JP2004049960A - Environmental cleaning method for eutrophication water area - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for persistently cleaning a water area by simply removing eutrophication substances. <P>SOLUTION: The method consists of a combination of the aeration from the bottom of a place for cleaning water by feeding air into the front strata of bottom sediment to promote the survival of organisms, and non-fed culture. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the development of a method for purifying the environment of a eutrophic water area and contributing to the fishing industry.
[0002]
[Prior art]
Coastal waters have long contributed to mankind as a place of familiarity with water or a place of production, but recently, the generation of anoxic water mass due to an increase in inflow load and attenuation of natural purification systems And the like, the original function of water is being impaired.
[0003]
This is mainly due to the fact that oxygen is consumed for decomposing the organic matter excessively accumulated in the water area, but it is a problem that cannot be dealt with merely by mineralizing incoming domestic wastewater and the like.
[0004]
Conventionally, dredging and sedimentation have been used as a method of purifying the environment of eutrophic waters, but both are only temporary effects, and sand covering and water flow promotion are fundamental eutrophic substances. Although dredging can remove eutrophic substances, other problems may arise in the treatment of the dredged soil.
Even with other methods, the eutrophic substances could not be reused, and the continuous input of funds was required, and the economic burden on the implementing bodies such as local governments was heavy.
[0005]
[Problems to be solved by the invention]
It is an object of the present invention to develop a method for easily removing eutrophic substances and continuously purifying water bodies.
[0006]
[Means for Solving the Problems]
The present inventors have made intensive efforts to solve the above-described problems, and as a result, have found that it can be solved by a combination of aeration from the water bottom and non-feeding type aquaculture.
[0007]
That is, the present invention provides (1) a method of purifying water by sending air to the surface of the sediment and promoting survival of living things;
(2) The method for purifying water according to (1), wherein the organism is a feed-free aquaculture organism and is a filter-eating organism.
(3) The method for purifying water according to (2), wherein the filtered food-eating organism is any of oysters, clams, and sea cucumber.
Growing an organism requires a lot of food, but it produces a lot of false feces.
[0008]
The present inventors have completed the present invention from the viewpoint that continuous purification is performed for the first time by purifying also including the artificial feces.
[0009]
The present invention seeks to achieve water purification by ensuring sufficient dissolved oxygen even in the surface layer of sediments, incorporating pseudofeces of cultured organisms into benthos, and using nutrients thoroughly to the end. Is what you do. If the number of creatures with bottom sediment, for example, creatures, increases, they become food for fish and shellfish, and eventually lead to an increase in fish and shellfish.
[0010]
By aeration near the water bottom, the water mass increases the dissolved oxygen concentration and at the same time generates a gentle vertical circulation flow. As a result, even in the case of benthic organisms, they do not die due to anoxia, and in particular, the filter-eating organisms can capture a large amount of food in the flow induced by aeration.
Oysters and clams also have the function of clearing water, so that the amount of sunlight that permeates into the water increases, thereby promoting the creation of seaweed beds and helping to form a spawning ground for fish and shellfish.
[0011]
In order to recover the eutrophic substance, it is preferable to use a filter-eating bivalve. For example, those that adhere to the base such as mussels and oysters, those that appear on the surface of sediments such as scallops, and those that are buried in sediments on the seabed such as clams and clams, and the like, By taking in suspensions and plankton at lower production levels, eutrophic substances can be recovered efficiently.
[0012]
In addition, sea cucumber swallows the bottom mud and feeds on organic matter contained in it, such as small crustaceans, fish eggs, mollusk larvae, detritus, and diatoms, so sea cucumber purifies organic matter on the sea floor. .
The comprehensive and complex activation of the inner bay ecosystem as described above is intended by the present invention.
[0013]
Estimation of the economic effect, which is one of the features of the present invention, shows that, taking Omura Bay as an example, the area occupied by the purification system required to take in all the annual inflow load is about one-third of the entire bay. Annual expenses were about 78 billion yen, revenue was 237.0 billion yen, and annual revenue was about 159.0 billion yen.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
(Experimental example 1) Suspension filtration experiment using clams As shown in Fig. 1, left and right beakers were equipped with devices for stirring and aeration, and filled with water filtered through a 100-micron filter. Insert 10 clams only in the right beaker.
[0015]
The same amount of muddy water in which the clay was dissolved was injected into the left and right beakers, and left for 1 hour, 2 hours, 2 hours 30 minutes, 3 hours, and 4 hours for observation. After 3 hours, the beaker with the right clam became almost transparent, but the beaker without the left clam remained muddy.
In a similar experiment on oysters, it became clear 10 times faster than in clams.
[0016]
(Experimental example 2) Aeration characteristics experiment As shown in Fig. 2, the water temperature, salinity, and DO concentration at nine points from point (1) near the floating pier to point (9) far from the floating pier were compared before and after aeration at each water depth. The value after aeration was measured. FIG. 3 is a graph of the measurement result. The amount of aeration was about 1 L / min per meter of the aeration tube.
[0017]
From this graph, it can be seen that the water temperature becomes almost constant irrespective of the water depth due to the aeration even for a short elapsed time of less than 2 hours, and the difference between the salinity and the DO concentration depending on the water depth is reduced. That is, it was proved that the mixing in the vertical direction actually occurred even in the open section.
[0018]
Regarding the amount of aeration, “Study of appropriate dissolved oxygen concentration in fishing grounds” (Fishing ground environmental capacity development project report, Japan Fisheries Resource Conservation Association, pp.931-1003 (1989)), as a study by the present inventors and others, In summary, we concluded that the minimum amount of dissolved oxygen that must be maintained at the fishing bay in the bay was 3.0 ml / l. "(P1003) In addition, it is required that the bottom layer has a DO concentration of 3.0 ml / l or more.
[0019]
【Example】
Aerating pipes will be laid on the sea floor, and aeration will be performed for about three months in summer, when the water area tends to become anoxia.
Laying spacing aeration pipe, an aeration amount of induced flow by aeration, in consideration of the oxygen consumption by the organism and the water mass, mud, so that the dissolved oxygen concentration of 3 ml / l or more concentrations up to water bottom adjust.
[0020]
In this way, non-feeding aquaculture such as filter-eating bivalves is performed in a water area where the whole water mass can secure a dissolved oxygen concentration of 3 ml / l or more throughout the year. For example, in oyster cultivation, 16 oyster rafts with a size of about 8 × 18 m are installed on a 100 m square sea surface and cultured throughout the year. At this time, the necessary aeration is performed by using an air compressor of about 7.5 kW and operating continuously for about three months from July to September. The length of the aeration tube is 100 m, and depending on the depth of the body of water, two to three tubes are suitable.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION By this invention, it became possible to purify a eutrophic water area easily and continuously, and to purify continuously while increasing profit.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of the present invention.
FIG. 2 shows a suspension filtration experiment using clams.
FIG. 3 is a diagram showing a characteristic experiment of aeration.
FIG. 4 is a graph showing the results of an aeration characteristic experiment.

Claims (3)

A method of purifying water by sending air to the surface of the sediment of eutrophic waters and promoting the survival of living organisms. The method for purifying water according to claim 1, wherein the organism is an unfeedable organism and is a filter-eating organism. The method for purifying water according to claim 2, wherein the filter-eating organism is any of oysters, clams, and sea cucumber.

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