News Feature | August 20, 2014

Reverse Osmosis Vs. Forward Osmosis: Which Is Better For Desalination?

By Sara Jerome
@sarmje

oceanreg

A new study pitted reverse osmosis desalination against forward osmosis in a test for the more efficient process. 

Reverse osmosis took the gold. 

Conducted by Massachusetts Institute of Technology researchers and published in the Journal of Membrane Science, the study found that "contrary to popular support, forward osmosis desalination of seawater is significantly less energy efficient, compared to reverse osmosis," according to an announcement from the Institute. 

"The scientists performed an energetic comparison of the two technologies to identify their respective energy consumptions and found that even if the second step of draw regeneration — in which the concentrated salt solution is dewatered, producing fresh water — can achieve the same level of efficiency as the RO process, the actual energy consumption of FO will consistently surpass that of RO," according to a write-up by the International Water Association. 

Ronan McGovern, a researcher that worked on the experiment, explained the implications of the findings. 

"According to McGovern, forward osmosis is better suited to alternate applications, such as the production of hydration drinks. In such applications, only the first step of the forward osmosis process is required — where a concentrated sugar syrup is diluted to a desirable level — placing forward osmosis at an advantage to reverse osmosis," the MIT write-up said. 

A lot is riding on the desalination market in light of severe droughts in the U.S. 

"Currently California is building the largest desalination plant in the Western Hemisphere in Carlsbad. At a cost of $1 billion, the plant will produce 50 million gallons a day for San Diego County by 2016. The plant, and others like it in California, use reverse osmosis technology. Fourteen other desalination plants are in the works. Critics say the process is too costly," the International Business Times reported. 

Check out Water Online's Desalination Solution Center

Image credit: "Blue Water" squeaks2569 © 2012, used under an Attribution-ShareAlike 2.0 Generic license: https://creativecommons.org/licenses/by-sa/2.0/

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