KR20140115820A - Apparatus and method for treating sludge - Google Patents

Abstract

The present invention relates to an apparatus and a method for treating sludge affiliated with biological digestion, solid-liquid separation, count current water treatment, etc. The apparatus for treating sludge is a sludge treating apparatus for treating sludge by using microorganisms, comprising: an aerobic digester which decomposes surplus sludge introduced from the outside by using aerobic microorganisms and operates at a temperature range of 45-70°C; an anaerobic digester which decomposes sludge introduced from the aerobic digester by using anaerobic microorganisms and operates at a temperature range of 35-38°C; a heat exchanger which transfers heat generated in a process of decomposing sludge by using microorganisms in the aerobic digester, to the anaerobic digester; and a struvite synthetic tank which synthesizes struvite by inputting magnesium into separation filtrate discharged from the anaerobic digester. According to the present invention, the temperature of the anaerobic digester can be maintained without using extra heating device, thereby cutting total operation costs, and additionally and chemically removing nitrogen and phosphorus of high concentration contained in the separation filtrate discharged from the anaerobic digester through struvite synthesis.

Description

[0001] Apparatus and method for treating sludge [0002]

The present invention relates to a sludge disposal apparatus and a sludge disposal method, and more particularly, to a sludge disposal apparatus and a sludge disposal method in which the overall operation cost is reduced because the temperature of the anaerobic digestion tank can be maintained without using a separate heating apparatus.

Sewage treatment methods for removing nitrogen (N) and phosphorus (P) from wastewater using microorganisms inevitably result in a large amount of sludge being discharged. Such sludge is a sediment formed in the sewage treatment process and has a high water content Since it contains about 50% organic matter, its treatment is becoming an environmental problem.

Since the implementation of the regulation of prohibition of marine dumping in 2012, the cost of sewage sludge (water content 80%) is over KRW 100,000 for land consignment treatment of sewage sludge, It is very important to reduce the amount of sludge generated. In recent years, the amount of sewage sludge has been increasing more and more because of the addition of drugs for treatment of total phosphorus (TP).

In addition, organic pollutants and nutrients such as nitrogen (N) and phosphorus (P) act as a cause of deterioration of water conditions and inhibition of use, such as destroying aquatic ecosystems and causing eutrophication in water bodies. (TP) concentration standards for domestic sewage treatment facilities have been strengthened since 2012, and a large amount of funds have been invested in order to deal with them.

The excess sludge from the sewage treatment plant is a waste that acts as an obstacle to both of the above major issues and is a microbial floc that generally occurs during the biological sewage treatment process. (P) in the aerobic state, and the phosphorus (P) is released in the case of exposure to anaerobic conditions.

In addition, since the microorganisms constituting the surplus sludge are surrounded by the cell membrane, it is difficult for the anaerobic digestion tank to decompose or solubilize the microorganisms in the surplus sludge alone. Therefore, in most sewage treatment facilities, the surplus sludge generated is directly condensed, dehydrated, and entrusted to prevent the phosphorus (P) from being released from the excess sludge.

In order to reduce such surplus sludge, a pretreatment that destroys the cell membrane of the microorganism constituting the surplus sludge is required, and various pretreatment methods have been conventionally devised. The pretreatment method is divided into a biological pretreatment, a physical pretreatment and a chemical pretreatment in a macroscopic manner. Specifically, methods using hot aerobic digestion, a ball mill, ultrasonic waves, cavitation, ozone, heat, have.

In addition to the conventional pretreatment methods described above, there is also a technology of reducing the amount of sludge by injecting a microorganism preparation inhibiting microbial growth. However, the pretreatment methods are inferior in economic efficiency such as drug costs and maintenance costs, There is a problem that commercialization is very few.

The present invention has been made to solve the above problem, and it is an object of the present invention to provide a sludge treatment apparatus improved in structure so that the temperature of the anaerobic digestion tank can be maintained without using a separate heating apparatus, It is for this reason.

