JP4583558B2 - Method of operating spiral membrane element and spiral membrane module - Google Patents

Description

【０１３３】
ただし、Ｒは２価の芳香族、脂環族もしくは脂肪族炭化水素基、またはこれらの炭化水素基が２価の有機結合基で結合された２価の有機基を示す。
【０１３４】
好ましくは、下記の構造式（化２）〜（化４）で示されるポリスルホンが用いられる。
【０１３５】
【化２】

【０１３６】
【化３】

【０１３７】
【化４】

【０１３８】
また、ポリスルホンの溶媒としては、Ｎ−メチル−２−ピロリドン、ジメチルホルムアミド、ジメチルアセトアミド、ジメチルスルホキシド等を用いることが好ましい。さらに、非溶媒としては、エチレングリコール、ジエチレングリコール、プロピレングリコール、ポリエチレングリコール、グリセリン等の脂肪族多価アルコール、メタノール、エタノール、イソプロピルアルコール等の低級脂肪族アルコール、メチルエチルケトン等の低級脂肪族ケトンなどを用いることが好ましい。
【０１３９】
溶媒と非溶媒の混合溶媒中の非溶媒の含有量は、得られる混合溶媒が均一である限り特に制限されないが、通常５〜５０重量％、好ましくは２０〜４５重量％である。
【０１４０】
多孔質構造の形成を促進し、または制御するために用いられる膨潤剤としては、塩化リチウム、塩化ナトリウム、硝酸リチウム等の金属塩、ポリエチレングリコール、ポリビニルアルコール、ポリビニルピロリドン、ポリアクリル酸等の水溶性高分子またはその金属塩、ホルムアミド等が用いられる。混合溶媒中の膨潤剤の含有量は、製膜溶液が均一である限り特に制限されないが、通常１〜５０重量％である。
【０１４１】
製膜溶液中のポリスルホンの濃度は、通常１０〜３０重量％が好ましい。３０重量％を超えるときは、得られる多孔質分離膜の透水性が実用性に乏しくなり、１０重量％より少ないときは、得られる多孔質分離膜の機械的強度が乏しくなり、充分な背圧強度を得ることができない。
【０１４２】
次に、上記の製膜溶液を不織布支持体上に製膜する。すなわち、連続製膜装置を使用し、不織布等の支持体シートを順次送り出し、その表面に製膜溶液を塗布する。塗布方法としてはナイフコータやロールコータ等のギャップコータを用いて製膜溶液を不織布支持体上に塗布する。例えば、ロールコータを使用する場合は、２本のロールの間に製膜溶液を溜め、不織布支持体上に製膜溶液を塗布すると同時に不織布の内部に充分含浸させ、その後低湿度雰囲気を通過させ、雰囲気中の微量水分を不織布上に塗布した液膜表面に吸収させ、液膜の表面層にミクロ相分離を起こさせる。その後、凝固水槽に浸漬し、液膜全体を相分離および凝固させ、さらに水洗槽で溶媒を洗浄除去する。これにより、分離膜２が形成される。
【０１４３】
このように、上記の分離膜２は背圧強度が高いため、図１および図６のスパイラル型膜エレメント１に用いた場合に０．０５〜０．３ＭＰａの背圧で逆流洗浄を行っても分離膜２の破損が生じることが防止される。
【０１４４】
【実施例】
以下の実施例１、実施例２および比較例においては、図７に示す構造を有する限外濾過膜を分離膜２として含むスパイラル型限外濾過膜エレメントを作製し、このスパイラル型限外濾過膜エレメントを備えた図１のスパイラル型膜モジュールを用いて連続通水濾過試験を行った。
【０１４５】
ここで、実施例１、実施例２および比較例のスパイラル型限外濾過膜エレメントに用いた限外濾過膜は、以下のようにして作製した。
【０１４６】
まずポリスルホン（アモコ社製、Ｐ−３５００）を１６．５重量部、Ｎ−メチル−２ピロリドンを５０重量部、ジエチレングリコールを２４．５重量部およびホルムアミドを１重量部で加熱溶解し、均一な製膜溶液を得た。そして、コータギャップを０．１３ｍｍに調整したロールコータを用いて厚み０．１ｍｍ、密度０．８ｇ／ｃｍ³ のポリエステル製不織布の表面に製膜溶液を含浸塗布した。
【０１４７】
その後、相対湿度が２５％、温度が３０℃の雰囲気（低湿度雰囲気）中を所定の速度で通過させ、ミクロ相分離を生じさせた後、３５℃の凝固水槽中に浸漬して脱溶媒および凝固させ、しかる後、水洗槽で残存溶媒を洗浄除去することにより分離膜２を得た。ここで、実施例１および実施例２の分離膜２は、ミクロ相分離時間（低湿度雰囲気を通過する時間）が４．５秒である。
【０１４８】
上記のようにして作製した限外濾過膜の透水量は１７００Ｌ／ｍ² ・ｈｒであり、背圧強度は０．３ＭＰａであり、平均分子量１００万のポリエチレンオキサイドの阻止率は９９％であった。
【０１４９】
なお、背圧強度は直径４７ｍｍの膜を背圧強度ホルダ（有孔直径２３ｍｍ）にセットし、多孔性補強シート２ａ側より水圧を徐々に加え、透過性膜体２ｂが多孔性補強シート２ａから剥離するか、または透過性膜体２ｂと多孔性補強シート２ａとが同時に破裂するときの圧力で規定される。
【０１５０】
また、ポリエチレンオキサイドの阻止率は、濃度５００ｐｐｍのポリエチレンオキサイド溶液を圧力１ｋｇｆ／ｃｍ² にて透過させ、原液および透過液の濃度から下式により求めた。
【０１５１】
阻止率（％）［１−（透過液濃度／原液濃度）］×１００
このようにして作製した限外濾過膜を備えたスパイラル型膜モジュールの連続通水濾過試験について、以下で説明する。
【０１５２】
実施例１、実施例２および比較例で用いたスパイラル型限外濾過膜エレメントの仕様を表１に示す。
【０１５３】
【表１】

【０１５４】
［実施例１］
実施例１では、工業用水（ｐＨ６〜８、水温１５〜３０℃）を原水としてスパイラル型限外濾過膜エレメントに供給し、連続通水濾過実験を行った。３日に１回濾過を停止し、逆流洗浄後に逆流洗浄に用いた洗浄液中に１時間浸漬した。逆流洗浄では、洗浄液として透過水を用い、０．２ＭＰａの背圧で６０Ｌ／分の洗浄液を供給した。運転条件を表２に示す。
【０１５５】
【表２】

【０１５６】
［実施例２］
実施例２では、実施例１と同様に、工業用水（ｐＨ６〜８、水温１５〜３０℃）を原水としてスパイラル型限外濾過膜エレメントに供給し、連続通水濾過実験を行った。１０日に１回濾過を停止し、逆流洗浄後に洗浄液中に１時間浸漬した。逆流洗浄では、洗浄液として次亜塩素酸ナトリウムを含む透過水を用い、０．２ＭＰａの背圧で６０Ｌ／分の洗浄液を供給した。封入液は、次亜塩素酸ナトリウムを含む透過水である。運転条件を表３に示す。
【０１５７】
【表３】

【０１５８】
［比較例］
比較例では、実施例１，２と同様に、工業用水（ｐＨ６〜８、水温１５〜３０℃）を原水としてスパイラル型限外濾過膜エレメントに供給し、連続通水濾過実験を行った。ただし、比較例では、逆流洗浄後に濾過を停止しての液中での浸漬は行わなかった。運転条件を表４に示す。
【０１５９】
【表４】

