JPH08215686A - Flocculation treatment of muddy water - Google Patents

Abstract

PURPOSE: To obtain a muddy water flocculation treatment method excellent in the consolidation of muddy water, good in solid-liquid separation and suitably utilizable in a civil enginearing field of dredging, landfilling or construction by adding cationic polysaccharides and an anionic polymeric compd. to muddy water. CONSTITUTION: By using cationic polysaccharides in place of an inorg. flocculant used together with an anionic polymeric flocculant heretofore, the consolidation property of sedimented muddy water is improved. That is, muddy water is subjected to flocculation treatment by adding cationic polysaccharides and an anionic polymeric compd. to muddy water. At this time, the degree of substitution of cationic polysaccharides is set, for example, to 0.01 or more. As cationic polysaccharides, for example, cationized starch or cationized guar gum is used. Further, the intrinsic viscosity of the anionic polymeric compd. measured at 30 deg.C using a 1N sodium chloride aq. soln. as a solvent is set, for example, to 2.0dl/g or more and the colloid equivalent thereof measured at pH=10 is set, for example, to -0.20meq/g or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coagulating mud water. More specifically, the present invention has good coagulation compaction of treated mud and excellent solid-liquid separation property, and is suitably used for treating mud water discharged at a dredged landfill site or a construction site in a river, lake, etc. The present invention relates to a method for coagulating muddy water that can be used.

[0002]

2. Description of the Related Art Conventionally, a combination method of an inorganic flocculant and an anionic organic synthetic polymer flocculant has been used as a method for coagulating mud discharged from a construction site, etc. in a river or lake. . This method is a method in which an inorganic coagulant and an anionic organic synthetic polymer coagulant are added to slurry-like muddy water to cause the solid content to coagulate and settle, and then be separated from the supernatant water. Usually, as the inorganic flocculant, polyaluminum chloride, aluminum sulfate, ferric chloride, etc. are used, and as the anionic organic synthetic polymer flocculant,
Copolymers of acrylamide and acrylic acid, hydrolysates of polyacrylamide, etc. are used. The combined use of an inorganic flocculant and an anionic organic synthetic polymer flocculant is said to be an indispensable method for efficiently performing solid-liquid separation of mud water, but has the following problems. That is, when an inorganic flocculant and an anionic organic synthetic polymer flocculant are used, although large flocculant flocs are formed, the density of the flocculant flocs is low, so the compaction of the sedimented mud is poor and the sludge volume easily decreases. It causes an unfavorable situation of not doing it. As a result, when the supernatant liquid is separated from the coagulated sludge and the solid content is disposed of, the high water content makes it difficult to carry the product, which increases the processing cost, and further the dewatering effect in the dewatering process is large. It is becoming a problem to decrease. In addition, at the dredging landfill site, sediment is drawn from the bottom of the seabed, lakes, ponds, etc. to reclaim the coast and lake shore. In this case, a flocculent is added to the pumped slurry-like soil to make it floc, the sediment is allowed to settle, and then the supernatant liquid is removed, and landfilling is carried out. It takes a long time before water can be drained and the land that has been reclaimed can be used, and improvements are required.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the conventional method and improves the compaction of mud,
The object of the present invention is to provide a method for coagulating mud water, which has good solid-liquid separation and can be suitably used in the field of civil engineering such as dredging landfill and construction.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that a cationic polysaccharide is used instead of the inorganic flocculant conventionally used in combination with an anionic polymer flocculant. It was found that the use of the above-mentioned method significantly improves the compaction property of the sedimented mud, and the present invention has been completed based on this finding. That is, the present invention provides (1) a method for coagulating mud water, which comprises adding a cationic polysaccharide and an anionic polymer compound to the mud water. Furthermore, in a preferred embodiment of the present invention, (2) the degree of substitution of the cationic polysaccharide is 0.
The method for coagulating mud water according to item (1), which is 01 or more;
(3) The cationic polysaccharide is a cationized starch or a cationized guar gum. The method for coagulating mud water according to (1) to (2), and (4) 1N sodium chloride aqueous solution as a solvent, measured at 30 ° C. The method for coagulating mud water according to any one of (1) to (3), wherein the anionic polymer compound has an intrinsic viscosity of 2.0 dl / g or more, and (5) a colloid of the anionic polymer compound measured at pH = 10. Equivalent weight is -0.20 meq /
The method for coagulating mud water according to any one of (1) to (4), which is less than or equal to g, (6) The method according to (1) to (5), wherein the anionic polymer compound is an anionic synthetic polymer compound. A method for coagulating muddy water, and (7) an anionic synthetic polymer compound,
The method for coagulating mud water according to item (6), which is a copolymer of acrylamide and acrylic acid or a partial hydrolyzate of polyacrylamide can be mentioned.

