JP4656466B2 - Artificial bottom - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates generally to water bottom maintenance technology, and particularly to an artificial water bottom suitable for sea areas and brackish water areas where sludge has accumulated.
[0002]
[Prior art]
As a technique for making the bottom of the sludge accumulated in coastal seas and brackish waters suitable for living organisms, there are conventionally known methods such as covering the bottom mud with sand and dripping the bottom mud. .
[0003]
As the sand covering material used here, a material having only an effect of covering the bottom mud without a chemical reaction such as sea sand or mountain sand is used. In addition, there is a case where the bottom mud is covered with natural stone in anticipation of the construction effect.
[0004]
However, when using natural sand such as sea sand or mountain sand that does not have an action to purify sediment and water by chemical reaction, it is necessary to prevent elution of nutrient salts from the bottom mud, for example. In some cases, it is necessary to increase the thickness of the sand to be laid, and there is a problem that the effect cannot be obtained unless sand is covered over a wide range.
[0005]
To solve the above problems, Japanese Patent Laid-Open No. 3-4988 discloses a technique using granular steelmaking slag as a sand covering material. Specifically, by using converter slag having a particle size of about 1 mm as granular steelmaking slag, its sand-capping effect and H ₂ S and PO ₄ ³⁻ due to CaO and Fe ₂ O ₃ components in converter slag are used. It has been reported that purification of sediment and water can be achieved by the chemical removal effect of.
[0006]
In addition, a technology for purifying water by contact oxidation between gravel with a natural stone mound and filtration, and a technology for providing a sand-capping effect by combining natural stone and natural sand are also used.
[0007]
[Problems to be solved by the invention]
However, since the inflow of contaminated floating mud is large in water areas that require purification of bottom sediment and water quality, for example, converter slag having a particle size of about 1 mm described in JP-A-3-4988 is used. In the early stage of sand-capping, it has the effect of purifying sediment and water quality, but the floating mud gradually settles and accumulates on the surface of the sand-capped surface, and the surface of the sand-capped sand is covered with floating mud within one year. The purifying effect disappears. Moreover, since converter slag having a particle size of about 1 mm is consolidated, the recovery of biota is slow and the bottom mud decomposition effect by living organisms cannot be expected as much as natural stone.
[0008]
To solve this problem, a method of laying steelmaking slag with a large particle size directly on the bottom mud can be considered, but in this case, the steelmaking slag sinks into the bottom mud. In order to effectively act as a bottom / water purification material, it is necessary to lay steelmaking slag more than the thickness of the bottom mud, and the amount of steelmaking slag is greatly increased. Moreover, simply laying steelmaking slag with a large particle size directly on the bottom mud is not suitable for the habitat of living organisms inhabiting sandy areas.
[0009]
The technology that purifies water by means of contact oxidation between gravel with natural stone mound and filtration action requires the mound to be built up to the surface of the sea, and the width of the mound must also be increased, resulting in increased construction costs. . In addition, when using a natural stone mound and natural sand as a covering sand inside the mound, it is possible to make the sand covering area smaller than when there is no mound. Since a 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]
Furthermore, when the sand covered with natural sand is combined with the mound, the natural sand does not have a sediment or water purification action by chemical reaction, so during the summer seawater stagnation period or when biological activities are active, There is a problem that several ppm of H ₂ S is generated by the action of sulfate-reducing bacteria in the pore water even in a state in which no sediment is deposited.
[0011]
In addition, natural stones and mountain sands need to be cut and collected, and due to environmental problems in recent years, it is becoming difficult to secure them.
[0012]
The present invention has been made to solve such problems, and even a small mound has an effect of purifying the bottom sediment and water, and organisms from sandy areas to reef areas can inhabit, and to provide an inexpensive artificial water bottom capable of suppressing the generation of H ₂ S.
[0013]
[Means for Solving the Problems]
The above problems are solved by the following invention. The first invention, Ri Tona steel slag at least partially containing CaO so as to surround substantially the sandy layer laid on the sea bed, 30 cm above 5m or less in average height with respect to the sandy layer, average width It is an artificial water bottom characterized by arranging mounds raised to 50 cm or more and 10 m or less .
[0014]
The second aspect, in the first aspect, an artificial water bottom, wherein the average thickness of the internal enclosed before Symbol mound sandy layer is 5cm or more.
[0015]
A third invention is the artificial water bottom according to the first invention or the second invention, wherein at least a part of the sandy layer is made of granulated blast furnace slag.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
[0017]
The artificial water bottom according to the present invention has a mound made of steel slag at least partially 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.
[0018]
When at least a part of the mound is made of steel slag, the steel slag in the mound absorbs P and S in the water contaminated by sludge, and H ₂ S is released from the surrounding water to the sandy layer laid in the mound. Prevent contamination. Although it is possible to prevent H ₂ S from being mixed by gravel contact oxidation, as in the case of natural stone, the steelmaking slag itself has the effect of adsorbing S, so near the bottom of the water where the gravel contact oxidation does not occur. Even when the mound is disposed only on the surface, the water purification effect is sufficiently exerted, and the mound can be downsized.
