KR100290578B1 - Method for Heavy Metal Bioleaching Using Sulfur-Oxidizing Bacteria - Google Patents

Abstract

The present invention relates to contaminated wastes containing heavy metals such as activated sludge and anaerobic and aerobic digestion sludge, sediment sludge in rivers and lakes, heavy metal contaminated soil, incineration ash, etc. thiooxidans MET) KCTC 8928P relates to a method for biologically eluting heavy metals.

In the present invention, in the removal of heavy metals of anaerobic, aerobic digested sludge and activated sludge, inoculated anaerobic, aerobic digested sludge or activated sludge to thiobacilli thiooxydans mT strain, which is a sulfated bacterium, When the strain is inoculated with sludge or activated sludge, free sulfur, which is an energy source of sulfated bacteria, is mixed and cultured while supplying air, and when the pH of the sludge or activated sludge is cultured, the strain reaches 1.5 to 2.5. The sludge or activated sludge is dehydrated, and the dehydrated solid sludge is neutralized with limestone, and the separated waste liquid is neutralized to precipitate.

It is possible to remove a significant amount of heavy metals contained in the waste, and even after several months of continuous operation, the activity of the bacteria is not lowered, thereby maintaining high heavy metal removal efficiency.

Description

Method for removing heavy metals from heavy metal-containing waste using sulfated bacteria {Method for Heavy Metal Bioleaching Using Sulfur-Oxidizing Bacteria}

The present invention relates to contaminated wastes containing heavy metals such as activated sludge and anaerobic / aerobic digestion sludge, sediment sludge in rivers and lakes, heavy metal contaminated soil, incineration ash, etc. thiooxidans MET) KCTC 8928P relates to a method for biologically eluting heavy metals. More specifically, the present invention (i) is present in various contaminants using thiobacilli thiooxydans methane, a sulfated bacterium capable of oxidizing free sulfur (S ^o ) at room temperature and atmospheric pressure to produce sulfate. Biological heavy metal removal method for converting insoluble heavy metals into soluble heavy metal ion forms to selectively elute them into aqueous phase, and (ii) biologically removing heavy metals from high concentration of heavy heavy metal contaminants using the sulfated bacteria. It is about.

As population growth, urban concentration, and industrialization progress, water consumption and sewage generation increase rapidly, and the amount of sludge generated from water and sewage treatment facilities is rapidly increasing. As a result, tens of millions of tons of heavy metal contaminants are generated annually worldwide. have. In the case of sewage treatment, the cost of landfilling of sludge treatment and final sludge is known to be about 50% of the total cost of wastewater treatment facilities. A major concern with sludge disposal is that toxic heavy metals such as Cd, Cr, Cu, Ni, Pb and Zn are concentrated during sludge treatment due to various physicochemical and biological actions. Generally, sewage sludge has a heavy metal content of 0.5% to 2.0% and in some cases a total metal content of 4.0%. Heavy metals in sludge are delivered to animals, including humans, by the adsorption of heavy metals by plants and a series of accumulations in the food chain, potentially leaving life threatening.

Due to the danger of such heavy metals, the heavy metal content standard of the sludge for preventing various environmental pollution by heavy metals is being enforced. Various methods and processes are used to safely dispose of these wastes, including landfill, offshore dumping and incineration. However, land reclamation method, which is one of the most common and easy methods, becomes more difficult to secure landfills, and if landfills containing heavy metals are reclaimed without pretreatment, soil, rivers and groundwater at the surface of landfills are secondaryly contaminated by leachate. The problem arises. In addition, landfill costs are rapidly increasing due to the reduction of landfills and tighter regulations.

In addition, marine dumping not only counters the growing global trend of environmental protection, but also causes secondary pollution in the long run. The incineration method requires expensive equipment for incineration, costs a considerable amount of money in operation, and is also difficult to become a fundamental treatment plan because of the problem of air pollution.