【０１６０】
図８は実施例１、実施例２および比較例のスパイラル型膜モジュールの膜間差圧の経時変化を示す図である。実施例１では、３日に１回逆流洗浄後に逆流洗浄液中に１時間浸漬状態にする運転を行った結果、膜間差圧の上昇が抑えられ、膜間差圧０．１ＭＰａ以下での連続運転が可能であった。
【０１６１】
実施例２では、１０日に１回、１００ｐｐｍの次亜塩素酸ナトリウムを含む逆流洗浄液中に１時間浸漬状態にする運転を行った結果、膜間差圧の上昇がさらに抑えられ、膜間差圧０．０６ＭＰａ以下での連続運転が可能であった。実施例２において、実施例１よりも低い膜間差圧で運転することができたのは、殺菌作用のある次亜塩素酸ナトリウムで洗浄した効果により膜面上での微生物の繁殖が抑えられたためであると考えられる。
【０１６２】
これに対して、比較例では、濾過を停止して液中での浸漬は行わなかったので、急激な膜間差圧の上昇が生じ、連続運転の継続が不可能であった。
【０１６３】
以上の実施例１，２および比較例において示すように、スパイラル型膜モジュールにおいて液封入停止を行うことにより、スパイラル型限外濾過膜エレメントの膜面に付着した汚染物質を剥離させ、膜間差圧の上昇を抑制することが可能となる。それにより、信頼性の高い安定した運転を行うことが可能となる。
【図面の簡単な説明】
【図１】本発明の一実施の形態におけるスパイラル型膜モジュールの一例を示す模式的断面図である。
【図２】本発明に係るスパイラル型膜モジュールの運転方法の一例を示す模式的断面図である。
【図３】本発明に係るスパイラル型膜モジュールの運転方法の一例を示す模式的断面図である。
【図４】本発明に係るスパイラル型膜モジュールの運転方法の他の例を示す模式的断面図である。
【図５】図１のスパイラル型膜モジュールに用いられるスパイラル型膜エレメントの一部切欠き斜視図である。
【図６】本発明に係るスパイラル型膜モジュールの運転方法のさらに他の例を示す模式的断面図である。
【図７】図５のスパイラル型膜エレメントに用いられる分離膜の断面図である。
【図８】実施例１、実施例２および比較例のスパイラル型膜モジュールの膜間差圧の経時変化を示す図である。
【符号の説明】
１ スパイラル型膜エレメント
２ 分離膜
３ 透過水スペーサ
４ 封筒状膜
５ 集水管
６ 原水スペーサ
７，３１ 原水
８ 透過水
１００ スパイラル型膜モジュール
１０，１１０ 圧力容器
１３，１３０ 原水入口
１４，１４０ 透過水出口
１５，１３１ 原水出口
２１ 洗浄水[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spiral membrane element used in a membrane separator such as a reverse osmosis membrane separator, an ultrafiltration membrane separator, and a microfiltration membrane separator, and a method for operating a spiral membrane module.
[0002]
[Prior art]
In recent years, the application of membrane separation technology to water purification and wastewater treatment has expanded, and membrane separation technology has been applied to liquid quality, which has been difficult in the past. In particular, there is a strong demand for the recovery and reuse of industrial wastewater using membrane separation technology.
[0003]
As a form of the membrane element used for such membrane separation, a hollow fiber membrane element is often used from the viewpoint of membrane area per unit volume (volume efficiency). However, the hollow fiber membrane element has a drawback that the membrane is easily broken, and when the membrane is broken, the raw water is mixed with the permeated water and the separation performance is lowered.
[0004]
Therefore, it has been proposed to apply a spiral membrane element instead of the hollow fiber membrane element. Similar to the hollow fiber membrane element, this spiral membrane element has the advantage that the membrane area per unit volume can be increased, the separation performance can be maintained, and the reliability is high.
[0005]
[Problems to be solved by the invention]
Since wastewater contains many suspended substances, colloidal substances, or dissolved substances, when membrane separation is performed on such wastewater, these suspended substances, colloidal substances, or dissolved substances are contaminated on the membrane surface. It accumulates and causes a decrease in the water transmission rate. In particular, when the total amount is filtered, contaminants are likely to be deposited on the membrane surface, the water permeation rate is significantly reduced, and it is difficult to continue a stable filtration operation.
[0006]
In order to prevent the accumulation of contaminants on the membrane surface, cross flow filtration is performed.
In this cross flow filtration, the raw water is allowed to flow parallel to the membrane surface, thereby preventing the deposition of contaminants on the membrane surface using the shearing force generated at the interface between the membrane surface and the fluid. In such cross-flow filtration, it is necessary to obtain a sufficient film surface linear velocity to prevent the deposition of contaminants on the film surface. For this purpose, a sufficient flow rate of raw water is made parallel to the film surface. Need to flow. However, when the flow rate of the raw water flowing parallel to the membrane surface is increased, the recovery rate per spiral membrane element is lowered, and the pump for supplying the raw water becomes large, resulting in a very high system cost.
[0007]
On the other hand, contaminants deposited on the film surface are also removed by backwashing. Backwashing is generally performed for hollow fiber membrane elements.
[0008]
For example, Japanese Patent Publication No. 6-98276 proposes application of backwashing to a spiral membrane element. However, since the separation membrane of the conventional spiral membrane element has low back pressure strength, the separation membrane may be damaged when back pressure is applied to the separation membrane during backflow cleaning. Therefore, according to the above publication, the spiral membrane element is 0.1 to 0.5 kg / cm. ² It is considered preferable to perform back-flow cleaning with a back pressure as low as (0.01 to 0.05 MPa).
[0009]
However, according to the inventors' experiment, when backwashing is performed with such a back pressure in a spiral membrane element, it is difficult to sufficiently remove contaminants, and a high permeation flux is obtained over a long period of time. It could not be maintained.
[0010]
On the other hand, the present inventor has disclosed a back pressure strength of 2 kgf / cm in JP-A-10-225626. ² The structure and manufacturing method of the above separation membrane are proposed. However, when a spiral membrane element is manufactured using a separation membrane having such back pressure strength, what back pressure can actually be used for backwashing, and what range It has not been fully verified whether a high permeation flux can be maintained over a long period of time when backwashing is performed with a back pressure of. Furthermore, the operation method of the spiral membrane element having the separation membrane having a high back pressure strength as described above and the operation method of the spiral membrane module provided with such a spiral membrane element have not been verified.
[0011]
Even when such a separation membrane with high back pressure strength is used, if the optimum washing conditions and washing method are applied and the filtration operation is not performed by the optimum operation method, the spiral membrane element and the spiral membrane module are long. A stable filtration operation cannot be continued without causing a decrease in permeation flux over a period of time.
[0012]
An object of the present invention is to provide a spiral membrane element and a method of operating a spiral membrane module that can perform a stable filtration operation at a low cost while maintaining a high permeation flux over a long period of time.
[0013]
[Means for Solving the Problems and Effects of the Invention]
The operation method of the spiral membrane element according to the present invention is such that a bag-like separation membrane is wound around the outer peripheral surface of a perforated hollow tube. And having first and second ends , A method of operating a spiral membrane element capable of backwashing with a back pressure of higher than 0.05 MPa and lower than 0.3 MPa. First While supplying the stock solution from the end, the permeate is taken out from at least one open end of the perforated hollow tube, and the cleaning solution is introduced from at least one open end of the perforated hollow tube at the time of backwashing. At least one of the first and second ends The separation membrane is backwashed at a back pressure of higher than 0.05 MPa and lower than 0.3 MPa by discharging the cleaning liquid from the back of the spiral membrane element during backwashing or after backwashing. Second end The stock solution is introduced through the spiral membrane element, and the stock solution is allowed to flow in the direction opposite to that during the filtration operation and the spiral membrane element First end The filtration operation or the backwashing is temporarily stopped and the spiral membrane element is immersed in the liquid for a predetermined time.
[0014]
In the operation method of the spiral membrane element according to the present invention, the spiral membrane element is held in a state immersed in a liquid for a predetermined time, so that contaminants attached to the membrane surface of the spiral membrane element are peeled off, and the spiral membrane element is removed. The membrane function of the mold membrane element can be restored. Thereby, it is possible to perform a highly reliable and stable operation. Such an operation can be easily performed without requiring any special equipment and can be performed at low cost because the contaminants can be peeled off without using cleaning chemicals.
[0015]
As a first aspect of the method of operating the spiral membrane element according to the present invention , Filter The overrun may be stopped and the spiral membrane element may be held for a predetermined time while being immersed in the liquid.
[0016]
In this case, the stock solution is a spiral membrane element. First While being supplied from the end, filtration is performed, and contaminants are trapped on the membrane surface of the spiral membrane element.
[0017]
Furthermore, by stopping the filtration operation and immersing the spiral membrane element in the liquid for a predetermined time, it is possible to peel off the contaminants attached to the membrane surface of the spiral membrane element during the filtration operation.
[0018]
In the above-described method of operating the spiral membrane element, a part of the stock solution may flow in the axial direction of the spiral membrane element at all times or regularly. Thereby, it is possible to suppress the contaminants in the undiluted solution from adhering to the membrane surface of the spiral membrane element due to the shearing force acting on the membrane surface, and a more stable operation can be performed.
[0019]
It is preferable that at least a part of the stock solution flowing in the axial direction in the spiral membrane element is returned again to the supply side of the spiral membrane element. By circulating the stock solution in this way, it is possible to obtain a permeate with a high recovery rate.
[0020]
As a second aspect of the method of operating the spiral membrane element according to the present invention The reverse You may hold | maintain for a predetermined time in the state which stopped flow washing | cleaning and immersed the spiral type | mold membrane element in the liquid.
[0021]
At the time of backwashing, cleaning liquid is introduced from at least one open end of the perforated hollow tube. The cleaning liquid is led out from the outer peripheral surface of the perforated hollow tube to the inside of the bag-shaped separation membrane, and permeates through the separation membrane in the direction opposite to that during filtration. As a result, the separation membrane is backwashed, and contaminants deposited on the membrane surface of the separation membrane are peeled off from the separation membrane.
[0022]
In this case, since the separation membrane is backwashed with a back pressure higher than 0.05 MPa and lower than 0.3 MPa, a necessary amount of cleaning liquid can be flowed in a short time. Thereby, contaminants deposited on the membrane surface of the separation membrane can be effectively removed. As a result, it is possible to perform a stable filtration operation while maintaining a high permeation flux over a long period of time even in the case of a total amount filtration in which contaminants easily deposit on the membrane surface.
[0023]
Thus, since filtration can be performed stably, it becomes possible to obtain a permeate efficiently. Moreover, it is not necessary to use a large pump for supplying the stock solution, and the scale of the system can be reduced. Thereby, the system cost is reduced.
[0024]
Furthermore, by stopping the back-flow cleaning and immersing the spiral membrane element in the liquid for a predetermined time, it becomes possible to more effectively remove contaminants attached to the membrane surface of the spiral membrane element during filtration. .
[0025]
In the first aspect, the filtration operation may be resumed after the spiral membrane element is immersed in the liquid for a predetermined time. In this case, by immersing the spiral membrane element in the liquid for a predetermined time, the contaminants attached to the membrane surface of the spiral membrane element can be peeled off, so high reliability and stability can be achieved in the restarted filtration operation. Is obtained.
[0026]
Alternatively, after holding the spiral membrane element in a liquid for a predetermined time The reverse Flow cleaning may be used. In this case, since the backwashing is performed after the spiral membrane element is immersed in the liquid for a predetermined time, the contaminants attached to the membrane surface of the spiral membrane element can be easily and reliably peeled off. This makes it possible to perform a highly reliable and stable filtration operation.
[0027]
In the second aspect, the backflow cleaning may be resumed after the spiral membrane element is held in the liquid for a predetermined time. In this case, since the backwashing is performed after the spiral membrane element is immersed in the liquid for a predetermined time, the contaminants attached to the membrane surface of the spiral membrane element can be easily and reliably peeled off. This makes it possible to perform a highly reliable and stable filtration operation.
[0028]
Alternatively, after holding the spiral membrane element in a liquid for a predetermined time , Filter Overrun may be performed. In this case, by immersing the spiral membrane element in the liquid for a predetermined time, the contaminants adhering to the membrane surface of the spiral membrane element can be peeled off. Therefore, high reliability and stability can be achieved in the filtration operation after immersion. Sex is obtained.
[0029]
