Rapid deterioration of concrete sewer pipes due to microbial activities has a major
impact on environmental health and safety, particularly in countries with warm climates, such
as the USA and Mexico. This is a process termed “Microbial Induced Concrete Corrosion”
(MICC).
An experimental system was set-up to demonstrate the mechanism of MICC by
measuring pH, sulfate formation, and loss of material in an accelerated setting and to later
investigate conditions that are similar to those commonly found in sewer collection systems.
In a system with the continuous water circulation and sulfur oxidizing microorganisms
(SOM) + Acidiphilium cryptum inoculation, significant pH drop (10 to 3), mass loss of 0.39%,
sulfate formation, and calcium release were observed within 100 days. A continuous hydrogen
sulfide concentration in the system keeps the MICC process going. It seems the corrosion is
initiated by neutrophilic sulfur oxidizing microorganisms (NSOM). Based on these results, the
mechanisms for the MICC can be explained by hypothesizing that the growth of NSOM
provides favorable conditions for the subsequent acidophilic sulfur oxidizing microorganisms
(ASOM) growth in a new concrete sewer pipe.