Iron-manganese inputs shape the coupling between deposit morphology and microbiome during the early-stage corrosion on cement mortar-lined pipe walls under drinking-water conditions.
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75% confidenceThe study investigates the impact of iron and manganese deposition on the morphology and microbiome of cement mortar-lined pipe walls in drinking water distribution systems. The results show that a specific dosing condition of 100 μg/L Fe with 10 μg/L Mn produces compact and adherent deposits with high charge-transfer resistance and low corrosion current density. This condition is attributed to the formation of cohesive biofilms dominated by certain bacterial species.
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Abstract
Maintaining water quality in drinking water distribution systems (DWDSs) requires resilient pipe-wall interfaces, yet the build-up of iron (Fe) and manganese (Mn), the most common metals in DWDSs, often initiates deposit growth and triggers discoloration events. However, the physicochemical impacts of early Fe-Mn deposition on pipe-wall surfaces have not been systematically elucidated. To elucidate their mechanistic role in the onset of scale development, self-designed electrodes were employed to monitor the electrochemical behavior of cement mortar-lined pipe surfaces under controlled Fe-Mn dosing (50-200 μg/L Fe with 10 μg/L Mn). Results showed that a dosing condition of 100 μg/L Fe with 10 μg/L Mn produced compact and adherent deposits with high charge-transfer resistance (R ct = 1.33 × 10 6 Ω) and low corrosion current density (i cor = 3.68 × 10 -5 mA/cm 2 ). This condition was attributed to cohesive biofilms dominated by Pseudomonas with co-dominant Hydrogenophaga and Sphingomonas, which, through assimilation-centered carbon and nitrogen pathways, secreted abundant extracellular polymeric substances, associated with minimized particulate metal accumulation in bulk water. In contrast, excessive Fe input (200 μg/L) generated scale-like, metal-oxide-bearing deposits accompanied by elevated Fe-Al contents, reduced R ct = 2.97 × 10 5 Ω, higher i cor = 1.70 × 10 -4 mA/cm 2 and metabolically diverse but weakly coordinated microbial communities. These results demonstrate that Fe-Mn-regulated morphology-microbiome coupling shapes early-stage corrosion behavior and that appropriate Fe-Mn levels are essential for promoting stable deposits and supporting long-term drinking-water safety.