JP6454621B2 - Sludge aggregation method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for aggregating sludge, for example, a method for agglomerating sludge in a concentration process or a dewatering process for sludge discharged from a wastewater treatment facility or a water purification treatment facility, and an apparatus used therefor.

  While it is required to reduce the amount of waste and reduce the environmental impact, dehydration technology and anaerobic treatment technology for reducing and reducing sludge discharged from wastewater treatment facilities and water purification treatment facilities are extremely It is important, and more efficient sludge dehydration technology and anaerobic treatment technology are desired.

  In general, the sludge dewatering treatment includes a coagulation step of coagulating the sludge using a coagulant and a dehydration step of dehydrating the coagulated sludge using a dehydrator. The success or failure of sludge dehydration depends largely on the efficient coagulation of the sludge with the coagulant.

  In the anaerobic treatment of sludge, the sludge is often aggregated using a flocculant, the aggregated sludge is concentrated using a concentrator, and the concentrated sludge is often anaerobically treated. Even in anaerobic treatment of sludge, efficient coagulation of sludge with a flocculant is important.

Among the methods of aggregating sludge using a flocculant, as a technique relating to a method of aggregating sludge by mixing sludge and aggregating agent using a stirring blade rotating at a rotation speed of 1000 min ⁻¹ or more, Such prior art is known.

In Patent Document 1, a flocculant that agglomerates various substances such as dissolved substances, suspended substances, and fine suspended substances in sludge is added to the sludge flowing through the sludge treatment line. Sludge treatment in which flocculant added sludge is stirred by an agitation pump installed in the middle of the sludge treatment line, and the flocculant is dispersed in the form of fine particles throughout the sludge in the sludge treatment line to form flocs by the coagulation reaction of the flocculant. A method is described. Patent Document 1 describes that the rotation speed of the stirring pump is preferably selected from about 200 to 2000 min ⁻¹ .

In Patent Document 2, the first polymer flocculant solution is poured into the sludge, and the sludge and the first polymer flocculant solution are mixed with a high-speed stirring device that rotates at a rotation speed of 1000 min ⁻¹ or more. A first stirring step for preparing mixed sludge by mixing, a solution of the second polymer flocculant is injected into the mixed sludge, and the mixed sludge is mixed with a low-speed stirring device that rotates at a rotational speed of 10 to 500 min ^−1. A method for coagulating sludge is described which includes a second stirring step in which a solution of a second polymer flocculant is mixed to form a floc floc.

JP 2002-307100 A International Publication No. 2012/108312

When sludge and flocculant are mixed with a stirring blade rotating at a rotation speed of 1000 min ⁻¹ or higher, the agglomeration reaction is promoted, but it is difficult to optimize the mixing conditions in accordance with changes in operating conditions such as sludge flow rate. It was. Moreover, it was necessary to optimize the shape of the stirrer so that rotational energy of 1000 min ⁻¹ or more can be efficiently used for the aggregation reaction.

An object of the present invention is to provide a sludge aggregation method and apparatus capable of efficiently aggregating sludge even if operating conditions such as a sludge flow rate are changed. It is another object of the present invention to provide a sludge coagulation method and apparatus capable of efficiently using a rotational energy of 1000 min ⁻¹ or more for the coagulation reaction.

In order to achieve the above-described object, one aspect of the present invention includes a high-speed stirring tank, a rotating shaft that is rotated by a driving machine, a high-speed stirring blade that is connected to the rotating shaft and disposed in the high-speed stirring tank. In which the sludge and the first polymer flocculant are fed into the high-speed stirring tank, and the high-speed stirring blade is rotated at 1000 min ⁻¹ or more. While mixing at a speed to mix the sludge and the first polymer flocculant to form a mixed sludge, while supplying the mixed sludge and the second polymer flocculant to the floc forming device, A floc forming step of forming a floc by mixing the mixed sludge and the second polymer flocculant in a floc forming apparatus, and a rotating body comprising the high-speed stirring blade and a rotating shaft in the high-speed stirring tank By rotating When the volume of the rotation region to be formed is Va [L] and the flow rate of the sludge passing through the high-speed stirring tank is Fb [L / sec], the value of the ratio of the volume Va to the flow rate Fb is 0.12 or more. Ah is, of the cross section of the rotation area, perpendicular to the flow direction of the sludge, the cross section having the largest area is D, the area of cross-section D and Ad [cm ^2], sludge stirring of the high-speed stirring tank A cross section of a region, where a cross section including the cross section D is E, and an area of the cross section E is Ae [cm ² ], the area Ad is 0.7 times or more the area Ae .

In a preferred aspect of the present invention, the volume Va of the rotation region is 0.3L to 3L.
In a preferred aspect of the present invention, the volume of the rotating body itself is not more than 0.5 times the volume Va of the rotating region .
In a preferred aspect of the present invention, the floc forming device is a low-speed stirring device including a low-speed stirring tank and a low-speed stirring blade rotated by a driving machine, and the low-speed stirring blade is rotated at a rotational speed slower than 1000 min ^−1. Rotating to mix the mixed sludge and the second polymer flocculant to form a floc.
In a preferred aspect of the present invention, the floc forming apparatus is a centrifugal dehydrator provided with a rotating reaction tank, and the mixed sludge and the second polymer flocculant are mixed in the rotating reaction tank, Is formed.

Another aspect of the present invention includes a high-speed stirring tank, a rotating shaft rotated by a driving machine, and a high-speed stirring blade connected to the rotating shaft and disposed in the high-speed stirring tank. A high-speed agitation device that mixes sludge and the first polymer flocculant to form mixed sludge by rotating at a rotation speed of 1000 min ⁻¹ or more, and mixes the mixed sludge and the second polymer flocculant. A floc forming device for forming a floc, and a volume of a rotation region formed by rotation of a rotating body composed of the high-speed stirring blade and a rotating shaft in the high-speed stirring tank is Va [L], When the flow rate of the sludge that passes through the high-speed stirring tank and Fb [L / sec], the value of the ratio to the flow rate Fb of the volume Va is Ri der least 0.12, of the cross section of the rotation region, the flow of the sludge A cross section perpendicular to the direction and having the largest area D, the area of the cross section D is Ad [cm ² ], the cross section of the sludge stirring region in the high-speed stirring tank, the cross section including the cross section D is E, and the area of the cross section E is Ae [cm ² ], the aggregating apparatus is characterized in that the area Ad is 0.7 times or more the area Ae .

