JP6824869B2 - Treatment method and treatment equipment for water to be treated - Google Patents

Description

The present invention relates to water treatment techniques such as water purification, wastewater treatment, and sludge treatment.

Conventionally, various treatment agents have been used in water treatment technologies such as water purification treatment, wastewater treatment, and sludge treatment. Specifically, powdered activated carbon that is added to raw water before water purification treatment to adsorb and remove odorous substances, solid-liquid separation of this powdered activated carbon, and inorganic aggregation to form turbid aggregate flocs in water purification and wastewater treatment. There are agents, organic coagulants, polymer coagulants that further coarsen the coagulating flocs, and these inorganic coagulants, organic coagulants, and polymer coagulants are also used for concentrated and dehydrating sludge.

However, while powdered activated carbon has high dispersibility, it has poor sedimentation property, so there is a problem of how efficiently powdered activated carbon after use can be removed from the water to be treated. Further, since the inorganic coagulant tilts the pH of the water to be treated to the acidic side, alkaline treatment of the water to be treated is required, and the organic coagulant does not require alkaline treatment like the inorganic coagulant, but the optimum addition amount. The width is narrow, and excessive addition may worsen the treatment.

The polymer flocculant can be widely used not only for water purification and wastewater treatment but also for sludge treatment, but the polymer flocculant is pH-dependent depending on the type, and pretreatment of the water to be treated (pH adjustment, etc.) ) May be required. Further, if a large amount of polymer flocculant is used in the sludge treatment, the water content of the dehydrated sludge may be increased, and the viscosity of the sludge may be increased to adhere to the dehydrator. Furthermore, in water purification treatment, there are strict restrictions on residual substances such as acrylamide under the Ordinance of the Ministry of Health, Labor and Welfare, so there are restrictions on the types and amounts of polymer flocculants that can be used.

Therefore, instead of the conventional treatment agent, a new treatment agent having high safety and capable of avoiding the above problems has been desired. As a highly safe treatment agent, for example, cellulosic materials are used in fields such as sludge treatment (Patent Documents 1 and 2).

As an application other than sludge dewatering, a water purification cartridge for granulated activated carbon in which cellulose fibers are bonded to particulate activated carbon is known (Patent Document 3).

Japanese Unexamined Patent Publication No. 2003-238278 Japanese Unexamined Patent Publication No. 2012-71296 Japanese Unexamined Patent Publication No. 2017-178697

However, in Patent Document 1, active regenerated cellulose is added to sewage sludge and dehydrated for the purpose of composting sewage sludge to obtain a raw material for producing fertilizer, and in Patent Document 2, sludge Only a fibrous material of regenerated cellulose fiber is applied as a dehydration aid for the purpose, and the adsorptivity of cellulose nanofiber is not applied.

Further, the conventional cellulosic materials in Patent Documents 1 and 2 are limited in use to sludge dehydration and the like, and their treatment capacity is not sufficient.

In Patent Document 3, granulated activated carbon is expensive, and its use is limited to small-scale water purification such as a water purification cartridge type for purifying tap water.

This granulated activated carbon is effective for adsorbing and removing odorous substances and organic substances in tap water, and is produced by combining particulate activated carbon and fiber cellulose nanofibers to form granulated activated carbon. In addition, cellulose nanofibers are applied instead of the binder, which is merely a drawback when the binder is applied, that is, a technique for producing granulated activated carbon for preventing a decrease in the adsorption rate of activated carbon.

There is still room for consideration as to whether the binding force or adsorption force of this cellulose nanofiber can be used for removing turbid components in treated water and removing used powdered activated carbon for general water purification, wastewater, and sludge water treatment. Therefore, in the conventional water treatment technology, there is no technology that effectively utilizes the binding and adsorption properties of cellulose nanofibers.

As a result of diligent studies in view of the above-mentioned problems, the present inventors have found that nano-level cellulosic materials have lower toxicity and higher safety than synthetic organic materials, as well as coagulation and separation of powdered activated carbon and turbid substances, and sludge. We have found that it exhibits high processing capacity in various applications such as concentrated dehydration of, and have completed the present invention.

In order to solve the above problems, the present invention can have the following configuration.
(1) This is a method of treating water to be treated by adding at least one of cellulose nanofibers and a cellulose nanofiber solution to the water to be treated selected from raw water, wastewater, and sludge.
(2) After adding at least one of the cellulose nanofibers and the cellulose nanofiber solution to the water to be treated, an inorganic coagulant, an organic coagulant, and at least one coagulant selected from a polymer coagulant are further added. You can also do it.
(3) After adding at least one of the inorganic coagulant and the organic coagulant to the water to be treated, a polymer coagulant can be further added.
(4) The water to be treated may contain powdered activated carbon as a substance to be removed.
(5) The present invention also provides a treatment device for treating one or more types of water to be treated selected from raw water, wastewater, and sludge, and this treatment device uses at least one of cellulose nanofibers and cellulose nanofiber solutions. It has a first treatment means for adding, stirring, and adhering the cellulose nanofibers to turbidity in the water to be treated.
(6) The present invention also provides a treatment device for treating one or more kinds of water to be treated selected from raw water, wastewater, and sludge, and this treatment device is provided with at least one of cellulose nanofibers and a cellulose nanofiber solution. In some cases, there is a first treatment means for adding and stirring one of them to attach the cellulose nanofibers to the powdered activated carbon in the water to be treated.
(7) The treatment apparatus is installed before the first treatment means, and is installed after the pretreatment means for treating the water to be treated before adding the cellulose nanofibers (solution) and the first treatment means. , One or more means selected from post-treatment means for treating water to be treated after addition of cellulose nanofibers (solution) may be installed. In this case, the pretreatment means is an apparatus or equipment capable of adding powdered activated carbon to the water to be treated. The post-treatment means include a second treatment means in which at least one of an inorganic coagulant and an organic coagulant is added to the water to be treated and stirred, and a third means in which the polymer coagulant is added to the water to be treated and stirred. It is also possible to install either one or both of the processing means. For example, when both the second and third processing means are used, the third processing means is installed after the second processing means, and the third processing means is slower than the stirring of the second processing means. It may be a device that performs slow-speed stirring. Further, in applications such as sludge treatment, only the third treatment means may be used without using the second treatment means, and the stirring speed at this time may be a relatively slow slow stirring.