Recently, land applications, such as the use of sludge as a fertilizer, have been evaluated as the most economical solution for the treatment of sludge. However, the toxic heavy metal contained in the sludge has become a restriction to make it difficult to use the sludge as a fertilizer. In order to use sludge as a fertilizer, the concentration of heavy metals should be lowered below the regulation level. The reduction of heavy metals in sewage sludge may be achieved by controlling pollutants emitted to the sewage or by removing heavy metals from the sludge. Among them, the main difficulty of source control is to identify the source. In other words, the control of heavy metal pollutants in industrial sites is costly, and even if the metal content is reduced, it is difficult to be sludge suitable for use in agriculture. In order to reduce the environmental pollution problem caused by heavy metals in sludge, heavy metals must be removed before the sludge is finally disposed of or recycled.

There are attempts to reduce wastes into the soil or to compost them to be recycled as resources. For example, the wastes are first treated and then recycled as fertilizers. However, these methods are also limited in that heavy metals in the waste must be removed.

Therefore, development of low-cost and high-efficiency heavy metal treatment technology is very important to solve the problems of sludge-related environmental pollution and landfill shortage, and ultimately, removing heavy metals prior to final disposal or recycling, especially fertilizer, of sludge such as sludge. It is essential.

Conventional methods for removing heavy metals contained in wastes, such as sludge, include the treatment of acids such as sulfuric acid, hydrochloric acid, and nitric acid to elute heavy metals to pH 1.5-2.0, and chlorination, ion exchange, and complex compounds. (chelating agent), and the like.

However, these chemical treatment methods are difficult to commercialize due to problems such as high cost, operation problems, and low efficiency of removing heavy metals, and thus, biological elution methods have been developed that can be efficiently applied at room temperature and atmospheric pressure. Conventional Thiobacillus ferrooxidans have been used for the biological elution of heavy metals, but the activity of this species is inhibited by organics, so it is only applicable to sludge with low solids concentration in the range of 1.3 to 4.0%. have. In the case of the biological heavy metal removal process, it is necessary to increase the content of solids to be processed in order to reduce the size of the associated equipment, reduce the operating cost, and minimize the generation of secondary pollutants. To this end, it is required to develop new strains and heavy metal removal methods that are excellent in dissolution efficiency while being less affected by organic substances or other inhibitors contained in waste such as sludge.

An object of the present invention is to use heavy metals such as activated sludge, anaerobic and aerobic digestion sludge, and sediment sludge in rivers and lakes, using the sulfated bacterium Thiobacillus thiooxidans MET KCTC 8928P strain. To provide a method for effectively removing heavy metals at a low solids concentration of 2 to 4% by weight of contaminated material.

The second object of the present invention is to achieve the removal of heavy metals at a high solids concentration of 5 to 10% by weight of the activated sludge, anaerobic and aerobic digestion sludge liquids produced in the wastewater treatment plant. The present invention provides a device for removing heavy metals by treating activated sludge or anaerobic / aerobic digested sludge solution with a low sludge solid concentration of ˜4% by weight together with solid waste.

1 is a schematic process chart showing a method for removing biological heavy metals from sludge waste using sulfated bacterium thiobacilli thiooxydans mT strain.

Figure 2 is a process chart showing a method for removing the biological heavy metals of the high concentration sludge waste using the sulfated bacteria thiobacillus thiooxydans m.

Figure 3 is a chart showing the pH and sulphate concentration change of the waste sludge liquid during the heavy metal removal process by batch treatment at 9% sludge solids concentration.

Figure 4 is a chart showing the pH, redox potential, and sulfate concentration change in the process of removing heavy metals in the sludge according to FIG.

* Explanation of symbols for main parts of the drawing

1: activated sludge tank or aerobic and anaerobic digester 2: bioreactor for heavy metal removal

3: sludge dehydrator 4: screw type sludge mixer

5: waste water neutralization tank 6: sedimentation tank

7: Treatment water outlet 8: free sulfur storage tank

9: lime storage tank 10: sludge return pipe

11: slurry waste mixing tank 12: treatment waste storage tank

13: Waste storage tank 14: Free sulfur feeder

15: lime feeder 16: dewatering waste feeder

17: Sludge Waste Thickener

In order to achieve the above object, the present invention, in the removal of heavy metals of anaerobic, aerobic digestion sludge and activated sludge, thiobacillus thiooxydans M, which is an anaerobic, aerobic digestion sludge containing insoluble heavy metal or sulfated bacteria in activated sludge Inoculated with Thiobacillus thiooxidans MET KCTC 8928P strain, and then mixed with the inoculated sludge or activated sludge by adding free sulfur, which is an energy source of sulfated bacteria, and incubating with air supply, the sludge cultured with the strain Or dewatering the sludge or activated sludge when the pH of the activated sludge reaches 1.5 to 2.5, and the dehydrated solid sludge is neutralized with limestone, and the separated waste liquid is neutralized to precipitate.

