JPH0655310B2 - Water treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water treatment method, and in particular, mud drainage generated during bridge construction in rivers, lakes and marshes, civil works such as seawall protection, and gravel extraction work, or sea areas. It is an object of the present invention to provide a water treatment method which is excellent in the effect of coagulation treatment and the safety to the environment in the treatment of mud water generated in civil engineering work in Japan.

(Prior Art) Conventionally, as a water treatment method, an aggregation treatment method using an inorganic flocculant such as polyaluminum chloride, aluminum sulfate, and aluminum chloride or an organic synthetic polymer flocculant such as a polyacrylamide-based or polyamine-based is widely used. There is.

However, civil engineering works in rivers, lakes and marshes, or construction works in the sea area have problems such as environmental safety and pollution due to residual problems of coagulating chemicals, and it is important to select the chemicals. The effect was not satisfactory either.

That is, the sewage generated in civil engineering works is generally composed of fine particles of mineral matter, and the treatment of this is done by a combination of an inorganic flocculant such as aluminum sulfate and an organic synthetic polymer flocculant such as polyacrylamide. It is well known that the flocculating effect is the most excellent, but the organic synthetic polymer flocculant is poor in degradability and is currently almost unusable due to environmental pollution.

Further, when this treatment is carried out by using the inorganic coagulant alone, not only a large amount of addition is required but also a sufficient treatment effect cannot be obtained even if a large amount is added.

Further, as a safe and harmless natural polymer flocculant, for example, sodium alginate, carboxymethyl cellulose and the like are known, but the flocculating effect is small and they have not been put to practical use.

(Problems to be Solved by the Invention) In view of such circumstances, the present inventors have an excellent treatment effect in treating wastewater containing fine particles of mineral substances, such as safety and harmless, no pollution to the environment, and civil engineering wastewater. As a result of investigating using various chemicals to find a coagulant that has the property, xanthan gum, which is generally used as a thickener and water retention agent for foods, is safe and harmless, and has very little pollution to the environment is used. However, it has been found that an excellent aggregation effect can be obtained by a specific combination of this with other gums and a water-soluble aluminum salt, and the present invention has been completed.

(Means for Solving the Problems) That is, the present invention is to treat water with xanthan gum and guar gum,
The present invention relates to a water treatment method comprising adding a mixture with gums selected from locust bean gum or tamarind, and then adding a water-soluble aluminum salt.

(Operation) Xanthan gum used in the present invention is one of fermenting polysaccharides, and the microorganism Xanthomonas canapestris (X
anthomonas campestris) is a natural gum that is produced by fermenting glucose and refining the polysaccharides accumulated outside the bacterial cells.

This xanthan gum is generally used as a thickener and water retention agent for foods such as frozen desserts, hams and sausages, and is safe and harmless, and because it is a metabolite by microorganisms, it has good degradability in the natural world and is environmentally friendly. There is no problem such as pollution.

Further, other gums used in the present invention include guar gum,
Use locust bean gum or tamarind.

All of these gums are natural polysaccharides isolated from plants, and are harmless and free from the problem of environmental pollution, like the xanthan gum.

Examples of the type of water-soluble aluminum salt used in the present invention include polyaluminum chloride, aluminum sulfate, aluminum chloride and the like.

The present invention performs water treatment using these agents, and regarding the treatment method, first, xanthan gum and guar gum, gums selected from locust bean gum or tamarind are mixed, and the water to be treated is stirred. While adding this mixture.

Regarding the mixing ratio of these gums, the mixing ratio of the mixture of xanthan gum (A) and guar gum, a gum (B) selected from locust bean gum or tamarind (A) /
Mix in (B) in the range of 1/20 to 20/1.

That is, in the present invention, the mixing ratio of these gums is particularly important, and if it deviates from this range, the effect of the present invention cannot be obtained.

The amount of this mixture added to the water to be treated differs depending on the turbidity concentration, turbid species, pH, etc. of the water to be treated, and cannot be generally stated.
It is generally in the range of 1 to 50% by weight with respect to ₂ O ₃ .

