Sedgefield a huge success.

THE new state-of-the-art desalination plant in Sedgefield has only been operating for a month, but already Knysna’s municipal officials are sold on the idea that the purification of sea water offers a long-term and environmentally friendly solution to the Garden Route’s ongoing drought problems.

The “reverse osmosis” purifying process used at the plant to desalinate sea water is not a new concept, but a number of the technological innovations employed in the Sedgefield operation are considered groundbreaking.

Foremost is the new plant’s ability to harness and re-use the pressure energy produced in the reverse osmosis process, a bit like a turbocharger recycles energy in a car. This results in a saving of a up to 40% of the electrical energy required to run the plant.

As a result, the cost of producing quality potable water has been cut to about R3 per kilolitre – only slightly more than the R2 to R3 per kilolitre cost to harvest and purify water using traditional methods.

Also, desalination will become even cheaper in the future as new energy technology is developed.

Rodney Nay, head of Knysna’s project management unit, and

councillor Andrew Finn, chairman of the infrastructure and development

committee, show off the workings of the desalination plant in Sedgefield.Picture: NEIL OELOFSE

Reverse osmosis works by forcing sea water through many layers of a specialised membrane under high pressure, leaving the salt concentrate on one side of the membrane and desalinated water on the other.

Concerns about the environmental impact of the Sedgefield plant have been largely allayed since the production of potable water started on December 23.

The ratio of waste water to purified water produced at the Sedgefield plant is roughly 55:45, which means that the waste or “brine” returned to the ocean has slightly less than double the salt content of normal sea water.

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