KR100522716B1 - Removal method for methyl ethyl ketone using geotrichum-immobilized biofilter - Google Patents

Abstract

The present invention relates to a biofilter in which a strain of genus Geotricum is fixed, and a method of removing methyl ethyl ketone using the same. In particular, the present invention is geotricum in a carrier selected from the group consisting of vermiculite, pearlite, and peat moss By providing a method of removing methyl ethyl ketone by using a biofilter immobilized strain, it is relatively inexpensive compared to conventional methods such as adsorption and incineration by activated carbon, and does not generate nitrogen oxides or secondary pollutants. It is friendly and has the advantage that no pressure loss occurs in the biofilter.

Description

Biofilter fixed in Geotricum strain and removal method of methyl ethyl ketone using same {REMOVAL METHOD FOR METHYL ETHYL KETONE USING GEOTRICHUM-IMMOBILIZED BIOFILTER}

[TECHNICAL FIELD OF THE INVENTION]

The present invention relates to a biofilter in which a strain of the genus Geotrikum is fixed and a method of removing methyl ethyl ketone using the same, more specifically, the genus Geotrikum strain on a carrier selected from the group consisting of vermiculite, pearlite, and peat moss. The present invention relates to a method for removing methyl ethyl ketone using an immobilized biofilter.

[Private Technology]

Methyl ethyl ketone (MEK) is a colorless solvent that smells like acetone and is one of 189 harmful compounds established by the US Clean Air Act Amendments (CAAA) in 1990. MEK is widely used mainly for protective coatings, adhesives, print inks, paint removers, and the like. More than 545 million pounds are produced annually in the United States, and over 3 million workers are estimated to be exposed to MEK annually (U.S. EPA, 1994; NIOSH, 1992). MEK can cause headaches, nausea and dizziness when inhaled at high concentrations in the short term, and even coma. Long-term inhalation can also cause central nervous system disorders and toxicity to the liver and kidneys (U.S. EPA, 1994).

 Because MEKs are highly volatile, they are released into the environment and almost all exist in the atmosphere. Most of them are released from solvents such as coatings, synthetic resins, adhesives, and also from tobacco smoke and automobile exhaust. It is also found in small quantities in foods such as ice cream, cheese and cream (U.S. EPA, 1994). According to a report from the Toxic Chemical Release Inventory (TRI92, 1994), a total of 91.3 million pounds of MEK were released from industry in one sector in the United States in 1992, with 99% of the remaining 1% in the atmosphere. Reported releases to surface water, groundwater, and soil.

 The main decomposition pathway of MEK released into the atmosphere is the process by which MEK reacts with photochemically produced hydroxyl radicals to produce acetaldehyde. The half-life of MEK in reaction with hydroxyl radicals is known to be about 2.3 days (U.S. EPA, 1994). In addition, some may be moved from the atmosphere by sedimentation by rain or fog. In soil, photolysis can occur at the surface of the soil as MEK is volatilized into the atmosphere. MEK has high mobility in the soil and may be leached by water or degraded by soil microorganisms (U.S. EPA, 1985). The main route of movement of MEK in water is mainly volatilization to the atmosphere. Complete aerobic biodegradation of MEK is known to take about 5 to 10 days when introduced into sewage or contaminated surface water.

Methods of treating volatile contaminants (VOCs) such as MEK include physical and chemical treatments and biological treatments. However, the physical and chemical treatment can remove various kinds of volatile contaminants with high efficiency, but it is expensive. On the other hand, biological treatment has the advantage of being relatively inexpensive compared to traditional methods such as adsorption or incineration by activated carbon, and is environmentally friendly because it does not generate nitrogen oxides or secondary pollutants. Pollutants are generally carbon dioxide harmless to microorganisms Biological purification technology is widely adopted to remove low odors, volatile organic compounds and harmful air pollutants. Biofilter, one of the biological purification technologies, is known to remove inorganic contaminants such as sulfur dioxide, nitrogen oxides and hydrogen sulfide as well as contaminants that are difficult to decompose such as methane, ethane and carbon monoxide.

Generally, odor and volatile organic carbon contained in contaminated air include physicochemical methods such as chemical liquid cleaning and catalytic oxidation, biofilter, biowasher, air lift, and tree. There are biochemical methods such as Trickling biofilter. In most biofilter experiments using fungi, pressure loss is high, which causes channeling by disturbing the flow of contaminants in the filter (Woertz et al., Exophiala lecanii-corni . Biotechnol. Bioeng. 75 : 550-558. 2001).