In a preferred aspect of the present invention, the volume Va of the rotation region is 0.3L to 3L.
In a preferred aspect of the present invention, the volume of the rotating body itself is not more than 0.5 times the volume Va of the rotating region .
In a preferred aspect of the present invention, the floc forming device is a low-speed stirring device including a low-speed stirring tank and a low-speed stirring blade rotated by a driving machine, and the low-speed stirring blade is rotated at a rotational speed slower than 1000 min ^−1. Rotating to mix the mixed sludge and the second polymer flocculant to form a floc.
In a preferred aspect of the present invention, the floc forming apparatus is a centrifugal dehydrator provided with a rotating reaction tank, and the mixed sludge and the second polymer flocculant are mixed in the rotating reaction tank, Is formed.

The present invention has the following effects.
(1) Since the polymer flocculant has high viscosity, it is difficult to uniformly disperse the polymer flocculant in the sludge. In the present invention, since the sludge and the polymer flocculant are mixed using high-speed stirring of 1000 min ⁻¹ or more, the polymer flocculant can be uniformly dispersed in the sludge, and the sludge surface of the polymer flocculant has Charge neutralization and adsorption or crosslinking can be utilized to the maximum. In the present invention, first, in the mixing step, the first polymer flocculant is uniformly dispersed in sludge to form mixed sludge. In the next floc forming step, the mixed sludge and the second polymer flocculant are mixed and grown to a larger floc. As a result, the filterability is high and a strong floc can be formed. By forming such flocs, when the sludge is dehydrated, the moisture content of the cake can be reduced and the amount of the polymer flocculant used can be reduced. When the sludge is concentrated, the concentrated sludge concentration can be increased and the amount of the polymer flocculant used can be reduced.
(2) According to the present invention, the value of the ratio between the volume Va of the rotating region of the rotating body and the sludge flow rate Fb [L / sec] is 0.12 or more. Even if the sludge flow rate Fb is changed, the optimum mixing condition can be obtained by designing the high-speed stirring device so that the value of the ratio of the volume Va to the flow rate Fb is 0.12 or more, or by connecting a plurality of high-speed stirring devices. Can be achieved. Alternatively, when the volume Va of the rotation region is fixed, the optimum mixing condition can be achieved by changing the sludge flow rate Fb.
(3) According to the present invention, the ratio value of the volume Va to the flow rate Fb is 0.12 or more, and the volume Va is 0.3L to 3L. By designing a high-speed stirring device under such conditions, it is possible to manufacture a high-speed stirring device of an optimal size, so there is no need to manufacture an unnecessarily large high-speed stirring device, the manufacturing cost of the device, the installation space of the device, Electricity cost required for stirring can be reduced.

It is the schematic which showed one Embodiment of the sludge aggregation apparatus. It is the schematic which showed other embodiment of the sludge aggregation apparatus. It is the schematic which showed other embodiment of the sludge aggregation apparatus. It is the schematic which showed other embodiment of the sludge aggregation apparatus. It is the schematic which showed other embodiment of the sludge aggregation apparatus. It is a side view of a high-speed stirring apparatus. It is sectional drawing in the AA of FIG. It is sectional drawing in the BB line of FIG. It is the schematic which shows the other example of a high-speed stirring apparatus. It is the schematic which shows the other example of a high-speed stirring apparatus. Fig.11 (a) is a schematic diagram which shows the rotary body comprised from a high-speed stirring blade and the rotating shaft in a high-speed stirring tank, FIG.11 (b) shows the rotary body shown to Fig.11 (a). It is a schematic diagram which shows the rotation area | region formed by rotating. It is a schematic diagram which shows the rotation area | region of the sludge stirring area | region in a high-speed stirring tank, and the rotary body in this sludge stirring area | region.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of a sludge aggregation apparatus. 1 includes a sludge storage tank 1, a high speed stirring device 11, a low speed stirring device 21, and a dehydrator 31. More specifically, the high-speed stirring device 11 is connected to the sludge storage tank 1 via the supply pipe 2, and the low-speed stirring device 21 is connected to the high-speed stirring device 11 via the supply pipe 3, and the dehydrator 31. Is connected to the low-speed stirring device 21 via the supply pipe 4. A first polymer flocculant dissolution tank 41 is connected to the high-speed agitator 11 via a first polymer flocculant pump 44, and a second polymer flocculant dissolution tank 42 is connected to the low-speed agitator 21. Two polymer flocculant pumps 45 are connected.

  The high-speed stirring device 11 includes a high-speed stirring tank 12, a driving machine 13, a rotating shaft 14 that is rotated by the driving machine 13, a high-speed stirring blade 15 that is connected to the rotating shaft 14, and is disposed in the high-speed stirring tank 12. It has. The low-speed stirring device 21 includes a low-speed stirring tank 22, a driving machine 23, a rotating shaft 24 rotated by the driving machine 23, a low-speed stirring blade 25 connected to the rotating shaft 24, and disposed in the low-speed stirring tank 22. It has. The low speed stirring blade 25 is configured to rotate at a lower rotational speed than the high speed stirring blade 15.

  Sludge is stored in the sludge storage tank 1, and the sludge in the sludge storage tank 1 is supplied into the high-speed stirring tank 12 of the high-speed stirring apparatus 11 through the supply pipe 2. The solution of the first polymer flocculant is supplied from the first polymer flocculant dissolution tank 41 into the high-speed stirring tank 12 of the high-speed stirring device 11 by the first polymer flocculant pump 44, and the high-speed stirring tank The first polymer flocculant is injected into the sludge within 12. The high-speed stirring device 11 mixes sludge and the first polymer flocculant with a high-speed stirring blade 15 that rotates at a high speed to form mixed sludge. The mixed sludge is supplied from the high-speed stirring device 11 into the low-speed stirring tank 22 of the low-speed stirring device 21 through the supply pipe 3. However, the supply pipe 3 may be omitted, and the high speed stirring device 11 and the low speed stirring device 21 may be integrated.

