JP2009183888A - Sludge dehydration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digested sewage sludge treatment method which is suitable for dehydration treatment by a centrifugal dehydrator or a screw press dehydrator, enables a further reduction of water content in a dehydrated cake, and enables a reduction of the generation of magnesium ammonium phosphate (MAP) scales. <P>SOLUTION: An inorganic coagulant is added to digested sewage sludge, and then a polymer coagulant composition containing a polyamidine-based coagulant and an amphoteric polymer coagulant is added thereto to subject the material to be treated to hydration treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for dewatering sewage digested sludge.

Organic sludge generated from organic wastewater such as sewage, human waste treatment plant, and food industry is dehydrated with a screw decanter (centrifugal dehydrator), screw press type dehydrator, belt press, etc. using a polymer flocculant, and then landfilled or It is incinerated. Most of the fuel used for incineration of dewatered sludge (hereinafter referred to as dehydrated cake) is used for evaporation of moisture in the dehydrated cake. Generally, when the moisture in the dehydrated cake is reduced by 1%, the fuel used for incineration can be saved by about 10%.
However, in recent years, the water content of the dehydrated cake tends to be high due to reasons such as advanced water treatment and an increase in sludge organic content. For this reason, the fuel cost in incineration disposal is increasing, and in addition to the fuel cost reduction, reduction of the moisture content in the dehydrated cake is also desired from the viewpoint of CO ₂ gas reduction and prevention of global warming.

By the way, generally, mixed raw sludge (mixed sludge of primary sludge and excess sludge) or primary sludge that has been anaerobically digested by microorganisms is called sewage digested sludge. Such sewage digested sludge is as follows: It has characteristics and it is difficult to reduce the water content compared to other sludges.
1. The suspended fixed matter (SS) has a small particle size and low specific gravity.
2. There is little sand and fiber as the core of the aggregated floc.
3. It contains a large amount of colloidal material having negative charge shown in the sludge colloid value.
4). Contains a large amount of inorganic salts such as phosphates and carbonates.

In particular, in a dehydration process using a centrifugal dehydrator or a screw press type dehydrator, it is preferable that the aggregated floc is large and the strength is high, but it is difficult to form such an aggregated floc in the treatment of sewage digested sludge.
For this reason, when dewatering the sewage digested sludge, the water content is high in the method using a centrifugal dehydrator, and the shape of the obtained dewatered cake becomes a highly sticky lump, making it difficult to carry and incinerate. Also, in the method using a screw press type dehydrator, the formed flock is broken in the pressing zone and SS is leaked from the punching plate, resulting in poor separation and high moisture content in many cases.

Regarding the sludge dewatering treatment, as a method of reducing the moisture content of the dewatered cake, (1) a method of adding an inorganic flocculant to organic sludge and then performing a dewatering treatment using an amphoteric polymer flocculant (Patent Document 1), (2) After adding an inorganic flocculant to sewage digested sludge, a method of dehydrating using an acrylate cationic polymer flocculant (Patent Document 2), (3) After adding polyiron sulfate to the sludge, containing polyamidine In addition, a method of adding and mixing a cationic polymer flocculant having a cation equivalent value of 5 or more and dehydrating with a Pelto press type dehydrator (Patent Document 3) is disclosed.
JP 63-158200 A JP-A-7-214100 JP-A-8-173999

The method (1) is effective for general organic sludge, and can significantly reduce the water content. However, for sewage digested sludge, the alkalinity of the sludge is so high that it is necessary to add a large amount of an inorganic flocculant. For this reason, compared with the case where a cationic type flocculant is used independently, a chemical | medical cost will result in 2 times or more, and it is not practical.
Compared with the method (1), the method (2) enables a good dehydration treatment with a relatively small amount of inorganic flocculant added and is put to practical use as an effective means. However, the water content is further reduced. Is required.
The method (3) is not necessarily optimal for various dehydrators.
Further, in the dewatering treatment of sewage digested sludge, magnesium ammonium phosphate (MAP) scale is generated in the dewatered separation liquid piping, etc., and troubles that block the piping are likely to occur. Therefore, it is required to reduce the generation of such MAP scale. The

  The present invention has been made in view of the above circumstances, and in the method for dewatering sewage digested sludge, it is also suitable for dewatering by a centrifugal dewatering machine or a screw press type dewatering machine, and the water content in the dewatered cake can be further reduced. At the same time, it is an object to reduce the generation of the MAP scale.

