JP4072075B2 - Oil-containing wastewater treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating oil-containing wastewater. Specifically, after adding a cationic water-soluble polymer obtained by polymerizing a monomer mixture containing at least 5 mol% of a specific cationic monomer. Furthermore, the present invention relates to a method for treating oil-containing wastewater, wherein an anionic water-soluble polymer is added to agglomerate to separate flocs.
[0002]
[Prior art]
[Patent Document 1]
Conventionally, oil-containing wastewater has been subjected to a combination treatment of an inorganic flocculant such as polyaluminum chloride or sulfuric acid band and an anionic polymer flocculant. However, the inorganic flocculant has a weak floc strength, and even when combined with an anionic polymer flocculant, the strength is not sufficiently improved, and there are many restrictions in handling in the next treatment step, and efficient treatment is difficult. Also, a method of treating a waste water containing oil by adding a cationic water-soluble polymer obtained by polymerizing a monomer containing a quaternary ammonium base by benzyl quaternization of dialkylaminoethyl (meth) acrylates. Is disclosed (Patent Document 1). However, this method does not describe a method for treatment in combination with an anionic water-soluble polymer. Furthermore, the cationic water-soluble polymer alone does not have sufficient floc strength and cannot be separated efficiently with a screen or the like.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for treating oil-containing wastewater that can efficiently separate agglomerated flocs with a screen or the like after the step of agglomeration treatment in treating oil-containing wastewater.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventor has reached the following invention. That is, the invention of claim 1 of the present invention provides a cationic property obtained by polymerizing a monomer mixture containing at least 5 mol% of a cationic monomer represented by the following general formula (1) in oil-containing wastewater. A method for treating oil-containing wastewater, comprising adding a water-soluble polymer and then adding an anionic water-soluble polymer to agglomerate to separate flocs.
[Chemical 1]
R1 is hydrogen or a methyl group, R2 and R3 are lower alkyl groups or alkoxy groups, which may be the same or different. A1 represents an oxygen atom or NH, B1 represents an alkylene group or an alkoxylene group, and X1 represents an anion.
According to a second aspect of the present invention, the cationic water-soluble polymer is prepared from a dispersion having a particle size of 100 μm or less produced by a dispersion polymerization method in the presence of a polymer dispersant soluble in the aqueous salt solution in the aqueous salt solution. The oil-containing wastewater treatment method according to claim 1, wherein:
[0006]
Invention of Claim 3 is the processing method of the oil-containing wastewater of Claim 1 or 2 characterized by the pH of the said oil-containing wastewater just before adding the said cationic water-soluble polymer being 7 or less. .
[0007]
Invention of Claim 4 is the processing method of the said oil-containing wastewater, The formed floc is isolate | separated with a screen, The processing method of the oil-containing wastewater in any one of Claims 1-3 characterized by the above-mentioned.
[0008]
The invention according to claim 5 is the method for treating oil-containing wastewater according to claim 4, wherein the screen is one type selected from an inclined screen, a rotary screen, a vibrating screen, and a wedge wire screen.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The cationic water-soluble polymer used in the present invention is obtained by polymerizing a monomer mixture containing the cationic monomer represented by the general formula (1). Such cationic monomers can be produced by quaternizing dialkylaminoethyl (meth) acrylates with benzyl chloride. This is copolymerized with other cationic monomers and nonionic monomers. Benzyl group-containing monomers are (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxyethyldiethylbenzylammonium chloride, (meth) acryloyloxy (2-hydroxypropyl) dimethylbenzylammonium chloride, And (meth) acryloylaminopropyldimethylbenzylammonium chloride.
[0010]
Another cationic monomer that may be copolymerized is dialkylaminoethyl (meth) acrylate or a quaternized product thereof. Examples of the dialkylaminoethyl (meth) acrylate include dimethylaminomethyl (meth) acrylate, diethylaminomethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylamide. Examples of quaternary ammonium group-containing monomers include (meth) acryloyloxyethyltrimethylammonium chloride and (meth) acryloyloxy 2-hydroxypropyltrimethyl, which are quaternized products of the tertiary amino-containing monomers with methyl chloride. Examples thereof include ammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, dimethyldiallylammonium chloride and diallylmethylbenzylammonium chloride.
