JPH0481002B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method that can efficiently purify intake water even if a turbid water phenomenon occurs in a dam lake due to a flood or the like.
More specifically, a sheet-like material with an opening extending horizontally is placed vertically around the water intake of a dam lake, and the precipitation accelerator is applied locally using the rapid flow of lake water generated near the opening. This invention relates to a method for purifying turbid water from a dam, which improves water quality by dispersing and settling turbidity.

[Conventional technology]

Our country's rivers have many rapids and are short, so when they become cloudy due to floods, they drain away within a few days and return to their original clear waters. However, once a dam is constructed, the turbidity composed of fine particles of a few microns or less, such as clay minerals, settles extremely slowly, so the turbid water does not settle during the period that it is stored in the dam lake, and the flow rate decreases. Because the water is released in a controlled manner, it is unavoidable that the river will remain cloudy for a long period of time. Turbid water from dams has a major economic impact on the environment, including river landscapes and freshwater fisheries, as well as on the agricultural, domestic and industrial water sources that use the water.

However, not all dams cause turbid water phenomena, and it depends on the surface characteristics of the catchment area due to the natural environment such as topography, geology, vegetation, and social environment such as development activities, and also depends on the size of the dam. Experience has shown that when the annual exchange frequency index α (=annual total inflow/total reservoir capacity) of dam lake water is 30 or higher, problems with turbid water do not occur. This index α is also an indicator of whether the dam lake is a stratified type (thermocline), and α
If it is small (especially below 10), it becomes a stratified (thermocline) dam lake. The thermocline is formed during the summer when the temperature of the lake water surface rises and the density of the water decreases, but if turbid water flows in due to a flood during this formation period, the temperature of the flood generally becomes lower than that of the lake surface water. Because it is lower and contains turbidity, its density is almost equal to the density at the cline, and the turbid water flows into the lake by sinking into this position. When turbid water enters such a stable stratification, it becomes difficult to dilute and diffuse, and sedimentation of the turbidity is hindered. If a dam takes water from the location of this cline, the water will remain murky for a long time until the water in this layer is exhausted.

One of the measures against turbid water in dam lakes is the selective water intake method.
This is a method of adjusting the water intake level, avoiding areas with high turbidity, and avoiding stirring the lake as much as possible.

Other methods include creating turbid water in a dam due to vegetation in the catchment area, mixing sedimentation accelerators into the entire dam lake, and creating multiple dams upstream to temporarily store turbid water during floods to adjust the water volume. Another method being considered is to release the water downstream through a tunnel.

[Problem that the invention seeks to solve]

The selective water intake method is currently the most effective measure to prevent turbid water, but since the intake port must be raised and lowered mechanically, it is often difficult to change the equipment of existing dams, and it is not a fundamental solution. No. Furthermore, if the scale of the flood increases, the entire area above the thermocline becomes turbid, so there is no effect on selective water intake. This is because if water is taken under the thermocline, the water temperature will drop and have a negative impact on crops. Although protection with vegetation and the installation of sand prevention equipment are effective to some extent, they are impossible in cases where there are landslides or collapses, and in Japan, it is often difficult to completely suppress turbidity in mountainous areas. Furthermore, even if it is attempted to mix the precipitation accelerator into the entire lake water, it is not only very expensive but also impossible to mix and stir, making it impractical. The method of constructing multiple dams upstream requires large-scale civil engineering work, which is not only economically disadvantageous, but also cannot be implemented in cases where the terrain does not allow the construction of multiple dams.

As described above, each of the conventional techniques has various problems to be solved, and at present no countermeasures other than the selective water intake method have been adopted.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, to be able to efficiently purify only effluent water when turbid water occurs using relatively simple equipment, and to provide a selective water intake function. The aim is to provide an economical method that can be used.

