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  • Writer's pictureGraytec Global

(Translated) Interview with the Dagens Nyheter

"The water that radiates from the shower is clear and heated," said Jens Holmberg, PR and communications manager for the housing company HSB Living Lab (at Chalmers University) in swim shorts during the water flows as he test-showered Graytec AB's system.

"It feels just as usual."

It is not as usual as it is. The water Jens washes in has recently been used for hair washing and tooth brushing by other residents in the house. Since then, it has taken the detour via a cleaning device (i.e. The Blue Circle System) located on the first floor of the house.

The system seems simple. Through a parallel drain, water from showers and sinks in the bathroom of the house is led down to a treatment plant on the first floor of the house. Once the water has been filtered and heated, it is returned to showers and sinks. Per Ericson, who developed the system, showed off a container of purified water.

"Generally, it can be said that it holds higher quality than is required by drinking water," he said.

But he really doesn't want to use that comparison. The purified water is sterile and therefore not suitable for drinking in large quantities. The point of the parallel sewer system is not to produce drinking water, but to take advantage of the large quantities used for hygiene care.

"This is a circular, local system for water recycling. In theory, we could reuse 60 percent of the water and save 80 percent of the energy needed to heat it," said Ericson. Exactly how large the proportion will be and how much energy is saved, the researchers will not know until after the turn of the year.

Jesper Knutsson, a researcher at Chalmers University of Technology, gives an example of what the results looked like in a part experiment. "Eight showers with recycled water saved 200 liters and 6 kilowatt hours," he said.

"The property in the Johanneberg district of Gothenburg is called HSB Living Lab. Here are a number of research projects in which the residents participate in different ways. So far, about ten people have tried to shower in recycled water. Some have described a mental barrier," said Knutsson.

"There are psychological factors involved. Here we have an important research question: how can we build up acceptance to shower in the neighbor's water?," said Ericson. Another obstacle is the regulation of water and sewerage systems in Sweden. It is forbidden to connect water that does not maintain drinking water quality in properties. Ericson hopes that the regulations will change.

This is how the system works Greywater is led from showers and sinks within bathrooms to a tank on the first floor of the facility. Then it is purified using ultrafilter technology and it is then passed through several filter stages, including a carbon filter. After the water has passed through it, it is heated, and then returned to showers and bathrooms.

The research project is carried out in the property called HSB Living Lab and is located in the area at Chalmers University of Technology in Gothenburg. There are several research projects in which the tenants participate.

This greywater project is financed by the Swedish Environmental Protection Agency, Boverket and Vinnova. The company, Graytec AB, founded by Per Ericson, has developed and applied for a patent on the system. The project at HSB Living Lab is run in collaboration with Chalmers University of Technology and Bengt Dahlgren AB.


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