JPH1057985A - Water quality purifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and inexpensively purify water quality by covering the water bottom in the water region of seas, lakes and marshes and rivers, etc., with a covering material such as sands, and feeding surface water in this region into a bottom layer with a prescribed water transportation means. SOLUTION: In the case that this method is applied to a closed water region 1 such that exchange of seawater with the open sea is performed with only a floodgate, the sea bottom 2 of the closed water region 1 is covered with sands 3 and also an intermittently air pumping cylinder 4 is disposed on sands 3. The air pumping cylinder 4 is composed of a cylinder 6 and an air room 8, and by mooring the bottom end of the cylinder 6 to a sinker 11 via a chain 10, the cylinder 6 is stood on one's own legs nearly vertically with a self-supporting float 5 attached on the upper end. Air is fed into the air room 8 from a compressor via an air feed pipe, and by ejecting the air in the air room with one blow into the cylinder 6, the water in the cylinder 6 is raised, while it is pushed up, and the water near the bottom layer is made to flow in from a water suction port 9 of the cylinder 6 and then a circulation flow flowing from the surface layer to the bottom layer and from the bottom layer to the surface layer is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water purification method for purifying water in seas, lakes, marshes, rivers and the like.

[0002]

2. Description of the Related Art Water pollution due to eutrophication of water quality has become a problem in waters such as the sea, lakes and rivers, particularly in closed waters. That is, when the concentration of nutrients such as phosphorus and nitrogen increases, phytoplankton and algae grow abnormally in the surface layer with high solar radiation, and in the bottom layer, a large amount of oxygen is consumed by the decomposition of organic matter such as dead algae, resulting in anoxia. State.

[0003] Such abnormal occurrence of algae on the surface layer causes adverse effects such as clogging of a filtration device in a water purification treatment plant, dyeing of tap water in green, and adding a musty odor. Hypoxia causes the disadvantage that higher aquatic organisms are killed and anaerobic environment causes ammonia and hydrogen sulfide to elute from bottom mud and organic matter in water, and that tap water emits an odor. And, in the summer season when the upper layer and the bottom layer are stratified without circulation, such a tendency becomes more remarkable.

[0004]

In order to improve such water pollution, for example, methods such as reduction of inflow load, sediment dredging, algae removal, sediment coating and lake water circulation have been tried. For nutrient water bodies, it is difficult to improve water quality only by reducing the inflow load due to the establishment of a circulating system of nutrients in the water bodies.If the bottom mud is dredged, the dredged soil will become industrial waste. In removing algae, there has been a problem that it is practically impossible to remove the algae at a faster pace than the growth of the algae.

On the other hand, although it has been found that a certain effect can be obtained with respect to sediment coverage and lake water circulation, in the former, organic substances are gradually eluted from the inside of the former and oxygen is consumed even though it is coated. However, in the summer months, phytoplankton, which is abundantly generated in the surface layer, becomes a dead body and newly settles down on the water floor, which makes it difficult to prevent hypoxia in the bottom layer for a long time. Although water circulation is performed, oxygen consumption of organic matter settled in the bottom mud is inevitable, so there is a limit to suppress anoxia near the bottom layer, and to raise a certain effect, The question is that it is difficult to actually adopt the system unless it is necessary to find a value that would require substantial water circulation facilities and a large economic ripple effect by improving water quality. Also it has occurred.

The present invention has been made in view of the above circumstances, and has as its object to provide a water purification method capable of efficiently purifying water at low cost.

[0007]

In order to achieve the above object, the water purification method of the present invention covers a water bottom of a water area such as a sea, a lake, a river or a river with a covering material such as sand. At the same time, the surface water in the water area is sent to the bottom layer by a predetermined water transfer means.

Further, in the water purification method of the present invention, a predetermined water circulating device is installed in the water area to serve as the water transfer means,
The surface water is carried on the circulating flow generated by the water circulation device and sent to the bottom layer.

