JP2020025920A - Coagulation/sedimentation apparatus, control method for the same and sedimentation tank - Google Patents

Abstract

To provide a coagulation/sedimentation apparatus and a sedimentation tank which can suppress solidification and fixation of sediments in a pit of the sedimentation tank, and a control method for a coagulation/sedimentation apparatus.SOLUTION: The coagulation/sedimentation apparatus comprises: first and second coagulation tanks 2 and 3 in which suspended substances in raw water are added with sedimentation accelerating materials and coagulants to be coagulated as a flock; a sedimentation tank 4; a cyclone 20 in which slurry pulled out from the sedimentation tank 4 is separated into sludge and the sedimentation accelerating materials and the separated sedimentation accelerating materials are returned to the coagulation tank 3; and a stirring member 30 including a bar-shape or a belt-shape lengthy member extending downward provided in a pit 17 of the sedimentation tank 4. The stirring member 30 has an arm 33 in a radiation direction and stirring bars 34 and 35 vertically installed in the arm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coagulation sedimentation apparatus and a control method thereof, in which a sedimentation promoting material and a coagulant are added to raw water containing a suspended substance to cause coagulation and sedimentation to separate sludge and treated water, and a method for controlling the same. The present invention relates to a coagulation sedimentation apparatus configured to separate sludge and a sedimentation promoting material by a cyclone, and to return the sedimentation promoting material to a coagulation tank, and a control method thereof. Further, the present invention relates to a sedimentation tank suitable for use in the coagulation sedimentation apparatus.

  A coagulation sedimentation device that separates and removes suspended substances (hereinafter, also referred to as SS [Suspended Solid]) from raw water by coagulation and sedimentation, consists of granular material (sand etc.) having a particle size of about 10 to 200 μm in raw water. A flocculation tank for forming a flocculated floc by adding a settling accelerator and a flocculant; a sedimentation tank for sedimenting and separating flocculated floc flowing out of the flocculation tank; There are known devices configured to return particulate matter to a flocculation tank and discharge sludge (Patent Documents 1 to 3).

  In the coagulation sedimentation apparatuses of Patent Documents 1 to 3, the inorganic coagulant is added to the raw water introduced into the coagulation tank and stirred by a stirrer, and then the polymer coagulant is added and introduced into the coagulation tank. To form coagulated flocs with the particulate matter (sand, etc.). The coagulated water is introduced into a sedimentation tank to separate it by sedimentation, and the treated water flows out from the upper part of the sedimentation tank. Also, the slurry is extracted from the lower part of the settling tank by a drawing pump and sent to a cyclone. In the cyclone, the sludge and the particulate matter are centrifuged, and the separated sludge is discharged outside the coagulation and sedimentation device. The particulate matter separated by the cyclone is returned to the flocculation tank and reused for sedimentation.

JP 2000-317220 A JP 2002-355507 A JP 2014-237122 A

  In a pipe of such a coagulating sedimentation apparatus or a pit of a sedimentation tank, a sediment or the like may be solidified and clogged because the slurry contains a sedimentation promoting material.

  In order to prevent clogging of the pit of the sedimentation tank, it is conceivable to provide a rotating blade in the pit.

When a rotating wing is provided in the pit, the contact area between the wing and the sediment in the pit is large. Therefore, when the sediment solidifies or when the sediment becomes large, the blades may not be driven. Further, in order to prevent this, it is necessary to install a driving device having a large torque.
In addition, if a rotary wing is used, there is a possibility that coagulated flocs in the pit rotate together with the liquid in the pit and co-rotate. In this case, there is a concern that the effect of suppressing the solidification of the precipitate may be weakened.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a coagulating sedimentation apparatus and a sedimentation tank capable of sufficiently dispersing sediment in a pit of a sedimentation tank so that the sediment does not solidify, and a method of controlling the coagulation sedimentation apparatus.

