JP5614644B2 - Membrane filtration method - Google Patents

Membrane filtration method Download PDF

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JP5614644B2
JP5614644B2 JP2010234788A JP2010234788A JP5614644B2 JP 5614644 B2 JP5614644 B2 JP 5614644B2 JP 2010234788 A JP2010234788 A JP 2010234788A JP 2010234788 A JP2010234788 A JP 2010234788A JP 5614644 B2 JP5614644 B2 JP 5614644B2
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絵美 加藤
絵美 加藤
村田 直樹
直樹 村田
優治 川瀬
優治 川瀬
伸浩 青木
伸浩 青木
佳彦 松井
佳彦 松井
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Hokkaido University NUC
Taki Kasei Co Ltd
Metawater Co Ltd
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Taki Kasei Co Ltd
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Description

本発明は、ろ過膜を用いて被処理水をろ過する膜ろ過方法に関し、特に、浄水場等において被処理水をろ過する際に好適に使用し得る膜ろ過方法に関するものである。   The present invention relates to a membrane filtration method for filtering treated water using a filtration membrane, and particularly to a membrane filtration method that can be suitably used when filtering treated water in a water purification plant or the like.

従来、上水処理、下水処理、工業用水処理、工業排水処理などの各種水処理分野において、被処理水をろ過して被処理水中の懸濁物質(SS:suspended solids)を除去し、清浄なろ過水を得る方法として、膜ろ過法が用いられている。そして、この膜ろ過法では、一般に、硫酸アルミニウムやポリ塩化アルミニウム等の凝集剤を用いて被処理水中の懸濁物質を凝集(フロック化)させた後に、微細孔が形成されたろ過膜を用いて被処理水をろ過している。   Conventionally, in various water treatment fields such as water treatment, sewage treatment, industrial water treatment, and industrial wastewater treatment, water to be treated is filtered to remove suspended solids (SS) and clean A membrane filtration method is used as a method for obtaining filtered water. In this membrane filtration method, generally, a filtration membrane in which fine pores are formed after agglomerating (flocculating) suspended substances in the water to be treated using an aggregating agent such as aluminum sulfate or polyaluminum chloride is used. The treated water is filtered.

ここで、膜ろ過法で被処理水を連続的にろ過する場合、ろ過の継続に伴い、ろ過膜が閉塞(ファウリング)して膜差圧が上昇し、ろ過膜が所望のろ過性能を発揮できなくなることがある。そのため、膜ろ過法を用いて被処理水を処理する際には、定期的にろ過膜を逆流洗浄(以下「逆洗」という。)し、ろ過膜に付着した懸濁物質のフロック等のファウリング原因物質を定期的に除去している。   Here, when the water to be treated is continuously filtered by the membrane filtration method, the filtration membrane is clogged (fouling) with the continuation of filtration and the membrane differential pressure increases, and the filtration membrane exhibits the desired filtration performance. It may not be possible. For this reason, when treating the water to be treated using the membrane filtration method, the filtration membrane is periodically backwashed (hereinafter referred to as “backwashing”), and the suspended matter adhering to the filtration membrane is fouled. The ring-causing substances are regularly removed.

しかし、逆洗を実施してもろ過膜からファウリング原因物質を完全に除去することはできないため、被処理水の膜ろ過を長時間実施すると、定期的に逆洗を実施していても、ろ過膜の閉塞が次第に激しくなり(即ち、ろ過膜の閉塞が進行し)、膜差圧が徐々に上昇してしまう。そして、ろ過の継続が不可能なレベルまでろ過膜の閉塞が進んだ場合には、薬品を用いたろ過膜の洗浄(CIP:薬品洗浄)を実施する必要が生じる。また、薬品洗浄を実施してもろ過膜の閉塞が解消しない場合には、ろ過膜自体を新たなろ過膜に交換する必要が生じる。   However, even if backwashing is performed, fouling-causing substances cannot be completely removed from the filtration membrane, so when membrane filtration of treated water is performed for a long time, even if backwashing is carried out regularly, The filtration membrane is gradually clogged (that is, the filtration membrane is clogged), and the membrane differential pressure gradually increases. When the filtration membrane is blocked to a level at which filtration cannot be continued, it is necessary to perform cleaning of the filtration membrane using chemicals (CIP: chemical cleaning). In addition, if the clogging of the filtration membrane is not eliminated even after the chemical cleaning, the filtration membrane itself needs to be replaced with a new filtration membrane.

そこで、ろ過膜の閉塞の進行を抑制し、膜差圧の上昇速度を低減することにより、ろ過膜の薬品洗浄頻度やろ過膜の交換頻度を低減して長時間の膜ろ過を低コストで実現する方法として、凝集剤添加後の被処理水のpHを被処理水の水質に応じた所定のpHに調整した後で被処理水をろ過する方法が提案されている(例えば、特許文献1参照)。   Therefore, by suppressing the progress of clogging of the filtration membrane and reducing the rate of increase in the membrane differential pressure, long-term membrane filtration is realized at low cost by reducing the frequency of chemical cleaning of the filtration membrane and the frequency of replacement of the filtration membrane. As a method for this, a method of filtering the water to be treated after adjusting the pH of the water to be treated after adding the flocculant to a predetermined pH according to the quality of the water to be treated has been proposed (for example, see Patent Document 1). ).

特開2008−221168号公報JP 2008-221168 A

しかし、特許文献1に記載の膜ろ過方法には、ろ過膜の薬品洗浄頻度や交換頻度を更に低減して被処理水のろ過に必要な運転コストを更に低減するという点において改善の余地があった。   However, the membrane filtration method described in Patent Document 1 has room for improvement in that the frequency of chemical cleaning and replacement of the filtration membrane is further reduced to further reduce the operating cost required for filtering the water to be treated. It was.

そこで、本発明は、ろ過膜の閉塞の進行を抑制してろ過膜の薬品洗浄頻度およびろ過膜の交換頻度を低減することが可能な膜ろ過方法を提供することを目的とする。   Therefore, an object of the present invention is to provide a membrane filtration method capable of suppressing the progress of clogging of the filtration membrane and reducing the frequency of chemical cleaning of the filtration membrane and the replacement frequency of the filtration membrane.

