JPH10274628A - Method for treating liquid penetrant inspection waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reuse the processing water by adding an additive to any one of penetrant water or cleaning waste water thereby accelerating aggregation and separation of penetrant liquid in the cleaning waste water. SOLUTION: A cationic, anionic or nonionic polymer or a surfactant is employed as an additive. The polymer is principally added to cleaning waste water by 0.1-1000 ppm or less while the surfactant is added principally to penetrant liquid by 0.01-3% and both of which accelerate adhesion, condensation, aggregation and separation of dispersed penetrant liquid due to neutralization of charges. The penetrant liquid is a hydrophobic penetrant liquid and prepared by adding several kinds of dilution solvent and a red dye or a fluorescent dye to a several kinds of petroleum based solvent satisfying the basic conditions of penetration, viscosity, and the like. According to the arrangement, condensation and aggregation of penetrant liquid in the cleaning waste water are accelerated, the penetrant liquid is separated easily from the water and the processing can be reused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a wastewater of a washing wastewater discharged by a penetrant flaw detection method for facilitating separation of water and a permeate from washing wastewater generated when the permeate is washed in a permeation test. It is about.

[0002]

2. Description of the Related Art Penetrant testing is broadly divided into fluorescent penetrant testing and dyeing penetrant testing. In each case, the penetrant used in these methods is based on basic conditions such as permeability, viscosity, temperature and storage stability. Several types of petroleum-based solvents satisfying the above conditions include a red dye or a fluorescent dye, and are classified into three types of solvent-removing, water-washing, and post-emulsifiable according to the difference in the washing method for removing excess permeate (JIS-Z). -2343 1992).

[0003] In the water-washing property, a permeating solution contains a surfactant in advance by a method of washing with water after the permeation treatment, and the permeating solution is emulsified and removed at the time of washing with water. In the post-emulsification method, a step of applying an emulsifier containing a surfactant as a seed component to an object to be inspected after a permeation treatment is added, followed by washing with water. In the solvent removal method,
This is a method of wiping using a solvent after the infiltration treatment.
Water washability is often used in terms of workability and applicability.

[0004] In recent years, due to environmental pollution and economic problems, a chloride recycling system that collects washing wastewater generated in a washing step of excess permeate and separates and reuses the water and permeate in a wastewater treatment device has been developed. It has been proposed and partially put into practical use.
Under such circumstances, washing wastewater containing a surfactant is discharged into washing wastewater using a water-washing method or post-emulsifiability, and the wastewater treatment methods include a coagulation sedimentation method using an adsorbent and a separation membrane. Filtration and concentration methods using sorbents are carried out. In general, flocculation and sedimentation methods using sorbents use adsorbents (activated aluminum oxide, clay such as activated clay, etc.) in washing wastewater. Then, an adsorbent such as polyaluminum chloride (PAC) is added and stirred, and the permeate component in the washing wastewater is adsorbed by the adsorbent. Next, when the coagulant is injected, the adsorbent is coagulated, flocculated and precipitated. By filtering this, the treated water from which the permeate component has been separated and removed can be obtained. Also, a filtration and concentration method using a separation membrane is known.

On the other hand, a water-washing method using a hydrophobic penetrating liquid has been proposed and partially put into practical use. Since the washing wastewater using the hydrophobic permeate is a dispersed oil, it is separated into water and the permeate with a difference in specific gravity over time, and floats on the surface to become floating oil. The floating oil can be easily separated and collected by using a conventionally known belt-type oil skimmer or a surface-oil-absorption suction-type floating oil recovery device.

There is a coalescer method as a method for effectively separating and recovering residual oil droplets in washing wastewater. The coalescer method uses a microfiber filter having a micron fiber diameter. By passing the washing wastewater through this filter, the dispersed minute oil droplets are aggregated and gradually coarsened. The coarse oil droplets generate buoyancy and float on the water surface. As described above, the coalescer method is a method in which the dispersed oil of the permeating liquid component floating in the washing wastewater is coagulated, coarsened, and changed into floating oil, and the floating oil is easily separated and collected as described above. . The treated water separated into permeate and water by this method is
Reusable.

