KR100598081B1 - Preparation method of porous carriers for microorganism - Google Patents

Abstract

The present invention relates to a method for preparing a microorganism-supporting porous carrier, and more particularly, after mixing powder dried rice straw obtained by grinding and drying to a specific size and waste polyethylene pulverized to a specific size in a certain component ratio, The carriers obtained by molding under specific conditions are significantly more porous than conventional carriers, so they are excellent in adhesion of microorganisms and are economical and environmentally friendly because they use by-products of industrial wastes and agricultural products as materials of carriers. It relates to a method for producing a porous carrier for supporting microorganisms effective in the field of water treatment.

Rice straw, waste polyethylene, porosity, porous carrier

Description

Preparation method of porous carrier for supporting microorganisms {Preparation method of porous Carriers for microorganism}

1 shows a schematic view of an injection molding machine for molding a porous carrier according to the present invention.

[Explanation of symbols on the main parts of the drawings]

1, 2 and 3: thermoelectric thermometer 4: heater

5: Transfer screw 6: Waste polyethylene and straw straw storage hopper

Figure 2 shows an electron micrograph of the surface of the porous carrier of Example 3 according to the present invention.

Figure 3 shows an electron micrograph attached to the microorganisms on the surface of the porous carrier of Example 3 according to the present invention.

Figure 4 shows a schematic view of the batch aeration device for water treatment to evaluate the performance of the porous carrier prepared according to the present invention.

[Explanation of symbols on the main parts of the drawings]

1: Rubber Bubble Disperser (Diffuser) 2: Fluidized Bed Media

3: air flow meter

Figure 5 shows by measuring the contact angle to the water in order to examine the affinity of the porous carrier prepared in Example 1 according to the present invention.

The present invention relates to a method for preparing a microorganism-supporting porous carrier, and more particularly, after mixing powder dried rice straw obtained by grinding and drying to a specific size and waste polyethylene pulverized to a specific size in a certain component ratio, The carriers obtained by molding under specific conditions are significantly more porous than conventional carriers, so they are excellent in adhesion of microorganisms and are economical and environmentally friendly because they use by-products of industrial wastes and agricultural products as materials of carriers. It relates to a method for producing a porous carrier for supporting microorganisms effective in the field of water treatment.

Due to the rapid economic development, the explosive growth of urban population, and the improvement of living standards, the discharge of various industrial wastes, domestic waste and septic tanks, septic tanks, and livestock wastes, including the increase of water volume, will increase. As such, as the discharge of wastewater increases rapidly, environmental problems such as serious water pollution have emerged, and development of a method for treating wastewater efficiently and economically is required.

In general, there are many problems due to the increase in the proportion of inorganic and organic components in the waste water and wastewater, and efforts to remove inorganic and organic components have been actively conducted.

As a result, the standard activated sludge method and its variations using floating growth of microorganisms are almost universally applied in Korea as a method of treating domestic sewage, agricultural and livestock wastewater, and industrial wastewater.

First, a method of treating wastewater by the activated sludge method is to purify by microorganisms stuck to a contact medium serving as a carrier, and various bio phases are fixed to the contact medium, thereby increasing the efficiency of water treatment. This activated sludge method has the advantage of fast biochemical reaction rate, small amount of excess sludge because it promotes self-oxidation of sludge, and excellent treatment efficiency for low concentration wastewater treatment.

The most important parameter of the catalytic oxidation method using the contact media is the performance of the contact media. In general, various materials such as sand, gravel, glass, ceramic, charcoal, plastics and fibers are used as the contact media.

Among these contact media, in the case of sand, gravel, glass, etc., the surface is smooth and difficult to attach microorganisms, and ceramics are made of porous materials, and are excellent in performance, but are difficult to manufacture and economically disadvantageous. In addition, the use of polyethylene, polypropylene, polyvinyl chloride and nylon fibers has been attempted as a medium for plastic materials, but despite the advantages of easy processing, the rate of microorganisms is low and the specific surface area is generally low. Development is required.

Accordingly, the present inventors have tried to solve problems such as the material, economical efficiency and efficiency of the contact medium to support the biological material in the method for treating wastewater by the activated sludge method as described above. As a result, when the powder-dried rice straw obtained by grinding and drying to a specific size and the waste polyethylene ground to a specific size are mixed, the carrier obtained by molding it in a specific temperature range is applied to the activated sludge method. The use of this high rice straw improves the porosity of the carrier as compared to the conventional one, thereby improving the adhesion of microorganisms as well as improving the economical efficiency by using recycled materials.

Accordingly, an object of the present invention is to provide a porous carrier having a porosity in the range of 20 to 30% by molding a specific waste material under specific conditions.

