Full Description

In studies of the UV inactivation of microorganisms, it is necessary to determine the UV response of a given microorganism in the water matrix in which the organism is found or is spiked. The UV response is usually determined using a collimated beam apparatus, in which part of the output of a UV lamp is directed down a long collimator, consisting of a cylindrical tube or the equivalent, usually painted black on the inside. The cell suspension to be irradiated is placed below the bottom of the tube opening. Various workers have used a variety of procedures and types of collimated beam apparatus. However, in many peer reviewed published literature, it is not clear how the UV irradiations were carried out, nor how the average fluence (or UV dose) given to the microorganisms has been determined. Thus the quality of the data in the literature needs to be assessed with this fact in mind. A detailed protocol for the determination of the fluence (UV dose) in a collimated beam apparatus containing either a low pressure (monochromatic emission at 254 nm) or a medium pressure (broadband emission over the entire germicidal range of 200 - 300 nm) mercury lamps is described in this paper. This protocol includes: specifications for the construction of a collimated beam apparatus (including shutter, window, power supply, collimating tube, platform, stirring, and lamp); determination of the average irradiance in the water [including proper use of a calibrated radiometer, the Reflection Factor, the Petri Factor, the Water Factor and (for a medium pressure lamp) the Sensor Factor and the Germicidal Factor]; calibration of the radiometer and its detector (including discussion of primary irradiance standards, actinometry, acceptance angle, and spectral sensitivity of the detector); microbiological considerations (including stirring or not stirring, replicates and random order, handling of samples prior to analysis and statistical analysis); and, description of sample runs (including sample spreadsheets). Includes reference.

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Edition: Vol. - No. Published: 01/01/2001 Number of Pages: 7File Size: 1 file , 190 KB