JPH0698246B2 - Dam turbid water purification device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for purifying turbidity in a dam lake caused by flooding, scouring of the bottom of a dam lake, wave erosion of a dam lake shore, eutrophication phenomenon, and the like. .

[Prior Art] Since rivers in Japan are often short and rapid, turbidity due to floods, etc. will flow back to the original clear stream within a few days. However, once the dam is constructed, sedimentation of clay minerals and other fine particles of a few microns or less is extremely slow to settle, so the sediment does not settle within the period until the reservoir flows out of the dam lake, and the flow rate is It is inevitable that the turbidity of the river is prolonged because it is controlled and released.

When the water level of the dam drops during the dry season, sediment and mud in the backwater area are exposed on the water surface, and unconsolidated mud is brought into the dam lake by the river water and turbid water is generated. In addition, nutrients contained in livestock, factories, and domestic wastewater that flow into the dam lake activate biological activities in the lake, which causes turbidity and offensive odors, resulting in eutrophication that deteriorates water quality.

The dam turbid water generated by such various causes has a great economic impact on the environment such as river landscapes and freshwater fisheries, as well as agriculture, domestic water, industrial use, etc. where the water is taken.

However, not all dams cause turbid water phenomena, which depends on the topography, geology, natural environment such as vegetation, social environment such as development activities, and the surface properties of the catchment area, and also depends on the scale of the dam. Empirically, the annual index of the number of dam lake water exchanges α
If the (total annual inflow / total reservoir capacity) is 30 or more, it is said that the problem of turbid water due to flooding will not occur. This index α is also an indicator of whether or not the dam lake is stratified (thermocline) type, and if α is small (especially 10 or less), it becomes a stratified dam lake. The thermocline is formed when the temperature of the lake surface rises and the density of the water decreases in the summer, and when turbid water flows in at this time due to flooding, etc., its temperature is generally lower than that of the lake surface and turbidity. The density of the turbid water is almost equal to that of the stratocline, and turbid water flows into the lake in such a form that it sunk into this position. When turbid water enters such a stable stratification, it becomes difficult to dilute and diffuse, and sedimentation of suspended matter is prevented. If it is a dam that draws water from the position of this layer, turbid water will be prolonged until the water in this layer is exhausted.

The selective water intake method is one of the measures against turbid water in dam lakes. This is a method of adjusting the water intake level to avoid high turbidity and to avoid water agitation in the lake as much as possible.

In addition, methods to prevent the generation of dam turbid water by vegetation in the catchment area, methods of mixing sedimentation accelerators in the entire dam lake, or building a secondary dam upstream to temporarily store the turbid water at the time of flood and adjust the amount of water And then releasing it in a tunnel downstream,
A method of dredging sand is also considered.

[Problems to be solved by the invention] Although the selective water intake method is the most effective turbid water prevention measure at the present time, it may be difficult to change the equipment of an existing dam because the intake has to be mechanically moved up and down. Many,
In many cases, the required degree of cleaning is too high to be handled by selective water intake, and it cannot be a drastic solution. If the scale of flood increases, the entire upper part of the thermocline becomes muddy water, and the effect of selective water intake will be lost.

Although the protection by vegetation and the installation of erosion control facilities are effective to some extent, it is not possible in the case of landslides or collapses, and since the mountains are steep in Japan, it is not possible to completely suppress turbidity by taking measures against them. There are many difficult aspects. In addition, even if it is attempted to mix the precipitation promoter into the whole lake water, it is not only very expensive, but also the mixing and stirring are impossible, so the effect is small. The method of constructing the secondary dam upstream is not only economically disadvantageous because it requires large civil engineering work, but also cannot be implemented in the terrain where the secondary dam cannot be constructed.

As described above, the conventional techniques have various problems to be solved, and at present, no measures other than the selective water intake method are taken.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an economical apparatus capable of efficiently purifying only discharge water when turbid water is generated by a relatively simple facility.

[Means for Solving the Problems] The present invention that can achieve the above-mentioned object is provided with an opening, a float is attached to the upper edge, and a weight is attached to the lower portion, so that the intake or the outlet of a dam is provided. A water-impervious fence that vertically extends from the water surface so as to surround the water intake, or concentrates the water flow toward the intake or discharge outlet through the opening, and arranges a chemical injection pipe along the float. A chemical injection means in which a nozzle at the tip of the chemical injection pipe opens near the opening, and a bubble generator installed in water near the opening,
It is located between the water intake or water discharge outlet and the impermeable fence so as to surround the water intake or water discharge outlet, and a float is attached to the upper edge and a weight is attached to the lower portion so as to hang down from the water surface to the water. This is a configuration having a water-permeable fence that blocks the outflow of suspended water substances.

Here, the "impermeable fence" refers to one that blocks the flow of water and controls the flow of water so that it concentrates almost only at the openings. There are openings and gaps in which water can pass through to some extent.

As a preferred embodiment, the opening formed in the impermeable fence is formed into a rectangular shape cut out just below the water surface, a gutter-shaped water channel is extended from the opening edge to the upstream side, and the medicine injection nozzle is provided on the upstream side. In addition to being provided at the end, the bubble generator is arranged at the bottom of the water channel. It is effective to attach a baffle plate to the water channel.

