Oxidative mineralisation of petroleum refinery effluent using Fenton-like process

► Literature on Fenton oxidation treatment of petroleum refinery effluent (PRE) is scarce. ► Optimised classical Fenton process treatment of a raw PRE within 30min attained a reduction of 98.1% in chemical oxygen demand (COD) and 70% in total organic carbon (TOC). ► Further work at the optimised conditions may establish the method as an economically attractive approach that would negate the need for a pre-treatment step in PRE treatment. Petroleum refinery effluents (PREs) are wastewaters characterised by high values of chemical oxygen demand (COD) and total organic carbon (TOC). Mineralisation of PRE is not commonly reported. For Fenton oxidation, in particular, reported PRE mineralisation is low. In this paper, treatability of a petroleum refinery effluent using a Fenton-like oxidative reaction is described. A statistically designed experimental matrix was used to evaluate the individual and combined effects of process variables based on a five-level central composite design (CCD). Response surface methodology (RSM) was employed to optimise the parameters of interest (COD and TOC), and response surface equations were subsequently developed. These parameters were optimised from studies of the independent variables, for reaction time [tr]=30–240min, molar ratio of hydrogen peroxide to the organic wastewater [H2O2]:[PRE]=2–12 and mass ratio of hydrogen peroxide to catalyst [H2O2]:[Fe3+]=5–20. The COD and TOC of the PRE at an initial pH of 7 were 1343mg O2/L and 398mg C/L, respectively. Under optimal conditions, maximal TOC and COD reduction achieved within 30min of oxidation reaction were 70% and 98.1%, respectively. The obtained models had correlation coefficients (R2 and Radj2) of 0.9984 and 0.9916 for TOC and 0.9636 and 0.8835 for COD. At a pH of 3, corresponding optimal oxidation conditions were found to be [H2O2]=1008.0mM and [Fe3+]=686.0mg, that is, a molar ratio of [H2O2]:[PRE]=12 and mass ratio of [H2O2]:[Fe3+]=5.