Could solving for MIC in wastewater plants come down to type of cement used?
July 8, 2020 •Corrosion CONTROLLED, Corrosion Essentials, MIC
![](https://5764240.fs1.hubspotusercontent-na1.net/hub/5764240/hubfs/Microbiologically%20influenced%20corrosion%20%28MIC%29%20can%20cause%20significant%20damage%20to%20concrete%20wastewater%20assets.%20Photo%20courtesy%20of%20TU%20Graz..png?height=630&name=Microbiologically%20influenced%20corrosion%20%28MIC%29%20can%20cause%20significant%20damage%20to%20concrete%20wastewater%20assets.%20Photo%20courtesy%20of%20TU%20Graz..png)
According to researchers from the Graz University of Technology (TU Graz) (Graz, Austria), geopolymer-based concrete (GPC) offers superior resistance to acids, abrasions, and are less permeable than OPC-based (Ordinary Portland Cement) materials, which are formed via cement hydration reactions. These calcium-rich hydration products are generally acid dissolvable, the researchers explain, thus making OPC prone to corrosion from microbial-induced acid attack. They say their research shows that concrete made from geopolymers can have a greater lifespan than conventional concretes, thus extending the service life of wastewater assets.
Microbiologically influenced corrosion (MIC) often corrodes the conventional types of concrete used in wastewater treatment plants at a rate of 1 cm or more per year,” says a professor at TU Graz’s Institute of Applied Geosciences. “Accordingly, the concrete elements can be destroyed in a matter of only a few years, causing significant damage to wastewater systems. Closing the manhole covers and looking the other way is not the answer.”
Acid attack process in OPC
With OPC, microbial-induced acid corrosion in wastewater treatment facilities usually results from a sequence of biogenic sulfate reduction reactions, followed by reoxidation. Initially, the researchers explain, sulfate in pressurized pipelines or standing water is reduced by bacteria under oxygen-free conditions, thus forming hydrogen sulfide (H2S).
From there, the H2S gas escapes into the sewer air and diffuses into sewer pipes and manholes. Autotrophic bacteria on the walls of the concrete then oxidize the H2S into sulfuric acid (H2SO4), which reacts with the concrete’s construction elements.
“This leads to the vigorous formation of a biofilm on the surface of the concrete, a reduction of the pH value to below two,” says a research team leader and professor at Tu Graz’s Institute of Molecular Biosciences. “In other words, [it is] highly acidic, and [leads to] extensive formation of new minerals, mainly in the form of gypsum. The combination of these processes results in the rapid destruction of the concrete.”
Advantages of geopolymer technology
In contrast to OPC, which is formed through hydration reactions, GPC is produced through the polycondensation of aluminosilicates. In this ion-exchange reaction process, materials like blast furnace slag, fly ash, or metakaolin are mixed with alkaline reagent solutions such as sodium- or potassium-soluble silicates to form a hardened, concrete-like texture. These geopolymer materials also offer a lower carbon footprint, potentially making them a “greener” alternative.
According to the researchers, the framework vacancies formed by the dissolution of aluminum are mostly reoccupied by the silicates. This results in an amorphous, highly siliceous framework that is relatively hard but brittle. This undissolved corroded layer can effectively inhibit the process of further corrosion by acting as a barrier to the transport of acid protons.
“Thus, compared to the neutralization capacity achieved by dissolution of hydration products, the permeability of the acidified [geopolymer] layers governs the rate of further ingress of acids,” the researchers write. In essence, they continue, the microorganisms that trigger the initial oxidation process in OPC corrosion cases and the formation of H2SO4 are unable to settle on the surface.
The alkali-activated specimens produce a layer of aluminosilicate gel, which studies have shown remains in place even after decalcification and offers chemical stability even at a low pH, they explain. X-ray diffraction (XRD), electron microscopy, and mechanical tests have been conducted on the acid resistance of a metakaolin material exposed to 0.01 M of hydrochloric acid (HCl) for 28 days, finding that the network structure remained practically intact while still showing excellent binding properties.
TU Graz believes the addition of antimicrobial cation additives could further help in reducing bacterial colonization, though it acknowledges more research is needed.
