Application of a CPC-based photocatalytic reactor to detoxification of washing waters from agricultural industries

Abstract
A practical application consisting of solar-driven photocatalytic detoxification of washing waters from a factory of oranges packaging in Casablanca (Morocco) is presented. Water was collected and transported from Casablanca to Rabat and tested via photocatalytic oxidation in a solar CPC pilot plant. Catalyst loadings of 0.5 g.L^-1 (P-25 slurry) were used in all the experiments. The water had initial concentrations of Aldrin, Dieldrin and EPTC in the range of 100-200 µg.L^-1. It contained some surfactants, as well as ions like nitrate, nitrite, chloride and orthophosphate. The complexity of the water and competition between pesticides led to the result of different degradation rates depending on the pollutant. Dieldrin underwent complete degradation (concentration below 0.1 µg.L_-1 ) after 30 min. of illumination, but EPTC (125 min.) and Aldrin (220 min.) required higher residence times. Compared to previous tests carried out with single pollutants in deionized water residence time is more than double the one for real multicomponent water. Estimation of water treatment costs for reducing one order of magnitude the highest recalcitrant pesticide (Aldrin) in the mixture leads to a figure of 0.58 $.m^-3.