WO2020004582A1 - Sludge thickening apparatus and sludge thickening method - Google Patents

Abstract

A sludge thickening device according to this embodiment of the present invention comprises a condensation reaction tank that reacts sludge with flocculent to generate condensed sludge, a thickening machine that thickens the condensed sludge extracted from the condensation reaction tank to form thickened sludge, a sludge supply path that supplies the condensed sludge from the condensation reaction tank to the thickening machine, a sludge reflux path that refluxes a part of the thickened sludge formed by the thickening machine to the condensation reaction tank, and a discharge path that discharges the rest of the thickened sludge formed by the thickening machine to the outside.

Description

Sludge thickening device and sludge thickening method

The present invention relates to a sludge concentration device and a sludge concentration method.
Priority is claimed on Japanese Patent Application No. 2018-124461 filed on June 29, 2018, the content of which is incorporated herein by reference.

汚 Sludge generated in the treatment of sewage, human waste, wastewater, etc. is subjected to a dehydration treatment to remove water contained in the sludge by a dehydrator in order to discard or incinerate. In the sludge dewatering treatment, the higher the sludge concentration, the higher the sludge dewatering efficiency. Therefore, prior to the dehydration treatment, a treatment for condensing sludge is performed. Various methods have been proposed for the sludge concentration treatment.

Patent Document 1 discloses that the concentrated sludge is refluxed to the coagulation reaction tank, and the flocculation, concentration and coagulation of the sludge are repeated, thereby increasing the denseness and mechanical strength of the flocculent floc and improving the concentration of the concentrated sludge. A method is described.
Patent Literature 2 discloses an apparatus for coagulating sludge with a coagulant prior to sludge dewatering treatment and then concentrating the sludge to a coagulated sludge concentration suitable for dewatering treatment.
Patent Document 3 discloses that an inorganic flocculant is added to sludge before a reactor, a polymer flocculant is added to sludge after flocculation reaction after a reactor, and an inorganic flocculant is added to concentrated sludge after concentration. A method is described in which a coagulant is added to further reduce the water content of a dehydrated cake obtained by dehydrating the same.

JP-A-2003-285100 Japanese Patent No. 4711071 Japanese Patent No. 5423256

In the technology described in Patent Document 1, the entire amount of the concentrated sludge is returned to the coagulation reaction tank and the sludge is discharged from the coagulation reaction tank. However, the sludge that has not sufficiently coagulated in the coagulation reaction tank is concentrated sludge. And the water content of the dewatered cake after dewatering may not be reduced. In addition, since the entire amount of concentrated sludge is returned to the coagulation reaction tank, the required capacity of the reflux pump is excessively increased, and the scale of the equipment becomes large, and there is a problem that a large amount of energy is required to operate the equipment. is there.
Further, in the technique described in Patent Literature 2, since the concentrated sludge is not refluxed to the coagulation reaction tank, it was necessary to reduce the sludge treatment flow rate or increase the capacity of the coagulation reaction tank in order to increase the concentration of the concentrated sludge. However, when decreasing the sludge treatment flow rate, a problem may occur in which the target treatment amount or the dehydrator operation time cannot be cleared. In addition, when increasing the volume of the agglutination reaction tank, a problem that a large installation space must be ensured may occur.
Further, in the technology described in Patent Document 3, a polymer flocculant is added to the sludge after the flocculation reaction. However, if a polymer flocculant is excessively added in the course of the flocculation treatment, the filterability of the sludge decreases, and the flocculated sludge is reduced. There is a problem that overflow occurs because the amount of separated liquid separated from the wastewater is reduced and the amount of sludge supplied to the concentrator exceeds the amount of concentrated sludge and the amount of separated liquid.
In addition, any of the methods has a problem that the amount of the coagulant added increases.

The present invention has been made in view of the above circumstances, and reduces the water content of a dewatered cake obtained by dewatering concentrated sludge without increasing the size of equipment, and / or reduces the amount of a coagulant added. An object of the present invention is to provide a possible sludge concentrating device and a sludge concentrating method.

In order to solve the above problems, the present invention employs the following configurations.
The sludge concentrating device of the present invention is a coagulation reaction tank that reacts sludge with a coagulant to generate coagulated sludge, and a concentrator that forms coagulated sludge by condensing coagulated sludge extracted from the coagulation reaction tank. A sludge supply path for supplying coagulated sludge from the coagulation reaction tank to the concentrator, a discharge path for discharging the concentrated sludge formed by the concentrator to the outside, and charging the coagulant into the coagulation reaction tank. A first flocculant charging device; and a second flocculant charging device for charging another flocculant into the discharge passage through which the concentrated sludge flows.
Further, the sludge concentrating device of the present invention may further include a sludge ring flow path for recirculating a part of the concentrated sludge formed by the concentrator to the flocculation reaction tank.
The sludge concentrating device of the present invention is a coagulation reaction tank that reacts sludge with a coagulant to generate coagulated sludge, and a concentrator that forms coagulated sludge by condensing coagulated sludge extracted from the coagulation reaction tank. A sludge supply path for supplying coagulated sludge from the coagulation reaction tank to the concentrator, a sludge ring flow path for recirculating a part of the condensed sludge formed by the concentrator to the coagulation reaction tank, formed by the concentrator And a discharge path for discharging the remaining portion of the concentrated sludge to the outside.
Further, in the sludge concentrating apparatus of the present invention, the concentrator includes a filtration filter on a peripheral wall, and a coagulated sludge extracted from the coagulation reaction tank is introduced from one end of the cylinder, and inside the cylinder. A helical screw that is provided coaxially and is driven to rotate and guides the coagulated sludge to the other end while compressing the coagulated sludge, and a separated liquid provided over the cylindrical body and separated from the coagulated sludge via the filtration filter And an outer container for collecting and discharging the same to the outside.
Further, in the sludge concentrator of the present invention, the concentrator may be any one of an inclined screen, a filter cloth traveling type, a rotary screen type, and a screw press type.
Moreover, the sludge concentrating device of the present invention may be provided with a dehydrator for dehydrating the concentrated sludge at a point ahead of the discharge path.