After the addition of this mixture of gums, the water-soluble aluminum salt is then added thereto with moderate stirring.

In the present invention, the order of addition of the gums and the water-soluble aluminum salt is particularly important, and the effect of the present invention cannot be obtained even if the gums are added after the addition of the water-soluble aluminum salt.

Regarding the amount of addition of this water-soluble aluminum salt, it is approximately 0.1 to ₂ as Al ₂ O _{3 with} respect to the turbid mass (suspended mass) of the water to be treated.
It is used in the range of 5% by weight. After the addition of the water-soluble aluminum salt, it is further stirred and allowed to stand, so that flocs generated by agglomeration settle. By using an appropriate solid-liquid separation means, the turbid component may be separated and removed.

(Effects of the Invention) In the water treatment method of the present invention, a simple and excellent water treatment effect can be obtained by the aggregation treatment method as described above.

Further, gums such as xanthan gum and guar gum used in the present invention are safe and harmless because they are substances derived from microorganisms or natural products, and there is no pollution to the environment because of their good degradability, and rivers. Optimal for water treatment in lakes and marine areas.

Further, regarding the effect, compared with sodium alginate, carboxymethyl cellulose, etc., which have been conventionally known as water treatment agents, the method of the present invention is remarkably excellent in treatment effect, and polyacrylamide etc. whose use is limited due to environmental pollution problems. It is possible to obtain a treatment effect comparable to the use of the synthetic polymer flocculant.

(Examples) Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

Further, in the present invention, all% are by weight unless otherwise specified.
Indicates.

Example 1 43 g of kaolin (manufactured by Merck & Co., Inc., reagent grade) was added to tap water 10, stirred well, and allowed to stand for one day to be used as test suspension water.

The turbidity of the turbid water in the aggregation test was 4000 ppm, and the pH was 7.60.

Take 100 ml of the sampled turbid water in a 100 ml graduated cylinder with a stopper, and add the prescribed amount of the mixture of xanthan gum and other gums (mixing ratio 4/1) shown in Table 1 to the graduated cylinder. The stopper was closed, and the mixture was inverted over 10 times.

After adding 100 ppm of polyaluminum chloride (Al ₂ O ₃ 10.2%, manufactured by Taki Kagaku Co., Ltd.) to this, the mixture was further inverted and stirred 10 times.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was sampled and the turbidity was measured.

For comparison, the same test was performed using sodium alginate and carboxymethylcellulose instead of the mixture of xanthan gum and other gums, and the turbidity of the supernatant water was measured.

The results of these measurements are shown in Table 1.

Example 2 8 g of kaolin (manufactured by Merck & Co., Inc., reagent grade) was added to tap water 10, stirred well, and allowed to stand for one day to be used as test suspension water.

The turbidity of the turbid water in the coagulation test was 700 ppm, and the pH was 7.20.

100 ml of the test suspension water is put into a 100 ml measuring cylinder with a stopper, and a mixture of xanthan gum (Dainippon Pharmaceutical Co., Ltd.) and guar gum (Dainippon Pharmaceutical Co., Ltd.) (mixing ratio 2 /
The predetermined amount of 1) was added, the graduated cylinder was plugged, and the mixture was inverted over 10 times.

Furthermore, after adding predetermined amounts of various water-soluble aluminum salts shown in Table 2 thereto, the mixture was further inverted over 10 times.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was sampled and the turbidity was measured.

For comparison, the same test was performed without adding the water-soluble aluminum salt in the above test, and the turbidity of the supernatant water was measured.

The results of these measurements are shown in Table 2.

Example 3 43 g of kaolin (manufactured by Merck & Co., Inc., reagent grade) was added to tap water 10, stirred well, and left for one day to be used as a test suspension water.

The turbidity of the turbid water in the aggregation test was 4000 ppm, and the pH was 7.60.

