The adverse effect of disrupted water-borne bacteria cells on flotation

Existing studies have demonstrated the potential threat of bacteria to copper and gold flotation when mineral processing operations use bacteria-laden water, such as treated sewage effluent, as an alternative water source. Once being introduced into a mine water system, water-borne bacteria may experience cell disruption causing the release of constituent organic molecules into process water. However, little is known about the potential impact of these organic molecules released from disrupted bacteria cells on flotation performance. In this study, using the same representative system as previously used with intact cells, we investigated the effect of disrupted cells on flotation. This representative system consists of E. coli cells disrupted by sonication (also called lysed cells) as the model bacterium and three copper-containing mineral systems of increasing complexity as the ore model. It was found that the disrupted cells had a negative effect on copper flotation, which tended to weaken as ore composition became more complex. The negative effect of the disrupted cells on copper flotation was more pronounced than that of the intact cells. Flotation of gold and pyrite was found to be depressed as well possibly due to the preferential adhesion of the lysed cells on pyrite. Findings in this study enhance understanding and management of the risk posed by bacteria-laden water which is being increasingly used as an alternative water source for mineral processing.