JPS61155508A - Cleaning method of turbid water in dam - Google Patents

Abstract

PURPOSE:To clean up the water of a dam by a simple facility in which a sheet material having an opening is hung down from a place higher than the intake level down to the temperature-changing layer and a precipitation accelerator is dispersed from a disperser provided to the sheet. CONSTITUTION:The flow of water is interrupted by the sheet 24 of a water disturbance preventive fence 18 and passed through an opening 26 to an intake port 16 with partly increased speeds. When a liquid precipitation accelerator from the nozzle 30 of a grout injection pipe 28 is dispersed, the precipitation accelerator is mixed with stirring by local rapid stream and Kalman swirl generated in the neighborhood of the opening 26, thereby accelerating the aggregation and precipitation of suspended particles in turbid water to clean up it.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for efficiently purifying intake water even if a turbid water phenomenon occurs in a dam lake due to a flood or the like.
A sheet-like material with an opening extending in the horizontal direction is vertically installed on the upstream side of the water intake of a dam lake across both lake shores, and the sedimentation accelerator is locally dispersed using the rapid flow of lake water that occurs near the opening. The present invention relates to a method for purifying turbid water from a dam, which improves water quality by settling turbid substances.

[Prior Art] Rivers in Japan 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, turbidity composed of fine particles of a few microns or less, such as clay minerals, settles extremely slowly. Because the water is released in a controlled manner, it is inevitable that rivers will become 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.
It depends on the surface characteristics of the watershed, including the natural environment such as topography, geology, and vegetation, and the social environment such as development activities, as well as the scale 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 more, 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 lO), the lake 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, which prevents the turbid from settling. If a dam takes water from the cline, the water will remain murky for a long time until the water from 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 to avoid areas with high turbidity and to avoid agitating the lake as much as possible.

Other methods include preventing the occurrence of turbid water in dams using 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 discharge the water downstream through a tunnel.

[Problems to be solved by the invention] The selective water intake method is currently the most effective measure to prevent turbid water, but since the water intake must be raised and lowered mechanically, it may be difficult to change the equipment of existing dams. In most cases, it cannot be a fundamental solution. 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. Further, even if it is attempted to mix a precipitation accelerator into the entire lake water, it is not only very expensive but also impossible to mix and stir, making it impracticable. 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 that need to be solved, and at present no countermeasures outside of the Selective Water Intake Law have been taken.

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 also provide a selective water intake function. The aim is to provide an economical way to wander around.

[Means for solving the problems] The present invention, which can achieve the above objects,
The sheet-like material regulating the flow of lake water has an opening extending in the horizontal direction, and extends from above the water intake or water discharge level to below the thermocline level on both sides of the dam lake on the upstream side of the water intake or water outlet of the dam lake. The method is characterized in that the sedimentation accelerator is dissipated into the lake water from the dispersion means disposed horizontally along the opening. This is a method of purifying turbid water from a dam by creating local rapids of lake water nearby, mixing and stirring the lake water and a sedimentation accelerator, promoting the association of turbid particles and causing them to settle, thereby purifying the discharged water.

The discharge amount from the dam lake is regulated by the storage amount, and one way to further increase 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's curvature can be adjusted to achieve the most efficient mixing of the precipitation accelerator into the lake water.

[Function] The flow rate of a dam lake is usually very small, about several centimeters 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. The flow of lake water in the vicinity becomes locally quite fast, 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, so that association of turbid particles is promoted and a small amount of the sedimentation accelerator is dispersed. This makes it possible to purify efficiently.

Furthermore, 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 has grown to a large particle size due to contact with the sedimentation accelerator can be removed sufficiently for sedimentation. can give residence time,
As a result, the lake water discharged from the water intake or outlet becomes 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. Dam lake 1
0, the water flowing from the river 12 is blocked by the dam 14 and temporarily stored, and the stored water is discharged downstream from the water intake port 16.

Now, in the present invention, as shown in FIGS. 1 and 2, a muddy water prevention fence 18 is provided upstream of the water intake 16 of the dam lake 10 so as to regulate the flow of lake water. The turbid water prevention fence 18 consists of a sheet-like material with an opening extending in the horizontal direction, which is suspended between both lake shores from above the water intake level to below the thermocline, and a sedimentation accelerator is placed near the opening. It is equipped with a dissipation means.

