JP2008006382A - Method of treating oil-containing waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating oil-containing waste water, which can efficiently reduce concentrations of oil and suspended solid, and suppress the amount of consumed inorganic coagulant. <P>SOLUTION: Before the oil-containing waste water is treated, a cationic dispersion (co)polymer is added concurrently or separately with the inorganic coagulant, and then the waste water is subjected to coagulating sedimentation treatment and dehydration treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for treating oil-containing wastewater. More specifically, the present invention relates to a method for treating oil-containing wastewater that can efficiently reduce the concentration of oil and suspended solids.

  Oil-impregnated wastewater in industries such as steel, petrochemical, food processing, and automobile industry includes polyaluminum chloride (PAC), sulfuric acid ban earth, iron salt and other inorganic flocculants, organic cationic flocculants, organic anionic flocculants, etc. It is processed by a method such as an agglomeration treatment by adding an organic flocculant, a floc separation treatment by sedimentation separation or pressurized flotation separation.

As a conventional method for treating oil-containing wastewater, for example, JP-A-2004-255349 (Patent Document 1) polymerizes a monomer mixture containing at least 5 mol% of a specific cationic monomer. A method is disclosed in which a cationic water-soluble polymer obtained in this manner is added to oil-containing wastewater, and then an anionic water-soluble polymer is added for treatment.
Japanese Patent Laid-Open No. 7-96284 (Patent Document 2) discloses a method in which an oil adsorbent and a flocculant are added to an oil-containing wastewater, and Japanese Patent No. 2881384 (Patent Document 3) discloses an oil-containing wastewater. A method of adding and mixing tannin to an inorganic flocculant, adding an inorganic flocculant and an organic cationic flocculant, adjusting the pH and then adding an organic nonionic flocculant and / or an organic anionic flocculant; Japanese Patent Application Laid-Open No. 60-238193 (Patent Document 4) discloses a method of treating oil-containing wastewater with lignin sulfonic acid, an inorganic flocculant and a cationic polymer flocculant.

  However, an oil-containing wastewater treatment method combining a cationic dispersion type (co) polymer and an inorganic flocculant is not known.

JP 2004-255349 A JP-A-7-96284 Japanese Patent No. 2881384 JP 60-238193 A

  This invention makes it a subject to provide the processing method of the oil-containing wastewater which can reduce the density | concentration of an oil component and a suspended solid efficiently, and can suppress the usage-amount of an inorganic flocculant.

  The inventors of the present invention, as a result of earnest research to solve the above-mentioned problems, resulted in efficient use of the oil content of the oil-containing wastewater by using the inorganic flocculant and the cationic dispersion type (co) polymer in combination. It has been found that the concentration of suspended solids can be reduced and the amount of inorganic flocculant used can be suppressed, and the present invention has been completed.

  Thus, according to the present invention, when the oil-containing wastewater is treated with the inorganic flocculant, the cationic dispersion type (co) polymer is added simultaneously with or separately from the inorganic flocculant, and then subjected to the coagulation precipitation treatment and the dehydration treatment. An oil-containing wastewater treatment method is provided.

  According to the method for treating oil-containing wastewater of the present invention, it is possible to efficiently reduce the concentration of oil and suspended substances in the oil-containing wastewater, and to suppress the amount of inorganic flocculant used. Moreover, since the generation amount of sludge can be suppressed by suppressing the amount of inorganic flocculant used, and the cost of sludge disposal can be reduced, the method for treating oil-containing wastewater of the present invention is extremely useful industrially.

  In the method for treating oil-containing wastewater of the present invention, in treating oil-containing wastewater with an inorganic flocculant, a cationic dispersion type (co) polymer is added simultaneously with or separately from the inorganic flocculant, and then coagulation-precipitation treatment and dehydration treatment are performed. It is attached to.

The cationic dispersion type (co) polymer used in the method of the present invention can be produced, for example, by the method described in JP-A-62-215251.
The cationic dispersion type (co) polymer is a dispersion of a cationic monomer or a cationic monomer and a nonionic monomer made of an ionic polymer soluble in the aqueous salt solution in the aqueous salt solution. It is preferably made of a dispersion of polymer fine particles having a particle size of 100 mμ or less, preferably 5 to 100 μm, produced by polymerization with stirring in the presence of an agent.
In the present invention, “(co) polymer” means a polymer and a copolymer.