  The first coagulation and sedimentation apparatus according to the first aspect of the invention includes a first coagulation tank into which raw water is introduced and coagulation treatment with a first coagulation agent, and a first coagulation treatment water discharged from the first coagulation tank. A second flocculation tank for performing flocculation treatment with the sedimentation promoting material, a second flocculation treatment water discharged from the second flocculation tank, introduced thereinto, and settled and separated into treated water and slurry, and a bottom portion of the precipitation tank A pit provided in the pit, a drawing pump for extracting the slurry from the pit, a cyclone for separating the slurry extracted from the pit into a separated sludge and a sedimentation promoting material, and returning the separated sedimentation promoting material to the second flocculation tank. In the coagulation sedimentation apparatus provided with, pit stirring means for stirring the slurry in the pit is provided, the pit stirring means, a rotating shaft extending in the vertical direction, a driving means for rotating the rotating shaft, , One end of the rotating shaft Is constant, the other end and having a stirring member which is the lower end extends downwards as long member of the bar-shaped or strip-shaped positioned in a pit.

  In one embodiment of the present invention, the stirring member includes an arm extending radially from the rotation axis and a stirring bar extending downward from the arm.

  In one aspect of the present invention, a plurality of the arms are provided at intervals in a circumferential direction of the rotating shaft, and a plurality of the stirring bars are installed on each arm at intervals in the arm longitudinal direction. ing.

  In one embodiment of the present invention, the stirring bar has an L-shaped horizontal cross-sectional shape including a first piece and a second piece that intersect vertically, and the first piece is oriented in the radiation direction. I have.

  In one aspect of the present invention, the side peripheral surface of the pit has a smaller diameter toward the lower side, and the first stirring bar whose lower end is located above the bottom surface of the pit as the stirring bar, and the lower end is the side peripheral surface And a second stir bar located above the first stir bar. The lower end of the first stir bar is lower than the lower end of the second stir bar.

  In one embodiment of the present invention, the apparatus further includes a stirring control unit that intermittently or continuously activates the stirring unit of the second flocculation tank during a suspension period of the flocculation / sedimentation treatment operation by the flocculation / sedimentation apparatus.

  In one aspect of the present invention, a control unit is provided for stopping supply of raw water to the first coagulation tank and stopping the drawing pump after a predetermined time has elapsed.

  In the control method of the coagulation sedimentation apparatus according to the second invention, a raw water is introduced, a first coagulation tank for coagulation treatment with a first coagulant, and a first coagulation treatment water discharged from the first coagulation tank are introduced. (2) a second coagulation tank for coagulating with a coagulant and a sedimentation promoting material, a sedimentation tank into which the second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimented and separated into treated water and slurry; A pit provided at the bottom of the tank, a drawing pump for extracting the slurry from the pit, and separating the slurry extracted from the pit into a separated sludge and a sedimentation promoting material, and separating the separated sedimentation promoting material into the second flocculation tank. A coagulating sedimentation apparatus provided with a returning cyclone, comprising a control unit for stopping supply of raw water to the first coagulating tank and stopping the drawing pump after a predetermined time has elapsed.

  In one aspect of the second invention, the coagulation-sedimentation apparatus stirs the inside of the second coagulation tank intermittently or continuously during the suspension period of the coagulation-sedimentation treatment operation.

  In the control method of the coagulation sedimentation apparatus of the third invention, the raw water is introduced, the first coagulation tank for coagulation treatment with the first coagulant, and the first coagulation treatment water discharged from the first coagulation tank are introduced. (2) a second coagulation tank for coagulating with a coagulant and a sedimentation promoting material, a sedimentation tank into which the second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimented and separated into treated water and slurry; A pit provided at the bottom of the tank, a drawing pump for extracting the slurry from the pit, and separating the slurry extracted from the pit into a separated sludge and a sedimentation promoting material, and separating the separated sedimentation promoting material into the second flocculation tank. In the method for controlling the coagulation and sedimentation apparatus including the returning cyclone, when the coagulation and sedimentation apparatus is stopped, supply of raw water to the first coagulation tank is stopped, and after a predetermined time has elapsed, the drawing pump is stopped. Specially to control To.

