JP3496217B2 - Sludge treatment method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment method using a multi-disc type sludge treatment device and an improved technique for the device.

[0002]

2. Description of the Related Art (Separation) sludge liquid generated from wastewater (wastewater) treatment system using activated sludge method is finally vacuum dehydration, centrifugal dehydration, pressure dehydration, roll dehydration (belt press, etc.) The dehydrated cake obtained by being physically dehydrated and concentrated by such techniques is carbonized and reused as fertilizer.

As one of the techniques for dewatering and concentrating the sludge liquid, a publicly known method utilizing the "multiple disc type sludge treatment method (rotating filter body sludge treatment method)" disclosed in JP-A-10-137795 and the like is used. There is a method.

More specifically, a rotary filter body in which a large number of discs are arranged in the direction of the rotation axis is supplied to a dehydration treatment tank provided with a plurality of filter body rows arranged in a row so as to intersect with each other. A multi-disc sludge that concentrates and conveys suspended solids in sludge liquid while filtering and dehydrating sludge liquid (raw mud liquid) by the rotation of the rotary filtration body and discharging it as a dehydrated cake out of the dehydration treatment tank. It is a dehydration method using a dehydrator.

This dewatering method is smaller in size than the other dewatering methods described above, the adjustment of the water content of the dewatering cake and the maintenance of the apparatus are easy, and Since the rotation is slow, there are advantages such as low noise, ability to maintain dehydration capacity even during continuous operation, and low odor emission.

[0006]

However, in the above-mentioned multi-disc type sludge treatment method, if the sludge liquid to be treated has poor dewatering property, the drainage of water in the gravity filtration section (gravity dewatering section) becomes poor. Therefore, it was necessary to reduce the feed rate (rate of feeding sludge to the dehydration treatment tank) until the water could be drained sufficiently. Therefore, there is a problem that the amount of dehydration treatment is reduced. Further, if the water drainage is poor, there is a problem that the water content of the dehydrated cake eventually increases and the amount of the dehydrated cake increases.

In order to solve such a problem, there has been proposed a technique for increasing the drainage (dehydration property or easiness of dehydration) of the sludge to be treated supplied to the multi-disc sludge dewatering device. That is, an improved technique has been proposed for forming stronger (harder pellet-like) aggregated flocs in the sludge liquid to be treated in the heat treatment step which is a pretreatment step of the dehydration treatment step. The applicant of the present application has already disclosed in JP-A-10-1559.
In the 9th report, we proposed a sludge treatment method that includes a refining technology that combines an inorganic coagulant and a polymer coagulant.

However, in the conventional tempering process,
Inorganic coagulation because it is a method that mainly uses coagulant
Agents such as ferrous sulfate (FeSO_Four・ 7H₂O) and chloride
Ferric iron (FeCl₃・ 6H₂O) etc. are added to the raw mud liquid
And bound water (H ₂O) is also added at the same time
Will end up.

Therefore, even if a certain coagulation effect is obtained, it is not necessarily a suitable technique in that the water content of the dehydrated sludge (dehydrated cake) is effectively reduced. Further, when the present method was applied to inorganic sludge, strong flocs could not be obtained, and as a result, the water content of sludge could not be sufficiently reduced.

Therefore, an object of the present invention is to provide a sludge treatment method capable of enhancing the dewaterability of sludge by surely aggregating the suspended matter in the raw mud liquid and reducing the water content of the dehydrated cake. is there.

[0011]

In order to solve the above technical problems, the present invention provides a sludge treatment method including the following steps (1) and (2) and the following (3) and (4): There is provided a sludge treatment device including the treatment means.

(1) The first step of reacting the sludge liquid with a flocculant selected from anionic polymer flocculants and cationic polymer flocculants, and the sludge liquid treated in the first step A refining process comprising a second process of reacting a polymer flocculant having a different sign from the first process.

