JPH0938415A - Flocculant for muddy water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flocculant excellent in solid-liq. separating performance, ensuring satisfactory compactibility of solid matter after flocculation, generating no hydrogen sulfide and not contg. an org. synthetic polymer whose safety is low by incorporating cationized guar gum. SOLUTION: This flocculant contains cationized guar gum. The degree of substitution of the cationized guar gum is preferably about 0.01-0.5. The amt. of this flocculant added to muddy water is properly selected in accordance with the properties of the muddy water and the flocculant usually produces a satisfactory effect when it is added by about 0.01-0.2wt.% of the solid content of the muddy water. This flocculant may be made of only the cationized guar gum, may be blended with an inorg. flocculant such as polyaluminum chloride, aluminum sulfate or ferric chloride and may further be blended with an inorg. salt such as NaCl, CaCl2 or MgCl2 .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flocculant for muddy water. More specifically, the present invention is excellent in solid-liquid separation property, has good aggregation and consolidation of solids after treatment, and
The present invention relates to a muddy water flocculant which does not contain an organic synthetic polymer flocculant which is concerned about safety.

[0002]

2. Description of the Related Art Conventionally, an inorganic coagulant and an organic synthetic polymer coagulant have been used together as a coagulant for mud water discharged from a river in a river, a lake or a marsh, or discharged from a construction site, or wastewater discharged from various industries. Often. Usually, polyaluminum chloride, aluminum sulfate, ferric chloride, etc. are used as the inorganic coagulant, and as the organic synthetic polymer coagulant, a copolymer of acrylamide and acrylic acid or a hydrolyzate of polyacrylamide. And polyacrylamide are used. The combined use of an inorganic coagulant and an organic synthetic polymer coagulant is indispensable for efficiently performing solid-liquid separation of mud water, but has the following two problems. That is, the first problem is that the organic synthetic polymer flocculant has poor degradability and may adversely affect the environment. The second problem is that when an inorganic coagulant and an organic synthetic polymer coagulant are used together, large aggregated flocs are formed, but since the density of the aggregated flocs is low,
This is an unfavorable situation in that the settled solid matter has poor compaction properties and the sludge volume is not easily reduced. As a result, when the supernatant is separated from the coagulated sludge to dispose of the solid matter, the high water content causes a troublesome transportation work and increases the disposal cost. In addition, at the dredging landfill site, it is difficult to drain water from the accumulated sediment due to the poor consolidation of floc flocs, and it takes a long time before the landfill can be used, and improvement is required. In order to ameliorate such a problem, so far, the flocculation treatment with an inorganic flocculant alone, the flocculation treatment with an anionic natural polymer flocculant such as sodium alginate or carboxymethylcellulose, chitosan, cationized starch, etc. Coagulation treatment using a cationic natural polymer flocculant has been investigated, but both have low coagulation treatment effects, and muddy water coagulated with cationized starch causes a bad odor and is highly toxic. It has not been put to practical use because hydrogen is generated.

[0003]

DISCLOSURE OF THE INVENTION The present invention is excellent in solid-liquid separation property and good in compaction property of solid matter after aggregation treatment,
The purpose of the present invention is to provide a flocculant for muddy water which does not contain hydrogen sulfide and does not contain an organic synthetic polymer, which is a safety concern.

[0004]

As a result of intensive studies to solve the above problems, the present inventor has found that a flocculant containing a cationized guar gum has an excellent solid-liquid separation property against muddy water. Based on this finding, the present invention has been completed. That is, the present invention provides (1) a flocculant for muddy water, which comprises a cationized guar gum. Furthermore, in a preferred embodiment of the present invention, (2) the degree of substitution of the cationized guar gum is
The coagulant for muddy water according to item (1), which is 0.01 to 0.5, can be mentioned.

