Issue Date: July 13, 2009
Solutions For 'Wallboard Woes'
I would like to submit an alternative hypothesis to the one suggested in the article regarding wallboard imported from China (C&EN, May 4, page 50). It appears there is "something stinky in Florida."
Instead of just looking at abiotic sources of sulfur-based molecules found in wallboard from China, why not look at possible biotic sources such as sulfur-reducing bacteria (for example, Desulfovibrio sp., Altermonas sp., Clostridium sp., Desulfotomaculum sp., and so on) or sulfur-oxidizing bacteria (for example, Thiobacillus sp., Beggiatoa sp., Thiotrix sp.)?
Finding these or related microorganisms would help explain the increased gaseous emissions during temperature and humidity increases. In a related manner, any hydrogen sulfide produced by sulfate-reducing bacteria would react with most metals spontaneously in an abiotic manner and explain the metal sulfide. Perhaps we are looking for a nail in a haystack when in fact we should be looking for the hammer. Please remember this idea is testable according to Koch's postulates.
If such reactions are found, it may be possible to tease out whether these microbes are endemic to the mine in China or the moist organic soils of Florida. I am certain a microbiologist could expedite this research, with the potential to isolate causative microbes.
I hope this hypothesis helps dissipate the odor around this investigation.
S. M. Armstrong
Halifax, Nova Scotia
It was acknowledged around the 1970s that upper-wall corrosion of underground concrete sewage collection conduits was aggravated by microbial action taking place in municipal wastewater flowing within partly filled conduits. The widespread and troublesome corrosion was attributed to gaseous hydrogen sulfide generated biologically from the aqueous sewage underflow within the conduits and the subsequent gaseous contact with the moist upper-wall surfaces.
Furthermore, it is known that landfilled calcium sulfate may undergo decomposition to produce malodorous gases, including hydrogen sulfide, during ongoing landfill exposure to the surrounding environment.
It has been proposed that the present inquiry into nontypical, imported wallboard also take into consideration the possibility of latent microbe populations that become active when exposed to increased temperature and humidity.
"Wallboard Woes" was particularly interesting to me because I had seen the hubbub about it in Florida on a recent vacation. Is the problem of sulfide gas emission from drywall under warm, humid conditions the fault of contamination of such drywall with sulfate-reducing bacteria? Also, if other factors for growth of such bacteria, perhaps iron, are in the offending drywall, is this why the emission is limited to drywall from China? Are processing temperatures a factor?
Certainly there is plenty of available sulfate in drywall. The trick to eliminating the odor might involve killing the bacteria. At the factory, this could be as simple as making sure the processing temperature in the casting machines is high enough. Adding a disinfectant to the mix might work, too. This could be proven by inoculating some drywall with the bacteria and looking for sulfide.
I have had personal experience with these annoying beasts. When I come back from vacation to my home in Illinois, I find the water coming from my undersink filter has a sulfide odor; my suburb gets its water from Lake Michigan. When I change the cellulose particulate filter, I find a bacterial slime and use a bleach solution to clean the housing.
At Sohio in the 1970s, a friend of mine solved a problem with hydrogen sulfide generation in the holds of tankers sailing from Alaska to California by adding dilute hydrogen peroxide. Presumably, this killed the bacteria that were causing the odor.
Further data on these nuisance bacteria can be found at Wikipedia under "Sulfate-reducing bacteria."
Joseph P. Bartek
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