Biogas production from municipal wastewater sludge containing polyacrylamide

Bangkok generates 39,420 t/year of municipal wastewater sludge. This study investigates its potential as a biogas feedstock, focusing on the impact of polyacrylamide (PAM), a polymer used in sludge dewatering. A 5 L anaerobic reactor, seeded with mixed cultures from brewery wastewater treatment, is operated at 30 °C with a 43-day hydraulic retention time. The reactor is fed semi-continuously every 5 days with sludge containing 41.60 g chemical oxygen demand (COD)/L. Daily methane (CH 4 ) production and gas composition are analyzed. At steady state, CH 4 production averages 426 mL per 5 days with a CH 4 content of 53.57 %, achieving 44.36 % COD degradation and yielding 29.45 L/kg COD degradation. Although this study focuses on CH 4 , the findings are also relevant to hydrogen (H 2 ) research due to shared microbial pathways. Results suggest that PAM inhibits microbial activity, and under controlled conditions, the inhibition is attributed to both PAM and the limited biodegradability of the feedstock. Experimental workflow and key findings. • Biogas production from municipal wastewater sludge with PAM is studied. • Semi-continuous operation at OLR of 0.972 kg COD/m 3 .day and HRT of 43 days. • PAM at 1.35 g/kg of municipal wastewater sludge (DW) reduces biogas production. • The methane content and yield obtained are 53.57 % and 29.45 L/kg COD degradation. • PAM negatively impacts bacterial function via methane yield.