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Recycle Urine into Drinking Water for Astronauts

Abstract

Have you ever wondered how astronauts eat and drink in space? Where does their food and water come from? Water, in particular, is quite heavy, so delivering it to space is incredibly expensive. Instead, on spaceships and space stations like the International Space Station (ISS), it is most efficient to recycle water. This includes recycling urine! In this science project, you will use methods similar to those used on the ISS to investigate how urine can be recycled into clean drinking water. 

Summary

Areas of Science
Chemistry
Space Exploration
Human Biology & Health
Difficulty
Method
Scientific Method
Time Required
Short (2-5 days)
Prerequisites

None.

Material Availability

A kit for this project is available from our partner Home Science Tools®. See the Materials section for details.

Cost
Average ($50 - $100)
Safety
  • Adult assistance is needed with using the stove and boiling liquids.
  • Avoid dispersing the powdered activated carbon into the air and try not to breathe in the particles.
  • We recommend testing this project idea with simulated urine, as described below, and do not recommend testing it with real urine, as it produces a terrible smell when boiled.
  • Do not drink the "purified" water as it may contain residual contaminants that could make you sick.
Credits
Teisha Rowland, PhD, Science Buddies
Andrew Bonham, PhD, Metropolitan State University of Denver

April Hill, PhD, Metropolitan State University of Denver 

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.
https://www.youtube.com/watch?v=fQNwPLl7kQY

Objective

Determine how well different methods used on the ISS can purify simulated urine into drinking water. 

Introduction

How do astronauts get drinking water in space? Because delivering water to space stations is incredibly expensive, the International Space Station (ISS) has engineered a way to recycle liquids on the station, including astronauts' breath, sweat, and urine, into drinking water. The system, called the Water Processing Assembly (WPA), can process these fluids to produce 36 gallons of drinking water each day to help meet the astronauts' water needs. 

The WPA includes many steps and methods to purify and recover waste liquids for use as drinking water, with key methods including distillation and filtration. Distillation is one of the first steps that urine undergoes in the WPA. Distillation is a method that typically involves heating a liquid mixture, such as urine, to separate it into clean water and leave behind any impurities, such as salts. How does it work? As the contaminated liquid is heated, the boiling point of water is reached, and the water begins to evaporate. The salts and other contaminants do not boil and evaporate, and remain in the liquid mixture below. The evaporated water can be collected as condensation. Because of this, the condensation is purer than the original liquid, as the heavier impurities are left behind. In the WPA, when urine undergoes distillation, it is separated into a purer liquid and waste "urine brine." Sensors are used following distillation and throughout the WPA to check the purity of the liquid to make sure it meets purity standards.

Following distillation, the liquid is filtered to further purify it. Filtration is a process where the liquid is passed through a material that absorbs some of the contaminants, and purer liquid emerges from the other side. As part of the filtration process, activated carbon (also known as activated charcoal) is used. Most of the filters that are used for home water treatment are carbon filters containing activated carbon. Why activated carbon? What makes activated carbon special is that it is a very porous form of carbon, almost like a sponge. It has many tiny microscopic pores that can cling onto the contaminants. Activated carbon can come in many forms and particle sizes. Two types you will be using in this experiment are the granular and powdered forms. Granular carbon can be compared to small pebbles, while powdered carbon can be compared to sand. Powdered carbon has a larger surface area-to-volume ratio, meaning there is more available binding surface area to interact with contaminants.

Watch the video below to learn more about the WPA on the ISS. The WPA has undergone upgrades over the years to increase the amount of drinkable water that can be reclaimed from the waste fluids. For example, in 2021, the WPA was upgraded with a Brine Processor Assembly (BPA) to remove additional salts from astronauts' urine, which helped increase the urine recovery rate to 93% to 94%. Following additional improvements to the BPA, NASA announced in 2023 that 98% of the wastewater on the ISS is recovered. This means that if, for example, 100 liters (L) of water are brought onto the space station, 2 L may be lost as permanently contaminated brine, but 98 L are retained and continue to be recycled. Why is 98% important? It is calculated that for a human-operated mission to Mars, where water cannot be resupplied along the way, at least 98% of water needs to be reclaimed. 

