JP2010279877A - Method for treating emulsion type wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating O/W type emulsion wastewater capable of reducing the use amount of an expensive wastewater treatment agent (emulsion breaker) and capable of also enhancing the clarity of wastewater after clarification treatment. <P>SOLUTION: The wastewater treatment agent comprising an inorganic flocculant or based on the inorganic flocculant and containing a polymer flocculant is added to and mixed with O/W type emulsion wastewater to form macro flocs, and the emulsion wastewater is treated through oil-water separation treatment for removing and separating the macro flocs and the clarification treatment of the separated, formed water after the removal of the macro flocs. When the wastewater treatment agent is added to and mixed with the O/W type emulsion wastewater, 50-250 pts.mass of bentonite is added based on 100 pts.mass of the wastewater treatment agent (inorganic flocculant and polymer flocculant). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for treating O / W type emulsion wastewater such as used cutting water (aqueous metal working oil).

  Here, description will be made by taking used cutting water as an example of the O / W type emulsion wastewater, but the wastewater treatment method of the present invention is also applicable to other O / W type emulsion wastewater.

  Examples of other O / W type emulsion wastewater include flaw detection agent wastewater, die-cast release agent wastewater, and aqueous paint wastewater.

  In recent years, cutting water (water-soluble cutting oil: the oil component is a mineral oil) as a cooling liquid at the time of metal working cutting is becoming the mainstream instead of the conventional oil-based cutting oil because of its low environmental load.

  For this reason, a large amount of used cutting water has been generated during metal working cutting in the automobile industry and the like.

  And used cutting water, which is O / W type emulsion wastewater, cannot be drained (discarded) as it is to rivers, etc., but is purified and drained until it reaches a clarification level that meets the drainage standards of each local government. There is a need.

  Usually, wastewater treatment consisting of the following oil / water separation treatment (1) and clarification treatment (2) is performed on used cutting water and drained into rivers and the like.

(1) Oil / water separation treatment:
To the used cutting water (O / W type emulsion), a composite type waste water treatment agent (emulsion breaker) mainly containing an inorganic flocculant and containing a polymer flocculant is added.

  Then, the inorganic flocculant (usually a polyvalent metal salt) neutralizes the charge (negative ions) of the oil particles, and the production of micro flocs (coagulated mass) proceeds. Furthermore, in the micro floc, the generation of macro floc (agglomeration) proceeds by the cross-linking action of the polymer by the polymer flocculant (see FIG. 1A).

  The treatment liquid after the macro floc is generated is separated into oil and water by separating and removing floc as an oil component from the water component by solid-liquid separation operation such as filtration.

(2) Clarification treatment:
The separated water after oil-water separation (battered water) is purified using activated carbon, ion exchange resin or the like.

  Recently, however, wastewater standards are becoming stricter from the viewpoint of reducing environmental impact.

  On the other hand, wastewater treatment agents are relatively expensive, and there has been a demand for reducing the amount of used wastewater when treating a large amount of used cutting water.

  In addition, although it does not affect the patentability of this invention, there exist patent document 1 * 2 etc. as related prior art literature.

  The water-soluble waste oil sewage treatment method described in Patent Document 1 is described as follows: “After injecting water-soluble cutting sewage into a receiving tank, diluting with water and storing the water, it is aerated by continuous aeration, and stirred to keep the water quality uniform. This is a continuous aeration system characterized by providing a sewage treatment process that suppresses anaerobic microorganisms, promotes the growth of aerobic microorganisms, promotes the reaction of the contained components, and forms fine aggregated frogs. '' (Claim 1).

  The wastewater treatment method described in Patent Document 2 is “in the wastewater treatment method containing an oil component of an emulsion, by separating the wastewater by distillation under reduced pressure, thereby separating into distilled condensed water and concentrated liquid, and It is characterized in that the emulsion is decomposed by acid treatment of the liquid, and the oil component is separated by centrifuging the concentrated solution obtained by decomposing the emulsion.

Japanese Patent Laid-Open No. 2000-301196 (see claims) Japanese Patent Laying-Open No. 2005-46657 (see claims)

  The present invention can reduce the amount of expensive wastewater treatment agent (emulsion breaker) used in a method for treating O / W type emulsion wastewater, and can also improve the clarification of waste water after clarification treatment. It is an object (problem) to provide a method for treating an O / W type emulsion wastewater.

  The present invention solves the above problems by the following configuration.

Oil / water that removes and separates macrofloc by adding and mixing a wastewater treatment agent composed of an inorganic flocculant or mainly containing an inorganic flocculant and containing a polymer flocculant into O / W emulsion wastewater. In the method of treating emulsion wastewater through separation treatment and clarification treatment of separated product water after macro floc removal,
When adding and mixing the wastewater treatment agent, 50 to 250 parts by mass of bentonite is added to 100 parts by mass of the wastewater treatment agent (inorganic flocculant and polymer flocculant).

  By adding a large amount of bentonite, the amount of waste water treatment agent (emulsion breaker) used can be reduced compared to the prior art, and the clarification of the separated water (oil-water) after oil-water separation is improved. Separation of macro floc becomes easy.

