Constructed Wetlands for Wastewater Treatment and Reuse in Neotropical Regions: Hydraulic, Biogeochemical, and Sustainability Challenges

Constructed wetlands (CWs) are increasingly used for decentralized wastewater treatment and reuse where conventional infrastructure is difficult to sustain. This review integrates evidence on hydraulic reliability, biogeochemical performance, reuse safety, sustainability trade-offs, and process-based modeling, and derives design implications for Neotropical settings. Organic-matter and suspended-solids removal is generally more robust than nitrogen, phosphorus, and pathogen control. More reliable performance is associated with controlled hydraulic loading, solids-limiting pretreatment, stable flow distribution and water levels, and protection against stormwater-driven short-circuiting and clogging. Reuse should therefore be evaluated against fit-for-purpose microbial, nutrient, salinity, and chemical endpoints rather than removal efficiency alone. We propose seasonal monitoring, tracer or residence-time-distribution assessment where decisions depend on hydraulic efficiency, locally calibrated design envelopes, and a minimum reporting set covering climate/season, flow and loading, HRT/HLR, configuration, pretreatment, media, monitoring duration, influent/effluent concentrations, and hydraulic indicators. This study is a structured narrative review with thematic synthesis; literature identification and corpus reporting were informed by applicable PRISMA 2020 principles. Three Scopus searches yielded 593 records; after removal of 37 duplicates, 556 unique records remained. The final thematic corpus comprises 80 reports, of which 30 are present in the Scopus exports and 50 were identified through complementary routes.