本発明者らは、上記目的を達成するため鋭意研究を行い、所定の塩基度を有するポリ塩化アルミニウム溶液(PAC溶液)を凝集剤として用いて被処理水の膜ろ過を実施することで、ろ過膜の閉塞の進行を抑制してろ過膜の薬品洗浄頻度および交換頻度を低減し得ること(即ち、薬品コストおよび運転コストを低減し得ること)を見出し、本発明を完成させた。   In order to achieve the above-mentioned object, the present inventors have conducted intensive research and conducted membrane filtration of water to be treated using a polyaluminum chloride solution (PAC solution) having a predetermined basicity as a flocculant. The inventors have found that it is possible to reduce the frequency of chemical cleaning and replacement of the filtration membrane by suppressing the progress of membrane clogging (that is, the chemical cost and the operating cost can be reduced), and the present invention has been completed.

即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の膜ろ過方法は、被処理水と、塩基度が65%以上75%以下のポリ塩化アルミニウム溶液とを急速撹拌槽で混和し、前記被処理水中の懸濁物質を凝集させて微細なフロックを形成した後、緩速撹拌槽で前記微細なフロックを粗大化させて凝集処理水を得る前処理工程と、前記凝集処理水をろ過膜でデッドエンドろ過し、ろ過水を得る膜ろ過工程と、前記ろ過膜を所定の間隔で逆流洗浄する逆洗工程とを含み、前記ろ過膜が、多孔質セラミックの内部に複数の通水貫通孔を設けてなるモノリス型セラミック膜であり、前記凝集処理水は、前記通水貫通孔に流入し、当該通水貫通孔の表面に位置する分離層でろ過されることを特徴とする。このように、塩基度が65%以上75%以下のポリ塩化アルミニウム溶液を用いて被処理水を前処理し、得られた凝集処理水を膜ろ過すれば、ろ過膜に付着するファウリング原因物質の逆洗時の剥離性(除去性)を向上させることができる。従って、本発明の膜ろ過方法に従い被処理水をろ過すれば、ろ過膜の閉塞の進行を抑制してろ過膜の薬品洗浄頻度および交換頻度を低減することができる。 That is, this invention aims to solve the above-mentioned problems advantageously, and the membrane filtration method of the present invention comprises water to be treated and a polyaluminum chloride solution having a basicity of 65% to 75%. Are mixed in a rapid agitation tank, the suspended substances in the water to be treated are aggregated to form fine flocs, and then the fine flocs are coarsened in a slow agitation tank to obtain an agglomerated treated water. And a membrane filtration step of subjecting the agglomerated treated water to dead-end filtration with a filtration membrane to obtain filtrate water, and a backwashing step of backwashing the filtration membrane at a predetermined interval, wherein the filtration membrane is a porous ceramic. Is a monolithic ceramic membrane having a plurality of water passage through holes, and the agglomerated treated water flows into the water passage through holes and is filtered by a separation layer located on the surface of the water passage through holes. It is characterized by that. Thus, if the water to be treated is pretreated with a polyaluminum chloride solution having a basicity of 65% or more and 75% or less , and the resulting agglomerated treated water is subjected to membrane filtration, a fouling causative substance adhering to the filtration membrane is obtained. The peelability (removability) at the time of backwashing can be improved. Therefore, if the water to be treated is filtered according to the membrane filtration method of the present invention, the progress of clogging of the filtration membrane can be suppressed, and the chemical cleaning frequency and replacement frequency of the filtration membrane can be reduced.

また、塩基度が65%以上75%以下のポリ塩化アルミニウム溶液と被処理水とを混和して得た凝集処理水を膜ろ過した際にろ過膜に付着するファウリング原因物質は、ろ過膜がセラミック製の場合に逆洗時の剥離性が特に良好であるため、ろ過膜をセラミック製にすれば、ろ過膜の閉塞の進行を更に抑制することができる。また、ろ過膜がセラミック製の場合、逆洗時にろ過膜から剥離したファウリング原因物質の沈降性が良好になり、逆洗時に生じる排水(逆洗排水)を低コストで容易に処理することができる。 In addition, when the agglomerated treated water obtained by mixing a polyaluminum chloride solution having a basicity of 65% or more and 75% or less and the water to be treated is subjected to membrane filtration, the fouling causative substance adhering to the filtration membrane is a filtration membrane. In the case of a ceramic product, the releasability at the time of backwashing is particularly good. Therefore, if the filter membrane is made of ceramic, the progress of the clogging of the filter membrane can be further suppressed. In addition, when the filter membrane is made of ceramic, the sedimentation of the fouling-causing substances separated from the filter membrane at the time of backwashing becomes better, and the wastewater generated during backwashing (backwash wastewater) can be easily treated at low cost. it can.

更に、セラミック製のろ過膜が多孔質セラミックの内部に複数の通水貫通孔を設けた所謂モノリス形状である場合、凝集処理水のろ過時に凝集処理水中のフロックが通水貫通孔内で互いに接触して更に緻密化および粗大化するので、逆洗時のファウリング原因物質の剥離性が更に向上し、ろ過膜の閉塞の進行をより一層抑制することができる。また、逆洗時にろ過膜から剥離したファウリング原因物質の沈降性が更に良好になり、逆洗排水を更に低コストで容易に処理することができる。なお、凝集処理水中のフロックは、PAC溶液として塩基度が65%以上75%以下のポリ塩化アルミニウム溶液を用いた際に特に顕著に通水貫通孔内で緻密化・粗大化する。
なお、本発明における「ポリ塩化アルミニウム溶液の塩基度」は、日本水道協会(JWWA)の規格JWWA K 154に従って求めることができる。また、本発明において、逆流洗浄を実施する「所定の間隔」は、ろ過膜の性能等に応じて既知の手法で定めることができ、例えば、予め定めた一定の時間間隔としても良いし、ろ過膜の膜差圧の大きさに応じて定まる間隔としても良いし、ろ過水の水質に応じて定まる間隔としても良い。
Furthermore, when the ceramic filtration membrane has a so-called monolithic shape in which a plurality of water passage through holes are provided inside the porous ceramic, flocs in the coagulation treated water contact each other in the water passage through holes during filtration of the coagulation treated water. Further, since the densification and coarsening are further performed, the peelability of the fouling-causing substance at the time of backwashing is further improved, and the progress of clogging of the filtration membrane can be further suppressed. Further, the sedimentation property of the fouling-causing substance peeled from the filter membrane during backwashing is further improved, and the backwash wastewater can be easily treated at a lower cost. In addition, flocs in the agglomerated water are remarkably densified and coarsened in the water passage through holes when a polyaluminum chloride solution having a basicity of 65% to 75% is used as the PAC solution.
The “basicity of the polyaluminum chloride solution” in the present invention can be determined in accordance with the standard JWWA K 154 of the Japan Water Works Association (JWWA). Further, in the present invention, the “predetermined interval” for performing the backwashing can be determined by a known method according to the performance of the filtration membrane, for example, it may be a predetermined time interval, or may be filtered. The interval may be determined according to the magnitude of the membrane differential pressure, or may be determined according to the quality of the filtered water.

