photocatalytic inactivation of cryptosporidium parvum with tio2 and lowpressure ultraviolet irradiation this study investigated the efficacy of lowpressure ultraviolet uv irradiation and the synergistic effect of uvtitanium dioxide tio2 photocatalysis on cryptosporidium parvum oocyst inactivation at uv doses of 27 80 and 40mjcm2 oocyst inactivation was 13 26 and 33log10 respectively reactive oxygen species ros generated by longwave uv radiation 315nm and tio2 achieved less than 028log inactivation however the synergistic effect of germicidal 254nm uv and tio2 resulted in 2log and 3log oocyst inactivation with 40 and 110mjcm2 respectively therefore using tio2 in combination with uv reduced the dose requirement for 3log inactivation by 56 an approximate 1log decrease in inactivation of oocysts was observed with nanopure water in comparison to buffered water whereas changes in ph from 6 to 8 had little effect on the photocatalytic inactivation of oocysts in either matrix p01