JPH07256298A - Dewatering method by sludge granulation concentration - Google Patents

Abstract

(57) [Abstract] [Purpose] The first coagulant is added to sludge and stirred, and then the second coagulant is added and stirred, or the sludge is filtered together with the second coagulant. In a method in which the sludge is introduced into a granulation concentrating tank having a part and the filtrate is taken out from the filtration part to condense and granulate the sludge, and the granulated product is dehydrated with a dehydrator, the amount of the coagulant added is reduced. At the same time, it enables stable operation of the dehydrator. [Structure] The second flocculant is dividedly injected into the granulation concentration tank 7 or a liquid containing a granulated substance flowing out from the granulation concentration tank 7. (Piping 10A, 10B) [Effect] The amount of coagulant added can be reduced, the separation water SS can be reduced, the gravity filtration property of granulated sludge can be improved, the operation of the dehydrator can be stabilized, and sludge can be efficiently produced at low cost. Can be processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating sludge by granulation and concentration, and in particular, a first flocculant is added to the sludge and stirred, and then a second flocculant is added and stirred. Afterwards, or together with the second flocculant, the sludge is introduced into a granulation concentrating tank having a filtering section, and the filtrate is taken out from the filtering section to condense the sludge and granulate it, and the granulated product is dehydrated. The present invention relates to a dehydration method by granulating and concentrating sludge, which reduces the amount of coagulant added and enables stable operation of the dehydrator.

[0002]

2. Description of the Related Art Conventionally, organic sludge produced by treatment of sewage, night soil or organic industrial wastewater, as well as metal sludge, dredging, sediment slurry at landfill, sewage / wastewater when coagulating with an inorganic coagulant As a method for treating inorganic sludge such as coagulated sludge, inorganic coagulant, cationic organic polymer coagulant (cationic polymer), anionic organic polymer coagulant (anion polymer), nonionic organic polymer coagulant (nonion Polymers, amphoteric organic polymer flocculants (amphoteric polymers) and the like are added in combination, and the mixture is subjected to conditioning by various mixing and stirring methods and then dehydrated, which is widely adopted.

[0003] In particular, as a dehydration treatment method for dilute sludge, there is a method in which a polymer is added to sludge, a pretreatment such as a rotary screen and centrifugal concentration is performed, and then dehydration is performed with a dehydrator such as a belt press.

On the other hand, a granulation concentration method is known as a sludge treatment process. Specifically, it is a method in which an organic flocculant is used in combination with an inorganic flocculant and an intramolecular amphoteric polymer, and the mixture is subjected to a granulation concentration treatment in a granulation concentration tank and then subjected to a dehydration treatment.

FIG. 2 is a standard flow chart of such a granulation concentration method. In FIG. 2, sludge is put and stored in the original sludge storage tank 1. 1a is a stirrer. The sludge in the storage tank 1 is introduced into the bottom of the auxiliary agent reaction tank 3 via the pump 2a and the pipe 2 and stirred. 3a is a stirrer. The inorganic coagulant in the auxiliary diluent tank 4 is injected into the auxiliary reaction tank 3 through the auxiliary injection pump 5a and the pipe 5, and the sludge is sufficiently mixed with the inorganic coagulant. 4a is a stirrer.

The sludge in which the inorganic coagulant is mixed is then fed to the granulation / concentration tank 7 through the pipe (supply pipe) 6 and the polymer with the agitator 8a which is fed through the pump 10a and the pipe (chemical injection pipe) 10. It is introduced together with the amphoteric organic polymer flocculant in the dissolution tank 8. In the granulation thickening tank 7, as the liquid is swirled by the rotation of the stirrer 7a, the sludge is granulated into granules (pellets). The liquid that has not been pelletized in the granulation concentrating tank 7 passes through the filtering unit 7b and is sent as a separated liquid to the initial settling tank (not shown) via the pipe 11. The granulated product is
A small amount of liquid is sent to a mechanical dehydrator such as a belt press 13 through a sludge drawing pump 12a and a pipe (transfer pipe) 12. Reference numeral 16 is a discharge pipe for cleaning and draining the filter cloth of the belt press 13.

