JP2009297600A - Method for treating dispersant-containing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating dispersant-containing water which can reduce the amount of the sludge to be generated in treatment by the flocculating setting of dispersant-containing raw water. <P>SOLUTION: In the method for treating dispersant-containing water where dispersant-containing raw water is treated by flocculating sedimentation, the dispersant comprises at least one unit having a carboxyl group, and at least an inorganic coagulant is added to the raw water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for treating a dispersant-containing water in which raw water containing a dispersant used for applications such as prevention of hardness scale and dispersion of suspended particles is treated by coagulation precipitation.

  As a treatment method to remove pollutants contained in wastewater, an inorganic flocculant such as polyaluminum chloride (PAC) and polymer flocculant are injected into the wastewater to form flocculent flocs, and the flocculent flocs are separated by settling. A coagulating precipitation method is generally used.

  On the other hand, wastewater discharged from factories often contains a dispersant used for the purpose of stabilizing suspended particles and preventing hardness scale. These dispersants generally have an anionic charge and can act by adsorbing to suspended particles so that the particles repel each other, or by blocking cations such as calcium to suppress precipitation. Prevent scaling.

  When the wastewater containing such a dispersant is to be treated by the coagulation sedimentation method, the formation of coagulated floc is inhibited by the dispersant, and the quality of the treated water often deteriorates. This is because the injected inorganic coagulant is cationic and consumed by reacting with the anionic dispersant, and the injection amount of the inorganic coagulant becomes insufficient.

  In order to treat such a dispersant-containing wastewater, an inorganic coagulant may be injected in excess for the amount of reaction with the dispersant. However, in such a method, the amount of inorganic coagulant added becomes large, and thus the amount of generated sludge increases significantly.

  As another method, there is a method of adding a calcium salt together with an inorganic coagulant. In this method, the influence on aggregate floc formation can be reduced by reacting the dispersant with calcium ions to block the anionic group of the dispersant. Calcium salts include slaked lime and calcium chloride. However, since slaked lime has a low solubility in water, it is usually handled in a slurry state. Therefore, it is easy to cause clogging of pumps and piping, and the handling is complicated. In addition, since the reaction between the calcium salt and the dispersant is stoichiometric, the amount of added calcium salt increases as the amount of the dispersant in the wastewater increases, resulting in a significant increase in the amount of generated sludge. is there.

  Furthermore, in order to reduce the amount of the inorganic coagulant used, for example, Patent Document 1 describes that an organic coagulant such as polydiallyldimethylammonium chloride is used in combination with the inorganic coagulant. Patent Document 2 describes a treatment method in which an organic coagulant such as polyamine or an inorganic coagulant and an organic coagulant are added to and mixed with raw water for water purification, and then a polymer flocculant is added and mixed. Yes.

Japanese Examined Patent Publication No. 7-41247 Japanese Patent No. 4004016

  However, for wastewater containing a dispersant, even if the organic coagulant as described above is used in combination with an inorganic coagulant, the amount of generated sludge is still large, resulting in an economic burden and an environmental burden. I'm leaving.

  The present invention is a method for treating dispersant-containing water that can reduce the amount of sludge generated in the treatment by coagulation sedimentation of raw water containing a dispersant.

  The present invention is a method for treating a dispersant-containing water in which raw water containing a dispersant is treated by coagulation sedimentation, wherein the dispersant contains at least one constituent unit having a carboxyl group, and the raw water contains at least inorganic coagulation. It is the processing method of the dispersing agent containing water which adds an agent.

  Moreover, in the processing method of the said dispersing agent containing water, it is preferable that pH of the said raw | natural water is the range of 3-6.

  In the method for treating water containing a dispersant, it is preferable to further add an organic coagulant to the raw water.

  Moreover, in the processing method of the said dispersing agent containing water, it is preferable to add a clay mineral to the said raw | natural water as a coagulant aid.

  In the present invention, the amount of sludge generated by adding at least an inorganic coagulant to raw water containing a dispersant containing at least one constituent unit having a carboxyl group in the treatment by coagulation and precipitation of the raw material containing dispersant is reduced. Can be reduced.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Water treatment apparatus and water treatment method>
The outline of an example of the water treatment apparatus for enforcing the processing method of the dispersing agent content water concerning this embodiment is shown in Drawing 1, and the composition is explained. The water treatment apparatus 1 includes a pH adjustment tank 10, a reaction tank 12, a coagulation tank 14, and a coagulation sedimentation tank 16.

