Treatment apparatus and treatment method for circulating water in a wet painting booth

Abstract

To provide a wet coating booth circulation water processing apparatus and a processing method capable of efficiently removing an obtained coating material sludge in which a surplus coating material taken by the circulation water is treated to efficiently obtain coating material sludge (sludge), and the obtained coating material sludge can be efficiently removed.SOLUTION: A system consists of capturing excess paint generated in a wet paint booth 1 in circulating water, sending circulating water containing the trapped excess paint to a circulating water pit, temporarily retaining the circulating water in the circulating water pit, injecting water containing micro-nano bubbles in the circulating water retained in the circulating water pit to raise sludge consisting of excess paint, removing all or part of the raised sludge from the circulating water, and then returning the circulating water with the sludge removed from the circulating water pit to the wet paint booth.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for treating circulating water in a wet painting booth. More specifically, the present invention efficiently obtains paint sludge by subjecting surplus paint captured by circulating water to treatments such as non-stickification, condensation, and aggregation, and relates to an apparatus and a method for treating circulating water in a wet painting booth that can efficiently remove the obtained paint sludge by floating it up.

Background Art

[0002] Surplus paint that has not been applied in a wet painting booth is captured by circulating water. Next, the surplus paint captured in the circulating water is removed, and the circulating water from which the surplus paint has been removed is reused in the wet painting booth. For this purpose, various methods for removing surplus paint captured in the circulating water of a wet painting booth have been proposed.

[0003] For example, Patent Document 1 discloses a method for treating circulating water in a wet painting booth, which includes allowing circulating water containing surplus paint and water discharged from the wet painting booth to stay in a pit for a predetermined time, and adding a phenol resin solution or dispersion, a low molecular weight cationic polymer solution or dispersion, a tannin alkali solution, a polymer cationic polymer solution or dispersion containing a benzyl group, and a polymer anionic polymer solution or dispersion to the circulating water in the upper stream of the pit, adding micro-nano bubbles thereto to form paint floating sludge, and then removing all or part of the paint floating sludge from the circulating water.

[0004] Patent Document 2 discloses a method for treating circulating water in a wet painting booth, which includes adding micro-nano bubbles to at least one selected from the group consisting of circulating water flowing from the wet painting booth toward one end or the vicinity thereof in a pit, and circulating water flowing into one end or the vicinity thereof in the pit and mixing with the circulating water accumulated in the pit to form paint floating sludge, then removing all or part of the paint floating sludge from the circulating water, and then returning the circulating water to the wet painting booth from the other end or the vicinity thereof in the pit.

[0005] Patent Document 3 discloses a method for treating paint in circulating water of a wet painting booth containing paint by adding an alkaline solution of a phenolic resin to the circulating water, wherein the pH of the circulating water is adjusted to 6.5 to 8.0, and when the pH of the circulating water reaches a predetermined value of 8.0 or less, the addition amount of the alkaline solution of the phenolic resin is increased. A method for treating circulating water in a wet painting booth is disclosed.

[0006] Patent Document 4 discloses a method for controlling the dosing of a treatment chemical into the circulating water of a wet painting booth for non-sticking, agglomeration or floating of the paint in the circulating water, characterized in that the addition of the treatment chemical to the circulating water is controlled based on the amount of foam generated in the circulating water (for example, the height of the foam in the circulation tank). A method for controlling the dosing of a treatment chemical for circulating water in a wet painting booth is disclosed.

[0007] Patent Document 5 discloses a method for controlling the dosing of a treatment chemical into the circulating water of a wet painting booth for non-sticking, agglomeration or floating of the paint in the circulating water, characterized in that the addition of the treatment chemical to the circulating water is controlled based on the turbidity or suspended solid concentration of the circulating water. A method for controlling the dosing of a treatment chemical for circulating water in a wet painting booth is disclosed.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] Generally, sludge composed of surplus paint floating in the circulating water retained in the circulating water pit is floated and removed. However, the sludge composed of floating surplus paint has high adhesiveness, easily adheres to the inner walls of pipes, tanks, etc., and once adhered, it is difficult to remove. Also, even after floating and removing, the efficiency of solid-liquid separation is low, and there may be only sludge waste with a high water content. On the other hand, sludge composed of surplus paint deposited in the circulating water retained in the circulating water pit is often difficult to lift and remove by conventional methods, especially when it is in a consolidated state. The removal of the deposited sludge can be carried out by temporarily stopping the use of the circulating water pit, dredging the bottom, and taking out the deposited sludge, but it takes time and cost, such as temporarily stopping the use of the circulating water pit.

[0010] An object of the present invention is to provide a treatment apparatus and a treatment method for wet painting booth circulating water that can efficiently obtain paint sludge (sludge) by subjecting surplus paint captured by circulating water to treatments such as non-sticking, coagulation, and aggregation, floating the obtained paint sludge, and efficiently removing it.

Means for Solving the Problems

[0011] As a result of investigations to achieve the above object, the present invention including the following aspects has been completed.

[0012] 〔1〕Capturing surplus paint generated in a wet painting booth with circulating water, Sending the circulating water containing the captured surplus paint to a circulating water pit, Temporarily retaining the circulating water in the circulating water pit, Injecting water containing micronano bubbles into the circulating water retained in the circulating water pit to promote the floating of sludge composed of surplus paint, Removing all or part of the floated sludge from the circulating water, and then Returning the circulating water from which the sludge has been removed from the circulating water pit to the wet painting booth, And Adding a water treatment agent to the circulating water, Measuring the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water, and Based on the measured values, adjusting the addition amount of the water treatment agent and / or the injection amount of the water containing micronano bubbles so that the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water are within a predetermined value range, including A method for treating the circulating water of a wet painting booth.

[0013] [2] Capturing the surplus paint generated in the wet painting booth with the circulating water, Sending the circulating water containing the captured surplus paint to a circulating water pit, Temporarily storing the circulating water in the circulating water pit, Injecting water containing micronano bubbles into the circulating water stored in the circulating water pit to promote the floating of the sludge composed of surplus paint, Removing all or part of the floating sludge from the circulating water, and then Returning the circulating water from which the sludge has been removed from the circulating water pit to the wet painting booth, And Adding a water treatment agent to the circulating water, and Adjusting the addition amount of the water treatment agent or the injection amount of the water containing micronano bubbles in response to events in the wet painting booth, including A method for treating the circulating water of a wet painting booth.

[0014] [3] The treatment method according to [2], wherein the event in the wet painting booth is the start or stop of the wet painting booth, the start or stop of painting, the disposal of paint or paint cleaning liquid into the circulating water, blow-off or primer, intermediate coat, or top coat. [4] The treatment method according to any one of [1] to [3], wherein the injection of the water containing micronano bubbles is performed toward the bottom of the circulating water pit.

