GCSE›AQA GCSE Chemistry›Mind mapsWater Treatment and Potable WaterAQA GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsPotable waterSafe to drinkNot the same as pure waterCan contain dissolved mineralsPure water is only HX2O\ce{H2O}HX2OUK treatment1 Sedimentation: heavy particles settle2 Filtration: sand and gravel beds3 Sterilisation: kills microorganismsFiltration alone does not kill all microbesSterilising agentsChlorine: cheap, protects in pipes, toxic gasOzone: strong oxidiser, no residual protectionUV light: damages microbe DNA, no by-productsDrinking watertreatment and potable waterDesalinationRemoves salt from sea waterDistillation: boil, then condense steamReverse osmosis: high pressure through membraneEnergy-intensive and expensiveUsed where freshwater is scarceChlorine v fluorideChlorine kills pathogensChlorine can form harmful by-productsFluoride prevents tooth decayFluoride: consent concerns, dental fluorosisExam tipsSay safe to drink, not necessarily pureGive stages in orderLink method to resource availabilityShow both sides on fluoride