JP4925652B2 - River water treatment methods - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a water treatment method and apparatus for improving the location of a closed water area mainly by a man-made structure in a river or the like and enhancing the role of a river that nurtures the sea.

In closed water areas, weir and dam water pollution problems occur especially when the river flow is low. Water exchange and circulation are important to solve this problem. Moreover, when water stagnates and the bottom sediment and bottom layer water become oxygen-free, some measures have been taken to solve it. The cause of oxygen depletion that occurs in the bottom layer is caused by sediments rich in organic matter in the bottom layer and bottom layer. The excrement of plankton and cultured fish shellfish produced on the surface layer, etc., sinks on the bottom sediment and then drifts on the bottom surface layer, causing oxygen consumption in the bottom of the water area.
Dissolved oxygen depletion at the bottom of rivers such as dams and weirs can cause serious damage to aquatic ecosystems. In addition, oxygen deficiency in harbors and bays deprives the growth environment of benthic organisms that inhabit sediments and causes a decrease in fish, shrimp, shellfish, and the like.
In order to solve the water quality problem due to such oxygen deficiency, there are methods such as aeration, circulation, dredging and bottom sediment improvement. However, these methods do not last long and require continuous measures.

At present, the procedures for dredging and sludge treatment in closed water areas are 1) dredging using ships, 2) transport of sediment / sludge from the water area to land, 3) sediment treatment or dehydration, etc. 4) disposal It was transported to yard and landfill. In this way, once sludge-like sediments are deposited in a closed water area, a lot of labor and energy are required to solve the problem.
An approach for forcibly sending oxygen into a closed water area can also be found (for example, see Patent Document 1). In addition to the aeration method that has been used for a long time, such a method has been proposed in which dissolved oxygen is dissolved in water and sent.
There is also a method of using a pump or a machine as a method for discharging sediment deposited in a dam by water exchange. Attempts have also been made to discharge sediment by providing through holes in existing dams. There are also systems where the flow rate is adjusted by opening and closing gates in dams and dams, and water in the water area and sediment with a low specific gravity are discharged.
There is also a proposal of passing water through a filtration system containing sand or sludge (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 7-8998 JP 2002-355589 A

  However, no method has been proposed in which water is passed through a layer in which the submerged trees are made into chips. In addition, there has been no proposal of using a chip that is a sinking sink of driftwood, which is a major problem in river management, for use in an environmental conservation system.

By the way, there are so-called “bottom sediment” and “floating mud” formed by sedimentation and accumulation of plankton drifting in water on the sediment. Sediment and floating mud that are rich in organic substances and in a reduced state are called sludge and have a high oxygen consumption rate. The oxygen consumption proceeds greatly in two stages. The scale of each of the two stages depends on the reduction state, but when the sediment is ready to receive oxygen, oxygen consumption (chemical oxidation) occurs at a high rate first, followed by slow oxygen consumption due to microbial respiration. Happens. Among these, since the chemical oxidation rate is large, this portion is superior to the oxygen supply rate in normal oxygen supply, and therefore the bottom sediment is not easily oxidized. Moreover, there is a problem that the duration of chemical oxidation is short.
The sediment with such characteristics accumulated in the bottom layer with little movement of water in the closed water area, causing sludge formation. Therefore, if it is possible to prevent so-called sludge formation such as “floating mud” formed by sedimentation and accumulation in the bottom layer, and black sediment in a reduced state that contains a large amount of organic matter, water pollution derived from the bottom can be solved. .

  In addition, in order to create a river environment that nurtures the sea in consideration of cooperation between forests, rivers, and the sea, there are places where it is necessary to reduce organic matter and nitrogen in the river, and places where silicic acid supply is effective. It is desirable for this problem to be a system that can purify and create ecosystems, including not only bottom sediments but also suspended matter contained in water and river water.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a river water treatment method and apparatus that effectively uses a sink to prevent purification of a closed water area and prevent sludge formation.

  The water treatment method for a river according to the present invention forms a sedimentation chip filtration layer by spreading the sedimentation chip broken into pieces of sedimentation on the bottom near the upstream side of the weir body, allowing water to pass through the sedimentation chip filtration layer Water is discharged from the drainage channel of the weir body to the downstream side.

  In the present invention, a sedimented wood chip filtration layer is formed on the bottom of the upstream side of the weir body using a sedimentation chip made of sedimented wood as a filter medium, and water in a closed water area passes through the sedimented wood chip filtration layer. By doing so, organic substances and nitrogen can be removed by microorganisms attached to the settled wood chip and a humic substance can be supplied. Therefore, it is possible to purify the closed water area of the river and to prevent the lower layer from becoming sludge. Furthermore, since humic substances are eluted in the water that has passed through the sedimentation chip filtration layer, it can be enriched by flowing into the sea, thereby creating a river environment that nurtures the sea. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an outline of a river water treatment apparatus in an embodiment of the present invention in a partial cross section, and FIG. 2 is a plan view thereof.
This water treatment device uses a sink where a driftwood sinks, and fills a net cage 2 such as a gabion with a set of shredded chips 1 broken into chips having a length of 20 cm or less. A sinking wood chip filtration layer 4 is formed by spreading on the bottom of the dam body 3 in the vicinity of the upstream side.

