Sequential disinfection of adenovirus type 2 with UV-chlorine-chloramine

Bench-scale experiments determined the inactivation rates of adenovirus serotype 2 with low-pressure, high-output ultraviolet (UV) light, chlorine (Cl-2), and preformed chloramines. Studies with sequential chloramines were also done to mimic water treatment practices. Sequential experiments with adenovirus serotype 2 suspended in laboratory-grade water and natural waters containing ammonia were exposed to either UV light followed by Cl-2/chloramines or the reverse sequence. Adenovirus log reductions were quantified through cell culture techniques. A free Cl-2 C x T (concentration x time) of 1.22 mg-min/L resulted in a 3.72-log reduction, a preformed chloramine C x T of 264.5 mg-min/L resulted in a 1.2-log reduction, a sequential chloramine C x T of 40.5 mg-min/L results in a 1-log reduction, and a UV dose of 40 mJ/cm(2) resulted in a 1-log reduction. Up to 4-log reductions were achieved with a UV dose of 40 mJ/cm(2) followed by a sequential chloramine C x T of 27.2 mg-min/L. This suggests that sequential disinfection may be the best option for dealing with UV-resistant organisms such as adenoviruses.