High resolution 3D model of desalination brine spreading: Test cases and field case El-Gouna, Egypt

Mahmoud Shehata, Mohamed Mahgoub, Reinhard Hinkelmann

Thursday 2 july 2015

15:05 - 15:20h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment

Parallel session: 12G. Environment - Impact

Water scarcity has become a big issue in many parts of the world. For Egypt, water security is now one of the main concerns because the increasing water demand is stressing the existing water resources. Therefore, finding new sources of fresh water is essential in facing this challenge. Currently, sea water desalination is one of the promising alternatives. However, discharging the resulting brine concentrate back to the sea could cause severe damage to the marine environment, especially if the ecosystem is sensitive like the case of the Red Sea. In this research, numerical modeling was used to investigate the propagation and spreading of the desalination brine after being discharged to the sea. TELEMAC-3D modeling system was used to build 3D models of the brine propagation under different scenarios. Based on experience of similar previous work, the version using non-hydrostatic pressure distribution was chosen and the impact of different turbulence models was analyzed. Firstly, academic test cases were setup to examine different numerical and physical parameters and conditions in order to understand their degree of influence over the brine plume propagation. These parameters and conditions include the bed characteristics, outlet configuration, brine salinity and the water velocity. Then, a 3D model for a field case representing El-Gouna Region on the Red Sea was setup, and a study of the influence of the Red sea hydrodynamics on the plume behavior was performed. The parameters’ study showed that the bed bathymetry (slope and deformations) and the water body hydrodynamics are the most critical factors. According to the results, the outlet location of a desalination plant should be selected in an area which is characterized by good mixing conditions. Locations which have steep bed slopes, high velocity field and high turbulence are favorable, to decrease the plume size and consequently its environmental impact. The 3D model simulations constructed for El-Gouna region confirmed the previous results and showed that the tidal range in the Red Sea has minor influence on the brine plume. Velocity fields induced by wind were found to have high influence on the brine plume, especially if the outlet is located in a relatively shallow area near the coast.