In this study, the cometabolic degradation of carbazole (CA), dibenzofuran (DBF), and dibenzothiphene (DBT) by immobilized Arthrobacter sp. W1 cells pregrown with naphthalene was investigated. Four kinds of polymers were evaluated as immobilization supports for strain W1. After comparison with agar, alginate, and kappa-carrageenan, gellan gum was selected as the optimal immobilization support. Furthermore, magnetic Fe3O4 nanoparticle was selected as most suitable nanoparticle for immobilization and the optimal concentration was 80 mg/L. The relationship between specific degradation rate and the initial concentration of CA, DBF and DBT was described well by Michaelis-Menten kinetics. The recycling experiments demonstrated that the magnetically immobilized cells coupling with activation zeolite showed highly bioremediation activity on the coking wastewater containing high concentration of phenol, naphthalene, CA, DBF and DBT during seven recycles. Toxicity assessment indicated the treatment of the coking wastewater by magnetically immobilized cells with activation zeolite led to less toxicity than untreated wastewater. (C) 2014 Elsevier Ltd. All rights reserved.