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CASE STUDIES IN THE INTEGRATED USE OF SCALE ANALYSES TO SOLVE LEAD PROBLEMS
Citation:
REGO, C. A. AND M. R. SCHOCK. CASE STUDIES IN THE INTEGRATED USE OF SCALE ANALYSES TO SOLVE LEAD PROBLEMS. Presented at AWWA 2007 Research Symposium: The Next Frontier, RENO, NV, March 02 - 03, 2007.
Description:
All methods of controlling lead corrosion involve immobilizing lead into relatively insoluble compounds that deposit on the interior wall of water pipes. Many different solid phases can form under the disparate conditions that exist in distribution systems, which range in how they react to changes in important distribution system water quality parameters arising from natural water quality fluctuations, or treatment impacts such as chemical feed disruptions, improved organics removal, changes in coagulant, installation of oxidizing removal processes, or changes in disinfection chemistry. Analysis of scales from pipes that reflect actual distribution system conditions provides a direct indication of the effectiveness of a current treatment protocol to provide a reality check on theoretical models. Knowledge of the characteristics and behavior of the lead solids that have been formed in the system can be integrated with water quality and operational information to: • Understand mechanisms of corrosion inhibition and uniformity throughout the system • Understand speciation of metals and predict mobility/stability • Follow impacts of treatment changes • Avoid making a major treatment change mistake by answering such questions as: – Is the operative corrosion control treatment method what you think? – What should be tested in corrosion control studies? – What “simultaneous compliance” issues exist? Knowing how a contaminant is chemically associated in distribution system scale materials can help with estimating the probability of unintended adverse consequences of treatment or water quality changes. Utilizing a variety of case studies, this presentation illustrates the investigatory procedures that can be used to understand scale development and relationship to water chemistry – both past and present conditions as well as potential future changes. The case studies represent both diagnosis of treatment problems as well as prognosis to anticipate both positive and negative impacts of various types of treatment changes.