It is another object of the present invention to provide an improved sludge treatment method that can maintain the temperature of the anaerobic digestion stage without using a separate heating device, thereby reducing the overall operation cost.

In order to accomplish the above object, the present invention provides a sludge treatment apparatus for treating sludge using microorganisms, which comprises disposing excess sludge introduced from outside using aerobic microorganisms, Aerobic digester operating in the temperature range; An anaerobic digester operated in the temperature range of 35 ° C to 38 ° C to decompose the sludge introduced from the aerobic digestion tank using anaerobic microorganisms; A heat exchanger for transferring heat generated in the process of decomposing sludge by the microorganisms in the aerobic digestion tank to the anaerobic digestion tank; And a struvite synthesis tank for synthesizing struvite by adding magnesium to the separation filtrate discharged from the anaerobic digestion tank.

The membrane separation apparatus separates the solid and the liquid from each other by a membrane. The sludge introduced from the anaerobic digestion tank is solid-liquid separated from the concentrated sludge by separation filtration, and the concentrated sludge is returned to at least one of the aerobic digestion tank and the anaerobic digestion tank And a solid-liquid separator for introducing the separated filtrate into the struvite synthesis tank.

Here, the surplus sludge introduced into the aerobic digestion tank is preferably highly concentrated to a moisture content of 95% or less.

According to another aspect of the present invention, there is provided a sludge treatment method for treating sludge using microorganisms. The sludge treatment method comprises dissolving and solubilizing excess sludge introduced from outside using aerobic microorganisms, An aerobic digestion step carried out in a temperature range of 70 ° C; An anaerobic digestion step of decomposing and reducing the solubilized sludge in the aerobic digestion step using an anaerobic microorganism and performed at a temperature ranging from 35 ° C to 38 ° C; A heat exchange step of transferring heat generated in the process of decomposing sludge by the microorganisms to the anaerobic digestion step in the aerobic digestion step; And a struvite synthesis step of synthesizing struvite by adding magnesium to the separated filtrate discharged from the anaerobic digestion step.

Here, the sludge treated in the anaerobic digestion step is subjected to solid-liquid separation as a separation filtrate from the concentrated sludge, and the concentrated sludge is conveyed to at least one of the aerobic digestion step and the anaerobic digestion step to reprocess the treated sludge, And a solid-liquid separating step of sending the treated liquid to the struvite synthesis step.

Here, it is preferable that the excess sludge is concentrated to a moisture content of 95% or less and then sent to the aerobic digestion stage.

According to the present invention, by including the aerobic digestion tank, the anaerobic digestion tank, and the heat exchanger for transferring heat generated from the aerobic digestion tank to the anaerobic digestion tank, the temperature of the anaerobic digestion tank can be maintained without using a separate heating device It is possible to chemically add and remove high concentrations of nitrogen and phosphorus contained in the separated filtrate discharged from the anaerobic digestion tank through the synthesis of struvite.

1 is a schematic view for explaining a sludge disposal apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a sludge treatment method according to an embodiment of the present invention.
FIG. 3 is a view showing an embodiment of the heat exchanger shown in FIG. 1. FIG.
Fig. 4 is a view showing another embodiment of the heat exchanger shown in Fig. 1. Fig.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view for explaining a sludge processing apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart for explaining a sludge processing method, which is an embodiment of the present invention.

1 and 2, a sludge treatment apparatus 100 according to a preferred embodiment of the present invention is a sludge treatment apparatus for treating a sludge generated from sewage such as sewage or wastewater using microorganisms, An aerobic digestion tank 10, an anaerobic digestion tank 20, a heat exchanger 30, a struvite synthesis tank 40, and a solid-liquid separator 50.

The aerobic digestion tank 10 is a container for decomposing and solubilizing surplus sludge introduced from the outside using aerobic microorganisms. In this embodiment, the surplus sludge introduced into the aerobic digestion tank 10 is highly concentrated at a water content of 95% or less.

The aerobic digestion tank 10 is a so-called "self-heating" aerobic digestion tank in which aerobic microorganisms induce a high-temperature exothermic phenomenon in the process of decomposing sludge as shown in the following equation (1) .