It is not necessary for the two types of fences to completely surround them around the intake and the like. It is also possible to use both sides of the dam lake to stretch the fences upstream of the intake and the like. In the present invention, "surrounding the intake, etc." also includes a mode in which it surrounds in cooperation with a lake shore, a dam, etc. These fences are suspended in water with a float attached to the upper edge and a weight attached to the lower edge.

[Operation] Normally, the flow velocity of a dam lake is very small, about several mm per second, but the flow of the dam lake concentrates only on the opening so that only the opening becomes a channel by the impermeable fence. The flow in the vicinity locally becomes considerably faster and a Karman vortex is generated. The chemicals supplied from the chemical injection means are sufficiently mixed and stirred by the local rapid flow of the lake water generated near the opening.

When a precipitation promoting agent is used as a drug, the suspension particles are promoted to be associated with each other and the particles and the precipitation promoting agent, so that the particles can be efficiently purified with a small amount of the drug. At this time, if large bubbles are generated from the bubble generator, the mixing and stirring can be performed more efficiently. In the case of dam lakes with advanced eutrophication, plankton is often the main turbidity, and if these are settled, the water quality in the dam lake may be further deteriorated. At that time, it is also possible to float and separate the suspended matter by selecting an appropriate agent such as a surfactant, operating the bubble generating device, supplying fine bubbles and adhering them to the suspended matter. This bubble generation
It also effectively acts on the decomposition and purification of organic matter in water evaluated by BOD (biochemical oxygen demand) and the like.

In the present invention, the entire lake water is not targeted for purification, but only the turbid water passing through the opening is targeted,
It is economically very advantageous in combination with the small amount of treatment and the effect of stirring the chemicals.

The mesh-like water-permeable fence provided inside the impermeable fence has the function of preventing the aggregated particles or suspended particles from flowing out to the intake, etc. In addition to forming an accumulation area of suspended matter between
The vicinity of the water-permeable fence becomes a turbidity concentrated part called a slurry blanket, and also functions to occlude and adhere fine turbidity in water. The water-permeable fence also acts to reduce the area of the fence that surrounds the water intake and the like. as a result,
It is possible to remarkably reduce the constraint of strength against water pressure applied to each fence.

[Embodiment] FIG. 1 is a layout view showing an embodiment of a dam turbid water purification device according to the present invention, and FIG. 2 is a sectional view thereof. Dam lake 10
Is for damming the running water from the river by the dam 12 and storing it once, and the stored water is discharged from the intake 14.

In the present invention, an impermeable fence 16 is provided so as to surround the intake 14 of the dam lake 10, and a fence 18 such as a net is provided between the fence 16 and the intake 14. As the impermeable fence 16, for example, a synthetic resin film, a non-woven fabric, a dense woven fabric or the like is used. These fences 16,1
8, a float 20 is attached to the upper edge and a weight 22 is attached to the lower edge, and they are vertically hung from the water surface to below the thermocline T. The impermeable fence 16 is provided with an opening 24 in a part thereof, and has a function of concentrating the flow of lake water substantially only in the opening 24. In addition to these fences, the device according to the present invention comprises a drug injection means for supplying a drug to the flow of lake water through the opening 24 and a bubble generating device for passing air through the flow.

Details of the impermeable fence 16 and the flow path connected to it are shown in FIG. The opening 24 is formed by cutting out a part of the upper end of the fence 16 in a rectangular shape, and a gutter-shaped water channel 30 extends from the opening 24 to the upstream side. The trough-shaped water channel 30 is also formed by a water-impermeable sheet, and the float 20 is attached to the upper portion and the weight 22 is attached to the lower portion to maintain a predetermined shape. This waterway is an impermeable fence 16 as shown in Fig. 1.
A plurality of them may be provided at appropriate places.

The medicine injection pipe 32 is arranged along the float 20, and the nozzle 34 at the tip thereof opens near the upstream end of the water channel 30.
A bubble generator 36 is attached to the bottom of the water channel 30. A baffle plate 38 is preferably attached inside the water channel 30. The chemical solution is diffused into the lake water from the nozzle 34 through each chemical solution injection pipe 32. Pressurized air is supplied to the bubble generation device 36 through the air supply pipe 40 to generate fine bubbles in the flow containing the drug.

Next, the operation of the device of the present invention will be described with reference to FIGS. A fence 16 is hung around the water intake 14 from the water surface to below the thermocline T, and the water intake 14 is set within the range from the water surface to the thermocline T so as not to take in cold water mass at the lake bottom. Since this is common, intake level flow is well regulated by this fence 16. This is because, if the water is hung vertically below the stratocline T, the water flowing therebelow is caught by the cold water mass having a high density and the flow is obstructed. Therefore, all of them try to flow through the water passage 34 and the opening 24 (see arrow A), and the flow velocity at that portion locally increases.

