Comparison and validation of UV dose calculations for low- and medium-pressure mercury arc lamps

A method for calculating UV dose for microbial disinfection that includes a measure of the wavelength-dependent factors of UV lamp output, quartz sleeve UV transmission, microbial action spectra, and wastewater UV transmission is presented. The method is validated by comparing UV dose-response curves for the disinfection of a secondary effluent achieved using collimated beams of UV light generated from low- and medium-pressure mercury arc lamps. The wastewater UV transmittance is artificially altered as part of the validation process. A simplified and practical method of UV dose calculation that relies only on a measure of the UV transmission at 254 nm is proposed for the disinfection of domestic wastewaters by medium-pressure lamps. The proposed method is validated using wastewater samples obtained from 21 wastewater treatment plants located across North America.