In the water purification method of the present invention, the bottom mud on the water bottom is covered with the covering material, so that the consumption of oxygen by organic matter in the bottom mud is suppressed. Also, by sending surface water to the bottom layer, oxygen-rich water near the surface layer flows into the bottom layer, and phytoplankton and algae are sent from the vicinity of the surface layer with high solar radiation to the bottom layer with low solar radiation,
Abnormal breeding near the surface layer is eliminated, and the amount of dead carcass as organic matter is reduced.

That is, in the bottom layer, the action of suppressing oxygen consumption in the bottom mud by the coating material, the action of reducing the amount of sedimentation of organic matter by transferring water, and the action of supplying oxygen-rich water by transferring water are also synergistic with each other to dissolve dissolved oxygen. The concentration increases significantly.

As the water transfer means, any means can be used as long as surface water can be sent to the bottom layer. For example, a predetermined water circulation device is installed in the water area to serve as a water transfer device, and the surface water is used as the water circulation device. It can be sent to the bottom layer by carrying on the circulating flow generated in the above.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the water purification method according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 (a) shows an example in which the water purification method according to the present embodiment is applied to a closed water body 1 in which seawater is exchanged with the open sea only at a sluice surrounded by a seawall (not shown). It is shown. As can be seen from the figure, in the water purification method of the present embodiment, the seabed 2 of the closed water area 1 is covered with sand 3 as a covering material, and an intermittent air pump as a water circulating device is provided on the sand 3. A canteen 4 is installed.

Here, the sand 3 is dropped from the sea using a sanding ship or the like, and the sand 3 is accurately spread to a thickness of, for example, about 50 cm so as not to disturb the organic sludge deposited on the seabed 2.

As shown in FIG. 1 (b), the intermittent air pump 4 is generally composed of a hollow cylinder 6 and an air chamber 8 installed near the lower end of the cylinder. Is moored to the sinker 11 via the chain 10, the self-supporting float 5 attached to the upper end makes it stand substantially vertically in water.

In the intermittent air pump 4, a compressor (not shown) installed on the ground supplies an air supply pipe 7.
Is continuously sent to the air chamber 8 through the air chamber. When a certain amount of air is accumulated in the air chamber, the air in the air chamber 8 gushes into the cylindrical body 6 at once by the reverse siphon action. (Thin line arrows), which become air bullets and rise while pushing up the water in the cylindrical body 6, and water near the bottom layer flows in through the water inlet 9 at the lower end of the cylindrical body 6.

Such a series of operations is performed intermittently every time the air in the air chamber 8 reaches a certain amount. Thus, in the closed water body 1, as shown by the thick arrow in FIG. A large circulating flow occurs from the surface layer to the bottom layer and from the bottom layer to the surface layer.

The intermittent air pump 4 is preferably operated continuously from spring to autumn, when stratification occurs without natural circulation in the closed water body 1.

In the water purification method according to the present embodiment, since the bottom mud on the seabed 2 is covered with the sand 3 as a covering material, oxygen consumption by organic matter in the bottom mud is suppressed.

When the intermittent air pump 4 is operated, the oxygen-deficient water near the bottom layer taken in from the water inlet 9 at the lower end of the cylinder 6 rises due to the above-mentioned air bomb and rises in the cylinder 6.
Is discharged from the upper end opening and further rises to near the surface layer to mix with oxygen-rich water near the surface layer. Then, the mixed water descends on the circulating flow and flows into the bottom layer.

Further, when the surface water in the closed water body 1 is sent to the bottom layer, phytoplankton and algae are also sent from the vicinity of the surface layer having a large amount of solar radiation to the vicinity of the bottom layer of a small amount of solar radiation. In addition, the risk of mass generation near the surface layer is reduced, and the amount of dead carcass as organic matter is also reduced.

As described above, according to the water purification method of this embodiment, the effect of suppressing the consumption of oxygen in the bottom mud by the sand 3, the effect of reducing the amount of sedimentation of organic matter by the water circulation, and the function of the oxygen-rich water By the supply operation, the dissolved oxygen concentration near the seabed 2 can be greatly increased. Regarding the increase of the dissolved oxygen concentration, not only the sum of the effect obtained only with the sand cover but the effect obtained only with the water circulation, but a significant increase can be expected due to their synergistic effect.