  In the water treatment apparatus 1, the pH adjustment tank 10, the reaction tank 12, the coagulation tank 14, and the coagulation sedimentation tank 16 are respectively connected in series with an inlet and an outlet through a pipe or the like. The pH adjusting tank 10, the reaction tank 12, and the aggregating tank 14 are provided with stirring devices 18, 22, and 24, which are stirring means including a motor and stirring blades, respectively. The pH adjustment tank 10 is provided with a pH meter 20 that is a pH measuring means.

  First, a dispersant-containing raw water containing a dispersant (hereinafter sometimes simply referred to as “raw water”) is temporarily stored in a raw water tank or the like, and then sent to the pH adjustment tank 10, where the pH adjustment tank 10. In FIG. 2, the pH adjusting agent is added and the pH is adjusted to a predetermined range while being stirred by the stirring device 18 and measured by the pH meter 20 (pH adjusting step). If the pH of the raw water is within a predetermined range, the pH adjustment of the raw water may not be performed, and the pH adjustment tank 10 is not necessary. Thereafter, the pH adjusted liquid whose pH has been adjusted is sent to the reaction tank 12.

  The raw water to be treated in this embodiment is not particularly limited as long as it is water containing a dispersant. Examples thereof include dispersant-containing wastewater discharged from semiconductor factories, food factories, paper / pulp factories, chemical factories, etc., concentrated water in reverse osmosis membrane (RO membrane) treatment, blow water discharged from a cooling water system, and the like.

The dispersant contained in the raw water is usually used for the purpose of stabilizing suspended particles and preventing hardness scale. The dispersant is not particularly limited as long as it contains at least one structural unit having a carboxyl group. For example, a polyacrylic acid-based polymer containing a monomer unit represented by the following structural formula (1) A polymer, a copolymer containing a monomer unit represented by the following structural formula (1) and a monomer unit represented by the following structural formula (2), an acrylic acid multi-component copolymer ((1 ) And (2) copolymerization weight ratio: for example, 50:50 to 90:10), and polymaleic acid polymers containing monomer units represented by the following structural formula (3).
^{_{- (CH 2 -CR 1 COOX)}} - (1)
_{- (CH 2 -CHCONHY) - (} 2)
^{- (CR 2 OOZ-CR 3} COOW) - (3)
(In Formula (1), R ¹ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, a monovalent or divalent metal atom such as sodium, an ammonium group, or an organic ammonium group. In Formula (2) , Y represents an alkylsulfonic acid group or a salt thereof In the formula (3), R ² and R ³ each independently represent a hydrogen atom or a methyl group, Z and W each independently represent a hydrogen atom, 1 Represents a divalent or divalent metal atom, an ammonium group or an organic ammonium group.)

  The weight average molecular weight of these dispersants is, for example, in the range of 500 to 50,000.

In the pH adjustment tank 10, the pH of the raw water is preferably adjusted in the range of pH 3-6, and more preferably adjusted in the range of 4-5. By adjusting the pH of the raw water to a pH lower than that in the normal flocculation treatment, preferably in the range of 3-6, more preferably in the range of 4-5, the carboxyl group contained in the dispersant is changed from COO ^- type to COOH. By converting it into a mold, the ionicity of the dispersant can be weakened. By weakening the ionicity of the dispersant, flocs produced by the addition of a coagulant and coagulation aids such as clay minerals are added, making it easier for the dispersant to adsorb on the clay mineral and removing the dispersant. It is thought that it becomes easy to do.

  As the pH adjuster, an acid such as hydrochloric acid or sulfuric acid, or an alkali such as sodium hydroxide or calcium hydroxide is used.

  Next, an inorganic coagulant is added to and mixed with the pH adjusting liquid by a pump or the like while being rapidly stirred by the stirring device 22 in the reaction tank 12 to perform a coagulation reaction (coagulant adding step). By rapid stirring in the reaction vessel 12, the condensation reaction proceeds. At this time, in order to reduce the amount of the inorganic coagulant used, it is preferable that an organic coagulant is used in combination. Thereafter, the reaction liquid to which the inorganic coagulant is added and mixed is sent to the aggregation tank 14.

  As the inorganic coagulant, an inorganic coagulant such as iron or aluminum generally used as a coagulant can be used. Specific examples include a sulfuric acid band, polyaluminum chloride (PAC), aluminum chloride, polyferric sulfate (polyiron), ferric chloride, and a mixture thereof.

