JP7693501B2 - Method and apparatus for purifying emulsion-type oil-containing wastewater - Google Patents

Description

The present invention relates to a method and apparatus for purifying emulsion-type oil-containing wastewater. More specifically, the present invention relates to a method and apparatus for purifying emulsion-type oil-containing wastewater that can purify emulsion-type oil-containing wastewater to a higher level than conventional methods.

In recent years, reducing the environmental burden by reducing waste has become a major issue in the industrial world. In particular, in industries that generate oil-containing wastewater, reducing the amount of oil-containing wastewater discharged is a major issue. For example, for car washes that use large amounts of water, technologies have been proposed that efficiently remove oil and other substances contained in the wastewater, enabling it to be reused as washing water (see, for example, Patent Documents 1 and 2). Also, for factories that use emulsions as lubricants and/or cutting oils to perform plastic processing and/or cutting processing, an oil-water separation method has been proposed that can efficiently separate oil from water in emulsion-type oil-containing wastewater discharged from such factories (see, for example, Patent Document 3).

In factories where hydroforming is performed, emulsions are widely used as a fluid (hereinafter, sometimes referred to as a "pressurized fluid") for applying high pressure to the inside of tubular workpieces (pipes). In the emulsion-type oil-containing wastewater discharged from such factories, the oil droplets (hereinafter, sometimes referred to as "oil droplets") that constitute the emulsion are further refined due to the high pressure applied during processing. In addition, other oils used as lubricants and/or cutting oils and sludge may gradually be mixed into the emulsion-type oil-containing wastewater. The oils thus mixed also become fine oil droplets due to the high pressure applied during processing and are dispersed in the emulsion-type oil-containing wastewater. It is extremely difficult to obtain water purified to a level that can be reused by the purification technology related to the conventional technology described above.

In other words, there is a demand in this technical field for a technology that can purify emulsion oil-containing wastewater to a higher level than ever before.

JP 2003-326105 A JP 2005-074294 A JP 2019-181416 A

As mentioned above, there is a demand in this technical field for a technology that can purify emulsion oil-containing wastewater to a higher level than ever before.

The inventors have therefore conducted extensive research and discovered that by subjecting emulsified oil-containing wastewater containing oil-in-water emulsions and separated oil that does not form an emulsion to a process for coagulating and removing the separated oil and breaking the emulsion, and then contacting the wastewater with activated carbon before passing the wastewater through a reverse osmosis membrane, it is possible to obtain water that has been purified to a higher level than before.

Specifically, the method for purifying emulsion-type oil-containing wastewater according to the present invention (hereinafter, sometimes referred to as the "method of the present invention") is a method for purifying emulsion-type oil-containing wastewater in which water is recovered from emulsion-type oil-containing wastewater that contains an oil-in-water emulsion and separated oil, which is oil that does not constitute an emulsion. The method of the present invention includes a flocculation process, an emulsion destruction process, an adsorption process, and a reverse osmosis process.

The flocculation step is a step in which a flocculant is added to the emulsion oil-containing wastewater to flocculate and remove the separated oil.
The emulsion breaking step is a step in which an oil-water separating agent is added to the emulsion-type oil-containing wastewater to break the emulsion.
The adsorption step is a step in which the oil-containing emulsified wastewater that has been subjected to the coagulation step and emulsion breaking step is brought into contact with activated carbon, thereby adsorbing the oil separated by emulsion breaking onto the activated carbon and removing it.
The reverse osmosis process is a process in which the emulsion-like oil-containing wastewater that has been subjected to the adsorption process is passed through a reverse osmosis membrane to remove impurities.

On the other hand, the purification apparatus for emulsion oil-containing wastewater according to the present invention (hereinafter, sometimes referred to as the "apparatus of the present invention") is an apparatus configured to carry out the above-mentioned method of the present invention. Specifically, the apparatus of the present invention is an apparatus for purifying emulsion oil-containing wastewater that recovers water from emulsion oil-containing wastewater that contains oil-in-water type emulsions and separated oil, which is oil that does not constitute an emulsion. The apparatus of the present invention has a flocculation section, an emulsion destruction section, an adsorption section, and a reverse osmosis section.

The flocculation unit includes a flocculation tank, which is a container for storing emulsion-type oil-containing wastewater, and a flocculation agent adding means configured to add a flocculation agent to the emulsion-type oil-containing wastewater stored in the flocculation tank. The flocculation unit is configured to execute a flocculation process in which a flocculation agent is added to the emulsion-type oil-containing wastewater by the flocculation agent adding means to flocculate and remove the separated oil.

The emulsion breaking section includes an emulsion breaking tank, which is a container for storing emulsion-type oil-containing wastewater, and an oil-water separating agent adding means configured to add an oil-water separating agent to the emulsion-type oil-containing wastewater stored in the emulsion breaking tank. The emulsion breaking section is configured to execute an emulsion breaking process in which the oil-water separating agent is added to the emulsion-type oil-containing wastewater by the oil-water separating agent adding means to break the emulsion.

The adsorption unit includes activated carbon and an adsorption tank, which is a container for storing the activated carbon. The adsorption unit is configured to carry out an adsorption process in which the oil-containing emulsion wastewater that has been subjected to the flocculation process and emulsion breaking process is brought into contact with the activated carbon, thereby adsorbing the oil separated by emulsion breaking onto the activated carbon and removing it.

The reverse osmosis section includes a reverse osmosis tank, which is a container whose internal space is partitioned by a reverse osmosis membrane, and a pressurizing means configured to apply pressure to the emulsion-containing wastewater that has undergone the adsorption process and is contained on one side of the reverse osmosis membrane of the reverse osmosis tank. The reverse osmosis section is configured to perform a reverse osmosis process in which the emulsion-containing wastewater is pressurized by the pressurizing means, thereby passing the emulsion-containing wastewater through the reverse osmosis membrane to remove impurities.

As described above, in the method and device of the present invention, emulsified oil-containing wastewater containing oil-in-water emulsions and separated oil that does not form an emulsion is subjected to coagulation removal of the separated oil and emulsion destruction, and is then brought into contact with activated carbon before being passed through a reverse osmosis membrane. As a result, the method and device of the present invention make it possible to recover water that has been purified to a higher level than before.

Other objects, features and associated advantages of the present invention will be readily understood from the description of the embodiments of the present invention described below with reference to the drawings.

1 is a schematic flow chart showing an example of the flow of each step included in the method for purifying emulsion oil-containing wastewater (first method) according to the first embodiment of the present invention. 1 is a schematic flow chart showing an example of the flow of each step included in a purification method for emulsion oil-containing wastewater (second method) according to a second embodiment of the present invention. 1 is a schematic flow chart showing an example of the flow of each step included in a method for purifying emulsion-type oil-containing wastewater (third method) according to a third embodiment of the present invention. FIG. 1 is a schematic block diagram showing an example of the configuration of an emulsion oil-containing wastewater purification device (first device) according to a fourth embodiment of the present invention. FIG. 11 is a schematic block diagram showing an example of the configuration of an emulsion oil-containing wastewater purification device (second device) according to the fifth embodiment of the present invention. FIG. 13 is a schematic block diagram showing an example of the configuration of an emulsion oil-containing wastewater purification device (third device) according to the sixth embodiment of the present invention. 1 is a schematic perspective view showing an example of the configuration of a purification apparatus for emulsion oil-containing wastewater according to an embodiment of the present invention (embodiment apparatus).

