KR101916120B1 - Sludge treatment system and method before dehydration - Google Patents

Abstract

The present invention relates to a system and a method for pre-treating wastewater sludge to increase pressurized dehydration efficiency prior to pressurized dehydration treatment of the wastewater sludge. According to the present invention, in the sludge treatment system provided before a final dehydration facility of a sewage treatment facility, a diffuser is provided on a dehydration facility connection pipe for transferring sludge, which is discharged through one or more steps of precipitation, biological reaction, concentration, and digestion treatment on sewage and stored, from a sludge storage tank toward pressurized dehydration facility. The diffuser comprises: an air diffusion part formed in the dehydration facility connection pipe; an air guide part forming and covering a space around the air diffusion part; and an air inlet pipe coupled to the air guide part. A drainage passage is formed in the sludge by fine bubbles such that the moisture content of a sludge cake finally discharged through the pressurized dehydration facility is lowered.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment system,

The present invention relates to a system and method for pre-treating wastewater sludge to increase pressurized dewatering efficiency prior to pressurized and dewatered treatment of wastewater sludge.

It has become an urgent task to reduce the water content of wastewater sludge in order to fuel or compost the wastewater sludge, because the marine dumping of wastewater sludge is prohibited and land reclamation becomes difficult due to the rejection of the disgusting facilities in each province.

Recently, wastewater sludge has been discharged at a moisture content of 66% through a filter press, but it has not yet reached the level of self-combustion, so it is necessary to further lower the water content.

Various methods for lowering the water content of the wastewater sludge have been proposed in the past, and some examples are as follows.

Open No. 10-2015-0053993, entitled "Dewatering Method and Dewatering Apparatus for Sludge", discloses a method of directly heating sludge by heated water vapor or hot air at the sludge inlet side and dehydrating the sludge in a heated state in a screw press , There is a problem of having to cope with a lot of energy costs in order to obtain a sufficient effect.

In the method of re-dewatering the water content in the sludge cake to 40% level by mechanical mixing and compression in the presence of an additive, the first dehydrated sludge cake is coated with 1 ~ 3 mm cellulose powder such as wood flour, At least one excipient powder selected from the group consisting of powder, palm powder, arsomel powder, cornstarch powder and corn powder is added to the mixture, and the mixture is rapidly rotated within a period of 1 to 2 minutes at a rotation speed of 150 to 200 rpm with a stirrer to obtain a sludge moisture content of 60 3% , The sludge cake having a water content of 40 ± 3% was obtained by rehydration within 12 minutes while repeating compression and stopping at 50 to 200 kg / cm 2 with a filter press compactor, and the sludge cake was put into a mixer at 150 to 200 rpm And crushing and pulverizing the mixture for 2 to 3 minutes, and then selecting and collecting the excipient only by a vibration screen having a diameter of 1 to 3 mm. However, in this case, it is necessary to construct a facility for applying a high pressure of 50 to 200 kg / cm 2 in view of the fact that the equipment for recovering the excipient and the operation cost thereof are enormous and the pressure of the general filter press apparatus is about 15 kg / It is not realistic.

In the "method and apparatus for flocculation and dehydration of sewage sludge", the amount of the polymer flocculant added is divided by 75:25 ratio, first 75% is added, the initial flocc is crushed through high-speed stirring, and then 25% And a method of reducing the number of voids and free water in the flocs is proposed. However, this method only treats sludge with a water content of 80% at a water content of 77.4%, and does not provide final pressurized dehydration (filter press, etc.).

In the "treatment method of sewage sludge and the dehydrated cake produced therefrom", in the sludge treatment process of the sewage sludge, a carbon additive such as coal is mixed into the digested sludge to prepare a digested sludge mixture, And a carbon additive are mixed to prepare a centrifugally concentrated sludge mixture, and each of them is dehydrated, thereby reducing the water content of the dehydrated cake and improving the calorific value.

However, the amount of the carbon additive added to the digested sludge is 2 to 10% by weight, the centrifugally concentrated sludge mixture comprises 60 to 70% by weight of the centrifugally concentrated sludge, 20 to 30% by weight of the waste paper solution and 10% by weight of the carbon additive, The solution is mixed with 98 to 99% by weight of water and 1 to 2% by weight of waste paper, so that the solid content of the sludge cake is increased to 4 to 5 times.

