Sustainable approach to anaerobically treat high-strength distillery wastewater for renewable energy recovery: Start-up strategy, reactor performance, and kinetic evaluation

Abstract

Distillery spent wash (DSW), high-strength wastewater discharged in large amounts from bio-ethanol production process has high potential to producing biogas for further being utilized as sustainable energy carrier. Wet-lab experiment and kinetic-model-guided framework were integrated to optimize anaerobic digestion of DSW. Volatile solid (VS) based substrate-to-inoculum (S/I) ratio of 1:4 was optimally identified in batch assay for having highest methane yield and stable digestion performance, comparing to other ratios of 1:3, 1:2, and 1:1. These results were simulated using modified ADM-1 model incorporating volatile fatty acid (VFA) and sulfide inhibition, as well as sulfate-reducing bacteria (SRB) kinetics. The calibrated model revealed the reduced disintegration rate of 0.17 d⁻¹ and elevated acetate inhibition constant of 2333 g-COD m⁻³, indicating microbial adaptation to high-VFA environments. Model-based estimation predicted 30-day optimal hydraulic retention time (HRT) for step anaerobic baffled (SAB) reactor, which achieved stable performance with methane yield of 299.0 mL-CH<inf>4</inf>/g-COD and 85.4% COD removal. Dynamic simulation validated the transferability of batch-calibrated kinetics and highlighted the role of phase separation and syntrophic stability in sustaining methane production. Microbial profiles confirmed spatial stratification of microbial communities, with acidogenic bacteria prevailing in early compartments and methanogenic archaea dominating downstream. The integration of kinetic modeling, simulation, and microbial analysis provides a robust design approach for stable and energy-efficient anaerobic treatment of complex industrial effluents.