Photocatalytic Removal of Escherichia Coli and Streptococcus Faecalis from Water Using Immobilized ZnO Nanoparticles

Abstract

Background and Objectives: Among different water treatment methods, photocatalytic process is applied as a new efficient technology with appropriate potential to remove inorganic, organic and microbial contaminants from water. This study aimed to evaluate photocatalytic removal of Escherichia coli and Streptococcus faecalis bacteria as microbial indicators of drinking water using immobilized ZnO nanoparticles on glass plates. Methods: In this study, at first characteristics of ZnO nanoparticles were determined using scanning electron microscope (SEM) equipped with EDX system and X-ray diffraction (XRD), then ZnO nanoparticles were immobilized on glass plates using thermal method. The water samples containing the studied bacteria were irradiated by different intensities of UV-A and the effects of intensity and duration of irradiation , number of bacteria, number of immobilized ZnO nanoparticles layers, and reactor flow on the photocatalytic removal of the bacteria were evaluated. Results: The optimal photocatalytic removal for both Escherichia coli and Streptococcus faecalis bacteria using one layer of immobilized ZnO nanoparticles, under 360 µWs/cm 2 UV-A radiation for 2-40 and 2-50 minutes was 10-1000 CFU/100 ml. Photocatalytic process efficiency was promoted by increasing the duration and intensity of radiation intensity up to 360µWs/cm 2 and was decreased by increasing the numbers of bacteria. In addition, Streptococcus faecalis bacteria were more resistant to photocatalytic process than Escherichia coli . Conclusion: photocatalytic removal of bacterial contaminations using immobilized ZnO nanoparticles on glass plates is a novel technology and effective process that could be considered for water disinfection .

Keywords

• photocatalytic removal
• immobilized zno nanoparticles
• escherichia coli
• streptococcus faecalis