JPH0459100A - Organic sludge dewatering method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for dewatering organic sludge, and particularly relates to an improvement in a method for dewatering organic sludge using an inorganic flocculant and an organic polymer flocculant. .

[Prior Art] Conventionally, as a method for dewatering organic sludge generated from the treatment of sewage, human waste, or organic industrial wastewater, a method has been proposed in which an inorganic flocculant and an organic polymer flocculant are added to the sludge. (Japanese Unexamined Patent Publication No. 129200/1983).

JP-A-60-129200 discloses a method in which an inorganic flocculant is added, and then an amphoteric polymer flocculant consisting of a composition containing a cationic polymer and an anionic polymer is added for dehydration treatment.

[Problems to be Solved by the Invention] However, in the method of JP-A No. 1-129200, when the amount of inorganic flocculant added is increased to sufficiently neutralize the charge of sludge, the flocculating property There is a problem that the dehydration process is significantly reduced, making it impossible to carry out subsequent dehydration treatment.

Furthermore, instead of the above-mentioned cationic polymer and anionic polymer, a method of adding an amphoteric polymer flocculant having a cationic group and an anionic group may also be considered. For example, there is a method in which an amphoteric organic polymer flocculant is added to organic sludge whose pH value after addition of the inorganic flocculant is 5 to 8, and then the sludge is dehydrated. However, this method does not produce strong flocs depending on the type of amphoteric organic polymer flocculant, so it is not possible to increase the throughput per unit time during mechanical dewatering, and the water content of the dehydrated cake also decreases. There is a problem that if the temperature is lowered sufficiently, the crucian carp will not be eaten.

The present invention solves the above conventional problems, has a large sludge processing capacity per unit time, has a high recovery rate of SS (suspended solids), and has good peelability of the dewatered cake from the filter cloth. It is an object of the present invention to provide a method for dewatering organic sludge that can significantly reduce the water content of the dehydrated cake.

[Means for Solving the Problems] The method for dewatering organic sludge of the present invention includes adding an inorganic flocculant to organic sludge and stirring it, further adding an organic polymer flocculant, or adding an organic polymer flocculant to the organic sludge. A method of introducing the organic sludge together with a flocculant into a granulation thickening tank having a filtration section, taking out the filtrate from the filtration section to concentrate and granulate the sludge, and dewatering the granulated product using a dehydrator. In the above, the organic polymer flocculant is an amphoteric organic polymer flocculant having an anionic structural unit and a cationic structural unit, and has a pH of 3.
The colloid equivalent value (a value) is 1.0 to 3.7 me
q/g, colloid equivalent value (b value) at pH 7 is -1
, 7 to 0.7 meq/g, and the value of (a-b)/a, which is the quantitative ratio of anionic constitutional units/cationic constitutional units, is 0.8 to 1.8. .

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a flowchart showing an example of the present invention. In FIG. 1, organic sludge is put into a raw sludge storage tank 1 and stored therein. 1a is a stirrer. The sludge in the storage tank 1 is introduced into the bottom of the sludge conditioning tank 3 via the pump 2a and piping 2b, and is stirred. 3a is a stirrer. The inorganic flocculant in the auxiliary agent dilution tank 4 is injected into the sludge conditioning tank 3 via the auxiliary agent injection pump 5a and piping 5b, and the sludge is thoroughly mixed with this inorganic flocculant.

As will be explained in detail later, the addition of this inorganic flocculant neutralizes the charge of the sludge and strengthens the floc core.

The sludge mixed with the inorganic flocculant is then transferred to piping (supply pipe)
6 and then introduced into granulation concentration 4f17.

An amphoteric organic polymer flocculant in a polymer dissolution tank 8 equipped with an agitator 8A is introduced into this granulation concentration tank 7 via a pump 8a and piping (chemical injection pipe) 8b. As the liquid is swirled by the rotation of the agitator 7a, the sludge is granulated into pellets. The liquid that was not pelletized in the granulation concentration tank 7 passes through the filtration section 7b,
The separated liquid is sent to an initial settling tank (not shown) via piping 9a and separated liquid discharge pump 9b. The granulated material is sent to a dehydrator (not shown) through a pipe (sludge removal pipe) 9c together with a small amount of liquid.

