Whether IT is implemented as direct or indirect potable reuse, recycling water alters the water chemistry compared to the sources used prior to reuse

The Bureau of Reclamation awarded a Cooperative Agreement valued at $264,133.31 to The Regents of the University of Colorado under the Water Desalination Research and Development program (CFDA 15.506) effective May 28, 2025, with completion scheduled for September 30, 2026. The University of Colorado will develop an innovative methodology to proactively assess toxic metal release and mobilization risk in potable water distribution systems affected by water recycling initiatives. Current assessment methods lack the capability to correlate toxic metal presence with actual release probability into drinking water supplies, particularly in aging cast iron pipe infrastructure where corrosion-induced discolored water events can mobilize hazardous metals such as chromium, arsenic, and uranium.

The project deliverables will include a comprehensive analytical approach that identifies which reactive iron phases associate with toxic metals and predicts release likelihood under changing water chemistry conditions. This advancement addresses a critical gap in existing scale analysis and coupon/pipe loop testing methodologies by integrating water chemistry analysis with explanatory chemical mechanisms. The research conducted at the Boulder, Colorado facility will minimize hazardous product releases in water distribution systems transitioning to recycled water sources, supporting the program's core objective of augmenting the United States' usable water supply while managing environmental and public health impacts associated with water reuse.

Changes in water chemistry can increase corrosion in distribution systems. For utilities with cast iron pipes, corrosion destabilizes the iron scale layers leading to discolored or red water events. Since iron scales act as a sink for other trace metals, discolored water events can mobilize toxic metals, such as chromium, arsenic, or uranium. This project will develop a new method for proactively assessing the presence of toxic metal release and the susceptibility of release due to changing water conditions. Current methods are limited, because they do not link the presence of a toxic metal to the likelihood of release into potable water. Scale analyses digest samples using aggressive acids and cannot distinguish to which reactive iron phases the toxic metals were originally associated. Similarly, coupon and pipe loop studies with representative waters are typically not paired with a comprehensive analysis method that can explain why metals were or were not released. The project seeks to develop a better understanding of why and minimize the release of hazardous products into distribution systems due to water reuse.