Further MIC testing needed
Going forward, the researchers say more thermodynamic data are needed on the performance of geopolymer concretes in the field before commercial advances can be made on the technology. Nonetheless, even considering the relative uncertainty with the GPC process, the researchers believe the vulnerability of traditional concrete to MIC makes further research a priority.
“While the overall process mechanisms and environmental parameters responsible for MIC are fairly well understood, to date, no commercially available concrete can satisfactorily withstand the adverse conditions in such aggressive environments over its projected operating life,” they write. “Accordingly, further research should focus on how to constrain concrete-microorganism interactions.”
Source: Originally appeared on materialsperformance.com
FREE DOWNLOADS
White Paper: An Action Plan for Reducing Pipeline Failures, Costs with Corrosion in the Water Sector
Special Report: The Future of Corrosion Control, Insights from the Experts
Get Updates
Featured Articles
Categories
- 2024 olympics (1)
- abrasive blasting (1)
- advanced coating materials (9)
- Advanced Corrosion Control in Oil and Gas Industry (2)
- advocacy (1)
- ai (2)
- aircraft (1)
- alkanization (1)
- AMPP (2)
- AMPP Annual Conference + Expo (1)
- ampp chapters (1)
- AMPP logo (1)
- amusement parks (3)
- Architectural (1)
- architectural coatings (1)
- artificial intelligence (1)
- asset integrity (9)
- Asset Protection (1)
- biodeterioration of materials (5)
- biofouling (4)
- blasting (1)
- bridges (3)
- cathodic protection-CP (14)
- ceramic epoxies (1)
- certification (1)
- Chemical Injection (1)
- coatings (11)
- coatings application (1)
- Coatings failures (1)
- coatings industry (1)
- coatings measurement and inspection (9)
- coatings systems (1)
- concrete (11)
- conference and events (2)
- corrosion (8)
- corrosion basics (5)
- corrosion control (11)
- corrosion control and management (22)
- corrosion essentials (19)
- crevice corrosion (1)
- Data Monitoring (1)
- Department of Defense (3)
- deposition corrosion (1)
- dissolved gases (1)
- DoD (3)
- education (1)
- energy industry (9)
- epoxy (2)
- fireproofing (1)
- flexible coatings (2)
- Flint, Michigan (1)
- fluoropolymer coating (3)
- forms of corrosion (3)
- freshwater salinization (1)
- galvanic corrosion (2)
- general corrosion (2)
- hand tools (1)
- industrial application (3)
- intergranular corrosion (1)
- Intumescent Coatings (1)
- machine learning (1)
- Maintenance (1)
- maritime coatings (11)
- maritime industry (11)
- Master Painters Institute (1)
- membership (1)
- membership benefits (1)
- michio kaku (1)
- microbiological forms (1)
- microbiologically influenced corrosion-MIC (11)
- military (2)
- Mineral constituents (1)
- mpi (1)
- navy (1)
- non-destructive testing (1)
- Oil Fields (1)
- organic matter (1)
- oxgen (1)
- paint and protective coatings (31)
- Paint specification (1)
- personal protective equipment (2)
- Petrochemical Plant Fireproofing Methods (1)
- Petrochemical Plants (1)
- pitting corrosion (2)
- pitting detection (1)
- power plant (1)
- power tools (1)
- ppe (2)
- Protective Coatings (2)
- Real-Time Corrosion Monitoring in Oil Fields (1)
- reliability (1)
- remote monitoring and drones (4)
- repaint (1)
- restoration (1)
- Road deicers (1)
- roads and bridges (1)
- roller coaster (1)
- rust (1)
- safety (3)
- salt pollution (1)
- sensors (1)
- ship coatings (9)
- shiptanks (1)
- standards (7)
- steel (7)
- stress corrosion cracking (1)
- Structural Steel (1)
- surface preparation (12)
- sustainability and corrosion (7)
- tools (1)
- turbine (1)
- uniform corrosion (1)
- Water crisis (1)
- Water pipe corrosion (1)
- water quality (1)
- water tank coatings (5)
- water/treatment infrastructure (19)
- Waterway salinity (1)
- workforce development (1)