JP6744526B2 - Wastewater treatment method and wastewater treatment agent - Google Patents

Description

The present disclosure relates to a wastewater treatment method and a wastewater treatment agent, and particularly to a wastewater treatment method and a wastewater treatment agent for treating wastewater having a high salt concentration.

Anionic and nonionic polymer flocculants are generally used for clarification of industrial wastewater by coagulation and sedimentation. The anionic polymer flocculant has an anionic dissociative group such as a carboxyl group or a sulfone group in the polymer chain. At the same time, it often has a hydrophilic group such as an amide group which is a non-dissociative group, and both are considered to be involved in the performance.
As the polyacrylamide-based anionic polymer flocculant, those having an anion group ratio of 5% referred to as weak anions to 40 mol% of anion groups referred to as strong anions are generally used. Anionic polymer flocculants having an anion group ratio of about 20 mol% called anion are widely used. The reason is that, in addition to the charge balance due to the anion chain, the hydrogen bonding force due to the nonionic chain (acrylamide) of the polymer coagulant is considered to be an important factor for the aggregation effect of the polyacrylamide-based anionic polymer coagulant. Because there is. Therefore, it is considered that those having a large number of nonionic chains in the molecule, that is, those having a low anion group ratio are preferable for the aggregation action. It is also considered that those having a large molecular weight are suitable (for example, see Non-Patent Document 1).

Patent Document 1 discloses a treatment agent for wastewater containing inorganic fine particles, which comprises an aqueous solution containing an anionic or nonionic polyacrylamide polymer flocculant and an alkali metal carbonate. This document discloses that a polyacrylamide partial hydrolyzate having a hydrolysis rate of 40 mol% or less can be used as an example of the polyacrylamide polymer flocculant.
Patent Document 2 discloses a water treatment method in which an anionic polymer flocculant is added to water to be treated, then stirred and granulated, and then solid-liquid separated to obtain treated water. It is disclosed that a cationic polymer flocculant is added to the water to be treated before the addition. The document discloses that an anionic polymer flocculant having an anion group ratio of 5 to 30 mol %, particularly 5 to 20 mol% is suitable (see paragraphs 0023 and 0047). ..
Patent Document 3 discloses a method of adding a condensation-type polyamine and then adding a polymer flocculant to waste paper pulp wastewater. The same document discloses that a nonionic or anionic polymer coagulant such as polyacrylamide is preferable as the polymer coagulant (paragraph 0008).
In Patent Document 4, a cationic polymer flocculant having a cation group ratio of 10 to 50 mol% is added to wastewater containing inorganic ions, stirred to generate flocs, and then an anionic polymer flocculant is added. Disclosed is a method for treating wastewater containing inorganic ions, which comprises granulating the floc.

Japanese Patent Laid-Open No. 06-335605 (Patent No. 3344431) WO2014/038537A1 JP, 11-033563, A JP, 2005-066546, A

"Fundamental and Applied Technologies of Water-Soluble Polymers", CMC Co., Ltd., published on August 27, 2014, in the second edition (pages 136-137, ((3) Characteristics of polymer flocculant (1) Anion, (Refer to the section of nonionic polymer flocculant)

When treating wastewater with a high salt concentration discharged from soda industry, food factories, plating factories, etc. by coagulation sedimentation, conventional methods do not provide sufficient coagulation effect, for example, flocs are difficult to form, or form. However, since the size is small, it is difficult to separate due to coagulation and precipitation, and there is a problem that a sufficient treatment effect cannot be obtained.

The present disclosure provides, in one or a plurality of embodiments, a new wastewater treatment method and a wastewater treatment agent capable of treating wastewater having a wide pH range and a high salt concentration.

In one aspect of the present disclosure, a polyacrylamide anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less is added to water to be treated, and the polymer coagulant is added. The present invention relates to a wastewater treatment method including solid-liquid separation of water to be treated, wherein the water to be treated is wastewater having a high salt concentration.

In another aspect, the present disclosure relates to a wastewater treatment agent containing, as an active ingredient, a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less.

According to the present disclosure, in one or a plurality of embodiments, a floc capable of solid-liquid separation is formed in a wide pH range from an acidic range to an alkaline range, and a treatment effect is improved. According to the present disclosure, in one or a plurality of embodiments, it is possible to provide an effect of providing a wastewater treatment method and a wastewater treatment agent having low turbidity and good water quality after treatment. According to the present disclosure, in one or a plurality of embodiments, an effect that the amount of a drug used can be reduced can be obtained.

