JP2002136983A - Floating island comprising porous concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a floating island capable of efficiently cleaning water, capable of being used even in seawater and withstanding even long-term use. SOLUTION: The floating island is formed using porous concrete and salt- resistant plants are planted therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floating island for purifying water quality and beautifying the environment.

[0002]

2. Description of the Related Art In recent years, waterside spaces such as rivers, ponds, lakes and marshes have been developed.
The development focused on flood control and efficiency has increased the number of places surrounded by stone walls and concrete structures rising vertically from the waterfront, giving a sense of intimidation and blockage. In order to overcome this, research and development of environmental purification technology using plants, that is, phytoremediation, has been activated.

On the other hand, in European countries, "biotope"
The project has been implemented, and the company has begun to secure space for living things. One means of this biotope is an artificial floating island. Conventionally, various artificial floating islands have been devised, but they are roughly classified into a dry type in which plants do not contact with water and a wet type in which plants contact with water.

As an example, there are many wet types and few dry types.
As the dry material, concrete or styrene foam is used, but there are drawbacks that a water purification effect cannot be expected and the cost is large. On the other hand, various materials such as FRP, Styrofoam, concrete, wood, coconut fiber, plastic bottles, old tires and the like are used in the wet process. This method has the advantages that a water purification effect can be expected, aquatic plants can be directly installed, and the cost is relatively low.

[0005] However, floating islands made of these conventional materials have the drawback that if they float in water for a long time, they will gradually sink and become useless. Also,
It cannot be said that it is sufficient from the viewpoint of water purification, and furthermore, the conventional floating island is used only in freshwater areas (Japanese Patent Laid-Open No. 8-13099).
No. 8, JP-A-8-58683), even when used in seawater, plants could not be vegetated, resulting in a meaningless floating island. Therefore, there is a demand for the development of floating islands that can overcome the above-mentioned drawbacks.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to develop a floating island that can purify water efficiently, can be used in seawater, and can withstand long-term use.

[0007]

Means for Solving the Problems The present inventors have made intensive efforts to solve the above-mentioned problems, and as a result, have found that floating islands can be created using porous concrete and salt-tolerant plants can be vegetated there. I found it.

That is, the present invention is characterized in that (1) a floating island made of porous concrete, (2) a floating island described in (1), which is vegetated with a salt-tolerant plant, and (3) a floating body is buried in the porous concrete. Related to the floating island described in (1) or (2).

A floating vegetation island is a structure that floats on water, which is composed of a float part that retains its function and a base part necessary for aquatic plants to thrive and settle. When vegetation floating islands grow aquatic plants and roots extend from the pores of the porous concrete into the water, it is possible to adsorb and fix excess nitrogen and phosphorus in the water, and various animals can be active and breed, It is a structure that is very effective for environmental improvement, as it is a place to grow shores and at the same time the waterside scenery is improved and the shore is protected by the wave breaking effect.

Floating islands can be roughly classified into a mat type and a raft type, and there are five types of mat types, and FIG. 1 shows these types. Porous concrete is a multi-porous concrete material in which aggregate having a substantially uniform particle size is bonded with a cement paste, and is characterized by continuous voids to the inside.

As a result of research conducted by the present inventors, it has been found that this porous concrete can create various environmental conditions by oxygen dependency, light and dark conditions, dry and wet conditions, and the like. For example, there is sufficient dissolved oxygen on the concrete surface that is in direct contact with water, and even in an aerobic environment, the inside of the void where the biofilm has grown changes from microaerobic to anaerobic.
An environment in which aerobic and anaerobic microorganisms coexist can be formed. In addition, autotrophic fungi and the like are dominant on the surface with light and unevenness, but algae cannot grow in voids under dark conditions.

Further, even if the water surface is lowered and the concrete surface is dried, the inside of the void can be kept wet due to the water retention of the pores. In addition, plants grown in the present invention include, for example, lycopodium, sekisho, kishobu, reed, watercress, etc., and when floating in brackish waters or coasts, it is preferable to grow salt-tolerant plants.

The inventors of the present invention have already applied for a patent on a salt-tolerant plant (Japanese Patent Application No. 11-860).
Phoenix dactylifera, Crinum asiaticum, Ophiopogo
njaponicus, Juncus sp.Iran, Festuca arundinace
Plants such as a are suitable. The following examples illustrate the invention.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Example 1) Water purification performance of porous concrete Porous concrete and natural stone of approximately the same size are piled up in an outdoor water tank (3.0 x 1.0 x 0.7 m) in the form of a levee, respectively. The change in water quality when the actual seawater at the back was circulated in the tank was investigated. The porous concrete used had an aggregate particle diameter of 2 mm and 5 mm, and the surface roughness was changed.

