JPS63240999A - Dehydration of organic sludge - Google Patents

Abstract

PURPOSE:To reduce water content in cake by mixing a powdery product prepd. by pulverizing an org. fibrous material having condensed polyamine adsorbed thereto, and powder of an org. high molecular coagulant, adding the powdery product to org. sludge, then adding an anionic org. high molecular coagulant, and dehydrating the mixture. CONSTITUTION:A mixture consisting of (A) a powdery org. fibrous materials (e.g. cotton) contg. a condensed polyamine (e.g. a condensed product of an amine with formaldehyde) having >=6.0meq electric charge of colloidal cation per 1g dry product of said condensed polyamine at 4 pH and <=300,000mol.wt., being adsorbed to the org. fibrous material, and (B) powder of an org. high molecular coagulant (e.g. polyacrylaminoethyl acrylate) having >=3.5meq electric charge of colloidal cation per 1g dry product of said org. high molecular coagulant at 4 pH and >=800,000mol.wt., is admixed with org. sludge. Then, an anionic org. high molecular coagulant (e.g. sodium polyacrylate) is admixed therewith, and the mixture is subjected to coagulating treatment and mechanical dehydration. Water content of cake after the mechanical dehydration is reduced by this simple operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for dehydrating and treating organic sludge discharged from sewage treatment plants, human waste treatment plants, food factories, chemical factories, etc.

Specific types of organic sludge targeted by the present invention include surplus sludge generated in sewage treatment, initial settling sludge, tertiary treatment sludge, anaerobic digested sludge of human waste, aerobic digested sludge of human waste, and human waste septic tank. Sludge, surplus sludge or flocculated sludge generated from various industrial wastewater treatments, etc. These sludges can be treated alone or in combination.

[Conventional technology]

Conventionally, the above sludge is dehydrated using a vacuum dehydrator or a pressure dehydrator by adding iron salts such as ferric chloride and slaked lime as dehydration aids, but the addition rate is higher than drying with ferric chloride. The solid content is 95 to 20 weight tS, and the dry solid content with slaked lime is 15 to 80 weight%, which is a large amount.Not only does the cake obtained by dehydration have a high moisture content, but the amount of sludge generated increases and sludge Problems such as corrosion of the furnace and increased amount of ash occurred during incineration.

In recent years, in order to solve these problems, various organic polymer flocculants have been developed as dehydration aids and are used in combination with belt-displacement V-type dehydrators and centrifugal separators. Also,
Dehydration methods that use an organic polymer flocculant alone have a high moisture content in the cake after dehydration, so methods that use a combination of a cationic organic polymer flocculant and an anionic organic polymer flocculant are often used ( For example, JP-A-56-87500, JP-A-58-70898).

[Problems to be solved by the present invention]

However, even in the method of using a cationic organic polymer flocculant and an anionic organic polymer flocculant in combination, the addition rate of the cationic organic polymer flocculant is high, and the dehydration effect is not satisfactory. There was a need for a method for dewatering sludge. In view of the above-mentioned conventional problems, the present invention was completed as a result of various studies on dehydration treatment methods for organic sludge. This provides an effective method for treating sludge.

[Means for solving problems]

That is, in the present invention, the amount of colloidal cation charge at pH 4 is 6. Omeq / g - A condensed polyamine with a dry weight or more and a molecular weight of 300,000 or less is adsorbed onto an organic fiber material and powdered, and the amount of colloidal cation charge is! L
5 meq/g - After adding and mixing a mixture with organic polymer flocculant powder with a dry weight of more than 800,000 and a molecular weight of 800,000 or more to organic sludge, add and mix an anionic organic polymer flocculant to flocculate. This is a method for dewatering organic sludge, which is characterized by treating it and then mechanically dewatering it.

The present invention and its effects will be explained in detail below.

In the present invention, the amount of colloidal cation charge at pH 4.0 is 6. Omeq / g - Molecular weight 3 with dry weight or more
00,000 or less (hereinafter referred to as Boriafin-A), condensates of alkylene dichloride and alkylene polyamines, condensates of amines and formalin,
condensate of alkylene diamine and epichlorohydrin,
Examples include condensates of ammonia and epichlorohydrin and condensates of sialkylamine and dihalogenoalkane. These polyamines can be synthesized with various chemical structures, but those with a colloidal cation charge amount of 6.0 meq/g-dry weight or more at pH 4. effective. Further, the molecule hl used is 300,000 or less.

