JP2023019641A - Reusing method of waste water - Google Patents

Abstract

To provide a reusing method of waste water capable of reusing the waste water containing a surfactant and an oil by purification in a simple method.SOLUTION: In a reusing method of waste water where (a) a polymer coagulant (hereafter described as (a) component) having spinnability and (b) bentonite (hereafter described as (b) component) are mixed in the waste water and an aqueous layer is reused as water after standing,: the waste water containing a surfactant and an oil is mixed with the (b) component at a ratio of 5 pts.mass or more and 100 pts.mass or less to 1,000 pts.mass of the waste water; and the (a) component and the (b) component are mixed so that a mass ratio (b)/(a) becomes 100 or more and 3,000 or less.SELECTED DRAWING: None

Description

The present invention relates to a method for recycling waste water.

Securing safe water is one of the most important activities in general life. In developed countries, the development of infrastructure related to water use is progressing. However, there are still many areas on the earth where sufficient water cannot be secured, and people living in such areas are currently forced to exert a great deal of effort to secure water. Therefore, there is a strong demand for a technology capable of easily purifying contaminants such as sludge present in river water, lake water, groundwater, rainwater, and the like. In addition, examples of water that requires treatment include wastewater discharged from washing objects contaminated with oil in general life and various industrial fields. Some of them contain oils such as oil, animal and vegetable oils and petroleum hydrocarbons, which are sources of pollution, and surfactants contained in detergents and the like.

Patent Document 1 describes a coagulation-sedimentation treatment method using bentonite alone as an adsorbent and coagulation aid for the removal of water-soluble substances from industrial wastewater, or using this together with an inorganic or organic sedimentation agent alone or in combination. .
Patent Document 2 describes a surfactant-containing wastewater treatment agent containing a formaldehyde condensate obtained by condensation reaction of dihydroxydiphenyl sulfones, an aromatic compound having a sulfonic acid group, and formaldehyde.
In Patent Document 3, in a method for treating wastewater containing resin particles (A) having a volume average particle size of 0.0005 to 500 μm, a surfactant (B) and/or a water-soluble polymer (C), an inorganic A method for treating waste water is described which includes the steps of adding a flocculant (a), adding a polymeric flocculant (b) and optionally adding an organic coagulant (c).

JP-A-48-40260 JP-A-2001-96279 Japanese Unexamined Patent Application Publication No. 2006-7208

Wastewater discharged from laundry, washing dishes, washing the body, etc. is currently discarded as it is, and it is difficult to say that it is reused sufficiently. This is because wastewater often contains surfactants and oils, and surfactants, oils themselves, and oil stains emulsified, solubilized, and dispersed by surfactants cannot be easily separated from water. Reuse of wastewater requires consideration from a different perspective from the viewpoint of reuse of industrial water and waste liquid treatment that meets environmental standards. That is, in order to treat and reuse wastewater in general households, for example, when contaminants are aggregated to form aggregates (also referred to as flocs) and separated, the aggregates can be easily formed in a short time. There is a demand for a method that can be easily reused, such as sedimentation in a short period of time and the ability to use the supernatant without filtering. Further, by purifying the waste water containing the surfactant and the oil, water resources can be effectively utilized as gray water used for cleaning oil stains, cleaning toilets, and the like.

The present invention provides a method for reusing waste water, which enables waste water containing a surfactant and oil to be purified by a simple method and reused.

In the present invention, (a) a polymer flocculant having stringiness [hereinafter referred to as component (a)] and (b) bentonite [hereinafter referred to as component (b)] are mixed with wastewater, and after standing, a water layer is reused as water,
the effluent contains surfactants and oils;
Component (b) is mixed in a proportion of 5 parts by mass or more and 100 parts by mass or less with respect to 1,000 parts by mass of waste water,
(a) component and (b) component are mixed so that the mass ratio of (b)/(a) is 100 or more and 3000 or less,
It relates to a method for reusing wastewater.

ADVANTAGE OF THE INVENTION According to this invention, the recycling|reuse method of waste_water|drain which can purify and reuse the waste_water|drain containing surfactant and oil by a simple method is provided. The method of the present invention is excellent in the effect of purifying wastewater containing surfactants and oils. and oil can be removed efficiently. And the water layer after treatment obtained by the method of the present invention is clear and clean. That is, in the waste water reuse method of the present invention, reusable water can be produced from waste water.

