Occurrence of Giardia and Cryptosporidium in Italian water supplies.

A total of 21 samples: raw water (RW) samples; water samples after coagulation with aluminium sulfate (clarified water: CW); and water after chlorination (treated water: TW) from a water purification plant that treats river surface water from the neighbourhood of Foggia (Italy), were analysed for the presence of Giardia cysts and Cryptosporidium oocysts. Bacteriological indicator of faecal contamination (total and faecal coliforms, faecal streptococci,), total bacterial count at 22 and 36 degrees C and physicochemical parameters (turbidity, temperature, pH) were evaluated. Cryptosporidium oocysts were not found in any samples examined, while Giardia cysts were found only in RW samples, with the maximal concentration of 8 cysts/100 l. A positive correlation was found between the Giardia densities and quality parameters such as TC, FC and TBC at 22 degrees C. Giardia levels in raw water samples correlated (p < 0.05) with TC, FC and with temperature. No other water quality parameters was consistently correlated with cysts level.