JP2017013029A - Flocculation tank and flocculation treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculation tank capable of making the significant space saving of an installation area in combination of a sand sedimentation pond and the flocculation tank and generating water flow in a lower slow agitation tank by using water flow in an upper agitation tank.SOLUTION: In a flocculation tank,: the inside of the tank 2 is divided into an upper side rapid agitation chamber 4 and a lower side slow agitation chamber 5 by a partition plate 3; a feed well 7 is vertically disposed from the center of the partition plate 3; a baffle 8 is disposed so as to face the lower end of the feed well 7. Raw water and a flocculation agent are supplied into the rapid agitation chamber 4, agitated by an agitator 6, flown from the feed well 7 into the slow agitation chamber 5 and ascended while slowly swirling. Treated water is taken out from a water collecting pipe 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coagulation tank used in a water treatment process, and more particularly to a coagulation tank in which a coagulation chamber and a precipitation chamber are provided in one tank. The present invention also relates to a coagulation treatment method using this coagulation tank.

  As a conventional water treatment apparatus, a mixing vessel for mixing continuously supplied wastewater and a flocculant, a stirring vessel for stirring the mixed wastewater by a water flow, and a coagulation forming vessel for agglomerating the stirred wastewater And a coagulation sedimentation tank containing a coagulation formation container and coagulating and precipitating primary treated water discharged from the aggregation formation container (Patent Document 1). However, since a plurality of tanks are installed, there is a problem that the installation area is large.

  A coagulation tank is known in which the inside of a cylindrical container is rapidly stirred and the outside is slowly stirred, and a sludge discharging means is provided at the bottom (Patent Document 2). However, since the rapid stirring tank and the slow stirring tank are in a positional relationship between the inside and the outside, there is a problem that the installation area becomes large. In addition, both the inner and outer tanks are equipped with stirring blades, and there is no settling chamber. Moreover, the energy by stirring may be applied excessively, and the grown flocs may be destroyed.

  In addition, although providing the stirring chamber in the upper and lower multistage in one tank is described in patent documents 3-6, providing a sedimentation chamber is not described.

  In Patent Document 7, a mixing tank, a coagulation tank, and a settling tank are integrally formed in a lateral direction, and when the coagulation tank is supplied from the coagulation tank to the settling tank, a solid liquid is subjected to a precipitation process as a swirling flow. Although a separation apparatus is described, if a relatively heavy component such as sand is contained in the turbid component, there is a possibility that it is deposited in the coagulation tank before being sent to the precipitation tank. Moreover, since the coagulation tank and the precipitation tank are integrated in the lateral direction, there is a problem that the installation area is large.

JP 2006-43626 A JP2007-237014A Japanese Patent No. 4623431 JP2007-260614 JP2007-260615 JP2007-260616 JP2013-046898A

  The conventional coagulation sedimentation apparatus has the following problems to be solved. First, the agglomeration tank and the sedimentation tank are provided separately in the horizontal direction, so that the installation space is large and space saving is necessary. Secondly, when the turbidity component is contained in the raw water, it is necessary to remove the turbid component in the previous stage. Third, when a substance with a large specific gravity such as sand enters, the mixing tank may be blocked. Fourthly, a structure for causing a slow stirring flow without the rapid stirring water flow to the slow stirring tank is required.

  The present invention solves the above-mentioned conventional problems, and enables a significant space saving of the installation area by combining the sand basin and the agglomeration tank up and down, and by utilizing the water flow in the upper rapid stirring chamber, An object of the present invention is to provide a coagulation tank and a coagulation treatment method capable of generating a slow stirring water flow in the slow stirring chamber.

  The flocculation tank of the present invention is a flocculation tank in which the inside of the tank is partitioned into at least two upper and lower chambers by a partition plate, raw water is supplied to the upper chamber, and the advancing means transfers the upper chamber to the lower chamber. The upper chamber is a rapid stirring chamber equipped with a stirrer, and the lower chamber is a slow stirring chamber in which a swirling flow is generated by advection from the rapid stirring chamber, and is placed above the slow stirring chamber. A water collecting member for removing treated water is provided, and a mud discharge port is provided at the bottom of the slow stirring chamber.

  In one aspect of the present invention, the advection means includes a feed well that is continuous with the central portion of the partition plate and extends downward. A baffle may be provided facing the lower end of the feed well.