According to the above-mentioned sludge concentration apparatus, the flocculation reaction tank, the concentrator, the sludge supply path, the discharge path for discharging the concentrated sludge to the outside, and the first flocculant charging apparatus for charging the flocculant into the flocculation reaction tank And a second flocculant charging device for charging another flocculant in the discharge passage through which the concentrated sludge flows. The flocculant is re-condensed into the flocculated sludge after concentration by the second flocculant charging device. Since it is charged, the concentrated sludge can be re-agglomerated in the drainage channel, the dewatering property of the concentrated sludge can be further improved, the water content of the dewatered cake after dewatering can be further reduced, and / or the amount of the coagulant added can be reduced. .
Further, by further providing a sludge ring flow path for recirculating a part of the concentrated sludge to the flocculation reaction tank, it is possible to extend the residence time of the concentrated sludge in the flocculation reaction tank. By increasing the strength, the water content of the dewatered cake after dehydration can be further reduced and / or the amount of the coagulant added can be reduced.

Further, according to the above-mentioned sludge concentrator, the coagulation reaction tank, the concentrator, the sludge supply path, the sludge ring flow path for recirculating a part of the condensed sludge to the coagulation reaction tank, and discharging the remaining part of the condensed sludge to the outside. And a part of the concentrated sludge is recirculated to the coagulation reaction tank, and the remaining part of the concentrated sludge is discharged to the outside, so that the residence time of the concentrated sludge in the coagulation reaction tank can be extended. Thereby, the denseness and mechanical strength of the aggregated floc can be increased. In addition, since the remaining portion of the concentrated sludge concentrated in the concentrator is discharged to the outside without passing through the flocculation reaction tank, sludge having a low flocculation density remaining in the flocculation reaction tank may flow out together with the concentrated sludge. Thus, the water content of the dewatered cake after dewatering the concentrated sludge can be reduced and / or the amount of the coagulant added can be reduced.

Next, the sludge enrichment method of the present invention comprises the steps of: adding a flocculant to the sludge; reacting the sludge with the flocculant to generate a flocculated sludge; and forming the concentrated sludge by concentrating the flocculated sludge. A thickening step, a discharging step of discharging the concentrated sludge after the thickening step to the outside, and a flocculant re-feeding step of feeding another flocculant to the concentrated sludge during the discharging step. Prepare.
Further, the sludge concentration method of the present invention may further include a return step of returning a part of the concentrated sludge after the concentration step to the flocculation step.
Further, the sludge concentration method of the present invention, a coagulant is added to the sludge, a coagulation step of generating the coagulated sludge by reacting the sludge and the coagulant, forming a concentrated sludge by concentrating the coagulated sludge A concentration step; a return step of returning a part of the concentrated sludge after the concentration step to the coagulation step; and a discharge step of discharging the remaining part of the concentrated sludge after the concentration step to the outside.
Further, in the sludge concentration method of the present invention, a return rate of the concentrated sludge in the return step may be in a range of 10 to 70%.
Further, in the sludge concentration method of the present invention, the flocculant fed in the flocculating step may be an inorganic flocculant and a polymer flocculant.
In the sludge concentration method of the present invention, the flocculant to be charged in the flocculant recharging step may be a polymer flocculant.
In the method for concentrating sludge of the present invention, the flocculant charged in the flocculating step is an inorganic flocculant and a polymer flocculant, and the flocculant charged in the flocculant recharging step is a polymer flocculant. When the total amount of the polymer flocculant in the flocculating step and the flocculant re-charging step is 100%, the proportion of the polymer flocculant charged in the flocculating step is 40 to 90%, The proportion of the polymer flocculant to be charged in the flocculant recharging step may be 10 to 60%.

Further, according to the above-mentioned sludge concentration method, the coagulation step, the concentration step, and the coagulant re-injection step of injecting another coagulant into the concentrated sludge in the discharge step are provided. In, because the coagulant is re-introduced into the coagulated sludge after concentration, it is possible to re-aggregate the concentrated sludge in the drainage process, to further improve the dewaterability of the concentrated sludge, and / or the water content of the dewatered cake after dewatering. The addition amount of the flocculant can be further reduced.
Furthermore, by further providing a return step of returning a part of the concentrated sludge to the flocculation step, it is possible to extend the residence time of the concentrated sludge in the flocculation step, thereby increasing the denseness and mechanical strength of the flocculated floc. In addition, the water content of the dewatered cake after dehydration and / or the amount of the coagulant added can be further reduced.

According to the above-mentioned sludge concentration method, it has a flocculation step, a concentration step, a sludge ring flow path for returning part of the concentrated sludge to the flocculation step, and a discharge step for discharging the remaining part of the concentrated sludge to the outside. In addition, a part of the concentrated sludge is returned to the coagulation step, and the remaining part of the concentrated sludge is discharged to the outside in the discharging step, so that the residence time of the concentrated sludge in the coagulation step can be extended. And the mechanical strength can be increased. Also, since the remaining portion of the concentrated sludge concentrated in the concentration step is discharged to the outside without going through the flocculation step, there is no possibility that sludge having a low flocculation density staying in the flocculation step flows out together with the concentrated sludge. In addition, the water content of the dewatered cake after dewatering the concentrated sludge and / or the amount of the coagulant added can be reduced.

According to the present invention, it is possible to provide a sludge concentrating apparatus and a sludge concentrating method capable of reducing the water content of the dewatered cake after dewatering the concentrated sludge and the addition amount of the flocculant without increasing the size of the equipment.

Drawing 1 is a mimetic diagram showing the sludge concentration device of a 1st embodiment of the present invention. FIG. 2 is a diagram illustrating a material balance in an agglutination reaction tank. Drawing 3 is a mimetic diagram showing the sludge concentration device of a 2nd embodiment of the present invention.