Organic solid material + O ₂ -> byproduct + CO ₂ + H ₂ O + NH ₄ + heat ------ (1)

The aerobic digestion tank 10 can be operated within a predetermined temperature range depending on the concentration of organic matter present in the digestion tank, the thermal conductivity of the digestion tank, the type of oxygen injected into the digestion tank, and the feeding mode. In this embodiment, Lt; RTI ID = 0.0 > 70 C < / RTI >

The oxygen supply to the aerobic digestion tank 10 is supplied in the form of compressed air or pure oxygen by using separate power. In this embodiment, compressed air is used.

In the aerobic digestion tank 10, 1.42 kg of oxygen is required to decompose 1 kg of volatile suspended solids (VSS) contained in the sludge, and heat of about 20,000 kJ (4,800 kcal) is generated in this process

The anaerobic digestion tank 20 is a container for secondarily decomposing and reducing the sludge primarily decomposed from the aerobic digestion tank 10 using anaerobic microorganisms.

Energy materials, such as the anaerobic digestion tank 20, in, as shown in equation (2) below, and decomposing an organic matter containing the internal digester microorganisms in the sludge while oxygen is not introduced, the methane gas in the process (CH ₄₎ And a large amount of phosphorus (P) are generated.

CH ₃ COOH + 0.032 NH ₃ -> 0.032 C ₅ H ₇ NO ₂ + 0.92 CO ₂ + 0.92 CH ₄ + 0.096 H ₂ O (2)

That is, the reaction of equation (2) generated in the anaerobic digestion tank 20 is absolutely under conditions oxygen is not present, methane gas (CH ₄₎ and carbon dioxide (CO ₂ is degradable organic biologically through the biochemical reaction ). ≪ / RTI >

In the anaerobic digestion tank 20, it is generally known that about 30% of the organic matter contained in the sludge introduced is decomposed and reduced through the digestion process as shown in Equation (2), and 1 kg of volatile suspended solids (VSS) About 300 L to about 500 L of methane gas is generated.

It is preferable that the anaerobic digestion tank 20 is operated in a temperature range in which the digestion efficiency is the best. In this embodiment, a so-called "medium temperature" anaerobic digestion tank operated in a temperature range of 35 to 38 ° C. is used.

The biogas such as methane gas (CH ₄ ) generated from the anaerobic digestion tank 20 is stored in a gas storage tank 70 connected to the anaerobic digestion tank 20 and is usefully used for domestic city gas, .

On the other hand, the sludge discharged from the anaerobic digestion tank 20 is dewatered by the dewatering device 60 and discarded in a dewatered cake state.

The heat exchanger 30 is a heat exchanger for transferring the heat generated from the aerobic digestion tank 10 to the anaerobic digestion tank 20. As shown in FIG. 3 or 4, (31) and a second container (32).

The first container 31 is a metal container having an inner space and is formed at one end thereof with a first container inlet 311 for communicating the inner space with the anaerobic digestion tank 20, A first container outlet 312 for communicating the space with the anaerobic digestion tank 20 is formed.

Accordingly, the sludge B in the anaerobic digestion tank 20, that is, the mixed liquor suspended solid (MLSS) contained in the sludge B is continuously supplied to the first container inlet 311 And then flows out to the anaerobic digestion tank 20 again through the first container outlet 312. In this case,

The second container 32 is a hollow metal pipe disposed in the inner space of the first container 31 and has a second container inlet 321 for communicating the hollow with the aerobic digestion tank 10 And a second container outlet 322 for communicating the hollow and the aerobic digestion tank 10 is formed at the other end.

The second container 32 may be formed in a zigzag shape in the inner space of the first container 31 as shown in FIG. 3, and the first container 31 31 may be formed in a coil shape in a spiral shape in the inner space.

