Impact of real and simulated municipal solid waste leachates on the hydraulic and swelling behaviour of bentonites for landfill application

For the efficient functioning of a landfill, compacted bentonite is an acclaimed liner element due to its excellent adsorption capability, minimal hydraulic conductivity, and superior specific surface area (SSA). However, the leachate generation within the landfill worsens the liner material’s quality, causing migration of the leachates, contaminating groundwater, and causing pollution of surrounding environment. With this perspective, a comparative assessment of the influence of real and simulated municipal solid waste (MSW) leachate on two different bentonites has been carried out in the present investigation. The two bentonites, differing precisely by their cation exchange capacity (CEC), liquid limit (LL), and swelling capability, were examined for variation in their LL, free swell (FS), and hydraulic behaviour concerning their interaction with both leachates. Results depicted that in both the leachates, LL and FS, swelling potential (SP) and pressure declined, whereas hydraulic conductivity (HC) rose. Furthermore, the bentonite quality greatly influenced the LL, FS, SP, swelling pressure, and hydraulic behaviour. Bentonite having higher CEC, SSA, and swelling ability experienced a higher variability in the LL (55.5 and 65.2% decrease), free swelling (76.9 and 83.1% decrease), SP, swelling pressure (53.3 and 56.4% decrease), and HC (13.1 and 49.4 times increase) values when permeated with simulated and real MSW leachates, respectively. The study also showed that the real MSW leachate interaction causes a higher variation in bentonite behaviour than its simulated counterpart. The study’s findings would prove beneficial to design engineers for selecting bentonite types for landfill liners.