DESALINATION: AN OVERVIEW
Water, water everywhere, nor any drop to drink. 71% of the Earth’s surface is covered by water but of this 96.5% is found in seas and oceans. Population growth, urbanisation and industrialisation have directly or indirectly brought about the situation that a water crisis exists or one is looming. For many access to safe water has improved but this has exacerbated the shortage to the point that future geo-political developments may target ownership of this limited resource. The solutions are varied but desalination of seawater or brackish water is one of them.
In the southern African context the very low rainfall in the Cape has raised the profile of the use of desalination as one means to relieve the shortage of safe water but in fact the trend started in 2010 with a number of small regional plants. Although not seawater fed, there have also been a number of plants set up to treat polluted water resulting from mining and industrial activity. The processes used may be classified according to the technology used – membrane (reverse osmosis and nanofiltration) or thermal (distillation, evaporation and crystallisation). Each has their pro’s and con’s but membrane technology has been favoured in South Africa for seawater desalination and sea water reverse osmosis SWRO is the focus of this review.