JP3787774B2 - Floating separation method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is treated water (hereinafter also referred to as “raw water”) containing substances to be removed such as suspended particles such as industrial wastewater, sewage, and raw water, phosphate ions, fluorine ions, metal ions, chromaticity components, and COD components. ) Is a novel floating technology that can float and separate substances to be removed in raw water at an ultra-high speed 50 times or more than the conventional coagulation sedimentation method or the floating separation method.
INDUSTRIAL APPLICABILITY The present invention is an innovative technology that is particularly suitable as a technology for ultra-high-speed solid-liquid separation of rainwater overflow (abbreviated as CSO) in a combined sewer containing organic suspended particles or sewage flowing into a sewage treatment facility. About.
[0002]
[Prior art]
Recently, the pollution load of public waters due to rainwater overflow (CSO) in the combined sewer has become a major problem. Since rainwater overflow (CSO) in a combined sewer generates a huge amount of water in a short time, a device that can remove CSO contaminants with a very compact device is eagerly desired.
In addition, the sewage flowing into the sewage treatment facility is first precipitated and separated in the settling basin, and then treated with activated sludge. However, since the SS removal rate of the first settling basin is poor, a coagulant is added to the flocculated sedimentation treatment. An example of this is prevalent in Scandinavia. However, this method has a disadvantage that the coagulation sedimentation rate is small and a large sedimentation basin is required. Therefore, an innovative technology that can solid-liquid separate CSO and sewage at an extremely high speed is awaited.
Conventionally, a method is known in which pressurized dissolved air-containing water or fine bubbles are blown into raw water, and suspended particles are attached to the bubbles to float and separate.
[0003]
[Problems to be solved by the invention]
However, the conventional levitation separation method has a drawback that the levitation separation speed is as low as about 100 to 200 mm / min, and additional facilities such as an air compressor and an air melting facility are required.
The present invention has been made based on such a situation, and solves the problems of the conventional floating separation technology, and by simple operations, various raw water such as river water, lake water, drainage, sewage, etc. New floating separation method capable of floating and separating substances to be removed such as suspended particles, phosphate ions, fluorine ions, metal ions, chromaticity components and COD components at an extremely high speed, and which does not require an air dissolution facility, and It is an object to provide an apparatus.
[0004]
[Means for solving problems]
The present invention has solved the above-described problems by the following means.
(1) At least a polymer flocculant is added to the water to be treated containing the substance to be removed, and the floating solid particles are supplied to a fluidized tank in the liquid, and the flocs of the substance to be removed are agglomerated. While adhering to the surface of the buoyant solid particles in the tank, the floc-attached buoyant solid particles are separated from the treated water using its levitation force, and the treated water is taken out from the treated water separation part located at the bottom of the fluidized tank. The separated floc-attached floating solid particles are transferred from the fluidized tank to the floc peeling part, the flocs are peeled off from the floating solid particles, the flaking flocs are excluded from the system, and the floating solid particles separated from the flocs are A flotation separation method characterized by returning to the agglomerated floc adhering portion of the fluidized tank.
[0005]
(2) A fluidized tank in which floating solid particles are present in the liquid and water to be treated containing a polymer flocculant is introduced to attach the aggregated flocs to the surface of the floating solid particles , and floc adhesion and floatability from the fluidized tank A floc peeling tank that receives solid particles and peels off the flocs from the floating solid particles, and an effluent from the floc peeling tank is supplied to wash the floating solid particles from which the flocs have been peeled off to remove the flocs. a cleaning device for discharging, consists of a transport means comprising a passage for returning the washed flying solid particles by the cleaning device at the top of the fluidization vessel, the flow tank, in the tank water and the tank bottom flying solid particles flow section located between the treated water separating unit, the vessel treated water separation section provided on the lower, discharge end of the treatment water disposed on the treated water separation section, and upwardly from said fluidized section before extending toward the It has a passage communicating with flock stripping vessel, flotation device, characterized in that said at flock adhesion flying solid particles in the fluidized section that includes a flock adhesive solid particles circulating unit to send to the flock stripping vessel.
