Life cycle performance and associated environmental risks of constructed wetlands used for micropollutant removal from municipal wastewater effluent

Wastewater treatment systems produce environmental impacts in their construction and operation, and nature-based treatment processes offer opportunities to reduce the environmental burdens. Constructed wetlands represent such a solution that can remove micropollutants from municipal effluent. This study evaluates life cycle impacts and environmental risk of constructed wetlands for improved treatment performance. The assessment of laboratory- and pilot-scale installation performance provides insights into sustainability of scaling fundamental research to technology demonstration. The normalised life cycle assessment showed that the laboratory installation generated higher environmental impacts than the pilot, due to the cooling tank and its associated electric power (∼60% of the total burdens for five impact categories). The avoided environmental impacts through the micropollutants' elimination ranged from 50% to 99.9% (for freshwater ecotoxicity and human toxicity, respectively). A sensitivity and uncertainty analysis highlighted how the substrate and electricity demands represented the highest environmental impacts, thus extending lifespan of a full-scale system whilst maintaining treatment performance represents the most notable opportunity to improve the environmental performance. The findings support measures to enhance sustainability through design, procurement and operation stages of development. Constructed wetlands represent a sustainable nature-based form of wastewater treatment, and this study offers lessons to further enhance their environmental performance.