Sustainable Microbial Bioremediation of Heavy Metal Contamination: Mechanisms, Microbially Induced Carbonate Precipitation, Limitations, and Future Perspectives

Abstract

Heavy metal contamination represents a persistent environmental concern because of the long-term stability, mobility, and potential bioavailability of these contaminants in water, soils, and sediments. Anthropogenic activities, including mining, metallurgical and industrial processes, agriculture, energy production, and waste disposal, can substantially increase metal concentrations above natural geochemical background levels, with potential consequences for ecosystem functioning and human health. This critical narrative review examines current remediation strategies, with particular emphasis on biological approaches and microbially induced carbonate precipitation (MICP). The relevant literature was identified through a structured, topic-driven search in Scopus and Google Scholar using the keywords “MICP” and “heavy metals”, individually and in combination, and was selected according to its relevance to remediation mechanisms, process performance, environmental constraints, technological limitations, and field-scale applicability. The review distinguishes the major biological mechanisms involved in metal remediation, including biosorption, bioaccumulation, biotransformation, phytoremediation, and biomineralization, and critically evaluates their advantages and limitations. Attention is given to carbonate-associated metal immobilization by MICP and to its application to cadmium remediation, while comparative evidence for other metals is also considered. Although high removal efficiencies have been reported for MICP under controlled laboratory conditions, their direct extrapolation to complex environmental matrices remains constrained by metal speciation, pH, salinity, microbial activity, reagent requirements, ammonium generation, and long-term mineral stability. Comparison with biosorption, sulfate-reducing microbial systems, phytoremediation, and physicochemical approaches indicates that remediation performance should not be evaluated on removal efficiency alone, but also in terms of treatment time, matrix complexity, resource requirements, secondary residues, recovery potential, and long-term contaminant stability.