凝集 The coagulated sludge generated by the reaction between the sludge and the coagulant is further concentrated to reduce the volume to form concentrated sludge. In order to densify the concentrated sludge, it is effective to extend the reaction time between the flocculant and the sludge. However, when the coagulation reaction time of the sludge is extended, the treatment amount of the concentrated sludge decreases, and the volume of the coagulation reaction tank increases in order to store a large amount of sludge. Therefore, the present inventors have studied and found that a part of the concentrated sludge is refluxed to the coagulation reaction tank to extend the coagulation reaction time, and the remaining sludge is discharged outside without passing through the coagulation reaction tank. It was found that dense sludge was discharged. Further, they have found that the concentrated sludge being discharged is further coagulated by re-introducing the flocculant into the concentrated sludge discharged after the concentration. As a result, without increasing the size of the sludge concentrating device, the concentrated sludge was densified to form concentrated sludge that was easily dewatered, and the volume of sludge was successfully reduced.

Hereinafter, a sludge concentration apparatus and a sludge concentration method according to embodiments of the present invention will be described with reference to the drawings.

(1st Embodiment)
As shown in FIG. 1, a sludge concentrator 1 according to a first embodiment of the present invention includes a coagulation reaction tank 2, a concentrator 3, a sludge supply path 4, a discharge path 5, a sludge ring flow path 6, Is provided. A dehydrator (not shown) may be provided at the end of the discharge path 5.

The coagulation reaction tank 2 generates coagulated sludge by reacting sludge with a coagulant. The coagulation reaction tank 2 has a reaction tank 21. A raw mud supply pipe 22 for supplying raw sludge is provided below the reaction tank 21.
A supply device 23 for supplying an inorganic flocculant to sludge and a supply device 24 for supplying a polymer flocculant to sludge are provided in the middle of the raw mud supply pipe 22. The position of the inorganic coagulant supply device 23 is on the upstream side of the raw mud supply pipe 22 in the raw mud supply direction with respect to the polymer coagulant supply device 24.

The reaction tank 21 is provided with a stirring means 26 which is rotationally driven by a motor 25 provided coaxially therein to stir the sludge and the flocculant to promote the generation of the flocculated sludge. The stirring means 26 is, for example, one in which a rotating blade 26a is attached to the tip of a rotating shaft 27. At the upper part of the reaction tank 21, a supply outlet 28 for supplying the coagulated sludge to the concentrator 3 is provided.

The sludge supply passage 4 is provided to supply the coagulated sludge from the coagulation reaction tank 2 to the concentrator 3 through the supply outlet 28.

The concentrator 3 condenses the coagulated sludge extracted from the coagulation reaction tank 2 to form concentrated sludge.
The concentrator 3 includes a cylindrical body 31 and an outer container 32 provided to cover the cylindrical body 31.
The cylindrical body 31 has a supply inlet 34a on the wall near the upper end through which the flocculated sludge is supplied from the flocculation reaction tank 21 through the sludge supply passage 4, and a filtration filter 35 for separating and filtering the liquid contained in the sludge on the peripheral wall. It has. The filtration filter 35 is made of, for example, a punching plate or / and a wedge wire, and the hole diameter of the punching plate or the slit width of the wedge wire is arbitrarily selected. Improves the flock separation performance. Further, the cylindrical body 31 is provided with an outlet 38 for discharging the concentrated sludge on a wall surface near the lower end thereof.

Further, the cylindrical body 31 is provided with a pressurizing means 33 for transporting the sludge supplied from the supply inlet 34a toward the outlet 38 while compressing the sludge therein. The pumping means 33 includes a screw rotating shaft 36 provided coaxially inside the cylindrical body 31 and a helical screw 37 attached to the screw rotating shaft 36, and is rotationally driven by the motor 30. The coagulated sludge is guided from the upper part to the lower part of the cylindrical body 31 while being compressed by the rotation of the spiral screw 37.

An upper connecting pipe 41, a central connecting pipe 42, and a lower connecting pipe 43 are connected to the upper end 32a, the central part 32b, and the lower end 32b of the outer container 32, respectively, and the respective connecting pipes 41, 42, 43 are separated. It is connected to the liquid tank 44.

The separated liquid tank 44 stores the separated liquid separated from the concentrated sludge. An overflow pipe 45 is provided inside the separation liquid tank 44. One end 45a of the overflow pipe 45 is inside the separation liquid tank 44, and the other end 45b is outside the separation liquid tank 44. The separation liquid is discharged to the outside of the separation liquid tank 44 by the overflow pipe 45.

The discharge path 5 is provided for discharging the concentrated sludge from the concentrator 3 to the outside through the outlet 38 of the concentrator 3. A sludge recirculation path 6 is provided branching in the middle of the discharge path 5, and a part of the concentrated sludge flows into the sludge recirculation path 6, and the rest of the concentrated sludge flows through the discharge path 5. A dehydrator (not shown) is provided at the end of the discharge path 5. Further, a discharge pump 5 a is provided in the middle of the discharge passage 5, and sends the concentrated sludge discharged from the outlet 38 of the concentrator 3 to the downstream side of the drain passage 5.

The sludge recirculation path 6 is provided to branch off from the middle of the discharge path 5 and to recirculate a part of the concentrated sludge from the concentrator 3 to the coagulation reaction tank 2. The sludge return path 6 is connected to a raw mud supply pipe 22. The connection position of the sludge recirculation path 6 to the raw mud supply pipe 22 is a position between the polymer flocculant supply device 24 and the reaction tank 21. In the middle of the sludge return passage 6, a return pump 6a is provided. The recirculation pump 6 a sends a part of the concentrated sludge discharged from the outlet 38 of the concentrator 3 to the downstream side of the sludge recirculation path 6. The return rate of the concentrated sludge can be adjusted in the range of 10 to 70% by the reflux pump 6a.

Next, a sludge concentration method using the sludge concentration device 1 shown in FIG. 1 will be described. The sludge concentration method of the present embodiment includes a flocculation step, a concentration step, a return step, and a discharge step. Hereinafter, each step will be described.

In the flocculation step, a flocculant is introduced into the sludge, and the sludge and the flocculant are reacted to generate flocculated sludge. Specifically, raw sludge is supplied to the reaction tank 21 by the raw mud supply pipe 22 of FIG. At this time, the supply device 23 supplies an inorganic flocculant to the raw sludge, and the supply device 24 supplies a polymer flocculant to the raw sludge. The raw sludge to which the inorganic flocculant and the polymer flocculant are added is guided from the lower part to the upper part of the reaction tank 21 while being stirred by the stirring means 26 inside the reaction tank 21, during which the raw sludge and the flocculant are mixed. Reaction proceeds to form coagulated sludge. The flocculated sludge that has reached the upper part of the reaction tank 21 is supplied to the upper part of the concentrator 3 (cylindrical body 31) through the sludge supply path 4.