By using cellulose nanofibers for water treatment, the efficiency of removing substances to be removed is improved when the water to be treated is raw water or wastewater, and the concentration and dehydration of sludge are improved when the water to be treated is sludge. ..

The figure which shows the present invention schematically The figure explaining the processing method of the 1st example The figure explaining the processing method of the 2nd example The figure explaining the processing method of the 3rd example

Hereinafter, the present invention will be specifically described, but the present invention is not limited to a specific specific example.

FIG. 1 is a diagram showing a typical treatment flow of the present invention. In the present invention, a step of adding cellulose nanofibers to water to be treated selected from raw water, wastewater, sludge, etc. is essential, but other steps are required. The drug or process is not particularly limited. For example, in addition to the cellulose nanofibers, any flocculant may be used, or other treatment steps may be added before and after the addition of the cellulose nanofibers, and a combination of these steps, the flocculant, and other agents may be used. Is not particularly limited. First, the water to be treated used in the present invention will be specifically described.

[Water to be treated]
The water to be treated of the present invention is an object to be treated and is not particularly limited as long as it contains water, and raw water for purified water or irrigation water, wastewater, sludge and the like are also included in the water to be treated.

-Raw water Raw water is used for tap water and irrigation water (industrial water, industrial water, agricultural and livestock water), and specifically, fresh water or seawater, especially river water, groundwater (well water), lake water. , Rainwater and the like can be used in the present invention as one or more kinds of water to be treated.

-Drainage Drainage as treated water is not particularly limited, for example, factory effluent, domestic effluent, mining effluent, construction site effluent, agricultural and livestock effluent, commercial facility effluent, urine, other effluent (so-called sewage including rainwater, etc.) ) To one or more can be used in the present invention as water to be treated.

-Sludge The sludge as the sludge to be treated is not particularly limited, but for example, one or more kinds of sludge from surplus sludge, first-precipitated sludge (raw sludge), purified sludge, or concentrated sludge of these sludges are used in the present invention as water to be treated. It can be used and includes sludge generated by the treatment of raw water and wastewater. Among these, organic sludge generated in the treatment process of wastewater containing a large amount of organic substances such as sewage and human waste, particularly surplus sludge, is particularly suitable for the present invention.

[Cellulose nanofibers]
Cellulose nanofibers are elongated nano-shaped substances. Specifically, the average width of the cellulose nanofibers is, for example, 0.1 nm to 100 nm, preferably 1 to 50 nm, more preferably 1 to 20 nm, and those having an average width of less than 10 nm can also be used. The average width is the cross-sectional diameter of the cross section orthogonal to the longitudinal direction of the fiber, and can be measured using, for example, a scanning electron microscope or the like.

The average length of the cellulose nanofibers is not particularly limited as long as it is longer than the average width, and the length is usually about 100 times or more the average width, for example, 0.1 μm to 50 μm, preferably 0.2 μm to 20 μm. , More preferably 0.5 to 10 μm, and an average length of less than 10 μm can also be used. Like the average width, the average length can be measured using an electron microscope or the like.

As the cellulose nanofibers, an organic-inorganic nanocomposite or the like can be used, but those containing cellulose as a main component (50% by mass or more, usually 80% by mass or more is cellulose) are preferable, and usually substantially cellulose is substantially used. (95% by mass or more is cellulose).

The raw material of the cellulose nanofiber is not particularly limited, and is selected from wood-based pulp such as broadleaf tree, softwood, and bamboo; recycled pulp such as used paper; and further, cellulose-like substances such as CMC (carboxymethyl cellulose), chitin, and chitosan. One or more types can be used as the main raw material. Commercially available products can also be used for cellulose nanofibers. Cellulose nanofibers range from low defibration (broad fiber diameter distribution) to high defibration (sharp fiber diameter distribution), but the defibration degree is not particularly limited.

The degree of polymerization and molecular weight of the cellulose constituting the cellulose nanofibers are not particularly limited, but for example, the degree of polymerization measured by the copper ethylenediamine method is about 200 to 800, preferably about 200 to 650, and the molecular weight calculated from the degree of polymerization is It is about 30,000 to 150,000, preferably about 60,000 to 110,000.

Cellulose nanofibers are generally produced by unraveling pulp, which is a main raw material, to nanosize by one or more nanofiber treatments such as chemical treatment, mechanical treatment, and enzyme treatment.

