Summary auto-generated
This 1983 study identified and characterized thiobacilli bacteria in the Hamburg sewer system, which were causing concrete corrosion. Researchers sampled six sites with varying degrees of concrete deterioration and found marked enrichment of thiobacilli on sewer walls above the sewage level, with the highest populations (10^8 cells per mg protein) at the most corroded site. Ten isolates were identified as four species: Thiobacillus thiooxidans, T. neapolitanus, T. intermedius, and T. novellus. The composition of bacterial communities varied with corrosion severity and pH. Facultative chemolithotrophic bacteria predominated in early corrosion stages at neutral pH, while T. thiooxidans dominated severely corroded areas with very low pH (1-2). When sewage was aerated with pure oxygen, T. thiooxidans populations decreased dramatically and the concrete surface pH rose from 2 to 6, suggesting that preventing anaerobic conditions could reduce corrosion. The findings indicate that microbial sulphuric acid production drives concrete degradation in the Hamburg system, with elemental sulphur as the primary energy source for these thiobacilli.
Key findings
- Four Thiobacillus species were identified in corroded Hamburg sewers: T. thiooxidans, T. neapolitanus, T. intermedius, and T. novellus, with different species predominating at different pH and corrosion levels
- Thiobacilli populations were highly enriched on concrete walls (up to 10^8 cells/mg protein) compared to sewage, indicating selective colonization of the corroded surface
- T. thiooxidans dominated severely corroded areas (pH 1-2), while facultative chemolithotrophic species predominated in minimally corroded areas (pH 6), suggesting a succession pattern during corrosion
- Aerating sewage with pure oxygen significantly reduced T. thiooxidans populations and raised concrete surface pH from 2 to 6, demonstrating that inhibiting anaerobic sulphide production prevents acid-producing bacterial growth
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Abstract
Summary: Thiobacilli were estimated in samples taken from the Hamburg sewer system at six sites showing different degrees of concrete corrosion. There was a marked enrichment of thiobacilli on the sewer pipe surface above the sewage level in comparison to the liquid phase. The highest number [108 thiobacilli (mg protein)-1] was found at the site of the greatest corrosion. Ten isolates of the genus Thiobacillus were characterized and identified as Thiobacillus neapolitanus, T. thiooxidans, T. intermedius and T. novellus. Facultative chemolithotrophic bacteria predominated at sites of early corrosion, whereas T. thiooxidans was most abundant in severely corroded areas. The cell number of T. thiooxidans could be greatly decreased by aerating the sewage with pure oxygen.