[0015] [5] Searching for the sludge composed of surplus paint deposited at the bottom of the circulating water pit, The treatment method according to any one of [1] to [4], further comprising adjusting the position or direction of injecting water containing micro-nano bubbles based on the search results.

[0016] 〔6〕Circulating water pit, A discharge path for flowing circulating water from the wet painting booth towards the circulating water pit, Micro-nano bubble generator, A supply path for flowing circulating water from the circulating water pit towards the wet painting booth, A mechanism for adding a water treatment agent to the circulating water, A measuring device for measuring the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water, and Based on the measured values obtained by the measuring device, an adjustment device having a control algorithm for adjusting the addition amount of the water treatment agent or the injection amount of the water containing micro-nano bubbles so that the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water are within a predetermined value range. The micro-nano bubble generator is installed such that the injection port of the water containing micro-nano bubbles can inject the water containing micro-nano bubbles into the circulating water retained in the circulating water pit. A treatment device for wet painting booth circulating water.

[0017] 〔7〕Circulating water pit, A discharge path for flowing circulating water from the wet painting booth towards the circulating water pit, Micro-nano bubble generator, A supply path for flowing circulating water from the circulating water pit towards the wet painting booth, A mechanism for adding a water treatment agent to the circulating water, Comprising an adjustment device having a control algorithm for adjusting the addition amount of the water treatment agent or the injection amount of the water containing micro-nano bubbles in response to an event in the wet painting booth. The micro-nano bubble generator is installed such that the injection port of the water containing micro-nano bubbles can inject the water containing micro-nano bubbles into the circulating water retained in the circulating water pit. Treatment device for circulating water in a wet painting booth.

[0018] 〔8〕The treatment device according to 〔6〕 or 〔7〕, wherein a water injection port containing micronano bubbles is installed so as to be able to inject water containing micronano bubbles toward the bottom of the circulating water pit.

[0019] 〔9〕The treatment device according to any one of 〔6〕 to 〔8〕, further comprising a sensor for detecting sludge composed of surplus paint deposited on the bottom of the circulating water pit. 〔10〕The micronano bubble generator has a mechanism for adjusting the position or direction of the water injection port containing micronano bubbles. 〔13〕The adjustment device further has a control algorithm for adjusting the position or direction of the water injection port containing micronano bubbles. The treatment device according to any one of 〔6〕 to 〔9〕.

Advantages of the Invention

[0020] According to the treatment device and treatment method for circulating water in a wet painting booth of the present invention, surplus paint captured by the circulating water is subjected to treatments such as non-sticking, coagulation, and aggregation to efficiently obtain paint sludge (sludge), and the paint sludge (sludge) can be floated and efficiently removed. Further, the treatment device and treatment method for circulating water in a wet painting booth of the present invention can be expected to promote the decomposition of harmful substances and organic substances in the sludge by aerobic microorganisms. According to the present invention, in the treatment of circulating water in a wet painting booth, the wasteful addition and injection of water treatment agents and water containing micronano bubbles are reduced, the operating cost can be reduced, and sludge with a low water content can be obtained, so that the disposal cost of waste can be reduced. In the present invention, by adopting automatic control, the work safety, stability, or security level can be improved, and the labor cost can be reduced.

Brief Description of the Drawings

[0021]

Figure 1

Embodiments for Carrying Out the Invention

[0022] The method for treating the circulating water of the wet painting booth of the present invention captures surplus paint generated in the wet painting booth 1 with circulating water A, sends the circulating water containing the captured surplus paint to the circulating water pit 25, temporarily stores the circulating water in the circulating water pit, removes all or part of the floated sludge from the circulating water, and then returns the circulating water from which the sludge has been removed from the circulating water pit to the wet painting booth.

[0023] In addition, the apparatus for treating the circulating water of the wet painting booth of the present invention includes a circulating water pit 25, a discharge path for flowing the circulating water from the wet painting booth toward the circulating water pit, and a supply path for flowing the circulating water from the circulating water pit toward the wet painting booth.

[0024] Examples of the wet painting booth to which the apparatus and method for treating the circulating water of the wet painting booth of the present invention can be applied include a water flow plate type (water film type) painting booth that captures surplus paint with water film-like circulating water, a shower type painting booth that captures surplus paint with shower-like circulating water, a water film - shower type painting booth that combines the water film type and the shower type, a Venturi type painting booth that captures surplus paint separated by centrifugal force in a scroll chamber with water film-like circulating water, and the like.

[0025] In a wet painting booth, various events occur. For example, when the vehicle 24 enters the wet painting booth 1 on the conveyor, the spraying (painting) of the paint is started, and when the painting is completed, the spraying (painting) of the paint is stopped, and the painted vehicle exits the wet painting booth. In such events, surplus paint may be intermittently generated in the wet painting booth. Also, for the main event of painting, there are modes such as waste spraying or primer, intermediate coat, or top coat, and for each of these modes, the properties of the paint, the usage amount, the generation amount of surplus paint, etc. may be different. Furthermore, as an event, the disposal of paint or paint cleaning liquid into the circulating water may be carried out. When the painting booth is operated only during the day, or when work for the maintenance and inspection of the painting booth is carried out, an unsteady operation for starting or stopping the wet painting booth is performed. In the unsteady operation, compared with the steady operation, the properties of the paint, the usage amount, etc. may be different, or different substances such as thinning liquid and cleaning liquid may be used. The method of one embodiment of the present invention further includes adjusting the addition amount of the water treatment agent or the injection amount of the water containing micro-nano bubbles by an empirical rule, an expert system, a learned AI, etc. corresponding to the occurrence of such events in the wet painting booth. Also, in the apparatus of one embodiment of the present invention, an adjustment device having a control algorithm for adjusting the addition amount of the water treatment agent or the injection amount of the water containing micro-nano bubbles corresponding to the events in the wet painting booth is further provided. It can include transmitting the execution information of the above events in the wet painting booth to the adjustment device and using it for the automatic control described later.

[0026] Circulating water (untreated circulating water Au) containing surplus paint and water, obtained by capturing surplus paint in a wet painting booth, flows through a discharge path from the wet painting booth towards a circulating water pit. When there is a distance (drop) between the outlet of the discharge path and the water surface of the circulating water accumulated in the circulating water pit, it moves towards the water surface of the circulating water accumulated in the circulating water pit from the outlet of the discharge path, and the circulating water flowing out from the outlet of the discharge path in the circulating water pit mixes with the circulating water previously retained in the circulating water pit, and then is temporarily retained in the circulating water pit. While the circulating water is retained in the circulating water pit, sludge composed of surplus paint is removed from the circulating water to clarify the circulating water. Next, the treated circulating water At flows through a supply path from the circulating water pit towards the wet painting booth, is returned to the wet painting booth, and is reused for capturing surplus paint in the wet painting booth. The residence time of the circulating water in the circulating water pit is not particularly limited, but for example, it is preferably 1 to 20 minutes, more preferably 2 to 5 minutes.