[0007]

However, washing wastewater containing a surfactant (washability, post-emulsifiability) is difficult to separate water and permeate, and is obtained by a wastewater treatment method using an adsorbent. The treated water is unsuitable for reuse because many salts are mixed under the influence of an adsorbent, an adsorption aid and the like. In the filtration and concentration methods using a separation membrane, the washing wastewater is passed through a separation membrane (ultrafiltration membrane, reverse osmosis membrane, etc.) while pressurizing the wastewater with a circulating pump, so that the permeate component in the washing wastewater is converted into a membrane. It cannot permeate, and only water is separated as permeated water and the permeate component is concentrated. Although such permeated water can be reused, it is not common yet due to problems such as high initial cost, maintenance / management due to clogging / regeneration, and a small throughput.

[0008] Recovery of floating oil by a water-washing method using a hydrophobic permeate can be easily performed by using a conventionally known belt-type oil skimmer or a water-absorbing suction-type floating oil recovery device. Although it can be separated and recovered, in practice, the permeate dispersed in large particles in the separation tank can be easily separated as floating oil with a difference in specific gravity, but the permeate dispersed and suspended as fine (micron-order) oil droplets is It requires a considerable residence time (1 to 3 hours) and has the disadvantage of requiring a large capacity separation tank.

In the coalescer method as described above, since a filter having a network structure of ultra-fine fibers is used in an actual site, clogging is always a problem in maintenance. The contamination of the fine inorganic material directly blocks the mesh of the filter. In addition, due to the occurrence of bacteria, an anaerobic bacterium (a bacterium that grows in an environment without oxygen) acts to decompose the permeate component that becomes floating oil, and the decomposed permeate component directly passes through the mesh of the filter. There is a problem in that the filter is clogged, clogged and cannot be used, the filter needs to be replaced in a short time, and the running cost increases.

The inventors of the present invention have conducted various studies on the above-mentioned problems and disadvantages, and found that
Additives were added to the washing wastewater that was produced using the method of washing with permeate or excess permeate to remove water and permeate. It has been found that separation of the permeate can be facilitated, and that the treated water thus obtained can be used again as washing water depending on the treatment conditions. It was done. Therefore, the problem to be solved by the present invention is to easily separate a permeate from wastewater used for cleaning and make it usable again as cleaning water, and it is preferable for environmental problems and excellent in economical running cost. It is an object of the present invention to provide a wastewater treatment method for washing wastewater discharged at the same time.

[0011]

The above-mentioned object to be solved by the present invention is achieved by the following inventions.

(1) From a permeation step of applying a permeating liquid to a test object to permeate a defect, a cleaning step of removing excess permeating liquid on an inspection surface, an optional developing step, and a detecting step of detecting a surface defect In the wastewater treatment method for washing wastewater discharged by the penetrant flaw detection method, an additive is added to at least one of the above-mentioned permeate and the washing wastewater to promote coagulation and separation of the permeate in the washing wastewater. A wastewater treatment method for washing wastewater discharged by the penetrant inspection method. (2) The wastewater treatment method according to (1), wherein the permeate is hydrophobic. (3) The wastewater treatment method for washing wastewater discharged by the penetrant flaw detection method according to the above (1) or (2), wherein bubbles are present in the washing wastewater.

[0013] The wastewater treatment method for washing wastewater discharged by the penetrant flaw detection method according to the present invention comprises adding an additive to at least one of the permeating solution and the washing wastewater to remove fine particles of the permeating solution in the washing wastewater. Aggregation and separation can be promoted. In addition, when the permeate is hydrophobic, especially in the washing wastewater, the permeate in the water is dispersed, and in the case of a permeate having a large particle diameter, the permeate can be easily separated due to the difference in specific gravity, and can not be further separated easily. Also in the penetrating liquid having a particle diameter, a natural attractive force (Van der Waals force) acts due to the added additive, and the particles are neutralized and coagulated, and aggregation and separation are promoted. As a result, it is possible to adsorb the condensed permeate particles and form crosslinks between the additives, form large flocs, and facilitate aggregation and flotation (when the specific gravity of the permeate is 1 or less).