In order to solve the problems of the prior art, the present invention is geotricum in a carrier selected from the group consisting of vermiculite, pearlite, and peat moss (peat moss) An object of the present invention is to provide a biofilter for removing MEK immobilized strains.

Still another object of the present invention is to provide a method for removing MEK, including operating by injecting methyl ethyl ketone-containing gas into the MEK removal biofilter.

The present invention to achieve the above object geometry tree glutamicum (Geotrichum) on vermiculite, perlite, peat moss, and at least one member from the group consisting of (peat moss) selected carrier The present invention provides a biofilter for removing methyl ethyl ketone, wherein the genus strain is immobilized at 0.7 to 0.8 mg per 1 g of the dry weight of the carrier based on the cell protein mass.

In addition, the present invention injects the methyl ethyl ketone-containing gas into the methyl ethyl ketone removal biofilter, the pH 5 ~ 8, surface load 1.27 ~ 3.63 m ³ m ^-2 h ^-1 and inlet concentration 0.05 at 20 ~ 27 ℃ It provides a method for removing methyl ethyl ketone, including operating at ˜1.25 gm ⁻³ .

Hereinafter, the present invention will be described in detail.

The inventors of the present invention, while studying a biofilter for removing methyl ethyl ketone, identified a strain of Geotricum as a microorganism that decomposes using methyl ethyl ketone as a metabolic substrate in soil, and the biofilter immobilized on the carrier is methyl. It was confirmed that the ethyl ketone can be effectively removed to complete the present invention.

The present invention relates to a geotrikum strain comprising methyl ethyl ketone resolution, a biofilter in which the strain is adsorbed on a carrier, and a methyl ethyl ketone removal method using the biofilter.

Geotrikum strain of the present invention is a microorganism classified into the genus Geotrikum, for example, Geotrichum candidum ( Geotrichum candidum ), Geotrichum fermentans ( Geotrichum fermentans ), Geotrichum lactis ( Geotrichum lactis ) , Geotrichum rubrum , Geotrichum crustacea , Geotrichum aurianticum and Geotrichum caseovorans , including but not limited to no.

Geotricum genus strains are cultivable in conventional yeast media, in particular 1 to 10 g of Na ₂ HPO ₄ 7H ₂ O, 0.5 to 5 g of KH ₂ PO ₄ , 0.1 to 1 micronutrient medium, such as 1 L of distilled water. 3 g of (NH ₄ ) ₂ SO ₄ , 0.1-50 mg nitrilotriacetinic acid, 0.1-10 mg KOH, 1-50 mg MgSO ₄ 7H ₂ O and 0.1-10 mg CaCl ₂ Medium can be used. In particular, the minimum nutrient medium is 1 L of distilled water: 5.52 g Na ₂ HPO ₄ 7H ₂ O, 2.4 g KH ₂ PO ₄ , 1 g (NH ₄ ) ₂ SO ₄ , 5 mg nitrilotriacetinic acid, 3.65 mg KOH, 14.8 mg Preference is given to MgSO ₄ 7H ₂ O and 1.68 mg CaCl ₂ . The strain of genus Geotrikum can be cultured under the condition that MEK is provided, the MEK can be supplied in a vapor state and the supply amount is 150 to 300 mg / ml preferably may be the maximum solubility level, such as 250 mg / ml. . Culture conditions of the genus Geotrikum is aerobic culture at 25 to 35 ℃, preferably 28 to 32 ℃. Geotricum strains are biodegradable using MEK as a metabolic substrate, and some of them are adsorbed, especially since they do not accumulate intermediate metabolites or secondary contaminants after using MEK as a metabolic substrate.

Geotrikum strain according to the invention can be provided as a composition for removing MEK, in one embodiment the strain can be provided as a biofilter by fixing to a carrier. The carrier may be a material usable as a conventional biofilter, such as peat, sawdust, pearlite, ceramic, synthetic resin, vermiculite, and peat moss, and the like, and preferably, at least one carrier selected from the group consisting of vermiculite, pearlite, and peat moss. . The vermiculite, perlite and peat moss have high porosity and have a large surface area for microorganisms to grow, and are very suitable in consideration of efficient mass transfer, minimum pressure drop and compaction. Do. In addition, pearlite, vermiculite, and pit have appropriate physical and chemical properties as carriers, and are economical due to their low cost.

