eng Science and Education Publishing American Journal of Microbiological Research 2013-12-05 1 4 92 97 10.12691/ajmr-1-4-5 AJMR2013145 article Maulin P Shah shahmp@uniphos.com 1 Industrial Waste Water Research Laboratory, Applied & Environmental Microbiology Lab, Enviro Technology Limited (CETP), Ankleshwar, Gujarat, India 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. http://pubs.sciepub.com/ajmr/1/4/5/ajmr-1-4-5.pdf azo dyesPseudomonas aeruginosacombined wastewater treatment