  The solution of the second polymer flocculant is supplied from the second polymer flocculant dissolution tank 42 into the low-speed stirring tank 22 of the low-speed stirring apparatus 21 by the second polymer flocculant pump 45, and the low-speed stirring tank The second polymer flocculant is injected into the mixed sludge in 22. The low speed agitation device 21 mixes the mixed sludge and the second polymer flocculant by the low speed agitation blades 25 rotating at a low speed, agglomerates the mixed sludge, and forms floc. The low speed stirring device 21 in the present embodiment is a flock forming device. The flock is sent to the dehydrator 31 through the supply pipe 4 and dehydrated by the dehydrator 31. The dehydrated flock is discharged from the dehydrator 31 as a dehydrated cake.

  FIG. 2 is a schematic view showing another embodiment of the sludge aggregation apparatus. Since the configuration of the present embodiment that is not specifically described is the same as that of the embodiment shown in FIG. In the embodiment shown in FIG. 2, the first polymer flocculant dissolution tank 41 is connected to a supply pipe 2 that connects the sludge storage tank 1 and the high-speed stirring device 11. Therefore, the first polymer flocculant solution is injected from the first polymer flocculant dissolution tank 41 into the sludge flowing through the supply pipe 2 by the first polymer flocculant pump 44. The sludge and the first polymer flocculant are supplied into the high-speed stirring tank 12 of the high-speed stirring device 11 through the supply pipe 2. The second polymer flocculant dissolution tank 42 is connected to the supply pipe 3 that connects the high-speed stirrer 11 and the low-speed stirrer 21, and the second polymer flocculant solution is the second polymer flocculant solution. The flocculant pump 45 injects the mixed sludge flowing through the supply pipe 3 from the second polymer flocculant dissolution tank 42. The mixed sludge and the second polymer flocculant are supplied into the low speed stirring tank 22 of the low speed stirring device 21 through the supply pipe 3. However, the supply pipe 3 may be omitted, and the high speed stirring device 11 and the low speed stirring device 21 may be integrated.

  FIG. 3 is a schematic view showing still another embodiment of the sludge aggregation apparatus. Since the configuration of the present embodiment that is not specifically described is the same as that of the embodiment shown in FIG. In the embodiment shown in FIG. 3, the same polymer flocculant is used for the first polymer flocculant and the second polymer flocculant. The polymer flocculant solution is stored in the polymer flocculant dissolution tank 46. The solution of the polymer flocculant is injected from the polymer flocculant dissolution tank 46 into the sludge flowing through the supply pipe 2 by the first polymer flocculant pump 44. The sludge and the polymer flocculant are supplied into the high-speed stirring tank 12 of the high-speed stirring device 11 through the supply pipe 2. Further, the solution of the polymer flocculant is supplied from the polymer flocculant dissolution tank 46 into the low-speed stirring tank 22 of the low-speed stirring apparatus 21 by the second polymer flocculant pump 45 and mixed in the low-speed stirring tank 22. Polymer flocculant is injected into the sludge.

  FIG. 4 is a schematic view showing still another embodiment of the sludge aggregation apparatus. Since the configuration of the present embodiment that is not specifically described is the same as that of the embodiment shown in FIG. In the embodiment shown in FIG. 4, a centrifugal dehydrator 51 is provided as a floc forming device. The centrifugal dehydrator 51 has the functions of both the low-speed stirring device 21 and the dehydrator 31 shown in FIGS. 1 and 2.

  The centrifugal dehydrator 51 is connected to the high-speed stirring device 11 through the supply pipe 3. The centrifugal dehydrator 51 includes a reaction tank 52 connected to a rotation shaft 54, a drive unit 53 that rotates the reaction tank 52 via the rotation shaft 54, and a screw conveyor (not shown) disposed in the reaction tank 52. Are provided with a back drive motor 55 and a gear box 56 for rotating them at a differential speed relative to the reaction tank 52. The screw conveyor is disposed coaxially with the reaction tank 52 and is rotatable with a relative speed difference from the reaction tank 52. The axial center of the reaction tank 52 and the rotating shaft 54 extend horizontally.

  The mixed sludge formed by the high speed stirring device 11 is supplied to the reaction tank 52. The second polymer flocculant dissolving tank 42 is connected to the reaction tank 52, and the second polymer flocculant solution is dissolved in the second polymer flocculant pump 45 by the second polymer flocculant pump 45. It is supplied from the tank 42 into the reaction tank 52. When the reaction tank 52 and the screw conveyor are rotated at a relative differential speed by the drive unit 53, the back drive motor 55, and the gear box 56, the mixed sludge in the reaction tank 52 and the second polymer flocculant are mixed. , Floc is formed. The flock is dewatered by receiving a centrifugal force in the rotating reaction tank 52, and is further squeezed by a screw conveyor and discharged from the centrifugal dehydrator 51 as a dehydrated cake. A known device can be used for the centrifugal dehydrator 51 that dehydrates flocs using such centrifugal force.

  FIG. 5 is a schematic view showing still another embodiment of the sludge aggregation apparatus. The configuration of the present embodiment that is not specifically described is the same as that of the embodiment shown in FIG. In the embodiment shown in FIG. 5, the first polymer flocculant dissolution tank 41 is connected to the supply pipe 2 that connects the sludge storage tank 1 and the high-speed stirring device 11. Therefore, the first polymer flocculant solution is injected from the first polymer flocculant dissolution tank 41 into the sludge flowing through the supply pipe 2 by the first polymer flocculant pump 44. The second polymer flocculant dissolution tank 42 is connected to the supply pipe 3 that connects the high-speed stirrer 11 and the centrifugal dehydrator 51, and the second polymer flocculant solution is the second polymer flocculant solution. The flocculant pump 45 injects the mixed sludge flowing through the supply pipe 3 from the second polymer flocculant dissolution tank 42. The mixed sludge and the second polymer flocculant are supplied into the reaction tank 52 of the centrifugal dehydrator 51 through the supply pipe 3. However, as in the embodiment shown in FIG. 4, the mixed sludge is supplied to the reaction tank 52 through the supply pipe 3, and the second polymer flocculant is not supplied to the reaction tank 52 without passing through the supply pipe 3. It may be supplied.

