Efecto de la Peroxidación Catalítica en Fase Húmeda activada por una Arcilla Pilarizada con Al/Fe sobre la viabilidad de Quistes de Giardia Intestinalis en agua superficial del río Pasto
Thesis
Giardia intestinalis is a protozoan parasite with a global distribution, infecting a wide range of vertebrate hosts. It has two life stages, trophozoites (replicative stage) and cysts (transmissible and infective stage) found in either contaminated food or water. In this study, the mRNA of cysts was monitored, as a response to the disinfection of surface water by Catalytic Wet Peroxide Oxidation (CWPO) activated by an Al/Fe-pillared clay catalyst (Al/Fe-PILC); CWPO is an Advanced Oxidation Process (AOP) assessed in our study for the removal of cysts that exhibit high resistance to chlorination and other standard disinfection methods. Cysts of G. intestinalis (strain WB, assemblage A) were cultured in vitro; the RNA was extracted (1x105 cysts/mL) and a RT-qPCR analysis was standardized for detection and quantification using the molecular markers 18S-rRNA and β-giardin. The catalytic experiments were carried out in a 1 L semicontinuous reactor using surface water from Pasto River (Colombia) that was doped with 100 equivalent Giardia cysts/L considering the experimental factors pH (6.0 - 7.0) and the concentration of active iron in the solid catalyst (100 - 300 mg/L). All the catalytic experiments caused loss of the cyst viability of at least 4 Log (99.99 %); besides, up to around 35 % of Dissolved Organic Carbon (DOC) and 30 % of Dissolved Total Nitrogen (DTN) vanished by using a low dose of hydrogen peroxide (0.037 mg H2O2/mg active Fe.mg DOC) under pretty middle ambient conditions of temperature (11 °C) and pressure (73 kPa). The analysis of variance showed the concentration of active Fe (mg/L) to exhibit a significant effect on the elimination of G. intestinalis cysts, DOC elimination, and fraction of reacted H2O2 (p < 0.05, 95 % confidence level). Meanwhile, in the statistical multiple-response optimization, a value of 0.95 was obtained in the Desirability function, where all the responses reached the optimum when the concentration of active Fe was approximately 80 mg/L and pH 6.3, whereas the pH did not display a significant effect on the catalytic performance. This approach could allow in the short term to monitor at low cost the presence of Giardia cysts in water as well as to prevent the spread of infectious diseases that are of public health concern by complementing conventional water disinfection with Catalytic Wet Peroxide Oxidation in the presence of Al/Fe-PILCs.
