KR100506400B1 - Method for dewatering sewage sludge using radiation and starfish powder - Google Patents

Abstract

The present invention relates to a method for dewatering sewage sludge using radiation and starfish powder, specifically, irradiating sewage sludge with radiation (step 1), mixing and stirring starfish dehydration adjuvant to irradiated sewage sludge (step 2), Sewage sludge dewatering comprising mixing and stirring the flocculant in the sewage sludge obtained in step 2 (step 3), and dewatering the floc using a dewatering device to obtain a sludge cake (step 4). It is about a method.

The sewage thickening sludge dewatering method of the present invention uses a combination of radiation and invisible dehydration aids, thereby reducing the moisture content of the sludge cake by freeing the adhered water through the destruction of the sludge by radiation and at the same time the general bacteria and pathogenicity of the sludge cake. The effect of sterilization of bacteria, removal of organic matter, and odor removal can be obtained, and the problem of flocculation caused by dehydration of sewage sludge by radiation only can be solved. Not only can this result in a reduction and thus a reduction in processing costs, but also the digester process can be omitted, simplifying the process. In addition, by reducing the volume reduction and water content of the sludge cake, landfill can be made possible by satisfying the environmental regulations for inland and marine transportation costs, preserving the marine environment, and landfill.

In particular, by expanding the range of use of starfish that adversely affects the marine ecosystem, it can contribute to revitalization of the starfish relief and purchase business and conservation of the marine environment, and the use of such starfish can be beneficial for the composting of sludge cakes and recycling as a covering agent. We can contribute to rehabilitation of waste.

Description

Sewage sludge dewatering method using radiation and starfish powder {METHOD FOR DEWATERING SEWAGE SLUDGE USING RADIATION AND STARFISH POWDER}

The present invention relates to a sewage sludge dewatering method, and more particularly, to a sewage sludge dewatering method using radiation and starfish powder.

Millions of tonnes of sludge are emitted annually from wastewater treatment plants, which contain about 80% water. Sludge is generally classified into fresh sludge, surplus sludge, mixed sludge, thickened sludge and digested sludge. The sludge is finally dehydrated.

These sludges are generally disposed of by the use of fertilizers, landfilling or incineration. At this time, when the sludge is treated by landfill, problems such as securing the site due to the volume due to the large amount of water content occurs, and in the case of incineration of the sludge, a lot of problems such as equipment costs and incineration fuel costs occur. In particular, due to the large amount of water in the sludge, a large amount of energy is consumed to evaporate the water, thereby increasing the fuel cost and decreasing the treatment efficiency. Therefore, it is necessary to reduce the water content in the sludge generated during the treatment of sewage water to reduce the sludge volume and the amount of fuel used during the incineration treatment.

As described above, the removal of water present in the sludge is called sludge dewatering, and the research on such sludge dewatering has been studied a lot.

The sludge generated during the treatment of sewage water is first subjected to a digestion process, and then concentrated through a concentration tank of sludge generated in a sedimentation tank of water treatment, and then dehydrated in a dehydration apparatus.

The digestion process is applied for the generation of odors and harmful substances due to the organic substances contained in the sewage sludge, the killing of parasites and pathogens, and the reduction of sludge. However, problems such as the digestion period for digestion, difficulty in operating the digester, and stability of the digester have been raised as problems.

On the other hand, in general, in order to effectively dewater the sludge, a process of improving the properties of the concentrated sludge has been introduced mostly before dewatering. In this process, floc is formed by increasing cohesion between solid materials forming sludge, and solid-liquid separation occurs by separating water using a dehydration device. As a result, sludge cake is obtained.

Coagulant is to increase the bond between the solid materials forming the sludge. Specifically, there are cationic, nonionic, anionic and polymer coagulant. Cationic and anionic coagulants are strong, heavy and weak ionic depending on the ionicity. Are classified as flocculants. Generally, flocculants that are commonly used in the market are polymer synthetic chemicals and strong-cationic flocculants YCX-686; SC-050 as a medium-cationic flocculant; N-302P etc. are mentioned as a nonionic flocculant.

