Migration of inorganic ions from the leachate of the Rio das Ostras landfill: a comparison of three different configurations of protective barriers

Batch tests and diffusion tests were performed to analyze the efficiency of a protective barrier in a landfill consisting of compacted soil with 10% bentonite compared to the results obtained for only compacted soil and for compacted soil covered with a 1-mm-thick HDPE geomembrane; the soil and leachate were collected from the Rio das Ostras Landfill in Rio de Janeiro, Brazil. The diffusion tests were performed for periods of 3, 10 and 60 days. After the test period, the soil pore water was analyzed and the profiles for chloride, potassium and ammonium were determined along a 6-cm soil depth. The results of the batch tests performed to define sorption parameters were used to adjust the profiles obtained in the diffusion cell experiment by applying an ion transfer model between the interstitial solution and the soil particles. The MPHMTP model (Multi Phase Heat and Mass Transfer Program), which is based upon the solution of the transport equations of the ionic contaminants, was used to solve the inverse problem of simultaneously determining the effective diffusion coefficients. The results of the experimental tests and of the model simulation confirmed that the compacted soil with 10% bentonite was moderately efficient in the retention of chloride, potassium and ammonium ions compared to the configurations of compacted soil with a geomembrane and compacted soil alone, representing a solution that is technically feasible and requires potentially lower costs for implementation in landfills.