Resources and potable water

The idea

Humans use the Earth's resources for warmth, shelter, food and transport; sustainable development meets present needs without stopping future generations meeting theirs. Potable water is safe to drink. In the UK, fresh water is filtered and then sterilised with chlorine, ozone or ultraviolet light. Where fresh water is scarce, seawater can be desalinated by distillation or reverse osmosis, which need a lot of energy. Waste water is treated by screening, sedimentation, anaerobic digestion of sludge and aerobic treatment of effluent.

1. Choose the water source.
2. Describe the treatment steps in order.
3. Weigh the energy cost of desalination.

Watch out Potable water is not pure water: it contains dissolved substances, but is safe to drink.