[0007] This method is said to be an especially effective means for dilute sludge, but the treatment amount and water content increase as the sludge concentration increases, but the polymer addition amount increases and the separation water decreases when the polymer addition amount decreases. There is a drawback that SS tends to be high.

It is considered that this is because floc destruction occurs in the granulation concentrating tank having a long residence time, and it is necessary to add an excessive amount of polymer in order to secure appropriate particles and keep the separation water SS low. .

Even when the inorganic sludge is dehydrated, the treatment amount and water content are improved and the operating condition of the dehydrator is improved by applying the granulation concentration method. In this case as well, the polymer is used. If the amount of addition is reduced, the amount of separated water SS rises, the shape of the concentrated sludge in particular is broken, the gravity filterability deteriorates, and stable operation of the dehydrator becomes difficult. For this reason, the amount of polymer added must be increased.

From the above, it has been conventionally desired to reduce the amount of polymer added, to reduce the separation water SS, and to improve the gravity filterability of the concentrated sludge when treating the sludge by the granulation and concentration method.

Conventionally, as a method for improving the above problems, a first cationic polymer is added to organic sludge,
The flocs or pellets produced by mixing are partially dehydrated, and a second cationic polymer having a higher cationic strength than the first cationic polymer is added to the resulting dehydrated product.
It is known that they are mixed and mechanically dehydrated (Japanese Patent Publication No. 1-1.
7760).

[0012]

However, in the above method, since different cationic polymers are added, a plurality of polymer injecting equipments are required, the equipment cost is increased, and the polymer addition amount is large and the treatment cost is high. There's a problem.

The present invention solves the above-mentioned conventional problems, and after adding the first flocculant to the sludge and stirring it, and then adding the second flocculant and stirring, or after the second flocculation. With the agent
In the method of introducing sludge into a granulation concentrating tank having a filtering section, concentrating the sludge by removing the filtrate from the filtering section and granulating, and dehydrating this granulated product with a dehydrator,
An object of the present invention is to provide a dehydration method by granulating and concentrating sludge that enables stable operation of a dehydrator while reducing the amount of coagulant added.

[0014]

The method of dehydration by sludge granulation and concentration according to the present invention comprises adding a first flocculant to a sludge and stirring the mixture, and then adding a second flocculant and stirring the mixture. Or, together with the second flocculant, the sludge is introduced into a granulation concentrating tank having a filtering section, the filtrate is taken out from the filtering section, the sludge is concentrated and granulated in the granulating concentrating tank, Then, in a method of introducing a liquid containing the granulated product into a dehydrator to dehydrate, the same aggregating agent as the second aggregating agent is added to the aggregating tank or the aggregating agent which flows out from the aggregating tank. It is characterized by injecting into a liquid containing.

[0015]

According to the method of the present invention, the following effects are obtained when the polymer as the second flocculant is dividedly injected into the granulation concentrating tank.

The sludge and polymer supplied to the granulation thickening tank, whether organic or inorganic, are "entangled" in the sludge flocs staying in the tank, but the flocs are destroyed over time. . This phenomenon is severe when the amount of the polymer added is small, which causes deterioration of the separated water SS. In order to recapture the destroyed SS, a part of the polymer was dispensed to the central part of the granulation concentrating tank or the part for separating the separated water, and re-granulation occurred with an extremely small addition amount, and the separated water SS And the operating condition of the dehydrator can be improved.

When the polymer as the second flocculant is dividedly injected into the liquid containing the granules flowing out from the granulation concentrating tank, the following effects can be obtained.

In both organic and inorganic sludges, when the amount of polymer added is reduced or when the strength of the floc itself is low, the concentration ratio does not increase and the particles are broken, resulting in drainage of the granulated concentrated sludge. Becomes worse. In such a case, when a part of the polymer is dispensed into the granulated thickened sludge, flocs develop at one time, gravity filtration property and squeezability are improved in a short time, and the operating condition of the dehydrator is improved.

