JPH11651A - Apparatus for removing suspended matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for removing suspended matter suitable for treating a raw water having a low suspended-matter content without using a flocculant. SOLUTION: This apparatus for removing suspended matter comprises a mixed water feed pipe 2 for feeding a mixed water produced by injecting bubbles through a bubble generating device 2 into raw water containing the suspended matter, a floatation tank 3 having a circular cylindrical shape having a bottom part thereof connected to the mixed water feed pipe 1 in a tangential direction of an outer circumference for causing bubbles including the suspended matter adhering thereto to float when the mixed water swirls in the tank, a condensed water introducing pipe 4 provided vertically on a bottom of a central axis part of the floatation tank 3 and having an opening 4a in a top part for introducing the condensed water containing the suspended matter caused to float in the floatation tank 3 through overflowing, and a treated water discharge pipe 5 connected to an outer circumference of a lower part of the floatation tank 3 in a tangential direction of a swirling flow downstream of the swirling flow of the mixed water for discharging remaining treated water from which the suspended matter has been caused to float.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspended matter removing apparatus for treating a large amount of raw water such as lake water containing a suspended matter at a low concentration.

[0002]

2. Description of the Related Art Various solid-liquid separation apparatuses have been proposed and implemented as a technique for removing suspended matter from polluted water. Among these solid-liquid separation apparatuses, an apparatus utilizing fine bubbles is disclosed in Japanese Patent Application Laid-Open No. H7-185528. This is a device that captures suspended matter by the surface tension of fine bubbles and lifts the suspended matter to the water surface by buoyancy to separate the suspended matter.

[0003] Most of these apparatuses are usually of the type in which a flocculant is added to raw water to flocculate a suspension, followed by flotation. However, as an example of not using a flocculant in a flotation device in order to reduce the amount of flocculant used and the cost of post-treatment of collected sludge, see the paper `` Sewage treatment using a combined system of non-chemical injection pressurized flotation and filtration. "
The technology described in (Sewerage Association Transactions vol. 31 No. 375 (1995)) is known. For the purification of lake water, it has been considered to apply the flotation method without using a flocculant in consideration of the influence of ecosystems in recent years. The above prior art paper is one example.

[0004]

The prior art (Japanese Unexamined Patent Application Publication No. 7-18
No. 5528), when suspended matter floats and separates in a flotation tank, air bubbles and the suspended matter are attached via a flocculant to form a large floc, which increases buoyancy to achieve effective purification. Is going. However, due to the structure in which there are two flows, an ascending flow and a descending flow, in the flotation tank, the suspended matter attached to the bubbles with weak buoyancy will settle down along the descending flow, and the suspended matter will be floated and separated. Can not.

[0005] In the case of raw water having a low suspension concentration, not only the amount of the suspension is generally small but also the size thereof is small. Since small suspensions adhere well to fine air bubbles, effective purification cannot be achieved when the conventional technology is applied to raw water having a low suspension concentration or when a flocculant is not used. Therefore, when flotation is performed on raw water having a low concentration of suspended matter, it is an issue to provide an apparatus that can effectively purify the suspension regardless of the size of the suspended matter.

[0006] Further, in the paper "Regarding sewage treatment using a combined system of non-chemical injection pressurized flotation and filtration" (Sewer Association of Japan, vol. 31 No. 375 (1995)), sewage having a high suspended solids concentration is described. Therefore, the particle size of the suspension is large, the floating speed of the suspension is high, and the distance required for floating separation is short. However, when the concentration of the suspension is low, the floc does not form unless a flocculant is used, so the floating speed of the suspension is low, and the distance required for flotation is not long to sufficiently float the suspension. Not be. That is, when a suspension having a low concentration is separated and removed by the suspension removing apparatus described in the above-mentioned paper, the apparatus itself needs to be upsized. Therefore, it is an issue to effectively purify the apparatus regardless of the concentration of the suspension and to reduce the size of the apparatus itself.

[0007] The present invention has been made in view of the above points, it is possible to always effectively remove the suspension in raw water even if the concentration of the suspension in the raw water or the nature of the suspension changes. An object of the present invention is to provide a flotation device.

