Boil water notices are not an infrequent event in New Zealand. They're a precaution, issued when there's a risk that disease-causing microbes have entered a drinking water supply. Boiling water for at least one minute kills bacteria, protozoa and viruses, including Cryptosporidium which can cause gastrointestinal illness.
When a boil water notice is issued, residents have questions, like how long was the water unsafe, and why didn't we find out sooner? These questions might not need to be asked in future.
PHF scientists, including Dr Sujani Ariyadasa (senior microbiologist) and Dr Louise Weaver (science leader/ technical lead), are working on early warning systems for risks to our drinking water. Their research aims to move water safety monitoring from reactive to proactive, shifting to real-time detection methods that would flag a problem before it reaches communities.
“The way we currently test water, there's an unavoidable lag,” says Dr Ariyadasa. Conventional water testing works like a blood test: you take a sample, wait for a result, and then learn something has changed.
The research team is working on new techniques to check water quality without needing to grow microbes in a lab. Instead of waiting several days for lab results, these methods can spot changes in the water straight away.
One approach they are interested in is a flow system, which works more like a continuous blood glucose monitor. Water passes through a laser beam, and the system looks at every microbial cell in real time. Over time, the system learns what ‘normal’ looks like for a particular water source. The goal is that any sudden change from normal triggers an alert, enabling extra testing and risk mitigation measures to be taken before water reaches anyone’s tap, and long before a lab culture would give you an answer.
Another project aims to provide an additional layer of protection by looking at the health of the groundwater systems many communities rely on for drinking water. Dr Weaver’s Groundwater Health Index (GHI) combines microbial, ecological and water quality indicators to detect early signs of contamination, or stress from land use or changing environmental conditions. By identifying where groundwater is vulnerable or deteriorating, the GHI can help councils and water suppliers make better decisions about source-water protection and risk management, before problems affect drinking water supplies.
Safe drinking water is fundamental to public trust and community health, reducing illness, economic costs and the burden on healthcare. Water is tested at treatment plants to ensure it meets microbiological and chemical standards, and new drinking water quality rules introduced in 2022 are pushing councils to improve water treatment infrastructure, requiring them to have a protozoa barrier such as UV treatment.
However, drinking water safety does not end at the treatment plant. Even with more stringent treatment requirements, risks can still arise as water moves through pipes and plumbing systems on its way to household taps. The team is in the early stages of exploring new techniques to reduce bacteria inside plumbing systems, providing one more layer of protection.
This multi-layered approach has attracted national attention, with Dr Ariyadasa recently named a finalist in the Science New Zealand Awards 2026, Early Career Researcher category, in recognition of the scope of important interdisciplinary research she has undertaken to improve water treatment technologies and reduce the burden of waterborne disease. The award nomination noted that her career trajectory “suggests she will become a world leading authority in water security, driving innovations that safeguard communities against emerging microbial threats.... demonstrating vision and initiative well beyond her career stage”.
Further work conducted by Dr Ariyadasa integrates molecular microbiology, biotechnology, and environmental engineering to tackle the urgent challenges posed by pathogens including Cryptosporidium, and the emerging risk of Legionella within free-living amoebae.
The amoeba is one example of a climate-dependent emerging pathogen Dr Ariyadasa intends to help New Zealand prepare for. Some free-living (non-parasitic) amoebae host pathogens such as Legionella, and as amoeba populations grow in warmer water – expected under climate change – there are more hosts for Legionella to multiply in. “While our waters are still too cold for amoeba to be an immediate threat,” she says, the risk becomes “more likely with continuing global warming.”
Keeping our drinking water safe as climate change exposes new risks may require even more layers of protection: treatment plants with multiple barriers, new biological research, and real-time monitoring to alert us to dangers as they appear. Boiling water will remain a dependable fallback, but Dr Ariyadasa and PHF Science are working towards a future where risks are caught in hours, rather than discovered after people fall ill.