More preferably, the carrier may include vermiculite, pearlite, and peat moss in a volume ratio of 1: 1: 0.5 to 1, and most preferably, vermiculite and pearlite in a volume ratio of 1: 1. The vermiculite, pearlite and peat moss can be used commercially available products, the size of the 2 to 5 mm diameter, various shapes, such as round, oval ball, rod, square, triangle Or it may include a polygon, the porosity thereof may be 30 to 80 v / v%.

The biofilter according to the present invention includes the carrier and the strain of the genus Geotrikum fixed thereto. The biofilter is geotrichum on the carrier The genus strain may be immobilized at 0.7 to 0.8 mg per g dry weight of the carrier on the basis of cell protein mass. The immobilization of the genus Geotrikum strain can be carried out by mixing the strain of the genus Geotrikum with the medium to be 30 to 60% of the water-holding capacity of the carrier. If the moisture content of the carrier is less than 30% of the moisture retention capacity, the carrier may be too dry to inhibit the initial growth of the geotricum strain, and if it exceeds 60%, an anaerobic environment is present at the pore area of the carrier. The composition may be deteriorated because the composition is inhibited from the smooth supply of oxygen. The carrier and the microorganism immobilized on the carrier may be filled in a conventional container such as glass, acrylic or PVC, and the shape of the container may be differently applied depending on the installation method and location of the biofilter for MEK removal.

The biofilter for removing MEKs according to the present invention not only provides optimum growth conditions for the strain of genus Geotricum, but also provides optimum MEK degradation conditions, thereby showing excellent MEK removal efficiency even during long-term use. In addition, the biofilter has a very low pressure loss, so that no channeling phenomenon caused by the pressure loss occurs.

The MEK removal biofilter according to the present invention passes the MEK-containing gas to remove the MEK, wherein the temperature in the biofilter is 20 to 27 ° C., and the pH may be 5 to 8, preferably 6 to 7. The MEK-containing gas is applied at a concentration of 0.05 to 1.25 gm ⁻³ and the surface load can be set at 1.27 to 3.63 m ³ m ⁻² h ⁻¹ . However, the above conditions are most preferably applied differently depending on the type of biofilter.

Hereinafter, examples of the present invention will be described. The following examples are only for illustrating the present invention and the present invention is not limited to the following examples.

Example 1: Strain Separation

Soil was harvested from Hupyeong Industrial Complex in Chuncheon to isolate strains capable of degrading MEK. 1 g of the soil collected is 100 ml of mineral salts basal (MSB) medium (hereinafter per 1 L of distilled water: 5.52 g Na ₂ HPO ₄ 7H ₂ O, 2.4 g KH ₂ PO ₄ , 1 g (NH ₄ ) ₂ SO ₄ , 5 mg nitrilotriacetic acid, 3.65 mg KOH, 14.8 mg MgSO ₄ 7H ₂ O and 1.68 mg CaCl ₂ ) were fed MEK as a single carbon and energy source. MEK was cultivated by supplying a vial containing wet cotton wool to MEK in a stopper wrapped with Teflon to be supplied at a constant concentration in the medium. The culture was shaken at 30 ° C. at 200 rpm (Model 3585-5, Lab-line Instruments, Inc.). The volatilized MEK was continuously supplied at regular intervals, and the stopper was opened for about 10 minutes each day to provide oxygen for aerobic decomposition. As the strain grew and the turbidity of the medium increased, the passage was passaged several times in new MSB medium to form stable mixed cells. Isolation of the strain was carried out in MSB plate medium in which the liquid medium was floated with platinum and solidified with 2% Noble agar (Difco). In this case too, MEK was supplied as a single carbon source and energy source to the cotton in the duram tube in steam. In order to promote the growth rate of the strain, plate culture was used by adding 0.2% yeast extract to MSB medium. A total of three bacterial species and two fungi were isolated, and each MEK resolution was measured in a test container. As a result, the fatty acid structure of the cell membrane was analyzed by morphological characteristics and gas chromatography. Based on (fatty acid methyl ester; FAME) (FIG. 1), it was identified as Geotrichum sp., which was named 'MF01 strain' and conducted a study.

