Abstract

The elimination of total and fecal coliforms, from raw surface water, was carried out by electrochemical oxidation using either boron doped diamond (BDD/Ti) or graphite (GP) anodes, in a chloride-free medium. The optimal values of the operation parameters, maximizing the coliform elimination percentage, were determined using statistical experimental design. The current density (j: 2–20 mA/cm2), the conductivity (σ: 500–900 μS/cm) and the anode materials (An) were considered as variables to perform the Box-Behnken experimental design together with the response surface methodology analysis for optimization. The statistical analysis indicated that, in the evaluated range, the disinfection efficiency increased with an increase in j and decreased with an increase in σ. The following optimal conditions for the elimination of total and fecal coliforms were found: j: 10 mA/cm2, σ: 500 μS/cm and BDD/Ti used as anode material. The BDD/Ti electrode let to achieve complete coliform elimination after ca. 20 min of reaction while the GP one needed ca. 27 min. In water treated with both BDD/Ti and GP anode, after 7 days, any coliforms growth was observed. As a result of the oxidation process, the total organic carbon and nitrite concentration decreased while nitrate concentration increased.

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