JP4525083B2 - Wastewater treatment method - Google Patents

Description

  The present invention relates to a wastewater treatment method for treating wastewater containing at least silica generated from a predetermined production process.

  Conventionally, as waste water generated from a toner manufacturing factory, waste water containing an aqueous surfactant solution, a pigment dispersion, a wax dispersion, a silica dispersion, an aqueous emulsion, and the like has been generated. Since these wastewater contains the above-mentioned surfactant, pigments which are coloring components, etc., they cannot be discharged into rivers, sewers or the like as they are. For this reason, these wastewaters are discharged outside after being treated at a wastewater treatment facility in the factory. As the wastewater treatment, coagulation sedimentation treatment is often used. Coagulation and sedimentation treatment is the most commonly used in the field of wastewater treatment, as described in the 5th edition pollution prevention technology and regulatory water quality edition (supervised by the Ministry of International Trade and Industry, Environmental Location Bureau, issued in 2001) p141. This is one of the solid-liquid separation operations that are widely used. The coagulation sedimentation treatment is a treatment method in which flocs (coarse particles generated by coagulation) are generated by adding a coagulant to the wastewater, and the flocs precipitate due to the difference in specific gravity between water and flocs to perform solid-liquid separation. The floc thus separated as a solid is treated as sludge for industrial waste, and the water from which the solid has been separated is discharged into rivers, sewers and the like.

  In Patent Document 1, in a wastewater treatment method for solid-liquid separation of organic pollutant-containing wastewater, a wastewater treatment method that facilitates final treatment of sludge by returning a part of the generated sludge to the treated raw water side and circulating it. Is disclosed. However, when this method is used for the treatment of silica-containing wastewater, the mechanism of the silica is not well understood due to the action of the silica, but there is a problem that sludge is difficult to settle. On the other hand, Patent Document 2 discloses a method of performing pressure levitation separation for the treatment of emulsion wastewater. However, this method can treat emulsion wastewater, but cannot be applied as it is to all types of wastewater generated from toner manufacturing plants.

JP-A-7-136408 Japanese Patent Laid-Open No. 9-225474

  For example, in the coagulation sedimentation treatment of wastewater containing multicomponents generated from a toner manufacturing factory, the sedimentation property in a floc sedimentation tank or the like is poor, and a very long sedimentation treatment is required for solid-liquid separation. Furthermore, in order to coagulate and precipitate the silica component contained in the waste water, it is necessary to add a large amount of a flocculant, which causes a problem that a large amount of sludge is generated as industrial waste.

  Then, an object of this invention is to provide the waste water treatment method which reduces the usage-amount of a flocculant and the generation amount of sludge.

  The present invention has the following features.

(1) A wastewater treatment method for treating wastewater containing at least silica generated from a toner production process, wherein the wastewater containing silica component generated from the toner production process is coagulated and precipitated or pressurized and floated. after the treatment, the step of ionizing the silica component, and a step of removing separated by membrane ion-like silica component, wherein the coagulating sedimentation treatment or, floatation on the processing and polymer flocculating inorganic coagulant Both of the agent are used, the addition amount of the inorganic flocculant is 500 mg / L to 5000 mg / L, the addition amount of the polymer flocculant is 0.5 mg / L to 5 mg / L, and the silica The step of ionizing the components comprises a step of contacting ozone gas with waste water containing silica and a step of irradiating ultraviolet rays, and the concentration of the ozone gas is 0.5 ppm or more and 10 p. m or less, wherein the ultraviolet irradiation, and 400nm emission wavelengths from 170 nm, the light quantity of the ultraviolet is 30 Wh / m ³ or more 200Wh / m ³ or less is waste water treatment method.

( 2 ) In the wastewater treatment method according to ( 1), the membrane is a reverse osmosis membrane.

  According to the present invention, it is possible to reduce the amount of flocculant used in the treatment of wastewater containing at least silica and the amount of sludge generated by wastewater treatment generated from the production process.

