Download Aim: To use a graphite electrode as the final electron acceptor for

Decreasing concrete corrosion through mitigation of
hydrogen sulfide during organic waste transport in
concrete pipes
Elizabeth R Mathews1, Dean Barnett2 & Ashley E Franks1
1 Department
of Physiology, Anatomy & Microbiology, La Trobe University, Bundoora, Victoria
2 Western Water, Sunbury, Victoria
Email: [email protected]
Aim: To use a graphite electrode as the final electron acceptor for microbial communities
to prevent sulfur-driven biogenic sewer corrosion.
Sulfur-driven biogenic sewer corrosion
Concrete corrosion is a major
destructive problem of sewer
infrastructure worldwide, costing
billions in damages every year1,2.
Sulfur cycling within the pipe leads
to sulfuric acid attack. As corrosion
progresses the concrete cracks,
which leads to increased surface
area and further attack from sulfuric
acid1. This results in smooth
concrete becoming pitted and losing
concrete mass (Figure 1).
A
Removing sulfide from wastewater
Providing a simple graphite
electrode (anode) to the microbial
community
facilitates
the
spontaneous abiotic oxidation of
sulfides (S2-) to elemental sulfur
(S0)3. This is further oxidised
microbially at the anode to sulfate
(SO42-). This process effectively
removes S2- from wastewater
reducing the formation of H2S gas
and H2SO4 (Figure 2)3.
B
Figure 1 – A) Smooth concrete (left) and pitted
corroded concrete (right) B) Microbial sulfur
cycling: Hydrogen sulfide (H2S) gas is formed
following reduction of sulfates (SO42-), by sulfatereducing bacteria (SRB). The H2S is oxidised to
sulfuric acid (H2SO4) by sulfur-oxidising bacteria
(SOB) resulting in concrete corrosion.
Figure 2 – Organic matter is fermented to acetate,
lactate and other fermentation products. The products
fuel the reduction by sulfate-reducing bacteria (SRB) of
sulfates (SO42-) to sulfides (S2-). These are abiotically
oxidised to elemental sulfur (S0) and then further
oxidised by sulfur-oxidising bacteria (SOB) back to SO42-.3
Investigating microbial diversity and using biofilm dynamics using ARISA
and FISH in sewer communities
Figure 3 - NMDS ordination of the bacterial communities
compared by stream type. Industrial stream, Residential stream,
Mg-dosed stream and Biochemically-dosed stream. Ordinations
use the Bray-Curtis coefficient applied to a species by stream
matrix.
Automated ribosomal intergenic spacer analysis
(ARISA) of the sewer communities produces a
community fingerprint, analysed using nonmetric multidimensional scaling (NMDS) and
visualised as an ordination. The ordination shows
the industrial communities clustering away from
the residential and chemical-dosed communities,
indicating a different bacterial community
composition (Figure 3).
Fluorescent in situ hybridisation (FISH) reveals
the morphology of an industrial sewer
community, which form bacterial aggregates with
Geobacter spp. located towards the aggregate
centre (Figure 4).
Figure 4 – FISH uses oligonucleotide probes which bind to specific bacteria revealing the
structure of the biofilm from an industrial sewer stream. DIC – Differential interference
contrast, DAPI – stains for DNA (blue), DL-1 – Geobacter sulfurreducens probe (red), Eub –
Eubacteria (all bacteria) probe. Merge all images overlayed. Magnification 100x.
Future industrial and agricultural applications for electrode technology
in shaping microbial communities
Electrode technology is not limited to mitigation of corrosion. Given favourable redox
conditions, electrodes can be used to manipulate the composition and structure of
natural microbial communities in situ. This technology can be utilised in many areas
including:
• Microbiologically influenced corrosion – Steel and concrete corrosion also affects
agriculture particularly dairy effluent in milking sheds and farm buildings4
• Bioremediation and industrial rehabilitation – Particularly in chemical refineries
and mining applications5
• Agriculture – The improvement of soil fertility for increased crop growth and
productivity
References
1.
2.
Jiang, G., Wightman, E., Donose, B. C., Yuan, Z., Bond, P. L. & Keller, J. (2014). The role 3.
of iron in sulfide induced corrosion of sewer concrete. Water Res 49, 166-174.
Wells, T., Melchers, R. E. & Bond, P. (2009). Factors involved in the long term corrosion
of concrete sewers. Australasian corrosion association proceedings of corrosion and 4.
prevention, Coffs Harbour, Australia 11.
Wardman, C., Nevin, K. P. & Lovley, D. R. (2014). Real-time monitoring of
subsurface microbial metabolism with graphite electrodes. Front
Microbiol 5, 1-7.
Babu, B. R., Maruthamuthu, S., Rajasekar, A., Muthukumar, N., &
Palaniswamy, N. (2006). Microbiologically influenced corrosion in dairy
effluent. Int J Environ Sci Tech 3, 159-166.
5.
Anderson, R. T., Vrionis, H. A., Ortiz-Bernad, I. & other authors (2003).
Stimulating the in situ activity of Geobacter species to remove uranium
from the groundwater of a uranium-contaminated aquifer. Appl Environ
Microb 69, 5884-5891.
Acknowledgments
This work is partly funded by Western Water.