JP5429005B2 - Pretreatment method for hollow fiber membrane module and water purifier using its own weight filtration system - Google Patents

Description

  The present invention relates to a pretreatment method for a hollow fiber membrane module and a water purifier using a self-weight filtration system including the same.

  As a water purifier equipped with a hollow fiber membrane module, the faucet direct-coupled water purifier can remove fine turbidity, germs, odors, etc. in tap water source water, and can be easily attached to faucets in each household. Widely used in urban areas where there is anxiety. Furthermore, as a simpler water purifier that does not choose the place of use, a water purifier using a self-weight filtration method called a pot type or a pitcher type has recently attracted attention.

  Filter cartridges include activated carbon for removing organic substances such as trihalomethane, ion exchangers for removing metal ions such as lead, and hollow fiber membranes for removing iron rust, turbidity, etc. There are many things to do. Among the filter media, the hollow fiber membrane has a hole of about 0.05 to 10 μm called a microfiltration membrane, and therefore has a high water resistance, and the filtration flow rate as a cartridge is almost determined by the hollow fiber membrane portion.

  In the case of a faucet-directly connected water purifier, filtration is performed by tap water pressure. Therefore, if the tap water pressure is stable at around 0.1 MPa, the filtration flow rate is not a problem. However, in the case of a self-weight filtration type water purifier using cartridges such as Patent Document 1 and Patent Document 2, the pressure applied to the filter medium is only the head difference between the filter medium and the liquid surface, and is about 10 to 20 kPa (head difference of 10 ˜20 cm). For this reason, the filtration flow rate is extremely low, and it takes 10 minutes or more to obtain 1 L of purified water. Furthermore, the variation in filtration time is large, making it extremely inconvenient and fatal compared to a faucet-direct water purifier. Problem.

JP 2009-125664 A JP 2004-230335 A In Japanese Utility Model Publication No. 5-9063, in order to stabilize the filtration flow rate, an air vent hole is formed in the water purification cartridge. However, mention is made as to whether a sufficient filtration flow rate is ensured. Not.

  In Patent Document 2, the filtration flow rate is increased by avoiding the hollow fiber membrane and the adsorbent partition member in the filter medium, but the filtration time of 1 liter of water at that time is a difference of 50 to 100 seconds. There is a large variation, and a stable filtration flow rate is not obtained.

  An object of the present invention is to provide a pretreatment method for obtaining a stable filtration flow rate from the initial stage of water flow of a water purifier using a self-weight filtration method.

  According to the knowledge of the present inventors, the filtration flow rate is low in a state in which the filter medium is not familiar with water, that is, in a state where the air in the filter medium cannot be removed, but among them, the hollow fiber membrane is particularly difficult to blend with water. I found out. It has been found that this is because bubbles remaining inside the fine holes of the hollow fiber membrane cannot be removed. By repeating the filtration several times, the air staying in the filter medium is released, so that the filtration flow rate is gradually increased to some extent, but the instability is due to residual bubbles inside the hollow fiber membrane.

  As a method of using a self-weight filtration type water purifier, it is common to wash with tap water to remove the activated carbon adhering to the cartridge, soak the bottom of the cartridge in water for a predetermined time, and then filter the raw water several times Is.

  According to the knowledge of the present inventors, when attention is paid to the hollow fiber membrane portion, this operation first allows water to permeate from the outside of the hollow fiber membrane and then soaks the lower part of the cartridge in water. Will penetrate. In other words, the air staying in the pores inside the hollow fiber membrane left so as to be sandwiched between the water penetrating from the outside and the inside of the hollow fiber membrane cannot be completely removed, and the air inhibits water flow. The filtration flow rate is not stable. Furthermore, since the hollow fiber membrane used for the water purifier uses a hydrophilized membrane, bubbles remaining inside the membrane are extremely difficult to remove, which is one reason that the filtration flow rate is not stable.

