Loadings, trends, comparisons, and fate of achiral and chiral pharmaceuticals in wastewaters from urban tertiary and rural aerated lagoon treatments.

A comparison of time-weighted average pharmaceutical concentrations, loadings and enantiomer fractions (EFs) was made among treated wastewater from one rural aerated lagoon and from two urban tertiary wastewater treatment plants (WWTPs) in Alberta, Canada. Passive samplers were deployed directly in treated effluent for nearly continuous monitoring of temporal trends between July 2007 and April 2008. In aerated lagoon effluent, concentrations of some drugs changed over time, with some higher concentrations in winter likely due to reduced attenuation from lower temperatures (e.g., less microbially mediated biotransformation) and reduced photolysis from ice cover over lagoons; however, concentrations of some drugs (e.g. antibiotics) may also be influenced by changing use patterns over the year. Winter loadings to receiving waters for the sum of all drugs were 700 and 400 g/day from the two urban plants, compared with 4 g/day from the rural plant. Per capita loadings were similar amongst all plants. This result indicates that measured loadings, weighted by population served by WWTPs, are a good predictor of other effluent concentrations, even among different treatment types. Temporal changes in chiral drug EFs were observed in the effluent of aerated lagoons, and some differences in EF were found among WWTPs. This result suggests that there may be some variation of microbial biotransformation of drugs in WWTPs among plants and treatment types, and that the latter may be a good predictor of EF for some, but not all drugs.