  Examples of the cationic monomer used in the production of the cationic dispersion type (co) polymer include (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride and (meth) acryloyloxyethylbenzyldimethylammonium chloride. It is done. Here, “(meth) acryloyl” means acryloyl and methacryloyl.

  Nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide and 2-hydroxyethyl (meth) acrylate. Etc.

Examples of the aqueous salt solution used for the polymerization include aqueous solutions of sodium sulfate, ammonium sulfate, magnesium sulfate, aluminum sulfate, and the like.
Examples of the dispersant made of an ionic polymer include acryloyloxyethyltrimethylammonium chloride and acryloyloxyethylbenzyldimethylammonium chloride.

As the cationic dispersion type (co) polymer, a copolymer of a cationic monomer and a nonionic monomer is preferable, and a copolymer of a cationic monomer and acrylamide is particularly preferable.
The molecular weight of the cationic dispersion type (co) polymer is about 1,000,000 to 10,000,000 although it varies depending on the type and combination of monomers.
As such a (co) polymer, a commercially available product can be used. For example, “Himoloc E series (dispersion type)” manufactured by Hymo Co., Ltd., “Floclan SC-” manufactured by Katayama Chemical Industry Laboratory Co., Ltd. 680 ".

The cation density of the cationic dispersion type (co) polymer used in the method of the present invention is 0.1 to 1 meq / g, preferably 0.2 to 0.7 meq / g.
If the cation density is within the above range, the concentration of oil and suspended solids in the oil-containing wastewater can be efficiently reduced, and the amount of inorganic flocculant used can be suppressed.
The cation density (also referred to as “cationicity”) is determined by colloidal titration using (co) polymer titrant as a (1/400) potassium polyvinyl sulfate (PVSK) solution and 0.1% toluidine blue solution as an indicator. It is a value measured and obtained by the following formula.

  The addition amount of the cationic dispersion type (co) polymer used in the method of the present invention is 0.5 to 2 mg / liter, preferably 1 to 1.5 mg / liter with respect to the oil-containing wastewater. If the addition amount of the cationic dispersion type (co) polymer is within the above range, the concentration of the oil and the suspended solids in the oil-containing wastewater can be efficiently reduced, and the amount of the inorganic flocculant used can be suppressed.

  Examples of the inorganic flocculant used in the method of the present invention include aluminum sulfate (sulfuric acid band), ferric chloride, polyaluminum chloride (PAC) and the like, and they are used alone or in combination depending on the situation of the wastewater treatment facility. be able to.

The amount of the inorganic flocculant used in the method of the present invention is preferably 5 to 150 mg / liter, particularly preferably 50 to 80 mg / liter with respect to the oil-containing wastewater. If the addition amount of the inorganic flocculant is within the above range, the oil content and the concentration of suspended substances can be efficiently reduced, and the amount of the inorganic flocculant used can be suppressed.
When the added amount exceeds 150 mg / liter, the amount of sludge generated increases, and the disposal cost increases, which is not preferable.

In the method of the present invention, first, an inorganic flocculant and a cationic dispersion type (co) polymer are added to oil-containing wastewater simultaneously or separately, and then subjected to a coagulation precipitation treatment and a dehydration treatment.
The aggregation precipitation treatment and the dehydration treatment can be performed using a known apparatus or method. Examples of such devices include solid-liquid separation devices such as sedimentation separation devices, flotation separation devices, filtration separation devices, and centrifugal separation devices such as agglomeration reaction tanks and thickeners.

  The method for treating oil-containing wastewater of the present invention can be applied to oil-containing wastewater in industries such as steel, petrochemicals, food processing, and the automobile industry, for example.

  The present invention will be specifically described with reference to test examples, but the present invention is not limited to these test examples.

