JP2000051900A - Sludge conditioning and dehydration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject method capable of stably obtaining a dehydrated cake low in water content without being effected by sludge properties or a sludge kind. SOLUTION: When sludge such as residue in water treatment is hedydrated, the sludge is successively introduced into blenders 1, 3 and 7 and flocculants A, B and C are successively added to the introduced sludge to be mixed therewith each time under stirring to condition the sludge and the conditioned sludge is dehydrated by a dehydrator 9. Sludge particles can be certainly flocculated by the successive addition and mixing of the flocculants A, B and C and, by this constitution, sludge particles and the flocculants can be sufficiently brought to a contact (reaction) state without performing stirring bringing about the re-destruction of flocs and, by this synergistic action, even hardly dehydrating sludge can be sufficiently conditioned (modified).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining and dewatering sludge such as residues in water treatment such as sewage and wastewater treatment.

[0002]

2. Description of the Related Art Sludge such as residues in water treatment such as sewage / wastewater treatment is recycled and reduced by decomposing it into cakes and then composting or incineration / melting treatments. Therefore, it is necessary to stably supply a dehydrated cake having a low water content regardless of the sludge properties.

For this purpose, conventionally, as shown in FIG.
The raw sludge was introduced into the mixer 11 and added with one type of coagulant at a time for tempering, and then dewatered by the dehydrator 12 to form a dewatered cake. This method is widely used because it is simple and the equipment cost is low.

[0004] However, with changes in dietary habits and sophistication of water treatment, sludge generated is becoming harder to dehydrate year by year, and in view of environmental issues, incineration and melting of dehydrated cake can be easily performed. Is gone.

[0005] In order to cope with such a situation, a dehydration method replacing the conventional method has been developed and put to practical use.
One of them is to introduce sludge into sludge conditioning tank, reform ferric chloride as an auxiliary, then introduce into sludge concentration tank, granulate with amphoteric polymer, concentrate, and then dehydrate. There is a two-liquid dehydration method designed to do this. In this method, when the mixed sludge is used as raw sludge and dewatered by a belt press dewatering machine, the cake moisture content is 70 to 72%, the sludge recovery rate is 99% or more. Good results with a recovery of 98% or more have been reported.

[0006]

Incidentally, the sludge to be dehydrated usually changes its properties every day, and it is necessary to change the addition rate of the flocculant accordingly. Normally, the addition rate is adjusted based on the amount of solids (that is, the concentration) in the sludge, but the work requires skill and a stable moisture content can be obtained even if the adjustment is performed appropriately. Not necessarily.

Particularly in the case of sludge which is difficult to dehydrate, a large amount of coagulant must be added. However, the viscosity of the liquid component is increased by the added coagulant, and consequently the water content increases.
Problems such as increased incineration costs and conveyors may occur. Also, the processing amount per unit time cannot be increased.

Also, when digested sludge, which is a representative of hardly dewaterable sludge, is treated by the above-described two-liquid dewatering method, a large amount of an inorganic coagulant must be added. I have to say that he is not suitable.

The present invention solves the above-mentioned problems, and provides a sludge refining and dewatering method capable of stably obtaining a low-moisture content dewatered cake irrespective of sludge properties and sludge type. It is intended for.

[0010]

Means for Solving the Problems To solve the above problems, a method for refining and sludge refining sludge according to claim 1 of the present invention is characterized in that when sludge generated as a residue in water treatment is dewatered, sludge is removed from the sludge. A plurality of coagulants are sequentially added, and the mixture is stirred and mixed by a stirring means each time it is added, and the refined sludge is dewatered by a dehydrator.

According to a second aspect of the present invention, a sludge refining and dewatering method comprises adding a plurality of types of flocculants in ascending order of cationity. The sludge refining and dewatering method according to claim 3 is such that a plurality of types of coagulants are added in order of increasing molecular weight.