In addition, the dehydration device is a pressurized dehydration device is the most common, and after the flocculant is injected into the sludge formed floc between the filter cloth and applying a certain pressure to the filter cloth to separate the sludge into water (filtrate) and solids (dehydration cake) I use it. Specific examples of the pressurized dewatering device are a belt press, a filter press, a screw decanter or a centrifugal separator.

Belt press dewatering device is a dehydration equipment that is most widely used and used at present. It is a dewatering device that moves and compresses the superfiling fabric and subfoam with a roller and injects and filters sludge therebetween. The filter press dewatering device compresses a plurality of filter plates having a certain constitution with a hydraulic cylinder, and then inserts sludge into the space to compress and concentrate the sludge dewatering cake inside the filter plate and discharge the filtrate. When the screw decanter is continuously fed into the rotating bowl through feed pipe without sludge and flocculant at the same time, centrifugal consolidation force is applied to thousands of times of gravity to separate solids and water, and solids It is a dewatering device discharged to the cake by the action of the pressing force. In addition, the centrifugal separator uses the principle of centrifugal separation, which causes some noise, but is widely used in the case of continuously dehydrating a relatively small capacity, and the types thereof include a horizontal centrifuge and a vertical centrifuge. . Among them, horizontal centrifuges are frequently used because of their low energy consumption and low investment per unit volume.

The sludge cake thus obtained is subjected to post-treatment such as incineration or landfilling. At this time, the treatment cost and treatment efficiency are influenced by the water content of the sludge cake.

Dehydration aid is used as one of the methods for improving the dewatering efficiency of such sludge cake. The dehydration aid serves to remove moisture by the volume of the dehydration aid added in the dehydration cake by adding before the flocculant and to improve the compressibility in the pressurized dehydrator. Conventionally known dehydration aids include diatomaceous earth, sawdust, incineration ash and paper pulp, but such dehydration aids have the disadvantages of costly and resource waste to secure additionally and varying in utility depending on subsequent processing.

In addition, one of the methods for improving the dewatering efficiency of the sludge cake is a method of irradiating the radiation in the pre-treatment process of sewage sludge dewatering. It is intended to enhance dewatering efficiency by irradiating sewage sludge with the destruction of sludge, but due to the limitation of sludge destruction, the water content reduction efficiency has a limit of not more than 5 ~ 7%. It is not applied to the actual processing.

Therefore, the development of economical and wide range of dehydration improving agent is required with the use of the existing pressurized dewatering equipment.

An object of the present invention is to solve and improve the above problems, and to provide a sewage sludge dewatering method for improving sewage sludge dewatering efficiency and improving the cohesion rate by irradiation.

In addition, to provide a sewage sludge dehydration method that can kill the bacteria without performing the digester process.

In order to achieve the above object, the present invention provides a sewage sludge dewatering method using a radiation and starfish powder.

Specifically, in the sewage sludge dewatering method,

Irradiating sewage sludge (step 1),

Mixing and stirring the starfish dehydration adjuvant to the irradiated sewage sludge (step 2),

Mixing and stirring the flocculant to the sewage sludge obtained in step 2 to form a floc (step 3), and

It provides a sewage sludge dewatering method comprising the step (step 4) of obtaining a sludge cake by dewatering the floc using a dewatering device.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for dewatering sewage sludge using radiation and starfish powder, as shown in Figure 1a, can be divided into radiation irradiation step, physicochemical improvement step and dehydration. In the above-described step, step 1 is a irradiation step, steps 2 and 3 are physicochemical improvement steps, and step 4 is a dehydration step.

This will be described in detail with reference to the drawings of FIG. 1B more specifically.

In step 1, the sewage sludge is irradiated.

Sewage sludge refers to sludge generated from sewage and wastewater treatment equipment including sewage sludge, which contains a large amount of water in the sludge and mixed sludge containing all kinds of organic sludge, inorganic sludge and organic sludge and inorganic sludge. In addition, these sludges include sludges before the extinguishing process.

