TWI752214B - Water treatment method and water treatment method containing nonionic surfactant - Google Patents

Abstract

A method for treating water containing a non-ionic surfactant, comprising: using water containing a non-ionic surfactant as supply water, passing through a microfiltration membrane or an ultra-microfiltration membrane to obtain a reduced concentration of the nonionic surfactant The permeated water is used as the adsorption step of the treated water, and at least one of an alkali agent, an anionic surfactant and an oxidant is brought into contact with the microfiltration membrane or ultra-microfiltration membrane, and the nonionic surfactant adsorbed on the filter membrane is removed. The desorption step of adsorption. A water treatment method in which the treated water is subjected to osmotic membrane treatment.

Description

Water treatment method and water treatment method containing nonionic surfactant

The present invention relates to a nonionic surfactant-containing water treatment method for removing the nonionic surfactant-containing water from the nonionic surfactant-containing water. Furthermore, the present invention relates to a water treatment method for performing reverse osmosis (RO) membrane treatment on water from which the nonionic surfactant has been removed by the nonionic surfactant-containing water treatment method of the present invention.

Non-ionic surfactants are often contained in the washing and drainage of the electronic industry or the conveying machinery industry. Nonionic surfactants are low-molecular-weight compounds that are difficult to decompose, and are difficult to remove even by coagulation treatment or biological treatment. Although nonionic surfactants can be excluded by RO membranes, they are contaminants that reduce the permeate flux of polyamide-based RO membranes that have become mainstream in recent years. Water, as the supply water for the RO membrane, will become a big obstacle to stable operation. It is difficult to recover the performance of RO membranes contaminated by non-ionic surfactants by cleaning. In this way, it is difficult to recover the waste water containing the nonionic surfactant.

When water containing a nonionic surfactant is used as feed water, there is a method of passing water at pH 9.5 or higher as a means of not reducing the permeation flux of the RO membrane (Patent Document 1). In this method, a relatively stable permeation flux can be obtained, but in order to make the supply water alkaline, a large amount of an alkali agent is required, and the quality of the permeated water is deteriorated.

A method of adsorbing and removing a nonionic surfactant with an adsorbent having a pseudo-polyamide structure before RO membrane treatment has been proposed (Patent Document 2). In this method, regeneration of the adsorbent is not considered. In addition, since it takes labor and cost to manufacture a special adsorbent, a technique for removing the nonionic surfactant more simply is required.

A method of cleaning an RO membrane using a detergent suitable for cleaning an RO membrane contaminated with a nonionic surfactant has been proposed (Patent Documents 3 and 4). Although the membrane performance can be recovered by cleaning the RO membrane, the RO membrane treatment device must be stopped in order to clean the RO membrane. When the pollution caused by the nonionic surfactant is serious, the RO membrane treatment device will be frequently stopped.

[Patent Document 1] Japanese Patent No. 4496795 [Patent Document 2] Japanese Patent No. 3864817 [Patent Document 3] Japanese Patent No. 4458039 [Patent Document 4] Japanese Patent Laid-Open No. 2015-97991

The object of the present invention is to provide a nonionic surfactant-containing water treatment method that efficiently removes nonionic surfactants from nonionic surfactant-containing water, and to reduce the amount of nonionic surfactants by this method. The concentration of the treated water is a water treatment method in which the RO membrane treatment is performed for the supply water.

The inventors found that the non-ionic surfactant will be adsorbed on the microfiltration (MF) membrane or ultra-microfiltration (UF) membrane, and the adsorbed non-ionic surfactant can be removed by alkaline agent, anionic surfactant or oxidant Therefore, in order to remove the nonionic surfactant from water containing the nonionic surfactant, it is effective to repeat the step of adsorbing the nonionic surfactant on the MF membrane or the UF membrane and the step of desorption.

The gist of the present invention is as follows.

