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 8 microbial degradation 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 9 states, and multiple samples collected from one WWTP monitored for 12 months. Time-course analysis of significant mass fluxes (a = 0.01) suggested that microbial degradation of TCC (dechlorination) and TCS (methylation) occurred during sewage conveyance and treatment. All 8 target analytes co-occurred at most sites (64%) and strong linear correlations were found between TCC and the human metabolite 2'hydroxy-TCC (r = 0.84), and between the TCC-dechlorination products dichlorocarbanilide (DCC) and monochlorocarbanilide (r = 0.99). Mass ratios of DCC-to-TCC and of methyl-triclosan (MeTCS)-to-TCS, serving as indicators of microbial activity, revealed that biotransformation was widespread under different treatment regimes across the WWTPs sampled, though the degree of transformation varied significantly among study sites (a =  0.01). Finally, analysis of sludge before and after different unit operation steps (i.e., anaerobic digestion, heat treatment, and sludge drying) yielded insights into the extent and location of TCC and TCS degradation. Results suggest the contribution of anaerobic digestion is limited for TCC dechlorination (0.4�2.1%), but important for MeTCS degradation (37-74%). This longitudinal study is the first to report the occurrence of TCS, TCC, their degradates, and human metabolites in sewage sludge from across the United States. Opportunities are identified to evaluate degradation by localizing the specific stages where TCC dechlorination and MeTCS formation occur in conventional sewage delivery systems and WWTPs.

Nationwide survey of degradation products and human metabolites of triclocarban and triclosan in United States sewage sludge

248th National Meeting (2014)

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