Such a phenomenon becomes more remarkable as the total amount of the polymer added is reduced, and the larger the coagulation reserve is, the more effective it is.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a flow chart showing an embodiment of a dehydration method by sludge granulation concentration according to the present invention. In FIG. 1, 9 is a polymer reaction tank equipped with a stirrer 9a, 15a is a pump, 10A, 10B, 10C, 1
5, 15A, 15B are pipes, V ₁ , V ₂ , V ₃ , V ₄ ,
V ₅ is a valve, and other members having the same functions as those shown in FIG. 2 are designated by the same reference numerals.

When treating the organic sludge by the apparatus shown in the figure, the valve V ₁ and the valves V ₃ , V ₄ or V ₅ are opened and the polymer in the polymer dissolving tank 8 is piped 15, 15.
The polymer is added to the polymer reaction tank 9 via A, and a part of the granulation concentrate tank 7 is passed through the pipe 10, 10A, 10B or 10C.
Is injected into the middle portion, the bottom portion, or the pipe 12 in the height direction of.

That is, in this embodiment, the sludge is put into and stored in the original sludge storage tank 1. The sludge in the storage tank 1 is introduced into the bottom of the auxiliary agent reaction tank 3 via the pump 2a and the pipe 2 and stirred. The inorganic coagulant in the auxiliary diluent tank 4 is injected into the auxiliary reaction tank 3 through the auxiliary injection pump 5a and the pipe 5, and the sludge is sufficiently mixed with the inorganic coagulant. By adding this inorganic coagulant, the sludge charge is neutralized and the floc nuclei are enhanced.

The sludge mixed with the inorganic coagulant is then introduced into the polymer reaction tank 9 through the pipe 6A, and the pipe 15,
Well mixed with the polymer injected from 15A,
Further enhancement of flocs is made. The sludge flowing out from the polymer reaction tank 9 is introduced into the granulation thickening tank 7 through the pipe 6B, and the liquid is swirled by the rotation of the stirrer 7a, whereby the sludge is granulated and becomes a granulated product (pellet), The liquid that has not been pelletized in the concentrating tank 7 passes through the filtering unit 7b and is sent as a separated liquid to the first settling tank (not shown) via the pipe 11, while the granulated material is sludge together with a small amount of liquid. It is sent to a mechanical dehydrator such as a belt press 13 via a drawing pump 12 a and a pipe (transfer pipe) 12.

In the present embodiment, when the granulation concentrate or the granulated product is transferred, an intermediate portion in the height direction of the granulation concentrate tank 7,
In the bottom or the transfer pipe 12, the polymer in the polymer dissolution tank 8 is pipes 10 and 10A, pipes 10 and 10B, or pipe 1.
Split injection is performed through 0 and 10C.

In this case, the dispensing rate of the polymer (that is, the ratio of the polymer to be divided and injected with respect to the total amount of the polymer added)
Is appropriately determined by using the separated water SS discharged from the granulation concentrating tank 7 as an index, but in the normal case, when dispensing into the granulation concentrating tank, the dispensing rate is 10 to 20%, and the transfer pipe is When dispensing, the dispensing rate is preferably 5 to 30%.

In the present invention, the following effects can be obtained when dispensing is carried out in the middle or bottom of the granulating thickener in the height direction. The greatest merit is the reduction of the amount of polymer added. By adopting the dispensing method according to the present invention, the amount of polymer added can be reduced by 15 to 30% as compared with the case where dispensing is not performed. The water content of the obtained dehydrated cake can be reduced. About 0.5 to 1.0% of the reduction rate of the water content is recognized for the 75 to 80% cake by the conventional method. Since the floating SS is reduced, the operating state of the dehydrator (particularly gravity filtration) is stable. The dispensing method according to the present invention has immediate effect and facilitates operation adjustment.

Further, when the liquid containing the granulated product flowing out from the granulation concentrating tank is dispensed to the pipe for transferring to the dehydrator, the following effects are exhibited. The gravity filterability of the dehydrator is greatly improved and the operation becomes easier. The interlocking with the operation state of the granulation concentrating tank is cut off, and even if the operation state of the granulation concentrating tank is poor, the dehydrator can always be stably operated, and the immediate effect is excellent. It is possible to reduce the amount of polymer added.
A reduction of up to 30% can be achieved. By improving the operation state of the dehydrator, SS leak is reduced and the solid content recovery rate is improved.

