Desalination Breakthrough Could Lead to Cheaper Clean Water

Paper co-author Kaitlin Brickey, a Penn State graduate student in chemical engineering, stands in front of the scanning electron microscope that allowed researchers to examine how dense pockets in membranes could hinder efficient water filtration efforts. (Credit: Tyler Henderson/Penn State)

(CN) — A major advancement in water filtration technology revealed Thursday may lead to lower water prices and greater availability throughout otherwise dry areas of the globe.

The vast majority of water on Earth is found in oceans, so lowering the cost of filtering seawater could dramatically improve the quality of life for people living in regions without much rainfall or groundwater.

Whether found in a home kitchen or a giant industrial facility, most water filters work the same way. 

Water is pumped under pressure through one or more cylinders containing a porous material which separates out particulates like salt and sand, along with other adulterants like chemicals in a process called reverse osmosis. 

Reverse osmosis has always been fairly inefficient, using a lot of energy and wasting a lot of water, so there is certainly room for improvement.

To this end, a team of scientists from the University of Texas at Austin and Penn State have identified a few snags in the process that could reduce its cost and the amount of wastewater produced, which they describe in a study published in the journal Science.

“Fresh water management is becoming a crucial challenge throughout the world,” said Enrique Gomez in a statement, a professor of chemical engineering at Penn State who co-led the research. “Shortages, droughts — with increasing severe weather patterns, it is expected this problem will become even more significant. It’s critically important to have clean water availability, especially in low-resource areas.”

Researchers managed to improve reverse osmosis efficiency a whopping 30% to 40% by analyzing nanoscale reconstructions of the filtering membrane using an electron microscope, then running the output data through a supercomputer.

By modeling the pathways water takes through a membrane, the team discovered that membranes aren’t constructed in a uniform width. 

Because water follows the path of least resistance, thinner areas of the membrane lead to water molecules bottlenecking in certain places in the filter. The researchers determined that structurally uniform membranes are a major key to improving their efficiency.

The impetus for the study came when researchers from DuPont, a company that makes numerous desalinization products, counterintuitively found that thicker membranes were better at filtering water. Their discovery flew in the face of conventional wisdom which had long held thicker filters to be slower and less efficient than thinner versions.

“Reverse osmosis membranes are widely used for cleaning water, but there’s still a lot we don’t know about them,” said Manish Kumar, an associate professor at UT Austin, who co-led the research. “We couldn’t really say how water moves through them, so all the improvements over the past 40 years have essentially been done in the dark.”

Reverse osmosis filtration is responsible for 66% of the world’s desalination capacity and produces 21 billion gallons of fresh water per day. 

The country of Israel, located between a Middle Eastern desert and a giant body of salt water, produces over half of its total water supply using reverse osmosis, allowing for a renowned agricultural belt to thrive in one of the world’s driest regions.

The technology also plays a critical role in any plan for deep space travel — it costs over $80,000 to place a single gallon of water in orbit — thus without a fresh supply at the ready, wastewater will need to be safely cleaned and recycled if humans are to explore further into the solar system.

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