Biomineralization of calcium and magnesium crystals from seawater by halotolerant bacteria isolated from Atacama Salar (Chile)

Antofagasta (Chile) is an arid region, and the climate is strongly influenced by the Atacama Desert, with few sources of fresh water. The pressure to use non-conventional water sources has boosted the construction of numerous desalination plants. High concentrations of secondary ions as calcium and magnesium cause problems in reverse osmosis plants and in other industries such as copper mining and cooling system. Biomineralization process based on hydrolysis of urea has been described in a wide variety of bacterial species with diverse applications. The selection of ureolytic halotolerant bacteria from Atacama Salar and their ability to precipitate calcium and magnesium crystals in seawater is described. Besides crystal structure and morphology were determined by electron microscopy analysis and X-ray diffraction. When assessing the mineral precipitate ability, Rhodococcus erythropolis precipitates a ~ 95% soluble calcium and 8% magnesium. The analysis of crystals showed that correspond to ~ 12.69% monohydrocalcite, ~ 30.72% struvite and ~ 56.59% halite. These results demonstrate that the biomineralization by ureolytic bacteria in seawater has great potential for its application as a pretreatment to improve water quality for industrial processes.