TOXIC EFFECT OF COLORED OLIVE COMPOUNDS ON THE ANAEROBIC-DIGESTION OFOLIVE OIL MILL EFFLUENT IN UASB-LIKE REACTORS

Anaerobic sludge digestion of olive oil mill effluent (OOME) in upflow Anaerobic Sludge Blanket (UASB) reactors was shown to be unstable as a result of both chemical and biological parameters. The study was com plicated by the fact that Chemical Oxygen Demand (GOD) was removed by growth and maintenance of active biomass and by adsorption in and on t he sludge. Coloured compounds caused an inhibition effect on the anaer obic digestion of the wastewater. This inhibition, shown at low COD co ncentrations of diluted COME, was due to accumulation of recalcitrant coloured compounds in the sludge, inducing irreversible inhibition of bacterial growth. Partial decolourization of COME through resin (Duoli te XAD 761) treatment reduced the toxic effect.