Microbial corrosion and mitigation of ductile iron pipes in drinking water distribution systems under alternating anoxic–aerobic conditions: Dynamic corrosion roles of functional bacteria

Microbiologically influenced corrosion (MIC) threatens the safety and durability of drinking water distribution systems (DWDS), while the effects of fluctuating redox conditions on microbial corrosion evolution remain unclear. In this study, an alternating anoxic–aerobic system was established to investigate the corrosion behaviors of Bacillus cereus (iron-reducing bacteria) and Acidovorax defluvii (iron-oxidizing bacteria) on ductile iron surfaces. The results demonstrated that B. cereus continuously promoted corrosion through an “anoxic Fe(III) reduction–aerobic Fenton reaction” cycle, maintaining biofilm stability through EPS production and antioxidant defense. Conversely, A. defluvii exhibited an initial corrosion-promoting effect followed by late-stage corrosion inhibition. During aerobic shifts, microbially generated O 2 •- was dismutated into H 2 O 2 via SOD, driving H 2 O 2 accumulation; however, biologically catalyzed Fe(II) oxidation concurrently regulated H 2 O 2 availability, limiting further •OH generation as Fe(II) was depleted. Coupled with lipid peroxidation and subsequent formation of protective α-FeOOH/Fe 3 O 4 mineral layers, interfacial resistance was enhanced to suppress corrosion. Overall, this study reveals that microbial corrosion roles are dynamically regulated by the coupling of microbial metabolism, oxidative stress responses, and mineral phase transformation under fluctuating redox conditions.