Oil-Refinery Wastewater Treatment by Biofilm Processes: Moving Bed Reactor and Biological Activated Carbon Filter

Biological treatment of an oil-refinery wastewater was investigated in a moving bed biofilm reactor (MBBR) followed by a biological activated carbon filter (BAC) to investigate the possibility of treated wastewater reuse.The MBBR was operated at different hydraulic retention times (HRT) (12, 9, 6 and 3 h) and the best performance was achieved with a HRT of 6 hours, employing a bed to bioreactor volume ratio (VB/VR) of 0.6. COD and N-NH4+ MBBR effluent concentrations ranged from 46 to 62 mg.l−1 (removal efficiency of 74 - 86%) and 2 to 6 mg.l-1 (removal efficiency of 45 - 86%), respectively. This effluent was further polished in biological activated carbon filters (BAC) or granular activated carbon filters (GAC).Operation of the BAC filters with a retention time of 0.43 h was able to produce an effluent with low dissolved organic carbon (DOC) content (2 to 4 mg.l−1) (removal efficiency of 52 and 75%). The quality of the BAC effluent was achieved during 107 days of operation. Granular activated carbon filters (GAC) were operated in parallel with BAC filters and, after 18 days running they were completely saturated.After the sequential treatment in biofilm reactors, the effluent met the required quality for reuse in the oil-refinery.