The coagulant for muddy water of the present invention is applied to muddy water dredged in rivers, lakes, seas, ponds, mud discharged at construction sites and civil engineering sites, and discharged at various industries. Examples include waste water. The flocculant for muddy water of the present invention contains cationized guar gum. The cationized guar gum used in the present invention is a compound obtained by cationizing guar gum, which is a polysaccharide. Guar gum is a guar plant (Cyamopsis tetragonolobus), which is an annual plant of the legume family.
L. ) Is a refined and crushed part of the endosperm part of the seed,
It usually contains 80% by weight or more of galactomannan polysaccharide. The main chain is D-mannose, and D-galactose is bonded as 1 unit side chain for every 2 units of mannose. The guar plant can be used as an industrially stable raw material because it is cultivated and produced, while most other natural gums depend on trees that naturally grow. In the present invention, as the cationized guar gum,
Tertiary amine type cationized guar gum or quaternary ammonium salt type cationized guar gum can be used. The method for producing these cationized guar gums is not particularly limited, and the tertiary amine type cationized guar gum can be produced, for example, by reacting guar gum with a dialkylaminoalkyl halide in the presence of an alkali. Further, quaternary ammonium salt type cationized guar gum is, for example, a method of reacting guar gum with epihalohydrin and a tertiary amine, a method of reacting guar gum with a quaternary ammonium salt having a halogenated alkyl group in the presence of an alkali, It can be produced by a method of reacting guar gum with a quaternary ammonium salt having a glycidyl group. Usually, the cationized guar gum has a nitrogen content of about 0.1 to 3% by weight.

In the present invention, the degree of substitution of the cationized guar gum is preferably 0.01 to 0.5. The degree of substitution is the average value of the number of substituted hydroxyl groups per monosaccharide constituting the polysaccharide. For example, the substitution degree is 0.01
Means that one hydroxyl group is substituted for 100 monosaccharides. The degree of substitution of cationized guar gum is 0.0
If it is less than 1, the cohesiveness of the solid content may be insufficient. Even if the degree of substitution of the cationized guar gum exceeds 0.5, the cohesiveness of the solid content does not improve in proportion to the increase in the degree of substitution. The addition rate of the muddy water coagulant of the present invention to muddy water can be appropriately selected according to the properties of the muddy water, but normally 0.01 to 0.2% by weight is added to the solid content in the muddy water. By doing so, it exerts a sufficient effect. If the addition rate of the muddy water coagulant is less than 0.01% by weight with respect to the solid content in the muddy water, the cohesiveness of the solid content may be insufficient. Addition rate of muddy water coagulant is 0.2% by weight based on solid content in muddy water
Even if it exceeds, the cohesiveness of the solid content does not improve in proportion to the increase of the addition rate. The muddy water flocculant of the present invention can have only cationized guar gum as its component, and can be compounded with an inorganic flocculant such as cationized guar gum and polyaluminum chloride, aluminum sulfate, ferric chloride. Inorganic salts such as sodium chloride, calcium chloride and magnesium chloride can be added. Alternatively, during the muddy water treatment, cationized guar gum, inorganic coagulant, inorganic salt and the like can be separately added to the muddy water and then mixed. When the coagulant for muddy water of the present invention is used, the coagulability of the solid content in the muddy water is excellent, the pressure density of the solid matter after the coagulation treatment can be improved, and further harmful hydrogen sulfide may be generated from the treated mud water. There is no. The mechanism capable of improving the pressure density of the solid matter after the coagulation treatment by the coagulant for muddy water of the present invention is
Since cationized guar gum has biodegradability and does not remain in the solid matter after the coagulation treatment for a long period of time, it is presumed that the solid matter is rapidly compressed. When a conventional inorganic coagulant and an organic synthetic polymer coagulant are used together, the degradability of the coagulant is poor, and it is considered that the coagulant remains in the solid matter after the treatment and the compaction property is deteriorated.

