Additional reporting for this article was provided by Jana Crouch.

Colorado State University researchers are set to launch two projects aimed at finding ways to reduce the energy cost of water desalinization and purification.

Both projects are funded through grants from the U.S. Department of Energy’s National Alliance for Water Innovation. The five-year, $110 million research program and public-private partnership aims to radically lower the cost and energy of desalination. As global access to water supplies changes, making saltwater drinkable will become an increasingly valuable solution.

The most advanced and efficient way for desalinating water is by using reverse osmosis filtration systems. In these systems, saltwater is forced through tiny passages in membranes, requiring a great deal of pressure exerted over an extended period. This process is energy intensive, especially at scale.

Institutions across the country are focused on reducing the energy intensity of desalination. Currently, simply transporting fresh water on vehicles and watercraft is usually less financially expensive. But it is still expensive in terms of energy use and other costs to both the environment and human health.

Energy grid efficiency

The first project, headed by Steven Conrad, associate professor of systems engineering will seek to find energy conservation and management opportunities between filtration desalinization plants and the power grids to which they connect.

This team will model and select the best ways to integrate existing water treatment plants with modern electric grids. They will then identify where improvements in the process will have the most positive impact.

“Water treatment plants like these are high-energy environments, so they offer opportunities for doing things like cycling power back into the grid,” Conrad said. “We seek to leverage new technology and sustainable energy processes to reduce the costs of these systems.”

This project will be done in collaboration with the Electric Power Research Institute, the National Renewable Energy Laboratory, The Salt River Project (AZ), and the Water Replenishment District (CA). The project is collectively worth about $900,000, with CSU receiving about $325,000 from NAWI and the Colorado Higher Education Competitive Research Authority.

Lower the cost of avoiding liquid pollution

The second project, co-led by Tiezheng Tong, associate professor of civil and environmental engineering, and Jason Quinn, professor of mechanical engineering, seeks to reduce the cost and energy needed to achieve zero-liquid discharge in desalination.

Brine crystallization is the final and most energy-consumptive, carbon-intensive step in achieving ‘zero-liquid discharge.’ This step ensures that waste removed from the water is in a solid state, reducing the cost of disposal and the environmental pollution of highly concentrated saltwater.

In addition to being a pollution prevention measure, zero-liquid discharge allows for a truly sustainable system where all water can circulate back into use without waste.

While Tong advocates for a more sustainable approach to crystallization, there is currently a significant amount of energy expended in traditional processes. Usually, the last stage in zero-liquid discharge is to boil the salt water, creating water vapor and leaving the salt behind, or freeze the water, forcing most of the salt out as the water hardens into ice. Both heat and freezing require high energy use, resulting in carbon emissions.

Inhibitive antiscalants are an additional challenge for most desalination systems, which prevent the buildup of mineral crystals on the membrane filter. The final step in achieving zero-liquid discharge requires salt crystallization, and antiscalants may inhibit the process further down the chain.

The research team will work to identify the impact of antiscalants on the brine crystallization step of zero-liquid discharge desalination, to improve the efficiency of the process and reduce its carbon intensity.

“I am really excited to be working with such a dynamic and talented team on a problem that, if solved, can have a real impact,” said Quinn.

The team will work in collaboration with Washington University in St. Louis, Clarkson University, Argonne National Laboratory, and OLI Systems, Inc. The award is worth $1.3 million total, with CSU receiving $295,000.

Looking forward

Better desalinization technology could lower the adverse impacts of complicated water issues. The emissions of traditional water transportation can be problematically high. Freshwater transportation is also not always a feasible option, such as in cases of natural disasters, inadequate infrastructure, drought, or conflict.

The goal of these projects is to achieve ‘pipe parity,’ which means processed water has the same quality and costs of water as springtime snow melt.

“We hope to create water treatment systems that have minimal negative impacts on the planet, and that are more accessible to people who would otherwise struggle to access clean drinking water,” Conrad said. “Like those in the U.S. Pacific Southwest region.” 

Both projects are expected to start in December 2023, last for at least two years, and help fund the research of several graduate students.

“I’m excited for our students and collaborators to find value in these projects, but I also expect us to provide value far more broadly,” Conrad said. “If we can decrease the high energy costs of desalinization, we could provide the world with a useful tool for meeting our collective water needs.”

Tong agreed, adding that CSU has a broad commitment to improving the future of water systems.

“These projects reflect CSU’s strength in water technology and the opportunities for collaboration across disciplines on campus to help society at a high level,” he said.