Fraunhofer IIS and IZM researchers have developed a new sensor system for detecting pollutants in affected wastewater.
Placed in a sewage canal, the new system can detect relevant substances and helps isolate and expose polluters.
While the majority of companies dispose of their wastewater properly, a few quietly and surreptitiously discharge their hazardous wastewater into the sewage canals to avoid associated costs.
Safety agencies have so far been unable to detect this kind of environmental crime on a broad scale.
Fraunhofer’s new sensor system comprises of two sensor components – physical sensors and a chemical sensor – as well as an energy management system, a control and communication system and a sampling system.
To take the measurements, a robot places three rings in the sewage pipe. The first ring is positioned directly in front of the suspect company’s inlet and the second directly behind it.
Both rings are equipped with a physical sensor for measuring various parameters, such as temperature, pH and water conductivity.
According to the scientists, the two rings communicate with each other wirelessly and compare the measurement data from their sensors.
The third ring, which is mounted a bit further back in the sewage canal, is equipped with a chemical sensor and a sampling system. If the second ring transmits a special signal, these systems ‘wake up.’
A micropump then withdraws a few micro-liters 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.
Since this cannot be used as evidence in a court of law, 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.
Image and content: Volker Mai/Fraunhofer IZM