THE USE OF OZONE, OZONE PLUS UV RADIATION, AND AEROBIC MICROORGANISMS IN THE PURIFICATION OF SOME AGRO-INDUSTRIAL WASTEWATERS

ABSTRACT

The oxidation of the pollutant organic matter present in wastewaters generated during different stages in the black table-olive industry was investigated by using ozone alone or combined with UV radiation; by using aerobic microorganisms; and finally, by aerobic degradation of the previously ozonated wastewaters. In the ozonation processes, the removal of substrate (COD) and aromatic compounds, the decreases in BOD₅ and pH, and the ozone consumed in the reaction were evaluated. A kinetic study was conducted that led to the evaluation of the stoichiometric ratio for the chemical reaction, as well as the rate constants for the substrate reduction and ozone disappearance. In the single aerobic degradation treatment, the evolution of substrate and biomass was monitored during the process, and a kinetic study was performed by applying the Contois model to the experimental data, giving the specific biokinetic constant, the cell yield coefficient, and the rate constant for the microorganism death phase. Finally, a combined process was performed, consisting in the aerobic degradation of pre-ozonated wastewaters, and the effect of such chemical pretreatment on the substrate removal and kinetic parameters of the later biological stage is discussed.

Keywords:

• Wastewaters
• Black table-olives
• Ozone alone and combined with UV radiation
• Aerobic degradation
• Ozonation followed by aerobic treatment

ACKNOWLEDGMENTS

This research has been supported by the “Comision Interministerial de Ciencia y Tecnologia” (CICYT) of Spain, under Project 1FD 97-1866. Also, the research group wishes to thank Junta de Extremadura for the financial support under Grant IPR98A014.