Biofilter | Removal efficiencies (%) | ||
COD | BOD5 | SS | |
Sand 1 - 2mm | 67.35a | 78.04a | 87.10a |
Sand 2 - 4 mm | 33.05ab | 63.62a | 87.53a |
Lateritic gravel 2 - 4 mm | 13.26bc | 30.12ab | 65.53ab |
Lateritic gravel 4 - 6 mm | −2.23c | 18.16b | 45.82bc |
Granitic gravel 1 - 2 mm | 55.67a | 72.48a | 81.26a |
Granitic gravel 2 - 4 mm | 15.25bc | 41.36ab | 65.77ab |
Granitic gravel 4 - 6 mm | 2.03c | 27.33ab | 34.97c |