JP2014155898A - Sludge dehydration treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge dehydration treatment method which targets sludge having an electric conductivity of 0.5 to 50 mS/cm, a fiber content of 0.5 to 10%/TS and a volatile total solid (VTS) in the range of 5 to 65%/TS, and enables a flocculated flock to be formed, the flocculated flock having enough particle diameter and strength stably for a long period of time and therefore having excellent draining and dewaterability, consequently can provide separated liquid having fully little SS amount and a dewatered cake having low water content.SOLUTION: There is provided the sludge dehydration treatment method using a sludge dewatering agent which is composed of a mixture of a specific amidine-based cationic polymer (A), an amphoteric polymer (B) and a non-amidine-based cationic polymer (C), and which has the percentage of the amidine-based cationic polymer (A) of 10 to 50 mass%, the percentage of the amphoteric polymer of 10 to 40 mass% and the percentage of the non-amidine-based cationic polymer (C) of 10 to 80 mass% based on the total mass amount of each polymer.

Description

  The present invention relates to a sludge dewatering treatment method, and more particularly to a sludge dewatering treatment method for sludge having a specific property in which agglomerated flocs do not grow and only fine agglomerated flocs can be formed with conventional sludge dewatering agents.

  Conventionally, sludge generated from sewage treatment plants, human waste treatment plants, and various industrial wastewater treatment facilities cannot be dehydrated as it is, so usually a dehydrator such as a screw press, screw decanter or belt press with a polymer flocculant added. The machine is dehydrated. In general, the sludge dewatering method using a polymer flocculant includes (1) a method using a cationic polymer flocculant alone such as dimethylaminoethyl (meth) acrylate quaternary salt, and (2) as described above. There are a method in which a cationic polymer flocculant and an anionic polymer flocculant are used in combination, and (3) a method in which an inorganic flocculant and an amphoteric polymer flocculant are used in combination.

  However, in recent years, sludge has become difficult to dehydrate due to advanced water treatment, changes in the properties of wastewater to be treated, and diversification. For example, sludge (surplus, coagulation sedimentation, floating scum, etc.) generated from wastewater treatment facilities such as the resin / textile industry, dyeing industry, and food industry contains a large amount of inorganic salts, oils, and surfactants. . In addition, due to diversification of wastewater treatment targets and changes in the wastewater treatment environment, the properties of sludge constantly change. In sludge generated from industrial wastewater treatment facilities, surplus sludge generated by biological treatment is particularly large, and the main component of surplus sludge is microbial cells, and moisture contained in the cells cannot be dehydrated by mechanical methods such as pressing. Therefore, the sludge properties are generally difficult to dehydrate. Therefore, in the conventional dewatering method using the flocculant as mentioned above, the strength and water drainage of the obtained flocs are insufficient, and when the sludge is dewatered, the sludge treatment amount is reduced and the water content of the dehydrated cake is reduced. There were problems such as rising.

  On the other hand, amidine-based cationic polymers containing polyamidine structural units have a high cation density, so they are particularly excellent in coagulation and dehydration against sludge generated from industrial wastewater treatment facilities (excess, coagulation sedimentation, floating scum, etc.). It is known to exert. In general, surplus sludge from industrial wastewater treatment is degraded by microorganisms, and therefore the sludge has a low fiber content and hardly dehydrates. For such a hardly dewatering sludge, a blended flocculant of an amidine-based cationic polymer and various drugs has been proposed. For example, a sludge dewatering method using a combination of an amidine-based cationic polymer, a specific amphoteric polymer and a methacrylate-based cationic polymer (Patent Document 1), or a combination of an amidine-based cationic polymer and two or more specific amphoteric polymers. A sludge dewatering method to be used (Patent Document 2) has been proposed. However, these are intended for the treatment of sludge with low fiber content and hardly dewatering, but depending on the state of the sludge, the effect is insufficient, and surplus generated from the biological treatment facility of industrial factory wastewater treatment. The demand for reducing the moisture content of dewatered cake of sludge has not been met.

  In surplus sludge for industrial wastewater treatment, the content of inorganic salts and sludge organic matter always changes depending on the environment and operating conditions for biological treatment. In particular, for sludge containing a large amount of inorganic salt and septic organic matter produced by anaerobic treatment or sludge rot, the use of amidine-based water-soluble polymer alone forms only aggregate flocs with a small particle size. The high dehydration characteristic of amidine-based cationic polymers tends not to be observed. A sludge dewatering method (Patent Document 3) has been proposed that improves coagulation by using a combination of an amidine-based cationic polymer and a specific anionic polymer for sludge containing a large amount of inorganic components. However, the inorganic components here are dispersed in the sludge as suspended matter and have little influence on the cohesiveness. Therefore, the sludge contains a large amount of inorganic salts and septic organic substances as described above. As a result, no floc growth is observed, and the effect of improving the cohesiveness is insufficient.

JP 2002-177709 A JP 2004-209413 A JP 2000-176499 A

  The characteristics of sludge with a small effect of the amidine-based cationic polymer can be seen from the analysis value of the sludge. The electrical conductivity of the sludge is 0.5 to 50 mS / cm, the fiber content is 0.5 to 10% / TS, and The ignition loss (hereinafter referred to as VTS) is 5 to 65% / TS. For such sludge species, the amidine-based cationic polymer alone can form only extremely small flocs, and particularly with a dehydrator such as a screw press, there is a lot of leakage and good dehydration cannot be expected. An object of the present invention is to form a coagulated floc having a sufficient particle size and strength stably for a long period of time as a sludge dewatering method having the above-described characteristics, and thus having good water drainage and high dewaterability. Therefore, an object of the present invention is to provide a sludge dewatering treatment method in which a separated liquid with a small amount of SS and a dehydrated cake with a low water content can be obtained.

