Located in Tuakau, the Waikato Treatment Plant was opened in 2002 and can supply up to 75 million litres per day. Using a four-stage, ultra-filtration treatment process, the water coming through the treatment plant has all microbiological, chemical and radiological contaminants eliminated either completely or to the point where any residual amounts are safe. The pores of the membrane filters are so small (about 15 times smaller than the filter system in household water filters) that they prevent the spores of parasites, giardia, and cryptosporidium from passing through. International experts agree that this technology is a fully effective barrier to pathogenic organisms in the water and guarantees against contamination from parasites and most viruses.
How is the Waikato River water treated?
Step 1: Coagulation and clarification
After first passing through a screening filter to remove large debris such as leaves and branches, coagulant (aluminium sulphate or ‘alum’), lime, and carbon dioxide are mixed into the water. This makes the tiny dirt particles stick together or for easier removal. The water is then piped into settling tanks. As the alum and dirt particles stick together (which then become known as ‘floc’) they sink to the bottom of the tank.
Step 2: Membrane filtration
The clarified water is then treated by advanced, ultra-filtration membrane technology to remove pathogenic organisms.
Step 3: Granular activated carbon filtration
During this stage, any organic compounds are absorbed into carbon particles. Carbon also removes any unpleasant taste or odours from the water.
Step 4: Chlorine treatment
In the final stage, chlorine is added to the water to kill any remaining viruses and prevent bacterial growth during storage and transportation. The Waikato Water Treatment Plant uses around 30-40 percent less chlorine than Watercare’s other treatment plants because water at this stage is of a much higher standard.