**Abstract**

One way in order to reduction energy consumption and providing the required water in both well-established technologies such as reverse osmosis (RO) and electrodialysis is use of the strengths of two or more processes through hybridization. Other key objectives of hybridization include increasing the capacity of the plant flexibility in operation and meeting the specific requirements for water quality. At this section, has been provided a critical review of hybrid desalination systems, and methods used to optimize such systems with respect to these objectives. For instance, coupling two process like as electrodialysis with RO is very effective in order to overcome the low recovery in RO systems. On the other hand, we can use for two or more processes such as RO with membrane distillation (MD) or zero liquid discharge (ZLD) for treatment of hypersaline feed solutions. At this section, also have been reviewed the applicability of salinity gradient power technologies with desalination systems and we identified the gaps that for effective upscaling and execution and implementation of such hybrid systems need to be addressed.

**Keywords:** energy recovery, desalination, hybrid systems, reverse osmosis, membrane