  In view of the above circumstances, the present inventors have obtained the following knowledge as a result of earnest search. That is, regarding the sludge having the above-mentioned properties, the amidine-based cationic polymer efficiently adsorbs to the anionic-amphoteric organic polymer component such as a suspension in the sludge, but it further binds the amphoteric polymer and the complex. The reactivity of the process of forming and growing into agglomerated flocs depends on the viscosity of the amphoteric polymer. A 1 V sodium chloride aqueous solution containing 0.1 g / dl of an amphoteric polymer is used in combination with a high-viscosity amphoteric polymer and amidine-based cationic polymer whose reduced viscosity at 25 ° C. (hereinafter referred to as reduced viscosity) exceeds 10.0 dl / g. In some cases, in the stage of growing into an aggregated floc, self-crosslinking immediately after a part of the functional group showing the cationic property of the amidine-based cationic polymer and a part of the functional group showing the anionic property of the high-viscosity amphoteric polymer reacts. Since it is insolubilized, the reaction is suppressed. On the other hand, when a low-viscosity amphoteric polymer having a reduced viscosity of 10.0 dl / g or less is used in combination with an amidine-based cationic polymer, insolubility due to self-crosslinking is small in the process of agglomeration floc growth, and the reaction proceeds efficiently. The floc does not contain moisture, and a floc floc having excellent strength is formed, and the dewatering performance of the sludge dewatering agent in the sludge dewatering treatment is improved.

  The present invention has been achieved based on the above findings, and the gist thereof is that the electrical conductivity is 0.5 to 50 mS / cm, the fiber content is 0.5 to 10% / TS, and the VTS is 5 In the sludge dewatering method of adding a sludge dehydrating agent to sludge in the range of ~ 65% / TS, the amidine cationic polymer (A), the amphoteric polymer (B) and the non-amidine cation described below The ratio of the amidine-based cationic polymer (A) to the total mass of each polymer is 10 to 50% by mass, the ratio of the amphoteric polymer (B) is 10 to 40% by mass, the non-amidine type The present invention resides in a sludge dewatering treatment method using a sludge dewatering agent having a cationic polymer (C) ratio of 10 to 80% by mass.

（ただし、一般式（１）、（２）中、Ｒ^１、Ｒ^２はそれぞれ独立に水素原子又はメチル基であり、Ｘ⁻は陰イオンである。） [Amidine-based cationic polymer (A)]
An amidine-based cationic polymer containing an amidine structural unit represented by the following general formula (1) and / or the following general formula (2).

(However, in general formula (1), (2), R < ¹ >, R < ² > is a hydrogen atom or a methyl group each independently, and X < ^- > is an anion.)

（式中、Ｒ^３は、水素原子又はメチル基であり、Ｒ^４及びＲ^５は、水素原子又は炭素数が１〜４のアルキル基であり、Ｒ^６は、炭素数が１〜４のアルキル基又はベンジル基であり、Ｙは、酸素原子又はＮＨであり、Ｚ⁻は、Ｃｌ⁻、Ｂｒ⁻、又は１／２ＳＯ_４ ^２−であり、ｎは１〜３の整数である。） [Amphoteric polymer (B)]
1 standard including a cationic structural unit represented by the following general formula (3), at least one amphoteric polymer containing an anionic structural unit and a nonionic structural unit, and 0.1 g / dl of the amphoteric polymer An amphoteric polymer having a reduced viscosity at 25 ° C. of a sodium chloride aqueous solution of 0.1 to 10.0 dl / g.

(Wherein R ³ is a hydrogen atom or a methyl group, R ⁴ and R ⁵ are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ is an alkyl having 1 to 4 carbon atoms. Y is an oxygen atom or NH, Z ⁻ is Cl ⁻ , Br ⁻ , or 1 / 2SO ₄ ²⁻ , and n is an integer of 1 to 3).

[Non-amidine cationic polymer (C)]
The at least 1 type non-amidine type cationic polymer containing the cationic structural unit represented by the said General formula (3), and a nonionic structural unit.

  According to the sludge dewatering method of the present invention, sludge having a specific property that is difficult to dewater with the prior art (the electric conductivity is 0.5 to 50 mS / cm, and the fiber content is 0.5 to 10% / TS. And sludge with a VTS in the range of 5 to 65% / TS), which is stable for a long period of time and has a sufficient particle size and strength. Therefore, a separated liquid with a small amount of SS and a dehydrated cake with a low water content can be obtained.

  Hereinafter, the present invention will be described in detail.

<Sludge dewatering agent>
First, the sludge dehydrating agent used in the present invention will be described. In the present invention, a specific amidine-based cationic polymer (A), a specific amphoteric polymer (B), and a non-amidine-based cationic polymer (C) are used in combination.

  The amidine-based cationic polymer (A) contains an amidine structural unit represented by the general formula (1) and / or the general formula (2). The content of the amidine structural unit in the amidine-based cationic polymer (A) is usually 30 to 90 mol%, preferably 40 to 80 mol%. If the content is from 30 to 90 mol%, an agglomerated floc with good drainage is formed.

  The production method of the amidine-based cationic polymer (A) is not particularly limited, but an ethylenically unsaturated monomer having a primary amino group or a substituted amino group capable of forming a primary amino group by a conversion reaction, and acrylonitrile or Examples thereof include a method in which a copolymer with nitriles such as methacrylonitrile is produced, and a cyano group and a primary amino group in the copolymer are acidified to be amidined.

As the ethylenically unsaturated monomers, the general formula _CH 2 ⁼ CR 7 -NHCOR ⁸ (wherein, ^{R 7} is a hydrogen atom or a methyl group, ^{R 8} represents an alkyl group or a hydrogen atom having 1 to 4 carbon atoms. ) Is preferred. In the copolymer, substituted amino groups derived from such compounds are easily converted to primary amino groups by hydrolysis or alcoholysis. Furthermore, this primary amino group reacts with an adjacent cyano group to be amidineated. Specific examples of the compound represented by the above general formula include N-vinylformamide (R ⁷ = H, R ⁸ = H), N-vinylacetamide (R ⁷ = H, R ⁸ = CH ₃ ) and the like. It is done.

  The use ratio (molar ratio) of the ethylenically unsaturated monomer and the nitrile in the copolymer is usually 20:80 to 80:20, preferably 40:60 to 60:40.

