Biochar enhanced floating root mats to reduce recalcitrant contaminants of emerging concern from wastewater effluents

This bench-scale study assessed a novel biochar-intensified floating root mat (FRM) system to reduce contaminants of emerging concern (CEC) from secondary-treated wastewater. Three configurations were evaluated: (1) FRM with plants (Cyperus alternifolius) and biochar, (2) FRM with plants only, and (3) unplanted control reactors, under two hydraulic loading rates (12 and 24 mm/day) over six months. The planted FRM enhanced CEC removal by 15 and 28 %, while the addition of biochar further increased removal by 35 % and 41 %, achieving CEC attenuation ranging from 41 to 99 %. Untargeted analysis corroborated this performance, and microbiological analysis linked CEC reduction to increased abundance of genera such as Exiguobacterium, Nocardia, Rodobacter and Amaricoccus, associated with biodegradation processes. This work therefore demonstrates that integrating biochar into FRMs enhances the attenuation of CEC and, for the first time, links biochar addition to microbial community shifts, offering a new strategy to tackle CEC pollution in wastewater treatment plants.