In order to install the sinking wood chip filtration layer 4, the bottom portion in the vicinity of the weir body 3 is dug down to construct a housing portion 5 formed by a concrete enclosure, and a water collecting pipe or One or a plurality of water collecting channels 6 made of grooves or the like are provided, and a plurality of net cages 2 filled with the sinking wood chips 1 are laid in the accommodating portion 5.
The water collecting channel 6 communicates with a drainage channel 7 that penetrates the inside of the weir body 3. Moreover, although the position of the drain port 8 is not particularly limited, it is preferably provided between the overflow port 9 and the sinking wood chip filtration layer 4. The drainage channel 7 may be provided with an on-off valve or a gate (not shown).

  Furthermore, the sinking wood chip filtration layer 4 can be configured as a single layer or a plurality of layers. In this case, the lower layer portion may be filled with a larger (rougher) settled wood chip, and the upper layer portion may be filled with a smaller (thinner) settled wood chip to form a filtration layer having a dense structure. The coarse and dense filtration layer may be formed in a plurality of layers so as to be dense in the same mesh basket 2 or formed by stacking the coarse basket basket 2 and the narrow basket basket 2 May be.

  In the present embodiment, a chip manufacturing machine, a crane, and the like are carried into the site, and a sinking tree sinking in a river or a dam is picked up and applied to the chip manufacturing machine to make a sinking chip 1. This sinking wood chip 1 is filled into a net cage 2 and the net cage 2 is spread by a crane in a concrete housing part 5 constructed at the bottom of the upstream side in the vicinity of the weir body 3 to form the sinking wood chip filtration layer 4. Thereafter, an open / close valve or a gate (not shown) is opened to connect the water collection channel 6 and the drainage channel 7.

As shown by the arrow in FIG. 1, the water blocked by the weir body 3 flows into the sinkwood chip filtration layer 4 and flows down the sinkwood chip filtration layer 4. At this time, the sludge bottom sediment layer 10 containing sand also flows into the sedimented wood chip filtration layer 4. Then, when the water level on the upstream side rises, the water that has passed through the settled wood chip filtration layer 4 flows from the drainage channel 6 through the drainage channel 7 to the downstream side from the drainage port 8.
In the water treatment apparatus of this embodiment, since the filtration layer 4 uses the sedimented wood chip 1 as a filter medium, organic substances and nitrogen can be removed by microorganisms attached to the sedimented wood chip 1. Further, the sinking wood chip 1 supplies humic substance in water. The humic substance is one of the important substances to enrich the sea because it supports the supply of iron to the sea. Its components are classified as humic acid, fulvic acid and himatomelanic acid. Of these, humic acid and fulvic acid are particularly effective.

  Therefore, according to the present embodiment, the organic matter and nitrogen that cause water pollution are removed, and the humic substance and silicic acid are supplied. Therefore, it is possible to enrich the sea while purifying the river water. Moreover, by making the area of the sinking wood chip filtration layer 4 as large as possible, sludge formation in the closed water area can be prevented over a wide range. Furthermore, since it effectively uses the sinking trees that are a problem in river management, it is also meaningful as an environmental conservation measure.

  The effect of the present invention by using a sinking chip is shown in FIGS. FIG. 3 is an experimental result showing the elution amount of the humic substance with time, and FIG. 4 is an experimental result showing the state of nitrogen removal with time.

  As shown in FIG. 3, the ultraviolet absorbance uv 260 nm tended to increase with the passage of time from the start of the experiment. The ultraviolet absorbance uv 260 nm is a selective wavelength of humic substances and is known to have a strong correlation with iron (dissolved Fe) mainly in rivers. The humic substances eluted from wood chips are thought to be useful for the production of seaweed and phytoplankton in the sea, such as iron, which is widely known to be deficient in the rich sea.

FIG. 4 shows changes in the total nitrogen concentration in the water measured in a state where a sink tree is placed in a column filled with river water and the water is circulated.
Nitrogen removal in river water is hardly expected in nature. There is a need for a system that focuses on nitrogen removal even in sewage treatment. However, a specific tendency of nitrogen removal as shown in FIG. In nitrogen removal, organic substances are used for the action of denitrifying bacteria on the tree surface, so organic substances such as BOD components that can be decomposed by microorganisms decrease with nitrogen removal.

The block diagram which shows the outline | summary of the water quality improvement apparatus of the river in embodiment of this invention in a partial cross section. The top view of a water quality improvement apparatus. The graph of the experimental result which shows the time-dependent change of the elution amount of the humic substance with a sinking wood chip. The graph of the experimental result which shows the time-dependent change of nitrogen removal by a sinking wood chip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sunk wood chip 2 Net basket 3 Weir body 4 Sunk wood chip filtration layer 5 Concrete container 6 Catchment channel 7 Drainage channel 8 Drainage port 9 Overflow port 10 Bottom sediment layer

Claims (1)

  Sediment chips broken into pieces are spread on the bottom near the upstream side of the weir body to form a sedimented chip filtration layer. A method for water treatment of rivers characterized by being discharged into the river.

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