  The sedimentation tank of the fourth invention is a sedimentation tank having a pit at the bottom, wherein a pit stirring means for stirring the slurry in the pit is provided, and the pit stirring means comprises a rotating shaft extending in a vertical direction; Driving means for rotating the rotating shaft, and a stirring member having one end fixed to the rotating shaft, the other end extending downward as a rod-shaped or band-shaped elongated member, and a lower end positioned in the pit. It is characterized by having.

  In the coagulation sedimentation apparatus of the present invention, the stirring member includes a rod-shaped or band-shaped long member extending downward, and the slurry in the pit can be sufficiently stirred. Therefore, when the effect of the coagulation / sedimentation treatment is deteriorated, it is possible to perform an operation of increasing the amount of the coagulant or the sedimentation promoting material while suppressing the clogging in the pit.

  In one embodiment of the present invention, when stopping the coagulation and sedimentation device, after stopping the supply of raw water to the first coagulation tank, the drawing pump is stopped, so that the sedimentation promoting material remains in the pit, the drawing line, and the cyclone. Is prevented or suppressed. Therefore, when the effect of the coagulation and sedimentation treatment is deteriorated, it is possible to perform an operation of increasing the amount of the coagulant or the sedimentation promoting material while suppressing the clogging in the pit, the drawing line, and the cyclone.

  In one embodiment of the present invention, by stirring the inside of the second flocculation tank during the suspension period of the flocculation and sedimentation device, solidification or fixation of the precipitate in the second flocculation tank can be prevented.

It is a block diagram of the coagulation sedimentation apparatus which concerns on embodiment. It is a longitudinal cross-sectional view of the pit part of a sedimentation tank. FIG. 3 is a sectional view taken along line III-III of FIG. 2.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a coagulation sedimentation apparatus 1 according to an embodiment. This coagulation-sedimentation apparatus 1 includes a first coagulation tank 2, a second coagulation tank 3, and a sedimentation tank 4 disposed adjacent to the first coagulation tank 2. Raw water is introduced into the first flocculation tank 2 from a raw water tank (not shown) via a raw water pump 5, and an inorganic flocculant (PAC in FIG. 1) is added as a first flocculant by a first chemical injection device 6. Then, the mixture is stirred by the stirrer 7. In the first flocculation tank 2, the inorganic flocculant flocculates the suspended substance to generate fine flocs. Although not shown, the first flocculating tank 2 is provided with a pH adjusting device having a pH meter and a device for adding a pH adjusting agent (caustic soda, sulfuric acid, hydrochloric acid, etc.). It is configured so that the pH can be maintained in a predetermined range.

The first coagulation treatment water from the first coagulation tank 2 is introduced into the second coagulation tank 3 through the advection port 8, and a polymer coagulant (polymer) is added as a second coagulant by the second chemical injecting device 9. You. A sedimentation promoting material such as sand is added to the second flocculation tank 3, and the agglomerated floc having a large specific gravity and incorporating the sedimentation promoting material grows by stirring by the stirrer 10.
Each of the stirrers 7 and 10 (stirring means) includes a rotating shaft, a drive motor M at an upper portion thereof, and a lower stirring blade.

  As the sedimentation promoting material, not only sand but also crushed materials of various slags can be used. The average particle diameter of the sedimentation promoting material is preferably about 0.01 to 0.5 mm, and the true specific gravity is preferably 2 or more, particularly 2.5 or more and 4 or less, but is not limited thereto.

  The second flocculated water containing the flocculated flocs that have grown flows over the overflow weir 12 and is introduced into the sedimentation tank 4. In the sedimentation tank 4, flocculated flocs in the second flocculated water are precipitated. At the upper part in the sedimentation tank 4, a separator composed of a plurality of inclined plates 13 is provided to promote sedimentation and separation of flocculated flocs. The treated water that has passed through the separator is taken out of the outflow pipe 16 through the outflow chamber 15. The bottom surface of the sedimentation tank 4 has a tapered shape inclining above the angle of repose of the sedimentation promoting material and decreasing in diameter downward.

  The sedimentation tank 4 is provided with a rake 14 that swivels along the bottom surface. A rubber spatula (not shown) is provided on the lower side of the rake 14. A stirring member 30 is provided in the pit 17. The pit 17 has a side peripheral surface 17a and a bottom surface 17b. The side peripheral surface 17a has a tapered shape whose diameter decreases toward the lower side.

