A review of constructed wetlands as a sustainable solution for wastewater treatment

In the context of the current environmental crises, sustainable wastewater treatment, particularly for decentralized
applications and micropollutant removal, has become an urgent priority. Constructed wetlands (CWs)
represent a promising nature-based solution due to their low energy demand and additional ecosystem service
potential. This review critically evaluates Life Cycle Assessment (LCA) studies of CWs treating municipal, domestic,
agricultural, industrial, and specialized wastewaters. Based on a systematic synthesis of 98 relevant
articles, the review addresses major research gaps related to environmental hotspots, operational sustainability
factors, and methodological inconsistencies in CW LCAs.
The reviewed studies identify construction and operation as the dominant contributors to environmental
impacts, primarily influenced by substrate production, aeration intensity, and system boundaries. Climate
change, land use, and eutrophication consistently emerged as the key impact categories. Aeration was identified
as the main intensification strategy improving treatment efficiency; however, continuous active aeration substantially
increased energy-related impacts, while passive, natural, and intermittent aeration showed more
favourable environmental performance. Operational parameters such as hydraulic retention time (HRT), hydraulic
loading rate (HLR), operational lifetime, and substrate selection were also identified as major sustainability
drivers.
Beyond wastewater treatment, CWs can contribute to carbon sequestration, nutrient recovery, biomass valorisation,
and bioenergy production. The review further highlights inconsistencies in current LCA methodologies,
particularly regarding system boundaries, end-of-life inclusion, and greenhouse gas accounting, and proposes
recommendations for more harmonized sustainability assessments of CWs.