Mitigation of adverse effects of calcium on struvite biomineralization for phosphorus recovery

Calcium ions may adversely affect struvite biomineralization, but the exact role remains elusive and the way to eliminate its adverse effect needs to be explored. Herein, Shewanella oneidensis MR-1 was selected to induce struvite biomineralization. The increase of Ca/Mg ratios from 0 to 2:1 resulted in a decrease of struvite yield from 98.6 mg to 0 mg. Calcium ions inhibited struvite crystallization by forming amorphous calcium phosphate (ACP) at the early stage of biomineralization. The increase of disodium ethylenediaminetetraacetate (EDTA) concentrations from 1 mM to 3 mM led to a rise of struvite mass from 0 mg to 86.3 mg. As the use of disodium EDTA is environmentally safe, it is feasible to employ disodium EDTA to mitigate adverse effects of calcium ions on struvite biomineralization. These findings deepen the understanding of struvite biomineralization and provide an effective method to deal with calcium ions in wastewater.