The present invention has found that the above problems can be solved by any of the following configurations.
(1) A plurality of U-shaped hollow fiber membrane bundles are loaded into the casing, the ends of the hollow fiber membranes are sealed with an adhesive, and the bonded portion is cut to separate the raw water side and the permeate water side. A pretreatment method for a hollow fiber membrane module for obtaining purified water, characterized in that water is permeated only from the inside of the hollow fiber membrane in advance before obtaining purified water. Method.
(2) The pretreatment method for a hollow fiber membrane module according to (1), wherein water is permeated from the entire bonding cross section of the hollow fiber membrane.
(3) The hollow fiber membrane module according to (2), wherein, when water is permeated from the entire bonding cross section of the hollow fiber membrane, the U-shaped end of the hollow fiber membrane bundle is submerged below the water surface. Pre-processing method.
(4) The pretreatment of the hollow fiber membrane module according to any one of (1) to (3), wherein the hollow fiber membrane to be loaded is a microfiltration membrane or a membrane having smaller pores Method.
(5) A water purifier using a self-weight filtration system, which is equipped with the hollow fiber membrane module subjected to the pretreatment according to any one of (1) to (4) and a cartridge including the module.

  According to the present invention, since it is possible to obtain a stable filtration flow rate from the initial stage of water purifier using a self-weight filtration method, it is possible to utilize it as an easy-to-use water purifier without feeling stress in obtaining purified water. it can.

Manufacturing schematic diagram of hollow fiber membrane module Manufacturing schematic diagram of hollow fiber membrane module Module with U-shaped hollow fiber membrane Module with two sets of U-shaped hollow fiber membranes Module with hollow fiber membrane knitted fabric Schematic diagram of pretreatment method for hollow fiber membrane module Cartridge equipped with a hollow fiber membrane module whose raw water introduction part is protected by a seal

  The pretreatment method according to the present invention can be applied to all water purifiers using the self-weight filtration method, and is preferably used for pot type water purifiers and pitcher type water purifiers. Furthermore, it is suitably used for a large capacity water purifier such as a water server.

  Although the hollow fiber membrane module used for this invention can be manufactured using a well-known method, an outline is as FIG. First, as shown in FIG. 1 (a), a hollow fiber membrane bundle 2 in which a plurality of hollow fiber membranes are U-shaped is loaded in a casing 10, and a combination with a casting tray 4 is placed on an adhesive tray 3 And pour the adhesive 5. As shown in FIG. 1B, the hollow fiber membrane module 1 can be obtained by cutting with the cutting blade 7 when the adhesive 5 is cured.

  The hollow fiber membrane module is often combined with other filter media such as activated carbon and provided as a cartridge. However, the hollow fiber membrane module and other filter media can be separated as separate units. At that time, only the hollow fiber membrane module portion may be subjected to the pretreatment method according to the present invention.

  Embodiments of the present invention will be described below.

  For the hollow fiber membrane module 1 in the present invention, for example, a U-shaped hollow fiber membrane bundle 2 shown in FIG. 2 is used. As a form of the U-shaped hollow fiber membrane bundle 2, a predetermined number is folded in two to make one bundle U-shaped, or a plurality of bundles U-shaped like FIG. 3 are used. Also, by using a hollow fiber membrane knitted fabric as described in Patent Document 3 as shown in FIG. 4, the casing 10 is loaded, and one end of the hollow fiber membrane is sealed with the adhesive 5, and the bonded portion is cut. By doing so, it can be set as a U-shaped hollow fiber membrane bundle.

  The pretreatment in the present invention should be carried out before obtaining purified water, and is preferably just before the start of use from the viewpoint of hygiene.

  As a pretreatment method, water is infiltrated from the inside of the hollow fiber membrane portion of the hollow fiber membrane module 1. What is important here is that the portion of the hollow fiber membrane that comes into contact with water for the first time is inside the hollow fiber membrane, and it must be avoided that the outside of the hollow fiber membrane gets wet. More specifically, water is allowed to permeate from the bonded portion cut surface 9 of the hollow fiber membrane. Furthermore, in order to pre-treat all the hollow fiber membranes of the module, it is necessary to pay attention to bringing the entire bonded portion cut surface into contact with water and allowing water to penetrate. When the entire cut surface of the adhesive part is brought into contact with water, if it is vigorously manipulated, it may cause splashing and wet the outside of the module hollow fiber membrane. As a result, the water that has permeated the inside of the hollow fiber membrane is gradually filled by capillary action and reaches the outside of the hollow fiber membrane.

