Anodic control for methane production in bioelectrochemical systems with a heat-treated stainless-steel cathode

• Anodic control for simultaneous wastewater/sludge treatment and methane production. • Up to 89 % CH 4 was produced with a heat-treated stainless steel cathode. • Increasing NH 4 + abatement was observed with time. Bioelectrochemical systems have emerged as an environmentally friendly technology used for various operational purposes, including biomethane production and pollutant removal. This study investigates the application of anodic control to enhance methane production in a single-chambered bioelectrochemical reactor, utilising a heat-treated stainless-steel (HTSS) cathode and an ammonium-rich substrate (> 2 g NH 4 + L -1 ). The HTSS cathodic surface can positively contribute to methane production directly through electromethanogenesis via electron transfer from the cathodic surface, and indirectly through H 2 production, by subsequently stimulating hydrogenotrophic methanogenesis. Methane-rich gas with up to 89 % CH 4 was obtained using the HTSS cathode. In addition, an increase in NH 4 + abatement was observed over time, reaching a maximum reduction of 10.2 %. The inoculum displayed a high abundance of Alphaproteobacteria (21.7 %) and Planctomycetes (15.1 %), but a significant shift in the microbial culture was observed after inoculation in the bioelectrochemical reactor, with an anodic biofilm dominated by Desulfuromonas (32.9 %) and the cathodic biofilm by Methanobacterium (45.3 %).