[0027] The circulating water pit 25 is not particularly limited by its shape as long as it can store circulating water. For example, those having a rectangular parallelepiped-shaped storage space (rectangular pit), those having a cylindrical or annular cylindrical storage space (circular pit), etc. can be used. And in order to make it difficult for the untreated circulating water to mix with the treated circulating water, the supply port of the untreated circulating water to the circulating water pit, that is, the outlet of the discharge path, is preferably installed at a position as far as possible from the extraction port of the treated circulating water from the circulating water pit, that is, the inlet of the supply path. For example, the supply port of the untreated circulating water to the circulating water pit and the extraction port of the treated circulating water from the circulating water pit can be provided at diagonal positions of the storage space. More specifically, for example, the outlet of the discharge path can be provided at one end or near it of the circulating water pit, and the inlet of the supply path can be provided at the other end or near it of the circulating water pit. Note that the end of the pit means at least one place on two opposite sides of the rectangle in a rectangular pit, and in a circular pit, it means at least one place on the edge of the center well (inner circumference) and at least one place on the outer circumference edge. The vicinity of the end is a location within the range recognized by those skilled in the art as the end of the pit in consideration of the size of equipment necessary for actual operation, etc.

[0028] Remove all or part of the floated sludge from the circulating water. The removal of all or part of the floated sludge is preferably carried out by taking surface water containing the floated sludge and water with a water intake device. Examples of the water intake device include surface liquid discharge devices such as a float weir and a float pump.

[0029] It is preferable to subject the water intake liquid taken by the water intake device to a floating treatment, preferably a pressurized floating treatment. By performing the floating treatment, the aggregated floating sludge can be floated. Note that the pressurized floating treatment is a treatment method for generating air bubbles and floating suspended matter by injecting a supersaturated solution of air (pressurized) into a liquid containing suspended matter (atmospheric pressure). The average diameter of the bubbles generated in the pressurized floating treatment is preferably 120 μm or less, more preferably 30 μm or more and 120 μm or less. The average diameter of the bubbles generated in the pressurized floating treatment is preferably larger than the average diameter of the micro-nano bubbles described later.

[0030] The water intake liquid subjected to the pressurized floating treatment can be subjected to a filtration treatment and / or a dehydration treatment. In the filtration treatment, a wedge wire screen, a rotary screen, a bar screen, a flexible container bag, etc. can be used. In the dehydration treatment, a cyclone, a centrifuge, a pressure filtration device, etc. can be used. The taken-out sludge can be incinerated, landfilled, or composted. Also, the water obtained by the filtration treatment and / or the dehydration treatment of the water intake liquid can be reused as circulating water.

[0031] On the other hand, the treated circulating water (treated circulating water At) from which all or part of the floating sludge has been removed is supplied to the wet painting booth via a supply path and reused for capturing excess paint. In order to make it difficult for slag, sludge, floc, etc. to be carried out with the circulating water, it is preferable to provide a weir, a filter, a net, etc. at or near the outlet of the treated circulating water from the circulating water pit.

[0032] The method for treating the circulating water in a wet painting booth according to an embodiment of the present invention further includes adding a water treatment agent to the circulating water, injecting water containing micro-nano bubbles into the circulating water retained in the circulating water pit to promote the floating of sludge composed of surplus paint, measuring the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water, and adjusting the addition amount of the water treatment agent and / or the injection amount of the water containing micro-nano bubbles based on the measured values so that the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water are within a predetermined value range. Also, the treatment device for the circulating water in a wet painting booth according to an embodiment of the present invention further includes a mechanism for adding a water treatment agent to the circulating water, a micro-nano bubble generator, a measuring device for measuring the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, or the pH of the circulating water, and a control algorithm for adjusting the addition amount of the water treatment agent or the injection amount of the water containing micro-nano bubbles based on the measured values obtained by the measuring device so that the amount of bubbles in the circulating water, the turbidity or suspended substance concentration of the circulating water, or the pH of the circulating water are within a predetermined value range.

[0033] Examples of the water treatment agent include an anti-sticking agent, a coagulant, a flocculant, a pH adjuster, an antifoaming agent, and the like.

[0034] The anti-sticking agent is not particularly limited as long as it can reduce the adhesion force on the surface of the surplus paint. For example, alumina sol, sepiolite, phenol resin, melamine formaldehyde resin, phenol formaldehyde resin, melamine dicyandiamide condensate, bentonite, hectorite, linear cationic polyamine, sodium zincate, carboxylic acid polymer, tannin, tannin-based compound, tannin-based polymer, cellulose acetate, etc. can be mentioned. Among these, phenol resin is preferable. Phenol resin is suitable for water treatment in circulating water with a large amount of surface foam capturing aqueous paint or circulating water capturing organic solvent paint with almost zero surface potential. Therefore, in response to such events in a wet painting booth, phenol resin can be selected as the anti-sticking agent.

[0035] The phenolic resin is preferably added in the form of a phenolic resin solution or dispersion (hereinafter referred to as a phenolic resin-containing liquid) obtained by dissolving or dispersing it in a solvent or dispersion medium having a high affinity for water. The phenolic resin is a condensate of phenols and aldehydes or a modified product thereof, and may be a product before crosslinking and curing or a product after crosslinking and curing. Specific examples of the phenolic resin include condensates of phenol and formaldehyde, condensates of cresol and formaldehyde, condensates of xylenol and formaldehyde, and the like. Examples of the modified product include alkyl-modified phenolic resins and polyvinylphenol. These phenolic resins may be novolak type or resol type. Further, the phenolic resin is not particularly limited by its molecular weight and other physical properties, and can be appropriately selected and used from those generally used for treating circulating water in a wet painting booth. The phenolic resin may be used alone or in combination of two or more. The phenolic resin used in the present invention preferably has a weight average molecular weight of 10,000 or less, more preferably 7,000 or less.

[0036] Examples of the solvent or dispersion medium that can be used in the phenolic resin-containing liquid include ketones such as acetone, esters such as methyl acetate, alcohols such as methanol, aqueous alkali solutions, and amines. Among these solvents, an aqueous alkali solution is preferred. Examples of the aqueous alkali solution include an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution. The product obtained by dissolving or dispersing the phenolic resin in an aqueous alkali solution preferably has an alkali component concentration of 1 to 25% by mass and a phenolic resin concentration of 1 to 50% by mass.

