JPH042320B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an organic sludge dehydrating agent comprising a polymer obtained by partially hydrolyzing poly-N-vinylacetamide. For more details, please refer to PolyN-
The present invention relates to a dehydrating agent for organic sludge that has the effect of significantly reducing the water content of organic sludge made of a high molecular weight polycation partially having a polyvinylamine structure obtained by partially hydrolyzing vinyl acetamide. In recent years, treatment of urban sewage, human waste, and industrial wastewater with activated sludge has become widespread, but the organic sludge generated has a high moisture content, so it is necessary to efficiently dewater it in order to dispose of it, incinerate it, or make it into fertilizer. be. Conventionally, the common method is to flocculate organic sludge using neutralized salts of dimethylaminoethyl (meth)acrylate, polymers of quaternary salts, Mannitz reaction products of polyacrylamide, etc., and then dewatering using a high-speed centrifuge, etc. However, in this case, although the treatment speed was fast, the water content of the organic sludge could not be lowered sufficiently. On the other hand, press-type dehydrators are advantageous for the purpose of lowering the water content of organic sludge, but if the above-mentioned flocculants used in high-speed centrifuges are used as the dehydrating agent, huge flocs with high water content will be formed. In addition to not reducing the water content sufficiently, sludge tends to protrude during press dehydration, and the ability to remove sludge from cloth deteriorates, making it impossible to dewater smoothly. Press dehydrators generally undergo a gravity passing process of organic sludge, a pressure pressing process, and a process of peeling the sludge from the cloth. It is desirable for the flocculant added as a dehydrating agent to have good aqueous properties under gravity, to reduce the water content quickly during pressure pressing, and to be able to be easily peeled off from the fabric. No drug was obtained. The present inventors conducted intensive studies on dehydrating agents that can significantly reduce the water content of organic sludge. As a result, a high molecular weight polymer having a polyvinylamine structure obtained by partially hydrolyzing polyN-vinylacetamide has a high dehydration rate of organic sludge. The inventors have discovered that the present invention has the effect of significantly reducing the That is, the gist of the present invention consists of structural units represented by the following general formulas [] and [], (Here, X represents an anion) The molar ratio of structural units []:[] is 85:15~
45:55 range, 0.1g/dl in 1 normal saline
The reduced viscosity measured as a solution at 25℃ is 2 dl/g.
The present invention relates to an organic sludge dehydrating agent comprising the above water-soluble polymer. Hereinafter, to explain the present invention in more detail, the organic sludge dehydrating agent of the present invention has the general formula () obtained by partially hydrolyzing a polymer of N-vinylacetamide. (Here, X represents an anion) and general formula [] It is a water-soluble polymer containing structural units represented by the formula in a molar ratio of 85:15 to 45:55. If the structural unit of the general formula [] is less than this, the cohesive force and the effect of lowering the water content of organic sludge will be reduced, and if it is larger than this, the cohesive force for organic sludge will be reduced, and depending on the type of sludge, it may not coagulate at all. . X represents a halogen ion, a nitrate ion, a carboxylate ion, a sulfonate ion, etc., and preferably a chloride ion or an acetate ion. The dehydrating agent of the present invention is 0.1 g/dl in 1 normal saline solution.
The reduced viscosity measured at 25℃ is 2 dl/
g or more is used. Preferably, the reduced viscosity is 3 dl/g or more. The higher the reduced viscosity, the higher the dewatering performance, but if the reduced viscosity exceeds 10 dl/g, it becomes difficult to mix with sludge. The organic sludge dehydrating agent of the present invention is added to organic sludge as a 0.1 to 5% by weight aqueous solution. The amount of the dehydrating agent used is in the range of 10 to 5000 ppm, preferably 50 to 500 ppm, based on the organic sludge slurry. Although the method for producing the organic sludge dehydrating agent of the present invention is not limited to that method, the following method is preferred. 20-60% by weight of N-vinylcarboxylic acid amide
An aqueous solution with a pH of 6 to 10 was heated at 40 to 80°C under substantially oxygen-free conditions using a radical polymerization initiator.
Partially hydrolyzed polyN is produced by hydrolyzing a high molecular weight water-soluble polymer obtained by polymerization at a temperature of
-vinylacetamide is obtained. As the radical polymerization initiator, a general initiator used for the polymerization of ordinary water-soluble vinyl monomers can be used, but in order to obtain a high molecular weight polymer in a good yield, a water-soluble azo compound is preferable. Preferred radical polymerization initiators include hydrochloride and acetate of 2,2'-azobis-2-amidinopropane; sodium salt of 4,4'-azobis-4cyanovaleric acid;
These include hydrochloride, sulfate and acetate of N,N'-dimethyleneisobutyramidine, and are usually used in a weight range of 100 to 10,000 ppm based on the monomer. The hydrolysis reaction may be either basic or acidic, but acidic hydrolysis is preferred. A preferred hydrolysis method is to add a mineral acid such as hydrochloric acid to a 5 to 10% aqueous solution of the polymer by 0.4 to 10 times the mole of the raw material monomer, preferably 1 to 5 times the mole, and heat the mixture to 60 to 100°C. This can be achieved by doing. The hydrolysis rate can be appropriately adjusted by adjusting the amount of acid used, temperature, and reaction time. Thus, the organic sludge dewatering agent of the present invention is used in the same manner as a cationic flocculant, such as a homopolymer of a quaternized dimethylaminoethyl methacrylate, by adding it to an organic sludge. By adding the dehydrating agent for organic sludge of the present invention, a strong coagulated floc is formed, and by performing dehydration or centrifugation, the water content of the sludge can be significantly reduced. Moreover, the effect is particularly excellent in press dehydration treatment. It has good aqueous properties in the gravity process of the press dehydrator, has a fast pressure overspeed in the pressure press process, significantly reduces the water content, and has excellent peelability from fabrics. Organic sludge that can be subjected to dewatering treatment includes primary sedimentation sludge in sewage treatment, surplus sludge in activated sludge treatment, and mixtures thereof, surplus sludge in activated sludge treatment of human waste, digested sludge, and activated sludge treatment of various organic matter-containing wastewater. Examples include surplus sludge generated by Organic sludge dehydrated using the organic sludge dehydrating agent of the present invention has less stickiness and a lower water content, so it is easier to handle and can significantly reduce fuel and costs when incinerated or turned into fertilizer. The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the Examples unless the gist thereof is exceeded. Polymer production example: 10 g of N-vinylacetamide was dissolved in 10 g of demineralized water, and equipped with a stirrer, a nitrogen introduction tube, and a cooling tube.
It was introduced into a 50 mg four-necked flask. After bringing the temperature to 60°C with stirring under a nitrogen gas stream, 0.3 g of 10% 2,2'-azobis2-amidinopropane hydrochloride was added and polymerized at 60°C for 8 hours. The product is the polymerization rate
99.6%, and the reduced viscosity was 6.4 dl/g. After dissolving 4.8 g of the product (2.4 g pure) in 135 mg of water, 62 ml of concentrated hydrochloric acid was added under ice cooling. Table 1 shows the compositions of polymers A to H, which were heated under reflux for the time shown in Table 1, dehydrated with isopropanol, and dried under vacuum to obtain partially hydrolyzed poly-N-vinylacetamide. The reduced viscosity was measured using an Ostwald viscometer (t ₀ = 30.24
It was determined from the value (t seconds) measured at 25°C using t seconds). Reduced viscosity ηsp/C = (t-t ₀ /t ₀ )/0.1 (dl/g) The hydrolysis rate is the colloid titration value using toluidine blue as an indicator under PH3 conditions with a 1/400 normal polyvinyl potassium sulfate aqueous solution. It was calculated from the cationic group equivalent determined from

