KR101954139B1 - Method for treatment sludge of sewage using alkane solvent - Google Patents

Abstract

The present invention relates to a method for treating sewage sludge by a solvent extraction method. In particular, the present invention relates to a method for treating sewage sludge using an alkane-based solvent which significantly reduces the water content of the sewage sludge by using an alkane-based solvent which is liquid and nonpolar at atmospheric pressure and at room temperature.

Description

TECHNICAL FIELD The present invention relates to a sewage sludge treatment method using an alkane-based solvent,

The present invention relates to a sewage sludge treatment method using a solvent extraction method, and more particularly, to a sewage sludge treatment method using an alkane-based solvent that significantly reduces the water content of sewage sludge by using an alkane- And a method of processing the same.

Recently, there has been developed a technology that can treat sewage sludge efficiently because the unauthorized discharge or speculation of sewage sludge causing environmental pollution such as prohibition of marine dumping of the sewage sludge is prohibited.

Conventionally, organic aggregates such as organic sludge and microorganisms contained in wastewater are aggregated and precipitated in a lump together with water by using a polymer flocculant. According to this treatment method, the specific gravity is separated and recovered into a sludge mass of about 12.

However, since the above-mentioned sewage sludge agglomerated by organic matter including microorganisms is subjected to a mechanical dehydration process by centrifugal separator, it still contains more than 80% moisture, so that the weight reduction is not sufficient.

The first reason for not being reduced is that the outermost number of microorganisms outside the microorganism can not be easily dehydrated as the microfloc is bound to each other by the capillary phenomenon between groups of organic sludge particles having a size of less than 150 μm .

Furthermore, the second reason for the lack of weight reduction is that the microorganisms present in the sewage are not destroyed, and the crystal water (water in the body) existing in the microorganisms accounts for about 40% of the total water remaining in the sewage sludge after the flocculation treatment do.

Therefore, there is a problem in that a secondary treatment such as heat treatment and dry incineration is necessary in order to meet the water content standard suitable for recycling or landfill treatment after dehydration of sewage sludge coagulated and separated as described above by a mechanical method.

In Korean Patent Laid-Open Nos. 2015-0056429, 2015-0056472, and 2015-0056473, the organic matter of the sewage sludge is extracted and separated using a hydrocarbon-based organic solvent to further lower the water content .

When a hydrocarbon-based organic solvent is added to the sewage sludge, the organic sludge and the microorganism migrate to the organic solvent and are attached and extracted. Therefore, there is an effect of extracting crystal water in the microorganism due to the outermost number of organic sludge and microbial destruction.

However, since the hydrocarbon organic solvent used conventionally is in a solid state at room temperature and atmospheric pressure, it is difficult to evenly diffuse the organic sludge into the whole of the sludge during the addition, and thus the solvent extraction effect is low, which limits the overall water content.

In addition, conventionally used hydrocarbon-based organic solvents have a relatively long carbon chain and thus are not only disadvantageous in terms of rheology, but also have a low selective adsorption rate on the fine organic matters present in the sewage sludge.

Some of the conventional hydrocarbon-based organic solvents have a specific gravity smaller than that of water but are not sufficient. Therefore, the floatability in which the organic substances are adsorbed and floated over the water is deteriorated, and the residence time (R / T) there is a problem.

Korean Patent Publication No. 2015-0056429 Korean Patent Publication No. 2015-0056472 Korean Patent Publication No. 2015-0056473

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an alkane- And to provide a method for treating sewage sludge using a solvent.

To this end, the method for treating sewage sludge using an alkane-based solvent according to the present invention is characterized in that, in the extraction and treatment of organic matter in sewage sludge including water, microorganisms and organic sludge, Separating the microorganism and the organic sludge attached to the solvent from the outermost water present in the microorganism by injecting a solvent; An organic substance concentration step of diffusing the non-polar solvent into the inside of the microorganism to induce destruction of the microbial cell membrane due to the expansion of the microbial cell, and separating out the crystal water remaining in the microorganism by cell membrane destruction; And a solvent recovery step of separating and recovering the solvent adhered to the microorganism and the organic sludge, wherein the solvent introduced in the organic matter separation step is a solvent which is present in a liquid state at atmospheric pressure and at room temperature in the alkane- .