In Japanese Laid-Open Patent Application No. 1-111498 entitled " Method of dewatering sewage sludge ", a moisture content of 88% is obtained by adding 40% of wood chips to a solid content of condensed sludge as a dehydrating aid, and when this is dewatered under pressure of 5 kg / And is capable of self-burning in an incinerator. However, this is merely aimed at lowering the water content by adding a dry wood chip. As a result, the solids content of the sludge is increased about 1.4 times.

 In the " sludge thickening and dewatering system and method of wastewater treatment process ", microbubbles are supplied to the secondary sludge introduced into the thickening section and aeration to aerate them, whereby the odor due to the stabilization of nitrogen contained in the secondary sludge And the load on the dehydrator is reduced to thereby reduce the dewatering efficiency and the amount of the flocculant used, as well as the stabilized nitrogen contained in the discharged sludge, so that it is advantageous that commercial use such as composting is easy without any post-treatment . However, this is about the process of aerating a concentrated slurry at a water content of 97%, and does not enhance the efficiency of the final dewatering process (sludge cake discharging process).

In the "Venturi pipe with micro bubble generator and sludge treatment device using the micro bubble generator", microbubbles are introduced into the sludge introduced into the concentrating part by using a micro bubble generator, so that the sludge agglomerates are finely crushed to be easily digested The effect of increasing the digestion efficiency of sludge by microorganisms and increasing the production of combustible biogas has been proposed. However, this does not increase the efficiency of the final dewatering process (sludge cake discharge process).

1. Patent Document 10-2015-0053993 "Dewatering Treatment Method and Dewatering Treatment Device of Sludge" 2. A method of re-dewatering the moisture content in a sludge cake to 40% level by mechanical mixing and compression in the presence of an additive (Japanese Patent No. 10-1237828) 3. Patent No. 10-0891023 "Method for coagulating and dewatering sewage sludge and apparatus therefor" 4. A method of treating sewage sludge and a dehydrated cake produced therefrom, 5. Japanese Unexamined Patent Publication No. 1-111498 entitled "Method of dewatering sewage sludge" 6. Open Patent 10-2017-0116591 "Sludge Concentration and Dewatering System and Method in Wastewater Treatment Process" 7. Patent No. 10-1162533 entitled " Venturi tube equipped with micro bubble generator "and sludge treatment device using the same

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system and a method for enhancing sludge dewatering effect by a pressure dewatering device while minimizing energy consumption. To this end, a system (apparatus) and a method capable of forming a slurry discharged through various treatment processes (sedimentation, biological reaction, concentration, microbial digestion treatment, chemical treatment, etc.) .

The present invention relates to a sludge treatment system provided before a final dewatering facility of a sewage treatment facility, comprising: a sludge treatment unit for sludge discharged from the sludge storage tank through one or more stages of sedimentation, biological reaction, The air diffuser includes an air diffuser formed in the connection pipe of the dewatering apparatus. An air guide portion covering and forming a space around the air diffusion portion; And an air inlet pipe coupled to the air guide portion; And a water drainage passage in the sludge is formed by the minute bubbles so as to lower the water content of the sludge cake finally discharged through the pressure dewatering facility. .

The air diffusion unit may be provided with a porous material part having a plurality of micropores formed on the channel of the dewatering equipment connection pipe or a porous material part having a part of the connection pipe of the dewatering equipment formed thereon, And a chemical injection pipe communicating with the pipe. In addition, an inline mixer may be further provided after the air diffusion section forming section in the dewatering apparatus connecting pipe.

The present invention also provides a method for pretreating sludge transferred to a final dewatering facility of a sewage treatment plant, comprising the steps of: (a) discharging the sludge through at least one of precipitation, biological reaction, concentration, To a pressure dewatering facility; And (b) injecting microbubbles in an amount exceeding solubility in the sludge conveyed in the direction of the pressurized dewatering facility; A sludge drainage passage is formed by the microbubbles so that the moisture content of the sludge cake finally discharged through the pressure dewatering facility is lowered.

In the step (b), a surfactant may be added to the sludge conveyed in the direction of the pressurizing and dewatering equipment, or an oxidizing agent may be added together, and step (c) of dispersing the microbubbles by applying a rotational force to the microbubble- . ≪ / RTI >

According to the system and method provided by the present invention, the following effects can be expected.

