JPS62110706A - Membrane treatment in reverse osmosis - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reverse osmosis separation device composed of a semipermeable composite membrane made of a crosslinked polymer containing furfuryl alcohol as an essential component or a polyamide semipermeable membrane. This invention relates to a method for separating liquids using

[Prior Art] In the past, various semipermeable membranes have been proposed as selective separation membranes using reverse osmosis, and these semipermeable membranes have been widely used in fields such as desalination of seawater and can water and recovery of valuables. It is being used.

These semipermeable membranes include asymmetric membranes typified by cellulose acetate membranes, that is, so-called Loeb membranes, as well as semipermeable barrier layers on the surface of various porous supports. There are various types of membranes including composite membranes provided with ultra-thin membranes made of polyamides different from the polymer constituting the support, crosslinked polymers of furfuryl alcohol, and the like. For example, composite membranes in which a thin film made of a crosslinked polymer of furfuryl alcohol is provided as a barrier layer on a porous support made of polysulfone, chlorinated polyvinyl chloride, etc. (U.S. Pat. No. 3,926,798), polyethylene A composite membrane with a barrier layer made of renimine crosslinked polymer (Japanese Patent Application Laid-open No. 52-1
No. 27481).

The present inventors also developed a semipermeable composite membrane using furfuryl alcohol, polyhydric alcohols such as inoyl, sorbitol, and 1-lishydroxyethyl isocyanurate in the presence of WL acid. A semipermeable composite membrane with a crosslinked polymer obtained by polycondensation as a barrier layer retains the characteristics of the composite membrane, and is resistant not only to seawater and can water but also to many water-soluble organic and inorganic compounds. We have already proposed that it has excellent selective separation performance even for
No. 24602) In addition, as polyamide semipermeable membranes, aromatic polyamides, polyaminohydrazides (U.S. Pat. No. 3
, 567, 632), polyamic acid (Special Publication No. 52-1)
52879) or a porous support membrane, and a composite membrane consisting of a crosslinked polymer obtained by reacting an amine-modified polyepihalohydrin with a polyfunctional crosslinking agent (Japanese Patent Application Laid-Open No. 52-198).
40436), and a composite membrane in which a thin polymer film, which is an interfacial reaction product of a diamine and a difunctional acid chloride, is provided on a porous support (US Pat. No. 3,744,642). An example using a mixture containing a water-soluble amino group-containing polymer and a polyfunctional amine (Japanese Unexamined Patent Publication No. 56-404)
No. 03) is also disclosed.

However, one of the most important problems in practical application of separation technology using reverse osmosis membranes is the proliferation of microorganisms on the membrane surface.

The most common method for preventing the proliferation of microorganisms on the membrane surface is to constantly or intermittently add a disinfectant to the liquid to be treated. For example, for microorganisms that adhere to and multiply on the surface of a reverse osmosis membrane, a method is known in which a disinfectant is intermittently added to the liquid to be treated (Japanese Patent Laid-Open No. 56-33009
issue). However, when selecting a disinfectant, there are many restrictions due to the characteristics of the reverse osmosis membrane material.

For example, a disinfectant with strong oxidizing power, such as free chlorine, causes deterioration of any reverse osmosis membrane other than a reverse osmosis membrane whose main component is acetic acid chloride. Also,
It is known that free chlorine reacts with organic matter in the liquid to be treated, producing 1-helihalomethane, a carcinogenic substance.
This is a serious problem when attempting to produce drinking water using reverse osmosis membranes.

From the perspective of preventing reverse osmosis membrane deterioration, disinfectants with weak oxidizing power such as chloramine are sometimes used. But in this case,
Its effectiveness as a disinfectant is often inferior to that of free chlorine. Furthermore, although the reverse osmosis membrane itself is less likely to deteriorate compared to free chlorine, it is difficult to constantly use oxidizing substances as a disinfectant, considering that the service life of reverse osmosis membranes is usually three years or more.