Further, in the present invention, the presence of air bubbles in the washing wastewater absorbs the condensed permeate particles and forms crosslinks between the additives to form a large floc. The charge is neutralized and condensed, which can further promote aggregation and separation.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically. The wastewater treatment method of the cleaning wastewater discharged by the penetrant flaw detection method of the present invention is a method of applying a permeate to an object to be inspected, a permeation step of permeating a defect, a cleaning step of removing excess permeate on an inspection surface, an optional step. In a wastewater treatment method for a washing wastewater discharged by a penetrant flaw detection method comprising a development step and a detection step of detecting a surface defect, washing is performed by adding an additive to at least one of the permeate and the washing wastewater. It promotes coagulation and separation of permeate in wastewater. Here, the cleaning step is usually performed by spraying cleaning water to remove excess permeate on the inspection surface. However, the cleaning water is not limited to spraying, and other means such as water discharge may be used. . In the present invention, as a wastewater treatment method using the additive, a method of adding an additive to a permeate, particularly a hydrophobic permeate, a method of adding an additive to washing wastewater, and a method of treating a permeate with washing There are at least three ways of adding additives to both wastewater.

When the additive is added to the permeate, it is necessary to dissolve or disperse the additive in the permeate used as uniformly as possible. When an additive is added to the washing wastewater, the additive is added to the washing wastewater, and various kinds of stirring means such as pump stirring, propeller stirring, and stirring by supplying fine bubbles are performed so as to be mixed as evenly as possible. Is preferred. "Supply of fine bubbles" here means
There are a generally known method of passing compressor air through an air diffuser and a method of using a fine bubble generator.

In the present invention, in order to separate the permeate component from the washing wastewater to which the additive has been added, the washing wastewater is introduced into a separation tank, where it is retained or fine bubbles are supplied to the washing wastewater. I do. The permeate components dispersed in the washing wastewater are neutralized and coagulated, adsorbed,
By forming cross-linked coarse flocs, flocculating and floating, they are easily floated and separated from water. The osmotic liquid component (oil) that has floated and separated can be easily separated and removed because of the floating oil. In particular, it is preferable to add an additive to the washing wastewater and to treat the wastewater in the presence of fine bubbles in that a material having excellent treatment performance can be obtained. The treated water that has been subjected to wastewater treatment is reused as washing water for the penetrant inspection method.

More specifically, the treated water subjected to the wastewater treatment uses a fine bubble generator in the presence of bubbles. As one mode of the microbubble generator used in this wastewater treatment, a drive shaft having a hollow and a fine hole at a distal end portion is connected to a rotating shaft of a motor through a support pipe and a bearing, and an impeller is mounted at the distal end. When the motor rotates at high speed in water, negative pressure is generated on the back of the impeller wing attached to the tip, air is sucked into the hollow part of the drive shaft and air is ejected from the pore at the tip Then, it is sheared into fine bubbles by a high-speed rotating impeller at the tip, and becomes fine bubbles and sprayed into wastewater.

Further, in this fine bubble generator, the fine bubbles can be filled in the entire processing tank by rotating the impeller at a high speed. When such an apparatus is used, the stirring of the additive added to the washing wastewater and the floating separation of the aggregate of the permeate in the treatment tank can be effectively and continuously performed. Furthermore, the present invention can be used as a small-sized wastewater treatment device incorporating a device for removing the floated and separated permeate and an effective discharge mechanism for treated water. In addition, since oxygen (air) is introduced into the washing wastewater at the same time, the action of anaerobic microorganisms can be suppressed and the growth can be prevented, which has a positive effect on the reuse of treated water.