  In another aspect of the present invention, the advection means includes a feed well that is continuous with the peripheral edge of the partition plate and extends downward, and is provided at the lower end of the feed well along the inner peripheral surface of the tank. An outflow part is provided for draining water.

  In still another aspect of the present invention, the advection means includes a plurality of outflow holes provided at peripheral edges of the partition plate at intervals in the circumferential direction, and a slow stirring chamber passing through the outflow holes. And a slope plate for guiding water flowing into the swirl direction.

  In the present invention, a floating filter medium layer may be provided in the slow stirring chamber, and the water collecting member may be positioned in the floating filter medium layer.

  The flocculation treatment method of the present invention is a flocculation treatment method using the flocculation tank according to the present invention, wherein raw water and a flocculant are supplied to the rapid stirring chamber and stirred by a rapid stirrer. Water that reaches the water collecting member through the slow stirring chamber is taken out as treated water.

  When the coagulation tank has a feed well, the lower end of the feed well is preferably positioned in the blanket layer at the bottom of the slow stirring chamber.

  The agglomeration tank of the present invention is composed of a vertical two-stage structure of a rapid stirring chamber located in the upper part of the tank and a slow stirring room in the lower part. The upper chamber is agitated by a stirrer, and the lower chamber is gently agitated by the water flow generated by liquid feeding from the upper chamber.

  The agglomeration tank of the present invention comprises a rapid stirring chamber and a slow stirring chamber installed in a vertical two-stage structure, and can save space.

  In the upper rapid stirring chamber, the flow path is not clogged even when turbid matter having a large specific gravity such as sand enters because it is not stirred by a water flow but by a stirrer. In addition, by controlling the rotational speed of the rapid stirring at the upper part, it is possible to create a water flow in the lower tank and have a slow stirring function without using a structure such as a conventional spiral plate or a stirring blade. It is.

  In the lower slow stirring chamber, it is possible to precipitate and separate gravel, sand having a large particle size and agglomerated floc.

  For this reason, in the flocculation tank of the present invention, it is possible to greatly reduce the installation area by combining the sand basin and the flocculation tank, and by using the water flow in the upper stirring chamber, A slow stirring water stream can be generated in the slow stirring chamber.

It is a longitudinal cross-sectional view of the aggregation tank which concerns on embodiment. It is the II-II sectional view taken on the line of FIG. It is a longitudinal cross-sectional view of the aggregation tank which concerns on embodiment. It is the IV-IV sectional view taken on the line of FIG. It is a longitudinal cross-sectional view of the aggregation tank which concerns on embodiment. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. It is the VII-VII sectional view taken on the line of FIG. It is a perspective view of a partition plate.

  Hereinafter, embodiments will be described with reference to the drawings. 1 and 2 show a flocculation tank according to the first embodiment. The agglomeration tank 1 includes a cylindrical tank body (hereinafter simply referred to as a tank) 2 and a horizontal partition plate 3 provided in the middle of the tank 2 in the vertical direction. Are provided with a rapid stirring chamber 4 and a slow stirring chamber 5 is provided below the partition plate 3.

  A stirrer 6 is installed in the rapid stirring chamber 4. The stirrer 6 includes a rotary shaft 6a extending in the vertical direction at the axial center of the rapid stirring chamber 4, a paddle 6b provided on the rotary shaft 6a, and a motor 6c connected to the upper end of the rotary shaft 6a. And have.

  An opening 3 a is provided at the center of the partition plate 3, and the upper end of a feed well 7 made of a cylindrical tube member coaxial with the opening 3 a is connected to the partition plate 3. The feed well 7 extends to the lower part in the slow stirring chamber 5. A horizontal disk-shaped baffle 8 is installed facing the lower end of the feed well 7. The baffle 8 is supported at the lower end of the feed well 7 by a plurality of thin rod-like connecting members (not shown), but may be supported by the tank 2. The lower end of the feed well 7 and the baffle 8 are located in the blanket layer B accumulated at the bottom in the slow stirring chamber 5.

  In addition, the baffle 8 is not limited to a horizontal plate shape, and may be a tapered shape such as a Jinkasa shape, or a shape obtained by inverting it upside down.