  Before obtaining purified water with the hollow fiber membrane module, by performing the pretreatment as described above, when obtaining purified water, an appropriate filtration flow rate can be stably obtained from the initial stage of the water. .

  In order to more reliably execute the pretreatment of the present invention in a short time, it is more effective to sink the U-shaped end of the hollow fiber membrane bundle below the water surface as shown in FIG. In this case, since the liquid level inside the hollow fiber membrane rises to the water level due to water pressure, the inside of the hollow fiber membrane can be instantaneously filled with water. The time required for the pretreatment also affects the pore diameter, film thickness, and degree of hydrophilicity of the membrane, but in the case of a microfiltration membrane, according to the present invention, it is at least within 20 seconds, preferably within 10 seconds, more preferably 5 seconds. Can be completed within. Since the pretreatment operation is very short, for example, the water 13 is stored in a certain container 12 so that the hollow fiber membrane module can be immersed, and the upper end of the casing 2 is supported by hand, while the hollow fiber membrane is supported as shown in FIG. What is necessary is just to sink in the container 12 so that the U-shaped end of the module 1 may become below the water surface. For example, in the case of a cartridge 14 for a pot type water purifier, water is stored in the pot type water purifier body to such an extent that the cartridge is just immersed in the state where the cartridge is incorporated in the water purifier body, and is brought into contact with water from the water purification outlet side 18 of the cartridge. You can also.

  Self-weight filtration type water purifier cartridges are often equipped with a filter medium such as activated carbon in addition to the hollow fiber membrane module on the upstream side, but when the water enters the activated carbon layer, the outside of the hollow fiber membrane will eventually get wet. Therefore, in order not to wet the outside of the hollow fiber membrane, the raw water introduction portion of the water purifier cartridge can be protected by the seal 19 as shown in FIG. In this case, when carrying out the pretreatment method according to the present invention, it is not necessary to pay much attention to the fact that the outside of the hollow fiber membrane is not wetted. For example, before carrying out the pretreatment, fine powder such as activated carbon is added to the cartridge. Even if it adheres to the cartridge, the cartridge can be washed with water, and then the seal can be peeled off to perform pretreatment.

  In order to perform the pretreatment of the present invention more effectively, a hollow fiber membrane having a pore of about 0.05 to 10 μm is suitably used as a microfiltration membrane, but for a water purifier, bacteria and microorganisms are used. Those having a pore diameter of 0.3 μm or less are preferably used for the purpose of removing red rust and the like. Furthermore, a smaller ultrafiltration membrane of about 0.01 μm is preferably used for a water purifier for virus removal.

  In the case of a membrane having pores larger than 10 μm, the air inside the membrane is easily removed, so a special method is not necessary. However, as the membrane has a smaller pore diameter, it is necessary to surely remove the air inside the membrane. The effect of the pre-processing is remarkable.

  As the hollow fiber membrane material, there is almost no problem as long as it has the above pore diameter, but various materials such as cellulose-based, polyolefin-based, polyvinyl alcohol-based, polysulfone-based, polymethyl methacrylate-based, polyamide-based materials are appropriately selected. The hydrophobic material is used as a water purifier membrane after being subjected to a known hydrophilic treatment. If the membrane is made hydrophilic, the micropores are held once filled with water. Therefore, if sufficient consideration can be given to hygiene, the filtration flow rate does not decrease even if the membrane is left for a while after the pretreatment.

  The membrane structure may be a homogeneous membrane or an asymmetric membrane, but in order to reduce the pretreatment time, the membrane structure is sparse on the inside and the outside on the outside so that water can easily penetrate from the inside to the outside of the hollow fiber membrane. Since a membrane having a dense asymmetric structure can exert a more remarkable effect of the invention, among the above-mentioned membrane materials, cellulose-based and polysulfone-based materials are preferably used because an asymmetric structure can be easily formed from a film-forming method. .