  The amount of the inorganic coagulant added is not particularly limited as long as it is determined according to the properties of the raw water to be treated. For example, it is in the range of 20 mg / L to 10,000 mg / L, and is used in combination with the organic coagulant. In the case, for example, the range is from 10 mg / L to 5,000 mg / L.

  As organic coagulants, condensed polyamines such as condensates of alkylene diamine and epichlorohydrin such as dimethylamine and epichlorohydrin condensates generally used as coagulants, and polydialkyldiallyls such as polydiallyldimethylammonium chloride Organic coagulants such as ammonium salts can be used.

  The amount of the organic coagulant that may be used in combination is not particularly limited as long as it is determined according to the properties of raw water to be treated, but is, for example, in the range of 0.1 mg / L to 2,000 mg / L.

  The organic coagulant and the inorganic coagulant may be used either alone or in the form of a mixture. However, the organic coagulant, the inorganic coagulant, or a mixture of these coagulant and inorganic coagulant previously diluted with a solvent such as water. The suspension may be used in a state such as a suspension. When the organic coagulant and the inorganic coagulant are used in combination, the order of addition of the organic coagulant and the inorganic coagulant to the pH adjusting liquid is not particularly limited.

  In the step of adding a coagulant, it is preferable to add a clay mineral as an agglomeration aid prior to the addition of a coagulant such as an inorganic coagulant or an organic coagulant or together with the addition of the coagulant. The present inventors pay attention to the physicochemical adsorption performance of the dispersant and intentionally adsorb the clay mineral and the dispersant added to the pH adjusting liquid, thereby reducing the amount of chemicals such as inorganic coagulant used. It was found that the amount of sludge generated can be further reduced, and the processing cost can be remarkably suppressed.

  The clay mineral is not particularly limited as long as it is a powder of about 20 μm or less, and examples thereof include kaolin, bentonite, talc, acid clay, fly ash, and Kanto loam.

  The amount of clay mineral that may be used in combination is not particularly limited as long as it is determined according to the properties of raw water to be treated, but is, for example, in the range of 10 mg / L to 1,000 mg / L. When the raw water to be treated is raw water with a small amount of SS components such as concentrated water in RO membrane treatment (for example, SS is less than 100 mg / L), it is preferable to add a clay mineral as an agglomeration aid. On the other hand, when the raw water is raw water with many SS components (for example, SS is 100 mg / L or more), it is not always necessary to add a clay mineral as an agglomeration aid.

  Next, in the agglomeration tank 14, the polymer flocculant is added and mixed as necessary (polymer) while the agitation device 24 performs gentle stirring on the reaction liquid sent from the reaction tank 12. Flocculant addition step), agglomeration reaction is performed, and flocs are formed. The floc grows with slow agitation.

  Examples of the polymer flocculant used include known anionic, nonionic, and cationic polymer flocculants.

  Examples of the anionic polymer flocculants include polyacrylamide partial hydrolysates, anionic monomer copolymers, and copolymers of anionic monomers and nonionic monomers such as acrylamide.

  As anionic monomers, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, styrene sulfonic acid, 2-allylamidoethanesulfonic acid, 2-acrylamide-2 -Methylpropanesulfonic acid, 2-methacrylamideamidoethanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, and the like, and metal salts or ammonium such as alkali metals and alkaline earth metals thereof And the like. These anionic monomers may be used alone or in combination of two or more.

  Nonionic monomers include acrylamide, methacrylamide, methacrylonitrile, vinyl acetate and the like. These nonionic monomers may be used alone or in combination of two or more.

  Preferable copolymers are acrylamide, acrylate copolymer, and acrylamide-2-acrylamido-2-methylpropanesulfonic acid copolymer.

  The nonionic polymer flocculant is a polymer or copolymer of the above-mentioned nonionic monomer, preferably polyacrylamide.

  The cationic polymer flocculant has a cationic monomer as an essential component, and is a copolymer of a cationic monomer or a copolymer of a cationic monomer and the nonionic monomer.

  Examples of the cationic monomer include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate and the like, or neutralized salts and quaternary salts thereof. A cationic polymer flocculant containing an amidine unit in the molecule can also be used.

  Examples of the polymer flocculant include so-called amphoteric polymer flocculants obtained by copolymerizing a cationic monomer unit, an anionic monomer unit, and a nonionic monomer unit.

  The polymer flocculant may be any of anionic, nonionic, and cationic, but anionic or nonionic polymer flocculants are preferred from the standpoint of floc sedimentation.

