Assessment of Microbial Consortia for Biogenic Mineralization Potential of Lead (Pb) using Microbiologically Induced Calcite Precipitation and Nitrate Reduction

Groundwater contamination by lead (Pb ⁺² ) and nitrate (NO₃⁻) exceeding the permissible limits of the World Health Organization (WHO) and the Bureau of Indian Standards (BIS) (10500:2012) of 10 ppb Pb ⁺² and 45–50 ppm NO₃⁻, poses a severe health risk of systemic toxicity in humans and animals. Microbial nitrate reduction coupled with microbiologically induced calcite precipitation (MICP) proved to be a novel bioremediation strategy to transform soluble lead nitrate [Pb(NO₃)₂] into insoluble lead biominerals. This study presents statistical optimization of operational parameters for nitrate reduction and co-precipitation of biogenic lead carbonate-calcium carbonate by nitrate-reducing bacterial consortia. The SEM, TEM with SEAD, and XRD analysis of the biomineral confirmed PbCO₃ co-precipitaion with CaCO ₃ . A two-level factorial design was applied to screen significant variables and interactive factors that influence nitrate reduction and biomineral precipitation. The highest nitrate reduction, maximum ammonia production, and biogenic Pb-mineralization efficiency of> 90% were obtained at the optimum conditions (initial nitrate requirement of 600ppm, temperature 37 °C, pH 8, and carbon content of 5.5 g/L) compared to those obtained under the common process parameters. ANOVA with a high correlation coefficient (R ² > 0.99) corroborated the linear model for the biogenic mineralization process. This study on the biogenic removal of Pb by nitrate-reducing bacterial consortia revealed possible opportunities for large-scale treatment of Pb-contaminated surface and sub-surface water bodies.