JP2012143673A - Fluidized bed type biological treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluidized bed type biological treatment apparatus which can radiate adherent bubbles from a carrier while preventing or suppressing the peeling of a biofilm.SOLUTION: The fluidized bed type biological treatment apparatus 1 includes: a cylindrical tank body 2 with a cylinder axis direction as a vertical direction; a drive shaft 3 arranged at the shaft core position of the tank body 2; a rotary blade 4 stuck to the drive shaft 3; a fixed plate 8 provided at the upper part of the tank body 2; a rotary plate 7 provided at the drive shaft 3; and a treated water ejection trough 6 provided at the upper part of the tank body 2. The rotary plate 7 circles, a floated carrier is sandwiched between the rotary plate 7 and the lower part made of rubber of the fixed plate 8, and bubbles radiate.

Description

  The present invention relates to a fluidized bed biological treatment apparatus for treating wastewater, and more particularly to a fluidized bed biological treatment apparatus provided with means for diffusing bubbles attached to a carrier.

  In biological treatment, fluidized bed biological treatment apparatuses are widely used in which microorganisms are attached to a carrier and the MLVSS in the tank is kept high. In this fluidized bed biological treatment apparatus, in general, the carrier filled in the tank is fluidized by stirring with stirring blades or an upward flow of water.

  When denitrification is performed by this fluidized bed biological treatment apparatus, nitrogen gas is generated by the denitrification reaction. Since nitrogen gas is contained inside the biofilm formed on the carrier, it floats by the buoyancy of the gas and stays on the water surface. When the amount of the floating carrier is increased, the contact between the carrier and the substrate in the liquid in the tank is deteriorated, and the treatment efficiency of the fluidized bed biological treatment apparatus is lowered. In addition to nitrogen, gas such as methane during anaerobic treatment may adhere to the carrier and the carrier may float.

  Japanese Patent Application Laid-Open No. 2006-218371 describes that a draft tube is installed vertically in the center of a tank, an impeller device is installed in the draft tube, and the carrier is defoamed by the impeller device. That is, the carrier that has floated in the tank due to the adhering of bubbles is sucked into the draft tube from the upper end of the draft tube and circulated. Given and degassed (paragraph 0027 of the publication).

JP 2006-218371 A

  When applying a shearing force to the carrier by the impeller to defoam the attached bubbles as in the above-mentioned Patent Document 1, since the shearing force applied to the carrier by the impeller is too strong, the biofilm attached to the carrier may be peeled off. is there.

  It is an object of the present invention to provide a fluidized bed biological treatment apparatus that can dissipate attached bubbles from a carrier while preventing or suppressing biofilm peeling.

  The fluidized bed biological treatment apparatus according to claim 1 is a fluidized bed biological treatment apparatus in which a tank is filled with a granular carrier, and has a stirring means for stirring the carrier and a bubble diffusing means for diffusing bubbles attached to the carrier. In the apparatus, the bubble diffusing means is configured to diffuse bubbles by sandwiching a carrier floating in the tank between a rotating plate and a stationary plate.

  A fluidized bed biological treatment apparatus according to a second aspect is the fluidized bed biological treatment apparatus according to the first aspect, wherein the rotating plate is attached to a drive shaft so as to swivel below the water surface in the tank, and the stationary plate is submerged in water. The rotating plate rotates so that the upper portion of the rotating plate comes into contact with the lower portion of the stationary plate, and at this time, the upper portion of the rotating plate and the lower portion of the stationary plate are The rotating plate is configured to pass under the stationary plate when at least one of them is retracted.

  The fluidized bed biological treatment apparatus according to claim 3 is the fluidized bed biological treatment apparatus according to claim 2, wherein at least a lower portion of the stationary plate is made of a soft material, and a lower portion of the stationary plate is in contact with a lower portion of the stationary plate. Is characterized by retreating.

  A fluidized bed biological treatment apparatus according to a fourth aspect is characterized in that, in the third aspect, the rotating plate is inclined so that the upper part is rearward in the swivel direction.

