Big cost savings to be realised through treatment plant rationalisation

Next week we will put the smaller of two treatment plants that process water from the Waikato River into standby mode until early 2025, resulting in annual savings of about $4 million.
The ‘Waikato 50’ plant was designed and built very quickly in response to Auckland’s severe drought of 2020 and has been operating for the past two years. It sits alongside our original treatment plant near Tuakau.
Chief operations officer Mark Bourne says the company had originally planned to deliver a second treatment plant in 2026, but the drought prompted the company to bring forward its construction.
“Not all water sources are equal when it comes to droughts,” Bourne explains. “While water storage dams are greatly impacted by drought, a lot of rivers and underground aquifers can withstand months of dry weather. So, back in 2020, we set about increasing the volume of water we could treat from rivers and aquifers.
Bourne says the incredibly wet weather Auckland has experienced over the past 10 months mean Auckland’s dams have stayed above 95% full since July last year.
“For a few months after the January storm, our Huia Water Treatment Plant – which treats water from four of our Waitākere dams – was operating at a reduced capacity because of the increased turbidity (dirtiness) in the dam water caused by multiple landslips.
“Now that it’s operating at its normal production levels, and dam storage remains very high, we can take the Waikato 50 plant offline and put it on standby to achieve considerable cost savings.”
Operational costs at the Waikato 50 treatment plant are higher as it requires more manual monitoring and intervention.
“The cost of chemicals needed to treat water from the Waikato River are also significant. For example, we use significant amounts of carbon dioxide, which has more than quadrupled in the past year after the closure of the Marsden Point Oil Refinery and its CO2 plant,” Bourne says.
“The Waikato 50 plant has served Auckland well over the past two years. But with the drought firmly behind us, we can return to our original plan of having the second plant up and running in a few years’ time.
“It’s important to stress that the Waikato 50 plant will be maintained in a state of readiness so it can return to service if needed – for example, if we experience another drought. This means our operators will continue to check its equipment regularly to ensure everything remains in good operational condition.
“Our newest Waikato River resource consent, which we activated in January, enables us to take full advantage of our original Waikato Water Treatment Plant. This means we can currently treat up to 168 million litres of water a day from the Waikato River year-round. Previously, we could only plan to treat up to 127.5 million litres a day in summer. The increase of around 40 million litres of water a day is the same as the long-run capacity of the Waikato 50 plant – only the original plant costs less to operate. This will make a tremendous difference in terms of keeping our total water supply situation stable.”
When the Waikato 50 is brought back into service in early 2025, we will be able to treat up to 225 million litres of water a day from the river. In the 2030s, the company will transform the Waikato 50 plant into the permanent Waikato A Water Treatment Plant and install a second pipeline from Tuakau to the city. Ultimately, Auckland will receive up to 300 million litres of water a day from the Waikato River.