[0037] The addition of the anti - sticking agent can be carried out with respect to the circulating water in the wet - painting booth, the circulating water flowing from the wet - painting booth towards the circulating - water pit, the circulating water that has flowed into the circulating - water pit and is mixed with the circulating water accumulated in the circulating - water pit, the circulating water accumulated in the circulating - water pit, or the circulating water flowing from the circulating - water pit towards the wet - painting booth. It is preferable to carry out the addition with respect to the circulating water flowing from the wet - painting booth towards the circulating - water pit, the circulating water that has flowed into the circulating - water pit and is mixed with the circulating water accumulated in the circulating - water pit, the circulating water accumulated in the circulating - water pit, or the circulating water flowing from the circulating - water pit towards the wet - painting booth.

[0038] The coagulant has the function of neutralizing and coagulating the charge of fine microparticles in water. Coagulants are roughly classified into organic coagulants and inorganic coagulants. Examples of organic coagulants include sodium alginate; chitin / chitosan - based coagulants; bio - coagulants such as TKF04 strain and BF04; cationic polymer coagulants, etc. Examples of cationic polymer coagulants include those composed of cationic polymers (hereinafter referred to as low - molecular - weight cationic polymers) having a weight - average molecular weight of preferably 1,000 or more and 1,000,000 or less, more preferably 5,000 or more and 300,000 or less.

[0039] Examples of inorganic coagulants include aluminum - based coagulants such as aluminum sulfate (alum), polyaluminum chloride (PAC), polyaluminum hydroxy - chloride, pseudo - boehmite alumina sol (AlO(OH)), aluminum chloride, basic aluminum chloride, etc.; iron - salt - based coagulants such as ferrous hydroxide, ferrous sulfate, ferric chloride, polyferric sulfate, iron - silica inorganic polymer coagulants, etc.; zinc - based coagulants such as zinc chloride; activated silicic acid, polysilica - iron coagulants, etc.

[0040] As the coagulant used in the present invention, a low molecular weight cationic polymer is preferred. The low molecular weight cationic polymer is preferably added in the form of a low molecular weight cationic polymer solution or dispersion (hereinafter referred to as a low molecular weight cationic polymer-containing liquid) obtained by dissolving or dispersing it in a solvent or dispersion medium having a high affinity for water.

[0041] Examples of the low molecular weight cationic polymer include polyethyleneimine, cation-modified polyacrylamide, polyamine, polyamine sulfone, polyamide, polyalkylene polyamine, amine-crosslinked polycondensate, dimethylaminoethyl polyacrylate, dimethyldiallylammonium chloride (DADMAC) polymer, polycondensate of alkylamine and epichlorohydrin, polycondensate of alkylene dichloride and polyalkylene polyamine, polycondensate of dicyandiamide and formalin, homopolymer or copolymer of acid salt or quaternary ammonium salt of DAM (dimethylaminoethyl methacrylate), homopolymer or copolymer of acid salt or quaternary ammonium salt of DAA (dimethylaminoethyl acrylate), polyvinylamidine, copolymer of diallyldimethylammonium chloride and acrylamide, polycondensate of melamine and aldehyde, polycondensate of dicyandiamide and aldehyde, polycondensate of dicyandiamide and diethylenetriamine, etc. Examples of the alkylamine in the polycondensate of alkylamine and epichlorohydrin include monomethylamine, monoethylamine, dimethylamine, diethylamine, etc. Examples of the aldehyde in the melamine-aldehyde condensate and the dicyandiamide-aldehyde polycondensate include formaldehyde, acetaldehyde, propionaldehyde, paraformaldehyde which is a trimer of formaldehyde, etc. The low molecular weight cationic polymer may be used alone or in combination of two or more.

[0042] Examples of the solvent or dispersion medium that can be used in the low molecular weight cationic polymer-containing liquid include water, acetone, methanol, etc.

[0043] The addition of the coagulant can be carried out on the circulating water in the wet painting booth, the circulating water flowing from the wet painting booth towards the circulating water pit, the circulating water mixed with the circulating water flowing into the circulating water pit and accumulating in the circulating water pit, the circulating water accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit towards the wet painting booth. It is preferable to carry out the addition on the circulating water flowing from the wet painting booth towards the circulating water pit, the circulating water mixed with the circulating water flowing into the circulating water pit and accumulating in the circulating water pit, the circulating water accumulated in the circulating water pit, or the circulating water flowing from the circulating water pit towards the wet painting booth. By adding the coagulant, it is possible to neutralize the charge of the surplus paint in the circulating water and facilitate the formation of fine flocs.

[0044] The non-sticking agent and the coagulant can be added to the circulating water separately or in combination. For the combined addition or mixed addition of the non-sticking agent and the coagulant, it is possible to facilitate the formation of fine flocs with low adhesiveness.

[0045] The flocculant can be added for the formation of coarse flocs. The addition of the flocculant aggregates the solidified flocs of the surplus paint obtained by the action of the coagulant to form coarse flocs, thereby promoting sedimentation separation and centrifugal separation and obtaining sludge waste with a low water content.

[0046] Examples of the flocculant include polymer flocculants composed of anionic polymers, cationic polymers, amphoteric polymers, etc. Such polymers usually have a weight average molecular weight exceeding 1 million, preferably 5 million or more. Examples of the polymer flocculant composed of an anionic polymer include sodium polyacrylate, sodium acrylate - amide derivative, partially hydrolyzed polyacrylamide, partially sulfomethylated polyacrylamide, poly(2 - acrylamido)-2 - methylpropane sulfate, etc. Examples of the polymer flocculant composed of a cationic polymer include polyaminoalkyl acrylate, polyaminoalkyl methacrylate, polyethyleneimine, halogenated polydiallylammonium, chitosan, urea-formalin resin, and the like. Examples of the polymer flocculant composed of an amphoteric polymer include a copolymer of acrylamide, aminoalkyl methacrylate, and sodium acrylate.

[0047] As the polymer flocculant composed of a cationic polymer, it is preferable to use a high molecular weight cationic polymer solution or dispersion (hereinafter, these may be collectively referred to as "high molecular weight cationic polymer-containing liquid").

[0048] The high molecular weight cationic polymer-containing liquid is, for example, a solution in which a high molecular weight cationic polymer is dissolved in a solvent having a high affinity for water or a dispersion obtained by dispersing the high-concentration solution in a hydrophobic liquid (W / O type emulsion), etc. The high molecular weight cationic polymer has, for example, a weight average molecular weight of preferably more than 1 million, more preferably 5 million or more, and still more preferably 6 million to 11 million.