  Next, the high speed stirring apparatus 11 used in the above-described embodiment will be described in detail. FIG. 6 is a side view of the high-speed stirring device 11. 7 is a cross-sectional view taken along the line AA in FIG. 6, and FIG. 8 is a cross-sectional view taken along the line BB in FIG. The high-speed stirring device 11 includes a driving source 13 such as a motor, a rotating shaft 14 connected to the driving source 13 and rotated by the driving source 13, a high-speed stirring blade 15 connected to the rotating shaft 14, and a rotating shaft 14. And a cylindrical high-speed stirring tank 12 disposed on the same axis. The high speed stirring blade 15 is accommodated in the high speed stirring tank 12.

  An inflow pipe 60 for introducing sludge into the high-speed stirring tank 12 and a discharge pipe 61 for discharging the sludge from the high-speed stirring tank 12 are connected to the side surface of the high-speed stirring tank 12. The inflow pipe 60 and the discharge pipe 61 constitute a part of the high-speed stirring device 11. The inflow pipe 60 and the discharge pipe 61 are connected to the supply pipe 2 and the supply pipe 3, respectively.

  The high speed stirring blade 15 has four blades 18 extending radially. However, the number of blades 18 is not limited to this embodiment, and the number of blades 18 may be less than or greater than four. Moreover, although the shape of the blade | wing 18 of this embodiment is a rectangular shape, other shapes, such as trapezoid and semicircle shape, may be sufficient.

  A plurality of baffles 65 adjacent to the high-speed stirring blade 15 are provided on the inner peripheral surface of the high-speed stirring tank 12. The sludge stirred by the high speed stirring blade 15 collides with a baffle 65 provided on the inner peripheral surface of the high speed stirring tank 12 to form a turbulent flow and generate a vortex in the high speed stirring tank 12. As a result, the sludge and the flocculant can be mixed efficiently in a short time. However, the baffle 65 may not be provided.

  The front end side disk 67 and the rear end side disk 68 are arranged along the longitudinal direction of the rotary shaft 14 so as to sandwich the high speed stirring blade 15. The front end side disk 67 and the rear end side disk 68 are arranged close to the high speed stirring blade 15. The front end side disk 67 and the rear end side disk 68 are constituted by a disk perpendicular to the longitudinal direction of the rotation shaft 14, and the centers of the front end side disk 67 and the rear end side disk 68 are the rotation shafts. It coincides with the center of 14. The front end side disk 67 and the rear end side disk 68 have a diameter smaller than the inner diameter of the high speed stirring tank 12 and larger than the diameter of the high speed stirring blade 15. In the high-speed stirring tank 12, a sludge stirring area 12A is formed. This sludge stirring area 12A is formed by the inner peripheral surface of the high-speed stirring tank 12, the front end side disk 67, and the rear end side disk 68.

  The rear end side disk 68 is fixed to the rotating shaft 14 and rotates together with the rotating shaft 14. The tip side disk 67 is fixed to the plug 69, and the tip side disk 67 does not rotate even if the high speed stirring blade 15 rotates. A uniform narrow gap is formed between the front end side disk 67 and the high speed stirring blade 15 and between the rear end side disk 68 and the high speed stirring blade 15. The gap between the disks 67 and 68 and the high-speed stirring blade 15 is almost the same size as the gap between the baffle 65 and the high-speed stirring blade 15. Thus, since the uniform clearance gap is formed in the whole high-speed stirring blade 15, the high-speed stirring blade 15 can stir sludge efficiently. As a result, the sludge and the flocculant can be mixed efficiently.

  The high-speed stirring device 11 may have other configurations. For example, as shown in FIG. 9, the high-speed stirring device 11 may have a high-speed stirring tank 12 composed of a T-shaped pipe (a so-called cheese pipe), and the sludge is high-speed as shown in FIG. You may have the high-speed stirring tank 12 which flows into the axial direction of the stirring blade 15. FIG.

(1) Sludge The sludge to be treated may be either organic sludge or inorganic sludge.
Examples of the organic sludge include organic sludge generated in sewage treatment, human waste treatment, and wastewater treatment in various industries. More specifically, there may be mentioned first sedimentation basin sludge, surplus sludge, anaerobic digested sludge, aerobic digested sludge, live urine, septic tank sludge, digestion desorption liquid, coagulated sediment sludge, coagulated pressure floating sludge, etc. . The organic sludge may contain an inorganic substance.
Examples of the inorganic sludge include water purification treatment, construction wastewater treatment, and inorganic sludge generated in various industrial wastewater treatment. Here, the sludge generated in the water purification treatment is sludge discharged from a settling pond, a waste mud pond, a concentration tank, or the like in the water purification treatment facility. The inorganic sludge may contain organic matter.

In this treatment method, both organic sludge and inorganic sludge can be treated. From the viewpoint that the effects of the present invention can be more enjoyed, organic sludge is preferred, and among them, hardly dewatering property Anaerobic digested sludge is particularly preferred. In this treatment method, an inorganic flocculant or an organic coagulant may be injected into the sludge in advance.
However, the above is an example, and the sludge to be treated is not limited to these.

(2) First polymer flocculant and second polymer flocculant The first polymer flocculant and the second polymer flocculant include cationic polymer flocculants, amphoteric polymer flocculants, anions. And the like, and nonionic polymer flocculants.
Examples of the cationic polymer flocculant include a polymer of a cationic monomer, a copolymer of a cationic monomer and a nonionic monomer, and the like. Examples of the amphoteric polymer flocculant include a copolymer of a cationic monomer and an anionic monomer, and a copolymer of a cationic monomer, an anionic monomer, and a nonionic monomer. Examples of the anionic polymer flocculant include a polymer of an anionic monomer and a copolymer of an anionic monomer and a nonionic monomer. Examples of nonionic polymer flocculants include nonionic monomer polymers.