First Embodiment
Hereinafter, a method for purifying emulsion oil-containing wastewater according to a first embodiment of the present invention (hereinafter, sometimes referred to as the "first method") will be described with reference to the drawings.

<composition>
The first method is a method for purifying emulsive oil-containing wastewater, which involves recovering water from emulsive oil-containing wastewater containing an oil-in-water emulsion and separated oil, which is oil not constituting an emulsion, and includes a coagulation step, an emulsion breaking step, an adsorption step, and a reverse osmosis step.

Figure 1 is a schematic flow chart showing an example of the flow of each process included in the first method. In the first method illustrated in Figure 1, the emulsion breaking process (step S20) is performed after the aggregation process (step S10). However, as described later, the order of execution of the aggregation process (step S10) and the emulsion breaking process (step S20) does not necessarily have to be as illustrated in Figure 1, and the aggregation process (step S10) may be performed after the emulsion breaking process (step S20). Also, as described later, the aggregation process (step S10), emulsion breaking process (step S20), and adsorption process (step S30) are basically the same as those processes included in the conventional method for purifying emulsion-type oil-containing wastewater (hereinafter, sometimes referred to as the "conventional method").

The oil-in-water emulsion is not particularly limited, and the first method can be applied to emulsions having various compositions and/or uses. The oil-in-water emulsion to which the first method is applied may, for example, contain a surfactant (e.g., an ionic surfactant and a nonionic surfactant) as an emulsifier, or may not contain a surfactant. The oil-in-water emulsion to which the first method is applied may, for example, be used as a lubricant, cutting oil, and/or the pressurized fluid described above.

Separated oil is an oil that does not constitute an oil-in-water emulsion, such as a lubricating oil and/or cutting oil that is mixed into an oil-in-water emulsion at a processing site where plastic processing such as hydroforming and/or cutting processing is performed. In the emulsion-type oil-containing wastewater, the separated oil exists in a state separated from the oil-in-water emulsion, for example as a separation layer and/or relatively large liquid droplets. In addition to the oil-in-water emulsion and separated oil, the emulsion-type oil-containing wastewater may further contain foreign matter such as sludge.

The flocculation step (step S10) is a step in which a flocculant is added to the emulsion-type oil-containing wastewater to flocculate and remove the separated oil. The flocculant used in the flocculation step (step S10) can be appropriately selected from flocculants that are widely used in the technical field, depending on the composition and/or properties of the oil agent that constitutes the separated oil (and the foreign matter, such as sludge, if the emulsion-type oil-containing wastewater contains such foreign matter).

Examples of organic flocculants include alginates such as sodium alginate, as well as cationic polymer flocculants such as polyamines, polydicyandiamides, cationic starch, cationic poly(meth)acrylamide, water-soluble aniline resins, polythiourea, polyethyleneimine, quaternary ammonium salts, polyvinylpyridines, and chitosan.

Other organic flocculants include, for example, acrylic copolymers, which are copolymers of hydrophilic monomers such as (meth)acrylic acid and/or (meth)acrylamide, sodium salt of carboxymethylcellulose, maleic acid copolymers, poly(meth)acrylamide, sodium ligninsulfonate, surfactants such as polyoxyethylene dipropylamine, polyoxyethylene lauryl ether, and polyoxyethylene octylphenyl ether, anionic or nonionic polymer flocculants such as copolymers of (meth)acrylic acid and acrylamide, amphoteric polymer flocculants, and low molecular weight amine flocculants such as propylene diamine. In this specification, the term "(meth)acrylic" collectively refers to "acrylic" and "methacrylic".

Ionic minerals used as inorganic flocculants include, for example, clay minerals such as bentonite, montmorillonite, kaolin, and zeolite, as well as aluminum sulfate, polyaluminum chloride, magnesium chloride, ferric chloride, ferrous sulfate, ferric sulfate, hydrated lime, sodium silicate, sodium aluminate, and aluminum alums.

In the flocculation step (step S10), one or a combination of two or more of the various flocculants described above can be used as the flocculant. In addition to the flocculant, a so-called "flocculation promoter" may be used in the flocculation step. The flocculation promoter can also be appropriately selected from flocculation promoters widely used in the technical field depending on the composition and/or properties of the oil agent constituting the separated oil (and the foreign matter such as sludge if the emulsion oil-containing wastewater contains such foreign matter) and the agent used as the flocculant. For example, an agent other than the agent selected as the flocculant from the various flocculants described above can be selected and used as such a flocculation promoter. Alternatively, an flocculation promoter other than the agents listed above may be used as the flocculant.

The separated oil that has been coagulated in the above manner (and the foreign matter, if the emulsified oil-containing wastewater contains sludge or other foreign matter) floats to the top of the emulsified oil-containing wastewater or sinks to the bottom of the emulsified oil-containing wastewater, and can therefore be easily removed from the emulsified oil-containing wastewater. Whether the coagulated separated oil (and foreign matter) floats to the top or sinks to the bottom of the emulsified oil-containing wastewater is determined by the relative density of the oil-in-water type emulsion contained in the emulsified oil-containing wastewater and the density of the coagulated separated oil (and foreign matter).

The method for removing the coagulated separated oil (and foreign matter) from the emulsion-type oil-containing wastewater can be appropriately selected depending on whether the coagulated separated oil (and foreign matter) floats to the top or sinks to the bottom of the emulsion-type oil-containing wastewater. When the coagulated separated oil (and foreign matter) floats to the top of the emulsion-type oil-containing wastewater, the emulsion-type oil-containing wastewater can be extracted from the bottom of the container in which the emulsion-type oil-containing wastewater is stored in the coagulation process. On the other hand, when the coagulated separated oil (and foreign matter) sinks to the bottom of the emulsion-type oil-containing wastewater, the emulsion-type oil-containing wastewater can be extracted from the top of the container in which the emulsion-type oil-containing wastewater is stored in the coagulation process. Furthermore, depending on the amount, composition and/or properties of the coagulated separated oil (and foreign matter), the coagulated separated oil (and foreign matter) may be removed by filtration.

The emulsion destruction step (step S20) is a step in which an oil-water separator is added to the emulsion-type oil-containing wastewater to destroy the emulsion. As is well known to those skilled in the art, the so-called "emulsion destruction" (sometimes called "emulsion collapse") is a phenomenon in which an emulsion, which is a dispersion solution consisting of dispersoids and a dispersion medium, both of which are liquids, cannot be maintained. This emulsion destruction may occur at least partially as a result of the flocculation and removal of separated oil (and foreign matter) by the addition of a flocculating agent in the flocculation step (step S10). However, as mentioned above, in the hydroforming process, high pressure is applied to the emulsion used as the pressurized fluid, so that the oil droplets that make up the emulsion are further refined, making emulsion destruction more difficult.

