Evaluation of chlorine treatment levels on inactivation of human norovirus and MS2 bacteriophage during sewage treatment

Authors: Kingsley, David; FAY, JOHNNA - Us Food & Drug Administration (FDA); CALCI, KEVIN - Us Food & Drug Administration (FDA); POUILLOT, REGIS - Us Food & Drug Administration (FDA); WOODS, JACQUELINE - Us Food & Drug Administration (FDA); CHEN, HAIQIANG - University Of Delaware; Niemira, Brendan; VAN DOREN, JANE - Us Food & Drug Administration (FDA)

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2017
Publication Date: 9/15/2017
Citation: Kingsley, D.H., Fay, J., Calci, K., Pouillot, R., Woods, J., Chen, H., Niemira, B.A., Van Doren, J.M. 2017. Evaluation of chlorine treatment levels on inactivation of human norovirus and MS2 bacteriophage during sewage treatment. Applied and Environmental Microbiology. 83:e01270-17.

Interpretive Summary: Human norovirus (HuNoV) viability cannot be reliably assessed in the laboratory. In this publication, the PGM-MB receptor-binding assay was utilized to evaluate the effect of chlorine on HuNoV during sewage treatment. Results indicate that traditional chlorine-based sewage treatment probably does not inactivate substantial quantities of HuNoV. Results also indicate that the bacteriophage MS2, a common HuNoV indicator, is not substantially inactivated by chlorine-based sewage treatment at typical levels used in sewage treatment, suggesting that male-specific coliphage may have some utility as an environmental indicator of possible sewage and HuNoV contamination. These results provide important information for designing and validating more effective treatments to inactivate HuNoV in sewage systems.

Technical Abstract: This study examined the inactivation of human norovirus (HuNoV) GI.1 and GII.4 by chlorine under conditions that mimic sewage treatment. Using a porcine gastric mucin-magnetic bead (PGM-MB) assay, no statistically significant loss in HuNoV binding (inactivation) was observed for secondary effluent treatments of less than 25 ppm total chlorine, while for both strains 50 and 100 ppm treatments resulted in less than 0.8 log and greater than 3.9 log reductions, respectively. Treatments of 10, 25, 50, and 100 ppm chlorine inactivated 0.31, 1.35, greater than 5, and greater than 5 log of the norovirus indicator, MS2 bacteriophage, respectively. Evaluation of treatment time indicated that the vast majority of MS2 and HuNoV inactivation occurred in the first 5 min for 0.2-um filtered, pre-chlorinated secondary effluent. Free chlorine measurements of secondary effluent seeded with MS2 and HuNoV demonstrated a substantial oxidative burden. For 25, 50, and 100 ppm treatments, free chlorine after 5 min exposure time ranged between 0.21-0.58, 0.28-16.7, and 11.6-53 ppm, respectively. At chlorine treatment levels of greater than 50 ppm, statistically significant differences were observed between reductions for PGM-MB-bound HuNoV (potentially infectious) particles as compared with that for unbound (non-infectious) HuNoV particles or total norovirus particles. While results suggest that MS2 and HuNoV (as measured with PGM-MB binding) behave similarly, although not identically, both have limited susceptibility to chlorine treatments of less than 25 ppm total chlorine. Since sewage treatment is performed at less than 25 ppm total chlorine, targeting a free chlorine level of 0.5-1.0 ppm, these results suggest that traditional chlorine-based sewage treatment does not inactivate HuNoV efficiently.