Water treatment Flashcards
Freshwater treatment
Screens Sedimentation Aeration Flocculation/coagulation and clarification Filtration Active carbon filters Sterilisation Fluoridation
Seawater treatment
Reverse osmosis
Distillation
High energy requirements
Desalinated water is very expensive
Screens
Metal grilles/meshes
Removes solids from water
Eg. plastic packets, shopping trolleys, poop bags
Sedimentation
Water is left still
Removes suspended solids
Eg. silt
Aeration
Bubbles of air/water sprays
Increases dssolved O2 content
Removes some heavy metals
Removes bad smell/taste
Flocculation/ coagulation and clarification
Flocculants added
Eg. Aluminium sulfate, polyelectrolytes
Water moved into clarifier tank
Clay clumps together and drops out of water
Filtration
Sand filters
Removes any remaining solids
Removes bacteria
Active carbon filters
Film of activated carbon
Removes organic chemicals
Eg. Pesticides
Removes bad taste
Sterilisation
Addition of chlorine, O3 Exposure to UV light Removes pathogens Chlorine is most common Peaty water sources may contain humus Chlorine reacts with humus to form carcinogenic trihalomethanes O3 helps break down pesticides
Fluoridation
Fluorides added
Improves dental health
Only in some areas
Reverse osmosis
Saline water pressured through partially permeable membrane
Freshwater collected is half of what was pushed through
Remaining half is extra salty
Remaining half returned to sea
Distillation
Water is boiled
Steam is condensed and collected
