Sewer sensor to unmask water polluters

A new sensor system developed by researchers in Germany could play a valuable role in the battle against the illegal polluters.

sewer sensor
Sensor ring for use in wastewater treatment plants (© Volker Mai)

The brainchild of a team including experts from the Fraunhofer Institutes for Integrated Circuits IIS and for Reliability and Microintegration IZM, the technology is able to detect hazardous pollutants in wastewater treatment facilities and identify the polluter.

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“The sensor system is designed to detect certain substances that are typically found in affected wastewater,” explained Dr. Matthias Völker, group manager at Fraunhofer IIS. “It comprises 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.”

If tainted waste-water is detected then safety agencies can then use the technology to examine the sewage system at certain points and, by taking multiple measurements, gradually close in on and ultimately expose the perpetrator.

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. The two rings communicate with each other wirelessly and compare the measurement data from their sensors.

Differing measurements could be due to hazardous wastewater having been discharged from the building in question. 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 withdraws a few microlitres 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 system also draws a small sample of the wastewater that can then be thoroughly tested by hand in the lab.

Trials of the technology in an artificial wastewater system and also in a real sewage pipe have proved promising, said Fraunhofer IZM’s Harald Pötter: “The system detected suspect sewage and triggered a corresponding alarm.”

The researchers now want to conduct a large-scale test run of the system’s physical sensors with partners in five European cities.