Sugarcane Vinasse and Glycerol as Potential Carbon Sources for Sulfate-Rich Wastewater Treatment: Mitigating the Impacts of Acid Mine Drainage

This study investigated the anaerobic co-digestion of sugarcane vinasse (SV) and glycerol (GOH) as potential carbon sources for treating a sulfate-rich and acidic wastewater (pH 4.0-5.4). The sulfidogenic bioreactor operation was divided into six phases, varying carbon sources and COD/SO₄ ^{2^-} (chemical oxygen demand/sulfate) ratios. In Phases I-III, SV was the sole carbon source (COD/SO₄ ^{2^-} = 1.6-1.2). Phase IV employed co-digestion of SV and GOH, while Phases V and VI used GOH alone, with metals added in Phase VI to simulate acid mine drainage. The highest sulfate reduction (99%) was achieved under co-digestion of SV and GOH for a COD/SO₄ ^{2^-} ratio of 1.4, demonstrating that co-substrate addition can markedly enhance sulfidogenesis. Sulfate reduction was coupled with significant bicarbonate alkalinity generation (>900 mg of CaCO₃ L^-1) which stabilized the effluent pH near neutrality (5.3-7.4). In contrast, metal toxicity in Phase VI reduced the biomass performance, highlighting the importance of gradual microbial acclimation under inhibitory conditions. <i>Desulfovibrio</i> (5.3%) dominated among sulfate-reducing bacteria, while fermentative genera such as <i>Zymophilus</i> (24.8%), <i>Clostridium</i> (13.0%), and <i>Bacteroides</i> (11.5%) played key syntrophic roles in sustaining sulfidogenesis. Acetate accumulation was associated with pH shifts and incomplete microbial oxidation during later operational stages. Overall, the results demonstrate that co-digestion of SV and GOH is a sustainable and efficient strategy for simultaneous sulfate removal, alkalinity generation, and metal immobilization, providing a promising alternative for the treatment of acid mine drainage and sulfate-rich wastewaters.