JP2001336128A - Artificial bottom of water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive artificial bottom of water having an effect for purification of the bottom quality and water quality even if it is a small mound on which creatures ranging from a sandy area to sunken rock area can inhabit and further which can prevent generation of H2S. SOLUTION: The artificial bottom of water has a mound formed at least partly of furnace slag so as to substantially surround a sandy layer laid on the bottom of water as the feature in the first invention, and the average height of the mound at least partly formed of furnace slag in the first invention is 30 cm or higher and its average width is 50 cm or larger and the average thickness of the sandy layer in the inside surrounded by the mound is 5 cm or larger as the feature in the second invention. Further, at least a part of the sandy layer is formed of water-granulated slag obtained from blast furnace in the first and second inventions as the feature in the third invention.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a technique for improving water bottoms, and more particularly to an artificial water bottom suitable for sea areas and brackish water areas where sludge is deposited.

[0002]

2. Description of the Related Art Conventionally, as a technique for making the water bottom where sludge is deposited in coastal seas or brackish waters an environment suitable for habitat of living organisms, there are conventionally methods such as covering sand with bottom mud or dredging bottom mud. It has been known.

[0003] As the sand covering material used here, a material such as sea sand or mountain sand that has only an effect of covering the bottom mud without a chemical reaction is used. In some cases, the bottom mud is covered with natural stones in anticipation of the Tsukiiso effect.

However, when natural sand such as sea sand or mountain sand which does not have a purifying action on sediment and water quality by a chemical reaction is used as a covering sand material, for example, an effect of preventing the elution of nutrients from sediment. When it is necessary, the thickness of the sand to be laid must be increased, and the effect cannot be obtained unless the sand is covered over a wide area.

To solve the above problem, Japanese Patent Laid-Open Publication No. 3-49
No. 88 discloses a technique using granular steelmaking slag as a covering material. Specifically, by using converter slag having a grain size of about 1 mm as granular steelmaking slag, the sand covering effect and H ₂ S and PO ₄ ³⁻ due to the CaO and Fe ₂ O ₃ components in the converter slag are used. Bottom sediment due to the chemical removal effect of
It is reported that purification of water quality can be achieved.

[0006] Further, a technique of purifying water by contact oxidation between gravel by a mound of natural stone and a filtering action, and a technique of providing a sand covering effect by combining natural stone and natural sand are also used.

[0007]

[Problems to be solved by the invention]
In a water area where purification of water quality is required, a large amount of contaminated floating mud flows in. For example, when a converter slag having a particle size of about 1 mm described in JP-A-3-4988 is used, the Has the effect of purifying sediment and water, but the mud gradually sinks and accumulates on the surface of the sediment, and within one year, the surface of the sediment is covered with the mud and the effect of purifying the sediment and water is lost. Resulting in. Further, since converter slag having a particle size of about 1 mm solidifies, recovery of biota is slow, and the effect of decomposing bottom mud by living organisms cannot be expected as much as natural stone.

To solve such a problem, a method of laying steelmaking slag having a large particle diameter directly on the bottom mud is conceivable. In this case, however, the steelmaking slag sinks into the bottom mud.
In order for the laid steelmaking slag to effectively act as a sediment / water purification material, the steelmaking slag must be laid more than the thickness of the bottom mud, and the laying amount of the steelmaking slag becomes extremely large. Further, simply laying steelmaking slag having a large particle size directly on bottom mud is not suitable for the habitat of living organisms living in sandy areas.

The technology of purifying water quality by contact oxidation between gravel and filtration by a mound of natural stone requires the mound to be built up to the surface of the sea, and the mound must be thicker, which increases the construction cost. There's a problem. When a mound of natural stone and natural sand inside the mound are used in combination as a cover sand, it is possible to make the sand cover area smaller than when there is no mound. Since the large mound necessary for the inter-contact oxidation and the inter-gravel filtration effect to function sufficiently is required, the effect of reducing the construction cost is small.

[0010] Further, when sand covering with natural sand is combined with a mound, natural sand does not have a purifying action on sediment and water quality by a chemical reaction. Means that a few ppm of H ₂ S is produced by the action of sulfate-reducing bacteria in pore water even when sludge is not deposited.
Is generated.

