A Comparison of Two Methods for Measuring the UV Output of Low Pressure Mercury Lamps in Air

A standard bioassay has never been accepted for sizing UV systems for disinfecting non-reuse wastewaters. The majority of UV systems for non-water reuse applications are sized using a computer program called UVDIS. This requires the use of the UV output of a lamp measured in air. Over estimates of lamp output can lead to undersized UV systems. A standard measurement method does not exist, but one has been proposed by the IUVA Manufacturers' Council based on the Keitz method. This method and another method called ‘integration over a sphere’ were compared using a low pressure high output UV lamp. The two methods gave the same results within experimental error. The results also showed that the conditions for testing a lamp must be carefully defined for that particular lamp. A standard bioassay must be developed for UV systems for non-reuse wastewater.