KR20100073812A - Treatment method for solubilization of sludge and recycling method of sludge using the same - Google Patents

Abstract

PURPOSE: A solubilization processing method of sludge and a recycling method of the sludge using the same are provided to reduce sludge by solubilizing sludge discharged from a biological treatment process by alkali. CONSTITUTION: A solubilization processing method of sludge includes the following steps: solubilizing sludge produced in a biological treating process with alkali; transferring supernatant water gained in a solubilization process into a biological treatment process; transferring the supernatant water supplying microorganism; dehydrating the sludge separated from the supernatant water; and transferring filtrate supplying filtrate as nutrients of the microorganism.

Description

Treatment method for solubilization of sludge and recycling method of sludge using same {Treatment method for solubilization of sludge and recycling method of sludge using the same}

The present invention relates to a method for treating solubilization of sludge and a method for recycling sludge using the same, and more particularly, solubilization of the sludge by achieving solubilization by adding alkali to the sludge generated in the biological treatment process of sewage / wastewater. The present invention relates to a method for recovering a dehydration aid in the form of an oxide from a sludge cake of low moisture content dehydrated using a dewatering aid.

At present, most of the sewage and wastewater treatment methods have been developed by the activated sludge method developed at the beginning of the 20th century as a representative process of sewage treatment, and the progress of the treatment process has been advanced as the treatment goal is changed from organic matter, suspended solids to nitrogen, phosphorus and trace materials. There was this.

Sewage and wastewater biological treatment is basically a method of treating wastewater by using microorganisms or oxidizing organic substances and converting them into H ₂ O or CO ₂ or microorganisms that can be precipitated. In order to operate the biological treatment process efficiently, an environment suitable for the active microorganism operating conditions is required. In particular, maintaining an adequate amount of microorganisms in the system is a very important factor in the operation of the process.

However, in the biological treatment of sewage and wastewater, only about 25-30% of organic matter is mineralized and the remainder remains in the form of waste activated sludge or primary sludge. Sewage sludge is a generic term for liquid suspended solids generated during sewage treatment. Sewage sludge is called primary sludge, surplus sludge, conveying sludge, concentrated sludge and digested sludge in a narrow sense. And scums are also included.

In the conventional biological treatment of sewage waste water, some of the sludge discharged from the secondary settling basin is returned to the aeration tank, and the rest is discharged through a concentration tank, a digestion tank, and a dehydration process as waste sludge.

To treat waste sludge, it relies on a process of concentration, low efficiency anaerobic digestion, dehydration and landfilling. This conventional waste sludge treatment method is expensive because it requires a site for landfill. In fact, in this case, it is known that the cost of waste sludge treatment is about 40% of the total sewage treatment cost. Meanwhile, since 2001, the sludge is to be banned from the final landfill, and a new method for waste sludge treatment is required.

In addition, waste sludge incineration method has recently been discussed as an alternative to landfill, but in the case of incineration treatment, it is disadvantageous for resource recovery, and incidental environmental pollutants generated during incineration become a problem.

As such, large amounts of contaminants in the sewage treatment process are separated into treated water and contaminants (sludge), but complete treatment does not occur. It is therefore known that sludge is recognized as a waste to be reprocessed and that 38% of the total energy and 40% of the total cost of the sewage treatment is used for the treatment.

Despite this situation, sludge disposal has not developed much over the past decades compared to the advancement of wastewater treatment systems. In addition, it is reluctant to bring in the final disposal site of waste, and since 2001, it is forbidden to bring landfill into Korea, so it is time for the development of new disposal technology.

Sludge treatment facilities are aimed at biochemical stabilization of organic matter in sludge, mineralization of hygiene to remove pathogens, reduction in the amount of disposal targets, and certainty of disposal. Effective disposal of sewage sludge would be best to recycle and recover energy and resources.

This technology has already been studied in developed countries, some of which have been put to practical use. Sludge reuse includes soil reduction, solid fuels, construction materials, ornaments, energy production, and resource recovery.

