| Organisms | Coagulation and sedimentation (% removal) | Rapid filtration (% removal) | Slow sand filtration (% removal) |
| Total coliforms | 74 - 97 | 50 - 98 | >99.999 |
| Fecal coliforms | 76 - 83 | 50 - 98 | >99.999 |
| Enteric viruses | 88 - 95 | 10 - 99 | >99.999 |
| Giardia | 58 - 99 | 97 - 99.9 | >99 |
| Cryptosporidium | 90 | 99 - 99.9 | 99 |