Further, in the first and second aspects, the spiral membrane element is passed through the stock solution inlet and the stock solution outlet of the pressure vessel in parallel with or after back washing. First end and Second end The stock solution is supplied in order in the same direction and in the opposite direction to the stock solution supply direction during the filtration operation, and the stock solution flows in the axial direction in the spiral membrane element, and the stock solution that has flowed in the axial direction can be taken out of the pressure vessel. Good. In this case, it is possible to uniformly remove the contaminants distributed throughout the spiral membrane element and discharge it to the outside.
[0030]
Furthermore, when the spiral membrane element is immersed in the liquid, a liquid containing a chemical having a bactericidal action or a contaminant peeling action is supplied to the spiral type membrane element, and the spiral type membrane element is immersed in the liquid containing the chemical. May be. As a result, it is possible to sterilize germs that have propagated on the membrane surface of the spiral membrane element, or to more effectively and reliably remove contaminants attached to the membrane surface of the spiral membrane element. Become.
[0031]
The operating method of the spiral membrane module according to the present invention is an operating method of a spiral membrane module in which one or a plurality of spiral membrane elements are accommodated in a pressure vessel having a stock solution inlet, No bag-shaped separation membrane is wound around the outer peripheral surface of the perforated hollow tube. And having first and second ends , Back flow cleaning with a back pressure higher than 0.05 MPa and lower than 0.3 MPa is possible. First end And the permeate is taken out from at least one open end of the perforated hollow tube, and the cleaning solution is introduced from at least one open end of the perforated hollow tube at the time of back-flow cleaning. At least one of the first and second ends The separation membrane is backwashed at a back pressure of higher than 0.05 MPa and lower than 0.3 MPa by discharging the cleaning liquid from the back of the spiral membrane element during backwashing or after backwashing. Second end The stock solution is introduced through the spiral membrane element, and the stock solution is allowed to flow in the direction opposite to that during the filtration operation and the spiral membrane element First end And the filtration operation or backwashing is temporarily stopped, and the liquid is sealed in the pressure vessel and held for a predetermined time.
[0032]
In the operation method of the spiral membrane module according to the present invention, the liquid adhered in the pressure vessel and the spiral membrane element is immersed in the liquid, thereby removing the contaminants attached to the membrane surface of the spiral membrane element. Thus, the membrane function of the spiral membrane element can be recovered. As a result, the spiral membrane module can be operated with high reliability and stability. Such an operation can be easily performed without requiring any equipment, and can be performed at low cost.
[0033]
The liquid may contain a chemical having a bactericidal action or a contaminant peeling action. As a result, it is possible to sterilize germs that have propagated on the membrane surface of the spiral membrane element, or to more effectively and reliably remove contaminants attached to the membrane surface of the spiral membrane element. Become.
[0034]
The separation membrane may be formed by bonding a permeable membrane body to one surface of the porous sheet material, and the permeable membrane body may be bonded to one surface of the porous sheet material in a throwing state. In such a separation membrane, the bonding between the porous sheet material and the permeable membrane body is strengthened, and the back pressure strength of the separation membrane is improved. Thereby, it is possible to sufficiently perform back-flow cleaning without causing damage to the separation membrane of the spiral membrane element at a back pressure higher than 0.05 MPa and lower than 0.3 MPa.
[0035]
In particular, the back pressure strength of the separation membrane is preferably 0.2 MPa or more. As a result, back-flow cleaning with a high back pressure becomes possible, and membrane separation treatment stable for a long period of time can be performed by sufficiently performing membrane cleaning.
[0036]
In particular, the porous sheet material is preferably made of a woven fabric, a nonwoven fabric, a mesh net, or a foamed sintered sheet made of a synthetic resin.
[0037]
Further, the porous sheet material has a thickness of 0.08 mm or more and 0.15 mm or less and a density of 0.5 g / cm. ^Three 0.8 g / cm or more ^Three It is preferable to consist of the following nonwoven fabrics.
[0038]
Thereby, while obtaining the back pressure intensity | strength of 0.2 Mpa or more, the increase of a permeation | transmission resistance and peeling of a permeable membrane body can be prevented, ensuring the intensity | strength as a reinforcement sheet.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic cross-sectional view showing an example of a spiral membrane module according to an embodiment of the present invention.
[0040]
As shown in FIG. 1, a spiral membrane module 100 includes a spiral membrane element 1 housed in a pressure vessel (pressure vessel) 10. The pressure vessel 10 includes a cylindrical case 11 and a pair of end plates 12a and 12b. A raw water inlet 13 is formed in one end plate 12a, and a raw water outlet 15 is formed in the other end plate 12b. A permeated water outlet 14 is provided at the center of the other end plate 12b. The structure of the pressure vessel is not limited to the structure of FIG. 1, and a side-entry pressure vessel in which a raw water inlet and a raw water outlet are provided in a cylindrical case as will be described later may be used.
[0041]
The spiral membrane element 1 having a packing 17 attached in the vicinity of one end of the outer peripheral surface is loaded into the cylindrical case 11, and both open ends of the cylindrical case 11 are sealed with end plates 12a and 12b, respectively. One open end of the water collecting pipe 5 is fitted to the permeate outlet 14 of the end plate 12b, and an end cap 16 is attached to the other open end. The internal space of the pressure vessel 10 is separated into a first liquid chamber 18 and a second liquid chamber 19 by the packing 17.
[0042]
The raw water inlet 13 of the spiral membrane module 100 is connected to the raw water tank 500 through a pipe 25. A valve 30a is inserted in the pipe 25, and a pipe 26 in which the valve 30b is inserted is connected to the downstream side of the valve 30a. On the other hand, the raw water outlet 15 is connected to a pipe 27 having a valve 30c inserted therein, and a pipe 27a having a valve 30d inserted therein is connected to the upstream side of the valve 27c of the pipe 27. The raw water outlet 15 is connected to the raw water tank 500 through the pipe 27a. The permeated water outlet 14 is connected to a pipe 28 having a valve 30e interposed therein, and a pipe 29 having a valve 30f inserted is connected to the upstream side of the valve 30e.
[0043]
FIG. 5 is a partially cutaway perspective view of a spiral membrane element used in the spiral membrane module of FIG.
[0044]
As shown in FIG. 5, the spiral membrane element 1 has an envelope-like membrane (bag-like membrane) 4 by superposing separation membranes 2 on both sides of a permeated water spacer 3 made of a synthetic resin net and adhering three sides. Is formed, and the opening of the envelope-like membrane 4 is attached to the water collecting pipe 5 and spirally wound around the outer peripheral surface of the water collecting pipe 5 together with the raw water spacer 6 made of a synthetic resin net. The outer peripheral surface of the spiral membrane element 1 is covered with an exterior material.
[0045]
In this spiral membrane element 1, it is possible to perform back-flow cleaning with a back pressure of 0.05 to 0.3 MPa by using a separation membrane 2 having a structure to be described later.
[0046]
2 and 3 are schematic cross-sectional views showing an example of a method for operating the spiral membrane module according to the present invention. In the operation method of this example, the spiral membrane module of FIG. 1 is used, FIG. 2 shows the operation method during filtration, and FIG. 3 shows the operation method during cleaning.
[0047]
As shown in FIG. 2, during filtration, the valve 30a of the pipe 25 and the valve 30e of the pipe 28 are opened, and the valve 30b of the pipe 26, the valve 30c of the pipe 27, the valve 30d of the pipe 27a, and the valve 30f of the pipe 29 are closed. .
[0048]
The raw water 7 taken from the raw water tank 500 is supplied to the inside of the pressure vessel 10 from the raw water inlet 13 through the pipe 25. In the spiral membrane module, the supplied raw water 7 is introduced from the raw water inlet 13 into the first liquid chamber 18 of the pressure vessel 10, and further, from one end of the spiral membrane element 1 to the inside of the spiral membrane element 1. Supplied.
[0049]
As shown in FIG. 5, in the spiral membrane element 1, the raw water 7 supplied from one end face side is directed to the other end face side in the direction (axial direction) parallel to the water collecting pipe 5 along the raw water spacer 6. Flowing in a straight line. In the process in which the raw water 7 flows along the raw water spacer 6, a part of the raw water 7 permeates the separation membrane 2 due to a pressure difference between the raw water side and the permeated water side. The permeated water 8 flows along the permeated water spacer 3 into the water collecting pipe 5 and is discharged from the end of the water collecting pipe 5. On the other hand, the remaining raw water 7 a that has not permeated the separation membrane 2 is discharged from the other end face side of the spiral membrane element 1.
[0050]
As shown in FIG. 2, the permeated water 8 discharged from the end of the water collecting pipe 5 is taken out from the pressure vessel 10 through the permeated water outlet 14 through the pipe 28. On the other hand, the raw water 7 a discharged from the other end face side of the spiral membrane element 1 is led out to the second liquid chamber 19. In this case, since the valve 30c of the pipe 27 and the valve 30d of the pipe 27a connected to the raw water outlet 15 are closed, the permeation of the separation membrane 2 in the spiral membrane element 1 is promoted and the entire amount is filtered.
[0051]
In the filtration process as described above, suspended substances, colloidal substances, or dissolved substances contained in the raw water are deposited as contaminants on the membrane surface of the separation membrane 2 of the spiral membrane element 1. In particular, contaminants are likely to deposit on the membrane surface of the separation membrane 2 in total filtration.
Such deposition of contaminants causes a decrease in the permeation rate of water, so the contaminants are removed by performing the following cleaning.
[0052]
During the filtration operation of the spiral membrane module 100, the valve 30a of the pipe 25 is once closed to stop the supply of the raw water 7 and the extraction of the permeated water 8 from the permeated water outlet 14 is stopped. In this way, the filtration operation is temporarily stopped, and the pressure vessel 10 is held for a predetermined time with the raw water 7 and 7a and the permeated water 8 sealed (liquid filling stop). In this way, after the liquid filling is stopped for a predetermined time, the valve 30a of the pipe 25 is opened again to supply the raw water 7 to the spiral membrane element 1, and the permeated water 8 is taken out from the permeated water outlet 14 to perform a filtration operation. To resume. In addition, when performing the filtration operation while opening the valve 30c of the pipe 27 and taking out part of the raw water 7a, the valve 30c of the pipe 27 is opened and closed in accordance with the valve 30a of the pipe 25.
[0053]
As described above, during the operation period of the spiral membrane module, the above filtration operation and liquid sealing stop are repeated.
[0054]
In the spiral membrane module 100 in which liquid filling is stopped during the filtration operation, the pressure on the raw water side and the pressure on the permeate side of the separation membrane of the spiral membrane element 1 are maintained at substantially atmospheric pressure, and the raw water side and the permeate side are permeated. No liquid flow is formed on the water side. By stopping the liquid sealing in this manner, contaminants attached to the membrane surface of the spiral membrane element 1 can be peeled off along with the continuous filtration operation of the spiral membrane module. As a result, the membrane function of the spiral membrane element 1 that has been lowered due to the adhesion of contaminants is restored.
[0055]
In addition, the liquid sealing stop at the time of the filtration operation as described above may be performed regularly or irregularly. As an example of performing irregularly, for example, when the permeate flow rate is reduced in the spiral membrane module, the liquid sealing is stopped.
[0056]
Next, as shown in FIG. 3, at the time of cleaning, first, the valve 30a of the pipe 25, the valve 30e of the pipe 28, and the valve 30d of the pipe 27a are closed, and the valve 30b of the pipe 26, the valve 30f of the pipe 29, and the pipe 27 The valve 30c is opened and backflow cleaning is performed.
[0057]
At the time of backwashing, cleaning water 21 is supplied from the permeate outlet 14 to the open end of the water collecting pipe 5 through the pipe 29 and the pipe 28, and the cleaning water 21 is introduced into the water collecting pipe 5. For example, permeated water is used as the cleaning water 21. The washing water 21 introduced into the water collection pipe 5 is led out from the outer peripheral surface of the water collection pipe 5 to the inside of the separation membrane 2 and permeates the separation membrane 2 in the direction opposite to that during filtration. At this time, contaminants deposited on the membrane surface of the separation membrane 2 are peeled off from the separation membrane 2. Since the outer peripheral surface of the spiral membrane element 1 is covered with an exterior material, the cleaning water 21 that has permeated through the separation membrane 2 flows along the raw water spacer 6 in the axial direction inside the spiral membrane element 1 to form a spiral type. The liquid is discharged from both ends of the membrane element 1 to the first liquid chamber 18 and the second liquid chamber 19. Further, the washing water 21 is taken out from the raw water inlet 13 and the raw water outlet 15 through the pipe 26 and the pipe 27, respectively.