[Means for solving problems]

In the present invention, which can achieve the above objects, the sheet-like material regulating the flow of lake water is provided with an opening that extends in the horizontal direction, and the sheet-like material that regulates the flow of lake water is provided with an opening that extends in the horizontal direction, and the water intake or discharge is carried out so as to surround the water intake or water outlet of the dam lake. The device is characterized by being arranged vertically from above the level to below the thermocline, and configured so that the precipitation accelerator is dissipated into the lake water from a dissipation means disposed horizontally along the opening. The dam thereby creates a local rapid flow of lake water near the opening, mixes and stirs the lake water and the sedimentation accelerator, promotes the association of turbid particles and causes them to settle, thereby purifying the discharged water. This is a method of purifying turbid water.

The water intake or water outlet of a dam may be surrounded by only a sheet-like material, or by using the dam lakeshore or the dam itself and surrounding it with a sheet-like material stretched between both banks. good.

The discharge amount from the dam lake is adjusted by the storage amount, and a method for further increasing the effect of the present invention in response to fluctuations in these amounts is to adjust the area of the opening. Thereby, the flow rate of the lake water passing through the opening and the strength of the Karman vortex can be adjusted to achieve the most efficient mixing of the precipitation accelerator into the lake water.

[Effect]

The flow rate of a dam lake is usually very low, about several millimeters per second, depending on its size, but the sheet-like material restricts the flow of the dam lake and only the opening becomes a waterway, so the flow rate near the opening The flow of lake water locally becomes considerably faster, creating Karman vortices that are effective for mixing precipitation accelerators. When a means for dispersing the sedimentation accelerator is provided at the opening, the sedimentation accelerator is mixed and agitated by local rapids of lake water generated near the opening, which promotes association of turbid particles and forms a small amount of sediment. It becomes possible to purify efficiently with an accelerator.

In addition, since dam lakes have a large surface area, by adjusting the installation position of the sheet-like material equipped with means for dispersing the sedimentation accelerator, the turbidity that comes into contact with the sedimentation accelerator and grows to a large particle size can be Sufficient residence time can be provided, so that the lake water discharged from the water intake or outlet will be clean and free of turbid particles.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on the drawings. FIG. 1 is an explanatory diagram of a dam lake showing a method for purifying turbid water from a dam to which the present invention is applied, and FIG. 2 is a sectional view thereof. The dam lake 10 blocks water flowing from the river 12 with a dam 14 and temporarily stores it, and the stored water is discharged downstream from the water intake 16.

Now, in the present invention, as shown in FIGS. 1 and 2, a turbid water prevention fence 18 is installed on the upstream side of the water intake 16 of the dam lake 10 to regulate the flow of lake water.
is provided. In this embodiment, the turbid water prevention fence 18 is a sheet-like material with an opening extending horizontally, which is vertically installed between both lake shores from above the water intake level to below the thermocline layer T, to prevent sedimentation near the opening. Promoting agent dissipation means are provided.

An example of the muddy water prevention fence used in the present invention is shown in FIG. In this example, a sheet-like material 2 has a float 20 attached to its upper part and a weight 22 at its lower end.
4 extends from one lakeshore to the other lakeshore. This sheet 24 has a plurality of openings 26 extending in the horizontal direction, and a chemical liquid injection pipe 28 is provided horizontally along each opening 26. The chemical liquid injection pipe 28 is equipped with a large number of nozzles 30, and has a liquid sending pipe 33 at its upper end.
connected to. Each chemical injection pipe 28 is installed at a predetermined position by a support wire 32, and reinforcing materials made of the same material as the wire 34 or the sheet are provided at both upper and lower ends of the opening 26 to prevent it from opening excessively. It seems like there is no such thing. The liquid precipitation accelerator sent from the liquid sending pipe 33 passes through each chemical injection pipe 28 to the nozzle 3.
It will be pressurized and released into the lake water from zero.

