The University of Erlangen and PPU Umwelttechnik GmbH have implemented a fourth treatment stage in the Hausen municipal wastewater treatment plant near Erlangen. Together, they are taking the next step in municipal wastewater treatment towards a cleaner future.
PPU realises fourth treatment stage
What is a fourth treatment stage?
Municipal wastewater is traditionally treated in three stages: The first, mechanical stage is screening to separate coarse components. The second, biological stage is treatment by microorganisms, which break down most of the contaminants. The third stage is either separation of the resulting sludge or additional chemical treatment.
Nevertheless, trace substances remain in the wastewater. These include drug residues, certain non-biodegradable cleaning agents, colourants, pesticides, hormones, and biocides. Current research is focussing on the impact of these trace substances on the environment and shows a potential danger, especially for stagnant waters. The fourth treatment stage uses processes to break down these trace substances. Activated carbon can be used here, as can oxidation processes.
Hausen wastewater treatment plant relies on diamond electrodes
The Hausen municipal wastewater treatment plant has launched a pilot project to implement an oxidation process using diamond electrodes. This comes from the research department of the University of Erlangen, which has developed it together with PPU Umwelttechnik GmbH from Bayreuth in recent years. When electrical voltage is applied to the diamond electrodes, they serve as anode and cathode. In the wastewater, they form strongly oxidising OH radicals with the help of the current, which oxidises the trace substances in the wastewater. This reaction produces hydrogen and ozone.
The ability to oxidise trace substances from wastewater has been known for around 30 years. Since 2015, the University of Erlangen has been working on the development of diamond electrodes capable of oxidation. In PPU Umwelttechnik GmbH from Bayreuth, the researchers have found a company that uses the technology in industrial projects and is investigating its practical suitability. The focus is on the food and beverage industry, the oil and gas industry, the textile industry, and the plastics recycling industry. In all these areas, the oxidation rate of diamond electrodes is between 80 and 90 per cent.
Diamond electrodes are being used more and more
Dr Sabine Düreth-Joneck, Head of the Research and Development Department at the PPU in Bayreuth, has been working on the industrial application of the diamond electrode in recent years: “We know that biological wastewater treatment reaches its limits with certain substances,” says Düreth-Joneck. “We are already using the oxidation process in industrial projects to treat highly contaminated industrial wastewater. However, using it in municipal wastewater treatment as a fourth treatment stage is also a new experience for us. However, we are certain that the diamond electrode will bring decisive added value,” concludes Düreth-Joneck.
