Urban stormwater: the untapped resource

Cities around the world are facing shortages of drinking water, and the problem is only expected to worsen with climate change and prolonged dry spells. Researchers are now looking for solutions that capture and reuse stormwater.

Climate change and population growth are proving a deadly combination for drinking water resources. Dry regions are getting drier while wetter ones are depleting their underground drinking water aquifers as their urban populations grow.

This is leading many to see urban runoff – the rainfall collected from a city’s roadways and rooftops – as a possible solution to a growing problem. But there is one major problem: urban stormwater can contain harmful contaminants from pesticides, asphalt, vehicle exhaust, consumer products, and human and animal waste, according to an article on Smart Cities Dive.

Researchers around the world are now developing solutions to remove pollutants from urban stormwater before introducing it into underground reservoirs.

At University of California, Berkeley, researchers are experimenting with engineered mineral-coated sands that can break down some of the chemicals found in herbicides and consumer products, including low concentrations of the hormone-disrupting chemical bisphenol A (BPA).

They are now planning a small-scale field project in Los Angeles using actual stormwater: “We want to see how well it performs over time under several different stormwater conditions,”  UC Berkeley environmental engineer David Sedlak said in the article.

Sedlak has also teamed up with researchers at Stanford University to see if combining biochar with mineral-coated sands can further enhance the removal of organic pollutants related to automative use, insecticides and herbicides.

In Australia, Ana Deletic, a water-engineering expert at the University of New South Wales, is investigating how plants can be used to remove nutrients, such as nitrogen and phosphorus, from stormwater. When these nutrients accumulate, they can lead to algal blooms in ground and surface water, which in turn harms drinking water sources. Deletic has found that plants with long, fine root systems are best at removing these nutrients.

Ultimately, there is no “one size fits all” solution for urban stormwater as different chemicals are found in urban runoff depending on the type of land use, according to Smart Cities Dive. The goal is to create a “menu of technologies” that can be implemented together or separately to match the needs of a particular environment.

Image credit: Lily Banse via Unsplash

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