The experiment is ongoing in conjunction with a new sewage treatment that is being tested in Helsingborg.

The goal is to recover nutrients and water from the sewage.

The system is called "three pipes out" and is being tested for a few hundred newly built apartments in the port of Helsingborg.

The three drains contain "grey water", i.e. kitchen waste, "black water" from the toilets and food residues from a waste grinder in the kitchen sink.

Wastewater from both kitchens and toilets often contains phosphorus and nitrogen, which are nutrients for many species.

- When we have nutrition and water, we can also see if the algae can be used as a purification factory.

And then if they can produce goods for us.

It can be as feed for land animals or fish, it can be as a substrate for biogas, or even as human food, says Kenneth M Persson, professor of water purification at Lund University of Technology. 

Are you allowed to drink the water?

The study is about seeing which kind of algae grows best in which kind of wastewater for the best purification effect.

Evaluation of the first results is ongoing.

Using microalgae as a water purifier is something that is being tested in several places around the world, but the method is not used on a large scale.

A disadvantage is that the purification takes longer because the organisms only need to grow over a few weeks. 

Then people must be convinced not to recoil at the thought of drinking before this drain.

Astronauts and cosmonauts in space orbit have long been drinking water from purified, recycled urine. 

With other methods used in Helsingborg, gray water can be made cleaner than normal drinking water:

- We push the gray water through nano-membranes in pipes.

Anything larger than a water molecule gets stuck in the membrane, and we get water with drinking water quality, says Amanda Haux, developer at RecoLab in Helsingborg. 

Summer plague Baltic Sea algae

In the Baltic Sea, the algae are a scourge in the summer.

Could that pain be alleviated in any way if you started using the algae like this instead? 

- It is a very interesting and relevant question.

The problem is that the algae are quite diluted out at sea.

You would have to concentrate the harvest, answers Kenneth M Persson.