In this paper, outbreaks of cryptosporidiosis in swimming pools in the last 20 years are summarized. Cryptosporidium oocysts are very resistant to many disinfectants, including chlorine, one of the most widely-used disinfectants in swimming pools. Ozone or UV is shown to inactivate Cryptosporidium, while not effective to newly introduced Cryptosporidium and bacteria because of no residual ozone or UV in the treated swimming pool water. Additionally, swimming pool sand filters or cartridge filters are not able to effectively remove Cryptosporidium (removal rate <50%). Above 99% Cryptosporidium removals are achieved in drinking water treatment, but swimming pool water treatment is different from drinking water treatment: no coagulation is performed prior to filtration in most US swimming pools, filtration rate is four to five times higher for swimming pool water treatment compared with drinking water treatment, and the input compounds and microorganisms from bathers continuously recirculate in the swimming pool. Moreover, up-to-date Cryptosporidium or Cryptosporidium surrogate removals from swimming pools are discussed, and alternative swimming pool treatment techniques are reviewed.

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