(2) Filter bodies formed by arranging a plurality of rotary filter bodies, in which a large number of discs are arranged in the direction of the rotation axis, in a contiguous row, are arranged opposite to each other in upper and lower two stages. ,
A dehydration treatment step of filtering and dehydrating the conditioned sludge liquid by rotating the rotary filter body.

(3) First coagulation reaction processing means for reacting sludge liquid with a coagulant selected from anionic polymer coagulant and cationic polymer coagulant, and this first coagulation reaction processing means A second coagulation reaction processing means for reacting the sludge liquor treated in step 1 with a polymer coagulant having a sign different from that of the first coagulation reaction processing means.

(4) Filter bodies formed by arranging a plurality of rotary filter bodies, in which a large number of discs are arranged in the direction of the rotation axis, in a contiguous row, are arranged opposite to each other in upper and lower two stages. ,
Dehydration treatment means comprising at least a dehydration treatment tank configured to convey the sludge liquor which has been conditioned by filtering and dewatering by rotating the rotary filter body and discharge the dehydrated cake.

First, the inorganic coagulant is excluded from the refining step (1) or the refining means (3) constituting the present invention.
That is, by selecting and using only the organic polymer flocculant, it is possible to avoid adding water (bound water in the inorganic flocculant) to the sludge liquid in the tempering step or the refining means.
As a result, the water content of the dehydrated sludge (dehydrated cake) can be easily reduced, and the water content can be easily controlled. Further, in the present invention, since the organic polymer coagulant is used, it is possible to obtain an effective coagulation effect with a smaller addition amount as compared with the inorganic coagulant.

Further, in the present invention, by using a combination of an anionic polymer coagulant and a cationic polymer coagulant as the coagulant, a positively charged suspension substance contained in the raw mud liquid is obtained. Both (SS) and negatively charged suspended solids are allowed to aggregate.

Then, the addition of the anionic polymer flocculant and the cationic polymer flocculant is carried out in separate steps so that the anionic polymer flocculant and the positively charged suspended substance are brought into close proximity to each other. The cationic polymer flocculant and the negatively charged suspended solids are designed so that they can be brought into close proximity to each other separately and reliably, so they are either positively or negatively charged suspended solids. However, it will surely be able to aggregate.

Here, as the anionic polymer flocculant which can be employed in the present invention, a copolymer of acrylamide and acrylic acid (salt), a partially hydrolyzed salt of polyacrylamide, a maleic acid copolymer, CMC sodium salt. , Sodium alginate, sodium polyacrylate, etc. can be adopted, and as the cationic polymer flocculant,
Hydrolysis and amidation of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride copolymer with acrylamide, chitosan and acrylonitrile copolymer with N-vinylformamide described in JP-A-5-192516. It is possible to adopt the one that has been done.

In the sludge treatment method having the above-mentioned refining step or the sludge treatment apparatus having the refining means, the sludge liquid in which strong floc flocs are formed (dehydrated property is improved) is
Since the water is transferred to the dehydration treatment step (2) or the dehydration treatment means of (4), the dehydration treatment by rotating the rotary filter provided in the dehydration treatment tank can be smoothly performed. That is, the dehydrated sludge can be promptly formed and transported without leaving the accumulated sludge in the sludge transport path on the rotary filter.

In addition, in the refining process or refining means,
As a result of preventing excess water from being added to the sludge liquid, it is easy to reduce the water content of the dehydrated cake, which has been one of the problems in the conventional multi-disc type dehydrator.

As described above, the sludge treatment method and apparatus according to the present invention have the technical significance of solving the technical problem of the conventional multi-disc type dewatering apparatus.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION First, a flow of steps of a sludge treatment method according to the present invention will be briefly described with reference to FIG. 1 showing a step flow of the method. As shown in FIG. 1, the sludge treatment method according to the present invention comprises a tempering step X for forming a floc of flocs in the raw mud liquid R to enhance the dewaterability of the sludge liquid, and a tempering step X
And a dehydration treatment step Y for obtaining a dehydrated cake T by dehydrating and concentrating the sludge liquid S having an improved dehydration property.