In the method of the present invention, a cationic polysaccharide and an anionic polymer compound are added to muddy water and mixed and stirred. Examples of the target mud water include mud water dredged in rivers, lakes, seas, ponds, and the like, and mud water discharged at construction sites and civil engineering sites. The order of addition of the cationic polysaccharide and the anionic polymer compound is not particularly limited, but usually, the cationic polysaccharide is first added and stirred, and then the anionic polymer compound is added and mixed. Cationic polysaccharides and anionic polymer compounds,
It is usually added as an aqueous solution for easy handling, but the same performance can be obtained by adding it in the form of powder. The cationic polysaccharide used in the method of the present invention is a compound obtained by cationizing a polysaccharide. The polysaccharides include, for example, starch, cellulose, glycogen, etc., rhizome polysaccharides such as mannan, sap polysaccharides such as gum arabic, tragacanth, karaya gum, locust bean gum, guar gum, seed polysaccharides such as tara gum, agar, Seaweed polysaccharides such as carrageenan and algin, animal polysaccharides such as chitin and chitosan, microbial polysaccharides such as dextran, cyclodextrin and xanthan gum can be used. There is no particular limitation on the method of cationizing these polysaccharides, for example, a method of reacting epihalohydrin with a tertiary amine,
Examples thereof include a method of reacting a halogenated alkylamine salt in the presence of an alkali catalyst, and a method of reacting a quaternary ammonium salt having a glycidyl group or a halohydrin group. The cationic polysaccharide used in the method of the present invention preferably has a substitution degree of 0.01 or more. The substitution degree is the average value of the substituted hydroxyl groups per monosaccharide constituting the polysaccharide. For example, the degree of substitution is 0.0
1 represents substitution of 1 in 100 monosaccharides.

As the cationic polysaccharide used in the method of the present invention, cationized starch, cationized guar gum, cationized cellulose and chitosan are preferable, and among these, cationized starch can be particularly preferably used. Cationized starch is a compound obtained by reacting starch with a cationizing agent, and its nitrogen content is usually about 0.1 to 3% by weight. Examples of starch used as a raw material include natural starch such as potato starch, sweet potato starch, corn starch, waxy corn starch, high amylose corn starch, wheat starch, rice starch, tapioca starch, sago starch, and their degradation products, amylose and Amylopectin fraction, cross-linked starch, etherified starch, oxidized starch, esterified starch, acid-treated starch, graft-modified starch, enzyme-treated starch, modified starch such as dextrin, starch such as wheat flour, corn flour, dried sweet potato, dried dried tapioca Examples thereof include inclusions. Further, as a cationizing agent, 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloro-2-
Examples thereof include halogenated alkyl quaternary ammonium salts such as hydroxypropyltriethylammonium chloride and 2-chloroethyltrimethylammonium chloride, and glycidyl quaternary ammonium salts such as glycidyltrimethylammonium chloride and glycidyltriethylammonium chloride.