Therefore, the sludge A in the aerobic digestion tank 10, and more specifically the mixed solution suspended solids (MLSS) A contained in the sludge A, continuously flows through the second container inlet 321, Flows into the hollow of the aerobic digestion tank 32 and stays for a predetermined time, and then flows out to the aerobic digestion tank 10 again through the second container outlet 322.

When the sludge A in the aerobic digestion tank 10 flows along the second vessel 32 and at the same time the sludge B of the anaerobic digestion tank 20 flows along the first vessel 31, The heat generated from the sludge in the aerobic digestion tank 10 is gradually transferred to the sludge in the anaerobic digestion tank 20 via the first vessel 31.

The struvite synthesis tank (40) is a vessel for synthesizing struvite from the separated filtrate introduced from the anaerobic digestion tank (20). Here, the separation filtrate is also commonly referred to as a side stream.

The struvite synthesis tank 40 is formed of struvite (NH ₄ MgPO ₄ .6H ₂ O) which is a kind of crystalline mineral by injecting magnesium (Mg) into the reflux water flowing from the anaerobic digestion tank 20. ).

The struvite synthesis tank (40) is provided with a stirring device (not shown) for evenly mixing the reflux water contained therein and the magnesium charged therein.

A struvite sedimentation tank 41 is connected to the struvite synthesis tank 40. The struvite sedimentation tank 41 separates the struvite sedimentation tank 41 from the reflux water flowing in from the struvite synthesis tank 40 And the supernatant liquid is discharged into the treated water.

In the present embodiment, the treated water discharged from the Struvite sedimentation tank 41 is returned to the bottom / wastewater treatment facility for generating surplus sludge introduced into the aerobic digestion tank 10 and used again.

The solid-liquid separator 50 is disposed between the anaerobic digestion tank 20 and the struvite synthesis tank 40. The solid-liquid separator 50 separates the sludge fed from the anaerobic digestion tank 20 from the concentrated sludge, And the concentrated sludge is transferred to the aerobic digestion tank 10 and the anaerobic digestion tank 20, respectively, and the separated filtrate is introduced into the struvite synthesis tank 40.

Here, the dissolved phosphorus (P) concentration of the separated filtrate that has passed through the membrane separation apparatus 50 is significantly increased as compared with that before passing through the membrane separation apparatus 50, The increased separation filtrate is a suitable raw material for struvite synthesis.

In the present embodiment, the solid-liquid separator 50 uses a membrane separator 50 for separating solid and liquid from each other by a membrane.

The membrane separation device 50 is a device using a principle of separation by membrane. Usually, a membrane of an organic polymer material is used. Depending on the pore diameter formed in the membrane, microfiltration (MF) Filtration (UF), reverse osmosis (RO), or hyperfiltration (HF). In this embodiment, microfiltration (MF) or ultrafiltration (UF) is used.

Hereinafter, an example of a method of treating sludge using the sludge processing apparatus 100 having the above-described structure will be described.

First, before the surplus sludge is introduced into the aerobic digestion tank 10, the surplus sludge is concentrated to a moisture content of 95% or less by using a separate device (not shown). (Sludge concentration step S10)

Then, the concentrated sludge concentrated in the sludge concentration step (S10) is introduced into the aerobic digestion tank (10) and dissolved in the aerobic digestion tank (10) using aerobic microorganisms to be solubilized. (Aerobic digestion step S20)

The sludge solubilized in the aerobic digestion tank 10 is introduced into the anaerobic digestion tank 20 and degraded in the anaerobic digestion tank 20 by using the anaerobic microorganism. (Anaerobic digestion step; S30)

The heat generated in the aerobic digestion tank 10 using the heat exchanger 30 is continuously supplied to the anaerobic digestion tank 20 while the aerobic digestion step S20 and the anaerobic digestion step S30 are being performed, The temperature of the anaerobic digestion tank 20 is maintained in the range of 35 占 폚 to 38 占 폚. (Heat exchange step: S40)

The sludge treated in the anaerobic digestion tank 20 is solid-liquid separated from the concentrated sludge and the separated filtrate by the membrane separation device 50. The concentrated sludge is separated from the aerobic digestion tank 10 and the anaerobic digestion tank 20, , And the separated filtrate is sent to the struvite synthesis tank 40. [0050] (Solid-liquid separation step: S50)

