Bench‐scale experiments determined the inactivation rates of adenovirus serotype 2 with low‐pressure, high‐output ultraviolet (UV) light, chlorine (Cl2), 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 Cl2/chloramines or the reverse sequence. Adenovirus log reductions were quantified through cell culture techniques. A free Cl2 C × T (concentration × time) of 1.22 mg‐min/L resulted in a 3.72‐log reduction, a preformed chloramine C × T of 264.5 mg‐min/L resulted in a 1.2‐log reduction, a sequential chloramine C × T of 40.5 mg‐min/L resulted in a 1‐log reduction, and a UV dose of 40 mJ/cm2 resulted in a 1‐log reduction. Up to 4‐log reductions were achieved with a UV dose of 40 mJ/cm2 followed by a sequential chloramine C × 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.
