How We Can Learn from Water Recovery Systems on the ISS to Improve Water Recycling on Earth 🌎🛰️
By Aika Lanes
It takes about $30,000 to send a single water bottle to space.
With astronauts living on the International Space Station, it is incredibly costly to continue to provide them the resources that they need in order to both work and survive day-to-day in space. Due to the awfully high expenses of resupply missions, scientists and engineers have been designing systems that will allow astronauts to live as close to 100% sustainably as they can.
So, astronauts on the ISS drink and use water recycled from urine, sweat, and condensation. This allows up to 98% of the water on the station to be reused.
Here on Earth, we have quite a water problem. Well, multiple problems. Here are a couple of them:
- Water contamination & human health: Ever think about where your water goes when you flush it down the toilet? Most flushes end up in the city sewers where it will *hopefully* be treated at a wastewater treatment plant before directed into a local waterway. However, 860 billion gallons of sewage manages to escape sewer systems across the United States every year. That is an immensely large amount of sludge, and it’s all enough to flood the entire state of Pennsylvania with sewage that would reach the top of your ankles. This untreated sewage ending up in local rivers are chock-full of diseases ranging from illnesses such as hepatitis and dysentery. Even after the sewage smell leaves water, the germs can still remain. Perfectly healthy people going for a late-afternoon swim in the hot summer may not even realize that their ear infection the next day came from the water they had recently relaxed in, which they believed was safe. It is estimated that annually 7.2 million Americans get sick from waterborne disease, and 852,000 people around the world die due to diarrhea caused by contaminated water every year.
- Droughts: At the end of September 2023, 33% of the contiguous United States was affected by moderate to extreme drought on the Palmer Drought Index. Drought can cause drinking water shortages as well as poor quality of drinking water. Drought can also lead to a reduction in stream flows, causing an increase in the concentration of contaminants in the water as well as a rise in water stagnation. Heat during droughts results in an increase in high water temperatures, reducing oxygen levels in water. This can damage the health of aquatic life and fish while decreasing water quality. Additionally, drought can produce conditions that cause pest and disease infestation within crops while limiting the growing season. This leads to an increase in food shortages and prices.
- Access to water: In 2022, 3 out of 4 people used safely managed drinking water services (located on premises, accessible and available for use, and contaminant-free). There are over 2 billion people living in countries that are water-stressed, impacted heavily by climate change and population growth. Unavailable access to drinking water impacts men and women differently. In every 2 out of 3 households, women are responsible for collecting water. 1.8 billion people around the world need to go off-premises to collect their water. The average walk to water in a developing country is 3.5 miles, all while carrying 42 pounds of water. With women being the primary water carriers, this allows them to be more susceptible to fatigue, injury, harassment, assault, and causes girls to be less likely to attend school. Additionally, lack of access to clean drinking water causes dehydration, malnutrition, and spread of disease.
In order to combat these problems concerning water access and supply on Earth, let’s take a look at water recovery systems in space and how they work.
How do water recovery systems work in space?
The Environmental Control and Life Support System (ECLSS) on the International Space Station is a combination of hardware designed to keep astronauts alive by maintaining breathable air, cabin pressure, temperature and humidity levels, and recycling water.
Every day, each astronaut requires about 1 gallon of water for use, whether that be for consumption, hygiene, or food preparation.
Let’s take a closer look at the three key subsystems within the ECLSS’s Water Recovery System: the Urine Processor Assembly (UPA), Water Processor Assembly (WPA), and Brine Processor Assembly (BPA).
- Urine Processor Assembly: this system collects urine to reclaim water. Using vacuum distillation, the UPA produces water and separates a urine brine, which still has some water capable of reclamation. The water produced gets sent to the WPA.
- Water Processor Assembly: the Water Recovery System collects wastewater, sending it to the WPA to make potable water. There are specialized dehumidifiers on the ISS that capture moisture from the air caused by astronaut sweat and breath!
- Brine Processor Assembly: the BPA takes the urine brine from the UPA and extracts the remaining water. The addition of the BPA to the ECLSS has helped the Water Recovery System get to the goal of 98% water recovery.
The Urine Processing Assembly solely treats urine. On the other hand, the Water Processing Assembly treats hygiene wastewater, condensed humidity, water produced by the Sabatier reaction (producing methane and water from hydrogen and carbon dioxide), and water that gets treated by the UPA.
It is important to note that water recovery functions differently in space than it does on Earth.