[0008]

[Means for Solving the Problems] The concentration of the suspension is several tens mg / l.
When fine bubbles are injected into the raw water, the bubbles mix with the raw water, and the bubbles adhere to the suspension in the raw water. The suspended matter to which air bubbles adhere floats near the water surface, forms a concentration distribution in which the concentration of the suspended matter is high near the water surface, and the concentration of the suspended material decreases as the distance from the water surface increases (the depth of the water increases). Further, the distribution of the concentration of the suspended substance in the depth direction changes with time. This concentration distribution, as schematically shown in FIG. 11, shows that as time passes after the introduction of air bubbles, the concentration of the suspended solids becomes higher nearer to the surface of the water, and the concentration of the suspended solid on the surface of the water reaches a peak at a certain point in time. . This is the optimal time to remove the suspension. As the time elapses, the water bubbles disappear and the concentration of the suspension gradually becomes uniform.

In the case of continuous processing, the above-mentioned temporal change in the concentration distribution becomes a change in the suspended solid concentration distribution in the water depth direction from the upstream side to the downstream side in the flotation tank with the flow. That is, the time change is replaced by the flow direction distance in the flotation tank, and (flow direction distance / raw water average flow velocity) corresponds to the change time. FIG. 12 shows this concentration distribution. The flotation tank 3 used for the concentration distribution measurement was cylindrical.
A mixed water supply pipe 1 for supplying a mixed water composed of raw water containing bubbles and containing suspended matter is tangentially attached to the lowermost part of the peripheral wall of the peripheral wall of the peripheral wall opposite to the mixed water supply pipe 1. In the lower part, a treated water discharge pipe 5 for discharging treated treated water is provided.
Is attached. The inflow direction of the mixed water and the outflow direction of the treated water are opposite. Here, H is the height of the flow of the mixed water flowing from the mixed water supply pipe 1 as viewed from the bottom of the flotation tank 3, and H ′ is discharged from the treated water discharge pipe 5 as viewed from the same bottom. The height of the flow of treated water. In FIG. 12, since the X section has just flowed in from the mixed water supply pipe, no concentration distribution is provided in the range of the height H. As the mixed water goes along the Y-section and the Z-section along the inner periphery of the flotation tank, the higher the height, the higher the concentration within the range of the heights H and H '.

[0010] In the flotation method, a difference in the rising speed of the air bubbles occurs depending on the size of the air bubbles adhering to the suspension. The rising speed of the bubble increases in calculation in proportion to the square of the bubble diameter. Therefore, as a device for efficiently separating and removing the suspension without using a flocculant, even if the rising speed of the suspension is different,
It is necessary to have a structure that can always separate and remove the suspension at every place where the suspension floats, regardless of the floating time.

Therefore, while the floating of the suspended matter occurs in the whole area of the flotation tank, the treated water after the floating of the suspended substance is limited to the swirl flow region formed at the lower part of the flotation tank. In the present invention, however, the flotation tank is provided with a region H in which suspended matter is floated from raw water to generate treated water, and a flow in which the suspended matter which floats separately from the flow of treated water flows to a location where concentrated water flows out. Are formed in two layers, upper and lower, substantially with the region h in which is formed. This allows the suspended matter to float independently of the flow of the treatment water, so that the suspended matter can be removed regardless of the floating speed of the attached air bubbles.

That is, in order to achieve the above object, a first suspension removing apparatus of the present invention is a mixed water for supplying a mixed water obtained by injecting bubbles from a bubble generator into raw water containing a suspension. A supply pipe and a cylindrical tank, and a mixed water supply pipe is connected in a tangential direction on the outer periphery of the lower part of the tank. When the mixed water swirls in the tank, flotation to float air bubbles to which suspended matter adheres. A tank and an opening at the top provided vertically from the bottom of the flotation tank, and the concentrated water containing the suspended solids floating in the flotation tank is supplied from the water surface located above the opening to the opening. And a concentrated water inlet pipe flowing down and flowing down,
Downstream of the swirling flow of the mixed water, tangential to the swirling flow, connected to the outer periphery of the lower part of the floating separation tank, and configured to discharge the remaining treated water in which the suspended matter floats up.