  The polymer flocculants can be used alone or in combination of two or more. The amount of the polymer flocculant added is not particularly limited as long as it is determined according to the properties of raw water to be treated, but is, for example, in the range of 0.5 mg / L to 10 mg / L.

  The weight average molecular weight of these polymer flocculants is, for example, in the range of 500,000 to 30,000,000.

  Next, the reaction liquid in which the polymer flocculant is added and mixed in the aggregation tank 14 is sent to the aggregation precipitation tank 16. The reaction liquid sent to the coagulation sedimentation tank 16 is separated into sediment (sludge) in which flocs are concentrated and separated water (treated water) by natural sedimentation separation or the like.

  The treated water separated from the sludge in the coagulation sedimentation tank 16 is sent to the next biological treatment process or the like, and then reused or discharged into a river or the like. On the other hand, the sludge separated from the treated water in the coagulation sedimentation tank 16 is further subjected to a concentration process, a dehydration process, and the like.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Examples 1-35>
Aggregation by the jar tester method shown below using simulated wastewater (turbidity 0.0 degree) adjusted to pH shown in Table 1 containing 100 mg / L of the type of dispersant shown in Table 1 as the water to be treated A precipitation test was performed. For pH adjustment, hydrochloric acid (35% hydrochloric acid 1: water 9 (volume ratio)) or sodium hydroxide (prepared to 5%) was used. First, 200 mg / L of kaolin as a clay mineral was added and mixed, and then organic coagulants and inorganic coagulants of the types shown in Table 1 were added to the water to be treated at predetermined effective concentrations and addition concentrations and mixed. Furthermore, 1 mg / L of the polymer flocculant was added and mixed. The following AA / AMPS or PAA was used as the dispersant, the following (A) or (B) was used as the organic coagulant, and the following anionic acrylic acid / acrylamide copolymer was used as the polymer flocculant. In the test, a solution dissolved in pure water was used so that the organic coagulant was 2% (w / v) and the polymer flocculant was 0.1% (w / v). The inorganic coagulant was used in the form of an aqueous solution. Table 1 shows the results of the coagulation sedimentation test using a jar tester.

(Dispersant)
Acrylic acid binary copolymer (AA / AMPS) 100 mg / L TOC: 16.4 mg / L
Polyacrylic acid (PAA) 100 mg / L TOC: 16.9 mg / L
The acrylic acid-based binary copolymer is a water-soluble copolymer comprising a monomer unit of the following structural formula (1) and a monomer unit of the following structural formula (2) (weight ratio 60:40), polyacrylic acid Is a water-soluble homopolymer comprising monomer units represented by the following structural formula (1).
_{- (CH 2 -CHCOOX) - (} 1)
_{- (CH 2 -CHCONHY) - (} 2)
(In formula (1), X represents a hydrogen atom, a monovalent or divalent metal atom. In formula (2), Y represents an alkylsulfonic acid group or a salt thereof.)

(Organic coagulant)
(A) Dimethylamine / epichlorohydrin condensate (weight average molecular weight Mw = 40,000)
(B) Polydimethyldiallylammonium salt (weight average molecular weight Mw = 300,000)

(Inorganic coagulant)
PAC (polyaluminum chloride)
Ferric chloride

(Polymer flocculant)
Acrylic acid / acrylamide copolymer (anion colloid equivalent value -1.0 meq / g, salt viscosity 150 mPa · s)

(Jar tester method)
(1) The simulated waste water adjusted to the pH shown in Table 1 is dispensed into a 500 mL beaker.
(2) Add 200 mg / L of kaolin as a clay mineral and stir at 150 rpm for 60 seconds.
(3) Add a predetermined amount of inorganic coagulant, or inorganic coagulant and organic coagulant, and stir at 150 rpm for 60 seconds.
(4) Add 1 mg / L of polymer flocculant, stir at 150 rpm for 60 seconds, and gently stir at 40 rpm for 60 seconds.
(5) After allowing to stand for 5 minutes, the floc diameter, turbidity, and TOC of the topped liquid are measured (TOC is measured after filtering the supernatant with a 0.45 μm filter).

  The floc diameter was measured visually. For the turbidity measurement, “Water Analyzer 2000N” manufactured by Nippon Denshoku Industries Co., Ltd., which is an integrating sphere photoelectric photometry method, was used as a measurement principle. Turbidity was measured based on JIS standard JIS K0101: 9.4 "Integral sphere turbidity". The TOC was measured based on JIS standard JIS K0102: 22.1 “combustion oxidation-infrared TOC analysis method”.