  In this embodiment, the sedimentation tank 4 has a square horizontal cross section of the side peripheral surface, and a tapered shape in which the bottom surface is reduced in diameter toward the bottom, and the rotating shaft 14a of the rake 14 is installed vertically at the axis of the sedimentation tank 4. ing. On the bottom surface of the pit 17, a bearing 14b for supporting the rotating shaft 14a is provided. The rotation shaft 14a is rotationally driven by an upper drive motor M (drive means). Pit stirring means is constituted by the rotating shaft 14a, the drive motor M above the rotation shaft 14a, and the stirring member.

  A drawing line 18 is connected to a lower portion (or bottom surface 17b) of the side peripheral surface 17a of the pit 17 for extracting slurry containing precipitated floc. The connecting portion of the drawing line 18 is preferably located as low as possible in order to reduce the amount of the sedimentation promoting material remaining in the pit 17. The drawing line 18 is provided with a drawing pump 19 for feeding the extracted slurry to the cyclone 20. It is preferable that the slurry flow rate in the drawing line 18 is designed to be 500 m / h or more.

  The cyclone 20 is installed such that the axial direction is a vertical direction. In the cyclone 20, the sent slurry is separated by centrifugation into sludge collected at the center of the cyclone and sedimentation promoting material collected at the peripheral surface on the cyclone side. The separated sedimentation promoting material is returned from the bottom of the cyclone 20 to the second flocculation tank 3 again by the pipe 21 and used for circulation.

  The separated sludge collected on the axis side by the cyclone 20 flows out to the pipe 22 connected to the sludge outlet at the center of the upper surface of the cyclone 20.

  This coagulation sedimentation apparatus is provided with a raw water pump 5, a drive motor M above the stirrers 7, 10, a drive motor M above the stirrer 30 (rake 14), and a controller 25 for controlling the drawing pump 19.

  As shown in detail in FIGS. 2 and 3, the stirring member 30 is fixed to a flange 31 fixed to the rotating shaft 14 a of the rake 14 and a base end side thereof is fixed to the flange 31 by fixing means 32 such as rivets and bolts. A plurality of arms 33 extending in the radial direction, and first and second stirring bars 34 and 35 as rod-shaped long members extending downward from the arms 33 in the pit 17. And

  In this embodiment, the flange 31 is installed at a height near the upper end of the pit 17, but may be installed slightly above or below it. Further, a total of four arms 33 are provided at every 90 ° in the circumferential direction of the rotating shaft 14a, but the number is not limited to this.

  The stirring bar 35 is provided on the tip side of the arm 33. The stirring bar 35 is located above the side peripheral surface 17 a of the pit 17. The stirring bar 34 is provided between the stirring bar 35 and the flange 31. The stirring bar 34 is located above the bottom surface 17 b of the pit 17. The vertical distance between the lower end of the stirring bar 35 and the side peripheral surface 17a of the pit 17 and the distance between the lower end of the stirring bar 34 and the bottom surface 17b of the pit 17 are preferably as small as possible.

  Each of the stirring bars 34 and 35 is formed of an angle material having an L-shaped horizontal cross section. The stirring bars 34, 35 have first pieces 34a, 35a overlapping the arm 33, and second pieces 34b, 35b perpendicular to the first pieces 34a, 35a. The width of the first pieces 34a, 35a and the second pieces 34b, 35b is preferably about 40 to 150 mm, particularly preferably about 60 to 90 mm. The interval between the stirring bars 34 and 35 is preferably about 80 to 200 mm, particularly preferably about 120 to 160 mm.

  In this embodiment, two stirring bars are provided for each arm 33, but three or more stirring bars may be provided.

  In this embodiment, the installation positions (distance from the rotation shaft 14a) of the stirring bars 34 and 35 are the same in each arm 33. However, the installation positions of the stirring bars 34 and 35 are changed to some of the arms 33. Or for each arm 33.

  The stirring member 30 is driven to rotate clockwise in FIG. 3, but may be driven to rotate counterclockwise.

