A few years ago, I purchased a red car. I didn't really notcie how many red cars were on the road until after I owned one. Now I seem to find them everywhere. There must be a red car epidemic in our society. When I hear people talk about the issue of this biogenic corrosion caused by the Thiobacillus bacteria, I wonder if the same thing isn't occuring. A septic tank has the signs of corrosive activity in one locality, and it heightens our awareness. We now become more sensitized to installations where this might be occuring and think it must be an epedimic.
While I do not want to minimize the impact that Microbial Induced Corrosion has, both financial and environmental, in our society, I want to point out that in a decade and a half of research on this topic, the number of actual cases is small compared to the number of precast systems installed and funtioning for many, many years. The cases of MIC, as uncovered in the current research, tend to be concentrated in specific regions. The area affected is possibly only 1% -2% of the land in the United States. This may be true in other parts of the world as well.
The research has pinpointed several characteristics that seem to be common at sites where septic tanks are known to be corroding. The factors include, high amounts of sulfur in the water, extremely hard water, the presence of gas or oil wells in the area, iron content, venting, lack of venting, and chemicals in the waste stream. The conditions that are necessary for the microbial induced concrete to occur are also difficult to replicate. This make the process of designing resistent materials very difficult.
As this topic becomes more widely known, it will improve the information that is available for research. The data from a larger population will lead to more information about the sites which will eventually isolate a common set of characteristics that are always present when concrete corrosion due to MIC is found.
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