Green membrane is a step toward eco-friendly desalinationSiobhan Treacy | November 17, 2020
Researchers from KAUST created a non-toxic coating that would provide a safe and more efficient alternative for cleaning reverse osmosis systems. Typically, harmful chemicals are used to clean these water desalination systems.
In reverse osmosis desalination, pressure is used to filter seawater through a semipermeable membrane to create fresh drinking water. This method is an energy-efficient approach to desalination. But its performance is stalled by bacteria and other microorganism growth on the membrane’s surface. Also, the biofilm used cannot be completely removed from the membrane system, which creates permanent fouling, elevated energy consumption and toxic chemicals end up in the sea.
The team’s new biofilm can be removed and doesn’t use any toxic chemicals to attach the membrane. It can be safely flushed out of a reverse osmosis system with brine and a stronger flow, leaving the membrane surface clear of biofilm.
The coating attaches to the surface by electrostatic interactions. There are no chemicals involved and it doesn’t need to be pretreated.
The team tested the coating with a membrane fouling simulator, a small device that mimics the conditions in reverse osmosis desalination plants. They circulated the coating through the system five times to create layers on the surface of the membrane. They added biodegradable nutrients to encourage biofilm growth. After eight days, they flushed the system with a strong flow of high saline solution for 24 hours to remove the coating.
Researchers used transmission electron microscopy and found that their coating remained stable in salty water, which means it can be used for seawater desalination. By increasing the strength of the water flow and water salinity, the team found they could remove the coating and attached the biofilm from the membrane.
After the cleaning process, the flow of liquid through coated membranes was two times higher than non-coated control.
A paper on the new membrane was published in Desalination.