When the amount of colloidal cation load at pH 4.0 of polyamine-A is less than & Omeq/g-dry weight,
Since polyamine-A does not react sufficiently with anionic substances on the surface of particles in the sludge, the moisture content of the cake after dehydration decreases little. Further, even if the molecular weight of polyamine-A is 300,000 or more, the polyamine-A is not sufficiently adsorbed on the particle surface in the sludge, so the decrease in water content of the cake after dehydration is small.

In the present invention, organic fibers include natural fibers such as wood, straw, cotton, and wool, synthetic fibers such as rayon, acrylic, and polyester, and binders such as mechanical fibers, chemical pulp, and paper. use. These organic fiber materials having a length of 0.01 to 3 m+ are effective in reducing the moisture content of the cake after dehydration and improving the peeling of the dehydrated cake from the filter cloth.

The amount of colloidal cation charge that can be maintained at pH 4.0 is 5 s m
The cationic organic polymer flocculant having a molecular weight of 800,000 or more and a dry weight of 800,000 or more (hereinafter referred to as high molecular weight polymer B) is polyacrylaminoethyl acrylmethacrylate, a copolymer of these and polyacrylamide, or a copolymer of these and polyacrylamide. Examples include quaternized products of polyacrylamide, Mannich-modified products of polyacrylamide or quaternized products thereof, polyvinylimidacillin, and homopolymers of dimethyldiallylammonium chloride. These polymers have conventionally been used alone for dewatering sludge. Those with a colloidal cation charge amount of 55 meq/g-dry weight or more at pH 4.0 are effective in reducing the moisture content of the cake after dehydration, and those with a molecular weight of 800,000 or more have a high overall cationic organic content. Effective in reducing the addition rate of molecular flocculants.

If the colloidal cation charge amount of high molecular weight polymer B at pH 4.0 is less than l 5 meq / g-dry weight, high molecular weight polymer B will not react sufficiently with the anionic substances on the particle surface in sludge, The decrease in moisture content of the cake is small. Moreover, if the molecular weight of the high molecular weight polymer B is 800,000 or less, the total addition rate of the cationic organic polymer flocculant becomes large in order to generate a dewaterable floc.

In the present invention, the amount of colloid charge refers to the amount measured and determined according to the following measurement method.

0, 2 to 1. Make an ion-exchange aqueous solution of 0% polymer flocculant. An O solution with a concentration of 50 ppm is prepared using ion-exchanged water, and the constant f1k (100d) is accurately placed in a container, and N/10HC1 is added to adjust the pH to 4.0. After adding toluidine blue to the solution, titration is performed with N/400 PVSK (potassium polyvinyl sulfate) while stirring well. The end point is the point where the color changes from blue to reddish-purple. A blank test shall be conducted using the same procedure.

The calculation formula is the colloid equivalent value at pH 4 (meq/g-
dry matter) = [titration ik (+d) X N/4 0
0PVSK titer]/2 When polyamine-A1 organic fiber material and high molecular weight polymer B are added to organic sludge, polyamine-A and high molecular weight polymer B are dissolved separately or simultaneously in the same dissolution tank, Although adding the dissolved liquid to organic sludge together with organic miscellaneous substances has a dewatering effect, it is extremely inconvenient. That is, organic fiber materials are bulky and require large facilities for transportation and storage, and polyamine-A is usually in liquid form and polymeric polyamide.
Since 3 is a powder, polyamines with different physical states can be used.
Handling A, organic fibrous material, and high molecular weight polymer B requires complicated operations. Therefore, it is important to add to the organic sludge a mixture of polyamine-A adsorbed onto organic fiber material and powdered and high molecular weight polymer B powder.

The ratio of the organic fiber material, polyamine-A and high molecular weight polymer B is such that when polyamine-A is 100 dry weight, the organic fiber material is 10 to 1000 dry weight,
Preferably, the proportion of high molecular weight polymer B is in the range of 10 to 1000 parts by weight. It is difficult to powder polyamine-A when the organic fiber material is less than 10% by dry weight per 100% by dry weight of polyamine-A, and the amount to be handled is more than 1000% by dry weight. This is inconvenient.

In addition, if high molecular weight polymer B is used in a ratio of 10 parts by weight or less of dry weight per 100 parts by weight of dry weight of polyamine-A, it is necessary to increase the overall addition rate of the cationic organic polymer flocculant, and the high molecular weight polymer When B is used in a proportion of 1,000 parts by dry weight or more, the decrease in moisture content of the cake after dehydration is small.