As noted above, wastewater often contains surfactants and oils. The present invention recycles wastewater containing surfactants and oils. In the present invention, the component (b) aggregates dirt components such as surfactants and oils in waste water to form aggregates, and the component (a) intervenes between the aggregates to bond the aggregates together. is presumed to promote Since the component (a) has stringiness, it is presumed that it entangles the aggregates and further promotes the bonding of the aggregates. As a result, in the present invention, even if the wastewater contains a surfactant or oil, it is believed that aggregates are quickly formed and an excellent purification effect is exhibited. Even among polymer compounds known as flocculants, those that do not have stringiness take a long time for the flocculate to settle, and the effects of the present invention cannot be obtained.

Component (a) is a stringy polymer flocculant.

In the present disclosure, the term "stringiness" refers to the so-called "stringing" property in which the extensibility property of an object appears, such as "stringing of natto". Spinnability, in one or more embodiments, exhibits a continuous filamentous structure without breaking to form droplets when the liquid composition is dropped at a low speed or held at one end and stretched. It is a property, for example, "stringing of mucus of animals and plants". Spinnability is one of the elastic relaxation phenomena of liquid compositions, and is generally known to be a physical property completely independent of surface tension and viscosity.
Regarding the component (a), the presence or absence of stringiness can be determined by the following method. For example, using an aqueous solution obtained by dissolving a polymer flocculant in purified water so as to have a predetermined concentration (e.g., 10% by mass), it is determined by a method according to the following [Determination method for stringiness]. If it has stringiness, it can be determined to be a polymer flocculant with stringiness.

[Method for judging stringiness]
When gently dripping from a Pasteur pipette with a tip inner diameter of 1 mm (glass, for example, ASAHITECHNOGLASS, IK-PAS-5P), the aqueous solution that draws strings can be an aqueous solution that exhibits stringiness in the present disclosure. .

Component (a) is preferably a polymer flocculant whose aqueous solution at a concentration of 30 g/L or less exhibits stringiness, and more preferably a polymer flocculant whose aqueous solution at a concentration of 10 g/L or less exhibits stringiness. and more preferably a polymer flocculant whose aqueous solution at a concentration of 5 g/L or less exhibits stringiness.

The weight average molecular weight of component (a) is preferably 500,000 or more, more preferably 800,000 or more, still more preferably 2,000,000 or more, and preferably 15,000,000 or less, more preferably 12,000,000 or less. It is preferably 10,000,000 or less. The weight-average molecular weight of component (a) is calculated from the intrinsic viscosity for polyethylene oxide, and is calculated from gel permeation chromatography (GPC) for the others.

The polymer flocculant of component (a) is a water-soluble (co)polymer having a water-soluble monomer (a1) as a constituent unit and is a water-soluble (co)polymer having spinnability. agents. Water-soluble monomers (a1) include the following nonionic monomers (a11), cationic monomers (a12), anionic monomers (a13) and mixtures of two or more thereof. Water-soluble monomers are preferably water-soluble unsaturated monomers. As the monomers constituting the water-soluble (co)polymer, in addition to the water-soluble monomer (a1), a water-insoluble unsaturated monomer (x) and a crosslinkable monomer (y) may be used as long as the effect of the present invention is not impaired. may be used together. Among the water-soluble copolymers containing the following water-soluble monomers as structural units, those having spinnability can be used as the component (a) of the present invention.

Here, the water-soluble monomer or water-soluble (co)polymer means a monomer or (co)polymer whose solubility in water (20 ° C.) is 1 g / 100 g of water or more, and the water-insoluble monomer means It means a monomer whose solubility (20° C.) is less than 1 g/100 g of water.

In the following, number average molecular weight and weight average molecular weight measured by gel permeation chromatography (GPC) are abbreviated as GMn and GMw, respectively, and GMn and GMw are determined under the following GPC measurement conditions.
<GPC measurement conditions>
Apparatus: HLC-802A, manufactured by Tosoh Corporation Column: TSKgelGMH6 (2 pieces)
Measurement temperature: 40°C
Sample solution: 0.5 mass% tetrahydrofuran solution Injection amount: 200 µl
Detection device: refractive index detector Standard: polyethylene glycol