The present disclosure is based on the finding that a suspension component contained in wastewater having a high salt concentration can be effectively captured by a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% to 85% mol. ..

Mechanism of effectively trapping suspended components in wastewater even if the wastewater has a high salt concentration by using a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% to 85% mol The details are not clear, but it is estimated as follows. As described above, it is considered that the aggregating effect of the polyacrylamide type anionic polymer aggregating agent is an important factor for the charge balance by the anion group and the hydrogen bonding force by the nonionic group. Therefore, polyacrylamide-based anionic polymer flocculants having an anion group ratio of about 20 to 30 mol% are usually used for wastewater treatment. However, in the case of wastewater having a high salt concentration, the anion group is charge-neutralized by a large amount of salts contained in the wastewater, resulting in a change in charge balance and contraction of the molecular chain in the polyacrylamide anionic polymer flocculant. Therefore, in the case of the usual polyacrylamide-based anionic polymer flocculant having the above-mentioned anion group ratio, the adsorptivity to the suspension component and the crosslinkability between the anionic polymer flocculants decrease. On the other hand, by using a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less, which has a higher anion group ratio than a normal polyacrylamide-based anionic polymer flocculant, Even if the sum occurs, the change in charge balance and the atrophy of the molecular chain are suppressed. Therefore, it is possible to achieve a balance between adsorption to a suspension component suitable for aggregation and crosslinking between polyacrylamide-based anionic polymer flocculants, and to exhibit the cohesive ability originally possessed by polyacrylamide-based anionic polymer flocculants. it can. As a result, flocs capable of solid-liquid separation can be formed, and the treatment effect can be improved. However, the present disclosure may not be limited to this mechanism.

[Wastewater treatment method]
In one embodiment of the present disclosure, a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less is added to water to be treated that is wastewater having a high salt concentration, and The present invention relates to a wastewater treatment method including solid-liquid separation of water to be treated to which a polymer flocculant has been added.

[Water to be treated]
The high-salt-concentration wastewater that is the water to be treated in the wastewater treatment method of the present disclosure includes, in one or a plurality of embodiments, wastewater having an electrical conductivity of 100 mS/m or more. Further, in one or a plurality of embodiments, waste water having an electric conductivity of 500 mS/m or more can be mentioned. The electrical conductivity is 1000 mS/m or more, 2000 mS/m or more, 5000 mS/m or more and 10000 mS/m or more, or 20000 mS/m or more in one or a plurality of embodiments. In one or a plurality of embodiments, the electric conductivity is 1000 mS/m or more, 20000 mS/m or less, or 5000 mS/m or more, or 10000 mS/m or more, or 20000 mS/m or more and 100000 mS/m or less. The electric conductivity can be measured by the method described in Examples.

Examples of the high-salt-concentration wastewater include, in one or more embodiments, wastewater discharged from soda industry, food factories, plating factories, stainless factories, paper mills, and the like.
The electrical conductivity of wastewater discharged from the soda industry is, in one or more embodiments, 10,000 mS/m or more, or 20,000 mS/m or more, and 100,000 mS/m or less.
The electrical conductivity of the wastewater discharged from the plating plant is, in one or more embodiments, 20000 mS/m or more, or 40,000 mS/m or more, and 100,000 mS/m or less.
The electric conductivity of the wastewater discharged from the stainless steel plant is 5000 mS/m or more or 10000 mS/m or more and 100000 mS/m or less in one or a plurality of embodiments.
The electric conductivity of the wastewater discharged from the paper mill is 1000 mS/m or more, 2000 mS/m or more, and 20000 mS/m or less in one or more embodiments.

In one or a plurality of embodiments, the water to be treated contains one or more kinds of salts or ions such as sodium, potassium, calcium, chlorine, fluorine, sulfate ion and nitrate ion.

[Polyacrylamide-based anionic polymer flocculant]
The wastewater treatment method of the present disclosure uses a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% to 85% mol. In the present disclosure, the “anion group ratio” means the ratio of the constituent unit having an anion group in the constituent unit of the polymer flocculant, and can be calculated, for example, from the following formula.
Anion group ratio (mol %)={Mole ratio of constituent unit having anion group/(Mole ratio of constituent unit having anion group+Mole ratio of constituent unit having nonion group)}×100

The polyacrylamide-based anionic polymer flocculant is not particularly limited as long as the anion group ratio is 55 mol% or more and 85% or less, and those used as the polyacrylamide-based anionic polymer flocculant are Applicable. A preferable anion group ratio is 60 mol% or more and 80 mol% or less.

