The structure of biofilm grown in a drinking water distribution system with heat exchange analyzed with scanning electron microscopy and energy-dispersive X-ray spectroscopy

Abstract

Due to climate change, our society must become more climate resilient, and this is also the case for drinking water distribution systems. Climate change implicates that temperatures of the atmosphere are getting higher. This may lead to that the drinking water may become warmer. One of the consequences of climate change is that alternative ways of using and making energy has to be developed. One of the options is to use drinking water as cooling water. This will however require careful investigation. In this study the effect of higher water temperatures is examined for the purpose of using drinking water as cooling water, and enquires are made as to what effect this has on the structure of the biofilm inside drinking water distribution systems. A model system, with three setups using PVC pipes, was constructed. The first set up was a reference system with drinking water from the Dutch drinking water system, second set up was a reference system with heat exchange equipment where the water from the Dutch drinking water system goes through the equipment but no heat exchange occurs, the last set up was a thermal exchange system in which the drinking water is heated to a constant 25 degrees with the help of heat exchange. From each system biofilm samples were taken after 1,2,4,12,20 and 32 weeks. These samples were then analysed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Some visual trends were seen that were caused by age, and between the system with different temperatures with help of the scanning electron microscopy imaging. However, element analysis with the energy-dispersive X-ray spectroscopy showed no such trends. Whether this was due to no trends being present, or to the limitation of the technique, is unclear. From the result found in this research it is hard to make any conclusion of the effect of higher water temperatures on the structure biofilm in drinking water distribution systems, and further methods should therefore be tried