Greening the Islands Foundation


As Islands Move Towards a Green Economy, Water Desalination and Reuse Can Play a Crucial Role

Recently, I happened to send my publisher a book on the history of desalination going back thousands of years, which I have been working on for a long time. If one thing is clear from this account, it is that desalination became relevant and was used extensively on ships and islands before anywhere else. Between the 16th and 19th centuries, we already find desalination used on several islands, from Djierba and Malta in the Mediterranean to islands in the Caribbean, from Helgoland in the North Sea to Kamaran in the Red Sea, and many others.

This is not surprising: if an island, like a ship, does not receive enough fresh water to sustain its population, economy and agriculture, its safest bet is to rely on its own produced water. If this was true in some cases in the past, it is certainly true today, when desalination has become a well-established and environmentally safe technology with production costs similar to those of producing potable and safe drinking water from traditional natural resources such as surface and groundwater.

In fact, in most cases it is now much cheaper and more reliable to desalinate water directly on the islands to be served than to transport it by tanker or pipeline from the mainland. What is more, as the World Health Organisation (WHO) clearly states in the fourth edition of its Guidelines for Drinking Water Quality, published in 2017, desalination is the only process known to date that guarantees the production of safe drinking water in only one step: all that is needed after this is some disinfection to maintain its quality. 

Even the remineralisation step normally applied to desalinated water is mainly used to stabilise the water produced so that it is not corrosive to the metals – especially iron – in the distribution system, rather than to improve the quality of the desalinated water. This, in fact, is already potable when it comes out of the desalination plant and the salts needed by humans come mainly from the food they eat and not from the water they drink.

It is therefore not surprising that islands are increasingly turning to desalination. For example, I am pleased to see that islands in the archipelago of my region, Tuscany, such as Capraia and Giglio, and soon the largest, Elba, have now solved their long-standing problem of water shortage – especially during the tourist season when their population multiplies – by installing their own desalination plants. They no longer have to rely on the very expensive water brought in by tanker and the uncertainty of supply during periods of prolonged rough seas. 

With the cost of desalinated water now decreasing below US$1 per cubic metre for the largest plants in different regions, the cost is not much higher even on islands where such economies of scale cannot be achieved. With the rapid advances in renewable energy, be it wind, solar, wave or tidal, islands are perfectly placed to take full advantage of desalination in the context of a green economy. 

Renewable energy makes islands independent of external fuel supplies and, as the cost of renewable energy falls, the cost of desalinated water will continue to fall as well.

In the quest for reliable water supplies, another type of supply that takes advantage of desalination techniques at a much lower cost, and which is crucial to achieving a fully green economy, is the reuse of wastewater produced on an island. This is a well-established practice worldwide, although islands are lagging behind.

Once an island has collected its wastewater and treated it to a secondary level for safe discharge into the environment, usually the sea, it is only a further step to bring it to the level required for safe use, be it in agriculture, industry, washing and flushing. It can even be made perfectly safe for drinking, as is increasingly being done around the world, but this requires that the population concerned is properly informed and that the practice is widely understood and accepted.

For reuse, the main challenge on islands is often to collect most of the wastewater produced and deliver the appropriately treated water to users. As on the mainland, it is important that desalination is not seen as a panacea and used unnecessarily.  All natural water resources that can be used sustainably should be used, and losses in any distribution system should be reduced to an economic minimum: there is no point in even thinking about a desalination plant if the losses in the distribution network are 40 or 50%!

However, especially under the pressure of seasonal tourism, more and more islands are simply running out of water, and desalination and reuse are now the best options, in most cases certainly not bringing in water from outside, be it by tanker or pipeline. In reality, one viable option for bringing in fresh water from outside is possible in principle and is now gaining some momentum. 

This is where islands in an archipelago or in relatively close proximity are supplied with water by a dedicated boat carrying a desalination plant onboard, which can move from island to island with a production schedule that ensures it can keep up with demand on each island it serves. This practice is not yet widespread, but is attracting increasing attention.

Despite all the features that make desalination a very desirable option for islands, we must be aware that for many citizens and local governments desalination and reuse are still rather novel concepts, even though more than 5% of the world’s population already relies on desalinated water for their water supply. As a result, the trend in desalination development is still below what would benefit islands.

Public acceptance is not helped by the often unjustified concerns about the disposal of brine, which is nothing more than more concentrated seawater that can be safely returned to the sea and diluted with a properly designed system. Negative environmental impacts have only been reported in cases where the brine return system has been poorly designed or not designed at all, as happens with any poorly designed solution in any field.

In any case, concerns about brine should not persist for long, because the time is coming when brine will also become a resource to be exploited. In fact, it is already being explored as a source of the rare metals so badly needed by industry, particularly renewable energy.

Within the overall context described above, Greening the Islands is committed to disseminating useful and reliable information and to helping islands to analyse where they are and to chart a course that their inhabitants will be happy to follow, to ensure that their water supplies are secured within an overarching green economy. If there is any place where this is potentially achievable, it is certainly in the islands.

Emilio Gabbrielli

Emilio Gabbrielli

On Key

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