In the present invention, the organic sludge to be treated is not particularly limited, but includes, for example, sewage primary sedimentation tank sludge, human waste,
Coagulated sludge generated during tertiary treatment of sewage, etc., each f! Examples of organic sludge include flocculated sludge of industrial wastewater, sludge of anaerobic digestion of human waste, sludge of aerobic digestion of human waste, sludge of human waste septic tank, filtration desorption liquid, sewage, and surplus sludge from activated sludge treatment of various industrial wastewater. be able to.

Examples of the inorganic flocculant used in the present invention include ferrous chloride, aluminum sulfate, aluminum chloride, polyaluminum chloride, polyferrous sulfate, and the like. The amount of these inorganic flocculants added depends on the type of compound used, but it is preferably added so that the pH of the organic sludge to be treated falls within the range of 3.0 to 5.0. For example, iron-based inorganic flocculants such as ferric chloride and polyferric sulfate have a pH of 3,
5-4,5, aluminum-based inorganic flocculants such as aluminum sulfate, aluminum chloride, and polyaluminum chloride exhibit the highest addition effect when added at a pH of 4.0 to 5.0.

When the pH after addition of the inorganic flocculant is higher than 5, an acid may be added to adjust the pH.

The amphoteric organic polymer flocculant used in the present invention is a cationic structural unit (cationic group)! - (hereinafter referred to as "r cation amount"), the colloidal equivalent value (
a value) is 1.0 to 37 meq/g, and the colloid equivalent value obtained by colloid titration at pH 7, which indicates the difference between the amount of anionic constituent positions (anionic groups) (hereinafter referred to as "anion amount") and the amount of cationic constituent units. (b value) is -1.7 to 0.7meq
/g, and indicates the ratio of anion amount/cation amount (
The value of a − b )/a is in the range of 0.8 to 1.8.

Under the condition of pH 3, the anionic groups in the amphoteric organic polymer hardly dissociate, and on the contrary, it is thought that most of the cationic groups dissociate. The value (a value) can be regarded as the total amount of cations in the amphoteric organic polymer.

On the other hand, the colloidal equivalent value of the anionic group is usually pH 10,
However, at this pH, the cationic groups in the amphoteric organic polymer may be hydrolyzed to become anionic groups, so in the present invention, the value titrated at pH 7 is used. In this case, since both the cationic group and anionic group in the amphoteric organic polymer dissociate, the result of colloid titration is the amount of extra anion or cation that cancels out the cation and anion. Therefore, the total amount of anions in the amphoteric organic polymer is the colloidal equivalent value titrated at pH 3 and p
It can be considered as the difference (a-b) in colloidal equivalent values titrated with H7.

The amphoteric organic polymer flocculant that can be used in the present invention includes p
Colloidal equivalent value (a) in H3 is 1, 0-3,
7 meq/g, the colloidal equivalent value (b) at P H7 is -1.7 to 0.7 meq/g, and the anion amount/cation amount ratio ((a-b)/a) is 0.
Any amphoteric organic polymer in the range of 8 to 1,8 can be used. Examples of such materials include copolymers of anionic monomer components and cationic monomer components, copolymers of anionic monomer components, cationic monomer components, and nonionic monomer components, or copolymers of anionic monomer components and nonionic monomer components; Examples include Mannich-modified products or Hofmann-decomposed products of copolymers of monomer components and nonionic monomer components.

Examples of anionic monomer components include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid, and sodium methacrylate. Examples of cationic monomer components include dimethylaminoethyl acrylate, dimethylaminoethyl (
Examples include meth)acrylate (DAM), dimethylaminopropyl(meth)acrylate, and quaternized products thereof. Specific examples of the quaternized product include dimethylaminoethyl acrylate methyl chloride quaternized product (DAA). In addition, dimethylaminopropylacrylamide hydrochloride (DAPA
Am) may also be used. Examples of nonionic monomer components include acrylamide (AAm), methacrylamide, N,N''-dimethyl(meth)acrylamide, etc. Also, as a copolymer of these compounds, specifically D A A/A A/ A A
m copolymer, DAM/AA/AA
m copolymer, D A P A A m / A A /
A A m copolymer, D A A/A A copolymer,
Alternatively, Mannich modified products of N a A / A Am copolymers can be mentioned.

