Effects of the Organic-Loading Rate on the Performance of an Anaerobic Fluidized-Bed Reactor Treating Synthetic Wastewater Containing Phenol

An anaerobic fluidized-bed bioreactor (AFBR), consisting of a vertical acrylic tube containing polystyrene particles as a support material for microbial adhesion, was operated for an extended period of time to treat synthetic wastewater containing phenol as the sole carbon source, at progressively increasing concentrations of 50–700 mg L−1, corresponding to organic-loading rates (OLRs) of 0.12–1.67 kg chemical oxygen demand (COD) m−3 day−1. The inoculum used was sludge from an upflow anaerobic sludge blanket reactor treating swine-manure wastewater. The AFBR was operated at a hydraulic retention time of 24 h at 30°C. The reactor performance was evaluated with respect to OLR and differences between influent and effluent phenol concentrations, COD, bicarbonate alkalinity, volatile acidity, volatile suspended solids and pH. The pH values varied between 6.59 and 8.21 over the operating period. The alkalinity concentrations of the influent and effluent were 180 and 294 mg L−1, respectively. The system achieved phenol- and COD-removal efficiencies greater than 93% and 91%, respectively, indicating the high capability of the proposed system for degrading liquid effluents containing phenol.