Artesian landfill liner system: numerical and cost optimization models for preliminary design

Sanitary landfilling is the solid waste disposal technique most widely practiced today. In conventional landfill design, the leachate generated in the landfill is contained by a low conductivity liner constructed at the base of the landfill. However, due to the inherent limitations of natural materials and the inevitable imperfections of installing plastic or rubber liners, escape of leachate is inevitable in conventional landfills. The concept of the artesian landfill system - in which the downward movement of leachate is prevented by reversing the hydraulic gradient so that seepage occurs into, and not out of, the landfill - is illustrated in this paper. A two-dimensional, transient saturated-unsaturated finite element flow model developed in the paper demonstrates that the reverse gradient eliminates or limits the loss of leachate from the landfill even if the integrity of the landfill liner is imperfect or deteriorates over time. A geometric programming model is also developed for the least-cost design of artesian landfill system components based on the capital and operating costs of the system.