Aqueous treatment solution and wastewater treatment method

Abstract

To provide an aqueous treatment solution that allows activated carbon to be added quantitatively to wastewater without scattering, and that can efficiently adsorb and remove unwanted substances from the wastewater, and a wastewater treatment method using the same. [Solution] The aqueous treatment solution is characterized in that it contains at least activated carbon, a swellable clay mineral, and water, and by imparting structural viscosity to the aqueous treatment solution, the activated carbon is dispersed and stabilized, and the handling properties are improved so that the activated carbon can be added quantitatively to the wastewater without scattering; a wastewater treatment method using the aqueous treatment solution; and a method for reducing the TOC of wastewater.

Description

Technical Field

[0001] The present invention relates to an aqueous treatment liquid, a method for treating waste liquid using the aqueous treatment liquid, etc., and also relates to a method for reducing the organic matter concentration (TOC, etc.) of waste liquid.

Background Art

[0002] Activated carbon is used because it can adsorb unnecessary substances in waste liquid on its surface and remove the unnecessary substances from the waste liquid.

[0003] For example, Patent Document 1 describes a method for purifying heavy metal-contaminated soil in which heavy metals are adsorbed and removed by an adsorbent from the heavy metal-contaminated soil, and the outflow of the heavy metals with water is suppressed. As the adsorbent, any one of zeolite, bentonite, silica gel, activated alumina, activated carbon, or a plurality of these are mixed and stirred into the soil, and a method for purifying the soil is described.

[0004] In addition, Patent Document 2 describes a purification / improvement agent for composite contaminated soil obtained by mixing and stirring natural zeolite, artificial zeolite, carbonized carbon, activated carbon, carbonized pulp sludge ash, rice husk activated carbon, titanium oxide, aluminum sulfate, sodium carbonate, bentonite, and slaked lime.

[0005] Patent Document 3 describes a coagulation sedimentation tank having a coagulation section, a sedimentation section, and a storage section, which is used in combination with a membrane separation device. As the coagulant used therein, bentonite, aluminum sulfate, sodium alginate, and cationic polyacrylamide are used, and it is described that an activated carbon section may be provided as necessary.

[0006] Patent Document 4 describes a method for treating emulsion-type wastewater by adding and mixing a wastewater treatment agent containing an inorganic coagulant or a polymer coagulant to O / W type emulsion-type wastewater to generate macroflocs, removing and separating the macroflocs in an oil-water separation treatment, and then clarifying the separated water after the removal of the macroflocs. The patent document describes using bentonite as the inorganic coagulant and using activated carbon in the clarifying treatment.

[0007] Patent Document 5 describes a water purification method that includes adding a purification agent containing an adsorbent, an iron-based coagulant, and an alkaline substance to water, allowing pollutants in the water to be adsorbed onto the adsorbent, and then allowing the adsorbent with the adsorbed pollutants to settle by the action of water-insoluble iron hydroxide produced by the reaction of the iron-based coagulant and the alkaline substance, and removing the settled material from the water. Examples of the adsorbent include activated carbon, alumina, hydrotalcite, or Schwertmanite.

[0008] Patent Document 6 describes a water treatment apparatus for treating wastewater discharged in a penetrant testing method for detecting defects on the inspection surface of an object under inspection, which contains a penetrant testing agent and has a fluorescent color. The apparatus is equipped with a coagulation means for adsorbing and coagulating the coloring components of the wastewater by adding bentonite to the wastewater and stirring it. Furthermore, it is described that the apparatus is equipped with an activated carbon filtration means for filtering the treated water, which has been treated by an ultraviolet oxidation means, with activated carbon.

[0009] However, the bentonite used in these applications is used as an adsorbent and coagulant to remove unwanted substances from contaminated soil and wastewater, and does not impart structural viscosity to the aqueous treatment solution added to the wastewater.

[0010] Furthermore, the activated carbon used in these applications was either mixed directly into the contaminated soil or liquid in powder form and stirred, or it was used by being supported on a carrier or the like, or it was incorporated into a filter medium or membrane to filter out wastewater.

[0011] Thus, while activated carbon is extremely effective in adsorbing and removing unwanted substances from wastewater, its applications have been limited.

[0012] On the other hand, for spray painting of large objects such as automobiles, dry paint booths that do not use water curtains are increasingly being used instead of wet paint booths that utilize water curtains. In addition to solvent-based paints, water-based and emulsion-based paints are also commonly used for spray painting.

[0013] With the conversion to a dry paint booth, a problem has arisen: the thinner used for maintaining spray paint machines (waste thinner) cannot be disposed of in the circulating water. There are two types of waste thinner: waste solvent thinner and waste water-based thinner. The former can be recycled through distillation, but the latter must be disposed of as industrial waste, which is causing concern. Regarding the latter, improvements, responses, and countermeasures were required. [Prior art documents] [Patent Documents]

[0014] [Patent Document 1] Japanese Patent Publication No. 2004-188250 [Patent Document 2] Japanese Patent Publication No. 2005-048147 [Patent Document 3] Japanese Patent Publication No. 2006-007176 [Patent Document 4] Japanese Patent Publication No. 2010-279877 [Patent Document 5] Japanese Patent Publication No. 2013-000696 [Patent Document 6] Japanese Patent Publication No. 2021-146331 [Overview of the Initiative] [Problems that the invention aims to solve]

[0015] The present invention has been made in view of the above-mentioned background art, and its objective is to solve the aforementioned problems and provide an "aqueous treatment liquid to be added to wastewater" that can be quantitatively added to wastewater without scattering activated carbon and can efficiently adsorb and remove unwanted substances in the wastewater.

[0016] Furthermore, the objective is to provide an aqueous treatment solution that can suitably treat wastewater by adding it to an aeration tank in activated sludge treatment, a wastewater treatment method using the aqueous treatment solution, and a method for efficiently reducing the concentration of organic matter in wastewater. [Means for solving the problem]

[0017] As a result of diligent research to solve the aforementioned problems and challenges, the inventors have discovered an aqueous treatment solution that allows activated carbon to be added quantitatively to wastewater without scattering. Furthermore, we discovered that this aqueous treatment solution is particularly useful for treating "waste liquid generated in paint booths," and is also extremely suitable for treating "waste liquid containing wastewater thinner used in the maintenance of spray painting machines for water-based paints," thus completing the present invention.

