Electrolytic reduction improves treatability of humic acids containing water streams

BACKGROUND: An understanding of the structure of humic acids is essential for their degradation or physical removal from wastewaters. This work aims at targeting the reactivity of these molecules by modifying their properties. Structural alterations were carried out by electrolytically reducing the solution containing humic acid in an electrolytic cell to convert them into less polar structures. RESULTS: Overall it was observed that electrolytic reduction of humic acids strongly facilitated their further treatability. First, the reduced forms of humic acids exhibited improved adsorption on activated carbon. For I kW h of electrical energy consumed during electrolytic reduction, the additional chemical oxygen demand (COD) adsorbed was 60 g for a synthetic humic acid solution. Similarly, the additional COD adsorbed (kW h)(-1) was found to be 35 g and 112 g for humic acid-rich effluent and landfill leachate, respectively. In comparison with non-reduced control samples, a 200-fold decrease in the chloroform formation was observed when electrolytically reduced drinking water samples were supplemented with a chlorine dosage of 150 mg L-1. Moreover, an enhanced membrane flux was obtained with electrically reduced samples, indicating their improved membrane filterability. CONCLUSION: The electrolyzed humus species were characterized by analyzing their surface tension and particle size. This work addresses an alternative technology for the treatment of water streams containing humic acids. (c) 2007 Society of Chemical Industry.