- Envirobot collects and analyzes water samples in real-time
- Biological sensors react to overall water quality, not just specific compounds
- Autonomous bot can choose its own course and track pollutants to their source
A slick of oil spilled into a river may be a challenge to clean up, but it’s easy to detect. You can see it on the surface of the water and coating the unfortunate birds and animals that live nearby.
But other kinds of water pollution are not so easy to recognize—and they’re just as harmful.
Untreated sewage, agricultural run-off, and industrial waste containing heavy metals such as lead and mercury all enter our lakes and rivers, creating an invisible toxic soup.
Scientists regularly monitor water quality to determine if a body of water is safe for drinking, swimming, and fishing. But researchers must travel to the testing locations to collect water samples, sometimes facing hazardous conditions.
Such expeditions are not only expensive, but the time from on-site collection to laboratory analysis may be as long as three months.
Hoping to improve the process, scientists in Switzerland have invented Envirobot, an eel-like robot that glides through the water collecting samples and analyzing them in real-time.
The autonomous robot can even choose its own route in response to the conditions it encounters, tracking and locating a pollution source.
“Operating a robot has several advantages compared to a human mission, as it can be more quickly and easily deployed in case of need, and can operate at any time,” says Behzad Bayat, researcher at the Biorobotics laboratory, Swiss Federal Institute of Technology in Lausanne (EPFL).
Learning from nature
Envirobot is the product of several generations of earlier robots based upon the natural swimming motion of lampreys. Its modular construction allows researchers to attach or detach segments as needed.
“Robots like Envirobot are not just tools to accomplish a specific task but an instrument to study animals and learn from them,” says Bayat.
Each of the bot’s water-tight modules is independent and contains its own battery-powered motor. The segments are connected via two data bus networks, and the bot’s head contains WiFi and radio antennas, a GPS receiver, and an embedded computer.
In addition to sensors that collect information about water temperature, salinity, oxygen, and pH, Envirobot also contains sophisticated biological sensors that use living organisms to detect toxins.
“Most chemical methods detect a very specific compound,” says Jan van der Meer, a microbiologist at The University of Lausanne (UNIL). “But biological sensors can detect things broadly, like ‘good water quality’ or ‘bad water quality.’”
The modules containing biological sensors have small chambers that fill up with water as the robot swims. Inside, organisms such as Daphnia (water fleas) or rainbow trout gill cells react to contaminants, providing a more complete picture of water quality.
Biological sensors work well in a laboratory setting, but the challenge for researchers was to miniaturize them and then devise a way for the results to be transmitted to Envirobot’s computer, which requires an electrical signal.
For example, freeze-dried bacteria are reconstituted as water floods the chamber. The cells react to the presence of mercury compounds by emitting light, which is then measured by a luminometer that transmits the signal to the robot.
The robot is currently able to record and visualize data for up to one hour in a single expedition, depending upon battery and weather conditions. All the data Envirobot collects is logged in its onboard computer, but it can also be monitored by a remote researcher in real-time.
Probability of success
Envirobot has completed several successful missions in Lake Geneva, setting out from the shore, navigating into deeper water, pursuing a programmed course, and returning to shore.
But it can also use a probability mode to determine its own course. From any position in the water, it takes a sample, and then decides where to go next, leading researchers to sources of pollutants.
Future versions of Envirobot may even be able to dive and collect samples from deeper waters.
“If robots do the physical sampling and measuring, it gives humans more time to concentrate on more challenging and important matters,” says Alessandro Crespi, researcher at the Biorobotics laboratory, Swiss Federal Institute of Technology in Lausanne (EPFL). “Such as deciding what steps to take in response to the collected data, or developing measures to mitigate ongoing pollution.”