[0018] In other words, the present invention is an aqueous treatment solution for treating wastewater by being added to said wastewater, The present invention provides an aqueous treatment solution characterized by containing at least activated carbon, a swellable clay mineral, and water, and by imparting structural viscosity to the aqueous treatment solution, the activated carbon is dispersed and stabilized, and the handling properties are improved so that the activated carbon can be added quantitatively to the wastewater without scattering.

[0019] Furthermore, the aqueous treatment liquid of the present invention is a non-Newtonian liquid with strong structural viscosity, and its flowability is characterized by changes in response to external forces (shear stress) such as vibration and pressure. Accordingly, the present invention provides the aqueous treatment liquid having structural viscosity such that the thixotropic index (TI value) is 1.7 or higher and the viscosity at a rotation speed of 6 rpm of a type B viscometer is 30 mPa·s or higher.

[0020] The present invention also provides the above aqueous treatment liquid, wherein the swelling clay mineral belongs to the swelling clay minerals of the smectite group.

[0021] The present invention also provides the above aqueous treatment liquid, wherein the swelling clay mineral is montmorillonite, stibnite, or saponite.

[0022] The present invention also provides the above aqueous treatment liquid, wherein the waste liquid contains at least organic substances and water.

[0023] The present invention also provides the above aqueous treatment liquid, wherein the waste liquid is waste aqueous thinner generated when a device used for painting, a member or booth in the device, or a path or pipe of a paint used in the device is washed with an aqueous thinner.

[0024] The present invention also provides a waste liquid treatment method for treating the waste liquid by adding the above aqueous treatment liquid to the waste liquid containing organic substances and water, wherein the aqueous treatment liquid contains at least activated carbon, a swelling clay mineral, and water, and provides a waste liquid treatment method for improving the dispersion stability of the activated carbon by imparting structural viscosity to the aqueous treatment liquid.

[0025] The present invention also provides the above waste liquid treatment method for treating the waste liquid by adding the aqueous treatment liquid to the waste liquid in an agglomeration treatment tank or the waste liquid in an aeration tank in activated sludge treatment.

[0026] The present invention also provides a method for reducing the TOC (Total Organic Carbon) of waste liquid, characterized by using the above aqueous treatment liquid.

[0027] The present invention also provides a "waste liquid treatment method by carrier method" using activated carbon supported by microorganisms in activated sludge as a carrier, characterized by using the above aqueous treatment liquid. [Effects of the Invention]

[0028] The aqueous treatment solution of the present invention has high thixotropy and structural viscosity, and therefore exhibits good dispersion stability despite containing fine activated carbon, which is generally the case with such solutions. Furthermore, the aqueous treatment solution of the present invention has extremely superior storage, transportability, and handling properties compared to powdered activated carbon, such as not scattering and allowing for quantitative feeding, making it suitable for handling as a liquid.

[0029] Furthermore, activated carbon that has been pulverized to increase its adsorption capacity is typically used by incorporating it into filter media or packing it into columns, through which waste liquid is passed. It is also used by being supported on a carrier for easier handling, or placed in cassettes (such as those used in gas masks and exhaust systems), or in dedicated containers or bags, depending on the application. In contrast, the present invention has discovered an aqueous treatment solution that allows activated carbon to be added quantitatively to wastewater without scattering, making it possible to adsorb and remove unwanted substances from the wastewater very efficiently and simply.

[0030] In the present invention, where activated carbon is not in the form of an aqueous treatment solution, or in other words, not in the form of so-called "liquefied activated carbon," but rather in the form of powdered activated carbon added to the wastewater, there is a problem of the powder scattering.

[0031] However, since the aqueous treatment solution of the present invention is in liquid form and is added to the wastewater, there is no problem of activated carbon powder scattering.

[0032] In this specification, “aqueous treatment solution” means a treatment solution in which the dispersion medium is water, “aqueous liquid that is miscible with water,” and / or “a mixture of water and said aqueous liquid.”

[0033] The aqueous treatment solution of the present invention can be used to treat any type of wastewater and is not particularly limited, but it is especially suitable for treating wastewater generated from circulating water used in wet paint booths that utilize water curtains, etc., and for treating wastewater generated from wastewater thinner used for cleaning dry paint booths. In this specification, "wastewater thinner" refers to "water-based thinner" that is to be discarded (or is scheduled to be discarded), and "water-based thinner" refers to a cleaning solution that contains water.

[0034] In recent years, with the conversion of large wet paint booths to dry paint booths, large quantities of wastewater thinner that could no longer be disposed of are being discharged into the circulating water used in wet paint booths. The aqueous treatment solution of the present invention is used by adding it to coagulation treatment tanks, activated sludge treatment tanks, etc. Therefore, it is also effective in reducing the concentration of organic matter (TOC, etc.) contained in wastewater thinner.

[0035] Furthermore, while the aqueous treatment solution of the present invention can be used to treat waste liquids from all types of paints, it is particularly suitable for treating waste liquids from water-based paints such as emulsion paints (generated during painting). Moreover, it is especially suitable for treating stains caused by water-based paints and the aforementioned wastewater thinners generated by cleaning them.

[0036] The above-mentioned wastewater thinner has recently become a problem due to the increasing volume of wastewater and the costs associated with its disposal, as it is being converted to dry paint booths. However, by using the aqueous treatment solution of the present invention, it is possible to reduce the volume of wastewater thinner and the associated disposal costs, thereby enabling the establishment of a superior treatment process. This makes it possible to meet the wastewater acceptance standards (standards for TOC, BOD, COD, residual organic matter concentration, etc.) of prefectures, other regions, or within companies or factories.

[0037] The aqueous treatment solution of the present invention can be used for the treatment of all types of wastewater containing water, and is suitably used for wastewater that is generated directly, as well as wastewater obtained by diluting such wastewater with water, and also for wastewater in a drainage reservoir containing such wastewater, i.e., wastewater.

[0038] Furthermore, the aqueous treatment solution is suitably used for "waste liquid in a coagulation treatment tank" in combination with organic coagulants, inorganic coagulants, and / or polymer coagulants for coagulating "organic matter contained in paint". In other words, the aqueous treatment solution of the present invention can be used in combination with organic coagulants, inorganic flocculants, and polymer flocculants without causing any adverse effects.