  A water collecting pipe 9 is provided in the upper part of the slow stirring chamber 5. The water collecting pipe 9 has a ring shape that circulates around the slow stirring chamber 5 along the inner periphery of the tank 2, and a large number of water collecting holes 9 a are formed on the lower surface thereof at predetermined intervals. In addition, you may provide the slit extended in the circumferential direction instead of the water collection hole 9a.

  The tip of the treated water outlet pipe 10 is connected to the water collecting pipe 9. The treated water extraction pipe 10 extends through the tank 2 and out of the tank 2.

  The bottom 2a of the tank 2 has a taper shape with a downward slope toward the center. The upper end of the mud pipe 11 is connected to the mud outlet 2 b of the bottom 2 a of the tank 2. The lower part of the mud discharge pipe 11 is curved to the side. The mud drain pipe 11 can be opened and closed by a mud drain valve (not shown).

  In the coagulation tank 1 configured as described above, the raw water is preferably introduced from the raw water inflow pipe 12 as a surface area load in the tank 2 at 2 to 30 m / h. Examples of the raw water include, but are not limited to, river water, lake water, industrial water, and industrial waste water containing dissolved organic matter and turbid components such as soil and sand.

  The turbidity of the raw water is usually 200 to 500 degrees, particularly about 250 to 350 degrees, but is not limited thereto.

Further, according to the raw water quality, an inorganic flocculant, preferably polyaluminum chloride (PAC), is preferably injected into the rapid stirring chamber 4 through the drug injection tube 13 at a concentration of 200 mg / L or less, for example, 10 to 200 mg / L. The raw water and the inorganic flocculant are rapidly mixed by the stirrer 6. The stirring intensity at this time is preferably 60 to 200 s ⁻¹ . The residence time can be changed by changing the size and flow rate of the tank 2. If aggregation is insufficient, a polymer flocculant may be added to the rapid stirring chamber 4.

  The raw water sufficiently mixed with the flocculant in the rapid stirring chamber 4 is sent from the opening 3 a of the partition plate 3 to the lower slow stirring chamber 5 through the feed well 7.

  The effluent that has flowed downward from the feed well 7 hits the baffle 8, the flow direction is reversed, and an upward flow is generated.

  Since the raw water swirls within the rapid stirring chamber 4, the raw water descending the feed well 7 also descends while spirally swirling. Therefore, the raw water flowing out from the feed well 7 and hitting the baffle 8 rises and causes a slow swirling flow in the slow stirring chamber 5. Thereby, aggregation is accelerated | stimulated by the shear force with the wall surface of the tank 2. FIG. In addition, gravel and sand having a large particle size accumulate on the bottom of the tank. Moreover, the coarse floc produced | generated by the aggregation effect accumulates, and the blanket layer B is formed. When the flocs in the raw water discharged from the feed well 7 pass through the blanket layer B, the flocs collide with each other, and the aggregation reaction is promoted. Further, since the treated water passes through the minute gaps between the flocks in the blanket layer B, a rectifying effect and a filtering effect are also obtained. The treated water from which the gravel, sand, aggregated floc and the like have been separated is taken out from the water collection pipe 9 through the extraction pipe 10.

  When gravel, sand, or the blanket layer B is excessively accumulated at the bottom of the slow stirring chamber 5, the mud valve is opened to discharge them, and the level of the blanket layer B is maintained within a predetermined range.

  The baffle 8 may be omitted. Even in the absence of the baffle 8, since the coarse floc tends to settle, the blanket layer B is formed, and the aggregation promotion and filtration functions are exhibited. However, in the case where the baffle 8 is provided, the area of the discharge portion is reduced as compared with the case where the baffle 8 is not provided, so that a pressure loss occurs and agitation energy increases. Aggregation is promoted by adding stirring energy. In addition, the presence of the baffle 8 creates a lateral flow, creates a stronger swirling flow, and enhances the slow stirring function.

  A coagulation tank 1A according to the second embodiment will be described with reference to FIGS.

  In the aggregation tank 1 </ b> A, the opening 3 a of the partition plate 3 </ b> A and the feed well 7 </ b> A are located in the vicinity of the inner peripheral surface of the tank 2. The feed well 7 </ b> A extends downward along the inner peripheral surface of the tank 2, and a lower end portion thereof is curved to form an outflow portion 7 a extending along the inner peripheral surface. The outflow portion 7a is located in the blanket layer B. Other configurations are the same as those of the coagulation tank 1, and the same reference numerals indicate the same parts.