(3) The floating separation apparatus according to (2), wherein a stirrer is provided in the fluidized tank.
(4) Floating separation according to (2) above, wherein the means for transferring the floc-attached floating solid particles in the floc-attached solid particle circulating section from the fluid tank to the floc peeling tank is a pump or an air lift. apparatus.
[0006]
The essence of the present invention is to use “floating solid fine particles” such as expanded polystyrene particles instead of bubbles in the conventional flotation separation method, and add organic polymer flocculant or inorganic flocculant and organic polymer flocculant to raw water. The flocculating solid particle group is supplied to the fluidized tank, and the inside of the tank is caused to flow down as a downward flow. This is a basic technical idea of flotation and separation of flock-attached levitating solid particles at high speed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of the ultrahigh-speed levitation separation apparatus of the present invention.
After adding the inorganic flocculant 3 to the raw water 1 and stirring in the flocculant tank 2 for about 30 seconds, the polymer flocculant 4 is added, and the specific gravity is 0.2 or less in the form of fine particles having a particle size of about 50 to 1000 microns ( Preferably, the raw water 1 is supplied to a fluidized tank 6 in which a large number of floating solid particles (for example, polystyrene fine particles) 5 having an extremely high floating force of 0.01 to 0.1) are present, and the floating solid particles are obtained by means of a descending water flow. While 5 is prevented from floating on the water surface, the floating solid particles 5 are caused to flow under the condition that they do not flow into the treated water. In addition, by performing stirring at that time, the descending speed of the descending water flow can be adjusted, and the speed at which the floating solid particles 5 float on the water surface can be changed. Although the descent speed of the lower precipitation stream can be variously changed, a range of 3 to 6 m / min is preferable.
[0008]
Surprisingly, according to the present invention, during a short time (several tens of seconds) of passing through the fluid tank 6, the aggregated micro flocs of the substance to be aggregated and removed in the raw water 1 are formed on the surface of the floating solid particles 5. It has been found that it floats and separates from the treated water while being firmly attached to the coating.
Floating solid particles (also referred to as “floc-adhering particles” for simplicity) 10 to which flocs are attached are automatically transferred from the lower end of the fluid tank wall to the adjacent floating particle circulation part 8, floated, and separated. 13 flows in. The clear treated water 12 flows out from the lower part of the fluidized tank 6.
The floating speed (that is, the descending flow rate of the fluidized tank section 6) of the present invention “in the state in which the substance to be removed in the raw water 1 is attached to the surface of the floating solid particles 5” is extremely large. It is 3 to 6 m / min, which is about 50 times larger than a conventional flotation separation apparatus using pressurized dissolved air bubbles.
[0009]
When the floc-adhering particles 10 are transferred to the flock peeling tank 13 by an arbitrary transfer means (airlift in the illustrated example) and stirred vigorously with an impeller or irradiated with ultrasonic waves, the flocs are separated from the flock-adhering particles 10. Shear peeling.
The preferred types of transfer pumps for washing and floating objects of the present invention are air lift pumps, mixed-jet pumps (which supply air and pressure water to the lower part of the pipe to provide driving force for water), screw pumps, screw conveyors, etc. Is preferred. The air lift pump and the mixed-air jet pump do not require a mechanical rotation mechanism, have a simple structure, and have an important advantage that no blockage occurs during floating object transfer. The screw pump is preferable because the floating solid particles 3 are not blocked in the pump. If a pump (an axial flow pump, a centrifugal pump, etc.) or an air lift is applied as the floc transfer means, a shear force is applied to the floc adhering particles 10 in the floc transfer path, and the floc can be peeled off, so that a separate peeling portion is omitted. You can also.
[0010]
A hydrocyclone can also be used to peel and separate the adhering floc from the buoyant solid particles. That is, when the floc-attached particles 10 are sent to the liquid cyclone by the pump, the flocs are separated from the floating solid particles 5 by the shearing force when passing through the pump, and the specific gravity of the floating solid particles 5 in the cyclone is much larger than that of water. Because the flocs flocs at the center of the cyclone due to centrifugal force and the specific flocities greater than 1 are collected at the outer periphery of the cyclone, the flocculent flocs and levitation properties are extracted by extracting the floating solid particles 5 from the center of the cyclone. The solid particles 5 can be easily separated.
