JPH0613115B2 - 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.

Dam turbid water caused by such various causes has a great economic impact on environments such as river landscapes and freshwater fisheries, as well as agriculture, domestic water, or industrial use that uses the water.

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 nature of the surface 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 (= 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 index of whether the dam lake is stratified (thermocline) type. If α is small (especially 10 or less), it becomes a stratified dam lake. The thermocline is formed when the surface temperature of the lake rises and the density of the water decreases in the summer, and when turbid water flows in during this period, the temperature is generally lower than that of the surface water and 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 throughout the dam lake, or building a secondary dam upstream to temporarily store the turbid water during floods and adjust the water volume And then releasing it in a tunnel downstream,
Methods such as dredging sediment are also being 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, if the precipitation accelerator is mixed in the whole lake water, it is not only very expensive, but also expensive because the mixing and stirring is impossible. 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] In the present invention that can achieve the above-mentioned object, a float is attached to the upper edge and a weight is attached to the lower portion so as to surround a water intake or a water outlet of a dam. Impermeable fence that hangs in water from above, and float on the upper edge, attach a weight to the lower part to keep the shape like a gutter, and pass through the notched opening just below the water surface of the impermeable fence. The water conduit extending to the bottom, an air bubble generator installed at the bottom of the water conduit near the tip, and the water intake or water discharge port and the impermeable fence so as to surround the water intake or water discharge port. It is a structure having a water-permeable fence which is located at the upper edge and has a float attached to the upper edge and a weight attached to the lower portion so as to hang vertically from the water surface into the water.

Here, the "impermeable fence" refers to one that blocks the flow of water and controls the flow so that the water flow is concentrated almost exclusively in the headrace, and "permeable fence" is structurally numerous. There are openings and gaps in which water can pass through to some extent.

Further, it is desirable to arrange a drug injection means in the water conduit so that various coagulants and the like can be mixed.

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.

[Operation] Normally, the flow velocity in a dam lake is very small, about several mm per second, but since the flow of the dam lake is restricted by the impermeable fence and concentrates only in the headrace, the flow in the headrace is local. It becomes considerably faster and a Karman vortex is generated, and it is sufficiently stirred.

The fine bubbles generated from the bubble generating device adhere to the suspended matter, whereby the suspended matter floats and separates. If a coagulant is added at the same time, the agitation effect further promotes the association of the suspended particles with each other, and it becomes possible to efficiently purify with a small amount of the drug.

In the present invention, the entire lake water is not targeted for purification, but only the turbid water that passes through the headrace is targeted for processing. Therefore, it is economically very advantageous even when a small amount of chemical is used and a chemical is used. is there.

The mesh-like water-permeable fence provided in the enclosure of the impermeable fence functions to partition the accumulation area of suspended suspended suspended matter, and prevents aggregated suspended suspended matter from flowing out to the intake port. In addition to the function of preventing it, the vicinity of the water-permeable fence also functions as a turbidity concentrated part called a slurry blanket that absorbs and adheres fine suspended matter in water. Therefore, due to the action of the water-permeable fence, it is possible to reduce the area of the fence surrounding the water intake and the like, and it is possible to significantly reduce the restriction of the strength against the 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 1
No. 0 means that the water flowing from the river is dammed by the dam 12 and stored once, and the stored water is discharged from the intake 14.

In the present invention, a water-impermeable fence 16 is provided so as to surround the intake 14 of the dam lake 10, and a net-like fence 18 is provided between the fence 16 and the intake 14.
As the water-impermeable fence 16, for example, a synthetic resin film, non-woven fabric, dense woven fabric, or the like is used. The fences 16 and 18 have a float 20 attached to the upper edge and a weight 22 attached to the lower edge, and are suspended from the water surface to below the thermocline T by these. A plurality of openings 24 are formed in the water-impermeable fence 16, and a gutter-shaped water conduit 30 is connected to the openings 24. The impermeable fence 16 has a function of restricting the flow of lake water and concentrating it only on the water conduit 30. The apparatus according to the present invention includes, in addition to the fence and the water conduit 30, a bubble generating device 36 for imparting fine bubbles to the flow of lake water passing through the water conduit 30.