By the way, below the concentrated water introduction pipe, FIG.
As shown in FIG. 3, there is a possibility of forming an ascending and descending secondary flow N4. In the secondary flow region, the suspension attached to the bubbles having weak buoyancy settles down along the secondary flow N4 and rises. There is a possibility that the water reaches the bottom surface of the separation tank 3 and mixes with the treated water along the main stream N5 and flows out from the treated water discharge pipe 5a.

In order to cope with the settled suspended matter, the second suspended matter removing apparatus of the present invention further comprises a first suspended matter removing apparatus and a standing suspension tank at the bottom of the flotation tank. A cylindrical partition wall is provided concentrically around the water inlet pipe, and the upper end of the partition wall is located below the upper end of the concentrated water inlet pipe and above the mixed water supply pipe and the treated water discharge pipe. It is assumed to have a structure.

Further, when the mixed water is swirled from the mixed water supply pipe to the position for discharging the treated water, a concentration distribution is formed in which the concentration of the turbid matter increases as going upward in the flotation tank as shown in FIG. . In the present invention, the b-layer having a relatively low concentration flowing through the lower portion of the flotation tank is discharged as treated water.
At this time, the lower stream is discharged to the treated water discharge pipe at the inlet of the treated water discharge pipe so that the lower stream flows together with the swirling flow to the mixed water supply pipe side and the flow to the upper layer side does not flow into the treated water discharge pipe. It is possible to discharge only the b-layer as treated water by guiding to.

In order to guide the underflow to the treated water discharge pipe,
The third suspended solids removing apparatus of the present invention further includes, in addition to the first suspended solids removing apparatus, an inlet of the treated water discharge pipe in a region where the mixed water flows from the mixed water supply pipe toward the treated water discharge pipe. A partition plate connecting the outer wall surface of the concentrated water introduction pipe and the inner wall surface of the flotation separation tank is provided so as to form a flow path to the tank, and the height of this partition plate is equal to or higher than the height of the treated water discharge pipe. And

Similarly, in order to guide the underflow to the treated water discharge pipe, the fourth suspended solids removing apparatus of the present invention includes, in addition to the second suspended solids removing apparatus, a mixed water supply pipe through which the treated water is supplied. In the region where the mixed water flows toward the discharge pipe, a partition plate is provided that connects the outer wall surface of the cylindrical partition wall and the inner wall surface of the flotation separation tank so as to form a flow path to the inlet of the treated water discharge pipe. The height of the partition plate shall be equal to or higher than the height of the treated water discharge pipe.

Further, in the fourth suspension removing apparatus,
A guide plate may be provided between the flotation tank and the cylindrical partition wall so as to form a downward slope in the flow direction of the mixed water from the partition plate to just before the mixed water supply pipe. With this lid plate, the treated water having a relatively low concentration of the turbid substance flows under the mixed water flowing out of the mixed water supply pipe.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIGS. Fig. 1 is a plan view of a main part of a suspended matter removing apparatus according to the present invention, and Fig. 2 is a sectional view taken along the line AA'-A "of Fig. 1. The suspended matter removing apparatus shown in Figs. A mixed water supply pipe 1 for supplying mixed water obtained by injecting bubbles from the bubble water generator 2 into raw water containing a suspension, a flotation / separation tank for floating and separating the suspended matter in the mixed water together with the bubbles 3, and a concentrated water introduction pipe 4 for removing suspended matter floated and separated in the flotation tank 3, a treated water discharge pipe 5 for discharging treated water in which suspended matter is floated and the suspended matter concentration is lowered, and And a sludge drain valve 6 which has a large specific gravity and cannot regularly float, and periodically discharges a suspended matter precipitated at the bottom of the flotation tank 3.

