JP7359709B2 - Sedimentation pond - Google Patents

Description

The present invention relates to a sedimentation tank, and particularly to a sedimentation tank that can be suitably used as a final sedimentation tank in a sewage treatment plant.

Conventionally, in sewage treatment plants and the like, water treatment systems including an initial sedimentation tank, a biological reaction tank, and a final sedimentation tank have been used.

In recent years, as settling tanks such as the initial settling tank and the final settling tank, there is a settling part that precipitates solids in the water to be treated, and a filtration part that filters the water to be treated after some of the solids have been precipitated in the settling part. It has been proposed to use a settling tank equipped with: According to this sedimentation basin equipped with a settling section and a filtration section, the water to be treated in which a portion of the solid content has been precipitated in the settling section can be further filtered in the filtration section, so that the solid content is sufficiently removed. You can get water.

Here, in the above-mentioned conventional settling tank equipped with a filtration section, the filter medium of the filtration section is usually cleaned at predetermined time intervals or when the solid-liquid separation performance of the filtration section deteriorates. The cleaning of the filter medium is usually performed by injecting a gas such as air into the filtration section to aerate it, and by shaking the filter medium with the water flow generated at this time.

On the other hand, the cleaning wastewater after cleaning the filter media is discharged and stored in a storage tank outside the sedimentation tank using the power of a drainage pump, and then returned to the inlet of the sedimentation tank via piping. (For example, see Patent Documents 1 and 2).

Patent No. 3015274 Patent No. 3394839

However, as mentioned above, a drainage pump and piping are essential in order to discharge the washing wastewater outside the sedimentation tank and return it to the inlet of the sedimentation tank, which has been a problem in terms of cost. Furthermore, since a place is required to install the drainage pump and piping, there is also the problem of securing such an installation place. Furthermore, the pump requires maintenance and management, which poses additional cost problems, as well as problems such as the inability to clean it in the event of an abnormality.

An object of the present invention is to provide a sedimentation basin that has a sedimentation part and a filtration part, and is capable of cleaning the filter material of the filtration part with a simple and inexpensive configuration that does not use a pump or piping. shall be.

The present inventors have proposed that in a sedimentation pond in which a settling part is arranged on the upstream side with respect to the inflow side of the water to be treated and a filtration part is arranged in the downstream part, an outflow trough is arranged adjacent to the filtration part, and They discovered that by disposing a gate at a predetermined location of this outflow trough and opening and closing this gate, the washing wastewater that has washed the filtration part can be returned to the sedimentation part, and the present invention was conceived.

That is, the sedimentation tank of the present invention includes a sedimentation section that precipitates solid content contained in the water to be treated, and a partition wall extending in the depth direction to partition the surrounding area from the sedimentation section, and a bottom portion between the sedimentation section and the sedimentation section. A filtration section that communicates with the filtration section, a filter layer held in the filtration section, an outflow trough that is disposed adjacent to the upper opening of the filtration section and into which treated water that has overflowed from the filtration section flows, and a filter layer held in the filtration section. an aeration section disposed below or inside to aerate and clean the filter layer; , a washing waste water discharge gate for returning the washing waste water that has flowed into the outflow trough to the settling section is provided, and when the filter medium layer is washed by aeration from the aeration section, the treated water discharge gate is provided. The washing waste water discharge gate is closed, the washing waste water discharge gate is opened, and the washing waste water flowing into the outflow trough from the filtration part is returned from the washing waste water discharge gate to the settling part.

In the present invention, there is provided a water quality sensor that detects the water quality of the washing wastewater, and when the cleanliness of the washing wastewater detected by the water quality sensor becomes better than a predetermined value, aeration from the aeration section is terminated. It is preferable to configure it so that.

In the present invention, the water level sensor includes a water level sensor that detects the water level in the settling section, and the gate height when the cleaning wastewater discharge gate is opened is determined according to the water level detected by the water level sensor. It is preferable.

In the present invention, it is preferable that the washing water discharge gates are provided at a plurality of locations in the outflow trough.