Examples of the polyacrylamide-based anionic polymer flocculant include, in one or more embodiments, a copolymer of acrylamide and an anionic monomer, a hydrolyzate of polyacrylamide, and the like. Examples of the anionic monomer include a monomer containing at least one of acrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid (AMPS).
As a copolymer of acrylamide and an anionic monomer, an acrylamide-acrylic acid copolymer, an acrylamide-AMPS copolymer, and an acrylamide-acrylic acid-AMPS copolymer are mentioned in one or a plurality of embodiments.
The polyacrylamide-based anionic polymer flocculant of the present disclosure may be an alkali metal salt. Examples of the alkali metal salt include potassium salt and sodium salt.

In one or a plurality of embodiments, the molecular weight of the polyacrylamide-based anionic polymer flocculant is 9 million or more and 22 million or less, and from the viewpoint of improving the treatment effect, 10 million or more, 12 million or more, or 14 million or more. Can be mentioned.

The addition concentration of the polyacrylamide-based anionic polymer flocculant can be appropriately set according to the type of water to be treated, and in one or more embodiments, is 0.5 mg/L or more or 1 mg/L or more, and 10 mg. /L or less or 3 mg/L or less.

The form of the polyacrylamide-based anionic polymer coagulant is not particularly limited, and those generally distributed for the coagulation treatment of wastewater can be used. In one or a plurality of embodiments, a powder, a W/O type emulsion, a dispersion in which anionic polymer coagulant particles are dispersed in an aqueous medium, or the like can be mentioned.

In one or a plurality of embodiments, the wastewater treatment method of the present disclosure may include stirring water to be treated to which a polyacrylamide-based anionic polymer flocculant has been added, from the viewpoint of improving floc formation efficiency.

The solid-liquid separation of the water to be treated can be performed in one or a plurality of embodiments by allowing the formed aggregate (floc) to settle or float.

The wastewater treatment method of the present disclosure may be used in combination with an inorganic coagulant, an organic coagulant, or the like in one or more embodiments from the viewpoint of improving the coagulation effect. According to the wastewater treatment method of the present disclosure, when used in combination with an inorganic coagulant and/or an organic coagulant, in one or a plurality of embodiments, it is possible to reduce the amount of a chemical used in the treatment. In one or a plurality of embodiments, the inorganic coagulant and the organic coagulant are preferably added before the polyacrylamide-based anionic polymer flocculant is added.
Inorganic coagulants include, in one or more embodiments, those capable of forming hydroxides. Examples of the inorganic coagulant include PAC (polyaluminum chloride), polyiron (ferric sulfate sulfate), iron salt (ferric chloride), and a sulfate band in one or more embodiments. When the water to be treated contains fluorine, phosphoric acid, etc., a calcium compound such as slaked lime can be used as one or more embodiments. The addition amount of the inorganic coagulant is, in one or a plurality of embodiments, 10 mg/L or more or 20 mg/L or more, and 1000 mg/L or less or 500 mg/L or less with respect to the water to be treated.
Examples of the organic coagulant include a low molecular weight alkylamino(meth)acrylate quaternary salt polymer, secondary amine-epichlorohydrin, diallyldimethylammonium, and the like, as one or a plurality of embodiments.

[Wastewater treatment agent]
In another aspect, the present disclosure relates to a wastewater treatment agent containing, as an active ingredient, a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less. The polyacrylamide-based anionic polymer flocculant is as described above. The wastewater treatment agent of the present disclosure can efficiently perform treatment of wastewater having a high salt concentration in a wide pH range, for example, pH 4.5 to 12 in one or a plurality of embodiments.

Forms of the wastewater treatment agent of the present disclosure include powder, solid, aqueous dispersion and emulsion in one or more embodiments. In the case of an aqueous dispersion, the content of the polyacrylamide-based anionic polymer flocculant in the wastewater treatment agent of the present disclosure is 10% by weight or more and 30% by weight or less in one or a plurality of embodiments. In the case of an emulsion, the content of the polyacrylamide anionic polymer flocculant in the wastewater treatment agent of the present disclosure is 40% by weight or more and 65% by weight or less in one or more embodiments.

