JPH0731999A - Dehydrating method of sludge - Google Patents

Abstract

PURPOSE:To enable dehydration efficiently and economically favorably even in the case of the org. sludge low in dehydrating property by supplying the preconcentrated sludge containing a high polymer flocculant hydrate phase to a screw press in the case of the dehydration of the org. sludge. CONSTITUTION:In the dehydration of the org. sludge, when the preconcentrated sludge containing the high polymer flocculant hydrate phase is supplied to the screw press 7, by the rotation of a screw 10, the preconcentrated sludge supplied to one end of a cylinder 12 is propelled towards the other end in a hopper 6 by a screw 11. Then, when the dehydration proceeds in the screw press 7, the high polymer flocculant hydrate phase is made finer and kneaded by a shearing force and dispersed uniformly in the sludge gradually, and the phase easy to be drawn is recondensed. In such a way, the discharge of the phase easy to be drawn is hardly caused through the mesh of a cylinder 10, the strength of whole flocculated matter becomes higher, does not destroyed any longer by the pressure in the screw press 7 and is dehydrated under ideal pressure rising.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating organic sludge, and more specifically, to efficiently use a screen press having a screen pre-concentrator,
The present invention also relates to a method of dehydrating organic sludge, particularly wastewater treatment sludge of a paper mill, in an economically advantageous manner.

[0002]

2. Description of the Related Art Organic sludge generated from biological treatment facilities such as sewage treatment plants, human waste treatment plants, wastewater treatment sludge of paper mills and activated sludge method in various mills is mixed with an appropriate dehydrating agent and then filtered or centrifuged. It is mechanically dehydrated by separation. Acrylic organic polymer flocculant as a dehydrating agent is added to such organic sludge to agglomerate the sludge, and aluminum hydroxide such as polyaluminum chloride, sulfuric acid band, and polyferric sulfate is added, and metal hydroxide is added. A method in which an organic polymer coagulant is used in sludge to coagulate the sludge, which is then pre-concentrated with a rotary screen and then dehydrated with a filter press.
9-183896), a method in which organic sludge is aggregated and then dehydrated by a belt press or a decanter, or a method in which ferric chloride and calcium hydroxide are added to sludge and vacuum filtration is proposed.

On the other hand, a rotating screw is built in an outer cylinder composed of a punching plate, coagulated sludge is supplied to one end of the outer cylinder, and sludge is moved to the other end in the outer cylinder by rotation of the screw while sludge is being transferred between them. A screen press for removing the water content from the pores of the outer cylinder and obtaining the dehydrated cake at the other end of the outer cylinder is conventionally known, and in recent years, a preconcentrating device using a rotary screen is provided to improve the processing capacity. The method is often used for dewatering wastewater treatment sludge in paper mills. To obtain coagulated sludge to be supplied to the sludge dewatering machine,
A general method is to add and mix an organic polymer flocculant aqueous solution to sludge.

In this screw press, sludge is suitable for the screw press because it depends on the rotation of the screw both for transporting the sludge in the outer cylinder and for increasing the pressure in the outer cylinder, which is the pressing force for dehydration. In this case, the pressure rises smoothly, dehydration can be performed efficiently, the structure is simple, operation management is easy, noise is not generated, and the water content of sludge can be further reduced by heating the screen. Have the advantages of. Further, by pre-concentrating the coagulated sludge obtained by adding and mixing the aqueous solution of the organic polymer coagulant to the sludge in a highly fluidized state with a rotary screen, the sludge dewatering capacity can be improved as compared with the case where the screw press alone is used. It is often used for sludge dewatering of paper mill wastewater, which has a high fiber content and good dewaterability. However, if a large amount of activated sludge or hydrous silicic acid is mixed into the wastewater sludge of a paper mill, the dewaterability deteriorates. Generally, the organic polymer coagulant is added as a low-concentration aqueous solution so as to be uniformly dispersed in the sludge, and is not visually observed in the sludge after coagulation.

