JPH0143589B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a solid-liquid separator that performs solid-liquid separation of water to be treated, such as various types of wastewater containing solids, such as sewage. .

[Conventional technology]

In general, overflow water discharged untreated from combined sewer systems during rainy days poses important problems as a source of water pollution in public waters.

In order to improve the quality of this overflow water, the combined sewage overflow control device used requires a sewerage system that strengthens two functions (control of quantity and quality). That is, solid matter in sewage is concentrated and sent to an interceptor pipe (sewage treatment plant), and excess sewage on rainy days is diverted to an outlet.

A so-called swirl water diversion tank is known as a conventional solid-liquid separation device used in this overflow adjustment device. For example, an example of a swirl water tank is shown in Figures 1 and 2, where 1 is a cylindrical outer shell of the swirl water tank, and 2 is located at the bottom of the water tank to collect inflowing sewage or wastewater containing pollutants. An inflow conduit that is introduced into the tank in the tangential direction; 3 is a flow direction control plate for distributing inflow sewage over a long distance around the periphery of the tank; 4 is a bottom of the tank for discharging treated water; A pipe installed perpendicular to (downshaft),
5 is a water collection basin attached to the top of the downshaft 4; 6 is an overflow weir attached to the periphery of the water collection basin 5;
Reference numeral 7 denotes a scum ring that surrounds the outer periphery of the overflow weir 6 and is provided at a distance therefrom to block scum floating on the water surface.

8 is a spoiler, scum ring 7 is in water collection basin 5
This system reduces the rotational energy of water above the water collection basin and between the scum ring and overflow weir, increasing the capacity of the downshaft and increasing solid-liquid separation efficiency. Reference numeral 9 indicates a scum trap for collecting substances floating on the water surface and guiding them to the bottom of the water collection basin 5; 10 indicates a sewage drain pipe; and 11 indicates an inlet drain 2 to prevent solids from accumulating on sunny days. A guide groove is provided on the floor of the tank to connect the sewage discharge pipe 10, and 12 is a treated water discharge pipe.

Treatment of inflowing sewage (or wastewater) by the swirl water diversion tank having the above structure is performed as follows. Inflow sewage flows into inflow drain 2 installed at the bottom of the swirl diversion tank.
The sewage is introduced into the tank in a tangential direction and ascends through the tank while being rotated around the downshaft 4 by the flow direction control plate 3. During this time, the sediment or sedimentary suspended matter in the sewage is absorbed by gravity and inertia. It settles under the force and is collected in the center of the tank, and is discharged through the sewage discharge pipe 10. The sewage from which sedimentary floating substances have been removed is removed by blocking the substances that float on the water surface with the scum ring 7, and the clear water passes through the lower edge of the scum ring 7 and collects over the upper edge of the overflow weir 6. The water collects in the water basin 5, has its rotational energy reduced by the spoiler 8, and is discharged through the downshaft 4 as treated water from the treated water discharge pipe 12.

The substances that float on the water surface that are intercepted by the scum ring 7 float around the scum ring, are collected by the scum trap 9, and are drawn under the water collection basin 5 by the water flow, and the overflow weir 6 collects the water. It is stored inside the downwardly extending part of the tray. When the water level in the tank decreases, these substances that float on the water surface gather in the center of the tank and are discharged from the wastewater discharge pipe 10.

In sewage treatment using such a swirl diversion tank, when the amount of sewage is low on sunny days, all inflowing sewage is guided directly to the wastewater pipe along the guide groove and transported to the sewage treatment plant. When it rains and the water level in the tank becomes high due to the large amount of inflow, the solids are separated as described above. The amount of highly concentrated sewage containing many solids is reduced as a result of concentration and is sent to the sewage pipe from the orifice. On the other hand, the remaining clear sewage is large in volume and flows over the overflow weir. Depending on the water quality standards at the destination, this overflow water may be further treated or released.

[Problem that the invention seeks to solve]

However, this swirl water tank has the following drawbacks.

