JP2002045888A - Phosphorus elution suppressing agent, method for preparing the same and method for suppressing elution of phosphorus in bottom mud - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement the application of calcium nitrate known to have a suppressing effect on the elution of phosphorus included in the form of impurities in the bottom mud of rivers, lakes and ponds, and the seashore under a reductive environment not by injection of an aqueous calcium nitrate solution into the bottom mud which is a known technique but by a means of feeding the solid thereof. SOLUTION: The phosphorus elution suppressing agent is prepared by using the calcium nitrate as an essential component (10 to 30%), adding calcium carbonate and calcium sulfate (total 50 to 90%) thereto, adding stearic acid or its salt (1 to 20%) as a hydrophobic material to retard the elution of a calcium nitrate salt and a sucrose fatty acid isobutyl ester and p-oxybezoic acid isobutyl ester (1 to 20%) as a binder thereto, then molding the mixture to tablets and briquettes. An air gun is preferably used for application of the agent to the bottom mud.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for insolubilizing phosphorus immobilized in lakes, rivers, canals or sea sediments, and present in the sediments and eluted under reducing conditions. The present invention relates to a phosphorus elution inhibitor, including a method for producing the agent and a method for suppressing the elution of phosphorus in bottom mud using the same.

[0002]

2. Description of the Related Art Phosphorus compounds mainly originating from domestic wastewater are present in sediments of lakes, rivers, canals or the sea.
The amount is relatively large in some places. This type of phosphorus compound is usually solid, but elutes again when the environment of the bottom mud is reduced. When organic matter in the bottom mud is decomposed, oxygen is consumed, so that reducing conditions are often realized. Phosphorus eluted in water is undesirable because it causes water bloom and red tide and must be removed.

Conventionally, the only way to eliminate the effect of phosphorus compounds in water is to remove bottom mud, and dredging has been performed. However, dredging damages ecosystems by damaging benthic animals and aquatic plants, and also causes the mud to soar and spread, which is not as effective as expected. Another problem is how to dispose of the dredged mud.

[0004] Therefore, efforts have been made to fix the phosphorus compound in the sediment in situ so as not to be eluted even under reducing conditions and to cause eutrophication. For example, Shiga Prefecture is trying to inject an aqueous solution of calcium nitrate into the bottom sediment to improve the water quality of Lake Biwa and prevent the occurrence of blue-green algae and freshwater red tides, which give off odor to the water supply. 1997
According to an article on the first page of the Mainichi Newspaper dated 0/5, ferric chloride, alum and calcium nitrate were selected as substances that could be expected to act as an oxidizing agent, and when their aqueous solutions were added, the sediment in the sediment was reduced. The following results were obtained by examining how much phosphorus eluted.

Oxidant concentration (%) Eluted phosphorus (μg / L) Ferric chloride 0.32 402 0.16 234 Alum 0.42 490 0.21 407 Calcium nitrate 0.70 13 0.35 67 This data Indicates that the injection of a 0.7% aqueous solution of calcium nitrate can suppress the dissolution of phosphorus by as much as 98%.

However, if the injection of the aqueous solution is not properly performed in the bottom sediment, the effect is low. Therefore, it is necessary to manufacture and use a special device suitable for the work. The above-mentioned newspaper article contains a photograph of a device in which a number of nozzles are planted on a steel plate. When used in liquid form, calcium nitrate does not always work with high efficiency, partly due to diffusion into the water during injection. In addition, the effects of calcium nitrate occur at the time of infusion, but are poorly persistent and require frequent infusions.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to use calcium nitrate, which has been confirmed to have an effect of suppressing the dissolution of phosphorus in sediment, rather than by injecting an aqueous solution. An object of the present invention is to provide a phosphorus eluting agent which is cost effective but high in effect, and has a long-lasting effect. It is also an object of the present invention to provide a method for producing such a phosphorus elution inhibitor and a method for suppressing the elution of phosphorus present in sediment.

[0008]

The phosphorus elution inhibitor of the present invention comprises an oxidizing agent and a soluble calcium salt as main components, and further comprises a hydrophobic substance and a binder for delaying the elution of the soluble calcium salt. The product is pressurized in a mold and formed into a tablet or briquette, which fixes phosphorus in the bottom mud of rivers, lakes and shores and suppresses its elution.

The above-mentioned method for producing the phosphorus elution inhibitor of the present invention comprises an oxidizing agent and a soluble calcium salt which are the main components of the phosphorus elution inhibitor, a hydrophobic substance and a binder which delay the elution of the soluble calcium salt. In some cases, the method further comprises mixing the composition to which the ferric salt is added, placing the composition in a mold, pressurizing, and molding into tablets or briquettes.

[0010] The method of the present invention for suppressing the dissolution of phosphorus present in sediment using the phosphorus dissolution inhibitor comprises the steps of:
Injecting into river, canal or sea bottom mud and fixing phosphorus.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As the oxidizing agent constituting the phosphorus elution inhibitor of the present invention, a sodium, potassium, ammonium, calcium, magnesium or manganese salt of nitric acid or alum can be used.

