KR100332932B1 - A Biofuel Cell Using Wastewater and Activated Sludge for Wastewater Treatment - Google Patents

Abstract

The present invention provides a biofuel cell using wastewater as a fuel. The electrochemically active microorganisms in the wastewater and activated sludge used in the present invention emit electrons generated by oxidizing organic matter in the wastewater to the outside of the cell and directly transfer them to the electrode to generate an electric current, thereby purifying the wastewater. The electric current generated in the biofuel cell using the electrochemically active bacterium according to the present invention generated electrical energy up to 0.22 mA, and reduced the CODcr of the wastewater used as fuel from 1900 ppm up to 55 ppm. The efficiency of the fuel cell differed according to the wastewater type and the wastewater concentration.

Description

Biofuel Cell Using Wastewater and Activated Sludge for Wastewater Treatment

The present invention relates to a biofuel cell using wastewater. More specifically, the present invention relates to a biofuel cell that uses organic matter that can generate electricity while treating wastewater containing organic matter as a fuel, wherein the reducing power generated when the organic matter in the wastewater is metabolized by microorganisms is converted into electrical energy. A biofuel cell that can be converted directly.

A biofuel cell is a device that converts the reducing power generated in the energy metabolism of the organism into electrical energy by using a living organism or a part thereof. In the microbial fuel cell, the reducing power generated when the microorganism acting as a catalyst oxidizes a substrate to electrical energy. To convert, electrons from energy metabolism must be transferred from the microorganism to the electrode. However, most biological cells, including microorganisms, are wrapped in lipid membranes, which are non-conductors, so that direct electron exchange between microorganisms and electrodes cannot be achieved. Therefore, when using microbial cells as a catalyst, an appropriate electron transfer medium should be used to facilitate electron transfer between the organism and the electrode. Therefore, both the oxidized type and the reduced type used an electron transporter having a high lipophilic property that can easily pass through the membrane.

In particular, the roller (Roller) such as the Proteus vulgaris (Proteus vulgaris), E. coli (Escherichia coli), alkali jeneseu oil Trojan Perth (Alcaligenes eutrophus), azo Sat bakteo croissant OKO glutamicum (Azotobacter chroococum), Bacillus sub-blocks bus (Bacillus subtilis) And thionine, methylene blue, brilliant cresyl blue, benzyl viologen, etc., as an electron transporting medium. Can be. In biofuel cells, the efficiency of biofuel cells compared with oxygen consumption differed significantly depending on the type of bacterial and electron transfer mediators (Roller et al., 1984, Journal of Chemical Technology and Biotechnology 34B: 3-12). .

Beneto et al. Produced up to 44 C (Coulomb) of current by constructing a fuel cell using sugar as fuel, bacteria from Proteus as catalyst, and thionine as electron transfer medium. Bennetto et al., 1985, Biotechnology letters, 7: 699-704. Robin (Robin) and the like as the biological catalyst Proteus vulgaris (Proteus vulgaris), as the electron transfer mediator-hydroxy-1,4-naphthoquinone (2-hydroxy-1,4-naphthoquinone : HNQ) using glucose as a fuel A biofuel cell with an electromotive force of 0.5 mA, 0.7 V was constructed (Robin et al., 1993, Applied Biochemistry and Biotechnology 30/40: 27-40). In addition, Harberman and Pommer also use a cobalt oxide, molybdenum / vanadium alloy, etc. as electrodes, and construct a fuel cell that uses hydrogen sulfide produced by sulfate-reducing bacteria in wastewater as fuel. mA / cm 2) was produced (Harbermann and Pommer, 1991, Applied Microbiology and Biotechnology 33: 128-133).