The present disclosure may relate to one or more of the following embodiments;
[1] Adding a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less to water to be treated and solidifying the water to be treated to which the polymer flocculant has been added. Including liquid separation,
The wastewater treatment method, wherein the water to be treated is wastewater having a high salt concentration.
[2] The polyacrylamide-based anionic polymer flocculant is a partial hydrolyzate of polyacrylamide, and a copolymer of acrylamide and an anionic monomer containing at least one of acrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid. The water treatment method according to [1], which is selected from the group consisting of polymers and combinations thereof.
[3] The water treatment method according to [1] or [2], wherein the electrical conductivity of the water to be treated is 1,000 mS/m or more.
[4] A wastewater treatment agent containing, as an active ingredient, a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less.
[5] The polyacrylamide-based anionic polymer flocculant is a partial hydrolyzate of polyacrylamide, a copolymer of acrylamide and an anionic monomer containing at least one of acrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid. The wastewater treatment agent according to [4], which is selected from the group consisting of polymers and combinations thereof.
[6] The wastewater treatment agent according to [4] or [5], which is used for treating wastewater having a high salt concentration.

The present disclosure will be described based on the following examples and comparative examples, but the present disclosure is not limited thereto.

[Polymer Flocculant]
The polyacrylamide type anionic polymer flocculants having the anion group ratios shown in Table 1 below were used.

[Measurement of electrical conductivity]
The electrical conductivity of wastewater is JIS K0102 (2008) "Factory wastewater test method" 13. It measured based on the term of electrical conductivity.
[Measurement of turbidity]
The turbidity was obtained from a calibration curve prepared by using the kaolin standard solution by measuring the absorbance of the collected sample with a spectrophotometer.

[Test Example 1: Soda factory wastewater]
A 0.1 wt% aqueous solution was prepared by adding water to the polyacrylamide type anionic polymer flocculant 1 or 2 (1 g) shown in Table 1 and dissolving the resulting mixture to 1000 mL. An aqueous solution of the polymer flocculant was added to a beaker containing 500 mL of salt-containing wastewater (electrical conductivity 40,000 mS/m) of an actual soda factory so that the concentration of the polymer flocculant added was 1 mg/L. .. The pH of the water to be treated before addition of the aqueous polymer flocculant solution (untreated) was around 11, and the turbidity (standard kaolin turbidity) was 100.
After adding the polyacrylamide type anionic polymer flocculant, the mixture was stirred at 120 rpm for 1 minute and further at 60 rpm for 1 minute. The formed flock was collected and the diameter of the flock was measured using a ruler. Further, after stirring for 1 minute, the mixture was allowed to stand for 1 minute, a supernatant was collected, and the turbidity was determined. The results are shown in Table 2 below.

As a comparative example, the same procedure as described above was performed except that the polyacrylamide-based anionic polymer flocculant 4 or 5 in Table 1 was used instead of the polyacrylamide-based anionic polymer flocculant 1 or 2. The results are shown in Table 2 below.

As shown in Table 2, by the method of Examples 1-1 and 1-2, large flocs were formed as compared with Comparative Examples 1-1 and 1-2, and the turbidity of the supernatant liquid was increased. It was low.
Further, a cationic polymer flocculant (alkylaminoacrylate quaternary salt polymer (DAM) cationic group ratio: 10 to 100 mol %, molecular weight: 9 million) is used instead of the polyacrylamide anionic polymer flocculant. The same test as above was performed. As a result, both the size of flocs and the turbidity of the supernatant were the same as those of the comparative example.
In other words, by treating with a polyacrylamide type anionic polymer flocculant having an anion group ratio of 60 or 70 mol %, the suspended components contained in the soda factory wastewater having an electric conductivity of 40,000 mS/m can be obtained. It was possible to efficiently remove and obtain treated water having a turbidity of less than 10.

[Test Example 2: Plating factory wastewater]
Instead of the waste water of Test Example 1, waste water containing fluorine and titanium (electrical conductivity of 60,000 mS/m) in an actual plating factory was used, and the concentration of polyacrylamide-based anionic polymer coagulant added was 3 mg/L. Except for this, the procedure was the same as in Test Example 1. As the polymer coagulant, the polyacrylamide type anionic polymer coagulants 1 to 4 shown in Table 1 were used. The results are shown in Table 3 below. The water to be treated before the addition of the aqueous solution of the polymer flocculant (untreated) was neutralized with an aqueous sodium hydroxide solution so as to have a pH of about 5 to 6. Turbidity (kaolin turbidity standard) was so cloudy that it could not be measured.

