TW201938257A - Method for cleaning membrane separation apparatus - Google Patents

Abstract

This method for cleaning a membrane separation apparatus provided with a membrane module, the inside of which is partitioned into a raw water chamber and a permeated-water chamber by a separation membrane, comprises a cleaning step for bringing an amphoteric surfactant-containing cleaning solution into contact with a raw water chamber-side membrane surface of said separation membrane. The cleaning solution contains 0.01-5 wt% of the amphoteric surfactant and does not contain phosphorus and an oxidizing agent. It is preferable to dry the raw water chamber-side membrane surface by bringing air into contact with the raw water chamber of the membrane module before the cleaning step.

Description

Method for cleaning membrane separation device

The invention relates to a method for cleaning a membrane separation device for water treatment. The present invention relates to a method for dissolving suspended substances or organic · inorganic colloids · organic · inorganic materials in water by using, for example, an ultrafiltration membrane (UF membrane) or a microfiltration membrane (MF membrane) (precise filtration membrane). A method for effective cleaning of a membrane separation device (turbidity membrane removal device) for separating and removing matter.

In membrane separation devices (turbidity membrane removal devices) that use UF membranes (ultrafiltration membranes) or MF membranes (precision filtration membranes) for the purpose of removing turbidity, stains adhere to the separation membrane during filtration. The filtration time of seconds to 60 minutes intermittently supplies the cleaning fluid (water and / or gas) to the raw water chamber of the membrane module or permeates the membrane to physically clean the membrane.

If contamination that cannot be removed during physical cleaning is deposited on the membrane surface or inside the membrane, the filtration capacity of the membrane is gradually reduced. When turbid matter is contained in raw water or when the device is operated with a high water recovery rate, solid components such as turbidity are accumulated into a cake shape between the membrane or between the membrane and the housing, which is effective Membrane filtration area is reduced. Therefore, in the turbidity-removing film device, it is necessary to periodically or irregularly use medicines to perform medicine cleaning or to strengthen physical cleaning for the purpose of removing turbidity.

For pharmaceutical cleaning, acid agents (sulfuric acid, hydrochloric acid, nitric acid, citric acid, and oxalic acid), alkali agents (sodium hydroxide), and oxidants (sodium hypochlorite) are generally used (Non-Patent Document 1). Which agent is used depends on the raw material of the film or the fouling component of the film. In order to strengthen the physical cleaning, in order to make the membrane vibrate, in addition to vigorously blowing cleaning fluid (water and / or gas) to the raw water chamber side of the membrane module, there are also means for contacting ultrasonic waves (Non-Patent Document 2) .

Medicine cleaning and enhanced physical cleaning are rarely used alone, and usually a combination of medicine cleaning and enhanced physical cleaning is performed for half to several days. In particular, when turbidity contamination in which solid components such as turbidity are accumulated on the surface of the membrane or inside the module, the cleaning effect is not sufficient if only chemical cleaning is performed, so it must be combined with enhanced physical cleaning.

In the turbidity removing film device in which the film end portion is fixed to the module case, there is a case that even if intensive physical cleaning is performed, the film does not sufficiently vibrate, so that a sufficient turbidity removal effect cannot be obtained. Especially for the turbidity removal membrane device using an internal pressure type hollow fiber membrane module, since the raw water chamber is located in the hollow fiber membrane module with a diameter of about 1 mm, it is difficult to discharge the turbidity of the raw water chamber to the outside of the membrane module. Furthermore, it is not possible to use a physical cleaning method in which the membrane is swung by blowing air into the raw water chamber.
The internal pressure type hollow fiber membrane module has a structure prone to turbid pollution, and it is difficult to clean the turbid pollution, and it is desirable to improve the cleaning method thereof.

The surfactant is used as a solvent, a dispersant, and a pore-opening agent for the raw resin in the production process of the separation membrane of the membrane separation device (Patent Document 1).

In an operation process, a surfactant is rarely used for the purpose of cleaning a membrane separation device. However, in Patent Document 2, a surfactant is used for cleaning an ultrapure water production device. Patent Document 3 describes the use of an amphoteric surfactant for modification for imparting antibacterial properties to a separation membrane.
Neither of Patent Literature 2 and Patent Literature 3 is a technology for the purpose of cleaning the turbid film removing device.

