KR20190050475A - Sludge decomposition system and operating method of the same - Google Patents

Abstract

The present invention relates to a plasma generating device-based sludge decomposition system capable of efficiently decomposing not only aerobic sludge using plasma but also anaerobic sludge which was difficult to be decomposed in the conventional technology, and to an operating method thereof. According to the sludge decomposition system, sludge is decomposed by a plasma-based sludge decomposition apparatus installed at any two or more of a front end of an anaerobic digestion tank (70), the anaerobic digestion tank (70), or a rear end of the anaerobic digestion tank (70). The plasma-based sludge decomposition apparatus has a plasma specific energy of 4800 kJ/kgTS or more to achieve a solubilization increase of 3000 mg COD/L in waste sludge at the front end of the anaerobic digestion tank (70) and a plasma specific energy of 6300 kJ/kgTS or more to achieve a solubilization increase of 3000 mgCOD/L in digested sludge separated from effluent and concentrated in a solid-liquid separation tank (80) at the rear end of the anaerobic digestion tank (70).

Description

[0001] The present invention relates to a sludge pretreatment system,

The present invention relates to a sludge pretreatment system and a method of operating the same, and more particularly, to a sludge decomposition system based on a plasma generator capable of efficiently decomposing not only aerobic sludge using plasma but also anaerobic sludge, And a method of operating the same.

Sludge is a secondary product that occurs in the sewage treatment process of a sewage treatment plant and can be defined as a form in which microorganisms and undissolved organic substances existing in domestic sewage, drinking waste water, livestock manure and sewage are present as solids together with moisture. The sludge is usually subjected to concentration and extinguishing processes, followed by dewatering into a cake form and then transported out of the sewage treatment plant. In this process, the decomposition of the sludge is performed by an important performance factor directly related to energy generation through volumization and extinguishing, , Which is recognized as an important factor in terms of sludge treatment efficiency and cost. Accordingly, a separate sludge pretreatment process is provided before the concentration and extinguishing process. In the pretreatment process, the sludge has been pretreated with a focus on pyrolysis for the purpose of improving the treatment efficiency in the present process such as digestion. However, the decomposition of sludge through the pretreatment process shows a considerable difference depending on the aerobic sludge and the anaerobic sludge. For example, in the case of anaerobic sludge, decomposition due to extracellular polymeric substances (EPS) And the anaerobic sludge is difficult to decompose relative to the aerobic sludge because of the extracellular walls of the microorganisms composed of a hard layer to protect the microorganism from osmotic pressure. In order to directly treat the sludge in this process such as a digester, it is necessary to keep the digestion tank for 20 ~ 30 days for a long time or to increase the size of the digestion tank. In order to solve this problem, There have been various sludge pre-treatments that can destroy the cell walls by facilitating the hydrolysis. In order to maximize the efficiency of the digester by converting the polymer-type sludge into a low-molecular state that is easy to use in the digestion step by the pretreatment of the sludge as described above, Korean Patent No. 10-1367765 discloses a method of reducing the pressure in the liquid to below the vapor pressure A technique of pretreating the sludge using the generated cavitation phenomenon has been proposed. Korean Patent No. 10-1651080 discloses a pretreatment technique for increasing the solubility by oxidizing microorganisms by adding liquid iron nitrate to sludge treated and discharged through a biological advanced treatment unit composed of anaerobic tank, anoxic tank and aerobic tank. Japanese Patent Laid-Open No. 2010-089023 proposes a pretreatment technique in which a pretreatment agent (inorganic acid, organic acid, and alcohol) is added to sludge treated with aerobic microorganisms to reduce the adhesion of microorganisms in the sludge and make the surface of microorganisms thin , Japanese Patent Application Laid-Open No. 2006-326438 proposes a pretreatment technique in which sludge is solubilized by an alkali solution such as sodium hydroxide and the solubilized sludge is digested by an alkaline microorganism. In the above conventional techniques, cavitation techniques, techniques of oxidizing microorganisms by injecting liquid iron salts, techniques using one or more pretreatment agents selected from the group consisting of inorganic acids, organic acids and alcohols, and alkaline solutions such as sodium hydroxide, Techniques for digesting sludge with alkaline microorganisms have been used for the pretreatment of sludge, but all of these techniques have been used for the decomposition of aerobic sludge and are not intended for the decomposition of anaerobic sludge, And it was found that the pretreatment of sludge had a considerable limit. In particular, although the sewage treatment process is composed of a microbial base and microbial sludge treatment is an essential component, it has been limited to treating aerobic microbial sludge. Therefore, in the existing sewage treatment process, the sludge pretreatment is located only at the front end of the anaerobic digestion tank, and thus there is a problem that a system capable of accelerating the pretreatment while flexibly coping with the environment of the sludge and the sewage treatment process is not established.