[1] A method for treating water containing a nonionic surfactant, comprising: taking the water containing the nonionic surfactant as supply water, passing through a microfiltration membrane or an ultrafine filtration membrane to obtain a nonionic surfactant The permeated water with reduced concentration is used as the adsorption step of the treated water, and at least one of the alkali agent, anionic surfactant and oxidant is contacted with the microfiltration membrane or ultra-microfiltration membrane, and will be adsorbed on the non-ionic interface of the filter membrane The desorption step of active agent desorption.

[2] The method for treating water containing a nonionic surfactant according to [1], wherein the concentration of the nonionic surfactant supplied to the water is 20 mg/L or more.

[3] The method for treating water containing a nonionic surfactant according to [1] or [2], wherein the nonionic surfactant is not biologically treated.

[4] The method for treating water containing a nonionic surfactant according to any one of [1] to [3], wherein the microfiltration membrane or ultrafine filtration membrane is a polyvinylidene fluoride-based filtration membrane, fiber Plain filter membrane, polyether silt filter membrane or polytetrafluoroethylene filter membrane.

[5] The method for treating water containing a nonionic surfactant according to any one of [1] to [4], wherein the oxidizing agent is hypochlorous acid and/or a salt thereof.

[6] A water treatment method characterized by subjecting the treated water obtained by the treatment method for nonionic surfactant-containing water according to any one of [1] to [5] to RO membrane treatment. [Effect of invention]

According to the present invention, the nonionic surfactant in the water containing the nonionic surfactant can be efficiently removed, and the treated water whose concentration of the nonionic surfactant has been reduced by this method can be used as the supply water, and the stabilization can be continuously performed. RO membrane treatment.

Embodiments of the present invention will be described in detail below.

[Method for treating water containing nonionic surfactant] The method for treating water containing nonionic surfactant according to the present invention comprises the following steps: using water containing nonionic surfactant as supply water, and passing through microfiltration (MF) Membrane or ultra-fine filtration (UF) membrane to obtain permeated water with reduced concentration of non-ionic surfactant as the adsorption step of treated water, and at least one of alkali agent, anionic surfactant and oxidant is contacted with the MF Membrane or UF membrane, a desorption step that desorbs the nonionic surfactant adsorbed on the filter membrane.

In the present invention, "filtration" and "permeation", and "filtrate" and "permeate water" are synonymous.

<Supply water> The feed water of the present invention is water containing a nonionic surfactant. The nonionic surfactant contained in the feed water is not particularly limited. For example, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene glycol, sorbitan fatty acid ester, fatty acid glyceride, pentaerythritol fatty acid can be mentioned. Esters, propylene glycol monofatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines, fatty acid alkanolamides, etc.

Among these, a polyoxyethylene-based nonionic surfactant is preferred from the viewpoint of the adsorption properties to the MF membrane or the UF membrane. Examples of polyoxyethylene-based nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene nonylbenzene. base ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene laurate, polyoxyethylene stearate, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan monolaurate, polyoxyethylene Sorbitan monooleate, etc.

Feed water may contain only 1 type of these nonionic surfactants, or may contain 2 or more types.

The concentration of the nonionic surfactant in the feed water is not particularly limited. However, as shown in Comparative Examples 1 to 4 described later, the present invention is directed to nonionic surfactants containing a relatively high concentration that cannot be removed by the coagulation treatment of ordinary inorganic coagulants. The supply water of the surfactant is effective. The supply water is preferably a supply water with a nonionic surfactant concentration of 20 mg/L or more, for example, about 20 to 2000 mg/L.

The water containing the nonionic surfactant is not particularly limited, and examples thereof include cleaning drainage in the electronics industry or conveying machinery industry, or process drainage and domestic drainage in the food industry or cosmetic industry.

Since the non-ionic surfactant will be semi-decomposed, and it is not easy to adsorb on the MF membrane or the UF membrane, the non-ionic surfactant is preferably one that has not been biologically treated.

<Adsorption step> In the present invention, the feed water is passed through the MF membrane or the UF membrane, and the nonionic surfactant in the water is adsorbed and removed by these filter membranes.

