CASE STUDY

Improving resilience in the aftermath of the Tasman Tempest

Efforts are well under way to improve the resilience of our water supply infrastructure and ensure we continue to provide a safe and reliable supply to Aucklanders.

In the autumn of 2017, an unprecedented amount of rain fell in 24 hours in the Hünua Ranges, causing numerous slips, depositing significant amounts of silt into our water storage lakes and affecting the treatment processes at our largest water treatment plant in Ardmore.

In the following weeks, our staff worked hard to stabilise the systems at Ardmore and maximise production at our Waikato and Huia water treatment plants to ensure that no one was without water.

More than a year has passed and it’s a very different picture now. Our dams are returning to a state that we normally see in these sources, with lower turbidity levels.

Our headworks team has been working hard to improve the stability of the areas hardest hit by this event. They have been hydroseeding a number of areas with grass and native tree seed to stabilise the slopes and prevent further sedimentation in our dams.

 

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These improvements will put Watercare in a stronger position to face future incidences of extreme weather.

Work is also in progress on a number of initiatives to upgrade our Ardmore, Waikato and Huia water treatment plants.

Ardmore: To increase the capacity of our sludge dewatering process, which was a major process constraint during the storm, we will be installing a new centrifuge and a filter press. The centrifuge dewaters the sludge by spinning it – similar to a salad spinner. The filter press works by squeezing the sludge to separate the solids from the water in the same way as a coffee plunger separates coffee grounds.

Design is also under way for a new ultraviolet (UV) disinfection facility at Ardmore, expected to be the largest UV drinking water installation in New Zealand. We hope to have it operating by the summer of 2019.

Waikato: Upgrades at Waikato have allowed us to expand our maximum production capacity from 150 to 175 million litres a day. To achieve this additional production, we have added an extra super-pulsator clarifier, two more membrane filtration trains and a hydro-cyclone separation system to remove suspended material like sand.

Huia: The solids handling systems have been upgraded with a new centrifuge and new sludge process storage. A new powder-activated carbon dosing system, expected to arrive in late 2018, will allow the plant to better handle changes in water quality. The upgrades at Huia mean the plant can continue operating reliably and sustainably to produce 110 million litres a day until the replacement plant is built.

VALUE BEING CREATED:

  • Leading-edge resource efficiency
  • Industry-leading thinking and processes