Potassium Ferrioxalate as Chemical Actinometer in Ultraviolet Reactors

The ultraviolet doses delivered by a quartz‐sleeve and a Teflon‐tube design ultraviolet disinfection reactor at various flow rates are estimated using a Bacillus subtilis bioassay and compared to dose estimates made using a potassium ferrioxalate chemical actinometric technique. The volumetric dose estimates obtained with the potassium ferrioxalate actinometer are converted to areal dose estimates by multiplying them by the irradiated volume to irradiated surface area ratio. Conservative estimates of dose are consistently achieved by assuming 100% reflectance of UV radiation off of reactor walls when approximating the irradiated surface area. Potassium ferrioxalate actinometry is found to provide reproduceable dose estimates but is sensitive to procedural variation. The relatively high cost of potassium ferrioxalate actinometry combined with the difficulties associated with preparing and using the actinometer suggest that it is impractical for regular use in field situations. However, potassium ferrioxalate actinometry does appear to have the potential for being a useful tool in design evaluations and comparative studies of UV system efficiencies.