[0049] Examples of the high molecular weight cationic polymer include polymers having a cationic structural unit derived from a quaternary ammonium salt of (meth)acrylic acid ester (for example, copolymers of acrylamide / [2-(acryloyloxy)ethyl]benzyldimethylammonium chloride / [2-(acryloyloxy)ethyl]trimethylammonium chloride, acrylamide / [3-(acryloyloxy)propyl]benzyldimethylammonium chloride / [2-(acryloyloxy)ethyl]trimethylammonium chloride, acrylamide / [2-(acryloyloxy)ethyl]benzyldimethylammonium chloride / [3-(acryloyloxy)propyl]trimethylammonium chloride, acrylamide / [3-(acryloyloxy)propyl]benzyldimethylammonium chloride / [3-(acryloyloxy)propyl]trimethylammonium chloride, etc.), polyaminoalkyl acrylate, polyaminoalkyl methacrylate, polyethyleneimine, halogenated polydiallylammonium, chitosan, urea-formalin resin, etc. The high molecular weight cationic polymer can be used alone or in combination of two or more kinds. By adding the high molecular weight cationic polymer, redispersion of the flock (floating sludge) can be prevented, and the efficiency of the filtration treatment and / or dehydration treatment (such as sedimentation separation and centrifugation) that may be performed after the pressurized flotation treatment can be enhanced, and sludge waste with a lower water content can be obtained.

[0050] As the high molecular weight flocculant composed of an anionic polymer, it is preferable to use an anionic polymer solution or dispersion (hereinafter, these may be collectively referred to as "anionic polymer-containing liquid"). The anionic polymer-containing liquid is, for example, one obtained by dissolving an anionic polymer in a solvent having a high affinity for water or dispersing the high-concentration solution in a hydrophobic solvent (W / O type emulsion), etc. Examples of anionic polymers include sodium polyacrylate, sodium acrylate - amide derivatives, partially hydrolyzed polyacrylamide, partially sulfomethylated polyacrylamide, poly(2 - acrylamido)-2 - methylpropane sulfate, etc. The anionic polymer can be used alone or in combination of two or more. The anionic polymer preferably has an anionic degree of 10 - 30 mol%. The weight - average molecular weight of the anionic polymer is preferably more than 1 million, more preferably 5 million or more, and still more preferably 8 million - 15 million.

[0051] As the polymer flocculant composed of an amphoteric polymer, it is preferable to use an amphoteric polymer solution or dispersion (hereinafter, these may be collectively referred to as "amphoteric polymer - containing liquid"). The amphoteric polymer - containing liquid is, for example, a solution obtained by dissolving an amphoteric polymer in a solvent having a high affinity for water or a high - concentration solution dispersed in a hydrophobic solvent (W / O type emulsion). Examples of the amphoteric polymer include a copolymer of (meth)acrylamide, quaternary ammonium alkyl (meth)acrylate, and sodium (meth)acrylate. The molar ratio of anion / cation of the amphoteric polymer is preferably 0.2 - 2.0. The weight - average molecular weight of the amphoteric polymer is preferably more than 1 million, more preferably 5 million or more, and still more preferably 8 million - 10 million.

[0052] The addition of the flocculant can be carried out on the circulating water in the wet - painting booth, the circulating water flowing from the wet - painting booth towards the circulating - water pit, the circulating water mixed with the circulating water flowing into the circulating - water pit and accumulating in the circulating - water pit, the circulating water accumulated in the circulating - water pit, the circulating water flowing from the circulating - water pit towards the wet - painting booth, the surface water or the intake water, but it is preferably carried out on the surface water or the intake water. The high - molecular - weight cationic polymer is preferably added to the surface water (circulating water containing floating sludge). The anionic polymer solution or dispersion is preferably added to the intake water (circulating water taken from the surface water). The amphoteric polymer solution or dispersion is preferably added to the water intake (recirculated water taken from surface water).

[0053] Examples of the pH adjuster include water-soluble alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; and the like. Note that the pH of the recirculated water may also vary depending on other water treatment agents such as non-sticking agents, coagulants, and flocculants, and these may also function as pH adjusters. The addition of the pH adjuster can be carried out on the recirculated water flowing from the wet painting booth towards the recirculated water pit, the recirculated water flowing into the recirculated water pit and mixing with the recirculated water accumulated in the recirculated water pit, the recirculated water accumulated in the recirculated water pit, the recirculated water flowing from the recirculated water pit towards the wet painting booth, the recirculated water present in the wet painting booth, the surface water, or the water intake.

[0054] Each of the water treatment agents can be prepared and stored in advance in the tank 13 or the like. The storage amount of the water treatment agent can be measured by a liquid level gauge 14 attached to the tank, and the measured value can be incorporated into the control system to issue warnings such as insufficient or lacking water treatment agent.

[0055] Examples of the micro-nano bubble generator 16 include a generator of the crushing method that utilizes a rapid pressure change generated by ultrasonic waves, shock waves, etc. (crushing method), a generator of the shearing method that atomizes gas by turbulent flow generated by a Venturi tube, a high-speed rotating rotor, etc. in a state where gas and liquid are mixed (shearing method), a generator of a combined method of the crushing method and the shearing method, a generator of a method that mixes and compresses the gas and liquid supplied to a cylinder to obtain a liquid containing bubbles and discharges this through a bubble diffusion hole, a generator of a method that forcibly dissolves gas into the liquid by pressurization with a compressor or the like, a generator of a method that mixes liquid and gas with a turbo-type pump and dissolves the gas in the liquid, and the like.

[0056] The water containing micro-nano bubbles used in the present invention (hereinafter sometimes referred to as micro-nano bubble water) has a volume ratio of air to water at 20 °C and 1 atm that is preferably 0.01 or more, more preferably 0.05 or more. The upper limit of the volume ratio is determined according to the micro-nano bubble generator.

[0057] The water used for producing micro-nano bubble water may be water supplied from outside the system or treated recycled water. For example, a part of the treated recycled water (recycled water from which sludge has been removed) At may be supplied to the micro-nano bubble generator through a diversion path or the like without being returned to the wet painting booth.

[0058] The micro-nano bubble generator has an injection port for micro-nano bubble water. The injection port is provided so that micro-nano bubble water can be injected into the recycled water retained in the recycled water pit. The injection port for micro-nano bubble water is preferably provided so that micro-nano bubble water can be injected toward the bottom of the recycled water pit. By injecting micro-nano bubble water toward the bottom of the recycled water pit, the sludge deposited on the bottom of the recycled water pit can be lifted up, suspended in the recycled water, and given buoyancy by the adhesion of micro-nano bubbles to float it up.