Separation rate of floating objects with specific gravity less than 1 is poor.
Floating solids with specific gravity less than 1 (commonly known as S.
Regarding S), it has a separation function, but its storage capacity is limited because the discharge function does not work unless the water level in the tank decreases. Therefore, when this value is exceeded, suspended matter is mixed with the discharged (overflow) water and flows out, resulting in a decrease in separation performance.
When the water level in the water tank rises and the water overflows, the flow velocity flowing into the overflow weir 6 from the lower end of the scum ring 7 increases, and floating solids are entrained in this fast flow, and the treated water discharge pipe 12 Separation efficiency decreases due to outflow. The reason why the flow rate increases is that when the inflow amount increases significantly compared to the outflow amount from the wastewater discharge pipe 10, the water level rises and the amount of water overflows, resulting in a large amount of water. In other words, the overflow water flows from the lower end of the scum ring over the water collection basin and into the downshaft, but due to the large amount of water, the flow rate is fast and the solids suspended in the water are entrained in the overflow water. and flows into the downshaft, reducing the separation rate. Floating solids that initially flow into the basin are accumulated at the bottom of the catchment basin, but when the water level rises and water begins to flow from the overflow weir, the ability to separate floating solids decreases significantly.

It is not possible to separate and discharge floating objects all the time. For example, it cannot be carried out all the time when it is raining.

Swirl-type water tanks simply store separated floating solids in the lower part of the water collection basin, and do not have the function of discharging them to the outside of the tank until the water level drops. This is because the solids are floating in the water and are blocked by a layer of water between the sewage discharge pipe installed at the bottom of the tank and the lower layer of accumulated solids. Therefore, floating solids contained in the inflowing sewage after the water level rises are not collected by the scum trap 9, but are entrained by the flow flowing from the lower end of the scum ring over the overflow weir (because the flow velocity is faster). The amount received will be greater.

It is difficult to drain the sediment.

A scum trap or scum ring is installed to collect floating solids, which inhibits the development of secondary flow within the tank. In particular, the secondary flow generated within the tank is generated in a narrow space between the projected cylindrical portion of the diameter of the scum ring and the outer circumferential wall, so its momentum is weak and the force of accumulating sediment in the center of the tank is weak. For this reason, solids with a high specific gravity remain in the position settled on the bottom surface and are unlikely to move to the opening of the wastewater discharge pipe. Therefore, maintenance such as manually removing deposits is required on sunny days.

Solids can easily clog.

Since the swirl type is equipped with scum rings, scum traps, etc., there is a possibility that large solids may become entangled in these.

The present invention eliminates these drawbacks of the conventional ones,
It is an object of the present invention to provide a solid-liquid separator that can collect floating objects at the center of the water surface and effectively discharge them.

[Means for solving problems]

The present invention provides a tank having a circular horizontal cross section with a side wall and a bottom wall, and an inlet for allowing water to be treated to flow in in a tangential direction to the side wall. a floating object overflow pipe that is open and whose lower end passes through the bottom wall;
The solid-liquid separator is characterized in that a drainage section is provided from a part of the side wall or the bottom wall to drain the separated water to be treated.

The present invention makes effective use of the effect of the secondary flow associated with the circulation flow to concentrate the floating objects at the upper end of the overflow pipe, thereby effectively eliminating them.

[Effect]

To explain the secondary flow, fluid that flows in from the tangential direction of a water tank having a circular horizontal cross section rotates within the water tank. This becomes the mainstream (primary flow) in the aquarium. Due to the effect of surface friction, this flow causes the fluid near the water surface to flow faster than the fluid near the bottom of the tank, so it is subject to a strong centrifugal force. Moreover, the pressure in a fluid at a certain depth is high on the outside and low near the center. The fluid near the bottom has a small circumferential velocity due to the surface friction of the bottom plate, so the centrifugal force is small, but the pressure gradient is the same as in other parts due to the water flow, so the balance of forces is broken and the flow moves toward the center. will occur. This flow is a secondary flow, which merges at the center and rises vertically, flows radially at the water surface, reaches the outer edge, and descends along the side wall to become a circulating secondary flow.

〔Example〕

To give an overview of the embodiments of the present invention, an inlet is provided at the vertical center of the side surface of the aquarium or at the bottom, and the inflow water is introduced tangentially, and the force of the water is used to prevent sedimentation. In addition to precipitating the solids, two flows are generated over almost the entire circumference of the overflow pipe, from the top to the bottom of the side wall of the water tank and then downward, and then from the outer periphery of the bottom to the center, thereby removing the precipitable solids. promotes sedimentation and moves the precipitate from the periphery to the center.

In addition, floating substances rise while circulating in the water,
This secondary flow allows for faster surfacing to the water surface.

