Removal of norovirus from water by coagulation, flocculation and sedimentation processes

Abstract

In this study, we determined the removal of a prototype human norovirus (Norwalk virus, NV) by bench-scale alum coagulation, flocculation and sedimentation processes using reverse transcriptase polymerase chain reaction (RT-PCR) for norovirus assays. After determining optimum conditions for the coagulation, flocculation and sedimentation processes in terms of turbidity reduction, jar tests were performed using the same waters seeded with test viruses. For comparison, two other important health-related viruses, poliovirus 1 (PV1) and coliphage MS2, were included in this study. The removal of NV by coagulation, flocculation and sedimentation processes based on RT-PCR assay in this study was 1.5 log10, which was similar to that of PV1 and a little lower than that of coliphage MS2 (2 log10) based on the same RT-PCR assay. The removal of NV in this study (1.5 log10) is considerably higher than the one in a recent study using recombinant norovirus virus-like particles (∼0.7 log10). Overall, the results of this study suggest that human noroviruses can be appreciably reduced by a properly-operated coagulation, flocculation and sedimentation processes and the contamination of drinking water by noroviruses should be controlled by conventional water treatment processes with conventional physico-chemical processes and disinfection.