However, the effective use of such sludge is not yet generalized as an economical alternative since it requires an effective pretreatment of sludge.

Therefore, a more aggressive countermeasure is a technique for reducing and recycling sludge generation (mass or volume reduction). Representative of these technologies can be said to be the decomposition and solubilization technology of the sludge.

However, even if solubilization is used to reduce the sludge, the remaining sludge can be another source of environmental pollution. In addition, these remaining sludges are difficult to dehydrate as fine sludge.

The present invention has been made to improve the above-mentioned problems, and the solubilized sludge discharged from the biological treatment process of sewage water by alkali and the solubilized sludge can be reused in the biological treatment process to reduce the amount of sludge discharged. The purpose of the present invention is to provide a solubilization treatment method and a method for recycling sludge using the same.

It is another object of the present invention to recover the dehydration aid in the form of oxide from the low water content sludge cake dewatered from the sludge after the solubilization by using the dehydration aid, and ultimately zero the amount of sludge discharged from the sewage treatment plant. Is to provide a way to make this happen.

The solubilization treatment method of the sludge of the present invention for achieving the above object comprises a solubilization step of solubilizing by introducing alkali into the sludge generated in the biological treatment process; A supernatant conveyance step of returning the supernatant water obtained in the solubilization step to the biological treatment process and supplying the nutrients of the microorganisms; A dehydration step of dewatering the remaining sludge separated from the supernatant in the solubilization step; Characterized in that it comprises a; filtrate conveying step of returning the filtrate separated in the dehydration step to the biological treatment process to supply the nutrients of the microorganisms.

The solubilization step is characterized in that it is carried out under heating conditions.

The heating condition is characterized in that it is carried out at 50 to 100 ℃.

In the solubilization step, the alkali is sodium hydroxide, the sodium hydroxide is characterized in that 10 to 20g is added to 1 liter of the activated sludge.

And the sludge recycling method of the solubilization treatment of the present invention for achieving the above object is a solubilization step of solubilizing the alkali by inputting the sludge generated in the biological treatment process; A supernatant conveyance step of returning the supernatant water obtained in the solubilization step to the biological treatment process and supplying the nutrients of the microorganisms; A dehydration step of adding an inorganic compound as a dehydration adjuvant to the remaining sludge separated from the supernatant in the solubilization step and then dehydrating; A filtrate conveying step of returning the filtrate separated in the dehydration step to the biological treatment process to supply the nutrients of the microorganisms; And a recovery step of recovering the inorganic oxide by sintering the sludge cake obtained in the dehydration step.

The solubilization step is characterized in that it is carried out under heating conditions.

The inorganic compound of the dehydration step is characterized in that any one selected from hydrolyzable iron compounds, aluminum compounds, calcium compounds, titanium compounds.

As described above, according to the present invention, the sludge discharged from the biological treatment step can be solubilized with alkali to reduce the sludge. In particular, the supernatant and filtrate separated in the solubilization step and the dehydration step can be further returned to the biological reactor to further increase the treatment efficiency of the sludge.

In addition, the dehydration aid may be used to increase the dehydration efficiency, and the inorganic compound used as the dehydration aid may be recovered as an inorganic oxide, thereby ultimately zeroing the amount of sludge discharged from the sewage treatment plant.

In addition, the recovered inorganic oxide has the advantage that it can be usefully recycled throughout the industry.

As described above, the present invention is expected to solve the problem of waste sludge discharged from the industrial site by dissolving and solubilizing the sludge discharged from the biological treatment process of wastewater and recycling the sludge at the same time.