1. Drainage passage is formed in the sludge through injection and dispersion of fine bubbles, thereby improving the dewatering efficiency by the pressure dewatering device.

2. The addition of fine air to the sludge before entering the pressure dewatering process improves the dispersibility of fine bubbles by adding a surfactant.

3. An oxidizing agent such as ozone or hydrogen peroxide is added to the sludge before entering the pressurized and dewatered process, whereby the cell walls of the microorganisms in the sludge are destroyed and the cell liquid can be dehydrated.

4. Further application of the inline mixer can evenly disperse the micropore, surfactant and / or oxidizer.

5. In order to lower the water content of the final discharged sludge cake, it is necessary to increase the volume of the sludge by adding heat energy or various additives to the sludge cake, or to increase the pressure of the pressure dewatering facility, The present invention can be simply applied only by introducing the apparatus.

6. The final sludge cake is self-combustible in the incinerator because the water content is lowered to less than 60%.

[Fig. 1] schematically shows a sewage treatment facility.
[Fig. 2] shows the concept of a sludge drainage passage formed by fine bubbles.
FIG. 3 shows various embodiments of the oxidizer device applied to the present invention.

The present invention relates to a pressurized dehydration treatment method of lowering the water content of wastewater sludge.

The present invention relates to a sludge treatment system provided before a final dewatering facility of a sewage treatment facility, comprising at least one step of sedimentation, biological reaction, concentration and digestion treatment for sewage, discharging the stored sludge to a dewatering facility Wherein the air diffuser is provided in the connection pipe of the dewatering apparatus for conveying the air, the air diffuser comprises: an air diffuser formed in the dewatering apparatus connection pipe; An air guide portion covering and forming a space around the air diffusion portion; And an air inlet pipe coupled to the air guide portion; And a drainage passage in the sludge is formed by minute bubbles supplied into the dewatering apparatus connecting pipe through the diffusion unit to lower the water content of the sludge cake finally discharged through the pressure dewatering unit (Hereinafter referred to as "the present invention system").

The present invention also provides a method for pretreating sludge transferred to a final dewatering facility of a sewage treatment plant, comprising the steps of: (a) discharging the sludge through at least one of precipitation, biological reaction, concentration, To a pressure dewatering facility; And (b) injecting microbubbles in an amount exceeding solubility in the sludge conveyed in the direction of the pressurized dewatering facility; A sludge drainage passage is formed by microbubbles supplied into the dewatering apparatus connecting pipe via the diffusion unit and the water content of the sludge cake finally discharged through the pressure dewatering facility is lowered, (Hereinafter referred to as the " present invention method ").

The generalized wastewater sludge pressure dewatering process will be briefly described with reference to the conceptual diagram of the wastewater treatment facility of FIG. The wastewater (wastewater) flowing into the wastewater treatment facility is removed by sedimentation of heavy materials such as soil, sand, etc. from the gypsum 100, and various organic matter and inorganic substances are precipitated by floatation and coagulation in the initial settler 200. (The sedimentation material or the water existing thereon after the solid material is precipitated in the initial sedimentation tank) can be sent to the final sedimentation material 400 and the sedimented slurry is sent to the biological reaction tank 300 or the concentration tank 500 .

The slurry having a large organic component is transferred to the bioreactor 300 to decompose the organic component using microorganisms (mainly aerobic microorganisms in this process).

The treated water in the bioreactor 300 is settled in the final settling tank 400, the treated water is discharged after sterilization, and the settled slurry is concentrated in the centrifugal concentrator 700 and transferred to the slurry storage tank 800.

When the organic substance in the slurry settled in the initial sedimentation tank 200 is small, the slurry is transferred to the concentration tank 500, is concentrated, is transferred to the digester 600, and is then digested by the microorganism. In this process, anaerobic microorganisms are generally used to generate methane gas and the methane gas is used as fuel. When the slurry having undergone the concentration process is transferred to the digester 600, a heat exchanger 610 is used for temperature control when necessary. The digested slurry is again conveyed to the sludge storage tank 800.

When the sludge is supplied from the sludge storage tank 800 to the pressurized and dewatered facility 1000, necessary medicines are injected using the medicament injection equipment 900 and the dehydration is performed. The effluent discharged during dehydration is transferred to the pre-stage equipment (the first settling tank or concentrator or bioreactor or the appropriate place in the digester) and the dehydrated sludge cake is disposed of.

