Removal of Cryptosporidium -Sized Polystyrene Microspheres from Swimming Pool Water with a Sand Filter with and without Added Perlite Filter Media

Abstract

Waterborne disease outbreaks in U.S. swimming pools have been increasing in recent years, and the majority of the outbreaks are caused by Cryptosporidium oocysts. This research project evaluates sand filtration for swimming pools without and with an amendment, perlite. The evaluation was formed on the basis of removing 5-μm polystyrene microspheres, as a surrogate for Cryptosporidium oocyst, from simulated pool water stored in a 757 L (200 gal) tank. The results showed that a sand filter, without perlite, was not efficient at removing Cryptosporidium-sized particles (i.e., the 5-μm microspheres), with removals averaging 19% (or 0.09 log). The sand filter with a thin layer (1.2 kg/m2 or 0.25 lbs/ft2) of perlite media on top demonstrated removals of 98% (or 1.8 log). The filtration rate was maintained at 49 m/h (20 gpm/ft2) in all experiments. These results indicate that perlite may hold promise in reducing the likelihood of outbreaks of cryptosporidiosis associated with swimming pools.