The present invention

1 step of oven drying the rice straw powder;

Mixing 2 to 20 wt% of the dried rice straw powder prepared above and 80 to 95 wt% of waste polyethylene powder; And

Molding the mixture at a temperature of 100 to 250 ℃ temperature is characterized in that the method for producing a porous carrier for supporting a microorganism comprising three steps to produce a porous carrier having a porosity of 20 to 30%.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing a porous carrier for supporting microorganisms, and mixing powdered rice straw and waste polyethylene pulverized to a specific size under a certain condition in a certain component ratio and molding at a specific temperature, thereby forming a range of 20 to 30%. The present invention relates to an efficient porous carrier in the field of water treatment such as wastewater and wastewater by forming a porosity to improve the adhesion of microorganisms and consequently to improve the decomposition rate of organic matter.

In addition, since the waste material of the industrial waste polyethylene and the straw straw by-products of the crop is mixed as a material of the carrier, the production cost is low, and it is excellent in degradability compared with the conventional, thereby obtaining an environmentally friendly effect.

Conventionally, sand, gravel, glass, ceramics, charcoal, plastics, and fibers have been used as materials for carriers, but these have limitations in use due to disadvantages in microbial adhesion and material economy and efficiency. The present invention is characterized in the technical configuration in the method for producing a porous carrier molded in a specific manner by industrial wastes and by-products of crops in order to improve the above disadvantages. Compositions using industrial wastes and by-products of crops have already been known in the literature (Korean Patent Laid-Open Publication No. 2000-9566), but the present invention is not characterized by the use of such components, but rather improves the adhesion of microorganisms. In order to improve the porosity of the carrier, waste polyethylene having a high generation amount in the above industrial wastes and rice straw having strong hydrophilicity among by-products of crops are selected and pretreated under specific conditions, respectively, and then mixed in a certain component ratio. It is characterized by improving the porosity by forming and molding under the following specific conditions.

In general, a resin component such as polyethylene has a small surface free energy, strong hydrophobicity, and has a surface charge of negative charge in the neutral region. Therefore, in the case of forming a carrier prepared from the raw material, the carrier has to have high hydrophilicity in order to facilitate the adsorption and growth of the microorganisms on the carrier since the adsorption power of the microorganisms having a negative surface charge and a high hydrophilicity is not easy. .

Looking at the method for producing a porous carrier for waste water treatment according to the present invention in more detail.

First, the rice straw powder is oven dried. The rice straw is not particularly limited to a general grinding method used in the art, but in the present invention, after cutting to a certain size, the rice straw is pulverized using a willy mill, the rice straw is properly formed but preferably 40 to 80 It is better to form a range of mesh. Since the size of the rice straw is an important factor acting on the specific surface area and dispersibility, it is preferable to use it in the above range. If the particle size is fine and the specific surface area is large, it absorbs moisture in the air, which makes it difficult to carry out molding operations. On the contrary, if the particle size is large, the degree of miscibility is low, resulting in uneven dispersibility. Size is also important.

Thereafter, the rice straw powder is dried for 4 hours or less, preferably 3 to 4 hours at a temperature of 100 to 120 ℃ bar, if the drying temperature is less than 100 ℃ free water contained in tissue cells of rice straw (Free water) is not completely removed, a problem occurs during molding, and when it exceeds 120 ℃, the problem of physical properties change due to deformation of the cell structure. In addition, when the drying time is out of the condition does not occur, it is preferable to maintain the above range.

Next, 5 to 20% by weight of the dried rice straw powder prepared above and 80 to 95% by weight of waste polyethylene powder are mixed. At this time, the waste polyethylene is used in a suitable size for the process efficiency, preferably 5 to 10 mm pulverized. If the size of the powder is too fine, it is preferable to maintain the above range because a problem of causing a load on the motor of the molding machine occurs when the raw material transfer is not smooth and the particles are large.

 Preferably, the waste polyethylene is mixed with 80 to 95% by weight and 5 to 20% by weight of powdered rice straw. If the amount of the powdered rice straw is less than 5% by weight, the formation of pores in the formed carrier is small, and microorganisms are fixed. If the efficiency is reduced, if the amount exceeds 20% by weight, rice straw powder absorbs moisture in the air, so that molding is difficult, so it is preferable to maintain the above range.

 In addition to the waste polyethylene and rice straw described above, an additive used for the purpose of improving the adsorption of microorganisms may be additionally used in the art without departing from the object of the present invention, and the additive may include clay, activated carbon, and the like. have.

 Next, a carrier is prepared by molding the mixture prepared above. The molding is used in the art, but is not particularly limited, and in particular, a carrier having a plate shape, a tubular shape, a cylindrical shape, and an irregular shape may be prepared according to the use used by extrusion molding, injection molding, and the like.

