| In this study, a Cryptosporidium and Giardia detection method, which uses membrane filtration, membrane dissolution and density gradient separation, for concentration and purification, and immunofluorescence assay for identification and counting was applied in the detection of Cryptosporidium oocysts and Giardia cysts, was developed in reclaimed wastewater systems. For the reclaimed influents and the reclaimed effluents with excess coagulant, the ethyl acetate floatation and acid dissociation were suggested to be added to enhance the purification and increase the recovery, respectively. Then an immunofluorescence assay and density gradient separation method for detection of Cryptosporidium oocysts and Giardia cysts, was developed in reclaimed wastewater systems. The Cryptosporidium oocysts and Giardia cysts of reclaimed wastewaters were detected in T and B cities in north China using immunofluorescence assay and density gradient separation method. The acceptable recoveries obtained from reclaimed influents and effluents were in the range of 18%-31% oocysts and 24%-95% cysts. The results showed that Cryptosporidium were detected in 89% samples with mean concentration of 26 oocysts/10L,while Giardia were detected in 100% samples with mean concentration of 138 cysts/10L in the influents of 5 reclaimed wastewater systems. Besides, Cryptosporidium oocysts and Giardia cysts were also present in the effluents of some reclaimed wastewater systems.21-95 cysts/10L reclaimed effluent was detected using Immunofluorescence Assay and Density Gradient Separation method during a survey of Giardia in the reclaimed water plant in north-China . An exponential dose-response model was applied to assess the risk of infection by Giardia cysts. The observed Giardia cysts concentrations in the reclaimed effuent disinfected by chlorine present 1.09×10-2 annual risk , more than the acceptable 1.00×10-4 annual risk value, while ozone or UV disinfection can reduce the annual risk to 3.47×10-5 . In addition , genotype analyses which arrived at the presence of Giardia duodenalis assemblage A assemblage and B are suggesting potential risk to public health.
|
PDF Full Text Request