UV System Checkpoint Bioassays: Looking Back and Moving Forward, Applying the Lessons

The NWRI/AwwaRF “Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse” (the Guidelines), require that UV systems be sized based on bioassays, which are done on reactors up to some practical size and capacity. To treat higher flows, scale-up must be considered. Once installed, a UV system is evaluated in a Checkpoint (commissioning) Bioassay, which can often be done only at a lower level of accuracy than a product validation at a test center. This paper will outline the challenges in obtaining high accuracy results in checkpoint bioassays, and techniques to maximize the accuracy. Methods for comparing test results from checkpoint bioassays to product validation bioassays will be discussed. Limitations on the usefulness of Checkpoint Bioassays will be discussed, together with a summation of experience that supports alternative methods for having confidence in UV systems.