そして、本発明の膜ろ過方法は、前記逆洗工程において、逆洗水を150kPa以上の圧力でろ過膜に流通することが好ましい。逆洗水を150kPa以上の圧力でろ過膜に流通させた場合、ファウリング原因物質がろ過膜から良好に剥離し、ろ過膜の閉塞の進行を更に抑制することができるからである。   And it is preferable that the membrane filtration method of this invention distribute | circulates backwash water to a filtration membrane by the pressure of 150 kPa or more in the said backwashing process. This is because when the backwash water is circulated through the filtration membrane at a pressure of 150 kPa or more, the fouling-causing substance is satisfactorily peeled from the filtration membrane, and the progression of the filtration membrane can be further suppressed.

本発明の膜ろ過方法によれば、ろ過膜の閉塞の進行を抑制し、ろ過膜の薬品洗浄頻度および交換頻度を低減することができる。   According to the membrane filtration method of the present invention, the progress of clogging of the filtration membrane can be suppressed, and the chemical cleaning frequency and replacement frequency of the filtration membrane can be reduced.

本発明に従う代表的な膜ろ過方法を用いて被処理水をろ過する際に適用し得る膜ろ過システムの構成を示す説明図である。It is explanatory drawing which shows the structure of the membrane filtration system which can be applied when filtering to-be-processed water using the typical membrane filtration method according to this invention. 本発明に従う膜ろ過方法で使用し得るセラミック膜の構造を、セラミック膜の一部を切り欠いて示す説明図である。It is explanatory drawing which cuts off a part of ceramic membrane and shows the structure of the ceramic membrane which can be used with the membrane filtration method according to this invention. 実施例および比較例に係る方法を用いて被処理水を膜ろ過した場合における、ろ過時間と、逆洗直後の膜差圧との関係を示すグラフである。It is a graph which shows the relationship between the filtration time at the time of carrying out the membrane filtration of the to-be-processed water using the method which concerns on an Example and a comparative example, and the membrane differential pressure immediately after backwashing.

以下、図面を参照して本発明の実施の形態を詳細に説明する。本発明の膜ろ過方法は、凝集剤として塩基度が65%以上75%以下のポリ塩化アルミニウム溶液(以下「PAC溶液」と称する。)を用いることを特徴とする。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The membrane filtration method of the present invention is characterized in that a polyaluminum chloride solution (hereinafter referred to as “PAC solution”) having a basicity of 65% or more and 75% or less is used as a flocculant.

ここで、本発明の膜ろ過方法の一例は、特に限定されることなく、例えば図1に示すような膜ろ過システムを用いて実施することができる。そして、本発明の膜ろ過方法の一例は、例えば、浄水場において河川水や湖沼水などの被処理水をろ過して水道水を製造する際に用いることができる。なお、本発明の膜ろ過方法は、特に限定されることなく膜分離活性汚泥法(MBR)を用いた下水の処理等でも用いることができる。   Here, an example of the membrane filtration method of this invention is not specifically limited, For example, it can implement using a membrane filtration system as shown in FIG. And an example of the membrane filtration method of the present invention can be used, for example, when water to be treated is filtered to produce tap water at a water purification plant, such as river water or lake water. The membrane filtration method of the present invention is not particularly limited, and can be used for sewage treatment using a membrane separation activated sludge method (MBR).

図1に示す膜ろ過システム10は、被処理水と所定の塩基度のPAC溶液とを混和して凝集処理水を得る凝集混和槽1と、凝集混和槽1から凝集処理水ポンプ4を介して供給された凝集処理水をろ過膜(図示せず)でろ過してろ過水を得る膜ろ過ユニット5と、膜ろ過ユニット5のろ過膜の逆流洗浄(逆洗)に用いる逆洗水を貯留する逆洗水槽6とを備えている。   A membrane filtration system 10 shown in FIG. 1 includes a flocculation / mixing tank 1 for mixing treated water and a PAC solution having a predetermined basicity to obtain flocculated water, and a flocculation / mixing tank 1 through a flocculated water pump 4. A membrane filtration unit 5 that obtains filtered water by filtering the supplied agglomerated treated water through a filtration membrane (not shown), and backwash water used for backwashing (backwashing) of the filtration membrane of the membrane filtration unit 5 are stored. And a backwash tank 6.

ここで、凝集混和槽1は、被処理水と塩基度が65%以上75%以下のPAC溶液とを急速撹拌条件下で混合する急速撹拌槽2と、急速撹拌槽2で混合した被処理水とPAC溶液との混合物を緩速撹拌条件下で混合する緩速撹拌槽3とからなる。 Here, the agglomeration mixing tank 1 includes a rapid stirring tank 2 for mixing the water to be treated and a PAC solution having a basicity of 65% to 75% under rapid stirring conditions, and the water to be treated mixed in the rapid stirring tank 2. And a slow stirring tank 3 for mixing a mixture of the PAC solution and the PAC solution under slow stirring conditions.

急速撹拌槽2は、槽内を撹拌する撹拌機21と、塩基度が65%以上75%以下のPAC溶液を急速撹拌槽2中の被処理水に添加するPACポンプ22とを備えている。そして、この急速撹拌槽2では、被処理水とPAC溶液とが急速な撹拌によって直ちに混合され、被処理水中の懸濁物質が凝集して微細なフロックを形成する。 The rapid stirring tank 2 includes a stirrer 21 for stirring the inside of the tank, and a PAC pump 22 for adding a PAC solution having a basicity of 65% to 75% to the water to be treated in the rapid stirring tank 2. In the rapid stirring tank 2, the water to be treated and the PAC solution are immediately mixed by rapid stirring, and suspended substances in the water to be treated are aggregated to form fine flocs.

