Cleaning water without chemicals?

First cleaning prototype for electrochemical water purification in use in the Upper Palatinate region of Germany

Clean water using electricity instead of chlorine: In the future, water systems such as fountains and cisterns, but also sewage treatment plants could be cleaned without using chemical substances. As part of the Bavarian research project DiaKerWa, a research team from FAU is currently testing a cleaning method that uses only diamond electrodes and electricity.

World premiere in Tirschenreuth

It is the first installation of its kind in the world: In the Upper Palatinate town of Tirschenreuth, diamond ceramic electrodes are currently freeing the new fountain in front of the district administration office from micro-pollutants. The integrated double diamond electrodes (iDDE) require only a little current to cause oxidation in carbon-based contaminants such as germs from bird droppings or algae. This means that the dirt is burned “cold” in the water, as it oxidizes at temperatures so low that no flame is visible. Specifically, the electrodes at the positive terminal generate OH radicals, molecules that each consist of one hydrogen and one oxygen atom, which convert carbon compounds into water and a small amount of carbon dioxide. At the same time, hydrogen is produced at the negative pole, which can be used energetically if required.

Franconian material replaces metals from abroad

The system, which can be remotely controlled from Erlangen, was developed by the Chair of Materials Science and Engineering for Metals and the mechanical and electronics workshop at FAU. The innovative diamond electrodes, which are already patented, were designed in collaboration with Upper Franconian ceramic artist Barbara Flügel.

The iDDE manufactured from porcelain from the Franconian town of Selb are not available anywhere else in the world. The material replaces rare and expensive metals from more distant parts of the world, such as niobium from Brazil.

Electrochemical water purification for wastewater treatment plants

Through remote monitoring, the university now wants to observe how strongly and how long the iDEE can clean water reliably. If the project is successful, the iDDEs could be used in more than just fountains. “We hope that in the not-too-distant future, purification will also be used in rainwater harvesting or wastewater treatment plants. With the iDDE, the fourth treatment stage for wastewater treatment plants currently under discussion in Bavaria can be realized and, at the same time, part of the energy used can be recovered via hydrogen production. This could go a long way toward conserving our waters and also consumers’ wallets,” explains Prof. Stefan Rosiwal, deputy head of the department.

iDDE water purification currently lacks European approval and cannot yet be used either in wastewater or drinking water plants. “Closed-loop systems like fountains are less critical and a good basis for testing,” says Rosiwal. “There are are also initial applications for industrial wastewater that use electrical oxidation for detoxification”.

The DiaKerWa project, funded by the Bavarian Research Foundation, will run for three years.

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