As a result of examining the properties and dewatering performance of sewage digested sludge in detail, the present inventors have found that the sewage digested sludge contains a large amount of inorganic substances such as alkali phosphates and organic substances such as polysaccharides and proteins. It was found that the substance has a great influence on the dewaterability of sludge.
Then, by adding an inorganic flocculant to the sewage digested sludge, metal ions such as Al and Fe contained in the inorganic flocculant react with phosphate ions, polysaccharides, proteins, etc. in the sludge, It has been found that it can be insolubilized, and as a result, generation of MAP scale can be prevented and dehydration can be improved.
In addition, sewage digested sludge simply condensed with an inorganic flocculant is very fine and difficult to dehydrate as it is, but if a polymer flocculant is used, larger flocs can be formed. is there. As a result of further studies by the present inventors, by using a polyamidine flocculant and an amphoteric polymer flocculant in combination as a polymer flocculant, coarser flocculent flocs are formed, and the moisture content of the dehydrated cake is further reduced. In addition, the present inventors have found that the aggregated floc formed at this time is coarse and strong, and that the sewage digested sludge can be dehydrated using a centrifugal dehydrator or a screw press type dehydrator.

That is, in the sludge dewatering method of the present invention, an inorganic flocculant is added to sewage digested sludge, and then an object to be treated is added with a polymer flocculant composition containing a polyamidine flocculant and an amphoteric polymer flocculant. It is characterized by dehydrating.
The polymer flocculant composition preferably further contains an aminoalkyl (meth) acrylate cationic flocculant.
The dehydration treatment is preferably performed using a centrifugal dehydrator or a screw press dehydrator.

  According to the sludge dewatering method of the present invention, the sewage digested sludge can be dewatered with high efficiency, and the water content in the dewatered cake can be further reduced. Further, a dehydration process using a centrifugal dehydrator or a screw press dehydrator can be applied.

<Sewage digestion sludge>
The sewage digestion sludge in the present invention means mixed sludge (mixed sludge of primary sludge and excess sludge) or sludge obtained by subjecting primary sediment sludge to an anaerobic digestion treatment.

<Inorganic flocculant>
As the inorganic flocculant used in the present invention, known inorganic flocculants such as sulfate band (aluminum sulfate), ferric chloride, ferrous sulfate, polyiron sulfate and the like can be used. These can be obtained from commercial products. An inorganic flocculant may be used individually by 1 type, and may use 2 or more types together.

<Polymer flocculant composition>
The polymer flocculant composition in the present invention contains a polyamidine flocculant and an amphoteric polymer flocculant. Furthermore, you may contain an aminoalkyl (meth) acrylate type cationic flocculant.
[Polyamidine flocculant]
The polyamidine flocculant used in the present invention comprises a polymer (P) having a repeating unit (I) represented by the following chemical formula (I). The polymer (P) may have a repeating unit other than the repeating unit (I). The content ratio of the repeating unit (I) in the polymer (P) is 50 mol% or more, preferably 80 mol% or more, and may be 100 mol%.

The polymer (P) having the repeating unit (I) can be produced by a known production method, for example, a method described in Japanese Patent No. 2624089.
The polymer (P) is obtained by copolymerizing N-vinylformamide and acrylonitrile, hydrolyzing the resulting copolymer under hydrochloric acid acidity, and then performing a heat treatment, so that the primary amino group and the cyano group on the inner chain of the molecule are converted. Polymers that are cyclized to form amidine rings are preferred.

The molecular weight of the polymer (P) is preferably 100,000 to 5,000,000, more preferably 1,000,000 to 5,000,000. Below 100,000, the cohesive strength decreases and it is currently difficult to produce a polymer with a molecular weight exceeding 5 million on a commercial basis.
The cation equivalent value Cv (unit: meq / g) of the polymer (P) is preferably 4.0 to 8.0, and more preferably 5.0 to 7.0. If it is smaller than the lower limit of the above range, although the floc is large, the moisture content is inferior, and if it is larger than the upper limit, the floc is small, weakens and dewaters.
The intrinsic viscosity [η] indicating the molecular weight of the polymer (P) is preferably 4 dl / g or more, and more preferably 5 dl / g or more. The higher [η], the easier it is to form larger and stronger flocs, and the better the dehydration process. If [η] is less than 4 dl / g, the flocs are small and tend to be weak, and the dewaterability in centrifugal dewatering and screw press dewatering is deteriorated.
The upper limit of the intrinsic viscosity [η] of the polymer (P) is not particularly limited, but is preferably 12 dl / g or less and more preferably 10 dl / g or less from the viewpoint of productivity.
The method for measuring the cation equivalent value Cv and the intrinsic viscosity [η] of the polymer will be described later.
One polyamidine flocculant may be used alone, or a plurality of polyamidine flocculants may be used in combination.

