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Title: Removal of triclocarban and triclosan in a wastewater treatment plant and their accumulations onto the solids

item Rice, Clifford

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/12/2009
Publication Date: 4/27/2009
Citation: Lozano, N., Rice, C., Ramirez, M., Torrents, A. 2009. Removal of triclocarban and triclosan in a wastewater treatment plant and their accumulations onto the solids. Meeting Abstract.

Interpretive Summary: .

Technical Abstract: The objective of this study was to investigate the fate of Triclosan (5-chloro-2-[2,4-dichloro-phenoxy]-phenol (TCS) and triclocarban (N-(4-chlorophenyl)-N’-(3,4-dichlorophenyl)urea) (TCC) within a wastewater treatment plant (WWTP). TCS and TCC are bactericidal compounds that have been detected in natural waters and it is believed that wastewater effluents are a major source of these compounds. Most studies dealing with the fate of TCS and TCC do not distinguish between losses due to biodegradation and sorption to particulates; and the few studies that account for the concentrations of these compounds in sludge, do not present concentrations in the sludge at the stages in the WWTP. Furthermore, very few studies show biodegradation products like the methyl-triclosan (MeTCS) which is more persistent than his parent TCS. In this study, a WWTP consisting of primary treatment (sedimentation), secondary (activated sludge) and tertiary (nitrification-denitrification, filtration and disinfection) was sampled for liquid samples. Liquid samples were 24 h. composites. The sludge line consisted of separation of solids using gravity thickeners and DAF (Dissolved Air Flotation) followed by a dewatering centrifuge to remove any remaining water. Finally, lime is added to the solids before land application. Sludge samples were collected for all treatments in order to account for the percentage removal of those compounds that are lost due to sorption and not to biodegradation. All samples were extracted to measure TCC, TCS and MeTCS. Aqueous phase TCC and TCS concentrations were both measured at µg/L levels. TCC concentrations found in the influent were higher than TCS. Both TCC and TCS were most concentrated in the particulate phase of the influent. High removal percentages were found for both TCS and TCC (> 90%) with concentrations measured in the effluent at ng/L levels. A mass balance was done to calculate the sorption percentages of these compounds to the solids and they were higher than 50% for both compounds, showing that the main mechanism for removal is sorption onto solids. The possibility that transformation of TCS to Me-TCS was evaluated by measuring Me-TCS in the samples.