JPH1099867A - Treatment of waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To flocculate a suspended substance and to efficiently remove flocs by filtering by successively adding two kinds of polymeric flocculants having ion groups same in code and different in mol. wt. to waste water. SOLUTION: When waste water from a home is treated, two kinds of polymeric flocculants having ion groups same in code and different in mol.wt. are successively added to waste water to flocculate a suspended substance and the formed flocs are removed by filtering. At this time, pref., as the polymeric flocculant with a low mol.wt. added at the beginning, an anionicpolymeric flocculant with a wt. average mol.wt. of 5000-1000000 having a sulfone group is desirably used and, as the polymeric flocculant with a high mol.wt. added next, an anionic polymeric flocculant with a wt. average mol.wt. of 5000000 or more and having a carboxyl group is desirably used. By this constitution, the polymeric flocculant with a high mol.wt. having a sulfone group can be allowed to correspond to one with a low mol.wt. and cost reduction can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for treating wastewater using a polymer flocculant.

[0002]

2. Description of the Related Art At present, there is a great deal of global interest in environmental issues, but securing water resources is one of the most important issues. In such a situation,
From the viewpoint of environmental pollution prevention, laws and regulations on wastewater from factories and home economics, such as the Water Pollution Control Law, have become more stringent.

As a countermeasure for wastewater, purification treatment of wastewater with various polymer flocculants is performed. Currently, commonly used polymer flocculants include nonionic anionic flocculants for treating industrial wastewater and cationic flocculants for treating sewage and human waste. Each of these coagulants is used properly depending on the application, and in each case, excellent clarification ability is required.

[0004] Under such circumstances, it has been proposed to use a metal compound and a polymer coagulant in combination or to use a combination of a plurality of polymer coagulants. For example, as a technique of using a plurality of polymer flocculants in combination,
Examples include those in which a polymer flocculant having an ionic group having a different sign is sequentially added, and those in which an anionic flocculant and a nonionic and / or anionic flocculant are mixed and used.

[0005]

However, in the conventional methods, sufficient performance has not been obtained with respect to the sedimentation speed at the time of wastewater treatment, the filtration speed at the time of dewatering, the releasability of the filter cloth, and the water content of the cake.

Accordingly, an object of the present invention is to provide a wastewater treatment method excellent in sedimentation speed in wastewater treatment, filtration speed in dewatering, filter cloth releasability, and cake moisture content.

[0007]

SUMMARY OF THE INVENTION A wastewater treatment method according to the present invention achieves the above-mentioned object. Two kinds of polymer flocculants having ionic groups of the same sign and different molecular weights in wastewater are provided. By successively adding to aggregate the suspended material,
Aggregates are removed by filtration.

In particular, it is desirable to add a low molecular weight polymer flocculant first, and then add a high molecular weight polymer flocculant.

As the low molecular weight polymer flocculant, it is desirable to use an anionic polymer flocculant having a weight average molecular weight of 50,000 to 1,000,000 and having a sulfone group. Or a sulfoalkylated polyacrylamide, or a vinyl sulfonic acid-based polymer.

As the high molecular weight polymer flocculant, it is preferable to use an anionic polymer flocculant having a weight average molecular weight of 5,000,000 or more and having a carboxyl group, and a partial hydrolyzate of polyacrylamide or polymethacrylamide. It is preferable to use at least one selected from a decomposition product, a copolymer of acrylic acid or methacrylic acid and acrylamide or methacrylamide, and salts thereof.

As described above, in the wastewater treatment method according to the present invention, a high-density, high-strength aggregate is formed in a high yield by adding a low-molecular-weight polymer flocculant first, and then a high-molecular-weight flocculant is formed. By adding the polymer coagulant, a coarse aggregate is formed. By performing the above steps, it is possible to improve the sedimentation speed at the time of aggregation, the filtration speed at the time of dehydration, the releasability of the filter cloth, and the water content of the cake. In addition, this makes it possible to shorten the wastewater treatment time, improve the coagulation yield, and reduce the amount of waste (dewatered cake).