なお、急速撹拌槽2で被処理水に添加する塩基度が65%以上75%以下のPAC溶液は、例えば特開2009−203125号公報に記載の方法で製造することができる。具体的には、上記PAC溶液は、例えば、Al23濃度が5〜17質量%、Cl/Al23(モル比)が1.80〜3.60、SO4/Al23(モル比)が0〜0.35で且つ塩基度が40〜63%の塩基性塩化アルミニウム溶液に、85℃以下の温度下でアルカリ金属および/またはアルカリ土類金属の化合物を添加した後、65〜85℃の温度で0.5〜2時間熟成を行うことによって製造することができる。 A PAC solution having a basicity of 65% or more and 75% or less added to the water to be treated in the rapid stirring tank 2 can be produced by, for example, a method described in JP-A-2009-203125. Specifically, the PAC solution has an Al 2 O 3 concentration of 5 to 17% by mass, a Cl / Al 2 O 3 (molar ratio) of 1.80 to 3.60, SO 4 / Al 2 O 3, for example. After adding an alkali metal and / or alkaline earth metal compound to a basic aluminum chloride solution having a (molar ratio) of 0 to 0.35 and a basicity of 40 to 63% at a temperature of 85 ° C. or lower, It can be produced by aging at a temperature of 65 to 85 ° C. for 0.5 to 2 hours.

緩速撹拌槽3は、槽内を撹拌する撹拌機31を備えており、緩速撹拌槽3には、急速撹拌槽2で被処理水とPAC溶液とを混合して得た、微細なフロックを含有する被処理水が流入する。そして、緩速撹拌槽3では、被処理水とPAC溶液との混合物である、微細なフロックを含有する被処理水が例えばGT値=23000〜210000の緩速撹拌条件下で混合され、被処理水中のフロックが粗大化する。   The slow stirring tank 3 includes a stirrer 31 for stirring the inside of the tank. The slow stirring tank 3 includes fine flocs obtained by mixing the water to be treated and the PAC solution in the rapid stirring tank 2. The treated water containing And in the slow stirring tank 3, the to-be-processed water containing the fine floc which is a mixture of to-be-processed water and a PAC solution is mixed on the slow stirring conditions of GT value = 23000-210000, for example, Underwater flocs become coarse.

即ち、急速撹拌槽2および緩速撹拌槽3からなる凝集混和槽1では、PAC溶液の凝集作用により被処理水中の懸濁物質が凝集して、粗大なフロックを含有する凝集処理水が得られる That is, in the agglomeration mixing tank 1 composed of the rapid stirring tank 2 and the slow stirring tank 3, suspended substances in the water to be treated are aggregated by the aggregating action of the PAC solution, and agglomerated treated water containing coarse floc is obtained. .

凝集処理水ポンプ4は、凝集混和槽1の緩速撹拌槽3から膜ろ過ユニット5へと凝集処理水を送水するポンプである。そして、この膜ろ過システム10では、凝集処理水ポンプ4と膜ろ過ユニット5との間に、開閉自在の凝集処理水弁51が設けられている。   The agglomerated water pump 4 is a pump that feeds the agglomerated water from the slow stirring tank 3 of the agglomeration mixing tank 1 to the membrane filtration unit 5. In the membrane filtration system 10, an agglomerated treated water valve 51 that can be freely opened and closed is provided between the agglomerated treated water pump 4 and the membrane filtration unit 5.

膜ろ過ユニット5は、凝集処理水が流入する流入口とろ過水が流出する流出口とを有する容器をろ過膜で一次側(凝集処理水が流入する側)と二次側(ろ過水が流出する側)に区画して構成されており、この膜ろ過ユニット5では、容器に流入した凝集処理水の全量がろ過(デッドエンドろ過)される。そして、膜ろ過ユニット5で凝集処理水をろ過して得たろ過水は、開閉自在のろ過水弁52を介してろ過水槽(図示せず)に送られる The membrane filtration unit 5 includes a container having an inflow port through which the flocculated treated water flows in and an outflow port through which the filtered water flows out, on the primary side (the side into which the flocculated treated water flows) and the secondary side (the filtered water flows out). In this membrane filtration unit 5, the entire amount of the coagulated treated water that has flowed into the container is filtered (dead-end filtration). Then, the filtrate obtained by filtering the flocculated water with the membrane filtration unit 5 is sent to a filtrate water tank (not shown) via an open / close filtered water valve 52 .

ここで、膜ろ過ユニット5で用いるろ過膜としては、特に限定されることなく無機材料製の精密ろ過膜または限外ろ過膜を挙げることができる。具体的には、ろ過膜としてはセラミック膜を用いることができる。 Here, the filtration membrane used in the membrane filtration unit 5 is not particularly limited , and examples thereof include a microfiltration membrane or an ultrafiltration membrane made of an inorganic material. Specifically , a ceramic membrane can be used as the filtration membrane.

逆洗水槽6は、開閉自在の逆洗弁61を介して膜ろ過ユニット5の二次側(膜ろ過ユニット5を構成する容器の流出口)と接続しており、逆洗水槽6には、膜ろ過ユニット5のろ過膜の逆洗に用いる逆洗水が貯留されている。そして、この膜ろ過システム10では、膜ろ過ユニット5のろ過膜を逆洗する際には、逆洗水槽6へ加圧空気を供給して逆洗水槽6内の逆洗水を押し出すことで、高圧の逆洗水が逆洗水槽6から膜ろ過ユニット5の二次側へと逆洗弁61を介して送られる。なお、膜ろ過ユニット5のろ過膜を逆洗する際に膜ろ過ユニット5の一次側(膜ろ過ユニット5を構成する容器の流入口)から流出する逆洗排水は、凝集処理水弁51と膜ろ過ユニット5との間から分岐する配管を通り、開閉自在の逆洗排水弁62を介して排水処理設備(図示せず)へと送られる。因みに、逆洗水としては、特に限定されることなく、膜ろ過ユニット5で凝集処理水をろ過して得たろ過水を用いることができる。   The backwash water tank 6 is connected to the secondary side of the membrane filtration unit 5 (the outlet of the container constituting the membrane filtration unit 5) via a freely openable and reverse backwash valve 61. Backwash water used for backwashing the filtration membrane of the membrane filtration unit 5 is stored. And in this membrane filtration system 10, when backwashing the filtration membrane of the membrane filtration unit 5, by supplying pressurized air to the backwash water tank 6 and pushing out the backwash water in the backwash water tank 6, High-pressure backwash water is sent from the backwash water tank 6 to the secondary side of the membrane filtration unit 5 via the backwash valve 61. In addition, when the membrane of the membrane filtration unit 5 is backwashed, the backwash waste water flowing out from the primary side of the membrane filtration unit 5 (the inlet of the container constituting the membrane filtration unit 5) It passes through a pipe branched from the filtration unit 5 and is sent to a wastewater treatment facility (not shown) through an openable / closable backwash drainage valve 62. Incidentally, the backwash water is not particularly limited, and filtered water obtained by filtering the agglomerated treated water with the membrane filtration unit 5 can be used.

