Chemical-Biological Treatment of Table Olive Manufacturing Wastewater

Wastewater generated in the table olive processing industries has been treated by means of an integrated wet air oxidation-aerobic biodegradation process. Chemical oxygen demand (COD) conversion in the range of 30-60% (6 h of treatment) has been achieved by using relatively mild conditions (443-483 K and 3.0-7.0 MPa of total pressure using air). Use of the homogeneous catalysts [copper (II)] or radical promoters (hydrogen peroxide) resulted in a higher efficiency of the process (roughly between 16 and 33% COD removal improvement depending on operating conditions). Biodegradability tests, conducted after the oxidation pretreatment, showed a negative effect with the addition of copper to the reaction media. Promoted experiments resulted in the highest values of biodegradability (measured as the ratio of biological oxygen demand to COD). The rate of the COD biodegradation was compared to the kinetics of the aerobic process without a previous chemical preoxidation. The calculated kinetic parameters showed the positive effect of the pretreatment (maximum growth rate of 0.03 ± 0.006 h-1 and 0.014 ± 0.00014 h-1). Acclimation of microorganisms to oxygenated species formed in a chemical preoxidation step enhanced the efficacy of the biodegradation (maximum growth rate of 0.04 ± 0.007 h-1).