JP2008100176A - Method for eliminating oxygen-poor water area in dam lake, lake, marsh or the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the water quality conservation by supplying high-concentration or saturated oxygen-containing water to a restricted water area to increase the dissolved oxygen concentration and to improve the area to an aerobic environment, since in the bottom layer water of a dam lake, a lake, a marsh, a closed sea area, or the like, the dissolved oxygen concentration of the restricted water area reaches zero or almost an anaerobic state mainly in summer to deteriorate the water quality. <P>SOLUTION: A layer of discontinuity is developed in the middle water layer or lower of the dam lake, the lake, the marsh, the closed sea area, or the like in the seasons except a specific season due to a temperature difference or a density difference of the salt content, dissolved metals, or the like and consequently the water is hardly mixed vertically. A gas-liquid dissolution apparatus (underwater type), in which a suction port, a discharge port, an underwater pump and a gas-liquid dissolution part are integrated with one another, is arranged in the objective water area. The oxygen dissolved in the predetermined water layer of the objective water area is increased and the water quality of all of oxygen-poor water areas is improved by successively vertically moving the gas-liquid dissolution apparatus or an oxygen spout. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

Generally, water below the middle layer, such as dam lakes, lakes, and closed waters, especially bottom water, becomes anaerobic with a concentration of dissolved oxygen of zero or close to it, especially in summer, causing the loss of various organisms and hydrogen sulfide. Water quality is deteriorated due to generation and elution of metals from the bottom mud. In order to solve such water environment problems such as dam lakes and lakes, it is necessary to increase the dissolved oxygen concentration in the hypoxic water area below the middle layer to improve the aerobic environment.

Even if an anoxic state is improved once, oxygen is consumed by the decomposition of organic substances existing in the water, and the anoxic water area is reproduced. In order to prevent this phenomenon, the dissolved oxygen concentration is continuously measured from the temperature climbing layer to the bottom layer. It is necessary to increase the concentration to conserve water quality in all water areas.

In dam lakes, lakes, and closed waters in various places, the water quality is eutrophied by the inflow of domestic wastewater and agricultural wastewater, and plankton grows greatly on the surface. The plankton becomes a dead body and settles down to the bottom of the lake. At that time, a large amount of oxygen is consumed, so there is anaerobic water in the vicinity of the lake bottom, and an anaerobic environment is formed where living organisms cannot live, generating hydrogen sulfide from the bottom mud and leaching of metals. Invite. It is known that this hypoxic phenomenon does not stop near the bottom of the lake, but spreads to the middle water area below the thermal stratum.

In order to improve such an aquatic environment, it is necessary to improve the aerobic environment by increasing the dissolved oxygen concentration in the middle layer and below, particularly in the aquifer near the lake bottom. In an aerobic environment, heavy metals and salts that are dissolved in the water are oxidized and coagulated, and the elution of heavy metals and salts from the bottom of the lake is prevented, and a variety of organisms can live on the bottom of the lake. The water quality is improved.

Methods for creating such an aerobic environment include dam lakes, methods of supplying oxygen gas and high-concentration oxygen water into the water of lakes, and methods of sending surface water with a high dissolved oxygen concentration to the bottom layer. Some have been put to practical use.

However, the method of increasing the dissolved oxygen concentration of bottom layer water by injecting air or oxygen gas sent through the hose from an oxygen generator or compressor installed on land with a diffuser tube or nozzle is used to release released air and oxygen. No matter how small the gas bubbles are, the force of horizontal diffusion is weak and easy to rise at deep water points, so the dissolved oxygen concentration cannot be increased efficiently. Moreover, if a diffuser plate or a nozzle is installed in the bottom layer, a bottom mud-up phenomenon may occur and the bottom layer water may be further deteriorated. The oxygen generator and oxygen dissolver are placed on land, the bottom layer water is pumped to land, the dissolved oxygen concentration is increased, and the dissolved oxygen concentration is sent back to the bottom layer. Foaming occurs due to pressure fluctuations between them, which is an efficient problem.

In the normal aeration method, it is impossible to increase the dissolved oxygen concentration of the bottom layer water, particularly to improve a wide range of anoxic water areas. On the other hand, the method of sending surface water to the bottom layer is because phytoplanks grown on the surface layer such as dam lakes and lakes and organic matter contained in the inflow water are sent to the bottom layer together, so that they consume a lot of oxygen when they decompose. There is a possibility that the water quality is further deteriorated, and since the surface water has a high water temperature, the specific gravity and density difference of the bottom layer water is different, so that the surface water does not diffuse horizontally and becomes an upward flow, so the effect is small.