As the pressurizing and dewatering apparatus 1000, a belt press, a filter press, or the like can be applied. In the case where moisture in the sludge is trapped in solid matter, dehydration can not be performed properly.

The present invention is intended to maximize the dewatering efficiency in a pressurized and dewatered facility by injecting and dispersing minute bubbles into sludge transferred from the sludge storage tank 800 to the dewatering apparatus 1000. As shown in FIG. 2, when the pressure is applied to the sludge through the pressurized and dewatered facility, the water trapped in the solid part is easily discharged.

Accordingly, the moisture content of the sludge cake finally discharged through the pressurized dewatering facility can be lowered.

1, a diffuser 1100 is installed between the sludge storage tank 800 and the dewatering apparatus 1000. [ That is, the dewatering facility connection pipe 1110 for transferring the stored sludge from the sludge storage tank 800 toward the pressurized dewatering apparatus 1000 through at least one of the precipitation, biological reaction, concentration, The air diffuser 1100 is provided.

In order to inject minute bubbles into the air diffuser 1100, a micro bubble generator may be introduced. However, in order to minimize the energy requirement, air is supplied through the air compressor 1200, It is preferable to be constructed so as to be broken into a fine particle in the process of being sucked.

FIG. 3 shows various embodiments of the air diffuser 1100. The air diffuser 1100 is a device for injecting air into the dewatering equipment connecting pipe 1110 for moving the sludge to the dewatering facility. The air diffuser 1100 includes a micro-hole drilling machine The air introduced through the porous material portion formed of the porous material may be supplied in the form of fine bubbles. Hereinafter, the micropores or the porous material forming unit formed on the channel of the dewatering apparatus connecting pipe 1110 will be referred to as an air diffusing unit 1120. An air introducing pipe 1130 is connected to the dehydrating equipment connecting pipe 1110 and the air introducing pipe 1140 is connected to the air introducing pipe 1130. The air diffusion portion 1120, the air guide portion 1130 and the air inlet pipe 1140 are common components of the embodiments of the diffuser 1100 shown in FIG.

(A) of FIG. 3 shows an embodiment of a diffuser 1100 configured to supply compressed air provided by an air compressor 1200 to the air diffuser 1120. Therefore, one end of the air inlet pipe 1140 is communicated with the air compressor 1200, and the other end is communicated with the air guide part 1130.

(B) of FIG. 3 shows a flow control unit 1160 installed inside the dewatering apparatus connecting pipe 1110 and in the section where the air diffusion unit 1120 is formed to reduce the cross-sectional area of the flow path through which the sludge flows, It is. The flow control unit 1160 may be formed as a streamlined body to lower the flow resistance, and a spiral bent flow guide plate 1170 may be installed at the head to rotate the sludge in a spiral manner. In this case, the air diffuser 1100 may be configured to receive the compressed air from the air compressor 1200, but without connecting the air inlet pipe 1140 to the air compressor 1200, the flow controller 1160 (Air in the air) may be sucked through the air inlet pipe 1140 by a negative pressure inside the dewatering equipment connecting pipe 1110 which is generated while the flow rate of the sludge moves at a high speed.

(C) of FIG. 3 shows a configuration in which the diameter of the section of the dewatering apparatus connecting pipe 1110 in which the air diffusion unit 1120 is formed is narrowed so that the pressure of the corresponding section is lowered, Is an embodiment of an air diffuser configured to be sucked through tube (1140).

If all of the air injected through the air diffuser is dissolved in the sludge, it is impossible to obtain the desired effect of the present invention, so it is important to inject the air amount exceeding the solubility.

In the step (b) of the method of the present invention, a surfactant may be added to the sludge conveyed in the direction of the pressurizing and dewatering facility. That is, as the surfactant is injected through the chemical injection tube 901 communicated with the dewatering apparatus connecting pipe 1110, air entrapped in the sludge can be dispersed in the micropores.

