Treatment of high strength olive mill wastewater by Fenton's reagent and aerobic biological process

Abstract

The present work describes the application of a Fenton's reagent pretreatment combined with an aerobic biological process to remove the olive mill wastewater (OMW) pollutant load. Wastewater treatment was monitored by means of global parameters directly related to the concentration of organic compounds in OMW effluents: chemical oxygen demand (COD) and total phenolic content (TP). The biologic treatment itself allowed conversions from 67 to 83% of COD and 55 to 61% of TP. In the Fenton's reagent process a fixed H₂O₂/COD ratio of 0.20, a pH = 3.5 and a H₂O₂/Fe²⁺ molar ratio of 15 were defined as optimal conditions to treat the OMW. For an initial COD load of 92.5 g/L⁻¹) the Fenton reagent-biologic combined process allowed a global removal of 80.7% COD and 93.7% TP. A kinetic study was performed resorting to the Grau model. The application of this model allowed observing an increase in the kinetic constant of the combined process (k_FB = 24.7 g/L⁻¹ day) when compared to the single aerobic process (k_B = 19.4 g/L⁻¹ day).

Keywords:

• Olive mill effluent
• chemical oxidation
• biological treatment
• combined Fenton-biologic treatment
• Grau model kinetic study.

Acknowledgments

The authors are grateful for the financial support provided by the Fundação para a Ciência e a Tecnologia (Portugal) to the Centro de Química de Vila Real through the PEst-C/QUI/UI0616/2011 project.