Modeling RBF Efficacy for Mitigating Chemical Shock Loads

Abstract

Riverbank filtration (RBF) offers several advantages over the direct use of surface water. A number of dissolved and suspended contaminants of surface water—including pathogens and microscopic particles—are removed during passage of surface water through the river sediment–aquifer system. Many dissolved chemicals undergo biogeochemical reactions and dilution, leading to reductions in concentrations of parent species. This research examined the potential of RBF systems to attenuate chemical shock loads that may result from chemical spills or spring flooding in agricultural watersheds. Scenarios simulated both horizontal and vertical wells, with riverbed and bank hydraulic properties varying as a function of river stage. The solute transport equation considered a range of reaction parameters. Sensitivity analysis showed that the hydraulic conductivity of the riverbed or bank materials had a pronounced effect on filtrate quality. For materials with low hydraulic conductivity, the effect on filtrate quality would be minimal, and the lag time between the contaminant peak concentrations in the surface water and the pumped water would be significant. However, further biogeochemical modeling is needed to predict the fate of contaminants during their transit to the pumping wells. Use of backup vertical wells or selected laterals of a collector well could effectively mitigate the risks.