The present invention having such a configuration utilizes the free sulfur oxidation ability as the reaction below of the sulfated bacterium thiobacilli thiooxydans mT.

2S ⁰ + 3O ₂ + 2H ₂ O → 2H ₂ SO ₄

In the present invention, thiobacilli thiooxydans mT uses sulfuric acid inorganic sulfur compounds such as free sulfur and thiosulphate as energy sources to produce sulfuric acid as a final metabolite. In addition, the strain is resistant to high concentrations of heavy metals, sulfates and organics, such as maintaining a wide range of pH 1.5-8.0 and high concentrations of heavy metals and sulfates, and heavy metals from various wastes contaminated with heavy metals Can be used for elution and removal.

The thiobacillus thiooxydans mT strain, which is a sulfated bacterium used in the present invention, is a strain of strains showing free sulfur oxidation ability and the ability to elute heavy metals of wastes from the anaerobic digestion sludge of a sewage treatment plant. Separation was carried out from the intensive culture.

The concentrated culture was carried out with sulfated bacterial culture medium (KH ₂ PO ₄ 3.0g, MgSO ₄ · 7H ₂ O 0.5g, CaCl ₂ · 2H ₂ O, 0.3g, NH ₄ Cl 0.4g, FeSO ₄ · 7H ₂ O 0.01g, 10g (dry weight) of anaerobic digested sludge collected from sewage treatment plant was added to 100 mL of free sulfur 10.0g, 1 liter of distilled water, pH 4.0) as an energy source, followed by shaking culture at 30 ° C. and 180 rpm. When (SO ₄ ^2- ) was detected in a culture medium of 6000 ppm or more and the pH dropped to 2.0 or less, the culture solution was reinoculated with 10% (v / v) of fresh sulfated bacterial culture medium.

This procedure was repeated about 20 times to obtain several strains by smearing and incubating the pure broth obtained in a solid medium for culturing sulfated agar containing agar, and the pH, heavy metals, sulfates and One strain showing the best resistance was isolated through the resistance evaluation for organic matter.

Gram staining, oxidase, catalase, use of organic matter, optimum pH, oxidation of reduced iron (Fe ²⁺ ) based on the general experimental methods (Pelczar and Chan, 1977) And biochemical properties such as nitric acid breathing were investigated. In addition, the analysis of the organic acid and quinone component of the cell wall components of the strain was analyzed by the Gene Bank (KCTC) in the Biotechnology Research Institute attached to the Korea Institute of Science and Technology. As a result, the isolate was identified as a new strain belonging to Thiobacillus thiooxidans, and was deposited with the gene bank (KCTC) in the Institute of Biotechnology, affiliated with the Korea Institute of Science and Technology, and assigned the strain number KCTC 8928P. Bacillus thiooxydans MT.

The isolated thiobacilli thiooxydans mT is 1 micrometer in length and is motility and gram negative. The colonies in the sulfated bacterial culture medium are opaque white and the aging bacteria are dark yellow. Negative and positive for the cytochrome oxidase and catalase activity tests, respectively. It is an independent microbial bacterium that is not capable of performing oxidation reactions of divalent iron ions and of nitric acid breathing ability. The coenzyme of the electron transport system has ubiquinone 8, and the major components of cell wall fatty acids are non-hydroxy 16: 0 and hydroxy 3-OH 14: 0. Isolates such as fatty acids and ubiquinone components, nitric acid respiration and iron oxidizing ability are characterized by Thiobacillus thiooxidans. Thiobacilli thiooxydans are produced by sulfuric acid, a metabolite by free sulfur oxidation. It reduces the pH of heavy metal contaminated wastes such as sludge or sedimentary sludge and dissolves insoluble heavy metals contained in the wastes in the form of ions in the aqueous phase.

