Table 4.
The characteristics of the WAS before and after ultrasonic pretreatment—direct effects (n = 7).
| Parameter | Unit | WAS_NUD | WAS_A | WAS_B |
|---|---|---|---|---|
| Mean; CV | ||||
| pH | - | 7.0 (2.0%) | 6.9 (2.2%) | 6.8 (2.7%) |
| TS | g·L−1 | 41.1 (26.9%) | - | - |
| VS | g·L−1 | 29.8 (29.2%) | - | - |
| SCOD0 /SCODUD | mg·L−1 | 66.8 (22.8%) | 1061.7 (34.8%) | 4573.4 (39.2%) |
| NTOT | mg·L−1 | 10.9 (16.3%) | 139.9 (23.8%) | 470.4 (37.5%) |
| PTOT1 | mg·L−1 | 25.1 (31.4%) | 135.6 (22.5%) | 177.0 (18.7%) |
| Proteins | mg·L−1 | 888.9 (24.9%) | 784.0 (35.1%) | 927.5 (29.2%) |
| Carbohydrates | mg·L−1 | 598.4 (35.6%) | 480.7 (47.5%) | 507.0 (46.9%) |
| CST | s | 9.0 (24.8%) | 343.1 (70.0%) | 1175.1 (10.2%) |
| ΔT | °C | - | 14.0 (39.7%) | 34.0 (29.5%) |
WAS_NUD—WAS before pretreatment; WAS_A—WAS after pretreatment in the WK-2010; WAS_B—WAS after pretreatment in the ultrasonic washer; CV—coefficient of variation; TS—total solids; VS—volatile solids; SCOD0—SCOD of the supernatant of the original sludge; SCODUD—SCOD value of the supernatant of the disintegrated sludge; TN—total nitrogen; TP—total phosphorus; CST—capillary suction time; ΔT—temperature increase.