New method could make removal of salt from industrial wastewater more energy-efficient

Researchers at Vanderbilt University, in collaboration with scientists from Colorado State University, have developed an innovative method for removing salt from hypersaline industrial wastewater. This breakthrough technology, called electrodialytic crystallization (EDC), aims to make the process of salt removal more energy-efficient and cost-effective compared to current methods.

While reverse osmosis has made significant progress in desalinating seawater at a low cost, it still falls short when it comes to eliminating saline from industrial wastewater and inland brackish water. Current disposal methods, such as deep geological injection or evaporation ponds, face increasing regulatory and environmental challenges.

Zero liquid discharge (ZLD) and minimal liquid discharge (MLD) techniques, which utilize engineered treatment systems to eliminate or minimize brines, are becoming mandatory in some countries for certain industries. However, the prevalent technology used in ZLD/MLD, called mechanical vapor compression (MVC), incurs high capital and operating costs, rendering it unaffordable for many users.

The team, led by Associate Professor Shihong Lin, believes that EDC can offer a solution to this dilemma. The researchers describe EDC as a novel brine treatment technology based on the principles of electrodialysis. Electrodialysis employs an electric field to pull ions through ion exchange membranes, resulting in the production of deionized water and concentrated brine streams. By modifying this process, EDC retains the brine within the system and induces salt crystallization using an electric field, eliminating the need for costly evaporation methods.

The elimination of evaporation is crucial in developing energy-efficient brine crystallization processes, as stated in the research paper published in Nature Water. However, one significant challenge faced by EDC is electro-osmosis, where certain ions transport excessive water across the ion exchange membranes, hindering effective brine concentration. The researchers believe that improved membrane design and optimized operation can address this challenge and make EDC more universally applicable.

Preliminary analysis conducted by the team demonstrated that EDC, when combined with reverse osmosis, has the potential to consume significantly less energy than MVC for brine crystallization. This promising finding suggests that EDC could revolutionize salt removal from industrial wastewater, offering a more energy-efficient and cost-effective alternative to existing methods.

Source: Vanderbilt University

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