Suchergebnisse

AbstractMicrobial biofilms are complex communities that form when planktonic bacterial species attach to surfaces in many settings where they can provide a source of pathogenicity. The relative ineffectiveness of conventional disinfectants such as free chlorine and monochloramine for the inactivation of some species found in water has led to evaluation of alternative disinfectants for drinking and wastewater treatment. In recent years, novel pulsed power electrotechnologies have been introduced and are being considered as possible alternatives to current methods for inactivating problematic species in water. This study focuses on the ultraviolet (UV) inactivation of bacterial biofilms using a pulsed UV light approach as a potential disinfection method for water treatment operating systems. Biofilms were stimulated to form attached to polyvinyl chloride coupons using a recommended Centre for Disease Control biofilm reactor followed by exposure to a range of UV doses. Findings show that this method is highly effective at inactivating both planktonic and biofilm cells with significant inactivation rates obtained for both test species. Specifically, a 7.2 and 5.9 log10 inactivation was achieved with up to 21.6 μJ/cm2 UV for Pseudomonas aeruginosa and Staphylococcus aureus, respectively. Findings from this study highlight the effectiveness of pulsed UV for the inactivation of Pseudomonas biofilms among other test species. Research conducted by this group suggests that this pulsed UV system may offer a useful method for the disinfection of drinking and wastewater supplies.

AbstractDevelopment of a pulsed ultraviolet (PUV) light system as an alternative disinfection method for water treatment has been investigated, yet little is known about the impact of applying such emerging technologies on the natural aquatic environment. This study reports on the use of a battery of ecotoxicological tests representative of different ecological trophic levels to determine the safety and potability of PUV‐treated water containing known pathogens. Water samples containing Cryptosporidium oocysts and Escherichia coli were treated with PUV light, and the ecotoxicological safety was determined by assessing toxicity in a range of representative microbiotests and the Rainbow Trout Hepatocyte (RTH)‐149 fish cell line. Results show that PUV rapidly inactivated Cryptosporidium and the selected microbial species; greater rates of inactivation were observed at higher ultraviolet doses. PUV‐treated samples did not elicit ecotoxicological effects in the trophic levels studied. This study highlights that PUV is an effective means of disinfecting water containing pathogens such as Cryptosporidium.

Pulsed UV (PUV) technology is accepted commercially for disinfection within the food packaging industry, but has yet to be deployed by the water/wastewater sector. This is partly due to a lack of robust, independently validated data for submerged or flow-through treatment applications. This study evaluated the efficacy of PUV for water disinfection under flow-through conditions. Bacterial pathogens of interest in the food and water/wastewater sector, namely Escherichia coli, Staphylococcus aureus and Listeria innocua (surrogate for L. monocytogenes) were used to investigate the potential for photoreactivation and/or dark repair post PUV flow-through disinfection. A continuous-flow low-pressure UV was also analysed under similar experimental conditions. Bacterial inactivation via flow-through PUV was dependant on energy output with E. coli exhibiting greatest sensitivity to PUV treatment (5.3 log 10 inactivation after treatment at 1539 mJ/cm 2 - output in UV range < 300 nm); L. innocua exhibited the highest PUV resistance (3.0 log 10 inactivation after treatment at 1539 mJ/cm 2 – output in UV range < 300 nm) under similar treatment conditions. Greater photoreactivation occurred at lower PUV outputs for both S. aureus and E. coli after flow-through PUV treatment. Thus exposure of treated bacteria to natural light, immediately post flow-through PUV treatment, should be avoided to minimise photoreactivation. The LPUV demonstrated inactivation of all bacteria below the limit of detection (1 CFU/mL) and inhibited the occurrence of photoreactivation. This study highlights the importance of considering bacterial repair potential and the need for further development of PUV technology for such applications ; The authors would like to acknowledge the Department of Agriculture, Food and the Marine of Ireland (Ref: 13-F-507) for funding this research. Dr. Val del Rio was supported by the Spanish Government (CTM2014-55397-JIN project co-funded by FEDER) and Xunta de Galicia postdoctoral fellowship ; SI

AbstractThe increase in pathogen levels in seawater threatens the safety of entire aquatic ecosystems. Foodborne pathogens can potentially accumulate in shellfish, especially in filter feeders such as bivalves, requiring an efficient depuration process before consumption. Alternative approaches to promote a cost-efficient purge at depuration plants are urgently needed. A small prototype pulsed ultraviolet (PUV) light recirculation system was designed, and its depuration potential was tested in a seawater matrix artificially contaminated with high levels of microbial pathogens Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Bacillus cereus and Candida albicans. The analysis of treatment parameters including voltage, number of pulses and duration of treatment was performed to ensure the highest reduction in contaminant levels. Optimal PUV disinfection was attained at 60 pulses/min at 1 kV for 10 min (a UV output of 12.9 J/cm2). All reductions were statistically significant, and the greatest was observed for S. aureus (5.63 log10), followed by C. albicans (5.15 log10), S. typhimurium (5 log10), B. cereus (4.59 log10) and E. coli (4.55 log10). PUV treatment disrupted the pathogen DNA with the result that S. aureus, C. albicans and S. typhimurium were not detectable by PCR. Regulations were reviewed to address the applicability of PUV treatment as a promising alternative to assist in the reduction of microbial pathogens at depuration plants due to its high efficiency, short treatment period, high UV dose and recirculation system as currently employed in shellfish depuration plants.