Hereinafter, the sludge solubilization treatment method of the present invention and the sludge recycling method using the same will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a method of recycling sludge by solubilization according to an embodiment of the present invention, Figure 2 is a graph showing the amount of sludge according to the amount of alkali added in the non-heating conditions, Figure 3 is a heating condition In Figure 4 is a graph showing the amount of sludge according to the amount of alkali added, Figure 4 is a graph showing the removal rate of organic matter after dehydration according to the addition amount of titanium salt as a dehydration aid, Figure 5 is the supernatant after solubilization treatment and the filtrate after dehydration into the bioreactor FIG. 6 is an XRD pattern of titanium oxide obtained by sintering at a temperature of 600 ° C., FIG. 7 is a SEM photograph of titanium oxide obtained by sintering at a temperature of 600 ° C., and FIG. 8 is It is a mapping photograph of the titanium oxide obtained by sintering at the temperature of 600 degreeC, and FIG. 9 is an acid obtained by sintering at the temperature of 600 degreeC. A graph showing the experimental results of the acetaldehyde decomposition reaction of the vapor of titanium.

The present invention relates to a method for recovering useful resources by sintering solubilized sludge while solubilizing sludge to reduce the amount produced. Examples of sludge in the present invention is not particularly limited, constant, sewage, industrial wastewater sludge is all applicable. Sludge is a generic term for liquid suspended solids from biological treatment processes and includes conventional activated sludge, surplus sludge, return sludge, concentrated sludge, digested sludge and the like. Examples of the sludge to which the present invention is applicable are not particularly limited, and water, sewage, and industrial wastewater sludge are all applicable.

First, the sludge solubilization treatment method according to an embodiment of the present invention will be described. The sludge solubilization treatment method of the present invention includes a solubilization step, a supernatant conveyance step, a dehydration step, and a filtrate conveyance step.

In the solubilization step, the sludge discharged from the biological reaction tank is transferred to an alkali treatment tank, and alkali is added to decompose and solubilize the sludge to destroy microorganisms in the sludge. In this case, the solubilization liquid contains a large amount of organic, nitrogen, and phosphorus components. Examples of the alkali include sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium chloride (NH ₄ Cl), and the like. In particular, when sodium hydroxide was added 10 to 20 g per 1 liter of sludge as alkali, the reduction efficiency of the sludge increased significantly.

In the solubilization step, solubilization is carried out under heating conditions to solubilize the sludge more effectively. In this case, it is preferable to advance heating conditions at 50-100 degreeC.

If it is less than 50 ℃ amount of reduced sludge is not significantly different from the case of alkali treatment only in the non-heating condition, and if it exceeds 100 ℃, the treatment efficiency is not high compared to the energy consumption. In other words, the amount of inorganic matter remaining in the sludge is not significantly different as compared with the heating conditions of 100 ° C. or less.

In case of solubilization under heating condition, the efficiency of sludge reduction was significantly higher than that under no heating condition. Particularly, when the amount of sodium hydroxide added in the heating condition was 10 to 20 g per 1 liter of sludge, the reduction efficiency of the sludge increased, and when the addition of 17.6 g, the reduction efficiency of the sludge increased by about 2 times or more.

The solubilization step may be further applied alone or in parallel with ozone treatment or ultrasonic treatment after alkali treatment.

After performing the solubilization step it is concentrated in a concentration bath. In this case, the supernatant in the solubilized sludge is returned to the biological reactor so that it can be used as a nutrient for microorganisms. The sediment separated from the supernatant is transferred to a storage tank and then dewatered.

In the dehydration step, the sludge is separated into filtrate and solid sludge cake. As a dehydration apparatus, a conventional belt press, a filter press, a screw decanter, a centrifuge, or the like can be used. At this time, in order to effectively lower the water content of the sludge can be dehydrated after the addition of a dehydration aid. The filtrate separated in the dehydration step is returned to the biological reactor is utilized as nutrients of the microorganisms.

As described above, the solubilization treatment method of the sludge of the present invention can effectively reduce the amount of sludge discharged. In particular, the supernatant and filtrate separated in the solubilization step and the dehydration step can be further returned to the biological reactor to further increase the treatment efficiency of the sludge.