[0058]
In this case, the pressure on the permeate outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the raw water outlet 15 side are set so that a back pressure of 0.05 to 0.3 MPa is applied to the separation membrane 2. Accordingly, a necessary amount of the cleaning water 21 can be flowed in a short time, and the contaminants deposited on the membrane surface of the separation membrane 2 can be effectively peeled off. Further, it is possible to prevent the pollutant from being removed by the raw water spacer 6 before the peeled pollutant is discharged from the end of the spiral membrane element 1, thereby effectively removing the pollutant.
[0059]
In this example, the entire amount of the wash water 21 taken out from the raw water inlet 13 is discharged out of the system as drainage. However, a part of the wash water 21 is discharged out of the system as drainage and part of the wash water 21 is discharged. It may be reused as raw water 7. For example, a part of the cleaning water 21 may be returned to the raw water tank 500 by providing a pipe further downstream of the valve 30 b of the pipe 26 and connecting this arrangement to the raw water tank 500.
[0060]
Further, in this example, the entire amount of the washing water 21 taken out from the raw water outlet 15 is discharged out of the system as waste water, but a part of this washing water 21 is discharged out of the system as waste water and part of it is discharged. It may be reused as raw water 7. For example, the valve 30c of the pipe 27 and the valve 30d of the pipe 27a may be opened, and a part of the cleaning water 21 may be returned to the raw water tank 500 through the pipe 27a.
[0061]
In the example of FIG. 3, the washing water 21 is discharged from both ends of the spiral membrane element 1 during backwashing, and is taken out from the raw water inlet 13 and the raw water outlet 15 through the pipe 26 and the pipe 27, respectively. The pressure on the permeate outlet 14 side and the pressure on the raw water inlet 13 side so that the washing water 21 is discharged from one end of the spiral membrane element 1 to the first liquid chamber 18 and taken out from the raw water inlet 13 through the pipe 26. May be set. In this case, the valve 30c of the pipe 27 is closed and the raw water outlet 15 is closed. Alternatively, the pressure on the permeate outlet 14 side and the raw water outlet 15 so that the cleaning water 21 is discharged from the other end of the spiral membrane element 1 to the second liquid chamber 19 and taken out from the raw water outlet 15 through the pipe 27. The side pressure may be set. In this case, the valve 30b of the pipe 26 is closed and the raw water inlet 13 is closed.
[0062]
You may stop liquid enclosure at the time of said backwashing. In this case, the valve 30b of the pipe 26 is closed to stop the discharge of the cleaning water 21, and the introduction of the cleaning water 21 into the water collecting pipe 5 is stopped, and the cleaning water 21 is sealed in the pressure vessel 10 for a predetermined time. Hold. In this way, after the liquid sealing is stopped for a predetermined time, the valve 30b of the pipe 26 is opened to discharge the cleaning water 21, and the cleaning water 21 is introduced into the water collecting pipe 5 to restart the backflow cleaning.
[0063]
In the spiral membrane module 100 in which liquid sealing is stopped at the time of backwashing, the pressure on the raw water side and the pressure on the permeate side of the separation membrane of the spiral membrane element 1 are maintained at substantially atmospheric pressure. No liquid flow is formed on the water side. Such a liquid sealing stop makes it possible to more effectively remove contaminants attached to the membrane surface of the spiral membrane element 1.
[0064]
After the backwashing is performed as described above, the valve 30b of the pipe 26 and the valve 30f of the pipe 29 are closed and the valve 30a of the pipe 25 is opened. As a result, the raw water 31 taken from the raw water tank 500 is supplied from the raw water inlet 13 into the pressure vessel 10 through the pipe 25 and introduced into the first liquid chamber 18. The raw water 31 is supplied from one end of the spiral membrane element 1 to the inside, flows in the spiral type membrane element 1 along the raw water spacer 6 in the axial direction, and then is discharged from the other end. As a result, contaminants separated from the separation membrane 2 are washed away from the one end portion of the spiral membrane element 1 together with the raw water 31 to the other end portion, and the spiral membrane element 1 together with the cleaning water 21 remaining inside the spiral membrane element 1. The other end of the liquid is discharged into the second liquid chamber 19. Further, the pollutant is taken out together with the raw water 31 from the raw water outlet 15 through the pipe 27 to the outside of the pressure vessel 10.
[0065]
As described above, by performing flushing in which the raw water 31 flows in the same direction as the raw water supply direction at the time of filtration after the backflow cleaning, the contaminants separated from the separation membrane 2 in the spiral membrane element 1 are quickly discharged out of the system. can do. Thereby, it is possible to prevent the contaminants separated from the separation membrane 2 from adhering to the separation membrane 2 again.
[0066]
According to the operation method at the time of cleaning as described above, it is possible to effectively remove the contaminants deposited on the separation membrane 2 at the time of filtration. It becomes possible to operate stably without causing a decrease in permeation flux over a long period of time.
[0067]
In this example, flushing is performed in which the raw water 31 is flowed in the axial direction after backflow cleaning, but flushing may be performed in which the raw water 31 is flowed in the axial direction before backwashing. According to this cleaning method, most of the contaminant trapped on the membrane surface of the spiral membrane element 1 is removed by flushing, and further, the cleaning water 21 is introduced to remain on the membrane surface of the spiral membrane element 1. Contaminants can be removed. Therefore, also in this case, the same effect as the above-described backwashing can be obtained.
[0068]
Or you may perform the flushing which flows the raw | natural water 31 to an axial direction in parallel with backwashing. For example, in the above, the valves 30a, 30b, 30c, and 30f of the pipes 25, 26, 27, and 29 may be simultaneously opened at the time of cleaning to supply the cleaning water 21 from the permeate side and the raw water 31 from the raw water side. In this case, the same effect as that obtained when the raw water 31 is allowed to flow after the backwashing as described above can be obtained.
[0069]
In this example, the raw water 31 is supplied from the raw water inlet 13 and taken out from the raw water outlet 15. However, the raw water is supplied from the raw water outlet 15 and taken out from the raw water inlet 13, and is filtered inside the spiral membrane element 1. The raw water may flow in the direction opposite to the raw water supply direction. In this case, the same effect as that obtained when the raw water 31 is allowed to flow in the same direction as the raw water supply direction at the time of filtration as described above can be obtained.
[0070]
In addition, when flowing raw water in the same direction as the raw water supply direction at the time of filtration, in particular, contaminants deposited on the side close to the second liquid chamber 19 of the spiral membrane element 1 should be easily removed and discharged. Is possible. On the other hand, when the raw water flows in the direction opposite to the supply direction of the raw water at the time of filtration, in particular, contaminants deposited on the side close to the first liquid chamber 18 of the spiral membrane element 1 are easily removed and discharged. Is possible.
[0071]
Moreover, you may flow raw | natural water in order in the same direction as the supply direction of raw | natural water at the time of filtration, and a reverse direction. In this case, contaminants distributed throughout the spiral membrane element 1 can be uniformly removed and discharged.
[0072]
In this example, the entire amount of the raw water 31 taken out from the raw water outlet 15 is discharged out of the system as waste water. However, a part of the raw water 31 is discharged out of the system as waste water and a part of the raw water 31 is recycled as raw water. May be used. For example, in the above, the valve 30c of the pipe 27 may be opened and the valve 30d of the pipe 27a may be opened, and a part of the raw water 31 may be returned to the raw water tank 500 through the pipe 27a.
[0073]
As described above, according to the operation method of this example shown in FIGS. 2 and 3, the contaminant deposited on the film surface of the spiral membrane element 1 can be sufficiently removed. In the module 100, it is possible to stably filter the whole amount while maintaining a high permeation flux, and to obtain the permeated water 8 efficiently. In this case, since the entire amount is filtered, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.
[0074]
As described above, by stopping the liquid sealing of the spiral membrane module 100 during the filtration operation or the backflow cleaning, the contaminants attached to the membrane surface of the spiral membrane element 1 are peeled off, and the reliability is more reliable and stable. Can be performed. Such liquid sealing stop can be performed by opening / closing the valves 30a and 30b of the pipes 25 and 26, and therefore, no special equipment is required and the operation is easy. In addition, since contaminants can be peeled off using a liquid that does not contain cleaning chemicals, the cost for cleaning chemicals can be reduced, and implementation at a low cost is possible.
[0075]
Here, it is preferable that the liquid sealing stop time is 1 minute or more and 24 hours or less during the filtration operation or backwashing of the spiral membrane module 100 described above. When the liquid sealing is stopped for less than 1 minute, since the sealing time is short, the contaminant cannot be sufficiently peeled off from the membrane surface of the spiral membrane element 1. In addition, when the liquid sealing stop exceeds 24 hours, it is not appropriate because the contaminant removal effect exceeds a certain level and is not improved, and the original filtering operation time is compressed. Furthermore, it is not preferable because miscellaneous bacteria and the like are propagated by the retention of the liquid.
[0076]
In addition, the liquid sealed in the pressure vessel 10 is not limited to raw water or permeated water when stopping the liquid sealing during the filtration operation and backwashing of the spiral membrane module 100 described above. You may enclose liquids other than raw | natural water or permeated water, for example, pure water. In this case, pure water is supplied into the pressure vessel 10 during filtration operation and backflow cleaning, and this pure water is sealed in the pressure vessel 10. Even when pure water is sealed in this way, contaminants can be peeled off from the membrane surface of the spiral membrane element 1 in the same manner as when raw water or permeated water is sealed.
[0077]
In the spiral membrane module 100, the liquid filling is stopped during the filtration operation or the liquid filling is stopped during the backwashing. However, the timing for stopping the liquid filling is not particularly limited, and the operation period is not limited. It may be performed at a time other than the above.
[0078]
For example, the liquid sealing may be stopped after the filtration operation, and the backflow cleaning may be performed immediately after that. Alternatively, the liquid filling may be stopped after the filtration operation, the raw water may be flushed after the liquid filling is stopped, and then the filtration operation may be resumed. The flushing is performed by the same method as described above during the backflow cleaning. Alternatively, the liquid sealing may be stopped after the backwashing, and the filtration operation may be resumed immediately after that.
[0079]
Alternatively, after the liquid filling is stopped at the time of filtration operation or backflow cleaning, raw water or permeated water containing chemicals is further supplied to the spiral membrane module 100, and the spiral membrane element 1 is immersed in a liquid containing chemicals (chemical solution) Immersion). In this case, chemicals having bactericidal action or pollutant removing action, for example, sodium hypochlorite with a concentration of 10 to 10000 ppm, chloramine with a concentration of 0.1 to 10 ppm, hydrogen peroxide with a concentration of 10 to 10000 ppm, sulfuric acid with a pH of 1 to 3, pH 1-3 hydrochloric acid, pH 10-13 sodium hydroxide, concentration 10-10000 ppm peracetic acid, concentration 0.1-50% isopropyl alcohol, concentration 0.2-2% citric acid or concentration 0.2-2 % Oxalic acid is used. By soaking the chemical solution in the spiral membrane element 1 as described above, it is possible to more effectively peel off contaminants attached to the spiral membrane module 100, particularly the membrane surface of the spiral membrane element 1, and to eliminate germs. Breeding can be more effectively suppressed. After performing such chemical immersion, filtration operation or backwashing is performed.