In the present invention, the additives used in the method for adding to the permeate and / or the washing wastewater include a high molecular polymer and a surfactant, which will be described later. It promotes agglomeration and separation of the oil droplets of the permeated liquid component. Some additives and their combinations can effectively perform charge neutralization, aggregation, cross-linking adsorption, and separation promotion. Appropriate. As a preferred additive, it is particularly effective to use a high molecular polymer and a surfactant alone or in combination. Further, in the present invention, it is also possible to use a wastewater treatment method for washing wastewater discharged by a penetrant detection method using washing properties and post-emulsifying properties, and the surfactant contained in this case is used as a flocculant. And different surfactants.

Examples of additives that can be used include: 1) high-molecular polymer: cationic (polyacrylate, polyacrylamide, poamine, dicyandiamide,
Vinyl formamide, poamine, chitosan), anionic (polyacrylamide, sodium polyacrylate), nonionic (polyacrylamide), and zwitterionic (protein, polymethacrylate) are preferred. 2) Surfactant: anionic (sulfonic acid type,
Sulfate ester type, phosphate ester type), cationic (nitrogen-containing ionic), nonionic (sorbitan derivative, alkylamine type), 3) alkylalkanolamine type, and the like. The cationic, anionic, nonionic, and zwitterionic here represent the charge that is taken when dissolved in water. The cationic is a positive charge (+), and the anionic is
Negative charge (-), nonionic is no charge, zwitterionic is both positive (+) and negative charge (-).

The amount of the additive used in the present invention may be a small amount, and if it is too large, the aggregation and the separation deteriorate. On the contrary, an appropriate amount is added depending on the state of the wastewater, the combination of the additives and the treatment method. There is a need. Polymer additives are mainly used for addition to washing wastewater, and their role is to neutralize, adhere and coagulate, cross-link and adsorb the dispersed permeate components, resulting in coarse flocs. Form and agglomerate,
Promotes flotation. The addition amount may be a very small amount, and about 2000 ppM or less is sufficient in the washing wastewater as an active ingredient, and the usual addition is 0.1 to 1000 ppM.
Preferably it is 0.5-100 ppM, more preferably 0.5-20 ppM.

In the present invention, as the method of using the additive, when the additive is used alone, a combination of an additive having an ionic or zwitterionic charge opposite to the charge of the wastewater is effective. Which neutralizes the charge and promotes aggregation and separation. The use of the nonionic property is effective when the particles in the wastewater are coarse particles, and is in the formation of coarse flocs due to adhesion, coagulation, cross-linking and adsorption. In addition, when various additives are used in combination, the electric charge of the wastewater is taken into consideration, and the synergistic effect of the additive used in combination (additives having the opposite electric charge, Neutralization, adhesion, coagulation, cross-linking, adsorption, and formation of coarser flocks.) To promote aggregation and separation.

When a surfactant is used as an additive used in the present invention, it is mainly used by adding it to a permeate, and its role is when a permeate is dispersed in washing wastewater. Promotes adhesion and coagulation, flocculation, and flotation by neutralizing the electric charge of the wastewater, or utilizes a synergistic effect (combination of additives having opposite charges) by combination with an additive to be added to the washing wastewater. The addition amount may be a small amount, and 5% or less with respect to the permeate is sufficient. The usual addition amount is 0.01 to 3%, preferably 0.01 to 2%, and more preferably 0 to 2%. 0.01 to 0.5%.

The cationic and nonionic surfactants are effective when the permeate component has a negative charge in the washing wastewater, and utilizes the neutralization and coagulation of the charge. It is considered that the nonionic surfactant described above has a portion that is strongly unevenly distributed to positive charges in the structural formula. The anionic property is effective when the permeate component has a positive charge in the washing wastewater. In the case of cationic or anionic, a synergistic effect of charge neutralization, coagulation, aggregation, and separation by combination with an additive to be added to the washing wastewater can be used. Alkyl alkanolamine-based additives are mainly used as additives for permeating liquids, and are used for neutralization and coagulation of charges because there are locations where positive charges are strongly unevenly distributed in the structural formula.

