The microbiology of oxalate degradation in bioreactors treating Bayer liquor organic wastes

[Truncated abstract] During the initial stages of the Bayer process, humic and fulvic materials that are associated with bauxite are co-digested to produce a large range of organic impurities, including oxalate. If not removed from the process stream, oxalate co-precipitates with alumina precursors, reducing the quality and yield of the alumina produced by Bayer processing. Traditional treatment methods and storage of oxalate are typically expensive and environmentally detrimental due to costs associated with the construction and maintenance of storage facilities and the potential release of volatile organic compounds and CO2 into the atmosphere. Investigations into the use of pilot-scale bioreactors as a more economically feasible and environmentally friendly way to manage oxalate wastes have previously been carried out. However, studies have not focused on the characterisation of the microorganisms involved in the biological degradation of oxalate or their physiological requirements for optimal growth and activity. Following the successful demonstration of continuous-flow oxalate degradation in bioreactors at laboratory-scale, the Technology Delivery Group at Alcoa Australia (Kwinana, WA) commissioned and implemented pilot- and full-scale bioreactors for the treatment of oxalate-containing wastes. The study presented here aimed to improve the fundamental understanding of the biological degradation of oxalate in bioreactors operating at Alcoa Australia by: 1. Characterising the microbial ecology of pilot- and full-scale oxalate-degrading bioreactors; 2. Isolating, identifying and characterising the key microbial members from the oxalate-degrading microbial communities within these bioreactors; 3. Defining the physiological requirements of the oxalate-degrading microbial communities to promote optimal growth and activity and; 4. Identifying the critical and optimal operating parameters of the full-scale process.