TABLE 1.
Main features of treatment plants and removal of Giardia cysts
| Plant | Population served | Primary treatment | Secondary treatment | Disinfection | % Removal of Giardia cysts (mean geometric value) |
|---|---|---|---|---|---|
| 1 | 153,000 | Screening and grit separation | Oxidation with O2 and Sedimeutation | None | 94.5 |
| 2 | 300,000 | Screening, grit separation, and sedimentation | Activated sludge and sedimentation | Chlorination (0.05-1 ppm) | 87.0 |
| 3 | 330,000 | Screening, grit separation, and sedimentation | Activated sludge and sedimentation | Chlorination (0.05-1 ppm) | 96.0 |
| 4 | 100,000 | Screening, grit separation and sedimentation | Activated sludge and sedimentation | Filtration (60-μm pore) and peracetic acid (4 ppm) | 98.4 |