Simultaneous removal of selenite and phenol from wastewater in an upflow fungal pellet bioreactor

BACKGROUND The simultaneous treatment of selenite and phenol containing wastewater in batch and continuous systems, inoculated with pellets of Phanerochaete chrysosporium, was evaluated in this study. RESULTS Synthetic oil refinery wastewater containing 15 mg L-1 selenite and 100 - 600 mg L-1 phenol was used in batch incubations for 5 days. Orange-red colored pellets developed during selenite incubations in the presence of up to 400 mg L-1 of phenol, which confirms the formation of elemental selenium with removal efficiencies ranging from 57 - 78.5% and 75 - 90.8% for, respectively, phenol and selenite. Continuous experiments in two upflow fungal pelleted bioreactors (30 oC, pH 4.5, hydraulic retention time of 16.7 h) fed the synthetic oil refinery wastewater containing phenol or phenol with selenite were performed for 38 days. The maximum removal efficiency of phenol in the fungal bioreactor was 100% (up to day 26). CONCLUSION The selenite mass balance showed the overall maximum removal efficiency of selenite in the presence of phenol was 67.3%. The critical phenol and selenite loading rates of the upflow bioreactors were ~12 and 4.3 mg L-1.h-1, respectively.