[0039] Furthermore, the aqueous treatment solution is particularly suitable for use in combination with microorganisms in activated sludge, and is especially suitable for "wastewater from the aeration tank in the activated sludge treatment." In other words, the aqueous treatment solution of the present invention not only does not cause any adverse effects when used in combination with microorganisms in activated sludge, but it is also expected to increase the adsorption effect of the activated carbon by the attachment of these microorganisms to the surface of the activated carbon. In other words, it enables "wastewater treatment by carrier method" in which microorganisms are supported on an activated carbon carrier.

[0040] As stated above, in this specification, "waste liquid" can be suitably used in any wastewater treatment, including the generated "waste liquid containing organic matter and water," waste liquid obtained by diluting said waste liquid with water, and wastewater that is to be disposed of as is. Furthermore, the term "wastewater" in this specification includes wastewater from a water storage tank, wastewater from a flocculant in a flocculant treatment tank containing organic matter such as polymers, and wastewater from an activated sludge treatment tank containing microorganisms, and this specification is particularly suitable for use with these.

[0041] By using the aqueous treatment solution of the present invention, the concentration of organic matter in the wastewater described above can be reduced. Specifically, the values ​​of COD, BOD, TOC, etc. in the wastewater can be reduced. [Brief explanation of the drawing]

[0042] [Figure 1] This graph shows the effect of the aqueous treatment solution of the present invention on promoting oxidative decomposition, as evaluated in Evaluation Example 44. [Modes for carrying out the invention]

[0043] The present invention will be described below, but it is not limited to the following specific forms and can be modified as desired within the scope of the technical idea.

[0044] The aqueous treatment solution of the present invention is an aqueous treatment solution for treating wastewater by being added to said wastewater, characterized in that the aqueous treatment solution contains at least activated carbon, a swellable clay mineral, and water, and the dispersion stability of the activated carbon is improved by imparting structural viscosity to the aqueous treatment solution.

[0045] <Waste liquid to be treated> The wastewater treated by the aqueous treatment solution of the present invention is not particularly limited and includes "raw wastewater containing organic matter" directly generated by washing, breeding, cooling, synthesis, etc., as well as wastewater obtained by diluting the "raw wastewater" with water. The aqueous treatment solution of the present invention can be suitably used for any of these.

[0046] Furthermore, the aqueous treatment solution of the present invention can be used in combination with organic coagulants, inorganic coagulants, or polymer coagulants to remove organic matter from wastewater containing organic matter. In other words, the wastewater in the coagulation treatment tank (a tank for coagulating unwanted materials) containing the wastewater can be treated by adding the aqueous treatment solution of the present invention.

[0047] Furthermore, the aqueous treatment solution of the present invention is particularly suitable for use in combination with microorganisms in activated sludge for "wastewater in an aeration tank in the activated sludge treatment." In other words, by adding the aqueous treatment solution of the present invention to an activated sludge treatment tank containing microorganisms, the wastewater in the activated sludge treatment tank can be treated simultaneously with the activated sludge treatment. As a result, as described above, the microorganisms in the activated sludge adhere to the surface of the activated carbon contained in the aqueous treatment solution of the present invention, thereby increasing the adsorption effect of the activated carbon, which is a so-called "wastewater treatment effect by carrier method."

[0048] <Waste liquid treatment> The aqueous treatment solution of the present invention is for treating waste liquids as described above. Herein, "treatment" refers to treatment that makes the waste liquid more easily disposable, or to making it disposable. Specifically, this includes treatment to reduce BOD (biochemical oxygen demand), COD (chemical oxygen demand), TOC (total organic carbon), organic matter, odor removal, decolorization, etc.

[0049] The aqueous treatment solution of the present invention can be suitably used at any stage from the wastewater immediately after generation to the final wastewater (i.e., drainage) in storage tanks, coagulation treatment tanks, activated sludge treatment tanks, etc.

[0050] <Activated carbon> The aqueous treatment solution of the present invention contains activated carbon as an essential component. The activated carbon is not particularly limited as long as it has adsorption properties, and the raw materials include woody materials such as coniferous trees, broad-leaved trees, and coconut shells; carbonaceous materials such as coal, charcoal, and petroleum; and so on. Furthermore, while there are no particular limitations on the carbonization temperature, it is desirable to carbonize at 200-700°C, preferably 500-700°C, with the air supply removed.

[0051] Furthermore, there are no particular limitations on the activation method; chemical activation, gas activation, etc., can be used. Examples of the chemical include phosphoric acid, calcium chloride, magnesium chloride, zinc chloride, sulfuric acid, sodium hydroxide, potassium hydroxide, etc., and examples of the gas include water vapor, carbon dioxide, air, etc.

[0052] <Swelling clay minerals> The aqueous treatment solution of the present invention contains a swelling clay mineral as an essential component. The swelling clay mineral is not particularly limited as long as it can impart viscosity and structural viscosity to a liquid (especially water), but it is preferably in the form of flattened or needle-shaped particles.

[0053] The size of the swelling clay mineral (length and diameter of needle-shaped particles; length and thickness of flattened particles) is determined to suitably impart structural viscosity to the aqueous treatment solution of the present invention, such as a high thixotropic index (TI value).

[0054] As the clay mineral constituting the swelling clay mineral, clay minerals belonging to the smectite group are preferred because they easily impart structural viscosity to the aqueous treatment solution of the present invention, and more specifically, montmorillonite, bydelite, nontronite, saponite, souconite, hectorite, stivunsite, and the like are more preferred. Among the clay minerals belonging to the smectite group, montmorillonite, saponite, and stivunsite are particularly preferred in relation to the aqueous treatment solution of the present invention due to their own dispersion stability and their ability to impart structural viscosity, thereby contributing to "dispersibility (stability) in the aqueous treatment solution of the present invention for activated carbon." Among these, refined high-purity montmorillonite is the most preferred for the reasons mentioned above.

[0055] Bentonite is an aggregate (solid solution, rock) of montmorillonite, quartz, mica, feldspar, calcite, zeolite, etc. In the present invention, the swelling clay mineral is particularly preferably high-purity montmorillonite, which is a clay mineral contained in the rock bentonite. Specifically, it is particularly preferable that the swelling clay mineral is high-purity montmorillonite obtained by removing quartz and feldspar from "bentonite, which is mainly composed of montmorillonite and has silicate minerals such as quartz or feldspar as minor components."