In the wastewater treatment method according to the present invention, a high-molecular-weight flocculant having a sulfone group, which is difficult and expensive to manufacture, can be used with a low-molecular-weight flocculant. I can plan.
Furthermore, since this low molecular weight polymer flocculant can be produced from waste plastics, in addition to the above-mentioned cost reduction effect, it leads to effective use of resources.

[0013]

Embodiments of the present invention will be described below in detail.

In the wastewater treatment method to which the present invention is applied, a suspended substance is agglomerated by sequentially adding two types of polymer flocculants having the same sign of ionic groups and different molecular weights to the wastewater. Aggregates are removed by filtration.

In particular, it is preferable to add a low molecular weight polymer flocculant first, and then add a high molecular weight polymer flocculant.

The low molecular weight polymer flocculant has a weight average molecular weight of 50,000 to 1,000,000, preferably 11 to 1,000,000.
It is desirable to use an anionic polymer flocculant having a molecular weight of 880,000 and having a sulfone group.

When the molecular weight of the low molecular weight polymer flocculant is lower than the above range, not only does the flocculation effect on wastewater decrease, but also the suspended particles are dispersed. Conversely, if the molecular weight of the low-molecular-weight polymer flocculant is higher than the above range, it becomes difficult to form a high-density agglomerate, and the filtration rate during dehydration, the filter cloth releasability of the cake, and the water content of the cake are reduced. Will drop.

Examples of the anionic polymer flocculant having a sulfone group include sulfonated styrene polymers,
Sulfoalkylated products of polyacrylamide and vinyl sulfonic acid polymers.

(1) Sulfonated Styrene Polymer ○ Production by Sulfonation of Styrene Polymer A styrene polymer is reacted with a sulfonating agent in a sulfonating agent or a solvent, and then neutralized with an alkali compound. Obtainable.

The polystyrene-based polymer may be a styrene unit alone, or may be a copolymer with another monomer. Monomers other than styrene include butadiene, acrylonitrile, (meth) acrylic acid, (meth)
Acrylic esters (aliphatic hydrocarbons having 1 to 4 carbon atoms), maleic anhydride, itaconic anhydride, and acrylamide are exemplified. These other monomers other than styrene may be contained in one kind or two or more kinds,
Preferably, it is within two types.

The content of the styrene unit in the polystyrene-based polymer is 40 to 100 mol%, preferably 60 to 100 mol%. When the content is low, the introduction rate of the sulfone group is low, and the water solubility of the polystyrene-based polymer and the dehydration performance at the time of wastewater treatment are reduced.

The introduction ratio of sulfone groups in the polystyrene-based polymer is at least 40 mol%, preferably at least 60 mol%.
That is all.

The above-mentioned polystyrene-based polymer may be used, or may be an alloy with another resin.
It may contain additives such as facial dyes, stabilizers, flame retardants, plasticizers, fillers, and other auxiliaries. From the viewpoint of effective utilization of earth resources, it is desirable to use used resin as a raw material of the present invention. Further, a mixture of used waste material and virgin material may be used.

The other polymer that can be mixed with the above-mentioned polystyrene-based polymer is preferably a polymer that does not inhibit the sulfonation reaction, and examples thereof include polyphenylene ether, polycarbonate, polyphenylene sulfide, polyethylene terephthalate, and polybutylene terephthalate. Of these, polyphenylene ether and polycarbonate are preferred.

It is desirable that these polymers are mixed at 60% by weight or less based on the total amount of the polymer components. When the content of these resins is 60% by weight or more, the reforming reaction according to the present invention is inhibited.

The wastewater treatment method of the present invention also modifies these other polymers together with the polystyrene-based polymer, but does not particularly affect the performance as a polymer flocculant. However, when the content of these other polymers increases, the active ingredient as the drug decreases.

The sulfonic acid (salt) -containing monomer (co)
Production by polymerization As a method for producing a sulfonated product of a polystyrene-based polymer, in addition to the sulfonation of the styrene-based polymer,
It may be produced by (co) polymerizing a styrenesulfonic acid (salt) monomer.