In the suspension removing apparatus, the flotation tank 3
Has a cylindrical shape, and the mixed water supply pipe 1 has a bubble water discharge port 2a.
The raw water and the bubble water have a length sufficient to sufficiently mix between the water and the flotation tank 3, and are installed at the lower part of the peripheral wall of the flotation tank 3 in the outer peripheral tangential direction. The treated water discharge pipe 5 is also connected to the floating separation tank 3 in a circumferential tangential direction at a position circumferentially separated from the mixed water supply pipe 1. Further, the concentrated water introducing pipe 4 has a cylindrical shape whose upper end 4a is open, and the upper end 4a is located slightly below the water surface W (FIG. 3) in the floating separation tank 3 and is concentric with the floating separation tank 3. Are located in

Since the suspension removing apparatus according to the present invention has the above configuration, it can efficiently suspend even raw water containing suspended particles having different particle sizes and concentrations as shown in the schematic diagram of the flow in FIG. Things can be removed. That is, in FIG. 3, 3 is a flotation tank, 4 is a concentrated water introduction pipe, 5 is a treated water discharge pipe, 5a is a treated water discharge pipe inlet, W is a water surface, and S1 is a suspension attached to bubbles having relatively strong buoyancy. The substance, S2, is a suspension attached to bubbles having relatively weak buoyancy, and N1, N2 indicate respective swirling flows.
The purifying action and effects are shown below. In order to effectively carry out the pressurized levitation method, the structure is such that the levitation speed of the suspended matter attached to the bubbles determined by the rising speed of the bubbles and the flow rate of the raw water can be raised above the inlet 5a of the treated water discharge pipe. Since the suspended matter S1 with air bubbles floats larger than the inlet diameter of the treated water discharge pipe 5 due to the buoyancy of the air bubbles, the suspended matters S1, S2 flowing from the mixed water supply pipe 1 become swirling flows N1, N2. Flows along,
When it reaches the treated water discharge pipe inlet 5a, it passes above the treated water discharge pipe inlet 5a. Therefore, the suspensions S1 and S2 are not discharged to the treated water discharge pipe 5 along the swirling flows N1 and N2. The concentrated water introduction pipe 4 is installed such that the upper end face of the concentrated water introduction pipe 4 is located below the upper end face of the flotation separation tank 3 with respect to the flotation separation tank 3. Above the upper end surface, the suspensions S1 and S2 naturally overflow to the concentrated water introduction pipe 4 in the order in which they float on the water surface W. As described above, first, the swirling flow is generated in the flotation / separation tank 3 by connecting the mixed water supply pipe 1 in the tangential direction of the outer circumference of the flotation / separation tank 3 having a cylindrical shape. The suspension S1 having relatively strong buoyancy immediately rises to the surface of the water W, but the suspension S2 having relatively weak buoyancy also floats while turning, so that the suspension floats rather than only in the axial direction. The process distance becomes longer, and the vehicle turns many times and floats on the water surface W. Therefore, the effect that the suspended matter can be efficiently removed from the suspended matter having different buoyancy is obtained.

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a plan view of a main part of the suspended solid removing device according to the second embodiment, and FIG.
FIG. 3 is a cross-sectional view of A ″. This suspension removing device is obtained by further providing a cylindrical partition wall 7 in the device of the first embodiment.

