Table 37-3 Activated sludge
| Aeration Retention Time, hr | MLSS, ppm | Aeration D.O., ppm | Sludge Recycle, % | BOD Loading, lb/Mft3 | F/M lb BOD/lb MLVSS | Sludge Production, lb/lb of BOD | BOD Removal % | |
| High rate | ½-3 | 300-1,000 | 0.5-2.0 | 5-15 | 2.5 | 1.5-5.0 | 0.65-0.85 | 75-85 |
| Conventional activated sludge | 6-8 (diffused) | 1,000-3,000 | 0.5-2.0 | 20-30 | 20-40 | 0.2-0.5 | 0.35-0.55 | 85-90 |
| 9-12 (mechanical) | 500-1,500 | 0.5-2.0 | 10-20 | 20-40 | 0.2-0.5 | 0.35-0.55 | 80-95 | |
| Extended aeration | 18-36 | 3,000-6,000 | 0.5-2.0 | 75-100 | 10-25 | 0.03-0.15 | 0.15-0.20 | 90-95 |
| Step aeration | 3-5 | 2,000-3,500 | 0.5-2.0 | 25-75 | 40-60 | 0.2-0.5 | 0.35-0.55 | 85-90 |
| Contact stabilization | 3-6 | 1,000-3,000 (aeration) | 0.5-2.0 | 25-100 | 60-75 | 0.2-0.6 | 0.35-0.55 | 85-90 |
| 4,000-10,000 (contact basin) | 0.5-2.0 | 25-100 | 60-75 | 0.2-0.6 | 0.35-0.55 | 85-90 | ||
| Pure Oxygen | 1-3 | 3,000-8,000 | 2-6 | 25-50 | 100-250 | 0.25-1.0 | 0.35-0.55 | 95-98 |
| Complete mix | 3-5 | 3,000-6,000 | 0.5-2.0 | 25-100 | 50-120 | 0.2-0.6 | 0.35-0.55 | 85-95 |