The configuration for achieving the first object of the present invention is as follows in detail. First, inoculate the sulfated bacterium Thiobacillus thiooxydans mT into slurry slurried by mixing solid waste and water or contaminated waste in the form of slurry, and adding free sulfur necessary for growth of sulfated bacteria as an energy source. Incubation is carried out while supplying air of ˜1.0 vvm (0.5 to 1.0 times the liquid volume per minute). While maintaining the agitation and aerobic conditions, incubation is performed for about 0.5 to 10 days depending on the operating conditions. During the incubation, the sulfuric acid produced by the free sulfur oxidation of sulfated bacteria lowers the pH of the slurry to 1.5 to 2.5 Heavy metals contained in contaminated waste turn into water-soluble form. The slurry liquid treated up to this stage is separated into waste and liquid phase through dehydration process, and the heavy metal contained in the separated liquid is neutralized with lime and precipitated and removed by insoluble material, and the dehydrated waste is neutralized with lime to remove heavy metal. To obtain waste.

In the method of the present invention, the growth and free sulfur oxidation activity of the thiobacilli thiooxydans M. bacteria can be maintained in the pH range of the waste slurry from 1.5 to 7.0, but the initial pH of the slurry liquid can be adjusted to 6.0 or less. When the heavy metal removal efficiency is the best. Since heavy metal removal efficiency is closely related to pH, it is preferable to treat the slurry until the pH of the slurry liquid is lowered to 2.0 or less.

Various types of slurry bioreactors, such as an airlift reactor, aeration reactor, and agitation reactor, may be used for the biological heavy metal elution reaction of the waste according to the present invention, and the residence period of the waste bioreactor may vary depending on the solid concentration of the slurry liquid. However, since the bioreactor is about 0.75 to 3.0 days, it is preferable to use a multistage slurry bioreactor rather than a single stage. The residence time is adjusted so that the pH of the sludge discharged from the bioreactor is kept below 2.0, and the aeration rate is preferably 0.5 to 1.0 vvm (0.5 to 1.0 times the liquid volume per minute). The supply amount of free sulfur to the bioreactor as an energy source is preferably 5 to 10% of the dry weight of the solid waste. At the beginning of the operation, the inoculum of sulfated bacteria is about 10% (v / v) of the bioreactor slurry. After the steady state is reached, the return of the treated slurry can be used as an inoculum of sulfated bacteria, and the inoculum concentration of the strain can be controlled by adjusting the amount of return. The treated waste slurry liquid from which heavy metals are removed is dewatered to have a water content of 75 to 80%, and neutralized by adding about 0.4-0.5% (w / v) of lime to the dehydrated waste and the generated waste liquid, respectively.

Features of the configuration for achieving the first object of the present invention as described above can be described in more detail through the following description described by the accompanying drawings shown as an example.

The heavy metal removal device of the waste provides agitation and aerobic conditions by blowing air into the slurry tank of various slurry wastes such as active sludge / aerobic / aerobic digestion tanks or sedimentary sludges in wastewater treatment plants, and waste slurry liquids inoculated with sulfated bacteria. The sulfuric acid is produced by the growth of sulfated bacteria and oxidation of free sulfur, and the bioreactor eluting heavy metals from the waste, the free sulfur storage tank and feeder to supply free sulfur to the substrate, and the slurry liquid discharged from the bioreactor. Conveying tube and mixer to mix with incoming waste slurry liquid for use as inoculum, dehydrator for solid-liquid separation of slurry liquid from which heavy metal is eluted, mixer for neutralizing dehydrated waste with lime, and heavy metal Neutralization tank for neutralization of waste liquor, separating heavy metals and lime precipitated as solids during the neutralization process It can be configured as a settling tank, lime reservoir and feeder and heavy metals are removed, including waste reservoir to. Hereinafter, an example of the present invention will be described in detail with reference to FIG. 1.

