Drinking water may be monitored more strictly than almost anything in the developed world. It should be cool, colorless, tasteless, and odorless. It may not have any pathogens or impair your health.
Although modern water supply networks are put through a series of screenings at regular intervals, they aren't immune to accidents, targeted attacks, errors, or failure from normal deterioration. And analytical techniques are time-consuming, providing test results from random samples hours after testing. Often, they are also attuned to specific substances; limiting their application spectrum.
Now, researchers at the Fraunhofer Institute (Germany) have created a system for constant, real-time monitoring of drinking water that can warn authorities of a wide range of potentially hazardous substances in a matter of minutes. The AquaBioTox project has a biosensor that quickly reacts to such substances as cyanide, ricin, or toxic metabolic products from bacteria that can be fatal even in concentrations of nanograms per liter.
Camera picks up glow
The system works by diverting some drinking water from the main line into a sensor in a branching, descending line that contains two different strains of bacteria and mammalian cells. These micro-organisms in the sensor are modified so that they produce a red fluorescent protein when they come into contact with toxic substances. Those substances can then be detected and analyzed by a highly sensitive camera.
"We tested various classes of substances that might occur in water, even though they shouldn't, and to date our sensor has reacted to each of these substances," says Iris Trick, a co-developer and scientist from the Fraunhofer Institute for Interdisciplinary Engineering and Biotechnology (IGB) in Stuttgart. "Our sensor can document even very slight concentrations."
Thomas Bernard, the group manager at the Fraunhofer Institute of Optronics, System Technologies, and Image Exploitation (IOSB), came up with an analysis unit for the camera that registers even the most minute changes in fluorescence and analyzes them automatically.
The red fluorescent bacteria in the glass tube at right change color when the micro-organisms in the biosensor come into contact with toxic substances. The measuring probe shows the intensity of fluorescence.
"The monitoring unit has a machine-learning process," Bernard says, for determining from historical data which fluctuations in the physical, chemical, and biological parameters are normal. "It sets off an alarm if an unusual pattern shows up in the signals," he says.
Another component of the AquaBioTox system is a daphnia toximeter from project partner bbe Moldaenke of Kiel, Germany. The environmental manufacturing company noticed that water fleas are particularly sensitive to nerve poisons, so researchers are testing this imaging/monitoring system in a closed-performance route on the grounds of Berlin's water company, another partner in this project. The idea behind it is making the system as small and cost-effective as possible so that a network of sensor units communicating with one another could be distributed over sensitive points in the drinking water network.
Because the micro-organisms in the biosensor are critical to the detector, and the detector must be operated continuously, IOSB researchers have developed a companion system that automatically monitors and regulates important parameters such as temperature and inflow of nutrients to guarantee optimum life conditions for the micro-organisms.
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