As shown in FIG. 1, the sludge recycling method according to an embodiment of the present invention uses the sludge solubilization treatment method described above.

The dehydration step is carried out using a dehydration aid. Dehydration aids are added to the sludge to be treated. The sludge that has been concentrated can be stored preliminarily in a storage tank. Therefore, the dehydration aid may be supplied to the storage tank. Alternatively, a mixing tank is provided between the concentration tank and the storage tank, and a dehydration aid may be supplied thereto.

In the present invention, an inorganic compound is used as the dehydration aid. This is to reduce the water content of sludge by using inorganic compounds and to recover the inorganic compounds used as dehydration aids from sludge in the form of inorganic oxides, thereby reducing sludge emissions and recycling resources.

As an inorganic dehydration adjuvant, an inorganic inorganic compound such as titanium titanium compound, aluminum inorganic compound such as Al ₂ (SO ₄ ) ₃ · 8H ₂ O or Al (OH) ₂ Cl, FeCl ₃ · H ₂ O, FeSO ₄ · H ₂ O or Fe ₂ Iron inorganic compounds such as (SO ₄ ) ₃ .H ₂ O or calcium inorganic compounds such as Ca (OH) ₂ may be used. Preferably, a hydrolyzable titanium compound is used as the inorganic dehydration aid.

Hydrolyzable titanium compounds useful as dehydration aids are provided in the form of chlorides, sulfates. Specifically, examples of the hydrolyzable titanium compound include titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxysulfate and titanium iron sulfate. These hydrolyzable titanium compounds have the advantage of increasing the cohesive efficiency with organic matters and improving the efficiency of dehydration treatment, and can be recovered and recycled into a photocatalyst.

The titanium compound may be added together with the iron or aluminum inorganic compound. The titanium compound is preferably added to have a titanium content of 25 to 90 mg based on 1 liter of sludge. The pH of the sludge is preferably adjusted in the range of 2-6.

Titanium salt compounds form titanium hydrate in water and adsorb to the negative charge of the sludge to destabilize the water to agglomerate small sludges together to form agglomerates of large substances. At this time, the larger the size of the aggregate, the better the dehydration effect. Titanium salt dehydration aids formed aggregates of about 47.54 μm. This provided a higher flocculation effect than the aluminum-based dehydration aids formed agglomerates of 16.91 μm, and the iron-based dehydration aids formed agglomerates of 42.50 μm, which provided a decrease in moisture content and an increase in processing efficiency.

The sludge to which the dehydration aid is added is transferred to a dehydration apparatus and a dehydration step is performed. Specifically, the sludge to which the dehydration aid is added is injected between the filter cloths and a predetermined pressure is applied to the filter cloths to separate the sludge into water (filtrate) and solids (sludge cake). As a pressurized dewatering device, a conventional belt press, filter press, screw decanter or centrifugal separator can be used.

The filtrate separated from the dehydrator is returned to the biological reactor for use as a nutrient for the microorganisms. Then, the sludge cake separated from the filtrate is sintered to perform a recovery step for recovering the inorganic oxide. And a drying step may be added between the dehydration step and the recovery step. The drying step may be natural drying at room temperature or heat drying at 90 to 150 ℃.

Aggregates of inorganic compounds and organics used as dehydration aids in the recovery step are recovered in the form of inorganic oxides through sintering. It is preferable that the sintering temperature at this time is 500-800 degreeC. If the sintering temperature is less than 500 ° C., sintering is not performed properly and a black sintered body is obtained. And it is inefficient in terms of energy efficiency to perform sintering at the temperature whose sintering temperature exceeds 800 degreeC.

In the sintering step of the recovery step, excess water and organic compounds are decomposed and removed, and finally an incineration ash containing an inorganic oxide is obtained. In particular, titanium oxide is recovered when the dehydration aid is a titanium compound. Titanium oxide can be used as a building material that requires photocatalytic activity, or can be used to remove organic matter and pathogenic microorganisms by photocatalytic activity using sunlight when applied to landfills or soil contaminated areas.

