On Mars, a colony’s water recycling system recovers 85% of used water daily. If colonists consume 400 liters per day, how much new water must be imported after 7 days to sustain the colony, assuming no initial reserves? - Redraw

Understanding the Context

In the harsh environment of Mars, every drop of water is a precious resource. With no natural reservoirs and limited supply chains from Earth, colonies rely heavily on advanced water recycling technologies to survive. A recent breakthrough by a Martian settlement shows remarkable efficiency: their water recycling system recovers 85% of daily used water. But how does this tecnology impact the colony’s need for new water imports over time?

How the Water Recycling System Works

The colony’s cutting-edge water recovery process captures and purifies 85% of all used water—from showers, toilets, and industrial processes—preventing waste in the thin, arid atmosphere. This means only 15% of daily water consumption becomes lost. For a population consuming 400 liters per person per day, this translates into immediate savings on both supply and waste management.

Daily Water Use and Recycling Breakdown

Key Insights

• Daily consumption per colonist: 400 liters
  
• Total daily consumption for colony (n colonists): 400 × n liters
  
• Water recovered through recycling: 85% of used water
  
• Water lost daily (must be imported): 15% of daily consumption = 0.15 × 400 × n = 60n liters per day

Thus, each colonist’s daily water loss indirectly exceeds 60 liters when fully accounting for imperfect recycling.

Total Water Needed Over 7 Days

For a full week of supply:

• Total water needed: 7 × (400 × n) = 2,800n liters
  
• Total recycled water over 7 days: 7 × (0.85 × 400 × n) = 7 × 340n = 2,380n liters
  
• Net water loss over 7 days: (2,800n – 2,380n) = 420n liters

Final Thoughts

This 420n liters of new water must be imported to replace water lost daily through the recycling inefficiency.

Practical Implications

With 85% recovery, a colony of 10 colonists uses 4,000 liters daily and loses 600 liters per day—approximately 42 liters per colonist—to unrecover water. After 7 days, total import needs reach 4,200 liters, ensuring no deficit despite a dry Martian environment.

This smart water management not only reduces dependency on Earth resupply missions but also exemplifies sustainable living beyond our planet.

Conclusion:
Thanks to the Martian colony’s 85% water recycling system, only 15% of daily consumption becomes irreplaceable, enabling efficient sustainability. After 7 days, the colony must import 420n liters of fresh water—less than with older systems—making long-term habitation far more viable. Recycling isn’t just innovation—it’s survival on Mars.