The material of MF membrane or UF membrane is cellulose, such as cellulose acetate (CA), cellulose mixed ester (CE), polyether sintered (PES), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc., any of these can be used. The hydrophobic PVDF or PTFE is preferably subjected to hydrophilization treatment in order to improve the water permeability. It is believed that adsorption occurs due to the interaction of the hydrophilic groups of the nonionic surfactants with the hydrophilic sites of these membranes.

As shown in Examples 1-1 to 1-6 to be described later, the adsorption and desorption properties of nonionic surfactants differ depending on the membrane material, and even if the amount of adsorption is large, it is not suitable if the amount of desorption is small. for continued use. It is preferable to select and use an appropriate membrane material according to the treatment purpose in consideration of the amount of adsorption and the amount of desorption.

The smaller the pore size of the MF membrane and the UF membrane, the more the adsorption capacity of the nonionic surfactant tends to increase. From the viewpoint of water permeability or pressure loss, the larger pore size is preferred. The pore size of the MF membrane is preferably 0.01 to 1 μm, especially 0.01 to 0.45 μm, although it also varies depending on the coexisting substances or the desired properties of the treatment. The pore size of the UF membrane is preferably 0.002-0.01 μm, especially 0.005-0.01 μm.

The nonionic surfactant concentration of the permeated water (treated water) obtained in the adsorption step by the filter membrane also varies depending on the use of the treated water (how to further treat the treated water). When the treated water is subjected to the RO membrane treatment, the lower the concentration of the nonionic surfactant, the better the stable operation of the RO membrane treatment. Although it also depends on the concentration of the nonionic surfactant in the feed water, it is preferable to adsorb and remove 20 mg/L or more of the nonionic surfactant in the feed water by MF membrane or UF membrane to obtain the nonionic surfactant concentration. In the form of permeating water below 1 mg/L, the material or pore size of the filter membrane is selected, and the operating conditions of the adsorption step or the conditions of the subsequent desorption step are appropriately controlled.

<Deadsorption step> In the present invention, at least one of an alkali agent, an anionic surfactant, and an oxidizing agent is brought into contact with the MF membrane or UF membrane to which the nonionic surfactant in the feed water is adsorbed in the adsorption step, so that the adsorbent is adsorbed on the MF membrane or the UF membrane. Desorption of nonionic surfactants in filter membranes.

The alkaline agent used for desorption of the nonionic surfactant includes inorganic alkaline agents such as sodium hydroxide and potassium hydroxide.

The anionic surfactants include one or more of alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and alkyl sulfates such as sodium dodecylsulfate, sodium octylsulfate, and the like.

Examples of the oxidizing agent include halogen oxyacids such as hydrogen peroxide, peracetic acid, percarbonic acid, hypochlorous acid, and their salts (for example, alkali metal salts, alkaline earth metal salts), peroxides, halogens such as chlorine, bromine, and iodine, and the like. 1 or more of them. Among these, hypochlorous acid and hypochlorite are preferred from the viewpoint of oxidizing power, ease of handling, and cost.

The desorption step is preferably carried out by passing a solution containing one or more of these alkaline agents, anionic surfactants and oxidants (hereinafter referred to as "desorption solution") through the adsorbed nonionic interface MF membrane or UF membrane of the active agent, or backwashing the MF membrane or UF membrane with the desorption solution.

The desorption liquid is preferably an aqueous solution containing about 0.01 to 1% by weight of an anionic surfactant and adjusted to an alkaline pH of about 11 to 13 by an alkali agent. In such a desorption solution, when the nonionic surfactant adsorbed on the filter membrane cannot be sufficiently desorbed, it is preferable to treat the filter membrane with the following desorption solution: further add about 0.01 to 5% by weight of an oxidizing agent. , in the case of hypochlorous acid and/or its salts, it is a desorption solution with a concentration of about 0.001 to 1 wt % calculated based on the effective chlorine concentration.

The desorption step can also be performed when the adsorption performance of the MF membrane or the UF membrane is reduced in the adsorption step, for example, the nonionic surfactant concentration of the permeated water obtained by passing the water through the feed water exceeds the nonionic surfactant concentration of the feed water. 5% of the time. The desorption step can also be performed periodically, for example after the adsorption step at a specified time, or after a specified amount of feed water.