As described above, according to the present invention, the sludge is destroyed by solubilization by alkali under high temperature heating conditions, and the organic substances generated at this time are provided as food for microorganisms and decomposed into water and organic substances. In addition, the remaining sludge is separated into the filtrate and the sludge cake by dehydration, the filtrate is introduced into the bioreactor to be used as a food for microorganisms, and the remaining sludge cake is subjected to a sintering process. The excess water and organic compounds are removed by the sintering process and the dehydration aid is recovered in the form of inorganic oxide.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these examples are presented for understanding the present invention and the scope of the present invention is not limited by these examples.

(Example 1: Sludge Reduction According to pH Change)

The sludge was tested under normal temperature conditions by adding NaOH as alkali to the return sludge generated in the sewage treatment plant. The amount of NaOH was added from 0.04 to 17.6 g per 1 liter of sludge, and the results are shown in FIG. 2. As shown in Figure 2 it can be seen that as the amount of NaOH increases, the sludge reduction efficiency increases. When 17.6 g of NaOH was added, the amount of sludge was reduced by about 30%.

In the case of the solubilization treatment, the sludge was reduced to 70% as shown in FIG. The sludge reduction efficiency was significantly improved compared to the case of solubilization at room temperature.

(Example 2: Titanium salt availability as dehydration aid)

The organic sludge removal efficiency and pH change are shown in FIG. 4 by adding TiCl ₄ as a dehydration adjuvant to the remaining sludge from which the supernatant is removed after solubilizing NaOH 17.6g in a return sludge generated in a sewage treatment plant under a heating condition of 60 ° C. . As a result, when TiCl ₄ 25mg / L or more was added, the organic matter removal efficiency was high.

Example 3: Effect on Solubilized Supernatant and Titanium Salt Supernatant on Microorganisms

After the solubilization in the same manner as in Example 2, the effect of the supernatant separated from the concentration bath on the microorganisms was investigated. In addition, the effects of the filtrate separated in the dehydration process on the microorganisms were investigated. At this time, the filtrate was solubilized by adding 17.6 g of NaOH to a return sludge generated in a sewage treatment plant under a heating condition of 60 ° C., and 25 mg / L of TiCl ₄ was added to the remaining sludge from which the supernatant was separated, followed by dehydration in a centrifuge to obtain a filtrate. .

Referring to FIG. 5, it was confirmed that the filtrate obtained by the titanium salt as well as the supernatant obtained by cell destruction was reused for microbial metabolism as a carbon source under aerobic conditions.

Example 4 Properties of Recovered Titanium Oxide

In the same manner as in Example 3, the sludge cake obtained by dehydration in a centrifuge was dried at 105 ° C. and then sintered at 600 ° C. to obtain titanium dioxide.

The XRD pattern of the obtained titanium dioxide was measured, and the results are shown in FIG. At 600 ° C., the XRD pattern showed anatase crystals. This indicates that organic / inorganic elements are doped independently of TiO ₂ without being formed independently in oxide form.

And the components of the sintered titanium dioxide was measured and shown in Table 1 below.

division weight% C 8.56 O 65 P 5.72 Ti 17.49 Other elements Si (1.45), Fe (0.62), Al (0.85), Mg (0.01), K (0.13), S, Ca, Na, Ni

The results of Table 1 show that the sintered powder of titanium oxide is doped with organic / inorganic elements, in addition to a small amount of Fe, Al, Mg, and the like. From this, titanium dioxide doped with organic / inorganic materials, for example, by adding a small amount of transition metals such as iron or aluminum, thereby reducing the band gap energy of titanium dioxide and photocatalyst even at a low energy wavelength, that is, 400 nm or more visible light. It is expected to have activity.