The above-mentioned amphoteric organic polymer flocculants can reduce the S of organic sludge.
It is preferable to add O in a proportion of 2.0% by weight to S.

To dehydrate organic sludge according to the present invention, first, an inorganic flocculant is added to the sludge and mixed and stirred, and then an amphoteric organic polymer flocculant is added, or together with the amphoteric organic polymer flocculant, The mixture is introduced into a granulation concentration tank having a filtration section.

As this granulation concentration tank 7, a flocculation reaction tank proposed in Japanese Patent Application No. 62327190 is suitable. This reaction tank is equipped with a stirring means having a stirring blade in the center in a cylindrical tank, and a filter cylinder having a bottom through which water can pass above the stirring blade, and the sludge supplied into the tank is A flocculant is stirred with the above-mentioned stirring means to form flocs, and
The flocculation reaction tank is such that the filtrate entering the filtration cylinder from the bottom is drained out of the tank, characterized in that the bottom of the filtration cylinder is provided with an arcuate slit concentric with the cylindrical tank.

This granulation concentration tank (agglomeration reaction tank) is shown in Figure 2.3. In FIG. 2.3, 11 is a cylindrical tank, and the cylindrical tank 11
The agitator 7a is provided at the center of the holder. The stirrer 7a includes a rotating shaft 12 that is rotatably driven by a motor and a transmission, and stirring blades 13 and 14 that are radially provided in two stages above and below the rotating shaft 12 at a phase of 180''. The filter section 7b includes a bottomed filter tube 17 that is slightly smaller than a semicircle and is installed along the inner periphery of the cylindrical tank 11 with an arcuate portion of the same curvature, and a bottom 17' of the filter tube 17. It comprises a layer 11 and a large number of arc-shaped slits 18 provided concentrically.

The filter tube 17 is provided with a hook 15, and when the hook 15 engages with the upper edge of the cylindrical tank 11, the filter tube 17 is fixed.

The upper end of the filter cylinder 17 and the upper end of the cylindrical tank 11 are on the same level. The bottom 17' of the filter cylinder 17 is located close to the upper edge of the upper stirring blade 13, with a distance of only about 1 to 10 mm. If necessary, a rubber plate may be attached to the upper edge of the stirring blade 13, and the bottom 17' of the filter cylinder 17 may be stroked by this rubber plate during rotation. The width of the slit 18 is 5 mm or less, preferably about 1 to 2 mm, the interval between adjacent slits in the circumferential direction is about 2 mm, and the radial interval between the inner and outer slits is about 5 mm.

The upper stirring blade 13 is preferably a flat plate fixed to the rotating shaft 12 and having a constant width in the vertical direction over the entire length from the base to the tip, as shown in the figure.

The cylindrical tank 11 is also provided with a drain pipe 9a for discharging filtered water from the filter cylinder 17 through the tank wall.

The sludge and amphoteric organic polymer flocculant supplied to the center of the bottom of the tank from the supply pipe 6 and the chemical injection pipe 8b, respectively, are transferred to the rotating shaft 12.
Due to the stirring action of stirring blades 13 and 14 attached to the tank, the mixture is uniformly mixed and reacted while flowing in the tank. Water (separated liquid) injected into the filter cylinder 17 through the slit 18 at the bottom of the filter cylinder 17 is discharged to the outside of the tank from the drain pipe 9a by the pump 9b. As a result, the continuously supplied sludge is sufficiently concentrated and becomes granulated material with high strength. This granulated material is in the sludge pipe 9
It is discharged from q.

Immediately below the bottom 17' of this filter cylinder 17, the stirring blade 1
3 generates a horizontal swirling flow a. A slit 18 provided at the bottom 17' of the filter cylinder allows this horizontal swirling flow a
It is said to have a concentric arc shape along the . For this reason,? During the night, flocs and fibrous materials flow under the bottom 17' in the same direction as the slit 18. As a result, flocs and the like are not caught in the slits 18, and the agglomerated flocs roll under the bottom 17' to form denser and stronger granules.