  Most typically, the amidine-based cationic polymer (A) is obtained by copolymerizing N-vinylformamide and acrylonitrile as described above, and heating the resulting copolymer in the presence of hydrochloric acid for hydrolysis. It is produced by forming an amidine structural unit from a cyano group adjacent to the produced amino group. In this case, the amidine-based cationic polymer (A) having various compositions can be obtained by selecting the molar ratio of N-vinylformamide and acrylonitrile to be used for copolymerization and the amidination conditions of the copolymer. The amidine-based cationic polymer (A) may be selected from commercially available products.

  The amphoteric polymer (B) is basically a polymer containing a structural unit represented by the general formula (3) as a cationic structural unit. Examples of the cationic structural unit include a cationic structural unit derived from an amine salt of a dialkylaminoalkyl (meth) acrylate or an alkyl chloride quaternary compound that is a cationic monomer, or an amine salt of a dialkylaminoalkyl (meth) acrylamide, Examples include cationic structural units derived from alkyl chloride quaternized compounds. In particular, a quaternary dialkylaminoalkyl (meth) acrylate alkyl chloride is preferable. As the monomer, one type of cationic monomer may be used alone, or two or more types may be used in combination.

  The content of the cationic structural unit in the amphoteric polymer (B) is usually 25 to 80 mol%, preferably 25 to 55 mol%. The amphoteric polymer (B) containing such a constitutional unit can form an agglomerated floc having good water drainage and strong floc strength.

  The amphoteric polymer (B) is a polymer containing an anionic structural unit, and examples of the structural unit having a functional group exhibiting anionicity include (meth) acrylic acid and 2-acrylamido-2methylpropanesulfonic acid. Of these, acrylic acid is preferred. The content of the anionic structural unit in the amphoteric polymer (B) is usually 5 to 75 mol%, preferably 10 to 55 mol%.

  The amphoteric polymer (B) is a polymer containing a nonionic structural unit in addition to the cationic structural unit and the anionic structural unit, but the structural unit having a functional group exhibiting nonionicity is (meth). Examples include acrylamide. The content of the nonionic structural unit in the amphoteric polymer (B) is usually 1 to 70 mol% or less.

  The physical property value indicating the viscosity of the amphoteric polymer (B) is that the 1 V sodium chloride aqueous solution containing 0.1 g / dl of the amphoteric polymer has a reduced viscosity at 25 ° C. of 0.1 to 10.0 dl / g. 0.0 to 7.5 dl / g is preferable. When the reduced viscosity is from 0.1 to 10.0 dl / g, it is possible to form an agglomerated floc having good water drainage and high dewaterability.

  In the amphoteric polymer (B), when the content of the anionic structural unit contained in the amphoteric polymer is Ma mol% and the content of the cationic structural unit is Mc mol%, the content of the anionic structural unit and the cationic structural unit is The ratio Ma / Mc (hereinafter referred to as “A / C”) is usually 0.35 to 1.65, preferably 0.50 to 1.30. The amphoteric polymer (B) having an A / C of 0.35 to 1.65 has good drainage and can form agglomerated flocs with stronger floc strength, so that the dewatering performance is easily improved.

  The non-amidine cationic polymer (C) is basically a polymer containing a structural unit represented by the general formula (3) as a cationic structural unit. Examples of the cationic structural unit include a cationic structural unit derived from an amine salt of a dialkylaminoalkyl (meth) acrylate or an alkyl chloride quaternary compound that is a cationic monomer, or an amine salt of a dialkylaminoalkyl (meth) acrylamide, Examples include cationic structural units derived from alkyl chloride quaternized compounds. In particular, a quaternary dialkylaminoalkyl (meth) acrylate alkyl chloride is preferable. As the monomer, one type of cationic monomer may be used alone, or two or more types may be used in combination.

  The content of the cationic structural unit in the non-amidine cationic polymer (C) is usually 30 to 90 mol%, preferably 50 to 80 mol%. In addition, as the cationic structural unit, at least 30 to 90 mol% of a methyl chloride quaternary salt monomer structural unit of dimethylaminoethyl acrylate and a methyl chloride quaternary salt of dimethylaminoethyl methacrylate as a proportion of all the structural units. It is preferable to contain 0-30 mol% of monomer structural units. The non-amidine cationic polymer (C) containing such a constitutional unit can form agglomerated flocs with good water drainage and strong floc strength.

  The non-amidine cationic polymer (C) is a polymer containing a nonionic structural unit, and examples of the nonionic structural unit include (meth) acrylamide. The content of the nonionic structural unit in the nonamidine-based cationic polymer (C) is usually 1 to 70 mol% or less.

  When an anionic or amphoteric organic polymer component is present in sludge, such as organic sludge, the use of amidine-based cationic polymers tends to form aggregated flocs. This is because the component reacts with the amidine-based cationic polymer to form a complex. However, in the sludge properties targeted by the present invention, the anionic-amphoteric organic polymer component in the sludge is decomposed by the microorganisms in the biological treatment process, and the content is reduced, so that the formation of complex is small, Aggregated floc cannot grow. When the agglomeration function is replaced with an amphoteric polymer, the molecular weight is usually large, and when an amphoteric polymer having a high viscosity is used, the sludge particles have a high crosslinking ability and often act effectively.

  However, in the case of the sludge targeted by the present invention, on the contrary, the amphoteric polymer having a relatively low molecular weight and low viscosity has a higher ability to form agglomerated floc. This is probably because the diffusion rate and reaction rate of molecules are more important factors than the spread of molecular chains. Therefore, when the reduced viscosity of the amphoteric polymer (B) is in the range of 0.1 to 10.0 g / dl, it is possible to form an agglomerated floc that has good water drainage and high floc strength. When the reduced viscosity is larger than the above, the reaction rate becomes slow, the reaction of the growth process of the aggregated floc is suppressed by the insolubilization by the self-crosslinking, and the large aggregated floc cannot be formed. Small, small floc flocs produced, low strength, low filtration performance, high moisture content of dehydrated cake.

