How Seawater Becomes Drinking Water
Reverse osmosis pushes seawater against a membrane whose pores pass water molecules and block dissolved salt. Because seawater naturally pulls fresh water toward itself, the pump has to overcome that force first, which takes pressure of around sixty bar. Roughly forty litres of drinking water come from every hundred litres fed in.
Those two numbers carry most of the lesson. The pressure explains why desalination is energy-intensive and therefore expensive; the recovery ratio explains why the other sixty litres leave as concentrated brine that has to go somewhere. A class given only the membrane diagram learns a filtration process; a class given the pressure and the ratio can argue about whether a proposed plant is a good idea. What belongs in the file rather than the frames is plant-specific operational data: intake locations, membrane suppliers, and discharge permits belong in the utility's own documentation.
The template follows one litre of seawater across eight scenes: one on why salt cannot simply be filtered out, one on osmosis and what makes it reverse, two on pretreatment and why it exists, two on the membrane stage and the pressure required, one on post-treatment and remineralisation, and one on brine and energy as the two costs.
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