Note that the lower stirring blade 14 has a rotating shaft 1 that is about half of the total length.
The vertical width of the base 20 on the side attached to 2 is narrow,
It is preferable that the remaining free end portion 21 has a battledore shape with a wide vertical width. In this way, the upper stirring blade 1
Under the horizontal swirling flow a generated by 3, the lower stage stirring blade 14 pushes water outward with its wide free end 21, and the flow swirls upward near the inner periphery of the oak, creating a downward flow b' The upward flow contacts the horizontal swirling flow a produced by the flat plate stirring blade 13 above and descends toward the center, while the downward flow b' rises at the center along the bottom of the tank, thus A swirling vertical circulation flow occurs at the center and bottom of the tank.
The sludge and flocculant supplied to the center of the bottom of the tank ride on this stream b', efficiently mix and contact with the already formed flocs, and coagulate well. If the wide free end 21 is bent at an angle (for example, 45°) that recedes with respect to the rotating direction of the blade as shown in the figure, it becomes easier for this free end to push the water toward the inner periphery of the rice cake. As a result, a stronger swirling circulation flow, b', is obtained, which further improves the mixing and contacting efficiency. Furthermore, the lower end of the inner circumference of the cylindrical tank 11 and
A guide plate 22 which is located in the middle between the upper stirring blade 13 and the lower stirring blade 14 and extends in the direction of rotation of the stirring blade, and is linear or curved as shown in the figure and gradually moves away from the inner periphery toward the tip. :23, the upper circulating flow flows along the horizontal swirling flow a and then downwards at the center, and the lower circulating flow b' flows along the elliptical bottom and then upwards at the center. In addition, mixing and contacting efficiency can be improved as well.

As for the filtration tank, as described above, the case where it is provided inside the cylindrical tank has been described, but the filtration tank may be provided outside the cylindrical tank. In that case, the filtration tank is installed outside the upper outer periphery of the tank wall of the cylindrical tank,
A slit is provided horizontally at the top of the tank wall of a cylindrical tank surrounded by a filtration tank to filter the liquid in the cylindrical tank and put it into the filtration tank.
And, the outer edge of the stirring blade is attached to the upper inner circumference of the tank wall of the cylindrical tank.
It is sufficient if they are placed close to each other at an interval of 10 mm. If necessary, a rubber plate may be attached to the outer edge of the agitating blade, and during rotation, the rubber plate may stroke the inner circumference of the tank wall of the cylindrical tank provided with a slit. Even in a granulation thickening tank with this type of structure, the sludge and flocculant supplied from the bottom of the cylindrical tank are stirred and reacted in the tank, and during that time, the water that enters the filtration tank through the slit in the tank wall is pumped, etc. In order to drain the water outside the tank, the continuously supplied sludge is sufficiently concentrated and grows into a strong floc, which is then discharged from the sludge pipe and guided to the dehydrator. The flocs generated in the cylindrical tank are pushed by a stirring blade that rotates horizontally close to the inner periphery of the upper part of the sieve wall of the cylindrical tank provided with slits, and roll along the slits along the inner periphery of the tank wall. Not only does it not get caught and clog, but it also becomes dense and strong by rolling along the inner circumference of the tank wall along the slit.

The granulated material thus produced in the granulation concentration tank is supplied to a dehydrator as it is or after removing the separated liquid, and is dehydrated in the same manner as in the conventional method. As the dehydrator, conventionally used dehydrators such as a centrifugal dehydrator, a vacuum dehydrator, a belt press type dehydrator, a screw press, or a filter press can be used.

[Function] The mechanism of action of the dehydration method of the present invention is estimated as follows.

First, inorganic flocculants have very small molecular weights and do not form flocs, so they can sufficiently react with the anionic mucilage on the surface and inside of sludge particles.
Due to the decrease in H, the carboxyl groups of mucilage substances such as proteins and polysaccharides are nonionized, thereby neutralizing the charges.

As charge neutralization by the inorganic flocculant progresses, the water held by the sludge particles decreases, and at the same time the number of adsorption points where the cationic groups of the polymeric flocculant react decreases, while the adsorption of anionic groups and the reactive acidic metal Hydroxide increases. For this reason, when a cationic organic polymer flocculant or an amphoteric organic polymer flocculant with a large amount of cations is used, it becomes impossible to generate flocs strong enough to allow mechanical dewatering. Also,
When an anionic organic polymer flocculant is used, the adsorption and reactivity of anionic groups is too large, so the anionic organic polymer flocculant sticks to each sludge particle, and the anionic organic polymer The molecules themselves shrink and precipitate,
It becomes impossible to crosslink and aggregate other particles to form coarse flocs.

