Potential of river bank filtration (RBF) in Egypt

Abstract

Drinking water supply in Egypt is based on surface water abstraction (91.4 %), groundwater (8.3 %) and desalination (0.24 %). As Egypt is currently facing problems with the pollution of surface water by industrial, agricultural and municipal inflows, riverbank filtration would offer a low cost alternative for pre-treatment of raw water for potable use. The objective of this paper is to evaluate the potential of riverbank filtration in Egypt based on drilling at potential sites and monitoring of both water level and water quality parameters. The evaluation of six sites receiving a bank filtration share of more than 50 % and producing drinking water has proven the feasibility of riverbank filtration in Egypt. Favorable hydrogeological conditions exist both along the river Nile in Upper Egypt and on main canals in the desert fringes. Key issues for the feasibility of riverbank filtration in Egypt were found to be the hydraulic connection between surface waters and the adjacent aquifer and the landside groundwater quality. The river Nile in Upper Egypt has fully to partially cut through surficial clayey sediments and is in hydraulic connection with a Quaternary aquifer that is comprised of sandy riverine sediments. The sandy riverbed and coarse aquifer materials have a sufficient hydraulic conductivity for riverbank filtration. Islands and stretches of the river channel that have convex sides are favorable for siting RBF schemes to receive a high portion of bank filtrate and limit mixing with land-side groundwater, which contains high concentrations of iron and manganese. The main benefits of RBF would be the removal of pathogens, algae and turbidity. It is recommended that wells are constructed at short distances from the river bank, to get a high share of bank filtrate.