Effect of Synthetic Leachate on Stabilized Pond Ash in Msw Landfill

Abstract

Municipal Solid Waste dumping in landfill site generates hazardous liquid that may pollute surface water bodies. As leachate contains heavy metals that is hazardous to health as well as soil beneath the landfill, landfill is integrated with a barrier layer called liner. To mitigate the effect of leachate and make landfill system sustainable, bottom liners are expected to behave as nonporous layer prohibiting leachate penetration below the bottom layer. As most of the coal ash in India are actually available in the form of pond ash or lagoon ash, in the present investigation, it is attempted to study the feasibility of using pond ash, with some modification, as a landfill liner material.  In this study, pond ash has been collected from Nalco Captive Power Plant, Angul, Odisha. Falling head permeability tests have been conducted on seven types of mixes serially named S1 to S7 indicating varying proportions of pond ash, lime and gypsum specimens. Each stabilized sample was permeated with water, acetic acid, and methanol solutions after regular intervals of curing time. Among all stabilized sample, Sample S7 mix having 85% pond ash,14 % lime and 1% gypsum mix showed minimum permeability substantially for both the acidic and alkaline permeant. Sample having minimum permeability in various liquids was chosen further to test the coefficient of permeability with a synthetic leachate solution. The leachate solution was prepared in the laboratory and the concentration used in it resumed the concentration parameters of minerals present in MSW leachate.S7 sample was permeated with the synthetic leachate solution for both cured and noncured conditions of sample and varying continuous flow periods. The permeability was found to be 3x10^-7 cm/sec after 30 days of continuous flow in 180 days cured sample after synthetic leachate permeation. All the effluent liquid coming out of the permeability apparatus outlet was examined for pH, Total Dissolved Solid (TDS), and Electrical Conductivity (EC) and showed the controlled value of pH, TDS, and EC as per “Municipal Solid Waste Management and Handling Rules,2000,India” when checked for inland surface water quality. On account of the results received, it is expected that in a real scenario this landfill liner will show minimal permeability and permissible value of pH, TDS, and EC keeping the ground and ground water protected.