[0056] <Other substances> In addition to the activated carbon, swelling clay mineral, and water described above, the aqueous treatment solution of the present invention may contain other substances. Examples of "other substances" include dispersion stabilizers for activated carbon or swelling clay minerals. These are used insofar as they do not diminish the effectiveness of the aqueous treatment solution of the present invention.

[0057] <Composition of aqueous treatment solution> <<Content of swelling clay minerals>> The content of the swelling clay mineral in the aqueous treatment solution of the present invention is not particularly limited, as long as it can adequately impart structural viscosity to the aqueous treatment solution without being excessively large, depending on the type of swelling clay mineral. However, it is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1.0% by mass or more and 8% by mass or less, even more preferably 1.5% by mass or more and 7% by mass or less, particularly preferably 2% by mass or more and 6% by mass or less, and most preferably 2.5% by mass or more and 5% by mass or less.

[0058] If the content of swelling clay minerals is too low, it may be difficult to impart structural viscosity to the aqueous treatment solution, and the activated carbon may not be stably and suitably dispersed in the aqueous treatment solution. On the other hand, if the content of swelling clay minerals is too high, the aqueous treatment solution may become excessively viscous, resulting in a paste-like consistency and reduced handling properties.

[0059] <<Activated Carbon Content>> The activated carbon content in the aqueous treatment solution of the present invention is not particularly limited, depending on the type of activated carbon, as long as the activated carbon is well dispersed in the aqueous treatment solution and has sufficient wastewater treatment capacity. However, it is preferably 1.5% by mass or more and 40% by mass or less, more preferably 2% by mass or more and 30% by mass or less, even more preferably 2.5% by mass or more and 25% by mass or less, particularly preferably 3% by mass or more and 20% by mass or less, and most preferably 3.5% by mass or more and 15% by mass or less.

[0060] If the activated carbon content is too low, the wastewater treatment effect may decrease when compared with the same amount added, or it may become necessary to add a large amount of aqueous treatment solution to the wastewater. On the other hand, if the activated carbon content is too high, it may become paste-like, reducing its handling properties.

[0061] <Structural viscosity of aqueous treatment solution> The aqueous treatment solution of the present invention is given structural viscosity by containing a swellable clay mineral, thereby improving the dispersion stability of the activated carbon contained therein. It is essential that the aqueous treatment solution of the present invention has improved dispersion stability of activated carbon due to the structural viscosity resulting from the inclusion of a swellable clay mineral.

[0062] The aqueous treatment liquid of the present invention is a non-Newtonian liquid with high thixotropy and structural viscosity, and is characterized by its flowability changing in response to external forces (shear stress) such as vibration and pressure. It is preferable that the structural viscosity has a "thixotropic index (TI value)" indicating thixotropy and structural viscosity of 1.7 or higher, and a viscosity of 30 mPa·s or higher when the B-type viscometer rotates at 6 rpm.

[0063] The "thixotropic index (TI value)" mentioned above is the value obtained by dividing the viscosity at 6 rpm, measured with a B-type viscometer, by the viscosity at 60 rpm. In this invention, "structural viscosity" refers to the property that viscosity decreases as the shear rate increases. In other words, "structural viscosity" increases as the TI value increases.

[0064] As described above, the TI value of the aqueous treatment solution of the present invention is preferably 1.7 or higher, but considering the dispersion stability of activated carbon, it is more preferably 2.0 or higher, and particularly preferably 3.0 or higher. Furthermore, while there is no particular upper limit to the TI value, considering quantitative addition to the waste liquid, the TI value is preferably 7.0 or less, more preferably 6.0 or less, even more preferably 5.0 or less, and particularly preferably 4.0 or less.

[0065] The viscosity of the aqueous treatment solution of the present invention is preferably 30 mPa·s or more when measured at a rotation speed of 6 rpm on a type B viscometer, more preferably 80 mPa·s or more, even more preferably 140 mPa·s or more, and particularly preferably 300 mPa·s or more. On the other hand, the viscosity of the B-type viscometer at a rotation speed of 6 rpm is preferably 17,000 mPa·s or less, more preferably 6,500 mPa·s or less, even more preferably 3,000 mPa·s or less, and particularly preferably 2,000 mPa·s or less.

[0066] When the TI value and viscosity of the aqueous treatment solution of the present invention are within the above range, the activated carbon is less likely to settle or separate in the aqueous treatment solution, is well dispersed, and the stability of the dispersion is maintained over time. Furthermore, stirring reduces viscosity, allowing for quantitative addition to the waste liquid and improving handling.

[0067] <Particularly desirable waste liquids> As described above, the wastewater to be treated by the aqueous treatment solution of the present invention is preferably composed of at least organic matter and water, in order to take advantage of the features of the aqueous treatment solution of the present invention described above. Here, "organic matter" specifically refers to solvents, resins, fatty acids, amines, surfactants, etc. The waste liquid is particularly preferably composed of at least an organic polymer, an organic solvent, and water. The aqueous treatment solution of the present invention can be used to remove organic matter in coagulation treatment and activated sludge treatment, and is suitable for treating wastewater containing the above-mentioned substances.

[0068] In particular, the waste liquids include waste circulating water that constitutes the water curtain generated during painting such as spray painting, and waste water thinner discharged from the cleaning fluid of the bell tip and pathway of painting robots that spray water-based paints. These are used because they are extremely large in volume, contain high concentrations of organic matter, and allow us to take advantage of the feature of the present invention, which is to "directly introduce and add activated carbon into the tank."

[0069] Furthermore, it is particularly preferable that the waste liquid to be treated is wastewater thinner generated when a painting apparatus, components or booths in the apparatus, or the paint pathways or piping used in the apparatus are cleaned with water-based thinner. This is because it allows us to take advantage of the aforementioned features of the aqueous treatment solution of the present invention, and because, in painting equipment, a particularly large amount of waste liquid such as cleaning solution (waste water thinner) and circulating water is generated, making the usage method of the aqueous treatment solution of the present invention, which involves adding a large amount of activated carbon to the waste liquid, particularly suitable.

