A pinch of salt: Can desalination solve water scarcity?

Ani Talwar discusses whether desalination holds the answers to the developing water crisis.

You may have heard of the term ‘Water Crisis,’ or ‘Water Scarcity,’ or seen the adverts on telly teaching us about how little water some people have and how careful we need to be with how we use what we have. You might also have heard that despite this, 71% of the Earth’s surface is actually ocean, which begs the questions: why can’t we just use seawater, and how are we running out of water in the first place?

Although the oceans contain over 96% of all water on Earth, this is not water available for human consumption. Seawater in its natural form is actually toxic to humans, owing to the salt content that our bodies cannot tolerate. Freshwater is needed in human bodies in order to dilute the salt that the kidneys usually remove, and if we were to drink seawater, the level of salt would throw the natural levels in our body out of sync, which would have dire effects on our bodies.

Image Credits: Ani Talwar.

This effectively limits humans to consumption of freshwater, which poses a whole variety of different problems. Firstly, we are unable to consume 97.5% of the water on Earth, and secondly, temperature rise and population expansion are set to exacerbate the struggle we have to reach the little water we can safely consume. In fact, between 2000 and 2050, water demand is predicted to rise by 55%, with increased demand for agriculture, which is already responsible for nearly three quarters of our freshwater consumption.

NASA led a study into the depletion and replenishment of our freshwater supplies and found that we are depleting our water sources faster than they can naturally be refilled. The evidence of this has been clear in the last few years, with the worst drought in California in over 1000 years between 2011-2016, recovery of which would require ‘four years of above-average rainfall,’ as reported by the BBC.

So it’s abundantly clear the baseline supply of water we can actually consume is far less than what it may seem, but how is it we are still running out of water, even though we know the limits of our supply?

Even if you may try to save water by making changes like having showers not baths, other aspects of our daily life are surprisingly water heavy. Did you know a single pair of jeans requires 10,000 litres of water to make? Or that a t-shirt requires 2500 litres alone, and 130 litres of water needed to produce but one cup of coffee?

‘The problem is that most of the Earth’s water resources are as inaccessible as if they were on Mars,’ - The Guardian.

But what if all that seawater wasn’t so inaccessible? What if with all the advances in technology we seem to be making, we can make seawater more consumable?

Image Credits: Ani Talwar.

Desalination is the name of a process by which saline water is treated to become freshwater. Solar Stills are portable devices through which water is evaporated and condensed again to make it fresh and remove the salt. By boiling water, collecting the steam produced, and condensing it back into water- a process known as distillation, one can turn seawater into water we can drink, but we have to do this on a massive scale.

Desalination is actually an old science, one of the earliest ways humans treated water, dating back to ancient ships who used this method to make seawater drinkable whilst at sea. It can even be carried out in your own back garden, or in a pinch if you find yourself unfortunately stranded by digging a pit, placing a bowl at the bottom to collect water, and a plastic sheet over the top to prevent escape. In fact, as of 2015, there were nearly 18,500 desalination plants working around the globe, providing water for 300 million people at a rate of 86.8 million metres cubed a day.

Reverse osmosis is another form of desalination. This involves forcing water through a membrane which the water molecules can fit through, but not the salt molecules- like a sieve. Whilst this is also highly effective, it is more expensive than other methods of desalination.

This form of desalination has four basic steps:

1. Pretreatment. Here, larger particles are removed from the water to make it able to go through the membranes effectively.

2. Pressurisation. A pump creates a higher pressure for the water.

3. Separation. The water passes through the membrane, where salts are prevented from travelling.

4. Stabilisation: where the filtered water is then treated to make it able to be distributed as drinking water.

Despite the apparent simplicity of the above steps, this process is quite energy intensive, and the membranes are sensitive.

Already, countries are attempting to seize the benefits of this technology. Saudi Arabia’s Ras Al Khair uses Reverse Osmosis technology as well as another science MSF and was termed the ‘desalination heavyweight of the world,’. This is a developed project, with the plant being put for sale in 2017 regarding privatisation plans, but newer projects such as the Taweelah, UAE which had over 40 companies interested and has the potential to raise the proportion of desalinated water available to 30% by 2022, up from 13%.

Alternate versions of the technology are also rolling out with Sorek in Israel termed as the ‘heavyweight membrane plant of the world,’ with a capacity of over 600,000 metres cubed per day. In fact, there are plans in the works for a Sorek 2 which will have a further 548,000 metres cubed per day too.

Regardless of this, where once seawater was no more than a toxic form of liquid we couldn’t consume, technology and our understanding of what it’s made of has helped make desalination a more realistic thought. Maybe right now we can’t just use the water in the ocean, but in the future this technology may just come to our aid as we attempt to stave off the water crisis we are warned about. As these projects progress, the question of whether desalination will become an affordable and sustainable solution for all countries will become increasingly pressing.

About the Author: Ani Talwar is the Deputy Wildlife and Environment Editor at WILD Magazine. Ani can be found at @Mischief.weavers, she wrote the book ‘ATRO- CITY THE FLOOD’ and cares passionately about sustainability.