[0059] The number average diameter of the micro-nano bubbles when injected into the recycled water is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. The lower limit of the number average diameter of the micro-nano bubbles when injected into the recycled water is not particularly limited, but is preferably 0.1 μm, more preferably 0.5 μm, and even more preferably 1 μm.

[0060] The injection speed of the micro-nano bubble water is preferably 0.1 m / s or more, more preferably 0.2 m / s or more. The higher the injection speed, the easier it is to lift the sludge deposited at the bottom of the circulating water pit. The injection speed increases as the size of the injection port decreases and the injection volume increases. The injection volume of the micro-nano bubble water can be changed by adjusting the discharge volume or discharge pressure of the pump. The injection port is preferably provided in a nozzle. The injection of the micro-nano bubble water may be continuous or intermittent at a fixed period or an indefinite period.

[0061] In the present invention, it is preferable to include searching for sludge composed of surplus paint deposited at the bottom of the circulating water pit. By this search, the deposition location and deposition amount of the sludge are grasped. The search can be performed by the naked eye, a sensor, or the like. As the sensor 21 for the search, for example, an interface meter can be mentioned. The interface meter is not particularly limited in the detection method, and examples thereof include an optical interface meter, an ultrasonic interface meter, an impedance interface meter, and a capacitance interface meter. Generally, in the management of sludge, ultrasonic interface meters are frequently used. However, the detection value of the ultrasonic interface meter is easily affected by bubbles. When using an interface meter whose detection value is easily affected by bubbles, it is preferable to remove the influence of bubbles from the detection value with a noise filter or the like, use an interface meter of another detection method in combination, or ensure that the injection time of the micro-nano bubble water does not overlap with the measurement time by the interface meter, etc., and search in a way that reduces the influence of bubbles.

[0062] In the present invention, it is further preferable to include adjusting the position or direction of injecting water containing micro-nano bubbles. The injection position or direction may be changed along a predetermined path or based on the search result. The injection position or direction preferably includes a place where the deposition amount of the sludge is likely to exceed the upper limit value. The mechanism for changing the injection position or direction is not particularly limited, and examples thereof include those composed of a movable arm and those composed of a combination of a pulley and a rail.

[0063] The measurement of the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water can be carried out by known methods.

[0064] The amount of foam in the circulating water can be measured, for example, with a scale or a foam level meter provided on the side of the circulating water pit. The foam level meter is not particularly limited in the detection method, and examples thereof include an optical level meter, an ultrasonic level meter, an impedance level meter, and a capacitance level meter. Among these, a capacitance level meter is preferred. In a small-sized circulating water pit, foam often occurs on the entire surface of the liquid in the circulating water pit, so it is preferable to provide at least one foam level meter. In a large-sized circulating water pit, foam may occur on a partial surface of the liquid in the circulating water pit, so it is preferable to install at least one foam level meter at a location where foam is likely to occur. In a large-sized circulating water pit, a camera or the like for monitoring the entire surface of the liquid in the circulating water pit may be installed to grasp the distribution of the occurrence of foam, and accordingly, the foam level meter may be installed at an appropriate location. By using the liquid level meter 11 and the foam level meter 10 in combination, the level of the interface between the foam and the liquid and the level of the surface of the foam can be grasped. It can be inferred that the stronger the strength of the film of the generated foam, the larger the amount of foam generated. Foam is generated when conditions such as the temperature, surface tension, and viscosity of the circulating water are intertwined. The surface tension varies depending on anionic surfactants, nonionic surfactants, etc. in the paint. Therefore, it is considered that the amount of water treatment agent contained in the circulating water, the amount of surplus paint, etc. affect the variation in the amount of foam generated.

[0065] The turbidity of the circulating water can be measured, for example, by visual comparison with a standard solution of known turbidity or with a turbidimeter. The suspended solid concentration can be measured, for example, with an SS meter. SS is an abbreviation for Suspended Solid and refers to suspended substances. Turbidity is classified in JIS K 0101 "Industrial Water Test Methods" into visual turbidity, transmitted light turbidity, scattered light turbidity, and integrating sphere turbidity. The turbidimeter or SS meter 13 is not particularly limited in the detection method, and examples thereof include (1) scattered light / transmitted light method, (2) surface scattered light method, (3) transmitted light method, (4) scattered light method, (5) integrating sphere method, and (6) fine particle counting method. There are also those that pseudo-display the SS concentration according to the correlation formula between turbidity and SS. In the present invention, the chromaticity of the circulating water may be measured as necessary. The chromaticity of the circulating water can be measured, for example, with a chromaticity meter. Chromaticity includes, for example, chromaticity by platinum-cobalt and chromaticity by stimulus value Y and chromaticity coordinates x, y. Chromaticity by platinum-cobalt is applied when the color of the sample is light yellow to yellowish brown due to substances dissolved or present in colloidal form in the sample. When measuring samples of various other colors, chromaticity by stimulus value Y and chromaticity coordinates x, y is used. Note that when using a turbid chromaticity meter, it is possible to obtain values of turbidity and chromaticity corrected for the influence of mutual interference. Turbidity depends on the amount, size, and color of the suspended substances. As substances suspended in the circulating water, in addition to flocs or sludge of excess paint, water treatment agents composed of water-insoluble components can be cited, and it is considered that these amounts affect the variation in turbidity.

[0066] The pH of the circulating water can be measured, for example, with litmus test paper or a pH meter 12. pH affects the corrosion of equipment, the life of aquatic animals and plants, and the growth of agricultural and aquatic products. Also, pH affects the effects of the water treatment agents described above, specifically, the generation amount, sedimentation rate, sedimentation amount, floating rate, floating amount, etc. of flocs or sludge of excess paint. It is considered that various substances dissolved in the circulating water affect the variation in pH.

[0067] Measurement of the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water can be carried out at various positions. Measurement of the amount of foam in the circulating water can usually be carried out on the circulating water in the circulating water pit. Measurement of the turbidity or suspended substance concentration of the circulating water can be carried out on the circulating water in the wet painting booth, the circulating water flowing from the wet painting booth towards the circulating water pit, the circulating water flowing into the circulating water pit and mixing with the circulating water accumulated in the circulating water pit, the circulating water accumulated in the circulating water pit, the circulating water flowing from the circulating water pit towards the wet painting booth, the surface water, or the intake liquid. Measurement of the pH of the circulating water can be carried out on the circulating water in the wet painting booth, the circulating water flowing from the wet painting booth towards the circulating water pit, the circulating water flowing into the circulating water pit and mixing with the circulating water accumulated in the circulating water pit, the circulating water accumulated in the circulating water pit, the circulating water flowing from the circulating water pit towards the wet painting booth, the surface water, or the intake liquid.