[0080]
FIG. 4 is a schematic cross-sectional view showing another example of the operation method of the spiral membrane module according to the present invention. FIG. 4 shows an operation method at the time of filtration, and the spiral membrane module 100 of FIG. 1 is also used in this example. In addition, the operation method at the time of washing | cleaning in this example is the same as the operation method of above-mentioned FIG.
[0081]
As shown in FIG. 4, at the time of filtration, the valve 30a of the pipe 25, the valve 30e of the pipe 28, and the valve 30d of the pipe 27a are opened, and the valve 30b of the pipe 26, the valve 30c of the pipe 27, and the valve 30f of the pipe 29 are closed. .
[0082]
In this case, as in the example of FIG. 2, the raw water 7 taken from the raw water tank 500 is introduced into the first liquid chamber 18 of the pressure vessel 10 from the raw water inlet 13 through the pipe 25. Further, the raw water 7 is supplied from one end of the spiral membrane element 1 into the spiral membrane element 1.
[0083]
As shown in FIG. 5, in the spiral membrane element 1, some raw water passes through the separation membrane 2 and flows into the water collection pipe 5, and is discharged from the end of the water collection pipe 5 as permeate 8. On the other hand, the remaining raw water 7 a that has not permeated the separation membrane 2 is discharged from the other end face side of the spiral membrane element 1.
[0084]
As shown in FIG. 4, the permeated water 8 discharged from the end of the water collecting pipe 5 is taken out from the pressure vessel 10 through the permeated water outlet 14 through the pipe 28. On the other hand, the raw water 7 a discharged from the other end face side of the spiral membrane element 1 is led out to the second liquid chamber 19, taken out from the raw water outlet 15 through the pipe 27 a, and returned to the raw water tank 500. . Thus, in this example, filtration is performed in the spiral membrane module while part of the raw water 7a is taken out from the raw water outlet 15 to the outside.
Thereby, it is possible to suppress the accumulation of liquid in the gap between the outer peripheral surface of the spiral membrane element 1 and the inner peripheral surface of the pressure vessel 10. Further, since a flow of raw water in the axial direction from one end to the other end is formed inside the spiral membrane element 1, a part of the pollutant is supplied to the raw water while suppressing sedimentation of the pollutant in the raw water. It becomes possible to discharge to the outside of the pressure vessel 10 together with 7a.
[0085]
In the above description, the valve 30d is always opened to take out the raw water 7a. However, the valve 30d may be opened intermittently to take out the raw water 7a. Even in this case, it is possible to suppress the contaminants from adhering to the separation membrane 2 as in the case of always taking out the raw water 7a.
[0086]
In the above description, the entire amount of the raw water 7a taken out of the pressure vessel is returned to the raw water tank 500. However, a part of the extracted raw water 7a may be discharged out of the system.
For example, the valve 30d may be opened and the valve 30c may be opened, and a part of the raw water 7a may be discharged out of the system through the pipe 27.
[0087]
Also in this example, at the time of cleaning, back-flow cleaning is performed with a high back pressure by the cleaning operation method shown in FIG. Thereby, it is possible to effectively remove the contaminants deposited on the separation membrane 2 during filtration.
[0088]
As described above, according to the operation method in this example, the contaminants deposited on the film surface can be sufficiently removed, so that the operation can be stably performed without causing a decrease in permeation flux over a long period of time. It becomes possible.
[0089]
In particular, in this example, as shown in FIG. 4, a part of the raw water 7 a is taken out of the pressure vessel 10 at the time of filtration, thereby suppressing the settling of the contaminants in the raw water onto the film surface. Since the part can be discharged to the outside of the pressure vessel 10 together with the raw water 7a, a more stable filtration operation can be performed. In this case, since the raw water 7a taken out from the raw water outlet 15 is circulated through the pipe 27a, it is possible to obtain the permeated water 8 with a high recovery rate. Moreover, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.
[0090]
Also in this case, as described above with reference to FIG. 2, the liquid filling is stopped during the filtration operation of the spiral membrane module 100. Thereby, the contaminant attached to the membrane surface of the spiral membrane element 1 with the continuous filtration operation of the spiral membrane module 100 can be peeled off, and the membrane function of the spiral membrane element 1 lowered due to the adhesion of the contaminant. Can be recovered.
[0091]
After performing the filtration operation for a certain period during the operation period, the spiral membrane element 1 is back-washed by the same method as the cleaning method described above with reference to FIG.
[0092]
Even during the above-described back-flow cleaning, the liquid sealing may be stopped using the cleaning water 21 as described above with reference to FIG. Thereby, it becomes possible to more effectively peel the contaminants attached to the membrane surface of the spiral membrane element 1.
[0093]
As described above, by stopping the liquid sealing of the spiral membrane module during filtration operation or backwashing, the contaminants attached to the membrane surface of the spiral membrane element 1 are peeled off, making it more reliable and stable. It becomes possible to drive. Such liquid sealing stop can be performed by opening / closing the valves 30a and 30b (FIG. 4) of the pipes 25 and 26, so that no special equipment is required and the operation is easy. In addition, since contaminants can be peeled off using a liquid that does not contain cleaning chemicals, the cost for cleaning chemicals can be reduced, and implementation at a low cost is possible. Note that the time for stopping the liquid filling, the timing for stopping the liquid filling, and the liquid to be filled during the filtration operation or the backwashing are as described above with reference to FIGS.
[0094]
In the above description, the case where the spiral membrane module including one spiral membrane element is operated has been described. However, the operation method according to the present invention includes a spiral membrane including a plurality of spiral membrane elements. It can also be applied to modules.
[0095]
FIG. 6 is a schematic cross-sectional view showing still another example of the operation method of the spiral membrane module according to the present invention.
[0096]
As shown in FIG. 6, the spiral membrane module 100 of this example includes a plurality of spiral membrane elements 1 housed in a pressure vessel 110. The pressure vessel 110 includes a cylindrical case 111 and a pair of end plates 120a and 120b. A raw water inlet 130 is formed at the bottom of the cylindrical case 111, and a raw water outlet 131 is formed at the top. Thus, the pressure vessel 110 has a side entry shape. The raw water outlet 131 is also used for venting air. Further, a permeate outlet 140 is provided at the center of the end plates 120a and 120b.
[0097]
A plurality of spiral membrane elements 1 in which the water collecting pipes 5 are connected in series by the interconnector 116 are accommodated in the cylindrical case 111, and both open ends of the cylindrical case 111 are sealed with end plates 120a and 120b, respectively. The Here, the spiral membrane element 1 of FIG. 5 is used. One end of the water collecting pipe 5 of the spiral membrane element 1 at both ends is fitted to the permeate outlets 140 of the end plates 120a and 120b via the adapter 115, respectively. A packing 170 is attached in the vicinity of one end portion of the outer peripheral surface of each spiral membrane element 1, and the packing 170 separates the internal space of the pressure vessel 110 into a plurality of liquid chambers.
[0098]
The raw water inlet 130 of the spiral membrane module 100 is connected to the raw water tank 500 through the pipe 55. A valve 60a is inserted in the pipe 55, and a pipe 56 in which a valve 60b is inserted is connected to the downstream side of the valve 30a. On the other hand, the raw water outlet 131 is connected to a pipe 57 in which a valve 60c is inserted, and a pipe 57a in which a valve 60d is inserted is connected to the upstream side of the valve 57c of the pipe 57. The raw water outlet 131 is connected to the raw water tank 500 through the pipe 57a. A pipe 58a having a valve 60e inserted therein is connected to the permeate outlet 140 on the end plate 120a side, and a pipe 59a having a valve 60g inserted therein is connected to the upstream side of the valve 60e. On the other hand, the permeate outlet 140 on the end plate 120b side is connected to a pipe 58b with a valve 60f inserted therein, and a pipe 59b with a valve 60h inserted into the upstream side of the valve 60f. Yes.
[0099]
During filtration of the spiral membrane module 100, the valve 60a of the pipe 55, the valve 60e of the pipe 58a and the valve 60f of the pipe 58b are opened, the valve 60b of the pipe 56, the valve 60g of the pipe 59a, the valve 60h of the pipe 59b, and the pipe 57. The valve 60c and the valve 60d of the pipe 57a are closed.
[0100]
The raw water 7 taken from the raw water tank 500 is supplied from the raw water inlet 130 into the pressure vessel 110 through the pipe 55. In the spiral membrane module 100, the raw water 7 supplied from the raw water inlet 130 is introduced into the spiral membrane element 1 from one end face side of the spiral membrane element 1 located at the end on the end plate 120a side. The In this spiral membrane element 1, as shown in FIG. 5, some raw water permeates the separation membrane 2 and flows into the water collection pipe 5, and is discharged from the end of the water collection pipe 5 as permeate 8. . On the other hand, the remaining raw water 7a that has not permeated the separation membrane 2 is discharged from the other end face side. The discharged raw water 7a is introduced into the spiral membrane element 1 from one end face side of the subsequent spiral membrane element 1 and separated into the permeated water 8 and the raw water 7a in the same manner as described above. Thus, membrane separation is performed in each of the plurality of spiral membrane elements 1 connected in series. In this case, since the valve 60c of the pipe 57 and the valve 60d of the pipe 57a are closed, the permeation of the separation membrane 2 is promoted in each spiral membrane element 1 as in the example of FIG. Is done.
[0101]
During the filtration operation of the spiral membrane module 100 described above, the supply of the raw water 7 is once stopped and the extraction of the permeate 8 from the permeate outlet 140 is stopped. In this way, the filtration operation is temporarily stopped, and the raw water 7 and the permeated water 8 are sealed in the pressure vessel 110 and held for a predetermined time. After the liquid sealing is stopped for a predetermined time in this way, the raw water 7 is supplied again, and the permeated water 8 is taken out from the permeated water outlet 140, and the filtration operation is resumed.
[0102]
As described above, in the operation period of the spiral membrane module 100 of FIG. 6, the filtration operation and the liquid sealing stop are repeatedly performed as in the operation method of the spiral membrane module 100 shown in FIGS.
[0103]
In the spiral membrane module 100 in which liquid filling is stopped during the filtration operation, the pressure on the raw water side and the permeate side pressure of the separation membrane are maintained at atmospheric pressure in each spiral membrane element 1. No liquid flow is formed on the permeate side. By stopping the liquid sealing as described above, contaminants attached to the membrane surface of each spiral membrane element 1 can be peeled off along with the continuous filtration operation of the spiral membrane module 100. As a result, the membrane function of each spiral membrane element 1 lowered due to the adhesion of contaminants is restored.
[0104]
In the above filtration process, contaminants contained in the raw water are deposited on the membrane surface of the separation membrane 2 of each spiral membrane element 1. In particular, when the entire amount is filtered in the spiral membrane module 100 including the plurality of spiral membrane elements 1 as described above, contaminants are likely to be deposited on the membrane surface of the separation membrane 2. Such deposition of contaminants causes a decrease in the permeation rate of water, so the contaminants are removed by performing the following cleaning.
[0105]
When cleaning, first, the valve 60a of the pipe 55, the valve 60e of the pipe 58a, the valve 60f of the pipe 58b and the valve 60d of the pipe 57a are closed, and the valve 60b of the pipe 56, the valve 60c of the pipe 57, the valve 60g of the pipe 59a and the pipe The valve 60h of 59b is opened to perform back-flow cleaning.
[0106]
At the time of backwashing, on the end plate 120a side, the wash water 21 is supplied from the permeate outlet 140 to one end of the water collecting pipe 5 through the pipe 59a and the pipe 58a. On the end plate 120b side, the wash water 21 is supplied from the permeate outlet 140 to the other end of the water collecting pipe 5 through the pipe 59b and the pipe 58b. In this way, the wash water 21 is introduced into the water collection pipe 5 from both ends of the water collection pipe 5. The wash water 21 introduced into the water collection pipe 5 is led out from the outer peripheral surface of the water collection pipe 5 to the inside of the separation membrane 2 in each spiral membrane element 1 and permeates the separation membrane 2 in the direction opposite to that during filtration. At this time, contaminants deposited on the membrane surface of the separation membrane 2 are peeled off from the separation membrane 2. The washing water 21 that has passed through the separation membrane 2 flows in the axial direction inside the spiral membrane element 1 along the raw water spacer 6, and is discharged from both ends of each spiral membrane element 1. The discharged wash water 21 is taken out from the raw water inlet 130 and the raw water outlet 131 to the outside through the pipe 56 and the pipe 57, respectively.
