Inactivation of bacteria using Fe3+-loaded montmorillonite

Abstract

Water treatment in developing countries must treat pathogenic microorganisms such as Escherichia coli bacteria using locally available materials. In this study, a typical clay mineral, montmorillonite (MT), was loaded with Fe(III), which has bactericidal properties. Then, the Fe3+-loaded montmorillonite (Fe3+-MT) was used to treat pure E. coli cultures, secondary effluents, and wastewater. Experimental data showed that Na+-MT could not eliminate viable bacteria. On the other hand, using the colony count method to evaluate treatment efficiency, Fe3+-MT was found to be effective for treating E. coli, coliforms, and standard place count bacteria. However, the efficiency differed depending on the type of bacteria; Fe3+-MT treated E. coli and coliform bacteria with approximately equal efficiency and had a lesser effect on the overall bacterial assemblage. The effect of Fe3+-MT also depended on the water quality: a greater treatment efficiency was found in wastewater than in secondary effluents. Additionally, this study investigated the treatment mechanism of Fe3+-MT by measuring the number of viable bacteria and total bacteria using a fluorescent staining method. This analysis showed that the number of viable bacteria decreased, unlike the total number of bacteria, demonstrating that there was an increase in the number of dead bacteria. This confirmed that Fe3+-MT effectively treats bacteria through inactivation.