ELECTRICITY GENERATION IN MICROBIAL FUEL CELL BY THE DECOMPOSITION OF ORGANIC SLURRY USING E-COLI

Transcription

1 VSRD International Journal of Technical & Non-Technical Research, Vol. IV Issue XI December 2013 / 245 e-issn : , p-issn : VSRD International Journals : RESEARCH ARTICLE ELECTRICITY GENERATION IN MICROBIAL FUEL CELL BY THE DECOMPOSITION OF ORGANIC SLURRY USING E-COLI 1Durgesh Singh Songera* and 2 Akshay Kabra 1Assistant Professor, 2 Scholar, 1,2 Department of Chemical Engineering, Institute of Engineering & Science, IPS Academy, Indore, Madhya Pradesh, INDIA. *Corresponding Author : durgesh.songera@gmail.com ABSTRACT The microbial fuel cells (MFCs) are a new form of renewable energy technology that can generate electricity from organic waste. The aim of our research work is to fabricate two-compartment system and study various parameters with respect to time. The MFC setup consists of two compartments of 500 ml capacity each, embedded with thin copper plate as electrodes (1.5*7cm 2 ). Anode compartment consists of organic sludge composed of septic tank water and cow dung. Cathode compartment consists of weak electrolyte acetic acid. Agar- agar salt bridge is essential part to complete the circuit. To enhance ions mobility, 100 ml liquid ammonia is added to salt bridge. Controlled anaerobic decomposition of organic waste done by, E-coli culture at constant temperature 37 C. The maximum voltage and power density is achieved on 13 th day.832v, m-w/cm 2 respectively. Appreciable amount of B.O.D (63%) and C.O.D (35%) also reduced. Keywords : Anode, Cathode, E.Coli, Microbial Fuel Cell, B.O.D, C.O.D. 1. INTRODUCTION Today, high energy requirement for conventional sewage treatment systems are demanding for the alternative treatment technology, which will be cost effective and require less energy for its efficient operation. It has been known for almost one hundred years that bacteria could generate electricity. Only in the past few years has this capability become more than a laboratory novelty. Microbial fuel cells (MFCs) are electrochemical conversion devices, excepting that the power generated is derived from bacterial metabolism. Microbial fuel cells (MFCs) combine the generation of electricity with the treatment of wastewater through the metabolic oxidation of organic and inorganic substrates by bacterial species living within a bio film. [1] Microbial Fuel cell basically having two types mediator and mediator free microbial fuel cell. In mediated fuel cells, bacteria are suspended in the anode solution together with the nutrient, and because of some sort of electron carrier that is added to the liquid in the anode chamber, the electrons can be transported from the bacteria through the liquid to the electrode. Almost any type of bacteria can be used in this type of MFC, but a lot of electrons and energy is however lost in the process, which limits the total efficiency of the fuel cell drastically. Most of the microbial cells are electrochemically inactive. The electron transfer from microbial cells to the electrode is facilitated by mediators such as thionine, methyl blue, methyl viologen, humic acid, and neutral red and so on. Most of the mediators available are expensive and toxic. [1-2] Mediator-free microbial fuel cells or Mediator-less fuel cells however, are fuel cell that does not require any additional electron carrier in the solution in order to transport electrons from the bacteria to the electrode. This process gives better control over the fuel cell and allows for a higher efficiency potential. However, they do require very special bacteria. Although there is great potential of MFCs as an alternative energy source, novel wastewater treatment process, and biosensor for oxygen and pollutants, extensive optimization is required to exploit the maximum microbial potential. [2-3] Bacteria can be used in fuel cell to catalyze the conversion of organic matter, present in the wastewater, into electricity. [4-5] 2. MATERIALS AND METHODS Formulation of Setup : Two poly vinyl chloride containers having capacity of 500 ml each were purchased from local market. The shape of containers was rectangle and thread top so it can air tied well. Containers are round holed just 5cm above their bottom to introduce a salt bridge (hollow glass rod) in it. In the centre of the glass rod, an opening is provided to pore solution in the salt bridge. Salt Bridge Preparation : In order to make a salt bridge solution, 5 gm of McConkey agar powder was dissolved in 100 ml of distilled water. The solution continues heated and agitated till it not gets properly mixed. After some time as the temperature of Agar solution was decreased to nearly about 50 C, 2.5 ml of ammonia was added. The slurry is poured in salt bridge and after a certain time, this thick solution is converted into a semisolid layer. This feature allows the protons produced to pass from the anode chamber to the cathode chamber. Anode & Cathode Chambers : The anode compartment

