Sustainable desalination of industrial wastewater

Vanderbilt researchers are part of a team that has developed a cutting-edge method that seeks to make the removal of salt from hypersaline industrial wastewater far more energy-efficient and cost-effective.

Vanderbilt University researchers are part of a team that has developed a cutting-edge method to make removing salt from hypersaline industrial wastewater far more energy-efficient and cost-effective.

Desalination through reverse osmosis has made tremendous strides by allowing salt removal from seawater for less than a penny per gallon. However, it still falls short of eliminating saline in wastewater from industries like mining, oil and gas, and power generation. The industrial brines are currently injected into deep geological formations or transferred to evaporation ponds. Both disposal methods are facing more regulatory and environmental challenges.

Zero and minimal liquid discharge use engineered treatment systems to eliminate or minimize brine volume. These techniques are already required in some countries for certain industries and are expected to become more widely adopted soon. Current ZLD/MLD treatments typically involve mechanical vapour compression, which generates heat from electricity to evaporate brines until the salt remains. Because of MVC’s high capital and operating costs, these processes are unaffordable for many users.

Associate Professor of Civil and Environmental Engineering and 2023 Chancellor Faculty Fellow Shihong Lin and his team, including researchers from Colorado State University, believe they have an answer to this dilemma.

What was done for the desalination of industrial wastewater?

In a paper featured on the cover of the June 2023 issue of the journal Nature Water, Lin and his colleagues describe a novel brine treatment technology called electrodialytic crystallization that can potentially reduce the energy consumption and cost of brine crystallization. According to the researchers, the fundamental principle of EDC is like electrodialysis.

In ED, an electric field pulls ions through ion exchange membranes. By placing different types of IEMs in a certain way, ED can produce streams of deionized water and concentrated brine. With some configuration changes to that process, the researchers say EDC keeps the brine within the integrated system. They use an electric field to induce salt crystallization without using costly evaporation methods.

“The elimination of evaporation is the key to developing potentially energy efficient brine crystallization processes,” according to the paper.

Challenges of technique

One major technical challenge is that when certain ions transport through the IEMs, they drag too much water across. Too much water reduces the effectiveness of the process in concentrating the brine stream. This phenomenon, called electro-osmosis, prevents some salts from being crystallized out effectively. The researchers said that better membrane design and optimized operation could potentially address this challenge and make EDC more universally applicable.

Nevertheless, the team performed a preliminary analysis of the salts that EDC can handle. It showed that EDC coupled with reverse osmosis could potentially consume much less energy than MVC for brine crystallization.

The National Alliance of Water Innovation funded the study. This public-private partnership brings together world-class industry and academic partners to examine the critical technical barriers and research needed to radically lower the cost and energy of desalination. NAWI is led by DOE’s Lawrence Berkeley National Laboratory in collaboration with National Energy Technology Laboratory, National Renewable Energy Laboratory and Oak Ridge National Laboratory, and it is funded by the Office of Energy Efficiency and Renewable Energy’s Industrial Efficiency and Decarbonization Office.

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