Turbid water phenomena occur significantly in stratified (thermocline) dams where the annual exchange frequency index α of the dam lake is small.
The thermocline (the area indicated by the symbol T in Figure 2) is created by the temperature of the lake water surface rising during the summer, the density of the water becoming smaller, and the flow velocity within the dam lake being lower. During the winter, the surface layer cools, becoming denser and sinking, causing water at the bottom to rise and create a general circulation. Floods, which are the main causes of turbid water, and backwater scouring due to drought occur from summer to autumn, and this is the period when cline T occurs. In the case of small-scale floods, the floodwaters that infiltrate into the lake will infiltrate to the same depth within the lake, depending on the specific gravity determined by the water temperature and the degree of turbidity.
When the scale is larger than that, the entire area above the cline T is mixed and stirred. In addition to the above-mentioned density flow, water flow within the lake includes surface flow influenced by wind and flow at the intake level caused by water intake. Of these, the flow generated by water intake is the largest, but as mentioned above, the flow velocity is extremely small (about a few mm per second).
The velocity distribution of the flow is considered to be a Gaussian distribution curve (see the reference numerals in Figure 2) with the peak at the water intake level.

By the way, when the muddy water prevention fence 18 is provided on the upstream side of the water intake according to the present invention as described above, the flow of lake water is obstructed by the sheet 24, as is clear from FIG. Part 2
6 (see arrow A), the flow velocity locally increases in that part. In the above example, the sheet 24 is suspended from the surface layer of the lake water to below the thermocline layer T. Generally, the water intake is set within the range from the surface layer to the cline T so as not to take in the cold water mass at the bottom of the lake, and the flow at the water intake level can be sufficiently inhibited by the sheet 24. If the sheet 24 is installed vertically below the cline T, the water that attempts to flow below will be intercepted by the dense cold water mass and the flow will be obstructed, so the flow of lake water will only flow through the opening 26. This is because the water passes through the water intake port 16 and reaches the water intake port 16. However, the length of the sheet that should be provided below the cline T is calculated from the difference in water temperature above and below the cline and the pressure generated by obstructing the flow (this pressure is determined by the flow rate and the area of the opening 26). It can be found by This length is unique to each dam lake, and must be determined under the most severe conditions for each dam lake. Of course, if it is economically acceptable, a sheet that reaches the bottom of the lake may be provided. The upper end of the sheet 24 may be located above the water intake level, but it is preferably located at the surface of the lake water.

When the liquid precipitation accelerator is released from the nozzle 30 of the chemical injection pipe 28 provided in the opening 26 (see arrow B in FIG. 4), the opening 26
The precipitation accelerator is mixed and stirred by the Karman vortex, a local rapid current generated near the turbid water, which promotes the association of turbid particles in the turbid water, making it possible to effectively settle and purify the turbid water.

Moreover, this turbid water prevention fence can produce the same effect as selective water intake. In FIG. 5, it is assumed that the water intake port 16 has a fixed structure without a selective water intake function. Now, if the turbid water prevention fence 18 is set at the position shown by the imaginary line and the opening 26 is located at the depth Lb, a flow shown by a Gaussian distribution curve Vb with the apex at this depth Lb will occur. There is.

If a small-scale flood occurs and the density current intrudes into this depth, the turbid water prevention fence 18 is rolled up and set at the position shown by the solid line, and the opening 26 is set at the depth.
Place it in La. Then, the flow of lake water becomes a Gaussian distribution curve Va with the peak at this depth La, and it is possible to prevent the flow of turbid water. In this way, by using a turbid water prevention fence having openings in the horizontal direction, it is possible to have exactly the same effect as selective water intake, and it is also highly effective as a selective water intake device for existing dams.

By the way, the pressure exerted on such a muddy water prevention fence can be classified into three types: hydrostatic pressure, flow pressure, and wave pressure. Of these, the wave pressure generated during strong winds is the largest and depends on the strength of the fence. There is also a risk of destruction. In order to deal with this, a shaft core connected by a universal joint is passed through the center of the float 20, and it is rotated by power from the lake shore or power attached to the float, so that the sheet can be hoisted up. is desirable. By adding such a winding device, it is also possible to adjust the depth position of the opening. In that case, it is necessary to separate the float 20 into joints, and at the same time use a ball joint or the like for the horizontal part of the liquid sending pipe 33 to the chemical injection pipe 28, and use a flexible tube that can be rolled up in the vertical part. use

FIG. 6 shows another example of the pollution prevention fence used in the present invention. Although the means for dispersing the precipitation accelerator is not shown in order to make the drawing easier to understand, it is actually installed as shown in FIG. In this embodiment, two sheets 24, 44 each having an opening 26 are arranged close to each other, and by moving one or both of them relative to each other in the vertical direction, the opening can be adjusted according to the flow of lake water. Part 26
The area can be adjusted freely.

