Method of treating dam lake water
By adding flocculants to dam lake discharge water and treating it with solid alkali materials, the method clarifies the water within a limited downstream area, addressing the issue of murky water release and maintaining suitable conditions for fish farms and natural fishing spots.
Patent Information
- Application Number
- JP2023188734
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-02
- Publication Date
- 2025-05-16
AI Technical Summary
The release of murky water from dam lakes into downstream rivers causes water quality issues, affecting fish farms and natural fishing spots by preventing the growth of sphagnum moss and other food sources due to the lack of clarity.
A method involving the addition of 10 to 100 PPm of flocculant per ton of discharged water in a limited area of the river, followed by contact treatment with solid alkali materials, such as baked oyster shells, to clarify the water within a one-kilometer downstream area.
The method effectively clarifies the discharged water within a limited area, maintaining water quality suitable for fish farms and natural fishing spots without significant adverse effects.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to a method for treating turbid reservoir water. [Background technology]
[0002] Generally, there are more than 10 dam lakes in a first-class river. The purpose of dam lakes is diverse, including as a source of water for hydroelectric power generation, agricultural irrigation, drinking water supply and industrial water supply, and storage during floods and overflows. Meanwhile, the sediment that accumulates in the dam lake is discharged as highly turbid water when drained, which inevitably makes the downstream river muddy. However, downstream of the dam lake, there are generally fish farms and fishing spots for wild fish such as sweetfish. Since fish usually feed on sphagnum moss in clear water environments, discharging muddy water has been problematic because the sphagnum moss that attaches to stones and rocks on the riverbed cannot grow. In the past, gravel contact materials were installed to solve these problems, but they required a certain amount of time to have a certain effect, and when the amount of discharged water increased, they had no practical effect on clarifying the water. Summary of the Invention [Problem to be solved by the invention]
[0003] The inventors therefore carried out various studies on methods for clarifying turbid water within a limited area of a river even if a large amount of turbid water is discharged therein, and as a result, they have completed the present invention. [Means for solving the problem]
[0004] That is, the present invention relates to a method for treating dam lake water, which comprises adding 10 to 100 ppm of a coagulant per ton of effluent within a limited river area when discharging the dam lake water, and then treating the effluent to which the coagulant has been added by contacting it with a solid alkaline material, and / or adding a coagulant when returning the dam lake water near the discharge port of the dam lake through a water supply pipe to the upstream of the dam lake. Effect of the Invention
[0005] According to the method of the present invention, the discharge water (turbid water) is clarified within a limited area of 1 kilometer downstream from the dam discharge outlet, so there is no adverse effect on the fish that usually live in fish farms, fishing spots, etc. downstream. [Brief description of the drawings]
[0006] [Figure 1] A plan view showing metal cages arranged in parallel horizontally in a river. [Diagram 2] A plan view showing metal cages placed in parallel with horizontal intervals in a river. [Diagram 3] A plan view showing metal cages arranged horizontally in a staggered pattern in a river. [Figure 4] A plan view showing metal cages arranged in an inverted V shape relative to the flow direction of the river. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0007] In the present invention, an injection pipe for adding a coagulant to the discharged water is provided near the inside of the discharge port of a dam lake, and the coagulant is added to the discharged water from the injection pipe. The amount of the coagulant to be added varies depending on the turbidity of the discharged water, but is generally in the range of 10 to 100 PPm, preferably 25 to 50 PPm, per ton of the discharged water. If the amount added is less than 10 PPm, it becomes difficult to obtain the desired clarification effect in the downstream region, whereas if the amount added is more than 100 PPm, the treatment cost increases, which is undesirable.
[0008] As the flocculant used in the present invention, N / T Flock (trade name of Nippon Solid Co., Ltd.), polyaluminum chloride, aluminum sulfate, polyiron, etc. can be suitably used.
[0009] The effluent (turbid water) to which the coagulant has been added is then contact-treated with a solid alkaline material in a downstream desired treatment area. The solid alkaline material is generally enclosed in a cubic metal cage made of wire mesh, and the metal cage containing the solid alkaline material is placed in the river. The cubic metal cage made of wire mesh includes gabions and futon cages. The cages can be arranged in various configurations, such as in parallel as shown in Figure 1, in parallel with gaps as shown in Figure 2, in a staggered pattern as shown in Figure 3, or in an inverted V shape toward the upstream of the river as shown in Figure 4. Placing these metal cages in multiple locations can further improve the clarification effect.
[0010] As the solid alkaline material used in the present invention, calcined oyster shells (product name: Celca, manufactured by Nippon Solid Co., Ltd.), calcined limestone, etc. are used.
[0011] The present invention will now be described with reference to examples. Example 1 A polyaluminum chloride coagulant is added to turbid water (turbidity 150 PPm) discharged from a dam lake at a rate of 30 PPm per ton of turbid water, and then the water is discharged into a river. Metal cages 1 containing baked oyster shells are placed in the river 100 meters downstream from the dam lake outlet as shown in Figure 1. Another metal cage is placed 50 meters downstream from the previously placed metal cages, as shown in Figure 3. The turbidity of the river water is then measured 1 kilometer downstream from the dam lake outlet, and is found to be 1 PPm. In addition, when N / T floc and aluminum sulfate were used instead of polyaluminum chloride as the coagulant, almost the same results were obtained.
[0012] Example 2 In Example 1, when the dam lake water (turbidity 150 ppm) was returned to the upstream of the dam lake through a water supply pipe, 30 ppm of N / T floc per ton of dam lake water was added to the water supply pipe. The turbidity of the dam lake water at the water supply pipe outlet was measured and found to be 100 ppm. The turbidity of the dam lake water 100 meters downstream from the water supply pipe outlet was measured and found to be 10 ppm. [Explanation of symbols]
[0013] 1...wire mesh basket
Claims
[Claim 1] A method for treating dam lake water, comprising: adding 10 to 100 ppm of a coagulant per ton of discharge water within a limited river area when discharging the dam lake water; then contacting the discharge water to which the coagulant has been added with a solid alkaline material for treatment; and / or adding a coagulant when returning the dam lake water near the discharge port of the dam lake through a water supply pipe to the upstream of the dam lake.