There are little literatures about the accelerating effect of redox mediators on the denitrification processes. In this paper, a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology was first explored, and the accelerating effect of redox mediator on the denitrification processes was conducted with immobilized anthraquinone. Anthraquinone as a redox mediator was able to increase the denitrification rate, and was immobilized by entrapment in calcium alginate (CA). The results suggested that the artificial redox mediator anthraquinone was found to be capable of raising about 2-fold denitrification rate, and the stabilized oxidation reduction potential (ORP) values with anthraquinone immobilization beads were lower around 20 mV than the control without anthraquinone immobilization beads. The results of repeated-batch operations shown that anthraquinone immobilization beads appeared to exhibit good reusability. The study explored a great improvement of the redox mediator application and the new bio-treatment concept for the denitrification processes. (C) 2010 Elsevier Ltd. All rights reserved.