In the present invention, the penetrant used for the penetrant detection method is not particularly limited, but is preferably a hydrophobic penetrant, and the penetrant has basic properties such as permeability, viscosity, temperature and storage stability. For several petroleum solvents that meet the requirements,
It is formed by adding several kinds of diluting solvents and a red dye or a fluorescent dye as needed. Such penetrants are conventionally known in the art. The basic composition is the same as the generally known post-emulsifiable penetrant, and is appropriately adjusted by the removability by washing with water. Cleaning wastewater is
After the infiltration step, using a hydrophobic permeate, the surplus permeate can be washed properly by spraying it from a spray nozzle with appropriate water pressure. The resulting wash wastewater has a specific gravity of 1%. A smaller permeate (small specific gravity that facilitates flotation) is dispersed as small droplets in water.

In the method for treating washing wastewater used in the penetrant inspection method of the present invention, the washing wastewater generated in the washing step of the excess permeate is collected, separated into water and the permeate by a wastewater treatment device, and reused. -It can also be used preferably in a drain recycling system. In the present invention, the treatment method of the washing wastewater used in the penetrant detection method has been described. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to the separation of general oil water having the same configuration.

[0028]

According to the present invention, in the wastewater washed with the washing water, a small particle size permeate which cannot be easily separated is dispersed in the water for a long time. Basically, van der Waals's force acts between the particles as in the case of dispersed general particles, and the particles are attracted by this attractive force. There are parts where the charge is unevenly distributed, divided into a polar part and a non-polar part, so if the suspended particles are penetrant components (oil), the negative ions are usually adsorbed on the particle surface and On the other hand, they have a negative charge and repel each other, or because of the presence of a large amount of water molecules, the particles are too far apart to exert an attractive force, and cannot be easily aggregated or separated, and are dispersed long. In order to neutralize the electric charge of the particles (permeate) dispersed in such washing wastewater, the natural suction force (Van der Waals force) is added by the addition of an additive having the opposite electric charge. ) Acts to coagulate particles and promote aggregation and separation. As a result, due to the use of the additive, the condensed permeate particles are adsorbed and cross-links are formed between the additives, forming a large floc, which facilitates aggregation and flotation (when the specific gravity of the permeate is 1 or less). Can be

[0029]

EXAMPLES The present invention will be described below with reference to examples.
The invention is not limited by these examples.

Example 1 54 parts of Exol D-80 (manufactured by Exxon Chemical Co., Ltd.), 10 parts of o-solvent L (manufactured by Nippon Oil Co., Ltd.), 10 parts of DOP (manufactured by Daihachi Chemical Co., Ltd.)
Parts, TCP (produced by Daihachi Chemical Co., Ltd.) 5 parts, Solvesso 15
0 (manufactured by Exxon Chemical Co., Ltd.), 0.3 parts of Solvent Yellow 116 (manufactured by Orient Chemical Co., Ltd.), and 0.7 parts of white fluor B (manufactured by Sumitomo Chemical Co., Ltd.) Penetrant (Washable fluorescent penetrant FB-2000:
A permeate obtained by adding 0.2% of a cationic surfactant (1-hydroxyethyl-2-laurylimidazoline) as an additive to Eishin Chemical Co., Ltd. was used, and the washing water pressure was 5K.
Washing is performed by spraying from a spray nozzle at g / cm ² , and the resulting washing wastewater is used. Wastewater treatment was performed by supplying fine bubbles to the washing wastewater, and the treatment performance was evaluated by examining the oil concentration of the permeate component (oil) dispersed in the washing wastewater according to the treatment time.