Therefore, in the first method, the emulsion is reliably broken by the emulsion breaking step (step S20) in which an oil-water separating agent is added to the emulsion-type oil-containing wastewater to break the emulsion. The oil-water separating agent is also called an "emulsion breaker." Specific examples of the oil-water separating agent include inorganic compounds such as acids (e.g., hydrochloric acid or sulfuric acid), alkalis (e.g., sodium hydroxide or sodium hypochlorite), and salts, as well as organic compounds such as surfactants, phenol derivatives, and polycations. The oil-water separating agent preferably used in the emulsion breaking step (step S20) can be appropriately selected depending on the composition and/or properties of the oil-in-water emulsion contained in the emulsion-type oil-containing wastewater.

When an anionic surfactant is used as an emulsifier, for example, a polyvalent metal salt cationic surfactant or a polycation is added as an oil-water separating agent to the emulsion-type oil-containing wastewater to insolubilize the anionic surfactant, thereby causing emulsion destruction. Alternatively, when a nonionic interfacial lubricant such as ethylene oxide is used as an emulsifier, for example, a phenol derivative is added as an oil-water separating agent to the emulsion-type oil-containing wastewater to insolubilize the surfactant, thereby causing emulsion destruction. Alternatively, when a surfactant is not used as an emulsifier, for example, a mineral acid such as sulfuric acid or an alkali such as sodium hypochlorite is added as an oil-water separating agent to bias the pH of the emulsion-type oil-containing wastewater toward the acidic or alkaline side, thereby causing emulsion destruction.

The emulsion breaking step (step S20) may be performed after the above-mentioned flocculation step (step S10), or may be performed before the flocculation step (step S10). In the former case, the oil-water separator can be appropriately selected depending on the composition and/or properties of the oil-in-water emulsion contained in the emulsion-type oil-containing wastewater. On the other hand, in the latter case, the emulsion-type oil-containing wastewater subjected to the emulsion breaking step contains separated oil (and foreign matter if the emulsion-type oil-containing wastewater contains foreign matter such as sludge), so the oil-water separator can be appropriately selected depending on the composition and/or properties of not only the oil-in-water emulsion, but also the oil agent constituting the separated oil (and foreign matter if the emulsion-type oil-containing wastewater contains foreign matter such as sludge).

In the latter case, the oil newly separated from the emulsion by the emulsion destruction and the separated oil, which is the oil that was not originally part of the emulsion, can be condensed together, so the condensation effect is high. However, since the emulsion-type oil-containing wastewater that does not go through the condensation process (step S10) and still contains the separated oil (and foreign matter) is often cloudy, it is difficult to visually confirm the effect of the emulsion destruction. In addition, since the emulsion-type oil-containing wastewater that has not gone through the condensation process (step S10) contains the separated oil (and foreign matter) in addition to the oil droplets that make up the emulsion, it is necessary to add more oil-water separator than the emulsion-type oil-containing wastewater that has gone through the condensation process (step S10). Therefore, depending on the content of the separated oil (and foreign matter) contained in the emulsion-type oil-containing wastewater, it may be desirable to perform the emulsion destruction process (step S20) after performing the condensation process (step S10).

Furthermore, in the emulsion breaking step (step S20), in addition to adding an oil-water separating agent, the emulsion-type oil-containing wastewater may be heated to promote emulsion breaking. For example, when sulfuric acid is used as the oil-water separating agent, emulsion breaking can be promoted by heating the emulsion-type oil-containing wastewater to approximately 100°C.

The adsorption step (step S30) is a step in which the oil-containing emulsion wastewater that has been through the coagulation step (step S10) and emulsion breaking step (step S20) is brought into contact with activated carbon to adsorb the oil separated by emulsion breaking and remove it. The activated carbon used in the adsorption step (step S30) is not particularly limited as long as it is capable of effectively adsorbing the oil separated by emulsion breaking, and can be appropriately selected from a wide variety of activated carbons that are widely used in the technical field for wastewater treatment applications, etc. The form of the activated carbon is also not particularly limited, and can be appropriately selected from activated carbons having various forms, such as powdered activated carbon, granular activated carbon, and granulated activated carbon, depending on the equipment in which the first method is carried out.

In the adsorption step (step S30), for example, the emulsified oil-containing wastewater that has been through the coagulation step (step S10) and emulsion breaking step (step S20) is passed through a container (e.g., a column, etc.) that contains or is filled with activated carbon as described above, and the wastewater is brought into contact with the activated carbon, so that the oil separated by emulsion breaking is adsorbed onto the activated carbon and removed. Note that in the adsorption step (step S30), the oil separated by emulsion breaking (and foreign matter such as sludge, if present in the emulsified oil-containing wastewater) can be removed not only by adsorption with activated carbon, but also by filtration with activated carbon.

The above-described flocculation process (step S10), emulsion destruction process (step S20), and adsorption process (step S30) are, as mentioned above, basically the same as those processes included in the conventional method for purifying emulsion-type oil-containing wastewater (conventional method).

The reverse osmosis process (step S40) is a process in which the emulsion-like oil-containing wastewater that has been through the adsorption process (step S30) is passed through a reverse osmosis membrane to remove impurities. The reverse osmosis membrane used in the reverse osmosis process (step S40) is not particularly limited as long as it is capable of removing impurities by reverse osmosis. Specific examples of reverse osmosis membranes include hollow fiber membranes and spiral membranes formed from polymeric materials such as cellulose acetate or aromatic polyamide. As is well known to those skilled in the art, impurities remaining in the emulsion-like oil-containing wastewater that has been through the adsorption process can be removed by applying a predetermined pressure (exceeding the osmotic pressure) to the emulsion-like oil-containing wastewater contained on one side of such a reverse osmosis membrane to cause it to permeate to the other side of the reverse osmosis membrane.

The magnitude of pressure applied to the emulsion-type oil-containing wastewater in the reverse osmosis process (step S40) can be appropriately determined depending on, for example, the composition and/or properties of the emulsion-type oil-containing wastewater that has been subjected to the adsorption process (step S30) and/or the configuration and/or material of the reverse osmosis membrane.

In addition, after performing at least some of the steps included in the first method, a step may be provided for confirming the purification effect of performing each step based on a predetermined index (e.g., turbidity, transparency, and/or degree of coloration, etc.). Furthermore, after performing the reverse osmosis step, a step may be provided for confirming the purity of the water recovered through the reverse osmosis step (hereinafter, sometimes referred to as "recovered water") using a predetermined measuring device (e.g., a water purity meter and/or a conductivity meter, etc.).

<effect>
As described above, in the first method, the emulsified oil-containing wastewater containing the oil-in-water emulsion and the separated oil not forming an emulsion is subjected to the coagulation removal of the separated oil and the emulsion destruction, and is then contacted with activated carbon and passed through a reverse osmosis membrane. As a result, the first method makes it possible to recover water that has been purified to a higher level than before.

Second Embodiment
Hereinafter, a method for purifying emulsion oil-containing wastewater according to a second embodiment of the present invention (hereinafter, sometimes referred to as the "second method") will be described with reference to the drawings.

