Index | BOD (biochemistry) | Ammonia nitrogen | Petroleum category | Total nitrogen | Total phosphorus | COD |
I Class | ≤3 | ≤0.015 | ≤0.05 | ≤0.2 | ≤0.01 | ≤15 |
II Class | 3 | 0.5 | 0.05 | 0.5 | 0.025 | 15 |
III Class | 4 | 1.0 | 0.05 | 1.0 | 0.05 | 20 |
IV Class | 6 | 1.5 | 0.5 | 1.5 | 0.1 | 30 |
V Class | 10 | 2.0 | 1.0 | 2.0 | 0.2 | 40 |