Cost of Desalination of Sea Water in Cape Town.

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Desalination plant Picture this scar between your home and the sea.

While doing some work for an informal settlement in Stellenbosch I came across some fantastic research.  A Zimbabwean woman Rejoice Melisa doing her Ph.D at Stellenbosch on treatment of Acid Mine Drainage (AMD) she had concentrated her efforts on producing desalinated water from this toxic water not by Reverse Osmosis (RO) but by freezing the water to create ice which is removed as a slurry in the form of pure but frozen  water.

The freezing process of sea water too removes the salt.  When I queried the energy cost of the process of purifying the water through this desalination process, she boldly informed me that this was a seventh of the cost of flash evaporation and condensation.  I was not provided with any details of the comparison of the desalination cost of her freezing and thawing method against the cost of RO.


When one considers the cost of building a RO plant, turn your eyeballs into Dollar signs.  Based on other plants globally for the supply of water to just over a million people the cost of building that size of RO plant will be upwards of 120 billion Rand.  That is just the start!  The cost of electricity is around 10 kilowatt hours per kilolitre.  This means that for Cape Town  at say 200 000 kilolitres per day the electricity energy would be 2 million kilowatt hours per day or 2000 megawatts, the size of a medium sized power station.  Clearly we do not have the money  in the form of capital or the energy from ESKOM for this.

We await a court ruling as to whether Cape Town City will be allowed to get some power from IPP’s (Independent Power Producers).  If not then please abandon all prospects of building a desalination plant in Cape Town.

This though is only the money.  What about environmental concerns as well as history in Cape Town of desalination plants.  What have we learnt?

Cape Town has built four such plants, only small ones, but they wanted and tried to build more but were stopped from doing so as those living nearby objected strongly to this and simply asked to see the EIA (Environmental Impact Assessment) of which of course there was a blissful ignorance.  In other words no such impact assessment was carried out.

Just as well for us that the City did not know what they were letting themselves in for by only having four built for many reasons but the best ones are these.

  • Day Zero never happened. The power of demand management through whatever means saw Cape Town through.
  • All of the desalination plants that were completed ceased to work. This was for various reasons but chiefly some failed thanks to an algal bloom in the water, and the one in the Waterfront found that there was too much sewerage effluent from the Citie’s own pumped outfall sewerage lines for them to cope.*
  • The Department of Water Affairs gave them a licence for only three years for these desalination plants and time is running out.
  • Every one of the temporary desalination plants built in the drought in the Garden Route area have all been abandoned and are now dysfunctional. Cape Town is not alone in this, but have we not learnt our lesson?

It was fascinating to hear how the Mayor – now Minister of Public Works boasted about how a well-run city will “never run out of water”.  She was right of course but it was more thanks to a very diligent and compliant population than from the City.  The citizens came to the party big time.  Every house I visit still today has grey water buckets for flushing toilets.  If ever I requested to use the toilet, I would be told sternly “not to flush” which was one step further yet in the old adage “if its yellow let it mellow, and if its brown flush it down”.  That used to be using municipal water , but now the flush is done with grey water.  In this line, I came across a very endearing ditty: “in this land of sea and sun, we do not flush for a number one”

Now we have Councillor Xanthea Limburg promising that we will get permanent desalination plants.  Best of luck Councillor, but I don’t know where you are going with this given our history of

Rather like energy, those ways that make lots of money (water and energy) they want their pound of flesh.  On this topic they have turned very nasty if one uses too little water or energy.  These two however are inextricably linked.

Water and Energy are inextricable linked.


Environmentally, desalination of sea water is a long fuse but  big explosion.  Those in the Mediterranean and around the Arabian Peninsula all pour brine into the seas which have no current action to remove the brine and mix this into an ocean.  The brine is super saline water that needs to be discarded, and the pure water is the water that is used in the pipelines for drinking purposes. Even in fast moving current action, the brine is denser than sea water and sinks to the bottom of the ocean and fills undersea valleys where everything will eventually die forming new desserts under the sea.

If the energy for desalination in South Africa must come from far afield as the coal powered power stations in Mpumalanga and or near the Botswana border, the amount of carbon dioxide produced only to make water will be an ironic joke.  If however the city is able to persuade ESKOM to allow them to buy clean energy which ESKOM does not supply, then it may start to make sense even though very little.

To compare costly desalinated water at say at cheapest R30 per kilolitre for the City Councial and deliver this water at present rates of under R20 per kilolitre makes no sense whatsoever.

*Cape Town City put out the specifications for the temporary desalination plants.  The specification read that there would be a variance of 10% in water quality.  It was found that the quality varied by 400% causing the contractors to change filter cartridges every 8 hours instead of every 2 months.  Naturally the City disputes this. And it looks like the whole issue will end up in court.  Meanwhile the plant is not operating at all nor is any water being produced.

Like this as your neighbour?  Possibly the largest desalination plant in the world.


There has been massive anger in Australia over desalination plants dotted around the coast.  Protests drawing hundreds of people objecting to the plants sprung up all over the coastline.

If Demand management works so well, and Cape Town has proven that it works so well that demand for water is around one third of what it used to be, why then invest in the high fruit when low hung fruit is readily available?

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