| The practice of indirect potable water reuse is becoming more common in the Western United States and other arid regions. One concern related to this practice is the possibility that pharmaceutically active compounds (i.e., human pharmaceuticals, endogenous hormones and related compounds) present in municipal wastewater effluent could enter the drinking water supply. To determine the extent of this problem, a group of pharmaceuticals that are likely to be present municipal wastewater effluent in high concentrations were identified. These compounds were quantified in different types of water reuse systems, including conventional wastewater treatment, soil aquifer treatment (SAT), reverse osmosis, and engineered treatment wetlands. The pharmaceuticals were detected in the effluent from all of the conventional treatment systems studied at concentrations as high as 10,000 ng/L. Reverse osmosis and SAT effectively removed the compounds, while some of the compounds persisted in engineered treatment wetlands.;Many of the human pharmaceuticals detected in municipal wastewater effluent, surface water and groundwater contain functional groups that could undergo transformation reactions during chlorine disinfection. To assess the potential importance of these reactions to the environmental fate of pharmaceuticals, the rate of transformation of a group of compounds was measured over a pH range of 5 to 10. Several of the pharmaceuticals reacted rapidly with free chlorine (i.e., HOCl/OCl-) and would be expected to undergo transformation under the conditions typically encountered in chlorine disinfection systems. For compounds containing aromatic ether functional groups, the rate of transformation was strongly affected by the other substituents on the ring. The amine-containing pharmaceuticals underwent a rapid reaction with hypochlorous acid to form chlorinated amines, which could be converted back into the parent compound by reaction with thiosulfate. In the absence of thiosulfate, the chlorinated amines slowly decomposed to form species that could not be converted back into the parent compound. The reaction rates of the pharmaceuticals with combined chlorine (i.e. , chloramines) were significantly slower and transformation of the compounds would not be expected under the conditions encountered during disinfection with chloramines. (Abstract shortened by UMI.)... |