On the other hand, when the specific amphoteric organic polymer flocculant of the present invention is used, when the anion group reacts and adsorbs to the sludge particles, the flocculant sticks to the sludge because there is a cation group in the same molecule. Some of the groups will exist in a free state without being attached.

The free groups of such amphoteric organic polymer flocculants adsorb each other and crosslink, thereby making it possible to bind sludge particles and form large and strong coagulated flocs.

Such agglomerated flocs are granulated in a granulation concentration tank, and become granulated products (beret l-') with good dehydration properties. By mechanically dehydrating this pellet, efficient dehydration treatment can be performed.

In the present invention, flocculation is promoted using an inorganic flocculant and an amphoteric organic polymer flocculant whose ratio of anion and cation amounts is specified, and the flocs are further granulated in a granulation concentration tank and dehydrated. As a result, in the dewatering treatment of organic sludge, the processing capacity per unit time is greatly increased and S
It is possible to increase the recovery rate of S, improve the peelability of the dehydrated cake from the filter cloth, and lower the water content of the dehydrated cake.

[Example] The present invention will be described in more detail by giving Examples and Comparative Examples below. In addition, in the following, "%" is "weight%"
It shows.

Table 1 lists the amphoteric organic polymer flocculants used in Examples and Comparative Examples, and Table 2 lists the polymer flocculants used in Comparative Examples. That is, in each of the Examples and Comparative Examples, an organic polymer flocculant selected from among the polymer flocculants shown in Table 1 or Table 2 was used.

Table 1 Amphoteric organic polymer flocculants *IDAA, methyl chloride quaternization product of dimethylaminoethyl acrylate AA, acrylic acid AAm/acrylamide DAM, methyl chloride quaternization product of dimethylaminoethyl methacrylate NaA; sodium acrylate DAPAAm; dimethyl Aminobrobyl acrylamide hydrochloride Table 2 Polymer flocculant 11: PAH; Polyacrylic acid hydrazide and others are listed in Table 1.
Same as table *2: 45 parts by weight of sodium hydrogen sulfate was added to 100 parts by weight of flocculant to make a homogeneous solution.

Examples 1 to 13, Comparative Examples 1 to 19 Excess sludge from activated sludge treatment at a sewage treatment plant was granulated and agglomerated in a granulation thickening tank according to the treatment flow shown in Figure 1 and under the treatment conditions shown in Table 3. At the same time, the resulting aggregates were subjected to gravity filtration and compression dehydration tests.

The properties of the filtrated sludge are as follows.

Sludge properties TS: 5400-5700mg/nSS: 52
00~5500mg/IVSS/SS: 82.0~
82.4% In addition, the granulation concentration tank used was a sieve having an effective volume of 100° C. and having the structure shown in FIG. 2.3. Concentration mechanism has a width of 1.5
A half-moon-shaped drainage slit with a concentric opening of mm was provided, and the slurry supply amount was 1 m'/hr. The peripheral speed of the stirring blade was in the range of 30 to 40 m/min. The inorganic flocculant was prepared in advance with an organic volume of 5011 and a circumferential speed of 120 m/
The reaction was carried out in a min.

The gravity filtration test was conducted using Held Breath dehydration filter cloth (Ryokanbasu P-1189) at 0.1°, 0.2, 0.3, 0.
．． The test was carried out under a load condition of 4 g-DS/cm'. These values are 60 and 12, respectively, assuming a filter cloth running speed of 1 m/min.
This corresponds to the condition of 0180.240kg-037m-h. The evaluation was based on the time required for filtration (in seconds) to reduce the water content ratio (water content to 1 solid content) to 20 or less. Note that a water content ratio of 20 corresponds to a water content of 95.2%.

In the squeezing test, the cake was pre-squeezed at 0.05 kg/crn' at squeezing pressures of 0.25, 0.5, 1.0°2, OK.
It was dehydrated by pressing under the conditions of g/crn', and the moisture content was measured, and its releasability was visually evaluated on the following three scales.

Peelability evaluation criteria ○: Good removability △, peelability normal ×: Poor peelability The results are shown in Table 3 (Part 1) and (Part 2).

Each side shown in Table 3 adopts the following setting conditions.