(a11) (Meth)acrylates include the following and mixtures thereof.
(a11-1) (Meth)acrylic acid ester A carbon number (hereinafter abbreviated as C) of 4 or more and a number average molecular weight [measured by gel permeation chromatography (GPC). Hereinafter abbreviated as GMn. ] 5,000 or less, for example, hydroxyl group-containing (meth) acrylate [for example, hydroxyethyl-, diethylene glycol mono-, polyethylene glycol (degree of polymerization 3 or more to 50 or less) mono- and polyglycerol (degree of polymerization 1 or more to 10 or less) mono (meth) acrylate] and alkyl acrylate (alkyl group is C1 or more and 2 or less) ester (C4 or more and 5 or less, e.g. methyl acrylate, ethyl acrylate)
(a11-2) (meth)acrylamide and derivatives thereof C3 to 30, such as (meth)acrylamide, N-alkyl (C1 to 3) (meth)acrylamide [N-methyl and isopropyl (meth)acrylamide, etc.], N - Alkylol (meth)acrylamide [N-methylol (meth)acrylamide, etc.]
(a11-3) Nitrogen atom-containing ethylenically unsaturated compounds other than the above C3 or more and 30 or less, such as acrylonitrile, N-vinylformamide, N-vinyl-2-pyrrolidone, N-vinylimidazole, N-vinylsuccinimide, N-vinyl Carbazole and 2-cyanoethyl (meth)acrylate (a11-4) alkylene oxide ethylene oxide, propylene oxide

(a12) Cationic monomers, salts thereof [e.g. inorganic acid (hydrochloric, sulfuric, phosphoric, nitric, etc.) salts, methyl chloride, dimethyl sulfate and benzyl chloride salts, etc.], and mixtures thereof mentioned.
(a12-1) Nitrogen atom-containing (meth)acrylate C5 to 30, such as aminoalkyl (C2 to 3) (meth)acrylate, N,N-dialkyl (C1 to 2) aminoalkyl (C2 to 3) (Meth)acrylates [N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate etc.], heterocycle-containing (meth) acrylate [N-morpholinoethyl (meth) acrylate, etc.]
(a12-2) Nitrogen atom-containing (meth)acrylamide derivative C5 or more and 30 or less, such as N,N-dialkyl (C1 or more and 2 or less) aminoalkyl (C2 or more and 3 or less) (meth)acrylamide [N,N-dimethylaminoethyl (Meth) acrylamide, etc.];
(a12-3) Ethylenically unsaturated compound having an amino group C5 or more and 30 or less, such as vinylamine, vinylaniline, (meth)allylamine, p-aminostyrene, etc.]
(a12-4) Compound having an amine imide group C5 or more and 30 or less, such as 1,1,1-trimethylamine (meth)acrylimide, 1,1-dimethyl-1-ethylamine (meth)acrylimide, 1,1-dimethyl- 1-(2'-phenyl-2'-hydroxyethyl)amine (meth)acrylimide, etc. (a12-5) Nitrogen atom-containing vinyl monomers other than the above C5 or more and 30 or less, such as 2-vinylpyridine, 3-vinylpiperidine, vinylpyrazine, vinylmorpholine

(a13) Anionic monomers The following acids, salts thereof [alkali metal (lithium, sodium, potassium, etc., the same shall apply hereinafter.) salts, alkaline earth metal (magnesium, calcium, etc., the same shall apply hereinafter.) salts, ammonium salts and amine (C1 or more and 20 or less) salts], and mixtures thereof.
(a13-1) unsaturated carboxylic acid C3 or more and 30 or less, such as (meth)acrylic acid, (anhydrous) maleic acid, fumaric acid, (anhydrous) itaconic acid, vinyl benzoic acid, allylacetic acid (a13-2) unsaturated sulfone Acids C2 to 20 aliphatic unsaturated sulfonic acids (vinylsulfonic acid, etc.), C6 to 20 aromatic unsaturated sulfonic acids (styrenesulfonic acid, etc.), sulfonic acid group-containing (meth)acrylates [sulfoalkyl (C2 20 or less) (meth)acrylates [2-(meth)acryloyloxyethanesulfonic acid, 2-(meth)acryloyloxypropanesulfonic acid, 3-(meth)acryloyloxypropanesulfonic acid, 2-(meth)acryloyloxybutane sulfonic acid, 4-(meth)acryloyloxybutanesulfonic acid, 2-(meth)acryloyloxy-2,2-dimethylethanesulfonic acid, p-(meth)acryloyloxymethylbenzenesulfonic acid, etc.], sulfonic acid group-containing ( meth)acrylamide [2-(meth)acryloylaminoethanesulfonic acid, 2- and 3-(meth)acryloylaminopropanesulfonic acid, 2- and 4-(meth)acryloylaminobutanesulfonic acid, 2-(meth)acryloylamino -2,2-dimethylethanesulfonic acid, p-(meth)acryloylaminomethylbenzenesulfonic acid, etc.], alkyl (C1 to 20) (meth)allylsulfosuccinate [methyl(meth)allylsulfosuccinate, etc.], etc. (a13-3) (meth)acryloylpolyoxyalkylene (C1 or more and 6 or less) sulfate ester (meth)acryloylpolyoxyethylene (polymerization degree of 2 or more and 50 or less) sulfate ester and the like.

