Development of Methods to Measure the Hydrogen Sulfide Production Potential of Sulfur-Containing Wastes
Investigators: North Carolina State University
The presence of hydrogen sulfide (H2S) in landfill gas is problematic for several reasons: (1) it is corrosive to landfill gas treatment systems, (2) it is toxic to humans, and (3) it exerts a bad odor, even at 0.5 – 10 ppb. In addition, H2S is toxic to the microorganisms that generate both methane and H2S. As described in this proposal, H2S toxicity has implications for the manner in which we assess the H2S production potential of a waste. Preliminary data from our laboratory suggests that current methods to measure the H2S production potential of a waste may underestimate the true potential because the test is influenced by toxicity. During testing, we often measure H2S concentrations in excess of 20,000 ppm and have recently shown inhibition at 5000 ppm. This suggests that better test methods are required.
The production of H2S in landfills originates with the burial of various wastes that contain sulfur (e.g. fly ash, wall board, MRF fines), typically in the form of sulfate (SO4) but also in the form of elemental sulfur (S) and sulfite (SO3). While the chemical and biological processes associated with H2S production are well understood, our ability to predict the rate and extent of H2S production from a specific sulfur-containing waste is poor. I have visited landfills that receive several hundred tons a day or ash that contains sulfur. In one case, the H2S concentration in landfill gas was about 10,000 ppm while in the second case, the H2S concentration was below 100 ppm and acceptable for the landfill gas treatment system.
The overall objective of the proposed research is to develop and document a protocol to assess the H2S production potential of sulfur-containing wastes. Once developed, the protocol will be applied to at least five different fly ashes. The results will include (1) a documented protocol to assess H2S production potential; (2) an understanding of the relationship between a small-scale (serum bottle) test which is cheaper and faster, and a more realistic but slower and more costly reactor test; and (3) an evaluation of whether the H2S production potential of various fly ashes can be predicted from a chemical characterization.