In this suspension removing apparatus, the cylindrical partition wall 7 has a hollow cylindrical shape, and is attached to the bottom surface of the floating separation tank 3 concentrically with the floating separation tank 3. In order to transfer the swirling energy in the flotation tank 3 to the flow in the cylindrical partition wall 7, it is desirable that the height of the cylindrical partition wall 7 is not so high, but it is set at a position higher than the inlet 5 a of the treated water discharge pipe. . Hereinafter, the purifying action and effect of the present invention will be described with reference to FIG. In FIG. 6, 3 is a flotation tank, 4 is a concentrated water introduction pipe, 7 is a cylindrical partition wall, S2 is a suspension adhered to small bubbles, N3 is an ascending flow, and N4 is a secondary reflux which flows vertically. Show the flow. The suspended matter adhering to the bubbles is in an upward flow N3.
Gathering near the center of the flotation tank 3 while ascending. The suspended matter attached to the bubbles having weak buoyancy starts to settle in the flotation tank 3 along the secondary flow N4. The suspended matter adhering to the bubbles that have begun to settle proceed to settle, settle to the vicinity of the bottom of the flotation tank 3, and if there is no partition wall, mix with the lower layer of treated water and flow out to the treated water discharge pipe 5. Therefore, the treated water layer is partitioned by the cylindrical partition wall 7 so that the suspended matter settled to the bottom of the flotation tank 3 is not mixed with the treated water. And
The suspended matter settled to the bottom is periodically discharged by opening the sludge drain valve 6. By the above operation, the effect of improving the separation efficiency can be obtained.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a plan view of a main part of the suspended solid removing device according to the third embodiment, and FIG. 8 is a sectional view taken along line AA of FIG. The suspension removing apparatus shown in FIGS. 7 and 8 is obtained by adding a partition plate 8 to the suspension removing apparatus of the second embodiment. In FIG. 8, reference numeral 1a denotes a mixed water supply pipe outlet, and 5a denotes a treated water discharge pipe inlet. In the present suspension removing device, while the raw water flowing from the mixed water supply pipe 1 is swirled, the suspended matter is floated by the buoyancy of the bubbles, and the treated water having a reduced concentration is discharged to the treated water discharge pipe 5. Treated water discharge pipe inlet 5a
Even in the vicinity, since there is a swirl component in the flow, it may flow along the swirl flow without flowing to the treated water discharge pipe 5.
In the third embodiment, a partition plate 8 is provided for guiding treated water so that the treated water can be discharged from the treated water discharge pipe 5. The partition plate 8 is provided between the treated water discharge pipe inlet 5a and the mixed water supply pipe outlet 1a when the raw water is swirled from the mixed water supply pipe 1 to the treated water discharge pipe 5, and the wall surface of the cylindrical partition wall 7. And the wall of the flotation tank 3 are connected so that the height of the partition plate 8 is higher than the height of the inlet 5a of the treated water discharge pipe. Hereinafter, the purifying action and effect of the present invention will be described. 1a is a mixed water supply pipe outlet,
5a is the inlet of the treated water discharge pipe, and the treated water after the separation of the suspended matter is discharged along the swirl flow to the treated water discharge pipe 5, but the flow near the treated water discharge pipe inlet 5a has a swirl component. However, the water is forcibly discharged to the treated water discharge pipe 5 by the partition plate 8. Further, as shown in FIGS. 9 and 10, when the swirling flow reaching the treated water discharge pipe inlet 5a passes over the partition plate 8 and further swirls to the mixed water supply pipe outlet 1a, a guide plate 9 is provided and treated water is provided. The treated water that could not be discharged to the discharge pipe 5 may be sunk below the mixture flowing from the mixed water supply pipe 1. Since the treated water thus sunk can be collected when it reaches the treated water discharge pipe 5, the treated water can be drained more effectively.

The above-mentioned members such as the partition plate 8 and the guide plate 9 can be employed in the second embodiment.
In this case, the partition plate is provided between the concentrated water introduction pipe and the flotation tank.

The above-described suspended matter removing apparatus of the present invention is capable of removing suspended suspended matter, if any, regardless of the concentration distribution of suspended matter in the flotation tank. It is clear that it is effective.

[0027]

According to the present invention, the suspended matter removing apparatus supplies the mixed water obtained by mixing bubbles to the raw water containing the suspended matter to the flotation / separation tank so as to swirl from the lower part thereof, and swirls. Bubbles bubbles to which the suspended matter adheres are floated, and the concentrated water containing the suspended matter is allowed to overflow from around the opening of the concentrated water introduction pipe provided at the center of the flotation separation tank and to flow therethrough.
Since the remaining clean treated water in which the suspended matter floats is discharged from the lower part of the flotation tank, no floc of the suspended matter is formed when removing the suspended matter without using a flocculant. Even in the case of such low-concentration raw water, a suspension having large and small particle diameters can be efficiently removed by floating on the water surface, and the size of the apparatus can be reduced.

Further, the suspended material that has floated or is rising upward in the flotation / separation tank always rotates around the concentrated water introduction pipe by a swirling flow, and can be finally discharged regardless of the floating speed. The processing speed in the separation tank can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part of a suspended solid removing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line A-A'-A "of FIG.

FIG. 3 is a schematic diagram showing flows of two types of suspended matter having large and small buoyancy in the suspended matter removing device according to the first embodiment.