According to the present invention, it is possible to provide a sedimentation tank that has a sedimentation part and a filtration part, and is capable of cleaning the filter material of the filtration part with a simple and inexpensive configuration that does not use a pump or piping. I can do it.

BRIEF DESCRIPTION OF THE DRAWINGS It is a top view which shows the sedimentation tank of 1st Embodiment of this invention. FIG. 2 is a sectional view taken along line II-II of the settling tank shown in FIG. 1. FIG. 2 is a cross-sectional view taken along line AA of the settling tank shown in FIG. 1. FIG. 2 is a sectional view taken along line BB of the settling tank shown in FIG. 1. It is a figure explaining the washing|cleaning operation of the filter medium in the filtration part of the sedimentation tank in 1st Embodiment of this invention. It is a figure explaining the washing|cleaning operation of the filter medium in the filtration part of the sedimentation tank in 1st Embodiment of this invention. It is a figure explaining the washing|cleaning operation of the filter medium in the filtration part of the sedimentation tank in 1st Embodiment of this invention. It is a figure explaining the washing|cleaning operation of the filter medium in the filtration part of the sedimentation tank in 1st Embodiment of this invention. It is a top view which shows the sedimentation tank of 2nd Embodiment of this invention. It is a top view which shows the sedimentation tank of 3rd Embodiment of this invention.

(First embodiment)
FIG. 1 is a plan view showing the settling tank of this embodiment, FIG. 2 is a sectional view taken along line II-II of the settling tank shown in FIG. 1, and FIG. 3 is a plan view showing the settling tank shown in FIG. 4 is a sectional view taken along line A, and FIG. 4 is a sectional view taken along line BB of the settling tank shown in FIG.

As shown in FIGS. 1 to 4, the settling tank 10 of the present embodiment has a settling section 11 on the upstream side with respect to the inflow side of the water to be treated, and has a settling section 11 adjacent to the settling section 11 on the downstream side of the water to be treated. It has a filtration section 12 arranged in this way. Note that the filtration section 12 is circumferentially divided from the settling section 11 by a partition plate (partition wall) 13 extending in the depth direction. The upper end of the partition plate 13 is higher than the water surface, and the lower end thereof extends to the middle of the water depth, specifically, to a depth that reaches the lower end of the filter medium of the filtration section 12, which will be described below.

Further, as shown in FIGS. 1 to 4, the bottom of the filtration section 12 communicates with the sedimentation section.

Further, an outflow trough 14 formed in a gutter shape is arranged adjacent to the filtration part 12 (in this embodiment, on both sides of the filtration part 12), and the purified treated water flowing out from the filtration part 12 is The water overflows from the upper edge of the filtration part 12 and flows into the outflow trough 14, and is taken out of the settling tank 10 through a pair of treated water discharge gates 15 disposed on the downstream side of the outflow trough 14.

Further, a pair of first cleaning waste water discharge gates 16 are arranged on the upstream side of the outflow trough 14, specifically, in substantially the same plane as the part where the partition plate 13 is arranged, and on the downstream side of the outflow trough 14, Specifically, a pair of second wash water discharge gates 17 are disposed inside the outflow trough 14 so as to be in orthogonal contact with the treated water discharge gates 15 .

The sedimentation section 11 is not particularly limited, and is a cross-flow type sedimentation tank that separates the solid content from the water to be treated by settling the solid content in the water to be treated by gravity sedimentation. A solid content discharge pipe having a solid content discharge valve (not shown) is provided at the bottom of the settling part 11, and the solid content precipitated in the settling part 11 is removed from the solid content discharge valve provided in the solid content discharge pipe. is discharged from the sedimentation tank 10 and processed by keeping it open at a predetermined opening degree or at predetermined intervals, for example.

Note that the sedimentation section 11 may include an inclined plate that promotes sedimentation of the solid content, a reciprocating scraper that scrapes the solid content that has settled to the bottom, or the like.

