AWWA JAW62059

Even if water quality complies with the most stringent regulations, water distribution systems can never be free of particles or microorganisms. Particulate materials accumulate as loose deposits in distribution systems as a result of several mechanisms. A number of adverse effects on water quality are associated with the presence of loose deposits in networks, including coliforms and consumer complaints. The objective of this article was to evaluate the extent of loose deposit accumulation in distribution systems in three Canadian cities to determine optimal flushing frequency. In this study, the quantity and nature of loose deposits removed during unidirectional flushing (UDF) procedures is documented and the role of treated water characteristics and network configuration on the rate of loose deposit accumulation is identified. The collection of data and the analysis of the results obtained by UDF was found to be useful to water utilities because it enables utilities to characterize the efficiency of UDF programs with relatively simple protocols, evaluate the potential adverse effects of resuspended loose deposits on water quality, and read the current situation of the network. The combined practice (flushings and analyzing the procedure effectiveness) can be a useful tool in the decision-making process of maintenance operations, especially during the first years following the implementation of this operations and maintenance procedure. Includes 31 references, tables, figures.