Investigation of Microbiologically Influenced Corrosion of Concrete in Sanitary Sewer Pipes and Manholes: Field Surveys and Laboratory Assessment

Abstract

Microbiologically influenced corrosion (MIC) of concrete in sanitary sewer pipe and manholes is the result of dilute sulfuric acid (H2SO4) dissolving the cement matrix. The acid is produced by a complex series of chemical and biochemical reactions. The objectives of this paper are: (1) to review the basic science of the MIC process starting with the various biological processes leading to the production of dilute sulfuric acid; (2) to discuss historical attempts to fortify concrete; (3) to present methods to reduce odors and corrosion; (4) to evaluate the technology behind the use of antimicrobial admixture. The literature review and authors’ on-site and laboratory investigations suggest that MIC of concrete is a complex process that involves varied surface interactions. The addition of liquid antimicrobial additive as per ASTM standard procedure shows the resistance of concrete to MIC and its direct relation with the mixing time of admixture. Many empirical inputs like corrosion areas, corrosion rates, the impact of cement, and aggregate types varying with installation and repair of sewer structures are identified. The results of this study show that with the use of antimicrobial in the concrete, there was no growth of Thiobacillus bacteria and hence no acid production. This research facilitates both the science and long-term field experiences for the use of antimicrobial technology to provide reductions in the acid causing bacteria in sanitary manholes, pump stations and other concrete structures.