As described above, in the emulsion destruction process, an acid (e.g., hydrochloric acid or sulfuric acid, etc.) or an alkali (e.g., sodium hydroxide or sodium hypochlorite, etc.) may be added as an oil-water separating agent to bias the pH of the emulsion-type oil-containing wastewater toward the acidic or alkaline side. In addition, depending on the application of the oil-in-water emulsion, the pH of the emulsion-type oil-containing wastewater may be biased toward the acidic or alkaline side due to, for example, the inclusion of an acid or alkali in the usage environment.

As described above, emulsion oil-containing wastewater with a pH biased toward acidic or alkaline may damage the components constituting the equipment in which each process included in the purification method is carried out. Specifically, for example, if the pH of the emulsion oil-containing wastewater is biased toward acidic or alkaline, the activated carbon used in the adsorption process may be damaged.

<composition>
Therefore, the second method is the above-mentioned first method, which is a method for purifying emulsion-type oil-containing wastewater, further comprising a neutralization step between the emulsion breaking step and the adsorption step. The neutralization step is a step of adding a neutralizing agent to the emulsion-type oil-containing wastewater that has been subjected to the emulsion breaking step at a point in time after the emulsion breaking step and before the adsorption step to bring the pH of the emulsion-type oil-containing wastewater closer to neutral.

The neutralizing agent used in the neutralization step is not particularly limited, so long as it can bring the pH of the emulsion-containing wastewater that has been subjected to the emulsion destruction step closer to neutral and does not adversely affect the purification action of the emulsion-containing wastewater by the second method. If the pH of the emulsion-containing wastewater to be subjected to the neutralization step is biased toward acidic, the pH of the emulsion-containing wastewater can be brought closer to neutral by adding an alkali such as sodium hydroxide or sodium hypochlorite as a neutralizing agent. On the other hand, if the pH of the emulsion-containing wastewater to be subjected to the neutralization step is biased toward alkaline, the pH of the emulsion-containing wastewater can be brought closer to neutral by adding an acid such as hydrochloric acid or sulfuric acid as a neutralizing agent.

Figure 2 is a schematic flow chart showing an example of the flow of each process included in the second method, which differs from the flow chart of the first method shown in Figure 1 only in that a neutralization process (step S25) is included between the emulsion destruction process (step S20) and the subsequent adsorption process (step S30).

In the second method illustrated in FIG. 2, the emulsion breaking step (step S20) is performed after the aggregation step (step S10), and the neutralization step (step S25) is performed between the emulsion breaking step (step S20) and the next adsorption step (step S30). However, as described in the explanation of the first method, the order of the aggregation step (step S10) and the emulsion breaking step (step S20) does not necessarily have to be as illustrated in FIG. 1 and FIG. 2, and the aggregation step (step S10) may be performed after the emulsion breaking step (step S20).

When the coagulation step (step S10) is performed after the emulsion destruction step (step S20), the neutralization step (step S25) can be performed between the emulsion destruction step (step S20) and the coagulation step (step S10) or between the coagulation step (step S10) and the adsorption step (step S30). However, if there is concern that adverse effects such as a decrease in the coagulation effect in the coagulation step (step S10) may occur if the pH of the emulsion-type oil-containing wastewater subjected to the coagulation step (step S10) is biased toward acidic or alkaline, it is desirable to perform the neutralization step (step S25) between the emulsion destruction step (step S20) and the coagulation step (step S10).

<effect>
As described above, in the second method, a neutralization step is carried out after the emulsion breaking step and before the adsorption step, in which a neutralizing agent is added to the emulsion oil-containing wastewater that has been subjected to the emulsion breaking step to bring the pH of the emulsion oil-containing wastewater closer to neutral. As a result, according to the second method, the possibility that the activated carbon used in the adsorption step is damaged due to the bias in the pH of the emulsion oil-containing wastewater can be reduced.

Third Embodiment
Hereinafter, a method for purifying emulsion oil-containing wastewater according to a third embodiment of the present invention (hereinafter, sometimes referred to as the "third method") will be described with reference to the drawings.

As described above, in the method for purifying emulsified oil-containing wastewater according to various embodiments of the present invention, including the first and second methods (the method of the present invention), emulsified oil-containing wastewater containing an oil-in-water emulsion and separated oil that does not form an emulsion is subjected to coagulation removal of the separated oil and emulsion destruction, and is then contacted with activated carbon before being passed through a reverse osmosis membrane. As is well known to those skilled in the art, the reverse osmosis process can effectively remove impurities larger than water molecules. Therefore, the method of the present invention can recover water that has been purified to a higher level than before.

When it is required to recover water of even higher purity, it is desirable to subject the water recovered through the reverse osmosis process (recovered water) to an ion exchange treatment using a resin with ion exchange capacity (ion exchange resin) to remove even trace amounts of ions that may be contained in the recovered water.

<composition>
Therefore, the third method is a method for purifying emulsion-type oil-containing wastewater, which is the above-mentioned first or second method, and further includes an ion exchange step after the reverse osmosis step. The ion exchange step is a step of removing ionic impurities contained in the emulsion-type oil-containing wastewater by contacting the emulsion-type oil-containing wastewater that has been subjected to the reverse osmosis step with an ion exchange resin.

The ion exchange resin used in the ion exchange step is not particularly limited as long as it is capable of adsorbing trace amounts of ions (counterions) that may be contained in the recovered water through ion exchange action. Specifically, as is well known to those skilled in the art, an ion exchange resin having ion exchange groups capable of selectively adsorbing the counterions (e.g., sodium ions and/or chloride ions) to be removed by adsorption is selected. The form of the ion exchange resin is also not particularly limited, and can be appropriately selected from ion exchange resins having various forms such as granular, fibrous, and membrane forms, depending on the equipment in which the third method is carried out.

Figure 3 is a schematic flow chart showing an example of the flow of each process included in the third method, which differs from the flow chart of the second method shown in Figure 2 only in that it includes an ion exchange process (step S50) after the reverse osmosis process (step S40). The order of execution of the flocculation process (step S10), emulsion destruction process (step S20), and neutralization process (step S25) is as described in the explanation of the second method.

<effect>
As described above, in the third method, after the reverse osmosis step, an ion exchange step is carried out, which is a step of removing ionic impurities contained in the emulsion-containing wastewater by contacting the emulsion-containing wastewater that has been subjected to the reverse osmosis step with an ion exchange resin. As a result, according to the third method, even trace amounts of ions that may be contained in the recovered water can be removed to obtain water with a higher purity (hereinafter, sometimes referred to as "purified water").

Fourth Embodiment
As described at the beginning of this specification, the present invention relates not only to a method for purifying emulsion-type oil-containing wastewater, but also to an apparatus for purifying emulsion-type oil-containing wastewater. The apparatus for purifying emulsion-type oil-containing wastewater according to the present invention (apparatus of the present invention) is an apparatus configured to carry out the method for purifying emulsion-type oil-containing wastewater according to various embodiments including the above-mentioned first to third methods (method of the present invention).
Hereinafter, an apparatus for purifying emulsion-type oil-containing wastewater according to a fourth embodiment of the present invention (hereinafter, sometimes referred to as the "first apparatus") will be described with reference to the drawings.