Example 2: Biodegradation Kinetics of MEK

2-1. MEK resolution method

In order to measure the MEK resolution of the strain, the cells were incubated for 24 hours by injecting MEK into a single carbon source and energy source in MSB medium and centrifuged at 8,000 ㅧ g for 10 minutes. The obtained cells were suspended in fresh MSB, diluted at 600 nm to have an absorbance of 1.0 (= 0.65 g dry weight / L), and 10 ml each were injected into 160 ml test containers. The initial MEK concentration was injected in the range of 1 to 11.2 mM, and the culture conditions were set at 200 rpm and 30 ° C. The MEK removal rate was obtained by taking a 100 μl gas sample from the test chamber headspace and using a gas ion chromatography detector with a flame ionization detector and a capillary column of 0.53 mm diameter x 30 m. Packard Model 5890 Series II plus, USA). The concentration of MEK was analyzed using a standard straight line representing the GC recorder area according to a certain concentration. The GC operating conditions for analyzing MEK are shown in Table 1.

Injector temperature 100 ℃ Oven temperature 50 ℃ Detector temperature 250 ℃ Nitrogen Gas Flow Rate 10 ml / min

All experiments were performed in multiples, and the biological degradation by MF01 alone was determined by experimenting with abiotic control without addition of the strain. The results are expressed as a specific removal rate, i.e. r (MEK removal amount / dry weight / time), with time, and the following equation is used to obtain the substrate affinity constant ( K _m ) and the maximum removal rate (r _max ). The Michaelis-Menten equation of 1 was used.

(Equation 1)

2-2. result

After injection of 3 μl of MEK into a 10 ml strain suspension, the measured MEK degradation rate and growth curve are shown in FIG. 3. Initial cell weight was 0.03 g dry weight / L. After lag phase of about 30 minutes, the MF01 strain degraded MEK at a constant rate and completely degraded at 4 hours. In addition, the strains grew after 1 hour and grew simultaneously with the degradation of MEK, and no longer grew after the complete degradation of MEK. This shows that MEK is being used as a substrate by the strain.

In addition, as a result of measuring the biodegradation kinetics of the strain, MEK did not show an inhibitory effect (inhibition) in the measured concentration range (1.1 ~ 11.2 mM) was determined to follow the Michaelis-Menten kinetics. Therefore, the substrate affinity constant ( K _m ) and the maximum degradation rate (r _max ) were calculated using the Lineweaver-Burk transformation obtained by taking the inverse of the substrate concentration and removal rate (r), which were 5.85 mM and 1.59 h ^-1, respectively ( 4). 4 shows the MEK degradation kinetics of strain MF01. In FIG. 4, the experimental results indicated by the curves and the trend lines were compared with each other, showing a good agreement between the two results.

Example 3: Strain Adsorption of MEK

MEK adsorption isotherm experiments were performed to determine the amount of MEK decomposed physically and removed by the hyphae. The experiment was performed under the same conditions as in the MEK biodegradation kinetics experiment of Example 2, except that the killed cells were used.

The amount of MEK adsorbed per dry weight of the strain according to the MEK concentration is shown in FIG. 5. When the MEK concentration was increased, adsorption occurred from 2 mM, so that 0.008 mg of MEK was absorbed per mg of strain at 11.2 mM. In addition, when the ratio of adsorption and degradation after 1 hour after inoculation of the strain was expressed as a ratio, the adsorption amount was about 7.5% of the total injection amount at 11.2 mM, which is about 0.62 mg when 8.07 mg of MEK was injected. It means that it was adsorbed to this strain (Fig. 6). In other words, a small amount of adsorption was involved in the removal of MEK by strain MF01, and most of it was biodegradation.

Example 4 MEK Degradation pH Conditions and Intermediate Metabolite Production Experiments

4-1. Optimal pH conditions

In order to determine the optimum decomposition conditions according to pH, the degree of decomposition was measured by adjusting the pH 4 to 9 range, and as a result, the optimum removal rate was confirmed between pH 6 and 7 (FIG. 7). In addition, the removal rate of 80% or more was observed at pH 5 and 8, indicating that the strain was able to degrade MEK over a relatively wide range of pH.