  The reason is estimated as follows (see FIG. 1B).

  When bentonite is not used, the macro floc is destroyed and the separability in oil / water separation becomes insufficient. That is, bentonite becomes a nucleus when agglomerating macro flocs, and it becomes easier to form macro flocs having a relatively large diameter, the sedimentation rate is remarkably increased, and the productivity of waste water treatment is improved.

  Further, the breaking strength of the macro floc increases, and the flocs once aggregated are not easily broken (partially decomposed) again. Therefore, the clarification action of bentonite also synergistically improves the clarification of separated product water after oil-water separation. And in order to obtain the same clarity, the usage-amount of a waste-water treatment agent (emulsion breaker) can be reduced. As for the current market price, the average price of the emulsion breaker is about 20 times that of bentonite.

(A) is explanatory drawing which shows the former, (B) is explanatory drawing which respectively shows the production | generation mechanism of the macro floc in this invention. (A), (B) is a graph which shows the relationship between the addition amount and density | concentration (clarity) of the waste-water-treatment agent in Test Example 1 and 2, respectively. (A), (B) is a model perspective view which shows the state of the production | generation flock in the test examples 1 and 2, respectively.

  Hereinafter, embodiments of the present invention will be described. In the following description, the blending unit is a mass unit unless otherwise specified.

  The method for treating emulsion wastewater according to the present invention comprises mixing an O / W type emulsion wastewater with a wastewater treatment agent (emulsion breaker) comprising an inorganic flocculant or containing a polymer flocculant mainly composed of an inorganic flocculant. Then, it is assumed that the macro floc is generated and the oil / water separation process for removing and separating the macro floc and the clarification of the separated water after the macro floc removal are performed.

  Here, as the O / W type emulsion waste water, cutting water (water-soluble cutting oil) is representative. As the above-mentioned inorganic flocculant and polymer flocculant, for example, those listed below can be used (Chemical Engineering Association edited by “Chemical Engineering Handbook 4th revised edition” (Akira 53-10-25) Maruzen, p1092, Table 14・ See 10.

  Inorganic flocculants: Aluminum salts such as polyaluminum chloride (PAC) and aluminum sulfate (sulfuric acid band); iron salts such as ferrous sulfate, ferric sulfate and ferric chloride can be mentioned. Usually, it is desirable to use an aluminum salt (main component aluminum oxide) having an applied pH of 6 to 8 so that it can be drained in a neutral region.

  ・ Polymer flocculants: anionic polymers such as sodium alginate, CMC sodium salt, sodium polyacrylate, polyacrylamide partial hydrolysis salt; water-soluble aniline resin hydrochloride, polythiourea hydrochloride, polyethyleneimine, Cationic polymers such as quaternary ammonium salts, polyvinyl pyridine hydrochlorides, vinyl pyridine copolymer salts; and nonionic polymers such as polyacrylamide, polyoxyethylene, and catalyzed starch. Among these, polyacrylamide, which is a nonionic polymer having a wide pH application range, is desirable because of its versatility.

  The wastewater treatment agent may be formed only with an inorganic flocculant, but it is desirable to use a polymer flocculant in combination because it is easy to form macro flocs and increases the breaking strength of the macro flocs. The blending ratio of the polymer flocculant with respect to 10 parts of the inorganic flocculant varies depending on the type of the inorganic flocculant / polymer flocculant and the SS level of the wastewater, but is usually 0.001 to 1 part.

  Here, when adding and mixing the wastewater treatment agent, 50 to 300 parts (preferably 80 to 220 parts) of bentonite are added to 100 parts of the wastewater treatment agent (total amount of inorganic flocculant and polymer flocculant).

  If the added amount of bentonite is too small, it is difficult to obtain the effect of adding bentonite, and even if the added amount of bentonite is excessive, no further effect can be expected.

  The amount of wastewater treatment agent added varies depending on the type of wastewater to be treated, but is generated in the case of treated water (two times diluted cutting water with a normal aqueous cutting oil concentration (5%)). The amount is 15 to 20 g (preferably 15 to 18 g) with respect to 1 L of water to be treated (before dilution). When the concentration of the wastewater treatment agent (flocculant) is less than 15 g as in the test examples described later, it is difficult to obtain the floc formation rate and floc agglomeration strength due to the addition of bentonite, and the treated water pH after treatment is difficult to be neutral. . This is because the inorganic flocculant that is the main component of the wastewater treatment agent is usually a weakly acidic compound. Therefore, if the amount of the wastewater treatment agent is excessive, the pH of the water to be treated becomes an acidic region, which is not desirable.

  The generated treated water is preferably diluted 1.5 to 2.5 times. This is because the aggregating action of the aggregating agent is hardly inhibited.

  The macro floc removal / separation may be performed by sedimentation or centrifugation, but is preferably performed by filtration using a filter press or the like because of good productivity.

  The clarification treatment of the separated water may be performed using an ion exchange resin or the like, but it is advantageous in terms of cost to use activated carbon.