<composition>
The first device is an apparatus for purifying emulsion-type oil-containing wastewater, which recovers water from emulsion-type oil-containing wastewater containing an oil-in-water type emulsion and a separated oil that is not an emulsion. The first device is an apparatus for purifying emulsion-type oil-containing wastewater, which has a flocculation section, an emulsion destruction section, an adsorption section, and a reverse osmosis section.

Figure 4 is a schematic block diagram showing an example of the configuration of the first device. The first device 101 shown in Figure 4 has an aggregation section 10, an emulsion destruction section 20, an adsorption section 30, and a reverse osmosis section 40.

The flocculation unit 10 includes a flocculation tank 11, which is a container for storing emulsion-type oil-containing wastewater, and a flocculation agent adding means 12 configured to add a flocculation agent to the emulsion-type oil-containing wastewater stored in the flocculation tank 11. Furthermore, the flocculation unit 10 illustrated in FIG. 4 also includes a flocculation promoter adding means 13 configured to add a flocculation promoter to the emulsion-type oil-containing wastewater stored in the flocculation tank 11. The configurations of the flocculation agent adding means 12 and the flocculation promoter adding means 13 can be appropriately determined according to the composition and/or properties of the chemicals added as the flocculation agent and the flocculation promoter. In addition, the flocculation unit 10 illustrated in FIG. 4 includes a stirring means driven by a motor M1 for the purpose of promoting mixing of the emulsion-type oil-containing wastewater with the flocculation agent and the flocculation promoter in the flocculation tank 11, but a stirring means such as a bubble stirring unit that promotes stirring by fine bubbles of gas such as nitrogen or air may also be used. However, the flocculation promoter adding means 13 and the stirring means are not essential components of the first device 101.

The flocculation unit 10 is configured to perform a flocculation process in which a flocculant is added to the emulsion-type oil-containing wastewater by the flocculant adding means 12 to flocculate and remove the separated oil. Furthermore, the flocculation unit 10 illustrated in FIG. 4 is equipped with the flocculation promoter adding means 13 and the stirring means as described above, which promote the flocculation of the separated oil and allow the separated oil to be effectively removed. Details of the flocculation process have already been described in the explanation of the method for purifying emulsion-type oil-containing wastewater according to the first embodiment of the present invention (first method), so a detailed explanation will be omitted here.

In the flocculation section 10 illustrated in FIG. 4, it is assumed that the flocculated separated oil (and foreign matter) floats to the top of the emulsion-type oil-containing wastewater, and the emulsion-type oil-containing wastewater from which the separated oil (and foreign matter) has been removed by the flocculation process is discharged from the bottom of the flocculation tank 11 and supplied to the next emulsion destruction section 20. However, as described above, the method for removing the flocculated separated oil (and foreign matter) from the emulsion-type oil-containing wastewater can be appropriately selected depending on whether the flocculated separated oil (and foreign matter) floats to the top or sinks to the bottom of the emulsion-type oil-containing wastewater.

The emulsion destruction unit 20 includes an emulsion destruction tank 21, which is a container for storing emulsion-type oil-containing wastewater, and an oil-water separator adding means 22 configured to add an oil-water separator to the emulsion-type oil-containing wastewater stored in the emulsion destruction tank. The configuration of the oil-water separator adding means 22 can be appropriately determined according to the composition and/or properties of the agent added as the oil-water separator. In addition, the emulsion destruction unit 20 illustrated in FIG. 4 includes a stirring means driven by a motor M2 for the purpose of promoting mixing of the emulsion-type oil-containing wastewater and the oil-water separator in the emulsion destruction tank 21, but a stirring means such as a bubble stirring unit that promotes stirring by tiny bubbles of gas such as nitrogen or air may also be used. However, such a stirring means is not an essential component of the first device 101.

The emulsion destruction unit 20 is configured to execute an emulsion destruction step in which an oil-water separator is added to the emulsion-type oil-containing wastewater by the oil-water separator adding means 22 to destroy the emulsion. The emulsion destruction unit 20 illustrated in FIG. 4 is equipped with stirring means as described above, which allows for more effective emulsion destruction. Details of the emulsion destruction step have already been described in the explanation of the method for purifying emulsion-type oil-containing wastewater (first method) according to the first embodiment of the present invention, and therefore will not be described here.

In the emulsion breaking section 20 illustrated in FIG. 4, the emulsion-containing wastewater that has undergone the emulsion breaking process is pumped out of the emulsion breaking tank 21 by the pump P1 and supplied to the next adsorption section 30. However, the configuration for supplying the emulsion-containing wastewater that has undergone the emulsion breaking process in the emulsion breaking section 20 to the next adsorption section 30 is not limited to a configuration including such a pump P1, and can be appropriately selected depending on the amount, composition and/or properties of the emulsion-containing wastewater that has undergone the emulsion breaking process.

The adsorption unit 30 includes activated carbon (not shown) and an adsorption tank 31, which is a container that contains the activated carbon. Typically, the adsorption unit 30 is a container such as a column that has an inlet for the emulsion-type oil-containing wastewater to be subjected to the adsorption process and an outlet for the emulsion-type oil-containing wastewater that has been through the adsorption process, and in which activated carbon is contained or packed.

The adsorption section 30 is configured to execute an adsorption process in which the emulsion-containing wastewater that has undergone the coagulation process and the emulsion breaking process is brought into contact with activated carbon to adsorb the oil separated by emulsion breaking onto the activated carbon and removed. In the adsorption section 30 illustrated in FIG. 4, the emulsion-containing wastewater that has undergone the emulsion breaking process is supplied from the emulsion breaking tank 21 to the adsorption section 30 by the pump P1, and comes into contact with the activated carbon while flowing inside the adsorption tank 31. This allows the oil separated by emulsion breaking to be adsorbed onto the activated carbon and removed from the emulsion-containing wastewater. Details of the adsorption process have already been described in the description of the method for purifying emulsion-containing wastewater (first method) according to the first embodiment of the present invention, so a description thereof will be omitted here.

As described in the explanation of the first method, after at least a part of each process is performed, a process for confirming the purification effect of each process based on a predetermined index (e.g., turbidity, transparency, and/or degree of coloration, etc.) may be provided. Therefore, in the first device 101 illustrated in FIG. 4, an adsorption effect confirmation unit 30' is provided downstream of the adsorption unit 30 for the purpose of confirming the purification effect of the adsorption process. The adsorption effect confirmation unit 30' includes an adsorption effect confirmation tank 31', which is a container for storing the emulsion-type oil-containing wastewater discharged from the adsorption tank 31, and a pump P2 for pumping the emulsion-type oil-containing wastewater from the adsorption effect confirmation tank 31' and supplying it to the next reverse osmosis unit 40. In the adsorption effect confirmation unit 30', the purification effect of the adsorption process is confirmed based on the turbidity, transparency, and/or degree of coloration, etc. of the emulsion-type oil-containing wastewater stored in the adsorption effect confirmation tank 31'.