As shown in FIG. 1, the apparatus for removing biological heavy metals using wastes belonging to the genus Thiobacillus is an anaerobic / aerobic digester / activated sludge tank or slurry waste storage tank (1), bioreactor (2), and slurry dehydrator (3). ), Screw type slurry mixer (4), wastewater neutralization tank (5), sedimentation tank (6), treated water outlet (7), free sulfur storage tank (8), lime storage tank (9), conveying pipe (10), treatment waste It may be composed of a reservoir 12, a free sulfur feeder 14 and a lime feeder 15 and the like. According to the apparatus of this structure, the slurry solution discharged from the anaerobic / aerobic digestion tank and the activated sludge tank 1, or the various slurry waste liquids generated in other processes at a constant rate and the return liquid 10 of the bioreactor 2 and Mixed and injected into the bioreactor 2 continuously or intermittently. A certain amount of concentrated sulfated bacteria is inoculated into the bioreactor 2, and a small amount of inorganic salts, which are nutrients to the bacteria, and free sulfur, which is an energy source, are supplied from the reservoir 8 by a screw feeder 14 to the bioreactor 2 It is injected into a certain amount. While stirring under air injection, the sulfuric acid produced by the free sulfur oxidation of the sulfated bacteria reduces the pH of the slurry to 2.0 or less, and insoluble heavy metals contained in the waste are eluted in the form of ions in the liquid phase. Slurry liquid is discharged through a certain period of stay, some of which is returned and mixed with the inflow slurry into the inoculum of sulfated bacteria and circulated to the bioreactor (2), and the slurry liquid from which heavy metal is eluted is passed through the dehydrator (3). It is dewatered. The dehydrated slurry is mixed with the lime supplied from the lime storage tank 9 in a screw mixer 4 at a constant ratio and neutralized. The heavy metal is removed and the neutralized slurry is stored in the reservoir 12 and used as a material for improving soil such as fertilizer. On the other hand, the dehydrated liquid containing the eluted heavy metal is neutralized to pH 7.0 with lime in the neutralization tank (5), and the eluted heavy metal precipitates in the precipitation tank (6) as an insoluble metal compound, and the precipitated heavy metal is removed and the heavy metal is removed. Treated water is discharged.

The solids concentration of the waste in the slurry liquid can be treated from 1 to 20% (w / v) on a dry weight basis, depending on the type of waste, and 3 to 10% when considering solids precipitation and mixing and heavy metal removal efficiency. It is suitable to operate at solid waste concentrations of (w / v). The second method of the present invention for providing a method for treating such a high concentration of waste also has the following technical configuration.

That is, prior to the inoculation step of inoculating the thiobacilli thiooxydans M. strain, the sulfated bacterium, a high concentration sludge is added to the anaerobic / aerobic digested sludge or activated sludge containing the insoluble heavy metal in advance. Is to add a step to manufacture the waste. In other words, the present invention relates to a storage tank for various slurry wastes, such as an activated sludge / anaerobic / aerobic digestion tank or a sedimentation sludge tank in a wastewater treatment plant, a dehydrator for concentrating a waste slurry liquid, or a dehydrated or dried solid waste storage tank, a slurry dewatering liquid. Mixing tank of heavy and return liquid, bioreactor eluting heavy metal from waste, free sulfur storage tank and feeder, return pipe, dehydrator for solid and liquid separation of slurry liquid from which heavy metal was eluted, and neutralization treatment of dehydrated waste with lime It consists of a mixing tank, a neutralization tank for neutralization of waste liquid containing a large amount of heavy metals, a precipitation tank for separating heavy metals and lime precipitated as solids in the neutralization process, a lime storage tank and a feeder, and a waste storage tank from which heavy metals are removed.

An example of the second method of the present invention as described above will be described in more detail with reference to the accompanying drawings. As shown in Figure 2, the biological heavy metal removal device of the waste is anaerobic, aerobic digester / activated sludge tank or sludge waste storage tank (1), sludge waste concentrator (17) or dehydration (or dried solid waste) waste storage tank (13) And feeder (16), sludge mixture and return liquid (11), bioreactor (2), sludge concentrator (3), screw type sludge mixer (4), wastewater neutralization tank (5), sedimentation tank (6), It is composed of a treated water outlet 7, a free sulfur storage tank 8, a lime storage tank 9, a conveying pipe 10, a waste treatment tank 12, a free sulfur feeder 14, a lime feeder 15, and the like. .