In the desorption step, preferably more than 50%, such as 80 to 100%, of the nonionic surfactant adsorbed on the MF membrane or the UF membrane in the adsorption step can be desorbed to control the composition of the desorption liquid or pH, amount of desorption solution or time of desorption step, etc.

By alternately repeating the adsorption step and the desorption step, the nonionic surfactant adsorbed on the MF membrane or the UF membrane in the adsorption step is desorbed by the desorption step, and the nonionic interface of the MF membrane or UF membrane can be recovered. Active agent adsorption. Therefore, the nonionic surfactant in the water containing the nonionic surfactant can be efficiently removed, and the treated water with a low concentration of the nonionic surfactant suitable for the supply water of the RO membrane or the like can be obtained.

[Water treatment method] The water treatment method of the present invention is to perform RO membrane treatment on the treated water whose nonionic surfactant concentration has been reduced by the treatment method of the nonionic surfactant-containing water of the present invention. It can prevent RO membrane fouling caused by nonionic surfactants and reduce the permeation flux caused by it, and perform stable RO membrane treatment.

The material of the RO membrane used for the RO membrane treatment is not particularly limited, and examples thereof include polyamide-based RO membranes, cellulose ester-based RO membranes, polyamide-based RO membranes, and polyimide-based RO membranes. Among these, the effect of the present invention can be remarkably obtained when a polyamide-based RO membrane having a great influence on the reduction of the permeation flux due to the nonionic surfactant is used.

The form of the RO membrane module used in the RO membrane treatment is also not particularly limited, for example, a tubular module, a flat membrane module, a spiral module, a hollow fiber module, and the like can be mentioned. [Example]

The following examples are given to illustrate the present invention in more detail.

<Nonionic Surfactant> The following nonionic surfactants were used. Polyoxyethylene (10) octyl phenyl ether "Triton X-100" (hereinafter abbreviated as "POEOPE") manufactured by Kishida Chemical Co., Ltd. Polyoxyethylene polystyryl phenyl ether "DTD51" manufactured by Takemoto Oil Co., Ltd. (hereinafter abbreviated as "POEOPE") called "POEPSPE")

<Desorption agent> The following are used as alkali agents and anionic surfactants for desorption. Sodium hydroxide (6N solution): manufactured by Kishida Chemical Co., Ltd. Sodium dodecyl sulfate: manufactured by Wako Pure Chemical Industries, Ltd. (hereinafter abbreviated as "SDS") Sodium hypochlorite solution: manufactured by Wako Pure Chemical Industries Ltd.

<Filter Membrane> As the MF membrane and UF membrane of the filter membrane, the following are used.

<MF membrane> MCE-M membrane: Cellulose mixed ester MF membrane manufactured by Merck Millipore (pore size 0.22 μm) MCE-Ms membrane: Cellulose mixed ester MF membrane manufactured by Merck Millipore Corporation (pore size 0.025 μm) MCE-A membrane: Advantec Cellulose mixed ester MF membrane (pore size 0.2 μm) manufactured by the company PES membrane: Polyether MF membrane (pore size 0.22 μm) manufactured by Merck Millipore Co., Ltd. PVDF membrane: Hydrophilic polyvinylidene fluoride MF membrane manufactured by Merck Millipore Corporation (pore size 0.22 μm) ) PTFE membrane: Hydrophilic polytetrafluoroethylene MF membrane (pore size 0.2 μm) manufactured by Merck Millipore Co., Ltd. CA membrane: Cellulose acetate MF membrane (pore size 0.2 μm) manufactured by Advantec Corporation

<UF membrane> PVDF-UF membrane: Hollow fiber polyvinylidene fluoride UF membrane (pore size 0.01 μm) manufactured by Toray Industries

The concentration of the nonionic surfactant in the liquid was measured by fluorescence analysis using a fluorescence analyzer "Aqualog" manufactured by Shimadzu Corporation.

