Nanofiltration: a “magic bullet” for water treatment in a warming world

How can we solve big problems in water that climate change will doubtlessly make worse? Nanofiltration is one major answer: it enables water manager to reuse H2O in an energy- and cost-efficient way.

Ensuring that an increasingly thirsty world has enough water will be a huge challenge in the years to come. Nothing is simultaneously more vital to the functioning of society and subject to the ravages of climate change. Managers of long-established water collection, storage, processing and distribution networks are scrambling to adapt to the realities of a warming world; according to the UN, the number of people living in “severely water-scarce areas” could increase by as much as 68% from the early to mid-2010s to 2050. This is over 1 billion people.

This does not just affect human health, nutrition and survival, although the world will feel the impacts most acutely in those areas. Virtually everything in the modern economy depends on water; the industrial sector, for instance, uses 19% of all global water supplies. Though this pales in comparison to agriculture’s 69%, it demonstrates the centrality of water in powering production and commerce.

Usable water has long been unevenly spread around the world. East and South Asia—home to India and China, the world’s two most populous countries—both have less than 2,200 m3 of fresh water per person; the comparable figure in Latin America is nearly 14 times that. Climate change will complicate this picture further. This is compelling governments in those two Asian giants, among others, to mandate water reuse as aquifers dry up and reservoirs yo-yo between extremes. China, for one, will force its driest cities to recycle more than 25% of their waste water by 2025, up from a national average of less than 20% today.

Membrane matters 

The question of how to do this is one that Emerald is examining closely. We believe that nanofiltration (NF), a type of water processing technology, will be a major part of the solution. Simply put, nanofiltration sees water pushed through highly selective membranes that remove various pollutants and unwanted materials. Globally, NF treats about 430 Olympic-sized swimming pools’ worth of water every day—a figure we expect to rise rapidly in the future.

NF is one of several filtration methods water processors can leverage. These are generally classified by level of coarseness: the finer-grained processes can remove the most stubborn bits, leaving nothing but 100% H2O. At the purest end of the spectrum, reverse osmosis (RO) can make seawater drinkable. Located a step below this in the hierarchy of technological sophistication, NF can work for virtually every other application, from treating human sewage to removing dyes from clothing factory run-off.

Crucially, it also requires less energy to run than RO—as much as 50% less. This is because far less pressure is required to move water through NF filters. Innovative companies, including several startups, are working to bring these costs down further. They are doing this by increasing the lifespan of individual nanofilters, boosting their resistance to corrosion by chemicals and particulates, and producing NF tools that can process more water in a shorter period of time.

For these reasons, NF can reasonably be seen as a “magic bullet” for cost-effective water services. It can separate different streams of liquid waste, so that water managers can extract and reuse, say, salty solutions. It can help protect other pieces of waste water kit from degrading. This can strengthen and streamline entire treatment facilities, enabling them to meet increasingly stringent water regulations and carbon-emissions targets alike.

Particularly for drinking water, NF holds immense promise. Among its largest current use cases is a plant on China’s Yangtze River that is using NF to supply 1.5 million people. Here, NF is replacing older, inefficient multistep processes with a single pass through the membrane. Given that more than 550 million people depend on the Yangtze for water, the room for growth is significant.

Looking ahead, we expect costs of NF to continue to come down and adoption to continue to spread. “A lot of startups are trying to make the production of NF components simpler and more efficient,” says Kelven Lam, our water specialist. Helping startups commercialize their solutions to the world’s biggest environmental and industrial challenges—and link up with the large conglomerates that can scale them—is our bread and butter. When it comes to water, we could not be more excited to be at the forefront of transformation for this vitally important sector.