The surfactant makes the cell walls of the microorganisms in the sludge thin to easily break the cell walls. The microorganisms contained in the sludge confine the cell fluid in the cell wall, and such a cell fluid is one of the reasons why the water content of the sludge cake is not lowered. There has been a conventional method of increasing digestion efficiency by allowing organic matter in the sludge to be utilized as food for microorganisms in the digestion tank through addition of chemicals in the digestion tank 600. However, even if this is done, ultimately, the cell walls of newly- The problem remains. Accordingly, the cell wall of the microorganisms in the sludge is made thin by the surfactant, and the cell wall is broken by the pressure transferred by the microbubbles when the sludge is pressurized, thereby discharging the cell fluid, which contributes to lowering the water content of the sludge cake.

In the step (b) of the method of the present invention, oxidizing agents such as hydrogen peroxide and ozone may be added to the sludge conveyed toward the pressurizing and dewatering facility in terms of destroying the cell walls of the microorganisms in the sludge. The oxidizing agent dissolves the cell wall of the microorganisms in the sludge and discharges the cell fluid, thereby improving the dewaterability of the sludge. In particular, when hydrogen peroxide is added, hydrogen peroxide bubbles (fine bubbles) are generated while destroying the cell walls of the microorganisms in the sludge. Hydrogen peroxide bubbles (micro bubbles) generated by this process transfer pressure to the microorganisms during the pressurizing and dewatering process for the sludge, so that the cell walls are blown, and the above-described drainage path also plays a role. In addition, when the hydrogen peroxide and the surfactant are used together, the hydrogen peroxide foam (fine bubbles) are uniformly dispersed in the sludge, thereby preventing the hydrogen peroxide bubbles from being counted before the pressurizing and dewatering process.

The oxidizing agent may be added together with the surfactant or may be added separately to the inlet of the dewatering apparatus connection pipe 1110 through the chemical injection pipe 903 connected to the inside of the sludge storage tank 800 in the chemical injection facility 900 Or indirectly to the sludge in the sludge storage tank to be sucked toward the dewatering equipment connection pipe 1110) or directly into the chemical injection pipe 901 connected to the diffusion device 1100 or directly to the dewatering equipment 1000 Can be injected into the sludge through the connected chemical injection tube 902 (direct communication system).

On the other hand, the fine bubbles can be dispersed by applying a rotational force to the sludge into which the fine bubbles have been injected. Specifically, the inline mixer 1150 may be installed in the dewatering apparatus connecting pipe 1110 to apply a rotational force to the sludge into which the fine bubbles have been injected.

Hereinafter, the effects of the present invention will be described together with experimental data.

[Table 1] and [Graph 1] summarize the results of simulating the present invention with 200 ml of sludge having a solid content of 2% (moisture content 98%) (hereinafter referred to as "test sludge sample"). A 38% solution of ferric chloride was used as the coagulant. However, unless the system of the present invention is actually installed, it is difficult to reproduce the step (b) of the method of the present invention in which an amount of fine bubbles exceeding the solubility is injected into the sludge being transported, so that the bubbles are generated in the sludge by stirring the sludge And the water content of the sludge cake after pressurized dehydration was compared with the sludge agitation time. The water content of the sludge cake tended to decrease with increasing agitation time. However, increasing the agitation time from 22 to 38 minutes was not effective in increasing the agitation time by only 0.2%.

However, these results are not the result of faithfully reproducing the system and method of the present invention. It is difficult to say that sufficient microbubbles are formed in the sludge only by stirring. However, in this experiment, it is significant that the effect of pressure dewatering improves as the bubbles are generated in the sludge.

Stirring time (min) Moisture content 0 62.6% 5 61.9% 22 61.6% 38 61.4%

[Graph 1]

[Table 2] and [Graph 2] were prepared by adding sodium lauryl sulfate as a surfactant to the test sludge sample and stirring for 3 minutes, followed by adding 2 ml of a 38% ferric chloride solution as a flocculant Followed by stirring for 3 minutes. The results of comparing the water content of the pressurized and dehydrated sludge cake are summarized by the sodium lauryl sulfate addition ratio.

By the addition of the sodium lauryl sulfate, the bubbles are dispersed and fine bubbles are uniformly formed, and accordingly, the pressure dewatering effect is improved and the water content of the sludge cake is lowered.

Sodium lauryl sulfate addition ratio (wt%) Moisture content of discharged sludge cake 0.00 62.2% 0.05 60.0% 0.15 58.5% 0.25 57.1%

[Graph 2]

[Table 3] and [Graph 3] summarize the results of comparing the water content of the pressurized and dehydrated sludge cake according to the type of surfactant added to the test sludge sample. In the test method, the surfactant was added to the test sludge sample and the bubbling operation was performed for 1 minute. Then, 2 ml of a 38% ferric chloride solution was added as a flocculant, and the stirring operation was performed for 3 minutes.

