Additive prevents biofouling in reverse osmosis membranes

Flinders University has been granted a provisional patent through Flinders Partners, the commercialisation arm of the university, for an additive that prevents biofilms from clogging up membranes used in the desalination of seawater.

The provisional patent is between Flinders University, US membrane manufacturer NanoH₂O, SA Water and Adelaide-based global renewable energy company Wind Prospect. The additive was developed by nanotechnologists led by Associate Professor Amanda Ellis.

Associate Professor Ellis explained that reverse osmosis membranes help produce pure water by filtering out salt and other effluent materials from the ocean under high pressure. The problem with these membranes, she said, is biofouling, “which occurs when microorganisms accumulate and grow on top of the membrane and stop water from flowing through”.

“This means the membranes have to be cleaned more frequently and it also drives up energy consumption, because you have to increase the pressure in the membranes to get the same amount of fresh water through.

“But the major issue is that the membranes are not recyclable, so when there’s biofouling they don’t last as long.”

The new additive can be easily incorporated into the membrane manufacturing process for just a few cents per membrane, said Associate Professor Ellis, making the surface of the membrane appear ‘neutral’ so organisms do not recognise the surface and therefore keep moving through the saline flow stream.

“It’s just an added chemical in the membrane manufacturing process - there’s nothing complicated about it and the cost is insignificant from a manufacturer’s perspective,” she said.

She said laboratory tests have confirmed the additive removes nearly all biofouling from the membrane while having no impact on salt rejection. Other advantages are: “These new membranes lower energy use because you don’t need to apply as much pressure to maintain the flow rate; you don’t need to clean the membranes as often because there’s virtually no biofouling; and you don’t need to replace them as often, which reduces environmental waste.”

The project was initially funded through a $60,000 grant from the South Australian Department for Manufacturing, Innovation, Trade, Resources and Energy in December 2012. Now NanoH₂O is now making membranes containing the additive - with a key aim for the membranes to be used in South Australia’s desalination plants - while Associate Professor Ellis hopes to lodge an application for full patent by April 2014.