| n˚ exp | Factors | Phosphate removal Yexp (%) | Theoretical phosphate removal Ycalc (%) | Coefficient of variation (%) | |||||
| Coded variables | Real variables | ||||||||
| X1 | X2 | X3 | U1 (˚C) | U2 (N) | U3 (H) | ||||
| 1 | −1 | −1 | −1 | 65 | 0.5 | 8 | 31.25 | 34.22 | 9.5 |
| 2 | +1 | −1 | −1 | 90 | 0.5 | 8 | 51.25 | 48.28 | 5.8 |
| 3 | −1 | +1 | −1 | 65 | 2 | 8 | 38.75 | 35.78 | 7.66 |
| 4 | +1 | +1 | −1 | 90 | 2 | 8 | 42.5 | 45.47 | 6.99 |
| 5 | −1 | −1 | +1 | 65 | 0.5 | 12 | 43.75 | 40.78 | 6.79 |
| 6 | 1 | −1 | +1 | 90 | 0.5 | 12 | 53.76 | 56.72 | 5.51 |
| 7 | −1 | +1 | +1 | 65 | 2 | 12 | 43.75 | 46.72 | 6.79 |
| 8 | +1 | +1 | +1 | 90 | 2 | 12 | 61.25 | 58.28 | 4.85 |