Solar wastewater treatment could bring clean water to remote places

by | Sep 22, 2023

This cost-effective solar evaporation device could supplant lengthy and expensive filtration systems normally used in wastewater treatment.
A pool of rippling water.

Wastewater and seawater purification can be an energy-intensive process. According to some estimates, wastewater treatment plants account for between 1% and 3% of total global energy output. And as climate scientists predict longer, more intense periods of drought through the end of the century and beyond, it’s clear that the world needs more efficient ways of delivering clean, drinkable water to the communities that need it the most.

Researchers at the National Engineering Research Center for Marine Aquaculture, Marine Science and Technology College at Zhejiang Ocean University in Zhoushan, China are helping advance this goal with a solar-powered device that can turn wastewater into clean water.

Addressing a global need

In their paper published in Advanced Materials, the researchers said similar studies have focused primarily on desalination, or removing salt from seawater. Their research is different, they wrote, because it focuses on removing organic pollutants from industrial and domestic wastewater.

Their device — called CCMs-x — uses solar vaporization technology to purify and desalinate water at a reduced cost and with greater efficiency compared to conventional water purification systems. They believe a device that can both desalinate and remove pollutants would have practical applications for inland and remote areas as well as coastal regions.

Yingtang Zhou, one of the researchers who worked on the project, said his team developed the technology because they saw a need for an inexpensive wastewater purification system that could be used in economically disadvantaged communities.

Across the world, around two billion people don’t have reliable access to clean water. For at least part of each year, close to half of the world’s population also experiences water scarcity. This leaves communities vulnerable to water-borne diseases as well as water scarcity problems like thirst and crop failure.

Bringing clean drinking water to vulnerable communities isn’t always easy, though. Disadvantaged communities, especially those in remote parts of the world, “encounter challenges in affording the maintenance costs of large-scale desalination plants,” Zhou said. Some treat contaminated water with basic techniques like prolonged exposure to sunlight or ceramic or biosand filtering, but these methods don’t always remove all contaminants.

Better results at a reduced cost

In their paper, the researchers said the CCMs-x device can remove more than 95% of pollutants in less than one hour. Zhou said the device is not only remarkably more efficient than conventional devices, it’s also significantly safer and exceedingly easier to use. These qualities could potentially make the CCMs-x a practical alternative to more complex and expensive water purification systems.

The CCMs-x device is made using organic–inorganic hybrid nanocomposites, which contain both organic molecules and inorganic materials. The researchers made their device more efficient by placing photothermal materials—which absorb light energy and convert it into heat—close to an evaporation surface. The concentrated heat speeds up the production of steam, which quickly and efficiently separates the water from the impurities.

“This device features a specialized sponge with numerous channels for efficient water flow, along with advanced materials like [silicon dioxide] and [cobalt oxide] to maintain a slippery surface and break down pollutants,” said Zhou.

The CCMs-x device would be less expensive to install and operate than conventional systems, and it would have other advantages, too. The researchers said their device can be scaled up for areas with higher demand. Importantly, it would also be easy to transport. The materials can be bent and folded, making them more practical for storage and transportation to remote places. The researchers also said the device is durable, salt-resistant, and resistant to bacterial contamination.

It may take a little more time and research before the CCMs-x will be ready for practical use, but the technology’s potential is clear.

“Cost-effective solar evaporation devices have the potential to supplant lengthy and costly filtration systems utilized in wastewater treatment,” Zhou said. “This not only confers substantial economic benefits but also addresses the issue of freshwater scarcity in remote areas.”

Reference: Y. Zhou, et al., Customized Microenvironments Spontaneously Facilitate Coupled Engineering of Real-Life Large-Scale Clean Water Capture and Pollution Remediation, Advanced Materials (2023). DOI: 10.1002/adma.202306103

Feature image credit: Cia Gould on Unsplash

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