In addition, when non-oxidizing substances such as copper sulfate (I) are used as a disinfectant, their disinfecting power may only act selectively against certain bacteria. If the bacteria is a sulfate-reducing bacterium that can occur in an anaerobic atmosphere, the hydrogen sulfide produced by the sulfate-reducing bacteria reacts with copper ions, producing insoluble copper sulfide, leading to blockage of the reverse osmosis membrane module. In addition, when oxidizing disinfectants such as chlorine are used, oxidized colloidal sulfur of hydrogen sulfide is generated, causing similar problems.In particular, furfuryl alcohol-based semipermeable sulfur, which is one of the objects of the present invention, In order to maintain the excellent selective separation ability of the semipermeable membrane over the long term, it is necessary to remove dissolved oxygen from the raw solution to be treated in the reverse osmosis process. From this point of view, it is necessary to develop non-oxidizing disinfectants that can be used in an anaerobic atmosphere.

Under these circumstances, even if quaternary ammonium salts are placed in an anaerobic atmosphere where hydrogen sulfide is generated, it has been shown that they exhibit a bactericidal effect and do not produce insoluble reactants. However, one thing that has been shown is that it has the same bactericidal effect even in minute amounts.

[Problems to be solved by the invention] Quaternary ammonium salts have bactericidal properties against many bacteria and some fungi (molds and yeast), and are known as reverse soaps. ing. In particular, benzalkonium chloride and benzethonium chloride are listed under these names in the Japanese Pharmacopoeia Law. Its usage is 0.005 to 0
．． It is used as a 1% by weight aqueous solution to disinfect hands, surgical sites, and mucous membranes, as well as cans and machinery in the food manufacturing industry.

The present inventors have discovered that the quaternary ammonium salt of the furfuryl alcohol-based semipermeable composite membrane has the ability to restore or improve the selective separation ability of the semipermeable membrane in addition to the above-mentioned bactericidal ability. I found out what was effective and proposed it. but,
While the quaternary ammonium salt -〇- exhibits excellent sterilizing ability, it has a strong affinity with the furfuryl alcohol-based semipermeable membrane and the polyamide-based semipermeable membrane, so the amount of permeated liquid from the semipermeable membrane decreases. However, it is not practical as it is.

Under these circumstances, the present invention provides an economical and industrial solution that prevents the occurrence of the above problems without impairing the reverse osmosis separation performance of the furfuryl alcohol semipermeable membrane and polyamide semipermeable membrane. This paper examines various methods.

That is, the present invention aims to remove quaternary ammonium salts fixed on the membrane surfaces of the furfuryl alcohol-based semipermeable composite membrane and the polyamide-based semipermeable membrane in a short time and economically. This provides great benefits in the operation of actual processes using the semipermeable reverse osmosis membrane.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

A quaternary ammonium salt is intermittently added to the stock solution to be treated using a semipermeable composite membrane or polyamide semipermeable membrane equipped with a thin film made of a crosslinked polymer containing "furfuryl alcohol" as an essential component. A membrane treatment method in reverse osmosis, characterized by post-treatment with an anionic surfactant during reverse osmosis separation. A feature of the present invention is that when performing reverse osmosis separation using a semipermeable composite membrane and a polyamide semipermeable membrane provided with a thin film made of a crosslinked polymer containing furfuryl alcohol as an essential component, quaternary disinfectant can be used as a bactericidal agent. When sterilizing using ammonium salts intermittently, a sterilizing effect can be obtained without impairing the separation performance of the semipermeable reverse osmosis membrane by post-treating with an aqueous solution containing an anionic surfactant or an undiluted solution to be treated. At the point.

Examples of shells of the anionic surfactants listed above are:
Alkyl sulfates such as sodium lauryl (or dodecyl) sulfate, polyoxyethylene alkyl ether sulfates, and alkyl sulfates.
~liethanolamine and alkylbenzenesulfonic acid I~thulium.

The required concentration of the anionic surfactant is at most 0.0%, since the rate of recovery of the amount of permeate reduced by membrane treatment with a quaternary ammonium salt is only slightly faster.
At about 1 to 1% by weight, the critical micelle concentration is sufficiently reached and the amount of permeate is recovered. If it is less than 0.1% by weight, sufficient 4
Therefore, the recovery rate of the amount of permeated liquid is small, and even at a concentration of 1% by weight or more, an increase in the effect commensurate with the increase in concentration cannot be expected.