As an invention (patent) related to the present invention, there is a method in which an injection nozzle is provided on a moving body that moves along a water bottom pulled from a ship on the water. A method of supplying oxygen water to different depths in water using a pumping means and an air jetting means that can be lifted and lowered from a base boat by placing an oxygen generator and an oxygen dissolving device on a base boat floated on water. A device that can adjust the water depth of the air diffuser with a remote device so that the water depth of the air diffuser can be automatically maintained even if the water level fluctuates in the dam lake or lake. A water quality meter attached to the tip of the wire with a wire winch device installed on the float and an underwater sensor having a water quality data storage memory are used to reciprocate in the water at regular intervals for each depth. There are methods for measuring and storing water quality.

Japanese Patent Application Laid-Open No. 7-136691 Method and apparatus for improving water quality in bottom water area of Japanese Patent Application Laid-Open No. 2004-290863 JP-A-7-1000049 Underwater diffuser remote lifting device JP-A-6-18518 Water quality data measuring apparatus

Eliminate the anaerobic conditions from the middle to bottom of dam lakes, lakes, and closed sea areas,
Iron, manganese, phosphorus, etc. dissolved in the water are oxidized, coagulated and precipitated to improve water quality, bottom layer aerobic, and bottom mud surface oxidation, iron, manganese, To prevent the elution of metals such as phosphorus, and to prevent the generation of ammonia and hydrogen sulfide to preserve the water environment.

A gas-liquid dissolution device (underwater type) with a suction port, discharge port, submersible pump, and gas-liquid dissolution unit are installed in anoxic water areas below the bottom layer and temperature stratum such as dam lakes and lakes. The high-concentration oxygen water is horizontally diffused into a water layer (usually 2 m to 6 m thick) having the same water temperature or density as the place where the apparatus is installed without rolling up the bottom mud. After the poor oxygen state of the water layer (block) is eliminated, the dissolved oxygen concentration of the water layer (block) is increased by moving the apparatus to the upper or lower poor oxygen water layer (block). Thus, the dissolved oxygen concentration of the whole water area below the middle layer in an anoxic state is raised by repeating raising / lowering of the apparatus in the vertical direction.

  In the water area where the oxygen-poor state has been eliminated as described above, the water quality meter such as the float or dissolved oxygen meter connected from the land to the tip of the wire is moved up and down periodically from the middle layer to the lower layer. To monitor the water quality below the middle layer. If there is a decrease in dissolved oxygen concentration or an increase in dissolved metals due to the decomposition of newly introduced organic matter or plankton carcasses, move the equipment to the water layer and operate it. Therefore, the water quality is improved only for the water layer. Thereby, the dissolved oxygen concentration of all dam lake water is maintained efficiently in an aerobic state throughout the year with low energy consumption.

As described above in detail, according to the present invention, low-level anoxic conditions such as dam lakes, lakes, and closed sea areas and anaerobic conditions of sediments can be eliminated throughout the year.
As a result, the following water environment can be improved.
B) Oxidized iron, manganese, phosphorus, etc. dissolved in anoxic water can be coagulated and precipitated.
B It is possible to prevent the elution of metals such as iron, manganese and phosphorus from the bottom mud.
C Gas such as ammonia and hydrogen sulfide from the bottom mud can be prevented.
D) The bottom mud is improved to an aerobic environment, and living inhabitants becomes possible.

As a first step, the suction port, discharge port, submersible pump, and gas-liquid dissolution unit attached to the tip of the winch rope provided on the float are integrated in dam lakes, lakes, closed waters, etc. In order to keep the distance between the device and the bottom of the lake constant, a lake bottom sensing device is installed, and a weight is attached to the tip from the device to the bottom of the lake. (The device has buoyancy, so if the weight is set on the bottom of the lake, a constant distance can be maintained between the device and the bottom of the lake). Thereby, even if there is a water level fluctuation on the water surface, the installation water depth of the apparatus does not change.

In this way, a high-concentration or saturated oxygen water from the discharge port of the submerged gas-liquid dissolution apparatus installed at a constant water depth and a water layer (usually 2m to 6m at the same water temperature and density as the apparatus is installed) Thickness) to increase the dissolved oxygen concentration in the water layer. When it is confirmed that the dissolved oxygen concentration in the water layer has reached the target value, the dissolved oxygen concentration in the upper water layer is improved by raising the apparatus to the upper oxygen-deficient water layer and operating it. In this way, by moving the apparatus from the lower layer sequentially to the middle layer and operating, the water quality of the entire poor oxygen region below the middle layer is improved.