As the inorganic coagulant, an iron coagulant such as ferric chloride and polyiron sulfate, an aluminum coagulant such as aluminum sulfate, aluminum chloride and polyaluminum chloride can be used. These may be used alone or in combination of two or more.

(4) The inorganic flocculant is usually acidic, and the pH value of the sludge is lowered by adding the inorganic flocculant to the raw sludge. When the polymer coagulant used in combination with the inorganic coagulant is an amphoteric polymer coagulant, the lower limit of pH at which coagulation can be performed with the amphoteric polymer coagulant is about 3.5. The pH is preferably 3.5 or more, for example, about 4.5 to 5.0.

As the polymer flocculant to be added to the sludge after adding the inorganic flocculant and conditioning, it is preferable to use an amphoteric polymer flocculant. Examples of the amphoteric polymer flocculant include a copolymer of an anionic monomer component and a cationic monomer component, a copolymer of an anionic monomer component, a copolymer of a cationic monomer component and a nonionic monomer component, or an anionic monomer component. And a nonionic monomer component, such as a Mannich modified product or a Hoffman decomposition product.

Examples of the anionic monomer component include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid, sodium methacrylate, and the like.

(4) Examples of the cationic monomer component include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and quaternized products thereof. Specific examples of the quaternary compound include dimethylaminoethyl acrylate quaternary compound (DAA) and dimethylaminoethyl methacrylate quaternary compound (DAM). Alternatively, dimethylaminopropylacrylamide hydrochloride (DAPAAm) may be used.

Examples of the nonionic monomer component include acrylamide (AAm), methacrylamide, and N, N-dimethyl (meth) acrylamide.

Specific examples of these copolymers include a DAA / AA / AAm copolymer, a DAM / AA / AAm copolymer, a DAA / DAM / AA / AAm copolymer, and a DAPAAm / AA / AAm copolymer. , DAA / AA copolymers, and Mannich-modified NaA / AAm copolymers.

Next, in the concentration step, the concentrated sludge generated by the flocculation step is concentrated to form a concentrated sludge. Specifically, the coagulated sludge supplied to the inside of the cylindrical body 31 is transferred toward the lower part of the cylindrical body 31 while being compressed by the helical screw 37 rotating inside the cylindrical body 31. In this process, the liquid component contained in the coagulated sludge is separated as a separated liquid through the filter 35 and continuously discharged to the outer container 32 side. Then, with the separation of the separated liquid, the concentration of the coagulated sludge proceeds.

The separated liquid separated into the outer container 32 is sent to the separated liquid tank 44 through the upper connecting pipe 41, the central connecting pipe 42, and the lower connecting pipe 43. The balance between the amount of the separated liquid remaining in the outer container 32 and the amount discharged from the upper connecting pipe 41, the central connecting pipe 42, and the lower connecting pipe 43 is determined by the overflow pipe 45 installed in the separated liquid tank 44. It is adjusted by the height of one end 45a. When the liquid level of the separated liquid is higher than one end 45 a of the overflow pipe 45, the separated liquid is discharged to the outside through the overflow pipe 45. By maintaining the balance of the amount of the separated liquid in this manner, a differential pressure corresponding to the amount of the separated liquid taken out at the filtration surface is generated, and there is no clogging of the filtration surface, no SS leak, and smooth filtration of the separated liquid is achieved. it can.

On the other hand, in the discharge step, the concentrated sludge is transferred through the cylindrical body 31 and then discharged from the outlet 38 to the discharge path 5. The concentrated sludge is sent to the downstream side of the drainage channel 5 by a drainage pump 5 a provided in the middle of the drainage channel 5. Part of the concentrated sludge is returned to the reaction tank 21 in a return step as described later, but the remaining part of the concentrated sludge that has not been returned further moves through the discharge path 5 and reaches a dehydrator (not shown). The concentrated sludge that has reached the dehydrator is dehydrated by the dehydrator to be a dewatered cake.

Next, as a return step, a part of the concentrated sludge is returned to the reaction tank 21 through the sludge ring channel 6 branched from the middle of the drainage channel 5. At this time, the return rate of the concentrated sludge is adjusted to a range of 10 to 70% by the reflux pump 6a. The return rate is a ratio of the amount of concentrated sludge returned to the total amount of concentrated sludge discharged from the thickener 3. This ratio is a volume ratio.
If the return rate of the concentrated sludge is less than 10%, it is not preferable because the densification of the concentrated sludge and the improvement in mechanical strength cannot be achieved. On the other hand, if the return rate exceeds 70%, the concentrated sludge exceeding the treatment capacity of the flocculation reaction tank 2 is returned, and the flocculation reaction tank overflows, which is not preferable.

濃縮 The concentrated sludge returned to the reaction tank 21 through the sludge ring flow path 6 joins the raw sludge flowing through the raw sludge supply pipe 22 at a position between the supply device 24 and the reaction tank 21. Since the raw sludge has already been added with the inorganic flocculant and the polymer flocculant, a part of the flocculant acts on the returned concentrated sludge. The returned concentrated sludge is released from the concentrated state in the reaction tank 21, forms a flocculated floc, and flows in the reaction tank 21. Such flocculated floc is mixed with the raw sludge and the flocculant and the flocculation reaction proceeds, during which the particle size is larger, and the denseness and mechanical strength are larger.

繰 り 返 す By repeating the coagulation, concentration and coagulation of the sludge in this way, the growth of the particle size of the coagulated floc, the increase in the denseness and the mechanical strength are promoted, and the sludge is concentrated.

FIG. 2 shows the material balance in the agglutination reaction tank 2. In FIG. 2, V is the volume of the coagulation reaction tank [m ³ ], Q is the flow rate of the sludge and the separated liquid [m ³ / h], C is the solid content concentration (sludge concentration) in the reaction tank [% TS], and n is the concentration. Sludge concentration ratio [times], R is the return ratio of the concentrated sludge [%] (0 ≦ R <100), i is the inflow sludge, f is the concentrated sludge supplied to the dehydrator, and r is the returned sludge. , B indicate a separated solution.