[Adsorption, removal and desorption of nonionic surfactants made of MF membranes with different materials] <Example 1-1> The MCE-M membrane was placed on a plastic holder PFA-47 manufactured by Advantec, and 100 mg of raw water was used as /L POEOPE aqueous solution was filtered 3 times with 10 mL each time, and the POEOPE concentration of each filtrate was measured. Next, a 0.15 wt % SDS aqueous solution adjusted to pH 12 with sodium hydroxide (6N solution) as a desorption solution was passed through 10 mL of an MF membrane with POEOPE adsorbed by the permeation of an aqueous nonionic surfactant solution, and the obtained filtrate was measured. POEOPE concentration.

<Example 1-2> The same procedure as in Example 1-1 was carried out except that a PES film was used as the MF film.

<Example 1-3> The same procedure as in Example 1-1 was carried out except that a PVDF membrane was used as the MF membrane.

<Example 1-4> The same procedure as in Example 1-1 was carried out except that a PTFE membrane was used as the MF membrane.

<Example 1-5> The same procedure as in Example 1-1 was carried out except that the MCE-A film was used as the MF film.

<Example 1-6> The same procedure as in Example 1-1 was carried out except that the CA film was used as the MF film.

The POEOPE concentrations of the filtrates during adsorption and desorption in Examples 1-1 to 1-6, and the adsorption and desorption amounts obtained from the concentrations are shown in Table 1 (Table 1A to Table 1F). The ratio (percentage) of the desorption amount to the total adsorption amount is also described as the desorption rate (%).

From Table 1, the following matters can be understood. In all the examples, during the adsorption, the first 10 mL of POEOPE in the raw water was adsorbed to remove more than 20%. The MCE-M film and MCE-A film of the cellulose mixed ester film have a large amount of adsorption, and do not desorb all the adsorbed POEOPE. PES membrane, PVDF membrane and PTFE membrane have less adsorption capacity, and all POEOPE after adsorption is desorbed. The amount of desorption is larger than the amount of adsorption, which is caused by a part of POEOPE remaining on the filtrate side during adsorption, the error of the liquid amount or the measured value. The adsorption capacity of CA membrane is less than that of MCE-M and A membrane, and more than that of PES membrane, and the desorption rate is low.

[Adsorption and removal of nonionic surfactant by MF membrane with small pore size] <Reference Example 1> The MCE-Ms membrane with a pore size of 0.025 μm was placed on a plastic holder “PFA-47” manufactured by Advantec, and the raw water was used as a The 100 mg/L POEOPE aqueous solution was filtered 10 times per 10 mL, and the POEOPE concentration of the filtrate was measured. The POEOPE concentration and adsorption capacity in the filtrate are shown in Table 2.

As apparent from Table 2, compared to the results of Example 1-1 using an MCE-M membrane with a pore size of 0.22 μm, the POEOPE concentration in the filtrate was kept below 1 mg/L until the filtrate amount was 50 mL. From the results, it was found that the amount of adsorption can be increased by making the pore diameter of the MF membrane used small.

[Adsorption, removal and desorption of non-ionic surfactant by UF membrane] <Example 2> Using PVDF-UF membrane to make a mini module (6 hollow fibers, membrane length 10 cm, effective membrane area 26.4 cm ² (= 4.4cm ² x 6 strips)). The 100 mg/L POEOPE aqueous solution as raw water was passed through the hollow fiber membrane under the conditions of flux of 1 m/d, flow rate of 1.8 mL/min, and time of 5 min to make POEOPE adsorbed.

Next, the UF membrane adsorbed by POEOPE was adjusted to a 0.15 wt% SDS aqueous solution with pH 12 using sodium hydroxide (6N solution) as a desorption solution, with a flux of 1 m/d, a flow rate of 1.8 mL/min, and a time of 5 min. Backwashing conditions were performed for backwashing.