According to a fourth aspect of the present invention, the same type of coagulant is added in plural times. In the sludge refining and dewatering method according to the fifth aspect, the sludge to which the coagulant has been added and mixed is concentrated by a concentration means, and another type of coagulant is added to and mixed with the concentrated sludge.

Generally, sludge particles (sludge colloid) are negatively charged and are stable by repelling each other.
Therefore, by adding an electrolyte having the opposite sign to the sludge colloid, that is, a polyvalent metal salt, a coagulant such as a polymer substance, the negative charge of the sludge colloid is neutralized and gelled, and metal hydroxide and the like are added. , Surrounded by floc formed by flocculant, gradually release moisture, settle with floc, adsorb other ions and colloids on floc, aggregate flocs together, make a lump,
Thereby, the dewatering property is improved.

According to the structure of the first aspect, by adding and mixing a plurality of types of flocculants, the sludge particles can be surely formed into flocculated flocs.
The sludge particles and the flocculant can be sufficiently contacted (reacted) without agitation so as to cause re-destruction of the flocculated floc. Due to the synergistic effect of these, the sludge can be sufficiently refined (reformed) regardless of the sludge properties. Quality) As a result, a dehydrated cake having a low water content can be obtained stably.

According to the second aspect of the present invention, since a plurality of types of flocculants are added in ascending order of cationity, that is, in ascending order of sludge conditioning (reforming) ability, floc is added with a minimum necessary flocculant. Can be formed, and the amount of the coagulant having a high degree of cation (that is, expensive) can be reduced.

According to the third aspect of the present invention, since a plurality of types of flocculants are added in order of increasing molecular weight, that is, in order of increasing floc forming ability, floc formation in the initial stage of addition is sufficiently performed. Sludge refining in late stage (reformation)
The effect can be fully exhibited.

According to the fourth aspect of the present invention, since the same type of coagulant is added in a plurality of times, the sludge particles and the coagulant react with each other reliably, compared with the case where the coagulant is added at once. Even when the total amount is the same, the flocculation of the sludge particles becomes more reliable.

According to the fifth aspect of the present invention, the sludge to which the coagulant is added and mixed is once concentrated, and the next coagulant is added and mixed with the concentrated sludge. The reaction can be effectively performed, and not only can the increase in the water content due to insufficient stirring due to the increase in the viscosity of the liquid component due to excessive addition of the flocculant, but also the amount of the flocculant added, Can be reduced.

As a flocculant, DAM (dialkylaminoethyl methacrylate), DAA (dialkylaminoethyl acrylate), diallylammonium halide and the like can be used.

The stirring means may be mixing in a tube,
A stirring tank, a drum type mixer or the like may be used. As a concentrating means, a concentrating screen, a gravity concentrating tank, or the like, and as a dehydrator, a centrifugal dehydrator, a rotating disk type dehydrator, preferably a belt press type dehydrator. A dehydrator having a pressurizing means such as a filter press can be used.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a first embodiment of the present invention is shown.
In the sludge refining and dewatering method in the embodiment, the raw sludge is introduced into the mixer 1 and the coagulant A is injected and the two are stirred and mixed, thereby introducing the sludge 2 in which the sludge particles are aggregated into the mixer 3. At the same time, another type of flocculant B (the degree of cation is ≧ coagulant A) is injected, and the two are mixed with stirring. Concentrate by draining syneresis.

Then, the concentrated sludge 6 is introduced into the mixer 7 and another coagulant C (the degree of cation is ≧ coagulant B) is further injected and mixed by stirring, whereby the sludge particles are further coagulated. The sludge 8 thus obtained is introduced into a dehydrator 9 to be dehydrated, and the dehydrated filtrate is discharged to obtain a dehydrated cake.

At this time, the coagulants A, B and C are respectively
The coagulant is added in such an amount that a flocculant having good dehydration property is formed, but from the viewpoint of preventing re-destruction of the flocculent floc in the pulverizer 1, the coagulant A: coagulant B = 5: 5 to 7: 3. It is desirable that The ratio of the coagulant C, that is, the ratio of the third and subsequent coagulants is not particularly limited.

