Microbial mineralization of struvite: Salinity effect and its implication for phosphorus removal and recovery

Microbial mineralization of struvite from wastewater with cheap magnesium source is a very promising means to remove and recover phosphorus and nitrogen. Seawater, as a cheap and efficient magnesium source, may be potentially applied to struvite bio-recovery. However, high salinity in seawater may have potential effect on microbial growth and its biomineralization for struvite. In present work, a halophilic marine actinomycete, Micro bacterium marinum sp. nov. H207 was selected as a model microbe to induce struvite mineralization under different saline conditions. The identification and characterization of the mineralized products were done using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), and field emission scanning electron microscopy (FESEM). The results showed that this strain has good ability to mineralize struvite within the pale of seawater salinity, and the salinity levels have a negligible effect on phosphorus removal and recovery capability of this strain, but the induction period for struvite precipitation increases with elevated salinity, and such retardation can be attributed to the high salinity stress on bacterial metabolism of carbonaceous and nitrogenous organics. Meanwhile, the salinity can also affect the morphogenesis of bio-struvite, and the high saline conditions result in the significant elongations of the struvite crystals along its crystallographic [1 0 0] direction. Current results could have particular relevance to the feasibility of using seawater in microbial phosphorus recovery processes.