#WaterWatch

Reverse osmosis water is purer than our tap water - engineering professor

On Friday the TimesLive reported that seventeen years of work aimed at purifying mine wastewater could start paying off close to home for the University of Cape Town.

Professor Alison Lewis, Dean of Engineering and the Built Environment at the University of Cape Town (UCT) says all of this work has been done by post-graduate students who studied at UCT.

What's really cool about it, is you take your mine water and drop the temperature to a point where the water in the brine freezes out as pure ice and because it's lighter, water will float.

Prof. Alison Lewis, Dean of Engineering and the Built Environment at the University of Cape Town (UCT)

And the contaminates in the water will crystallise out as pure salt and because they are heavier than water, will sink.

Prof. Alison Lewis, Dean of Engineering and the Built Environment at the University of Cape Town (UCT)

So you have a very simple conceptual separation process with ice floating and the salt sinking, almost deconstructing the decontaminated water, adds Lewis.

Lewis explains that should Cape Town opt for desalination then the city needs to bear in mind that reverse osmosis is very inefficient.

What you're doing is, you're pumping the salty sea water through a very fine membrane that will reject the salt on one side and recover the water on the other. Its only 40% efficient.

Prof. Alison Lewis, Dean of Engineering and the Built Environment at the University of Cape Town (UCT)

But, reverse osmosis water is purer than our tap water says Lewis.

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