That is, even if the sand cover alone can suppress the oxygen consumption of the bottom mud, it cannot control the oxygen consumption of the organic substances newly settling from the surface layer. Even in a short period of time, the bottom layer may become hypoxic again, but if water circulation is also used, the growth of algae and phytoplankton on the surface layer will be suppressed and the oxygen-rich water on the surface will flow into the bottom layer As a result, these dead bodies of algae and the like are rapidly aerobicly decomposed during sedimentation, do not accumulate much on the sand cover, and the oxygen consumption of the bottom mud by the sand cover can be maintained for a long time.

In addition, it was difficult to eliminate hypoxia in the bottom layer by using only water circulation unless a large-scale circulation facility was used. , And oxygen-rich water can be supplied near the bottom layer, so that the dissolved oxygen concentration in the bottom layer can be maintained at a high value.

Therefore, natural circulation hardly occurs in lakes and seas where the water depth is large and stratification occurs in the summer and the water temperature changes rapidly at the boundary of the thermocline, so that algae and phytoplankton on the surface layer Mass production and anoxia near the bottom layer were serious, but if the water purification method according to this embodiment is applied, on the surface layer, propagation of algae and the like would be suppressed and the transparency of the sea surface would increase, and the landscape In addition to the improvement, in the bottom layer, the dissolved oxygen concentration greatly increases and the habitat of aquatic organisms is remarkably improved, and the elution of ammonia and hydrogen sulfide from the bottom mud is also suppressed,
There is no odor. Moreover, the synergistic effect of sand covering and water circulation makes it possible to considerably reduce the scale of the water circulation equipment, in this embodiment, the intermittent air pumping cylinder,
Accordingly, operating costs can be reduced.

Next, the effect of the sand covering and the water circulation on the dissolved oxygen concentration was predicted, and the outline will be described below.

FIG. 2 shows a model used for the simulation. As can be seen from the figure, in this simulation, the closed water area was defined as having a water depth of 5 m and a water area of 200,000.
m ² , bottom area 100,000 m ² , water volume 1 million m ³ upper water mass, water depth 5 m, water area 100,000 m ² , bottom area 100,000 m ² , water volume 500,000
divided into a lower water mass of m ^3, for the upper water mass performs water exchange per day Qin m ³ with the outside the port, between the upper water mass and lower water mass, Qm per day Assuming that the water circulation in Step ³ was performed, the change with time of the dissolved oxygen concentration was calculated based on the following reaction basic formula and mixing basic formula.

First, the basic reaction formula is as follows: Upper water mass; (d / dt) [DOH] = -kwH • [DOH]-DmH • SH Lower water mass; (d / dt) [DOL] = -kwL · [ DOL]-DmL ・ SL Next, the basic mixing formula is: Upper water mass; [DOH (t + Δt)] = ([DOH (t)] ・ (VH-Qin ・ Δt-Q ・
Δt) + [DOin] ・ Qin ・ Δt + [DOL (t)] ・ Q ・ Δt) / VH Lower water mass; [DOL (t + Δt)] = ([DOL (t)] ・ (VL-Q ・ Δt ) + [DOH
(t)] ・ Q ・ Δt) / VL where [DOin], [DOH], [DOL]; dissolved oxygen concentrations in the outer, upper and lower layers kwH and kwL; oxygen consumption rate of water in upper and lower layers Coefficients DmH, DmL; Oxygen consumption rate of sediment in upper and lower layers SH, SL; Bottom area of upper and lower layers VH, VL; Water volume of upper and lower layers Figure 3 shows the results of simulation,
Figures (a) to (c) show no sand covering (both DmH and DmL are 0.
2 g / m ² / hr), the exchange water volume Q between the upper and lower layers is 10,000, 15
10,000,000, which was varied between 300,000 m ^3.

