Wastewater You Can Drink

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As the world celebrates Water Day (March 22nd), projected water trends make for grim reading. With almost 60% of the world's population moving into the middle class by 2030, water demand is expected to outstrip supply by 40%.

One response will be to lower consumption.Desalination also holds promise. Last, but not least, scaling up water recycling will be critical to ensure access to supplies of clean water.

By far, the highest purification standards are required for domestic water recycling.Today advanced treatment plants use a combination of ultrafiltration or microfiltration membranes and reverse osmosis membranes coupled with ultraviolet lamps and hydrogen peroxide to filter out and oxidize wastewater contaminants.

According to Giulio Boccaletti, the Nature Conservancy's global managing director for water, with recycling technologies well established, most innovation now focuses on lowering energy costs and extending the life of filters by using nanotechnology, among other methods. MIT and Lockheed Martin, for example, have separately been working on the use ofultra-thin graphene-based molecular filtersfor the removal of selected water impurities and the reduction of energy consumption in water desalination. While patents have been filed, there is still some way to go before commercial deployment.

Attention is also turning to direct potable reuse, which returns recycled water directly to the drinking-water supply instead of putting it through an aquifer or storing it in a reservoir. "People are getting more serious about direct potable-water recycling," says David Sedlak, co-director of the Berkeley Water Center at the University of California, Berkeley. This, he says, has less to do with technology than changing public perceptions and research validating its safety.

Water for domestic consumption is essential, as is the water needed for industrial use. This is particularly true of the energy sector, where increasing competition for water and climate change are leading large utilities to assesstheir exposure to water risk and look for ways to optimize water use. US utility Exelon, for example, has been mapping the exposure of its power fleetwater risks to since 2012.The main driver of water demand growth, however, will be the manufacturing sector. According to the UN, its need for water will rise by 400% by 2050, versus 140% for thermal electricity generation and 130% for domestic use.

This is putting waste-water treatment at the centre stage of water-recycling and water-reuse efforts. Saudi Arabia, for example, is expected to triple its investments in waste-water treatment over the next five years, reaching $35bn by 2020, according to a GE report published last month. The goal, says the report, is to reach 90% of industrial water reuse by 2020—from just 10% in 2010.

Overall, the market for industrial water-treatment technologies is predicted to grow by more than 50% to reach $11bn by 2020, according to new research by Global Water Intelligence (GWI).

GWI predicts that micro-filtration and ultra-filtration will be the segments growing fastest, at 7% a year. Companies will have more than one technology to choose from. Massachusetts-based ThermoEnergy's flash-vacuum distillation process, for example, uses temperature and reduced pressure to separate chemicals, metals and nutrients from waste water.

As the industrialised world expands to include ever-greater numbers of wealthy consumers, the ability of companies to use water more than once will become critical, not only to business success but also to global water security.

source: The Economist