Orange County Water District (OCWD), in cooperation with CH2M HILL and BioVirLaboratories, Inc., is conducting ultraviolet (UV) disinfection pilot studies as a part of a100-million-gallons-per-day (mgd) groundwater recharge and reuse project. The objectivesof the pilot studies are: 1) to compare commercially available UV disinfection lamptechnologies and reactor configurations, 2) to study the inactivation of microorganisms in avariety of water qualities, and 3) to study inactivation of a variety of microorganisms suchas coliphage MS2 (coliphage), Bacillus subtilis (B. subtilis), and Giardia muris (G. muris) bydifferent UV lamp technologies. The funding for this research was provided by theCalifornia Energy Commission via the Public Interest Energy Research (PIER) program, inan effort to encourage the use of innovative, energy-efficient electrotechnologies inmunicipal water and wastewater treatment facilities.This paper presents the results of the bench-scale testing, which includes low-pressure,medium-pressure, and pulsed UV collimated beam units. The performances of thesecollimated beam units were compared using the biodosimetry method. Because of problemsassociated with pathogens, surrogates were used in this study. The surrogates used inbench-scale testing included coliphage, B. subtilis, and G. muris. G. muris is accepted as a testmicroorganism by NSF/EPA and has the advantage of being noninfectious to humans.Testing was conducted with different water qualities including filtered secondary effluent,microfiltered secondary effluent, reverse osmosis (RO) permeate, potable water, anddeionized (DI) water to bracket the full range of drinking and reclaimed water qualities. Theresult of this testing with the full range of water qualities with these UV technologies allowscomparing the effect of the water quality matrix and UV technologies on inactivation ofmicroorganisms and pathogens.In addition to the collimated beam work discussed here, testing has already been completedwith low-pressure low-intensity (Trojan UV 3000), low-pressure high-intensity (PCIWEDECOTAK55 and TAK33), and medium-pressure high-intensity (Aquionics in-linesystem Model 1250) UV pilot units using seeded and indigenous microorganisms. Otherpilot units currently planned for testing include closed reactor low-pressure, mediumpressurehigh-intensity, and pulsed UV technologies.
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