[Amotropic polymer flocculants]
The amphoteric polymer flocculant is composed of a polymer (R) containing a repeating unit having an anionic group and a repeating unit having a cationic group in the molecule. Furthermore, you may have a nonionic repeating unit.
Examples of the anionic group include a carboxy group and a sulfonic acid group. Examples of the cationic group include tertiary amines, neutralized salts thereof, quaternary salts and the like.
The polymer (R) is preferably a copolymer of an anionic monomer, a cationic monomer, and an optional nonionic monomer.
Examples of the anionic monomer include acrylic acid, maleic acid, acrylamide-2-methylpropanesulfonic acid, and acrylic acid is preferable.
Cationic monomers include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, allyldimethylamine or neutralized salts thereof, quaternary Examples include salts. Of these, dimethylaminoethyl (meth) acrylate methyl chloride quaternary salt is preferred.
Nonionic monomers include (meth) acrylamide, N, N-dimethyl (meth) acrylamide and the like. Of these, acrylamide is preferred.
Any of these monomers can be used alone or in combination of two or more.

The polymerization method of the polymer (R) is not particularly limited, and examples thereof include precipitation polymerization, bulk polymerization, dispersion polymerization, and aqueous solution polymerization.
A solid acid may be used together with the polymer (R) for the purpose of improving the solubility and improving the storage stability of the solution. Examples of the solid acid include sulfamic acid and acidic sodium sulfite.
The polymer (R) can be obtained from a commercially available polymer flocculant.

1.0-4.0 are preferable and, as for the cation equivalent value Cv (unit: meq / g) of a polymer (R), 2.0-3.0 are more preferable. If it is smaller than the lower limit of the above range, the water content is undesirably high. If it is larger than the upper limit value, the flocs are small and weak and the dehydrating property is deteriorated.
The intrinsic viscosity [η] of the polymer (R) is preferably 10 dl / g or more, and more preferably 12 dl / g or more. Higher [η] tends to form larger and stronger flocs, and better dehydration treatment. If [η] is less than 10 dl / g, the flocs are small and weak, and the dewaterability in centrifugal dewatering and screw press dewatering is deteriorated.
The upper limit of the intrinsic viscosity [η] of the polymer (R) is not particularly limited, but is preferably 20 dl / g or less and more preferably 18 dl / g or less from the viewpoint of productivity.
One amphoteric polymer flocculant may be used alone or a plurality of amphoteric polymer flocculants may be used in combination.

[Aminoalkyl (meth) acrylate cationic flocculant]
The aminoalkyl (meth) acrylate cationic flocculant used in the present invention is a homopolymer of an aminoalkyl (meth) acrylate cationic monomer, or an aminoalkyl (meth) acrylate cationic monomer and a nonionic monomer. (Hereinafter, these may be collectively referred to as a polymer (K)).
Examples of aminoalkyl (meth) acrylate cationic monomers include dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylamino-2-hydroxypropyl (meth) acrylate. Tertiary salts such as hydrochlorides and sulfates of
Quaternary salts such as halogenated alkyl adducts such as methyl chloride adducts of the dialkylaminoalkyl (meth) acrylate and aryl halide adducts such as benzyl chloride;
Tertiary salts such as hydrochlorides and sulfates such as dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide;
And quaternary salts such as halogenated alkyl adducts such as methyl chloride adducts of dialkyl (meth) acrylamide and aryl halide adducts such as benzyl chloride adducts.
Of these, methyl chloride adduct quaternary salt of dialkylaminoalkyl (meth) acrylate is preferable, and methyl chloride quaternary salt of dimethylaminoethyl (meth) acrylate is more preferable.

