Enhancing bioenergy recovery from biomass-rich saline starch wastewater via advanced UASB Systems: Roles of bioelectrochemical and iron-based strategies

Abstract

Biomass-rich saline wastewater from modified tapioca starch processing presents a promising yet underutilized feedstock for bioenergy production. However, high salinity and volatile fatty acid (VFA) accumulation pose challenges to anaerobic digestion. This study focuses on enhancing bioenergy recovery from organic biomass in saline effluents by employing three advanced Upflow Anaerobic Sludge Blanket (UASB) configurations: bioelectrochemical system (BES-UASB), zero-valent iron addition (ZVI-UASB), and salt-tolerant microbial adaptation (STM-UASB). Among them, BES-UASB demonstrated the highest methane yield (0.34 m³/kg COD_removed-day) and COD removal efficiency (88.65 %) under high total dissolved solids (∼20,000 mg/L), reflecting effective bioconversion of biomass into bioenergy. BES-UASB also showed stable operation at an organic loading rate of 25 kg/m³·day and enhanced methane content (63.1–67.4 %). In contrast, ZVI-UASB and STM-UASB yielded lower methane and exhibited limited adaptability. The findings confirm the potential of integrating bioelectrochemical and iron-based enhancements to improve the anaerobic conversion of organic biomass into renewable bioenergy, particularly in saline agro-industrial wastewater systems. This work significantly contributes to sustainable biomass utilization and circular bioeconomy solutions, aligning with UN Sustainable Development Goals for affordable and clean energy (SDG 7) and climate action (SDG 13) in water-stressed regions.