Examples of the water-insoluble unsaturated monomer (x) that may be used in combination with (a) if necessary include the following (x1) to (x5) and mixtures thereof.

(x1) C6 to 23 (meth)acrylates Aliphatic or alicyclic alcohol (C3 to 20) (meth)acrylates [propyl-, butyl-, lauryl-, octadecyl- and cyclohexyl (meth)acrylate, etc.] and epoxy group (C4 or more and 20 or less) containing (meth) acrylate [glycidyl (meth) acrylate, etc.]

(x2) [monoalkoxy (C1 or more and 20 or less)-, monocycloalkoxy (C3 or more and 12 or less)- or monophenoxy] polypropylene glycol (hereinafter abbreviated as PPG) (degree of polymerization of 2 or more and 50 or less) unsaturated carboxylic acid Monoester monool (C1 or more and 20 or less) or monohydric phenol (C6 or more and 20 or less) propylene oxide (hereinafter abbreviated as PO) adduct (meth)acrylic acid ester [ω-methoxy PPG mono (meth) acrylate, ω -ethoxy PPG mono (meth) acrylate, ω-propoxy PPG mono (meth) acrylate, ω-butoxy PPG mono (meth) acrylate, ω-cyclohexyl PPG mono (meth) acrylate, ω-phenoxy PPG mono (meth) acrylate, etc.] and (meth)acrylic acid esters of PO adducts of diols (C2 or more and 20 or less) or dihydric phenols (C6 or more and 20 or less) [ω-hydroxyethyl (poly)oxypropylene mono(meth)acrylate, etc.], etc.

(x3) C2 to 30 unsaturated hydrocarbons ethylene, nonene, styrene, 1-methylstyrene, etc. (x4) unsaturated alcohol [C2 to 4, for example, vinyl alcohol, (meth)allyl alcohol] carboxylic acid (C2 30 or less) ester (vinyl acetate, etc.)
(x5) a halogen-containing monomer (C2 or more and 30 or less, such as vinyl chloride)

Further, as the crosslinkable monomer (y), the following (y1) to (y5), salts thereof [for example, basic monomers include inorganic acids (hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, Sulfurous acid, phosphoric acid, nitric acid, etc.) salts, methyl chloride salts, dimethyl sulfates and benzyl chloride salts. , cyclohexylamine) salts], and mixtures thereof.

(y1) Bispoly (2 or more and 4 or less) (meth)acrylamide C5 or more and 30 or less, for example, N,N'-methylenebisacrylamide

(y2) Poly(2 or more and 4 or less) (meth)acrylate C8 or more and 30 or less, such as ethylene glycol di(meth)acrylate, pentaerythritol [poly(2 or more and 4 or less)] (meth)acrylate

(y3) Vinyl group (2 or more and 20 or less) monomer C4 or more and GMn 6,000 or less, such as divinylamine, polyvalent (2 or more and 5 or less) amine [C2 or more and GMn 3,000 or less, such as ethylenediamine, polyethyleneimine (C4 or more and GMn 3,000 or less)] poly(2 or more and GMn 3,000 or less)] vinylamine, divinyl ether, polyhydric alcohol [C2 or more and GMn 3,000 or less, for example, alkylene (C2 or more and 6 or less) alkylene glycol [ethylene glycol, propylene glycol , 1,6-hexanediol (hereinafter abbreviated as EG, PG, HD, respectively), etc.], polyoxyalkylene [GMn 2,000 or more and 3,000 or less, for example, polyethylene glycol (hereinafter abbreviated as PEG) (molecular weight of 106 or more and GMn 3,000 or less), PPG (molecular weight 134 or more and GMn 3,000 or less), polyoxyethylene (molecular weight 106 or more and GMn 3,000 or less) / polyoxypropylene (molecular weight 134 or more and GMn 3,000 or less) block copolymer], tri methylolethane, trimethylolpropane, (poly) (2 to 50) glycerin, pentaerythritol, sorbitol (hereinafter abbreviated as TME, TMP, GR, PE, SO), starch] poly(2 to 20) vinyl ether etc

