JP2002001371A - Method and apparatus for cleaning eutrophic water area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method and an apparatus capable of cleaning eutrophic water area efficiently and at low cost. SOLUTION: A water take-in pipe 2 for sucking water of the surface layer of the water area, a filter 3 for removing phytoplankton and organic materials contained in raw water from the water take-in pipe 2, an air mixer 4 for increasing the dissolved oxygen in the water from the filter, a water discharge pipe 5 for discharging the resultant treated water to the water bottom and a pump 6 for forming the water flow from the water take-in until the water discharge are loaded on a hull 1 capable of navigating in the water area to be cleaned. As a result, the recovery of the propagated phytoplankton, the removal of the organic materials to become bait for the plankton, the aeration of the water bottom deposit to suppress the elution of phosphorous accelerating the propagation of the plankton are simultaneously performed in a series of treating processes and the water area is cleaned efficiently with small power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for purifying water bodies that have caused water pollution due to eutrophication, and more particularly to dams, lakes and marshes which are remarkably eutrophic and easily deposit sludge on the water bottom. The present invention relates to a purification method and apparatus suitable for purifying closed water areas and rivers with gentle flows.

[0002]

2. Description of the Related Art In a water area where eutrophication has progressed due to an increase in nutrients such as nitrogen and phosphorus, phytoplankton abnormally proliferates, causing water quality disorders such as generation of offensive odors and deterioration of transparency, and particularly discharge of algae. The severe toxicity of microcystin poses a serious problem when used as tap water.

[0003] In order to purify water bodies that have caused water pollution due to such eutrophication, conventionally, a water-bloom recovery boat that recovers water-blooming blue-green algae or an anaerobic condition to restore the natural purifying function of water bodies have been used. There is used an aeration apparatus for increasing the concentration of dissolved oxygen in the deep part of the aerosol and aerobically.

[0004]

However, only the collection of blue-green algae does not drastically improve the water quality, which leads to the re-growth of the blue-green algae, which is extremely inefficient. In addition, the method using aeration requires a long time until a clear effect is obtained, and cannot cope with a water quality disorder that requires an immediate solution.

[0005] On the other hand, if these methods are used in combination and the water quality is improved by performing a purification process such as filtration by pumping up with a pump, a considerable effect can be obtained. Therefore, a huge purification cost is required as a whole. Further, if denitrification and dephosphorization treatments are added to reduce the amount of nutrients such as nitrogen and phosphorus which influence the growth of phytoplankton, complicated treatment operations are required, so that treatment costs are further increased.

[0006] The present invention has been devised to solve such problems of the prior art, and its main objects are as follows.
It is an object of the present invention to provide a purification method and a purification device configured so that a eutrophic water area can be purified efficiently and at low cost.

[0007]

According to the present invention, in purifying a eutrophic water area, phytoplankton and organic substances are removed from surface water of the water area and oxygen is removed. The amount of dissolved oxygen in water was increased by contact with a gas containing, and the resulting treated water was discharged to the bottom of the water.

Further, in the present invention, the water purification device includes a water intake means for taking in surface water of the water area, a filtration means for removing phytoplankton and organic substances contained in raw water from the water intake means, and a water intake means. A gas-liquid contact means for increasing the amount of dissolved oxygen in the raw water, a water discharge means for discharging treated water to the bottom of the water, and a pump for generating a flow of water from water intake to water discharge.

According to the purification method and the purification apparatus, phytoplankton such as blue-green algae floating on the surface layer is collected by taking water from the surface layer of the water area, and then the phytoplankton bait is discharged by discharging the treated water to the water bottom. At the same time, the concentration of organic matter in the water is reduced, and at the same time, the anaerobic submerged sediment (sludge) is aerobicized to suppress the dissolution of phosphorus from the submerged sediment, thereby lowering the phosphorus concentration in the water. The growth of phytoplankton can be suppressed. By simultaneously recovering phytoplankton, removing organic matter, and aerobizing aquatic sediment in a series of processing steps, power costs can be reduced and the water area can be purified efficiently.

In particular, when the water intake means, the filtration means, the gas-liquid contact means, the water discharge means, and the pump are constructed such that the water area to be purified is mounted on a navigable hull, the water intake position and the water discharge position are appropriately moved. Therefore, it is possible to efficiently purify the entire water area.

In order to remove the phytoplankton, a coagulation separation treatment is effective. It is preferable to add a required coagulant to the raw water taken in. Aerobic biofilm treatment is effective for removing organic matter. To increase the amount of dissolved oxygen, a gas-liquid contact device for bringing gas containing oxygen into contact with raw water may be used. This gas-liquid contact device is used for aeration for promoting aerobic biological treatment in the process of removing organic substances. Although it is possible to use it as a device, it is also possible to supply a stable amount of dissolved oxygen to the water bottom if it is provided separately in the subsequent stage and operated as necessary to obtain the required amount of dissolved oxygen. Can be.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a purification apparatus constructed according to the present invention. This purifying apparatus includes a water intake pipe (water intake means) 2 for taking in surface water of a water area into a hull 1 capable of navigating a water area A to be purified, and removing phytoplankton and organic substances contained in raw water from the water intake pipe 2. (Filter means) 3, an air mixer (gas-liquid contact means) 4 for increasing the amount of dissolved oxygen in water from the filter 3, and a water discharge pipe for discharging treated water obtained thereby to the bottom of the water (Water discharge means) 5;
A pump 6 for generating a flow of water from water intake to water discharge is mounted.