2 Durgesh Singh Songera and Akshay Kabra VSRDIJTNTR, Vol. IV (XI) December 2013 / 246 consists of organic waste; which is prepared of septic tank water and cow dung cakes (100gms) mixed together and 500ml thick slurry was prepared. Dilute Acetic acid was used as an electrolyte in cathode compartment. Thin Copper electrodes having dimensions (1.5*7cm 2 ) were typically placed in both the compartments. Anaerobic decompose is done with the help of E.coli culture in organic slurry on the anode side. To enhance the kinetic growth, a constant 37 C temperature was maintained with the help of incubator. To maintain anaerobic condition, every joint was fixed with m- seal. Continuous voltage and current values were taken with the help of multi-meter and same study was continued for 18 days. Data Capture and Calculations of Efficiency: Electrode output was recorded in volts V (mv) against time by using a multi-meter (mastch model no m3900 with ± 2% error). Current density was calculated as i = I/A, I (ma), and A (10.5 cm 2 ) the projected surface area of the studied electrode. Power density was calculated according to P= iv (mw/cm 2 ). The efficiency was calculated as described by The MFC second law of thermodynamics. Efficiency can be evaluated by relating the theoretical electromotive force to the measured cell potential based on the assumption that the simple reactions evaluated at the anode and cathode are similar to that of the more complicated reactions involved with the bio-degradation of wastewater. [6] η MFC = Wactual Wmax = Vmeasured (n.f) Eemf (n.f) = Vmeasured Eemf Overall, the maximum amount of voltage potential in a MFC with acetate oxidation and oxygen reduction in the cell emf or, E (emf) = 1.03 V. [7] Where η MFC = MFC second law efficiency W (actual) = Actual work output V (measured) = Measured voltage potential. B.O.D. and C.O.D Calculation: To calculate the BOD and COD value of slurry, first pass it through a fine mesh and then the BOD value was calculated by 5 days standard method. The concentration of organic matter in the MFC was measured by COD analysis via Standard Methods as per IS: 3025(part 58) - reaffirmed COD removal was calculated as ECOD = [(CODin - CODout)/CODin]*100%, where CODin is the influent COD and CODout is the effluent COD and the same thing is repeated for EBOD also. [8] Fig. 1 : Schematic Diagram of Double Chamber Microbial Fuel Cell

3 Durgesh Singh Songera and Akshay Kabra VSRDIJTNTR, Vol. IV (XI) December 2013 / RESULTS AND DISCUSSIONS Currant (ma)/ cm Currant (ma)/ cm No. of days Fig. 2 : Numbers of Days Versus Potential and Current Density of MFC According to the figure 2 we noticed that there is increase in the current and voltage due to the appreciable growth of E.Coli bacteria in the anode chamber which generates a large number of charges in the chamber. Maximum voltage and current density was generated on day 13 th (.823V,.034mA/cm 2 ) Power density mw/ cm Power density mw/ cm No. of days Fig. 3 : Numbers of Days Versus Potential and Power Density of MFC From the figure 3 it is very clear that voltage and power density from day one (.25V, E-05 mw/cm 2 ) to till day twelve (0.826, mw/cm 2 ) gradually increases. In this region, the microorganism present in slurry shows growth phase. Constant growth rate was achieved in day twelve and thirteen. The maximum amount of voltage and power density was obtained on day thirteen (.832, mw/cm 2 ) respectively. After then, death phase starts and microorganism start to die and voltage value decreases gradually. [9]

