Determining the optimization of seawater concentrate discharge of coastal desalination plants into the marine environment, based on numerical modeling

Abstract

In recent years, due to a decrement in water quality and scarcity, desalination systems have gained popularity for desalination purposes. Synchronously, with the development of this system, particularly, in concern with the littoral regions, seawater concentrate disposal consisting of various pollutants was taken into consideration. In this research, two desalination plants near each other were selected and four scenarios have been foreseen, for the discharge of seawater concentrate and the desalination intake, which are taken under study in the Ramin-Chabahar region, based on dual-dimensional hydrodynamic simulation, comprising of diffusion and release, by utilizing the MIKE 21 Software. Due to the proximity of the two desalination plants, to reduce the costs of piping in the sea, the location of discharge and intake were considered common. On the grounds pertaining to the modeling results, the discharge of seawater concentrates, at a distance of 300 m (5 m of depth) from the coast and the intake point, at a distance of 800 m, in elongation, has had the minimum environmental impact; as well as having no undesirable effect on the water quality of the intake, in addition to being cost-effective, from the economic viewpoint. To dilute seawater concentrate to a standardized level, it is appropriate to discharge through a diffuser with 10 nozzles, which are spaced out at 3.25 m from each other, being positioned linearly on one side, at an angle of 60 degrees. With the optimal selection of intake and discharge points of seawater concentrate in marine desalination plants, in addition to increasing the quality of treated water and reducing adverse environmental effects, construction and operation costs are also reduced.