Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2016
Publication Date: 1/3/2017
Citation: Armstrong, D., Rice, C., Ramirez, M., Torrents, A. 2017. Influence of thermal hydrolysis-anaerobic digestion treatment of wastewater solids on concentrations of Triclosan, Triclocarban, and their transformation products in biosolids. Chemosphere. 171:609-616. Interpretive Summary: A local waste water treatment plant has brought on line a new processing method, thermal hydrolysis (TH)-presssurized anerobic digestion (AD) to attempt to produce cleaner solid wastes; their former treatment method was lime stabilization. The biosolids produced by this TH-AD system were tested to see whether improved removal of two widely used bacteriostats, triclosan (TCS) and triclocarban (TCC) were occuring. The measured values were compared to measurement on samples collected when the plant was operating with the lime treatment system. TCC removal was significantly improved over lime stabilization; while TCS amounts actually were greater than during lime-treated samples. This apparent increase in TCS could be explained by the greater mass reduction afforded by the newer system. Measurements at various points in the processing system determined that the enhanced removal of TCC occurred in the thermal hydrolysis step while the apparent increase in concentrations of TCS and the TCS-derived degradates, Me-TCS and 2,4-dichlorophenol were occurring in the the anaerobic digestion and dewatering stage. Thus the new TH-AD system had mixed performance for removing these two high-use bacteriostatic compounds. Reviews of the effectiveness of new systems at removing trace contaminants is important for addressing environmental releases of these compounds especially when the biosolids are applied to agricultural land which is the major end-use for these materials. This information will be of use to urban planners considering treatment methods at water resource recovery facilities.
Technical Abstract: The growing concern worldwide regarding the presence of emerging contaminants in biosolids calls for a better understanding of how different treatment technologies at water resource recovery facilities (WRRFs) can influence concentrations prior to biosolids land application. This study focuses on the influence of thermal hydrolysis-anaerobic digestion (TH-AD) solids treatment on concentrations of triclosan (TCS), triclocarban (TCC), and their transformation products in biosolids and sludges. Concentrations of the target analytes in biosolids from the TH-AD process (Class A), sludges from the individual TH-AD treatment steps, and limed biosolids (Class B) from the same WRRF were compared. TCC concentrations were significantly lower in Class A biosolids than those in the Class B product - a removal that occurred during thermal hydrolysis. Concentrations of TCS-derived, methyl triclosan, and 2,4-dichlorophenol, conversely, increased during anaerobic digestion, leading to significantly higher concentrations of these compounds in Class A biosolids when compared to Class B biosolids. Implementation of the TH-AD process had mixed effect on contaminant concentrations.