  In the fluidized bed biological treatment apparatus of the present invention, the carrier floating in the tank is sandwiched between the rotating plate and the stationary plate, so that the bubbles attached to the carrier are diffused. According to this bubble diffusing mechanism, the impact applied to the carrier can be reduced, and the bubbles can be radiated while preventing or suppressing biofilm peeling.

  In the fluidized bed biological treatment apparatus according to the second aspect, the rotating plate swirls under the surface of the water, the floated carrier is sandwiched between the upper part of the rotating plate and the lower part of the stationary plate, and bubbles are diffused from the carrier. When the rotating plate and the stationary plate come into contact, at least one of the upper portion of the rotating plate and the lower portion of the stationary plate is retracted, so that the impact given to the carrier is reduced and the biofilm is prevented from peeling off. It is suppressed.

  In the fluidized bed biological treatment apparatus according to claim 3, since the lower part of the stationary plate is made of a soft material, the lower part of the stationary plate moves backward when the rotating plate comes into contact with the lower part of the stationary plate, The impact given to is reduced.

  In the fluidized bed biological treatment apparatus according to claim 4, the rotating plate is inclined, and the carrier in the vicinity of the water surface in the tank moves upward along the rotating plate so as to be lifted up by the rotating rotating plate. Then, the air bubbles are diffused from the carrier by being sandwiched between the rotating plate and the stationary plate.

It is a longitudinal cross-sectional view of the fluidized bed type biological treatment apparatus which concerns on embodiment. It is a perspective view which shows the bubble diffusion means of FIG. It is a longitudinal cross-sectional view of a rotating plate and a stationary plate.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a fluidized bed biological treatment apparatus according to an embodiment.

  The fluidized bed biological treatment apparatus 1 includes a cylindrical tank body 2 whose vertical direction is a cylinder axis direction, a drive shaft 3 disposed at the axial center position of the tank body 2, and an anchor to the drive shaft 3. A rotary blade (stirring blade) 4, a motor 5 for rotating the drive shaft 3, and a treated water extraction trough 6 with a carrier outflow prevention screen provided at the upper part of the tank body 2 are provided. The overflow level of the treated water extraction trough 6 is the water level WL in the tank body 2. A rotating plate 7 and a stationary plate 8 are provided in the upper part of the tank body 2 as means for diffusing attached bubbles from the carrier.

  In this embodiment, the rotary blade 4 has a flat plate shape with the plate surface in the vertical direction, and extends from the drive shaft 3 in the diameter direction of the tank body 2. That is, in this embodiment, two rotor blades 4 are provided in the opposite direction of 180 °. However, three or more blades may be provided in the radial direction, and usually about 2 to 4 blades are suitable. What is necessary is just to make a support | carrier flow, and the shape of a wing | blade is not limited.

  The swirl diameter of the rotor blade 4 (the distance between the tips of the two rotor blades 4 in this embodiment) is preferably about 20 to 80%, particularly about 50 to 70% of the diameter of the tank body 2.

  The rotary blade 4 is disposed near the middle of the tank body 2 in the vertical direction. The height of the upper edge of the rotor blade 4 (height from the bottom surface of the tank body, hereinafter the same) is preferably about 20 to 80%, particularly about 50 to 70% of the tank body water depth. The vertical width of the rotary blade 4 is preferably about 5 to 60%, particularly about 10 to 40% of the tank body water depth.

  In this embodiment, only one stage of the rotary blade 4 is provided in the vertical direction, but it may be provided in two or more stages.

  In this embodiment, a bearing portion is provided on the bottom surface of the tank body 2, and the lower end of the drive shaft 3 is supported by this bearing portion.

  A granular carrier C is accommodated in the tank body 2.

  The carrier may be any material, but is preferably a granular polymer crosslinked material that is resistant to wear.

  Examples of the carrier resin include polyolefin, PVA, PEG, (poly) acrylamide, N-substituted acrylamide, (poly / meth) acrylic acid or an alkali metal salt thereof, alginic acid, polyalkylene oxide, dimethylaminoethyl (meth) acrylate ( DAM), diacetone alcohol (DAA), polyalkylene oxide and the like. More specifically, sodium polyacrylate, copolymer of sodium acrylate and acrylamide, copolymer of sodium acrylate and sodium acrylamide 2-methylpropanesulfonate, sodium acrylate, acrylamide and sodium acrylamide 2-methylpropanesulfonate And a terpolymer of dimethylaminoethyl (meth) acrylate, a homopolymer of quaternary ammonium or a copolymer with acrylamide and the like.