汚 The sludge concentration C in the reaction tank 21 is represented by the following equation (1).

If the sludge concentration ratio n = 4 [times] and the return ratio of the concentrated sludge R = 30 [%] is compared with the case where the concentrated sludge is not returned (R = 0%), the reaction tank 21 The sludge concentration inside is about 1.3 times as shown in the following equation (2).

Further, the residence time SRT of the sludge in the reaction tank 21 is represented by the following equation (3).

Similarly to the above, when the sludge concentration ratio n = 4 [times], a comparison is made between the case where the return rate RR of the concentrated sludge is 30% and the case where the concentrated sludge is not returned (R = 0%). The SRT in the reaction tank 21 becomes about 1.3 times as shown in the following equation (4).

Note that, under the condition of the concentration ratio n = 1 to 5 [times], when the return ratio R of the concentrated sludge is 80% or more, the flow rate of the returned sludge is equal to or four times the flow amount of the raw sludge. It is expected that the sludge recirculation mechanism will be enlarged or the equipment cost of the recirculation pump will increase. Therefore, in this embodiment, the return rate R of the concentrated sludge is set to 70% or less in view of safety.

As described above, according to the sludge concentrating apparatus 1 of the present embodiment, the flocculation reaction tank 2, the concentrator 3, the sludge supply path 4, and the sludge reflux for recirculating a part of the concentrated sludge to the coagulation reaction tank 2. The apparatus is provided with a passage 6 and a discharge path 5 for discharging the remaining portion of the concentrated sludge to the outside. The part of the concentrated sludge is returned to the coagulation reaction tank 2 and the remaining portion of the concentrated sludge is discharged to the outside. The residence time of the concentrated sludge in the tank 2 can be prolonged, whereby the denseness and mechanical strength of the flocculated floc can be increased. In addition, since the remaining sludge concentrated in the concentrator 3 is discharged to the outside without passing through the coagulation reaction tank 2, the sludge having a low coagulation density remaining in the coagulation reaction tank 2 is discharged to the outside together with the concentrated sludge. No risk of spill. As described above, the water content of the dewatered cake after dewatering the concentrated sludge can be reduced. Further, the amount of the coagulant added can be reduced.

Further, according to the sludge concentrating apparatus 1 of the present embodiment, the concentrator 3 is provided with the filtration filter 35 on the peripheral wall, and is provided inside the cylindrical body 31 into which the flocculated sludge is introduced from one end thereof. Since it has the helical screw 37 and the outer container 32 for collecting and discharging the separated liquid separated from the coagulated sludge through the filtration filter 35, the sludge is continuously concentrated to concentrate the sludge and the separated liquid. And the amount of concentrated sludge can be improved.
Further, according to the sludge concentration apparatus 1 of the present embodiment, since the dewatering device for dewatering the concentrated sludge is provided at the end of the discharge passage 5, the concentrated sludge can be efficiently reduced in volume to a dewatered cake. .

Next, according to the sludge concentration method of the present embodiment, the flocculation step, the concentration step, a return step of returning part of the concentrated sludge to the flocculation step, and a discharge step of discharging the remaining part of the concentrated sludge to the outside Since a part of the concentrated sludge is returned to the coagulation step and the remaining part of the concentrated sludge is discharged to the outside in the discharge step, the residence time of the concentrated sludge in the coagulation step can be extended. The density and mechanical strength of the floc can be increased. Further, since the remaining portion of the concentrated sludge concentrated in the concentration step is discharged outside without going through the flocculation step, there is no possibility that sludge having a low flocculation density staying in the flocculation step flows out together with the concentrated sludge. As described above, the water content of the dewatered cake after dewatering the concentrated sludge and / or the amount of the coagulant added can be reduced.

According to the sludge concentration method of the present embodiment, since the return rate of the concentrated sludge in the return step is in the range of 10 to 70%, the denseness and mechanical strength of the flocculated floc can be increased.

(Second embodiment)
As shown in FIG. 3, a sludge concentrating device 51 according to a second embodiment of the present invention includes a coagulation reaction tank 2, a concentrator 3, a sludge supply passage 4, a discharge passage 5, a sludge ring passage 6, , A first flocculant charging device 52 and a second flocculant charging device 53. A dehydrator (not shown) may be provided at the end of the discharge path 5.

The coagulation reaction tank 2, the concentrator 3, the sludge supply path 4, the discharge path 5, and the sludge ring flow path 6 in the present embodiment are the same as the coagulation reaction tank 2, the concentrator 3, and the sludge supply path 4, described in the first embodiment. Since the discharge channel 5 and the sludge ring channel 6 are the same, the description is omitted or simplified in this embodiment.

The coagulation reaction tank 2 has a reaction tank 21. Further, a lower part of the reaction tank 21 is provided with a raw mud supply pipe 22 for supplying raw sludge. In the middle of the raw mud supply pipe 22, a first flocculant charging device 52 is provided. The first flocculant charging device 52 includes a supply device 23 that supplies an inorganic flocculant to sludge, and a supply device 24 that supplies a polymer flocculant to sludge. The position of the inorganic coagulant supply device 23 is on the upstream side of the raw mud supply pipe 22 in the raw mud supply direction with respect to the polymer coagulant supply device 24. At the upper part of the reaction tank 21, a supply outlet 28 for supplying the coagulated sludge to the concentrator 3 is provided.

The concentrator 3 includes a cylindrical body 31 and an outer container 32. The peripheral wall of the cylindrical body 31 is provided with a filter 35 for separating and filtering the liquid contained in the sludge. Further, the cylindrical body 31 is provided with an outlet 38 for discharging the concentrated sludge on a wall surface near the lower end thereof.

Furthermore, the cylindrical body 31 is provided with a pressure feeding means 33. The pumping means 33 includes a screw rotating shaft 36 and a helical screw 37, and is driven to rotate by the motor 30.

分離 Further, a separation liquid tank 44 is connected to the outer container 32 via an upper connecting pipe 41, a central connecting pipe 42, and a lower connecting pipe 43. An overflow pipe 45 is provided inside the separation liquid tank 44.