The styrene sulfonic acid (salt) may be polymerized by itself or may be copolymerized with another monomer. Monomers copolymerized with styrene sulfonic acid (salt) include styrene, α-methylstyrene, p-alkyl (aliphatic hydrocarbon having 1 to 6 carbon atoms) styrene,
Vinyl naphthalene, butadiene, isoprene, (meth)
Acrylonitrile, (meth) acrylic acid, (meth) acrylic acid ester (aliphatic hydrocarbon having 1 to 4 carbon atoms),
Acrylamide, maleic anhydride, itaconic anhydride, vinyl acetate, vinyl sulfonic acid, alkyl (hydrogen or aliphatic hydrocarbon having 1 to 4 carbon atoms) acrylamide sulfonic acid (salt) can be mentioned.

The content of the sulfone group in the copolymer is as follows:
It is at least 40 mol%, preferably at least 60 mol%. If the content of the sulfone group is less than this range, the water solubility of this polymer and the dewatering performance during wastewater treatment will be reduced.

These monomers may be contained in a plurality of the above-mentioned polymers, but are preferably three or less.

2) Sulfoalkylated polyacrylamide ○ Production by sulfoalkylation of polyacrylamide Polyacrylamide is mixed with various aldehyde compounds (formalin and aldehyde compounds having an aliphatic hydrocarbon having 1 to 4 carbon atoms as an alkyl group). It is produced by reacting with a sulfonating agent such as sodium acid sulfite.

Production of sulfoalkylated acrylamide by (co) polymerization In addition to sulfoalkylation of the above-mentioned polyacrylamide, alkyl (hydrogen or aliphatic hydrocarbon having 1 to 4 carbon atoms) acrylamide sulfonic acid (salt) is added ) It may be produced by polymerization. Alkyl acrylamide sulfonic acid (salt) may be polymerized by itself, or
It may be copolymerized with another monomer.

The monomers copolymerized with the sulfoalkylated acrylamide include styrene, α-methylstyrene, p-alkyl (aliphatic hydrocarbon having 1 to 6 carbon atoms) styrene, vinylnaphthalene, butadiene, isoprene,
(Meth) acrylonitrile, (meth) acrylic acid, (meth) acrylic acid ester (aliphatic hydrocarbon having 1 to 4 carbon atoms), acrylamide, maleic anhydride, itaconic anhydride, vinyl acetate, vinyl sulfonic acid, styrene sulfone Acids (salts) and other types of alkyl acrylamidosulfonic acids (salts).

These monomers may be contained in a plurality of the above-mentioned polymers, but preferably up to three kinds.

The content of the sulfone group in the above copolymer is as follows:
It is at least 40 mol%, preferably at least 60 mol%. If the content of the sulfone group is less than this range, the water solubility of this polymer and the dewatering performance during wastewater treatment will be reduced.

3) Vinyl sulfonic acid (salt) -based polymer As a method for producing vinyl sulfonic acid (salt) -based polymer,
Examples include homopolymerization of vinyl sulfonate or copolymerization with another monomer.

The monomers copolymerized with vinyl sulfonic acid (salt) include styrene, α-methylstyrene, p-alkyl (aliphatic hydrocarbon having 1 to 6 carbon atoms) styrene, vinylnaphthalene, butadiene, isoprene, ( (Meth) acrylonitrile, (meth) acrylic acid, (meth) acrylic acid ester (aliphatic hydrocarbon having 1 to 4 carbon atoms), acrylamide, maleic anhydride, itaconic anhydride, vinyl acetate, alkyl (1 to 4 carbon atoms) 4 aliphatic hydrocarbons)
Acrylamide sulfonic acid (salt) and styrene sulfonic acid (salt) are exemplified. Although a plurality of these monomers may be contained in the above-mentioned polymer, the number of these monomers is preferably three or less.

The content of the sulfone group in the above copolymer is as follows:
It is at least 40 mol%, preferably at least 60 mol%. If the content of the sulfone group is less than this range, the water solubility of this polymer and the dewatering performance during wastewater treatment will be reduced.

As described above, these low molecular weight flocculants having a sulfone group may be used alone or in combination of two or more.

Next, after adding the low molecular weight polymer flocculant, a polymer flocculant higher in molecular weight than the low molecular weight polymer flocculant is added.

As the high molecular weight polymer flocculant, it is desirable to use an anionic polymer flocculant having a weight average molecular weight of 5,000,000 or more, preferably 10,000,000 or more and having a carboxyl group. When the molecular weight of the high molecular weight polymer flocculant is lower than the above range, it is difficult to make the aggregate coarse, and the flocculation speed becomes slow.