  As a manufacturing process that requires the waste water treatment, a toner manufacturing process will be described below as an example.

  The toner manufacturing process is roughly divided into a manufacturing process of a latex polymer that is a raw material of toner and a manufacturing method of a developing toner. Below, an example is given and demonstrated about each.

[Latex polymer production process]
In order to produce a latex polymer, a monomer and an anionic surfactant are usually added to water and stirred to form an emulsion. Once the monomer emulsion is formed, 25 wt% or less of the monomer emulsion (ie, a small amount of monomer emulsion) and the free radical initiator are added to the aqueous phase and mixed to initiate seed polymerization at the desired reaction temperature. After the seed particles are formed, a monomer emulsion is further added to the seed particle-containing composition, and polymerization is continued at a specified temperature for a desired time to complete the polymerization, thereby forming a latex polymer. When the latex polymer is formed, it is aggregated together with the colorant to form aggregate particles, which are then fused to form toner particles, as described in the developer toner production method described below. From the latex polymer production process, an emulsion aqueous solution that is no longer necessary in the production process or generated during equipment maintenance in the production process is discharged.

  The monomer is not particularly limited as long as it can react with a free radical initiator. Specific examples of the monomer include homopolymers or copolymers of styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, acrylic Homopolymers or copolymers of esters having vinyl groups such as lauryl acid, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; acrylonitrile And homopolymers or copolymers of vinyl nitriles such as methacrylonitrile.

  Further, a resin such as polyester or polyurethane having self-emulsifying properties may be sheared and dispersed in an aqueous medium together with a surfactant.

[Method for producing developing toner]
The latex polymer obtained by the above preparation method is used for toner preparation by the following method. A flocculant and / or a charge additive and / or other additives are mixed with the latex polymer prepared by the method described in the present invention and a plurality of dispersions containing at least a colorant as required, and the resulting mixture is obtained. Is heated at a temperature near the Tg of the latex polymer, preferably Tg ± 10 ° C. of the latex polymer for an effective time, for example 1 to 8 hours, to form toner-sized aggregates. The aggregate suspension is then heated to a latex polymer Tg or higher temperature, for example about 60 to about 120 ° C. to coalesce or coalesce to granulate the toner particles, and the toner particles are filtered, etc. It is separated from the mother liquor by means, washed with ion-exchanged water or the like (washing process), and then dried.

  The latex polymer is usually used as a binder resin for toner, and is present in the toner at about 75 to 98% by weight. The size of the latex polymer suitable for the production method of the present invention can be measured with a laser diffraction type particle size distribution analyzer, for example, a volume average particle size measured with a microtrack (manufactured by Nikkiso Co., Ltd.), 0.05 to It is about 1 μm.

  The colorant is usually present in an effective amount in the toner, for example, about 1 to 15% by weight, preferably about 3 to 10% by weight of the toner. Moreover, the magnitude | size is a volume average particle diameter measured with this microtrack, for example, and is about 0.05-0.5 micrometer.

  The flocculant can be used in an effective amount, for example, about 0.01 to 10% by weight based on the solid content of the toner. As the aggregating agent to be used, a compound having a monovalent or higher charge is preferable. Specific examples of the compound include the above-mentioned ionic surfactants, acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid, and chloride. Examples thereof include, but are not limited to, magnesium, sodium chloride, aluminum sulfate, calcium sulfate, ammonium sulfate, aluminum nitrate, silver nitrate, copper sulfate, sodium carbonate, and polyaluminum chloride. Preferred flocculants include those having a multivalent charge such as polyaluminum chloride.

  An effective amount of the charge control agent may be used, for example, 0.1 to 5% by weight of the toner. Suitable charge control agents include, but are not limited to, alkyl pyridinium halides, bisulfates, charge control agents such as silica, and negative charge control agents such as aluminum complexes. Examples of other additives used include waxes that act as mold release agents. A preferable amount of the wax is about 5 to 20% by weight based on the solid content of the toner.

