From The Editor | May 18, 2017

Weighing The Power Of Simplified Membrane Systems

Peter Chawaga - editor

By Peter Chawaga, Associate Editor, Water Online

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Membrane technology seems to be one area where water treatment is taking consistent strides forward. There have been recent projects to explore the future of 3D-printing, the use of nanotechnology, and ways of incorporating artificial intelligence into membranes.

But problems with mainstream membrane technology persist and there are still opportunities for work to be done. While some problems are being solved with space-age solutions, others aim to make use of the simplest forms of technology.

With this approach in mind, researchers from the University of British Columbia (UBC) are the latest to take membranes to the next level. They have developed fiber membranes that utilize a biofilm as a second line of defense and, while this isn’t particularly novel, the system’s use of good old gravity to clean the membranes (known as “scouring”) has unlocked an innovative potential for cost- and labor-savings.

“We do not use blowers and pumps to generate the turbulence to scour the membranes and we do not use chemicals to remove material that cannot effectively be removed by scouring,” said Pierre Berube, the research lead and a civil engineering professor at UBC. “Turbulence is generated by gravity. The approach that we developed generates very turbulent conditions at the membrane surface, without the need for pumps and blowers.”

Berube compares the process to “what happens when you flip over a bottle full of water.” As the water pours from the bottle, air rushes in to replace it, generating turbulence inside. The biofilm on the membrane surface is capable of eating away at whatever this gravity-powered scouring cannot remove.

The research was inspired by a common problem at treatment operations in Canada and the U.S., as well as the rest of the world.

“For many small communities, the greatest challenge is access to financial and technical resources for the long-term operation of water treatment systems,” Berube said. “So, we wanted to develop a system that could effectively treat water, but that would require limited maintenance.”

The researchers conducted a four-year, systematic study into the components of a membrane system in order to identify areas where tradeoffs could be made to reduce labor but maintain performance. After two additional years of design, their pilot system incorporates all of these tradeoffs, with gravity scouring being a first-of-its-kind component.

“Conventional systems use blowers and/or pumps to add air and water into membrane systems, generating turbulence at the membrane surface… Conventional systems also use chemicals to remove material that cannot be removed by scouring,” said Berube. “Although effective, these systems are responsible for most of the complexity and cost of membrane systems. Because the goal was to limit operational complexity, we needed to reinvent how cleaning could be applied.”

The researchers are currently piloting the system at commercial scale and plan to begin a second pilot soon. Within six months to a year, they hope to move beyond piloting. Though the systems are built around commercially available membranes, it is unlikely that a simple retrofit will be enough to incorporate the technology at treatment operations.

“The design is completely different than conventional membrane systems because the blowers, pumps, and chemical systems typical of conventional systems are not required,” Berube said. “This not only significantly decreases the complexity of operation, it also significantly decreases the complexity of the design.”

As the project moves forward it aims to show that the simplest solutions can have the biggest impact.