Short Communication
Electricity Generation from Slaughterhouse Wastewater using Microbial Fuel Cell Technology Ghanapriya .K1*, Sachindri Rana2 and P.T. Kalaichelvan1 1. Centre for Advanced Studies in Botany, University of Madras, Chennai 600025, Tamil Nadu, India 2. Department of Biotechnology, VELS University, Pallavaram, Chennai, India
Abstract Proper treatment of animal waste and resource recycling to reduce its environmental impact are currently important issues for the livestock industry. Slaughterhouse wastewater contains organic matter available for microbial energy recovery. This can be accomplished with Microbial Fuel Cells (MFCs). A microbial fuel cell is expected to play roles in both waste-water purification and energy recovery. It is a device that converts chemical energy into electricity through the catalytic activities of microorganisms like bacteria. Although there is great potential of MFCs as an alternative energy source, extensive optimization is required to exploit the maximum microbial potential. Keywords: Microbial Fuel Cell (MFCs), Slaughterhouse wastewater; Electricity generation; Wastewater treatment
Introduction Global energy demand is increasing. Problems of pollution and global warming associated with petroleum products are acting as a major impetus for research into alternative renewable energy technologies. The proper treatment of slaughterhouse wastewater to reduce its environmental impact is also an important issue for the livestock industry (Jeffrey et al., 2009). It contains organic matter available for microbial energy recovery. Reducing the BOD value in it is necessary for its purification. Microbial Fuel Cells offer a possible (and partial) solution to this problem. MFC treatment can reduce the BOD in wastewater by degrading organic matter (Liu et al., 2004). While the detailed mechanism of generating electricity by MFC is not completely understood, many bacterial capable of generating electricity have been identified (Kim et al., 2002; Bond and Lovley, 2003; Rabaey et al., 2004). Microbial fuel cells seek to add the diversity of microbial catalytic abilities to this high-efficiency design, allowing waste organic matter to be converted into electricity (Wingard et al., 1982). They are an alternative to conventional methods of generating electricity, for small scale applications (Bennetto, 1990). Microbial fuel cells have potential to generate electricity from organic wastes while oxidising them to less harmful forms (Moon et al., 2006; Ieropoulos et al., 2005; Liu et al., 2004). Thus MFC Technology plays two roles: wastewater purification and energy recovery (Yokoyama et al., 2006). Microbial fuel cell usually comprise of four major components – anode compartment, cathode compartment, ion exchange membrane and the electrodes. Anode compartment forms the biological compartment of MFC, as it consists of microbes (biocatalyst) either in pure/mixed form (Bond and Lovley, 2003, 2005; Chaudhuri and Lovley, 2003; Holmes et al., 2004; Kim et al., 1999), which oxidizes the organic substances in the wastewater and releases free electrons. The bacterial growth in this chamber produces the necessary protons and electrons through metabolic reactions. The metabolic reactions are not allowed to proceed to completion and the intermediate electrons are drawn from the cell to do the electrical work (Venkatamohan et al., 2007). Cathode compartment is the abiotic compartment of MFCs where the released electrons (from anode) are
transferred to oxygen as a terminal electron acceptor. The ion exchange membrane helps in the transfer of protons from the anode compartment to the cathode compartment and helps to physically block oxygen diffusion into the anode chamber (Chae et al., 2008). Hence it is generally called Proton Exchange Membrane (PEM). Commonly used Proton Exchange Membranes are Nafion or Ultrex. Since PEMs are costly, here we have used salt-bridgesto maintain electroneutrality and allow current to flow (Booki et al., 2005). The salt-bridge contains a saturated solution of some inert salt, usually Sodium chloride. The salt is chosen specifically to be inert based on the rest of the reagents in the system. The major role of electron transfer is due to electrodes. Some commonly used electrodes are carbon rod, carbon/graphite sheet (Venkatamohan et al., 2008; Pham et al., 2004), stainless steel, glassy carbon, etc.
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Materials and Methods
Slaughterhouse wastewater was collected from Saidapet Slaughterhouse, Corporation of Chennai, Tamil Nadu (India). A two chambered fuel cell was constructed. Two plastic containers each with diameter 20 mm were taken and marked cathode and anode. Two holes of diameter 6 mm and 1.5 mm were made on each of the lids for the insertion of the salt-bridge and electrodes as shown in Figure (1). In the anode container, 100 mL of the Anodic Inoculation was used and in the cathode container 100 mL Potassium permanganate solution was used and the container lids were closed and sealed with tape as shown in Figure (2).
Salt-bridge was made with 5 mm diameter level tube. The salt-bridge contained a mixture of 1M Potassium chloride with 5% Agar. The mixture was sucked into the level tube. This salt-bridge was inserted into both the containers through one hole on both containers and sealed with
*Corresponding Author E mail :
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Time hrs
Series Connection, V
Parallel Connection, V
0
3.97
0.64
24
4.12
0.66
48
4.44
0.63
72
4.69
0.69
96
4.97
0.71
120
5.15
0.74
144
5.32
0.66
168
5.49
0.79
192
5.65
0.85
216
5.84
0.88
240
5.98
1.03
264
6.18
1.06
288
6.01
1.01
312
5.84
1.00
336
5.62
0.88
360
5.58
0.87
384
5.31
0.88
Results and Discussion
408
5.28
0.82
The bacteria adhering to the anode surface degrade organic matter under anaerobic conditions. As a consequence of the degradation reaction, carbon dioxide, protons and electrons are thought to be produced (Yokoyama et al., 2006). The electrons flow through a circuit and the protons pass through the salt-bridge that is attached to the cathode. The protons and electrons react with oxygen on the cathode and become water (Venkatamohan et al., 2008). The slaughterhouse wastewater contains various types of anaerobic bacteria derived from the animals and birds and we therefore used them as the seed bacteria for the MFC (Yokoyama et al., 2006).
