Powering desalination with the sun — in India and New Mexico

Natasha WrightPhoto/Bryce Vickmark

When graduate student Natasha Wright began her PhD program in mechanical engineering, she had no idea how to remove salt from groundwater to make it more palatable, nor had she ever been to India, where this is an ongoing need.

Now, three years and six trips to India later, this is the sole focus of her work.

Wright joined the lab of Amos Winter, an assistant professor of mechanical engineering, in 2012. The lab was just getting established, and the aim of Wright’s project was vague at first: Work on water treatment in India, with a possible focus on filtering biological contaminants from groundwater to make it safe to drink.

There are already a number of filters on the market that can do this, and during her second trip to India, Wright interviewed a number of villagers, finding that many of them weren’t using these filters. She became skeptical of how useful it would be to develop yet another device like this.

Although the available filters made water safe to drink, they did nothing to mitigate its saltiness — so the villagers’ drinking water tasted bad and eroded pots and pans, providing little motivation to use these filters. In reviewing the list of questions she had prepared for her interviews with locals, Wright noticed that there were no questions about the water’s salty taste…

Almost 60 percent of India has groundwater that’s noticeably salty, so later, after returning to MIT, Wright began designing an electrodialysis desalination system, which uses a difference in electric potential to pull salt out of water.

This type of desalination system has been around since the 1950s, but is typically only used municipally, to justify its costs. Wright’s project aims to build a system that’s scaled for a village of 5,000 people and still cost-effective…

Wright’s solution offers an alternative to grid power: She’s designed a village-scale desalination system that runs on solar power. Since her system is powered by the sun, operational and maintenance costs are fairly minimal: The system requires an occasional cartridge filter change, and that’s it.

The system is also equipped to treat the biological contaminants that Wright initially thought she’d be treating, using ultraviolet light. The end result is safe drinking water that also tastes good

Although Wright’s work is currently focused on rural villages in India, she sees many uses for the technology in the United States as well. In isolated areas, such as the ranches in New Mexico where she tested her system at full scale, poor access to water pipelines often leads to a heavy reliance on well water. But some ranchers find that even their livestock won’t tolerate the saltiness of this water.

“It’s useful to install a small-scale desalination system where people are so spread out that it’s more costly to pump in water from a municipal plant,” she says. “That’s true in India and that’s also true in the U.S.”

It’s certainly true in downstate New Mexico. We have beaucoup brackish fossil water in great quantities. Not being used for much of anything, now.

Thanks, Om

3 thoughts on “Powering desalination with the sun — in India and New Mexico

  1. Update says:

    “Radical desalination approach may disrupt the water industry : Columbia Engineering researchers design new desalination method for hypersaline brines that is low-cost, efficient, and effective; could address the growing water challenges across the globe.” (Columbia University School of Engineering and Applied Science press release May 6, 2019) https://www.eurekalert.org/pub_releases/2019-05/cuso-rda050619.php (includes link to video). A Columbia Engineering team reports that they have developed a radically different desalination approach–“temperature swing solvent extraction (TSSE)”–for hypersaline brines. The study, published online in Environmental Science & Technology Letters, demonstrates that TSSE can desalinate very high-salinity brines, up to seven times the concentration of seawater. This is a good deal more than reverse osmosis, the gold-standard for seawater desalination, and can hold handle approximately twice seawater salt concentrations.
    “Membrane-less and Non-Evaporative Desalination of Hypersaline Brines by Temperature Swing Solvent Extraction” https://pubs.acs.org/doi/10.1021/acs.estlett.9b00182

  2. Science be damned says:

    Desalination breakthrough could lead to cheaper water filtration (12/31/20) https://www.sciencedaily.com/releases/2020/12/201231141511.htm
    Researchers measure, model desalination membranes to maximize flow, clean more water https://www.eurekalert.org/pub_releases/2020-12/isu-rmm123020.php
    Nanoscale control of internal inhomogeneity enhances water transport in desalination membranes. Science, Jan 1st, 2021 https://science.sciencemag.org/content/371/6524/72
    This 3D model of a polymer desalination membrane shows water flow — the silver channels, moving from top to bottom — avoiding dense spots in the membrane and slowing flow. (click image to enlarge)

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