No abstract

The objective of this project was to evaluate the extent of loose deposit accumulation in distribution systems in three Canadian cities to determine optimal flushing frequency. Unidirectional flushing was used to remove the deposits. The results obtained were found to be highly system‐dependant. The normalized mass of flushed deposits varied from less than 0.1 g/m (0.03 g/ft) to approximately 40 g/m (12 g/ft). For the range of velocities attained during flushing (0.65–2.3 m/s [2.1–7.6 fps]), the quantity of collected deposits was not a function of velocity. Analysis of the composition of the deposits confirmed the specificity of each water system. In all systems, the major fraction was iron corrosion compounds (38–72%), but organic matter (14–24%) and silicoaluminum compounds (7–16%) were also found to account for an important part of the deposits. Microbiological analyses revealed concentrations of total bacteria of approximately 1010 bacteria/g, but the presence of total coliforms was limited to 1.2% of the samples (n = 258).

A 1 year study was undertaken on groundwater that was a source of drinking water in the province of Quebec, Canada. Twelve municipal wells (raw water) were sampled monthly during a 1 year period, for a total of 160 samples. Using historic data, the 12 sites were categorized into 3 groups: group A (no known contamination), group B (sporadically contaminated by total coliforms), and group C (historic and continuous contamination by total coliforms and (or) fecal coliforms). Bacterial indicators (total coliform, Escherichia coli, enteroccoci), viral indicators (somatic and male-specific coliphages), total culturable human enteric viruses, and noroviruses were analyzed at every sampling site. Total coliforms were the best indicator of microbial degradation, and coliform bacteria were always present at the same time as human enteric viruses. Two samples contained human enteric viruses but no fecal pollution indicators (E. coli, enterococci, or coliphages), suggesting the limited value of these microorganisms in predicting the presence of human enteric viruses in groundwater. Our results underline the value of historic data in assessing the vulnerability of a well on the basis of raw water quality and in detecting degradation of the source. This project allowed us to characterize the microbiologic and virologic quality of groundwater used as municipal drinking water sources in Quebec.