When bauxite is digested during Bayer processing, associated organic compounds and humic acids are degraded to produce sodium salts of organic acids, including sodium oxalate. If not removed from the liquor stream, sodium oxalate co-precipitates with the aluminium hydroxide resulting in poor crystallization and alumina and soda loss. Aerobic bioremediation processes have been developed as an economic and environmentally sound option for oxalate removal. Little research has been directed at characterising the microbial communities and biological processes underpinning these processes. Analysis of samples from both a moving bed biofilm reactor and bioreactor effluent using PCR-DGGE of 16S rRNA genes showed microorganisms of the genus Halomonas dominated the process. Most Probable Number (MPN) analyses also showed Halomonas spp. to be numerically dominant in all bioreactor samples.