At this time, it is preferable that the molding temperature is maintained at a range of 150 to 250 ° C. If the molding temperature is less than 150 ° C., the raw material is not smoothly transferred from the molding machine. It is advisable to maintain this range because one problem arises.

Next, Figure 1 is an example, a method for producing a carrier using an injection molding machine, mixed with powdered dried rice straw in the pulverized waste polyethylene into the hopper (6) and stirred for 5 to 30 minutes at a rotational speed of 50 to 100 rpm The mixture obtained by mixing is transferred forward by melting with a transfer screw 5 at 10 to 30 rpm under the condition that the thermoelectric thermometer 1-3 is maintained at a temperature of 170 to 200 ° C by the heater 4. The molded product passed by the transfer is cut into a predetermined length of 10 mm with a cutter to produce a pellet.

Fibers of rice straw by the method according to the present invention as described above is bonded to the polyethylene like a network structure, and some carbonized shrinkage to form a rough surface to increase the specific surface area and to form a lot of voids in the outer surface and the inside.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention thereto.

Example 1

The straw was cut into a 3 cm size with a cutter, then pulverized with a Willie mill, passed through a 40-80 mesh sieve, and then powdered, and dried at 105 ° C. for 1 hour.

95% by weight of waste polyethylene cut to a size of about 5 mm was mixed by molding 5% by weight of the rice straw powder.

At this time, as the molding is shown in the schematic diagram of the injection molding machine of FIG. 1, the mixture is stirred and mixed for 10 minutes at a rotational speed of 70 rpm in the hopper 6, and the mixture is heated to the thermoelectric thermometer 1-3. Maintained at a temperature in the range of 170 ~ 200 ℃ and was transferred forward while melting with a transfer screw (5) of 15 rpm. The molded product passed through the transfer was cut into a predetermined length of 10 mm with a cutter to prepare a porous carrier on a cylindrical pellet having a diameter of 5 mm.

Example 2

In the same manner as in Example 1, using a waste polyethylene 90% by weight and rice straw powder 10% by weight to prepare a porous carrier.

Example 3

In the same manner as in Example 1, a porous carrier was prepared using 85% by weight of waste polyethylene and 15% by weight of straw straw powder.

An electron micrograph of the surface of the porous carrier prepared above and an electron micrograph of microorganisms attached to the surface of the carrier are shown in FIGS. 2 and 3, respectively.

Example 4

In the same manner as in Example 1, a porous carrier was prepared using 80% by weight of waste polyethylene and 20% by weight of straw straw powder.

Comparative Example 1

Carried out in the same manner as in Example 1, using 100% by weight of waste polyethylene.

Comparative Example 2

The carrier was prepared in the same manner as in Example 1, using 90 wt% of waste polyethylene and 10 wt% of clay.

Comparative Example 3

A carrier was prepared in the same manner as in Example 1, using 90 wt% of waste polyethylene and 10 wt% of activated carbon.

The porosity of the porous carriers prepared in Examples 1 to 4 and Comparative Examples 1 to 3 was measured, and the results are summarized in Table 1 below.

division Porosity (%) Example 1 21.93 Example 2 23.20 Example 3 27.30 Example 4 28.56 Comparative Example 1 7.15 Comparative Example 2 18.00 Comparative Example 3 22.67

As shown in Table 1, it was confirmed that the porosity of the carriers of Examples 1 to 4 using the mixed straw in accordance with the present invention is equal or higher.

Experimental Example 1

In order to determine the performance of the porous carrier prepared in Examples 1 to 4, the following experiment was performed.

Next, as shown in Figure 4, the batch acrylic aeration device consisting of four zones, each 10L of food wastewater and 10% by volume of each of the porous carriers prepared in Examples 1 to 4, and then the Bacillus powdery seed Each system (BioENT, Biomax) was added 1,000 mg / L each. Thereafter, while maintaining 30 L / min was supplied to be uniformly distributed through the diffuser. At this time, the food wastewater chemical oxygen demand (COD) was 17,700 mg / L, biological oxygen demand (BOD) was maintained at 18,120 mg / L.

The process is a process in which the microorganisms adhere to the porous carrier, and the change in the chemical oxygen demand and the biological oxygen demand is observed for 7 days while the performance of the porous carrier is shown in Table 2 below.

division COD / BOD (mg / L) 0 days 2 days 4 days 6 days 7 days Example 1 17,700 / 18,120 9,800 / 7,500 / 2,200 / 2,400 / 5,196 Example 2 17,700 / 18,120 7,500 / 8,600 / 2,400 / 1,200 / 4,776 Example 3 17,700 / 18,120 7,000 / 5,600 / 3,000 / 1,140 / 3,318 Example 4 17,700 / 18,120 7,100 / 5,100 / 1,300 / 750 / 2,052