If for some reason the dissolved oxygen concentration in a water layer at a certain depth is lowered, the device is moved to that depth and the dissolved oxygen concentration is increased only in that water layer.

The results of experiments conducted in actual dam lakes are described below.
Improvement of dissolved oxygen concentration and maintenance of aerobic condition (5mg / L or more) in the anoxic water area occurring below the middle layer of the objective dam lake.
The scale of the dam lake where the experiment was conducted: 54.5 m, effective water storage capacity: 6,400,000 cubic meters Maximum water depth during the experiment: about 30 m
Dissolved oxygen concentration in the dam lake before the experiment at a depth of 11 m (temperature striking layer) or less: around 2 mg / L (Apr is almost 0 in summer)
Water temperature at depth of 11 m or less: About 5 to 10 degrees Water quality: High concentration of metals such as iron, manganese, etc. Apparatus gas-liquid dissolution apparatus (underwater type) used in experiments from late April to early May (capacity 120 Cubic meter / h), PSA oxygen generator, compressor
Experimental method First, a gas-liquid dissolving device (underwater type) was installed at a position 0.5 m above the lake bottom (water depth of about 27 m), and oxygen sent from the land to the lake water (water around the device) sucked from the inlet of the device. Dissolve gas (concentration 90%), diffuse high-concentration oxygen water in the horizontal direction from the discharge port, and increase the dissolved oxygen concentration in the same water layer as the installation water depth. When the dissolved oxygen concentration in the water layer reached the target value, the apparatus was lifted to a point about 6 m above, and the dissolved oxygen concentration in the water layer (approximately 4 m in thickness) corresponding to the water depth was increased. The same operation was repeated four times, and an attempt was made to increase the dissolved oxygen concentration (repair to an aerobic state) of the dam lake water at a depth of 11 m or less (about 20 m from the bottom of the lake).
As a result of the experiment, it was possible to eliminate the poor oxygen in the water area below the middle layer as follows.

The present invention can eliminate the anoxic state of bottom water such as dam lakes, lakes, and closed seas, and is useful for water quality conservation of dam lakes, effective use of water resources, and promotion of fishery.

It is a figure which shows the system which eliminates the anoxic state from the middle layer of a dam lake to sediment. It is a figure which shows the method of installing a gas-liquid dissolution apparatus (underwater type) on the basis of one point of a lake bottom.

Explanation of symbols

1 Lake bottom 2 Anoxic water area 1
3 Anoxic waters 2
4 Anoxic waters 3
5 Normal dissolved oxygen concentration water area 6 Dam level 7 Dam bank 8 Gas-liquid dissolution device (underwater type) or water quality meter 9 Float 10 Winch 11 Wire
12 Lake bottom sensing device 13 Fixed weight 14 Lake bottom

Claims (5)

In deep dam lakes, lakes, etc., the dam lake can be operated by moving and operating the gas-liquid dissolution device (underwater type) in which the suction port, discharge port, submersible pump, and gas-liquid dissolution unit are integrated. A method to improve the water quality by increasing the dissolved oxygen concentration in anoxic water areas. A cross-sectional view of an anoxic water area such as a dam lake is created and divided into water layers (blocks) with a thickness of approximately 2 to 6 m in the vertical direction with the lake bottom as a reference. Based on the drawings, an underwater type gas-liquid dissolution device is installed and operated for each water layer (block), and after eliminating the poor oxygen of the water layer (block), the device is installed in the upper or lower part. By moving to the water layer and operating, the poor oxygen in the water layer (block) is eliminated. A method of increasing the dissolved oxygen concentration in the anoxic water areas occurring in dam lakes, lakes, etc. by repeating this method. The water depth of the underwater type gas-liquid dissolving device is set to the bottom of the lake by using a bottom sensing device attached to the bottom of the underwater type gas-liquid dissolving device or a method of lowering the wire with a fixed length from the device to the bottom of the lake. The installation method of the apparatus which is not influenced by the fluctuation of the surface water level. A method in which a wire or cable attached to an underwater gas-liquid dissolution apparatus is installed at a predetermined depth by a winch operation from the float or land, or the water is moved up and down. When the dissolved oxygen concentration at a certain depth falls below a certain level, the bottom water such as dam lakes and lakes is prevented from becoming locally poorly oxygenated by moving the device to that depth and operating it. Method.

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