The application of conventional physicochemical and microbiological techniques for the removal of organic pollutants has limitations for its utilization on wastewaters as landfill leachates because of their high concentration of not easily biodegradable organic compounds. The use of ozone-based technologies is an alternative and complementary treatment for this type of wastewaters. This paper reports the study of the degradation of landfill leachates from different stages of a treatment plant using ozone and ozone + UV. The experimental work included the determination of the temporal evolution of COD, TOC, UV254, and color. Along the experimental runs, the instantaneous off-gas ozone concentration was measured. The reaction kinetics follows a global second order expression with respect to COD and ozone concentrations. A kinetic model which takes into account the gas liquid mass transfer coupled with the chemical reaction was developed, and the corresponding parameters of the reacting system were determined. The mathematical model is able to appropriately simulate COD and ozone concentrations but exhibiting limitations when varying the leachate type. The potential application of ozone was verified, although the estimated efficiencies for COD removal and ozone consumption as well as the effect of UV radiation show variations on their trends. In this sense, it is interesting to note that the relative ozone yield has significant oscillations as the reaction proceeds. Finally, the set of experimental results demonstrates the crucial importance of the selection of process conditions to improve ozone efficiencies. This approach should consider variations in the ozone supply in order to minimize losses as well as the design of exhaustion methods as multiple stage reactors using chemical engineering design tools.

This work reports the degradation of Reactive Blue 19 (RB19) dye using ozone and ozone/UV. The effects of operational parameters such as pH, ozone concentration and UV radiation were examined. A two factor with three levels factorial design was carried out and the interaction between variables was studied. Response surface methodology was applied in order to optimize ozone concentration, pH and UV radiation in terms of the half life time required for discoloration and/or mineralization of the solution. Equations of color and TOC half-life time with respect to operational conditions were determined. Contour plots and a desirability function were used to find the local points of optimization. Optimized reaction conditions were established as pH 8.26, UV radiation of 40 W and ozone concentration of 50 g Nm −3 . A specific experiment was carried out under the optimal conditions where RB19 half life time was 1.59 min and TOC half life time was 30.98 min, confirming the agreement between model and experimental results. The obtained results confirm ozonation as a promising alternative for treatment of wastewater with a high content of recalcitrant reactive dyes.