4 Durgesh Singh Songera and Akshay Kabra VSRDIJTNTR, Vol. IV (XI) December 2013 / E fficie ncy 0.6 Efficiency N o. o f da ys Fig. 4 : Number Day vs. Efficiency of MFC As the time passes, E.coli growth becomes rapid at the beginning which results in better power output. On day one efficiency is 22.7±2% and it becomes maximum on the 13 th day with a value of ±2%, after that, growth cycle of bacteria starts decaying and hence efficiency decreases on 18 th day to ±2%. S. no Table 1 : BOD and COD value of MFC Parameters Initial (mg/liter) Final (mg/liter) Removal % 1 BOD (63%) 2 COD (35%) It is already well studied that power density increases with the increase in COD concentration and vice versa. The power density was modeled as a function of COD concentration using the Monod-type equation. The effect of COD value in wastewater on power generation was investigated in the range. [10-11] 4. CONCLUSION After analyzing the organic slurry, which was the homogeneous mixture of organic waste & sewage water, we concluded that organic sewage contains an appreciable amount of chemical energy which can be converted in usable form. The current was generated at the outer circuit of the cell to utilize it for the various purposes. By treating the liters of slurry, 2-3 milli amperes current was generated which was more than enough to glow a LED. The Microbial Fuel Cell was used effectively for synthetic wastewater treatment with COD and BOD removal. The power generation by this system can be increased by replacing the various parameters such as electrolyte solution, electrodes and modification of the cell. MFC technology may provide a new method to wastewater treatment with low operating cost, making wastewater treatment more affordable for developing and developed nations. 5. REFERENCES [1] Frank Davis, S eamus, P.J. Higson Biofuel cells Recent advances and applications, Biosensors and Bioelectronics Elsevier 22, , [2] Patrick D. Kiely, Roland Cusick, Douglas F. Call, Priscilla A. Selembo, John M. Regan, Bruce E. Logan, Anode microbial communities produced by changing from microbial fuel cell to microbial electrolysis cell operation using two different wastewaters, Bioresource Technology, Elsevier, 102, , [3] Cassandro Murano and Keith Scott Microbial fuel cells utilizing carbohydrates, Journal of Chemical Technology and Biotechnology, wiley inter science,82:92 100, [4] Chang seop, Hyunsoo Moon,Orianna Bretschger, Byung Hong Kim et.al,electrochemical active bacteria(eab)and mediatorless microbial fuel cells, microbial biotechnology, the koreascoity of microbiogy and boitechlogy,16(2), ,2006 [5] Byung Hong Kim & In Seop Chang & Geoffrey M. Gadd Received, Challenges in microbial fuel cell development and operation, Appl Microbiol Biotechnol, Springer-Verlag 76: , 2007 [6] Ieropoulos Dincer hydrogen and fuel cell technologies for sustainable future, Jordan journal of mechanical and industrial engineering, , 2008.

5 Durgesh Singh Songera and Akshay Kabra VSRDIJTNTR, Vol. IV (XI) December 2013 / 249 [7] Eric A Zielke thermodynamic analysis of a single chamber microbial fuel cell report, may 5, [8] Shaoan Cheng a, Hong Liu b, Bruce E. Logan Increased performance of single-chamber microbial fuel cells using an improved cathode structure Electrochemistry Communications (2006) [9] Metcalf & eddy wastewater engineering treatment and reuse, tata mcgraw- hill fouth edition,, 2005 [10] Min B., Kim, J.R., Oh, S.E., Regan, J.M., Logan, B.E., Electricity generation from swine wastewater using microbial fuel cells. Water Res. 39, , [11] Feng Zhu, Wancheng Wang, Xiaoyan Zhang, Guanhong Electricity generation in a membrane-less microbial fuel cell with down-flow feeding onto the cathode Tao Bioresource Technology, (2011).

6 Durgesh Singh Songera and Akshay Kabra VSRDIJTNTR, Vol. IV (XI) December 2013 / 250