Submitted to: Water Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2013
Publication Date: 5/20/2013
Citation: Lozano, N., Rice, C., Ramirez, M., Torrents, A. 2013. Fate of triclocarban, triclosan and methyltriclosan during wastewater and biosolids treatment processes. Water Research. 47:4519-4527. Interpretive Summary: Improving waste management is an issue that concerns everyone, especially regarding the need to better manage two widely used household bacteriostats, triclosan and triclocarban. These materials occur at high levels, greater than 10 ppm, in US waste water plant biosolids; and greater than 90% of this type of waste material is used as soil amendments. This study examined in-plant processes in a large capacity waste water treatment plant by utilizing careful sampling and analysis, and then employed a mass balance approach to calculate in-process transport and fate of these two chemicals. Greater than 97% of these compounds were removed at the sludge collection stages in this plant. Furthermore, recently improved nutrient removal steps in the plant were found to be the primary sites where destruction of the two compounds was occurring, e.g., 22.6% for triclosan and 18% for triclocarban. This information will assist plant operators at improving processing of these and other compounds with similar physical chemical properties.
Technical Abstract: Triclocarban (TCC) and Triclosan (TCS) are two antibacterial chemicals present in household and personal care products. Methyltriclosan is a biodegradation product of TCS formed under aerobic conditions. TCC and TCS are discharged to Waste Water Treatment Plants (WWTP) where they are removed from the liquid phase mainly by concentrating in the solids. This study presents a thorough investigation of TCC, TCS and MeTCS concentrations in the liquid phase (dissolved + particulate) as well as solid phases within a large WWTP. TCC and TCS were removed from the liquid phase at percentages = 97% however around 79% of the TCC and 64% of the TCS was transferred to the solids. The highest TCC and TCS removal rates from the liquid phase were reached in the primary treatment mainly though sorption and settling of solids. The TCC mass balances showed that TCC levels remain unchanged through the secondary treatment (activated sludge process) and about a 18% decrease was observed through the nitrification-denitrification process. On the other hand, TCS levels decreased in both processes (secondary and nitrification-denitrification) by 10.4 and 22.6%, respectively. The decrease in TCS levels correlated with observed increased levels of MeTCS in secondary and nitrification-denitrification process providing evidence of TCS biodegradation. Dissolved-phase concentrations of TCC and TCS remained constant during filtration and disinfection. TCC and TCS highest sludge concentrations were analyzed in the primary sludge (13.1 ± 0.9 µg g-1 dry wt. for TCC and 20.3 ± 0.9 µg g-1 dry wt. for TCS) but for MeTCS, the highest concentrations were analyzed in the secondary sludge (0.25 ± 0.04 µg g-1 dry wt.). Concentrations of 4.15 ± 0.77; 5.37 ± 0.97 and 0.058 ± 0.003 kg d-1 are leaving the WWTP with the sludge and 0.13 ± 0.01; 0.24 ± 0.07 and 0.021 ± 0.002 kg d-1 with the effluent that is discharged.