Artificial aeration of Auckland's lakes

Through effective management of source waters, suppliers can improve raw water quality thereby reducing the overall cost of treatment and, ultimately, the cost to the consumer.

Watercare manages ten man-made lakes, which combined can provide up to 480,000m3 /day of water for treatment at three main Water Treatment Plants.

These lakes are susceptible to seasonal stratification, which historically resulted in elevated iron and manganese concentrations and unpleasant taste and odours. These could not be sufficiently removed by the downstream treatment processes, therefore the aesthetic quality of the treated water deteriorated.

From 1974, Watercare implemented artificial aeration systems in each of its lakes in order to prevent stratification over the summer period. The systems successfully reduced iron and manganese concentrations and prevented unpleasant taste and odours.

As the systems ran continuously between October and April, this was identified as an area where efficiency gains could be realised. In 2007, a revised aeration strategy was developed that successfully minimised energy consumption while maintaining water quality.

Further strategies for improving the efficient aeration and management of Auckland’s lakes are also being investigated.