According to the World Health Organization (2012), about 780 million – about 1 in 9 – people lack access to clean water and 3.4 million peopled died as a result of contaminated water, with 99% of those deaths occurring in the developing world (2008). And, while communities and organizations struggle to improve the quality of drinking water in these areas, methods for detecting water contaminants may be necessary to determine whether or not a water supply is safe. Relying on a sample of electricity producing bacteria and 3D printing technology, researchers at the University of Bath’s Department of Chemical Engineering have developed a low-cost solution to this problem, that doesn’t require expensive lab equipment.
In conjunction with Bristol Robotics Laboratory at the University of the West of England, Bath scientists developed a low-cost sensor for the continuous monitoring of water quality in lakes and rivers. The sensor contains a microbial fuel cell, manually embedded within 3D printed layers, that produces a steady flow of electricity as the bacteria within feed and grow; however, when introduced to a pollutant, the electric current decreases, signaling contamination in the water.
The researchers explain in their report, published in Biosensors and Bioelectronics, that current methods for testing water quality involve the use of fish or daphnia, a costly, time consuming, and sometimes unreliable process. Otherwise, mass spectrometry may be implemented, but, due to the equipment and expertise involved, it is difficult for developing countries to adopt. With their low-cost solution, the scientists at Bath were able to pick up traces cadmium, a pollutant produced by the electronics industry, in quantities below accepted safe levels, demonstrating the sensitivity of their device.
Dr. Mirella Di Lorenzo, Lecturer in Chemical Engineering at Bath and lead author on the study, elaborated, “When the bacteria feed in a microbial fuel cell, they convert chemical energy into electrical energy that we can measure. We found that when we injected a pollutant into the water there was an immediate drop in the electric current they produced. The drop was proportional to the amount of toxin present and the current is recovered once the toxin levels fell. This means we are able to monitor the level of pollutants in the water in real time without having to collect multiple samples and take them to a laboratory. Because this system uses live bacteria, it acts a bit like a canary in a mine, showing how these chemicals affect living organisms.”
The next step for Di Lorenzo and her team is to test their sensor with toxins other than cadmium and to develop methods for detecting multiple pollutants at once. The report does not yet indicate when such a device may be used in the field. Nor does it mention whether or not it can be used in developed countries with hazardous industrial practices.