Can phosphobacteria simultaneously achieve phosphorus recovery and Pb2+ removal from wastewater by biomineralization?

Biomineralization of struvite is a promising approach to recover dissolved organic phosphorus (DOP) from wastewater. However, toxic heavy metal Pb2+ widely found in phosphorus (P)-rich wastewaters may affect the process and has not yet been studied. Here, Shewanella oneidensis MR-1 with high organic P-mineralizing (OPM) ability was used to mineralize struvite from simulated Pb2+-bearing wastewaters. The phase composition, structure, and morphology of the products were characterized by various techniques, including SEM-EDS, FT-IR, XPS, TEM, XRD and Rietveld refinement. Our results reveal that strain MR-1 can not only efficiently mineralize struvite from wastewater with Pb2+ concentrations of 1–50 mg/L but also pyromorphite (Pb5(PO4)3Cl), and the pyromorphite particles are tightly associated with the bacterial biomass, facilitating the effective separation of pyromorphite from struvite. As a result, phosphorus recovery and Pb2+ removal from wastewater can be concurrently achieved by a biomineralization. Furthermore, biomimetic mineralization experiments reveal that the extracellular polymeric substances (EPS) bound to bacterial cells play crucial roles in the bioconcentration of Pb2+ and the formation of pyromorphite. This study can promote the development of the simultaneous remediation of wastewaters polluted with P and the heavy metal Pb2+.