  Further, the sludge targeted by the present invention contains a large amount of inorganic salts, and these inorganic salts are often mixed as 1 to 3 anions, that is, anionic components in the sludge. The amidine-based cationic polymer reacts with anionic components derived from these inorganic salts to neutralize the charge, so that an aggregated floc having good water drainage and high dehydrating property can be formed. However, the complex produced by the adsorption of the amidine-based cationic polymer (A) and the anionic-amphoteric organic polymer component in the sludge and the amphoteric polymer (B) by the reaction with the anionic component derived from the inorganic salt is further provided. Since the function of cross-linking adsorption necessary for growing into agglomerated flocs is reduced, if the content of inorganic salt in the sludge increases, a large amount of addition is required to form coarse agglomerated flocs. On the other hand, the non-amidine-based cationic polymer (C) has a lower reactivity with the anionic component derived from the inorganic salt than the amidine-based cationic polymer (A), and is not easily affected by the crosslinking adsorption by the inorganic salt. Therefore, by using the non-amidine-based cationic polymer (C) in combination, the cross-linking adsorption during the growth process is improved to the above-mentioned aggregated floc, and an aggregated floc having a superior strength can be formed with a small addition amount.

  The method for producing the amphoteric polymer (B) and the non-amidine cationic polymer (C) is not particularly limited, but a monomer aqueous solution in which the above monomer is dissolved in water is made into a uniform sheet and visible using a photoinitiator. Aqueous photopolymerization method for copolymerization by irradiation with light or ultraviolet light, adiabatic polymerization to obtain an aqueous gel polymer by adding one or more initiators to an aqueous monomer solution, and an aqueous monomer solution in a nonaqueous solvent Methods such as dispersion polymerization for polymerization by dispersion and emulsion polymerization for polymerization by emulsifying an aqueous monomer solution using an emulsifier in a non-aqueous solvent can be freely selected. In the case of photopolymerization, adiabatic polymerization, etc., the polymer is obtained as an aqueous gel, and therefore, it is preferably pulverized and dried to form a powder.

  The method for adjusting the reduced viscosity of the amphoteric polymer (B) is not particularly limited, but is appropriately determined in consideration of the viscosity of the polymer for producing conditions such as polymerization time, polymerization temperature, and chain transfer agent addition amount in the production process. Select. In the present invention, the reduced viscosity is preferably adjusted according to the condition of the chain transfer agent addition amount. The type of chain transfer agent is not particularly limited, and examples thereof include thiol compounds such as mercaptoethanol and mercaptopropionic acid, and reducing inorganic salts such as sodium sulfite, sodium bisulfite, and sodium hypophosphite. Of these, sodium hypophosphite is particularly preferable. The addition amount of the chain transfer agent is usually about 1 to 3000 ppm with respect to all raw materials monomers.

  The sludge dehydrating agent used in the present invention is composed of an amidine-based cationic polymer (A), an amphoteric polymer (B), and a non-amidine-based cationic polymer (C). In order to form an aggregated floc, it is necessary to use the amidine-based cationic polymer (A), the amphoteric polymer (B), and the non-amidine-based cationic polymer (C) at a predetermined mixing ratio. That is, the mixing ratio of the amidine-based cationic polymer (A) to the total mass of each polymer is 10 to 50% by mass, the ratio of the amphoteric polymer (B) is 10 to 40% by mass, and the non-amidine-based cationic polymer ( The ratio of C) is 10 to 80% by mass. Such a mixing ratio is more efficient because it can form agglomerated flocs with excellent strength.

<Sludge>
Next, the target sludge of the present invention will be described. The target sludge of the present invention is a sludge having an electric conductivity of 0.5 to 50 mS / cm, a fiber content of 0.5 to 10% / TS, and a VTS of 5 to 65%. Specifically, surplus sludge, coagulated sediment sludge, pressurized scum sludge generated from wastewater treatment facilities such as chemistry (dyeing, resin, fiber, chemical products), pharmaceuticals, food industry, industrial waste treatment plant, landfill disposal site, etc. Etc.

  Inorganic salts contained in sludge having such properties include inorganic salts contained in large amounts in wastewater before being supplied to wastewater treatment facilities, inorganic salts produced by the decomposition of organic components by biological treatment, and coagulation precipitation. And inorganic salts generated due to the use of a large amount of an inorganic agent such as an inorganic coagulant in wastewater treatment such as pressure levitation. Examples of the inorganic salt in the sludge include sulfates, phosphates, silicates and the like, but are not particularly limited. The electrical conductivity of sludge is an indicator of the amount of inorganic salt contained in the sludge. The sludge targeted by the present invention contains a large amount of inorganic salt and has a high electrical conductivity. Yes, and the value is as described above, preferably 3.0 to 30 mS / cm.

  In the case of surplus sludge generated from wastewater treatment facilities, organic polymer components derived from living organisms contained in sludge such as fibers are decomposed by the progress of biotreatment or sludge decay, and the content decreases. The value of is in a low state, and the value is as described above, but is preferably 0.5 to 5% / TS.

  In general, there are anionic and amphoteric organic polymer components in sludge, and the amidine-based cationic polymer (A) is strongly adsorbed to these components to form a complex, which is adsorbed on the sludge particles and cross-linked. By doing so, an aggregated floc is formed. Sludge VTS is an indicator of anionic-amphoteric organic polymer components in this sludge. The lower the VTS value, the less the content of components that can react with the amidine-based cationic polymer (A). It is thought that. In the sludge properties targeted by the present invention, the anionic-amphoteric organic polymer components in the sludge are decomposed by the microorganisms in the process of biological treatment, and therefore the VTS value of the sludge tends to be low. Thus, it is considered that the combined use of the amidine-based cationic polymer (A) and the amphoteric polymer (B) capable of substituting the function of forming a complex is more effective for sludge having a low VTS. The VTS of the sludge targeted by the present invention is 5 to 65% / TS, preferably 5 to 50% / TS. By adding the present sludge dehydrating agent to the sludge, it is possible to form an agglomerated floc with good drainage and superior strength.

  The electrical conductivity indicates the amount of various ions and salts in the sludge. The electrical conductivity is measured in accordance with the Japanese Industrial Standards Committee database “JIS, K0102, Factory Wastewater Test Method”.

