Bleaching of olive mill wastewater by clay in the presence of hydrogen peroxide

Treatment of olive mill wastewater (OMW) with clayey soils in the presence of hydrogen peroxide (H2O2) allows the elimination of phenolic compounds re sponsible for the black-brownish color of this industrial effluent. The aim of this research was to define optimal physicochemical parameters for the bleaching of OMW with clay in the presence of hydrogen peroxide. Two clayey soil powders were tested (A and B) and the results obtained indicate that high bleaching could be reached after 24 hours exposure of OMW to 7% (W/V) clay material A in the presence of 0.5% (VN) hydrogen peroxide. Under these conditions, the bleaching led to about 87% decrease of polyphenols (PF) an d a 66% decrease of the Chemical Oxygen Demand (COD). The structure of clay and its concentration in iron salts have an effective adsorbent and cataly tic effect on the removal of the majority of polyphenols.