The anionic polymer compound used in the method of the present invention is not particularly limited, and examples thereof include sodium polyacrylate, a copolymer of acrylamide and acrylic acid, a partial hydrolyzate of polyacrylamide, a partial sulfomethylated polyacrylamide, Examples thereof include anionic synthetic polymer compounds such as poly (2-acrylamido) -2-methylpropane sulfate, anionic semi-synthetic polymer compounds such as carboxymethyl cellulose, and anionic natural polymer compounds such as sodium alginate. . The anionic polymer compound used in the method of the present invention has an intrinsic viscosity (measured at 30 ° C. with a 1N sodium chloride aqueous solution as a solvent), which is an index of molecular weight, of 2.0 dl.
/ G or more, more preferably 5.0 dl / g or more. The anionic polymer compound used in the method of the present invention has a colloid equivalent (measured at pH = 10) used as an index of the amount of anions.
It is preferably less than 0.20 meq / g, -0.50 m
More preferably, it is eq / g or less. The aggregating property of the cationic polysaccharide used in the method of the present invention is superior to the aggregating property of the inorganic aggregating agent, and the addition amount of the anionic polymer compound can be reduced as compared with the case of using the inorganic aggregating agent, Alternatively, an anionic polymer compound having a lower molecular weight can be used. Therefore, as compared with the conventional method using an inorganic flocculant, the amount of the flocculant remaining in the mud after the flocculation treatment can be reduced or the molecular weight of the flocculant can be reduced, so that the compaction property of the mud can be reduced. It is thought that it can be improved. Moreover, since the cationic polysaccharide has biodegradability and does not remain in the treated mud for a long period of time, it does not adversely affect the compaction property of the mud.

[0008]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Table 1 shows the aggregating agents used in Examples and Comparative Examples.

[0009]

[Table 1]

Further, as the test mud, dredging mud was used.
The properties of the muddy water used are shown in Table 2.

[0011]

[Table 2]

Example 1 1000 ml of test mud water 1 was placed in a 1000 ml beaker and stirred at 150 rpm with a jar tester so that the concentration of the cationized polysaccharide (A, cationized starch) shown in Table 1 was 150 mg / liter. Add and stir for 1 minute. Then, an anionic polymer compound (C, a copolymer of acrylamide and acrylic acid) shown in Table 1 was added to have a concentration of 3 mg / liter, and the mixture was stirred for 1 minute.
Immediately after the stirring was stopped, the muddy water which had been agglomerated was mixed with a volume of 1000 ml,
It was transferred to a measuring cylinder having an inner diameter of 60 mm. Flock formed an interface and settled. Settling interface is 2, 5, 1 from the water surface
Measure the time to reach the depth of 0, 15, 20 cm,
When the relationship between the elapsed time and the sedimentation distance was shown in the figure, the floc sedimentation velocity in the constant velocity sedimentation region was 7.6 m / hr. The turbidity of the supernatant water after 10 minutes was 4.3 degrees. Also,
The change with time of the sludge volume was measured and shown in Table 4 and FIG. Example 2 Instead of adding the cationized polysaccharide (A, cationized starch) shown in Table 1 of Example 1 to a concentration of 150 mg / liter, the cationized polysaccharide shown in Table 1 (B,
The same operation as in Example 1 was repeated except that cationized guar gum) was added so that the concentration was 70 mg / liter. The floc sedimentation speed was 7.9 m / hr, and the supernatant water turbidity after 10 minutes was 4.5 degrees. The change with time of the sludge volume was as shown in Table 4 and FIG. Comparative Example 1 Instead of adding the cationized polysaccharide (A, cationized starch) shown in Table 1 of Example 1 so as to have a concentration of 150 mg / liter, polyaluminum chloride had a concentration of 600 mg.
/ L, and instead of adding the anionic polymer compound (C, a copolymer of acrylamide and acrylic acid) shown in Table 1 to a concentration of 3 mg / L, adjust the concentration to 8 mg / L. Except for the addition, the same operation as in Example 1 was repeated. The floc sedimentation speed was 7.2 m / hr and the supernatant water turbidity after 10 minutes was 4.5 degrees. The change with time of the sludge volume was as shown in Table 4 and FIG. The floc sedimentation rate and supernatant water turbidity are indicators of cohesiveness, and the change over time in the sludge volume is an indicator of compaction. Table 3 shows the amount of chemicals added, the floc sedimentation rate, and the supernatant turbidity of Examples 1 and 2 and Comparative Example 1, and Table 4 and FIG.