In the tempering step X, the first flocculant G ₁ is
The first flocculant G ₁ selected from either the anionic polymer flocculant A or the cationic polymer flocculant C is added to the raw sludge R
In a first step X ₁ to be added to the polymeric flocculant is employed in the first step X ₁ is composed of a second step X ₂ that polymeric flocculants of different signs are added.

Here, the reason why the anionic polymer flocculant A and the cationic polymer flocculant C are used in combination in the tempering step X is that the positively charged suspended substance and the negatively charged suspended substance are used. It is possible to surely agglomerate both of the suspended substances present, and finally, the interaction of the polymeric flocculants A and C causes the suspended substances to be strongly crosslinked, resulting in stronger flocculation flocs. This is because it is possible to form In addition, it was clarified by an experiment described later that it is also suitable for enhancing the dehydration property of the inorganic sludge.

The reason for dividing into the first step X ₁ and the second step X ₂ is that when both the anionic polymer coagulant A and the cationic polymer coagulant C are added at the same time, the anionic polymer coagulant A And the cationic polymer flocculant C react with each other before the flocculation reaction with the suspended substance, and the cohesive force is reduced, or the contact frequency of each polymer flocculant and the suspended substance This is because it is considered that it is difficult for each aggregation reaction to proceed smoothly, which is not preferable. That is, it is preferable to add the anionic polymer coagulant A and the cationic polymer coagulant C separately and perform the respective agglutination reactions.

When the anionic polymer coagulant A is selected as the first coagulant G ₁ , the cationic polymer coagulant C is used as the second coagulant G ₂ and the first coagulant G _{1 is used.} When the cationic polymer flocculant C is selected as, the anionic polymer flocculant A is adopted as the second flocculant G ₂ .

Next, the construction of a sludge dewatering treatment apparatus suitable for carrying out the above sludge treatment method will be described with reference to FIG. First, a sludge dewatering treatment apparatus indicated by reference numeral D is a refining apparatus 1 for performing the refining step X, and a multi-disc type that is connected to the refining apparatus 1 and performs the dewatering step Y. The dehydration processing apparatus 2 is provided.

The refining apparatus 1 injects and adds the first flocculant G ₁ into the connecting pipe 103 to which the raw mud liquid R is fed, and causes the raw mud liquid R to flocculate with the first flocculant G ₁ . the first coagulant injection device used for carrying out the first step X ₁ 1
01 and the connecting pipe 103 are connected to the bottom region of the tank, and the second flocculant G ₂ is added to the flocculation reaction tank 104 equipped with the stirrer 105 and the like, and the raw mud liquid R is treated with the second flocculant G ₂ . And a second flocculant injection device 102 used to carry out the second step X _{2 of} causing flocculation. In addition,
Reference numeral P shown in FIG. 2 represents a pump for feeding the coagulant to a predetermined addition point.

Here, the first flocculant G₁Is the connecting pipe 103
Midway through the injection pipe 106 communicating with the communication pipe 103.
Then add. This is the raw mud in the connecting pipe 103.
The first flocculant G₁And raw mud liquid R
Promote the agglutination reaction by attempting to approach the suspended solids relatively
Because it can In addition, this first flocculant G ₁
The place of addition of is not limited to the connecting pipe 103.
No first coagulant G₁A separate coagulation reaction tank for the addition of
May be.

Next, in the flocculation reaction tank 104, after stirring for a predetermined time to sufficiently perform the flocculation reaction with the first flocculation agent G ₁ , the sludge liquid in the flocculation reaction tank 104 is further treated with the second flocculation agent G 1. Add ₂ and stir for a predetermined time to accelerate the agglutination reaction.

In the refining step X described above, the positive and negative charged suspended substances contained in the raw mud liquid R can be reliably aggregated, respectively, and as a result, A strong floc can be formed.

Next, in order to perform a dehydration treatment step Y in which the sludge liquid S tempered in the aforementioned tempering step X is dehydrated and filtered to obtain a dehydrated cake T, a multi-disk dewatering apparatus 2 (hereinafter referred to as "apparatus 2""
I will explain).

