Pilot-scale evaluation of UV reactors' efficacy againstin vitroinfectivity ofCryptosporidium parvumoocysts

Abstract

An experimental protocol was developed to assess the efficacy of two UV reactors (medium-pressure UVaster s , and a low-pressure reactor) on the infectivity of Cryptosporidium parvum oocysts under conditions mimicking small-or mediumsize water distribution units. The protocol included purification of large amounts of viable oocysts from experimentally infected calf feces, pilot spiking, sample concentration and purification after UV radiation, oocyst quantification and in vitro evaluation of oocyst infectivity on HCT-8 cells. Water samples were collected at intervals upstream and downstream from the UV reactor after spiking. Oocysts were concentrated by centrifugation, purified by immunomagnetic capture and quantified using laser-scanning cytometry. An enhanced in vitro infectivity test on HCT-8 cells was developed, where oocysts were pretreated in order to obtain maximized in vitro infectivity, and infectious foci were enumerated after immunofluorescence staining after 3 days of culture. This method was superior to viability measured by excystation for assessing oocyst infectivity. The infectivity rate of untreated oocysts ranged between 9% and 30% in replicate experiments. The method allowed us to determine inactivation rates 4 4.92 (log) with UVaster s and 4 4.82 with the LP reactor after exposition of oocysts to an effective dose of 400 J m À2 at flow rates of 15 and 42 m 3 h À1 , respectively.

Evaluation of water treatment plant UV reactor efficiency against Cryptosporidium parvum oocyst infectivity in immunocompetent suckling mice

“…2002). Oocyst infectivity of HCT‐8 cell cultures was reduced by (log 10 ) 4·92 and more than 4·82 after exposing oocysts to an effective dose of 40 mJ cm −2 in a medium pressure (MP) or a low pressure (LP) reactor, respectively (Entrala et al. 2007).…”

“…(Hijnen et al 2006). In another pilot-scale study in which water passed through low-and medium-pressure UV reactors, irradiation was found effective in reducing oocyst infectivity in vitro (Entrala et al 2007). Studies evaluating oocyst viability using their in vitro excystation capability and ⁄ or uptake of vital dyes suggested that very high UV (up to 8700 mJ cm )2 ) was necessary to achieve a 99% decrease in viable oocysts (Campbell et al 1995).…”

“…2006). In another pilot‐scale study in which water passed through low‐ and medium‐pressure UV reactors, irradiation was found effective in reducing oocyst infectivity in vitro (Entrala et al. 2007).…”

“…Studies evaluating oocyst viability using their in vitro excystation capability and ⁄ or uptake of vital dyes suggested that very high UV (up to 8700 mJ cm )2 ) was necessary to achieve a 99% decrease in viable oocysts (Campbell et al 1995). In vitro log 10 reductions of oocyst infectivity in HCT-8 cell cultures of >4AE92 and >4AE82 were obtained after exposing oocysts to an effective dose of 40 mJ cm )1 with medium-and lowpressure reactor, respectively (Entrala et al 2007). In vivo infectivity in mice was reduced by 99AE99-100% after 7AE6-40 mJ cm )2 UV irradiation, respectively (Al-Adhami et al 2007;Rochelle et al 2004).…”

Performance evaluation of UV reactor using optical diagnostic techniques

“…The conventional method of evaluating the performance of a UV reactor is to compare the concentrations of pollutants or active microorganisms at the outlet of the reactor with those at the inlet 8–12. There has been considerable effort put into improving this technique by introducing various chemicals and new methods.…”