JP3185959B2 - Organic sludge dewatering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating organic sludge, and more particularly to a method of combining an anionic organic polymer flocculant and a cationic organic polymer flocculant having a specific molecular structure. By using
The present invention relates to a method for dehydrating organic sludge economically.

[0002]

2. Description of the Related Art Conventionally, as a method for dehydrating organic sludge, a two-liquid formulation in which an anionic organic polymer flocculant is added to and mixed with sludge, and further a cationic organic polymer flocculant is added and mixed to perform flocculation treatment. It has been known. The basic concept of these sludge dewatering methods is that organic sludge has strong anionic properties, but as the amount of hydroxide of aluminum and iron having cationic properties caused by coagulation and sedimentation increases, the anionicity of sludge increases. When the amount of these hydroxides is neutralized and the amount of addition of these hydroxides further increases, the surface of the sludge becomes cationic, so that the cationic hydrophilic protective colloid on the sludge particle surface is destroyed with an anionic flocculant to break down the sludge particles. After coagulating and making the surface of the particles negatively charged, the coagulated particles are to be coagulated with a cationic coagulant.

[0003] The above-mentioned coagulation is caused by a colloidal electrostatic adsorption reaction between a polycation of a hydrophilic colloid and an anionic polymer flocculant. There is a phenomenon of destruction of agglomerates due to agglomeration, and the above-mentioned aggregation has a phenomenon of reinforcing the agglomerates by insolubilization and precipitation due to a reaction between a cationic polymer flocculant and an anionic polymer flocculant. Therefore, due to these peculiar phenomena, the reaction of the two-liquid formulation is different from the reaction of simple low-molecular compounds.

[0004] For these reasons, various proposals have been made to optimize the combination of an anionic polymer flocculant and a cationic polymer flocculant. For example, it is known that an organic polymer flocculant can be reduced by adding and mixing an anionic organic polymer flocculant to sludge and further adding and mixing a cationic organic polymer flocculant and performing flocculation treatment ( JP-B-39-17492) and an anionic organic polymer flocculant having a colloid anion charge of 5.0 meq. / G or more are added and stirred and mixed. Then, as a cationic organic polymer flocculant, the charge amount of colloidal cation at pH 4.0 is 4.0 meq. It has been known that the addition of a sludge / g or more is effective in dehydrating organic sludge including coagulated sediment sludge (JP-A-61-25700). A combination of an anionic organic polymer coagulant and a cationic organic polymer coagulant or a cationic inorganic coagulant (Japanese Patent Laid-Open No. 61-2570).
No. 0) has been proposed. Further, a cationic organic polymer flocculant containing an amidine group is known as a cationic organic polymer flocculant (JP-A-5-1925).
No. 13).

[0005]

However, according to the conventionally known two-liquid formulation, the strength of the floc is insufficient, so that when the aggregate is mechanically dewatered by a screw press or the like, it cannot be dewatered stably. Low processing capacity,
There are problems such as high water content of the treated sludge,
It was not always satisfactory in terms of economy or sludge adaptability. An object of the present invention is to use a two-part formulation to strengthen flocs and to stably dehydrate when aggregates are mechanically dewatered by a screw press or the like. An object of the present invention is to provide a method for dehydrating organic sludge, which has features such as being able to reduce the water content, being excellent in economy and sludge adaptability.

[0006]

Means for Solving the Problems The present inventors have made intensive studies in view of the above problems, and as a result, after adding and mixing an anionic organic polymer flocculant to organic sludge, a cationic organic compound having an amidine structural unit is added. It has been found that the addition of a polymer flocculant exerts an extremely excellent sludge dewatering effect, and has reached the present invention.

That is, the invention of claim 1 of the present invention provides:
(A) After adding and mixing the anionic organic polymer flocculant to the organic sludge, (B) adding and mixing the cationic organic polymer flocculant having an amidine structural unit and performing a flocculation treatment, and obtaining the obtained flocculant. This is a method for dehydrating organic sludge, which is characterized by mechanical dehydration.

[0008] The invention of claim 2 of the present invention relates to (A) 10
After adding and mixing an anionic organic polymer flocculant having an anionic group of 60 mol% to the organic sludge, (B) the repeating unit represented by the following formula (Chem. 3) and / or (Chem. 4) is added to 35 to 90%. The organic sludge dewatering method according to claim 1, wherein the coagulation treatment is performed by adding and mixing a mol% -containing cationic organic polymer coagulant, and the obtained agglomerate is mechanically dewatered.