  The type of wax is not particularly limited. For example, low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point; fatty acids such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide Amides; plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax And mineral waxes such as petroleum waxes; ester waxes of higher fatty acids such as stearyl stearate and behenyl behenate and higher alcohols.

  Examples of inorganic fine particles to be wet-added include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate, all of which are usually used as external additives on the toner surface, such as ionic surfactants and polymers. It can be dispersed in water with an acid or a polymer base and added wet.

  From the toner manufacturing process, surfactant aqueous solutions, pigment dispersions, wax dispersions, and silica dispersions that are no longer necessary in the manufacturing process or generated during equipment maintenance in the manufacturing process are discharged. As for the drainage rate, the silica dispersion discharged from the washing step accounts for about 1% by weight of the whole.

  According to the study by the present inventors, when waste water containing a trace amount of silica is mixed with waste water containing an aqueous surfactant solution that accounts for 80% by weight of the total amount of waste water discharged from the toner production process. In addition, since the dispersion state of the silica becomes more stable due to the action of the surfactant, the settling time in the coagulation sedimentation process becomes longer, and the addition of an inorganic coagulant used for coagulation precipitation, such as ferric chloride As a result, the amount of coagulated sediment increases, that is, a large amount of sludge to be treated as industrial waste is generated. This is because a certain amount of ferric chloride used as an inorganic flocculant undergoes charge neutralization reaction with the silica contained in the wastewater and the surfactant that stably disperses the silica in the wastewater. It is because the action as an agent is inhibited.

  That is, as a result of intensive studies, the present inventors have ionized the silica component in the wastewater containing silica, and then separated the ionic silica component with, for example, a reverse osmosis membrane device so that it is present in water and inhibits aggregation. The silica that is a factor can be removed, and as a result, the amount of the inorganic flocculant necessary for the coagulation and precipitation can be reduced. Thus, the inventors have found that the object of the present invention can be achieved and completed the present invention. It has come.

[Wastewater treatment method]
The waste water treatment method of the present embodiment will be described with reference to the drawings.

  FIG. 1 shows a wastewater treatment method according to the embodiment, and FIG. 2 shows a conventional wastewater treatment method.

  In FIG. 1, wastewater containing at least silica is first subjected to a coagulation sedimentation process or a pressure levitation process. Hereinafter, the silica removal process from the wastewater will be described by taking the coagulation sedimentation process as an example.

  In the coagulation sedimentation treatment, first, ferric chloride, which is an inorganic coagulant, is added to the wastewater in the reaction tank to generate floc. This flock contains mainly pigments and waxes. Next, in the flocculation tank, a polymer flocculant is added, and flocs generated with the inorganic flocculant grow. Finally, the precipitated floc is removed in the settling tank. Components other than silica are removed by this aggregation and precipitation treatment.

  Next, after the floc is removed, ozone treatment and ultraviolet treatment are performed in the ionization treatment step, and membrane separation treatment, for example, reverse osmosis membrane treatment is performed on the wastewater subjected to the ionization treatment.

  After each of these treatments, they are released into rivers. On the other hand, the precipitate (floc) after coagulation sedimentation is processed as sludge of industrial waste through a sludge dewatering process.

  As the flocculant used in this wastewater treatment facility, an inorganic flocculant and an organic flocculant are used. As the inorganic flocculant, for example, aluminum sulfate, ferric chloride, polyaluminum chloride and the like are used. The amount of the inorganic flocculant added is about 500 to 5000 mg / L. However, the inorganic flocculant is not necessarily limited to these. Furthermore, for growing flocs, for example, an acrylamide anionic flocculant can be used as the polymer flocculant. The amount added is about 0.5 to 5 mg / L. The polymer flocculant is not necessarily limited to acrylamide anionic flocculants, and other anionic flocculants, cationic flocculants, and nonionic flocculants can be used. Moreover, you may use combining these.

  In the ionization treatment, ozone treatment and ultraviolet treatment are performed in the present embodiment, but are not limited thereto. In the ionization process, for example, radiation such as X-rays, α-rays, β-rays, and γ-rays may be used depending on the processing apparatus and application.