The intake pipe 2 has an inlet opened in the surface water of the water area, and takes in the surface water together with the phytoplankton floating on the water surface. In addition, as a water intake means, a configuration in which an intake port for surface water is provided at an appropriate position on the hull 1 and this is connected to the filter 3 via an introduction path is also possible.

Upstream of the filter 3, a chemical injection treatment of injecting an inorganic coagulant (metal salt coagulant) such as aluminum sulfate or polyaluminum chloride into the raw water taken in from the water intake pipe 2 is performed. Are aggregated, settle at the bottom of the filter 3, and are appropriately collected from the drain 7. Also,
By injecting the inorganic coagulant, phosphorus (orthophosphoric acid) in water forms an insoluble compound and is trapped in the filter 3.
Thereby, the phosphorus concentration in water can be reduced.

The filter 3 has therein a filter layer 8 filled with a large number of floating filter media made of a plastic foam that can float in water. The filter layer 8 includes a microbial membrane formed on the surface of the floating filter media. The SS and soluble components in the water are ingested and fixed by contact between the water and the raw water, and the amount of organic matter in the water is reduced. An aeration device 9 is provided below the filter layer 8 to promote the treatment of the aerobic biofilm in the filter layer 8.

The air mixer 4 is provided in parallel with the bypass pipe 10 and is filtered as necessary so that the amount of dissolved oxygen required to aerobize the bottom sediment to the extent that phosphorus elution can be suppressed can be obtained. The filtered water from the vessel 3 is introduced. When a sufficient amount of dissolved oxygen is obtained by the aeration device 9 in the filter 3, the gas is discharged as it is via the bypass pipe 10, thereby saving power costs.

The air mixer 4 is preferably a gas-liquid contact device as shown in FIG. 2 for a large-sized device. In this gas-liquid contact device, a pressure vessel 21 is filled with a large number of fillers 22 of non-uniform particle size made of a plastic foam that can float in water, an inlet 23 for water and air at the bottom, and water and air at the top. Each of the air outlets 24 is provided, and when water and air are allowed to flow simultaneously and pass at a pressure higher than the atmospheric pressure, the water and the air are vigorously stirred by the turbulence caused by the filler 22, and the dissolved oxygen amount is reduced. A mixture of increased water and fine bubbles is discharged, and since the fine bubbles last for a long time,
Dissolution of oxygen into water is promoted even after water discharge, which is convenient for aerobizing aquatic sediments and deep water.

In the case of a small-sized apparatus, a static mixer which can be inserted in the middle of a pipe, for example, as shown in FIG. A static mixer (manufactured by Noritake Co., Ltd.) having the above configuration is preferable.

The outlet of the water discharge pipe 5 is opened in the vicinity of the water bottom, and the water bottom sediment B is aerobically gasified by contact with the treated water rich in dissolved oxygen. As the water discharge pipe 5, for example, a flexible hose may be used, and the water discharge pipe 5 is suspended from the hull 1 so that the tip of the water discharge pipe 5 reaches a required water depth near the water bottom.

In the thus constructed purifying apparatus, the purifying process is performed while the hull 1 is being navigated according to the pollution state of the water area A and the water intake position and the water discharge position are appropriately moved, and the total water within the closed water area is obtained. If the apparatus has a processing capacity capable of performing a single round of water treatment in 30 to 60 days, it becomes possible to efficiently perform the entire purification treatment of the water area.

[0022]

EXAMPLE Using a test plant equipped with a filter and an air mixer by the biofilm filtration method, a purification test of lake water containing a blue-green algae collected in Kasumigaura was performed. First, when raw water was treated with a filter, aoko was able to remove 98% of it, and COD, BOD, and phosphorus were all about 70%.
% Removal rate was achieved. By injecting air into the filtered water, the dissolved oxygen concentration could be maintained at 7 mg / l or more.

[0023]

As described above, according to the present invention, the phytoplankton which has already grown is recovered, the organic matter serving as a feed for the phytoplankton is removed, and the water bottom for suppressing the elution of phosphorus which promotes the growth of phytoplankton is obtained. The aerobicization of the sediment can be performed simultaneously in a series of processing steps, whereby the water area can be efficiently purified with a small power cost.

[Brief description of the drawings]

FIG. 1 is a schematic view of a purification device according to the present invention.

FIG. 2 is a sectional view showing an example of a gas-liquid contact device according to the present invention.

FIG. 3 is a sectional view showing an example of a gas-liquid contact device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hull 2 Intake pipe 3 Filter 4 Air mixer 5 Drain pipe 6 Pump 7 Drain 8 Filtration layer 9 Aerator 10 Bypass pipe 21 Pressure vessel 22 Filler 23 Inlet 24 Outlet 31 Element 32 Casing A Water area B Water bottom sediment

Claims (3)

[Claims] 1. A method for removing phytoplankton and organic matter from surface water of a water body, increasing the amount of dissolved oxygen in the water by contact with a gas containing oxygen, and discharging the treated water obtained thereby to the bottom of the water. A method for purifying eutrophic waters, characterized in that: 2. A water intake means for taking in surface water of a water area, a filtration means for removing phytoplankton and organic substances contained in raw water from the water intake means, and a gas for increasing the amount of dissolved oxygen in the raw water from the water intake means. Liquid contact means, water discharge means for discharging treated water treated by the filtration means and gas-liquid contact means to the bottom of the water, and a pump for generating a flow of water from water intake to water discharge. A eutrophication water purifier. 3. The water intake means, the filtration means, the gas-liquid contact means, the water discharge means, and the pump are mounted on a hull capable of navigating a water area to be purified. Eutrophic water body purification equipment.