[0007]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 An aggregation test of dredged mud water was conducted using cationized guar gum. The properties of the dredged mud used were pH 6.3, electric conductivity 0.12 mS / cm, SS 2.90% by weight, VSS 8.7.
% By weight / SS. The cationized guar gum used was cationized with glycidyltrimethylammonium chloride, the degree of substitution was 0.03, and the intrinsic viscosity was 11.7 dl / g measured at 30 ° C. with 1N sodium chloride as a solvent. Is. 1,
To a 000 ml beaker, 1,000 ml of dredged mud water was added, and while stirring with a jar tester at 150 rpm, cationized guar gum was added to a concentration of 40 mg / liter and stirred for 1 minute. After stopping the stirring,
Immediately, it was transferred to a graduated cylinder having a volume of 1,000 ml and an inner diameter of 60 mm. Flock formed an interface and settled. The time required for the settling interface to reach a depth of 2, 5, 10, 15, 20 cm from the water surface was measured, and the relationship between the elapsed time and the settling distance was shown in the figure. It was 0.6 m / hr. The supernatant turbidity after 10 minutes was 9.3 degrees. Further, the change with time of the sludge volume was measured and shown in Table 1 and FIG. When the hydrogen sulfide concentration of the supernatant water after 30 days was measured, it was 0.2 mg / liter or less. Example 2 The same aggregation test of dredged mud water as in Example 1 was conducted by using polyaluminum chloride and cationized guar gum in combination. Instead of adding cationized guar gum to a concentration of 40 mg / l, polyaluminum chloride concentration of 10 mg
The same operation as in Example 1 was repeated, except that the same cationized guar gum as in Example 1 was added so as to have a concentration of 20 mg / liter. The floc sedimentation velocity was 9.7 m / hr and the supernatant water turbidity after 10 minutes was 8.6 °. Further, the change with time of the sludge volume was measured and shown in Table 1 and FIG. When the hydrogen sulfide concentration of the supernatant water after 30 days was measured, it was 0.2 mg / liter or less. Comparative Example 1 The same aggregation test as in Example 1 was conducted using cationized starch. The cationized starch used is
Cationized with glycidyl trimethyl ammonium chloride, the degree of substitution was 0.05, and the intrinsic viscosity measured at 30 ° C. with 1N sodium chloride as a solvent was 1.0 dl.
/ G of cationized starch. The same procedure as in Example 1 was repeated except that cationized starch was added at a concentration of 80 mg / liter instead of adding cationized guar gum at a concentration of 40 mg / liter. Floc sedimentation speed is 6.9 m / hr,
The supernatant water turbidity after 10 minutes was 8.9 degrees. Further, the change with time of the sludge volume was measured and shown in Table 1 and FIG. The hydrogen sulfide concentration of the supernatant water after 30 days was measured and found to be 21.0 mg / liter. Comparative Example 2 A coagulation test of the same dredged mud water as in Example 1 was performed using polyaluminum chloride and a copolymer of acrylamide and acrylic acid together. The copolymer used had a molar ratio of acrylamide to acrylic acid of 80/20, and an intrinsic viscosity measured at 30 ° C. with 1N sodium chloride as a solvent was 22.0 d.
l / g. Instead of adding cationized guar gum to a concentration of 40 mg / liter, add polyaluminum chloride to a concentration of 100 mg / liter,
Then, Example 1 was repeated except that a copolymer of acrylamide and acrylic acid was added so as to have a concentration of 5 mg / liter.
The exact same operation was repeated. Floc sedimentation rate is 9.
It was 6 m / hr, and the turbidity of the supernatant water after 10 minutes was 9.6 degrees. Also, measuring the change over time of the sludge volume,
The results are shown in Table 1 and FIG. When the hydrogen sulfide concentration of the supernatant water after 30 days was measured, it was 0.2 mg / liter or less. The floc sedimentation rate and the supernatant water turbidity are indicators of cohesiveness, the change over time in the sludge volume is an index of compaction, and the hydrogen sulfide concentration of the supernatant water is an indicator of the presence or absence of malodor. Table 1 shows the amounts of coagulant added, floc sedimentation rate, supernatant water turbidity, sludge volume over time, and hydrogen sulfide concentration in the supernatant water after 30 days in Examples 1 and 2 and Comparative Examples 1 and 2.

[0008]

[Table 1]

Regarding the cohesiveness, Example 1, Example 2,
The treated mud of Comparative Example 2 has almost the same floc sedimentation speed and supernatant turbidity, but the treated mud of Comparative Example 1 is slightly inferior. Regarding the compaction property, as seen in the change with time of the sludge volume, Example 1, Example 2, and Comparative Example 1
The treated mud of No. 2 is superior to the treated mud of Comparative Example 2. Regarding the generation of hydrogen sulfide, the treated mud water of Example 1, Example 2, and Comparative Example 2 does not generate hydrogen sulfide, but Comparative Example 1
The treated mud water of the above produces hydrogen sulfide. Examples 1, 2,
The cohesiveness, compaction property, and hydrogen sulfide generation of Comparative Examples 1 and 2 are summarized in Table 2.