https://www.youtube.com/watch?v=I-Rc-kS9HPQ

In this science project, you will use methods similar to those on the ISS, specifically distillation and filtration (with activated carbon), both alone and in combination, to investigate how urine can be recycled into clean drinking water, including the impact of these methods on the purity and yield of the resultant water. Instead of real urine, you will use simulated urine comprised of urea, table salt, and yellow food coloring. Urea is the primary normal waste component of urine and is representative of other small polar carbon-based, or organic, molecules found in urine. Urine also contains salts and charged molecules, which will be represented by table salt (sodium chloride), and colored organic compounds, which will be represented by yellow food dye. To measure the purity of your resultant liquid, you will use two standard meter devices: A Brix meter, or refractometer, which measures the total dissolved solids in a water sample (including urea and salt), and a total dissolved solids (TDS) conductivity meter, which measures the salts but not the urea. How effective will the different methods be in producing relatively pure drinking water with good yields? 

Terms and Concepts

Questions

Bibliography

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Experimental Procedure

Download PDF of Procedure
This project follows the Scientific Method. Review the steps before you begin.

In this experiment, you will investigate how well different methods can purify simulated urine into drinking water. You will test distillation alone, filtration alone, and distillation combined with filtration. For each method, you will investigate how the total dissolved solids, the dissolved salts, and the color of the resultant samples are all impacted. Before you start the experiment, read the entire Procedure section below and create a data table to collect your data from at least three trials.

Preparing and Measuring the Simulated Urine

  1. You will be preparing simulated urine by creating a solution that contains 200 millimolar (mM) urea, 100 mM sodium chloride (salt), and yellow food coloring for color. You can prepare the simulated urine directly in the cooking pot. Specifically prepare the simulated urine as follows:
    1. Measure and add 6 cups (C) of distilled water.
    2. On a digital scale, measure 17.3 grams (g) of urea. Add the urea to the water in the pot.
    3. On a digital scale, measure 8.4 g of salt. Add the salt to the pot.
    4. Add 3 drops of yellow food coloring to the pot.
    5. Use a spoon to mix everything together in the pot until it is completely dissolved.
  2. Measure the simulated urine using the Brix Refractometer so that you have a baseline for your experimental measurements. The refractometer measures the total dissolved solids in a water sample, which includes the total dissolved urea and salt in your samples.
    1. Before measuring a sample with the Brix Refractometer, read through the user manual. 
    2. Use the provided cleaning cloth to gently clean the sample well.
    3. Use the eye dropper to deposit one drop of your sample in the well.
    4. Power on the refractometer and press the play (or measure) button.
    5. Record the measurement. Does the measurement make sense to you?
    6. Clean the well using distilled water and the cleaning cloth. If the well is not cleaned, residual dissolved solids from samples can interfere with measurements over time.
  3. Measure the simulated urine using the digital Total Dissolved Solids (TDS) meter so that you have a baseline for your experimental measurements. The TDS meter measures the dissolved salts, but not the dissolved urea, in your samples. 
    1. Before measuring a sample with the TDS meter, read through the user manual.
    2. Power on the meter and submerge its tip into the sample.
    3. Record the measurement. Does the measurement make sense to you?
    4. Clean the tip using a sample of distilled water. If the meter is not cleaned, residual dissolved solids from samples can interfere with measurements over time.
  4. Repeat steps 2 to 3 using a sample of distilled water. Record the measurements. Do your results make sense to you?

