Phenol degradation was carried out by using a modified three-stage airlift packing-bed bioreactor. A laboratory-scale airlift packing-bed reactor, with hydrodynamic flexible packing material in the three-stage bioreactor, was constructed and operated for phenol removal from synthetic wastewater. The airlift packing-bed reactor successfully degraded phenol and lowered the chemical oxygen demand (COD) of wastewater. High COD removal was observed, and much lower sludge effluent was obtained in this investigation. This airlift bioreactor showed a superior hydrodynamics performance and broad operating conditions for phenolic material removal. Different operating modes were discussed to obtain the optimal condition for phenol degradation (i.e., hydraulic retention time [HRT] and gas flowrate of airlift). The HRT and feed phenol concentration of wastewater dominated the removal efficiency of phenol and COD. In this bioreactor, surface loading up to 2.84 g phenol/ m2 x d, almost 100% phenol removal, and over 90% COD removal was achieved. The lower operating cost combined with higher phenol-removal efficiency and a low sludge effluent concentration can be achieved by using this reactor for phenol wastewater treatment.
