A water treatment plan in Poland relies on mussels to detect changes in the quality of the Warta River, the main source of water for the city of Poznań, a metropolitan area home to 1.4 million people. Water Source describes a creative method that uses mussels as bioindicators, that is, they give an idea of the health of the ecosystem.
The Warta River flows through densely populated and industrial regions of Poland. Of particular concern for river water quality are heavy metals. To help address this, water treatment plant engineers have put the talents of molluscs to work. Mussels filter water to feed on microscopic organisms; while the water is clean, they stay open. They are good indicator organisms because not only are they very sensitive to pollutants in their environment, but they also exhibit a clear reaction to poor water quality: they close their shells.
The Dębiec Water Treatment Plant relies on the sensitivity of mussels – eight of them – to alert them of water quality problems. Sensors glued on to the mussel shells tell a computer when the shells close. When four mussels close at the same time, the system shuts down. While water quality parameters are also monitored using artificial sensors, bioindicators give a reliable assessment of overall water quality, because they take into account different factors at the same time, explains ZME Science.
The beauty of the system is that it is ingenious, yet simple. It has been working since 1994 in Poznań. It caught the eye of Julia Pelka, a film director who tells the story of a similar clam-based water monitoring system in Warsaw in a documentary titled Fat Kathy, first screened in 2019. She explains that the clams are released after three months of hard work. We might think of this as a nice gesture, but it is done because they become resistant to water pollution.