Point-of-use water disinfection using UV light-emitting diodes to reduce bacterial contamination.

The treatment process described in this research explores the impact of exposing water samples containing fecal coliforms to the radiation produced by single ultraviolet (UV) light-emitting diodes (LEDs) operating at 265 nm. UV LEDs are long lasting, compact in size and produce more efficient light output than traditional mercury-vapour bulbs, making them ideal for application in point-of-use disinfection systems, such as in remote areas. In this study, contaminated water samples containing either a pure culture of Escherichia coli or tertiary effluent from the City of Regina Wastewater Treatment Plant were used to study the application and efficiency of using UV LEDs for water disinfection. The results indicate that bacterial inactivation was achieved in a time-dependent manner, with 1- and 2.5-log E. coli reductions in water following 20 and 50 min of UV LED exposure, respectively. Ultraviolet radiation was less effective in reducing coliform bacteria in wastewater samples due to the elevated turbidity levels. Further work remains to be completed to optimize the application of UV LEDs for point-of-use disinfection systems; however, the results from this study support that bacterial inactivation using UV LEDs is possible, meriting further future technological development of the LEDs.

A rapid methodology using fatty acid methyl esters to profile bacterial community structures in microbial fuel cells.

A new methodology is presented here as an effective, preliminary technique for the identification of indigenous aerobic and facultatively anaerobic bacterial communities found within microbial fuel cells (MFCs). The dual-phased method, named Rapid Agitation Static Incubation-Microbial Identification, or RASI-MIDI, is comprised of rapidly agitating the sample within a SLYM-BART tester followed by stationary incubation which produces a biomass that is subjected to extraction of methyl ester fatty acids. These distinctive fatty acid profiles represent a bacterial community fingerprint unique to the MFC, and are stored in a library for analysis. A total of 84 samples were analyzed for bacterial community structures from seven different groups of MFCs, with each MFC group comprised of a different bacterial community. Results showed that comparisons of replicate MFCs comprising the same bacterial communities generated high similarity index (SI) numbers (SI values ranging from 0.77 to 0.97), indicating highly correlated fatty acid profiles. In contrast, comparisons of MFCs having known dissimilar community structures did not consistently generate SI values in the analysis considered to be a significant match. It was found that this protocol described herein uniquely and accurately produced MFC fatty acid profiles contained in bacterial communities and thus provides a potential method for routinely studying MFC bacterial community fingerprints.