JPH05115900A - Method and device for dehydration of sludge - Google Patents

Abstract

PURPOSE:To obtain a cake low in water content by filtrating and dehydrating a sludge flocculated, by irradiating with ultrasonic wave while stirring the cake, by flocculating again a primary dehydrated slurry dispersed and fluidized and by pressing and dehydrating to obtain a secondary dehydrated cake. CONSTITUTION:The sludge fed from a throw-in hole 8 is flocculated by a high molecular coagulant to make large floc, is rapidly filtrated and separates water with a screen 1 in accordance with revolution of the feeding shaft 1 and is transferred to a flocculating chamber 2 by a screw propeller 5. The sludge is made to be a cake-like matter having 80-85% water by filtration with pressing. The cake is stirred with the screw propeller 6, is irradiated with ultrasonic wave from the ultrasonic irradiation device 9 and is crushed and dispersed, and fluidized and a lowmolecular coagulant is added to the fluidized cake to form a small floc in the fluidized slurry. The flocculated slurry is strongly pressed during the slurry is fed to the rotary screen 3 of the next stage and free water in the slurry is filtrated and dehydrated to obtain the cake low in water content.

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 sewage sludge and the like and improvement of the apparatus.

[0002]

2. Description of the Related Art Conventionally, as a method for dehydrating sewage sludge of this type and its dehydrating means, sewage is concentrated with a polymer flocculant or the like to a concentrated sludge of about 3 to 5%, which is then pressed with a belt or the like. It is known to perform pressure filtration with a pressure dehydrator of No. 1 and discard or incinerate it as a cake having a water content of about 80%. To give a concrete example of conventional concentrating means,
For example, there is the invention of Japanese Examined Patent Publication No. 62-35804, and in this invention, a filter plate is hung in the concentration tank so that the sludge concentrated by separating water is drawn out from the bottom of the tank.
Even if concentrated by such mechanical means, the concentration is 3-5%.
And, while putting a heavy burden on the dehydrator after the fact,
The cake obtained from the dehydrator also has a water content of 80 as described above.
%.

[0003]

As described above, according to the conventional concentration method and dehydration method, the concentration can be only about 3 to 5%, which is an enormous amount from the amount of sludge generated every day. As the digestion tank in the facility will be large,
The large amount of sludge sent to the dehydrator also requires a large dehydrator. Furthermore, the cake treated with this dehydrator also has a large water content of about 80% and is still in large quantity, so it is necessary to dispose of it for transportation and to secure a place, and for incineration, there are many problems such as incinerator and fuel. I have left.

[0004]

Therefore, according to the present invention,
By concentrating the sludge in two stages and dehydrating it, the amount of the cake was reduced as a cake with a low water content.
The following methods and means are adopted as the concentration and dehydration methods and means. That is, the sludge aggregated by adding a polymer flocculant is rapidly filtered and dehydrated, and the cake is stirred and irradiated with ultrasonic waves to be dispersed and fluidized. After the agent is added and re-aggregated, it is dehydrated under pressure to obtain a secondary dehydrated cake. Then, as a means for obtaining the above-mentioned secondary dehydrated cake, a rapid dehydrator consisting of a screen drum or the like equipped with an aggregating device using a high molecular weight aggregating agent in the preceding stage, and provided in the subsequent stage of this rapid dehydrator, and equipped with a stirring device and It comprises a flocculating device using a low-molecular-weight flocculating agent equipped with a sonic wave irradiating device, and a pressure dehydrator provided at the subsequent stage of this flocculating device. Further, as a specific configuration of the pressure dehydrator and the aggregating device using a low molecular weight aggregating agent, the configuration of this pressure dehydrator is configured in the form of a screw press provided with a screw shaft in the outer cylinder, An aggregating cylinder provided with a device for adding a low-molecular-weight coagulant is provided between the terminal end and the starting end of the pressure dehydrator, and the stirring device and the ultrasonic projection device are provided in the aggregating cylinder.