Korean Patent No. 10-1367765 Korean Patent No. 10-1651080 Japanese Patent Laid-Open No. 2010-089023 Japanese Patent Application Laid-Open No. 2006-326438

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sludge pretreatment system and a method of operating the sludge pretreatment system capable of flexibly coping with the characteristics of the sludge and the operation environment of the wastewater treatment process while accelerating the pretreatment.

In this connection, it is an object of the present invention to provide a sludge decomposition integrated system capable of simultaneously decomposing aerobic microbial sludge and anaerobic microbial sludge.

Further, it is an object of the present invention to provide a sludge decomposition technique in which the energy consumption rate is relatively low as compared with the conventional pyrolysis technology which has constituted the sludge pretreatment system.

In addition, the sludge pretreatment system according to the present invention aims at constructing a sludge pretreatment system capable of coping with characteristics of the inflow sewage, operation environment, and operation target in a manner that can avoid the conventional sludge pretreatment process once.

In order to achieve the above object, the sludge pretreatment system according to the present invention is characterized in that the sludge is decomposed by a plasma-based sludge decomposition apparatus at any two or more of the front end of the anaerobic digestion tank, the anaerobic digestion tank, or the rear end of the anaerobic digestion tank Wherein the plasma-based sludge decomposition apparatus has a plasma specific energy of 4800 kJ / kgTS or more to achieve an increase in the dissolved amount of waste sludge of 3000 mg COD / L at the front end of the anaerobic digestion tank, The plasma specific energy is 6300 kJ / kg TS or more in order to achieve an increase in the dissolved amount of the transport fire extinguishing sludge separated from the effluent in the solid-liquid separation tank of 3000 mg COD / L.

Here, the plasma-based sludge disintegration apparatus has a plasma specific energy of 3200 kJ / kgTS or more in order to achieve an increase of the dissolved sludge dissolution amount of 2000 mg COD / L at the front end of the anaerobic digestion tank, And the plasma specific energy is 4200 kJ / kg TS or more to achieve an increase in the dissolved amount of the transport fire extinguishing sludge separated from the effluent and 2000 mg COD / L.

In the sludge pretreatment system according to the present invention, the dissolution rate according to the plasma specific energy of the plasma-based sludge decomposition apparatus at the upstream side of the anaerobic digestion tank has the relationship of Equation (1).

(Equation 1)? SCOD = 0.617 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kg TS).

In the sludge pretreatment system according to the present invention, the dissolution rate according to the plasma specific energy of the plasma-based sludge decomposition apparatus of the carrier-digested sludge separated and concentrated in the solid-liquid separation tank at the downstream of the anaerobic digestion tank is expressed by the following equation .

(2)? SCOD = 0.475 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kgTS).

Further, in the sludge pretreatment system according to the present invention, the sludge is decomposed by the plasma-based sludge decomposition apparatus at the front end and the rear end of the anaerobic digestion tank, and a plasma generator is formed inside the anaerobic digestion tank.

Here, the plasma generator in the anaerobic digestion tank is configured to be capable of discharging plasma within a dead volume area in which anaerobic sludge in the anaerobic digestion tank is deposited, wherein the dead volume area is defined by the diameter of the anaerobic digester Of not more than 50%.

Further, in the sludge pretreatment system according to the present invention, the plasma-based sludge decomposition apparatus is composed of an electrode for generating plasma and a power source for supplying electricity to the electrode.

In addition, the method of operating the sludge pretreatment system according to the present invention may include a first stage in which concentrated sludge is introduced; A second step of decomposing the concentrated activated sludge in a plasma-based sludge decomposition apparatus; A third step in which the decomposed concentrated activated sludge is introduced into the anaerobic digestion tank and is digested; Wherein the digested sludge digested in the anaerobic digestion tank is concentrated and decomposed in a plasma-based sludge digestion apparatus.

The sludge pretreatment system according to the present invention is provided with a sludge disintegration means in the anaerobic digestion tank itself as well as the front end and the rear end in the anaerobic digestion tank, thereby accelerating the pretreatment while coping flexibly with the characteristics of the sludge and the operation environment of the wastewater treatment process There is an effect that can be.

