Hydrogen Sulfide (H2s) Transport Through Simulated Interim Covers With Conventional And Co-Extruded Ethylene-Vinyl Alcohol (Evoh) Geomembranes

Transport of odiferous hydrogen sulfide (H2S) gas was evaluated using column tests simulating interim covers for waste containment consisting of a thin geomembrane overlain by cover soil. Tests were conducted with co-extruded geomembrane (GM) comprised of a thin inner layer (0.05 mm) of ethylene-vinyl alcohol (EVOH) sandwiched between two layers of linear low-density polyethylene (LLDPE), a 0.1-mm-thick polyethylene (PE) sheet, a 0.76-mm LLDPE GM, and a 0.76-mm polyvinyl chloride ( PVC) GM. In each case, the GM or sheet was overlain with a thin layer of silt intended to protect and anchor the GM. Breakthrough of H2S occurred from the column with an EVOH GM (approximate to 30 d) was five times slower than from columns with LLDPE and PVC GMs (approximate to 6 d). Relative concentrations on the cover surface from the column with the EVOH GM was lower than for all other GMs (relative concentrations were in the following order: PE > PVC > LLDPE >> EVOH). The diffusion coefficient for H2S in the EVOH GM back-calculated from the column test data was approximately 100 times lower than diffusion coefficients for the PE sheet and other GMs (1.1 x 10(-12) m(2)/s for co-extruded EVOH GM, 1.14 x 10(-10) m(2)/s for 0.1-mm PE GM, 0.87 x 10(-10) m(2)/s for the 0.76-mm LLDPE GM, and 1.06 x 10(-10) m(2)/s for the 0.76-mm PVC GM). These findings suggest that interim covers with co-extruded EVOH GMs can be effective at reducing emission of odiferous H2S relative to interim covers with other geomembranes.