As an example of the use of an amphoteric surfactant for cleaning of a turbid film removing device, there is Patent Document 4. Patent Document 4 describes the use as a cleaning agent for a turbid film removing device in a food processing process. However, the cleaning liquid of Patent Document 4 contains phosphonates, hypochlorites, alkali agents, and polymeric phosphates as essential active ingredients, and an amphoteric surfactant is arbitrarily added to these essential active ingredients. In the case of using phosphorus in the cleaning solution as in Patent Document 4, high concentration of phosphorus is contained in the cleaning drainage and the turbidity-removing membrane filtered water after the cleaning. Therefore, biofouling may occur during the cleaning and drainage treatment and after the cleaning is started risk. When the oxidizing agent is contained in the cleaning liquid as in Patent Document 4, a large amount of flushing water and time are required in order to prevent deterioration of the rear stage device when water is passed after cleaning.

Patent Literature 1: Japanese Patent Laid-Open No. 2005-146230 Patent Literature 2: Japanese Patent Laid-Open No. 2004-122020 Patent Literature 3: Japanese Patent Laid-Open No. 2009-112927 Patent Literature 4: Japanese Patent Laid-Open No. 2012-106160 Bulletin

Non-Patent Document 1: Shigera Sawa, "Membrane Filtration Technology Useful at the Site" (2006) p120-121
Non-Patent Document 2: Shigera Sawa, "Membrane Filtration Techniques Useful at the Site" (2006) p94-95

An object of the present invention is to provide a cleaning method that is effective for turbidity pollution even in a turbidity removing membrane device having an internal pressure type hollow fiber membrane module using a cleaning liquid that does not contain phosphorus and an oxidant.

The inventors have discovered that the turbidity contamination of the separation membrane of the turbidity removal membrane device can be effectively cleaned and removed by a cleaning solution containing an amphoteric surfactant and containing no phosphorus and oxidant.
That is, the present invention is based on the following points.

[1] A method for cleaning a membrane separation device, which is a method for cleaning a membrane separation device including a membrane module in which an interior is separated into a raw water chamber and a permeated water chamber by a separation membrane. In the method, the method includes: A cleaning step in which the cleaning solution containing the amphoteric surfactant is in contact with the surface of the raw water chamber side membrane of the separation membrane.

[2] The method for cleaning a membrane separation device according to [1], wherein the cleaning solution contains 0.01 to 5% by weight of the amphoteric surfactant, and does not contain phosphorus and an oxidant.

[3] The method for cleaning a membrane separation device according to [1] or [2], comprising a drying step of drying the surface of the side membrane of the raw water chamber by contacting the raw water chamber with air, and The washing step is performed after the drying step.

[4] The method for cleaning a membrane separation device according to any one of [1] to [3], wherein the cleaning step includes: passing in the membrane module from a water-permeable chamber side to a raw water chamber side Either or both of the step of the cleaning solution and the step of circulating the cleaning solution on the raw water chamber side of the membrane module.

[5] The method for cleaning a membrane separation device according to any one of [1] to [4], wherein the membrane module is an internal pressure type hollow fiber membrane module.

[Effect of the invention]
According to the present invention, by bringing a cleaning solution containing an amphoteric surfactant into contact with the surface of the raw water chamber side membrane, turbid contamination on the membrane surface is effectively floated and discharged to the outside of the system, even if the inner pressure type hollow fiber membrane mold A high cleaning effect can also be obtained in the turbidity removing film device of the group.

The cleaning solution used in the present invention does not contain phosphorus or an oxidant, and there is no problem of biological fouling caused by phosphorus or an excessive flushing operation for oxidant discharge.
In the present invention, before the washing step performed by the washing solution, a pretreatment is performed in which the raw water chamber is exposed to the air and the surface of the raw water chamber side film is dried, thereby obtaining a higher turbidity removal effect.

Hereinafter, the embodiment of the cleaning method of the membrane separation apparatus of this invention is demonstrated in detail.

＜ Mechanism ＞
The cleaning effect of the cleaning solution containing the amphoteric surfactant in the cleaning method of the membrane separation device of the present invention, and the effects produced by the drying operation before cleaning can be considered as follows.

The surfactant has the effect of infiltrating into the interior of turbid contamination by its penetrating action, and then floating and removing it from the surface of the membrane by emulsifying and dispersing action. The amphoteric surfactant has both anionic and cationic groups in the hydrophilic part of the molecule. Therefore, the binding of the adjacent amphoteric surfactant molecules to each other becomes strong and tight. Therefore, compared with micelles formed from positive, negative, or nonionic surfactants, microsomes formed from amphoteric surfactants do not contain turbidity in the microsomes. Will destroy the microsomes and easily discharge turbidity out of the system.

