Biocorrosion and biofilm formation in a nutrient limited heating system subjected to alternating microaerophilic conditions

Abstract

Severe biofilm formation and biocorrosion have been observed in heating systems even when the water quality complied with existing standards. The coupling between water chemistry, biofilm formation, species composition, and biocorrosion in a heating system was investigated by adding low concentrations of nutrients and oxygen under continuous and alternating dosing regimes. Molecular analysis of 16S rRNA gene fragments demonstrated that the amendments did not cause changes in the overall bacterial community composition. The combined alternating dosing of nutrients and oxygen caused increased rates of pitting (bio-) corrosion. Detection of bacteria involved in sulfide production and oxidation by retrieval of the functional dsrAB and apsA genes revealed the presence of Gram-positive sulfate- and sulfite-reducers and an unknown sulfur-oxidizer. Therefore, to control biocorrosion, sources of oxygen and nutrients must be limited, since the effect of the alternating operational conditions apparently is more important than the presence of potentially corrosive biofilm bacteria.

Keywords:

• biocorrosion
• biofilm
• heating systems
• sulfate reducing bacteria (SRB)
• functional genes dsrAB and apsA

Acknowledgments

The authors thank Susanne Bielidt and Merete Fredsgaard for technical assistance and patience in handling the CMUs connected to the heating system. The Danish Energy Authority (Program EFP-2000) and The Danish Research Council supported this study under the framework program ‘Activity and Diversity in Complex Microbial Systems’.