Distillation

  1. Prepare the distillation setup as follows:
    1. Poke 3 to 4 holes in the sides of the aluminum ramekin, carefully using a pen or scissors, as shown in Figure 1. This will allow water to flow into the ramekin so that it does not float, but the ramekin should still provide enough support to hold the collection container on top of it. 
    2. In the large pot with the simulated urine, place the ramekin in the center so that the bottom is facing up. The level of the liquid should not quite reach the top of the ramekin.
    3. On top of the ramekin, place the Pyrex collection cup, as shown in Figure 2.
    4. Rinse the pot lid with distilled water, then dry the lid. Place it upside down on the pot, as shown in Figure 3. The lid should create a convex shape, with the rounded part facing down into the pot, so that any condensation will roll down and collect at the center of the lid. From there, it should drip into the collection cup, which should be directly below the lowest point of the lid. 
      1. Safety warning: Slightly crack the lid so that it does not completely seal. If it completely seals, there may be an unsafe buildup of steam within the pot. 
    5. Place approximately three ice packs on top of the lid, as shown in Figure 4. This will help the condensation (on the other side of the lid) to form and collect.
aluminum ramekin with holeImage Credit: Teisha Rowland / Science Buddies

aluminum ramekin with hole

Figure 1. An aluminum ramekin with three to four small holes poked in its sides to allow water to easily flow through it.
Ramekin with Pyrex collection cup on top inside a large potImage Credit: Teisha Rowland / Science Buddies

Ramekin with Pyrex collection cup on top inside a large pot

Figure 2. A Pyrex cup set on top of the upside-down aluminum ramekin in the large cooking pot.
Distillation setup with lid upside down to collect condensation in the collection cupImage Credit: Teisha Rowland / Science Buddies

Distillation setup with lid upside down to collect condensation in the collection cup

Figure 3. Pot lid placed upside down on the pot. The lid should create a convex shape, with the rounded part facing down into the pot, so that any condensation will roll down and collect at the center of the lid and drip into the collection cup directly below it.
Distillation setup in pot with ice packs on topImage Credit: Teisha Rowland / Science Buddies

Distillation setup in pot with ice packs on top

Figure 4. Ice packs placed on top of the lid.
  1. Have an adult help you turn on the stove to a medium-high setting and collect condensation. 
    1. Safety warning: During this experiment, the pot will become very hot and generate steam, all of which can cause burns. Use oven mitts to handle any part of the pot, including the lid, and stand back when cracking the lid so that steam does not burn your face or hands. 
    2. Carefully monitor the lid from the outside, wearing oven mitts as needed and avoiding any steam. When the liquid begins to boil, which may take approximately 10 minutes, turn the stove down to medium heat. The liquid should continue to simmer. Beads of condensation should also start collecting on the inside of the lid at this point and rolling down into the collection cup.
    3. Continue to let the liquid simmer in the pot until it is nearly empty, or there is approximately 1 centimeter (cm) of liquid left in the pot. This may take more than one hour total. During this time, carefully check on the pot approximately every 5 minutes to make sure the pot does not run dry and to see if the ice packs have thawed. Replace the ice packs with new ones as needed. Running the process for this long will help maximize the amount of distilled condensate you collect. 
  2. Once you are done collecting condensation, turn the stove off and let the pot sit and cool for approximately 10 minutes.
  3. After 10 minutes, use oven mitts to carefully open the pot and remove the collection cup. Let the collection cup sit and cool for approximately 5 minutes.
  4. Use the measuring cup to measure your yield.
    1. How many milliliters (mL) did you collect in the collection cup?
    2. Optional: You know that you started with 6 C of liquid in the pot, and some was collected in the collection cup, but some may also have been lost as steam. If you want to determine how much was lost to steam, also measure the amount remaining in the pot.
    3. Note: You will need to collect at least 50 mL to perform the filtration step, since some liquid is lost to the filtration system. If you did not collect at least 50 mL, create more simulated urine (as described in the first section) and then repeat steps 1 to 4 of this section. 
  5. Once the liquid in the collection cup has cooled, take measurements of the collected liquid using the Brix Refractometer and TDS meter, as described in steps 2 to 3 of the "Preparing and Measuring the Simulated Urine" section, above. Record your measurements.
    1. How do these measurements compare to the ones you took using the original simulated urine samples?
    2. What does this tell you about how effective distillation can be for purifying urine into drinking water?
  6. Measure the change in color of the collected liquid by following the steps in the "Measure the Color of Your Results Using a Serial Dilution" section, below. Do not lose any of this liquid as you will want to use it for the filtration step.

