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The implementation of groundwater conservation measures has forced utilities with a historical reliance on groundwater sources to consider alternative sources to augment their supplies or to eliminate their groundwater dependence. Switching from traditional source water, however, can cause unacceptable changes in water quality that result from destabilization and the release of chemical and biological films from the interior surfaces of the existing distribution systems. Data from a two‐year study were used to identify significant water quality parameters and to develop a predictive nonlinear model to estimate the corrosivity of blends based on water quality. The results of the statistical analysis indicate that alkalinity, chlorides, sulfates, sodium, and dissolved oxygen of the source water or blend of source waters have a significant effect on release of corrosion by‐products in the form of red water. Temperature and hydraulic retention time were the significant physical and operational parameters identified.

Utilities must understand the issues involved when multiple source waters are blended, particularly the effect on distribution system water quality. This article describes a multiobjective technique that can help evaluate blends to identify acceptable water quality for simultaneous control of lead, copper, iron, and monochloramine levels in distribution systems. Blends of three source waters—groundwater, surface water, and desalinated water—were evaluated. Modeling results indicated that different pipe materials often have conflicting water quality requirements for release abatement. For example, corrosion of copper and lead pipes was increased by increasing alkalinity, whereas increasing alkalinity was beneficial in reducing the release of iron corrosion products from pipes. Increasing sulfates reduced lead release but increased iron release. These conflicting water quality requirements for lead, copper, and iron release mean that utilities must evaluate the tradeoffs between water quality and corrosion response.

Effects of water chemistry, temperature, pipe material, and hydraulic conditions on total chlorine dissipation were investigated using laboratory-and pilot-scale experiments. Chlorine demand in the bulk phase depends on water chemistry, and the bulk-phase dissipation constant (k b ) generally increased with increasing dissolved organic carbon. A 10 o C rise in temperature resulted in a threefold increase in k b . Pipe material significantly influenced total chlorine dissipation rates in the following order: galvanized iron > unlined cast iron > polyvinyl chloride (PVC) > lined cast iron. Total chlorine consumption predominantly occurred at the wall surface in small-diameter unlined cast-iron and galvanized-iron pipes and predominantly in the bulk phase for lined cast-iron and PVC pipes. The mass transfer coefficient (k f ) and the overall dissipation constant (K ) increased with increasing Reynolds numbers. The wall constant (k w ) is an intrinsic pipe property and is therefore a true constant; an increase in k w with increasing Reynolds number was observed. However, this may be attributed to dynamic changes in particulate surface area associated with release of corrosion products from the pipe surface.

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