The filtration part 12 may be provided, for example, at a position from 1/4 to 3/4 of the total length of the pond from the introduction part of the water to be treated. A floating filter medium 121 is disposed in the filter section 12, and the filter medium 121 can be made of any suitable material such as foamed plastic with a specific gravity of less than 1.0, sponge, or fibrous, and its shape can be selected as appropriate. A granular shape, a cylindrical shape, a spherical shape with hollow holes, a spiral shape, etc. with a size of about 3 to 100 mm and a large contact area with wastewater are used. The filter medium 121 is held on a mesh-like support plate (not shown) disposed in the filter section 12 .

In the sedimentation tank 10 shown in FIGS. 1 to 4, for example, in order to remove organic components from the water to be treated, first, the treated water discharge gate 15 is opened, and the first washing waste water discharge gate 16 and the second washing waste water discharge gate are opened. The gate 17 is kept closed. Then, the water to be treated is biologically treated in a biological reaction tank (not shown) so that the SS concentration is in the range of 1000 to 10000 mg/l, and then introduced into the sedimentation tank 10. The introduced water to be treated causes relatively coarse solids to naturally settle in the sedimentation section 11 and is deposited on the bottom. As a result, coarse solids are removed from the water to be treated, and the SS concentration is reduced to, for example, 5 to 30 mg/l. The accumulated solids are discharged to the outside of the settling tank 10 from the solids discharge pipe via the solids discharge valve (not shown) as described above.

In this way, the water to be treated flows into the settling section 11, and when the water level in the settling section 11 becomes higher than the water level in the filtration section 12, the water to be treated in the settling section 11 flows into the filtration section 12, and the filter material in the filtration section 12 121 upward, fine solid matter is captured and removed by the filter medium 121. When the water level in the filtration part 12 becomes higher than the outflow trough 14, the treated water that has passed through the filtration part 12 overflows the boundary wall between the filtration part 12 and the outflow trough 14 and flows into the outflow trough 14. The treated water then flows out of the settling tank 12 through the treated water discharge gate 15 . In this way, the treated water that has passed through the filtration section 12 can be discharged into a river or the like, for example.

As described above, when the water to be treated is purified in the settling tank 10 shown in FIGS. 1 to 4, fine solid matter adheres to the filtration section 12, especially the filter medium 121, and the filtration efficiency decreases. Therefore, it is necessary to clean the filter medium 121.

5 to 8 are diagrams illustrating the cleaning operation of the filter medium 121 in the filtration section 12 of the settling tank 10. Note that the arrows in the figure indicate the flow of water or air.

First, as shown in FIG. 5, the treated water discharge gate 15 is closed to stop the wash water from flowing out of the settling tank 10 from the filtration section 12. Further, the first wash water discharge gate 16 and the second wash water discharge gate 17 are also kept closed. At this time, as shown in FIG. 5, since there is a difference between the water level in the settling section 11 and the water level in the filtration section 12, the water to be treated in the settling section 11 flows into the filtration section 12. Note that arrow A in FIG. 5 indicates the flow of water. However, as shown in FIG. 6, when the water levels in the settling section 11 and the filtration section 12 become equal, water flow to the settling basin 10 is stopped.

Next, as shown in FIG. 7, air is sent from the blower 18 disposed in the settling basin 10 to the filter medium 121 of the filtration unit 12 via the aeration part 20a of the piping 20 provided below the filtration unit 12. The filter medium 121 is aerated by the water flow generated at that time. Note that arrow B in FIG. 7 indicates the flow of air. As a result, the solid matter adhering to the filter medium 121 is peeled off and resuspended in the water (washing waste water). Note that the aeration section 20a of the piping 20 may be disposed within the filtration section 12, that is, within the filter medium 121.