Cellulose may be chemically modified by this nanofiber formation treatment and one or more steps before and after the treatment, but since the dispersibility in the water to be treated decreases when the cellulose is made hydrophobic, the non-hydrophobicized cellulose nanofibers are hydrophilic. Cellulose-modified nanofibers are suitable for the present invention. Further, the cellulose nanofibers which have been subjected to the nanofiber formation treatment without chemical modification can be used as they are.

The cellulose nanofibers are in the form of powder (solid content of 90% by mass or more), wet powder (solid content of 20% by mass or more), sheet, pellet, paste, slurry, or diluted and dispersed by diluting these with a dispersion solvent. Various forms such as a solution can be used, but from the viewpoint of handling, a solution of cellulose nanofibers such as a paste, a slurry, or a dilution / dispersion solution is preferable, and a slurry or a dilution / dispersion solution is particularly preferable.

However, the present invention is not limited to this, and one or more of these cellulose nanofiber solutions and cellulose nanofibers other than the solution (powder, pellets, etc.) can be selected and used together.

The above-mentioned solution of cellulose nanofibers is obtained by dispersing cellulose nanofibers in a solvent as a solid content. The content of the cellulose nanofibers is, for example, less than 20% by mass, preferably 5 to 15% by mass, usually about 10% by mass in the case of a paste product, and 1 to 5% by mass in the case of a slurry product. It is usually around 1% by mass, and in the case of a diluted dispersion solution, it is, for example, less than 1% by mass, preferably 0.005 to 0.5% by mass, and particularly 0.01 to 0.1% by mass.

The solvent for the cellulose nanofibers is not particularly limited as long as it contains water or a hydrophilic solvent, but preferably water is the main component (50% by mass or more), and the water content is preferably 80% by mass. A solvent consisting of 90% by mass or more, most preferably 95% by mass or more, and water can also be used. If necessary, one or more additives such as preservatives, surfactants, pH adjusters, and pH buffers may be added to the solvent.

Cellulose nanofibers as described above have properties such as excellent strength and elasticity because their molecules are aligned, and they are highly safe because they have extremely low toxicity, have a small environmental load, and are wide. It also has the advantage of being able to handle water to be treated in the pH range (eg, pH 2 to 13).

Furthermore, cellulose nanofibers adsorb to various substances such as inorganic substances, organic substances, turbid substances (SS), which is a complex of one or more of these substances, and powdered activated carbon, and aggregate these substances. In a state where aggregated flocs are formed by other agents such as an organic coagulant, the aggregated flocs are grown.

Further, when cellulose nanofibers are added to sludge, sludge particles are aggregated to promote sludge concentration, and the viscosity of the aggregated concentrated sludge is also lowered, so that dehydrated sludge is less likely to adhere to the dehydrator, and as a result, sludge. The solid-liquid separability of is also improved. As described above, cellulose nanofibers can be widely used as a treatment agent for water purification treatment, wastewater treatment, sludge treatment, etc., and are also conventional treatment agents (inorganic coagulant, organic coagulant, polymer coagulant). ), The amount of these treatment agents used can be reduced.
The present invention does not limit the use of the cellulose nanofibers in combination with other agents. Hereinafter, other drugs will be described.

[Coagulant]
In the treatment method of the present invention, any flocculant can be used in combination. The coagulant is not particularly limited, and one or more of the inorganic coagulant, the organic coagulant, and the polymer coagulant can be selected and used.

As the inorganic flocculant, known sulfuric acid bands, polyaluminum chloride (PAC), ferric polysulfate (polyiron), ferric chloride or a mixture thereof can be used. The amount of the inorganic flocculant added can be appropriately changed depending on the type of water to be treated and the water quality thereof.

Organic coagulants include, for example, condensing polyamines, dicyandiamide / formalin condensates, polyethyleneimine, polyvinylimidarin, polyvinylpyridine, diallylamine / sulfur dioxide copolymers, polydimethyldialylammonium salts, polydimethyldialylammonium salts / sulfur dioxide. One or more kinds can be selected and used from the group consisting of a copolymer, a polydimethyldiallyl ammonium salt / acrylamide copolymer, a polydimethyldiallyl ammonium salt / diallylamine hydrochloride derivative copolymer, and an allylamine salt polymer.

Specific examples of the condensing polyamine include a condensate of alkylene dichloride and alkylene polyamine, a condensate of aniline and formarin, a condensate of alkylenediamine and epichlorohydrin, and a condensate of ammonia and epichlorohydrin. Examples of the alkylene diamine that condenses with epichlorohydrin include dimethylamine, diethylamine, methylpropylamine, methylbutylamine, and dibutylamine.

As the polymer flocculant, one or more kinds can be selected and used from an anionic polymer flocculant, a nonionic polymer flocculant, a cationic polymer flocculant, and an amphoteric polymer flocculant. The type of the polymer flocculant is not particularly limited, but in the treatment methods of the first and second examples described later, at least one of the nonionic polymer flocculant and the anionic polymer flocculant is preferable, and the third example described later In the treatment method, at least one of a cationic polymer flocculant and an amphoteric polymer flocculant is preferable.

Preferred examples of the anionic polymer flocculant include a polyacrylamide partial hydrolyzate, a copolymer of an anionic monomer, and a copolymer of an anionic monomer and a nonionic monomer. Anionic monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl sulfonic acid, allyl sulfonic acid, metharyl sulfonic acid, styrene sulfonic acid, 2-allylamide ethane sulfonic acid, 2-acrylamide- 2-Methylpropanesulfonic acid, 2-methacrylamide ethanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid , 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, and metal salts or ammonium salts such as these alkali metals and alkaline earth metals can be preferably mentioned.

