JPH0716662B2 - Plankton growth control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing the growth of plankton, which often propagates in the surface layer of water storage areas such as dams and lakes.

[0002]

2. Description of the Related Art In water storage areas such as dams that have become eutrophication, plankton proliferates actively in the light-bearing layer of the surface layer when the water temperature rises and the amount of solar radiation increases from early summer to autumn. Plankton colonies such as cyanobacteria and green algae are generated. Such a plankton community makes the water surface of the water storage area dirty and deteriorates the hydrophilicity of the water storage area, thereby deteriorating the environment of the water storage area. Further, it causes an off-flavor in the tap water to deteriorate the quality as drinking water, and causes troubles such as clogging of the water treatment facility.

Therefore, conventionally, as a means for suppressing the growth of such plankton, a method of spraying a chemical such as copper sulfate on the water surface of the water storage area, or pumping up the water of the water storage area with a pump and adding sulfuric acid or hydrochloric acid thereto. Alternatively, a method has been adopted in which the activity of plankton contained in the pumped water is reduced by adding and mixing sulfurous acid gas, and then the water is returned to the original storage area.

[0004]

However, in the above-mentioned conventional method, since chemicals are used, there is a risk that the chemicals may remain in the water storage area and pollute the surrounding environment. The present invention has been made in view of such problems of the conventional art, and an object of the present invention is to provide a method capable of effectively suppressing the growth of plankton without using a chemical agent.

[0005]

In order to achieve the above object, the plankton suppressing method of the present invention takes out water containing plankton in the surface layer portion of a water storage area and removes the water in a predetermined space.
Hold for more than a second, crush the plankton air bubbles contained in this water by pressurizing the water to 0.4 MPa or more in this space, then returning this water to the water storage area,
It is characterized in that the water containing plankton in which the air bubbles are crushed is allowed to settle in a deep layer in the water storage area.

[0006]

[Function] Algae, which are representative of plankton existing in the surface layer of the water storage area, have a specific gravity slightly higher than 1,
It is considered to be suspended in water because it has air bubbles and oil droplets in the cells. Fig. 1 shows the appearance of cells of the blue-green alga Microcystis. In this figure, the white honeycomb-like portion A or the rod-like portion B is the alveolar cell, There are air bubbles.

In the method of the present invention, the water containing such plankton is taken out from the surface layer of the water storage area, retained in a predetermined space for a certain period of time, and pressurized to crush the air bubbles in the cells of the plankton. FIG. 2 shows photographs of microcystis cells observed with an optical microscope before and after pressurization. 2A corresponds to before pressurization, and FIG. 2B corresponds to after pressurization. In the cells shown in the central portion of FIG. 2A, white cells are vesicles, which are shown in FIG. 2B. Can be seen to disappear and the inside of the cell has become uniform.

When the pressurized water is returned to the water storage area, the plankton contained in this water and having a significantly reduced buoyancy due to the disappearance of air bubbles cannot exist in the euphotic layer and settle in the deep layer. become. That is, the plankton that existed in the euphotic layer before the water intake was driven to the deep layer where the solar radiation did not reach, and the plankton that had been driven to this deep layer could not perform photosynthesis, resulting in a decrease in activity.
Therefore, the number of plankton existing in the light-bearing layer capable of actively performing photosynthesis is reduced, so that the proliferation of plankton is suppressed.

On the other hand, FIG. 3 examines the difference in the plankton sedimentation rate when the pressure is changed among the pressurizing conditions for the microcyste and formium of cyanobacteria, which are the representative plankton that cluster in the water storage area. The graph of the result is shown. Here, the sedimentation rate is measured after each pressure is applied for 5 seconds and allowed to stand for one day. As can be seen from this graph, the plankton's settling rate increases as the pressure value increases, but the increase rate of the settling rate becomes extremely small with the inflection point at a pressure of 0.4 MPa. In the invention, the pressure value of pressurization is 0.4 MPa or more.

FIG. 4 shows the results of examining the relationship between the pressurization time and the plankton abundance for each alga.
FIG. 4A shows the results in the case of Microcystis, FIG. 4B shows the results in the case of Pandrina of green algae, and FIG. In particular, formium is the cause of the offensive odor of tap water. As can be seen from this graph, the plankton abundance rate rapidly decreases when the pressurization time is up to 5 seconds, but when the pressurization time is 5 seconds or more, the degree of decrease almost reaches a saturation state. Pressure time 5
More than a second.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a schematic diagram showing a fountain ship capable of implementing the method of the present invention. This fountain boat is used by floating it on the surface layer of the water storage area 1. It is equipped with a hull portion 11 provided with a device for taking out water from the water storage area 1 and pressurizing the water, and above it. And a sprinkler 12 provided with a device for returning the pressurized water into the water storage area 1.
Below the hull portion 11, a water intake device 2 for taking in surface water is connected.

