02 May 2019 Story Ecosystems and Biodiversity

Towards sustainable desalination

Photo Credit: Starsend (Wikimedia Commons)

Did you know that several countries, such as the Maldives, Malta and the Bahamas, meet all their water needs through the desalination process—that is, they convert seawater to freshwater?

Oceans cover 70 per cent of the planet. They provide nourishment for over three billion people and absorb 30 per cent of carbon dioxide released into the atmosphere and 90 per cent of the heat from climate change. Increasingly, they are also providing freshwater for a burgeoning population.

While there’s no shortage of seawater, it’s important to understand and monitor the impact of the rapidly growing number of desalination plants on the environment. Desalination is the process of removing salts from water and a by-product of the process is toxic brine which can degrade coastal and marine ecosystems unless treated.

Al Kaluf desalination plant in Oman
Photo Credit: Starsend at English Wikipedia

In most desalination processes, for every litre of potable water produced, about 1.5 litres of liquid polluted with chlorine and copper are created. When pumped back into the ocean, the toxic brine depletes oxygen and impacts organisms along the food chain.

“Increased salinity and temperature can cause a decrease in the dissolved oxygen content, resulting in conditions called hypoxia,” says Manzoor Qadir, Assistant Director of the United Nations University Institute for Water, Environment and Health (UNU-INWEH).

This can harm organisms living on or in the bottom of a water body and translate into observable effects throughout the food chain. In addition, certain compounds (e.g. copper, chloride) used in the desalination pre-treatment process can be toxic to organisms in the receiving water, according to Qadir.

Saudi Arabia (population 34 million) gets about 50 per cent of its drinking water from desalination.

A 2018 United Nations study says there are now almost 16,000 desalination plants operating in 177 countries, producing a volume of freshwater equivalent to almost half the average flow over the Niagara Falls. However, the toxic brine which is usually dumped in the sea, risks contaminating food chains if left untreated.

Rising water demands associated with population growth, increased water consumption per capita and economic growth, coupled with diminishing water supplies due to climate change and contamination, are exacerbating water scarcity in most world regions.

The study says unconventional water resources, such as those resulting from desalination, are key to support Sustainable Development Goal 6 (to ensure availability and sustainable management of water and sanitation for all), but that innovation in brine management and disposal is required: seawater desalination can extend water supplies beyond what is available from the hydrological cycle.

Challenges and opportunities

Brine production and high-energy consumption are key downsides of desalination. Disposal of toxic brine is both costly and associated with negative environmental impacts. “Our estimates reveal brine production to be around 142 million m3 /day, approximately 50 per cent greater than previous quantifications,” says the study.

On a more positive note, many desalination plants are in areas with plenty of sunshine where solar power can provide a more sustainable energy solution.

Research suggests there are also economic opportunities associated with brine, such as commercial salt, metal recovery and the use of brine in fish production systems.

Desalination plants are not new. This picture of a desalination plant in Eilat, Israel, was taken in 1964.
Photo Credit: Moshe Pridan (Israel National Photo Collection)

Desalination is currently concentrated in high-income and developed countries. For affordable and environmentally friendly systems to be rolled out in low-income and lower middle-income countries, technological innovations are necessary, along with innovative financial mechanisms to support the sustainability of desalination schemes, says the study produced by the United Nations University Institute for Water, Environment and Health (UNU-INWEH) Canada project on Unconventional Water Resources.

Concentrated brine is wastewater—we have the means to tackle it

Globally, 80 per cent of wastewater ends up in our seas, rivers, lakes, and wetlands. Under the Global Programme of Action for the Protection of the Marine Environment from Land-based Activities, UN Environment is working to prevent degradation from land-based activities, such as the operation of desalination plants. The Global Programme also hosts and acts as the secretariat for the Global Wastewater Initiative.

This Initiative is getting people to move away from waste removal and towards resource recovery. It focuses on capacity-building and training, promotion of best practices and technologies, awareness raising and communication, and addressing data gaps.

In March 2019, the United Nations Environment Assembly adopted a resolution on the protection of the marine environment from land-based activities.

Among other things, Member States agreed to “enhance the mainstreaming of the protection of coastal and marine ecosystems in policies, particularly those addressing environmental threats caused by increased nutrient, wastewater, marine litter and microplastics in support of the 2030 Agenda as a framework for sustainable development.”

Financing wastewater improvements can be challenging, so UN Environment is in the process of setting up a facility to engage the private sector to upscale business models for wastewater management,” says UN Environment wastewater expert Birguy Lamizana. “It is also developing scientific knowledge and policy recommendations to support decision-making.”

For further information please contact Birguy Lamizana: [email protected]