4-2. Confirmation of intermediate metabolite production

In order to determine the intermediate metabolites that MF01 strain is likely to accumulate while decomposing the MEK, the culture solution was collected at intervals of 2 hours while culturing the strain and analyzed by scanning the absorbance in the wavelength range of 200 ~ 500 nm (Fig. 8). As a result, the absorbance decreased with time at a wavelength of 260 nm, which gradually decreased as it was resolved by the strain as a peak representing MEK, and the increase in absorbance of a peak close to 200 nm was generally generated as cells grew. It is not considered to be a substance.

Therefore, the peaks in the specific wavelength range were not measured during MEK decomposition, and as a result, it was estimated that no intermediate metabolites were accumulated.

Example 5: Biofiltration of MEK

5-1. Operation of the biofilter

In order to examine the removal of MEK using a biofilter, vermiculite and pearlite sterilized by exposure to high pressure steam three times at 121 ° C. for 30 minutes were mixed at a ratio of 1: 1 (v / v) and immobilized the degradation strain MF01 in a glass column (6 cm diameter x 50 cm length) (FIG. 2). Geotrikum strains were immobilized by mixing the strains of the genus Geotrikum with the medium to be 50% of the water-holding capacity of the carrier. The inoculation amount of the strain was such that the cell protein per dry weight of the carrier was 0.7-0.8 mg.

Pre-culture of the decomposed strain was used as a liquid medium provided MEK as the only carbon source in the MSB up to the maximum solubility limit (250 mg MEK / ml), and the cells recovered by centrifugation after 36-48 hours incubation . At this time, the recovered cells were suspended in fresh MSB medium calculated to be 50% of the water retention capacity of the carrier and mixed together.

The air flowing through the air pump passes through the MEK and the water trap, and the flow rate and the concentration of the MEK were controlled by the number of air bubbles per hour using a flow meter (Dwyer Instrument, Inc.). The total flow rate of the incoming air was measured using a flowmeter (Hewlett Packard, USA), and the pressure loss that could occur during the operation of the biofilter was measured using a manometer (Dwyer Instrument, Inc.).

The biofilter was operated at room temperature of 20 ~ 27 ℃, and the removal rate of MEK was analyzed by gas chromatography for the concentration of inflow and outflow into the biofilter, and the amount of MEK removed per carrier filling per hour (g MEK removed / m ³ filter volume / h).

5-2. Determination of the biomass of microorganisms attached to the carrier

To measure the biomass of the microorganisms attached to the carrier in the biofilter, 5 g (wet weight) of the carrier was taken from the biofilter and mixed with 25 ml of 1 M NaOH and boiled for 7 minutes (Cox et al., Exophiala jeanselmei. Biotechnol. Bioeng 0.53: 0.259 to 266 in 1997). Then Bradford method in 5,000 g 10 ㅧ bun centrifugation using Coomassie blue by taking the supernatant for (Bradford, Anal Biochem 72:. .. 248-254 1976) was quantified by the amount of cell protein used. Standard protein was expressed with 595 nm absorbance using bovine serum albumin (BSA) with Coomassieblue reagent, and the absorbance measured in the sample was substituted into this standard straight line to calculate the protein concentration.

5-3. Optimal Carrier Selection

In order to select a suitable carrier in the biofilter operation, the biofilter was operated for 30 days by mixing perlite, vermiculite, and peat moss at an appropriate ratio. The mixing ratio of the carrier (volume basis) is three kinds of mixtures of perlite and vermiculite (1: 1), perlite, vermiculite and pit (1: 1: 0.5), and perlite, vermiculite and pit (1: 1: 1). Carriers were tested. Each material was used as a commercially available product for the flower, and the particle size was used to select only 2-5 mm to minimize the pressure loss. The surface loads of all three biofilters were in the range of 0.36 m ³ m ^-2 h ^-1 and the inlet concentration was 1.4 ~ 10.2 gm ^-3 h ^-1 .

Filling materials for biofilters should be selected in consideration of the large surface area required for microbial attachment, efficient mass transfer, minimal pressure loss and consolidation. Pearlite, vermiculite, and pit have moderate physical and chemical properties as carriers and are economical due to their low cost.