Wherein the solvent is N-PENTANE in which n = 5 and a specific gravity of less than 1 in the alkane (C _n H _{2n + 2} ), ISO-PENTANE or NEO-PENTANE which is an isomer of the N-pentane, It is preferable that the microorganism and the organic sludge are separated from water by floating on the upper side of the water by a solvent having a specific gravity smaller than 1.

In addition, the solvent recovery step preferably includes a liquid solvent recovery step of separating and recovering the liquid state solvent attached to the microorganism and the organic sludge by using a de-liquor.

The solvent recovery step may further include a gaseous solvent recovery step of recovering the gaseous solvent vaporized by using the vaporization activated tank and condensing the vaporized gaseous solvent into a liquid solvent.

Further, the method may further include a pretreatment step for injecting the solvent, wherein the pretreatment step comprises: a concentration detecting step of detecting a mixed liquor suspended solid (MLSS) concentration, which is an average suspended solids concentration of the mixed liquid with respect to the sewage sludge; And an input amount detecting step of determining an input amount of the introduced solvent according to the detected MLSS concentration.

In addition, the pretreatment step may further include a concentration adjusting step of diluting the MLSS concentration of the sewage sludge to less than 5,000 [ppm].

It is preferable that at least one of the outermost water separated in the organic material separation step or the crystal water separated in the organic matter concentration step is recycled to the sewage sludge so as to maintain the MLSS concentration of the sewage sludge at a system optimum value Do.

The pretreatment step may further include a stirring step of removing contaminants contained in the sewage sludge and uniformly stirring the sewage sludge with a stirrer.

Preferably, the sewage sludge introduced in the organic material separation step is sewage sludge treated in the aerobic tank or the sedimentation tank among the chemical treatment tank, the oxic tank, the sedimentation tank, the concentration tank, and the dewatering device which are sequentially installed in the sewage treatment plant.

As described above, the present invention treats sewage sludge by a solvent extraction method in which an organic matter is selectively adsorbed and suspended in water. In particular, the solvent is an alkane-based solvent which is liquid at atmospheric pressure and at room temperature and is nonpolar.

Therefore, despite the capillary phenomenon between the small size organic matter, the organic matter is adsorbed on the solvent and separated from the water, and the extraction reaction is caused by flowing and expanding between the sewage sludge by the liquid state solvent.

In addition, the nonpolar solvent permeates the phospholipid bilayer constituting the cell membrane of the microorganism through simple diffusion, and the cell membrane of the microorganism is destroyed by the expansion of the solvent diffused into the microorganism, thereby separating and removing the water inside the microorganism.

1 is a flowchart illustrating a method for treating sewage sludge using an alkane-based solvent according to the present invention.
2 is a view showing a sewage sludge treatment system to which the present invention is applicable.
3 is a view showing a state in which an organic material is selectively adsorbed on the solvent of the present invention.
4 is a characteristic table of treated water and sludge powder treated according to the present invention.

Hereinafter, a method for treating sewage sludge using an alkane-based solvent according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the method for treating sewage sludge using an alkane-based solvent according to a preferred embodiment of the present invention includes an organic matter separation step (S 110), an organic matter concentration step (S 120), and a solvent recovery step (S 130).

The solvent recovery step S130 may include a gas solvent recovery step S132 in addition to the liquid solvent recovery step S131 and preferably further includes a preprocessing step S110-P before the organic material separation step S110 do.

As described above, the non-polar alkane-based solvent is introduced into sewage sludge (or slurry) containing water, microorganisms, organic sludge as well as other inorganic substances and heavy metals, and the like to extract and remove organic matter such as microorganisms and organic sludge. .

At this time, in the organic material separation step (S110), as the organic matter is adsorbed to the alkane-based solvent, the outermost water contained in the sewage sludge is separated from the organic matter. The outermost number means the water that remains between the organic materials in the sewage sludge.

In the organic substance concentration step (S120), as the non-polar alkane-based solvent is simply diffused into the microorganism, the cell membrane of the microorganism is destroyed by the expansion pressure and the crystal water (water in the body) remaining in the microorganism flows out, Respectively.