(y4) allyl group (2 or more and 20 or less) containing monomer C6 or more and GMn 3,000 or less, such as di(meth)allylamine, N-alkyl (C1 or more and 20 or less) di(meth)allylamine, polyvalent amine (above poly(2 or more and 20 or less) (meth)allylamine, di(meth)allyl ether, poly(2 or more and 20 or less) (meth)allyl ether of polyhydric alcohol (the above), poly(2 or more and 20 below) (meth)allyloxyalkane (C1 or more and 20 or less) (tetraallyloxyethane, etc.)

(y5) Epoxy group-containing monomer C8 or more and GMn 6,000 or less, such as EG diglycidyl ether, PEG diglycidyl ether, GR triglycidyl ether

Component (a) consists of a water-soluble (co)polymer having constituent units of one or more water-soluble monomers selected from the nonionic monomer (a11) and the anionic monomer (a13). Examples include polymer flocculants having stringiness.
As the component (a), a water-soluble (co)polymer having the nonionic monomer (a11) as a structural unit and a water-soluble (co)polymer having the anionic monomer (a13) as a structural unit Polymer flocculants having stringiness, which are composed of one or more selected water-soluble (co)polymers, may be mentioned.
As the water-soluble (co)polymer having the nonionic monomer (a11) as a structural unit, (a11-2) (meth)acrylamide and derivatives thereof, and (a11-4) one selected from alkylene oxide Examples include water-soluble (co)polymers having constituent units of the above nonionic monomers and one or more nonionic monomers selected from the above (a11-4) alkylene oxides.
Examples of the water-soluble (co)polymer having the anionic monomer (a13) as a structural unit include a water-soluble (co)polymer having (a13-1) unsaturated carboxylic acid as a structural unit. Component (a) is preferably one or more stringy polymer flocculants selected from stringy nonionic polymer flocculants and stringy anionic polymer flocculants. Component (a) is more preferably a spinnable nonionic polymer flocculant. Component (a) includes at least one stringy polymer flocculant selected from polyalkylene oxide, polyacrylamide, and polyacrylic acid or a salt thereof. Component (a) is preferably a polyalkylene oxide having stringiness, and more preferably a polyethylene oxide having stringiness.

The polyalkylene oxide preferably contains ethylene oxide as a polymerized unit.
Polyalkylene oxide is preferably polyethylene oxide. Polyethylene oxide is preferably polyethylene oxide having a weight average molecular weight of 500,000 or more.

Component (b) is bentonite.
The component (b) bentonite is a general term for clay containing montmorillonite as a main component. Since bentonite contains a large amount of layered aluminum phyllosilicate, it has high water absorption and ion exchange properties. Some bentonites contain cations such as sodium, calcium, and potassium in addition to aluminum as cations, and are classified according to the type of these cations, such as sodium bentonite and calcium bentonite.

In the present invention, the degree of swelling of the component (b) bentonite is 5 mL/2 g or more, preferably 10 mL/2 g or more, and 50 mL/2 g or less, preferably 40 mL/2 g or less, from the viewpoints of cohesion performance improvement and handling. , more preferably 35 mL/2 g or less.

The degree of swelling is measured according to the swelling test method for bentonite (powder) specified by the Japan Bentonite Industry Association JBAS104:77. Specifically, 2.0 g of a sample adjusted to have a water content of 8.0% by mass is added in about 10 portions to a 100-ml stoppered graduated cylinder containing 100 ml of distilled water. At this time, the next addition is made after the previous addition has settled on the bottom of the graduated cylinder. After the final addition, the apparent volume of the swelling of the sample mass at the bottom of the graduated cylinder when left at 25 ° C. ± 0.5 ° C. for 24 hours was read from the scale of the graduated cylinder, and the degree of swelling (mL / 2 g ).

In the present invention, from the viewpoint of improving flocculation performance and handling, component (b) is added to 1,000 parts by mass of wastewater at 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, More preferably 20 parts by mass or more and 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less are mixed.

In the present invention, from the viewpoint of improving flocculation performance and handling, component (a) and component (b) are mixed so that the mass ratio of (b)/(a) is 100 or more, preferably 300 or more, more preferably 500 or more. , more preferably 800 or more, and 3000 or less, preferably 2500 or less, more preferably 2000 or less, still more preferably 1500 or less.

