JP2018140334A - Sludge dehydration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge dehydration method in which external pressure is applied to sludge in a solid-liquid separator to dehydrate in a state in which the sludge contains micro bubbles.SOLUTION: Micro bubbles generated in a micro bubble generating portion 5 are mixed into sludge, and the sludge is dehydrated in a solid-liquid separator 4 in a state in which the sludge contains the micro bubbles. Thus, the micro bubbles form a filtrate passage within the sludge, and improve dehydration efficiency, and a dehydrated cake with a low moisture content is generated. The dehydrated cake with a low moisture content can be generated without using a dehydration auxiliary and a chemical, and post treatment and secondary use of the dehydrated cake become easy.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sludge dewatering method in which sludge is solid-liquid separated to produce a dehydrated cake, and the sludge is dehydrated by a solid-liquid separator in a state where fine bubbles are included.

2. Description of the Related Art Conventionally, solid-liquid separators that concentrate and dehydrate inorganic sludge such as tap water and organic sludge such as sewage, human waste, and food production processing wastewater are known. Inorganic sludge is pressure-dehydrated with a filter press, and organic sludge is agglomerated with a polymer flocculant and then pressure-dehydrated with a belt press or screw press to separate a dehydrated cake and a filtrate.

And as a technique to further reduce the moisture of the dehydrated cake, high pressure air is supplied from the filtrate outlet of the filter plate to pass the high pressure air through the dehydrated cake, and it is difficult to extrude with mechanical pressing pressure An air blow device that excludes moisture between particles with high-pressure air is known as described in Patent Document 1, for example. In addition, there is a technique in which air or washing water is passed for the purpose of cake washing by the same technique.

Further, as a technique for performing solid-liquid separation using fine bubbles, Patent Document 2 discloses a method of supplying fine bubbles to a sludge treatment tank and floating and concentrating sludge by attaching fine bubbles. In addition, in the sludge treatment field, fine bubbles are used for sludge reforming, washing, biological treatment, and the like.

JP-B-2-24567 Japanese Utility Model Publication No. 5-009700

In general, when an external pressure such as pressurization or squeezing is applied by a solid-liquid separator, the solids are consolidated, moisture intervening between the solids (particles) is pushed out, permeates through the filtration surface, and externally To be discharged. However, the sludge supplied to the position away from the filtration surface is compacted on the spot and separated into solids and moisture.However, the sludge particles are compacted by pressing, and the moisture is transferred to the filtration surface. There is no gap to move, and the water content may not be sufficiently reduced.

Patent Document 1 is designed to exclude moisture between cake particles by high-pressure air by air blow, but there is no gap through which high-pressure air can pass between consolidated cakes, and moisture between cakes cannot be discharged sufficiently. Sometimes. Also, if the gap between the cakes is narrow, high-pressure air is required to pass through, and a large compressor and electricity bill are required.

Although patent document 2 performs solid-liquid separation using a microbubble, since it is an application to the floating concentration with a high moisture content, it is effective as a pretreatment of sludge treatment, but the moisture content is high. Therefore, secondary processing and tertiary processing are required.

  In the present invention, the sludge is dehydrated by a solid-liquid separator in a state in which fine bubbles are included, thereby forming a filtrate passage between the sludges by the fine bubbles, thereby improving the dewatering efficiency and reducing the dehydrated cake having a low water content. A method for dewatering generated sludge is provided.

  In the present invention, fine bubbles generated in the fine bubble generation unit are mixed with sludge, supplied to the solid-liquid separator in a state where the fine bubbles are included in the sludge, and separated into dehydrated cake and filtrate by the solid-liquid separator. Thus, a filtrate passage is formed between cake particles in the filtration chamber of the solid-liquid separator, and moisture inside the filtrate is discharged through the filtrate passage, thereby improving dehydration efficiency.

  When the filtrate discharged from the solid-liquid separator is returned to the fine bubble generating unit, it is not necessary to supply moisture from the fine bubble generating unit from the outside. Moreover, the polymer aggregating agent in an unaggregated state remains in the filtrate, and the coagulation property of the sludge is improved by mixing the sludge together with the fine bubbles.

  When fine bubbles are supplied to the coagulation mixing tank and mixed with sludge, the coagulation efficiency of the sludge can be improved and the amount of the polymer coagulant used can be reduced.

  If the solid-liquid separator is a pressure type, a pressure reduction type, or a centrifugal type, a filter press, a belt press, or a screw press can be applied to the pressure type, a vacuum dehydrator can be applied to the pressure type, and a centrifugal dehydrator can be applied to the centrifugal type. Applicable.

  After dehydration by a pressurized solid-liquid separator, high-pressure air is supplied to the dehydrated cake in the filtration chamber, or after dehydration by the solid-liquid separator, the dehydrated cake is depressurized in the filtration chamber, resulting in fine bubbles between the dehydrated cakes. An air passage is formed so that air can easily pass through, moisture is easily discharged from the air passage, and the moisture content can be further reduced.

