Microbially-driven strategies for bioremediation of bauxite residue

Abstract

Globally, 3 Gt of bauxite residue is currently in storage, with an additional 120 Mt generated every year. Bauxite residue is an alkaline, saline, sodic, massive, and fine grained material with little organic carbon or plant nutrients. To date, remediation of bauxite residue has focused on the use of chemical and physical amendments to address high pH, high salinity, and poor drainage and aeration. No studies to date have evaluated the potential for microbial communities to contribute to remediation as part of a combined approach integrating chemical, physical, and biological amendments. This review considers natural alkaline, saline environments that present similar challenges for microbial survival and evaluates candidate microorganisms that are both adapted for survival in these environments and have the capacity to carry out beneficial metabolisms in bauxite residue. Fermentation, sulfur oxidation, and extracellular polymeric substance production emerge as promising pathways for bioremediation whether employed individually or in combination. A combination of bioaugmentation (addition of inocula from other alkaline, saline environments) and biostimulation (addition of nutrients to promote microbial growth and activity) of the native community in bauxite residue is recommended as the approach most likely to be successful in promoting bioremediation of bauxite residue.

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

“…The volume of bauxite residue generated per ton of alumina product is approximately 0.5-2 tons [3][4][5]. Raising demand for alumina worldwide has increased the rate of bauxite residue production.…”

Characterization of Alkaliphilic Bacteria Isolated from Bauxite Residue in the Southern Region of Minas Gerais, Brazil

“…Brazil is one of the three biggest bauxite producers, with an annual output of ~30 megatons 1 . Alumina extraction from bauxite using concentrated sodium hydroxide in the Bayer process generates a slurry and an extremely alkaline (pH of 9 to 13) byproduct known as bauxite residue or red mud.…”

“…Alumina extraction from bauxite using concentrated sodium hydroxide in the Bayer process generates a slurry and an extremely alkaline (pH of 9 to 13) byproduct known as bauxite residue or red mud. For each ton of alumina extracted from bauxite, approximately 1.5-2.0 tons of bauxite residue is generated 1,2 . Disposal of such a byproduct is a serious problem at alumina plants because of environmental risks and financial costs.…”

“…Disposal of such a byproduct is a serious problem at alumina plants because of environmental risks and financial costs. The use of alkaliphilic microorganisms is considered an attractive alternative method for treatment of industrial alkaline residues, owing to their ability to metabolically reduce alkalinity and their tolerance of high concentrations of ions and metals and low availability of organic carbon and nutrients [1][2][3][4][5][6][7][8] . Few research groups have studied alkaliphilic bacteria from bauxite residues [5][6][7] , and there are no reports addressing the microbial composition in such an environment in Brazil.…”

“…Few research groups have studied alkaliphilic bacteria from bauxite residues [5][6][7] , and there are no reports addressing the microbial composition in such an environment in Brazil. Because climatic, geological, and other environmental conditions as well as variations in alumina extraction methods are strong determinants of biological characteristics of bauxite residue deposits 1,2 , it is important to perform microbial analysis of bauxite residues from unexplored geographic locations. The aim of this study was to isolate and characterize bacterial strains in bauxite residue from the region of Poços de Caldas, Brazil.…”