Mathematical modelling of contaminant transport in riverbank filtration systems

Abstract

Analytical study of contaminant transport in riverbank filtration (RBF) systems is significant in providing a guide for managing and operating drinking water supplies from pumping wells. The pumping process and the distance of the pumping well from the river are two important factors for producing permissible drinking water from the system. Simulation of the impact of pumping rate and pumping time on contaminant transport based on analytical studies are not yet extensive. Thus, there is a lack of mathematical models for RBF systems to determine the shortest distance of the pumping well to the river, that produces quality water. This research aimed to provide a mathematical model based on advection dispersion equation and Green’s function approach to determine the potential effects of pumping rate and pumping time, on one and two-dimensional contaminant transport models in RBF systems. The model would be able to show how the pumping time and pumping rate affect the contaminant concentration in RBF systems. By considering an inverse problem, the Green’s function solution was applied to the problem in order to determine the shortest distance from the pumping well to the river, to increase the percentage of the quality of river water. This distance was computed when the contaminants were released from a few scenario which include a single polluted river and two polluted rivers. The distance evaluated was based on three simulated scenarios containing the varying pumping times, pumping rates and different initial concentrations from the river. The model was assessed using parameters related to nitrate (NO3) compound obtained from RBF pilot project which had been conducted in Malaysia. The results confirmed the suitability of the proposed model in simulating the effect of pumping process on the quality of the produced water and in locating the pumping well. The proposed model is helpful in providing guide to manage the existing RBF systems as well as in establishing new sites.