Water taken straight from rivers or underground sources may look clean, but it can contain microbiological contaminants - protozoans (single-celled organisms such as giardia and cryptosporidium), bacteria and viruses - which may cause illness and in extreme cases can even cause death. In addition, water absorbs an array of minerals from the ground that it passes over and through. Some of these minerals, particularly some metals, can cause health problems if consumed in higher than recommended quantities over many years.
The purpose of water treatment is to remove microbiological contamination from water for supply and to ensure that the mineral content is at safe levels. We also remove any colour, from dirt or rotting vegetation, which isn't harmful, but makes the water look unappealing.
The Ministry of Health has established guidelines for safe drinking water: the Drinking Water Standards for New Zealand (2000). Our treatment methods are designed to produce water that meets these standards and satisfies the needs of our customers: Wellington's four city councils. For more information about the Ministry of Health Drinking Water Standards visit their website.