A micropump withdraws a few microliters of the wastewater, dilutes it and channels it to the chemical sensor, which features six electrodes that are each coated with a special polymer coating.
The unique feature of this system is that these polymer layers contain various gaps that are each perfectly sized to accommodate certain pollutants. When these pollutants bind to the polymer layer, their electrical capacity changes, so when the electrodes sense such a change, it suggests that the wastewater contains certain pollutants.
However, this cannot be used as evidence in a court of law, so the system also draws a small sample of the wastewater that can then be thoroughly tested by hand in the lab. To enable the chemical sensor to be used for multiple measurements, a cleaning solution flushes the attached molecules out again after each measurement.
The Fraunhofer IIS researchers developed the electronics, the sensor module’s signal acquisition and evaluation, and the system energy supply. Their colleagues at Fraunhofer IZM were responsible for the BUS system on the metal ring and for the design of the waterproof plug contacts for the individual components and the waterproof and chemical-proof casing. They also miniaturized the physical sensors.
The components have been tested individually in project partners’ labs, then all together in an artificial wastewater system with real wastewater. In a third step, different components were tested in a real sewage pipe, showing promising results. The Fraunhofer IZM researchers now want to conduct a large-scale test run of the system’s physical sensors with partners in five European cities.
Fraunhofer IZM - www.fraunhofer.de