そして、この膜ろ過システム10では、以下のようにして、所定間隔で膜ろ過ユニット5のろ過膜の逆洗を実施しながら、被処理水のろ過が行われる。なお、ろ過膜の逆洗間隔は、予め定めた一定の時間間隔としても良いし、ろ過膜の膜差圧の大きさに応じて定まる間隔としても良いし、ろ過水の水質に応じて定まる間隔としても良い。   In the membrane filtration system 10, the water to be treated is filtered while backwashing the filtration membrane of the membrane filtration unit 5 at predetermined intervals as follows. The backwash interval of the filtration membrane may be a predetermined time interval, may be determined according to the size of the membrane differential pressure of the filtration membrane, or may be determined according to the quality of the filtrate water. It is also good.

まず、被処理水のろ過を実施する際には、凝集処理水弁51、ろ過水弁52を開き、逆洗弁61および逆洗排水弁62を閉じた状態で、被処理水と所定の塩基度のPAC溶液とを混和して得た凝集処理水を(前処理工程)、凝集混和槽1から膜ろ過ユニット5の一次側へと凝集処理水ポンプ4で送り、膜ろ過ユニット5のろ過膜でろ過する(膜ろ過工程)。   First, when the water to be treated is filtered, the water to be treated and a predetermined base are opened with the flocculation water valve 51 and the filtration water valve 52 open and the backwash valve 61 and the backwash drain valve 62 are closed. The agglomerated water obtained by mixing the PAC solution with a certain degree (pretreatment step) is sent from the agglomeration mixing tank 1 to the primary side of the membrane filtration unit 5 by the agglomeration water pump 4, and the membrane of the membrane filtration unit 5 (Membrane filtration step).

そして、一定のろ過時間が経過した際、或いは、凝集処理水中に含まれているフロック等のファウリング原因物質のろ過膜への付着などにより膜ろ過ユニット5の膜差圧が所定の圧力まで上昇した際には、例えば以下の手順でろ過膜を逆流洗浄する(逆洗工程)。具体的には、まず、凝集処理水弁51、ろ過水弁52を閉じると共に凝集処理水ポンプ4を停止し、逆洗弁61を開いた状態で、加圧空気で加圧した逆洗水を逆洗水槽6から膜ろ過ユニット5の二次側へと送り、ろ過膜を加圧した状態で保持する(加圧工程)。次に、逆洗排水弁62を開き、逆洗水を逆洗排水弁62から排出することによってろ過膜を逆洗する(ブロー工程)。なお、ブロー工程で排出される、ろ過膜の表面に付着したフロック等のファウリング原因物質を含む逆洗水(逆洗排水)は、逆洗排水弁62を介して排水処理設備(図示せず)へと送られ、処理される。   Then, when a certain filtration time has elapsed, or due to adhesion of fouling-causing substances such as flocks contained in the flocculated water to the filtration membrane, the membrane differential pressure of the membrane filtration unit 5 increases to a predetermined pressure. In this case, for example, the filtration membrane is backwashed by the following procedure (backwashing step). Specifically, first, the coagulation water valve 51 and the filtration water valve 52 are closed and the coagulation water pump 4 is stopped, and the backwash valve 61 is opened, and the backwash water pressurized with pressurized air is supplied. It sends to the secondary side of the membrane filtration unit 5 from the backwash water tank 6, and hold | maintains in the state which pressurized the filtration membrane (pressurization process). Next, the filtration membrane is backwashed by opening the backwash drain valve 62 and discharging backwash water from the backwash drain valve 62 (blow process). In addition, the backwash water (backwash drainage) containing the fouling causative substances such as flocks attached to the surface of the filtration membrane discharged in the blow process is discharged through a backwash drain valve 62 (not shown). ) And processed.

ここで、この膜ろ過システム10を用いた膜ろ過方法では、塩基度が65%以上75%以下のPAC溶液を使用して被処理水中の懸濁物質を凝集させているので、被処理水が河川水などのpH6〜8.5程度の水であれば、被処理水のpHを調整しなくても懸濁物質を十分に凝集させることができ、pH調整に必要な薬品コストを低減し得ると共に、PAC溶液からのアルミニウムの溶出を抑制し得る。また、被処理水中の懸濁物質と共に有機物もフロック中に取り込まれて除去されるので、有機物濃度の低い清浄なろ過水を得ることができる。 Here, in the membrane filtration method using this membrane filtration system 10, the suspended water in the treated water is aggregated using a PAC solution having a basicity of 65% or more and 75% or less. If the water has a pH of about 6 to 8.5, such as river water, the suspended matter can be sufficiently aggregated without adjusting the pH of the water to be treated, and the chemical cost required for pH adjustment can be reduced. At the same time, elution of aluminum from the PAC solution can be suppressed. Moreover, since organic matter is taken into the floc and removed together with suspended substances in the water to be treated, clean filtered water having a low concentration of organic matter can be obtained.

また、塩基度が65%以上75%以下のPAC溶液を使用して被処理水中の懸濁物質を凝集させた場合、ろ過膜からの剥離性が良好なフロックが形成される。従って、この膜ろ過システム10を用いた膜ろ過方法では、フロックがろ過膜に付着してファウリング原因物質となっても、逆洗によりろ過膜から容易に剥離除去することができる。よって、所定間隔での逆洗によりファウリング原因物質の蓄積によるろ過膜の閉塞の進行を抑制し、ろ過膜の薬品洗浄頻度およびろ過膜の交換頻度を低減することができる。なお、剥離性が良好なフロックが形成されるのは、明らかではないが、塩基度が65%以上75%以下のPAC溶液を用いて形成したフロックは荷電の中和が進んでいるためと推察されている。また、塩基度が65%以上75%以下のPAC溶液は固体状態のアルミニウムを多く含み、PAC溶液中のアルミニウムの大半が分画分子量3kDa以上で溶液中のアルミニウムの結晶化が進んでおり、更に、塩基度が65%以上75%以下のPAC溶液が高い荷電中和力を持つためであると推察されている。 In addition, when a suspended substance in the water to be treated is aggregated using a PAC solution having a basicity of 65% or more and 75% or less , a floc having good peelability from the filtration membrane is formed. Therefore, in the membrane filtration method using the membrane filtration system 10, even if the floc adheres to the filtration membrane and becomes a fouling-causing substance, it can be easily peeled and removed from the filtration membrane by backwashing. Therefore, the backwashing at a predetermined interval can suppress the progress of clogging of the filtration membrane due to the accumulation of fouling-causing substances, and the frequency of chemical cleaning of the filtration membrane and the replacement frequency of the filtration membrane can be reduced. In addition, although it is not clear that flocs having good peelability are formed, it is presumed that the neutralization of charges is progressing for flocs formed using a PAC solution having a basicity of 65% to 75%. Has been. A PAC solution having a basicity of 65% to 75% contains a large amount of solid aluminum, and most of the aluminum in the PAC solution has a molecular weight cut-off of 3 kDa or more, and the crystallization of aluminum in the solution proceeds. It is speculated that this is because a PAC solution having a basicity of 65% or more and 75% or less has high charge neutralization power.