In Examples 1 to 10, after tempering with an inorganic flocculant (FeCf13), a specific intramolecular amphoteric organic polymer flocculant was added to granulate and concentrate.

In Comparative Examples 1 to 4, after tempering with an inorganic flocculant (FeCf13),
Pelletized and concentrated by adding an intramolecularly amphoteric organic polymer flocculant with a composition other than the above.

Comparative Examples 5 to 12 were tempered with an inorganic flocculant (FeCu3),
Composition polymer (containing an anionic polymer and cationic polymer, or acrylic acid hydrazide polymer and cationic polymer) is added and granulated and concentrated.
13) If 2% is added, the coagulation effect is poor, and the process cannot be performed unless the amount is reduced to 1%. ).

Comparative Examples 13 and 14 used an anionic polymer as an organic polymer flocculant.

Comparative Examples 15 and 16 used a cationic polymer as an organic polymer flocculant.

Comparative Example 17 was treated with a cationic polymer alone (in this case, no granulation was performed (agglomerates were small) and SS recovery was poor).

In Comparative Example 18, the cationic reamer was subjected to ordinary agglomeration treatment.

Examples 11 to 13 use PAC (polyaluminum chloride) and Aj2Cj2s (aluminum chloride) polyferrous sulfate as inorganic flocculants. Good results are obtained.

In Comparative Example 19, after tempering with an inorganic flocculant, a specific intramolecular amphoteric organic polymer flocculant was used, but normal flocculation treatment was performed (no shrinkage).

Among the results shown in Table 3, the following can be said about the SS concentration and SS recovery rate of the separated water.

That is, unless the coagulated flocs are sufficiently large and have high strength, a large amount of SS will leak into the separated water and the SS recovery rate will be poor, but according to the method of the present invention, good results can be obtained.

Furthermore, the following can be said about gravity filtration when the water content is 20 or less. That is, belt press dehydration is performed in the order of gravity dehydration, preliminary compression, compression, and high pressure compression. At this time, the gravity dewatering zone is approximately 0.5m to 2m, and the filter cloth speed is 1
For m/min, 0.5 minutes (30 seconds) to 2
It is necessary to complete gravity dehydration within minutes (120 seconds), ideally within 30 seconds. Note that a water content ratio of 20 is a standard for completion of gravity dehydration. According to the method of the present invention, the load amount in the desktop gravity filtration test is 0.4 g/crn' (! Cloth running speed 1.
0/min, 4kg/rn'x1. On/m i
n x 60 min / h = 240 k
g/m-h), gravity dehydration is fully possible. Therefore, it can be seen that the throughput can be significantly increased.

Furthermore, the following can be said about the squeezing test. That is,
During compression dewatering, as the pressure increases, the water content of the dehydrated cake decreases, but on the other hand, the peelability of the dehydrated cake from the filter cloth becomes worse, making dewatering impossible. Therefore, it is necessary to set the mechanical conditions of the belt press to a compression pressure that can maintain peelability. According to the method of the present invention, even when dewatering is performed by pressing at a pressure of 2.0 kg/cr+f or more, the peelability is good and the water content of the dehydrated cake can be significantly reduced.

Example 14, Comparative Examples 20 to 22 Excess sludge from a sewage treatment plant was granulated and concentrated in the same manner as in Example 1, and then dehydrated using a belt press dehydrator with a filter cloth width of 40 cm and a high-pressure squeezing mechanism. The water content of the dehydrated cake and the amount of sludge treated were measured.

The properties of the treated sludge are as follows.

Sludge properties TS: 5500-5700mg/uSS: 53
00-5500mg/IVSS/SS: 82.1-82
5% That is, F e C,fls is added to the sludge as an inorganic flocculant.
After adding and tempering in the amount shown in Table 4 (not added in Comparative Example 20), the organic polymer flocculant shown in Table 4 was added and granulated and concentrated to the concentration ratio shown in Table 4. did. After granulation and concentration, it was dehydrated and the moisture content of the dehydrated cake and the amount of sludge processed were measured. Note that the filter cloth tension of the dehydrator was changed to a maximum squeezing pressure of 03 to 3.0 kg/cnf to provide stable dehydration cake releasability. In addition, the amount of sludge supplied was increased or decreased, and the filter cloth traveling speed at this time was set to the lowest filter cloth speed at which no side leakage of sludge occurred in the gravity filtration section and the press dewatering section. The results are shown in Figure 4.