In the apparatus shown in FIG. 1, when the organic sludge is treated, an inorganic flocculant is used as the first flocculant and an intramolecular amphoteric organic polymer flocculant is used as the second flocculant. This second coagulant addition was used with the valve V ₁
Is preferably opened and the valve V ₃ or V ₄ is opened so that the liquid is dispensed to the bottom of the granulation thickening tank 7 or the transfer pipe 12.

On the other hand, in the treatment of inorganic sludge, the first
It is preferable to use various organic polymer coagulants in combination as the coagulant and the second coagulant and perform the same dispensing as described above.

In the present invention, the organic sludge to be treated is not particularly limited. For example, sewage first settling basin sludge, coagulated sludge generated in the tertiary treatment of human waste, sewage, etc., coagulated sludge of various industrial wastewater, Examples of the organic sludge include anaerobic digestion sludge of human waste, aerobic digestion sludge of human waste, human waste septic tank sludge, human waste digestive desorption liquid, sewage, and excess sludge in the treatment of activated sludge of various industrial wastewater. Examples of the inorganic sludge include metal sludge, dredging / land / sand slurry at landfill, and coagulated sludge generated when coagulating sewage / wastewater with an inorganic coagulant.

Examples of the inorganic flocculant used in the present invention include ferric chloride, aluminum sulfate, aluminum chloride, polyaluminum chloride and polyiron sulfate.

Among the organic polymer flocculants used in the present invention, the amphoteric organic polymer flocculant is a cationic constituent unit (cation group) amount (hereinafter referred to as "cation amount").
Colloid equivalent value (a
Value) is 1.0 to 3.7 meq / g, colloid titration at pH 7 showing the difference between the amount of anionic constitutional unit (anion group) (hereinafter referred to as “anion amount”) and the amount of cationic constitutional unit. Value (b value) is -1.7 to 0.7 meq
It is preferable that the amphoteric organic polymer flocculant has a ratio of (a / b) / a, which is a ratio of anion amount / cation amount of 0.8 to 1.8.

Under the condition of pH 3, it is considered that the anionic group in the amphoteric organic polymer hardly dissociates, and conversely, most of the cation group dissociates. Therefore, it was determined by colloid titration under the condition of pH 3. The colloid equivalent value (a value) can be regarded as the total cation amount of the amphoteric organic polymer.

On the other hand, the colloid equivalent value of the anion group is usually titrated at pH 10.5. At this pH, however, the cation group in the amphoteric organic polymer may be hydrolyzed to become the anion group. Is a value titrated at pH 7. In this case, since both the cation group and the anion group in the amphoteric organic polymer are dissociated, the result of colloid titration is to measure the excess amount of anion or the amount of cation in which the cation and anion are offset. Therefore, the total amount of anions in the amphoteric organic polymer is the difference between the colloid equivalent value titrated at pH 3 and the colloid equivalent value titrated at pH 7 (a
-B) can be considered.

The amphoteric organic polymer flocculant usable in the present invention has a colloid equivalent value (a) of 1.
The colloid equivalent value (b) at 0 to 3.7 meq / g, pH 7 is -1.7 to 0.7 meq / g, and the anion amount / cation amount ratio ((ab) / a) is 0.8 to. 1.8
Any amphoteric organic polymer in the range can be used. As such, for example, a copolymer of an anionic monomer component and a cationic monomer component, an anionic monomer component, a copolymer of a cationic monomer component and a nonionic monomer component, or an anionic monomer Examples thereof include a Mannich modified product or a Hoffmann degradation product of a copolymer of the component and a nonionic monomer component.

Examples of the anionic monomer component include acrylic acid (AA) and sodium acrylate (Na).
A), methacrylic acid, sodium methacrylate, etc. can be mentioned. Examples of the cationic monomer component include dimethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate (DAM), dimethylaminopropyl (meth) acrylate, and quaternized products thereof. Specific examples of the quaternary compound include dimethylaminoethyl acrylate methyl chloride quaternary compound (DAA). Alternatively, dimethylaminopropyl acrylamide hydrochloride (DAPAAm) may be used. Examples of the nonionic monomer component include acrylamide (AA
m), methacrylamide, N, N′-dimethyl (meth) acrylamide and the like. Also,
As a copolymer of these compounds, specifically, DAA /
AA / AAm copolymer, DAM / AA / AAm copolymer, DAPAAm / AA / AAm copolymer, DAA / A
Examples thereof include A copolymers and Mannich modified products of NaA / AAm copolymers.

