Biomineralization of struvite by Shewanella oneidensis MR-1 for phosphorus recovery: Cr(VI) effect and behavior

Abstract

Bacterial mineralization of struvite from wastewaters is one of the promising approaches to recover phosphorus. However, the information about whether and how the heavy metal Cr(VI) affect the bacterial mineralization system is still lack. Here a model microbe Shewanella oneidensis MR-1 was used to induce struvite mineralization in simulated Cr(VI)-bearing wastewaters and the composition, morphology, and Cr content of precipitates were characterized by a wide range of techniques. Our results reveal that the yield of struvite and Mg transformation efficiency are almost not affected by the concomitant Cr(VI), but pitting and roughening of struvite surfaces are observed. Meanwhile, the struvite mineralized from model wastewaters with 0.1 or 0.2 mM Cr(VI) can meet the regulatory standard of Cr content as fertilizer. Strain MR-1 can not only create an alkaline environment for struvite precipitation, but also completely reduce Cr(VI) to Cr(III), helping to form soluble organo-Cr(III) complexes in the supernatant, hence significantly reducing the Cr content in struvite. And the loaded Cr(III) exists in the form of amorphous Cr(III) species (e.g., Cr(OH)3) on the struvite surface instead of the crystal lattice substitution in abiotic case. Current results serve as a guidance for further development of struvite biomineralization and P recovery from Cr(VI)-containing wastewaters.