The content of the carboxyl group in the anionic polymer coagulant is 1 mol% or more, preferably 5 mol%.
It is more preferably at least 15 mol%. When the content of the carboxyl group is small, the effect of coagulating the suspended substance is reduced.

The anionic polymer coagulant having a carboxylic group is selected from polyacrylamide and polymethacrylamide partially hydrolyzed products, copolymers of acrylic acid or methacrylic acid with acrylamide or methacrylamide, and salts thereof. At least one of them may be used.

As described above, these high molecular weight coagulants having a carboxyl group may be used alone or in combination of two or more.

The above polymer flocculant may be used in combination with various inorganic flocculants, inorganic flocculants, organic flocculants and the like.

Examples of the inorganic coagulant include polyaluminum chloride (PAC), ferrous sulfate 1-3, aluminum sulfate (sulfate band), sodium amate, sodium aluminate,
Modified basic aluminum sulfate, activated silicic acid, chlorinated copper palas and the like can be mentioned.

Examples of the inorganic coagulation aid include slaked lime, sodium silicate, bentonite, fly ash and the like.

Examples of the organic coagulant include aniline-formaldefoxide double complex hydrochloride, polyhexamethylenethiourea acetate, polyvinylbenzyltrimethylammonium chloride, dimethyldiallylammonium chloride,
Examples thereof include an alkylamine / epichlorohydrin condensate, an alkylene polyamine salt, and a dicyandiamide / formalin condensate. As described above, in the wastewater treatment method according to the present invention, the low molecular weight polymer flocculant having a sulfone group and the high molecular weight polymer flocculant having a carboxyl group are sequentially added in this order.

The amount of the two types of polymer flocculants having different molecular weights varies depending on the type of the wastewater, but is usually 0.01 to 500 ppm, preferably, 0.01 to 500 ppm, based on the volume of the wastewater.
0.1 to 50 ppm.

The optimum amount of the low-molecular-weight polymer flocculant to be added is estimated when a high-molecular-weight polymer flocculant is used alone (an inorganic flocculant, a coagulant and a flocculant may be used in combination).
In addition, it is 10 to 90% of the minimum addition amount at which the aggregation rate is maximized. The standard of the optimal amount of the high-molecular-weight polymer flocculant is 90 to 10% of the optimal minimum amount (the minimum amount at which the aggregation speed is maximized).

This is because, if the amount of the low molecular weight coagulant added is too large, the (positive) charge of the suspension or coagulant will be completely neutralized and the coagulation crosslinking point will be eliminated.
This is because even if a high-molecular-weight polymer flocculant is added, coarse aggregates are not formed. For this reason, the low molecular weight polymer flocculant is set to 90% or less of the optimum minimum addition amount (minimum addition amount at which the coagulation rate is maximized) to leave 10% or more of the aggregation crosslinking point of the high molecular weight polymer flocculant. It is desirable to keep.

As described above, the ionic groups having the same sign are provided,
When polymer coagulants having different molecular weights are sequentially added,
Compared with the case where a high molecular weight polymer flocculant is used alone, the same flocculation speed can be achieved with a small amount of addition.
This makes it possible to shorten the wastewater treatment time, improve the cohesion yield, and reduce the amount of waste (dewatered cake).

By adding a low molecular weight polymer flocculant at first, a high-density and high strength aggregate is formed in high yield, and then by adding a high molecular weight polymer flocculant. , Coarse aggregates are formed. Therefore, in the above-mentioned wastewater treatment method, the sedimentation speed at the time of aggregation, the filtration speed at the time of dehydration, the removability of the filter cloth, and the water content of the cake can be improved.

On the other hand, when only a high molecular weight coagulant having a molecular weight is used, the suspension particles are likely to be missed and the coagulation yield is deteriorated. In addition, the filtration speed at the time of dehydration and the removability of the cake from the filter cloth are reduced, and the water content of the cake is increased.

Further, the polymer flocculant containing a sulfone group can be applied to a wide range of pH and has a high decolorizing effect.
Excellent effects can be achieved in treating wastewater or colored wastewater with large fluctuations in water quality.

