| The performance of a membrane bioreactor treating oily wastewater generated by a petroleum refinery was
investigated at mixed liquor suspended solids concentrations of 6.5 and 8.5 g/l with hydraulic retention times
ranging from 12 to 24 h. An evolutionary polynomial regression technique and multi-kinetic models consisting of
the first-order, Grau second-order, and modified Stover-Kincannon were applied for predicting the performance
of the bioreactor. The results showed that a maximum chemical oxygen demand reduction of 97% is achievable
at the mixed liquor suspended solids of 8.5 g/l and hydraulic retention time of 24 h. The results also revealed
positive influence of higher mixed liquor suspended solids and hydraulic retention time values on the bioreactor
performance. In addition, the high accuracy of the evolutionary polynomial regression evidenced its capability in
investigating the membrane bioreactor. Based on the analysis performed by the resulted model from the evolutionary polynomial regression, the optimum operating conditions (hydraulic retention time of 21 h; mixed
liquor suspended solids of 8.2 g/l) were recommended. According to the kinetic evaluation, the Grau secondorder and modified Stover-Kincannon kinetics seemed to be the best approach in describing the chemical oxygen
demand reduction in the membrane bioreactor. |