The apparatus 2 is provided with a substantially box-shaped dehydration treatment tank 3 surrounded by wall surfaces on all sides. To the front wall surface 301 of the dehydration treatment tank 3, the sludge liquid S transferred through the above-described conditioning process is supplied (introduced) to the dehydration treatment tank 3 with the sludge liquid S that has been conditioned by the conditioning device 1. A supply path 4 is provided.

A rear wall surface 302 facing the front wall surface 301
Is provided with a discharge port 5 for discharging (outflowing) the dehydrated and concentrated dehydrated cake T to the outside. At the bottom portion 303 of the dehydration treatment tank 3, a filtrate outlet 9 for discharging the water (filtrate) 15 filtered out by the filter body rows 6 and 7.
a and 9b are provided.

A chute 10 that is inclined slightly downward is attached to the discharge port 5, and a dehydration pressure adjusting device 11 is provided above the chute 10. The dehydration pressure adjusting device 11 includes a resistance plate 13 that closes the discharge port 5 by the weight of the weight plate 12, and the resistance plate 13 limits the flow rate of the dehydration cake T to adjust the dehydration pressure of the sludge liquid S. Plays.

Next, inside the dehydration treatment tank 3, rotating shafts 8, 8, 8 are provided in the left and right side walls (not shown) of the dehydration treatment tank 3.
Are horizontally mounted, and the shaft ends are rotatably supported on the left and right side walls. These rotary shafts 8 are simultaneously rotated by a motor M (not shown) via gears (not shown) arranged in the outer wall side region of the side wall, and the number of rotations can be adjusted or controlled as a whole. There is.

On the rotary shaft 8, ring-shaped large discs L and small discs M each having a predetermined thickness and diameter are alternately fixedly arranged on the rotary shaft 8, and a substantially normal ring-shaped rotary filter 6a. ~
6e and 7a to 7j are formed. In addition, in the present invention, the arrangement configuration of the disks of the rotary filtration bodies 6a to 6e and 7a to 7j can be appropriately selected and is not limited to the above configuration.

Adjacent rotary filters 6a and 6b, 6b and 6
c, 7a and 7b, 7b and 7c ... are gaps between the large discs L formed so that a partial region of the outer peripheral edge of the large disc L sandwiches the small disc M that functions as a spacer (see FIG. (Not shown) and mesh with each other in a crossing row to form two rows of upper and lower filter bodies 6, 7.
Is formed.

Here, as shown in FIG. 1, the filter body rows 6 and 7 are disposed inside the dehydration treatment tank 3 from the side of the supply passage 4 to the outlet 5.
They are arranged in two rows, upper and lower, so that the distance gradually narrows toward the side. Sludge liquid S supplied into the dehydration treatment tank 3
Of the rotary filter bodies 6a to 6e and 7a to 7j are simultaneously rotated to be concentrated and promoted through the sludge passage 14 which is gradually narrowed while being dehydrated and concentrated, and is moved to the discharge port 5 side. Is discharged as dehydrated cake T.

The dehydration process Y of the present invention is performed by using the apparatus 3 having the above-mentioned structure. The dehydration treatment step Y that can be employed in the present invention is not limited to the device 2 having the above-described configuration, and any dehydration treatment device provided with a multi-disc type dehydration treatment mechanism may be used.
It can be widely adopted. Examples of the sludge treatment method and apparatus according to the present invention will be described below.

Example 1 Experimental method. To the scum sludge collected from the food factory, the cationic polymer flocculant C ₁ was added into the connecting pipe 103 at a rate of 30 g per cubic meter of the raw mud liquid R. Then, in the flocculation reaction tank 104, the anionic polymer flocculant A ₁ was added at a rate of 10 g per cubic meter of the raw mud liquid R, and dehydration treatment was carried out by the multi-disc type dehydration treatment apparatus 3.