Here, a strong secondary flow occurs because only an overflow pipe is provided vertically in the center without any ring or spoiler inside the water tank. A strong secondary flow phenomenon occurs along the sides of the overflow pipe from the bottom to the surface, which causes the solids suspended in the water to float up to the water surface along the outer circumference of the overflow pipe, where they are accumulated and dislodged from the opening of the overflow pipe. The water is collected in the overflow pipe by the water flowing into the section.

In order to further strengthen the secondary flow, it is best to slope the bottom of the tank from the outer periphery toward the center so that the center is lower.

An embodiment of the present invention will be described with reference to FIGS. 3 and 4. The water tank has a side wall 13 and a bottom wall 1 having a circular horizontal cross section.
It consists of 6. A sewage inlet tube 14 is provided on the side wall 13. The shape of the inlet pipe 14 may be circular or rectangular in cross section, but water is introduced into the water tank in a tangential direction to the side wall 13 so that a circulating flow is likely to occur along the side wall 13. The overflow pipe 15 is installed upright in the center of the aquarium, has an open upper end, and a lower end that penetrates the bottom wall 16 to discharge solid matter floating on the surface of the water from the bottom of the aquarium together with the water. It is. The amount of water to be discharged changes depending on the diameter of the overflow pipe 15, which also affects the strength of the secondary flow. The height of the overflow pipe 15 affects the treatment capacity and separation efficiency of the water tank. An orifice may be provided inside the overflow pipe 15 to adjust the amount of water discharged from the pipe.

The bottom wall 16 may be a flat plate and placed horizontally, but if it is tapered as shown in Figure 4, the secondary flow will become stronger, increasing the separation efficiency and directing the solids that settle at the bottom to the center of the tank. The ability to gather people in a club becomes stronger. The bottom discharge pipe 17 is provided near the center of the bottom wall 16 to discharge solid matter having a specific gravity greater than 1 in the sewage, which settles and accumulates at the bottom, out of the tank together with the water. The opening of the bottom discharge pipe 17 is provided as close as possible to the periphery of the overflow pipe 15 on the bottom plate. It is preferable to make the diameter of this opening as small as possible in order to reduce the amount of water to be discharged, but it must also be considered that it may be blocked by large solids. This bottom discharge pipe 17
may be provided in a plural number instead of a single number, or may be provided around the bottom of the overflow pipe 15.

The outlet 18, which serves as a water distribution section for discharging the water to be treated after separation, is located above the bottom at the longest pass line farthest from the inlet of the inflow pipe 14 on the water tank side, and below the upper end of the overflow pipe 15. It's open.

The reason for providing the outlet 18 at this position is as follows. The solids contained in the sewage that flows in from the inlet are caused by circulation flow and secondary flow, with sedimentable solids settling to the bottom and floating solids floating to the center above the water surface. At the location of the outlet, the water near the side wall 13 contains relatively few solids. This phenomenon is based on knowledge gained from observing water flow.

To explain the state of the water flow near the outlet 18, the water flow is swirling along the side wall 13, and the solid matter has a force in the swirling direction due to the swirling flow.
Even in the vicinity of the outlet 18, the water flows along the side wall as it is, but depending on the water level, the water flows toward the outlet 18, but solid matter is not entrained therein. The reason for this is thought to be due to the difference in the influence of inertial force exerted by the swirling flow between solids and water, and that solids cannot change direction as quickly as water.

A discharge weir 19 is provided on the downstream side of the discharge port, and when water exceeding the specified amount flows in, the water level of the tank is raised to the discharge weir 19.
The overflow water is allowed to flow from this discharge weir 19 into the discharge channel only when it reaches the upper end of the discharge weir. The so-called first flush phenomenon occurs in which pollutants with a high concentration of organic matter flow into this weir at the beginning of a rainfall. It is meant to be sent to a treatment plant.

In the figure, 20 is a stabilizing plate for preventing wave motion. Stabilizer plate 2 from the upper end of the overflow pipe 15
The height of 0 is appropriately selected depending on the overflow amount, rotation speed, etc. Lower than the position shown in Figure 4,
The position may be slightly above the upper end of the overflow pipe 15. To explain the operation, inflowing sewage (wastewater) is introduced into the lower part of the tank through the inlet of the inflow tube 14, swirls along the side wall 13, and as the amount of inflow water increases, the water level in the tank rises and the water level reaches the overflow pipe. When reaching the upper end of 15, the overflow pipe 15
It flows downward from the top of the tank and out of the tank.

Note that when the water level rises to the upper end of the discharge weir 19, water flows from the discharge weir 19 to the discharge channel.