In the present invention, after satisfying the mass ratio (b) / (a), the concentration of the component (a) in the wastewater to be treated is 1 ppm or more, further 5 ppm or more, and further It can be mixed so that it is 10 ppm or more, 500 ppm or less, further 100 ppm or less, and further 50 ppm or less.

In the present invention, after satisfying the mixing amount and the mass ratio (b)/(a) with respect to the waste water, the component (b) is added, for example, the concentration of the component (b) in the waste water to be treated is 3000 ppm or more. , further 5000 ppm or more, further 10000 ppm or more, and further 80,000 ppm or less, further 50,000 ppm or less, further 30,000 ppm or less.

In the present invention, optional components include water-soluble inorganic compounds, bleaching agents, disinfectants, antibacterial agents, preservatives, pH adjusters, and anti-redeposition agents (excluding components (a) and (b)). can be mixed.

The wastewater targeted by the present invention contains a surfactant and oil. The wastewater includes, for example, wastewater after washing an oil-contaminated object with a detergent containing a surfactant. Wastewater includes those discharged as domestic wastewater, urban wastewater, industrial wastewater, and the like. Drainage such as domestic wastewater generally contains various fouling components. The fouling components contained in the waste water may be formed of organic substances, inorganic substances, and composites thereof.
In addition to surfactants and oils, dirt components include, for example, soil (which may include clay, mud, etc.), bacteria, heavy metals and their ions, sebum, lipids, dyes, keratin, hair, dyes, and pigments. , food, and fiber. Contamination components other than the surfactant and oil contained in the wastewater may be determined according to the use of the water after treatment.

The present invention is directed to wastewater containing surfactants and oils. In the present invention, it has been found that when the components (a) and (b) are used under conditions where surfactants and oils coexist in waste water, an excellent water purification effect can be obtained. Surfactants and oils may be included in the wastewater as soiling components and/or as separately added components.

The surfactant contained in the wastewater includes one or more surfactants selected from anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. The surfactant may be a surfactant with a molecular weight of less than 500,000. From the viewpoint of high removal effect from the waste water according to the present invention, it is preferable that the waste water contains a nonionic surfactant as a surfactant.
Nonionic surfactants include polyoxyalkylene alkyl or alkenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, fatty acid monoglycerides, polyethylene glycol fatty acid esters, and the like.
Examples of anionic surfactants include anionic surfactants having a hydrocarbon group having 8 to 24 carbon atoms and a sulfonic acid group or a sulfate ester group. A sulfonic acid group or a sulfate ester group may be a salt. Anionic surfactants having a sulfate group include alkyl or alkenyl sulfates, polyoxyalkylene alkyl or alkenyl ether sulfates. Anionic surfactants having sulfonate groups include alkylbenzene sulfonates. Other anionic surfactants include fatty acids having from 12 to 24 carbon atoms or salts thereof.
Cationic surfactants include quaternary ammonium type surfactants and tertiary amine type surfactants.
The amphoteric surfactant is not particularly limited, but for example N-alkyl-N,N-dimethyl having an alkyl group having 8 or more, preferably 10 or more, and 18 or less, preferably 16 or less carbon atoms. Amine oxide, N-alkylcarbonylaminopropyl-N,N-dimethylamine oxide having an alkyl group having a carbon number within the above range, N-alkyl-N,N-dimethylaminoacetic acid betaine having an alkyl group having a carbon number within the above range , N-alkylcarbonylaminopropyl-N,N-dimethylaminoacetic acid betaine having an alkyl group having a carbon number within the above range, N-alkyl-N,N-dimethyl-N-( 2-hydroxysulfopropyl)ammonium sulfobetaine and the like.

The concentration of the surfactant in the waste water is, for example, 1 ppm or more, further 10 ppm or more, further 50 ppm or more, further 100 ppm or more, further 500 ppm or more, and further 50,000 ppm or less, further 10,000 ppm or less, further 5,000 ppm or less, Furthermore, it is 3,000 ppm or less. The waste water before adding the components (a) and (b) may contain the surfactant at this concentration. Alternatively, a surfactant may be added to the waste water containing the surfactant or to the waste water not containing the surfactant to adjust the concentration to this level.