Further, it is necessary to collect natural stones and mountain sand by cutting down the mountain, and it is becoming difficult to secure natural stones and mountain sand due to recent environmental problems.

The present invention has been made to solve such a problem, and has an effect of purifying sediment and water quality even with a small mound, and can inhabit organisms from a sandy area to a reef area. Therefore, an object of the present invention is to provide an artificial water bottom capable of further suppressing the generation of H ₂ S at a low cost.

[0013]

The above object is achieved by the following invention. A first invention is an artificial water bottom characterized in that a mound at least part of which is made of steelmaking slag is arranged so as to substantially surround a sandy layer laid on the water bottom.

According to a second aspect of the present invention, in the first aspect, a mound comprising at least a part of a steelmaking slag has an average height of 30 cm or more and an average width of 50 cm or more, and a sandy material surrounded by the mound. An artificial water bottom characterized in that the average thickness of the layer is 5 cm or more.

A third invention is the artificial water bottom according to the first or second invention, wherein at least a part of the sandy layer is made of granulated blast furnace slag.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

The artificial water bottom according to the present invention is provided with a mound at least partially made of steelmaking slag so as to substantially surround a sandy layer laid on the water bottom. Here, the water bottom is a water bottom such as a sea area or a brackish water area.

Since at least a part of the mound is made of steelmaking slag, the steelmaking slag in the mound adsorbs P and S in the water contaminated with sludge, and forms H from the surrounding water into a sandy layer laid in the mound. to prevent _{the 2} S is mixed. As in the case of using natural stone, it is possible to prevent H ₂ S from being mixed by intergranular contact oxidation, but since the steelmaking slag itself has an adsorption effect of S, near the water bottom where intergranular contact oxidation does not occur. Even when the mound is provided only in the mound, the water purification effect is sufficiently exhibited, and the mound can be reduced in size.

The mound having at least a portion made of steelmaking slag preferably has an average height of at least 30 cm and an average width of at least 50 cm.
If the average height of the mound is less than 30 cm or the average width is less than 50 cm, the water passing through the upper part of the mound will easily reach the sand cover even if the mound exhibits a water purification function. Is in contact with the same water as when there is no mound, and the water purification effect of the mound cannot be sufficiently exerted in the sand covering portion. In addition, in seas and brackish waters, during the stagnation period in summer,
A nepheloid layer is formed about 30 cm from the sea floor, which makes the environment very unsuitable for habitat of living things. The height of the mound is preferably 30 cm or more in order to prevent the seawater of the nepheloid layer from entering the sand cover portion. The upper limit of the height and width of the mound is not particularly limited, but it is preferable to determine the upper limit in consideration of industrial properties or layability, etc., as an average height of the mound of 5 m or less, and as an average thickness of the mound width. It is preferably 10 m or less.
Here, the height and width of the mound are defined by the average height and width, because some variations may occur in the height and width of the mound depending on the laying method.

Here, the ratio of the steelmaking slag to the entire mound is preferably at least 50%, more preferably at least 80%. In addition, as steelmaking slag occupying at least a part of the mound, not only slag generated in a converter, an electric furnace, a mixed iron wheel, etc., but also hot metal pretreatment slag such as desiliconized slag, desulfurized slag, and dephosphorized slag is used. In addition, the steelmaking slag may contain metal.

The steelmaking slag can be used without adjusting the grain size (crushing or sieving). However, it is preferable to use one containing 85 mass% or more of those having a particle size of 10 mm or more. Here, as a method of adjusting the particle size of the steelmaking slag, after cooling and solidifying the molten slag,
Crushed by heavy equipment or crushing plant, etc.
For example, a method of selecting using a sieve having a sieve of 10 mm or more, a method of washing with water or a method of air classification, and the like can be used. If the steelmaking slag has a particle size of 10 mm or more,
By containing at least mass%, the solidification between the steelmaking slags is prevented, the gap in the mound is largely empty, and the floating mud does not settle in the gap, so that the surface of the mound is not covered with the sludge. Purification effect is maintained for a long time. In addition, the gap in the mound becomes a suitable habitat for living organisms in the reef area such as adherent diatoms, oysters, shrimp, etc., and the biota can be attached and recovered early, and the water quality can be purified by the attached organisms. Water purification effect is maintained for a long time. Furthermore, by making the particle size of the steelmaking slag 20 mm or more, the gap in the mound becomes larger, the sustainability of the water purification effect is further improved, and it is also effective as a habitat for fish such as goby, eel, eel. Become.