Table 4 *1: Amount added as iron atoms to SS.

*2: Amount added to SS.

*3 Magnification of 1.0 indicates no concentration.

From FIG. 4, in Example 14, the throughput of the belt press is 2.
The moisture content of the dehydrated cake at 50 kg-DS/m-hr was 80%, indicating that a dehydrated cake with a low moisture content can be obtained with a high sludge throughput. On the other hand, Comparative Example 2o is substantially unprocessable;
1.22, the amount of sludge treated with a moisture content of 80% is 67 kg-D.
S/m-hr, 83 kg-D S/m-h
r, and is lower than the station of Example 14.

Example 15, Comparative Examples 23 to 25 Initial settling sludge and surplus sludge from a sewage treatment plant The mixed raw sludge was granulated and concentrated, and the water content of the dehydrated cake and the amount of sludge treated were measured using the same Held Breath dehydrator as in Example 12. did.

The properties of the treated sludge are as follows.

Sludge properties TS: 11000-12200mg/uSS:
10400～114QQmg/j2V S S/S S
・80.8 to 81.3% After adding PAC as an inorganic coagulant to the above A5 mud in the amount shown in Table 5 (not added in Comparative Example 23) and refining, the organic high content shown in Table 5 was added. After adding a molecular flocculant and granulating and concentrating the mixture to the concentration ratio shown in Table 5, it was dehydrated using a dehydrator. The amounts of the inorganic flocculant and organic polymer flocculant added were the optimum amounts determined in a preliminary test. The results are shown in Figure 5.

Table 5 *1: Amount added to SS.

*2: Amount added to SS.

*31 Magnification of 1.0 indicates no concentration.

Figure 5 also shows that according to the method of the present invention, the processing amount is 130 kg-DS/1, which is the standard treatment efficiency for mixed raw sewage sludge.
m-hr, water content 78%, throughput 425kg-
It is clear that the treatment can be carried out at a high treatment efficiency of DS/m-hr and water content of 75%, and that a good dehydrated cake can be obtained.

[Effects of the Invention] As described above, according to the method for dewatering organic sludge of the present invention,
In the dewatering treatment of organic sludge, it is possible to increase the processing capacity per unit time, increase the recovery rate of SS, improve the peelability of the dehydrated cake from the filter cloth, and lower the water content of the dehydrated cake. Therefore, it is possible to save costs such as fuel costs necessary for incinerating the dehydrated cake and transportation costs of the dehydrated cake, and efficient dehydration processing can be performed at low cost.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one implementation method of the organic sludge dewatering method of the present invention. FIG. 2 is a partially sectional perspective view showing an example of a granulation concentration tank suitable for carrying out the present invention, and FIG. 3 is a plan view thereof. Figure 4 shows Example 14 and Comparative Examples 20-
22 is a graph showing the results of No. 22. FIG. 5 is a graph showing the results of Example Go 5 and Comparative Examples 3 to 25. 1... Raw sludge storage tank, 3... Sludge conditioning tank, 4...
- Auxiliary agent dilution tank, 7... Granulation concentration tank, 7a... Stirrer, 7b... Filtration section, 8... Polymer dissolution tank, 11... Cylindrical tank, 12... Rotating shaft, 1
3.14... Stirring blade, 17... Filter cylinder.

Claims (1)

[Claims] (1) After adding an inorganic flocculant to organic sludge and stirring,
Further, after adding an organic polymer flocculant, or together with the organic polymer flocculant, the organic sludge is introduced into a granulation concentration tank having a filtration section, and the sludge is concentrated by taking out the filtrate from the filtration section. In the method of granulating and dehydrating the granulated product using a dehydrator, the organic polymer flocculant is an amphoteric organic polymer flocculant having an anionic constitutional unit and a cationic constitutional unit, and p
Colloid equivalent value (a value) in H3 is 1.0 to 3.7
meq/g, the colloidal equivalent value (b value) at pH 7 is -1.7 to 0.7 meq/g, and the amount ratio of anionic constitutional unit/cationic constitutional unit is (a-b)/
A method for dewatering organic sludge, characterized in that the value of a is 0.8 to 1.8.