The fiber content is specifically measured by the following procedure.
(I) 100 ml of sludge is filtered through a 200-mesh sieve, and the residue is thoroughly washed.
(Ii) Dry at 105 ° C. for 12 hours and weigh.
(Iii) Then, it heats at 600 degreeC for 2 hours, weighs after ashing.
(Iv) A value obtained by subtracting the value after ashing from the value after drying at 105 ° C. (fiber amount in sludge) (g) is calculated.
(V) 100 ml of the original sludge is directly dried at 105 ° C. for 6 hours, and the remaining amount (total solid content) (g) is weighed.
(Vi) The fiber content (% / TS) is calculated by the following formula.

The VTS is specifically measured by the following procedure.
(I) 100 ml of sludge is directly dried at 105 ° C. for 6 hours, and the remaining amount (total solid content) (g) is weighed.
(Ii) Thereafter, the mixture is heated at 600 ° C. for 2 hours, and the remaining amount after incineration (incineration weight) (g) is weighed.
(Iii) Calculate the ignition loss (VTS) (% / TS) by the following formula.

<Sludge dewatering method>
Next, the sludge dewatering method of the present invention will be described. In the present invention, known methods can be applied as a method for adding a sludge dewatering agent to sludge and a method for forming agglomerated floc.

  As a method for adding the sludge dewatering agent, it is preferable that the sludge dewatering agent is dissolved in water at a concentration of 0.05 to 0.5% by mass and then added to the sludge. Moreover, it is preferable to add a sludge dehydrating agent as a 1 agent type | mold chemical | medical agent which mixed the amidine-type cationic polymer (A), the amphoteric polymer (B), and the non-amidine-type cationic polymer (C). In some cases, the sludge dehydrating agent may be added to the sludge in a powder form. Further, an acidic substance may be added in order to improve the solubility of the sludge dewatering agent in water. Examples of the acidic substance include sulfamic acid.

  After the aggregation is formed, the sludge dewatering treatment can be completed by dehydrating the aggregated flocs using a dehydrator and obtaining a dehydrated cake. Examples of dehydrators include filter press dehydrators, screw press dehydrators, press-fit screw press dehydrators, vacuum dehydrators, belt press dehydrators, centrifugal dehydrators, multiple disk dehydrators, etc. In particular, the effect of the present invention is remarkable in a screw press type dehydrator or a centrifugal type dehydrator whose dehydration effect is greatly influenced by the floc diameter of sludge.

  The amount of sludge dehydrating agent varies depending on the properties and concentration of the sludge and cannot be generally specified, but as a rough guideline, it is usually 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the dried sludge solids, Preferably it is 0.5-2.0 mass parts. If the added amount of the sludge dehydrating agent is 0.1 parts by mass or more, agglomerated flocs having a sufficient particle size and strength are easily formed. Moreover, if the amount of sludge dehydrating agent added is 5.0 parts by mass or less, the particle size of the aggregated floc formed by the excess sludge dehydrating agent is reduced, the processing speed is reduced, or the dehydrated cake It is easy to suppress that the moisture content of becomes high.

  In the present invention, an inorganic coagulant and / or an organic coagulant (hereinafter collectively referred to simply as “coagulant”) may be used in combination with the sludge dewatering agent. Even if the sludge dehydrating agent in the previous period is used in combination with a coagulant, it can sufficiently exert the dewatering effect on the sludge. Examples of the inorganic coagulant include sulfuric acid band, polyaluminum chloride, ferric chloride, ferrous sulfate, ferric sulfate, polyiron (polyiron sulfate, polyiron chloride, etc.). Examples of the organic coagulant include polyamine, polydiallyldimethylammonium chloride, alkyl chloride quaternary salt of polydialkylaminoalkyl methacrylate, and cationic surfactant.

  The timing of adding the coagulant is not particularly limited, but it is preferably added in the step before adding the sludge dewatering agent. The addition amount of the coagulant is usually 5 to 3000 parts by mass with respect to 100 parts by mass of the present sludge dehydrating agent. When the addition amount of the coagulant is less than 5 parts by mass, the effect of using the coagulant is difficult to obtain, and depending on the sludge, the performance of the present sludge dehydrating agent is difficult to be exhibited. Moreover, when the addition amount of a coagulant exceeds 3000 mass parts, especially in an inorganic coagulant, there exists a tendency for the moisture content of a dewatering cake to increase with the increase in addition amount.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not limited by the following description, unless the summary is exceeded. Note that “%” in this example represents “% by mass” unless otherwise specified. About each polymer obtained by the following manufacture examples, the reduced viscosity shown below was measured. For the measurement, a powdery sludge dehydrating agent was used.

[Measurement of reduced viscosity]
It measured with the Ostwald viscometer at 25 degreeC as a 0.1g / dl solution in 1N sodium chloride aqueous solution.

The raw materials used in this example are shown below.
[monomer]
(I) Cationic monomer:
(A) N, N-dimethylaminoethyl acrylate methyl chloride quaternary salt (hereinafter referred to as “DME”), manufactured by Osaka Organic Chemical Industry Co., Ltd., 80% aqueous solution (b) N, N-dimethylaminoethyl methacrylate methyl chloride 4 Grade salt (hereinafter referred to as “DMC”), manufactured by Osaka Organic Chemical Industry Co., Ltd., 80% aqueous solution (ii) anionic monomer:
Acrylic acid (hereinafter referred to as “AA”), manufactured by Mitsubishi Chemical Corporation, 50% aqueous solution (iii) nonionic monomer:
(A) Acrylamide (hereinafter referred to as “AAM”), manufactured by Daianitrix, 50% aqueous solution (b) Acrylonitrile (hereinafter referred to as “AN”), manufactured by Diaanitrix, 99% purity
(C) N-vinylformamide (hereinafter referred to as “NVF”), manufactured by Diatrix, Inc., 91% pure aqueous solution [initiator]
(I) 2-hydroxy-2-methyl-1-phenylpropan-1-one (DAROCUR1173) (hereinafter referred to as “D-1173”), (ii) 2,2′-azobis (2- Amidinopropane) dihydrochloride (V-50) (hereinafter referred to as “V-50”), manufactured by Wako Pure Chemical Industries, Ltd. [chain transfer agent]
Sodium hypophosphite (hereinafter referred to as “HPA”), manufactured by Wako Pure Chemical Industries, Ltd.

