Sorption of Pharmaceuticals On Model Sorbent Systems: Implications for Wastewater Reuse.

One concern with the reuse of wastewater is the presence of pharmaceuticals and other similar compounds in wastewater. Different classes of pharmaceuticals have been reported in over 100 rivers and streams in the US and in drinking water. Development of a system that could effectively and efficiently remove pharmaceuticals and their metabolites from wastewaters would inform environmental risk assessment. Sorption processes play an important role in determining mobility, (bio) availability and, hence, persistence of contaminants in soil. Clay minerals and soil organic matter (SOM) are generally considered to be the two most active soil components in the sorption of aqueous phase organic contaminants. We determined the distribution coefficient of a range of pharmaceuticals to clay minerals, mineral-coated sands, biofilm coated activated carbon, and soil as a function of ionic strength and pH. Results to date are that smectites (pH 4) and aluminum oxide coated sand (Al-sand) (pH 7) were equally effective at sorbing sulfamethoxazole. Sulfamethoxazole sorption to kaolinite (pH 4 and 7) was lower by a factor of 10 compared to smectite (pH 4) and Al-sand (pH 7). Further studies will investigate the sorption coefficients (K_d) for sorption of other pharmaceuticals and pharmaceutical mixtures to model sorbent systems influenced by concentration of dissolved organic matter, ionic strength, pKa of pharmaceutical, and saturating cation of the system. This study will ultimately delineate any risks from wastewater reuse.