Bioaugmentation coupled with phytoextraction for the treatment of Cd and Sr, and reuse opportunities for phosphogypsum rare earth elements.

The environmental and health impacts caused by phosphogypsum (PG) make it necessary to carefully manage these wastes. Bioaugmentation of a PG-compost mix with Bacillus cereus was associated with Trifolium pratense or Helianthus annuus for the phytoextraction of metal trace elements (MTE). In hydroponics, MTE concentrations in sunflower shoots are higher than in clover; however, as opposed to clover, it regulates their accumulation. The MTE accumulation levels by plants cultivated in pots with the PG-compost mix are much lower than in hydroponics due to lower concentration in available MTE. The bacteria-plant coupling has served to raise MTE concentrations, especially for rare earth elements (REE), i.e., Ce, La, Nd, Y, in the AP of sunflower, by factors of 4.4, 38.3, 3.4 and 21, respectively, compared to non-bioaugmented control. The translocation factor was also increased for all MTE and is ranged between 1.1 for Sr and 6.8 for Y. Moreover, the presence of bacteria raises plant biomass by a factor of 3.7 for shoots and 2.9 for the roots as regards clover. Results showed that in addition to phytoextraction of REE elements, all providing the promise of some kind of economic opportunity, the dispersion of PG stockpiles dust and erosion should be reduced.