On the other hand, as the cationic organic polymer flocculant, a homopolymer of aminoalkyl (meth) acrylate or a copolymer with acrylamide or another monomer, a Mannich modified product of polyacrylamide, a Hoffmann degradation product of polyacrylamide, Polyamide polyamine,
One or more selected from polyvinylimidazoline, polyethyleneimine and polydialkyldiallylammonium salts can be used, and as the anionic organic polymer flocculant, polyacrylic acid or a salt thereof, a partial hydrolyzate of polyacrylamide, Acrylic acid or its salt and acrylamide or 2-acrylamide-2-
One or more kinds selected from a copolymer of ethylpropanesulfonic acid or a salt thereof and a terpolymer of acrylic acid or a salt thereof and acrylamide and vinylsulfonic acid or a salt thereof can be used. As the organic polymer coagulant, one selected from polyacrylamide and polyethylene oxide can be used.

In the present invention, preferred examples of the combination of coagulants for treating various sludges are shown in Table 1 below.

[0040]

[Table 1]

The apparatus shown in FIG. 1 is an embodiment of the apparatus suitable for carrying out the present invention, and the present invention is not limited to what is shown. For example, the polymer reaction tank is not always necessary, and the polymer may be directly injected into the supply pipe from the auxiliary reaction tank 3 to the granulation concentration tank 7. Also,
The portion of the second flocculant to be dispensed into the granulation concentrating tank 7 can also be located near the bottom of the granulation concentrating tank. As the mechanical dehydrator, in addition to the belt press shown in the figure, any conventionally used dehydrator such as a centrifugal dehydrator, a vacuum dehydrator, a screw press or a filter press can be used.

The present invention will be described in more detail below with reference to specific examples and comparative examples.

The polymer flocculants used are as shown in Tables 2 and 3.

[0044]

[Table 2]

[0045]

[Table 3]

Example 1, Comparative Examples 1-1 and 1-2 In FIG. 1, V ₁ and V ₃ were opened and V ₂ , V ₄ and V ₅ were closed. Fe in a ferric chloride solution is added to excess sludge (VSS 85.9%) in the activated sludge treatment of food factory wastewater.
After adding 2.3% of SS to Cl ₃ and stirring, Table 2
The amphoteric organic polymer flocculant having the symbol AC-1 described in
Add 0.9% and stir, introduce into the granulation thickener, add 0.2% of SS-1 to the AC-1 in the middle of the granule thickener, and remove the filtrate from the filter to remove sludge. Granulate and concentrate, belt press type dehydrator (model: Kurita Water Industries Ltd.)
Manufactured by "Hidepress PA750") with a filter cloth area load of 9
0kg-DS / m ・ hr Filter cloth running speed 0.8m / min
It dehydrated on condition of. Water content of dehydrated cake is 82.2%
(Example 1).

Incidentally, for comparison, AC-1 was added to the sludge after the ferric chloride solution was added and stirred without adding AC-1 to the intermediate portion of the granulation concentrating tank in an amount of 1.1% of SS. The same operation was performed except that the water content of the dehydrated cake was 83.1% (Comparative Example 1-1). Moreover, in order to achieve the same dehydration cake water content of 82.2% as in the case of performing the above-mentioned split injection according to the present invention without performing the above-mentioned split injection, the addition amount of AC-1 was set to SS1.3. %When,
An increase of 18% was required as compared with the case of the present invention (Comparative Example 1).
-2).

Example 2, Comparative Examples 2-1 and 2-2 A mixed sludge (VSS 80.8%) of the first settling tank sludge of the sewage treatment plant and the excess sludge in the activated sludge treatment was treated in the same manner as in Example 1. . However, the amphoteric organic polymer flocculant is AC
-3 was used, and the addition amount was as shown in Table 4. The water content of the obtained dehydrated cake is shown in Table 4 (Example 2). For comparison, the results when split injection was not performed are also shown in Table 4 (Comparative Examples 2-1 and 2-2).

