Invention produces cleaner water with less energy and no filter

Morgan Kelly ・ Princeton Environmental Institute

Researchers in the lab of Howard Stone, professor of mechanical and aerospace engineering and PEI-associated faculty, have reported in the journal Nature Communications a technique for using carbon dioxide in a low-cost water treatment system that eliminates the need for costly and complex filters.

The same technology that adds fizz to soda can now be used to remove particles from dirty water. Researchers at Princeton University have found a technique for using carbon dioxide in a low-cost water treatment system that eliminates the need for costly and complex filters.

The system injects CO2 into a stream of water as a method of filtering out particles. The gas, which mixes with the water in a system of channels, temporarily changes the water’s chemistry. The chemical changes cause the contaminating particles to move to one side of the channel depending on their electrical charge. By taking advantage of this migration, the researchers are able to split the water stream and filter out suspended particles. 

“You could potentially use this to clean water from a pond or river that has bacteria and dirt particles,” said Sangwoo Shin, an assistant professor of mechanical engineering at the University of Hawaii at Manoa. Shin, the lead author of a paper describing the process, performed the research as a post-doctoral researcher in the laboratory of Howard Stone, the Donald R. Dixon ’69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering at Princeton.

In a paper published May 2 in the journal Nature Communications, the researchers describe how they built a laboratory-scale filter that removed particles three orders of magnitude (1,000-fold) more efficiently than conventional microfiltration systems. The system is low energy, with bottled carbon dioxide as the only moving part (besides the pump responsible for the flow), and has no physical filter or membrane that can clog or require replacement.