By drying the surface of the raw water side membrane, the cake-shaped turbid contamination attached to the surface of the membrane can be dried and shrunk to cause a gap between the turbid contamination and the membrane surface or cracks between the turbid contamination. Thereby, the effect that the contact area between the turbidity and the cleaning solution is increased and the turbidity is easily floated from the surface of the film can be obtained.

＜ Cleaning solution ＞
In the present invention, the amphoteric surfactant used as an active ingredient of the cleaning solution includes the following surfactants and the like.
Amino acid type amphoteric surfactants: Betaine type amphoteric surfactants such as higher alkyl alkyl propionates having 12 to 18 carbon atoms in alkyl groups: alkyl dimethyl groups having 12 to 18 carbon atoms in alkyl groups Sulphate ester type amphoteric surfactants such as alkyl betaine, alkyl dihydroxyethyl betaine having 12 to 18 carbon atoms: sodium sulfate of higher alkyl amines having 8 to 18 carbon atoms in alkyl group Salt, hydroxyethyl imidazoline sulfate sodium salt and other sulfonate type amphoteric surfactants: pentadecyl thiotaurine (pentadecyl sulfotaurine), imidazoline sulfonic acid, etc. These may be used alone or in combination More than two. Among these, a betaine-type amphoteric surfactant is preferable.

The content of the amphoteric surfactant in the cleaning solution is 0.01% by weight or more, and particularly preferably 0.5% by weight or more. When the content of the amphoteric surfactant is too small, a sufficient cleaning effect may not be obtained. The upper limit of the content of the amphoteric surfactant in the cleaning solution is caused by the microcellular concentration of the amphoteric surfactant. Although it is not particularly limited, if it is too large, there may be problems such as foaming, increased load on the drainage equipment, or Since the washing water and time may increase, it is preferably 5% by weight or less.

The cleaning solution used in the present invention is basically an aqueous solution of an amphoteric surfactant, and it is important that it does not contain other components, especially phosphorus and an oxidant.

In terms of peeling and removing effects of turbidity, the pH of the cleaning solution used in the present invention is preferably a strong alkaline of about 11 or more, particularly about 12 to 13. To adjust the pH, the cleaning solution may contain alkali agents such as sodium hydroxide and potassium hydroxide.

The cleaning solution used in the present invention is preferably a cleaning solution containing an amphoteric surfactant at a concentration of 1% to 5% by weight under strong alkaline conditions at a pH of 13 or more.

＜ Cleaning steps ＞
In the present invention, the cleaning solution containing the amphoteric surfactant is brought into contact with the surface of the raw water chamber side membrane of the membrane module that separates the interior into the raw water chamber and the permeate water chamber through the separation membrane, thereby cleaning the separation membrane. Specifically, the cleaning step is preferably performed by the following (1) step and / or (2) step.
(1) The step of feeding the cleaning solution from the side of the membrane module through the water chamber to the side of the raw water chamber (2) The step of circulating the cleaning solution on the side of the raw water chamber of the membrane module

In the case where step (1) and step (2) are performed, either step may be performed first, but step (1) is preferably performed first. Perform step (1) first, and then step (2) to remove the turbid contamination on the membrane surface to hydrophilize the membrane surface of the raw water chamber side. The contact efficiency between the cleaning solution and the membrane surface of the raw water side is improved, so it can be reduced in a short time. Hydrophilization treatment was performed within time. Steps (1) and (2) can also be repeated alternately.

The cleaning conditions such as the cleaning time or the flow rate of the cleaning solution also vary depending on the amphoteric surfactant concentration or pH of the cleaning solution used, and the degree of contamination of the separation membrane to be cleaned. Therefore, the method to obtain the desired cleaning effect is appropriately set. Just fine.

After washing, it is preferable to perform washing according to a conventional method.

＜ Drying step ＞
In the present invention, it is preferable to perform a drying step of drying the surface of the raw water chamber side membrane by contacting the raw water chamber of the membrane module with air before the cleaning step. By performing the drying step, a higher turbidity removal effect can be obtained.

The specific method of the drying step is not particularly limited, and a method of blowing compressed air into the raw water chamber side of the membrane module, a method of leaving the membrane module in contact with outside air, and the like can be adopted.

