Emerging chemical and biological contaminants fate and removal in a full-scale multi-cell integrated constructed wetland.

The stringent wastewater regulation is being expanded to include chemical micropollutants and strengthened antimicrobial resistance (AMR) surveillance, prompting the evaluation of evolving nature-based solutions for wastewater treatment. This study investigated a full-scale Integrated Constructed Wetland (ICW) in Ireland, combining chemical analysis, metagenomics, and quantitative PCR to assess pharmaceutical micropollutants, microbial community composition, and antibiotic resistance genes (ARGs) across the treatment wetland cells. A total of 67 pharmaceuticals were analysed, with 21 compounds consistently detected in water. Median concentrations decreased from 450 ng/L in the influent to 245 ng/L in the final effluent, despite a temporary increase to 710 ng/L in an intermediate cell. Compound-specific apparent removal ranged from <30% to >99%, and most compounds showed low ecological risk, although clarithromycin, lidocaine, and diclofenac exhibited risk quotient (RQ) values >1 at discharge. In sediments, micropollutant concentrations ranged from 8.7 to 36.7 ng/g dry weight, with higher concentrations observed in downstream cells and an RQ > 1 for benzotriazole. Relative ARG abundance in water decreased from 5.53 × 10⁻⁶ to 9.62 × 10⁻8 ARGs/16S (∼2.5-log reduction), while sediment samples showed higher relative abundance (2.12 × 10⁻2 to 4.48 × 10⁻4 ARGs/16S) with an overall 1.8-log reduction. These results demonstrate that full-scale ICWs can effectively attenuate both chemical and biological contaminants while highlighting the importance of sediment-associated retention, providing important evidence to support their role in future risk-based wastewater management and nature-based solutions for wastewater treatment strategies.