Intermittent water supply (IWS), the provision of potable water non-continuously, leads to periods of stagnation with conditions favorable for biofilm growth. Regular repressuring of pipes at the beginning of each supply cycler has been shown to shear off biofilms from pipewalls and transfer inhabiting microorganism into the bulk water phase, potentially contaminating the drinking water with opportunistic pathogens.
Here we assess the effects of IWS and continuous supply (CWS) on the quality of drinking water in an aboveground testbed in a tropical climate. Non-microbiological water quality was measured in the bulk water and correlated with flow cytometrical analysis of microorganisms. Microbial parameters such as size, shape and relative genome content were used for phenotypic fingerprinting and subsequently, to compare community dynamics in biofilms of pipes operated intermittently (turbulent flow) or continuously (laminar flow).
Significant increases in the concentrations of total and live cells as well as an increase in alpha and beta diversity are observed within each pipe during the initial flushing phase (≤ 60 seconds) when compared to both the CWS and inflowing water. Changes in monochloramine levels as well as nitrogen species further indicate the detachment of biofilm during initial flushing and that consumers might be exposed to microbial hazards and its discarding is recommended to minimize the risk to the consumer.
While the phenotypic analysis utilized here does not allow for the level of detailled insight into the composition of biofilms and bulk water as sequencing would, it is affordable as well as relatively easy to use and thus allows to monitor changes in the microbial composition in close to real-time.