Measure the Color of Your Results Using a Serial Dilution

  1. To analyze how the color of the liquid changes as you distill and filter it (for example, if it becomes lighter yellow), you will want to create a serial dilution. You can learn more about serial dilutions by watching this video on How to Make a Serial Dilution. Perform the serial dilution analysis as follows:
    1. Label six baby food jars as follows: 100%, 50%, 25%, 12.5%, 6.25%, and 3.13%.
    2. Fill all jars, except the one labeled 100%, with 1/4 C water (you can use normal tap water for this).
    3. Into a large cup or bowl, add 2 C of water and 1 drop of yellow food coloring. This is the same relative amount of food coloring that you used in the simulated urine. Fill the 100% jar with 1/2 of this solution. 
    4. Measure out 1/4 C from the 100% jar and pour it into the 50% jar. 
    5. Measure out 1/4 C from the 50% jar and pour it into the 25% jar.
    6. Measure out 1/4 C from the 25% jar and pour it into the 12.5% jar.
    7. Measure out 1/4 C from the 12.5% jar and pour it into the 6.25% jar.
    8. Measure out 1/4 C from the 6.25% jar and pour it into the 3.13% jar.
    9. Your serial dilution series is now complete and should look similar to the jars shown in Figure 5.
  2. Measure the color of your sample liquid as follows:
    1. Rinse the clean baby food jar with distilled water before use with your sample to prevent contamination to your sample from the jar. Take the sample you want to analyze and carefully pour it into the cleaned jar. 
    2. Hold the jar with your sample next to your serial dilution jars and try to match the darkness or lightness of your sample as closely as you can to the serial dilution jars. Try the best you can to find the closest matches in color. It may be that your sample is in between two of the serial dilution jars. For example, if your sample looks slightly darker in color than the 12.5% jar but slightly lighter than the 25% jar, then you could consider it to be between 12.5% and 25%. 
  3. Record your observations in your lab notebook.
Jars with serial dilutions of yellow solution.Image Credit: Teisha Rowland / Science Buddies

Jars with serial dilutions of yellow solution.

Figure 5. Prepared serial dilutions in the baby food jars using the simulated urine.

Filtration

  1. Prepare the activated carbon (i.e., activated charcoal):
    1. The amount of activated carbon you use will depend on your yield of liquid collected from the "Distillation" section. You want to keep the ratio of activated carbon to liquid the same, since how efficiently the activated carbon works depends on the amount of water it is treating. Specifically, for each 50 mL of liquid collected, you should use 1.28 g of activated carbon. To calculate the amount of activated carbon to use (in grams) with different volumes of liquid collected, multiply the volume by (1.28 g / 50 mL). For example, if you collected 75 mL of liquid, you should use 1.92 g of activated carbon.
      1. Note: If you did not collect at least 50 mL of condensate from the "Distillation" section, repeat the distillation until you have collected at least 50 mL total. Otherwise, you will not have enough collected liquid to filter and measure your results after filtration.
    2. Use the digital scale to weigh out the correct amount of granular activated carbon that you calculated in step 1a for your sample and pour it into a plastic cup.
    3. Pour your sample into the cup with the activated carbon, mix it, and wait at least 10 minutes.
    4. While waiting on step 1c, prepare your filters. Take 4 coffee filters and stack them. As shown in Figure 6, press the stack of filters into the top of a cup, fold their edges over the cup's rim, and secure them with a rubber band. 
    5. After step 1c is complete, slowly pour the water sample (with activated carbon) over the prepared coffee filter basket. Wait a few minutes until the liquid is done dripping through the filter and into the cup below.
Filter cup setup.Image Credit: Teisha Rowland / Science Buddies

Filter cup setup.

