Kinetic and hydrodynamic assessment of an aerobic purification system for petroleum refinery wastewater treatment in a continuous regime

Different petroleum refinery wastewater (PRWW) loading rates and solid retention times were employed to determine the coefficients of chemical oxygen demand (COD) removal kinetics using a continuous stirred tank reactor (CSTR). To evaluate kinetic coefficients, a new approach that could be useful for all recalcitrant wastewater samples was developed. The observed range of COD removal was from 89.9% to 96.5%, with an organic loading rate range of 0.177 kg COD kg−1 mixed liquor volatile suspended solids per day (MLVSS.d) to 0.744 kg COD kg−1 MLVSS.d. Different kinetic parameters were computed and compared with the theoretical parameters. The specific growth rate obtained in this study exhibited the efficiency and faster biodegradation rate of the proposed method compared with the previous respirometric method for treating PRWW. High sensitivity was observed for effluent COD toward Ks and μmax. Bacterial identification determined that the predominant bacteria were Pseudomonas putida, Acidovorax delafieldii, and Aeromonas hydrophila. Residence time distribution (RTD) curve analysis provided a better estimate for complete mixing at a hydraulic retention time (HRT) than at 19.2 h HRT and 25.6 h HRT.