＜ membrane module ＞
There is no particular limitation on the membrane separation device to be cleaned by the cleaning method of the membrane separation device of the present invention. Since the cleaning method of the present invention is particularly effective in removing turbidity, it is effective for suspensions in water, organic / inorganic colloids, and organics. • The UF membrane or MF membrane of the turbidity removal membrane device used for separation and removal of inorganic dissolved matter is effective. The invention is particularly suitable for the removal of turbidity in an internal-pressure hollow fiber module in a raw water chamber, which is difficult to discharge to the outside of the module, and it is difficult to apply a physical cleaning method.
[Example]

The following examples illustrate the present invention in more detail.

The surfactants used in the following examples and comparative examples are as follows.

＜ Amphoteric surfactants ＞
Double-sided surfactant A: "LEBON CIB" manufactured by Sanyo Chemical Industry Co., Ltd. (alkyl carboxymethyl hydroxyethyl imidazolium betaine represented by the following structural formula)

[Chemical 1]

Amphoteric Surfactant B: "LEBON MY-30" manufactured by Sanyo Kasei Kogyo Kogyo Co., Ltd. (myristic acid amidopropyl betaine represented by the following structural formula)

[Chemical 2]

＜ Nonionic surfactants ＞
Non-ionic surfactant A: "Naroacty ID-40" (polyoxyethylene alkyl ether) manufactured by Sanyo Chemical Industry Co., Ltd.
Nonionic Surfactant B: "Naroacty ID-60" (polyoxyethylene alkyl ether) manufactured by Sanyo Chemical Industries, Ltd.

＜ Negative Surfactant ＞
Negative surfactant A: "Sanded EN" (polyoxyethylene alkyl ether sodium sulfate) manufactured by Sanyo Chemical Industry Co., Ltd.

[Example 1, Example 2, Comparative Example 1 to Comparative Example 4]
The following cleaning test was conducted to investigate the effect of cleaning the turbidity originating from the liquid crystal factory drainage.

(1) The liquid crystal factory was drained into an MF membrane with an aperture of 0.45 μm to make an MF contaminated membrane.
(2) Pass 10 mL of pure water to the MF contaminated membrane, and find the time T0 required for water passing.
(3) Immerse the MF-contaminated membrane in the cleaning solution for 3 minutes, and then pass in 10 mL of pure water to find the time T1 required for the water to pass through.

As the cleaning solution, those shown in Table 1 were used. The blank group of Comparative Example 1 was water adjusted to pH 12 with NaOH, and the other cleaning solutions were obtained by dissolving each surfactant at a concentration of 1% by weight and adjusting the pH to 12 with NaOH.

(4) Change the drainage volume through the MF membrane, and perform (1) to (3) on the three specimens of the MF contaminated membrane with deviations in T0.
(5) T0 is plotted on the horizontal axis and T1 is plotted on the vertical axis. The cleaning effect is evaluated by the slope T1 / T0 derived from the test results at three points.
The larger T1 / T0, the lower the cleaning effect, and the smaller T1 / T0, the higher the cleaning effect.

The results are shown in Table 1 and FIG. 1.

[Table 1]

It can be seen from Table 1 and FIG. 1 that the cleaning effect is amphoteric surfactant> negative surfactant ≒ nonionic surfactant> blank group, and the amphoteric surfactant shows the most excellent cleaning effect.

[Example 3]
Take out the hollow fiber membrane from the internal pressure type hollow fiber membrane module (hollow fiber UF membrane, pore diameter 0.03 μm, membrane inner diameter 0.9 mm, membrane raw material polyether 碸) contaminated in the liquid crystal factory drainage and recycling equipment, and carry out the following procedures Cleaning test.

As the cleaning solution, an amphoteric surfactant A was dissolved in water at a concentration of 1% by weight and adjusted to pH 13 with NaOH.

(1) An internal pressure type small module test device (film length 7.5 cm, area 10.6 cm ² ) as shown in Fig. 2a and Fig. 2b was produced using five contaminated films.

In Fig. 2a, 1 is a polluted hollow fiber membrane, 2 is a potting agent, 3 is a water outlet, 4 is a module housing, and 5 hollow fiber membranes 1 are filled inside.
Raw water is introduced into the membrane from both ends of the hollow fiber membrane 1, and the permeated water transmitted through the membrane is taken out from the take-out port 3.
As shown in FIG. 2b, a pipe is connected to the internal pressure type small module 10 to form an internal pressure type small module test device. In this test device, by opening the valves V ₁ and V ₄ and closing the valves V ₂ and V ₃ , air can be introduced into the hollow fiber membrane 1 from the pipes 11, 12, and 13. The pump P is operated, and the valve V _{3 is} opened, and the valves V ₁ , V ₂ , and V _{4 are} closed, whereby the cleaning solution in the cleaning solution tank 5 can be circulated in the pipes 14, 12, and 13. 6 is through the sink.