  Examples of cationic monomers include dialkylaminoalkyl (meth) acrylates, tertiary salts of dialkylaminoalkyl (meth) acrylates, quaternary salts of dialkylaminoalkyl (meth) acrylates, and examples include dimethylaminoethyl (meth). Examples thereof include acrylates, tertiary salts of dimethylaminoethyl (meth) acrylate, and quaternary salts of dimethylaminoethyl (meth) acrylate. Examples of the anionic monomer include (meth) acrylic acid and sodium (meth) acrylate. Nonionic monomers include (meth) acrylamide, N, N-dimethyl (meth) acrylamide and the like. Acrylate or methacrylate is represented as (meth) acrylate. Moreover, acrylic acid or methacrylic acid is represented as (meth) acrylic acid. Further, acrylamide or methacrylamide is represented as (meth) acrylamide.

Examples of the cationic polymer flocculant include amidine polymer flocculants having amidine units, polymer flocculants obtained by mixing amidine polymer flocculants and the above-mentioned non-amidine polymer flocculants, and the like.
Further, the first polymer flocculant and the second polymer flocculant may be the same or different.
Examples of the solvent for dissolving the first polymer flocculant and the second polymer flocculant include pure water, tap water, industrial water, ground water, treated water for various wastewater treatment, seawater, and the like. From the viewpoint of maximizing the cohesive strength of the polymer flocculant, it is preferable to use pure water or tap water. On the other hand, from the viewpoint of economy, it is preferable to use factory water, groundwater, or treated water for various wastewater treatment.
However, the above is an example, and the first polymer flocculant, the second polymer flocculant, and the solvent are not limited to these.

(3) Mixing process In the mixing process, the high-speed stirring apparatus 11 mentioned above is used. In the mixing step, while adding the first polymer flocculant solution to the sludge, the high-speed stirring blade 15 is rotated at a rotation speed of 1000 min ⁻¹ or more to thereby add the sludge and the first polymer flocculant solution. Mix to form mixed sludge. Since the sludge and the first polymer flocculant are mixed by high-speed stirring, the first polymer flocculant can be uniformly dispersed in the sludge, and the sludge surface charge of the first polymer flocculant can be reduced. The neutralizing action and the adsorption or crosslinking action can be utilized to the maximum. The solution of the first polymer flocculant may be added to the sludge in the high-speed stirring device 11 as shown in FIG. 1, or may be added to the sludge flowing in the supply pipe 2 as shown in FIG.

  When the inorganic flocculant is added to the sludge and stirred, only the charge neutralizing action on the sludge surface is used for the agglomeration. In the present embodiment, by adding the first polymer flocculant to sludge and stirring at high speed, the adsorption or cross-linking action can be used together with the charge neutralizing action of the first polymer flocculant. A strong flock can be formed. For this reason, compared with the case where only the inorganic flocculant is added to the sludge and stirred, the filtration rate is much higher, and the dehydration process with a higher pressing force becomes possible. Further, the concentrated sludge concentration can be further increased, and more efficient concentration treatment can be performed.

The rotation speed of the high-speed stirring blade 15 in the mixing step is preferably 1000 min ⁻¹ or more. A more preferable rotation speed is 1500 min ⁻¹ or more. An even more preferable rotation speed is 2000 min ⁻¹ or more. The upper limit of the rotational speed of the high-speed stirring blade 15 is not particularly required, but it has been confirmed by experiments that the problem does not particularly occur until the rotational speed of the high-speed stirring blade 15 is 10,000 min ⁻¹ . In practice, the rotational speed of the high speed stirring blade 15 is 1000min ^-1 or 5000 min ^-1 or less. The peripheral speed of the end of the high speed stirring blade 15 is preferably 3 to 20 m / sec.

  FIG. 11A is a schematic diagram showing a rotating body 70 composed of a high-speed stirring blade 15 and a rotating shaft 14 in the high-speed stirring tank 12. The rotating body 70 includes a high speed stirring blade 15 and a part of the rotating shaft 14 located in the high speed stirring tank 12. FIG. 11B shows a rotation region 70A formed by the rotation of the rotating body 70 shown in FIG.

The volume Va [L] of the rotating region 70A formed from the rotating rotating body 70 depends on the type of sludge, the sludge properties, the physical properties of the first polymer flocculant, the dissolution concentration of the first polymer flocculant, and the like. It is preferable to determine together. In particular, when the volume of the rotation area 70A is Va [L] and the flow rate of the sludge passing through the high-speed stirring tank 12 is Fb [L / sec], the value R of the ratio of the volume Va to the flow rate Fb is 0.12 or more. It is important that The value R of the ratio of the volume Va to the flow rate Fb is expressed by the following equation (1).
R = Va / Fb (1)
The value R of the ratio of the volume Va to the flow rate Fb is preferably 0.15 or more, more preferably 0.20 or more. The upper limit of the ratio value R of the volume Va to the flow rate Fb is not particularly limited, but from the viewpoint of causing a significant change, the ratio value R of the volume Va to the flow rate Fb is preferably 5.0 or less. Preferably it is 3.0 or less.

  The volume Va of the rotation region 70A is preferably 0.3L to 3.0L, and more preferably the volume Va is 0.3L to 2.0L. More preferably, the volume Va is 0.3L to 1.5L. The volume Va of the rotation region 70A can be changed by connecting a plurality of high-speed stirring devices 11 in series or in parallel.

  The volume Vc [L] of the rotating body 70 itself shown in FIG. 11A is preferably 0.5 times or less the volume Va [L] of the rotating region 70A. More preferably, the volume Vc of the rotating body 70 is not more than 0.4 times the volume Va of the rotating region 70A. Even more preferably, the volume Vc of the rotating body 70 is not more than 0.35 times the volume Va of the rotating area 70A.

FIG. 12 is a schematic diagram showing the sludge stirring region 12A in the high-speed stirring tank 12 and the rotating region 70A of the rotating body 70 in the sludge stirring region 12A. Of the cross section of the rotation area 70A, the cross section perpendicular to the sludge flow direction and having the maximum area is D, the area of the cross section D is Ad [cm ² ], and the cross section of the sludge stirring area 12A is the cross section D. Is E and the area of the cross section E is Ae [cm ² ], it is important that the area Ad is 0.7 times or more the area Ae. More preferably, the area Ad is 0.8 times the area Ae. Even more preferably, the area Ad is 0.9 times the area Ae.