On the other hand, since the cleaning waste water of the filter medium 121 contains air from the aeration, the water level of the cleaning waste water rises. At this time, by opening the pair of first cleaning waste water discharge gates 16 (lowering the gates) using the actuator 161, as shown in FIG. As shown, the water flows out through the outflow trough 14 from the first washing wastewater discharge gate 16 to the settling section 11 . In addition, by opening the pair of second washing waste water discharge gates 17 (lowering the gates) using the actuator 171, the washing waste water mainly downstream of the filtration section 12 flows through the outflow trough 14 as indicated by the arrow in the figure. The water flows out from the second washing wastewater discharge gate 17 to the settling section 11 .

Note that the heights of the first washing wastewater discharge gate 16 and the second washing wastewater discharge gate 17 are determined depending on the water level of the settling section 11. That is, the water level is set to be lower than the water level flowing through the outflow trough 14 and higher than the water level in the settling section 11. The water level can be measured using a water level sensor 19 such as an ultrasonic type or an electrode type.

The washing waste water flows into the filtration section 12 again after the solid matter contained therein is settled and removed in the settling section 11 . Thereafter, the water flows out through the outflow trough 14 again from the first wash water discharge gate 16 to the sedimentation section 11, and flows out through the outflow trough 14 from the second wash water discharge gate 17 into the sedimentation section 11. After the solid matter is sedimented and removed again in the sedimentation section 11, the obtained washing wastewater flows into the filtration section 12 again.

As described above, the filter medium 121 of the filtration unit 12 is circulated between the filtration unit 12 and the settling unit 11, and is washed using cleaning wastewater from which solids are gradually removed, that is, purified water. Therefore, unlike in the past, there is no need to use a drainage pump or piping, so problems such as cost and installation location can be avoided, and problems such as maintenance and management of the pump can also be avoided. Therefore, the filter medium 121 of the filtration section 12 of the settling tank 10 having the settling section 11 and the filtration section 12 can be cleaned with a simple and inexpensive configuration that does not use a pump or piping.

Moreover, in this embodiment, since the filter medium 121 is washed with circulating water that has been circulated through the settling section 11 and the filtration section 12, the cleaning effect of the filter medium 121 can be improved.

Furthermore, in this embodiment, a plurality of washing wastewater discharge gates, that is, a first washing wastewater discharge gate 16 and a second washing wastewater discharge gate 17, are provided on the upstream and downstream sides of the outflow trough 14 disposed on both sides of the filtration section 12. Since the washing wastewater is used, the washing wastewater can be dispersed and returned to the sedimentation tank 11, and the purification effect of the circulating washing wastewater can be enhanced.

However, the number of cleaning waste water discharge gates is arbitrary and can be freely controlled according to the type and size of the filter medium of the filtration section 12.

Furthermore, in the present embodiment, the first washing wastewater discharge gate 16 disposed substantially on the same plane as the partition plate 13 is opened to allow the washing wastewater of the filter medium 121 of the filtration part 12 to flow out into the settling part 11. During the cleaning operation, the height of the partition plate 13 may be appropriately adjusted so that the cleaning wastewater flows over the partition plate 13 and flows into the settling section 11.

After the blower 18 is driven for a certain period of time, or when a water quality sensor (not shown) detects that the water quality of the cleaning wastewater, such as turbidity or SS concentration, is below a predetermined value or the light transmittance is above a predetermined value, the filtration section 12 is After the filter medium 121 has been sufficiently cleaned, the blower 18 is stopped, the treated water discharge gate 15 is opened, the first cleaning wastewater discharge gate 16 and the second cleaning wastewater discharge gate 17 are closed, and the above-mentioned process is performed. Purify the water to be treated.

(Second embodiment)
FIG. 9 is a plan view showing the settling tank in this embodiment. Note that the same reference numerals are used for components similar to or the same as those in FIGS. 1 to 8 in the first embodiment.

As shown in FIG. 8, the sedimentation basin 20 of this embodiment is constructed such that the outflow trough 14, which is also provided with a trough on the upstream side of the sedimentation part 11 of the filtration part 12, surrounds the filter medium 121 of the filtration part 12. It is formed in the shape of a letter. Further, a partition plate 13 is provided at a location adjacent to the sedimentation section 11 on the downstream side of the filtration section 12, and a movable partition plate 23 is provided at a location adjacent to the sedimentation section 11 on the upstream side of the outflow trough 14. has been done.

