Application of in-situ H2-assisted biogas upgrading in high-rate anaerobic wastewater treatment

The H-2-assisted biogas upgrading approach has recently attracted much interest as a low-cost and environmentally friendly alternative to commonly used ex-situ/physiochemical biogas upgrading techniques. However, most studies conducted to date have been limited to anaerobic solid-waste treatment characterized by flocculant sludge and low organic loading rates (OLR). In an attempt to expand its application to high-rate anaerobic wastewater treatment, an innovative two-stage up-flow anaerobic sludge blanket reactor system was employed using anaerobic granular sludge. We found that the CH4 content of product gas was consistently > 90% and that H-2 and CO2 concentrations stayed below 5%, even when OLR was increased from 1 to 5 g L-1 d(-1) and H-2 feeding rates were increased from 0.13 to 0.63 g L-1 d(-1). We were also able to show that CO (5-10%) in H-2-rich syngas didn't inhibit methanogenesis or had significant impact on microbial community structure, suggesting that H-2-assisted biogas upgrading with H-2-rich syngas is feasible.