Optimum Hydraulic Design of Riverbank Filtration Wells

Abstract

Egypt faces a great challenge of water poverty due to several reasons such as population increase, climate change, pollution of some water resources, and the impact of Grand Ethiopian Renaissance Dam (GERD), in addition to the economic challenges. The rapid increase in water demand requires urgent and economic solutions, especially in remote areas, where the costs are high to connect these areas to potable water. The high capital costs of conventional treatment plants do not allow the authorities to accommodate the rising water demand. In addition, the surface water and groundwater are getting more polluted with industrial, agricultural, and municipal inflows. This pollution constrains the ability to use these resources and achieve the maximum benefit of these resources. Thus, riverbank filtration (RBF) becomes a promising solution that offers potable water at a low cost. RBF is the process of extracting water from a river by pumping wells located adjacent to the river, where river water is purified through natural physical, biological & chemical filtration mechanisms including filtration, adsorption, biodegradation, chemical precipitation, and redox reactions. RBF is considered a green, sustainable, and economic technology. There are various factors affecting RBF efficiency; for instance; aquifer characteristics, river hydrology/hydraulics, site geometry, riverbed characteristics, water quality, and operation of RBF wells. RBF is already located in several locations in Egypt, and there are much more potential locations. Numerical modeling is one of the most crucial methods that can be used to determine the efficiency of RBF system in a specific site. In this work, the Idrasiya RBF site, which contains three RBF units, in Beni Suef, was selected to apply a numerical model to study the effect of four design parameters on both river filtrate portion and travel time, assuming that the extracted water quality is improved by increasing the river filtrate portion. These parameters are; 1) the extraction rates of the RBF wells, 2) the number of operating wells, 3) the apart distance between wells and the river, and 4) the spacing between the wells. A numerical model was constructed using Groundwater Modeling System (GMS) v. 10.3 by Aquaveo, which is a friendly graphical interface