[0011]
As the buoyant solid particles 5, foamed polystyrene (fine particles) is suitable, and the foamed polystyrene has a very small specific gravity, so the collision energy (proportional to the particle mass) is very small, and the cyclone, piping, and pump are worn. Absent.
On the other hand, there is an example in which sand is collected with a hydrocyclone in a known coagulation sedimentation method in which particles such as sand having a large specific gravity are attached to the floc to form a floc weight. As a result, cyclones, pipes, pumps, and the like are subject to wear.
[0012]
Next, the effluent from the floc peeling tank 13 is supplied to the peeling floc removing unit 14. Washing water (a part of the raw water 1 can be used) 15 is supplied from above the peeling floc exclusion section 14 , drainage 17 is taken out from below, the flocs flaking off are discharged, and the washed floating solid particles 16 are flowed Return to tank 6.
[0013]
Therefore, the range suitable for the circulation amount of the washed floating solid particles 16 to the fluidized tank 6 is that if the amount is too small, the amount of unattached floc leaking to the treated water 12 increases, and if it is too large, the floating solid particles 5 This is disadvantageous because the amount of transfer, peeling and cleaning increases. Therefore, the circulation amount of the floating solid particles 5 is preferably 5 to 100 (ml floating solid particles / liter raw water level) in terms of “bulk volume” per raw water treatment amount, more preferably 10 to 40 (ml The range of floating solid particles / liter raw water).
Since the amount of water discharged from the floc stripping tank 13 is small, in the case of CSO treatment, it flows directly to the sewage treatment plant. In other cases, it is supplied to a normal sedimentation tank, and the precipitated sludge is disposed of in the sludge treatment process. You can do it.
[0014]
As a result of various investigations on the optimal floating solid particles 5 to be applied to the present invention, it is important to use the smallest possible specific gravity of the floating solid particles 5 in order to obtain a large floating separation speed, and the specific gravity is 0. .2 or less is preferred. In particular, expanded plastic particles such as expanded polystyrene, especially expanded polystyrene, can change the specific gravity from 0.04 to 0.15 arbitrarily by changing the expansion ratio, extremely high levitation force, low price, easy to obtain So it is optimal.
[0015]
The particle size of the floating solid particles 5 added to the raw water 1 is also an important factor. If the particle size is excessively large, there is a problem that the flocs are difficult to adhere to the floating solid particles. The particle size is preferably in the range of about 300 to 1500 μm, more preferably about 500 to 800 μm.
[0016]
The appropriate addition rate of inorganic flocculant 3 such as aluminum sulfate, PAC, ferric chloride, iron sulfate, polyiron sulfate, iron silica flocculant varies depending on the quality of raw water 1, but when treating sewage according to the present invention PAC is about 100 to 150 mg / liter, and ferric chloride is about 50 to 100 mg / liter.
Addition of the inorganic flocculant 3 is indispensable when removing ions such as phosphate ions and fluorine ions, but in other cases, addition of the inorganic flocculant 3 is not indispensable, and the cationic polymer alone or the cationic polymer. And a combination of an amphoteric polymer, a combination of a cationic polymer and an anionic polymer, or a combination of a cationic polymer and a nonionic polymer.
[0017]
In the present invention, the polymer flocculant (polymer) 4 is indispensable for flocking to the floating solid particles 5, and either an anionic, nonionic, cationic or amphoteric polymer or a combination thereof is used. . When removing the target substance for coagulation removal in sewage, an injection rate of about 1 to 5 mg / liter is sufficient.
In addition, in the case of water treatment, it is sufficient that the amount of the polymer flocculant 4 added is about 0.5 to 1 mg / liter.