The cleaning of the filter medium 121 of the filter section 12 in this embodiment is basically performed in the same manner as shown in FIGS. 5 to 8 of the first embodiment. That is, since the washing wastewater containing the air above the filter medium 121 contains the air from the aeration, the water level of the washing wastewater rises.

At this time, by opening the movable partition plate 23 using an actuator (not shown) or the like (for example, by lowering the partition plate or overturning the partition plate), the cleaning waste water that has passed through the filtration section 12 can flow out as shown by the arrow in the figure. It flows out from the movable partition plate 23 to the settling section 11 via the trough 14. Further, by opening the pair of second cleaning waste water discharge gates 17 using an actuator (not shown) (for example, lowering the gates), the cleaning waste water that has passed through the filtration section 12 passes through the pair of second cleaning waste water discharge gates 17 and flows into the outflow trough 14. It also flows out to the settling section 11 from the downstream side.

In this embodiment, the movable partition plate 23 and the second washing wastewater discharge gate 17 are used on the upstream and downstream sides of the outflow trough 14 arranged in a U-shape around the filter medium 121 of the filtration section 12. , the cleaning wastewater that has passed through the filtration section 12 can be allowed to overflow from a wide area around the outer periphery of the filtration section 12 and flow into the outflow trough 14, thereby reducing the unevenness of the water passing through the filtration material 121. The upstream and downstream sides can be cleaned almost uniformly and stably.

Other features and advantages are the same as those in the first embodiment, so their description will be omitted.

(Third embodiment)
FIG. 10 is a plan view showing the settling basin in this embodiment. Note that the same reference numerals are used for drawings that are similar or similar to the drawings related to FIGS. 1 to 7 in the first embodiment.

As shown in FIG. 10, in the sedimentation basin 30 of this embodiment, an upper horizontal outflow trough 141 exists between the sedimentation part 11 and the filtration part 12 on the filtration part 12; A ladder-shaped outflow trough 14 is disposed in which there is a central horizontal outflow trough 142, and a vertical outflow trough 143 is arranged in orthogonal contact with the central horizontal outflow trough 142. Furthermore, the filtration section 12 is surrounded by outflow troughs 141, 142, and 143 and arranged at two locations. An opening that communicates with the sedimentation tank 11 is provided on the downstream side of each filtration section 12 . A pair of first washing wastewater discharge gates 16 are arranged inside the vertical outflow trough 143 so as to be in orthogonal contact with the central horizontal outflow trough 142, and the sediment is passed through the first washing wastewater discharge gates 16. Washing waste water can be returned to the pond 11. Further, similarly to the first embodiment, a pair of second washing wastewater discharge gates 17 are provided inside the vertical outflow trough 143 so as to be in orthogonal contact with the downstream side of the outflow trough 14, specifically with the treated water discharge gate 15. The washing wastewater can be returned to the settling tank 11 even through the second washing wastewater discharge gate 17.

Note that the words "horizontal" and "vertical" in the above are used for convenience to distinguish the members, and do not specify the absolute positional relationship of these members.

The cleaning of the filter medium 121 of the filter section 12 in this embodiment is basically performed in the same manner as shown in FIGS. 5 to 8 of the first embodiment.

That is, since the washing wastewater containing air above the filter medium 121 contains air from aeration, when the water level of the washing wastewater rises and overflows into the outflow trough 14, the pair of first By opening the cleaning waste water discharge gate 16 with an actuator (not shown) (lowering the partition plate), the cleaning waste water flowing through the vertical outflow trough 143 adjacent to the filtration section 12 disposed on the upstream side flows through the first cleaning waste water discharge gate 16. It flows out into the settling section 11 from there.

In addition, by opening the pair of second washing waste water discharge gates 17 (lowering the gates) using an actuator (not shown), the washing waste water flowing through the vertical outflow trough 143 adjacent to the filtration section 12 disposed on the downstream side is discharged to the second washing waste water. The cleaning wastewater flows out from the discharge gate 17 to the settling section 11 .

