Two key microbial community functions, sulfate reduction and oxidation, contribute to concrete corrosion of sewer infrastructure. Sulfates in the sewer stream are utilised as electron acceptors by sulfate-reducing bacteria (SRB) producing to hydrogen sulfide (H2S) and the oxidation of H2S to sulfuric acid by sulfur-oxidizing bacteria (SOB). Sulfuric acid is the cause of concrete corrosion in sewer infrastructure causing loss of concrete mass, pipe cracking and eventual collapse. If the sulfur-cycling occurring within these microbial communities can be disrupted, then the formation of sulfuric acid and consequently the corrosion of sewer infrastructure can be halted.
The aim of this project, in collaboration with Western Water, is to establish how the microbial ecology of a live sewer environment shifts over time both temporally and spatially in response to abiotic and environmental inputs. Chemical dosing with magnesium hydroxide, a commonly used treatment for sewer corrosion, was controlled on live streams and monitored in comparison to a high rain fall event. To examine the effects on bacterial community structure and function microbial community fingerprints were generated by automated ribosomal intergenic spacer analysis (ARISA) and H2S concentrations were monitored. Community responses were tracked both spatially and temporally within the sewer system at town level. Dosing with magnesium hydroxide was shown to shift the bacterial community composition and relative abundance at a H2S producing site to closely resemble the composition of a site without H2S problems. Next generation sequencing of the 16S rRNA gene was used identify community members responsible for the observed community shifts and was also utilised to provide predictive shifts in the function of these altered microbial communities.
Shifting the function of microbial communities away from sulfur-cycling has bioremediation applications beyond sewer corrosion including maritime corrosion, other forms of metallic corrosion and various industries.
Acknowledgements
This research is funded by a collaborative research grant from Western Water.