AWWA WQTC69460

Adenovirus has been shown to have a high resistance to low pressure ultraviolet (UV). For 4-log virus credit in the LT2ESWTR, a low pressure UV dose of 186 mJ/cm² is required. UV reactors must be bioassay validated to achieve credit per the LT2ESWTR, but currently available challenge microorganisms are not able to demonstrate these high dose values. For example, using MS2 bacteriophage, which ranges in resistance from 18-25 mJ/cm²/log, 7.4-10.3 log reductions of MS2 would be required. This is operationally very difficult to do at any reasonable scale. This study set out to find a highly UV resistant microorganism that could be cultured to high titers, for doing practical demonstrations of high UV resistances. The study used spores of the fungus Aspergillus niger, and characterized them with a low pressure UV collimated beam. To show the feasibility of their practical usage, A. niger spores were used to do full scale challenges of a residential scale low pressure UV reactor (up to 68 L/min flow) and a municipal drinking water scale medium pressure UV reactor (up to 2100 L/min flow). The study successfully demonstrated reduction equivalent doses > 400 mJ/cm² using the A. niger spores, making these spores a viable choice for high dose UV reactor challenges such as those required to achieve multi-log virus credit for the LT2ESWTR. Includes figures.