AWWA ACE59981

Conventional validation testing of ultraviolet (UV) reactors use cultured microorganisms spiked into test water flowing through a reactor. The objective of this study was to examine the UV inactivation of indigenous aerobic spores naturally occurring in raw/unfiltered water supplies and to assess their use as an alternative indicator for validation testing of UV reactor performance. Spores were found in all raw waters tested in concentrations ranging between 20-12,000 CFU/100 ml and were very resistant to UV irradiation. The inactivation of indigenous natural aerobic spores followed first order kinetics with an inactivation coefficient ranging between 0.013-0.022 cm²/mJ. It was determined that naturally occurring aerobic spores can be a useful tool when validating plant performance, and can be used as a regular monitor of UV fluence and performance in a water treatment plant. Includes table, figures.