Exploring the use of ceramic disk filter coated with Ag/ZnO nanocomposites as an innovative approach for removing Escherichia coli from household drinking water

Ceramic water filter is suitable for low-income families and rural communities in developing countries to obtain safe drinking water because of its low cost and good performance. As an innovative effort, the ceramic disk filter coated with Ag/ZnO nanocomposites (AZ-CDF) was proposed in this study. The manufacture of AZ-CDFs was optimized by experiments based on the Box-Behnken design. The results of thermal field emission scanning electron microscopy (TFE-SEM) and very powerful elemental and structural probe employing radiation from a synchrotron (VESPERS) indicated that Ag/ZnO nanocomposites were mainly distributed on the upper surface of AZ-CDF. The antibacterial activity of AZ-CDF was investigated by detecting the variation of cell status and intracellular reactive oxygen species during a period of time using flow cytometry. Both non-photocatalytic and photocatalytic antibacterial activities of Ag/ZnO nanocomposite contributed to the bacterial reduction property of AZ-CDF. During filtration, the initial Escherichia coli (E. coli) concentration and illumination intensity also influenced the E. coli removal performance of AZ-CDF. When the light illumination intensity was 7000 Lux, AZ-CDF was appropriate to treat the water contaminated by E. coli concentration of less than 10³ cfu/mL. Increasing illumination intensity resulted in the improvement of E. coli removal performance of AZ-CDF. It was concluded the main mechanisms for the E. coli removal of AZ-CDF were filtration, non-photocatalytic and photocatalytic antibacterial activities.