Science and Education Publishing American Journal of Microbiological Research 1 4 2013 12 05 Combined Application of Biological-Photocatalytic Process in Degradation of Reactive Black Dye: An Excellent Outcome 92 97 EN Maulin P Shah Industrial Waste Water Research Laboratory, Applied & Environmental Microbiology Lab, Enviro Technology Limited (CETP), Ankleshwar, Gujarat, India AJMR2013145 10.12691/ajmr-1-4-5 2013 09 24 2013 11 23 2013 12 05 In the present study, the decolorization and degradation of Reactive Black 5 azo dye was investigated by biological, photocatalytic (UV/TiO2) and combined processes. An application of Pseudomonas aeruginosa ETL-2211 in treatment of the synthetic medium containing RB5 indicated complete decolorization of the dye with 200 mg/L in less than 24 h. Degradation of the aromatic rings, resulting from the destruction of the dye, did not occur during the biological treatment. Mineralization of 50 mg/L RB5 solution was obtained after 80 min by photocatalytic process (in presence of 0.2 g/L TiO2). COD (chemical oxygen demand) was not detectable after complete decolorization of 50 mg/L RB5 solution. However, photocatalytic process was not effective in the removal of the dye at high concentrations (≥200 mg/L). With 200 mg/L concentration, 74.9% of decolorization was achieved after 4 h illumination under photocatalytic process and the absorbance peak in UV region (attributed to aromatic rings) was not completely removed. A two-step treatment process, namely, biological treatment by bacteria followed by photocatalytic degradation, was also assessed. In the combined process (with 200 mg/L RB5), absorbance peak in UV region significantly disappeared after 2 h illumination and about 60% COD removal was achieved in the biological step. It is suggested that the combined process is more effective than the biological and photocatalytic treatments in the remediation of aromatic rings.