Assessing the Environmental and Economic Performance of Constructed Wetlands for Wastewater Treatment: A Systematic Review of Life Cycle, Techno-Economic, and Integrated Approaches

Abstract

Nature-based Solutions such as Constructed wetlands (CWs) are increasingly promoted as sustainable approaches for wastewater treatment due to their expected environmental and economic benefits. To evaluate their performance, a growing body of research has applied life cycle assessment (LCA) and techno-economic methods. This review systematically analyses 101 peer-reviewed articles assessing the environmental and/or economic performance of CWs, following the PRISMA framework. The review examines methodological practices related to functional unit (FU) definition, system boundaries, cost and benefit accounting, key financial assumptions, and sensitivity and uncertainty analysis in both environmental and economic assessments. The results reveal substantial methodological heterogeneity and wide variability in scope and assumptions across studies, due to the absence of harmonized methodological approaches. Only a limited number of studies attempt to integrate environmental and economic analyses beyond parallel assessments. The review discusses pathways toward more robust and integrated environmental–economic assessment frameworks for CWs. Key recommendations include incorporating life-cycle thinking into economic analysis, adopting a removal-efficiency-based FU, and using literature-based values, supported by sensitivity analyses, to account for excluded process. Together, these measures would strengthen CW sustainability assessments, improve comparability across studies, and enhance their usefulness as decision-support tools for nature-based wastewater management and planning.