Application of Hybrid Activated Sludge Reactor to Improve Activated Sludge Process for Oily Wastewater Treatment

Activated sludge process is one of the well-establish methods for biological treatment of oily wastewater, which use in Iranian oil refineries. However, the process involved many problems such as low efficiency at high concentration of hydrocarbon, instability during hydraulics shocks and bulking phenomena. In this paper attached and suspended growth was used to improve conventional activated sludge treatment process. A hybrid activated sludge reactor, with 34.5 liter capacity, was used in order to treat synthetic high CODs oily wastewater and the results were compared with those obtained from conventional activated sludge reactor. Novel media used in this fixed-film biofilm bioreactor, provided a high surface area-to-volume ratio (600m2/m3). Reactor biodegradability for COD and TPH was evaluated for different hydraulic retention time (HRT) and oil pollution concentration. In optimum condition (T= 27 ºC, pH= 7.5, DO= 4.1mg/l, recycle sludge ratio= 1 and COD/TPH= 2.5) the removal efficiency of HASBR for TPH and COD were 90% and over 95% respectively which showed a significant difference in comparison with the conventional activated sludge reactor in the same conditions. Therefore, existing conventional activated sludge plants could be upgraded and improved by changing the reactor configuration and introducing support media into aeration tank.