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Decades of reactions - how pipe scale analyses can help to answer questions
Citation:
Tully, J., M. Schock, Mike DeSantis, S. Triantafyllidou, D. Lytle, AND S. Harmon. Decades of reactions - how pipe scale analyses can help to answer questions. AWWA Water Quality Technology Conference, Cincinnati, OH, November 13 - 17, 2022.
Impact/Purpose:
While a priority has been placed on removing all existing lead service lines (LSLs) in the US, LSLs will likely continue to serve drinking water and expose consumers for many decades. Therefore, understanding the scales present on LSLs is a critical piece of information that will help water systems limit consumer exposure to lead. Scale analysis is one of several tools that can be used to create a comprehensive understanding of lead release to drinking water. This presentation will focus on potential questions a drinking water utility may have about pipe scales and the different analyses that would be needed. A particular focus will be paid to what questions may be left unanswered given various analyses for a particular question.
Description:
Drinking water utilities have many tools (e.g., bench scale studies, background water quality monitoring, solubility modeling, investigative sampling, etc.) at their disposal to evaluate lead release within their systems. Each tool has a specific purpose(s) in understanding lead release and corrosion control, that when considered together, can develop a holistic understanding of lead release and reduction within a system. Pipe scale analyses have been demonstrated as one of the valuable tools in assessing the state of corrosion control, predicting the impact of source or treatment changes on metal release, and assessing effectiveness of corrosion control strategies. Pipe scale analyses, however, are not as widely applied by water systems as other approaches, due to method complexity, limited laboratory capabilities, lack of experienced analysts, and interpretation challenges. Furthermore, pipe scale analyses can also be an expensive and time-consuming process. Given the value of pipe scale analyses, there is a critical need to educate the drinking water field on aspects of scale analyses to help make decisions. A recent paper published in AWWA Water Science aims to better explain pipe scale analyses, the analytical techniques involved, the questions they can answer, and potential pitfalls/cautions. This presentation will walk through some potential questions a drinking water utility may have about pipe scales and what information the different analytical techniques would provide along with what information would be missing. Case study data will be shown to illustrate the resulting information from various analyses (e.g., powder X-ray diffraction, scanning electron microscopy, etc.) and demonstrate the conclusions that can be drawn. One critical piece of pipe scale analysis is understanding the limits of the data given the variables at hand, and what questions scale analyses cannot answer (such as if a scale is forming, static, or dissolving) without being coupled with additional evaluation tools. The strength of conclusions that can be drawn at the completion of a pipe scale analysis depends on many factors. Properly qualifying those conclusions requires understanding of various limitations such as number of samples analyzed, pipe harvesting contamination, or the type of pipe scale sampling involved, and suggested best practices in the paper can help to overcome the majority of the limitations. Focus will be paid to what questions can be answered, but also what questions may be left unanswered if a complete set of pipe scale sample preparation techniques and analyses is not possible.