The biological treatment of low-pH effluents presents a significant challenge from both a biochemical and engineering perspective, particularly due to the unclear relationship between the sulphur and iron cycles in these environments. Thermodynamically, sulphate reduction is more favorable at pH levels above 7.0. However, under acidic conditions, the free energy derived from iron reduction is five times greater than that released in sulfate reduction. Despite this, there is a lack of studies examining the competition between iron (III) and sulfate at pH levels below 7.0. Whether iron (III) serves as the primary electron receptor in acidic environments when sulphate is present remains a matter of debate. This project aims to explore the relationship between Fe (III) and sulphate as electron receptors in low pH environments, and to identify the factors that influence the use of sulphate and/or Fe (III) by sulphate-reducing bacteria (SRB) under acidic conditions. To date, no studies have been published demonstrating this behavior in real systems; existing knowledge is based solely on simulations.