Removal and reductive dechlorination of triclosan by Chlorella pyrenoidosa

•Triclosan was rapidly removed efficiently by alga Chlorella pyrenoidosa during 6-h exposure.•Reductive dechlorination of triclosan was detected as the biodegradation pathway of triclosan for the first time.•The influence of triclosan on C. pyrenoidosa was investigated with growth curves.•It was found that trilcosan exposure resulted in the disruption of chloroplast of C. pyrenoidosa cell. Triclosan that is widely used as antimicrobial agent has been detected as contaminant in various aquatic environments. In this work, removal and biodegradation of triclosan in water by using a ubiquitous green alga, Chlorella pyrenoidosa was investigated. When C. pyrenoidosa was exposed to a series concentration of triclosan from 100 to 800ngmL−1, more than 50% of triclosan was eliminated by algal uptake from the culture medium during the first 1h exposure and reached equilibrium after the 6h treatment. In the biodegradation experiments, a removal percentage of 77.2% was obtained after C. pyrenoidosa was cultivated with 800ngmL−1 triclosan for 96h. A major metabolite from the reductive dechlorination of triclosan was identified by using liquid chromatography coupled with electrospray ionization-mass spectrometry. The ultrastructural morphology of algal cells grown in the presence of triclosan was observed by using transmission electron microscopy and the growth of algal cells was detected. It was found that the trilcosan treatment resulted in the disruption of the chloroplast and the release of organic material into aquatic environment, which indicated that triclosan may affect membrane metabolism.