The completion of the Sewer District Wastewater Plant and Collection System in October 2022 capped off a decade-long effort to improve the quality of wastewater treatment in Cape Girardeau County, Missouri, USA.
The Penetron Group (East Setauket, New York, USA), a leading manufacturer of specialty construction products for concrete waterproofing and repairs, developed an antimicrobial concrete admixture that provides permanent protection for the lift station’s wet well structures from microbially induced corrosion (MIC), which can rapidly compromise and disable concrete structures.
The Cape Girardeau County sewage collection project in southeastern Missouri has been under development by the Cape Girardeau County Sewer District and Strickland Engineering for almost 10 years. The $19.3-million project has now consolidated several smaller sewer systems and a series of septic tanks into a centralized sewage collection and treatment system located in Fruitland, Missouri, USA.
As of October 2022, the system is fully operational with all connections completed. Construction of the new wastewater collection and treatment system includes:
- 30 miles (48.3 km) of gravity sewer lines
- 13 miles (21 km) of sanitary force main sewer lines
- 16 lift stations
- Sequencing batch reactor with 0.425 million gallons per day capacity
- 502 concrete manholes
Stopping MIC
Christopher Chen, director of The Penetron Group, describes his company’s involvement in the project thusly: “The general contractor, Carstensen Contracting, needed a robust solution to prevent [MIC] in the concrete structures of the wet well structures of the new lift stations. We suggested Penetron’s antimicrobial concrete admixture as a solution to the problem.”
MIC is a widespread problem that causes billions of dollars in damage to wastewater- and sewage-related concrete structures every year. These underground concrete sewage systems can deteriorate rapidly when exposed to thiobacillus bacteria that convert hydrogen sulfide gas (H2S) found in raw sewage into biogenic sulfuric acid (H2S04) that eats away at the cement paste of the concrete matrix.
This can potentially expose the embedded steel reinforcement to corrosion when exposed t water, oxygen, chlorides, and possibly carbon dioxide (CO2).
“Such a process can rapidly lead to the severe concrete deterioration known as MIC, which is often the cause of catastrophic corrosion failures in concrete structures,” adds Chen.
One Application for Permanent Protection
Penetron’s antimicrobial admixture prevents MIC by using an electro-physical mechanism to destroy the cell walls of the acid-producing bacteria. Eliminating the bacterial growth on and in concrete stops the formulation of H2S04, thus preventing damage caused by MIC.
Penetron worked with concrete supplier SEMO Ready-Mix to add its antimicrobial admixture to the concrete mix during batching. The antimicrobial admixture is permanent—it forms part of the concrete matrix and is leach resistant. Repeated contact with the bacteria does not lessen the effectiveness of the admixture.
“Thanks to ease of use and attractive cost, Penetron’s antimicrobial admixture provided the long-term protection from MIC that the general contractor needed,” says Chen. “Our new admixture will ensure the needed durability to the concrete and minimize the need for future repairs of the treated wet wall concrete structures.”
Source: Penetron, www.penetron.com.