Recently, anaerobic bacteria using metal salts of ferric ions, tetravalent manganese, hexavalent uranium, hexavalent molybdenum and the like as electron acceptors have been isolated. Substances which can be used as substrates by these metal salt reducing bacteria include aliphatic compounds such as lactic acid, pyruvic acid, acetic acid, propionic acid, valeric acid and alcohol, and aromatic compounds such as toluene, phenol, cresol, benzoic acid, benzyl alcohol, and benzaldehyde. Lovley and Klug, 1990, Appilied and Environmental Microbiology 556: 1858-1864. Anaerobic bacteria are classified as fermenting bacteria and respiratory bacteria according to the characteristics of energy metabolism. Fermented bacteria break down sugars, proteins, and the like into organic acids, and respiratory bacteria completely oxidize fermentation products using reduction reactions of appropriate electron acceptors. The electron acceptors available for anaerobic hob bacteria to oxidize organic materials include ferric oxide [Fe (III)], nitrates, manganese dioxide, sulfates, and carbonates, and the most energy is due to the reducing power generated by the oxidation reaction of the same electron donor. Is produced when ferric oxide is reduced, which is known to be lowered in the order of nitrates, sulfates, and carbonates [Byeong Hong Kim, Microbiological Physiology, Academy Books, 1995].

Iron-reducing bacteria are fermented by the ferric compound used as an electron acceptor, so that the solubility in water is so low that when cultured in anaerobic conditions, about 65% of the cytochrome is placed in the outer membrane of the cell to transport the reducing power generated by the oxidation of organic matter inside the cell. It is known to reduce ions extracellularly (Myers and Myers, 1992, Jounrnal of Bacteriology 174: 3429-3438). Further, cheolhwan wonsegyun the city and Nella Fu tray Pacific Enschede (Shewanella putrefaciens) IR-1 has been reported that there may occur an electric current without an electron transfer mediator by supplying lactic acid or hydrogen as an electron donor [see: Park et al., 1996,. Abstract, IEC Special Symp., Sept .: 16-19].

On the other hand, the wastewater flowing into the wastewater treatment plant may contain a high concentration of iron, and because ferric hydroxide is used as a phosphorus remover, iron is present in the wastewater treatment apparatus at a relatively high concentration [ See Ledecke et al., 1989, Water Sceience and Technology 21: 325-337. Thus, ferric reducing bacteria are present in most activated sludges in wastewater treatment plants (Nielsen et al., 1996, Water Science and Technology 34: 129-136), and the reduction of ferric iron by microorganisms in activated sludge is anaerobic of sludge. It has been reported that it occurs in storage and that many iron-reducing bacteria are present. Rasmussen et al., 1994, Water Research 28: 417-425].

Based on the above facts, if anaerobic culture of various microorganisms in activated sludge or wastewater is carried out anaerobically, only microorganisms capable of using electrodes with constant potential as electron acceptors instead of the electron acceptors of the medium components will survive. Will be. Therefore, by this method, it is possible to selectively enrich and culture the electrochemically active bacteria among the various microorganisms present in the wastewater or activated sludge, and to have the unique electrochemically active activities in the various kinds of wastewater. Microbial species can be isolated.

It is an object of the present invention to provide a biofuel cell capable of producing electricity while purifying wastewater by performing an efficient electrode reaction using various wastewater and sludge without using an electron transfer medium.

It is also an object of the present invention to provide a method for generating an electric current using microorganisms having electrochemical activity in wastewater and activated sludge, and treating the wastewater using the same.

An object of the present invention is a biofuel cell comprising a positive electrode and a negative electrode, a conductive medium of these positive electrodes and a negative electrode, and an ion exchange membrane between these two poles, wherein the negative electrode includes wastewater and activated sludge in the biofuel cell. Can be achieved.

1 is a schematic diagram of a biofuel cell according to the present invention using a graphite nonwoven fabric as an electrode and comprising a positive and negative electrodes and a cation exchange membrane separating them.

Figure 2 is a graph showing the reduction in current, cool room and COD generated as a result of using starch wastewater and aerobic sludge in the biofuel cell according to the present invention.

Figure 3 is a graph showing the reduction of current, cool room and COD generated as a result of using starch wastewater and anaerobic sludge in the biofuel cell according to the present invention.

Figure 4 is a graph showing the reduction of current, cool room and COD generated as a result of using livestock wastewater and anaerobic sludge in a biofuel cell according to the present invention.