なお、本発明の膜ろ過方法は、上記一例に限定されることなく、本発明の膜ろ過方法には、適宜変更を加えることができる。   In addition, the membrane filtration method of this invention is not limited to the said example, A change can be suitably added to the membrane filtration method of this invention.

具体的には、本発明の膜ろ過方法においては、ろ過膜ユニット5のろ過膜として、セラミック製のろ過膜、例えばアルミナ、チタニア、ジルコニア、シリカ、ムライト、スピネル、或いは、これらの混合物などからなるセラミック膜を用いることが好ましい。具体的には、膜ろ過ユニット5のろ過膜としては、図2にその一部を切り欠いて示すような、被処理水が流入する蓮根状の孔(通水貫通孔)71を有するモノリス型のセラミック膜7を用いることが好ましい。なお、このモノリス型のセラミック膜7を容器の内部に収納してなる膜ろ過ユニット5では、セラミック膜7の孔71に流入した凝集処理水が、各孔71の表面に位置する分離層(緻密な膜面)でろ過されて外表面72から流出する。即ち、このセラミック膜7を用いた膜ろ過ユニット5では、セラミック膜7の蓮根状の孔71側が一次側となり、分離層より後側が二次側となる。   Specifically, in the membrane filtration method of the present invention, the filtration membrane of the filtration membrane unit 5 is made of a ceramic filtration membrane, such as alumina, titania, zirconia, silica, mullite, spinel, or a mixture thereof. It is preferable to use a ceramic membrane. Specifically, the membrane of the membrane filtration unit 5 is a monolith type having a lotus root-like hole (water passage through hole) 71 into which water to be treated flows, as shown in FIG. The ceramic film 7 is preferably used. In the membrane filtration unit 5 in which the monolithic ceramic membrane 7 is accommodated inside the container, the agglomerated water that has flowed into the holes 71 of the ceramic membrane 7 is separated from the separation layers (dense The membrane surface) and flows out of the outer surface 72. That is, in the membrane filtration unit 5 using this ceramic membrane 7, the lotus root-like hole 71 side of the ceramic membrane 7 is the primary side, and the rear side from the separation layer is the secondary side.

このように、ろ過膜としてセラミック製のろ過膜を使用すれば、逆洗時にろ過膜からフロック等のファウリング原因物質がより良好に剥離除去されるので、有機材料製のろ過膜を使用した場合と比較して、ろ過膜の閉塞の進行を更に抑制し、ろ過膜の薬品洗浄頻度およびろ過膜の交換頻度を更に低減することができるからである。また、セラミック製のろ過膜を使用した場合、逆洗時にろ過膜から剥離したフロック等のファウリング原因物質の沈降性が良好になるので、逆洗排水の処理に用いる沈殿槽の設置面積等を小さくして、逆洗排水の処理を容易かつ低コストで実施することができるからである。なお、セラミック製のろ過膜を用いた場合にファウリング原因物質の剥離性および沈降性が向上する原因は、明らかではないが、塩基度が65%以上75%以下のPAC溶液を用いて形成した、荷電の中和が進んだフロックと、セラミック膜表面との親和性が低く、緻密なフロックが容易に剥離するためであると推察されている。 In this way, if a filter membrane made of ceramic is used as the filter membrane, fouling-causing substances such as flocks are better peeled off from the filter membrane during backwashing, so when using a filter membrane made of organic material This is because the progress of clogging of the filtration membrane can be further suppressed, and the chemical cleaning frequency of the filtration membrane and the replacement frequency of the filtration membrane can be further reduced. In addition, when a ceramic filter membrane is used, the sedimentation of fouling-causing substances such as flocks peeled off from the filter membrane during backwashing becomes better, so the installation area of the settling tank used for the treatment of backwash wastewater, etc. This is because the backwash waste water treatment can be carried out easily and at low cost. The reason why the fouling-causing substance is improved in peelability and sedimentation when a ceramic filter membrane is used is not clear, but it was formed using a PAC solution having a basicity of 65% or more and 75% or less . It is presumed that this is because the flocs with neutralization of charge and the surface of the ceramic film have a low affinity and the dense flocs easily peel off.

また、モノリス型のセラミック膜からなるろ過膜を使用すれば、孔(通水貫通孔)71内で凝集処理水中のフロック同士が効率的に接触するので、フロック相互の接触効率を向上して粗大かつ緻密なフロックの形成を促進することができるからである。   In addition, if a filtration membrane made of a monolithic ceramic membrane is used, flocs in the coagulated water are efficiently in contact with each other in the hole (water passage through hole) 71, so that the contact efficiency between the flocs is improved and coarse. In addition, the formation of dense flocs can be promoted.

従って、本発明の膜ろ過方法では、ろ過膜としてモノリス型セラミック膜を用いれば、逆洗時のファウリング原因物質の剥離性が更に向上するので、ろ過膜の閉塞の進行をより一層抑制し、ろ過膜の薬品洗浄頻度およびろ過膜の交換頻度をより一層低減することができる。また、逆洗時にろ過膜から剥離したフロック等のファウリング原因物質の沈降性を良好にして、逆洗排水の処理を容易かつ低コストで実施することができる Therefore, in the membrane filtration method of the present invention, if a monolithic ceramic membrane is used as the filtration membrane, the releasability of the fouling-causing substance during backwashing is further improved, so that the progression of the filtration membrane blockage is further suppressed, The frequency of chemical cleaning of the filtration membrane and the replacement frequency of the filtration membrane can be further reduced. Moreover, the sedimentation property of the fouling-causing substances such as flocks peeled off from the filter membrane during backwashing can be improved, and the backwash wastewater treatment can be carried out easily and at low cost .