Examples of nonionic monomers include (meth) acrylamide, styrene, acrylonitrile, vinyl acetate, alkyl acrylate, and the like. Of these, (meth) acrylamide is preferred.
Any of these monomers can be used alone or in combination of two or more.
The polymerization method of the polymer (K) is not particularly limited, and examples thereof include precipitation polymerization, bulk polymerization, dispersion polymerization, and aqueous solution polymerization.
In addition to the polymer (K), the solid acid may be used for the purpose of improving the solubility and improving the storage stability of the solution.

The cation equivalent value Cv of the polymer (K) is not particularly limited, and good dehydrating performance can be obtained by adjusting the mixing ratio with the polyamidine flocculant (polymer (P)).
The intrinsic viscosity [η] of the polymer (K) is appropriately 5 dl / g or more, and the higher [η], the larger and stronger the floc becomes and the better dehydration treatment becomes possible. If [η] is less than 5 dl / g, the flocs are small and weak, and the dewaterability in centrifugal dewatering and screw press dewatering is deteriorated. The upper limit of the intrinsic viscosity [η] of the polymer (K) is not particularly limited, but is preferably 25 dl / g or less and more preferably 20 dl / g or less from the viewpoint of productivity.
The aminoalkyl (meth) acrylate cationic flocculant may be used alone or in combination of two or more.

[Combination ratio]
The flocculant composition (A) in the present invention is used for dehydration as an aqueous solution dissolved in water. Although the density | concentration of this aqueous solution is not specifically limited, 0.05-1.5 mass% is preferable and 0.2-0.5 mass% is more preferable.
In the polymer flocculant composition, the total amount of the polyamidine flocculant and the aminoalkyl (meth) acrylate cationic flocculant and the blending ratio of the amphoteric polymer flocculant (the total amount / amphoteric polymer flocculant) are: Although there is no restriction | limiting in particular, 70 / 30-99 / 1 are preferable on a mass basis, and 80 / 20-95 / 5 are more preferable. If the blending ratio of the amphoteric polymer flocculant is less than 1% by mass, the effect of blending the amphoteric polymer flocculant cannot be sufficiently obtained, and if it exceeds 30% by mass, the amount of the polymer flocculant added is large, As a result, the water content increases and the dehydration is poor.
The blending ratio of the polyamidine flocculant and the aminoalkyl (meth) acrylate cationic flocculant is not particularly limited, and can be adjusted to an appropriate blending ratio corresponding to the sludge properties and the amount of inorganic flocculant added.

[Method for Measuring Cation Equivalent Value Cv]
The cation equivalent value Cv (unit: meq / g) in the present invention is a value determined by the colloid titration method shown below.
(1) Take 90 ml of deionized water in a conical beaker, add 10 ml of a 500 ppm sample solution prepared by the method of (2) below, bring the pH to 3.0 with an aqueous hydrochloric acid solution, and stir for about 1 minute. Next, a few drops of toluidine blue indicator are added and titrated with N / 400-polyvinyl potassium sulfate reagent (N / 400-PVSK). The titration rate is 2 ml / min, and the end point is the time when the sample water changes from blue to magenta for 10 seconds or longer. From the titration amount of N / 400-polyvinyl potassium sulfate reagent, the cation equivalent value (Cv) is obtained by the following formula (1).
(2) The sample 500 ppm solution is prepared by the following method. That is, 0.2 g (not converted to a dry product) of the sample is precisely weighed and dissolved with 100 ml of deionized water using a triangular corben with a stopper. The 25 ml is made up with deionized water in a 100 ml volumetric flask.

[Measurement method of intrinsic viscosity [η]]
The intrinsic viscosity [η] in the present invention is a value determined by the following method.
(1) First, the viscosity of the solvent blank is measured.
That is, an Ubbelohde viscometer is set in a thermostat adjusted to 30 ± 0.05 ° C., a 1N-sodium nitrate solution is placed in the viscometer, and after standing for 10 to 30 minutes, the solution is raised. The flow time required for passing between the upper and lower marked lines displayed on the viscometer when it is allowed to flow naturally is measured three times or more, and the average value is taken as the viscosity (t0) of the solvent blank.
(2) Next, the reduced viscosity is calculated by the following method.
The same operation as described above was performed using each 1N-sodium nitrate solution having a sample concentration of 0.10 to 0.02% by mass to pass between the upper and lower marked lines displayed on the viscometer of each solution. The average flow time required is measured, and the average value thereof is taken as the viscosity (t) of each sample solution. Next, the ratio t / t0 for each sample was determined to obtain the relative viscosity η _r, and the specific viscosity η _sp = η _r −1 was determined from these, and these were divided by the respective sample concentrations to obtain the respective samples. The reduced viscosity η _sp / C is calculated.
(3) Next, the intrinsic viscosity is calculated by the following method.
The concentration (g / d1) of the sample solution and the reduced viscosity are plotted, and the intrinsic viscosity [η] is obtained by extrapolation.

