Methods of treating a high salinity liquid, such as seawater, containing boron are provided, including adjusting the pH of the liquid to about 8 to about 9.5, optionally adding a scale inhibitor to the liquid, passing the liquid through a reverse osmosis device, and recovering a permeate having a boron concentration less than about 2 ppm. One embodiment includes removing colloidal matter from the liquid using a membrane filtration system, such as ultrafiltration or microfiltration, prior to passing the liquid through the reverse osmosis device, and preferably prior to adjusting the pH of the liquid.