Mitigation of Microbially Influenced Corrosion of Concrete Sewers Using Nitrite
Biotechnological Innovations for Environmental Bioremediation
Sewer systems are essential compartments of urban life, preventing human exposure to unhygienic sewage and sewage-borne diseases. However, microbially influenced concrete corrosion (MICC) occurs in sewers globally and ultimately leads to severe structural deterioration and early failure of those concrete structures. The MICC in sewers is mainly caused by hydrogen sulfide (H2S) that occurs in the headspace gas. In sewers, H2S is produced due to the metabolism of sulfate-reducing bacteria (SRB) under anaerobic conditions in parts of sewers and is subsequently released into headspace sewer gas in the gravity sections of the sewer system. In gravity sewers, H2S in the headspace gas is further oxidized into sulfuric acid by sulfide-oxidizing microorganisms (SOMs) on concrete surfaces, leading to concrete corrosion. The remediation and replacement of corroding concrete sewers could cost billions of dollars annually, which becomes a huge financial burden worldwide. In recent years, advanced understanding of inhibitory and biocidal effects of nitrite or free nitrous acid (HNO2, FNA), the protonated form of nitrite, on microorganisms, has led to the development of a series of nitrite-based applications in the bioremediation of sewer corrosion. These applications target at (1) reducing H2S production in anaerobic sewers, (2) mitigating the corrosion development of existing corroding sewers, and (3) implementing new concrete with nitrite admixture for long-term corrosion control with minimum maintenance. This chapter provides a comprehensive summary of the current status of nitrite-based applications in the remediation and control of concrete sewer corrosion.
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