As the copolymer of the anionic monomer and the nonionic monomer, an acrylamide / acrylic acid copolymer and an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer can be preferably mentioned.

As the nonionic polymer flocculant, a homopolymer or copolymer of a nonionic monomer can be preferably used, and for example, acrylamide, methacrylamide, metaacrylonitrile, vinyl acetate and the like, and combinations thereof can be used. Preferably polyacrylamide can be used.

In the step of adding the polymer flocculant, it is also possible to use a two-agent method in which the above-mentioned cationic polymer flocculant is added and then the above-mentioned anion-based polymer flocculant is further added.

As the cationic polymer flocculant, a cationic polymer having a cationic monomer as an essential component and composed of a homopolymer or copolymer of the cationic monomer or a copolymer of the cationic monomer and the nonionic monomer. A flocculant and a cationic polymer flocculant having an amidin unit in the molecule can be preferably used.

Preferred examples of the cationic monomer include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, a neutralized salt thereof, a quaternary salt, and a combination thereof.

As the nonionic monomer, acrylamide, methacrylamide, metaacrylonitrile, vinyl acetate and the like, and combinations thereof can be preferably mentioned. Examples of the cationic polymer flocculant composed of a copolymer of a cationic monomer and a nonionic monomer that can be used in the present invention include at least one of dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate (both are methyl 4 chloride). A copolymer of (preferably a graded product) and acrylamide can be preferably used.

Further, as the cationic polymer flocculant having an amidine unit in the molecule that can be used in the present invention, for example, an amidine product of an N-vinylformamide / acrylonitrile copolymer can be preferably mentioned.

As the amphoteric polymer flocculant, a copolymer of a cationic monomer unit, an anionic monomer unit and a nonionic monomer unit can be preferably used. Examples of the amphoteric polymer flocculant that can be used in the present invention include at least one of dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate (preferably methyl quaternary chloride), acrylamide, and acrylic acid. Polymers can be preferably mentioned.

The agent used in the present invention is not limited to the above, and a pH adjusting agent such as an acid or an alkali can be added to the water to be treated as needed.

Hereinafter, specific examples of the treatment method of the present invention using cellulose nanofibers will be described in detail.

Reference numerals 1a, 1b, and 1c in FIGS. 2 to 4 indicate specific examples of the processing apparatus used in the present invention, and the same members are designated by the same reference numerals and the description thereof will be omitted.

[Treatment method of the first example (removal of turbidity)]
FIG. 2 shows a treatment device 1a used in the treatment method of the first example, and the treatment device 1a has a first treatment means 16 for adding at least cellulose nanofibers or a solution thereof to water to be treated. ..

The first processing means 16 is not particularly limited, and includes, for example, a supply means 5 containing at least one of the cellulose nanofibers and the cellulose nanofiber solution. When accommodating the cellulose nanofiber solution, the supply means 5 may contain a solution containing the cellulose nanofibers having a suitable concentration, or the cellulose nanofibers or the solution thereof (for example, slurry) and the solvent (for example, water) are separately separated. It may be stored in a solution and diluted 5 to 200 times, preferably 10 to 100 times with a solvent at the time of use.

The amount of cellulose nanofibers added is not particularly limited and can be appropriately changed according to the water quality of the water to be treated. For example, when a slurry having a solid content of 1% by mass is used, the amount added as the slurry is applied. A solution of cellulose nanofibers is added to the water to be treated so as to be 0.1 mg to 1000 mg, preferably 1 mg to 1000 mg (0.001 mg to 10 mg, preferably 0.01 mg to 10 mg in solid content) per 1 L of treated water. ..

The place where the cellulose nanofibers are added is not particularly limited, but preferably, the cellulose nanofibers are added to the water to be treated at one or more places in the treatment tank 11 provided with a stirring means, and the cellulose nanofibers and the water to be treated are stirred and mixed. To do. Therefore, in the treatment apparatus 1a of FIG. 2, the treatment tank 11 and the supply means 5 form a part or all of the first treatment means 16 for adding and mixing the cellulose nanofibers to the water to be treated.

In the treatment method of the first example, either raw water or wastewater can be used as the water to be treated, and these waters to be treated include organic substances (sugars, proteins, oils and fats, fibers, microorganisms, etc.). A turbid substance containing one or more substances selected from inorganic substances (minerals, clays, etc.) is dispersed. When cellulose nanofibers are added to the water to be treated, cellulose nanofibers adhere (adsorb) to this turbidity.

The water to be treated after adding the cellulose nanofibers may be post-treated by the post-treatment means 19, for example, one or more coagulants may be added and mixed. Specifically, the post-treatment means 19 has one or more treatment means (second and third treatment means 17, 18), and the treatment means 17 and 18 have the coagulant supply means 7, respectively. , 9 can be installed. Preferably, from the supply means 7 of the second treatment means 17, at least one of the inorganic coagulant and the organic coagulant (hereinafter, "inorganic coagulant (organic coagulant)" is added to the water to be treated after adding the cellulose nanofibers. ) ”), Particularly preferably an inorganic flocculant is added.