The addition rate of polyamine-A, organic fiber material, and high molecular weight polymer B to organic sludge is Q, 1 weight % or more, preferably cL5 to 10% by weight, for each component in terms of dry weight.

A mixture of polyamine-A, organic fiber material and high molecular weight polymer B (referred to as Sakashita blend-A) is used by mixing blend-A with water to a concentration of α1 to ILs, Preferably, the liquid is added to organic sludge.

As the anionic organic polymer flocculant, partially hydrolyzed modified polyacrylamide, sodium polyacrylate, polyvinylsulfonic acid, etc. are used.

The addition rate of the anionic organic polymer flocculant varies depending on the type of sludge, but the addition rate of the anionic organic polymer flocculant differs depending on the type of sludge, but it is 0.05 to 5% by weight in terms of dry solids of the anionic organic polymer flocculant. It may be added within this range.

The method for mixing organic sludge and Blend-A is to first add and mix Blend-A, and then add and mix the anionic organic polymer flocculant. When adding and mixing Blend-A, the purpose is not to generate flocs, so make sure that the organic sludge and cationic organic polymer flocculant react sufficiently.
The sludge is mixed with stronger agitation than the normal agitation used when flocculating sludge. When adding and mixing an anionic organic polymer flocculant, the purpose is to generate flocs, so the mixing is carried out using the usual agitation that is used when converting sludge into flocs.

Conventionally, the combination of polyamine-A and anionic organic polymer flocculant lowers the moisture content of the cake after dehydration, but the flocs produced are weak and require a very large amount of flocs to be suitable for dehydration. Requires polyamine. The combination of organic fiber material and Polymer B increased the flock strength, lowered the moisture content of the dehydrated cake, and improved the peelability from the filter cloth.Furthermore, the combination of Polymer B and anionic organic polymer flocculant It was observed that a small amount of polymer B produces flocs suitable for dehydration, but that the decrease in moisture content of the cake after dehydration is small.

From the above, although the mechanism of the phenomenon that occurs when treated according to the present invention is not necessarily clear, it is thought to be as follows. Since polyamine-A is a low molecular weight polymer with a very strong cationic degree, polyamine-A strongly modifies the surface of particles contained in organic sludge, and organic fiber substances are incorporated into the floc in a network form. Since polymer B is a strong cationic high molecular weight polymer, polymer B
It is thought that the particle surface is modified and, at the same time, the anionic organic polymer flocculant added later puts the particle surface into a state where strong flocs are generated. In other words, the synergistic effect of polyamine-A, organic fiber material, and polymer B improves the particle surface and generates strong flocs necessary for dewatering organic sludge, dramatically more efficiently than when each is used alone. It is assumed that this will be done.

Next, an example will be described.

Example 1 Mixed sludge (pH 6,4
, concentration 3a5,9/l) was subjected to dehydration treatment using a v-dobress type dehydrator.

In the method of the present invention, the cation charge amount is aOmeq /
g - Dry weight, molecular weight 4.000 condensed polyamine (
Condensate of amine and epichlorohydrin. paper powder (hereinafter referred to as cellulose-1).

) and the cationic load? lE amount is 6.0 m
Blend-1, which is a mixture of eq/g-dry weight, 1 million molecules and a cationic organic polymer flocculant (diallyldimethylammonium chloride, hereinafter referred to as Polymer 1), was used. In addition, as an anionic organic polymer flocculant, a partially hydrolyzed modified polyacrylamide (hereinafter referred to as anion-1) with a molecular weight of 7 million and a hydrolysis ratio of 50 was used. In the additive force method, Blend-1 was added to water and mixed (at a ratio of 0.3% by weight), and the mixed liquid was added to the mixed sludge and thoroughly mixed by vigorous stirring.

Next, anion-1 was added and mixed to form flocs, and the mixture was dehydrated using a belt press type dehydrator.

For comparison, ■ When Polymer 1 was added and mixed alone and dehydrated, ■ Cation charge bt was 2.5 meq.
/ g-dry weight, when a cationic organic polymer flocculant (polyacrylaminoethyl acrylic V-1-based, hereinafter referred to as Polymer 1') with a molecular weight of 6 million is added or mixed alone and subjected to dehydration treatment, ('Absorbed polymer 1' and cellulose-
When dehydrating after adding and mixing Polyamine-1, when dehydrating after adding and mixing Polyamine-1, and dehydrating after adding and mixing Polyamine-1, after adding and mixing Polyamine-1, anion-
(6) When polyamine-1 and polymer 1 are added and mixed, anion-1 is added and mixed and dehydrated, and (in the method of the strength-grip invention, polyamine-1 Instead of , the amount of cationic charge is 2.
A test was conducted using a condensed polyamine with a dry weight of 8 meq/g and an average molecular weight of 20,000 (a condensate of amine and formalin, hereinafter referred to as polyamine 1'). The test results are shown in Table 1.