  In the coagulating sedimentation apparatus 1, when the stirring member 30 rotates, the reaction force received by the stirring bars 34 and 35 from the sediment in the pit 17 is relatively small. Further, since the stirring bars 34 and 35 are provided at intervals in the longitudinal direction of the arm 35, the entire sediment in the pit 17 can be sufficiently stirred while preventing co-rotation.

In this embodiment, since the stirring bars 34 and 35 have the second pieces 34b and 35b perpendicular to the first pieces 34a and 35a, the stirring bars 34 and 35 have high rigidity and bend when the stirring member 30 rotates. Is prevented.
In this embodiment, a straight bar-shaped bar is provided as a long member in the vertical direction, but may be provided diagonally, may be curved, and may be a band rather than a bar. (For example, a ribbon screw), it is not particularly limited as long as co-rotation hardly occurs and the entire slurry in the pit can be sufficiently loosened.

  In the coagulating sedimentation apparatus 1, when the water level in a raw water tank (not shown) falls below a specified water level, the raw water pump 5, the first and second chemical injection devices 6, 9 and the stirrer 10 are connected. The operation is stopped, and the pH adjuster (not shown), the stirrer 7 and the drawing pump 19 are continuously operated.

  When stopping the operation of the coagulation sedimentation apparatus 1, first, the raw water pump 5 and the first and second chemical injection apparatuses 6, 9 are stopped, and then a predetermined time (for example, about 5 to 20 minutes, especially about 5 to 10 minutes) After the elapse), it is preferable to stop the stirrers 7, 10, the stirring member 30, and the drawing pump 19. By doing so, the sedimentation promoting material and other precipitates remaining in the pit 17, the drawing line 18, and the cyclone 20 are reduced, and the sedimentation promoting material and the like are prevented from solidifying or sticking.

  In the coagulation and sedimentation apparatus 1, even if the inside of the second coagulation tank 3 is intermittently or continuously stirred even during the operation stop period in which the raw water is not treated, it is possible to prevent the sediment from sticking or caking. Good. In the case of intermittent stirring during the operation stop period, the power cost is lower than in the case of continuous operation.

  The coagulating sedimentation apparatus and the method for controlling the same according to the present invention are suitable for treating yard wastewater in steel works and cement plants, but can also be applied to the treatment of other various wastewater.

  The type of the inorganic coagulant and the polymer coagulant used in the present invention is not particularly limited, and examples of the inorganic coagulant include polyaluminum chloride (PAC), ferric chloride, ferric sulfate, and polyiron sulfate. Can be used. As the polymer flocculant, for example, a nonionic, cationic, anionic or amphoteric polymer flocculant can be used.

  The above embodiment is an example of the present invention, and the present invention may be applied to other aspects. For example, in the above-described embodiment, the stirring member 30 rotates around the rotation shaft 14a together with the rake 14, but the stirring member 30 may be rotationally driven by a rotation shaft and driving means different from the rake 14.

  The above description relates to the coagulating sedimentation apparatus, and the sedimentation tank 4 is incorporated in the coagulation sedimentation apparatus 1. However, the sedimentation tank 4 having the above configuration is used as a solid-liquid separation facility independent of the coagulation sedimentation apparatus 1. You may be.

DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation apparatus 2 1st coagulation tank 3 2nd coagulation tank 4 Sedimentation tank 5 Raw water pump 6 1st chemical injection device 9 2nd chemical injection device 19 Extraction pump 20 Cyclone 30 Stirring member 33 Arm 34 1st stirring bar 35th 2 stirrer bars 34a, 35a first piece 34b, 35b second piece

Claims (11)

