Local university teams create protein membranes

As PUB works to improve its water treatment technologies, it seems to have found a promising resource in nature.

This comes in the form of a protein called aquaporin, which acts as a gate that allows only water molecules through. Hence, when seawater is pushed through it, for example, salts such as sodium chloride and various pollutants are filtered out.

Aquaporin is found in all living things, including bacteria, in mangroves and even in the human kidney. And Singapore researchers have used it to successfully create membranes that can be used at desalination plants to treat water.

Aquaporin membranes can purify water at lower pressures than is required for conventional polymeric membranes, which helps reduce energy costs.

Associate Professor Tong Yen Wah, from the department of chemical and biomolecular engineering at the National University of Singapore, said the flat-sheet membrane developed by his team could lower the cost of water purification here by up to 30 per cent.

The membrane, which the team started developing in 2009, requires only about a tenth of the pressure needed by conventional membranes - which could theoretically reduce the energy used and electricity costs incurred by 70 per cent, said Prof Tong.

However, his team's aquaporin membrane costs two to three times more than conventional membranes. As a result, the cost savings come to 30 per cent.

Prof Tong noted that tests in the laboratory show the membrane's water permeability is at least six times better than that of commercial membranes.

The team will test the membrane at a PUB water-reclamation plant next year.

Meanwhile, Nanyang Technological University has developed its own version of aquaporin membranes, which it began to sell in 2013 through a start-up company called Aquaporin Asia.

The search for a new technology, which started around 2010, was done at its Singapore Membrane Technology Centre.

The centre's director, Professor Wang Rong, who led the team, said the flat-sheet membrane that it developed in 2012 has a water permeability that is about 40 per cent better than that of conventional membranes. The energy required is about 25 per cent less, which also means cost savings.

Last year, the team went a step further and used aquaporin proteins to develop tube-shaped hollow-fibre membranes, which are easier to scale up than flat-sheet membranes, said Prof Wang.

Tests show the hollow-fibre membranes have an improved water permeability of twofold compared with conventional membranes, which could reduce the energy needed by 40 per cent.

Said Prof Wang: "The next step is to scale up. We are also in discussions with industry players to commercialise the hollow-fibre membranes."

samboh@sph.com.sg

This article was first published on November 27, 2015.
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