2 research outputs found
Transformation Products and Human Metabolites of Triclocarban and Triclosan in Sewage Sludge Across the United States
Removal
of triclocarban (TCC) and triclosan (TCS) from wastewater
is a function of adsorption, abiotic degradation, and microbial mineralization
or transformation, reactions that are not currently controlled or
optimized in the pollution control infrastructure of standard wastewater
treatment. Here, we report on the levels of eight transformation products,
human metabolites, and manufacturing byproducts of TCC and TCS in
raw and treated sewage sludge. Two sample sets were studied: samples
collected once from 14 wastewater treatment plants (WWTPs) representing
nine states, and multiple samples collected from one WWTP monitored
for 12 months. Time-course analysis of significant mass fluxes (α
= 0.01) indicate that transformation of TCC (dechlorination) and TCS
(methylation) occurred during sewage conveyance and treatment. Strong
linear correlations were found between TCC and the human metabolite
2′-hydroxy-TCC (<i>r</i> = 0.84), and between the
TCC-dechlorination products dichlorocarbanilide (DCC) and monochlorocarbanilide
(<i>r</i> = 0.99). Mass ratios of DCC-to-TCC and of methyl-triclosan
(MeTCS)-to-TCS, serving as indicators of transformation activity,
revealed that transformation was widespread under different treatment
regimes across the WWTPs sampled, though the degree of transformation
varied significantly among study sites (α = 0.01). The analysis
of sludge sampled before and after different unit operation steps
(i.e., anaerobic digestion, sludge heat treatment, and sludge drying)
yielded insights into the extent and location of TCC and TCS transformation.
Results showed anaerobic digestion to be important for MeTCS transformation
(37–74%), whereas its contribution to partial TCC dechlorination
was limited (0.4–2.1%). This longitudinal and nationwide survey
is the first to report the occurrence of transformation products,
human metabolites, and manufacturing byproducts of TCC and TCS in
sewage sludge
Occurrence of Triclocarban and Triclosan in an Agro-ecosystem Following Application of Biosolids
Triclocarban
(TCC) and triclosan (TCS), two of the most commonly
used antimicrobial compounds, can be introduced into ecosystems by
applying wastewater treatment plant biosolids to agricultural fields.
Concentrations of TCC and TCS were measured in different trophic levels
within a terrestrial food web encompassing land-applied biosolids,
soil, earthworms (<i>Lumbricus</i>), deer mice (<i>Peromyscus maniculatus</i>), and eggs of European starlings
(<i>Sturnus vulgaris</i>) and American kestrels (<i>Falco sparverius</i>) at an experimental site amended with biosolids
for the previous 7 years. The samples from this site were compared
to the same types of samples from a reference (biosolids-free) agricultural
site. Inter-site comparisons showed that concentrations of both antimicrobials
were higher on the experimental site in the soil, earthworms, mice
(livers), and European starling eggs, but not American kestrel eggs,
compared to the control site. Inter-species comparisons on the experimental
site indicated significantly higher TCC concentrations in mice (TCC:
12.6–33.3 ng/g) and in starling eggs (TCC: 15.4–31.4
ng/g) than in kestrel eggs (TCC: 3.6 ng/g). Nesting success of kestrels
only was significantly lower on the experimental site compared to
the reference site due to nest abandonment. This study demonstrates
that biosolids-derived TCC and TCS are present throughout the terrestrial
food web, including secondary (e.g., starlings) and tertiary (i.e.,
kestrels) consumers, after repeated, long-term biosolids application