RAPID: Assessing the ecosystem impact of drinking water orthophosphate addition on urban watersheds

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The city of Pittsburgh is planning to add corrosion inhibitors (e.g., orthophosphate -PO43−), at the end of March 2019 to the 70 million gallons of drinking water (DW) it produces, to combat lead leaching from lead service lines. The planned rate of addition is 2-3 orders of magnitude higher than current levels of reactive phosphorus (P) in DW and urban streams. This substantial change in P concentration, alongside the fact that Pittsburgh's DW pipe network loses an estimated 15 million gallons/day due to leaks, suggests that elevated concentrations of P are likely to infiltrate into groundwater and could ultimately impact the health of urban streams. This Rapid Response Research (RAPID) project will assess changes in the microbial ecology, water chemistry and nutrient availability in water collected from DW pipes and hydrologically connected urban streams before and after PO43− addition.The primary goal of this RAPID is to determine whether PO43− addition in the Pittsburgh DW pipe system will impact the ecology and geochemical cycling in hydrologically connected urban streams. Water samples will be collected from urban streams and DW pipe locations eight times before and eight times after PO43− addition. By performing comprehensive water chemistry analysis, microbial community characterization and quantification of specific genera and species linked to PO43− accumulation and nitrogen fixation, the scientists will observe whether broad-scale ecological or nutritional shifts occur. Likewise, algal nutritional limitation studies will provide insight into the eutrophication potential of urban stream water after PO43− addition. Overall, the study will help answer fundamental ecological questions relating to how leaking DW infrastructure can impact nutrient cycling and aquatic ecosystems in hydrologically connected urban streams.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.