Friday, May 22, 2020

Making More Water 1 – Desalination


Turning sea water into drinking water -interior of a Reverse Osmosis desalination plant 

Image byJames Grellier / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)


With water demand tipped to exceed supply by 40% by 2050, many countries have been availing themselves of new technology to avert this possibility, particularly when prompted by climate change in the form of more frequent and more severe droughts, drying rivers and higher temperatures. Broadly speaking there are two major ways   – not counting conservation, in which water supplies can be scaled up. The first is desalination – that is, taking sea water or brackish water and turning it into fresh water.  The second involves making better use of waste water.  

Desalination - Costly Magic

Currently there are 137 countries using desalination in one form or another. Already known to the ancient Greeks, the first modern distillation plants appeared in landlocked Kuwait in 1951 to supply water for domestic users. In the 1970's, faced with shrinking aquifers and the drying of its main water source, Israel began to adopt the process in earnest. Initially these plants used thermal distillation – boiling water and capturing the steam as it condenses, a method also adopted by oil rich states such as Saudi Arabia. For most other arid regions a major barrier to wider uptake was the high cost of energy, especially after the price of oil tripled in the 1970's.

In the 1980's another severe drought prompted the use of reverse osmosis (RO), a way of physically filtering water by forcing salt water through tiny membranes which trap salt molecules and other impurities, leaving chemically pure water behind. Israel's Sorek Desal Plant built in 2013 is currently the largest in the world and produces enough water for 3.8 million people.  Having now built a number of plants using this less energy intensive process, which also produces higher yields, Israel  produces enough water not only for its own needs, but has enough to export. It has also shared its expertise with other countries and remains a leader in the field.

International Co operation -India's Minister of State for Agriculture & Farmers Welfare and Parliamentary Affairs, Shri S.S. Ahluwalia, leading a Parliamentary delegation through the Sorek Plant, June 5, 2017
Image Courtesy of Ministry of Parliamentary Affairs (GODL-India)

Too much of a good thing?
In response to the millenial drought, other water -poor regions and cities such as Perth in Western Australia (2006) and Barcelona (2009), soon followed suit, but both infrastructure and energy costs still made such facilities an expensive way to ensure water security. They also added to CO2 emissions thus indirectly contributing to global warming and future droughts. For example, the biggest RO plant outside the Middle East, the Poseidon Desal Plant built in San Diego in 2015, provides enough water for around 400,000 people, but still uses as much power as 30,000 homes. 

To avoid this problem, India developed the first solar powered village -scale RO desalination plant in 2006. However, there are other environmental concerns too. For example, unless placed deep under the surface, the water intakes can be harmful to marine species as can the highly concentrated saline brine and chemicals contained in the outflows. Some mitigation measures may be possible here. 

According to Matt Simon, science writer at Wires, having land - based settling ponds and turning the waste into a useful product, diluting the brine with sea -water before release, or releasing it at high tide or in strong currents would all ensure better dispersal. 

Sorek uses both pre and post treatment to minimise its environmental impact. The San Diego Poseidon plant is now restoring its wetlands which will help to remove pollutants before they reach the sea. With 16,000 desal plants either operating or under construction and projected growth of  9%  over the next four years, we should certainly give these measures some thought.  


In recent years advances in renewable energy, falling costs due to longer lasting membranes and the recapture of energy from the process itself, has made this technology both more affordable and less damaging. In 2019 Saudi Arabia completed the world's largest solar powered reverse osmosis facility - enough to provide water for 150,000 people, but capable of being upscaled to serve many more, at El Khafji in the north east of the country and plans to build eight more. [Sorry if that clip looks like an ad for Siemens - it's the only one which mentions completion rather than the proposal].

The next big thing 'largest in the world' appears to be the Taweelah RO plant in Abu Dhabi, which is to be completed in 2022. It will produce 200 million UK gallons of water per day and be run on 30% to 55% solar, so that water can be produced at lowest cost to date. There are few English language reports on Russia, China and other countries for that matter, but a 2011 report on China says that it had 57 projects either completed or in the pipeline, mostly for industrial purposes, but also to meet the needs of its burgeoning cities.

Could it be that we are witnessing a kind of arms race between the major powers in the provision of water? If that's the case, then I must say I much prefer it to the other kind. If it greens the world's deserts and becomes a path to peace and prosperity, rather than war and division, then I say bring it on.

Making clean water available to all

Despite such advances the cost of desalination is still prohibitive for many, especially for those who need it most, but progress is being made here too. See for example the small plant being demonstrated by Hamza Farrukh below, which can  provide clean drinking water for around 2000 people at a cost of $10K, or the one by Desolenator in the next video, which could supply a small family for $US 450. Both operate on solar panels and need no further inputs. They are also highly transportable which would make them ideal for say, refugee camps or emergencies.






These are excellent solutions for dealing with groundwater or polluted water, but what happens when wells and rivers run dry?

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