Industrial wastewater treated by galvanic, galvanic Fenton, and hydrogen peroxide systems

Abstract

Industrial wastewater containing effluents from 190 factories located at an industrial park in Toluca State, Mexico, was subjected to galvanic (GT), galvanic Fenton (GF), and hydrogen peroxide treatments to remove organic matter. The galvanic system uses iron-copper electrodes to produce Fe2+ in situ. For the GF system, hydrogen peroxide was applied to produce hydroxyl radicals. The GF system does not require energy, unlike the analogous electro-Fenton system, and, in fact, it is possible to generate an electric current (∼220 mV) from the chemical reactions. A synergistic effect was observed with GF treatment at pH 2.8 and a H2O2/Fe2+ ratio of 19:1 (i.e. 7840 mg H2O2/L and 408 mg Fe2+/L), leading to high removal percentages for color (76%), soluble chemical oxygen demand (71%), and total organic carbon (79%), while degradations of 43% and 48% were achieved for biochemical oxygen demand and nitrates, respectively. Fluorescence and IR spectroscopy analyses of raw and treated wastewater samples were performed with the aim of establishing the anthropic origin of the dissolved organic matter. Fluorescence spectroscopy showed that GF treatment eliminated the anthropogenic organic matter associated with aromatic groups and proteins, enhanced effluent biodegradability, did not increase toxicity, and reduced the sub-lethal effects observed for lettuce radicles. Most importantly, the removal efficiencies of GF treatment were comparable with those of analogous electrochemical advanced oxidation processes based on Fenton reactions.