Water production has become a serious concern nowadays due to many environmental and social factors. Conventional desalination processes are considered as energy-intensive, as energy consumption represents 50–60% of water production cost. As an example, multistage flash evaporation (MSF), requires 19.58–27.25 kWh_e/m³, and reverse osmosis (RO) 1.5–6 kWh_e/m³. Thus, developing forward osmosis (FO), a membrane technology for water desalination considered as a potentially energy-efficient process, has gained growing interest. However, the technology is facing serious limitations concerning the availability of a high-performance draw solution and membrane, which represent the core of the process. In addition to the lack of energy-efficient recoverable draw solutes, as the regeneration process represents the main energy consumption of the overall FO process. In this paper, an updated state of the art of newly developed draw solutes such as deep eutectic solvents, ionic liquids, smart materials, and classical FO draw solutes have been carried out. Finally, FO technology challenges, opportunities, and future prospects have been discussed. Draw solutes have been categorized according to their recovery methods, innovations and draw solutes strengths and limitations have been critically reviewed. The necessity of theoretical energy consumption and water production costs estimation have been outlined, in addition to pilot-scale testing to demonstrate the process feasibility.

This work aims in developing a static layer crystallizer for freezing desalination of sea water. The experiments were performed with a simple system of H2O-NaCl and with samples of sea water from Rabat. The pilot crystallizer consists in a tube cooled bymeans of a thermostatic bath. The tube is immerged in a cylindrical double jacketed tank cooled by means of a second thermostatic bath. The brine is poured into the tank and the crystallization takes place on the external surface of the tube. The global process is divided into 4 steps: (i) crystallization of the ice layer by controlling the cooling rate in the tube (ii) draining off the concentrated brine (iii) purification of the layer by sweating and (iv) melting of the ice to recover the fresh water. A parametric study of the effect of the operating parameters has allowed us to quantify the role of the different key parameters of the crystallization step. Within the studied domain, the purity of the crystalline layer was mainly affected by the initial s...