As the soluble calcium salt, calcium nitrate, sulfate, carbonate or hydrogen carbonate can be used. Calcium nitrate, which acts as an oxidizing agent and is also a soluble calcium salt, is the most suitable material for the phosphorus elution inhibitor of the present invention.

[0013] The hydrophobic substance is a component for delaying the dissolution of the soluble calcium salt and maintaining the action of inhibiting the dissolution of phosphorus. Suitable ones are aliphatic carboxylic acids which have a carbon number of about 11 to 31 and are solid at room temperature, specifically, stearic acid, myristic acid, behenic acid and the like. These fatty acids may be salts, for example salts of calcium and magnesium. Esters such as isobutyl sucrose fatty acid and isobutyl paraoxybenzoate are also useful.

The binder is a binder for each of the above components, and the above-mentioned aliphatic carboxylic acids or esters thereof, or aromatic carboxylic acids or esters thereof are preferred. Depending on the choice of material, it is also possible to use one that has the properties of a hydrophobic substance and a binder.

It has been found that the presence of iron is preferable because iron ions form ferric phosphate and insolubilize them in suppressing the elution of phosphorus in the bottom mud. In an environment where phosphorus flows into lake water or the like, iron often flows at the same time, but in some cases, it is desirable to supplement iron. In such a case, an embodiment in which the composition of the present invention further contains a ferric salt, for example, ferric chloride as a component is preferable.

The proportion of each component constituting the phosphorus elution inhibitor composition of the present invention is, by weight, 10 to 30% of an oxidizing agent, 50 to 90% of a soluble calcium salt, and 1 to 2 of a hydrophobic substance.
0% and 1-20% binder are suitable. If ferric salt is added to this, 10% of the composition
Is appropriate. When using calcium nitrate, which is both an oxidizing agent and a source of soluble calcium,
The composition should be selected so that this accounts for 10 to 30%.

In addition to the above, the phosphorus elution inhibitor of the present invention comprises
Any additional components can be included as long as the purpose is not adversely affected.

In order to form the composition of the phosphorus elution inhibitor into tablets or briquettes, a conventional tabletter or briquetting machine may be used. As will be seen in the examples below, considerable pressure (eg, 20-1
In order to achieve the sustained release (slow release effect) intended in the present invention, it is necessary to add 00 kg / cm ² ) so as to obtain a well-tightened body. Although the size is arbitrary, for example, the diameter 30
A flat cylindrical shape having a height of 45 mm and a height of 15 to 30 mm is suitable.

However, on the other hand, there is a case where quick effect is required, and in such a case, it is desirable to form a product molded at a relatively low pressure. Thus, the degree of fast-acting to slow-acting properties can be adjusted by the amount of the hydrophobic substance and the amount of the binder in addition to the pressure during molding. Therefore, depending on the situation where the phosphorus elution inhibitor is used, it is desirable to select a fast-acting or slow-acting agent and use it in combination.

The application of the tablet or briquette-like phosphorus elution inhibitor is carried out by feeding it to an appropriate position in the bottom mud. Usually, it is sufficient to throw in the water, but depending on the state of the bottom mud, it is effective to give a momentum using an air gun or the like and drive deep into the area.

[0021]

EXAMPLES Example 1 The following ratios ("parts" are parts by weight,
The same shall apply hereinafter), blend each component, and apply to a tabletter.
Pressurized with pressure of 0kg / cm ² , 37mm in diameter, 20mm in height
Thus, a cylindrical tablet weighing about 40 g was obtained. Calcium nitrate 20 parts Calcium carbonate 60 parts Silicic acid (white carbon) 3 parts Stearic acid 15 parts Sucrose fatty acid ester 2 parts

[Example 2] A cylindrical tablet having a diameter of 37 mm, a height of 18 mm and a weight of about 40 g was prepared by blending the respective components in the following proportions, applying a tablet to the tablet, and applying a pressure of 100 kg / cm ^2. did. Calcium nitrate 20 parts Calcium carbonate 65 parts Silicic acid (white carbon) 4 parts Magnesium stearate 10 parts Isobutyl paraoxybenzoate 1 part

[Example 3] Each component was blended at the following ratio, and the mixture was applied to a tablet and pressurized at a pressure of 80 kg / cm ² .
A cylindrical tablet having a diameter of 45 mm, a height of 25 mm and a weight of about 55 g was obtained. Calcium nitrate 30 parts Calcium carbonate 55 parts Stearic acid 10 parts Magnesium stearate 3 parts Sucrose fatty acid ester 1 part

[Example 4] A cylindrical tablet having a diameter of 37 mm, a height of 18 mm and a weight of about 40 g was prepared by blending the following components at the following ratio, applying the mixture to a tablet, and applying a pressure of 100 kg / cm ² to the tablet. did. Calcium nitrate 10 parts Magnesium nitrate 10 parts Calcium sulfate 20 parts Calcium carbonate 50 parts Silicic acid (white carbon) 3 parts Isobutyl paraoxybenzoate 2 parts

[Solubility test] The tablet prepared in Example 3 was placed in a water bath at room temperature, and the tablet was gradually dissolved while replacing water at a rate of 1 L / hr.
Once a week, tracking was performed by measuring the amount of residual tablet. In 3 years and several days, it completely dissolved and disappeared. An average of 5-6 mg eluted per day. The change in the dissolution rate during that time is shown in the graph of FIG. Here, the “dissolution rate” is calculated based on the calcium concentration in the liquid. The curve in the figure represents the change in the dissolution rate of calcium nitrate, and the straight line indicates the tendency of the cumulative dissolved amount.

