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Forward Osmosis – Solving Tomorrow’s Water Challenges Using Nature’s Remedy

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.

 

Oasys Water 

Porifera

HTI Water

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.

Counting the Cost of Water

I was contacted last week by a journalist doing a story on ‘the future of water’. When I asked what the publication was, I was told it was for Esquire. Needless to say I was only too glad to help, – it’s not often I have the opportunity to have my name in print alongside the Jolie-Pitts of the world!

Some of the questions I was asked were: ‘Where is our water going to come from?”Is it going to be from desalination?’, ‘How much growth can we expect to see in desalination, and what breakthroughs if any in this area are we on the verge of?’

There was a very good session on water at the Always On Going Green Conference in San Francisco last week chaired by Christopher Gasson of Global Water Intelligence (GWI). I am going to borrow a little bit here from that session and from the GWI report “Desalination Markets 2007: A Global Industry Perspective’.

Desalination is a rapidly growing industry and there is no shortage of the raw material required. The Global Desalination industry is predicted to grow from 39.9 million m3/d at the beginning of 2006 to 64.3 million m3/d in 2010, and to 97.5 million m3/d in 2015. This represents a 61% increase in capacity over a five-year period, and a 140% increase in capacity over a ten-year period.

Beyond 2015, the rate of growth in the industry is expected to accelerate, as large markets such as the US, China and India will by then have established the financial and political models to pursue large-scale desalination projects. The rate at which the installed capacity increases is expected to move into double figures, and the annual increment to capacity is expected to increase by an average of more than 15% between 2015 and 2020.

To understand why desalination is so important, you first have to understand just how little of the world’s water is actually fresh water. If all the water on Earth were compressed to a single gallon, only four ounces would be fresh water. Only two drops would be readily accessible and human beings already use one of those drops. But about 92 percent of that single drop is used by agriculture and industry; just 8 percent goes to cities, towns, and municipalities. So for every gallon of water on the planet, only 8 percent of one drop is available for drinking, bathing, and other personal consumption.

A number of other factors compound this scarcity:
· Political & economic instability
· Uneven freshwater distribution
· Population growth in areas of limited natural resources
China has only 8 percent of the world’s fresh water to meet the needs of 22 percent of the world’s population, while Canada has 30 times more water and only 0.5 percent of the world’s population. While Global warming has no predictable impact on overall scarcity it is believed to increase the risk of both floods and droughts.

The good news is that costs for desalination have been dropping dramatically. Forty years ago the cost was $10 per m3. Now it’s down to $0.50/m3 (GWI). However 50% of the current costs are associated with energy use, and energy costs are only going one way. Given the huge impact that energy has on the cost of desalinating water, it is difficult to see how the industry can continue to deliver further significant reductions in desalination costs.

So what’s the next big thing going to be in desal membranes? Some say nanotechnology. Oak Venture Partners and Khosla Ventures clearly think so as they have just invested $15M into the UCLA spin-out company, NanoH20 to help them commercialize their Thin‐Film Nanocomposite (TFN) membrane system.
What NanoH2O are doing is very clever, they are nano-engineering the characteristics of the membrane so that it ‘wants’ to let water through’ and ‘wants’ to repel other contaminants. Its almost Taoist in principle, as opposed to trying to push water through a very small aperture with brute force, you are engineering that aperture so that its natural tendency is to let water pass through it and to repel other contaminants.

If desalination continues to increase, the water produced will have to be metered. Smart metering technology with remote on-line data collection is an area to watch.

Paul O’Callaghan is the founding CEO of the Clean Tech development consultancy O2 Environmental . He lectures on Environmental Protection technology at Kwantlen University College is a Director with Ionic Water Technologies and an industry expert reviewer for Sustainable Development Technology Canada.