  The hollow fiber membrane module of the present invention can be used in the form of a cartridge by a known method in combination with other filter media within a range that does not hinder the pretreatment operation. In addition, when the other filter medium and the hollow fiber membrane module are made independent, first, after pre-treating only the hollow fiber membrane module, the other filter medium is pre-treated to obtain an appropriate filtration flow rate from the beginning of the water flow. Can do.

Hereinafter, the present invention will be described in detail using examples. The method for measuring the filtration flow rate is as follows.
(1) Filtration flow measurement 1:
It is a filtration flow rate when a predetermined amount of water is poured into a funnel to purify water like a pot type or pitcher type water purifier, and is a measurement method in actual use, which is 6.1 of JIS S3201 (2004). Evaluation is performed according to the method described in (b). In the present invention, 1 liter of raw water is filtered using PT301 manufactured by Toray Industries Inc. (maximum head difference to the cartridge raw water inlet is 100 mm), and the filtration flow rate is calculated from the time until the filtered water reaches 0.98 liter. The average value of n = 3 was taken as the measured value, and the results are shown in Table 1.
(2) Filtration flow rate measurement 2:
Unlike the above, the filtration flow rate when the head difference is controlled so as to be a constant pressure condition, and as a method for measuring the substantial filtration flow rate of the filter medium, the head difference is maintained at 25 cm and obtained from the hollow fiber membrane module. The filtrate obtained was collected for 1 minute, the filtration flow rate was measured, the average value of n = 3 was taken as the measurement value, and the results are shown in Table 2.
<Example 1>
500 polysulfone-based hollow fiber membranes (hollow fiber membrane outer diameter of 0.46 mm), which are microfiltration membranes with a hollow inner side of the hollow fiber membrane and a dense outer side, are U-shaped to form a hollow fiber membrane module, and an activated carbon unit is added. A prepared cartridge was prepared. The height from the water purification outlet of the hollow fiber membrane module to the U-shaped end of the hollow fiber membrane was 70 mm, and the thickness of the adhesive layer was 15 mm. Pretreatment was carried out in the main body container of the pot type water purifier. Soak water in the main container filled with water so that water can permeate from the bonding surface of the hollow fiber membrane module, and submerge the water surface until it reaches the height of the U-shaped end of the hollow fiber membrane bundle for 5 seconds. Then, when the filtration flow rate was evaluated along the filtration flow rate measurement 1, the initial filtration flow rate was 0.133 L / min. Further, after 3 liters and 10 liters of water were passed, the same measurement was performed. The results were 0.135 and 0.136 L / min, respectively, and the filtration flow rate was stable.

