The objective of this project was to demonstrate and validate the retrofit of existing buildings with an integrated suite of water efficiency and reuse technologies that support building level cascade of water use thereby reducing potable water consumption. An existing administrative building was retrofit with a cascading water use system that combined the proven technologies of water efficiency with newer, less applied concepts of graywater reuse to provide an optimized, highly efficient system for minimizing potable water use in Department of Defense (DoD) buildings. A new training barracks that was constructed with a building scale graywater reuse system in place was monitored for its ability to meet the project’s performance objectives.

Technology Description

The project considered a range of water saving technologies that building managers could consider. Based on demonstration site factors, the project focused primarily on efficient water fixtures and graywater reuse technologies. Most of the technologies studied were at the bathroom scale, though one building scale system was evaluated as well. For bathroom retrofits, the technologies investigated included 0.5 gallons per minute (gpm) sink faucets with infrared auto-off sensors, an under-sink gray-water reuse system, low flush toilets and/or alternate toilet sensor settings, and 2 gpm showerheads in building locker rooms. The building scale system that was investigated was a graywater reuse system that treated graywater from sinks and showers such that it could be reused for toilet flushing. The primary metric for the project was to reduce water demand at the building level by 30%. Impacts on operations and maintenance, as well as energy consumption, were also measured.

Demonstration Results

In the case of a building comprised primarily of office space, conservation fixtures achieved a reduction in overall facility water use of 7% as compared to the target rate of 30%. An additional 7% reduction was realized by adjusting toilet automatic flush mechanisms, for a total building potable water reduction of 14%. Several factors contributed to this lower than projected reduction. First, faucets and showers represented a small fraction of the building water demand, which included specialized research facilities with high water needs, so associated improvements had limited overall impact. Second, recommendations for toilet retrofits were limited to flush valve sensor adjustments, with toilet and flush valve replacements planned by the facility for an upcoming remodel. Despite this low figure, the faucet and shower retrofits paid for themselves in less than a year with the cost of water alone. Lastly, the undersink graywater system did not recover enough water from the sinks to support the toilet flushing.

Implementation Issues

This study confirmed that conservation technologies such as efficient fixtures can improve sustainability and resiliency in a cost effective manner. On the other hand, water reuse at the building scale is still a maturing technology space, and challenges with automation, retrofit cost, and a relatively low ratio of water cost to capital costs still present barriers to the adoption. Higher levels of water reuse through advanced treatment could be one option for improving payback, though regulatory challenges may limit that approach in the near term. Alternatively, non-market-cost valuations based on the need for DoD facilities to meet water demand reduction targets within Executive Order 13693, Net Zero policy, and water security capabilities described in Army Directive 2017-07, could still drive technology adoption. During the study, it was also noted that some facilities at installations, such as off-grid training areas, incur very high water and wastewater costs that are on the order of 100-fold the cost for on-grid buildings. Targeting these areas may provide an alternative cost-effective approach for maturing water reuse technology for future building scale applications. Overall, there is considerable work remaining to provide building scale solutions to support integrated capabilities that can fully address current DoD guidance and policies for water resilience and security.
  • Reuse ,

  • Gray Water