From the above calculation results, it can be seen that the dissolved oxygen concentration in the lower layer water increases with an increase in the amount of exchanged water, but the dissolved oxygen concentration in the lower layer cannot be maintained at 2 mg / liter even under the condition of 300,000 m ³ .

FIG. 3 (d) shows that sand covering was performed (for both DmH and DmL).
0.02 g / m ² / hr), and the calculation results when the exchange water amount Q between the upper layer and the lower layer is 10,000 m ³ . From these results, it can be seen that it is difficult to recover the dissolved oxygen concentration of the underlayer water using only the cover sand.

FIGS. 3 (e) and 3 (f) show that sand covering is performed (DmH,
DmL is 0.02 g / m ² / hr), and the calculation results are obtained when the exchange water amount Q between the upper layer and the lower layer is 150,000 and 300,000 m ³ . From these results, when the sand cover and the water cycle are used together, the dissolved oxygen concentration in both the upper and lower layers is extremely high, and furthermore, due to the synergistic effect of the sand cover and the water cycle, only (b) + (d) or (c) ) + (d)
It can be seen that an effect equal to or greater than the sum of

In this embodiment, an intermittent air pump is used as the water circulating device. However, it is not always necessary to use an intermittent air pump, and air is continuously blown out through a perforated pipe installed near the sea floor. Is also good.

In the present embodiment, the water circulating device is used as the water transfer means. However, the water transfer means of the present invention includes all means capable of sending the surface water to the bottom layer. Fig. 4
As shown in (2), a pump 23 in which the water intake port 21 communicates with the surface layer side and the water discharge port 22 communicates with the bottom layer side may be adopted. In such a configuration, the surface water is once pump 2
It is sufficient to suck up at 3 and send it to the bottom layer.

With this configuration, the same effect as that of the present embodiment can be obtained, but the description is omitted here.

[0035]

As described above, according to the water purification method of the present invention, the bottom of the water area such as the sea, lake, marsh or river is covered with the covering material such as sand and the surface water in the water area is transferred to the predetermined water. Since the water is sent to the bottom layer by means, the dissolved oxygen concentration in the water area can be kept high by the synergistic effect of the sand covering and the water transfer, and therefore, it is possible to carry out the water purification efficiently at low cost.

[0036]

[Brief description of the drawings]

FIG. 1 is a view showing a water purification method according to the present embodiment, wherein (a) is an overall view and (b) is a detailed view showing an intermittent air pumping cylinder.

FIG. 2 is a model diagram obtained by performing a simulation.

FIG. 3 is a graph showing a simulation result;
(a) to (c) were performed without sand covering (both DmH and DmL were 0.2 g /
m ² / hr), the exchange water volume Q between the upper and lower layers is 10,000, 150,000, 3
The calculation result when changing to 100,000 m ³ , d) is to cover the sand (DmH and DmL are both 0.02 g / m ² / hr), and the exchange water amount Q between the upper layer and the lower layer is reduced to 10,000 m ³ (E) and (f)
Graph showing performing Kutsugaesuna (DMH, DmL with ^{0.02 g / m 2 / hr)} , a calculation result when the replacement water Q between the upper layer and the lower layer 15, 30 ten thousand m ^3, respectively.

FIG. 4 is a schematic view showing a state in which a water purification method according to a modification is being performed.

[Explanation of symbols]

1 Closed water area 2 Sea bottom (water bottom) 3 Sand (covering material) 4 Intermittent air pumping cylinder (water circulation device,
Water transfer means) 21 Pump (water transfer means)

Claims (2)

[Claims] 1. A water purification method comprising: covering a water bottom of a water area such as a sea, a lake, a river, or a river with a covering material such as sand, and sending surface water in the water area to a bottom layer by a predetermined water transfer means. 2. A water purification system according to claim 1, wherein a predetermined water circulating device is installed in said water area to serve as said water transfer means, and said surface water is sent to said bottom layer by being circulated on a circulating flow generated by said water circulating device. Construction method.