Editor’s note: NASA announced that September 2017 to September 2018 is A Year of Education on Station for the International Space Station (ISS), featuring a variety of education-related events for students and teachers. Astronaut Richard (Ricky) Arnold, a volunteer board member for the Project WET Foundation, is the educator on board currently. This post, written by Ricky’s fellow Project WET Foundation Board member and water reuse expert Alan Rimer, examines the system that is used to provide water to astronauts on ISS and how it could provide lessons for water reuse on our blue planet of Earth.
On Earth, we rely on the water cycle to renew our water supply. In simplest terms, precipitation falls, the runoff flows to the sea or replenishes groundwater, water evaporates and the cycle begins again. However, as climate change, localized drought and other factors reduce our confidence that we will always have potable water where and when we want it, water reuse is becoming part of the water cycle. Water reuse is the reclamation of wastewater by advanced treatment methods that permit its use for a variety of purposes. While it began as a watering source for basic crops or landscape irrigation, very recently we have begun to apply very sophisticated wastewater treatment processes on a wide scale. Through a process called direct potable reuse (DPR) we can use the recycled water as a water supply resource.
Astronauts on board the International Space Station (ISS) can teach us a lot about water reuse. On ISS, astronauts like Ricky eat and drink many of the same foods we do, but their urine, humidity condensate and other system waters is then recycled in a specially built treatment unit. This treatment unit has many similarities to the “earthly” units that produce DPR, except it is much more sophisticated and must work in the stressful conditions of space. In simple terms, crew urine is collected, and to maintain chemical and microbial control prior to further treatment, the urine is treated with chemicals and flush water. This pretreated urine goes through a urine distiller which produces a urine distillate that is pumped to a storage tank where it is combined with the humidity condensate and other water. This partially treated water is further treated through a particulate filter followed by two multi filtration beds where inorganic and nonvolatile organic contaminants are removed. Further treatment is accomplished in a catalytic reactor to remove the last traces of organic matter. Finally, the water flows through an ion exchange bed and then into the product water tank as potable water the astronauts can drink.
People in states that are subject to almost yearly droughts—for example, California, Texas and Arizona—have seen the implementation of major water reuse projects including several DPR projects. This is driven by their need to better utilize their water resources due to increasing demand and dwindling water resources. In the end, the drivers for water reuse vary and are significantly impacted by location and climate. For example, in California, the “produce basket” of the United States, the availability of water to provide the abundance of fresh vegetables we all enjoy is significantly impacted when water resources are constrained. Water reclamation supplements the water resources available to the utilities serving the citizens of California for a variety of non-potable uses. Increasingly, however, water reclamation is providing potable water for many communities throughout the United States through sophisticated treatment processes just like on the ISS.
Water reuse has obviously played an important part in making space exploration possible. Here in the United States it will play an increasingly key role in the water portfolio adopted by utilities and the agricultural community in the decades ahead. Educating the public about the importance of reclaimed waters will be a significant challenge.
If you would like to learn more about the treatment systems on ISS, you can download a PDF of “Status of ISS Water Management and Recovery”, an article about water management activities on the ISS US Segment: https://ntrs.nasa.gov/search.jsp?R=20120016427
Dr. Alan Rimer (PhD, DEE, P.E.) has served on the Project WET Foundation Board of Directors since 2012. With a varied, 49-year career in environmental engineering, Dr. Rimer has been involved with planning and design for a variety of water reuse, water resources, wastewater treatment, solid waste management and environmental management projects for local, state and the federal governments, as well as a wide variety of industries, across the United States, Asia, Europe and South America. He retired from Black & Veatch in 2016 but continues to consult on water reuse projects.
To compare your water use to that of an astronaut, take the Water Use Challenge.