An example of the muddy water prevention fence used in the present invention is shown in FIG. In this example, a sheet 24 having a float 20 attached to the upper end and a weight 22 at the lower end extends from one lake shore to the other lake shore. This sheet 2
4 has a plurality of openings 26 extending in the horizontal direction, and a chemical liquid injection vibrator 28 is installed along each opening 26.
is provided horizontally. The chemical liquid injection pipe 28 includes a number of nozzles 30 and is connected to a liquid sending vibrator 33 at its upper end. Each drug injection vibrator 28 (and each support wire 3
2 is installed in a predetermined position, and the opening 2
A reinforcing material made of the same material as the wire 34 or the sheet is provided at both the upper and lower ends of the seat 6 to prevent it from opening excessively. The liquid precipitation accelerator sent from the liquid sending pipe 33 passes through each chemical injection pipe 28 to the nozzle 30.
It will be released under pressure into the lake water.

Turbid water phenomena occur significantly in stratified (thermocline) dams where the annual exchange frequency index α of the dam lake is small. thermocline (second
The range (indicated by the symbol T in the figure) is caused by the rise in lake surface temperature during summer, which reduces the density of water, and the low flow velocity west of the dam lake. 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 cause of turbid water, occur from summer to autumn, which is the period when cline T occurs. In the case of a small-scale flood, the flood mass that intrudes into the west part of the lake will infiltrate to the same depth as the west part of the lake, depending on the specific gravity determined by the water temperature and the degree of turbidity mixed in. If the scale is larger than that, the entire area above the cline T will be mixed and stirred. be done.

In addition to the above-mentioned density flow, water flow in the west part of 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 centimeters per second), and the velocity distribution of the flow is a Gaussian distribution curve with the peak at the water intake level (see symbol V in Figure 2). )it is conceivable that.

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, as is clear from FIG. (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 stopped 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 it passes through and reaches the water intake 16. However, the length of the sheet that should be provided below the cline T can be determined by calculation 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). Be able to do it. This is the unique length of the dam, and must be determined under the most severe conditions for each dam period. Of course, if it is economically acceptable, a sheet that reaches the bottom of the lake may be provided.

Although the upper end of the sheet 24 may be located above the water intake level, it is preferably located at the water intake surface.

When the liquid precipitation accelerator is released from the nozzle 30 of the chemical injection vibrator 28 provided in the opening 26 (fourth
(see arrow B in the figure), the local rapids and Karman vortices generated near the opening 26 mix and stir the sedimentation accelerator, promoting the association of turbid particles in the turbid water, resulting in effective sedimentation and purification. be.

Also, this turbid water prevention fence should be able to 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, suppose that 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 b as its apex is occurring.

If a small-scale flood occurs and a density current intrudes into this depth, the turbid water prevention fence 18 should be rolled up and set at the position shown by the solid line, and the opening 26 should be located at the depth La. Then, the flow of lake water becomes a Gaussian distribution surface @Va with the apex at this depth La, and the flow of turbid water can be prevented. 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 applied to 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 problem, it is desirable to pass a shaft connected by a universal rod through the center of the floating zO, so that it can be rotated by power from the lakeshore and the sheet can be rolled up. 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 by joint, and at the same time use a ballge indica etc. for the horizontal part of the liquid sending pipe 33 to the chemical injection vibe 28, and use a flexible tube that can be rolled up for 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, opening 2
The openings 26 are arranged in close proximity to each other, and by moving one or both of them relative to each other in the vertical direction, the openings 26
The area can be adjusted freely.

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

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

In addition, according to the present invention, since a turbid water prevention fence with means for dispersing sedimentation prevention agent 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, and only when the turbid water flows downstream, it is possible to treat the amount of turbid water discharged. Extremely economical.

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, turbid water can be prevented during small-scale floods. This has the effect of making the process more reliable. In other cases, such as water intake,
Since the turbid particles settle in the dam interior, there is also the advantage that sludge treatment facilities required for treatment after water intake are not required.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the method for purifying a dam lake according to the present invention;
Fig. 2 is a sectional view of the rod, Fig. 3 is an explanatory diagram showing an example of a turbid water prevention fence suitable for use in the method of the present invention, Fig. 4 is an explanatory diagram of its operation, and Fig. 5 is a selective water intake of the turbid water prevention fence. FIG. 6 is an explanatory diagram showing another example of the turbid water prevention fence. 10...dam lake, 12...river, 14...dam, 1
6... Water intake, 18... Muddy water prevention fence, 20...
Float, 22... Weight, 24, 44... Sheet, 28
... Chemical injection pipe, 30... Nozzle.

Claims (1)

[Scope of Claims] 1. Turbid water in which a sheet-like material is suspended in water so that a water flow section is formed, and a sedimentation accelerator is diffused from the vicinity of the sheet-like material to precipitate turbid particles. In the purification method, the sheet-like material regulating the flow of lake water is provided with an opening extending horizontally, and extends from above the water intake or water discharge level across both sides of the dam lake on the upstream side of 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 dissipated into the lake water from a dispersion means installed vertically below the thermocline and 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.