Remote assessment of operational drinking water distribution networks

Abstract

Drinking water distribution systems are responsible for the safe transportation of potable water to the consumer and thus play an essential role in public health. Along main distribution pipes, excessive microbial growth may occur in the water as bacteria, archaeal and protozoa are released from biofilms. This is undesirable as it could cause microbiologically induced pipe corrosion or become a public health concern when opportunistic pathogens are involved. Therefore, ensuring good biological stability of the bulk water is of utmost importance. In this study, samples were taking from two large-scale and operational testbeds (Testbed A and B) which differ in drinking water storage and distribution. Sampling was conducted three times over the course of four months directly at the water mains. Flow cytometry was used to quantify live and total cell counts and to differentiate bacteria populations based on their morphology and relative genome content. Physico-chemical water quality parameters such as conductivity, temperature and residual monochloramine concentration in the bulk water samples were measured and correlated with microbial community diversity. Results indicate that all categories of bulk water from both testbeds fulfil Singapore’s drinking water requirements but that bulk water obtained from Testbed A shows significantly lower quality in terms of monochloramine and nitrogen species. Flow cytometry results also indicate significantly higher live and total bacteria counts on Testbed A when compared to both city bulk water and samples taken at Testbed B. The same could be observed for their specific microbial community composition. More iterations of sampling are recommended to increase confidence in these results and genotypic analysis is suggested to gain deeper insights into the composition of microbial communities on the species or family level.