Since March, 1995, Amsterdam Water Supply of the Netherlands has been usingbiological activated carbon filtration (BACF) at the Leiduin plant that pretreatsRhine River water prior to artificial recharge in the dune area west ofAmsterdam. Post treatment comprises rapid sand filtration, ozonation, hardnessremoval, biological activated carbon filtration, and slow sand filtration. At thestart, the carbon reactivation frequency was set at 18 months, based on removalefficiencies for AOX (adsorbable organic halogens), dissolved organic carbon,pesticides, and micropollutants. After four years of operating a pilot plant inparallel with the full-scale plant, the remaining removal capacity and thebreak-through profile of the carbon filters were investigated. In contrast to thefull-scale plant, no carbon reactivation was applied in the pilot plant duringthe 4 years of operation. This paper discusses the results of the study. Includes 4 references, table, figures.