Characterization of contaminants of emerging concern in a cold-climate two-stage vertical flow treatment wetland

• 38 CECs detected in a two-stage cold-climate treatment wetland (TW) influent. • Performance on par with other systems despite cold climate (wastewater 2–4 °C). • Potential ecotoxicity reduced for CECs through treatment in the wetland. • Most CECs had higher percent removal in the unsaturated treatment wetland stage. • Solid media and biofilms were analyzed for CECs to assess retention in solid phase. Contaminants of emerging concern (CECs), particularly pharmaceuticals, are detected in wastewater in low concentrations, but pose environmental and public health risks, and are resistant to conventional treatment. As these compounds are increasingly monitored and studied, treatment methods are required to improve their removal. This study evaluates a well-characterized two-stage vertical flow treatment wetland (VFTW) designed to treat high-strength municipal wastewater in a cold climate. Conventional wastewater contaminants were removed with high efficiency, including 96% removal of chemical oxygen demand (COD) and 98% removal of ammonia at water temperatures of 2–4 °C. Thirty-eight CECs were quantified in the influent wastewater during the winter operating season (December-April), with removal >80% observed for many of these compounds. Most CECs demonstrated higher removal in the unsaturated, aerobic stage of the VFTW. A ranking of the relative abundance of CECs found in liquid samples and solid media samples (porous media and associated biofilm) provided insights into the retention of certain compounds by solid media. It was found that the VFTW significantly reduced the concentrations of most CECs detected in the influent. Compared to literature values for similar systems, the Bridger VFTW demonstrated equal or superior removal for several CECs, despite lower ambient temperatures than found in the literature, although removal varied by compound. This study contributes to a broader understanding of VFTWs, adding data that supports the feasibility of VFTWs to remove select CECs, and demonstrating the adaptability of VFTWs to cold climates without compromising their conventional treatment capabilities and their potential for CEC removal.