EVOLVING TOOLS IN CONSTRUCTED WETLAND RESEARCH: FROM RADIOISOTOPE TRACERS TO PREDICTIVE HYDROLOGICAL MODELS

Constructed wetlands (CWs) have become a key nature-based technology for sustainable wastewater treatment and ecological restoration, yet their performance remains highly dependent on complex interactions among hydrodynamics, biogeochemistry, vegetation, and operational conditions. This paper traces the evolution of research and troubleshooting tools used in CW studies, starting from early radiotracer applications and progressing towards contemporary data rich, model driven frameworks. The paper then presents the recent advances including remote sensing and UAV based monitoring, sensor networks, computational fluid dynamics (CFD), process based hydrological and reactive transport models, integrated systems, and the renewed but regulated use of radioisotope and dye tracers. In parallel, the role of dedicated simulation software in CW design and optimization is analyzed through six main platforms: BIO_PORE, HYDRUS Wetland Module, Wetland Water Quality Model (WWQM), WEST, AQUASIM, and SWAT. A comparative assessment highlights how each tool targets specific spatial scales and processes, from pore scale clogging dynamics to watershed level pollutant loading. The results demonstrate that no single technique or software package can capture the full multi scale complexity of CWs; instead, maximum benefit is achieved by combining complementary tools into integrated monitoring–modelling frameworks. The paper concludes by emphasising the need for multi model, multi-source strategies and outlines future directions involving AI, digital twins, and tighter coupling between field diagnostics and predictive simulation to support more resilient, efficient, and sustainable CW systems.