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Int. J. Environ. Res. Public Health 2014, 11(4), 3689-3704; doi:10.3390/ijerph110403689
Article

Precipitation of Phosphate Minerals by Microorganisms Isolated from a Fixed-Biofilm Reactor Used for the Treatment of Domestic Wastewater

1
, 2,* , 3
, 4
, 3
 and 3
1 Department of Electronic and Computer Technology, Higher Technical School of Computer Engineering and Telecommunications , University of Granada, University Campus of Almanjayar, Granada 18071, Spain 2 Department of Civil Engineering, Advanced Technical School of Civil Engineers, University of Granada, Fuentenueva Campus, Granada 18071, Spain 3 Departament of Microbiology, Faculty of Pharmacy, University of Granada, University Campus of Cartuja, Granada 18071, Spain 4 Department of Mineralogy and Petrology, Faculty of Science, University of Granada, Fuentenueva Campus , Granada 18071, Spain
* Author to whom correspondence should be addressed.
Received: 12 January 2014 / Revised: 3 March 2014 / Accepted: 25 March 2014 / Published: 2 April 2014
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Abstract

The ability of bacteria isolated from a fixed-film bioreactor to precipitate phosphate crystals for the treatment of domestic wastewater in both artificial and natural media was studied. When this was demonstrated in artificial solid media for crystal formation, precipitation took place rapidly, and crystal formation began 3 days after inoculation. The percentage of phosphate-forming bacteria was slightly higher than 75%. Twelve major colonies with phosphate precipitation capacity were the dominant heterotrophic platable bacteria growing aerobically in artificial media. According to their taxonomic affiliations (based on partial sequencing of the 16S rRNA), the 12 strains belonged to the following genera of Gram-negative bacteria: Rhodobacter, Pseudoxanthobacter, Escherichia, Alcaligenes, Roseobacter, Ochrobactrum, Agromyce, Sphingomonas and Paracoccus. The phylogenetic tree shows that most of the identified populations were evolutionarily related to the Alphaproteobacteria (91.66% of sequences). The minerals formed were studied by X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive X-ray microanalysis (EDX). All of these strains formed phosphate crystals and precipitated struvite (MgNH4PO4·6H2O), bobierrite [Mg3(PO4)2·8H2O] and baricite [(MgFe)3(PO4)2·8H2O]. The results obtained in this study show that struvite and spherulite crystals did not show any cell marks. Moreover, phosphate precipitation was observed in the bacterial mass but also near the colonies. Our results suggest that the microbial population contributed to phosphate precipitation by changing the media as a consequence of their metabolic activity. Moreover, the results of this research suggest that bacteria play an active role in the mineral precipitation of soluble phosphate from urban wastewater in submerged fixed-film bioreactors.
Keywords: struvite; spherulites; bobierrite; baricite; urban wastewater; phosphate precipitation; submerged fixed-film bioreactor struvite; spherulites; bobierrite; baricite; urban wastewater; phosphate precipitation; submerged fixed-film bioreactor
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Rivadeneyra, A.; Gonzalez-Martinez, A.; Gonzalez-Lopez, J.; Martin-Ramos, D.; Martinez-Toledo, M.V.; Rivadeneyra, M.A. Precipitation of Phosphate Minerals by Microorganisms Isolated from a Fixed-Biofilm Reactor Used for the Treatment of Domestic Wastewater. Int. J. Environ. Res. Public Health 2014, 11, 3689-3704.

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