[0026]

Industrial Applicability The phosphorus elution inhibitor of the present invention suppresses the elution of phosphorus contained in sediment of rivers, lakes, marshes and coasts under reducing conditions by the synergistic action of an oxidizing component and a calcium component. In order to enjoy the known effect of calcium nitrate, tablets or briquettes are injected or sprayed with an air gun without the trouble of injecting the aqueous solution into the bottom mud with a special device, which is the conventional method Thereby, the phosphorus elution inhibitor can be given to an appropriate position in the bottom mud.

Since the tablet briquette is dissolved and acts gradually in the bottom mud, the effect of suppressing the dissolution of phosphorus is maintained for a long time. Slow solubility can be adjusted within a certain range by selecting molding conditions, so if the effect of suppressing phosphorus elution should be exerted relatively early, if a soluble one corresponding to that is manufactured and used Also, as described above, it is also significant to use two or more kinds having different solubility in combination. Since the solids are not diffused and lost in water without being useful for suppression unlike aqueous solutions, the use efficiency is high.

In general, nitrate has high water solubility and is more or less deliquescent. However, by using a hydrophobic substance according to the present invention, the phosphorus elution inhibitor has no deliquescent and special measures can be taken for a long time. You can save without taking. The phosphorus elution inhibitor of the present invention can be produced at a low cost, as is clear from both the material and the production method.

As described above, if the elution of phosphorus in the bottom mud is suppressed according to the present invention, the occurrence of blue-green algae and red tide can be prevented, the water quality can be maintained, and the impact on the fishery can be eliminated. .

[Brief description of the drawings]

FIG. 1 is a graph showing data of the present invention, showing a situation in which a phosphorus elution inhibitor produced in an example is gradually dissolved in water.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironobu Hirasawa 1-113 Kusakabe Matsunocho, Inazawa-shi, Aichi (72) Inventor Noboru Yamada 64-8 Hashimoto Kurigaya, Yawata-shi, Kyoto F-term (reference) 4D059 AA09 AA19 BK30 DA01 DA03 DA08 DA24 DA27 DB03 DB08

Claims (7)

[Claims] The present invention relates to a method for producing a bottom mud by press-molding a composition comprising an oxidizing agent and a soluble calcium salt as main components, and a hydrophobic substance and a binder for delaying the dissolution of the soluble calcium salt. A phosphorus elution inhibitor that fixes phosphorus and suppresses elution. 2. A sodium, potassium, ammonium, calcium, magnesium or magnesium salt or alum of nitric acid as an oxidizing agent, and calcium nitrate, sulfate, carbonate or bicarbonate as a soluble calcium salt, and a hydrophobic substance. 2. The phosphorus elution inhibitor according to claim 1, wherein a fatty acid or a salt thereof is used as the binder, and an aliphatic carboxylic acid or its ester or an aromatic carboxylic acid or its ester is used as the binder. 3. The method according to claim 1, wherein calcium nitrate is selected as a component which is both an oxidizing agent and a soluble calcium salt, stearic acid or a salt thereof is selected as a hydrophobic substance, and isobutyl sucrose fatty acid or isobutyl paraoxybenzoate is selected as a binder. Or 2) a phosphorus elution inhibitor. 4. The phosphorus elution inhibitor according to claim 1, wherein the composition further comprises a ferric salt as a component. 5. An oxidizing agent comprising 10 to 3% by weight in the composition.
5. The composition of claim 1, wherein 0%, 50-90% of the soluble calcium salt, 1-20% of the hydrophobic substance and 1-20% of the binder and 0-10% of the ferric salt. Kano phosphorus elution inhibitor. 6. An oxidizing agent and a soluble calcium salt as main components, a hydrophobic substance and a binder for slowing the dissolution of the soluble calcium salt, and a binder, and optionally a composition further containing a ferric salt, are mixed, A method for producing a phosphorus elution inhibitor, comprising fixing a phosphorus in a bottom mud and suppressing elution by placing the mixture in a mold and pressing to form a tablet or a briquette. 7. A tablet or briquette of the phosphorus elution inhibitor according to any one of claims 1 to 5, comprising:
A method for suppressing the dissolution of phosphorus existing in sediment by pouring into river sediment or canal or sea sediment and fixing phosphorus.