A Comparison of Uv Sensors - Success and Challenges

Transmittance is one of the key control parameters used by UV system to adjust the applied dose. Validation equations and thus control of the UV system can be controlled using an on-line sensor. So if the on-line UV sensor is measuring higher than the actual transmittance value then the system is wasting energy and if the system is measuring lower than the actual transmittance value then potential for compliance may occur. The facility selected for the testing had installed a HACH UVAS sensor as part of a UV installation. Two additional On-line UV transmittance sensors were selected based on availability and ease of installation. Data was collected for 30 days at 5 minute intervals from the three sensors and compared to spot check grab sampling data collected by City staff. Results of from all three sensors did find variability between the on-line measurements and data collected from the City’s laboratory. A present worth analysis was completed to evaluate each of the three sensors.