The Reconquista River, the second most polluted river in Argentina, accumulates large amounts of organic matter and persistent toxic pollutants in its sediments. These conditions drive the selection of microorganisms with the potential to degrade contaminants and facilitate bioremediation. Notably, these microorganisms form biofilms on clay minerals, enabling them to survive under extreme conditions and alter the properties of the sediments.
This study explores the interactions between microorganisms, contaminants, and clays in degraded sediments, with the goal of improving bioremediation processes, specifically focusing on the bioleaching of heavy metals from contaminated sediments.
Samples were collected from two representative sites in the Reconquista River:
❑ Troncos del Talar (TT) (34°27'22.1"S, 58°35'55.3"W): highly contaminated.
❑ Dique Roggero (DR) (34°41'0.5"S, 58°51'29"W): used as a control site.
Indigenous bacteria were isolated from TT, including metal-bioleaching species (S-oxidizing and A. ferrooxidans). These bacteria were incubated with clay fractions extracted from TT to promote biofilm formation and assess physicochemical changes in the sediments. Using the data obtained from these experiments, heavy metal bioleaching assays in sediments from the TT area were optimized at the laboratory scale. Various systems were tested, combining different substrate alternatives in culture media and bacterial biofilm formation. The most effective system, achieving the highest percentage of heavy metal extraction, was subsequently scaled up to a pilot-scale adapted air-lift reactor.
Based on the results obtained thus far, the long-term objective is to optimize the bioleaching process by reducing the volume of bioleaching solutions required for metal extraction. Additionally, the goal is to design a system that minimizes energy consumption in the reactor and overall resource utilization, enhancing the sustainability and efficiency of the process.