[0018]
As a result of examining the most effective flocculation method, after adding the inorganic flocculant 3 or the cationic polymer 4 to the raw water 1 and stirring, the method of adding the nonionic polymer and the amphoteric polymer or the anionic polymer and the amphoteric polymer is very It has been found that flocs having high adhesion and high floc strength are formed, and the aggregated flocs can be adhered to the surface of the floating solid particles 5 very effectively.
[0019]
As described above, the addition position of the polymer flocculant 4 is added to the upper part of the flow tank 6 of the floating solid particles 5 or the raw water 1 inflow pipe so that the flocs are effectively attached to the surface of the floating solid particles 5. Therefore, it is not necessary to separately provide a stirring tank for adding the polymer flocculant 4 to form a floc.
[0020]
As another preferred embodiment, a part of the floating separation may be withdrawn as it is and circulated to the raw water 1, and only the remaining part of the floating separation may be sent to the flock peeling unit 13. If it does in this way, a new floc will adhere to the surface of the floc adhesion floating particle 5 like a snowman. However, since there is an upper limit on the amount of adhesion, the remainder of the floating separation is sent to the floc peeling part 8 so that the floating solid particles 5 are washed and then returned to the raw water 1. According to this method, the amount of the floating solid particles 5 sent to the floc peeling tank 13 is smaller than that of the method of FIG. 1, and the volume of the floc peeling tank 13 and the stirrer are small.
In FIG. 1, 2 is a flocculation tank for a substance to be removed by flocculation in the raw water 1 by the inorganic flocculant 3, and 7 is a stirring blade of a stirrer of the fluidized tank 6.
[0021]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the examples.
[0022]
Example 1 Treatment test of stormwater overflow (CSO) in combined sewers Ferric chloride was added at 40 mg / liter to CSO (SS 230 mg / liter) at a flow rate of 50 m ³ / h, and rapid stirring was performed for 20 seconds. Thereafter, 1.5 mg / liter of a polymer (anionic polymer, molecular weight 15 million, brand Ebagulose A151) was added, and after stirring for 2 seconds, spherical expanded polystyrene fine particles having an average particle size of 600 μm and a specific gravity of 0.1 were added. Was supplied to a fluidized tank in a fluidized state by a descending flow rate.
The fluid tank was swirled by a vertical impeller. The raw water residence time in this fluid tank was 15 seconds. As a result, the agglomerated floc was firmly adhered to the surface of the expanded polystyrene particles while passing through the fluidized tank, and separated by floating.
From the lower part of the fluid tank, clear treated water was separated at a descending flow rate of 5 m / min and flowed out of the system.
Further, from the lower end portion of the fluid tank wall, the floc-attached floating particles naturally moved to the adjacent floating separation portion and floated almost instantaneously.
[0023]
The float was transferred to a floc peeling tank by an air lift and stirred for 1 to 2 minutes in a screw blade stirring tank with a rotation speed of 450 rpm. As a result, the floc adhered to the floating solid particles was peeled off. Next, the peeling floc and the expanded polystyrene particles were transferred to the peeling floc exclusion part under natural flow.
A part of the raw water was supplied as cleaning water from above the peeling floc removal tank, and the peeling floc was discharged out of the system.
As a result of such continuous operation, the treated water SS was stably 8 to 12 mg / liter, and the SS in the CSO was highly removed at a very high speed.
[0024]
Comparative Example 1
It tested with the floating separation apparatus using a conventionally well-known pressurized dissolved air. The raw water is the same as in Example 1. 40 mg / liter of ferric chloride was added to sewage (SS 230 mg / liter), and after rapid stirring for 30 seconds, 3 mg / liter of nonionic polymer, molecular weight 15 million, brand Eva Claus N800 was added and stirred rapidly for 1 minute. After that, water containing pressurized dissolved air was supplied and allowed to flow into a flotation separation apparatus set to a flotation separation speed of 200 mm / min. As a result, flocs adhering to the floating solid particles floated slowly. The treated water SS was 12 mg / liter, and SS in the sewage was removed.
However, when operating with the ascent rate set at 300 mm / min, the floc hardly floated up, and it flowed into the treated water along with the downward flow, and the treated water SS deteriorated significantly to 185 mg / liter and could not be treated. It was.
