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Abstract

Nitrate and selenium are common contaminants of concern at mining operations. Effective treatment of mine contact water is essential for environmental protection, often becoming a legacy issue in the post-closure phase. Passive biological water treatment systems offer technical, economic, and sustainable solutions. Nitrate and selenium are removed through biologically mediated redox (reduction-oxidation) processes. However, bioreactors are often designed based on empirical data from laboratory or field-based studies, which may not capture all necessary biogeochemical information. Bioreactor design typically focuses on water quality data and results from laboratory and field studies testing the removal of contaminants from the water. Results from the geochemical testing are scaled up based on experience and the physical and chemical properties of the bioreactor. Characteristics of the biological processes that drive the geochemical changes are often not considered, though the kinetics of these microbially driven reactions are crucial. An improved understanding of biogeochemistry requires interpreting laboratory or field-scale data using a reactive transport model that includes microbially based kinetics. By integrating chemical reactions and microbial kinetics with physical transport processes in a reactive transport model, we can more accurately predict contaminant behaviour within the treatment system. A model-based approach provides essential information for the design of water treatment systems, ensuring that these systems are neither oversized nor undersized. Here, we demonstrate the use of published laboratory and field-based data in a reactive transport model to optimize the design of biological water treatment systems.