[0011]
Nonionic monomers that can be copolymerized include methacrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, and N-vinyl pyrrolidone. N-vinylformamide, N-vinylacetamide and the like.
[0012]
The copolymerization ratio of the cationic water-soluble polymer is 5 mol% to 100 mol%, preferably 10 mol% to 100 mol%, more preferably as the monomer represented by the general formula (1). Is 20 to 80 mol%. If it is less than 5 mol%, sufficient cohesive force cannot be obtained.
[0013]
The weight average molecular weight of the cationic water-soluble polymer is 1 million to 20 million, preferably 3 million to 15 million. If it is less than 1 million, a floc having a sufficient size and strength is not generated, and there is a possibility that the floc may pass through when separated by a screen. Even if it is higher than 20 million, the effect is not changed, and the dispersibility is deteriorated and there is no merit. Therefore, it is the above range.
[0014]
The product form can be any solution such as aqueous solution, powder, water-in-oil emulsion polymer, or dispersion polymer in salt aqueous solution. However, considering the speed of dissolution and dispersibility in papermaking raw materials, A dispersion polymer is preferred.
[0015]
A water-soluble polymer comprising a polymer fine particle dispersion dispersed in an aqueous salt solution can be produced according to Japanese Patent Application Laid-Open No. 62-15251. In this method, a cationic monomer or a cationic monomer and a nonionic monomer are stirred in a salt aqueous solution in the presence of a dispersant composed of an ionic polymer soluble in the salt aqueous solution. It consists of a dispersion of polymer fine particles having a particle size of 100 mμ or less. When polymerizing an amphoteric water-soluble polymer, an anionic monomer is allowed to coexist during polymerization. As the polymer dispersing agent, a homopolymer of dimethyldiallylammonium chloride or (meth) acryloyloxyethyltrimethylammonium chloride or a copolymer with a nonionic monomer is used. Alternatively, nonionic polyvinyl pyrrolidone or the like is also used. The inorganic salts constituting the aqueous salt solution are more preferably polyvalent anion salts, and sulfates or phosphates are suitable. Specifically, ammonium sulfate, sodium sulfate, magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate, hydrogen phosphate Sodium and potassium hydrogen phosphate. The salt concentration in the dispersion is from 15% by mass to saturation.
[0016]
The polymer dispersant used can be either ionic or nonionic, but is preferably ionic, and more preferably cationic. First, examples of the cationic polymer include (meth) acryloyloxyethyltrimethylammonium chloride and dimethyldiallylammonium chloride, which are cationic monomers. These cationic monomers and nonionic monomers These copolymers can also be used. Examples of nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, 2-hydroxyethyl (meth) acrylate A copolymer with acrylamide is preferred.
[0017]
Nonionic polymers include amide groups and some hydrophobic groups such as polyvinylpyrrolidone, acrylamide / polyvinylcaprolactam copolymers, acrylamide / styrene copolymers, and fully amidated products of maleic anhydride / butene copolymer. A water-soluble polymer is effective.
[0018]
The molecular weight of these cationic polymer dispersants is 5,000 to 2,000,000, preferably 50,000 to 1,000,000. The molecular weight of the nonionic polymer dispersant is 1,000 to 100,000, preferably 1,000 to 50,000. The addition amount of these nonionic or ionic polymer dispersants to the monomer is 1/100 to 1/10, preferably 2/100 to 8/100, relative to the monomer.
[0019]
The polymerization conditions are usually appropriately determined according to the polymerization method, the monomer used and the copolymerization mol%, and the temperature is in the range of 0 to 100 ° C. For the initiation of polymerization, a radical polymerization initiator is used. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo, peroxide, and redox systems.
[0020]
Next, an anionic water-soluble polymer will be described. The anionic water-soluble polymer used in the present invention can be prepared by polymerizing a monomer mixture comprising an anionic monomer and a nonionic monomer by a known polymerization method. Examples of the anionic monomer used include methacrylic acid, acrylic acid, maleic acid, itaconic acid, styrene sulfonic acid, vinyl sulfonic acid, and 2-acrylamido 2-methylpropane sulfonic acid.
