Photocatalytic ozonation of winery wastewaters.

The combination of UV-A/vis radiation and ozone, in the presence of titanium dioxide, has been investigated as a potential destructive technology for the treatment of winery wastewaters. The contribution of the adsorption stage, single ozonation, photolytic ozonation, and photocatalysis has previously been assessed. Adsorption onto the TiO 2 surface accounts for a 15-20% removal of the initial chemical oxygen demand (COD). The rest of the subsystems attain COD conversion values in the range of 37-43%. The photocatalytic ozonation of the effluent, under the operating conditions investigated, increases the COD depletion to a value close to 80%. The working pH was studied in the range of 3-11, the optimum value being located in the acidic region (pH 3). A saturation-like behavior is experienced when the amount of TiO 2 used is varied in the interval of 0-3 g L(-1). Contrary to the use of ozone alone, the system UV-A/vis/O3/TiO2 leads to the total mineralization of the COD removed. A proposed pseudoempirical model suggested the existence of a synergistic effect when radiation, ozone, and titanium dioxide are combined.