Authors:

Katie Nicole Smith

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About Paper:

Water systems that are shut down seasonally, such as water parks and splash pads, may have very specific water treatment needs upon start-up. It is unclear how microbial biofilms react to long-term stagnation. Pipe wall biofilms have a strong effect on the bacterial cell concentrations in these water systems, and potentially exposure to pathogens surviving in biofilms. This study investigates the differences in bacterial cell concentrations in a system that has been shut down for 6 months to previous experiments in which the system was under consistent daily operation. The system contains three different pipe materials in triplicate: ice maker lines, shower hose, and CPVC pipe. After approximately 6 months of system disuse, wherein some of the system may have dried out, water samples were collected after varying lengths of stagnation. For sample collection, each pipe was flushed for 2 minutes, with the initial 15 mL of water taken for measurement. The chlorine concentration was measured immediately following sample collection using a chlorine pocket colorimeter. Flow cytometry was used to measure total and intact cell concentrations. Similar experiments were performed one year ago, when the system had been in constant use. It was found that the pipe wall biofilm and thus water characteristics changed substantially following the system shutdown. While cell concentrations in first flush samples had a similar order of magnitude, the maximum reached during stagnation was lower than when the system was in constant use. This demonstrates that system shutdowns that allow dry out may help with biofilm management in water parks and splash pads, but disinfection upon start-up is still important. A changing climate and lack of shutdowns for these systems could potentially increase exposure to pathogens surviving in biofilms. Keywords: Biofilm; Water; Pathogens; Chlorination

Source:

Purdue University / 2024

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Co-authors:

Katie Nicole Smith