Novel hybrid biochar-based constructed wetlands for contaminant of emerging concern removal in water reuse

Constructed wetlands (CWs) have emerged as a sustainable polishing treatment to target contaminants of emerging concern (CECs) in wastewater treatment plant effluents. However, limitations specially on land requirement have motivated the search for more efficient intensified designs. This study integrates two intensification strategies: substrate modification and hybrid wetland use for CEC removal from wastewater. A comparative experiment between biochar, coke and sand placed biochar as the most efficient substrate, achieving 99% ammonia, 85% COD, and 98% CEC removal. Biochar was subsequently integrated in a hybrid CW combining a floating root mat with a horizontal flow CW. The biochar hybrid CW maintained high CEC removal (>99%) across varying hydraulic loading rates, effectively treating both hydrophobic and hydrophilic/persistent compounds. Nontarget analysis confirmed a 70-80% reduction in chemical complexity, with limited formation of transformation products. These results present biochar-enhanced hybrid CWs as robust, scalable, low-energy solutions aligned with EU regulatory targets.