Water Treatment

Freshwater and Seawater treatment processes

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Freshwater Treatment

Screens - Metal grills or meshes are used to remove floating vegetation, plastic and paper that would clog later processes

Sedimentation - The water is allowed to remain static to enable suspended solids such as silt to settle

Aeration - Bubbles of air/water sprays are used to aerate the water and ensure a high dissolved oxygen content.

Flocculation/Coagulation and Clarification - clay particles don't settle in the sedimentation lagoons because electrostatic charges on their surfaces cause them to repel each other. Neutralised by adding flocculants such as aluminium sulfate. They are mixed in the water then passed into the carifier tank where the particles are allowed to settle

Filtration - Filters like sand filters used to remove any remaining suspended solids and bacteria

Activated carbon filters - Particles of activated carbon are used to remove organic chemicals such as pesticides and some substances that cause bad tastes

Sterilisation - Addition of chlorine, ozone or UV exposure to sterilise water and kill pathogens

Fluoridation - Fluorides are added to water in some areas to improve the dental health of people that drink the water

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Seawater Treatment

Reverse osmosis - Saline water is filtered at very high pressure through a partially permeable membrane of small polyamide tubes. The freshwater collected is around half the original volume and the remaining salty water is returned to the sea

Distillation - Water is boiled by heating and reducing the pressure. The steam that is produced is condensed and collected

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