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Sequential application of multi-disinfectants in water treatment presents apromising approach to inactivating pathogens and minimizing disinfection byproducts(DBPs), while providing necessary residual protection. This study investigated theinactivation kinetics of MS2 coliphage with sequential disinfection approaches using ultraviolet (UV)irradiation as a primary disinfectant and free chlorine or monochloramine as a secondarydisinfectant at neutral pH. UV irradiation was provided by a low-pressure (LP) UV lamp(254nm) and a medium-pressure (MP) UV lamp (220 to 580nm). Purified MS2coliphage suspensions were exposed to the collimated UV radiation at a UV dose up to51 mJ/cmsup2/sup before or after the addition of chlorine or monochloramine up to 1.5 or 7 mg/Las Clsub2/sub, respectively.Two types of synergistic effects were observed. UV pretreatment with either LPor MP UV irradiation resulted in the enhancement in the rate of secondary inactivationwhen either free chlorine or monochloramine was used. The secondary inactivation ratewas 1.28-2.74 (free chlorine) and 2-5 (monochloramine) times faster than those dataobtained without UV pretreatment. The enhancement was also found to increase withincreasing UV dose. Synergistic effects in MS2 coliphage inactivation were alsoobserved by simultaneous exposure to both LPUV and free chlorine. The resulting loginactivation under such simultaneous exposures was 0.36-1.7 log larger than the sum oflog inactivation achieved by the two disinfectants along at the same doses in the primarydisinfection stage. The co-exposures also led to an enhancement in the followingsecondary disinfection stage by residual free chlorine or monochloramine. Similar trendswere observed in most cases when using different UV irradiation (LP and MP lamps) andsecondary disinfectant (free chlorine or monochloramine). Includes 6 references, figures.

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Edition: Vol. - No. Published: 11/15/2004 Number of Pages: 8 File Size: 1 file , 330 KB