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Then and Now: Direct Potable Reuse Demonstration in Denver 30 Years Later

Authors: Rehring, J., Nealey, M., and Parker, A.

Water Efficiency, November 2019

Municipal water utilities are aiming to use existing water supplies more efficiently and to enhance the robustness and diversity of their water systems to protect against drought and other risks. To support this goal, many utilities are turning to direct potable reuse (DPR), in which purified reclaimed water is introduced directly into a potable water supply distribution system or into the raw water supply immediately upstream of a water treatment plant.

In the late 1980s and early 1990s, Denver Water pioneered DPR in the United States with a 1 million gallon per day (mgd) offline treatment facility. With this facility, they demonstrated treatment processes that could reliably clean secondary effluent from a water reclamation facility to potable water quality.

The DPR project of the 1980s achieved its water quality and public education goals. However, the need for implementing DPR in Denver Water’s system has not yet materialized, in part due to Denver Water’s aggressive water conservation efforts. Still, DPR remains an important option in Denver Water’s long-term water supply planning.

Nearly 30 years after Denver Water’s pioneer project, several Colorado water utilities are now considering DPR as part of their plans to take full advantage of reusable supplies. In 2018, a coalition of Colorado water providers and industry members conducted a DPR demonstration to advance regulatory development, public outreach, and engagement, and to show the viability of a treatment process that does not generate significant waste products.

Both pilots provided many lessons that utilities everywhere can use when considering and implementing DPR.


Rehring, J., Nealey, M., and Parker, A. “Then and Now: Direct Potable Reuse Demonstration in Denver 30 Years Later.” Water Efficiency.14(7): 8-11, November/December 2019.