A biotrickling filter (BTF) for treating high ethanol loads was operated for one year and the effect of operating conditions was studied. The BTF was operated in a range of ethanol inlet concentrations of 0.2-15.0 g m(-3) and at three different residence times (30, 65 and 130 s). The experiments show that removal efficiency decreased with increasing ethanol inlet concentration and decreasing air residence time. Removal efficiency varied in the range of 60-100%. A maximum elimination capacity of 970 g m(-3) h(-1) was obtained for an inlet load of 1610 gm(-3) h(-1). At a. constant residence time, the carbon dioxide (CO2) production rate varied with ethanol inlet concentration. BTF presented the maximum CO2 production rate in the range of inlet concentration of 3.0-7.0gm(-3). Two strategies for controlling biomass accumulation were applied: one consisted in periodical washing; the other combined periodical washing with nutrient starvation by consuming less water and energy. Both strategies led to maintaining the BTF stable, with high adaptability and reproducibility.