In addition, if the adsorption effect confirmation unit 30' determines that the purification effect by performing the adsorption process is insufficient, the emulsion-type oil-containing wastewater may be returned from the adsorption effect confirmation unit 30' to the adsorption unit 30 and circulated. In this case, the adsorption effect confirmation unit 30' is provided with a means (e.g., a pump, etc.) for returning the emulsion-type oil-containing wastewater from the adsorption effect confirmation tank 31' to the adsorption tank 31 (see the two-dot chain arrow R1 shown in the figure). This means may be a dedicated means provided only for the purpose of returning the emulsion-type oil-containing wastewater from the adsorption effect confirmation tank 31' to the adsorption tank 31. Alternatively, this means may be a shared means in which a similar means (e.g., pump P1, etc., arranged in the emulsion destruction tank 21) provided in other components constituting the first device 101 is transferred to the adsorption effect confirmation tank 31'. However, the adsorption effect confirmation unit 30' is not an essential component of the first device 101. If the first device 101 does not have an adsorption effect confirmation unit 30', the emulsion oil-containing wastewater may be returned directly from the downstream side to the upstream side of the adsorption tank 31 without passing through the adsorption effect confirmation unit 30'.

The reverse osmosis unit 40 includes a reverse osmosis tank 41, which is a container whose internal space is divided by a reverse osmosis membrane (not shown), and a pressurizing means (not shown) configured to apply pressure to the emulsion oil-containing wastewater that has undergone the adsorption process and is contained on one side of the reverse osmosis membrane of the reverse osmosis tank. The pressurizing means included in the reverse osmosis unit 40 may be constituted by the pump P2 included in the adsorption effect confirmation unit 30' described above.

The reverse osmosis section 40 is configured to carry out a reverse osmosis process in which the emulsion-type oil-containing wastewater is pressurized by a pressure means, and the emulsion-type oil-containing wastewater is passed through a reverse osmosis membrane to remove impurities. This makes it possible to remove impurities remaining in the emulsion-type oil-containing wastewater that has been through the adsorption process. Details of the reverse osmosis process have already been described in the explanation of the method for purifying emulsion-type oil-containing wastewater (first method) according to the first embodiment of the present invention, and therefore will not be described here.

The first device 101 illustrated in FIG. 4 has a water storage section 60 downstream of the reverse osmosis section 40 that stores water (recovered water) discharged from the reverse osmosis section 40 after the reverse osmosis process, and the water storage section 60 has a recovered water tank 61 that is a container for storing the recovered water. However, the water storage section 60 is not an essential component of the first device 101.

As is well known to those skilled in the art, in the reverse osmosis section 40, concentrated water in which impurities that could not pass through the reverse osmosis membrane are concentrated is continuously discharged. This concentrated water is generally discharged from the reverse osmosis section 40 through a path such as a waste pipe (not shown) and discarded. However, from the viewpoint of reducing the amount of discarded concentrated water, it is desirable to return the concentrated water to the upstream side of the reverse osmosis membrane of the reverse osmosis tank 41 and circulate it. In this case, the reverse osmosis section 40 is provided with a means for returning the concentrated water discharged from the reverse osmosis tank 41 to the upstream side of the reverse osmosis membrane of the reverse osmosis tank 41 (for example, the adsorption effect confirmation tank 31') (see the arrow R2 of the two-dot chain line shown in the figure). This means may be, for example, a flow path that returns the concentrated water by pressure applied to the emulsion-type oil-containing wastewater by a pressurizing means, or a flow path equipped with a pump or the like for actively returning the concentrated water.

As described in the description of the first method, the order of the aggregation step (step S10) and the emulsion breaking step (step S20) does not necessarily have to be as illustrated in Fig. 1, and the aggregation step (step S10) may be performed after the emulsion breaking step (step S20). Therefore, the arrangement of the aggregation section 10 and the emulsion breaking section 20 in the first device 101 does not necessarily have to be as illustrated in Fig. 4, and the aggregation section 10 may be arranged downstream of the emulsion breaking section 20.
<effect>
As described above, in the first device, the emulsified oil-containing wastewater containing the oil-in-water emulsion and the separated oil that does not form an emulsion is subjected to the coagulation removal of the separated oil and the emulsion destruction, and is then contacted with activated carbon and passed through a reverse osmosis membrane. As a result, the first device can recover water that has been purified to a higher level than before.

Fifth Embodiment
Hereinafter, a purification apparatus for emulsion oil-containing wastewater according to a fifth embodiment of the present invention (hereinafter, sometimes referred to as the "second apparatus") will be described with reference to the drawings.

As described in the explanation of the method for purifying emulsion-type oil-containing wastewater according to the second embodiment of the present invention (second method), in the emulsion destruction step, an acid (e.g., hydrochloric acid or sulfuric acid, etc.) or an alkali (e.g., sodium hydroxide or sodium hypochlorite, etc.) may be added as an oil-water separating agent to bias the pH of the emulsion-type oil-containing wastewater toward the acidic or alkaline side. In addition, depending on the application of the oil-in-water emulsion, the pH of the emulsion-type oil-containing wastewater may be biased toward the acidic or alkaline side due to, for example, the inclusion of an acid or alkali in the usage environment.

As described above, emulsion oil-containing wastewater with a pH biased toward acidic or alkaline may damage the components that constitute the emulsion oil-containing wastewater purification device (the present invention device) according to various embodiments of the present invention, including the first device described above. Specifically, for example, if the pH of the emulsion oil-containing wastewater is biased toward acidic or alkaline, the activated carbon in the adsorption section may be damaged.

<composition>
Therefore, the second device is the above-mentioned first device, which is a purification device for emulsion oil-containing wastewater, further having a neutralization section. Figure 5 is a schematic block diagram showing an example of the configuration of the second device. The second device 102 illustrated in Figure 5 has a different configuration from the first device 101 illustrated in Figure 4 in that it further has a neutralization section 25 in addition to the flocculation section 10, the emulsion destruction section 20, the adsorption section 30 and the reverse osmosis section 40.

The neutralization section 25 includes a neutralization tank 26, which is a container for storing the emulsion-type oil-containing wastewater that has undergone the emulsion breaking process, and a neutralizing agent adding means 27 configured to add a neutralizing agent to the emulsion-type oil-containing wastewater stored in the neutralization tank. In the second device 102 illustrated in FIG. 5, it is assumed that the emulsion-type oil-containing wastewater that has undergone the emulsion breaking process is subjected to the neutralization process without being transferred from the emulsion breaking tank 21 to another container. Therefore, the emulsion breaking tank 21 provided in the emulsion breaking section 20 is configured to also function as the neutralizing tank 26, but the emulsion breaking tank 21 and the neutralizing tank 26 may each be configured as separate containers. The configuration of the neutralizing agent adding means 27 can be appropriately determined depending on the composition and/or properties of the agent added as the oil-water separating agent.

The neutralization section 25 is configured to execute a neutralization process in which a neutralizing agent is added to the emulsion-type oil-containing wastewater by a neutralizing agent adding means at a point in time after the emulsion destruction process and before the adsorption process, to bring the pH of the emulsion-type oil-containing wastewater closer to neutral. That is, from the viewpoint of the execution order of each process, the neutralization section 25 is disposed at a position downstream of the emulsion destruction section 20 and upstream of the adsorption section 30. This can reduce the possibility that the activated carbon provided in the adsorption section 30 will be damaged due to a bias in the pH of the emulsion-type oil-containing wastewater.

