Experimental investigations and numerical modelling of Cryptosporidium parvum transport behaviour in aquifers

The purpose of this study was to improve understanding of the potential for transfer of the protozoan pathogen Cryptosporidium parvum through aquifers to drinking water wells. Therefore, the factors characterising this transport were experimentally determined. We have developed a continuously recirculating column assay. The latter allows small amounts of C. parvum oocysts to be manipulated providing as much protection as possible from the risks of contamination. As the analysis of oocyst samples is time consuming, a numerical model, simulating the transport phenomena of oocysts under the experimental conditions of assays, was developed to establish the whole experimental curve of results using a small number of experimental points. The comparisons drawn between analytic solutions, experimental results with tracer (NaCl solution) and numerical simulation were in good agreement. A continuously recirculating column assay was performed using oocysts in suspension (flow rate = 1.43 mL/min). Treated sand was used as previous experiments had shown that no adsorption occurs. We observed almost total filtration (99.85%). To check this result, an assay with an open column was carried out under the same conditions. We observed a filtration value of 97%. Consequently, we may say that the continuously recirculating column assay provides satisfactory results.