Microbial Fermentation of Organic Carbon Substrates Drives Rapid pH Neutralization and Element Removal in Bauxite Residue Leachate

Globally, mineral processing activities produce an estimated 680 GL/yr of alkaline wastewater. Neutralizing pH and removing dissolved elements are the main goals of wastewater treatment prior to discharge. Here, we present the first study to explicitly evaluate the role of microbial communities in driving pH neutralization and element removal in alkaline wastewaters by fermentation of organic carbon, using bauxite residue leachate as a model system, and evaluate the effects of organic carbon complexity and microbial inoculum addition rates on the performance of these treatment systems at laboratory scale. Rates and extents of pH neutralization were higher in bioreactors fed with simpler organic carbon substrates (glucose and banana: 6 days to reach pH