That Unpleasant Odor May Not Be Hydrogen Sulfide
To the Editor:

This is in reference to your article "Board Continues To Tackle Sewer Dilemma," which appeared in your May 15 issue, in which some problems are attributed to hydrogen sulfide, characterized as "corrosive sewer gas."Evidently this issue is behind a lawsuit with a New York insurance company having to do with corrosion damage of sewer components.

Contrary to your article, the unpleasant odor around the pumping stations is not, in fact, hydrogen sulfide, although this is a somewhat common misconception when talking about human waste, because the odor does vaguely resemble hydrogen sulfide. I notice that some Internet sites even make the same mistake.

The so-called sewer gas is actually 3-methyl indole, also known as skatole. This is an aromatic amine with the molecular formula C9H9N. It is created by the digestion of protein by mammals. As can be seen, it does not contain any sulfur. It also is not particularly corrosive.

On the other hand, hydrogen sulfide is corrosive and extremely toxic, having a toxicity on the order of that of hydrogen cyanide. A concentration of only 800 parts per million of hydrogen sulfide causes instant death.

If the odor actually was due to hydrogen sulfide, corrosion would be the least of our problems.

So, looking at the issue logically, rather than only scientifically, if human waste contained a significant amount of hydrogen sulfide, then we would kill ourselves whenever we went to the bathroom.

Bruce F. Caswell

Dearborn

Editor's note: Brevort Township Supervisor Edward Serwach provided the following response to Mr. Caswell's letter:

The issue has nothing to do with a lawsuit with the New York bonding agency. That lawsuit is related to the company that walked away from the sewer project and left unfinished work.

Highly knowledgeable Michigan Department of Environmental Quality (DEQ) inspectors have been on site to test, and they have diagnosed the odor as H2S (hydrogen sulfide) gas.

It is our understanding that the gas is a result of the breakdown of waste within the sewer lines; the gas builds up when there is insufficient movement of the material in the lines. This is treated by flushing the lines as part of system maintenance.

The hydrogen sulfide odor has been present since the installation of the system. The original odor was at the lift station, where metal equipment components became extremely corroded by the hydrogen sulfide in a short period of time. The township created an underground bypass at the lift station to completely enclose the process and contain the gas.

This spring, H2S corrosion was in the manhole at the lagoon, which is a sequestered location that is not open to the public.

The DEQ has advised all people working with the H2S gas that concentration of the gas can be lethal and therefore trained personnel must follow all regulations and be cautious when entering the manhole.

The DEQ continues to monitor the situation.