oa Environmental Fate Modelling Of Contaminants In Constructed Wetlands

Background: Water management is a key focus area globally, and especially for the state of Qatar given its extremely arid environment. As such, research to develop technologies to enhance beneficial re-use of treated industrial waste water is recognized as a key challenge in this region. As a part of the Water Re-Use Research Program at ExxonMobil Research Qatar, a model was developed in collaboration with Simon Fraser University (Canada) for predicting the environmental fate of contaminants in constructed wetlands. Objective: This work will aid in design and monitoring of engineered wetlands to support water reuse applications. Methods: This model provides a method to estimate the extent to which contaminants of various kinds can be expected to be removed from wetlands through a combination of transformation and transport processes under various environmental conditions and wetland characteristics. The model was constructed to represent steady-state conditions and is based on conservation of mass principles. The model was developed for the use of Type I and Type II chemicals. Type I chemicals include organic substances and Type II chemicals include trace metals and inorganic substances .The model combines calculations for (i) environmental distribution of contaminants in aquatic systems; (ii) uptake, translocation and biotransformation of contaminants in vegetation; (iii) bioaccumulation in aquatic biota of wetlands; and (iv) toxicity in aquatic biota. Model inputs include wetland characteristics (e.g. compartment volumes, dimensions, organic carbon content, biotic growth rates); environmental conditions (e.g. Inflow& temperature); contaminant properties (e.g. molecular weight, degradation half-lives). The model outputs include predicted concentrations in various wetland compartments and mass balance inventory characterizing mass distribution and various loss processes. Results: Application of the model was tested for pyrene, arsenic and a naphthenic acid. The results show distinct differences in the predicted ability of wetlands to remove these contaminants from waste water. Conclusion: The evaluative model presented in this study provides useful insights that can guide further studies for designing and monitoring the effectiveness of engineered wetlands for wastewater reclamation purposes.