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Actual vs. Predicted: Lead Scale Observations from the Field
Citation:
Tully, J., M. DeSantis, AND M. Schock. Actual vs. Predicted: Lead Scale Observations from the Field. EPA Small Systems Webinar, Cincinnati, Ohio, March 26, 2019.
Impact/Purpose:
This presentation reports the results of an FY15-FY16 Regional Applied Research project with EPA Region 5 and was part of the efforts under the Safe and Sustainable Water Resources Program’s research for distribution system corrosion analysis and modeling project. The results of this presentation will be of interest to water utilities implementing corrosion control programs, as well as researchers and government officials interested in this topic.
Description:
The conventional wisdom of lead solubility has been built over the years by geochemical solubility models, experimental studies, and field sampling of drinking water lead levels using differing protocols. These models predict that lead solubility and release would be controlled by an expected mineral phase in a system with given specific water quality parameters. Rarely, have the phases formed in real world drinking water distribution system (DWDS) pipes been compared back to theoretical predictions. In this study, EPA researchers analyzed the pipe scale from lead service lines (LSL) from 22 drinking water distribution systems (DWDSs) in the US EPA’s Region 5 and compared the results to model predictions. This study indicated that the scales observed in real world DWDSs often do not follow the model predictions, but rather contain a mixture of expected and unexpected lead phases. Of the different corrosion control treatment types, pH/alkalinity adjusted and lime softened systems most frequently matched the predicted phase, whereas phosphate dosed systems were the least predictable. In total, 13 of the 22 systems were found to have <50% of the predicted phase in their pipe scales.