[0005]

However, a method in which sludge is coagulated using a low-concentration aqueous solution of an organic polymer coagulant, preliminarily concentrated by a rotary screen, and then dehydrated by a screen press has poor dewatering property. In the case of organic sludge, the sludge treatment amount cannot be increased, the sludge recovery rate cannot be improved,
There is a problem that the water content of sludge cannot be reduced. In this case, even if the amount of the aqueous solution containing the organic polymer coagulant added was increased, the sludge after preconcentration with the rotary screen was only sticky, and the problem could not be solved. An object of the present invention is to provide a method for solving the above problem even in the case of an organic sludge having a poor dewatering property, for efficiently and economically dewatering the organic sludge.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that, for example, an organic polymer coagulant is dispersed in oil or an aqueous salt solution in an amount of about 10% by weight or more. The dispersion is added to the coagulated sludge in a highly fluidized state and then pre-concentrated with a rotary screen, or the sludge is coagulated using an aqueous solution containing an organic polymer coagulant and then pre-concentrated with a rotary screen, and then the dispersion Is added with water to form a flocculant containing a polymer flocculant hydrate phase, and by supplying this to a screen press for dehydration, an extremely excellent sludge dewatering effect is exhibited. The present invention has been found.

According to the first aspect of the present invention, when the organic sludge is dehydrated by using a screen press having a screen pre-concentrator, a pre-concentrated sludge containing a polymer flocculant hydrate phase is screened. It is a sludge dewatering method characterized by supplying it to Eupress.

The invention of claim 2 of the present invention is characterized in that the concentration of the polymer flocculant in the water phase of the polymer flocculant is 0.3 to 3% by weight, and the sludge dewatering according to claim 1. Is the law.

According to the third aspect of the present invention, when the organic sludge is dehydrated by using a screenless press having a screen pre-concentrating device, the sludge after the pre-concentrating operation has a polymer coagulant content of 0. The sludge dewatering method according to claim 1, wherein after adding a liquid of 3 to 3% by weight, the liquid is supplied to a screen press.

The acrylic polymer used in the present invention has a molecular weight of 1,000,000 or more, preferably 2,000,000 or more, selected from copolymers of 5 to 100 mol% of an ionic monomer and 0 to 95 mol% of acrylamide. The acrylic water-soluble polymer is used as a fine particle having a particle size of 100 μm or less, and is used in a state of being dispersed in an oil or salt aqueous solution. A method for producing such a dispersion is known, and water-in-oil emulsions are disclosed in JP-B-34-10644 and JP-B-52.
JP-B-39-417 and JP-B-55-45783, the method for producing a dispersion in an aqueous salt solution is described in JP-B-46-
14907 and Japanese Patent Laid-Open No. 62-20511.

As the ionic monomer to be copolymerized with acrylamide, an acrylic cationic monomer such as a salt of dialkylaminoalkyl (meth) acrylate and / or its quaternary product, a salt of dialkylaminoalkyl (meth) acrylamide and / or its quaternary product. In addition, acrylic anion monomers such as acrylate or 2-acrylamidoalkyl sulfonate are used. Two or more of these ionic monomers may be used in combination and copolymerized with acrylamide. It is also excluded from the present invention to copolymerize a nonionic monomer such as acrylonitol or diacetone acrylamide with the above ionic monomer or acrylamide as long as the amount is 20% by weight or less and does not adversely affect aggregation. Not a thing.

When applying these anionic, cationic or amphoteric polymer flocculants to the present invention, not only one polymer flocculant is added, but two or more polymer flocculants are individually added. Can be added to, mixed with, or used in combination with other sludge modifiers, and can be appropriately selected according to sludge properties.

[0013]

The operation of the present invention will be described below based on the dehydration method of the present invention illustrated in FIGS. 1 and 2 are coagulant mixing tanks having variable speed stirring blades. An aqueous polymer flocculant solution (concentration 0.1 to 0.2% by weight) was added to each mixing tank from the chemical injection pipes 3 and / or 4 to agglomerate the sludge into coarse particles to facilitate solid-liquid separation. Supply to the pre-concentrator of. Reference numeral 5 denotes a sludge pre-concentrator comprising a rotary screen, and the coagulated sludge is concentrated to a sludge concentration of 5% by weight or more by removing particulate pore water by gravity filtration. The pre-concentrated sludge discharged from the rotary screen 5 is supplied to the screw press 7 through the hopper 6.
In order to carry out the present invention, a conventional chemical injection dehydrator is provided with a chemical injection pipe 8 and / or a polymer coagulant dispersion solution in which a low-viscosity polymer coagulant dispersion solution is added to a coagulant mixing tank as a raw solution. A chemical injection pipe 9 for adding to the hopper 6 while mixing with water is provided.

The screen press 7 has a hopper 6 at one upper end of a horizontally elongated cylinder 12 made of a perforated punching plate having a hole diameter of about 1 mm. A tapered screw 10 is concentrically installed in the cylinder so that the small diameter portion faces one end and the large diameter portion faces the other end inside the cylinder, and is rotationally driven by a motor or the like. A screw 11 having an outer diameter adapted to the inner diameter of the cylinder 12 is provided on the outer circumference of the screw 10, and the screw 11 propels the pre-concentrated sludge supplied to one end of the cylinder by the hopper 6 toward the other end by rotation of the screw. .