The water channel 30 has a function of promoting the mixing and stirring of the inflowing lake water and the injected chemical solution. When it is desired to precipitate the suspended matter, a precipitation accelerator is supplied from the nozzle 34. As a result, the lake water and the precipitation promoting agent are mixed and stirred, and after passing through the opening 24, the turbidity aggregates and becomes large and the flow velocity extremely decreases, and the sedimentation immediately occurs. At this time, if large bubbles are generated from the bubble generator 36, the mixing and stirring can be further promoted. The mesh fence 18 serves to prevent suspended matter from reaching the intake 14. In the vicinity of the mesh fence 18, diatoms and suspended matter adhere to form a suspended matter concentrated portion (slurry blanket), which acts as a kind of filter medium and promotes purification of flowing water. In the case of a dam lake where eutrophication has progressed, chemicals such as surfactants are supplied and minute bubbles are emitted from the bubble generation device 36 to attach bubbles to turbidity, thereby causing plankton, etc. Impervious fence separating the suspended matter 42 of the
Collect in the area between 16 and the mesh fence 18.

Generally, as a method for removing suspended matter, separation by sedimentation,
Although there are separations by levitation and separation by adhesion, in the present invention, it is possible to select sedimentation and adhesion or floatation and adhesion according to the properties of inflowing muddy water and to perform separation under optimum conditions.

In the above embodiment, the water channel is connected to the opening of the water impermeable fence, but only the opening may be used. If a water channel is provided and a baffle plate or the like is further attached, the mixing and stirring distance with the chemical solution becomes long, the effect of the chemical solution can be sufficiently enhanced, and the interval between both fences can be shortened, which is advantageous in that the device can be downsized. Although a mesh fence is used as the water-permeable fence in the above-mentioned embodiments, a fence having a large number of holes, a fence-shaped fence, or a fence-shaped fence may be used instead. Of course, a fence may be provided up to the bottom of the lake. Further, by constructing such a fence between the two shores of the dam lake, a part such as the intake may be surrounded. Both fences can also have multiple structures. In order to control the amount of flow, a mechanism that can change the size of the opening may be provided, or the water channel may be opened and closed.

By the way, the pressure applied to such a fence is the hydrostatic pressure,
It can be considered by classifying into three types of fluid pressure and wave pressure, but the wave pressure generated during strong wind is the largest. In order to deal with this, it is desirable to have a structure in which the fence can be rolled up by the power from the lake shore or the power attached to the float.

EFFECTS OF THE INVENTION According to the present invention, the flow of the dam lake is regulated by the fence so that the rapid flow is locally formed to supply and mix the drug, so that the drug and the muddy water can be efficiently mixed and stirred. It can be carried out, and has an excellent effect that the removal of suspended matter is promoted. When a precipitation accelerating agent is used as a drug, the association of suspended particles is promoted, and the particles are concentrated between the suspended particles and the fence to facilitate sedimentation removal. When the suspended matter is a harmful substance or an organic substance, the suspended matter can be floated and separated and collected by using a surfactant or the like and adhering fine bubbles.
In other words, according to the present invention, three types of suspended matter removing methods, that is, sedimentation, floating, and adhesion, can be used properly, so that it has an extremely excellent effect of being able to deal with any suspended matter.

Further, in the present invention, since the structure surrounds the water intake, etc., the chemicals are added only for the amount of water intake, and the mixture is mixed and stirred for separation, which is different from the case where the water volume of the entire dam lake is treated. The amount can be greatly saved, and a stirring flow can be created in the dam lake which is almost stationary without using any power, whereby the drug can be effectively acted, and the present invention deteriorates the muddy water condition. Since it is only necessary to drive the vehicle, the operating cost is low and it is extremely economical.

Further, since the present invention is made of a relatively flexible material, it has an excellent effect that it can be easily installed and maintained and can be applied to an existing dam.

[Brief description of drawings]

FIG. 1 is a layout drawing showing an embodiment of a dam turbid water purification apparatus according to the present invention, FIG. 2 is a sectional view thereof, and FIG. 3 is an explanatory view showing an example of an impermeable fence and a water channel connected to it. Fourth
FIG. 5 and FIG. 5 are operation explanatory views of the device according to the present invention. 10 …… Dam lake, 12 …… Dam, 14 …… Intake, 16 …… Impermeable fence, 18 …… Mesh fence, 24 …… Opening, 30
...... Water channel, 32 …… Chemical injection pipe, 34 …… Nozzle, 36…
… Bubble generator.

Claims (1)

[Claims] 1. An opening is provided, a float is attached to the upper edge, and a weight is attached to the lower part, and it is hung vertically from the water surface so as to surround the intake or outlet of the dam, and goes to the intake or outlet. A water-impermeable fence that concentrates the water flow so as to pass through the opening, and a medicine injection pipe that is arranged along the float, and a nozzle at the tip of the medicine injection pipe opens near the opening, and medicine injection means, A bubble generator installed in the water in the vicinity of the opening, and between the water intake or the water discharge outlet and the impermeable fence are located so as to surround the water intake or the water discharge outlet, and float at the upper edge. , A dam turbid water purification device having a water-permeable fence that has a weight attached to the lower part to prevent the outflow of turbid water substances suspended from the water surface into the water.