The crude oil concentration of the washing wastewater is 1000 pp
M and the oil concentration after 20 minutes of wastewater treatment time is 140
ppM. As a comparative sample, the washing wastewater without additives stayed in the separation tank and the oil concentration after 2 hours was 20%.
It was 0 ppM. Further, in wastewater treatment in which only fine bubbles are supplied, the oil concentration after a treatment time of 20 minutes is 320 ppM.
Met. It can be seen that the wastewater treatment method using the additive facilitates aggregation and separation of the oil droplets of the permeate component dispersed in the washing wastewater and facilitates separation. This is because the cationic (positive charge) additive added to the permeating solution neutralizes the negative charge of the permeating solution dispersed in the washing wastewater and coagulates the fine permeate, resulting in fine permeation. Easy to agglomerate the oil droplets of the liquid. Also, by the fine bubbles added to the washing wastewater, the stirring effect, the absorption of the permeate dispersed by the air / liquid interface of the bubbles, the concentration, and the flocculation by the floating action. And good separation.

The degree of treatment in the wastewater treatment method using this additive is as follows: if the oil concentration (the amount of n-hexane extracted) is experimentally 150 ppM or less, the treated water is recycled and used as washing water. No problem. Further, in the present invention described above, even without supplying fine bubbles, excellent processing performance was obtained as compared with the comparative sample.

Example 2 Using the hydrophobic penetrant described in Example 1 (washable fluorescent penetrant FB-2000: manufactured by Eishin Chemical Co., Ltd.), a spray nozzle was used at a washing water pressure of 5 kg / cm ^2. Use cleaning wastewater that is sprayed. The washing wastewater is put into a separation tank, and as an additive in the separation tank, cationic polymeric acrylamide • [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride • [2- (acryloyloxy) ethyl] trimethylammonium chloride The copolymer｝ is added at 3 ppM, and fine bubbles are supplied to the washing wastewater to perform wastewater treatment.

The oil concentration of the permeated liquid component (oil) dispersed in the washing wastewater according to the treatment time is examined. The stock solution oil concentration of the washing wastewater is 1000 ppM and the wastewater treatment time 2
The oil concentration after 0 minute was 60 ppM. It can be seen that the wastewater treatment method using the additive facilitates aggregation and separation of the oil droplets of the permeate component dispersed in the washing wastewater and facilitates separation. This is because the cationic (positive charge) additive of the high molecular polymer added to the permeate has the effect of neutralizing the negative charge of the permeate dispersed in the washing wastewater, the coagulation action, The cross-linking and adsorbing action facilitates aggregation and separation of the oil droplets of the fine permeate. Also,
The fine bubbles supplied into the washing wastewater make it even better by the stirring effect, adsorption and flotation. In addition, the degree of treatment in the wastewater treatment method using this additive is such that the oil concentration (the amount of n-hexane extracted) is experimentally 150.
If it is ppM or less, there is no problem even if the treated water is recycled and used as washing water.

Example 3 An anionic surfactant (dioctyl sulfosuccinate) was used as an additive to the hydrophobic permeate described in Example 1 (washable fluorescent permeate FB-2000: manufactured by Eishin Chemical Co., Ltd.). Washing wastewater sprayed from a spray nozzle at a washing water pressure of 5 kg / cm ² is used using a permeate containing 0.5% of an acid salt). Next, as an additive, high molecular polymer cationic acrylamide
3 ppm of [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride / [2- (acryloyloxy) ethyl] trimethylammonium chloride copolymer is added to the washing wastewater, and fine bubbles are supplied to treat the wastewater. Do.

The oil concentration of the permeate component (oil) dispersed in the washing wastewater due to the treatment time is examined. The crude oil concentration of the washing wastewater is 1050 ppM, and the wastewater treatment time is 2
The oil concentration after 0 minute was 110 ppM. As a comparative sample, the washing wastewater without additives stayed in the separation tank and had an oil concentration of 190 ppM after 2 hours. The wastewater treatment method using the additive facilitates aggregation and separation of the oil droplets of the permeate component dispersed in the washing wastewater, and can be easily separated. This is because the permeate dispersed in the washing wastewater has the anionic (negative charge) additive added to the permeate and the cationic (positive charge) of the polymer added to the wash wastewater. The action of neutralizing the negative charge, the coagulation action, and the synergistic action of the additives promote the aggregation and separation of the oil droplets of the fine permeate.

