Bio-energy and water recovery from wastewater spiked with reverse osmosis reject concentrate using microbial fuel cell

• An MFC system was developed using wastewater and ROR water. • MFC 1 (75% ROR + 25% WW) achieved highest power density (233 mW/m 2 ) and COD removal (76%). • ROR water enhanced microbial activity and electron transfer due to higher ion content. • Coulombic efficiency was highest (14.6%) in MFC 1 due to lower organic load. • The study demonstrates a sustainable approach for ROR reuse and energy recovery. The global demand for freshwater and the environmental concerns related to reverse osmosis reject (ROR) water have highlighted the need for sustainable wastewater treatment solutions. Microbial fuel cells (MFCs) have emerged as an innovative solution for simultaneous wastewater treatment and bioelectricity production. This study developed a multi-chamber MFC system to evaluate the potential of bioelectricity generation from institutional wastewater supplemented with ROR water. The MFC consisted of three anodic chambers, referred to as MFC 1 , MFC 2 , and MFC 3 , filled with different compositions of ROR and wastewater: 75% ROR and 25% WW, 50% ROR and 50% WW, and 25% ROR and 75% WW, respectively, and a central cathodic chamber filled with aerated distilled water. The study analyzed key performance parameters including open circuit voltage (OCV), voltage, power density, current density, chemical oxygen demand (COD), and coulombic efficiency (CE). MFC 1 demonstrated the highest performance, recording a maximum OCV of 374 mV, a power density of 233 mW/m 2 , and 76% COD removal with a CE of 14.6%. The findings show that the supplementation of ROR water enhances microbial metabolism and electron transfer due to its higher content of inorganic ions, resulting in improved energy recovery and wastewater treatment. This study demonstrates the feasibility of integrating ROR water in MFC systems as a substrate amplifier for sustainable energy and water recovery.