According to the present invention, when the sludge is separated into solid and liquid, it is supplied to the solid-liquid separation device in a state where fine bubbles are included in the sludge, and the sludge is dehydrated by applying an external pressure to thereby remove cake particles in the filtration chamber. A filtrate passage is formed between them, moisture inside is discharged through the filtrate passage, and dewatering efficiency is improved.
Moreover, since the filtrate channel | path by a fine bubble is formed between the cake particles after spin-drying | dehydration, it becomes easy to exclude the water | moisture content between cake particles by the air blow from the outside.

It is a flowchart of the dehydration method of the sludge which concerns on this invention. It is a flowchart of the dehydration method of the sludge of the other Example 1 which concerns on this invention. Similarly, it is the flowchart of the dehydration method of the sludge of other Example 2. FIG. It is sectional drawing in the filtration chamber of the solid-liquid separator which concerns on this invention. It is the schematic which air blows the dewatering cake which concerns on this invention. Similarly, it is the schematic which decompresses the dewatering cake.

FIG. 1 is a flowchart of a sludge dewatering method.
Inorganic sludge, organic sludge such as sewage, human waste, and food production processing wastewater (hereinafter referred to as “sludge”) is temporarily stored in the sludge supply tank 2 through a sludge supply pipe 3 by a sludge supply pump 2. Then, the sludge is transferred to the solid-liquid separator 4.

In the fine bubble generating unit 5, fine bubbles are generated by the fine bubble generating device 7 in the fine bubble mixing tank 6 supplied with water. The fine bubbles are transferred to the sludge supply pipe 3 through the fine bubble supply pipe 9 by the fine bubble supply pump 8.

Sludge and fine bubbles are mixed in the sludge supply pipe 3 in the previous stage of the solid-liquid separator 4, and the sludge containing fine bubbles is supplied to the solid-liquid separator 4. In the solid-liquid separator 4, sludge containing fine bubbles is subjected to solid-liquid separation, and separated into a filtrate and a dehydrated cake.

In order to facilitate the diffusion of the fine bubbles into the sludge, a line mixer may be disposed in front of the solid-liquid separator 4 after mixing the sludge and the fine bubbles.

<Microbubble generator>
The fine bubble generation device 7 is a device that generates bubbles of about 50 microns or less, and there are known devices such as a chemical solution method, a supersaturation method, and a gas-liquid two-phase flow swirl method. It can be appropriately selected according to the specifications of the device 4. In this embodiment, a gas-liquid two-phase flow swirling method is used in which air is taken in from the outside, and the taken-in air is made into fine bubbles by turbulent flow generation and stirring shearing by a rotating mechanism in the apparatus.

The solid-liquid separation device 4 performs solid-liquid separation of the sludge containing moisture to generate a filtrate and a dehydrated cake. The pressure applied to the sludge is adjusted by the pressure variable means included in the solid-liquid separation device 4. This means that water is separated from sludge.

As the solid-liquid separator 4, for example, a dehydrator such as a filter press, a belt press, a screw press, or the like can be applied in a pressurization type. Further, for example, a vacuum dehydrator can be applied to the reduced pressure type, and a centrifugal dehydrator can be applied to the centrifugal type.

The dehydrated cake here is a solid substance having a moisture content of about 60 to 90% as a result of firmly compacting the dehydrated cake produced by the dehydrating action of the solid-liquid separator 4, and having a solid content concentration Is different from 1 to 4% concentrated sludge (slurry).

FIG. 2 is a flowchart of the sludge dewatering method according to another embodiment.
The filtrate is returned from the solid-liquid separator 2 to the fine bubble mixing tank 6 through the filtrate supply pipe 10 to generate fine bubbles. The filtrate discharged from the solid-liquid separator 4 can be reused, and there is no need to supply moisture from the fine bubble generating unit 5 from the outside.

FIG. 3 is a flow chart of the sludge dewatering method of another embodiment 2.
A coagulation / mixing tank 11 is disposed in the front stage of the solid-liquid separation device 4, and the fine bubbles generated by the fine bubble generating unit 5 are transferred to the coagulation / mixing tank 11. The agglomeration mixing tank 11 is an apparatus for aggregating sludge by stirring the sludge and the polymer flocculant with the stirring blade 12. The fine bubbles are moderately agitated in the flocculation / mixing tank 11, efficiently attached to the sludge flocculation flocs, and supplied to the solid-liquid separation device 4 through the flocculation sludge supply pipe 13 in a state of including the fine bubbles. Since the fine bubbles are negatively charged, the sludge aggregation efficiency can be improved and the amount of the polymer flocculant used can be reduced.

In addition, when the filtrate is returned from the solid-liquid separator 4 to the fine bubble mixing tank as shown in FIG. 2, the non-aggregated polymer flocculant remaining in the filtrate can be effectively reused.
In addition, the fine bubble generating device 7 may be provided in parallel or in the coagulation / mixing tank 11, and the fine bubbles may be directly generated in the coagulation / mixing tank 11.