  The sludge stirring area 12A in the high-speed stirring tank 12 is a space where the sludge and the first polymer flocculant are substantially mixed. The high-speed agitation tank 12 is provided with an air layer, baffle plates, spacers, etc., to suppress the inflow of sludge and the first polymer flocculant sludge, and limit the space where the sludge and the first polymer flocculant are mixed. In this case, the space limited by the air layer, baffle plate, spacer, or the like becomes the sludge stirring region 12A in the high-speed stirring tank 12. The radius of the rotating shaft 14 in the high speed stirring tank 12 is preferably in the range of 0.25 to 0.65 times the maximum rotating radius of the high speed stirring blade 15. The high-speed stirring blade 15 and the rotating shaft 14 may be rotated in the opposite direction to the normal direction in accordance with the operating conditions for the purpose of removing residue and the like entangled with the high-speed stirring blade 15 and the rotating shaft 14.

(4) Flock forming step In the flock forming step, a solution of the second polymer flocculant is added to the mixed sludge formed in the mixing step, and the mixed sludge and the second polymer flocculant solution are mixed to form a floc. To form. In the floc forming step, the low-speed stirring device 21 described above is used as the floc forming device. By mixing the mixed sludge and the second polymer flocculant relatively slowly with the low-speed stirring device 21, flocs can be grown and large flocs can be formed, and a strong floc with good filterability can be obtained. Can do. Low-speed stirring is stirring slower than high-speed stirring of 1000 min ⁻¹ or more. The rotational speed of the low speed stirring blade 25 of the low speed stirring device 21 is preferably 10 to 500 min ⁻¹ .

  In the flock forming step, the centrifugal dehydrator 51 may be used as a flock forming device instead of the low-speed stirring device 21. The centrifugal dehydrator 51 can rotate the reaction tank 52 to grow flocs by using the centrifugal force to mix the mixed sludge and the second polymer flocculant, thereby forming large flocs.

(5) Dehydration After the flocs are formed in the floc forming step, the solids and liquids are separated by the dehydrator 31 shown in FIGS. 1 and 2, and the dehydrated cake and the filtrate are discharged from the dehydrator 31. As a dehydrating method, a means for dehydrating by applying pressure is generally adopted, but it is not particularly limited. For example, a dehydrator conventionally used for sludge dehydration can be used, for example, a screw press, a belt press, a centrifugal dehydrator, a vacuum dehydrator, a multiple disk type dehydrator, a multiple disk type screw press, a filter press, A rotary press or the like can be used.

  It is also possible to perform the flock formation step and the dehydration step simultaneously. For example, the centrifugal dehydrator 51 shown in FIGS. 4 and 5 can simultaneously perform the flock formation step and the dehydration step. As a specific example of the centrifugal dehydrator 51, for example, an apparatus disclosed in JP 2010-264417 A can be cited. This centrifugal dehydrator has a space inside, a rotating bowl (corresponding to the reaction tank 52) that separates sludge into cake and dehydrated separation liquid by the action of centrifugal force, and rotates at a speed different from that of the rotating bowl. A screw conveyor for transferring the cake formed in the rotating bowl to the discharge port, means for supplying sludge into the rotating bowl, and means for supplying polymer flocculant to the sludge supplied into the rotating bowl . In such a centrifugal dehydrator, the sludge and the polymer flocculant supplied into the rotating bowl are mixed by the action of centrifugal force, and flocs are formed in the rotating bowl. The formed floc is dehydrated by the action of centrifugal force.

(6) Concentration After the floc is formed in the floc forming step, solid-liquid separation may be further performed by a concentrator. As a concentration method, a gravity concentration method or a mechanical concentration method is generally employed, but is not particularly limited. For example, a concentration device conventionally used for sludge concentration can be used, for example, a gravity concentration tank, a pressurized flotation tank, a screw press, a belt press, a centrifugal concentrator, a multiple disk type concentrator, a multiple disk type screw. A press or the like can be used.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples.
[Example 1]
In this test, a solution of the first polymer flocculant is added to the sludge, and the sludge and the first polymer flocculant are mixed by high-speed stirring to form a mixed sludge. The floc was formed with a floc forming apparatus, and finally the floc was dehydrated with a screw press. In this test, it was confirmed that the moisture content of the cake can be reduced by high-speed stirring of 1000 min ⁻¹ or more, and the total injection amount of the first polymer flocculant and the second polymer flocculant can be reduced.

In this test, anaerobic digested sludge was used as the sludge. A cationic polymer flocculant was used as the first polymer flocculant and the second polymer flocculant. The dissolution concentrations of the first polymer flocculant and the second polymer flocculant were both 2 g / L. The volume Va [L] of the rotation area 70A shown in FIG. 11B is 0.5L, and the volume Vc [L] of the rotation body 70 shown in FIG. 11A is equal to the volume Va [L] of the rotation area 70A. A high-speed stirring device 11 that is 0.3 times was used. The area Ad [cm ² ] of the maximum cross section D of the rotation region 70A was 0.8 times the area Ae [cm ² ] of the cross section E of the sludge stirring region 12A in the high-speed stirring tank 12. The low speed stirring device 21 shown in FIGS. 1 and 2 was used as the floc forming device, and the rotational speed of the low speed stirring blade 25 was set to 50 min ⁻¹ .

The test procedure is as follows. The first polymer flocculant solution of 65% of the total injection amount is added to sludge (sludge flow rate 1.5 m ³ / h), and the high-speed stirring device 11 (the rotational speed of the high-speed stirring blade 15 is 500 to 3000 min ⁻¹ ). Sludge and the first polymer flocculant were mixed to form mixed sludge. Next, a solution of the second polymer flocculant of 35% of the total injection amount is added to the mixed sludge, and the mixed sludge and the second polymer are mixed by the low speed stirring device 21 (the rotational speed of the low speed stirring blade 25 is 50 min ⁻¹ ). The flocculant was mixed to form floc. Finally, the floc was dehydrated with a dehydrator 31 comprising a screw press (see FIGS. 1 and 2), and the moisture content (%) of the obtained cake was measured. The total injection amount of the first polymer flocculant and the second polymer flocculant was 1.4 to 1.8% by mass with respect to TS (Total Solids) of sludge.

