Overview of modeling applications and radioactive tracers for the hydrodynamic determination of groundwater flow in...

Constructed wetlands (CWs) are treatment engineered systems designed to mimic the processes of natural wetlands for the purpose of treating wastewater or stormwater. These wetlands use vegetation, soil, and microbial processes to remove pollutants and improve water quality. CWs have been employed as an environmentally friendly and cost-effective alternative to conventional wastewater treatment methods. CWs contribute to sustainable water management by utilizing natural processes and promoting environmental conservation. Their design and operation should be tailored to specific site conditions and treatment objectives. Groundwater modelling applications and the use of tracers play crucial roles in understanding and optimizing the performance of constructed wetlands. A detailed literature overview was performed to identify the various modelling methods and tracer applications commonly used around the globe for assessing CWs' development and operation. The most widely applied groundwater models include MODFLOW-MODPATH for simulating groundwater flow and transport processes, as well as MT3DMS and HYDRUS for evaluating contaminant transport. Additionally, coupled hydrological models and reactive transport simulations provide insights into the hydraulic and biochemical processes occurring within CWs. In terms of tracer applications, both natural and artificial radioactive tracers are frequently utilized to assess hydrodynamics and pollutant removal efficiency. Key radiotracers include isotopes such as ²²²Rn, ⁷Be, ¹³⁷Cs, and ²¹⁰Pb for sediment transport and water movement analysis, as well as ³H and ²³⁴U/²³⁸U for groundwater interactions. These tracers, in combination with numerical modelling, enhance the accuracy of hydrodynamic assessments and improve the predictive capacity of CW performance under various operational scenarios. This integrated approach enhances the efficiency and reliability of constructed wetlands in treating wastewater and stormwater, providing an effective solution and contributing to sustainable water management practices.