Figure 5 is a graph showing the reduction of current, cool room and COD generated as a result of using septic tank wastewater and anaerobic sludge in the biofuel cell according to the present invention.

Figure 6 is a scanning electron micrograph of the microorganisms having the electrochemical activity attached to the electrode surface and after use before use in the biofuel cell according to the present invention.

The biofuel cell according to the present invention comprises an anode and a cathode, a conductive medium of these anodes and a cathode, and an ion exchange membrane between these two poles, and the cathode portion includes wastewater and activated sludge.

As described above, the microbial species having electrochemical activity among the microorganisms contained in the wastewater and activated sludge of the biofuel cell according to the present invention are grown by using an electrode having a constant potential as an electron acceptor to grow and culture. Therefore, the biofuel cell according to the present invention operates by using the enriched cultured microorganism as a catalyst and organic matter present in the wastewater as the fuel.

1 is a schematic view showing the structure of a biofuel cell according to the present invention.

Graphite felt, a kind of graphite electrode, may be used as the anode and cathode of the biofuel cell, and a cation exchange membrane may be used to minimize the resistance of the fuel cell itself. Buffer is used as the conductive medium of the positive electrode, and it is preferable to use 50 mM phosphate buffer adjusted to pH 7.0. In addition, the anode maintained the anaerobic state by continuously injecting air to maintain a saturation state, the cathode by injecting nitrogen through the gas oven to remove oxygen completely.

By anaerobic conditions as described above, only the microorganisms that can use the electrode among the bacteria present in the wastewater and the activated sludge as the electron acceptor can finally survive, thereby selectively enriching and culturing only the electrochemically active bacteria, By using the concentrated cultured microbial species as a microbial catalyst of a biofuel cell, the microorganisms can metabolize various organic substances present in the wastewater, and generate power by using the reducing power generated in the reaction with the electrode. In addition, the organic matter in the wastewater is metabolized by the enriched microorganisms, thereby reducing the concentration of organic matter in the wastewater can achieve the wastewater treatment effect.

Preferably, in the biofuel cell according to the present invention, starch wastewater and anaerobic sludge may be used at the negative electrode portion, and starch wastewater and aerobic sludge may be formed at the positive electrode portion. At the negative electrode site, which is maintained in anaerobic state, the enriched electrochemically active bacteria generate electric current by using organic matter in the waste water as fuel, and the generated cations pass through the cation exchange membrane separating the negative electrode and the positive electrode, and move to the positive electrode to oxygen. It is converted to water at the saturated anode, allowing for continuous current generation. At this time, the wastewater component of the positive electrode can be reduced COD by metabolizing organic matter by aerobic microorganisms. Therefore, by this method, the wastewater of all parts of the cathode and the anode can be treated simultaneously.

Hereinafter, the present invention is described in more detail by the following examples, but is not limited thereto.

<Example 1>

In this embodiment, in the biofuel cell according to the present invention, the change in the number of colonies of microorganisms using iron as an electron acceptor among the microorganisms present in the wastewater was measured. The medium used was phosphate buffer basal medium (PBBM), and the medium components were yeast extract 1 g / L, ammonium chloride 1 g / L, Macro-mineral (II) 25 ml / L (6 g KH ₂ PO ₄ per 1 L). , 12 g NaCl, 2.4 g MgSO ₄ · 7H ₂ O, 1.6 g CaCl ₂ · 2H ₂ O), trace elements 2 ml / L (12.8 g nitroacetic acid, 0.1 g FeSO ₄ · 7H ₂ O, 0.1 g MnCl ₂ 4H ₂ O, 0.17 g CoCl ₂ 6H ₂ O, 0.1 g CaCl ₂ 2H ₂ O, 0.1 g ZnCl ₂ , 0.02 g CuCl ₂ H ₂ O, 0.01 g H ₃ BO ₃ , 0.01 g molybdenum salt, 1.0 g NaCl, 0.017 g Na ₂ SeO ₃ 0.026 g NiSO ₄ · 6H ₂ O), 0.1 ml / L of vitamin liquid (0.002 g biotin, 0.002 g folic acid, 0.010 g B ₆ (pyridoxine) HCl, 0.005 g B ₁ (thiamine) HCl, 0.005 g B ₂ (riboflavin), 0.005 g nicotinic acid (niacin), 0.005 g pantothenic acid, 0.0001 g B ₁₂ (cyanocorpalamine) crystals, 0.005 g PABA, 0.005 g riphonic acid (thioctic acid), resazurin (0.2 %) 1 ml / L and 1.8% of agar was added to prepare a flat medium.