By irradiating such sewage sludge, it is possible to first reduce the moisture content of the dewatered cake through the glass of the adhered water, and secondly, microbial sterilization and organic matter removal in the sludge can be carried out simultaneously.

The term "attached water" refers to water that cannot be easily removed by a mechanical method as part of the water distribution form in the sludge, and includes a part of the pore water, adjacent water, and hydrated water.

The radiation uses an E-beam generated from a gamma ray or an electron beam accelerator generated from Co ⁶⁰ , Co ⁵⁶ , Sc ⁴⁶ , Na ²² , Cs ^134, etc., in which the irradiation dose is considered in consideration of the effects of irradiation and sewage sludge properties. Is adjusted to 1 to 10 k㏉. If the radiation dose is less than the above range can not reduce the moisture content of the dehydrated cake through the glass of the adhered water, if it exceeds the above range, the moisture content reduction efficiency can not be obtained due to the limitation of sludge destruction, especially the cohesion efficiency is reduced have.

In step 2, the starfish dehydration adjuvant is mixed and stirred in the sewage sludge obtained in step 1 above.

The starfish dehydration adjuvant is to use a starfish commonly used in a powder form after a predetermined treatment, specifically using a powder form obtained by washing and drying the collected starfish with natural water and then crushed. The natural water is tap water, groundwater and surface water as washing water for removing salt and impurities present in the collected starfish. Grinding is using a conventional mill and the size of the final powder obtained after grinding is preferably 20 to 80 mesh (mesh) in the present invention does not limit the size of the powder.

In addition, the starfish dehydration adjuvant uses a powder form in which the obtained powder is subjected to heat treatment. The heat treatment temperature is preferably 50 to 1500 ° C., and to increase efficiency by removing impurities and volatile organic substances in the starfish through such heat treatment. When the heat treatment temperature is less than the above range, impurities and volatile organic substances are not dried. There is a disadvantage that remains, and if the above range is exceeded, there is a disadvantage that the heat treatment cost is excessively increased.

In this step, the use of starfish powder as a dehydration aid can improve the sewage sludge dewatering efficiency and can also prevent the reduction of the flocculation efficiency by irradiation, thereby reducing the amount of flocculant used.

In this step, the amount of the starfish dehydration aid is preferably 1 to 200 parts by weight based on the sludge dry solids, and when the amount is less than the above range, the effect of the addition of the dehydration adjuvant cannot be obtained. Can not get.

In step 3, floc is formed by mixing and stirring the flocculant in the sewage sludge obtained in the above step.

In the present invention, the term "floc" refers to a large mass in which fine particles such as suspended matter, organic matter and microorganisms in the sludge are aggregated with a flocculant.

The flocculant is to increase the bond between the solid material forming the sludge, all synthetic polymer flocculant such as cationic, nonionic, anionic, etc. used in the field can be used, for example, the cationic system mainly used in the market Use the SC-050.

By using the starfish auxiliary dehydrating agent in step 2 can solve the problem of coagulation by irradiation to reduce the amount of flocculant used, specifically the amount of flocculant in the present invention is 0.6 to 1 parts by weight based on the sewage sludge dry solids . When the amount of the flocculant used is less than the above range, the sewage sludge cannot be caused to aggregate, and when the amount of the flocculant is exceeded, the significant effect of the addition cannot be obtained.

In step 4, the floc is dewatered using a dehydration device to obtain a sludge cake.

In the present invention, the "sludge cake" refers to the solid content remaining after removing a certain amount of water by using a pressurized dehydration apparatus after flocculating the sludge.

The dehydration device is a device for separating the obtained floc and water, any dehydration device used in the art can be used, preferably a belt press, a filter press, a screw decanter or a centrifugal separator.

The sludge cake thus obtained can be treated by a post-treatment method such as ocean dumping, landfilling or incineration, but the present invention is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to Examples.

However, the following examples are illustrative of the present invention, and the content of the present invention is not limited by the examples.

