Recebido em 12/12/08; aceito em 24/7/09; publicado na web em 8/1/10 Pharmaceutical compounds have been detected in sewage treatment plant (STP) effluents, surface waters and, less frequently, in groundwater and drinking water, all over the world. Different sources are responsible for their appearance in the aquatic environment, however, it is widely accepted that the main sources of this type of pollutant are STP effluents. The adverse effects of pharmaceuticals in the environment include aquatic toxicity, development of resistance in pathogenic bacteria, genotoxicity and endocrine disruption. Thus, the discharge of these compounds to the environment in STP effluents should be minimized.
Bezafibrate (BF), a frequently detected pharmaceutical in the aquatic environment, could be effectively removed by ozonation. However, the toxicity of treated water increased, suggesting the generation of toxic oxidation products (OPs). In this study, eight OPs of BF ozonation were identified using a LTQ Orbitrap hybrid mass spectrometer coupled with HPLC, and six of them have not been previously reported during BF ozonation. Based on the abundant fragments and high assurance of accurate molar mass, structure elucidation was comprehensively performed and discussed. Hydroxylation, loss of methyl propionic acid group, and Crigée mechanism were observed as the oxidation mechanisms of BF ozonation. The toxicity of identified OPs calculated by quantitative structure activity relationship indicated that three OPs were probably more toxic than the precursor compound BF. This result together with the evolution of identified OPs in the treated solutions, indicated that two OPs, namely N-(3,4-dihydroxyphenethyl)-4-chlorobenzamide and N-(2,4-dihydroxyphenethyl)-4-chlorobenzamide, were the potential toxicity-causing OPs during BF ozonation. To the best of our knowledge, this is the first attempt to identify toxicity-causing OPs during the BF ozonation.
Organic compounds from influent and effluent wastewater were concentrated on C18 bonded phase cartridges and sequentially eluted with organic solvents of different polarity. About 80% of the toxicity (Microtox) arised from organic matter eluted with ether. Approximately 50% decrease in the overall toxicity of the influent was observed during the treatment process. More than 50 individual compounds were identified in the eluates for both influent and effluent by GC-MS and FIA-MS analysis. Perfume additives to washing powders and cleaning agents and a number of industrial volatile hydrophilic solvents were quantitatively removed by volatilization in the treatment process. Only a partial removal was observed for less volatile compounds (benzophenone, dibutyl formamide, dimethyl quinoline, benzothiazole, phosphate esters) of industrial origin. Substituted phenols, used as antioxidants in both industrial and domestic products were transformed to corresponding -ene-ones in the biological stage of the water treatment process. Polyglycols and polyglycol ether type surfactants are not removed in the activated sludge prosess, only partly transformed to highly persistant acids by oxidation of the terminal hydroxyl function. The treatability in municipal wastewater plants should be paid much more attention when introducing polar non-volatile constituents in new “environmentally friendly” water based products or processes.
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