Biodegradation of reactive yellow dye using mixed cells immobilized in different biocarriers by sequential...

In this study, the application of immobilized mixed cells for decolourization, biodegradation, and detoxification of reactive yellow dye (RY15) in textile wastewater was investigated via a sequential anaerobic-aerobic process in bench-scale bioreactors and lab-scale bioreactors as well. The mixed cultures were immobilized using three different biocarriers which were sodium alginate (SA), starch (St), and Gelatin (Ge), by the cross-linking with polyvinyl alcohol (PVA). Results revealed that the immobilized cultures had a potential degrading efficiency in the anaerobic and aerobic environment, targeting the initial structure and the formed compounds, respectively. Complete decolourization (100%) of RY15 was observed with a significant chemical oxygen demand (COD) removal, which enhanced the subsequent aerobic phase. Results demonstrated that COD removals were 92% ± 6.8, 96% ± 3.5, and 100%, using PVA-SA, PVA-St, and PVA-Ge at RY15 initial concentrations of 10 mg/L, respectively. The experimental work was extended to investigate the dye biodegradation in real textile wastewater using mixed cells in immobilized in PVA-SA. The Overloading rate (OLR) and Hydraulic retention time (HRT) of the aerobic bioreactor are 24.5 mg/L h and 41.37 h, respectively. The experimental profiles of RY concentration, COD reduction along with biomass growth, were in good agreement with the model predicted profiles. The effectiveness factors were 0.96 and 0.99 for the anaerobic and aerobic phases, respectively.