Test Example 1 (Confirmation test for removing impurities in oil-containing wastewater)
In a wastewater treatment facility in Sakai Steel Works, polyaluminum chloride (PAC) as an inorganic flocculant was added to wastewater (oil content: 35 mg / liter, suspended solids (SS); 15 mg / liter) in a coagulation reactor (capacity: 100 m ³ ). Was added so as to have an effective concentration shown in Table 1. Next, after adding a cationic dispersion type (co) polymer as a polymer flocculant to an effective concentration shown in Table 1 and coagulating and precipitating, the concentration of oil and suspended substances in the supernatant (each mg / Liter), and after dehydration using a dehydrator, the amount of sludge generated (ton) for one month was measured. In addition, the strainer was checked for clogging.
Moreover, it replaced with the cation system dispersion type | mold (co) polymer, and tested similarly to the above except having added the various polymer flocculants shown below so that it might become the effective density | concentration shown in Table 1. .
The obtained results are shown in Table 1.

(Various polymer flocculants)
CD: Cationic dispersion type (co) polymer Cation density: 0.29 to 0.44 meq / g, particle size: 5 to 10 μm
(Made by Katayama Chemical Research Laboratory Co., Ltd., trade name "Froclan SC-680")
A: Anionic copolymer (manufactured by Katayama Chemical Industry Co., Ltd., trade name “Froclan A-238”)
N: Nonionic copolymer (Katayama Chemical Industry Co., Ltd., trade name "Froclan N-123")

From the above test results, in the method for treating oil-containing wastewater of the present invention (Examples 1 and 2), the concentrations of the oil and suspended solids (SS) in the supernatant liquid after the coagulation precipitation treatment were less than 0.5 mg / liter and 2 mg, respectively. It can be seen that both of these removal rates are high. There is no strainer clogging.
The amount of sludge generated depends on the amount of polyaluminum chloride (PAC) added, and the amount of sludge generated can be suppressed by reducing the amount of polyaluminum chloride added. In the method for treating oil-containing wastewater of the present invention, good results can be obtained as the water quality of the supernatant liquid even when the amount of polyaluminum chloride added in the case of using the conventional polymer flocculant and polyaluminum chloride is halved. (Example 2).

It can be seen that the combined use of the conventional polymer flocculant and polyaluminum chloride (Comparative Examples 2 and 5) reduces the oil content of the supernatant liquid to some extent, but does not reduce the concentration of suspended solids (SS). There is no strainer clogging.
In addition, in the combined use of the polymer flocculant of an anionic copolymer and polyaluminum chloride (Comparative Example 3), the quality of the supernatant liquid is good, but the strainer is clogged, making it impossible to feed water, resulting in oil-containing wastewater. It turns out that it is unsuitable for processing.
In the single use of conventional polymer flocculants (Comparative Examples 1 and 4), the single use of cationic dispersion type (co) polymer (Comparative Example 6) and the single use of polyaluminum chloride (Comparative Example 7), the supernatant It can be seen that the concentration of oil in the liquid is not improved, or the concentration of suspended solids (SS) is not improved even if the concentration of oil is improved. There is no strainer clogging.

Claims (5)

  In treating oil-containing wastewater with an inorganic flocculant, an oil-containing wastewater characterized by adding a cationic dispersion type (co) polymer simultaneously with or separately from the inorganic flocculant, and then subjecting it to coagulation precipitation treatment and dehydration treatment. Processing method.   A cationic monomer in which the cationic dispersion type (co) polymer is selected from (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride and (meth) acryloyloxyethylbenzyldimethylammonium chloride, or the cation Selected from acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide and 2-hydroxyethyl (meth) acrylate Polymer fine particles having a particle diameter of 5 to 100 μm, produced by polymerizing a nonionic monomer with stirring in the presence of a dispersant composed of an ionic polymer soluble in the salt aqueous solution. A dispersion of Method of processing oil-containing wastewater as claimed in claim 1.   The method for treating oil-containing wastewater according to claim 1 or 2, wherein the cation density of the cationic dispersion type (co) polymer is 0.1 to 1.2 meq / g.   The method for treating oil-containing wastewater according to any one of claims 1 to 3, wherein the inorganic flocculant is polyaluminum chloride.   The addition amount of the inorganic flocculant is 50 to 150 mg / liter with respect to the oil-containing wastewater, and the addition amount of the cationic dispersion type (co) polymer is 0.5 to 2 mg / liter with respect to the oil-containing wastewater. The method for treating oil-containing wastewater according to any one of Items 1 to 3.