(2) Pass 0.15 MPa of compressed air to the raw water chamber side for 1 hour to dry the membrane.
(3) Then, circulate the cleaning solution on the side of the raw water chamber for 6 hours, and then replace the cleaning solution in the cleaning solution tank 5 with pure water, make the pump P operate, and open the valve V ₄ and close the valves V ₁ and V ₂ And valve V ₃ , whereby the inside of the hollow fiber membrane 1 is sufficiently rinsed with pure water, thereby removing the cleaning liquid.

(4) Regarding the water permeability of the new membrane before the test, the polluted membrane before cleaning and the membrane after cleaning, the pump P is operated, and the valve V _{2 is} opened, and the valves V ₁ , V ₃ , and V _{4 are} closed, thereby , The pure water corresponding to the flow rate (Flux) (transmitted stream) of 2 m ³ / m ² / d is filtered into the hollow fiber membrane 1 by total filtration, and the pressure at this time is measured using a pressure gauge PI. Calculate the water permeability of each of the new film, the contaminated film before cleaning, and the cleaned film (equivalent to the permeated flux at operating pressure of 1 bar, in lmh). Furthermore, the water permeability recovery rate was calculated by the following formula.
Water permeability recovery rate (%)
= Water permeability after cleaning [lmh] / Water permeability of new film [lmh] × 100
The results are shown in Table 2.

[Example 4]
A cleaning test was performed in the same manner except that the step (2) was omitted in Example 3. The results are shown in Table 2.

[Table 2]

As can be seen from Table 2, the water-recovery recovery rate of Example 4 which was cleaned without drying was about 30%. In contrast, the water-recovery recovery rate of Example 3 which was dried before cleaning was 99%. The cleaning effect is significantly improved.
The reason is considered to be that the turbid contamination fixed to the surface of the film is dried and shrunk by drying, thereby being easily peeled from the film, and the cleaning effect of the amphoteric surfactant is increased.

Although the present invention has been described in detail with a specific aspect, it is clear to those having ordinary knowledge in the technical field that various changes can be made without departing from the intention and scope of the present invention.
This application is based on Japanese Patent Application No. 2018-038748 filed on March 5, 2018, and the entire contents thereof are incorporated by reference.

1‧‧‧ hollow fiber membrane

2‧‧‧ potting agent

3‧‧‧ Take out through water

4‧‧‧Module housing

5‧‧‧Cleaning solution tank

6‧‧‧ through the sink

10‧‧‧Inner pressure type hollow wire small module

11, 12, 13, 14‧‧‧ Piping

P‧‧‧Pump

PI‧‧‧Pressure gauge

V ₁ , V ₂ , V ₃ , V ₄ ‧‧‧ valve

FIG. 1 is a graph showing the results of Example 1, Example 2, and Comparative Examples 1 to 4.

2a and 2b are configuration diagrams showing an internal pressure type minimodule test device manufactured in Example 3. FIG.

Claims (5)

A method for cleaning a membrane separation device is a method for cleaning a membrane separation device including a membrane module that divides an interior into a raw water chamber and a permeated water chamber by a separation membrane. In the method, the method includes an amphoteric interface. A cleaning step of the cleaning solution of the active agent contacting the membrane surface of the raw water chamber side of the separation membrane. The method for cleaning a membrane separation device according to item 1 of the scope of the patent application, wherein the cleaning solution contains 0.01% to 5% by weight of the amphoteric surfactant, and does not contain phosphorus and an oxidant. The method for cleaning a membrane separation device according to item 1 or item 2 of a patent application scope, comprising a drying step of drying the surface of the side membrane of the raw water chamber by contacting the raw water chamber with air, and The washing step is performed after the drying step. The method for cleaning a membrane separation device according to any one of claims 1 to 3 in the scope of the patent application, wherein the cleaning step includes: passing in the membrane module from a water-permeable chamber side to a raw water chamber side Either or both of the step of the cleaning solution and the step of circulating the cleaning solution on the raw water chamber side of the membrane module. The method for cleaning a membrane separation device according to any one of claims 1 to 4, wherein the membrane module is an internal pressure type hollow fiber membrane module.