JPH0349606B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for dewatering organic sludge. More specifically, the present invention relates to a method for treating sludge containing inorganic salts, and particularly to a dewatering method effective for sludge containing a large amount of inorganic salts of 0.1% by weight or more. The gist of the present invention is to add polymerizable vinyl monomers represented by general formulas (1), (2), and (3) below to sludge containing inorganic salts as one structural unit, and to is (1):(2):(3)=5~45:5~45:50
This is a dewatering method for sludge containing inorganic salts, which is characterized by adding a cationic flocculant whose main component is a water-soluble polymer (terpolymer) in a range of 90 (mol %). With the tightening of wastewater regulations to preserve water quality and the spread of sewage and human waste treatment equipment, various cationic polymer compounds are being used to dehydrate various types of sludge generated in industrial wastewater treatment, sewage treatment, human waste treatment, and other processes. It is used. These cationic polymer compounds exhibit superior flocculating performance at lower amounts than conventional inorganic flocculants, and have other advantages such as less residue generated when the cake is incinerated after dehydration. Because of this, it is now widely used in the treatment of sludge in place of inorganic flocculants. These cationic polymer compounds include homopolymers of dimethylaminoethyl methacrylate, copolymers of dimethylaminoethyl methacrylate and acrylamide, homopolymers or copolymers of quaternary dimethylaminoethyl methacrylate, Mannitz modified polyacrylamide, or There are quaternized products thereof, polyvinylimidazoline, homopolymers of dimethyldiallylammonium chloride, and the like. These cationic polymer compounds exhibit extremely excellent flocculation performance against ordinary sludge, and are extremely effective in dewatering sludge. However, these cationic polymer compounds also have a markedly reduced flocculation performance for the special sludge that is the subject of the present invention, that is, sludge containing a large amount of inorganic salts, and even if they flocculate, the floc strength is weak. However, there were phenomena such as easy breakage, and the disadvantage was that a satisfactory dehydration effect could not be obtained. In addition, for sludge with high salt concentration, a homopolymer of benzyl chloride quaternized dimethylaminoethyl methacrylate or a copolymer of this with acrylamide produces flocs, but the dewatering effect is not always satisfactory. Ta. That is, it has been impossible to perform stable dewatering of sludge with a high salt concentration that varies in salt concentration. The present invention was achieved as a result of intensive research in order to solve the problems of the prior art as described above. That is, the present invention uses polymerizable vinyl monomers represented by the following general formulas (1), (2), and (3) as one structural unit, and the proportion thereof is (1):
(2):(3)=5-45:5-45:50-90 (mol%) Cationic aggregation mainly composed of a water-soluble polymer (terpolymer) The present invention provides a sludge dewatering method characterized by adding an agent to sludge. general formula, [However, in formula (1), R1 is a lower alkyl group, R2 is a lower alkylene group, R3 and R4 are lower alkyl groups, R5 is a benzyl group, and X is a negative group that forms a salt with ammonium nitrogen] General formula , [However, in formula (2), R1 is a lower alkyl group, R2 is a lower alkylene group, R3 and R4 are a lower alkyl group, R6 is a lower alkyl group, and X is a negative group that forms a salt with ammonium nitrogen.] General formula, [However, R1 in formula (3) is a hydrogen atom or a lower alkyl group] The sludge that is the object of the present invention is a sludge that contains a large amount of inorganic salts, and a typical example thereof is human waste or human waste. There is surplus sludge produced when the digested and desorbed fluid is diluted with seawater and treated with activated sludge, or a mixed sludge of this surplus sludge and other sludge. Other sludges include sludges such as coagulated sedimentation sludge of activated sludge treated water and digested sludge, which can be mixed in any proportion. In the seawater dilution process mentioned above, a large amount of seawater is used, about 20 times the amount after digestion and desorption, and the surplus sludge produced when this diluted digestion and desorption liquid is treated with activated sludge has a high concentration. Contains inorganic salts.
However, this surplus sludge is rarely subjected to dewatering treatment alone, and is often subjected to dewatering treatment as mixed sludge by mixing it with other sludge. When mixing surplus sludge with other sludge, the mixing is performed at an arbitrary ratio, and the concentration of inorganic salts mixed in the mixed sludge also varies. In other words, mixed sludge with a high proportion of surplus sludge has a high concentration of inorganic salts, but mixed sludge with a low proportion of surplus sludge has a low concentration of inorganic salts.