A pump 3 for pressurization, which is connected to the water intake device 2 by a pipe 2a, and a storage tank 4 which is connected to the pump 3 by a pipe 3a, are installed at the bottom of the hull portion 11. The storage tank 4 is provided with a pressure control valve 41 so that the pressure inside the storage tank 4 can be set to a predetermined value. Further, in this storage tank 4, as shown in FIG. 6, an elbow pipe 42 bent upward by 90 ° is arranged inside the inlet side, and a circulating flow is generated in water flowing from the pipe 3a, The inflow water does not flow to the outlet 43 side as it is and stays in the storage tank 4 for a predetermined time.

Further, in this storage tank 4, FIG.
As shown in (a) and (b), an exhaust valve 44a is provided above the water level gauge 44 for adjusting the storage time. For example, opening this exhaust valve 44a allows the compressed air in the storage tank 4 to escape. By lowering the water level and reducing the amount of stored water, the pressurization time for the water flowing into the storage tank 4 can be shortened.

The outlet of the storage tank 4 is connected to a pipe 5 directed to the upper sprinkler 12, and the pipe 5 branches into three branch pipes 5a to 5c to form the sprinkler 12. Are connected to the respective headers 6a to 6c. Each of the headers 6a to 6c has a watering nozzle 7 at predetermined intervals.
Is installed. Further, an upward pipe 3b is branched and connected to a midway portion of the pipe 3a connecting the pump 3 and the storage tank 4, and the tip of the pipe 3b has a sprinkling port above the uppermost header 6c. It is connected to the launch nozzle 8. The launch nozzle 8 is a sprinkler of a fountain and is installed for the purpose of giving a landscape.

In addition to the hull portion 11, a control panel 11a and a dehumidifier 11b are provided inside, and an outdoor illumination lamp 1 is provided at the upper outside.
1c, the air blower 11d, etc. are installed. Therefore, by operating the pump 3, the surface water in the water storage area 1 is introduced from the water intake device 2 into the storage tank 4. Here, for example, if the pressure adjusting valve 41 and the exhaust valve 44a are adjusted so that the pressure in the storage tank 4 is 0.5 MPa and the pressurizing time is 5 seconds, the surface water in the storage tank 4 is adjusted. The plankton such as the microalgae Microcystis and Fordium that were introduced together with the plankton disappeared due to the destruction of the air cells of the cells by pressurization.

After pressurizing for a certain period of time, the water discharged from the storage tank 4 passes through the pipe 5 and the branch pipes 5a to 5c toward the headers 6a to 6c, is jetted from each water spray nozzle 7, and is stored in the water storage area. Go back to 1. At this time, since the plankton contained in the water does not have air bubbles, the buoyancy is remarkably reduced and the plankton settles in the deep layer of the water storage area 1. In this way, the plankton is driven from the surface layer, which is the light layer, to the deep layer where the solar radiation does not reach, so that the number of plankton that can be photosynthesized is reduced and the proliferation of plankton is suppressed.

[0017]

As described above, according to the present invention, the water containing plankton is pressurized to crush the air cells in the cells to significantly reduce the buoyancy of the plankton. Plankton existing in the surface water is allowed to settle in the deep layer. As a result, the number of plankton existing in the surface layer portion, which is a light-emitting layer, is reduced, so that the growth of plankton is effectively suppressed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing cells of Microcystis, which is an example of plankton existing in a water storage area.

FIG. 2 is a photograph showing the morphology of an organism for explaining the action of the present invention.

FIG. 3 is a graph showing the results of examining the difference in plankton sedimentation rate when the pressure is changed among the pressurizing conditions in the present invention.

FIG. 4 is a graph showing the results of examining the relationship between the pressure time and the abundance of plankton in the pressurizing conditions of the present invention.

FIG. 5 is a schematic diagram showing a fountain ship capable of implementing the method of the present invention.

FIG. 6 is a side view showing the storage tank in FIG.

FIG. 7 is an explanatory diagram showing a storage tank in FIG.

[Explanation of symbols]

 1 Reservoir Area 2 Water Intake Device A Air Vessel B Air Vesicle

Claims (1)

[Claims] 1. The water containing plankton in the surface layer of the water storage area is taken out and held in a predetermined space for 5 seconds or more, and the water is contained in the water by pressurizing the water to 0.4 MPa or more. A method for suppressing the growth of plankton, which comprises crushing plankton air vesicles, returning the water to the water storage area, and allowing water containing plankton crushed in the water vesicles to settle in a deep layer in the water storage area.