| The accelerating effect of anthanquinone as a redox mediator in the bio-decolorization was conducted. Decolorization of azo dyes was carried out experimentally using the salt-tolerant bacteria under immobilized anthanquinone and high salt conditions. Anthnaquinone used as a redox mediator was able to increase the decolorization rate of wastewater containing azo dyes, and was immobilized by entrapment in calcium alginate (CA), Polyvinyl alcohol (PVA)-H3BO3, Polyvinyl alcohol (PVA)-calcium alginate (CA) and agar, respectively. The effects of various operating conditions such as anthnaquinone bead number and dissolved oxygen on microbial decolorization were investigated experimentally. At the same time, immobilized anthanquinone was tested to assess the effects on the change of the Oxidation-Reduction Potential (ORP) values during the decolorization processes. High decolorization rate was obtained in the presence of 200 anthnaquinone immobilization beads at 30°C, which increased 1.5～2 fold, in comparison with the control of free-anthanquinone. The oxidation-reduction potential (ORP) values stabilized around –260～265 mV after 6 hours anoxic conditions, which lowered ORP values around –10～15 mV by anthanquinone。The reusability of the anthnaquinone immobilization beads was evaluated with repeated-bacth decolorization experiments. After four repeated experiments, the decolorization rate of calcium alginate (CA) immobilized anthnaquinone retained over 90% of their original activity. The experiments explored a great improvement of the redox mediator application and the new bio-treatment concept. |