The place where the inorganic coagulant (organic coagulant) is added is not particularly limited as long as it is downstream from the place where the cellulose nanofibers are added, and the amount of the inorganic coagulant (organic coagulant) added is also not particularly limited. For example, the amount of the inorganic flocculant added is 10 mg to 1000 mg per 1 L of water to be treated after the addition of cellulose nanofibers. This addition amount is, for example, an addition amount (solid content) as an inorganic coagulant product, and the inorganic coagulant product may contain an additive other than a component having a coagulation action.

The water to be treated after adding the inorganic coagulant (organic coagulant) is stirred and mixed in the treatment tank 11 or another treatment tank 21 in which the cellulose nanofibers are stirred and mixed. Therefore, the treatment tanks 11 and 21 used for this stirring and mixing and the supply means 7 for the inorganic coagulant (organic coagulant) constitute a part or all of the second treatment means 17 for adding and stirring the coagulant. To.

The stirring speed S _{2 at} this time is not particularly limited, but is set to be about the same as the speed S ₁ when stirring the cellulose nanofibers, and the inorganic flocculant (organic coagulant) is stirred and mixed.

The inorganic flocculant (organic coagulant) aggregates the turbidity in the water to be treated to form flocs, but since cellulose nanofibers are attached to the turbidity in advance, the cohesiveness is high and the growth of flocs is promoted. Will be done.

When performing further mixed by stirring the third processing unit 18 is placed downstream of the second processing means 17, the third processing unit 18, the water to be treated floc is formed, the stirring speed S _1, It is preferable to further grow the flocs by stirring slowly at a stirring speed S ₃ slower than S ₂ . Slow sand stirring may be performed in the same processing tank 21 or in another processing tank 22.

That is, the treatment tanks 21 and 22 used for slow sand stirring form at least a part of the third treatment means 18. Further, the supply means 9 may be installed in the third processing means 18, and the polymer flocculant may be added at the time of slow sand stirring or before slow sand stirring.

The polymer flocculant is not particularly limited, and one or more of the above-mentioned polymer flocculants can be selected and used. However, when used in combination with an inorganic flocculant, a nonionic polymer flocculant and an anionic polymer It is preferable to use at least one of the flocculants. Further, as in the above two-agent method, even if one or more polymer flocculants (eg, cationic type) are added and then one or more other polymer flocculants (eg, anionic type) are added. Good. The amount of the polymer flocculant added is not particularly limited, but is, for example, about 0.01 mg to 20 mg, preferably 0.05 mg to 5 mg (solid content, total amount of the polymer flocculant) per 1 L of water to be treated.

With or without the addition of the polymeric flocculant, the water to be treated, on which flocs have grown by slow agitation, is usually subjected to one or more other post-treatments such as precipitation, biological treatment, filtration, etc. As a solid-liquid separation. At this time, since the cellulose nanofibers are contained in the flocs, the solid-liquid separability in precipitation and filtration is also high.

The treated water after the flocs are solid-liquid separated is used for water supply, irrigation water, etc. when the treated water is raw water, and is discharged to sewers and rivers when the treated water is wastewater. The sludge generated at this time can be used as water to be treated in the treatment method of the third example described later.
The above has described the case where the cellulose nanofibers are used for removing the turbidity of the water to be treated, but the present invention is not limited thereto.

[Treatment method of the second example (powdered activated carbon removal)]
FIG. 3 shows a processing device 1b used in the processing method of the second example, and the processing device 1b may have the same device configuration as the processing device 1a of the processing method of the first example, but in the second example, , The pretreatment means 15 that performs the pretreatment before the addition of the cellulose nanofibers is essential.

The pretreatment is to add powdered activated carbon to the water to be treated before adding cellulose nanofibers in the treatment tank 11 or its pre-stage (water landing well or intake point), and is a supply means (device) for powdered activated carbon. However, the powdered activated carbon may be added by spraying by an operator. Further, a stirring means for mixing the powdered activated carbon with the water to be treated can be separately installed. That is, a part or all of the pretreatment means 15 is composed of a treatment tank 11, a water landing well, a means for stirring powdered activated carbon, a means for supplying powdered activated carbon, and the like, which are places where cellulose nanofibers are added.

Here, the powdered activated carbon is activated carbon particles having a diameter smaller than that of granular activated carbon (usually having a particle size of 150 μm or more). For example, as the powdered activated carbon, powdered activated carbon for water supply (JWWA K113: 2005) or the like can be used, and for example, the sieve residue of the 75 μm mesh is 10% or less.

This powdered activated carbon is added to the water to be treated in an addition amount according to the water quality or a preset addition amount. The amount added at this time can be appropriately changed depending on the water quality of the raw water and the object to be removed by the powdered activated carbon, and is, for example, 1 to 1000 mg, more preferably about 2 to 100 mg per 1 L of water to be treated.

Similar to the treatment method of the first example, the water to be treated is raw water or wastewater, and includes odorous substances and harmful substances such as trihalomethane precursors in addition to the above-mentioned turbidity, but these substances are powders. It is adsorbed on activated carbon and removed from the liquid phase of the water to be treated. Since powdered activated carbon has a smaller diameter than granular activated carbon, it has high dispersibility in water to be treated and high efficiency of adsorption and removal of the above substances, but removal from water to be treated has a problem because of its high dispersibility.