更に、この発明の膜ろ過方法では、膜ろ過ユニット5の二次側から一次側へ逆洗水を流してろ過膜を逆洗する際の逆洗水の圧力を150kPa以上、好ましくは300〜500kPaとすることが好ましい。圧力150kPa以上の加圧水を逆洗水としてろ過膜に流通させた場合、ファウリング原因物質がろ過膜から良好に剥離するからである。なお、逆洗水の通水条件は、逆洗水槽6に供給する加圧空気の流量などを調整することにより制御することができる。   Furthermore, in the membrane filtration method of the present invention, the pressure of backwash water when backwashing the filtration membrane by flowing backwash water from the secondary side to the primary side of the membrane filtration unit 5 is 150 kPa or more, preferably 300 to 500 kPa. It is preferable that This is because, when pressurized water having a pressure of 150 kPa or more is circulated through the filtration membrane as backwash water, the fouling-causing substances are favorably separated from the filtration membrane. In addition, the water flow conditions of the backwash water can be controlled by adjusting the flow rate of the pressurized air supplied to the backwash water tank 6.

また、この発明の膜ろ過方法は、凝集処理水をデッドエンド方式で膜ろ過ユニット5に供給し、ろ過することが好ましい。凝集処理水をデッドエンド方式でろ過した場合、ファウリング原因物質が剥離し易い状態でろ過膜に付着し、逆洗時のファウリング原因物質の剥離性が良好になるからである。なお、膜ろ過ユニット5での凝集処理水のろ過条件は、凝集処理水ポンプ4の吐出流量や吐出圧などを調整することにより制御することができる。   Moreover, it is preferable that the membrane filtration method of this invention supplies the aggregation process water to the membrane filtration unit 5 by a dead end system, and filters. This is because when the agglomerated treated water is filtered by the dead end method, the fouling-causing substance adheres to the filtration membrane in a state where it can be easily peeled off, and the fouling-causing substance is easily peelable during backwashing. The filtration conditions of the flocculated water in the membrane filtration unit 5 can be controlled by adjusting the discharge flow rate, the discharge pressure, etc. of the flocculated water pump 4.

また、この発明の膜ろ過方法では、PAC溶液として、塩基度が65%以上75%以下で、且つ、Al23濃度が10.2質量%のときのSO4濃度が1〜4質量%、更に好ましくは1.5〜3.5質量%のPAC溶液を用いることが好ましい。PAC溶液の塩基度が65%未満になると、残留アルミニウムが多くなる傾向があるので好ましくない。また、SO4濃度が1質量%未満になると、PAC溶液の安定性がより増加するものの凝集性が悪くなる傾向があり、4質量%超になると、PAC溶液の安定性が低下する傾向がある。なお、PAC溶液の塩基度については68%以上72%以下が更に好ましい。塩基度が68%以上72%以下であれば、本発明の効果が最もよく得られ、且つ、残留アルミニウムを少なくすることができる。また、PAC溶液中のAl23濃度は、9〜11質量%の範囲であることが好ましく、10質量%前後の範囲であることが更に好ましい。
In the membrane filtration method of the present invention, the PAC solution has a basicity of 65% to 75% and an SO 4 concentration of 1 to 4% by mass when the Al 2 O 3 concentration is 10.2% by mass. More preferably, it is preferable to use a PAC solution of 1.5 to 3.5% by mass. If the basicity of the PAC solution is less than 65%, residual aluminum tends to increase, such being undesirable. In addition, when the SO 4 concentration is less than 1% by mass, the stability of the PAC solution is increased, but the cohesiveness tends to deteriorate. When the SO 4 concentration exceeds 4% by mass, the stability of the PAC solution tends to decrease. . Note that the basicity of PAC solution, more preferably 72% or less 68% or more. If the basicity is 68% or more and 72% or less, the effect of the present invention is best obtained and the residual aluminum can be reduced. Further, the Al 2 O 3 concentration in the PAC solution is preferably in the range of 9 to 11% by mass, and more preferably in the range of about 10% by mass.

以下、実施例により本発明を更に詳細に説明するが、本発明は下記の実施例に何ら限定されるものではない。   EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

(実施例)
図1に示す膜ろ過システムを用いて、長野県沓沢湖を水源とする湖沼水を図2に示すようなモノリス型のセラミック製ろ過膜(孔径0.1μm、外径:φ30mm、長さ:1000mm)でろ過し、ろ過水を得た。
なお、被処理水には、特開2009−203125号公報の実施例1に従い製造した塩基度が70%のPAC溶液(Al23:10.2質量%、Cl:7.0質量%、SO4:2.8質量%、Ca:0.4質量%、Na:1.2質量%、塩基度:70%)を被処理水1Lに対して25mgの割合で添加し、急速撹拌槽での撹拌速度は83rpm(滞留時間:3分間)、緩速撹拌槽での撹拌速度は60rpm(滞留時間:6分間)とした。因みに、被処理水のpH調整は実施しなかった。また、膜ろ過ユニットへの凝集処理水の通水量は、3.0m3/m2・日とし、180分毎に圧力500kPaの逆洗水で逆洗(加圧工程:10秒間、ブロー工程:5秒間)した。
そして、逆洗直後の膜差圧を測定し、評価した。結果を図3に示す。また、被処理水およびろ過水の性状を上水試験法(VI−1−3、VI−1−9、VI−1−21、VI−3−7)に従い評価した。結果を表1に示す。更に、逆洗排水中のフロックの沈降性について評価した。結果を表2に示す。
なお、フロックの沈降性の評価は、逆洗排水を容量2Lのメスシリンダーに入れて静置した際の汚泥界面高さの経時変化を、静置0分の汚泥界面高さを100%として評価することにより行った。
(Example)
Using the membrane filtration system shown in FIG. 1, a monolith-type ceramic filtration membrane (pore diameter: 0.1 μm, outer diameter: φ30 mm, length: 1000 mm) is shown in FIG. ) To obtain filtered water.
In addition, in the water to be treated, a PAC solution having a basicity of 70% (Al 2 O 3 : 10.2% by mass, Cl: 7.0% by mass, manufactured according to Example 1 of JP 2009-203125A, SO 4 : 2.8% by mass, Ca: 0.4% by mass, Na: 1.2% by mass, basicity: 70%) at a ratio of 25 mg to 1 L of water to be treated. The stirring speed was 83 rpm (residence time: 3 minutes), and the stirring speed in the slow stirring tank was 60 rpm (residence time: 6 minutes). Incidentally, pH adjustment of to-be-processed water was not implemented. Moreover, the flow rate of the coagulated treated water to the membrane filtration unit is 3.0 m 3 / m 2 · day, and backwashing is performed with backwashing water at a pressure of 500 kPa every 180 minutes (pressurization process: 10 seconds, blow process: 5 seconds).
And the membrane differential pressure immediately after backwashing was measured and evaluated. The results are shown in FIG. Moreover, the property of to-be-processed water and filtered water was evaluated according to the water supply test method (VI-1-3, VI-1-9, VI-1-21, VI-3-7). The results are shown in Table 1. Furthermore, the sedimentation of flocs in backwash wastewater was evaluated. The results are shown in Table 2.
The floc sedimentation was evaluated by measuring the time-dependent change in the sludge interface height when the backwash wastewater was placed in a graduated cylinder with a capacity of 2 L, and the sludge interface height at 0 minutes was set as 100%. It was done by doing.

