Microbial enhanced corrosion of hydraulic concrete structures under hydrodynamic conditions: Microbial community composition and functional prediction

Abstract

Microbial corrosion has long been a threat to engineered structures, but the effects of microbial action on hydraulic concrete structures (HCSs), particularly those in freshwater environments, have not been systematically investigated. In this study, the composition and succession of bacterial communities in biofilms attached to HCSs and the mass loss of concrete were analyzed in a simulated hydrodynamic reactor. After a 335-day experiment, the mass losses of aseptic concrete in flowing and static water were 3.55% and 2.96%, respectively. Biofilms clearly formed on concrete cultured in representative freshwater, and the mass losses of biofilm-attached concrete placed in flowing and static water were 4.65% and 4.04%, respectively, at the end of the experiment. These results indicate that microbial action was actively involved in the corrosion process, contributing 32.3–36.6% of the total mass loss. Obvious differences were found in the microbial community distribution under flowing and static water conditions, in which temperature and surface pH were the main factors. The formation of a relatively stable community structure of attached biofilms was observed in flowing water since day 165, whereas the community structure plateaued and was prolonged to 225 days for concrete cultivated in static water. A functional prediction analysis revealed that functional bacteria related to nitrogen and sulfur metabolism accounted for 70% of all functionally metabolizing bacteria cultivated under both conditions. The abundances of sulfate reducers and nitrite reducers decreased remarkably with the succession of microbial communities in flowing and static water, while the percentages of sulfur oxidizers and sulfide oxidizers increased gradually. Our results provide future hypotheses for more quantitative studies focusing on special groups and functional genes in HCSs and contribute to optimizing microbial control in water conservancy projects for freshwater environments.