When cellulose nanofibers are added from the first treatment means 16 to the water to be treated after the powdered activated carbon is added and mixed by stirring in a treatment tank 11 or the like as necessary, the cellulose nanofibers are adsorbed and aggregated on the powdered activated carbon. The powdered activated carbon settles and is solid-liquid separated from the water to be treated. Therefore, the powdered activated carbon can be removed from the water to be treated without using special equipment or chemicals.

The amount of cellulose nanofibers added can be appropriately changed according to the amount of powdered activated carbon added and the like. For example, when a slurry having a solid content of 1% by mass is used, the amount added as a slurry is 0 per 1 L of water to be treated. . 1 mg to 1000 mg, preferably 1 mg to 1000 mg (0.001 mg to 10 mg in solid content, preferably 0.01 mg to 10 mg).

In order to increase the removal efficiency of the powdered activated carbon, after adding the cellulose nanofibers, an inorganic coagulant, an organic coagulant, and one or more coagulants selected from the polymer coagulant are added to the post-treatment means 19 It is also possible to add from the above, preferably at least a second treatment means 17 is installed as the post-treatment means 19, and after the addition of the cellulose nanofibers, first, at least one of the inorganic flocculant and the organic coagulant is more preferable. Adds an inorganic flocculant.

The amount of the inorganic flocculant added can be appropriately changed depending on the amount of powdered activated carbon added and the water quality of the water to be treated. For example, 10 mg to 1000 mg per liter of water to be treated after the addition of cellulose nanofibers (for example, an inorganic flocculant product). Addition amount, solid content). The addition of the inorganic flocculant or the organic coagulant further promotes the sedimentation of the powdered activated carbon to which the cellulose nanofibers are attached.

If the amount of powdered activated carbon added is not extremely large, the powdered activated carbon can be sufficiently separated by using cellulose nanofibers alone or in combination with an inorganic coagulant or an organic coagulant. The use of other drugs is not restricted in any way.

For example, similarly to the treatment method of the first example, the polymer flocculant can be added from the third treatment means 18 to the water to be treated after adding at least one of the inorganic coagulant and the organic coagulant. In this case, as in the first example, after adding the polymer flocculant, it is desirable to stir slowly at a stirring speed slower than the stirring speed of the second processing means 17.

With or without the addition of a flocculant as described above, one or more other post-treatments such as precipitation, filtration, preferably precipitation, separate the powdered activated carbon from the water to be treated with the cellulose nanofibers. .. The treated water after solid-liquid separation is used for water supply, irrigation water, etc., or is discharged to sewerage and river water.

Both the treatment method of the first example and the treatment method of the second example can use both raw water and wastewater as the water to be treated, but since cellulose nanofibers have a small environmental load and extremely low toxicity, tap water It is particularly suitable for water and water applications, that is, when raw water is used as water to be treated.

In the above, raw water or wastewater is used as water to be treated, but the present invention is not limited to this. Next, a third example treatment method using sludge as water to be treated will be described.

[Treatment method of the third example (sludge)]
FIG. 4 shows a processing device 1c used in the processing method of the third example, in which the processing device 1c includes a first processing means 16 for supplying cellulose nanofibers and a concentrating tank 31 (concentrating pond) as needed. The sludge is concentrated in the concentrating tank 31, and then dehydrated in the dehydrating device 35.

The supply means 5 of the first processing means 16 is connected to one or more places from the front stage of the concentration tank 31 to the dehydrator. More specifically, the supply means 5 is connected to at least one or both of the front stage of the concentrating tank 31 and between the concentrating tank 31 and the dehydrating device 35, and either the sludge before concentration or the sludge after concentration. Cellulose nanofibers are added to one or both.

When the cellulose nanofibers are added to the sludge before concentration, when the sludge and the cellulose nanofibers are stirred and mixed in the concentration tank 31 or the like, the sludge particles are aggregated by the cellulose nanofibers and the sludge concentration proceeds. The concentrated sludge (concentrated sludge) is usually sent to the dehydrator 35.

The dehydrator 35 is used by selecting one or more from, for example, a centrifugal dehydrator, a belt press dehydrator, a screw press dehydrator, a filter press dehydrator, a vacuum dehydrator, a multi-disc dehydrator, a filtration device, and the like. Is possible.

When any of the dehydrating devices 35 is used, the concentrated sludge is dehydrated and the separated water is separated, and the dehydrated sludge is removed from the dehydrating device 35 as a dehydrated cake. However, if the sludge is highly sticky, a part of the dehydrated cake or All may remain unremoved from the dewatering device 35, which is a particular problem when the highly sticky organic sludge is mechanically dewatered using the dewatering device 35.

In the treatment method of the third example, when the cellulose nanofibers for sludge concentration are not added, or when the addition amount is small, the cellulose nanofibers can be added to the concentrated sludge before being sent to the dehydrator 35.

The addition of the cellulose nanofibers improves the dehydration efficiency and suppresses the stickiness of the sludge, so that the detachability of the dehydrated cake is improved and the dehydration device 35 is prevented from being contaminated.

As described above, in the treatment method of the third example, cellulose nanofibers can be used for one or both of sludge concentration and sludge dewatering. Since the cellulose nanofibers contribute to dehydration if they are contained in the concentrated sludge, for example, the cellulose nanofibers added in the concentration use also function in the dehydration use.