Also, the sludge pretreatment system according to the present invention can decompose the aerobic microbial sludge and the anaerobic microbial sludge at the same time, and has a relatively low energy consumption rate compared to the conventional pyrolysis technology which has constituted the sludge pretreatment system.

In addition, the sludge pretreatment system according to the present invention has the effect of providing a sludge pretreatment system capable of coping with characteristics of the inflow sewage, operation environment, and operation target in a wide range by eliminating the conventional sludge pretreatment process.

Fig. 1 shows the construction of a sludge pretreatment system according to the present invention.
2 shows changes in voltage and current during plasma discharge in the sludge pretreatment system according to the present invention.
FIG. 3 is a graph showing the dissolution rate versus specific energy at the upstream of the anaerobic digester of the sludge pretreatment system according to the present invention.
FIG. 4 is a graph showing the dissolution rate of anaerobic digestion tank and anaerobic digestion tank by specific energy of the sludge pretreatment system according to the present invention.

Hereinafter, the technical structure of the sludge pretreatment system according to the present invention will be described with reference to the accompanying drawings.

The use of the terms "comprises", "having", or "having" in this application is intended to specify the presence of stated features, integers, steps, components, parts, or combinations thereof, But do not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

FIG. 1 is a schematic view showing a sludge pretreatment system according to the present invention. FIG. 1 is a schematic view showing a sludge pretreatment system according to the present invention. FIG. 1 is a schematic view showing a sludge pretreatment system according to an embodiment of the present invention. The plasma generator generates an electric field by discharging between the two electrodes by applying a high voltage. At this time, a shockwave is generated together with a strong sound wave to impinge on the microbial cells to destroy the hard cell walls, . At this time, the plasma generating apparatus of the sludge pretreatment system according to the present invention can be selected from a corona plasma, an arc plasma, and a dielectric barrier plasma generator, and achieves 3000 mg COD / L increase in waste sludge solubility at the front end of the anaerobic digestion tank 70 In order to achieve a concentration of 3000 mg COD / L of digested sludge separated from the effluent in the solid-liquid separation tank 80 at the end of the anaerobic digestion tank 70 at a plasma specific energy of 4800 kJ / kg TS or more, And an energy of 6300 kJ / kg TS or more.

The sludge decomposition apparatus of the sludge pretreatment system according to the present invention is configured so that two or more plasma generation apparatuses are installed in a reactor having a predetermined shape. In this case, the plasma generating apparatus may be installed in the upper, lower, or side surface of the reactor, but it is preferable to secure the contact time with the sludge when the sludge is conveyed. When the plasma generator-based sludge decomposition apparatus is installed at the front end of the anaerobic digestion tank 70, a sedimentation tank, an aerobic tank 30, a mixing tank 50, and a concentration tank 60 are formed in front of the anaerobic digestion tank 70, A primary settling tank 20 is disposed at the front end and a secondary settling tank 40 is disposed at the rear end, In the mixing tank 50, the solids precipitated and removed in the first settling tank 20 and the second settling tank 40 are mixed. Then, the concentrated solids in the center of the microorganism are concentrated through the concentrating tank 60. Therefore, in the sludge pretreatment system according to the present invention, when the above-described plasma generator-based sludge decomposition apparatus is installed at the front end of the anaerobic digestion tank 70, the characteristics of the introduced sludge are determined by the sedimentation As the solids are introduced, sludge is formed around the aerobic microorganisms. Since the aerobic microorganisms have a cytochrome-based enzyme in composition compared to the anaerobic microorganisms, the decomposition of microorganisms is relatively easy due to the rapid decomposition of organic substances, and the specific energy of the plasma generating apparatus is required to be 4800 kJ / kgTS or more Do. This value is relatively low compared to the plasma specific energy of 6300 kJ / kg TS or more in order to achieve the same digestion sludge solubility increase of 3000 mg COD / L for anaerobic microorganisms which are relatively difficult to decompose than aerobic microorganisms.