[0021]
Nonionic monomers to be copolymerized are, for example, (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinyl. Examples include pyrrolidone, N-vinylformamide, N-vinylacetamide and the like.
[0022]
The product form can be any solution such as aqueous solution, powder, water-in-oil emulsion polymer, or dispersion polymer in salt aqueous solution. However, considering the speed of dissolution and dispersibility in papermaking raw materials, it can be dispersed in salt aqueous solution. It is convenient to use a polymer or a water-in-oil emulsion polymer. The dispersion polymer in salt aqueous solution can be produced by the same method as the cationic water-soluble polymer dispersion.
[0023]
As an addition method, the cationic water-soluble polymer dispersion is diluted to 0.1 to 0.5% aqueous solution, and the aqueous solution is added with stirring in a tank such as an agglomeration reaction tank. Thereafter, an anionic water-soluble polymer is added under stirring in the same tank or another tank to form a floc, which is then sent to a screen to separate the floc. The oil-containing wastewater pH during the treatment is weakly alkaline to acidic, but more preferably on the acidic side. That is, the wastewater pH is more preferably 7 or less. If it is higher than 7, the floc strength becomes weak, and even when the floc is separated by the screen, even if it is broken by the screen or passes through the screen, the moisture content of the dehydrated cake by the dehydrator does not decrease.
[0024]
It is preferable to use the following screen. For example, an inclined screen, a rotary screen, a vibrating screen, a drum screen, and a wedge wire screen. Also particularly preferred is a wedge wire screen. That is, a normal mesh screen is likely to cause troubles such as clogging immediately. The wedge wire screen includes a general inclined type and a drum screen type, but the drum screen type is more preferable for preventing clogging and reducing the water content.
[0025]
The reason why the wedge wire screen is preferable is considered as follows. In other words, a general mesh screen has warps and wefts, and the mesh shape is usually a relatively thin line with a circular shape, and the wire constituting the mesh is not a straight line but a shape close to a zigzag because the mesh is woven. . Therefore, the finished mesh is not flat on the surface and the sticky floc is caught in the mesh and does not pass smoothly. As a result, it tends to adhere to the mesh. On the other hand, in the wedge wire screen, as shown in FIG. 2, the wedge wire corresponding to the warp is fixed by the support rod, and a slit is formed instead of the mesh. The surface of the wire is smooth and there is no equivalent to the weft of the net. As a result, even if the surface of the net on which the wires are arranged is uneven, the floc smoothly passes through the smooth wire surface. Moreover, it is hard to roll and adhere on the wire surface by using a rotating drum type.
[0026]
In the treatment method of the present invention, the BOD component removal rate may be lower than that of the inorganic flocculant formulation, but generally, the treated water is subjected to biological treatment thereafter, and there is no problem. Therefore, it can be said that it is a very valuable treatment method as a pretreatment method of biological treatment. Since the treatment method of the present invention does not use a large amount of an inorganic flocculant as a pretreatment for biological treatment, the generation of sludge can be reduced. In addition, there is no need for equipment that requires complicated adjustments such as pressure levitation, and it is compact, inexpensive, and easy to operate. Furthermore, since sludge is strong, most of it can be separated with a screen. If drained, it can be disposed of as industrial waste, and it may be possible to eliminate the need for a sludge dehydrator. If it is necessary to further reduce the water content, it can be dehydrated by a dehydrator.
[0027]
Examples of the oil-containing wastewater to be treated in the method for treating oil-containing wastewater of the present invention include food processing wastewater, that is, confectionery production, dressing, mayonnaise, milk processing, cream production, fried food, soup production, bento box and side dish production, etc. Oil production, hotel / restaurant kitchen drainage, and other industries such as petrochemical wastewater, machinery wastewater, and automobile industry wastewater can be treated with wastewater mixed with vegetable oil, animal oil, and mineral oil.
[0028]
The addition amount of the cationic water-soluble polymer is 0.001 to 0.1% by mass, preferably 0.002 to 0.05% by mass, based on the amount of pure polymer with respect to the amount of oil-containing wastewater. The addition amount of the anionic water-soluble polymer is 0.001 to 0.1% by mass, preferably 0.002 to 0.05% by mass, based on the pure amount of the polymer with respect to the amount of the oil-containing wastewater.