According to the configuration as described above, the sludge solution discharged from the anaerobic, aerobic digestion tank and activated sludge tank (1) or various sludge waste liquids generated in other processes is 5 to 10% by weight of solid waste concentration in the concentrator (17). It is concentrated so that it is mixed in the slurry conveyance liquid and the mixing tank 11, it is mixed with the conveyance liquid 10 of the bioreactor 2 at a constant speed, and it is injected into a bioreactor 2 continuously or intermittently. Or after mixing the non-concentrated sludge solution from the anaerobic / aerobic digestion tank and activated sludge tank (1) with the dehydrated or dried waste in the mixing tank (11) to adjust the solid waste concentration to 5 to 10% by weight. It may be mixed with the return liquid 10 of the bioreactor 2 at a constant rate and injected into the bioreactor 2 continuously or intermittently. Heavy metals in the waste sludge liquid injected into the bioreactor 2 are removed through the same process as described in FIG.

The heavy metal removal device of the present invention is a bacterium used to remove heavy metals, and is not limited to only thiobacilli thiooxydans mT strains, but is not limited to thiobacilli thiooxydans (ATCC 19377), thiooxydans thioparus (ATCC 55128), and the like. Sulfated bacteria can also be used.

Hereinafter, the present invention will be described in detail through examples. In the examples, the strain of the present invention was fixed and tested on a carrier as necessary. However, the following examples merely illustrate the present invention by way of example, the technical spirit and scope of the present invention is not affected by this.

Example 1 Cultivation method of thiobacilli thiooxydans mT strain

The composition of the medium for the cultivation of sulfated bacteria Thiobacillus thiooxydans mT for heavy metal removal was 1 L of distilled water (KH ₂ PO ₄ 3.0g, MgSO ₄ · 7H ₂ O 0.5g, CaCl ₂ · 2H ₂ O , 0.3 g, NH ₄ Cl 0.4 g, FeSO ₄ · 7H ₂ O 0.01 g) and 10.0 g of free sulfur (S ^o ) as an energy source. The initial pH of the medium is 4.0. After culturing for 3 to 5 days while supplying air to the sterilized reactor to 1.0 vvm (1.0 times the volume of liquid per minute), the culture medium with the pH of the medium was 1.5 to 2.0 as a seed.

Example 2 Biological heavy metal removal using thiobacilli thiooxydans in high concentration sewage sludge

According to the present invention, the heavy metal removal efficiency of the waste having a solid concentration of 3 to 10% was investigated. Anaerobic digestion sludge from sewage treatment plant was the representative waste. The heavy metal removal efficiency survey was carried out in a batch treatment using a 30 liter airlift type reactor. Sewage sludge dewatering cake with 80% water content was filled with 18 liters of slurry liquid adjusted to 3-10% solids concentration of sewage sludge, and 2 liters of seedling of thiobacilli thiooxydans obtained in Example 1 was inoculated and used as an energy source. After adding 10 g of free sulfur per 1 liter of sludge liquid, batch culture was performed while supplying air at 0.5 to 1.0 vvm (0.5 to 1.0 times the liquid volume per minute). Sludge liquid was collected from the bioreactor once a day during the cultivation and the heavy metal removal efficiency was analyzed by ICP.

As a representative example, the pH and sulphate concentration change over time of the waste during biological treatment at 9% solids concentration are shown in FIG. 3. It was confirmed that the concentration of sulfate produced by the sulfation action of thiobacilli thiooxydans began to increase rapidly after 2 days of cultivation, and then decreased from pH 5.0 of the initial sludge waste liquid to less than pH 2.5 after 5 days of cultivation. Could. As the pH of the waste liquid is lowered, heavy metals contained in the waste are eluted. Table 1 shows the heavy metal removal efficiencies of the sludge waste at the solid concentration of each sludge subjected to biological treatment for about 10 days.

Table 1.Efficient removal of heavy metals according to the solid concentration of sewage sludge waste

As shown in Table 1, according to the present invention, heavy metals contained in wastes can be removed from a high concentration waste liquid having a solids concentration of 3 to 10%. As the solid concentration of the waste increased, the removal efficiency of heavy metals decreased, but most of the heavy metals except chromium were effectively removed even in the high concentration of 10% solid waste liquid.

