Assessment on non-linear models for demonstrating heavy metals release behavior from solid waste block

To reduce the solid waste load and minimize the contaminant like heavy metals migration to the surrounding environment at landfill sites, solid waste was incorporated in paving mortar block by following the solidification/stabilization treatment technique. Two well established nonlinear methods such as diffusion equation derived for a plane source model and empirical method employing a polynomial equation were used for the better understanding of the heavy metals like Fe, Cu and Ni migration phenomena. Experimental data representing the releasing heavy metal from paving block were used for non-linear models for calibration. The accuracy of the models was statistically evaluated followed by models parameter estimation. The study showed that polynomial equation is better than diffusion equation for explaining experimental observation. Moreover, in this current study, polynomial equation was extended further three different longer terms namely Model 1, Model 2 and Model 3 respectively using the least squares procedure for examining the best fit profile with the observations. All the three extended models were justified against statistical point of view. Calibration results shows that the polynomial equation with 2.5 degree (Model 2) explains better leaching behavior of Fe and Cu, whereas the Model 3 having third degree polynomial equation is found to be perfect for representing Ni release pattern from the solid waste block. Apart from the calibration approach, the accuracy of Model 2 and Model 3 were validated with respective experimental observation followed by the model parameters estimation with 95% confidence interval.