Oils contained in the waste water include oils selected from animal and vegetable oils and petroleum hydrocarbons.
Animal and vegetable oils include drying oils (iodine value 130 or more) such as linseed oil and sunflower oil, semi-drying oils (iodine value 100 to 130) such as soybean oil, sesame oil, and rapeseed oil, castor oil, olive oil, palm oil, Non-drying oils such as coconut oil (iodine value of 100 or less) are included.
Petroleum hydrocarbons include compounds contained in petroleum-derived products such as gasoline, light oil, heavy oil, and mineral oil.

The concentration of oil in waste water is, for example, 0.1 ppm or more, further 1 ppm or more, further 5 ppm or more, further 10 ppm or more, further 50 ppm or more, and 10,000 ppm or less, further 5,000 ppm or less, further 1,000 ppm or less, Furthermore, it is 500 ppm or less. The wastewater before adding the components (a) and (b) may contain animal and vegetable oils and petroleum hydrocarbons at this concentration. Alternatively, the concentration may be adjusted by adding animal or vegetable oils or petroleum hydrocarbons to waste water containing animal or vegetable oils or petroleum hydrocarbons or to waste water not containing animal or vegetable oils or petroleum hydrocarbons.

Waste water may contain soil as a fouling component. The concentration of the soil in the waste water before adding the components (a) and (b) is, for example, 0.1 ppm or more, further 1 ppm or more, further 10 ppm or more, and 100,000 ppm or less, further 10,000 ppm or less, Furthermore, it is 5,000 ppm or less.

In the present invention, although the order and form of adding the components (a) and (b) to the waste water are not limited, it is preferable to add the component (a) after adding the component (b).

In the present invention, the components (a) and (b) are mixed in the waste water in a predetermined ratio, and after standing, the water layer is reused as water. In the present invention, the concentration of the surfactant and the concentration of the oil in the wastewater after mixing the components (a) and (b) and before standing are preferably within the above ranges.

In the present invention, it is preferable that the pH of the wastewater containing the components (a) and (b) is 4 or more, more preferably 5 or more, and 9 or less, more preferably 8.5 or less. That is, it is preferable to leave the waste water at rest after adjusting the pH of the waste water to the above range. The pH can be adjusted with alkaline agents such as caustic soda, sodium carbonate, sodium hydrogen carbonate, sodium silicate and monoethanolamine, and acid agents such as organic acids such as sodium hydrogen sulfate, citric acid and lactic acid.

Mixing may be performed with stirring.
Standing can be performed by leaving the mixture to stand after mixing. The standing time can be, for example, 1 minute or longer, 5 minutes or longer, and 60 minutes or shorter, and 30 minutes or shorter. The stationary temperature can be, for example, 5° C. or higher and 80° C. or lower.
By standing, the aggregate settles, and the aqueous layer is reused as water, for example, domestic water, industrial water, and the like. After standing, the waste water in which the aggregates have settled can be subjected to a method such as filtration, decantation, or extraction of the underlying aggregate layer to obtain a water layer, if necessary.
The obtained water in the water layer can be used, for example, as gray water for cleaning oil stains, flushing toilets, and the like.

(1) Preparation method of model domestic wastewater Put 450g of ion-exchanged water in a 1000ml glass beaker, add the surfactant shown in Table 1 so that the concentration in the model domestic wastewater becomes the value shown in Table 1, magnetic Stir with a stirrer for 1 minute. Next, mineral oil [Mobil DTE 22 by adding 0.4% by mass of Sudan IV (manufactured by Fujifilm Wako Pure Chemical Industries) for dyeing] was added so that the concentration in the model domestic wastewater became the value shown in Table 1. It was added and stirred with a magnetic stirrer for 60 minutes to prepare a model domestic wastewater.

(2) Evaluation The purification effect of the model domestic wastewater prepared above was evaluated. Table 1 shows the results.
(2-1) Sedimentation time of aggregates While stirring the model domestic wastewater with a magnetic stirrer, add the component (b) so that the concentration in the model domestic wastewater for evaluation becomes the value shown in Table 1, and 15 After a minute, an aqueous solution prepared with ion-exchanged water so that the concentration of the component (a) was 1,000 ppm was added so that the concentration of the component (a) in the evaluation model domestic wastewater became the value shown in Table 1. Finally, ion-exchanged water was added so that the total liquid volume was 1000 g, and the mixture was stirred for a total of 25 minutes to obtain a model domestic wastewater for evaluation. After stirring, the mixture was allowed to stand in a room whose temperature was adjusted to 25°C. After standing, the aggregates were observed, and the time until the volume of the aggregates reached 500 ml was measured and taken as the sedimentation time of the aggregates.

