Numerical Analysis of Pharmaceutical Transport Through Turf/Soil Systems.

In arid and semi-arid regions, wastewater for landscape irrigation is becoming a commonly-used and significant asset in water-limited regions. A recently-completed study from Henderson, NV showed that mass fluxes of 13 target pharmaceutical compounds found in treated wastewater were significantly attenuated after vertical transport through 120 cm of soil.  In this study, 24 drainage lysimeters were exposed for two years to treated wastewater as an irrigation source. Lysimeters were varied by soil type (two types), soil cover (bare versus turf-covered) and leaching fraction (5% and 25%). Upper and lower boundary conditions were monitored/controlled throughout the study, as was water content and redox conditions. Water samples were collected periodically after water breakthrough. Results showed that mass fluxes were reduced to less than 1 g/ha/yr for all compounds, with most showing less than 0.001 g/ha/yr. Solute breakthrough tended to be concentrated during fall and winter periods when turf was overseeded and sites received winter precipitation.  In this follow up study, we used HYDRUS-1D as a numerical model to simulate flow and transport of several target compounds (e.g., Carbamazepine, Primidone and Sulfamethoxazole) that were most commonly observed in drainage water. Input to the model was primarily from laboratory- and field-measured data. Modeling results will be discussed.