Table 2 shows the average influent load, removal efficiency and removal rate obtained by operating the biofilter on each carrier for 30 days. Here, the carrier mixed with pearlite and vermiculite 1: 1 (v / v) showed the best efficiency with average removal efficiency and removal rate of 96.7% and 18.8 gm ^-3 h ^-1 , respectively. The efficiency was the lowest at. Therefore, a carrier mixed with pearlite and vermiculite in a 1: 1 ratio was applied to subsequent biofilter experiments.

Inflow load (gm ^-3 h ^-1) Removal efficiency (%) Removal rate (gm ^-3 h ^-1) Pearlite and vermiculite (1: 1. v / v) 20.0 96.7 18.8 Pearlite, Vermiculite and Pittmoss (1: 1: 0.5 .v / v) 20.2 88.8 17.4 Pearlite, Vermiculite and Pittmoss (1: 1: 1. v / v) 15.4 71.4 11.6

Example 6: Long term biofilter operation

6-1. MEK removal rate according to surface load and inflow concentration

The removal rate obtained by operating the temperature in the range of 20 ~ 27 ℃ while changing the surface load and inlet concentration for 334 days by inoculating MF01 strain is shown in Figure 9. Initially, the surface load of 1.27 m ³ m ^-2 h ^-1 was supplied at a concentration of 0.05 gm ^-3 for 8 days, and the concentration was gradually increased to 0.5 gm ^-3 by 87 days. At this time, the removal efficiency of MEK was 100% and the maximum removal rate was 2.2 gm ⁻³ h ⁻¹ . Since then, the surface load was increased to 3.63 m ³ m ^-2 h ^-1 and operated with a concentration range of 0.1 to 1.25 gm ^-3 . The maximum removal rate obtained while driving for 334 days was 12 gm ⁻³ h ⁻¹ . After 210 days, the removal rate gradually decreased due to the accumulation of toxic metabolites or contamination of other microorganisms during long-term operation.

Chou et al. (1997) obtained a MEK removal rate of up to 40 gm ⁻³ h ⁻¹ using a trickling biofilter. These results are higher than 12 gm ^-3 h ^-1 obtained in this experiment, but the previous study was obtained from a short-term experiment for 14 days. Considering the economical efficiency, the biofilter used in this experiment was used for long-term operation at low concentration. (Chou, MS and JJ Huang, Treatment of methylethylketone in air system by biotrickling filters, J. Environ. Eng., 123: 569-576, 1997).

10 shows the relationship between the inflow load and elimination capacity (EC) according to the surface load. Air flow rate (m ³ m ^-2 h ^-1 ) was applied to 1.27 (■), 1.82 (△), 2.55 (●) and 3.64 (○). In analyzing the obtained results, the limit removal rate increased proportionally as the inflow load increased. However, when the surface load was further increased to 3.64 m ³ m ^-2 h ^-1 , the limit removal rate reached the maximum and then decreased after the inflow load of 4 gm ^-3 h ^-1 . Similarly, when the limit removal rate was measured according to the inflow concentration, diffusion limitation except for the surface load of 3.64 m ³ m ^-2 h ^-1 was shown (FIG. 11). Also, at 3.64 m ³ m ^-2 h ^-1 , the marginal removal rate does not increase from about 0.3 gm ^-3 , which is often called the critical gas concentration. After this concentration, the reaction limitation is a major regulator of the biofilter, and the overall rate of degradation is determined by the micro-kinetics of the microorganisms present in the biofilm (Choi and Oh, 2002). The critical removal rate, which is one of the important factors in the design of the biofilter, was affected by the surface load as well as the concentration. The higher the surface load at the same concentration, the higher the efficiency.

6-2. pH, water content, and cell mass

When the pH, water content and biomass of biofilters were measured at 334 days after starting operation and compared with initial values, the average pH was 6.65, which was not significantly different from the beginning of operation. not due to a change in pH (Table 3).

The moisture content was 67.13%, which was maintained under the proper conditions for the growth of microorganisms. There was no significant change depending on the depth of the biofilter.

Biomass increased to 1.24 (mg protein weight / g dry weight), which was increased from the initial 0.76 (mg protein weight / g dry weight), and based on the results showing similar amounts depending on depth, artificial mixing was not allowed during long-term operation. In spite of the absence, biomass was uniformly distributed throughout the biofilter. Table 3 shows the results of chemical analysis on the filter after starting the biofilter and after 334 days of operation.

