In a field-scale groundwater recharge study, subsurface
flow of six to twelve months reduced a surrogate for x-ray
contrast media by 50%, and six to ten years of saturated,
anoxic flow led to 60% removal (Drewes et al., 2001). In another
full scale groundwater recharge study, hydraulically corresponding
regional groundwater samples highlighted the
variations possible among different compounds, reporting
99% removal of gemfibrozil, ibuprofen, and naproxen, but
concentration increases for carbamazapine and primidone
(Drewes et al., 2002).