Example 3 Heavy Metal Removal from Sewage Sludge Concentration of Thiobacilli Thiooxydans M. Strain

The sludge concentrate having a sludge solid concentration of 3% generated from an anaerobic digestion tank of a sewage treatment plant was subjected to heavy metal removal using a thiobacilli thiooxydans mT strain in a biological heavy metal removal apparatus as shown in FIG. 1. The bioreactor 2 used used a 30 liter airlift reactor, with a slurry volume of 20 liters in the reactor. Fill the reactor 2 with 18 liters of sludge, inoculate 2 liters of thiobacilli thiooxydans spawn, add 10 g of free sulfur per liter of sludge as an energy source, and then air 0.5 to 1.0 vvm (per minute). Batch cultivation was performed while supplying 0.5 to 1.0 times the volume of the liquid, and when the pH of the sludge solution was lowered to 2 or less from the initial 6 to 7 during the culturing, it was converted to continuous culture. The feed rate of the sewage sludge liquid was changed from the sludge liquid storage tank 1 so that the residence time of the sludge in the reactor 2 was 1.5 to 3 days, and the treated sludge which passed through the reactor 2 was 10%. In order to use the inoculum was recycled through the return pipe (10) and mixed with the sludge solution introduced into the reactor. After a certain residence time, the heavy metal removal efficiency of the sludge flowing out from the reactor (2) was analyzed by ICP, and the pH, redox potential, and sulfate concentration of the sludge solution were measured by pH meter and ion chromatography respectively. Analyzed using.

As a representative example of the embodiment, the pH, redox potential, and sulfate concentration in the process of removing heavy metals of the sludge with the Thiobacilli thiooxydans mT strain under conditions of 2 days residence time are shown in FIG. 4. As shown in FIG. 4, the pH of the sludge solution was maintained at about 1.5, and the oxidation and reduction potential was maintained at about 350 mV, while operating for about 6 days under conditions of 2 days of sludge residence time. In addition, the concentration of sulfate produced by the free sulfur oxidation of the thiobacilli thiooxydans mT strain was also kept constant at 12-16 g / L after about 1.5 days of culture. The constant pH, oxidation / reduction potential, and sulfate concentrations in the sludge solution are indirect evidence of the stable removal of heavy metals. Table 2 shows the heavy metal removal efficiency of sludge according to the residence time of each sludge.

Table 2. Heavy metal removal efficiency of sewage sludge concentrate using biological heavy metal removal device of waste sludge (Fig. 1)

As shown in the table, the removal efficiency of heavy metals improved with increasing residence time. When the residence time is 1.5 ~ 2.0 days, manganese, nickel, copper and zinc can be removed up to 56 ~ 99% except chromium and cadmium. When the residence time is 2.5 ~ 3.0 days, the removal efficiency of chromium and cadmium is 70% and It was able to remove 34-52% and manganese, nickel, zinc, etc., up to 91-99%. Therefore, the present invention was able to effectively remove a significant amount of heavy metals contained in the sludge.

Example 4 Removal of Heavy Metals from Highly Concentrated Sludge Waste Using Thiobacilli Thiooxydans M. Strain

Heavy metal removal was performed in the biological heavy metal removal apparatus of FIG. 2 using a thiobacilli thiooxydans mT strain of sludge concentrate and dewatered cake having a solid concentration of 3% sludge generated from an anaerobic digestion tank of a sewage treatment plant. The bioreactor 2 used was the same as used in Example 3. After the dehydration cake was added to the sludge solution with a solid concentration of 3%, the reactor 2 was filled with 18 liters so that the solid concentration of the sewage sludge was 6%. Then, 2 liters of spawn of thiobacilli thiooxydans were inoculated and 1 liter as an energy source. 10 g of free sulfur per sludge solution was added, followed by batch culturing while supplying air at 0.5 to 1.0 vvm (0.5 to 1.0 times the volume of liquid per minute). When lowered to less than 2 at was converted to continuous culture. In the continuous culture, the sludge concentrate having a solid concentration of 3% from the slurry waste storage tank (1) and the dehydration cake having a water content of 80% from the dehydration waste storage tank (13) are mixed in the stirring tank (11) so that the sludge concentration is 6%. After adjusting, the feed rate was changed so that the residence time of the sludge liquid in the reactor 2 was 2-3 days. 10% of the treated sludge solution passed through the reactor 2 was recycled through the return pipe 10 to be used as an inoculum, and mixed with the sludge solution introduced from the stirring tank 11. After a certain residence time, the heavy metal removal efficiency of the sludge liquid flowing out from the reactor (2) was analyzed by ICP, and the pH, redox potential, and sulfate concentration of the sludge liquid were measured by pH meter and ion chromatography respectively. Analyzed using.

