Technoeconomic Framework for Evaluating Desalination and Brine Management Pathways across the United States

Water is the most essential resource for human life, yet the way we access it is changing. For centuries, societies have relied on rivers, lakes, and underground aquifers to fill their needs. But as populations grow and climates shift, these traditional sources are becoming strained or depleted. In response, engineers have turned to the oceans and the earth's deeper, saltier layers for fresh water. The process of removing salt from water, known as desalination, is a powerful tool, but it creates a byproduct: a thick, salty liquid called brine. Managing this waste is just as critical as making the fresh water itself. If left untreated, brine can harm the environment, but getting rid of it costs money and energy. The central question facing water planners today is not just how to make fresh water, but how to do it in a way that is affordable and safe, depending on where a community is located and what kind of salty water they have to start with.

A team of researchers at the Georgia Institute of Technology has developed a new way to answer this question for the entire United States. They created a detailed map that calculates the true cost of turning different types of salty water into fresh water, while also accounting for the expense of dealing with the leftover brine. Their work looks at three main sources of salty water: seawater from the coast, brackish groundwater found inland, and produced water, which is a salty liquid brought to the surface during oil and gas drilling. For each source, they tested three different ways to handle the waste: dumping it back into the ocean, injecting it deep underground, or using a complex system to evaporate all the water and recover the solid salt. By running thousands of calculations across the country, they found that the best solution depends entirely on two things: how salty the water is and how far the site is from the ocean.

The researchers discovered that for coastal cities, the simplest approach is often the best. If a plant is near the sea, it can pump seawater through a filter to make fresh water and then return the salty brine to the ocean. This method is cheap, costing between one and one and a half dollars for every cubic meter of water produced. However, this option becomes impractical the further inland a city is. Transporting fresh water from the coast to a place like Denver, for example, adds so much cost that the total price jumps to about three and a half dollars per cubic meter. The study shows that for inland areas, it makes more sense to treat local salty water rather than shipping water from the coast.

When looking at inland sources, the type of water matters greatly. For areas with slightly salty groundwater, the most economical way to handle the waste is to pump it deep underground into geological formations, a method called deep well injection. This avoids the high cost of transporting the heavy, salty liquid back to the ocean. The researchers found that for low-salt water found far from the coast, trying to recover the salt is usually a losing financial proposition. The equipment needed to boil off the water and collect the salt is expensive to build and run, and the small amount of salt recovered cannot pay for the process. In these cases, the cost of making the water remains between one and three dollars per cubic meter, but the salt recovery system adds too much extra expense to be worth it.

The situation changes when the water is very salty, such as the produced water from oil and gas operations. In these high-salinity cases, the economics flip. Because there is so much salt in the water, a system that recovers the salt can actually make money by selling it. This revenue helps offset the high cost of the equipment needed to concentrate and crystallize the brine. The study suggests that for these specific, very salty inland sources, a zero-liquid-discharge system—where no water leaves the plant as waste—is a viable and sometimes preferred option. The researchers noted that for these high-salt feeds, the salt recovery can turn a costly waste problem into a revenue stream, making the entire process more affordable.

To visualize these findings, the team created a guide that acts like a decision tool for water planners. It shows that if a community is within roughly 500 to 700 kilometers of the coast, pumping seawater and discharging the brine into the ocean is the cheapest path. If the community is further inland but has water with low salt content, injecting the waste underground is the best choice. If the inland water is very salty, then recovering the salt becomes the most sensible economic strategy. This framework helps move beyond a one-size-fits-all approach, recognizing that a solution that works for a coastal city in California will not work for a town in the middle of the country.

The study also compared these desalination methods to another emerging technology: pulling water directly from the air. While capturing moisture from the atmosphere might seem like a perfect solution for dry places, the researchers found it to be significantly more expensive than desalination, costing roughly eleven to thirteen dollars per cubic meter. This high price tag means that pulling water from the air is only a realistic option for very small, remote communities where no salty water is available and transporting water from anywhere else is impossible. For the vast majority of the population, the path forward lies in managing the saltier water sources already present in the ground and the sea.

Ultimately, this research provides a clear, data-driven roadmap for the future of water in the United States. It confirms that while desalination is a necessary tool to combat water scarcity, its success depends on matching the right technology to the right location. By understanding the specific costs of transport, the salinity of the local water, and the value of the waste products, communities can choose a path that is not only technically possible but also economically sustainable. The work suggests that with careful planning, the United States can expand its fresh water supply to meet the needs of its growing population without breaking the bank or harming the environment.