  Also in the coagulation tank 1A, the raw water stirred with the coagulant in the rapid stirring chamber 4 flows out from the outflow portion 7a into the slow stirring chamber 5 through the feed well 7A in the direction along the inner peripheral surface of the tank 2. To do. This raw water gradually rises while slowly swirling in the slow stirring chamber 5, during which gravel, sand, flocks, etc. settle, and treated water is taken out from the water collection pipe 9 and the extraction pipe 10.

  In addition, the outflow direction from the outflow part 7a is not limited to the substantially horizontal direction shown by FIG.4 (b), The diagonally upward direction and the diagonally downward direction may be sufficient. 4A, the extending direction of the outflow portion 7a is substantially parallel to the inner peripheral surface of the tank 2. However, the present invention is not limited to this, and the end side of the outflow portion 7a (outflow) It may extend so that it may approach the inner peripheral surface of the tank 2, and may extend in the opposite direction.

  With reference to FIGS. 5-8, the aggregation tank 1B which concerns on 3rd Embodiment is demonstrated.

  In this agglomeration tank 1B, the partition plate 3B that partitions the rapid stirring chamber 4 and the slow stirring chamber 5 includes a plurality of slit-like outflow holes 13 provided in the vicinity of the outer peripheral edge at intervals in the circumferential direction, And a slope plate 14 provided below each outflow hole 13. The outflow hole 13 extends in an arc shape along the inner peripheral surface of the tank 2.

  Although the number of outflow holes 13 is eight in this embodiment, it may be about 4-12. The slope plate 14 extends in the circumferential direction so as to overlap the outflow hole 13 in the plan view of the partition plate 3B. One end side in the longitudinal direction of the slope plate 14 is connected to one end side in the longitudinal direction of the outflow hole 13. The slope plate 14 has a downward slope from the one end side to the other end side. The length of the slope plate 14 (the length in the circumferential direction of the tank 2) is preferably about the same as or slightly shorter than the length of the outflow hole 13.

  The downward gradient direction of each slope plate 14 is the same direction in the direction around the axis of the partition plate 3B. In this embodiment, the downward gradient direction of each slope plate 14 is clockwise with respect to the axis of the partition plate 3B.

  In this embodiment, no feed well is provided.

  A water collection box 15 having an open lower surface is installed at the center of the upper part in the slow stirring chamber 5, and a treated water discharge pipe 16 is connected to the water collection box 15.

  The other structure of this coagulation tank 1B is the same as that of coagulation tank 1 and 1A, and the same code | symbol has shown the identical part.

  In this flocculation tank 1B, the raw water mixed with the flocculant in the rapid stirring chamber 4 passes through each outflow hole 13, is guided by the slope plate 14, and flows into the slow stirring chamber 5 in the swirling direction. 2 slowly descends in the slow stirring chamber 5 while turning along the inner peripheral surface. The water that reaches the bottom of the slow stirring chamber 5 gathers and rises in the center of the slow stirring chamber 5. During this time, gravel, sand and floc are settled and separated, and the treated water is taken out from the water collection box 15 via the take-out pipe 16. The sediment is taken out from the mud pipe 11 as appropriate.

  In this agglomeration tank 1B, unlike the feed well method, a blanket layer is not formed. In the coagulation tank 1B, the water flow from the upper rapid stirring chamber 4 flows along the slope plate 14, thereby generating a swirling flow having high stirring strength, and the stirring force promotes the growth of the coagulation flocs. .

  Each of the above embodiments is an example of the present invention, and the present invention may be configured other than illustrated. For example, in the coagulation tank 1A of FIGS. 3 and 4, a plurality of feed wells 7A may be provided, and raw water may flow out from each feed well 7A in the same circumferential direction (for example, clockwise in the plan view).

  In the present invention, the floating filter medium is disposed in the upper part of the slow stirring chamber 5, the water collecting pipe 9 or the water collection box 15 is positioned in the floating filter medium layer, and the water in the slow stirring chamber 5 is filtered by the floating filter medium. After that, it may flow into the water collection pipe 9 or the water collection box 15.