The water-passing and backwashing were alternately repeated 5 times. The permeate water obtained by water flow and the backwash solution obtained by backwashing were collected, and POEOPE concentrations were measured respectively. Table 3 shows the POEOPE concentration and adsorption amount in the permeated water during water adsorption, and the POEOPE concentration and desorption amount in the backwash solution during backwashing and desorption.

It is obvious from Table 3 that the POEOPE in the POEOPE aqueous solution with a concentration of 100 mg/L was adsorbed and removed on the UF membrane, and the POEOPE concentration in the permeated water was reduced to below 1 mg/L. In this example, it can be seen that the desorption amount of POEOPE obtained by backwashing is less than the adsorption capacity obtained by passing water, so it is necessary to increase the pH of the backwashing solution, increase the SDS concentration, add oxidants such as sodium hypochlorite, etc., more powerful Backwash.

[Adsorption, removal and desorption of different nonionic surfactants] <Reference Example 2> The PVDF membrane was placed on a plastic holder "PFA-47" manufactured by Advantec, and 10 mL of a 50 mg/L POEPSPE aqueous solution as raw water was used each time. Filter 3 times, and measure the POEPSPE concentration of each filtrate.

<Example 3-1> After the adsorption operation of filtering 10 mL of the POEPSPE aqueous solution, the desorption operation of passing through 10 mL of a 0.15 wt% SDS aqueous solution adjusted to pH 12 with sodium hydroxide (6N solution) as a desorption solution was repeated. The adsorption and desorption were carried out in the same manner as in Reference Example 2 except that the adsorption and desorption were performed three times.

<Example 3-2> After the adsorption operation of filtering 10 mL of the POEPSPE aqueous solution, sodium hypochlorite was further added to the 0.15 wt% SDS aqueous solution adjusted to pH 12 with sodium hydroxide (6N solution) as a desorption solution until effective. The chlorine concentration was calculated to be 0.1 wt % and a desorption operation of 10 mL was carried out, and the adsorption and desorption were repeated three times, except that it was carried out in the same manner as in Reference Example 2.

The filtrate concentrations of POEPSPE during adsorption and desorption in Reference Example 2 and Examples 3-1 to 3-2 are shown in Table 4 (Table 4A to Table 4C).

From Table 4, the following matters can be understood. In Reference Example 2, in the first filtration, the POEPSE concentration of the filtrate was reduced to about 40% relative to the raw water, and 60% of POEPSPE was removed. With the second and third times, the POEPSPE removed decreased.

In Example 3-1, 60% of the adsorbed POEPSPE was desorbed in the desorption step, and the second and third adsorptions were stably repeated.

In Example 3-2, POEPSPE detected from the filtrate during desorption decreased. This is considered to be due to the decomposition of POEOPE due to sodium hypochlorite. From these results, it is considered that desorption can be efficiently performed by using an oxidizing agent such as sodium chlorate in combination.

[Removal of nonionic surfactant by coagulation treatment using an inorganic coagulant] <Comparative Example 1> To a 20 mg/L POEOPE aqueous solution (raw water), a polyaluminum chloride aqueous solution (Al concentration 5.3 wt%, manufactured by Sanhui Chemical Co., Ltd.) was added , PAC) 40 mg/L, and agglutination treatment was performed at pH 7 at 150 rpm for 15 minutes. The coagulation-treated water was filtered through a hydrophilic polyvinylidene fluoride MF membrane (pore size: 0.1 m) manufactured by Merck Millipore, and the POEOPE concentration of the filtrate was measured.

In order to eliminate the influence of the adsorption of POEOPE on the MF membrane, 30 mL of pre-wash was carried out when it was used for the filtration treatment for the determination of POEOPE concentration, and the filtered water obtained after the breakthrough of the adsorption of POEOPE to the MF membrane was used as the measurement test. Sample.

<Comparative Example 2> The same procedure as in Comparative Example 1 was carried out, except that the addition amount of PAC was changed to 60 mg/L.

<Comparative Example 3> The same procedure as Comparative Example 1 was carried out, except that PAC was replaced with an aqueous solution of polyiron (III) sulfate (Fe concentration of 11.0% by weight or more, manufactured by Nippon Steel Mining Co., Ltd.).