Due to buoyancy, gravity on Earth causes gas and liquid to separate. However, in a microgravity environment, air bubbles created in water do not “float up” to the surface like they do in a Pepsi because there is not really an “up.” It instead sits and stays in the liquid, having the potential to interfere with the water treatment process as the bubbles may indefinitely stay when it gets attached to the surface due to surface tension. These tiny bubbles are called microbubbles, and space agencies are investigating how they affect the water treatment process to gain insights into advancing water recovery systems.
How does the Urine Processor Assembly work?
Refer to part A of the image above for visualization.
Urine from the crew is sucked up and put down a hose. In order to prevent microbial growth and chemical stability, at the start, the urine collected is stabilized using a mixture of phosphoric acid and hexavalent chromium. This then gets stored in the Wastewater Storage Tank Assembly (WSTA) until it reaches a quantity that is sufficient to begin treatment. The stored urine from the WSTA gets pumped into the distillation assembly. The urine goes to a rotating centrifuge that uses vapor compression distillation, distilling it at high temperatures and low pressure. The vapor created from the evaporating liquid gets collected, which is generally clean but still not potable. It then gets condensed and sent through the gas separation unit consisting of a rotary separator, actively separating the liquid from the gas. The liquid goes back through the distillation assembly before being sent off to the Water Processor Assembly for further treatment.
How does the Water Processor Assembly work?
Refer to part B of the image above for visualization.
The distilled water from the Urine Processor Assembly is combined with condensate collected by the humidity control system and the water produced by the Sabatier reaction. The liquid is separated from the gas and sent through a particulate filter, which removes suspended materials and particles. It then gets sent through multi-filtration beds, where non-volatile organic as well as inorganic compounds are separated from the water. Next, the organic compounds with low molecular weight found in the water get oxidized when sent through the catalytic reactor. The remaining gases and gaseous byproducts are purged through another gas/liquid separator. Afterwards, through an ion-exchange bed, the bicarbonate and carbonate ions that were produced during the recent oxidation get removed. And now the water is now drinkable!
How does the Brine Processor Assembly work?
The BPA is a fairly new thing. Remember the brine that was separated from the water in the UPA? That brine gets collected in storage tanks and then sent to the BPA for further water recovery. Before the BPA was developed, the total water recovery capable by the system maxed out at about 93–94%. The BPA has helped the Water Recovery System reach the goal of 98% water recovery.
Refer to the image below for visualization.
The Brine Processor Assembly takes advantage of the cabin air to help facilitate the water recovery process from the brine. Through an inlet filter, cabin air can enter the assembly. The air flows through the electronics cooling room which houses electronics that convert the 120VDC received by the space station down to the system’s used voltages. The airflow cools the electronics, picks up the extra heat, and then goes into an in-line axial heater, warming up the air to the necessary processing temperature. This heat helps encourage the brine to evaporate. The heated air then goes into the Detrusor assembly, where the temperature of the air is being monitored at the inlet and outlet. At the start of a cycle in the assembly, there are high evaporation rates, where there is more energy being transferred from the air to the brine, creating cool air temperatures at the outlet. When evaporation starts to slow, the air temperature at the outlet increases. As soon as the evaporation ends, the air temperature at the outlet is similar or very close to the inlet air temperature, making the process complete. This initiates the microcontroller to turn off the fan and the heater and stop the cycle.
Within the Detrusor assembly, there are hydrophobic filters on the internal side of the inlet and outlet air plenums in order to avoid brine release to the cabin if a leak ever occurs with the brine bladder. A fan is located downstream to the airflow of the Detrusor, which generates a slight negative pressure that allows for the Detrusor to be stable with the bladder when processing the brine by creating a compressive force. The airflow leaves the Brine Processor Assembly and enters the cabin. The water vapor that gets recovered from the BPA gets condensed and enters the water recovery system again to finish becoming potable.
JEM Water Recovery System
Let’s check out the JEM Water Recovery System (JWRS), developed by the Japan Aerospace Exploration Agency (JAXA).
This is a special water recovery system operating in the Kibo module of the International Space Station in the Multipurpose Small Payload Rack. This is a scale-model of a unique water recovery system that is hoping to test new ways to recover water with hardware that is smaller in size, has a greater recovery rate, uses less power, and is easier to maintain than the Water Recovery System currently being used in the ECLSS.
Key operational water treatment processes:
- Ion exchange: Magnesium and calcium found in urine are removed using cation-exchange resin. This is the first step in preventing the clogging of filters and pipes in the next stages of treatment.
- Electrolysis: Organic matter and ammonia found in the water treated by the cation-exchange resin is broken down using electrolysis. When electrolysis is done at high pressure and high temperature, it is possible to completely break down organic matter even when it is typically difficult to do so.