20 mM of acetic acid, 30 mM of lactic acid, and 20 mM of glucose were used as electron donors, and 20 mM of ferric pyrophosphate, which is a water-soluble iron, was used as an electron acceptor. In the first stage, samples of aerobic sludge and anaerobic sludge of the fuel cell were diluted with physiological saline (0.8% brine) to measure CFU (Colony Forming Unit / ml). After months, the same media and methods were used for measuring the results.

Cell count changes in fuel cells sample Electron donor (mM) Electron Receptor (mM) Primary Secondary 3rd Aerobic sludge Acetic acid (20) Ferric Pyrophosphate (20) 2.8 × 10 ⁷ 0.9 × 10 ⁴ 5.1 × 10 ³ Glucose (20) Ferric Pyrophosphate (20) 8.0 × 10 ⁷ 1.3 × 10 ⁵ 4.2 × 10 ⁴ Lactic Acid (30) Ferric Pyrophosphate (30) 6.4 × 10 ⁷ 1.1 × 10 ⁵ 4.1 × 10 ⁴ Anaerobic sludge Acetic acid (20) Ferric Pyrophosphate (20) 3.6 × 10 ⁵ 5.4 × 10 ⁵ 1.5 × 10 ⁵ Glucose (20) Ferric Pyrophosphate (20) 2.1 × 10 ⁵ 8.4 × 10 ⁵ 1.4 × 10 ⁵ Lactic Acid (30) Ferric Pyrophosphate (20) 1.7 × 10 ⁵ 1.5 × 10 ⁵ 2.3 × 10 ⁵

As can be seen in Table 1, the aerobic sludge sample is made to anaerobic state of the negative electrode portion of the fuel cell is selected as the only non-ferrous anaerobic strain, and continues to decrease, it is judged that only the microorganisms with electrochemical activity thickening culture, anaerobic sludge The sample increased anaerobic bacteria in the second phase and decreased in the third phase, so that only certain microorganisms with electrochemical activity were enriched.

<Example 2>

This embodiment looks at the characteristics of biofuel cells using starch wastewater (source: Samyang Genex, Incheon, Korea) and aerobic sludge (source: starch wastewater treatment sludge of Samyang Genex Plant, Incheon, Korea). It is for. 350 mg of graphite nonwoven fabric was used as an anode and a cathode. 50 mM phosphate buffer was used as the conductive medium of the positive electrode, and the positive electrode and the negative electrode were connected using a cation exchange membrane. Air was continuously injected into the conductive medium of the positive electrode to maintain the oxygen saturation state, and the negative electrode maintained the anaerobic environment by removing nitrogen dissolved by injecting nitrogen completely removed through the gas purification oven. The pH of all buffers used for the test was adjusted to 7.0. The resistance of the fuel cell was set to infinity at the beginning of the reaction, and when the voltage reached its maximum value, the current produced at 1 mA was measured. The biofuel cell was used by mixing aerobic sludge and starch wastewater in a 1: 4 ratio, and the total reaction amount was 25 ml. Wastewater supply was replaced by 5 ml after the current generation was reduced by using organic matter in the wastewater of the microorganism. Voltage generation was measured at 120 second intervals using a potential start meter (2000 multimeter, keithley Instrument, Inc, USA). The current generation amount was converted by dividing the measured voltage by the resistance (1kΩ). The chemical oxygen demand (COD) of wastewater was analyzed using standard methods (see Standard Method for the Examination of Water and Wastewater, Closed Reflux Method, 19th edition, 1995). As shown in FIG. 2, the current was generated up to 0.21 mA, the coolum amount increased to 26.5 C (coulumb), and the chemical oxygen demand decreased from 1100 ppm to 58 ppm. This experiment confirmed that the reducing power generated when the substrate of the wastewater is oxidized is consumed through the direct electrode instead of the electron acceptor to generate a current and to purify the starch wastewater.

