Table 2.
Heavy metal concentrations and regulatory limits
| Element | Human urine struvite (mg∙kg−1) | Permitted limit (mg∙kg−1) |
|---|---|---|
| Al | 296.89 ± 19.31 | - |
| As | 2.01 ± 0.12 | 10 |
| Ba | 9.33 ± 0.42 | - |
| Cd | 0.08 ± 0.01 | 20 |
| Cr | 6.14 ± 0.06 | 200 |
| Cu | 110.94 ± 6.45 | 250 |
| Fe | 169.51 ± 16.20 | - |
| Hg | < LD | 0.2 |
| Mn | 76.40 ± 19.89 | - |
| Na | 9774.9 ± 104.9 | - |
| Nb | < LD | - |
| Ni | 0.94 ± 0.08 | 50 |
| Pb | 5.89 ± 0.07 | 100 |
| Se | 0.27 ± 0.04 | 2.0 |
| Ti | 4.90 ± 0.15 | - |
| Zn | 175.43 ± 30.93 | 2.500 |
*LD: Limit of Detection Note: Concentrations of trace metals and metalloids in human urine–derived struvite compared with Brazilian regulatory limits for mineral fertilizers (IN SDA No. 27/2006, amended by IN SDA No. 7/2016)