Removal of Cryptosporidium from river water by crossflow microfiltration: a pilot-scale study

The major advantage of microfiltration in water treatment is the ability to clarify and decontaminate water in one step. A pilot tangential microfiltration system (a tubular ceramic membrane porosity 0.2μm, surface area 0.135m2) was tested for Cryptosporidium removal. Samples (2201) of artificially contaminated river water were filtered and a removal rate >4.3 log was obtained in nine tests. The viability of rejected oocysts was simultaneously conducted as it is important to be aware of the infectious potential of microfiltration concentrates produced and discharged into the environment. Oocyst viability was unaltered in the rejected concentrates after a normal filtration cycle. However, the process of membrane unclogging by sequential washing with NaOH and HNO3 proved to significantly decrease the number of surviving oocysts in rejected water. Indeed, the washing solutions collecting with the filtration concentrates before disposal resulted in a significant decrease of the viability of oocysts measured by inclusion/exclusion of fluorogenic vital dyes (DAPI and PI).