<Dehydration method>
First, an inorganic flocculant is added to and mixed with sewage digested sludge, and then a polymer flocculant composition is added. The time from the addition of the inorganic flocculant to the addition of the polymer flocculant composition is not particularly limited.
In this way, the treatment object to which the inorganic flocculant and the polymer flocculant composition are added is dehydrated by a known technique. The dehydration treatment can be performed using a known dehydrator such as a screw decanter (centrifugal dehydrator), a screw press type dehydrator or a belt press.
In the present invention, it is possible to perform the dehydration process well even by a centrifugal dehydrator or a screw press type dehydrator, which has conventionally been difficult to dehydrate the sewage digested sludge.
The time from the addition of the polymer flocculant composition to the dehydration treatment is not particularly limited.

According to the present invention, phosphate ions, polysaccharides, proteins and the like in sludge can be insolubilized by adding an inorganic flocculant to sewage digested sludge. After that, by adding a polymer flocculant composition containing a polyamidine flocculant and an amphoteric polymer flocculant, it is coarse and sufficiently dehydrated using a centrifugal dehydrator or a screw press dehydrator. A strong floc can be formed.
Therefore, the sewage digested sludge can be dehydrated with high efficiency, and the water content in the dehydrated cake can be further reduced. Thereby, reduction of sludge treatment cost is realizable. Moreover, a dehydration process can be performed suitably using a centrifugal dehydrator or a screw press type dehydrator.
In addition, since the phosphorus concentration in the dehydrated separation liquid can be reduced, the production of MAP scale can be suppressed thereby.

Here, the polyamidine flocculant has a relatively low molecular weight compared to the acrylate flocculant, but has a strong adsorptivity to sludge, and has a small amount of addition compared to the inorganic flocculant to hydrophilic polysaccharides, proteins, etc. Can be hydrophobized. However, according to the knowledge of the present inventors, the polyamidine-based flocculant has a low molecular weight, so it is often difficult to form a large and strong floc alone, especially when an inorganic flocculant is used in combination. However, when an amphoteric polymer flocculant is used in combination, a large and strong floc suitable for a centrifugal dehydrator and a screw press dehydrator can be formed.
Further, by adding an aminoalkyl (meth) acrylate cationic flocculant to the polymer flocculant composition, high floc strength is required in various digested sludges, centrifugal dehydrators and screw press dehydrators, etc. In the dehydrator to be used, it is possible to perform a wide and highly efficient dehydration process.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
The polymer flocculant compositions used in the following Examples and Comparative Examples were prepared by blending the polymers shown in Table 1 as shown in Table 2 to form a 0.3 mass% aqueous solution.

Table 1 shows the monomers used in the synthesis of each polymer and their ratios. Abbreviations of monomers shown in this table are as follows.
PVAD: polyvinylamidine.
DMC: dimethylaminoethyl methacrylate / methyl chloride quaternary salt.
DME: dimethylaminoethyl acrylate / methyl chloride quaternary salt.
AAm: acrylamide.
AA: acrylic acid.

[Examples 1-8]
Using the inorganic flocculant and the polymer flocculant composition shown in Table 3, a dewatering test of sewage digested sludge was performed in the following procedure.
In the following, each characteristic was measured by the following method.
-SS concentration: Measured based on a standard method (edited by the Japan Sewerage Association, “Sewage Test Method, Vol. 1997,” published on August 25, 1997, p. 116).
・ VTS (loss on ignition) value: Measured based on a regular method (edited by Japan Sewerage Association, “Sewerage Test Method Vol. 1997 edition” p297).
Aggregated floc average particle diameter: measured by visual observation.
Colloid charge amount: Measured based on a conventional method (edited by Tokyo Sewerage Service Co., Ltd., Polymer Flocculant Guide p47-49).
-M alkalinity: Measured based on a standard method (edited by Japan Sewerage Association, “Sewerage Test Method, Vol. 1997, p300”).
-Water content of dehydrated cake: Measured based on a standard method (edited by Japan Sewerage Association, “Sewerage Test Method, Vol. 1997, p. 296-297)”.