In this embodiment, the ladder-shaped outflow trough 14 as described above is provided, and the first wash water discharge gate 16 is provided on the upstream side of the vertical outflow trough 143 that is perpendicular to the outflow trough 142 at the center horizontal step. However, since the second washing wastewater discharge gate 17 is used on the downstream side, the washing wastewater that has passed through the filter media 121 of the filtration section 12 arranged in two locations is efficiently dispersed and returned to the settling tank 11. be able to. Therefore, the purification effect of the circulating cleaning waste water can be enhanced.

Other features and advantages are the same as those in the first embodiment, so their description will be omitted.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

For example, in the above embodiment, a partition plate 13 or the like is provided between the sedimentation section 11 and the filtration section 12 to separate them, but as shown in the second or third embodiment, the sedimentation section 11 and the filtration section 12 are separated. An outflow trough 14 may be disposed between the filter section 12 and the outflow trough 14, and the outflow trough 14 may be partitioned by its wall surface.

10, 20, 30 Sedimentation tank 11 Sedimentation section 12 Filtration section 121 Filter medium 13 Partition plate 14 Outflow trough 15 Treated water discharge gate 16 First wash wastewater discharge gate 17 Second wash wastewater discharge gate 18 Blower 19 Water level sensor 20 Piping 20a Aeration Part 23 Movable partition plate 141 Upper horizontal outflow trough 142 Center horizontal outflow trough 143 Vertical outflow trough

Claims (3)

a settling section that precipitates solids contained in the water to be treated; a filtration section whose periphery is divided from the settling section by a partition wall extending in the depth direction and which communicates with the settling section at the bottom;
a filter medium layer held in the filtration section;
an outflow trough that is disposed adjacent to the upper opening of the filtration section and into which treated water that has overflowed from the filtration section flows;
an aeration unit disposed below or inside the filter layer for aerating and cleaning the filter layer ;
Equipped with a water quality sensor that detects the water quality of cleaning wastewater.
The outflow trough includes a treated water discharge gate for allowing the treated water that has flowed into the outflow trough to flow out to the outside, and a wash water discharge gate that allows the wash water that has flowed into the outflow trough to directly flow down to the settling section. is provided,
When the filter media layer is aerated and washed by the aeration section, the treated water discharge gate is closed, and the washing waste water discharge gate is opened to allow the water to be treated to flow from the outside into the settling section. is configured such that the washing wastewater flowing out from the filtration part flows directly into the settling part via the outflow trough and the washing wastewater discharge gate,
The sedimentation basin is characterized in that the aeration from the aeration section is terminated when the cleanliness of the washing wastewater detected by the water quality sensor becomes better than a predetermined value. a settling section that precipitates solids contained in the water to be treated;
a filtration part whose periphery is divided from the precipitation part by a partition wall extending in the depth direction and communicates with the precipitation part at the bottom;
a filter medium layer held in the filtration section;
an outflow trough that is disposed adjacent to the upper opening of the filtration section and into which treated water that has overflowed from the filtration section flows;
an aeration section disposed below or inside the filter layer for aerating and cleaning the filter layer; and a water level sensor for detecting the water level of the settling section;
The outflow trough is provided with a treated water discharge gate for allowing the treated water that has flowed into the outflow trough to flow out to the outside, and a wash water discharge gate for returning the wash water that has flowed into the outflow trough to the settling section. has been
When cleaning the filter layer by aeration from the aeration section, the treated water discharge gate is closed, the cleaning wastewater discharge gate is opened, and the cleaning wastewater that has flowed from the filtration section into the outflow trough is discharged. It is configured to return from the gate to the precipitation section, and
A sedimentation basin characterized in that the height of the washing wastewater discharge gate when opened is determined in accordance with the water level detected by the water level sensor. The sedimentation basin according to claim 1 or 2, wherein the washing wastewater discharge gates are arranged at a plurality of locations in the outflow trough.