Live cells of a phenol-degrading bacterium, Rhodococcus sp. DCB-p0610, were immobilized on granular activated carbon (GAC) by adsorption and in alginate beads by entrapment. These immobilized particles were packed separately into two column reactors, which were used for continuous treatment of a mineral medium containing high phenol concentrations. The GAC was made of coconut shell. The alginate beads contained 1% powder activated carbon, 4% calcium alginate and 1% wet microbial cells. The beads were hardened by immersion in a polyethylenimine (PEI) solution. The activated carbon contained in the alginate beads adsorbed phenol to provide a local condition that inhibited growth of other bacteria, except the designated Rhodococcus sp. p0610. Saturated GAC also supported the growth of strain p0610. A comparison of both materials for cell immobilization showed that the phenol removal rate on alginate beads was higher than that on GAC when the influent contained 1000 ppm phenol. However, the GAC reactor was more stable in providing consistent cellular activity during DO and pH changes.