A two-stage hybrid depuration of a recalcitrant petroleum
refinery effluent (PRE) was investigated. The [H2O2]:[COD]0 molar
ratio of 6 was found suitable to improve the biodegradability of the
raw PRE from 0.14 to 0.37 making it feasible to be treated by SBR
effectively. Fenton system could eliminate total oil and grease and
more than 95% of the phenol present in the effluent. In addition,
76.5% of COD and 45% of TOC were removed at this stage. The
recalcitrant compounds were degraded into innocuous compounds
since no inhibitory effect on the SBR microorganisms
was observed. The SBR for one single cycle of 10 h HRT decreased
the remaining COD and TOC to the levels below the discharge
standards and no residual catalyst in the final treated effluent was
detected. The results indicated that the treatment of highly
recalcitrant PRE can be successfully attained at low Fenton
reagent’s concentration and running SBR for one cycle.