A first coagulation tank into which raw water is introduced and subjected to coagulation treatment with a first coagulant, and a first coagulation treatment water discharged from the first coagulation tank are introduced and coagulated by a second coagulation agent and a sedimentation promoting material. (2) a coagulation tank, a sedimentation tank into which the second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimentation and separation into treated water and slurry; a pit provided at the bottom of the sedimentation tank; A coagulating sedimentation apparatus comprising: a drawing pump for extracting slurry from the pit, and a cyclone for separating the slurry extracted from the pit into a separated sludge and a sedimentation promoting material, and returning the separated sedimentation promoting material to the second coagulation tank.
Pit stirring means for stirring the slurry in the pit is provided,
The pit stirring means includes a rotating shaft extending vertically, a driving means for rotating the rotating shaft, and one end fixed to the rotating shaft and the other end in a downward direction as a rod-shaped or band-shaped elongated member. And a stirring member whose lower end is located in the pit.   The apparatus according to claim 1, wherein the stirring member includes an arm extending radially from the rotation axis and a stirring bar extending downward from the arm. A plurality of the arms are provided at intervals in a circumferential direction of the rotation shaft,
The coagulating sedimentation apparatus according to claim 2, wherein a plurality of the stirring bars are provided at intervals in the arm longitudinal direction on each arm. The stirring bar has an L-shaped horizontal cross-sectional shape with a first piece and a second piece that intersect vertically,
4. The coagulating sedimentation apparatus according to claim 3, wherein the first piece is oriented in the radiation direction. The side peripheral surface of the pit has a smaller diameter as it goes down,
As the stirring bar, a first stirring bar whose lower end is located above the bottom surface of the pit, and a second stirring bar whose lower end is located above the side peripheral surface are provided,
5. The coagulating sedimentation apparatus according to claim 3, wherein the lower end of the first stirring bar is lower than the lower end of the second stirring bar.   6. A stirring control means for intermittently or continuously operating a stirring means of the second flocculation tank during a suspension period of a flocculation / sedimentation treatment operation by the flocculation / sedimentation apparatus, wherein: The coagulation sedimentation apparatus according to claim 1.   The coagulation sediment according to any one of claims 1 to 5, further comprising a control unit that stops supply of raw water to the first coagulation tank and stops the drawing pump after a predetermined time has elapsed. apparatus. A first coagulation tank into which raw water is introduced and subjected to coagulation treatment with a first coagulant, and a first coagulation treatment water discharged from the first coagulation tank are introduced and coagulated by a second coagulation agent and a sedimentation promoting material. (2) a coagulation tank, a sedimentation tank into which second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimentation and separation into treated water and slurry, and a pit provided at the bottom of the sedimentation tank;
A coagulating sedimentation apparatus comprising: a drawing pump for extracting slurry from the pit; and a cyclone for separating the slurry extracted from the pit into a separated sludge and a sedimentation promoting material, and returning the separated sedimentation promoting material to the second coagulation tank. ,
A coagulation sedimentation apparatus comprising: a control unit for stopping supply of raw water to the first coagulation tank and stopping the drawing pump after a predetermined time has elapsed.   The coagulation-sedimentation apparatus according to claim 8, wherein the coagulation-sedimentation apparatus intermittently or continuously stirs the inside of the second coagulation tank during a period in which the coagulation-sedimentation processing operation is stopped. A first coagulation tank into which raw water is introduced and subjected to coagulation treatment with a first coagulant, and a first coagulation treatment water discharged from the first coagulation tank are introduced and coagulated by a second coagulation agent and a sedimentation promoting material. (2) a coagulation tank, a sedimentation tank into which second coagulation treatment water discharged from the second coagulation tank is introduced, and sedimentation and separation into treated water and slurry, and a pit provided at the bottom of the sedimentation tank;
A coagulating sedimentation device comprising a drawing pump for extracting the slurry from the pit and a cyclone for separating the slurry extracted from the pit into separated sludge and a sedimentation promoting material and returning the separated sedimentation promoting material to the second coagulation tank. In the method of controlling,
A method for controlling a coagulation-sedimentation apparatus, comprising: stopping supply of raw water to the first coagulation tank when the coagulation-sedimentation apparatus is stopped, and stopping the drawing pump after a predetermined time has elapsed. In a sedimentation tank with a pit at the bottom,
Pit stirring means for stirring the slurry in the pit is provided,
The pit stirring means includes a rotating shaft extending vertically, a driving means for rotating the rotating shaft, and one end fixed to the rotating shaft and the other end in a downward direction as a rod-shaped or band-shaped elongated member. And a stirring member whose lower end is located in the pit.

Images