Project Page Views: [ 3974 ]
| Project Metadata Element | Details |
| Project Title | Pulsed-UV light inactivation of Cryptosporidium spp. oocysts in drinking water supplies in Ireland |
| Research Area | Water |
| Project Acronym | |
| Principal Investigator or Lead Irish Partner | Neil J Rowan |
| Lead Institution or Organisation | Athlone Institute of Technology (AIT) |
| Lead Country | Ireland |
| Latitude, Longitude (of Lead Institution) | 53.41673, -7.90356 |
| Lead Funding Entity | Environmental Protection Agency |
| Approximate Project Start Date | 01/10/2006 |
| Approximate Project Finishing Date | 11/09/2011 |
| Project Website (if any) | |
| Links to other Web-based resources | |
| Project Keywords | Pulsed-UV light; Cryptosporidium; Oocysts; Drinking water |
| Project Abstract | Aim and rationale: The aim of this timely and pressing multi-disciplinary study was to investigate development and optimization of a high-intensity pulsed UV light (PUV) source for the novel disinfection of Cryptosporidium parvum oocysts suspended in water. The rationale and need for same is due to the fact that C. parvum is an enteric coccidian parasite that is recognised as a frequent cause of illness in humans due to its resistance to disinfection with chlorine at concentrations typically applied in drinking water treatmentplants. Development of alternative methods of Cryptosporidium disinfection for waterapplications (such as UV) has been hindered by numerous factors including the uncertainty surrounding efficacy of in vitro surrogate viability assays to quantify oocyst survivors post treatment and the lack of critical data focusing on congruence of in vitro cell culture and invivo animal based infectivity bioassays to evaluate efficacy of using conventional and emerging disinfection techniques. Methods and Results: due to numerous factors including (but not limited to) the lack of availability of oocysts due to the fact that this parasite has a complex life cycle that requires use of an animal host (with obvious ethical implications) initial findings identified critical inter-related factors affecting the destruction of other relevant bacteria and yeast undervarying operational conditions. These studies were used to inform subsequent treatments using the more recalcitrant C. parvum. Albeit extensive in scope and depth the latter study proved essential in terms of limiting use of animals for important infectivity studies the former element being factored into a successful animal licence application that was awarded by the Department of Health and Children for this purpose. The in vitro HCT-8cell culture combined with quantitative (real-time) PCR was then compared to the SCIDmouseinfectivity bioassay to evaluate these PUV operating conditions in order to reduce oreliminate C. parvum oocyst infectivity when treated in water. Each treated dose of oocystswas inoculated into 3 replicates of 4 mice or 8 cell culture wells. Infections post UVtreatments were detected by immunofluorescence (IF) microscopy and by quantitative PCR in cell culture and by IF staining of faeces and by haematoxylin and eosin staining of intestinal villi in mice. There was good agreement between using cell culture-qPCR and the mouse assay for determining reduction or elimination of C. parvum infectivity as a consequence of varying UV operating conditions. Reduction in infectivity depended on the intensity of lamp discharge energy or UV dose (mJ/cm2) applied amount of pulsing and population size of oocysts (P 0.05). Use of surrogate vital staining over-estimated survivoris post-UV treatments compared to use of infectivity assays (P 0.05). Incorporation of humic acid at a concentration above that found in surface water (i.e. 10ppm) did not significantly affect PUV disinfection capability irrespective of parameterstested (P 0.05). It took ca. 3.9 times longer to eliminate C. parvum infectivity using continuous low-pressure monochromatic light at a UV dose of 327 mJ/cm2 compared to treating similar populations of oocysts with PUV at 4.6 mJ/cm2. Use of ATP technique was shown to be an inferior technique for evaluating PUV disinfection performance compared to use of cell culture i- qPCR or using the mouse-model. Studies revealed an inability of C.parvum to photo-repair post exposure to lethal doses of conventional (L-P) or PUV. An extensive battery of eco-toxicity testing revealed that PUV treatment of water containing different pre-determined levels of C. parvum oocysts were safe to release into the environment and were of satisfactory potability quality. |