Dialysis – a method of treating kidney disease – might also be the best method for treating certain types of wastewater, according to a new study.

The researchers, who have published a paper in Nature Water, are not suggesting we send expensive medical equipment to sewers.

Instead, they’ve developed a method that uses the same principles as kidney dialysis, and found it works “astonishingly” well at taking the salt out of high-salinity wastewaters.

“Dialysis was astonishingly effective in separating the salts from the organics in our trials,” says corresponding author Professor Menachem Elimelech, a researcher at Rice University, USA.

“It’s an exciting discovery with the potential to redefine how we handle some of our most intractable wastewater challenges.”

Lots of industries, such as petrochemicals, pharmaceuticals, and textiles, produce wastewaters very high in both inorganic salts and organic substances.

These 2 byproducts are hard to treat simultaneously. Salts tend to mess with biological treatments designed to handle organics, while pressure-driven desalination techniques fall prone to membrane fouling from organic substances.

“Traditional methods often demand a lot of energy and require repeated dilutions,” says co-first author Dr Yuanmiaoliang Chen, a postdoctoral student at Rice.

The researchers trialled a dialysis-style experiment in the lab instead.

Dialysis works with a semi-permeable membrane, that separates a patient’s blood from a specially designed waste fluid called a dialysate. The concentration of the dialysate means that small toxic molecules are leached through to the other side, while cells and proteins stay in the blood.

The researchers used the same principle, but with wastewater instead of blood.

They found that the technique could remove salts very easily from the salt-organic mixes, without needing large amounts of freshwater to do it.

“We found that one of the biggest advantages of dialysis for wastewater treatment is the potential for resource recovery,” says Elimelech.

“Beyond simply treating the wastewater, we can also recover valuable salts or chemicals, contributing to a more circular economy.”

The process is also much more resistant to membrane fouling, which vexes many a desalination process.

“By forgoing hydraulic pressure altogether, we minimised the risk of fouling, which is one of the biggest hurdles in membrane-based treatment,” says co-author Professor Zhangxin Wang, from Guangdong University of Technology, China.

“This allows for a more stable and consistent performance over extended operating cycles.”

While the method doesn’t purify wastewater, the team says it makes it much easier to treat in subsequent steps.

“Dialysis offers a sustainable solution for treating complex, high-salinity waste streams by conserving freshwater, reducing energy costs and minimising fouling,” says Elimelech.

“Its diffusion-driven approach could revolutionise the treatment of some of the most challenging industrial wastewaters.”