The Water Services Authority — Taumata Arowai (the Authority) continues to ensure that council suppliers are implementing critical barriers necessary to ensure safe drinking water.
In 2023, the Authority advised 29 council drinking water suppliers whose supplies lacked protozoa, bacterial, or residual disinfection treatment barriers of its expectation that they provide a funded plan for implementing these barriers. At the time, this involved 98 supplies (drinking water sources) serving 655,150 people.
As of early March 2025, critical treatment barriers are now up and running at 41 drinking water supplies managed by 14 councils that provide 227,038 people with safer drinking water. Eight councils have now completed installation of the required barriers across all of their supplies.
Since September 2024 when the Authority last reported on critical barrier progress, an additional 18 supplies serving 141,345 people have had barriers installed.
Local and central government are by far the largest providers of drinking water to New Zealanders. Councils collectively operate 529 supplies across the country, serving approximately 4.4 million people.
Authority Head of Operations, Steve Taylor says the council suppliers have made significant progress towards getting cost-effective treatment barriers in place and improving drinking water safety.
“Our focus is on ensuring that the public is provided with safe drinking water. It’s very good to see the headway that suppliers have made towards this. We appreciate the work put in by councils to make this happen.
“A multi-barrier approach is a critical principle of safe drinking water. It is a regulatory requirement for drinking water suppliers and requires a range of safeguards in place to prevent people from getting sick from their drinking water. No single barrier is effective against all sources of contamination – for example, chlorine is a highly effective treatment against bacteria and viruses, but it’s not effective against protozoa.
“Not having a protozoa treatment barrier was identified as a likely factor in the 2023 Queenstown cryptosporidiosis outbreak. Multibarrier protection is now in place for Queenstown.
“Having multiple barriers in place means that if one fails, others are there as back-ups to help prevent, or reduce, the chance of public health being impacted,” says Mr Taylor.
Mr Taylor says there is still work to do but expects most suppliers will have installed the critical treatment barriers by the end of the year.
“A further 14 supplies serving 430,073 people are in the process of implementing their funded plans and are on track to meet their 2025 deadlines. We will continue to ensure that these suppliers are undertaking the necessary work throughout the year,” added Mr Taylor.
More information
Suppliers make progress implementing critical treatment barriers – 10 September 2024
Links to additional information
- Find out more about the multi-barrier approach to drinking water safety: taumataarowai.govt.nz/multi-barrier
- Find out more about chlorine and safe drinking water: taumataarowai.govt.nz/chlorine
What is a protozoa barrier?
While chlorine can kill bacteria and viruses in drinking water, it doesn’t protect against protozoa.
Protozoa are single-celled parasites, like cryptosporidium and giardia, that can make people sick. But they can be removed from water using some filters or inactivated using ultraviolet light, so that they don’t pose a health risk.
These filters and UV (ultraviolet) treatment tools are known as protozoa barriers because they help prevent protozoa from making people sick.
What is a bacterial barrier?
A bacterial barrier is used during the primary disinfection stage in the drinking water treatment process. It’s designed to remove, kill or deactivate bacteria present in water that’s been collected from lakes, rivers, aquifers or rainwater. The most common bacterial barriers are chlorination, UV treatment and some types of filters.
What is residual disinfection?
Once water has been treated, it needs to be sent out to people – usually through pipes. Things like damage to drinking water pipes create an opportunity for bacteria to contaminate treated drinking water. So, a small amount of chlorine is also added when drinking water leaves the treatment plant to keep treated water safe as it travels from the treatment plant to people. In the water services sector, this is called residual disinfection.