A process is provided for the recovery of one or more useful products including fertilizer, animal feed supplements, iron oxide, magnesia, salt, purified brine, and purified water from brines. The source of the brines can be oil and gas field wastes, seawater or effluent from a seawater desalination plant, or other inland brine sources. Iron and magnesium are initially precipitated from the brine. Then phosphoric acid is added to the brine followed by an alkaline agent to produce precipitates useful as fertilizer and animal feed supplements. The remaining salt in the brine may then be removed and recovered along with purified water.