Microbial Induced Corrosionor

Microbially Influenced Corrosion

Presented by:

Steven J. Duranceau, Ph.D., P.E.

Professor

Director, Environmental Systems Engineering Institute

College of Engineering and Computer Science

Department of Civil and Environmental Engineering

UNIVERSITY OF CENTRAL FLORIDA

Orlando, Florida

Prepared for:

Water Bugs Lunchtime Learning

Wednesday, November 4, 2020

Webinar Series

There are Many Types of Corrosion!

Source: Mechasource.blogspot.com

Basic Iron CorrosionChemically a two-step process – a REDOX process

Source: Zumdahl. Chemistry 5th Ed., Houghton Mifflin Harcourt.

Corrosion is one of the most commonproblems affecting domestic waterSupplies.

Simplified Anode and Cathode ReactionsSource: USEPA Corrosion Manual 1984 (EPA 570.9-84-001)

Corrosion is a REDOX reaction, and one of the most commonproblems affecting domestic watersupplies.

Anodic – Cathodic ProcessesMediated by Microorganisms

Source: Chemistry by LibreTexts 2020.

Rust, the Result of Corrosion of Metallic Iron. Iron is oxidized to Fe2+(aq) at an anodic site on the surface of the iron, which is often an impurity or a lattice defect. Oxygen is reduced to water at a different site on the surface of the iron, which acts as the cathode. Electrons are transferred from the anode to the cathode through the electrically conductive metal. Water is a solvent for the Fe2+ that is produced initially and acts as a salt bridge. Rust (Fe2O3•xH2O) is formed by the subsequent oxidation of Fe2+ by atmospheric oxygen.

Anodic – Cathodic Processes (cont)Mediated by Microorganisms

Source: Chemistry by LibreTexts 2020.

Small Scratches in a Protective Paint Coating Can Lead to the Rapid Corrosion of Iron. Holes in a protective coating allow oxygen to be reduced at the surface with the greater exposure to air (the cathode), while metallic iron is oxidized to Fe2+(aq) at the less exposed site (the anode). Rust is formed when Fe2+(aq) diffuses to a location where it can react with atmospheric oxygen, which is often remote from the anode. The electrochemical interaction between cathodic and anodic sites can cause a large pit to form under a painted surface, eventually resulting in sudden failure with little visible warning that corrosion has occurred.

What is Microbially Induced Corrosion?

◼ Microorganisms, including bacteria,

fungi, archaea, and microalgae, can

influence corrosion directly or

indirectly, depending on

microorganism, material, electrolyte

specific reactions.

◼ There are thousands of studies that

have been done over the past 20-30

years with regards to MIC; however,

the primary focus has been

industrial, construction, oil & gas

and food manufacturing industries.

◼ Note. Drinking water systems are

not sterile, but they do contain

residual disinfectant!

B.J. Little, Microbially influenced corrosion: any progress? Corrosion Science. 170 (2020).

Grey Cast Iron Pipe CorrosionTubercles harbor microorganism, Fe, Pb, S, V, Mn

Source: McWane Ductile, Provo, UT.

◼ Many water systems still have

tuberculated cast iron pipe in service.

Typical tubercles consist of:

◆ Hard shell layer, black – magnetite

◆ Thin surface layer, tan – amorphous iron.

◆ Crust - geothite

◆ Soft core, orange-red -- dominantly goethite

◼ Microbial community protected by

outer layer:

◆ Typically dominated by Firmicutes,

Actinobacteria, and Proteobacteria.

◆ Iron reducing bacteria remain dominant for

pipes with stable tubercles.

◼ Today, cast iron has been replaced

with cement-lined ductile iron pipe

(typically).

Iron Corrosion by SRBPhylogenetric tree example

❖Phylogenetic tree constructed from full-

length 16S rRNA gene sequences of

cultivated sulfate-reducing bacteria

within Deltaproteobacteria.

❖The tree shows SRB isolates capable of

direct electron uptake and

hydrogenotrophic SRB that cannot

corrode iron directly unless in the

presence of suitable electron donors.

❖Tree does not include all cultivated SRB.

❖ I, Desulfobulbaceae;

❖ II, Desulfobacteraceae;

❖ III, Desulfovibrionaceae.

❖The scale bar represents a 10% difference

in sequence similarity.

❖MIC damage: 8 to 16 mpy!

Source: Enning & Garrelfs, Appl.Env.Micro. 80(4), 1226 (2014).

◼ A damaging, localized, non-uniform corrosion

◼ Pits or holes in the pipe surface can occur in water supplies that meet the regulatory action level for copper.

◼ Although the Pitting Resistance Equivalency Number can predict pitting, it is only valid for stainless steels. No such number exists for copper.

◼ Linear polarization resistance measurements allow the collection of qualitative data on Pitting Resistance.

Source: USEPA

Copper Pitting Corrosion

A word about MIC of Homeowner Copper Pipes

❖When MIC occurs, microorganisms cause a decrease of the pH at the copper-water interface,

increasing the dissolution of protective layer (Davidson et al., 1996).

❖Although the inner surfaces of copper pipes in rural houses (stagnant conditions with no

disinfectant residual) typically have porous deposits of malachite and cuprite, they also may

have extracellular polymeric substances, rod-shaped microorganisms, and pits. A bacterial strain

identified as Variovorax sp. was isolated in one study from bacterial biofilms.

❖In contrast, the copper pipes of urban houses where chlorine residuals were maintained (free or

combined) did not contain bacterial biofilms, the deposit of malachite and cuprite were

homogenous and showed uniform attack.