Height (cm) pH Moisture content (%) Biomass (mg protein / g) ^a 0-20 6.64 69.81 1.32 20-40 6.55 67.30 1.12 40-60 6.76 64.29 1.27 Average 6.65 67.13 1.24 Initial figures 6.43 66.11 0.76 ^a : dry weight for the filter carrier

6-3. Pressure drop

The pressure loss in the biofilter during the 334 days after the start of operation was almost as low as 1.2 mmH ₂ O as a whole. The change pattern started to increase gradually after 120 days and slightly increased when the air flow was changed, but did not significantly affect the overall pressure loss (FIG. 12). In most biofilter experiments using fungi, pressure loss is high, which causes channeling by disrupting the flow of contaminants in the filter (Woertz et al., Exophiala lecanii-corni . Biotechnol. Bioeng. 75: 550-558. 2001). The biofilter applied in this study was able to limit the increase of excessive biomass compared to the case of applying the organic carrier by applying the optimal combination of inorganic carriers. It is assumed to act as one advantage. 12 shows the pressure loss measured periodically in the filter bed during the operation. At this time, the dotted line indicates the change of the surface load.

6-4. Scanning Electron Microscopy (SEM) Analysis

After long-term operation of the biofilter, the carrier recovered from the biofilter was observed by SEM to observe the morphological changes of the carrier and the microbial community.

The carrier sample was fixed with a solution made by dissolving 1% glutaraldehyde and 1% paraformaldehyde in 0.1 M phosphate buffer, washed twice with 0.1 M phosphate buffer, and then 50 to 100% Dehydrated with ethanol for 30 minutes each. The samples were then coated with Pt / Pd by critical point drying and observed using a digital scanning electron microscope (Model S-4300, Hitachi).

When the carrier sample was collected from the biofilter at 334 days after the start of the experiment and the attached microorganisms were observed using a scanning electron microscope, the carrier of the biofilter showed that the mycelium adhered well to the carrier in the form of a reticular membrane. (FIG. 13). This type is thought to be an effective form of decomposition of air pollutants through the carrier and is believed to contribute to low pressure loss. In Fig. 13, the samples (a) and (b) are of a biofilter operated for 334 days, with a magnification of 40x, (c) of 150x, and (d) of 1,000x.

6-5. Surface load effect

12.48 m ³ m when the surface load was gradually increased from 2.54 to 14.63 m ³ m ^-2 h ^-1 at a MEK concentration of 0.1 gm ^-3 to determine the effect of surface load changes with constant concentration. ^The maximum removal rate was shown at ^-2 h ^-1 (Table 4). The residence time at this time is only 43 seconds, which corresponds to a very short residence time. On the other hand, when the surface load was increased to 14.63 m ³ m ^-2 h ^-1 , the removal rate was reduced, because the residence time was too short, so that there was not enough time for complete biodegradation of contaminants in the biofilm or diffusion of MEK into the biofilm. I think it's because it didn't happen enough. When the surface load was increased in the applied range, the pressure loss hardly occurred below 1.0 mmH ₂ O.

Gas flow rate (m ³ m ^-2 h ^-1 ) Inflow concentration (gm ^-3 ) % Removal efficiency Inflow load (gm ^-3 h ^-1 ) Limit removal rate (gm ^-3 h ^-1 ) 2.54 0.096 ± 0.05 100 0.93 ± 0.10 0.93 ± 0.10 5.30 0.120 ± 0.05 100 1.95 ± 0.30 1.95 ± 0.30 7.90 0.111 ± 0.02 100 3.05 ± 0.13 3.05 ± 0.13 10.52 0.103 ± 0.01 100 3.75 ± 0.55 3.75 ± 0.55 12.48 0.096 ± 0.02 81.2 4.97 ± 2.14 4.02 ± 2.31 14.63 0.102 ± 0.01 38.5 6.02 ± 0.95 2.26 ± 0.46

6-6. Effects of shut-down and restart-up and sudden fluctuations

An important issue in operating biofilters is the proper control of pollutant gas flow rates and concentrations, and the study of biofilm stability against rapid concentration changes when applied to practical operation is very important (Arulneyam & Swaminathan, 2000). In order to determine the stability of the biofilm present in the biofilter was carried out the following experiment.