[0025]
【The invention's effect】
According to the present invention, the following excellent effects can be obtained.
(1) Aggregate and remove substances such as suspended particles, phosphate ions, chromaticity components, and COD components in raw water at an extremely high solid-liquid separation rate, which was impossible at all by conventional airborne flotation methods. Can float and separate. The solid-liquid separation speed of the present invention is literally astonishing, can easily be 5 (m / min), and can be about 50 times as high as the conventional floating separation method.
(2) Therefore, it is extremely suitable for raw water that generates a huge amount of water in a short time, such as rainwater overflow (CSO) in a combined sewer system, and suspended particles of CSO can be removed with a very compact device. .
[0026]
(3) There is no need to install a flocculent stirring tank for floc formation by adding a polymer flocculant separately from the floating separator main body, and only the polymer flocculant is added to the upper part of the fluidized solid particle flow tank. Thus, floating separation can be achieved while effectively attaching floc to the surface of the floating solid particles. Therefore, the configuration of the entire apparatus can be simplified and the installation area can be reduced.
(4) An air compressor, an air dissolution tank, and the like, which are indispensable in the conventional pressurized dissolved air flotation separation method, are unnecessary, and equipment costs and power costs can be reduced.
(5) The floating solid particles that have been floated and separated can be easily recovered and reused, and do not need to be disposable.
(6) Flock peeling (cleaning) from the levitated object is easy, and equipment costs and power costs can be reduced.
(7) Since particles having a large specific gravity such as sand are not used for the flock weight, the pump, cyclone and piping are not worn by the sandblast effect.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a flotation separation apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water 2 Coagulation tank 3 Inorganic flocculant 4 Polymer flocculant 5 Floating solid particle 6 Fluid tank 7 Stirring blade 8 Flock adhesion particle circulation part 9 Air lift air 10 Flock adhesion particle 11 Treated water separation part 12 Treated water 13 Flock peeling tank 14 Peeling floc exclusion part 15 Washing water 16 Washed floating solid particles 17 Drainage

Claims (4)

  At least a polymer flocculant is added to the water to be treated containing the substance to be removed, and the floating solid particles are supplied to the fluidized tank in the liquid, and the aggregated floc of the substance to be aggregated is contained in the fluidized tank. While adhering to the surface of the buoyant solid particles, the floc-attached buoyant solid particles are separated from the treated water using its levitation force, and the treated water is taken out from the treated water separation part located at the bottom of the fluidized tank and separated. The floc-attached floating solid particles are transferred from the fluid tank to the floc peeling part, the flocs are peeled off from the floatable solid particles, the flaking flocs are excluded from the system, and the floatable solid particles separated from the floc are removed from the fluid tank. A flotation separation method characterized by returning to the agglomerated floc adhesion part. A flow tank in which floating solid particles are present in the liquid and water to be treated containing a polymer flocculant is allowed to flow to attach the aggregated flocs to the surface of the floating solid particles, and floc-attached floating solid particles from the flow tank A floc peeling tank for receiving and flaking off the flocs from the floc-attached floating solid particles, and a effluent from the floc peeling tank is supplied to wash the floating solid particles from which the flocs have been peeled off and discharge the flocs device and, said washed with washing device the floating solid particles composed of a transfer means comprising a passage for returning to the top of the fluidization vessel, the flow tank, treated water separation of the water surface and the tank bottom of the tank flying solid particles flow section located between the parts, the vessel treated water separation section provided on the lower, discharge end of the treatment water disposed on the treated water separation section, and from the fluidized section upwardly extending the flow It has a passage communicating with click peeling vessel, flotation device, characterized in that said at flock adhesion flying solid particles in the fluidized section that includes a flock adhesive solid particles circulating unit to send to the flock stripping vessel.   The flotation separator according to claim 2, wherein a stirrer is provided in the fluidized tank. The levitation separation apparatus according to claim 2 , wherein a means for transferring floc-attached floating solid particles in the floc-attached solid particle circulation section from the flow tank to the flock peeling tank is a pump or an air lift.

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