Funding: A portion of this work was funded by NSF RAPID grant (#DEB-1929843), and ISW was supported through a Pitt STRIVE Fellowship at the University of Pittsburgh.

Personnel associated with the project: Isaiah Spencer-Williams, Mitchell Meyer, William DePas, Emily Elliott, Sarah-Jane Haig

Summary: Orthophosphate (PO₄^-3) is an established lead corrosion inhibitor that forms low solubility lead solids (e.g., a protective scale). Alongside pH and alkalinity adjustments, PO₄^-3 is among the most widely used approaches for lead corrosion control due to its versatility in waters with variable water quality parameters. However, the addition of excess PO₄^-3 into the system (to promote scale formation, which can take weeks to months) may result in unexpected challenges from a microbial perspective. Drinking water distribution systems host a diverse aquatic ecosystem that can be altered by several factors including source water quality, temperature, treatment processes, disinfection methods, piping materials, and nutrient availability. Additionally, drinking water distribution systems are oligotrophic environments where diverse microbial communities, including communities containing drinking water-associated pathogens that can infect the immunocompromised (DWPIs), compete for limited nutrient availability.

Study Aims:

1. Assess the impacts of full scale PO₄^-3 addition on the drinking water distribution system microbiome.
2. Examine how DWPI abundance changes as a result of full scale PO₄^-3addition in the distribution system.
3. Elucidate the impacts of full scale PO₄^-3 addition on biofilm formation potential.

Key results of this study

1. Distribution system microbial community composition was impacted by orthophosphate addition
2. Increases in total bacteria, nontuberculous mycobacteria (atpE gene), and Legionella pneumophila (mip gene) were detected throughout the distribution system after orthophosphate addition
3. Phosphate addition appears to impact the biofilm formation potential of mycobacterial species in different ways and at different concentrations.

Publications and Conference Presentations:

1. Spencer-Williams, I., Meyers, M., DePas, W., Elliott, E., Haig, S.J. (2023). Assessing the Impacts of Full-Scale Distribution System Lead Corrosion Control on Drinking Water Associated Pathogen Abundance and Drinking Water Microbial Communities. Environmental Science & Technology. 57(48), pp.20360-20369.
2. Spencer-Williams, I., Meyers, M., DePas, W., Elliott, E., Haig, S.J. PO43- Corrosion Control: The Unintended Consequences on Nontuberculous Mycobacteria in a Full-scale Drinking Water Distribution System. AEESP Annual Conference 2023. June 20 – 23, 2023.
3. Spencer-Williams, I., Meyers, M., DePas, W., Elliott, E., Haig, S.J. A Delicate Balance: Addressing Lead Contamination and Drinking Water-Associated Pathogen Abundance in a Full-Scale Drinking Water System. PA-American Water Works Association Southwest District Spring Meeting 2023. April 14, 2023.
4. Spencer-Williams, I., Haig, S.J. Exploring the Impacts of Full-Scale Distribution System Lead Corrosion Control on Drinking Water-Associated Pathogens. Pennsylvania Water Environment Association Annual Technical Conference. June 7, 2022.
5. Spencer-Williams, I., Mohammadshafie, N., Haig, S.J. Assessing the Impact of Orthophosphate Corrosion Control on Microbial Abundance in a Full-Scale Drinking Water Distribution System. AEESP Annual Conference 2019. May 14 – 16, 2019.