The fine bubbles added to the washing wastewater further improve the aggregation and separation by the stirring effect, the adsorption of the permeate by the air / liquid interface of the bubbles, the concentration and the floating separation. Also, the degree of treatment in the wastewater treatment method using this additive is not problematic even if the treated water is recycled and used as washing water when the oil concentration (the amount of n-hexane extracted) is experimentally 150 ppM or less. Did not.

Example 4 Using the permeating solution described in Example 1 (washable fluorescent permeating solution FB-2000: manufactured by Eishin Chemical Co., Ltd.), spraying was performed from a spray nozzle at a washing water pressure of 5 kg / cm ^2. Use the washing wastewater that comes out. The washing wastewater is put into a separation tank, and the polymer polymer cationic {acrylamide • [2- (acryloyloxy) ethyl] benzyldimethylammonium chloride • [2-
(Acryloyloxy) ethyl] trimethylammonium chloride copolymer ３ was added at 3 ppM, fine bubbles were supplied to the washing wastewater, and the mixture was stirred (about 10 seconds). Further, an anionic polymer (acrylamide / sodium acrylate) of a polymer was obtained. (Copolymer) is added at 3 ppM, and fine water bubbles are supplied to perform wastewater treatment.

The oil concentration of the permeate component (oil) dispersed in the washing wastewater according to the treatment time is examined. The crude oil concentration of the washing wastewater is 1100 ppM, and the wastewater treatment time is 2
The oil concentration after 0 minute was 150 ppM. The wastewater treatment method using the additive facilitates aggregation and separation of the oil droplets of the permeate component dispersed in the washing wastewater, and can be easily separated. This is because the cationic polymer (positive charge) and anionic (negative charge) of the polymer polymer added to the washing wastewater neutralize the negative charge of the permeate dispersed in the washing wastewater. The flocculation action, cross-linking adsorption action and synergistic action of additives facilitate the aggregation and separation of oil droplets of fine permeate. In addition, fine bubbles supplied into the washing wastewater further improve the stirring effect, adsorption and flotation. Also, the degree of treatment in the wastewater treatment method using this additive is not problematic even if the treated water is recycled and used as washing water when the oil concentration (the amount of n-hexane extracted) is experimentally 150 ppM or less. Did not.

[Effect of the Invention] As described above, in the wastewater treatment method for cleaning wastewater discharged by the penetrant detection method of the present invention, an additive is added to at least one of the permeating solution and the cleaning wastewater, whereby It promotes the coagulation and separation of the permeate so that the permeate and water can be easily separated.
It is reusable and has a particularly remarkable effect of being excellent in environmental problems from washing wastewater and economical in running costs. In the present invention, especially when the permeate is hydrophobic and bubbles are supplied to the washing wastewater, the above-mentioned effect is more excellent.

Claims (3)

[Claims] 1. An infiltration step in which an infiltration liquid is applied to an object to be inspected to penetrate a defect, a cleaning step in which an excessive infiltration liquid is removed from an inspection surface, an optional development step, and a detection step in which a surface defect is detected. In the wastewater treatment method for cleaning wastewater discharged by the penetrant flaw detection method, an additive is added to at least one of the permeate and the cleaning wastewater to promote aggregation and separation of the permeate in the cleaning wastewater. A wastewater treatment method for washing wastewater discharged by the penetrant inspection method. 2. The method according to claim 1, wherein the permeate is hydrophobic. 2. The method of claim 1, wherein the permeate is hydrophobic. 3. The wastewater treatment method according to claim 1, wherein bubbles are present in the washing wastewater.