<Synthesis of Amidine Cationic Polymer (A)>
[Production Example 1]
A mixture of 6 g of a mixture of AN and NVF (molar ratio 55:45) and 34 g of distilled water was placed in a 50-ml four-necked flask equipped with a stirrer, a nitrogen introduction tube, and a cooling tube. While stirring in nitrogen gas, the temperature was raised to 60 ° C., 0.12 g of V-50 was added, and the mixture was further maintained for 3 hours to obtain a suspension in which the polymer was precipitated in water. 20 g of distilled water was added to the suspension, and concentrated hydrochloric acid was added in an equivalent amount to the formyl group of the polymer and kept at 100 ° C. for 4 hours to obtain a yellow high-viscosity liquid. This was added to a large amount of acetone, the polymer was precipitated, chopped, dried at 60 ° C. for one day and then pulverized to obtain an amidine cationic polymer (A) (polymer A).

Polymer A was dissolved in heavy water, and a ¹³ C-NMR spectrum was measured with an NMR spectrometer (manufactured by JEOL Ltd., 270 MHz). The composition of each unit was calculated from the integrated value of the peak corresponding to each repeating unit of the ¹³ C-NMR spectrum. The structural units of the general formulas (1) and (2) were determined as the total amount without distinction. The results are shown in Table 1.

<Synthesis of amphoteric polymer (B)>
[Production Example 2]
822.8 g of DME, 600.0 g of AA, and 100.0 g of AAM were put into a brown heat resistant bottle with an internal volume of 2000 ml, 3.0 g of HPA and distilled water were added, and an aqueous monomer solution (DME: total mass of 2000 g) was added. AA: AAM = 27.0: 36.2: 36.8 (mol%), monomer concentration 50%) was prepared. Furthermore, D-1173 was added so that it might become 150 ppm with respect to the total mass of monomer aqueous solution, and the temperature of monomer aqueous solution was adjusted to 20 degreeC, blowing nitrogen gas into this for 30 minutes.

Thereafter, the aqueous monomer solution is transferred to a stainless steel reaction vessel, and sprayed with water at 16 ° C. from below the vessel, using a chemical lamp, the surface thermometer reaches 40 ° C. with an irradiation intensity of 5 W / m ² from above the vessel. Light was irradiated until After the surface thermometer reached 40 ° C., light was irradiated for 30 minutes at an irradiation intensity of 0.3 W / m ² . Furthermore, in order to reduce the residual amount of monomer, the irradiation intensity was 50 W / m ² and irradiation was performed for 10 minutes. Thereby, a hydrogel polymer was obtained. Thereafter, the same operation as in Production Example 1 was performed to obtain an amphoteric polymer (B) (polymer B-1). The obtained hydrogel polymer was taken out from the container, crushed using a small meat chopper, and then dried at a temperature of 60 ° C. for 16 hours. Thereafter, the dried polymer was pulverized using a Willet pulverizer, and the amphoteric polymer (B) (polymer B-1)

[Production Examples 3 to 14]
In Production Example 2, the amount of each monomer and HPA was adjusted, and the same operation as in Production Example 2 was carried out except that the proportions shown in Table 2 were changed, and the amphoteric polymer (B) (Polymers B-2 to 11, b-1 and 2) were obtained.

<Synthesis of non-amidine cationic polymer (C)>
[Production Examples 15 to 17]
In Production Example 2, the same operations as in Production Example 2 were performed except that the amounts of each monomer and HPA were adjusted and changed to the ratios shown in Table 2, and the non-amidine cationic polymer (C) (polymer C- 1-3) were obtained.

[Measurement of electrical conductivity of sludge]
The electrical conductivity of sludge was measured by the above-described method for measuring electrical conductivity.

[Measurement of fiber content of sludge]
The fiber content of sludge was measured by the above-described fiber content measurement method.

[Measurement of sludge VTS]
The VTS of sludge was measured by the above-described VTS measurement method.

[Measurement of sludge TS]
The sludge concentration (hereinafter referred to as TS) was specifically measured by the following measuring method.
(I) 100 ml of sludge is collected and weighed (total sludge weight) (g).
(Ii) 100 ml of sludge is dried as it is at 105 ° C. for 6 hours, and the remaining amount (total solid content) (g) is weighed.
(Iii) The sludge concentration (TS) (%) is calculated by the following formula.

[Examples 1 to 11]
(Used sludge)
As the excess sludge generated from the wastewater treatment facility in the chemical industry, surplus sludge collected at the wastewater treatment facility at the resin / fiber factory of T Corporation was used. That is, the VTS of sludge measured using the analysis method described in the JIS standard is 30.2%, TS is 1.14%, electrical conductivity is 25.7 mS / cm, and fiber content is 0.5% / Sludge that is TS.

(Dehydration test)
First, 300 ml of the sludge was collected in a 500 ml beaker. Next, the polymer shown in Table 1 was dissolved in 0.3% at each mixing ratio shown in Table 4 to prepare a sludge dewatering agent aqueous solution, and this was added to the concentration shown in Table 4, and then the spatula Thus, agitation flocs were formed by stirring and mixing under the conditions of stirring speed: 180 rotations / minute, stirring time: 60 seconds, and sludge was dehydrated. The evaluation results described later are shown in Table 3.

[Comparative Examples 1 to 7]
Except that the polymer used in the sludge dehydrating agent was changed as shown in Table 3, coagulated flocs were formed in the same manner as in Example 1, and sludge was dehydrated. The evaluation results described later are shown in Table 3.

[Evaluation method]
(Agglomerated floc particle size, filtration performance, SS amount of filtered water)
In each example, after agglomerated floc was formed, stirring was stopped and the agglomerated floc particle size was measured visually. Thereafter, the coagulated sludge was transferred to Nutsche previously laid with a filter cloth, and the filtration performance (the amount of filtered water for 10 seconds) was measured. At this time, the SS amount of filtrate after filtration for 60 seconds was visually evaluated according to the following criteria.