Subsequently, magnesium (Mg) is added to the separated filtrate which has been filtered by the membrane separating apparatus 50 and then introduced into the struvite synthesis tank 40, thereby producing struvite, which is a kind of crystalline mineral The struvite sedimentation tank 41 is used to precipitate struvite from the reflux water introduced from the struvite synthesis tank 40 and to recover the supernatant from the struvite sedimentation tank 41 Liquid) is discharged to the treated water. Here, the treated water discharged from the Struvite sedimentation tank 41 is transported back to a wastewater treatment facility for generating surplus sludge that flows into the aerobic digestion tank 10 and used again. (Struvite synthesis step S60)

Finally, the sludge discharged from the anaerobic digestion tank 20 is dewatered by the dewatering device 60, and is then disposed of in a dewatered cake state, and the treatment of the excess sludge is completed. (Dehydration step: S70)

The sludge treatment apparatus 100 of the above-described construction comprises an aerobic digestion tank 10 for decomposing surplus sludge introduced from the outside using aerobic microorganisms, and a sludge disposal unit 10 for decomposing the sludge introduced from the aerobic digestion tank 10 using anaerobic microorganisms. And a heat exchanger 30 for transferring the heat generated from the aerobic digestion tank 10 to the anaerobic digestion tank 20. Therefore, the anaerobic digestion tank 20 20) can be maintained, and the overall operation cost is reduced.

In this embodiment, sludge primarily solubilized in the aerobic digestion tank 10 having a relatively high temperature is secondarily digested in the anaerobic digestion tank 20, which is relatively warm, so that, as described below in Table 1, The removal efficiency of the volatile solids (VS) in the sludge can be maintained at 60% or more, and the amount of the final dewatered cake can be reduced by 20% to 40% by increasing the removal efficiency of the volatile solids (VS).

Comparison of processing efficiency between this embodiment and the conventional system division Characteristics of inflow sludge Total solids (TS)
Removal efficiency Volatile solids (VS)
Removal efficiency Dehydrated cake
Generation
(80% wt) flux TS ratio VS / TS ratio In this embodiment 0.8 m ³ / s 6% 70% 50% 65% 120 ton Conventional method 2.0 m ³ / s 2.5% 70% 20 to 30% 30 to 40% 188 ton

Here, the inflow sludge shown in Table 1 means excess sludge that flows into the aerobic digestion tank 10, and the conventional method means that only a general anaerobic digestion tank is used without using an aerobic digestion tank. The flow rate and the total solids (TS) ratio between the present embodiment and the conventional system to be compared are different from each other, but the total amount of solids (TS) introduced into the aerobic digestion tank 10 during the same time is the same.

Since the sludge treatment apparatus 100 includes the struvite synthesis tank 40 for synthesizing struvite from the separation filtrate introduced from the anaerobic digestion tank 20, the concentration of the high concentration It is advantageous to chemically add and remove nitrogen (N) and phosphorus (P). Here, the sludge treating apparatus 100 is a device for treating sludge containing phosphorus (P) at a high concentration (generally 1,000 mg / L or more) discharged from the anaerobic digestion tank 20 due to the characteristics of the excess sludge, The nutrient load due to the reflux water discharged from the anaerobic digestion tank 20 can be greatly reduced.

The sludge disposal apparatus 100 includes a solid-liquid separator 50 for solid-liquid separating the sludge introduced from the anaerobic digestion tank 20 into a separated filtrate from the concentrated sludge. Therefore, the concentrated sludge is introduced into the aerobic digestion tank 10 and the anaerobic digestion tank 20, and only the separated separated filtrate is introduced into the struvite synthesis tank 40, which is a phosphorus recovery device, to thereby increase the solubilization efficiency of the solids.

