Influent samples were obtained by directly withdrawing
7-mL samples from influent flasks. Effluent samples were
collected for several hours in foil-covered glass vials, which
were then subsampled for 7-mL volumes. Samples taken
before day 170 of column operation were collected as single
samples, while all samples collected after day 170 were
subsampled three times to permit PPCP analysis in triplicate.
Each aqueous influent and effluent sample was combined
with 7 mL acetonitrile in 20 mL screw-top glass test tubes with
rubber-lined caps. Samples were covered with aluminum foil
and stored at 4 C until derivatization.