Iron and Manganese Oxidizing Bacteria in Water: Challenges and Management

Iron and manganese in water can present significant challenges for water treatment systems and infrastructure, leading to the proliferation of bacteria which can cause substantial issues. Understanding the microbiology and the chemical cycles of iron and manganese is crucial for managing and mitigating these problems.

Manganese Cycle

The Manganese Cycle involves the interconversion between Mn2 and Mn4 , a process that occurs in various aquatic environments, such as hydrothermal vents and bogs. This cycle plays a vital role in the ecosystem and is influenced by different bacterial species.

Leptothrix, Arthrobacter, and Pedomicrobium play a role in oxidizing Mn2 to Mn4 . However, Shewanella and other chemoorganotrophic bacteria like Geobacter reduce Mn4 back to Mn2 . The reduction and oxidation processes are critical for maintaining the manganese cycle in aquatic ecosystems.

Iron Cycle

The Iron Cycle involves the interconversion between Fe2 and Fe3 . Iron oxidation, or rusting, occurs at neutral pH levels by bacteria such as Gallionella species. In acidic conditions, Thiobacillus ferrooxidans and Sulfolobus carry out iron oxidation. Additionally, Sphaerotilus and Leptothrix also oxidize Fe2 to Fe3 .

Iron reduction, which converts Fe3 back to Fe2 , occurs under anaerobic conditions. Various bacteria, such as Geobacter metallireducens, Geobacter sulfurreducens, Ferribacterium limneticum, Shewanella putrefaciens, Pelobacter carbinolicus, Geovibrio ferrireducens, and Desulfuromonas acetoxidans, are involved in these processes and utilize ferric ions as electron acceptors.

Impact of Bacteria in Water Systems

The presence of iron and manganese in water can promote the growth of various bacteria, leading to the formation of thick slimes on the walls of pipes and other water systems. These bacteria obtain energy from the chemical reactions that occur when iron and manganese react with dissolved oxygen. The resulting slime is dark in color, with rusty iron leading to rust and black manganese causing the black coloration.

Examples of Iron Oxidizing Bacteria

Examples of Manganese Oxidizing Bacteria

Managing Bacterial Growth in Water Systems

To manage the growth of these bacteria, several strategies can be employed, including the use of biocides, pH adjustment, and the installation of proper disinfection systems. Regular maintenance and monitoring of water systems are also crucial to prevent the accumulation of bacteria and the formation of slimes which can cause blockages and corrosion.

Understanding the microbiology and the chemical cycles of iron and manganese helps in developing effective management strategies. By controlling the levels of iron and manganese in water, it is possible to minimize the growth of problem-causing bacteria and maintain healthy, efficient water systems.

Conclusion

The microorganisms responsible for the oxidation of iron and manganese in water present significant challenges for water treatment facilities. Knowledge of the bacterial cycles and their specific environmental requirements is essential for developing effective management strategies. Regular monitoring, proper maintenance, and the use of biocides and disinfection systems can help mitigate the adverse effects of these bacteria on water systems.