(Evaluation criteria for SS amount of filtered water)
-: Filtration water is almost transparent and suspended matter is hardly seen (SS amount standard: less than 50 ppm).
+: Part of the filtered water is turbid, and there is a slight amount of suspended matter (SS amount guideline: 50 ppm or more and less than 100 ppm).
++: Partly turbidity is observed in the filtered water, and there are some floating substances (SS amount guideline: 100 ppm or more and less than 200 ppm).
+++: Numerous turbidity is observed in the filtered water, and the suspended matter is entirely present (SS guideline: 200 ppm or more and less than 500 ppm).
++++: Many turbidity is observed in the filtered water as a whole, and the suspended matter is present as a whole, and is partially present in a coarse size (SS guideline: 500 ppm or more and less than 1000 ppm).
X: The filtered water is completely turbid, and there are many coarse suspended matters (SS amount guideline: 1000 ppm or more).

(Cohesive floc strength)
The filtered and concentrated sludge (aggregated floc) was rotated 50 times on the filter cloth, and the strength (aggregation property) of the aggregated floc was evaluated according to the following criteria.

AA: Water is cut off by rolling on the filter cloth, and the aggregated flocs form several dumplings.
A: Water is cut off by rolling on the filter cloth, and the aggregated flocs become one lump.
B: Water is cut by rolling on the filter cloth, but the aggregated floc is broken and does not form a lump.
C: By rolling on the filter cloth, the coagulated sludge flows and becomes muddy.

(Water content of dehydrated cake)
After measurement of the aggregate floc strength, the aggregate floc was press dehydrated at a pressure of 0.1 MPa for 60 seconds to obtain a dehydrated cake, and the water content was measured. The water content was measured according to the Japan Sewerage Association, “Sewerage Test Method, Vol. 1997 edition” p296-297.

  As shown in Table 3, in Examples 1 to 11 using the sludge dehydrating agent of the present invention, coarse agglomerated flocs were generated, and the moisture content of the dehydrated cake was low. In particular, Examples 1, 2, and 7 in which the reduced viscosity of the amphoteric polymer (B) is in the range of 1.0 to 7.5 dl / g and A / C is in the range of 0.50 to 1.30. 8 and 11, aggregated flocs having excellent strength and excellent dewaterability were obtained.

  Comparative Examples 1 and 2 are examples using a sludge dehydrating agent in which the reduced viscosity of the amphoteric polymer (B) deviated from the predetermined range of the present invention. Both produced aggregate flocs were small, and the strength of the aggregate flocs was weak. The performance was low and the moisture content of the dehydrated cake was high.

  Comparative Examples 3 to 7 are examples using a sludge dehydrating agent in which the mixing ratio of each polymer is outside the range of the predetermined ratio of the present invention. The floc diameter of the flocs is small, the strength of the flocs is low, and the filtration performance is low. It was.

[Examples 12 to 16, Comparative Examples 8 to 14]
(Used sludge)
As surplus sludge generated from the wastewater treatment facility of the food industry, surplus sludge collected at the wastewater treatment facility of the sugar factory of H Co., Ltd. and having the following characteristics was used. That is, the VTS of sludge measured using the analysis method described in the JIS standard is 41.3%, TS is 1.36%, electric conductivity is 6.7 mS / cm, and fiber content is 1.4% / Sludge that is TS.

(Dehydration test)
A dehydration test similar to Example 1 was performed except that the polymer used for the sludge dehydrating agent was changed as shown in Table 4. The evaluation results in Examples 12 to 16 and Comparative Examples 8 to 14 are shown in Table 4.

  As shown in Table 4, in Examples 12 to 16 using the sludge dehydrating agent of the present invention, coarse aggregated flocs were generated, and the moisture content of the dehydrated cake was low. In particular, Examples 12, 13, and 16 in which the reduced viscosity of the amphoteric polymer (B) is in the range of 1.0 to 7.5 dl / g and A / C is in the range of 0.50 to 1.30. Then, an agglomerated floc having excellent strength and excellent dewaterability was obtained.

  Comparative Examples 8 and 9 are examples using a sludge dehydrating agent in which the reduced viscosity of the amphoteric polymer (B) deviated from the predetermined range of the present invention. Both produced aggregated flocs were small, and the strength of the aggregated flocs was weak. The performance was low and the moisture content of the dehydrated cake was high.

  Comparative Examples 10 to 14 are examples using a sludge dehydrating agent in which the mixing ratio of each polymer deviates from the predetermined ratio range of the present invention. The floc diameter of the floc floc is small, the floc floc strength is weak, and the filtration performance is low. The

[Examples 17 to 20 and Comparative Examples 15 and 16]
(Used sludge)
As the coagulated sediment sludge generated from the wastewater treatment facility at the landfill disposal site, the coagulated sediment sludge collected at the wastewater treatment facility of O Co., Ltd. was used. That is, the VTS of sludge measured using the analysis method described in the JIS standard is 18.4%, TS is 2.77%, electrical conductivity is 16.8 mS / cm, and fiber content is 0.4% / Sludge that is TS.

(Dehydration test)
A dehydration test similar to that of Example 1 was performed except that the polymer used for the sludge dehydrating agent was changed as shown in Table 5. The evaluation results in Examples 17 to 20 and Comparative Examples 15 and 16 are shown in Table 5.

  As shown in Table 5, in Examples 17 to 20 using the sludge dewatering agent of the present invention, coarse agglomerated flocs were generated, and the moisture content of the dewatered cake was low. In particular, in Examples 17 and 18 where the reduced viscosity of the amphoteric polymer (B) is in the range of 1.0 to 7.5 dl / g and A / C is in the range of 0.50 to 1.30, Agglomerated flocs having excellent strength and excellent dewaterability were obtained.