During this time, among the solids contained in the sewage (wastewater), the sediment content or settleable solids settle to the bottom of the tank due to gravity, the swirling flow in the tank, and the fluid force of the secondary flow generated by this. At the same time, the water is collected at the center bottom of the tank, and is discharged from the bottom discharge pipe 17 together with water to the outside of the tank.

The floating solids floating on the water surface flow into the tank, float while swirling due to the swirling flow, and collect at the upper end of an overflow pipe 15 provided at the center of the tank.
At this time, the floating solids are promoted to float due to the secondary flow 21 generated in the tank. This is considered to be due to the secondary flow rising around the overflow pipe 15 from the bottom toward the water surface. The floating solids floating on the water surface are carried by the flow flowing from the free surface into the overflow pipe, are discharged outside the tank, and are sent to the sewage treatment plant via the sewer pipe. The sewage from which solids have been removed flows from a discharge port 18 provided in the side wall 13 of the water tank, over a discharge weir 19, and into a discharge channel.

〔Effect of the invention〕

The present invention provides a tank having a side wall and a bottom wall with a circular or spiral horizontal cross section, and is provided with an inlet for allowing water to be treated to flow in in a tangential direction to the side wall, and an inlet which stands upright in the center of the tank. By providing a floating object overflow pipe whose upper end is open and whose lower end penetrates the bottom wall, and a drainage section that drains the separated water to be treated from a part of the side wall or the bottom wall, The floating solids are collected at the center of the water surface, resulting in a good separation rate for floating solids with low specific gravity, and the floating solids with low specific gravity can be effectively discharged outside the tank at all times during rain, allowing them to be treated at a sewage treatment plant. At the same time, precipitates having a large specific gravity can be efficiently discharged from the bottom of the tank to the outside of the tank without being deposited on the bottom surface of the tank. That is, because the secondary flow is developed, the solids that have settled on the bottom surface flow toward the center of the tank due to the secondary flow, are concentrated, and are discharged from the bottom discharge pipe to the outside of the tank. Furthermore, by sloping the bottom of the water tank so that the center is lower than the outer periphery, the secondary flow becomes stronger, improving the separation effect, and the degree to which sediment accumulates in the center increases, concentrating it and discharging it to the bottom. effectively discharged from the pipe,
In addition, since the mechanism is simple, it is difficult for solid matter to become clogged, maintenance is simplified, and furthermore, the floating solid matter can be effectively and reliably separated and removed, which is a useful effect.

[Brief explanation of drawings]

Figure 1 is a plan view of an example of a conventional swirl water tank.
FIG. 2 is a partially sectional front view thereof, FIG. 3 is a plan view of an embodiment of the present invention, and FIG.
The figure is a sectional front view taken along the line -- in FIG. 3. 1...Outer shell, 2...Inflow conduit, 3...Flow direction control plate, 4...
Downshaft, 5...water collection basin, 6...overflow weir, 7...
Scum ring, 8... Spoiler, 9... Scum trap, 10... Sewage discharge pipe, 11... Guide groove, 12... Treated water drain pipe, 13... Side wall, 14... Inflow pipe, 15...
Overflow pipe, 16...bottom wall, 17...bottom discharge pipe, 18...discharge port, 19...discharge weir, 20...stabilizer, 21...secondary flow.

Claims (1)

[Scope of Claims] 1. A tank having a circular horizontal cross section with a side wall and a bottom wall is provided with an inlet that allows the water to be treated to flow in in a tangential direction to the side wall, and an inlet that is erect in the center of the tank. A floating object overflow pipe whose upper end is open and whose lower end penetrates the bottom wall, and a drainage section for draining the separated water to be treated from a part of the side wall or the bottom wall are provided. Solid-liquid separation equipment. 2. The device according to claim 1, wherein the drainage section is a discharge port provided at an intermediate height of the side wall. 3 A tank having a side wall and a bottom wall having a circular horizontal cross section is provided with an inlet for allowing the water to be treated to flow in in a tangential direction to the side wall, and stands upright in the center of the tank with an open top end, and A floating matter overflow pipe whose lower end penetrates the bottom wall, a drainage section for draining the separated treated water from a part of the side wall or the bottom wall, and a sedimentation area provided near the penetration section of the overflow pipe. A solid-liquid separator characterized in that it is equipped with a material discharge port. 4. The device according to claim 3, wherein the drainage portion is a discharge port provided at an intermediate height of the side wall.