Occurrence of Giardia cysts and Cryptosporidium oocysts in raw and treated water from two water treatment plants in Selangor, Malaysia

The occurrence of Giardia cysts and Cryptosporidium oocysts was determined both in the raw water and the treated waters from two water treatment plants in Selangor, Malaysia between July 1994 and January 1995. At each treatment plant, raw and treated water samples were collected fortnightly on 10 separate occasions. Physical parameters, including dissolved oxygen, pH, temperature, conductivity, turbidity and free and total chlorine were measured, and samples were also taken for faecal coliform analyses. The isolation and enumeration of cysts and oocysts was according to UK standard methods. Whilst Giardia cysts were detected in 90% of the raw water samples (range 0–60 cysts per litre) no Cryptosporidium oocysts were detected. Higher concentrations of cysts were detected in the raw water of the first treatment plant. All raw water samples were faecally contaminated, as faecal coliform counts ranged from 4.6 × 104 to 1.3 × 105 colony forming units per 100 ml. No correlation between the concentration of Giardia cysts and the concentration of faecal coliforms could be demonstrated statistically, nor was there any correlation between the concentration of Giardia cysts and the physical parameters tested for any of the raw waters. No cysts, oocysts or faecal coliforms were detected in samples of treated water.