As a representative example of the embodiment, pH, redox potential, and sulfate concentration in the process of removing heavy metals from sludge with the Thiocillus thiooxydans mT strain under conditions of 2 to 3 days residence time are 1.5 to 2.5, 300 to 400 mV, and 6, respectively. It was confirmed that the operation was stably maintained at ˜10 g / L. Sludge heavy metal removal efficiency according to the residence time of each sludge is shown in Table 3.

Table 3. Heavy Metal Removal Efficiency of Sewage Sludge Concentrate Using Biological Heavy Metal Removal System of Waste Sludge

As shown in Table 3, the present invention was able to effectively remove chromium, manganese, nickel, copper, and zinc, except for cadmium, when the residence time was 2.0 to 3.0, even in a high concentration sludge solution of 6%.

Example 5 Removal of Heavy Metals Using Sulfated Bacteria from Power Plant Incinerators

The heavy metal removal efficiency of the incineration ash of the power plant was investigated using the thiobacilli thiooxydans mT strain. 200 mL of MW medium was added to a 500 mL Erlenmeyer flask, and 2 g / L of free sulfur was added to the power plant incinerator at a dry weight of 2-15%, and each flask was seeded with thiobacilli thiooxydans MT strain. After 10% inoculation was performed in a stirred incubator at 180rpm, 30 ℃. Table 10 shows the heavy metal removal efficiency according to the concentration change of the power plant incinerator after 10 days of culture.

Table 4. Comparison of removal rates of heavy metals at various incineration concentrations

As the ash concentration increased, the heavy metal removal efficiency decreased. According to the ash concentration, zinc was removed 69-40% from the ash, 99-45% copper and 44-31% manganese. Therefore, the use of the thiobacilli thiooxydans mT strain of the present invention showed that not only sludge but also heavy metals containing heavy metals such as incineration ash can be removed.

According to the biological heavy metal removal method of the waste as described above (Fig. 2), the sludge waste with low solid concentration is concentrated in the concentrator to significantly increase the treatment capacity per unit volume of the reactor, or the dehydrated concentrated waste sludge waste with low solid concentration. It can be mixed with and treated to remove a significant amount of heavy metals contained in the waste, even if the operation for several months in a row does not lower the activity of the bacteria, it is possible to maintain a high heavy metal removal efficiency. In addition, the heavy metal elution method using the thiobacilli thiooxydans miti strain according to the present invention has the advantages of simple operation, convenient operation, high heavy metal dissolution efficiency because it operates at room temperature and atmospheric pressure.

Claims (4)

In heavy metal removal of anaerobic, aerobic digested sludge and activated sludge, An inoculation step of inoculating anaerobic / aerobic digested sludge or activated sludge containing insoluble heavy metals with sulfated bacteria; A culturing step of adding and adding free sulfur as an energy source of sulfated bacteria to the sludge or activated sludge inoculated with the strain, and culturing while supplying air; A dehydration step of dehydrating the sludge or activated sludge when the strain is cultured sludge or activated sludge reaches 1.5 to 2.5; The dehydrated solid sludge is neutralized by limestone, and the separated waste solution is neutralized by a post-treatment step of precipitating the sludge. The method for removing biological heavy metals from sludge or activated sludge waste using sulfated bacteria. The method of claim 1, wherein prior to the inoculation step of inoculating the sulfated bacteria, a high concentration sludge waste is prepared by adding a concentrated sludge or activated sludge to an anaerobic / aerobic digested sludge or activated sludge containing the insoluble heavy metal. Biological heavy metal removal method of sludge or activated sludge waste using sulfated bacteria comprising a. The sludge or activated sludge waste using sulfated bacteria according to claim 1 or claim 2, wherein a portion of the sludge or activated sludge solution obtained through the culturing step is used as an inoculum of sulfated bacteria in the inoculation step. To remove biological heavy metals. The method according to claim 1 or 2, wherein the sulfated bacteria are Thiobacillus thiooxidans MET KCTC 8928P, Thiobacillus thiooxydans (ATCC 19377) and Thiooxydans thioparus (ATCC 55128). Method for removing biological heavy metals from sludge or activated sludge waste using sulfated bacteria, characterized in that at least one strain selected from the group consisting of.