In order to determine the effect of the suspension, the biofilter operated for about 120 days was stopped for 15 days and then supplied with the same inflow load (1.27 to 12.48 m ³ m ^-2 h ^-1 ) as before (FIG. 14). At this time, the inflow concentration of MEK was set to 0.1 gm ⁻³ . When the MEK and air were not supplied for 15 days and then started again, they quickly recovered to the same removal rate, which indicates that the microorganisms were well preserved in the carrier during the starvation, so that the biomass was not greatly reduced and the sudden concentration of Adapted well to increase.

On the other hand, when the inflow load was temporarily increased from 5 gm ^-3 h ^-1 to 20 gm ^-3 h ^-1 for 30 minutes, the removal rate decreased slightly from 100% to 97%. By showing the results of recovery again, it can be seen that the biofilm adapts and stabilizes relatively rapidly against rapid changes in concentration (FIG. 15). The inflow load of the applied air was 6.36 m ³ m ^-2 h ^-1 , and the inlet concentration of MEK was tested in the range of 0.46 ~ 1.83 gm ^-3 .

The present invention is a geotrichum ( geotrichum ) on a carrier By removing the methyl ethyl ketone using the biofilter immobilized strain, it is relatively inexpensive compared to traditional methods such as adsorption and incineration by activated carbon, and is environmentally friendly because it does not generate nitrogen oxide or secondary pollutants. There is an advantage that no pressure loss occurs.

Figure 1 shows the fatty acid structure analysis (fatty acid methyl ester; FAME) results of the cell membrane using gas chromatography.

2 is a schematic diagram of a biofilter used to remove methyl ethyl ketone (hereinafter referred to as "MEK").

Figure 3 shows the MEK degradation rate and growth curve of the genus Geotrikum strain.

Figure 4 shows the MEK biodegradation kinetics of geotricum genus strain.

Figure 5 shows the results of the MEK adsorption experiment by the genus strain Geotrikum.

Figure 6 shows the ratio of the MEK adsorption amount and degradation amount measured for 1 hour for the strain and live strain killed by heat.

7 is a graph showing the effect of pH on the degradation of MEK by the strain of genus Geotricum, the optimal pH is 6.0 to 7.0.

Figure 8 shows the spectral change during MEK degradation by the genus strain Geotrikum, each spectrum was scanned every 2 hours, the arrow shows the spectral change over time intervals.

FIG. 9 shows the operation results of the biofilter for 11 months, (A) shows surface loading, (B) shows inlet MEK concentrations, and (C) shows MEK removal rate.

FIG. 10 shows the relationship between inlet loading and elimination capacity (EC) according to surface loading.

11 shows the relationship between elimination capacity and MEK injection concentration.

12 shows the pressure drop of the biofilter after 11 hours of operation, and the dotted line shows the change in surface loading.

FIG. 13 is a scanning electron microscopy (SEM) photograph of the genus Geotrikum grown on a carrier mixed with a volumetric ratio of pearlite and vermiculite 1: 1.

FIG. 14 shows the response of the biofilter to shut down and restart-up operation for 15 days.

Figure 15 shows the transient response of the biofilter with a sudden change in concentration of MEK.

Claims (5)

Geotrichum on at least one carrier selected from the group consisting of vermiculite, pearlite, and peat moss Biofilter for removing methyl ethyl ketone in which the genus strain is immobilized at 0.7 to 0.8 mg per 1 g of the dry weight of the carrier on the basis of cell protein mass . The method of claim 1, wherein the carrier is methyl ethyl ketone removal biofilter containing perlite and vermiculite in a 1: 1 volume ratio. The method of claim 1, wherein the carrier is a methyl ethyl ketone removal biofilter containing perlite: vermiculite: pitmos in a volume ratio of 1: 1: 0.5 to 1: 1: 1. The biofilter for removing methyl ethyl ketone according to claim 1, wherein the strain of the genus Geotrichum is immobilized on the carrier by mixing the culture solution thereof to 30 to 60% of the carrier's water retention capacity. A methyl ethyl ketone-containing gas is injected into the methyl ethyl ketone removal biofilter according to any one of claims 1 to 4, and the pH is 5 to 8 and the surface load is 1.27 to 3.63 m ³ m ^-2 at 20 to 27 ° C. Method for removing methyl ethyl ketone comprising operating at h ^-1 and influent concentration of 0.05 ~ 1.25 gm ^-3 .