Preparation Example 1 Preparation of Starfish Dehydration Aid 1

Starfish collected from the shore was washed with natural water and dried in a dryer at 105 ℃ for 3 hours. The dried starfish was pulverized with a grinder (Micro-mill, Scienceware, Inc.) and then sieved to 300 µm or less to prepare a dehydration aid.

Preparation Example 2 Preparation of Starfish Dehydration Aid 2

Starfish collected from the shore was washed with natural water and dried in a dryer at 105 ℃ for 3 hours. The dried starfish was pulverized with a mill (Micro-mill, Scienceware Co., Ltd.) and then sieved to a size of 300 μm or less to obtain starfish powder. Thereafter, the starfish powder was heat-treated at 600 ° C. for 3 hours to prepare a dehydration aid.

Example 1 Dewatering Method of Sewage Sludge of the Present Invention

(Step 1) Irradiation

In 500 ml of sewage sludge having an initial total solids content (TS) of 4%, gamma rays generated from Co ⁶⁰ were irradiated at a dose of 1 to 10 kGy.

(Step 2) mixing and stirring starfish dehydration aid

10 g of the starfish dehydration adjuvant obtained in Preparation Example 1 or Preparation Example 2 was mixed with the sewage sludge subjected to irradiation of step 1, followed by stirring for 30 minutes.

(Step 3) mixing and stirring the flocculant

SC-050, a cationic polymer coagulant, was prepared in a 0.3% solution and mixed with the sewage sludge to which the starfish dehydration aid was added, followed by stirring for 30 minutes to form a floc.

(Step 4) Dehydration

The floc was dewatered using a belt press pressurized dehydrator (SP-1000, Yucheon) or a centrifuge (VS-5000N, Vision) to obtain sludge cake.

Experimental Example 1 Measurement of Water Content Change of Sludge Cake According to Irradiation

It is the result of aggregation and dehydration only through the irradiation step of Example 1 at all times.

The sludge with an initial total solids content (TS) of 4% was irradiated with 0-15 kGy of radiation and then mixed with a 0.3% solution of SC-050, a cationic polymer coagulant, and stirred for 30 minutes to form a floc. The floc thus formed was dehydrated using a pressurized dehydrator (SP-1000, Yucheon).

The results are shown in FIG.

As shown in Figure 2, when irradiated with radiation of 0 to 15 kGy it can be seen that the water content decreases with the irradiation amount. Treatment of sewage thickening sludge with a dose of 15 kGy resulted in a reduction of more than 10% compared to the water content of the untreated initial sewage sludge dewatering cake. This means that the sewage sludge inside the sewage sludge, which had not been dewatered when the sewage thickening sludge was dewatered using the existing physical dehydration device, was released out of the sewage sludge by the radiation and was converted into a state capable of being dehydrated by the physical dehydration device. In addition, when the concentrated sludge was simply irradiated, it can be seen that addition of starfish powder used in this process is not necessary because aggregation does not occur even when an excessive amount of polymer flocculant is added.

Experimental Example 2 Measurement of Changes in Sludge Destruction and Turbidity According to Irradiation

Changes in sludge destruction and turbidity were measured after the irradiation step of Example 1 at all times.

(1) The sludge fracture degree was calculated using the following method, which is calculated from the change of COD according to irradiation. The COD was measured by the COD _Cr method using the filtrate after the sludge was filtered by GFC (see Equation 1 below).

COD _Irradiated : COD of sludge after irradiation

COD _NaOH : NaOH 1 Mole and sludge mixed at a ratio of 1: 1, after 10 minutes heat treatment at 90 ℃ measured value

COD ₀ : COD of the initial sample sludge used

(2) Turbidity was measured using the DR-4000 of HACH company using the UV method.

The results of sludge fracture and turbidity are shown in Figs. 3a and 3b.

Figure 3a is a graph showing the sludge destruction according to the radiation, Figure 3b is a graph showing the turbidity.