FIG. 4 is a plan view of a main part of a suspended solid removing device according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along the line A-A′-A ″ of FIG. 4;

FIG. 6 is a schematic diagram showing a flow of a suspended matter in a suspended matter removing device according to a second embodiment.

FIG. 7 is a plan view of a main part of a suspended solid removing device according to a third embodiment of the present invention.

FIG. 8 is a sectional view taken along line AA of FIG. 7;

FIG. 9 is a plan view showing a modified mold of the suspended solid removing device according to the third embodiment.

FIG. 10 is a sectional view taken along line AA of FIG. 9;

FIG. 11 is a schematic view of the principle on which the concentration distribution of a suspension occurs.

FIG. 12 is a schematic diagram of a concentration distribution of suspended solids on the X, Y, and Z cross sections of the flotation tank.

FIG. 13 is an explanatory diagram of a secondary flow in the flotation tank according to the first embodiment of the present invention.

FIG. 14 is a diagram showing the concentration distribution of suspended solids in the height direction of a flotation tank at the inlet of a treated water discharge pipe.

[Explanation of symbols]

 Reference Signs List 1 mixed water supply pipe 1a mixed water supply pipe outlet 2 bubble generator 2a bubble generator outlet 3 flotation tank 4 concentrated water introduction pipe 4a concentrated water introduction pipe upper end 4b concentrated water discharge pipe 5 treated water discharge pipe 5a treated water discharge Pipe inlet 6 Sludge drainage valve 7 Cylindrical partition wall 8 Partition plate 9 Partition plate S1 Suspended matter attached to large bubbles S2 Suspended matter attached to small bubbles H Mixed water supply pipe height H 'Treated water discharge pipe height Sa

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiro Nagaoka 502, Kandachicho, Tsuchiura-shi, Ibaraki Pref.

Claims (5)

[Claims] 1. A mixed water supply pipe for supplying mixed water obtained by injecting bubbles from a bubble generator into raw water containing a suspension;
A mixed water supply pipe is connected to a cylindrical tank that is tangential to the outer periphery of the lower part of the tank, and when mixed water from the mixed water supply pipe turns in the tank, air bubbles to which suspended matter adheres float. The flotation tank and the flotation tank have an opening provided on the bottom of the axial center of the flotation tank, and the concentrated water containing the suspended material that floated in the flotation tank is separated from the water surface located above the opening. A concentrated water introduction pipe that flows in through the opening and flows downward, and a tangential direction of the swirling flow downstream of the swirling flow of the mixed water, which is connected to the outer periphery of the lower portion of the flotation separation tank, and the remaining suspended material floats. And a treated water discharge pipe for discharging treated water. 2. A concentric cylindrical partition wall is provided around the concentrated water introduction pipe on the bottom of the flotation tank, and the upper end of the partition wall is located below the upper end of the concentrated water introduction pipe and the mixed water 2. The suspended solid removing device according to claim 1, wherein the height is higher than the supply pipe and the treated water discharge pipe. 3. An outer wall surface of a concentrated water introduction pipe and a floating separation tank in a region where mixed water flows from a mixed water supply pipe to a treated water discharge pipe so as to form a flow path to an inlet of the treated water discharge pipe. 2. The apparatus for removing suspended solids according to claim 1, wherein a partition plate is provided for connecting to an inner wall surface of the wastewater treatment apparatus, and a height of the partition plate is equal to or higher than a height of the treated water discharge pipe. 4. An outer wall of a cylindrical partition wall and a floating separation tank so as to form a flow path to an inlet of the treated water discharge pipe in a region where the mixed water flows from the mixed water supply pipe toward the treated water discharge pipe. 3. The apparatus for removing suspended matter according to claim 2, wherein a partition plate is provided for connecting to an inner wall surface of the device, and a height of the partition plate is equal to or higher than a height of the treated water discharge pipe. 5. A guide plate is provided between the flotation tank and the cylindrical partition wall, the guide plate forming a downward slope in the flow direction of the mixed water from the partition plate to just before the mixed water supply pipe.
A suspension removal device as described.