Flexing their mussels: Fish and mollusks collect bio-digital data for water utilities

Posted: November 01, 2024

Critical data can come from unexpected places. For example, municipal water plants from Poland to Minnesota have hooked their digital water quality monitors up to powerful biological sensors: mussels.

How do mussels monitor water quality?

Mussels feed by siphoning in water and filtering out any organic matter that’s in it. They’re extremely sensitive to a wide range of pollutants in the water they take in. Just small traces of pollutants in the mussels’ water supply will cause them to quickly clamp their shells shut and slow down their metabolism. Municipal water utilities have been capitalizing on this reaction by putting mussels in the water that feeds their drinking supply and monitoring the movement of their shells.  

In Warsaw, eight mussels are employed by the city’s water utility to feed on water coming in from the Vistula river. The mussels have springs glued to their shells that are attached to magnets. Computers monitor electric field changes that occur when the mussels close their shells, displacing the magnets. If four or more mussels clam up at once, the system will automatically shut off the water supply and notify operators so they can check whether there are pollutants that need remediation before water can start flowing again.

The short film, Fat Kathy, got social media buzzing about the project recently. You can watch the whole film—including footage of the mussels hard at work—here.

Similar programs are operating at 50 sites across Poland and several in the United States as well, including Minneapolis, Minnesota and Moline, Illinois. George Kraynick, the Water Quality Manager for the City of Minneapolis told the Apple Valley Sun ThisWeek:

“If there’s a spill that’s not reported...[w]e’re not relying on us visually seeing something in our process, we have these mussels that are looking out for us and giving us that early warning that there is something out there.”

Mussels are especially useful because of the broad spectrum of pollutants they’re sensitive to and the speed at which they react. Water quality crews don’t have to spend time screening for all possible pollutants before getting an alert that the water supply might be contaminated.

That said, the mussels aren’t perfect: they may not be quite as sensitive to pharmaceuticals as they are to heavy metals and other contaminants. So, water plant operators still independently test water supplies for specific pollutants.

Both Minneapolis and Warsaw provide excellent retirement benefits to retired mussels. Warsaw’s swan mussels work just three-month stints before being returned to the wild. The seven fat mucket mussels that had been monitoring Minneapolis’ water for the last five years just received a cushy retirement at the Minnesota Zoo. Fat mucket mussels can live up to 50 years, and they eventually grow too large for their tank at the water plant. A new crew of mussels started monitoring the city’s water in 2023.

These water-monitoring mussels are participating in the long tradition of sentinel species, which have worked beside humans in industrial operations for decades. Up until the 1980s canaries were still monitoring carbon monoxide levels in coal mines in Britain. The colorless, odorless gas would cause canaries to collapse, letting miners know they should escape soon lest they suffer the same fate. The success of the sentinel mussels has researchers looking for other animals that can do the same job for water quality. 

Can crayfish monitor water quality?

The Protivin Brewery in the Czech Republic is using crayfish to monitor the quality of the water it uses to make its beer. The brewery diverts some of the water supplying its facility to aquariums in which the crayfish live. Infrared sensors monitor the crayfish’s pulse rates and movement. Digital analyses of these readings trigger alerts when they identify irregularities in crayfish activity.

We can react quickly because we have the result within three minutes," Head Brewer Michal Voldrich told Reuters. Pavel Kozac, Director of the South Bohemia University Research Institute of Fish Culture and Hydrobiology, said:

"The crayfish react very fast on any non-specific change, which is different than any other detectors, which react fast on a very low concentration (of pollution) but only on one specific agent."

How the military uses fish to detect poisons in water

The startup, Blue Sources, is doing similar water monitoring with bluegill fish. It sets up a device that diverts water from the target source into aquariums with eight individual chambers. Each chamber houses one bluegill fish about two or three inches long. As the bluegills breathe, their respiratory muscle movements generate electric fields. Sensors monitor these electric fields and a neural network algorithm identifies changes that indicate whether the fish’s breathing patterns are consistent with getting clean water or water contaminated with pollutants like arsenic, cyanide, nerve agents or strychnine. 

The technology was developed at the U.S. Army Center for Environmental Health Research at Fort Detrick, and now the company licenses it from the U.S. military to operate on a “monitoring-as-a-service” (MaaS) model. It installs and maintains its own equipment on sites such as military installations, public utilities and an EPA superfund site.

These cyber organisms go to show that the centuries-old technology of using animals as early warning systems is not a relic of a bygone age, but a technique that can provide very useful sensor data, which can then be further enhanced with the right digital analytics.