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LIFE IN ALUMINA REFINERIES: A CROSS-REFINERY STUDY OF MICROBIAL COMMUNITIES IN BAUXITE RESIDUE

Santini, T.C. Warren, L.A.

The harsh chemical and physical processing conditions associated with the Bayer process generate a highly alkaline, saline tailings material (bauxite residue) that is generally considered inhospitable to microbial life. In situ remediation strategies promote soil formation from bauxite residue by enhancing leaching of saline, alkaline pore water, and through incorporation of amendments to boost organic matter content, decrease pH, and improve physical structure. During rehabilitation, microbial communities should become more diverse and develop wider functional capacity, indicating progression towards communities more commonly observed in natural grassland and forest soils; however, few studies have evaluated this in bauxite residue, and none have linked these shifts to environmental conditions in order to inform improvement of current remediation strategies. Here, bauxite residue samples from Salinity and active sodicity (water extractable sodium) were identified as the major drivers of bacterial community composition and diversity across treated and untreated tailings widely ranging in pH (4-11). Results identify that improvement of the physical properties of bauxite residue is key to establishing a diverse microbial community and improve remediation success.