Optimizing source water blends for corrosion and residual control in distribution systems

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