The concentration of ozone gas used in this embodiment is 0.5 ppm or more and 10 ppm or less, preferably 1 ppm or more and 5 ppm or less, and the ultraviolet irradiation is performed with an emission wavelength of 170 to 400 nm and a light quantity of 30 WH / m ^3. It is 200 WH / m ³ or less, preferably 70 WH / m ³ or more and 100 WH / m ³ or less. The ozone gas concentration and the amount of ultraviolet irradiation are preferably adjusted as appropriate according to the amount of silica contained in the waste water. The ionization processing time is 2 seconds / L to 4 seconds / L. In addition, the particle diameter of the silica which performs an ionization process is about 10 nm to 1000 nm.

  Any reverse osmosis membrane may be used as long as it is used for general wastewater treatment. For example, a reverse osmosis membrane manufactured by Toray Industries, Inc. (trade name “Romenbra SU-SERIES”) Etc. can be used. In the reverse osmosis device using the reverse osmosis membrane, the water pressure on the inlet side of the initial reverse osmosis membrane is preferably 1.0 to 2.0 MPa.

  In the conventional wastewater treatment of FIG. 2, only the coagulation sedimentation treatment or the pressure levitation treatment is performed, and then discharged into a river or the like. On the other hand, the precipitate (sludge) after the coagulation sedimentation is processed as sludge of industrial waste through a sludge dehydration process.

  Next, the present invention will be described more specifically with reference to Examples and Comparative Examples.

(Composition of drainage A)
The waste water A is waste water that is actually discharged from a factory, and includes waste water containing at least silica in addition to a pigment dispersion, a wax dispersion, an emulsion aqueous solution, and a surfactant aqueous solution. The main composition of the drainage A is shown below.

Silica (particle diameter: 100 nm): 0.006 parts by weight Anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 0.0008 parts by weight Latex polymer: 0.0004 parts by weight Colorant: 0.0016 Part by weight wax ("Polywax 725" manufactured by Toyo Petrolite Co., Ltd.): 0.0012 parts by weight Water: 999.9 parts by weight

(Composition of drainage B)
Drainage B has the same composition as drainage A but has a different concentration. The main composition of the waste water B is shown below.

Silica (particle size: 100 nm): 30 parts by weight anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 4 parts by weight Latex polymer: 2 parts by weight Colorant: 8 parts by weight wax ("Polywax 725 “Toyo Petrolite Co., Ltd.”): 6 parts by weight Water: 950 parts by weight

Example 1
Wastewater A Treated wastewater A having a solid content concentration of 0.01 wt% was treated using the wastewater treatment facility shown in FIG. For the coagulation sedimentation treatment, 1000 mg / L of an inorganic flocculant (ferric chloride) and 1 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100, manufactured by Hymo Co., Ltd.) are added, and 18 m ^In a wastewater treatment facility having ³ coagulation sedimentation tanks, treatment was performed in a normal operation (14 m ³ / h). The ionization treatment was performed at an ozone gas concentration of 1 ppm, and the ultraviolet irradiation was performed at an emission wavelength of 170 to 400 nm and 70 WH / m ³ . As a result, the amount of sludge generated was 1.1 g / L, and the treated wastewater was transparent without coloration, and there was no problem with the processability.

(Example 2)
Wastewater B processable wastewater B having a solid content concentration of 5 wt% was treated in the same manner as in Example 1 using the wastewater treatment facility shown in FIG. At this time, 2000 mg / L of an inorganic flocculant (ferric chloride) and 2 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100) are added, and an 18 m ³ coagulation sedimentation tank is provided. The wastewater treatment facility was used for normal operation (14 m ³ / h). The ionization treatment was performed at an ozone gas concentration of 5 ppm, and the ultraviolet irradiation was performed at an emission wavelength of 170 to 400 nm and 100 WH / m ³ . As a result, the amount of sludge generated was 74 g / L, and the treated wastewater was transparent without coloration, and there was no problem with the processability.

