Crystallization of salts from super-concentrate produced by tandem RO process

We continue to address the challenge of improving concentrate disposal for the large 15 mgd (2370 m3h) inland reverse osmosis (RO) plant in El Paso, Texas. For the first time on a pilot scale, the feasibility of using two RO systems in tandem and using appropriate antiscalants and pH control, continuous production of permeate to limiting osmotic pressure of about 1000 psi (69 Bars) is possible [1,2,12]. Recovery is simply limited by the highest pump pressure available to overcome the resulting osmotic pressure [2]. Tandem RO without interstage treatment is being demonstrated. We envision that such a continuously operated tandem RO process can recover all the water possible to be produced from brackish ground waters at the highest possible pump pressures. At the maximum system pressure of 1000 psi, the highest total dissolved solids attainable in the concentrate are about 8–9% by weight. Anticipating the universal application of the continuous tandem RO process to generate super RO concentrates, an alterna...