The test results are shown in Table 1. From these test results, it was found that when the rotational speed of the high-speed stirring blade 15 was 1000 min ⁻¹ , the moisture content of the cake could be reduced and the total amount of the polymer flocculant injected could be reduced.

[Example 2]
In this test, a solution of the first polymer flocculant is added to the sludge, the sludge and the first polymer flocculant are mixed by high speed stirring, and then the second polymer flocculant is added to the mixed sludge. In addition, a flock was formed by a flock forming apparatus, and finally the flock was dehydrated by a belt press. In this test, the relationship between the value R of the ratio Va [L] of the rotation region 70A and the sludge flow rate Vb [L / sec] and the moisture content of the cake was examined.

In this test, anaerobic digested sludge was used as the sludge. A cationic polymer flocculant was used as the first polymer flocculant and the second polymer flocculant. The dissolution concentrations of the first polymer flocculant and the second polymer flocculant were both 2 g / L. The volume Va [L] of the rotation area 70A shown in FIG. 11B is 0.5L, and the volume Vc [L] of the rotation body 70 shown in FIG. 11A is equal to the volume Va [L] of the rotation area 70A. A high-speed stirring device 11 that is 0.3 times was used. The area Ad [cm ² ] of the maximum cross section D of the rotation region 70A was 0.8 times the area Ae [cm ² ] of the cross section E of the sludge stirring region 12A in the high-speed stirring tank 12. The low speed stirring device 21 shown in FIGS. 1 and 2 was used as the floc forming device, and the rotational speed of the low speed stirring blade 25 was set to 50 min ⁻¹ .

The test procedure is as follows. The first polymer flocculant solution of 65% of the total injection amount is added to the sludge (sludge flow rate 1.5-18 m ³ / h), and the high-speed stirring device 11 (the rotational speed of the high-speed stirring blade 15 is 2000 min ⁻¹ ) Sludge and the first polymer flocculant were mixed to form mixed sludge. Next, a solution of the second polymer flocculant of 35% of the total injection amount is added to 250 mL of mixed sludge, and the mixed sludge and the second sludge are mixed with the low speed stirring device 21 (the rotational speed of the low speed stirring blade 25 is 50 min ⁻¹ ). Polymer flocculants were mixed to form flocs. Finally, the floc was dehydrated with a dehydrator 31 comprising a belt press (see FIGS. 1 and 2), and the moisture content (%) of the obtained cake was measured. The total injection amount of the first polymer flocculant and the second polymer flocculant was 1.8% by mass with respect to TS (Total Solids) of sludge.

The test results are shown in Table 2. As can be seen from these test results, the cake moisture content could be reduced when R was 0.12 or more.

[Example 3]
In this test, a solution of the first polymer flocculant is added to the sludge, the sludge and the first polymer flocculant are mixed by high speed stirring, and then the second polymer flocculant is added to the mixed sludge. In addition, a flock was formed by a flock forming apparatus, and finally the flock was dehydrated by a belt press. In this test, the relationship between the value R of the ratio Va [L] of the rotation region 70A and the sludge flow rate Vb [L / sec] and the moisture content of the cake was examined. In this test, a sludge different from that in Example 2 and another high-speed stirring device were used.

The sludge used in this test is anaerobic digested sludge, but is different from the sludge of Example 2. Cationic polymer flocculants were used for the first polymer flocculant and the second polymer flocculant. The dissolution concentrations of the first polymer flocculant and the second polymer flocculant were both 2 g / L. The volume Va [L] of the rotation area 70A shown in FIG. 11B is 0.95L, and the volume Vc [L] of the rotation body 70 shown in FIG. 11A is equal to the volume Va [L] of the rotation area 70A. A high-speed stirring device 11 that is 0.3 times was used. The area Ad [cm ² ] of the maximum cross section D of the rotation region 70A was 0.8 times the area Ae [cm ² ] of the cross section E of the sludge stirring region 12A in the high-speed stirring tank 12. The low speed stirring device 21 shown in FIGS. 1 and 2 was used as the floc forming device, and the rotational speed of the low speed stirring blade 25 was set to 50 min ⁻¹ .

The test procedure is as follows. The first polymer flocculant solution of 65% of the total injection amount is added to the sludge (sludge flow rate 5 to 25 m ³ / h), and the high-speed stirring device 11 (the rotational speed of the high-speed stirring blade 15 is 2000 min ⁻¹ ) The first polymer flocculant was mixed to prepare mixed sludge. Next, a solution of the second polymer flocculant of 35% of the total injection amount is added to 250 mL of mixed sludge, and the mixed sludge and the second sludge are mixed with the low speed stirring device 21 (the rotational speed of the low speed stirring blade 25 is 50 min ⁻¹ ). Polymer flocculants were mixed to form flocs. Finally, the floc was dehydrated with a dehydrator 31 comprising a belt press (see FIGS. 1 and 2), and the moisture content (%) of the obtained cake was measured. The total injection amount of the first polymer flocculant and the second polymer flocculant was 2.0 mass% with respect to TS (Total Solids) of sludge.

  The test results are shown in Table 3. As can be seen from these test results, the cake moisture content could be reduced when R was 0.12 or more.

[Example 4]
In this test, a solution of the first polymer flocculant was added to the sludge, the sludge and the first polymer flocculant were mixed by high-speed stirring, and then a reaction tank 52 was provided as a floc forming device. Using the centrifugal dehydrator 51 (see FIGS. 4 and 5), the mixed sludge and the second polymer flocculant are supplied to the centrifugal dehydrator 51, and the mixed sludge and the second polymer flocculant are fed in the rotating reaction tank 52. Were mixed to form floc and the floc was dehydrated. In this test, it was investigated whether the dewatering of sludge was made efficient even when the centrifugal dehydrator 51 provided with the reaction tank 52 was used as the floc forming apparatus.

