Abstract
The EPA method 1623 is designed specifically for the detection of Cryptosporidium and Giardia, but the method has some issues with low and variable recoveries. Ultrafiltration has been used effectively for microorganism recovery from water samples but is not approved by the EPA. To determine the efficacy of using ultrafiltration, 10-L tap water and surface water samples were seeded with Cryptosporidium and Giardia and concentrated with either a pleated capsule filter or a hollow-fiber ultrafilter. For Cryptosporidum, oocyst recovery in tap water was significantly higher for ultrafiltration (68%) versus the capsule filter (37%); ultrafiltration recovered 65% of oocysts in surface water versus 61% for the capsule filter. However, Giardia cyst recovery was mixed. In tap water, the capsule filter produced a significantly better recovery (85%) of Giardia compared with ultrafiltration (63%), but the surface water ultrafiltration recovery (81%) was significantly better than the capsule filter recovery (40%). Overall, ultrafiltration recoveries were equal to or better for Cryptosporidium, but recoveries of Giardia were varied depending on the filter used and the type of water analyzed.