[0068] In the present invention, the addition amount of the water treatment agent and / or the injection amount of the micro-nano bubble water are adjusted based on the measured values of the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water, so that the amount of foam in the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water are within a predetermined value range. This adjustment can be carried out by an ON-OFF control method, a P control method, a PI control method, a PID control method, a PD control method, a fuzzy control method, etc. In the ON-OFF control method, for example, when the measured value becomes equal to or greater than a predetermined value A, it is adjusted to start or increase the addition of the water treatment agent whose value is known to decrease that value, or to stop or decrease the addition of the water treatment agent whose value is known to increase that value. When the measured value becomes equal to or less than a predetermined value B, it is adjusted to start or increase the addition of the water treatment agent whose value is known to increase that value, or to stop or decrease the addition of the water treatment agent whose value is known to decrease that value. In the P control method, PI control method, PID control method, PD control method, and fuzzy control method, the measured value X m and the target value X TBased on the difference (ΔX) therefrom, the start or increase in the addition amount of the water treatment agent or the stop or decrease in the addition amount is adjusted. P is the part ΔF proportional to ΔX P only increases or decreases the addition amount F, and I is the part ΔF proportional to the integral value of ΔX I only increases or decreases the addition amount F, and D is the part ΔF proportional to the differential value of ΔX D only increases or decreases the addition amount F, which is a control algorithm. For example, the PID control method is a combination of P, I, and D The fuzzy control method, for example, collects rules such as "output B1 when condition A1 is met", "output B2 when condition A2 is met", and "output B3 when condition A3 is met", calculates the degree of membership of the state quantity X to each condition (A1, A2, and A3) by a membership function, cuts the output part of the function of the output (B1, B2, and B3) for the condition that exceeds the degree of membership, overlaps the functions of the cut outputs, obtains the maximum area, and determines the output corresponding to the centroid thereof as the manipulated variable

[0069] The present invention includes adjusting the addition amount of the water treatment agent and / or the injection amount of micro-nano bubble water (manipulated variable) in place of or in combination with the adjustment based on the aforementioned measured values, corresponding to events in the wet painting booth. The adjustment corresponding to the event can be performed so that the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water are within a predetermined value range. For example, in a certain wet painting booth, the amount of surplus paint generated by painting one vehicle is almost determined, so information on the number of vehicles painted per unit time can be transmitted to the control system to determine how much to adjust the manipulated variable. Also, the amount of surplus paint generated during unsteady operation accompanying the startup or stop of the wet painting booth can be grasped empirically, so in response to the event of starting or stopping the wet painting booth, the event control system 3 transmits a control signal 26 to determine how much to adjust the manipulated variable

[0070] The water treatment apparatus of the present invention is a multivariable process in which the dosage of the water treatment agent and / or the injection amount of micro-nano bubble water (a plurality of operating variables), the foaming amount of the circulating water, the turbidity or suspended substance concentration of the circulating water, and / or the pH of the circulating water, and optionally events (a plurality of state variables) serve as inputs and outputs. In the present invention, for the adjustment, the operating variables may be determined by a decentralized multivariable control method based on classical control theory (for example, multiple-loop control, cascade control, mutual interference compensation, etc.), or the operating variables may be determined by a centralized multivariable control method based on modern control theory. From the perspective of being easy to grasp the malfunctions of the control system and enabling relatively stable control by the remaining control systems even if some control systems stop operating due to failures or malfunctions, the decentralized multivariable control method can be used. Specifically, the control signal 26 corresponding to the event, the control signal 17 for the injection amount of micro-nano bubble water, the control signal 18 based on the pH measurement value, the control signal 19 based on the measured value of the foaming amount, and the control signal 20 based on the measured value of the turbidity are processed for information in the central control device, and a command for the supply amount is transmitted to the supply pump or valve of the tank storing each water treatment agent. The supply amount of the water treatment agent may be monitored by a discharge sensor 15 or the like so that abnormalities such as failures can be detected and warnings can be issued. When it is predicted that the foaming amount may exceed the allowable amount in the circulating water pit due to disturbances, a predetermined antifoaming agent can be added manually or automatically.

[0071] The control system performed in the present invention may be a control method (feed-forward control method) that performs control based on the values of the state variables measured or observed in the front stage of the multivariable process, or may be a control method (feedback control method) that performs control based on the values of the state variables measured or observed in the rear stage of the multivariable process. A control system combining both may have both control stability and control rapidity.

[0072] In the present invention, priorities may be set for each control system in the distributed multivariable control method. For example, the control with the highest priority is performed by a feed-forward control method corresponding to an event, the control with the second highest priority is performed by a feedback control method that keeps the pH within a predetermined value range, and the control with the third highest priority is performed by a feedback control method that keeps the amount of foam within a predetermined value range. This is preferable from the viewpoints of process stability, low cost, etc. Also, the state of the control system can be monitored on-site by display on a control panel or the like, and can be monitored remotely by information transmission via communication means.

[0073] The addition amount of the water treatment agent and / or the injection amount (operation amount) of the micro-nano bubble water is adjusted by the control system as described above, and the operation amount realized by the adjustment is, for example, as follows. The supply amount of the micro-nano bubbles (air supply amount) is preferably 0.005 to 0.30 g, more preferably 0.05 to 0.15 g, per 1 g of the surplus paint (solid content). The addition amount of the non-sticking agent is, for example, in the case of a phenolic resin (solid content), preferably 1 mg or more, more preferably 5 mg or more, per 1 L of the circulating water. From the viewpoint of suppressing excessive foaming and an increase in operating cost, the upper limit of the addition amount of the phenolic resin (solid content) is preferably 1000 mg, more preferably 200 mg, per 1 L of the circulating water. Also, the addition amount of the phenolic resin (solid content) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, based on the surplus paint (solid content). Also, the upper limit of the addition amount of the phenolic resin (solid content) is preferably 100 mass%, more preferably 10 mass%, based on the surplus paint (solid content).

[0074] The addition amount of the coagulant (solid content) is, for example, in the case of a low molecular weight cationic polymer, preferably 0.1 to 100 mg, more preferably 0.3 to 30 mg per 1 L of the circulating water. Further, the addition amount of the low molecular weight cationic polymer (solid content) is preferably 10% by mass or less, more preferably 2% by mass or less with respect to the surplus paint (solid content). The lower limit of the addition amount of the low molecular weight cationic polymer (solid content) is preferably 1% by mass, more preferably 5% by mass with respect to the surplus paint (solid content).

