Brine outfall modeling of the proposed desalination plant of Fortaleza, Brazil

Seawater desalination has been considered an important solution for the water scarcity in coastal areas. Brazil has an 8,000 km long coastline where population and tourism have grown tremendously in the last years. Fortaleza is the fifth-largest city in Brazil with nearly 2.6 million inhabitants, representing an important economic, recreational and touristic area in the Northeast. In addition, it is the city with the greatest gross domestic product (GDP) in the region, and ninth in the country. In the past 7 y, the dams that supply water to the Metropolitan Region of Fortaleza have undergone droughts. This led the government to start a large-scale seawater desalination project that shall produce desalinated water at about 1.0 m3/s, for which plant location, water intake and brine disposal studies were performed. The most common environmental impact associated with desalination plants is the high concentration brine discharge. Aiming to evaluate the possible impact of such discharges, environmental modeling has become an important tool for projects, environmental management and studies, due to the complexity of these environments. With this tool, it is possible to integrate a large number of variables and processes to obtain a dynamic vision of those systems and evaluate present and future conditions. This work presents outcomes from brine discharge modeling in the water quality of the coast of Fortaleza, in particular, increased salinity, using Visual Plumes to evaluate near-field dilution and SisBaHiA (Environmental Hydrodynamic Base System) software to generate a hydrodynamic model and evaluate far-field dilution. Hydrodynamic models, forced by wind and tide, were coupled with a wave propagation model and then used in a Lagrangian transport model, which was fed by the outcomes of the near-field model. From the results generated, it was identified that the installation of the proposed desalination plant in Fortaleza does not compromise water quality and is consistent with the results reported in the literature, regarding the reduced impact caused by the disposal of this type of concentrate.