432
5.09
0.79
456
4.95
0.66
480
4.87
0.65
tape. Pencil lead with diameter 1 mm and length 18 mm was used as electrodes to collect the electrons in both anode and cathode with copper wire connections at the other hole on both the containers and sealed with tape. Carbon rod of 2 mm (diameter) X 20 mm (length) and Graphite sheet of 0.5 mm (thick) X 20 mm (length) X 10 mm (breadth) were also used as electrodes. These electrodes were relatively inexpensive and available easily. The electrodes were first soaked in 100% ethanol for 30 min. After this the electrodes were washed in 1 M Hydrochloric acid followed by 1 M Sodium hydroxide, each for 1 hr to remove possible metal and inorganic contaminations and to neutralize them. They were then stored in distilled water before use. 100 mL of slaughterhouse wastewater was directly inoculated in the anodic chamber. For the cathode chamber, 0.1 M Potassium permanganate solution was prepared. Variations were done using 0.1 M Potassium dichromate and 0.1 M Potassium ferricyanide solutions. The voltage was checked with a Multimeter (UNITY DT-830D). Time (hrs) Carbon rod (V) All the operations were carried out with different electrodes and 0 0.79 electrolytes. The MFCs were operated for 20 days at a room 24 0.82 temperature of 28°C. The specific MFCs with various electrodes and 48 0.84 various electrolytes which showed 72 0.89 the maximum electricity generation were combined and 96 0.97 connected in series and parallel connections to give higher 120 1.05 electricity. The voltage generation was noted. It was also connected to 144 1.12 LED to see if it glowed. 168
1.19
192
1.25
216
1.34
240
1.44
264
1.48
288
1.41
312
1.34
336
1.30
360
1.25
384
1.21
408
1.18
432
1.14
456
1.09
480
1.02
Change in the voltage output is p ossible through various Table1.Slaughterhouse wastewater with Potassium permanganate and modifications of the MFC. There is an increase in the electrical Carbon rod 38 l Advanced Biotech. Vol. 10
Table 2. Slaughterhouse wastewater with Carbon rod and Potassium permanganate in Series and Parallel connections using 5 MFCs.
Figure 1. Pictorial representation of Microbial Fuel Cell set-up using Salt-bridge Issue 03 l September 2010
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Figure 2. Microbial Fuel Cell set-up using Salt-bridge
Figure 3. Graph showing the voltage generation by MFC using Slaughterhouse wastewater with Pencil lead and various catholytes
Figure 4. Graph showing the voltage generation by MFC using Slaughterhouse wastewater with Potassium permanganate and various electrodes
Figure 6. Glowing LED by voltage generation using a set yp of MFC potential generation associated with the catholytes used (Park and Zeikus, 2003). MFC using permanganate generated more voltage than that produced by hexacyanoferrate (Kim et al., 2007). The Slaughterhouse wastewater yielded voltage generation with various electrolytes like Potassium permanganate, Potassium dichoromate and Potassium ferricyanide as shown in Figure (3) with a maximum generation of 0.73 V with Potassium permanganate solution. When different electrodes like Pencil lead, Graphite sheet and Carbon rod were used; the wastewater generated more voltage with Carbon rod as shown in Figure (4) with a maximum generation of 1.48 V. On analysis, it was found that, MFCs using Potassium permanganate as catholyte and Carbon rod as electrode yielded more voltage as seen in Table (1). Connecting several stacked MFCs in a series enabled the production of increased voltages (Kim et al., 2007). Now when several MFCs were connected with each other in Series and Parallel connections, it was seen that, maximum voltage generation was seen in Series connections (6.18 V) as shown in Table (2). This was quite higher when compared to the Parallel connection output as shown in Figure (5) enough to glow LED for 3 hrs as shown in Figure (6). Salt-bridge MFC is the simplest biological fuel cell that can be designed and studied (Venkatamohan et al., 2008). It was easy to make and was very economic also. MFC treatment can reduce the BOD in wastewater by degrading organic matter (Liu et al., 2004). Microbial fuel cells have potential to generate electricity from organic wastes while oxidising them to less harmful forms (Moon et al., 2006; Ieropoulos et al., 2005; Liu et al., 2004). Thus MFC Technology plays two roles: wastewater purification and energy recovery (Yokoyama et al., 2006).
Conclusions Slaughterhouse wastewater can be used to generate electricity by MFC Technology. MFCs yielded more volatage with Potassium permanganate as catholyte and carbon rod as electrode. When the MFCs were connected in Series the voltage generation was high enough to glow LED for 3 hrs. The MFC construction is easy with the utilization of Saltbridge. The idea of using Salt-bridge instead of the Proton exchange membrane is more economic as it is cost effective and easily available.
Acknowledgement
Figure 5. Graph showing the voltage generation by Series and Parallel connections of MFCs using Slaughterhouse wastewater 38 l Advanced Biotech. Vol. 10
The authors sincerely thank Dr. Rengasamy, Director, Centre for Advanced Studies in Botany, University of Madras, for providing necessary laboratory facilities.
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Citation: Ghanapriya. K, Sachindri Rana and P.T. Kalaichelvan, 2012. Electricity generation from slaughterhouse wastewater using microbial fuel cell technology. Adv. Bio Tech.
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