Table 1 From Table 1, it can be seen that in the method according to the present invention, after jlQl soaking -
It can be seen that a reduction in the moisture content of the wood and an increase in the throughput of solids are achieved.

Example 2 Mixed raw sludge (pTH&6, concentration 5s89/l) generated in a city sewage treatment plant was dehydrated using an organic polymer flocculant in a belt press type dehydrator.

In the method of the present invention, the cation charge amount is 70, meq
/g-dry weight, molecular weight f, condensed polyamine (condensation product of alkylene diamine and epichlorohydrin, hereinafter referred to as polyamine-2) adsorbed on wood powder (hereinafter referred to as cellulose-2) and cations. The amount of charge is a
Blend 2, which is a mixture of a cationic organic polymer flocculant (a quaternary salt of polyacrylaminoethyl acrylate, hereinafter referred to as Polymer 2) having a dry weight of 4 million and a molecular weight of 4 million, was used. Further, as an anionic organic polymer flocculant, a polyacryl reamide partial angle hydrolysis modified product having a molecular weight of 6 million and a hydrolysis freshness of 60 was used (hereinafter referred to as anion-2). As for the addition method, Blend-2 was added to water and mixed (at a ratio of 0.2% by weight), and the liquid was added to the mixed raw sludge and thoroughly mixed by vigorous stirring. Next, an anionic organic polymer flocculant was added and mixed to form flocs, and the mixture was dehydrated using a belt press type dehydrator.

For comparison, ■ When Polymer 2 was added and mixed alone and dehydrated, ■ When Polymer 2 and Cellulose-2 were added and mixed,
When mixed and dehydrated, (while adding Nobolyamine-2, adding anion-2 after mixing, and when mixing and dehydrating, ■ Adding polymer 2, adding anion-2 after mixing,
In the case of mixing and dehydration treatment and ■ In the method of the present invention, the cationic charge amount is 2 instead of polymer 2, s me
A test was also conducted when a cationic organic polymer flocculant (polyacrylaminoethyl acrylate type, hereinafter referred to as Polymer 2') with a dry weight of q/g and an average molecular weight of 6 million was added and mixed and dehydrated. Ta. The test results are shown in Table 2.

Table 2 It can be seen from Table 2 that the method according to the invention achieves a reduction in the water content of the cake after dewatering and an increase in the throughput of solids.

Claims (3)

[Claims] (1) Colloidal cation charge amount at pH 4 is 6.0
meq/g - A condensed polyamine with a dry weight or more and a molecular weight of 300,000 or less adsorbed onto an organic fiber material and powdered, and the colloidal cation charge amount at pH 4 is 3.5 m
eq/g - A mixture of organic polymer flocculant powder with a dry weight of 800,000 or more and a molecular weight of 800,000 or more is added to organic sludge.
A method for dewatering organic sludge, which comprises, after mixing, adding and mixing an anionic organic polymer flocculant to perform flocculation treatment, followed by mechanical dewatering. (2) The amount of colloidal cation charge at pH 4 is 6
．． 0 meq/g - a condensed polyamine with a dry weight or more and a molecular weight of 300,000 or less, the organic fiber material and the colloidal cation charge amount 3.5 meq/g - The addition rate of an organic polymer flocculant having a dry matter amount or more and a molecular weight of 800,000 or more to organic sludge is 0.5 to 10% by weight in terms of dry matter weight. The method described in Section 1. (3) The colloidal cation charge amount at pH 4 adsorbed on the organic fiber material is 6.0 meq/g - a condensed polyamine with a dry weight or more and a molecular weight of 300,000 or less and the colloidal cation charge amount of 3.5 meq/g - The proportion of each component in the mixture of an organic polymer flocculant having a dry weight or more and a molecular weight of 800,000 or more is such that the colloidal cation charge amount at pH 4 is 6.0 meq/g - The dry weight or more and a molecular weight of 30
When the dry weight of the condensed polyamine of 10,000 or less is 100, the organic fiber material has a dry weight of 10 to 1000,
The organic polymer flocculant having a colloidal cation charge amount of 3.5 meq/g or more and a molecular weight of 800,000 or more is 10
10. The method according to claim 1, wherein the amount is 1000 parts by weight.