Biotreatment using immobilized cells (IC) technology has proved to be the most promising and most economical approach for the removal of many toxic organic pollutants found in petroleum-refinery wastewater (PRW) such as phenol. This study was undertaken to evaluate the degradation of phenol by Pseudomonas cells individually immobilized in two different bio-carrier matrices including polyvinyl alcohol-guar gum (PVA-GG) and polyvinyl alcohol-agar agar (PVA-AA). Results of batch experiments revealed that complete removal of phenol was attained in the first cycle after 150 min using immobilized cells (IC) in both PVA-GG and PVA-AA. Additional cycles were confirmed to evaluate the validity of recycling beads of immobilized cells for phenol biodegradation. Results revealed that the phenol percentage removals were 95, 92, 86, and 84 % for second, third, fourth, and fifth cycles, respectively using Pseudomonas immobilized in PVA-GG beads. Whereby they were 96, 92, 90, and 84 % using Pseudomonas immobilized in PVA-AA beads for the same sequence of cycles.