[0075] The addition amount of the flocculant (solid content) is, for example, in the case of a high molecular weight cationic polymer, preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass with respect to the surplus paint (solid content). The addition amount of the high molecular weight cationic polymer is, for example, as the colloid equivalent value with respect to the circulating water, preferably 0.001 to 1 meq / L, more preferably 0.002 to 0.5 meq / L. By adding the high molecular weight cationic polymer, redispersion of the floc (floating sludge) can be prevented, and the efficiency of the filtration treatment and / or dehydration treatment (such as sedimentation separation and centrifugation) that may be performed after the pressurized flotation treatment can be improved. The addition amount of the anionic polymer (solid content), which is a kind of flocculant, is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass with respect to the surplus paint (solid content). The addition amount of the amphoteric polymer (solid content), which is a kind of flocculant, is preferably 0.1 to 10% by mass, more preferably 0.2 to 3% by mass with respect to the surplus paint (solid content).

Explanation of symbols

[0076] 1: Wet painting booth 2: Vehicle counter or clock 3: Event control system 4; Central control device 5: Communication network 6: Remote control 7: pH control system 8: Foam generation amount control system 9: Turbidity control system 10: Foam level meter 11: Liquid level meter 12: pH meter 13: Water treatment agent preparation tank 14: Liquid level gauge 15: Discharge sensor 16: Micro-nano bubble generator 17: Micro-nano bubble water injection amount control signal 18: Control signal based on pH measurement value 19: Control signal based on foam generation amount measurement value 20: Control signal based on turbidity measurement value 21: Sediment detection sensor 22: Water treatment agent supply amount adjustment mechanism 23: SS meter 24: Vehicle 25: Circulating water pit 26: Control signal corresponding to the event A: Circulating water Au: Untreated circulating water At: Treated circulating water

Claims

1. Capturing surplus paint generated in a wet painting booth with circulating water, sending the circulating water containing the captured surplus paint to a circulating water pit, temporarily retaining the circulating water in the circulating water pit, injecting water containing micronano bubbles into the circulating water retained in the circulating water pit to promote the floating of sludge composed of surplus paint, removing all or part of the floated sludge from the circulating water, and then returning the circulating water from which the sludge has been removed from the circulating water pit to the wet painting booth, and adding a water treatment agent to the circulating water, adjusting the addition amount of the water treatment agent and / or the injection amount of the water containing micronano bubbles in response to an event in the wet painting booth, measuring the foaming amount of the circulating water and the pH of the circulating water, and adjusting the addition amount of the water treatment agent and / or the injection amount of the water containing micronano bubbles based on the measured values of the foaming amount of the circulating water and the pH of the circulating water so that the foaming amount of the circulating water and the pH of the circulating water are within a predetermined value range, the number average diameter of the micronano bubbles when injected into the circulating water is 0.1 μm to 100 μm, the adjustment of the addition amount of the water treatment agent and / or the injection amount of the water containing micronano bubbles is given priority over the adjustment performed so that the pH of the circulating water is within a predetermined value range in response to an event in the wet painting booth, and the adjustment performed so that the pH of the circulating water is within a predetermined value range is given priority over the adjustment performed so that the foaming amount of the circulating water is within a predetermined value range, A method for treating circulating water in a wet painting booth.

2. Measuring the turbidity or suspended substance concentration of the circulating water, and further adjusting the addition amount of the water treatment agent and / or the injection amount of the water containing micronano bubbles based on the measured value of the turbidity or suspended substance concentration of the circulating water so that the turbidity or suspended substance concentration of the circulating water is within a predetermined value range, according to the treatment method described in Claim 1.

3. The event in the wet painting booth is the startup or stop of the wet painting booth, the start or stop of painting, the disposal of paint or paint cleaning liquid into the circulating water, blow-off or primer, intermediate coat, or top coat. The treatment method according to Claim 1 or 2.

4. The injection of water containing micronano bubbles is performed toward the bottom of the circulating water pit. The treatment method according to any one of Claims 1 to 3.

5. Searching for sludge composed of surplus paint deposited at the bottom of the circulating water pit, The processing method according to any one of claims 1 to 4, further comprising adjusting the position or direction of spraying water containing micronano bubbles based on the search results.

6. Circulating water pit Discharge path for flowing circulating water from the wet painting booth towards the circulating water pit Micronano bubble generator Supply path for flowing circulating water from the circulating water pit towards the wet painting booth Mechanism for adding a water treatment agent to the circulating water Measuring device for measuring the foaming amount of the circulating water and the pH of the circulating water, and A control algorithm for adjusting the addition amount of the water treatment agent and / or the injection amount of water containing micronano bubbles corresponding to events in the wet painting booth, and based on the measured values of the foaming amount of the circulating water and the pH of the circulating water obtained by the measuring device, so that the foaming amount of the circulating water and the pH of the circulating water are within a predetermined value range, a control algorithm for adjusting the addition amount of the water treatment agent and / or the injection amount of water containing micronano bubbles, and an adjusting device for the addition amount of the water treatment agent and / or the injection amount of water containing micronano bubbles is provided. The adjustment of the addition amount of the water treatment agent and / or the injection amount of water containing micronano bubbles is prioritized over the adjustment performed corresponding to events in the wet painting booth so that the pH of the circulating water is within a predetermined value range, and the adjustment performed so that the pH of the circulating water is within a predetermined value range is prioritized over the adjustment performed so that the foaming amount of the circulating water is within a predetermined value range. The micronano bubble generator is installed such that the injection port of the water containing micronano bubbles can inject the water containing micronano bubbles into the circulating water retained in the circulating water pit. The number average diameter of the micronano bubbles when injected into the circulating water is 0.1 μm to 100 μm. Treatment device for wet painting booth circulating water.

7. Further having a measuring device for measuring the turbidity or suspended substance concentration of the circulating water, and The adjusting device further has a control algorithm for adjusting the addition amount of the water treatment agent and / or the injection amount of water containing micronano bubbles so that the turbidity or suspended substance concentration of the circulating water is within a predetermined value range based on the measured value of the turbidity or suspended substance concentration of the circulating water obtained by the measuring device. The treatment device according to claim 6.

8. The processing apparatus according to claim 6 or 7, wherein an injection port for water containing micro-nano bubbles is installed so as to be able to inject water containing micro-nano bubbles toward the bottom of the circulating water pit.

9. The processing apparatus according to any one of claims 6 to 8, further comprising a sensor for detecting sludge composed of surplus paint deposited on the bottom of the circulating water pit.

10. The micro-nano bubble generator has a mechanism for adjusting the position or direction of the injection port of the water containing micro-nano bubbles. The processing apparatus according to any one of claims 6 to 9, wherein the adjusting device further has a control algorithm for adjusting the position or direction of the injection port of the water containing micro-nano bubbles.

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