<Example 3>

In this example, current productivity and wastewater treatment were tested in biofuel cells using starch wastewater and anaerobic sludge (Source: Samyang Genex, Incheon, Korea). The conditions and analysis of the fuel cell were the same as in Example 1.

The biofuel cell was used by mixing anaerobic sludge and starch wastewater in a 1: 4 ratio, and the total reaction amount was 25 ml. As shown in FIG. 3, the current was generated up to 0.22 mA, the coolum amount increased to 26.7 C (Coulumb), and the chemical oxygen demand decreased from 1,940 ppm to 55 ppm. Therefore, this experiment confirmed that the reducing power generated when the substrate in the starch wastewater is oxidized is consumed through the direct electrode to generate a current and to purify the starch wastewater.

On the other hand, in order to determine the degree of microbial cultivation on the electrode after use in the biofuel cell according to the present invention, the microorganisms having the electrode surface before use and the electrochemical activity attached after use were examined by electron microscopy (S-4100, FE-SEM, Hitachi, Japan) and the results are shown in FIG. As shown in Figure 6, it was confirmed that the microorganisms having electrochemical activity is attached to the electrode surface.

<Example 4>

In this example, the current productivity and wastewater treatment in the biofuel cell were tested in the same manner as in Example 2 except that the wastewater was replaced with livestock wastewater (source: Ansan Livestock, Ansan, Korea). The conditions and analysis of the fuel cell were the same as in Example 1. As shown in FIG. 4, the current generation amount was generated up to 0.21 mA, the coolum amount was increased to 12 C (Coulumb), and the chemical oxygen demand was decreased from 1,030 ppm to 350 ppm. Through this experiment, it was confirmed that the reducing power generated when the substrate in the livestock wastewater is oxidized can be directly transmitted to the electrode to generate an electric current and purify the livestock wastewater.

Example 5

In this example, current generation and wastewater treatment were tested in a biofuel cell using a septic tank wastewater (source: Korea Institute of Science and Technology). The operating conditions and analysis method of the fuel cell were the same as in Example 1. As shown in FIG. 5, the current generation amount was generated up to 0.05 mA, the coolum amount was increased to 2.3 C (Coulumb), and the chemical oxygen demand was reduced from 680 ppm to 250 ppm. Through this experiment, it was confirmed that the reducing power generated when the substrate was oxidized in the septic tank wastewater was directly transmitted to the electrode to generate an electric current and to purify the septic tank wastewater.

In the biofuel cell according to the present invention, by using wastewater and sludge, the microorganisms having electrochemical activity in the sludge use substrates in the wastewater, and part of the reducing power generated in energy metabolism is used for cell production, and the rest is used as electron acceptors. The wastewater can be purified by generating a current. Therefore, when various wastewaters are used as fuels of the biofuel cell, effects of electric energy production and wastewater treatment can be simultaneously obtained.

Claims (4)

A biofuel cell comprising an anode and a cathode, a conductive medium of these anodes and a cathode, and an ion exchange membrane between these two poles, wherein the cathode portion contains activated sludge and wastewater. The biofuel cell of claim 1, wherein the activated sludge and the wastewater are selected from the group consisting of starch wastewater, livestock wastewater, and clarification wastewater. The biofuel cell according to claim 1, wherein sludge and waste water are also contained in the anode portion. In the biofuel cell according to claim 1, the anaerobic conditions are created by injecting nitrogen into the cathode to remove dissolved oxygen, and the oxygen is saturated by continuously injecting air into the anode to create an electrochemical activity present in wastewater and activated sludge. A method of enriching and culturing bacteria, using the cultured active bacteria as a microbial catalyst, and using organic matter in the wastewater as a fuel to produce electricity and simultaneously treat wastewater.