As shown in Figures 3a and 3b, it can be seen that there is an effect of destroying the sewage sludge by radiation of the present invention. Specifically, in the case of sewage sludge that has been irradiated with 10 kGy, more than 50% of the sludge destruction occurs, and thus, the turbidity of the sludge filtrate is also increased. Sludge destruction by radiation can destroy the cells and microbial floc present in the sewage sludge, as shown in this experimental example, it can bring about the effect of reducing the moisture content and at the same time sterilization effect.

Experimental Example 3 Measurement of Removal of General Bacteria in Concentrated Sludge by Irradiation

Changes in the general bacteria present in the sewage sludge obtained after the irradiation step of Example 1 at all times were measured by the plate colonization method of the water pollution process test method, and the general bacteria were measured as the number of mesophilic general bacteria. It was.

The results are shown in FIG.

Figure 4 is a graph showing the change in the number of general bacteria in concentrated sludge according to irradiation.

As shown in Figure 4, it can be seen that there is an effect of killing the general bacteria in sewage sludge by radiation of the present invention. In the case of sewage sludge with 10 kGy irradiation, more than 99% of general bacteria with initial 6,200,000,000 CFU / ml were removed and showed 5,100 CFU / ml. It can be seen that the radiation irradiation process has a superior effect on the removal of general bacteria than the digester process with the number of general bacteria less than 16,200,000 CFU / ml.

Experimental Example 4 Measurement of E. coli Removal in Concentrated Sludge by Irradiation

The change of E. coli present in the sewage sludge obtained after the irradiation step of Example 1 was always measured by the plate colonization method in the water pollution process test method, and in the case of general bacteria, it was measured as the number of mesophilic bacteria. .

The results are shown in FIG.

5 is a graph showing the change in the number of Escherichia coli in the concentrated sludge according to the irradiation.

As shown in Figure 5, it can be seen that the E. coli in the sewage sludge is killed by the radiation of the present invention. In the case of sewage sludge that had been irradiated with 10 kGy, more than 99% of E. coli, which had an initial number of 840,000 CFU / ml without radiation, was removed and showed 30 CFU / ml. With less than 36700 CFU / ml E. coli of coarse digested sludge, the radiation irradiation process is more effective in removing E. coli than the digester process.

Experimental Example 5 Measurement of Water Content Change of Sludge Cake by Dehydration Method of the Present Invention

Sludge cake was prepared in the same manner as in Example 1 using the Jar-tester. At this time, the radiation dose was adjusted to 0 to 10 kGy to prepare a sludge cake. The sludge cake was taken in a certain amount and weighed, and dried in an oven at 105 ° C. for 4 hours, and then weighed to obtain a water content. The moisture content calculation was based on Equation 1 below.

In order to compare the effects of the irradiation and the starfish powder of the present invention, only the radiation of the dehydration method was irradiated, the sludge cake was prepared without the addition of the starfish dehydration aid of step 2, and the water content was measured and compared.

(W ₁ is the evaporation plate weight, W ₂ is the evaporation plate weight + dry sample weight (sludge cake), W ₃ is the evaporation plate weight + dry sample weight (sludge cake).)

The results are shown in FIG.

As shown in FIG. 6, in the case of the dehydrated cake agglomerated and dehydrated by the addition of the starfish dehydration aid after irradiation, the dehydrated cake agglomerated and dehydrated after the irradiation showed a 10% or more water content reduction effect. In addition, as the addition amount of the starfish dehydration aid increases, a reduction effect of up to 50% or more can be obtained. From these results, it can be seen that the amount of the starfish dehydration adjuvant can be used by varying the secondary treatment and utilization of the dehydrated cake.

Experimental Example 6 Change of Coagulant Dose According to the Present Invention

In the irradiation step, the flocculant dose when agglomerates the flocculant at the time of agglomeration after adding 100 parts by weight of the starch dehydration adjuvant used in the present invention to the sewage sludge dry solids in the irradiated sludge and the irradiated sludge was applied. Samples were identified through Jar test.

The results are shown in FIG.