  From Table 1, it can be seen that at pH 4 to 5, both TOC and turbidity are the lowest, and the floc diameter is large, which is the optimum pH for treating the dispersant. From the comparison between Examples 1-4, 6-9 and Examples 11-14, the addition of an organic coagulant in addition to the inorganic coagulant improves the TOC (dispersant) removal performance and increases the floc diameter. I understand that

<Comparative Examples 1-5>
In the above “Jatester method”, coagulation precipitation treatment was performed in the same manner as in Examples 1 to 35 except that the following HDP (1-hydroxyethylidene-1,1-diphosphonic acid) was added as a dispersant. . The results are shown in Table 2. The total phosphorus concentration was measured based on JIS standard JIS K0102: 46.3.1 “Potassium peroxodisulfate decomposition method”.

(Dispersant)
1-hydroxyethylidene-1,1-diphosphonic acid (HDP) 100 mg / L total phosphorus: 16.0 mg / L

  From Comparative Examples 1 to 5, in the case of a dispersant that does not have a carboxyl group such as HDP, even if the pH of the wastewater is 4 to 5, the total phosphorus concentration and turbidity do not decrease, and the dispersant is sufficient. It turns out that it cannot be processed.

<Examples 36 to 40>
In the above “jar tester method”, coagulation precipitation treatment was performed in the same manner as in Examples 1 to 35 except that kaolin was not added. The results are shown in Table 3.

  From Examples 37 and 38, it can be seen that even when kaolin is not added, both TOC and turbidity are lowest at pH 4 to 5, and the pH is optimal for treating the dispersant. Moreover, by comparing Examples 1-4 and Examples 36-39, it can be seen that the addition of kaolin as a clay mineral improves the TOC (dispersant) removal performance and increases the floc diameter.

<Examples 41 and 42>
In the above “jar tester method”, except that (3) the organic coagulant and inorganic coagulant were added, the pH was adjusted to 7 using sodium hydroxide (adjusted to 5%), and the mixture was stirred at 150 rpm for 60 seconds. In the same manner as in Examples 1 to 35, the coagulation sedimentation treatment was performed. The results are shown in Table 4.

  By comparing Examples 2 and 3 with Examples 41 and 42, it can be seen that Examples 2 and 3 in which pH adjustment is not performed after adding an inorganic coagulant or an organic coagulant have better processing performance. Recognize. The neutralization treatment with a neutralizing agent such as sodium hydroxide, which is necessary in the normal coagulation sedimentation treatment, becomes unnecessary in this treatment method.

<Examples 43 to 46>
Using concentrated water of a reverse osmosis membrane device containing a dispersant as the water to be treated, the pH was adjusted using sodium hydroxide (adjusted to 5%) as shown in Table 5 (Examples 44 and 46 only). Table 5 shows the results of the coagulation precipitation test by the above-mentioned jar tester method using kaolin, organic coagulant, inorganic coagulant, and polymer coagulant. The pH of the concentrated water of this reverse osmosis membrane device was 5.0, and the TOC was 8.2 mg / L.

  A comparison between Example 43 and Example 44 shows that the non-pH adjusted Example 43 is superior in treatment performance to the pH adjusted Example 44. Moreover, it can be seen from the comparison between Example 43 and Example 45 that the treatment performance is better when kaolin is added.

It is a schematic structure figure showing an example of the water treatment equipment concerning the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Water treatment apparatus, 10 pH adjustment tank, 12 Reaction tank, 14 Coagulation tank, 16 Coagulation sedimentation tank, 18, 22, 24 Stirrer, 20 pH meter.

Claims (4)

Dispersant-containing water treatment method for treating raw water containing a dispersant by coagulation sedimentation,
The dispersant includes at least one structural unit having a carboxyl group,
A method for treating water containing a dispersant, comprising adding at least an inorganic coagulant to the raw water. It is a processing method of the dispersing agent containing water according to claim 1,
A method for treating a water containing a dispersant, wherein the raw water has a pH of 3 to 6. It is a processing method of the dispersing agent containing water according to claim 1 or 2,
An organic coagulant is further added to the raw water. A method for treating a dispersant-containing water. A method for treating a dispersant-containing water according to any one of claims 1 to 3,
A method for treating a water containing a dispersant, wherein a clay mineral is added as a coagulation aid to the raw water.

Images