The details of the water-impervious fence and the water conduit connected to the opening 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.
A trough-shaped water conduit 30 is extended from 4 to the upstream side. The trough-shaped water conduit 30 is also formed of 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. As shown in FIG. 1, a plurality of water conduits 30 may be provided at appropriate places on the impermeable fence 16.

In this embodiment, a pipe 32 for injecting a drug is provided and is arranged along the float 20, and the nozzle 34 at the tip thereof opens near the upstream end of the water channel 30. The bubble generating device 36 is the headrace 3
It is attached to the bottom of 0. It is desirable to install a baffle 38 inside the water conduit 30. The chemical liquid is diffused into the lake water in the water conduit 30 from the nozzle 34 through each chemical liquid injection pipe 32. Aerated water is supplied to the bubble generator 36 through a pipe 40 to generate fine bubbles in the flow.

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 surface of the water 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 it is general, the flow at the intake level is sufficiently 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, since all of them try to flow through the water conduit 34 (see arrow A), the flow velocity at that portion locally increases.

The water conduit 30 has a function of promoting mixing and stirring of the inflowing lake water and the chemical solution to be injected and adhesion of fine bubbles. An inorganic or organic flocculant is supplied from the nozzle 34.
As a result, the lake water, the fine air bubbles, and the coagulant are mixed and stirred, and the suspended matter aggregates and the air bubbles adhere to the surface to float. The suspended suspended matter 42 collects in the area between the impermeable fence 16 and the mesh fence 18. In addition, the mesh fence 18 serves to prevent suspended matter from reaching the water intake port 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.

If a baffle plate etc. is attached to the water conduit as in the above embodiment,
This is advantageous in that the stirring distance of the lake water becomes long, the effect of floating separation can be sufficiently enhanced, the interval between both fences can be shortened, and 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 conduit may be opened and closed.

In the above embodiment, the water conduit is provided upstream of the water impermeable fence. This has the advantage that the area enclosed by the impermeable fence can be reduced. However, the water conduit may be provided on the downstream side of the impermeable fence. Then, there is an advantage that it is easy to keep the headrace in a predetermined shape. Of course, it is also free to install it on the upstream side and the downstream side of the impermeable fence.

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 and the rapid flow is locally formed by the water conduit to adhere the fine bubbles, so that the muddy water can be efficiently stirred. The excellent effect that floating of suspended matter is promoted by the adhesion of fine bubbles is exhibited. Since the suspended turbidity accumulates in a narrow area between the water-permeable fence and the water-impermeable fence, the removal thereof is extremely easy.

Further, in the present invention, since it is a structure that surrounds the water intake, etc., it will be treated only for the amount of water intake and stirred to separate,
Even when a chemical is used unlike the case where the water volume of the entire dam lake is treated, the amount of the chemical used can be greatly saved, and a stirring flow can be created in the dam lake that is almost stationary without using any power. In addition, since the operation can be performed only when the muddy water state deteriorates, the operating cost is low and it is extremely economical.

Further, since the present invention has a relatively simple structure, it has an excellent effect that it can be easily installed and maintained and can be easily 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 port, 16
…… Impermeable fence, 18 …… net fence, 24…
… Opening part, 30 …… water conduit, 36 …… bubble generator.

Claims (1)

[Claims] 1. An impermeable fence vertically suspended from the water surface so as to surround a dam intake or discharge port with a float attached to the upper edge and a weight attached to the lower portion, and a float attached to the lower edge. A weight is attached to the gutter to maintain the shape like a gutter, and a water conduit extending so as to pass through an opening cut out just below the water surface of the impermeable fence, and bubbles installed on the upstream side bottom of the water conduit. It is located between the generator and the water intake or water discharge port and the impermeable fence so as to surround the water intake or water discharge port. A device for purifying dam turbid water, which has a vertically permeable fence.