JPH047100A - Sludge dewatering method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial use amount ￥f] The present invention relates to a sludge dewatering method, and in particular, it is capable of dewatering sludge with high salt concentration, which is difficult to dehydrate using conventional methods, with excellent flocculation and dewatering properties. 5) A method for dewatering mud that can be dehydrated.

[Prior Art] Cationic polymer dehydrating agents have conventionally been used to dehydrate organic sludge generated in sewage treatment, human waste treatment, organic industrial wastewater treatment, and the like. However, in the conventional method using a cationic polymer dehydrating agent, water content and SS
Satisfactory results have not always been obtained in terms of recovery rate, removability of the cake from the filter cloth, etc., and improvements are desired. Among these, improvements are particularly required for sludge with a high salt concentration (that is, high electrical conductivity), such as seawater diluted human waste sludge, human waste digested sludge, and sewage digested sludge. That is, although the salt concentration in the method itself is high, a large amount of water is required as dilution water when biologically treating it, so seawater is sometimes used as dilution water. Therefore, surplus sludge discharged from such a treatment system using seawater contains salts at a high concentration. Furthermore, when digested sludge from human waste or sewage is digested aerobically or anaerobically, the concentration of salts in the sludge increases due to salts eluted from bacterial cells, organic acids derived from amino acids, ammonia, etc. Sludge containing such high concentrations of salts cannot be dehydrated using conventional cationic polymer dehydrating agents due to its cohesiveness, SS recovery rate,
The effect was poor in terms of peelability from the filter cloth and cake moisture content, and improvements were needed.

On the other hand, as an improvement to the method of dewatering sludge containing high concentrations of salts, we used Hensyl halide to quaternize it (meth).
Method of using acrylate type cationic polymer dehydrating agent for dehydration treatment of seawater diluted human waste sludge (Japanese Patent Publication No. 61-4455
No. 9) has been proposed.

[Problems to be Solved by the Invention] The method of Japanese Patent Publication No. 61-44559 proposes a dehydrating agent that is effective for sludge containing a large amount of inorganic salts, but the basic skeleton of the polymer itself of the dehydrating agent Since it is the same as conventional cationic polymer dehydrating agents, there is no particular improvement in its performance.

Although there have been proposals aimed at solving the drawbacks of conventional cationic polymer dehydrating agents,
No method has been proposed that provides a sufficiently satisfactory effect. In particular, no effective dewatering method has been found for sludge with a high salt concentration (ie, sludge with high electrical conductivity), which is called sludge that is difficult to dewater.

The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of efficiently treating sewage with high salt concentration and difficult to dewater, digested sludge of human waste, or sludge treated with seawater dilution of human waste with high flocculation and dewatering properties. The purpose of the present invention is to provide a sludge dewatering method that can treat sludge.

[Means for Solving the Problems] The sludge dewatering method of the present invention involves dewatering sludge from sewage digestion, digested human waste sludge, or seawater diluted human waste sludge alone, or by mixing them with other sludge. When the sludge is dehydrated, a cationic polymer flocculant containing a structural unit represented by the following general formula (1) is added to the sludge for dewatering.

-CH2-C- In the above formula, the salt-forming anion group represented by X- includes a halogen ion or an anion such as CH3SO4-.

The present invention will be explained in detail below.

The sludge to be treated in the present invention is digested sludge from sewage, human waste, etc., which has a high salt concentration and is difficult to dehydrate using conventional polymer dehydrating agents due to its poor flocculation and dewatering properties. Digested sludge or human waste diluted with seawater. The present invention is particularly effective for highly concentrated salt-containing sludge with electrical conductivity of 3000 μs/cm or more, particularly 4000 μs/cm or more.

The cationic polymer flocculant used in the present invention contains a structural unit represented by the above general formula (hereinafter sometimes referred to as "-thousand unit of formula (1)"), -Even if it is a homopolymer of the monomer unit of the formula (1), -a copolymer of the monomer unit of the formula (1) and other monomer units copolymerizable, such as a monomer having a vinyl group (vinyl monomer). It may be. Examples of vinyl monomers copolymerizable with the 1,000 mer unit of general formula (1) according to the present invention include the following (1) to (2).

■ ■ ■ Cationic monomers Nonionic monomers such as tertiary salts or quaternized products of dimethylaminoethyl (meth)acrylate, tertiary salts or quaternized products of diethylaminoethyl (meth)acrylate: (meth)acrylamide, (meth)acrylate The cationic polymer flocculant according to the present invention, such as acrylonitrile, alkyl (meth)acrylate, vinyl acetate, styrene, etc.;
When the copolymer is a copolymer of the monomer unit represented by (1) and the vinyl monomer (1) to (2) described above, the content of the 1,000-mer unit of general formula (1) in the copolymer is preferably 20 mol % or more. If the content of 1000 mer units of general formula (1) in the copolymer is less than 20 mol %, the proportion of monomer units of formula (1) is too small, and the present invention cannot obtain sufficient aggregation and dehydration effects. I can't.

The homopolymer or copolymer having 1,000 units of formula (1) can be easily produced by polymerization using conventional solution polymerization, suspension polymerization, emulsion polymerization, or the like. For example, in the case of production by aqueous solution polymerization, the initiators may be ammonium persulfate, potassium persulfate, 2.2゛-azobis(2
-amidinopropane) dihydrochloride or the like under normal polymerization conditions.