[0019]
As a mound comprising at least a part of steel slag, the average height of the mound is preferably 30 cm or more and the average width is preferably 50 cm or more. 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 covering part even if the mound exhibits the water purification function. This is because the sand-covered portion of the water comes into contact with the same water as when there is no mound, and the water quality purification effect of the mound cannot be sufficiently exhibited in the sand-covered portion. In addition, in the sea and brackish water areas, during the stagnation period in summer, a nepheloid layer is formed about 30 cm from the bottom of the sea, which makes the environment extremely unsuitable for living organisms. In order not to allow the seawater of this nepheloid layer to enter the sand cover part, the height of the mound is preferably 30 cm or more. The upper limit of the height and width of the mound is not particularly limited, but is preferably determined in consideration of industriality or laying properties, etc. The average height of the mound is 5 m or less, and the average thickness of the mound is as follows. 10 m or less is preferable. Here, the height and width of the mound are defined by the average height and width. This is because the height and width of the mound may vary slightly depending on the laying method.
[0020]
Here, as a ratio of the steelmaking slag to the entire mound, it is desirable that the steelmaking slag is 50% or more, preferably 80% or more. Steelmaking slag that occupies at least a part of the mound includes not only slag generated in converters, electric furnaces, kneading vehicles, but also hot metal pretreatment slag such as desiliconized slag, desulfurized slag, and dephosphorized slag. In addition, the steelmaking slag may contain metal.
[0021]
The steelmaking slag can be used even if the particle size is not adjusted (crushed or sieved), but it is preferable to use one containing 85 mass% or more of particles having a particle size of 10 mm or more. Here, as a method of adjusting the particle size of the steelmaking slag, after the molten slag is cooled and solidified, the molten slag is crushed by a heavy machine or a crushing plant, and sorted using, for example, a sieve having a sieve size of 10 mm or more, by water washing or air classification. A method or the like can be used. By including 85 mass% or more of steelmaking slag having a particle size of 10 mm or more, solidification between the steelmaking slags is prevented, and there is a large gap in the mound, and the floating mud sinks into the gap so that the surface of the mound becomes sludge. As a result, the purification effect of water quality is maintained for a long time. In addition, the gap in the mound becomes a suitable place for living organisms in the reef area such as adherent diatoms, turtles, shrimp, etc., the biota attaches and recovers early, and water quality purification by attached organisms is also performed. Water purification effect is maintained for a long time. Furthermore, by making the steelmaking slag particle size 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 and eel Become.
[0022]
Since steelmaking slag contains CaO, when it comes into contact with water for a long period of time, the steelmaking slag collapses due to the reaction of CaO + H ₂ O → Ca (OH) ₂ , and small grains are produced. Although there is a concern that water enters the gap between the steelmaking slag and reduces the purification effect of water quality, the steelmaking slag contains a particle size of 10 mm or more and 85 mass% or more, compared with the case of using a steelmaking slag having a particle size of about 1 mm. And has a long-term water purification effect. As a method for preventing the collapse of steelmaking slag, it is also effective to use steelmaking slag that has been aged with air, steam, autoclave, carbon dioxide, or the like.
[0023]
Here, natural stone, concrete material, concrete waste material, porcelain plate, steel frame, reinforcing bar, etc. can be used for the part other than the steelmaking slag of the mound, at least part of which is made of steelmaking slag.
[0024]
By arranging a sandy layer inside the mound made of steel slag at least partially, the sandy layer covers the bottom mud and prevents the elution of nutrients from the bottom mud, together with the water purification effect by the mound. Living habitat is maintained.
[0025]
Here, after the sandy layer is laid, the mound may be placed on the sandy layer, or after the mound is constructed, the sandy layer is laid inside the mound. However, in the case of a water bottom where the mound is likely to sink, it is preferable that the mound is placed on the sandy layer. By adopting a structure in which the mound is placed on the sandy layer, the sinking of the mound into the water bottom is reduced, and the construction amount of the material used for the mound can be reduced.
[0026]
That is, a preferred embodiment in this case is an artificial water bottom characterized in that a mound made of steel slag is disposed on the sandy layer so as to substantially surround the sandy layer laid on the water bottom. .
[0027]
Here, the thickness of the sandy layer is appropriately changed depending on the state of the bottom mud covered by the sandy layer, but the average thickness of the sandy layer is preferably 5 cm or more. This is because when the average thickness of the sandy layer is 5 cm or more, the sand covering effect of the bottom mud is more effectively exhibited.
[0028]
Moreover, it is preferable that at least a part of the sandy layer is made of granulated blast furnace slag. By incorporating blast furnace granulated slag into the sandy layer, the blast furnace granulated slag itself becomes more suitable as a habitat for organisms due to its S adsorption effect and H ₂ S generation suppression effect, and the sandy layer is made thinner. Because it becomes possible to do.
