Oxidative degradation of textile waste water. Modeling reactor performance

This study reports on the Fenton and photo-assisted Fenton treatment of textile waste waters from nanofiltration of biologically treated secondary textile industry effluents produced in a large scale plant in Northern of Italy. The influence of the hydrodynamic and chemical parameters affecting the degradation of the non-biodegradable residues of textile waters being continuously replaced near the light source were studied in a flow reactor. Cu2++Fe2+/3+-ions mediated oxidation processes under light analogous to the Haber–Weiss cycle were found to be suitable to degrade the recalcitrant part of the textile waters after the initial biological treatment. The optical absorption of the iron-chromophore and the spectral emission of the light source used but not the intensity of the applied light were the most important factors determining the kinetics and efficiency of the applied treatment. A single polynomial exponential expression was constructed for the treatment of the experimental data to make the most economical use of the oxidant, electrical energy and processing time. This approach allowed the prediction of the lowest final TOC values when optimizing the main variables affecting the degradation via phenomenological modeling. Insight is given into the way of handling simultaneously the optimization of five chemical and physical variables intervening in the degradation process by way of a program on a desk computer. As a result the data from the degradation runs were used to evaluate the coefficients of the polynomial exponential expression rendering 2D-contour surface plots. A correlation factor >95% was found between the experimental and the values predicted by the mathematical expression following an exponential decay law.