Micropollutants contaminate the water worldwide, and among them are steroid hormones that cannot be efficiently eliminated by conventional processes.
Researchers at the Karlsruhe Institute of Technology (KIT) have now developed an innovative filtration system that combines a polymer membrane with activated carbon. The size of the carbon particles is small enough to reach the reference value of one nanogram estradiol – the most effective oestrogen, physiologically – per litre of drinking water proposed by the European Commission.
Reference value of the European Commission reached
Professor Andrea Iris Schäfer, head of KIT’s Institute for Advanced Membrane Technology (IAMT), explained how she and her team developed their method for the quick and energy-efficient elimination of steroid hormones from wastewater by combining a polymer membrane with activated carbon.
“First, water is pressed through a semipermeable membrane that eliminates larger impurities and microorganisms,” Schäfer said. “Then, water flows through the layer of carbon particles behind, which bind the hormone molecules.”
At IAMT, researchers have further developed and improved this process together with filter manufacturer Blücher GmbH, Erkrath. Colleagues at KIT’s Institute of Functional Interfaces (IFG), Institute for Applied Materials (IAM), and the Karlsruhe Nano Micro Facility (KNMF) supported this further development by characterising the material. This is reported by the scientists in Water Research. “Our technology allows to reach the reference value of one nanogram estradiol per litre of drinking water proposed by the European Commission,” the professor of Water Process Engineering said.
Particle size and oxygen concentration of importance
Scientists studied the processes in the activated carbon layer in more detail and used modified carbon particles (polymer-based spherical activated carbon – PBSAC). “It all depends on the diameter of the carbon particles,” Matteo Tagliavini of IAMT explained.
“The smaller the particle diameter is, the larger is the external surface of the activated carbon layer available for adsorption of hormone molecules.”
In an activated carbon layer of 2mm thickness, the researchers decreased the particle diameter from 640µm to 80µm and succeeded in eliminating 96% of the estradiol contained in the water. By increasing the oxygen concentration in the activated carbon, adsorption kinetics was further improved and a separation efficiency of estradiol of more than 99% was achieved.
“The method allows for a high water flow rate at low pressure, is energy-efficient, and separates many molecules without producing any harmful by-products. It can be used flexibly in systems of variable size, from the tap to industrial facilities,” Schäfer said.