Codigestão anaeróbia de glicerol e esgoto sanitário para adequação ambiental e geração de metano em reator anaeróbio de leito fluidizado em batelada sequencial (AnSBFBR)

Abstract

The increasing production of biodiesel in Brazil has generated significant volumes of crude glycerol, a low-value byproduct with potential environmental liability. In this context, wnaerobic digestion emerges as a promising alternative for the energetic valorization of these residues. This study evaluated the anaerobic codigestion of glycerol and synthetic domestic wastewater in anaerobic sequential batch fluidized bed reactors (AnSBFBRs), investigating organic matter removal efficiency, cosubstrate conversion, methane generation, and removal of emerging micropollutants. Two reactors were operated with different support materials (sand – AnSBFBR/A and shredded tire – AnSBFBR/P), varying cycle time, feeding mode, and organic loading rate. Operational parameters (pH, alkalinity, volatile acids) and the removal of seven micropollutants—caffeine, ibuprofen, diclofenac, atenolol, propranolol, sucralose, and carbamazepine—were monitored. Under intermediate operational conditions, both reactors maintained high organic matter removal efficiencies, above 75% during the first five phases, reaching maximum values of 91.7% for AnSBFBR/A (Phase 3: CT – 8 h; B – 15 min; 0.5 gCOD·L-1) and 96% for AnSBFBR/P (Phase 2: CT – 8 h; FB – 3 h; 0.5 gCOD·L-1). The addition of glycerol as a cosubstrate favored methane production (44.91% and 53.69% in AnSBFBR/A and AnSBFBR/P, respectively) but also intensified acidogenesis. From Phase 6 (CT – 8 h; 0.7 gCOD·L-1) onward, a progressive accumulation of volatile fatty acids (VFA) was observed, leading in Phase 8 (highest glycerol load applied, 1.5 gCOD·L-1) to a decrease in COD removal efficiency (74.4% in AnSBFBR/A and 64.7% in AnSBFBR/P), an increase in VFA concentrations (≈48 mg·L-1 in AnSBFBR/A and ≈45.8 mg·L-1 in AnSBFBR/P), and a reduction in pH (6.90 in AnSBFBR/A and 6.80 in AnSBFBR/P), indicating acidification and organic overload that inhibited methanogenic activity. Regarding micropollutant removal, compounds such as caffeine, atenolol, propranolol, and sucralose showed the highest removal rates, especially in AnSBFBR/P, which achieved up to 98.2% removal for caffeine and 90.9% for atenolol. In contrast, recalcitrant pharmaceuticals such as diclofenac and carbamazepine exhibited modest or even negative removal efficiencies, indicating persistence in the medium and the need for complementary technologies for their mitigation. The results demonstrate that the AnSBFBR configuration is a promising alternative for treating wastewater containing emerging micropollutants, combining high organic matter removal, efficient cosubstrate conversion, and renewable biogas generation. This study contributes to advancing the understanding of micropollutant behavior in anaerobic fluidized bed systems and provides insights for operational optimization aimed at improving wastewater treatment efficiency.