In the solvent recovery step (S130), the solvent adsorbed on the organic substances separated from the water (the outermost water number and the crystal water number) is collected and reused. The recovered solvent may be a liquid phase and a gas phase vaporized therefrom as described later.

Hereinafter, the present invention will be described in more detail from the pre-processing step.

First, in the pretreatment step S110-P, an alkane-based solvent (hereinafter referred to as "solvent") and sewage sludge are maintained at system optimum values optimized for the treatment. To this end, it includes a concentration detecting step, an input amount detecting step, a concentration adjusting step and a stirring step.

At this time, in the concentration detecting step, MLSS (mixed liquor suspended solid) concentration, which is an average suspended suspension concentration of sewage sludge, is detected. In the input amount detecting step, the amount of the solvent to be injected is determined according to the MLSS concentration detected as described above.

It is very important to maintain the MLSS concentration of the sewage sludge at the system proper value, as it is necessary to optimize the MLSS concentration, such as when the solid fuel is burned in an incinerator, it is completely combusted and the inside is prevented from incomplete combustion.

For example, it is preferable that the MLSS concentration of the sewage sludge is less than 5,000 [ppm]. If the MLSS concentration of the sewage sludge exceeds 5,000 [ppm], it is difficult to selectively adsorb the organic material and the alkane-based solvent of the sewage sludge as an input raw material.

Next, when the MLSS concentration of the sewage sludge does not satisfy the system optimum value, the MLSS concentration of the sewage sludge is adjusted to the appropriate value by controlling the ratio of the water to the organic matter.

For example, if the MLSS concentration of sewage sludge exceeds 5,000 [ppm], water is added to dilute to less than 5,000 [ppm]. The water to be supplied for maintaining the system proper value preferably recycles the outermost water number separated in the organic matter separation step (S110) and / or the number of crystals separated in the organic matter concentration step (S120).

Next, in the stirring step, the contaminants contained in the sewage sludge are removed, and the sewage sludge is uniformly stirred in an agitator equipped with various sensors. Here, the impurity means a solid material or the like which is not extracted by the solvent.

As described above, it is preferable that the sewage sludge charged in the pre-treatment step (S110-P) is supplied from the sewage treatment plant. To this end, the system to which the present invention is applicable may be interlocked (or parallel connected) to the sewage treatment facility.

As shown in FIG. 2, the chemical treatment tank 10, the oxic tank 20, the settling tank 30, the thickener tank 40 and the dewatering device 50 are basically constructed in the sewage treatment plant. The treated sewage sludge in the aerobic tank 20 or the sedimentation tank 30 can be pretreated and introduced into an organic material separation step (S110) described later.

The aerobic tank 20 biologically treats the chemically treated sewage sludge in the chemical treatment tank 10. The aerobic tank 20 is also referred to as aeration tank, and air (aeration) is supplied to treat the organic matter using microorganisms when the activated sludge process is performed.

The aerobic tank 20 is supplied with the conveying sludge from the subsequent sedimentation tank 30, and the remaining excess sludge is supplied to the concentration tank 40. The surplus sludge is sewage sludge except for the conveying sludge used as the nutrient (carbon component) necessary for maintaining the microbial ecosystem in the aerobic tank 20.

In this case, when the sewage sludge is supplied from the aerobic tank 20, the sewage sludge of the aerobic tank 20 is injected after the removal and agitation of the sewage sludge without adjusting the concentration of the sewage sludge because the MLSS concentration is less than 5,000 [ppm] . Of course, if the MLSS concentration exceeds 5,000 [ppm], the MLSS concentration can be lowered by adding the number of steps.

The MLSS concentration of the oxic tank 20 can be monitored using an MLSS concentration meter installed in the sewage treatment plant. For example, the MLSS densitometer can use energy averaging using ultrasonic attenuation and envelope signals, which monitors each facility in the sewage treatment plant.

On the other hand, since the sewage sludge in the sedimentation tank 30 normally has an MLSS concentration of 20,000 [ppm] or higher, the number of processings (that is, the outermost number and / or the number of crystals) It should be adjusted to less than 5,000 [ppm].