As shown in Table 3, by treating with the method of Examples 2-1 to 2-3, large flocs were formed as compared with Comparative Example 2, and the turbidity of the supernatant could be significantly reduced. It was
Also, a cationic polymer flocculant (alkylaminoacrylate quaternary salt polymer (DAM) cationic group ratio: 30 to 80 mol%, molecular weight: 9 million) is used in place of the polyacrylamide anionic polymer flocculant. The same test as above was performed. As a result, almost no floc sedimentation was observed and the turbidity was almost the same as that before the treatment.
That is, by performing treatment with a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 60 to 80 mol %, the suspension components contained in the plating factory wastewater having an electric conductivity of 40,000 mS/cm can be removed. It was possible to efficiently remove and obtain treated water having a turbidity of 15 or less.

[Test Example 3: Wastewater of white water recovery facility of paper mill]
2 mg/L of diallyldimethylammonium chloride as an organic coagulant was added to a beaker containing 500 mL of white water recovery facility wastewater (electrical conductivity 2000 mS/cm) of an actual paper mill in place of the wastewater of Test Example 1. Then, a 0.1 wt% polymer flocculant aqueous solution was added so that the concentration of the polymer flocculant added was 2 mg/L. After the addition, the mixture was stirred at 120 rpm for 1 minute and further at 60 rpm for 1 minute. As the polymer coagulant, the polyacrylamide type anionic polymer coagulants 1 to 3 and 4 shown in Table 1 were used. The pH of the water to be treated before the addition of diallyldimethylammonium chloride was 7 to 8, and the turbidity (kaolin turbidity standard) was 200.
The measurement of the floc size and the measurement of the turbidity were performed in the same manner as in Test Example 1. The results are shown in Table 4 below.

As shown in Table 4, by treating with the method of Examples 3-1 to 3-3, large flocs were formed as compared with Comparative Example 3, and the turbidity of the supernatant was also reduced. Therefore, a suspension component contained in the wastewater of a white water recovery site of a paper mill having an electric conductivity of 2000 mS/m is obtained by performing treatment with a polyacrylamide-based anionic polymer flocculant having an anion group ratio of 60 to 80 mol %. Could be removed.

In addition, by using an organic coagulant and a polyacrylamide anionic polymer flocculant having an anion group ratio of 60 to 80 mol% in combination, a conventional flocculant (a polyacrylamide system having an anion group ratio of 30 mol% is used). The amount of organic coagulant added is lower than the combined use of anionic polymer coagulant) and organic coagulant, and larger flocs can be formed than in the conventional method, and the turbidity of the supernatant after treatment can be reduced. It was

Claims (4)

A polyacrylamide-based anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less (provided that the polyacrylamide-based anionic polymer flocculant is (A) a water-soluble vinyl monomer, (B) ) Water, (C) an oily substance consisting of at least one hydrocarbon, (D) at least one surfactant having an HLB and an amount effective to form a water-in-oil emulsion, and (E) the following general. The polyoxy compound represented by the formula (1) and/or (2) is mixed, stirred vigorously to form a water-in-oil emulsion, and then polymerized to obtain an emulsion particle size of 0.1 to 50 μm. (Excluding the case of a water-in-oil type water-soluble polymer emulsion characterized in that) is added to the water to be treated, and the water to be treated to which the polymer flocculant is added is subjected to solid-liquid separation. ,
The water to be treated is a high-salt-concentration wastewater having an electric conductivity of 1,000 mS/m or more, and is discharged from a group consisting of a soda industry, a food factory, a plating factory, a stainless steel factory, and a paper manufacturing factory. (However, the organic sludge to which the cationic organic polymer flocculant is added is excluded).

The polyacrylamide anionic polymer flocculant is a partial hydrolyzate of polyacrylamide, a copolymer of acrylamide and an anionic monomer containing at least one of acrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid, And the wastewater treatment method according to claim 1, which is selected from the group consisting of a combination thereof. A polyacrylamide type anionic polymer flocculant having an anion group ratio of 55 mol% or more and 85 mol% or less is contained as an active ingredient,
Wastewater treatment agent for use in waste water treatment method according to claim 1 or 2. The polyacrylamide anionic polymer flocculant is a partial hydrolyzate of polyacrylamide, a copolymer of acrylamide and an anionic monomer containing at least one of acrylic acid and 2-acryloylamino-2-methylpropanesulfonic acid, And the wastewater treatment agent according to claim 3 , which is selected from the group consisting of a combination thereof.