AWWA WQTC65788

Ultraviolet (UV) reactors are validated by determining the Reduction Equivalent Dose (RED) that they supply at a given operating condition. A new method is described whereby the log-inactivation of any organism affected by a UV reactor can be predicted as a function of the flow rate, the UV sensor value, the UV transmittance of the water, and the UV sensitivity of the organism as determined by collimated beam tests. (The UV sensitivity is the dose required per log inactivation.) The method can be used to compute directly the log inactivation of a target organism by a reactor, without consideration of RED or RED bias. Therefore for a target organism such as Cryptosporidium, the reactor system controls would be programmed to calculate the log-inactivation directly based on the flow, UV transmittance and UV sensitivity of the target organism (Cryptosporidium) with uncertainty values subtracted. Includes reference, figures.