With the world's population increasing and climate change affecting rainfall patterns, large parts of the planet are facing severe water shortages. Several regions that traditionally had reliable water supplies are now experiencing water scarcity issues. According to the United Nations, over 1.1 billion people globally lack access to water and a total of 3.6 billion face water scarcity for at least one month each year. If no action is taken, it is estimated that two-thirds of the world may be living under water stressed conditions by 2025. With current freshwater reserves unable to meet demand, nations are looking at new water sources and technologies to secure their water needs.
Emergence of Desalination as a Water Desalination Industry
One technology that has emerged as a promising method to augment freshwater supplies is desalination. Global Water Desalination By removing salt and other minerals from seawater or brackish water, desalination plants can convert non-potable water into fresh drinking water. Traditionally an expensive option, advances in membrane technology coupled with increasing water scarcity have made desalination economically viable in recent decades. The global installed capacity of desalination plants rose from around 30 million cubic meters per day (m3/d) in 2000 to over 90 m3/d currently. The Middle East leads the world in desalination with over 50% of global capacity located in the region. Countries like Saudi Arabia and United Arab Emirates obtain over 50% of their drinking water needs from desalination.
Growing Desalination Markets Outside the Middle East
While the Middle East pioneered large scale desalination, newer markets are emerging globally propelled by water scarcity. In Australia, desalination plants play a key role in securing urban water supplies for cities like Perth and Sydney. California too has built several new plants, with one facility in San Diego providing over 50% of the region’s water needs. With depleting groundwater levels affecting agriculture, India has launched an ambitious program to construct over 1,000 village-level desalination plants. Countries in Africa and Latin America are also actively exploring brackish and seawater desalination projects to address water security concerns. Multilateral agencies are supporting such initiatives through concessional loans and technical assistance.
Membrane Technology Drives Down Costs
At the heart of modern desalination is membrane technology that acts as a semi-permeable filter to separate salt from water. Early plants used thermal distillation that consumed huge amounts of energy. However, the proliferation of reverse osmosis (RO) membrane systems since the 1990s has boosted efficiency while lowering energy usage. Continual material science innovations have improved membrane tolerance to fouling and increased throughput. These advances along with plant design optimisations and use of renewable energy have helped reduce desalination costs significantly. Energy requirements for seawater RO have dropped by over 60% in the last two decades. Today, desalination costs are estimated at US$0.50-1.00/m3 for large plants, making it economically viable for many new locations.
Challenges of Environmental Impacts and Brine Disposal
While desalination expands access to freshwater, its uptake does pose some environmental challenges. Construction and operation of large plants involves substantial land use and carbon footprint from power consumption. Often situated along coastlines for logistical reasons, the plants can negatively impact local marine ecosystems. Additionally, for every one unit of freshwater produced, desalination creates one unit of brine discharge that is 1.5-2 times more concentrated than seawater. If not handled properly, brine disposal can damage coastal and marine life. Regulations differ globally but focus on minimizing pollution by deep well injection or diffusers to dilute effluents. Still, long term impacts on marine ecology need careful evaluation, especially in biologically sensitive areas. Other issues include suitable siting away from habitats and considering alternatives like brine concentration and reuse wherever feasible.
Desalination is firmly established as an important technology to augment freshwater supplies in water scarce regions around the world. While higher upfront capital costs remain a barrier, the technology has achieved significant reductions in water production expenses driven by membrane innovation. As climate change exacerbates water insecurity, desalination capacity is projected to triple by 2040, presenting new investment opportunities. Going forward, sustainable plant design and effluent management will be critical to minimize environmental footprints as desalination scales up to help slake the planet's growing thirst.
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