Experimental Example 2

After performing Experimental Example 1, in order to evaluate the performance of the porous carrier to which the microorganisms were fixed, the new food wastewater was replaced by 10 L, and the chemical oxygen demand and the biological content for 7 days while dispersing 30 L / min of air were filled. The change in oxygen demand was observed and the results are shown in Table 3. At this time, the chemical oxygen demand (COD) of the food wastewater is 5,250 mg / L, biological oxygen demand (BOD) is 7,230 mg / L.

division COD / BOD (mg / L) 0 days 1 day 2 days 3 days 4 days 5 days 6 days 7 days Example 1 5,250 / 7,230 3,900 / 3,275 / 2,600 / 1,100 / 1,020 / 720 / 670 / 2,862 Example 2 5,250 / 7,230 3,100 / 1,375 / 1,100 / 860 / 790 / 650 / 600 / 2,103 Example 3 5,250 / 7,230 3,100 / 1,250 / 1,900 / 1,300 / 230 / 270 / 230/317 Example 4 5,250 / 7,230 2,300 / 2,375 / 1,620 / 1,400 / 470 / 210 / 120/335

Experimental Example 3

Experimental Example 1 was carried out in the same manner, but the performance of the carrier of Example 2 and Comparative Examples 1 to 3 were measured and compared, and the results are shown in Table 4 below. In this case, the chemical oxygen demand (COD) of food wastewater is 47,000 mg / L, the biological oxygen demand (BOD) is 69,200 mg / L, and the change in chemical oxygen demand and biological oxygen demand for 12 days was observed and the results are shown in the table. 4 is shown.

division COD / BOD (mg / L) 0 days 3 days 6 days 9 days 12 days Comparative Example 1 47,000 / 69,200 41,400 / 39,000 / 31,800 / 29,400 / 19,900 Comparative Example 2 47,000 / 69,200 39,200 / 37,800 / 33,200 / 26,300 / 20,100 Comparative Example 3 47,000 / 69,200 36,300 / 26,700 / 24,800 / 23,700 / 18,200 Example 2 47,000 / 69,200 38,900 / 34,700 / 27,400 / 16,100 / 16,700
Tables 2 and 3 show the performance of the carriers prepared in Examples 1 to 4 according to the present invention. As the amount of rice straw used as the reaction material increases, the COD and BOD levels decreased.

In addition, Table 4 shows a carrier (Example 2) prepared by using straw straw in the waste polyethylene prepared according to the present invention, and a carrier prepared by mixing clay and activated carbon in waste polyethylene alone, waste polyethylene as a comparative example thereof ( Comparing the performance of Comparative Examples 1 to 3), the carrier of Example 2 according to the present invention was confirmed that the water treatment performance is improved compared to the carriers of Comparative Examples 1 to 3, the value of COD and BOD over time As the reduction rate was large, it was confirmed that the carrier of Example 2 was excellent in the storage stability of the microorganism.

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Experimental Example 4

In order to examine the affinity according to the material of the porous carrier prepared in Example 1 was measured in the contact angle to the water shown in Figure 5 below.

Next, as shown in FIG. 5, polyethylene alone (PE) was measured as high as 75 °, but when 5% by weight of straw (RS) was added as in Example 1, the contact angle was significantly lowered to 46 °. However, when rice starch and starch with similar chemical composition were mixed, it was measured as high as 65 °. That is, it was confirmed that the hydroxyl group of glucose, which is the main component of rice straw, strongly bound with water to swell the fiber, and the hydrophilicity was different from starch due to the difference in the binding structure of the glucose unit.

Therefore, in summary, when the pepolyethylene and rice straw were molded under specific conditions according to the present invention, it was found that porosity was formed so that microorganisms were well adhered and propagated, and efficient water treatment was possible.

As described above, the carrier obtained by molding waste polyethylene, which is an industrial waste, and rice straw, which is a by-product of crops, under certain conditions, according to the present invention, has improved porosity compared to the conventional carrier, thereby increasing the fixing and propagation effect of microorganisms, thereby increasing organic matter. It is possible to maximize the decomposition effect of, and use of wastes and by-products, high economical efficiency, especially in the field of water treatment using microorganisms, such as waste water.

Claims (4)

1 step of oven drying the rice straw powder; Mixing 2 to 20 wt% of the dried rice straw powder prepared above and 80 to 95 wt% of waste polyethylene powder; And Three steps to prepare a porous carrier having a porosity of 20 to 30% by molding the mixture at a temperature of 100 ~ 250 ℃ Method for producing a porous carrier for supporting a microorganism, characterized in that consisting of. The method of claim 1, wherein the porous carrier has a shape selected from plate, tubular, cylindrical, and irregular shapes. The method of claim 1, wherein the porous carrier is used in the form of a fluidized or fixed bed. delete

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