About 70,000 subject to non-compliant water

PHOTO: ODT FILES

About 70,000 people across the South may have been drinking from council water supplies that should have protozoa barriers but do not.

Most supplies yet to comply with regulations in effect since November last year are small-scale schemes, but Queenstown and Wānaka stand out as exceptions.

The Dunedin and Invercargill city councils are fully compliant.

Protozoa such as cryptosporidium and giardia can be spread through drinking-water supplies, causing illness.

More than 60 cases of cryptosporidium have been confirmed from an outbreak in Queenstown in recent weeks.

Investigations by Te Whatu Ora Health New Zealand concluded the most likely source was human faecal contamination of the water supply.

A boil water notice still applies to part of the resort town.

National water regulator Taumata Arowai last week wrote to all providers of council, government and private supplies that shared the same characteristics as Queenstown and asked them to update information and ensure it was accurate.

"Now that we have assessed the information provided, we have identified 27 council suppliers across Aotearoa that have drinking water treatment plants that should have a protozoa barrier in place, but have told us that they don’t," regulatory head Steve Taylor said.

The total population potentially affected by 84 drinking water supplies lacking a protozoa barrier was about 310,000, including about 169,000 people in Christchurch.

Councils have been told in a letter they are expected to have funding plans agreed by June 30 next year.

A deadline of the end of next year has been indicated for installation and operation of protozoa barriers for surface water sources.

They would need to be operating for bore water sources by the end of 2025.

"We are considering what regulatory action is required should suppliers not respond satisfactorily within the timelines set out in our letter," Mr Taylor said.

"Shortly we will be writing to council and government suppliers we have identified without other required forms of treatment, such as residual disinfection in the distribution network, to set out our expectations of compliance for these matters."

The Queenstown Lakes District Council is putting in place a temporary solution at its Two Mile treatment plant.

Larger ultraviolet reactors have been ordered and will be used long term and the temporary systems will then be used elsewhere in the district for supplies at Western Wānaka, Beacon Point in Wānaka, and Luggate.

In Gore, treatment is to be centralised at one plant, which will ensure compliance.

The Central Otago District Council is developing business cases for Patearoa and Ranfurly supply options and construction of a new Cromwell plant could start in July.

The Clutha District’s Tuapeka West supply is to be replaced by the Greenfield rural drinking water scheme next year.

In the Southland District, a replacement plant for Eastern Bush/Otahu Flat is being designed and protozoa compliance will be part of the new upgraded plant.

The Tuatapere plant in Southland also has an issue with the age of its filtration and UV system and is being considered for relocation because of flooding risk.

Invercargill and Bluff are served by a single water source, the Ōreti River, and the Branxholme Water Treatment Plant had a $12 million upgrade in 2017.

It has two treatment barriers to remove protozoa.

"The first process involves physically removing protozoa from the water, while the second is an ultraviolet process that inactivates any remaining protozoa," Invercargill City Council infrastructure group manager Erin Moogan said.

The Dunedin City Council has protozoa barriers at all its water treatment plants.

"We monitor the performance of all our water treatment plants, as well as water quality, in accordance with our drinking water safety plans and New Zealand’s drinking water regulatory requirements," a council spokesman said.