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Abstract
The mechanism of bacteria abatement during an electrocoagulation treatment was investigated with the soluble aluminum electrodes on Escherichia coli cultures in model solutions. The efficiency of E. coli abatement was established under two kinds of experiments: in a 1 L batch reactor and in a 10 L pilot reactor with flowing solution. About 97% of abatement was obtained after 35 min with a current intensity of 0.22 A. Electrocoagulation exhibited greater bacteria abatements by a 2-log factor than for a chemical coagulation using identical quantities of aluminum. The decanted flocs of electrocoagulation were analyzed by X-ray diffraction which showed that electrogenerated alumina contained nanocrystallites of boehmite AlOOH. Moreover, these flocs contained living bacteria. This observation suggests that bacteria removal during electrocoagulation could be attributed to a strong bacteria adhesion on the surface of electrogenerated alumina particles followed by a separation of the decanted solids. The abatement of E. coli by electrocoagulation was the result of concomitant processes: mortality due to depletion of oxygen and nutrient species and adsorption on alumina and sedimentation. Redox potential measurement showed that during electrocoagulation the solution was not oxidizing and that E. coli removal can not be attributed to chlorine formation. The electrocoagulation treatment led to bacteria removal but it was not a true disinfection process.
Acknowledgments
The authors are grateful to Yvane Lelièvre of Ecole des Métiers de l’Environnement for her helpful assistance during the bacteria analyses.