And as the sintering temperature increased, the sintered powder changed from black to some white powder. The color of the sintered powder was black when the sintering temperature was lower than 500 ° C., but gradually changed to white as the sintering temperature increased at 500 ° C. This seems to be due to residual organic matter.

7 and 8 show SEM photographs and mapping photographs of the recovered titanium dioxide. As a result of the characteristics of titanium dioxide, nanoparticles having a size of about 10 nm were formed, and it was confirmed that organic / inorganic elements were evenly doped in titanium dioxide.

Example 5 Organic Photodegradation of Titanium Oxide Recovered from Sludge

Acetic aldehyde gas phase decomposition reaction was carried out to determine the photolysis capacity of the titanium dioxide powder recovered in the same manner as in Example 4. 9 is a graph showing the experimental results of acetaldehyde gas phase decomposition reaction. 1 g of titanium oxide powder was added to a sealed photocatalytic gas phase reactor, 2000 ppm of acetaldehyde was injected, and then adsorbed for 1 hour, and the concentration of acetaldehyde with time was measured by irradiation with 450 nm ultraviolet light. As a result of analyzing the concentration of acetaldehyde, about 50% of acetaldehyde was decomposed about 2 hours after ultraviolet light irradiation.

As described above, the present invention has been described with reference to one embodiment shown in the drawings, which is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. .

Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

1 is a block diagram showing a method of recycling sludge by solubilization treatment according to an embodiment of the present invention;

2 is a graph showing the amount of sludge according to the amount of alkali added under no heating conditions,

3 is a graph showing the amount of sludge according to the amount of alkali added under heating conditions,

Figure 4 is a graph showing the organic matter removal rate after dehydration according to the addition amount of titanium salt as a dehydration aid,

5 is a graph showing the effect on microorganisms when supernatant and filtrate were introduced into a bioreactor after solubilization,

6 is an XRD pattern of titanium oxide obtained by sintering at a temperature of 600 ° C.,

7 is a SEM photograph of titanium oxide obtained by sintering at a temperature of 600 ° C.,

8 is a mapping picture of titanium oxide obtained by sintering at a temperature of 600 ℃,

9 is a graph showing experimental results of acetaldehyde gas phase decomposition reaction of titanium oxide obtained by sintering at a temperature of 600 ° C.

Claims (7)

 A solubilization step of solubilizing by injecting alkali into the sludge generated in the biological treatment process; A supernatant conveyance step of returning the supernatant water obtained in the solubilization step to the biological treatment process and supplying the nutrients of the microorganisms; A dehydration step of dewatering the remaining sludge separated from the supernatant in the solubilization step; And a filtrate conveying step of returning the filtrate separated in the dehydration step to the biological treatment process to supply the nutrients of the microorganisms. The method of claim 1, wherein the solubilization step is performed under heating conditions. The method of claim 2, wherein the heating conditions are carried out at 50 to 100 ℃. The method of claim 1, wherein the alkali in the solubilization step is sodium hydroxide, The sodium hydroxide solubilization treatment method of the sludge, characterized in that 10 to 20g is added to 1 liter of the activated sludge. A solubilization step of solubilizing by injecting alkali into the sludge generated in the biological treatment process; A supernatant conveyance step of returning the supernatant water obtained in the solubilization step to the biological treatment process and supplying the nutrients of the microorganisms; A dehydration step of adding an inorganic compound as a dehydration adjuvant to the remaining sludge separated from the supernatant in the solubilization step and then dehydrating; A filtrate conveying step of returning the filtrate separated in the dehydration step to the biological treatment process to supply the nutrients of the microorganisms; And a recovery step of recovering inorganic oxide by sintering the sludge cake obtained in the dehydration step. 6. The method of claim 5, wherein the solubilization step is carried out under heating conditions. 6. The method of claim 5, wherein the inorganic compound in the dehydration step is any one selected from hydrolyzable iron compounds, aluminum compounds, calcium compounds, and titanium compounds.

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