Mass balance assessment of triclosan removal during conventional sewage treatment.
ABSTRACT The antimicrobial agent triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol; TCS) is a member of a larger group of polychlorinated binuclear aromatic compounds frequently associated with adverse environmental and human health effects. Whereas the structure and function of TCS would suggest significant resistance to biotransformation, biological wastewater treatment currently is considered the principal destructive mechanism limiting dispersal of and environmental contamination with this compound. We explored the persistence of TCS in a typical full-scale activated sludge US sewage treatment plant using a mass balance approach in conjunction with isotope dilution liquid chromatography electrospray ionization mass spectrometry (ID-LC-ESI-MS) for accurate quantification. Average influent and effluent concentrations (mean +/- SD) of 4.7+/-1.6 and 0.07+/-0.06 microg 1(-1), respectively, revealed an apparent (liquid-phase) removal efficiency of 98+/-1%. However, further analyses demonstrated that the particle-active TCS (80+/-22% particle-associated in influent) was sequestered into wastewater residuals and accumulated in dewatered, digested sludge to concentrations of 30000+/-11000 microg kg-1. Overall, 50+/-19% (1640+/-610 g d-1) of the disinfectant mass entering the plant (3240+/-1860 g d-1) remained detectable in sludge, and less than half of the total mass (48+/-19%) was biotransformed or lost to other mechanisms. Thus, conventional sewage treatment was demonstrated to be much less effective in destroying the antimicrobial than the aqueous-phase removal efficiency of the plant would make believe. Furthermore, study findings indicate that the common practice of sludge recycling in agriculture results in the transfer of substantial quantities of TCS to US soils used, in part, for animal husbandry and crop production.
Article: Agricultural wastesWater Environment Research 10/2008; 80(10):1340-1396. · 1.00 Impact Factor
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ABSTRACT: The occurrence and the removal efficiency of natural estrogens, estrone (E1), 17β-estradiol (E2) and estriol (E3), as well as a synthetic estrogen, 17α-ethinylestradiol (EE2), were investigated in two sewage treatment plants (STPs) employing different activated sludge processes in Tunisia, by monitoring their concentrations in dissolved wastewater. The analytes were extracted by solid-phase extraction and then analyzed by gas chromatography coupled with mass spectrometry (GC-MS). Results indicate that natural and synthetic estrogens were detected in the STP influent samples. The concentrations of natural and synthetic estrogens (except E1) detected in the effluents of alternating activated sludge process were generally lower than the limit of detection. On the other hand, all estrogens were not totally removed through the simple activated sludge process; as a result, they were detected in effluent samples. E3 showed the highest concentration in the influent samples at 98 ng L -1 in the alternating anoxic/aerobic activated sludge process, and at 102 ng L -1 in the simple activated sludge. Two different types of diurnal variation of estrogens discharge were identified. The two STPs had approximately similar daily loads of estrogens in influents at 112.7 µg d -1 and 109.58 µg d -1 , respectively. The distribution of estrogens in the STPs is affected by their metabolisms in human body and their transition through biological treatment processes. Removal efficiency varied among STPs; high removal of estrogens (84-97%) with the exception of E1 (80%), were generally achieved in alternating anoxic/aerobic activated sludge process with a high hydraulic retention time (40 h) and treatment stages for removal of nitrogen. E1 showed the lowest removal of all estrogens in the two STPs. This could be caused by conversion of E2 to E1 in the treatment process, or by cleavage of estrogen conjugates. On the other hand, E3 showed the highest removal of all estrogens both in alternating anoxic/aerobic and simple activated sludge processes at 97.5% and 85.5%, respectively). EE2, which is particularly sensitive to human consumption as the oral contraceptive, were removed by approximately 77.5%) in the simple activated sludge process. Filamentous bacteria were less effective in removal estrogens than protozoa.01/2013; 8(1):2319-2399.
- Journal Of Environmental Science, Toxicology And Food Technology. 01/2014; 8:100-108.