Assessment of transient negative pressures at the site ofthe Payment's drinking water epidemiological studies

摘要

Continuous monitoring of water pressure using up to 12 high-speed pressure transientdata loggers has been performed for over a year in the distribution system where Paymentet al. conducted their epidemiological studies. The duration of monitoring was dividedinto 4 phases with reduced monitoring during winter time. Transient and sustainednegative pressures have been measured in the distribution system due to power failures atthe plant (WTP), closure of a transmission main and localized pipe repairs. Under normalsystem operation, a total of 9 low pressure events were recorded at the WTP during thefirst year of monitoring (June 2006-June 2007) resulting in 4 confirmed and 5 suspectedtransient negative events in the distribution system. Characterization of potential sourcesof microbial intrusion was also performed with the investigation of soil and watersamples in pipe trenches and water samples from flooded air-and-vacuum relief valvechambers.