OCCURRENCE AND REMOVAL OF CRYPTOSPORIDIUM SPP OOCYSTS AND GIARDIA SPPCYSTS IN KENYAN WASTE STABILIZATION PONDS

This study was designed to determine the occurrence and removal of Cry ptosporidium spp. oocysts and Giardia spp. cysts, in municipal waste-w ater by waste stabilisation ponds in the Republic of Kenya. Eleven was te stabilisation pond systems located in towns across Kenya were inclu ded. A total of 66 waste-water samples were examined for the presence of oocysts and cysts, comprising 11 raw waste-water and 55 pond efflue nt samples over a two month period. Cryptosporidium spp. oocysts were detected in 6 and Giardia spp. cysts in 9 of the designated pond syste ms analysed demonstrating their ubiquitous nature throughout Kenya. Oo cyst levels detected in raw waste-water samples ranged from 12.5 - 72. 97 oocysts/l and various pond effluents between 2.25 - 50 oocysts/l. C yst levels detected in raw waste-water samples ranged from 212.5 to 62 12.5 cysts/l and in various pond effluents from 3.125 to 230.7 cysts/l . No Cryptosporidium spp. oocysts were detected in the final effluent from any pond systems studied (11/11). Whereas no Giardia spp. cysts w ere detected in the final effluent from 10 of 11 waste stabilisation p ond systems studied, one pond system was found to be consistently disc harging cysts in the final effluent at concentrations ranging from 40 to 50 cysts/l. The minimum retention period for the removal of Cryptos poridium spp. oocysts and Giardia spp. cysts was 37.3 days. Laboratory experiments were performed to assess physico-chemical and microbiolog ical parameters to express relationships between pond performance and protozoa removal.