Poland's cities, including Warsaw and Poznan, employ unusual teams of monitors to ensure that their water supply is safe to drink. Each water filtration plant has a crack team of eight mussels that tirelessly track the water entering the system, and have the authority to shut down the flow. Link to an article by Cara Giaimo in Atlas Obscura is here.
The concept is simple. All kinds of pollutants can sneak into drinking water: Heavy metals seep up from industrial waste sites; pesticides and fertilizers trickle in after big rainstorms. Because chemical tests are contaminant-specific, it's impossible to check the water for every possible problem before it's piped out to the populace.
Mussels, however, aren't picky. If something is wrong, they clam up. Their broad sensitivity and predictable response have allowed engineers to build them into a straightforward quality control system, which runs alongside other mollusk-free monitoring schemes.
Worker mussels are recruited from nearby lakes and rivers. They're deployed in teams of eight, each equipped with a magnetic sensor that connects them to a computer system that can register whether they are open or shut. When four or more mussels close off, so does the water supply.
Each of 50 water treatment plants in Poland have these teams of eight mussels working 24 hours a day ensuring only safe water enters the system. They are retired after three months of duty — if they get too accustomed to their surroundings they become less sensitive to contaminants — after which they are returned to the lake or river they were taken from.
Of course, if something goes very wrong with the water supply, the mussels will die as they warn the city of the crisis, so their service is both risky and heroic.
Water supply systems in Maryland are safeguarded in a similar way by bluegill fish. A colony of 100-300 bluegills are kept at two locations, and are monitored for biological responses to the water quality. A change in those responses, such as their respiratory rates, can act as an early warning system that something is wrong.
These fish are put on duty for fourteen days at a time. Between tours of duty, they are moved to a special holding tank where they can rest and are given a feast of brine shrimp in thanks for their service.
Link to a scientific paper on the use of freshwater mussels as sentinels for safe drinking water is here.
h/t @mrcultdaddy