Furthermore, as long as the treatment time with the anionic surfactant is at an appropriate concentration, a sufficient quaternary ammonium salt removal effect can be obtained within several hours.

In the present invention, the semipermeable composite membrane made of furfuryl alcohol-based polymer refers to polysulfone, polyvinyl chloride,
Furfuryl alcohol or furfuryl alcohol, hydroxyethyl isocyanuric acid, inositol, or A composite film formed by applying an aqueous solution containing sulfuric acid, phosphoric acid, toluene/sulfonic acid, preferably sulfuric acid, as a reactive component system consisting of Solbi 1 Hel, etc. and heating and polymerizing it as a barrier layer as an acid catalyst. membrane, and more specifically, as described in U.S. Pat.
．． No. 926.798, Japanese Patent Publication No. 57-21364, Japanese Patent Application Publication No. 55-15'J807, and Japanese Patent Application Publication No. 1987-5
Preferred are the reaction component systems disclosed in, for example, US Pat. No. 6-15804.

In the present invention, polyamide-based semipermeable membranes include aromatic polyamides, polyamide hydrazides, and polyamic acids, specifically, those described in U.S. 'Bj.
This is a lob-type membrane disclosed in Japanese Patent No. 2-152879. In addition, crosslinked polymers obtained by reacting amine-modified polyepihalohydrin and polyfunctional acid chloride on a porous support membrane, interfacial reaction products and products consisting of diamine and polyfunctional acid chloride, water-soluble amino bases, and It is a composite membrane provided with a thin film made of an interfacial polycondensate etc. obtained by reacting a mixture containing a polymer and a polyfunctional amine with a polyfunctional acid chloride. , U.S. Patent No. 3.744.642 and JP-A-56-40
Preferred are the reactive component systems disclosed in US Pat. No. 403, for example.

[Example] Hereinafter, the effects of the present invention will be explained in more detail with reference to the following example.

Example 1 A composite membrane having a diameter of 8 inches and a length of 1 meter was made using a composite membrane provided with a thin film made of furfuryl alcohol crosslinked polymer, which was prepared based on Example 28 of Japanese Patent Publication No. 57-21364.
A reverse osmosis plant for seawater desalination using spiral-shaped elements was built on the Arabian Gulf coast. The operating conditions of the reverse osmosis equipment are: salinity 5.0%, 68ki1
0+f, pH 6.5, water temperature was 25-35°C, and water recovery rate was 40-45%. In this plant, after reducing the dissolved oxygen in the feed raw water to 1 ppm or less using vacuum degassing equipment, 20 pl) m of sodium bisulfite is added to completely remove dissolved oxygen. ing. The salt concentration in the permeated water at the start of operation was 3 ooppm, which is well within the permissible value for drinking water as stipulated by the World Health Organization (Wl-1o)! :) 00 [) r;) rTI '<h”a In addition, the amount of water produced was 2,500 liters per 7 days, which fully satisfied the design value.However,
Approximately two years after the start of operation, the vacuum degassing membrane fiii became contaminated with sulfate-reducing bacteria, and the permeated water also smelled of hydrogen sulfide. Regarding the reverse osmosis performance at that time, the salt concentration in the permeated water was 40 oppm, and the amount of water produced was 2600 liters per 7 days. Therefore, fill the entire reverse osmosis plan 1~ with the feed stock solution to which 0.1% benzene chloride 1~nium is added. Upon inspection, either the hydrogen sulfide odor had disappeared or black contaminants were present. When the reverse osmosis performance was confirmed at that time, the salt concentration in the permeated water improved to 25 Or) I) m, but the amount of produced water decreased to 22,001 m/[-1]. The entire reverse osmosis plan 1 was then again filled with feed water containing 0.2% sodium dodecyl sulfate, and the vacuum degassing equipment and reverse osmosis loading were installed in step 11. Circulation cleaning was carried out for about 2 hours each, and then immersion cleaning was carried out overnight. After blowing out the cleaning fluid, the operation of the reverse osmosis plant was restarted, and the amount of water produced recovered to 25,001 m/day.