The discharge path 5 is provided for discharging the concentrated sludge from the concentrator 3 to the outside through the outlet 38 of the concentrator 3. A sludge recirculation path 6 is provided branching in the middle of the discharge path 5, and a part of the concentrated sludge flows into the sludge recirculation path 6, and the rest of the concentrated sludge flows through the discharge path 5. A dehydrator (not shown) is provided at the end of the discharge path 5. Further, a discharge pump 5 a is provided in the middle of the discharge path 5, and sends the concentrated sludge discharged from the outlet 38 of the concentrator 3 to the downstream side of the drain path 5.

排水 The drainage channel 5 downstream of the junction between the drainage channel 5 and the sludge recirculation channel 6 is provided with a second coagulant charging device 53. The second coagulant charging device 53 adds a coagulant to the coagulated sludge flowing through the drainage channel 5. The coagulant added in the second coagulant charging device 53 is preferably a polymer coagulant.

The sludge recirculation path 6 is provided to branch off from the middle of the discharge path 5 and to recirculate a part of the concentrated sludge from the concentrator 3 to the coagulation reaction tank 2. The sludge return path 6 is connected to a raw mud supply pipe 22. The connection position of the sludge recirculation path 6 to the raw mud supply pipe 22 is a position between the polymer flocculant supply device 24 and the reaction tank 21. A return pump 6a is provided in the middle of the sludge return path 6, and the return rate of the concentrated sludge can be adjusted within a range of 10 to 70% by the return pump 6a.

Next, a sludge concentration method using the sludge concentration device 51 shown in FIG. 3 will be described. The sludge concentration method of the present embodiment includes a flocculation step, a concentration step, a return step, a discharge step, and a flocculant re-charging step. Hereinafter, each step will be described.

In the flocculation step, a flocculant is introduced into the sludge, and the sludge and the flocculant are reacted to generate flocculated sludge. Specifically, raw sludge is supplied to the reaction tank 21 by the raw mud supply pipe 22 of FIG. At this time, the inorganic flocculant is supplied to the raw sludge by the supply device 23 of the first flocculant supply device 52, and the polymer flocculant is further supplied to the raw sludge by the supply device 24. The raw sludge to which the inorganic flocculant and the polymer flocculant are added is guided from the lower part to the upper part of the reaction tank 21 while being stirred, and the floc is formed. The flocculated sludge that has reached the upper part of the reaction tank 21 is supplied to the upper part of the concentrator 3 (cylindrical body 31) through the sludge supply path 4. The same inorganic coagulant and polymer coagulant as in the first embodiment can be used.

Next, in the concentration step, the concentrated sludge generated by the flocculation step is concentrated to form a concentrated sludge. Specifically, the coagulated sludge supplied to the inside of the cylindrical body 31 is transferred toward the lower part of the cylindrical body 31 while being compressed by the spiral screw 37. In this process, the liquid component contained in the coagulated sludge is separated through the filtration filter 35 as a separated liquid. Then, with the separation of the separated liquid, the concentration of the coagulated sludge proceeds.

The separated liquid separated into the outer container 32 is sent to the separated liquid tank 44 through the upper connecting pipe 41, the central connecting pipe 42, and the lower connecting pipe 43, as in the case of the first embodiment. Is discharged to the outside through

In the discharge step, the concentrated sludge is transferred through the cylindrical body 31 and then discharged from the outlet 38 to the discharge path 5. The concentrated sludge is sent to the downstream side of the drainage channel 5 by a drainage pump 5 a provided in the middle of the drainage channel 5. A part of the concentrated sludge is returned to the reaction tank 21 by a return step as described later, but the remaining part of the concentrated sludge that has not been returned further moves through the discharge path 5 and reaches a dehydrator (not shown). The concentrated sludge that has reached the dehydrator is dehydrated by the dehydrator to be a dewatered cake.

(4) After passing through the branch with the sludge recirculation path 6, the concentrated sludge moving in the drainage path 5 is added with the polymer flocculant by the second flocculant supply device 53 before reaching the dehydrator. The concentrated sludge to which the polymer flocculant has been added reacts with the flocculant while moving in the discharge path 5 and is coagulated, and is less likely to be broken while moving in the drain path. In addition, since the flocculant is added to the concentrated sludge after passing through the concentrator 3, the solid-liquid separation of the sludge by the filter 35 in the concentrator 3 is not adversely affected.

Next, as a return step, a part of the concentrated sludge is returned to the reaction tank 21 through the sludge ring flow path 6 branched from the middle of the drainage channel 5. At this time, the return rate of the concentrated sludge may be adjusted to a range of 10 to 70% by the reflux pump 6a.

The concentrated sludge returned to the reaction tank 21 through the sludge ring flow path 6 is mixed with the raw sludge flowing through the raw sludge supply pipe 22 at a position between the supply device 24 and the reaction tank 21 as in the first embodiment. Join. The returned concentrated sludge is released from the concentrated state in the reaction tank 21, forms a flocculated floc, and flows in the reaction tank 21. The flocculated floc is mixed with the raw sludge and the flocculant and the flocculation reaction proceeds, during which the particle size is larger, and the denseness and mechanical strength are larger.

Here, the input amount of the polymer flocculant will be described. When the total input amount of the polymer flocculant in the flocculating step and the flocculant re-charging step is 100%, the ratio of the polymer flocculant to be charged in the flocculating step is 40 to 90%, and the ratio is charged in the flocculant re-charging step. The proportion of the polymer flocculant is preferably set to 10 to 60%.
By setting the ratio of the polymer coagulant to be added in the coagulation step to 40% or more, the coagulant in the coagulation step becomes sufficient and the coagulated sludge can be surely formed. Further, by setting the content to 90% or less, the amount of unreacted coagulant in the coagulation step is reduced, so that clogging of the filtration filter 35 can be prevented at the time of solid-liquid separation of sludge in the next concentration step.
Further, by setting the ratio of the polymer flocculant to be charged in the flocculant re-charging step to 10% or more, the concentrated sludge flowing through the drainage channel 5 can be further flocculated, and the destruction of the moving concentrated sludge can be prevented. . Further, by setting the content to 60% or less, excessive aggregation can be prevented, and the solid-liquid separation in the dehydrator can be efficiently performed.