As shown in FIG. 7, in contrast to the conventional dehydration method by radiation only, the combination of radiation and starfish dehydration aid of the present invention is a problem of aggregation, which is the biggest problem of the dehydration method by irradiation alone. It can be seen that it can be effectively improved. When 100 parts by weight of starfish dehydration adjuvant was used for sewage sludge dry solids after 10 kGy of radiation, the amount of polymer coagulant for sewage sludge flocculation could be lowered to less than half, which can greatly reduce the cost of dehydration. It can be seen.

As described above, the sewage thickening sludge dewatering method of the present invention uses a combination of radiation and invisible dehydration aids to reduce the water content of the sludge cake by freeing the adhered water through the destruction of the sludge by radiation, and at the same time in the existing digester Sterilization effect, removal of organic matter, and odor removal of general bacteria and pathogenic bacteria can be obtained, and the problem of flocculation caused by dehydration of sewage sludge by radiation irradiation alone can be solved. Therefore, not only can the volume of sludge cake be reduced and the treatment cost is reduced, but also the digester process can be omitted, thereby simplifying the process. In addition, by reducing the volume reduction and water content of the sludge cake, landfill can be made possible by satisfying the environmental regulations for inland and marine transportation costs, preserving the marine environment, and landfill.

In particular, by expanding the range of use of starfish that adversely affects the marine ecosystem, it is possible to contribute to revitalization of the starfish relief and purchase business and to preserve the marine environment. We can contribute to rehabilitation of waste.

Figure 1a is a diagram illustrating the separation of the dehydration method of the present invention into a radiation irradiation step and physicochemical improvement step,

Figure 1b shows a specific step of the dehydration method of the present invention,

2 is a graph showing the water content change of the sludge cake according to the irradiation of the present invention,

Figure 3a is a graph showing the change in sludge size according to the irradiation of the present invention,

Figure 3b is a graph showing the change in turbidity according to the irradiation of the present invention,

4 is a graph showing the change in the number of general bacteria in sewage sludge according to the irradiation of the present invention,

5 is a graph showing the change in the number of E. coli bacteria in sewage sludge according to the irradiation of the present invention,

6 is a graph showing the water content change of the sludge cake according to the starfish powder addition and irradiation of the present invention,

Figure 7 is a graph showing the change in the coagulant dosage according to the addition of starfish powder and irradiation of the present invention.

Claims (10)

In the sewage sludge dewatering method, Irradiating sewage sludge (step 1), Mixing and stirring the starfish dehydration aid in the irradiated sewage sludge (step 2), Mixing and stirring the flocculant to the sewage sludge obtained in step 2 to form a floc (step 3), and And dewatering the floc using a dewatering device to obtain a sludge cake (step 4). The sewage sludge dewatering method according to claim 1, wherein the radiation dose is 0.5 to 50 kPa. The sewage sludge dewatering method according to claim 1, wherein the radiation is an E-beam generated from a gamma ray or an electron beam accelerator generated from a group selected from Co ⁶⁰ , Co ⁵⁶ , Sc ⁴⁶ , Na ²² and Cs ¹³⁴ . . The sewage sludge dewatering method according to claim 1, wherein the starfish dehydration aid is in the form of a powder obtained by washing and drying the collected starfish with natural water. The sewage sludge dewatering method according to claim 1, wherein the starfish from which the starfish dehydration aid is collected is pulverized after washing and dried with natural water, and the obtained powder is heat-treated. The sewage sludge dewatering method according to claim 5, wherein the heat treatment temperature is 50 to 1500 ° C. The sewage sludge dewatering method according to claim 1, wherein the amount of the starfish dehydration aid is 1 to 200 parts by weight based on the sludge dry solid content. The sewage sludge dewatering method according to claim 1, wherein the amount of the flocculant used is 0.6 to 1 parts by weight based on the sludge dry solid content. The sewage sludge dewatering method according to claim 1, wherein the dewatering device is a belt press, a filter press, a screw decanter or a centrifugal separator. The sewage sludge dewatering method according to claim 1, wherein the sludge is sludge generated in sewage and wastewater treatment apparatus including sewage sludge or sludge before the extinguishing process as the sludge.