Table 6 Average, minimum and maximum values of the critical, strategic and precious element content in mg per kg of sludge DW from the studied WWTPs. The different ranges of the ordinate axes are presented in separate panels (A to E) in order to better visualize the results
Element | Unit | Average | Minimum | Maximum | Median | WWTP with maximum content |
|---|---|---|---|---|---|---|
Li | mg/kgDW | 11.9 ± 5.1 | 6.2 ± 0.3 | 20.0 ± 1 | 10.8 | WWTP7 |
Cr | mg/kgDW | 99.8 ± 33.3 | 63 ± 3 | 165 ± 5 | 92.5 | WWTP7 |
Ni | mg/kgDW | 51.1 ± 12.1 | 42 ± 1 | 79 ± 3 | 47 | WWTP7 |
As | mg/kgDW | 16.6 ± 2.2 | 5.3 ± 0.3 | 71 ± 2 | 8.7 | WWTP7 |
Sb | mg/kgDW | 7.4 ± 1.4 | 1.4 ± 0.1 | 41 ± 2 | 2.65 | WWTP7 |
Co | mg/kgDW | 8.6 ± 2.8 | 6.7 ± 0.3 | 15.0 ± 0.4 | 7.4 | WWTP4 |
Al | mg/kgDW | 19,273 ± 741 | 11,166 ± 390 | 35,246 ± 1445 | 17,177 | WWTP4 |
Mg | mg/kgDW | 6678 ± 2741 | 3147 ± 120 | 12,407 ± 510 | 6176 | WWTP4 |
Mn | mg/kgDW | 690 ± 45 | 346 ± 10 | 1625 ± 66 | 505 | WWTP4 |
Ti | mg/kgDW | 1731 ± 367 | 1293 ± 50 | 2366 ± 85 | 1661 | WWTP4 |
V | mg/kgDW | 49.8 ± 25.6 | 16.8 ± 0.7 | 90 ± 2 | 46.6 | WWTP4 |
Cu | mg/kgDW | 239 ± 82 | 188 ± 4 | 434 ± 13 | 202 | WWTP4 |
Pd | mg/kgDW | 1.2 ± 0.4 | 0.82 ± 0.05 | 1.9 ± 0.2 | 1.2 | WWTP4 |
Sr | mg/kgDW | 220 ± 88 | 102 ± 5 | 358 ± 11 | 228 | WWTP8 |
B | mg/kgDW | 46.5 ± 15.4 | 28.0 ± 0.8 | 69 ± 3 | 45.5 | WWTP8 |
Ga | mg/kgDW | 20.9 ± 6.1 | 12.9 ± 0.4 | 33 ± 1 | 19.3 | WWTP6 |
Ag | mg/kgDW | 5.4 ± 2.4 | 2.3 ± 0.1 | 10.0 ± 0.6 | 4.5 | WWTP6 |
Au | mg/kgDW | 1.1 ± 0.8 | 0.36 ± 0.02 | 2.7 ± 0.2 | 0.86 | WWTP2 |