Abstract
This study identified biotransformation products formed from three anthropogenic trace organic compounds (TOrCs) (benzotriazole, triclosan, and trimethoprim) in aerobic and anoxic sludge from a biological nutrient removal (BNR) wastewater treatment system. Liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF) was used to identify intermediate transformation products. A user-defined compound library was used to target unknowns in samples with a mix of TOrCs without requiring chemical standards and developed using EAWAG-BDD predictive software, which included 37 potential transformation products. Biotransformation batch experiments were conducted using activated sludge from anoxic and aerobic redox regimes of a BNR treatment plant located in Southern Nevada, United States. Four intermediates were observed for benzotriazole in both aerobic and anoxic activated sludge, which consisted of two isomers of hydroxy benzotriazole and two isomers of methoxy benzotriazole. Four intermediates were observed for trimethoprim under aerobic conditions, which formed 2,4-diaminopyrimidin-5-yl)(3,4,5-trimethoxyphenyl)methanol (TMP 306) and 2,6-diamino-5-hydroxy-5-(3,4,5-trimethoxybenzyl)-5,6-dihydropyrimidin-4(1H)-one (TMP 324) and two demethylation isomers of desmethyl trimethoprim. Triclosan had one confirmed transformation product, triclosan-o-sulfate, formed in both conditions. The identification of these transformation products will allow for more thorough risk assessments to be performed for the target TOrCs.
Highlights
Biological nutrient removal (BNR) treatment, which utilizes anaerobic, anoxic, and aerobic treatment processes, has emerged as a cost-effective process for reducing nitrogen and phosphorus from wastewater
A 4-hydroxybenzotriazole standard was used and its retention time and mass spectrum matched the second peak observed in the BNR sample chromatograms, indicating the first peak was the 5-OH BTA isomer [Fig. 3(a)]
The primary goal of the project was to identify the formation of biotransformation products from benzotriazole, trimethoprim, and triclosan in wastewater activated sludge samples under anoxic and aerobic conditions using a targeted-QTOF screening technique and comprehensive user-defined personal compound database and library
Summary
Biological nutrient removal (BNR) treatment, which utilizes anaerobic, anoxic, and aerobic treatment processes, has emerged as a cost-effective process for reducing nitrogen and phosphorus from wastewater. Since the focus to date of BNR treatment has been on nutrient reduction, few studies have investigated the fate of anthropogenic trace organic compounds (TOrCs), such as pharmaceuticals, personal care product ingredients, and industrial chemicals, in BNR systems. BNR systems are not designed to remove TOrCs, microorganisms in the activated sludge can play a key role in the removal of TOrCs. Because of biological reactions, an organic compound may undergo alterations (i.e., biotransformation) and sometimes to complete mineralization (i.e., biodegradation). An organic compound may undergo alterations (i.e., biotransformation) and sometimes to complete mineralization (i.e., biodegradation) For these reactions to occur, the chemical must be accessible to the organism and the organism must have the necessary enzymes to bring about the transformation
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