Water in dams (and rivers) is called raw water, and contains a lot of dust, dirt and decomposing leaves. Before we can use the water, this material must be removed. At the water treatment plant on Mount Kynoch the dirt particles are removed through a processes of flocculation and filtration. Even the fine particles are removed - they are made to join into large clumps that will be heavy enough to sink. The flocculation process uses a coagulant mixed in the water to cause this to happen. The coagulant itself is removed from the water following this process.
Raw water also contains many kinds of living organisms such as tiny plants and animals and bacteria. Most bacteria are harmless, but there are some - the pathogenic types - which can cause illness in humans. These bacteria can be removed by various treatment processes, including chlorination.
More detailed information about the water treatment process can be seen in our related documents below: