Desalination: a sustainable solution for drinking water supply

While climate change heralds drier years, many of the world's inhabitants are rethinking their traditional expectations of water supply. Population and demand are also increasing, and new supplies will be needed..

In many parts of the world, this situation is changing, as desalination comes into play. Several factors are converging to bring new plants on stream. The population has boomed in many water-stressed areas, including parts of China, India, South Africa and the USA. In addition, drought - part of which is attributable to climate change - is affecting many regions which, not so long ago, thought they had sufficient reserves.

Algeria's response to the challenges posed by rising demand, climate change and high population growth (around 1.9% per year), combined with significant urban expansion, must be tackled in order to cope with water scarcity.

In the early 2000s, Algeria experienced the worst drought in living memory (known as the millennium drought). We applied a number of techniques, including conservation, water trading, water recycling, interconnecting the city's drinking water supply network with dams, water transfer, desalination, organizing water distribution by tanker trucks to the worst-affected neighborhoods, and building artesian boreholes. However, by far the biggest response in terms of capital investment has been a multi-billion dollar program for seawater desalination.

Among the measures taken in response, the contribution of desalination through 11 plants along the Algerian coast has enabled a cumulative production capacity of 2.2 million m3/d. These plants produce 18% of the total quantity of drinking water consumed nationwide, equivalent to 770 M m3/year. It is thanks to desalinated seawater that Algeria's coastal cities will be able to ensure their long-term water security. With this in mind, experts generally recognize the importance of climate-resilient water sources offered by desalination.

Despite all the obvious benefits of desalination, critics of this choice have been vocal. However, desalination plants will be in operation for at least 25 years, during which time there will inevitably be more droughts, growing demand and a likely drier, hotter climate. Due to this summer's dry conditions, water storage in dams has fallen below 50%, triggering the need to launch five new desalination plants with a production capacity of over 300,000 m3/day each in the east, west and center of the country in order to preserve the country's strategic water reserves and put an end to the water shortage problem that has persisted for months.

On the other hand, the adoption of desalination in Algeria as a means of securing the country's drinking water supply has not only led to the training of qualified personnel and the creation of specialized academic courses in the field, but also to the launch of a dynamic in the area of national integration through the national industrial sector, marked in particular by the construction of several demineralization plants, either through our own efforts or in partnership, which will undeniably reduce investment costs and save foreign currency.

This was made possible in part by the reduction in capital expenditure (CAPEX), which can be subdivided into two main categories: direct and indirect costs.? Direct costs include equipment, buildings and other structures, pipelines and site development, and generally represent between 50 and 85% of total CAPEX.? The remaining indirect costs include usual bank rate and financing costs, engineering, legal and administrative fees, and contingencies. Indeed, national integration has helped to substantially reduce this CAPEX.

Furthermore, such a choice could be motivated by the fact that desalination technologies are indeed suitable for treating water from a wide variety of sources, including, but not limited to, brackish groundwater, surface water, seawater and domestic and industrial wastewater.? As desalination technologies have developed and improved, the cost of building desalination plants has fallen.? This lower cost has been one of the main factors in the acceptance, growth and success of desalination.? Today, in some locations, the cost of desalination has fallen by up to 20% compared with 2010, due to technological developments linked to lower membrane prices and longer membrane lifetimes.? Technological improvements in membrane design and system integration have also reduced the cost of desalination.

One of the important lessons we learned in Algeria is the importance of developing a portfolio of water sources, some of which are independent of weather and climate. So it's not a question of having to choose between desalination and other sources of supply or economic instruments - it's wise to consider them all.

Worldwide, it is estimated that by 2025, two-thirds of the world's population will face water shortages, for which governments need to establish functional policies that address social concerns about access to water for the population, while securing the resource for industrial and agricultural purposes. The UN's 2030 Agenda aims to: "ensure the availability and sustainable management of water and sanitation for all". Different water management strategies, as well as decarbonized desalination and improved irrigation systems, are key elements in achieving this sustainable development goal.

At Mediterranean level, according to a report by UNEP/MAP and Plan Bleu 2020, desalination capacity in the Mediterranean basin has increased in recent decades, and desalinated seawater production in the MENA region should be thirteen times higher in 2040 than in 2014, with the most advanced countries currently being Algeria, Egypt, Italy and Spain.

Investment in safe water sources such as seawater desalination will provide fast, affordable solutions without negative environmental impact. Such supplies are always available in times of drought and scarcity, and will ensure that generations of people living in coastal cities will enjoy a lifestyle based on a secure water supply.

?