  Unused cutting water was prepared by diluting a water-soluble cutting oil “Unisolve” (registered trademark) manufactured by Nippon Oil Co., Ltd. to a concentration of 5%. Furthermore, the wastewater treatment agent “emulsion breaker A” (custom product) is a mixed emulsion breaker containing an inorganic flocculant containing aluminum oxide as a main component and a nonionic water-soluble polymer as a polymer flocculant.

<Test example 1-1 (conventional example)>
100 ml of the above-mentioned unused cutting water was put into a 200-mL beaker 10 and distilled water was added to 200 mL (2 times dilution). “Emulsion breaker A” 0.4 g, 0.8 g, 1.2 g, 1. 6 g and 2 g were added, stirred for 2 minutes, and allowed to stand for 30 seconds.

  At this time, as shown in FIG. 3A, an oil phase composed of a cotton-like flock (floating matter) 14 was formed on the upper portion of the aqueous phase 12.

  Then, for each test example in which the amount of the emulsion breaker added after standing was different, each filtrate that was filtered with the paper (1 type) was used as a test object.

<Test Example 1-2 (Example)>
In Test Example 1-1, bentonite was further added in equal amounts, stirred for 2 minutes, and allowed to stand for 30 seconds.

  At this time, as shown in FIG. 3B, an oil phase composed of cotton-like flocks (precipitates) 16 was formed below the aqueous phase 12.

  Then, as in Test Example 1-1, for each test example in which the added amount of the emulsion breaker and the bentonite after being left is different, each of the filtrates filtered with the paper (one type) was used as a test object.

  And the clarity test and pH were measured about each to-be-tested body (boil).

<Clarity test>
The cutting oil concentration in the filtrate was measured with a pocket cutting oil concentration meter “ATAGO PAL-91S” (registered trademark) manufactured by Atago Co., Ltd. From FIG. 2 (A) showing the results, when bentonite is used in combination with emulsion breaker A, the effect on the clarity of bentonite is not affected until the concentration of emulsion breaker A is about 7 g / L (1.4 g / 200 mL). Although there is almost no, at about 8 g / L (1.6 g / 200 mL), the concentration is 1.4 when no bentonite is added (Test Example 1-1), whereas when the bentonite is added (Test Example 1-2), the concentration is 0.9. It was confirmed that the clarity was significantly different.

  For this reason, the reduction amount of 10 to 30% of the addition amount of the emulsion breaker A can be expected. For example, when the price of an emulsion breaker is about 20 times that of bentonite as described above, if the equivalent amount of bentonite is added and the emulsion breaker can be reduced by 20%, the total cost of the wastewater treatment agent (chemical) is 0.85 times. (0.8 + 1/20).

<PH test>
Measured with litmus paper. FIG. 2 (B) showing the result shows that there is almost no influence on the pH due to the addition of bentonite in the range of the emulsion breaker A addition amount from 2 g / L (0.4 g / 200 mL) to 10 g / L (1.6 g / 200 mL). I was able to confirm. And it has confirmed that pH became neutral (about 7) in emulsion breaker A addition amount 8g / L.

<Test Example 2 (Example)>
Prepared by diluting a water-soluble cutting oil “Unisolve” (registered trademark) manufactured by Nippon Oil Co., Ltd. to a concentration of 5%, and cutting 1L of used cutting water generated by cutting (of aluminum products). Emulsion breaker A 32 g (addition amount 16 g / L) and bentonite 60 g (addition amount 30 g / L) were added to 2.0 L obtained by adding water to 2.0 L (2 times dilution), The mixture was stirred for 2 minutes with a magnetic stirrer and allowed to stand for 30 seconds.

  And about the test body, after passing through the paper (1 type), the activated carbon 30g was added and the decoloring process was carried out.

  When visually observed, it had the same appearance as fresh water. And when SS (floating matter) measurement and pH measurement were carried out, they were SS: 12 mg / L, pH: 6.8.

Claims (6)

A macro floc is formed by adding and mixing a waste water treatment agent composed of an inorganic flocculant or mainly containing an inorganic flocculant and containing a polymer flocculant to an O / W type emulsion waste water, and removing and separating the macro floc. In the method of treating the emulsion wastewater through the oil-water separation treatment and the clarification treatment of the separated water after the macro floc removal,
When adding and mixing the wastewater treatment agent, 50 to 300 parts by weight of bentonite are added to 100 parts by weight of the wastewater treatment agent (total amount of inorganic flocculant and polymer flocculant). Processing method.   The method for treating emulsion wastewater, wherein the added amount of the bentonite to 100 parts by weight of the wastewater treatment agent is 80 to 220 parts by weight.   The method for treating emulsion wastewater according to claim 1 or 2, wherein the macro floc is removed and separated by filtration.   The method for treating an emulsion wastewater according to claim 1, 2 or 3, wherein the clarification treatment of the separated water is performed using activated carbon.   The emulsion according to any one of claims 1 to 4, wherein the inorganic flocculant in the wastewater treatment agent is an aluminum salt type, and the addition amount of the wastewater treatment agent to the water to be treated is 5 to 15 g / L. System wastewater treatment method.   6. The method for treating emulsion wastewater according to claim 5, wherein the water to be treated is obtained by diluting used metalworking cutting water 1.5 to 2.5 times.

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