Table 5 Hazardous heavy metal and metalloid content in mg per kg of sludge DW from the studied WWTPs
WWTP 1 | WWTP 2 | WWTP 3 | WWTP 4 | WWTP 5 | WWTP 6 | WWTP 7 | WWTP 8 | Sewage Sludge Directive 86/278/EEC | National Ordinance 339/2004 for the Use of Sludge in Agriculture | |
|---|---|---|---|---|---|---|---|---|---|---|
Cr | 127 ± 4 | 105 ± 4 | 67 ± 2 | 87 ± 4 | 63 ± 4 | 86 ± 4 | 165 ± 5 | 98 ± 5 | – | 500 |
Ni | 52.9 ± 0.6 | 48.2 ± 0.9 | 41.8 ± 0.7 | 54 ± 1 | 43.1 ± 0.9 | 45.7 ± 0.8 | 79 ± 2 | 43.5 ± 0.9 | 300 | 350 |
Cu | 201 ± 6 | 249 ± 9 | 195 ± 4 | 188 ± 7 | 435 ± 9 | 240 ± 7 | 201 ± 6 | 202 ± 7 | 1000 | 1600 |
Zn | 546 ± 8 | 1393 ± 30 | 1089 ± 20 | 833 ± 18 | 1058 ± 31 | 1712 ± 56 | 2036 ± 51 | 2688 ± 78 | 2500 | 3000 |
As | 7.9 ± 0.6 | 9.6 ± 0.5 | 9.5 ± 0.5 | 15.7 ± 0.8 | 6.5 ± 0.3 | 7.2 ± 0.4 | 71 ± 4 | 5.3 ± 6 ± 0.3 | – | 25 |
Cd | 0.77 ± 0.02 | 0.97 ± 0.03 | 1.88 ± 0.07 | 1.23 ± 0.05 | 1.56 ± 0.04 | 2.34 ± 0.08 | 11.3 ± 0.4 | 1.1 ± 0.1 | 20 | 30 |
Hg | 0.51 ± 0.03 | 1.15 ± 0.06 | 0.72 ± 0.04 | 0.43 ± 0.02 | 0.39 ± 0.02 | 0.30 ± 0.02 | 0.23 ± 0.01 | 0.40 ± 0.02 | 16 | 16 |
Pb | 27 ± 1 | 41 ± 1 | 54 ± 1 | 59 ± 2 | 59 ± 2 | 54 ± 2 | 3268 ± 162 | 42 ± 2 | 750 | 800 |