Manganese Pollution and Its Remediation: A Review of Biological Removal and Promising Combination Strategies

Abstract

Manganese (Mn), as a cofactor of multiple enzymes, exhibits great significance to the human body, plants and animals. It is also a critical raw material and alloying element. However, extensive employment for industrial purposes leads to its excessive emission into the environment and turns into a significant threat to the ecosystem and public health. This review firstly introduces the essentiality, toxicity and regulation of Mn. Several traditional physicochemical methods and their problems are briefly discussed as well. Biological remediation, especially microorganism-mediated strategies, is a potential alternative for remediating Mn-polluted environments in a cost-efficient and eco-friendly manner. Among them, microbially induced carbonate precipitation (MICP), biosorption, bioaccumulation, bio-oxidation are discussed in detail, including their mechanisms, pivotal influencing factors along with strengths and limitations. In order to promote bioremediation efficiency, the combination of different techniques is preferable, and their research progress is also summarized. Finally, we propose the future directions of Mn bioremediation by microbes. Conclusively, this review provides a scientific basis for the microbial remediation performance for Mn pollution and guides the development of a comprehensive competent strategy towards practical Mn remediation.

Keywords: bio-oxidation; bioaccumulation; biosorption; heavy metal; manganese-oxidizing bacteria; microbially induced carbonate precipitation (MICP); removing manganese.

Figure 1

Sources, transfer processes and toxicity of Mn in the biogeochemical cycles.

Figure 2

Illustration of four main biological treatments for Mn removal (where three−dimensional structures of a kind of MCOs and urease are presented). Reprinted with permission from Refs. [140,141].

Figure 3

Mechanisms of synergies between Acinetobacter sp. AL-6 and pomelo peel biochar in a hybrid process. Reprinted with permission from Ref. [158].