Biodegradation of three selected benzotriazoles in aquifer materials under aerobic and anaerobic conditions

• Three benzotriazoles were biodegraded in aquifer under aerobic and anaerobic conditions.
• The biodegradation efficiency and degradation products were dependent on the redox conditions.
• Aerobic conditions are more favorable for the biodegradation of benzotriazole and 5-methyl-benzotriazole.
• Anaerobic conditions are the most favorable for biodegradation of 5-chloro-benzotriazole.

We investigated the biodegradation of three selected benzotriazoles (BTs), namely benzotriazole (BT), 5-methyl-benzotriazole (5-TTri) and 5-chloro-benzotriazole (CBT), in aquifer materials. Biodegradation experiments were conducted in microcosms with fresh groundwater and aquifer sediment materials under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three BTs were degraded by microorganisms in aquifer materials under aerobic and anaerobic conditions. Under aerobic conditions, BT and 5-TTri were found to be degraded fastest with their half-lives of 43 days and 31 days, respectively, among the redox conditions used. Under anaerobic conditions, CBT was found to be degraded better with its half-life of 21 days under nitrate reducing conditions than under aerobic conditions with its half-life of 47 days. The two BT derivatives 5-TTri and CBT could be biotransformed into BT via demethylation and dechlorination reactions, respectively.

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