The difference in the water content depending on the use of the surfactant was large, but the effect of the type of the surfactant was not significant.

Type of surfactant Moisture content No additives 62.2% sodium lauryl sulfate dosage 0.25% 57.1% ASCO-28 (28%) 1% 57.0%

[Graph 3]

Hydrogen peroxide (35% aqueous solution) was added as an oxidizing agent for destruction of cell walls and bubbles in the test sludge samples as shown in the following [Table 4] and [Graph 4], and stirred for 3 minutes. 38% solution of ferric chloride Ml, and stirred for 3 minutes, and the water content of the sludge cake subjected to pressure dehydration was compared according to the addition ratio of hydrogen peroxide. The effect of improving the dewatering ability with increase of the hydrogen peroxide input amount can be confirmed.

Hydrogen peroxide (35%) Moisture content 0% 62.5% 0.1% 60.1% 0.5% 58.3%

[Graph 4]

The present invention has been described in detail with reference to the preferred embodiments. However, it should be understood that the present invention is not limited to the above-described embodiment, but may be modified and changed without departing from the gist of the present invention. The claims of the present invention thus include such modifications and variations.

100: Gypsum bed 200: First settling basin
300: Bioreactor 400: Final clarifier
500: Enrichment tank 600: Digester
610: Heat exchanger 700: Centrifugal concentrator
800: Sludge storage tank 900: Chemical filling equipment
901, 902, 903: chemical injection pipe 1000: pressure dewatering equipment
1100: Diffusion device 1110: Dewatering device connection pipe
1120: air diffusion part 1130: air guide part
1140: Air inlet pipe 1150: Inline mixer
1160: Flow control unit 1170: Flow guide plate
1200: air compressor

Claims (8)

A sludge treatment system provided before a final dewatering facility of a sewage treatment facility,
There is provided an air diffuser in a dewatering apparatus connection pipe for transferring the stored and discharged sludge from the sludge storage tank toward the pressurized dewatering apparatus through at least one of precipitation, biological reaction, concentration, and digestion treatment for sewage,
The above-
An air diffuser formed in the dewatering equipment connection pipe;
An air guide portion covering and forming a space around the air diffusion portion; And
An air inlet pipe coupled to the air guide; And,
Wherein the water sludge drainage passage is formed by microbubbles supplied into the dewatering apparatus connecting pipe through the diffusion unit and the moisture content of the sludge cake finally discharged through the pressure dewatering equipment is lowered. Processing system.
The method of claim 1,
Wherein the air diffusing portion is a porous material portion in which a plurality of micropores are pierced on a pipe of the dewatering device connection pipe or a portion of the connection pipe of the dewatering device is formed of a porous material.
The method of claim 1,
A drug infusion conduit communicated with the dewatering equipment connection pipe; Wherein the sludge treatment system further comprises:
4. The method according to any one of claims 1 to 3,
An inline mixer provided after an air diffusion section forming section in the dewatering apparatus connecting pipe; Wherein the sludge treatment system further comprises:
A method for pretreating sludge transferred to a final dewatering facility of a sewage treatment plant,
(a) transferring the sludge discharged and stored through at least one of the steps of sedimentation, biological reaction, concentration, and digestion to sewage in a sludge storage tank through a dewatering equipment connection pipe in the direction of the pressurized dewatering equipment; And
(b) injecting an amount of fine bubbles in excess of solubility into the sludge conveyed in the direction of the pressurized dewatering facility; Including,
A sludge drainage passage is formed by microbubbles supplied into the dewatering apparatus connecting pipe through a diffusion device and a water content of the sludge cake finally discharged through the pressure dewatering facility is lowered.
The method of claim 5,
Wherein the step (b) comprises adding a surfactant to the sludge conveyed in the direction of the pressurizing and dewatering facility.
The method of claim 5,
Wherein the step (b) comprises adding an oxidizing agent to the sludge conveyed in the direction of the pressurizing and dewatering facility.
8. The method according to any one of claims 5 to 7,
(c) dispersing the fine bubbles by applying a rotational force to the sludge into which the fine bubbles have been injected; Further comprising the steps of:

Images