That can be said. Therefore, in order to make the dewatering of mixed sludge stable, it is necessary to take a different approach from dewatering treatment of surplus sludge alone. We endeavored to understand the relationship with the concentration of inorganic salts in the water. The results revealed that the electrical conductivity of sludge containing inorganic salts changes depending on the concentration of inorganic salts. In addition, when the proportion of surplus sludge in the mixed sludge changes, the concentration of inorganic salts contained in the mixed sludge is calculated by subtracting the suspended solids [SS] from the total solids [TS] of the sludge. It can also be interpreted as a change in concentration. Therefore, the concentration of inorganic salts and the concentration of soluble substances in sludge are
This can be interpreted as a change in electrical conductivity. Therefore, even if the mixed sludge has a varying proportion of surplus sludge, the concentration of inorganic salts in the sludge can be instantly determined by measuring the electrical conductivity. The electrical conductivity of mixed sludge is usually more than 2000μS/cm, and as the proportion of surplus sludge increases,
It is more than 30000μS/cm, and it can be easily confirmed that the concentration of inorganic salts is high. Incidentally, if the soluble substance concentration is 0.2%, the electrical conductivity is about 5000 μS/cm, and if it is 2%, it is extremely high at 30000 μS/cm. For this reason, the homopolymer of benzyl chloride quaternized dimethylaminoethyl methacrylate, which is said to be effective for sludge with high salt concentration, or the copolymer of this and acrylamide, has a high electrical conductivity of sludge. sometimes,
We examined whether it is effective. At the same time as this study, methyl chloride 4 of dimethylaminoethyl methacrylate, which shows excellent performance against ordinary sludge, was developed.
We also investigated homopolymers of these compounds and copolymers of them with acrylamide. As a result, when the electrical conductivity is less than 2000μS/cm,
A homopolymer of methyl chloride quaternary of dimethylaminoethyl methacrylate or a copolymer of this with acrylamide exhibits excellent flocculation performance. homopolymers of compounds or
A copolymer of this with acrylamide showed excellent performance. However, the electrical conductivity is 2000~
Between 30,000 μS/cm, none of the above-mentioned types of polymers could exhibit excellent performance when used alone. The cationic polymer that can be used in the present invention has polymerizable vinyl monomers represented by the general formulas (1), (2), and (3) as structural units, and the ratio thereof is (1):( It is a cationic flocculant whose main component is a water-soluble polymer (terpolymer) in the range of 2):(3)=5 to 45:5 to 45:50 to 90 (mol%). The quaternary ammonium salt represented by the general formula (1), which is a constituent unit of this cationic polymer, is generally obtained by quaternizing dialkylaminoalkyl (meth)acrylate with benzyl halide; As already mentioned, homopolymers or copolymers of homopolymers and acrylamide are relatively effective against sludge with high salt concentrations. In addition, the quaternary ammonium salt represented by the general formula (2) is generally obtained by quaternizing dialkylaminoalkyl (meth)acrylate with methyl halide, and a homopolymer thereof or a copolymer of this and acrylamide is used. It is well known that it is effective against ordinary sludge. In other words, the quaternary ammonium salt homopolymer represented by the general formula (1) or the copolymer of this with acrylamide has a high electrical conductivity of sludge.
If it exceeds 30,000 μS/cm, flocs with sufficient size and strength for solid-liquid separation will be formed, the rate of filtration and dewatering of flocculated sludge will be high, and the water content of the resulting dehydrated cake will be low. In addition, the quaternary ammonium salt homopolymer represented by general formula (2) or the copolymer of this with acrylamide has a sufficient size for solid-liquid separation if the electrical conductivity of the sludge is less than 3000 μS/cm. It forms flocs that have both strength and strength, allows rapid filtration and dehydration of flocculated sludge, and results in a low moisture content of the resulting dehydrated cake. However, if the electrical conductivity of the sludge is 3,000 to 30,000 μS/cm, none of the above polymers will form flocs with sufficient size and strength for solid-liquid separation, and the rate of filtration and dewatering of flocculated sludge will be slow. , the resulting dehydrated cake has a high moisture content. Therefore, the electrical conductivity of sludge is 3000~
In the case of 30000 μS/cm, a homopolymer of a quaternary ammonium salt represented by the general formula (1), a copolymer of this with acrylamide, a homopolymer of a quaternary ammonium salt represented by the general formula (2), or
Copolymers of this and acrylamide do not exhibit excellent performance. On the other hand, the polymerizable vinyl monomers represented by the general formulas (1), (2), and (3) are used as structural units, and the ratio is (1):(2):(3)=5 to 45:5~45:50~90
The water-soluble polymer (terpolymer) in the range of (mol%) forms flocs with sufficient size and strength for solid-liquid separation, and the rate of filtration and dewatering of coagulated sludge is fast. The resulting dehydrated cake has a low moisture content and exhibits excellent flocculation performance. The results of these studies will be explained in detail using examples and comparative examples, but the test method is one that has been widely used in sludge dewatering tests, and the effectiveness and effectiveness of dewatering machines used in treatment plants. This is a highly correlated test method and was conducted in the same manner as described in the Examples.
However, the addition rate of each chemical depends on the properties of the sludge [PH,
SS, VSS/SS, electrical conductivity], so it is not limited to the examples, and is 0.5 to 10
% by weight [vs. SS], preferably 1 to 5% by weight [vs.