When the system to which the present invention can be applied as described above is interlocked with or installed in parallel with the existing sewage treatment plant facility, the thickening tank 40 and the dehydrating apparatus 50 installed in the aerobic tank 20 or the settling tank 30, It can be stopped or unnecessary. Further, in the case of installing a new sewage treatment plant, the concentration tank 40 and the dewatering device 50 can be omitted.

1, a non-polar Alkane-based solvent is introduced into the sewage sludge in the organic material separation step (S110), and the microorganisms and organic sludge attached to the solvent are introduced into the outermost number of microorganisms Separate.

For example, when the sewage sludge and the solvent in which the system proper value is maintained through the preprocessing step (S110-P) are mixed with the in-line mixer and then introduced into the separation tank, the organic material is selectively adsorbed to the solvent as shown in FIG. Organic matter includes organic sludge and microorganisms.

As will be described later, a solvent having a specific gravity of less than 1 is separated from water as it floats on top of the water together with organic matter in the separation tank. That is, the solvent in which the organic sludge and microorganisms are adsorbed in the separation tank floats on the upper side and the water is separated on the lower side.

The water separated in the lower layer in the separation tank means the above-mentioned outermost number and is distinguished from the number of crystals (internal water) in the microorganism. In the present invention, particles of organic sludge having a microfloc size of less than 150um And the water remaining between them is separated.

In addition, since the outermost number is a polar substance having an acid-base interaction force, even when water particles act on a strong attraction force, it is possible to separate the outermost number of water, which was difficult to separate in the conventional mechanical dewatering method .

As described above, the outermost water number separated in the organic matter separation step (S110) is stored in the water storage tank (S111) and then supplied to the pre-processing step (S110-P) And discharged to the treatment plant.

At this time, the outermost water number is not changed in the sewage treatment plant because there is no PH or property change compared with the state contained in the first sewage sludge, and it can be used as a process water to be recycled to the pretreatment step (S110-P) .

As described above, the non-polar alkane-based solvent to be introduced together with the sewage sludge in the organic material separation step (S110) is preferably an alkene-based solvent that exists in a liquid state at atmospheric pressure and at room temperature among alkane series.

When the solvent is liquid at room temperature and atmospheric pressure, it has excellent rheological properties such that the liquid state solvent diffuses and uniformly disperses among the sewage sludge which is the medium. Therefore, the solvent extraction effect is remarkably superior to that when the solvent is solid.

Among the alkane (C _n H _{2n + 2} ), n = 1 to n = 4 exist in a gaseous state at atmospheric pressure and at room temperature, so that it is difficult to inject into the sewage sludge or diffuses into the atmosphere without solvent extraction And so on.

In the alkane having n = 18 or more, since it exists in a solid state at atmospheric pressure and room temperature, there is a problem that the rheological characteristic of diffusion and homogeneous dispersion between sewage sludge drops sharply, and the molecular weight is large and the length of the carbon ring is excessively long.

Therefore, the present invention maximizes the effect of extracting organic substances contained in sewage sludge by using a solvent existing in a liquid state at atmospheric pressure and at room temperature by applying the system that n = 5 to n = 17 in alkane.

Particularly, it is preferable that the solvent is N-PENTANE having a specific gravity of n = 5 and a specific gravity of less than 1 or an ISO-PENTANE or NEO-PENTANE which is an isomer of N-PENTANE. Specifically, the specific gravity of N-PENTANE is 0.6 to 0.7.

As a result, the present invention provides a method of extracting and purifying an organic substance using N-PENTANE or an isomer thereof, which has the shortest carbon ring in an alkane-based solvent present in a liquid state at atmospheric pressure and at room temperature and has the best selective adsorption characteristic with organic matters in sewage sludge Separate.

Furthermore, N-PENTANE and its isomers have the smallest molecular weight among alkanes in liquid state, and their specific gravity is as small as 0.6 to 0.7. Therefore, N-PENTANE and isomers have the best floatation ability after selective adsorption with organic substances, And detachable.

Next, the organic substance concentration step (S120) diffuses the non-polar solvent into the inside of the microorganism to induce destruction of the microorganism cell membrane due to the expansion, and separates the crystal water remaining inside the microorganism by the cell membrane destruction.

For example, the sludge composed of the microorganism, the organic sludge, and the solvent from which the outermost water number is separated is sent to the concentration tank through the organic material separation step (S110) in the separation tank, and a step for separating the crystal water is performed in the concentration tank.