FIG. 4 is a cross-sectional view of the filtration chamber of the solid-liquid separator.
In this embodiment, a pressure type filter press is used as the solid-liquid separation device 4. In the sludge containing fine bubbles supplied to the filtration chamber 14 of the filter press, small sludge particles are compacted together with primary dehydration by press-fitting pressure or squeezing, etc., and moisture between the particles moves to the filtration surface 15. Discharged.

Since the fine bubbles are negatively charged, they easily adhere to the surface of the sludge particles, and when the sludge particles are consolidated, the adhering fine bubbles form voids between the sludge particles and serve as a moisture passage. Therefore, moisture is efficiently discharged from between the sludge particles consolidated in the filtration chamber 14 to the filtration surface, and the dehydration efficiency is improved.

Moreover, the density of sludge falls by containing a fine bubble, and the surface tension of the water | moisture content between sludge particles falls. As a result, moisture remaining between the sludge particles or inside the sludge particles is easily discharged to the outside, and the dewatering efficiency is improved.

In the pressurizing belt press and screw press, the sludge containing fine bubbles supplied to the filtration chamber 14 is consolidated by pressurization, and moisture is efficiently discharged from the sludge particles to the filtration surface 15.

In the vacuum type vacuum dehydrator, sludge containing fine bubbles sucked from the filtration surface 15 is consolidated on the filtration surface 15, and moisture is efficiently sucked and discharged from between the sludge particles to the filtration surface 15.

In the centrifugal centrifugal dehydrator, sludge containing fine bubbles is consolidated and accumulated on the inner wall of the rotating cylinder by centrifugal action, and moisture is efficiently discharged between the sludge particles.

FIG. 5 is a schematic view of air blowing the dehydrated cake.
After the primary dehydration by the solid-liquid separator, high-pressure air (air blow) is supplied from one side of the dehydrated cake, the high-pressure air is passed through the dehydrated cake, and moisture between the sludge particles is entrained and discharged from the filtration surface 15. Since the dehydrated cake is formed with fine bubbles between the sludge particles, an air passage is formed and air easily passes through, moisture is easily discharged from the air passage, and the moisture content can be further reduced. .

The same technique can be applied to the solid-liquid separator 4 of another type, and a high effect can be obtained particularly when it is applied after primary dehydration by press-fitting pressure or squeezing of a filter press.
The technique can also be applied to a cake washing technique for supplying washing water at a high pressure to the filtration chamber 14 that has produced a dehydrated cake.

FIG. 6 is a schematic view for depressurizing the dehydrated cake.
After primary dehydration by the solid-liquid separator, the water between the sludge particles is discharged from the filtration surface 15 by suction from one side of the filtration chamber 14 and decompressing the dehydrated cake. Since the dehydrated cake is formed with fine bubbles between the sludge particles, an air passage is formed, moisture easily passes through, moisture is easily discharged from the air passage, and the moisture content can be further reduced. .
The same technique can be applied to the solid-liquid separator 4 of another type, and a high effect can be obtained particularly when applied after the primary dehydration by squeezing the belt press.

  The sludge dewatering method according to the present invention is an excellent method capable of improving the sludge dewatering efficiency by dewatering in a state in which fine bubbles are included in the sludge when the sludge is squeezed by a solid-liquid separator. is there. Since solid dehydration aids are not used, there is no need to worry about inventory management and storage location of dehydration aids, the amount of dehydrated cake discharged does not increase, and there is no burden on post-treatment of the dehydrated cake. Moreover, since no special chemicals are used, the cost is light and the secondary use of the dehydrated cake can be applied in many ways.

4 Solid-Liquid Separator 5 Fine Bubble Generation Unit 11 Coagulation Mixing Tank 14 Filtration Chamber

Claims (6)

The fine bubbles generated in the fine bubble generation part (5) are mixed with sludge,
Supply the solid-liquid separator (4) with fine bubbles in the sludge,
A method for dewatering sludge, characterized in that it is separated into a dehydrated cake and a filtrate by a solid-liquid separator (4).
The sludge dewatering method according to claim 1, wherein the filtrate discharged from the solid-liquid separation device (4) is returned to the fine bubble generating section (5).
The sludge dewatering method according to claim 1, wherein the fine bubbles are supplied to the coagulation mixing tank (11) and mixed with the sludge.
The sludge dewatering method according to any one of claims 1 to 3, wherein the solid-liquid separator (4) is a pressure type, a pressure reduction type, or a centrifugal type.
The method for dewatering sludge according to claim 4, wherein high-pressure air is supplied to the dewatered cake in the filtration chamber after dewatering by the pressurized solid-liquid separator (4).
The dewatering method for sludge according to claim 4, wherein after the dehydration by the solid-liquid separator (4), the dewatered cake is decompressed in the filtration chamber (14).

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