In the treatment method of the third example, the installation of the post-treatment means 19 is not restricted at all, and in addition to the cellulose nanofibers, any one or more selected from an inorganic flocculant, an organic coagulant, and a polymer flocculant. It is also possible to use a flocculant, preferably at least a third treatment means 18 for the polymeric flocculant is provided and the polymeric flocculant is added. It is also possible to install the second treatment means 17 in the front stage or the rear stage, preferably the front stage of the third treatment means 18, and use at least one of the inorganic flocculant and the organic coagulant in combination with the polymer flocculant.

When the above-mentioned flocculant is added to the sludge before dehydration, preferably after the addition of cellulose nanofibers, the dehydration efficiency of the concentrated sludge is further improved. Further, although the viscosity of the dehydrated sludge may increase due to the use of the polymer flocculant, the viscosity of the dehydrated sludge is suppressed by the cellulose nanofibers, and the peelability of the dehydrated cake is maintained.

The amount of the coagulant used is not particularly limited and can be appropriately changed depending on the sludge condition and the like, but in the case of the inorganic coagulant, 100 mg to 5000 mg per liter of sludge (for example, the amount added as an inorganic coagulant product, the solid content) is In the case of a polymer flocculant, it is preferably 0.1 to 10% by mass, more preferably about 0.5 to 2% by mass, based on the sludge suspension substance SS.

In the treatment method of the third example, the amount of cellulose nanofibers added can be appropriately changed depending on the state of sludge and its use (concentration, dehydration or both). For example, when a slurry having a solid content of 1% by mass is used, the total amount of slurry added from the pre-concentration step to the dehydration step is preferably 0.1 mg to 10000 mg, preferably 1 mg to 10000 mg per 1 L of sludge. (The solid content is 0.001 mg to 100 mg, preferably 0.01 mg to 100 mg).

Of the processing methods of the first to third examples, two or more processing methods may be combined. For example, since the sludge generated by the treatment methods of the first and second examples contains cellulose nanofibers, when this sludge is used in the treatment method of the third example, the addition of cellulose nanofibers is omitted, or the sludge thereof is omitted. The amount of addition can be reduced.

Next, the processing methods of the first to third examples will be described more specifically by way of examples, but none of the processing methods is limited thereto.

In each of the following examples, hardwood bleached pulp was used as a raw material, and cellulose nanofibers having an average degree of polymerization of about 600 and an average molecular weight of about 100,000 were used as a 1% by mass slurry.

− Treatment method of the first example (removal of turbidity)
[Examples A1 to A4, Comparative Example A1]
River water (pH 7.5, turbidity 4.30, chromaticity 4.43) was used as the water to be treated (raw water), and a jar tester was used as the test agitator. 500 ml of the target water was placed in a beaker, the amount of cellulose nanofibers shown in Table 1 was injected, and the mixture was mixed at 150 r.pm for 1 minute. Then, the amount of PAC shown in Table 1 was injected and stirred at 150 r.pm for 3 minutes, and then at 50 r.pm for 5 minutes. The water quality of the supernatant water was measured 5 minutes after the stirring was stopped. The results are shown in Table 1.

[Examples A5 to A8, Comparative Examples A2 to A3]
River water (pH 7.0, turbidity 24.0, chromaticity 25.1) was used as the water to be treated (raw water), and a jar tester was used as the test agitator. 500 ml of water to be treated was placed in a beaker, cellulose nanofibers were injected in the amounts shown in Table 2, and the mixture was mixed at 150 r.pm for 1 minute.

Then, PAC was injected as shown in Table 1 and stirred at 150 r.p.m for 3 minutes. Further, an anionic polymer flocculant (acrylamide-soda acrylate copolymer, molecular weight 12 million) was injected in the amount shown in Table 2 and stirred at 50 r.p.m for 5 minutes. The water quality of the supernatant water was measured 5 minutes after the stirring was stopped. The results are shown in Table 2.

In Tables 1 and 2 above and Tables 3 to 6 below, the cellulose nanofiber injection rate is the injection rate of 1% by mass slurry, and the injection rate of PAC (inorganic flocculant) is the flocculant as a solid content with respect to the water to be treated. The injection rate, and the injection rate of the polymer flocculant is the injection rate of the flocculant as a solid content in the water to be treated.

From the results in Tables 1 and 2, cellulose nanofibers should be used for water treatment (river water) as compared with the conventional coagulation / precipitation treatment using an inorganic coagulant alone or a combination of an inorganic coagulant and a polymer coagulant. It can be seen that the water quality of the treated water (supernatant water) is improved. Therefore, it was confirmed that cellulose nanofibers are effective for general water treatment such as water purification treatment and wastewater treatment.

− Treatment method of the second example (powdered activated carbon)
[Examples B1 to B4, Comparative Example B1]
Commercially available powdered activated carbon (Evadia 5LPD; manufactured by Swing Corporation) was dispersed in tap water to prepare test water containing 200 mg of powdered activated carbon per liter. A jar tester was used to stir each test.

500 ml of test water was placed in a beaker, cellulose nanofibers were injected in the amounts shown in Table 3, and the mixture was stirred at 180 r.p.m for 3 minutes. The water quality of the supernatant water was measured 5 minutes after the stirring was stopped. The results are shown in Table 3.

From the results in Table 3, in Comparative Example B1, the powdered activated carbon settled slowly even when left to stand, and a large amount remained in the supernatant water. However, due to the addition of cellulose nanofibers, the powdered activated carbon aggregated and precipitated, and almost remained in the supernatant water. It was confirmed not to.

