Effect of Municipal Solid Waste Incineration Fly Ash Leachate on the Hydraulic Performance of a Geosynthetic Clay Liner

The ability of a geosynthetic clay liner (GCL) manufactured using sodium-activated bentonite as a barrier for municipal solid waste incineration (MSWI) fly ash is examined. The GCL specimens were permeated with two different man-made MSWI fly ash leachates to test the hydraulic conductivity (k). The effects of type of permeant solution, prehydration with distilled water (DW), and effective stress (15 vs. 150 kPa) were assessed. Results indicated that the permeation of MSWI fly ash leachates produced a significantly negative effect on the hydraulic performance of the GCL and resulted in equilibrium k values ranging from 8.5 × 10–10 to 7.45 × 10–7 m/s, which were 17 and 14,900 times higher than the maximum value typically allowed for MSWI fly ash landfill base barriers (5.0 × 10–11 m/s). Although prehydration with DW and increase in effective stress could somewhat minimize the negative impact of MSWI fly ash leachates on the hydraulic performance of GCL, the k values of GCL samples were not able to be reduced to the required value (≤ 5.0 × 10–11 m/s). Thus, the GCL investigated in this study may not be a suitable barrier for the landfill of MSWI fly ash.