**6. Conclusion**

Considering that consumption of the Energy in hybrid systems, especially for FO-MD, RO-MD and FD-MD processes, due to different operating conditions in many studies are still unclear, we need more research to expand their use in the desalination industry. Research efforts should be directed towards design improvement and evaluation of energy consumption.

Elimination of the restrictions on the use of salinity gradient power technologies and directing them towards commercialization would render hybrid desalination systems more economically and also could use the salinity gradient power as an energy recovery system on their own or with other ERDs in desalination systems as could be used as. In addition to the development of low-cost high power density


**Table 12.**

*Some experimental results of PRO-RO hybrid system [135].*

membranes and systems for reverse electrodialysis and pressure retarded osmosis, the implementation and testing of pilot plants would speed up their transition and make them more commercially viable for industrial scale operation with other desalination processes [80].
