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What is UVCalc®?

UVCalc® is a software program, developed by Bolton Photosciences Inc., allowing the user to map out the fluence rate or irradiance distribution in a UV Reactor. From this data, one can then determine the ‘average fluence rate’ (irradiance) in the UV rector. If one assumes perfect plug flow in the reactor, the exposure time can be determined from the volume and the flow rate. The product of the average fluence rate (irradiance) (mW/cm² or W/m²) and the exposure time (in seconds) provides an estimate of the fluence (UV dose) (mJ/cm² or J/m²) delivered by the UV reactor.

UVCalc® is based on the assumption that a UV lamp can be modeled as a linear array of cylindrical segments, each emitting UV light from the edge of the segment. Proper account is taken of reflection and refraction of the UV light as it passes through the air/quartz/water interface of a quartz sleeve surrounding the UV lamp. The mathematics of this model has been published by Dr. Bolton.

The fluence rate (irradiance) distributions predicted by UVCalc® have been tested experimentally, using small spherical quartz spheres filled with an actinometer solution.

In addition, experimental studies have been carried out to test the predictions of UV Calc® versus biodosimetry tests, where a microorganism (e.g., MS2 colliphage) is injected upstream of the UV reactor and samples taken of the influent and effluent. From the drop in viable microorganisms in the effluent versus the influent, it is possible to determine what is called the ‘Reduction Equivalent Fluence’ (REF) (also called ‘Reduction Equivalent Dose’). In one particular study of a UV reactor with low pressure UV lamps parallel to flow, the ratio of the REF to the UVCalc® prediction of the fluence (UV Dose) was 0.82. This is as expected because the UVCalc® fluence prediction is a ‘theoretical maximum’, since it assumes perfect radial mixing as the water passes through the UV reactor. The 0.82 factor is often called the ‘hydraulic efficiency’ or the ‘mixing efficiency’. The above result indicates that the UVCalc® predictions are accurate.

Bolton Photosciences Inc. offers a free calculation to demonstrate how UVCalc® can help you in the design of your UV reactor. If you are interested in a free trial please visit