[0070] While not limited to these, the waste liquid to be treated is particularly preferably wastewater thinner, which is generated when the paint pathways and piping in a painting apparatus, the paint spray nozzles, or the bell or "the area around the bell such as the bell cup" in a painting robot are cleaned with a water-based thinner, which is a cleaning solution.

[0071] As stated above, in this specification, "waste water-based thinner" refers to "water-based thinner" that is discarded, and "water-based thinner" refers to "cleaning solution containing water" used in painting.

[0072] The wastewater thinner described above contains organic polymers, which are components of paint, and water and aqueous solvents, which are components of aqueous thinner, and the aqueous treatment solution of the present invention is suitable for treating these. With the recent shift towards dry paint booths, the thinner used for maintaining spray paint machines (waste thinner) cannot be disposed of in circulating water as it can in wet paint booths. There are two types of waste thinner: waste solvent thinner and waste water thinner. The former can be recycled through distillation, but the latter becomes industrial waste. The aqueous treatment solution of the present invention is particularly suitable for the latter, "treatment of waste aqueous thinner" in a dry paint booth.

[0073] Examples of aqueous solvents that are components of the aqueous thinner include mono, di, or triethylene glycol, or mono, di, or tripropylene glycol, or their monoalkyl (C ≤ 6) ethers; ketones such as acetone and methyl ethyl ketone; alcohols such as ethanol and propanol; polyhydric alcohols such as glycerin; and the like. Since aqueous thinners, and therefore wastewater thinners, typically contain 2 to 30% by mass of the above-mentioned aqueous solvent, and in many cases 3 to 10% by mass, the aqueous treatment solution of the present invention can be suitably used.

[0074] <Waste liquid treatment method> The present invention is also a wastewater treatment method characterized by using the aqueous treatment solution described above. Furthermore, the present invention relates to a wastewater treatment method for treating wastewater by adding the aqueous treatment solution of the present invention to wastewater containing organic matter and water, This wastewater treatment method also improves the dispersion stability of the activated carbon by providing structural viscosity to the aqueous treatment solution, which contains at least activated carbon, a swellable clay mineral, and water.

[0075] Furthermore, it is preferable that the waste liquid is "a waste liquid containing organic matter and water" in order to take advantage of the features of the aqueous treatment solution of the present invention. Examples of such organic matter include a mixture of an organic polymer and an organic solvent.

[0076] The present invention is a wastewater treatment method characterized by using the aqueous treatment solution described above, and further, a wastewater treatment method that reduces the TOC of a wastewater by adding the aqueous treatment solution to a "wastewater containing organic matter and water," particularly a "wastewater containing organic polymers, organic solvents, and water," wherein the aqueous treatment solution contains at least activated carbon, swellable clay minerals, and water, thereby providing structural viscosity to the aqueous treatment solution, stabilizing the dispersion of the activated carbon, and improving handling so that the activated carbon can be added quantitatively to the wastewater without scattering.

[0077] Furthermore, the waste liquid treatment method is also such that the waste liquid is wastewater thinner generated when a painting apparatus, a component or booth in the apparatus, or a paint pathway or piping used in the apparatus is cleaned with water-based thinner. Since circulating water in painting equipment and wastewater thinner obtained by washing paint adhering to painting equipment with water-based thinner are usually produced in large quantities, it is necessary to treat them appropriately; these waste liquids contain a large amount of water; and for these reasons, the aqueous treatment solution of the present invention is particularly effective when used in the above applications.

[0078] The aqueous treatment solution of the present invention is not limited to, but is particularly preferably added to, for example, wastewater in the following tanks. Furthermore, as mentioned above, the waste liquid also includes waste liquid that has been diluted (in large quantities) with water. Furthermore, in the following description, "(addition)" indicates the addition of the aqueous treatment solution of the present invention to the tank. The parentheses around "(water storage tank)" and "(coagulation treatment tank)" indicate that they may or may not be present. Other tanks may also be inserted, or added before or after them. The following specific examples are preferable, but not limited to, the treatment of wastewater thinner generated by painting. This also includes methods of adding the substance to two or more tanks. The term "activated sludge treatment tank" below refers to tanks such as aeration tanks used in activated sludge treatment.

[0079] [Waste liquid] →→ Water storage tank (added) [Waste liquid] → (Storage tank) → → Coagulation treatment tank (added) [Waste liquid] → (Water storage tank) → → Coagulation treatment tank → → → Water storage tank (added) [Waste liquid] → (Water storage tank) → (Coagulation treatment tank) → (Water storage tank) → Activated sludge treatment tank (added) [Waste liquid] → (Storage tank) → (Coagulation treatment tank) → (Storage tank) → Activated sludge treatment tank → Activated sludge tank (Addition)

[0080] In the wastewater treatment method of the present invention, it is particularly preferable to add the aqueous treatment solution to the wastewater in the coagulation treatment tank or to the wastewater in the aeration tank in the activated sludge treatment. The present invention also relates to a wastewater treatment method, which involves adding the aqueous treatment solution to a coagulation treatment tank or an aeration tank in activated sludge treatment to treat the wastewater.

[0081] <<Agglutination>> In the wastewater treatment method of the present invention, it is preferable to remove organic matter in colloidal particles contained in the wastewater by coagulation in a coagulation treatment tank. The aqueous treatment solution of the present invention can be added to the coagulation treatment tank together with a coagulant, or it can be added to the tanks before and after the coagulation treatment tank.

[0082] The present invention also relates to the wastewater treatment method, in which, when adding the aqueous treatment liquid to a coagulation treatment tank, an organic coagulant or an inorganic coagulant, and a polymer coagulant to promote the sedimentation and separation of the generated flocs are used in combination.

[0083] Examples of organic or inorganic flocculants include cationic high molecular weight polymers with a weight-average molecular weight of 200,000 or more, anionic high molecular weight polymers with a weight-average molecular weight of 200,000 or more, and polyvalent inorganic salts. Specifically, examples include ionic high molecular weight polymers such as poly(meth)acrylic acid (co)polymers (salts), poly(meth)acrylamide (co)polymers (partial) hydrolysates (salts), (partial) sulfomethylated poly(meth)acrylamide (salts), poly(meth)acrylamide methylpropane sulfate (salts), N-vinylformamide (co)polymers, and polyvinylamines; aluminum-based flocculants such as aluminum sulfate and polyaluminum chloride (PAC); and iron-based flocculants such as ferric chloride and polyferric sulfate.

