Salty Water Tempts Drought-plagued State

It may all depend on how far below ground, abundance of supply, and pollutant contents of the available brackish waters.. vs. How far the ocean waters are to the end-users should be the main concerns. Ultimately together with the system reliability factor considered will increase the total processing and consumer's costs?

Not only that, there are places (like Terlingua) in Texas, that have radioactive ground water. Go figure out how to treat that, and you will have something. ( I know the guy that sold the system, services the system, and troubleshoots the system that takes care of that job).

At some point forward osmosis will be a real player in the market to purify any and all sorts of water we currently find to be impalatable. The use of pyrolytic ammonium bicarbonate as draw solution, with waste heat, solar heat, or geothermal heat (where available) which only has to meet the 60°C requirement, and a really robust membrane that can withstand way more stress than RO membranes, offers way higher membrane integrity (lack of porous faults), and requires little in the way of driving pressure (FO only requires the draw solution osmotic pressure be higher than the supply solution). Pure water is a result, and heat can be recycled for the most part, making FO a really attractive option if the membrane polarization effects have been or can be completely worked out.

The use FO systems is a big possibility / advantage over an RO system operations. Operational advantage specially when it comes to the area and magnitude of wasted energy as well as the amount of electrical power needed for proper RO system operation..

How about the abundance of natural gas, in your area, to provide energy for the system?

Yes, one could direct heat the draw solution of FO to drive the process, and also use the natural gas on genset (if you don't want to buy electricity) to run the minimal pump energy to move water around.

The by-products of natural gas are CO2 + H2O so you could make carbonated water too!

Usually, one would see the FO system coupled to a low grade waste heat source, or solar thermal. Natural gas could easily be utilized to heat the draw solution to drive away the thermolytic ammonium bicarbonate.

The main problem with FO up to this point has been maintaining sufficient turbulent flow against the membrane surfaces (feed and draw) to reduce concentration polarization to tolerable levels. This is critical to the successful operation of FO.