Enhancing biomethane recovery from source-diverted blackwater through hydrogenotrophic methanogenesis dominant pathway

Developments in energy recovery from decentralized wastewater streams provide a critical contribution to reducing greenhouse gases (GHGs) and promoting resource recovery. Source-diverted blackwater collected from vacuum toilets contains high solids organic content and is ideal for wastewater resource recovery. In the present study, an upflow anaerobic sludge blanket (UASB) reactor was operated under the mesophilic temperature condition (35 °C) to investigate methanogenic pathways and microbial development under high-loading conditions. We achieved the highest maximum organic loading rate (OLR) reported to date, at 4.1 kg chemical oxygen demand (COD)/m3/day (hydraulic retention time [HRT] 2.6 days), with a CODt removal efficiency of 84% (±5%), and methane production of 0.68 (±0.08) m3 CH4/ m3 reactor/day. This high efficiency resulted from domination of the H2/CO2 methanogenic pathway. Hydrogenotrophic methanogens with the genus Methanogenium were specifically enriched with the continuous treatment of blackwater