Comparison of batch and column methods for assessing leachability of hazardous waste

Various laboratory techniques have been proposed for generating and characterizing leachate from hazardous wastes, and experiments were carried out to compare the differences in the composition of leachates obtained from four representative solid wastes by batch and column methods. The column method involved passage of water through a static bed of the waste material, and the batch method involved constant agitation of a water and waste suspension. Statistical analysis of the results showed that the leachate profiles produced by the two methods were significantly different for 12 of the 16 constituents examined, and that the variation in experimental data was twice as great for the column method as for the batch method; this was attributed to the effects of channelling in the column method. It was concluded that, although the column method gave better simulation of actual leaching processes, the batch extraction procedure had advantages in its simplicity and better reproducibility.