[Table] Examples 1 to 5 and Comparative Examples 1 to 8 200 ml of sludge was placed in a 500 ml beaker, and then
A predetermined amount of a 0.25% aqueous solution of the polycation shown in the table was added. Stirring was carried out at 1000 rpm for 10 seconds using a stirring rod with three round rods each having a diameter of 5 mm and a length of 20 mm attached to the tip. The flocculated sludge was passed through a 60 mesh nylon cloth by gravity, and Table 1 shows the elapsed time until the liquid volume reached 100ml. The sludge after passing under gravity was sandwiched between two 30 cm square pieces of polyester monofilament cloth (OLh-C manufactured by Nippon Filcon), which was then sandwiched between polyvinyl chloride plates with grooves for drainage, and subjected to piston pressure using a hydraulic press with a piston diameter of 20 mm. 50Kg/ ^cm2
Press dehydration was performed for 30 seconds while maintaining the pressurized conditions. The water content ratio of the dehydrated sludge was determined from the weight of the dehydrated sludge and the weight of the solid content of the sludge after drying at 120°C for 3 hours, and is shown in Table 2. Water content ratio = weight of water content in dehydrated sludge / weight of solid sludge The amount added was expressed as the weight relative to the volume of the sludge slurry. Regarding Polymers C, D, and I, the relationship between the amount of polymer added when sludge is passed through gravity and the elapsed time to reach a liquid volume of 100 ml, and the relationship between the amount of polymer added when sludge is press-dehydrated and the water content ratio of dehydrated sludge. The relationships are shown in Figures 1 and 2, respectively.

【table】

[Table] Examples 6 to 9 and Comparative Examples 9 to 11 Excess sludge from activated sludge treatment equipment of Company M (solid content 1.51
%) was placed in a 200 ml beaker, and then 10 ml of a 0.1% aqueous solution of the polycation shown in Table 2 was added. The mixture was stirred and filtered under the same conditions as in Example 1.
A 60-mesh nylon cloth with a diameter of 3.3 cm was placed in an aluminum cylindrical container with a diameter of 3.5 cm and a depth of 5 cm with a perforated plate on the bottom, and the sludge after gravity was placed on top of it. held for seconds.
After measuring the weight of the dehydrated sludge, it was dried at 120℃ for 3 hours, and the water content ratio of the dehydrated sludge was measured from the weight.
Shown in the table.

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows Example 1 using polymers C, D and I.
2 is a graph showing the relationship between the amount of polymer added and the elapsed time to reach a liquid volume of 100 ml when sludge is gravity-filtered using the method described above. FIG. 2 is a graph showing the relationship between the amount of polymer added and the water content ratio of dehydrated sludge when sludge was press-dehydrated by the method of Example 1 using Polymers C, D, and I.

Claims (1)

[Claims] 1 Consists of structural units represented by the following general formulas [] and [], (Here, X represents an anion) Structural unit []: [] molar ratio is 85:15-45:
A dehydrating agent for organic sludge comprising a water-soluble polymer having a reduced viscosity of 2 dl/g or more measured as a solution of 0.1 g/dl in 1N saline at 25°C.