[0009]

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[0010]

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The anionic organic polymer flocculant according to claim 3 of the present invention, wherein the anionic organic polymer flocculant is dissolved in 1N saline at a concentration of 0.1 g / dl and the reduced viscosity measured at 25 ° C. is 7 dl / g or more. The organic sludge according to claim 1 or 2, wherein the cationic organic polymer flocculant having a reduced viscosity of 2 dl / g or more measured under the same measurement conditions is sequentially added and mixed. Dehydration method.

Hereinafter, the present invention will be described in detail. The anionic organic polymer flocculant of the component (A) used in the sludge dewatering of the present invention is not particularly limited, but an organic polymer flocculant having an anionic group of 10 to 60 mol% in the molecule is preferable. Preferably, a polymer compound having a reduced viscosity of at least 7 dl / g, particularly preferably at least 10 dl / g, dissolved in 1N saline at a concentration of 0.1 g / dl and measured at 25 ° C. is used. Preferred examples of the anionic organic polymer flocculant include a partial hydrolyzate of polyacrylamide, and a copolymer of acrylamide with acrylate and / or acrylamide-2-methylpropanesulfonate.

The constituent units of the anionic organic polymer flocculant of the component (A) used in the present invention include, in addition to the above-mentioned acid amide group, an alkylacrylamide group, a nitrile and a nitrile group within a range that does not adversely affect the flocculating ability. Groups, acid hydrazide groups and any other functional groups.

The component (B) used in the sludge dewatering of the present invention is a cationic organic polymer flocculant having an amidine structural unit, and is preferably represented by the above formulas (3) and / or (4). It contains 35 to 90 mol% of repeating units (amidine units), and more preferably has a reduced viscosity value of 2 dl / g or more measured at 25 ° C. as a 0.1 g / dl solution in 1 N saline. belongs to. The amidine unit represented by the above (Chemical Formula 3) and (Chemical Formula 4) has an amidine structure composed of a five-membered ring, and is used for nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), and the like. In the analysis, it is usually observed equivalently, and (Chem. 3) and (Chem. 4)
Quantified as the total amount of

The amidination reaction of the polymer is shown by the following formula (Formula 5). In the molecular structure of the resulting polymer, two types of repeating units (amidine units) represented by the above (Chemical Formula 3) and (Chemical Formula 4)
And nitrile units and amino units that did not participate in the amidation reaction. Here, the amidine units represented by the above (Chemical Formula 3) and (Chemical Formula 4) are shown as free amino groups.

[0016]

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That is, in order to produce a polymer having an amidine structure as the component (B) used in the present invention, first,
A copolymer consisting of acrylonitrile or methacrylonitrile and a vinyl monomer capable of forming a vinylamine unit by chemical modification after polymerization is synthesized, and then a vinylamine unit is formed by chemical modification, and a ring-closing reaction between a primary amino group and a nitrile group is performed. It is necessary to do.

A repeating unit (Chem. 3) and / or (Chem. 4)
In order to synthesize a polymer having an amidine unit of 35 to 90 mol%, it is necessary that 35 to 65 mol%, preferably 40 to 60 mol% of acrylonitrile or methacrylonitrile is present in the copolymer. .

Vinyl monomers capable of forming vinylamine units by chemical modification after polymerization include N-vinylformamide, N-vinylacetamide, N-vinylphthalimide, N-vinylsuccinimide, N-vinylurethane and the like. Vinyl amides, acrylamide, methacrylamide and the like can be mentioned.

As a method for producing a vinylamine unit from a polymer, in the case of polyN-vinylamides, a solvent addition reaction such as hydrolysis with an acid base, alcoholysis, ammonolysis and the like is used. In the case of polyacrylamide or polymethacrylamide, a Hoffman reaction using a basic hypohalogen compound is used.

In order to efficiently form an amidine structure, a nitrile group must be present at a position adjacent to an amino group of a vinylamine unit. Therefore, a monomer which forms a copolymer having high alternating properties with acrylonitrile or methacrylonitrile must be used. It is preferred to use. N for this purpose
Particular preference is given to using copolymers of -vinylformamide.

The amidination reaction between the nitrile group and the amino group is usually carried out under acidic conditions under an acidic condition, regardless of the production method.
The heating is performed at 150 ° C, preferably 90 to 120 ° C. The repeating unit having an amidine structure produced by the method as described above is represented by the above formula (Chem. 3) and / or (Chem. 4).

