The widespread use of precious metals (i.e., palladium) for drinking water treatment applications raises some concern due to their limited supply. In this Tretinoin study, the hybrid IX/catalyst system is estimated to require 7.8 kg of Pd every 10 years for a system treating 2.5 MGD of nitrate-contaminated source water. There are approximately 20 water treatment plants in California that treat nitrate using an IX system (information based on personal communication). Even if hybrid IX/catalyst systems were implemented at 100 comparably sized water treatment plants, total Pd use would only constitute ca. 0.1% of total annual U.S. consumption, estimated to be ∼60,000 kg/yr in 2012 (U.S. Geological Survey, 2013). Therefore, the impact of precious metal use in drinking water treatment to the precious metal life cycle is anticipated to be small. Furthermore, technologies are already well established for recovery of precious metals like Pd from catalytic converters used in automobile (Sibley, 2004), and similar approaches could be readily implemented to further reduce consumption of Pd and related metals used in centralized water treatment applications. Future study is needed to verify that lifetime of Pd–In/C catalyst since usable catalyst lifetime is an important factor both for overall environmental impacts of the hybrid system as well as sustainable use of precious metals.