Forward osmosis (FO), an osmotic-driven membrane process, has been gaining attention for being a low-energy alternative for several applications usually performed by pressure-driven membranes, such as reverse osmosis (RO) and nanofiltration (NF). The FO process requires a draw solution (DS) to create the osmotic pressure as a driving force to separate fresh water from the saline feed water acting as the feed solution (FS). A solution of an ammonium salt (a mixture of ammonium bicarbonate, ammonium carbonate and ammonium carbamate) has shown its potential to be a favorable, thermolytic DS since it can be easily treated by moderate heating (e.g. waste heat) to remove the ammonium salt solutes, producing fresh water and recovering the DS components (McCutcheon et al., 2005). In the present study, an ammonium bicarbonate solution was employed as the DS to desalinate natural seawater (SW) from the Red Sea. The performance of the process, including the flux patterns and reverse draw solute leakage was evaluated. Special attention was given to the scaling on the membrane surface.