Removal of Escherichia coli after Treatment Using Ozonation-Ultrafiltration with Iron Oxide-Coated Membranes

Abstract

The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900°C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, ∼50%, ∼86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.

Keywords:

• Ozone
• Ceramic membranes
• Ozonation
• Nanofiltration
• Iron Oxide
• Bacteria
• Catalytic Ozonation
• Membrane Filtration
• Scanning Electron Microscopy (SEM)
• Assimilated Organic Carbon (AOC)

ACKNOWLEDGMENTS

The authors would like to acknowledge the US Environmental Protection Agency (US EPA) Science To Achieve Results (STAR) Program (Grant No. RD830090801) and Michigan section of American Water Works Association (Mi-AWWA) for financial support of this work. Thanks are also due to Ms. Ewa Danielewicz, from the Center for Advanced Microscopy for her assistance during SEM sample preparation. We would also like to thank Mr. David Jackson for his assistance with the membrane coating process and Mr. Michael Satoh and Yolanda Brooks for assistance in the laboratory analysis. Ms. Deborah Rodrigues from Microbiology and Molecular Genetics is also acknowledged for her co-operation and assistance in using the equipment.