Biodegradation of Acid Orange 7 dye using consortium of novel bacterial strains isolated from Persian Gulf water and soil contaminated with petroleum compounds

In this study, the biological degradation of acid orange 7 (AO7) dye in textile wastewater was investigated using a consortium of novel bacterial strains isolated from Persian Gulf water and soil contaminated with petroleum compounds. In this experimental study, a pilot-scale-activated sludge bioreactor with a discontinuous flow was utilized. In this bioreactor, design parameters such as organic load rate (OLR), hydraulic retention time (HRT), and solids retention time (SRT) were considered to be 0.075–0.6 mg COD/L.day, 0.5–4 day, and 10.5–15.5 day, respectively. Bacterial species with the ability to degrade AO7 were identified using the 16S rRNA-PCR method. The results represented that the consortium of azo dye-degrading bacteria isolated from Persian Gulf water and soil contaminated with petroleum compounds in this study included Bacillus paramycoides strain M2 , Pseudomonas putida strain M2a , Pseudoxanthomonas mexicana strain M10 , Microbacterium oxydans strain M7 , and Lysinibacillus macrolides strain M1 . Also, the results were indicative of offering the highest removal efficiency of > 95% by the bioreactor in removing AO7 from textile wastewater, and with increasing OLR and decreasing HRT, the removal efficiency decreased. The values of K s , μ max , K d , and Y using the Monod kinetic model were obtained to be 14.73 mg/L, 0.145 day −1 , 0.625 mg VSS/mgCOD, and 0.052 day −1 , respectively. Graphical Abstract