Continuous Monitoring of Bacteria in Drinking Water
Svendsen, Winnie E ; Bertelsen, Christian Vinther ; Skands, Gustav ; Dimaki, Maria ; Clausen, Casper Hyttel
Real-time continuous monitoring of bacteria concentrations in drinking water is of great importance in drinking water management. The methods used today are time-consuming and give a warning up to 1-2 days after a potentially dangerous bacterial outbreak. Continuous monitoring of water will enable better control of the drinking water that reaches the households, by stopping the delivery of water automatically, should the presence of bacteria be detected. In this study we developed a microfluidic sensor, which enables accurate real-time assessment of the bacteria level in drinking water. Multi-frequency electrical impedance spectroscopy is applied to the drinking water, which is passed through the sensor. The frequencies are chosen to differentiate particles based on their size and on their surface properties - or membrane properties in case of bacteria. Fecal contaminations in drinking water are always of the gram-negative bacteria type. Thus, a sensor, which can differentiate gram-positive from gram-negative bacteria and measure the overall bacteria level, can be used to indicate whether or not the drinking water is contaminated. In the developed impedance flow cytometer the gram-negative Escherichia coli and the gram-positive Staphylococcus aureus are electrically differentiated based on their cell membrane composition and properties. Furthermore, it is shown that Escherichia coli and Staphylococcus aureus can be clearly differentiated from non-biological polystyrene beads.