Inhibition of hydrogen sulfide generation from disposed gypsum drywall using chemical inhibitors

Abstract

Disposal of gypsum drywall in landfills has been demonstrated to elevate hydrogen sulfide (H 2S) concentrations in landfill gas, a problem with respect to odor, worker safety, and deleterious effect on gas-to-energy systems. Since H 2S production in landfills results from biological activity, the concept of inhibiting H 2S production through the application of chemical agents to drywall during disposal was studied. Three possible inhibition agents – sodium molybdate (Na 2MoO 4), ferric chloride (FeCl 3), and hydrated lime (Ca(OH) 2) – were evaluated using flask and column experiments. All three agents inhibited H 2S generation, with Na 2MoO 4 reducing H 2S generation by interrupting the biological sulfate reduction process and Ca(OH) 2 providing an unfavorable pH for biological growth. Although FeCl 3 was intended to provide an electron acceptor for a competing group of bacteria, the mechanism found responsible for inhibiting H 2S production in the column experiment was a reduction in pH. Application of both Na 2MoO 4 and FeCl 3 inhibited H 2S generation over a long period (over 180 days), but the impact of Ca(OH) 2 decreased with time as the alkalinity it contributed was neutralized by the generated H 2S. Practical application and potential environmental implications need additional exploration.