  The average particle diameter of the carrier can be 1 mm to 20 mm, preferably 1 mm to 5 mm, particularly preferably 1.2 mm to 3.5 mm. If it is smaller than this, it will be difficult to separate the carrier and water, and if it is larger, flow will be hindered.

  The porosity of the carrier is preferably 20 to 50%, particularly preferably 30 to 40%. When the porosity is low, there is little adhesion of sludge and the processing efficiency is lowered, and when it is high, gas is easily included.

The density of the carrier is desirably 0.96 to 1.02 g / cm ³ on average, and the density of the carrier of 80% or more is 0.98 to 1.01 g / cm ^3, particularly 0.985 to 1. It is preferably 00 g / cm ³ .

  The filling amount of the carrier is preferably such that the bulk volume of the carrier is 5 to 50% with respect to the volume below the water level WL of the tank body 2. If the amount of the carrier is less than this, the processing efficiency is lowered, and if it is more than 50%, the stirring power becomes excessive.

  FIG. 2 is a perspective view of the rotating plate 7 and the stationary plate 8 for diffusing air bubbles adhering to the carrier, and FIG. 3 is a longitudinal sectional view of the state where the rotating plate 7 is about to contact the stationary plate 8. is there.

  Two rotating plates 7 are provided so as to extend in the radial direction from the drive shaft 3. The number of sheets is preferably about 2 to 4 sheets. The rotating plate 7 is inclined so as to be rearward toward the upper part with respect to the turning traveling direction. The inclination angle θ of the front surface of the rotating plate 7 is preferably 60 ° or less, particularly about 30 to 60 °. The rotating plate 7 is preferably attached to the drive shaft 3 so that the inclination angle can be adjusted.

The radial length of the rotating plate 7, that is, the turning radius, is preferably about 10 to 100%, particularly about 20 to 60% of the solid turning radius where the circulating flow is weak and the carrier gathers. The formula for calculating the solid turning radius (r _c ) is as follows.
2r _c = 1.23 {0.57 + 0.35 (d / D)} (b / D) ^0.036 n _p ^0.116 Re / (10 ³ +1.43 Re) d
r _c : solid turning radius (m)
d: Stirring blade diameter (m)
D: Tank diameter (m)
b: Wing width (m)
n _p : number of blades of wings Re: Reynolds number

  The rotating plate 7 is preferably provided so as to be immersed in water. The constituent material of the rotating plate 7 is arbitrary, such as metal or synthetic resin, but at least the upper surface (contact surface with the stationary plate 8) that contacts the stationary plate 8 is flexible natural rubber or synthetic rubber (for example, It is desirable that it be made of silicon rubber).

  The stationary plate 8 is installed such that its lower part is submerged in water in the swivel region of the rotating plate 7. In this embodiment, two stationary plates 8 are installed symmetrically with the drive shaft 3 in between. The stationary plate 8 is installed such that the plate surface is in the radial direction with respect to the drive shaft 3. The radial width of the stationary plate 8 is preferably about 20 to 120%, particularly about 40 to 100% of the turning radius of the rotating plate 7.

  The distance from the end of the stationary plate 8 on the drive shaft 3 side to the drive shaft 3 is preferably about 5 to 40%, particularly about 10 to 30% of the turning radius of the rotating plate 7. The distance from the end of the stationary plate 8 on the side far from the drive shaft 3 to the drive shaft 3 is preferably about 25 to 130%, particularly about 50 to 100% of the turning radius of the rotary plate 7.

