In the food industry, reverse osmosis is used to concentrate a variety of liquids, ranging from fruit juices, to whey (to make whey protein concentrates), to maple sap (to make syrup).
It should be easy to design a counter-current osmotic filtering device, with two fluid inputs, and two fluid outputs.
As each fluid passes by the other, water moves from one fluid to the other, through the membrane, pushed by the difference in water potential.
If one fluid is, for example, fruit juice, and the other is a concentrated salt brine, water will move from the juice to the brine, resulting in concentrated juice, and dilute saltwater. No high pressure pumps are needed, so this is a very low energy consuming process.
If you have a cheap source of concentrated brine, then this will surely be more economical than reverse osmosis... You'd probably have to build your factory next to a desalination plant for this, but it could happen.
Even if you don't have a cheap external source of brine, it still might be more economical to re-concentrate the dilute saltwater into brine, than to run the high pressure pump needed for reverse osmosis. For example, if you have a solar thermal collector that can produce the necessary temperatures to boil down the salt water.