The biological abatement of 2,4,6-trichlorophenol (246TCP) and its chlorinated degradation byproducts using anaerobic and aerobic biological reactors coupled in series has been studied. The performance of an anaerobic fluidized bed biofilm reactor (FBBR) and expanded granular sludge bed (EGSB) reactors bioaugmented with Desulfitobacterium strains was compared within a wide range of 246TCP loading rates. The bioaugmentation of an EGSB reactor with Desulfitobacterium strains enhanced the chlorophenols removal efficiency and the stability against high toxic shocks. The FBBR showed an even higher stability, but also improved the dechlorination efficiency and required a shorter start-up period than the bioaugmented EGSB reactor. Thus, it was selected as the preferred anaerobic system. The subsequent treatment of the effluents from the anaerobic reactors in an aerobic sequencing batch reactor allowed complete dechlorination and improved mineralization up to 85% TOC reduction with a substantial abatement of the ecotoxicity, which was diminished in more than 80%. (C) 2014 Elsevier B.V. All rights reserved.