The distance (water immersion depth) H ₁ from the lower end of the stationary plate 8 to the water surface is preferably 30 cm or less, particularly 5 to 30 cm, and particularly preferably about 5 to 10 cm. The submerged depth H ₁ of the stationary plate 8 is larger than the submerged depth H ₂ of the upper edge of the rotating plate 7, and the upper portion of the rotating plate 7 contacts the lower portion of the stationary plate 8 when the rotating plate 7 turns. It is configured as follows. The submergence depth H ₁ of the stationary plate 8 is about 150 to 1500% (1.5 to 15 times), particularly 200 to 500% (2 to 5 times) of the submergence depth H ₂ of the upper edge of the rotating plate 7. It is preferable. At least the lower part of the stationary plate 8 is made of a flexible rubber (for example, a synthetic rubber such as natural rubber or silicon rubber) so as to be pushed backward by the rotating plate 7 when it contacts the rotating plate 7. It is desirable.

  In the fluidized bed biological treatment apparatus configured as described above, raw water (organic matter-containing wastewater) is supplied into the tank body 2 from the raw water supply pipe 9 into the tank body 2 while rotating the rotor blades 4 and the rotating plate 7. And biological treatment.

  It is preferable to adjust the rotational speed of the drive shaft 3 of the rotor blade 4 so that the G value is 50 to 200, particularly 80 to 150.

  The liquid in the tank body 2 (liquid in which the water to be treated and the carrier is mixed) flows in a radial direction and a swiveling direction in the vicinity of the middle in the vertical direction of the tank body 2 due to the centrifugal force and the turning force received from the rotor blades 4. 2 divides into a swirl flow that is directed upward and a swirl flow that is directed downward.

  The liquid that turns into the upward swirling flow rises while swirling along the inner peripheral surface of the tank body 2. During this time, the carrier in the liquid is loosened. The liquid changes its direction in the centripetal direction when it reaches the vicinity of the water surface level WL, then flows in a spiral shape, collects in the vicinity of the center near the water surface level, and then settles and returns to the vicinity of the rotary blade 4.

  On the other hand, the liquid that has turned downward from the middle in the vertical direction of the tank body 2 descends while swirling along the inner peripheral surface of the tank body 2, and flows in a spiral shape when reaching the bottom surface of the tank body 2. Then, they gather near the bottom center of the tank body 2, rise near the center of the tank body 2, and return to the rotary blade 4.

  In this embodiment, the specific gravity of the carrier is preferably about 1 or less. In this case, most of the carrier rises while swirling along the inner peripheral surface of the tank body 2 together with the rising swirl flow, and is loosened during this time. Therefore, along with the spiral flow in the centripetal direction near the water surface level WL, it smoothly flows from the peripheral part (near the inner peripheral surface of the tank body 2) near the water level toward the central part, and then from the central part near the water level WL. Settling with downflow. In this way, the carrier circulates well in the tank body 2 and the biological treatment efficiency is improved.

  When bubbles adhere to the carrier, the carrier does not settle due to the descending water flow, but remains floating on the water surface. In this embodiment, the carrier C that has floated on the water surface due to bubbles adhering to it gathers in the vicinity of the center of the water surface, is pushed by the rotating plate 7 and swivels between the upper portion of the rotating plate 7 and the lower portion of the stationary plate 8. The carrier C is impacted and the bubbles are diffused. The carrier C from which the bubbles have diffused settles with the descending water flow and circulates in the tank body 2.

  In this embodiment, since the rotating plate 7 is an inclined plate, the carrier near the water surface moves upward along the plate surface of the rotating plate 7 as the rotating plate 7 turns, and the rotating plate 7 and the stationary plate 8 The air bubbles are diffused by being sandwiched between. Further, since at least the lower part of the stationary plate 8 is made of a soft material such as rubber, when the upper part of the rotating plate 7 abuts against the stationary plate 8, the lower part of the stationary plate 8 is pushed by the rotating plate 7 and retracts. To do. For this reason, the impact applied to the carrier C becomes moderate, and peeling of the biofilm attached to the carrier is prevented or suppressed.

  In the above embodiment, the lower portion of the stationary plate 8 is made of a soft material, but the upper portion of the rotating plate 7 is made of a soft material, and the upper portion retreats when contacting the stationary plate 8. You may comprise. Moreover, you may comprise both the upper part of the rotating plate 7, and the lower part of the stationary plate 8 with a soft material.