  Comparative Examples 15 and 16 are examples using a sludge dehydrating agent in which the reduced viscosity of the amphoteric polymer (B) is out of the predetermined range of the present invention. In Comparative Example 15, no floc flocs are formed, and in Comparative Example 16, it is generated. The flocs produced were small, the strength of the produced flocs was weak, the filtration performance was low, and the moisture content of the dehydrated cake was high.

[Comparative Examples 17 to 19]
(Used sludge)
As surplus sludge generated from the wastewater treatment facility of the chemical industry, surplus sludge collected at the wastewater treatment facility of the resin / fiber factory of Y Corporation was used. That is, the VTS of sludge measured using the analysis method described in the JIS standard is 58.0%, TS is 0.83%, electric conductivity is 0.3 mS / cm, and fiber content is 8.5% / Sludge that is TS.

(Dehydration test)
A dehydration test similar to Example 1 was performed except that the polymer used for the sludge dehydrating agent was changed as shown in Table 6. The evaluation results in Comparative Examples 17 to 19 are shown in Table 6.

  Table 6 shows the results of a dehydration test using sludge whose sludge has an electrical conductivity outside the predetermined range of the present invention. Comparative Example 17 is an example using the sludge dehydrating agent of the present invention, and Comparative Example 18 is an example using a sludge dehydrating agent in which the mixing ratio of each polymer is out of the predetermined ratio range of the present invention. In both cases, coarse flocculated flocs were formed, the moisture content of the dehydrated cake was low, and the flocculation performance was the same.

  On the other hand, Comparative Example 19 is an example using a sludge dehydrating agent in which the reduced viscosity of the amphoteric polymer (B) is outside the predetermined range of the present invention, but the floc diameter, floc strength, and dehydrated cake moisture content are comparative examples. The result was equivalent to 17.

[Comparative Examples 20 and 21]
(Used sludge)
The surplus sludge collected at the wastewater treatment facility at the textile factory of N Corporation was used as sludge having the following characteristics as surplus from the wastewater treatment facility at the chemical factory. That is, the VTS of sludge measured using the analysis method described in the JIS standard is 60.5%, TS is 1.63%, electric conductivity is 6.7 mS / cm, and fiber content is 11.5 / TS. Is sludge.

(Dehydration test)
A dehydration test similar to that of Example 1 was performed except that the polymer used for the sludge dehydrating agent was changed as shown in Table 7. The evaluation results in Comparative Examples 20 and 21 are shown in Table 7.

  Table 7 shows the results of a dehydration test using sludge whose sludge fiber content is out of the predetermined range of the present invention. Comparative Example 20 is an example using the sludge dehydrating agent of the present invention, and Comparative Example 21 is an example using a sludge dehydrating agent in which the mixing ratio of each polymer is out of the predetermined ratio range of the present invention. In both cases, coarse flocculated flocs were formed, the moisture content of the dehydrated cake was low, and the flocculation performance was the same.

[Comparative Examples 22 and 23]
(Used sludge)
As the excess sludge generated from the wastewater treatment facility of the chemical factory, the sludge having the following characteristics was used as the excess sludge collected at the wastewater treatment facility of the dyeing factory of S Corporation. That is, the VTS of the sludge measured using the analysis method described in the JIS standard is 70.5%, TS is 1.23%, electric conductivity is 0.9 mS / cm, and the fiber content is 3.4% / Sludge that is TS

(Dehydration test)
A dehydration test similar to that of Example 1 was performed except that the polymer used for the sludge dehydrating agent was changed as shown in Table 8. The evaluation results in Comparative Examples 22 and 23 are shown in Table 8.

  Table 8 shows the results of a dehydration test using sludge whose sludge VTS deviated from the predetermined range of the present invention. Comparative Example 22 is an example using the sludge dehydrating agent of the present invention, and Comparative Example 23 is an example using a sludge dehydrating agent in which the reduced viscosity of the amphoteric polymer (B) is out of the predetermined ratio range of the present invention. In both cases, coarse agglomerate flocs were produced, the moisture content of the dehydrated cake was low, and the agglomeration performance was equivalent.

Claims (2)

Sludge dehydrating agent for sludge having electrical conductivity of 0.5-50 mS / cm, fiber content of 0.5-10% / TS and ignition loss (VTS) of 5-65% / TS. In the sludge dewatering treatment method in which the dewatering treatment is performed after the addition of water, the sludge dehydrating agent comprises a mixture of the following amidine-based cationic polymer (A), amphoteric polymer (B) and non-amidine-based cationic polymer (C). The ratio of the amidine cationic polymer (A) to the total mass of each polymer is 10 to 50% by mass, the ratio of the amphoteric polymer (B) is 10 to 40% by mass, and the ratio of the non-amidine cationic polymer (C) is A sludge dewatering method characterized by using a sludge dewatering agent of 10 to 80% by mass.
[Amidine-based cationic polymer (A)]
An amidine-based cationic polymer containing an amidine structural unit represented by the following general formula (1) and / or the following general formula (2).

(However, in general formula (1), (2), R < ¹ >, R < ² > is a hydrogen atom or a methyl group each independently, and X < ^- > is an anion.)
[Amphoteric polymer (B)]
1N sodium chloride, an amphoteric polymer containing a cationic structural unit represented by the following general formula (3), an anionic structural unit, and a nonionic structural unit, and 0.1 g / dl of the amphoteric polymer An amphoteric polymer having a reduced viscosity of 0.1 to 10.0 dl / g at 25 ° C. of an aqueous solution.

(Wherein R ³ is a hydrogen atom or a methyl group, R ⁴ and R ⁵ are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁶ is an alkyl having 1 to 4 carbon atoms. Y is an oxygen atom or NH, Z ⁻ is Cl ⁻ , Br ⁻ , or 1 / 2SO ₄ ²⁻ , and n is an integer of 1 to 3).
[Non-amidine cationic polymer (C)]
A non-amidine cationic polymer containing the cationic structural unit represented by the general formula (3) and a nonionic structural unit.   When the content of the anionic structural unit contained in the amphoteric polymer (B) is Ma mol% and the content of the cationic structural unit is Mc mol%, the ratio Ma / Mc is 0.35 to 1.65. The sludge dewatering method according to claim 1.