A biogeochemical model of microbially induced concrete corrosion in sewer systems

Microbially induced corrosion (MIC) of concrete in sewer systems is a complex, multi-stage process driven by both geochemical transformations and microbial activity. Sulfur-oxidizing bacteria (SOBs) play a pivotal role in this degradation mechanism, particularly through the formation of biofilms that convert hydrogen sulfide into sulfuric acid, thereby favoring the deterioration of concrete surfaces. This paper presents a novel mathematical model that captures the biogeochemical and ecological processes governing MIC in wastewater pipelines. The model, based on a system of ordinary differential equations, describes the dynamics of key microbial populations - neutrophilic and acidophilic SOBs - and their pH-dependent growth, succession, and contribution to acid production. It integrates gas-liquid mass transfer, acid-base equilibria, dissolution and precipitation of solid phases, and ionic charge balance to simulate the evolution of critical variables such as pH, calcium ion concentration, and the formation of deterioration products like gypsum and calcite. Numerical simulations explore the impact of microbial activity and hydrogen sulfide gaseous concentration on the corrosion process, under both carbonated and unaltered concrete conditions. The results provide insight into the intricate feedback between microbial ecology and physicochemical conditions, offering a predictive tool for understanding and potentially mitigating MIC in sewer infrastructure.