Evaluating the efficacy of biochar columns for two pharmaceuticals, methyl paraben and nutrient removal in...

This study assessed the effectiveness of constructed floating wetlands (CFWs) amended with biochar and bioactive biochar hanging columns in removing three pharmaceuticals and personal care products (PPCPs: metronidazole (MNZ), naproxen (NAP), and methylparaben (MeP)) along with residual organics and nutrients. The impact of biochar amendments on the removal of organics, nutrients, and targeted PPCPs was evaluated under both batch and continuous operations. In batch-scale experiments, CFWs incorporating bioactive/biochar columns and plants achieved over 80% removal of organics and 70% reduction in nutrients, driven primarily by the synergistic actions of plants, microbes, and biochar. PPCP removal rates were notably high, exceeding 80-90% in systems with plants and hanging biochar columns. In continuous mode, reductions of PPCPs and organics exceeded 75% at a 6-day hydraulic retention time (HRT), with performance declining at shorter HRTs. CFWs combining biochar columns and plants reduced ecotoxicological risk to aquatic life by up to 90%, outperforming units with only biochar or plants. Mass balance analysis indicated that 35-71% of PPCPs were removed through a synergistic action of plants, microbes and biochar in the CFWs. Pollutant reduction in biochar-amended CFWs occurred through multiple mechanisms, including adsorption onto biochar, photodegradation, microbial degradation, and plant uptake. Oxidative stress in plants, reactive oxygen species (ROS) accumulation, was plants due to PPCPs exposure, however amended biochar column can reduce the PPCP-induced phytotoxicity. Microbial analyses further revealed enrichment of biodegradation-associated genera (Pseudomonas and Nitrospira). These results reveal the synergistic role of biochar, plants, and microbial communities in enhancing pollutant attenuation in CFWs.