Biodegradation of triclosan in diatom Navicula sp.: Kinetics, transformation products, toxicity evaluation and the effects of pH and potassium permanganate

Triclosan (TCS) is one of the most widely used pharmaceutically active compounds and frequently detected in treated wastewater and the impacted aquatic environment. However, the fate and toxicity of TCS in aquatic organisms is poorly known, including in particular the potential for the formation of incomplete biological transformation products. In this study, TCS posed high toxic effects (e.g., growth inhibition and damage of photosynthesis) to typical freshwater diatom Navicula sp., with the 24 h and 72 h EC50 values of 173.3 and 145.6 mu gL(-1), respectively. The bioaccumulation of TCS in diatom cells increased with the increasing exposure to TCS and showed to be time-dependent. The higher intracellular. TCS lead to higher toxicity on Navicula sp. The intracellular TCS concentration and the growth inhibition of TCS in Navicula sp. at pH 7.5 was obviously higher than that at pH 8.3, which was likely due to the higher abundance of unionized TCS in the culture. KMnO4 reduced both bioaccumulation and toxicity of TCS in Navicula sp., especially at pH 8.3. A total of seven products were detected by liquid chromatography tandem mass spectrometry (LC-MS/MS). These findings will provide a reference for the risk assessment of TCS in aquatic environment. (C) 2017 Elsevier B.V. All rights reserved.