JP6765041B2 - How to maintain the treatment environment in the outdoor sedimentation basin - Google Patents

Description

The present invention relates to a method for maintaining a treatment environment in an outdoor sedimentation basin for clarification treatment of polluted water.

Conventionally, typical sedimentation basins for clarifying polluted water containing pollutants include, for example, a cross-flow type ordinary sedimentation basin, a cross-flow type chemical sedimentation basin, a radial flow type ordinary sedimentation basin, and a radioactive flow type chemical sedimentation basin. , High-speed coagulation sedimentation basin, etc. are known. These sedimentation basins are generally installed outdoors.
When the sedimentation basin was installed outdoors in this way, the treatment conditions at the time of design could not be maintained due to the climate and meteorological conditions, and as a result, the desired clarification of polluted water could not be performed. That is, in general, the main flow of the sedimentation basin is concentrated near the water surface, so it was necessary to partially accelerate the flow with a rectifying wall to widen the cross section of the water flow under the water depth. Therefore, a rectifying facility is provided to reduce the drift in the sedimentation pond and increase the removal rate. However, in an actual sedimentation basin, the water flow in the pond may be turbulent, which is far from the ideal state, due to the turbulence of the water flow itself, the climate, and the weather conditions. For example, when the wind speed is 5 m / S or more, water disturbance occurs up to a depth of 0.5 m, and the temperature difference between the surface layer surface and the bottom of the treated water in the settling pond is 1 ° C., which makes the flow velocity 10 times faster, which is sufficient. The clarification process cannot be performed.

Therefore, in recent years, a settling basin that covers the ceiling of the settling basin has been proposed as a settling basin that can respond to changes in weather conditions (Patent Document 1).
However, there is a drawback that it costs a huge amount of money to cover the ceiling of the sedimentation basin and the equipment provided inside cannot be replaced.

Japanese Unexamined Patent Publication No. 2013-146685

Therefore, the present inventor obtains satisfactory results by maintaining the processing environment even when the weather conditions change, and by conducting various studies on a method that satisfies a certain clarification processing condition, and by providing simple equipment. I was able to.

That is, in the present invention, at least one mesh-like film is spread on the water surface of the outdoor settling basin at an arbitrary position at a height from the water surface to the upper edge of the side wall of the outdoor settling basin. It is a method of maintaining the treatment environment of the outdoor type sedimentation basin.

In the method of the present invention, a boundary layer can be provided by the mesh-like membrane by spreading at least one mesh-like membrane on the water surface of the outdoor sedimentation basin, whereby the treated water in the sedimentation basin by wind can be provided. It is possible to prevent disturbance, prevent the water temperature from rising due to sunlight, and prevent the water temperature from dropping due to radiant heat and snowfall in winter, and the raw water can be treated under stable treatment conditions. In addition, since the mesh-like membrane can be easily installed, the cost can be significantly reduced and the maintenance inside the settling tank can be easily performed.

It is a side sectional view of the conventional cross flow sedimentation basin. It is a top view of the cross flow sedimentation pond of FIG. It is a front view of the water flow gradient film. It is a side view of the water flow gradient film of FIG. It is a perspective view of the mesh-like film of this invention. It is a side sectional view of the cross-flow sedimentation basin in which the mesh-like film of the present invention is spread. It is a side sectional view of the radiant flow type ordinary sedimentation basin in which the mesh-like film of the present invention is spread. It is a top view of the radiant flow type ordinary sedimentation pond in which the mesh-like film of this invention was spread.

A cross-flow sedimentation basin as shown in FIG. 1 is known as a typical outdoor sedimentation basin of the present invention. The structure of this cross-flow sedimentation basin is composed of a mixing tank 1, a floc forming tank 2, a rectifying wall 4 provided with a hole 3, a sedimentation tank 5, an intake trough 6, a treated water discharge pipe 7, and a mud drain 8.

Next, a case where raw water containing a pollutant is treated by the cross-flow sedimentation basin shown in FIG. 1 will be described.
The raw water containing the pollutant is rapidly stirred in the mixing tank 1 after the coagulant is added, then slowly stirred in the floc forming tank 2, and then passed through the rectifying wall 4 having the holes 3 and settled in the settling tank 5. Pass through. At that time, the flocked pollutants are separated and removed, and the mud is collected in the mud drain 8 at the bottom. The flocked pollutants collected in the mud collecting culvert 8 are discharged from the sludge collecting pipe. The treated water that has passed through the settling tank 5 is discharged from the treated water discharge pipe 7 to the outside of the settling basin via the catchment trough 6.