[0010]

[Table 2]

From the results shown in Table 2, it can be seen that the treated muddy water of Examples 1 and 2 using the muddy water flocculant of the present invention is excellent in cohesiveness and compaction and does not generate hydrogen sulfide. Example 3 A flocculation test of dredged mud water was conducted using cationized guar gum. The properties of the dredged mud used were pH 6.5, electric conductivity 24.5 mS / cm, SS 4.24% by weight, VSS 10.
It is 7% by weight / SS. The cationized guar gum used was the same cationized guar gum as used in Example 1. 1,000 ml beaker, dredged muddy water 1.00
While taking 0 ml of the mixture, while stirring at 150 rpm with a jar tester, cationized guar gum was added to have a concentration of 12 mg / liter, and the mixture was stirred for 1 minute. After the stirring was stopped, the aggregated muddy water was immediately transferred to a graduated cylinder having a volume of 1,000 ml and an inner diameter of 60 mm. Flock formed an interface and settled. Settling interface is 2, 5, 10, 15, 20 from the water surface
When the time required to reach the depth of cm was measured and 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 8.9 m / hr. The turbidity of the supernatant water after 10 minutes was 8.6 degrees. Further, the change with time of the sludge volume was measured and shown in Table 3 and FIG. 3
When the hydrogen sulfide concentration of the supernatant water after 0 days was measured,
It was less than 0.2 mg / liter. Comparative Example 3 The same aggregation test of dredged mud water as in Example 3 was performed using cationized starch. The cationized starch used is
It is the same cationized starch as that used in Comparative Example 1. The exact same procedure as in Example 3 was repeated except that cationized starch was added at a concentration of 30 mg / l instead of adding cationized guar gum at a concentration of 12 mg / l. The floc sedimentation speed was 5.5 m / hr, and the supernatant water turbidity after 10 minutes was 9.2 degrees. Further, the change with time of the sludge volume was measured and shown in Table 3 and FIG. After 30 days, the concentration of hydrogen sulfide in the supernatant water was measured and found to be 4.2 mg / liter. Comparative Example 4 The coagulation test of the same dredged mud water as in Example 3 was performed using polyaluminum chloride and a copolymer of acrylamide and acrylic acid together. The copolymer used was the same copolymer of acrylamide and acrylic acid as used in Comparative Example 2. Instead of adding cationized guar gum to a concentration of 12 mg / liter, add polyaluminum chloride to a concentration of 300 mg / liter, and then add a copolymer of acrylamide and acrylic acid to a concentration of 4 mg / liter. The same operation as in Example 3 was repeated except that the same was added. Floc sedimentation speed is 7.9 m / hr
The turbidity of the supernatant water after 10 minutes was 9.3 degrees. Further, the change with time of the sludge volume was measured and shown in Table 3 and FIG. When the hydrogen sulfide concentration of the supernatant water after 30 days was measured, it was 0.2 mg / liter or less.
Table 3 shows the amount of chemicals added in Example 3 and Comparative Examples 3 and 4, the floc sedimentation rate, the turbidity of the supernatant water, the change over time in the sludge volume, and the hydrogen sulfide concentration of the supernatant water after 30 days.

[0012]

[Table 3]

Regarding the cohesiveness, the treated mud waters of Example 3 and Comparative Example 4 have almost the same good floc sedimentation rate and supernatant water turbidity, but Comparative Example 3 is slightly inferior. Regarding the compaction property, the treated mud water of Example 3 and Comparative Example 3 is superior to the treated mud water of Comparative Example 4 as seen in the change with time of the sludge volume. Regarding the generation of hydrogen sulfide,
The treated mud water of Example 3 and Comparative Example 4 did not generate hydrogen sulfide, but the treated mud water of Comparative Example 3 generated hydrogen sulfide. The cohesiveness, compaction property, and hydrogen sulfide generation of Example 3 and Comparative Examples 3 and 4 are summarized in Table 4.

[0014]

[Table 4]

From the results shown in Table 4, the treated muddy water of Example 3 using the muddy water flocculant of the present invention was excellent in cohesiveness and compaction.
It turns out that hydrogen sulfide is not generated.

[0016]

EFFECT OF THE INVENTION The flocculant for muddy water containing the cationized guar gum of the present invention is excellent in solid-liquid separation property, has good compaction of solid matter after flocculation treatment, and generates hydrogen sulfide which is a source of malodor. And do not use organic synthetic polymers, which have safety concerns.

[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 flocculant for muddy water, which comprises a cationized guar gum.