As described above, the screen has a taper, and the annular space between the outer circumference of the screen and the inner circumference of the horizontally elongated cylinder is gradually narrowed from one end to the other end of the horizontally elongated cylinder. Therefore, the pre-concentrated sludge supplied into one end of the horizontal cylinder moves toward the other end at a low pressure while dehydrating water through the pores of the cylinder on the one end side where the current gap is wide, and in the middle of the horizontal cylinder an annular shape. Since the gap is narrowed to a certain extent, it is moderately pressurized and dehydrated in the same manner, and the other end side is pressurized to the maximum and dehydrated similarly, and finally the dehydrated cake is formed from the other end of the horizontal cylinder. Is discharged.

The pre-concentrated sludge supplied to the screw press is crushed when shearing force is applied to the coagulated sludge matrix, squeezed out, and is easily discharged together with water through the pores of the cylinder. It covers the physical aspects. Polymer flocculant The concentration of the polymer flocculant in the hydrated phase is 0.3 to 3% by weight, preferably 0.5 to 2% by weight. If it is less than 0.3% by weight, it is discharged and removed from the pores of the outer cylinder before the aggregation effect is exhibited, and if it is 3% by weight or more, it is difficult to be dispersed in sludge due to its high viscosity.

As the dehydration progresses in the screen press 7, the polymer coagulant hydrate phase is finely divided by shearing force, and is kneaded and then uniformly dispersed in the sludge to re-aggregate the easily squeezed phase. As a result, the above-mentioned squeezable phase is not discharged through the pores of the cylinder and the strength of the whole agglomerate becomes high, so that the pressure in the screen press no longer breaks, so the screen press has an ideal pressure rise. The agglomerates can be dewatered under the condition that the sludge dewatering efficiency can be greatly improved.

If necessary, steam may be supplied into the screen to heat the screen. Thus, according to the present invention, when the organic sludge is dehydrated using the screen press having the preconcentrating device with the rotary screen, first, the agglomerates containing the polymer coagulant hydrate phase are prepared, and the screen press is used. By continuously supplying to the press, the function of the screen press can be maximized and the sludge can be dehydrated.

[0019]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto. Fig. 1 shows the configuration of the sludge dewatering device used in this test.
1 and 2 are coagulant mixing tanks having variable speed stirring blades, and standard mixing conditions are a residence time of 1.5 minutes in each tank and a stirring blade peripheral speed of 1 m / sec. The polymer coagulant aqueous solution (concentration 0.1 to 0.
2% by weight) and the sludge is agglomerated into coarse particles to facilitate solid-liquid separation and then supplied to the next preconcentrator. Reference numeral 5 is a sludge pre-concentrator comprising a rotary screen having openings of 40 mesh, and the coagulated sludge is concentrated to a sludge concentration of 5% by weight or more by removing particulate pore water by gravity filtration. The pre-concentrated sludge discharged from the rotary screen 5 is supplied to the screw press 7 through the hopper 6. The above is the conventional chemical injection dehydrator. In order to carry out the present invention, a conventional chemical pouring dehydrator is provided with a chemical pouring pipe 8 for adding a low-viscosity polymer coagulant dispersion as it is to a coagulant mixing tank and / or a polymer coagulant dispersion. Chemical injection pipe 9 to be added to hopper 6 while mixing with water
Equip. Table 1 shows the composition of the polymer flocculant used in this test. The results of the dehydration test conducted using the apparatus of FIG. 1 are described below.

[0020]

[Table 1]

(Example 1 and Comparative Example 1) An organic sludge (pH 6.7, SS1.SS) composed of a mixture of coagulation sedimentation sludge discharged from a paper mill and surplus sludge of activated sludge biological treatment.
6 wt%, TS 1.7 wt%, VTS / TS 58 wt%, 200 mesh residue / SS 14.5 wt%) were tested. A 0.1 wt% aqueous solution of anionic polymer flocculant P-1 was added from the chemical injection pipe 3 in FIG.
A 0.2% by weight aqueous solution of the cationic polymer flocculant P-2 was added to the sludge agglomerate to perform gravity filtration to obtain a pre-concentrated sludge having a dry solid content of 6.2% by weight from the rotary screen 5. Was discharged. The addition amount of the polymer (polymer flocculant) in the standard state is a polymer pure content per sludge TS (dry solid content) and is 0.2% by weight for both P-1 and P-2. Table 2 shows a comparison in which the standard state was used as a blank, and the chemical injection method was further changed for the additional chemical injection of P-2.