According to the conventional mechanical dewatering method (for example, centrifugal dehydration or various filter methods), the water content of the sewage sludge exceeds 80%, and the number of crystals in the microorganism accounts for 40%.

However, it is difficult to remove the crystal water remaining in the interior of the microorganism by only the driving force of the mechanical dehydration method, and it is practically impossible to separate mechanically because the crystal water is distributed in small amounts in the microorganisms.

Accordingly, the present invention uses a non-polar alkane-based solvent that is easily diffused into the cell membrane. Particularly, N-PENTANE and its isomers of n = 5, which are liquid at room temperature and have the shortest carbon ring, are used.

Accordingly, the present invention provides a simple diffusion through a cell membrane of a microorganism composed of a phospholipid bilayer using a solvent having a non-polar, liquid state at room temperature and a short carbon ring, thereby destroying the cell membrane of the microorganism by the generated pressure.

The microorganisms in which the cell membrane is destroyed are separated from the solvent in the crystal water (water in the body) present therein, and the crystalline water having a specific gravity larger than that of the solvent sinks to the bottom. The organic matter adsorbed on the solvent floats on the upper side together with the solvent And is separated from the crystal number.

The number of crystals separated in the organic substance concentration step S120 is stored in a water storage tank (S121) and then supplied to the pretreatment step S110-P as process water. Alternatively, . The sludge that has passed out of the water of crystallization becomes concentrated.

As described above, the number of crystals can be used as the number of steps to be recycled to the pretreatment step (S110-P) or the like without changing the water balance in the sewage treatment plant because there is no PH or property change compared with the state contained in the first sewage sludge Do.

Next, in the solvent recovery step (S130), the solvent passed through the sewage sludge in the pre-treatment step (S110-P) and separated through the organic material separation step (S110) and the organic material concentration step (S120) is separated and recovered.

The solvent recovery step (S130) includes a liquid solvent recovery step (S131) for recovering the liquid state solvent. Further, as a preferred embodiment, it includes a gas solvent recovery step (S132) in which the gas solvent is recovered in addition to the recovery of the liquid solvent.

At this time, in the liquid solvent recovery step (S131), the liquid state solvent attached to the microorganism and the organic sludge is separated and recovered by using a dehydrator. A variety of de-liquor may be used, such as a vacuum desorber, a pressure desorber, and a centrifugal desorber.

The liquid solvent recovered in the liquid solvent recovery step S131 is stored in the solvent storage tank (S131a), and the stored solvent is supplied to the pretreatment step S110-P described above. In some cases, it may be directly supplied to the organic material separation step S110.

Next, in the gaseous solvent recovery step (S132), the surface of the liquid solvent or the gaseous solvent vaporized in the air is recovered during the treatment of the sewage sludge with the solvent extraction method using the liquid state solvent.

In order to recover the gaseous solvent, entropy of the gaseous solvent is increased by using compressed air in the vaporization activated tank, and the collected gaseous solvent is sent to the condenser to condense (S132a). The compressed air is supplied to an air cyclone apparatus or the like installed in the vapor activation tank.

The recovered and condensed liquid solvent in the gaseous solvent recovery step (S132) is also stored in the solvent storage tank, and the stored solvent is supplied to the pretreatment step S110-P described above. In some cases, it may be directly supplied to the organic material separation step S110.

Particularly, in order to maximize the collection efficiency of the gaseous solvent, the vaporization active tank and the peripheral device can constitute a closed circuit isolated from the external environment, and preferably, the previous process is constituted by a closed circuit.

As described above, when the sewage sludge generated in the conventional sewage treatment plant is applied to the present invention, there is an advantage that the reduction technology (mechanical dehydration technology, thermal drying technology, etc.), the recycling technology and the embedding technology are integrated into one.

In addition, the sewage sludge discharged through the mechanical dewatering process at the conventional sewage treatment plant contains about 80% moisture. In addition, the present invention can further reduce the amount of 78%, thereby enabling it to be used as alternative energy having a high calorific value .

Further, even if the sewage sludge generated in the sewage treatment plant is reduced by the mechanical method in the related art, since it still contains a lot of water, further heat treatment and dry incineration process are required, so that the present invention can omit such a process.

