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Abstract
Culture-independent investigations of the bacterial diversity and activity in district heating systems with and without corrosion did not make it possible to relate one group of microorganisms with the observed corrosion. Fluorescence in situ hybridization by oligonucleotide probes revealed the dominance of β-proteobacteria, sulphate reducing prokaryotes and α-proteobacteria. Analysis of a clone library from one Danish heating (DH) system showed that the most sequences formed two clusters within the α-proteobacteria affiliated to the families Rhizobiaceae and Acetobacteraceae and two clusters within the β-proteobacteria belonging to the family Comamonadaceae. Functional groups were determined by microautoradiography showing aerobic and anaerobic bacteria (sulphate reducing and methanogenic bacteria). The corrosion study showed that pitting corrosion rates were five to ten times higher than the general corrosion rates, suggesting the presence of biocorrosion. The results indicate that several bacterial groups could be involved in corrosion of DH system piping including sulphate reducing prokaryotes, Acidovorax (within the β-proteobacteria), methanogenic bacteria and others.
Acknowledgements
The Danish Energy Authority (Programme EFP-2000) and several Danish District heating companies have supported this study. M. Fredsgaard and M. Stevenson are acknowledged for technical assistance and M. Shirtliff for aid in editing the English grammatical content.