Unlike the previous stage of the anaerobic digestion tank 70 described above, in the case of the anaerobic digestion tank 70 located at the downstream end of the concentration tank 60, digestion is carried out under anaerobic conditions, and therefore, anaerobic microorganisms The sludge should be decomposed under conditions different from the sludge decomposition conditions based on aerobic microorganisms. In other words, since most of the substrates used by the anaerobic microorganisms are surrounded by the cell membrane, the residence time for decomposing the organic matter with the cell enzyme of the anaerobic microorganism is long, so that there is a great restriction on the decomposition of the sludge. And long decomposition time. The decomposition conditions must be different from those of the anaerobic digestion tank 70 which already has a certain level of digestion temperature and the subsequent stage of the anaerobic digestion tank 70 which does not need to maintain the digestion temperature. The plasma specific energy should be set to 6300 kJ / kg TS or more to achieve an increase in dissolved amount of digested sludge 3000 mg COD / L separated from the effluent in the solid-liquid separation tank 80 at the subsequent stage. When the amount is less than the above range, the decomposition of the sludge becomes difficult. In the sludge pretreatment system according to the present invention, the plasma-based sludge decomposition apparatus 200 constructed in the anaerobic digestion tank 70 is configured to discharge the plasma within the dead volume region in which the anaerobic sludge in the anaerobic digestion tank 70 is deposited, The dead volume region is characterized in that it is 50% or less of the diameter of the anaerobic digestion tank (70) from an edge where two or more faces intersect. Even if the anaerobic digestion tank 70 having a predetermined shape such as a circular shape or a polygonal shape generates a certain level of flow circulation within the digestion tank 70, the flow circulation is limited to occur continuously in the entire digester, There arises a situation in which the accumulation of solid components such as sludge can not be achieved. In the present invention, the dead volume area in which the solid material is immersed due to insufficient flow circulation can be defined as 50% or less of the diameter of the reactor from an edge where two or more faces in the digester are crossed. In the sludge pretreatment system according to the present invention, the plasma-based sludge decomposition apparatus is constructed in the dead volume region of the anaerobic digestion tank 70, so that the sludge deposited in the dead volume region can be effectively decomposed. In the sludge pretreatment system according to the present invention, the plasma-based sludge decomposition apparatus comprises an electrode for generating plasma and a power source for supplying electricity to the electrode.

The operation method of the sludge pretreatment system according to the present invention is a method for operating a sludge pretreatment system, comprising a first step of introducing a concentrated sludge, a second step of decomposing the concentrated activated sludge in a plasma-based sludge disintegration device, And the digested sludge digested in the anaerobic digestion tank 70 is concentrated in the solid-liquid separating tank 80 and then decomposed in the plasma-based sludge digestion apparatus.

In the sludge pretreatment system according to the present invention, the dissolution rate of the sludge indicates the decomposition rate of the sludge, which can be defined as the cell wall of the sewage sludge is destroyed and the organic matter in the sludge cell is dissolved. Usually, the solubilization rate of the sludge is affected by the decomposition temperature and the decomposition time, and the higher the temperature, the higher the solubilization rate. The following examples illustrate the sludge degradation rate of the sludge pretreatment system according to the present invention and are expressed as the dissolution rate depending on the temperature.

Example

The sedimented solid discharged from the first settling tank 20 and the second settled tank 40 was treated in the first settling tank 20 and the aerobic tank and the second settled tank 40 after the inflow of the sewage amount of 20 L / Mixed and then treated through the anaerobic digestion tank 70 via the concentration tank 60. [ A plasma-based sludge disintegration device is installed at the front end of the anaerobic digestion tank 70, at the rear end of the anaerobic digestion tank 70 and the anaerobic digestion tank 70. A 12-phase AC power supply device, a tungsten- A plasma generator having a discharge cycle of 60 Hz composed of a cathode made of a capillary anode and a platinum was used. As shown in FIG. 2, a plasma discharge with a discharge voltage of approximately 1200 to 1400 V and a discharge current of 1.7 to 2.0 A by a plasma apparatus was measured in the sludge using an oscilloscope.

The sludge having a solid content concentration of 1.6% and a chemical oxygen demand (COD) of 17,000 mg / L was subjected to plasma treatment and the soluble COD (SCOD) The relative dissolution rate was measured. The sludge decomposition apparatus in the upstream of the anaerobic digestion tank 70 is located between the thickening tank 60 and the anaerobic digestion tank 70 and the sludge decomposition apparatus in the anaerobic digestion tank 70 is located between the dead volume region 70 of the anaerobic digestion tank 70, Respectively. In addition, the sludge decomposition apparatus located at the rear end of the anaerobic digestion tank 70 is configured to be positioned between the anaerobic digestion tank 70 and the discharge port.