[0084] By using a coagulant and installing a coagulation treatment tank, it is possible to coagulate organic matter and organic polymers in colloidal particles in the wastewater, or to coarseen the flocs which are the coagulated materials, thereby reducing the load on the activated carbon in the aqueous treatment liquid of the present invention.

[0085] <Methods to reduce the TOC of waste liquid> This invention also provides a method for reducing the TOC (Total Organic Carbon) of wastewater, characterized by the use of the above-mentioned aqueous treatment solution. Since a decrease in TOC inevitably leads to a decrease in BOD (biochemical oxygen demand), COD (chemical oxygen demand), and organic matter concentration, the present invention is also a method for reducing BOD, COD, TOC, organic or inorganic matter, odorless treatment, and decolorization treatment using the above-mentioned aqueous treatment solution.

[0086] Furthermore, the aqueous treatment solution of the present invention not only does not cause any adverse effects when used in combination with microorganisms in activated sludge, but it is also expected to increase the adsorption effect of the activated carbon as the microorganisms adhere to the surface of the activated carbon. In other words, it is possible to realize a "so-called carrier method of wastewater treatment" in which microorganisms are supported on an "activated carbon carrier". Therefore, the present invention is also a "wastewater treatment method using a carrier method" characterized by using the aforementioned aqueous treatment liquid, and using activated carbon on which microorganisms in activated sludge are supported as a carrier. Furthermore, this "wastewater treatment method using a carrier" is also a method for reducing the TOC (Total Organic Carbon) of wastewater. [Examples]

[0087] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples unless it exceeds the essence of the invention.

[0088] Evaluation Examples 1-5 <Evaluation of activated carbon based on the reduction rate of TOC in wastewater> To investigate the types of activated carbon to use, we first added activated carbon in powder form to the evaluation solution and measured the reduction rate of TOC.

[0089] The evaluation solution was prepared by adding 99% pure water to 1% by mass of Toyogent T-SW5, a water-based paint thinner manufactured by Toyota Chemical Co., Ltd.

[0090] To 100g of this evaluation solution, 1.0g of each activated carbon listed in Table 1 was added, and the mixture was stirred at room temperature for 5 minutes to disperse each activated carbon in the evaluation solution. Then, the solution was filtered using ADVANTEC No. 5B filter paper, and the TOC of the filtrate was measured. Furthermore, the added activated carbon was in powder form, making it difficult to handle as it tended to scatter.

[0091] TOC was measured using a conventional method with Shimadzu Corporation's TOC-L series (combustion catalyst oxidation method).

[0092] In Table 1, Wood A is sawdust, and Wood B is lumber. Furthermore, carbonization was carried out at 500-700°C, followed by the activation treatment described in Table 1 according to conventional methods.

[0093] The results are shown in Table 1. The values ​​in Table 1, when relating to the amount of the ingredient, are in "parts by mass." Blank spaces in Table 1 indicate that the ingredient was not included (0 parts by mass).

[0094] [Table 1]

[0095] Evaluation Examples 11-19 <Study of swelling clay minerals based on the stability of water-soluble treatment solutions and the resulting structural viscosity> To investigate the types of swelling clay minerals, swelling clay minerals were added to water and their stability was measured. Viscosity was measured at 6 rpm and 60 rpm using a B-type viscometer, and the thixotropic index (TI value = [viscosity at 6 rpm] / [viscosity at 60 rpm]) was determined. A higher TI value indicates greater structural viscosity (higher thixotropy).

[0096] In Table 2, montmorillonite, stivunsite, and saponite are all clay minerals classified as belonging to the smectite group. In Table 2, "high-purity montmorillonite" refers to a powder made from montmorillonite, a clay mineral contained in bentonite, a rock, with increased purity.

[0097] <<Evaluation of the stability of swelling clay minerals>> To assess the "stability of swelling clay minerals," 6g of swelling clay minerals were added to 194g of water, which was being stirred with a three-motor agitator, and stirred for 1 hour to uniformly disperse the swelling clay minerals. The dispersed swelling clay minerals were collected in a 250mL transparent bottle and left to stand at room temperature (25°C) for 5 days. The stability of the swelling clay minerals (presence or absence of sedimentation or separation) was visually confirmed and evaluated according to the following criteria.

[0098] <<<Criteria for determining the stability of swelling clay minerals>>> ×: Unusable due to insufficient structural viscosity and poor stability. △: Although structural viscosity is imparted, it is difficult to use due to poor stability. ○: It is preferable to use this product because it has sufficient structural viscosity and good stability.

[0099] <<Evaluation of Structural Viscosity>> For "structural viscosity," a B-type viscometer was used to measure the viscosity at room temperature (25°C) at 6 rpm and at 60 rpm. The thixotropic index (TI value) was calculated by taking the ratio of these two values.

[0100] The composition and results are shown in Table 2 below. In Table 2, the unit of viscosity is [Pa·s]. The values ​​in Table 2 that relate to the amount of ingredients are in "parts by mass". Blank spaces in Table 2 indicate that the ingredient was not included (0 parts by mass).

[0101] [Table 2]

[0102] Good results were obtained with sepiolite, high-purity montmorillonite, synthetic stivunsite, and synthetic saponite. When the synthetic saponite content was reduced to less than 3 parts by mass, it ceased to form a gel and yielded the "dispersion stability of activated carbon" results shown in Table 4 below.

[0103] Evaluation Examples 21-25 <Evaluation as an aqueous treatment solution> The composition of activated carbon, evaluated using evaluation examples 1-5, was further enhanced by adding "high-purity montmorillonite," which was the best-performing type of swelling clay mineral evaluated using evaluation examples 11-19, to create an aqueous treatment solution for evaluation.

[0104] <Structural viscosity of aqueous treatment solution> The structural viscosity of the aqueous treatment solution containing activated carbon and swelling clay minerals was also measured in the same manner as described above for "<<Evaluation of Structural Viscosity>>", and judged according to the following criteria.