- Electrodialysis: Any leftover ions from the previous steps get removed
Since the JWRS is working to create water recovery systems that have small size, have lower power consumption, and are more efficient, this can be applied to help advance water reclamation on Earth in areas that experience drought, have frequent natural disasters, and other places that struggle with access to water.
So, how can all of this apply to combatting our water problem on Earth?
To understand how this ties into solving problems with water here on Earth, let’s take a look at the benefits of recycling and reusing our water.
What exactly is water recycling?
When we recycle our water, we reuse treated wastewater for different advantageous purposes such as flushing toilets, supplying water for landscape and agricultural irrigation, groundwater recharge, and industrial processes. We can tailor the treatment of wastewater to suit the water quality standards of the direction of planned reuse (for example, recycled water for irrigation would need less treatment than drinking water). Additionally, water recycling allows for savings of finances and resources.
How does water recycling create environmental benefits?
Water recycling offers a locally-controlled and reliable supply of water. This can allow us to discover ways of reducing water diversion from ecosystems that are sensitive.
On top of this, by reducing discharges of wastewater, we can decrease and prevent pollution of local watersheds, therefore reducing waterborne illnesses.
Clean, recycled water can additionally be used to strengthen riparian habitats or wetlands, decreasing likelihood of droughts and water stagnation.
Plus, with stronger and healthier ecosystems, the habitat and flora can help absorb and store more carbon dioxide, helping reduce the concentration of greenhouse gases in the atmosphere.
Water recycling can also save energy. More water needs to be taken, treated, and transported across far distances as the water demand rises, requiring great amounts of energy. As groundwater levels lower, pumping water to the surface also requires more energy. By recycling water near or on-site, we can reduce the energy needed to treat and supply water.
How does water recycling benefit society?
If we can implement water reclamation systems in areas that are water-stressed, we can reduce the need for long, exhausting journeys for people to fetch water by foot while decreasing likelihood of injury and waterborne illness. This reduces healthcare costs as well.
Additionally, with reduced contamination due to water reclamation, we can reduce illnesses caused by unsafe water and improve public health.
Recycling water decreases the necessity to desalinate water or transport water over long distances due to an increasing demand. The reduced energy and costs required to treat and supply water will allow us to save money and resources.
How do water recovery systems in space play a role in water recycling on Earth?
Since the International Space Station does not have access to a steady, clean, ample supply of water from sources such as lakes and is very far from any sort of quick external support, this makes the water recovery systems on the station a perfect example of technology to use on places on Earth, especially locations that are isolated and water-stressed.
As explained in the section concerning water recovery systems in space, these innovations are designed to:
- Reduce energy required to treat water
- Become smaller in size
- Increase water recovery rates and speed
- Require less maintenance
- Be cost-effective
These qualities are incredibly beneficial for developing an efficient, reliable supply of recycled water. By using similar systems and processes, we can use this space technology to benefit communities and ecosystems here on Earth.
What does the future of water recycling look like?
Water recycling allows us to save money in the long run while taking a sustainable approach to the water crisis.
The demand for water is growing with climate change and population growth. Water recycling and conservation can help play a role in maintaining a sufficient supply of water while responsibly managing our resources.
Here are some ways we can help implement water recycling into communities and drive a push towards responsible water use:
- Create awareness on the water crisis and water conservation, and educate the public about the environmental and societal benefits of water recycling.
- Support water conservation nonprofits.
- Establish water conservation goals and plans in communities.
- Implement regulations and policies into local, state, and federal governments regarding water use and reclamation.
- Integrate water recycling systems into public facilities, businesses, individual homes, neighborhoods, farms, etc. to pave the way towards more integration.
- Set an example of sustainable water recycling for individuals and communities to get inspired to follow.
Wrapping it up
Turns out, the space technology we are investing so much in can support us here on Earth.
As climate change and population growth rises, so does our demand for water. Across the world, people struggle with water insecurity and waterborne illnesses.
Managing our water more wisely and implementing water recycling systems can help us solve many of these pressing problems.
Water recovery systems on the International Space Station have been developed for maximum efficiency, water recovery rates, sustainability, and cost-effectiveness. This makes it a perfect technology to work off of when creating water recycling systems for implementation on Earth.
So the next time you think about the ISS, remember how the technology being developed up there can benefit communities here on Earth.
With global efforts towards water conservation, we are making progress on water recycling around the world. All while taking advantage of the knowledge gained from the development of sustainable water recovery systems in space as a base to support the people and ecosystems of our planet.