100 ml of the test suspension water was placed in a 100-ml graduated cylinder with a stopper, and xanthan gum (Dainippon Pharmaceutical Co., Ltd.) and locust bean gum (Dainippon Pharmaceutical Co., Ltd.) are shown in Table 3. A predetermined amount of the mixture was added at a certain ratio, the graduated cylinder was plugged, and the mixture was inverted over 10 times.

After adding 100 ppm of polyaluminum chloride (Al ₂ O ₃ 10.2%, manufactured by Taki Kagaku Co., Ltd.) to this, the mixture was further inverted and stirred 10 times.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was sampled and the turbidity was measured.

For comparison, the same test was carried out by adding and using xanthan gum and locust bean gum individually without mixing them, and the turbidity of the supernatant water was measured.

The results of these measurements are shown in Table 3.

Example 4 A coagulation test was conducted using muddy water (Kakogawa City, Hyogo Prefecture) discharged along with the dredging work in seawater as a test muddy water.

The turbidity of this muddy water during the test was 11000 ppm,
The pH was 7.43.

Dispense 500 ml of the sampled turbid water into a 500 ml graduated cylinder with a ground-in stopper, add the prescribed amount of the mixture of xanthan gum and other gums (mixing ratio 1/4) shown in Table 4 to the graduated cylinder. The stopper was closed, and the mixture was inverted over 10 times.

After adding 400 ppm of polyaluminum chloride (Al ₂ O ₃ 10.2%, manufactured by Taki Kagaku Co., Ltd.), the mixture was further stirred 10 times by inversion.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was sampled and the turbidity was measured.

Further, for comparison, instead of a mixture of the xanthan gum and other gums, the same test was performed using only a commercially available synthetic polymer flocculant and polyaluminum chloride,
The turbidity of the supernatant water was measured.

The results of these measurements are shown in Table 4.

Example 5 A coagulation test was carried out using the turbid water (Kakogawa City, Hyogo Prefecture) discharged along with the dredging work of the Kakogawa Riverbed as the test turbid water.
The turbidity of this muddy water was 9600 ppm and the pH was 7.21.

Take 500 ml of the sampled turbid water in a 500 ml graduated cylinder with a stopper, add a predetermined amount of a mixture of xanthan gum and other gums (mixing ratio 4/1), and plug the graduated cylinder to 10 Inversion stirring was performed once.

After adding 300 ppm of polyaluminum chloride (Al ₂ O ₃ 10.2%, manufactured by Taki Kagaku Co., Ltd.), the mixture was further inverted and stirred 10 times.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was collected to measure the turbidity.

Also, for comparison, xanthan gum and other gums are added separately without mixing, so as to have the same addition amount as above,
The same test was performed to measure the turbidity of the supernatant water.

In addition, in this case, stirring was performed after adding xanthan gum.
10 times in total, 5 times after addition of other gums.

The results of these measurements are shown in Table 5.

Example 6 An agglutination test was conducted in the same manner using the test turbid water used in Example 5.

Take 500 ml of the sampled turbid water in a 500 ml graduated cylinder with a stopper, add a predetermined amount of a mixture of xanthan gum and locust bean gum (mixing ratio 4/1), plug the graduated cylinder 10 times. Inverted stirring was performed.

After adding 300 ppm of polyaluminum chloride (Al ₂ O ₃ 10.2%, manufactured by Taki Kagaku Co., Ltd.), the mixture was further inverted and stirred 10 times.

After stirring, this was left to stand, and after 10 minutes, 20 ml of supernatant water was collected to measure the turbidity.

For comparison, the order of addition of the gum mixture and polyaluminum chloride was reversed, and after the addition and stirring of polyaluminum chloride, the gum mixture was added and stirred, and the same test was conducted.

The results of these measurements are shown in Table 6.

Claims (2)

[Claims] 1. A water treatment method comprising adding a mixture of xanthan gum and gums selected from guar gum, locust bean gum or tamarind to water to be treated and then adding a water-soluble aluminum salt. 2. A gum (B) selected from xanthan gum (A) and guar gum, locust bean gum or tamarind.
The water treatment method according to claim 1, wherein the mixture ratio of (A) / (B) is 1/20 to 20/1.