Biological stability in drinking water distribution systems: A novel approach for systematic microbial water quality monitoring

Challenges to achieve biological stability in drinking water distribution systems Drinking water is distributed from the treatment facility to consumers through extended man-made piping systems. The World Health Organization drinking water guidelines (2006) stated that “Water entering the distribution system must be microbiologically safe and ideally should also be biologically stable”. The biological stability criterion refers to maintaining the microbial drinking water quality in time and distance from the point of drinking water production up to the point of consumption. However, uncontrolled growth of indigenous bacteria during water transport can result in the deterioration of aesthetic aspects of water, such as taste, colour, and odour, in exceeding of guideline values, and/or in technical problems. Controlling bacterial growth in piping systems and premise plumbings is very challenging (Chapter 2), and changes in drinking water microbial characteristics are often measured in networks distributing water with or without residual disinfectant such as chlorine, monochloramine or chlorine dioxide. In the Netherlands, drinking water is distributed without detectable residual disinfectant. Quantitative and qualitative knowledge on the indigenous bacterial communities and microbiological processes taking place during drinking water distribution is limited and in-depth investigations are required. New opportunities with novel analytical methods One reason for the lack of knowledge on bacterial growth controlling factors in drinking water distribution systems is that methods for characterizing drinking water bacterial communities are still relying heavily on culture-based techniques such as plate counts, developed more than 130 years ago. The conventional cultivation-based methods have major limitations: only a minute fraction (