In the method for dewatering organic sludge of the present invention,
After adding and mixing the component (A) anionic organic polymer flocculant to the organic sludge, adding and mixing the component (B) cationic organic polymer coagulant, and performing a flocculation treatment, The object of the present invention is achieved by mechanical dehydration. The anionic organic polymer flocculant is used in a weight range of 10 to 10000 ppm with respect to the organic sludge, and is usually used in the form of an aqueous solution of 0.01 to 0.5% by weight. The cationic organic polymer flocculant is used in a weight range of 20 to 20,000 ppm based on the suspension containing the organic sludge, and is usually added in the form of an aqueous solution of 0.1 to 2.5% by weight. In the method of dewatering organic sludge of the present invention, the method of adding the anionic organic polymer flocculant and the cationic organic polymer flocculant is not particularly limited, but the mixing method is not particularly limited. It is preferable that stirring is performed more sufficiently than under addition of the cationic organic polymer flocculant or under strong stirring conditions so that contact with organic sludge is sufficiently performed.

The organic sludge that has been subjected to the coagulation treatment by the method of the present invention forms a strong agglomerate, and is subjected to mechanical dehydration such as compression dehydration by a belt press, rotary screen, screw press, or filter press, centrifugal dehydration, or vacuum filtration. This significantly improves the processing efficiency. In particular, if the dewatered sludge obtained by the method of the present invention is treated by a screw press, it can be dewatered stably, and the treatment capacity of organic sludge can be improved, and the sludge is also excellent in adaptability, and the treated sludge contains water. The rate is reduced and the load for incineration or fertilization can be reduced.

[0025]

The operation of the present invention when the dehydration method of the present invention is performed by the apparatus illustrated in FIGS. 1 and 2 will be described below. 1 and 2 are flocculant mixing tanks having variable speed stirring blades. In each mixing tank, an anionic organic polymer flocculant aqueous solution (concentration 0.1 to 0.2)
% By weight) and an aqueous solution of a cationic organic polymer flocculant (concentration: 0.1 to 0.2% by weight) to aggregate sludge into coarse particles, facilitate solid-liquid separation, and supply to the next preconcentrator. . Reference numeral 5 denotes a sludge pre-concentrator comprising a rotary screen. The coagulated sludge is removed by gravity filtration to remove interstitial water from the sludge and is concentrated to a sludge concentration of 5% by weight or more. The pre-concentrated sludge discharged from the rotary screen 5 is supplied to a screw press 7 via a hopper 6 and dewatered 8 to obtain a dewatered cake 9.

The screw press 7 has a hopper 6 at one upper end of a horizontally long cylinder 12 made of a perforated punching plate having a hole diameter of about 1 mm. A tapered screw 10 is concentrically installed in the cylinder with the small-diameter portion facing one end of the cylinder and the large-diameter portion facing the other end of the cylinder, and is rotationally driven by a motor or the like. A screw 11 whose outer diameter matches the inner diameter of the cylinder 12 is provided on the outer periphery of the screw 10. The screw 11 drives the pre-concentrated sludge supplied to one end in the cylinder by the hopper 6 toward the other end by rotation of the screw. .

As described above, the screw has a taper, and the annular space between the outer periphery of the screw and the inner periphery of the horizontal cylinder gradually narrows from one end to the other end of the horizontal cylinder. Therefore, the pre-concentrated sludge supplied into one end of the horizontal cylinder moves toward the other end at a low pressure while dewatering water through the hole of the cylinder at one end side where the current gap is wide, and at the middle part of the horizontal cylinder, When the gap is narrowed to some extent, the pressure is moderately increased and dehydration 8 is similarly performed. At the other end, dehydration 8 is similarly performed with the highest pressurization. And is discharged.

If the strength of the coagulated sludge supplied to the screw press is weak, the coagulation is broken by the shearing force and slips, and dehydration becomes impossible. According to the dewatering method of the present invention, the strength of the entire aggregate is increased, and the aggregate is not broken by the pressure in the screw press. Therefore, even if the properties of the sludge are slightly changed, the screw press is subjected to an ideal pressure increase. In addition, it is possible to stably dehydrate aggregates by maximizing its function and greatly improve sludge dewatering efficiency.

[0029]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Table 1 shows the compositions of the anionic organic polymer flocculants (A1 to A6) and the cationic organic polymer flocculants (C1 to C4) used in this test.