<Comparative Example 4> The same procedure as in Comparative Example 2 was carried out except that PAC was replaced with an aqueous solution of polyiron (III) sulfate.

Table 5 shows the POEOPE concentrations of the raw water and the coagulation-treated water in Comparative Examples 1 to 4.

As can be seen from Table 5, even if the concentration of the nonionic surfactant is 20 mg/L, the nonionic surfactant can hardly be removed by the coagulation treatment by the inorganic flocculant.

On the other hand, as shown in the previous examples, the adsorption and removal of MF membrane and UF membrane can reduce the nonionic surfactant with a concentration of 100 mg/L by more than 20%. In addition, depending on the membrane material, pore diameter, and operating conditions, it can be less than 1 mg/L, and the effectiveness of the present invention is very clear.

[Confirmation of RO membrane fouling by nonionic surfactant] <Experimental example 1> Using "ES20" manufactured by Nitto Denko Corporation as the RO membrane, the temperature was 25°C, the permeation flux was 1m ³ /(m ² d), Under the condition that the recovery rate is 80%, the water solution of the nonionic surfactant is passed through water, and the change of the operating pressure is measured. As the nonionic surfactant, POEOPE and POEPSPE were used, and the concentrations thereof were 0.1, 1, and 10 mg/L. Fig. 1 and Fig. 2 show the converted permeation flux [m ³ /(m ² ･d)] obtained from the measured operating pressure at 0.75 MPa. The converted permeation flux is obtained by the following equation. Converted permeate flux=1×0.75/operating pressure

The following items can be understood from Figures 1 and 2. POEPSPE is more fouling than POEOPE membrane. When the concentration of POEOPE is 1 mg/L or less, and the concentration of POEPSPE is about 0.1 mg/L, membrane fouling can be reduced.

The present invention has been described in detail using specific aspects, but it is clearly understood by those skilled in the art that various modifications can be made without departing from the intent and scope of the present invention. This application is based on Japanese Patent Application No. 2017-105653 filed on May 29, 2017, the entirety of which is incorporated herein by reference.

[ Fig. 1] Fig. 1 is a graph showing the change over time of the permeation flux when the POEOPE aqueous solution was passed through in Experimental Example 1. [Fig. [Fig. 2] Fig. 2 is a graph showing the change over time of the permeation flux when the POEPSPE aqueous solution was passed through in Experimental Example 1. [Fig.

Claims (7)

A method for treating water containing a non-ionic surfactant, comprising: using water containing a non-ionic surfactant as supply water, passing through a microfiltration membrane or an ultra-microfiltration membrane to obtain a reduced concentration of the nonionic surfactant The permeated water is used as the adsorption step of the treated water, and the solution containing alkali agent and anionic surfactant is contacted with the microfiltration membrane or ultra-microfiltration membrane, and the nonionic surfactant adsorbed on the filter membrane is desorbed and removed. adsorption step. The method for treating water containing a nonionic surfactant according to claim 1, wherein the concentration of the nonionic surfactant supplied to the water is 20 mg/L or more. The method for treating water containing a nonionic surfactant according to claim 1 or 2, wherein the solution further contains an oxidizing agent. The method for treating water containing a nonionic surfactant according to claim 1 or 2, wherein the aforementioned nonionic surfactant has not been biologically treated. The method for treating water containing a nonionic surfactant as claimed in claim 1 or 2, wherein the microfiltration membrane or ultra-microfiltration membrane is a polyvinylidene fluoride-based filter membrane, a cellulose-based filter membrane, or a polyether susceptor-based filter membrane. Filter membrane or Teflon-based filter membrane. The method for treating water containing a nonionic surfactant according to claim 3, wherein the oxidizing agent is hypochlorous acid and/or a salt thereof. A water treatment method characterized by subjecting the treated water obtained by the treatment method for water containing a nonionic surfactant according to any one of claims 1 to 6 to RO membrane treatment.

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