The salt concentration in the permeated water was 350 ppm, and black contaminants in the vacuum degassing equipment had also disappeared.

Examples 2 to 4, Comparative Examples 1 to 3 Furfuryl alcohol composite membrane produced based on Example 28 of Japanese Patent Publication No. 57-21364, Japanese Patent Publication No. 52-127
Polyamide composite membranes prepared based on Example 1 of No. 481 and Example 1 of JP-A No. 56-40403 were heated at a salt concentration of 3.5%, an operating pressure of 56, 9/Cl1f, and 25°C1P.
Reverse osmosis performance was evaluated under H6.5 seawater desalination test conditions. After that, 0.1% Alkonium chloride was added to the raw water for evaluation, and after operating for 1 hour, the reverse osmosis test device was thoroughly blown 1 to 1 with distilled water, and the reverse osmosis test equipment was again subjected to the above seawater desalination test conditions. Penetration performance was evaluated. Thereafter, 0.2% sodium toluenesulfonate was added to the raw water for evaluation, and after operating for 2 hours, the reverse osmosis performance was evaluated again under the above seawater desalination test conditions. The reverse osmosis performance evaluation tests of the 8 membranes are shown in Examples 2 to 4 in Table 1. In addition, for 8 membranes, the same test as above was carried out using 0.5% of polyoxyethylene dodecyl ether instead of 1)
% concentrations are shown in the same table as Comparative Examples 1 to 3.

＋／、! Example 4 Spicil-type niremen 1~ with a diameter of 4 inches and a length of 1 meter were made using a polyamide composite membrane produced based on Example 7 described in JP-A-56-40403. Niremen 1 ~ has a salinity concentration of 4000 ppm with a hydrogen sulfide odor and dissolved oxygen in the raw water is 1 ppm or less, 22 ~ 28 °
Operating pressure 30ki/cnf, PH6 using can water of C
A can water desalination test was conducted at ~7. At the start of operation, reverse osmosis 11hi had a desalination rate of 98% and a permeated water volume of 0.52 m'
/m2・day. However, 2000 hours after the start of operation, membrane contamination due to anaerobic microorganisms occurred.
The B2 salt rate decreased to 97%, and the amount of permeated water decreased to 0.40 m
'/m2・day. At the same time, the pressure drop of Niremen 1 also increased from 0.5 kCJ/cJ to 3-/d. Therefore,
The entire reverse osmosis equipment was immersed and sterilized in feed water to which 0.01% benzyl-9-ruconium chloride had been added for 2 hours, and then thoroughly blown and sterilized with feed water. There was no recovery, and the amount of permeated water increased by an additional 0°3.
It decreased to 0 m'/m2·day. Therefore, after circulating the feed water to which 0.2% sodium dodecyl sulfate was added for 2 hours, and after immersion cleaning at night and thoroughly blowing out the cleaning agent with the feed water, the reverse osmosis performance was evaluated again. , the desalination rate has recovered to 98%, and the amount of permeated water is 0.48m!
/m2·day. Also, the element pressure loss is 0.
．． It improved to 7ks/-.

[Effects of the Invention] According to the present invention, when performing reverse osmosis separation using a furfuryl alcohol-based semipermeable composite membrane and a polyamide-based semipermeable membrane, after using a quaternary ammonium salt as a disinfectant,
By post-treatment using an anionic surfactant, (1) a bactericidal effect can be obtained without impairing the separation performance of the semipermeable reverse osmosis membrane;

■ Clean and remove dead microorganisms and some surviving microorganisms.

It is of great industrial significance for the practical application of furfuryl alcohol-based semipermeable composite membranes and polyamide-based semipermeable membranes.

Claims (1)

[Claims] (1) A quaternary ammonium salt is intermittently added to the stock solution to be treated using a semipermeable composite membrane or polyamide semipermeable membrane provided with a thin film made of a crosslinked polymer containing furfuryl alcohol as an essential component. A membrane treatment method for reverse osmosis, characterized by post-treatment with an anionic surfactant during reverse osmosis separation.