Two packed-bed bioreactors filled with carriers of foamed glass beads were tested at 14 degrees C (bioreactor RA) or at 23 +/- 1 degrees C (bioreactor RB) for the continuous treatment of a mixture of 2-chlorophenol (2CP), 4-chlorophenol (4CP), 2,4-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP). The reactors were inoculated by mixed bacterial consortia acclimatized to the pollutants at each temperature during 4 months and continuously fed with a mixture of 2CP, 4CP, DCP and TCP at equal concentrations (25-37.5 mg l(-1)) at various hydraulic retention times (HRT). The best removal efficiencies were achieved at a total pollutant loading rate (PLR) of 11 mg l(-1) h(-1) (8.7 h HRT for a total inlet chlorophenols concentration of 100 mg l(-1)) when all pollutants were degraded by more than 99% in both reactors and their concentrations in the effluents were below the detection limit (0.1 mg F 1). The highest chlorophenol removal rates (48.3 and 60.6 mg l(-1) h(-1) in RA and RB bioreactors, respectively), were achieved at a PLR of 81 mg l(-1) h(-1) (1.86 h HRT and at total chlorophenol inlet concentration of 150 mg, l(-1)). Under all conditions, chloride was released to 84 +/- 9% of the theoretical value calculated from the amount of degraded chlorophenols. The dissolved oxygen concentration in the liquid correlated well with the removal of contaminants. (c) 2005 Elsevier Ltd. All rights reserved.