As described above, according to the sludge concentration apparatus 51 of the present embodiment, the coagulation reaction tank 2, the concentrator 3, the sludge supply path 4, the discharge path 5 for discharging the concentrated sludge to the outside, the coagulation reaction tank 2 is provided with a first flocculant charging device 52 for charging a flocculant, and a second flocculant charging device 53 for charging another flocculant in the discharge passage 5 through which the concentrated sludge flows. The coagulant is re-introduced into the coagulated sludge after the concentration by the coagulant charging device 53 of the above, so that the concentrated sludge can be re-coagulated in the drainage channel 5, the dewaterability of the concentrated sludge is further improved, The water content of the dehydrated cake and / or the amount of the coagulant added can be further reduced.
Further, since the coagulant is added again to the concentrated sludge after passing through the concentrator 3, the clogging of the filtration filter 35 can be suppressed without affecting the solid-liquid separation of the sludge by the filtration filter 35 in the concentrator 3.
Further, by further providing a sludge ring flow path 6 for recirculating a part of the concentrated sludge to the flocculation reaction tank 2, the residence time of the concentrated sludge in the flocculation reaction tank 2 can be extended, thereby increasing the density of the flocculated floc. The mechanical strength can be increased, and the water content of the dewatered cake after dehydration and / or the amount of hand-operated flocculants can be further reduced.

Further, according to the sludge concentration method of the present embodiment, there is provided a flocculation step, a concentration step, and a flocculant re-feeding step of feeding another flocculant to the concentrated sludge in the discharging step. In the charging step, since the flocculant is re-charged to the flocculated sludge after the concentration, the concentrated sludge can be re-coagulated in the drainage step, and the dewaterability of the concentrated sludge is further improved, and the water content of the dewatered cake after the dehydration and And / or the amount of the coagulant added can be further reduced.
Furthermore, by further providing a return step of returning a part of the concentrated sludge to the flocculation step, it is possible to extend the residence time of the concentrated sludge in the flocculation step, thereby increasing the denseness and mechanical strength of the flocculated floc. In addition, the water content of the dewatered cake after dehydration and / or the amount of the coagulant added can be further reduced.

As described above, according to the present invention, a sludge concentrator capable of reducing the water content of a dewatered cake and / or the amount of a coagulant added after dewatering a concentrated sludge without increasing the size of the equipment. A sludge concentration method can be provided.

In the first and second embodiments, the concentrator 3 is an example of the concentrator 3 including the cylindrical body 31 having the filtration filter 35 on the peripheral wall, the spiral screw 37, and the outer container 32. However, the present invention is not limited to this, and the concentrator 3 may be any of a sludge screen, a filter cloth traveling type, a rotary screen type, and a screw press type sludge concentrator. .
In the first and second embodiments, the supply device 23 for the inorganic coagulant and the supply device 24 for the polymer coagulant are provided in the raw mud supply pipe 22. Both may be provided in the reaction tank 21, or the supply device 23 may be provided in the raw mud supply pipe 22, and the supply device 24 may be provided in the reaction tank 21. The supply device 23 of the inorganic coagulant may be omitted, and when the supply device 23 is omitted, it is preferable to use a cationic polymer coagulant as the polymer coagulant.
Although the sludge recirculation path 6 is connected to the raw mud supply pipe 22 at a position between the polymer coagulant supply device 24 and the reaction tank 21, it may be connected to the reaction tank 21 or may be connected to the inorganic coagulation pipe. The raw sludge supply pipe 22 may be connected to a position upstream of the agent supply device 23 or between the supply device 23 and the supply device 24.

Further, in the second embodiment, the sludge concentration device 51 having the sludge circulation channel 6 and the sludge concentration method having the return step have been described. Alternatively, a sludge concentration method having no return step may be used. That is, a polymer flocculant is added to all of the concentrated sludge concentrated by the concentrator 3 by the second flocculant charging device 53 to aggregate the concentrated sludge, and the concentrated sludge is not returned to the flocculation reaction tank 2. Is also good.
In this case, since the concentrated sludge is not returned to the coagulation reaction tank 2, the residence time of the sludge in the coagulation reaction tank 2 is reduced, and the denseness and mechanical strength of the coagulated floc cannot be increased. Since the polymer sludge is added to the concentrated sludge by the agent feeding device 53 to coagulate the concentrated sludge, the reaction time between the sludge and the flocculant can be substantially extended, and the denseness and mechanical strength of the concentrated sludge can be reduced. Can increase.

(Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2)
Hereinafter, examples of the present invention will be described. The sludge concentrator shown in FIG. 3 was installed in a sewage treatment plant, and a flocculation step and a concentration step were performed on raw sludge, and a return step and a recondensing step were further performed as necessary. The raw sludge is a mixed raw sludge having a TS of about 0.86 to 1.20%, and the inorganic coagulant is an iron-based inorganic coagulant (trade name: Polytec, manufactured by Nittetsu Mining Co., Ltd.). Used an amphoteric polymer flocculant (trade name: Chrisbest P-353, manufactured by Kurita Water Industries Ltd.). In addition, a rotary snail dehydrator was used as the dehydrator. Table 1 shows the results.

Comparative Example 1-1 and Comparative Example 1-2 are examples in which the return step and the re-aggregation step were not performed. In this case, the amount of the polymer coagulant added was 0.55% · TS and 0.48% · TS, and the water content of the dehydrated cake was 76.9% and 78.4%, respectively.

On the other hand, Example 1-1 is an example in which the return step was performed and the re-aggregation step was not performed. In this case, the water content of the dehydrated cake was 75.8%, which was lower than Comparative Examples 1-1 and 1-2.
Example 1-2 is an example in which the reaggregation step was performed without performing the return step. In this case, even if the addition rate of the flocculant is lower than that of Comparative Example 1-1, the water content of the dewatered cake is 77.1%, and a dewatered cake having substantially the same water content as Comparative Example 1-1 can be obtained. Was completed. Further, in Example 1-2, the addition rate of the coagulant was the same as that of Comparative Example 1-2, but in Example 1-2, the water content of the dehydrated cake was lower than that of Comparative Example 1-2.
Further, Embodiment 1-3 is an example in which both the returning step and the re-aggregation step are performed. In this case, the water content of the dehydrated cake was 75.2% even if the addition rate of the flocculant was lower than that of Comparative Example 1-1 or Comparative Example 1-2. It became lower than -2.