[0107]
In this case, the pressure on the permeate outlet 140 side, the pressure on the raw water inlet 130 side, and the pressure on the raw water outlet 131 side are set so that a back pressure of 0.05 to 0.3 MPa is applied to the separation membrane 2 of each spiral membrane element 1. Set. Accordingly, a necessary amount of the cleaning water 21 can be flowed in a short time, and the contaminants deposited on the membrane surface of the separation membrane 2 can be effectively peeled off. Further, it is possible to prevent the polluted substances from being trapped by the raw water spacers 6 until they are discharged from the end of each spiral membrane element 1 and effectively remove the pollutants.
[0108]
In this example, the entire amount of the washing water 21 taken out from the raw water inlet 130 is discharged out of the system as waste water, but a part of the washing water 21 is discharged out of the system as waste water, and part of it is discharged. It may be reused as raw water 7. For example, a part of the cleaning water 21 may be returned to the raw water tank 500 by providing a pipe further downstream of the valve 60 b of the pipe 56 and connecting this arrangement to the raw water tank 500.
[0109]
Further, in this example, the entire amount of the washing water 21 taken out from the raw water outlet 131 is discharged out of the system as waste water, but a part of this washing water 21 is discharged out of the system as waste water, and part of it is discharged. It may be reused as raw water 7. For example, the valve 60c of the pipe 57 and the valve 60d of the pipe 57a may be opened, and a part of the cleaning water 21 may be returned to the raw water tank 500 through the pipe 57a.
[0110]
In the example of FIG. 6, the cleaning water 21 is taken out from the raw water inlet 130 and the raw water outlet 131 through the pipe 56 and the pipe 57 at the time of backwashing. The pressure on the permeate outlet 140 side and the pressure on the raw water inlet 130 side may be set so as to be taken out. In this case, the valve 60c of the pipe 57 is closed and the raw water outlet 131 is closed. Alternatively, the pressure on the permeated water outlet 140 side and the pressure on the raw water outlet 131 side may be set so that the wash water 21 is taken out from the raw water outlet 131 through the pipe 57. In this case, the valve 60b of the pipe 56 is closed and the raw water inlet 130 is closed.
[0111]
You may stop liquid enclosure at the time of said backwashing. In this case, the introduction of the cleaning water 21 to the water collecting pipe 5 is stopped, the discharge of the cleaning water 21 to the outside is stopped, and the pressure water 110 is held for a predetermined time with the cleaning water 21 sealed. After the liquid sealing is stopped for a predetermined time in this way, the cleaning water 21 is introduced again into the water collecting pipe 5 and the cleaning water 21 is discharged to the outside to resume the backflow cleaning.
[0112]
In each spiral membrane element 1 of the spiral membrane module 100 whose liquid filling is stopped at the time of backwashing, the pressure on the raw water side and the pressure on the permeate side of the separation membrane are maintained at substantially atmospheric pressure. No liquid flow is formed on the permeate side. Such a liquid sealing stop makes it possible to more effectively remove contaminants attached to the membrane surface of the spiral membrane element 1.
[0113]
After the backflow cleaning is performed as described above, the valve 60b of the pipe 56, the valve 60g of the pipe 59a, and the valve 60h of the pipe 59b are closed, and the valve 60a of the pipe 55 is opened. Thereby, the raw water 31 taken from the raw water tank 500 is supplied from the raw water inlet 130 into the pressure vessel 110 through the pipe 55. In each spiral membrane element 1, the raw water 31 is introduced from one end portion of the spiral membrane element 1 into the spiral membrane element 1, flows axially along the raw water spacer 6 in the spiral membrane element 1, and then is discharged from the other end portion. Is done. As a result, the contaminants peeled off from the separation membrane 2 are pushed away from the one end to the other end of the spiral membrane element 1 by the raw water 31, and together with the cleaning water 21 remaining inside the spiral membrane element 1, the spiral membrane element 1. It is discharged from the other end. Further, the pollutant and the washing water 21 are taken out from the pressure vessel 110 through the pipe 57 from the raw water outlet 131 together with the raw water 31.
[0114]
In this way, by performing flushing in which the raw water 31 is flowed in the same direction as the raw water supply direction at the time of filtration after the backflow cleaning, the contaminants peeled off from the separation membrane 2 in each spiral membrane element 1 can be quickly discharged out of the system. Can be discharged. Thereby, it is possible to prevent the contaminants separated from the separation membrane 2 from adhering to the separation membrane 2 again.
[0115]
In this example, flushing is performed in which the raw water 31 is flowed in the axial direction after backflow cleaning, but flushing may be performed in which the raw water 31 is flowed in the axial direction before backwashing. According to this cleaning method, most of the contaminant trapped on the membrane surface of the spiral membrane element 1 is removed by flushing, and further, the cleaning water 21 is introduced to remain on the membrane surface of the spiral membrane element 1. Contaminants can be removed. Therefore, also in this case, the same effect as the above-described backwashing can be obtained.
[0116]
Alternatively, the raw water 31 may flow in the axial direction in parallel with the backwashing. For example, in the above, at the time of cleaning, the valves 60a, 60b, 60c, 60g, 60h of the pipes 55, 56, 57, 59a, 59b are simultaneously opened to supply the cleaning water 21 from the permeate side and the raw water 31 from the raw water side. Also good. In this case, the same effect as that obtained when the raw water 31 is allowed to flow after the backwashing as described above can be obtained.
[0117]
In this example, the raw water 31 is supplied from the raw water inlet 130 and taken out from the raw water outlet 131. However, the raw water is supplied from the raw water outlet 131 and taken out from the raw water inlet 130, and is filtered inside each spiral membrane element 1. The raw water may be flowed in the direction opposite to the direction in which the raw water is supplied. In this case, the same effect as that obtained when the raw water 31 is allowed to flow in the same direction as the raw water supply direction at the time of filtration as described above can be obtained. Or you may flow raw | natural water in order in the same direction as the supply direction of raw | natural water at the time of filtration, and a reverse direction. In this case, contaminants distributed throughout the spiral membrane element 1 can be uniformly removed and discharged.
[0118]
Further, in this example, the entire amount of the raw water 31 taken out from the raw water outlet 131 is discharged out of the system as waste water. However, a part of the raw water 31 is discharged out of the system as waste water and part of the raw water 7 is discharged. May be reused as For example, in the above, the valve 60c of the pipe 57 and the valve 60d of the pipe 57a may be opened, and a part of the raw water 31 may be returned to the raw water tank 500 through the pipe 57a.
[0119]
According to the operation method at the time of cleaning as described above, it is possible to effectively remove contaminants deposited on the separation membrane 2 during filtration.
[0120]
As described above, according to the operation method in this example, the contaminants deposited on the film surface can be sufficiently removed, so that a high permeation flux can be obtained even in the total amount filtration where the contaminants easily deposit on the film surface. It is possible to operate stably while maintaining and to obtain the permeated water 8 efficiently. In this case, since the entire amount is filtered, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.
[0121]
In the above description, the case where the total amount filtration is performed using the spiral membrane module 100 of FIG. 6 as in the example of FIG. 2 has been described. However, the spiral membrane module 100 of FIG. As described above, filtration may be performed while taking out a part of the raw water 7 a to the outside of the pressure vessel 110.
[0122]
For example, during the filtration of the spiral membrane module of FIG. 6, the valve 60d of the pipe 57a is opened constantly or intermittently and permeates the separation membrane 2 of the spiral membrane element 1 in the raw water 7 supplied into the pressure vessel 110. A part of the raw water 7 a that has not been taken may be taken out of the pressure vessel 110 from the raw water outlet 131 through the pipe 57 a and returned to the raw water tank 500. Thereby, it is possible to suppress the accumulation of liquid in the gap between the outer peripheral portion of each spiral membrane element 1 and the inner peripheral surface of the pressure vessel 110. In addition, since the flow of the raw water in the axial direction from one end to the other end is formed inside each spiral membrane element 1, a part of the pollutants is supplied to the raw water while suppressing sedimentation of the pollutants in the raw water. It becomes possible to discharge to the outside of the pressure vessel together with 7a.
[0123]
According to such an operation method of performing filtration while taking out a part of the raw water, it becomes possible to perform operation more stably without causing a decrease in permeation flux over a long period of time. In this case, since the raw water 7a taken out is circulated through the pipe 57a, it is possible to obtain the permeated water 8 with a high recovery rate. Moreover, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.
[0124]
Further, by stopping the liquid sealing of the spiral membrane module 100 during the filtration operation or backwashing, the contaminants attached to the membrane surface of each spiral membrane element 1 are peeled off, and the operation is more reliable and stable. Can be performed. In this case, the timing of stopping the liquid filling during the filtration operation or the washing, the time for stopping the liquid filling, and the liquid to be filled are as described above with reference to FIGS. Such a liquid sealing stop requires no equipment and is easy to operate. Furthermore, since contaminants can be peeled off using a liquid that does not contain cleaning chemicals, the cost for cleaning chemicals can be reduced, and implementation at low cost is possible.
[0125]
FIG. 7 is a cross-sectional view of a separation membrane used in the spiral membrane element of FIG. The separation membrane 2 is formed by tightly integrating a permeable membrane body 2b having a substantial separation function on the surface of a porous reinforcing sheet (porous sheet material) 2a.
[0126]
The permeable membrane body 2b is formed from one type of polysulfone resin, or a mixture of two or more types of polysulfone resins, or a copolymer or mixture of a polysulfone resin and a polymer such as polyimide or fluorine-containing polyimide resin. Is done.
[0127]
The porous reinforcing sheet 2a is formed from a woven fabric, a nonwoven fabric, a mesh net, a foamed sintered sheet or the like made of polyester, polypropylene, polyethylene, polyamide or the like, and is preferably a nonwoven fabric from the viewpoint of film forming property and cost. .
[0128]
The porous reinforcing sheet 2a and the permeable membrane body 2b are joined in a throwing state in which a part of the resin component constituting the permeable membrane body 2b is filled in the pores of the porous reinforcing sheet 2a.
[0129]
The back pressure strength of the separation membrane 2 backed by the porous reinforcing sheet 2a exceeded 0.2 MPa and improved to about 0.4 to 0.5 MPa. A method for defining the back pressure strength will be described later.
[0130]
In order to obtain a back pressure strength of 0.2 MPa or more using a nonwoven fabric as the porous reinforcing sheet 2a, the nonwoven fabric has a thickness of 0.08 to 0.15 mm and a density of 0.5 to 0.8 g / cm. ^Three It is preferable that If the thickness is less than 0.08mm or the density is 0.5g / cm ^Three If it is smaller, the strength as the reinforcing sheet cannot be obtained, and it is difficult to secure the back pressure strength of the separation membrane 2 of 0.2 MPa or more. On the other hand, the thickness is thicker than 0.15 mm or the density is 0.8 g / cm. ^Three If larger, the filtration resistance of the porous reinforcing sheet 2a is increased, the anchoring effect on the nonwoven fabric (porous reinforcing sheet 2a) is reduced, and peeling is likely to occur at the interface between the permeable membrane body 2b and the nonwoven fabric. Become.
[0131]
Next, the manufacturing method of said separation membrane 2 is demonstrated. First, a solvent, a non-solvent, and a swelling agent are added to polysulfone and dissolved by heating to prepare a uniform film forming solution. Here, as shown in the following structural formula (Chemical Formula 1), the polysulfone resin has at least one (—SO 2) in the molecular structure. ₂ If it has a-) site | part, it will not specifically limit.
[0132]
[Chemical 1]