The properties of the scum sludge used in this Example 1 are SS: 2% and VSS / SS: 65%. Here, VSS means ignition loss. Among the solids,
It is the amount lost by strong heat (600 ° C.) and serves as an index of the organic component in the solid content. The smaller the VSS, the smaller the proportion of the organic component. Sludge with a VSS / SS of 70% or less
Since it can be said that the sludge contains a relatively large amount of inorganic components, the scum sludge used in Example 1 falls into the category of inorganic sludge.

The main component of the cationic polymer flocculant C ₁ used in this example is a copolymer of acryloyloxyethyltrimethylammonium chloride (40 mol%) and acrylamide (60 mol%). The main components of the anionic polymer flocculant A ₁ are sodium acrylate (40 mol%) and acrylamide (60 mol).
%) Is a copolymerization product thereof.

Experimental results. As a result of the above experiment, the water content of the dehydrated cake T was 78%, and the dehydration treatment work could be performed smoothly.

Comparative Example 1 Experimental method. For comparison with Example 1, the scum sludge having the same properties as in Example 1 collected from the same food factory as above was used as raw mud liquid R,
Polyferric sulfate, which is an inorganic coagulant, was injected into the connecting pipe 103 at a rate of 800 g per cubic meter of the raw mud liquid R.

The amphoteric polymer flocculant Am was added to the flocculation reaction tank 104 at a rate of 30 g per cubic meter of the raw mud liquid R and dehydrated by the multi-disc type dehydrator 3 (various conditions for dehydration). Is the same as in Example 1 above). The main component of the amphoteric polymer flocculant Am is acryloyloxyethyl trimethyl ammonium chloride (30 mol%)
And acrylic acid (10 mol%) and acrylamide (60
(mol%).

Experimental results. As a result of Comparative Example 1, the water content of the dehydrated cake T was 83%.

To compare the experimental results of Example 1 and Comparative Example 1 described above, the results of both experiments are summarized in Table 1 below.

[0050]

[Table 1]

As shown in Table 1 above, the present invention has a constitution in which the cationic polymer coagulant C ₁ is the first coagulant G ₁ and the anionic polymer coagulant A ₁ is the second coagulant G _2. This sludge treatment method (Example 1) is more inorganic coagulant (polyiron sulfate)
Since the water content of the dehydrated cake T can be reduced by 5% and a result of less than 80% was obtained as compared with Comparative Example 1 in which the amphoteric polymer coagulant Am was added in combination, the effectiveness and the effectiveness are it is obvious.

Example 2 Experimental method. Next, the inventors of the present application used a sludge liquid (mixture of scum sludge, coagulation sedimentation sludge, and excess sludge) collected from a chemical factory as a raw mud liquid R, and anionic polymer coagulation in the connecting pipe 103. The agent A ₂ was added at a rate of 10 g per cubic meter of the raw mud liquid R, and the cationic polymer flocculant C ₂ was added to the flocculation reaction tank 104 at a rate of 20 g per cubic meter of the raw mud liquid R, Multi-disc type dewatering device 3
(The various conditions of the dehydration treatment are the same as in Example 1 above).

The properties of the raw mud liquid R used were SS:
It was 1.5% and VSS / SS: 68%. The main components of the anionic polymer flocculant A ₂ are sodium acrylate (20 mol%) and acrylamide (80 mol).
%), A cationic polymer flocculant C ₂
Is a copolymer of acryloyloxyethyltriethylammonium chloride (60 mol%) and acrylamide (40 mol%).

Experimental results. As a result of Example 2 above, the dehydrated cake T obtained from the device 3
Had a water content of 82%.

Comparative Example 2 Experimental method. The sludge liquid collected from the same chemical factory as in Example 2 (similar to Example 2 above) was used as the raw mud liquid R, and the connecting pipe 103 was used.
In addition, the same amphoteric polymeric flocculant Am as in Comparative Example 1 was added at a rate of 20 g per cubic meter of the raw mud liquid R, and dehydration treatment was performed by the multi-disc type dehydration treatment apparatus 3 (various conditions of dehydration treatment are The same as in Example 1 above).

Experimental results. In Comparative Example 2, the water content of the dehydrated cake T obtained from the device 3 was 87%.