(Example 3)
Wastewater A Treated wastewater A having a solid content concentration of 0.01 wt% was treated using the wastewater treatment facility shown in FIG. For the pressure levitation treatment, 1000 mg / L of an inorganic flocculant (ferric chloride) and 1 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100, manufactured by Hymo Co.) are added, In a wastewater treatment facility having a pressurized floating tank of 18 m ³ , it was treated in normal operation (14 m ³ / h). In the ionization treatment, the ozone gas concentration was 0.5 ppm, and in the ultraviolet irradiation, the emission wavelength was set to 170 to 400 nm and 30 WH / m ³ . As a result, the amount of sludge generated was 1.1 g / L, and the treated wastewater was transparent without coloration, and there was no problem with the processability.

Example 4
Wastewater B processable wastewater B having a solid content concentration of 5 wt% was treated in the same manner as in Example 1 using the wastewater treatment facility shown in FIG. At this time, 2000 mg / L of an inorganic flocculant (ferric chloride) and 2 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100) were added, and a 18 m ³ pressurized floating tank was added. The wastewater treatment facility had a normal operation (14 m ³ / h). The ionization treatment was performed at an ozone gas concentration of 10 ppm, and the ultraviolet irradiation was performed at an emission wavelength of 170 to 400 nm and 200 WH / m ³ . As a result, the amount of sludge generated was 74 g / L, and the treated wastewater was transparent without coloration, and there was no problem with the processability.

(Comparative Example 1)
Wastewater A Treated wastewater A having a solid content concentration of 0.01 wt% was treated using the wastewater treatment facility of FIG. At this time, 5000 mg / L of an inorganic flocculant (ferric chloride) and 1 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100) are added, and an 18 m ³ coagulation sedimentation tank is provided. The wastewater treatment facility was used for normal operation (14 m ³ / h). As a result, the amount of sludge generated was 5.1 g / L, and about 5 times as much sludge was generated as in Example 1, but there was no problem with the processability.

(Comparative Example 2)
Wastewater B Treated wastewater B having a solid content concentration of 5 wt% was treated using the wastewater treatment facility of FIG. At this time, 5000 mg / L of an inorganic flocculant (ferric chloride) and 2 mg / L of a polymer flocculant (acrylamide polymer flocculant: Hymolock SS-100) are added, and an 18 m ³ coagulation sedimentation tank is provided. The wastewater treatment facility was used for normal operation (14 m ³ / h). As a result, the amount of sludge generated was 185 g / L, and about 2.5 times as much sludge was generated as in Example 2. Further, even after the coagulation sedimentation treatment, the waste water was still colored with pigments and the like, and the processability was poor.

It is a figure explaining the waste water treatment method concerning an embodiment. It is a figure explaining the conventional waste water treatment method.

Claims (2)

A wastewater treatment method for treating wastewater containing at least silica generated from a toner manufacturing process,
A step of ionizing the silica component after subjecting the wastewater containing the silica component generated from the toner production process to a coagulation sedimentation treatment or a pressure levitation treatment ;
Separating and removing ionic silica components with a membrane;
Equipped with a,
Both the inorganic flocculant and the polymer flocculant are used for the coagulation sedimentation treatment or pressure flotation treatment, and the amount of the inorganic flocculant added is 500 mg / L to 5000 mg / L. The addition amount is 0.5 mg / L to 5 mg / L,
The step of ionizing the silica component comprises a step of contacting ozone gas with waste water containing silica, and a step of irradiating ultraviolet rays.
The ozone gas has a concentration of 0.5 ppm or more and 10 ppm or less, and the ultraviolet irradiation has an emission wavelength of 170 nm to 400 nm, and the amount of the ultraviolet light is 30 WH / m ³ or more and 200 WH / m ³ or less. Wastewater treatment method. The waste water treatment method according to claim 1 ,
The waste water treatment method, wherein the membrane is a reverse osmosis membrane.

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