Evaluation of riverbank filtration in the removal of pesticides: an approximation using column experiments and contaminant transport modeling

The potential of riverbank filtration in the removal of five pesticides commonly used in Colombia (atrazine, ametryn, carbofuran, diuron and propanil) was evaluated through a series of column experiments and solute transport modeling. The experiments consisted of two soil columns run under saturated regime, with sediments and water collected from the rivers Loessnitztal and Elbe (East Germany), respectively. Six experiments were performed at 10 and 20 °C, and the final concentrations of the pesticides were used to solve the one-dimensional advection–dispersion equation using an inverse approach. Variables such as retardation factor, first-order degradation coefficient, and dispersion coefficient were assessed for all the pesticides except propanil, which rapidly degraded in solution. The parameters obtained for one of the experiments were introduced into a groundwater flow model from the Loessnitztal site, and the code MT3DMS was used to simulate a contaminant pulse coming from the river. Four different scenarios were considered to determine the effect of adsorption and degradation on the fate of the pesticides. The results showed that, although the persistence of pesticides depends on the properties of each compound, a maximum of 30% removal was achieved during the column experiments, and a log removal of 9 through the numerical modeling. Because of the sensitivity of the fate of contaminants to sorption and degradation, field and laboratory work should be carried on to determine the removal coefficient of the dissolved and adsorbed phases of the compounds, the type of degradation to be expected, and the real values of longitudinal and transverse dispersivity.