In this test, a mixed sludge of surplus sludge and coagulated sediment sludge discharged from the wastewater treatment facility of the human waste treatment plant was used as the sludge. A cationic polymer flocculant was used as the first polymer flocculant and the second polymer flocculant. The dissolution concentrations of the first polymer flocculant and the second polymer flocculant were both 2 g / L. The volume Va [L] of the rotation area 70A shown in FIG. 11B is 0.5L, and the volume Vc [L] of the rotation body 70 shown in FIG. 11A is equal to the volume Va [L] of the rotation area 70A. A high-speed stirring device 11 that is 0.3 times was used. The area Ad [cm ² ] of the maximum cross section D of the rotation region 70A was 0.8 times the area Ae [cm ² ] of the cross section E of the sludge stirring region 12A in the high-speed stirring tank 12.

The test procedure is as follows.
The sludge (sludge flow rate 2.4 m ³ / h) is added with the first polymer flocculant solution of 50% of the total injection amount, and the high-speed stirrer 11 (rotation speed 2100 min ⁻¹ of the high-speed stirrer blade 15) A polymer flocculant was mixed to prepare a mixed sludge. Next, the mixed sludge and the second polymer flocculant solution of 50% of the total injection amount were supplied to the centrifugal dehydrator 51 (the rotational speed of the reaction tank 52 was 3000 min ⁻¹ ). In the centrifugal dehydrator 51, the mixed sludge and the second polymer flocculant were mixed to form a floc and the floc was dehydrated. Finally, the moisture content (%) of the obtained cake was measured. The total injection amount of the first polymer flocculant and the second polymer flocculant was 1.1 mass% with respect to TS (Total Solids) of sludge.

As a comparative test, sludge (sludge flow rate 2.4 m ³ / h) and polymer flocculant (1.1% by mass with respect to TS of the sludge) were added to the centrifugal dehydrator 51 (rotation speed 3000 min ⁻¹ of the reaction tank 52). Supplied. In the centrifugal dehydrator 51, sludge and polymer flocculant were mixed to form a floc and the floc was dehydrated. Finally, the moisture content (%) of the obtained cake was measured. As the polymer flocculant, the same cationic polymer flocculant as the first polymer flocculant and the second polymer flocculant was used.

The test results are shown in Table 4. From these test results, it was confirmed that the moisture content of the cake could be reduced and the sludge dewatering was made efficient even when a centrifugal dehydrator equipped with a rotating reaction tank was used in the floc forming apparatus.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 Sludge storage tank 2, 3, 4 Supply piping 11 High-speed stirring apparatus 12 High-speed stirring tank 13 Driver 14 Rotating shaft 15 High-speed stirring blade 21 Low-speed stirring device 31 Dehydrator 22 Low-speed stirring tank 23 Drive machine 24 Rotating shaft 25 Low-speed stirring blade 41 First polymer flocculant dissolution tank 44 First polymer flocculant pump 42 Second polymer flocculant dissolution tank 45 Second polymer flocculant pump 46 Polymer flocculant dissolution tank 51 Centrifugal dehydrator 52 Reaction Tank 54 Rotating shaft 53 Drive unit 70 Rotating body 70A Rotating region

Claims (6)

A coagulation method in which sludge is agglomerated using a high-speed agitation device comprising a high-speed agitation tank, a rotary shaft rotated by a driving device, and a high-speed agitation blade connected to the rotary shaft and disposed in the high-speed agitation tank There,
While supplying the sludge and the first polymer flocculant into the high-speed stirring tank, the high-speed stirring blade is rotated at a rotation speed of 1000 min ⁻¹ or more to mix the sludge and the first polymer flocculant. Mixing step to form mixed sludge,
A flock forming step of forming the flock by mixing the mixed sludge and the second polymer flocculant in the flock forming device while supplying the mixed sludge and the second polymer flocculant to the flock forming device. Including
The volume of the rotation region formed by the rotation of the rotating body composed of the high-speed stirring blade and the rotating shaft in the high-speed stirring tank is Va [L], and the flow rate of the sludge passing through the high-speed stirring tank is Fb. When [L / sec], the value of the ratio to the flow rate Fb of the volume Va is Ri der 0.12 or more,
Of the cross sections of the rotating region, the cross section perpendicular to the sludge flow direction and having the largest area is D, the area of the cross section D is Ad [cm ² ], and the cross section of the sludge stirring region in the high-speed stirring tank An aggregating method is characterized in that the area Ad is 0.7 times or more the area Ae, where E is a section including the section D and the area of the section E is Ae [cm ² ] .   The aggregation method according to claim 1, wherein the volume Va of the rotation region is 0.3L to 3L. The floc forming device is a centrifugal dehydrator equipped with a rotating reaction tank,
The coagulation method according to claim 1 or 2, wherein the mixed sludge and the second polymer flocculant are mixed in the rotating reaction tank to form a floc. A high-speed stirring tank, a rotary shaft which is rotated by the drive motor, connected to a rotary shaft, said and a high-speed stirred tank high-speed stirring blades arranged in the rotational speed of the high-speed stirring blade of 1000min ^-1 or A high-speed stirring device that is rotated at a speed to mix the sludge and the first polymer flocculant to form a mixed sludge;
A floc forming apparatus for mixing the mixed sludge and the second polymer flocculant to form a floc;
The volume of the rotation region formed by the rotation of the rotating body composed of the high-speed stirring blade and the rotating shaft in the high-speed stirring tank is Va [L], and the flow rate of the sludge passing through the high-speed stirring tank is Fb. When [L / sec], the value of the ratio to the flow rate Fb of the volume Va is Ri der 0.12 or more,
Of the cross sections of the rotating region, the cross section perpendicular to the sludge flow direction and having the largest area is D, the area of the cross section D is Ad [cm ² ], and the cross section of the sludge stirring region in the high-speed stirring tank The aggregating apparatus is characterized in that when the cross section including the cross section D is E and the area of the cross section E is Ae [cm ² ], the area Ad is 0.7 times or more the area Ae .   The volume Va of the said rotation area | region is 0.3L-3L, The aggregation apparatus of Claim 4 characterized by the above-mentioned. The floc forming device is a centrifugal dehydrator equipped with a rotating reaction tank,
The coagulation apparatus according to any one of claims 4 and 5, wherein the mixed sludge and the second polymer flocculant are mixed in the rotating reaction tank to form a floc.

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