Waste not on World Water Day: Bob McDonald

Our water supplies seem to be running low because we keep taking from the source. It's time to turn our attention to another huge source, the water we throw away.

We should be saving the pure potable water to drink, then recycle wastewater for everything else

A boy drinks drops of water dripping from a public tap in Solukhumbu District. (REUTERS/Navesh Chitrakar)

This year's theme for the United Nations World Water Day is, "Why Waste Water?" As the world demands more and more of our most precious resource, and sources seem to be drying up, the UN says there is a huge untapped reservoir that could help to meet the demand: wastewater.

The UN estimates that the amount of wastewater produced annually is about 1,500 cubic kilometres, six times more water than exists in all the rivers of the world. Of that, only four per cent is treated to advanced levels. The rest is dumped back into the environment raw.

Water in developing countries

In developing countries, it often ends up back in the very source people use for drinking, causing disease, plagues and pestilence. In richer countries, effluent from wastewater treatment plants may contain a whole cocktail of hormones, pharmaceuticals and other drugs that pass through our bodies, while industrial waste can contain heavy metals and other toxins. But if this water was treated properly, it becomes a valuable source of water that be used for non-drinking purposes, such as for washing the car, street cleaning, industrial processes and some household uses. Even the energy from the wastewater can be captured to heat buildings.  

A girl collects drinking water at Dala river outside Yangon, Myanmar March 3, 2016. Some 650 million people, or one in 10 of the world's population, have no access to safe water, putting them at risk of infectious diseases and premature death. (Soe Zeya Tun/Reuters)

It is a simple fact that people are demanding more water from Earth, yet the planet is not making any more of it, and that is not sustainable. Since 1993, the United Nations has tried to focus the world's attention on water conservation and preservation from pollution. But this year's focus is on a huge supply of water that is literally slipping through our fingers.

Recycling wastewater

A report called "Global Experiences In Water Reuse" outlines success stories around the world where cities have repurposed wastewater for agriculture and other activities, as well as public misconceptions and political barriers that stand in the way of wastewater recycling.

It makes much more sense to save the pure potable water for human consumption, then recycle wastewater for everything else. Toilets, lawns and gardens don't need pure water. Nor is it needed for heating and cooling purposes. Wastewater even contains nutrients that are beneficial for non-food agriculture.

A crop gets irrigated near Enchant, Alta. Hot, dry conditions in parts of southern Alberta are forcing farmers to spend more to irrigate their crops. (Kyle Bakx/CBC)

Our cities go to great expense to ensure our drinking water is safe. In the household, a lot of that pure water has a useful lifetime of less than one second as it drops from the tap to the drain, then another expensive network takes over to remove whatever we dumped into it. That's a lot of trouble to go through to make sure that water is clean. And we use a lot of it. In Canada, we are one of the highest consumers of water in the world, gulping down about 250 litres per person per day. If you include the water we use for cleaning, washing and energy production, it goes even higher. Compare that to Africa where the average consumption is about 10 litres per day, and people there usually have to travel some distance to get it.

The technology to recycle domestic wastewater already exists, with grey water systems that link sinks to filter systems then up to your toilet or to a rain barrel so the water can be used for outdoor purposes.

Of course, there is work to be done before the public will fully buy into this idea. There will be extra pressure on wastewater treatment facilities to ensure the public that harmful contaminants such as pathogens, pharmaceuticals and heavy metals have been removed. That will mean extra costs, but when you consider the costs of building new dams to create reservoirs, or drilling for new sources of clean water, investing in treatment plants upgrades could end up costing a lot less.

Nature already recycles water

The idea or recycling water is not new. Nature has been doing it for more than three billion years. That is one of the most remarkable aspects of water. Every time it evaporates into the sky, it leaves contaminants behind, then eventually fall as clean rain. Thanks to that water cycle, Earth has been able to support life by continually recycling it back into fresh supplies. In other words, the water you drink today has already been through a dinosaur.

Over the last ten thousand years, since we humans decided to live in towns, getting rid of waste has been a constant problem, costing millions of lives through the spread of disease. Our water supplies seem to be running low because we keep taking from the source. Now it's time to turn our attention to another huge source, the water we throw away.

About the Author

Bob McDonald

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.