Biotransformation of Benzotriazoles: Insights from Transformation Product Identification and Compound-Specific Isotope Analysis

Abstract

Benzotriazoles are widely used domestic and industrial corrosion inhibitors and have become omnipresent organic micropollutants in the aquatic environment. Here, the range of aerobic biological degradation mechanisms of benzotriazoles in activated sludge was investigated. Degradation pathways were elucidated by identifying transient and persistent transformation products in batch experiments using liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS). In addition, initial reactions were studied using compound-specific isotope analysis (CSIA). Biodegradation half-lives of 1.0 days for 1H-benzotriazole, 8.5 days for 4-methyl-1H-benzotriazole, and 0.9 days for 5-methyl-1H-benzotriazole with activated sludge confirmed their known partial persistence in conventional wastewater treatment. Major transformation products were identified as 4- and 5-hydroxy-1H-benzotriazole for the degradation of 1H-benzotriazole, and 1H-benzotriazole-5-carboxylic acid for the degradation of 5-methyl-1H-benzotriazole. These transformation products were found in wastewater effluents, showing their environmental relevance. Many other candidate transformation products, tentatively identified by interpretation of HR-MS/MS spectra, showed the broad range of possible reaction pathways including oxidation, alkylation, hydroxylation and indicate the significance of cometabolic processes for micropollutant degradation in biological wastewater treatment in general. The combination of evidence from product analysis with the significant carbon and nitrogen isotope fractionation suggests that aromatic monohydroxylation is the predominant step during the biotransformation of 1H-benzotriazole.

Sorption and biodegradation of selected benzotriazoles and hydroxybenzothiazole in activated sludge and estimation of their fate during wastewater treatment

“…2); it therefore seems that biodegradation of target compounds occurs due to co-metabolic phenomena by microorganisms utilizing a wide range of carbon sources. The aerobic co-metabolic biotransformation of BTR due to hydroxylation of the aromatic benzene ring and methylation of the triazole ring was recently shown by Huntscha et al (2014).…”

“…Regarding BTR, CBTR and XTR, the lowest estimated half-life values were 23 h (Experiment C: aerobic conditions, SRT 18 d, addition of organic substrate), 18 h (Experiment D: anoxic conditions, SRT 18 d, addition of organic substrate) and 14 h (Experiment C: aerobic conditions, SRT 18 d, addition of organic substrate), respectively. So far, contradictory half-life values have been reported in the literature for BTR, ranging from 1 d (Huntscha et al, 2014) to 49 d (Herzog et al, 2014a); whereas no data is available for XTR. Table 3 First order kinetics (k), half-life values and biodegradation constants (k bio ) calculated in batch experiments with activated sludge under different experimental conditions.…”

“…Specifically, in experiments with activated sludge and initial concentration of target compounds equal to 1 mg L À1 , Liu et al (2011) studied the biodegradation potential of BTR, 5TTR and 5-chlorobenzotriazole (CBTR) under aerobic conditions and proposed their biotransformation pathways. In a recent study, Huntscha et al (2014) investigated the biotransformation of BTR, 4TTR, and 5TTR under aerobic conditions (initial concentrations: 0.5-2.4 mg L À1 ), determined their half-lives and identified the major biotransformation products. Finally, Herzog et al (2014a, b) studied the removal efficiency of BTR, 4TTR and 5TTR under different experimental conditions at initial concentrations ranging between 0.2 and 34 mg L À1 , and reported that sludge acclimatization enhanced biodegradation of some compounds.…”

Non-target screening with high-resolution mass spectrometry: critical review using a collaborative trial on water analysis

“…A number of strategies for the selection of candidates for suspect and non-target screening of environmental substances using HR-MS/MS information have been developed and put into practice recently. Suspect screening has been performed using predicted transformation products (TPs) [18][19][20], registered pesticides and their TPs in Switzerland [21], surfactants in wastewater [3] and fracking fluids [22], site-specific chemicals [5] and high-consumption pesticides and pharmaceuticals in sediments [23]. Other lists, such as the potentially persistent and bioaccumulative organics in commerce [24], pharmaceuticals [25], as well as impurities, by-and transformation products [26] from Howard and Muir can also be used in suspect screening.…”

Targeted and non-targeted liquid chromatography-mass spectrometric workflows for identification of transformation products of emerging pollutants in the aquatic environment

“…One successful example of the application of a non-target workflow is the identification of biotransformation products of three benzotriazoles [36].…”