EXPLORATION
LIFE SUPPORT

WATER RECOVERY OVERVIEW

Currently, on-orbit water recovery hardware is limited to collection of humidity condensate by Russian and U.S. systems and recovery of humidity condensate by Russian equipment. Stabilized urine is stored and returned to Earth for disposal. Regenerative ECLSS hardware that will be deployed on ISS will increase the capability to recover wastewater by processing pretreated urine in a Vapor Compression Distillation (VCD) subsystem. Humidity condensate and urine distillate will be treated through a combination of adsorption/ion exchange processes and thermal catalysis, collectively known as the Water Processing Assembly (WPA). When these subsystems are deployed on ISS, approximately 93% of wastewater will be recovered to potable standards. The remaining wastewater will be disposed of as a concentrated brine solution.

Technology gaps that will be addressed for the near term short duration missions by the Water Recovery Element include the development of an effective biocide that does not require removal of the disinfection agent prior to crew consumption and a less toxic system urine pretreatment system. In addition to advanced development in areas of urine stabilization and potable water disinfection, certain alternate approaches to processing wastewater to potable drinking water may be of value for near term missions beyond ISS.

For Lunar Outpost missions, the requirements levied upon a water recovery system expand. Longer duration outpost missions are expected to have greater water requirements and therefore greater wastewater volumes. The sources of wastewater increase from stabilized urine to include humidity condensate, Extravehicular Activity Mobility Unit (EMU) condensate, and hygiene and laundry wastewater. Recovery of potable water from wastewater is essential. The primary technology gap is to reduce resupply requirements by increasing loop closure and reducing consumable rates while increasing system reliability.

Tasks

To support CEV and LSAM development, a set of immediate technology development needs have been identified. They include:

  • Urine pretreatment system
  • Disinfection systems
  • Short Duration Mission Water Recovery Systems

 

To prepare for intermediate and long duration missions such as Lunar Outpost, technology development needs have been identified to enable recovery of potable water from drinking water. These tasks include:

  • Distillation technologies

- Vapor Phase Catalytic Ammonia Removal System (VPCAR)
- Cascade Distillation System (CDS),
- Direct Osmotic Concentration (DOC)
- Advanced Vapor Compression Distillation Water Recovery System (AVCD WRS)

As these technologies increase in maturity, they will be evaluated in comparison testing. The most promising systems will be selected for further development to TRL 6.

  • Improved post-processing systems
  • Microgravity assessments

Additional tasks have been identified as technology development needs through the ESAS report, section 7C, Air and Water Recovery Systems Technology Development Summary. Although recognized as technology needs, these tasks support later exploration missions; therefore, work in these areas has been deferred. These tasks include:

  • Biological systems.
  • Brine dewatering systems