Desalination is used to produce fresh drinking water from seawater, but it also generates a highly concentrated waste stream known as brine. Disposing of this brine is a major challenge and is often achieved through deep-well injection, in which the waste is pumped underground, an approach that can be expensive. Oil and gas production creates similarly saline wastewater, which is often managed in the same way.

In this work, the researchers developed a modelling platform to evaluate different strategies for managing these waste streams and to determine whether it is more cost effective to dispose of brine or to treat it further and recover additional water using solar-powered technologies. They applied the framework to two case studies: the Kay Bailey Hutchison Desalination Plant in Texas, a large inland desalination facility, and produced water from the Permian Basin, one of the most productive oil-producing regions in the United States.

The study compared a range of desalination technologies, including reverse osmosis, which uses membranes to separate water from dissolved salts, and thermal desalination methods that use heat to evaporate and recover water. Solar technologies included photovoltaic panels that generate electricity and solar thermal systems that provide heat. The researchers found that for desalination brine, the most cost-effective solar-powered option was photovoltaic combined with reverse osmosis, while solar-thermal desalination remained relatively expensive because of the cost of solar collectors and heat storage. For highly saline oilfield wastewater, zero-liquid-discharge systems, which recover almost all of the water and leave behind solid salts, could be economically attractive because they reduce or eliminate costly brine disposal.

More broadly, the findings suggest that renewable energy could help make desalination and wastewater treatment more sustainable, particularly in water-stressed regions. By identifying cost-effective ways to increase water recovery and reduce brine disposal, the work could support wider water reuse and potentially enable valuable minerals to be recovered from waste streams rather than discarded.

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Energy efficiency and renewable energy utilization in desalination systems by Veera Gnaneswar Gude and Vasilis Fthenakis (2020)