As sewage digestion sludge, SS concentration: 2.35 mass%, pH: 7.5, VTS: 65.2 mass%, colloid charge amount: -1.2 meq / l, M alkalinity: 5,600 mg / l Sludge was used.
The stirring device shown in FIG. 1 was used. This stirrer has a variable stirrer 11 and a telescopic stand 12. The variable stirrer 11 includes, for example, a stirring shaft 11a having a diameter of 7.5 to 7.9Φ, a width W of 60 mm, and a thickness T of 2 mm. The stirring blade 11b is provided.

(1) First, 300 ml of the sludge was collected in a 500 ml beaker and set in the stirring device of FIG.
(2) The inorganic flocculant shown in Table 3 was added so as to have the addition amount shown in Table 3, and stirred and mixed for 10 seconds at a rotation speed of 900 rpm.
(3) Next, the polymer flocculant composition shown in Table 3 was added so as to have the addition amount shown in Table 3, and the mixture was stirred and mixed at a rotation speed of 900 rpm for 20 seconds.
(4) Next, the agglomerated sludge was filtered through a Nutsche lined with a filter cloth, and the filtrate amount for the first 10 seconds was measured. The result is shown in the column of “filtrate” in Table 3. The filtrate was collected and the total phosphorus content (TP concentration) was measured. The measurement method is described in “Sewage test method, first volume”, p. 199, “3. Decomposition method with total phosphorus (1) potassium peroxodisulfate”. The results are shown in Table 3.
(5) Subsequently, after 1 minute had elapsed, the concentrated sludge on the filter cloth was sandwiched between filter cloths and squeezed and dehydrated at a pressure of 0.1 MPa for 1 minute to determine the moisture content of the dehydrated cake. The results are shown in Table 3.

[Comparative Examples 1 and 2]
The polymer flocculant composition in Example 1 was changed to an aminoalkyl (meth) acrylate cationic flocculant in Comparative Example 1, and changed to polyvinylamidine in Comparative Example 2. Others were the same as in Example 1. Table 3 shows the addition amount and each measurement result.

[Comparative Examples 3 and 4]
In Comparative Example 3, the same procedure as in Example 1 was performed except that the inorganic flocculant was not added and the amount of the polymer flocculant composition added was 1.5 times that in Example 1.
In Comparative Example 3, almost no flocculated flocs were formed and dehydration was impossible. Therefore, in Comparative Example 4, an inorganic flocculant was not added, and the amount of the polymer flocculant composition added was twice that of Example 1. It was. Others were the same as in Example 1. Table 3 shows the addition amount and each measurement result.

In each of Examples 1 to 8, the particle size of the formed floc was large, and the filtration rate (the amount of filtrate for 10 seconds), the TP concentration of the filtrate, and the moisture content of the dehydrated cake were very excellent.
Comparative Example 1 using only an aminoalkyl (meth) acrylate cationic flocculant as a polymer flocculant and Comparative Example 2 using only a polyamidine flocculant have a smaller floc particle size than the examples, and filtration. The speed was slower than in Examples 1 to 8, and the moisture content was inferior by about 4% compared to Examples 1 to 8.
In Comparative Example 4 in which the addition amount of the polymer flocculant composition was increased without adding the inorganic flocculant, flocs were formed, but the filtration rate was slower than in Examples 1 to 8, and the TP concentration of the filtrate The water content was large and inferior.

It is the schematic which shows the stirring apparatus used in the Example.

Explanation of symbols

11 Variable stirrer, 11a Stirrer shaft, 11b Stirrer blade, 12 Telescopic stand.

Claims (3)

  Sludge dewatering characterized by adding an inorganic flocculant to sewage digested sludge and then dewatering the material to be treated to which a polymer flocculant composition containing a polyamidine flocculant and an amphoteric polymer flocculant is added. Processing method.   The method for dewatering sludge according to claim 1, wherein the polymer flocculant composition further contains an aminoalkyl (meth) acrylate cationic flocculant.   The sludge dewatering method according to claim 1 or 2, wherein the dewatering process is performed using a centrifugal dewatering machine or a screw press type dewatering machine.

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