Note that the molecular weight of the cationic polymer coagulant used in the present invention at 30° C., when expressed as intrinsic viscosity [η]1N-NaNOs, is sufficient to be 2 dIl/g or more, but it is sufficient to achieve stable dehydration treatment. It is preferable that it is 5 dIl/g or more.

Examples of the monomer that provides the monomer unit of formula (1) that is suitable for the present invention include salts of dialkylaminopropyl (meth)acrylamide or quaternary ammonium salts, specifically the following 1 to 2.

■ Hydrochloride of dimethylaminopropyl acrylamide ■ Sulfate of dimethylaminopropylacrylamide ■ Quaternary ammonium salt of dimethylaminopropylacrylamide with methyl chloride ■ Hydrochloride of dimethylaminopropyl methacrylamide ■ Sulfate of dimethylaminopropyl methacrylamide ■ Dimethyl Quaternary ammonium salt of aminopropylmethacrylamide with methyl chloride■ Quaternary ammonium salt of dimethylaminopropylacrylamide with benzyl chloride To carry out the method of the present invention, the cationic polymer flocculant of the present invention is dissolved in an aqueous solution, etc. It is added as a solution to the sludge to be treated, stirred, sufficiently coagulated, and then dehydrated in a dehydrator. In this case, the amount of the cationic polymer flocculant according to the present invention added is not particularly limited, but it is preferably added to the sludge to be treated in an amount of 02 to 3.0% based on the solid content. . In addition, dehydrators include belt press type dehydrators, centrifugal dehydrators, screw press type dehydrators,
A filter press dehydrator or the like can be used.

In addition, in the present invention, the cationic polymer flocculant according to the present invention may be added alone to the sludge, but an anionic polymer flocculant may also be added, and if necessary, the cationic polymer flocculant may be added to the sludge. Adding other cationic polymers to the polymer flocculant solution
Nonionic polymer An anionic polymer may be added to form a liquid mixture, or it may be used in combination with other components that do not adversely affect the dehydration treatment, such as sodium hydrogen sulfate, sodium sulfate, and sulfamic acid. Furthermore, an inorganic flocculant can also be used in combination. In this case, as the inorganic flocculant, for example, aluminum sulfate, polyaluminum chloride, ferrous chloride, ferrous sulfate, polyferrous sulfate, etc. can be used.

[Function] Although the details of the mechanism of action of the cationic polymer flocculant according to the present invention for excellent flocculation performance and dewatering performance for sludge containing high concentration salts are not clear, (1) conventional (meth)acrylate type cationic It has a higher pKa value and is more basic than polymers. Incidentally, dimethylaminoethyl acrylate has a pKa of 7.90. Dimethylaminoethyl methacrylate has p a = 7.94, and dimethylaminopropylacrylamide has pKa = 10.35.

(11) While conventional (meth)acrylate type cationic polymers are esters, the cationic monomer unit according to the present invention is an amide, and therefore has good hydrolysis resistance.

It is believed that the excellent effects of the present invention can be achieved without delay.

[Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Examples 1 to 26, Comparative Examples 1 to 11 A dewatering test was conducted on the sludge shown in Table 1 using the flocculant shown in Table 2 according to the test method described below.

Test method 200 mfl of sludge shown in Table 3 in 300 mj2 beakers
A coagulant aqueous solution dissolved at 0.4% by weight was added to the sludge shown in Table 3, and the mixture was stirred at 50 rpm using a turbine blade agitator.
The mixture was stirred at m for 60 seconds to coagulate the sludge.

After measuring the size of the flocculated flocs at this time, the flocculated sludge was poured into a Buchner funnel lined with a filter cloth.
Measure the amount of filtrate after seconds and calculate the amount of SS leaked from the amount of SS.
The recovery rate of S was determined. Next, a certain amount of the sludge on the Buchner funnel was sandwiched between two pieces of filter cloth and squeezed for 60 seconds at a pressure of 0.5 kg/cm'', and the state of peeling of the cake from the filter cloth and the moisture content of the cake were measured. The peeling state of the cake from the filter cloth was calculated by washing the filter cloth (two upper and lower sheets) with high aqua regia after scraping off the cake with a spatula, and measuring the amount of adhering solid matter.

The results are shown in Table 3.

[Effects of the Invention] As is clear from the results of the above examples, the sludge dewatering method of the present invention can dewater sewage, digested sludge of human waste, or sludge treated with seawater dilution of human waste, which has a high temperate concentration and is difficult to dewater. During processing, ■ Excellent cohesiveness and large flocs formed.

■ Good filtration performance.

■ Cake moisture content is low.

■High SS recovery rate.

■ Good cake removability from filter cloth.

Excellent effects such as these are achieved, making it possible to treat sludge with high efficiency.

Agent: Patent attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) When dewatering digested sewage sludge, digested human waste sludge, or seawater diluted human waste sludge alone or by mixing them with other sludge, the following general formula (1) is used. A sludge dewatering method characterized in that the sludge is dehydrated by adding a cationic polymer flocculant containing a structural unit to the sludge. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) [However, R^1 is hydrogen or a methyl group, R^2 is an alkyl group with 1 to 4 carbon atoms, R^3 is hydrogen or a carbon number 1 ~4 alkyl group or benzyl group, X^- represents a salt-forming anion group. ]