AWWA ACE60059

While previous studies have extensively focused on treating water in order to prevent corrosion, the factors that affect stability of corrosion scales and the role they play on the quality of drinking water within distribution systems have not been considered relevant until now. This investigation assessed the response of corrosion scales from aged galvanized water distribution systems under alternative water sources - groundwater and a blend of ground and surface water. A pilot project using pipes from various distribution systems has been designed and monitored for variations in water quality. The system is designed to simulate the actual operating conditions of a distribution system with 2, 20 and 40 years of service. Continuous monitoring of water quality has been recorded over the course of 18 months. Results showed that under similar water characteristics each pipe responded differently, suggesting that both the structure and composition of scale play an important role in maintaining the quality of water within the distribution system. The introduction of a new water source (the surface and groundwater blend) produced general reductions in iron release, turbidity and color values. The influent water quality parameters that showed significant variations compared to the base-line were dissolved oxygen, pH, alkalinity, and sulfates. In general, older pipes, which have much more developed oxide scales, were more sensitive to water quality variations than the new pipe. Overall, the main factors affecting water quality within the pipes were identified as increase in temperature, increase in dissolved oxygen, increase in pH, decrease in alkalinity, and increase in sulfates. Includes 8 references, tables, figures.