Industrial testing platform for clean water

Thanks to its rigorous regulations on discharging wastewater into rivers as well as its efficient wastewater treatment plants with multi-stage filters and biological purification systems, Germany can be proud of its high water quality and first-class drinking water. However, quality requirements are on the rise and water management is facing new challenges. On one hand, this is due to water shortages: while supply has been decreasing due to climate change, demand has been growing — for example in agriculture and as a result of the widespread switch to the hydrogen economy.

Modern analysis methods are now able to detect the most miniscule concentrations of harmful substances in water that previously went unnoticed, including pharmaceutical and chemical residues (also known as micropollutants).

“The water quality in Germany is just as good as ever before,” said Dr Burkhardt Faßauer, head of the Circular Technologies and Water department at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS. “However, we do need to prepare ourselves for the challenges of the future.”

Fraunhofer has now started a project that will take the treatment of industrial wastewater to the next level and should enable bodies of water and drinking water to be more efficiently protected. Another objective of this project is to collect recyclable materials from the wastewater.

“Some of the residuals or process chemicals in industrial wastewater can be reused in industry as raw materials. This holds true for various salts and metals, for example. We are developing processes to retrieve these raw materials from wastewater,” Faßauer said.

Fraunhofer researchers deployed a range of test containers on-site at the joint water treatment plant in Bitterfeld-Wolfen. This is one of the most modern wastewater treatment plants in central Germany. As well as community wastewater, the plant primarily treats industrial wastewater from just under 300 businesses in the Bitterfeld-Wolfen Chemical Park, one of the largest in Europe.

“Our on-site presence means that we have targeted, consistent access to the relevant amount of wastewater. As such, we are able to conduct our experiments on an almost industrial scale and under real-world conditions,” said André Wufka, Group Manager for Systems Engineering for Water and Wastewater.

A major advantage of the technology platform comes from its modular design. Aggregates and systems can be replaced at any time or moved to another location in the process. As such, the teams of experts can reproduce, analyse, reposition and optimise the technical processes at the wastewater treatment plant however they desire.

The team of scientists is using state-of-the-art equipment to tackle the issue of wastewater. They are continuing to develop existing processes, combining conventional methods to develop new processes and working on innovative and — ideally — disruptive technologies. An example of this is intelligent, switchable membranes that detect specific micropollutants and separate them out.

In addition to membranes and biological and electrochemical methods, the researchers are also using the latest sensor technology.

“We are testing, for example, the performance of new sensor systems that work on the basis of surface plasmon resonance (SPR) spectroscopy,” Wufka said. “In these systems, the pollutant molecules to be detected adhere to a nanostructured sensor substrate and when this happens, the light refraction changes. The sensor registers the change in the refractive index and can use this to measure the pollutant concentration in the water. This could be used to control a cleaning process.”

Fraunhofer experts are also tackling the problem of residues such as salts that accumulate during cleaning processes. These are often found in production wastewater, but even the cleaned water still contains a certain level of salts.

“If large quantities of these salts enter rivers, this can cause problems. During heatwaves such as those we’ve experienced this summer, river water levels drop, meaning that the concentration of substances present in the water increases,” Wufka said. “This can have serious consequences for flora and fauna in rivers.”

Fraunhofer IKTS researchers are therefore working with partner institutes to develop not only more effective solutions for removing salts from wastewater but also solutions for recycling these extracted salts.

The filter and cleaning technologies developed in the project benefit wastewater treatment plants but can also be directly used in industrial production. In this case, Fraunhofer researchers can make use of their technology platform’s flexibility to test suitable cleaning strategies for industrial customers’ specific problems or needs.

“Companies in the chemical industry, for instance, can set up a system that we developed for recovering raw materials from wastewater directly in their production hall,” Faßauer explained.

Image: Test container at the joint water treatment plant in Bitterfeld-Wolfen. © Fraunhofer IKTS.