Mass Loading and Fate
of Linear and Cyclic Siloxanes
in a Wastewater Treatment Plant in Greece
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Abstract
The occurrence and fate of 5 cyclic (D3 to D7) and 12
linear (L3
to L14) siloxanes were investigated in raw and treated wastewater
(both particulate and dissolved phases) as well as in sludge from
a wastewater treatment plant (WWTP) in Athens, Greece. Cyclic and
linear siloxanes (except for L3) were detected in all influent wastewater
and sludge samples at mean concentrations of (sum of 17 siloxanes)
20 μg L<sup>–1</sup> and 75 mg kg<sup>–1</sup>, respectively. The predominant compounds in wastewater were L11
(24% of the total siloxane concentration), L10 (16%), and D5 (13%),
and in sludge were D5 (20%) and L10 (15%). The distribution of siloxanes
between particulate and dissolved phases in influents differed significantly
for linear and cyclic siloxanes. Linear siloxanes showed higher solid–liquid
distribution coefficients (log <i>K</i><sub>d</sub>) than
did cyclic compounds. For 10 of the 16 compounds detected in influents,
the removal efficiency was higher than 80%. Sorption to sludge and
biodegradation and/or volatilization losses are important factors
that affect the fate of siloxanes in WWTPs. The mean total mass of
siloxanes that enter into the WWTP via influent was 15.1 kg per day<sup>–1</sup>, and the mean total mass released into the environment
via effluent was 2.67 kg per day<sup>–1</sup>
