Nature has an ingenious way of extracting water, but does it have the potential to solve many of today’s global water challenges? Before going into more details on how nature’s way of extracting water can help cut energy usage in water treatment processes, an appreciation is needed of why energy reduction in water treatment is an essential prerequisite for continued global development.
Since water is used in all energy production processes and energy is used to generate fresh, potable water from impaired sources, water and energy are two sides of the same coin. Factor in that global fresh water resources are rapidly declining and energy prices are one the rise due to over-utilization of fossil fuels, you quickly realize that energy reduction in water treatment processes will make a tremendous positive impact on the challenges faced in this water-energy nexus.
Moving back to nature’s way of extracting water, you may have wondered how trees are able to extract water from the soil in which they grow to the leaves in the treetops? Or how mangroves are able to extract fresh water from the seawater surrounding their roots? Given the obvious lack of electrically powered high pressure pumps, nature has come up with it’s own way of generating the pressure needed to transport water in trees and to extract fresh water from seawater in mangroves. It turns out that nature extracts water by utilizing the principle of forward osmosis in which water diffuses spontaneously (and without the input of energy) across a semi-permeable membrane from a low concentration solution on one side of the membrane to a high concentration solution on the other side of the membrane. The driving force for forward osmosis processes being the difference in osmotic pressure between the aqueous streams on either side of the forward osmosis membrane.
Coming back to the trees and mangroves mentioned earlier, the intracellular solution of root cells contains high concentrations of sugars and other dissolved molecules, which in turn generate a large enough osmotic pressure to extract water from soil and seawater respectively and transport this water throughout the stems and leaves of these amazing biological systems.
Now, how can water transport in trees help solve the looming water challenges facing our world today? Well, fortunately scientists have been able to develop artificial forward osmosis membranes and systems for industrial water treatment applications. And since forward osmosis systems do not require electrical energy inputs other than the energy needed to pump solutions across its membranes, it is potentially possible to reduce the overall energy consumption of water extraction by 90% compared to traditional pressure driven technologies such as reverse osmosis and nano-filtration.
Wide-spread adoption of forward osmosis systems in industry is still limited due to lack of high-performing, large-scale system capacity as well as industry preference towards proven technologies with long-term operational track records.
A number of startups and tech companies are working in the area.
As well as ongoing research projects at a number of universities and labs around the world are working hard to commercialize forward osmosis technologies, so don’t be surprised if you – in the near future – start running into examples of forward osmosis being used to treat water in industries or even households.