The overarching objective of this project is to provide new scientific insights into lead phosphate nucleation, aggregation, and deposition that will enable efficient application of phosphate to control both dissolved and total lead concentrations in water. The specific objectives are to (1) identify factors that control the behavior of lead phosphates in solution and quantify the effects of water chemistry on those processes; (2) determine the rates of precipitation and deposition of lead phosphate particles on scales that form on pipe surfaces; and (3) enable optimization of phosphate application strategies that can be tailored to a particular water chemistry and scale type. The approach will build from fundamental studies of processes in solution (Task 1) and on surfaces (Task 2) to the consideration of processes occurring in intact pipes (Task 3). The project is funded through a Memorandum of Understanding (MOU) between WRF and the National Science Foundation (NSF). Under the MOU, WRF will fund Task 3 of the study; while the NSF will fund Tasks 1 and 2. The researchers will publish the results as a single final report.
The new lead pipes have now been conditioned to a stage at which a substantial scale of lead(IV) oxide (PbO2, plattnerite) has been developed and is maintaining both total and dissolved lead concentrations at consistently low levels.
Two sets of lead pipes are being conditioned for use in studying the timing and mechanisms for orthophosphate to effectively control lead concentrations.