(Example 2 and Comparative Example 2)
The sludge concentrator shown in FIG. 3 was installed in a sewage treatment plant, and a flocculation step and a concentration step were performed on raw sludge, and a return step and a recondensing step were further performed as necessary. The raw sludge is a mixed raw sludge having a TS of about 0.86 to 1.20%, and the inorganic coagulant is an iron-based inorganic coagulant (trade name: Polytec, manufactured by Nittetsu Mining Co., Ltd.). Used an amphoteric polymer flocculant (trade name: Chrisbest P-353, manufactured by Kurita Water Industries Ltd.). A belt press dehydrator was used as the dehydrator. Table 2 shows the results.

Comparative Example 2 is an example in which the return step and the re-aggregation step were not performed. In this case, the water content of the dehydrated cake was as high as 78.8%.

On the other hand, Example 2 is an example in which the return step was performed and the re-aggregation step was not performed. In this case, the water content of the dehydrated cake was 77.5%, which was lower than Comparative Example 2.

As described above, according to the present invention, the water content of the dewatered cake after dewatering the concentrated sludge and / or the amount of the coagulant added can be reduced without increasing the size of the equipment.

The present invention can reduce the water content of the dewatered cake and / or the amount of the coagulant added after dewatering the concentrated sludge without increasing the size of the equipment, and therefore has high industrial utility value.

DESCRIPTION OF SYMBOLS 1, 51 ... Sludge concentrating apparatus, 2 ... Coagulation reaction tank, 3 ... Concentrator, 4 ... Sludge supply path, 5 ... Discharge path, 6 ... Sludge ring flow path, 31 ... Cylindrical body, 32 ... Outer container, 35 ... Filtration filter Reference numeral 37 denotes a helical screw, 52 denotes a first flocculant feeding device, and 53 denotes a second flocculant feeding device.

Claims (13)

1. A flocculation reaction tank that reacts sludge with a flocculant to produce flocculated sludge,
   A concentrator for concentrating the coagulated sludge extracted from the coagulation reaction tank to form a concentrated sludge,
   A sludge supply path for supplying coagulated sludge from the coagulation reaction tank to the concentrator,
   A discharge path for discharging the concentrated sludge formed by the concentrator to the outside,
   A first flocculant charging device for charging the flocculant into the flocculation reaction tank,
   A second flocculant charging device for charging another flocculant into the discharge passage through which the concentrated sludge flows,
   Sludge concentrator equipped with.
2. The sludge concentrator according to claim 1, further comprising: a sludge ring flow path for recirculating a part of the concentrated sludge formed by the concentrator to the flocculation reaction tank.
3. A flocculation reaction tank that reacts sludge with a flocculant to produce flocculated sludge,
   A concentrator for concentrating the coagulated sludge extracted from the coagulation reaction tank to form a concentrated sludge,
   A sludge supply path for supplying coagulated sludge from the coagulation reaction tank to the concentrator,
   A sludge ring channel that recirculates a part of the concentrated sludge formed by the concentrator to the flocculation reaction tank,
   A sludge concentrating device comprising: a discharge path for discharging the remaining sludge formed by the concentrator to the outside.
4. The concentrator has a filtration filter on the peripheral wall, a cylindrical body into which the flocculated sludge extracted from the flocculation reaction tank is introduced from one end thereof,
   A helical screw that is coaxially provided inside the cylindrical body, is driven to rotate, and guides the flocculated sludge to the other end while compressing the sludge.
   4. An outer container provided to cover the cylindrical body and collects a separated liquid separated from the flocculated sludge through the filtration filter and discharges the separated liquid to the outside. The sludge concentrator according to claim 1.
5. The sludge concentrator according to any one of claims 1 to 3, wherein the concentrator is any one of a slant screen, a filter cloth traveling type, a rotary screen type, and a screw press type.
6. The sludge concentrator according to any one of claims 1 to 5, wherein a dehydrator for dehydrating the concentrated sludge is provided at the end of the discharge path.
7. A flocculating step of feeding a flocculant to the sludge, and reacting the sludge with the flocculant to generate a flocculated sludge;
   A concentration step of concentrating the coagulated sludge to form a concentrated sludge,
   A discharge step of discharging the concentrated sludge after the concentration step to the outside,
   A coagulant re-injection step of injecting another coagulant into the concentrated sludge in the discharging step.
8. The sludge concentration method according to claim 7, further comprising a return step of returning a part of the concentrated sludge after the concentration step to the coagulation step.
9. A flocculating step of introducing a flocculant into the sludge, and reacting the sludge with the flocculant to generate a flocculated sludge,
   A concentration step of concentrating the coagulated sludge to form a concentrated sludge;
   A return step of returning a part of the concentrated sludge after the concentration step to the flocculation step,
   A discharge step of discharging the remaining portion of the concentrated sludge after the concentration step to the outside.
10. The sludge concentration method according to claim 8, wherein a return rate of the concentrated sludge in the return step is in a range of 10 to 70%.
11. The method for concentrating sludge according to any one of claims 7 to 10, wherein the coagulant to be added in the coagulation step is an inorganic coagulant and a polymer coagulant.
12. 凝集 The method for concentrating sludge according to any one of claims 7, 8, 10 and 11, wherein the coagulant charged in the coagulant recharging step is a polymer coagulant.
13. The coagulant to be added in the coagulation step is an inorganic coagulant and a polymer coagulant,
    The flocculant to be charged in the flocculant recharging step is a polymer flocculant,
    Assuming that the total amount of the polymer flocculant added in the flocculating step and the flocculant re-charging step is 100%, the ratio of the polymer flocculant charged in the flocculating step is 40 to 90%, The sludge concentration method according to any one of claims 7, 8, 10 and 11, wherein the proportion of the polymer flocculant charged in the agent recharging step is 10 to 60%.

Images