Table 1 shows the removal rate of total organic carbon (TOC) with respect to the initial concentration when circulating seawater for 92 hours in the September period. It can be seen from Table 1 that, in particular, the porous concrete having an aggregate particle diameter of 2 mm shows a removal rate of 70% with respect to 25% of natural stone. This indicates that the porous concrete with a larger amount of attached organisms has higher water purification performance.

[0016]

[Table 1]

(Example 2) Field experiment of porous concrete A water purification water channel (15 m x 2 m x 0.4 m) in which porous concrete was laid was provided in a small river in the park, and water quality items involved in purification were measured. Of these items, the relationship between residence time, water temperature and BOD removal rate is shown in FIGS.

From this figure, it can be seen that the BOD removal rate increases from 80% to 90% as the residence time increases. In relation to the water temperature, it can be seen that the higher the water temperature, the better the purification performance. Table 2 shows the species that appeared in the porous concrete.

[0019]

[Table 2]

The species observed are bacteria and algae (diatoms, green algae, cyanobacteria, and dinoflagellates), protozoa (rhizopods and rotifers), and metazoans (nematodes and poor hairs). Species, gastropods, leeches, isopods, crustaceans, aquatic insects).

Example 3 Seawater Planting Experiment on Artificial Floating Islands Materials for artificial floating islands made of porous concrete are shown below. Material: Lightweight, non-water-absorbing, thermally reduced styrofoam styrene was used as the aggregate. The heat-reduced styrene foam is a recycled material obtained by crushing used styrene foam and shrinking it by applying heat. Auxiliary Float: The buoyancy equivalent to the weight of soil and vegetation appearing on the water balanced the blocks with styrofoam. Reinforcing material: Stainless steel bars having a wire diameter of 3 to 6 mm were installed at appropriate intervals as core reinforcing bars.

The physical properties of the porous concrete are as follows: density: 0.8 to 0.9, bulk density: 0.6 to 0.7, porosity: 25 to 35%, compressive strength: 1.0 to 1.5N.
/ Mm ² . Diameter 44 made of such material
cm of an artificial floating island made of porous concrete was floated in a water tank filled with tap water, and plants were planted on the floating island for planting experiments.

The soil on the floating island was cultivated for raising rice seedlings, and was planted with tight sesame, tamarix, matsubakik, and pasparan (turf). Cultivation in a high temperature room for one month, then switch to Tokyo Bay seawater (Akanehama, Narashino city, salt concentration 2.5%),
The cultivation test was performed for about a month. FIG. 4 shows the results. It has been proved that various plants grow on artificial floating islands in seawater.

(Embodiment 4) Example of Field Installation of Artificial Floating Island FIGS. 5 and 6 show a situation where an artificial floating island made of porous concrete is installed in a pond. This structure was moored with a nylon rope or the like to a concrete block submerged in a pond as shown in FIG. Porous concrete with many voids can be a habitat for various creatures and can restore ecosystems to the waterside environment. The floating island made of other materials gradually sinks in a short time, and the floating island of the present invention maintains its original state even after a long period of time.

[0025]

According to the present invention, not only can the landscape be improved and the environment be improved over a long period of time, but also the water quality can be purified and the wave breaking effect can be exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram showing types of floating islands.

FIG. 2 is a diagram showing a relationship between a residence time and a BOD removal rate.

FIG. 3 is a diagram showing a relationship between a water temperature and a BOD removal rate.

FIG. 4 is a view showing a seawater planting experiment on an artificial floating island.

FIG. 5 is a diagram showing an example of an artificial floating island.

FIG. 6 is a diagram showing an example of an artificial floating island.

FIG. 7 is a view showing the shape and dimensions of an artificial floating island installed in a field.

FIG. 8 is a diagram showing a method of mooring an artificial floating island installed in a field.

[Explanation of symbols] Tight Gome Tamarix Matsubagiku Passparan (turf)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 38/08 C04B 38/08 C E02B 15/10 E02B 15/10 Z (72) Inventor Mitsuyoshi Yoshida Tokyo No. 25-1, Nishi Shinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Noboru 1-25-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo In Taisei Construction Co., Ltd. (72) Miho Akiyoshi Shinjuku, Tokyo 1-25-1, Nishishinjuku-ku, Taisei Construction Co., Ltd. (72) Inventor Ken Tsuruta 1-7-116, Kamikaido, Suginami-ku, Tokyo Ozawa Concrete Industry Co., Ltd. F term (reference) 2D025 BA00 4D003 AA01 AA06 CA08 DA30 EA19 EA22 4D040 BB51 CC02 4G019 DA04 LA02 LB04 LC00

Claims (3)

[Claims] 1. A floating island made of porous concrete. 2. The floating island according to claim 1, wherein a salt-tolerant plant is vegetated. 3. The floating island according to claim 1, wherein a floating body is buried in the porous concrete.