Abstract
Microbially Induced Corrosion of Concrete (MICC) is a progressive three-stage deterioration process that is primarily associated with sulfur-oxidizing bacteria (SOB). One strategy for mitigating MICC is the use of antimicrobial additives. It is hypothesized that the performance of antimicrobial products is influenced by the pH of the environment, the bacterial population, and the level of bacterial activity. To test this hypothesis, three bacterial activity-population levels were tested in environments with different pH levels to evaluate the efficacy of a typical antimicrobial product against planktonic SOB. The ability of the antimicrobial product to prevent or delay the biogenic acidification was considered as the criterion for its efficacy. The tested antimicrobial product was successful in delaying or preventing MICC with low and moderate bacterial populations and activity for all pH levels greater than 4. Lower pH levels were not tested in this investigation. Antimicrobial products were successful in delaying or preventing MICC with severe bacterial populations and activity for all pH levels tested greater than 6. The results support the main hypothesis of the research; therefore, the selection of whether to utilize an antimicrobial product requires an understanding of the operational pH of the environment as well as knowledge on the target bacterial population and activity.
Highlights
The service life of concrete wastewater infrastructure such as sewer pipelines, manholes, wastewater digesters and septic tanks could be reduced significantly by microbially induced corrosion of concrete (MICC)
The primary objective of the study is to perform a fundamental investigation to determine limitations associated with the use of antimicrobial additives against planktonic sulfur oxidizing bacteria (SOB) leading to biogenic acidification in bacterial suspensions where the pH and bacterial population and bacterial activity are varied
It should be noted that that neutrophilic sulfur oxidizing bacteria (NSOB) are the dominant bacteria in the Stage II of MICC, which is the initiation of bacterial succession stage
Summary
The service life of concrete wastewater infrastructure such as sewer pipelines, manholes, wastewater digesters and septic tanks could be reduced significantly by microbially induced corrosion of concrete (MICC). MICC is a progressive deterioration process that is primarily associated with sulfur oxidizing bacteria (SOB) [1,2,3]. The process begins with the production of hydrogen sulfide (H2S) under anaerobic conditions by reduction of sulfate ions (SO4‐2) present in the wastewater by anaerobic sulfate reducing bacteria (SRB) residing below the waterline [4]. Hydrogen sulfide on concrete could either remain as it is or could be converted chemically to elemental sulfur, sulfite, and thiosulfate depending on the environmental chemical conditions. In the last cycle of the biological process, SOB consume the sulfur compounds as their nutrient source and oxidize them to sulfuric acid, which is the final product of the biogenic cycle [9]. The final products associated with the deterioration processes are expansive gypsum and ettringite [10,11,12]
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