[0105] <<Criteria for determining structural viscosity>> ○: The viscosity of the B-type viscometer at a rotation speed of 6 rpm is 30 mPa·s or higher, and the TI value is 1.7 or higher, making it usable. △: The viscosity at 6 rpm of the Type B viscometer is too high, or the TI value is too high, resulting in poor handling, but the dispersion stability of the activated carbon is achieved, so it is usable. ×: The structural viscosity is too low; it is almost a Newtonian fluid and therefore unusable.

[0106] <Dispersion stability of activated carbon in aqueous treatment solution> The "dispersion stability of activated carbon in aqueous treatment solution" was evaluated by visually observing the degree of sedimentation and separation of activated carbon, according to the following criteria. Furthermore, the degree of sedimentation and separation of swelling clay minerals and activated carbon showed a very good correlation with the magnitude of the TI value.

[0107] <<Criteria for determining the dispersion stability of activated carbon (in aqueous treatment solution)>> ○: No sedimentation of activated carbon. △: Activated carbon settles slightly. ×: Activated carbon settles.

[0108] The results are shown in Table 3 below. The values ​​in Table 3 represent parts by mass. Blank spaces in Table 3 indicate that the substance was not included (0 parts by mass).

[0109] [Table 3]

[0110] In evaluation examples 22-25, the structural viscosity, as measured by the TI value, was optimal, and the dispersion stability of the structural viscosity-imparting powder and activated carbon was particularly good. Furthermore, while the TOC reduction rate was good regardless of the activated carbon used, it was particularly good when using the "woody A phosphate-activated" activated carbon.

[0111] Evaluation Examples 31-39 <Evaluation as an aqueous treatment solution> The compositions evaluated for structural viscosity-imparting powders in Evaluation Examples 11-19 were combined with "Woody A Phosphate-Activated," which was the best-performing type of activated carbon evaluated in Evaluation Examples 1-5, and evaluated as an aqueous treatment solution. The results are shown in Table 4 below. The values ​​in Table 4 represent parts by mass. Blank spaces in Table 4 indicate that the substance was not included (0 parts by mass).

[0112] [Table 4]

[0113] <Results of Evaluation Examples 31-39 (Table 4)> In evaluation examples 31-39, "woody A phosphate-activated" was used as the activated carbon, and in all cases the TOC reduction rate was approximately 63%, indicating a good TOC reduction rate. The dispersion stability of the structural viscosity-imparting powder and activated carbon is shown in Table 4. In evaluation examples 31, 32, 37, 38, and 39, which used powders without structural viscosity-imparting properties, the dispersion stability of the activated carbon was somewhat poor.

[0114] Although not shown in Table 4, sepiolite exhibited structural viscosity, but tended to precipitate slightly over time. Synthetic stivunsite and synthetic saponite tended to increase viscosity too much even in small amounts, making it somewhat difficult to adjust the concentration. When the synthetic saponite content was reduced to less than 3 parts by mass, it ceased to form a gel and yielded the "dispersion stability of activated carbon" results shown in Table 4.

[0115] Examples 1-10, Comparative Example 1 <Content (concentration) of swelling clay minerals> Using "Woody A Phosphate-Activated" (Evaluation Example 4), which was the best-performing activated carbon in Evaluation Examples 1-5, and "High-Purity Montmorillonite" (Evaluation Example 14), which was the best-performing swelling clay mineral in Evaluation Examples 11-19, the range of suitable and optimal content (concentration) and suitable and optimal viscosity (structural viscosity) of the swelling clay mineral (high-purity montmorillonite) were determined. The composition and evaluation results of the aqueous treatment solution are shown in Table 5 below. The values ​​in Table 5 represent the mass percentage of the total aqueous treatment solution.

[0116] The evaluation method for "dispersion stability of activated carbon" in Table 5 was performed visually as described above, and the evaluation criteria are as follows.

[0117] <<Criteria for determining the dispersion stability of activated carbon>> ○: No sedimentation of activated carbon. △: Activated carbon settles slightly. ×: Activated carbon settles.

[0118] [Table 5]

[0119] Examples 11-20, Comparative Example 2 <Activated carbon content (concentration)> Using "Woody A Phosphate-Activated" (Evaluation Example 4), which was the best-performing activated carbon in Evaluation Examples 1-6, and "High-Purity Montmorillonite" (Evaluation Example 14), which was the best-performing swelling clay mineral in Evaluation Examples 11-19, the range of suitable and optimal activated carbon content (concentration) and the range of suitable and optimal viscosity (structural viscosity) were determined.

[0120] <Dispersion stability of activated carbon in aqueous treatment solution> The "dispersion stability of activated carbon in aqueous treatment solution" was evaluated by visually observing the degree of dispersibility and dispersion stability of activated carbon in aqueous treatment solution after the activated carbon had been completely dispersed, and then using the following criteria. The composition and evaluation results are shown in Table 6 below.

[0121] <<Criteria for determining the dispersion stability of activated carbon in aqueous treatment solution>> ○: The dispersion stability of activated carbon in aqueous treatment solution is extremely good. △: Although it has a high activated carbon content and is paste-like, it can be used if the aqueous treatment solution is stirred before adding it to the wastewater (at the time of use). ×: The activated carbon content is too high, so even if the aqueous treatment solution is stirred before adding it to the wastewater (at the time of use), it does not have fluidity and cannot be used.

[0122] [Table 6]

[0123] The evaluation liquids evaluated in evaluation examples 11-19 (Table 2), with swelling clay minerals removed (i.e., "water"), do not exhibit structural viscosity. As shown in Comparative Example 1 (Table 5), none of the evaluation solutions that did not contain swelling clay minerals exhibited structural viscosity, regardless of the type of activated carbon they contained.

[0124] Evaluation Example 41 In the evaluation solutions (evaluation solutions that do not contain swelling clay minerals) shown in evaluation examples 17-19 in Table 2, activated carbon was added to create aqueous treatment solutions, and regardless of the amount of activated carbon present, the "dispersion stability of the activated carbon" was extremely poor. In other words, whether talc, sodium carbonate, or barium sulfate were included at 3% by mass or 6% by mass relative to the total aqueous treatment solution, sufficient structural viscosity could not be imparted. Therefore, the results were the same as Comparative Example 1 (without high-purity montmorillonite) in Table 5, and the "dispersion stability of activated carbon in the aqueous treatment solution" in Table 6 was extremely poor.