FIG. 3 is a graph showing the solubilization rate of the sludge pretreatment system according to the plasma output energy at the front end of the anaerobic digestion tank 70 according to the present invention. Based on the plasma specific energy of the plasma-based sludge disintegration apparatus at the upstream of the anaerobic digestion tank 70, the dissolution rate was found to have the relationship of Equation (1).

(Equation 1)? SCOD = 0.617 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kg TS).

FIG. 4 is a graph showing the solubilization rate of the sludge concentrated in the solid-liquid separation tank 80 by the plasma output energy at the downstream of the anaerobic digestion tank 70 of the sludge pretreatment system according to the present invention. The dissolution rate of the plasma-based sludge disintegration apparatus at the downstream of the anaerobic digestion tank (70) and the anaerobic digestion tank (70) in accordance with the plasma specific energy has a relation of Equation (2)

(2)? SCOD = 0.475 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kgTS).

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

10: sewage inlet 20: primary settling tank
30: aerobic tank 40: secondary settling tank
50: mixing tank 60: concentrated tank
70: Anaerobic digester
80: Solid-liquid separation tank
100: sludge pretreatment device (anaerobic digestion tank shear)
200: sludge pretreatment device (anaerobic digestion tank)
300: sludge pretreatment device (after the anaerobic digestion tank)

Claims (8)

Characterized in that the sludge is decomposed by the plasma-based sludge decomposition apparatus at any two or more of the front end of the anaerobic digestion tank (70), the anaerobic digestion tank (70), or the rear end of the anaerobic digestion tank (70)
The plasma-based sludge disintegration apparatus has a plasma specific energy of 4800 kJ / kgTS or more at the front end of the anaerobic digestion tank 70, and a specific energy of 4800 kJ / kgTS or more at the rear end of the anaerobic digestion tank 70 to achieve an increase of the dissolved sludge- And a plasma specific energy of 6300 kJ / kg TS or more to achieve an increase in dissolved amount of digested sludge of 3000 mg COD / L separated from the effluent in the solid-liquid separation tank (80). The sludge pretreatment system
The plasma-based sludge disintegration apparatus of claim 1, wherein the plasma-based sludge disintegration apparatus has a plasma specific energy of 3200 kJ / kgTS or more to achieve an increase of dissolved sludge dissolution amount of 2000 mg COD / L at the front end of the anaerobic digestion tank, 70 or more, the plasma specific energy is 4200 kJ / kg TS or more in order to achieve an increase in the dissolved concentration of digested sludge of 2000 mg COD / L separated from the effluent in the solid-liquid separating tank 80. In the sludge pretreatment system
The sludge pretreatment system according to claim 1, wherein the dissolution rate according to plasma specific energy of the plasma-based sludge decomposition apparatus at the upstream end of the anaerobic digestion tank (70)

(Equation 1)? SCOD = 0.617 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kg TS).
The sludge pretreatment system according to claim 1, wherein the solubilization ratio of the plasma-based sludge decomposition apparatus at the downstream end of the anaerobic digestion tank (70) and the anaerobic digestion tank (70)

(2)? SCOD = 0.475 SE where? SCOD represents the sludge solubilization amount (mg / L) and SE represents the specific energy (kJ / kgTS).
The method according to claim 1, wherein the sludge is decomposed by a plasma-based sludge decomposition apparatus at the front end and the rear end of the anaerobic digestion tank (70), and a plasma generator is formed inside the anaerobic digestion tank (70) system
The apparatus of claim 5, wherein the plasma generator in the anaerobic digestion tank (70) is configured to release plasma within a dead volume region in which anaerobic sludge in the anaerobic digestion tank (70) is deposited, Wherein the sludge has a diameter of 50% or less of the diameter of the anaerobic digestion tank (70)
The sludge pretreatment system according to claim 1, wherein the plasma-based sludge decomposition apparatus comprises an electrode for generating plasma and a power source for supplying electricity to the electrode.
A first stage in which concentrated sludge is introduced;
A second step of decomposing the concentrated activated sludge in a plasma-based sludge decomposition apparatus;
A third step in which the decomposed concentrated activated sludge flows into the anaerobic digestion tank 70 and is digested; The digested sludge digested in the anaerobic digestion tank 70 is concentrated in the solid-liquid separation tank 80 and decomposed in a plasma-based sludge digestion apparatus.

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