However, the condition of chemical injection from each pipe in Table 2 is different, and the pipe 4 has a 0.2 wt% aqueous solution added,
The pipe 8 was added with the stock solution of the 12.5 wt% dispersion liquid, and the pipe 9 was added while mixing the polymer dispersion liquid and water so that the polymer content in the diluting liquid was 1 wt%. Further, the display of the treatment amount is shown in the standard state, that is, in the ratio based on the sludge treatment amount in the blank. Test numbers 4 and 5
In the pre-concentrated sludge discharged from the rotary screen, particles of P-2 water-containing phase having a particle size of 0.5 to 3 mm were observed, and the polymer concentration in the particles was about 1 to 2% by weight.

[0023]

[Table 2]

(Example 2 and Comparative Example 2) The same dehydration test as in Example 1 was carried out except that the polymer concentration in the P-2 diluted solution to be additionally injected through the pipe 9 was changed. The results are shown in Table 3.
Shown in.

[0025]

[Table 3]

(Example 3 and Comparative Example 3) Organic sludge (pH; 6.5, SS) obtained by adding 200 ppm of liquid band to a mixture of coagulation sedimentation sludge discharged from a paper mill and surplus sludge of biological treatment by activated sludge method. 2.1% by weight, VTS
/ TS; 65% by weight, 200 mesh residue / SS; 1
6.7% by weight) was subjected to the test. Preliminary concentration of 6.5% by weight of dry solids was obtained by gravity filtration of sludge aggregate obtained by adding 0.2% by weight aqueous solution of amphoteric polymer flocculant P-3 from the chemical injection pipe 4 in FIG. Sludge is a rotary screen 5
More discharged. The addition amount of the polymer (polymer flocculant) in the standard state was 0.4% by weight in terms of polymer pure content per sludge TS, and no effect of increasing the amount was recognized. This standard state was used as a blank, and P-3 was mixed with water, and additional chemicals were injected through the pipe 9. The results are shown in Table 4.

[0027]

[Table 4]

(Example 4 and Comparative Example 4) The same test as in Example 3 was conducted except that the amphoteric polymer flocculant used in the experiment was P-4. The results are shown in Table 5. The amount of P-4 added was increased from the standard state of 0.4% by weight of TS to sludge, and 2
Even when 0.8 wt% was added to the sludge TS, which was double the amount, the sludge dewatering state was almost the same as the standard state, that is, the blank.

[0029]

[Table 5]

[0030]

INDUSTRIAL APPLICABILITY The present invention relates to a method for dehydrating organic sludge. For example, a dispersion of an organic polymer flocculant dispersed in oil or an aqueous salt solution in an amount of about 10% by weight or more is a highly fluidized flocculated sludge. After being concentrated in a rotary screen to give a flocculant containing a polymer flocculant hydrate phase, the flocculate is supplied to a screen press for dehydration to produce a papermaking product containing activated sludge or hydrous silicic acid. The sludge treatment amount can be increased even in the case of organic sludge, which has poor dewaterability and weak sludge strength such as wastewater sludge in factories.
It is possible to obtain an extremely excellent sludge dewatering effect such that the sludge recovery rate can be improved and the water content of the sludge can be reduced. INDUSTRIAL APPLICABILITY The present invention is capable of dehydrating organic sludge efficiently and economically, and thus has high industrial utility value.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

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

[Explanation of symbols]

 1, 2 Flocculant mixing tank 3, 4 Chemical injection pipe 5 Rotary screen 6 Hopper 7 Screen press 8, 9 Chemical injection pipe 10 Screw 11 Screw 12 Cylinder

Claims (3)

[Claims] 1. When dewatering an organic sludge using a screen press having a screen pre-concentrator, a pre-concentrated sludge containing a polymer coagulant hydrate phase is supplied to the screen press. Sludge dewatering method. 2. The sludge dewatering method according to claim 1, wherein the concentration of the polymer flocculant in the water phase of the polymer flocculant is 0.3 to 3% by weight. 3. When the organic sludge is dehydrated by using a screen press having a screen pre-concentration device, the sludge after the pre-concentration operation has a polymer coagulant content of 0.3.
The sludge dewatering method according to claim 1, wherein the liquid is added to the screen press after adding 3 to 3 wt% of the liquid.