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Spaceship city: drinking wastewater, and going back to the future

Sintana Vergara's picture

Seattle, WA

One of the marvels of the modern city is its ability to make waste disappear. Along with electricity, water, and the internet, sophisticated waste networks allow residents to discard or flush away any signs of urban consumption. But this may be changing. As cities increasingly face the prospect of droughts and uncertainty about future water availability due to climate change, a new source of water is now being explored that might prompt city residents to pay close attention to its origin and fate: their toilets.

Wastewater reuse – known as “reclaimed water” to proponents, and “toilet to tap” to critics – is used to augment supply in two prime water-scarce environments: spaceships and urban areas. Though resistance to wastewater reuse is mostly psychological, citizen’s disgust is balanced by three realities:

  • Many cities practice de-facto wastewater reuse, as long as there is a city upstream of theirs.
  • Advanced technological treatment, comprising of physical barriers (filtration, reverse osmosis), chemical disinfection (hydrogen peroxide), and ultraviolet disinfection, can achieve an effluent water quality often far superior to local water quality.
  • Severe water scarcity and depleted groundwater aquifers leave cities with few choices of water supply.

These facts have tipped the balance in places like Orange County, CA, which is recharging its groundwater supply with 70 million gallons per day of reclaimed water; Singapore, where 15% of the water is recycled; and Windhoek, Namibia, the only city in the world that directly uses treated wastewater for drinking.

Using wastewater as a water supply resource has implications for the modernization and sustainability of cities. It challenges conceptions of the modern city – as a place connected miraculously and invisibly to endless natural resources, and as an aesthetic place – but does so through technological advancement, also a hallmark of modernity. But perhaps more importantly, drinking wastewater re-conceptualizes waste as a resource, and in so doing, re-conceptualizes the city.

Cities were once built as importers and exporters: importing natural resources and exporting waste. But wastewater recycling is a step towards the closed loop resource use of the past, when the products of a small human population and limited consumption could be easily assimilated by the planet, and of self-sustaining natural ecosystems (You can read about resource flows through a cherry tree in William McDonough and Michael Braungart’s Cradle to Cradle). The highly technological city of the future might be taking a cue on sustainability from the past.

Comments

Sintana, Water, whether recycled or not, works it's way back into the ecosystem. Are you aware of potential unintended consequences that might occur as cities avail themselves of these measures? For instance, if there are five cities on a river, and they all start water reclamation measures, is the river noticeably lower downstream afterwards? Thanks!

Submitted by Sintana on
Hi David, Thanks for your post! You are absolutely right that all water on earth is recycled via the natural hydrologic cycle. But the idea behind using reclaimed wastewater is precisely to reduce the amount of water that a city requires for its operation. Instead of withdrawing water, polluting it, partially treating and releasing it into a water body, over and over, cities would instead treat the water they have already withdrawn and reuse it. Essentially, with reuse, cities get more use out of each water withdrawal. As a simple example, say the city requires 1 L of water for drinking, and 1 L of water for cooling. Instead of drawing 2 L, it would instead draw 1 L for drinking, treat the resulting wastewater, and use that same liter for cooling. When cities reuse their wastewater, they require less freshwater, and so they leave the nearby river with more water than it would have under conventional water withdrawal and use.

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