title: Point-of-use water disinfection using ultraviolet and visible light-emitting diodes.
abstract: Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different commercial or semi-commercial LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6h. Five log10 and greater reductions were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6h). No significant disinfection was observed with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were observed, particularly with UV-A wavelengths. The radiation doses required for >3-log10 reduction of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were observed with both indicators. The design process revealed cost and technical constraints pertaining to LED electrical efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technology is already technically possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work.
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia; School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: gough@student.unsw.edu.au.
authors.forename: Gough Yumu
authors.initials: GY
authors.lastname: Lui
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: djroser@unsw.edu.au.
authors.forename: David
authors.initials: D
authors.lastname: Roser
authors.affiliation: School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: r.corkish@unsw.edu.au.
authors.forename: Richard
authors.initials: R
authors.lastname: Corkish
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia; School of Public Health, South Academic Building, University of Alberta, Edmonton, Alberta T6G 2G7, Canada. Electronic address: ashbolt@ualberta.ca.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ashbolt
authors.affiliation: UNSW Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Electronic address: r.stuetz@unsw.edu.au.
authors.forename: Richard
authors.initials: R
authors.lastname: Stuetz
mesh_terms: D004203:Disinfection / Q000379:methods; D014466:Ultraviolet Rays; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods
keywords: Disinfection; LED; Pathogen; Regional communities; Ultraviolet