の原水流入部に送液手段により処理済汚泥を返戻させ、汚泥を無酸素槽又は嫌気槽とばっ気槽との間を循環させること、
を含んでなることを特徴とする膜分離活性汚泥処理方法。
An anaerobic tank or an anaerobic tank and an aeration tank, and a membrane filtration unit is immersed in the anaerobic tank, and the wastewater is biologically processed sequentially from the anaerobic tank side to separate activated sludge into solid and liquid. An activated sludge treatment method,
From the upstream side in the processing direction of the aeration tank to the downstream side, four or more membrane filtration units are immersed and arranged at a required interval;
Suctioning and discharging filtrate water through the filtrate suction pipe connected from the membrane module of each membrane filtration unit via a branch pipe;
Generating air bubbles from the air diffuser of each membrane filtration unit, and from the bottom of the tank below the membrane filtration unit disposed farthest from the upstream raw water inlet in the processing direction in the aeration tank by-return the treated sludge by feeding means water inlet of the anoxic tank or anaerobic tank, circulating between the sludge anoxic or anaerobic tank and aeration tank,
A membrane separation activated sludge treatment method comprising:
前記各膜モジュールにおける1以上のろ過水吸引源により吸引されるろ過水の吸引量及び/又は各散気発生装置から発生する気泡の発生量を、排水流入側から排出側の順に漸次増加させることを更に含んでなる請求項1記載の膜分離活性汚泥処理方法。 The amount of filtered water sucked by one or more filtered water suction sources in each membrane module and / or the amount of bubbles generated from each air diffuser is gradually increased from the drainage inflow side to the discharge side. The membrane separation activated sludge treatment method according to claim 1 , further comprising: 前記ばっ気槽の最も排出側に配された膜ろ過ユニット下方の槽底部と前記無酸素槽又は嫌気槽の原水流入部とを接続する汚泥返戻管路に、切替バルブを介して接続された余剰汚泥回収管路から余剰汚泥を回収することを含んでなる請求項1又は2に記載の膜分離活性汚泥処理方法。 A surplus connected via a switching valve to a sludge return pipe connecting the bottom of the membrane filtration unit disposed on the most discharge side of the aeration tank and the raw water inflow part of the anaerobic tank or anaerobic tank. The membrane separation activated sludge treatment method according to claim 1 or 2 , comprising recovering excess sludge from the sludge recovery pipeline.
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