C14.2 Water safe to drink

➢ Water that is safe to drink

➢ Rainwater dissolves some gases from the air as it falls to the ground

➢ Water is passed through a special filter made of fine sand gravel. ➢ Removes any remaining particles of mud or grit

➢ Water enters the water treatment works ➢ Passes through a screen that is made from bars of metal placed close together ➢ Removes large objects such as leaves and twigs

➢ Water is transferred to a settlement tank - where the sand and soil settle out ➢ Aluminium sulfate and lime are added to the water ➢ Small particles of dirt clump together so they sink to the bottom of the water

➢ A small amount of chlorine is added to kill any bacteria or microorganisms ➢ Alternatively ozone can be added or UV light used

➢ pH of the water is checked and corrected so that it is neutral ➢ It then is stored in large tanks and service reservoirs ready to be pumped to homes or schools etc

➢ Because in a drier climate there is a lack of water

➢ Because of the energy costs involved in boiling large volumes of water

➢ When water is under reduced water ➢ This reduces the boiling point ➢ Making it cheaper

➢ Converting salty water to potable - useable water

➢ Uses the membranes to separate the water and salts dissolved in it ➢ No heating involved so uses less energy than distillation ➢ Energy is still needed to pressurise the water passing through ➢ Corrosion of pumps by salty water is also a problem

➢ Damp blue litmus paper ➢ It is bleached if chlorine is present