3 years ago

Evaluation of Chlorine Treatment Levels on Inactivation of Human Norovirus and MS2 Bacteriophage during Sewage Treatment.

Van Doren, Fay, Niemira, Woods, Pouillot, Kingsley, Chen, Calci
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 ≤25 ppm total chlorine, while for both strains 50 and 100 ppm treatments resulted in ≤0.8 log10 and ≥3.9 log10 reductions, respectively. Treatments of 10, 25, 50, and 100 ppm chlorine inactivated 0.31, 1.35, >5, and >5 log10 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-μm 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 >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 ≤ 25 ppm total chlorine. Since sewage treatment is performed at ≤ 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.IMPORTANCE HuNoV is ubiquitous in sewage. A receptor binding assay was used to assess inactivation of HuNoV by chlorine-based sewage treatment given that the virus cannot be routinely propagated in vitro Results reported here indicate that chlorine treatment of sewage is not effective for inactivating HuNoV unless chlorine levels are above those routinely used for sewage treatment.

Publisher URL: http://doi.org/10.1128/AEM.01270-17

DOI: 10.1128/AEM.01270-17

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