Comparative study of energy production and treatment of municipal and dairy wastewater via microbial fuel cell technology: process evaluation towards optimization

Microbial fuel cells (MFCs) produce clean energy and treat wastewater simultaneously. In this study, real wastewater from municipal and dairy sources were used for power generation and wastewater treatment in MFC. The same media and anaerobic conditions were used for keeping them in the 100-ml beaker before being applied to the MFCs. Performance of the MFC is affected by operating conditions, so they must be optimized. Aeration (60-200 ml/min) and yeast extract (2-10 g/l) are important operating parameters used to achieve the best response for power density and COD removal. These parameters are optimized using central composite design (CCD) coupled with response surface methodology (RSM). Based on experimental results, power density and COD removal models are well supported by experimental data. For both wastewater types, the optimal amount of aeration and yeast extract is about 125 ml/min and 2 g/l, respectively. The optimal operating conditions resulted in a power density of 481 mW/m(2) for municipal wastewater microorganisms in 1180 mV, and 410 mW/m(2) for dairy wastewater in 1070 mV.The MFC which works with municipal wastewater microorganisms has a lower internal resistance compared to dairy wastewater. MFC reduced COD in municipal and dairy wastewater by 84% and 70%, respectively, and their coulombic efficiencies (CE) were 37% and 17%, respectively. The scanning electron microscopy (SEM) results showed that microorganism attachment to the electrode in municipal wastewater was significantly higher than in dairy wastewater. Further, the CE found that more organic matter could be degraded into electricity in municipal wastewater than in dairy wastewater. According to this study, MFC works better with higher and more complex wastewater due to the various bacteria embedded on the electrodes and a higher wastewater content.