[0133]
R represents a divalent aromatic, alicyclic or aliphatic hydrocarbon group, or a divalent organic group in which these hydrocarbon groups are bonded by a divalent organic bonding group.
[0134]
Preferably, polysulfone represented by the following structural formulas (Chemical Formula 2) to (Chemical Formula 4) is used.
[0135]
[Chemical 2]

[0136]
[Chemical 3]

[0137]
[Formula 4]

[0138]
As the polysulfone solvent, it is preferable to use N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, or the like. Further, as the non-solvent, aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol and glycerin, lower aliphatic alcohols such as methanol, ethanol and isopropyl alcohol, lower aliphatic ketones such as methyl ethyl ketone, and the like are used. It is preferable.
[0139]
The content of the non-solvent in the mixed solvent of the solvent and the non-solvent is not particularly limited as long as the obtained mixed solvent is uniform, but is usually 5 to 50% by weight, preferably 20 to 45% by weight.
[0140]
Swelling agents used to promote or control the formation of porous structures include metal salts such as lithium chloride, sodium chloride, and lithium nitrate, and water solubility such as polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylic acid. A polymer or a metal salt thereof, formamide or the like is used. The content of the swelling agent in the mixed solvent is not particularly limited as long as the film-forming solution is uniform, but is usually 1 to 50% by weight.
[0141]
The concentration of polysulfone in the membrane forming solution is usually preferably 10 to 30% by weight. When it exceeds 30% by weight, the water permeability of the resulting porous separation membrane is poor in practicality, and when it is less than 10% by weight, the mechanical strength of the resulting porous separation membrane is poor and sufficient back pressure is obtained. Can't get strength.
[0142]
Next, the above film forming solution is formed on a nonwoven fabric support. That is, using a continuous film forming apparatus, a support sheet such as a nonwoven fabric is sequentially sent out, and a film forming solution is applied to the surface. As a coating method, the film forming solution is coated on the nonwoven fabric support using a gap coater such as a knife coater or a roll coater. For example, when using a roll coater, the film forming solution is stored between two rolls, and the film forming solution is applied onto the nonwoven fabric support and simultaneously impregnated inside the nonwoven fabric, and then passed through a low humidity atmosphere. Then, a minute amount of moisture in the atmosphere is absorbed on the surface of the liquid film coated on the nonwoven fabric, and microphase separation is caused in the surface layer of the liquid film. Then, it is immersed in a coagulation water tank, the entire liquid film is phase-separated and coagulated, and the solvent is washed away in the water washing tank. Thereby, the separation membrane 2 is formed.
[0143]
As described above, since the separation membrane 2 has high back pressure strength, even when the separation membrane 2 is used for the spiral membrane element 1 of FIGS. The separation membrane 2 is prevented from being damaged.
[0144]
【Example】
In the following Example 1, Example 2, and Comparative Example, a spiral type ultrafiltration membrane element including an ultrafiltration membrane having the structure shown in FIG. 7 as the separation membrane 2 was produced, and this spiral type ultrafiltration membrane was used. A continuous water filtration test was conducted using the spiral membrane module of FIG. 1 equipped with elements.
[0145]
Here, the ultrafiltration membranes used in the spiral ultrafiltration membrane elements of Example 1, Example 2 and Comparative Example were produced as follows.
[0146]
First, 16.5 parts by weight of polysulfone (Amoco, P-3500), 50 parts by weight of N-methyl-2pyrrolidone, 24.5 parts by weight of diethylene glycol, and 1 part by weight of formamide were heated and dissolved to obtain a uniform product. A membrane solution was obtained. And using a roll coater with the coater gap adjusted to 0.13 mm, the thickness is 0.1 mm and the density is 0.8 g / cm. ^Three The film forming solution was impregnated and applied to the surface of the polyester nonwoven fabric.
[0147]
Then, after passing through an atmosphere (low humidity atmosphere) having a relative humidity of 25% and a temperature of 30 ° C. at a predetermined speed to cause microphase separation, it was immersed in a coagulated water tank at 35 ° C. to remove the solvent. After solidification, the separation solvent 2 was obtained by washing and removing the remaining solvent in a water washing tank. Here, the separation membrane 2 of Example 1 and Example 2 has a microphase separation time (time for passing through a low-humidity atmosphere) of 4.5 seconds.
[0148]
The ultrafiltration membrane produced as described above has a water permeability of 1700 L / m. ² -Hr, the back pressure strength was 0.3 MPa, and the rejection of polyethylene oxide having an average molecular weight of 1,000,000 was 99%.
[0149]
For the back pressure strength, a membrane having a diameter of 47 mm is set in a back pressure strength holder (having a hole diameter of 23 mm), and water pressure is gradually applied from the porous reinforcing sheet 2a side. It is defined by the pressure at which the permeable membrane body 2b and the porous reinforcing sheet 2a are simultaneously ruptured.
[0150]
The rejection rate of polyethylene oxide is such that a polyethylene oxide solution having a concentration of 500 ppm is applied at a pressure of 1 kgf / cm. ² And obtained from the concentration of the stock solution and the permeate by the following formula.
[0151]
Blocking rate (%) [1- (permeate concentration / stock solution concentration)] × 100
The continuous water filtration test of the spiral membrane module provided with the ultrafiltration membrane thus produced will be described below.
[0152]
Table 1 shows the specifications of the spiral ultrafiltration membrane element used in Example 1, Example 2, and Comparative Example.
[0153]
[Table 1]