(比較例)
被処理水に添加するPAC溶液の塩基度を54%とした以外は実施例と同様にして被処理水をろ過し、ろ過水を得た。
そして、逆洗直後の膜差圧、被処理水およびろ過水の性状、並びに、逆洗排水中のフロックの沈降性について、実施例と同様にして評価した。結果を図3および表1,2に示す。
(Comparative example)
The treated water was filtered in the same manner as in Example except that the basicity of the PAC solution added to the treated water was set to 54% to obtain filtered water.
And the membrane differential pressure immediately after backwashing, the property of to-be-processed water and filtered water, and the sedimentation property of the floc in backwashing waste_water | drain were evaluated similarly to the Example. The results are shown in FIG.

図3に示すように、被処理水のろ過開始から30日経過時における逆洗直後の膜差圧は、実施例が21.3kPaであり、比較例が48.0kPaである。従って、比較例に比べて実施例では膜差圧の上昇が抑制されており、ろ過膜の閉塞の進行が抑制されていることが分かる。なお、若干の膜差圧の上昇は、スケーリングの発生などの不可避的なろ過膜の閉塞によるものであると推察される。また、表1より、実施例のろ過水は残留Alが少ないことが分かる。更に、表2より、実施例の逆洗排水中のフロックは沈降性が非常に良好であることが分かる。   As shown in FIG. 3, the membrane differential pressure immediately after backwashing after 30 days from the start of filtration of the water to be treated is 21.3 kPa in the example and 48.0 kPa in the comparative example. Therefore, it can be seen that the increase in the membrane differential pressure is suppressed in the example as compared with the comparative example, and the progression of the blocking of the filtration membrane is suppressed. A slight increase in the membrane pressure difference is presumed to be due to an unavoidable filtration membrane blockage such as the occurrence of scaling. Moreover, it turns out from Table 1 that the filtered water of an Example has little residual Al. Furthermore, it can be seen from Table 2 that the flocs in the backwash waste water of the examples have very good sedimentation properties.

本発明の膜ろ過方法によれば、ろ過膜の閉塞の進行を抑制し、ろ過膜の薬品洗浄頻度や交換頻度を低減することができる。   According to the membrane filtration method of the present invention, the progress of clogging of the filtration membrane can be suppressed, and the chemical cleaning frequency and replacement frequency of the filtration membrane can be reduced.

1 凝集混和槽
2 急速撹拌槽
3 緩速撹拌槽
4 凝集処理水ポンプ
5 膜ろ過ユニット
6 逆洗水槽
7 セラミック膜
10 膜ろ過システム
21 撹拌機
22 PACポンプ
31 撹拌機
51 凝集処理水弁
52 ろ過水弁
61 逆洗弁
62 逆洗排水弁
71 孔
72 外表面
DESCRIPTION OF SYMBOLS 1 Coagulation mixing tank 2 Rapid stirring tank 3 Slow stirring tank 4 Coagulation water pump 5 Membrane filtration unit 6 Backwash water tank 7 Ceramic membrane 10 Membrane filtration system 21 Stirrer 22 PAC pump 31 Stirrer 51 Aggregation water valve 52 Filtration water Valve 61 Backwash valve 62 Backwash drain valve 71 Hole 72 Outer surface

Claims (2)

被処理水と、塩基度が65%以上75%以下のポリ塩化アルミニウム溶液とを急速撹拌槽で混和し、前記被処理水中の懸濁物質を凝集させて微細なフロックを形成した後、緩速撹拌槽で前記微細なフロックを粗大化させて凝集処理水を得る前処理工程と、
前記凝集処理水をろ過膜でデッドエンドろ過し、ろ過水を得る膜ろ過工程と、
前記ろ過膜を所定の間隔で逆流洗浄する逆洗工程と、
を含み、
前記ろ過膜が、多孔質セラミックの内部に複数の通水貫通孔を設けてなるモノリス型セラミック膜であり、
前記凝集処理水は、前記通水貫通孔に流入し、当該通水貫通孔の表面に位置する分離層でろ過されることを特徴とする、膜ろ過方法。
The water to be treated and a polyaluminum chloride solution having a basicity of 65% or more and 75% or less are mixed in a rapid stirring tank, and suspended substances in the water to be treated are aggregated to form fine flocs. A pretreatment step of coarsening the fine flocs in a stirring tank to obtain agglomerated treated water;
A membrane filtration step of dead-end filtering the agglomerated treated water with a filtration membrane to obtain filtered water;
A backwashing step of backwashing the filtration membrane at predetermined intervals;
Including
The filtration membrane is a monolithic ceramic membrane in which a plurality of water passage through holes are provided inside a porous ceramic,
The membrane filtration method, wherein the agglomerated treated water flows into the water flow through hole and is filtered by a separation layer located on a surface of the water flow through hole.
前記逆洗工程において、逆洗水を150kPa以上の圧力でろ過膜に流通することを特徴とする、請求項1に記載の膜ろ過方法。   2. The membrane filtration method according to claim 1, wherein in the backwashing step, backwash water is circulated through the filtration membrane at a pressure of 150 kPa or more.
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