Effects of Retention Time, pH, Temperature and Type of Fruit Wastes on the Bioelectricity Generation Performance of Microbial Fuel Cell during the Biotreatment of Pharmaceutical Wastewater: Experimental Study, Optimization and Modelling

In this study, response surface methodology through Box-Behnken design was used to evaluate the interactive effects and optimization of retention time (8-166 days), pH (4.5-7.5), temperature (25-60 °C), and quantity of fruit waste additives (10-50 g) on the power generation performance of double-chamber microbial fuel cell (MFC) in the biotreatment of pharmaceutical wastewater (PWW). The effects of fruit wastes (mango fruit waste (MFW), orange fruit waste (OFW), pineapple fruit waste (PFW) as single and all (mixed) fruit wastes (AFW) on the coulombic efficiency (CE) of the MFC, as well as the biochemical oxygen demand (BOD) and chemical oxygen demand (COD) removal efficiencies of the PWW were investigated. A quadratic regression model was formulated based on the four operating variables to predict the power generation. From statistical analysis, the four operating variables significantly affected the power generation performance of MFC. The power generation performance of MFC was significantly influenced by the interaction between the retention time and pH, retention time and temperature, retention time and quantity of additives, pH and quantity of additives, and temperature and quantity of additives. A retention time of 38 days, a pH of 7.13, a temperature of 55 °C, and a quantity of additive of 38 g were obtained as the optimum operating conditions for achieving an optimum power generation of 228479.70 mW. The MFC performance with regards to maximum power density, COD and BOD removal efficiencies, as well as CE, can be ranked as follows: (AFW + PWW) > (PFW + PWW) > (OFW + PWW) > (MFW + PWW) > (PWW alone without Fruit Wastes).