(2-2) Surface tension of supernatant liquid 20 ml of the supernatant at the time when the sedimentation time of the aggregates was determined in (2-1) was collected, and a surface tension meter (AN-526P manufactured by Nippon Oil Testing Machine Industry Co., Ltd.) was used. The surface tension was measured and calculated as a value corrected with distilled water (literature value: 72.75 mN/m) and ethanol (literature value: 22.55 mN/m). The higher the surface tension, the smaller the amount of surfactant in the supernatant, which means the better effect of removing the surfactant.

(2-3) Oil content of supernatant (ppm)
10 ml of the supernatant collected in (2-2) above was sampled, and the absorbance at 260 nm was calculated using a UV-visible spectrophotometer (UV-160A manufactured by Shimadzu Corporation). A calibration curve was prepared using a sample of mineral oil dissolved in n-hexane.

The ingredients in the table are as follows. The surfactant POE is an abbreviation for polyoxyethylene, and the number in parentheses is the average added mole number. The numbers in parentheses for component (a) are weight average molecular weights.
(a) Component ・PEO (7 million): Polyethylene oxide, Alcox E-300, Meisei Chemical Industry Co., Ltd., with spinnability ・PEO (5 million): Polyethylene oxide, Alcox E-240, Meisei Chemical Industry Manufactured by Co., Ltd., with spinnability ・PEO (2 million): Polyethylene oxide, Alcox E-75, Meisei Chemical Industry Co., Ltd., with spinnability ・PEO (800,000): Polyethylene oxide, Alcox E-45 , Meisei Chemical Industry Co., Ltd., with stringiness ・AAm (5 million): Polyacrylamide, Fujifilm Wako Pure Chemical Industries, Ltd., with stringiness (b) component ・Bentonite: TB-250, Tachibana Co., Ltd. Material Swelling degree 14mL/2g
(b') component (comparative component of (b) component)
・ Kasaoka clay: Kasaoka clay, manufactured by Kasanen Industry Co., Ltd. Swelling degree 2 mL / 2 g
・Pulverized clay for civil engineering: Sumiclay, manufactured by Sumitomo Osaka Cement Co., Ltd.

From the surface tension values of the supernatants of Examples 1-1 to 1-13, it is assumed that the surfactant concentration in the supernatant is below the critical micelle concentration (CMC). For example, in Examples 1-12, the surfactant is polyoxyethylene (EO=6) lauryl ether, and the surface tension of the supernatant is 46.2 mN/m. Here, the relationship between the concentration of the polyoxyethylene (EO = 6) lauryl ether aqueous solution and the surface tension is 0.0002% by mass (68.3 mN/m), 0.0005% by mass (56.9 mN/m), 0 0008% by mass (52.3 mN/m). From this, it was confirmed that at least 99% by mass or more of the surfactant was removed in Examples 1-1 to 1-13. Also, from the oil content of the supernatant liquids of Examples 1-1 to 1-13, it was confirmed that 94.5% by mass or more of the oil was removed in these Examples. In other words, it was confirmed that the examples are highly effective in removing both the surfactant and the oil.

Claims (7)

(a) a polymer flocculant having stringiness [hereinafter referred to as component (a)] and (b) bentonite [hereinafter referred to as component (b)] are mixed with wastewater, and after standing still, the water layer is regenerated as water. A method for reusing wastewater, comprising:
the effluent contains surfactants and oils;
Component (b) is mixed in a proportion of 5 parts by mass or more and 100 parts by mass or less with respect to 1,000 parts by mass of waste water,
(a) component and (b) component are mixed so that the mass ratio of (b)/(a) is 100 or more and 3000 or less,
How to reuse waste water. The method for recycling waste water according to claim 1, wherein the waste water contains 10 ppm or more and 10,000 ppm or less of surfactant. The method for recycling wastewater according to claim 1 or 2, wherein the wastewater contains 10 ppm or more and 10,000 ppm or less of oil. The method for recycling wastewater according to any one of claims 1 to 3, wherein the wastewater contains oil selected from animal and vegetable oils and petroleum hydrocarbons. The method for recycling wastewater according to any one of claims 1 to 4, wherein component (a) is a polymer flocculant having a weight average molecular weight of 500,000 or more. The method for recycling wastewater according to any one of claims 1 to 5, wherein the wastewater contains a nonionic surfactant. The method for recycling wastewater according to any one of claims 1 to 6, wherein the component (a) is mixed after the component (b) is mixed with the wastewater.