A Survey of Source and Finished Water Supplies for Giardia Cysts and Cryptosporidium Oocysts

Field: Environmental Science (Physical Sciences)

Abstract: The occurrence of Giardia lamblia cysts and Cryptosporidium parvum oocysts was determined from source and treated drinking water supplies at selected water treatment facilities in Eastern Kentucky. Giardia and Cryptosporidium are two human protozoan parasites often found in water supplies due to fecal contamination. Characteristic cysts and oocysts were identified from large volume water samples, typically 100 gallons for raw samples and 1,000 gallons for finished water, using an indirect fluorescent antibody specific for Giardia and Cryptosporidium. Source water from four different water treatment facilities utilizing a reservoir, river, and two creeks were assayed. All sites exhibited Giardia lamblia cysts while Cryptosporidium parvum oocysts were detected at all sites except those collected from the reservoir for a 100% and 75% occurrence rate for these two protozoans, respectively. Samples from two of the four (50%) water treatment facilities surveyed yielded Cryptosporidium oocysts in finished water whereas no Giardia cysts were detected utilizing this method. Water quality indicators, including pH, turbidity, and fecal coliform bacteria levels were taken on all raw water samples in an effort to predict Giardia and Cryptosporidium contamination in water sources. Statistical analysis of specified indicators determined that neither pH, turbidity, nor fecal coliform bacteria exhibited significant correlations with detected cysts or oocyst levels. The treatment train of each water treatment facility was surveyed to determine if Giardia and Cryptosporidium levels were influenced by physical/chemical parameters. Of the three filtration methods utilized: 1)direct; 2) slow sand; and 3) rapid sand filtration, none were shown to be significantly different from each other in affecting protozoa levels. Disinfection and purification of raw water sources varied at each facility surveyed. An analysis of chemical additions and chlorine contact times also proved to be insignificant in their affects on detected Giardia cysts and Cryptosporidium oocysts levels. No oocysts were detected in treated water in plants using a polymer (cat-floc-tl) as a coagulant; however, those that utilized alum as a coagulant, Cryptosporidium oocysts were detected in their finished water. Giardia lamblia cysts and Cryptosporidium parvum oocysts were demonstrated to be present in source water utilized by four water treatment plants in Eastern Kentucky. Of the standard water quality indicators often utilized for raw water sources, none were shown to be reliable indicators in alerting water treatment facilities of possible Giardia or Cryptosporidium contamination. Nonetheless, Cryptosporidium oocysts were detected in two of four treated drinking water supplies. This study has demonstrated that current filtering and disinfection techniques need to be improved, along with best management practices in the watersheds, to deminish the threat of infection by Giardia lamblia and Cryptosporidium parvum by drinking treated water, especially in immunosuppressed individuals.