Further, as shown in FIG. 4, according to the present invention, BOD, COD, SS, TOC and treated water with improved electrical conductivity are discharged. In particular, the outermost water and crystalline water are removed to produce a sludge powder having a moisture content of less than 10%.

The sludge powder containing less than 10% of water provides a heat quantity of about 3,876 [Kcal / Kg], thereby making it unnecessary to fill the sewage sludge treated sludge powder and use it as renewable energy.

The specific embodiments of the present invention have been described above. It is to be understood, however, that the spirit and scope of the invention are not limited to these specific embodiments, but that various changes and modifications may be made without departing from the spirit of the invention, If you are a person, you will understand.

Therefore, it should be understood that the above-described embodiments are provided so that those skilled in the art can fully understand the scope of the present invention. Therefore, it should be understood that the embodiments are to be considered in all respects as illustrative and not restrictive, The invention is only defined by the scope of the claims.

10: chemical treatment tank
20: arousal trough
30: Settling tank
40: Enrichment tank
50: Dewatering device
100: solvent extraction system

Claims (9)

A sewage sludge treatment method using an alkane-based solvent for extracting and treating organic matter from sewage sludge containing water, microorganisms and organic sludge,
An organic matter separation step (S110) of injecting a non-polar Alkane-based solvent into the sewage sludge to separate the microorganisms adhered to the solvent and the organic sludge from the outermost water present in the microorganism;
An organic substance concentration step (S120) of diffusing the non-polar solvent into the inside of the microorganism to induce destruction of the microbial cell membrane due to the expansion of the microbial cell and separating out the crystal water remaining in the microorganism by the cell membrane destruction; And
And a solvent recovery step (S130) for separating and recovering the solvent attached to the microorganism and the organic sludge,
The solvent introduced in the organic substance separation step (S110) is a solvent present in the alkane-based solvent at atmospheric pressure and at room temperature in a liquid state,
The sewage sludge introduced in the organic matter separation step S110 is introduced into the chemical treatment tank 10, the oxic tank 20, the settling tank 30, the concentration tank 40 and the dehydrating apparatus 50 The sewage sludge is treated in the aerobic tank (20) or the settling tank (30)
The pretreatment step S110-P further comprises a pretreatment step S110-P for introducing the solvent, wherein the pretreatment step S110-P is a step of purifying the mixed suspension of the sewage sludge supplied from the aerobic tank 20 or the sedimentation tank 30, a mixed liquor suspended solids concentration; And an input amount detecting step of determining an input amount of the introduced solvent according to the detected MLSS concentration,
At least one of the outermost water separated in the organic matter separation step (S110) or the crystal water separated in the organic matter concentration step (S120) may be added to the sewage sludge so as to maintain the MLSS concentration of the sewage sludge at a system optimum value. Wherein the sludge is introduced into the sludge tank. The method according to claim 1,
The solvent may be,
N-PENTANE in which n = 5 and a specific gravity of less than 1 in the alkane (C _n H _{2n + 2} ), ISO-PENTANE or NEO-PENTANE which is an isomer of N-PENTANE,
Wherein the microorganism and the organic sludge adhered to the solvent are separated from water by floating on the upper side of the water by a solvent having a specific gravity of less than 1. The method for treating sewage sludge using an alkane-based solvent according to claim 1, The method according to claim 1,
The solvent recovery step (S130)
And a liquid solvent recovery step (S131) for separating and recovering the liquid state solvent adhered to the microorganism and the organic sludge by using a dewatering machine. The method of claim 3,
The solvent recovery step (S130)
Further comprising a gaseous solvent recovery step (S132) of recovering the gaseous solvent vaporized by the liquid solvent using the vaporization activated tank and condensing the vaporized gaseous solvent with a liquid solvent (S132). delete The method according to claim 1,
The preprocessing step (S110-P)
Further comprising a concentration adjusting step of diluting the MLSS concentration of the sewage sludge to less than 5,000 [ppm]. delete The method according to claim 1,
The preprocessing step (S110-P)
And removing the contaminants contained in the sewage sludge and uniformly stirring the sewage sludge with an agitator. The method for treating sewage sludge using an alkane-based solvent according to claim 1,
delete

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