[0030]

[Table 1]

(Dehydration test 1) Mixed sludge of mixed raw sludge generated from municipal sewage and tertiary treated sludge (pH 6.0, SS1
6.7 g / l) to perform a dehydration test. In the dehydration test, 200 ml of the above-mentioned sludge was weighed into a glass beaker having a capacity of 300 ml, and a predetermined amount of anionic organic polymer flocculants (A1 to A6) dissolved in a polymer concentration of 0.1% was added thereto. The mixture was changed 20 times and mixed by stirring. A predetermined amount of a cationic organic polymer flocculant (C1 to C4) dissolved at a polymer concentration of 0.2% was added to the pretreated sludge, and the mixture was stirred and mixed by transferring between beakers 20 times, and the mixed sludge was obtained. Was gravity filtered through a 60-mesh nylon filter cloth, and the filtrate amount after 5 seconds was measured. The sludge after gravity filtration is sandwiched between two pieces of nylon filter cloth (# 202) manufactured by Nakao Filter Co., Ltd., and further sandwiched between polyvinyl chloride plates having water drainage grooves, and squeezed at a pressure of 5 kg / cm ² for 5 minutes to form a cake. Was measured for water content. Table 2 summarizes the results. Test numbers 1 to 8 are examples of the present invention, and test numbers 9 to 17 are comparative examples.

[0032]

[Table 2]

(Dehydration test 2) Mixed sludge of mixed raw sludge generated from municipal sewage and tertiary treated sludge (pH 6.0, SS1)
(6.9 g / l) to perform a dehydration test. FIG. 1 shows the configuration of the sludge dewatering apparatus used in this test. Reference numerals 1 and 2 denote flocculant mixing tanks having variable-speed stirring blades. Standard mixing conditions are a residence time of 1.5 minutes in each tank and a peripheral speed of the stirring blade of 1 m / sec. In each mixing tank, an organic polymer flocculant aqueous solution (concentration: 0.1 to 0.2% by weight) is added from the chemical injection pipes 3 and 4, and the sludge is flocculated into coarse particles to facilitate the solid-liquid separation to prepare the next preliminary liquid. Supply to the concentrator. Reference numeral 5 denotes a pre-concentrator for sludge comprising a rotary screen having a mesh size of 40 mesh. The coagulated sludge is concentrated to 5% by weight or more of sludge concentration by removing pore water by gravity filtration. The pre-concentrated sludge discharged from the rotary screen 5 is supplied to a screw press 7 via a hopper 6. Chemical injection pipe 3 in FIG.
More anionic organic polymer flocculant aqueous solution was added, and after stirring and mixing under the above conditions, a cationic organic polymer flocculant aqueous solution was added from the chemical injection pipe 4 in the flocculant mixing tank 2,
Agglomerated sludge obtained by stirring and mixing was gravity filtered by a rotary screen, and then dehydrated by a screw press. Table 3 summarizes the results. Test numbers 18 to 21 are examples of the present invention, and test numbers 22 to 23 are comparative examples.

[0034]

[Table 3]

[0035]

The present invention relates to a method for dewatering organic sludge. Since the coagulated organic sludge forms a strong agglomerate, it can be used for press dewatering such as a belt press, a rotary screen, a screw press and a filter press. By performing mechanical dehydration such as centrifugal dehydration and vacuum filtration, the processing efficiency can be remarkably improved. In particular, if the dewatered sludge obtained by the method of the present invention is treated by a screw press, it can be dewatered stably, and the treatment capacity of organic sludge can be improved, and the sludge is also excellent in adaptability, and the treated sludge contains water. Since the rate is reduced and the load for incineration or fertilization can be reduced, it is excellent in economical efficiency and has high industrial utility value.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of steps for carrying out the method of the present invention.

FIG. 2 is an explanatory sectional view of a screw press.

[Explanation of symbols]

 1, 2 Coagulant mixing tank 3, 4 Chemical injection pipe 5 Rotary screen 6 Hopper 7 Screw press 8 Water 9 Dehydration cake 10 Screw 11 Screw 12 Cylindrical

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 11/14

Claims (3)

(57) [Claims] (1) After adding and mixing (A) an anionic organic polymer flocculant to an organic sludge, (B) adding and mixing a cationic organic polymer flocculant having an amidine structural unit and performing a flocculation treatment, A method for dewatering organic sludge, comprising mechanically dewatering the obtained aggregate. 2. After adding (A) an anionic organic polymer flocculant having an anionic group of 10 to 60 mol% to an organic sludge and mixing, (B) the following formula (1) and / or (2) )
2. A coagulation treatment is carried out by adding and mixing a cationic organic polymer coagulant containing 35 to 90 mol% of a repeating unit represented by the formula, and the obtained agglomerate is subjected to mechanical dehydration. How to dewater organic sludge. Embedded image Embedded image 3. An anionic organic polymer flocculant dissolved in 1N saline at a concentration of 0.1 g / dl and having a reduced viscosity of 7 dl / g or more measured at 25 ° C., and under the same measurement conditions as those described above. 3. The method for dewatering organic sludge according to claim 1, wherein said cationic organic polymer flocculant having a reduced viscosity of not less than 2 dl / g is sequentially added and mixed.