Figure 6. A cup set up with four stacked coffee filters secured by a rubber band.
  1. Use the measuring cup to measure your yield.
    1. How many milliliters (mL) did you collect after filtration?
  2. Take measurements of the collected liquid using the Brix Refractometer and TDS meter, as described in steps 2 to 3 of the "Preparing and Measuring the Simulated Urine" section, above. Record your measurements.
    1. How do these measurements compare to the ones you took using the original simulated urine samples and the sample after distillation?
    2. What does this tell you about how effective distillation and filtration can be for purifying urine into drinking water?
  3. Measure the change in color of the collected liquid by following the steps in the "Measure the Color of Your Results Using a Serial Dilution" section, above. 
  4. Repeat the filtration process (steps 1 to 4) using a sample of simulated urine prepared as described in the first section. You can use 75 mL of simulated urine per filtration trial. This will provide you with data on how efficient the filtration system is when used alone (and not in combination with distillation).
  5. Repeat the entire experiment at least three times so you have collected data from at least three trials.

Analyze Your Results

  1. Create a data table in your lab notebook similar to Table 1, below, to summarize and analyze your results.
  2. Calculate the average of the three trials for each of the data samples collected and fill in your data table with your results.
  3. Spend some time analyzing your data and answering the following questions:
    1. How well did distillation alone purify the simulated urine? Why do you think this is?
    2. How well did filtration alone purify the simulated urine? Why do you think this is?
    3. How well did distillation and filtration together purify the simulated urine? Why do you think this is?
    4. How did the yields and resultant colors from the different methods, alone and together, compare? Why do you think this is?
    5. What do your results tell you about how efficient the different methods are at removing dissolved solids, salts, and dyes from liquid? 
    6. Overall, which method(s) resulted in the best purity, color, and/or yield of liquid? Why do you think this is?
  4. Based on your results, what method(s) would you recommend for using purifying urine into drinking water? How do you think a water purification system could be improved based on your results?
Swipe left to see more
Table 1. Create a data table like this one to summarize your results.
Test

Simulated Urine

(Average of 3 trials)

Distilled Water

(Average of 3 trials)

Distillation Alone

(Average of 3 trials)

Filtration Alone

(Average of 3 trials)

Distillation and Filtration Together

(Average of 3 trials)
Brix Refractometer (%)
TDS Meter (ppm)
Color (%)
Yield (mL) Not applicable Not applicable

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Global Goals

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Clean Water and Sanitation: Ensure access to water and sanitation for all.

Variations

  • In this science project, you used granular activated carbon, but the kit recommended includes both granular activated carbon and powdered activated carbon. You can conduct this experiment using the powdered activated carbon and compare your results. Does one type of carbon work better than the other? Why do you think this is? 
  • In this science project, you use simulated urine. It is not recommended to boil real urine because it creates a terrible smell due to the waste products in the urine. However, there are other ways you could test simulated urine, such as by including creatine powder or using simulated urine from a Urinalysis Using Simulated Urine Kit from Home Science Tools®. How well do distillation and filtration work to purify other types of simulated urine? 
  • In addition to activated carbon, water filtration systems sometimes use zeolite powder as well. You can purchase zeolite powder online; check to make sure it is high purity and not a mix with other chemicals. Develop a filtration system to test activated carbon and/or zeolite. How well do the different molecules work to purify contaminated water?
  • In this science project, you performed distillation followed by filtration. If you reverse the order, and perform filtration first and distillation second, how does this impact your results?
  • Spacesuits that convert urine into drinking water are being developed for astronauts for when they need to conduct a space walk outside of the spaceship for an extended amount of time. Do some research into spacesuit technology. How do they work? Could you model part of the process and try to engineer a better system to use in spacesuits?
  • Making sure that people around the world, here down on Earth, have enough safe drinking water is a challenge. You can watch this video Can You Safely Drink Your Own Pee? by Mark Rober and MrBeast (#TeamWater) to learn more. What different methods are being used around the world to solve this problem? How do they compare to the methods of distillation and filtration used in this science project? You can create a science project to test and compare different methods. Which are most efficient? 

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Rowland, Teisha, and Andrew Bonham. "Recycle Urine into Drinking Water for Astronauts." Science Buddies, 28 Aug. 2026, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p121/chemistry/urine-recycle-drinking-water-astronauts. Accessed 28 Aug. 2026.

APA Style

Rowland, T., & Bonham, A. (2026, August 28). Recycle Urine into Drinking Water for Astronauts. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p121/chemistry/urine-recycle-drinking-water-astronauts


Last edit date: 2026-08-28

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