Table 2. P and Main Element Composition of Recovered Solids and Comparison with Sewage Sludge Ash, Phosphate Rock, and the Requirements of the Fertilizer Industrya.
| recovered
solids (cheese wastewater,
this study) |
||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| applied current (mA) |
precipitation pH |
|||||||||||||||||
| 50 | SD | 100 | SD | 200 | SD | 300 | SD | 7 | SD | 9 | SD | 11 | SD | sewage sludge ash43 | phosphate rock44 | requirement of fertilizer industry45 | ||
| wt % | P | 13.4 | 11.9 | 10.2 | 9.4 | 12.3 | 11.6 | 11.0 | 9 | 13 | >11 | |||||||
| g/kg | P | 134 | 2 | 119 | 3 | 102 | 5 | 94 | 4 | 123 | 4 | 116 | 1 | 110 | 0 | na | na | na |
| Ca | 290 | 12 | 287 | 10 | 287 | 7 | 276 | 5 | 236 | 6 | 234 | 1 | 227 | 0 | na | na | na | |
| Mg | 10 | 1 | 10 | 0 | 8 | 1 | 10 | 1 | 3 | 1 | 8 | 0 | 13 | 0 | na | na | na | |
| mg/kg | Fe | 1188 | 173 | 508 | 44 | 319 | 39 | 249 | 46 | 674 | 6 | 577 | 3 | 543 | 4 | 58500 | 2253 | <10000 |
| Al | 321 | 90 | 148 | 25 | 105 | 62 | 79 | 14 | 309 | 7 | 283 | 1 | 267 | 3 | 67200 | 2642 | na | |
| Zn | 256 | 19 | 127 | 8 | 76 | 4 | 67 | 7 | 129 | 4 | 108 | 1 | 103 | 0.4 | 2330 | 426 | <1000 | |
| Mn | 37 | 1 | 23 | 2 | 15 | 2 | 13 | 1 | 30 | 0 | 25 | 0 | 24 | 0.1 | na | na | na | |
| Cr | 8.9 | 1.4 | 8.8 | 1.7 | 8.6 | 1.7 | 7.5 | 0.3 | 6.0 | 0.0 | 6.2 | 0.1 | 6.5 | 0.0 | 159 | 148 | na | |
| Cu | <3 | <2 | <3 | <3 | 2.3 | 0.7 | <2 | <2 | 767 | 31 | <500 | |||||||
| Cd | <3 | <2 | <3 | <3 | <2 | <2 | <2 | 2.0 | 23 | na | ||||||||
| As | <13 | <10 | <11 | <12 | <6 | 6.9 | 0.1 | <7 | 11 | 14 | na | |||||||
| Ni | <3 | <2 | <3 | <3 | <2 | <2 | <2 | 73 | 41 | na | ||||||||
a
SD, standard deviation; na, not available/not applicable.