Treatment of real non-biodegradable wastewater: Feasibility analysis of a zero-valent iron/H2O2 process

Textile industries present notable environmental problems related mainly to the use and management of water resources. The application of advanced oxidation technologies (AOT) to a real and complex system was analyzed. The degradation of a real textile effluent in the presence of commercial steel wool (CSW, zero-valent iron) and H2O2 as oxidant was studied. The effects of H2O2 concentration (0-0.08 mol L-1), mass of CSW (0-0.4 g L-1) and temperature (15-45 degrees C) on the reduction of the chemical oxygen demand (COD) of the textile effluent were evaluated. Kinetic studies were performed at laboratory and pilot scales at different temperatures under optimal conditions (0.037 mol L-1 of H2O2 and 0.247 g L-1 of CSW). Iron species (Fe2+, Fe3+ total Fe) were quantified in solution for different experiments as a function of time. COD reductions of 87.69% at lab scale and 89.55% at optimized pilot scale in 300 min (140.66 mgO(2) L-1 of COD, final discharge) were obtained. A metallurgical residue was tested as iron source, obtaining high COD removal (65%). Operating costs were calculated. Phytotoxicity tests performed before and after treatment showed that the effluent treated under optimal conditions was non-toxic.