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Influences of pH and organic carbon on oxalate removal by alkaliphilic biofilms acclimatized to nitrogen-deficient and supplemented conditions

Weerasinghe Mohottige, T.N., Cheng, K.Y., Kaksonen, A.H., Sarukkalige, R. and Ginige, M.P. (2018) Influences of pH and organic carbon on oxalate removal by alkaliphilic biofilms acclimatized to nitrogen-deficient and supplemented conditions. Journal of Cleaner Production . In Press.

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Link to Published Version: https://doi.org/10.1016/j.jclepro.2018.03.153
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Abstract

Accumulation of organic impurities (specifically oxalate) in Bayer liquor is a significant constrain to refine alumina. Microbial oxidation is a low-cost approach to remove organics, but hostile conditions of Bayer liquor (pH > 14 and nitrogen (N) deficiency) makes it challenging. The solution remains with selection of an appropriate haloalkaliphilic culture and alumina refineries currently have access to two types of bacterial cultures (N-supplemented and N-deficient cultures). To date there is no comparative assessment of the two cultures to examine which one is more suitable to reduce operational risks (i.e. with higher removal efficiencies over a broader range of pH) and costs.

Hence, this study compared oxalate removal efficiencies of two packed bed biofilm reactors (N- supplemented and N-deficient) on exposure to a range of influent pH and simple organic compounds. Both reactors were operated (>265 days) at pH 9 and pH influence was compared in batch experiments. Results suggested that both biofilms could tolerate a broad pH range (7-10). The optimal specific oxalate removal rate of N-supplemented reactor was restricted to pH 9, whereas the maximal rate was maintained over a wider pH range (7 - 8) in N-deficient reactor. In this range, the N-deficient system outperformed the N-supplemented system (105 vs. 130 mg-oxalate /h.g-biomass). Although acclimatized primarily with oxalate, both biofilms simultaneously oxidized other organics (acetate, formate, malonate and succinate) without a noticeable influence on oxalate removal. This study suggests that N-deficient systems are more versatile and better suited to remove organic impurities in Bayer liquor.

Publication Type: Journal Article
Murdoch Affiliation: School of Engineering and Information Technology
Publisher: Elsevier Limited
Copyright: © 2018 Elsevier Ltd.
URI: http://researchrepository.murdoch.edu.au/id/eprint/40550
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