More and more utilities are using chloramines in place of free chlorine for greater residual stability and better compliance with both the Total Coliform Rule and the stringent requirements of the Disinfectants/Disinfection Byproducts Rule. However, new information about disinfectantinduced changes in oxidation reduction potential, lead and copper chemistry, scale formation, and scale destabilization involving natural organic matter has contributed to greater understanding of factors influencing increased corrosion and metals release. This article consolidates and updates information about potential effects of changing disinfectants on lead and copper release in drinking water distribution systems. The findings indicate the importance of chemical properties and electrochemical behavior in understanding how corroding metals and alloys respond to transition from free chlorine to chloramines and vice versa.

This article presents case studies that detail the activities by water utilities to investigate microbial occurrences. The following investigative strategies are described: sampling and detection methods; disinfectant concentration; speciation; additional monitoring and analysis; biofilm pipe coupons; and, nutrients. The case studies also highlight mitigation strategies such as distribution system disinfectant, change in treatment, water quality, operation and maintenance, and source water monitoring.