❖NOTE: Water purveyor and municipal/private water utilities are not responsible for the

integrity of homeowner and customer plumbing and fixtures other than that prescribed

under the lead and copper rule (LCR).

❖NOTE2: There are many causal factors of pitting corrosion! Soft water; microbiologically

induced corrosion of copper pipes in low-pH water with no disinfectant present; stray-

currents; lightening; workmanship.

❖NOTE3: The key legal case Brynwood vs. Clearwater in 1980’s relieved utility of

responsibility of pitting in condo units serves as the base case for utility defenses in

Florida.

Chromatic Elemental Image[Copper Pipe Scale]

Chromatic Elemental Image[Galvanized Iron Pipe Scale]

MIC can reduce service life of piping

Source: TNOL, Alberta, Canada

Corrosion of Concrete

◼ By itself, concrete is a very durable construction material. For example, the Pantheon in Rome, the world’s largest non-reinforced concrete dome, is in excellent condition after nearly 1,900 years!

◼ Surprisingly, many concrete structures from the last century –bridges, highways, buildings, basins –are crumbling. Why?

◼ The critical difference is the modern use of steel (iron) reinforcement (rebar) concealed within the concrete.

◼ AND iron’s most unalterable property is that it rusts!

Pantheon Dome (Rome – 126 A.D.)

Reinforced Concrete Structures (2020)

Microbial Corrosion of Sewers

◼ A diagram of a cross section of a sewer gravity concrete pipe summarizing the major processes that lead to acid formation in the aerobic biofilms and the onset of sewer corrosion.

◼ Microbial corrosion of concrete in sewers is known to be caused by hydrogen sulfide, although the role of wastewater in regulating the corrosion processes is poorly understood.

◼ The presence of other organisms, such as nitrifying bacteria, fungi and organic acids also contributes to the degradation of the concrete.

Source: Hvitved-Jacobsen (2013)

Hydrogen Sulfide and Microbials in Sewers

◼ Corrosion of concrete sewer is a complex process.

◼ A tale of two cities:

◆ In the anaerobic sections of the sewer, sulfate-reducing bacteria (SRB) will thrive in the sewer biofilms and sediments, generating hydrogen sulfide. (Desulfovibro)

◆ In the aerobic section of the sewer, sulfide-oxidizing bacteria (SOB) on the exposed surface of the concrete will thrive and produce sulfuric acid.(Acidiphilium; Mycobacterium )

◆ Eventually, if left unaddressed, the structural integrity of the concrete will weaken and collapse.

Note: Fungus also detected in sewers that complicates corrosion rates. (Cladosporium)

Manchester England Hyde Fall’s TunnelSource: Substorm,UK

Microbiological Testing Methods have Matured!We have come a long way since BART™ tests!

◼ Use of targeted microbial DNA testing has increased

our understanding of microbially-mediated corrosion.

◼ Field kits have been developed for several

applications

◆ Adenosine triphosphate

◆ Bacterial qPCR

◆ Archaea qPCR

◆ Sulfate reducing bacteria qPCR

◆ Iron-reducing bacteria qPCR

◆ Methanogens qPCR

◼ Technology has advanced where field qPCR devices

that rely on freeze-dried testing reagents are available,

developed originally for off-shore oil platforms.

◆ Luminultra Microbial Monitoring qPCR

◆ InstantLabs Hunter qPCR

◆ Battele DNA Detection SystemSource: Instalabs, Baltimore, MD.

Source: Luminultra, New Brunswick, Canada

Use of ATP methods increasing in water industry

◼ Adenosine Triphosphate (ATP) is the primary energy carrier for all forms

of life on Earth. Use of adenosine triphosphate (ATP) is a method that

directly assesses living cells from any type of microbe.

◼ The advantage of ATP testing over traditional culture tests are that the

results are obtained in mere minutes.

◼ ATP can be easily measured with high specificity via the firefly luciferase

assay. Luciferase is a naturally occurring enzyme that is most commonly

found in the tails of fireflies.

◼ ATP has application real-time data collection after line breaks, repairs,

flushing, and troubleshooting activities, as distribution operators are

typically required to confirm microbial water quality (compliance testing).

◼ Although a valuable assay as it can be performed easily in the field the

ATP-assay does not divulge which microbes are present. However, ATP

assay may hold added value as a method to acquire DNA for downstream

molecular analyses.

◼ We at UCF have recently completed a multi-year study using ATP

measurements as pre- and post- infrastructure change assessments within a

watershed and throughout a water system from source to tap.

Source: Hygiena, Canada.

◼ American Society for Testing and Materials Special Technical Publication STP 906, Baltimore, Maryland (1986).

◼ Bentur, A., Diamond, S., and Berke, N.S. Modern Concrete Technology 6 Steel Corrosion in Concrete: Fundamentals and Civil Engineering Practice E&FN Spon, an imprint of Chapman and Hall, London, United Kingdom (1997).

◼ Broomfield, J.P. Corrosion of Steel in Concrete: Understanding, Investigation and Repair. Taylor and Francis, New York (2006).

◼ Internal Corrosion of Water Distribution Systems, 2nd Edition No. 90508.

◼ Peabody’s Control of Pipeline Corrosion, 2nd Edition, No. 20487.

◼ External Corrosion-Introduction to Chemistry and Control (M27), 1st Edition No. 30027.

Disclaimer: The views and opinions of this presentation are those of the presenter and do not necessarily reflect the views of the University of Central Florida, its Board of Trustees, or the state of Florida’s Board of Governor’s. Mention of trade names or companies does not constitute endorsement.

Sources (in addition to those cited previously)