New application of gelatin and starch as biocarriers for the biodegradation of reactive blue azo dye using immobilized mixed cells.

Reactive azo dyes, if discharged in unmonitored manner to natural water bodies, can cause remarkable irreversible damage. The current study is centered on the decolorization and biodegradation of reactive blue (RB4) azo dye in an integrated sequential anaerobic-aerobic batch mode process. The biodegradation of reactive blue (RB4) was accomplished using alternatively both starch and gelatin-immobilized mixed cells. Activated sludge freshly collected from a sewage treatment plant was used as the biocatalyst. Complete decolorization of 10 mg/L RB4 under anaerobic conditions observed within 30 h by using individually mixed bacterial cells immobilized with; (1) starch cross-linked with polyvinyl alcohol (PVA-St beads), and (2) gelatin cross-linked with polyvinyl alcohol (PVA-Ge beads). The results revealed that maximum removal efficiencies of chemical oxygen demand (COD) under aerobic conditions were 89, 88, and 86%, using PVA-St beads, whereby they were 90, 85, 84% using PVA-Ge beads occurred within 70, 90 and 100 h at detected concentrations of 10, 20, and 40 mg/L, respectively. The effect of biocarrier has been proven to be negligible as the results were comparable using both bio-carriers.

Biodegradation of reactive yellow dye using mixed cells immobilized in different biocarriers by sequential anaerobic/aerobic biotreatment: experimental and modelling study.

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.