[0125] On the other hand, when activated carbon was added to the evaluation solutions of evaluation examples 11-16 in Table 2 to create aqueous treatment solutions, the "dispersion stability of activated carbon" was almost identical to the results of evaluation examples 11-16 (Table 2). In other words, even when using "other swelling clay minerals" from Evaluation Examples 11-13, 15, and 16 instead of high-purity montmorillonite, the dispersion stability of activated carbon in the resulting aqueous treatment solution varied depending on the degree of structural viscosity shown in Table 2 (some worsened), but the trend and good results were almost the same as in Examples 11-18 (Table 6).

[0126] Evaluation Example 42 In evaluation examples 1-5, "Wood A Phosphate Activation" was added as activated carbon to the evaluation solution at concentrations of 1.0% and 2.0% by mass, respectively. The extent to which unwanted substances were removed from the wastewater thinner generated during actual painting was visually confirmed. TOC was also measured.

[0127] In all cases, the TOC was reduced, similar to the results shown in Evaluation Example 4, and visual inspection also confirmed that unwanted materials had been removed, indicating a good result.

[0128] Evaluation Example 43 The following was conducted as a model experiment for adding an aqueous treatment solution to a coagulation treatment tank. To remove solid components from wastewater thinner using a coagulant, polyaluminum chloride (PAC) was added to generate flocs, and then a cationic high molecular weight polymer or anionic high molecular weight polymer was added, and the flocculated flocs were filtered through filter paper. To remove residual dissolved organic matter, aqueous treatment solutions were added as activated carbon (calculated in terms of activated carbon content) at concentrations of 1.0% by mass and 2.0% by mass, respectively, and the reduction of dissolved organic matter was confirmed by TOC (Theoretical Oxygen Concentration).

[0129] In all cases, TOC was reduced, similar to the results shown in Evaluation Example 4, and dissolved organic matter that could not be removed by flocculants was removed simply and effectively.

[0130] Evaluation Example 44 The following was conducted as a model experiment for adding aqueous treatment solution to the aeration tank in activated sludge treatment. A filtrate was prepared by removing solid matter from wastewater thinner using a coagulant. The solution was diluted to approximately 1000 ppm using TOC, and activated sludge was added to 1500 ppm using MLSS before aeration. 0.5% by mass of the aqueous treatment solution from Example 6 was added to the solution, and the presence or absence of an effect in promoting oxidative decomposition was confirmed (see Figure 1). As a result, when comparing the number of days until the TOC reached 500 ppm or less, it was found that the blank sample took 7-8 days, while the sample treated with aqueous solution took 2-3 days to reach 500 ppm or less. It is believed that microorganisms in the activated sludge colonized the activated carbon, using it as a support, and that oxidative decomposition proceeded efficiently. [Industrial applicability]

[0131] The aqueous treatment solution of the present invention can be quantitatively added to wastewater without scattering activated carbon, and can efficiently adsorb and remove unwanted substances from the wastewater. Furthermore, it is expected to promote oxidative decomposition when added to the aeration tank of activated sludge treatment. Therefore, it is suitable for use in factories with painting processes and is widely used in the painting industry, the automobile and other vehicle manufacturing industries, the large home appliance manufacturing industry, and other fields of manufacturing "products that require painting".

Claims

1. An aqueous treatment solution for treating wastewater by being added to the wastewater, The aqueous treatment solution is characterized in that it contains at least activated carbon, a swellable clay mineral, and water, and by imparting structural viscosity to the aqueous treatment solution, the activated carbon is dispersed and stabilized, and the handling properties are improved so that the activated carbon can be added quantitatively to the wastewater without scattering.

2. The aqueous treatment liquid according to claim 1, wherein the thixotropic index (TI value) is 1.7 or higher, and the viscosity at a rotation speed of 6 rpm of a B-type viscometer is 30 mPa·s or higher, and the structural viscosity is such that the aqueous treatment liquid has structural viscosity.

3. The aqueous treatment solution according to claim 1, wherein the swelling clay mineral is a swelling clay mineral belonging to the smectite group.

4. The aqueous treatment solution according to claim 1, wherein the swelling clay mineral is montmorillonite, stivunsite, or saponite.

5. The aqueous treatment solution according to claim 1, wherein the swelling clay mineral is high-purity montmorillonite obtained by removing quartz and feldspar from bentonite, which has montmorillonite as the main component and silicate minerals such as quartz or feldspar as minor components.

6. The aqueous treatment solution according to claim 1, wherein the waste liquid contains at least organic matter and water.

7. The aqueous treatment liquid according to claim 1, wherein the waste liquid is waste aqueous thinner generated when an apparatus used for painting, a component or booth in the apparatus, or a paint path or piping used in the apparatus is cleaned with an aqueous thinner.

8. The aqueous treatment liquid according to claim 1, wherein the wastewater to which the aqueous treatment liquid is added is wastewater in a coagulation treatment tank or wastewater in an aeration tank in activated sludge treatment.

9. A wastewater treatment method characterized by using the aqueous treatment solution described in any one of claims 1 to 8.

10. A wastewater treatment method characterized by treating a wastewater containing organic matter and water by adding an aqueous treatment solution according to any one of claims 1 to 8 to the wastewater.

11. The wastewater treatment method according to claim 9, wherein the wastewater is wastewater thinner generated when a painting apparatus, a component or booth in the apparatus, or a paint pathway or piping used in the apparatus is cleaned with water-based thinner.

12. The wastewater treatment method according to claim 9, wherein the aqueous treatment solution is added to a coagulation treatment tank or an aeration tank in activated sludge treatment to treat the wastewater.

13. The wastewater treatment method according to claim 12, wherein when the aqueous treatment liquid is added to the coagulation treatment tank, an organic coagulant or an inorganic coagulant and a polymer coagulant are used in combination to promote the sedimentation and separation of the generated flocs.

14. A method for reducing the TOC (Total Organic Carbon) of wastewater, characterized by using the aqueous treatment solution described in any one of claims 1 to 8.

15. A wastewater treatment method using a carrier-based method, characterized by using an aqueous treatment liquid according to any one of claims 1 to 8, wherein activated carbon on which microorganisms in activated sludge are supported is used as the carrier.

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