This was devised to obtain the optimum mixing condition of the precipitation accelerator in accordance with the amount of discharged water, and is carried out by the above-mentioned hoisting device.

In the above embodiment, a sheet-like material is stretched between both banks and the dam water intake or water outlet is surrounded using the lake shore and the dam, but the present invention also includes an embodiment in which the dam water intake or water outlet is surrounded by only the sheet-like material. included. In particular, the latter configuration is advantageous in that even if the water level of the dam lake changes, the upper edge of the sheet will move up and down to follow it, making it easier to hold the sheet at an appropriate position. It is.

〔Effect of the invention〕

According to the present invention, the flow of the dam lake is regulated by the sheet-like material to locally form a rapid current or Karman vortex near the opening, and the sedimentation accelerator is diffused from the opening. As a result, the effect of mixing and agitating the sedimentation accelerator and turbid water is extremely high, which promotes the association of turbid particles and allows them to quickly settle on the lake bottom. It becomes possible to purify it.

In addition, according to the present invention, since a turbid water prevention fence with means for dispersing sedimentation accelerator is simply installed vertically, the equipment is extremely simple compared to other methods, and it can be applied to existing dam lakes. In addition, the amount of sedimentation accelerator used is much smaller than when it is dispersed throughout the dam lake, making it possible to treat only the amount of turbid water discharged when the sewage flows downstream, making it extremely economical. It is true.

Furthermore, by adjusting the position of the horizontal opening by rolling up or unrolling the sheet material, selective water intake can be achieved, so even in dam lakes that do not have a selective water intake mechanism, it is possible to prevent turbid water during small-scale floods. This has the effect of making it even more reliable. Another advantage is that when tap water is being taken in, turbid particles will settle in the dam lake, eliminating the need for a sludge treatment facility that would be required to treat the water after it is taken.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the dam lake purification method according to the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is an explanatory diagram showing an example of a muddy water prevention fence suitable for use in the method of the present invention, and FIG. FIG. 5 is an explanatory diagram showing the selective water intake function of the muddy water prevention fence. FIG. 6 is an explanatory diagram showing another example of the muddy water prevention fence. 10...dam lake, 12...river, 14...dam, 16
... Water intake, 18 ... Muddy water prevention fence, 20 ... Float, 22 ... Weight, 24, 44 ... Sheet, 28 ... Chemical injection pipe, 30 ... Nozzle.

Claims (1)

[Claims] 1. Turbid water purification in which a sheet-like material is suspended in water to form a water flow area, and a sedimentation accelerator is dispersed from the vicinity of the sheet-like material to precipitate turbid particles. In the method, the sheet-like material regulating the flow of lake water has an opening extending in the horizontal direction, and is vertically installed from above the water intake or water discharge level to below the thermocline so as to surround the water intake or water outlet of the dam lake. A method for purifying turbid water in a dam, characterized in that the sedimentation accelerator is dispersed into lake water from a dispersion means disposed horizontally along the opening. 2. The method according to claim 1, wherein two sheet-like materials each having an opening are provided adjacent to each other, and the opening area can be adjusted by relative surface movement between the two. 3. The sheet-like material is stretched between both banks of the dam lake on the upstream side of the water intake or water outlet of the dam lake, and surrounds the water intake or water outlet together with the lakeshore and the dam as claimed in claim 1 or 2. Method described. 4. The method according to claim 1 or 2, wherein the sheet-like material is floated by itself so as to surround the water intake or water outlet of the dam lake.