Welcome to the Sunday ChemistryViews Quiz!

We explore a chemistry topic in this fun and short quiz which will be out in irregular intervals on a Sunday morning. Test your knowledge and learn something new in just a few minutes.

Ready to dive in? Let’s go!

The International Space Station (ISS) has a water-recycling system that recovers drinking water from urine, some of which is used for oxygen production—true or false? 🤔

See answer

✅ True!

🔬 NASA has worked on water recycling systems since 1986 and can now recover over 90% of wastewater on the ISS as clean water.

🚀 Long-term space missions, such as trips to Mars, will require efficient water recycling. Guideline values—Spacecraft Water Exposure Guidelines (SWEGs)—have been established for 30 chemical compounds.

🚰Water Recovery System on the ISS

🦠 Urine is pre-treated with CrO₃ and an inorganic acid (e.g., H₂SO₄) to decompose microbes and chemicals.
⚙️ The liquid then enters the Urine Processor Assembly (UPA), where water and volatiles evaporate under low temperature and pressure.

🌍 On Earth, gravity separates vapor from residue; on the ISS, a rotating drum creates artificial gravity ➡️
🌀 Heavy substances stick to the drum’s interior.
💨 Water vapor remains in the middle and is pumped to a multi-filter system:

    🧲 Large organic compounds are adsorbed
    🧪 Inorganic ions are removed by ion exchangers
    🔥 Small molecules are removed via catalytic oxidation

💧 The final product is pure water.

👉 Fun Fact

🌍 On Earth, the urine processor was tested with 90 mg of Ca per liter
🪐 The ISS crew’s urine contained 230 mg of Ca/L due to natural bone degradation under microgravity

⚗️ Problem: CaSO₄ precipitated in the distiller, leading to system calcification and failure.
🔧 Solution: The water recovery rate was reduced to 75%, which prevented further calcification.
Changing the chemical mixture increased the recovery rate back to 85%.