We have to recycle water on a massive scale – this is how we can

newscientist.com • 10 August 2016 • by Sally Adee

The world is running out of drinkable water, and putting a price on the stuff won’t work. But we are well on the way to building a circular water economy

drought in California
Parts of California are sinking  [Damon Winter/NYT/Redux/eyevine]

ZIKA isn’t the only thing hanging over the Rio Olympics. The city’s water problems are so intractable that swimmers have been told to keep their mouths closed so that they don’t ingest sewage. The situation is an important consequence of the shoddy way we all treat our water.

Beyond Rio, evidence of our disregard for the wet stuff is all around, and it is starting to bite. Beijing has sucked so much water out of the ground that the city is sinking by 11 centimetres a year. That’s positively glacial compared with parts of California’s Central Valley, which are dropping by 5 centimetres per month.

In Connecticut, nuclear power plants have shut down for lack of water to cool the furious reactions inside, and coal power stations in India have shut due to droughts. Concerns have been raised that California may run out of water to fight its wildfires. And in February, protesters sabotaged a canal supplying Delhi’s water – two were killed by armed forces sent to secure the canal.

In the not-too-distant future, we could see entire cities abandoned – ghost town casualties of drought and water mismanagement. It is not overly dramatic to say that the world’s “use once and throw away” attitude has enabled a slow-motion water apocalypse. “We’re going to have to do something or we’re all going to be juddering to a halt,” says Dominic Waughray, head of environment at the World Economic Forum.

“Rather than treating water like oil, we should think of it the way we think of renewables”

At its heart, the issue can be traced back to a simple but perplexing question: how do you give water a value? One way is to assign a price that reflects its importance or scarcity. In other words, treat water as a commodity like oil. This was a fashionable refrain in the water world for much of the last decade.

But the biggest problem with setting a price is that the value of water is incalculable. All humans are reliably dead after a week without it, which is why the UN in 2010 declared access to clean water a universal human right. That limits the price you can put on municipal water. Then there’s the issue of what happens when people can’t pay.

Wealth from waste

Perhaps rather than commoditising water like oil, we should be thinking of water the same way we think of renewables.

This isn’t about building hydropower dams on every river, but considering whether it is possible to contain an area’s water inside a reusable, closed loop system that reduces waste while making money from the stuff the water carries.

At the moment, it’s common to take water from a source like an aquifer or a river, use it once for drinking, agriculture or industry, and then flush the result into a central municipal treatment plant. This is referred to as the linear model of water use. This processing requires huge amounts of energy and leaves behind a foul sludge that is costly to dispose of.

Several things have happened in the past few years that could provide alternative ways of doing things, with the advantage of extracting value in the process. First, water purification techniques have advanced. “You can take the worst industrial waste and turn it into incredibly high quality drinking water,” says Peter Gleick of global water think tank the Pacific Institute. “It’s just a matter of economics.” The process is expensive, but now there are several designs for microbial fuel cells that generate electricity from sewage and industrial waste, mitigating the expense. It has also become cheaper to recover useful substances from water. For example, we can now extract agricultural fertilisers like ammonia, phosphorus and nitrates from sewage.

As a result, people everywhere, from the European Commission to the corporate advisers who inform policy makers in places like water-stressed South Africa, are talking about replacing the linear model with a circular approach (see “Closing the loop”).

The most radical vision is a city based on a perfectly closed loop, with water flowing from one application to the next on the basis of the purity required for each. For example, your drinking water could become household sewage that irrigates agricultural fields, whose run-off then goes to industrial use or to enable fracking. After its final use, the water returns to a treatment plant. “Then you treat it all again, and return it to drinking water, and the whole thing starts again,” says Waughray. “But now the plants can get energy and fertiliser out of the water and monetise treatment.”

This may sound far-fetched, but various components of this model have been around for a long time. The technology is now at a point where it’s possible to envisage the separate parts being stitched together.

Closing the loop

Singapore is the most advanced in treating sewage – its NEWater is so pure it is used in hypersensitive microchip fabrication plants, and supplies 30 per cent of the population’s water needs. Other places around the world, including Texas and Orange County, California, are beginning to accept the idea of toilet to tap recycling.

Switching to renewable water is a formidable task. To pull all these aspects together into a water-efficient city will require a huge infrastructure overhaul.

However, many cities are already starting to look at distributing water treatment instead of centralising it, which would make it possible to harvest its valuable contents at different points along the cycle – and reduce the formidable cost of pumping it around a city. “It takes a lot of energy to move water around,” says Gleick. One of the goals in Sydney’s 2030 vision statement is to have distributed treatment points around the city.

More worryingly, many countries don’t prioritise water at the most basic administrative level. In the US, for example, “there’s no department of water,” Waughray says.

While it’s tempting to think of that as a bug in the system, Waughray thinks it can become a feature, because sectors that need water should be motivated to invest in ways to improve access.

In the case of energy, every method of generation requires massive amounts of water. According to the US Geological Survey, cooling the turbines of the country’s coal fired power plants requires up to 320 trillion litres of water per year – that’s the amount of water that runs off Niagara Falls in five months. “Get the energy companies on side,” Waughray says, “and all of a sudden you have some really powerful people pulling strings to make it happen.”

So where will the first true closed loops be? Waughray is betting on the pop-up towns and cities that are attracting millions of people from rural areas in places like China. These places are being constructed from scratch so can be built around the guiding principle of clean water.

All the unknowns

Even if the logistics pan out before these water-centric cities can be built, some big questions need to be answered about how to make sure what re-enters the loop as drinking water is safe.

The biggest concern for Ernest Blatchley, at Purdue University in Indiana, is the chlorine that is still used in places like London to kill any biological pathogens – not the chemical itself, but its disinfection by-products. “We have identified more than 700 chlorination by-products,” he says. Whether these are present in concentrations that elicit adverse human health effects is not fully known, but there’s definitely potential for them to negatively affect human health, he says.

The good news is that many utilities are moving away from chlorine and toward UV for disinfection, says Fred Royan, an analyst at global business research firm Frost & Sullivan. One of the world’s biggest UV-treatment plants has just opened in Washington DC.

No one is saying it will be easy, but we need to solve the problem sooner rather than later, says Gleick. If we continue business as usual, it is estimated that by 2030 global demand for water will exceed viable resources by 40 per cent.

And if the worst case scenario happens – we ruin the planet so the whole things looks like Rio’s oceans of sewage – we’ll have an even more pressing case for perfecting this circular water economy. “Anyone who wants to get off the planet has to bring all their water with them,” Blatchley says. “And that’s all they’ll have.”

Whose wee is it anyway?

If you live in London, the joke is that your tap water has already been through seven people. Like all good jokes, there’s some truth in it, but realistically none of us uses new water. “All the water in the world has been here since the dinosaurs,” says Ernest Blatchley at Purdue University in Indiana. “In fact, the water you’re drinking has probably been through a dinosaur.”

Figuring out how many humans your water has been through will make more sense when cities use a closed water cycle. By 2060, Singapore will get 55 per cent of its water directly from sewage.

The joke reflects our discomfort with water that has been “pre-owned”, something that’s likely to be worse in a smaller hydrological cycle. But anything undesirable in the small system also exists in the bigger one – just dispersed more widely. “We all live downstream,” says Blatchley. “It’s just a matter of scale.”


This article appeared in the print edition of NewScientist under the headline “Not a drop to drink”


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s