[0005]

The present invention is constructed as described above. First, sludge agglomerated by a polymer coagulant has large flocs and good dewatering property, and can be rapidly dewatered by a filter dewatering machine. And the like can be used to obtain a cake having a water content of about 80%. Most of the 80% of the water in the cake at this time is the internal water in the floc,
It exists in the cake in a state in which it is difficult to separate under pressure. Next, by irradiating ultrasonic waves while stirring the cake, the large flocs are broken and the water inside is released, liquefied and allowed to flow. That is, a concentrated slurry having a concentration of about 80% is obtained, and by adding a low molecular weight aggregating agent to this slurry, flocs having a small solid content are formed and aggregated. This small floc has a small amount of water retained, and since the fluidized slurry has a high concentration of about 80% as described above, a cake with a low water content (about 60%) can be efficiently obtained by the subsequent pressure dehydration. be able to. Hereinafter, the present invention will be specifically described with reference to the drawings.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a vertical sectional side view of a concentrating and dehydrating apparatus for carrying out the present invention. Reference numeral 1 is a cylindrical screen on which a metal mesh is stretched, 2 is a coagulation chamber, and 3 is a metal mesh. It is a cylindrical rotating screen in which is stretched.
Reference numeral 4 denotes a rotatable feed shaft that is provided through the screen 1, the agglomeration chamber 2, and the rotary screen 3 so as to penetrate therethrough, and a portion corresponding to the screen 1 has a spiral blade whose pitch is gradually reduced. 5 is wound, a large number of stirring blades 6 are attached to a portion corresponding to the agglomeration chamber 2, and a spiral blade 7 is multiply wound around a portion corresponding to the rotary screen 3. The term “multiple” means that the spiral blades 7 having the same pitch are wound with their phases shifted in the circumferential direction. Next, reference numeral 8 denotes a coagulation sludge charging port, and the sludge charged from this charging port 8 is sludge coagulated with a high molecular weight coagulant. Code 9
Is an ultrasonic irradiator whose irradiation body is directed to the inside of the aggregation chamber 2,
0 is an addition pipe of a low molecular weight coagulant. That is,
In this concentrating and dehydrating device, the dehydrating part is formed in a screw press type, and the cake dispersing and re-aggregating part of the cake generated in the rapid dehydrating device is provided between the former dehydrating device part and the latter high-pressure dehydrating part. Therefore, these devices can be operated continuously in a series.

The concentrating and dewatering device according to the present invention is constructed as described above, and the sludge fed from the feeding port 8 is agglomerated by the high molecular weight flocculant and has a large floc, which is accompanied by the rotation of the feed shaft 4. The water is rapidly filtered and separated by the screen 1, and is sent to the aggregation chamber 2 by the spiral blade 5. The sludge sent to the flocculation chamber 2 is pressed by the spiral blades 5 and is filtered by the screen, so that the water content is usually 80%.
~ 85% cake like. In the agglomeration chamber 2, the cake is agitated by the agitating blades 6 and, at the same time, ultrasonic waves are radiated from the ultrasonic irradiator 9 to be crushed, dispersed, and fluidized,
A low molecular weight flocculant is then added to the fluidized cake, causing the solids to aggregate within the fluidized slurry to form small flocs, as shown in FIG.

2 to 5 schematically show how the solid content of the above sludge slurry is aggregated by the addition of the flocculant, and FIG. 2 is shown in FIG. 2 in the slurry by the addition of the high molecular weight flocculant. Shows a state in which large flock F is formed, and Wf indicates free water. 3 and 4
Shows a floc F taken out. In the figure, reference symbol W indicates internal water, and Ws indicates surface-adhered water. Screen 1
Inside, the free water Wf in the slurry aggregated as shown in FIG. 2 is rapidly separated by the polymer aggregating agent and caked to a water content of about 80% to 85% as described above.