[0029]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in more detail with an Example and a comparative example, this invention is not restrict | limited to a following example, unless the summary is exceeded.
[0030]
Synthesis Example 1 Cationic Water-Soluble Polymer A 20% aqueous solution of acryloyloxyethyltrimethylammonium chloride homopolymer in a five-necked separable flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube 23 1.0 g (4.0% monomer), ion-exchanged water 154.7 g, ammonium sulfate 115.0 g, acrylamide (AAM) 50% aqueous solution 35.8 g, acryloyloxyethyltrimethylammonium chloride (DMQ) 80% aqueous solution 81. 3 and 84.9 g of 80% aqueous solution of acryloyloxyethylbenzyldimethylammonium chloride (DMB) were charged and completely dissolved. After maintaining the internal temperature at 33 to 35 ° C. and replacing with nitrogen for 30 minutes, 1% of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride as an initiator 2.3 g of aqueous solution (0.02% monomer) was added and polymerization was continued for 5 hours. Thereafter, 1.2 g of the initiator solution was added and polymerization was further performed for 5 hours. The resulting dispersion has a squeeze monomer concentration of 30% and a copolymerization ratio of AAM / DMQ / DMB = 30/40/30. The polymer particle size was 10 μm or less, and the viscosity of the dispersion was 260 mPa · s. Moreover, as a result of measuring a weight average molecular weight with the molecular weight measuring device (Otsuka Electronics DLS-7000) by a static light scattering method, the weight average molecular weight was 5 million.
[0031]
(Synthesis Example 2; Comparative Cationic Water-Soluble Polymer) A copolymer comprising acryloyloxyethyltrimethylammonium chloride and acrylamide = 70/30 was produced in the same manner as in Synthesis Example 1.
[0032]
(Synthesis Example 3) In a reaction vessel equipped with a stirrer and a temperature control device, 126.0 g of isoparaffin having a boiling point of 190 ° C to 230 ° C, 6.0 g of sorbitan monooleate, and polyricinoleic acid / polyoxyethylene block copolymer 0 .6 g was charged and dissolved. Separately, 45.0 g of deionized water and 87.5 g of a 60% aqueous solution of acrylic acid (abbreviated as AAC) were mixed, and this was neutralized by 90 mol% with 75.0 g of a 35% aqueous sodium hydroxide solution. After neutralization, 245.0 g of 50% aqueous solution of acrylamide (abbreviated as AAM) was added and completely dissolved. Thereafter, the oil and the aqueous solution were mixed and stirred and emulsified with a homogenizer at 1000 rpm for 15 minutes. The monomer composition at this time is AAC / AAM = 30/70 (mol%).
[0033]
After adding 2.0 g of isopropyl alcohol 40% aqueous solution (0.5% by weight of monomer) to the obtained emulsion, keeping the temperature of the monomer solution at 30 to 33 ° C. and performing nitrogen substitution for 30 minutes, 2,5′-Azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 10% aqueous solution 0.35 g (0.02% by weight of monomer) was added and polymerized. The reaction was started. The reaction was completed at a reaction temperature of 32 ± 2 ° C. for 12 hours to complete the reaction. After polymerization, 10.0 g of polyoxyethylene tridecyl ether (2.0% by weight with respect to the liquid) was added and mixed as a phase inversion agent to the resulting water-in-oil emulsion. The final monomer equivalent concentration of the water-in-oil emulsion is 35%. Moreover, the weight average molecular weight was measured with the molecular weight measuring device (DLS-7000 by Otsuka Electronics) by a static light scattering method.
[0034]
[Example 1 ]
Pastry manufacturing wastewater was treated by combining cationic water-soluble polymer and anionic water-soluble polymer. Table 1 shows the wastewater physical properties before treatment. pH 4.5, SS content 1032 mg / L, BOD 1984 mg / L, n-hexane extract 411 mg / L. While stirring in the first agglomeration reaction tank, 60 mg / L (about 0.006%) of the cationic water-soluble polymer was added to the liquid, and then the anionic water-soluble polymer was added to the liquid under agitation in the second agglomeration reaction tank. 10 mg / L (about 0.001%) was added. The processing liquid in which the formed floc was dispersed was sent to a wedge wire type rotary screen to separate the floc. The water content and treated water quality of the separated floc were measured. The results are shown in Table 1.
