| Levels | Factors | |||
| Dosage (g) | Contact time (min) | Temperature (˚C) | pH | |
| 1 | 1.0 | 30 | 20 | 3 |
| 2 | 1.5 | 45 | 30 | 5 |
| 3 | 2.0 | 60 | 40 | 7 |
| 4 | 2.5 | 75 | 50 | 9 |
| 5 | 3.0 | 90 | 60 | 11 |