Smart municipal wastewater treatment sludge management: Enhancement of biogas production from anaerobic digestion amended by optimized sludge-derived biochar

Attribution 4.0 International

This research was financially supported by an NSERC Discovery Grant (K. McPhedran) and NSERC Alliance-Mitacs Accelerate grants.

Peer Reviewed

Improving anaerobic digestion (AD) efficiency at municipal wastewater treatment plants (MWTPs) is essential for enhancing renewable energy recovery and achieving sustainable sludge management, especially in cold climates where AD performance is often limited. This study introduces an integrated approach using phosphoric acid-activated sludge-derived biochar (ASBC), produced from thickened waste-activated sludge (TWAS), to enhance biogas production. The effects of ASBC particle size and concentration were evaluated using response surface methodology (RSM), while computational fluid dynamics (CFD) simulations were applied to optimize reactor mixing and minimize dead zones. The optimized condition (15 g/L ASBC, 500 μm particle size; R-500-15) resulted in the highest biogas yield of 285 mL/g volatile solids (VS), a 48 % increase compared to the control. Additionally, the methane content in biogas increased to 68 %, which was 9.6 % higher than the control sample (62 %). Microbial community analysis showed that the bacteria family Peptostreptococcaceae (known for anaerobic fermentation) and archaea family Methanomicrobiales (known for methane production) had increased relative abundances of 0.760 and 30.2 % relative to the control in this optimized ASBC treatment. CFD modelling confirmed that tailored intermittent mixing (60 rpm for 55 s every 5 min) effectively reduced reactor dead zones to 13 %, contributing to improved substrate distribution and microbial interaction. This work demonstrates a cost-effective and sustainable strategy to optimize AD performance using waste-derived biochar and hydrodynamic enhancement. The approach supports energy-positive wastewater treatment and aligns circular economy and climate action goals, offering valuable guidance for MWTPs seeking to improve operational efficiency and environmental performance.