| Abstract
| - Many of the human pharmaceuticals detected in municipalwastewater effluent, surface water, and groundwatercontain functional groups that could undergo transformationreactions during chlorine disinfection. To assess thepotential importance of these reactions to the environmentalfate of pharmaceuticals, the rate of transformation of agroup of compounds was measured over a pH range of 5−10.Several of the pharmaceuticals reacted rapidly with freechlorine (i.e., HOCl/OCl-) and would be expected to undergotransformation under the conditions typically encounteredin many chlorine disinfection systems. For compoundscontaining aromatic ether functional groups, the rate oftransformation was strongly affected by the other substituentson the ring. The amine-containing pharmaceuticalsunderwent a rapid reaction with hypochlorous acid toform chlorinated amines, which could be converted backinto the parent compound by reaction with thiosulfate. In theabsence of thiosulfate, the chlorinated amines slowlydecomposed to form species that could not be convertedback into the parent compound. The reaction rates ofthe pharmaceuticals with combined chlorine (i.e., chloramines)were significantly slower, and transformation of thecompounds would not be expected under the conditionsencountered during chloramination.
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