Since steelmaking slag contains CaO, if it comes into contact with water for a long time, CaO + H ₂ O
→ Steel slag collapses due to the reaction of Ca (OH) ₂ , and small particles are generated, and there is a concern that the generated small particles may enter the gaps of the steel slag to reduce the water purification effect. 85ma for particle size of 10mm or more
By containing ss% or more, a long-term water purification effect is obtained as compared with a case where steelmaking slag having a particle size of about 1 mm is used. As a method of preventing the collapse of the steelmaking slag, it is also effective to use a steelmaking slag that has been aged with air, steam, an autoclave, carbon dioxide gas, or the like.

Here, the part other than the steelmaking slag of the mound at least a part of which is made of steelmaking slag is made of natural stone,
Concrete materials, waste concrete materials, porcelain plates, steel frames, reinforcing bars, and the like can be used.

By disposing a sandy layer inside a mound at least partly made of steelmaking slag, the sandy layer covers the bottom mud to prevent elution of nutrients from the bottom mud, and the water quality by the mound is reduced. The habitat of living things is maintained together with the purification effect.

Here, the construction may be such that the mound rides on the sandy layer after laying the sandy layer, or after the mound is constructed, the sandy layer is placed inside the mound. Although a configuration in which the mound is laid may be adopted, it is preferable that the mound ride on the sandy layer in the case of a water bottom state where the mound easily sinks. By adopting a configuration in which the mound rides on the sandy layer, it is possible to reduce the sinking of the mound to the bottom of the water and to reduce the amount of the material used for the mound.

That is, a preferred embodiment in this case is:
An artificial water bottom, wherein a mound at least partly made of steelmaking slag is arranged on the sandy layer so as to substantially surround the sandy layer laid on the water bottom.

Here, the thickness of the sandy layer is appropriately changed depending on the condition of the bottom mud covered by the sandy layer.
cm or more. Average thickness of sandy layer is 5
cm or more, the effect of covering the bottom mud with sand is more effectively exhibited.

Preferably, at least a part of the sandy layer is made of granulated blast furnace slag. By including the granulated blast furnace slag in the sandy layer, the granulated blast furnace slag becomes more suitable as a habitat for living organisms due to the S adsorption effect and the H ₂ S generation suppressing effect of the granulated blast furnace slag itself, and the sandy layer is further reduced in thickness. This is because it becomes possible.

The granulated blast furnace slag is used immediately after the blast furnace is laid.
Maintain the pH of the lug gap at about 8.5 to maintain the activity of sulfate-reducing bacteria
Sulphate ions in water in the granulated blast furnace slag
H _TwoS is suppressed. In addition, the gap of the granulated slag is
It is a suitable habitat for shellfish and creatures as well as natural sand.

The mound at least partly made of steelmaking slag and the sandy layer can be laid on the bottom of the water by a method using, for example, a gut ship.

In a place where the seabed structure is locally convex due to seabed rocks or the like, the thickness of the sandy layer may be locally zero, but the effect of the present invention is not obtained. It will not be compromised. When the artificial water bottom according to the present invention is constructed near a reef or breakwater, the effect of the present invention is not impaired even if a part of the mound is replaced with a reef or breakwater, but a part of the mound is not damaged. If missing, dirty water outside the mound will enter the mound without being affected by the water purification effect of the mound, thus deteriorating the water quality inside the mound and reducing its effectiveness as a habitat for underwater organisms .