The sludge treatment device 100 is a membrane separation device in which the solid-liquid separation device 50 separates solid and liquid from each other by a membrane. Therefore, it is easy to maintain and manage the solid-liquid separation device 50, It is advantageous in that the solid-liquid separation efficiency is excellent as compared with the apparatus.

Since the surplus sludge introduced into the aerobic digestion tank 10 is highly concentrated at a water content of 95% or less in advance, the amount of heat generated in the aerobic digestion tank 10 is increased, There is an advantage that the synthesis efficiency of struvite in the synthesis tank 40 is increased.

Since the sludge treatment apparatus 100 includes the gas storage tank 70 for storing the biogas generated from the anaerobic digestion tank 20, the methane gas (CH ₄ ) generated from the anaerobic digestion tank 20 ) Can be usefully used for domestic city gas and power plant fuel.

The sludge treatment apparatus 100 includes a dewatering device 60 for dewatering sludge discharged from the anaerobic digestion tank 20 so that the sludge discharged from the anaerobic digestion tank 20 is relatively small in volume It is possible to dispose the dewatered cake in a cake state, thereby reducing the transportation and disposal cost of the whole dewatered sludge.

The technical scope of the present invention is not limited to the contents described in the above embodiments, and the equivalent structure modified or changed by those skilled in the art can be applied to the technical It is clear that the present invention does not depart from the scope of thought.

[Description of Reference Numerals]
100: sludge treating apparatus 10: aerobic digester
20: anaerobic digester 30: heat exchanger
31: first container 32: second container
40: Struvite synthetic tank 41: Struvite sedimentation tank
50: solid-liquid separator, membrane separator 60: dehydrator
70: Gas storage tank

Claims (6)

A sludge treatment apparatus for treating sludge using microorganisms,
An aerobic digestion tank operated in the temperature range of 45 ° C to 70 ° C to decompose surplus sludge introduced from outside using aerobic microorganisms;
An anaerobic digester operated in the temperature range of 35 ° C to 38 ° C to decompose the sludge introduced from the aerobic digestion tank using anaerobic microorganisms;
A heat exchanger for transferring heat generated in the process of decomposing sludge by the microorganisms in the aerobic digestion tank to the anaerobic digestion tank;
A struvite synthesis tank for synthesizing struvite by adding magnesium to the separation filtrate discharged from the anaerobic digestion tank;
Characterized in that the sludge treatment device The method according to claim 1,
Wherein the sludge introduced from the anaerobic digestion tank is subjected to solid-liquid separation in a separation filtrate from the concentrated sludge, the concentrated sludge is returned to at least one of the aerobic digestion tank and the anaerobic digestion tank, Characterized in that the separation filtrate includes a solid-liquid separator for introducing the separated filtrate into the struvite synthesis tank The method according to claim 1,
Wherein the excess sludge introduced into the aerobic digestion tank is highly concentrated at a water content of 95% or less. A sludge treatment method for treating sludge using microorganisms,
An aerobic digestion step of decomposing and solubilizing the excess sludge introduced from the outside using aerobic microorganisms and performing in a temperature range of 45 ° C to 70 ° C;
An anaerobic digestion step of decomposing and reducing the solubilized sludge in the aerobic digestion step using an anaerobic microorganism and performed at a temperature ranging from 35 ° C to 38 ° C;
A heat exchange step of transferring heat generated in the process of decomposing sludge by the microorganisms to the anaerobic digestion step in the aerobic digestion step;
A struvite synthesis step of synthesizing struvite by adding magnesium to the separated filtrate discharged from the anaerobic digestion step;
And a sludge treatment method 5. The method of claim 4,
Wherein the sludge treated in the anaerobic digestion step is subjected to solid-liquid separation by a separation filtrate from a concentrated sludge, and the concentrated sludge is conveyed to at least one of the aerobic digestion step and the anaerobic digestion step to reprocess the treated sludge, And a solid-liquid separation step of treating the sludge by sending it to a truvite synthesis step 5. The method of claim 4,
And a sludge concentration step of concentrating the excess sludge to a moisture content of 95% or less and then sending the sludge to the aerobic digestion step

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