  Further processing can be performed by combining a pressure flotation device, a sand filtration device, a membrane treatment and the like in the subsequent stage of the device of the present invention.

[Example 1]
The agglomeration tank shown in FIG. 1 was constituted by a column having a cylindrical radius of 150 mm. The height of the rapid stirring chamber 4 was 1250 mm, the height of the slow stirring chamber 5 was 1250 mm, and the rapid stirring chamber 4 was provided with a stirrer 6 having two rectangular stirring blades 50 mm long and 100 mm wide. In a state where the column was full, tap water was fed from the top of the column with a pump so that the flow rate became 256 L / h. PAC was added to the tap water so that the concentration of polyaluminum chloride (PAC) was 120 mg / L. At this time, the rotation speed of the stirrer was 100 rpm.

  To this rapid stirring chamber 4, the red bean clay suspended solution was added so that the concentration of red bean clay would be 300 mg / L. Thereafter, the red bean clay suspension was added every 30 seconds so that the red bean clay concentration would be 300 mg / L with respect to the amount of tap water that flowed in.

  In the case of the above test conditions, the residence time in the upper agitation tank is 5 minutes and the residence time in the lower agitation tank is 5 minutes, so that the treated water 20 minutes after the start of the test is collected as twice the time that the water is replaced. The turbidity was measured. The results are shown in Table 1.

  In addition to red ball soil, Kanuma soil and black soil were added, and the treatment was performed under the same test conditions. In addition, the raw water SS was 600 mg / L at the time of black soil addition. The results are shown in Table 1.

  As a result of the above treatment, it was confirmed that when any soil was added, the raw water containing 300 mg / L or more of the turbid component (SS) was discharged with a turbidity of about 6 degrees.

1, 1A, 1B Coagulation tank 2 tanks 3, 3A, 3B Partition plate 4 Rapid stirring chamber 5 Slow stirring chamber 6 Stirrer 7, 7A Feed well 8 Baffle 9 Water collecting pipe 13 Outflow hole 14 Slope plate 15 Water collecting box

Claims (8)

The inside of the tank is divided into at least two upper and lower chambers by a partition plate, raw water is supplied to the upper chamber, and is a coagulation tank that is transferred from the upper chamber to the lower chamber by the advection means,
The upper chamber is a rapid stirring chamber with a stirrer,
The lower chamber is a slow stirring chamber in which a swirling flow is generated by advection from the rapid stirring chamber,
A water collecting member for removing treated water is provided at the upper part of the slow stirring chamber,
A coagulation tank characterized in that a drainage port is provided at the bottom of the slow stirring chamber.   2. The agglomeration tank according to claim 1, wherein the advection means includes a feed well that is continuous with a central portion of the partition plate and extends downward.   The coagulation tank according to claim 2, wherein a baffle is provided so as to face a lower end of the feed well. The advection means according to claim 1,
Continuing to the peripheral edge of the partition plate, comprising a feed well extending downward,
An agglomeration tank characterized in that an outflow part for allowing water to flow out along the inner peripheral surface of the tank is provided at the lower end of the feed well. The advection means according to claim 1,
A plurality of outflow holes provided at intervals in the circumferential direction on the peripheral edge of the partition plate;
And a slope plate for guiding water flowing into the slow stirring chamber through the outflow hole in a swirling direction.   6. The coagulation tank according to claim 1, wherein a floating filter medium layer is provided in the slow stirring chamber, and the water collecting member is located in the floating filter medium layer. A flocculation treatment method using the flocculation tank according to any one of claims 1 to 6,
Supply the raw water and flocculant to the rapid stirring chamber and stir with a rapid stirrer,
A coagulation treatment method characterized in that water reaching the water collecting member is taken out as treated water from the rapid stirring chamber through a slow stirring chamber. A flocculation treatment method using the flocculation tank according to any one of claims 2 to 4,
A blanket layer is formed at the bottom of the slow stirring chamber,
Supply the raw water and flocculant to the rapid stirring chamber and stir with a rapid stirrer,
Water in the rapid stirring chamber is guided by a feed well into a blanket layer at the bottom of the slow stirring chamber;
A coagulation treatment method characterized in that water that passes through the blanket layer and rises in the slow stirring chamber and reaches the water collecting member is taken out as treated water.

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