Here, when a mound is constructed from steelmaking slag, for example, a method can be employed in which a wire mesh basket filled with steelmaking slag is installed. In this case, it is preferable that the particle size of the steelmaking slag is such that almost no steelmaking slag flows out of the wire mesh basket. In addition, the size of the wire mesh basket when the mound is constructed using the wire mesh basket, the length of one side is 1 to 2 in consideration of the workability when forming the mound.
It is preferable to have a rectangular parallelepiped shape of about m. In this case, too, by laying a sandy layer on the water floor in advance and installing a wire mesh cage on the laid part, the sinking of the wire mesh cage into the water bottom is reduced, so the size of the wire mesh basket and the steelmaking slag to be used are reduced. This has the effect of reducing the amount of construction.

1 to 4 show examples of laying an artificial water bottom according to the present invention. FIG. 1 is a plan view of an artificial water bottom in which a mound 1 is circumferentially constructed on a water bottom 5 and a sandy layer 2 is laid inside the mound 1, and FIG. 2 shows a cross-sectional structure taken along the line AA in FIG. FIG. FIGS. 3 and 4 show the cross-sectional structure of an artificial water bottom when a wire mound basket 4 filled with steelmaking slag 3 is circumferentially installed to construct a mound. FIG. FIG. 4 shows a case where the wire mesh basket 4 is placed on the water bottom 5 and then the sandy layer 2 is laid inside the wire mesh basket 4. FIG. 4 shows the wire mesh basket filled with the steelmaking slag 3 after the sandy layer 2 is laid on the water bottom 5. 4 are arranged in a circumferential shape.

The artificial bottom composed of the mound and the sandy layer constructed in this manner serves as a habitat for various living things from the sandy area to the rocky reef area, and the mound may be small. It leads to reduction.

[0035]

[Example 1] (Example 1) The mound height is 1 m above the sea floor and the mound width is 1 m on the bottom of the sea floor where the inflow of floating mud is large.
Then, a mound was constructed by stacking steelmaking slag on a circumference of 30 m in diameter so that the cross-sectional shape became an approximately isosceles triangle having a slope of 40 degrees, and natural sand was spread in the mound in a thickness of 15 cm. The mound was constructed by lowering steelmaking slag to the sea floor by glove from a gut ship and then manually stacking steelmaking slag by divers. After that, natural sand was thrown into the mound, which was also handed by a diver. One year after the construction, the creatures were surveyed. As a result, a large number of shellfish, molluscs, and goby were observed, and it was confirmed that a favorable habitat for the creatures was provided.

(Example 2) A mound is constructed by arranging steelmaking slag in a square wire mesh basket having a mound height of 50 cm from the sea bottom and a mound width of 70 cm on the bottom of the seabed where the inflow of floating mud is large. , Granulated slag in it, thickness 10c
m. One year after the construction, the creatures were surveyed. As a result, a large number of shellfish, molluscs, and goby were observed, and it was confirmed that a favorable habitat for the creatures was provided.

[0037]

As described above, according to the present invention, even a small mound has an effect of purifying sediment and water quality,
It can inhabit creatures from sandy areas to rocky reef areas, and H ₂
An artificial water bottom capable of suppressing the generation of S is provided at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of laying an artificial water bottom according to the present invention.

FIG. 2 is a diagram showing a cross-sectional structure along AA in FIG.

FIG. 3 is a view showing a cross-sectional structure of an artificial water bottom when a mound is constructed by circumferentially arranging a wire mesh basket filled with steelmaking slag.

FIG. 4 is a diagram showing another example of the cross-sectional structure of the artificial water bottom in the case where a wire mesh basket filled with steelmaking slag is circumferentially installed to construct a mound.

[Explanation of symbols]

 1 Mound 2 Sandy Layer 3 Steelmaking Slag 4 Wire Mesh Basket 5 Water Bottom

Claims (3)

[Claims] 1. An artificial water bottom, wherein a mound at least partly made of steelmaking slag is arranged so as to substantially surround a sandy layer laid on the water bottom. 2. A mound at least partially composed of steelmaking slag has an average height of at least 30 cm, an average width of at least 50 cm, and an average thickness of a sandy layer inside the mound of at least 5 cm. The artificial water bottom according to claim 1, wherein: 3. The artificial water bottom according to claim 1, wherein at least a part of the sandy layer is made of granulated blast furnace slag.