<effect>
As described above, in the second device, a neutralization step is carried out after the emulsion breaking step and before the adsorption step, in which a neutralizing agent is added to the emulsion oil-containing wastewater that has been subjected to the emulsion breaking step to bring the pH of the emulsion oil-containing wastewater closer to neutral. As a result, the second device can reduce the possibility that the activated carbon used in the adsorption step is damaged due to the bias in the pH of the emulsion oil-containing wastewater.

Sixth Embodiment
Hereinafter, a purification apparatus for emulsion oil-containing wastewater according to a sixth embodiment of the present invention (hereinafter, sometimes referred to as the "third apparatus") will be described with reference to the drawings.

As described above, in the purification apparatus for emulsified oil-containing wastewater according to various embodiments of the present invention, including the first and second apparatuses (the apparatus of the present invention), emulsified oil-containing wastewater containing oil-in-water emulsions and separated oil that does not form an emulsion is subjected to coagulation removal of the separated oil and emulsion destruction, and is then brought into contact with activated carbon before being passed through a reverse osmosis membrane. As is well known to those skilled in the art, the reverse osmosis process can effectively remove impurities larger than water molecules. Therefore, the apparatus of the present invention can recover water that has been purified to a higher level than before.

When it is required to recover water of even higher purity, it is desirable to subject the water recovered through the reverse osmosis process (recovered water) to an ion exchange treatment using a resin with ion exchange capacity (ion exchange resin) to remove even trace amounts of ions that may be contained in the recovered water.

<composition>
The third device is the first or second device described above, further comprising an ion exchange unit. The ion exchange unit is a purification device for emulsion oil-containing wastewater, comprising an ion exchange resin and an ion exchange tank that is a container for accommodating the ion exchange resin.

Figure 6 is a schematic block diagram showing an example of the configuration of the third device. The third device 103 shown in Figure 6 has a different configuration from the second device 102 shown in Figure 5 in that it further has an ion exchange section 50 in addition to the flocculation section 10, emulsion destruction section 20, neutralization section 25, adsorption section 30, and reverse osmosis section 40.

The ion exchange section is configured to carry out an ion exchange process in which the emulsion-type oil-containing wastewater that has been subjected to the reverse osmosis process is brought into contact with an ion exchange resin to remove ionic impurities contained in the emulsion-type oil-containing wastewater. This makes it possible to remove even trace amounts of ions that may be contained in the water (recovered water) recovered through the reverse osmosis process, thereby obtaining water of even higher purity (purified water). Details of the ion exchange process have already been described in the explanation of the method for purifying emulsion-type oil-containing wastewater according to the third embodiment of the present invention (third method), and therefore will not be described here.

In the third device 103 illustrated in FIG. 6, a reverse osmosis effect confirmation section 40' is provided downstream of the reverse osmosis section 40 for the purpose of confirming the purification effect by performing the reverse osmosis process. The reverse osmosis effect confirmation section 40' includes a reverse osmosis effect confirmation tank 41', which is a container for storing the emulsion-type oil-containing wastewater discharged from the reverse osmosis tank 41, and a pump P3 for pumping the emulsion-type oil-containing wastewater from the reverse osmosis effect confirmation tank 41' and supplying it to the next ion exchange section 50. In the reverse osmosis effect confirmation section 40', the purification effect by performing the reverse osmosis process is confirmed based on the turbidity, transparency and/or degree of coloration of the emulsion-type oil-containing wastewater stored in the reverse osmosis effect confirmation tank 41'.

Furthermore, the third device 103 illustrated in FIG. 6 has a water storage section 60 downstream of the ion exchange section 50 that stores the water (purified water) discharged from the ion exchange section 50 after the ion exchange process, and the water storage section 60 has a purified water tank 62 that is a container for storing the purified water.

In addition, in the third device 103 illustrated in FIG. 6, a water purity meter 52 is provided between the ion exchange section 50 and the water storage section 60 in order to confirm the purification effect of the ion exchange process. The water purity meter 52 can measure the purity of the water based on, for example, electrical conductivity.

However, the reverse osmosis effect confirmation unit 40', the water storage unit 60, and the water purity meter 52 are not essential components of the third device 103.

<effect>
As described above, in the third device, after the reverse osmosis process, an ion exchange process is carried out, which is a process of removing ionic impurities contained in the emulsion oil-containing wastewater by contacting the emulsion oil-containing wastewater that has been subjected to the reverse osmosis process with an ion exchange resin. As a result, the third device can remove even trace amounts of ions that may be contained in the recovered water, thereby obtaining water with a higher purity (purified water).

The following describes an example of the method for purifying emulsion-type oil-containing wastewater according to various embodiments of the present invention, including the first to third methods described above, and the apparatus for purifying emulsion-type oil-containing wastewater according to various embodiments of the present invention, including the first to third devices, with reference to the drawings. However, the example described below is merely illustrative and does not limit the scope of the present invention.

Figure 7 is a schematic perspective view showing an example of the configuration of an emulsion oil-containing wastewater purification device (embodiment device) according to an embodiment of the present invention. The embodiment device 110 illustrated in Figure 7 has a configuration corresponding to the emulsion oil-containing wastewater purification device (third device 103) according to the sixth embodiment of the present invention described above with reference to Figure 6. That is, the embodiment device 110 has, in order from the upstream side in the flow of emulsion oil-containing wastewater, a flocculation section 10, an emulsion destruction section 20, a neutralization section 25, an adsorption section 30, an adsorption effect confirmation section 30', a reverse osmosis section 40, a reverse osmosis effect confirmation section 40', an ion exchange section 50, and a water storage section 60.

As with the third device 103 described above, the flocculation unit 10 includes a flocculation tank 11 and a flocculant addition means and flocculation promoter addition means (not shown), and the emulsion destruction unit 20 includes an emulsion destruction tank 21 and an oil-water separator addition means (not shown). The neutralization unit 25 uses the emulsion destruction tank 21 as a neutralization tank 26 and includes a neutralizer addition means (not shown), the adsorption unit 30 includes an adsorption tank 31 filled with activated carbon, and the adsorption effect confirmation unit 30' includes an adsorption effect confirmation tank 31'. Furthermore, the reverse osmosis unit 40 includes a reverse osmosis tank 41 whose internal space is divided by a reverse osmosis membrane (not shown), and the reverse osmosis effect confirmation unit 40' includes a reverse osmosis effect confirmation tank 41'. In addition, the ion exchange unit 50 includes an ion exchange tank 51 containing an ion exchange resin (not shown) and a conductivity type water purity meter 52, and the water storage unit 60 includes a purified water tank 62.

In the flocculation process carried out in the flocculation section 10, commercially available inorganic flocculants and flocculation promoters were used. In the emulsion destruction process carried out in the emulsion destruction section 20, sodium hypochlorite was used as an oil-water separating agent, and in the neutralization process carried out in the neutralization section 25, hydrochloric acid was used as a neutralizing agent. In addition, the emulsion destruction tank 21/neutralization tank 26 was provided with a pump P1 for supplying the emulsion-containing oil-containing wastewater that had undergone the emulsion destruction process and the neutralization process to the next adsorption section 30, the adsorption effect confirmation tank 31' was provided with a pump P2 for supplying the emulsion-containing oil-containing wastewater that had undergone the adsorption process to the next reverse osmosis section 40, and the reverse osmosis effect confirmation tank 41' was provided with a pump P3 for supplying the emulsion-containing oil-containing wastewater that had undergone the reverse osmosis process to the next ion exchange section 50.

