COMBINED PHYSICOCHEMICAL AND BIOLOGICAL TREATMENT OF REFINERY WASTEWATER

Petroleum refining industries are producing wastewater that contains hydrocarbons,
phenol and dissolved minerals. These compounds result in environmental and health
effects. In this study, actual petroleum refinery wastewater was treated using the Fenton
process to improve its biodegradability for post treatment by a laboratory-scale
Sequencing Batch Reactor (SBR). Response Surface Methodology (RSM) was applied
for optimization and data analysis of the Fenton process. The maximum biodegradability
was achieved at the reaction time of 60 minutes and at a constant H2O2/COD molar ratio
of 2 and H2O2/Fe2+ molar ratio of 5 to give 0.44 BOD5/COD with 79 and 77% COD and
BOD removal efficiency, respectively. The results is considered acceptable and satisfied
based on ANOVA analysis (P: <0.0001, R2:0.95, Adj. R2 : 0.91, AP: 16.479 and CV: 6.09).
Preliminary performance of the SBR indicated wastewater load (food) to microorganisms
ratio (F/M) of 0.1 was the most suitable ratio as the lowest COD concentration was
achieved in the effluent.