In order to compare the experimental results of Example 2 and Comparative Example 2 described above, the results of both experiments are summarized in Table 2 below.

[0058]

[Table 2]

As shown in Table 2 above, the sludge according to the present invention, wherein the anionic polymer flocculant A ₂ is the first flocculant G ₁ and the cationic polymer flocculant C ₂ is the second flocculant G _2. The treatment method (Example 2) was able to reduce the water content of the dehydrated cake T by 5% compared to Comparative Example 2 in which only the amphoteric polymer flocculant Am was added, and moreover, a good result close to 80% was obtained. Since it was obtained, its effectiveness and effectiveness can be recognized.

As demonstrated in the above Examples 1 and 2, the sludge treatment method and apparatus according to the present invention are VS
S / SS: It is possible to surely improve the dehydration property of the inorganic sludge of 70% or less, to realize a smooth sludge treatment work, and to obtain the dehydrated cake T having a low water content. Therefore, the sludge treatment method and apparatus according to the present invention are particularly suitable for the dehydration treatment of inorganic sludge.

[0061]

In the sludge treatment method and apparatus according to the present invention, since sludge liquid in which strong floc flocs are formed (improved dehydration property) can be supplied to the dehydration treatment tank, dehydration by rotation of the rotary filter body can be performed. The treatment process can be smoothly performed. In the tempering step, excess water is not added to the sludge liquid, so that the water content of the dehydrated cake can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a process flow of a sludge treatment method according to the present invention.

FIG. 2 is a schematic view showing a preferred embodiment of a sludge treatment device (D) according to the present invention.

[Explanation of symbols]

2 Multiple Disk Type Dehydration Treatment Device 3 Dehydration Treatment Tanks 6 and 7 Filter Body Rows 6a to 6e, 7a to 7j Rotating Filter Body 8 Rotation Axis A (A ₁ , A ₂ ) Anionic Polymer Flocculant C (C ₁ , C ₂ ) Cationic polymer flocculant D Sludge treatment device L Large disc M Small disc R Raw mud liquid (sludge liquid to which flocculant is added) S Conditioned sludge liquid T Dewatered cake X Conditioning process X ₁ First process X ₂ Second process Y Dehydration process

Continuation of front page (56) Reference JP-A-10-137795 (JP, A) JP-A-3-275830 (JP, A) JP-A-10-192900 (JP, A) JP-A-4-78500 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) C02F 11 / 12,11 / 14

Claims (2)

(57) [Claims] 1. An inorganic sludge liquid having a VSS / SS of 70% or less.
A first step of reacting a flocculant selected from any of anionic polymer flocculants and cationic polymer flocculants,
A heat treatment step consisting of a second step of reacting the inorganic sludge liquid treated in this first step with a polymer flocculant having a sign different from that of the first step, and a number of discs arranged in the rotation axis direction. Filter rows formed by arranging a plurality of rotating filtration bodies arranged side by side in intersecting rows are arranged facing each other in upper and lower two stages, and the inorganic filter sludge is conditioned by rotating the rotating filtration bodies. A sludge treatment method comprising a dehydration treatment step of filtering and dehydrating a liquid . 2. An inorganic sludge liquid having a VSS / SS of 70% or less.
A first flocculation reaction treatment means for reacting a flocculation agent selected from anionic polymer flocculants and cationic polymer flocculants, and an inorganic sludge liquid treated by the first flocculation reaction treatment means A refining means consisting of a second flocculation reaction treatment means for reacting a polymer flocculant having a different sign from the first flocculation reaction treatment means, and rotary filtration in which a large number of discs are arranged in the rotation axis direction. Filter bodies formed by arranging a plurality of bodies in juxtaposed rows are arranged in opposition to each other in upper and lower two stages, and by rotating the rotary filtration body, the conditioned inorganic sludge liquid is filtered and dehydrated. A sludge treatment device comprising: a dehydration treatment means having at least a dehydration treatment tank configured to convey and discharge the dehydrated cake.