  The stationary plate 8 is installed by being attached to an appropriate member such as an installation base of the motor 5. This mounting portion is configured by a hinge, and when the stationary plate 8 is strongly pressed, the stationary plate 8 is rotated by the hinge portion. Then, it may be possible to prevent an excessive stress from being generated on the stationary plate 8.

  In the above embodiment, the rotary blade 4 and the rotary plate 7 are attached to the common drive shaft 3 and are configured to rotate at the same rotational speed. For example, the rotary shaft of the rotary plate 7 is a hollow tube. The driving shaft 3 may be passed through the rotating shaft, the rotating blade 4 may be rotated by the driving shaft 3, and the rotating plate 7 may be rotated at a rotational speed different from that of the rotating blade 4 by a tubular rotating shaft.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
Tank body 2 having a diameter of 120 cm, depth 180cm, _NO 3 -N concentration using a fluidized bed biological treatment apparatus shown in FIG. 1-FIG. 3 of the tank capacity _{^{2m 2 80mg / L, PO 4}} -P concentration 2 mg / L The synthetic waste water was supplied at a tank load of 1 kg-N / m ³ / d for treatment. Methanol was added 3 times as much as N.

As a carrier, a polyolefin gel carrier (average particle diameter: 3 mm) having a density of 1.01 g / cm ³ was filled at 15% of the tank volume.

In addition, the structure of the rotating plate 7, the stationary plate 8, and the rotary blade 4 is as follows.
Length (radius) of rotating plate 7: 140 mm
Vertical width of rotating plate 7: 70 mm
Submerged depth H ₂ of the upper edge of the rotating plate 7: 20 mm
Material of rotating plate 7: SUS
Radiation length of stationary plate 8: 110 mm
Deposition depth H ₁ of stationary plate 8: 50 mm
Distance between stationary plate 8 and drive shaft 3: 30 mm
Material of the lower part of the stationary plate: Natural rubber (vertical length 100mm)
Length of rotor blade 4: 720mm
Rotating blade 4 width: 360 mm

When the rotary blade 4 was operated at a G value of 80 to 150 (11 to 17 rpm, adjusted according to the flow state of the carrier), the NO ₃ —N concentration of the treated water was 5 mg / L or less. Further, almost no surfaced carrier was observed.

[Comparative Example 1]
The raw water was treated in the same manner as in Example 1 except that the rotating plate 7 and the stationary plate 8 were omitted. As a result, the NO ₃ —N concentration of the treated water was 10 mg / L, and the carrier floated to a surface area of 30%. Was visible.

  As is clear from this example and the comparative example, according to the example in which the rotating plate 7 and the stationary plate 8 are provided, the carrier is prevented from floating and the N removal rate is higher than that of the comparative example.

DESCRIPTION OF SYMBOLS 1 Fluidized bed type biological treatment apparatus 2 Tank body 3 Drive shaft 4 Rotary blade 5 Motor 6 Treated water trough 7 Rotating plate 8 Stationary plate

Claims (4)

In a fluidized bed biological treatment apparatus, the tank is filled with a granular carrier, and has a stirring means for stirring the carrier and a bubble diffusing means for diffusing bubbles attached to the carrier.
The fluidized bed biological treatment apparatus is characterized in that the bubble diffusing means is configured to diffuse bubbles by sandwiching a carrier floating in a tank between a rotating plate and a stationary plate. 2. The rotating plate according to claim 1, wherein the rotating plate is attached to the drive shaft so as to turn below the water surface in the tank, and the stationary plate is disposed in a turning region of the rotating plate so that the lower part is submerged in water. And
The rotating plate pivots so that the upper part of the rotating plate comes into contact with the lower part of the stationary plate. At this time, at least one of the upper part of the rotating plate and the lower part of the stationary plate retracts, so that the rotating plate becomes A fluidized bed biological treatment apparatus configured to pass through a lower side.   The fluidized bed system according to claim 2, wherein at least a lower portion of the stationary plate is made of a soft material, and the lower portion of the stationary plate retreats when the upper portion of the rotating plate contacts the lower portion of the stationary plate. Biological treatment equipment.   The fluidized bed biological treatment apparatus according to claim 3, wherein the rotating plate is inclined so that the upper part is rearward in the swivel direction.

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