In the flocculation chamber 2, the flocs F in the caked slurry are crushed by the stirring blades 6 and ultrasonic waves, and the water inside the flocs F and the water adhering to the surface become free water and fluidize. That is, it is dispersed,
By adding a low molecular weight coagulant to the fluidized slurry, a slurry composed of free water Wf from large flocs F and small flocs Fs reaggregated as shown in FIG. 5 is obtained.

The slurry thus aggregated is strongly pressed while being fed through the rotary screen 3 of the next stage, and the free water Wf is discharged.
Can be filtered and dehydrated to give a cake having a low water content (water content of about 60%). That is, this rotating screen 3
In the part, as shown in FIG. 1, the gap between the feed shaft 4 and the rotary screen 3 is narrowed in the feed direction to squeeze the slurry, and the spiral blades 7 are multiply provided to strongly press the slurry. is there. Further, the slurry sent to the rotary screen portion is primarily dehydrated in the screen 1 portion and the sludge concentration thereof is as high as 15 to 20%. Three
The filtration efficiency is extremely high as compared with a case where a slurry having a solid content concentration of about 5% is filtered and dehydrated all at once.

In the above description of the embodiments, the operations of primary dehydration, dispersion and re-agglomeration of the dehydrated cake, and secondary dehydration were performed in series using a screw press type dehydrator. The devices may be separated. In particular, in the secondary dehydrator, even if a belt press is used, the blades can be obtained, and if a filter press with a squeezing device is used, a cake having a lower water content can be obtained.

[0012]

As described above, according to the present invention, the slurry agglomerated by using the polymer flocculant is efficiently primary dehydrated, and the primary dehydrated cake is stirred and crushed to be dispersed and fluidized. By re-aggregating with a molecular coagulant and performing secondary dehydration, both primary and secondary filtration dehydration are efficient.
It is possible to obtain a cake having a much lower water content than the cake obtained by conventional primary dehydration. Needless to say, the present invention does not require a special flocculating device or dehydrator and is convenient to implement.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional side view of a concentrating and dehydrating apparatus used in the present invention.

FIG. 2 is an explanatory diagram of the content state of the primary agglomerated slurry according to the present invention.

3 is an explanatory diagram of a structure of flocs in the slurry of FIG.

FIG. 4 is an enlarged explanatory view of the structure of the flock of FIG.

FIG. 5 is an explanatory diagram of a content state of the secondary agglomerated slurry according to the present invention.

[Explanation of symbols]

 4 Feed shaft 6 Stirring blade 9 Ultrasonic irradiator

Claims (3)

[Claims] 1. A primary dehydrated slurry that is dispersed and fluidized by rapidly filtering and dehydrating sludge aggregated by adding a high molecular weight coagulant, stirring the cake, and irradiating ultrasonic waves to disperse and fluidize the sludge. A method for dehydrating sludge, characterized in that a secondary dehydration cake is obtained by adding a low-molecular-weight coagulant to the product, re-agglomerating it, and then pressurizing and filtering. 2. A rapid dehydrator comprising a screen drum or the like provided with an aggregating device using a high molecular weight aggregating agent in the preceding stage,
The rapid dehydrator comprises a stirring device 6 and an ultrasonic wave irradiation device 9, which are provided in the latter stage, and which is a flocculating device using a low molecular weight flocculant, and a pressure dehydrator, which is provided in the latter stage of the low molecular weight flocculating device. The sludge dewatering device is characterized in that the primary dewatering cake from the rapid filter is dispersed by the stirring device 6 and ultrasonic waves, and then the primary dewatering slurry is subjected to secondary dewatering with a pressure dewatering device. 3. The rapid dehydrator and the pressure dehydrator according to claim 2 are configured in a screw press form in which a screw shaft 4 is provided in an outer cylinder, and the end portion of the rapid dehydrator and the start end portion of the pressure dehydrator. A sludge dewatering device characterized in that a coagulation chamber 2 equipped with a device for adding a low-molecular coagulant is provided between and, and a stirring device 6 and an ultrasonic wave irradiation device 9 are provided in this coagulation chamber.