Using the embodiment device 110 having the above-mentioned configuration, purified water was recovered from emulsion-type oil-containing wastewater, the main component of which was an oil-in-water type emulsion (HYSOL X, manufactured by CASTROL LIMITED) used as a pressurized fluid in hydroforming processing. The emulsion-type oil-containing wastewater was contaminated with machine oil used in the hydroforming processing, and formed a layer separated from the emulsion. In other words, this machine oil corresponds to the separated oil described above.

As a result of purifying the above-mentioned emulsion oil-containing wastewater using the embodiment device 110, extremely clean water at the level of pure water could be recovered. In other words, according to the present invention, emulsion oil-containing wastewater can be purified to a higher level than before. Therefore, it has been confirmed that according to the present invention, it is possible to achieve excellent effects such as reducing the environmental load, saving water resources, and reducing costs in applications where emulsion oil-containing wastewater is discharged (e.g., plastic processing, etc.).

For the purpose of explaining the present invention, several embodiments and examples having specific configurations have been described above, sometimes with reference to the attached drawings. However, the scope of the present invention should not be construed as being limited to these exemplary embodiments and examples, and it goes without saying that appropriate modifications can be made within the scope of the claims and the matters described in the specification.

101, 102, 103, 110...Emulsion oil-containing wastewater purification device 10...Flocculation section 11...Flocculation tank 12...Flocculation agent adding means 13...Flocculation promoter adding means 20...Emulsion breaking section 21...Emulsion breaking tank 22...Oil-water separating agent adding means 25...Neutralization section 26...Neutralization tank 27...Neutralization agent adding means 30...Adsorption section 31...Adsorption tank 30'...Adsorption effect confirmation section 31'...Adsorption effect confirmation tank 40...Reverse osmosis section 41...Reverse osmosis tank 40'...Reverse osmosis effect confirmation section 41'...Reverse osmosis effect confirmation tank 50...Ion exchange section 51...Ion exchange tank 52...Purity meter 60...Water storage section 61...Recovered water tank 62...Purified water tank

Claims (6)

A method for purifying emulsion oil-containing wastewater, comprising recovering water from emulsion oil-containing wastewater containing an oil-in-water emulsion and a separated oil that is not an oil constituting the emulsion, comprising the steps of:
a flocculation step of adding a flocculant to the emulsion oil-containing wastewater to flocculate and remove the separated oil;
an emulsion breaking step of adding an oil-water separating agent to the emulsion-containing wastewater that has been subjected to the coagulation step to break the emulsion;
an adsorption step of contacting the emulsion oil-containing wastewater that has been subjected to the emulsion breaking step with activated carbon to adsorb the oil separated by the emulsion breaking onto the activated carbon and remove it;
a reverse osmosis process for removing impurities from the emulsion-type oil-containing wastewater that has been subjected to the adsorption process by passing the emulsion-type oil-containing wastewater through a reverse osmosis membrane;
Including,
A method for purifying emulsion-type oil-containing wastewater. The method for purifying emulsion-type oil-containing wastewater according to claim 1,
The method further includes a neutralization step of adding a neutralizing agent to the emulsion-containing wastewater that has been subjected to the emulsion breaking step at a point in time after the emulsion breaking step and before the adsorption step, thereby making the pH of the emulsion-containing wastewater closer to neutral.
A method for purifying emulsion-type oil-containing wastewater. A method for purifying emulsion-type oil-containing wastewater according to claim 1 or 2, comprising the steps of:
The method further comprises an ion exchange step of contacting the emulsion-type oil-containing wastewater that has been subjected to the reverse osmosis step with an ion exchange resin to remove ionic impurities contained in the emulsion-type oil-containing wastewater.
A method for purifying emulsion-type oil-containing wastewater. An apparatus for purifying emulsion oil-containing wastewater, which recovers water from emulsion oil-containing wastewater containing an oil-in-water emulsion and a separated oil that is an oil not constituting the emulsion, comprising:
a flocculation section including a flocculation tank which is a container for accommodating the emulsion-type oil-containing wastewater and a flocculation agent adding means configured to add a flocculation agent to the emulsion-type oil-containing wastewater accommodated in the flocculation tank, and configured to execute a flocculation step in which the flocculation agent is added to the emulsion-type oil-containing wastewater by the flocculation agent adding means to flocculate and remove the separated oil;
An emulsion breaking unit is provided with an emulsion breaking tank which is a container for accommodating the emulsion-type oil-containing wastewater, and an oil-water separating agent adding means configured to add an oil-water separating agent to the emulsion-type oil-containing wastewater accommodated in the emulsion breaking tank, and configured to execute an emulsion breaking step of adding the oil-water separating agent to the emulsion-type oil-containing wastewater by the oil-water separating agent adding means to break the emulsion;
an adsorption unit that includes activated carbon and an adsorption tank that is a container for accommodating the activated carbon, and is configured to perform an adsorption step in which the oil-containing emulsion wastewater that has been subjected to the coagulation step and the emulsion breaking step is brought into contact with the activated carbon to adsorb the oil separated by the emulsion breaking onto the activated carbon and remove it;
a reverse osmosis section including a reverse osmosis tank which is a container with an internal space partitioned by a reverse osmosis membrane and a pressurizing means configured to apply pressure to the emulsion oil-containing wastewater that has been subjected to the adsorption process and is accommodated on one side of the reverse osmosis membrane of the reverse osmosis tank, and configured to perform a reverse osmosis process in which the emulsion oil-containing wastewater is pressurized by the pressurizing means to pass the emulsion oil-containing wastewater through the reverse osmosis membrane to remove impurities;
having
The emulsion breaking step is performed after the aggregation step.
Emulsion oil-containing wastewater purification equipment. The apparatus for purifying emulsion-type oil-containing wastewater according to claim 4,
The method further comprises a neutralization unit including a neutralization tank which is a container for accommodating the emulsion-type oil-containing wastewater that has been subjected to the emulsion breaking step, and a neutralizing agent adding means configured to add a neutralizing agent to the emulsion-type oil-containing wastewater accommodated in the neutralization tank, and configured to execute a neutralization step of adding the neutralizing agent to the emulsion-type oil-containing wastewater by the neutralizing agent adding means at a time point after the emulsion breaking step and before the adsorption step to bring the pH of the emulsion-type oil-containing wastewater closer to neutral.
Emulsion oil-containing wastewater purification equipment. The apparatus for purifying emulsion-type oil-containing wastewater according to claim 4 or 5,
The apparatus further includes an ion exchange unit that is provided with an ion exchange resin and an ion exchange tank that is a container for accommodating the ion exchange resin, and is configured to carry out an ion exchange process for removing ionic impurities contained in the emulsion-containing wastewater by contacting the emulsion-containing wastewater that has been subjected to the reverse osmosis process with the ion exchange resin.
Emulsion oil-containing wastewater purification equipment.

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