Nov. 1 2018 12:58 AM

A researcher in Denmark invented the new process.

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Is it possible to clean the polluted runoff from urban streets that befouls groundwater and pressures sewage systems — and do it without using any electrical power or adding any chemicals? The answer is “yes,” according to a story in Water Online.

A researcher at the University of Copenhagen has invented a treatment method that is being used at a large, brand-new wastewater facility in Ørestad, Denmark. It is the first wastewater treatment facility of its kind, using new green technology to clean up to 110 liters of urban stormwater runoff per second.

The purification technique is the brainchild of University of Copenhagen Professor Marina Bergen Jensen. After a number of trials at smaller installations, her method has been put to use on a large scale, processing urban stormwater runoff from Ørestad which is subsequently clean enough to be released directly into Amager Nature Park.

"We have invented a green technology inspired by the way substances are transported through layers of soil in Denmark,” explains Bergen Jensen.

The method uses a double porosity filter. Urban runoff is diverted through pipes to the treatment facility, where leaves, plastic caps, bags and other large particles are captured.

From there, the water flows into a sandwich-filter system where the double-porosity filtering takes place. Using gravity, the runoff flows through the wastewater facility, where very small particles and other pollutants are captured. The water has been cleaned. Finally, the treated water is released into the park. No chemicals or power were needed.

After being treated by the double porosity filter, water quality if so good that runoff can be used for toilets, car washes and similar purposes.

Urban runoff is polluted by microplastics, heavy metals, nutrients and other things. Substances that the green industry uses on landscapes, such as pesticides and fertilizers, are part of that runoff pollution that contaminates lakes, waterways and groundwater if allowed to flow directly into the natural environment. Runoff requires energy if it is to be pumped to a sewage treatment plant.

This plant has allowed local water officials to reduce the amount of rainwater that flows into the sewer systems, relieving pressure on them during heavy rains.

"Engineers and developers from around the world are being challenged to make climate renovations in cities in preparation for the type of increased rainfall that we have experienced in recent years,” says Anne Skovbro, CEO of CPH City & Port Development, one of the partners in the stormwater runoff treatment facility.

“Since the beginning of our development in Ørestad, we have succeeded in locally managing rainwater that falls onto "clean" surfaces like rooftops or bicycle paths,” continues Skovbro. “Now, the dirty runoff from the city can be cleaned locally as well. It is a major gain for climate preparedness.”

"As a society, we have become increasingly aware of the need to protect aquatic environments, but environmental authorities have lacked the means of controlling urban discharge,” said Bergen Jensen. “I hope this solution paves the way for climate- resilient cities equipped with a high level of environmental protection, both across Denmark and abroad."

Bergen Jensen is currently focusing on further applications for this technology. Watercare, a company based on the Danish island of Funen, produces and markets the filter.

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