Feasibility study on anaerobic biodegradation of azo dye reactive orange 16

Anaerobic digestion of textile azo-dyes is very effective and widely used since it is cost-effective and energy efficient. The present study deals with the anaerobic degradation of reactive orange 16 (RO 16, an azo-dye) using mixed microbial culture. 80 mL each of three different concentrations of RO 16 (100, 200 and 300 ppm) were taken in 150 mL serum vials containing 20 mL of mixed microbial culture and studied periodically. HPLC and UV data revealed that more than 90% of the color was removed within the very first week of the reactor startup. A high COD removal efficiency (>= 80%) was achieved after the steady state. Methane and VFAs were produced, and monitored by Gas chromatography. The pH of the medium was slightly acidic favoring methanogenic activity. The diversity of the microbial community was studied by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) amplified products of the bacterial and archeal 16S rRNA and the results showed the presence of significant population of acetogens as well as methanogens in the reactor. Quantitative real time PCR (qPCR) was used for the quantitative analysis of some major genera. This study showed that strategic operation of the anaerobic digester can be a viable option for effective decolorization of a complex substrate resulting in energy (biogas) generation.