In this way, the degree of cation is such that the coagulant A ≦
Since an appropriate amount of three kinds of coagulant B ≦ coagulant C was added and agitated and mixed each time the coagulant was added, re-destruction of the coagulated floc was prevented in any of the mixers 1, 3, and 7. The sludge particles and the flocculant can be sufficiently contacted (reacted) without agitation so as to induce the sludge particles to be surely formed into flocculated flocs. Quality) as a result, a stable low-moisture content dehydrated cake is obtained.

Further, sludge 4 containing coagulants A and B added and mixed
Is once concentrated and the coagulant C is added to the concentrated sludge 6 and mixed, so that the coagulant C can be effectively reacted, and the excessive addition of the coagulant C increases the viscosity of the liquid component. In addition to preventing the increase in the water content due to this, the amount of the coagulant C added and the amount of dewatered cake generated can be reduced.

As the coagulant A-coagulant B-coagulant C,
DAM-DAA-diallylammonium halides and the like can be used. As a second embodiment, a coagulant A,
Processing may be performed in the same manner as in the first embodiment, except that the same type is used as B. In this case, since one type of coagulant is added as compared with the first embodiment, the water content may slightly increase depending on the sludge properties,
Since the same type of flocculant is added in two portions, even if the total amount is the same, the flocculation of the sludge particles becomes more reliable than when adding the flocculant at once. .

As a third embodiment, the molecular weight is determined as follows:
The treatment may be performed in the same manner as in the first embodiment, except that three types of coagulant B ≧ coagulant C are used. In this case, substantially the same result as in the first embodiment is obtained.

As the coagulant A-coagulant B-coagulant C,
DAM-DAA-diallylammonium halides and the like can be used. (Generally, if the degree of cation is small, the molecular weight is large, so the order is the same.) As the fourth embodiment, the same treatment as in the third embodiment may be performed except that the same type of coagulants A and B are used. . In this case, substantially the same result as in the second embodiment can be obtained.

[0029]

As described above, according to the present invention, a plurality of types of flocculants are sequentially added to the sludge, and the mixture is stirred and mixed each time the sludge is added. And a dehydrated cake having a low moisture content can be stably obtained regardless of the sludge properties. Therefore, unlike the conventional method of adding and mixing one kind of coagulant at once, it is not necessary to add an excessive coagulant, and even if the coagulant is excessively added due to the change in sludge properties, sufficient stirring is performed. Since mixing can be performed, an operation that is hardly influenced by property fluctuations is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a sludge refining and dewatering method according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a conventional sludge refining and dewatering method.

[Explanation of symbols]

 1,3,7 Mixer (stirring means) 5 Concentration tank 9 Dehydrator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Hiroaki Miyamoto 2nd-6-1, Nishijima, Nishiyodogawa-ku, Osaka-shi, Osaka F-term in Kubota Shin-Yodogawa Plant (reference) 4D059 AA03 BE07 BE08 BE12 BE13 BE16 BE19 BE46 BE57 BE61 BE70 BJ01 BJ11 CA30 DB25 DB26

Claims (5)

[Claims] When sludge such as a residue in water treatment is dewatered, a plurality of coagulants are sequentially added to the sludge, and the sludge is stirred and mixed by a stirring means each time the sludge is added. A sludge refining and dewatering method characterized by dewatering sludge by a dewatering means. 2. The method of claim 1, wherein the plurality of types of flocculants are added in ascending order of cationity. 3. The sludge refining and dewatering method according to claim 1, wherein the plurality of types of flocculants are added in order of increasing molecular weight. 4. The method for sludge refining and dewatering according to claim 1, wherein the same type of coagulant is added in plural times. 5. The sludge to which a coagulant has been added and mixed is concentrated by a concentrating means, and the following coagulant is added and mixed to the concentrated sludge. Sludge refining dewatering method.