The document discusses water usage and conservation on the International Space Station. It notes that water must be transported from Earth at a cost of $10,000 per pound since it cannot be produced on the ISS. Various daily activities like showering, brushing teeth, and flushing toilets use significant amounts of water. As a result, NASA has implemented strict conservation measures and reprocesses wastewater through systems that mimic natural water filtration on Earth. Recycling existing water is crucial since transporting enough water for a 4-person crew for a year would cost $400,000.