[0035]
[Comparative Examples 1-3 ]
When the confectionery wastewater used in Example 1 was treated with a cationic water-soluble polymer alone and added to the solution at 80 mg / L (about 0.008%) (Comparative Example 1), or the comparative cation produced in Synthesis Example 2 When water-soluble polymer and anionic water-soluble polymer are added to the respective solutions 60 mg / L (about 0.006%) and 15 mg / L (about 0.0015%) and processed in combination (Comparative Example 2) ), 500 mg / L (about 0.05%) of polyaluminum chloride solution, and 5 mg / L (about 0.0005%) of an anionic water-soluble polymer added and treated (Comparative Example 3). went. The results are shown in Table 1.
[0036]
[Table 1]
SS; mg / L, BOD; mg / L, n-HX; n-hexane extract mg / L
Flock moisture content; wt%
[0037]
[Example 2 ]
Mayonnaise production wastewater was treated by combining cationic water-soluble polymer and anionic water-soluble polymer. Table 2 shows the quality of waste water before treatment. After adjusting the drainage pH to 6.2 by adding an aqueous sodium hydroxide solution, 0.01% of a cationic water-soluble polymer is added to the second agglomeration reaction with stirring in the first agglomeration reaction tank. While stirring in the tank, 0.0015% of the anionic water-soluble polymer was added to the liquid. Then, the processing liquid was sent to the wedge wire type rotary screen to separate the floc. The water content of the separated oil-containing floc and the BOD of the separated water were measured. The results are shown in Table 2.
[0038]
[Comparative Examples 4-6 ]
When the mayonnaise production waste water is treated with 120 mg / L of the cationic water-soluble polymer alone (Comparison-4), or the comparative cationic water-soluble polymer and the anionic water-soluble polymer produced in Synthesis Example 2 are each 100 mg. / L, 15 mg / L added and processed (Comparison-5), polyaluminum chloride solution 800 mg / L added, anionic water-soluble polymer 10 mg / L added and processed (Comparative Example-6) A test was conducted. The results are shown in Table 2.
[0039]
[Table 2]
SS; mg / L, BOD; mg / L, n-HX; n-hexane extract mg / L
Flock moisture content; wt%
[Brief description of the drawings]
FIG. 1 shows a treatment flow diagram of oil-containing wastewater.
[Explanation of symbols]
(A) Oil-containing wastewater tank (b) First agglomeration reaction tank (c) Second agglomeration reaction tank (d) Cationic water-soluble polymer stock solution (e) Dissolution tank (f) Anionic water-soluble polymer stock solution (g) Dissolution tank [FIG. 2] A view showing a structure of a wedge wire screen.
[Explanation of symbols]
(A) Slit (Wedge wire spacing)
(B) Wedge wire (c) Support rod

Claims (5)

After adding a cationic water-soluble polymer obtained by polymerizing a monomer mixture containing at least 5 mol% of a cationic monomer represented by the following general formula (1) to oil-containing wastewater, anionic A method for treating oil-containing wastewater, comprising adding a water-soluble polymer to agglomerate to separate flocs.
R1 is hydrogen or a methyl group, R2 and R3 are lower alkyl groups or alkoxy groups, which may be the same or different. A1 represents an oxygen atom or NH, B1 represents an alkylene group or an alkoxylene group, and X1 represents an anion. The cationic water-soluble polymer comprises a dispersion having a particle size of 100 μm or less produced by a dispersion polymerization method in a salt aqueous solution in the presence of a polymer dispersant soluble in the salt aqueous solution. Item 2. A method for treating oil-containing wastewater according to Item 1. The method for treating oil-containing wastewater according to claim 1 or 2, wherein the pH of the oil-containing wastewater immediately before the addition of the cationic water-soluble polymer is 7 or less. The method for treating oil-containing wastewater according to any one of claims 1 to 3 , wherein the method for treating oil-containing wastewater separates formed flocs with a screen. The method for treating oil-containing wastewater according to claim 4, wherein the screen is a kind selected from an inclined screen, a rotary screen, a vibrating screen, and a wedge wire screen.