In the above wastewater treatment method, a high-molecular-weight flocculant having a sulfone group, which is difficult and expensive to manufacture, can be used with a low-molecular-weight one, so that a significant cost reduction can be achieved. I can do it. further,
Since this low-molecular-weight polymer flocculant can be produced from waste plastics, in addition to the cost reduction effect,
It also leads to effective use of resources.

[0057]

Hereinafter, waste water treatment is performed by applying this embodiment,
An experiment was conducted to examine the flocculating effect of the polymer flocculant (sedimentation speed during wastewater treatment, filtration speed during dehydration, filter cloth releasability, cake dewatering rate).

First, the following flocculant samples 1 to 6 were prepared.

Sample 1 Sulfonation was carried out by dropping sulfuric anhydride into a solution of a housing material for VHS cassette tape (high impact polystyrene) in 1,2-dichloroethane. The temperature was maintained at 20 to 25 ° C for 2 hours from the end of the dropping. Then, after neutralizing with an aqueous sodium hydroxide solution, the solvent is distilled off by heating distillation, so that the molecular weight (Mw) is 43%.
Thus, an aqueous solution of sodium polystyrene sulfonate having a sulfonation ratio of 80 mol% was obtained. This is designated as Sample 1.

Sample 2 Sulfomethylation was carried out by simultaneously reacting formalin and sodium acid sulfite on an aqueous solution of polyacrylamide to obtain an aqueous solution of sulfomethylated acrylamide having a molecular weight (Mw) of 500,000 and a sulfonation ratio of 50 mol%. This is designated as Sample 2.

Sample 3 By polymerizing acrylamide and sodium vinyl sulfonate in water, an aqueous solution of the same copolymer having a molecular weight (Mw) of 240,000 and a sulfonation ratio of 12 mol% was obtained. This is designated as Sample 3.

Sample 4 Commercially available polyacrylamide partial hydrolyzate (Mw: about 1)
5 million, hydrolysis ratio: 10 mol%) was dissolved in water, and this was designated as Sample 4.

Sample 5 A commercially available sodium alginate was used as Sample 5.

Sample 6 Low molecular weight polyacrylamide partial hydrolyzate (Mw:
(Approximately 400,000, hydrolysis rate: 80 mol%) was dissolved in water.

Next, the wastewater treatment shown below was performed using Samples 1 to 6 as a polymer flocculant.

Example 1 First, slaked lime was prepared by using wastewater from a semiconductor manufacturing plant (pH: 3.1, suspended solids concentration (SS): 1000 ppm).
After adding 300 ppm, a solution to which sulfuric acid band: 60 ppm was added was prepared as a suspension sample. 500 ml of this suspension sample was collected in a 500 ml beaker, and sample 1: 1 ppm was added first, and then sample 4: 3
ppm was added. After stirring with a jar tester, the mixture was allowed to stand, and the sedimentation speed of the suspended particles was measured.

Next, a Nutsche test was performed on the aggregated liquid using a filter cloth, and the amount of the filtrate after 1 minute was measured.

Further, the filtered product was squeezed with the same filter cloth for 1 minute using a small squeezing tester, and the water content of the cake and the removability of the cake were measured.

Example 2 To a 500 ml suspension sample, first add a sample 1: 2 ppm
Was added, followed by sample 4: 2 ppm. Otherwise, in the same manner as in Example 1, the sedimentation speed, the amount of filtrate,
Peelability and water content were examined.

Example 3 To a 500 ml suspension sample, firstly a sample 2: 2 ppm
Was added, followed by sample 4: 2 ppm. Otherwise, in the same manner as in Example 1, the sedimentation speed, the amount of filtrate,
Peelability and water content were examined.

Example 4 To a 500 ml suspension sample, firstly a sample 3: 2 ppm
Was added, followed by sample 4: 2 ppm. Otherwise, in the same manner as in Example 1, the sedimentation speed, the amount of filtrate,
Peelability and water content were examined.

COMPARATIVE EXAMPLE 1 First, a sample 5: 2 ppm was added to a 500 ml suspension sample.
Was added, followed by sample 4: 2 ppm. Otherwise, in the same manner as in Example 1, the sedimentation speed, the amount of filtrate,
Peelability and water content were examined.

