Bacterial mineralization of struvite using MgO as magnesium source and its potential for nutrient recovery

Bacterial mineralization of struvite is one of the novel approaches for the recovery of major nutrients nitrogen and phosphorus. However, previous studies were done by using expensive water-soluble magnesium salts, like MgCl2 and MgSO4, significantly limiting its large-scale application. In this context, our objective is to examine the potential of low-cost, naturally abundant MgO as Mg source in bacterial mineralization of struvite. Shewanella oneidensis MR-1 was selected as a model microbe to induce struvite mineralization. The structure, morphology and composition of the mineralized products were identified and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDX). Our results demonstrate that S. oneidensis MR-1 is able to enhance MgO dissolution, and transform organic nitrogen and organophosphorus into well-crystallized struvite. The process of bacterial mineralization not only increased the alkalinity of the culture, but also effectively transformed over 97% of Mg2+ from MgO into struvite, hence significantly cutting down the recovery cost of the major nutrients. Current results could provide an effective and economically feasible pathway for the nutrients removal and subsequent recovery as struvite from eutrophic waters.