[0154]
[Example 1]
In Example 1, industrial water (pH 6-8, water temperature 15-30 ° C.) was supplied as raw water to the spiral ultrafiltration membrane element, and a continuous water filtration experiment was conducted. Filtration was stopped once every 3 days, and the substrate was immersed for 1 hour in the cleaning solution used for backflow cleaning after backflow cleaning. In the backflow cleaning, permeated water was used as the cleaning liquid, and a cleaning liquid of 60 L / min was supplied at a back pressure of 0.2 MPa. Table 2 shows the operating conditions.
[0155]
[Table 2]

[0156]
[Example 2]
In Example 2, as in Example 1, industrial water (pH 6-8, water temperature 15-30 ° C.) was supplied as raw water to the spiral ultrafiltration membrane element, and a continuous water filtration experiment was conducted. Filtration was stopped once every 10 days, and the plate was immersed in the washing solution for 1 hour after backwashing. In the reverse flow cleaning, permeated water containing sodium hypochlorite was used as a cleaning liquid, and a cleaning liquid of 60 L / min was supplied at a back pressure of 0.2 MPa. The encapsulating liquid is permeated water containing sodium hypochlorite. Table 3 shows the operating conditions.
[0157]
[Table 3]

[0158]
[Comparative example]
In the comparative example, similarly to Examples 1 and 2, industrial water (pH 6 to 8, water temperature 15 to 30 ° C.) was supplied to the spiral ultrafiltration membrane element as raw water, and a continuous water filtration experiment was performed. However, in the comparative example, the immersion was not performed after stopping the filtration after the backwashing. Table 4 shows the operating conditions.
[0159]
[Table 4]

[0160]
FIG. 8 is a graph showing the change over time in the transmembrane pressure difference of the spiral membrane modules of Example 1, Example 2 and Comparative Example. In Example 1, as a result of performing an operation of dipping in the backwashing liquid for 1 hour after backwashing once every 3 days, an increase in the transmembrane pressure difference was suppressed, and the continuous transmembrane pressure difference was 0.1 MPa or less. Driving was possible.
[0161]
In Example 2, as a result of performing an operation of dipping in a backwashing liquid containing 100 ppm of sodium hypochlorite once every 10 days for 1 hour, an increase in transmembrane pressure difference was further suppressed. Continuous operation at a pressure of 0.06 MPa or less was possible. In Example 2, it was possible to operate with a transmembrane pressure difference lower than that in Example 1 because of the effect of washing with bactericidal sodium hypochlorite, the growth of microorganisms on the membrane surface was suppressed. This is probably because
[0162]
On the other hand, in the comparative example, since filtration was stopped and immersion in the liquid was not performed, a sudden increase in the transmembrane pressure difference occurred, and continuous operation could not be continued.
[0163]
As shown in the above Examples 1 and 2 and the comparative example, by stopping the liquid sealing in the spiral membrane module, the contaminants attached to the membrane surface of the spiral ultrafiltration membrane element are peeled off, and the intermembrane difference An increase in pressure can be suppressed. Thereby, it is possible to perform highly reliable and stable operation.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a spiral membrane module in an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of a method for operating a spiral membrane module according to the present invention.
FIG. 3 is a schematic cross-sectional view showing an example of a method for operating a spiral membrane module according to the present invention.
FIG. 4 is a schematic cross-sectional view showing another example of a method for operating a spiral membrane module according to the present invention.
5 is a partially cutaway perspective view of a spiral membrane element used in the spiral membrane module of FIG. 1. FIG.
FIG. 6 is a schematic cross-sectional view showing still another example of a method for operating a spiral membrane module according to the present invention.
7 is a cross-sectional view of a separation membrane used in the spiral membrane element of FIG.
FIG. 8 is a graph showing changes over time in transmembrane pressure differences of spiral membrane modules of Example 1, Example 2 and Comparative Example.
[Explanation of symbols]
1 Spiral membrane element
2 Separation membrane
3 Permeated water spacer
4 Envelope film
5 water collecting pipe
6 Raw water spacer
7,31 Raw water
8 Permeated water
100 spiral membrane module
10,110 pressure vessel
13,130 Raw water entrance
14,140 Permeate outlet
15,131 Raw water outlet
21 Washing water

Claims (12)

With bag-like separator film is wound around the outer peripheral surface of the perforated hollow pipe having first and second ends, 0. A method of operating a spiral membrane element capable of back-flushing with a back pressure of higher than 05 MPa and lower than 0.3 MPa, supplying a stock solution from the first end of the spiral membrane element during filtration operation The permeated liquid is taken out from at least one open end of the perforated hollow tube, and the cleaning liquid is introduced from at least one open end of the perforated hollow tube at the time of backwashing, whereby the first and second of the spiral-type membrane element are introduced. The separation membrane is backwashed at a back pressure higher than 0.05 MPa and lower than 0.3 MPa by discharging the cleaning liquid from at least one of the end portions of the spiral membrane element at the time of backwashing or after backwashing. The stock solution is introduced from the second end portion, and the stock solution flows in the spiral membrane element in the direction opposite to that during the filtration operation. Derived from the first end of the spiral membrane element, the filtration operation or backwashing is temporarily stopped, and the spiral membrane element is immersed in a liquid and held for a predetermined time. Operation method of spiral membrane element.   2. The method of operating a spiral membrane element according to claim 1, wherein the filtration operation is stopped and the spiral membrane element is kept in a state immersed in a liquid for a predetermined time.   2. The method of operating a spiral membrane element according to claim 1, wherein the backwashing is stopped and the spiral membrane element is held for a predetermined time while being immersed in a liquid.   3. The method of operating a spiral membrane element according to claim 2, wherein the filtration operation is restarted after the spiral membrane element is immersed in a liquid for a predetermined time.   3. The method of operating a spiral membrane element according to claim 2, wherein the backwashing is performed after the spiral membrane element has been immersed in a liquid for a predetermined time.   The method of operating a spiral membrane element according to claim 3, wherein the backwashing is resumed after holding the spiral membrane element in a liquid for a predetermined time.   4. The method of operating a spiral membrane element according to claim 3, wherein the filtration operation is performed after the spiral membrane element is immersed in a liquid for a predetermined time.   In parallel with the backflow cleaning or after the backflow cleaning, the stock solution during the filtration operation from the first end and the second end of the spiral membrane element through the stock solution inlet and the stock solution outlet of the pressure vessel The stock solution is supplied in order in the same direction and in the opposite direction to the feed direction, and the stock solution flows in the axial direction in the spiral membrane element, and the stock solution that has flowed in the axial direction is taken out of the pressure vessel. The operation method of the spiral membrane element according to any one of claims 1 to 7.   When the spiral membrane element is immersed in the liquid, a liquid containing a chemical having a bactericidal action or a contaminant peeling action is supplied to the spiral type membrane element, and the spiral type membrane element is placed in the liquid containing the chemical. The operation method of the spiral membrane element according to any one of claims 1 to 8, wherein the immersion is performed.   The separation membrane is formed by bonding a permeable membrane body to one surface of a porous sheet material, and the permeable membrane body is bonded to one surface of the porous sheet material in an anchored state. The operation method of the spiral-type membrane element in any one of 8.   An operation method of a spiral membrane module in which one or a plurality of spiral membrane elements are accommodated in a pressure vessel having a stock solution inlet, wherein the spiral membrane element is formed in a bag shape on the outer peripheral surface of a perforated hollow tube The separation membrane is wound and has first and second ends, and can be backwashed with a back pressure higher than 0.05 MPa and lower than 0.3 MPa. A stock solution is supplied from the first end of the element, a permeate is taken out from at least one open end of the perforated hollow tube, and a cleaning liquid is supplied from at least one open end of the perforated hollow tube during backwashing. By introducing and discharging the cleaning liquid from at least one of the first and second ends of the spiral membrane element, it is higher than 0.05 MPa and lower than 0.3 MPa. The separation membrane is backwashed with back pressure, and the stock solution is introduced from the second end of the spiral membrane element during the backwash or after the backwash, and the stock solution is filtered in the spiral membrane element. Flowing in the opposite direction of time and leading out from the first end of the spiral membrane element, the filtration operation or backwashing is temporarily stopped and the liquid is sealed in the pressure vessel for a predetermined time. A method for operating a spiral-type membrane module.   12. The method of operating a spiral membrane module according to claim 11, wherein the liquid contains a chemical having a bactericidal action or a pollutant peeling action.

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