Water, water, everywhere

S And not a drop to drink...

O you thought oil was big business? Try water. According to the experts, clean water – for drinking, irrigating, manufacturing and myriad other applications – is worth a staggering R3 000 billion annually.

It doesn’t take a rocket scientist to figure out why. Basically, there’s just not enough of it to go around. Although most of our planet’s surface is covered by H2O, most of it is in the form of seawater, and useless in terms of human survival (that is, if you discount the fish we eat). Freshwater sources such as lakes, rivers, aquifers and dams provide enough water for most of us, but storing, delivering and purifying it costs money – and if we live far from the source, we’re talking lots of money.

Many sociopolitical gurus expect water to overhaul oil as the most critical, and certainly the most emotive, commodity before the end of this century. It’s even possible that countries will go to war over it. As economies grow, so industry and agriculture will demand a bigger slice of the water pie. The general consensus is that we have about 30 years before population growth and global warming make us nasty. Botswana and Namibia have already squabbled over water rights to Etosha and Okavango, and that’s quite close to home.

Grahamtek Systems of Somerset West reckon they’ve got the answer. It’s a system called reverse osmosis desalination, and if all goes according to plan, it’s about to shake up the desalination industry. Company founder William Graham is so confident about the efficacy, affordability and potential of his patented system that he’s posted a bold slogan in his office: “Any water, anywhere, any time.”

This company’s revolutionary approach to desalination has dramatically reduced the cost, both financial and environmen- tal, to a point where it has become a genuinely practical alternative for thirsty regions such as ours. Its plants are already churning out fresh water at the coast, purifying brackish borehole water in the interior, and filtering out all manner of toxic industrial waste in between. Here’s the interesting bit: no chemicals are used in the process.

Knowing what he does about desalination, and his company’s cost-effective process in particular, Graham is puzzled by the apparent reluctance of municipalities to embrace the technology. “Why not make use of the immense reservoir around us?,” he asks.

He has a point. The salty sea accounts for about 97 per cent of our planet’s water and another 2 per cent is locked in ice caps and glaciers, leaving just 1 per cent (fresh water) for the billions of humans and animals who occupy terra firma. Reverse osmosis caught Graham’s attention while he was building a desalination plant on the Cape West Coast for what was then the Department of Water Affairs. He developed an interest in membranes, and began to explore ways in which the plants could achieve higher flux rates (fresh water yields). A strong magnetic field was one option, but there was another concept with even more potential. His next question: “Why doesn’t the world look at bigger membranes?”

It made perfect sense. A bigger membrane (filter) would produce a higher flux, bringing costs down. The conventional membrane diameter was 20 cm; Graham ended up designing a 38 cm diameter membrane – at that time the biggest in the world. So was born Grahamtek, a South African company with a truly global perspective.

But the big membrane is only one component in a system with many variables. Other innovations, including an integrated flow distributor, the use of electromagnetic fields, an energy recovery device and a modular skid platform, contribute to the overall efficiency of the system.

Each pressure vessel houses two membranes in series, encapsulating a membrane area of 316 m² in total. Their podgy appearance belies the fact that they take up considerably less space than desalination plans of conventional design. In a conventional vessel, you’d need up to seven membranes to achieve an equivalent membrane area. To put the Grahamtek design into perspective, a plant that can produce one million litres of drinking water a day fits into a 6 m container.

Each membrane is made up specifically to match its raw water source. For example, a synthetic plastic membrane with a pore size of 0,0002 microns is used to process seawater. It takes 46 leaves (individual membrane segments), each 1,4 m long, to construct one membrane.

Making these leaves is labour-intensive. The feed (raw water) spacer, membrane and permeate (fresh water) spacer are fed through rollers under tension before being folded in half and glued along the sides, making them look like open envelopes. The spacers keep the membranes from collapsing under pressure and blocking the flow of water. The open ends are then glued to the perforated permeate pipe running through the centre of the membrane before being wound around it under pressure and 1961 In the good old days of typewriters, correcting a mistake was not as simple as hitting backspace. Well at least not until the “white out” strip was invented. By placing the strip over your error and then re-typing over the strip, you would be left with a blank space to restart your sentence. PM