COMPARATIVE EXAMPLE 2 First, a sample 6: 2 ppm was added to a 500 ml suspension sample.
Was added, followed by sample 4: 2 ppm. Otherwise, in the same manner as in Example 1, the sedimentation speed, the amount of filtrate,
Peelability and water content were examined.

Comparative Example 3 Sample 4: 4 ppm was added to a 500 ml suspension sample. Except for this, the sedimentation velocity,
The filtrate volume, peelability, and water content were examined.

Comparative Example 4 To a suspension sample (500 ml), sample 1: 2 ppm and sample 4: 2 ppm were simultaneously added. Otherwise,
In the same manner as in Example 1, the sedimentation speed, the amount of filtrate, the releasability, and the water content were examined.

Evaluation of aggregation effect The results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

[0077]

[Table 1]

As can be seen from Table 1, Examples 1 to 4 show Comparative Examples 1 and 2 in which a low molecular weight polymer flocculant having an anionic group other than a sulfone group was used in combination. Comparative Example 3 in which a hydrophilic polymer flocculant was used alone, and Comparative Example 4 in which an anionic polymer flocculant having a low molecular weight sulfone group and an anionic polymer flocculant having a high molecular weight carboxyl group were simultaneously added. In comparison with the above, all of the sedimentation speed during wastewater treatment, the amount of filtrate during dehydration, the releasability, and the water content of the cake are improved.

From this fact, the coagulation effect is enhanced by sequentially adding the anionic polymer coagulant having a low molecular weight sulfone group and the anionic polymer coagulant having a high molecular weight carboxyl group, whereby the wastewater treatment is improved. It can be seen that the sedimentation speed at the time, the amount of filtrate during dehydration, the releasability, and the water content of the cake are improved.

[0080]

As is clear from the above description, in the wastewater treatment method according to the present invention, a low-molecular-weight polymer flocculant is added first to obtain a high-yield, high-density, high-strength coagulant. Aggregates are formed and then coarse aggregates are formed by adding a high molecular weight polymeric flocculant. By employing the above wastewater treatment method, it is possible to improve the sedimentation speed at the time of aggregation, the filtration speed at the time of dehydration, the releasability of the filter cloth, and the water content of the cake. In addition, this makes it possible to shorten the wastewater treatment time, improve the coagulation yield, and reduce the amount of waste (dewatered cake).

Furthermore, in the wastewater treatment method according to the present invention, a high-molecular-weight flocculant having a sulfone group, which is difficult and expensive to produce, can be used with a low-molecular-weight flocculant, so that the cost can be significantly reduced. I can plan. In addition, since the low-molecular-weight polymer flocculant can be produced from waste plastics, in addition to the above-described cost reduction effect, it leads to effective use of resources.

Continued on the front page (72) Inventor Miyuki Kuromiya 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (6)

[Claims] 1. A suspended substance is agglomerated by sequentially adding two types of polymer flocculants having an ionic group of the same sign and having different molecular weights to wastewater, and the aggregates are removed by filtration. Wastewater treatment method. 2. The wastewater treatment method according to claim 1, wherein a low molecular weight polymer flocculant is added first, and then a high molecular weight polymer flocculant is added. 3. An anionic polymer flocculant having a weight average molecular weight of 50,000 to 1,000,000 and having a sulfonic acid group is used as the low molecular weight polymer flocculant. 2. The wastewater treatment method according to 2. 4. The method according to claim 1, wherein the low molecular weight polymer coagulant is at least one selected from a sulfonated styrene polymer, a sulfoalkylated polyacrylamide, and a vinyl sulfonic acid polymer. Item 4. The wastewater treatment method according to Item 3. 5. The wastewater treatment according to claim 2, wherein an anionic polymer flocculant having a weight average molecular weight of 5,000,000 or more and having a carboxyl group is used as the high molecular weight polymer flocculant. Method. 6. The polymer coagulant having a high molecular weight, at least one selected from a partially hydrolyzed product of polyacrylamide or polymethacrylamide, a copolymer of acrylic acid or methacrylic acid and acrylamide or methacrylamide, and salts thereof. The wastewater treatment method according to claim 5, wherein any one of them is used.