SS]. In addition, in Examples and Comparative Examples, the floc diameter after stirring is 4 mm or more, which is a desirable size for solid-liquid separation, but it is important to have a dense structure, and the larger the better. isn't it. In addition, the amount of filtrate after 10 seconds is an indicator of the filtration dehydration rate and cake moisture content, and the larger the filtrate amount after 10 seconds, the faster the filtration and dehydration rate, and the lower the cake moisture content. I can say that. Next, the present invention will be specifically explained using examples.
[% and parts indicate weight basis] Example 1 Mixed sludge of surplus sludge and digested sludge produced when the digested and desorbed human waste was diluted with seawater and treated with activated sludge [PH6.6, electrical conductivity 20100 μS] /cm, SS;
11500mg/1, VSS/SS; 83.1%] was weighed out in a 300ml beaker, and 0.2% aqueous solutions of various drugs shown in Table 1 were added in the prescribed amounts shown in Table 1.
The mixture was stirred with a stirrer at 180 rpm for 30 seconds to form a floc. After measuring the floc diameter, the floc-forming sludge was poured into a Buchner funnel lined with a 100-mesh nylon filter cloth, and the amount of filtrate was measured after 10 seconds.Then, filtration was continued and the sludge was collected after filtration. 10g of the sludge was collected, sandwiched between a filter cloth [polyester satin weave] and a sponge, and squeezed for 3 minutes at a pressure of 1.5 kg/cm ² , and then the moisture content of the sludge cake was measured. The results are listed in Table 1. According to Table 1, the floc diameter of the example is larger than that of the comparative example, and the filtration and dewatering speed is faster.
It can be confirmed that the cake moisture content is low. Example 2 Mixed sludge of surplus sludge and digested sludge produced when the digested and desorbed liquid of human waste was diluted with seawater and treated with activated sludge [PH6.8, electrical conductivity 28000μS/cm, SS;
12100mg/1, VSS/SS; 82.9%] was weighed out in a 300ml beaker, and 0.2% aqueous solutions of various drugs shown in Table 2 were added in the prescribed amounts shown in Table 2.
The mixture was stirred with a stirrer at 180 rpm for 30 seconds to form a floc. After measuring the floc diameter, the floc-forming sludge was poured into a Buchner funnel lined with a 100-mesh nylon filter cloth, and the amount of filtrate was measured after 10 seconds.Then, filtration was continued and the sludge was collected after filtration. 10g of the sludge was collected, sandwiched between a filter cloth [polyester satin weave] and a sponge, and squeezed for 3 minutes at a pressure of 1.5 kg/cm ² , and then the moisture content of the sludge cake was measured. The results are listed in Table 2. According to Table 2, the floc diameter of the example is larger than that of the comparative example, and the filtration and dewatering speed is faster.
It can be confirmed that the cake moisture content is low. Example 3 Mixed sludge [PH7.1,
Electrical conductivity 10500μS/cm, SS; 10800mg/1,
Weigh out 200 ml of VSS/SS; 78.8%] into a 300 ml beaker, add the prescribed amounts of 0.2% aqueous solutions of various chemicals listed in Table 3, and use a stirrer to
Stir at 180 rpm for 30 seconds to form a floc.
After measuring the floc diameter, the floc-forming sludge was poured into a Buchner funnel lined with a 100-mesh nylon filter cloth, and the amount of filtrate was measured after 10 seconds.Then, filtration was continued and the sludge was collected after filtration. 10g was collected, sandwiched between a filter cloth [polyester satin weave] and a sponge, and squeezed for 3 minutes at a pressure of 1.5Kg/cm ² .
The cake moisture content of the sludge was measured. The result is the third
It is listed in the table. According to Table 3, the floc diameter of the example is larger than that of the comparative example, and the filtration and dewatering speed is faster.
It can be confirmed that the cake moisture content is low.

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Claims (1)

[Claims] 1. Polymerizable vinyl monomers represented by the following general formulas (1), (2) and (3) are considered as one structural unit, and the proportion thereof is
(1):(2):(3)=5-45:5-45:50-90 [mol%]
A sludge dewatering method characterized by adding to sludge a cationic flocculant whose main component is a water-soluble polymer (terpolymer) consisting of the following: general formula, [However, in formula (1), R1 is a lower alkyl group, R2 is a lower alkylene group, R3 and R4 are lower alkyl groups, R5 is a benzyl group, and X is a negative group that forms a salt with ammonium nitrogen] General formula , [However, in formula (2), R1 is a lower alkyl group, R2 is a lower alkylene group, R3 and R4 are a lower alkyl group, R6 is a lower alkyl group, and X is a negative group that forms a salt with ammonium nitrogen.] General formula, [However, R1 in formula (3) is a hydrogen atom or a lower alkyl group]