Thus, the filtration flow rate of the self-weight filtration type water purifier cartridge equipped with the hollow fiber membrane module of the present invention is 0.1 L / min or more, and 1 liter of raw water is obtained by performing the pretreatment shown in the present invention. It takes less than 10 minutes from the beginning to filter the water, and the flow rate of the filter is stable, so the user does not feel the stress of filtering raw water and can be stored in a general household refrigerator. It can be suitably used as a cartridge.
<Example 2>
900 polysulfone-based hollow fiber membranes (hollow fiber membrane outer diameter of 0.46 mm), which are microfiltration membranes with a hollow inner side of the hollow fiber membrane and a dense outer side, were U-shaped to form a hollow fiber membrane module. The height from the water purification outlet of the hollow fiber membrane module to the U-shaped end of the hollow fiber membrane was 70 mm, and the thickness of the adhesive layer was 15 mm. When only the hollow fiber membrane module was pretreated and the filtration flow rate was evaluated along the filtration flow rate measurement 2 only with the hollow fiber membrane module, the initial filtration flow rate was 0.635 L / min. Then, when the filtration flow rate was measured after passing water for 10 minutes and 30 minutes, the flow rate was changed to 0.636 and 0.629 L / min, respectively, and the filtration flow rate was stable.
<Example 3>
1400 polyethylene-based hollow fiber membranes (hollow fiber membrane outer diameter 0.40 mm), which are microfiltration membranes that are uniform throughout the hollow fiber membranes, were knitted into a U-shape to obtain a hollow fiber membrane module. The height from the water purification outlet of the hollow fiber membrane module to the hollow fiber membrane U-shaped end was 65 mm, and the thickness of the adhesive layer was 15 mm. Otherwise, only the hollow fiber membrane module was pretreated in the same manner as in Example 2, and the filtration flow rate was evaluated along the filtration flow rate measurement 2. The initial filtration flow rate was 0.350 L / min. Then, when the filtration flow rate was measured after passing water for 30 minutes, it was 0.340 L / min and the filtration flow rate was stable.
<Comparative Example 1>
The cartridge provided with the same hollow fiber membrane module as in Example 1 was washed with tap water as a whole, then pre-treated, and the filtration flow rate was evaluated according to the filtration flow rate measurement 1. The initial filtration flow rate was 0.00. 075 L / min. Further, when the same measurement was performed after passing 3 liters and 10 liters of water, 0.087 and 0.099 L / min were obtained respectively, and the filtration flow rate tends to increase gradually. Couldn't get.
<Comparative example 2>
When the outside of the hollow fiber membrane of the hollow fiber membrane module of Example 2 was wetted with water, it was pretreated and evaluated along filtration flow rate measurement 2. As a result, it was 0.240 L / min. Then, when the filtration flow rate was measured after passing water for 10 minutes and 30 minutes, they were 0.285 and 0.365 L / min, respectively, and the filtration flow rate tends to increase gradually. I couldn't.
<Comparative Example 3>
After the hollow fiber membrane outer side of the hollow fiber membrane module of Example 3 was wetted with water, pretreatment was performed and evaluation along the filtration flow rate measurement 2 was 0.240 L / min. Thereafter, when the filtration flow rate was measured after passing water for 10 minutes and 30 minutes, they were 0.249 and 0.255 L / min, respectively, and the filtration flow rate tends to increase gradually. Couldn't get.

<Summary>
From the results of Examples in Tables 1 and 2, it can be seen that a stable filtration flow rate is obtained from the initial stage of water flow to the cartridge or module.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane module 2 Hollow fiber membrane bundle 3 Adhesive receptacle 4 Casting tray 5 Adhesive 6 Adhesive inlet 7 Cut blade 8 Cutting waste 9 Cut surface 10 Casing 11 Knitting yarn 12 Container 13 Water 14 Cartridge 15 Cartridge case 16 Activated carbon 17 Raw water inlet 18 Clean water outlet 19 Seal

Claims (5)

A hollow fiber membrane bundle in which a plurality of hollow fiber membranes are U-shaped is loaded in a casing, the end of the hollow fiber membrane bundle is sealed with an adhesive, and the bonded portion of the end of the hollow fiber membrane bundle is A pretreatment method of a hollow fiber membrane module in which the raw water side and the permeate water side are partitioned by cutting, wherein water is infiltrated only from the inside of the hollow fiber membrane in advance before obtaining purified water. A pretreatment method for a hollow fiber membrane module. The pretreatment method for a hollow fiber membrane module according to claim 1, wherein water is permeated from the entire bonding cross section of the hollow fiber membrane. The pretreatment of the hollow fiber membrane module according to claim 2, wherein when water is permeated from the entire bonding cross section of the hollow fiber membrane, the U-shaped end of the hollow fiber membrane bundle is submerged below the water surface. Method. The hollow fiber membrane module pretreatment method according to any one of claims 1 to 3, wherein the hollow fiber membrane to be loaded is a microfiltration membrane or a membrane having smaller pores. A water purifier using a self-weight filtration system, wherein the pre-treated hollow fiber membrane module according to any one of claims 1 to 4 and a cartridge including the hollow fiber membrane module are mounted.

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