[0029]
Granulated blast furnace slag is laid immediately inhibits the activity of maintaining sulfate reducing bacteria the pH of the granulated blast furnace slag gap of about 8.5, H ₂ S of water sulfate ions in water-granulated blast furnace slag gap Suppress. Furthermore, the gap between the granulated slag becomes a suitable place for shells, shellfish and the like as natural sand.
[0030]
Laying at least a part of the mound made of steel slag and the bottom of the sandy layer can be performed by a method using a gut ship or the like, for example.
[0031]
In places where the seabed structure is locally convex due to rocks on the seabed, the thickness of the sandy layer may be locally zero, but the effect of the present invention is impaired. There is no. In addition, when constructing an artificial water bottom according to the present invention in the vicinity of 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. If it is missing, dirty water outside the mound enters the mound without receiving the water purification effect of the mound, so the water quality in the mound deteriorates and the effect as a habitat for underwater organisms is reduced. .
[0032]
Here, when constructing a mound with steelmaking slag, it can be performed, for example, by a method of installing a metal mesh slag filled with steelmaking slag. In this case, it is preferable that the particle size of the steelmaking slag is set so that most of the steelmaking slag does not flow out from the wire mesh cage. In addition, it is preferable that the size of the wire netting when the mound is constructed using the wire netting is a rectangular parallelepiped shape having a side length of about 1 to 2 m in consideration of workability when forming the mound. In this case as well, the sandy layer is laid on the bottom of the water in advance and the wire netting is installed on the laid part to reduce the sinking of the wire netting to the bottom of the water. This has the effect of reducing the amount of construction.
[0033]
1 to 4 show examples of artificial water bottom laying according to the present invention.
FIG. 1 is a plan view of an artificial water bottom in which a mound 1 is constructed circumferentially on a water bottom 5 and a sandy layer 2 is laid on the inside, and FIG. 2 shows a cross-sectional structure taken along line AA in FIG. FIG. 3 and 4 show a cross-sectional structure of the artificial water bottom when the mound is constructed by installing the wire mesh cage 4 filled with the steelmaking slag 3 in a circumferential shape, and FIG. 3 is filled with the steelmaking slag 3. FIG. 4 shows a case where a sandy layer 2 is laid on the inside of the water net 5 after the wire netting 4 is installed on the bottom 5. FIG. 4 is installed circumferentially.
[0034]
The artificial water bottom composed of the mound and the sandy layer constructed in this way becomes a habitat for various organisms that inhabit the sandy area to the reef area, and the mound may be small, so that construction costs can be reduced. Connected.
[0035]
【Example】
Example 1
A steelmaking slag with a mound height of 1 m from the sea floor, a mound width of 1 m, and a diameter of 30 m on the circumference of the seabed where the floating mud is flowing in. The mound was constructed by stacking so that natural sand was spread in a thickness of 15 cm. For the construction of the mound, the steelmaking slag was grabbed from the gut ship to the seabed and then piled up manually by a diver. After that, natural sand was put inside the mound, and this was also handed by a diver. One year after the construction, the organisms were investigated, and a large number of shellfish, shellfish and goby were observed, and it was confirmed that a good habitat was provided.
[0036]
(Example 2)
A mound is constructed by arranging steelmaking slag placed in a square wire mesh fence with a mound height of 50 cm from the bottom of the sea and a mound width of 70 cm on the bottom mud where the inflow of floating mud is located. It was spread with a thickness of 10 cm. One year after the construction, the organisms were investigated, and a large number of shellfish, shellfish and goby were observed, and it was confirmed that a good habitat was provided.
[0037]
【The invention's effect】
As described above, according to the present invention, even a small mound has an effect of purifying sediment and water, can be inhabited by organisms from sandy areas to rocky areas, and further generates H ₂ S. An artificial water bottom that can be suppressed 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 taken along line AA in FIG.
FIG. 3 is a diagram showing a cross-sectional structure of an artificial water bottom in the case where a mound is constructed by circumferentially installing wire mesh rods filled with steel slag.
FIG. 4 is a view showing another example of a cross-sectional structure of an artificial water bottom when a mound is constructed by installing wire mesh rods filled with steel slag in a circumferential shape.
[Explanation of symbols]
1 Mound 2 Sandy layer 3 Steelmaking slag 4 Wire netting 5 Water bottom

Claims (3)

At least a portion sandy layer laid on the sea bed so as to surround substantially the Ri steel slag Tona containing CaO, 30 cm above 5m or less in average height with respect to the sandy layer, to 50cm or more 10m or less in average width An artificial water bottom characterized by a raised mound. Artificial sea bed according to claim 1, the average thickness of the sandy layer inside surrounded by the prior SL mound, characterized in that at 5cm or more. The artificial water bottom according to claim 1 or 2, wherein at least a part of the sandy layer is made of granulated blast furnace slag.

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