[Examples B5 to B7, Comparative Example B2]
Kaolin was dispersed in tap water as an inorganic turbidity to prepare simulated tap water having a turbidity of 10. A jar tester was used to stir the treatment test. 500 ml of this simulated water was placed in a beaker, 20 mg / L of the above powdered activated carbon was added, and the mixture was mixed at 150 r.pm for 1 minute.

Next, the cellulose nanofibers were injected in the amounts shown in Table 4 below, and the mixture was stirred at 150 r.p.m for 1 minute. Then, PAC was injected in the amount shown in Table 4 and stirred at 150 r.p.m for 3 minutes, and further stirred at 50 r.p.m for 5 minutes. The water quality of the supernatant water was measured 5 minutes after the stirring was stopped. The results are shown in Table 4.

From the results in Table 4, the addition of cellulose nanofibers improved the water quality of the supernatant water as compared with the usual PAC single treatment, and almost no powdered activated carbon remained. Therefore, it can be seen that when powdered activated carbon is added in the water purification treatment, the outflow to the filtration pond can be prevented without excessive injection of the flocculant.

− Treatment method of the third example (sludge)
[Examples C1 to C2, Comparative Example C1]
Take 1 L of excess sludge (pH 6.4, TS 2600 mg / L, SS 2400 mg / L, VSS 89.0% by mass, fiber content 2.8% by mass) generated from the sewage treatment plant of the oxidation ditch method into a 1L beaker. Cellulose nanofibers were added in the amounts shown in Table 5 below, and the beakers were transferred 10 times for mixing. Immediately after mixing, the mixture was slowly transferred to a 1 L graduated cylinder, the interface between the sludge and the separated water was measured at predetermined time intervals, and the interface position was defined as the sludge volume. The results are shown in Table 5.

From the results in Table 5, it can be seen that the addition of cellulose nanofibers promotes sludge concentration.

[Examples C3 to C6, Comparative Example C2]
Take 200 ml of excess sludge (pH 6.2, TS 3500 mg / L, SS 3000 mg / L, VSS 61.5% by mass, fiber content 2.5% by mass) generated from the sewage treatment plant of the oxidation ditch method into a 300 ml beaker. , Cellulose nanofibers were added in the amounts shown in Table 6 below, and the beakers were transferred 10 times for mixing.

Next, a cationic polymer flocculant (methyl quaternary chloride / acrylamide copolymer of dimethylaminoethyl acrylate, molecular weight 4 million, adjusted to 0.2% by mass with tap water) was added in the amount shown in Table 6, and then. The transfer between beakers was performed 10 times to aggregate them. The coagulated sludge is dewatered by gravity with a 60-mesh nylon filter cloth, and the sludge after gravity filtration is sandwiched between two filter cloths and squeezed with a piston type dewatering device at a pressure of ² kg / cm ² for 1 minute to obtain the dewatering. The moisture content of the cake was measured. The results are shown in Table 6.

From the results in Table 6, it can be seen that the addition of cellulose nanofibers has the effect of lowering the water content of the cake. Further, if cellulose nanofibers are added at the time of concentration, the effects of both promotion of concentration and reduction of cake water content can be obtained.

1a, 1b, 1c: Processing devices 5, 7, 9: Supply means 11, 21, 22: Processing tank 15: Pre-processing means 16: First processing means 17: Second processing means 18: Third processing means 19: Post-treatment means 31: Concentration tank 35: Dehydrator

Claims (6)

Water to be treated is characterized in that at least one of cellulose nanofibers and cellulose nanofiber solution is added to water to be treated selected from raw water, wastewater, and sludge, and the water to be treated contains powdered activated carbon as a substance to be removed. Processing method. After adding at least one of the cellulose nanofibers and the cellulose nanofiber solution to the water to be treated, an inorganic coagulant, an organic coagulant, and at least one coagulant selected from a polymer coagulant are further added. The processing method according to claim 1. The treatment method according to claim 2, wherein at least one of an inorganic coagulant and an organic coagulant is added to the water to be treated, and then a polymer coagulant is further added . At least one of cellulose nanofibers and cellulose nanofiber solution is added to one or more kinds of water to be treated selected from raw water, wastewater, and sludge, and the mixture is stirred to attach the cellulose nanofibers to powdered activated carbon in the water to be treated. A device for treating water to be treated, which comprises the treatment means of 1. Pretreatment means for treating the water to be treated before adding at least one of the cellulose nanofibers and the cellulose nanofiber solution, and water to be treated after adding at least one of the cellulose nanofibers and the cellulose nanofiber solution. Has one or more means selected from post-processing means for processing
In the pretreatment means, powdered activated carbon is added to the water to be treated, and the powdered activated carbon is added.
The post-treatment means is a second treatment means in which at least one of an inorganic coagulant and an organic coagulant is added to the water to be treated and stirred, and a second treatment means in which the polymer coagulant is added to the water to be treated and stirred. The water treatment apparatus for water to be treated according to claim 4 , further comprising one or both of the three treatment means. At least one of the cellulose nanofibers and the cellulose nanofiber solution is added to one or more kinds of water to be treated selected from raw water, wastewater, and sludge, and the mixture is stirred to attach the cellulose nanofibers to the turbidity in the water to be treated. The water treatment apparatus for water to be treated according to claim 5, further comprising the treatment means of 1.

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