Narrow pH tolerance found for a microbial fuel cell treating winery wastewater.

AIMS: The use of microbial fuel cells (MFC) to treat winery wastewater is promising; however, an initial acidic pH, fluctuating chemical oxygen demand (COD) levels and a lack of natural buffering in these wastewaters make providing a suitable buffer system at an ideal buffer to COD ratio. METHODS AND RESULTS: A lab scale MFC was designed, inoculated with anaerobic winery sludge and fed with synthetic winery wastewater. It was observed that at pH 6·5, the MFC performed best, the maximum output voltage was 0·63 ± 0·01 V for 60 ± 3 h, and the COD removal efficiency reached 77 ± 7%. The electrogens were affected by pH much more than the bulk COD degrading organisms. Fluorescent in situ hybridization suggested Betaproteobacteria played a significant role in electron transfer. CONCLUSIONS: A ratio of 1 mmol l-1 phosphate buffer to 100 mg l-1 COD was ideal to maintain a stable pH for MFCs treating synthetic winery wastewater. SIGNIFICANCE AND IMPACT OF THE STUDY: The results find the narrow pH tolerance for MFCs treating winery wastewater and demonstrate the significance of pH and buffer to COD ratio for steady performance of MFCs.