Further, it is preferable to extend a water flow gradient film 10 as shown in FIG. 2, for example, in order to enhance the sedimentation effect of the flocculated pollutant in the early sedimentation tank 5. As shown in FIGS. 3 and 4, the water flow gradient film 10 can be configured by providing a float 12 on the upper part of the sheet-like film 11 and connecting the float 12 with a shackle or the like. At that time, it is necessary to provide an interval portion 13 between the sheet-like film 11 and the adjacent sheet-like film 11. Although the spacing portion 13 depends on the speed of the water flow, it is generally preferable to provide a spacing of 5 to 20 cm.

In the method of the present invention, a mesh-like film is stretched so as to cover the water surface of the sedimentation basin as described above. As shown in FIG. 5, examples of the mesh-like film 14 used in the method of the present invention include a knotted net, a knotless net, a molded net, and a cheesecloth. These mesh-like films 14 can be either variable or non-deformable in the form of thin plastic plates. The size of one eye of the mesh-like film 14 is preferably 1 mm ^{2 to} 100 cm ² .

The mesh-like film 14 extends at least the entire upper part of the water surface of the settling tank 5 of the settling basin or a part of it. As a specific extension position, it is preferable to extend the extension from the water surface to an arbitrary position (height) between the upper edge of the side wall of the settling tank 5. Further, a plurality of sheets may be stacked, or when the plurality of sheets are stacked, they may be provided at intervals between the upper and lower mesh-like films 14 of the mesh-like film 14. The effect is further improved by using a plurality of mesh-like films 14 in layers in this way.

As a method of spreading the mesh-like film 14 in the settling tank 5, when the water flow gradient film 10 as shown in FIG. 6 is used, the float 12 is used and the mesh is meshed on the float 12 by an appropriate means. It can be expanded by fixing the membrane 14. Further, the stretched mesh-like film 14 does not necessarily have to be entirely on the water surface, and in some cases, a part of the stretched mesh-like film 14 may be immersed in the water surface or water.

Further, the effect of the mesh-like film 14 used in the method of the present invention is further improved by spreading it in the mixing tank 1 and the floc forming tank 2 in addition to the precipitation tank 5.

As another method of spreading the mesh-like film 14 in the settling tank 5, in the case of a radiant flow type ordinary settling basin as shown in FIG. 7, it can be spread by fixing the mesh-like film 14 on the outer circumference. .. Further, the stretched mesh-like film 14 does not necessarily spread over the entire sedimentation basin, but can be spread by fixing a plurality of mesh-like films 14 evenly on the outer peripheral side as shown in FIG.

The method of the present invention can be used not only in a settling basin for clarifying polluted water containing a pollutant substance, but also in a settling basin used in a production process of, for example, calcium hydroxide or magnesium hydroxide.

Next, the method of the present invention will be described with reference to Example 1, but the present invention is not limited to the following examples.
Example 6 A mesh-like film 14 was stretched and fixed on a float 12 of a water flow gradient film 10 provided in a settling tank 5 of a transverse settling basin having a length of 30 m and a width of 10 m shown in FIG.
When raw water (turbidity 39000 mg / L, water volume 240 m ³ / hr) was treated in winter (air temperature 0 ° C, water temperature 26 ° C, wind speed 5 m / S) using this cross-flow sedimentation basin, it was collected from the treated water discharge pipe 7. The turbidity of the water was 60 mg / L.
On the other hand, when the raw water was treated under almost the same conditions as in the above-mentioned example except that the mesh-like membrane 14 was not used for comparison, the treated water collected from the treated water discharge pipe 7 had a turbidity of 350 mg / L.

5 ... Precipitation tank 14 ... Mesh-like film

Claims (1)

At least one mesh-like film is spread on the water surface of the outdoor settling basin at an arbitrary position at a height from the water surface to the upper edge of the side wall of the outdoor settling basin to provide a boundary layer. A method of maintaining the treatment environment of the characteristic outdoor settling basin.

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