[0013]

[Table 3]

[0014]

[Table 4]

The treated mud of Examples 1 and 2 both had a high floc sedimentation rate and a low supernatant water turbidity after 10 minutes. In the treated mud water of Comparative Example 1, the floc sedimentation rate and the supernatant water turbidity which are almost the same as those in Examples 1 and 2 were obtained by increasing the concentration of the chemicals added to Examples 1 and 2. However, the sludge volume of the treated mud of Examples 1 and 2 rapidly decreases with the passage of time, whereas the treated mud of Comparative Example 1 has a sludge volume of about 30 volumes over time. %. Example 3 1000 ml of test mud water 2 was added to a 1000 ml beaker, and the cationized polysaccharide (A, cationized starch) shown in Table 1 was added thereto at a concentration of 600 mg / l while stirring with a jar tester at 150 rpm. Stir for 1 minute. Then, an anionic polymer compound (D, a copolymer of acrylamide and acrylic acid) shown in Table 1 was added to a concentration of 20 mg / liter and stirred for 1 minute. Immediately after the stirring is stopped, the volume of muddy water that has been aggregated is increased to 1000
It was transferred to a graduated cylinder having an inner diameter of 60 mm and a volume of 60 mm. Flock formed an interface and settled. The sedimentation interface is 2, 5 from the water surface,
The time to reach the depth of 10, 15 and 20 cm was measured, and the relationship between elapsed time and sedimentation distance was shown in the figure.
The floc sedimentation velocity in the constant velocity sedimentation region was 6.4 m / hr. The turbidity of the supernatant water after 10 minutes was 2.1 degrees. Further, the change with time of the sludge volume was measured and is shown in Table 6 and FIG. Comparative Example 2 Instead of adding the cationized polysaccharide (A, cationized starch) shown in Table 1 of Example 3 to a concentration of 600 mg / liter, polyaluminum chloride was added at a concentration of 800.
Instead of adding the anionic polymer compound (D, a copolymer of acrylamide and acrylic acid) shown in Table 1 to a concentration of 20 mg / liter, the anionic polymer is added at a concentration of 20 mg / liter. The same operation as in Example 3 was repeated except that the compound (C, a copolymer of acrylamide and acrylic acid) was added so as to have a concentration of 20 mg / liter. The floc sedimentation speed was 6.2 m / hr, and the turbidity of the supernatant water after 10 minutes was 2.3 degrees. Also,
The change with time of the sludge volume was as shown in Table 6 and FIG. Table 5 shows the amount of chemicals added, the floc sedimentation rate, and the turbidity of the supernatant in Example 3 and Comparative Example 2, and Table 6 and FIG. 2 show the changes over time in the sludge volume.

[0016]

[Table 5]

[0017]

[Table 6]

The treated mud water of Example 3 has a high floc sedimentation rate and a low supernatant water turbidity after 10 minutes. In the treated mud water of Comparative Example 2, by using the anionic polymer compound having a large intrinsic viscosity, the floc sedimentation rate and the supernatant water turbidity which are almost the same as those of Example 3 were obtained. However, as seen in the change over time in the sludge volume, the treated mud of Example 3 is superior to the treated mud of Comparative Example 2 in terms of compaction.

[0019]

INDUSTRIAL APPLICABILITY By using a cationic polysaccharide and an anionic polymer compound in the coagulation treatment of muddy water,
The compactness of the mud after the coagulation treatment can be improved.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in sludge volume.

FIG. 2 is a graph showing changes over time in sludge volume.

Claims (1)

[Claims] 1. A method for coagulating mud water, which comprises adding a cationic polysaccharide and an anionic polymer compound to the mud water.