Example 3, Comparative Examples 3-1 and 3-2 Mixed sludge (VSS 68.1%) of excess sludge from beer factory effluent and tertiary treated sludge was used in Example 1 and Comparative Examples 1-1 and 1-.
Processed as in 2. The treatment conditions and the results are shown in Table 4.

Example 4, Comparative Example 4 In FIG. 1, V ₁ and V ₅ were opened and V ₂ , V ₃ and V ₄ were closed. To the mixed sludge (VSS 44.2%) of surplus sludge and coagulation sedimentation sludge of the general wastewater of the chemical factory, the cationic organic polymer flocculant of C-1 was added in an amount of 0.24% with respect to SS, and the mixture was mixed with A-1. 0.16% of the anionic organic polymer flocculant is added and stirred, then introduced into the granulation concentrating tank, and the liquid containing the granulated product flowing out from the granulating concentrating tank is transferred to the dehydrator. The above-mentioned A-1 is paired with SS0.0 in the pipe.
5% was added, and dehydration was performed using a belt press type dehydrator as in Example 1. The results are shown in Table 4 (Example 4). For comparison, the results obtained without split injection are also shown in Table 4 (Comparative Example 4).

Example 5, Comparative Example 5 Inorganic sludge (VSS 37.9%) in the wastewater from coated paper production was treated in the same manner as in Example 4 and Comparative Example 4. However, the coagulant used and its addition amount are shown in Table 4. The results are shown in Table 4.

Example 6, Comparative Example 6 Iron oxide sludge (VSS 8.8%) from the wastewater of a rolling mill was treated in the same manner as in Example 4 and Comparative Example 4. However, the coagulant used and its addition amount are shown in Table 4. The results are shown in Table 4.

From Table 4, it is clear that according to the method of the present invention, a dehydrated cake having a low water content can be obtained with a small amount of polymer added.

[0054]

[Table 4]

[0055]

As described above in detail, according to the dehydration method by sludge granulation concentration of the present invention, the first flocculant is added to the sludge and stirred, and then the second flocculant is added. The sludge is introduced into a granulation concentrating tank having a filtering section together with the second flocculant, and the sludge is concentrated and granulated by removing the filtrate from the filtering section. In the method of dehydrating the water with a dehydrator, the addition amount of the coagulant is reduced, the separation water SS is reduced, the gravity filterability of the granulated sludge is improved,
The operation of the dehydrator can be stabilized, and sludge can be efficiently treated at low cost.

The method of dehydration by sludge granulation concentration according to the present invention includes organic sludge produced by treatment of sewage, night soil or organic industrial wastewater, as well as metal sludge, dredging / landfill slurry at the time of landfill, and sewage. -It is extremely useful industrially as a method for treating inorganic sludge such as coagulated sludge generated when coagulating wastewater with an inorganic coagulant.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example method of a dehydration method by concentrating sludge granulation according to the present invention.

FIG. 2 is a flowchart showing a conventional method.

[Explanation of symbols]

 1 Raw Sludge Storage Tank 3 Auxiliary Reaction Tank 4 Auxiliary Dilution Tank 7 Granulation Concentration Tank 7a Stirrer 7b Filtration Section 8 Polymer Dissolution Tank 9 Polymer Reaction Tank 13 Belt Press

Front Page Continuation (72) Inventor Yuichi Hanami 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. (72) Inventor Yukio Goto 3-4-7 Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd. In the company

Claims (1)

[Claims] 1. A first coagulant is added to sludge and stirred,
Then, after adding and stirring the second flocculant, or together with the second flocculant, this sludge is introduced into a granulation concentrating tank having a filtration section, and the filtrate is taken out from the filtration section and In the method of concentrating sludge in a grain concentrating tank and granulating, and then introducing a liquid containing this granulated material into a dehydrator to dehydrate, the same flocculant as the second flocculant is granulated and concentrated. A dehydration method by granulating and concentrating sludge, which is characterized in that the sludge is poured into a liquid containing the granulated product flowing out from a tank or a granulating and concentrating tank.